JP2012226118A - Method for manufacturing electrophotographic roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrophotographic roller where a conductive elastic layer has low surface electric resistance and accelerates the decay of electric charge though being formed by applying a liquid silicone rubber material containing uncured liquid silicone rubber and conductive particles, around a shaft core body.SOLUTION: The method for manufacturing an electrophotographic roller including a shaft core body and a conductive elastic layer covering the peripheral surface of the shaft core body includes a step (1) of applying liquid silicone rubber containing conductive particles around the periphery of the shaft core body to form a coating layer and a step (2) of hardening the coating layer to form the elastic layer. Further, the method includes a step of electrifying the surface of the coating layer to bring about polarization in the conductive particles in the coating layer due to electrostatic induction, in a period from the end of the step (1) or from during the step (1) to the end of the step (2).

Description

  The present invention relates to an electrophotographic image forming apparatus such as a printer and a copying machine, and a method for manufacturing an electrophotographic roller used in an electrophotographic process cartridge.

  In the contact developing type electrophotographic image forming apparatus, for example, the developing roller has a high dimensional accuracy, so that the contact state with the photosensitive member is stably maintained, the toner development amount and the pressure distribution on the photosensitive member become uniform, The occurrence of uneven image density is prevented. Further, since the charging roller for bringing the photosensitive member into uniform contact with the photosensitive member needs to be charged uniformly, high dimensional accuracy is also required.

  Patent Document 1 discloses a method for manufacturing a high-precision electrophotographic roller using an annular coating head.

JP 2007-130589 A

  The present inventors have studied the method for producing the electrophotographic roller of Patent Document 1 and have found the following problems. Curing the coating layer obtained by applying a mixture of uncured liquid silicone rubber and conductive particles (hereinafter also referred to as “liquid silicone rubber material”) to the shaft core by the production method of Patent Document 1, A conductive elastic layer is formed. At this time, since the surface tension of the polysiloxane unit contained in the liquid silicone rubber material is small, the polysiloxane unit moves to the surface of the coating layer. As a result, the conductive particles contained in the liquid silicone rubber material are pushed away from the surface of the coating layer. When the coating layer is cured in this state, the ratio of the conductive particles present on the surface of the conductive elastic layer is decreased, and the electric resistance of the entire surface of the electrophotographic roller may be increased. If this electrophotographic roller is used as a contact developing type developing roller and printing durability is repeated in a low temperature and low humidity environment, electric charges accumulate on the developing roller and the surface potential of the developing roller fluctuates. In some cases, image defects such as fogging (a phenomenon in which a background portion that should originally become white) is developed are caused.

  Therefore, the object of the present invention is to form a conductive elastic layer by applying a liquid silicone rubber material around the shaft core body, so that the electrical resistance of the surface of the elastic layer is low and the charge decay is fast. The object is to provide a method for producing an electrophotographic roller.

  That is, according to one aspect of the present invention, there is provided a method for manufacturing an electrophotographic roller having a shaft core and a conductive elastic layer covering the peripheral surface thereof, and (1) a liquid containing conductive particles. A step of forming a coating layer by applying silicone rubber around the shaft core, and (2) a step of curing the coating layer to form the elastic layer, and after the step (1) is completed, Alternatively, the step of charging the surface of the coating layer between the step (1) and the end of the step (2) to cause the conductive particles in the coating layer to undergo polarization due to electrostatic induction. A method for producing an electrophotographic roller is provided.

  According to the present invention, even when a liquid silicone rubber material is applied around the shaft core to form a conductive elastic layer, the surface of the elastic layer has a low electrical resistance and a fast charge decay. Roller can be manufactured.

It is sectional drawing which shows the roller for electrophotography which concerns on this invention. It is a schematic diagram which shows the example of the coating apparatus which can be used for this invention. 1 is a schematic cross-sectional view for explaining an example of an electrophotographic process cartridge and an electrophotographic image forming apparatus according to the present invention. It is a schematic diagram which shows the example of the means to harden | cure the coating layer which can be used for this invention, and the example of a means to provide an electric charge to a coating layer.

The present invention will be described in detail below with reference to preferred embodiments.
FIG. 2 shows a schematic diagram of an electrophotographic roller manufacturing apparatus having an annular coating head (hereinafter also referred to as “ring coat machine”) that can be suitably used in the electrophotographic roller manufacturing method of the present invention. .

  In this ring coat machine, a column 5 is attached substantially vertically on a gantry 4, and a precision ball screw 6 is attached substantially vertically on the gantry 4 and the column 5. One precision ball screw 6 and two guides 7 are connected, and the two guides 7 are attached to the column 5 so as to be parallel to the column 5. The stage 8 connects the guide 7 and the precision ball screw 6, and the rotational motion is transmitted from the servo motor 9 via the pulley 10 so that the stage 8 can be moved up and down. A table 18 is attached to the column 5, and an annular coating head 11 is attached to the table 18.

  A pair of upper and lower brackets 12 are attached to the stage 8. A shaft core lower holding shaft 13 for holding and fixing the lower end portion of the shaft core body 1 is attached to the lower bracket 12 substantially vertically. The upper bracket 12 is attached with a shaft core holding shaft 14 for holding the upper end portion of the shaft core 1. The shaft core upper holding shaft 14 is disposed so as to face the shaft core lower holding shaft 13 so as to be substantially concentric with the center of the annular coating head 11, and holds the shaft core 1.

  A supply port 15 for supplying the liquid silicone rubber material into the annular coating head 11 is connected to a material supply valve 17 via a pipe 16. The material supply valve 17 is connected to a material supply pump (not shown). The material supply pump includes a mixing mixer, a material fixed amount discharge device, a material tank, and the like, and can discharge a fixed amount (a constant amount per unit time) of the liquid silicone rubber material. A certain amount of the liquid silicone rubber material is weighed from the material tank by a material dispensing device and mixed by a mixing mixer. Thereafter, the mixed liquid silicone material is sent from the material supply valve 17 to the supply port 15 via the pipe 16 by the material supply pump.

  The liquid silicone rubber material supplied from the supply port 15 passes through the flow path in the annular coating head 11 and is discharged from the discharge port of the annular coating head 11. At this time, in order to make the amount of the liquid silicone rubber material applied around the shaft core 1 constant, the discharge amount from the annular coating head 11 and the supply amount from the material supply pump are adjusted. A layer in which the liquid silicone rubber material is applied to the peripheral surface of the shaft core body 1 (hereinafter also referred to as “coating layer”) by moving the shaft body 1 vertically upward in accordance with the discharge of the liquid silicone rubber material. Cover and form. The coating layer is heated and cured to obtain a conductive elastic layer 2 to obtain an electrophotographic roller. In order to cure while maintaining the shape of the coating layer, a method of heating and curing the coating layer in a non-contact manner is preferable.

  Specific methods include infrared heating, hot air heating, and nichrome heat heating. Among these, infrared heating is particularly preferable because the apparatus is simple and the coating layer can be heated uniformly in the longitudinal direction of the shaft core 1. When performing the infrared heating, the infrared heating device 42 is fixed as shown in FIG. 4, and the shaft core 1 is rotated with the shaft core 1 having the coating layer in the gravitational direction (vertical). As the shaft core body 1 is rotated (rotated) in the circumferential direction, the coating layer is irradiated with infrared rays and heated. Then, the coating layer can be heated uniformly in the circumferential direction of the shaft core body 1.

  The heating temperature at this time is preferably 100 ° C. or higher at which the curing reaction of the liquid silicone rubber material starts and 250 ° C. or lower which is the heat resistant temperature of the liquid silicone rubber material. When heating with infrared rays, the distance between the infrared heating device and the coating layer, the output of the infrared heating means (infrared heater), etc. may be adjusted in order to uniformly heat the coating layer. In order to uniformly heat the coating layer with hot air, the temperature and direction of the hot air, the wind speed, etc. may be adjusted.

  Here, after the coating layer is cured, in order to improve the stability of the rubber physical properties of the conductive elastic layer 2 and to remove reaction residues and unreacted low molecules of the liquid silicone rubber material present in the elastic layer, The elastic layer 2 may be heated again (secondary curing).

Next, FIG. 4 shows a schematic diagram of a method for applying a charge 41 to the surface of the coating layer and charging the coating layer. The method for producing an electrophotographic roller of the present invention comprises the entire surface of the coating layer at an arbitrary timing after the coating layer is formed on the outer periphery of the shaft core 1 until the curing of the coating layer is completed. The most characteristic feature is that it has a step of charging the coating layer by applying a charge 41 to the coating layer. Specifically, after the step of applying liquid silicone rubber around the shaft core to form the coating layer, or during the coating layer formation, the step of curing the coating layer to form the elastic layer is completed. The process includes a step of charging the surface of the coating layer at an arbitrary timing until and causing polarization by electrostatic induction in the conductive particles contained in the coating layer. In particular, if the coating layer is charged at least before starting the curing reaction of the coating layer, the effect of the present invention is greatly preferred.
Furthermore, in order to maximize the effects of the present invention, it is preferable to continuously apply the charge 41 to the coating layer, but the application of the charge may be intermittent.

  In order to cure the liquid silicone rubber material while maintaining the shape of the coating layer, a method in which a member for charging the coating layer is not brought into contact with the coating layer is preferable. Specific methods include discharge methods such as corona discharge, arc discharge, glow discharge, and spark discharge. Among these, the coating layer charging device 39 using corona discharge can be suitably used because it can be obtained relatively easily. The charge 41 generated by the coating layer charging device 39 is released from the charge supply port 40 to the coating layer.

  In order to uniformly charge the entire surface of the coating layer, the coating layer may be charged while rotating (spinning) the shaft core body 1 in the circumferential direction about the shaft core body 1 as a rotation axis. Alternatively, a large number of coating layer charging devices 39 may be installed around the coating layer.

  The distance between the coating layer charging device 39 and the coating layer is adjusted by appropriately selecting the coating layer charging device 39 according to the environmental resistance (usable temperature, usable humidity, etc.) of the coating layer charging device 39. It ’s fine. When the distance between the coating layer charging device 39 and the coating layer is long, the charge 41 generated by the coating layer charging device 39 is applied to the entire surface of the coating layer by a blowing means (not shown) such as a blower and charged. Also good. At this time, it is necessary to appropriately adjust the wind direction, the wind speed, and the wind pressure of the blowing unit so that the shape of the coating layer is not deformed by the wind of the blowing unit. When a coating layer charging device incorporating a blower is used, the coating layer can be easily charged. Further, the surface potential of the coating layer may be adjusted by adjusting the ion balance adjusting function (charging amount adjusting function) of the coating layer charging device 39 to change the ion generation amount.

  If the coating layer is charged without electrically grounding the shaft core body 1 (without grounding), there is no escape field for the charge 41 applied to the coating layer, so that the charge 41 remains on the surface of the coating layer. The electric charge 41 staying on the surface of the coating layer polarizes the conductive particles existing near the surface in the coating layer by electrostatic induction. As a result, the charge 41 applied to the surface of the coating layer and the polarized conductive particles in the coating layer are strongly attracted by the Coulomb force, and the conductive particles are restrained near the surface of the coating layer. . For this reason, even if the polysiloxane unit contained in the coating layer moves to the surface of the coating layer, the conductive particles in the coating layer are not pushed away from the surface of the coating layer. By curing the coating layer while maintaining this state to obtain the conductive elastic layer 2, an electrophotographic roller having a low electrical resistance on the surface of the elastic layer 2 and a fast charge decay can be obtained. The charging of the coating layer is preferably set so that the surface potential of the coating layer is not less than 300V and not more than 1000V. When the surface potential of the coating layer is charged to be 300 V or more, the charge 41 applied to the surface of the coating layer and the conductive particles are more strongly attracted by the Coulomb force, so that the effect of the present invention can be obtained more reliably. be able to. On the other hand, if charging is performed so that the surface potential of the coating layer is 1000 V or less, generation of a micro discharge between the charge 41 applied to the surface of the coating layer and the conductive particles can be suppressed. It can suppress that the Coulomb force with particle | grains reduces. For this reason, the effect of this invention can be drawn out to the maximum.

FIG. 1 is a cross-sectional view showing an electrophotographic roller according to the present invention. The electrophotographic roller has an elastic layer 2 that covers the peripheral surface of the shaft core 1.
The thickness of the conductive elastic layer 2 of the electrophotographic roller is preferably in the range of 0.5 mm to 10.0 mm. More preferably, it is 1.0 mm or more and 6.0 mm or less. When the thickness of the elastic layer 2 is 0.5 mm or more, preferably 1.0 mm or more, the elastic characteristics of the elastic layer 2 can be exhibited well, and stress on the toner can be reduced. Further, when the thickness is 10.0 mm or less, preferably 6.0 mm or less, there is no change in the shape of the coating layer due to its own weight, and an excellent outer diameter and deflection can be realized.

  The elastic layer 2 may be a single layer or a multilayer. When forming a multilayer, it is also possible to form a new elastic layer on the already formed elastic layer 2.

The shaft body 1 of the electrophotographic roller according to the present invention is a solid or hollow cylindrical shape, and is made of a conductive material, for example, a metal such as carbon steel, alloy steel, cast iron, and a resin such as a conductive resin. It can be appropriately selected from among them.
Examples of the alloy steel include stainless steel, nickel chromium steel, nickel chromium molybdenum steel, chromium steel, chromium molybdenum steel, steel for nitriding added with Al, Cr, Mo and V.
The shaft core 1 is preferably made of metal from the viewpoint of strength. Furthermore, the shaft core body 1 can be plated and oxidized as a rust prevention measure. As the type of plating, both electroplating and electroless plating can be used.

  The liquid silicone rubber contained in the liquid silicone rubber material uses addition-type liquid silicone rubber because it has good processability, high dimensional stability, and no reaction by-products are generated during the curing reaction.

  The addition-type liquid silicone rubber is cured by addition reaction (crosslinking) of a polysiloxane containing an alkenyl group and a hydrogen polysiloxane containing a hydrosilyl group in the presence of a platinum catalyst.

The molecular weight of the polysiloxane containing an alkenyl group is preferably 10,000 or more and 500,000 or less. It is desirable that at least two alkenyl groups of polysiloxane are present in one molecule of polysiloxane. Although the kind of alkenyl group is not particularly limited, it is preferably at least one of a vinyl group or an allyl group highly reactive with active hydrogen, and a vinyl group is particularly preferable.
The molecular weight of polysiloxane is a weight average molecular weight when measured by gel permeation chromatography (GPC) (trade name: HLC-8220, manufactured by Tosoh Corporation). The measurement by GPC was performed as follows. Toluene was allowed to flow as a solvent at a flow rate of 0.5 ml / min through a column (trade name: KF-801-807, manufactured by shodex) stabilized in a 40 ° C. heat chamber. 50 μl to 200 μl of a sample solution adjusted to 3% by mass was injected. And the weight average molecular weight of the sample was computed from the calibration curve created with several types of monodisperse polystyrene standard samples.

  Hydrogen polysiloxanes containing hydrosilyl groups act as crosslinkers for polysiloxanes containing alkenyl groups. The number of hydrogen atoms bonded to silicon atoms in one molecule is two or more, and the number of hydrogen atoms bonded to silicon atoms in one molecule is three or more in order to perform the curing reaction optimally. It is preferable. The molecular weight of the hydrogen polysiloxane is preferably 1000 or more and 10,000 or less, and particularly preferably 1000 or more and 5000 or less in order to appropriately perform the curing reaction.

  In the present invention, the composition of the liquid silicone rubber is such that the number of hydrosilyl groups contained in the hydrogen polysiloxane is 1.0 to 3.0 times the number of alkenyl groups contained in the polysiloxane. Is preferred. When the number of hydrosilyl groups is 1.0 times or more, the liquid silicone rubber is well crosslinked and the compression set of the conductive elastic layer 2 can be reduced. Further, when the number of hydrosilyl groups is 3.0 or less, chemically unstable hydrosilyl groups are less likely to remain in the elastic layer 2, so that changes over time in the hardness and current value of the elastic layer 2 can be reduced.

A platinum catalyst can be used as a catalyst for the addition-type liquid silicone rubber. Specific examples include chloroplatinic acid, platinum olefin complexes, platinum vinylsiloxane complexes, and platinum triphenylphosphine complexes.
The blending amount of the catalyst is preferably 1 ppm or more and 1000 ppm or less as the platinum element amount with respect to the total mass of the polysiloxane having an alkenyl group and the hydrogen polysiloxane.

  The viscosity of the addition type liquid silicone rubber is preferably 10 Pa · s or more and 5000 Pa · s or less. When the viscosity is 10 Pa · s or more, since the polysiloxane unit is difficult to move, the action of pushing the conductive particles away from the surface of the coating layer is reduced, so that the effect of the present invention can be obtained more reliably. On the other hand, when the viscosity is 5000 Pa · s or less, the surface of the coating layer can be prevented from being rough due to a large shear stress.

A rheometer (trade name: Rheo Stress 600, manufactured by Haake) was used for viscosity measurement. Measurement with a rheometer was carried out as follows. 1 g of additional type liquid silicone rubber was sampled and placed on a sample table, and a cone plate (diameter 35 mm, inclination angle 1 °) was gradually approached to set a measurement gap at a position of 50 μm from the sample table. At this time, the sample pushed out around the cone plate was removed so as not to affect the measurement. After setting the temperature of the sample stage so that the sample temperature was 25 ° C., the sample was left for 10 minutes, and then the measurement was started. The shear stress was measured by applying a shear rate of 1 s ^-1 to the sample. The value obtained by dividing the shear stress by the shear rate of 1 s ⁻¹ was taken as the viscosity.

In order to adjust the electrical resistance value according to the use of the electrophotographic roller, it is necessary to mix conductive particles as a conductive agent with the liquid silicone rubber. Examples of the conductive particles include carbon black, graphite, aluminum, palladium, silver, iron, copper, tin, stainless steel, tin oxide, conductive zinc oxide (for example, zinc oxide doped with aluminum), conductive indium oxide ( For example, conductive titanium oxide doped with boron or lithium, etc.), antimony oxide, molybdenum oxide, tin oxide-antimony oxide solid solution, tin oxide-indium oxide solid solution, and a fine material composed of a substance obtained by coating an insulating substance with a conductive material. A conductive material such as powder can be used. In addition to the conductive particles, a perchlorate such as LiClO ₄ or NaClO ₄ or a quaternary ammonium salt can be used as an ionic conductive agent. Among these, carbon black can be suitably used because it is relatively easily available. The blending amount of the conductive particles is preferably 3 parts by mass or more and 16 parts by mass or less with respect to the liquid silicone rubber (polysiloxane containing an alkenyl group and polysiloxane containing a hydrosilyl group). When the blending amount of the conductive particles is 3 parts by mass or more, an electrophotographic roller having a lower electrical resistance on the surface of the conductive elastic layer 2 and faster charge decay can be obtained. On the other hand, when the blending amount of the conductive particles is 16 parts by mass or less, it is possible to prevent a phenomenon in which the charge 41 applied to the coating layer sinks into the coating layer through the aggregate of conductive particles. For this reason, the effect of this invention can be drawn out to the maximum, without reducing the force by which electroconductive particle is restrained by the surface of an application layer.

Moreover, a non-conductive filler can be suitably mix | blended with the liquid silicone rubber material containing electroconductive particle.
Non-conductive fillers include diatomaceous earth, quartz powder, dry silica, wet silica, titanium oxide, zinc oxide, aluminosilicate, calcium carbonate, zirconium silicate, aluminum silicate, talc, alumina, and iron oxide.

  In order to improve the abrasion resistance of the electrophotographic roller of the present invention, the surface layer 3 may be formed on the outer periphery of the conductive elastic layer 2. The surface layer 3 may be a single layer or a multilayer.

  For the surface layer 3, polyamide resin, fluorine resin, hydrogenated styrene-butylene resin, urethane resin, silicone resin, polyester resin, phenol resin, imide resin, or olefin resin can be used.

  In the surface layer 3, resin particles having a volume average particle diameter of 1 μm to 20 μm can be dispersed according to the application. Examples of such resin particles include polymethyl methyl methacrylate fine particles, silicone rubber fine particles, polyurethane fine particles, polystyrene fine particles, amino resin fine particles, and phenol resin fine particles.

In order to adjust the electric resistance of the electrophotographic roller, the surface layer 3 can be blended with the same conductive agent as that contained in the elastic layer 2.
By preparing a coating material for the surface layer 3 using a conventionally known dispersing device using beads such as a sand mill, a paint shaker, a dyno mill, and a ball mill, and spray coating or dipping the coating material on the elastic layer 2 The surface layer 3 can be formed.

  An example of a schematic cross-sectional view of an electrophotographic process cartridge and an electrophotographic image forming apparatus in which the electrophotographic roller of the present invention is mounted as the developing roller 27 is shown in FIG.

  The developing roller 27 develops the toner 25 in a state of being in contact with the photosensitive member 19 as a latent image carrier. The developing roller 27 visualizes the latent image as a toner image by applying the toner 25 to the photoconductor 19.

  In the image forming apparatus shown in FIG. 3, each one of the electrophotographic process cartridges 38 for forming yellow, cyan, magenta, and black images is provided in a tandem system. In addition, the photosensitive member 19, the charging roller 20, the developing device 22, and the cleaning device 23 are integrated to form an electrophotographic process cartridge.

  The developing device 22 includes a developing container 26 containing toner 25 and a developing roller 27 installed so as to face the photoconductor 19, and develops and visualizes the electrostatic latent image on the photoconductor 19. Further, the developing device 22 is provided with a toner application roller 28 having a function of supplying the toner 25 to the developing roller 27 and a function of scraping off the toner 25 remaining on the developing roller 27 without being developed. . Further, the developing device 22 is provided with a toner regulating member 29 having a function of frictionally charging the toner 25 on the developing roller 27 and a function of regulating the amount of the toner 25 supported on the developing roller 27.

  The surface of the photoreceptor 19 is uniformly charged to a predetermined polarity and potential by the charging roller 20, and image information is irradiated as a beam from the image exposure device 21 to form the electrostatic latent image. . Next, toner 25 is supplied from the developing device 22 to the electrostatic latent image, and the toner image is developed on the surface of the photoreceptor 19.

  In the image transfer section 24, the transfer conveyance belt 31 is stretched by a driving roller 32, a tension roller 33 and a driven roller 34, and a transfer roller 36 is installed inside the transfer conveyance belt 31 at a position facing the photoconductor 19. Yes. Then, by applying a bias to the electrostatic adsorption roller 35, the transfer material 30 is electrostatically adsorbed to the outer peripheral surface of the transfer conveyance belt 31, and the transfer material 30 is conveyed. When the transfer material 30 is conveyed to the transfer position, a bias having a polarity opposite to that of the toner image on the surface of the photoreceptor 19 is applied to the transfer roller 36. As a result, the toner image is transferred to the transfer material 30. The transfer material 30 onto which the toner image has been transferred is sent from the transfer conveyance belt 31 to the fixing device 37, where the toner image is fixed on the transfer material 30 and printing is completed.

  The electrophotographic roller of the present invention is not only used as the developing roller 27 described above, but also because the conductive elastic layer 2 has good chargeability, the charging roller 20, the transfer roller 36, the driving roller 32, the electrostatic roller It can also be used for a roller member such as the suction roller 35.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Example of production of roller for electrophotography>
[Production Example 1]
Nickel plating was applied to a round bar (free cutting steel SUM24L) with an outer diameter of 6 mm, and a primer (trade name: DY39-051, manufactured by Toray Dow Corning Co., Ltd.) was applied to a dry thickness of 1 μm, and then a temperature of 150 ° C. What was baked for 30 minutes was used as the shaft core.
Then, base material A1 which mix | blended the following (1-1), (1-2), (1-3) was prepared.

(1-1) Dimethylpolysiloxane substituted with vinyl groups at both ends (weight average molecular weight 34000): 100 parts by mass
(1-2) Carbon black (trade name: Raven 890, manufactured by Columbian Chemical): 10 parts by mass
(1-3) divinyltetramethyldisiloxane containing 3% by mass of chloroplatinic acid: 1 part by mass

  Moreover, base material B1 which mix | blended said (1-1), (1-2) and the following (1-4) was prepared.

  (1-4) Methyl hydrogen polysiloxane: 3 parts by mass (with respect to 1 mol of vinyl group contained in the above dimethyl polysiloxane substituted with a vinyl group, 1.2 mol of hydrosilyl group contained in methyl hydrogen polysiloxane) (Mole)

  Next, the base material A1 and the base material B1 were mixed at a mass ratio of 1: 1 to obtain a liquid silicone rubber material having a viscosity of 545 Pa · s.

  The liquid silicone rubber material was filled in a material tank (not shown) connected to the ring coater shown in FIG. Then, both ends of the shaft core were held by the shaft core upper holding shaft and the shaft core lower holding shaft, and the shaft core was moved vertically upward at a speed of 60 mm / s. In accordance with the movement of the shaft core body, the above liquid silicone rubber material was discharged at 5.0 ml / s, and a coating layer was formed around the shaft core body.

Immediately after the application of the liquid silicone rubber material is completed, the shaft core body having the coating layer around it is removed from the shaft core holding shaft and the shaft core lower holding shaft so that the orientation of the shaft core body matches the direction of gravity. The shaft core was rotated at 60 rpm.
And while irradiating the surface of the coating layer with an infrared lamp (trade name: HYL25, manufactured by Highbeck Co., Ltd., output 1000 W) for 4 minutes, a corona discharge type coating layer charging device (trade name: trade name: The coating layer was charged using SJ-R036 (manufactured by Keyence Corporation). At this time, 0.2 MPa of compressed air was supplied to the coating layer charging device, and air blowing to the coating layer and the above charging were performed simultaneously. In addition, as a result of measuring the surface potential of the coating layer 0.5 seconds after the end of heating with a surface potential meter (trade name: SK-035 / 200, manufactured by Keyence Corporation), it was 1000 V.
The distance between the surface of the coating layer and the surface of the infrared lamp was 60 mm, and the surface temperature of the coating layer immediately after the heating was 200 ° C.

  Thereafter, the cured coating layer was heated (secondary curing) in an electric furnace at 200 ° C. for 4 hours. In this way, a conductive elastic layer having a thickness of 3.0 mm was obtained on the peripheral surface of the shaft core body. A surface layer was provided on the elastic layer using a paint having the following composition. The coating composition for the surface layer is shown below.

Polyol (trade name: Takelac TE5060, manufactured by Mitsui Takeda Chemical Co.): 100 parts by mass
・ Isocyanate (trade name: Coronate 2521, manufactured by Nippon Polyurethane): 77 parts by mass
Carbon black (trade name: MA100, manufactured by Mitsubishi Chemical Corporation): 24 parts by mass
・ Methyl ethyl ketone (MEK): 180 parts by mass
Resin particles (trade name: Art Pearl C400, manufactured by Negami Kogyo Co., Ltd.): 20 parts by mass

These were dispersed with a horizontal disperser (trade name: NVM-03, manufactured by IMEX) for 1 hour under conditions of a peripheral speed of 7 m / s, a flow rate of 1 cc / min, and a dispersion temperature of 15 ° C.
After dispersion, MEK was further added to adjust the solid content to 25% by mass as a coating material for forming the surface layer.
The elastic layer was immersed in this paint and air dried for 10 minutes. Next, an electrophotographic roller A1 was obtained by heat treatment at a temperature of 140 ° C. for 1 hour.

[Production Example 2]
The following base material A2 and base material B2 were used for the liquid silicone rubber material.
A base material A2 containing the following (2-1), (2-2), and (2-3) was prepared.

(2-1) Dimethylpolysiloxane substituted with vinyl groups at both ends (weight average molecular weight 34000): 100 parts by mass
(2-2) Carbon black (trade name: Raven 890, manufactured by Columbian Chemical): 3 parts by mass
(2-3) divinyltetramethyldisiloxane containing 3% by mass of chloroplatinic acid: 1 part by mass

  Moreover, base material B2 which mix | blended said (2-1), (2-2) and the following (2-4) was prepared.

  (2-4) Methyl hydrogen polysiloxane: 3 parts by mass (with respect to 1 mol of vinyl group contained in the dimethyl polysiloxane substituted with the vinyl group, the hydrosilyl group contained in methyl hydrogen polysiloxane is 1.2. (Mole)

  Next, the base material A2 and the base material B2 were mixed at a mass ratio of 1: 1 to obtain a liquid silicone rubber material having a viscosity of 10 Pa · s, thereby forming a conductive elastic layer. At this time, the ion balance adjustment function (charge amount adjustment function) of the coating layer charging device was adjusted so that the surface potential of the coating layer was 1000 V, and the amount of generated ions was changed, as in Production Example 1. An electrophotographic roller A2 was produced.

[Production Example 3]
The following base material A3 and base material B3 were used for the liquid silicone rubber material.
A base material A3 containing the following (3-1), (3-2), and (3-3) was prepared.

(3-1) Dimethylpolysiloxane substituted with vinyl groups at both ends (weight average molecular weight 34000): 100 parts by mass
-(3-2) Carbon black (trade name: Raven 890, manufactured by Columbian Chemical): 16 parts by mass
(3-3) Divinyltetramethyldisiloxane containing 3% by mass of chloroplatinic acid: 1 part by mass

  Moreover, base material B3 which mix | blended said (3-1), (3-2) and the following (3-4) was prepared.

  (3-4) Methyl hydrogen polysiloxane: 3 parts by mass (1 mol of vinyl group contained in the dimethyl polysiloxane substituted with the vinyl group is 1.2 mol of hydrosilyl group contained in methyl hydrogen polysiloxane) (Mole)

  Next, the base material A3 and the base material B3 were mixed at a mass ratio of 1: 1 to obtain a liquid silicone rubber material having a viscosity of 5000 Pa · s, thereby forming a conductive elastic layer. At this time, the ion generation amount was adjusted by adjusting the ion balance adjusting function (charge amount adjusting function) of the coating layer charging device so that the surface potential of the coating layer was 300 V, and the coating layer was charged. An electrophotographic roller A3 was produced in the same manner as in Production Example 1 except that the charge amount of the coating layer was changed.

[Production Example 4]
Similar to Production Example 3, Production Example 2 except that the charge balance was changed by adjusting the ion balance adjustment function (charge amount adjustment function) of the coating layer charging device so that the surface potential of the coating layer was 300V. In the same manner as described above, an electrophotographic roller A4 was produced.

[Production Example 5]
Similar to Production Example 1, Production Example 3 except that the charge amount was changed by adjusting the ion balance adjustment function (charge amount adjustment function) of the coating layer charging device so that the surface potential of the coating layer was 1000V. An electrophotographic roller A5 was produced in the same manner as described above.

[Production Example 6]
Immediately after the liquid silicone rubber material of Production Example 1 was discharged at 5.0 ml / s and the coating layer was formed on the outer periphery of the shaft core, infrared rays were applied to the surface of the coating layer. The lamp was irradiated for 4 minutes. Otherwise, the electrophotographic roller A6 was produced in the same manner as in Production Example 1. At this time, the ion balance adjustment function (charge amount adjustment function) of the coating layer charging device was adjusted so that the surface potential of the coating layer was 1000 V, thereby changing the charge amount.

[Production Example 7]
An electrophotographic roller as in Production Example 6 except that the charge balance is changed by adjusting the ion balance adjustment function (charge amount adjustment function) of the coating layer charging device so that the surface potential of the coating layer is 300V. A7 was produced.

[Production Example 8]
The ion generation amount was adjusted by adjusting the ion balance adjustment function (charge amount adjustment function) of the coating layer charging device so that the surface potential of the coating layer was 200 V, and the coating layer was charged. An electrophotographic roller A8 was produced in the same manner as in Production Example 1 except that the charge amount of the coating layer was changed.

[Production Example 9]
The ion generation amount was adjusted by adjusting the ion balance adjustment function (charge amount adjustment function) of the coating layer charging device so that the surface potential of the coating layer was 1100 V, and the coating layer was charged. An electrophotographic roller A9 was produced in the same manner as in Production Example 1 except that the charge amount of the coating layer was changed.

[Production Example 10]
An electrophotographic roller B1 was produced in the same manner as in Production Example 1 except that the coating layer charging device was not used.

[Production Example 11]
An electrophotographic roller B2 was produced in the same manner as in Production Example 2 except that the coating layer charging device was not used.

[Production Example 12]
An electrophotographic roller B3 was produced in the same manner as in Production Example 3 except that the coating layer charging device was not used.

[Example 1]
The charge decay rate of the electrophotographic roller A1 produced in Production Example 1 was measured using the following method. Further, image evaluation was performed using the electrophotographic roller A1 of Production Example 1 as a developing roller. The image evaluation method is described below.

(Measurement method of charge decay rate)
A surface electrometer (trade name: DRA-2000L, manufactured by QEA) was used to measure the charge decay rate. The shaft body of the electrophotographic roller A1 was held at both ends, and the surface of the central portion in the longitudinal direction of the electrophotographic roller A1 was subjected to corona discharge. The surface potential (V ₁ ) 0.06 seconds after the start of discharge and the surface potential (V ₂ ) after 0.25 seconds were measured. Then, a ratio of _{V 1} and _{V 2 (V 2 / V 1} ), which was used as a charge decay rate. This charge decay rate was evaluated according to the following evaluation criteria.

A: The charge decay rate is less than 50.0%.
B: The charge decay rate is 50.0% or more and less than 70.0%.
C: The charge decay rate is 70.0% or more.

(Image evaluation method)
The electrophotographic roller A1 was incorporated into an electrophotographic process cartridge (trade name: toner cartridge 316 magenta, manufactured by Canon Inc.) as a developing roller. The electrophotographic process cartridge was allowed to stand for 24 hours in an environment of room temperature of 15 ° C. and humidity of 10%.
This electrophotographic process cartridge was incorporated into an electrophotographic image forming apparatus (trade name: LBP5050, manufactured by Canon Inc.). Then, using this electrophotographic image forming apparatus, a durability test was performed in an environment of room temperature of 15 ° C. and humidity of 10%. At the time of paper passing, a character image with a printing rate of 1% was output on genuine A4 paper (trade name: Select Paper SC-250, manufactured by Canon Inc.) every 20 seconds, and 2300 images were output. Thereafter, the developing roller was removed. Next, the removed developing roller was assembled in a new electrophotographic process cartridge of the same type, and 2300 images were output in the same manner. Such a durability test was repeated three times in total, and a total of 6,900 images were output to one developing roller.

  After the endurance test, all white images were output on genuine A4 paper. First, before outputting an all white image, the reflection density meter (trade name: TC-6DS / A, manufactured by Tokyo Denshoku Co., Ltd.) was used to measure the reflection density at any 10 points on the surface of genuine A4 paper. The arithmetic average value was defined as Dr. Similarly, after the output of the all-white image, the reflection density of the white background portion of the output all-white image was measured at arbitrary 10 points on the image, and the arithmetic average value was defined as Ds. And the difference (Dr-Ds) / 100 of Dr and Ds was calculated | required, and this was made into the fogging amount. This fogging amount was evaluated according to the following evaluation criteria.

A: The fogging amount is less than 1.0%.
B: The fogging amount is 1.0% or more and less than 3.0%.
C: The fogging amount is 3.0% or more.

  Table 1 shows the charge decay rate measured in Example 1 and the results of image evaluation. From the results of Table 1, it was confirmed that by having the step of charging the coating layer, an electrophotographic roller having a low surface electrical resistance and a fast charge decay was obtained, and as a result, the fog was improved. .

[Examples 2 to 9]
The charge decay rates of the electrophotographic rollers A2 to A9 produced in Production Examples 2 to 9 were measured in the same manner as in Example 1, and the results are shown in Table 1. Further, image evaluation was performed in the same manner as in Example 1 using the electrophotographic rollers A2 to A9 of Production Examples 2 to 9 as developing rollers. Table 1 shows the image evaluation results of Examples 2 to 9. In Examples 2 to 9, as in Example 1, it was confirmed that by including the step of charging the coating layer, an electrophotographic roller with fast charge decay was obtained, and the fog was improved.

[Comparative Examples 1-3]
The charge decay rates of the electrophotographic rollers B1 to B3 produced in Production Examples 10 to 12 were measured in the same manner as in Example 1, and the results are shown in Table 1. Further, image evaluation was performed in the same manner as in Example 1 using the electrophotographic rollers B1 to B3 of Production Examples 10 to 12 as developing rollers. Table 1 shows the image evaluation results of Comparative Examples 1 to 3. About Comparative Examples 1-3, since it did not have the process of charging an application layer, the roller for electrophotography in which attenuation | damping of electric charge was quick was not obtained, and it was not able to confirm improvement in fog.

DESCRIPTION OF SYMBOLS 1 Shaft core 2 Elastic layer 39 Application layer charging device 40 Charge supply port 41 Charge 42 Infrared heating device

Claims (1)

A method for producing an electrophotographic roller having a shaft core and a conductive elastic layer covering its peripheral surface,
(1) A step of applying a liquid silicone rubber containing conductive particles around the shaft core body to form a coating layer;
(2) curing the coating layer to form the elastic layer,
After the completion of the step (1) or during the period from the step (1) to the completion of the step (2), the surface of the coating layer is charged and the conductive particles in the coating layer are electrostatically charged. An electrophotographic roller manufacturing method comprising a step of causing polarization by induction.

Images