JP2007271731A - Electrifying roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrifying roll used for an electrophotographic apparatus using a two component type toner, in which the rigidity of the roll is appropriately set as a whole and carrier is prevented from biting or sticking into a surface layer. <P>SOLUTION: The electrifying roll is provided with: a shaft body 1; a base rubber layer 2 formed on an outer periphery of the shaft body 1; and the surface layer 5 formed directly on the outer periphery of the base rubber layer 2 or indirectly through another layer. The base rubber layer 2 is formed of a base rubber layer forming material mainly consisting of rubber component the JIS-A hardness of which is ≤15°. The surface layer 5 is formed of a surface layer forming material the elongation (Eb) based upon JIS K6251 of which is 5 to 90% and the tensile strength (TS) of which is ≥35MPa. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a charging roll used in an electrophotographic apparatus using a two-component toner among electrophotographic apparatuses such as an electrophotographic copying machine and a printer.

  In general, copying by an electrophotographic copying machine is performed as follows. That is, first, a photosensitive drum is charged, a document image is projected onto the surface of the photosensitive drum via an optical system, and an electrostatic latent image is formed by canceling off the charging of the light projected portion. Next, after a toner is attached to the electrostatic latent image to form a toner image, the toner image is transferred to a copy sheet to obtain a copy image. The toner remaining on the surface of the photosensitive drum is scraped off by a cleaning blade or the like, and is used for the next charging in a state where the toner does not remain on the surface of the photosensitive drum.

As a method of charging the surface of the photosensitive drum prior to the formation of the electrostatic latent image, in recent years, a charging method using a charging roll has been widely adopted. As the charging roll, a rubber elastic body is used around the outer periphery of the shaft body. A base rubber layer is formed, and on the outer periphery thereof, a softener migration preventing layer and a resistance adjusting layer are formed as necessary, and a surface layer made of a resin coating is generally used as the outermost layer. (For example, refer to Patent Document 1). In addition, the base rubber layer of the above-mentioned charging roll forms a roll shape, and the softener migration prevention layer has functions such as preventing blooming of softener and vulcanizing agent from the base rubber layer, and is durable as a whole. In addition, characteristics such as toner releasability and followability to the photosensitive drum are adjusted to be optimized.
JP 2000-291634 A

  In such a charging roll, recently, the base rubber layer has a low hardness for the purpose of reducing the stress on the toner and the photosensitive drum, improving the image quality by ensuring stable nip properties, and extending the service life by improving the durability image performance. There is a strong demand to reduce the hardness of the entire roll.

  However, in an electrophotographic apparatus using a two-component toner in which a toner and a carrier (magnetic powder) are combined as a developer, if the above-described low-hardness charging roll is used, the surface of the roll is greatly deformed. There is a problem in that the carrier and toner bite into the surface, and that portion is poorly charged and easily causes image defects.

  That is, after development, the carrier and toner remaining on the surface of the photosensitive drum are scraped off by the cleaning blade as described above, and are used for the next charging in a state where the toner does not remain on the surface of the photosensitive drum. However, in reality, the carrier or toner slips through the cleaning blade or the like, or the cleaning blade or the like is chipped so that the scraping of the portion becomes insufficient. And toner tends to remain. Recently, in order to improve image quality, a substantially spherical polymerized toner is frequently used in place of the conventional pulverized toner, and cleaning failure is likely to occur. This has an adverse effect on the charging roll.

  Therefore, it is conceivable to increase the hardness of the surface layer in order to suppress deformation of the roll surface and eliminate biting of residual toner, etc. However, if the hardness of the surface layer is increased, the deformation of the surface layer relative to the deformation amount of the base rubber layer Insufficient amount increases stress on the photosensitive drum and toner, and the meaning of lowering the hardness of the base rubber layer is lost. In addition, there is a problem that the surface layer is cracked or cracked by the contact between the hard surface layer and the hard carrier, and the carrier or toner pierces the opening, which easily causes image defects or leaks.

  The present invention has been made in view of such circumstances, and is a charging roll used in an electrophotographic apparatus using a two-component toner, wherein the hardness of the entire roll is set appropriately, and the carrier to the surface layer is An object of the present invention is to provide an excellent charging roll that does not cause biting or piercing.

  In order to achieve the above object, a charging roll of the present invention is a charging roll used in an electrophotographic apparatus using a two-component toner, and includes a shaft body and a base rubber layer formed on the outer periphery of the shaft body. And a base layer formed on the outer periphery of the base rubber layer directly or via another layer, the base rubber layer having a rubber component having a JIS-A hardness of 15 degrees or less as a main component. It is formed of a forming material, and the surface layer is formed of a surface layer forming material having an elongation (Eb) based on JIS K6251 of 5 to 90% and a tensile strength (TS) of 35 MPa or more.

  That is, in order to solve the above-mentioned problems, the present inventor has conducted research focusing on the surface layer of a charging roll used in an electrophotographic apparatus using a two-component toner. In the process, if the elongation of the surface layer forming material is large, as shown in FIG. 1A, when the hard carrier 10 is pressed against the surface layer 5, the surface layer 5 is recessed, and the carrier 10 and the toner 11 are in the recess. It was found that it bites in and causes the charging failure of the part. Further, if the tensile strength of the surface layer forming material is insufficient, as shown in FIG. 1B, the surface layer 5 is broken by the pressure contact of the hard carrier 10, and the carrier 10 is pierced into the opening, which also causes poor charging. There was found. Therefore, when a surface layer forming material having both moderate elongation and tensile strength is used, as shown in FIG. 1 (c), the biting and piercing of the carrier 10 and the toner 11 are suppressed, and a high-quality charging roll is obtained. As a result of further research from the viewpoint of whether or not the surface layer 5 can be formed, the base rubber layer is formed of a material having a rubber component as a main component having a JIS-A hardness of 15 ° or less. When a material having an elongation (Eb) based on JIS K6251 of 5 to 90% and a tensile strength (TS) of 35 MPa or more is used as the forming material, the entire roll has a preferable low hardness, and the carrier 10 bites into the surface layer 5. The inventors have found that the piercing and sticking are suppressed, and have reached the present invention.

  In the charging roll of the present invention, the base rubber layer is formed of a base rubber layer forming material whose main component is a rubber component having a JIS-A hardness of 15 ° or less, and the surface layer has an elongation based on JIS K6251 ( It is formed of a surface layer forming material having an Eb) of 5 to 90% and a tensile strength (TS) of 35 MPa or more. For this reason, the entire charging roll of the present invention has a preferable low hardness, and further, biting and piercing of the carrier into the surface layer are suppressed. Therefore, by incorporating the charging roll of the present invention into an electrophotographic apparatus using a two-component toner, a high-quality copy image and print image can be obtained over a long period of time.

  In particular, the use of a material mainly composed of silicone rubber as the base rubber layer forming material makes the characteristics of the base rubber layer more favorable, and it is possible to obtain a copy image or a printed image with better quality over a long period of time. it can.

  Next, an embodiment of the present invention will be described. The present invention is not limited to this embodiment.

  For example, as shown in FIG. 2, the charging roll of the present invention includes a base rubber layer 2 formed along the outer peripheral surface of the shaft body 1, and a softener migration preventing layer 3 formed along the outer peripheral surface. The roll has a four-layer structure including a resistance adjusting layer 4 formed along the outer peripheral surface and a surface layer 5 formed along the outer peripheral surface.

  The shaft body 1 is not particularly limited, and may be, for example, a cored bar made of a hollow cylindrical body other than the solid body shown in the figure. The forming material is not particularly limited, and examples thereof include metal materials such as aluminum and stainless steel. In addition, you may apply | coat an adhesive agent, a primer, etc. on the shaft body 1 as needed, and electroconductivity can be provided to these adhesive agents, a primer, etc.

  The material for forming the base rubber layer 2 formed on the outer peripheral surface of the shaft body 1 is not particularly limited, but must be a rubber component having a JIS-A hardness of 15 ° or less as a main component. Don't be. That is, when the JIS-A hardness of the rubber component exceeds 15 °, the hardness of the entire roll becomes too high, reducing the stress on the toner and the photosensitive drum, improving the image quality by ensuring stable nip properties, and durable images. Longer life due to improved performance cannot be achieved.

  Examples of the rubber component include styrene-butadiene rubber (SBR), polynorbornene rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), and butadiene. Examples thereof include rubber (BR), isoprene rubber (IR), natural rubber (NR), silicone rubber and the like, and they are used alone or in combination of two or more. Among these, the use of silicone rubber is preferable because the characteristics of the base rubber layer 2 are more preferable.

The base rubber layer 2 is made of carbon black, graphite, potassium titanate, iron oxide, c-TiO ₂ , c-ZnO, c-SnO ₂ , ionic conductive agent (four Conventionally known conductive agents such as quaternary ammonium salts, borates, surfactants, etc.) are appropriately added. Further, if necessary, a foaming agent, a crosslinking agent, a crosslinking accelerator, oil, and the like may be added as appropriate.

  As a material for forming the softener migration preventing layer 3 formed on the outer peripheral surface of the base rubber layer 2, for example, a conductive agent such as carbon black is blended with polyamide resin such as N-methoxymethylated nylon or polyester. Things can be raised. These may be used alone or in combination of two or more.

  Examples of the material for forming the resistance adjusting layer 4 formed on the outer peripheral surface of the softener migration preventing layer 3 include hydrin rubber, EPDM, SBR, NBR, H-NBR, polyurethane elastomer, carbon black, metal oxide, and the like. , Quaternary ammonium salts, borates, lithium perchlorate and other conductive agents. These may be used alone or in combination of two or more.

  An example of a method for preparing each layer forming material of the base rubber layer 2, the softening agent migration preventing layer 3 and the resistance adjusting layer 4 is as follows. First, the forming material (compound) of the base rubber layer 2 includes the above components as a kneader. It can be prepared by kneading with a kneader or the like. The forming material (coating liquid) for the softener migration preventing layer 3 and the resistance adjusting layer 4 is prepared by kneading the above components with a ball mill, a roll or the like, adding a solvent to the mixture, and mixing and stirring. Can do.

  The material for forming the surface layer 5 formed on the outer peripheral surface of the resistance adjusting layer 4 must have a property that the elongation (Eb) based on JIS K6251 is 5 to 90% and the tensile strength (TS) is 35 MPa or more. I must. That is, when the elongation is less than 5%, the flexibility derived from the base rubber layer 2 set to a low hardness of JIS-A hardness of 10 ° or less cannot be followed, and the hardness of the entire roll is reduced. Can not meet the demands. On the other hand, if the elongation exceeds 90%, the carrier and toner are likely to bite into the surface layer 5 and cause trouble. Further, if the tensile strength is less than 35 MPa, the surface layer 5 is cracked or cracked, the carrier is pierced, and trouble is likely to occur.

  The elongation (Eb) and tensile strength (TS) are measured, for example, by preparing a resin sheet (dumbbell test piece No. 2) using a surface layer forming material, and according to JIS K6251. Is a value obtained by

The material of the material for forming the surface layer 5 having such characteristics is not particularly limited. For example, polyamide-based resins such as N-methoxymethylated nylon, fluorine resins, acrylic resins, urethane resins, silicone resins, etc. Can be given. These may be used alone or in combination of two or more. In order to impart conductivity, a conventionally known conductive agent such as carbon black is appropriately added to the material. The electrical resistance of the surface layer 5 is preferably set in the range of 1 × 10 ⁶ to 1 × 10 ¹⁰ Ω · cm.

  Among the materials for forming the surface layer 5, N-methoxymethylated nylon having a repeating unit represented by the following formula (1) is used, and as its curing agent, 100 parts by weight of N-methoxymethylated nylon (hereinafter, The use of a resin composition containing 10 to 120 parts of melamine-based resin at a ratio of 30 to 100 parts relative to “parts” is particularly preferable for obtaining the desired characteristics. Is preferred. Among them, “8-nylon” in which m in the following formula (1) is 5 is particularly preferable.

  The melamine resins include trimethylol melamine and hexamethylol melamine obtained by reacting melamine, a material having a polyfunctional amino group such as urea, thiourea, guanidine, and guanamine with formaldehyde. Dimethylol urea dimethylol guanidine, melamine resin etherified with monohydric alcohol or methoxymethylated, and the like. These may be used alone or in combination of two or more. And the molecular weight of the said melamine-type resin is 100-4000 normally, Preferably it is the range of 100-500 molecular weight.

  The material for forming the surface layer 5 is usually dissolved in a solvent and used as a coating solution. Examples of the solvent include methanol, water, toluene, ethanol, methyl ethyl ketone (MEK), isopropyl alcohol, methyl cellosolve, dimethylformamide and the like. These may be used alone or in combination of two or more. In particular, a methanol / water mixed solution is preferably used as a solvent from the viewpoint of solubility in the material for forming the surface layer 5. And it is preferable at points, such as coating property, that the coating liquid obtained in this way shall be 0.005-6Pa.s of viscosity.

  In addition, you may add electrically conductive agents, such as carbon black, to the coating liquid of the said preparation. In addition to the above components, as necessary, fillers (rough surface forming particles, etc.), stabilizers, ultraviolet absorbers, antistatic agents, lubricants, mold release agents, dyes, pigments, flame retardants and the like are appropriately used. You may mix | blend with.

  The charging roll of the present invention can be produced, for example, as follows.

  That is, first, the base rubber layer 2 is integrally formed along the outer peripheral surface of the shaft body 1 by using a molding method using the forming material of the base rubber layer 2 prepared as described above. Next, the forming material (coating liquid) of the softener migration preventing layer 3 is applied to the outer peripheral surface of the base rubber layer 2 by an appropriate method such as a dipping method, a spray method, a roll coating method, and the like. By heating, the softener migration preventing layer 3 is formed. Then, the material for forming the resistance adjusting layer 4 (coating liquid) is applied to the outer peripheral surface of the softening agent migration preventing layer 3 by an appropriate method in the same manner as described above, and then dried and heated, whereby the resistance adjusting layer 4 is formed. In this way, a roll base in which the base rubber layer 2, the softener migration preventing layer 3, and the resistance adjusting layer 4 are laminated in this order is manufactured.

  On the other hand, each component for the surface layer 5 is dissolved in a solvent, dispersed with a sand mill or the like, and dissolved to prepare a surface layer 5 forming material (coating solution), and on the outer peripheral surface of the resistance adjusting layer 4 of the roll base. The above coating liquid is applied. This coating method is not particularly limited, and an appropriate method such as a dipping method, a spray method, or a roll coating method is used. And after application | coating, the solvent in a coating liquid is evaporated and removed by performing drying and heat processing (conditions: 60-170 degreeC), and also is bridge | crosslinked. In this way, a charging roll having a four-layer structure as shown in FIG. 2 can be produced.

  In the charging roll of the present invention, the thickness of each layer is appropriately determined depending on the intended use of the roll. For example, the thickness of the base rubber layer 2 is preferably set in the range of 1 to 10 mm, particularly preferably. The thickness is 2 to 6 mm. Moreover, it is preferable to set the thickness of the softening agent transition prevention layer 3 to the range of 3-30 micrometers, Especially preferably, it is 5-10 micrometers in thickness. Moreover, it is preferable to set the thickness of the resistance adjustment layer 4 to the range of 10-800 micrometers, Especially preferably, it is 100-300 micrometers in thickness.

  And it is preferable to set the thickness of the surface layer 5 to 1-30 micrometers, Most preferably, it is the range of thickness 3-20 micrometers. That is, when the thickness of the surface layer 5 is less than 1 μm, the thickness of the surface layer is too thin and tends to bloom, and conversely, when the thickness of the surface layer 5 exceeds 30 μm, processing such as coating properties is performed. This is because there is a tendency to become inferior.

The electrical resistance of the surface layer 5 is preferably set in the range of 1 × 10 ⁵ to 1 × 10 ¹¹ Ω · cm, more preferably 1 × 10 ⁸ to 1 × 10 ¹⁰ Ω · cm.

  As an example of the charging roll of the present invention, a four-layer structure as shown in FIG. 2 is given. However, the present invention is not limited to this, and two layers of a base rubber layer 2 and a surface layer 5 are used. It may be a structure. Moreover, it can be set as an appropriate structure such as forming a plurality of resistance adjusting layers 4 between the base rubber layer 2 and the surface layer 5 as necessary.

  The charging roll of the present invention can be applied to a general electrophotographic apparatus. In particular, the charging roll for an electrophotographic apparatus that performs development using a two-component toner in which a carrier and a toner are combined is used. It is optimal to use as a roll. By incorporating the charging roll of the present invention into an electrophotographic apparatus using the above two-component toner, a good copy image can be obtained over a long period of time.

  Next, examples will be described together with comparative examples.

[Examples 1 to 10, Comparative Examples 1 to 5]
(1) Formation of base rubber layer First, a core metal (diameter 6 mm, made of stainless steel (SUS304)) serving as a shaft body and three types of SBR (JIS-A hardness 10 ° having different hardnesses) as base rubber layer forming materials , 15 °, 25 °) prepared by adding 10 parts of carbon black to 100 parts. Then, one of the three types of SBR was selected according to Tables 1 to 3 below, and a base roll having a base rubber layer having a thickness of 3 mm formed on the outer peripheral surface of the core metal was produced by die molding.

(2) Formation of softener migration preventing layer and resistance adjusting layer Next, 100 parts of N-methoxymethylated nylon (manufactured by Nagase ChemteX Corporation, EF30T-C) and conductive agent (Ketjen Black EC, Ketjen Black 20 parts of International Co., Ltd.) and 400 parts of MEK were mixed to prepare a softener migration-preventing layer forming material (coating solution A). Also, 100 parts of NBR (Nippon Zeon, Nipol DN401), 1 part of quaternary ammonium salt (Wako Pure Chemical Industries, TBAHS), 30 parts of acetylene black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) And 0.5 parts of stearic acid (manufactured by Kao Corporation, LUNAC S30), 5 parts of zinc white (manufactured by Sakai Chemical Industry Co., Ltd.), and vulcanizing aid (manufactured by Sanshin Chemical Co., Ltd., Sunseller CZ-G) 1.07 Part, 0.49 part of vulcanization auxiliary (Ouchi Shinsei Chemical Co., Noxeller BZ-P) and 1 part of sulfur (Tsurumi Chemical Industry Co., Ltd., Sulfax PTC) are mixed and stirred, and the resistance adjustment layer A forming material (coating solution B) was prepared. And the said coating liquid A was first apply | coated to the outer peripheral surface of the said base roll by the roll coat method, and the softening agent transfer prevention layer with a thickness of 5 micrometers was formed by drying and heating. Next, the coating liquid B was applied by a roll coating method, dried and heated to form a resistance adjustment layer having a thickness of 150 μm. In this way, a roll base was produced in which a base rubber layer, a softener migration preventing layer, and a resistance adjusting layer were laminated in this order around the core metal.

(3) Formation of surface layer Next, the components shown in Tables 1 to 3 below are blended in the proportions shown in the same table, and this is added to 500 parts of a methanol-toluene mixed solution (methanol: toluene = 7: 3). It melt | dissolved and the formation material (coating liquid) for surface layers was prepared. And the coating liquid which is surface layer forming material was apply | coated to the outer peripheral surface of the said produced roll base | substrate using the roll-coating method. And the target charging roll was produced by drying and heat-crosslinking a coating liquid. In addition, the thickness of the surface layer in each charging roll is shown together in Tables 1 to 3 below.

  Each charging roll thus obtained was measured for elongation and tensile strength according to the method described above and evaluated according to the following criteria. These results are shown in Tables 1 to 3 below.

[Toner penetration]
Each obtained charging roll was incorporated into a laser printer (Fuji Xerox Co., Ltd., DocuPrint C1616) using a two-component toner, and after 10,000 images were printed, the state of the surface of the roll was measured with an optical microscope (× (1000 times). Then, even after 10,000 images were printed, the evaluation was evaluated as ◯ when there was no toner bite on the roll surface, and x when the toner bite occurred even on one roll surface.

[Carrier sticking property]
According to the same observation as described above, even after 10,000 images have been printed, the case where there is no carrier sticking on the roll surface is indicated by ○, and the case where even one piece of carrier sticking occurs is indicated by ×. evaluated.

(Image evaluation)
After 10,000 images were printed in the same manner as described above, the state of the printed image was visually evaluated. That is, even after 10,000 images have been printed, there is no problem with the print image, the print image is clear up to the fine line, and there is almost no contamination of the roll surface, and the print image has uneven density. Was evaluated as x.

  From these results, it can be seen that all of the example products can suppress the biting of the toner and the piercing of the carrier, and an excellent image can be obtained. On the other hand, the comparative product has a problem in any of the evaluation items, and an excellent image cannot be obtained.

(A), (b), (c) is a schematic explanatory drawing explaining the subject of this invention. It is sectional drawing which shows an example of the charging roll of this invention.

Explanation of symbols

1 Shaft body 2 Base rubber layer 5 Surface layer

Claims (2)

  A charging roll used in an electrophotographic apparatus using a two-component toner, comprising a shaft body, a base rubber layer formed on the outer periphery of the shaft body, and a direct or other layer on the outer periphery of the base rubber layer. The base rubber layer is formed of a base rubber layer-forming material whose main component is a rubber component having a JIS-A hardness of 15 ° or less, and the surface layer is compliant with JIS K6251. A charging roll characterized by being formed of a surface layer forming material having an elongation (Eb) based on 5 to 90% and a tensile strength (TS) of 35 MPa or more.   The charging roll according to claim 1, wherein the rubber component of the base rubber layer forming material is silicone rubber.

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