JP4887103B2 - Method for evaluating conductive roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive roller comprising at least one covering layer on the outer peripheral surface of a conductive shaft body, wherein variance in nip width is not caused in the shaft direction or the periphery direction of the roller during rotation of the roller when the roller is used while pressed on a photoreceptor or the like and one-sided adhesion of soiling such as paper powder is not caused on the outer peripheral surface of the roller even when the roller is used over a long term. <P>SOLUTION: The conductive roller has one or more covering layers formed on the outer peripheral surface of the conductive shaft body, wherein the deflection of its outer peripheral surface during rotation is 50 &mu;m or less in a shaft direction, and when measuring a distance E between a measurement reference bar put nearly in parallel with the roller and the surface of the covering layer of the roller by one round of the roller on both end sides (P1 and P3) and a center part (P2), setting measured values at the rotational angle &theta; of the roller as E1&theta;, E3&theta; and E2&theta; respectively, and obtaining a distance difference &Delta;Eä=E1&theta;(or E3&theta;)-E2&theta;} at the rotational angle &theta; of the roller, a difference (&omega; value) between a maximum value and a minimum value during one round of the roller is 30 &mu;m or less. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

The present invention is a copying machine, a printer, an electrophotographic device such as a facsimile, a conductive roller used in an image forming apparatus such as an electrostatic recording apparatus, method for evaluating particular charging roller.

  In a conventional electrophotographic apparatus, a contact charging device for uniformly charging the surface of a photosensitive member is a member to be charged by a method of applying a DC voltage to a charging roller, a method of simultaneously applying an AC power source and a DC power source, etc. A discharge electric field is formed between the photosensitive member and the surface of the photosensitive member is uniformly charged.

  As a configuration of the charging roller for uniformly charging the photosensitive member, a conductive elastic layer made of rubber or resin is generally provided on a conductive shaft body such as iron or stainless steel. A conductive material such as conductive carbon black or metal powder is added to the elastic layer to provide conductivity, and the elastic layer has a suitable elasticity for proper contact (nip width) with the photoreceptor. It is held. For the adjustment of elasticity, softeners such as oil and plasticizer are added, but these softeners are generally migratory and may contaminate the photoreceptor, so a surface layer is provided if necessary. It is done.

  The charging roller having such a configuration is pressed against the photoconductor with an appropriate pressing force in the contact charging device, and a voltage is applied to the photoconductor to charge the surface of the photoconductor. As a pressing mechanism, generally, a pressing means such as a spring is provided at both ends of the charging roller, and contact between the photosensitive member and the charging roller is formed as a nip width.

  In order to uniformly charge the surface of the photosensitive member, it is desirable that the charging roller forms a nip width by deformation in the axial direction with respect to the photosensitive member to form a uniform discharge state. Since the charging roller bends and is deformed as the end of the charging roller is deformed, the nip width formed on the contact surface with the photosensitive member is from the center to the end of the charging roller. When the deflection is remarkable, the contact between the charging roller and the photosensitive member may be impaired in the central portion in the axial direction.

  As a method of uniformly obtaining the nip width in the axial direction between the charging roller and the photosensitive member, a method of shaping the outer shape of the charging roller into a so-called crown shape in which the outer shape gradually decreases from the central portion toward both ends.

  As a charging roller having a crown shape, one in which an elastic resistance layer molded on a conductive shaft body is polished into a crown shape and then covered with a covering resistance layer is known (see, for example, Patent Document 1).

  However, even if the crown amount is appropriate, if the overall deflection in the axial direction of the roller or the elastic layer has a large deviation, the photosensitive member and the photosensitive member are rotated while the charging roller rotates once during the rotational movement of the photosensitive member. Variation in the nip width occurs, and an abnormal image due to defective charging occurs.

  In addition, even if the deflection in the roller axis direction and the elastic layer unevenness are small overall, if the variation in the roller axis direction is large, a difference in the nip width between the left and right when pressed against the photoconductor is caused. There is also a problem that a difference in right and left is caused even by vibration due to rotational movement with the photosensitive member.

The effect of this variation is noticeable when the contact charging device is used for a long time, and even when a normal image is initially obtained, paper dust or the like adhering to the outer peripheral surface of the charging roller during long-term use is charged roller. Due to non-uniform adhesion on the outer peripheral surface, an abnormal image due to poor charging is likely to occur.
JP-A-10-161390

Therefore, the present invention provides a conductive roller composed of at least one coating layer on the outer peripheral surface of the conductive shaft body. When the roller is pressed against a photosensitive member, the roller is rotated in the axial direction or the roller circumferential direction. Evaluation method of a conductive roller that can stably obtain a high-quality image without causing unevenness in the nip width, and even when used for a long period of time, dirt such as paper dust does not adhere unevenly on the outer peripheral surface of the roller . Is to provide.

  The present inventors have intensively studied to solve the above problems, and the center portion of the distance between the run-out of the conductive roller, the distance between the roller surface and a straight bar placed substantially parallel to the roller, and the end portion of the coating layer It was found that good roller properties can be obtained when the difference is within a predetermined range. The present inventors have further studied and arrived at the present invention.

In the present invention , a conductive roller is placed almost in parallel with a straight measurement reference rod, and the separation distance E between the measurement reference rod and the surface of the coating layer of the roller is set at both ends (P1, P3) and the central portion (P2). Measured for one rotation of the roller, and when the measured values at the roller rotation angle θ are E1θ, E3θ, and E2θ, respectively, the maximum value and the minimum value for one rotation of the roller are calculated for each of the separation distances E1θ, E2θ, and E3θ The maximum value is obtained, and the deviation of the outer peripheral surface of the roller is determined. Further, the difference ΔE {= E1θ (or E3θ) −E2θ} at the roller rotation angle θ is obtained. A method for evaluating a conductive roller is characterized in that a difference is obtained and set as a ω value, and the roller property is evaluated from the runout and the ω value .

In addition, it is preferable that the conductive roller has a deflection of the outer peripheral surface of the roller of 50 μm or less and a ω value of 30 μm or less .

Further, the conductive roller has a crown shape, and the crown amount {D2− (D1 + D3) / 2 when the roller outer diameters at P1, P2 and P3 for which the separation distance E is obtained are D1, D2 and D3, respectively. } Is preferably 30 μm or more and 500 μm or less .

  The conductive roller preferably has a micro hardness measured on the roller surface in the range of 30 ° to 85 °.

  According to the present invention, when used while being pressed against a photoreceptor, the nip width does not vary in the axial direction or the circumferential direction of the roller when the roller rotates, and a stable and high-quality image can be obtained even when used for a long period of time. A conductive roller is provided that can be obtained.

  Hereinafter, the present invention will be described in detail.

  In the conductive roller according to the present invention, one or more conductive coating layers are provided on the outer peripheral surface of the conductive shaft body, and the deflection of the outer peripheral surface when rotated is 50 μm or less in the axial direction.

  When the deflection of the conductive roller exceeds 50 μm, the nip width when it is pressed against a photoreceptor or the like and rotated is varied over the entire surface in the axial direction, so that a good image can be obtained even when assembled in an electrophotographic apparatus. Can not.

  Then, the separation distance E between the measurement reference rod and the surface of the coating layer of the roller, which is substantially parallel to the roller, is measured for one round of the roller at both ends (P1, P3) and the central portion (P2), and measured at the roller rotation angle θ. When the values are E1θ, E3θ, and E2θ, respectively, the difference (ω value) between the maximum value and the minimum value during one round of the roller of the separation distance difference ΔE {= E1θ (or E3θ) −E2θ} at the roller rotation angle θ. It is 30 μm or less.

  First, a method for measuring E1θ, E3θ, E2θ, which is important in the present invention, will be described with reference to FIG.

  In the conductive roller of the present invention, a conductive coating layer 2 is formed around the conductive shaft 1, and the outer diameter thereof preferably has a crown shape. The conductive roller is supported by fulcrums A and B of the conductive shaft body 1. A measurement reference bar 3 is placed almost in parallel with the conductive roller. The distance E between the coating layer surface and the measurement reference bar 3 is measured at positions P1 and P3 at a predetermined distance (L) from both ends of the conductive coating layer 2 of the conductive roller and at the position of the central portion P2. Next, the roller is rotated by a predetermined angle, and the separation distance E is measured again. In this way, one roller rotation is measured sequentially. The separation distances E measured at P1 to P3 at this time are E1θ, E2θ, and E3θ, respectively (note that θ means the angle at which the roller is rotated). Here, the predetermined angle to be rotated can be set every 1 ° as long as the number of times of measurement is large. However, it is preferable to set the angle so that the measurement is normally performed 10 to 15 times.

  Using the separation distances E1θ to E3θ, the separation distance difference ΔE (= E1θ (or E3θ) −E2θ) is calculated for each roller rotation angle, and the maximum value and the minimum value of one rotation of the roller are obtained. The difference between the maximum value and the minimum value is the ω value, which is an index for rotation in the evaluation of the roller. It is important that this ω value is 30 μm or less.

  When the ω value exceeds 30 μm, when the roller rotates, the roller rotates eccentrically at a specific position with respect to the axial direction as shown in FIGS. In particular, the nip width varies. In this case, a good image can be obtained at the initial stage of image output even if it is mounted on an electrophotographic apparatus as long as the above-mentioned deflection satisfies 50 μm or less. In particular, local stains are likely to occur, and high quality images cannot be obtained.

  The distance L from both end faces of the coating layer of the conductive roller to P1 and P3 is preferably an arbitrary distance corresponding to 5 to 20 when the roller coating layer surface length is 100. If it is less than 5, it may correspond to a non-image area that does not contribute to image formation in the roller axis direction when used by being assembled in an electrophotographic apparatus, and is not suitable in the present invention. In addition, when the number exceeds 20, the positions of P1 and P3 are too close to the central portion, so that the abnormality of the roller shape is not sufficiently reflected in the ω values represented by (E1θ−E2θ) and (E3θ−E2θ). It is also unsuitable because of poor correlation with images.

  The conductive roller according to the present invention has a crown shape in which the outer diameter of the roller gradually decreases from the center to both ends in order to maintain a uniform nip width when pressed against a photoconductor or the like. It is preferable to have. In this case, when the roller outer diameters at P1, P2, and P3 are D1, D2, and D3, respectively, the crown amount {D2- (D1 + D3) / 2} of the roller is 30 μm or more and 500 μm or less. This is preferable because a width can be obtained.

In addition, although the hardness of the conductive roller in the present invention is not particularly limited, the roller surface has a micro hardness of 30 ° or more and 85 ° or less so that a uniform nip width when pressed against a photoconductor or the like. This is preferable because it can be used for a long period of time without damaging the surface of the abutted member such as the photosensitive member during the rotational movement.

  The micro hardness of the conductive roller was measured in a 23.5 ° C./60% RH environment using a hardness meter “Micro Hardness Meter MD-1” (trade name) manufactured by Kobunshi Keiki Co., Ltd. It is. As a measurement method, place the conductive roller on a metal plate, fix it easily with a metal block so that the roller does not roll, and measure the conductive roller from the direction perpendicular to the metal plate. By touching the center exactly and reading the value shown in peak hold mode. In addition, a total of 9 positions were measured at a position (2 places) 30 mm from the edge of the coating layer of the roller and 3 places in the circumferential direction, respectively, and the average value of the obtained measured values was determined as the micro hardness of the roller. To do.

  The conductive roller in the present invention has a conductive coating layer, but the coating layer may be a conductive elastic layer itself or a multilayer including a conductive elastic layer.

  If the conductive roller has a conductive elastic layer formed in a crown shape, the one formed in a crown-shaped mold can also be used, but the conductive elastic layer should be polished into a crown shape. Is preferred. Therefore, it is preferable that the shaft body is formed through a process of gripping and fixing both end portions of the shaft with a collet chuck or a diaphragm chuck and grinding the outer peripheral surface of the elastic layer of the roller by a plunge method. This method is suitable because it is easy to adjust the shape such as runout accuracy and the accuracy can be maintained over a long period of time. As a method of adjusting the shape and accuracy of the roller, there is a method of molding using a mold having a cavity that has been processed into a desired shape in advance. However, although it depends on the raw material, shrinkage and deformation at the time of molding occur, it causes a variation in shape, and since it has a crown shape, it is difficult to take it out from the mold after molding.

  The conductive shaft used in the conductive roller of the present invention is not particularly limited, but those having strength as a shaft and having conductivity are suitable. For example, steel, aluminum, conductive plastic, etc. may be mentioned, and any of a hollow shape and a solid shape may be used.

  Moreover, conventionally well-known rubber can be used as a material of the electroconductive elastic layer which comprises a coating layer. For example, polybutadiene, natural rubber, polyisoprene, SBR (styrene butadiene rubber), CR (chloroprene rubber), EPDM (ethylene propylene diene rubber), IIR (butyl rubber), NBR (acrylonitrile butadiene rubber), silicone rubber, urethane rubber, epi Rubbers such as chlorohydrin rubber, polystyrene resins such as RB (butadiene resin) and SBS (styrene-butadiene-styrene elastomer), polyolefin resins, polyester resins, polyurethane, PVC (polyvinyl chloride), acrylic resins, A polymer material such as a styrene / vinyl acetate copolymer, a butadiene / acrylonitrile copolymer, or the like that has been given elasticity can be used. These materials may be used alone or in combination of two or more.

  Moreover, you may use a vulcanizing agent as needed. Depending on the type of rubber used as the vulcanizing agent, sulfur vulcanizing agent, organic peroxide, quinoid vulcanizing agent, resin crosslinking agent, metal oxide crosslinking agent, amine crosslinking agent, triazine crosslinking agent, maleimide type A known crosslinking agent such as a crosslinking agent can be appropriately selected. The blending amount of the vulcanizing agent may be determined as appropriate. In addition, a vulcanization accelerator, an antiaging agent, a plasticizer, and the like may be added.

  The method for producing the conductive elastic layer includes a method using a mold, a method of press-fitting a shaft after curing a tube-shaped material, and a method of covering and curing a material before curing on a shaft. The method can be used. Since the conductive roller of the present invention is desirably formed by polishing, it is formed to be larger than the desired outer diameter. The outer diameter is not particularly limited as long as it is larger than the desired outer diameter. However, considering material efficiency and cost, it is desirable that the outer diameter is in the range of 101% to 110% with respect to the desired outer diameter.

  Furthermore, the surface layer which comprises a coating layer is provided by coat | covering coating or a seamless tube. When the surface layer is provided by coating, it is preferable to provide a polyurethane layer obtained by polyisocyanate crosslinking of a polyol. When a plasticizer or the like is blended into the elastic layer, it can be prevented from oozing out from the urethane layer formed by crosslinking with the polyisocyanate when the polyol and polyisocyanate are cross-linked on the outer periphery of the elastic layer. It is. Even when a seamless tube is provided, it is preferably a crosslinkable resin in order to prevent the above-described bleeding. Examples of usable materials include polystyrene resins such as RB (butadiene resin) and SBS (styrene-butadiene-styrene elastomer), polyolefin resins, polyester resins, polyurethane, PVC (polyvinyl chloride), and acrylic resins. And polymer materials such as styrene / vinyl acetate copolymer and butadiene / acrylonitrile copolymer. These are used alone or in combination of two or more.

  In the elastic layer and the surface layer, a conductive agent may be blended in order to obtain desired conductivity, and an ion conductive conductive agent or an electronic conductive conductive agent can be appropriately selected. For example, conductive polymers such as polyaniline, polypyrrole and polyacetylene, quaternary ammonium salts such as trimethyl octadecyl ammonium perchlorate and benzyl trimethyl ammonium chloride, perchlorates such as lithium perchlorate and potassium perchlorate, phosphate esters , Aliphatic alcohol sulfate salts, aliphatic polyhydric alcohols, ionic surfactants, etc., metals such as graphite, tin, ruthenium, titanium, nickel, copper, silver, germanium and their oxides, ketjen black (trade name) ), Carbon black such as HAF, SAF, ISAF, SRF, and FT can be used. As a method for dispersing the polymer material used for the elastic layer and the surface layer, a roll kneader, a Banbury mixer, a ball mill, a sand grinder, a paint shaker, or the like may be used as appropriate.

  The conductive roller of the present invention is useful as a charging roller used to charge a photoreceptor such as an electrophotographic apparatus.

  Further, the above-described method for measuring E1θ to E3θ and obtaining the ω value is an evaluation method useful for evaluating the performance of the roller.

  Next, the present invention will be described in more detail with reference to examples. The present invention is not limited by these examples.

First, a method for evaluating a conductive roller in the following example will be described.
-Shape measurement The measurement of E1 (theta), E2 (theta), and E3 (theta) was performed as shown in FIG. In other words, the roller is supported by the fulcrums A and B of the shaft body 1 exposed at both ends of the conductive roller so that the roller does not rotate, and the measurement reference rod 3 that is substantially parallel to the center line in the axial direction of the shaft body 1 and 40 mm. They were spaced apart. In this state, the distance from the outer peripheral surface of the measurement reference bar 3 roller was measured at P1, P2 and P3, and was set as E1 ₀ , E2 ₀ and E3 ₀ , respectively. Then, (E1 ₀ -E2 ₀ ) and (E3 ₀ -E2 ₀ ) were calculated. Next, the roller was rotated 30 ° and measured in the same manner as described above, and (E1 ₃₀ -E2 ₃₀ ) and (E3 ₃₀ -E2 ₃₀ ) were calculated. This operation was sequentially rotated by 30 ° and measured for one round, and 12 values corresponding to (E1θ−E2θ) and (E3θ−E2θ) were each calculated, for a total of 24. Then, the maximum value and the minimum value were selected from these, the difference (ω value) was calculated, and the effect was evaluated based on this ω value. The measurement results in Example 1 are shown in FIG. 6 (E1θ to E3θ) and FIG. 7 ((E1θ−E2θ) and (E3θ−E2θ)).
-Runout measurement The maximum value and the minimum value were selected for each of E1θ to E3θ when E1θ to E3θ were measured in the above shape measurement, and the difference was regarded as the shake.
-Micro hardness Micro hardness was measured in a 23.5 degreeC / 60% RH environment with the hardness meter "micro hardness meter MD-1 type" (brand name) by a polymer instrument company. As a measuring method, place a conductive roller on a metal plate, fix it easily with a metal block so that the roller does not roll, and the measurement terminal is perpendicular to the metal plate from the center of the roller. The value when measured in the peak hold mode was read so that it was correctly hit. This was measured at a total of 9 locations, 30 mm from the edge of the coating layer of the roller (2 locations) and 3 locations in the circumferential direction of the central portion, and the average value was obtained to determine the micro hardness of the roller. did.
Image Evaluation The charging roller was incorporated as a charging roller of an electrophotographic apparatus “Color LaserJet 3700” (trade name) manufactured by Hewlett-Packard, and durability of 12,000 sheets was continuously performed. Halftone images were output before endurance (initial), immediately after endurance of 6000 sheets (endurance 1), and after end of endurance 12000 sheets (endurance 2). The occurrence of abnormal images due to poor charging appearing in the obtained halftone images was evaluated according to the following criteria. A DC voltage of −1500 V was applied to the charging roller, and the peripheral speed of the photosensitive member was 100 mm / sec. It was. Further, the electrophotographic apparatus used here has a structure as shown in FIG.
A: In the halftone image, there is no black belt-like unevenness caused by charging failure.
○: Black band-like unevenness due to charging failure is slightly observed in the halftone image, but there is no practical problem.
X: In a halftone image, there is a black belt-like unevenness caused by charging failure.
Example 1
・ Manufacture of rubber rollers Epichlorohydrin rubber “Epichromer CG102” (trade name, manufactured by Daiso Corporation) 100 parts by mass, zinc oxide (2 types, manufactured by Hakusui Tech Co., Ltd.) 5 parts by mass, stearic acid “stearic acid S” (trade name) 1 part by mass, manufactured by Kao Corporation, 5 parts by mass of carbon black “Asahi # 15” (trade name, manufactured by Asahi Carbon Co., Ltd.), 40 parts by mass of calcium carbonate “Silver W” (trade name, manufactured by Shiraishi Kogyo Co., Ltd.) , 5 parts by mass of plasticizer “Polysizer P-202” (trade name, sebacic acid polyester, manufactured by Dainippon Ink Co., Ltd.), ionic conductive agent “KS-555” (trade name, quaternary ammonium salt, Kao Corporation 2 parts by mass, dibenzothiazyl disulfide “Noxeller DM” (trade name, manufactured by Ouchi Shinsei Chemical Co., Ltd.), 1 part by mass, tetramethylthiura Mumon sulfide “Noxeller TS” (trade name, manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1 part by mass and sulfur “Sulfax 200S” (trade name, manufactured by Tsurumi Chemical Co., Ltd.) An unvulcanized rubber composition was obtained by kneading using a machine.

Next, using a 70 mm extruder equipped with a crosshead die, the unvulcanized rubber composition was extruded in a cylindrical shape together with a steel shaft body, and the unvulcanized rubber was coated on the periphery of the steel shaft body. The steel shaft was pre-coated with an adhesive "Metaloc U-20" (trade name, manufactured by Toyo Chemical Laboratory Co., Ltd.) and was electroless nickel plated with a diameter of 6 mm and a length of 250 mm. It is. The unvulcanized rubber layer coated on both ends of the shaft body was removed with a cutter blade at portions corresponding to 10 mm at both ends to expose the shaft body, thereby creating roller bearing portions. Then, the rubber roller which has a conductive elastic layer was created by heating 180 degreeC x 1h with a hot air furnace.
-Adjustment of the conductive elastic layer Next, using an NC grinder equipped with a mechanism that can rotate the shaft body exposed at both ends of the roller by gripping and fixing it from both sides with a collet chuck, it is axially moved from the center to both ends. A rubber roller having a crown shape whose outer diameter decreases as it approaches is adjusted. Specifically, a grindstone (φ220 mm, width 240 mm) to which an NC grinder is attached is dressed in a reverse crown shape, and the shape of the grindstone is transferred during roller polishing, so that the roller has a crown shape. The amount of crown was adjusted by the amount of reverse crown when dressing the grindstone so that it became 100 μm after polishing. Further, the conductive elastic layer was polished to have a length of 230 mm and a diameter of 9.0 mm at the center in the axial direction.
-Creation of surface layer ε-Caprolactone-modified acrylic polyol solution (diluent solvent: MEK (methyl ethyl ketone), solid content 20% by mass, hydroxyl value 50) 100 parts by mass and conductive tin oxide 20 parts by mass, dispersion media A horizontal sand mill of zirconia beads (average particle size 0.5 mm) was passed three times for dispersion. The beads were filtered and separated from this dispersion, and hexamethylene diisocyanate (HDI) was added so that OH / NCO = 1.0 to prepare a surface coating composition.

  Subsequently, the surface layer paint was dip coated on the surface of the conductive elastic layer of the rubber roller whose surface was polished as described above, and then dried at 150 ° C. for 1 hour in a hot air circulating dryer to obtain a conductive roller. In addition, the thickness of the surface layer (urethane layer) after drying was 30 μm. From the conductive roller thus obtained, a roller having the above measured ω value of 6 μm was selected as a charging roller A.

  The obtained charging roller A was subjected to the above-described shape, vibration, micro hardness, and image evaluation. These results are shown in Table 1. The shape measurement results are shown in FIGS.

As a result of the image evaluation, a very good image was obtained from the beginning, and no image defect due to charging failure occurred even when the sheet was continuously fed through 6000 sheets and 12000 sheets. In this charging roller, as shown in Table 1, FIG. 6, and FIG. 7, since the deflection of the outer peripheral surface of the roller is small over the entire axial direction, it can always be pressed against the photosensitive member in a stable shape even if the roller is rotated. Therefore, it is considered that a uniform nip width was stably obtained.
Example 2
From the conductive roller prepared in the same manner as in Example 1, the ω value was 15 μm and the deflection was less than 50 μm, but the larger one in Example 1 was selected and designated as charging roller B. Hereinafter, in the same manner as in Example 1, shape, vibration, micro hardness, and image evaluation were performed. These results are shown in Table 1. The shape measurement results are shown in FIGS.

As a result of image evaluation, a good image was obtained at the initial stage and after passing 6000 sheets, but after passing 12,000 sheets, although there was no practical problem, a slight black belt-like unevenness was observed. In this charging roller B, the deflection is not so good over the entire axial direction, but it can be seen that the phase is eccentric to the same phase over the entire roller axial direction when compared with each phase with respect to the roller rotation direction. Therefore, it is determined that a relatively uniform nip width is obtained even when the roller is pressed against the photosensitive member and rotated.
Example 3
A charging roller C was selected from a conductive roller prepared in the same manner as in Example 1 with a ω value of 29 μm and a deflection smaller than 50 μm, but larger than that in Example 1 and with poor deflection accuracy. Hereinafter, in the same manner as in Example 1, shape, vibration, micro hardness, and image evaluation were performed. These results are shown in Table 1. The shape measurement results are shown in FIGS.

As a result of the image evaluation, a good image was obtained in the initial stage. After passing through 6,000 sheets and after passing through 12,000 sheets, although there was no practical problem, a slight black belt-like unevenness was observed. In the charging roller C, the deflection is particularly large in the central portion, and variation is observed in the roller axial direction. However, when compared with each phase with respect to the roller rotating direction, it can be seen that the charging roller C is eccentric to the same phase in the entire roller axial direction. . Therefore, a relatively uniform nip width is obtained even when the roller is pressed against the photosensitive member and rotated, but compared with the second embodiment, the eccentricity is large only at the central portion in the axial direction, so that the performance is slightly improved. Inferior.
Example 4
A conductive roller produced in the same manner as in Example 1 with a relatively good runout accuracy but having a large ω value of 29 μm was selected as a charging roller D. Hereinafter, in the same manner as in Example 1, shape, vibration, micro hardness, and image evaluation were performed. These results are shown in Table 1. The shape measurement results are shown in FIGS.

As a result of the image evaluation, a good image was obtained in the initial stage. After passing through 6,000 sheets and after passing through 12,000 sheets, although there was no practical problem, a slight black belt-like unevenness was observed. In this charging roller D, the deflection is relatively good over the entire axial direction, but when compared with each phase with respect to the roller rotation direction, it can be seen that the phase is decentered although it is slight over the entire roller axial direction. Therefore, when the roller is pressed against the photosensitive member and rotated, the nip width seems to show a slight variation in the axial direction, but it was practically usable without any problem.
Example 5
As an unvulcanized rubber composition, epichlorohydrin rubber “Epichromer CG102” (trade name) 100 parts by mass, zinc oxide (2 types) 5 parts by mass, stearic acid “stearic acid S” (trade name) 1 part by mass, carbon Black “Asahi # 70” (trade name, manufactured by Asahi Carbon Co., Ltd.) 40 parts by mass, calcium carbonate “Silver W” (trade name) 40 parts by mass, ionic conductive agent “KS-555” (trade name) 2 parts by mass, Example 1 part by weight of dibenzothiazyl disulfide “Noxeller DM” (trade name), 1 part by weight of tetramethylthiuram monosulfide “Noxeller TS” (trade name) and 1 part by weight of sulfur “Sulfax 200S” (trade name) What was obtained by kneading in the same manner as in No. 1 was used. Further, a conductive roller was prepared in the same manner as in Example 1 except that the polishing was performed so that the crown amount was 48 μm. From the obtained conductive roller, a roller having a relatively good deflection accuracy but having a ω value of 23 μm was selected as a charging roller E. Hereinafter, in the same manner as in Example 1, shape, vibration, micro hardness, and image evaluation were performed. These results are shown in Table 1.

As a result of the image evaluation, a very good image was obtained from the beginning, and no image defect due to charging failure occurred even when the sheet was continuously fed through 6000 sheets and 12000 sheets. Therefore, even if the crown amount is reduced in order to obtain a high hardness and uniform nip width, the conductive roller can be determined by the evaluation method of the present invention.
Example 6
As an unvulcanized rubber composition, epichlorohydrin rubber “Epichromer CG102” (trade name) 100 parts by mass, zinc oxide (2 types) 5 parts by mass, stearic acid “stearic acid S” (trade name) 1 part by mass, carbon Black "Thermax MT N990" (trade name, manufactured by Can Carb) 5 parts by mass, calcium carbonate "Silver W" (trade name) 30 parts by mass, plasticizer "Polysizer P-202" (trade name, sebacic acid polyester) 15 parts by weight, 2 parts by weight of ionic conductive agent “KS-555” (trade name, quaternary ammonium salt), 1 part by weight of dibenzothiazyl disulfide “Noxeller DM” (trade name), tetramethylthiuram monosulfide “Noxeller” 1 part by weight of “TS” (trade name) and 1 part by weight of “Sulfax 200S” (trade name) were mixed in the same manner as in Example 1. Was used was obtained. Further, a conductive roller was prepared in the same manner as in Example 1 except that the crown was polished so as to have a thickness of 220 μm. From the obtained conductive roller, a roller having a relatively good deflection accuracy but having an ω value of 27 μm was selected as a charging roller F. Hereinafter, in the same manner as in Example 1, shape, vibration, micro hardness, and image evaluation were performed. These results are shown in Table 1.

As a result of the image evaluation, a very good image was obtained from the beginning, and no image defect due to charging failure occurred even when the sheet was continuously fed through 6000 sheets and 12000 sheets. Therefore, even if the crown amount is increased in order to obtain a low hardness and uniform nip width, the conductive roller can be determined by the evaluation method of the present invention.
Comparative Examples 1-3
A conductive roller was prepared in the same manner as in Example 1 except that when the conductive elastic layer was polished, a dust mark (commercially available tissue paper) was intentionally attached to the shaft gripping portion of the collet chuck. Since the produced conductive rollers were produced from those having relatively good runout, those having an ω value exceeding 30 μm were extracted, charged roller G (ω value 33 μm, Comparative Example 1), and charged roller H (ω The value was 37 μm, Comparative Example 2) and the charging roller I (ω value 42 μm, Comparative Example 3). Hereinafter, in the same manner as in Example 1, shape, vibration, micro hardness, and image evaluation were performed. These results are shown in Table 1. The shape measurement results are shown in FIGS. 14 and 15, FIGS. 16 and 17, and FIGS. 18 and 19, respectively.

As a result of image evaluation, an image having no practical problem was obtained at the initial stage for each roller, but black belt-like unevenness was observed after passing 6000 sheets and after passing 12,000 sheets. It can be seen that these charging rollers are eccentric to a disparate phase in the entire roller axial direction in spite of relatively small fluctuations. Therefore, a relatively good image was obtained because the shake was small in the initial stage, but due to the large eccentricity, the nip width varied, and when rotated for a long period of time, dirt such as paper dust was localized on the roller surface. That is, the image is defective.
Comparative Example 4
A conductive roller prepared in the same manner as in Example 1 having a good ω value of 22 μm but having a deflection exceeding 50 μm was selected as a charging roller J. Hereinafter, in the same manner as in Example 1, shape, vibration, micro hardness, and image evaluation were performed. These results are shown in Table 1. The results of the shape measurement are shown in FIGS.

  As a result of image evaluation, an image defect caused by a charging failure was recognized from the beginning. In this case, the variation in the nip width in the axial direction seems to be relatively small because the same phase is deviated in the entire roller axial direction, but a normal image is obtained because the overall shake is large. I couldn't.

It is a figure for demonstrating the measuring method of E1 (theta), E2 (theta), and E3 (theta). It is a conceptual diagram which shows the example of the state which does not rotate normally by eccentricity of a coating layer, when a roller rotates. It is a conceptual diagram which shows the other example of a state which does not rotate normally by eccentricity of a coating layer, when a roller rotates. It is a conceptual diagram which shows the other example of a state which does not rotate normally by eccentricity of a coating layer, when a roller rotates. It is a schematic block diagram of the electrophotographic apparatus used for image evaluation. (Example 1) which plotted E1 (theta), E2 (theta), and E3 (theta) for every phase. (E1θ−E2θ) and (E3θ−E2θ) are plotted for each phase (Example 1). FIG. 11 is a diagram in which E1θ, E2θ, and E3θ are plotted for each phase (Example 2). (E2θ−E2θ) and (E3θ−E2θ) are plotted for each phase (Example 2). (Example 3) which plotted E1 (theta), E2 (theta), and E3 (theta) for every phase. (E3 (theta) -E2 (theta)) and (E3 (theta) -E2 (theta)) are the figures plotted for every phase (Example 3). (Example 4) which plotted E1 (theta), E2 (theta), and E3 (theta) for every phase. (Example 4) which plotted (E1 (theta) -E2 (theta)) and (E3 (theta) -E2 (theta)) for every phase. It is the figure which plotted E1 (theta), E2 (theta), and E3 (theta) for every phase (comparative example 1). It is the figure which plotted (E1 (theta) -E2 (theta)) and (E3 (theta) -E2 (theta)) for every phase (comparative example 1). It is the figure which plotted E1 (theta), E2 (theta), and E3 (theta) for every phase (comparative example 2). It is the figure which plotted (E1 (theta) -E2 (theta)) and (E3 (theta) -E2 (theta)) for every phase (comparative example 2). It is the figure which plotted E1 (theta), E2 (theta), and E3 (theta) for every phase (comparative example 3). It is the figure which plotted (E1 (theta) -E2 (theta)) and (E3 (theta) -E2 (theta)) for every phase (comparative example 3). It is the figure which plotted E1 (theta), E2 (theta), and E3 (theta) for every phase (comparative example 4). It is the figure which plotted (E1 (theta) -E2 (theta)) and (E3 (theta) -E2 (theta)) for every phase (comparative example 4).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive shaft body 2 Conductive coating layer 3 Measurement reference | standard rod 4 Charging roller 5 Photoconductor 6 Base | substrate 7 Developing machine 8 Transfer roller 9 Cleaning blade 10 Process cartridge 11 Fixing machine 12 Laser beam (information writing)
13 Transfer member (paper)

Claims (4)

A conductive roller is placed almost parallel to a straight measurement reference rod, and the distance E between the measurement reference rod and the surface of the coating layer of the roller is measured for one round of the roller at both ends (P1, P3) and the central portion (P2). When the measured values at the roller rotation angle θ are E1θ, E3θ, and E2θ, respectively,
Calculate the maximum value and minimum value for one rotation of the roller at each of the separation distances E1θ, E2θ, E3θ, obtain the maximum value of the difference, and determine the runout of the outer peripheral surface of the roller.
The separation distance difference ΔE {= E1θ (or E3θ) −E2θ} at the roller rotation angle θ is obtained, the difference between the maximum value and the minimum value in one round of these rollers is obtained, and the ω value is obtained.
A method for evaluating a conductive roller, characterized in that the roller property is evaluated based on the deflection and the ω value. 2. The method for evaluating a conductive roller according to claim 1, wherein the conductive roller has a roller outer surface deflection of 50 μm or less and a ω value of 30 μm or less . The conductive roller has a crown shape, and the crown amount {D2− (D1 + D3) / 2} when the outer diameters of the rollers at P1, P2 and P3 obtained from the separation distance E are D1, D2 and D3, respectively. The method for evaluating a conductive roller according to claim 1, wherein the method is 30 μm or more and 500 μm or less .   The method for evaluating a conductive roller according to any one of claims 1 to 3, wherein the conductive roller has a micro hardness measured on a roller surface in a range of 30 ° to 85 °.

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