JP2017016035A - Conductive roll, transfer unit, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive roll that suppresses an increase in electric resistance after a repeated use.SOLUTION: A conductive roll 111 comprises: an ion conductive elastic layer 113 including a foam area 113A and a non-foam area 113B that is located in a surface layer part including an outer peripheral surface; and a surface resin layer 114 that includes polyimide or polyamide imide and a conductive agent and is arranged in contact with the outer peripheral surface of the elastic layer that is the non-foam area.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a conductive roll, a transfer unit, and an image forming apparatus.

  For example, Patent Document 1 discloses that “a rubber roller including a cored bar and an elastic body layer provided on the outer periphery thereof, wherein the elastic body layer includes a foamed rubber layer formed of a foamed rubber composition containing paraffin wax as a lubricant. Thus, a foamed rubber roller is disclosed in which the outer peripheral surface of the foamed rubber layer is vulcanized and molded using a cylindrical mold.

  Patent Document 2 states that “a base elastic layer including at least one conductive elastic layer on the outer peripheral surface of the conductive support, and a conductive surface layer provided on the outer peripheral surface of the base elastic layer; , In this order, the difference in common logarithm of the volume resistance value (Rv1) of the base elastic layer between 30 ° C. 85% RH and 10 ° C. 15% RH is 1.5 or less, Disclosed is a conductive roll characterized in that the difference in common logarithm of the volume resistance value (Rv3) of the conductive roll between 30 ° C. 85% RH and 10 ° C. 15% RH is 1.0 or less. ing.

  Patent Document 3 states that “a conductive tube is attached to the inner wall of a cylindrical mold, a core roller of a conductive roller is inserted into the cylindrical mold, and liquid rubber is injected between the core metal and the tube. In addition, there is disclosed a method for producing a conductive roller covered with a tube, wherein the liquid rubber is foamed and cured to adhere the tube inner surface and the foamed rubber.

JP 2001-74037 A JP 2004-271836 A Japanese Patent Laid-Open No. 11-223979

  The present invention has an electrical resistance when repeatedly used as compared with a conductive roll in which a surface layer portion of an elastic layer has a foam structure and a surface resin layer containing polyimide and a conductive agent is disposed on the outer peripheral surface of the elastic layer. It aims at providing the electroconductive roll by which a raise is suppressed.

  In order to achieve the above object, the following invention is provided.

The invention according to claim 1 is an ion conductive elastic layer having a foaming region and a non-foaming region located in a surface layer portion including an outer peripheral surface;
A surface resin layer that includes polyimide or polyamideimide, and a conductive agent, and is disposed in contact with an outer peripheral surface that is the non-foamed region of the elastic layer;
Conductive roll with
The invention according to claim 2 is the conductive roll according to claim 1, wherein the surface roughness Ra of the inner peripheral surface of the surface resin layer is 0.3 μm or more and 2.5 μm or less.
The invention according to claim 3 is an intermediate transfer member to which a toner image formed on the surface of the image carrier is transferred;
The conductive roll according to claim 1 or 2, which contacts the surface of the intermediate transfer member,
A transfer unit that transfers the toner image transferred onto the surface of the intermediate transfer member to a recording medium;
The invention according to claim 4 is an image holding member,
Charging means for charging the image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
Developing means for developing, as a toner image, an electrostatic charge image formed on the image carrier with an electrostatic charge image developer containing toner;
An intermediate transfer member to which the toner image formed on the surface of the image carrier is transferred;
Primary transfer means for primarily transferring the toner image formed on the surface of the image carrier to the surface of the intermediate transfer member;
3. The secondary transfer roll in contact with the surface of the intermediate transfer member includes the conductive roll according to claim 1, and the toner image transferred onto the surface of the intermediate transfer member is subjected to secondary transfer onto a recording medium. Secondary transfer means,
Fixing means for fixing the toner image transferred to the recording medium;
An image forming apparatus.

According to the invention of claim 1, the surface layer portion of the elastic layer has a foamed structure, and is repeatedly used compared to a conductive roll in which a surface resin layer containing polyimide and a conductive agent is disposed on the outer peripheral surface of the elastic layer. An electrically conductive roll is provided in which an increase in electrical resistance is suppressed.
According to the invention which concerns on Claim 2, compared with the case where surface roughness Ra of the inner peripheral surface of the said surface resin layer exceeds 0.3 micrometer, the electroconductive roll by which the cleaning defect of an outer peripheral surface is suppressed is provided.

According to the invention of claim 3, the secondary transfer roll is a conductive roll in which the surface layer portion of the elastic layer has a foamed structure, and the surface resin layer containing polyimide and a conductive agent is disposed on the outer peripheral surface of the elastic layer. As compared with the case of applying as a transfer unit, a transfer unit is provided in which occurrence of transfer failure of a toner image due to an increase in electrical resistance when repeatedly used is suppressed.
According to the invention which concerns on Claim 4, the surface layer part of an elastic layer has a foaming structure, and the electroconductive roll by which the surface resin layer containing a polyimide and a electrically conductive agent is arrange | positioned on the outer peripheral surface of an elastic layer is a secondary transfer roll. As compared with the case where it is applied as an image forming apparatus, an image forming apparatus is provided in which occurrence of transfer failure of a toner image due to an increase in electrical resistance when repeatedly used is suppressed.

It is a schematic perspective view which shows an example of a structure of the electroconductive roll which concerns on this embodiment. It is AA sectional drawing of the electroconductive roll shown in FIG. It is the schematic which expanded the cross-section part S enclosed with the dotted line of FIG. It is a schematic block diagram which shows an example of the coating device used in order to form the surface resin layer of the electroconductive roll which concerns on this embodiment. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. It is the schematic for demonstrating the measuring method of the volume electrical resistance value of the electroconductive roll (secondary transfer roll) in an Example.

  Hereinafter, an embodiment which is an example of the present invention will be described with reference to the drawings. In addition, the same code | symbol is provided to the member which has the substantially same function throughout all the drawings, and the overlapping description may be abbreviate | omitted suitably.

<Conductive roll>
The conductive roll according to the present embodiment includes an ion conductive elastic layer having a foamed region and a non-foamed region located in a surface layer portion including the outer peripheral surface, polyimide or polyamideimide, and a conductive agent, and the elasticity A surface resin layer disposed in contact with the outer peripheral surface which is the non-foamed region of the layer.
The conductive roll according to this embodiment suppresses an increase in electrical resistance when repeatedly used. The reason is presumed as follows.

  As an example of a conductive roll, for example, a secondary transfer roll in an intermediate transfer type image forming apparatus generally includes a conductive elastic layer, but toner attached to the surface of the secondary transfer roll is a recording medium. May be transferred to the back surface of the recording medium, and the back surface of the recording medium may be contaminated (hereinafter sometimes referred to as “paper back surface contamination”). In order to suppress the occurrence of contamination on the back side of the paper due to such toner transfer, a configuration in which a surface resin layer is provided on the elastic layer so that the toner adhering to the surface of the secondary transfer roll can be easily removed with a blade or the like Is done.

  However, when image formation is repeated in an image forming apparatus having a secondary transfer roll having a surface resin layer provided on an ion conductive elastic layer, transfer defects such as toner loss and toner image density reduction are likely to occur. I understood that. One cause of such transfer failure is an increase in the electrical resistance of the secondary transfer roll (hereinafter sometimes referred to as “resistance increase”). The increase in resistance of the secondary transfer roll is caused by accumulation of electric charges inside the roll. The causes of the accumulation of electric charge are as follows: (1) existence of an interface of different materials; (2) adhesion between the elastic layer and the surface resin layer. (3) Charge due to the narrower contact area between the secondary transfer roll and the opposing member (intermediate transfer member) than the diameter of the roll shaft (support) serving as the power supply source Inhibition of migration is considered. In particular, in a secondary transfer roll having an ion conductive elastic layer, charges are likely to accumulate at the interface between the elastic layer and the surface resin layer.

On the other hand, in the conductive roll according to the present embodiment, since the elastic layer and the surface resin layer are in contact with each other without an adhesive layer, there are few interfaces of dissimilar materials, and charge accumulation at the interface is suppressed. . Moreover, since the outer peripheral surface of the elastic layer is composed of a non-foamed region present in the surface layer portion, the elastic layer and the surface resin layer are in close contact without an adhesive layer.
And a wide contact area is securable between an elastic layer and a surface resin layer. Thereby, the conductive roll according to the present embodiment is considered to suppress the accumulation of electric charges at the interface between the elastic layer and the surface resin layer, and to suppress the increase in resistance when energized.

  In addition, since the elastic layer in the conductive roll according to the present embodiment has a foamed region, the surface resin layer repeats deformation with repeated deformation of the elastic layer due to contact with the opposing member, but the surface resin layer has durability. Since high polyimide or polyamideimide is included, deformation durability is high, and the occurrence of cracks in the surface resin layer can be suppressed.

  As described above, the problem that appears in the secondary transfer roll in the image forming apparatus has been described as an example. However, the conductive roll according to the present embodiment is not limited to this, and is used as, for example, a charging roll. Even in this case, an increase in resistance can be suppressed, and uneven density of an image due to charging failure can be suppressed.

FIG. 1 is a schematic perspective view illustrating an example of a configuration of a conductive roll according to the present embodiment. A conductive roll 111 shown in FIG. 1 includes a columnar or cylindrical support 112, a cylindrical elastic layer 113 provided on the outer peripheral surface of the support 112, and a surface resin provided on the elastic layer 113. A layer 114.
2 is an AA cross-sectional view of the conductive roll shown in FIG. 1, and FIG. 3 is an enlarged schematic view of a cross-sectional portion S surrounded by a dotted line in FIG.
The elastic layer 113 is ion-conductive, and has a foam region 113A and a non-foam region 113B located in the surface layer portion including the outer peripheral surface.
The surface resin layer 114 includes polyimide or polyamideimide and a conductive agent, and is disposed in contact with the outer peripheral surface which is the non-foamed region 113B of the elastic layer 113.

-Support-
The support 112 is a conductive member that functions as an electrode and a support member of the secondary transfer roll 111.
Examples of the support 112 include metal members such as iron (free-cutting steel, etc.), copper, brass, stainless steel, aluminum, nickel, and the like.
Further, examples of the support 112 include a member (for example, a resin or a ceramic member) whose outer surface is plated, a member in which a conductive agent is dispersed (for example, a resin or a ceramic member), and the like.
The support 112 may be a hollow member (cylindrical member) or a non-hollow member.

-Elastic layer-
The elastic layer 113 is a cylindrical layer having elasticity and ionic conductivity, and has a foam region 113A located on the inner peripheral surface side and a non-foam region 113B located on the surface layer portion including the outer peripheral surface.
The foam region 113A and the non-foam region (skin region) 113B are continuously formed of the same material in the elastic layer 113. The foam structure in the foam region 113A may be a closed cell structure or an open cell structure.

The elastic layer 113 includes, for example, a rubber material (elastic material), and may include an ionic conductive agent and other additives as necessary.
Examples of the rubber material (elastic material) included in the elastic layer include an elastic material having a double bond in at least a chemical structure.
Specific examples of the rubber material include, for example, isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, polyurethane, silicone rubber, fluorine rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber. , Epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), natural rubber, and rubbers obtained by mixing these.
Among these rubber materials, epichlorohydrin rubber, polyurethane, EPDM, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, NBR, and rubbers obtained by mixing them are preferable.

  The ionic conductive agent is used when the rubber material has low ionic conductivity or when the rubber material does not have ionic conductivity. In addition to the ionic conductive agent, there is an electronic conductive agent such as carbon black as the conductive agent, but the in-plane uniformity of resistance can be enhanced by using the ionic conductive agent rather than the electronic conductive agent.

Examples of the ionic conductive agent include quaternary ammonium salts (for example, lauryltrimethylammonium, stearyltrimethylammonium, octadodecyltrimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, perchlorates such as modified fatty acid and dimethylethylammonium urine, Chlorates, borofluorides, sulfates, etosulphate salts, benzyl halide salts (eg, benzyl bromide salts, benzyl chloride salts, etc.), aliphatic sulfonates, higher alcohol sulfates, higher Alcohol ethylene oxide addition sulfate ester salt, higher alcohol phosphate ester salt, higher alcohol ethylene oxide addition phosphate ester salt, various betaines, higher alcohol ethylene oxide, polyethylene glycol Fatty acid esters, polyhydric alcohol fatty acid esters.
An ionic conductive agent may be used independently and may be used in combination of 2 or more type.
The content of the ionic conductive agent is, for example, preferably in the range of 0.1 parts by weight or more and 5.0 parts by weight or less, and preferably 0.5 parts by weight or more and 3.0 parts by weight with respect to 100 parts by weight of the rubber material. It is below mass parts.

  Other additives that can be contained in the elastic layer or used for forming the elastic layer include, for example, foaming agents, foaming aids, softeners, plasticizers, curing agents, vulcanizing agents, vulcanization accelerators, and antioxidants. Examples thereof include materials that can be added to a normal elastic layer such as an agent, a surfactant, a coupling agent, a filler (silica, calcium carbonate, etc.).

The thickness of the elastic layer 113 is, for example, 5 mm or more and 20 mm or less, and desirably 5 mm or more and 15 mm or less.
The thickness of the non-foamed region 113B in the surface layer portion of the elastic layer 113 is, for example, 0.05 mm or more and 0.2 mm or less, and desirably 0.05 mm or more and 0.1 mm or less.

-Surface resin layer-
The surface resin layer 114 is a layer containing polyimide or polyamideimide and a conductive agent. The inner peripheral surface of the surface resin layer 114 is in contact with the outer peripheral surface formed by the non-foamed region 113B of the elastic layer 113.

The surface resin layer 114 contains polyimide or polyamideimide as a resin. In the conductive roll according to the present embodiment, the elastic layer 113 is repeatedly deformed due to contact with an opposing member such as an intermediate transfer member, and the surface resin layer 114 is also deformed accordingly, but the surface resin layer 114 is polyimide or polyamide. By including an imide, durability is high and generation | occurrence | production of the crack (crack) in the surface resin layer 114 can be suppressed.
The surface resin layer 114 may contain a resin other than polyimide or polyamideimide, but among the resins contained in the surface resin layer 114, it is preferable that the content of polyimide or polyamideimide is the largest, and 50% by mass or more. Is more preferably polyimide or polyamideimide.

  Examples of the conductive agent contained in the surface resin layer 114 include an electronic conductive agent and an ionic conductive agent.

Examples of the electronic conductive agent include carbon black such as ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, and stainless steel; tin oxide, indium oxide, and titanium oxide. And various conductive metal oxides such as tin oxide-antimony oxide solid solution, tin oxide-indium oxide solid solution; and the like.
The carbon black specifically includes “Special Black 350”, “Special Black 100”, “Special Black 250”, “Special Black 5”, and “Special Black” manufactured by Orion Engineered Carbons. 4 ”,“ Special Black 4A ”,“ Special Black 550 ”,“ Special Black 6 ”,“ Color Black FW200 ”,“ Color Black FW2 ”,“ Color Black FW2V ”,“ MONARCH1000 ”manufactured by Cabot Corporation "MONARCH1300" manufactured by Cabot Corporation, "MONARCH1400" manufactured by Cabot Corporation, "MOGUL-L", "REGAL400R", and the like.
An electronic conductive agent may be used independently and may be used in combination of 2 or more type.

Examples of the ionic conductive agent include quaternary ammonium salts (for example, lauryltrimethylammonium, stearyltrimethylammonium, octadodecyltrimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, perchlorates such as modified fatty acid and dimethylethylammonium urine, Chlorates, borofluorides, sulfates, etosulphate salts, benzyl halide salts (eg, benzyl bromide salts, benzyl chloride salts, etc.), aliphatic sulfonates, higher alcohol sulfates, higher Alcohol ethylene oxide addition sulfate ester salt, higher alcohol phosphate ester salt, higher alcohol ethylene oxide addition phosphate ester salt, various betaines, higher alcohol ethylene oxide, polyethylene glycol Fatty acid esters, polyhydric alcohol fatty acid esters.
An ionic conductive agent may be used independently and may be used in combination of 2 or more type.

  As the surface resin layer 114, for example, polyimide is a main component (the main component indicates that the content of polyimide in the surface resin layer exceeds 50% by mass), and a conductive agent such as carbon black is used as a conductive agent. A surface resin layer in which particles are dispersed is particularly preferably used because of its excellent mechanical strength and elasticity.

  Examples of other additives include materials that can be added to a normal resin layer such as a plasticizer, a curing agent, a softening agent, an antioxidant, and a surfactant.

Furthermore, what is necessary is just to select the thickness of the surface resin layer 114 according to the use etc. of an electroconductive roll.
When the conductive roll according to the present embodiment is used as, for example, a secondary transfer roll, it is possible to ensure surface smoothness to prevent paper backside contamination due to toner transfer, and to prevent ozone deterioration of the elastic layer 113. For the expression of the function and the wear resistance of the layer (preventing the film from disappearing and not functioning), for example, the thickness is preferably 5 μm to 60 μm, and more preferably 10 μm to 40 μm.

In addition, the conductive roll 111 has a part of the surface resin layer 114 in contact with another member, for example, an intermediate transfer body, and electrical conduction is ensured between the support 112 and the intermediate transfer body. If the surface roughness of the inner peripheral surface of 114 is large, the contact area with the outer peripheral surface (non-foamed region 113B) of the elastic layer increases, and it is easy to ensure a wide conduction path between the support 112 and the intermediate transfer member. Become. On the other hand, if the surface roughness of the inner peripheral surface of the surface resin layer 114 is too large, it is reflected in the irregularities on the outer peripheral surface of the surface resin layer 114, which may cause transfer failure and cleaning failure. From such a viewpoint, the surface roughness Ra of the inner peripheral surface of the surface resin layer 114 is preferably 0.3 μm or more and 2.5 μm or less, and more preferably 0.3 μm or more and 2.0 μm or less.
Here, the surface roughness Ra of the inner peripheral surface of the surface resin layer 114 is as follows. Surfcom 1500SD2 manufactured by Tokyo Seimitsu Co., Ltd. Measurement conditions are as follows: cutoff wavelength 0.8 mm, measurement length 3.0 mm, measurement speed 0.6 mm / s It is a measured value.

  As mentioned above, although the form of the secondary transfer roll was mainly demonstrated as an example of the electroconductive roll which concerns on this embodiment, it is not restricted to this, For example, charging rolls, primary transfer rolls, etc. which require electroconductivity Can be used as a roll.

[Method for producing conductive roll]
Although the manufacturing method of the electroconductive roll which concerns on this embodiment is not limited, For example, it can manufacture suitably with the following method.

-Formation of surface resin layer-
FIG. 4 is a schematic configuration diagram illustrating an example of a coating apparatus for forming the surface resin layer 114. In this coating apparatus, a nozzle 92 for discharging the coating liquid 80 onto the outer peripheral surface of the cylindrical mold 91 is disposed at a position along the outer peripheral surface of the cylindrical mold 91. The nozzle 92 is connected to the coating liquid container 93 through a pipe, and the coating liquid container 93 is connected to the pressurizing device 94 through another pipe. A blade 95 for leveling the discharged coating solution 80 on the outer peripheral surface of the cylindrical mold 91 is disposed below the nozzle 92.

First, a coating solution containing a polyimide precursor or a polyamideimide resin, a conductive agent, a solvent and the like as a resin material is prepared. In the coating solution 80, a conductive agent in an amount corresponding to the surface resistivity required for the surface resin layer is dissolved or dispersed. As a dispersion method, a known method such as a jet mill, a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, or a paint shaker may be used.
The solvent is selected according to the resin material. The solid content concentration of the coating liquid 80 may be, for example, 10 mass% or more and 40 mass% or less, and the viscosity may be 1 Pa · s or more and 100 Pa · s or less.

Also, a cylindrical mold 91 having an outer diameter corresponding to the inner diameter of the surface resin layer 114 (the outer diameter of the elastic layer 113) is prepared. For example, a release agent such as a silicone-based release agent is applied to at least the outer peripheral surface of the cylindrical mold 91 and subjected to a baking treatment to form a release agent layer on the surface.
In order to roughen the inner peripheral surface side of the surface resin layer, the outer peripheral surface of the mold 91 may be roughened before the release agent is applied to the outer peripheral surface of the mold 91. Examples of the roughening method include blasting, cutting, sandpaper peeling, and the like.

  The coating liquid 80 is applied to the cylindrical mold 91 having the release agent layer by the above-described coating apparatus. Specifically, the cylindrical mold 91 is rotated in the direction of the rotation of the cylindrical mold (arrow D), the coating liquid 80 is discharged from the nozzle 92 onto the outer peripheral surface of the cylindrical mold 91, and the blade 95. Level on the outer peripheral surface of the cylindrical mold 91. The nozzle 92 and the blade 95 move at a constant speed in the nozzle and blade movement direction (arrow E), and the coating liquid 80 is applied on the outer peripheral surface of the cylindrical mold 91 with a constant thickness. The coating solution 80 is adjusted so as to be discharged from the nozzle 92 by a pressurizing device 94. Thereby, the coating film of the coating liquid 80 is formed on the outer peripheral surface of the cylindrical mold 91. The thickness of the member constituting the surface resin layer 114 obtained is adjusted by the discharge amount of the coating liquid 80, the moving speed of the nozzle 92 and the blade 95, and the solid content concentration of the coating liquid 80.

Subsequently, the coating film of the coating solution 80 is dried by heating, further cooled, and then peeled off from the cylindrical mold 91, and the end portion is cut according to the target roll width, thereby forming the surface resin layer 114. A tubular member is obtained.
When a polyimide precursor is used as the resin material of the coating solution 80, after forming a coating film of the coating solution 80 on the outer peripheral surface of the cylindrical mold 91, the solvent is removed by drying at 80 ° C to 170 ° C. The polyimide film is formed by removing (drying process) and further imide conversion (baking process) by heating to 200 ° C. or higher and 350 ° C. or lower. After cooling, the polyimide film is peeled off from the cylindrical mold 91 and cut to a width corresponding to the width of the elastic layer 113, which may be referred to as a tubular member constituting the surface resin layer 114 (hereinafter referred to as “coated tube”). .)
Note that, by roughening the outer peripheral surface of the mold 91, a coated tube having an inner peripheral surface reflecting the surface roughness Ra of the mold is obtained.

-Formation of elastic layer-
A mixture containing a rubber material and, if necessary, an ionic conductive agent and other additives is kneaded and wound around a support (shaft) 112.
On the other hand, a cylindrical mold having an inner diameter corresponding to the outer diameter of the coated tube manufactured as described above is prepared, and after inserting the coated tube inside the mold, a shaft wound with the kneaded material is inserted. . By heating in this state, the kneaded material around the shaft is vulcanized and foamed. Thereby, a foam roll in which the surface resin layer is disposed on the outer peripheral surface of the elastic layer is produced, and then both ends of the roll are cut to obtain a conductive roll.
The conductive roll manufactured by such a method provides a conductive roll in which the outer layer surface of the elastic layer is a non-foamed region and the outer peripheral surface, which is the non-foamed region of the elastic layer, and the inner peripheral surface of the surface resin layer are in close contact. It is done.

<Transfer unit and image forming apparatus>
The transfer unit according to the present embodiment includes an intermediate transfer member to which a toner image formed on the surface of the image holding member is transferred, the conductive roll according to the above-described embodiment in contact with the surface of the intermediate transfer member, And a transfer unit that transfers the toner image transferred to the surface of the intermediate transfer member to a recording medium.

  The image forming apparatus according to the present embodiment includes an image carrier, a charging unit that charges the image carrier, an electrostatic image forming unit that forms an electrostatic image on the surface of the charged image carrier, A developing means for developing the electrostatic image formed on the image carrier as a toner image by an electrostatic image developer containing toner, and an intermediate where the toner image formed on the surface of the image carrier is transferred The transfer body, the primary transfer means for primarily transferring the toner image formed on the surface of the image holding body to the surface of the intermediate transfer body, and the book described above as the secondary transfer roll in contact with the surface of the intermediate transfer body A secondary transfer unit that includes the conductive roll according to the embodiment and that secondary-transfers the toner image transferred to the surface of the intermediate transfer member to a recording medium, and fixes the toner image transferred to the recording medium And an image shape having fixing means It is a device.

Hereinafter, the transfer unit and the image forming apparatus according to the present embodiment will be described with reference to FIG. Here, FIG. 5 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment.
The image forming apparatus shown in FIG. 5 is an intermediate transfer type apparatus in which a secondary transfer unit includes a transfer unit (a transfer unit according to this embodiment) including a conductive roll according to this embodiment.

Specifically, as shown in FIG. 5, the image forming apparatus according to the present embodiment includes yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data. Electrophotographic first to fourth image forming units 10Y, 10M, 10C, and 10K (an example of an image forming unit) that output an image of each color are provided. These image forming units (hereinafter sometimes simply referred to as “units”) 10Y, 10M, 10C, and 10K are arranged in parallel at a predetermined distance from each other in the horizontal direction.
The units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the image forming apparatus.

Above each of the units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 20 (an example of an intermediate transfer member) is provided to extend through each unit. The intermediate transfer belt 20 is provided by being wound around a driving roller 22 and a back roll 24 that is in contact with the inner surface of the intermediate transfer belt 20 that are spaced apart from each other from the left to the right in the drawing. The vehicle travels in the direction toward the unit 10K. The back roll 24 is applied with a force in a direction away from the drive roller 22 by a spring or the like (not shown), and tension is applied to the intermediate transfer belt 20 wound around both. An intermediate transfer member cleaning device 30 is provided on the outer peripheral surface of the intermediate transfer belt 20 so as to face the drive roller 22.
Each of the developing devices 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K has four colors of yellow, magenta, cyan, and black contained in the toner cartridges 8Y, 8M, 8C, and 8K. Toner is supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K described above have the same configuration, here, the first image that forms the yellow image disposed on the upstream side in the intermediate transfer belt traveling direction is formed. The unit 10Y will be described as a representative. It should be noted that reference numerals with magenta (M), cyan (C), and black (K) are attached to the same parts as those of the first unit 10Y instead of yellow (Y). Description of the units 10M, 10C, and 10K will be omitted.

The first unit 10Y has a photoreceptor 1Y (an example of an image holding member). Around the photoreceptor 1Y, a charging device 2Y (for example, a charging roll: an example of a developing unit) that charges the surface of the photoreceptor 1Y to a predetermined potential, a laser based on an image signal obtained by color-separating the charged surface. An exposure device 3 (an example of an electrostatic charge image forming unit) that forms an electrostatic charge image by exposure with light rays 3Y, and a developing device 4Y (an example of a development unit) that supplies toner charged to the electrostatic charge image to develop the electrostatic charge image ), A primary transfer roll 5Y (an example of a primary transfer unit) that transfers the developed toner image onto the intermediate transfer belt 20, and a photoreceptor cleaning device 6Y (cleaning) that removes toner remaining on the surface of the photoreceptor 1Y after the primary transfer. An example of means) is arranged in order.
The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20, and is provided at a position facing the photoreceptor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C, and 5K. Each bias power source varies the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described. First, prior to the operation, the surface of the photoreceptor 1Y is charged to a potential of about −600V to −800V by the charging device 2Y.
The photoreceptor 1Y is formed by laminating a photosensitive layer on a conductive substrate (volume resistivity at 20 ° C .: 1 × 10 ⁻⁶ Ωcm or less). This photosensitive layer usually has a high resistance (a resistance equivalent to that of a general resin), but has a property that the specific resistance of the portion irradiated with the laser beam changes when irradiated with the laser beam 3Y. Therefore, a laser beam 3Y is output to the surface of the charged photoreceptor 1Y via the exposure device 3 in accordance with yellow image data sent from a control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image of a yellow print pattern is formed on the surface of the photoreceptor 1Y.

The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flows. On the other hand, this is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the laser beam 3Y.
The electrostatic charge image formed on the photoreceptor 1Y in this way is rotated to a predetermined development position as the photoreceptor 1Y travels. At this development position, the electrostatic charge image on the photoreceptor 1Y is visualized (developed image) by the developing device 4Y.

  In the developing device 4Y, for example, an electrostatic charge image developer containing at least yellow toner and a carrier is accommodated. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as the charged charge on the photoreceptor 1Y, and a developer roll (developer holder). Is held on. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. . The photoreceptor 1Y on which the yellow toner image is formed continues to run at a predetermined speed, and the toner image developed on the photoreceptor 1Y is conveyed to a predetermined primary transfer unit.

When the yellow toner image on the photoreceptor 1Y is conveyed to the primary transfer, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoreceptor 1Y toward the primary transfer roll 5Y is applied to the toner image, so that the photoreceptor is exposed. The toner image on 1Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a (+) polarity opposite to the polarity (−) of the toner. For example, in the first unit 10Y, it is controlled to about +10 μA by the control unit (not shown).
On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the cleaning device 6Y.

Further, the primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K after the second unit 10M is also controlled in accordance with the first unit.
Thus, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in a multiple manner. The

  The intermediate transfer belt 20 onto which the four color toner images have been transferred through the first to fourth units is arranged on the image transfer surface side of the intermediate transfer belt 20, the rear roll 24 in contact with the inner surface of the intermediate transfer belt 20. The secondary transfer roll 26 (an example of a secondary transfer unit, the conductive roll according to the present embodiment) thus formed reaches a secondary transfer portion.

On the other hand, the recording paper P (an example of a recording medium) is fed at a predetermined timing into a gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are pressed through the supply mechanism, and the secondary transfer bias is applied. Applied to the back roll 24. The transfer bias applied at this time is a (−) polarity that is the same polarity as the polarity (−) of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P is applied to the toner image, and the transfer bias is applied to the intermediate transfer belt 20. The toner image is transferred onto the recording paper P. The secondary transfer bias at this time is determined in accordance with the resistance detected by a resistance detecting means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.
After the transfer, the surface of the secondary transfer roll 26 is cleaned by a blade (not shown).

  The recording paper P is sent to the contact portion (nip portion) of the pair of fixing rolls in the fixing device 28 (an example of the fixing unit), the toner image is heated, and the color-superposed toner image is melted. Established.

  Examples of the recording paper (recording medium) P to which the toner image is transferred include plain paper used in electrophotographic copying machines, printers, and the like. In addition to the recording paper P, an OHP sheet or the like may be applied as a recording medium.

  The recording paper P on which the color image has been fixed is unloaded to the discharge unit, and a series of color image forming operations is completed.

  The image forming apparatus according to the present embodiment is not limited to the above configuration, and may include a known intermediate transfer type image as long as it includes a transfer unit including the conductive roll according to the present embodiment (transfer unit according to the present embodiment). A forming device is applied.

Further, in the above configuration, the image forming apparatus in which the conductive roll according to the present embodiment is adopted as the secondary transfer roll is shown, but the conductive roll according to the present embodiment may be adopted as the primary transfer roll. .
Furthermore, the conductive roll according to the present embodiment is not limited to the intermediate transfer type image forming apparatus, and may be applied to a well-known direct transfer type image forming apparatus.
Further, the conductive roll according to the present embodiment may be employed as the charging roll 2.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
In the following, “part” and “%” are based on mass unless otherwise specified.

  The following coated tube was produced as the surface resin layer used in the examples.

[Preparation of coated tube 1]
N-methyl-2-pyrrolidone (NMP) solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (the solid content ratio after imide conversion is 18 mass%) with respect to 100 mass parts of solid content of polyamic acid, carbon black (Special Black 4: manufactured by Orion Engineered Carbons) was added to 80 mass parts. Using a jet mill disperser (Geanus PY [minimum cross-sectional area of collision part: 0.032 mm ² ]: manufactured by Genus Co., Ltd.), the dispersion unit part was dispersed and mixed by passing the dispersion unit part 5 times at a pressure of 200 MPa. )
An NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (solid after imide conversion) was added to the resulting dispersion (A). 18% by mass) is added so that carbon black is 27 parts by mass with respect to 100 parts by mass of polyamic acid, and mixed and stirred using a planetary mixer (Aiko Mixer: manufactured by Aikosha Seisakusho). Thus, a carbon black-dispersed polyimide precursor solution was prepared.

  An aluminum cylinder having an outer diameter of 28 mm, a length of 500 mm, and a thickness of 6 mm was prepared as a mold. The aluminum cylinder is roughened to a surface roughness Ra of 0.35 μm on the outer peripheral surface by blasting with spherical glass particles. The surface roughness Ra of the outer peripheral surface of the mold was measured with Surfcom 1500SD2.

Then, the cylindrical body made from aluminum which applied the silicone type mold release agent (brand name: KS700, Shin-Etsu Chemical Co., Ltd. product) to the outer peripheral surface, and performed the baking process at 300 degreeC for 1 hour was used.
The aluminum cylinder was rotated at 50 rpm, and the carbon black-dispersed polyimide precursor solution was applied to the outer peripheral surface of the cylinder to a thickness of 0.625 mm via a dispenser.
The cylindrical body coated with the carbon black-dispersed polyimide precursor solution on the outer peripheral surface is horizontally dried while being rotated at 6 rpm, and heated and dried at 60 ° C. for 25 minutes and 120 ° C. for 40 minutes to obtain a carbon black-dispersed polyimide precursor dried film. Obtained.
Subsequently, the dried film was heated at 200 ° C. for 30 minutes, 260 ° C. for 30 minutes, 300 ° C. for 30 minutes, and 320 ° C. for 20 minutes to form a carbon black-dispersed polyimide film. The coated tube 1 was obtained by cutting to a width of 410 mm.
When the surface roughness Ra of the inner peripheral surface of the coated tube 1 was measured, it was the same as the surface roughness of the outer peripheral surface of the mold.

[Preparation of coated tube 2]
Carbon black was prepared in the same manner as in the production of the coated tube 1 except that an aluminum cylinder roughened to a surface roughness Ra: 2.0 μm was used by changing the blast treatment with spherical glass particles on the outer peripheral surface of the cylinder. A dispersed polyimide film was formed to obtain a coated tube 2.

[Preparation of coated tube 3]
Carbon black was prepared in the same manner as for the coated tube 1 except that an aluminum cylinder whose surface roughness Ra was roughened to 3.0 μm was used by changing the blasting treatment with the spherical glass particles on the outer peripheral surface of the cylinder. A dispersed polyimide film was formed to obtain a coated tube 3.

[Preparation of coated tube 4]
Solvent-soluble polyamideimide resin (HPC-9000 manufactured by Hitachi Chemical Co., Ltd., solid content 18%, solvent: n-methyl-2-pyrrolidone) and carbon black (FW1, manufactured by Orion Engineered Carbons, primary particle size 13 nm) Was added 5 times using a high-pressure collision type disperser (manufactured by Genus Co., Ltd.) and passed through an orifice of φ0.1 mm at 200 MPa and collided with two divided slurries. A high-viscosity polyamideimide varnish was added to this dispersion with stirring so that the blending amount of carbon black was 20 parts by mass with respect to 100 parts by mass as a whole, to obtain a coating liquid (B).
The coating liquid (B) was applied to the outer peripheral surface (Ra: 0.35 μm) of the aluminum cylindrical body in the same manner as the production of the coated tube 1 and subjected to rotary drying at 120 ° C. for 20 minutes (drying step). Next, the solvent was removed in a furnace in which the first stage temperature was 130 ° C. for 20 minutes, the second stage temperature was 175 ° C. for 20 minutes, the third stage temperature was 220 ° C. for 20 minutes, and the fourth stage temperature was 250 ° C. for 20 minutes. Then, a resin film (B) was formed and cut into a width of 410 mm to obtain a coated tube 4.

<Example 1>
60 parts by mass of epichlorohydrin rubber (ECO: epichromer CG-102: manufactured by Daiso Corporation) having high ion conductivity and 30 parts by mass of acrylonitrile-butadiene rubber (NBR: Nipol DN-219: manufactured by Nippon Zeon Co., Ltd.) are mixed and sulfur ( 1 part by mass of Tsurumi Chemical Co., Ltd. (200 mesh), 1 part by mass, 1.5 parts by mass of a vulcanization accelerator (Noxera-M, manufactured by Ouchi Shinsei Chemical Co., Ltd.), and 6 parts by mass of benzenesulfonyl hydrazide as a foaming agent were added. The mixture obtained by kneading this mixture with an open roll was wound around a SUS shaft having a diameter of 12 mm and a length of 440 mm with a width of 410 mm so that the outer diameter was approximately 20 mm.

A cylindrical mold having an inner diameter of 28 mm and a length of 410 mm was prepared. After inserting the coated tube 1 inside this mold, a SUS shaft around which the kneaded material was wound was inserted, and the entire mold was heated at 160 ° C. Thus, the kneaded material around the shaft was vulcanized and foamed to form an elastic layer, and a foam roll having a surface resin layer having an outer diameter of 28 mm was produced. Subsequently, 5 mm of both ends of the roll were cut into a conductive roll.
By observing the cross section of the cut portion, the surface layer portion other than the surface layer portion was a foam, and the outer peripheral surface of the non-foamed region located in the surface layer portion of the elastic layer was in close contact with the inner peripheral surface of the surface resin layer.

<Example 2>
A conductive roll was produced in the same manner as in Example 1 except that the coated tube 2 was used as the surface resin layer.

<Example 3>
A conductive roll was produced in the same manner as in Example 1 except that the coated tube 4 was used as the surface resin layer.

<Example 4>
A conductive roll was produced in the same manner as in Example 1 except that the coated tube 3 was used as the surface resin layer.

<Comparative Example 1>
The kneaded material used in the production of the elastic layer of Example 1 was wound around a SUS shaft having a diameter of 12 mm and a length of 440 mm with a width of 410 mm and vulcanized and foamed at 160 ° C. The outer circumference of the produced roll was polished with a polishing machine to obtain a foamed rubber roll having an outer diameter of 28 mm.
A foamed rubber roll was inserted while air was fed into the coated tube 1 to produce a conductive roll having a surface resin layer.

<Comparative example 2>
Polyurethane urethane resin N, N-dimethylformamide solution (solid content 30%, trade name KK124, manufactured by Dainichi Seika Co., Ltd.) 100 parts by mass, N, N-dimethylformamide 250 parts by mass, methyl ethyl ketone 50 parts by mass 12 parts by mass of carbon black # 3030B (manufactured by Mitsubishi Chemical Corporation) was added to the resin diluent, and dispersed with a bead mill.
This dispersion was applied to the outer peripheral surface of a foam rubber roll produced in the same manner as in Comparative Example 1 by spraying and dried at 160 ° C. for 90 minutes to produce a conductive roll.

[Evaluation]
The conductive roll produced in each example was used as a secondary transfer roll in a secondary transfer type image forming apparatus, and an increase in electrical resistance before and after continuous printing and paper backside contamination after printing were evaluated.

<Measurement of volumetric electrical resistance>
In a state where the secondary transfer roll and the back roll were pressed against each other with a load of 5 kg, an evaluation device was prepared in which a Trek Japan 610E power source was connected between both rolls.
In this evaluation apparatus, the voltage was set to a current that would flow 100 μA between both rolls, energization was performed at a constant voltage, and the secondary transfer roll was driven to rotate at a rotational speed of 175 rpm for 10 hours. The test was conducted in a low-temperature and low-humidity environment at 10 ° C. and 30%.
The volume electrical resistance value of the secondary transfer roll after the 10-hour rotation energization test and the volume electrical resistance value of the secondary transfer roll before the energization test are each expressed in common logarithm, and the difference is calculated. The amount of resistance increase was determined.
Here, a measuring method of the volume electric resistance value will be described with reference to FIG.
As shown in FIG. 6, a secondary transfer roll (conductive roll) 60 is placed on a metal plate 70, and a temperature of 22 ° C. is applied with a load of 500 g applied to the locations indicated by arrows A1 and A2 on both ends of the cored bar 50. In an environment where the humidity is 55% RH, an applied voltage of 1000 V is applied between the metal core 50 and the metal plate 70, and the current value I (A) after 10 seconds is read. According to the equation “R = V / I” The volume resistance value (R) was calculated. This measurement and calculation were performed for four points by rotating the secondary transfer roll (conductive roll) 60 by 90 ° in the circumferential direction, and the average value was defined as the volume resistance value (R) of the secondary transfer roll.

<Stain on back side of paper>
The conductive roll produced in each example is used as a secondary transfer roll in a modified machine of Fuji Xerox Co., Ltd., trade name: DocuCentre-II C6500, and 200 × 1000 sheets of JD coated 157 gsm paper (A3) made by Fuji Xerox are supplied. Printed on paper. For every 10,000 printed sheets, 50% Magenta halftone is printed on a paper with a 40 mm × 40 mm hole, and a toner image is formed on the secondary transfer roll. The presence / absence (stain on the back side of the paper) of adhesion (toner cleaning performance on the secondary transfer roll) was visually evaluated according to the following criteria.
A: No toner adhered to the back side of the paper.
B: Toner adhered to the edge of the paper in the width direction.
C: Toner adhered to the entire width direction of the paper.

Table 1 shows the elastic layer of the conductive roll, the surface resin layer, and the evaluation results.
In addition, the conductive roll of the comparative example 2 was confirmed to be cracked after printing, and the durability was inferior to the conductive roll of the example.

1, 1Y, 1M, 1C, 1K photoconductor 2, 2Y, 2M, 2C, 2K charging roll 3L, 3Y, 3M, 3C, 3K laser beam 3 exposure device 4Y, 4M, 4C, 4K developing device 5Y, 5M, 5C 5K Primary transfer rolls 6Y, 6M, 6C, 6K Cleaning devices 8Y, 8M, 8C, 8K Toner cartridges 10Y, 10M, 10C, 10K Image forming unit 20 Intermediate transfer belt 22 Drive roll 24 Back roll 26 Secondary transfer roll 28 Fixing Device 30 Intermediate transfer member cleaning device 111 Conductive roll 112 Support member 113 Elastic layer 113A Foamed region 113B Non-foamed region 114 Surface resin layer P Recording medium

Claims (4)

An ion conductive elastic layer having a foamed region and a non-foamed region located in a surface layer portion including an outer peripheral surface;
A surface resin layer that includes polyimide or polyamideimide, and a conductive agent, and is disposed in contact with an outer peripheral surface that is the non-foamed region of the elastic layer;
Conductive roll with   2. The conductive roll according to claim 1, wherein the surface roughness Ra of the inner peripheral surface of the surface resin layer is 0.3 μm or more and 2.5 μm or less. An intermediate transfer member to which a toner image formed on the surface of the image carrier is transferred;
The conductive roll according to claim 1 or 2, which contacts the surface of the intermediate transfer member,
A transfer unit that transfers the toner image transferred onto the surface of the intermediate transfer member to a recording medium; An image carrier,
Charging means for charging the image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
Developing means for developing, as a toner image, an electrostatic charge image formed on the image carrier with an electrostatic charge image developer containing toner;
An intermediate transfer member to which the toner image formed on the surface of the image carrier is transferred;
Primary transfer means for primarily transferring the toner image formed on the surface of the image carrier to the surface of the intermediate transfer member;
3. The secondary transfer roll in contact with the surface of the intermediate transfer member includes the conductive roll according to claim 1, and the toner image transferred onto the surface of the intermediate transfer member is subjected to secondary transfer onto a recording medium. Secondary transfer means,
Fixing means for fixing the toner image transferred to the recording medium;
An image forming apparatus.

Images