JP5433594B2 - 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.

  A developing roller using such a developing device using a one-component developer, that is, a developing device of a one-component developing system is required to have high toner transportability. For this reason, the developing roller is required to have irregularities on its surface. In order to further improve the toner transportability, the surface is sometimes roughened by blasting or the like to form irregularities.

  The developing roller is considered to charge the toner as follows. The toner carried on the surface of the developing roller is rubbed against the surface of the developing roller when passing through the restriction position by the toner layer restriction member. This rubbing is considered to charge the toner. Therefore, the developing roller is required to have a surface made of a material capable of charging the toner so that the toner conveyed by the developing roller has a predetermined charge.

  Then, the developing roller which consists of a material different from a base material as a material which comprises the surface by carrying out the plating process on the surface of a developing roller is mentioned. Specific examples of the developing roller and the developing device in which such a surface is plated include those described in Patent Documents 1 to 6.

  In Patent Document 1, in a developer carrying member in which a resin layer in which a conductive material such as carbon is dispersed is provided on a metal substrate, the surface on which the resin layer has a high content of the conductive material such as carbon. A developer carrying member is described which is a laminated film composed of a layer and at least two layers of a lower layer in which the content of a conductive substance such as carbon is lower than that of the surface layer.

  Patent Document 2 has a lower layer having an uneven portion on the surface and a surface layer covering the surface of the lower layer, and the convex portion of the lower layer is substantially exposed on the surface of the surface layer, There is described a developing roller for an electrophotographic apparatus in which the hardness of the convex portion of the lower layer is harder than the hardness of the surface layer.

  Patent Document 3 describes a developer carrying member that carries and conveys a developer on the surface, the developer carrying member having a substrate, an electroless plating intermediate layer, and an electric hard plating layer. Has been.

  Further, Patent Document 4 discloses a container for containing a developer having toner, a developer carrier that has elasticity and is placed in contact with an image carrier and supplies the developer, and the developer carrier. In a developing device including a developer amount regulating blade that is attached to the container so as to be in contact with a body and regulates the amount of developer to be supplied, the developer amount regulating blade is at least a region in contact with toner Describes a developing device having a composite plating film containing fine particles of a fluororesin.

Patent Document 5 discloses an electrostatic latent image formed on an image carrier having a low resistance layer having a surface resistivity of 10 ⁹ to 10 ¹⁴ Ω · cm on a developer carrier having a built-in magnetic field generating means. Development is performed with a developer containing a toner and a magnetic carrier, and a developing portion including a DC voltage on which an AC voltage is superimposed, in a developing unit in which the image carrier and the developer face each other in contact with each other. In the developing device, the developer carrier has a plating film layer formed on the surface by plating, and a product σ × d of a volume resistance value σ of the developer carrier and a layer thickness d of the plating film layer. However, a developing device that satisfies the condition of 1 × 10 ⁻⁶ Ω · cm ² ≦ σ × d ≦ 1 × 10 ⁵ Ω · cm ² is described.

  Further, Patent Document 6 includes a developer carrying member that carries the developer in an endlessly movable manner, and a developer regulating member that regulates the amount of the developer carried on the surface of the developer carrying member. In the developing device for transporting the developer regulated by the agent regulating member to a development position facing the latent image carrier and developing the latent image on the latent image carrier, the developer is carried as the developer carrier. Using a plating film formed on the surface by a composite plating process, and the fine powder to be dispersed and deposited by the composite plating process, the wear resistance of the plated film is higher than that of the plating process in which the fine powder is not dispersed and deposited. A developing device using an increasing one is described.

JP-A-7-13416 JP 2009-75497 A JP 2000-284586 A Japanese Patent Laid-Open No. 2005-221978 JP 2004-37951 A Japanese Patent Laid-Open No. 2001-5281

  As described above, the developing roller provided in the one-component developing type developing device is required to have excellent toner transportability and to be able to charge the toner appropriately.

  According to Patent Document 1, two or more resin layers having different contents of conductive materials such as carbons are laminated on the base of the developer carrying member, and the surface layer has a high content of conductive substances. If the layer is a layer and the lower layer is a layer having a lower content of the conductive material than the surface layer, the charge imparting ability of the developer carrier can be controlled, and the developer placed on the developer carrier can be It is disclosed that a developer carrying member having a stable and appropriate charge and capable of obtaining a uniform high-quality image without unevenness in density and the like can be obtained.

  However, the developer carrier described in Patent Document 1 may not be able to sufficiently suppress a decrease in toner transportability over a long period of time. Therefore, the developing device provided with the developer carrying member cannot maintain a sufficiently high image density for a long period of time and may not be able to form a high-quality image. This is considered to be due to the following.

  First, the developer carrier described in Patent Document 1 has a surface layer having a high content of a conductive substance in the surface layer in a so-called initial state where development has started. Further, after the development over a long period of time, that is, the durable printing, even if the lower layer with a low content of the conductive material is exposed, this developer carrier is configured to adjust the charge imparting ability to the toner. It is thought that it was done. Therefore, it is considered that the developer carrying member described in Patent Document 1 cannot maintain excellent toner transportability over a long period of time even if the charge imparting ability to the toner can be adjusted.

  Further, Patent Document 2 discloses that it is possible to suppress the occurrence of a phenomenon in which toner adheres to the surface of the developing roller, that is, so-called filming, and adhesion of the toner to the blade.

  However, the developing roller described in Patent Document 2 may not be able to sufficiently suppress a decrease in toner transportability over a long period of time. Therefore, the developing device provided with the developer carrying member cannot maintain a sufficiently high image density for a long period of time and may not be able to form a high-quality image. This is considered to be due to the following.

  First, in the developing roller described in Patent Document 2, as described above, the lower layer convex portion is substantially exposed on the surface of the surface layer, and the hardness of the lower layer convex portion is greater than the hardness of the surface layer. Also hard. The blade that is the toner layer thickness regulating member is considered to be mainly in contact with the convex portion. From this, it can be considered that the convex portion with which the blade comes into contact is hardened so as to suppress the occurrence of toner fusion and to suppress the occurrence of filming. Therefore, it is considered that the developing roller described in Patent Document 2 suppresses the occurrence of problems due to toner fusion such as filming, and does not improve toner transportability.

  Further, the developing roller described in Patent Document 2 has an exposed lower layer from the initial stage, and does not improve toner transportability due to surface wear, but rather deteriorates toner transportability due to disappearance of convex portions. I think that.

  Further, according to Patent Document 3, since the surface of the member is improved and the merit of the hard plating layer can be fully utilized, the deterioration of the surface is small even with long-term durability, and a high-quality toner image is provided. It is disclosed that it is possible.

  However, the developer-carrying member described in Patent Document 3 may not be able to sufficiently suppress a decrease in toner transportability over a long period of time. Therefore, the developing device provided with the developer carrying member cannot maintain a sufficiently high image density for a long period of time and may not be able to form a high-quality image. This is considered to be due to the following.

  First, the developer-carrying member described in Patent Document 3 has a hard plating layer having a predetermined hardness or more and further 0.2 μm or more, and has sufficient merits such as high wear resistance of the hard plating layer. It is for making use of it. That is, it is considered that the hard plating layer is worn away and the lower electroless plating intermediate layer is exposed, and the toner transportability is not improved. For this reason, it is considered that the surface of the developing roller does not have a high toner conveying force even after durable printing. Accordingly, it is considered that the durability of toner decreases the toner transportability.

  Further, it is considered that the electroless plating intermediate layer does not contain fine particles and does not form irregularities due to the fine particles. For this reason, it is considered that the toner transportability is not sufficiently high.

  Further, Patent Document 4 discloses that a developer amount regulating blade capable of extending the life without causing image deterioration due to toner fusion even in long-term use can be provided.

  However, the developing device described in Patent Document 4 has a composite plating layer on the surface of the developer amount regulating blade, and does not have a plating layer formed on the surface of the developing roller. In this case, even if the toner can be suitably charged, the toner transportability is not sufficiently improved.

  Japanese Patent Application Laid-Open No. H10-260260 discloses that good image formation can be performed without causing fogging or a decrease in image density even when two-component contact development is performed. Patent Document 5 describes a developer carrier having a plating coating layer on the surface, and the plating coating layer is subjected to a plating treatment in which fine particles are dispersed in a plating solution. This developer carrier contains fine particles as large as 3 μm or more, and it is considered that both the toner transportability and the ability to impart charge to the toner cannot be improved. This is also clear from Patent Document 5 that describes a developing device using a two-component developer. An electroless plating layer is described as the plating film layer.

  Patent Document 6 discloses that the surface of the developing roller can be prevented from being scraped, and uniform developer conveyance by the developing roller can be stably performed over a long period of time.

  However, the developing device described in Patent Document 6 may not be able to form a sufficiently high-quality image over a long period of time. This is because if the plating film on which the fine powder is analyzed and deposited is the outermost layer, it is difficult to sufficiently charge the toner, or the other layer is not provided on the plating film. This is thought to be due to things that may occur.

  SUMMARY An advantage of some aspects of the invention is that it provides a developing device capable of forming a high-quality image over a long period of time. Another object of the present invention is to provide an image forming apparatus provided with the developing device.

  The inventors of the present invention have focused on the following as the reason why a sufficiently high-quality image cannot be formed over a long period of time.

  First, attention was paid to the fact that when a developing device is used, the toner in the developing device gradually deteriorates. This is considered to be due to the fact that when a developing device is used, new toner is replenished in the developing device, but there is toner that is not used for development but remains in the developing device. When the toner deteriorates, it is considered that the toner transportability by the developing roller is lowered.

  Further, in order to increase the image density, it is considered necessary to increase the amount of toner conveyed to the development area. In other words, the developing roller provided in the developing device is required to have high toner transportability. The toner transportability of the developing roller is considered to depend on the unevenness of the surface of the developing roller. However, when an image is formed over a long period of time, the surface of the developing roller is worn and the convex portion is gradually scraped. It is done. As a result, it is considered that toner transportability by the developing roller is lowered.

  For these reasons, it was assumed that the image density obtained gradually decreased when image formation was performed over a long period of time.

  Further, in order to improve toner transportability, it is conceivable that the developing roller is subjected to blasting or the like on the surface to form irregularities. However, even if such a developing roller has a high initial toner transportability, a decrease in toner transportability due to use tends to increase. Therefore, it is considered that a suitable toner transportability cannot be maintained over a long period of time simply by improving the toner transportability.

  Furthermore, when the surface is subjected to blasting or the like to form irregularities, the irregularities are large and the convex portion at the tip tends to be sharp. For this reason, it is considered that the toner easily deteriorates. In addition, the toner is considered to be easily fused to the surface of the developing roller.

  Further, as described above, since the toner is rubbed and charged on the surface of the developing roller, it is considered that the toner is difficult to be charged if the unevenness is large. Furthermore, since the electric field tends to concentrate on the edge portion, it is considered that the concentration of the electric field is likely to occur at the time of development when the convex and concave portions are sharp. It is considered that unevenness in image density is likely to occur due to the concentration of the electric field.

  Accordingly, the present inventors have arrived at the present invention as described below, which uses a developing roller in which a plating layer containing fine particles is formed instead of forming concavo-convex portions by blasting the surface or the like. .

  A developing device according to an aspect of the present invention includes a developing roller that is disposed to face an image carrier on which an electrostatic latent image is formed, and that transports toner carried on the surface to the image carrier, The roller includes a base material and a coating layer formed on the base material, and the coating layer includes at least two of an electrolytic plating layer and a base layer closer to the base material than the electrolytic plating layer. The underlayer is an electroless plating layer formed by an electroless plating process using a plating solution in which insulating fine particles are dispersed, and the electrolytic plating layer includes the lower layer. When the volume average particle size of the fine particles is R μm, the volume average particle size of the toner carried on the surface of the developing roller is L μm, and the content of the fine particles in the plating solution is V volume%. The following formulas (1) to (3) The developing device is characterized by satisfying.

250 ≦ (L ² / R ² ) × V ≦ 130000 (1)
10 ≦ R × L × V ≦ 400 (2)
L>R> 0 (3)
According to such a configuration, it is possible to provide a developing device that can form a high-quality image over a long period of time.

  This is considered to be due to the following.

  First, the developing roller is provided with a base layer that is an electroless plating layer formed by an electroless plating process using a plating solution in which insulating fine particles are dispersed. Even if it is coated with an electroplating layer on the side close to the surface, it is considered that the developing roller has irregularities derived from fine particles formed on the surface. In addition, since the unevenness formed on the surface of the developing roller is derived from fine particles, the convex portion is not sharp but is considered to be rounded. From this, it is considered that toner deterioration due to unevenness formed on the surface of the developing roller can be sufficiently suppressed.

  And since the base layer satisfy | fills said Formula (1)-(3), it is thought that the unevenness | corrugation formed in the surface of a developing roller is very fine, and many convex parts are formed. From this, it is considered that the toner carried on the surface of the developing roller is suitably charged by being rubbed against the developing roller. Therefore, it is considered that a high-quality image can be formed.

  Further, since the unevenness formed on the surface of the developing roller is considered not to have a sharp shape, it is considered that the occurrence of uneven image density due to the concentration of the electric field at the edge portion is suppressed.

  Further, when the toner is transported by the developing roller, it is considered that the surface of the developing roller is gradually worn and the underlying layer under the electrolytic plating layer is exposed. Since the underlayer contains fine particles and irregularities derived from the fine particles are formed, it is considered that the toner transportability of the developing roller is enhanced when the underlayer is exposed.

  In addition, it is considered that toner deterioration is progressing when such a base layer is exposed. That is, it is considered that the toner transportability is decreasing due to the deterioration of the toner.

  As described above, when the developing roller is used for development over a long period of time, it is considered that the toner deteriorates and the toner transportability of the toner itself is lowered. On the other hand, the toner transportability of the developing roller can be improved. it is conceivable that. That is, it is considered that the toner transportability can be maintained over a long period of time.

  In contrast to the case where the electrolytic plating layer is provided, it is considered that if the underlayer is exposed from the initial stage, the fine particles are likely to fall off. Further, it is considered that the toner transportability required for the developing roller is not as high as when the toner is deteriorated in a state where the toner transportability of the toner itself is not lowered. In addition, it is considered that the base layer can be suitably protected until the base layer is exposed by providing an electrolytic plating layer harder than the base layer on the side closer to the surface layer than the base layer in the initial stage. Therefore, by providing the electrolytic plating layer on the underlayer, it is considered that the toner transportability of the developing roller can be improved according to the deterioration of the toner, and the dropping of the fine particles can be suppressed.

  From the above, it is considered that a developing device capable of forming a high-quality image over a long period of time can be obtained.

  In the developing device, it is preferable that the following formula (4) and the following formula (5) are satisfied.

500 ≦ (L ² / R ² ) × V ≦ 130000 (4)
30 ≦ R × L × V ≦ 400 (5)
According to such a configuration, a higher quality image can be formed over a long period of time. This is considered to be because the surface of the developing roller has finer and more irregularities derived from fine particles contained in the underlayer.

  In the developing device, it is preferable that the following formula (6) and the following formula (7) are satisfied.

1000 ≦ (L ² / R ² ) × V ≦ 130000 (6)
50 ≦ R × L × V ≦ 400 (7)
According to such a configuration, a higher quality image can be formed over a long period of time. This is considered to be because the surface of the developing roller has finer and more irregularities derived from fine particles contained in the underlayer.

  In the developing device, the fine particles are preferably silicon carbide particles.

  According to such a configuration, a high-quality image can be formed over a longer period. This is considered to be because the underlayer can be made harder by using silicon carbide (SiC) particles as fine particles contained in the underlayer.

  In the developing device, it is preferable that the electrolytic plating layer is a layer containing Cr, and the base layer is a layer containing the fine particles and Ni.

  According to such a configuration, a higher quality image can be formed over a long period of time.

  This is considered to be due to the following.

  By using a layer containing Ni as the underlayer, the affinity between the fine particles contained in the underlayer and other components constituting the underlayer is increased, and it is considered that irregularities derived from the fine particles can be suitably formed. It is done. Moreover, the layer containing Ni is considered to have high affinity with the electrolytic plating layer. Therefore, it is thought that it is excellent in the adhesiveness of the said electroplating layer and a base layer, and hardly inhibits formation of an electroplating layer. Furthermore, it is considered that the underlying layer can be made harder by using a layer containing Ni together with fine particles as the underlying layer.

  Moreover, it is thought that a passive state can be formed even at normal temperature by using a layer containing Cr as the electrolytic plating layer. It is considered that the toner, particularly the positive polarity toner, is suitably charged when the toner is rubbed against the electroplating layer in which the passivation is formed.

  From these, it is considered that a higher quality image can be formed over a long period of time.

  In the developing device, the base material is preferably an aluminum base material.

  According to such a configuration, a higher quality image can be formed over a long period of time.

  This is considered to be due to the following.

  The aluminum-based substrate is soft and easily worn, but has fine irregularities on the surface layer. In the present invention, even if the surface of the base material is easily worn, the coating layer including the base layer and the electrolytic plating layer is formed on the base material. Absent. In addition, when a base layer containing fine particles is formed on a substrate having fine irregularities on the surface layer, the irregularities derived from the fine particles can be suitably formed by fixing the fine particles to the irregularities on the surface layer of the substrate. It is thought that it will become more difficult to drop off.

  From this, it is considered that a higher quality image can be formed over a long period of time.

  Moreover, it is preferable that the said base material is a base material which has not been roughened.

  According to such a configuration, a higher quality image can be formed over a long period of time.

  This is considered to be due to the following.

  First, it is considered that unevenness derived from fine particles can be formed on the surface of the developing roller by providing a base layer containing fine particles without using a base material subjected to roughening treatment. In addition, such a developing roller is considered to have less unevenness and better toner transportability than a substrate subjected to a roughening treatment. Further, as described above, it is considered that the toner is excellent in charge imparting ability, and it is possible to suppress the occurrence of problems due to electric field concentration.

  Moreover, when the roughened substrate is subjected to a roughening treatment such as blasting, pressure is applied to the substrate, and distortion may occur in the circumferential direction of the substrate. Due to this distortion, when an image such as a half image is printed, uneven pitch of the developing roller may occur.

  From these facts, it is considered that a higher quality image can be formed over a long period of time by using a base material that has not been subjected to roughening treatment as the base material.

  An image forming apparatus according to another aspect of the present invention includes the developing device and the image carrier.

  According to such a configuration, it is possible to provide an image forming apparatus capable of forming a high-quality image over a long period of time. This is considered to be due to the provision of the developing device.

  According to the present invention, it is possible to provide a developing device capable of forming a high-quality image over a long period of time. An image forming apparatus including the developing device is provided.

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 the schematic which shows an example of the thickness of each layer of the base layer of an image development roller, and an electroplating layer. 4 is a graph showing the relationship between the volume average particle diameter R of fine particles, the volume average particle diameter L of toner, the content V of fine particles in a plating solution used when forming an underlayer, and the evaluation results.

  Hereinafter, 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. Here, as the 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 printer is not limited to a monochrome type printer. 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 41 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, stirring rollers 73 and 74, and a blade 75 that 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 to be charged when the toner is rubbed against the surface of the developing roller when passing through the regulation position by the blade 75.

  Next, the developing roller 72 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 developing roller 72 according to the embodiment of the present invention, and also shows the photosensitive drum 21 together.

  The developing roller 72 includes a base material 103 and a coating layer 104 formed on the base material 103, and the coating layer 104 is an electroplating layer 101 and a base layer closer to the base material 103 than the electroplating layer 101. 102, in which at least two layers are laminated, and the underlayer 102 is an electroless plating layer formed by an electroless plating process using a plating solution in which insulating fine particles are dispersed. The layer 101 is harder than the underlayer 102, the volume average particle diameter of the fine particles is R μm, the volume average particle diameter of the toner carried on the surface of the developing roller is L μm, and the content of the fine particles in the plating solution is V volume%. In this case, the following expressions (1) to (3) are satisfied.

250 ≦ (L ² / R ² ) × V ≦ 130000 (1)
10 ≦ R × L × V ≦ 400 (2)
L>R> 0 (3)
If such a developing roller is used, a high-quality image can be formed over a long period of time.

  This is considered to be due to the following.

  First, the developing roller is provided with a base layer that is an electroless plating layer formed by an electroless plating process using a plating solution in which insulating fine particles are dispersed. Even if it is coated with an electroplating layer on the side close to the surface, it is considered that the developing roller has irregularities derived from fine particles formed on the surface. In addition, since the unevenness formed on the surface of the developing roller is derived from fine particles, the convex portion is not sharp but is considered to be rounded. From this, it is considered that toner deterioration due to unevenness formed on the surface of the developing roller can be sufficiently suppressed.

  And since the base layer satisfy | fills said Formula (1)-(3), it is thought that the unevenness | corrugation formed in the surface of a developing roller is very fine, and many convex parts are formed. From this, it is considered that the toner carried on the surface of the developing roller is suitably charged by being rubbed against the developing roller. Therefore, it is considered that a high-quality image can be formed.

  Further, since the unevenness formed on the surface of the developing roller is considered not to have a sharp shape, it is considered that the occurrence of uneven image density due to the concentration of the electric field at the edge portion is suppressed.

  Further, when the toner is transported by the developing roller, it is considered that the surface of the developing roller is gradually worn and the underlying layer under the electrolytic plating layer is exposed. Since the underlayer contains fine particles and irregularities derived from the fine particles are formed, it is considered that the toner transportability of the developing roller is enhanced when the underlayer is exposed.

  In addition, it is considered that toner deterioration is progressing when such a base layer is exposed. That is, it is considered that the toner transportability is decreasing due to the deterioration of the toner.

  As described above, when the developing roller is used for development over a long period of time, it is considered that the toner deteriorates and the toner transportability of the toner itself is lowered. On the other hand, the toner transportability of the developing roller can be improved. it is conceivable that. That is, it is considered that the toner transportability can be maintained over a long period of time.

  In contrast to the case where the electrolytic plating layer is provided, it is considered that if the underlayer is exposed from the initial stage, the fine particles are likely to fall off. Further, it is considered that the toner transportability required for the developing roller is not as high as when the toner is deteriorated in a state where the toner transportability of the toner itself is not lowered. In addition, it is considered that in the initial stage, by providing an electrolytic plating layer harder than the base layer above the base layer, the base layer can be suitably protected until the base layer is exposed. Therefore, by providing the electrolytic plating layer on the underlayer, it is considered that the toner transportability of the developing roller can be improved according to the deterioration of the toner, and the dropping of the fine particles can be suppressed.

  From the above, it is considered that a developing device capable of forming a high-quality image over a long period of time can be obtained.

  The developing roller 72 preferably satisfies the following formula (4) and the following formula (5).

500 ≦ (L ² / R ² ) × V ≦ 130000 (4)
30 ≦ R × L × V ≦ 400 (5)
Furthermore, it is more preferable that the developing roller 72 satisfies the following formula (6) and the following formula (7).

1000 ≦ (L ² / R ² ) × V ≦ 130000 (6)
50 ≦ R × L × V ≦ 400 (7)
As described above, when (L ² / R ² ) × V and R × L × V are increased, a higher quality image can be formed. This is considered to be because the surface of the developing roller has finer and more irregularities derived from fine particles contained in the underlayer.

That is, if at least one of (L ² / R ² ) × V and R × L × V is too small, there is a tendency that a sufficiently high-quality image cannot be formed over a long period of time. This is considered to be due to the fact that the surface of the developing roller has large and few irregularities derived from the fine particles contained in the underlayer.

  Each formula will be described below.

  The above formula (1), the above formula (4), and the above formula (6) are considered to indicate the following.

  As described above, the toner is considered to be charged by being rubbed against the developing roller. For this reason, when the convex portion derived from the fine particles is formed on the surface of the developing roller as in this embodiment, the toner is more likely to be charged as the chance of contact between the convex portion derived from the fine particles and the toner increases. Conceivable.

The chance of contact between the convex portions derived from the fine particles and the toner is considered to be proportional to the ratio of the cross-sectional area of the fine particles to the projected cross-sectional area of the toner onto the developing roller. The ratio of the cross-sectional area of the toner to the projected cross-sectional area of the toner onto the developing roller is equivalent to the square L ² of the volume average particle diameter L of the toner to the square R ² of the volume average particle diameter R of the fine particles. It is believed that there is.

  Further, it is considered that the higher the ratio of the fine particles contained in the underlayer, the greater the chances of contact between the convex portions derived from the fine particles and the toner. The ratio of the fine particles contained in the underlayer is considered to depend on the content (volume%) of the fine particles in the plating solution used when forming the underlayer.

From these facts, it is considered that the larger the (L ² / R ² ) × V, the greater the chance of contact between the convex portions derived from the fine particles and the toner. Therefore, it is considered that the toner is easily charged.

  Next, it is thought that the said Formula (2), the said Formula (5), and the said Formula (7) show the following things.

  The toner transportability is considered to increase as the particle size of the fine particles increases. Further, it is considered that the higher the ratio of fine particles contained in the underlayer, the greater the toner transportability. The ratio of the fine particles contained in the underlayer is considered to depend on the content (volume%) of the fine particles in the plating solution used when forming the underlayer as described above. Further, it is considered that the toner transportability increases as the particle diameter of the toner increases.

  From these facts, it is considered that the larger the R × L × V, the higher the toner transportability.

The larger (L ² / R ² ) × V is, the more easily the toner is charged. However, if (L ² / R ² ) × V is too large, specifically, it is as large as about 130,000. There is a tendency for toner to be unevenly conveyed. This is considered to be due to poor dispersion of the fine particles in the underlayer. That is, the upper limit of (L ² / R ² ) × V is 130,000.

  The larger R × L × V is, the higher the toner transportability is, but it is preferable. However, if R × L × V is too large, specifically up to about 400, fogging due to so-called layer disturbance tends to occur. There is. This is presumably because the toner transportability becomes too high and the toner transport amount becomes too large. That is, the upper limit value of R × L × V is 400.

  Moreover, V will not be specifically limited if the said relational expression is satisfy | filled. Further, although it varies depending on the composition of the plating solution, the limit is about 20% by volume. If V is too large, the underlying layer, which is an electroless plating layer formed by electroless plating using a plating solution in which insulating fine particles are dispersed, tends to be brittle. This is considered to be because there are too many fine particles and it becomes impossible to disperse | distribute suitably in a base layer.

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 is not particularly limited, and when a magnetic one-component developer is used, for example, a positively charged toner can be 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. That is, the volume average particle diameter L of the toner is preferably 6 to 8 μm. If the toner is too small, both (L ² / R ² ) × V and R × L × V tend to be small, and it tends to be difficult to satisfy the above formulas (1) and (2). Therefore, it tends to be difficult to form a high-quality image over a long period of time. On the other hand, if the toner is too small, the toner tends to be scattered in the atmosphere, and fogging or the like tends to occur. If the toner is too large, it tends to be difficult to form a high-definition image.

  Specifically, the developing roller 72 includes a base 103 and a coating layer 104 formed on the base 103. The covering layer 104 is formed by laminating an electrolytic plating layer 101 and a base layer 102 closer to the base material 103 than the electrolytic plating layer 101. Moreover, as the coating layer 104, the electroplating layer 101 and the base layer 102 should just be provided in this order, and the other layer may be provided. Specifically, a protective layer may be further provided on the surface layer of the electrolytic plating layer 101, and an intermediate layer may be provided between the electrolytic plating layer 101 and the base layer 102. Further, an intermediate layer may be provided between the base layer 102 and the base material 103 for the purpose of improving the adhesion of the covering layer 104.

  The substrate 103 is not particularly limited as long as it can be used as a developing roller, in this case, as a rotating sleeve. Specifically, for example, an aluminum base material such as an aluminum base tube is preferable. The aluminum-based substrate is soft and easily worn, but has fine irregularities on the surface layer. In this embodiment, even if the surface of the base material is easily worn, the base material is not directly worn because the coating layer including the base layer and the electrolytic plating layer is formed on the base material. . In addition, when a base layer containing fine particles is formed on a substrate having fine irregularities on the surface layer, the irregularities derived from the fine particles can be suitably formed by fixing the fine particles to the irregularities on the surface layer of the substrate. It is thought that it will become more difficult to drop off. From this, it is considered that a higher quality image can be formed over a long period of time.

  Further, the base material 103 may be a base material that has been subjected to roughening treatment, or may be a base material that has not been subjected to roughening treatment, but has been subjected to roughening treatment. It is preferable that there is no substrate. By using a base material that has not been roughened, a higher quality image can be formed over a long period of time.

  This is considered to be due to the following.

  First, it is considered that unevenness derived from fine particles can be formed on the surface of the developing roller by providing a base layer containing fine particles without using a base material subjected to roughening treatment. In addition, such a developing roller is considered to have less unevenness and better toner transportability than a substrate subjected to a roughening treatment. Further, as described above, it is considered that the toner is excellent in charge imparting ability, and it is possible to suppress the occurrence of problems due to electric field concentration.

  Moreover, when the roughened substrate is subjected to a roughening treatment such as blasting, pressure is applied to the substrate, and distortion may occur in the circumferential direction of the substrate. Due to this distortion, when an image such as a half image is printed, uneven pitch of the developing roller may occur.

  From these facts, it is considered that a higher quality image can be formed over a long period of time by using a base material that has not been subjected to roughening treatment as the base material.

  The underlayer 102 is not particularly limited as long as it is an electroless plating layer formed by an electroless plating process using a plating solution in which insulating fine particles are dispersed. That is, since the underlayer 102 is formed by electroless plating using a plating solution in which insulating fine particles are dispersed, it is considered that the underlayer 102 is an electroless plating layer in which fine particles are dispersed in the layer. In addition, the base layer 102 is preferably softer than the electrolytic plating layer 101 and harder than the base material 103. The underlayer 102 is preferably a layer containing Ni, for example. By using a layer containing Ni as the electroless plating layer 102, the affinity between the fine particles contained in the underlayer 102 and the other components constituting the underlayer 102 is increased, and irregularities derived from the fine particles are suitably formed. It can be formed. Moreover, the layer containing Ni is considered to have high affinity with the electrolytic plating layer 101. Therefore, it is considered that the adhesion between the electroplating layer 101 and the base layer 102 is excellent, and the formation of the electroplating layer 101 is hardly inhibited. Further, it is considered that the base layer 102 can be made harder by using a layer containing Ni together with fine particles as the base layer 102. Further, when a layer containing Ni is used as the underlayer 102, the Ni content is preferably 88 to 95% by mass with respect to the mass other than the fine particles of the underlayer 102. Further, the electroless plating layer 102 may be a layer made of fine particles and Ni. The underlayer may be an electroless plating layer formed by using a plating solution having a fine particle content V of 1 to 20% by volume in the plating solution. It is preferable that it is 1-20 mass% with respect to the formation 102.

  Further, the thickness of the base layer 102 is not particularly limited. For example, it is preferably about 3 to 5 μm, although it varies depending on the material constituting the underlayer. By doing so, it is possible to realize a thickness that can be maintained without being worn for a predetermined period after the upper electrolytic plating layer is worn and exposed by development.

  Further, the fine particles dispersed in the plating solution used when forming the base layer 102 are not particularly limited as long as they are insulating and can be used by being dispersed in the plating solution. Specific examples include silicon carbide (SiC) particles and alumina particles. Among these, SiC particles are preferable. It is considered that the use of SiC particles as fine particles contained in the underlayer can make the underlayer harder.

The particle diameter R of the fine particles varies depending on the composition and thickness of the underlayer, but is preferably, for example, a volume average particle diameter of 0.1 to 2 μm. If the fine particles are too small, R × L × V tends to be small, and it tends to be difficult to satisfy the above formula (2). Therefore, the toner transportability tends to be reduced. If the fine particles are too large, (L ² / R ² ) × V tends to be small, and it tends to be difficult to satisfy the above formula (1). Therefore, it becomes difficult to maintain the chargeability of the toner, and it tends to be difficult to form a high-quality image over a long period of time.

  The volume average particle diameter of the toner and fine particles can be measured using a general particle size meter.

  Further, the electroplating layer 101 is preferably a layer harder than the base layer 102. Examples of the electrolytic plating layer 101 include a Cr plating layer that is a layer containing Cr, a Ti plating layer that is a layer containing Ti, and a Zr plating layer that is a layer containing Zr. Moreover, it is preferable that the electroplating layer 101 is a layer containing Cr among the layers exemplified above. The Cr is preferably trivalent Cr. It is considered that a passive state can be formed even at room temperature by using a layer containing Cr as the electrolytic plating layer 101. It is considered that the toner, particularly the positive polarity toner, is suitably charged when the toner is rubbed against the electroplating layer in which the passivation is formed.

  Here, the hard and soft in each layer is hard and soft in comparison with other layers, and the method for measuring the hardness is not particularly limited, and examples thereof include Vickers hardness. Vickers hardness can be measured using a Vickers hardness tester.

  Further, the thickness of the electrolytic plating layer 101 is preferably 0.05 μm or more and less than 0.2 μm, and more preferably 0.1 to 0.18 μm. If the electrolytic plating layer 101 is too thin, there is a tendency that the electrolytic plating layer cannot be formed uniformly. Further, the lower base layer begins to be exposed before the toner transportability is lowered due to the deterioration of the toner, and it tends to be difficult to adjust the surface scraping and the toner transportability by providing the electrolytic plating layer. On the other hand, when the electrolytic plating layer 101 is too thick, there is a tendency that the image density cannot be maintained for a long time. This is because even if the toner transportability of the toner itself is lowered due to the deterioration of the toner, the electroplating layer is not worn, the underlying layer is not sufficiently exposed, and the decrease in toner transportability cannot be sufficiently suppressed. It is thought that. Therefore, by setting the thickness of the electrolytic plating layer 101 within the above range, it is considered that the surface abrasion and the toner transportability can be suitably adjusted, and further, the appropriately adjusted toner transportability can be maintained over a long period of time. It is done. Further, the lower limit of the thickness of the electrolytic plating layer 101 is 0.05 μm from the viewpoint that it is difficult to manufacture the thickness of the electrolytic plating layer 101 less than 0.05 μm.

  In addition, the film thickness of the electroplating layer 101 and the base layer 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.

  More specifically, after preparing calibration curves for Ni plating, Cu plating, Sn plating, Au plating, and Cr plating using a fluorescent X-ray film thickness meter, the film thickness of the electrolytic plating layer 101 and the base layer 102 Can be measured.

  Further, the surface roughness of the developing roller 72, here, the surface roughness of the electroplating layer 101 differs depending on the average particle diameter of the toner that is the one-component developer used, but the ten-point average roughness Rz is 7 It is preferably ˜9 μm. Further, the surface roughness Rz of the electrolytic plating layer 101 is preferably about 0.8 to 1.3 times the volume average particle diameter of the toner which is a one-component developer. 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 suitably 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.

  Further, the developing roller 72 can be manufactured as follows. Here, the case where an aluminum base material such as an aluminum base tube is used as the base material will be described as an example.

  First, before forming an underlayer by electroless plating, a pretreatment is performed on an aluminum-based substrate used as a substrate.

  As the pretreatment, first, degreasing treatment is performed on the base material. Examples of the degreasing treatment include alkali degreasing treatment. By this degreasing treatment, dirt on the substrate surface can be removed.

  Next, an etching process is performed with respect to the base material which performed the degreasing process. Examples of the etching process include a heated etching process using a mixed solution of phosphoric acid and sulfuric acid as an etching agent, a so-called acid etching process, and the like. By this etching treatment, the oxide film formed on the substrate surface can be removed.

  Next, a desmut treatment is performed on the substrate subjected to the etching treatment. Examples of the desmut treatment include a desmut treatment using nitric acid or the like. By the desmut treatment, the smut generated by the degreasing treatment or the etching treatment can be removed, and the abundance of aluminum in the surface layer can be increased.

  Next, a zincate process is performed with respect to the base material which performed the desmut process. Examples of the zincate treatment include a treatment of immersing in a zincate solution such as a solution containing zinc oxide and sodium hydroxide. By doing so, a substitution reaction between the aluminum of the base material and zinc contained in the zincate solution occurs, and a substituted zinc layer is formed on the surface layer.

  Then, the zincate treatment is performed again on the base material that has been subjected to the zincate treatment, after once removing the substituted zinc layer using nitric acid or the like. By doing so, a uniform substituted zinc layer is formed on the surface layer, and plating adhesion is enhanced.

  An electroless plating process is performed on the base material that has been subjected to the pretreatment as described above to form a base layer on the base material.

  A method for forming the underlayer is not particularly limited as long as it is an electroless plating process using a plating solution in which fine particles are dispersed. Specifically, a plating treatment in which the substrate is immersed in a plating solution in which fine particles are dispersed can be used. Specifically, for example, when forming a layer containing Ni as the underlayer, by adding fine particles to a plating solution used in a general electroless Ni plating process, and performing the electroless plating process An electroless plating layer containing Ni can be formed.

Further, the conditions for the electroless plating treatment are not particularly limited as long as the above-described electroless plating layer can be formed. Specifically, for example, an electroless plating treatment using a plating solution in which fine particles are dispersed can be mentioned. And it is preferable that the content rate V of the microparticles | fine-particles in a plating solution is 1-20 volume%. If the content of the fine particles in the plating solution is too low, both (L ² / R ² ) × V and R × L × V tend to be small, and satisfy the above formula (1) and the above formula (2). Tend to be difficult. Therefore, it tends to be difficult to form a high-quality image over a long period of time. That is, there is a tendency that the amount of fine particles contained in the formed underlayer is so small that the effect of containing the fine particles in the underlayer cannot be fully exhibited. Also, if the content of the fine particles in the plating solution is too high, the underlying layer, which is an electroless plating layer formed by an electroless plating process using a plating solution in which insulating fine particles are dispersed, tends to become brittle. . This is considered to be because there are too many fine particles and it becomes impossible to disperse | distribute suitably in a base layer.

  Moreover, as conditions for electroless plating treatment, the following conditions can be cited in addition to the above conditions.

  Here, the conditions for the electroless Ni plating process will be described.

  First, as the plating solution, the content of fine particles in the plating solution is 1 to 20% by volume, and the Ni content in the mass excluding the fine particles of the formed underlayer is 88 to 95% by mass, A plating solution in which the balance is P is exemplified.

  Moreover, it is preferable that it is 4-5 as pH of a plating solution. Moreover, as a liquid temperature of a plating solution, it is preferable that it is 80-90 degreeC. And as processing time of an electroless-plating process, it is preferable that it is 10 to 25 minutes.

  Next, an electroplating process is performed with respect to the base material in which the base layer was formed, and an electroplating layer is formed on a base layer.

  As a method for forming the electrolytic plating layer, when forming a layer containing Cr as the electrolytic plating layer, for example, an electrolytic plating layer containing Cr can be formed by performing a general electrolytic Cr plating treatment.

  The conditions for the electrolytic plating are not particularly limited as long as the above-described electrolytic plating layer can be formed. Specifically, it is preferable to carry out under the following conditions. The pH of the plating solution is preferably 3-4. Moreover, as a liquid temperature of a plating solution, it is preferable that it is 35-55 degreeC. And as an applied voltage at the time of an electroplating process, it is preferable that it is 3-6V. The treatment time for the electrolytic plating treatment is preferably 3 to 8 minutes.

  In addition, examples of the magnet member included in the rotating sleeve include a four-pole structure having a 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 developing method using the developing roller 72 includes the following two developing steps. First, toner that is a one-component developer carried on the surface of the electroplating layer 101 of the developing roller 72 is conveyed to the photosensitive drum 21 by the developing roller 72, so that it is formed in advance on the surface of the photosensitive drum 21. A step of developing the electrostatic latent image with a one-component developer (first development step). In this first developing step, the electroplated layer 101 is worn and the one-component developer carried on the surface of the developing roller 72 in a state where at least a part of the base layer 102 is exposed is exposed to the developing roller 72 by the photosensitive roller. A process of developing an electrostatic latent image previously formed on the surface of the photosensitive drum 21 with a one-component developer by being conveyed to the photosensitive drum 21 (second developing process) is provided.

  By providing these two development steps, a high-quality image can be formed over a long period of time. This is because, as described above, a developing roller capable of maintaining a sufficiently high toner transportability and chargeability to the toner is used as a developer carrier used for development. It is thought that.

  Specifically, first, in a state where toner deterioration is considered to be small, a first development step is performed in which development is performed using the developing roller 72 in a state where the electrolytic plating layer 101 is a surface layer. Then, after the first development step, a second development step is performed in which development is performed using the developing roller 72 in a state where the electrolytic plating layer 101 is worn and at least a part of the base layer 102 is exposed in the first development step. By doing so, even if the toner is deteriorated by the first development process and the toner transportability of the toner itself is lowered, in the second development process, at least one base layer capable of improving the toner transportability of the developing roller is provided. The part is exposed. Therefore, even if the toner transportability of the toner itself is lowered, it is considered that the toner transportability of the developing roller can be improved, and the toner transportability can be maintained over a long period of time. Further, even if the ease of charging of the toner itself due to the deterioration of the toner is changed by the first developing step, the charge applying force corresponding to the change in the ease of charging of the toner itself is applied in the second developing step. It is considered that the toner can be charged by the developing roller having the same. Therefore, it is considered that the charging of the toner can be maintained.

  From these facts, it is considered that high-quality images can be formed over a long period of time.

  In such a development method, it is preferable that the first development step shifts from the first development step to the second development step so that the number of times of development in the first development step is less than 450,000 sheets in terms of A4. Further, as described above, the number of times of development in the first development process until the transition from the first development process to the second development process is preferably the number of times that the number of printed sheets in terms of A4 is within 450,000 sheets. The number of times is preferably 20,000 to 450,000, and more preferably the number of times 30,000 to 400,000. If the number of times of development in the first development step is too large, and even if the toner transportability of the toner itself is reduced due to toner deterioration, the electroplating layer will not be worn, and the underlying layer below will not be sufficiently exposed, This is considered to be because the decrease in toner transportability cannot be sufficiently suppressed. Further, it is considered that the change in the charging force of the developing roller becomes difficult to cope with the change in the ease of charging of the toner itself due to the deterioration of the toner. If the number of developments in the first development step is too small, first, the lower base layer starts to be exposed before the toner transportability is lowered due to the deterioration of the toner, and the toner transportability is adjusted by providing an electrolytic plating layer. Tend to be difficult. In addition, adjustment of the charging force of the developing roller tends to be difficult. For these reasons, when the number of times of development in the first development step is within the above range, the property of the developing roller can be changed in accordance with the change in toner transportability and chargeability due to toner deterioration. This is considered to be due to the improvement of the chargeability and chargeability. Therefore, it is considered that a high-quality image can be formed over a longer period.

  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, a sufficiently high quality image can be formed over a long period of time.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

<Example A>
First, the relationship among the volume average particle diameter R of the fine particles, the volume average particle diameter L of the toner, and the content V of the fine particles in the plating solution used when forming the underlayer was examined.

[Example 1]
First, in order to improve the adhesion with the plating, the aluminum (Al) element tube was subjected to a general treatment as a pretreatment. Specifically, the degreasing treatment, the etching treatment, the desmut treatment, and the zincate treatment were performed on the aluminum (Al) element tube in this order. And after performing the zincate process, after peeling the substituted zinc layer formed in the surface, the zincate process was performed again. By doing so, an aluminum base tube in which a uniform substituted zinc layer was formed on the surface layer was obtained. As the base material, an aluminum base tube subjected to this pretreatment was used. The thickness of the aluminum base tube used for forming the substituted zinc layer by this pretreatment, that is, the aluminum base tube before the pretreatment was 600 μm, and the Vickers hardness was 50. The Vickers hardness was measured using a Vickers hardness meter.

  Next, an electroless Ni plating treatment was performed on the pretreated aluminum base tube so that an electroless plating layer having a thickness of 4.6 μm was formed as a base layer. During the plating treatment, a plating solution containing V volume% of SiC particles having a volume average particle diameter R (μm) shown in Table 1 was used as fine particles.

  Specifically, the content of fine particles in the plating solution is 17% by volume, the Ni content in the mass excluding the fine particles of the underlying layer to be formed is 88 to 95% by mass, and the balance is P. An electroless plating treatment was performed under such conditions that the pH of the plating solution was 4 to 5 and the temperature of the plating solution was 80 to 90 ° C. And the electroless-plating process was performed in the processing time from which the thickness of the electroless-plating layer formed becomes 4 micrometers. The treatment time was adjusted so that an electroless plating layer having a predetermined thickness was formed, and specifically, adjusted for 10 to 25 minutes.

  Next, an electrolytic Cr plating treatment was performed on the electroless plating layer so that an electrolytic plating layer having a thickness of 0.18 μm was formed as the uppermost layer. By doing so, a developing roller was obtained.

  Specifically, a plating solution that forms a trivalent Cr plating layer is used as the plating solution, the pH of the plating solution is 3 to 4, and the temperature of the plating solution is 35 to 55 ° C. There was an electrolytic plating process under the condition that the applied voltage was 5V. And the electrolytic plating process was performed in the processing time when the thickness of the formed electrolytic plating layer becomes 0.1 μm. In addition, the processing time is the time adjusted so that the electroplating layer of predetermined thickness may be formed, Comprising: Specifically, it adjusted between 3 to 8 minutes.

  The Vickers hardness of the formed electrolytic plating layer was 1000. In addition, the Vickers hardness of the Ni plating layer is 500, and the Vickers hardness of the above-described underlayer is about 500 although fine particles are contained, and is softer than the electrolytic plating layer.

  Moreover, the diameter of the obtained developing roller was 20 mm.

  Moreover, the thickness of each layer of the obtained developing roller undercoat layer and electrolytic plating layer was measured using SFT320 manufactured by Seiko Instruments Inc. From this measurement, it was found that the conceptual diagram showing each layer of the base layer and the electrolytic plating layer is a layer as shown in FIG. FIG. 4 is a schematic view showing an example of the thickness of each layer of the base layer and the electrolytic plating layer of the developing roller. The vertical axis represents the length in the thickness direction from a predetermined position of the developing roller, and the horizontal axis represents the distance in the direction perpendicular to the thickness direction from the predetermined position of the developing roller.

  In FIG. 4, a curve 201 indicates the position of the surface of the aluminum base tube that is the base material, a curve 202 indicates the position of the surface of the base layer, and a curve 203 indicates the position of the surface of the electrolytic plating layer. . That is, the vertical distance between the curve 201 and the curve 202 indicates the thickness of the underlayer. The vertical distance between the curve 202 and the curve 203 indicates the thickness of the electrolytic plating layer.

  The thickness of each layer of the electroplating layer and the electroplating layer was calculated using a calibration curve prepared from a measurement value of a standard sample whose thickness was previously known.

  When the developing roller according to Example 1 was measured by such a method, it was found that the thickness of the underlayer was about 4.6 μm and the thickness of the electrolytic plating layer was about 0.18 μm. In addition, it turns out from this FIG. 4 that the aluminum base tube which is a base material has an unevenness | corrugation on the surface. Further, the unevenness is an unevenness generated when the surface of the aluminum base tube is polished.

  Next, as the developer carrying member of the image forming apparatus provided with the one-component developing type developing device as shown in FIG. 1, one having the developing roller obtained as described above was prepared. The configuration of the image forming apparatus is as follows. The photosensitive drum is an amorphous silicon photosensitive drum having a diameter of 30 mm. The photoreceptor speed is 150 mm / second. The distance between the photosensitive drum and the developing roller (distance between DS: development gap) is 300 μm. The distance (regulation gap) between the developing roller and the blade is 300 μm. The blade is a blade made of SUS430. The developing bias applied to the developing roller is a superimposed voltage obtained by superimposing an AC voltage having a peak to peak voltage Vpp of 1700V on a DC voltage having an area center voltage Vdc of 175V. In addition, charging is performed so that the surface potential Vo of the photosensitive drum is 280V. The developer (one-component developer) to be used is a positively chargeable toner having a volume average particle diameter L (μm) shown in Table 1.

  An image was formed using such an image forming apparatus, and the following evaluation was performed.

(Image density)
Specifically, first, the image forming apparatus was turned on and stabilized. Thereafter, an image including a solid image was printed. The reflection density of this image was measured using a reflection densitometer (RD-918 manufactured by Gretag Macbeth). This reflection density was defined as the image density.

  If the image density is 1.4 or more, it is evaluated as “◎”. If the image density is 1.2 or more and less than 1.4, it is evaluated as “◯”. If it was less than 1.0, it was evaluated as “x”.

(Cover)
Further, the paper on which the image was formed was visually observed, and when almost no fog was confirmed, it was evaluated as “◎”. Also, the occurrence of fogging can be confirmed, but if it is not conspicuous, it is evaluated as “○”, and the occurrence of fogging can be confirmed. If so, it was evaluated as “×”.

(Comprehensive evaluation)
Finally, comprehensive evaluation was performed based on the evaluation based on the image density and the evaluation based on the fog. Specifically, if both the evaluation based on the image density and the evaluation based on the fog were “「 ”, the evaluation was“ ◎ ”. Further, among the evaluation based on the image density and the evaluation based on the fog, if the evaluation that is not preferable is “◯”, the evaluation is “◯”. Further, among the evaluation based on the image density and the evaluation based on the fog, if the evaluation that is not preferable is “Δ”, the evaluation is “Δ”. Further, among the evaluation based on the image density and the evaluation based on the fog, if the evaluation that is not preferable is “x”, the evaluation is “x”.

[Examples 2 to 12 and Comparative Examples 1 to 10]
Example 1 except that the volume average particle diameter R of the fine particles, the volume average particle diameter L of the toner, and the content V of the fine particles in the plating solution used when forming the underlayer are changed to the values shown in Table 1, respectively. It is the same.

  The evaluation results of Examples 1 to 12 and Comparative Examples 1 to 10 are the volume average particle diameter R of the fine particles, the volume average particle diameter L of the toner, and the inclusion of the fine particles in the plating solution used when forming the underlayer. Both the rate V are shown.

[Comparative Example 11]
The volume average particle diameter R of the fine particles is changed to 0.1 μm, the volume average particle diameter L of the toner is changed to 8.1 μm, and the content V of the fine particles in the plating solution used for forming the underlayer is 20 volumes. Example 1 is the same as Example 1 except for changing to%. Note that (L ² / R ² ) × V is 131220, and R × L × V is 16.2.

  An image was formed using the image forming apparatus according to Comparative Example 11. Specifically, an image similar to the image density evaluation was formed. As a result, the image formed here was visually confirmed to have uneven image density. This is considered to be due to unevenness in toner conveyance due to poor dispersion of the fine particles in the underlayer.

  Note that image density unevenness was not visually confirmed in images formed using the image forming apparatuses according to Examples 1 to 12.

[Comparative Example 12]
The volume average particle diameter R of the fine particles is changed to 2.5 μm, the volume average particle diameter L of the toner is changed to 9.0 μm, and the content V of the fine particles in the plating solution used for forming the underlayer is 20 volumes. Example 1 is the same as Example 1 except for changing to%. Note that (L ² / R ² ) × V is about 259, and R × L × V is 450.

  An image was formed using the image forming apparatus according to Comparative Example 12. Specifically, an image similar to the image density evaluation was formed. As a result, it was confirmed that spotted fog called blotch was generated in the image formed here. This is considered to be due to fogging due to layer disturbance due to an excessive amount of toner transport.

  In addition, generation | occurrence | production of the spot-like fog called a blotch was not confirmed in the image formed using the image forming apparatus which concerns on Examples 1-12.

  As can be seen from Table 1, when the above formulas (1) to (3) are satisfied (Examples 1 to 12), compared with the case where any one or more of the above formulas (1) to (3) is not satisfied. Thus, a high-quality image with high image density and little fogging can be formed. As can be seen from the examination results of Comparative Example 11 and Comparative Example 12, when the above formulas (1) to (3) are satisfied (Examples 1 to 12), the occurrence of uneven image density is also a spot-like shape called blotch. It is possible to form a high-quality image in which the occurrence of fog is suppressed.

  Furthermore, it turns out that it is preferable to satisfy | fill said Formula (4) and said Formula (6), and it is more preferable to satisfy | fill said Formula (5) and said Formula (7).

  Specifically, if the above equation (2) is satisfied, the image density evaluation is “◎”, “◯”, or “Δ”, and if the above equation (5) is satisfied, the image density evaluation is “◎”. Or “◯”, and if the above expression (7) is satisfied, the evaluation of the image density is “◎”.

  Moreover, if the above formula (1) is satisfied, the fogging evaluation is “◎”, “◯”, or “Δ”, and if the above formula (4) is satisfied, the fogging evaluation is “◎” or “○”. Thus, if the above formula (6) is satisfied, the fogging evaluation becomes “」 ”.

The results are shown in FIG. FIG. 5 is a graph showing the relationship between the volume average particle diameter R of the fine particles, the volume average particle diameter L of the toner, the fine particle content V in the plating solution used when forming the underlayer, and the evaluation results. . The horizontal axis represents (L ² / R ² ) × V, and the vertical axis represents R × L × V. And each point shows comprehensive evaluation.

  From FIG. 5, when the above formula (1) and the above formula (2) are satisfied, the region enters the area on the upper right side from the line 301 and the overall evaluation may be “「 ”,“ ◯ ”, or“ Δ ”. Recognize. Moreover, when satisfy | filling said Formula (4) and said Formula (5), it enters into the area | region of the upper right side from the line 302, and it turns out that comprehensive evaluation becomes "(double-circle)" or "(circle)". Moreover, when satisfy | filling said Formula (6) and said Formula (7), it enters into the area | region of the upper right side from the line 303, and it turns out that comprehensive evaluation becomes "(double-circle)".

<Example B>
Next, the configuration of the developing roller was examined.

[Example 13]
Example 1 is the same as Example 1 except that the following developing roller was used as the developing roller.

  First, the above-mentioned pretreated aluminum base tube was prepared as a base material. The Vickers hardness of this aluminum base tube was 50. The Vickers hardness was measured using a Vickers hardness meter.

  Next, an electroless Ni plating process was performed on the aluminum base tube so that an electroless plating layer having a thickness of 4.6 μm was formed as a base layer. During the plating treatment, a plating solution containing 10% by volume of SiC particles having a volume average particle diameter R (μm) of 0.3 μm was used as fine particles. Moreover, this foundation layer satisfies the above formulas (1) to (3).

  Next, an electrolytic Cr plating treatment was performed on the electroless plating layer so that an electrolytic plating layer having a thickness of 0.17 μm was formed as the uppermost layer. By doing so, a developing roller was obtained.

  The Vickers hardness of the formed electrolytic plating layer was 1000. In addition, the Vickers hardness of the Ni plating layer is 500, and the Vickers hardness of the above-described underlayer is about 500 although fine particles are contained, and is softer than the electrolytic plating layer.

  Further, the thickness of the electroless plating layer was about 4.6 μm, and the thickness of the electrolytic plating layer was about 0.17 μm.

[Example 14]
Example 1 is the same as Example 1 except that the following developing roller was used as the developing roller.

  The developing roller is the same as in Example 13 except that the above-described pre-treated aluminum base tube was subjected to blasting as the base material.

[Comparative Example 13]
Example 1 is the same as Example 1 except that the following developing roller was used as the developing roller.

  The developing roller is the same as in Example 13 except that no electrolytic plating layer is formed.

[Comparative Example 14]
Example 1 is the same as Example 1 except that the following developing roller was used as the developing roller.

  The developing roller is the same as in Example 14 except that no electrolytic plating layer is formed.

[Comparative Example 15]
Example 1 is the same as Example 1 except that the following developing roller was used as the developing roller.

  First, the above-mentioned pretreated aluminum base tube was prepared as a base material. The Vickers hardness of this aluminum base tube was 50. The Vickers hardness was measured using a Vickers hardness meter. The aluminum base tube was blasted.

  Next, an electroless Ni plating process was performed on the blasted aluminum base tube so that an electroless plating layer having a thickness of 4.6 μm was formed as a base layer. During the plating process, a plating solution not containing fine particles was used.

  Next, an electrolytic Cr plating treatment was performed on the electroless plating layer so that an electrolytic plating layer having a thickness of 0.17 μm was formed as the uppermost layer. By doing so, a developing roller was obtained.

  The Vickers hardness of the formed electrolytic plating layer was 1000. In addition, the Vickers hardness of a base layer is 500 and is softer than an electroplating layer.

  Further, the thickness of the electroless plating layer was about 4.6 μm, and the thickness of the electrolytic plating layer was about 0.17 μm.

[Comparative Example 16]
Example 1 is the same as Example 1 except that the following developing roller was used as the developing roller.

  The developing roller is the same as Comparative Example 13 except that no electrolytic plating layer is formed.

[Comparative Example 17]
Example 1 is the same as Example 1 except that the following developing roller was used as the developing roller.

  As the developing roller, the above-described pretreated aluminum base tube subjected to blasting was used.

[Comparative Example 18]
Example 1 is the same as Example 1 except that the following developing roller was used as the developing roller.

  As the developing roller, a SUS base tube having a thickness of 600 μm subjected to blasting was used.

[Comparative Example 19]
Example 1 is the same as Example 1 except that the following developing roller was used as the developing roller.

  First, the above-mentioned pretreated aluminum base tube was prepared as a base material. The Vickers hardness of this aluminum base tube was 50.

  Next, an electroless Ni plating process was performed on the aluminum base tube so that an electroless plating layer having a thickness of 4.6 μm was formed as a base layer. During the plating treatment, a plating solution containing 10% by volume of SiC particles having a volume average particle diameter R (μm) of 0.3 μm was used as fine particles.

  Next, an electrolytic Sn plating treatment was performed on the electroless plating layer so that an electrolytic plating layer having a thickness of 0.17 μm was formed as the uppermost layer. By doing so, a developing roller was obtained.

  The Vickers hardness of the formed electrolytic plating layer was 50. In addition, the Vickers hardness of the Ni plating layer is 500, and the Vickers hardness of the above-described underlayer is about 500 although fine particles are contained, and is harder than the electrolytic plating layer.

  Further, the thickness of the electroless plating layer was about 4.6 μm, and the thickness of the electrolytic plating layer was about 0.17 μm.

  Next, as the developer carrying member of the image forming apparatus provided with the one-component developing type developing device as shown in FIG. 1, one having the developing roller obtained as described above was prepared. The configuration of the image forming apparatus is as follows. The photosensitive drum is an amorphous silicon photosensitive drum having a diameter of 30 mm. The photoreceptor speed is 150 mm / second. The distance between the photosensitive drum and the developing roller (distance between DS: development gap) is 300 μm. The distance (regulation gap) between the developing roller and the blade is 300 μm. The blade is a blade made of SUS430. The developing bias applied to the developing roller is a superimposed voltage obtained by superimposing an AC voltage having a peak to peak voltage Vpp of 1700V on a DC voltage having an area center voltage Vdc of 175V. In addition, charging is performed so that the surface potential Vo of the photosensitive drum is 280V. The developer (one-component developer) to be used is a positively chargeable toner having a volume average particle diameter of 7.1 μm.

  An image was formed using such an image forming apparatus, and the following evaluation was performed.

(Image density)
Specifically, first, the image forming apparatus was turned on and stabilized. Thereafter, an image including a solid image was printed. This image was used as the initial image. Next, 1 million copies of this image were printed. The image printed on the 1st million sheets was taken as the 1 millionth sheet image. With respect to the initial image and the 1 millionth image, the reflection density was measured using a reflection densitometer (RD-918 manufactured by Gretag Macbeth Co.). This reflection density was defined as the image density.

  Then, when the difference between the image density of the initial image and the image density of the 1 millionth image (the decrease in image density due to durable printing) was 0.02 or less, it was evaluated as “◎”. In addition, when the reduction range of the image density by durable printing was larger than 0.02 and 0.07 or less, it was evaluated as “◯”. Further, when the range of decrease in image density by durable printing was larger than 0.07 and 0.15 or less, it was evaluated as “Δ”. Further, when the width of decrease in image density due to durable printing was larger than 0.15, it was evaluated as “x”.

  Further, image formation was performed in an environment of a temperature of 10 ° C. and a relative humidity of 15% RH. This image was used as a formed image in a low temperature and low humidity state. Then, image formation was performed in an environment of a temperature of 32.5 ° C. and a relative humidity of 85% RH. This image was a formed image in a high temperature and high humidity state.

  If the difference between the image density of the formed image in the low-temperature and low-humidity state and the image density of the formed image in the high-temperature and high-humidity state is 0.02 or less, “に よ る” It was evaluated. In addition, when the decrease in the image density due to the environmental change was greater than 0.02 and 0.07 or less, it was evaluated as “◯”. Further, when the range of decrease in image density due to environmental change was greater than 0.07 and 0.15 or less, it was evaluated as “Δ”. In addition, when the image density decrease due to environmental change was larger than 0.15, the evaluation was “x”.

  The evaluation results are shown in Table 2 together with an outline of the configuration of the developing roller.

  As can be seen from Table 2, a substrate and a coating layer formed on the substrate are provided, and the coating layer includes an electrolytic plating layer and a base layer closer to the substrate than the electrolytic plating layer. The underlayer is an electroless plating layer formed by an electroless plating process using a plating solution in which insulating fine particles are dispersed, and the electrolytic plating layer is the underlayer. When a developing roller that is harder and satisfies the above formulas (1) to (3) is used (Examples 13 and 14), it is possible to maintain a high image density over a long period of time as compared with other cases. In Examples 13 and 14, it can be seen that the image density is less affected by environmental changes than in other cases.

  Moreover, as a base material, when the blasting process is not performed (Example 13, Comparative Example 11, and Comparative Example 17), it is compared with the case where the blasting process is performed (Example 14 and Comparative Examples 12 to 16). Thus, the occurrence of pitch unevenness in the obtained image was sufficiently suppressed. Even when the blasting process is not performed, the image density is sufficiently high when the developing roller satisfying the above formulas (1) to (3) is used (Example 13). From these facts, it was found that a higher quality image can be formed when the base material is not subjected to blasting.

<Example C>
Finally, the wear rate of the uppermost electrolytic plating layer was examined.

  The electrolytic plating layer of the developing roller is considered to be worn from the convex portion. Therefore, when the decrease in the surface roughness Rz of the developing roller becomes equal to the thickness of the electrolytic plating layer, the electrolytic plating layer is worn down, It is thought that at least a part of the formation was exposed.

  Other than the change in the thickness of the electrolytic plating layer, etc., so that the decrease in the surface roughness Rz of the developing roller is equivalent to the thickness of the electrolytic plating layer, the number shown in Table 3 The same as in the first embodiment. Specifically, it is the same as Example 1 except that the conditions for forming the electrolytic plating layer as the uppermost layer are changed. Moreover, you may adjust by changing conditions other than the thickness of an electroplating layer in that case. The paper used here is A4 size paper.

  In Example C, the same evaluation as that in Example B in which the image density was lowered by durable printing was performed.

  The evaluation results are shown in Table 3. Table 3 also shows the results of the same examination as described above using the same developing roller as in Example 1 except that the base layer does not contain fine particles.

  As can be seen from Table 3, the decrease in the surface roughness Rz of the developing roller is equal to the thickness of the electroplating layer, that is, the electroplating layer is worn and at least a part of the electroless plating layer is exposed. Then, by adjusting the conditions such as the thickness of the electrolytic plating layer of the developing roller so that the number of sheets that can be considered is 20,000 to 450,000 sheets, even if one million sheets are printed, the decrease in image density is suppressed. ing. Further, it is more preferable to adjust the conditions such as the thickness of the electrolytic plating layer of the developing roller so that the number is 30,000 to 400,000, and development is performed so that the number is 50,000 to 300,000. It is more preferable to adjust conditions such as the thickness of the electrolytic plating layer of the roller.

  On the other hand, it can be seen that if the number of sheets is too small or too large, a decrease in image density cannot be sufficiently suppressed.

  Moreover, when the fine particle is not contained, it turns out that the said suitable range is narrow.

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 Electrolytic plating layer 102 Electroless plating layer 103 Base material 104 Coating layer

Claims (8)

A developing roller that is disposed opposite to an image carrier on which an electrostatic latent image is formed and conveys toner carried on the surface to the image carrier;
The developing roller includes a base material and a coating layer formed on the base material,
The coating layer is obtained by laminating at least two layers of an electroplating layer and a base layer closer to the substrate than the electroplating layer,
The underlayer is an electroless plating layer formed by an electroless plating process using a plating solution in which insulating fine particles are dispersed;
The electrolytic plating layer is harder than the underlayer,
When the volume average particle diameter of the fine particles is R μm, the volume average particle diameter of the toner carried on the surface of the developing roller is L μm, and the content of the fine particles in the plating solution is V volume%, the following formula ( 1. A developing device satisfying 1) to (3).
250 ≦ (L ² / R ² ) × V ≦ 130000 (1)
10 ≦ R × L × V ≦ 400 (2)
L>R> 0 (3) The developing device according to claim 1, wherein the following formula (4) and the following formula (5) are satisfied.
500 ≦ (L ² / R ² ) × V ≦ 130000 (4)
30 ≦ R × L × V ≦ 400 (5) The developing device according to claim 1, wherein the following formula (6) and the following formula (7) are satisfied.
1000 ≦ (L ² / R ² ) × V ≦ 130000 (6)
50 ≦ R × L × V ≦ 400 (7)   The developing device according to claim 1, wherein the fine particles are silicon carbide particles. The electrolytic plating layer is a layer containing Cr,
The developing device according to claim 1, wherein the underlayer is a layer containing the fine particles and Ni.   The developing device according to claim 1, wherein the substrate is an aluminum-based substrate.   The developing device according to claim 1, wherein the base material is a base material that has not been roughened.   An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

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