JP2011107547A - Method of manufacturing electrifying member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing, at a low cost, an electrifying member for certainly suppressing adhesion of toner or an external additive to a surface of the electrifying member. <P>SOLUTION: The method of manufacturing the electrifying member having a conductive elastic layer on the outer periphery of a support body and having a surface layer on the outer periphery of the conductive elastic layer, includes processes of: (1) preparing a mixture containing curable acrylic monomer and base polymer of three or more functions; (2) forming the layer of the mixture on the outer peripheral surface of the support body; (3) bleeding of the curable acrylic monomer and moving it to the surface of the layer of the mixture; and (4) forming the surface layer by curing the curable acrylic monomer moved to the surface of the layer of the mixture and forming the conductive elastic layer by bridging the base polymer. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing a charging member.

  Patent Document 1 discloses a method for producing a charging member in which an elastic layer surface is irradiated with energy rays such as ultraviolet rays and electron beams to provide a surface modification layer.

JP-A-11-149201

  However, according to the study by the present inventors, the effect of reducing the adhesiveness of the surface modification layer of the charging member formed by the method described in Patent Document 1 is not always sufficient, and the surface of the toner or external additive is not sufficient. In some cases, the influence on the image due to adhesion cannot be sufficiently suppressed. Accordingly, an object of the present invention is to provide a method for producing a charging member that can more reliably suppress the adhesion of toner and external additives to the charging member surface at a low cost.

A method for producing a charging member according to the present invention is a method for producing a charging member having a conductive elastic layer on the outer periphery of a support and a surface layer on the outer periphery of the conductive elastic layer,
(1) preparing a mixture containing a trifunctional or higher curable acrylic monomer and a base polymer;
(2) forming a layer of the mixture on the peripheral surface of the support;
(3) bleed the curable acrylic monomer and transfer to the surface of the layer of the mixture;
(4) curing the curable acrylic monomer transferred to the surface of the layer of the mixture to form the surface layer, and crosslinking the base polymer to form a conductive elastic layer. This is a method for manufacturing a charging member.

  According to the present invention, a charging member in which adhesion of toner and external additives to the surface can be suppressed can be manufactured at low cost.

FIG. 3 is a schematic cross-sectional view for explaining a configuration example of a charging roller. It is a typical sectional view for explaining the example of composition of an electrophotographic device. It is typical sectional drawing for demonstrating the structural example of a vent type extruder. It is a schematic diagram for demonstrating the structural example of a continuous vulcanizer. It is a schematic diagram for demonstrating the structural example of an electron beam irradiation apparatus.

The manufacturing method of the charging member which has a conductive elastic layer on the outer periphery of a conductive support and has a surface layer on the outer periphery of the conductive elastic layer according to the present invention includes the following steps (1) to (4). Have.
(1) A step of mixing a trifunctional or higher functional acrylic monomer that is cured by radiation or heat with a base polymer to obtain a conductive elastic layer composition;
(2) forming the conductive elastic layer composition to form a conductive elastic layer;
(3) a step of bleeding a trifunctional or higher functional acrylic monomer and unevenly distributing it on the surface of the formed conductive elastic layer; and
(4) A step of forming a surface layer by reacting a trifunctional or higher functional acrylic monomer unevenly distributed on the surface of the conductive elastic layer.

Hereinafter, the present invention will be described in detail by taking a charging roller as an example of the charging member according to the present invention.
FIG. 1 is a sectional view in a direction perpendicular to the axis of the charging roller according to the present invention. The conductive support 11, the conductive elastic layer 12 covering the peripheral surface, and the conductive elastic layer 12 are shown in FIG. And a surface layer 13 covering the peripheral surface. The charging member is formed through the following steps (1) to (4).

<Step (1)>
Step (1) is a step of preparing a composition containing a base polymer, a trifunctional or higher functional curable acrylic monomer, and a conductive agent. The mixing method of these materials is not particularly limited, and is a mixing method using a closed mixer such as a Banbury mixer or a pressure kneader, or a mixing method using an open mixer such as an open roll. Etc. can be illustrated. The added amount of the acrylic monomer is more preferably 1 to 30 parts by mass, and particularly 1 to 10 parts by mass with respect to 100 parts by mass of the base polymer. By setting the addition amount within the above range, sufficient acrylic monomer can be transferred in the step of transferring to the surface of the elastic layer, which will be described later, and a more uniform surface layer can be formed.

<< Curable acrylic monomer >>
The curable acrylic monomer is a radical polymerization type or cationic polymerization type material. In particular, a trifunctional or higher functional acrylic monomer is easy to design a molecule and has a low viscosity. Therefore, it is easy to control the bleed speed from the mixture with the base polymer, and the curing speed is also fast. Examples of the trifunctional or higher functional acrylic monomer include monomer molecules having three or more (meth) acrylic acid ester groups in the molecule. These acrylic monomers preferably have 3 or more and 5 or less functional groups in the molecule. Specific examples of the trifunctional or higher curable acrylic monomer include the following. Ethoxylated isocyanuric acid triacrylate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, ethoxylated pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol Pentaacrylate and the like.

<< Base polymer >>
The elastic layer contains a base polymer and additives such as a conductive agent. The base polymer is not particularly limited as long as it is a material exhibiting rubber elasticity in the actual use temperature range of the charging member. Specific rubber materials are as follows. Natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene (SBR), butyl rubber (IIR), ethylene-propylene-diene terpolymer rubber (EPDM), epichlorohydrin homopolymer (CHC) ), Epichlorohydrin-ethylene oxide copolymer (CHR), epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (CHR-AGE), acrylonitrile-butadiene copolymer (NBR), water of acrylonitrile-butadiene copolymer Thermosetting rubber materials, raw materials such as additives (H-NBR), chloroprene rubber (CR), acrylic rubbers (ACM, ANM), etc., cross-linking agents, polyolefin-based thermoplastic elastomers, polystyrene-based thermoplastic elastomers The Ester thermoplastic elastomers, polyurethane thermoplastic elastomers, polyamide thermoplastic elastomers, and thermoplastic elastomers such as vinyl chloride type thermoplastic elastomer.

<< Conductive agent >>
It is preferable to add a conductive agent to the base polymer for the purpose of adjusting the electric resistance of the conductive elastic layer. Examples of the conductive agent include the following. Carbon materials such as carbon black and graphite; oxides such as titanium oxide and tin oxide; metals such as Cu and Ag; electronic conductive agents such as conductive particles obtained by coating the surface of the particles with oxide or metal; Inorganic ionic substances such as lithium chlorate, sodium perchlorate, calcium perchlorate; lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, trioctylpropylammonium bromide , Cationic surfactants such as modified aliphatic dimethylethylammonium etosulphate; zwitterionic interfaces such as lauryl betaine, stearyl betaine, dimethylalkyl lauryl betaine Sex agents; such as ion conductive agent such as an organic lithium salt such as trifluoroacetic lithium methanesulfonate; tetraethylammonium perchlorate, tetrabutylammonium perchlorate, quaternary ammonium salts such as perchlorate trimethyloctadecylammonium. In addition, fillers, processing aids, crosslinking aids, crosslinking accelerators, crosslinking accelerators, crosslinking retarders, dispersants, etc. that are commonly used as rubber compounding agents are added to the base polymer as necessary. can do.

<Step (2)>
In step (2), the mixture prepared in step (1) is applied to the peripheral surface of the support to form a layer of the mixture. Examples of the method for forming the mixture layer include the following methods (i) to (iii). (I) A method in which the mixture is extruded into a tube shape by an extruder, a support is press-fitted into the tube, and the surface is polished to obtain a desired outer diameter. (Ii) A method of obtaining a molded body having a desired outer diameter by co-extruding the mixture into a cylindrical shape around the conductive support by an extruder equipped with a crosshead. (Iii) A method of obtaining a molded body by injecting the mixture into a mold having a desired outer diameter using an injection molding machine.

  Among these methods, the extrusion method using a crosshead extruder is most preferable because continuous production is easy, the number of steps is small, and it is suitable for production at low cost. FIG. 3 schematically shows an outline of extrusion molding using a vent type extruder. In the extruder 3, an extrusion screw 32 having a screw dam portion 37 is rotatably inserted in a cylinder 31. A cross head 33 is attached to the end of the cylinder 31 on the distal end side of the extrusion screw 32. The cylinder 31 is provided with a vent port 35. The vent port 35 is connected to a vacuum pump (not shown), and the inside of the cylinder 31 is evacuated by the vacuum pump. The rubber mixture charged from the material charging port 34 is conveyed to the crosshead 33 side by the rotation of the extrusion screw 32. As the rubber mixture passes through the cylinder, volatile components are removed by a vacuum pump connected to the vent port. Thereby, when a molded object is heat-processed in the subsequent process, generation | occurrence | production of the bubble (void) to an elastic layer can be suppressed because the volatile matter in the layer of a mixture vaporizes with the heat | fever at the time of vulcanization.

  The rubber mixture conveyed to the crosshead passes through the die 36 at the tip of the crosshead together with the support 11 supplied from a core metal supply device (not shown) and is coextruded with the support 11. At this time, a crown-shaped roller can be formed by continuously changing the feed rate of the conductive support supplied from the cored bar supply device. That is, the feed speed is slow until the core metal tip passes through the die outlet and passes through the metal core central part or the die outlet, and the metal core central part passes through the die outlet and the metal core rear end part. The feed speed is changed quickly until it passes. By controlling the core feed speed, a rubber mixture layer having a crown shape in which the roller center diameter is larger in an arc shape than the roller both end diameters is formed.

<< Step (3) >>
In step (3), the curable acrylic monomer in the rubber mixture layer is bleed (transferred) to the surface of the rubber mixture layer. The migration rate of the curable acrylic monomer depends on the difference in solubility constant (SP value) between the base polymer and the curable acrylic monomer. That is, the transition speed increases as the difference between the SP values increases. The solubility parameter difference (absolute value difference) between the acrylic monomer and the base polymer is preferably 0.5 to 3.0 (MPa) ^{1/2 and} more preferably 1.5 to 2.5 (MPa) ^1/2. . When the difference in SP value is 1.5 or more, the transfer amount of the monomer to the surface of the conductive elastic layer is ensured, and a uniform surface layer is formed. In addition, it is possible to suppress an increase in the thickness of the surface layer due to an excessive amount of transfer of the monomer at 2.5 or less, and to prevent the uncured monomer from exuding on the member surface even after the curing treatment. In addition, about SP value of the base polymer which is a high molecular material, it calculates from the molecular structure based on the molar attractive force of the atomic group which comprises a molecule | numerator (PASmall, J.Appl.Chem., Vol.3,71 ( 1953)). The monomer SP value is based on Hildebrand-Scatchard's solution theory (JHHildebrand, RLScott, “The Solubility of Nonelectrolytes” 3rd Ed., Reinhold Publishing cop., New York (1949)). Calculated from energy and molecular volume. For the above-mentioned constants specific to the atomic group used in the present invention, the values at 25 ° C. described in DW Van. Kreven “Prorerties of Polymer” 3rd Ed., Elsevier (1990) are used. Since bleeding of the acrylic monomer to the surface of the layer is promoted by increasing the molecular motion of the base polymer, it is preferable to heat in the step (3). The temperature range of the heat treatment can be set at least at a temperature lower than the curing temperature of the curable monomer, for example, 100 ° C. or more and 160 ° C. or less until the curable monomer is sufficiently transferred to the elastic layer surface. The heat treatment in the step (3) is more preferably performed in a continuous heating furnace. By using a continuous heating furnace, continuous part production is possible from the molding in step (2) to the heat treatment in step (3). In FIG. 4, the outline | summary of the continuous heating apparatus of the roller extruded from the extruder 3 was shown typically. The molded body in which the unvulcanized rubber is laminated on the outer periphery of the support 11 is continuously conveyed to the continuous heating furnace 4 by an extruder 3 (not shown). The continuous heating furnace 4 is kept at a predetermined temperature in advance, and is subjected to heat treatment for a predetermined time depending on the speed of conveyance and the length of the continuous heating furnace 4. The continuous heating furnace used in the present invention is configured to have two regions, and the molded product inlet side region 41 and the molded product outlet side region 42 can be set to different temperatures. It is also possible to set these temperature settings to the same temperature. When the conductive elastic layer is composed of a thermosetting polymer, the base polymer can be simultaneously crosslinked in the bleed process (3). In this case, the molecular mobility of the base polymer decreases due to the crosslinking reaction, and the tendency of the monomer migration rate to decrease is observed. Therefore, in order to efficiently transfer the surface of the elastic layer of the monomer and the crosslinking reaction of the base polymer, it is preferable to set the molded body inlet side 41 to a low temperature and the molded body outlet side 42 to a high temperature. On the low temperature side, the transition of the monomer is completed by setting the temperature and time so that the crosslinking of the base polymer is not sufficiently completed below the curing temperature of the monomer. On the high temperature side, the temperature and time are set to complete the crosslinking of the base polymer. As described above, the transfer of the monomer and the crosslinking reaction of the base polymer can be continuously performed.

<< Step (4) >>
Step (4) is a step of curing the acrylic monomer transferred to the surface of the rubber mixture layer to form a surface layer. The curing process is performed by heat treatment or electron beam irradiation. When the curing is performed by heat treatment, it is possible to simultaneously perform the crosslinking of the base polymer and the curing of the acrylic monomer in the step (3) described above. The heat treatment can be performed at a temperature higher than the curing temperature of the acrylic monomer. The curing treatment is preferably performed by electron beam irradiation that can increase the crosslinking density of the surface layer to be formed. By increasing the cross-linking density of the surface layer, it is possible to prevent contamination of the photoreceptor due to the leakage of low molecular components from the conductive elastic layer, and to reduce the friction coefficient of the surface of the charging member, so that the toner and external additives are charged. It becomes difficult to adhere to the member surface. In particular, electron beam irradiation has a high crosslinking efficiency, can shorten the curing time, and does not require the addition of a polymerization initiator. Moreover, since the penetration depth of radiation is deeper than that of ultraviolet rays and the treatment film thickness can be increased, it is even more preferable. FIG. 5 shows a schematic diagram of an electron beam irradiation apparatus. The electron beam irradiation apparatus used in the present invention irradiates the surface of a roller with an electron beam while rotating the roller, and includes an electron beam generator 51, an irradiation chamber 52, and an irradiation port 53 as shown in FIG. Is. The electron beam generator 51 includes a terminal 54 that generates an electron beam, and an acceleration tube 55 that accelerates the electron beam generated at the terminal 54 in a vacuum space (acceleration space). The inside of the electron beam generator is kept at a vacuum of 10 ⁻⁶ to 10 ⁻⁷ Torr by a vacuum pump (not shown) in order to prevent electrons from losing energy due to collision with gas molecules. When the filament 56 is heated by current from a power source (not shown), the filament 56 emits thermoelectrons, and only those thermoelectrons that have passed through the terminal 54 are effectively taken out as electron beams. Then, after being accelerated in the acceleration space in the accelerating tube 55 by the acceleration voltage of the electron beam, it penetrates the irradiation port foil 57 and is irradiated to the roller 58 conveyed in the irradiation chamber 52 below the irradiation port 53. As in this embodiment, when the roller 58 is irradiated with an electron beam, the inside of the irradiation chamber 52 is a nitrogen atmosphere. Further, the roller 58 is rotated by a roller rotating member 59 and is moved from the left side to the right side in FIG. The surroundings of the electron beam generator 51 and the irradiation chamber 52 are shielded from lead (not shown) so that X-rays that are secondarily generated during electron beam irradiation do not leak to the outside. The irradiation port foil 57 is made of a metal foil, and separates the vacuum atmosphere in the electron beam generator and the air atmosphere in the irradiation chamber, and takes out the electron beam into the irradiation chamber through the irradiation port foil 57. When an electron beam is applied to the irradiation of the roller, the inside of the irradiation chamber 52 where the roller is irradiated with the electron beam is a nitrogen atmosphere. Therefore, the irradiation port foil 57 provided at the boundary between the electron beam generating unit 51 and the irradiation chamber 52 has no pinhole, has a mechanical strength that can sufficiently maintain the vacuum atmosphere in the electron beam generating unit, and easily transmits the electron beam. It is desirable. For this reason, the irradiation mouth foil 57 is preferably made of a metal having a small specific gravity and a small thickness. The electron beam dose is defined below.

Dose (kGy) = [equipment constant K × electron current (mA)] / processing speed (m / min)
Here, the device constant K is a constant representing the efficiency of each device, and serves as an index of device performance. For example, in an electron beam irradiation apparatus, it is originally necessary to set K = 18 or more. Therefore, for a certain electron current and processing speed, the acceleration voltage is changed, the dose is measured, and the acceleration voltage is determined by obtaining the acceleration voltage so that the device constant K obtained from this is a predetermined value or more. Is obtained. What is necessary is just to select suitably about the dose of an electron beam according to the effect of surface treatment. The adjustment can be performed using either an electronic current or a processing speed, and it is sufficient to determine that a desired dose can be obtained. This time, the dose at an electron current and processing speed using a dose film was measured in advance, and the device constant K was calculated. Based on this, the dose of the electron beam was calculated.

  In the present invention, the surface layer is formed by curing the acrylic monomer transferred from the layer of the mixture of the base polymer and the acrylic monomer to the surface. As a method for confirming the formation of the surface layer, there are a method for confirming from morphological observation and a method for confirming using a surface analyzer, and there is no particular limitation. As morphological observation, there is a method of confirming the formation of the surface layer from observation with an optical microscope, a scanning electron microscope, a transmission electron microscope or the like. For surface analysis, the surface of the member and the internal composition are measured by a surface analyzer such as ATR method of Fourier transform infrared spectrophotometer, composite surface analyzer (ESCA), time-of-flight secondary ion mass spectrometer (TOF-SIMS). The formation of the surface layer can be confirmed by comparing. As described above, the conventional coating process for forming the surface layer by previously kneading the material for forming the surface layer into the rubber material and transferring the surface layer constituent material to the surface of the conductive elastic layer in the molding process. Can be made unnecessary. The charging member in the present invention can be provided with functional layers such as an adhesive layer, a diffusion prevention layer, a base layer, and a primer layer in addition to the elastic layer and the surface layer as necessary.

<Electrophotographic device>
FIG. 2 is a sectional view of an electrophotographic apparatus having a charging member according to the present invention. The electrophotographic photosensitive member 21 as a member to be charged has a drum shape having a conductive support 21b such as aluminum and a photosensitive layer 21a formed thereon. It is rotationally driven around the shaft 21c in the clockwise direction with a predetermined peripheral speed. The charging roller 1 is disposed in contact with the electrophotographic photosensitive member 21 to charge (primary charging) the electrophotographic photosensitive member to a predetermined polarity and potential. The charging roller 1 includes a conductive support 11, a conductive elastic layer 12 formed on the outer periphery thereof, and a surface layer 13 formed on the surface of the conductive elastic layer 12. Then, both ends of the conductive support 11 are driven to rotate by the rotation of the electrophotographic photosensitive member 21 by pressing means (not shown). The electrophotographic photosensitive member 21 is contact-charged to a predetermined polarity and potential by applying a predetermined direct current (DC) bias of the conductive support 11 by the rubbing power source 23a. The electrophotographic photosensitive member 21 whose peripheral surface is charged by the charging roller 1 is then subjected to exposure of target image information (laser beam scanning exposure, slit exposure of a document image, etc.) by the exposure means 24, so that the peripheral surface has a target. An electrostatic latent image corresponding to the image information is formed. The electrostatic latent image is then developed as a toner image by the developing member 25. The toner images are sequentially transferred onto a transfer material 27 conveyed to a transfer portion between the electrophotographic photosensitive member 21 and the transfer roller 26. The toner image on the electrophotographic photosensitive member 21 side is transferred to the transfer material 27 by charging from the back of the transfer material 27 with a polarity opposite to that of the toner. The transfer material 27 having received the transfer of the toner image on the surface is separated from the electrophotographic photosensitive member 21 and conveyed to a fixing means (not shown) to receive image fixing and output as an image formed product. Alternatively, in the case of forming an image on the back side, it is conveyed to a re-conveying means to the transfer unit. The peripheral surface of the electrophotographic photosensitive member 21 after the image transfer is subjected to pre-exposure by the pre-exposure means 28, and residual charges on the electrophotographic photosensitive drum are removed (static elimination). The peripheral surface of the electrophotographic photosensitive member 21 from which the charge has been removed is cleaned by the cleaning member 29 after removal of adhering contaminants such as toner remaining after transfer, and is repeatedly used for image formation. The charging roller 1 may be driven and driven by the electrophotographic photosensitive member 21 driven to move the surface, may not be rotated, or has a predetermined circumference in the forward or reverse direction in the surface moving direction of the electrophotographic photosensitive member 21. You may make it actively rotate at a speed. In addition, when the electrophotographic apparatus is used as a copying machine, exposure is performed by reflecting or transmitting light from a document, or by reading a document as a read signal, scanning a laser beam based on this signal, or using an LED array. This is done by driving. Examples of the electrophotographic apparatus according to the present invention include an electrophotographic application apparatus such as a copying machine, a laser beam printer, an LED printer, or an electrophotographic plate making system.

  The present invention will be described in more detail with reference to the following examples, but these examples do not limit the present invention. Hereinafter, unless otherwise specified, “parts” means “parts by mass”, and commercially available high-purity products were used unless otherwise specified.

<Example 1>
(Preparation of rubber material for elastic layer)
Using the 6 liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.), the materials shown in Table 1-1 below were mixed for 16 minutes at a filling rate of 70 vol% and a blade rotation number of 35 rpm to obtain an A kneaded rubber composition. Obtained.

Next, the materials shown in Table 1-2 below were subjected to a total of 20 turnings on the left and right sides with an open roll having a roll diameter of 12 inches, a front roll rotation speed of 8 rpm, a rear roll rotation speed of 10 rpm, and a roll gap of 2 mm. Thereafter, the roll gap was set to 0.5 mm, and thinning was performed 10 times to obtain an unvulcanized rubber composition for forming an elastic layer.

(Measurement of curing temperature of surface layer forming material 1)
The curing temperature of the surface layer forming material 1 was measured using a differential thermal balance (TG-DTA). A differential type differential thermobalance TG8120 manufactured by Rigaku Corporation was used as the analyzer, and the peak temperature of the calorific value was determined as the curing temperature by measuring at a temperature rising rate of 5 ° C./min. As a result, the curing temperature of the surface layer forming material 1 was 182 ° C.
(Molding of elastic layer)
Conductive vulcanizing adhesive (Metaloc U-20; Toyo Chemical Research Co., Ltd.) in the range of 228 mm in the axial center of the cylindrical surface of a cylindrical conductive support (steel, surface is nickel-plated) 6 mm in diameter and 252 mm in length Applied) and dried at 80 ° C. for 30 minutes. Next, the unvulcanized rubber composition is extruded into a cylindrical shape on the peripheral surface of the conductive support using an extruder connected to a crosshead, and a layer of the unvulcanized rubber composition is formed on the outer periphery of the conductive support. A formed unvulcanized rubber roller was produced. The extruder used was an extruder with a cylinder diameter of 45 mm (Φ45) and L / D = 20. The temperature during extrusion was 90 ° C., 90 ° C. cylinder, and 90 ° C. screw. The core metal feed speed was adjusted during extrusion to form an unvulcanized rubber roller having a crown-shaped elastic layer having an end diameter of 8.4 mm and a center diameter of 8.5 mm.
(Bleed process)
After cutting both ends of the unvulcanized rubber roller so that the width of the elastic layer portion is 228 mm, it is put into a continuous heating furnace to transfer the surface layer forming material 1 to the surface of the elastic layer, and the elastic layer is vulcanized. A vulcanized rubber roller was obtained. As the continuous heating furnace, a heating furnace having two temperature regions was used. First, heat treatment was performed at 120 ° C. for 30 minutes, and subsequently at 160 ° C. for 30 minutes.
(Surface treatment)
The surface of the vulcanized rubber roller was irradiated with an electron beam to form a surface layer to obtain a charging roller. An electron beam irradiation apparatus (manufactured by Iwasaki Electric Co., Ltd.) having a maximum acceleration voltage of 150 kV and a maximum electron current of 40 mA was used for electron beam irradiation, and nitrogen gas purge was performed during irradiation. The treatment conditions were acceleration voltage: 150 KV, electron current: 5 mA, treatment speed: 1 m / min, oxygen concentration: 100 ppm.
(Confirmation of surface layer)
The presence or absence of the surface layer of the charging roller was confirmed by the following method. FTIR-8300 manufactured by Shimadzu Corporation connected with a microscopic IR (AIM-8000R) was used as an analyzer, and measurement was performed by a total reflection measurement method (ATR method) using a germanium prism. The measurement is performed on the surface of the charging roller and the inside of the elastic layer cut 0.5 mm in the depth direction from the surface of the charging roller. did. As a result, in the measurement of the charging roller surface, as compared with the measurement inside the elastic body layer, a strong infrared absorption peak derived from the surface layer forming material 1 was observed, and it was confirmed that the surface layer was formed.
(Durable image evaluation)
The charging roller and the electrophotographic photosensitive member were incorporated into a process cartridge that integrally supports them, and this process cartridge was incorporated into an A4 paper longitudinal output electrophotographic apparatus (Color Laser Jet 3500; manufactured by Hewlett Packard) for image evaluation. Image evaluation was performed in a 15 ° C./10% RH environment, and a halftone image output after printing 3000 sheets at 1% printing density (after endurance) (width 1 dot in the direction perpendicular to the rotation direction of the electrophotographic photosensitive member) The image was drawn by visually observing the uniformity of the image drawn with 2 dots. The evaluation criteria are as follows.
A: No image defect due to adhesion of toner and external additives to the charging roller.
B: The image defect described above occurred very slightly.
C: The image defect described above occurred slightly.
D: The above image defect was clearly generated.
(Set image evaluation)
A cartridge incorporating a charging roller different from the above was prepared, and the cartridge was placed at 40 ° C./95% R.D. H. For 30 days. After being left, it was once again incorporated into an electrophotographic apparatus, and image evaluation was performed after leaving it in a harsh environment. For image output, 20 halftone images were output in an environment of 25 ° C./50% RH, and the image was output again after being left for 24 hours in the image output environment. The evaluation criteria are as follows.
A: An image with no defective image.
B: Image defect occurred slightly at the first output. However, the image defect disappears completely after 20 sheets are output.
C: A slight image defect occurs at the first output, and the image defect does not disappear completely even after 20 sheets are output.
D: An image defect occurs at the first output, and the image defect does not disappear completely even after being left for 24 hours.
E: An image defect occurs at the first output, and the image defect does not improve even after being left for 24 hours.
(Measurement of C set amount)
Using the conductive support of the charging roller as an axis, the radius of the roller is measured, and the difference in radius between the most deformed portion and the non-contact portion of the contact portion is defined as the C set amount. The measurement is carried out using a fully automatic roller measuring device manufactured by Tokyo Koden Kogyo Co., Ltd., and 360 ° measurement is performed by rotating the charging member by 1 °. This measurement was performed at three points, the central portion of the roller and 90 mm from the central portion, and the largest deformation amount was defined as the C set amount of the charging roller.

<Examples 2-3>
In Example 1, a charging roller was prepared in the same manner as in Example 1 except that the amount of the surface layer forming material 1 was changed as described in Table 2-1. It was confirmed that a surface layer was formed on these charging rollers in the same manner as in Example 1. These charging rollers were evaluated in the same manner as in Example 1.

<Example 4>
In Example 1, the surface layer forming material 1 having the following composition was converted to ditrimethylolpropane tetraacrylate represented by the following chemical formula (2) (trade name: NK ester AD-TMP, manufactured by Shin-Nakamura Chemical Co., Ltd., SP value 22.2 (MPa) ^1/2 ) (hereinafter “surface layer forming material 2”). Otherwise, a charging roller was obtained in the same manner as in Example 1. The curing temperature of the surface layer forming material 2 was 178 ° C. It was confirmed that a surface layer was formed on this charging roller as in Example 1. Further, this charging roller was evaluated in the same manner as in Example 1.

<Example 5>
First, heat treatment in a continuous furnace was carried out at 120 ° C for 30 minutes, followed by 185 ° C for 30 minutes, and the latter half of the heat treatment simultaneously vulcanized the elastic layer and cured the surface layer, and then performed electron beam irradiation. A charging roller was obtained in the same manner as in Example 1 except that this was not done. Using the above charging roller, the surface layer was confirmed in the same manner as in Example 1. As a result, it was confirmed that a surface layer was formed. In addition, the above-described charging roller was used, and durability image evaluation and set image evaluation were performed in the same manner as in Example 1.

<Example 6>
The surface layer-forming material 1 in Example 1 is trimethylolpropane triacrylate represented by the following chemical formula (3) (trade name: NK ester A-TMPT, manufactured by Shin-Nakamura Chemical Co., Ltd., SP value 19.8 (MPa) ^{1 / 2} ) The amount of addition was changed to 10 parts by mass instead of (hereinafter referred to as surface layer forming material 3). Otherwise, a charging roller was obtained in the same manner as in Example 1. The curing temperature of the surface layer forming material 3 was 174 ° C. It was confirmed that a surface layer was formed on this charging roller in the same manner as in Example 1. Further, this charging roller was evaluated in the same manner as in Example 1.

<Example 7>
A charging roller was obtained in the same manner as in Example 1 except that NBR was changed to butadiene rubber (trade name: Nipol BR1220L, manufactured by Nippon Zeon Co., Ltd., SP value 17.6 (MPa) ^1/2 ) in Example 1. This charging roller was evaluated in the same manner as in Example 1.

<Comparative Example 1>
The surface layer forming material 1 in Example 1 is represented by the following general formula (4): lauryl acrylate (trade name: NK ester LA, manufactured by Shin-Nakamura Chemical Co., Ltd., SP value 17.6 (MPa) ^1/2 ) ( Thereafter, the surface layer forming material 4) was changed. Otherwise, a charging roller was obtained in the same manner as in Example 1. The curing temperature of the surface layer forming material 4 was 177 ° C. It was confirmed that the surface layer was formed in the same manner as in Example 1 for the charging roller of Comparative Example 1. Further, this charging roller was evaluated in the same manner as in Example 1.

<Comparative example 2>
The surface layer forming material 1 in Example 1 is represented by the following general formula (5): phenoxyethyl acrylate (trade name: NK ester AMP-10G, manufactured by Shin-Nakamura Chemical Co., Ltd., SP value 20.3 (MPa) ^{1 / 2} ) (hereinafter referred to as surface layer forming material 5), and the addition amount was 5 parts by mass. Otherwise, a charging roller was obtained in the same manner as in Example 1.

  The curing temperature of the surface layer forming material 5 was 176 ° C. It was confirmed that a surface layer was formed on this charging roller in the same manner as in Example 1. The charging roller was evaluated in the same manner as in Example 1.

<Comparative Example 3>
The surface layer forming material 1 in Example 1 is neopentyl glycol diacrylate represented by the following general formula (6) (trade name: NK ester A-NPG, manufactured by Shin-Nakamura Chemical Co., Ltd., SP value 18.8 (MPa) ^1/2 ) (hereinafter referred to as surface layer forming material 6). Otherwise, a charging roller was obtained in the same manner as in Example 1. The curing temperature of the surface layer forming material 6 was 174 ° C. This charging roller was evaluated in the same manner as in Example 1.

<Comparative example 4>
A charging roller was obtained in the same manner as in Comparative Example 3 except that NBR was changed to butadiene rubber (trade name: NipolBR1220L, manufactured by Nippon Zeon Co., Ltd.) in Comparative Example 3. The obtained charging roller was evaluated in the same manner as in Example 1.

<Comparative Example 5>
The surface layer forming material 1 in Example 1 is 1,6-hexanediol diacrylate represented by the following general formula (7) (trade name: NK ester A-HD, manufactured by Shin-Nakamura Chemical Co., Ltd., SP value 19.9 (MPa) ^1/2 ) (hereinafter referred to as surface layer forming material 7). Otherwise, a charging roller was obtained in the same manner as in Example 1. The curing temperature of the surface layer forming material 7 was 177 ° C. This charging roller was evaluated in the same manner as in Example 1.

The evaluation results of Examples 1 to 7 and Comparative Examples 1 to 5 are shown in Table 2-1 and Table 2-2 below.

As is apparent from the table, Comparative Examples 1 to 5 are caused by the fact that the set images of the obtained charging rollers all have a C rank or less and the C set deformation amount is large. Examples 1 to 7 are within the scope of the present invention, and the durability image evaluation is A rank, and the set image evaluation is B rank or more, and good images with no practical problems are obtained.

DESCRIPTION OF SYMBOLS 1 Charging roller 11 Conductive support body 12 Conductive elastic layer 13 Surface layer

Claims (2)

A method for producing a charging member having a conductive elastic layer on the outer periphery of a support and a surface layer on the outer periphery of the conductive elastic layer,
(1) preparing a mixture containing a trifunctional or higher curable acrylic monomer and a base polymer;
(2) forming a layer of the mixture on the peripheral surface of the support;
(3) bleed the curable acrylic monomer and transfer to the surface of the layer of the mixture;
(4) curing the curable acrylic monomer transferred to the surface of the layer of the mixture to form the surface layer, and crosslinking the base polymer to form a conductive elastic layer. A method for producing a charging member. 2. The absolute value difference in SP value (Solubility Parameter) between the base polymer and the acrylic monomer is 1.5 ((MPa) ^1/2 ) to 2.5 ((MPa) ^1/2 ). Manufacturing method of the charging member.

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