JP2006017962A - Nip-forming member, and developing device, transfer device, charging device, image forming apparatus and process cartridge provided with the nip-forming member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nip-forming member superior in wear resistance and flexibility, and to provide a developing device, a transfer device, a charging device, an image forming apparatus and a process cartridge which are provided with the nip-forming member. <P>SOLUTION: The surface layer of a nip forming member for forming a nip between the member and an image bearing member which bears a toner image by pressing the image bearing member is made of a titanium alloy, the Young's modulus of which is ≤70[GPa] and the 0.2% proof stress is ≥700 [MPa], thereby obtaing the objective nip-forming member of superior wear resistance and flexibility. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a nip forming member that presses an image carrier that carries a toner image to form a nip with the image carrier. Specifically, a nip forming member that forms a nip with a photosensitive member as an image carrier such as a developing roller, a transfer roller, and a charging roller, and a developing device, a transfer device, a charging device, and an image provided with the nip forming member The present invention relates to a forming apparatus and a process cartridge.

  Conventionally, it is known that a nip is formed by a nip forming member that comes into contact with a photoconductor as an image carrier, and charging, transfer, or development is performed at the nip. In order to form a good nip with the photosensitive member, such a nip forming member is formed of a rubber layer as a surface layer so that the surface layer is flexible and elastically deformable. For example, there is a type in which a surface layer of a developing roller as a nip forming member that is brought into contact with a photosensitive member to form a nip is formed of a rubber material (Patent Document 1). In this way, by forming the surface layer of the developing roller with a flexible and elastically deformable rubber, it is possible to make contact with the photosensitive member with a uniform contact pressure in the axial direction, and to perform uniform development in the axial direction. . As a result, image degradation such as density unevenness can be suppressed.

JP 2000-47473 A

  However, the rubber material is easily worn and the life of the developing roller is short. Therefore, it has been necessary to frequently replace the apparatus. As a result of wear of the rubber material, the desired elasticity and flexibility cannot be ensured, and the surface layer comes into contact with the photoconductor almost without bending (inelastically). As a result, when there is a manufacturing error or assembly error in the axial direction of the photosensitive member or the developing roller, the contact pressure with the photosensitive member cannot be kept uniform in the axial direction, and the developing ability is constant in the axial direction. In other words, image deterioration such as density unevenness is caused.

In the case of a transfer roller, the surface layer is formed of a rubber material and brought into contact with the photosensitive member with a high contact pressure, whereby the surface layer is bent to form a transfer nip. Further, the adhesive force between the photosensitive member and the transfer roller is enhanced by the elastic repulsive force of the rubber material, and the cohesive force of the toner is increased at the transfer nip portion. Thereby, generation | occurrence | production of the transfer dust at the transfer nip exit can be suppressed, and deterioration of the image is suppressed.
However, as a result of wear of the rubber material, the desired elastic repulsion force cannot be secured, the toner cohesive force is reduced, the generation of transfer dust is increased at the time of diameter, and a good image cannot be maintained. .

In the case of a charging roller, the surface layer is formed of a rubber material, the surface layer is bent, a charging nip is formed in the circumferential direction of the photosensitive member, and a gap is formed between the charging roller surface and the photosensitive member surface before and after the charging nip. Form. By forming a charging nip to form a gap between the photoconductor and the charging roller, compared to a device in which the wire is disposed opposite to the photoconductor with a predetermined gap like a corotron charger or a scorotron charger, A minute gap can be obtained. Thereby, the charging bias can be reduced as compared with the corotron charger and the scorotron charger.
However, if the desired flexibility cannot be ensured as a result of wear of the rubber material, the surface layer abuts (inelastically) almost without bending with the photoreceptor. As a result, if there is a manufacturing error or assembly error in the axial direction on the photosensitive member or charging roller, the minute gap between the photosensitive member and the charging roller cannot be kept constant in the axial direction, resulting in charging failure, It will cause image degradation.

  As described above, the surface layer of the nip forming member that presses the photoconductor to form a nip with the photoconductor wears, and as a result, the flexibility and elasticity of the surface layer cannot be ensured and various problems cause image deterioration. You can see that

  The present invention has been made in view of the above problems, and its object is to provide a nip forming member excellent in wear resistance and flexibility, as well as a developing device, a transfer device, and the like provided with the nip forming member. A charging device, an image forming apparatus, and a process cartridge are provided.

In order to achieve the above object, the invention according to claim 1 is directed to a nip forming member for forming a nip between an image carrier and an image carrier that carries a toner image. ] The following metal materials are used.
According to a second aspect of the present invention, in the nip forming member according to the first or second aspect, the 0.2% proof stress of the metal material is set to 700 [MPa] or more.
The invention according to claim 3 is the nip forming member according to claim 1, 2 or 3, wherein the metal material is a sintered titanium alloy obtained by sintering a Va group (vanadium group) element and titanium. It is what.
The invention according to claim 4 is the nip forming member according to claim 4, wherein the sintered titanium alloy is cold worked.
The invention of claim 5 is characterized in that, in the nip forming member of claim 4 or 5, the sintered titanium alloy contains 2 to 8% by mass of tin.
According to a sixth aspect of the present invention, in the nip forming member according to the first, second, third, fourth, or fifth aspect, the nip forming member has an elastic layer.
According to a seventh aspect of the present invention, in the nip forming member according to the first, second, third, fourth, fifth or sixth aspect, the nip forming member is a developer carrying member.
According to an eighth aspect of the present invention, in the nip forming member according to the seventh aspect, the surface of the surface layer is coated with a resin.
According to a ninth aspect of the present invention, in the nip forming member according to the eighth aspect, the resin is a conductive resin.
According to a tenth aspect of the present invention, in the nip forming member according to the first, second, third, fourth, fifth or sixth aspect, the nip forming member is a charging member.
The invention of claim 11 is the nip forming member according to claim 1, 2, 3, 4, 5 or 6, wherein the nip forming member is a transfer member.
Further, the invention of claim 12 is a developing device provided with a developer carrier that is rotatably disposed opposite to the image carrier and supplies toner to the image carrier, wherein the developer carrier comprises: A nip forming member that presses the image carrier to form a nip with the image carrier, and the nip forming member according to claim 7, 8 or 9 is used as the developer carrier. It is what.
According to a thirteenth aspect of the present invention, in the developing device of the twelfth aspect, the toner having an average circularity of 1.00 to 0.96 is used as a toner for forming a toner image on the image carrier. It is characterized by using.
The invention according to claim 14 is the developing device according to claim 12 or 13, wherein the toner has a volume average particle diameter of 4 [μm] or more and 10 [μm] or less, and a particle diameter of an additive added to the toner. 50 [nm] or more and 150 [nm] or less is used.
According to a fifteenth aspect of the present invention, there is provided a charging device including a charging member disposed opposite to the image carrier, and charging the image carrier by applying a voltage to the charging member, wherein the charging member is the image carrier. A nip forming member that presses a body to form a nip with the image carrier, and the nip forming member according to claim 10 is used as the charging member.
According to a sixteenth aspect of the present invention, in the transfer device having a transfer member for transferring a toner image formed on the surface of the image carrier to a transfer material, the transfer member presses the image carrier to press the image carrier. A nip forming member that forms a nip between the nip forming member and the nip forming member according to claim 11 as the transfer member.
According to a seventeenth aspect of the present invention, there is provided an image carrier, a charging device comprising a charging member and applying a voltage to the charging member to charge the image carrier, and a developer supplying the developer to the image carrier. 16. The charging device according to claim 15, wherein the charging device is a developing device having a carrier and a transfer device having a transfer member that transfers a toner image formed on the surface of the image carrier to a transfer material. The developing device is characterized in that at least one of the developing device according to claims 12, 13, and 14 or the transfer device according to claim 16 is used as the transfer device.
The invention according to claim 18 includes an image carrier, a charging device that includes a charging member and applies a voltage to the charging member to charge the image carrier, and a developer carrier that supplies the developer to the image carrier. And a developing device comprising: at least one of the developing devices provided with an image forming apparatus, wherein the charging device is configured as an integral structure that is detachably attached to the main body of the image forming apparatus. The developing device according to claim 12, 13, or 14.

  According to invention of Claim 1 thru | or 18, it can be set as the nip formation member which can be bent flexibly and elastically by forming a surface layer with a metal material with a Young's modulus of 70 [GPa] or less. For this reason, the nip forming member can be elastically bent by the predetermined contact pressure and can contact the photoconductor, and can contact the image carrier with a desired nip width and uniform contact pressure in the axial direction. Moreover, since it forms with the metal material which is hard to wear compared with a rubber material like the past, abrasion of a nip formation member can be suppressed compared with the past. As a result, the flexibility and elasticity of the nip forming member do not change with time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an entire printer according to an embodiment of the present invention. This printer irradiates the photosensitive drum 1 with a charging roller 2 for uniformly charging the surface of the photosensitive drum 1 around the photosensitive drum 1 as an image carrier, a laser beam modulated based on image information, and the like. The exposure device 3, the developing device 4 that forms a toner image by attaching charged toner on the developing roller 41 to the electrostatic latent image formed on the photosensitive drum 1, and the toner image formed on the photosensitive drum 1 A transfer roller 5 for transferring the toner onto a transfer paper 20 as a transfer material, a cleaning device 6 for removing the toner remaining on the photosensitive drum 1 after the transfer, and the like are sequentially arranged. The latent image forming means for forming an electrostatic latent image on the photosensitive drum 1 is composed of the charging roller 2 and the exposure device 3.
In addition, a paper feeding / conveying device (not shown) that feeds and conveys transfer paper from a paper feeding tray (not shown) and a fixing device (not shown) that fixes the toner image transferred by the transfer roller 5 to the transfer paper P are provided. Yes.
Note that a part of the plurality of devices constituting the printer may be configured as an integral structure (unit) so as to be detachable from the printer body as indicated by a dotted line in the drawing. For example, the photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning device 6 may be configured as an image forming process cartridge 9 that is an integral structure so as to be detachable from the printer body.

  In the printer configured as described above, the surface of the photosensitive drum 1 rotating in the direction of arrow a is uniformly charged by the charging roller 2, and then a laser beam modulated based on image information is scanned in the photosensitive member axial direction and irradiated. Is done. Thereby, an electrostatic latent image is formed on the photosensitive drum 1. The electrostatic latent image formed on the photoconductive drum 1 is developed by attaching toner charged by the developing device 4 in the developing region to become a toner image. On the other hand, the transfer paper P is fed / conveyed by a paper feeding / conveying device (not shown), and is sent / conveyed by a registration roller 7 to a transfer portion where the photosensitive drum 1 and the transfer roller 5 face each other at a predetermined timing. Then, the toner image formed on the photosensitive drum 1 is transferred to the transfer paper P by applying a charge having a reverse polarity to the toner image on the photosensitive drum 1 to the transfer paper 20 by the transfer roller 5. . Next, the transfer paper P is separated from the photosensitive drum 1 and sent to a fixing device (not shown), and the transfer paper P on which the toner image is fixed by the fixing device is output. The surface of the photosensitive drum 1 after the toner image is transferred by the transfer roller 5 is cleaned by the cleaning device 6, and the toner remaining on the photosensitive drum 1 is removed.

  FIG. 2 shows the developing device 4 of this embodiment. The developing device 4 includes a developing roller 41 and a toner supply roller 42 that is in sliding contact with the developing roller 41 in order to supply toner to the developing roller 41. Further, in order to thin the toner on the developing roller 41, the thin layer regulating member 43 that contacts the developing roller 41, the toner holding portion 44 that holds the toner, and the toner in the toner holding portion 44 while stirring the toner An agitator 46 as a stirring member for supplying the supply roller 42 to the surface is also provided. The supply roller 42 is formed of foamed polyurethane or the like, has flexibility, and has a structure in which the toner is easily held by a cell having a diameter of 50 to 500 μm. Further, the hardness is relatively low at 10 to 30 ° (JIS-A), and the developing roller 41 can be brought into uniform contact.

  In the developing device 4, the toner held in the toner holding unit 44 is mechanically supplied and carried on the surface of the toner supply roller 42 while being stirred by the agitator 46. The toner supply roller 42 conveys the toner to a portion facing the developing roller 41 while carrying the toner, and supplies the toner while sliding on the developing roller 41. The toner supplied to the developing roller 41 is thinned to an appropriate layer thickness by the thin layer regulating member 43 in contact with the developing roller 41 via the toner, and is triboelectrically charged to a desired polarity. Then, the developing roller 41 is conveyed to a developing region which is a portion facing the photosensitive member 1 by rotation in the arrow direction.

  The thin layer regulating member 43 is attached to a holder (not shown), and the free end length from the holder is 10 to 15 [mm]. If it is set to 15 [mm] or more, the developing device 4 becomes large. On the other hand, if it is set to 10 [mm] or less, vibration is likely to occur when contacting the surface of the developing roller 41, and abnormal images such as unevenness are gradually generated on the image. The contact pressure of the thin layer regulating member 43 is preferably in the range of 0.049 to 2.45 [N · cm]. If the contact pressure exceeds the upper limit, the toner adhesion amount on the developing roller 41 after passing through the thin layer regulating member 43 decreases, and the toner charge amount increases too much. Decrease and image density decreases. On the other hand, if the lower limit is not reached, the thin layer is not formed uniformly, and the toner mass may pass through the thin layer regulating member 43, so that the image quality is remarkably lowered. The contact angle of the thin layer regulating member 43 is preferably 10 to 45 ° with respect to the tangent line of the developing roller 41 in the direction in which the front end faces the downstream side of the developing roller 41. In the developing device 4 of this embodiment, the thin layer regulating member 43 is a SUS plate having a thickness of 0.1 [mm], and the contact pressure is set to 60 [gf / cm], so that the thin layer regulating member is formed. The toner after passing through 43 could be formed into a thin layer having a uniform thickness of 0.4 to 0.8 [mg / cm 2] per unit area. Further, toner charging at this time was in the range of -10 to -30 [μC / g].

FIG. 3 is a cross-sectional view of the developing roller 41 of the present embodiment. The developing roller 41 shown in FIG. 3 has a core metal 41a having a diameter of 11 [mm] and an elastic layer 41b made of rubber having a thickness of 2.4 [mm], and further has a thickness of 0.1 [on the elastic layer. mm] a surface layer 41c made of a titanium alloy. As this titanium alloy, one having a Young's modulus of 70 [GPa] or less and a 0.2% proof stress of 700 [MPa] or more is used. Specifically, rubber metal manufactured by Toyota Central Research Laboratory can be mentioned. This rubber metal is composed of 30 to 60% by weight of a Va group (vanadium group) element and the balance being substantially made of titanium, and sintered titanium obtained by sintering the Va group (vanadium group) element and titanium. It is an alloy. Moreover, it is preferable that the sintered titanium alloy used for the surface layer of the developing roller 41 has been subjected to cold working. By cold working the sintered titanium alloy, the Young's modulus can be reduced and the 0.2% proof stress can be improved, and the metal can be made more elastic. Specifically, it is preferable that the sintered titanium alloy is compressed by 10% or more by cold working, and the higher the compression ratio, the lower the Young's modulus and the 0.2% yield strength. Furthermore, it is preferable that the sintered titanium alloy used for the surface layer contains tin. When 2 to 8% by mass of tin is blended, the Young's modulus of the sintered titanium alloy can be reduced and the strength can be improved.
The developing roller 41 includes the cored bar 41a, the elastic layer 41b, and the surface layer 41c. However, the present invention is not limited thereto, and the developing roller 41 may include only the cored bar 41a and the surface layer 41c. It is good also as two layers.

The developing roller 41 is produced by, for example, forming the rubber metal in a cylindrical shape and inserting a cored bar into the center of the rubber metal formed in the cylindrical shape. And it can create by filling rubber | gum between a metal core and rubber metal, and making it vulcanize | cure.
Further, the surface layer of the developing roller 41 may be coated with resin. The resin to be coated is preferably a material having excellent releasability from the toner. In the case of a conventional rubber material that easily wears, toner adhering to the wear is also scraped off, and toner filming is not a problem. However, since the developing roller 41 of the present embodiment has a surface layer 41c made of a metal material and is not easily worn, the toner attached to the surface of the developing roller is not removed over time. Therefore, by coating the resin having excellent releasability as described above, it is possible to maintain a good surface layer over time by suppressing the occurrence of filming due to toner adhesion. The resin material for coating the surface layer is more preferably a conductive material. By using a conductive resin as the resin material for coating the surface layer, the developing electric field formed between the developing roller and the photosensitive member is not lowered.

  FIG. 4 is a diagram showing a stress-strain diagram of a titanium alloy as an example of a stress-strain diagram of a general alloy. In a metal such as a general alloy, when the stress is σA or less, the elongation (strain) and the stress are in a proportional relationship as shown in FIG. 3, and the elongation increases linearly in proportion to the stress. In a region where the elongation increases linearly with respect to the stress, the metal is elastically deformed, and if the stress is removed, the elongation of the metal becomes zero. In general, the Young's modulus is the slope of the region in which the stress changes proportionally to this elongation. And when stress becomes more than (sigma) A, elongation will not increase proportionally with respect to stress, and a metal will start plastic deformation. When the stress reaches the proof stress σP, a permanent elongation of 0.2% occurs when the load is unloaded. Generally, the region until the permanent elongation at the time of unloading becomes 0.2% or less is defined as the region where the metal behaves elastically.

  As shown in FIG. 4, 0.2% proof stress is a stress that causes a metal to plastically deform to cause 0.2% permanent elongation. When stress is applied to the metal any more, the metal starts plastic deformation, Even if the stress is unloaded, the elongation does not return to zero and permanent elongation occurs. In other words, if the yield strength is 0.2% or less, the metal is elastically deformed, and if the stress is removed, the metal elongation can return to zero. Further, it can be said that the smaller the Young's modulus, the larger the elongation with respect to stress, and the more elastic the metal. However, if the 0.2% proof stress as the limit value at which the metal behaves elastically is low, the material immediately starts plastic deformation with a low stress, and it cannot have sufficient elastic deformation performance that can withstand use.

  The metal material used for the surface layer 41c of the developing roller 41 of the present embodiment is a metal material having a Young's modulus of 70 [GPa] or less and strong elastic properties. Therefore, the surface layer 41c can be elastically and flexibly deformed and contacted with the photoreceptor 1. Further, since a metal material having a 0.2% proof stress of 700 [MPa] or more is used, a metal layer that does not undergo plastic deformation even when the contact pressure with the photoreceptor is large can be obtained.

  Further, in recent years, as shown in FIG. 5, even if the elongation does not increase proportionally with respect to the stress, there is a metal material in which the elongation becomes 0 when the stress is removed and elastically deforms. In the case of such a metal, it is necessary to obtain the Young's modulus by a method different from the general metal material shown in FIG. Therefore, for a metal having such properties, the slope of 0.2% proof stress σe at (½) σe is defined as the Young's modulus. Even when used for the surface layer 41c of the developing roller 41 having such properties, the Young's modulus at (1/2) σe of the proof stress σe is 70 [GPa] or less and the 0.2% proof stress is 700 [MPa] or more. If it is a metal material, the surface layer 41c is not plastically deformed by the contact pressure with the photoreceptor, and a metal layer having good elastic deformation performance can be obtained. The rubber metal described above has the stress-strain diagram of FIG.

FIG. 6 is an enlarged schematic view showing a developing nip formed by the photosensitive member 1 and the developing roller 41 pressed against the photosensitive member 1 with sufficient pressure. As shown in FIG. 6, the photosensitive member 1 and the developing roller 41 are in contact with each other in a state where contact pressure is applied via the toner. The photosensitive member 1 is inelastic and hardly bent because the aluminum tube is coated with a resin containing a photosensitive material. On the other hand, the developing roller 41 includes a relatively flexible elastic layer 41b and a surface layer 41c made of a metal having an elastic property. For this reason, the developing roller 41 is flexibly deformed by the contact pressure, and a developing nip is formed in the circumferential direction. Since the surface layer 41c is made of a metal member having an elastic property, a force to elastically return the bent shape works (repulsive force), and the surface layer 41c elastically presses the photosensitive member 1. . By the pressing force of the surface layer 41c, the contact pressure between the photosensitive member and the developing roller can be kept uniform in the axial direction. As a result, it is possible to prevent image density unevenness.
[Verification test 1]

図７に示すように、表層材料のヤング率が７０［ＧＰａ］以上の現像ローラＣ、Ｄにおいては、画像ランクが３．５以下となり、初期時において、良好な画像を得ることができなかった。一方、表層材料のヤング率が７０［ＧＰａ］以下の現像ローラＡ、Ｂにおいては、画像ランクが３．５以上となり、初期時において良好な画像が得られた。ヤング率が７０［ＧＰａ］以上の表層からなる現像ローラＣ、Ｄは、弾性変形に乏しいため、感光体とほとんどたわまずに（非弾性的）に当接する。このため、感光体や現像ローラに軸方向の製造誤差や組付け誤差があった場合、感光体との当接圧を軸方向均一に保つことが難しい。その結果、表層材料のヤング率が７０［ＧＰａ］以上の現像ローラＣ、Ｄにおいては、軸方向均一な当接圧を得ることができず、濃度ムラなどが発生し、画像ランクの低い画像となったと考えられる。一方、表層材料のヤング率が７０［ＧＰａ］以下の現像ローラＡ、Ｂは、表層の弾性変形性が十分であり、表層が感光体とたわんで、弾性的に当接することができる。このため、表層が感光体とある程度の反発力をもって当接することができるので、製造誤差や組付け誤差が多少あったとしても、感光体との当接圧を軸方向均一に保つことができる。このため、表層材料のヤング率が７０［ＧＰａ］以下の現像ローラＡ、Ｂについては、画像ランクの高い良好な画像を得ることができたと考ええられる。
［検証試験２］ In order to verify the developing roller 41, as shown in Table 1, four developing rollers A, B, C, and D having different surface Young's moduli were prepared, and a verification test 1 was performed on the quality of the initial image. The developing roller A has a diameter of 16 [mm] and an elastic layer made of rubber on a core metal. Further, a thickness of 0.1 [mm], a Young's modulus of 3.63 [MPa], and a hardness of 60 are formed on this elastic layer. It has a rubber surface layer composed of ° (JIS-A). The developing roller B has a core metal and an elastic layer similar to the developing roller A, and has a titanium alloy surface layer with a thickness of 0.1 [mm] and a Young's modulus of 70 [GPa]. The developing roller C has a core metal and an elastic layer similar to those of the developing roller A, and has a titanium alloy surface layer with a thickness of 0.1 [mm] and a Young's modulus of 100 [GPa]. The developing roller D has the same core metal and elastic layer as the developing roller A, and has a titanium alloy surface layer with a thickness of 0.1 [mm] and a Young's modulus of 100 [GPa].
The diameter of the photoconductor was 30 [mm], and the width of the developing roller and the photoconductor was 300 [mm]. Further, the image quality at the initial stage was examined by bringing the developing roller into contact with the photosensitive member with a linear pressure of 3 to 20 [gf / mm]. The result is shown in FIG.

As shown in FIG. 7, in the developing rollers C and D in which the Young's modulus of the surface layer material is 70 [GPa] or more, the image rank is 3.5 or less, and a good image cannot be obtained at the initial stage. . On the other hand, with the developing rollers A and B having a Young's modulus of the surface layer material of 70 [GPa] or less, the image rank was 3.5 or more, and a good image was obtained at the initial stage. Since the developing rollers C and D having a surface layer with a Young's modulus of 70 [GPa] or more are poor in elastic deformation, the developing rollers C and D are in contact with the photosensitive body almost without bending (inelastic). For this reason, when there is a manufacturing error or an assembly error in the axial direction on the photosensitive member or the developing roller, it is difficult to keep the contact pressure with the photosensitive member uniform in the axial direction. As a result, in the developing rollers C and D whose surface layer material has a Young's modulus of 70 [GPa] or more, a uniform contact pressure in the axial direction cannot be obtained, density unevenness occurs, and an image with a low image rank is obtained. It is thought that it became. On the other hand, the developing rollers A and B whose surface layer material has a Young's modulus of 70 [GPa] or less have sufficient elastic deformation of the surface layer, and the surface layer bends with the photosensitive member and can elastically contact. For this reason, since the surface layer can contact the photoreceptor with a certain repulsive force, the contact pressure with the photoreceptor can be kept uniform in the axial direction even if there are some manufacturing and assembly errors. For this reason, it is considered that good images with high image ranks could be obtained for the developing rollers A and B having a Young's modulus of the surface layer material of 70 [GPa] or less.
[Verification test 2]

  In the verification test 1, the surface layer having a good initial image has a surface layer of a developing roller B made of a titanium alloy having a Young's modulus of 70 [GPa], and a developing roller A having a surface layer made of a rubber having a Young's modulus of 3.63 [MPa]. Verification test 2 was performed for image changes. Also in the verification test 2, the diameter and width of the photosensitive member and the developing roller, and the linear pressure between the developing roller and the photosensitive member are the same as those in the verification 1. The result is shown in FIG. In addition, changes in the surface layer thickness over time between the developing roller B made of a titanium alloy and the developing roller A made of rubber were also examined. The result is shown in FIG.

  As can be seen from FIG. 8, the developing roller B whose surface layer is a titanium alloy has no change in the rank of the image over time. However, in the developing roller A having a rubber surface layer, the image rank is lowered due to the use of the diameter. Further, as shown in FIG. 9, the surface thickness of the developing roller B whose surface layer is made of a titanium alloy is hardly changed, but the surface layer thickness of the developing roller A whose surface layer is rubber is reduced by use. I can see that That is, from FIG. 9, the developing roller B whose surface layer is made of a titanium alloy is hardly worn and maintains the initial state, but the developing roller A whose surface layer is made of rubber is worn at the time of diameter. I understand that. When the surface layer thickness changes due to wear, the volume resistance of the surface layer changes, making it impossible to obtain a desired development bias. As a result, it is considered that the image of the developing roller A having a rubber surface layer deteriorated with time as shown in FIG. On the other hand, the developing roller B whose surface layer is made of a titanium alloy is formed of a metal material, and therefore has higher wear resistance than rubber. Therefore, as shown in FIG. 8, the wear of the surface layer is suppressed over time, and the thickness of the surface layer does not change. As a result, the volume resistance of the developing roller B whose surface layer is made of a titanium alloy does not change. Therefore, it is considered that the developing roller B whose surface layer is made of a titanium alloy was able to suppress a decrease in image rank as shown in FIG.

  As can be seen from Verification 1 and Verification 2, the development roller capable of maintaining a good image over time can be obtained by making the surface layer of the development roller a titanium alloy having a Young's modulus of 70 [GPa] or less. I understand.

  Up to this point, the developing roller 41 has been described. However, the surface layer of the transfer roller 5 and the charging roller 2 as a nip forming member that forms a nip with the image carrier that carries a toner image such as the photoreceptor 1 has a Young's modulus of 70. If it is made of a metal material having a [GPa] or less and a 0.2% proof stress of 700 [MPa] or more, the transfer roller 5 and the charging roller 2 having excellent wear resistance and flexibility can be obtained.

  First, an example in which the surface layer of the transfer roller 5 is a metal material having a Young's modulus of 70 [GPa] or less and a 0.2% proof stress of 700 [MPa] or more will be described with reference to FIG.

  FIG. 10 is a side view showing the transfer roller 5 and its surroundings. The transfer roller 5 pressed toward the photosensitive member 1 includes a cored bar roller made of a rigid member such as stainless steel or iron, and an elastic layer 5a made of EPDM, silicon, NBR, urethane, or the like coated thereon. ing. On the elastic layer 4a, for example, a surface layer 5b made of a metal member having a Young's modulus of 70 [GPa] or less and a 0.2% proof stress of 700 [MPa] or more such as rubber metal is provided. Moreover, it has the axis | shaft 4c protruded by the both end surfaces of the said core metal roller. The shafts 4 c at both ends are rotatably supported by bearings 18, and these bearings 18 are urged toward the photoreceptor 1 by springs 19. By this urging, the transfer roller 5 is pressed toward the photoreceptor 1 with high pressure.

FIG. 11 is an enlarged schematic view showing a transfer nip formed by the photosensitive member 1 and the transfer roller 5 pressed against the photosensitive member 1 with sufficient pressure. As shown in the figure, the transfer roller 5 is pressed toward the photoreceptor 1 with sufficient pressure. In the transfer nip, the elastic layer 5a and the surface layer 5b of the transfer roller 5 are elastically deformed flexibly. Due to the elastic deformation of the surface layer 5b and the elastic layer 5a, the transfer paper P not only contacts the surface layer 5b of the toner image I carried on the surface of the photoreceptor 1, but also has a recess between adjacent toner images I. Is pressed so as to bite into the surface of the photosensitive member 1 and the adhesion to the surface of the photoreceptor 1 and the toner image I is enhanced. In order to obtain sufficient adhesion between the transfer paper P and the photosensitive member at the transfer nip, at least the surface layer 5b should have a 0.2% proof stress of 700 [MPa under the above-described conditions, Young's modulus of 70 [GPa] or less. ] It is necessary to set to above. As a result, an air gap formed between the photosensitive member 1 and the transfer paper P is reduced, and transfer dust in the transfer nip and before and after the nip is suppressed. Further, since the surface layer 5b of the transfer roller 5 is made of metal, the transfer roller 5 having excellent wear resistance can be obtained. As described above, since the surface layer is not easily worn, the surface layer and the elastic layer are not scraped by the use of the diameter, and the flexibility and elasticity of the transfer roller are not lowered. For this reason, the air gap and elastic force are maintained over time, and transfer dust can be suppressed. Further, since the thickness of the surface layer does not change due to wear, the volume resistance of the surface layer does not change. For this reason, since the transfer electric field between the photosensitive member and the transfer roller does not change over time, image deterioration such as transfer failure does not occur.
The transfer roller 5 includes a cored bar, an elastic layer, and a surface layer. However, the present invention is not limited to this, and only the surface layer having a Young's modulus of 70 [GPa] or less and a 0.2% proof stress of 700 [MPa] or more is used. The elastic layer may be two layers.

  Next, the surface layer 2b of the contact charging type charging roller 2 in which the charging roller 2 comes into contact with the photosensitive member to form a nip is a metal having a Young's modulus of 70 [GPa] or less and a 0.2% proof stress of 700 [MPa] or more. An example using materials will be described with reference to FIG.

  FIG. 12 is a cross-sectional view showing the charging roller 2 and its surroundings. The charging roller 2 has a metal shaft core 2a, an elastic layer 2b coated thereon, and a surface layer 2c coated thereon. A negatively charged charging bias is applied to the metal shaft core 2a by a power source (not shown). The elastic layer 2b is made of an elastic material such as epichrome hydrin rubber, nitrile rubber, chlorobrene rubber, acrylic rubber, or thermoplastic elastomer in which a conductive material such as carbon black is dispersed. By dispersing the conductive material, the entire elastic layer 2b exhibits conductivity, and the shaft core 2a and the surface layer 2c are electrically connected. As the surface layer 2c, a rubber metal having a Young's modulus of 70 [GPa] or less and a 0.2% proof stress of 700 [MPa] or more is used.

  In the image forming apparatus of the present embodiment, a charging device is configured by the charging roller 2, a bearing (not shown) that rotatably supports the roller, a spring that urges the charging roller 2 toward the photoreceptor 1, and the like. Yes. The charging roller 2 is brought into contact with the photoreceptor 1 with a predetermined pressure by the spring, thereby forming a charging nip. By providing the surface layer 2c of the above condition on the charging roller 2, it can be flexibly deformed by the contact pressure to form a long charging nip in the circumferential direction. Further, since the surface layer 2c is formed of a metal material, the charging roller 2 having excellent wear resistance can be obtained.

  As described above, the surface layer 2c is flexibly bent by the contact pressure and brought into contact with the photosensitive member, whereby the gap Gm in the vicinity of the charging nip can be made minute. When the minute gap Gm is formed, it is possible to easily cause discharge from the surface of the charging roller 2 to the surface of the photoreceptor 1. As a result, the charging bias can be reduced as compared with a corotron charger or a scorotron charger in which a wire is disposed opposite to a photoconductor with a predetermined gap. Further, deterioration of the charging roller 2, deterioration of the photoreceptor 1, image deterioration, and environmental pollution due to ozone can be suppressed. This is for the reason described below. That is, when discharge occurs, impurities adhere to the charging roller 2 and the photoreceptor 1. The amount of adhesion increases as the charging bias or gap increases. The adhering impurities are ionized to generate active oxygen (oxygen radicals, oxygen ions) and ozone. When active oxygen collides with the charging roller 2 or the photoreceptor 1, they are deteriorated by sputtering or oxidizing them. Further, if ozone, active oxygen, and nitrogen oxide are adsorbed on the photosensitive member 1, the electrical characteristics of the adsorbing portion are abnormal and image deterioration such as image blurring is caused. Furthermore, the generated ozone is released into the atmosphere, which pollutes the environment. In the method in which the charging roller 2 is brought into contact with the photosensitive member 1, the generation amount of ozone and active oxygen is greatly reduced by forming a minute gap as described above and reducing the charging bias. As a result, various deteriorations and environmental pollution due to ozone can be suppressed.

  Further, since the surface layer is hard to be worn, the surface layer and the elastic layer are not scraped by use at the time of diameter, and the flexibility and elasticity of the charging roller are not deteriorated. For this reason, the minute gap Gm is maintained over time. Further, since the thickness of the surface layer does not change due to wear, the volume resistance of the surface layer does not change. For this reason, since the charging bias applied to the photosensitive member does not change over time, charging failure does not occur over time.

Next, a toner that is preferably used in the present embodiment will be described. The toner of this embodiment is obtained by mixing a charge control agent (CCM) and a colorant in a resin such as polyester, polyol, or styrene acrylic, and an external additive such as silica or titanium oxide is added around the mixture. This improves the liquidity. Examples of the colorant include carbon black, phthalocyanine blue, quinacridone, and carmine. In some cases, the toner 10 may be a base toner in which a wax or the like is dispersed and mixed with an additive of the above type added to the base toner.
The volume average particle diameter of the toner is preferably in the range of 3 to 12 μm. The toner used in this embodiment has a volume average particle diameter of 7 μm and can sufficiently cope with a high-resolution image of 1200 dpi or more.
Further, in this embodiment, toner having a negative charge polarity is used, but a toner having a positive charge polarity according to the charge polarity of the photoreceptor 1 may be used.

  It is important that the toner has a specific shape and shape distribution. The shape of the toner can be defined by circularity. Specifically, the average circularity of the toner is desirably 0.96 or more and 1.00 or less. According to experiments, if the average circularity is less than 0.96, particularly less than 0.93, the toner becomes irregularly shaped away from the spherical shape, and a satisfactory high transfer quality and a high-quality image without dust cannot be obtained. Further, since the degree of circularity is high and it is easy to rotate, the toner hardly adheres to the developing roller, and the occurrence of filming can be suppressed. In particular, when the surface layer is made of a metal that is hard to be worn like the developing roller of the present embodiment, toner (filming) that adheres at the time of diameter may accumulate and a good image may not be maintained. However, by using toner having a high degree of circularity as described above, toner adhesion (filming) to the surface of the developing roller can be suppressed, so that a good image can be maintained over time. Furthermore, since the degree of circularity is high and it is easy to rotate, toner deterioration due to stirring can be suppressed. Therefore, toner does not aggregate over time, and filming of the developing roller due to the aggregated toner can be suppressed.

  As a method for measuring the shape, an optical detection band method is suitable in which a suspension containing particles is passed through an imaging unit detection band on a flat plate, and a particle image is optically detected and analyzed by a CCD camera. The average circularity is a value obtained by dividing the perimeter of an equivalent circle having the same projected area obtained by this method by the perimeter of the actual particle. This value can be measured as an average circularity by a flow type particle image analyzer FPIA-2000 (manufactured by Toa Medical Electronics Co., Ltd.). As a specific measurement method, 0.1 to 0.5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of water from which impure solids have been removed in advance. About 0.1 to 0.5 g. The suspension in which the sample is dispersed is obtained by performing dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser and measuring the shape and distribution of the toner with the above apparatus at a dispersion concentration of 3000 to 10,000 / μl. .

  A method for producing a toner suitably used in this embodiment and having a circularity of 0.96 to 1.00 will be described. In order to make the comparison easier to understand, it will be described in comparison with a general conventional toner.

Conventional toner preparation:
After thoroughly mixing the following raw materials with a Henschel mixer,
Kneaded for 2 hours.
Binder resin (styrene-methyl acrylate copolymer) 100.0 parts by weight Colorant (carbon black # 44, manufactured by Mitsubishi Carbon Corporation) 10.0 parts by weight Charge control agent (ditertiary butylsalicylate zinc salt)
(Orient Chemical's Bontron E-84) 2.0 parts by weight carnauba wax 5.0 parts by weight The obtained kneaded product was roughly pulverized with a palverizer equipped with a 2 mm screen, then pulverized with a lab jet, and classified with 100 MZR. 4 to 10 μm diameter colored particles were obtained. With respect to 95 parts by weight of the obtained colored particles, 3 parts by weight of silica and 2 parts by weight of titanium oxide particles (as additives for assisting the fluidity, developability, transferability, cleaning property, and chargeability of the toner) The average particle size of both additives (20 nm) was mixed with a Henschel mixer for 2 minutes and sieved to obtain a toner.
This is a conventional toner. Here, the circularity of the conventional toner is determined by the flow type particle image analyzer FPI.
It was 0.93 when measured by A-2000 (manufactured by Toa Medical Electronics Co., Ltd.). The weight average particle size was 5.73 μm.

Preparation of toner of this embodiment:
The colored particles obtained in the conventional toner manufacturing process are subjected to a heat treatment temperature of 250 ° C., a hot air flow rate of 1000 liters / minute, and a supply air flow rate of 100 using a Nippon Pneumatic Surffusion System.
Treatment was performed twice at a liter / minute to obtain new colored particles having a diameter of 4 to 10 μm. With respect to 95 parts by weight of the obtained colored particles, 3 parts by weight of silica and 2 parts by weight of titanium oxide particles (as additives for assisting the fluidity, developability, transferability, cleaning property, and chargeability of the toner) The average particle size of both additives (60 nm) was mixed with a Henschel mixer for 2 minutes and sieved to obtain a toner. This is a new toner. The roundness of the new toner was 0.96, and its weight average particle size was 5.56 μm.

  As described above, by subjecting the pulverized toner to heat treatment, a toner having a circularity of 0.96 or more can be obtained. Further, instead of heat treatment, for example, a method using a turbo mill (manufactured by Turbo Kogyo) described in JP-A-9-85741, a method using a kryptron (manufactured by Kawasaki Kogyo), a Q-type mixer (manufactured by Mitsui Mine) For example, the toner circularity can be increased to 0.96 or more by performing mechanical processing. In addition, a toner having a circularity of 0.96 or more can be prepared by a wet granulation method such as a suspension polymerization method, a dispersion polymerization method, or a dissolution suspension method. In the case of these manufacturing methods, there is a merit that it is excellent in terms of energy efficiency.

In the toner of the present embodiment, the base resin is 4 to 10 μm, and the average particle diameter of primary particles of the additive externally added to the toner base is 50 to 150 nm. If the average particle size of the primary particles of the additive is smaller than 50 nm, the additive is buried in the base resin earlier and is likely to deteriorate. On the other hand, if the thickness exceeds 150 nm, the toner is likely to be sandwiched between the developing roller and the regulating member, the thin layer cannot be made uniform, and white streaks are likely to occur in the image.
FIG. 13 is a result of examining the toner adhesion amount on the developing roller at the time of the diameter of the conventional toner having an average particle diameter of the additive of 20 nm and the toner of the present embodiment having the average particle diameter of the additive of 60 nm. . As shown in FIG. 13, by adding a large particle size additive to the spherical toner, it is possible to suppress an increase in the toner adhesion amount on the developing roller over the diameter compared with the conventional toner, and the image quality can be maintained. .

In the above embodiment, the case where the toner image formed on the photosensitive member 1 is directly transferred onto the transfer paper has been described. However, in the present invention, the toner image on the photosensitive member shown in FIGS. The present invention can also be applied to an image forming apparatus that transfers to a transfer body and then transfers the toner image on the intermediate transfer body onto transfer paper. The image forming apparatus of FIG. 14 sequentially forms toner images for each color on one photoconductor 21 and transfers each color toner image on the photoconductor 21 to an intermediate transfer belt 28 as an intermediate transfer member. This is a color image forming apparatus that collectively transfers the superimposed toner images on the transfer belt 28 onto transfer paper by the transfer roller 25. In the color image forming apparatus, the present invention can also be applied to the developing roller 241 and the charging roller 22 that are members that form a nip with the photosensitive member 21 that is an image carrier. The intermediate transfer belt 28 may be formed of a metal material having a Young's modulus of 70 [GPa] or less and a 0.2% proof stress of 700 [MPa] or more. Further, the present invention may also be applied to the intermediate transfer belt 28 that carries a toner image and the transfer roller 25 that forms a nip.
In the image forming apparatus of FIG. 15, a plurality of image forming units 18 including the photoconductors 40 are arranged side by side along a linear movement path portion of the intermediate transfer belt 10 as an intermediate transfer member. Toner images of different colors are formed on the photoconductor 40, and the toner images on the photoconductors 40 are superimposed and transferred onto the intermediate transfer belt 10 by the primary transfer device 62, and are superimposed on the intermediate transfer belt 10. The present invention can also be applied to a developing roller, a transfer roller, and a charging roller used in a tandem type color image forming apparatus that collectively transfers a toner image onto a transfer sheet by a secondary transfer device (not shown). Further, as described above, the present invention can also be applied to the intermediate transfer belt 10.

(1)
As described above, according to the nip forming member of the present embodiment, the surface layer is made of a metal material having a Young's modulus of 70 [GPa] or less. Since the surface layer is a metal member, wear of the surface layer is suppressed. As a result, the durability of the nip forming member can be improved. In addition, since the Young's modulus is 70 [GPa] or less, the surface layer can be elastically deformed flexibly. For this reason, the surface layer can be flexibly elastically deformed by a predetermined abutting pressure to abut against the photoreceptor, and a desired nip width can be formed.
(2)
Further, the 0.2% proof stress of the surface metal material is set to 700 [MPa] or more. Even if the Young's modulus of the metal is low and has an elastic property, if the 0.2% proof stress, which is the limit value for the metal to behave elastically, is low, it deforms by contacting the image carrier with a predetermined contact pressure. When this occurs, plastic deformation occurs, and the nip forming member cannot maintain a predetermined shape. As a result, a desired contact pressure and nip width with the photoreceptor cannot be secured. For example, when the nip forming member is a developing roller, the gap with the thin layer regulating member fluctuates, and toner cannot be formed to a desired thickness, resulting in density unevenness. Further, the contact pressure with the photoconductor changes, the developing ability is lowered, and the image is deteriorated. For example, when the nip forming member is a transfer roller, the air gap between the image carrier and the transfer body fluctuates and transfer dust occurs. Further, the cohesive force of the toner cannot be increased at the transfer nip, transfer dust is generated at the transfer nip exit, and the image is deteriorated. In the case of a charging roller, a minute gap with the photosensitive member cannot be maintained, which causes image deterioration and the like.
However, in the present embodiment, the 0.2% proof stress of the metal material is set to 700 [MPa] or more. Therefore, when the nip forming member is deformed by contact with the image carrier at a predetermined contact pressure, plastic deformation is caused. Waking up is suppressed. Thus, the above-described problems are suppressed and the deterioration of the image is suppressed.
(3)
Further, the nip forming member of the present embodiment is a sintered titanium alloy (rubber metal). By using rubber metal in this manner, a nip forming member having a Young's modulus of 70 [GPa] or less and a 0.2% proof stress of 700 [MPa] or more can be obtained.
(4)
Further, by using a sintered titanium alloy that has been cold worked, a nip forming member having a low Young's modulus and a high 0.2% proof stress can be obtained. Thereby, it can be set as the surface layer which has more favorable elasticity.
(5)
Moreover, by using a sintered titanium alloy containing 2 to 8% by mass of tin, a nip forming member having a low Young's modulus and a high 0.2% proof stress can be obtained. Thereby, it can be set as the surface layer which has more favorable elasticity.
(6)
Moreover, the nip forming member of this embodiment has an elastic layer, and the surface layer is comprised with the said metal material. Thereby, a nip formation member can be made into a more flexible member. Therefore, a desired nip width can be formed even if the contact pressure to the photosensitive member is low. Thereby, the torque of the photoconductor can be reduced.
(7)
According to this embodiment, the nip forming member is applied to a developing roller as a developer carrying member. Thereby, it can be set as the developing roller whose surface layer is flexible and has high wear resistance. Therefore, since the developing roller flexibly bends and contacts the photoconductor by a predetermined contact pressure, a certain development nip width can be formed. Further, since the surface layer has good elastic deformation performance, the surface layer can contact the photoreceptor with repulsive force. In this way, since the surface layer can abut against the photoconductor with a repulsive force in the development nip, even if there is an assembly error or a manufacturing error in the axial direction on the photoconductor or the developing roller, the contact pressure with the photoconductor is the axis. There is no significant shift in direction. Therefore, density unevenness can be suppressed. Further, since the surface layer is made of metal, the wear resistance is better than that of conventional rubber, so that the durability of the developing roller can be improved. For this reason, since the thickness of a developing roller does not change, it is suppressed that the volume resistance of a developing roller changes. As a result, the developing electric field between the photosensitive member and the developing roller can be kept constant over time, and the developing ability is not reduced over time, so that a good image can be maintained over time.
(8)
According to the present embodiment, the surface layer surface of the developing roller as the nip forming member is coated with the resin. For example, if the surface layer is coated with a toner and a resin having high releasability, toner filming on the surface of the developing roller can be suppressed even when the diameter is large. In particular, the developing roller of this embodiment has a surface layer formed of a metal having excellent wear resistance, and therefore, the conventional surface layer is not worn with filming due to wear unlike a rubber developing roller. Filming is easy to progress. However, as described above, the coating of the surface of the surface with a resin having a good releasability with respect to the toner suppresses the progress of filming even in the case of a metal and a surface layer with excellent wear resistance. It is possible to suppress image degradation at times.
(9)
Furthermore, by using the resin material as a conductive resin, the developing bias applied to the developing roller does not decrease in the developing nip. Therefore, stable development can be performed without increasing the developing bias applied to the developing roller.
(10)
According to the present embodiment, the nip forming member is applied to a charging roller as a charging member. Thereby, it can be set as a charging roller with a soft surface layer and high abrasion resistance. Accordingly, a desired charging nip can be formed by flexibly abutting the photosensitive member with a predetermined abutting pressure. Thereby, a minute charging gap can be formed between the photosensitive member and the charging roller, and the charging bias can be reduced to suppress the deterioration of the charging roller 2 and the photosensitive member and the deterioration of the image. Furthermore, environmental pollution by ozone can be suppressed. In addition, wear with the photoreceptor can be suppressed, and a highly durable charging roller can be obtained. For this reason, since the thickness of the charging roller does not change, the volume resistance of the charging roller is suppressed from changing. As a result, the charging bias applied to the photoreceptor can be kept constant over time, and a good image can be maintained over time. Further, since the surface layer and the elastic layer do not wear, good elastic performance can be maintained over time. Therefore, a minute gap can be maintained over time, and a good image can be maintained over time without deteriorating charging performance.
(11)
According to this embodiment, the nip forming member is applied to a transfer roller as a transfer member. Thereby, it can be set as the transfer roller whose surface layer is flexible and has high wear resistance. Therefore, the surface layer can be flexibly elastically deformed by a predetermined contact pressure and contacted with the photoconductor to form a desired transfer nip. Thereby, the air gap between the image carrier and the transfer body can be reduced, and the generation of transfer dust can be suppressed. Further, the cohesive force of the toner can be increased at the transfer nip, and the generation of transfer dust at the transfer nip exit can be suppressed. Further, wear with the photoconductor can be suppressed, and a highly durable transfer roller can be obtained. For this reason, since the thickness of the transfer roller does not change, the volume resistance of the transfer roller is suppressed from changing. As a result, the transfer electric field between the photoconductor and the transfer roller can be kept constant over time, and a good image can be maintained over time. Further, since the surface layer and the elastic layer do not wear, good elastic performance can be maintained over time. For this reason, the air gap can be maintained over time, and the cohesive force of the toner does not change, so that generation of transfer dust can be suppressed over time, and a good image can be maintained over time. Can do.
(12)
Further, according to the developing device of the present embodiment, since the developing roller is provided, it is possible to provide a developing device that can suppress image deterioration such as density unevenness. Further, a highly durable developing device can be obtained.
(13)
Further, according to the developing device of this embodiment, the average circularity of the toner particles is set to 1.0 to 0.96. By setting the toner in a shape close to a circle in this way, it is difficult to adhere to the surface of the developing roller, and the occurrence of filming is suppressed. Furthermore, since the degree of circularity is high and it is easy to rotate, toner deterioration due to stirring can be suppressed. Therefore, the toner does not aggregate over time, and filming due to the aggregated toner can be suppressed.
(14)
Further, according to the developing device of this embodiment, the volume average particle diameter is 4 [μm] or more and 10 [μm] or less, and the particle diameter of the additive added to the toner is 50 [nm] or more and 150 [nm] or less. Something is used. When the average particle size of the additive is smaller than 50 [nm], the additive is quickly buried in the base resin, and the toner is easily deteriorated. On the other hand, if it exceeds 150 [nm], the toner is likely to be caught between the developing roller and the regulating member, and the thin layer cannot be made uniform, resulting in white streaks in the image. Therefore, by setting the particle diameter of the additive to 50 [nm] or more and 150 [nm] or less, white streak images and toner deterioration can be suppressed.
(15)
Further, according to the charging device of the present embodiment, since the charging roller is provided, it is possible to provide a charging device that can suppress deterioration of the photoreceptor and image. Moreover, it can be set as the charging device which suppressed the environmental pollution by ozone. Furthermore, since the life of the charging roller is extended, a charging device having excellent durability can be obtained.
(16)
Further, according to the transfer device of the present embodiment, since the transfer roller is provided, a transfer device in which transfer dust is suppressed can be obtained.
(17)
Further, according to the image forming apparatus of the present embodiment, any one of the above-described charging device, developing device, and transfer device is provided. Therefore, it is possible to obtain an image forming apparatus that suppresses image deterioration and has excellent durability.
(18)
Further, according to the process cartridge of this embodiment, any one of the above-described charging device and developing device is provided. Therefore, it is possible to obtain a process cartridge that suppresses image deterioration and has excellent durability.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram of a developing device. Sectional drawing of a developing roller. A stress-strain diagram of a general titanium alloy. The stress-strain diagram of a sintered titanium alloy. Sectional drawing which shows the image development nip and its periphery. The graph which investigated the quality of the initial image of the developing roller of surface layer material from which Young's modulus differs. The graph which investigated the image quality at the time of the diameter of the developing roller whose surface layer material consists of rubber, and the developing roller whose surface layer material consists of a sintered titanium alloy. The graph which investigated the abrasion amount of the surface layer at the time of the diameter of the developing roller whose surface layer material consists of rubber, and the developing roller whose surface layer material consists of a sintered titanium alloy. The side view which shows a transfer nip and its circumference | surroundings. FIG. 3 is an enlarged schematic diagram illustrating an example of the transfer nip formed by a photoconductor and a transfer roller pressed with sufficient pressure toward the photoconductor. FIG. 3 is a cross-sectional view showing the charging roller 2 and its surroundings. 6 is a graph obtained by examining the toner adhesion amount on the developing roller at the time of diameter of a conventional toner having an average particle diameter of an additive of 20 nm and a toner of the present embodiment having an average particle diameter of an additive of 60 nm. FIG. 3 is a diagram illustrating an example of an image forming apparatus having an intermediate transfer member. The figure which shows a tandem type image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 3 Exposure apparatus 4 Developing apparatus 5 Transfer roller 6 Cleaning apparatus 41 Developing roller

Claims (18)

  A nip forming member for forming a nip between an image carrier and an image carrier that bears a toner image, wherein the surface layer is a metal material having a Young's modulus of 70 [GPa] or less. .   3. The nip forming member according to claim 1, wherein a 0.2% proof stress of the metal material is 700 [MPa] or more.   4. The nip forming member according to claim 1, 2, or 3, wherein the metal material is a sintered titanium alloy obtained by sintering a Va group (vanadium group) element and titanium.   5. The nip forming member according to claim 4, wherein the sintered titanium alloy is cold worked.   6. The nip forming member according to claim 4, wherein the sintered titanium alloy contains 2 to 8% by mass of tin.   6. The nip forming member according to claim 1, wherein the nip forming member has an elastic layer.   7. The nip forming member according to claim 1, wherein the nip forming member is a developer carrying member.   8. The nip forming member according to claim 7, wherein the surface of the surface layer is coated with a resin.   The nip forming member according to claim 8, wherein the resin is a conductive resin.   7. The nip forming member according to claim 1, wherein the nip forming member is a charging member.   7. The nip forming member according to claim 1, wherein the nip forming member is a transfer member.   In a developing device provided with a developer carrier that is rotatably disposed opposite to the image carrier and supplies toner to the image carrier, the developer carrier presses the image carrier and presses the image carrier. A developing device comprising a nip forming member for forming a nip with an image carrier, wherein the nip forming member according to claim 7, 8 or 9 is used as the developer carrier.   13. The developing device according to claim 12, wherein a toner having an average circularity of 1.00 to 0.96 is used as toner for forming a toner image on the image carrier.   14. The developing device according to claim 12, wherein the toner has a volume average particle diameter of 4 [μm] or more and 10 [μm] or less, and a particle diameter of an additive added to the toner is 50 [nm] or more and 150 [nm]. A developing device using the following.   In a charging device comprising a charging member disposed opposite to an image carrier and applying a voltage to the charging member to charge the image carrier, the charging member presses the image carrier to press the image carrier. A nip forming member that forms a nip with the nip forming member according to claim 10 as the charging member.   In a transfer device having a transfer member for transferring a toner image formed on the surface of an image carrier to a transfer material, the transfer member presses the image carrier to form a nip with the image carrier. 12. A transfer apparatus, comprising: a forming member, wherein the nip forming member according to claim 11 is used as the transfer member.   An image carrier, a charging device that includes a charging member and charges the image carrier by applying a voltage to the charging member, and a developing device that includes a developer carrier that supplies the developer to the image carrier; An image forming apparatus having a transfer device having a transfer member for transferring a toner image formed on the surface of the image carrier to a transfer material, wherein the charging device is the charging device according to claim 15, and the developing device is claim 12. An image forming apparatus, wherein at least one of the developing devices of 13 and 14 or the transfer device of claim 16 is used as the transfer device.   At least one of an image carrier, a charging device that includes a charging member and charges the image carrier by applying a voltage to the charging member, and a developing device that includes a developer carrier that supplies developer to the image carrier In the process cartridge configured to be detachable from the main body of the image forming apparatus, the charging device is the charging device according to claim 15, or the developing device is the developing according to claims 12, 13, and 14. A process cartridge which is an apparatus.

Images