JP2007033843A - Developing roller and developing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller which lowers the hardness of an elastic body and is free of contamination and filming while maintaining conductive performance of the resin by the developing roller composed of an elastic semiconductor constituted of a finely foamed conductive crosslinked polymer, and also to provide a developing apparatus which uses the non-contaminatable developing roller and with which a satisfactory image is obtainable. <P>SOLUTION: The developing roller 12 is a semiconductive roller consisting of a conductive shaft body 1, an elastic semiconductor 2 formed on the outer circumference of the conductive shaft body 1, and a surface resistance adjustment layer 3 formed on the surface of the elastic semiconductor 2, in which the rubber hardness is 15 to 70 (JIS A); the electric resistance between the conductive shaft body 1 and the surface resistance adjustment layer 3 is 1x10<SP>4</SP>to 10<SP>9</SP>Ω; the surface roughness (Rz) of the outer surface of the surface resistance adjustment layer 3 is 2 to 10 μm; and the average cell diameter of at least the elastic semiconductor is ≤40 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing roller having a conductive shaft and an elastic semiconductor positioned outside the conductive shaft, and a developing device including the developing roller.

  Conventionally, for example, in an electrophotographic developing apparatus such as a copying machine, a FAX, or a printer, a non-magnetic one-component developer is supplied to a photosensitive drum holding a latent image, and the developer is attached to the latent image on the photosensitive drum. A contact development method is known as a development method for visualizing a latent image.

  Then, a conductive shaft and an elastic semiconductor located on the outer periphery thereof are provided as a toner carrying layer, and formed on the latent image holding body by the frictionally charged toner carried in a thin film state on the toner carrying layer. A developing roller of a developing device that visualizes an electrostatic latent image is required to have characteristics such as conductivity, environmental resistance, low hardness, frictional charging characteristics, and toner transportability. In response to such demands, developing rollers made of urethane rubber, NBR, silicone rubber or the like and made semiconductive by adding a conductivity imparting agent are widely known (see, for example, Patent Document 1). )

  In recent years, with the increase in printing speed, the softening point (melting temperature) of toner tends to decrease. When non-magnetic one-component toner is used, the developing roller carries the toner by frictional charging between the developing roller and the toner. Therefore, when a developing roller having high hardness is used, high heat generation due to friction with the toner may occur, and the toner may melt (filming phenomenon).

  Further, in order to transfer the toner carried on the developing roller to the photosensitive member, a sufficient contact nip is required, and a developing roller constituted by a low hardness elastic semiconductor is required.

  The elastic semiconductor of the developing roller is made of a material obtained by adding a conductive filler to resin. Metal powder, carbon, etc. are used as the conductive filler. If the amount of conductive filler added is increased to obtain sufficient conductivity, the hardness of the elastic body tends to increase. To reduce the hardness, it is effective to add a softener (process oil). However, if a large amount of softener is added, the softener may leach out on the surface of the elastic body (bleed phenomenon). As a result, there is a risk that the photoreceptor is contaminated.

  On the other hand, a foam used for a roller member for a developing device such as a developing roller needs to have a fine cell diameter in order to obtain a good image. A foam in which cells are formed by foaming or the like and cells are formed by the action of a foaming gas does not satisfy this requirement when used as a roller member of a developing device such as a developing roller.

  Because these foams are foamed at normal pressure, the solubility of the foaming gas in the polymer is limited, and it is not possible to obtain fine-structured cells. As a result, the toner supply and scraping properties deteriorate, and a good image cannot be obtained.

In addition, the non-crosslinked rubber is impregnated with a supercritical fluid or subcritical fluid, and the impregnated supercritical fluid or subcritical fluid is discharged and foamed to be crosslinked in a foamed state having a cell diameter of 40 to 350 μm. There is also a method for producing a rubber foam for a developing device, but since a foam having a cell diameter of 40 to 350 μm has a large cell diameter, it is difficult to obtain a good image when used as a component of a developing device. It is. Moreover, since the impregnation method has poor production efficiency, it cannot be said that it is a practical production method.
JP 2002-286024 A

  Therefore, in order to solve the conventional problems as described above, the present invention provides an elastic semi-conductive roller composed of a finely foamed conductive cross-linked polymer, while maintaining the conductive performance of the resin. It is an object of the present invention to provide a developing roller having low hardness and no contamination / filming. It is another object of the present invention to provide a developing device that can obtain a good image using such a low hardness, non-contaminating developing roller.

  The present invention adopts the following means in order to realize the above-described problems.

The invention according to claim 1 includes a conductive shaft, a rubber-like elastic body formed on the surface of the conductive shaft, and a surface resistance adjusting layer formed on the surface of the rubber-like elastic body. A semiconductive roller having a rubber hardness of 15 to 70 (JIS A), an electrical resistance between the conductive shaft body and the surface resistance adjusting layer of 1 × 10 ⁴ to 10 ⁹ Ω, The surface roughness (Rz) of the outer surface of the surface resistance adjusting layer is 2 to 10 μm, and at least the average cell diameter of the elastic semiconductor is 40 μm or less.

  The invention according to claim 2 includes a step of simultaneously mixing and dissolving a supercritical fluid at a high speed when mixing an unvulcanized liquid rubber containing a vulcanizing agent and a vulcanization accelerator, and the supercritical fluid. 2. The method according to claim 1, comprising: a step of casting a mixed liquid rubber containing a mold into a mold; a step of partially opening and foaming the cast supercritical fluid; and a step of crosslinking the foamed rubber. In addition to the configuration, it is characterized by that.

  According to a third aspect of the present invention, there is provided the developing device according to the first aspect, wherein the triboelectrically charged toner is supported on the surface of the semiconductive roller and a thin film of the triboelectrically charged toner is formed. An electrostatic latent image is formed by contacting a latent image holding member capable of holding an electrostatic latent image on the surface, and causing the frictionally charged toner to adhere to the surface of the latent image holding member from the thin film of the frictionally charged toner. It is characterized by visualizing the electrostatic latent image.

  According to a fourth aspect of the present invention, there is provided a developing device including the semiconductive roller manufactured by the method of manufacturing the semiconductive roller according to the second aspect.

  Since the present invention employs the configuration as described above, according to the first and third aspects of the present invention, the elastic semi-conductor of the developing roller is an elastic layer of a conductive cross-linked polymer that is finely foamed. Therefore, the hardness is low, and a good image can be obtained by the developing device using this developing roller. Further, by defining the surface roughness of the toner carrying layer on the surface of the developing roller within a predetermined range, the action of attaching the toner to the charged portion of the photosensitive drum becomes more stable, in addition to the effect of fine foaming. According to the developing device using the developing roller, a high-definition and high-quality printed image can be obtained. Furthermore, since an appropriate developing bias can be obtained by defining the electric resistance value between the conductive shaft and the surface of the toner carrying layer within a predetermined range, the developing device using this developing roller can provide toner. A clear printed matter can be obtained without causing fogging or fading.

  According to the second and fourth aspects of the present invention, since the supercritical fluid is dissolved in the rubber simultaneously with the mixing of the rubber, an additional process is not required, and the production method of the developing roller and the developing device with high productivity is provided. can get.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

First, a semiconductive developing roller according to an embodiment of the present invention will be described.
FIG. 1 is a cross-sectional view showing a semiconductive developing roller according to an embodiment of the present invention.

  In FIG. 1, a semiconductive developing roller 12 includes a conductive shaft 1, an elastic semiconductor 2 made of rubber and / or elastomer formed on the conductive shaft 1, and the elastic semiconductor. 2 and a toner carrying layer (surface resistance adjusting layer) 3 made of a thermosetting polymer or a thermoplastic polymer.

  FIG. 2 shows an example of an electrophotographic developing device using a semiconductive developing roller.

  As shown in FIG. 2, the developing device G includes a photosensitive drum 10 as a latent image carrier, 11 a charging roller, 12 a developing roller, 13 a toner conveying roller, 14 a transfer roller, 15 a cleaning roller, 21 is a stirrer, 31 is a frictional charging blade as a layer forming member, 41 is an LED array, 51 is provided with a housing and the like, and is carried in a thin film state on the toner carrying layer 3 on the surface of the developing roller 12. The electrostatic latent image formed on the photosensitive drum 10 is transferred to the recording paper 61 and visualized by the frictionally charged toner.

  Further, by setting the 10-point average roughness Rz of the toner carrying layer (surface resistance adjusting layer) 3 in the range of 2 to 10 μm, more preferable printing characteristics can be obtained.

  As described above, the elastic semiconductor 2 of the semiconductive developing roller 12 according to the present invention is obtained by applying the elastic semiconductor 2 of rubber and / or elastomer composition on the conductive shaft 1 under appropriate conditions. After forming into a roller shape below, it is obtained by finishing to a desired surface state.

  The conductive shaft 1 is not particularly limited as a conductive material, but is a so-called “core metal” made of iron, aluminum, SUS, or brass, or a core of thermoplastic resin or thermosetting resin. A core obtained by plating a body, or a carbon resin, a thermosetting resin, or a core body in which carbon black, metal powder or the like is blended as a conductivity imparting agent is used.

  The elastic semiconductor 2 of the semiconductive developing roller 12 includes silicone rubber, ethylene-propylene-diene rubber, polyurethane, chloroprene rubber, natural rubber, butyl rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, nitrile rubber, ethylene. A filler such as fumed silica, precipitated silica, reinforcing carbon black, and conductive carbon black, nickel, aluminum, propylene rubber, acrylic rubber, and any one or more of rubbers or elastomers thereof; Metal powders such as copper, metal oxides such as zinc oxide and tin oxide, conductive fillers in which tin oxide is coated on a core material such as barium sulfate, titanium oxide or potassium titanate, and the like, peroxide, platinum catalyst Hydrogen siloxane and isocyan in the presence Those kneaded with vulcanizing agents over bets or the like is used.

  In molding, the conductive shaft 1 and the elastic semi-conductor 2 of rubber and / or elastomer composition are integrated and dispensed by using a crosshead with an extruder, and then primary in a gear oven or IR furnace. A method of vulcanization, a method of injecting a silicone rubber composition after setting the conductive shaft body 1 in a mold, and a primary vulcanization at room temperature or under heating, an elastic half of the conductive shaft body 1 and the silicone rubber composition A method of simultaneously heating and compressing the conductor 2 in a mold is used. Thereafter, the physical properties can be stabilized by performing secondary vulcanization for a certain period of time in a gear oven or the like.

  The molded product produced as described above is processed into a desired surface state (preferably Rz 3 to 15 μm) by a cylindrical grinder, a shot blaster, a sand blaster, a lapping machine, a buff or the like.

  The material of the thermosetting polymer or thermoplastic polymer used for the toner carrying layer (surface resistance adjusting layer) 3 is not particularly limited, but those having an amino group and / or a hydroxyl group are suitable. Examples include alkyd resins, modified alkyd resins such as phenol and silicone modifications, oil-free alkyd resins, acrylic resins, silicone resins, epoxy resins, fluororesins, phenol resins, polyamide resins, urethane resins and mixtures thereof. It is done. For the crosslinking, a crosslinking agent such as an isocyanate compound, a melamine compound, an epoxy compound, a peroxide, a phenol compound, or a hydrogen siloxane compound is used.

  Examples of fillers for resin layers mainly composed of thermosetting polymers or thermoplastic polymers include inorganic fillers such as wet silica, diatomaceous earth, aluminum oxide, zinc oxide, calcium carbonate, silicone resin powder, methyl methacrylate powder, etc. Organic fillers or the like can be used.

  The conductive shaft 1 used for the semiconductive developing roller 12 according to the present invention has one end grounded or a bias voltage applied to inject the charge into the toner, adsorb the toner, and the electrostatic latent image carrier. It is a support for the elastic semiconductor 2 formed on the outer periphery, which obtains the performance of electrostatic latent image development, charging and transfer by conveying toner to the surface.

  The elastic semiconductor 2 functions as an electrode for the development process, a contact charging to the toner, and an electrode for charge injection, and forms a uniform developing electric field with the photoreceptor due to its rubber elasticity. Is. In addition, the toner carrying layer (surface resistance adjusting layer) 3 formed on the elastic semiconductor 2 carries and conveys toner on the roller surface by the unevenness of the surface and van der Waals force, mirror image force, coulomb force and the like. To do.

  In order to manufacture the developing roller 12 according to the embodiment of the present invention, for example, a metal shaft having a diameter of 10 mm and a length of 275 mm obtained by electroless nickel plating on SUS22 is used as the conductive shaft 1. A primer is applied to a metal shaft and dried at room temperature and humidity for 1 hour.

  Next, the conductive shaft 1 is set in a molding die.

  As a material of the elastic semiconductor 2, for example, an insulating ether polyol 38.9%, a conductive ether polyol 38.9%, and an MDI isocyanate 22.2% are mixed in a vacuum state with a stirrer, and 12 MPa After impregnating with nitrogen in a supercritical state under the condition of × 35 ° C., the pressure in the mold is maintained at 8 MPa, and crosslinking is performed while releasing nitrogen and foaming at 150 ° C. for 30 minutes. Then, this is secondarily vulcanized at 60 ° C. for 10 hours to form the elastic semiconductor 2.

  Next, the outer peripheral surface of the secondary vulcanized elastic semiconductor 2 is polished to produce a roller base material having a diameter of 16 mm and a rubber part (elastic semiconductor 2) length of 230 mm.

  Next, on the surface of the polished elastic semiconductor 2 of the developing roller, for example, a coating liquid obtained by adding a fumed silica-based filler and a block isocyanate-based cross-linking agent to urethane paint is applied once by spray coating. The developing roller 12 as a finished product is obtained by heating and curing at 150 ° C. for 90 minutes.

  As described above, in the developing roller 12 according to the embodiment of the present invention, the elastic semiconductor 2 of the developing roller 12 is an elastic layer of a conductive cross-linked polymer finely foamed by supercritical inert gas. According to the developing device 51 using the developing roller 12, a good image can be obtained. Further, by regulating the surface roughness of the toner carrying layer (surface resistance adjusting layer) 3 on the surface of the developing roller 12 within a predetermined range, the action of attaching the toner to the charged portion of the photosensitive drum becomes more stable. In addition to the effect of fine foaming, the developing device 51 using the developing roller 12 can obtain a high-definition and high-quality printed image. Further, since the electric resistance value between the conductive shaft body 2 and the surface of the toner carrying layer (surface resistance adjusting layer) 3 is regulated within a predetermined range, an appropriate developing bias can be obtained. According to the developing device G using the toner, clear recording paper 61 can be obtained without causing toner fogging or blurring.

  In addition, since the supercritical fluid is dissolved in the rubber simultaneously with the mixing of the rubber, an additional process is not required, and a method for manufacturing the developing roller 12 and the developing device G with high productivity can be obtained.

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to the examples shown below.
[Example 1]

  As the conductive shaft 1, a SUS22 electroless nickel-plated metal shaft having a diameter of 10 mm and a length of 275 mm is used. A primer (trade name: Chemlock 213, Road Far East Incorporated, Ltd.) is used on the metal shaft. (Manufactured by DO Co., Ltd.) was applied and dried at room temperature and humidity for 1 hour.

  Next, the shaft is set in a molding die.

  As materials for the elastic semiconductor 2, insulating ether polyol (trade name: ON-E59, manufactured by Nippon Polyurethane Industry Co., Ltd.) 38.9% and conductive ether polyol (trade name: ON-E60, Japan polyurethane) 38.9% manufactured by Kogyo Co., Ltd.) and 22.2% MDI isocyanate (trade name: MC-C23, manufactured by Nippon Polyurethane Industry Co., Ltd.) were mixed in a vacuum with a stirrer, and nitrogen in the mold After impregnating supercritical nitrogen under a gas pressure of 12 MPa × 30 ° C. (as the impregnation method, the supercritical nitrogen is mixed while colliding the liquid polymer itself), and then the pressure in the mold is 8 MPa. (The pressure is maintained by providing an inlet / outlet connected to 8 MPa nitrogen gas on the opposite side of the resin injection port), and releasing nitrogen under conditions of 150 ° C. × 30 minutes for foaming. While crosslinking. Then, this is secondarily vulcanized at 60 ° C. for 10 hours to form the elastic semiconductor 2. The formed elastic foam (elastic semiconductor 2) had a cell diameter of 5 to 50 μm and an average cell diameter of 25 μm.

  Next, after secondary vulcanization, the outer peripheral surface of the elastic semiconductor 2 is polished with a cylindrical grinder equipped with a GC # 400 grindstone, and the diameter is 16 mm and the length of the rubber part (elastic semiconductor 2) is 230 mm. A roller base material is prepared.

  Next, on the surface of the elastic semiconductor 2, 100 parts by mass of urethane-based paint (trade name: NIPPOLAN 5196, manufactured by Nippon Polyurethane Co., Ltd.) and fumed silica-based filler (trade name: AEROSIL 200, Nippon Aerosil ( Co., Ltd.) 10 parts by mass and a coating solution added with 18 parts by mass of a blocked isocyanate crosslinking agent is applied once by spray coating and heat cured at a temperature of 150 ° C. for 90 minutes to form a toner carrying layer (surface resistance adjusting layer) ) 3 is formed. The formed toner carrier layer (surface resistance adjusting layer) 3 has a thickness of about 10 μm.

The surface roughness Rz of the developing roller 12 thus completed is 4 μm, and the electrical resistance value between the conductive shaft 1 and the surface of the toner carrying layer 3 is 1 × 10 ⁶ Ω (voltage : 100V).
[Example 2]

Example 2 is a manufacturing method similar to Example 1, but the setting of the nitrogen gas pressure in the mold during molding is 6 MPa, and the cell diameter of the formed elastic foam (elastic semiconductor 2) is 5 to 5. The average cell diameter is 70 μm and 35 μm. The thickness of the toner carrying layer (surface resistance adjusting layer) 3 was adjusted to 14 μm. The finished developing roller 12 had a surface roughness Rz of 5 μm. The electric resistance value between the conductive shaft 1 and the surface of the toner carrying layer 3 is 7 × 10 ⁶ Ω.
[Example 3]

Example 3 is a production method similar to Example 1, but the cell diameter of the formed elastic foam (elastic semiconductor 2) is 5 to 55 μm, and the average cell diameter is 26 μm. The thickness of the toner carrying layer (surface resistance adjusting layer) 3 was adjusted to 18 μm. The surface roughness of the completed developing roller 12 was Rz2.1. The electrical resistance between the conductive shaft 1 and the surface of the toner carrying layer 3 is 2 × 10 ⁴ Ω.
[Example 4]

Example 4 is the same production method as Example 1, but the cell diameter of the formed elastic foam (elastic semiconductor 2) is 5 to 55 μm, and the average cell diameter is 25 μm. The toner carrying layer (surface resistance adjusting layer) 3 was thinly coated twice and the thickness was adjusted to 4.6 μm. The finished developing roller 12 had a surface roughness of 9.7 μm. Further, the electric resistance between the conductive shaft 1 and the surface of the toner carrying layer 3 is 3 × 10 ⁸ Ω.
[Comparative Example 1]

Comparative Example 1 is the same production method as Example 1, but the setting of the nitrogen gas pressure in the mold during molding is 3 MPa, and the cell diameter of the formed elastic foam (elastic semiconductor 2) is 5 to 5. The average cell diameter is 100 μm and 45 μm. The thickness of the toner carrying layer (surface resistance adjusting layer) 3 was adjusted to 20 μm. The finished developing roller 12 has a surface roughness Rz of 5 μm. The electrical resistance value between the conductive shaft 1 and the surface of the toner carrying layer 3 is 2 × 10 ⁷ Ω.
[Comparative Example 2]

Comparative Example 2 is a production method similar to that of Example 1, but the cell diameter of the formed elastic foam (elastic semiconductor 2) is 5 to 55 μm, and the average cell diameter is 25 μm. The thickness of the toner carrying layer (surface resistance adjusting layer) 3 was adjusted to 20 μm. The finished developing roller 12 has a surface roughness Rz of 1.8 μm. The electric resistance value between the conductive shaft 1 and the surface of the toner carrying layer 3 is 7 × 10 ³ Ω.
[Comparative Example 3]

Comparative Example 3 is the same production method as Example 1, but the cell diameter of the formed elastic foam (elastic semiconductor 2) is 5 to 55 μm, and the average cell diameter is 25 μm. The toner carrying layer (surface resistance adjusting layer) 3 was thinly coated twice and the thickness was adjusted to 3.8 μm. The finished developing roller 12 has a surface roughness Rz of 10.5 μm. The electrical resistance between the conductive shaft 1 and the surface of the toner carrying layer 3 is 3 × 10 ⁹ Ω.

  For each of Examples 1 to 4 and Comparative Examples 1 to 3, the measurement results of average cell diameter, electrical resistance and hardness (JIS A), cell uniformity, uniformity of electrical resistance, development characteristics and storage properties were confirmed. The results are as shown in Table 1.

  Here, the uniformity of the cell was judged as good or bad by the electric resistance unevenness and the printed image. The uniformity of the electrical resistance was judged by the printed image. The development characteristics were evaluated by charging characteristics and evaluation of printed images. The storage quality was judged by the contamination on the OPC surface after storage.

  As a result, in Examples 1 to 4, the uniformity of the cell, the uniformity of the electrical resistance, the development characteristics and the storage property were all good, but in the comparative example 1, the uniformity of the cell and the uniformity of the electrical resistance. The development characteristics and storage properties were all poor, and Comparative Examples 2 and 3 had good cell uniformity and electrical resistance uniformity, but poor development characteristics and storage properties.

It is sectional drawing of the developing roller which concerns on embodiment of this invention. It is a conceptual diagram of the developing device in which the developing roller is incorporated.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive shaft body 2 Elastic semiconductor 3 Toner carrying layer (surface resistance adjustment layer)
10 Photosensitive drum (latent image carrier)
12 Developing roller 31 Friction charging blade (layer forming member)
G Developer

Claims (4)

A semiconductive roller comprising a conductive shaft, an elastic semiconductor formed on the outer periphery of the conductive shaft, and a surface resistance adjusting layer formed on the surface of the elastic semiconductor, The elastic semi-conductor has a hardness of 15 to 70 (JIS A), and an electric resistance between the conductive shaft and the surface resistance adjusting layer is 1 × 10 ⁴ to 10 ⁹ Ω, and the surface resistance adjusting layer A semiconductive roller characterized in that the outer surface has a surface roughness (Rz) of 2 to 10 μm and at least an average cell diameter of the elastic semiconductor is 40 μm or less. When mixing an unvulcanized liquid rubber containing a vulcanizing agent and a vulcanization accelerator, a process of simultaneously mixing and dissolving the supercritical fluid at a high speed and a mold for the mixed liquid rubber containing the supercritical fluid A process for producing a semiconductive roller, comprising: a step of casting a molded supercritical fluid; a step of partially opening and foaming the cast supercritical fluid; and a step of crosslinking the foamed rubber. 2. A latent image holding member capable of holding an electrostatic latent image on the surface thereof after the frictionally charged toner is supported on the surface of the semiconductive roller according to claim 1 to form a thin film of the frictionally charged toner. A developing device characterized in that an electrostatic latent image is formed by bringing the frictionally charged toner from the thin film of the frictionally charged toner into contact with the surface of the latent image holding member to form an electrostatic latent image, and visualizing the electrostatic latent image . A developing device comprising the semiconductive roller manufactured by the method of manufacturing a semiconductive roller according to claim 2.

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