JP4378145B2 - Manufacturing method of charging roller - Google Patents

Description

The present invention relates to a process for the production of a static-roller.

  As a conventional DC charging method in which only direct current is applied, a roller using hydrin rubber has been proposed (see, for example, Patent Document 1).

  In addition, as a manufacturing method of a roller for an image forming apparatus that forms a resin coating layer having a uniform thickness by a dip coating method, there is a method that proposes a coating cap (see, for example, Patent Document 2).

  The DC charging method is generally lower in cost than the AC charging method, but has a problem. That is, since there is no AC current leveling effect unlike AC + DC charging, the charging uniformity is inferior to that of the AC + DC charging method. In addition, since there is no leveling effect, there is a problem that dirt adhering to the surface of the charging roller and non-uniformity of the electric resistance of the charging roller itself are likely to appear in the image.

  In addition, when the electrophotographic apparatus is driven at two or more different process speeds to output an image due to the thickness of the print medium, the DC charging method is better than the AC charging method. There is also a problem that the range of the process speed that exhibits excellent charging characteristics is narrow.

  In order to solve this problem, it is effective to coat the surface of the charging roller thinly and uniformly and roughen it appropriately. However, if the surface of the charging roller is thinly and evenly coated and appropriately roughened, the coating film on the surface of the charging roller will not be able to withstand the practical use when used in an electrophotographic apparatus unless the coating film uniformity is further improved. is there.

When using a cap having a simple cylindrical shape as shown in FIGS. 28 (a) and 28 (b) and having a shape in which a portion in contact with the roller is in close contact with the end surface of the roller, It is very difficult to coat the surface of the charging roller thinly and uniformly enough to withstand the DC charging method.
Japanese Patent Laid-Open No. 5-341627 JP 2002-82523 A

An object of the present invention is to cope with such a problem. A charging roller capable of uniform charging even when a high-definition image such as a halftone image of 600 dpi is output by a DC charging method. It is to provide a manufacturing method .

According to the present invention, there is provided a method for producing a charging roller having a cored bar, an elastic base layer formed on the cored bar, and a surface layer formed on the elastic base layer,
(1) forming an elastic base layer on the core metal except the end portion of the core metal,
(2) has said obtained in step (1), and a step of coating a surface layer coating material to the core metal forming the elastic base layer is immersed in the surface layer coating material,
In the step (2) , a coating cap is attached to the end of the cored bar formed with the elastic base layer obtained in the step (1), and the end of the cored bar and the end surface of the elastic base layer are connected to the end of the cored base. Covering with a coating cap, and then rushing the cored bar into the surface layer coating with the side on which the coating cap is attached facing down,
When the coating cap is attached to the end of the cored bar, it contacts the end surface of the elastic base layer at the edge, and the cap does not touch the boundary between the elastic base layer and the cored bar. It is configured to create a space,
Coating Engineering caps, the side opposite to the side in contact with the elastic body base, the manufacturing method of the charging roller, characterized that you have a streamlined shape that its diameter is reduced is provided.

  According to the present invention, there is provided a coating cap for a conductive roller capable of uniform charging with good charging characteristics even when a high-definition image such as a halftone image of 600 dpi is output by a DC charging method. Can do.

  In addition, by using a conductive roller according to the present invention, a process cartridge and an electrophotographic apparatus that can perform uniform charging with good charging characteristics even when a high-definition image is output by a DC charging method. Became possible.

  Hereinafter, embodiments of the present invention will be described in detail.

  As a configuration of the charging member for DC charging, the present inventors provided a conductive support, a conductive elastic base layer provided on the conductive support, and provided on the conductive elastic base layer. When a roller having a surface layer is applied to the end of the coating substrate on which the base layer is formed on the core metal and the surface layer is dip coated, the elastic base layer, the core metal and the coating cap By providing a shape in which the three members are not in contact with each other at one point in space, a charging roller that provides a good image even when DC charging is performed and that has a uniform surface layer thickness is provided. It was discovered that it was possible to arrive at the present invention.

  Next, the conductive roller of the present invention, an image forming apparatus using the same, a charging method, and a process cartridge will be described.

<1> Conductive roller The conductive roller of the present invention includes a conductive support, a conductive elastic base layer provided on the conductive support, and a surface layer provided on the conductive elastic base layer. Have

  A specific configuration of the conductive roller of the present invention is shown in FIG. FIG. 32A shows a cross section of the conductive roller, and FIG. 32B shows a vertical section.

  The conductive roller of the present invention is a conductive roller having a conductive support 1, a conductive elastic base layer 2 formed on the outer periphery thereof, and a surface layer 3 covering the outer periphery of the conductive elastic base layer 2. .

  The conductive support 1 used in the present invention shown in FIG. 32 is a cylinder having a carbon steel alloy surface plated with nickel of 5 μm thickness. In addition to the materials constituting the conductive support, for example, metals such as iron, aluminum, titanium, copper and nickel, alloys such as stainless steel, duralumin, brass and bronze containing these metals, and carbon black and carbon fibers are also included. It is also possible to use a known material that is rigid and shows conductivity, such as a composite material hardened with plastic. Moreover, as a shape, it can also be set as the cylindrical shape which made the center part the cavity other than column shape.

  In the present invention, the conductive elastic base layer 2 is first formed on the outer periphery of the conductive support 1. The conductive elastic base layer 2 is made of a conductive elastic body. The conductive elastic body is formed by mixing a conductive agent and a polymer elastic body. The conductive agent contains at least an ionic conductive agent. As the polymer elastic body, epichlorohydrin rubber is particularly preferably used. Epichlorohydrin rubber has some conductivity in the rubber itself, can exhibit good conductivity even with a small amount of conductive agent added, and can also reduce variations in electrical resistance depending on the environment and position. Therefore, it is suitably used as a polymer elastic body.

  Epichlorohydrin rubber is a ring-opening polymer of a cyclic ether centered on epichlorohydrin. Examples of main monomers constituting the rubber include epichlorohydrin, ethylene oxide, and acryl glycidyl ether.

  Examples of the epichlorohydrin rubber that is a polymer include epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide copolymer, epichlorohydrin-allyl glycidyl ether copolymer, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer, and the like. Of these, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer is particularly preferably used since it exhibits stable conductivity in a medium resistance region. The epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer can control conductivity and workability by arbitrarily adjusting the degree of polymerization and composition ratio.

  The polymer elastic body is mainly composed of epichlorohydrin rubber, but may contain other general rubbers as necessary. Examples of other general rubbers include EPM (ethylene / propylene rubber), EPDM (ethylene / propylene rubber), norbornene rubber, NBR (nitrile rubber), chloroprene rubber, natural rubber, isoprene rubber, butadiene rubber, styrene- Examples thereof include butadiene block, chlorosulfonated polyethylene, urethane rubber, styrene block copolymers such as SBS (styrene / butadiene / styrene / block copolymer), SEBS (styrene / ethylene butylene / styrene / block copolymer), and silicone rubber. When it contains said general rubber, it is preferable that the content is 1-50 mass% with respect to the polymer elastic body whole quantity.

  As the conductive agent, an ionic conductive agent is preferably contained for the purpose of reducing unevenness of the electrical resistivity of the conductive elastic base layer. By uniformly dispersing the ionic conductive agent in the polymer elastic body and making the electronic resistivity of the conductive elastic body uniform, uniform charging can be obtained even when the charging roller is used with only DC voltage applied. be able to.

The ion conductive agent, for example, perchlorate such as LiClO ₄ and NaClO _4, include quaternary ammonium salts and the like can be used in combination singly or two or more kinds. Among ionic conductive agents, quaternary ammonium perchlorate is particularly preferably used because of its resistance to environmental changes.

  In addition to the ionic conductive agent, an electronic conductive conductive agent can be added within a range that does not cause unevenness in the electrical resistance of the conductive elastic body. The electroconductive conductive agent can be used in a range in which the electrical conductivity of the electronic conductive agent is smaller than the electrical conductivity of the ionic conductive agent. That is, the electron conductive conductive agent has a volume resistivity in the case of adding and adding an electron conductive conductive agent to the volume resistivity in the case where only the ionic conductive agent is added to the polymer elastic body. It can be used at a blending ratio of 2 or more. Examples of the electron conductive conductive agent include metal powders and fibers such as aluminum, palladium, iron, copper, and silver, carbon black, metal powders, metal oxides such as titanium oxide, tin oxide, and zinc oxide, Metal oxide powder such as copper sulfide and zinc sulfide, or the surface of appropriate particles tin oxide, antimony oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, chromium, cobalt, iron, lead, platinum, Examples of the powder include rhodium powder deposited by electrolytic treatment, spray coating, and mixed shaking, acetylene black, ketjen black, PAN (polyacrylonitrile) carbon, pitch carbon, and the like. These can be used alone or in combination of two or more.

In the present invention, the blending amount of these conductive agents is such that the volume resistivity of the conductive elastic body is a low temperature and low humidity environment (L / L: 15 ° C./10% RH), a normal temperature and normal humidity environment (N / N: 23 ° C. / 55% RH), in a high-temperature and high-humidity environment (H / H: 30 ° C./80% RH), the amount is such that the middle resistance region (volume resistivity is 1 × 10 ⁴ to 1 × 10 ⁷ Ω · cm). preferable.

  The volume resistance of the conductive elastic body was molded into a sheet having a thickness of 1 mm, and then metal and metal were vapor-deposited on both sides to produce an electrode and a guard electrode. ADVANTEST R8340A ULTRA HIGH RESISTANCE METER Co., Ltd. Advantest A voltage of 200 V is applied using a product, a current after 30 seconds is measured, and the current is calculated from the film thickness and the electrode area.

  If the volume resistivity of the conductive elastic body is smaller than this, if there is a pinhole in the photoconductor that is the image carrier, a large current will be concentrated in the pinhole, making the hole larger. There is a risk that a current may not flow in a place other than the hole and a black band may appear on a high-definition halftone image, and a portion with insufficient charging potential may appear. On the contrary, if the volume resistivity is too large, the applied voltage drops in the conductive elastic layer, and the required discharge current cannot be obtained and the photoreceptor cannot be uniformly charged to a desired potential. is there.

  Other additives such as plasticizers, fillers, vulcanizing agents, vulcanization accelerators, anti-aging agents, scorch preventing agents, dispersants and mold release agents are added to the conductive elastic body as necessary. It is also preferable.

  Examples of the method for forming the conductive elastic body include known methods such as extrusion molding, injection molding, and compression molding by mixing the raw materials for the conductive elastic body. The conductive elastic base layer may be produced by directly forming a conductive elastic body on the conductive support, or by covering the conductive support with a conductive elastic body formed into a tube shape. Also good. Note that the surface may be polished and the shape may be adjusted after the production of the conductive elastic base layer.

  The shape of the conductive elastic base layer is such that the diameter of the central part of the conductive elastic base layer roller is the end so that the contact nip width between the completed charging roller and the photoconductor is as uniform as possible in the longitudinal distribution of the roller. It is preferable that the crown shape is larger than the diameter. In addition, since the contact nip width of the completed roller becomes uniform, it is preferable that the conductive elastic base layer roller has a smaller runout.

  As shown in FIG. 33, the measured value of run-out is obtained by rotating a conductive elastic base layer roller about a conductive substrate as a rotation axis, and a non-contact laser length measuring device (in the present invention, Keyence Co., Ltd.) perpendicular to the rotation axis. The difference between the maximum value and the minimum value of the radius of the conductive elastic base layer measured by LS-5000) is obtained as a value. The difference between the maximum value and the minimum value of the radius is obtained at a pitch of 1 cm in the axial direction of the conductive elastic base layer, and the maximum value among the values is taken as the deflection value of the conductive elastic base layer roller.

  Similarly, the diameter of the roller is the maximum diameter of the conductive elastic base layer measured by a non-contact laser length measuring device perpendicularly to the rotational axis by rotating the conductive elastic base layer roller about the conductive substrate as the rotational axis. The average of the value and the minimum value.

  The difference between the diameter of the central portion in the axial direction of the conductive elastic base layer roller and the average of the two values of the diameter of the central portion 10 mm from both ends of the elastic body is determined as the value of the crown amount.

  A preferable value of the deflection of the conductive elastic base layer roller is 0.5% or less, more preferably 0.25% or less, of the diameter of the central portion of the roller. Since the diameter of the roller of the present invention is preferably about 12 mm, the runout value is specifically preferably 60 μm or less, and more preferably 30 μm or less.

  The value of the crown amount is determined so that the nip width of the finished roller is uniform, but is preferably 0.1 to 5.0% of the roller diameter, specifically 12 to 600 μm.

  The micro rubber hardness of the conductive elastic body is preferably 70 ° or less, and more preferably 60 ° or less. When the micro rubber hardness exceeds 70 °, the nip width between the conductive roller and the photosensitive member becomes small, the contact force between the conductive roller and the photosensitive member concentrates in a small area, and the contact pressure increases. Become. As a result, adverse effects such as charging becoming unstable or developer or the like being easily attached to the surface of the photoreceptor or the conductive roller become remarkable.

  The “micro rubber hardness” is the hardness of the conductive roller measured using a JIS-A hardness-compliant micro rubber hardness meter (manufactured by Kobunshi Keiki Co., Ltd.), and normal temperature and normal humidity (23 ° C./55%) The value measured 10 seconds after the hardness meter was brought into contact with the conductive roller left in the environment of (RH) for 12 hours or more with a force of 5N.

  In order to reduce the micro rubber hardness, a plasticizer is blended in the conductive elastic body. The amount is preferably 1 part by mass or more, more preferably 3 parts by mass or more. As the plasticizer, for example, an ester-based polymer plasticizer such as a copolymer of sebacic acid and propylene glycol can be used. Such ester plasticizers are close in polarity to epichlorohydrin rubber, can be blended in a relatively large amount, and have an advantage that the hardness of the base layer can be controlled small. The molecular weight of the polymer plasticizer is preferably 2000 or more, more preferably 4000 or more. If the molecular weight is less than 2000, the plasticizer may ooze out on the surface of the roller and contaminate the photoreceptor.

  The conductive elastic base layer is bonded to the conductive support through an adhesive as necessary. In this case, the adhesive is preferably conductive. In order to make it conductive, the adhesive may have a known conductive agent.

  Examples of the binder of the adhesive include resins such as a thermosetting resin and a thermoplastic resin, and known adhesives such as urethane, acrylic, polyester, polyether, and epoxy can be used.

The conductive agent, for example, perchlorate such as LiClO ₄ and NaClO _4, the ion conductive agent such as quaternary ammonium salts, aluminum, palladium, iron, copper, metal-based powder and fibers such as silver, carbon black , Metal oxide such as metal powder, titanium oxide, tin oxide, zinc oxide, metal compound powder such as copper sulfide, zinc sulfide, or the surface of appropriate particles of tin oxide, antimony oxide, indium oxide, molybdenum oxide, zinc, Aluminum, gold, silver, copper, chromium, cobalt, iron, lead, platinum, rhodium, electrolytic powder, powder applied by spray coating, mixed shaking, acetylene black, ketjen black, PAN (polyacrylonitrile) There are carbon powders such as carbon and pitch-based carbon. These can be used alone or in combination of two or more.

  After the conductive elastic base layer is completed, a surface layer is provided as a covering layer. The surface layer in the present invention is a surface treatment-type coating in which the coating liquid impregnates the inside of the base layer without forming a clear layer, as well as when provided as a layer on the conductive elastic base layer. This includes the case where a layer is provided.

  The coating cap used when the surface layer is provided is characterized in that the elastic base layer, the cored bar, and the coating cap have a cap shape in which the three members are not in contact with each other at one point in space. .

  As shown in Fig. 28 (a) or 28 (b), use a cap with a cylindrical cross section whose end on the roller side is vertical, and apply a low viscosity coating solution to provide a surface layer. In this case, it becomes very difficult to coat the end of the roller well.

  FIG. 30 is a view showing a state of an end portion when a surface layer is provided by applying a coating liquid having a low viscosity using a conventional coating cap. First, the state where the cap is attached before coating is the state (a). In the conventional cap, in order to mount the cap in this state A, compressed air remains in the portion surrounded by the inner wall of the cap and the cored bar, and a force that expands in the direction of removing the cap is applied. It becomes difficult to adhere to each other in a short time. Next, (b) of the figure shows a state immediately after the air is drawn out, the cap is completely fitted, and the roller is dip coated and pulled up. If the cap is pulled out from the state (b) while the coating film is still dry, the coating liquid is pulled to the cap as shown in (c) and applied to the core of the roller. Alternatively, when the cap is pulled out after the coating film is completely dried, the roller peripheral surface where the coating film is not formed is formed as shown in (d) and (e), where the coating film at the end is broken in an irregular shape. Or the coating film flutters and becomes a factor that hinders the smooth rotation of the roller and the photoreceptor.

  Such an adverse effect is not so noticeable when a roller having a large viscosity and a large surface layer is applied. However, when precise coating is required as in the case of a charging roller that requires a thin and uniform surface layer, such as that used for DC charging rollers, such adverse effects become significant. It will be very difficult.

  On the other hand, the coating cap of the present invention has a shape such that the end on the charging roller side does not contact the entire surface of the base layer as shown in FIG. 29, for example, and prevents the coating liquid from entering the cap. It has a shape that can be done.

  By coating using a cap having such a shape, as shown in FIG. 31, even if the cap is removed when the coating liquid is dry, the coating film on the roller end is not disturbed, and the film thickness is reduced. A uniform surface layer can be provided.

  The material of these caps may be anything as long as it has elasticity and is not affected by the coating liquid. For example, polyethylene, polypropylene, polyacetal, polyethylene tetrafluoroethylene, polyfluoroalkoxy resin, polyethylene terephthalate, polyimide, polyamide, polycarbonate , Plastics such as silicone resin, polyurethane and polyester, and thermosetting resins such as phenol resin and epoxy resin.

  In particular, it is desirable to have a property having high water and oil repellency in addition to the property of not being affected by the coating liquid. This is because the cap once used is easy to rinse and dry when washed for reuse. Examples of these particularly preferable materials include olefin resins such as polyethylene and polypropylene, and fluororesins such as polyethylene tetrafluoroethylene and polyfluoroalkoxy resins.

  An example of a preferable shape of the coating cap of the present invention is shown in FIG. A circumferential space is formed when the cap is mounted so that the cap contacts the boundary surface between the end surface of the base layer and the cored bar so that the cap contacts the edge of the base layer end surface of the roller.

  In order to prevent the cap from coming off from the cored bar, the inner surface of the cap has convex portions with extremely low heights at the circumference of the inner diameter slightly larger than the outer diameter of the cored bar. The mandrel is tightened with moderate strength to prevent the cap from falling off in unintended situations.

  The side where the cap enters the liquid surface during dip coating has a rotationally symmetric streamline shape, and prevents the bubbles from being entrained in the coating liquid when immersed.

  As shown in FIGS. 2 and 3, the edge on the cap base layer side can take various angles as long as the core metal is not soiled by the coating liquid.

  Alternatively, the end portion on the base layer side of the cap is not entirely an edge, but a part thereof may be a concentric plane as shown in FIG. 4 and only an edge close to the core metal may be an edge, or as shown in FIGS. A step may be provided. Furthermore, it is good also as a shape which made the edge into the plane like FIG. 7, and the cross-sectional shape which has a curvature like FIG.8 and FIG.9 may be sufficient. Further, as shown in FIG. 10, a concentric groove or mountain may be provided in the middle.

  As the shape of the inner surface of the cap, the shape of the convex portion may be a curved surface as shown in FIG. 1, or may be a square shape or a triangular shape as shown in FIGS.

  In the case where the flexibility of the material of the cap is large, as shown in FIG. 12, a shape having an air vent groove formed on a cap having an inner diameter slightly smaller than that of the cored bar may be used. Even if there is no groove, it can be attached if the cap is worn over time, but for work efficiency, a shape with a vent groove is better.

  A large number of air vent grooves may be formed as shown in FIG. 13, or only one as shown in FIG. The shape of the groove may be a quadrangular shape as shown in FIG. 13, a semicircular shape as shown in FIG. 15, or a triangular shape as shown in FIG. Or you may make it the inner surface of a cap fix to a metal core with the flexibility of a cap material as a polygon or a curved surface like FIG.17, FIG.18 or FIG.19 and FIG.20.

  The shape on the side where the cap enters the liquid surface during dip coating can also be any shape as shown in FIGS. 21, 22, 23, and 24 as long as the shape does not entrain bubbles in the coating liquid. If a step is provided in the middle of the cap as shown in FIG. 24, the cap can be caught when the cap is removed, so that it can be easily removed.

  Alternatively, the coating cap may have a penetrating shaft hole as shown in FIG. In this case, the pressure of the coating liquid is applied from the lower surface of the cap, and air is pushed out from between the base layer and the edge to prevent the inside of the cap from being immersed in the coating liquid. It may be inserted to prevent air leakage. Alternatively, in the case of a cap made of a material having sufficient elasticity, as shown in FIG. 26, it is possible to make a circumferential protrusion that is tightly attached to a cored bar to seal air. A plurality of the protrusions may be provided as shown in FIG.

  Examples of the method for producing the cap include injection molding and cutting, but injection molding is preferable from the viewpoint of workability.

  The diameter of the portion where the cap contacts the base layer should be slightly smaller than the diameter of the end face of the base layer. The difference in diameter is preferably about 0.01 mm or more.

  In order to create a space where the coating liquid does not enter the inner surface of the cap with the end surface of the base layer and the cap, it is preferable to insert the cap so as to bite into the base layer as shown in FIG.

  The coating cap is removed from the mandrel in a dry state in the latter half of the coating, and the coating liquid is washed with a washable solvent and reused for coating another roller.

  The surface layer of the conductive roller of the present invention preferably contains resin fine particles. More preferably, the resin fine particles are cross-linked fine particles. If it is not cross-linked, it may be dissolved when used as a coating for surface coating, which is not preferable. The monomer for forming the crosslinked polymer fine particles is not particularly limited, but vinyl monomers are preferably used from the viewpoint of ease of polymerization.

  Examples of the vinyl monomer used in the present invention include acrylic acid esters such as methyl acrylate, butyl acrylate and 2-ethylhexyl acrylate, and methacrylates such as methyl methacrylate, butyl methacrylate and hexyl methacrylate, Examples thereof include aromatic vinyl monomers such as styrene, p-methylstyrene, and α-methylstyrene, vinyl acetate, and acrylonitrile.

  In order to form polymer particles in which the resin particles are crosslinked, in the present invention, a crosslinkable vinyl monomer having two or more vinyl groups in the molecule is used in addition to the above vinyl monomer. Examples of such a crosslinkable vinyl monomer include ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and the like. The addition amount of these crosslinkable vinyl monomers is preferably 0.5 to 30 parts by mass with respect to the non-crosslinkable vinyl monomer.

  These crosslinked polymer fine particles are polymerized by seed emulsion polymerization, dispersion polymerization, suspension polymerization, etc., but are preferably polymerized by suspension polymerization because there is little residue of a low molecular surfactant or the like. . The polymerization initiator is not particularly limited, and examples thereof include peroxide catalysts such as benzoyl peroxide and lauroyl peroxide, and azo catalysts such as azobisisobutyronitrile.

  It is more preferable that the crosslinked polymer fine particles used in the present invention have a more nearly spherical shape.

  Specifically, the average circularity is preferably 0.95 or more. By precisely controlling the particle shape of the polymer fine particles so that the average circularity is 0.95 or more, the surface roughness of the charging roller becomes uniform, and even charging characteristics even when used at different process speeds Can be obtained.

  Furthermore, the circularity standard deviation is more preferably less than 0.040. By precisely controlling the particle shape of the polymer fine particles so that the standard deviation of the circularity is less than 0.04, the proportion of resin fine particles far away from the true sphere is reduced and suddenly appears on the surface of the charging roller. The probability that the protrusions of the resin particles are generated and disturb the charging is suppressed, the surface roughness of the charging roller becomes more uniform, and more uniform charging characteristics can be obtained even when used at different process speeds.

  The circularity in the present invention is used as a simple method for quantitatively expressing the particle shape. In the present invention, the particle shape is measured using a flow particle image analyzer FPIA-1000 manufactured by Toa Medical Electronics. The circularity is obtained by the following formula. Furthermore, as shown by the following equation, a value obtained by dividing the total roundness of all the measured particles by the total number of particles is defined as the average circularity.

  Here, the “particle projected area” is the area of the binarized resin particle image, and the “peripheral length of the particle projected image” is the length of the contour line obtained by connecting the edge points of the resin particle image. Define.

  In addition, “FPIA-1000”, which is a measuring apparatus used in the present invention, calculates the circularity of each particle, and then calculates the average circularity and the circularity standard deviation. Degrees of 0.400 to 1.000 at intervals of 0.010, 0.400 or more and less than 0.410, 0.410 or more and less than 0.420 ... 0.990 or more and less than 1.000 and 1.000 A calculation method is used in which the average circularity and the circularity standard deviation are calculated using the center value and frequency of the division points.

  Error between each value of average circularity and circularity standard deviation calculated by this calculation method and each value of average circularity and circularity standard deviation calculated by the above-described calculation formula that directly uses the circularity of each particle. Is very small and substantially negligible. Therefore, in the present invention, the circular shape of each particle described above is used for the reason of handling data such as a short calculation time and a simplified calculation formula. This calculation method is partially modified by using the concept of a calculation formula that directly uses the degree.

  The circularity in the present invention is an index indicating the degree of unevenness of particles, and is 1.000 when the particles are completely spherical, and the circularity becomes smaller as the surface shape becomes more complicated.

  As a specific measurement method, 10 ml of ion-exchanged water from which impure solids and the like are previously removed is prepared in a container, and a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant therein, and then further measurement is performed. Add 0.02 g of sample and disperse uniformly. As a means for dispersion, an ultrasonic disperser “UH-50 type” (manufactured by SMT Co., Ltd.) equipped with a titanium alloy chip of φ5 mm as a vibrator is used. To do. In that case, it cools suitably so that the temperature of this dispersion may not be 40 degreeC or more.

  For the measurement of the shape of the resin particles, the flow type particle image measuring apparatus is used, and the concentration of the dispersion is readjusted so that the resin particle concentration at the time of measurement is 3000 to 10,000 particles / μl. measure.

  The average particle size of the resin particles is preferably 100 μm or less. More preferably, it is 0.5 to 50 μm. More preferably, it is 1-25 micrometers. Moreover, it is preferable that there are substantially no resin particles having a particle size of 3 times or more the mass average particle size. If the particle size is too large, the charging roller surface becomes too rough and charging becomes uneven. On the other hand, if it is too small, the effect of stabilizing charging in the region of low process speed by adding resin particles does not appear.

  Below, the specific example of the particle size measurement of the resin particle in this invention is shown.

  0.1 to 5 ml of a surfactant (alkylbenzene sulfonate) is added to 100 to 150 ml of the electrolyte solution, and 2 to 20 mg of a measurement sample is added thereto. The electrolytic solution in which the sample is suspended is dispersed for 1 to 3 minutes using an ultrasonic disperser, and 0.3 μm based on the volume using an aperture that is appropriately matched to the resin particle size such as 17 μm or 100 μm by a Coulter counter multisizer. The particle size distribution of ˜40 μm is measured. The number average particle size and mass average particle size measured under these conditions are obtained by computer processing, and the cumulative ratio of the weight average particle size more than the triple diameter cumulative distribution is calculated from the volume-based particle size distribution. Find the cumulative value of.

  The addition amount of the resin particles is preferably 1 to 80% by mass as a mass ratio in the surface layer after coating. If the amount is too small, the effect of stabilizing the charging by adding resin particles cannot be obtained. If the amount is too large, it is difficult to control the viscosity of the surface coating material, and it is difficult to uniformly apply the coating.

  As the binder for the surface layer, a resin such as a thermosetting resin or a thermoplastic resin is used. As the binder for the surface layer of the present invention, a urethane resin obtained by crosslinking a lactone-modified acrylic polyol with isophorone diisocyanate and hexamethylene diisocyanate is particularly preferably used.

  When hexamethylene diisocyanate is used alone as the isocyanate to crosslink the polyol on the surface layer, the surface layer is flexible and the surface after the application of the roller is uniformly finished. There is a possibility that uncured components (for example, ionic conductive agent and plasticizer) in the base layer cannot be sufficiently prevented from oozing out to the roller surface. The presence of such a leachable substance may contaminate the photoreceptor.

  On the other hand, when isophorone diisocyanate is used alone as the isocyanate that crosslinks the polyol of the surface layer, the surface layer has a great effect of preventing the exudation of the exuding substance from the base layer, but the surface layer becomes too hard and heat shrinkage of the base layer rubber There is an adverse effect that it cannot follow, wrinkles are generated on the surface of the completed roller, and the desired roller cannot be obtained in terms of the surface roughness and shape of the roller.

  The surface layer of the roller according to the present invention provides a surface layer resin having good properties having both the isophorone diisocyanate exuding substance blocking property and the hexamethylene diisocyanate flexibility, and the exuding substance from the ionic base layer is the surface of the roller. It is possible to obtain a charging roller having a good surface shape while preventing bleeding.

  That is, the resin used for the surface layer in the present invention is such that lactone-modified acrylic polyol, isophorone diisocyanate, and hexamethylene diisocyanate are blended and cured, so that isophorone diisocyanate and hexamethylene diisocyanate react randomly with lactone-modified acrylic polyol. Thus, a crosslinked structure is formed.

  The isocyanate used in the present invention is more preferably an isocyanurate type trimer. The rigid trimer of the molecule serves as a cross-linking point, the surface layer can be cross-linked more closely, and the exuding substance from the ionic base layer is more effectively prevented from exuding on the roller surface. Can do.

  The isocyanate used in the present invention is more preferably a blocked isocyanate in which an isocyanate group is blocked with a blocking agent. The reason for this is that the isocyanate group is easy to react, and if the surface coating is left at room temperature for a long time, the reaction gradually proceeds and the characteristics of the coating may change. On the other hand, the blocked isocyanate has an advantage that the active isocyanate group is blocked and does not react up to the dissociation temperature of the blocking agent, so that the paint can be easily handled. Examples of the blocking agent for masking include phenols such as phenol and cresol, lactams of ε-caprolactam, and oximes such as methyl ethyl ketoxime. In the present invention, an oxime having a relatively low dissociation temperature. Are preferred.

  1 illustrates a trimer of a lactone-modified acrylic polyol and a blocked isocyanate constituting the surface resin of the present invention.

  On the other hand, the OH value of the lactone-modified acrylic polyol is preferably about 80 KOHmg / g. When the OH value is small, it is difficult to crosslink with an isocyanate, whereby the resin becomes too soft and easily sticks to the photoreceptor. If the OH group is too large, the coating film becomes too hard and easily cracks.

  The lactone-modified acrylic polyol is a copolymer of styrene and acrylic in the molecular chain skeleton, and has an appropriate hardness and non-contaminating property. In addition, the modified lactone group having a hydroxyl group at the terminal serves as a number of cross-linking points, and it is possible to cross-link closely with an isocyanate, thereby preventing the unvulcanized component from exuding from the base layer. Examples of such lactone-modified acrylic polyol include Plaxel DC2009 (manufactured by Daicel Chemical Industries, Ltd.).

  The glass transition temperature Tg of the resin used for the surface layer is a viscoelasticity measurement method, and the peak temperature is preferably 45 ° C. or higher, and particularly preferably 50 ° C. or higher. When the temperature is lower than 45 ° C., it is not preferable because it may be stuck to the photoconductor when left in contact with the photoconductor for a long time or the surface of the charging roller is easily contaminated with toner. .

  The measuring method of the glass transition temperature Tg in the present invention is as follows. First, the surface layer sample for measurement peels off a surface layer from a roller state, and cuts out into strips of about 5 mm × 40 mm. As a measuring device, a dynamic viscoelasticity measuring device RSA-II (manufactured by Rheometrics Scientific F.E.) is used, and a film tension fixture is used as a jig. The measurement was performed at a measurement frequency of 6.28 rad / sec and a temperature increase rate of 5 ° C./min. In an auto tension mode with an initial strain of 0.07 to 0.25%. The temperature dispersion of the loss tangent tan δ is measured, and the peak temperature is defined as Tg.

  Although not particularly limited, too high Tg is not preferable because the flexibility of the resin is lost and the coating film is easily broken. Tg is adjusted by the ratio or amount of isocyanate to be crosslinked.

  The blending ratio of the lactone-modified acrylic polyol resin and the isocyanate is the ratio of the number of NCO groups (A) in the isocyanate in the blended paint to the number of OH groups (B) in the lactone-modified acrylic polyol resin, NCO The / OH ratio = A / B is preferably 0.1 to 2.0, and particularly preferably adjusted to be in the range of 0.3 to 1.5.

  By cross-linking the lactone-modified acrylic polyol with isocyanate, it prevents the low-molecular component from oozing out from the conductive elastic base layer, and the surface layer on which the charging roller itself is not easily contaminated with toner and does not contaminate the photoreceptor. Can be formed.

  It is also preferable to mix various conductive agents and leveling agents into the resin coating that forms the surface layer. Examples of the leveling agent include silicone oil.

  Examples of the conductive agent used for the surface layer include metal powders and fibers such as aluminum, palladium, iron, copper, and silver, carbon black, metal powder, metal oxides such as titanium oxide, tin oxide, and zinc oxide, and copper sulfide. Electrolytic treatment, spray coating, metal compounds such as zinc sulfide, tin oxide, antimony oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, chromium, cobalt, iron, lead, platinum, rhodium, Examples thereof include powders adhered to the surface by mixed shaking, carbon powders such as acetylene black, ketjen black, PAN-based carbon, and pitch-based carbon.

  In the present invention, as the conductive agent, conductive tin oxide doped with antimony is particularly preferably used. The reason is that conductive tin oxide doped with antimony has a relatively large volume resistivity of the conductive agent itself, and the difference from the volume resistivity of the resin in which the conductive agent is dispersed is small compared to other conductive agents. When the conductive agent is dispersed to form a medium resistance surface layer material, a slight difference in the distribution of the conductive agent is unlikely to cause a difference in resistance of the surface layer material, and variation due to the position of the resistance can be suppressed to a relatively small level. This is because it is suitable as a conductive agent for the surface layer material of the present invention.

The amount of these conductive agents added to the surface layer resin is such that the volume resistivity of the surface layer resin is a low temperature and low humidity environment (L / L: 15 ° C./10% RH), a normal temperature and normal humidity environment (N / N: 23 ° C. / 55% RH) and a high-temperature and high-humidity environment (H / H: 30 ° C./80% RH) so that the medium resistance region (volume resistivity is 1 × 10 ⁶ to 1 × 10 ¹⁵ Ω · cm).

  If the volume resistivity of the surface layer is smaller than this, when used as a charging roller, when the photoconductor has a pinhole, an excessive current flows through the pinhole and leaks, and the leaked trace appears in the image. Therefore, it is not preferable. On the other hand, if the volume resistivity is too large, current does not flow through the charging roller, and the photosensitive member cannot be charged to a predetermined potential, so that the image does not have the desired density. Further, even if the potential is charged to a certain level, it is not preferable because the charging becomes non-uniform and appears on the image.

  For the volume resistance of the surface layer, the surface layer is peeled off from the roller state and cut into a strip of about 5 mm × 5 mm. Metal is vapor-deposited on both sides to produce an electrode and a guard electrode, and a voltage of 200V is applied using a microammeter (ADVANTEST R8340A ULTRA HIGH RESISTANCE METER Co., Ltd., Advantest) to measure the current after 30 seconds. And calculated from the film thickness and the electrode area.

  As a compounding quantity of electroconductive tin oxide, 10-80 mass% is preferable with respect to the surface layer after coating, Most preferably, it is 20-60 mass%. The primary particle size of the conductive tin oxide is preferably 0.1 μm or less by observation with a differential scanning electron microscope. Disperse by a known method until the secondary particles become small in the surface coating. The secondary particle size is a value of volume average particle size MEDIAN measured by a centrifugal sedimentation type particle size distribution meter (CAPA700: manufactured by Horiba Seisakusho), preferably 1.0 μm or less, and particularly preferably 0.5 μm or less. If the secondary particle diameter is large, the variation due to the position of the resistance of the surface layer material becomes large, which causes uneven charging.

  The surface of the conductive tin oxide used in the present invention is preferably surface-treated with a coupling agent. The coupling agent is a compound having a hydrolyzable group and a hydrophobic group in the same molecule and bonded to a central element such as silicon, aluminum, titanium or zirconium, and a long chain alkyl group in this hydrophobic group part. It is what has.

  As the hydrolyzable group, for example, alkoxy groups such as methoxy group, ethoxy group, propoxy group and butoxy group having relatively high hydrophilicity are used. In addition, an acryloxy group, a methacryloxy group, modified products thereof, halogen, and the like are also used. The hydrophobic group only needs to include a structure in which six or more carbon atoms are connected in a straight chain in the structure, and in the bonding form with the central element, carboxylate ester, alkoxy, sulfonate ester or phosphoric acid. It may be bonded via an ester or directly. Furthermore, functional groups such as ether bonds, epoxy groups and amino groups may be included in the structure of the hydrophobic group. By treating with a coupling agent, moisture adsorption on the surface of tin oxide can be suppressed, and a surface layer material with less environmental fluctuation can be obtained. As the coupling agent used in the present invention, a highly reactive silane coupling agent is preferable.

  Examples of silane coupling agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, trifluoropropyltrimethoxy. Examples include silane and hexyltrimethoxysilane, and trifluoropropyltrimethoxysilane is particularly preferable because the environmental variation of the volume resistivity of the conductive agent can be suppressed.

  As a method for forming the surface layer, the material constituting the surface layer is dispersed by a known method using a conventionally known dispersion apparatus using beads such as a sand mill, a paint shaker, a dyno mill, and a pearl mill, and the obtained surface layer is formed. The resin coating for coating is applied by dip coating on the surface of the conductive roller, in the present invention on the conductive elastic base layer.

  The film thickness of the surface layer is preferably 3 to 50 μm, more preferably 5 to 30 μm. When the film thickness of the surface layer is larger than 50 μm, the uniformity of charging is impaired, and fine white stripes are generated in the axial direction of the image upper roller, which is not preferable. The film thickness can be measured by cutting the roller cross section with a sharp blade and observing with an optical microscope or an electron microscope. In the present invention, using an electron microscope, a cross section of a roller cut out with a sharp blade is photographed at a magnification of 2000 times, film thicknesses at five locations are measured randomly in one screen, and the length is averaged at one location. The film thickness is calculated. This measurement was performed for a total of 6 points of 3 points in the axial direction and 2 points in the circumferential direction of the same roller, and averaged to obtain the total average film thickness. At this time, the position of the roller in the axial direction is the film thickness at a position away from the central portion and the central portion of 40% of the total length of the base layer of the roller.

  To adjust the surface layer thickness, the solid content of the surface layer paint and the coating pull-up speed are controlled. When the solid content of the resin in the surface coating is increased, the film thickness of the surface layer is increased, and when the solid content is decreased, the film thickness is also decreased. In the surface layer paint, the solid content of the resin with respect to the volatile solvent is adjusted to 10 to 40%. Further, when the coating pulling speed is increased, the film thickness is increased, and when the coating pulling speed is decreased, the film thickness is decreased. Adjust to.

  In the case of dip coating, in general, the film thickness varies depending on the location in the axial direction of the roller, and the film thickness varies relatively depending on the position in the circumferential direction of the roller. That is, since the surface layer coating liquid has a property of flowing downward due to gravity, when dip coating is performed, the film tends to be thicker toward the lower side of the roller. In the present invention, in order to suppress variations in film thickness due to the position in the roller axial direction, the roller is coated once and then coated again with the axial direction turned upside down. In other words, a single-time coating causes a gradient of the film thickness in the axial direction of the roller, but by reversing the coating, the gradient of the roller surface layer thickness is offset. It is possible to obtain a roller having substantially the same film thickness over the entire axial direction.

  By using the coating cap of the present invention, since the surface coating liquid does not penetrate into the cap, the boundary line between the base layer end face of the completed roller and the surface layer reflects the shape of the end of the cap. Become a shape. In order to measure the circular shape of the boundary line, in the present invention, as shown in FIG. 39, the end of the roller is photographed vertically by the digital camera 36 from the extension line of the shaft of the end of the roller, and the obtained image is obtained. The major axis a and minor axis b are measured above, and the value of minor axis / major axis is taken as the circularity of the boundary line. In the conductive roller of the present invention, the circularity is preferably 0.9 or more, more preferably 0.95. If the coating liquid of the surface layer wraps around the end surface of this base layer and forms a hardened film harder than the base layer, the amount of deformation with respect to the pressing force at the end of the conductive roller changes in the circumferential direction of the roller. Therefore, when it is used when a high-definition image such as a halftone image of 600 dpi is output as a primary charging roller incorporated in an image forming apparatus that requires a precise contact state such as DC charging, It appears as unevenness, which is not preferable.

  Moreover, when the coating cap of this invention is used, the completed surface layer protrudes a little in the roller edge part direction from the base layer end surface. This makes it possible to prevent contact between the base layer having low electrical resistance and the photoconductor, and it is possible to prevent current from leaking into the pinhole in the event that the photoconductor has a pinhole. The protrusion amount of the surface layer from the end face of the base layer is preferably uniform over the entire circumference of the roller. In the present invention, as shown in FIG. 40, the variation in the protruding amount is measured using a roundness measuring device RA600 (manufactured by Mitutoyo Corporation). While rotating the roller, using a stylus 37 having a spherical tip having a radius of 0.5 mm and made of SUS304, the unevenness in the roller axial direction of the surface end surface is measured. In the present invention, it is preferable that the variation in the protruding amount of the surface layer from the end face of the base layer is small. Preferably, the protrusion amount variation is determined by a difference between the maximum value and the minimum value of the protrusion amount of the surface layer from the end face of the base layer. In the present invention, the variation in the protrusion amount is preferably 0.5 mm or less, more preferably 0.3 mm or less. If the variation is large, the amount of deformation with respect to the pressing force at the end of the conductive roller will vary in the circumferential direction of the roller, resulting in unevenness, and an image forming apparatus that requires a precise contact state like DC charging is required. When used as a primary charging roller to output a high-definition image such as a halftone image of 600 dpi, for example, it appears as uneven charging, which is not preferable.

  As the surface roughness of the conductive roller of the present invention, preferably 10-point average roughness Rz according to JIS B 0601-1994 is 0.5 μm to 30 μm, Ra is 0.1 μm to 5 μm, more preferably 10-point average. The roughness Rz is 1 μm or more and 20 μm or less, and Ra is 0.2 μm or more and 3 μm or less. If the surface roughness is too large, uneven charging tends to appear in the output image, and if the surface roughness is too small, the effect of stabilizing the charging at a slow process speed by adding resin particles is not preferable.

  As a measuring method of average roughness (Ra, Rz), based on the surface roughness of JIS B 0601, a total of 6 points of 3 points in the axial direction and 2 points in the circumferential direction were measured with a surf coder SE3400 manufactured by Kosaka Laboratory. And take the average value. In the present invention, the contact needle is a diamond having a tip radius of 2 μm, a measurement speed of 0.5 mm / s, a cutoff λc of 0.8 mm, a reference length of 0.8 mm, and an evaluation length of 8.0 mm.

  In order to obtain a conductive roller having a surface roughness in the above range, the surface roughness of the base layer, the film thickness of the surface layer, the average particle diameter of the resin particles, and the addition amount are adjusted. The ten-point average roughness of the base layer is preferably 20 μm or less, more preferably 15 μm or less in terms of Rz.

Further, as shown in FIG. 38, the conductive roller is brought into contact with a circular cylindrical metal having the same curvature as that of the photosensitive member under the same stress as that in the usage state when used in the image forming apparatus, and the same as in the usage state. (In the present invention, a force of 5 N is applied to both ends of the shaft to bring it into contact with a metal cylinder having a diameter of 30 mm, and the metal cylinder is rotated at a peripheral speed of 45 mm / s.) ) The electrical resistance of the conductive roller when a DC voltage of -250 V is applied is 1 × 10 ⁶ Ω or more in a high temperature and high humidity environment of 30 ° C./80% RH, and low temperature and low humidity of 15 ° C./10%. In the environment, it is preferably 1 × 10 ⁸ Ω or less. More preferably, it is 2 × 10 ⁶ Ω or more in a high temperature and high humidity environment of 30 ° C./80% RH, and it is preferably 6 × 10 ⁷ Ω or less in a low temperature and low humidity environment of 15 ° C./10%.

  It is preferable that the resistance in a low-temperature and low-humidity environment is smaller than the above range because fine horizontal white lines on the halftone image due to charging unevenness hardly occur. Further, it is preferable that the resistance in a high-temperature and high-humidity environment is larger than the above range because even if there is a pinhole in the photoconductor, the applied current does not leak and the uneven density of charging does not appear on the halftone image.

In order to make the electric resistance within the above range, the volume resistivity of the conductive elastic base layer of the conductive roller is set to 1 × 10 ⁴ to 1 × 10 ⁷ Ω · cm, and the volume resistivity of the surface layer is set to 1 × 10 ⁸ to What is necessary is just to adjust so that it may be 1 * 10 < ¹⁵ > (omega | ohm) * cm and the film thickness of a surface layer may be 10-50 micrometers.

<2> Image Forming Apparatus FIG. 34 shows an image forming apparatus using a charging roller 6 which is an embodiment of a conductive roller. The photosensitive drum 5 serving as an image carrier is primarily charged by the charging roller 6 while rotating in the direction of the arrow, and then exposure 11 is irradiated by the exposure unit to form an electrostatic latent image. The toner in a thin layer on the developing roller 4 as developing means is charged by the toner charging roller 29 and then brought into contact with the surface of the photosensitive drum 5 to develop the electrostatic latent image and visualize the toner image. Is formed.

  The developed toner image is transferred from the photosensitive drum 5 to the printing medium 7 as the transfer target member in the developing portion between the transfer roller 8 as the transfer member and the photosensitive drum 5, and then heated and fixed in the fixing portion 9. It is fixed by pressure and becomes a permanent image. The latent image remaining on the photosensitive drum is exposed by the pre-charging exposure device 11, and the potential of the photosensitive drum returns to the ground potential. The untransferred toner that has not been transferred is collected by the cleaning blade 10.

  Voltages are respectively applied to the developing roller 4, the toner charging roller 29, the charging roller 6, and the transfer roller 8 from the power supplies 18, 19, 20, and 22 of the image forming apparatus.

  Here, a DC voltage is applied from the power source 20 to the charging roller 6 which is a conductive roller. By using a DC voltage as the applied voltage, there is an advantage that the cost of the power supply can be kept low. In addition, there is an advantage that no charging noise is generated when an AC voltage is applied.

  The absolute value of the DC voltage to be applied is preferably the sum of the discharge start voltage of air and the primary charging potential of the surface of the member to be charged (photosensitive member surface). Usually, the discharge start voltage of air is about 600 to 700 V, and the primary charging potential of the photoreceptor surface is about 300 to 800 V. Therefore, the specific primary charging voltage is preferably 900 to 1500 V.

  In the case of a color image forming apparatus, as shown in FIG. 35, the photosensitive drums 5a to 5d, image rollers, transfer rollers 8a to 8d, charging rollers 6a to 6d, toner charging rollers 29a to 29d, and elastic regulation blades 30a to 30d. d, exposures 11a to 11d, toner containers 31a to 31d and the like may be prepared for each of four colors and arranged in series.

<3> Charging method The present invention provides a charging method for charging an object to be charged by applying a DC voltage to a conductive roller.

<4> Process Cartridge The present invention relates to an image carrier, developing means for transferring toner to an electrostatic latent image formed on the image carrier and visualizing the toner, and forming a toner image on the member to be transferred. One or more selected from cleaning means for removing toner remaining on the image carrier after the image is transferred are supported integrally with the conductive roller, and are detachable from the image forming apparatus. Process cartridge.

  For example, as shown in FIG. 36, the process cartridge of the present invention is configured to be detachable from the main body of the image forming apparatus in which the photosensitive drum 5, the charging roller 6, the developing roller 4, the cleaning blade 10, and the like are integrally supported. It is.

  Before the electrophotographic process cartridge is used, it is preferable to avoid contact between the developing roller 4 and the toner by the toner seal 27.

  The present invention will be described below with reference to examples, but the present invention is not limited to the examples.

Example 1
<Production of charging roller>
(1) Preparation of conductive elastic body base layer 100 parts by mass of epichlorohydrin rubber (trade name: Epichromer CG102, manufactured by Daiso Corporation), 30 parts by mass of calcium carbonate as a filler, 1 part by mass of zinc stearate as a lubricant, polishing Colored grade carbon (trade name: SEAST SO, manufactured by Tokai Carbon Co., Ltd.) 4 parts by mass, zinc oxide 5 parts by mass as a plasticizer, and a copolymer of sebacic acid and propylene glycol as a plasticizer (molecular weight 8000) 5 parts by weight, 2 parts by weight of perchloric acid quaternary ammonium salt represented by the following formula, 1 part by weight of 2-mercaptobenzimidazole as an anti-aging agent are kneaded for 20 minutes with an open roll, and further as a vulcanization accelerator 1 part by weight of DM (2-benzothiazolyl disulfide), TS (tetramethylthiurammo) as a vulcanization accelerator Nosulfide) 0.5 parts by mass and 1.2 parts by mass of sulfur as a vulcanizing agent were added and further kneaded with an open roll for 15 minutes.

  This was extruded into a cylindrical shape with an outer diameter of 15 mm and an inner diameter of 5.5 mm using a rubber extruder, cut into a length of 250 mm, and primary in 40 ° C. steam for 40 minutes using a vulcanizing can. Vulcanized to obtain a primary vulcanized tube of conductive elastic base layer rubber.

  Next, a thermosetting adhesive of metal and rubber (trade name: product name: 231 mm in the axial central portion of the cylindrical surface of a cylindrical conductive support (made of steel, surface is nickel-plated) having a diameter of 6 mm and a length of 256 mm. Metallock U-20) was applied, dried at 80 ° C. for 30 minutes, and then dried at 120 ° C. for 1 hour. This conductive support is inserted into the conductive elastic base layer rubber primary vulcanization tube, and then subjected to secondary vulcanization and adhesive curing in an electric oven at 160 ° C. for 2 hours to obtain an unpolished layer. Got.

  Cut off both ends of the rubber part of this unpolished layer and make the length of the rubber part 231 mm, and then polish the rubber part with a rotating grindstone to form a crown shape with an end diameter of 12.00 mm and a central part diameter of 12.10 mm A charging roller having a conductive elastic base layer having a surface ten-point average roughness Rz of 6 μm and a deflection of 25 μm was obtained.

After measuring the resistance of the charging roller having the conductive elastic base layer after leaving the charging roller having the conductive elastic base layer in an N / N environment (normal temperature and humidity: 23 ° C./55% RH) for 24 hours or more. 3.0 × 10 ⁵ Ω. The micro rubber hardness of the rubber part was 49 °.

(2) Preparation of surface layer coating liquid 50 parts by mass of conductive tin oxide powder (trade name: SN-100P, manufactured by Ishihara Sangyo Co., Ltd.) and 500 parts by mass of a 1% isopropyl alcohol solution of trifluoropropyltrimethoxysilane And 300 parts by weight of glass beads having an average particle diameter of 0.8 mm are added and dispersed with a paint shaker for 70 hours. The dispersion is then filtered through a 500 mesh screen, and this solution is stirred at 100 ° C. with a Nauta mixer. The mixture was heated in a hot water bath to remove alcohol and dried, and a silane coupling agent was applied to the surface to obtain surface-treated conductive tin oxide powder.

  288 parts by mass of lactone-modified acrylic polyol (trade name: Plaxel DC2009, manufactured by Daicel Chemical Industries, Ltd.) was dissolved in 972 parts by mass of MIBK (methyl isobutyl ketone) to obtain a solution having a solid content of 16% by mass. 57 parts by mass of the surface-treated conductive tin oxide powder and 0.05 parts by mass of silicone oil (trade name: SH-28PA, manufactured by Toray Dow Corning Silicone Co., Ltd.) with respect to 200 parts by mass of the acrylic polyol solution. , Fluororesin powder (trade name: Lubron L2, manufactured by Daikin Industries, Ltd.), 16 parts by mass, crosslinked polymethyl methacrylate having an average particle size of 12 μm (trade name: MBX-12, manufactured by Sekisui Plastics Co., Ltd.) 200 parts by weight of glass beads having a diameter of 0.8 mm were added thereto, and the mixture was placed in a 450 ml mayonnaise bottle and dispersed for 5 hours using a paint shaker. A chart of the particle size distribution of the used crosslinked polymethylmethacrylate resin particles is shown in FIG.

  25.6 parts by mass of block type isocyanurate type trimer of isophorone diisocyanate (trade name: Bestanat B1370, manufactured by Degussa Huls) and isocyanurate type trimer of hexamethylene diisocyanate (product) Name: Duranate TPA-B80E (manufactured by Asahi Kasei Kogyo Co., Ltd.) was mixed with 16.4 parts by mass, stirred with a ball mill for 1 hour, and finally the solution was filtered through a 200-mesh net to obtain a surface paint. The viscosity of the paint was 8.0 mPa · s in an environment of 23 ° C.

  The surface coating was applied to the surface of the charging roller having the conductive elastic base layer by dip coating.

  At this time, a polyethylene coating cap having the shape of FIG. 1 was attached to the lower end portion of the conductive elastic base layer. As shown in FIG. 31 (a), the attachment was performed with a force of 100 N for 3 seconds so that the edge of the cap end bites into the end surface of the conductive elastic base layer. All excess air inside the cap was removed, and the entire circumference of the edge of the cap completely contacted the end of the conductive elastic base layer.

  The roller equipped with this cap was applied at a pulling speed of 400 mm / min, air-dried for 10 minutes, and then the cap was removed. As shown in FIG. 31C, the roller end face was uniformly coated over and around the entire circumference.

  Next, the axial direction at the time of roller application is reversed and coating is performed. 1 was attached to the end portion that was inverted to be under the roller, and was coated in the same manner as the first coating. After air-drying again for 30 minutes, it was dried in an oven at 80 ° C. for 30 minutes, and then dried in an oven at 160 ° C. for 60 minutes.

  A surface layer having a uniform film thickness of 22 μm was formed on the obtained charging roller over the entire image area of the roller. Further, the micro rubber hardness of the roller on which the surface layer was formed was 55 °. The roller thus obtained was used as the charging roller of Example 1.

<Evaluation of charging roller>
Image Evaluation The electrophotographic laser printer used in this test is an A4 vertical output machine, the output speed of the recording medium is 100 mm / sec and 30 mm / sec, and the image resolution is 600 dpi.

  The photoreceptor is a reverse development type photosensitive drum in which an aluminum cylinder is coated with an OPC layer having a film thickness of 16 μm, and the outermost layer is a charge transport layer using a modified polycarbonate as a binder resin.

  The toner is made by polymerizing a random copolymer of styrene and butyl acrylate containing a charge control agent and a pigment mainly with wax, further polymerizing a polyester thin layer on the surface, and adding silica fine particles and the like, glass transition temperature 63 ° C., mass This is a polymerized toner having an average particle size of 6 μm.

  For the primary charging, the charging roller of Example 1 obtained above was used, and a DC voltage of −1150 V was applied to the charging roller.

  In an environment of normal temperature and humidity (23 ° C / 55%), a halftone image (an image that draws a horizontal line with a width of 1 dot and an interval of 2 dots in the direction perpendicular to the rotation direction of the photoconductor) is output. A good image was obtained.

  The boundary line between the surface layer and the base layer at the end of the roller was taken with a digital camera, and the circularity was determined to be 0.99. Moreover, the variation in the protrusion amount of the surface layer was 0.2 mm. That is, the charging roller of Example 1 was formed in a concentric shape with a good surface layer up to the end.

(Comparative Example 1)
The roller of Comparative Example 1 was applied in the same manner as in Example 1 except that the shape of the coating cap was a closed cylindrical shape as shown in FIG.

  Then, the coating liquid enters between the coating cap and the conductive elastic base layer, and as shown in FIG. 30 (c), when the cap is removed, the undried coating liquid is stretched and the cored bar is applied. A good roller could not be applied.

(Comparative Example 2)
The same coating cap as in Comparative Example 1 was used, and the cap was removed 3 hours after the coating for both the first and second coatings.

  Then, the coating liquid that entered between the coating cap and the conductive elastic base layer was generally air-dried, but the coating film was brittle, and when the cap was removed, the surface layer at the end of the roller was irregular. As a result, a portion where the surface layer was not partially formed at the end portion was generated. When an image was output from this roller in the same manner as in Example 1, current leaked from the exposed portion of the conductive elastic base layer at the edge of the image, and density unevenness of the charging roller cycle was observed in the halftone image.

(Comparative Example 3)
The coating liquid of Example 1 was used in the same manner as in Example 1 except that the solvent was removed using a rotary evaporator to concentrate the coating liquid and the viscosity was 350 mPa · s. Moreover, the coating cap of the comparative example 1 was used for the coating cap.

  The film thickness of the obtained roller was as large as 53 μm. The micro rubber hardness of the roller was as large as 75 °. The coating liquid did not enter the contact surface between the cap and the base layer, and the circularity was 0.97, which was good, but the variation in the amount of protrusion was 0.5 mm. When this roller was used to output an image in the same manner as in Example 1, horizontal white streaks were generated and could not be used as a charging roller for DC charging.

It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap of a reference example . It is sectional drawing of the coating cap of a reference example . It is sectional drawing of the coating cap of a reference example . It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of the coating cap used by this invention. It is sectional drawing of another coating cap. It is sectional drawing of another coating cap. It is sectional drawing of another coating cap. It is sectional drawing of the coating cap used with the conventional method . It is a top view of the coating cap used by this invention. It is the schematic of the coating method using the coating cap used by this invention. It is the schematic of the coating method using the coating cap used by the conventional method . The schematic showing the cross section of one Embodiment of the electroconductive roller manufactured with the method of this invention is shown. (A) Cross section of conductive roller, (b) Cross section of conductive roller It is the schematic of the measuring method of the shake of the charging roller manufactured with the method of this invention. 1 is a schematic view of a full-color image forming apparatus using a charging roller which is an embodiment of a conductive roller manufactured by the method of the present invention. It is the schematic of another full-color image forming apparatus using the charging roller which is one embodiment of the electroconductive roller manufactured by this invention. It is the schematic of the process cartridge currently supported integrally with the electroconductive roller manufactured with the method of this invention. 2 is a chart of particle size distribution of resin particles used in Example 1. FIG. It is the schematic of the measuring method of the resistance of the charging roller used for the Example. It is the schematic of the measuring method of the circularity of the charging roller used for the Example. It is the schematic of the measuring method of the variation in the protrusion amount of the surface layer of the charging roller used for the Example.

Claims (1)

A core metal, a core and an elastic body base formed Kaneage method of charging roller having a surface layer formed on the elastic body base,
(1) forming an elastic base layer on the core metal except the end portion of the core metal,
(2) a step of immersing the metal core formed with the elastic base layer obtained in the step (1) in a surface coating material and applying the surface coating material ;
In the step (2) , a coating cap is attached to the end of the cored bar formed with the elastic base layer obtained in the step (1), and the end of the cored bar and the end surface of the elastic base layer are connected to the end of the cored base. Covering with a coating cap, and then rushing the cored bar into the surface layer coating with the side on which the coating cap is attached facing down,
When the coating cap is attached to the end of the cored bar, it contacts the end surface of the elastic base layer at the edge, and the cap does not touch the boundary between the elastic base layer and the cored bar. It is configured to create a space,
Coating Engineering caps, the side opposite to the side in contact with the elastic body base, the manufacturing method of the charging roller, characterized that you have a streamlined shape that its diameter becomes smaller.

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