JP2009020422A - Conductive roller, manufacturing method therefor, electrophotographic process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive roller having satisfactory environmental stability, to provide a manufacturing method for the conductive roller and to provide an electrophotographic process cartridge and an image forming apparatus. <P>SOLUTION: The conductive roller has a shaft core body, and a conductive rubber layer formed around it. The conductive rubber layer contains at least silicone rubber and as a filler, a carbon black (A) having a particle diameter of 10 nm to 40 nm and a combustion start temperature of 700°C to 800°C. The content of the carbon black (A) based on 100 parts by mass of the silicone rubber is 7.5 to 20.5 parts by mass. The density of the conductive rubber layer is 1.01 g/cm<SP>3</SP>to 1.07 g/cm<SP>3</SP>. The average diameter of the circle of a carbon black absence area of a cross section of the conductive rubber layer is 1.0 μm to 6.0 μm. A difference between the maximum and minimum diameters of the circle (Max-Min) is 5.0 μm or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an elastic roller used in an image forming apparatus such as a printer and a copying machine, and a manufacturing method thereof, and further relates to an electrophotographic process cartridge and an image forming apparatus using the elastic roller as a developing roller.

  A conventional electrophotographic image forming apparatus will be described below.

  An image forming unit is installed in the main body of the apparatus, and an image is output through processes of cleaning, charging, latent image, development, transfer, and fixing. The image forming unit includes a photosensitive drum as an image carrier, and a cleaning unit, a charging unit, a latent image forming unit, a developing unit, and a transfer unit are provided around the photosensitive drum. The developer image on the photosensitive drum formed by the image forming unit is transferred to a recording material by a transfer unit, conveyed to a fixing unit, heated and pressed by the fixing unit, fixed to the recording material, and recorded as a recorded image. Discharged.

  In a printer using an electrophotographic system, the photosensitive drum is uniformly charged by a charging roller, and an electrostatic latent image is formed on the surface by a laser on which image information is placed. With respect to the electrostatic latent image, the developer carried on the developing roller uniformly with an appropriate charge by the developer applying roller and the developer regulating member in the developing container is developed at the contact portion between the photosensitive drum and the developing roller. Done. Thereafter, the developer image on the photosensitive drum is transferred onto the recording paper by the action of the transfer roller at the transfer portion with or without the intermediate transfer member. The recording paper carrying the developer image is conveyed to a fixing unit and fixed by heat and pressure (pressure roller and fixing roller). On the other hand, the developer remaining on the photosensitive drum is removed by a cleaning blade, and a series of processes is completed.

  In this apparatus, the developing roller is in pressure contact with the photosensitive drum and the developer regulating member, and when the use is started, the developer is interposed between the developing roller and the photosensitive drum and between the developing roller and the developer regulating member. is doing. The developer remaining on the developing roller without being transferred to the photosensitive drum is peeled off by the developer applying roller in contact with the developing roller and returned to the developing container. The developer returned from the developing roller is stirred in the container and conveyed again onto the developing roller by the developer application roller. As these steps are repeated, the developer is under great stress. Therefore, in order to reduce stress on the developer, the developing roller is formed of a material made of an elastic body having a low hardness.

  Further, when the conductive roller is a developing roller or a charging roller, it always rotates in contact with other members, so that the contact state needs to be kept stable. That is, the developing roller and the charging roller are preferably in contact with other members with a predetermined contact width, so that they are easily deformable and at the same time have excellent deformation recovery force. If the contact state cannot be kept stable, the supply amount of the developer varies or the charged state becomes uneven, which adversely affects the image.

  The developing roller used in such a contact developing system is a conductive roller having a configuration in which a conductive rubber layer is provided on the outer periphery of the shaft core. Furthermore, there is also a conductive roller provided with a surface layer by applying various resin solutions on the conductive rubber layer, if necessary, in order to adjust the surface characteristics to the intended use.

  In recent years, the need for colorization and high image quality of electrophotography has increased, and further stability of the electrophotographic roller has been strictly demanded. For example, the environment in which the electrophotographic apparatus is handled needs to correspond to a wide range of temperature and humidity. Therefore, stability among environmental differences is one of the most important issues. In the environmental difference between high temperature and high humidity and low temperature and low humidity, if the resistance stability of the conductive member is poor, the bias applied to the developer (toner) and the photosensitive drum will fluctuate, and as a result, the amount of applied toner will change. It will be affected, and finally an image defect will occur.

  From the above required characteristics, it is important that the conductive roller has good resistance stability in the environmental difference between high temperature and high humidity and low temperature and low humidity. That is, it is required that variation is small in a high temperature and high humidity environment and a low temperature and low humidity environment.

  From such a viewpoint, liquid silicone rubber is used as the conductive rubber layer material. Silicone rubber includes an addition reaction crosslinking type, a condensation reaction crosslinking type, and a peroxide crosslinking reaction type. In particular, addition reaction cross-linkable liquid silicone rubber is used because of excellent productivity such as good workability, high stability of dimensional accuracy, and no generation of reaction by-products during the curing reaction.

  In addition, as a method for producing a conductive silicone rubber roll, a molding method using a cylindrical mold is generally performed, and among them, a technique capable of high precision molding with small variation in electric resistance is disclosed. ing. That is, the shaft core body is disposed in the molding space of the cylindrical mold, and the longitudinal direction of the shaft core body is substantially vertical, and the space between the shaft core body and the molding space inner peripheral surface is Then, a silicone rubber composition is injected, and the mold is heated to form a crosslinked rubber composition. Thereby, a semiconductive rubber layer is formed, and the semiconductive rubber layer satisfies specific requirements (Patent Document 1).

  At this time, a relatively high density filler is added to the silicone rubber composition to adjust the density. As a result, carbon black is not unevenly distributed in either the longitudinal direction or the axial direction of the shaft body of the roll, and is dispersed throughout the semiconductive rubber layer, so that a good semiconductive roller can be formed. Yes.

However, regarding these conductive rollers, there is no description of resistance stability among the environmental differences between the high temperature and high humidity and the low temperature and low humidity of the conductive roller that affect the colorization and high image quality of electrophotography. Furthermore, the influence on the toner and the image characteristics when a high-definition image is output are not clear.
JP 2001-227530 A

  As described above, in the developing roller, which is a conductive member using carbon black, even if the carbon black is uniformly dispersed in the roller, the roller is moved in the environmental difference between high temperature and high humidity and low temperature and low humidity. There is a case where the amount of charge given to the toner when energized varies. In the case of the developing roller, this is related to the scattered image. Compared to high temperature and high humidity environment, the resistance value of the roller increases in low temperature and low humidity environment, so the toner on the developing roller has an excess charge than the normal charge amount, and the toner that can no longer be controlled is fine. It seems that the scattered image is generated by scattering. In a high-temperature and high-humidity environment, it is considered that a toner image that is difficult to hold electric charge and further absorbs moisture and scatters in a certain amount due to a lack of electric charge is generated.

  An object of the present invention is to provide a developing roller, a manufacturing method thereof, an electrophotographic process cartridge, and an image forming apparatus that can obtain a good image with reduced scattered images in each environment.

  As a result of intensive investigations to solve this problem, the present inventors have found that when the conductive rubber layer is in a range where carbon black is uniformly dispersed and there is no area where carbon black is present, It came to solve. That is, the average diameter of the circle drawn in the carbon black non-existing area in the cross section of the conductive rubber layer is 1.0 μm or more and 6.0 μm or less, and the maximum-minimum value (Max-Min) of the circle diameter is 5.0 μm or less. When it is. Thereby, it is possible to maintain a stable energized state in each environment from a high temperature and high humidity environment to a low temperature and low humidity environment, and it is possible to obtain a good image in which the occurrence of scattering is reduced as compared with the conventional case.

  That is, the present invention has the following configuration.

[1] A conductive roller having a shaft core and a conductive rubber layer formed around the shaft core,
The conductive rubber layer contains at least silicone rubber, a platinum compound, and carbon black (A) having a particle size of 10 nm to 40 nm and a combustion start temperature of 700 ° C. to 800 ° C. as a filler,
The carbon black (A) is contained in an amount of 7.5 parts by mass or more and 20.5 parts by mass or less with respect to 100 parts by mass of the silicone rubber.
And the area equivalent ratio occupies 95% to 100% in the total filler,
And the density of the conductive rubber layer is not more than 1.01 g / cm ³ or more 1.07 g / cm ^3,
The average diameter of the circle drawn in the carbon black non-existing area in the cross section of the conductive rubber layer is 1.0 μm or more and 6.0 μm or less, and the maximum-minimum value (Max-Min) of the circle diameter is 5.0 μm or less. A conductive roller, characterized in that there is.

  [2] The conductive rubber layer satisfies the following (formula 1) when the roller resistance values (Ω) measured at 30 ° C., 80% RH, 15 ° C., and 10% RH are RV1 and RV2, respectively. The conductive roller according to [1] above.

−0.01 ≦ log (RV2 / RV1) ≦ 0.5 (Formula 1)
[3] The conductive rubber according to [1] or [2], wherein the silicone rubber is obtained by crosslinking and curing using an addition reaction type liquid silicone rubber as a raw material and a platinum compound as a catalyst. Sex roller.

[4] In a method for producing a conductive roller by providing a conductive rubber layer containing a filler around the shaft core body,
Arranging the ring-type coating head so as to be concentric with the shaft core, and moving the shaft core in the axial direction relative to the coating head;
Conductive rubber containing carbon black having a particle size of 10 nm or more and 40 nm or less and a combustion start temperature of 700 ° C. or more and 800 ° C. or less to 7.5 parts by mass or more and 20.5 parts by mass or less with respect to 100 parts by mass of silicone rubber Applying a layer material on the outer periphery of the shaft core;
The applied the conductive rubber layer material was cured by infrared heating method for manufacturing a conductive roller and a step of density to obtain a conductive rubber layer is not more than 1.01 g / cm ³ or more 1.07 g / cm ³ .

  [5] The method for producing a conductive roller as described in [4] above, wherein the yield stress in the uncured state of the conductive rubber layer is 50 Pa or more and 600 Pa or less.

  [6] The conductive material according to [4] or [5], wherein the silicone rubber is obtained by crosslinking and curing using an addition reaction type liquid silicone rubber as a raw material and a platinum compound as a catalyst. Roller manufacturing method.

  [7] A conductive roller manufactured by the manufacturing method according to any one of [4] to [6].

  [8] The conductive roller according to any one of [1] to [3] and [7], wherein the conductive roller is used as a developing roller.

  [9] In an electrophotographic process cartridge that visualizes an electrostatic latent image on the surface of the photosensitive drum by bringing a developer formed in a layer on the surface of the developing roller into contact with the photosensitive drum, the developing roller includes the above [1 ] An electrophotographic process cartridge comprising the conductive roller according to any one of [3] and [7].

  [10] In the image forming apparatus for visualizing the electrostatic latent image on the surface of the photosensitive drum by bringing the developer formed in a layer on the surface of the developing roller into contact with the photosensitive drum, the developing roller includes the above [1] An image forming apparatus comprising the conductive roller according to any one of [3] and [7].

  In the conductive roller of the present invention, since the conductive rubber layer is formed of a specific silicone rubber composition, it maintains a stable resistance state in the environmental difference between the high temperature and high humidity environment and the low temperature and low humidity environment, and is stable. Output image is obtained.

  Hereinafter, the present invention will be described in detail.

  FIG. 1 shows a perspective view of an example of a conductive roller according to the present invention. In FIG. 1, reference numeral 101 denotes a shaft core, and the conductive roller according to the present invention is provided with a conductive rubber layer 102 made of a silicone rubber composition containing specific carbon black around the shaft core 101. ing.

  The shaft core body 101 functions as an electrode and a support member of a conductive roller. The shaft core 101 is made of, for example, a metal or alloy such as aluminum, copper alloy, stainless steel, iron plated with chromium or nickel, or a synthetic resin material. The shape is preferably a columnar shape or a cylindrical shape with a hollow center. The outer diameter of the shaft core can be determined as appropriate, but is preferably in the range of 4 mm to 20 mm.

In the conductive roller of the present invention, the conductive rubber layer comprises at least silicone rubber and a filler containing carbon black (A) having a particle size of 10 nm to 40 nm and a combustion start temperature of 700 ° C. to 800 ° C. Composed. The carbon black (A) is contained in an amount of 7.5 parts by mass to 20.5 parts by mass with respect to 100 parts by mass of the silicone rubber. The carbon black (A) occupies 95% to 100% of the total filler in the area equivalent ratio. Furthermore, the density of the conductive rubber layer is 1.01 g / cm ³ or more 1.07 g / cm ³ or less. Furthermore, the average diameter of the circle that can be drawn in the carbon black non-existing area in the cross section of the conductive rubber layer is 1.0 μm or more and 6.0 μm or less, and the maximum-minimum value (Max-Min) of the diameter of the circle. ) Is 5.0 μm or less.

  In addition, it is preferable for the performance stability to include a platinum compound in the conductive rubber layer. In addition, as a platinum compound, what is used as a crosslinking catalyst of an addition reaction type liquid silicone rubber can be used as will be described later. As a crosslinking catalyst used in the crosslinking reaction of the addition reaction type silicone rubber, a compound containing a transition metal element is used. Examples of the transition metal element include Pt, Pd, Ni, Co, Ti, Ru, Ce, Cr, and the like. Is exemplified. In order to exhibit the effect in the present invention, it is essential to maintain a state in which the filler mixed in the silicone rubber is uniformly dispersed. Therefore, it is necessary to advance the curing reaction in a short time after molding. For this purpose, it is necessary to select one having high solubility in silicone and high activity for proceeding with the crosslinking reaction. When the platinum compound is used, the filler in the silicone rubber material begins to agglomerate during molding, and the curing reaction can proceed faster than the fine uniform dispersion state collapses. A uniform dispersion state can be obtained.

  As the base material of the conductive rubber layer, silicone rubber having a moderately low hardness and good deformation recovery ability is used. In particular, in the case of a developing roller, since it is used in a state where it is always in pressure contact with a toner regulating member, a photoreceptor, etc., it is required to have low hardness and good deformation recovery. Silicone rubber includes an addition reaction cross-linking type, a condensation reaction cross-linking type, and a peroxide curing type, and can be appropriately selected from these. Among these, addition reaction cross-linkable liquid silicone rubber is preferable because it has excellent workability, high dimensional accuracy stability, and no production of reaction by-products during the curing reaction.

  Addition reaction type liquid silicone rubber, which is a raw material for addition reaction crosslinking type liquid silicone rubber, is composed of organopolysiloxane (main agent) having alkenyl group and organohydrogenpolysiloxane (curing agent), and further catalyst and other additives. It is a composition suitably contained.

  The organopolysiloxane having an alkenyl group is a base polymer of a silicone rubber raw material, and the molecular weight thereof is not particularly limited, but the weight average molecular weight (Mw) is preferably 10,000 to 1,000,000, preferably 50,000 to 700,000. The following is more preferable.

  The alkenyl group of the organopolysiloxane is a site that reacts with the active hydrogen of the organohydrogenpolysiloxane to form a crosslinking point, and the type thereof is not particularly limited. However, for reasons such as high reaction with active hydrogen, at least one of a vinyl group and an allyl group is preferable, and a vinyl group is more preferable.

  Organohydrogenpolysiloxane functions as a crosslinking agent for addition reaction in the cross-linking curing process, and two or more silicon-bonded hydrogen atoms in one molecule are necessary, so that the curing reaction can be suitably performed. It is preferable that there are three or more. The molecular weight of the organohydrogenpolysiloxane is not particularly limited, and the preferred weight average molecular weight (Mw) is 1000 or more and 10,000 or less. In order to suitably perform the curing reaction, a polymer having a relatively low molecular weight and a weight average molecular weight of 1,000 to 5,000 is more preferable.

The addition reaction type liquid silicone rubber preferably contains a known platinum-based catalyst as a crosslinking catalyst. Examples of the platinum-based catalyst include platinum compounds such as chloroplatinic acid, alcohol compounds of chloroplatinic acid, ether compounds, and complexes with hydrates. The addition amount of the crosslinking catalyst is preferably in the range of 1 ppm to 2000 ppm with respect to the organopolysiloxane.

  The carbon black (A) that can be used in the present invention has a particle size of 10 nm to 40 nm. Examples of the carbon black (A) include SAF, ISAF, HAF, MAF, FEF, GPF, SRF, RCF, MCF, FT, MT and the like, and further, acidic carbon subjected to oxidation treatment, pyrolytic carbon, etc. General-purpose ones are listed. When the carbon black has a particle size of less than 10 nm, the carbon black itself is highly cohesive and it is difficult to uniformly disperse it in the silicone rubber. Thereby, the dispersion | variation in hardness and a deformation | transformation recovery force becomes large with respect to the axial direction and thickness direction of an elastic roller. On the other hand, when the particle size is larger than 40 nm, the cohesiveness of the carbon black itself is weak, and the material is sheared during molding or mixing of materials, so that the uniform dispersibility of the carbon black is improved. However, since it is difficult to form a carbon network in the silicone polymer, a large amount of carbon black is required, and as a result, physical properties such as strain characteristics are impaired. When the particle size of the carbon black (A) to be used is 10 nm or more and 40 nm or less, appropriate carbon black dispersibility is expressed in the silicone polymer, and the conductive stability is improved.

  Carbon black (A) must have a combustion start temperature of 700 ° C. or higher and 800 ° C. or lower. Carbon black has a great influence on the interaction with other substances in the conductive rubber layer due to its surface characteristics, and the surface is particularly important because the particles are very fine and the specific surface area is large. One of the characteristics.

  The combustion start temperature of carbon black is greatly influenced by the pore structure on the surface of carbon black, and it is considered that the temperature at which combustion starts due to the penetration of oxygen in the air varies depending on the pore structure. If the pore structure on the surface of the carbon black is developed, the surface area of the particles is increased, so that the probability of contact with oxygen in the air is increased, and combustion is likely to occur at a low temperature. The combustion start temperature is measured by the measurement method described later. The state of measurement is shown in FIG.

  A suitable combustion start temperature of carbon black is 700 ° C. or higher and 800 ° C. or lower. It is considered that adhesion strength is generated between the carbon black and the silicone polymer due to the entanglement of the pore structure on the surface of the carbon black and the silicone molecules surrounding it. When the carbon black is dispersed in the silicone polymer, the carbon black is very finely and uniformly dispersed by applying a high shearing force. Here, when the adhesion strength due to the entanglement between the carbon black and the silicone polymer is low, the agglomeration action of the carbon black works greatly, and the uniformly dispersed state cannot be maintained. The interaction due to the entanglement between the carbon black and the silicone molecule is a force related to the direction of hindering the aggregating action of fine particles such as carbon black. Therefore, it is considered that the dispersion state of the carbon black in the silicone rubber can be maintained by balancing the interaction due to the entanglement between the carbon black and the silicone molecule and the cohesive force of the carbon black.

  When the combustion start temperature is lower than 700 ° C., the interaction between carbon black and silicone rubber is strong, and a suitable carbon network cannot be formed, so that desired electrical characteristics cannot be obtained. When the temperature exceeds 800 ° C., the interaction between the carbon black and the silicone rubber is weak, and the carbon black tends to aggregate. For this reason, the uneven distribution of the carbon network in the silicone polymer increases, and the points of conduction become sparse, and the amount of charge given to each toner varies, so that a good image cannot be maintained.

The blending amount of carbon black (A) is 7.5 parts by weight or more and 20.5 parts by weight or less with respect to 100 parts by weight of silicone rubber, and is blended within this range so that the resistance value of the conductive rubber layer becomes predetermined. Is done. Note that the resistance value of the conductive roller used in the electrophotographic image forming apparatus is 10 ³ Ω · cm or more and 10 ⁸ Ω · cm or less, and is adjusted according to the application.

  If the blending amount of carbon black (A) is more than 20.5 parts by mass, the carbon black concentration of the conductive rubber layer becomes high and the physical properties of the silicone rubber elastic roller are lowered. On the other hand, when the amount is less than 7.5 parts by mass, sufficient electrical characteristics as a conductive roller cannot be obtained.

  The area equivalent ratio of carbon black in all fillers blended in the silicone rubber is 95% to 100%. When the ratio of carbon black is less than 95%, the influence of other fillers present in the conductive rubber layer is remarkably exhibited and the uniform dispersibility of carbon black is impaired. In addition, when the filler other than carbon black is a conductive filler, sedimentation and aggregation are inevitable because specific gravity and particle shape are greatly different from those of carbon black. When carbon black is 95% to 100% of the total filler, the desired dispersion state can be maintained without being affected by other fillers.

The average diameter of the circle that can be drawn in the carbon black nonexisting area in the cross section of the conductive rubber layer in the present invention is 1.0 μm or more and 6.0 μm or less.
The average diameter is an index representing the dispersion density of carbon black in the conductive rubber layer. When the area where carbon black does not exist is represented by a circle in the cross section of the conductive rubber layer, 11 from the circle with the largest diameter are represented. Select to represent the average diameter of 10 circles excluding the largest circle.
If this average diameter is less than 1.0 μm, carbon black is excessively dispersed, so that the sufficient amount of conduction points cannot be formed with the amount of carbon black in the present invention, and sufficient charge can be given to the toner. Absent.
Therefore, toner scattering is likely to occur particularly in a high temperature and high humidity environment. When it is larger than 6.0 μm, the carbon black in the polymer is excessively biased and easily affected by the external environment. Further, since the range of the insulating portion is too wide with respect to the size of the contact point of the toner, the amount of charge given to each toner varies. In other words, if the dispersion state of carbon black is biased, the individual charge amount of the toner on the developing roller varies greatly, and this tendency becomes remarkable particularly in a low-temperature and low-humidity environment, resulting in image defects. Become.

  The maximum value-minimum value (Max-Min) of the diameter of the circle that can be drawn in the carbon black non-existing area in the cross section of the conductive rubber layer in the present invention is 5.0 μm or less. The Max-Min is an index representing the carbon black dispersion uniformity. In the cross section of the conductive rubber layer, when a region where carbon black does not exist is represented by a circle, 11 pieces are selected from the circles having the largest diameter, and the largest circle among the ten circles excluding the largest circle is selected. Max-Min was calculated with Max as the diameter and Min as the diameter of the smallest circle. If this Max-Min is smaller than 5.0 μm, the dispersion state of the carbon black in the silicone rubber is uniform, so that it becomes possible to supply charges stably to the toner, and the effects of the present invention can be achieved. It can be pulled out.

  A filler other than carbon black may be added to the silicone rubber composition forming the conductive rubber layer in order to improve the carbon dispersion stability in the silicone rubber. Examples of fillers other than carbon black include silica, alumina, calcium carbonate, celite, quartz powder, zinc white, and the like, preferably silica and zinc white having an average primary particle size similar to that of carbon black (A). .

  The silicone rubber composition forming the conductive rubber layer has a plasticizer, a heat-resistant agent, a flame retardant, an antioxidant, a crosslinking accelerator, a crosslinking retarder, a crosslinking aid so that the desired performance can be obtained. Various additives such as an agent and a thixotropic agent may be appropriately blended within a range not impairing the effects of the present invention.

  Examples of the plasticizer include polydimethylsiloxane oil, diphenylsilanediol, trimethylsilanol, phthalic acid derivatives, and adipic acid derivatives.

Density of the conductive rubber layer of a silicone rubber molded product of the present invention is in the range of 1.01 g / cm ³ or more 1.07 g / cm ³ or less. When the density of the conductive rubber layer is less than 1.01 g / cm ³ , the filling rate of the filler with respect to the silicone polymer is small. Therefore, even if carbon black with high conductivity cannot be used, a sufficient carbon network cannot be formed. The desired volume resistance cannot be achieved. On the other hand, when the density of the conductive rubber layer exceeds 1.07 g / cm ³ , many fillers with large density differences are mixed, leading to deterioration of the dispersibility of carbon black in the vicinity of the shaft core, and as a developing roller. It may be difficult to obtain the necessary electrical characteristics.

The conductive roller of the present invention has the following resistance when the roller resistance value at a temperature of 30 ° C. and a humidity of 80% RH is RV1, and the roller resistance value at a temperature of 15 ° C. and a humidity of 10% RH is RV2. ) Is preferably satisfied.
When the roller resistance value satisfies the following (Equation 1), the resistance value variation in the environment is small, and a good image can be obtained.

−0.01 ≦ log (RV2 / RV1) ≦ 0.5 (Formula 1)
The method for producing the conductive roller of the present invention is not particularly limited as long as the conductive rubber layer having the above-described configuration is formed on the shaft core. It is preferable to use a production method in which pressure and shear force are not applied to the silicone rubber material as much as possible during molding because the dispersion state is not easily affected by heating conditions without causing reaggregation of carbon black. A method in which a concentric silicone rubber composition for a conductive rubber layer is formed under atmospheric pressure on a shaft core, and then the silicone rubber composition is heated and cured is more preferably used.

  That is, the elastic roller manufacturing method of the present invention includes the following steps.

  A step of arranging a ring-type coating head so as to be concentric with the shaft core, and moving the shaft core relative to the coating head in the axial direction.

  Simultaneously with the transfer step, a conductive material containing carbon black having a particle size of 10 nm to 40 nm and a combustion start temperature of 700 ° C. to 800 ° C. of 7.5 parts by mass to 20.5 parts by mass with respect to 100 parts by mass of the silicone rubber. Applying a conductive rubber layer material on the outer periphery of the shaft core.

Then, the conductive rubber layer material was cured by infrared heating, the step of density to obtain a conductive rubber layer is 1.01 g / cm ³ or more 1.07 g / cm ³ or less.

  In addition, it is preferable that the yield stress is 50 Pa or more and 600 Pa or less, and more preferably 100 Pa or more and 400 Pa or less in the uncured state of the silicone rubber composition containing the various components described above. That is, when the yield stress of the uncured silicone rubber composition is in the above-described range, the dimensional accuracy with respect to the coating thickness can be maintained and the balance with the smoothness of the coated surface can be achieved in the best condition. Here, the yield stress means a stress value at a point where the storage elastic modulus G ′ and the loss elastic modulus G ″ intersect in the viscoelasticity measurement graph.

  In other words, when the yield stress exceeds 600 Pa, the stress required to cause structural destruction of the material is too large, causing problems such as streaks on the surface after coating or unevenness. Occurs. If it is less than 50 Pa, the yield stress is too small for gravity to maintain the shape after the coating film is formed, so the outer diameter dimensional difference with respect to the coating thickness of the conductive roll after heat curing is large. The roll is not suitable for use.

  In the method for producing a conductive roller, as a method for forming the silicone rubber composition for the conductive rubber layer on the shaft core, a coating method using a ring-type coating head is preferable in the present invention.

  FIG. 2 shows a schematic explanatory diagram of a ring coater having a ring-type coating head that can be suitably used here.

  In this ring coat machine, a column 32 is attached substantially vertically on a gantry 31, and a precision ball screw 33 is attached substantially vertically on the gantry 31 and the column 32. Reference numeral 44 denotes a linear guide. Two linear guides 44 are attached to the column 32 in parallel with the precision ball screw 33.

  The LM guide 34 connects the linear guide 44 and the precision ball screw 33, and a rotary motion is transmitted from the servo motor 35 via the pulley 36 so that the LM guide 34 can be raised and lowered. A ring-shaped coating head 38 for applying an uncured silicone rubber composition on the outer periphery of the shaft core body is attached to the column 32 on the outer periphery side of the shaft core body 2.

  Further, a bracket 37 is attached to the LM guide 34, and a shaft core lower holding shaft 39 for holding and fixing the shaft core body 2 is attached to the bracket 37 substantially vertically. Further, the central axis of the shaft core upper holding shaft 40 that holds the shaft core body 2 of the opposite roller is attached to the upper portion of the bracket 37, and the shaft core upper holding shaft 40 faces the shaft core lower holding shaft 39. And it arrange | positions so that it may become substantially concentric, and the shaft core body is hold | maintained.

  The center axis of the ring-shaped coating head 38 is supported so as to be parallel to the moving direction of the shaft core lower holding shaft 39 and the shaft core upper holding shaft 40. Further, when the shaft core lower holding shaft 39 and the shaft core upper holding shaft 40 are moved up and down, the central axis of the discharge port which is an annular slit opened inside the coating head 38 and the shaft core lower holding shaft 39 are arranged. In addition, the central axis of the shaft core holding shaft 40 is adjusted so as to be substantially concentric.

  With such a configuration, the central axis of the discharge port formed in the annular slit of the coating head 38 can be aligned substantially concentrically with the central axis of the shaft core 2, and the inner peripheral surface of the ring-shaped coating head and the above-described A uniform gap is formed between the outer peripheral surface of the shaft core body 2.

  A supply port 41 for the liquid silicone rubber composition is connected to a supply valve 43 via a pipe 42. The material supply valve 43 includes a mixing mixer, a material supply pump, a material fixed amount discharge device, a material tank, and the like in front of the material supply valve 43, and can discharge a fixed amount (a constant amount per unit time) of liquid rubber. A predetermined amount of the silicone rubber composition is weighed from the material tank by a material dispensing device and mixed by a mixing mixer. Thereafter, the silicone rubber composition mixed by the material supply pump is sent from the material supply valve 43 to the supply port 41 via the pipe 42.

  The silicone rubber composition fed from the supply port 41 passes through the flow path in the ring type coating head 38 and is discharged from the nozzle of the ring type coating head 38. In order to make the thickness of the silicone rubber composition constant, the discharge amount from the ring-shaped coating head nozzle and the supply amount from the material supply pump are made constant, and the shaft core body 2 held in the vertical direction (axis Move upward in the direction of the central axis of the core. Thereby, the shaft core body 2 moves in the axial direction relative to the coating head 38, and a cylindrical (roll-shaped) uncured material layer made of a silicone rubber composition on the outer periphery of the shaft core body 2. 3 is formed. At this time, the clearance between the shaft core 2 and the ring-type coating head nozzle is preferably set to a clearance equal to or larger than the desired thickness of the conductive rubber layer because the silicone rubber composition shrinks due to curing. In particular, the clearance is preferably about 1.1 times the layer thickness.

  In the next step, the layer of the uncured silicone rubber composition is heat-treated by infrared heating and cured to obtain a conductive roller. The surface of the uncured silicone rubber composition has adhesiveness. For this reason, the heat treatment is preferably a non-contact, simple apparatus, and infrared heating that can uniformly heat the uncured layer of the silicone rubber composition in the longitudinal direction. At this time, the infrared heating device is fixed, and the shaft core body provided with the cylindrical (roll-shaped) uncured material layer made of the silicone rubber composition is rotated in the circumferential direction, so that the heat treatment is uniformly performed in the circumferential direction. Is called. The heat treatment temperature of the surface of the conductive rubber layer material of the silicone rubber composition is preferably 100 ° C. or higher and 250 ° C. or lower at which the curing reaction starts, although it depends on the silicone rubber composition used.

  Here, for the purpose of stabilizing physical properties of the conductive rubber layer after curing, removing reaction residues and unreacted low molecular components in the conductive rubber layer, the conductive rubber layer after infrared heating is further subjected to heat treatment and the like. Sub-curing may be performed. Thereafter, the conductive rubber layer is cut through both ends to make the conductive rubber layer a required length, and when the silicone rubber composition is formed on the shaft core, an abnormality is likely to occur when forming the conductive rubber layer. It is also preferable to remove the beginning and end of the film in advance.

  A surface layer may be further provided on the outer peripheral side of the conductive rubber layer formed as described above from the viewpoints of wear resistance, toner chargeability and releasability. Examples of the material for forming the surface layer include various polyamides, fluororesins, hydrogenated styrene-butylene resins, urethane resins, silicone resins, polyester resins, phenol resins, imide resins, olefin resins, and the like. These materials may be used alone or in combination of two or more. Various additives are added to these materials as necessary.

  These materials constituting the surface layer can be dispersed using a conventionally known dispersion apparatus using beads such as a sand mill, a paint shaker, a dyno mill, and a ball mill. The obtained coating material for forming the surface layer can be applied to the surface of the conductive rubber layer by a spray coating method, a dipping method or the like. The thickness of the surface layer is preferably 5 μm or more and 50 μm or less. 5 μm or more is preferable from the viewpoint of preventing the low molecular weight component from seeping out and contaminating the photosensitive drum, and 50 μm or less is preferable from the viewpoint of preventing the roller from becoming hard and causing toner fusion. More preferably, it is 10 μm or more and 30 μm or less.

  The conductive roller of the present invention can be used as a developing roller. The developing roller bears the developer while being in contact with or pressed against the photosensitive drum as a latent image carrier that carries the latent image. The developing roller has a function of forming a latent image as a developer image by applying toner as a developer in a layered manner on the surface of the photosensitive drum. Furthermore, the electrophotographic process cartridge and the image forming apparatus of the present invention use the conductive roller of the present invention as a developing roller.

  An example of an electrophotographic process cartridge and an electrophotographic image forming apparatus in which the conductive roller of the present invention is mounted as a developing roller is schematically shown in FIG.

  The electrophotographic image forming apparatus according to the present invention includes four image forming units 10a to 10d for forming yellow, cyan, magenta, and black images, respectively, and is provided in a tandem manner. The specifications of the photosensitive drum 11, the charging device 12 (charging roller), the image exposure device 13 (writing beam), the developing device 14, the cleaning device 15, the image transfer device 16 (transfer roller), etc. are slightly different according to the characteristics of each color toner. Although the adjustments are different, the basic structure is the same. Further, the photosensitive drum 11, the charging device 12, the developing device 14, and the cleaning device 15 are integrated to form a process cartridge.

  The developing device 14 includes a developing container 6 that contains the one-component toner 5 and a developing roller 1 that is located in an opening extending in the longitudinal direction in the developing container 6 and that is opposed to the photosensitive drum 11. The electrostatic latent image on the photosensitive drum 11 is developed and visualized. Further, the one-component toner 5 is supplied to the developing roller 1 and the one-component toner 5 carried on the developing roller 1 without being used for development is scraped and the one-component toner 5 on the developing roller 1 is carried. A developing blade 8 that regulates the amount and frictionally charges is provided.

  The surface of the photosensitive drum 11 is uniformly charged to a predetermined polarity and potential by the charging device 12, and image information is irradiated as a beam from the image exposure device 13 to the surface of the charged photosensitive drum 11, and an electrostatic latent image is formed. It is formed. Next, a one-component toner is supplied in a layer form from the developing device 14 having the elastic roller of the present invention as the developing roller 1 on the formed electrostatic latent image, and a toner image is formed on the surface of the photosensitive drum 11 to form an electrostatic latent image. The image is visualized. As the photosensitive drum 11 rotates, the toner image is transferred to a transfer material 25 such as paper that is supplied in synchronization with the rotation when the toner image comes to a position facing the image transfer device 16.

  In the drawing, four image forming units 10 a to 10 d are formed in a series of interlocking manner so that predetermined color images are superimposed on one transfer material 25. Therefore, the transfer material 25 is synchronized with the image formation of each image forming unit, that is, the image formation is synchronized with the insertion of the transfer material 25. Therefore, the transfer roller 17 for transporting the transfer material 25 is sandwiched between the photosensitive drum 11 and the image transfer device 16 so that the drive roller 18, the tension roller 19, and the driven roller 20 of the transfer roller belt 17 are sandwiched between them. It is laid around. Further, the transfer material 25 is conveyed in a form that is electrostatically adsorbed to the transfer conveyance belt 17 by the action of the adsorption roller 21. Reference numeral 22 denotes a supply roller for supplying the transfer material 25.

  The transfer material 25 on which the image has been formed is peeled off from the transfer conveyance belt 17 by the action of the peeling device 23 and sent to the fixing device 24, and the toner image is fixed on the transfer material 25 to complete the printing. On the other hand, the photosensitive drum 11 after the transfer of the toner image to the transfer material 25 is further rotated, and the surface of the photosensitive drum 11 is cleaned by the cleaning device 15 and is neutralized by a neutralizing device (not shown) as necessary. Thereafter, the photosensitive drum 11 is used for the next image formation. In the figure, reference numerals 26 and 27 denote bias power sources for the image transfer device 16 and the suction roller 21, respectively.

  Here, the apparatus for directly transferring the toner image of each color onto the tandem type transfer material has been described. However, any apparatus that uses the conductive roller of the present invention as the developing roller may be used. For example, monochrome monochrome image forming apparatuses, image forming apparatuses that form color images by superimposing each color toner image on a transfer roller or transfer belt, and then transferring them all at once to a transfer material, each color developing unit being arranged on a rotor, or photosensitive Examples thereof include an image forming apparatus arranged in parallel with a drum. Further, instead of the process cartridge, a photosensitive drum, a charging device, a developing device, and the like may be directly incorporated in the image forming apparatus.

  The conductive roller of the present invention can be used not only as the developing roller described above but also for applications requiring conductivity such as a charging roller and a transfer roller because the conductive rubber layer has good uniformity. is there.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, these do not limit this invention at all. First, various evaluations and measurement methods performed in the examples will be described.

<Method for measuring carbon particle size>
The particle size of carbon black (CB) can be a value determined by the following method.
As shown in FIG. 1, a sample is taken out from three points that divide the longitudinal direction of the roller into four equal parts (a sharp blade is inserted vertically from the side of the roller to reach the axial center body, and has a thickness of about several millimeters. A sample that can be cut in a circle and observed in a cross-section). An ultrathin section is prepared from the thickest layer in the cross section and used as a sample for observation. For preparation of ultrathin sections, for example, a section preparation apparatus (Leica Microsystems, Inc .; “Leica EM FCS” (trade name)) is used. An ultra-thin section having a thickness of about 50 nm can be produced using a diamond knife (“Cryo dry 35 °” (trade name)) manufactured by Diatome under an atmosphere of −120 ° C. or higher and −50 ° C. or lower. Three locations are selected from the prepared observation samples (near the surface of the conductive rubber layer, between the surface and the shaft core, and near the shaft core), and a total of nine locations are observed with a TEM to obtain measurement data. The direct observation magnification is 140,000 times. The photographed film is magnified twice and developed, and finally a 280,000 times photograph is obtained.

  From the photograph, 20000 particles of carbon black are arbitrarily selected, and the particle size of each carbon black particle is determined. If the carbon black particles selected arbitrarily have a lot of overlap with the adjacent carbon black particles, the particle size of the carbon black particles is not determined and other particles are selected. Determination of whether there is much or little overlap with adjacent carbon black particles will be described with reference to FIG. In FIG. 4, since the central carbon black particle Y is in contact with two adjacent carbon black particles X and Z, the exact contour of the particle Y is unknown. However, carbon black is a substance that easily forms an aggregate (structure), and most of the particles overlap as shown in FIG. As shown in FIG. 5, two points (the points A and B) where the contour lines of the particles Y and X intersect are connected by a straight line. Similarly, for the particles Y and Z, the points C and D are obtained and connected by straight lines to form a closed plane connected by the straight lines AB, BC, CD, and DA. The sum of the length of the line segment AB and the line segment CD is 40% or less of the sum of the length of the curve AD and the curve BC, and the length of the curve BC is the length of the line ABCDA Is 50% or more, the diameter of a circle obtained from a total of three points including one arbitrary point on the curve AD and two points that divide the curve BC into three equal parts is calculated. A value obtained by rounding the first decimal place of the calculated diameter (unit: nm) to an integer is defined as the particle size of the particle Y.

  With the above procedure, the particle size is determined for any 20,000 particles.

<Measurement method of carbon black area equivalent ratio>
A sharp blade is inserted vertically from the side of the roller so as to reach the shaft body, and is cut into a thickness of about several millimeters to obtain a sample whose cross section can be observed. Samples were taken from three places where the conductive rubber layer portion in the longitudinal direction of the roller was divided into four equal parts, and ten images were taken so as not to overlap each other. As shown in FIG. 7, using an SEM image with a magnification of 10000 times, the particles are separated into all aggregated units from those seen in the image. Each aggregation unit was selected, and irradiation was performed with the electron beam irradiation area narrowed down so that the particles occupied 60% or more on the image. An energy dispersive X-ray analyzer (manufactured by EDAX) attached to an electron microscope (“S4800” (trade name), manufactured by Hitachi) is used as a measuring device, and an atomic ratio (Atomic%) at an acceleration voltage of 10 kV and an acquisition time of 100 sec. ) Was measured. At this time, carbon black particles were those having a ratio C / O of atomic% of carbon C to atomic% of oxygen O of 2.0 or more, and particles other than carbon black were those having a ratio of less than 2.0. The areas of carbon black and other particles were summed from 30 images, and the area of the carbon black particles was calculated as a ratio.

<Measurement of carbon black content and combustion start temperature>
As shown in FIG. 1, a total of 9 parts in three depth directions (near the surface, in the middle of the surface and the shaft core, and near the shaft core) are divided into three parts that divide the conductive rubber layer portion in the roller longitudinal direction into four equal parts. A 10 mg sample was collected from each location as a sample. In accordance with JIS K6227: 1998, measurement was performed using “ThermoPlus2 TG8120” (trade name) manufactured by Rigaku Denki Co., Ltd., and the average value was used as measurement data. Measurement conditions are: keep nitrogen gas at 200 ml / min, keep at 50 ° C. for 5 minutes, and then raise the temperature to 800 ° C. at 50 ° C./min. Further, it is cooled to 300 ° C. at 50 ° C./min and held for 5 minutes to stabilize. Next, the temperature is similarly raised to 900 ° C. at 50 ° C./min while nitrogen gas is switched to air and flowing at 200 ml / min. Information on the weight of carbon black in the rubber component is obtained by weight reduction at the second temperature rise (in the air), and the content (mass%) of carbon black is obtained from the relationship with the ratio of the entire constituent material. The temperature at the weight reduction start point at this time was defined as the carbon combustion start temperature. This is shown in FIG. Depending on the cured product, there may be a slight increase in weight just before the start of weight reduction, but the temperature at the reduction start point is used as the carbon combustion start temperature.

<Measurement method for non-existing area of carbon black>
A sharp blade is inserted vertically from the side of the roller so as to reach the shaft body, and is cut into a thickness of about several millimeters to obtain a sample whose cross section can be observed. As shown in FIG. 1, samples were taken out from three places where the conductive rubber layer portion in the roller longitudinal direction was equally divided into four, and three images were taken so as not to overlap each other. As shown in FIG. 7, using a SEM image (approximately 32 μm in length and 42 μm in width) with a magnification of 3000 times, the particles are separated into all aggregated units. Each aggregation unit was selected, and irradiation was performed with the electron beam irradiation area narrowed down so that the particles occupied 60% or more on the image. An energy dispersive X-ray analyzer (manufactured by EDAX) attached to an electron microscope (“S4800” (trade name), manufactured by Hitachi) is used as a measuring device, and an atomic ratio (Atomic%) at an acceleration voltage of 10 kV and an acquisition time of 100 sec. ) Was measured. At this time, carbon black particles were those having a ratio C / O of atomic% of carbon C to atomic% of oxygen O of 2.0 or more, and particles other than carbon black were those having a ratio of less than 2.0. As shown in FIG. 8, a circle was drawn in an area where no carbon black was present in the image, and the diameter at that time was examined. Eleven of the largest diameters were selected, the largest one was excluded, and an average value was calculated from the remaining 10 data to obtain an average diameter. Further, the maximum value-minimum value (Max-Min) of the diameter of a circle was calculated by setting Max among the 10 data and Min as the minimum.

<Density measurement method>
A sample was cut from the conductive rubber layer of the roller, and measured with a solid density measuring device (“SGM-200” (trade name), manufactured by Shimadzu Corporation) at a sample temperature of 23 ° C. ± 2 ° C. About 3 ml of sample was used for one measurement, and 9 ml of three samples were taken and the average value measured three times was taken as the density of the conductive rubber layer.

<Roller resistance value>
The resistance value of the conductive roller of the present invention is as follows. First, the conductive roller is left in each environment (high temperature and high humidity: temperature 30 degrees, humidity 85% RH, low temperature and low humidity: temperature 15 ° C., humidity 10% RH) for 24 hours or more. did. Thereafter, the resistance value when a conductive roller carrying developer under each environment is pressed against a cylindrical metal roller (diameter 30 mm) with a constant pressure load of 500 g on one side, rotated at 60 rpm and applied with a DC voltage of 50 V. Was measured. X = log (RV2 / RV1) was calculated, assuming that the measured value in a high temperature and high humidity environment is RV1, and the measured value in a low temperature and low humidity environment is RV2.

<Yield stress of liquid rubber material for conductive rubber layer>
The yield stress of the liquid rubber material for the conductive rubber layer is determined by the viscoelasticity measuring device “RS” manufactured by Haake.
600 "(trade name) was used to determine the stress value at the point where the storage elastic modulus G 'and loss elastic modulus G''measured below were intersected.

  About 1 g of a liquid rubber material for the conductive rubber layer is collected and placed on the sample stage of the viscoelasticity measuring device, and a cone plate (diameter 35 mm, inclination angle 1 °) is gradually brought closer to about 50 μm from the sample stage. A measurement gap was set at the position. At that time, the material extruded around was removed cleanly so as not to affect the measurement. Next, the temperature of the plate base was set so that the sample temperature was 25 ° C., and after setting the sample, it was left for 10 minutes, and then the measurement was started. The stress applied to the sample was changed from 0.00 Pa to 50,000 Pa over 180 seconds (frequency was 1 Hz), and changes in storage elastic modulus G ′, loss elastic modulus G ″ and phase difference tan δ were measured at 32 points. The storage elastic modulus G ′ is a constant value in the first linear viscoelastic region, but changes thereafter. The relationship between the stress value and the storage elastic modulus G ′ and the loss elastic modulus G ″ is shown in a graph, and the stress value at the point where the storage elastic modulus G ′ and the loss elastic modulus G ″ intersect is read to obtain the yield stress.

<Image quality>
The developing roller produced was incorporated in an electrophotographic process cartridge (nominal life 6000 sheets, A4 size, printing rate 5%) of an image forming apparatus “HP Color LaserJet 3700” (trade name, manufactured by HP). This process cartridge was filled with black, cyan, magenta or yellow toner. In this state, place it at 30 ° C., 85% RH or 15 ° C., 10% RH for 24 hours or more, set it in the image forming apparatus in the same environment as the storage temperature of the process cartridge, and in that environment (solid image and halftone Image). The obtained image was visually observed, and the state of scattering (toner scattering level) was evaluated according to the following criteria.

  A: The overall image is good in any environment.

  B: Slight scattering is confirmed, but there is no practical problem.

  C: An image with severe scattering is observed.

  D: Image defects due to roller physical properties such as lateral stripes and density reduction are observed.

  Table 1 shows carbon blacks used in the following examples and comparative examples. In addition, an average primary particle size shows a manufacturer catalog value.

[Example 1]
(Preparation of silicone rubber composition)
The following materials were blended as silicone rubber to obtain a silicone rubber composition.

Molecular chain both-end vinyl group-capped dimethylpolysiloxane (vinyl group content 0.15 mass%) 100 parts by mass Molecular chain both-end trimethylsiloxy group-capped dimethylsiloxane-methylhydrogensiloxane copolymer (crosslinking agent, bonded to Si atom H content 0.30 mass%) 1.5 mass parts Complex of chloroplatinic acid and divinyltetramethyldisiloxane (platinum content 0.5 mass%) 0.5 mass parts 1-ethyl-1-cyclohexanol 0.04 parts by mass Carbon black CB-1 (Table 1) 7.5 parts by mass The yield stress of this silicone rubber composition was 84 Pa.

(Creation of conductive roller)
An iron shaft core having an outer diameter of φ6 mm is vertically placed on the shaft core body holding shafts (the shaft core upper holding shaft 10 and the shaft core lower holding shaft 9) of the ring coating machine having the ring type coating head shown in FIG. I set it. At this time, the clearance between the shaft core 102 and the nozzle of the ring-shaped coating head 38 having an inner diameter of 12.0 mm was set to 3.0 mm.

  The shaft core body was moved by vertically raising the shaft core body holding shaft (60 mm / sec). Accordingly, the silicone rubber composition is discharged at 5040 ml / sec to form a cylindrical (roll-shaped) layer made of the silicone rubber composition on the outer periphery of the shaft core body, thereby having an uncured molded product layer. A roller (hereinafter, uncured roller) was prepared.

  This uncured roller is rotated at 60 rpm around the shaft core body, and infrared light (output 1000 W) is applied to the surface of the uncured molded product layer using an infrared heating lamp “HYL25” (trade name) manufactured by Hibeck Co., Ltd. Irradiate for 4 minutes to cure. Note that the distance between the surface of the molded product layer and the lamp during infrared irradiation was 60 mm, and the temperature of the molded product layer surface was 200 ° C. Thereafter, the physical properties of the conductive rubber layer of the cured silicone rubber are stabilized, and the reaction residue and unreacted low molecular components in the conductive rubber layer of the silicone rubber are removed at 200 ° C. for 4 hours in an electric furnace. Was subjected to secondary curing to obtain a conductive roller 1. On the other hand, rubber pieces were collected from the conductive rubber layer of the conductive roller 1 and the combustion start temperature and rubber density of carbon black were measured.

(Production roller development)
Methyl ethyl ketone (MEK) was added to the following materials and dispersed with a sand mill for 1 hour.

Mitsui Takeda Chemical Co., Ltd. polyurethane polyol prepolymer “Takelac TE5060” (trade name) 100 parts by mass Nippon Polyurethane Co., Ltd. isocyanate “Coronate 2521” (trade name) 77 parts by mass Mitsubishi Chemical Corporation carbon black “MA100” (product) Name) 24 parts by mass After dispersion, MEK was further added to adjust the film thickness after coating and drying to 20 μm within a range of 20% by mass to 30% by mass of solid content to obtain a coating material for the surface layer.

  The conductive roller 1 was immersed in this paint, applied to the surface layer, and then naturally dried. Next, a heat treatment was performed at 140 ° C. for 60 minutes to cure the paint film and obtain a developing roller 1 having a surface layer formed thereon.

  The developed developing roller 1 was incorporated into a developing device, and this developing device was incorporated into an electrophotographic process cartridge to output an image for evaluation.

[Example 2]
A silicone rubber composition was prepared in the same manner as in Example 1 except that the amount of carbon black CB-1 used was 9.3 parts by mass. Hereinafter, in the same manner as in Example 1, the conductive roller 2 and the developing roller 2 were used. Was made. The evaluation was performed in the same manner as in Example 1.

Example 3
A silicone rubber composition was prepared in the same manner as in Example 1 except that the amount of carbon black CB-1 used was 20.5 parts by mass. Hereinafter, in the same manner as in Example 1, the conductive roller 3 and the developing roller 3 were used. Was made. The evaluation was performed in the same manner as in Example 1.

Example 4
The amount of carbon black CB-1 used is 10.6 parts by mass, and further, 0.6 parts by mass of silica “Nipsil E-220A” (trade name, average particle size 1.7 μm) manufactured by Tosoh Silica Co., Ltd. is blended. A silicone rubber composition was prepared in the same manner as in Example 1. In the same manner as in Example 1, the conductive roller 4 and the developing roller 4 were produced. The evaluation was performed in the same manner as in Example 1.

Example 5
The amount of carbon black CB-1 used was 11.0 parts by mass, and further, 0.1 part by mass of silica “Nipsil E-220A” (trade name, average particle size 1.7 μm) manufactured by Tosoh Silica Co., Ltd. was blended. A silicone rubber composition was prepared in the same manner as in Example 1. Further, hereinafter, the conductive roller 5 and the developing roller 5 were produced in the same manner as in Example 1. The evaluation was performed in the same manner as in Example 1.

Example 6
A silicone rubber composition was prepared in the same manner as in Example 1 except that 7.5 parts by mass of carbon black CB-2 (Table 1) was used as carbon black. 6 and the developing roller 6 were produced. The evaluation was performed in the same manner as in Example 1.

Example 7
As a carbon black, a silicone rubber composition was prepared in the same manner as in Example 1 except that 9.3 parts by mass of carbon black CB-2 was used. Hereinafter, in the same manner as in Example 1, the conductive roller 7 and the developing roller 7 was produced. The evaluation was performed in the same manner as in Example 1.

Example 8
A silicone rubber composition was prepared in the same manner as in Example 1 except that 20.5 parts by mass of carbon black CB-2 was used as carbon black. Hereinafter, in the same manner as in Example 1, the conductive roller 8 and the developing roller 8 was produced. The evaluation was performed in the same manner as in Example 1.

Example 9
As carbon black, 8.3 parts by mass of carbon black CB-2 was used, and further, 0.4 part by mass of silica “Nipsil E-220A” (trade name, average particle size 1.7 μm) manufactured by Tosoh Silica Co., Ltd. A silicone rubber composition was prepared in the same manner as in Example 1 except that. Thereafter, the conductive roller 9 and the developing roller 9 were produced in the same manner as in Example 1. The evaluation was performed in the same manner as in Example 1.

Example 10
A silicone rubber composition was prepared in the same manner as in Example 1 except that 7.5 parts by mass of carbon black CB-3 (Table 1) was used as the carbon black. 10 and the developing roller 10 were produced. The evaluation was performed in the same manner as in Example 1.

Example 11
As the carbon black, a silicone rubber composition was prepared in the same manner as in Example 1 except that 9.3 parts by mass of carbon black CB-3 was used. Hereinafter, in the same manner as in Example 1, the conductive roller 11 and the developing roller 11 was produced. The evaluation was performed in the same manner as in Example 1.

Example 12
A silicone rubber composition was prepared in the same manner as in Example 1 except that 20.5 parts by mass of carbon black CB-3 was used as carbon black. Hereinafter, in the same manner as in Example 1, the conductive roller 12 and the developing roller 12 was produced. The evaluation was performed in the same manner as in Example 1.

Example 13
As carbon black, 10.6 parts by mass of carbon black CB-3 was used. In addition, U.I. S. A silicone rubber composition was prepared in the same manner as in Example 1 except that 0.6 part by mass of silica powder “Min-U-Sil 5” (trade name, average particle size 5 μm) manufactured by Silica Company was blended. In the same manner as in Example 1, the conductive roller 13 and the developing roller 13 were produced. The evaluation was performed in the same manner as in Example 1.

Example 14
As carbon black, 10.6 parts by mass of carbon black CB-3 was used, and ZnO “Zinc Hana No. 1” (trade name) 0.6 parts by mass manufactured by Toho Zinc Co., Ltd. was further added. A silicone rubber composition was prepared. In the same manner as in Example 1, the conductive roller 14 and the developing roller 14 were produced. The evaluation was performed in the same manner as in Example 1.

Example 15
A silicone rubber composition was prepared in the same manner as in Example 1 except that the amount of carbon black CB-1 used was 9.3 parts by mass. Subsequently, the obtained silicone rubber composition was poured into a mold in which a shaft core was previously disposed and preheated to 100 ° C. Next, the mold was heated, and the injected silicone rubber was cured by heating at 150 ° C. for 30 minutes. After cooling and demolding, secondary curing at 200 ° C. for 4 hours was further performed to obtain a conductive roller 15. Further, a developing roller 15 was produced in the same manner as in Example 1. The evaluation was performed in the same manner as in Example 1.

[Comparative Example 1]
A silicone rubber composition was prepared in the same manner as in Example 1 except that the amount of carbon black CB-2 used was 5.3 parts by mass. Hereinafter, in the same manner as in Example 1, the conductive roller C1 and the developing roller C1 were formed. Produced. The evaluation was performed in the same manner as in Example 1.

[Comparative Example 2]
A silicone rubber composition was prepared in the same manner as in Example 1 except that the amount of carbon black CB-3 used was 25.0 parts by mass. Hereinafter, the conductive roller C2 and the developing roller C2 were formed in the same manner as in Example 1. Produced. The evaluation was performed in the same manner as in Example 1.

[Comparative Example 3]
As carbon black, 11.2 parts by mass of carbon black CB-3 was used, and 1.1 parts by mass of silica “Nipsil E-220A” (trade name, average particle size 1.7 μm) manufactured by Tosoh Silica Co., Ltd. A silicone rubber composition was prepared in the same manner as in Example 1 except that. In the same manner as in Example 1, a conductive roller C3 and a developing roller C3 were produced. The evaluation was performed in the same manner as in Example 1.

[Comparative Example 4]
A silicone rubber composition was prepared in the same manner as in Example 1 except that 9.3 parts by mass of carbon black CB-4 (Table 1) was used as the carbon black. C4 and developing roller C4 were produced. The evaluation was performed in the same manner as in Example 1.

[Comparative Example 5]
A silicone rubber composition was prepared in the same manner as in Example 1 except that 9.3 parts by mass of carbon black CB-5 (Table 1) was used as the carbon black. C5 and developing roller C5 were produced. Other evaluations were performed in the same manner as in Example 1.

[Comparative Example 6]
The amount of carbon black CB-1 used was 18.8 parts by mass, and silicone was added in the same manner as in Example 1 except that 6.3 parts by mass of ZnO “Zinc Hana 1” (trade name) manufactured by Toho Zinc Co., Ltd. was blended. A rubber composition was prepared. In the same manner as in Example 1, a conductive roller C6 and a developing roller C6 were produced. The evaluation was performed in the same manner as in Example 1.

[Comparative Example 7]
A silicone rubber composition was prepared in the same manner as in Example 1 except that the chloroplatinic acid was changed to Pd (PPh ₃ ) ₄ and blended (Pd content: 0.5 mass%). In the same manner as in Example 1, a conductive roller C7 and a developing roller C7 were produced. The evaluation was performed in the same manner as in Example 1.

  Table 2 and Table 3 show the filler composition and evaluation results.

* 1 Carbon black particle size obtained by particle size measurement method * 2 Content obtained by carbon black content measurement method * 3 Resistance ratio obtained by X = Log (RV2 / RV1)

It is a perspective view of an example of the conductive roller of the present invention. It is a schematic explanatory drawing of a ring coat machine. 1 is a schematic explanatory diagram of an image forming apparatus. It is explanatory drawing which calculates | requires the particle size of carbon black in this invention. It is explanatory drawing which calculates | requires the particle size of carbon black in this invention. It is a figure showing the combustion start temperature of carbon black. It is explanatory drawing which calculates | requires the carbon black ratio in this invention. It is a figure explaining the carbon black nonexistence area in the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing roller 2 Conductive shaft core 3 Conductive rubber layer 4 Conductive resin layer 5 Nonmagnetic one-component toner 6 Developing container 7 Toner supply roller 8 Developing blade 10a to d Image forming unit 11 Photosensitive drum 12 Charging device (charging roller) )
13 Image exposure device (writing beam)
14 Developing Device 15 Cleaning Device 16 Image Transfer Device (Transfer Roller)
DESCRIPTION OF SYMBOLS 17 Transfer conveyance belt 18 Drive roller 19 Tension roller 20 Driven roller 21 Adsorption roller 22 Supply roller 23 Separating device 24 Fixing device 25 Transfer material 26 Bias power supply (for image transfer device (transfer roller) 16)
27 Bias power supply (for suction roller 21)
31 stand 32 column 33 ball screw 34 LM guide 35 servo motor 36 pulley 37 bracket 38 coating head 39 shaft core lower holding shaft 40 shaft core upper holding shaft 41 supply port 42 piping 43 material supply valve 44 linear guide

Claims (10)

A conductive roller having a shaft core and a conductive rubber layer formed around the shaft core,
The conductive rubber layer contains at least silicone rubber, a platinum compound, and carbon black (A) having a particle size of 10 nm to 40 nm and a combustion start temperature of 700 ° C. to 800 ° C. as a filler,
The carbon black (A) is contained in an amount of 7.5 parts by mass or more and 20.5 parts by mass or less with respect to 100 parts by mass of the silicone rubber.
And the area equivalent ratio occupies 95% to 100% in the total filler,
And the density of the conductive rubber layer is not more than 1.01 g / cm ³ or more 1.07 g / cm ^3,
The average diameter of the circle drawn in the carbon black non-existing area in the cross section of the conductive rubber layer is 1.0 μm or more and 6.0 μm or less, and the maximum-minimum value (Max-Min) of the circle diameter is 5.0 μm or less. A conductive roller, characterized in that there is. The conductive rubber layer satisfies the following (Equation 1) when the roller resistance values (Ω) measured at 30 ° C., 80% RH, 15 ° C., and 10% RH are RV1 and RV2, respectively. The conductive roller according to 1.
−0.01 ≦ log (RV2 / RV1) ≦ 0.5 (Formula 1)   3. The conductive roller according to claim 1, wherein the silicone rubber is obtained by crosslinking and curing using an addition reaction type liquid silicone rubber as a raw material and a platinum compound as a catalyst. In a method for producing a conductive roller by providing a conductive rubber layer containing a filler around the shaft core body,
Arranging the ring-type coating head so as to be concentric with the shaft core, and moving the shaft core in the axial direction relative to the coating head;
Conductive rubber containing carbon black having a particle size of 10 nm or more and 40 nm or less and a combustion start temperature of 700 ° C. or more and 800 ° C. or less to 7.5 parts by mass or more and 20.5 parts by mass or less with respect to 100 parts by mass of silicone rubber Applying a layer material on the outer periphery of the shaft core;
The applied the conductive rubber layer material was cured by infrared heating method for manufacturing a conductive roller and a step of density to obtain a conductive rubber layer is not more than 1.01 g / cm ³ or more 1.07 g / cm ³ .   The method for producing a conductive roller according to claim 4, wherein the yield stress of the conductive rubber layer when uncured is 50 Pa or more and 600 Pa or less.   6. The method for producing a conductive roller according to claim 4, wherein the silicone rubber is obtained by crosslinking and curing using an addition reaction type liquid silicone rubber as a raw material and a platinum compound as a catalyst.   The electroconductive roller manufactured by the manufacturing method of any one of Claims 4 thru | or 6.   The conductive roller according to claim 1, wherein the conductive roller is used as a developing roller.   4. An electrophotographic process cartridge in which a developer formed in a layer on the surface of a developing roller is brought into contact with the photosensitive drum to visualize an electrostatic latent image on the surface of the photosensitive drum, wherein the developing roller comprises: 8. An electrophotographic process cartridge, which is the conductive roller according to any one of items 7 to 9.   8. The image forming apparatus for visualizing an electrostatic latent image on the surface of the photosensitive drum by bringing the developer formed in a layer on the surface of the developing roller into contact with the photosensitive drum, and the developing roller is defined in claims 1 to 3 and 7. An image forming apparatus comprising the conductive roller according to claim 1.