JP5470286B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus including the developing device.

  An image forming apparatus using an electrophotographic system, such as a copying machine, a printer, a facsimile machine, and a composite machine of these, includes an image carrier, a charging device that uniformly charges the surface of the image carrier, and a charged image carrier. An exposure device for forming an electrostatic latent image on the surface of the image carrier by exposing the surface of the body; and supplying toner to the surface of the image carrier on which the electrostatic latent image is formed. A developing device that develops an electrostatic latent image as a toner image, a transfer device that transfers the toner constituting the toner image from the image carrier to a recording medium, and paper that is heated and pressed by the transferred toner image A fixing device for fixing the recording medium to the recording medium. Such an image forming apparatus transfers the toner image formed on the image carrier to the recording medium by each of the above-described apparatuses, and then fixes the toner image on the recording medium, whereby the image is recorded on the recording medium. Form.

  As a developing device provided in an image forming apparatus using an electrophotographic system, there are various developing systems. Specifically, as a developing device using a one-component developer, for example, a developer tank is obtained by rotating the developing roller in a state where toner as a one-component developer is carried on the surface of the developing roller. And the like, and the electrostatic latent image previously formed on the surface of the image carrier is developed with the one-component developer by transporting the toner stored in the toner to a photosensitive drum as an image carrier. . Such a developing device is provided with a plate-like toner layer regulating member that is disposed with its tip close to the surface of the developing roller. By the toner layer regulating member, when the toner is conveyed by the developing roller, the toner is scraped off so that the toner layer carried on the surface of the developing roller has a predetermined thickness. At that time, the toner conveyance amount by the developing roller is adjusted and the toner is charged.

  Such a developing roller is usually made of stainless steel or aluminum. This is because these metals form a passive layer on the surface, and therefore, when a positively charged one-component toner is used, a stable positive charge can be given to the toner by the passive oxide film.

  However, if the stainless steel or aluminum is used for a long period of time, its surface is scraped by an external additive of the toner and streaky noise is generated in the circumferential direction of the surface, so that there is a problem in durability.

  In view of this, a method has been proposed in which a chromium film is formed on the surface of the developing roller, which is superior in wear resistance than aluminum or stainless steel and which forms a passive layer on the surface like stainless steel or aluminum. Specifically, chromium plating is performed on the surface of the developing roller (Patent Document 1), thereby maintaining the chargeability of the toner.

  A method for forming an oxide film such as anodized or chromium oxide on the surface of the developing roller has also been proposed. Specifically, a method for forming a chromium-based film on the developing roller surface using a chromic acid treatment solution containing hexavalent chromium has been reported (Patent Document 2).

JP 2000-284586 A Japanese Patent Laid-Open No. 7-44020

  However, the method described in Patent Document 1 is a charge application that relies on a non-conductive state, and is effective to some extent. However, when exposed to a high-temperature and high-humidity environment (HH), or when the toner deteriorates and the charge performance decreases. In this case, sufficient charge performance cannot be maintained with this non-conductive layer alone. If sufficient toner charging is not possible, problems such as image density reduction and ghosting occur.

The method for forming an oxide film on the surface as described in Patent Document 2 ensures chargeability rather than passivation, but usually hexavalent chromate is formed of CrO ₃ + Cr ₂ O ₃ + H ₂ O. In the case of a film (hexavalent chromate) containing CrO ₃ , fine cracks are generated on the surface. For this reason, when a developing roller having a film containing CrO ₃ is used, the external additive of the toner is buried in the crack, resulting in a problem that the toner transportability and chargeability are changed as well as durability.

  Therefore, the present invention provides a developing device using a one-component developer as a developer, which can stably and positively charge the toner, maintain the chargeability of the toner, and improve the toner transportability. It is an object to provide an image forming apparatus.

As a result of intensive studies in view of the above problems, the present inventors have developed a developing device having a coating layer containing a hexavalent chromium-free trivalent chromium compound (Cr ₂ O ₃ ) and cobalt (Co) as the outermost layer. The inventors have found that the chargeability and transportability of a one-component developer can be improved by using, and have further researched to complete the present invention.

That is, one aspect of the present invention for solving the above-described problems is a developing device including a developer carrier that carries a developer, wherein the developer carrier is a hexavalent chromium-free trivalent chromium compound. A developing device comprising: a coating layer containing (Cr ₂ O ₃ ) and cobalt (Co) in an outermost layer; and the developer is a one-component developer.

  With such a configuration, the surface of the developer carrying member becomes very dense and cracks do not occur. Therefore, it is possible to provide a developing device that can stabilize the chargeability of the toner, improve the toner transportability, and is excellent in durability.

It is thought that the reason for this crack is affecting the water content in the coating layer of the development carrier. The water content of hexavalent chromate is 1.8 μg / cm ₂ , whereas the water content of the coating layer according to the present invention is about 0.3 μg / cm ^2, which is about 1/6. For this reason, it is thought that the film of the present invention can suppress the occurrence of cracks.

Furthermore, since the coating layer of the present invention contains cobalt, a [Co (H ₂ O) ₆ ] ³⁺ film is formed on the surface to prevent moisture permeation.

In the developing device, it is preferable that the coating layer further includes at least one of silicon (Si) and phosphorus (P). As a result, when Si is present, a SiO ₂ film can be formed on the surface of the film to prevent moisture permeation, and when P is present, precipitation of CrPO ₄ .4H ₂ O is added. Membrane properties are enhanced. By such a structure, the surface of the carrier of the present invention becomes denser and the occurrence of cracks can be further suppressed.

  Further, when the developer carried by the developer carrying member is a positively charged one-component developer, the developing device according to the present invention works more effectively. This is because the developer carrying member according to the present invention can supply a stable positive charge to the toner.

  Still another aspect of the present invention for solving the above problem is an image forming apparatus including the developing device. According to the image forming apparatus of the present invention, it is possible to provide an excellent image over a long period of time because the toner is excellent in chargeability and transportability.

  According to the developing device and the image forming apparatus according to the present invention, since the toner is excellent in chargeability and transportability, a high-quality image can be obtained.

1 is a schematic diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is an enlarged schematic sectional view showing an image forming unit of an image forming apparatus according to an embodiment of the present invention. It is a schematic sectional drawing for demonstrating the layer structure of the surface part of the developing roller which concerns on embodiment of this invention. It is an image figure of the trivalent chromium compound membrane | film | coat of the developing roller which concerns on embodiment of this invention.

The present invention relates to a developing device including a developer carrying body for carrying a developer, wherein the developer carrying body contains a hexavalent chromium-free trivalent chromium compound (Cr ₂ O ₃ ) and cobalt (Co). The present invention provides a developing device characterized in that the outermost layer includes a coating layer including the developer, and the developer is a one-component developer, and an image forming apparatus including the developing device.

  First, an image forming apparatus including a developing device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  The image forming apparatus according to the embodiment of the present invention is not particularly limited as long as it includes a developing device described later. Here, as an image forming apparatus, an image forming apparatus having the configuration shown in the drawings, specifically, a monochrome type printer apparatus will be described as an example, but any image forming apparatus using an electrophotographic method may be used. The present invention is not limited to a monochrome type printer device. Specifically, it may be another image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine having these functions. The image bearing member will be described by taking a photosensitive drum as a drum-shaped photosensitive member as an example. However, the image bearing member is not limited to this, and a belt-shaped photosensitive member may be a sheet-shaped photosensitive member. There may be.

  FIG. 1 is a schematic diagram showing a schematic configuration of an image forming apparatus (printer) 1 according to an embodiment of the present invention. The image forming apparatus 1 includes a paper feeding unit 10 that stores a paper P that is a recording medium, an image forming unit 20 that forms a toner image on the paper P fed from the paper feeding unit 10, and the image forming unit. A fixing unit 30 that fixes the unfixed toner image formed on the paper P by the unit 20 on the paper P, and a paper discharge unit that discharges the paper P on which the toner image is fixed by the fixing unit 30 to the outside of the image forming apparatus. 40.

  The main body of the image forming apparatus 1 includes a paper transport unit 50 that transports the paper P from the paper feed unit 10 to the paper discharge unit 40 via the image forming unit 20 and the fixing unit 30. The sheet conveyance unit 50 includes a conveyance path 52 that connects the paper discharge unit 40 via the image forming unit 20 and the fixing unit 30 from the paper supply unit 10, and a conveyance roller pair 51 at an appropriate position of the conveyance path 52. The paper transport unit 50 discharges the paper P from the paper feed unit 10 via the image forming unit 20 and the fixing unit 30 by transporting the paper P in the transport path 52 by the transport roller pair 51. It is conveyed to the paper unit 40.

  The paper feed unit 10 includes a paper feed tray 11, a pickup roller 12, and a paper feed roller pair 13. The sheet feed tray 11 is detachably mounted at a position below the image forming unit 20 in the image forming apparatus main body, and stores a sheet bundle in which a plurality of sheets P are stacked. The pickup roller 12 is provided at an upper position on the upstream side in the conveyance direction of the paper P, and takes out the paper P on the uppermost surface of the paper bundle stored in the paper feed tray 11 one by one. The pair of paper feed rollers 13 sends the paper P taken out by the pickup roller 12 to the transport path 52. By doing so, the paper feeding unit 10 supplies the paper P to the image forming unit 20.

  The paper feeding unit 10 further includes a manual feed tray 14 and a pickup roller 15 that are attached to one side surface of the image forming apparatus 1, for example, the right side surface shown in FIG. The manual feed tray 14 is used for supplying the paper P toward the image forming unit 20 by manual feed operation. The pickup roller 15 takes out the paper P placed on the manual feed tray 14 and sends it out to the transport path 52. By doing so, the paper feeding unit 10 supplies the paper P to the image forming unit 20.

  The image forming unit 20 is disposed on the downstream side of the sheet feeding unit 10 in the sheet conveyance direction. The image forming unit 20 is for forming a toner image on the paper P fed from the paper feeding unit 10 based on image data transmitted from the outside (for example, a personal computer). . The configuration of the image forming unit 20 will be described later.

  The fixing unit 30 is disposed downstream of the image forming unit 20 in the sheet conveyance direction. The fixing unit 30 fixes the unfixed toner image formed on the paper P by the image forming unit 20 on the paper P. The fixing unit 30 includes a heating roller 31 provided with an energization heating element serving as a heating source therein, and a pressure roller 32 disposed to face the heating roller 31.

  The paper P supplied to the fixing unit 30 is heated and pressurized by passing through a fixing nip formed between the heating roller 31 and the pressure roller 32. As a result, the toner image transferred to the paper P by the image forming unit 20 is fixed to the paper P. The sheet P for which the fixing process has been completed is discharged toward a discharge tray 41 of a discharge section 40 provided at the top of the main body of the image forming apparatus 1 via a conveyance path 52 extending from the fixing section 30. Is done.

  The paper discharge unit 40 includes a paper discharge tray 42 that receives the paper P that is formed by recessing the top of the image forming apparatus 1 and is discharged to the bottom of the concave.

  The image forming apparatus 1 forms a toner image on the paper P fed from the paper feeding unit 10 by the image forming unit 20 and fixing the toner image by the fixing unit 30. Then, the paper P on which the image is formed is discharged by the paper discharge unit 40.

  Next, the image forming unit 20 will be described with reference to FIG. 2 in addition to FIG. FIG. 2 is an enlarged schematic cross-sectional view showing the image forming unit 20 of the image forming apparatus according to the embodiment of the present invention.

  In the image forming unit 20, a photosensitive drum 21 serving as an image carrier is disposed so as to be rotatable in a predetermined direction (clockwise in FIG. 2). The image forming unit 20 forms a toner image on the photosensitive drum 21 and transfers the toner image onto the paper P fed from the paper feeding unit 10. By doing so, the image forming unit 20 forms a toner image on the paper P fed from the paper feeding unit 10 based on image data transmitted from the outside (for example, a personal computer or the like).

  Then, when the position where the toner image is transferred from the photosensitive drum 21 to the paper P is the most upstream side in the rotation direction of the photosensitive drum 21, the image forming unit 20 is sequentially cleaned from there. The cleaning device 22, the charge removal device 23, the charging device 24, the exposure device 25, and the development device 70 so as to be a position to be discharged, a position to be discharged, a position to be charged, a position to be exposed, and a position to be developed. Each is provided around the photosensitive drum 21. The image forming unit 20 includes a conveyance belt 27 that conveys the paper P when the toner image formed on the photosensitive drum 21 is transferred to the paper P fed from the paper feeding unit 10. . In addition, the image forming unit 20 includes a transfer roller 26 via a conveyance belt 27 at a position where the toner image is transferred from the photosensitive drum 21 to the paper P.

  The photosensitive drum 21 is for forming a toner image based on image information on its peripheral surface by charging, exposure, development, cleaning, neutralization, and the like. The photoreceptor drum 21 is not particularly limited as long as it is a photoreceptor drum provided in the image forming apparatus. Specifically, for example, an amorphous silicon (a-Si) photosensitive drum, an organic photosensitive (OPC) drum, or the like can be given.

  The charging device 24 is for charging the peripheral surface of the photosensitive drum 21 rotated in the arrow direction. The charging device 24 is not particularly limited as long as it is a charging device provided in the image forming apparatus. Specifically, for example, a charging device including a charging roller and charging a peripheral surface of the photosensitive drum by applying a predetermined charging bias voltage to the charging roller, a corotron type or a scorotron type Examples thereof include a non-contact discharge type charging device.

  The exposure device 25 irradiates the peripheral surface of the photosensitive drum 21 whose peripheral surface is charged by the charging device 24 with exposure light L such as laser light or LED light based on the image information, and on the peripheral surface of the photosensitive drum 21. For forming an electrostatic latent image based on image information. The exposure device 25 is not particularly limited as long as it is an exposure device provided in the image forming apparatus. Specifically, an LED head unit, a laser scanning unit (LSU), etc. are mentioned, for example.

  The developing device 70 is for developing the electrostatic latent image formed on the peripheral surface of the photosensitive drum 21 into a toner image. The developing device 70 includes a developing roller 72 as a developer carrier, stirring rollers 73 and 74, and a blade 75, which are housed in a developing container 71.

  The developing container 71 is a developing tank that constitutes an outline of the developing device 70 and stores toner that is a one-component developer. The developing container 71 has an opening at a position facing the photosensitive drum 21. A developing roller 72 is provided so as to be exposed toward the photosensitive drum 21 from the opening. In the developing container 71, a developer storage portion 81 is formed in the lower part thereof.

  The developer storage unit 81 is composed of two adjacent developer storage chambers 82 and 83 extending in the longitudinal direction of the developing device 70 (perpendicular to the paper surface of FIG. 2). The developer storage chambers 82 and 83 are partitioned from each other in the longitudinal direction by a partition plate 84, but communicate with each other in the vicinity of both ends in the longitudinal direction.

  Further, stirring rollers 73 and 74 are mounted in the developer storage chambers 82 and 83, respectively. The agitating rollers 73 and 74 are for conveying the developer while being agitated by rotation. Since the agitation rollers 73 and 74 are arranged so that the conveyance directions are opposite to each other, the developer is conveyed in the developer storage chamber 82 and the developer storage chamber 83 while being agitated. The developer storage unit 81 is supplied with toner as a one-component developer from the toner cartridge 85.

  The developing roller 72 is for transporting the toner stored in the developer storage unit 81 to the vicinity of the photosensitive drum 21 by rotating in a state where the toner is carried on the peripheral surface thereof. The configuration of the developing roller 72 will be described later.

  The blade 75 is a toner layer regulating member that regulates the thickness of the toner carried on the developing roller 72. The blade 75 is a plate-like member, and one end thereof is disposed to face the peripheral surface of the developing roller 72. The blade 75 is not particularly limited as long as it is a blade provided in a one-component developing type developing device. Specifically, for example, a stainless steel (SUS) blade can be used.

  Further, the toner carried on the surface of the developing roller 72 is charged when passing through the restriction position by the toner layer restriction member. This is considered that the toner is rubbed against the surface of the developer carrying member when passing through the regulation position by the blade 75, thereby being charged.

  Next, the developing roller 72 as the developer carrying member will be described with reference to FIG. 3 in addition to FIGS. FIG. 3 is a schematic cross-sectional view for explaining the layer structure of the surface portion of the developer carrier 72 according to the embodiment of the present invention, and also shows the photosensitive drum 21.

In this embodiment, the developing roller 72 includes at least a base material 102 and a coating layer 101, and the coating layer 101 includes a hexavalent chromium-free trivalent chromium compound (Cr ₂ O ₃ ) and cobalt (Co). Yes. The coating layer 101 is provided so as to be the outermost surface of the developing roller 72.

By using such a developing roller, an image having a sufficiently high image density can be formed while maintaining the chargeability and transportability of the toner even when used for image formation over a long period of time. One of the main factors that can achieve such an effect is that the surface of the coating layer containing the hexavalent chromium-free trivalent chromium compound (Cr ₂ O ₃ ) and cobalt (Co) is very dense and cracks This is because the occurrence of this is difficult.

  Note that the coating layer of the developing roller as the developer carrying member according to the present invention is essentially hexavalent chromium-free and does not contain hexavalent chromium, but Cr (III) is caused by the reaction of Co contained in the coating layer. ) May be partially oxidized to Cr (VI). However, this is about 1/3000 relative to Cr (III), which is very small and hardly affects the performance of the coating layer.

  The content of the trivalent chromium compound in the coating layer is usually 90 to 97% by mass with respect to the entire coating layer. When the content of the trivalent chromium compound is less than 90% by mass or exceeds 97% by mass, the corrosion resistance is deteriorated and rust is easily generated.

  Further, the content of Co in the coating layer is usually 3 to 10% by mass with respect to the entire coating layer. If the Co content is less than 3% by mass or exceeds 10% by mass, the corrosion resistance deteriorates and rust is likely to occur.

Further, the coating layer preferably contains at least one of silicon (Si) and phosphorus (P). If Si is present, a SiO ₂ film can be formed on the surface layer of the film to prevent moisture permeation. If P is present, precipitation of CrPO ₄ .4H ₂ O is added to enhance the film forming property. When silicon (Si) is contained, the content is usually 30 to 50% by mass with respect to the entire coating layer. Moreover, when phosphorus (P) is included, the content is 3-40 mass% normally with respect to the whole membrane | film | coat layer.

  The thickness of the coating layer is usually about 0.03 to 1 μm, preferably 0.06 to 0.4 μm.

  The developing roller 72 is not particularly limited as long as it has the above configuration. Specifically, when a magnetic one-component developer is used as the developer, a developer comprising a rotating sleeve and a magnet member included in the rotating sleeve and fixedly arranged can be used. In this case, the magnetic one-component developer is attracted and carried on the rotating sleeve by the magnet member included in the rotating sleeve. In this state, the developer is conveyed by rotating the rotating sleeve.

  The developer used in the exemplary embodiment is not particularly limited as long as it is a one-component developer. However, when a magnetic one-component developer is used, for example, a positively charged toner is preferably used. The developer varies depending on the developer components and the like, and examples thereof include those having a volume average particle diameter of 6 to 8 μm.

More specifically, the rotating sleeve of the developing roller 72 includes a base material 102 and a coating layer 101. FIG. 4 shows an image diagram of the Cr ₂ O ₃ film on the surface of the developing roller according to this embodiment. Here, when the base material 101 has unevenness | corrugation by blasting etc., the film layer of a convex part will be shaved by use. However, since the film of the concave portion is difficult to be scraped, even if the base material 101 has irregularities, no streak is generated in the circumferential direction.

  As shown in FIG. 4, the coating layer 102 may be provided directly on the base material 101. However, as long as the coating layer 101 is on the outermost surface, the coating layer 102 is further interposed between the base material 102 and the coating layer 101. About one layer may be provided.

  The layer that may be further provided between the base material 102 and the coating layer 101 is preferably a layer capable of forming a passive state, such as an alumite layer, an electrolytic chromium (Cr) plating layer, or a Ti coat. This is because even when the coating layer 101 is worn away and scraped off, the chargeability of the toner can be ensured in a normal environment.

  It is also preferable to provide a layer such as an electroless nickel (Ni) plating layer or a Cu plating layer. If a material with a large friction coefficient such as Ni is used, the friction coefficient of the shaved portion will increase, so that the reduction in toner conveyance force due to shaving of the convex part and the increase due to the increase in friction coefficient will offset each other, so the conveyance force will result in Stabilize.

  Furthermore, a layer containing iron (Fe), nickel (Ni), or the like in the same composition as the coating layer 101 may be provided. This is because the durability of the developer carrying member is further improved by having such a layer.

  As for the thickness of each layer, in the case of an alumite layer, the thickness of the layer is 2 to 10 μm. In the case of an electrolytic Cr plating layer or Ti coat, the thickness of the layer is about 0.05 to 1.0 μm. It is. Furthermore, in the case of an electroless nickel (Ni) plating layer, a Cu plating layer, etc., it is about 2-6 micrometers. And when providing the layer etc. which contained iron (Fe), nickel (Ni), etc. in the same composition as a membrane | film | coat layer, the thickness of the layer is about 0.5-1.5 micrometers normally.

  The combination of these layers is not particularly limited as long as the coating layer is the outermost layer. For example, the substrate / electroless Ni plating or alumite / coating layer, the substrate / electroless Ni plating / electrolytic Cr plating / A combination of a coating layer, a substrate / electroless Ni plating or alumite / electrolytic Cr plating / a layer containing Fe · Ni, etc./a coating layer can be used.

  In addition, film thicknesses, such as an intermediate | middle layer between the membrane | film | coat layer 101 and the base material 102, can be measured using a fluorescent X-ray film thickness meter etc., for example. Specific examples of the fluorescent X-ray film thickness meter include SFT320 manufactured by Seiko Instruments Inc.

  Further, the substrate 102 is not particularly limited as long as it can be used as a developing roller, in this case, a rotating sleeve. Specifically, those having irregularities that can contribute to toner conveyance on the surface can be mentioned. For example, an aluminum base material such as an aluminum base tube is preferable. The aluminum-based substrate has suitably formed irregularities on the surface that can enhance the toner transportability. Furthermore, since aluminium can also form a passive state, chargeability can be ensured even when the coating layer is scraped.

  Further, the surface roughness of the developing roller 72, here, the surface roughness of the coating layer 101 varies depending on the average particle diameter of the toner that is the one-component developer used, but the ten-point average roughness Rz is 6 to 6. It is preferably about 9 μm. If the surface roughness is too small, the toner transportability tends to decrease. On the other hand, if the surface roughness is too large, the toner is not preferably rubbed against the developing roller 72 during conveyance by the developing roller 72, and the toner tends not to be charged appropriately.

  The ten-point average roughness Rz, which is the surface roughness here, is based on JIS and can be measured with a general surface roughness measuring instrument or the like. Specifically, for example, it can be measured using a surface roughness shape measuring machine (SURFCOM500DX) manufactured by Tokyo Seimitsu Co., Ltd.

  Next, although an example of the manufacturing method of the developing roller 72 is shown concretely below, it is not necessarily limited to the following method.

  First, a coating layer is formed on a base material by coating the base material with a coating layer composition containing a hexavalent chromium-free trivalent chromium compound (Cr2O3) and cobalt (Co).

  Such a composition for a coating layer is not particularly limited as long as the coating layer as described above can be formed.

  Specifically, for example, a coating composition can be obtained by adjusting a liquid composition containing 4 g / L of chromium nitrate, 3 g / L of cobalt nitrate, and 20 g / L of carboxylic acid to pH 4 with NaOH. .

  In addition, as pre-processing which apply | coats a film | membrane to a base material, a degreasing process (a degreasing agent for aluminum K-350 (Nippon Kanigen Co., Ltd.), 5 minutes at 50 degreeC) is performed, and an etching process (NaOH, 50 degreeC for 40 second) after that. And a further activation treatment (using 60% nitric acid for 20 seconds at room temperature) followed by drying (at 60 ° C. for 10 minutes).

  And after immersing in the processing liquid mentioned above at 30 degreeC for 60 second, the film layer on a base material can be formed by performing water washing and drying.

  Further, when an intermediate layer or the like is included between the coating layer and the base material, before forming the coating layer, the base material is subjected to various plating treatments or coating treatments, and the respective intermediate layers as described above. Can be formed. These treatment methods and treatment conditions are not particularly limited, and can be performed using a conventionally known method.

  In addition, examples of the magnet member included in the rotating sleeve include a four-pole structure having the following magnetic pole arrangement as shown in FIG. Specifically, an N pole as a developing pole at a position facing the photosensitive drum 21, an S pole at a position facing the blade 75, an N pole upstream of the rotating sleeve in the rotation direction, An S pole is disposed on the upstream side.

  The blade 75 is provided with a magnet 76 on the upstream side surface in the rotation direction of the developing roller 72. Further, the magnet 76 is arranged so that the side close to the developing roller 72 is an S pole. By such a magnet 76, it is considered that the toner carried on the surface of the developing roller 72 is preferably arranged when passing through the restriction position by the blade 75. Therefore, since such toner is rubbed against the surface of the developing roller, it is considered that the toner is suitably charged.

  Further, the developing roller 72 faces the photosensitive drum 21 and is spaced apart with the opposed peripheral surfaces being close to each other. The distance (DS distance) 105 between the developing roller 72 and the photosensitive drum 21 varies depending on the toner used, but is preferably 0.2 to 0.4 mm, for example.

  Further, as described above, the developing device 70 is disposed opposite to the photosensitive drum 21 which is an image carrier on which an electrostatic latent image is formed, and the one-component developer carried on the surface is transferred to the photosensitive drum 21. And a developer carrying member that is conveyed to the developing roller 72. The developer carrying member is the developing roller 72.

  Such a developing device 70 conveys the toner stored in the developer storing portion 81 while being carried on the surface of the developing roller 72, and at that time, when passing through the regulation position by the blade 75, the toner is suitably charged. Let Then, the toner is supplied to the photosensitive drum 21. Therefore, an image having a sufficiently high image density can be formed over a long period of time. This is considered to be due to the use of the developing roller capable of maintaining sufficiently high toner transportability over a long period of time as described above as the developer carrying member provided in the developing device.

  The image forming apparatus 1 is an image forming apparatus including the developing device 70 and the photosensitive drum 21 as described above. Since such an image forming apparatus includes the developing device 70, it is possible to maintain toner chargeability and transportability over a long period of time and form an image having a sufficiently high image density.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

1. Production of Developing Roller In addition, in the following examples, the composition of the electrolytic chromium plating solution (trivalent chromium plating solution) used is as follows:
・ Trivalent chromium compounds (chromium sulfate and basic chromium sulfate: 10 g / L)
・ Conductive salt (potassium sulfate 100g / L)
・ PH buffer (sodium borate 90 g / L)
-Sulfur compound (saccharin 2 g / L).

Example 1
A liquid composition containing 4 g / L of Cr nitrate, 3 g / L of Co nitrate and 20 g / L of carboxylic acid on the surface of an aluminum base (diameter 20 mm, wall thickness 0.6 mm, material A6063) is adjusted to pH 4 with NaOH. And the film layer was formed in the thickness of 0.2 micrometer on the base material by being immersed in the liquid at 30 degreeC for 60 second (s).

(Example 2) An alumite layer by treating the surface of an aluminum base (diameter 20 mm, thickness 0.6 mm, material A6063) in the order of degreasing, etching, neutralization, anodized film (alumite), and sealing treatment. Got. The alumite treatment solution and treatment conditions are:
Sulfuric acid (H ₂ SO ₄ ) 15 W / V%
20 ℃
Dissolved aluminum 20g / L
Dissolved chloride amount 0.2g / L
Current density 100A / m ²
By setting the time to 5 minutes, an alumite layer was formed with a thickness of 5 μm. Thereafter, a liquid composition containing 4 g / L of chromium nitrate, 3 g / L of cobalt nitrate, and 20 g / L of carboxylic acid was adjusted to pH 4 with NaOH, and a base material on which the above-mentioned anodized layer was formed was added to the liquid. By dipping at 60 ° C. for 60 seconds, a coating layer was formed with a thickness of 0.35 μm on the alumite layer.

(Example 3)
The surface of an aluminum substrate (diameter 20 mm, wall thickness 0.6 mm, material A6063) is first plated using an electroless Ni plating solution (“Kanizen (registered trademark)”, manufactured by Nihon Kanisen Co., Ltd.), and electroless Ni The plating layer was formed with a thickness of 4.2 μm. Thereafter, a liquid composition containing 4 g / L of chromium nitrate, 3 g / L of cobalt nitrate, and 20 g / L of carboxylic acid was adjusted to pH 4 with NaOH, and the above electroless Ni plating layer was formed on the liquid. By immersing the material at 30 ° C. for 60 seconds, a film layer having a thickness of 0.28 μm was formed on the electroless Ni plating layer.

Example 4
The surface of an aluminum substrate (diameter 20 mm, wall thickness 0.6 mm, material A6063) is first plated using an electroless Ni plating solution (“Kanizen (registered trademark)”, manufactured by Nihon Kanisen Co., Ltd.), and electroless Ni The plating layer was formed with a thickness of 4.5 μm. Further thereon, a plating process was performed using an electrolytic Cr plating solution to form an electrolytic plating layer having a thickness of 0.15 μm. Thereafter, a liquid composition containing 4 g / L of chromium nitrate, 3 g / L of cobalt nitrate, and 20 g / L of carboxylic acid was adjusted to pH 4 with NaOH, and the base material on which the electrolytic Cr plating layer was formed in the liquid Was soaked at 30 ° C. for 60 seconds to form a film layer having a thickness of 0.22 μm on the electrolytic Cr plating layer.

(Example 5)
The surface of an aluminum substrate (diameter 20 mm, wall thickness 0.6 mm, material A6063) is first plated using an electroless Ni plating solution (“Kanizen (registered trademark)”, manufactured by Nihon Kanisen Co., Ltd.), and electroless Ni The plating layer was formed with a thickness of 4.7 μm. Further thereon, a plating process was performed using an electrolytic Cr plating solution to form an electrolytic plating layer having a thickness of 0.19 μm. Thereafter, a liquid composition containing 4 g / L of chromium nitrate, 3 g / L of cobalt nitrate, and 20 g / L of carboxylic acid was adjusted to pH 4 with NaOH, and the base material on which the electrolytic Cr plating layer was formed in the liquid Was soaked at 30 ° C. for 60 seconds to form a film layer having a thickness of 0.06 μm on the electrolytic Cr plating layer.

(Example 6)
The surface of an aluminum substrate (diameter 20 mm, wall thickness 0.6 mm, material A6063) is first plated using an electroless Ni plating solution (“Kanizen (registered trademark)”, manufactured by Nihon Kanisen Co., Ltd.), and electroless Ni The plating layer was formed with a thickness of 5.1 μm. Further thereon, a plating process was performed using an electrolytic Cr plating solution to form an electrolytic plating layer having a thickness of 0.18 μm. In addition, a liquid composition containing 4 g / L of chromium nitrate, 3 g / L of cobalt nitrate, 20 g / L of carboxylic acid, and Fe, Ni, Co, and P (each in a trace amount) was added with NaOH to a pH of 4 The substrate on which the electrolytic Cr plating layer was formed was immersed in the solution at 30 ° C. for 60 seconds to form a further layer having a thickness of 0.5 μm on the electrolytic Cr plating layer.

  Thereafter, a liquid composition containing 4 g / L of chromium nitrate, 3 g / L of cobalt nitrate, and 20 g / L of carboxylic acid is adjusted to pH 4 with NaOH, and the substrate obtained above is added to the liquid 30 By immersing at 60 ° C. for 60 seconds, a coating layer was formed to a thickness of 0.06 μm on the outermost layer of the substrate.

(Comparative Example 1)
Stainless steel (SUS) (diameter 20 mm, wall thickness 0.6 mm, material SUS305) was blasted.

(Comparative Example 2)
An aluminum (diameter 20 mm, wall thickness 0.6 mm, material A6063) substrate was blasted.

(Comparative Example 3)
An alumite layer having a thickness of 6 μm was formed on the surface of an aluminum substrate (diameter 20 mm, wall thickness 0.6 mm, material A6063) by the same method as in Example 2 except that the treatment time was 6 minutes.

(Comparative Example 4)
The surface of an aluminum substrate (diameter 20 mm, wall thickness 0.6 mm, material A6063) is first plated using an electroless Ni plating solution (“Kanizen (registered trademark)”, manufactured by Nihon Kanisen Co., Ltd.), and electroless Ni The plating layer was formed with a thickness of 4.7 μm. Further thereon, a plating process was performed using an electrolytic Cr plating solution to form an electrolytic plating layer having a thickness of 0.18 μm.

(Comparative Example 5)
By immersing the surface of an aluminum substrate (diameter 20 mm, wall thickness 0.6 mm, material A6063) in an aqueous solution containing hexavalent chromium 20 g / L and ammonium hydrogen fluoride 1 g / L at 25 ° C. for 120 seconds, A film layer containing hexavalent chromium (CrO ₃ ) was formed on the material with a thickness of 0.3 μm. (Note that, as shown in the table, the coating layer contains trivalent chromium, which is a part of hexavalent that is reduced during processing to become trivalent).

2. Evaluation The developing roller (diameter 20 mm) manufactured in Examples 1 to 6 and Comparative Examples 1 to 5 was mounted on an image forming apparatus (“LS-4020DN”, manufactured by Kyocera Mita Corporation), and under the following conditions: An output durability test was conducted:
・ Photoconductor (Amorphous silicon photoconductor, diameter 30mm)
Photoconductor surface potential: Vo 280v
・ System speed: 125mm / s
・ Development gap: 300 μm
・ Regulation gap: 300μm
・ Development bias: Vpp 1700v
Vdc 175v
Toner: Positively charged toner, average particle size 7.1 μm
The surface roughness of the developing roller Rzjis: 7.5 ± 1.0 μm.

  The image density was measured with a Gretag Macbeth reflection densitometer (RD-918). The film thickness of each coating was measured after preparing calibration curves for Ni plating, Cr plating, and Cr coating using fluorescent X-rays and SEM.

The evaluation criteria are as follows:
(Environmental testing)
When the image density after enduring 10K sheets in an environment of temperature 32.5 ° C and humidity 85% drops by 0.3 or more compared to the density before 10K endurance (temperature 23 ° C, humidity 50%), x, The case of less than 0.3 was evaluated as ◯.

(An endurance test)
Under the same environmental conditions (temperature 20 ° C, humidity 50%), endurance of 500K, image density change is 0.5 or more x, image density change is less than 0.5 and 0.3 or more Was evaluated as ○, and less than 0.3 was evaluated as ◎.

(Circumferential longitudinal bars)
A case where image noise corresponding to a flaw in the circumferential direction of the developing roller in the circumferential direction of the developing roller was generated on the image was evaluated as x, and a case where no image noise was generated was evaluated as ◯.

  The results are shown in Table 1.

３．考察
本発明に係る実施例１〜６の現像ローラを用いた場合、全ての評価試験（環境・耐久・円周方向縦筋）において、結果が合格レベルであった。

3. Discussion When the developing rollers of Examples 1 to 6 according to the present invention were used, the results were acceptable levels in all the evaluation tests (environment, durability, and circumferential vertical stripes).

  On the other hand, the developing rollers of Comparative Examples 1 and 2 had streaks in the circumferential direction because of insufficient hardness.

  In the developing roller of Comparative Example 3, the hardness increased, but the image density increased in the durability test. This is probably because the external additive of the toner was buried in the fine holes on the surface, and the amount of toner transport increased.

  In Comparative Example 4, the charge decreased in the HH environment, and the concentration decreased.

  In Comparative Example 5, the image density was high in the durability test. This is presumably because the toner external additive was buried in the cracks on the surface, and the amount of toner transport increased.

  Further, the coating layer in the developing rollers of Examples 1 to 6 had durability and the coating layer of the convex portion was scraped, and the layer immediately below it was exposed. However, since the surface of the developing roller is uneven, the coating layer in the recess is difficult to be scraped. Therefore, it was also found that the chargeability can be maintained by leaving the film layer of the concave portion even if the film layer of the convex part is shaved.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Paper feeding part 20 Image forming part 21 Photosensitive drum 22 Cleaning apparatus 23 Static elimination apparatus 24 Charging apparatus 25 Charging apparatus 25 Exposure apparatus 26 Transfer roller 27 Conveyance belt 30 Fixing part 40 Paper discharge part 50 Paper conveyance part 70 Developing apparatus 71 Development Container 72 Developing roller 73 Stirring roller 75 Blade 76 Magnet 81 Developer reservoir 82, 83 Developer reservoir 84 Partition plate 101 Film layer 102 Base material

Claims (5)

A developing device including a developer carrying member for carrying a developer,
The developer carrier has a coating layer containing a hexavalent chromium-free trivalent chromium compound (Cr ₂ O ₃ ) and cobalt (Co) in the outermost layer;
The developer carrier is an aluminum-based substrate having irregularities on the surface;
The film thickness of the film layer is 0.06 to 0.35 μm, and the surface roughness of the film layer is 6 to 9 μm in terms of a ten-point average roughness Rz. A developing device, characterized by being an agent.   The developing device according to claim 1, wherein the coating layer further includes at least one of silicon (Si) and phosphorus (P).   The developing device according to claim 1, wherein the one-component developer is a positively charged toner. An electroless nickel (Ni) plating layer having a thickness of 4.2 to 5.1 μm is provided on the aluminum base material, and further an electrolytic chromium (Cr) plating having a thickness of 0.05 to 0.19 μm is provided thereon. The developing device according to claim 1, comprising a layer. Comprising a developing device according to any one of claims 1 to 4, the image forming apparatus.

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