JP2009223207A - Electrifying roll for electrophotographic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrifying roll for electrophotographic equipment effectively suppressing the occurrence of triboelectrification due to rubbing with an image carrier even if it is assembled in such a state that it is brought into contact with the image carrier, and suppressing image failure caused by the triboelectrification. <P>SOLUTION: The electrifying roll for the electrophotographic equipment assembled in a drum cartridge of the electrophotographic equipment in such a state that it is brought into contact with a surface of the image carrier is constituted by layering a low friction layer 14, an elastic layer 16 and a surface layer 18 in this order on an outer periphery of a conductive shaft 12 where a projected line 12a has been formed in an axial direction. At such a time, relation μ1>μ4 and μ2>μ3 is satisfied. Provided that μ1: coefficient of static friction of the image carrier, μ2: coefficient of static friction of the surface layer 18, μ3: coefficient of static friction of the low friction layer 14, and μ4: coefficient of static friction of the conductive shaft 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a charging roll for electrophotographic equipment.

  2. Description of the Related Art Conventionally, a so-called drum cartridge in which a charging roll is assembled around a photosensitive drum that is an image carrier is incorporated in an electrophotographic apparatus such as a copying machine, a printer, and a facsimile that employs an electrophotographic system. In this type of electrophotographic apparatus, the contact charging method is often used. In the contact charging method, the surface of the image carrier is charged by bringing the surface of the charge carrier into contact with the surface of the image carrier.

  In this type of drum cartridge, conventionally, before use, the charging roll is incorporated in a state where the surface of the image carrier and the surface of the charging roll are separated from each other. Then, when the electrophotographic apparatus is used, the surface of the image carrier and the surface of the charging roll are brought into contact with each other. However, recently, from the standpoint of reducing the manufacturing cost of the drum cartridge, a drum cartridge in which the surface of the image carrier and the surface of the charging roll are brought into contact with each other has been manufactured from the beginning.

  The drum cartridge is composed of a plurality of parts, and each part has a dimensional tolerance. Therefore, a clearance is generated between the shaft end portion of the charging roll and the bearing due to a dimensional tolerance between the entire length of the charging roll and its bearing position. Therefore, such a drum cartridge has a configuration in which the charging roll may move in the axial direction within the drum cartridge. In this case, for example, when the drum cartridge is subjected to vibration when being conveyed, the charging roll may move in the axial direction within the drum cartridge.

  In particular, from the standpoint of preventing adhesion of external toner additives, when a highly releasable material such as a fluorine-containing polymer or a silicone-containing polymer is used for the surface layer of the charging roll, the charging roll has a tackiness. descend. In this case, the coefficient of friction between the image bearing member and the charging roll becomes small, and the charging roll becomes even easier to move.

  When the charging roll moves in the axial direction in the drum cartridge, the image carrier and the charging roll are rubbed. As a result, the image carrier is frictionally charged. At this time, a positive charge remains in the rubbed portion on the image carrier. For this reason, there has been a problem that a color line of the drum pitch is generated on the output image.

  Therefore, various proposals have heretofore been made to solve the above problems. For example, it is known that a film-like member is interposed between the image carrier and the charging roll so that friction does not occur between the image carrier and the charging roll when the cartridge is transported. Patent Document 1 discloses that the image carrier and the charging roll are separated by using a removable fixing member for preventing the charging roll from rotating when the cartridge is transported.

JP 2007-57830 A

  However, the use of such another member inevitably increases the manufacturing cost of the drum cartridge. Therefore, development of a novel charging roll that effectively suppresses the generation of frictional charging described above has been desired from a viewpoint different from the conventional proposal.

  The problem to be solved by the present invention is to effectively suppress the generation of frictional charging due to rubbing with the image carrier even when assembled in contact with the image carrier, resulting in image defects. An object of the present invention is to provide a charging roll for an electrophotographic apparatus capable of suppressing the above-described problem.

In order to solve the above-mentioned problems, an electrophotographic apparatus charging roll according to the present invention is an electrophotographic apparatus charging roll that is brought into contact with the surface of an image carrier, and a shaft having a protrusion or a groove formed along the axial direction. A body, a low friction layer formed along the outer periphery of the shaft body, and a surface layer formed through one or more layers on the outer periphery of the low friction layer, and satisfying the following relationship: It is a summary.
μ1> μ4 and μ2> μ3
However,
μ1: Static friction coefficient of image carrier μ2: Static friction coefficient of surface layer μ3: Static friction coefficient of low friction layer μ4: Static friction coefficient of shaft

  At this time, the said surface layer is good to contain the 1 type (s) or 2 or more types selected from the fluorine-containing polymer and the silicone containing polymer.

  The low friction layer may have a volume resistivity lower than that of a layer formed on the outer periphery thereof.

  The charging roll for electrophotographic equipment according to the present invention includes a low friction layer on the outer periphery of a shaft body in which ridges or grooves are formed along the axial direction, and a static friction coefficient of an image carrier that is in contact with the surface of the charging roll. The static friction coefficient of the surface layer, the static friction coefficient of the low friction layer, and the static friction coefficient of the shaft body satisfy a specific relationship. Therefore, when this charging roll is incorporated in the drum cartridge in contact with the image carrier, when vibration is applied to the drum cartridge due to conveyance or the like, the axial direction is set between the shaft body and the low friction layer. Therefore, sliding between the image carrier and the surface layer can be suppressed. Thereby, it is possible to prevent the image carrier from being frictionally charged and to suppress image defects.

  At this time, the ridge or groove formed along the axial direction serves as a guide, and slides in the axial direction between the shaft body and the low friction layer. On the other hand, this protrusion or groove portion is resistant to slippage in the circumferential direction between the shaft body and the low friction layer. Therefore, sliding in the circumferential direction between the shaft body and the low friction layer can be suppressed. Thereby, the rotational drive from the shaft body to the low friction layer and its upper layer is reliably transmitted. Therefore, defective rotation of the charging roll during use can be prevented, and image defects can be suppressed.

  And when a surface layer consists of a composition containing a fluorine-containing polymer or a silicone-containing polymer, it is excellent in releasability. Such a material having excellent releasability tends to reduce the tackiness of the charging roll. Therefore, it becomes much easier to slide between the image carrier. Also, there is a tendency that the difference in the charged column from the material forming the image carrier is large. Therefore, the positive charge generated on the image carrier due to rubbing tends to increase. According to the charging roll for electrophotographic equipment according to the present invention, the above-described effects can be achieved even in the surface layer having the above-described configuration.

  Furthermore, when the low friction layer has a volume resistivity lower than the volume resistivity of the layer formed on the outer periphery thereof, resistance increase due to the provision of the low friction layer does not occur, thereby suppressing resistance unevenness. Can do.

  Next, a charging roll for electrophotographic equipment according to the present invention (hereinafter also referred to as a charging roll) will be described in detail with reference to the drawings. FIG. 1 is an axial sectional view showing a charging roll according to an embodiment. The charging roll is incorporated in an electrophotographic apparatus such as a copying machine, a printer, or a facsimile that employs an electrophotographic system.

  As shown in FIG. 1, the charging roll 10 includes a conductive shaft 12 that is a shaft, a low friction layer 14 formed on the outer periphery of the conductive shaft 12, and an elastic layer formed on the outer periphery of the low friction layer 14. 16 and a surface layer 18 formed on the outer periphery of the elastic layer 16. In the charging roll 10, the conductive shaft 12 and the low friction layer 14 are not bonded.

  As shown in FIG. 2, the charging roll 10 is used in contact with a photosensitive drum 20 which is an image carrier of an electrophotographic apparatus. In this case, the surface of the charging roll surface layer 18 is in contact with the surface (outer peripheral surface) of the photosensitive drum 20. Further, the surface (outer peripheral surface) of the conductive shaft 12 is in contact with the inner peripheral surface of the low friction layer 14.

  Here, the static friction coefficient of the photosensitive drum (image carrier) 20 is μ1, the static friction coefficient of the surface layer 18 is μ2, the static friction coefficient of the low friction layer 14 is μ3, and the static friction coefficient of the conductive shaft (shaft body) 12 is μ4. The charging roll 10 satisfies the relationship of μ1> μ4 and μ2> μ3. That is, the static friction coefficient μ 4 of the conductive shaft 12 is smaller than the static friction coefficient μ 1 of the photosensitive drum 20, and the static friction coefficient μ 3 of the low friction layer 14 is smaller than the static friction coefficient μ 2 of the surface layer 18. Therefore, in the charging roll 10, it is easier to slip between the conductive shaft 12 and the low friction layer 14 than between the photosensitive drum 20 and the surface layer 18.

  As shown in FIG. 2, for example, when a drum cartridge is configured by assembling the charging roll 10 in contact with the photosensitive drum 20, when an axial force acts on the charging roll 10, the charging roll 10 moves in the axial direction. try to. At this time, in the charging roll 10, it is easier to slip between the conductive shaft 12 and the low friction layer 14 than between the photosensitive drum 20 and the surface layer 18. Therefore, it slides in the axial direction between the conductive shaft 12 and the low friction layer 14. Thereby, rubbing between the photosensitive drum 20 and the surface layer 18 can be suppressed.

  In the charging roll 10, as the conductive shaft 12, for example, a metal core made of a metal solid body such as stainless steel, aluminum, iron, or an alloy thereof, a metal cylindrical body hollowed out inside, or these And the like that have been plated. A solid body or a cylindrical body made of a conductive resin can also be used. Further, a solid or cylindrical body made of a conductive or non-conductive resin or the like may be used as the base material, and a metal plated product may be used. More preferably, it is a solid body or cylindrical body made of metal such as stainless steel or aluminum.

  On the other hand, examples of the main material forming the surface of the photosensitive drum 20 include polycarbonate resin, polyester resin, and acrylic resin.

  A metal material is often used for the conductive shaft 12. On the other hand, a resin material such as polycarbonate is often used on the surface of the photosensitive drum 20 as an image carrier. When such materials are selected for the conductive shaft 12 and the photosensitive drum 20, the relationship of μ1> μ4 can be satisfied.

  The main material for forming the low friction layer 14 is, for example, a fluorine resin, a silicone resin, a (meth) acrylic resin, a polycarbonate, a urethane resin, a melamine resin, a nitrile rubber (NBR), or a hydrin rubber. Examples thereof include rubbers such as (CO, ECO, etc.), modified products obtained by modifying these resins and rubbers with silicone, fluorine, and the like. More preferred are fluorine-modified (meth) acrylate and silicone-modified (meth) acrylate. These may be used alone or in combination.

The low friction layer 14 preferably contains a conductive agent together with the main material. Examples of the conductive agent include electronic conductive agents such as carbon black and ionic conductive agents such as quaternary ammonium salts. At this time, the low friction layer 14 preferably has a volume resistivity lower than that of the elastic layer 16 by, for example, blending a conductive agent. Since the low friction layer 14 is provided between the conductive shaft 12 and the elastic layer 16, if the resistance is higher than that of the elastic layer 16, the resistance increase due to the provision of the low friction layer 14 occurs. is there. Thus, when there is a high resistance layer, uneven resistance is likely to occur. Therefore, it is preferable to keep the volume resistivity of the low friction layer 14 lower than that of the elastic layer 16. From such a viewpoint, the conductive agent is preferably in the range of 5 to 100 parts by mass with respect to 100 parts by mass of the main material. More preferably, it exists in the range of 10-30 mass parts. The volume resistivity of the low friction layer 14 is preferably 10 ³ Ω · cm or less.

  In addition, the low friction layer 14 may include a filler, an extender, a reinforcing agent, a processing aid, a curing agent, a vulcanization accelerator, a crosslinking agent, a crosslinking aid, an antioxidant, a plasticizer, Various additives such as ultraviolet absorbers, pigments, silicone oils, auxiliaries, and surfactants are appropriately added.

  On the other hand, the main material for forming the surface layer 18 is, for example, a resin such as fluorine resin, silicone resin, (meth) acrylic resin, polycarbonate, urethane resin, melamine resin, nitrile rubber (NBR), hydrin rubber (CO , ECO, etc.), and modified products obtained by modifying these resins and rubbers with silicone, fluorine, and the like. These may be used alone or in combination. Of these, fluorine-modified (meth) acrylate and silicone-modified (meth) acrylate, which are excellent in releasability, are preferable from the viewpoint of preventing adhesion of the toner external additive.

  The surface layer 18 contains one or more additives such as a conductive agent (an electronic conductive agent such as carbon black, an ionic conductive agent such as a quaternary ammonium salt), a release agent, and a curing agent. May be. As a compounding quantity of a electrically conductive agent, it is preferable to exist in the range of 10-50 mass parts with respect to 100 mass parts of said main materials from viewpoints, such as ensuring electroconductivity.

  The material of the low friction layer 14 is preferably a material having a static friction coefficient smaller than that of the surface layer 18 material. The material of the low friction layer 14 and the material of the surface layer 18 are prepared so as to satisfy the relationship of μ2> μ3.

  At this time, for example, when a highly releasable material is used for the surface layer 18 of the charging roll 10, the tackiness of the charging roll 10 decreases. In this case, the coefficient of friction between the photosensitive drum 20 and the charging roll 10 becomes small, and the charging roll 10 becomes easier to move. In addition, there is a tendency that the difference in the charge train with the material forming the photosensitive drum 20 is large. Therefore, the positive charge generated on the photosensitive drum 20 due to rubbing tends to increase. Even in such a case, by satisfying the relationship of μ2> μ3, it is possible to suppress sliding between the surface of the photosensitive drum 20 and the surface layer 18 of the charging roll, and image defects caused by rubbing between them. Can be suppressed.

  Examples of the main material for forming the elastic layer 16 include styrene-butadiene rubber (SBR), polynorbornene rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H -NBR), hydrin rubber (CO, ECO, etc.), butadiene rubber (BR), isoprene rubber (IR), natural rubber (NR), silicone rubber and the like. More preferred are hydrin rubber and NBR. These can be used alone or in combination of two or more. The elastic layer 16 may be a foam or a solid body.

During the elastic layer 16, for imparting conductivity, potassium carbon black, graphite, titanate, iron _{oxide, c-TiO 2, c-} ZnO, or an electron conductive agent such as c-SnO _2, quaternary ammonium salts, Conventionally known conductive agents such as ionic conductive agents such as borates and surfactants are appropriately added. Further, if necessary, a foaming agent, a crosslinking agent, a crosslinking accelerator, oil, and the like may be added as appropriate.

The volume resistivity of the elastic layer 16 is preferably in the range of 1 × 10 ³ to 1 × 10 ⁸ Ω · cm. When the volume resistivity of the elastic layer 16 is less than 1 × 10 ³ Ω · cm, the volume ratio of the conductive agent increases, and it is difficult to obtain a sufficient withstand voltage. On the other hand, when the volume resistance exceeds 1 × 10 ⁸ Ω · cm, the volume ratio of the conductive agent is reduced and resistance unevenness is likely to occur.

  The static friction coefficient of each member can be measured using a static friction coefficient meter. The static friction coefficient of each member can be obtained, for example, by preparing a test piece obtained by molding the composition forming each member into a sheet shape and measuring the static friction coefficient of the surface of the test piece. Further, for example, even when a charging roll as a product is used, the static friction coefficient of each member can be measured.

  As described above, the conductive shaft 12 and the low friction layer 14 are not bonded. Therefore, it is possible to remove the conductive shaft 12 from the charging roll 10. Then, the outer peripheral surface of the conductive shaft 12 and the inner peripheral surface of the low friction layer 14 appear. Thereby, about each surface, a static friction coefficient can be measured using a static friction coefficient meter. Further, since the photosensitive drum 20 and the surface layer 18 of the charging roll appear from the beginning, similarly, the static friction coefficient can be measured for each surface using a static friction coefficient meter.

  Examples of the static friction coefficient meter include “DFPM-S” manufactured by Kyowa Interface Science Co., Ltd. The static friction coefficient is a value measured when the stylus of a static friction coefficient meter is brought into contact with the surface of each member under the condition of a load of 100 g and the stylus is slid under the condition of speed 65.

  Here, as shown in FIG. 3, the conductive shaft 12 is formed with protrusions 12 a along the axial direction. The protrusions 12a are formed at four equal intervals in the circumferential direction. The protrusion 12a serves as a guide when sliding in the axial direction between the conductive shaft 12 and the low friction layer 14. Therefore, it does not hinder the axial slip.

  On the other hand, the protrusion 12a is resistant to slippage in the circumferential direction between the conductive shaft 12 and the low friction layer 14. Therefore, it is possible to suppress slipping in the circumferential direction between the conductive shaft 12 and the low friction layer 14. Thereby, the rotational drive from the conductive shaft 12 to the low friction layer 14 and its upper layer is reliably transmitted. Therefore, defective rotation of the charging roll 10 during use can be prevented, and image defects can be suppressed.

  As another form of the conductive shaft having such a function, as shown in FIG. 4, a conductive shaft 12 in which a groove 12b is formed along the axial direction can be shown. Similarly, this suppresses only slip in the circumferential direction and does not suppress slip in the axial direction. Moreover, you may provide both the protrusion 12a and the groove part 12b. Further, the shape and number of the protrusions 12a and the groove portions 12b are not particularly limited. That is, it is sufficient if only slip in the circumferential direction is suppressed and slip in the axial direction is not suppressed.

  The conductive shaft 12 having such a shape can be easily formed, for example, by changing the die shape when the wire is drawn.

  Although the thickness of the low friction layer 14 formed in the outer periphery of the electroconductive shaft 12 is not specifically limited, It is preferable to exist in the range of 5-30 micrometers. More preferably, it exists in the range of 10-20 micrometers. Moreover, it is preferable that the thickness of the elastic layer 16 exists in the range of 0.1-10 mm. More preferably, it exists in the range of 1-5 mm. The thickness of the surface layer 18 is not particularly limited, but is preferably in the range of 10 to 30 μm. More preferably, it exists in the range of 12-20 micrometers.

  In order to form the low friction layer 14, for example, first, components constituting the low friction layer 14 are mixed and liquefied with a solvent or the like to prepare a coating liquid. Next, after the coating liquid is applied to the outer peripheral surface of the conductive shaft 12, the low friction layer 14 can be formed by drying and heat-crosslinking treatment. The coating method is not particularly limited, and general methods such as a dipping method, a spray method, and a roll coating method can be applied. Examples of the solvent include methyl ethyl ketone (MEK), methanol, toluene, isopropyl alcohol, methyl cellosolve, dimethylformamide and the like. These can be used alone or in combination of two or more. In particular, MEK is preferable from the viewpoint of the solubility of each component of the material. When using a solvent, it is preferable to adjust the solution concentration within the range of 5 to 30% by mass from the viewpoint of improving the coating property by adjusting the viscosity to be easy to apply. The surface layer 18 can be formed according to the method for forming the low friction layer 14.

  In order to form the elastic layer 16, for example, first, components forming the elastic layer 16 are kneaded with a kneader such as a kneader to prepare a forming material. After that, the conductive shaft 12 on which the low friction layer 14 is formed is set in the hollow portion of the cylindrical mold and the forming material is cast. Then, the mold is covered and heated to crosslink the forming material. Thereafter, the elastic layer 16 can be formed on the outer periphery of the low friction layer 14 by removing from the cylindrical mold.

  The charging roll according to the present invention is not limited to the charging roll 10 having the layer structure shown in FIG. For example, one or more intermediate layers may be interposed between the elastic layer 16 and the surface layer 18. Examples of the intermediate layer include a softener migration prevention layer and a resistance adjustment layer. As an intermediate | middle layer, only a softening agent transfer prevention layer may be sufficient, and only a resistance adjustment layer may be sufficient. Moreover, the structure provided with both layers may be sufficient. As the layer configuration, for example, an elastic layer, a softener migration preventing layer, a resistance adjusting layer, and a surface layer laminated in this order on a low friction layer can be shown.

  Examples of the material for forming the softener migration preventing layer include a material in which a conductive material such as carbon black is blended with a main material such as polyamide resin such as N-methoxymethylated nylon or polyester. Examples of the material for forming the resistance adjusting layer include hydrin rubber, EPDM, SBR, NBR, H-NBR, polyurethane elastomer, carbon black, metal oxide, quaternary ammonium salt, borate, perchloric acid. The thing which mix | blended electrically conductive agents, such as lithium, is mentioned. These may be used alone or in combination of two or more.

  The thickness of the softener migration preventing layer is preferably in the range of 3 to 30 μm. In addition, the thickness of the resistance adjustment layer is preferably in the range of 10 to 800 μm. The method for forming the softener migration preventing layer and the resistance adjusting layer is not particularly limited, but a coating method is preferred. In the case of coating, it can be formed by the same method as the low friction layer 14.

The volume resistance of the charging roll 10 is preferably in the range of 1 × 10 ³ to 1 × 10 ⁸ Ω. When the volume resistance is less than 1 × 10 ³ Ω, the volume ratio of the conductive agent increases and it is difficult to obtain a sufficient withstand voltage. On the other hand, if the volume resistance exceeds 1 × 10 ⁸ Ω, the volume ratio of the conductive agent is reduced and resistance unevenness is likely to occur.

  When the charging roll 10 having the above configuration is viewed from the viewpoint of the manufacturing process, the number of processes for forming the low friction layer 14 is increased as compared with the conventional one. However, it does not have a process for forming a conventional adhesive layer. Therefore, it is only necessary to change from the process of forming the adhesive layer to the process of forming the low friction layer 14. Therefore, the number of processes is not increased.

  The structure of the drum cartridge using the charging roll 10 is not a structure using a separate member that separates the image carrier and the charging roll 10 when the drum cartridge is conveyed as in the prior art. Such a separate member generally increases the manufacturing cost, but can be omitted in the present invention.

  Hereinafter, the present invention will be described in detail using examples.

[raw materials]
・ Fluorine-modified acrylic polymer (Dainippon Ink & Chemicals, “Defenser TR-230K”)
・ Silicone-modified acrylic polymer (manufactured by Negami Industrial Co., Ltd., “Paracron W-197C”)
・ N-methoxymethylated nylon (manufactured by Teikoku Chemical Co., Ltd., “Tresin EF30T”)
・ Polyvinylidene fluoride resin (manufactured by Atofina Japan, “Kyner SL”)
・ SBR (manufactured by Nippon Elastomer Co., Ltd., “trade name“ Sorprene 1206 ”)
・ NBR (Zeon Corporation, “Nipol DN401”)
・ Carbon black (Ketjen Black International Ketjen Black EC)
Acetylene black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.)
・ Quaternary ammonium salt (Wako Pure Chemical Industries, “TBAHS”)
・ Stearic acid (manufactured by Kao Corporation, “Lunac S30”)
・ Zinc flower (manufactured by Sakai Chemical Industry Co., Ltd.)
・ Vulcanization aid (1) (manufactured by Sanshin Chemical Co., Ltd., “Sunceller CZ-G”)
・ Vulcanization aid (2) (Ouchi Shinsei Chemical Co., Ltd., “Noxeller BZ-P”)
・ Sulfur (Tsurumi Chemical Co., Ltd., “Salfax PTC”)

<Preparation of low friction layer coating solution>
By mixing 100 parts by mass of the low friction layer component shown in Table 1, 20 parts by mass of carbon black, and 400 parts by mass of a solvent (in the case of a defender or paraclone: MEK, in the case of a resin: methanol), a low friction layer is obtained. A coating solution was prepared.

<Preparation of elastic layer composition>
100 parts by mass of SBR and 10 parts by mass of carbon black were mixed and kneaded by a kneader such as a kneader to prepare an elastic layer composition.

<Preparation of softener migration prevention layer coating solution>
A softener migration prevention layer coating solution was prepared by mixing 100 parts by mass of N-methoxymethylated nylon, 20 parts by mass of carbon black, and 400 parts by mass of methanol.

<Preparation of resistance adjustment layer coating solution>
100 parts by weight of NBR, 1 part by weight of a quaternary ammonium salt, 30 parts by weight of acetylene black, 0.5 part by weight of stearic acid, 5 parts by weight of zinc white, and 1.07 parts by weight of a vulcanization aid (1) The resistance adjusting layer coating solution was prepared by mixing 0.49 parts by mass of the vulcanization aid (2), 1 part by mass of sulfur, and 400 parts by mass of MEK.

<Preparation of surface coating solution>
By adding 100 parts by mass of the surface layer components shown in Table 1 and 8 parts by mass of carbon black to 400 parts by mass of a solvent (in the case of a defender or paraclone: MEK, in the case of a resin: methanol), and mixing them, surface coating A liquid was prepared.

<Preparation of charging roll>
(Examples 1, 3, 5, 7)
By drawing, a conductive shaft (φ8 mm, made of SUS304) having protrusions (500 μm protrusion height) formed on the surface along the axial direction was produced. The surface of this conductive shaft was coated with a low friction layer coating solution by dipping, and then heat treated at 100 ° C. for 30 minutes to form a low friction layer having a thickness of 15 μm. Next, the elastic layer composition was poured into a cylindrical mold in which a conductive shaft on which a low friction layer was formed was coaxially set, heated at 180 ° C. for 50 minutes, then cooled and demolded. This produced the roll body which has a 3 mm-thick elastic layer in the outer periphery of an electroconductive shaft. Next, the surface of the roll body is coated with each coating solution by a roll coating method, and the softener transition prevention layer (5 μm thickness), resistance adjusting layer (150 μm thickness), and surface layer (14 μm thickness) are sequentially formed. ) Was formed. As described above, each charging roll according to Examples 1, 3, 5, and 7 was produced.

(Examples 2, 4, 6, 8)
A conductive shaft (φ8 mm, manufactured by SUS304) having a groove (groove depth of 500 μm) formed on the surface along the axial direction was produced by drawing. Each charging roll according to Examples 2, 4, 6, and 8 was produced in the same manner as Example 1 except that a conductive shaft having this groove portion was used.

(Comparative Example 1)
Example 1 except that a conductive shaft (φ8 mm, made of SUS304) with a round cross section was used, an adhesive was applied to the outer peripheral surface, and a low friction layer was not formed. A charging roll according to Comparative Example 1 was produced.

(Comparative Example 2)
A charging roll according to Comparative Example 2 was produced in the same manner as in Example 1 except that a conductive shaft having a round cross section (φ8 mm, manufactured by SUS304) was used.

(Comparative Examples 3-5)
In the same manner as in Example 1, each charging roll according to Comparative Examples 3 to 5 was produced.

<Evaluation of each conductive roll>
About each charging roll which concerns on an Example and a comparative example, the volume resistivity of the low friction layer and the elastic layer was measured, respectively. Further, the static friction coefficients of the conductive shaft, the low friction layer, the surface layer, and the photosensitive drum were measured. And image evaluation was performed based on the following evaluation methods. The results are shown in Tables 1 and 2.

(Volume resistivity)
For each charging roll, a low friction layer material and an elastic layer material were formed to a diameter of 100 mm and a thickness of 2 mm, respectively. Subsequently, the volume resistivity of the molded sample was measured according to JIS K6911.

(Static friction coefficient)
Using a static friction coefficient meter (manufactured by Kyowa Interface Science Co., Ltd., “DFPM-S”), the surface of each member was brought into contact with the stylus of the static friction coefficient meter at a load of 100 g, and the stylus was slid at a speed of 65 to The dynamic friction coefficient was measured. The surface of each charging roll and the photosensitive drum are measured on the surface that appears, and the conductive shaft surface that appears when the conductive shaft is pulled out of each charging roll for the conductive shaft and the low friction layer of each charging roll. The measurement was made on the inner peripheral surface of the low friction layer.

(Image evaluation)
Each charging roll was assembled in a commercially available drum cartridge (“CT350376” manufactured by Fuji Xerox Co., Ltd.), and conditions of vibration acceleration 7.35 m / s ² , frequency 50 Hz, time 1 hour (conditions were set with reference to JIS Z0200). The drum cartridge was vibrated in the axial direction. After the vibration, this drum cartridge was set in a commercially available laser printer (“DocuPrint C3540” manufactured by Fuji Xerox Co., Ltd.), and a halftone image was taken out in a 15 ° C. × 10% RH environment. As a result, “○” indicates that no image stripe (color stripe) occurred, and “X” indicates that an image stripe (color stripe) occurred.

  In Comparative Example 1, a charging roll having a conventional structure is used. That is, a conductive shaft having a round cross section is used. Moreover, the low friction layer is not provided in the outer periphery of the electroconductive shaft. Further, the elastic layer formed on the outer periphery of the conductive shaft and the conductive shaft are bonded with an adhesive. Therefore, when the charging roll moves in the drum cartridge due to vibration applied to the drum cartridge, the surface layer of the charging roll and the surface of the photosensitive drum are rubbed. As a result, generation of image streaks (color streaks) was confirmed in the image evaluation.

  In Comparative Example 2, a low friction layer is provided on the outer periphery of the conductive shaft. At this time, the static friction coefficient μ2 of the surface layer and the static friction coefficient μ3 of the low friction layer satisfy the relationship of μ2> μ3. Further, the conductive shaft and the low friction layer are not bonded. Therefore, when the charging roll moves in the drum cartridge due to vibration applied to the drum cartridge, it slides between the conductive shaft and the low friction layer. For this reason, the charging roll surface layer and the photosensitive drum surface are not rubbed. However, since a conductive shaft having a round cross section is used, when the image is taken out, it slips between the conductive shaft and the low friction layer, and these do not rotate. As a result, an image could not be output.

  In Comparative Examples 3 to 5, a low friction layer is provided on the outer periphery of the conductive shaft. Further, the conductive shaft and the low friction layer are not bonded. Furthermore, the electroconductive shaft which a protrusion is formed along an axial direction and has a convex-shaped cross section is used. However, the static friction coefficient μ2 of the surface layer and the static friction coefficient μ3 of the low friction layer do not satisfy the relationship of μ2> μ3. Therefore, when the charging roll moves in the drum cartridge due to vibration applied to the drum cartridge, the surface layer and the surface of the photosensitive drum are rubbed without sliding between the conductive shaft and the low friction layer. As a result, generation of image streaks (color streaks) was confirmed in the image evaluation.

  On the other hand, in each charging roll according to the embodiment, a low friction layer is provided on the outer periphery of the conductive shaft. At this time, the static friction coefficient μ2 of the surface layer and the static friction coefficient μ3 of the low friction layer satisfy the relationship of μ2> μ3. Further, the conductive shaft and the low friction layer are not bonded. Further, a conductive shaft having a protrusion or a groove formed along the axial direction and having a convex or concave cross section is used.

  Therefore, when the charging roll moves in the drum cartridge due to vibration applied to the drum cartridge, it slides between the conductive shaft and the low friction layer. For this reason, the charging roll surface layer and the photosensitive drum surface are not rubbed. Also, image output was possible. In the image evaluation, generation of image streaks (color streaks) was not confirmed. Therefore, according to each charging roll according to the embodiment, even when assembled in contact with the photosensitive drum, generation of frictional charging due to friction with the photosensitive drum can be suppressed, and image defects due to this can be suppressed. Was confirmed.

  Further, in the charging roll according to each example, the low friction layer has a volume resistivity lower than the volume resistivity of the elastic layer. Therefore, the resistance increase due to the provision of the low friction layer does not occur. As a result, no resistance unevenness occurs.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said Example at all, A various change is possible in the range which does not deviate from the summary of this invention.

It is an axial direction sectional view showing the charging roll for electrophotographic equipment concerning one embodiment. FIG. 3 is a circumferential cross-sectional view illustrating a state in which a charging roll and a photosensitive drum are in contact with each other. It is a circumferential direction sectional view showing the charging roll for electrophotographic equipment concerning one embodiment. It is a circumferential direction sectional view showing the charging roll for electrophotographic equipment concerning other embodiments.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Charging roll 12 for electrophotographic apparatuses Conductive shaft 12a Projection 12b Groove part 14 Low friction layer 16 Elastic layer 18 Surface layer 20 Photosensitive drum

Claims (3)

A charging roll for an electrophotographic apparatus that is brought into contact with the surface of an image carrier,
A shaft body having protrusions or grooves formed along the axial direction;
A low friction layer formed along the outer periphery of the shaft,
A surface layer formed through one or more layers on the outer periphery of the low friction layer,
A charging roll for electrophotographic equipment, characterized by satisfying the following relationship:
μ1> μ4 and μ2> μ3
However,
μ1: Static friction coefficient of image carrier μ2: Static friction coefficient of surface layer μ3: Static friction coefficient of low friction layer μ4: Static friction coefficient of shaft   2. The charging roll for electrophotographic equipment according to claim 1, wherein the surface layer contains one or more selected from fluorine-containing polymers and silicone-containing polymers.   The charging roll for an electrophotographic apparatus according to claim 1 or 2, wherein the low friction layer has a volume resistivity lower than a volume resistivity of a layer formed on an outer periphery thereof.

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