JP5183139B2 - Developing roller, process cartridge, image forming apparatus, and developing roller manufacturing method - Google Patents

Description

  The present invention relates to a developing roller and a manufacturing method thereof, a process cartridge using the same, and an image forming apparatus.

  For image formation of electrophotographic apparatuses such as copying machines and optical printers, a contact development method using a non-magnetic one-component developer is known. Specifically, in the contact development method, a photosensitive member such as a rotatable photosensitive drum is uniformly charged by charging means such as a charging roller, and the uniformly charged surface of the photosensitive member is exposed to laser light or the like. An electrostatic latent image is formed. A developing roller having a developer thin film formed on the surface thereof is opposed to the photosensitive member carrying the electrostatic latent image, and the photosensitive member and the developing roller are mutually rotated. At this time, when a developing bias is applied to the developing roller, the developer moves from the developing roller to the electrostatic latent image on the photosensitive member, and the electrostatic latent image is developed (visualized) as a toner image. Thereafter, the toner image on the photosensitive member is transferred to the recording material in the transfer portion, and fixed on the recording material by heating, pressurizing, etc. in the fixing portion, and the recording material on which image formation is completed is discharged out of the image forming apparatus. Is done.

  As such a developing device for supplying a developer to the electrostatic latent image carried by the photoconductor in the image formation, an apparatus having the following configuration can be exemplified. A developing roller is provided so that the opening of the developer container for storing the developer is closed and a part of the opening is exposed to the outside of the container, and the exposed portion faces the photosensitive member. In the developer container, there are provided a developer coating roller for supplying the developer to the developing roller, and a developing blade for forming the developer on the developing roller into a thin film and making the amount of developer on the developing roller constant. The developing blade is installed in contact with the developing roller in the vicinity of the tip, for example, at a position of 0.1 mm to 5.0 mm from the tip, and the developer on the developing roller supplied by the developer coating roller is removed. It is formed into a thin film with a uniform thickness.

  In such a non-magnetic one-component contact development method, a developer is fused on the surface of a developing roller that has been used for a long time, and there is a high tendency for image defects resulting from this, that is, so-called durable fusion.

  In order to suppress the durable fusion, it is effective to form the surface of the developing roller with a flexible material. However, when the surface of the developing roller is made flexible, the adhesion to the toner also tends to increase, and the toner adheres to the surface of the developing roller, and the adhered toner is crushed and exists as a film on the surface of the developing roller. In the developing roller on which the toner film is formed, the triboelectric charge imparting ability to the developer is different between the portion where the toner film is formed and the portion where the toner film is not formed. There is a strong tendency to ming. In order to suppress the initial filming, it is effective to harden the surface of the developing roller, and the suppression of the initial filming antagonizes the suppression of the durable fusion.

  On the other hand, in order to adjust the electric resistance of the developing roller, a conductive agent such as carbon black is added to the developing roller. However, the hardness of the developing roller surface varies depending on the type and amount of carbon black to be added. Specifically, the following tendencies are observed. When carbon black having a small arithmetic average particle size (hereinafter referred to as an average particle size) having an equivalent area diameter is used, high conductivity can be obtained with a small amount, and therefore the increase in the hardness of the resin due to the addition of carbon black is small. In addition, when carbon black having a large average particle size is used, it is necessary to add a large amount in order to obtain predetermined conductivity, and the hardness of the resin increases due to the addition of carbon black.

  That is, when carbon black having a small average particle size is used, the increase in the hardness of the surface of the developing roller is low, which is advantageous for suppressing durable fusion, but tends to be disadvantageous for suppressing initial filming. is there. On the other hand, when carbon black with a large average particle size is used, the increase in the hardness of the surface of the developing roller is large, which is advantageous for suppressing initial filming, but tends to be disadvantageous for suppressing durable fusion. It is in. In this way, the durable fusion suppression effect and the initial filming suppression effect obtained are antagonized by the particle size of the carbon black added to the surface of the developing roller, and both the durable fusion and the initial filming are obtained in a high dimension. Is not easy.

  In view of this, it is conceivable to combine carbon blacks having different particle diameters to achieve both advantages. In fact, various inventions using the technical idea of adjusting the electric resistance of resin or rubber in combination with carbon black having different particle diameters have been reported in the past. For example, a developing roller that adjusts to the desired electrical resistance value while keeping the total amount of carbon black added to a small amount by using a strong conductive carbon and a weak conductive carbon together in the elastic layer (base layer) of the developing roller has been reported. (Patent Document 1). Further, a developing roller having excellent toner chargeability in which channel black and furnace black are contained in an elastic layer in a specific blending ratio has been reported (Patent Document 2). Furthermore, a conductive roll (Patent Document 4) having a desired electric resistance value by mixing a rubber material with a strong conductive carbon black and a weak conductive carbon black has been reported.

The inventors of the present invention tried to achieve both high-dimensional durability fusion and initial filming by using carbon black having different particle diameters in combination. However, the balance between the durable fusion and the initial filming was the same level as the conventional developing roller using a single type of carbon black.
JP-A-9-114197 JP-A-5-332352 JP-A-9-90714

  An object of the present invention is to develop a development roller that can achieve both high durability suppression and initial filming suppression at a high level, and can obtain a uniform density image from the initial use to the long-term use, and The object is to provide an image forming apparatus and a process cartridge used.

The inventors of the present invention added a carbon black having various particle sizes to the surface layer of the developing roller, made a developing roller as a trial, and examined the effect of suppressing the durable fusion and the effect of suppressing the initial filming. As a result, we have found that there is the following tendency. In order to suppress the durable fusion, it is preferable to add carbon black having a particle size of approximately 30 nm or less at 25% by mass or less with respect to the mass of the resin. When the particle diameter exceeds 30 nm, unless the carbon black is contained in a range exceeding 25% by mass, the electrical resistance value in the range required for the surface layer (volume resistivity: 1 × 10 ⁸ Ωcm to 1 × 10 6 ¹² Ωcm) is difficult to obtain. However, when carbon black is contained in a range exceeding 25% by mass, the hardness of the surface layer increases and the anti-fusing property after long-term use decreases.

  On the other hand, in order to suppress initial filming, it is preferable to add 15% by mass or more of carbon black having a particle size of approximately 20 nm or more with respect to the mass of the resin. When the particle diameter is smaller than 20 nm, the electric resistance value required in the surface layer can be obtained even when the carbon black content is less than 15% by mass. However, when the content of carbon black is within this range, it is difficult to obtain the effect of suppressing initial filming, not reaching the hardness required for the surface layer from which the effect of reducing tackiness is obtained.

  From the above results, when carbon black having an average particle size of 20 nm to 30 nm is used as the carbon black added to the surface layer, it is possible to obtain both high durability suppression and initial filming suppression in the developing roller. We considered whether there was a particle size and examined it. First, each of carbon black having a particle size of 20 nm, 25 nm, and 30 nm was added alone to the surface layer of the developing roller. As a result, it was possible to achieve both durable fusion suppression and initial filming suppression, but the level of suppression was not different from the level achieved with conventional developing rollers. Therefore, two types of carbon blacks having different sizes in the range of 20 nm to 30 nm were mixed and examined. Currently, there are a wide range of grades of carbon black having an average particle diameter of about 10 nm to about 300 nm available on the market. In fact, in a conventional developing roller using a plurality of carbon blacks, carbon blacks having greatly different particle sizes such as an average particle size of 30 nm and 80 nm are used.

  However, the present inventors use 20 nm and 30 nm as the average particle diameter, and when used in combination with particle diameters that seem to be almost the same, it is possible to suppress toner component fusion and initial filming after long-term use. The knowledge that it may be obtained at a higher level than before is obtained. However, it has been found that even when carbon black particles having an average particle diameter in the range of 20 nm to 30 nm are combined, only the same effect as the conventional one can be obtained.

  Therefore, as a result of examining in detail the conditions under which toner fusion suppression and initial filming suppression after long-term use can be compatible at a higher level than before, it was found that the following conditions are important. The conditions are as follows: (1) When the resin of the developing roller surface layer is 100 parts by mass, the carbon black content is 15 parts by mass or more and 25 parts by mass or less. (2) The carbon black contains particles having an arithmetic mean value of equivalent area diameter of 21.0 nm or more and 27.0 nm or less. (3) Carbon black has a particle size distribution distortion degree of 0.25 or more and 0.63 or less.

  The reason why the distribution skewness of the particle size of the carbon black is related to coexistence of toner fusion suppression and initial filming suppression after long-term use is not clear, but can be considered as follows.

  Usually, the skewness of the particle size distribution curve of carbon black particles having an average particle size in the range of 20 nm to 30 nm is in the range of about -0.2 to +0.2. Here, when a plurality of types of carbon black having the above normal skewness are mixed within an average particle diameter of 20 nm to 30 nm, the skewness can be set to 0.25 or more and 0.63 or less. The fact that the skewness shows a positive value means that the distribution curve has a shape with a tail (toward the left) on the right side (the larger particle diameter side). When the skewness is in the above range, it means that the ratio of large particles increases when the particle size distribution of the normal carbon black is used as a reference. For this reason, it is possible to add a large amount of carbon black having a large particle size without increasing the amount of carbon black added, and it is considered that it acts advantageously on the initial filming suppression effect. Since carbon black having a small particle size is also included, the electrical resistance of the surface layer can be set to a desired value without increasing the amount of carbon black added to the surface layer. Therefore, it is possible to suppress the fusion resistance after long-term use. For these reasons, the initial filming suppression effect and durability can be achieved by setting the three parameters of carbon black average particle size (arithmetic mean value of particle size), particle size distribution skewness, and blending amount within a specific range. It was found that the fusion suppression effect can be achieved at a higher level than before.

  Even if any of the above three parameters is missing, it is impossible to obtain both the effects of suppressing toner fusion after long-term use and suppressing initial filming. For example, when a single grade is appropriately selected from an average particle diameter of 20 nm to 30 nm, the distribution distortion is within a range of −0.20 to +0.20. When the average particle size is increased, durable fusion suppression cannot be obtained, and when the particle size is decreased, initial filming suppression cannot be obtained, and it is difficult to achieve both at a high level. In addition, two types of carbon black having an average particle diameter of 20 nm to 30 nm may be selected and mixed, and the degree of distortion may fall within the range of the present invention. Even in this case, the arithmetic mean value of the carbon black particle diameter corresponding to the area equivalent diameter is out of the range of 21.0 nm to 27.0 nm, and the carbon black content is 15.5 parts relative to 100.0 parts by mass of the urethane resin. When the content is outside the range of 0 to 25.0 parts by mass, the effect of the present application cannot be obtained. By using carbon black that satisfies a specific range of average particle size, particle size distribution skewness, and content, it is possible to achieve both the prevention of toner fusion after long-term use and the suppression of initial filming, which were not conventionally obtained. Based on this finding, the present invention has been completed.

That is, the present invention includes a conductive shaft, successively an elastic layer provided on the conductive shaft member, in the developing roller having a surface layer, said surface layer contains at least a urethane resin and carbon black , the content of carbon black is the urethane resin 100.0 parts by mass with respect to 15.0 parts by mass or more, a range of 25.0 parts by weight, the arithmetic mean value of the area equivalent diameters of the carbon black is 21 The present invention relates to a developing roller characterized in that the degree of distortion in the distribution of equivalent area diameters of the carbon black is not less than 0.25 and not more than 0.63.

The present invention also relates to a method for producing the developing roller, wherein the polyether polyol, the isocyanate, and the furnace black of the particles having an arithmetic mean value of the equivalent area diameter of 20.0 nm or more and 25.0 nm or less (A ) and the area arithmetic mean value of the equivalent diameter of more than 26.0 nm, and a furnace black of particle (B) is not more than 30.0 nm, the mass ratio of the furnace black (a) and said furnace black (B) The present invention relates to a method for producing a developing roller, which comprises a step of coating a surface of a coating liquid containing a coating liquid containing 85:15 to 25:75 on an elastic layer.

  The present invention also includes at least a photosensitive drum carrying an electrostatic latent image, a developing roller for supplying a developer to the photosensitive drum, and a metal blade for applying a DC voltage to the developing roller. In a process cartridge detachably provided in an image forming apparatus main body, the developing roller is the developing roller described above, a photosensitive drum carrying an electrostatic latent image, and a developer on the photosensitive drum The present invention relates to an image forming apparatus in which at least a developing roller to be supplied and a metal blade for applying a DC voltage to the developing roller are mounted, wherein the developing roller is the developing roller.

  The developing roller of the present invention, the process cartridge using the same, and the image forming apparatus can achieve both high durability suppression and initial filming suppression at a high level. For this reason, an image having a uniform density can be obtained from the initial use to the long-term use.

  The developing roller of the present invention includes a conductive shaft, an elastic layer sequentially provided on the conductive shaft, and a surface layer.

  The conductive shaft body in the developing roller of the present invention has a strength capable of supporting the upper elastic layer and the surface layer, and has conductivity. The material of the conductive shaft is preferably a metal, and examples thereof include carbon steel, stainless steel, nickel chrome steel, nickel chrome molybdenum steel, chrome steel or chrome molybdenum steel. Another example is a nitriding steel alloy to which aluminum, chromium, cobalt, or vanadium is added. Further, as a rust prevention measure, the shaft body may be plated or oxidized. As the type of plating, either electroplating or electroless plating can be used, but electroless plating excellent in plating thickness uniformity is preferable. Examples of the electroless plating used here include nickel plating, copper plating, gold plating, Kanigen plating, and other various alloy plating. Examples of the nickel plating include Ni-P, Ni-B, Ni-WP, and Ni-P-PTFE composite plating, and the plating thickness is preferably 0.05 μm or more. From the effect, work efficiency, and price, 0.1 to 30 μm is more preferable.

  The shape of the shaft may be either a columnar shape or a cylindrical shape, and the outer diameter is preferably 3 mm or more and 10 mm or less. If the outer diameter of the shaft body is 3 mm or more, it has rigidity, suppresses the bending of the developing roller, and can obtain a uniform image density over the longitudinal direction of the roller. If the outer diameter of the shaft body is 10 mm or less, the diameter of the entire developing roller can be suppressed, the thickness of the elastic layer can be sufficiently secured, the apparent increase in the hardness of the developing roller surface is suppressed, and long-term use The effect of suppressing the subsequent toner fusion can be sufficiently obtained.

  Examples of the material of the elastic layer provided on the conductive shaft include silicone rubber (Q), urethane rubber (U), acrylonitrile-butadiene rubber (NBR), and ethylene-propylene-diene copolymer rubber (EPDM). Can be mentioned. These can be used alone or in combination of two or more. For these rubbers, materials containing a conductive agent such as carbon black can be used. In addition, various additives such as non-conductive fillers such as talc, silica, clay, zinc oxide and calcium carbonate can be added.

  The elastic layer may be either a solid layer or a foamed layer, and the thickness may be 1 mm or more and 5 mm or less.

The electric resistance value of the elastic layer is preferably in the range of 1 × 10 ³ Ω · cm to 1 × 10 ⁸ Ω · cm when a voltage of 250 V is applied. If the electric resistance value of the elastic layer is within this range, the toner can be uniformly charged, and both the effect of suppressing the durable fusion and the effect of suppressing the initial filming in the surface layer are not hindered.

  Here, the electrical resistance value is determined by a measurement method according to JIS K6911: 1995 by curing the elastic layer material under the same conditions as those for forming the elastic layer, producing a test piece, applying a 250 V voltage using the test piece. Measurements can be taken.

  The surface layer provided on the elastic layer contains at least a urethane resin and carbon black. The urethane resin contained in the surface layer acts as a base resin for the surface layer, and imparts mechanical strength required for the surface layer and flexibility that enables the developer to be conveyed. As the urethane resin, polyether polyurethane is preferable in order to improve the dispersion of carbon black in combination with carbon black, particularly carbon black having a pH of 4.0 or less. Carbon black having a pH of 4.0 or less has acidic groups such as carboxyl groups on its surface, and polyether polyurethane has many ether groups having oxygen atoms that form hydrogen bonds with hydrogen atoms of the carboxyl groups. Have. For this reason, the polyether polyurethane that exists so as to surround the carbon black by forming a hydrogen bond with the hydrogen atom of the carboxyl group of the carbon black improves the wettability of the carbon black and improves the dispersibility. By being able to uniformly disperse carbon black in the surface layer, it is possible to suppress the occurrence of a highly adhesive part with a high resin content and a low adhesive part with a high carbon black content. The occurrence of initial filming that occurs in the portion can be suppressed. As a result, the initial filming suppression effect and the toner fusion suppression effect after long-term use can be obtained in a high dimension.

As said polyether polyurethane, what is obtained by reaction of polyether polyol and isocyanate can be mentioned. Suitable polyether polyols include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These polyols can be used as a prepolymer by reacting with an isocyanate such as 2,4-tolylene diisocyanate (TDI), 1,4 diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI) in advance as required. In particular, a polyfunctional polyether polyol and a bifunctional isocyanate are reacted to obtain a poly having a weight average molecular weight of 10,000 to 200,000 and a molecular weight dispersity (weight average molecular weight Mw / number average molecular weight Mn) of 1.2 to 3.0. Ether polyols are preferred. By using such a polyether polyol, a flexible urethane resin can be obtained, and the mechanical stress imparted by the surface layer to a toner having a low melting point (glass transition temperature of 70 ° C. or less) can be reduced. An effect of suppressing toner fusion after use can be obtained. Suitable isocyanates include the following. Hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), paraphenylene diisocyanate (PDI). 1,5-naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (X ₆ DI), dicyclohexylmethane diisocyanate (X ₁₂ DI). These copolymers and block bodies of these copolymers.

  The carbon black contained in the surface layer may be any of channel black, furnace black, thermal black and the like. In particular, furnace black has a low oxygen content and high conductivity, and can impart the necessary electrical resistance value to the surface layer in a small amount, which is advantageous in suppressing durable fusion.

  As described above, it is preferable that the carbon black has a pH of 4.0 or less because high conductivity can be obtained and the effect of suppressing toner fusion after long-term use can be obtained. In particular, furnace black having a pH of 2.5 or more and 3.5 or less, which is obtained by an appropriate oxidation treatment, improves the dispersibility in the resin and increases the initial filming suppression effect. This is suitable because the effect of suppressing wearing can be obtained in a high dimension. If the pH of the carbon black is 2.5 or more, the number of hydrogen bonds between the oxygen atom of the ether group and the hydrogen atom of the carboxyl group of the carbon black increases, further improving the dispersibility in the resin, and initial filming. The suppression effect increases.

  Here, as the pH of the carbon black, a measured value measured by a method according to the measuring method described in JIS K6221: 1982 can be adopted.

  Carbon black has an arithmetic mean value of an equivalent area diameter of 21.0 nm or more and 27.0 nm or less, and a distribution distortion of 0.25 or more and 0.63 or less.

  The area equivalent diameter of carbon black can be a value determined by the following method.

  First, the surface layer is cut out from the developing roller, an ultrathin section is created from the cut out surface layer, and used as a sample for observation. An ultrathin section, specifically, a section having a thickness of about 50 nm can be prepared by the following method. A method using a diamond knife (Cryo dry 35 °) manufactured by Diatome in an atmosphere of −120 or higher and −50 ° C. in an atmosphere of −120 ° C. or lower and −50 ° C. using a sliced piece preparation apparatus (Leica Microsystems, Inc .; Leica EM FCS). The created observation sample is observed with a TEM. The direct observation magnification is 140,000 for 1 magnification. The photographed film is magnified twice and developed, and finally a photograph of 280,000 times and 280,000 times is obtained.

  From the photograph, 500 carbon black particles are arbitrarily selected and selected, and for each carbon black particle, an area equivalent diameter (a diameter of a circle having an area equal to the projected area) is obtained. If the carbon black particles selected arbitrarily have a lot of overlap with the adjacent carbon black particles, the equivalent particle diameter of the carbon black particles is not determined and other particles are selected. The determination of whether there is much or little overlap with adjacent carbon black particles will be described with reference to FIG. In FIG. 1, since the central carbon black particle Y is in contact with two adjacent carbon black particles X and Z, the exact contour of the particle Y is unknown. However, carbon black is a substance that easily forms an aggregate (structure), and most of the particles overlap as shown in FIG. As shown in FIG. 2, two points (referred to as points A and B) where the contour lines of the particles Y and X intersect are connected by a straight line. Similarly, for the particles Y and Z, the points C and D are obtained and connected by straight lines to form a closed plane connected by the straight lines AB, BC, CD, and DA. If the sum of the length of the line segment AB and the length of the line segment CD is 20% or less of the sum of the length of the curve AD and the length of the curve BC, the area of the particle Y is defined as an outline, a straight line AB, a curve The area of the closed plane connected by BC, straight line CD, and curve DA is obtained, and the diameter of a circle having an area equal to the area is calculated. A value obtained by rounding the first decimal place of the calculated diameter (unit: nm) to an integer is defined as the area equivalent diameter of the particle Y. When the sum of the length of the straight line AB and the length of the straight line CD is larger than 20% of the sum of the length of the curve AD and the length of the curve BC, the approximate accuracy of the area equivalent diameter is deteriorated. select.

  With the above procedure, the area equivalent diameter was obtained for any 500 particles, and the value obtained by rounding off the second decimal place of the arithmetic average value of the area equivalent diameters of the 500 particles was calculated as the area equivalent diameter of the carbon black. Use the arithmetic mean value.

  Further, the distribution skewness of the area equivalent diameter of the carbon black is a value obtained by rounding off the third decimal place obtained from the formula (1) from the area equivalent diameter of the 500 particles and the arithmetic mean value thereof. it can.

In the formula, xi represents an area equivalent diameter (μm) of each carbon black particle, and represents an arithmetic average value.

  Carbon black with an equivalent area diameter having such an arithmetic mean value and skewness can be obtained, for example, by the following method. Carbon black (A) having an average particle diameter of 20.0 nm or more and 25.0 nm or less and a distribution skewness of 0, and carbon having an average particle diameter of 26.0 nm or more and 30.0 nm or less and a distribution skewness of 0 Select black (B). Next, the ratio A: B of the carbon blacks (A) and (B) is set to a mass ratio in the range of 85:15 to 25:75, more preferably 82:18 to 28:72. . At this time, the carbon black is preferably furnace black.

  Such carbon black is contained in the surface layer in the range of 15.0 parts by mass to 25.0 parts by mass with respect to 100.0 parts by mass of the urethane resin. As described above, when the carbon black content is within this range, in combination with the particle diameter and the distribution thereof, it is possible to achieve both the effect of suppressing the durable fusion and the effect of suppressing the initial filming in the developing roller.

The surface layer preferably has an electrical resistance of 1 × 10 ⁸ Ωcm to 1 × 10 ¹² Ωcm. In order to adjust the electrical resistance value of the surface layer to such a value, the carbon black may be used. In addition, zinc oxide doped with aluminum, metal oxide coated with titanium oxide with tin oxide doped with antimony, polymer type such as polyether ester amide, polyether amide, or polyether ester. You may add an antistatic agent suitably.

  Here, the value of the electric resistance value is an applied voltage of 100 V, and a measured value obtained by a measuring method according to JIS K6911: 1995 can be adopted.

  The surface layer may contain fine particles having an average particle diameter of 1 μm or more and 20 μm or less based on the equivalent area diameter. Such a surface layer in which fine particles are dispersed is preferable because it has a large surface roughness that can facilitate the conveyance of the developer. Examples of the fine particles used for such a purpose include polymethyl methyl methacrylate fine particles, silicone rubber fine particles, polyurethane fine particles, and phenol resin fine particles. These fine particles are preferably added in the range of 5 to 50 parts by mass with respect to 100 parts by mass of the urethane resin. If the addition amount of the fine particles is 5 parts by mass or more, it is possible to impart surface roughness that facilitates the transport of the developer, and if it is 50 parts by mass or less, the surface layer is prevented from becoming brittle. it can.

  Other non-conductive fillers such as diatomaceous earth, quartz powder, dry silica, wet silica, titanium oxide, zinc oxide, aluminosilicate, calcium carbonate, zirconium silicate, aluminum silicate, talc, alumina, iron oxide, etc. Various additives and the like can also be added.

  The thickness of the surface layer is preferably 50 μm or less. If the thickness of the surface layer is 50 μm or less, an increase in the rigidity of the surface layer can be suppressed, and a durable fusion suppressing effect can be obtained. In order to avoid this, if the surface layer is made of a flexible material, the adhesiveness of the surface layer is increased, the initial filming suppression effect is reduced, and the durable fusion suppression and the initial filming suppression effect are obtained in a high dimension. It becomes difficult. A thickness of the surface layer of 1 μm or more is preferable because it has mechanical strength.

  In order to produce the developing roller, an elastic layer is formed on the surface of the conductive shaft body through an adhesive as necessary. Examples of the method for molding the elastic layer include a method in which the rubber composition is molded by various molding methods such as extrusion molding, press molding, injection molding, liquid injection molding, and cast molding, and heated and cured.

  Examples of the method for forming the surface layer on the elastic layer include a method of preparing a coating solution containing the uncured resin and coating the elastic layer on the elastic layer. Although it is possible to heat and knead urethane resin and carbon black with a residence time for a long time by making a screw to improve the dispersibility of carbon black on the screw with a biaxial kneader, it can be by extrusion molding, but mechanical shearing without heating A coating method capable of dispersing by force is preferred. The coating liquid is prepared by mixing polyether polyol, isocyanate, carbon black having a pH of 4.0 or less, and an appropriate solvent.

  The carbon black is preferably a mixture of the following furnace black (A) and furnace black (B) in a mass ratio of 85:15 to 25:75.

  Furnace Black (A): Particles having an area-average diameter arithmetic mean value of 20.0 nm or more and 25.0 nm or less.

  Furnace Black (B): Particles having an arithmetic mean value of area equivalent diameter of 26.0 nm or more and 30.0 nm or less.

  In preparing the coating liquid, a dispersion device using beads such as a paint shaker, dyno mill or pearl mill can be used. When the coating liquid is prepared in this manner, a coating liquid in which carbon black is uniformly dispersed can be obtained without thermally deteriorating the urethane resin. Using the obtained coating solution, a surface layer can be prepared by forming a coating film by a method such as dipping, coating or spraying, heating and curing.

The image forming apparatus of the present invention is equipped with at least a photosensitive drum carrying an electrostatic latent image, the developing roller for supplying a developer to the photosensitive drum, and a metal blade for applying a DC voltage to the developing roller. The developing roller is the above developing roller. As an example, the color image forming apparatus shown in FIG. 3 can be cited. The color image forming apparatus shown in the schematic configuration diagram of FIG. 3 is provided with a photosensitive drum 5 as a rotating electrostatic latent image carrier. The following are provided around the photosensitive drum.
A charging roller 8 for uniformly charging the photosensitive drum.
Exposure means (not shown) for forming an electrostatic latent image by irradiating a uniformly charged photosensitive drum with a laser beam.
A developing device that supplies toner to a photosensitive drum on which an electrostatic latent image is formed to develop the electrostatic latent image.

  In the developing device, a developer container 9 containing non-magnetic toner as a one-component toner and a developer container 9 are installed so as to close the opening of the developer container, and development is performed so as to face the photosensitive drum at a portion exposed from the developer container. A roller 4 is provided. In the developer container, while supplying the toner to the developing roller, the developer application roller 6 that scrapes off the remaining toner without being used on the developing roller, and the toner on the developing roller are formed in a thin film, A developing blade 7 that is frictionally charged is provided. The toner made into a thin film on the developing roller moves to an electrostatic latent image on the photosensitive drum facing the developing roller, and a toner image is formed on the photosensitive drum.

  This developing device is provided as 10-Y, 10-M, 10-C, and 10-K for yellow, magenta, cyan, and black, respectively.

  On the other hand, a recording material such as paper supplied by a paper feed roller is conveyed between the transfer roller 2 to which a transfer bias power is applied and the photosensitive drum, and here, the photosensitive drum is transferred by a transfer bias charge applied from the back surface of the recording material. The upper toner image moves onto the recording material. The toner image on the recording material is heated and pressed between the fixing roller and the pressure roller 3 to be fixed on the recording material, and the image formation is completed.

  On the other hand, a cleaning blade (not shown) is provided for removing residual toner remaining without being transferred onto the photosensitive drum and cleaning the surface, so that the cleaned photoconductor is ready for image formation and waits. It has become.

  The process cartridge of the present invention is equipped with at least a photosensitive drum carrying an electrostatic latent image, the developing roller for supplying a developer to the photosensitive drum, and a metal blade for applying a DC voltage to the developing roller. The process cartridge is configured to be detachable from the main body of the electrophotographic image forming apparatus. As an example, as shown in FIG. 4, the photosensitive drum 5, the developing roller 4 of the present invention, the charging roller 8, the developer coating roller 6, the developing blade (metal blade) 7, and the developer container 9. Can be integrated into one cartridge. This cartridge is detachably provided in the electrophotographic image forming apparatus. Since the function of each member is the same as that in the image forming apparatus, description thereof is omitted. In the electrophotographic process cartridge of the present invention, in addition to the above, the transfer roller for transferring the toner image on the photosensitive member to the recording material, the cleaning blade, etc. are replaced with the above members or with one or more of the above members. And may be provided integrally.

  Hereinafter, the developing roller, the process cartridge, and the image forming apparatus of the present invention will be described in detail, but the technical scope of the present invention is not limited to these. Hereinafter, “part” means “part by mass”.

[Example 1]
[Preparation of elastic layer]
A stainless steel metal rod having a diameter of 6 mm was used as a conductive shaft, and a primer (DY35-051: manufactured by Toray Dow Corning Silicone) was applied to the outer peripheral surface of the shaft (excluding both ends 10 mm) and baked. Next, the conductive shaft is placed at the position of the central axis of the hollow cylindrical mold heated to a temperature of 120 ° C. in advance, and silicone rubber is injected from the injection port provided on the end face of the cylindrical mold. The silicone rubber elastic layer was molded by heating and curing at 5 ° C. for 5 minutes. Next, the elastic layer integrated with the conductive shaft was taken out from the cylindrical mold and heated at a temperature of 180 ° C. for 4 hours to complete the curing reaction.

[Preparation of surface layer]
Polytetramethylene glycol (PTG1000SN: Hodogaya Chemical Co., Ltd.) and chain extension isocyanate compound (MDI) (Cosmonate MDI: Mitsui Takeda Chemical Co., Ltd.) were mixed in a MEK solvent. Subsequently, it was made to react at the temperature of 80 degreeC by nitrogen atmosphere for 5 hours. And the methyl ethyl ketone (MEK) solution of the polyether polyol (prepolymer) which has a hydroxyl group in both the ends of Mw = 50000 and Mw / Mn = 1.5 was obtained.

  Next, the MEK solution of the polyether polyol (prepolymer) and the isocyanate (Coronate 2521: manufactured by Nippon Polyurethane Industry Co., Ltd.) are blended so that the NCO / OH ratio is 1.2. Obtained. The sum of the polyether polyol solid mass and the isocyanate solid mass contained in Compound 1 is 100.0 parts by mass. Next, 20.0 parts by mass of urethane resin particles (Bernock CFB100: manufactured by Dainippon Ink Co., Ltd.) was mixed and mixed in the mixed liquid 1 to obtain a mixed liquid 2. Next, the solid content mass of the compounding liquid 2 is 100.0 parts by mass, and the compounding liquid 2 includes 3.0 parts by mass of carbon black B (MA230: manufactured by Mitsubishi Chemical Corporation) and carbon black A (SUN BLACK X15: Asahi 17.0 parts by mass of carbon). And it diluted with MEK so that the total solid content including carbon black might be 30.0 mass%, and the compounding liquid 3 was obtained. Compounding liquid 3 was uniformly dispersed by a sand mill to obtain a coating material for surface layer coating.

  The obtained coating material for surface layer coating is dip coated on the above elastic layer, dried at room temperature for 10 minutes, and then heat-treated at a temperature of 150 ° C. for 2 hours to prepare a surface layer having a film thickness of about 15 μm. A developing roller was obtained.

[Molecular weight measurement]
The molecular weight of the urethane resin was measured by the following procedure using a gel permeation chromatography (GPC) method.

  As the column, a polystyrene gel column (shodex GPC KF series: manufactured by Wako Denko) was used, and an RI (refractive index) detector was used as a detector.

First, the column temperature is stabilized in a 40 ° C. heat chamber, and tetrahydrofuran (THF) as a solvent is allowed to flow through the column at a flow rate of 1 ml / min. Next, the urethane polymer to be measured is adjusted to a THF solution having a concentration of about 0.1% by mass, and about 100 μl is injected into the column. The molecular weight distribution was calculated from the relationship between the logarithmic value of a calibration curve prepared with a polystyrene standard sample in advance and the count number (retention time). The polystyrene standard sample is polystyrene having a known molecular weight, 6 × 10 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , A total of 10 types of 3.9 × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , and 4.48 × 10 ⁶ were used.

[PH measurement of carbon black]
The measurement was performed according to the measurement method described in JIS K6221: 1982.

[Image evaluation]
The obtained developing roller was incorporated into an electrophotographic process cartridge (Q2670A: manufactured by Nippon Hewlett-Packard Co., Ltd.). Further, the developing blade and developer were replaced with the following. That is, as the developing blade 7, a developing blade 7 made of a phosphor bronze plate having a thickness of 100 μm was used, and the amount of the developer thin film (coating amount) on the developing roller was 0.35 (mg / cm ² ). The position of the developing blade relative to the developing roller was adjusted so that Further, as the developer, a non-magnetic one-component cyan polymerized toner having a glass transition temperature of 56 ° C. and a weight average particle size of 6.5 μm manufactured by the method described in Example 1 of JP-A-2006-106198. Was used.

  The electrophotographic process cartridge was incorporated into an image forming apparatus (ColorJaserJet 3700: manufactured by Hewlett-Packard Japan). In this image forming apparatus, a DC voltage is applied to the developer application roller. In addition to this, a DC voltage having a negative potential of 200 V is applied to the developing blade by an external power source (not shown). The image was output after remodeling.

[Evaluation of initial filming]
Halftone images in an environment with a temperature of 32.5 ° C. and a relative humidity of 85% (32.5 ° C./85% RH) and an environment with a temperature of 23 ° C. and a relative humidity of 50% (23 ° C./50% RH). The image was output, and the uniformity of the image density was visually observed and evaluated according to the following criteria. The results are shown in Table 1.
A: No horizontal stripe density unevenness (image defect) in the developing roller cycle is observed at all. B: Horizontal stripe density unevenness (image failure) in the developing roller cycle is slightly recognized. However, density unevenness disappears within 2 prints (a level that does not hinder practical use)
C: Horizontal stripe-like density unevenness (image defect) in the developing roller cycle is observed. However, the density unevenness disappears within 3 prints (a level that does not hinder practical use).

[Evaluation of durable fusion]
Continuous printing was performed in an environment having a temperature of 15 ° C. and a relative humidity of 10% (15 ° C./10% RH) and an environment having a temperature of 23 ° C. and a relative humidity of 50% (23 ° C./50% RH). As the output image, an image in which one vertical line having a width of 1 mm was drawn at the center of A4 paper was used. At the time when 20,000 sheets and 25,000 sheets were output, a halftone image was output on the entire surface of the A4 sheet, and the uniformity of the image density was visually observed and evaluated according to the following criteria. The results are shown in Table 1.
A: Vertical line-shaped density unevenness (image defect) with a width of 1 mm is not recognized at all. B: Vertical line-shaped density unevenness (image defect) with a width of 1 mm is slightly recognized (a level at which there is no practical problem).
C: Vertical line-shaped density unevenness (image defect) with a width of 1 mm is recognized (a level that does not impede practical use).

[Examples 2 to 20]
A developing roller was produced and image evaluation was performed in the same manner as in Example 1 except that the composition of carbon black was changed as shown in Table 1. The results are shown in Table 1.

[Example 21]
The coating material for the surface layer was prepared as follows.

The following materials were mixed in MEK solvent.
A polyester polyol obtained by an ester reaction of terephthalic acid (high-purity terephthalic acid PTA: manufactured by Mitsubishi Chemical) and diethylene glycol (manufactured by Mitsubishi Chemical).
Isocyanate compound (MDI) for chain extension (Cosmonate MDI: manufactured by Mitsui Takeda Chemical Co., Ltd.).

  This was reacted at 80 ° C. for 5 hours under a nitrogen atmosphere. And the MEK solution of the polyester polyol (prepolymer) which has a hydroxyl group in both the ends of Mw = 5000 and Mw / Mn = 1.1 was obtained.

  Next, the MEK solution of the polyester polyol (prepolymer) and the isocyanate (Coronate 2521: manufactured by Nippon Polyurethane Industry Co., Ltd.) are blended so that the NCO / OH ratio is 1.2 to obtain the blended liquid 4. It was. The sum of the polyester polyol solid content mass and the isocyanate solid content mass contained in compounded liquid 4 is 100.0 parts by mass. Next, 20.0 parts by mass of urethane resin particles (Bernock CFB100: manufactured by Dainippon Ink Co., Ltd.) was stirred and mixed in the blended liquid 4 to obtain a blended liquid 5. Next, the solid content mass of the blending solution 5 is 100.0 parts by mass, and the blending solution 5 includes 16.0 parts by mass of carbon black A (MA100: manufactured by Mitsubishi Chemical Corporation) and carbon black B (MA11: Mitsubishi Chemical Corporation). (Made) 4.0 mass part was mixed. And it diluted with MEK so that the total solid content including carbon black might be 30.0 mass%, and the compounding liquid 6 was obtained. The liquid mixture 6 was uniformly dispersed with a sand mill to obtain a coating material for surface layer coating.

  A developing roller was prepared in the same manner as in Example 1 except that the coating material for surface layer coating obtained in place of the coating material for surface layer coating used in Example 1 was used. Images were formed and evaluated. The results are shown in Table 1.

[Example 22]
10.0 parts by mass of carbon black A (MA100: manufactured by Mitsubishi Chemical Co., Ltd.) and carbon black B (MA11: manufactured by Mitsubishi Chemical Co., Ltd.) with respect to 100.0 parts by mass of thermoplastic polyether polyurethane (Curamil 9180, manufactured by Kuraray) 4.0 parts by mass were mixed. Next, after kneading with a twin screw extruder, pellets were produced. The pellets were put into a single screw extruder, and a tube having a thickness of 45 μm was extruded from a cylindrical slit formed at the mold outlet. The tube was cut to an appropriate length and placed on the outer peripheral surface of the elastic layer integrated with the conductive shaft body produced in Example 1 to obtain a developing roller.

  The obtained developing roller was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
A developing roller was produced in the same manner as in Example 1 except that the composition of carbon black was changed as shown in Table 1, and image evaluation was performed in the same manner as in Example 1 for the obtained developing roller. The combination of carbon black used was the same as in Example 4, the average particle size was 25.4 μm, and the total mass of carbon black was 18.0 parts by mass with respect to 100.0 parts by mass of urethane resin. Meets the requirements of the invention. However, the skewness is as small as 0.23 and does not satisfy the requirements of the present invention. In this developing roller, the initial filming is good, but the effect of suppressing the durable fusion is low.

[Comparative Example 2]
A developing roller was produced in the same manner as in Example 1 except that the formulation of carbon black was changed as shown in Table 1, and image evaluation was performed in the same manner as in Example 1 for the obtained developing roller. The combination of the carbon black used was the same as in Example 1, and the total mass of the carbon black was 24.0 parts by mass with respect to 100.0 parts by mass of the urethane resin, which satisfies the requirements of the present invention. However, the average particle diameter is as large as 28.0 μm and the degree of distortion is as small as 0.20, which does not satisfy the requirements of the present invention. In this developing roller, the initial filming is good, but the effect of suppressing the durable fusion is low.

[Comparative Example 3]
A developing roller was produced in the same manner as in Example 1 except that the formulation of carbon black was changed as shown in Table 1, and image evaluation was performed in the same manner as in Example 1 for the obtained developing roller. The combination of carbon black used was the same as in Example 2, the total mass of carbon black was 20.0 parts by mass with respect to 100.0 parts by mass of urethane resin, and the degree of distortion was 0.27. Meets the requirements of the invention. However, the average particle size is as small as 20.6 μm and does not satisfy the requirements of the present invention. In this developing roller, the initial filming is good, but the effect of suppressing the durable fusion is low.

[Comparative Example 4]
A developing roller was produced in the same manner as in Example 1 except that the formulation of carbon black was changed as shown in Table 1, and image evaluation was performed in the same manner as in Example 1 for the obtained developing roller. The combination of the carbon black used was the same as in Example 2, and the total mass of the carbon black was 16.0 parts by mass with respect to 100.0 parts by mass of the urethane resin, which satisfies the requirements of the present invention. However, the average particle size is as small as 20.3 μm and does not satisfy the requirements of the present invention. In this developing roller, the initial filming is good, but the effect of suppressing the durable fusion is low.

[Comparative Example 5]
A developing roller was produced in the same manner as in Example 1 except that the formulation of carbon black was changed as shown in Table 1, and image evaluation was performed in the same manner as in Example 1 for the obtained developing roller. The combination of carbon black used was the same as in Example 1, and the total mass of the carbon black was 20.0 parts by mass with respect to 100.0 parts by mass of the urethane resin, and the skewness was 0.25. Meets the requirements of the invention. However, the average particle diameter is as large as 28.6 μm and does not satisfy the requirements of the present invention. In this developing roller, the initial filming is good, but the effect of suppressing the durable fusion is low.

[Comparative Example 6]
A developing roller was produced in the same manner as in Example 1 except that the formulation of carbon black was changed as shown in Table 1, and image evaluation was performed in the same manner as in Example 1 for the obtained developing roller. The combination of carbon black used was the same as in Example 5. The average particle diameter of carbon black was 23.4 μm and the degree of distortion was 0.30, which satisfies the requirements of the present invention. However, the total mass is as small as 10.0 parts by mass with respect to 100.0 parts by mass of the urethane resin, and does not satisfy the requirements of the present invention. In this developing roller, the durable fusion suppressing effect is good, but the initial filming suppressing effect is low.

[Comparative Example 7]
A developing roller was produced in the same manner as in Example 1 except that the formulation of carbon black was changed as shown in Table 1, and image evaluation was performed in the same manner as in Example 1 for the obtained developing roller. The combination of carbon black used was the same as in Example 5. The average particle size of carbon black was 23.4 μm and the degree of distortion was 0.30, which satisfies the requirements of the present invention. However, the total mass is as large as 30.0 parts by mass with respect to 100.0 parts by mass of the urethane resin, and does not satisfy the requirements of the present invention. In this developing roller, the initial filming is good, but the effect of suppressing the durable fusion is low.

[Comparative Example 8]
A developing roller was produced in the same manner as in Example 1 except that the formulation of carbon black was changed as shown in Table 1, and image evaluation was performed in the same manner as in Example 1 for the obtained developing roller. The total mass of the carbon black is 17.0 parts by mass with respect to 100.0 parts by mass of the urethane resin, and the average particle diameter is 22.0 μm, which satisfies the requirements of the present invention. However, the skewness is as low as 0.11, which does not satisfy the requirements of the present invention. In this developing roller, the durable fusion suppressing effect is good, but the initial filming suppressing effect is low.

[Comparative Example 9]
A developing roller was produced in the same manner as in Example 1 except that the formulation of carbon black was changed as shown in Table 1, and image evaluation was performed in the same manner as in Example 1 for the obtained developing roller. The total mass of the carbon black is 24.0 parts by mass with respect to 100.0 parts by mass of the urethane resin, and the average particle size is 26.0 μm, which satisfies the requirements of the present invention. However, the skewness is as low as 0.13 and does not satisfy the requirements of the present invention. In this developing roller, the initial filming suppressing effect is good, but the durable fusion suppressing effect is low.

A1: Furnace Black (trade name: SUN BLACK X15, manufactured by Asahi Carbon Co., Ltd.)
Average particle size 20. 0 nm, pH = 2.5
A2: Furnace Black (trade name: SUN BLACK X65, manufactured by Asahi Carbon Co., Ltd.)
Average particle size 25.0 nm, pH = 3.0
A3: Furnace Black (trade name: MA100, manufactured by Mitsubishi Chemical Corporation)
Average particle size 22.0 nm, pH = 4.0
A4: Furnace Black (trade name: Talker Black # 7550SB, manufactured by Tokai Carbon Co., Ltd.)
Average particle size 21.0 nm, pH = 7.5
B1: Furnace Black (trade name: MA230, manufactured by Mitsubishi Chemical Corporation)
Average particle size 30.0 nm, pH = 4.0
B2: SUN BLACK X55 (Asahi Carbon Co., Ltd.)
Average particle size 26.0 nm, pH = 2.5
B3: Furnace Black (trade name: MA11, manufactured by Mitsubishi Chemical Corporation)
Average particle size 29.0 nm, pH = 3.0
B4: Furnace Black (trade name: Talker Black # 7400, manufactured by Tokai Carbon Co., Ltd.)
Average particle size 28.0 nm, pH = 7.0

It is explanatory drawing which calculates | requires the surface equivalent diameter of the carbon black particle of the surface layer of the image development roller of this invention. It is explanatory drawing which calculates | requires the surface equivalent diameter of the carbon black particle of the surface layer of the image development roller of this invention. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention. It is a schematic block diagram which shows an example of the process cartridge of this invention.

Explanation of symbols

5 Photosensitive drum 4 Developing roller 6 Developer application roller 7 Developing blade (metal blade)
8 Charging roller 9 Developer container

Claims (7)

In a developing roller having a conductive shaft, an elastic layer sequentially provided on the conductive shaft, and a surface layer,
The surface layer contains at least a urethane resin and carbon black,
The content of carbon black is the urethane resin 100.0 parts by mass with respect to 15.0 parts by mass or more, a range of 25.0 parts by weight, the arithmetic mean value of the area equivalent diameters of the carbon black is 21. 0 nm or more and 27.0 nm or less,
A developing roller having a skewness in a distribution of an equivalent area diameter of the carbon black of 0.25 or more and 0.63 or less. The carbon black is a furnace black (A) of particles having an arithmetic mean value of an area equivalent diameter of 20.0 nm or more and 25.0 nm or less,
The furnace black (B) of particles having an arithmetic mean value of equivalent area diameter of 26.0 nm or more and 30.0 nm or less,
Developing roller according to 請 Motomeko 1 weight ratio of said furnace black (A) and said furnace black (B) is area by der 25:75 to 85:15. The urethane resin is a polyether polyurethane, a developing roller according to the 請 Motomeko 1 or 2 carbon black Ru der pH4.0 or less. It is a manufacturing method of the development roller according to any one of claims 1 to 3,
Polyether polyol, isocyanate, furnace black (A) of particles having an area equivalent diameter of 20.0 nm or more and 25.0 nm or less, and an arithmetic equivalent value of area equivalent diameter of 26.0 nm or more and a furnace black of particle (B) is less than 30.0 nm, a coating liquid mass ratio of said furnace black (a) and said furnace black (B) is contained in a range from 85:15 to 25:75 A process for producing a developing roller, which comprises a step of coating the elastic layer on an elastic layer to produce a surface layer. Before SL furnace black (A) and furnace black (B) and method for producing a developing roller according to 請 Motomeko 4 carbon black Ru der pH4.0 or less including. At least a photosensitive drum carrying an electrostatic latent image, a developing roller for supplying a developer to the photosensitive drum, and a metal blade for applying a DC voltage to the developing roller are attached to and detached from the main body of the electrophotographic image forming apparatus. a process cartridge provided freely, a process cartridge, wherein the developing roller is a developing roller according to any one of claims 1-3. In the image forming apparatus, at least a photosensitive drum that carries an electrostatic latent image, a developing roller that supplies a developer to the photosensitive drum, and a metal blade that applies a DC voltage to the developing roller is mounted. image forming apparatus, characterized in that but a developing roller according to any one of claims 1 to 3.

Images