JP5511408B2 - Method for manufacturing charging member - Google Patents

Description

  The present invention relates to a method for manufacturing a charging member used in an electrophotographic apparatus.

  Generally, the charging member used in the contact charging method has an elastic layer containing rubber or a thermoplastic elastomer in order to ensure a nip width with the photoreceptor. In such a charging member, toner, external additives, and the like may adhere to the elastic layer surface due to the high adhesiveness of the elastic layer surface, which may affect the charging performance of the charging member. In Patent Document 1, the surface of the semiconductive elastic layer is modified by irradiating the surface of the semiconductive elastic layer with ultraviolet rays for the purpose of obtaining a charging member excellent in releasability with toner. It is disclosed that the object can be achieved by a method for manufacturing a charging member for forming a protective layer.

JP-A-11-149201

  However, according to the study by the present inventors, it has been concluded that the charging member described in Patent Document 1 may not yet have a sufficient effect of suppressing the adhesion of toner or the like to the surface.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for producing a charging member that can further suppress the adhesion of toner and external additives to the surface of the charging member.

That is, the manufacturing method of the charging member according to the present invention is:
(A) at least one raw material rubber selected from the group consisting of polyisoprene, polybutadiene, styrene butadiene copolymer, ethylene propylene copolymer, butyl rubber, nitrile rubber, hydrin rubber, chloroprene rubber, acrylic rubber, urethane rubber and fluororubber; Forming a layer of a mixture containing silsesquioxane on the mandrel;
(B) bleeding the silsesquioxane in the layer of the mixture on the surface of the layer of the mixture;
(C) curing the silsesquioxane bleed on the surface of the layer of the mixture.

  According to the present invention, it is possible to obtain a method for manufacturing a charging member in which adhesion of toner and external additives to the surface of the charging member is further suppressed.

FIG. 3 is a schematic cross-sectional view in a direction perpendicular to the axis of the charging roller according to the present invention. 1 is a schematic cross-sectional view of an electrophotographic apparatus. It is explanatory drawing of a vent type extruder. It is explanatory drawing of a continuous vulcanizer. It is explanatory drawing of an electron beam irradiation apparatus. (A) is a complete cage type | mold, (b) is explanatory drawing of the chemical structure of an incomplete cage type silsesquioxane derivative | guide_body. (A) is a ladder type, (b) is an explanatory view of the chemical structure of a random silsesquioxane derivative.

  FIG. 1 is a cross-sectional view of a charging roller according to the present invention cut in a direction perpendicular to the axis, 11 is a cored bar, 12 is an elastic layer, and 13 is a cured product of silsesquioxane. The surface layer is shown. Although FIG. 1 shows that there is a clear interface between the elastic layer 12 and the surface layer 13, as will be described later, according to the method for manufacturing a charging roller according to the present invention, the elastic layer 12 and the surface layer are formed. There may be no clear interface with the layer 13.

  The steps (A) to (C) relating to the method for producing a charging member according to the present invention will be sequentially described below.

<Process A>
In step A, at least one raw material selected from the group consisting of polyisoprene, polybutadiene, styrene butadiene copolymer, ethylene propylene copolymer, butyl rubber, nitrile rubber, hydrin rubber, chloroprene rubber, acrylic rubber, urethane rubber and fluororubber. A layer of a mixture containing rubber and silsesquioxane is formed on the cored bar.

<< Raw rubber >>
The raw rubber is a material that gives rubber elasticity to the elastic layer. One or more selected from the group consisting of polyisoprene, polybutadiene, styrene butadiene copolymer, ethylene propylene copolymer, butyl rubber, nitrile rubber, hydrin rubber, chloroprene rubber, acrylic rubber, urethane rubber and fluororubber are used.

  Examples of polyisoprene include isoprene rubber (IR), natural rubber (NR), which is a thermosetting rubber, and styrene-isoprene-styrene (SIS) copolymer, which is a thermoplastic elastomer. An example of polybutadiene is butadiene rubber (BR). Examples of the styrene-butadiene copolymer include styrene-based elastomers such as styrene-butadiene rubber (SBR), which is a thermosetting rubber, and styrene-butadiene-styrene (SBS) copolymers, which are thermoplastic elastomers. Examples of the ethylene propylene copolymer include ethylene-propylene rubber (EPT) and ethylene-propylene-diene terpolymer rubber (EPDM). Examples of butyl rubber include isoprene-isobutylene copolymer (IIR) and halides thereof. Nitrile rubber is an acrylonitrile-butadiene copolymer (NBR). Examples of hydrin rubber include epichlorohydrin homopolymer (CO), epichlorohydrin-ethylene oxide copolymer (ECO), and epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (GECO). Chloroprene rubber includes sulfur-modified products and non-sulfur-modified products. Urethane rubber includes liquid type, millable type and thermoplastic type. Any base polymer may use a terminal-modified or unsaturated bond water additive. These base polymers can be used alone or may be blended with other polymers.

<< silsesquioxane >>
Silsesquioxane is a general term for polysiloxanes having a unit represented by [(RSiO _3/2 )] as a basic structural unit. In the present invention, silsesquioxane represented by the following chemical formula (1) can be preferably used.

Chemical formula (1)
[(RSiO _3/2 )] _n
In the above chemical formula (1), R is a monovalent organic group. N in the formula (1) corresponding to the number of silicon atoms is an integer of 6 or more. When n is 6 or more, the crosslinking density after curing is particularly large, and a sufficiently hard surface layer can be easily obtained. Further, the upper limit of n is preferably 100 or less, particularly preferably 30 or less, in view of the ease of silsesquioxane bleeding in the step (B) described later. The monovalent organic group represented by R in the formula (1) may be the same between the units, or may be different from each other. The organic group is a part that causes a curing reaction to occur on the silsesquioxane bleed on the surface in the step C described later. As described later, various methods can be selected for curing the surface layer, and an organic group having a structure optimal for the curing method can be introduced into the silsesquioxane used in the present invention. The organic group preferably has a functional group in order to efficiently perform a curing reaction. Examples of the functional group introduced into the organic group include an acrylate group, a methacrylate group, an oxetanyl group, an epoxy group, a vinyl group, and a carbonyl group. When ultraviolet irradiation or electron beam irradiation is performed as a curing reaction, the organic group preferably contains at least one of an oxetanyl group and an acryloyl group because of good reactivity. The silsesquioxane used in the present invention preferably has at least one selected from an oxetanyl group and an acryloyl group in the molecule.

A commercially available compound can be used as the silsesquioxane derivative having a repeating unit represented by [(RSiO _3/2 )]. Specific examples of silsesquioxane derivatives containing an acryloyl group in the organic group include AC-SQ (trade name) manufactured by Toagosei Co., Ltd. Moreover, as a specific example of the silsesquioxane derivative containing an oxetanyl group in the organic group, trade names: OX-SQ (SI-20), OX-SQ (TX-100), OX- manufactured by Toagosei Co., Ltd. SQ (ME-20) is mentioned.

  Silsesquioxane includes a complete cage shown in FIG. 6 (a), an incomplete cage shown in FIG. 6 (b), a ladder shown in FIG. 7 (a), and FIG. 7 (b). Those having a random structure are known. In the present invention, these structural forms may be any form, and may be a mixture of these structural bodies. Silsesquioxane has an intermediate property between inorganic silica and organic silicone. Therefore, it is liquid in an uncured state and can be easily mixed with the raw rubber. In addition, since heat resistance is good, high temperature treatment is possible in the elastic layer cross-linking step (step D described later) and the surface bleed step (step B described later), and the processing time can be shortened. It is. Furthermore, it is possible to form a high hardness surface layer such as inorganic silica after curing. In addition to the silsesquioxane derivative, polymerization initiators of these functional groups can be mixed with the raw rubber at the same time. The polymerization initiator is preferably one that bleeds to the surface together with silsesquioxane. Examples of such polymerization initiators are listed below.

  Radical polymerization initiator: benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino-1- (4- Morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2- Hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- (4-methylthiophenyl)- 2-morpholinopropa 1-one, benzophenone, 4-phenyl benzophenone, isophthalphenone phenone, 4-benzoyl-4'-methyl - diphenyl sulfide.

  Cationic polymerization initiator: aromatic diazonium salt, aromatic iodonium salt, aromatic sulfonium salt, aromatic selenium salt.

  For mixing the silsesquioxane and the raw rubber, a closed mixer such as a known Banbury mixer or a pressure kneader, or an open mixer such as an open roll can be used. Silsesquioxane is preferably blended at a ratio of 1 to 30 parts by mass with respect to 100 parts by mass of the raw rubber. The transition to the surface of the silsesquioxane as the monomer is easily ensured at 1 part by mass or more, and a more uniform surface layer can be formed. In addition, the amount of transfer of silsesquioxane, which is a monomer, to the surface at 30 parts by mass or less increases the thickness of the surface layer, and the uncured monomer exudes to the surface of the member even after the curing process. Can be particularly suppressed. In addition, the preferable content rate of the raw rubber in the mixture after adding an additive etc. is 40 to 85 mass%. Further, it is preferable to add a conductive agent to the mixture (mixture) of silsesquioxane and raw rubber for the purpose of adjusting the electric resistance of the elastic layer. Examples of the conductive agent are listed below. Carbon materials (carbon black, graphite, etc.); 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 oxides and metals; Inorganic ionic substances such as lithium perchlorate, sodium perchlorate, and calcium perchlorate; cationic surfactants such as lauryltrimethylammonium chloride and stearyltrimethylammonium chloride; zwitterionic surfactants such as laurylbetaine and stearylbetaine Agents; quaternary ammonium salts such as tetraethylammonium perchlorate and tetrabutylammonium perchlorate; organic acid lithium salts such as lithium trifluoromethanesulfonate.

  Furthermore, in addition to the above-mentioned curing (polymerization) initiator for silsesquioxane, raw material rubber includes fillers, processing aids, crosslinking aids, crosslinking agents that are generally used as rubber compounding agents as necessary. Accelerators, crosslinking accelerators, crosslinking retarders, dispersants and the like can be added.

(Mixture layer forming process)
Specific examples of the method for forming a layer of a mixture of raw rubber and silsesquioxane on the peripheral surface of the core include the following methods (1) to (3).
(1) A method of forming a tube of the mixture using an extruder and press-fitting a cored bar into the tube.
(2) A method in which the mixture is coextruded with a mandrel using a crosshead to form a mixture layer on the peripheral surface of the mandrel.
(3) A method of injection-molding the mixture into a cavity equipped with a cored bar.

  Among these, the method (2) is preferable because it allows easy continuous production, has a small number of steps, and is suitable for low-cost production. 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 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 mixture passes through the cylinder, the volatile matter is removed by a vacuum pump connected to the vent port. Thereby, when a molded object is heat-processed in the subsequent process, the bubble (void) which arises when the volatile matter in the layer of a mixture vaporizes with the heat | fever at the time of vulcanization | cure can be prevented.

  The unvulcanized rubber (mixture) conveyed to the cross head is laminated on the outer periphery of the core metal 11 supplied from a core metal supply device (not shown), passes through the die 36 at the tip of the cross head, and is shared with the core metal 11 together. Extruded. At this time, a crown-shaped unvulcanized rubber roller can be formed by continuously changing the feed rate of the core bar supplied from the core 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 adjusting the core feed rate, a layer of a crown-shaped mixture in which the center diameter of the unvulcanized rubber roller is larger than the diameter of both ends of the unvulcanized rubber roller in an arc shape is formed.

<Process B>
In step B, at least a part of silsesquioxane in the layer of the mixture according to step A is transferred (bleeded) to the surface of the mixture layer, and silsesquioxane is unevenly distributed on the surface side of the mixture layer. . Bleed to the surface of the silsesquioxane mixture layer is facilitated by the active molecular motion of the raw rubber. Therefore, the bleed process is preferably performed by heating the mixture layer. One guideline for the heating condition is, for example, maintaining the temperature of the layer of the mixture in a temperature range of 50 ° C. to 250 ° C. for 10 minutes to 60 minutes. The heat treatment in step B is preferably performed in a continuous heating furnace. By using a continuous heating furnace, continuous and continuous production is possible from the formation process of the mixture layer to the heat treatment in the bleed process. In FIG. 4, the outline | summary of the example of the continuous heating apparatus of the unvulcanized rubber 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 core metal 11 is continuously conveyed to the continuous heating furnace 4 by an extruder 3 (not illustrated). 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 preferably composed of 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 a thermosetting polymer is used for the raw rubber, the step B and the step of crosslinking the thermosetting polymer, that is, the step D described later can be performed simultaneously. The following method is preferred from the viewpoint of suppressing the tendency of the molecular mobility of the base polymer to decrease due to the cross-linking reaction and the migration rate of the monomer (silsesquioxane) to decrease. That is, in order to efficiently transfer the surface of the layer of the monomer mixture and the cross-linking reaction of the base polymer, it is preferable to set the molded body inlet side 41 at a low temperature and the molded body outlet side 42 at a high temperature. On the low temperature side, the monomer transfer 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 monomer transfer (step B) and the base polymer cross-linking reaction (step D) can be continuously performed to obtain a vulcanized rubber roller.

<Process C>
In step C, the silsesquioxane bleeded on the surface of the mixture layer in step B is cured.

  The silsesquioxane can be cured by any one selected from heating, ultraviolet irradiation, and irradiation with an electron beam, or a combination thereof. When silsesquioxane is cured by heat treatment, silsesquioxane bleed (step B) and silsesquioxane (step C) can be continuously performed in the same apparatus.

  For the curing of the silsesquioxane, it is preferable to use a radiation treatment capable of increasing the crosslinking density of the crosslinked product of silsesquioxane to be formed. By particularly increasing the crosslink density of the surface layer, bleeding of low molecular components from the elastic layer of the charging roller can be more reliably suppressed. In addition, since the friction coefficient on the surface of the charging member can be reduced, adhesion of toner and external additives to the surface can be more effectively suppressed. In particular, electron beam irradiation has a particularly high cross-linking efficiency, can particularly shorten the curing time, and is more preferable from the viewpoint of adding 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 example. The electron beam irradiation apparatus that can be used in the present invention irradiates the surface of the mixture layer with an electron beam while rotating a roller (a vulcanized rubber roller when steps B and D have already been performed). Further, as shown in FIG. 5, the electron beam irradiation apparatus includes an electron beam generator 51, an irradiation chamber 52, and an irradiation port 53. 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). Further, the inside of the electron beam generator is 10 ⁻⁶ Torr or more and 10 ⁻⁷ Torr or less (133 × 10 ⁻⁶ Pa or more) by a vacuum pump (not shown) in order to prevent electrons from colliding with gas molecules and losing energy. 133 × 10 ⁻⁷ Pa or less). 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. When the roller 58 is irradiated with an electron beam, the inside of the irradiation chamber 52 can be 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. In the case where an electron beam is used for irradiation of the roller, as described above, the inside of the irradiation chamber 52 where the roller is irradiated with the electron beam can be in 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 required that K = 18 or more. Therefore, the acceleration voltage is set by measuring the dose by changing the acceleration voltage with respect to a constant electron current and processing speed, and obtaining the acceleration voltage so that the device constant K obtained from this is equal to or higher than a predetermined value. be able to. 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. For example, the dose at an electron current / processing speed using a dose film is measured in advance, the device constant K is calculated, and the dose of the electron beam can be calculated based on the device constant K.

  Formation of the crosslinked product of silsesquioxane according to the present invention can be confirmed by one or both of morphological observation and surface analysis. 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 charging member and the inside are measured by a surface analysis device such as ATR method of Fourier transform infrared spectrophotometer, composite surface analyzer (ESCA), time-of-flight secondary ion mass spectrometer (TOF-SIMS). The presence of a cross-linked product of silsesquioxane can be confirmed by comparing the composition of

<Process D>
In the present invention, depending on the material used for the raw rubber, as the step (D), a step of vulcanizing the raw rubber in the mixture layer to form an elastic body layer may be performed. That is, when a thermosetting rubber is used as the raw material rubber, as the process D, the curing process of the thermosetting rubber can be performed to adjust the hardness and the like of the charging member. Step D can be performed between steps A and B, between steps B and C, or subsequent to step C. Furthermore, the process D can be performed simultaneously with the process B or the process C. However, as described above, the silsesquioxane bleed is promoted as the molecular motion of the raw rubber in the mixture layer increases. Therefore, it is preferable to perform the process D after the process B. The cross-linking step of the elastic layer is usually performed by heat treatment, and the temperature is 120 ° C. or higher and 250 ° C. or lower for 5 minutes or longer and 60 minutes or shorter. Furthermore, the cross-linking step of the elastic layer can be performed by electron beam irradiation.

<< Electrophotographic device >>
FIG. 2 shows a schematic configuration of an electrophotographic apparatus that can use the charging member manufactured according to the present invention. Reference numeral 21 denotes an electrophotographic photosensitive member as a member to be charged. The electrophotographic photosensitive member shown in FIG. 2 includes a base 21b having conductivity such as aluminum and a photosensitive layer 21a formed on the support 21b. A drum-shaped electrophotographic photosensitive member. The electrophotographic photosensitive member 21 is rotationally driven around the shaft 21c in the clockwise direction in the drawing at a predetermined peripheral speed. Reference numeral 1 denotes a charging roller, and a charging member manufactured by the present invention can be used. 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 cored bar 11, an elastic layer 12 formed on the cored bar 11, and a cross-linked product of silsesquioxane (not shown) formed on the elastic layer 12 (13 in FIG. 1). The both ends of the cored bar 11 are driven to rotate by the pressing means (not shown) as the electrophotographic photosensitive member 21 is driven to rotate. The electrophotographic photosensitive member 21 is contact-charged to a predetermined polarity / potential by applying a predetermined direct current (DC) bias of the core metal 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 successively visualized as a toner image by the developing member 25. This toner image is then synchronized with the rotation of the electrophotographic photosensitive member 21 from a paper feeding unit (not shown) by the transfer unit 26 and transferred at a proper timing between the electrophotographic photosensitive member 21 and the transfer unit 26. Are sequentially transferred to the transfer material 27 conveyed to the substrate. The transfer means 26 in FIG. 2 is a transfer roller, and 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 the opposite polarity to 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 (not shown) 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. The charging member manufactured in the present invention can be used as a developing member, a transfer member, a charge eliminating member, and a conveying member such as a paper feed roller, in addition to the charging roller.

  Hereinafter, the present invention will be described in more detail by way of examples. Unless otherwise specified, “parts” means “parts by mass”, and commercially available high-purity products were used unless otherwise specified.

<Example 1>
(Step A-Preparation of the mixture)
Using the 6 liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.), the materials shown in Table 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. It was.

  Next, the materials shown in Table 2 below were turned 20 times in total on the open roll with a roll diameter of 12 inches (0.30 m) at 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 a raw rubber mixture.

(Step A-Formation of the layer of the mixture)
Conductive vulcanization adhesive (trade name: METALOC U-20; Toyo Chemical Co., Ltd.) in the axial central part 228mm of the cylindrical surface of a cylindrical conductive metal core (made of steel, surface is nickel plated) with a diameter of 6mm and a length of 252mm (Manufactured by Laboratory) and dried at 80 ° C. for 30 minutes. Next, the mixture was simultaneously extruded into a cylindrical shape coaxially with the cored bar as the center by extrusion molding using a crosshead, and an unvulcanized rubber roller having the mixture coated on the outer periphery of the cored bar was produced. At that time, an extruder having a cylinder diameter of 45 mm (Φ45) and an L / D of 20 was used as the extruder, and the temperature during extrusion was 90 ° C., 90 ° C. cylinder, and 90 ° C. screw. Further, the core metal feed speed was regulated during extrusion to obtain an unvulcanized rubber roller having a crown-shaped mixture layer having an end diameter of 8.4 mm and a center diameter of 8.5 mm.

(Process B and D-bleed process and raw rubber crosslinking process)
After cutting both ends of the formed unvulcanized rubber roller mixture layer to make the axial width of the mixture layer portion 232 mm, the mixture is placed in a continuous heating furnace to transfer silsesquioxane to the surface of the mixture layer. The elastic layer was vulcanized at the same time to obtain a vulcanized rubber roller. At that time, a heating furnace having two temperature regions was used as the continuous furnace, and heat treatment was first performed at 120 ° C. for 30 minutes, and then at 160 ° C. for 30 minutes.

(Process C)
The surface of the resulting vulcanized rubber roller was irradiated with an electron beam (EB) to cure the silsesquioxane, and a charging roller having a cured product of silsesquioxane on the surface was obtained. For the electron beam irradiation, 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, and nitrogen gas purge was performed during irradiation. The treatment conditions were acceleration voltage: 150 kV, electron current: 20 mA, treatment speed: 1 m / min, and oxygen concentration: 100 ppm.

(Confirmation of formation of silsesquioxane cured product)
About the said charging roller, it confirmed that the crosslinked material of silsesquioxane existed on the surface with the following method. FTIR-8300 (trade name, manufactured by Shimadzu Corporation) connected with a microscopic IR (trade name: AIM-8000R) was used as an analyzer. Moreover, it measured by the total reflection measuring method (ATR method) using the germanium prism. The measurement was performed on the surface of the charging roller and an elastic layer cut by 0.5 mm in the depth direction from the surface of the charging roller, the infrared absorption spectrum of the surface and the inside was analyzed, and the peak intensity derived from silsesquioxane was compared. . As a result, in the measurement of the surface of the charging roller, a strong infrared absorption peak (1080 cm ⁻¹ ) derived from a cured product of silsesquioxane was observed as compared with the measurement inside the elastic layer. This confirmed that a cross-linked product of silsesquioxane was present on the surface.

(Reuseability (image characteristics) evaluation)
The produced charging roller and the electrophotographic photosensitive member were assembled in a process cartridge that integrally supports them. This process cartridge was incorporated into an electrophotographic apparatus (product name: Color LaserJet 2025dn Hewlett Packard) for vertical output of A4 paper, and durability evaluation was performed. The evaluation was performed in a 15 ° C./10% RH (relative humidity) environment, and 3000 sheets were printed at a printing density of 4%. Thereafter, the charging roller was taken out, and its surface was wiped with a non-woven fabric soaked with water to remove deposits on the charging roller surface. The charged roller after cleaning was left to dry in a 23 ° C./50% RH environment for 24 hours, and then assembled again into a new process cartridge for durability evaluation. It was incorporated in the same electrophotographic apparatus as in the durability evaluation in the first cycle, was performed in a 15 ° C./10% RH environment, and 3000 sheets were printed at a printing density of 4%. Then, image evaluation was performed by visually observing the uniformity of the output halftone image (image in which a line having a width of 1 dot was drawn at intervals of 2 dots in the direction perpendicular to the rotation direction of the electrophotographic photosensitive member). The evaluation criteria are as follows.
A: No image defect caused by scratches on the charging roller, toner or external additives attached.
B: The above-mentioned image defect occurred slightly.
C: The above-mentioned image defect slightly occurred.
D: The above-mentioned image defect clearly occurred.

<Example 2>
Silsesquioxane used for the preparation of the kneaded rubber composition of Example 1 was converted to oxetanyl group-containing silsesquioxane (trade name: OX-SQ (SI-20), manufactured by Toagosei Co., Ltd.): 5 parts by mass changed. Otherwise, an unvulcanized rubber roller was formed in the same manner as in Example 1. With respect to the formed unvulcanized rubber roller, a charging roller was produced in the same manner as in Example 1 except that the temperature condition of the continuous vulcanizing furnace was first changed to 120 ° C. for 30 minutes and then to 180 ° C. for 30 minutes. Using the above charging roller, it was confirmed that a cured product of silsesquioxane was present on the surface in the same manner as in Example 1. In addition, reusability evaluation was performed in the same manner as in Example 1 using the above charging roller.

<Example 3>
The following points were changed in the materials used for the preparation of the kneaded rubber composition of Example 1. The raw rubber was changed to SBR (trade name: Nipol 1507, manufactured by Nippon Zeon Co., Ltd.) with the same mass parts. In addition, silsesquioxane was changed to oxetanyl group-containing silsesquioxane compound (trade name: OX-SQ (TX-100), manufactured by Toagosei Co., Ltd.): 5 parts by mass. Moreover, the following points were changed in the material used for preparation of the mixture of Example 1. The number of parts by mass of tetrabenzylthiuram disulfide (trade name: PERKACIT-TBzTD, manufactured by FLEXSYS), which is a vulcanization accelerator, was changed to 1 part by mass. Furthermore, as a vulcanization accelerator, Nt-butyl-2-benzothiazolsulfenimide (trade name: SANTOCURE-TBSI (abbreviated as TBSI), manufactured by FLEXSYS): 1.0 part by mass was added. Otherwise, a charging roller was obtained in the same manner as in Example 1. Using the obtained charging roller, the presence of a cured product of silsesquioxane was confirmed in the same manner as in Example 1. In addition, reusability evaluation was performed in the same manner as in Example 1 using the above charging roller.

<Example 4>
In the preparation of the kneaded rubber composition of Example 2, the silsesquioxane was changed to an oxetanyl group-containing silsesquioxane having the same number of parts (trade name: OX-SQ (ME-20), manufactured by Toagosei Co., Ltd.). did. Otherwise, the charging roller was molded in the same manner as in Example 2. About the obtained charging roller, presence of the hardened | cured material of silsesquioxane was confirmed similarly to Example 1. FIG. In addition, reusability evaluation was performed in the same manner as in Example 1 using the above charging roller.

<Example 5>
In the preparation of the kneaded rubber composition of Example 1, α-hydroxyketone as an initiator (trade name: DAROCURE 1173, manufactured by Ciba Specialty Chemicals Co., Ltd.): Example except that 1 part by mass was further added. In the same manner as in No. 1, a vulcanized rubber roller was molded. The surface of the obtained vulcanized rubber roller was irradiated with ultraviolet rays (UV) to cure the silsesquioxane to obtain a charging roller. For the irradiation of ultraviolet rays, a low-pressure mercury lamp manufactured by Harrison Toshiba Lighting Co., Ltd. was used, and ultraviolet rays having a wavelength of 254 nm were irradiated so that the integrated light amount became 15000 mJ / cm ² . The vulcanized rubber roller was irradiated with ultraviolet rays while being rotated by a roller rotating member at a speed of 60 rpm. The integrated light quantity of ultraviolet rays is defined as follows.

UV integrated light quantity [mJ / cm ² ] = UV intensity [mW / cm ² ] × irradiation time [s].

  The adjustment of the integrated amount of ultraviolet light can be performed by adjusting the irradiation time, the lamp output, the distance between the lamp and the object to be irradiated, etc., and the integrated UV light meter UIT-150-A (made by USHIO INC.) (Trade name). About the obtained charging roller, presence of the hardened | cured material of silsesquioxane was confirmed similarly to Example 1. FIG. In addition, reusability evaluation was performed in the same manner as in Example 1 using the above charging roller.

<Example 6>
The raw material rubber used for the preparation of the kneaded rubber composition of Example 3 was changed to BR of the same mass part (trade name: Nipol BR1220L, manufactured by Nippon Zeon Co., Ltd.), and Silsesquioxane was an example of the same mass part. The silsesquioxane used in 1 was changed. Otherwise, a charging roller was obtained in the same manner as in Example 3. About the obtained charging roller, presence of the hardened | cured material of silsesquioxane was confirmed similarly to Example 1. FIG. In addition, reusability evaluation was performed in the same manner as in Example 1 using the above charging roller.

<Example 7>
The raw rubber used for the preparation of the kneaded rubber composition of Example 6 was changed to EPDM (trade name: Esprene 5754, manufactured by Sumitomo Chemical Co., Ltd.) with the same parts by mass. Otherwise, an unvulcanized rubber roller was formed in the same manner as in Example 6. With respect to the formed unvulcanized rubber roller, a charging roller was produced in the same manner as in Example 6 except that the temperature condition of the continuous vulcanizing furnace was first changed to 120 ° C. for 30 minutes and then to 180 ° C. for 30 minutes. About the obtained charging roller, presence of the hardened | cured material of silsesquioxane was confirmed similarly to Example 1. FIG. In addition, reusability evaluation was performed in the same manner as in Example 1 using the above charging roller.

<Comparative Example 1>
The silsesquioxane used for the preparation of the kneaded rubber composition of Example 1 is a monofunctional acrylate monomer represented by the following chemical formula (2) with the same parts by mass (trade name: NK ester LA, manufactured by Shin-Nakamura Chemical Co., Ltd.). ). Otherwise, the charging roller was molded in the same manner as in Example 1.

  Reusability evaluation was performed in the same manner as in Example 1 using the above charging roller.

<Comparative example 2>
The silsesquioxane used for the preparation of the kneaded rubber composition of Example 1 is a bifunctional acrylate monomer (trade name: NK ester A-HD, Shin-Nakamura Chemical Co., Ltd.) represented by the following chemical formula (3) with the same parts by mass. Changed to Otherwise, the charging roller was molded in the same manner as in Example 1.

  Reusability evaluation was performed in the same manner as in Example 1 using the above charging roller.

<Comparative Example 3>
A vulcanized rubber roller was molded in the same manner as in Example 1 except that no silsesquioxane was added. The surface of the obtained vulcanized rubber roller was irradiated with ultraviolet rays in the same manner as in Example 5 to obtain a charging roller. For this charging roller, the reusability evaluation was performed in the same manner as in Example 1.

  Table 3 shows prescriptions of the charging rollers according to Examples and Comparative Examples, Table 4 shows manufacturing conditions, and Table 5 shows evaluation results.

  In the charging rollers according to Comparative Examples 1 and 2, a cured product of silsesquioxane was not formed on the surface, and the image evaluation result was C rank or less in the reusability evaluation of the obtained charging roller. Comparative Example 3 is an example in which surface modification by ultraviolet irradiation was performed without containing silsesquioxane, but the effect of reducing the friction coefficient and tackiness of the elastic body surface was not sufficient, and the surface hardness was low. Therefore, the image evaluation result is D rank in the reusability evaluation. Examples 1 to 7 are charging rollers manufactured according to the present invention, and the image evaluation result in the reusability evaluation is B rank or higher, and a good image is obtained.

DESCRIPTION OF SYMBOLS 1 Charging roller 11 Core metal 12 Elastic layer 13 Surface layer

Claims (3)

(A) at least one raw material rubber selected from the group consisting of polyisoprene, polybutadiene, styrene butadiene copolymer, ethylene propylene copolymer, butyl rubber, nitrile rubber, hydrin rubber, chloroprene rubber, acrylic rubber, urethane rubber and fluororubber; Forming a layer of a mixture containing silsesquioxane on the mandrel;
(B) bleeding the silsesquioxane in the layer of the mixture on the surface of the layer of the mixture;
(C) curing the silsesquioxane bleed on the surface of the layer of the mixture;
A method for producing a charging member, comprising:   The method for producing a charging member according to claim 1, wherein the silsesquioxane has at least one selected from an oxetanyl group and an acryloyl group in a molecule.   The method for manufacturing a charging member according to claim 1, wherein the step C includes a step of irradiating the surface of the layer of the mixture with an electron beam.

Images