JP2008046360A - Semiconductive member and image forming apparatus using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductive member capable of obtaining stable, satisfactory uniform transferability and image quality for a long period of time by restraining defects on the surface of a semiconductive member and preventing transfer performance deterioration resulting from wear and to provide an image forming apparatus having the semiconductive member and capable of stably obtaining high transfer image quality. <P>SOLUTION: The semiconductive member has an elastic layer and a surface layer formed on the elastic layer. The surface layer contains acid carbon black, a lubricant component, and fiber-like inorganic filler. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductive member used in an image forming apparatus such as a copying machine, a printer, and a facsimile machine, and an image forming apparatus using the semiconductive member.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, an image is formed by forming a latent image on an image carrier such as a photosensitive drum by a charging roll (semiconductive member), and this image is transferred to an intermediate transfer belt ( There have already been provided those that are indirectly transferred to a recording material via a semiconductive member) or directly transferred to a recording material on a paper conveying belt (semiconductive member). Thus, the semiconductive member is used for each member of the image forming apparatus. Further, in recent years, there is a tendency to use a small diameter spherical toner as a toner in order to obtain a high quality transfer image quality. Since the toner is reduced in diameter and spheroidized, the toner is easily moved by the transfer electric field, so that the problem that the toner scatters easily occurs.

  In this type of semiconductive member, for example, in the case of an intermediate transfer belt (paper conveyance belt), the intermediate transfer belt (paper conveyance belt) and the image carrier from the viewpoint of maintaining good image transfer performance from the image carrier. And the pressure in the nip region between the intermediate transfer belt (paper conveying belt) and the transfer member must be sufficiently increased and the adhesion must be increased.

  Therefore, an intermediate transfer belt (paper conveyance belt) having a belt base material itself formed of an elastic body such as a flexible rubber material has already been provided. Such an intermediate transfer belt generally has a structure in which a fluororesin layer is provided on the surface of an elastic base made of a rubber elastic body. That is, by using an elastic substrate, a sufficient nip width is secured between the surface of the photoreceptor on which the toner image to be transferred is formed and the recording material to which the toner image is transferred, and fluorine on the surface. By providing the resin layer, the releasability is improved and the friction coefficient is reduced.

  However, an intermediate transfer belt using an elastic substrate has a problem that a crack occurs in the surface fluororesin layer. That is, primary transfer (intermediate transfer) and secondary transfer (transfer to a recording material) are performed while the intermediate transfer member is moved by driving transmission to the elastic substrate, but the fluororesin layer on the surface is compared with the elastic substrate. Thus, the stretchability is poor and the followability to the elastic substrate is poor. For this reason, there is a problem that cracks occur in the fluororesin layer on the surface during repeated driving. As a countermeasure, it has been proposed to provide a silicon-acrylic copolymer resin layer between the fluororesin-containing surface layer and the elastic substrate surface (see, for example, Patent Document 1). However, the belt having this configuration has a problem in that the surface layer is reduced due to frictional wear with the image carrier, the cleaning member, etc. during long-term use, and the surface quality is changed to deteriorate the transfer image quality.

Further, when an elastic body such as chloropyrene rubber containing carbon black is used as a transfer / conveying belt, a 10 ⁹ Ωcm level semiconductive resistance region is a region where resistance control is difficult, and therefore, a normal rubber material It is difficult to stably produce a variation in resistance of the elastic belt within an order of magnitude (log Ωcm value), and it is almost impossible to stably obtain a desired resistance value only by adding ordinary conductive carbon black to . When the resistance in-plane variation is as large as one digit or more, there is a problem that the transfer image quality is not stable because the transfer voltage cannot be applied uniformly. Further, in order to hold the transfer material and transfer the toner image to the transfer material, a transfer voltage of 1 kV to 5 kV is applied, but the resistance value of the belt material changes due to the applied voltage, and a portion where the transfer material is present There is a problem that the resistance value varies depending on the area where there is no transfer material.

  In response to such technical problems, if a mixed base material of chloroprene rubber and EPDM is used as the belt base material of the paper conveyance belt, excellent ozone resistance and flame retardancy can be exhibited, and the bleed phenomenon A technology that can effectively avoid the above has already been provided (see, for example, Patent Document 2). In addition, in Patent Document 2, if acetylene black, furnace black and acetylene black, or acetylene black and ketjen black are dispersed in the belt base material, fluctuations in electrical resistance over time can be suppressed. It is also disclosed that this can be done.

However, in such a paper transport belt, the resistance value of the surface layer provided on the substrate needs to be higher than the resistance value of the substrate. In a surface layer containing a conductive agent such as carbon black, the resistance of the surface layer increases due to the influence of the non-uniform dispersibility of the conductive agent, and as a result, the resistance of the entire belt appears remarkably. In addition, when the resistance increase of the surface layer is large, a power storage effect is generated in the surface layer, and there is a problem that a secondary failure such as an image history occurs.
JP 2004-334029 A JP-A-9-179414

  The present invention has been made in view of the above technical problems, and prevents a decrease in transfer performance due to an increase in resistance of the surface layer and frictional wear, thereby obtaining a stable and good uniform transfer property over a long period of time. It is an object to provide a semiconductive member that can be used. Another object of the present invention is to provide an image forming apparatus that includes the semiconductive member and can stably obtain a high-quality transfer image quality.

Means for solving the above-described problems can be achieved by the present invention described below.
That is, the present invention
<1> An elastic body layer and a surface layer formed thereon, the surface layer being a semiconductive member comprising acidic carbon black, a lubricating component, and a fibrous inorganic filler. is there.
<2> The semiconductive member according to <1>, wherein the lubricating component is a compound containing a fluorine atom.
<3> The semiconductive member according to <2>, wherein the compound containing a fluorine atom is a fluororesin particle.
<4> The amount of the fibrous inorganic filler is 5 to 30 parts by mass with respect to 100 parts by mass of the resin component of the surface layer, according to any one of <1> to <3>. This is a semiconductive member.
<5> Image carrier, charging means for charging the surface of the image carrier, latent image forming means for forming a latent image on the surface of the image carrier, and developing the latent image with toner to form a toner image Developing means, transfer means for transferring the toner image to a recording medium, and fixing means for heat-fixing the toner image on the recording medium,
The transfer means has an elastic layer and a surface layer formed thereon, and the surface layer contains acidic carbon black, a lubricating component, and a fibrous inorganic filler. An image forming apparatus including the semiconductive member.
<6> The image forming apparatus according to <5>, wherein the lubricating component is a compound containing a fluorine atom.
<7> The image forming apparatus according to <6>, wherein the compound containing a fluorine atom is a fluororesin particle.
<8> The addition amount of the fibrous inorganic filler is any one of <5> to <7>, in a range of 5 to 30 parts by mass with respect to 100 parts by mass of the resin component of the surface layer. This is an image forming apparatus.
<9> The image forming apparatus according to any one of <5> to <8>, wherein the semiconductive member is used as a paper transport belt.
<10> The image forming apparatus according to any one of <5> to <8>, wherein the semiconductive member is used as an intermediate transfer belt.
<11> Any one of <5> to <10>, wherein the semiconductive member is stretched between a plurality of stretch rolls and is arranged in contact with the shape of a drum-shaped image carrier. The image forming apparatus according to claim 1.
<12> The image forming apparatus according to any one of <5> to <11>, wherein a spherical toner having a shape factor SF defined by the following formula (1) of 140 to 100 is used. .
Formula (1)
SF = [(maximum length of toner particles) ² ] / [(projected area of toner particles) × π × 1/4] × 100

  According to the present invention, there is provided a semiconductive member capable of preventing a decrease in transfer performance due to an increase in resistance of a surface layer and frictional wear, and obtaining a stable and good uniform transfer property over a long period of time. Can do. Further, the image forming apparatus provided with the semiconductive member of the present invention can stably obtain a high-quality transfer image quality.

<Semiconductive member>
The semiconductive member of the present invention has an elastic layer and a surface layer formed thereon, and the surface layer contains acidic carbon black, a lubricating component, and a fiber-shaped inorganic filler. It is characterized by becoming. Hereinafter, each structure of the semiconductive member of this invention is demonstrated in detail.

-Acidic carbon black-
In the present invention, acidic carbon black means acidic carbon black having a pH of 5 or less. Acidic carbon black can be produced by oxidizing carbon black, that is, by introducing a carboxyl group, a quinone group, a lactone group, a hydroxyl group, or the like on the surface. This oxidation treatment is performed by an air oxidation method that reacts with air in a high temperature atmosphere, a method that reacts with nitrogen oxides or ozone at room temperature, and a method that oxidizes ozone at a low temperature after air oxidation at a high temperature. be able to. Specifically, it can be manufactured by a contact method. Examples of the contact method include a channel method and a gas black method. Moreover, acidic carbon black can also be manufactured by the furnace black method which uses gas or oil as a raw material. Further, if necessary, liquid phase oxidation treatment with nitric acid or the like may be performed after performing these treatments. Acidic carbon black can be produced by a contact method, but is usually produced by a closed furnace black method. In the furnace black method, only carbon black having a high pH and a low volatile content is usually produced, but the pH can be adjusted by subjecting it to the above-described liquid phase acid treatment. For this reason, in the present invention, carbon black obtained by the furnace black method and adjusted to have a pH of 5 or less by post-treatment is also considered to be included in the acidic carbon black having a pH of 5 or less.

  The pH of the acidic carbon black is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.0 or less. Acidic carbon having a pH of 5.0 or less has good dispersibility in the resin due to the introduction of oxygen-containing functional groups such as carboxyl group, hydroxyl group, quinone group, and lactone group on the surface, and good dispersion stability. Thus, the resistance variation of the surface layer material can be reduced, and the electric field dependency is also reduced, so that the electric field concentration due to the transfer voltage is difficult to occur.

  The pH of acidic carbon black is determined by preparing an aqueous suspension and measuring it using a glass electrode. Further, the pH of the carbon black can be adjusted by conditions such as the treatment temperature and treatment time in the oxidation treatment step.

  The acidic carbon black preferably has a volatile component content of 2 to 25% by mass, more preferably 3 to 20%, and 3.5 to 15% by mass. More preferably. By making content of a volatile component into 2-25 mass%, dispersion | distribution in the said resin composition can be made more favorable. When the content of the volatile component is less than 2% by mass, the effect of the oxygen-containing functional group adhering to the outside is lost, and the dispersibility in the binder resin may be reduced. On the other hand, if the content of the volatile component is higher than 25%, it may be decomposed when dispersed in the resin composition, or the amount of water adsorbed on the outer oxygen-containing functional group is increased. The surface layer appearance may deteriorate. The content of the volatile component can be determined from the ratio of organic volatile components (carboxyl group, hydroxyl group, quinone group, lactone group, etc.) that come out when carbon black is heated at 950 ° C. for 7 minutes.

  Here, other carbon blacks may be used in combination with the acidic carbon black. At that time, these carbon blacks are preferably substantially different in conductivity from each other, for example, those having different physical properties such as degree of oxidation treatment, DBP oil absorption, specific surface area by BET method utilizing nitrogen adsorption, etc. Use. When adding two or more types of carbon blacks with different electrical conductivity in this way, for example, carbon black that exhibits high electrical conductivity is preferentially added, and then carbon black with low electrical conductivity is added to adjust the electrical resistance value. It is possible to do. Thus, even when two or more types of carbon black are contained, at least one of them is an acidic carbon black having a pH of 5.0 or less, thereby improving the mixing of both carbon blacks and the dispersibility into the component components. be able to.

  Specific examples of the acidic carbon black include “Printex 150T” (pH 4.5, volatile content 10.0% by mass) and “Special Black 350” (pH 3.5, volatile content 2) manufactured by Degussa Co., Ltd. 2% by mass), “Special Black 100” (pH 3.3, volatile matter 2.2% by mass), “Special Black 250” (pH 3.1, volatile matter 2.0% by mass), “Special Black” 5 ”(pH 3.0, volatile content 15.0% by mass),“ Special Black 4 ”(pH 3.0, volatile content 14.0% by mass),“ Special Black 4A ”(pH 3.0, volatile content 14) 0.0% by mass), “Special Black 550” (pH 2.8, volatile content 2.5% by mass), “Special Black 6” (pH 2.5, volatile content 18.0% by mass), “Color Black” FW 00 ”(pH 2.5, volatile content 20.0% by mass),“ Color Black FW2 ”(pH 2.5, volatile content 16.5% by mass),“ Color Black FW2V ”(pH 2.5, volatile content 16) .5 mass%), “MONARCH 1000” manufactured by Cabot (pH 2.5, volatile content 9.5 mass%), “MONARCH 1300” manufactured by Cabot (pH 2.5, volatile content 9.5 mass%), manufactured by Cabot “ “MONARCH1400” (pH 2.5, volatile matter 9.0% by mass), “MOGUL-L” (pH 2.5, volatile matter 5.0% by mass), “REGAL400R” (pH 4.0, volatile matter 3.5) Mass%) and the like.

  Acidic carbon black has better dispersibility in the resin composition due to the effect of oxygen-containing functional groups present on the surface as described above compared to general carbon black. Can be high. A content of acidic carbon black of 10 to 30% by mass is preferable because the effect of acidic carbon black can be exhibited, such as suppressing in-plane variation of the electrical resistance ground of the semiconductive belt. If the acidic carbon black is less than 10% by mass, the uniformity of the electrical resistance is lowered, and the in-plane unevenness of the volume resistivity and the electric field dependency may increase. On the other hand, if the content of acidic carbon black exceeds 30% by mass, it may be difficult to obtain a desired resistance value. Furthermore, it is more preferable to contain 18 to 30% by mass of acidic carbon black. By containing 18 to 30% by mass of acidic carbon black, the effect can be maximized, and in-plane unevenness of volume resistivity can be achieved. And the electric field dependency can be remarkably improved.

-Lubricity component-
The lubricant component is not particularly limited as long as it can impart lubricity, but a compound containing a fluorine atom is suitable, and examples of the compound containing a fluorine atom include a fluorine compound and a fluorine resin particle. it can. In particular, in the present invention, since it is used in combination with a fiber-shaped inorganic filler that imparts abrasion resistance, it is preferable to use a compound containing a fluorine compound in order not to increase the hardness of the surface layer.

(Fluorine compound)
Examples of the fluorine compound include polyalkyl (meth) acrylates, polyesters, polycarbonates, polyurethanes, etc., in which part of the molecular structure is substituted with fluorine atoms or fluorine atom groups. Specifically, for example, a compound obtained by grafting a polymethyl methacrylate side chain to the main chain of a methyl methacrylate-perfluoroalkyl methacrylate copolymer is suitable, and this compound is manufactured by Soken Kagaku Co., Ltd. Available as Chemitry LF-700. Such a compound containing a fluorine atom can be used alone or in combination of two or more.

  The addition amount of such a fluorine compound is preferably in the range of 10 to 40% by mass and more preferably in the range of 15 to 35% by mass with respect to the total amount of the surface layer. When the addition amount is less than 10% by mass, lubricity may not be exhibited. When the addition amount exceeds 40% by mass, the surface layer may be softened, resulting in a problem of low hardness.

(Fluorine resin particles)
Fluorine resin particles include ethylene tetrafluoride resin, ethylene trifluoride chloride resin, propylene hexafluoride resin, vinyl fluoride resin, vinylidene fluoride resin, ethylene difluoride dichloride resin, and copolymers thereof. It is desirable to appropriately select one or two or more types from the above, but particularly preferred are tetrafluoroethylene resin and vinylidene fluoride resin.

  The content of the fluororesin particles in the surface layer is suitably in the range of 5 to 40 parts by mass, particularly preferably 1 to 30 parts by mass with respect to 100 parts by mass of the resin component of the surface layer. If the content is less than 1 part by mass, the modification effect due to the dispersion of the fluororesin particles is not sufficient. On the other hand, if the content exceeds 40 parts by mass, the surface layer becomes hard and the problem of loss of flexibility may occur.

  The primary particle size of the fluororesin particles is preferably in the range of 0.05 to 1 μm, more preferably in the range of 0.1 to 0.5 μm. When the primary particle diameter is less than 0.05 μm, aggregation during dispersion tends to proceed. On the other hand, if it exceeds 1 μm, image quality defects are likely to occur. The primary average volume particle diameter can be measured using a laser diffraction particle size distribution analyzer SALD-2200 manufactured by Shimadzu Corporation.

  The fluororesin particles may be fluororesin particles that are crosslinked by irradiating ionizing radiation. As described in JP-A-2002-317055, by irradiating fluororesin particles with ionizing radiation of 1 kGy or more in an inert atmosphere of 300 ° C. or higher, the fluororesin particles have a three-dimensional molecular structure. Thus, the friction resistance of the surface layer is substantially the same as that before the crosslinking, but the wear resistance is dramatically improved. By including such a crosslinked fluororesin in the resin, for example, when a friction phenomenon occurs, the wear resistance of the resin itself can be increased. In addition, about the preferable compounding quantity and primary particle diameter of the fluororesin particle | grains bridge | crosslinked by irradiating this ionizing radiation, it is the same as that of the case of the above-mentioned fluororesin particle.

-Fiber-shaped inorganic filler-
The fiber-shaped inorganic filler is not particularly limited as long as it can impart abrasion resistance, but examples thereof include inorganic fibers such as potassium titanate, wollastonite, zonotlite, aluminum borate fibers, and magnesium borate fibers. be able to. Specifically, it can be suitably obtained as “Dentor WK200B” manufactured by Otsuka Chemical Co., Ltd., which is obtained by surface-treating potassium titanate whiskers with tin oxide.

  The addition amount of such a fibrous inorganic filler is preferably in the range of 5 to 30 parts by mass, more preferably in the range of 10 to 25 parts by mass with respect to 100 parts by mass of the resin component of the surface layer. When the amount added is less than 5 parts by mass, the effect of improving the abrasion resistance may not be obtained. When the amount added exceeds 30 parts by mass, the surface layer becomes hard and the flexibility is lost. There is a case.

The average fiber length of the fiber-shaped inorganic filler is preferably in the range of 5 to 30 μm, and more preferably in the range of 10 to 20 μm. If the average fiber length is less than 5 μm, there is a problem that aggregates are likely to be generated.
The average fiber diameter of the fiber-shaped inorganic filler is preferably in the range of 0.1 to 1.0 μm, and more preferably in the range of 0.4 to 0.7 μm. When the average fiber diameter is less than 0.1 μm, there is a problem that aggregates are likely to be generated. When the average fiber diameter is more than 1.0 μm, there is a problem that irregularities are generated on the surface and image quality defects are likely to occur.

  By using the fiber-shaped inorganic filler having the above-described shape, the dispersibility of the acidic carbon black in the member component can be further improved. Further, when fluororesin particles are used as the lubricating component, the dispersibility of the fluororesin particles can be improved. This is presumed to be due to the difference in shape between the two, so that they are dispersed so as to fill each other's gaps during mixing.

-Surface layer material-
The resin material used for the surface layer is preferably a resin material having a low adhesiveness to the toner. For example, urethane resin, fluororesin, acrylic resin, polyamide resin, melamine resin and the like can be used. It is preferable to use an aqueous resin such as a fluororesin, an aqueous acrylic resin, or an aqueous melamine resin.

Here, the water-based resin means a resin having such a property that the water swells between the polymers constituting the resin with a force greater than the attractive force between the polymers to swell the resin, and the polymer is dispersed in water. . Generally, the case where the size of dispersed particles is 10 ⁻³ μm or less is called a solution (solution), and 10 ⁻³ to 10 ⁻¹ μm is called colloid, and 10 ⁻¹ to 10 μm is called latex. And dispersion are not always clear, and what is provided for practical use in a state in which a polymer is dispersed in water is collectively referred to as an aqueous resin. For example, urethane resins include those that dissolve or disperse in water without using an emulsifier and those that are forcibly emulsified using an emulsifier. In the present invention, the aqueous resin includes both of these forms. It is out.

The swelling of the resin in water (dissolved or dispersed) is required to have a number of hydrophilic polar groups in the molecular chain, as these polar groups, for example, -NH ₂ (amino group), - NH - (imino group), - NH · NH ₂ (- hydrazino group), = N-(tertiary amine groups) cationic groups such as, -COOH (carboxyl group), - SO ₃ H anions (sulfonic group) And nonionic groups such as —OH (hydroxyl group), —O— (ether group) —CO · NH ₂ (amide group). In the present invention, it is particularly preferable to use an aqueous resin having a nonionic group.

  When the above aqueous resin is used as the surface layer material and acidic carbon black having an oxygen-containing functional group such as —COOH (carboxyl group) or —OH (hydroxyl group) is used on the surface, acidic carbon is used in the aqueous dispersion of the aqueous resin. Black can be dispersed very uniformly. Furthermore, the dispersibility of the crosslinked fluororesin particles can also be improved. When a surface layer is formed by applying a dispersion water solution of an aqueous resin in which the acidic carbon black and cross-linked fluororesin particles are dispersed to a base layer mainly composed of an elastic material, followed by heat drying and firing, Thus, a surface layer having a uniform surface property can be formed. Moreover, since water is used as a dispersion solvent, the influence on the human body of the operator is small, and there is no risk of fire in the heat drying and baking processes.

  When non-hydrophilic resins are used for the surface layer material, these are dissolved or dispersed in an appropriate organic solvent, and a dispersion solution in which fluorocarbon resin particles cross-linked with acidic carbon black are dispersed is obtained. A base layer, which is a material, is obtained by applying the dispersion solution to a coating layer by heat drying and baking. In the present invention, the surface base material solution in which the fluorocarbon resin particles cross-linked with the acidic carbon black are applied to the conductive base layer may be performed by various methods such as spray coating, dipping, and brushing. it can.

  The thickness of the surface layer is preferably in the range of 0.5 μm to 100 μm. When the thickness of the surface layer is smaller than 0.5 μm, the effect of preventing the contamination of the surface of the semiconductive belt member may not be obtained. On the other hand, when the thickness is larger than 100 μm, the surface hardness of the semiconductive belt member becomes unnecessarily large, so that sufficient adhesion to the surface of the image carrier may not be obtained.

-Elastic layer-
The semiconductive member of the present invention has an elastic layer. The elastic layer is provided to keep the semiconductive member within a predetermined resistance value and hardness so that the semiconductive member can be uniformly transferred by being pressed against the surface of the image carrier with an appropriate nip width or nip pressure. It is done.
This elastic layer is formed by dispersing conductive particles in a rubber material. Examples of the rubber material include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, urethane rubber, silicone rubber, fluorine rubber, SBR, NBR, EPDM, acrylonitrile-butadiene-styrene rubber, and blended rubbers thereof. Of these, isoprene rubber, silicone rubber, and EPDM are preferably used.

Here, in the present invention, the elastic body layer has a volume resistivity of 1 × 10 ⁸ Ωcm to 1 × 10 ¹¹ Ωcm. In the present invention, “having elasticity” in the elastic body layer means that the hardness of the semiconductive member is a durometer hardness based on JIS K6253 (1997) and is in the range of A30 to A80.

  In order to obtain desired conductivity, conductive particles can be added to the elastic layer of the present invention. As the conductive particles, known materials can be used, but it is preferable to use an electron conductive conductive agent in terms of effectively suppressing variation in resistance to environmental fluctuations. Examples of such electron conductive conductive agents include carbon black, graphite, aluminum, nickel, copper alloys and other metals or alloys, tin oxide, zinc oxide, kalim titanate, tin oxide-indium oxide, or tin oxide-antimony oxide composite. Known metal oxides such as oxides can be used.

  Carbon black suitable as an electron conductive conductive agent has a property of being bonded in a chain form in the rubber composition to which the carbon black is added, and the resistance value of the rubber composition varies depending on the length of the chain bond. become. If this chain bond is long, the conductivity of the elastic layer is improved and its resistance value is lowered. On the other hand, if the chain bond is short, the conductivity of the elastic layer is lowered and its resistance value is increased. That is, when carbon black that forms long chain bonds is added to the elastic layer, the amount of carbon black added to develop the desired resistance value should be less than that of carbon black that forms short chain bonds. However, since the resistance value largely fluctuates due to the change in the addition amount, the above-described variation in the resistance value in the elastic layer cannot be reduced.

  In addition, as the electron conductive conductive agent in the present invention, it is also preferable to use two or more types of carbon black having different characteristics such as surface characteristics. The length of the carbon black chain bond depends on the particle size and surface activity of the individual particles of the carbon black. As an index indicating this, DBP defined in ASTM D2414-6TT is used. (Dibutyl phthalate) has oil absorption. This DBP oil absorbency is expressed by whether the DBP amount (ml) absorbed by 100 g of carbon black is large or small. Carbon blacks with higher DBP oil absorption, that is, more oil absorption, are considered to form longer chain bonds.

  If only the carbon black having a high DBP oil-absorbing property is added to the rubber composition to adjust the resistance value of the elastic layer, the resistance value greatly changes even if the addition amount is slightly increased or decreased. Therefore, a predetermined resistance value cannot be imparted to the elastic layer unless the amount of carbon black added and the dispersion state are strictly defined. On the other hand, if only the carbon black having a low DBP oil absorbency is added to adjust the resistance value of the elastic layer, the carbon black is contained in the rubber composition as compared with the case where only the carbon black having a high DBP oil absorbency is added. Therefore, the rate of change in the resistance value accompanying the increase / decrease of the addition amount becomes small. However, in order to impart a predetermined resistance value to the elastic layer, it is necessary to add a larger amount of carbon black than when adding only carbon black having high DBP oil absorption. As a result, since the blending ratio of carbon black in the rubber composition is increased, when the rubber composition is kneaded with a Banbury mixer, a kneader or the like, the viscosity becomes high and processing becomes difficult. Moreover, the problem that the obtained elastic body layer becomes high hardness may generate | occur | produce. Therefore, it is preferable to use two or more types of carbon black having a high DBP oil absorbability and carbon black having a low DBP oil absorbability that are different in DBP oil absorbency.

  When two or more types of carbon black are added to the elastic layer, it is sufficient if there is a difference in DBP oil absorption, but if this difference is too small, it is the same as when one type of carbon black is added. Will produce negative results. Accordingly, carbon black having a certain difference in DBP oil absorption is preferable, and at least one carbon black having a different DBP oil absorption is a carbon black having a DBP oil absorption of 250 ml / 100 g or more (DBP oil absorption). The carbon black having a high oil absorption is preferably 150 ml / 100 g or less (carbon black having a low DBP oil absorption).

  The DBP oil absorption of carbon black having a high DBP oil absorption is 280 ml / 100 g or more, and the DBP oil absorption of carbon black having a low DBP oil absorption is more preferably 110 ml / 100 g or less. In the present invention, as the two or more types of carbon blacks having different DBP oil absorption properties, at least the carbon black having a high DBP oil absorption property and the carbon black having a low DBP oil absorption property may be used. Carbon blacks with different amounts may further be included.

  Specifically, as the carbon black having high DBP oil absorption, for example, HS-500 (manufactured by Asahi Carbon Co., Ltd.) having a DBP oil absorption of 447 ml / 100 g, Ketjen black (Lion Exo (product of Asahi Carbon Co., Ltd.)) And carbon black such as Vulcan XC-72 (manufactured by Cabot Corporation) having a DBP oil absorption amount of 288 ml / 100 g and DBP oil absorption amount of 265 ml / 100 g. Moreover, as carbon black with low DBP oil absorption, Asahi Thermal FT (Asahi Carbon Co., Ltd.) having a DBP oil absorption of 28 ml / 100 g, Asahi Thermal MT (Asahi Carbon Co., Ltd.) having a DBP oil absorption of 35 ml / 100 g are used. ) And the like.

  In general, carbon black having a higher DBP oil absorption tends to have a smaller primary particle size, and the carbon black having a higher DBP oil absorption has a primary particle size in the range of 5 to 50 nm. It is preferable to use carbon black having a low primary property with a primary particle size in the range of 20 to 100 nm.

  As a specific example, when adjusting the resistance value of an elastic layer using a mixture of carbon black having high DBP oil absorbency (such as acetylene black) and carbon black having low DBP oil absorbency (such as thermal black), the mixing ratio Is preferably in the range of 1: 1 to 1: 8 by mass ratio (mass of carbon black having high DBP oil absorbency: mass of carbon black having low DBP oil absorbency), and in the range of 1: 2 to 1: 6. More preferably, it is more preferably in the range of 1: 2 to 1: 5.

  In the mass ratio (A: B) of the mass of the carbon black having a high DBP oil absorbency and the mass of the carbon black having a low DBP oil absorbency, if B is less than 1, not only the resistance value variation is large, The resistance value of the elastic layer changes greatly as the amount added is increased or decreased. On the other hand, when the B is larger than 5, as described above, the rubber composition at the time of kneading becomes high viscosity, so that not only the molding process of the elastic body layer becomes difficult, but also the hardness of the elastic body layer is reduced. Get higher. Thus, the rapid change of the resistance value of the elastic body layer can be suppressed by adjusting the mixing ratio of the carbon black having different DBP oil absorbency and the blending amount with respect to the rubber material. At the same time, it is possible to form an elastic body layer having a small variation in resistance value with a small amount of addition as compared with the case of carbon black alone having a low DBP oil absorption.

  The amount of carbon black added to the rubber composition is added so as to obtain a desired volume resistivity, and is preferably about 5 to 40 parts by mass (parts by mass relative to 100 parts by mass of the rubber composition). If the blending amount is less than 5 parts by weight, the resistance is too high to obtain the desired resistance. On the other hand, if it exceeds 40 parts by weight, the resistance is too low and image quality defects such as white spots may occur.

  In addition to the carbon black, a crosslinking agent, a filler, and the like are appropriately blended in the elastic body layer as necessary. The crosslinking agent is not particularly limited, and conventionally known ones such as thiourea, triazine, sulfur and the like can be mentioned. Examples of the filler include insulating fillers such as silica, talc, clay and titanium oxide, and these may be used alone or in combination.

  The elastic layer of the present invention can be produced by mixing the above-mentioned components with a mixer such as a tumbler, V-type blender, nauter mixer, Banbury mixer, kneading roller, extruder or the like. In the production of the elastic layer in the present invention, the mixing method of each component and the order of mixing are not particularly limited. As a general method, all components are mixed in advance with a tumbler, V blender, etc., and uniformly melt-mixed by an extruder. Depending on the shape of the components, two or more types of molten mixtures in these components are used. Alternatively, a method of melt-mixing the remaining components can be used.

In order to improve the mechanical strength, the semiconductive member of the present invention may have a base material under the elastic body layer. The substrate is preferably made of a resin material having a Young's modulus of 1000 MPa or more. When a resin material having a Young's modulus of 1000 MPa or more is used as the base material, the amount of displacement of the semiconductive member due to disturbance (load fluctuation) during driving is reduced, so that the deformation of the semiconductive member with respect to stress during driving is reduced. The image quality is reduced and good image quality can be stably obtained. With this configuration, the semiconductive member can more effectively satisfy the balance between flexibility and rigidity that cannot be obtained with a single material configuration. The Young's modulus of the base material is more preferably 1500 MPa or more, and further preferably 2000 MPa or more. Moreover, although the larger Young's modulus of a base material is better, it is 8000 MPa or less for practical use, and preferably 6000 MPa or less. The Young's modulus of the substrate can be controlled within the above range by selecting the chemical structure of the resin material to be used, and the Young's modulus can be increased as the material includes an aromatic ring structure.
The Young's modulus is obtained by performing a tensile test according to JIS K7127 (1999), drawing a tangent line to the curve in the initial strain region of the obtained stress / strain curve, and determining the slope.

  Examples of the resin material used for the base material include polyimide resin, polyamideimide resin, fluorine resin, vinyl chloride vinyl acetate copolymer, polycarbonate resin, polyethylene terephthalate resin, vinyl chloride resin, ABS resin, polymethyl methacrylate resin, Examples include polybutylene terephthalate resin. These may be used alone or in combination of two or more. Among these, a polyimide resin is preferably used because it is excellent in both strength and bending fatigue.

-Volume resistivity-
The volume resistivity of the semiconductive member of the present invention is preferably in the range of 1 × 10 ⁸ to 1 × 10 ¹³ Ωcm, and in the range of 1 × 10 ⁹ to 1 × 10 ¹² Ωcm. Is more preferable. When the volume resistivity is 1 × 10 ⁸ to 1 × 10 ¹³ Ωcm, the toner is scattered around the image due to electrostatic repulsion between the toners and the fringe electric field near the image edge (blur). Fewer problems occur. In addition, within the above range, the volume resistivity of the semiconductive member (particularly when applied to an intermediate transfer member) is in a range where the charged charge is appropriately attenuated. Image formation can be performed continuously.

Here, the volume resistivity can be measured according to JIS K6911 (1995) using a circular electrode (for example, Hiresta UPMCP-450 type UR probe manufactured by Dia Instruments Co., Ltd.). 3 is a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of a circular electrode, wherein the circular electrode shown in FIG. And a second voltage application electrode B. The first voltage application electrode A ′ has a cylindrical electrode portion C ′, an inner diameter larger than the outer diameter of the cylindrical electrode portion C ′, and a circular shape. A cylindrical ring-shaped electrode portion D ′ surrounding the columnar electrode portion C ′ at regular intervals, and the columnar electrode portion C ′ and the ring-shaped electrode portion D ′ of the first voltage application electrode A ′ and the second voltage application. The semiconductive belt 1 is sandwiched between the electrode B ′ and the first voltage application The current I (A) that flows when the voltage V (V) is applied between the cylindrical electrode portion C ′ and the second voltage application electrode B ′ in A ′ is measured. The volume resistivity ρv (Ωcm) can be calculated, where t represents the thickness of the semiconductive belt 1.
Formula: ρv = 19.6 × (V / I) × t

-Ten-point surface roughness Rz-
The ten-point average surface roughness Rz of the surface layer in the semiconductive member of the present invention is preferably 1.5 μm or more and 9.0 μm or less. If the ten-point average surface roughness Rz is less than 1.5 μm, there is a concern that the ten-point average surface roughness Rz is in close contact with other members that come into contact. Since powder or the like tends to accumulate, and minute discharge unevenness occurs due to unevenness, uniform transferability and image quality may deteriorate with time. The ten-point average surface roughness Rz referred to in the present invention is the surface roughness defined in JIS B0601 (1994).

  The ten-point average surface roughness Rz can be measured using a surface roughness measuring instrument or the like. In the present invention, however, a contact-type surface roughness measuring device (in a 23 ° C./55 RH% environment) Surfcom 570A, manufactured by Tokyo Seimitsu Co., Ltd.) was used. When measuring the surface of the semiconductive belt member, the measurement distance was 2.5 mm, the tip of the contact needle was diamond (5 μmR, 90 ° cone), and the measurement was repeated three times at different locations. The average value was determined as the 10-point average surface roughness Rz of the charging member.

  The semiconductive member of the present invention can be suitably used in an image forming apparatus as a semiconductive belt such as a transfer conveyance belt or an intermediate transfer belt, a semiconductive roll such as a charging roll or a transfer roll.

<Image forming apparatus>
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is an explanatory view showing an outline of an image forming apparatus provided with a semiconductive member of the present invention as a semiconductive belt. As shown in FIG. 1, an image carrier 6 and a semiconductive belt 1 opposite to the image carrier 6 are provided, and a toner image formed on the image carrier 6 is transferred to the semiconductive belt (intermediate transfer belt) 1 or semiconductive. In the image forming apparatus for transferring to the recording material 7 on the conductive belt (transfer conveyance belt) 1, the above-described semiconductive belt is used as the semiconductive belt (transfer conveyance belt, intermediate transfer belt) 1. To do.

  Here, in the embodiment in which the semiconductive belt 1 is used as an intermediate transfer belt, as shown in FIG. 1, the toner image on the image carrier 6 is transferred to the semiconductive belt (intermediate transfer belt) by the primary transfer device 8a. After the primary transfer to the belt 1, the toner image on the semiconductive belt (intermediate transfer belt) 1 is secondarily transferred to the recording material 7 by the secondary transfer device 8 b.

  On the other hand, in a mode in which the semiconductive belt 1 is used as a transfer conveyance belt (recording material holding belt), a recording material 7 is held on the transfer conveyance belt (recording material holding belt) 1 as shown in FIG. After that, the toner image on the image carrier 6 is transferred to the recording material 7 on the transfer conveyance belt (recording material holding belt) 1 by the transfer device 8.

  In the image forming apparatus shown in FIG. 1, it is preferable that the semiconductive belt 1 is stretched around a plurality of stretching rolls 9 and is arranged in contact with the drum-shaped image carrier 6. According to this aspect, by causing the semiconductive belt 1 to follow the shape of the image carrier 6 as much as possible, discharge due to useless gaps before and after the nip area at the time of transfer is eliminated, and scattering of the toner image is prevented. be able to.

  Further, in the image forming apparatus shown in FIG. 1, it is preferable that one of the image carrier 6 and the semiconductive belt 1 is used as a drive source and the other is driven to rotate. According to this aspect, by adopting such a drive configuration, one drive mechanism can be omitted, the drive cost can be reduced correspondingly, and the drive between the semiconductive belt 1 and the image carrier 6 can be suppressed. Variation factors such as thickness variation of the semiconductive belt 1 due to interference and feed variation in the process direction can be excluded.

  FIG. 2 shows an embodiment of an image forming apparatus to which the present invention is applied. In FIG. 1, an image forming apparatus follows a shape of a photosensitive drum 10 in a predetermined area to the photosensitive drum 10 and a photosensitive drum 10 for transferring a toner image from the photosensitive drum (image carrier) 10. The intermediate transfer belt 20 in contact therewith. The above-described semiconductive member of the present invention is used for the intermediate transfer belt 20. In the present embodiment, the photosensitive drum 10 includes a photosensitive layer whose resistance value is reduced by light irradiation. Around the photosensitive drum 10, a charging device 11 for charging the photosensitive drum 10 and , An exposure device 12 for writing an electrostatic latent image of each color component (in this example, yellow, magenta, cyan, black) on the charged photosensitive drum 10, and each color component latent image formed on the photosensitive drum 10. Are provided with a rotary developing device 13 that visualizes each of the color component toners, an intermediate transfer belt 20, and a cleaning device 17 that cleans residual toner on the photosensitive drum 10.

Here, for example, a charging roll is used as the charging device 11. The exposure device 12 may be any device that can write an image on the photosensitive drum 10 with light. In this example, a print head using, for example, an LED (Light Emitting Diode) is used. However, the present invention is not limited to this. A print head using an EL (Electro Luminescence) scanner that scans a laser beam with a polygon mirror is also used. You can select as appropriate.
Further, the rotary type developing device 13 is rotatably mounted with developing units 13a to 13d containing respective color component toners. For example, the respective color component toners are attached to a portion of the photosensitive drum 10 where the potential is lowered by exposure. The toner to be used is not particularly limited in shape and particle size, and any toner may be used as long as it is accurately placed on the electrostatic latent image on the photosensitive drum 10. In this example, the rotary developing device 13 is used, but four developing devices may be used.
Furthermore, the cleaning device 17 may be appropriately selected as long as it cleans the residual toner on the photosensitive drum 10 and employs a blade cleaning method. However, there may be a mode in which the cleaning device 17 is not used when toner having a high transfer rate is used.

  Further, as shown in FIG. 2, the intermediate transfer belt 20 is stretched between four stretching rolls 21 to 24, and is a photosensitive drum positioned between the rotary developing device 13 and the cleaning device 17. Only a predetermined contact area is disposed in close contact with the 10th surface. Here, the intermediate transfer belt 20 and the photosensitive drum 10 may be driven by separate drive systems, but in the present embodiment, the intermediate transfer belt 20 is an elastic belt as described later, The intermediate transfer belt 20 is driven and rotated by using, for example, the photosensitive drum 10 as a driving source because it is disposed in contact with the circumferential surface of the photosensitive drum 10.

  A primary transfer roll 25 as a primary transfer device is disposed in contact with a part of the contact area where the intermediate transfer belt 20 is in close contact with the photosensitive drum 10 from the back side of the intermediate transfer belt 20, and a predetermined primary transfer bias is applied. Applied. Furthermore, a secondary transfer roll 30 as a secondary transfer device is disposed opposite to the tension roll 22 of the intermediate transfer belt 20 with the tension roll 22 as a backup roll, for example, the secondary transfer roll 30. A predetermined secondary transfer bias is applied to the tension roller 22 and the tension roll 22 that also serves as a backup roll is grounded. Furthermore, a cleaning blade 26 as a belt cleaning device is disposed at a portion of the intermediate transfer belt 20 that faces the stretching roll 23, and a predetermined cleaning bias is applied to the cleaning blade 26 to stretch the belt. The roll 23 is grounded.

  A recording material 40 such as paper is accommodated in a supply tray 41, supplied by a pickup roll 42, guided to a secondary transfer portion through a registration roll 43, and then to a fixing device 45 through a conveyance belt 44. It is conveyed and discharged to a discharge tray 48 through a transfer roll 46 and a discharge roll 47.

Next, the operation of such an image forming apparatus will be described.
In FIG. 2, when the image forming apparatus starts an image forming operation, each color component toner image on the photoconductive drum 10 is sequentially formed and sequentially transferred onto the intermediate transfer belt 20 by the transfer electric field of the primary transfer roll 25. Thereafter, the toner image primarily transferred to the intermediate transfer belt 20 is secondarily transferred to the recording material 40 by the transfer electric field of the secondary transfer roll 30, and is carried to the fixing step.

  Even if the photosensitive drum 10 and the intermediate transfer belt 20 are always in contact with each other, the bleed phenomenon can be prevented, so that a retract mechanism for separating the photosensitive drum 10 and the intermediate transfer belt 20 is not required, and an elastic body is provided. In accordance with the fact that an inexpensive elastic material can be used for the layer, it is possible to reduce the cost by eliminating the need for a retract mechanism.

Furthermore, in this embodiment, since the intermediate transfer belt 20 is driven and rotated by driving the photosensitive drum 10, the drive control cost of the intermediate transfer belt 20 can be greatly reduced. Furthermore, since the contact width of the intermediate transfer belt 20 to the photosensitive drum 10 in the primary transfer is set to be very wide, for example, 50 mm or more, stable follow-up to the intermediate transfer belt 20 can be realized, and the transfer nip can be realized. The toner is primarily transferred to the intermediate transfer belt in a state where toner is not scattered by discharge because there is no useless gap before and after the area.
In particular, in the present embodiment, since a wide transfer nip area between the photosensitive drum 10 and the intermediate transfer belt 20 is ensured, it is possible to reduce the pressure in the transfer nip area. The situation where the body drum 10 and the intermediate transfer belt 20 are completely in close contact with each other is more reliably avoided.

  In the present embodiment, the photosensitive drum 10 and the intermediate transfer belt 20 are placed in contact with each other in an overlapping state, and the intermediate transfer belt 20 is driven based on the driving force from the photosensitive drum 10. However, the present invention is not limited to this. The photosensitive drum 10 and the intermediate transfer belt 20 have separate drive systems, and the intermediate transfer belt 20 is linearly connected to the photosensitive drum 10. Of course, the present invention can also be applied to an embodiment in which contact is made.

  Furthermore, when the semiconductive belt of the present invention is incorporated and used as an intermediate transfer belt or transfer / conveying belt in an image forming apparatus, it is preferable to use a spherical toner as the toner. By using a spherical toner as the toner, the material constituting the transfer surface has a low surface hardness and a high volume resistance, thereby obtaining a high-quality transfer image quality free from image quality defects (holocharacter, blur, color registration). be able to.

However, the spherical toner means that the shape factor SF is 140 to 100. The shape factor is preferably 130 to 100 or less, and more preferably 120 to 100 or less. When the average shape factor SF is larger than 140, the transfer efficiency is lowered, and the deterioration of the image quality of the print sample can be visually confirmed. Here, the shape factor SF is a factor defined by the following formula (1).
Formula (1)
SF = [(maximum length of toner particles) ² ] / [(projected area of toner particles) × π × 1/4] × 100

  The maximum length of toner particles and the projected area of the toner particles are measured by using a Luzex image analysis device (manufactured by Nireco Corporation, FT) and an optical microscope image of the toner dispersed on the slide glass through a video camera. It was carried out by taking 100 pieces into an image analysis apparatus and processing the images.

  The spherical toner contains at least a binder resin and a colorant. The spherical toner can preferably use 2 to 12 μm particles, more preferably 3 to 9 μm particles.

  Binder resins include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isoprene, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate, and methyl acrylate. , Α-methylene aliphatic monocarboxylic esters such as ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate, vinyl Homopolymers and copolymers of vinyl ethers such as methyl ether, vinyl ethyl ether and vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone can be exemplified, Typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include coalescence, polyethylene, and polypropylene. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax, and the like can also be mentioned.

  Coloring agents include magnetic powders such as magnetite and ferrite, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, and lamp black. Rose Bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3 is a typical example.

  The spherical toner may be internally added or externally added with known additives such as a charge control agent, a release agent, and other inorganic fine particles. Typical examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, Fischer-Tropsch wax, montan wax, carnauba wax, rice wax, and candelilla wax.

  Known charge control agents can be used, but azo metal complex compounds, metal complex compounds of salicylic acid, and resin type charge control agents containing polar groups can be used. When the toner is manufactured by a wet manufacturing method, it is preferable to use a material that is difficult to dissolve in water in terms of controlling ionic strength and reducing wastewater contamination.

As other inorganic fine particles, small-diameter inorganic fine particles having an average primary particle size of 40 nm or less are used for the purpose of powder flowability, charge control, etc., and if necessary, larger diameters are used to reduce adhesion. Inorganic or organic fine particles may be used in combination. As these other inorganic fine particles, known ones can be used. Examples thereof include silica, alumina, titania, metatitanic acid, zinc oxide, zirconia, magnesia, calcium carbonate, magnesium carbonate, calcium phosphate, cerium oxide, and strontium titanate.
In addition, the surface treatment of the small-diameter inorganic fine particles is effective because the dispersibility becomes high and the effect of increasing the powder fluidity increases.

  The spherical toner is not particularly limited by the production method, and can be obtained by a known method. Specifically, for example, a kneading and pulverizing method in which a binder resin and a colorant and, if necessary, a release agent and a charge control agent are kneaded, pulverized and classified, and particles obtained by the kneading and pulverizing method are mechanically impacted. Method of changing shape by force or heat energy, emulsion polymerization of binder resin polymerizable monomer, dispersion of formed dispersion, colorant, release agent and charge control agent as required Liquid emulsion, agglomeration, heat fusion to obtain a spherical toner, emulsion polymerization aggregation method, polymerizable monomer to obtain a binder resin, colorant, if necessary, release agent, charge control agent A suspension polymerization method in which a solution such as a suspension is polymerized by suspending in an aqueous solvent, a binder resin and a colorant, and a release agent and a charge control agent as necessary are suspended in an aqueous solvent and granulated. Examples thereof include a dissolution suspension method. Further, a manufacturing method may be performed in which the spherical toner obtained by the above method is used as a core, and further, aggregated particles are attached and heat-fused to give a core-shell structure. When the external additive is added, it can be produced by mixing the spherical toner and the external additive with a Henschel mixer or a V blender. In addition, when the spherical toner is manufactured by a wet method, it can be externally added by a wet method.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

<Example 1>,
(Formation of elastic layer)
Granular acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd .: oil absorption 288 ml / 100 g) with respect to 100 parts by weight of a rubber material (NE40; manufactured by Nippon Synthetic Rubber Co., Ltd.) in which NBR and EPDM are blended at a weight ratio of 4: 6 ) A rubber composition having a blending ratio of 10 parts by weight and 20 parts by weight of Asahi Thermal FT (Asahi Carbon Co., Ltd .: oil absorption of 28 ml / 100 g and average particle size of 80 μm) was kneaded by two rolls. The obtained kneaded material was formed into a tube shape by a tube cross head extruder. Next, the molded blend rubber material was heated and vulcanized in a vulcanizing can with pressurized steam at a temperature of 126 ° C. and a pressure of 1.5 kg / cm ² G to form a conductive belt material. The obtained belt material is placed on the outside of a metal tube, and the surface is polished. An elastic layer having a thickness of 0.5 mm, an inner diameter of 140 mm, a width of 320 mm, a volume resistivity of 3 × 10 ⁹ Ωcm, and a durometer hardness of A70 A rubber belt made of
Volume resistivity is obtained by reading the current value 30 seconds after applying a voltage of 100 V according to JIS K6911 (1995) using a Hiresta UPMCP-450 type UR probe manufactured by Dia Instruments Co., Ltd. Value.

(Formation of surface layer)
A urethane resin component obtained by removing the fluororesin component (PTFE particles) from Emuralon 345 Clear (manufactured by Nippon Atchison Co., Ltd.) and a block isocyanate (WH-2: manufactured by Nippon Atson Co., Ltd.) as a curing agent is 100: 5. The mixture was obtained by mixing at a blending ratio. Next, 10 parts by mass of Degussa Co., Ltd. Special Black 4 (pH 3.0, volatile content 14.0% by mass) as acidic carbon black, and Soken Kagaku (to 100 parts by mass of the resin component), 35 parts by mass of “Chemtry LF-700” manufactured by Co., Ltd. and 25 parts by mass of “Dentor WK200B” manufactured by Otsuka Chemical Co., Ltd. were mixed using a ball mill to obtain a dispersion of an aqueous urethane resin coating. The dispersion is spray-coated on the surface of the obtained elastic body layer, and then heated and dried at 120 ° C. for 15 minutes to impart fluorine resin particles crosslinked with acidic carbon black and wear resistance. A surface layer having a thickness of 20 μm was formed. The volume resistivity of the semiconductive belt of Example 1 manufactured as described above was 3 × 10 ¹⁰ Ωcm, and the ten-point average surface roughness Rz was 7 μm.

<Example 2>
The surface layer was formed except that the blending amount of “Chemitry LF-700” manufactured by Soken Kagaku Co., Ltd. was 30 parts by mass and the blending amount of “Dentor WK200B” manufactured by Otsuka Chemical Co., Ltd. was 20 parts by mass. A semiconductive belt was produced in the same manner as in Example 1. The volume resistivity of the semiconductive belt of Example 2 obtained in this way was 1 × 10 ¹⁰ Ωcm, and the ten-point average surface roughness Rz was 6 μm.

<Example 3>
The surface layer was formed except that the amount of “Chemitry LF-700” manufactured by Soken Kagaku Co., Ltd. was 15 parts by mass, and the amount of “Dentor WK200B” manufactured by Otsuka Chemical Co., Ltd. was 20 parts by mass. A semiconductive belt was produced in the same manner as in Example 1. The volume resistivity of the semiconductive belt of Example 3 obtained in this manner was 8 × 10 ⁹ Ωcm, and the ten-point average surface roughness Rz was 3 μm.

<Example 4>
When forming the surface layer, instead of “Chemtory LF-700” manufactured by Soken Kagaku Co., Ltd., fluorine resin particles (manufactured by Mitsui DuPont Fluorochemical Co., Ltd., volume average particle size 0.3 μm Teflon (registered trademark)) 20 mass A semiconductive belt was produced in the same manner as in Example 1 except that the blending amount of “Dentor WK200B” manufactured by Otsuka Chemical Co., Ltd. was 20 parts by mass. The volume resistivity of the semiconductive belt of Example 4 obtained in this manner was 4 × 10 ¹⁰ Ωcm, and the ten-point average surface roughness Rz was 9 μm.

<Example 5>
A semiconductive belt was produced in the same manner as in Example 1 except that 4 parts by mass of “Dentor WK200B” manufactured by Otsuka Chemical Co., Ltd. was used for forming the surface layer. The volume resistivity of the semiconductive belt of Example 5 obtained in this manner was 4 × 10 ⁹ Ωcm, and the ten-point average surface roughness Rz was 1.5 μm.

<Example 6>
A semiconductive belt was produced in the same manner as in Example 1 except that 32 parts by mass of “Dentor WK200B” manufactured by Otsuka Chemical Co., Ltd. was used for forming the surface layer. The volume resistivity of the semiconductive belt of Example 6 obtained in this manner was 9 × 10 ⁹ Ωcm, and the ten-point average surface roughness Rz was 8.5 μm.

<Example 7>
Formation of polyimide substrate (Preparation of polyamic acid solution (A))
Tetracarboxylic dianhydride in which 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) are combined in a ratio of 2: 1 and a diamine component An N-methyl-2-pyrrolidone (NMP) solution of polyamic acid (solid content 20% by mass) was obtained from a certain 4,4′-diaminodiphenyl ether (DDE). In this solution, dry oxidized carbon black (SPECIAL BLACK4 (manufactured by Degussa Co., Ltd., pH 3.0, volatile content: 14.0%) is 24 parts by mass with respect to 100 parts by mass of the polyimide resin solid content. Using a collision-type disperser (Geanus PY made by Genus), this was mixed after being divided into two parts with a pressure of 200 MPa and a minimum area of 1.4 mm ² and then passing again through the path divided into two parts, A carbon black-containing polyamic acid solution (A) for the surface layer was obtained.

The polyamic acid solution (A) containing carbon black was applied to the inner surface of the cylindrical mold to 0.4 mm via a dispenser and rotated at 1500 rpm for 15 minutes to obtain a uniform thickness. Next, while rotating this at 250 rpm, hot air of 60 ° C. was applied from the outside of the mold for 30 minutes, and then heated at 150 ° C. for 60 minutes. Then, it returned to room temperature, peeled off from the metal mold | die, coat | covered the metal core, and heated up to 360 degreeC with the temperature increase rate of 2 degree-C / min. Furthermore, the mixture was heated at 360 ° C. for 30 minutes to remove the solvent, remove dehydrated ring-closing water, and complete the imide conversion reaction. Thereafter, the temperature was returned to room temperature, and the film was peeled from the mold to obtain a target polyimide film. The thickness of the film was 0.08 mm. The Young's modulus of this resin belt was 2500 MPa, and the volume resistivity at an applied voltage of 100 V was 5 × 10 ¹⁰ Ωcm.

(Formation of a three-layer belt)
A cylindrical mold was covered with the polyimide base material, and a conductive elastic layer was formed thereon in the same manner as in Example 1. Further, a surface layer was formed in the same manner as in Example 1 to obtain a three-layer belt. The thickness of each layer of the belt was a surface layer of 0.02 mm, an elastic layer of 0.5 mm, and a base material of 0.08 mm.
The volume resistivity of the semiconductive belt of Example 7 produced as described above was 5 × 10 ¹⁰ Ωcm, and the ten-point average surface roughness Rz was 7 μm.

<Comparative Example 1>
In forming the surface layer, 40 mass of fluorine resin particles (manufactured by Mitsui DuPont Fluorochemical Co., Ltd., volume average particle size 0.3 μm Teflon (registered trademark)) instead of “Chemtory LF-700” manufactured by Soken Kagaku Co., Ltd. A semiconductive belt member was prepared in the same manner as in Example 1 except that “Dentor WK200B” manufactured by Otsuka Chemical Co., Ltd. was not added. The volume resistivity of the semiconductive belt member of Comparative Example 1 obtained in this way was 3 × 10 ¹⁰ Ωcm, and the ten-point average surface roughness Rz was 10 μm.

<Comparative example 2>
70 parts by weight of chloroprene rubber is kneaded for 2 minutes using a 6-inch diameter open roll, and 30 parts by weight of ethylene / propylene / non-conjugated diene terpolymer (EPDM) is added thereto and kneaded for 13 minutes. Went. Next, 5 parts by weight of zinc oxide, 4 parts by weight of magnesium oxide, 1 part by weight of stearic acid, and 0.35 parts by weight of Sunseller 22C (ethylene thiourea manufactured by Sanshin Chemical Co., Ltd.) were added to the polymer kneaded product of chloroprene rubber and EPDM. Were added successively, and further Noxarer BZ (zinc di-n-butyl dithiocarbamate made by Ouchi Shinko Co., Ltd.), 1 part by weight Noxeller DM (dibenzothiazyl disulfide made by Ouchi Shinko Co., Ltd.), After adding 0.7 parts by weight of Noxeller TRA (dipentamethylene thiuram tetrasulfide manufactured by Ouchi Shinko Co., Ltd.) and 1.5 parts by weight of sulfur, thinning was performed 10 times using an open roll. After the rubber kneaded material is removed from the open roll, it is divided into three equal parts. Each of the rubber kneaded materials has 23 parts by mass of furnace black (manufactured by Asahi Carbon Co., Ltd.) and 6 parts by mass of Denka black (granular acetylene black produced by Electrochemical Co., Ltd.) Were added in respective amounts and kneaded with an open roll. The kneaded material to which carbon black was added in this way was formed into a belt shape using an extruder, and then vulcanized using a steam kettle. Then, the thickness of the belt was processed to 0.5 mm by grinding.

The belt surface was spray-coated with a mixture of 100 parts by weight of C-230U base (polyester urethane manufactured by Hirono Kagaku) and 30 parts by weight of C-230U curing agent (isocyanate manufactured by Hirono Kagaku) at 30 ° C. Firing was performed for a minute to form a surface layer, and a belt having an inner diameter of 140 mm and a width of 300 mm was produced. The volume resistivity of the semiconductive belt member of Comparative Example 2 obtained as described above was 6 × 10 ¹⁰ Ωcm, and the ten-point average surface roughness Rz was 12 μm.

<Evaluation>
About the semiconductive belts obtained in Examples 1 to 7 and Comparative Examples 1 and 2, volume resistivity, ten-point average surface roughness Rz, bleeding property, transfer image quality (holocharacter, blur), and continuous running test were evaluated. These results are shown in Table 1.

1) Volume resistivity The volume resistivity at the time of applying 100 volts was measured at 3 points in the length direction of the manufactured belt and 8 points in the circumferential direction (24 points in total), and the average value was determined as the volume resistivity of the belt. did.

2) Ten-point average surface roughness Rz
For the 10-point average surface roughness Rz, a contact type surface roughness measuring device (Surfcom 570A, manufactured by Tokyo Seimitsu Co., Ltd.) was used in an environment of 23 ° C. and 55 RH% in accordance with JIS B6010 (1994). When measuring the surface of the charging member, the measurement distance is 2.5 mm, and the contact needle has a diamond tip (5 μmR, 90 ° cone), and the average value is measured three times at different locations. The ten-point average surface roughness Rz of the semiconductive belt member was obtained.

3) Bleed property The obtained semiconductive belt was brought into contact with the OPC photoreceptor for 2 weeks in a high-temperature and high-humidity environment (48 ° C., 90% RH), and image quality evaluation was evaluated using the OPC photoreceptor. .
Judgment: ○: No problem in transfer image quality ×: There is a problem in the transfer image quality at the part where the semiconductive belt is in contact (whiteout occurs)

4) Evaluation of transfer image quality The obtained semiconductive belt is mounted on an image forming apparatus having the configuration of FIG. 2 modified from Fuji Xerox Co., Ltd. Docu Color 1255CP, and the transfer image quality after continuous output of 10,000 sheets is evaluated. did. As the toner, a spherical toner having a shape factor (SF) 132 and a volume average particle diameter of 5.5 μm was used, and an OPC photoconductor was used as the photoconductor.

For the volume average particle diameter of the toner, a Coulter Counter TA-II type (manufactured by Beckman-Coulter) was used as a measuring device, and ISOTON-II (manufactured by Beckman-Coulter) was used as the electrolyte.
As a measurement method, 1.0 mg of a measurement sample was added to 2 ml of a 5% aqueous solution of sodium alkylbenzene sulfonate as a dispersant. This was added to 100 ml of the electrolytic solution to prepare an electrolytic solution in which the sample was suspended. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for 1 minute, and the particle size distribution of particles having a diameter of 2 to 60 μm is measured using the Coulter counter TA-II with an aperture diameter of 100 μm. The average particle size was determined. The measured number of particles is 50,000.

(Holo character evaluation)
The occurrence of holo-characters was evaluated according to the following criteria.
○: No occurrence of holo-characters △: Little occurrence of holo-characters, few problems with image quality ×: There are occurrences of ears and characters, and there are problems with image quality

(Blur evaluation)
The occurrence of blur was evaluated according to the following criteria.
○: No blurring or slight blurring, no image quality problem ×: Bluring, image quality problem

5) Continuous running test The following criteria were used to evaluate the occurrence of white spots when copying a halftone of 30% magenta after continuously copying 100,000 sheets of A4 size J paper.
○: No white spots occur and there is no problem in image quality
Δ: Slight occurrence of white spots but no problem with image quality ×: There is white spot occurrence and there is a problem with image quality

-Comprehensive evaluation-
The evaluation criteria for comprehensive evaluation are as follows.
◎: No problem when using actual machine ○: No problem when using actual machine ×: Problem when using actual machine or cannot be used

From the results of Table 1, it can be seen that Examples 1 to 4 and 7 using the semiconductive member of the present invention had no image quality defects and could stably obtain excellent image quality over a long period of time. In Example 5, white spots hardly occurred. However, a paper jam may occur after running 50,000 sheets. In Example 6, the occurrence of a holocharacter was slightly observed. It was possible to use it without any practical problem even if it was installed in.
On the other hand, in Comparative Example 1, no occurrence of image quality defects of blur and holo-character was observed, but white-out image quality defects occurred in the continuous paper running test. Furthermore, in Comparative Example 2, a so-called bleed phenomenon was observed in which a low molecular oil component dispersed in the elastic layer was deposited on the surface of the conveyor belt.

1 is an explanatory diagram showing an outline of an image forming apparatus according to the present invention. 1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus according to an embodiment. It is a figure which shows the measuring method of volume resistivity.

Explanation of symbols

1 Conveyor belt 6 Image carrier (photosensitive member)
7 Recording material 8 Transfer device 8a Primary transfer device 8b Secondary transfer device 9 Stretch roll 10 Photosensitive drum 11 Charging device 12 Exposure device 13 Rotary developing device 17 Cleaning device 20 Intermediate transfer belts 21 to 24 Stretch roll 25 Primary transfer Roll 26 Cleaning blade 30 Secondary transfer roll 40 Recording material 41 Paper feed tray 42 Pickup roll 43 Registration roll 44 Conveying belt 45 Fixing device 46 Conveying roll 47 Discharging roll 48 Discharging tray

Claims (2)

  A semiconductive material comprising an elastic layer and a surface layer formed thereon, wherein the surface layer contains acidic carbon black, a lubricating component, and a fiber-shaped inorganic filler; Element. An image carrier, a charging unit for charging the surface of the image carrier, a latent image forming unit for forming a latent image on the surface of the image carrier, and a developing unit for developing the latent image with toner to form a toner image And a transfer unit that transfers the toner image to a recording medium, and a fixing unit that heat-fixes the toner image to the recording medium.
The transfer means has an elastic layer and a surface layer formed thereon, and the surface layer contains acidic carbon black, a lubricating component, and a fibrous inorganic filler. An image forming apparatus comprising: a semiconductive member.

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