JP5577207B2 - Conductive roller, manufacturing method thereof, developing device, and image forming apparatus - Google Patents

Description

  The present invention relates to a conductive roller, a method for manufacturing the same, a developing device, and an image forming apparatus. More specifically, the present invention suppresses the occurrence of band-like image defects even in a high-temperature and high-humidity environment and has a desired image density as a whole image. Conductive roller and developing device that contributes to the formation of high-quality images, suppresses the occurrence of band-like image defects even in high-temperature and high-humidity environments, and forms high-quality images with the desired image density as a whole image The present invention relates to an image forming apparatus capable of performing the same, and a method for manufacturing the conductive roller.

  Various image forming apparatuses using an electrophotographic method are employed in printers such as laser printers and video printers, copiers, facsimiles, and multi-function machines thereof. An image forming apparatus using an electrophotographic system includes various types of rollers. Examples of the various rollers include a conductive roller having conductivity or semi-conductivity, and an elastic roller having a relatively low hardness. Specifically, the conductive roller includes a charging roller for uniformly charging an image carrier such as a photoconductor, a developing roller for carrying and transporting the developer and supplying the developer to the image carrier, and a developer on the developing roller. Examples thereof include a developer supply roller that is supplied while being charged, and a fixing roller that fixes a developer image transferred to a recording material such as recording paper. These various rollers are usually provided with an elastic layer formed of various rubbers such as silicone rubber and urethane rubber, and a surface layer formed on the outer periphery thereof, and characteristics suitable for functions and uses, for example, It has surface roughness.

  For example, the developing roller needs to supply a predetermined amount of developer to the image carrier in order for the image forming apparatus to form an image having a predetermined image density. It is important to have a property of carrying and transporting physically (hereinafter, referred to as developer transportability) in addition to the property of carrying and transporting the toner. In order to secure a desired developer conveyance amount in the developing roller, it has been proposed to adjust the surface roughness to a specific value.

  As a technique for adjusting the surface roughness of the developing roller, a technique for incorporating fine particles into the elastic layer or the surface layer has been proposed. Specifically, Patent Document 1 discloses that “a shaft body, an elastic body layer whose outer peripheral surface is formed into a rough surface along the outer periphery of the shaft body, and a rough surface shape of the surface of the elastic body layer. And a conductive roll formed on the outer peripheral surface of the elastic body layer and containing insulating powder particles, the hardness of the elastic body layer (JIS-A) Is set to 5 to 30 °, the average particle size of the insulating powder particles contained in the conductive resin layer is set to 1.0 to 5.0 μm, and the surface roughness (Ra) of the developing roll is set to “Developing roll characterized in that it is set to 0.7 to 3.5 μm” (Claim 1).

  Patent Document 2 includes a “developing roll comprising a base roll, an intermediate layer formed directly on the outer periphery thereof or via another layer, and a surface layer formed on the outer periphery of the intermediate layer, A developing roll characterized in that particles for forming a surface roughness are dispersed in the intermediate layer and the surface layer, and the particle size of the particles in the surface layer is smaller than the particle size of the particles in the intermediate layer Is described (claim 1).

  Patent Document 3 states that “in a developing roller configured by arranging a conductive shaft on a central axis and laminating a single layer or a plurality of layers concentrically around the conductive shaft, the surface layer has pH. "Developing roller characterized in that it contains 5 or less fine particles" (Claim 1).

  Patent Document 4 states that “in the developing roller for an electrophotographic apparatus in which an inner layer and a surface layer having conductive elasticity are provided concentrically on the outer periphery of a rotating shaft and a developer is carried on the outer periphery of the surface layer, Is a developing roller for an electrophotographic apparatus, comprising a coating film obtained by adding a conductivity imparting agent to a synthetic resin and 5 to 70% by weight of inorganic particles having a particle diameter of 0.5 to 5 μm. (Claim 1).

  In Patent Document 5, “a conductive roll having a shaft, an inner layer formed along the outer peripheral surface of the shaft, and a rough surface formed on the outer peripheral surface of the inner layer, "Conductive roll characterized in that a surface layer containing particles having an average particle diameter equal to or less than the ten-point average roughness (Rz) of the rough surface of the inner layer is formed on the surface" is described ( Claim 1).

  In a roller containing such fine particles, for example, the developing roller of Patent Document 3, “configured by dip coating a base resin in which fine particles having a predetermined pH are uniformly dispersed on the outer periphery of the elastic layer” As shown (see column 0054), the fine particles are uniformly dispersed in the surface layer.

JP-A-10-254235 JP 2003-228231 A Japanese Patent Laid-Open No. 11-143212 Japanese Patent Laid-Open No. 11-174822 JP 2003-228213 A

  By the way, in the image forming apparatus as described above, as a method of supplying the developer to the image carrier, the developer roller of the developing device and the image carrier are brought into contact or pressure contact, and the developer is directly applied from the developer roller to the image carrier. There are a contact type to be supplied and a non-contact type in which the developing roller of the developing device and the image carrier are arranged apart from each other, and the developer carried on the developing roller jumps to the image carrier. In these image forming apparatuses, the developing roller is mounted with a part of the outer peripheral surface thereof exposed from the housing.

  When the image forming apparatus mounted with the developing roller in such a state is placed in a high temperature and high humidity environment, when the image forming apparatus is subsequently operated to form an image, a part of the image has a predetermined image density. It was newly confirmed that a deep high density portion was formed. Such a high density portion may be scattered in the image, but usually, it is often generated in a dotted line shape that is continuous along the axial direction of the developing roller or a continuous belt shape in the axial direction. . Therefore, in the present invention, the image defect in which the high density portion is formed is referred to as “strip image defect (banding defect)”. However, the strip image defect includes an image defect in which the high density portion is scattered in the image. Includes. The present inventors speculate that the belt-like image defect may be caused by the exudation of the silicone oligomer remaining in the silicone elastic layer on the surface of the developing roller that contacts the developer in a high-temperature and high-humidity environment. did.

  It has also been newly confirmed that such a strip-like image defect is a problem that conflicts with the developer transportability. That is, if the content of the fine particles is increased to increase the developer transportability of the developing roller in order to form an image having a predetermined image density, the belt-like image defect occurs remarkably, while the belt-like image is generated. If the content of the fine particles is reduced in order to prevent the occurrence of defects, the developer transportability may be lowered and an image having a predetermined image density may not be formed.

  The belt-like image defect is particularly noticeable when a halftone image is formed after an image forming apparatus equipped with a developing roller having a silicone elastic layer is placed in a high-temperature and high-humidity environment as in Patent Document 1. It was also confirmed that it would occur.

  As described above, when an image forming apparatus having a conventional developing roller, particularly a developing roller having a silicone elastic layer, is placed in a high-temperature and high-humidity environment, it is difficult to achieve both the belt-like image defect and the image density. It has been newly confirmed that a high-quality image having a desired image density cannot be formed as an entire image.

  Accordingly, the present invention provides a conductive roller that contributes to the formation of a high-quality image having a desired image density as an entire image, by suppressing the occurrence of band-like image defects even in a high-temperature and high-humidity environment. It is an object of the present invention to provide a developing device including a conductive roller.

  It is another object of the present invention to provide an image forming apparatus capable of suppressing the occurrence of a band-like image defect even under a high temperature and high humidity environment and forming a high quality image having a desired image density as an entire image. And aim.

  Furthermore, the present invention provides a method for producing a conductive roller that contributes to the formation of a high-quality image having a desired image density as a whole image by suppressing the occurrence of strip-like image defects even in a high-temperature and high-humidity environment. The purpose is to provide.

As means for solving the problems,
Claim 1 comprises a silicone elastic layer formed on the outer peripheral surface of the shaft body and a coat layer formed on the outer peripheral surface of the silicone elastic layer, and a ten-point average roughness Rz of 3 to 12.0 μm. a conductive roller is, the coating layer includes an inner area of the inorganic filler-free, the average particle size possess an outer region containing the inorganic filler of less than 5.0 .mu.m, the It was formed by applying the outer region forming resin composition containing the inorganic filler to the outer region forming resin composition in a coated state on the outer peripheral surface of the silicone elastic layer, and then curing the resin composition integrally. A conductive roller having a single layer structure, wherein the resin as the main component contained in the inner region and the resin as the main component contained in the outer region are of the same type ,
Region claim 2, wherein the outer region is a region having a thickness of up 1~20μm from the outer peripheral surface of the coating layer, the inner region having a thickness of up 1~20μm from the inner surface of the coating layer The conductive roller according to claim 1 , wherein
Claim 3 is a developing device comprising the conductive roller according to claim 1 or 2 ,
A fourth aspect of the present invention is an image forming apparatus including the conductive roller according to the first or second aspect .
According to a fifth aspect of the present invention, there is provided an inner region forming resin composition containing a solvent on the outer peripheral surface of the silicone elastic layer formed on the outer peripheral surface of the shaft body, and an average on the surface of the inner region forming resin composition. A step of applying an outer region forming resin composition containing an inorganic filler having a particle size of less than 5.0 μm, and heating and curing the inner region forming resin composition and the outer region forming resin composition; and a step of,
The resin component which is the main component contained in the inner region forming resin composition and the resin component which is the main component contained in the outer region forming resin composition are the same method for producing a conductive roller.

The conductive roller according to the present invention comprises a coat layer having an inner region substantially free of inorganic filler and an outer region containing an inorganic filler having an average particle size of less than 5.0 μm, ten-point average roughness (Rz) Ri 3~12.0μm der, outer region the coat layer containing an inorganic filler in the inner area forming resin composition on the outer peripheral surface is in the coating state of the silicone elastomer layer Resin which is a main component contained in the inner region and a resin which is a main component contained in the outer region, having a single-layer structure formed by applying the resin composition for formation repeatedly and curing integrally since Ru allogeneic der and the ten-point average roughness (Rz) without having to increase the expense of the developer conveying property obtained by said be formed even if the halftone image in the environment of high temperature and high humidity strip image The occurrence of defects can be prevented. The developing device and the image forming apparatus according to the present invention include the conductive roller according to the present invention. Therefore, according to the present invention, the conductive roller that contributes to the formation of a high-quality image having a desired image density as a whole image by suppressing the occurrence of band-like image defects even in a high-temperature and high-humidity environment, and A developing device including the conductive roller can be provided. In addition, according to the present invention, there is provided an image forming apparatus capable of suppressing the occurrence of a strip-like image defect even under a high temperature and high humidity environment and forming a high quality image having a desired image density as an entire image. be able to.

Furthermore, according to the method for producing a conductive roller according to the present invention , the resin component as the main component contained in the resin composition for forming the inner region and the resin component as the main component contained in the resin composition for forming the outer region Are the same, the step of applying the inner region forming resin composition to the outer peripheral surface of the silicone elastic layer, the step of applying the outer region forming resin composition to the surface of the inner region forming resin composition, and the inner side By sequentially performing the step of heating and curing the region forming resin composition and the outer region forming resin composition, the inner region substantially free of inorganic filler and the average particle size is 5.0 μm. A coat layer having an outer region containing less than the inorganic filler can be formed on the outer peripheral surface of the elastic layer. Therefore, according to the present invention, it is possible to manufacture a conductive roller that contributes to the formation of a high-quality image having a desired image density as a whole image by suppressing the occurrence of a band-like image defect even in a high-temperature and high-humidity environment. A method can be provided.

FIG. 1 is a perspective view showing a conductive roller of an embodiment of the conductive roller according to the present invention. FIG. 2 is an enlarged schematic view showing a cross section of the conductive roller according to one embodiment of the present invention when the conductive roller is cut along a plane perpendicular to the axis. FIG. 3 is a schematic view showing an example of an image forming apparatus according to the present invention.

  As shown in FIG. 1, the conductive roller 1 of one embodiment of the conductive roller according to the present invention includes a shaft body 2, a silicone elastic layer 3 formed on the outer peripheral surface of the shaft body 2, and a silicone elastic layer. 3 and a coat layer 4 formed on the outer peripheral surface. In the conductive roller 1 shown in FIG. 1, a silicone elastic layer 3 is formed on the outer peripheral surface of the shaft body 2 through an adhesive layer (also referred to as a primer layer) (not shown in FIG. 1) as desired. A coat layer 4 is formed on the outer peripheral surface of the silicone elastic layer 3 through an adhesive layer (also referred to as a primer layer) (not shown in FIG. 1) as desired.

  The conductive roller 1 has a 10-point average roughness Rz of 3 to 12.0 μm on the surface thereof, that is, the surface of the coat layer. If the ten-point average roughness Rz (μm) is less than 3 μm, the surface of the conductive roller 1 becomes too flat, and the developer transportability may be lowered, and the image density of the formed image may be reduced. When the ten-point average roughness Rz (μm) exceeds 12.0 μm, the surface of the conductive roller 1 is rich in undulations, and the developer is conveyed more than necessary, and density unevenness may occur in the formed image. . Therefore, when the ten-point average roughness Rz of the conductive roller 1 is within the above range, the surface state of the conductive roller 1 adapts to the developer, and the conductive roller 1 exhibits a desired developer transportability. The ten-point average roughness Rz (μm) is more preferably 5 to 10 μm, and particularly preferably 7 to 8 μm, in that the developer transportability is further improved. It is preferable that the conductive roller 1 has the ten-point average roughness Rz (μm) in the circumferential direction and the axial direction in the above-mentioned range from the viewpoint of uniform developer transportability in the circumferential direction and the axial direction. The ten-point average roughness Rz (μm) is determined according to JIS B 0601-1984 by a surface roughness meter (trade name “590A”, manufactured by Tokyo Seimitsu Co., Ltd.) equipped with a measuring probe having a tip radius of 2 μm. Set the roller 1 and measure the roughness of at least three points on the surface of the conductive roller 1 along the circumferential direction or the axial direction with a measurement length of 2.4 mm, a cutoff wavelength of 0.8 mm, and a cutoff type Gaussian. Let these be the arithmetic average values.

  The ten-point average roughness Rz (μm) in the conductive roller 1 is adjusted by the content and average particle diameter of particles such as an inorganic filler contained in the coat layer 4 described later, the thickness of the coat layer 4, and the like. Can do.

The conductive roller 1 has conductivity. When the conductive roller 1 has conductivity, in addition to the developer transportability, it exhibits the characteristics of electrostatically carrying and transporting the developer, so that an image having a desired image density can be formed. Can do. Examples of the conductivity include electrical resistance (temperature 20 ° C., relative humidity 50%). This electrical resistance (temperature 20 ° C., relative humidity 50%) is preferably 1 × 10 ⁴ to 1 × 10 ⁹ Ω. The electrical resistance is, for example, an electrical resistance meter (trade name: ULTRA HIGH RESISTANCE METER R8340A, manufactured by Advantest Co., Ltd.), the conductive roller 1 is placed horizontally, a thickness of 5 mm, a width of 30 mm, and conductivity A gold-plated plate having a length on which the entire silicone elastic layer 3 of the roller 1 can be placed is used as an electrode, and a load of 500 g is supported on both ends of the shaft 2 in the conductive roller 1 (total load 1000 g). Then, DC100V is applied between the shaft body 2 and the electrode, the value of the electric resistance meter after 1 second is read, and the measurement can be performed according to the method of setting this value as the electric resistance value.

The conductive roller 1 can charge the developer. For example, the charge amount for charging the developer is preferably about 10 to 60 μC / g or about −60 to −10 μC / g, and about 15 to 50 μC / g or about −50. A charge amount of ˜−15 μC / g is even more preferable, and a charge amount of about 35 to 50 μC / g or a charge amount of about −50 to −35 μC / g is particularly preferable. When the conductive roller 1 can charge the developer with the above charge amount, for example, when the conductive roller 1 is used as a developing roller, the developer charged with a desired charge amount is applied to the image carrier. It is possible to supply high-quality images. Here, the conductive roller 1 is mounted on an image forming apparatus (trade name “MICROLINE 1032PS” manufactured by Oki Data Corporation, equivalent to a resolution of 1200 dpi) in an environment where the developer is charged at 20 ° C. and 50% relative humidity. Then, after the black solid printing is performed, the black solid printing is forcibly stopped, the conductive roller 1 is taken out of the image forming apparatus, and the developer adhered to the surface of the conductive roller 1 It can be measured by a suction type small charge amount measuring device having a suction port of 0.25 cm ² , for example, a trade name “210HS q / M METER” (manufactured by Trek Japan Co., Ltd.).

  When the conductive roller 1 is mounted on a contact-type image forming apparatus, it has elasticity so that a large and uniform contact width with the image carrier can be secured over a long period of time. preferable. For example, the hardness of the conductive roller 1 preferably has a JIS A hardness of 30-80. The JIS A hardness can be measured according to JIS K6253. When the conductive roller 1 is mounted on a non-contact type image forming apparatus, it may or may not have elasticity.

  As shown in FIG. 1, the shaft body 2 constituting the conductive roller 1 only needs to have good conductive properties, and is usually a so-called “core” made of iron, aluminum, stainless steel, brass, or the like. The shaft is called “gold”. Further, the shaft body 2 may be a shaft body that is made conductive by plating an insulating core body such as a thermoplastic resin or a thermosetting resin. Furthermore, the shaft body 2 may be a thermoplastic resin or a thermosetting resin. The shaft body may be formed of a conductive resin in which carbon black or metal powder is blended as a conductivity imparting agent. The shaft body 2 is adjusted to an appropriate diameter and axial length according to the image forming apparatus to be mounted. For example, the diameter of the shaft body 2 is preferably 4 to 10 mm.

  The silicone elastic layer 3 constituting the conductive roller 1 has elasticity. When the silicone elastic layer 3 has elasticity, a large and uniform contact width with the image carrier can be secured over a long period of time when mounted on a contact type image forming apparatus, and non-contact type image formation is possible. When attached to the apparatus, the regulating blade can function sufficiently.

  The silicone elastic layer 3 is formed by curing a rubber composition described later on the outer peripheral surface of the shaft body 2. The silicone elastic layer 3 only needs to have a hardness with which the conductive roller 1 has a JIS A hardness in the above range, and preferably has a JIS A hardness of 10 to 90. When the silicone elastic layer 3 has a JIS A hardness of 10 to 90, for example, when the conductive roller 1 is mounted on the image forming apparatus, the conductive roller 1 and a contacted body such as an image bearing member A large nip width can be secured. In particular, when the conductive roller 1 is mounted as a developer carrier, for example, a development roller, a large nip width between the conductive roller 1 and the image carrier is ensured, and the developer is efficiently charged and conveyed to improve development efficiency. Can be made. The JIS A hardness of the silicone elastic layer 3 can be measured according to JIS K6253.

  The thickness of the silicone elastic layer 3 is preferably 1 mm or more, and more preferably 5 mm or more. On the other hand, the upper limit of the thickness of the silicone elastic layer 3 is not particularly limited as long as the accuracy of the outer diameter of the silicone elastic layer 3 is not impaired. Generally, if the thickness of the silicone elastic layer 3 is excessively increased, Since the production cost rises, considering the practical production cost, the thickness of the silicone elastic layer 3 is preferably 30 mm or less, and more preferably 20 mm or less. For example, the thickness of the silicone elastic layer 3 is preferably 3 to 7 mm.

The silicone elastic layer 3 has conductivity. Examples of the conductivity include electrical resistance (temperature 20 ° C., relative humidity 50%). The electrical resistance (temperature 20 ° C., relative humidity 50%) is preferably 1 × 10 ² to 1 × 10 ⁶ Ω. The electrical resistance of the silicone elastic layer 3 can be measured basically in the same manner as the electrical resistance of the conductive roller 1 with the coat layer 4 removed from the conductive roller 1.

  The silicone elastic layer 3 contains a silicone rubber, and optionally contains a filler, a conductivity imparting agent, various additives, and the like. Examples of the silicone rubber include silicone-modified rubber and the like in addition to normal silicone rubber. Examples of the filler include inorganic fillers described later. The conductivity-imparting agent may be liquid or solid, and examples thereof include conductive powder and ion conductive material. Specific examples of the conductive powder include carbons for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT, in addition to conductive carbon such as ketjen black and acetylene black. In addition, metals such as titanium oxide, zinc oxide, nickel, copper, silver, germanium, and conductive polymers such as metal oxides, polyaniline, polypyrrole, polyacetylene, etc. can be mentioned. Specifically, for example, inorganic ionic conductive materials such as sodium perchlorate, lithium perchlorate, calcium perchlorate, and lithium chloride can be used. The conductivity imparting agent is added in an appropriate content so that a desired volume resistivity is obtained when the conductive roller 1 is used alone or in combination of two or more. For example, the content of the conductivity imparting agent can be 2 to 80 parts by mass with respect to 100 parts by mass of the silicone rubber. Examples of the additive include various additives contained in a rubber composition and the like.

  As shown in FIGS. 1 and 2, the coat layer 4 constituting the conductive roller 1 is formed as a single-layered layer of a resin composition cured on the outer peripheral surface of the silicone elastic layer 3. Therefore, unlike the surface layer formed of a seamless tube, the coat layer 4 does not compress the silicone elastic layer 3 in the axial direction, so even if it is formed thin, deformation such as wrinkles due to stress concentration occurs on the surface. The outer peripheral surface maintains a uniform state over a long period of time. The coat layer 4 is usually formed as a thin layer, and specifically, preferably has a layer thickness of 2 to 50 μm, more preferably 10 to 30 μm.

  The coat layer 4 contains a resin, and optionally a conductivity imparting agent and various additives. The resin may be a resin other than a silicone resin, and examples thereof include a urethane resin, a fluororesin, an acrylic resin, an acrylic-urethane resin, a polyamide resin, an alkyd resin, an epoxy resin, a phenol resin, and a mixture thereof. The coat layer 4 preferably contains a conductivity-imparting agent and has basically the same conductivity as that of the conductive roller 1. The conductivity imparting agent contained in the coat layer 4 is basically the same as the conductivity imparting agent described in the silicone elastic layer 3, and the conductivity imparting agent contained in the coat layer 4 and the silicone elastic layer 3 are the same. It may be the same or different from the conductivity imparting agent contained. When the coating layer 4 contains a conductivity-imparting agent, it is preferably contained uniformly in the coating layer 4. In the conductive roller 1, as shown well in FIG. 2, the inner region 4A and the outer region 4B. And is contained in. The content of the conductivity imparting agent is preferably 2 to 15 parts by mass, particularly preferably 5 to 10 parts by mass with respect to 100 parts by mass of the resin that forms the entire coat layer 4. Moreover, various additives contained in the resin composition etc. are mentioned as various additives.

  The coating layer 4 containing a resin, and optionally a conductivity-imparting agent and various additives has at least two regions, an inner region 4A including an inner surface thereof and an outer region 4B including an outer peripheral surface thereof. The area is functionally differentiated. That is, as clearly shown in FIG. 2, the inner region 4A contains a resin and the inorganic filler 7 is substantially absent, that is, substantially free of the inorganic filler 7; The silicone oligomer etc. which exists in the silicone elastic layer 3 are prevented from exuding. Here, “substantially free of inorganic filler” means that the inorganic filler is not actively contained in the inner region 4A, and does not include the case where it is inevitably contained. . The outer region 4 </ b> B contains a resin and an inorganic filler 7, that is, the inorganic filler 7 is unevenly distributed, and the ten-point average roughness within the range in the conductive roller 1 is realized. In short, the inner region 4A of the coat layer 4 contains a resin, optionally a conductivity imparting agent and various additives, and the outer region 4B of the coat layer 4 is a resin, an inorganic filler, and optionally a conductivity imparting agent. And various additives. As described above, the inner region 4A of the coat layer 4 greatly prevents the low-molecular compound such as a silicone oligomer from exuding and prevents the occurrence of the band-like image defect, and the outer region 4B affects the ten-point average roughness. This greatly contributes to developer transportability. Therefore, although the conductive roller 1 has a single-layer structure having the inner region 4A and the outer region 4B, it is possible to achieve both prevention of the belt-like image defect and developer transportability.

  The inner region 4A is a region including the inner surface of the coat layer 4, and is preferably a region having a thickness of 1 to 20 μm from the inner surface of the coat layer 4 toward the outer peripheral surface in the radial direction. Particularly preferred is a region having a thickness of. For example, the inner region 4A can have a thickness of up to 10 μm from the inner surface toward the outer peripheral surface in the radial direction. In the inner region 4A, the inorganic filler 7 described later is substantially not present, and even if it exists, for example, the content of the inorganic filler 7 is 100 mass of the resin forming the coat layer 4. It is preferable that it is 5 mass parts or less with respect to a part. If the thickness of the inner region 4A is within the above range, and if the inorganic filler 7 is not substantially present in the inner region 4A, exudation of silicone oligomer or the like can be highly prevented. Moreover, when this inner side area | region 4A contains particles, such as an electroconductivity imparting agent, it is preferable that these particles are microparticles | fine-particles whose average particle diameter is smaller than the inorganic type filler 7 mentioned later.

  The outer region 4B is a region including the outer peripheral surface of the coat layer 4. A region having a thickness of 1 to 20 μm from the outer peripheral surface of the coat layer 4 in the radial direction toward the inner surface is preferable, and a region having a thickness of 20 μm is preferable. For example, the outer region 4B can have a thickness of up to 10 μm from the outer peripheral surface toward the inner peripheral surface in the radial direction. The outer peripheral surface of the coat layer 4 can be, for example, a “center average line” in the ten-point average roughness Rz (JIS B 0601-1984). In the outer region 4B, the inorganic filler 7 is unevenly distributed, and most of the total inorganic filler 7 contained in the coat layer 4, for example, 90% by mass or more of the inorganic filler 7 is present. doing. When the thickness of the outer region 4B is within the above range, and when the majority of the inorganic filler 7 is present in the outer region 4B, it contains a sufficient amount of the inorganic filler 7 and is conductive. The surface state of the roller 1 can be adjusted appropriately.

  The inner region 4A and the outer region 4B preferably have the same thickness, and are preferably regions having a thickness that is half the total thickness of the coat layer 4, for example, the total thickness of the coat layer 4 Is 20 μm, the inner region 4A and the outer region 4B are preferably regions each having a thickness of 10 μm.

  The inorganic filler 7 contained in the outer region 4B is also referred to as an inorganic filler, and may be in a solid form such as powder or particulate, and examples thereof include inorganic particles and inorganic powder. Examples of the inorganic particles and inorganic powder include silica (including fumed silica, colloidal silica, etc.), calcium carbonate, zinc oxide, magnesium carbonate, and the like. The inorganic filler 7 may be used alone or in combination of two or more.

  The shape of the inorganic filler 7 is not particularly limited as long as it forms a solid form such as particles or powder, and examples thereof include a spherical shape, an elliptical spherical shape, and a plate shape. The inorganic filler 7 has an average particle size of less than 5.0 μm, preferably 1.0 μm or more and less than 5.0 μm, preferably 2.0 to 4.0 μm. It is particularly preferred to have an average particle size. When the average particle diameter of the inorganic filler 7 is within the above range, the ten-point average roughness Rz can be adjusted within the above range, and the conductivity of the conductive roller 1 can be ensured. The average particle diameter was determined by measuring the maximum outer diameter of a plurality of inorganic fillers 7 observed at a magnification of 2000 using a scanning electron microscope JSM-5200 (manufactured by JEOL Datum Co., Ltd.). The arithmetic average value of diameters.

  The inorganic filler 7 contained in the outer region 4B is preferably 10 parts by mass or more, and 16 to 40 parts by mass with respect to 100 parts by mass of the resin forming the outer region 4B of the coat layer 4. More preferably, it is 16-30 mass parts. When the inorganic filler 7 is contained in the outer region 4B in the content, the ten-point average roughness Rz in the above range is imparted to the conductive roller 1 while ensuring the conductivity of the conductive roller 1. be able to.

  The content of the inorganic filler 7 and the content of the conductivity imparting agent contained in the inner region 4A and the outer region 4B can be determined by thermogravimetric analysis (JIS K7120). Specifically, the total mass T of the inorganic filler 7 and the conductivity-imparting agent remaining after heating the test piece (mass I.) cut out from the inner region 4A and the outer region 4B to 700 ° C. is measured. Then, the difference (IT) between the mass I before heating of the test piece and the total mass T is calculated as the mass R of the resin in the test piece. Next, this residue is heated to 900 ° C., and the mass F of the remaining inorganic filler 7 is measured, and the difference (T−F) between the total mass T and the mass F is calculated as the mass C of the conductivity imparting agent. To do. From the masses thus obtained, the mass F of the inorganic filler 7 is converted to the value when the mass R of the resin is 100 parts by mass to obtain the content of the inorganic filler 7, and the mass of the resin. When R is 100 parts by mass, the value C is converted to the content of the conductivity-imparting agent by converting the mass C of the conductivity-imparting agent.

  The conductive roller 1 includes a coating layer 4 having a single-layer structure. The coating layer 4 has a ten-point average roughness Rz (μm) in the above range, and an inorganic filler 7 is provided in the inner region 4A. Since it is substantially free and the inorganic filler 7 is unevenly distributed in the outer region 4B, the object of the present invention can be well achieved. In particular, even in a high temperature and high humidity environment, for example, a high temperature environment with a temperature of 40 to 60 and a relative humidity of 80 to 98%, even if it is left for a relatively long period of time, for example, about 7 to 14 days, the occurrence of strip-like image defects is high Is prevented. Examples of the state of being placed in such a high temperature and high humidity environment include, for example, shipping in summer or stopping. The above-described effects can be sufficiently exerted even in recent high-precision image forming apparatuses. The reason for this is that when the conductive roller 1, particularly the part exposed from the developing device, is exposed to a high temperature and high humidity environment, low molecular compounds such as silicone oligomers present in the silicone elastic layer tend to exude. It is speculated that the coat layer 4 may prevent the low molecular weight compound such as a silicone oligomer from being leached out.

  Since the conductive roller 1 has the above characteristics, it is preferably used as a conductive roller for an image forming apparatus, for example, a charging roller, a developing roller, a transfer roller, or the like.

  Next, a method for manufacturing a conductive roller according to the present invention (hereinafter sometimes referred to as a manufacturing method according to the present invention) will be described. The manufacturing method according to the present invention includes a step of applying an inner region forming resin composition containing a solvent to an outer peripheral surface of a silicone elastic layer formed on an outer peripheral surface of a shaft body, and an inner region forming resin composition. It includes a step of applying an outer region forming resin composition to the surface, and a step of heating and curing the inner region forming resin composition and the outer region forming resin composition.

  The manufacturing method according to the present invention will be described using the conductive roller 1 as an example. First, the shaft body 2 is produced from the material according to a conventional method, and a primer or the like is applied to the outer peripheral surface as desired. Next, the silicone rubber composition is heat-cured on the outer peripheral surface of the shaft body 2 by a known molding method to form the silicone elastic layer 3. The molding method is not particularly limited, for example, continuous vulcanization by extrusion molding, press molding, mold molding by injection, or the like. The heating temperature for curing the silicone rubber composition is appropriately selected according to the silicone rubber composition. The surface of the conductive elastic layer 3 formed in this way is polished and ground as required, and the outer diameter, surface state, and the like are adjusted. If desired, a primer or the like is applied to the outer peripheral surface of the conductive elastic layer 3.

  The silicone rubber composition contains silicone rubber, optionally a filler, optionally a conductivity imparting agent, and optionally various additives. The silicone rubber is as described above, and these silicone rubbers may be a liquid type or a millable type, and are appropriately selected according to the molding method of the silicone elastic layer 3, the characteristics required for the silicone elastic layer 3, and the like. You can choose. The filler and conductivity-imparting agent contained in the silicone rubber composition are basically the same as the filler and conductivity-imparting agent. The additive may contain various additives usually contained in rubber compositions and the like, for example, auxiliary agents such as chain extenders and crosslinking agents, catalysts, dispersants, foaming agents, anti-aging agents, Antioxidant, filler, pigment, colorant, processing aid, softener, plasticizer, emulsifier, heat resistance improver, flame retardant improver, acid acceptor, thermal conductivity improver, mold release agent, solvent Etc. These various additives may be commonly used additives or may be specially used additives depending on applications.

  Silicone rubber composition is prepared by using a rubber kneader such as a two-roller, three-roller, roll mill, Banbury mixer, and dough mixer (kneader). Until the agent is uniformly mixed, it can be obtained, for example, by kneading at normal temperature or under heating for several minutes to several hours, preferably 5 minutes to 1 hour.

  The silicone rubber composition preferably has a viscosity of 5 to 500 Pa · s at 25 ° C., particularly preferably 10 to 200 Pa · s. The viscosity of the silicone rubber composition can usually be adjusted by the type and / or blending amount of each component contained therein. If necessary, the viscosity can be adjusted with a solvent or the like.

  Examples of the silicone rubber composition that is preferably used include an addition curable millable conductive silicone rubber composition and an addition curable liquid conductive silicone rubber composition.

  The addition-curable millable conductive silicone rubber composition is (A) an organopolysiloxane represented by the following average composition formula (1), (B) a filler, and (C) other than those belonging to the component (B). A conductive material, that is, a conductivity-imparting agent. These components (A) to (C) are basically the same as the components in the “addition-curable millable conductive silicone rubber composition” described in, for example, JP-A-2008-058622.

R _n SiO _{(4-n) / 2} (1)
Here, R is a substituted or unsubstituted monovalent hydrocarbon group which may be the same or different, preferably a monovalent hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms. Yes, n is a positive number from 1.95 to 2.05.

The addition-curable liquid conductive silicone rubber composition comprises (D) an organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms in one molecule, and (E) bonded to silicon atoms in one molecule. An organohydrogenpolysiloxane containing at least two hydrogen atoms; (F) an inorganic filler having an average particle size of 1 to 30 μm and a bulk density of 0.1 to 0.5 g / cm ³ ; and (G). An addition-curable liquid conductive silicone rubber composition containing a conductivity imparting agent and (H) an addition reaction catalyst can be mentioned. These components (D) to (H) are basically the same as the components in the “addition-curable liquid conductive silicone rubber composition” described in JP-A-2008-058622, for example.

  The heating temperature for curing this addition-curable millable conductive silicone rubber composition is 100 to 500 ° C., particularly 120 to 300 ° C., and the time is several seconds to 1 hour, particularly 10 seconds to 35 minutes. Preferably, the heating temperature for curing the addition-curable liquid conductive silicone rubber composition is 100 to 300 ° C., particularly 110 to 200 ° C., and the time is 5 minutes to 5 hours, particularly 1 to 3 hours. preferable. In addition, in the case of an addition-curable millable conductive silicone rubber composition, if necessary, the curing conditions are about 100 to 200 ° C. for about 1 to 20 hours, and in the case of an addition-curable liquid conductive silicone rubber composition. Secondary vulcanization can be performed at 120 to 250 ° C. under curing conditions for about 2 to 70 hours.

  Subsequently, the process of apply | coating the resin composition for inner area | region formation containing a solvent to the outer peripheral surface of the silicone elastic layer 3 formed in the outer peripheral surface of the shaft body 2 in this way is implemented. Application | coating of the said resin composition for inner area | region formation is performed by well-known application | coating methods or coating methods, such as the apply | coating method, the dipping method, the spray coating method, and the roll coat method, for example.

  The resin composition for forming the inner region contains a resin component and a solvent, and optionally contains a conductivity-imparting agent and various additives, and is substantially free of an inorganic filler. Here, “substantially free of inorganic filler” means that the inorganic filler is not actively added and contained as a component of the resin composition for forming the inner region. Does not include the case where it is contained. The resin component may be any component that cures to form a resin, and is also referred to as a resin preparation component. The resin component may be a resin component that forms a resin other than a silicone resin, but is preferably a polyurethane preparation component that forms a urethane resin. The conductivity imparting agent and various additives are basically the same as, for example, the conductivity imparting agent and the additive.

  The polyurethane preparation component may be any component that can form polyurethane, and includes, for example, polyurethane obtained by reacting polyol and polyisocyanate. Accordingly, the polyurethane preparation component is, for example, at least selected from the group consisting of polyurethane, a mixture of polyol and polyisocyanate or block polyisocyanate, and a prepolymer obtained by reacting polyol and polyisocyanate or block polyisocyanate. One component may be mentioned.

  The polyol in the mixture of polyol and polyisocyanate may be any of various polyols usually used in the preparation of polyurethane, but at least one polyol selected from polyether polyols and polyester polyols is used as a coating. The layer 4 is preferable in that it is excellent in wear resistance, electrical stability, water resistance and the like. Examples of the polyether polyol include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polypropylene glycol-ethylene glycol, polytetramethylene ether glycol, copolymer polyols of tetrahydrofuran and alkylene oxide, and various modified products thereof. These mixtures etc. are mentioned. Examples of the polyester polyol include condensed polyester polyols, lactone polyester polyols, polycarbonate polyols, and mixtures thereof obtained by condensation of dicarboxylic acids such as adipic acid and polyols such as ethylene glycol. The polyether polyol and polyester polyol may be used singly or in combination of two or more, or a polyether polyol and a polyester polyol may be used in combination. The polyol is preferably a polyester polyol because it is excellent in thermal stability. The polyol preferably has a number average molecular weight of 1000 to 8000, more preferably 1000 to 5000, in view of excellent compatibility with polyisocyanate and the like described later. The number average molecular weight is a molecular weight when converted to standard polystyrene by gel permeation chromatography (GPC).

  The polyisocyanate in the mixture of polyol and polyisocyanate may be any of various polyisocyanates usually used in the preparation of polyurethane, and examples thereof include aliphatic polyisocyanates and aromatic polyisocyanates. The polyisocyanate is preferably an aromatic polyisocyanate in terms of excellent storage stability and easy control of the reaction rate. Examples of the aromatic polyisocyanate include xylylene diisocyanate (XDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), paraphenylene diisocyanate (PDI), and tolidine diisocyanate (TODI). It is done. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), norbornane diisocyanate methyl, transcyclohexane-1,4-diisocyanate, and hydrogenated MDI.

  In addition to these polyisocyanates, block polyisocyanates in which isocyanate groups are blocked with a blocking agent are preferably used as the polyisocyanate. Block polyisocyanate has high stability at room temperature and has advantages such as easy handling because the blocking agent is released by heating and the isocyanate group is regenerated. In particular, it has an advantage that it reacts stably even in summer when the humidity is high, and can be used in combination with a reagent having an active group having a high reactivity such as an amino group. Examples of the blocking agent include ε-caprolactams, methyl ethyl ketoximes, 3,5-dimethylpyrazoles, alcohols and phenols. Examples of the blocking agent include isocyanates. In this case, the blocked polyisocyanate is a polyisocyanate dimer (polyuretdione). As the blocking agent, any of the above can be used, but ε-caprolactams and methyl ethyl ketoximes are preferred from the viewpoint of excellent compatibility with the solvent.

  The polyisocyanate preferably has a molecular weight of 500 to 2000, more preferably 700 to 1500.

  The mixing ratio in the mixture of the polyol and the polyisocyanate is not particularly limited. Usually, a hydroxyl group (OH) contained in the polyol and an isocyanate group contained in the polyisocyanate (NCO, an isocyanate group which can be liberated in the case of a block polyisocyanate). ) Is preferably 0.7 to 1.15 in that the desired degree of crosslinking in the resulting polyurethane can be achieved. This molar ratio (NCO / OH) is more preferably 0.85 to 1.10. From the viewpoint that hydrolysis of polyurethane can be prevented.

  The mixture of polyol and polyisocyanate may contain, in addition to the polyol and polyisocyanate, auxiliary agents usually used for the reaction between the polyol and polyisocyanate, such as a chain extender and a crosslinking agent. Examples of chain extenders and crosslinking agents include glycols, hexanetriol, trimethylolpropane, and amines.

  The prepolymer and the polyurethane may be any prepolymer and polyurethane obtained by reacting the polyol and the polyisocyanate, and the molecular weight thereof is not particularly limited. The prepolymer and the polyurethane can be obtained by reacting a polyol and a polyisocyanate by the one-shot method or the prepolymer method in the presence of the auxiliary agent, if desired.

  The polyurethane preparation component is preferably a mixture of polyol and polyisocyanate, particularly preferably a mixture of at least one polyol selected from polyether polyol and polyester polyol and polyisocyanate. That is, the polyurethane preparation component particularly preferably contains a mixture of at least one polyol selected from polyether polyol and polyester polyol and polyisocyanate.

  As the solvent, various solvents that are usually used in a resin composition can be used, but a solvent having a property of volatilizing at a temperature lower than a curing temperature at which the resin component is cured, for example, a volatile solvent, or A solvent having a boiling point lower than the curing temperature can be suitably used. Examples of such a solvent include alcohols such as methanol and ethanol, and ketones such as acetone and methyl methyl ketone. The content of the solvent may be an amount that can be diluted to such an extent that the resin composition for forming the inner region can be applied. For example, the content of the solvent is preferably set so that the solid content concentration is 10 to 50% by mass.

  The inner region forming resin composition may be used, for example, from several minutes to several minutes until each component is uniformly mixed using a mixer such as a two-roller, three-roller, roll mill, Banbury mixer, and dough mixer (kneader). It is obtained by mixing for a time, preferably 5 minutes to 1 hour, at room temperature or under heating. This inner region forming resin composition can be easily formed on the outer peripheral surface of the silicone elastic layer 3, and for example, has a viscosity of 5 to 500 Pa · s at 25 ° C. It is particularly good to have a viscosity of ˜200 Pa · s. The viscosity of the resin composition for forming the inner region can usually be adjusted by the type and / or blending amount of each component contained therein.

  In the manufacturing method according to the present invention, the step of applying the outer region forming resin composition to the surface of the inner region forming resin composition applied to the outer peripheral surface of the silicone elastic layer 3 is then performed. At this time, the outer region forming resin composition is applied in a state where the solvent contained in the inner region forming resin composition is not removed, that is, in the coated state of the inner region forming resin composition. As described above, the outer region forming resin composition applied over the inner region forming resin composition in the applied state, in particular, the inorganic filler contained in the outer region forming resin composition is in the applied state. It is difficult to be mixed into the resin composition for forming the inner region. Application | coating of the said resin composition for outer area | region formation is performed by well-known application | coating methods or coating methods, such as the apply | coating method, the dipping method, the spray coating method, and the roll coat method, for example.

  The outer region forming resin composition is basically the same as the inner region forming resin composition except that it contains a filler. The resin component and the inorganic filler, and optionally a conductivity-imparting agent. , Solvent and various additives. The resin composition for forming the outer region is preferably a resin component in which the resin component as the main component is cross-linked with the resin component of the resin composition for forming the inner region, and the composition, in particular, the resin component is the same. Is preferred.

  In the manufacturing method according to the present invention, a step of heating and curing the resin composition for forming the inner region and the resin composition for forming the outer region is then performed. That is, curing of the inner region forming resin composition and solvent removal and curing of the outer region forming resin composition are simultaneously performed. The heating temperature at this time is set to a temperature equal to or higher than the temperature at which the solvent volatilizes and the curing temperature at which the resin component is cured, and the heating time is set to a time sufficient for the resin component to cure. For example, the heating temperature can be set to 120 to 180 ° C., particularly 150 to 160 ° C., and the heating time can be set to 20 to 80 minutes, particularly 30 to 40 minutes.

  Thus, when the inner region forming resin composition and the outer region forming resin composition are cured almost simultaneously, the inner region forming resin composition does not practically contain the inorganic filler 7. The cured inner region 4A is substantially free of the inorganic filler 7 and the outer region forming resin composition contains the inorganic filler 7, so that the cured outer region 5A is filled with the inorganic filler. The agent 7 is contained, and the inner region forming resin composition and the outer region forming resin composition can be integrally cured to form a coat layer 4 having a single layer structure. The ten-point average roughness Rz (μm) of the coat layer 4 can be adjusted to the above range by the average particle size and content of the inorganic filler 7 contained in the resin composition for forming the outer region.

  Thus, when the inner region forming resin composition and the outer region forming resin composition are cured almost simultaneously, the resin component of the inner region forming resin composition and the resin component of the outer region forming resin composition are cross-linked with each other. Curing increases the adhesion between the inner region 4A and the outer region 4B.

  Furthermore, when each layer is directly formed in this way, since there is no other layer such as an adhesive layer, the characteristics of the conductive roller 1, for example, the stability of the electrical characteristics is enhanced.

  Since the coating layer 4 formed in this way is cured on the outer peripheral surface of the silicone elastic layer 3, the silicone elastic layer 3 is compressed in the axial direction unlike the surface layer formed of a seamless tube. There is no. Therefore, even if the coat layer 4 is formed thin, deformation such as wrinkles due to stress concentration does not occur on the surface, and the outer peripheral surface can maintain a uniform state over a long period of time.

  In the production method according to the present invention, the surface state can be adjusted by subjecting the coat layer 4 to a polishing treatment, a surface roughness treatment such as a blast treatment, if desired.

  The developing device according to the present invention includes the conductive roller according to the present invention, and is provided, for example, in the image forming apparatus shown in FIG. A developing device which is an embodiment of the developing device according to the present invention will be described together with an example of an image forming device (hereinafter sometimes referred to as an image forming device according to the present invention).

  As shown in FIG. 3, the image forming apparatus 10 includes a plurality of image carriers 11B, 11C, 11M, and 11Y that are provided in the developing units B, C, M, and Y of each color in series on a transfer conveyance belt 6. Therefore, the developing units B, C, M, and Y are arranged in series on the transfer conveyance belt 6. The developing unit B includes an image carrier 11B such as a photosensitive member (also referred to as a photosensitive drum), a charging unit 12B such as a charging roller, an exposure unit 13B, a developing unit 20B, and an image carrier via the transfer conveyance belt 6. A transfer unit 14B that contacts the body 11B, such as a transfer roller, and a cleaning unit 15B are provided.

  The developing device 20B is an example of a developing device according to the present invention, and includes a conductive roller and a developer 22B according to the present invention, as shown in FIG. Therefore, in this image forming apparatus 10, the conductive roller 1 is mounted as a developer carrier 23B, 23C, 23M and 23Y. Specifically, the developing device 20B includes a casing 21B that houses a one-component non-magnetic developer 22B, a developing roller that is a developer carrier 23B that supplies the developer 22B to the image carrier 11B, and a developer. A developer amount adjusting means 24B for adjusting the thickness of 22B, for example, a blade is provided. In the developing device 20B, the developer amount adjusting means 24B is in contact with or in pressure contact with the outer peripheral surface of the developer carrier 23B as shown in FIG. That is, the developing device 20B is a so-called “contact developing device”. The developing units C, M and Y are basically configured in the same manner as the developing unit B.

  In the image forming apparatus 10, the developer carrier 23B of the developing device 20B is disposed such that the surface thereof is in contact with or in pressure contact with the surface of the image carrier 11B. Similarly to the developing device 20B, the developing devices 20C, 20M, and 20Y are arranged such that the surfaces of the developer carriers 23C, 23M, and 23Y are in contact with or pressed against the surfaces of the image carriers 11C, 11M, and 11Y. ing. That is, the image forming apparatus 10 is a so-called “contact image forming apparatus”.

  The fixing unit 30 is disposed on the downstream side of the developing unit Y. The fixing unit 30 includes a fixing roller 31, an endless belt support roller 33 disposed in the vicinity of the fixing roller 31, a fixing roller 31, and an endless belt support roller in a housing having an opening 35 through which the recording medium 16 passes. 33, an endless belt 36 wound around 33, and a pressure roller 32 disposed opposite to the fixing roller 31. The fixing roller 31 and the pressure roller 32 are in contact with or pressed against each other via the endless belt 36. It is a pressure heat fixing device which is supported in a freely rotatable manner. At the bottom of the image forming apparatus 10, a cassette 41 that houses the recording body 16 is installed. The transfer conveyance belt 6 is wound around a plurality of support rollers 42.

  Each of the developers 22B, 22C, 22M and 22Y used in the image forming apparatus 10 may be a dry developer or a wet developer as long as it can be charged by friction, and a non-magnetic developer or a magnetic developer. An agent may be used. One component non-magnetic black developer 22B, cyan developer 22C, magenta developer 22M and yellow developer 22Y are accommodated in the housings 21B, 21C, 21M and 21Y of the developing units.

  The image forming apparatus 10 forms a color image on the recording body 16 as follows. First, in the developing unit B, an electrostatic latent image is formed by the exposure unit 13B on the surface of the image carrier 11B charged by the charging unit 12B, and the black electrostatic latent image is developed by the developer 22B supplied by the developer carrier 23B. The image is developed. The black electrostatic latent image is transferred to the surface of the recording medium 16B when the recording medium 16 passes between the transfer means 14B and the image carrier 11B. Next, in the same manner as in the developing unit B, a cyan image, a magenta image, and a yellow image are superimposed on the recording medium 16 in which the electrostatic latent image is visualized as a black image by the developing units C, M, and Y, respectively. A color image is visualized. Next, the recording body 16 in which the color image is visualized is fixed to the recording body 16 by the fixing unit 30 as a permanent image. In this way, a color image can be formed on the recording medium 16.

  In the tandem image forming apparatus 10, when the conductive roller according to the present invention is used as the developer carrier 23, the belt-like image defect is caused even when the conductive roller forms a halftone image in a high temperature and high humidity environment. Therefore, the developing means 20 and the tandem type image forming apparatus 10 including the conductive roller according to the present invention can suppress the occurrence of the belt-like image defect even under a high temperature and high humidity environment, and the entire image can be prevented. As a result, a high-quality image having a desired image density can be formed.

  The image forming apparatus 10 is an image forming apparatus such as a copying machine, a facsimile machine, or a printer. The image forming apparatus 10 has been described with reference to an example in which the conductive roller according to the present invention is used as a developing roller that is an example of the developer carrier 23. However, the image forming apparatus 10 is provided in the image forming apparatus, In addition, even if the conductive roller according to the present invention is used as a roller that can come into contact with a developer or a recording medium, for example, a charging roller and a transfer roller, a belt-like image defect occurs even in a high-temperature and high-humidity environment. And a high-quality image having a desired image density as the entire image can be formed.

  The conductive roller, the developing device, and the image forming apparatus according to the present invention are not limited to the above-described embodiments, and various modifications are possible as long as the object of the present invention can be achieved.

  For example, each of the conductive rollers 1 has a so-called straight shape in which the outer diameter is substantially the same from one end to the other end in the axial direction. The shape is not particularly limited as long as it has a shape, for example, it may be a so-called reverse crown shape in which the outer diameter at the central portion in the axial direction is smaller than the outer diameter at both end portions, and the axial direction may be A so-called crown shape in which the outer diameter at the central portion is larger than the outer diameters at both ends thereof may be employed.

  Further, the conductive roller according to the present invention may have another layer between the silicone elastic layer and the coat layer. Examples of the other layer include a primer layer that adheres or adheres the silicone elastic layer and the coat layer. Examples of materials for forming the primer layer include alkyd resins, phenol-modified / silicone-modified alkyd resin modified products, oil-free alkyd resins, acrylic resins, silicone resins, epoxy resins, fluororesins, phenol resins, polyamide resins, urethanes. Examples thereof include resins and mixtures thereof. Moreover, as a crosslinking agent which hardens and / or bridge | crosslinks these resin, an isocyanate compound, a melamine compound, an epoxy compound, a peroxide, a phenol compound, a hydrogen siloxane compound etc. are mentioned, for example. The primer layer is formed with a thickness of 0.1 to 10 μm, for example.

  The image forming apparatus 10 is an electrophotographic image forming apparatus. However, in the present invention, the image forming apparatus is not limited to the electrophotographic system, and may be, for example, an electrostatic image forming apparatus. Good. Further, the image forming apparatus provided with the conductive roller according to the present invention is not limited to a tandem color image forming apparatus in which a plurality of image carriers having developing units of respective colors are arranged in series on a transfer conveyance belt. For example, a monochrome image forming apparatus provided with a single developing unit, a four-cycle color image forming apparatus that sequentially repeats primary transfer of a developer image carried on an image carrier onto an endless belt may be used. The developer 22 used in the image forming apparatus 10 is a one-component nonmagnetic developer. However, in the present invention, the developer may be a one-component magnetic developer or a two-component nonmagnetic developer. Or a two-component magnetic developer.

  The image forming apparatus 10 is a so-called “contact-type image forming apparatus” in which the image carrier 11 and the development carrier 23 of the developing device 20 are in contact or pressure contact. The apparatus may be a so-called “non-contact type image forming apparatus” that is arranged with a gap so that the surface of the developer carrier does not contact the surface of the image carrier.

  The developing device 20 in the image forming apparatus 10 is a so-called “contact type developing device” in which the developer regulating member 24 and the developer carrying member 23 are arranged in contact or pressure contact with each other. The apparatus may be a so-called “non-contact type developing device” arranged with a gap so that the developer regulating member does not contact the outer peripheral surface of the developer carrying member.

Example 1
The shaft body 2 (made by SUM22, diameter 7.5 mm, length 281.5 mm) subjected to electroless nickel plating was washed with toluene, and a silicone primer (trade name “Primer No. 16”, Shin-Etsu) on its surface Chemical Industries, Ltd.) was applied. The primer-treated shaft body 2 was fired at a temperature of 150 ° C. for 10 minutes using a gear oven, and then cooled at room temperature for 30 minutes or more to form a primer layer on the surface of the shaft body 2.

Next, 100 parts by mass of dimethylpolysiloxane (D) (degree of polymerization 300) blocked at both ends with dimethylvinylsiloxy groups, and hydrophobized fumed silica having a BET specific surface area of 110 m ² / g (Nippon Aerosil Co., Ltd.) Made by company, R-972) 1 part by mass, average particle size 6 μm, bulk density of 0.25 g / cm ³ diatomaceous earth (F) (Oplite W-3005S, manufactured by Hokuaki Diatomite Co., Ltd.) 40 parts by mass, and 5 parts by mass of acetylene black (G) (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) was placed in a planetary mixer, stirred for 30 minutes, and then passed once through three rolls. This is returned to the planetary mixer again, and as a crosslinking agent, methyl hydrogen polysiloxane (E) having Si—H groups at both ends and side chains (polymerization degree 17, Si—H amount 0.0060 mol / g) 2. 1 part by mass, 0.1 part by mass of ethynylcyclohexanol and 0.1 part by mass of platinum catalyst (H) (Pt concentration 1%) are added as reaction control agents, and the mixture is stirred for 15 minutes and added. A curable liquid conductive silicone rubber composition was prepared. The prepared addition-curable liquid conductive silicone rubber composition was molded on the outer peripheral surface of the shaft body 2 by liquid injection molding. The molded body was polished to form a silicone elastic layer 3 having an outer diameter of 20 mm. When the JIS A hardness of the silicone elastic layer 3 was measured according to the above method, it was 40, and when its electrical resistance was measured according to the above method, it was 1.0 × 10 ⁵ Ω.

Next, a resin composition for forming an inner region having the following composition was prepared according to a conventional method.
Polyisocyanate (Nippon Polyurethane Co., Ltd., trade name: Coronate-LJ) 10 parts by mass Polyol (Polyester polyol, trade name “Nipporan NIPPOLLAN 139”, Nihon Polyurethane Co., Ltd.) 30 parts by mass (molar ratio (NCO / OH = 1.05)
-Conductivity imparting agent (trade name "EC600JD", manufactured by Lion Corporation, average particle size 34 nm) 3 parts by mass (the content when the total mass of the polyisocyanate and the polyol is 100 parts by mass is 7.5. Part by mass)
・ 50 parts by mass of solvent (butyl acetate, Sankyo Chemical Co., Ltd.)

Moreover, the following fumed silica type filler was added to the said resin composition for inner area | region formation, and the resin composition for outer area | region formation was prepared in accordance with the conventional method.
・ 8 parts by mass of fumed silica-based filler (trade name “AEROSIL 200”, manufactured by Nippon Aerosil Co., Ltd., average particle size 2.0 μm) (the total mass of polyisocyanate and polyol in the resin composition for forming the outer region) (When the content is 100 parts by mass, the content is 20 parts by mass)

  The inner region forming resin composition is applied to the outer peripheral surface of the silicone elastic layer 3 formed on the outer peripheral surface of the shaft body 2 by a spray coating method so that the layer thickness after curing is 10 μm, The outer region-forming resin composition was applied to the outer peripheral surface of the inner region-forming resin composition at once by a spray coating method so that the layer thickness after curing was 10 μm. Next, the applied inner region forming resin composition and outer region forming resin composition were heated together with the shaft body 2 and the silicone elastic layer 3 at 150 ° C. for 30 minutes to be cured. In this way, a conductive roller was manufactured.

  The coated layer of the manufactured conductive roller is such that the urethane preparation component of the resin composition for forming the inner region and the urethane preparation component of the resin composition for forming the outer region are cross-linked with each other in the inner region 4A and the outer region 4B. The particle distribution difference was observed, but the interface could not be confirmed, and the single layer structure had a total thickness of 20 μm. In the conductive roller of Example 1, the outer region 4B in the coat layer 4 was assumed to have a thickness of 10 μm from the outer surface (in Table 1, the thicknesses of the outer region 4B and the inner region 4A described this assumed thickness. ). When the cross section of the coat layer 4 in a cross section perpendicular to the axis of the conductive roller 1 was confirmed, the entire inorganic filler 7 was unevenly distributed in the outer region 4B and was not present in the inner region 4A. The content of the inorganic filler 7 in the coat layer 4 was 10 parts by mass with respect to 100 parts by mass of the resin forming the entire coat layer 4.

(Examples 2 and 3)
Each conductive roller was basically the same as Example 1 except that the average particle size of the inorganic filler 7 in the resin composition for forming the outer region was changed from 2.0 μm to 3.0 μm or 4.0 μm. Manufactured. When the cross section of each coat layer in the cross section perpendicular to the axis of the conductive roller was confirmed, the interface between the inner region 4A and the outer region 4B could not be confirmed, and the single layer structure had a total thickness of 20 μm. In both the conductive rollers of Examples 2 and 3, the outer region 4B of the coat layer 4 was assumed to be 10 μm in thickness from the outer surface. In both conductive rollers, the entire inorganic filler 7 is unevenly distributed in the outer region 4B and not in the inner region 4A.

(Comparative Example 1)
A silicone elastic layer 3 was formed on the outer peripheral surface of the shaft body 2 in the same manner as in Example 1. The outer region forming resin composition is applied to the outer peripheral surface of the silicone elastic layer 3 by spray coating so that the layer thickness after curing is 20 μm, and the outer region forming resin composition is applied at 150 ° C. For 30 minutes to cure. In this way, a conductive roller was manufactured. In the conductive roller of Comparative Example 1, the outer region of the coat layer was assumed to be 10 μm in thickness from the outer surface. The coating layer of this conductive roller had a single layer structure containing the inorganic filler 7 in its entirety.

(Comparative Examples 2 and 3)
Each conductivity was basically the same as in Example 1 except that the average particle size of the inorganic filler 7 in the outer region forming resin composition was changed from 2.0 μm to 5.0 μm or 8.0 μm. A roller was produced. When the cross section of each coat layer in the cross section perpendicular to the axis of the conductive roller was confirmed, the interface between the inner region and the outer region could not be confirmed, and the single layer structure had a total thickness of 20 μm. In both the conductive rollers of Comparative Examples 2 and 3, the outer region of the coat layer was assumed to be 10 μm in thickness from the outer surface. In both conductive rollers, the entire inorganic filler 7 is unevenly distributed in the outer region and not in the inner region.

(Comparative Example 4)
Example 1 except that the inorganic filler 7 in the resin composition for forming the outer region was changed to urethane resin particles (trade name “MM-129TW”, manufactured by Negami Co., Ltd., average particle size 2.0 μm). A conductive roller was manufactured basically in the same manner. In the conductive roller of Comparative Example 4, the outer region of the coat layer was assumed to be 10 μm in thickness from the outer surface. When the cross section of the coat layer in the cross section perpendicular to the axis of the conductive roller was confirmed, the interface between the inner region and the outer region could not be confirmed, and the single layer structure with a total thickness of 20 μm was obtained. And was not present in the inner region. The content of the urethane resin particles in the coat layer was 10 parts by mass with respect to 100 parts by mass of the resin forming the entire coat layer.

  The results obtained by measuring the ten-point average roughness Rz in the circumferential direction, the ten-point average roughness Rz in the axial direction, the electrical resistance, the charge amount, and the JIS A hardness of each of the conductive rollers thus manufactured according to the above-described method are shown in FIG. Shown in the table. In addition, the content of the inorganic filler 7 and the content of the conductivity imparting agent measured by the thermogravimetric analysis method almost coincided with the content in each composition.

(Developer transportability evaluation)
The developer transportability of each manufactured conductive roller was evaluated by the developer adhesion amount as follows. That is, each conductive roller manufactured as a developing roller of an electrophotographic printer (made by Oki Data Corporation, trade name: “MICROLINE 1032PS”, equivalent to a resolution of 1200 dpi) is mounted, and this electrophotographic printer is set at a temperature of 20 ° C. After five black solid prints were performed in an environment with a relative humidity of 50%, the black solid print was forcibly stopped, the conductive roller was taken out of the image forming apparatus, and the development adhered to the surface of the extracted conductive roller Suction type small charge amount measuring device having a suction port with a cross-sectional area of 0.25 cm ² : The product name “210HS q / M METER” (manufactured by Trek Japan Co., Ltd.) The developer adhesion amount of each conductive roller was measured by measuring and converting to the mass per unit area. When the measured adhesion amount is 0.8 mg / cm ² or more and 1.1 mg / cm ² or less, “◯”, 0.6 mg / cm ² or more and less than 0.8 mg / cm ² or 1.1 mg / cm ² The case where it exceeded 1.3 mg / cm ² or less was designated as “Δ”, and the case where it was less than 0.6 mg / cm ² or exceeded 1.3 mg / cm ² was designated as “x”. The results are shown in Table 1.

(Strip image defect evaluation)
Each manufactured conductive roller is mounted as a developing roller on a contact-type image forming apparatus (trade name “MICROLINE 1032PS”, manufactured by Oki Data Co., Ltd.), and placed in a high temperature and high humidity environment with a temperature of 49 ° C. and a relative humidity of 80%. Let stand for days. Thereafter, a halftone image was printed on A4 paper (JIS) while maintaining this high temperature and high humidity environment. In the printed halftone image, the print density in an image region (also referred to as “development cycle”) formed by one rotation of the developing roller is measured, and the maximum image density among the measured print densities The difference between the print density and the minimum image density was obtained. If this print density difference is less than 0.02, there is no band-like image defect and the entire image has a desired image density. Therefore, the evaluation is “◯”, and the print density difference is 0.02 or more in most cases. Since the strip-like image defect can be confirmed, the evaluation is “x”. A high density portion extending in the short side direction of the A4 sheet in the image area is a “band image defect (banding defect)”. Note that, in the evaluation of strip-like image defects, the developer and developer amount adjusting means used were the developer and developer amount adjusting means attached to the image forming apparatus.

(Durable image evaluation)
Each manufactured conductive roller is attached as a developing roller to a contact-type image forming apparatus (trade name “MICROLINE 1032PS”, manufactured by Oki Data Corporation), and is A4 paper in an environment of a temperature of 23 ° C. and a relative humidity of 55%. (JIS) was printed 10,000 sheets of halftone images at a printing density of 2%. In the printed halftone image, the print density difference between the first sheet and the 10,000th sheet was measured. The case where the difference in print density was 0.1 or less was rated as “◯”, the case where it exceeded 0.1 and was 0.2 or less was “Δ”, and the case where it was 0.2 or more was “X”. As shown in Table 1, in the conductive roller whose outer region contains the inorganic filler 7, the inorganic filler 7 is unlikely to fall off the coating layer, and the occurrence of strip-like image defects can be prevented and the developer transportability can be improved. In contrast, the conductive roller of Comparative Example 4 was estimated to be evaluated as “x” because the urethane resin particles dropped from the surface of the coating layer during the printing of the halftone image. doing.

DESCRIPTION OF SYMBOLS 1 Conductive roller 2 Shaft body 3 Silicone elastic layer 4 Coat layer 4A Inner area | region 4B Outer area | region 7 Inorganic type filler 10 Image forming apparatus 11B, 11C, 11M, 11Y Image carrier 12B, 12C, 12M, 12Y Charging means 13B, 13C, 13M, 13Y Exposure means 14B, 14C, 14M, 14Y Transfer means 15B, 15C, 15M, 15Y Cleaning means 16 Recording body 20 Development means 21B, 21C, 21M, 21Y, 34 Housings 22B, 22C, 22M, 22Y Development Agents 23B, 23C, 23M, 23Y Developer carrier 24B, 24C, 24M, 24Y Developer regulating member 30 Fixing means 31 Fixing roller 32 Pressure roller 33 Endless belt support roller 35 Opening 41 Cassette 42 Support rollers B, C, M, Y Development unit

Claims (5)

A conductive roller comprising a silicone elastic layer formed on the outer peripheral surface of the shaft body and a coat layer formed on the outer peripheral surface of the silicone elastic layer, and having a ten-point average roughness Rz of 3 to 12.0 μm. a is, the coat layer, the inorganic filler and the inner region of the free content, average particle size possess an outer region containing the inorganic filler of less than 5.0 .mu.m, the outer periphery of the silicone elastic layer It is a single layer structure formed by applying the outer region forming resin composition containing the inorganic filler to the inner region forming resin composition in a coated state on the surface, and applying and curing the layered resin composition. The conductive roller , wherein the resin as the main component contained in the inner region and the resin as the main component contained in the outer region are of the same type . The outer region is a region having a thickness of 1 to 20 μm from the outer peripheral surface of the coat layer, and the inner region is a region having a thickness of 1 to 20 μm from the inner surface of the coat layer. The conductive roller according to claim 1 . A developing device comprising the conductive roller according to claim 1 . An image forming apparatus comprising the conductive roller according to claim 1 . A step of applying an inner region forming resin composition containing a solvent to the outer peripheral surface of the silicone elastic layer formed on the outer peripheral surface of the shaft body;
Applying an outer region forming resin composition containing an inorganic filler having an average particle size of less than 5.0 μm to the surface of the inner region forming resin composition;
Heating and curing the resin composition for forming the inner region and the resin composition for forming the outer region ,
A method for producing a conductive roller, wherein a resin component as a main component contained in the inner region forming resin composition and a resin component as a main component contained in the outer region forming resin composition are the same .

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