JP4876372B2 - Carbon black purification method - Google Patents

Description

  The present invention includes carbon black used for a conductive agent and the like, a method for purifying carbon black, and a thermoplastic resin in which carbon black is dispersed, such as an electrophotographic copying machine, a laser printer, a facsimile, and a composite OA device thereof. The present invention relates to a semiconductive member used in an image forming apparatus using an electrophotographic system.

  An image forming apparatus using an electrophotographic method forms a uniform charge on an image carrier, which is a photoconductive photosensitive member made of an inorganic or organic material, and uses an electrostatic image with a laser beam or the like that modulates an image signal. Then, the electrostatic latent image is developed with a charged toner to obtain a visualized toner image. Then, the toner image is electrostatically transferred to a transfer material such as a recording sheet through an intermediate transfer member or a required reproduction image is obtained. In particular, there is known an image forming apparatus employing an intermediate transfer body system in which a toner image formed on the image carrier is primarily transferred to an intermediate transfer body, and further, a toner image on the intermediate transfer body is secondarily transferred to a recording sheet. (For example, refer to Patent Document 1).

  Examples of materials used in the image forming apparatus employing the intermediate transfer body method include polycarbonate resin (for example, see Patent Document 2), PVDF (polyvinylidene fluoride) (for example, see Patent Documents 3 and 4), and polyalkylene. Phthalate (for example, refer to Patent Document 5), blend material of PC (polycarbonate) / PAT (polyalkylene terephthalate) (for example, refer to Patent Document 6), ETFE (ethylene tetrafluoroethylene copolymer) / PC, ETFE / A proposal has been made to use an endless belt obtained by imparting conductivity to a thermoplastic resin such as a PAT, PC / PAT blend material (see, for example, Patent Document 7).

However, the conductive materials of thermoplastic resins such as polycarbonate resin and PVDF (polyvinylidene fluoride) are inferior in mechanical properties, so the belt deformation is large with respect to stress during driving, and high-quality transfer image quality can be stably obtained. Absent. In addition, there is a problem that the belt life is short because a crack is generated from the belt end during driving.
Further, as a belt material used in an image forming apparatus adopting an intermediate transfer body method, an elastic belt with a reinforcing material formed by laminating a woven fabric such as polyester and an elastic member has been proposed (for example, Patent Document 8 and 9).
However, the elastic belt with a reinforcing material may cause a problem of color misregistration due to creep deformation of the belt material over time.
Further, as a semiconductive member (belt) used for such an intermediate transfer belt or transfer conveyance belt, an intermediate transfer belt obtained by dispersing a conductive filler (conductive agent) in a polyimide resin having excellent mechanical properties and heat resistance. Has been proposed (see, for example, Patent Documents 10 and 11).

However, the semiconductive belt made of polyimide resin proposed so far has a poor balance between flexibility and rigidity, and it could not be said that the intermediate transfer belt and transfer conveyance belt satisfy the characteristics. .
For example, in Patent Document 11, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, p-phenylenediamine and polyamic acid (U varnish-S), which is a polymer, are used as a raw material for polyimide resin. However, this type of intermediate transfer belt has a surface microhardness of 40 or more, excellent mechanical properties, no belt deformation due to driving stress, and color. A high-quality transfer image without deviation can be stably obtained. However, since the polyimide resin material is excellent in mechanical characteristics in the transfer portion, primary transfer is performed by electrostatically transferring the toner image by pressing the recording paper against the recording medium using a bias roller and applying an electric field. Since the deformation due to the pressing force by the bias roller at the part is small, the pressing force by the bias roller is concentrated. For this reason, the toner agglomerates and the charge density becomes high, thereby causing internal discharge of the toner layer and changing the polarity of the toner. There was a thing.

By the way, the semiconductive member mainly composed of a thermoplastic resin such as polyimide resin has its electric resistance adjusted by dispersing a conductive agent, and carbon black which is advantageous in terms of price is preferable as the conductive agent. It is used.
However, a thermoplastic resin such as a polycarbonate in which carbon black is dispersed, an ethylene tetrafluoroethylene copolymer in which carbon black is dispersed, and a polyimide resin in which carbon black is dispersed are used as an intermediate transfer body at 10 ° C. and 15% RH. In a low-temperature and low-humidity environment, when a half-tone image is transferred after continuously transferring 1000 sheets or more of a paper shorter than the width of the intermediate transfer such as a postcard, a problem occurs that the paper running portion is blanked out. The white spots in the paper running section are due to the peeling discharge between the intermediate transfer body and the paper when the paper is peeled off in the secondary transfer section. This is because the transfer efficiency is lower than the peripheral part.

A method for removing impurities from carbon black used by high-temperature processing has been proposed for the problem that the surface resistivity of the paper running section is lower than that of the surrounding area. And high temperature treatment is required for a long time, and it is not always a method with high industrial productivity from the viewpoint of thermal energy (see, for example, Patent Document 12).
JP-A-62-206567 JP-A-6-095521 Japanese Patent Laid-Open No. 5-200904 JP-A-6-228335 Japanese Patent Laid-Open No. 6-149081 Japanese Patent Laid-Open No. 6-149083 Japanese Patent Laid-Open No. 6-149079 Japanese Patent Laid-Open No. 9-305038 Japanese Patent Laid-Open No. 10-240020 JP-A-5-77252 Japanese Patent Laid-Open No. 10-63115 JP 2001-75369 A

An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention aims to provide a purification how the carbon black carbon black impurities such as low cost and easy metal element is removed can be obtained.

Means for solving the above problems are as follows.
<1> A slurry was prepared by mixing water, 5 to 30% by mass of carbon black with respect to the water, and 10% by mass or less of isopropyl alcohol with respect to the water, and the prepared slurry was stirred. A method for purifying carbon black having a total content of calcium element, iron element, potassium element, sodium element, magnesium element, silicon element, and phosphorus element of 100 ppm or less, comprising a purification step for separating carbon black later.
<2> The method for purifying carbon black according to <1>, wherein the carbon black after separation is heated and dried in an inert gas.

The present invention can provide a purification how the carbon black carbon black impurities such as low cost and easy metal element is removed can be obtained.

The carbon black of the present invention has a metal element content of 100 ppm or less. When the content of the metal element exceeds 100 ppm, the effect of small change in electrical resistance due to repeated use cannot be obtained when used for a semiconductive member.
The content of the metal element in the carbon black of the present invention is preferably 50 ppm or less, and more preferably 30 ppm or less. Here, examples of the metal element include calcium element, iron element, potassium element, sodium element, magnesium element, silicon element , and phosphorus element, and the content of the metal element in the carbon black of the present invention is 100 ppm or less. Indicates that the total content of these metal elements (calcium element, iron element, potassium element, sodium element, magnesium element, silicon element , phosphorus element) is 100 ppm or less.
In addition, the carbon black of the present invention preferably has a calcium element content, an iron element content, and a silicon element content of 10 ppm or less, and more preferably 5 ppm or less, among the above metal elements.

The content of the metal element in the carbon black of the present invention can be determined by the following measuring method.
Carbon black is heated to a high temperature of 700 ° C. or higher in a muffle furnace and burned, and residual ash is dissolved in ultrapure water, which is measured by atomic absorption spectrometry or high frequency inductively coupled plasma emission spectrometry (ICP-AES). .

The carbon black of the present invention can be obtained by the following carbon black purification method of the present invention.
Hereinafter, the carbon black purification method of the present invention will be described.

  The method for purifying carbon black of the present invention is a purification step of mixing carbon black at least with water to prepare a slurry, stirring the prepared slurry, and then separating the carbon black (hereinafter referred to as “purification step in the present invention”). There is a case.)

As water used for preparing the slurry in the purification step in the present invention, ion exchange water, ultrapure water, distilled water, and ultrafiltered water are preferably used in order to prevent impurities from being mixed.
In addition, in the slurry preparation, a substance having a surface active action such as a so-called surfactant or alcohol may be further added from the viewpoint of improving the wetness of the carbon black surface. Further, a water-soluble organic solvent may be added as necessary, but it is preferable that it does not remain in the intermediate transfer member after production. For this reason, as the substance having a surface active action, a solvent having a low boiling point and a surface active action is preferable. For example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, sec-butyl alcohol, tert-butyl alcohol , 2-methoxy alcohol, allyl alcohol and the like.
Further, an inorganic acid can be added at an appropriate time.

In the present invention, at least one selected from the group consisting of the surfactant, alcohols, and a water-soluble organic solvent is added, and the addition amount is 10% by mass or less with respect to water , and 5% by mass. % or less is good Masui.
On the other hand, the proportion of carbon black to water is 5 to 30 mass%, is good preferable 5 to 20 wt%. If the ratio of carbon black to water is less than 5% by mass, the amount of purified carbon black may be reduced, and productivity may be lowered. On the other hand, if it exceeds 30% by mass, the slurry becomes highly viscous and stirring becomes difficult, which may reduce the purification efficiency.

  It is desired that the stirring during the preparation of the slurry should break up the aggregates of carbon black to the primary particle size as much as possible. For this reason, it is preferable to mix the said slurry with a general disperser or a homogenizer. Specifically, colloid mill, flow jet mill, slasher mill, high speed disperser, ball mill, attritor, sand mill, sand grinder, ultra fine mill, Eiger motor mill, dyno mill, pearl mill, agitator mill, cobol mill, three roll mill Mix with a two-roll mill, an extruder, a kneader, a microfluidizer, a laboratory homogenizer, an ultrasonic homogenizer, a jet mill, or the like. These may be used alone or in combination. Furthermore, in order to prevent mixing of inorganic impurities, it is preferable to use a dispersion method that does not use a dispersion medium, and a microfluidizer, an ultrasonic homogenizer, a jet mill, or the like may be used.

  Stirring when preparing the slurry is preferably performed for 5 to 60 minutes, more preferably for 10 to 30 minutes.

Examples of a method for separating carbon black from the slurry include a method of centrifugation, a method of filtration, and a method of transferring to a water-insoluble organic solvent (a method of mixing a slurry in a water-insoluble solvent). Examples of the water-insoluble organic solvent include toluene, xylene, benzene, chloroform, hexane, heptane and the like. The separation method is preferably a centrifugation method or a filtration method from the viewpoint of safety.
Further, in the method of centrifuging, the carbon black is separated from the slurry for 10 to 60 minutes and more preferably for 20 to 30 minutes if the rotation is 6000 to 10000 rpm.

  The carbon black after separation is preferably heated and dried in an inert gas. However, when a semiconductive member containing the carbon black of the present invention to be described later is produced, the carbon black is not necessarily dried by heating. You don't have to.

  The carbon black of the present invention has good dispersion stability, and when used as a conductive agent in a semiconductive member, it is possible to reduce variation in electric resistance and to reduce electric field dependency, and transfer voltage. Oxidation-treated carbon black is preferable, and oxidation-treated carbon black having a pH of 5 or less is more preferable in that the stability of the electric resistance over time with which electric field concentration due to is improved is further improved.

  The oxidized carbon black can be produced by oxidizing the carbon black to give a carboxyl group, a quinone group, a lactone group, a hydroxyl group, or the like to the surface. This oxidation treatment is an air oxidation method in which contact is made with air in a high-temperature atmosphere to react, a method of reacting with nitrogen oxides or ozone at room temperature, and air oxidation at high temperature, followed by ozone oxidation at a low temperature. It can be performed by a method or the like. Specifically, the oxidized carbon black can be produced by a contact method. Examples of the contact method include a channel method and a gas black method. Oxidized carbon black can also be produced by a furnace black method using gas or oil as a raw material. If necessary, after these treatments, a liquid phase oxidation treatment with nitric acid or the like may be performed. Acidic carbon black can be produced by a contact method, but is usually produced by a closed furnace method. In the furnace 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-mentioned liquid phase acid treatment. For this reason, carbon black obtained by the furnace method and adjusted to have a pH of 5 or less by post-treatment is also considered to be included in the more preferable oxidized carbon black having a pH of 5 or less.

  The pH value of the oxidized carbon black in the present invention is more preferably pH 5.0 or less, still more preferably pH 4.5 or less, and particularly preferably pH 4.0 or less. Oxidation-treated carbon having a pH of 5.0 or less has good dispersibility in the resin because it has an oxygen-containing functional group such as a carboxyl group, a hydroxyl group, a quinone group, and a lactone group on the surface, so it is good when used as a conductive agent. Dispersion stability can be obtained, resistance variation of the semiconductive material can be reduced, electric field dependency is also reduced, and electric field concentration due to transfer voltage is less likely to occur.

  The pH value of the oxidized carbon black in the present invention can be determined by adjusting an aqueous suspension of carbon black and measuring it with a glass electrode. Further, the pH of the oxidation-treated carbon black can be adjusted according to conditions such as treatment temperature and treatment time in the oxidation treatment step.

  The oxidized carbon black in the present invention preferably contains 1 to 25% by mass of the volatile component, more preferably 2 to 20% by mass, and more preferably 3.5 to 15% by mass. More preferably. When the volatile content is less than 1%, the effect of the oxygen-containing functional group attached to the surface may be lost, and the dispersibility in the binder resin may be reduced. On the other hand, when the volatile content is higher than 25%, the volatile matter is decomposed when dispersed in the binder resin or obtained by increasing the amount of water adsorbed on the oxygen-containing functional group on the surface. Problems such as deterioration of the appearance of the molded product may occur. Therefore, the dispersion | distribution in binder resin can be made more favorable by making a volatile content into the range of 1-25 mass%. This volatile content 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.

  Specific examples of the oxidized carbon black include “Printex 150T” (pH 4.5, volatile content 10.0%) and “Special Black 350” (pH 3.5, volatile content 2.2) manufactured by Degussa. %), “Special Black 100” (pH 3.3, volatile content 2.2%), “Special Black 250” (pH 3.1, volatile content 2.0%), “Special Black 5” (pH 3. 0, volatile content 15.0%), "Special Black 4" (pH 3.0, volatile content 14.0%), "Special Black 4A" (pH 3.0, volatile content 14.0%), " "Special Black 550" (pH 2.8, volatile content 2.5%), "Special Black 6" (pH 2.5, volatile content 18.0%), "Color Black FW200" (pH 2.5, volatile content 20) . %), “Color Black FW2” (pH 2.5, volatile content 16.5%), “Color Black FW2V” (pH 2.5, volatile content 16.5%), “MONARCH1000” (pH 2. 5, volatile content 9.5%), “MONARCH 1300” (pH 2.5, volatile content 9.5%) manufactured by Cabot, “MONARCH 1400” (pH 2.5, volatile content 9.0%) manufactured by Cabot, “ MOGUL-L "(pH 2.5, volatile matter 5.0%)," REGAL400R "(pH 4.0, volatile matter 3.5%) and the like.

  Carbon black that has undergone the above-described purification process is preferably used as a conductive agent in the semiconductive member described later. However, since the surface of carbon black is highly active and very easily adsorbs substances, 72 hours after the purification process, The semiconductive member containing the carbon black of the present invention is preferably produced within a range of 48 hours, and the semiconductive member is more preferably produced within 48 hours. If the time from the purification step to the production of the semiconductive member exceeds 72 hours, impurities may be re-adsorbed on the carbon black surface, and the purification effect may be reduced.

  By the carbon black purification method of the present invention, impurities mixed in the carbon black production process, for example, residual oxidant, impurities such as treating agents and by-products, other inorganic impurities and organic impurities, and the above-described metal elements Can be easily removed at low cost. That is, carbon black obtained by a purification process in which at least water is mixed with carbon black to prepare a slurry, and carbon black is separated from the prepared slurry is carbon black with few impurities including metal elements.

  Furthermore, carbon black having a metal element content of 100 ppm or less can be easily obtained at low cost by the carbon black purification method of the present invention. In other words, among carbon blacks having a metal element content of 100 ppm or less, a slurry is prepared by mixing at least water with carbon black, and obtained by a purification process for separating carbon black from the prepared slurry. Carbon black with an amount of 100 ppm or less is particularly preferred.

  The semiconductive member of the present invention includes a thermoplastic resin containing the above-described carbon black of the present invention.

  When the semiconductive member of the present invention is used as an intermediate transfer member, the thermoplastic resin preferably has a Young's modulus of 3500 MPa or more as will be described later, and the material is not particularly limited. Examples thereof include resins, polyamide resins, polyamideimide resins, polyether ether ester resins, polyallelate resins, polyester resins, and polyester resins obtained by adding a reinforcing material. As the thermoplastic resin, a polyimide resin is preferably used because it is a high Young's modulus material. By using a polyimide resin as the thermoplastic resin, there is little deformation due to driving (stress of a support roll, a cleaning blade, etc.), so that the intermediate transfer body is less prone to image defects such as color misregistration.

A polyimide resin is usually obtained as a polyamic acid solution by polymerizing a substantially equimolar amount of tetracarboxylic dianhydride or its derivative and a diamine in a solvent.
As said tetracarboxylic dianhydride, what is shown by the following general formula (I) is mentioned, for example.

  In the general formula (I), R is a tetravalent organic group, and is an aromatic, aliphatic, cycloaliphatic, a combination of aromatic and aliphatic, or a substituted group thereof.

  Specific examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetra. Carboxylic dianhydride, 2,3,3 ′, 4-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic Acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) sulfonic acid dianhydride, perylene-3,4,9, Examples thereof include 10-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, and ethylenetetracarboxylic dianhydride.

On the other hand, specific examples of the diamine include 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 3,3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide. 3,3′-diaminodiphenylsulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3′-dimethyl4,4′-biphenyldiamine, benzidine, 3,3′-dimethylbenzidine 3,3′-dimethoxybenzidine, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylpropane, 2,4-bis (β-aminotert-butyl) toluene, bis (p-β-amino- Tert-butylphenyl) ether, bis (p-β-methyl-δ-aminophenyl) benzene, bi -P- (1,1-dimethyl-5-amino-benzyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, di (p-aminocyclohexyl) Methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-methylnonamethylenediamine 2 , 17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 12-diaminooctadecane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane , _{piperazine, H 2 N (CH 2)} 3 O (CH 2) 2 O (CH 2) NH 2, H 2 N (CH 2) 3 S (CH 2) 3 NH 2, H 2 N (CH 2) 3 _{N (CH 3) 2 (CH} 2) 3 NH 2 and the like.

  As the solvent for the polymerization reaction of the tetracarboxylic dianhydride and the diamine, a polar solvent (organic polar solvent) is preferably mentioned from the viewpoint of solubility. As the polar solvent, N, N-dialkylamides are preferable, and specific examples thereof include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide, which are low molecular weight compounds thereof. N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethyl sulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine, tetramethylenesulfone, dimethyltetramethylenesulfone and the like. These can be used singly or in combination.

In the semiconductive member of the present invention, the thermoplastic resin such as the polyimide resin contains the above-described carbon black of the present invention as a conductive agent.
Further, as described above, the carbon black of the present invention is preferably oxidized carbon black. Compared to general carbon black, the oxidized carbon black has good dispersibility in the resin composition due to the effect of oxygen-containing functional groups present on the surface as described above. It is preferable to increase the amount. As a result, the amount of carbon black in the semiconductive member is increased, so that the effect of using the oxidized carbon black that can suppress the in-plane variation of the electrical resistance value can be maximized. it can.

  Furthermore, in the semiconductive member of the present invention, two or more types of carbon black may be contained. At this time, these carbon blacks are preferably substantially different in conductivity from each other. For example, those having different physical properties such as the degree of oxidation treatment, the amount of DBP oil absorption, and the specific surface area by the BET method using nitrogen adsorption are used. . When two or more types of carbon blacks having different conductivity are added in this way, for example, carbon black that expresses high conductivity is preferentially added, and then carbon black with low conductivity is added to adjust the surface resistivity. It is possible to do. Thus, when two or more types of carbon black are contained, it is preferable to use oxidized carbon black for at least one of them, whereby the mixing and dispersion of both carbon blacks can be enhanced.

  The semiconductive member of the present invention preferably contains 10 to 30% by mass of the carbon black of the present invention. By containing 10 to 30% by mass of the carbon black of the present invention, the effect of the oxidation-treated carbon black can be sufficiently exhibited, such as suppressing in-plane variation of the surface resistivity of the semiconductive member. On the other hand, when the content of the carbon black is less than 10% by mass, the uniformity of electrical resistance is lowered, and in-plane unevenness of the surface resistivity and electric field dependency may be increased. On the other hand, if the content of the carbon black exceeds 30% by mass, it may be difficult to obtain a desired resistance value. The content of the carbon black is preferably 18 to 30% by mass, and by containing 18 to 30% by mass of the carbon black, the effect can be maximized and the surface resistivity can be improved. Unevenness and electric field dependency can be remarkably improved.

  The semiconductive member of the present invention may contain a known conductive agent in addition to the above-described carbon black of the present invention as a conductive agent within a range not impairing the effects of the present invention. As the known conductive agent, conductive or semiconductive fine powder can be used, and there is no particular limitation as long as a desired electric resistance can be stably obtained. However, carbon such as Ketchen Black, acetylene black, etc. Black; metals such as aluminum and nickel; metal oxide compounds such as tin oxide; and potassium titanate. These may be used alone or in combination.

  The semiconductive member of the present invention is preferably used as an intermediate transfer member and a transfer conveyance belt, more preferably used as an intermediate transfer member, and still more preferably used as an intermediate transfer belt. Hereinafter, a preferable embodiment when the semiconductive member of the present invention is used as an intermediate transfer member will be described.

When the semiconductive member of the present invention is used as an intermediate transfer member, the hardness of the transfer surface is preferably 30 or less, more preferably 25 or less in terms of surface microhardness. The surface microhardness is not a method of obtaining the diagonal length of the indentation like the Vickers hardness widely used for measuring the hardness of metal materials, but how much the indenter has entered the sample. It can be determined by the measurement method. Specifically, when the test load P (mN) and the amount of penetration of the indenter into the sample (indentation depth) D (μm), the surface microhardness DH is defined by the following formula (1).
Formula (1) DH≡αP / D ²
Here, α is a constant depending on the shape of the indenter, and α = 3.8854 (used indenter: in the case of a triangular pyramid indenter).

  The surface microhardness is the hardness obtained from the excessive weight and indentation depth in the process of indenting the indenter, and represents the strength characteristics of the material including not only plastic deformation of the sample but also elastic deformation. is there. In addition, the measurement area is very small, and more accurate hardness measurement is possible within a range close to the toner particle diameter. The present inventors have found that there is a very accurate correlation between the surface microhardness obtained here and the generation level of the holocharacter. That is, when the surface microhardness of the transfer surface of the intermediate transfer member is preferably 30 or less, more preferably 25 or less, the transfer surface of the intermediate transfer member is deformed by the pressing force of the bias roller in the secondary transfer portion described above. As a result, the pressing force concentrated on the toner on the intermediate transfer member is dispersed. For this reason, the toner does not aggregate, and image quality defects such as holocharacters in which the line image is lost do not occur.

The surface microhardness on the transfer surface of the intermediate transfer member was determined by the following method. A sheet of material (surface layer) constituting the transfer surface is cut to about 5 mm square, and the small piece is fixed to the glass plate with an instantaneous adhesive. The surface microhardness of the surface of this sample is measured using an ultra micro hardness meter DUH-201S (manufactured by Shimadzu Corporation). The measurement conditions are as follows.
Measurement environment: 23 ° C, 55% RH
Working indenter: Triangular pyramid indenter test mode: 3 (soft material test)
Test load: 0.70 gf
Load speed: 0.0145 gf / sec
Holding time: 5 sec

When the semiconductive member of the present invention is used as a belt-shaped intermediate transfer member (intermediate transfer belt), the relationship between the Young's modulus and the amount of belt displacement due to disturbance (load fluctuation) during belt driving is expressed by the following equation (2). ).
Formula (2) Δl = P · l · α / (t · w · E)
here,
Δl: Belt displacement (μm)
P: Load (N)
l: Belt length between two tension rolls (mm)
α: Coefficient t: Belt thickness (mm)
w: Belt width (mm)
E: represents the Young's modulus (N / mm ² ) of the belt material.

  When the intermediate transfer member has a belt shape, the expansion / contraction (displacement amount) of the belt due to disturbance (load fluctuation) during driving of the belt is inversely proportional to the Young's modulus and thickness of the belt material. When a belt material with a high Young's modulus is used, the amount of displacement of the belt due to disturbance (load fluctuation) during driving of the belt is reduced, and deformation of the belt with respect to stress during driving is reduced, so that good image quality can be stably obtained. . However, as the thickness of the belt increases, the amount of deformation of the outer surface of the belt at the belt bending portion such as the drive train roll increases, and it is difficult to obtain good image quality. Also, the amount of deformation between the outside and inside of the belt And the belt may be broken due to local repeated stress.

When the semiconductive member of the present invention is used as a belt-shaped intermediate transfer member, the total thickness of the belt is preferably 0.05 to 0.5 mm, and 0.06 to 0.30 mm. More preferably, it is 0.06-0.15 mm. When the total thickness of the belt is less than 0.05 mm, it may be difficult to satisfy the required mechanical properties as an intermediate transfer member (belt). Due to the deformation at, the stress on the belt surface may be concentrated and problems such as the generation of cracks in the surface layer may occur.

  Further, when the semiconductive member of the present invention is used as a belt-shaped intermediate transfer member, the Young's modulus varies depending on the thickness of the belt, but is preferably 3500 MPa or more, more preferably 4000 MPa or more. If the Young's modulus is 3500 MPa or more, the mechanical properties as a belt can be more sufficiently satisfied.

(Surface resistivity)
When the semiconductive member of the present invention is used as an intermediate transfer member, the surface resistivity of the transfer surface is preferably 1 × 10 ¹⁰ to 1 × 10 ¹⁴ Ω / □, and 1 × 10 ¹¹ to 1 × 10 ^13. More preferably, it is Ω / □. When this surface resistivity is higher than 1 × 10 ¹⁴ Ω / □, peeling discharge may easily occur at the post nip where the image carrier and the intermediate transfer member in the primary transfer portion peel off, and the discharge is generated. In such a portion, an image quality defect that causes white spots may occur. On the other hand, when the surface resistivity is less than 1 × 10 ¹⁰ Ω / □, the electric field strength at the pre-nip portion may increase, and gap discharge at the pre-nip portion is likely to occur. May get worse. Therefore, by setting the surface resistivity to 1 × 10 ¹⁰ to 1 × 10 ¹⁴ Ω / □, white spots are caused by discharge that occurs when the surface resistivity is high, and image quality deteriorates that occurs when the surface resistivity is low. Can be prevented.

The surface resistivity of the transfer surface described above can be measured in accordance with JIS K6991 using a circular electrode (for example, “HR probe” of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.). The method for measuring the surface resistivity will be described with reference to FIG. FIG. 1 is a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of a circular electrode for measuring the surface resistivity. The circular electrode shown in FIG. 1 includes a first voltage application electrode A and a plate-like insulator B. The first voltage application electrode A has a cylindrical electrode portion C and a cylindrical ring electrode having an inner diameter larger than the outer diameter of the cylindrical electrode portion C and surrounding the cylindrical electrode portion C at a constant interval. Part D is provided. The intermediate transfer body T is sandwiched between the cylindrical electrode portion C and the ring electrode portion D in the first voltage application electrode A and the plate insulator B, and the cylindrical electrode portion C and the ring in the first voltage application electrode A are sandwiched. Current I (A) that flows when a voltage V (V) is applied to the electrode portion D is measured, and the surface resistivity ρs (Ω / Ω) of the transfer surface of the intermediate transfer member T is calculated by the following equation (3). □) can be calculated. Here, in the following formula (3), d (mm) indicates the outer diameter of the cylindrical electrode portion C, and D (mm) indicates the inner diameter of the ring-shaped electrode portion D.
Formula (3) ρs = π × (D + d) / (D−d) × (V / I)

(Volume resistivity)
When the semiconductive member of the present invention is used as an intermediate transfer member, the volume resistivity is preferably 1 × 10 ⁸ to 1 × 10 ¹³ Ωcm, and preferably 1 × 10 ⁹ to 1 × 10 ¹² Ωcm. More preferred. When the volume resistivity is less than 1 × 10 ⁸ ΩCm, the electrostatic force that holds the charge of the unfixed toner image transferred from the image carrier to the intermediate transfer member becomes difficult to work. The electrostatic repulsion force and the fringe electric field force near the image edge may cause the toner to scatter around the image (blur), and an image with large noise may be formed. On the other hand, if the volume resistivity is higher than 1 × 10 ¹³ [Omega] cm, in order retention of charge is large, it is necessary to neutralizing mechanism for the intermediate transfer member surface by the transfer electric field at the primary transfer is charged Sometimes. Therefore, by setting the volume resistivity within the above range, it is possible to solve the problem of toner scattering and the need for a static elimination mechanism.

The above-mentioned volume resistivity can be measured according to JIS K6991 using a circular electrode (for example, HR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.). A method for measuring the volume resistivity will be described with reference to FIG. FIG. 2 is a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of a circular electrode for measuring volume resistivity. Instead of the circular electrode A ′ shown in FIG. 2 and the plate-like insulator at the time of measuring the surface resistivity, a voltage application electrode B ′ is provided. The circular electrode A ′ has a cylindrical electrode portion C ′ and a cylindrical ring shape having an inner diameter larger than the outer diameter of the cylindrical electrode portion C ′ and surrounding the cylindrical electrode portion C ′ at a constant interval. And an electrode part D ′. The intermediate transfer member T is sandwiched between the cylindrical electrode portion C ′ and the voltage application electrode B ′ in the circular electrode A ′, and between the cylindrical electrode portion C ′ and the voltage application electrode B ′ in the circular electrode A ′. The current I (A) that flows when the voltage V (V) is applied is measured, and the volume resistivity ρv (Ωcm) of the intermediate transfer member T can be calculated by the following formula (4). Here, in the following formula (4), t represents the thickness of the semiconductive belt T.
Formula (4) ρv = 19.6 × (V / I) × t

  Here, the resistance reduction due to the transfer voltage and the occurrence of white spots due to the resistance reduction will be described with reference to FIGS. FIG. 3 is a schematic diagram for explaining resistance reduction of the secondary transfer portion of the intermediate transfer member. As shown in FIG. 3, when a sheet (transfer object) 104 is passed through a secondary transfer portion (nip portion) formed by a support roller 102 and a transfer roller 103 via a belt-shaped intermediate transfer member 101. At the same time, a transfer voltage is applied to perform secondary transfer. Immediately after the secondary transfer, the surface of the belt-like intermediate transfer member 101 (paper side) is positively charged, and the surface of the paper 104 (intermediate transfer member side) is negatively charged. Peeling discharge occurs between the two. Due to this discharge phenomenon, the surface of the intermediate transfer member 101 is altered, a new conductive path is formed, and the resistance is lowered. Further, when the electric field dependency is large, electric field concentration occurs on the surface of the intermediate transfer member 101, and the surface of the intermediate transfer member 101 is easily deteriorated, so that the resistance is lowered.

  FIG. 4 is a schematic diagram for explaining a situation where white spots occur in a halftone. As shown in FIG. 4, the resistance decrease as shown in FIG. 3 occurs in the sheet running unit 201 in the intermediate transfer body 200 after 1000 sheets are continuously copied (for example, in a low temperature and low humidity environment of 10 ° C. and 15% RH). ((A) in FIG. 4). If a halftone of magenta 30% is copied in such a state, it is difficult to print on the paper travel unit 201 having a lower resistance than the non-paper travel unit 202 ((b) in FIG. 4). As a result, white spots occur. The occurrence of white spots is particularly likely to occur when the surface resistivity of the paper travel unit 201 is 1.1 digits (log Ω / □) or more lower than that of the non-paper travel unit 202.

  The semiconductive member of the present invention having the above-described configuration has an excellent property that a change in electric resistance due to repeated use is small, and stable image quality can be obtained when used in an image forming apparatus described later.

Although an example (when a thermoplastic resin is a polyimide resin) of the manufacturing method of the semiconductive member containing the thermoplastic resin containing the carbon black of this invention is illustrated, it does not limit to this.
First, the carbon black of the present invention is dispersed in an organic polar solvent to prepare a carbon black dispersion. The dispersion method is preferably a method of dispersing with a disperser or a homogenizer after preliminary stirring. Also, as with the carbon black purification method, the mixing of fine media reduces the carbon black purification effect. Therefore, a media-free dispersion method that does not use media is preferred, especially a jet mill that can uniformly disperse a high-viscosity solution. Is preferred.

Next, in the obtained carbon black dispersion, a diamine component and an acid dianhydride component are dissolved and polymerized to prepare a polyamic acid solution in which carbon black is dispersed. In this case, the monomer concentration (concentration of the diamine component and the acid anhydride component in the solvent) is set according to various conditions, but is preferably 5 to 30% by mass. On the other hand, the reaction temperature is preferably set to 80 ° C. or less, particularly preferably 5 to 50 ° C., and the reaction time is preferably 5 to 10 hours.
The resulting polyamic acid solution in which carbon black is dispersed is a high-viscosity solution, so air bubbles mixed during production do not escape naturally, and defects such as belt protrusions, dents, and holes caused by air bubbles are generated by application. There are things to do. For this reason, defoaming is desirable. Defoaming is preferably performed immediately before application as much as possible.

Further, when forming a seamless belt-like semiconductive member, for example, a method in which a polyamic acid solution is immersed in the outer peripheral surface of a cylindrical mold, a method in which the polyamic acid solution is applied to the inner peripheral surface, a method in which centrifugation is further performed, or a casting mold The ring is developed into a ring shape by an appropriate method such as a method of filling in, the formed layer is dried and formed into a bell-shaped shape, and the molded product is heat-treated to convert the polyamic acid to a polyimide, from the mold. It can be carried out by an appropriate method according to the conventional method such as a recovery method (described in JP-A-61-95361, JP-A-64-22514, JP-A-3-180309, etc.). In forming the seamless belt, a mold release treatment can be performed.
In order to convert the polyamic acid into polyimide, a high temperature treatment at 200 ° C. or higher is generally used. Sufficient imide conversion may not be obtained at 200 ° C or lower. On the other hand, high-temperature treatment is advantageous for imide conversion, and stable characteristics can be obtained.However, since thermal energy is used, thermal efficiency may be poor and cost may be increased, so the characteristics and productivity of the intermediate transfer member are taken into consideration. It is necessary to determine the heat treatment temperature.

  An example of an image forming apparatus provided with the semiconductive member of the present invention as an intermediate transfer member will be described. The image forming apparatus primarily transfers a toner image formed on an image bearing member onto an intermediate transfer member, and secondly transfers the toner image transferred onto the intermediate transfer member onto a transfer target. An intermediate transfer type image forming apparatus including a second transfer unit and using the semiconductive member of the present invention as the intermediate transfer member. By providing the semiconductive member of the present invention, a high-quality transfer image can be obtained stably for a long period of time.

  Further, the image forming apparatus provided with the semiconductive member of the present invention is not particularly limited. For example, a normal monocolor image forming apparatus in which only a single color toner is accommodated in the developing device, or an image carrier. Color image forming apparatus that repeats the primary transfer of the toner image carried on the intermediate transfer body sequentially, and a tandem type color image formation in which a plurality of image carriers having developing units for each color are arranged in series on the intermediate transfer body Apparatus. Specifically, as shown in FIG. 5, a tandem color image forming apparatus in which a photoconductor 9 for each color provided with a developing device 15 of four colors (black, yellow, magenta, cyan) is arranged on an intermediate transfer body 16. A charging roll 13 (charging device) for uniformly charging the surface of the photoconductor 9, a laser generator 8 (exposure device) for exposing the surface of the photoconductor 9 to form an electrostatic latent image, and a surface of the photoconductor 9. The latent image is developed using a developer to form a toner image, a developing device 15 (developing device), a photoreceptor cleaner 14 (cleaning device) that removes toner, dust and the like adhering to the photoreceptor 9, and a material to be transferred. A fixing roll 2 for fixing the upper toner image and the like can be optionally provided by a known method as necessary.

Further, an image carrier, a charging unit that uniformly charges the surface of the image carrier, an exposure unit that exposes the surface of the image carrier to form an electrostatic latent image, and a latent image formed on the surface of the image carrier using a developer. Developing means for forming a toner image, fixing means for fixing the toner image on the transfer material, cleaning means for removing toner or dust adhering to the image carrier, and remaining on the surface of the image carrier. A static elimination means for removing the electrostatic latent image is optionally provided by a known method as necessary.
As the image bearing member, a conventionally known one can be used, and as the photosensitive layer, a known one such as organic or amorphous silicon can be used. When the previous image carrier is cylindrical, it can be obtained by a known production method such as surface processing after extrusion molding of aluminum or an aluminum alloy. It is also possible to use the belt-shaped image carrier.

  The charging means is not particularly limited, and examples thereof include contact type chargers using conductive or semiconductive rollers, brushes, films, rubber blades, scorotron chargers and corotron chargers using corona discharge, etc. A charger known per se can be used. Among these, a contact-type charger is preferable in terms of excellent charge compensation capability. The charging unit normally applies a direct current to the electrophotographic photosensitive member, but an alternating current may be applied in a superimposed manner.

The exposure means is not particularly limited. For example, the surface of the electrophotographic photosensitive member is exposed to a light source such as a semiconductor laser light, an LED light, a liquid crystal shutter light, or a desired image from these light sources through a polygon mirror. An optical system device that can be used.
The developing means can be appropriately selected according to the purpose. For example, a known developing device that develops a one-component developer or a two-component developer in contact or non-contact with a brush, a roller, etc. Is mentioned.

As the first transfer means, for example, a contact transfer charger using a belt, a roller, a film, a rubber blade, etc., a known transfer charger such as a scorotron transfer charger using a corona discharge or a corotron transfer charger Is mentioned. Among these, a contact type transfer charger is preferable in that it has excellent transfer charge compensation capability. In addition to the transfer charger, a peeling charger can be used in combination.
Examples of the second transfer unit include a contact transfer charger such as a transfer roller exemplified as the first transfer unit, a scorotron transfer charger, a corotron transfer charger, and the like. Among these, a contact-type transfer charger is preferable like the first transfer unit. When the contact type transfer charger such as a transfer roller is pressed strongly, the image transfer state can be maintained in a good state. In addition, when a contact type transfer charger such as a transfer roller is pressed at the position of the roller that guides the intermediate transfer member, the toner image can be transferred from the intermediate transfer member to the transfer member in a good state. become.

Examples of the light neutralizing means include tungsten lamps and LEDs. Examples of the light quality used in the light neutralizing process include white light such as tungsten lamps and red light such as LED light. The irradiation light intensity in the photostatic process is usually set to output several times to about 30 times the amount of light indicating the half exposure sensitivity of the electrophotographic photosensitive member.
The fixing unit is not particularly limited, and examples thereof include known fixing devices such as a heat roller fixing device and an oven fixing device. The cleaning means is not particularly limited, and a known cleaning device or the like may be used.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
<Example 1>
(Production of carbon black 1)
The mixture having the composition shown in Table 1 below was pre-stirred and then mixed with an ultrasonic homogenizer for 30 minutes to prepare a carbon black slurry. Thereafter, the obtained carbon black slurry was treated with a centrifuge (10000 rpm, 30 minutes) to separate the carbon black from the carbon black slurry, and the supernatant solution was discarded to obtain wet carbon black. Since water and organic solvent remain in these, carbon black 1 of this invention was produced by further drying in nitrogen gas at 150 ° C. for 120 minutes to remove water and organic solvent.
The amount of metal elements (total of calcium element, iron element, potassium element, sodium element, magnesium element, silicon element and phosphorus element) of the obtained carbon black 1 was measured by the following method. The results are shown in Table 1.

  As for the amount of metal element, carbon black was overheated in a muffle furnace, the residual ash after combustion was added to ultrapure water and stirred to prepare an aqueous solution of ash. The aqueous solution was adjusted to have an ash concentration of 10%. The obtained aqueous solution was measured by high-frequency inductively coupled plasma emission analysis (ICP-AES SPS1200VR manufactured by Seiko Denshi Kogyo), and the amount of metal elements was measured.

(Production of polyimide belt)
Into the polyamic acid NMP solution composed of biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA), the amount of the carbon black 1 shown in Table 3 is added, and dispersion treatment is performed with a jet mill disperser. (200N / mm ² , 5pass). The produced carbon black-dispersed polyamic acid solution was vacuum degassed to produce a final coating solution. Next, the obtained polyamic acid solution is applied to the inner surface of the cylindrical mold to 0.5 mm via a dispenser, rotated at 1500 rpm for 15 minutes to form a spread layer having a uniform thickness, and then rotated at 250 rpm. However, hot air at 60 ° C. was applied for 30 minutes from the outside of the mold, and then heated at 150 ° C. for 60 minutes to remove NMP and demold in a semi-cured state. Thereafter, the removed belt was put on an iron core, heated to the firing temperature shown in Table 3, and heated in that state for 60 minutes for imide conversion to obtain a polyimide belt 1 (semiconductive member). The belt thickness was about 80 μm.

(Evaluation)
<Surface resistivity>
The (initial) surface resistivity of the obtained polyimide belt 1 was determined by the following method. The results are shown in Table 4.
Using a circular electrode shown in FIG. 1 (HR probe of HI-Lester IP manufactured by Mitsubishi Yuka Co., Ltd .: outer diameter Φ16 mm of the cylindrical electrode C, inner diameter Φ30 mm, outer diameter Φ40 mm of the ring electrode portion D), 22 ° C./55 Under a% RH environment, a voltage of 100 V was applied, and the current value after 10 seconds was determined to calculate the surface resistivity.

<< Fluctuation width of surface resistivity of paper running section after 10,000 times transfer >>
The obtained polyimide belt 1 is mounted on a resistance evaluation bench machine shown in FIG. 6, and the paper resistance of the paper running portion after continuous transfer of 10,000 times of the polyimide belt 1 using P paper A-4 manufactured by Fuji Xerox Co., Ltd. as the paper. The fluctuation range of the rate was obtained. FIG. 6 is a schematic configuration diagram for explaining the resistance evaluation bench machine. The resistance evaluation bench machine shown in FIG. 6 has three rolls of a drive roll 301, a BUR 302, and an idle 303, and further includes a counter roll 304 in which a sheet is wound at a position facing the BUR 302. The polyimide belt 305 to be measured is stretched between the BUR 302 and the idle 303, the polyimide belt 305 is sandwiched between the BUR 302 and the opposing roll 304, and a voltage is applied to the BUR 302 to transfer the polyimide belt 305 a desired number of times ( The counter roll 304 is rotated a desired number of times).
In the resistance evaluation bench machine shown in FIG. 6 described above, the facing roll 304 is disposed at a position facing the BUR 302 and a voltage is further applied to the BUR 302. The positions of the facing roll 304 are the drive roll 301, the BUR 302, and the idle roll. The position may be a position facing any one of 303, and the voltage may be applied to a roll facing the facing roll 304 among the drive roll 301, BUR 302, and idle 303.

  Measurement of the fluctuation range of the surface resistivity of the paper running portion after 10,000 transfer using the resistance evaluation bench machine shown in FIG. 6 is performed by using the drive belt 301, the BUR 302, and the idle 303 with the polyimide belt 305 (in the first embodiment). A polyimide belt 1) is stretched, and under an environment of 10 ° C./15% RH, a voltage is applied to the BUR 302 to apply a 2.6 KV electric field. In this state, the belt 305 is sandwiched and transferred 10,000 times (the counter roll 304 is rotated 10000 times the desired number of times), and the surface resistivity of the sheet running portion of the polyimide belt 305 after 10,000 times transfer is the above-mentioned << surface resistivity >>. Measured by the same method as the measurement, from the difference from the surface resistivity before 10,000 transfer (measured value of the above << surface resistivity >>), It was determined variation range of the surface resistivity of the paper guiding portion after connection 10,000 rpm shooting. The results are shown in Table 4.

<Copy image quality after 10,000 transfers>
A polyimide belt whose surface resistivity fluctuation width after the transfer of the paper with the resistance evaluation bench machine was measured was attached to Fuji Xerox DocuCentreColor 2220, and the copy image quality was A-3 paper (P paper made by Fuji Xerox). The density difference between the A-4 printing area and the A-3 printing area was visually determined according to the following criteria. The results are shown in Table 4.
Grade 1: Good (no difference in density is observed)
Grade 2: Normal (concentration difference is seen, but it is not a problem)
Grade 3: Poor (concentration difference can be clearly confirmed)
Grade 4: Very bad (white spots occur in the A-4 print area, and the image cannot be identified.)

< Reference Examples 1 and 2 >
Carbon blacks 2 and 3 were produced in the same manner as in the production of carbon black 1 except that the composition of carbon black slurry and the stirring conditions were changed to the conditions shown in Table 1 in the production of carbon black 1 in Example 1. . Further, the polyimide belts 2 and 3 were prepared in the same manner as in Example 1 except that the input amounts of the obtained carbon blacks 2 and 3 and the firing temperature at the time of imide conversion were changed to the compositions and conditions shown in Table 3. Produced. The obtained polyimide belts 2 and 3 were evaluated in the same manner as in Example 1. The results are shown in Table 4.

<Comparative Examples 1 and 2>
In Example 1, polyimide belts 4 and 5 were produced in the same manner as in Example 1 except that carbon blacks 4 and 5 shown in Table 2 were used instead of carbon black 1. The obtained polyimide belts 4 and 5 were evaluated in the same manner as in Example 1. The results are shown in Table 4.

Table 4 shows that the polyimide belts (semiconductive members) of Example 1 and Reference Examples 1 and 2 containing the carbon black of the present invention obtained by the purification method of the present invention are intermediate transfer members of image forming apparatuses. Even when the image is transferred 10,000 times, the fluctuation range of the surface resistivity is small, indicating that the obtained image is stable. On the other hand, the polyimide belts (semiconductive members) of Comparative Examples 1 and 2 that do not contain carbon black of the present invention are used as an intermediate transfer member of an image forming apparatus and have a large fluctuation range of surface resistivity when transferred 10,000 times. The obtained image is not stable.

It is the schematic plan view (a) and schematic sectional drawing (b) which show an example of the circular electrode which measures surface resistivity. It is the schematic plan view (a) and schematic sectional drawing (b) which show an example of the circular electrode which measures volume resistivity. FIG. 6 is a schematic diagram for explaining resistance reduction of a secondary transfer portion of an intermediate transfer member. It is a schematic diagram explaining the situation where a white spot occurs in a halftone. It is a block diagram which shows an example of an image forming apparatus provided with the semiconductive member of this invention. It is a schematic block diagram for demonstrating a resistance evaluation bench machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Toner cartridge 2 Fixing roll 3 Backup roller 4 Tension roller 5 Secondary transfer roller 6 Paper path 7 Paper tray 8 Laser generator 9 Photoconductor 10 Primary transfer roller 11 Drive roller 12 Transfer cleaner 13 Charging roll 14 Photoconductor cleaner 15 Developer 16 Intermediate transfer member 101 Intermediate transfer member 102 Support roller 103 Transfer roller 104 Paper 200 Intermediate transfer member 201 Paper traveling unit 202 Non-paper traveling unit 301 Drive roll 302 BUR
303 Idle 304 Opposite roll 305 Polyimide belt

Claims (2)

A slurry was prepared by mixing water, 5 to 30% by mass of carbon black with respect to the water, and 10% by mass or less of isopropyl alcohol with respect to the water, and after stirring the prepared slurry, A method for purifying carbon black having a total content of calcium element, iron element, potassium element, sodium element, magnesium element, silicon element and phosphorus element , comprising a purification step of separating black.   The method for purifying carbon black according to claim 1, wherein the carbon black after separation is heated and dried in an inert gas.