JP4555031B2 - Manufacturing method and sorting method for electrophotographic conductive roller - Google Patents

Description

  The present invention relates to an electrophotographic conductive roller used in an electrophotographic apparatus such as a printer / copier, and more particularly to an electrophotographic conductive roller used as a developing roller of an electrophotographic apparatus.

  Conventionally, a one-component development system is known as one of latent image development systems in electrophotographic apparatuses such as printers and copiers, among which a roller (with a conductive elastic body provided on the outer periphery of a core metal ( There are developing methods using a conductive roller (Patent Document 1 and Patent Document 2).

  One form of use of the conductive roller is a contact-type charging roller that charges the surface of the image forming body in the image forming process. As another form of use, there is a developing roller that is disposed in contact with or close to the surface of the image forming body while the toner is carried on the surface, and conveys the toner onto the image forming body. These conductive rollers are required to supply a uniform charge to the image forming body or to supply toner onto the image forming body without any unevenness. It is required that the discharge area and the development area are in contact or close to each other. Further, in the case of the developing roller, it is necessary to make the layer thickness regulating member uniformly contact with the surface thereof, so that the toner is thinned and is uniformly carried on the surface of the developing roller.

  Therefore, stable physical characteristics are indispensable for the conductive roller, and lack thereof causes various image defects. In order to avoid this, a plurality of physical properties to be satisfied by the conductive roller are conceivable, but the surface property is one of the important management properties. When this is not appropriate, when used as a charging roller, charging of the image forming body due to sticking of the charging roller to the image forming body or paper dust adhering to the surface of the charging roller is caused. When used as a developing roller, it causes image defects such as density unevenness based on toner transportability and fogging / developing streaks due to deterioration of the developing roller surface and toner.

In order to prevent such defects, conventionally, a developing roller formed so that various surface roughness values such as a ten-point surface roughness Rz, an arithmetic average roughness Ra, and an average difference Sm of unevenness fall within a predetermined range has been proposed. (Patent Document 3).
JP 52-125340 A Japanese Patent No. 2879962 JP 2003-015401 A

  However, remarkable progress in electrophotographic apparatuses in recent years has resulted in higher speeds of the apparatuses and higher image quality, and the characteristics required for the conductive roller have become more advanced. It is becoming insufficient to form the values of Rz, Ra, and Sm as described above as the surface roughness of the conductive roller so as to fall within the range described in Patent Document 3. In other words, considering the deterioration of the surface of the conductive roller and the change in characteristics due to the deterioration of the toner, even if the initial state is good, image defects may occur while outputting a large number of images. Although it exists, the range described in Patent Document 3 is set so as to satisfy the initial characteristics, and thus cannot cope with the influence of deterioration.

  If the range of values of Rz, Ra, and Sm is set again in consideration of deterioration, the range of each value becomes very narrow, and it is considered that the condition becomes more severe than necessary. In other words, these values are no longer appropriate as indicators of the surface characteristics of the conductive roller taking into account the effects of deterioration.

  In recent years, there has been a demand for a conductive roller that solves this difficult problem, and it is necessary to incorporate surface characteristics that take into account the mechanism of deterioration into the product. For this reason, further innovation is indispensable. It was broken.

  In view of the above situation, the object of the present invention is to provide electrophotographic conductivity having surface characteristics such that sticking to an image forming body, poor charging, fogging / development streaks in an output image do not occur even when deterioration is caused by continuous use. To provide a roller.

The present invention
In the method for producing a conductive roller for electrophotography in which at least a conductive elastic layer is provided on the outer periphery of the conductive metal core,
An electronic device characterized in that a spatial frequency spectrum obtained by frequency conversion of surface shape data measured by a surface roughness meter based on JIS B0601 satisfies the following two conditions as a management index. This is achieved by a method for manufacturing a photographic conductive roller.
(1) When a component having a spatial frequency of 5 cycles / mm or less is A, the component A occupies 35% or more of all the spatial frequency components.
(2) When the component A included in the spatial frequency range within the average value ± 30% of the component A is B, the component B occupies 50% or more of the component A.
The present invention also provides
In the screening method of the electrophotographic conductive roller in which at least the conductive elastic layer is provided on the outer periphery of the conductive metal core,
An electronic device characterized by selecting, as a management index, a spatial frequency spectrum obtained by frequency conversion of surface shape data measured by a surface roughness meter based on JIS B0601 satisfies the following two conditions: This is achieved by a method for sorting photographic conductive rollers.
(1) When a component having a spatial frequency of 5 cycles / mm or less is A, the component A occupies 35% or more of the total spatial frequency components.
(2) When the component A included in the spatial frequency range within the average value ± 30% of the component A is B, the component B occupies 50% or more of the component A.

  According to the present invention, it is possible to provide an electrophotographic conductive roller having surface characteristics such that sticking to an image forming body, poor charging, and fogging / development streaks in an output image do not occur even when deterioration is caused by continuous use.

  The inventors of the present invention have been studied to solve the above problems. As a result of the study, simply specifying the surface roughness value for the electrophotographic conductive roller makes it difficult to achieve the optimum range width, and it also reveals a clear relationship with image defects. It was found to be insufficient. In general, the surface roughness of Rz, Ra, Sm, etc. is an average value of minute irregularities, and is considered to be effective when referring to the toner transportability in the initial stage. However, on the other hand, fogging, development streaks, paper dust adhesion, and the like are often a problem not in the initial stage immediately after the start of use of the member but in a state in which the deterioration is considerably advanced. In such a state, it is considered that either or both of the toner and the roller surface are deteriorated and the toner is not properly charged. Therefore, the range of surface roughness allowed as a surface characteristic is further narrowed. turn into. Therefore, in order to manage surface characteristics more efficiently, management characteristics that are directly linked to the degradation mechanism are required.

  As a result of further investigation, the present inventors focused on the distribution of roughness rather than the average of roughness such as Rz, Ra, Sm, etc., and reached the conclusion that it is important to have surface characteristics that are difficult to progress. did.

That is, in this invention, at least a conductive elastic layer electrophotographic conductive roller provided on the outer periphery of the conductive core metal,
Production or selection is performed using a management index that the spectrum of the spatial frequency obtained by frequency conversion of the surface shape data measured by the surface roughness meter based on JIS B0601 satisfies the following two conditions.
(1) When a component having a spatial frequency of 5 cycles / mm or less is A, the component A occupies 35% or more of all the spatial frequency components.
(2) When the component A included in the spatial frequency range within ± 30% of the average value among the components A is B, the component B occupies 50% or more of the component A.

  The surface characteristics as described above indicate that the roller surface has few local protrusions and is covered with gentle unevenness as a whole, and the size of the unevenness is uniformly distributed. If the surface is in such a state, the force applied to the roller surface on the surface in contact with the image forming body is uniformly dispersed, and the pressure is reduced. The reason why the pressure is reduced is that the roller surface is rich in gentle undulations, so that the area in contact with the image forming body is increased (FIG. 1 (a)). For this reason, the force applied to the roller surface is distributed, and the undulations are almost uniform, so that pressure does not concentrate at a specific location on the roller surface, and sticks to the image forming body centering on the specific site. And the deterioration of the surface is not promoted. On the other hand, when the undulations on the roller surface are large, the area in contact with the image forming body is small, and the pressure concentrates on a specific place (FIG. 1B). The paper dust that may cover the surface of the charging roller and the toner covering the surface of the developing roller are affected by the pressure acting between the roller and the image forming body, so that the aspect of deterioration is considered to be similar to that of the roller surface. The paper dust sticks to the surface of the charging roller to cause deterioration of the surface of the charging roller, and the toner adheres to the surface of the developing roller soon after the external additive on the surface is peeled off. However, if the roller surface is uniform and gentle as described above, degradation is still minimized.

  As described above, by properly processing the shape data of the roughness measuring machine with respect to the surface shape of the electrophotographic conductive roller, image defects such as charging defects and fog / development streaks can be obtained without intentional image evaluation. Since it can be predicted with high probability whether or not it will occur during long-term use, it is suitable as a management index during production.

  The surface shape data is measured with a surface roughness meter based on JIS B0601. As the surface roughness meter, for example, a surface roughness meter SE3500 (trade name) manufactured by Kosaka Laboratory can be used. As measurement conditions, the probe moving speed is preferably set to 0.1 mm / sec, the measurement length is set to 8.0 mm, and 25600 data is acquired. During the measurement, the electrophotographic conductive roller is preferably fixed, and the measurement length is preferably as long as possible. Moreover, it is preferable to perform a measurement in multiple places about one electrophotographic conductive roller.

  Next, the surface shape data obtained as time series data is converted into frequency data by Fourier transform, and further converted into a spatial frequency spectrum in consideration of the scanning speed of the surface shape. Since the subtle irregularities on the surface are considered to be slightly different depending on the location of the electrophotographic conductive roller, each of the measurement data at a plurality of locations (preferably 9 to 18 locations) is subjected to Fourier transform processing and converted to a spatial spectrum. After that, it is preferable to take a mean and obtain a single spatial frequency spectrum representative of the electrophotographic conductive roller. An example of the obtained spatial frequency spectrum is shown in FIG. The hatched portion of the spatial frequency spectrum in FIG. In addition, among the components A, the range of the average value ± 30% is the component B.

  With this process, it becomes possible to determine how much unevenness with pitch is dominant, and general surface roughness data can be converted into quantitative numerical characteristics that are more related to image quality. it can.

  In the present invention, in the above spatial frequency spectrum, the ratio of the component A having a spatial frequency of 5 cycles / mm or less (wavelength of 200 μm or more) to the total spatial frequency components needs to be 35% or more. Preferably, it is 50% or more. Furthermore, it is necessary that the component B included in the spatial frequency range within the average value ± 30% of the component A occupies 50% or more of the component A. Preferably it is 60% or more. If this condition is satisfied, the gentle unevenness is sufficiently dominant, and it is homogeneous and the load is not concentrated at a specific location. It is thought that it will not affect.

  The electrophotographic conductive roller of the present invention has a structure in which at least a conductive elastic layer is provided on the outer periphery of a conductive metal core. Further, in view of functional necessity, a structure in which one or more coating layers are provided on the outer periphery of the conductive elastic layer may be used. The coating layer is expected to prevent drum contamination, improve charging characteristics, or prevent paper dust / toner adhesion. However, the conventional electrophotographic conductive roller is actually used to prevent paper dust / toner adhesion. It's not perfect for features. The electrophotographic conductive roller of the present invention is particularly suitable for use as a developing roller for an electrophotographic apparatus.

  As the conductive core metal of the electrophotographic conductive roller, for example, a cylindrical steel plate having a surface of carbon steel alloy with industrial nickel plating having a thickness of 5 μm can be used. In addition, for example, metals such as iron, aluminum, titanium, copper, and nickel, and alloys such as stainless steel, duralumin, brass, and bronze containing these metals can be used. In addition to the cylindrical shape, a cylindrical shape having a hollow central portion can also be used. What is necessary is just to select the outer diameter of the electroconductive core metal to be used suitably according to a use, for example, it can be set to 5-15 mm.

  In the electrophotographic conductive roller according to the present invention, a conductive elastic layer is formed on the outer periphery of the conductive core. As the material for forming the conductive elastic layer, it is desirable to use a material capable of obtaining an appropriate low hardness and low compression set in order to keep the contact surface with the image forming body uniform. Any type is possible as long as it is possible. What added the electrically conductive filler to rubber | gum is used suitably. An ion conductive rubber can also be used. Examples of rubber include natural rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber, (meth) acrylonitrile butadiene rubber, ethylene propylene rubber, ethylene propylene diene rubber, butyl rubber, halogenated butyl rubber, silicone rubber, fluorine rubber, urethane rubber, Examples thereof include ethylene vinyl acetate copolymer, ethylene- (meth) acrylate rubber, epichlorohydrin rubber and the like. These can be used alone or in combination of two or more. There is no restriction | limiting in particular in the molecular weight of the rubber | gum used, From low molecular weight (oligomer) to high molecular weight rubber | gum can be selected suitably and can be used. Such rubber can be used by obtaining a commercial product. Silicone rubber is one that satisfies the above characteristics, and can be suitably used.

  As the conductive filler, for example, metal powders and fibers such as aluminum, palladium, iron, copper, and silver can be used, and carbon black, metal oxides such as titanium oxide, tin oxide, and zinc oxide, You may use the powder of metal compounds, such as copper sulfide and zinc sulfide. In addition, tin oxide, antimony oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, chromium, cobalt, iron, lead, platinum, rhodium, etc. are subjected to electrolytic treatment, spray coating, mixed vibration. Powders deposited by means of, for example, can also be used, and carbon powders such as acetylene black, ketjen black, PAN-based carbon black, pitch-based carbon black and the like can be used.

  Carbon black is particularly preferable as the conductive filler. The electrical resistivity can be reduced by adding a small amount, and conductivity can be imparted without increasing the hardness of the conductive elastic layer. Examples of carbon black brands include Ketjen Black EC, Ketjen Black EC600JD (both are trade names manufactured by “Ketjen Black International”), and the like.

  What is necessary is just to set suitably content of the electroconductive filler in an electroconductive elastic layer so that the target characteristic may be expressed. For example, 2-50 mass% is preferable. More preferably, it is 5-30 mass%. If the amount is too small, it is difficult not only to achieve the intended conductivity, but also difficult to uniformly disperse, making it difficult to control the conductivity. Moreover, when there are too many, a conductive elastic layer may become hard.

  The rubber has various kinds of commonly used additives such as reinforcing fillers, extenders, plasticizers, softeners, anti-aging agents as long as they do not impair the characteristics of low hardness and low compression set. , Heat-resistant agents, processing aids, colorants, UV absorbers, flame retardants, oil resistance improvers, foaming agents, scorch inhibitors, tackifiers, lubricants, and the like can be added. These blends can be added in the process of producing the elastic layer material, if necessary.

Examples of the reinforcing filler and extender include conductive carbon black, conductive filler, conductive plasticizer, ion conductive materials such as KSCN, LiClO ₄ , NaClO ₄ and quaternary ammonium salts, fumed silica, wet type Silica, quartz fine powder, diatomaceous earth, carbon black, zinc oxide, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, mica powder, aluminum sulfate, calcium sulfate, barium sulfate, glass Mention may be made of fibers, organic reinforcing agents, organic fillers. The surface of these fillers may be hydrophobized by treatment with an organosilicon compound such as polydiorganosiloxane.

  As the plasticizer, for example, polydimethylsiloxane oil, diphenylsilanediol, trimethylsilanol, phthalic acid derivative, adipic acid derivative and the like can be used. As the softening agent, for example, lubricating oil, process oil, coal tar, castor oil can be used. As the anti-aging agent, for example, phenylenediamines, phosphates, quinolines, cresols, phenols, dithiocarbamate metal salts and the like can be used. As the heat-resistant agent, iron oxide, cerium oxide, potassium hydroxide, iron naphthenate, potassium naphthenate and the like can be used.

  As a method for forming the conductive elastic layer, a rubber composition in which the above materials are mixed is poured into a molding machine having a conductive metal core disposed at the center, and then cured by heating to a predetermined temperature. And it can carry out by the method of demolding after completion | finish of hardening.

  What is necessary is just to select the thickness of the electroconductive elastic layer to form suitably according to a use, for example, can be 1-10 mm.

  On the outer periphery of the conductive bullet layer formed as described above, one or more coating layers can be provided as necessary. Examples of the base resin for forming the coating layer include polyamide, fluororesin, hydrogenated styrene-butylene resin, urethane resin, silicone resin, polyester resin, phenol resin, imide resin, olefin resin, and the like. When the said coating layer is formed from a urethane resin, since the physical property can be changed in a wide range by changing the structure and compounding ratio of a polyol component and an isocyanate component variously, it is preferable.

  When a urethane resin is used as a material for forming the coating layer, a difunctional or trifunctional isocyanate or a modified isocyanate is usually used as an isocyanate component as a raw material. Among these aromatic compounds, 1,5-naphthalene diisocyanate, 2,4- / 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, p-phenylene diisocyanate, m- / P-xylylene diisocyanate, and the like. In the alicyclic system, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate and the like are listed, and in the aliphatic system, 1,6-hexamethylene diisocyanate. Examples include isocyanate, lysine diisocyanate, 1,6,11-undecane triisocyanate, and the like. As the polyol component, polyethers, polyesters, polybutadiene polyols, acrylic polyols, saponified ethylene-vinyl acetate copolymers having 2 to 3 functionalities and number average molecular weights of several hundred to several thousand are used. By appropriately adjusting the number of functional groups and the number average molecular weight of these isocyanate component and polyol component, the elastic modulus and the like of the coating layer can be set to desired physical properties.

  Fine particles having an average particle size of 1 to 50 μm may be dispersed in the coating layer, thereby imparting an appropriate roughness to the surface of the conductive roller to make it difficult to stick to the image forming body or the like. The toner can be easily conveyed so that a sufficient amount of toner can be supplied to the developing area, and the object of reducing stress on the toner on the contact surface with the image forming body can be easily achieved. Examples of the fine particles used for such purposes include plastic pigments such as polymethyl methacrylate fine particles, silicone rubber fine particles, polyurethane fine particles, polystyrene fine particles, amino resin fine particles, and phenol resin fine particles. Fine particles, polyurethane fine particles, and silicone rubber fine particles are preferred. These fine particles are preferably added in the range of about 5 to 200% by mass of the base resin.

  The material constituting these coating layers is a conventionally known dispersing device such as a dispersing device using beads such as a sand mill, a paint shaker, a dyno mill, a pearl mill, a visco mill, or a dispersing device using a ball mill together with an appropriately selected solvent. Use to disperse. The obtained coating material for forming the coating layer is applied to the surface of the conductive elastic layer by a spray coating method, a dipping method or the like.

  The thickness of the coating layer is preferably 5 to 500 μm, particularly preferably 5 to 30 μm. If it is too thin, there is a risk of contamination of the image forming body due to exudation of low molecular weight components in the conductive elastic layer. If it is too thick, the conductive roller will become hard, which may cause deterioration of fusing and set mark recovery. There is.

  The coating layer may be a single layer or two or more layers. In order to achieve a plurality of functions such as prevention of drum attack and prevention of toner adhesion to the surface, it may be easier to design two or more layers.

  As a method for adjusting the surface characteristics of the conductive roller, a method of changing the diameter and addition amount of urethane particles contained in the coating liquid for forming the coating layer can be used. Further, a large amount of high resistance carbon black can be added as a filler. The viscosity of the coating solution is adjusted so that the coating layer made of such a coating solution has a target surface shape that sufficiently reflects the diameter of the urethane particles. Further, in dipping, a coating layer having a desired thickness and surface characteristics can be obtained by adjusting the pulling speed after the conductive elastic layer is immersed in the liquid.

  Hereinafter, the effects of the present invention will be clarified by showing examples and comparative examples, but the present invention is not limited to the following examples.

[Examples and Comparative Examples]
(Production of electrophotographic conductive roller)
An electrophotographic conductive roller having an outer diameter of about 16 mm having a conductive elastic layer and one coating layer was produced around a cylindrical conductive core bar (material: stainless steel) having an outer diameter of 8 mm.

  The conductive elastic layer was formed of silicone rubber containing a conductive filler. Specifically, a rubber obtained by mixing 50 parts by mass of dimethylpolysiloxane as a main ingredient and 50 parts by mass of dimethylhydrogenpolysiloxane as a curing agent is used, and Ketjen Black (Ketjen Black EC; trade name, Ketjen A rubber composition in which 10 parts by mass of Black International Co., Ltd. and 30 parts by mass of filler were mixed was used. A conductive core was incorporated into the molding machine and preheated at 100 ° C., and the rubber composition was injected and cured at 115 ° C./4 h. Then, after cooling to 25 ° C. and demolding, the conductive elastic layer having a thickness of 4 mm was formed by secondary curing again at 140 ° C./4 h.

  The coating layer was formed as follows. First, 100 parts by mass of an ester polyurethane resin comprising 47 parts by mass of a polyester polyol (Nipporan N5033; trade name, manufactured by Nippon Polyurethane) and 53 parts by mass of toluene diisocyanate (B-830; trade name, manufactured by Mitsui Takeda Chemical) After dissolving in MEK, 10 parts by mass of Ketjen Black (Ketjen Black EC; trade name, manufactured by Ketjen Black International) was added thereto. Furthermore, after adding 50 parts by mass of high resistance carbon black (MA77; trade name, manufactured by Mitsubishi Chemical Corporation) as a filler and dispersing this with Viscomil for 5 hours, urethane particles having the average particle sizes shown in Tables 1 and 2 Was added in parts by mass as shown in Tables 1 and 2 and dispersed again for 2 to 3 hours and a half. A conductive core metal having a conductive elastic layer formed therein was dipped in the dispersion and pulled up to form a coating layer having a thickness of 20 μm to obtain a conductive roller for electrophotography. In addition, the coating layer of predetermined thickness was formed by adjusting appropriately the usage-amount (viscosity of a dispersion liquid) of MEK, and a raising speed | rate.

  Three electrophotographic conductive rollers were prepared for each condition. This takes into consideration that even if the average particle size and the number of parts by mass of the urethane particles used in the coating layer are the same, the surface characteristics can vary slightly due to individual differences.

(Measurement of surface characteristics)
The surface shape of each electrophotographic conductive roller was measured based on JIS B0601 at a total of nine locations: three in the axial direction (100 mm intervals) and three in the circumferential direction (120 ° C. intervals). The surface roughness meter SE3500 (trade name) manufactured by Kosaka Laboratory was used for the measurement, the probe moving speed was 0.1 mm / sec, the measurement length was 8.0 mm, and the number of data was 25600. The obtained data was converted into frequency data by Fourier transform, and further converted into a spatial frequency spectrum in consideration of the scanning speed of the surface shape. From the spatial frequency spectrum, the average value of the component A having a spatial frequency of 5 cycles / mm or less and the ratio of all the components, and the component B included in the spatial frequency range within ± 30% of the average value among the components A The ratio to component A was determined. In addition, ten-point surface roughness Rz, arithmetic average roughness Ra, and unevenness average difference Sm were also measured. The above measurements were performed on three electrophotographic conductive rollers prepared for each condition, and the average was taken. The results are shown in Tables 1 and 2.

(Durability evaluation of conductive roller)
Each of the produced electrophotographic conductive rollers was assembled as a developing roller in a cartridge of an electrophotographic printer and mounted on the printer for durability evaluation. Specifically, it is incorporated into a cartridge having black toner, and a printer is used to output 8000 continuous images for durability evaluation (images for passing paper consisting of characters, lines and solids with a printing rate of 2%). A halftone image for performance evaluation was output to and checked for development streaks.
Evaluation criteria ○: Development streaks are not observed.
Δ: A thin development streak is observed.
×: Clear development streaks are observed.

Further, after being left for 72 hours, a blank sheet was output to check whether fog was at a good level.
○: No fog is observed.
(Triangle | delta): Although some fog is seen, it is a favorable level.
X: Fog is observed, and this is a practically problematic level.

  The above results are summarized in Table 1 and Table 2.

It is a schematic diagram of the electrophotographic conductive roller surface, (a) is an electrophotographic conductive roller having surface characteristics satisfying the conditions of the present invention, (b) is an electron having surface characteristics not satisfying the conditions of the present invention. The surface shape of the photographic conductive roller (solid line: non-contact state with the image forming body, broken line: contact state with the image forming body) is shown. It is a figure which shows an example of the spatial frequency spectrum obtained by frequency conversion.

Explanation of symbols

1 Image forming body surface 2 Electrophotographic conductive roller surface (non-contact state with image forming body; solid line)
3 Electrophotographic conductive roller surface (in contact with the image forming body; broken line)
4 Electrophotographic conductive roller surface (non-contact with image forming body; solid line)
5 Electrophotographic conductive roller surface (in contact with the image forming body; broken line)

Claims (4)

In the method for producing a conductive roller for electrophotography in which at least a conductive elastic layer is provided on the outer periphery of the conductive metal core,
An electronic device characterized in that a spatial frequency spectrum obtained by frequency conversion of surface shape data measured by a surface roughness meter based on JIS B0601 satisfies the following two conditions as a management index. A method for producing a photographic conductive roller.
(1) When a component having a spatial frequency of 5 cycles / mm or less is A, the component A occupies 35% or more of all the spatial frequency components.
(2) When the component A included in the spatial frequency range within ± 30% of the average value among the components A is B, the component B occupies 50% or more of the component A. 2. The electrophotographic conductive roller manufacturing method according to claim 1 , wherein the electrophotographic conductive roller is used as a developing roller of an electrophotographic apparatus. In the screening method of the electrophotographic conductive roller in which at least the conductive elastic layer is provided on the outer periphery of the conductive metal core,
An electronic device characterized by selecting, as a management index, a spatial frequency spectrum obtained by frequency conversion of surface shape data measured by a surface roughness meter based on JIS B0601 satisfies the following two conditions: A method for selecting conductive rollers for photography.
(1) When a component having a spatial frequency of 5 cycles / mm or less is A, the component A occupies 35% or more of all the spatial frequency components.
(2) When the component A included in the spatial frequency range within ± 30% of the average value among the components A is B, the component B occupies 50% or more of the component A. The electrophotographic conductive roller selection method according to claim 3, wherein the electrophotographic conductive roller is used as a developing roller of an electrophotographic apparatus.

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