JP2008209668A - Developing roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roll having excellent flexibility and advantageously restraining the occurrence of toner filming while securing sag resistance. <P>SOLUTION: In the developing roll 10 constituted by forming an elastic body layer 14 on the outer peripheral surface of a shaft body and providing at least one coating layer 16 on the outer peripheral surface of the elastic body layer 14, the elastic body layer 14 is composed by foaming milable rubber material and also adjusted to have an average cell diameter of 20 to 200 μm and thickness (d) of a skin layer of 100 to 350 μm. Furthermore, the surface roughness of a roll surface 17 is set to Ra: <0.50 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing roll used in an electrophotographic printer, a copying machine, a facsimile, or the like.

  2. Description of the Related Art Conventionally, in electrophotographic apparatuses such as copying machines and printers, a conductive elastic material comprising a rubber elastic body layer, a foam layer or the like on the outer peripheral surface of a metal shaft body (core metal) such as SUS as a developing roll. A material layer (base layer) is formed, and at least one coat layer made of a resin layer is further laminated on the outer peripheral surface of the conductive elastic layer.

  In such a developing roll, a toner layer is formed on the surface of the developing roll by the toner regulating member, and in contact with the photosensitive drum on which the electrostatic latent image is formed while holding the toner layer, The electrostatic latent image is developed by rotating with the photosensitive drum.

  In recent years, electrophotographic apparatuses such as copiers and laser beam printers (LBPs) have been increasingly demanded for higher image quality and lower power consumption. For this reason, the particle size and particle size distribution are small, and the melting point is lowered. The applied toner is used so that the toner is uniformly charged. In such a toner, since the melting point is lowered, the toner particles are reduced when the contact pressure between the developing roll and the photosensitive drum or the contact pressure between the developing roll and the toner regulating member is large. There are inherent problems such as cracking, deformation, etc., which cause image defects such as filming (vertical streak image due to toner adhesion on the developing roll).

  In particular, when a developing roll in which the conductive elastic layer (base layer) is formed from non-foamed rubber is used, the distance between the axes of the developing roll and the photosensitive drum is fixed because the hardness of the base layer is high. Therefore, if the required contact width between the developing roll and the photosensitive drum is secured, the stress on the toner is greatly increased, and the toner adheres to the roll surface, and image defects such as filming are likely to occur. . For this reason, the developing roll is required to further reduce the hardness (softening) in the base layer that affects the hardness of the entire roll so that an increase in stress on the toner can be suppressed.

  However, by adding a large amount of plasticizer or the like to the non-foamed rubber constituting the base layer to reduce the hardness (softening), the required contact width is ensured even when the contact pressure is low, and the stress on the toner is reduced. Although the rise can be suppressed, a new problem such as contamination of the photosensitive drum is caused by the seepage of the plasticizer from the developing roll. In addition, when a developing roll having a base layer formed of a foam is used in order to reduce the hardness, the lower the hardness, the more likely it is that the part pressed against the photosensitive drum tends to stick. There is a problem that the deformed part cannot be recovered promptly after pressure welding, and it is difficult to achieve both low hardness (softening) and settling resistance (low compression set characteristics) at the same time. There was.

  On the other hand, in the developing roll, in order to improve the toner transportability in order to further improve the image quality, the base layer is conventionally made to have a predetermined surface roughness by a technique such as polishing or molding. A method of physically increasing the amount of toner transported by fine irregularities on the surface of the roll, such as by roughening the surface or adding roughening fine particles to the coating layer (intermediate layer or surface layer). However, as the surface roughness of the roll surface increases, the toner is more likely to deposit and adhere to the concave portion of the roll surface, which also causes image defects such as filming. It is.

  By the way, in Patent Documents 1 and 2, a rubber roll whose base layer is made of foamed rubber made of a millable rubber material is clarified. However, in Patent Document 1, the cell diameter of the foamed cells formed in the base layer and There is no description about the thickness of the skin layer, and Patent Document 2 discloses a skin layer (skin layer) having a thickness of about 100 μm to several hundred μm in which resin particles are dispersed on the surface. However, since the hardness of the roll surface is increased by the resin particles, the problem of toner filming is inherent.

JP-A-6-182784 Japanese Patent No. 3057200

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is that it has excellent flexibility and toner filming while ensuring anti-sag properties. An object of the present invention is to provide a developing roll that can be advantageously suppressed.

  And as a result of the present inventors' extensive investigation on the developing roll, a conductive layer having a foam cell having an average cell diameter of 20 to 200 μm and a skin layer having a thickness of 100 to 350 μm using a millable rubber material. By forming the toner, it is possible to achieve both reduction in hardness and resistance to sag, and furthermore, by forming the surface of the roll with a surface roughness of less than 0.50 μm, toner filming is advantageous. The present inventors have found that this can be prevented, and have completed the present invention.

  That is, the present invention is a developing roll in which a conductive elastic layer is formed on the outer peripheral surface of a shaft body, and at least one coat layer is further provided on the outer peripheral surface of the conductive elastic layer. The conductive elastic layer is made of foamed rubber obtained by foaming a millable rubber material, has an average cell diameter of 20 to 200 μm, and a skin layer having a thickness of 100 to 350 μm on its surface, The gist of the developing roll is characterized in that the surface roughness of the roll surface is Ra: less than 0.50 μm.

  In one desirable mode of the developing roll according to the present invention, the surface roughness of the conductive elastic layer is Ra: 1.35 μm or less.

  According to another preferred embodiment of the developing roll according to the present invention, the coat layer is formed with a thickness of 1 to 30 μm.

  As described above, in the developing roll according to the present invention, the conductive elastic layer is made of foamed type rubber that is not a solid (non-foamed) type, and the surface (outer periphery) of the conductive elastic layer. Surface) is formed so that the thickness of the skin layer is 100 to 350 μm, and the average cell diameter of the foamed cells is 20 to 200 μm. Therefore, low hardness (softening) is advantageous. In addition to being realized, the anti-sagging property can be secured well. Accordingly, the stress on the toner is relieved, and the occurrence of filming due to toner deformation or the like can be advantageously prevented, and the compression set is reduced, so that the deformed portion due to the press contact cannot be recovered from the press contact state. Such can be advantageously prevented.

  In addition, in such a developing roll, the surface roughness of the roll surface (product surface roughness) is Ra: less than 0.50 μm, and since the surface is smooth, toner accumulation on the roll surface is prevented. Thus, filming due to toner accumulation can be advantageously prevented.

  In addition, in the developing roll according to the present invention, the foamed rubber constituting the conductive elastic layer is formed from a millable rubber (meaning a rubber that can be kneaded and roll kneaded) instead of a liquid rubber material. Therefore, the average cell diameter of the foamed cells and the thickness of the skin layer can be advantageously adjusted within the above specific range, and the surface roughness of the roll surface can be adjusted to Ra: 0. It can be less than 50 μm. That is, it is difficult to control the cell diameter because the liquid rubber material has a small viscosity, and the foamed cells are bonded to each other, so that the average cell diameter is larger than the target cell diameter or near the surface. It is difficult to ensure a high degree of surface accuracy due to the large variation in cell diameter, but the millable rubber material has a moderate viscosity and forms fine foam cells. It is possible and the foam cells can be formed relatively uniformly, so that the roll surface can be a relatively smooth surface in the circumferential and axial directions.

  Therefore, in such a developing roll according to the present invention, the anti-sag property can be ensured well, the flexibility is excellent, and the occurrence of toner filming can be advantageously suppressed. .

  Further, according to one of the preferred embodiments of the developing roll according to the present invention, if the surface roughness of the conductive elastic layer is Ra: 1.35 μm or less, the outer periphery of the conductive elastic layer having such a surface roughness is provided. By forming at least one coat layer on the surface, the surface roughness (Ra) of the roll surface can be adjusted more advantageously within a desired range, and as a result, the occurrence of toner filming can be prevented. It can be effectively prevented.

  Furthermore, if the coating layer is formed in a thickness of 1 to 30 μm according to another preferred embodiment of the developing roll according to the present invention, it is possible to more advantageously prevent the roll surface from increasing in hardness.

  FIG. 1 shows an example of a typical roll structure of the developing roll according to the present invention in a cross section perpendicular to the axis. And in this image development roll 10, on the outer peripheral surface of the electroconductive shaft body (core metal) 12, from the inner side to the outer side in the roll radial direction, the conductive elastic layer 14 and the coat layer (the outermost layer) (Coating layer) 16 is sequentially laminated integrally at a predetermined thickness. That is, in the developing roll 10, one coat layer 16 is further provided as the outermost layer on the outer peripheral surface of the conductive elastic layer 14 as a base layer formed around the shaft body 12. It is configured.

  More specifically, the shaft body 10 is not particularly limited as long as it is a conductor. Examples of the material of the shaft body 10 include metals such as iron, aluminum, and stainless steel. In addition, if necessary, an adhesive, a primer, or the like may be applied to the outer peripheral surface. Further, the shape of the shaft body 10 may be a pipe-shaped hollow cylindrical body other than the rod-shaped solid body as shown in FIG.

Further, the conductive elastic layer 14 formed on the outer peripheral surface of the shaft body 10 is composed of a foam-like elastic body made of foamed rubber. In the present invention, the conductive elastic layer 14 is mainly composed of a millable rubber material. The foam rubber forming material is used. Here, the millable rubber means a type of rubber that can be kneaded and roll kneaded, and has a higher viscosity than a liquid type rubber (generally, Mooney viscosity ML _{1 + 4} (100 ° C.) is 35 to 35%. 160). For this reason, it is possible to easily control the cell diameter in the foamed rubber as compared with the case where liquid rubber is used, and it is possible to advantageously form a foam cell having an average cell diameter, which will be described later. Can be formed relatively uniformly in the circumferential direction and the axial direction.

  Examples of such millable rubber materials include butadiene rubber, styrene-butadiene rubber, ethylene-propylene-diene rubber (EPDM), nitrile rubber, epichlorohydrin rubber, acrylonitrile-butadiene rubber (NBR), and hydrogenated acrylonitrile-butadiene rubber (H-). NBR), chloroprene rubber, silicone rubber, urethane rubber, and other synthetic rubbers, natural rubber, and the like. These rubber materials may be used alone or in combination of two or more. Among these, butadiene rubber, styrene-butadiene rubber, and silicone rubber can be particularly preferably employed because they are low in hardness and excellent in set resistance.

And, such a millable rubber material is made of conductive carbon such as ketjen black, acetylene black, carbon black, graphite, metal powder, conductive metal oxide (for example, conductive tin oxide, conductive titanium oxide, conductive oxide). A conventionally known conductive agent such as zinc) is blended at a blending ratio similar to the conventional one, and the conductive elastic layer 14 can be adjusted to a predetermined volume resistivity (generally about 10 ³ to 10 ⁸ Ωcm). Thus, the conductive property is imparted to the developing roll 10 by this conductive agent.

  In addition, the conductive foam rubber-forming material mainly composed of this millable rubber material includes an inorganic foaming agent such as sodium bicarbonate, sodium bicarbonate, ammonium bicarbonate, azodicarbonamide, 4 to obtain a foam. A known foaming agent of an organic foaming agent such as 1,4-oxybisbenzenesulfonylhydrazide, dinitrosopentamethylenetetramine, etc. is blended, and the foaming ratio is generally within 5 times, preferably about 1.5 to 2.5 times. It is designed to be foamed so that

  Here, the blending amount of the foaming agent can be appropriately set according to the type of the rubber material, but is preferably 0.1 to 30 parts by weight, more preferably 100 parts by weight of the rubber material. The mixing ratio is 3 to 15 parts by weight. The reason for this is that if the blending amount of the foaming agent decreases, foaming may not sufficiently occur, while if the blending amount of the foaming agent increases too much, the foaming reaction may proceed too much. This is because the thickness of the skin layer formed on the body layer 14 and the average cell diameter of the foamed cells are out of the range described later.

  In addition to the conductive agent and foaming agent as described above, the foamed rubber forming material includes various combinations such as a retarder, a catalyst, a crosslinking agent, and a softening agent for adjusting the timing of curing and foaming of the rubber material. Additives and additives can be further added and mixed in an appropriate amount as necessary, as in the prior art.

  The conductive elastic layer 14 is formed by foaming and curing (vulcanizing or cross-linking) a foam rubber-forming material containing a conductive agent and a foaming agent as described above. The conductive elastic layer 14 is usually formed to have a thickness of about 0.5 to 10 mm, preferably about 0.5 to 6 mm.

  In addition, as shown in an enlarged view in FIG. 2, the conductive elastic layer 14 has a large number of single-bubble foam cells 20 in the vicinity of the shaft body of the conductive elastic layer 14. The surface 15 of the conductive elastic body layer 14 is formed in a dispersed state from the surface 15 to the vicinity of the surface 15, and a skin layer 18 having a predetermined thickness is formed on the surface 15 of the conductive elastic layer 14. In the present invention, the “skin layer” means a portion of the skin (non-foamed skin layer) where the foamed cells 20 formed integrally on the surface of the foamed rubber are not present, as is apparent from FIG. .

  And especially in this invention, the average cell diameter of this foaming cell 20 is adjusted so that it may become a small average cell diameter with 20-200 micrometers, Preferably it is 50-150 micrometers. For this reason, even if the skin layer 18 is thinned, it is possible to prevent the roll surface 17 from becoming uneven due to the foamed cells 20 located immediately below the skin layer 18, and as a result, the thickness of the skin layer Thus, it is possible to further reduce the thickness of the developing roll 10 and to advantageously reduce the hardness of the developing roll 10, thereby effectively reducing the stress on the toner. When the average cell diameter of the foamed cell is smaller than 20 μm, the hardness becomes the same as that of the non-foamed rubber, and there is a risk that the hardness can not be reduced by the foamed rubber. For example, irregularities corresponding to the shape of the foam cell 20 located immediately below the skin layer 18 appear on the roll surface 17, and the roll surface 17 is roughened. Ra) may not be possible. In particular, if the average cell diameter becomes too large, the sag resistance may be deteriorated.

  Here, in the foamed cell 20 of the conductive elastic layer 14, a gradient occurs in the cell diameter from the vicinity of the shaft body 12 to the vicinity of the surface 15 (in the thickness direction), and the cell diameter in the vicinity of the surface 15. However, in the present invention, the “average cell diameter” indicates the average value of the cell diameters of all the foamed cells 20 in the thickness direction. Yes. Incidentally, since the average cell diameter has substantially the same value as the average cell diameter of the foamed cells 20 existing in the middle part in the thickness direction of the conductive elastic body layer 14, the average cell diameter is arbitrarily selected from the foamed cells 20 present in the middle part. It can also be obtained by calculating the average cell diameter of the foamed cells 20 selected for. Further, in the present invention, the foam cell 20 is mostly a single-bubble type, but the major axis is not a true sphere, and when the shape does not become a constant diameter such as an oval sphere, the major axis is a cell. It is adopted as the diameter.

  Further, in the present invention, the thickness (d in FIG. 2) of the skin layer 18 formed on the conductive elastic layer 14 is adjusted to be in the range of 100 to 350 μm, preferably 150 to 300 μm. As a result, the hardness of the developing roll 10 can be advantageously reduced, and the stress on the toner can be alleviated. When the thickness of the skin layer 18 is less than 100 μm, the surface of the roll 17 is roughened because irregularities corresponding to the shape of the foamed cell 20 located immediately below the skin layer 18 appear on the roll surface 17. Thus, the roll surface 17 cannot be made to have the desired surface roughness (Ra). Conversely, if the roll surface 17 exceeds 350 μm, the surface hardness of the conductive elastic layer 14 is increased, and the effect of adopting foam rubber is adopted. Cannot be obtained.

  Thus, in the electroconductive elastic body layer 14 according to the present invention, the average cell diameter of the foamed cells is 20 to 200 μm, and the thickness of the skin layer is 100 to 350 μm. Specifically, the Asker C hardness is 65 ° or less and the MD-1 hardness is 40 ° or less), and the developing roll 10 is provided with excellent flexibility. In addition, by adjusting the average cell diameter of the foamed cells 20 and the thickness of the skin layer 18 to the above specific range, good anti-sag properties are ensured, deformation at the press contact portion becomes gentle, and press contact marks are generated. It becomes difficult to remain.

  The foaming state such as the average cell diameter of the foamed cell 20 and the thickness of the skin layer 18 as described above is not limited to the blending ratio of the foaming agent and the heating conditions (foaming / vulcanization or crosslinking conditions). It can also be changed by changing the blending ratio of the agent and adjusting the timing of curing and foaming of the millable rubber material. In general, when the curing is delayed, the cell diameter becomes large or the skin layer becomes thin. On the other hand, when the curing is accelerated, the foaming hardly proceeds, and the cell diameter tends to be small or the skin layer tends to be thick. Therefore, in the present invention, the heating conditions and the blending ratio of the foaming agent, the catalyst and the retarder are appropriately set so as to be in the above range.

  In the present invention, the surface roughness (Ra: arithmetic average roughness) of the conductive elastic layer 14 is preferably 1.35 μm or less, more preferably 1.25 μm or less. This is because the surface roughness of the roll surface 17 tends to be smaller than the surface roughness of the conductive elastic layer 14 when the coat layer 16 is formed on the outer peripheral surface (15) of the conductive elastic layer 14. Therefore, by setting the surface roughness (Ra) of the surface 15 of the conductive elastic layer 14 within the above range, the surface roughness (Ra) of the roll surface 17 is more advantageously adjusted according to the desired range. Because it becomes possible. In the present invention, the surface roughness (Ra) is measured according to JIS-B-0601-1994.

  A coat layer 16 made of a soft or soft material is integrally formed on the outer peripheral surface of the conductive elastic layer 14 as described above. Examples of the soft material include polyamide resin such as N-methoxymethylated nylon, polyester resin, urethane resin, fluorine resin, acrylic resin, acrylic silicone resin, butyral resin (PVB), alkyd resin, fluorine-modified acrylate resin, and the like. These resin materials and rubber materials such as nitrile rubber and urethane rubber can be used, and these resin materials and rubber materials are used alone or in combination of two or more. Among these, urethane resins can be particularly preferably employed because of their good flexibility.

Thus, the conductive agent as described above is blended with such a material, and the volume resistivity is generally adjusted to about 10 ³ to 10 ⁸ Ωcm. Further, in such a soft material, if necessary, a known crosslinking agent, various compounding agents, additives and the like are blended in the same blending ratio as in the past, and are used as a material for forming the coat layer 16. Used. By forming the coating layer 16 with such a forming material, the elastic body layer 14 is protected, toner deposition / adhesion on the roll surface 17 can be suppressed, and the developing roll 10 has high wear resistance. Can be secured.

  Further, the thickness of the coating layer 16 is not particularly limited, but in the present invention, in order to advantageously realize the reduction in hardness of the developing roll 10, it is preferably 1 to 30 μm, more preferably The thickness is preferably 5 to 20 μm. This is because when the coat layer 16 is thinner than the above range, the durability of the coat layer 16 is impaired, and there is a risk of scraping or peeling. Conversely, when the coat layer 16 is thicker than the above range, This is because the hardness of the roll surface 17 may increase.

  In FIG. 1, one coat layer (coating layer) 16 is formed on the outer peripheral surface of the conductive elastic layer 14. However, the conductive elastic layer 14 and the coat layer are formed as necessary. It is also possible to configure the coat layer with two or more layers by interposing or laminating another coat layer (coating layer) made of a rubber material or a resin material between the layer 16 and the outer peripheral surface of the coat layer 16. It is. Thus, when there are a plurality of coat layers, it is desirable that the total thickness of all the coat layers is within the above thickness range.

  In the present invention, the surface roughness of the coating layer 16, that is, the surface roughness (Ra) of the roll surface 17 that is the product surface is less than 0.50 μm, preferably 0.40 μm or less. As a result, toner accumulation / adhesion on the roll surface 17 can be prevented, and toner filming due to toner accumulation can be advantageously prevented. When the surface roughness of the roll surface 17 is 0.50 μm or more, toner accumulates and adheres to the recesses formed on the roll surface 17, and vertical stripes appear in the image (filming), etc. There is a risk of image quality deterioration.

  By the way, when manufacturing the developing roll 10 of this embodiment having such a structure, a conventionally known method can be adopted. For example, the operation is advanced in the following procedure.

  Specifically, first, a crosshead extrusion device is used, and the shaft body 12 is set in the extrusion device by passing the shaft body 12 through the head portion of the extrusion device, and the conductive material mainly composed of a millable rubber material. Conductive foam rubber forming material (conductive elastic layer forming material) is fed from the hopper of the extrusion apparatus. Thereafter, a cylindrical conductive foamed rubber-forming material is extruded directly onto the outer peripheral surface of the shaft body 12, thereby forming a layer (extrusion molding) of an unvulcanized (uncrosslinked) / unfoamed foamed rubber-forming material. Body) is formed on the surface of the shaft body 12 with a predetermined thickness. The extrusion method may be continuous extrusion or batch extrusion, and a general speed can be adopted regardless of the extrusion speed.

  Then, after the integrated product of the extruded product and the shaft 12 is set in a known cylindrical mold having a molding cavity larger than the outer diameter of the extruded product, a heating operation (foaming / vulcanizing or The foamed base roll in which the foamed rubber forming material is foamed and cured by forming a conductive elastic body layer 14 made of foamed rubber on the outer peripheral surface of the shaft body 12 is produced. It is done. At this time, the heating conditions are appropriately set according to the type of the rubber material and the blending amount of the foaming agent so as to obtain a foam cell and a skin layer of a desired size, and preferably A suitable combination of heating temperature and heating time is selected from a heating temperature of about 130 to 250 ° C. and a heating time of about 5 to 60 minutes.

  Thereafter, the foam base roll obtained by foam molding as described above is removed from the cylindrical mold. The surface of the foam base roll thus demolded has a predetermined surface roughness and can be used without polishing the surface, but is subjected to a polishing process if necessary. And the coating layer 16 is formed by the well-known coating method similarly to the past on the outer peripheral surface (15) of the conductive elastic body layer 14. More specifically, the coating layer forming material is dissolved in an organic solvent, and this is applied to the foam base roll surface (15) by a known coating technique such as dipping, spraying, or roll coating, Thereafter, a heat treatment is performed to form the coat layer 14. Under the present circumstances, generally as a heating condition, the heating temperature of about 140-200 degreeC and the heating time of about 30-90 minutes are employ | adopted.

  In this way, as shown in FIG. 1, the conductive elastic body layer 14 made of conductive foam rubber and the coat layer made of a soft material are formed around the shaft body 12 from the inner side to the outer side in the roll radial direction. Thus, the developing roll 10 in which 16 and 16 are sequentially laminated together is obtained.

  In the developing roll 10 having such a configuration, the conductive elastic body layer 14 is made of foamed rubber obtained by foaming a millable rubber material, which is compared with the case where a liquid rubber material is used. Thus, the foamed cells 20 having a small average cell diameter can be uniformly formed in the circumferential direction and the axial direction.

  Further, the thickness of the skin layer 18 formed on the surface of the conductive elastic layer 14 is formed to be 100 to 350 μm, and the average cell diameter of the foamed cells 20 is 20 to 200 μm. Therefore, a reduction in hardness (softening) can be realized advantageously, and a good settling resistance can be secured. Therefore, the stress on the toner is alleviated, and the occurrence of filming due to toner deformation or the like can be advantageously prevented, and the occurrence of horizontal stripes in the image due to the difficulty of leaving the pressure contact marks is advantageously prevented. Can be done.

  Moreover, in the developing roll 10, since the roll surface 17 has a surface roughness Ra of less than 0.50 μm and the roll surface 17 is smooth, toner accumulation on the roll surface 17 is prevented. Thus, filming due to toner accumulation can be advantageously prevented.

  The developing roll 10 according to the present invention as described above is used as a developing roll in a copying machine, a printer, a facsimile or the like using an electrophotographic system. In particular, in the developing roll 10 according to the present invention, since the roll surface 17 is a smooth surface, so that toner transportability can be satisfactorily achieved, by the electric mirror image force due to the charge of the toner, It can be advantageously used in an electrophotographic apparatus (for example, see JP-A-2002-6632) having a developing system in which charged toner is held on the surface of a developing roll.

  The exemplary embodiments of the present invention have been described in detail above. However, the embodiments are merely examples, and the present invention is limited in any way by specific descriptions according to such embodiments. It should be understood that it is not interpreted.

  For example, in the above example, as a method for producing the developing roll 10, in particular, as a layer forming method for the conductive elastic body layer 14, a layer made of a foam rubber forming material on the outer peripheral surface of the shaft body 12 using a crosshead extrusion device. Exemplified by the method of extrusion molding to form a single body and subject to heating operation, but after extruding a cylindrical body made of unvulcanized (uncrosslinked) and unfoamed foam rubber forming material, After inserting the shaft body 12 into the inner hole of the extruded molded body and performing a predetermined heating operation, or after setting the shaft body 12 in a known cylindrical mold, the inner surface of the cylindrical mold Other known methods such as a casting method in which a kneaded foam rubber-forming material is injected into a molding cavity formed between the shaft body 12 and the shaft body 12 and a predetermined heating operation is performed can be employed. .

  In addition, as a method of heating an integral body of the extrusion molded body and the shaft body 12 and foaming / curing the unvulcanized (uncrosslinked) / unfoamed foam rubber forming material, the mold foaming as in the above example can be performed. In addition, it is also possible to employ other known methods such as free foaming in which hot air is directly applied to the surface of the extruded product. In addition, in the case of mold foaming using an extrusion-molded body, the greater the distance between the inner surface of the mold and the extrusion-molded body, the more difficult heat is transferred to the surface of the extrusion-molded body, and foaming near the surface is caused. When the distance is short, the foaming ratio tends to be small and low hardness tends to be difficult, so it is more preferable to apply hot air to the surface. Can be adopted.

  In addition, although not enumerated one by one, the present invention can be carried out in a mode with various changes, modifications, improvements, etc. based on the knowledge of those skilled in the art. It goes without saying that any one of them falls within the scope of the present invention without departing from the spirit of the present invention.

  Some examples of the present invention will be shown below to clarify the present invention more specifically. However, the present invention is not limited by the description of such examples. Needless to say.

-Preparation of conductive foam rubber forming material (conductive elastic layer forming material)-
First, butadiene rubber (BR, UBEPOL-BR130B, manufactured by Ube Industries) and styrene butadiene rubber (SBR, NIPOL NS112R, manufactured by Nippon Zeon Co., Ltd.) are prepared as millable rubber materials, while silicone oil ( TSF484, manufactured by GE Toshiba Silicone Co., Ltd.) as a conductive agent, carbon (Ketjen EC300J, manufactured by Lion Corporation) as a blowing agent, sodium bicarbonate as a catalyst, chloroplatinic acid, and as a retarder, Each diallyl maleate was prepared. Then, 5 parts by weight of a cross-linking agent, 10 parts by weight of a conductive agent, 30 ppm of catalyst, and 0.5 parts by weight of a retarder are blended with 100 parts by weight of the millable rubber material. The foamed rubber forming materials according to Examples 1 to 10 and Comparative Examples 1 to 12 were prepared by blending so as to have the blending composition of

-Preparation of coating layer forming material-
Moreover, polyurethane (Himlen Y-258, manufactured by Dainichi Seika Kogyo Co., Ltd.) and carbon black (MA-8, manufactured by Mitsubishi Chemical Corporation) were prepared as various components constituting the coating layer forming material. Then, 100 parts by weight of polyurethane is dissolved in MEK so as to have the composition shown in Tables 1 and 2 below, and then 70 parts by weight of carbon black is blended therein to prepare a coating liquid for a coating layer forming material. did.

-Production of base roll-
On the outer peripheral surface of a shaft body (outer diameter: 6 mm) to which a predetermined conductive adhesive is applied in advance by a crosshead extrusion device using the foam rubber forming materials according to Examples 1 to 10 and Comparative Examples 1 to 12 The foamed rubber forming material was directly extruded. For Examples 1 to 10 and Comparative Examples 1 to 11 in which the foaming agent was blended, the outer diameter of the extruded product was 10 mm, while for Comparative Example 12 in which the foaming agent was not blended, extrusion molding was performed. The outer diameter of the body was 12 mm.

  Then, the obtained extrusion molded body and shaft body are set in a mold, oven-crosslinked and foamed, and then removed from the mold, on the outer peripheral surface of the core metal (shaft body). Base rolls according to Examples 1 to 10 and Comparative Examples 1 to 12 in which conductive elastic layers (outer diameter: 12 mm) were integrally formed were produced. In addition, as molding conditions (heating conditions), the temperature and time shown in the following Table 1 or Table 2 were respectively employed.

-Production of developing roll-
The surface of the base roll prepared above is coated with the coating liquid of the coating layer forming material using a roll coater, and this is subjected to oven crosslinking under the conditions of 180 ° C. × 60 minutes. A layer (thickness: 10 μm) was formed on the outer peripheral surface of the base roll to produce developing rolls according to Examples 1 to 10 and Comparative Examples 1 to 12.

  Then, the following measurements were performed using the base rolls according to Examples 1 to 10 and Comparative Examples 1 to 12 obtained above and the developing rolls according to Examples 1 to 10 and Comparative Examples 1 to 12. The results are shown in Table 3 and Table 4 below.

-Measurement of surface roughness-
The surface roughness (Ra: arithmetic average roughness) of the base roll (conductive elastic body layer) and the developing roll (coat layer) was measured using a surface roughness meter: Surfcom 1400D (manufactured by Tokyo Seimitsu Co., Ltd.) in the axial direction. A total of 9 points were measured in the vicinity of both ends and at the center, respectively, in the circumferential direction, and the average value was obtained. In addition, the measurement was performed based on JIS-B-0601-1994.

-Measurement of MD-1 hardness-
The MD-1 hardness of the base roll and the developing roll was measured by using a micro rubber hardness meter: Micro Durometer MD-1 UPX533M-A (manufactured by Kobunshi Keiki Co., Ltd.), in the vicinity of both ends in the axial direction and at the center. A total of 9 points were measured in each direction, and the average value was obtained. In the measurement of MD-1 hardness, the hardness of the surface portions of the base roll and the developing roll can be measured.

-Measurement of Asker C hardness-
Rubber hardness tester: Using Asker type C (manufactured by Kobunshi Keiki Co., Ltd.), measure 9 locations in total, 3 in the circumferential direction, near both ends in the axial direction of the base roll and developing roll, The average value was obtained.

-Evaluation of sag resistance (measurement of deformation)-
An environment of 40 ° C. × 95% RH in a state where a metal roller having a diameter of 30 mm is brought into contact with the base roll and the developing roll in an axially parallel state and a load is applied so that the pressing amount is 50 μm and the metal roller is pressed. Below, left for a week. Thereafter, the load was removed, and after 1 hour, the amount of deformation (sag amount) before pressing was measured. In addition, it has shown that this amount of deformation | transformation is excellent in the settling resistance, so that a value is small. In this measurement condition, if the amount of deformation is 12 micrometers or less, it will evaluate that a settling resistance is favorable. be able to.

-Measurement of average cell diameter-
The developing roll is cut in a direction perpendicular to the axis at the center in the axial direction, and the cross section is imaged at a magnification of 200 times using a laser microscope (manufactured by Keyence Corporation). From the image, the average cell diameter is determined. Asked. Specifically, the center part in the thickness direction of the conductive elastic layer is selected at 10 locations in the circumferential direction, arbitrarily measured by measuring the cell diameters at those 10 locations, and the average value is calculated. The cell diameter was determined.

-Measurement of skin layer thickness-
The developing roll is cut in a direction perpendicular to the axial center at the center in the axial direction, and the cross section is imaged at a magnification of 200 times using a laser microscope (manufactured by Keyence Corporation). The three points were measured at a pitch of 120 ° in the circumferential direction, and the average value was obtained. In measuring the thickness, the distance from the surface to the closest foam cell was measured at the measurement site (range of 1 mm in the circumferential direction).

-Filming evaluation-
In an environment of 40 ° C. × humidity of 95% RH, the toner cartridge assembled with the developing roll was attached to an idle rotating jig, and the developing roll was rotated (durability) for 48 hours. After the endurance, the toner cartridge is attached to a commercially available laser printer (HP CLJ-3800, manufactured by Hewlett-Packard Company), a black solid image is printed, and a vertical stripe (a stripe perpendicular to the axial direction of the roll) The presence or absence was visually observed. Then, the evaluation is performed based on the evaluation criteria that the image has no vertical stripes, the image has a slight vertical stripe confirmed, and the image has a vertical stripe clearly confirmed x. It was.

  As apparent from Table 3 above, in Examples 1 to 10 in which the average cell diameter, the thickness of the skin layer, and the surface roughness (Ra) of the roll surface are within the specific range, all It can be seen that the deformation amount is less than 12 μm, and that the settling resistance is sufficiently secured. In Examples 1 to 10, the MD-1 hardness and Asker C hardness of the developing roll are 40 ° or less and 63 ° or less, respectively, and flexibility can be imparted satisfactorily. . Further, the filming judgment is also “good”, and it is recognized that the stress on the toner can be alleviated and the toner can be prevented from being deposited on the toner surface.

  On the other hand, as apparent from Table 4, in Comparative Examples 1 to 5 in which the thickness of the skin layer exceeded 350 μm, the MD-1 hardness and Asker C hardness of the developing roll were 43 ° or more and 66, respectively. More than °, the flexibility is inferior and the filming judgment is x. Further, in Comparative Example 6 in which the average cell diameter exceeds 200 μm, the surface roughness (Ra) of the roll surface exceeds 0.50, and the determination of filming is x. Furthermore, even in Comparative Examples 7 and 8 in which the thickness of the skin layer is less than 100 μm, the surface roughness (Ra) of the roll surface exceeds 0.50, and the determination of filming is x. Furthermore, although the average cell diameter and the thickness of the skin layer are within the above specific range, even in Comparative Examples 9 and 10 where the surface roughness (Ra) of the roll surface exceeds 0.50, The determination of ming is x. Further, in Comparative Example 11 in which the average cell diameter exceeds 200 μm and the thickness of the skin layer is less than 100 μm, the surface roughness (Ra) of the roll surface is as large as 1.64, and the anti-sag property is inferior. In addition, the filming judgment is x. In addition, in Comparative Example 12 in which no foaming agent was contained and foamed cells were not formed, the MD-1 hardness and Asker C hardness of the developing roll were as extremely high as 58 ° and 81 °, respectively. The determination of ming is x.

It is a cross-sectional explanatory drawing which shows an example of the image development roll according to this invention. It is the elements on larger scale in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Developing roll 12 Shaft body 14 Conductive elastic body layer 15 Surface 16 Coat layer 17 Roll surface 18 Skin layer 20 Foam cell

Claims (3)

A developing roll in which a conductive elastic layer is formed on the outer peripheral surface of the shaft body, and at least one coat layer is further provided on the outer peripheral surface of the conductive elastic layer,
The conductive elastic layer is made of foamed rubber obtained by foaming a millable rubber material, has an average cell diameter of 20 to 200 μm, a skin layer having a thickness of 100 to 350 μm on the surface thereof, and a roll A developing roll characterized in that the surface roughness Ra is less than 0.50 μm.   The developing roll according to claim 1, wherein the surface roughness of the conductive elastic layer is Ra: 1.35 μm or less. The developing roll according to claim 1, wherein the coating layer is formed in a thickness of 1 to 30 μm.

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