JP2009265157A - Manufacturing method for conductive roller and conductive roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive roller and a manufacturing method for it, improving dispersion of a surface layer forming coating liquid for the conductive roller requiring precise control, stably controlling a surface layer to have surface roughness and surface area ratio higher than a certain level, and forming a favorable image. <P>SOLUTION: In this conductive roller, a conductive rubber substrate is provided on a conductive core, and the surface layer where crosslinking resin particles are dispersed is provided on the outermost surface. The surface roughness of the conductive roller is 1.5-2.5 μm, and the surface area ratio expressed by formula (I): (surface area ratio)=S/S<SB>0</SB>is 1.2-2.0. (in the formula, S is a measured surface area of the conductive roller surface, and S<SB>0</SB>is a theoretical surface area when the surface of the conductive roller is an ideal plane). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a conductive roller used in an electrophotographic apparatus, an electrostatic recording apparatus or the like. Specifically, the present invention relates to a conductive roller having a surface layer formed by a surface layer forming coating solution containing conductive carbon black.

  Generally, in an electrophotographic apparatus, the surface of a photoconductor having photoconductivity is charged, image light is exposed on the surface of the photoconductor to form an electrostatic latent image, and toner is electrostatically adsorbed on the electrostatic latent image. The toner image is manifested as a toner image, the toner image is transferred onto a sheet, and the transferred image is fixed on the sheet with pressure or heat. Further, after the transfer, the surface of the photoreceptor is freed of residual toner (cleaned), and charging, exposure, development, and the like are repeated again. Various rollers are used in these processes. That is, a charging roller in the charging process, a developing roller in the developing process, a transfer roller in the transferring process, and the like.

  In current electrophotographic apparatuses, a contact type one-component developing apparatus is mainly used. As a conductive roller used in such a contact type one-component developing device, a semiconductive elastic roller is mainly used. Specifically, the same conductive agent having a thickness of several μm to several tens of μm is formed on the peripheral surface of the elastic layer made of rubber having a thickness of several mm adjusted to the middle resistance region by adding the conductive agent. A roller composed of a resin layer (surface layer) adjusted to a medium resistance region by addition is used.

  For the formation of this surface layer, a method is adopted in which an additive such as a resin and a conductive agent is dissolved or dispersed in an organic solvent or the like to form a coating liquid, which is applied onto the surface of the elastic layer. Sometimes. As a method for producing this coating liquid, dispersion by a mill using beads or the like can be mentioned.

  In order to make the elastic layer and the surface layer conductive, a conductive agent is appropriately selected and used. Here, as the conductive agent, carbon black may be used because it is excellent in kneadability, dispersibility, moldability, economy, etc., in rubber and resin for elastic layers, and in resin for surface layers. Many.

  Incidentally, carbon black is an aggregate of fine spherical particles obtained by incomplete combustion of various hydrocarbons. Carbon black that can exhibit high conductivity only by filling a small amount of resin or rubber is called conductive carbon black, and is distinguished from ordinary carbon black. Along with this, conductive carbon black that exhibits higher conductivity than ordinary carbon black is difficult to finely disperse at a high concentration, has poor dispersion stability, and is inferior in economic efficiency. .

  Although conductive carbon black is widely spread as a conductive filler, the smaller the particle size and structure, the stronger the cohesive force between the particles. For this reason, dispersibility in resins and rubbers deteriorates, and even if dispersed, they tend to re-aggregate into aggregates, making dispersion difficult. Yes.

  On the other hand, the preparation of the surface layer coating liquid is performed by a procedure in which carbon black is first dispersed in the surface layer resin material, and the dispersed resin particles dispersed in the solvent are added when the dispersion has sufficiently progressed. . At that time, the addition of the crosslinked resin particle dispersion causes a so-called solvent shock due to contact between the carbon black dispersion and the solvent in which the crosslinked resin particles are dispersed, and the carbon black reaggregates. As a result, the coating liquid loses thixotropy and cannot retain a sufficient amount of the crosslinked resin particles on the elastic layer (conductive rubber base layer) during coating, which is an important function as a conductive roller. There is a problem that a certain surface roughness and surface area ratio cannot be increased by addition of crosslinked resin particles.

  As a means to prevent carbon black from re-aggregating, the concentration is adjusted with a diluent containing inorganic particles, dispersant, aqueous medium, and water-soluble thickener, although it is for aqueous dispersions. The method of performing is proposed (Patent Document 1).

However, in the method described in Patent Document 1, a component that is not related to the function of the conductive roller is included, and there is a risk of affecting the photosensitive member that directly contacts the conductive roller. In addition, increasing the amount of raw materials necessary for production also disadvantages the cost.
Japanese Patent Registration No. 0309191

  The object of the present invention is to improve the dispersion of the coating solution for forming the surface layer of the conductive roller that requires precise control, and to make the surface layer stable and controllable with a surface roughness and surface area ratio above a certain level. Another object of the present invention is to provide a conductive roller capable of forming a good image and a manufacturing method thereof.

  The present inventors have intensively studied a dispersion method that stably satisfies the performance as a coating liquid with respect to the dispersion of the coating liquid for forming a surface layer of a conductive roller that requires precise control. As a result, it was clarified that the surface roughness and the surface area ratio when formed as the surface layer of the conductive roller were changed by the method of adding the crosslinked resin particle dispersion. Further examination revealed that when a specific carbon black was used, the cross-linked resin particle dispersion was added as a surface layer of a conductive roller by adding it at a certain speed or less, so that a stable and constant level was obtained. It has also been found that a conductive roller having a surface roughness and a surface area ratio can be obtained. The present invention has been made based on these findings.

That is, the present invention is a conductive roller having a conductive rubber base layer on a conductive metal core and having a surface layer in which crosslinked resin particles are dispersed on the outermost surface, the surface roughness of the conductive roller being The conductive roller is characterized in that Ra is 1.5 to 2.5 μm, and a surface area ratio represented by the following formula (I) is 1.2 to 2.0.
Surface area ratio = S / S ₀ (I)
(In the formula, S is the measured surface area of the surface of the conductive roller, and S ₀ is the theoretical surface area when the surface of the conductive roller is an ideal plane.)

Further, the present invention is a method for producing the above conductive roller having a conductive rubber base layer on a conductive core metal and having a surface layer in which crosslinked resin particles are dispersed on the outermost surface. A method for producing a conductive roller, wherein the surface layer is formed by applying the prepared surface layer coating liquid to the conductive rubber base layer:
A step of dispersing 5 to 30% by mass of carbon black with respect to the resin for forming the surface layer in the resin material for forming the surface layer and the solvent mixture to obtain a liquid A;
A step of dispersing crosslinked resin particles having a particle diameter of 3 to 30 μm in a solvent at a concentration of 10 to 40% by mass to obtain a liquid B; and
In the liquid A being stirred, the addition rate is 1/200 or less of the B liquid amount per second, and the addition amount is 2 times or less in mass ratio (B / A) to the A liquid. Step of adding the B liquid.

  Further, according to the present invention, the carbon black has a DBP absorption of 120 ml / 100 g or less, an average primary particle size of 0.03 μm or less, a pH of 8.0 or less, a powder, and the carbon black This is a method for producing the above conductive roller, wherein the specific coloring power of carbon black is 90% to 150%.

  According to the present invention, since the dispersion of the coating liquid for forming the surface layer of the conductive roller that requires precise control is improved, the surface layer can be stably controlled to a surface roughness of a certain level or better. A conductive roller capable of forming a clear image is provided. In addition, a conductive roller having a stable surface roughness and a method for manufacturing the same are provided.

  The present invention relates to a conductive roller used at a charging, developing, and transfer site of an electrophotographic apparatus, having a conductive rubber base layer on a conductive metal core, and a surface on which crosslinked resin particles are dispersed on the outermost surface Over a conductive roller having a layer.

  The basic structure of the conductive roller of the present invention is as shown in FIG. 1 ((a) perspective view, (b) sectional view). In other words, as described above, the conductive roller 1 of the present invention is provided with the conductive rubber base layer 3 (also referred to as an elastic layer) around the conductive metal core 2, and the cross-linked resin particles 5 as an outer layer thereof. The surface layer 4 containing is formed.

In the present invention, the conductive roller 1 has a surface roughness Ra of 1.5 to 2.5 μm and a surface area ratio represented by the following formula (I) of 1.2 to 2.0. is required.
Surface area ratio = S / S ₀ (I)
(In the formula, S is the measured surface area of the surface of the conductive roller, and S ₀ is the theoretical surface area when the surface of the conductive roller is an ideal plane.)

  In addition, the surface roughness Ra is 3 points in the longitudinal direction and 3 places in the circumferential method using a surface roughness measuring instrument “Surf Corder SE3500” (trade name, manufactured by Kosaka Laboratory Co., Ltd.) in accordance with JIS B0601-2001. A total of 9 points were measured, and the measured values in the longitudinal direction were averaged. Here, the reference line length and the cutoff value were 25 mm and 2.5 mm, respectively.

  Further, the surface area of the surface of the conductive roller is in the range of 0.03 mm <2> using the ultra-deep shape measuring microscope "VK-8510" (trade name, manufactured by Keyence Corporation) at the center of the portion where the surface roughness Ra is measured. Is an actual measurement of the area. In addition, each measured value of a longitudinal direction is averaged and used for evaluation.

  If the surface roughness Ra exceeds 2.5 μm, the abutting photoconductor may be scraped if used continuously, resulting in irregularities in toner adhesion on the developing roller, resulting in image irregularities. There are problems that occur. On the other hand, when the surface roughness Ra is less than 1.5 μm, the toner transportability becomes inferior and it is difficult to obtain an appropriate density, which is not preferable.

  On the other hand, when the surface area ratio of the developing roller exceeds 2.0, the toner transportability becomes too large, causing unevenness in toner adhesion on the developing roller, and in particular, unevenness may occur in a halftone image. On the other hand, when the surface area ratio is less than 1.2, the toner transportability of the developing roller is lowered, and it may be difficult to obtain an appropriate density.

  The thickness of the surface layer is preferably 5 μm to 80 μm, particularly 10 μm to 50 μm. If the surface layer is thinner than 5 μm, low molecular weight components may ooze out from the elastic layer and may contaminate the photoreceptor, or the surface layer may peel off. If the surface layer is thicker than 80 μm, the surface of the developing roller becomes hard, and the toner Deterioration is likely to occur and image performance may be deteriorated.

  The conductive roller of the present invention has the above-described structure, but is preferably manufactured as follows.

  That is, a conductive rubber base layer is formed on a conductive metal core, and a surface layer in which crosslinked resin particles are further dispersed is formed thereon. Here, the surface layer coating solution prepared by the following steps is applied to the conductive rubber base layer.

Process 1: Disperse 5-30 mass% carbon black with respect to resin for surface layer formation in the resin raw material for surface layer formation, and a solvent liquid mixture, and obtain A liquid.
Step 2: Crosslinked resin particles having a particle diameter of 3 to 30 μm are dispersed in a solvent at a concentration of 10 to 40% by mass to obtain a liquid B.
Step 3: In the liquid A being stirred, the addition rate is 1/200 or less of the liquid B per second, and the addition amount is twice the mass ratio (B / A) with respect to the liquid A. Add solution B as follows.

  As the resin for forming the surface layer, a preferable one is appropriately selected depending on the material of the conductive rubber base layer (elastic layer), but it is easy to use as a coating liquid and the durability of the coating film (surface layer) is good. A polyurethane resin is preferred.

  When a polyurethane resin is used as the resin for forming the surface layer, the raw materials are polyol and isocyanate, and the dispersion medium in which carbon black is dispersed contains polyol and isocyanate. Further, the solvent is not particularly limited, but examples thereof include ketones such as methyl isobutyl ketone, methyl ethyl ketone and acetone, aromatics such as toluene, esters such as ethyl acetate, and ethers such as tetrahydrofuran. Is mentioned.

  The carbon black used in the present invention is added for adjusting the conductivity of the surface layer, and can be appropriately selected from those used for producing a conductive roller. However, in the present invention, it is preferable that the DBP absorption amount is 120 ml / 100 g or less, the average primary particle diameter is 0.03 μm or less, and the pH is contained in a neutral or acidic region.

  When the DBP absorption amount of carbon black exceeds 120 g / 100 g, when carbon black is dispersed at a high concentration, the viscosity is very high, the fluidity is poor, the dispersibility is inferior, and the conductivity is lowered. (Inferior jetness and hard to become fine particles). That is, with such a surface layer coating solution using carbon black, it is often difficult to make the conductive roller uniform in thickness and to have sufficient conductivity. Therefore, it is preferable that the DPB absorption is 120 ml / 100 g or less, preferably 60 ml / 100 g or less, which does not have such influence.

  The average primary particle size of the carbon black is 0.03 μm or less, preferably 0.025 μm or less, because the carbon black can be dispersed at a sufficiently high concentration. If it exceeds 0.03 μm, it is difficult to finely disperse to a high concentration, and dispersion stability tends to deteriorate, so that it is difficult to give the conductive roller the necessary conductivity, It is easy for carbon black to re-agglomerate in the coating solution.

  Furthermore, considering the compatibility with the polyol and isocyanate contained in the dispersion medium, the carbon black preferably has a pH of 8.0 or less, more preferably 7.0 or less. pH refers to the pH value of the sludge cooled after boiling the carbon black water suspension.

  Carbon black is preferably powdery from the viewpoint of excellent dispersibility, and its specific coloring power is preferably 90% to 150% from the viewpoint of coloring effect. The specific coloring power of carbon black is defined in JIS K6217-5: 2001, and represents the color density, that is, the degree of hiding with respect to the white pigment. The higher the value, the higher the coloring power. . In the case of carbon black, the smaller the particle size and the larger the specific surface area, the higher the specific coloring power. However, considering the dispersibility and the viscosity of the resulting dispersion, the specific coloring power is 95% or more, preferably 105% or more. It is desirable that it is 145% or less.

  In the present invention, carbon black as described above is preferably dispersed in the resin material for forming the surface layer and the solvent mixture.

  The carbon black is preferably added usually at 5 to 30% by mass with respect to the resin raw material. When the addition amount of carbon black is 5% by mass or more, conductivity can be imparted to the surface layer, and the conductivity can be controlled by adding a necessary amount of carbon black up to 30% by mass. .

  In step 1, for example, the apparatus shown in FIG. 2 can be used. The liquid before dispersion is placed in a tank 8 equipped with stirring blades, beads (media) are placed in a container (vessel) 7 having a rotating shaft (disk) 6 having a plurality of blades 5 inside, and the rotating shaft 6 The liquid is caused to flow from the tank 8 through the pipe 10 using the pump 9 into the container 7 while rotating the container. Partly dispersed in the vessel 7, returns to the tank 8 through the pipe 11, and the liquid flows and disperses from the tank 8 to the vessel 7 and further to the tank 8. That is, conductive carbon black is dispersed by a circulating bead mill method.

  The container is not particularly limited, and a commercially available cylindrical container can be used. Moreover, about the blade | wing and rotating shaft used here, what is marketed can be used, without being restrict | limited in particular.

The type of beads used as the medium can be used without limitation as long as the density is within a range of 2.0 to 7.0 g / cm ³ . Specific examples include glass beads, zirconia beads, zircon beads, alumina beads, silica beads and the like.

  It is desirable to disperse the carbon black until the dispersity is 1.5 μm or less by a method defined in JIS K5600-2-5: 1999. Thereby, when a developing roller is produced using this liquid and an image is output, it is possible to excellently prevent a mottled pattern from being generated on the image. Further, the lower limit is not limited as long as it is not particularly harmful as long as it can be visually confirmed on a grind gauge. Let the dispersion liquid obtained at this process 1 be A liquid.

  On the other hand, a solvent is added to the crosslinked resin particles weighed so as to obtain a predetermined surface roughness, and stirred to obtain a slurry in which the crosslinked resin particles are dispersed in the solvent. Let the dispersion liquid obtained at this process 2 be B liquid.

  As the cross-linked resin particles, those having an average particle diameter of 3 to 30 μm are suitable, and spherical resin particles made of a material such as polymethyl methacrylate, polystyrene, or polyurethane are often used. The spherical resin particles are required not to swell or dissolve depending on the solvent used.

  The concentration of the crosslinked resin particles in the liquid B is preferably 10 to 40% by mass. When the concentration is less than 10% by mass, the amount of the solvent added may be locally excessive when adding the B liquid to the A liquid, and a solvent shock is likely to occur. On the other hand, if it exceeds 40% by mass, although depending on the particle diameter of the crosslinked resin particles, the fluidity of the B liquid (slurry) becomes poor, and the operation of adding the B liquid to the A liquid tends to be difficult.

  By adding the liquid B while the liquid A is being stirred, a surface layer coating liquid for a developing roller containing crosslinked resin particles is obtained. At this time, the addition speed of the B liquid is set to a speed that is 1/200 or less, preferably 1/500 or less of the B liquid amount per second. When an amount exceeding 1/200 per second is added, so-called solvent shock is caused in mixing / contact with the solvent in which the crosslinked resin particles are dispersed, and the dispersion system is destroyed. That is, reaggregation of carbon black occurs and the thixotropy of the coating solution is lost. As a result, the crosslinked resin particles cannot be held on the conductive rubber base layer in a sufficient amount during dip coating, and the surface roughness and surface area ratio, which are important functions as a developing roller, are reduced. Further, the lower limit value is not particularly limited because there is no harmful effect caused by the slow addition. However, from the viewpoint of productivity, it is desirable to add it as fast as possible without causing a solvent shock.

  The amount of the B liquid relative to the A liquid is determined by the solid content concentration when the A liquid is dispersed, the solid content concentration when finally forming the coating solution for forming the surface layer, and the amount of the crosslinked resin particles to be added. The At this time, if the B liquid is excessively large with respect to the A liquid, the dilution rate increases, and reaggregation of the carbon black tends to occur. Specifically, it is preferable to add the B liquid in an amount of 2.0 times or less by weight ratio (B / A) to the A liquid.

  As the conductive metal core 2, any metal can be used as long as it functions as an electrode and a support member of the conductive rubber base layer. For example, it is composed of conductive materials such as metals or alloys such as aluminum, copper alloy, stainless steel, iron plated with chromium, nickel, etc., synthetic resins containing conductive pigments, and synthetic resins with a metal layer formed on the surface. A cylinder, a circular tube or a tube.

  In addition, in order to adhere | attach the metal core 2 and the elastic layer 3 formed in the surrounding surface, a primer can also be apply | coated to the metal core 2 surface. As the primer, a known primer that is usually used, for example, a silane coupling primer can be used.

  The elastic layer of the developing roller is a layer provided to give elasticity to the developing roller in order to obtain an appropriate contact area when pressed against the developer regulating member or the photosensitive drum. It is also possible to form a multilayer with

  As long as this elastic layer has elasticity, its form may be a foam or a solid, except that it is a conductive rubber.

  The elastic layer is formed on the core metal by providing a conductive member, for example, conductive carbon, metal powder, metal oxide, or the like, if necessary, to the elastic layer rubber material.

  The rubber material used here is not particularly limited, and includes the following materials. Ethylene-propylene-diene copolymer rubber (EPDM), silicone rubber, urethane rubber, styrene-butadiene rubber (SBR), isoprene rubber (IR), natural rubber (NR), acrylonitrile-butadiene rubber (NBR), hydrogen of NBR Compounds, epichlorohydrin rubber, chloroprene rubber (CR), fluoro rubber, polysulfide rubber, etc. In addition, these can be used individually or in mixture of 2 or more types. Among these, silicone rubber, urethane rubber or NBR is preferably used because of excellent compression set characteristics.

  Examples of the silicone rubber include dimethyl silicone rubber, methyl phenyl silicone rubber, methyl vinyl silicone rubber, and methyl phenyl vinyl silicone rubber.

  The thickness of the elastic layer is usually 1.0 mm to 6.0 mm, preferably 1.5 mm to 5.0 mm. That is, in order to ensure a uniform nip, the thickness is desirably 1.0 mm or more, and even if it exceeds 6.0 mm, not only does not lead to improvement in charging performance, but also increases raw materials and increases molding costs, resulting in production. It is disadvantageous in doing.

  Depending on the elastic layer material, the elastic layer is made of the above elastic layer material and pushes the metal core into a tube shape cut to a predetermined length. The elastic material is extruded together with the metal core. It is formed by injecting an elastic material into the mold, casting the elastic material on the surface of the core metal, or the like.

  In the present invention, as described above, the surface layer is formed on the elastic layer. The method of applying the surface layer coating liquid to the outer peripheral surface is not particularly limited as long as a uniform coating film can be obtained, but the dip coating method is preferable because a uniform coating film is formed.

  The electroconductive roller of the present invention is useful as an electroconductive member for electrically controlling an object to be contacted such as a roller-shaped developing member, a charging member, a transfer member, and a charge eliminating member in an electrophotographic image forming apparatus. Even in other shapes, the above-described concept can be applied to a conductive member that electrically controls an object to be contacted, such as a developer amount regulating blade or a cleaning blade.

  The present invention will be described in more detail with reference to the following examples, but these examples do not limit the present invention.

  The following materials were used as raw materials for the surface layer.

1) Resin raw material for surface layer formation The following polyurethane polyol and polyisocyanate were used as a resin raw material for surface layer formation.
Polyurethane polyol: “Nipporan N5033” (trade name), manufactured by Nippon Polyurethane Co., Ltd.
Polyisocyanate: “Coronate L” (trade name), manufactured by Nippon Polyurethane Co., Ltd.

2) Carbon black Table 1 shows the physical properties of carbon black blended with the raw material for forming the surface layer in Examples and Comparative Examples.

3) Crosslinked resin particles The crosslinked resin particles shown in Table 2 were used.

Production Example 1
"Production of roller with conductive rubber base layer"
An iron core with an outer diameter of 6 mm (conductive core) is placed concentrically in a cylindrical mold with an inner diameter of 12 mm, and a liquid conductive silicone rubber (manufactured by Toray Dow Corning Co., Ltd., with a volume resistivity of 107 Ωcm) Was cast in an oven at 140 ° C. for 5 minutes. After the molded product was removed from the mold, secondary curing was performed in an oven at 200 ° C. for 4 hours to obtain a roller having a conductive rubber base layer having a thickness of 3 mm and a length of 240 mm on a conductive cored bar.

Example 1
“Preparation of coating solution for surface layer: Solution A”
100 parts by mass of polyurethane polyol, 40 parts by mass of polyisocyanate and 23 parts by mass of carbon black (CB1) were added to methyl ethyl ketone so that the solid content concentration was about 35% by mass, and dispersed using a bead mill shown in FIG. A liquid was obtained. The glass beads having a diameter of 2 mm were placed in the vessel so that the filling rate was 80%, and the dispersion was completed while confirming the degree of dispersion using a grind gauge.

“Preparation of surface coating solution: B solution”
Methyl ethyl ketone was added to 65 parts by mass of polyurethane crosslinked resin particles (RP1) so as to have a solid content concentration of 30% by mass, and the mixture was stirred with a chemical stirrer at a speed of 50 rpm to obtain a resin particle slurry (liquid B).

"Mixing of liquid A and liquid B"
The solution B was added to the solution A obtained above with a chemical stirrer at a constant speed over 1000 seconds. Thereafter, the mixed solution was dispersed for 1 hour in a bead mill in which glass beads having a diameter of 2 mm were placed in a vessel so that the filling rate was 80%. Next, methyl ethyl ketone was added and mixed well, and the viscosity of the coating solution was adjusted to 10 mPa · s at a measurement temperature of 20 ± 1 ° C. Note that. For the viscosity measurement, a rotational viscometer “VISMETRON VDA” (trade name, manufactured by Shibaura System Co., Ltd.) was used. The test was performed at 1 rotor and a rotational speed of 60 rpm.

"Formation of surface layer"
The prepared coating liquid is charged into the coating tank, and held so that the center line of the cored bar is perpendicular to the liquid surface of the coating liquid. The created roller was lowered, dipped at a speed of 10 mm / s, lowered to the lowest point, and then stopped for 10 seconds. Thereafter, the roller was pulled up to form a coating layer on the outer peripheral surface of the elastic layer of the roller. The speed at the time of pulling was set to 300 mm / min immediately after the start of the pulling, and 200 mm / min when the lower end of the conductive elastic layer came out of the coating liquid surface. Thereafter, it was placed in an oven at 140 ° C. and heated and cured for 4 hours to form a surface layer to obtain a developing roller.

Example 2
A developing roller was obtained in the same manner as in Example 1 except that CB2 was used as the raw material carbon black.

Example 3
A developing roller was obtained in the same manner as in Example 1 except that CB3 was used as the raw material carbon black.

Example 4
A developing roller was obtained in the same manner as in Example 1 except that CB4 was used as the raw material carbon black.

Comparative Example 1
A developing roller was obtained in the same manner as in Example 1 except that CB5 was used as the raw material carbon black.

Comparative Example 2
A developing roller was obtained in the same manner as in Example 1 except that CB6 was used as the raw material carbon black.

Comparative Example 3
A developing roller was obtained in the same manner as in Example 1 except that granular CB7 was used as the raw material carbon black.

Comparative Example 4
In the production of the surface layer coating solution, the solution B was added to the solution A at a stretch. Other than that was carried out similarly to Example 1, and obtained the developing roller.

Comparative Example 5
A developing roller was obtained in the same manner as in Example 1 except that the addition speed of the B liquid was changed to 10 g / sec (so that the solid content of the B liquid was added to the A liquid at 3 g / sec).

Example 5
A developing roller was obtained in the same manner as in Example 1 except that acrylic crosslinked resin particles (RP2) were used as the raw material crosslinked resin particles.

Example 6
A developing roller was obtained in the same manner as in Example 1 except that acrylic crosslinked resin particles (RP3) were used as the raw material crosslinked resin particles.

Example 7
A developing roller was obtained in the same manner as in Example 1 except that polyurethane crosslinked resin particles (RP4) were used as the raw material crosslinked resin particles.

Comparative Example 6
A developing roller was obtained in the same manner as in Example 1, except that acrylic crosslinked resin particles (RP5) were used as the raw material crosslinked resin particles.

Comparative Example 7
A developing roller was obtained in the same manner as in Example 1 except that polyurethane crosslinked resin particles (RP6) were used as the crosslinked resin particles.

  About the developing roller obtained by the said Example and the comparative example, about the upper part of the roller at the time of raising of coating, the lower part, and the center part, surface roughness Ra of each three places of circumferential directions is surface roughness measuring instrument "Surf coder" Measured with “SE3500” (trade name). Further, the surface area ratio was measured with respect to the same position with an ultra-deep shape measuring microscope “VK-8510” (trade name). In addition, the upper part and the lower part centered on the position of 20 mm from each edge part. The obtained results are shown in Table 3.

The developing rollers obtained in the above examples and comparative examples were incorporated as developing rollers in the process cartridge of the electrophotographic laser beam printer, and solid images and halftone images were output and evaluated according to the following criteria. The results are shown in Table 3.
○: The image density is sufficiently dark and there is no density unevenness.
(Triangle | delta): Image density is inadequate or there exists a slight density nonuniformity, but it is practical. X: The image density is extremely thin or there is obvious density unevenness.

  The electrophotographic laser beam printer used in this evaluation is a machine for A4 size output, the output speed of the recording medium is A4 vertical 16 sheets / minute, and the image resolution is 600 dpi. The photosensitive member is a reversal developing type photosensitive drum in which an aluminum cylinder is coated with an OPC (organic photoconductor) layer, and the outermost layer is a charge transport layer using a modified polycarbonate as a binder resin. The toner image developed on the photoreceptor is transferred to a recording medium by a transfer roll and thermally fixed by a fixing unit. The toner that has not been transferred by the transfer roll is scraped off from the photoreceptor by a cleaning blade. The developing portion is formed into a cartridge, and a developing blade, which is a toner layer thickness regulating member, contacts the developer carrying roll in the counter direction to regulate the toner layer thickness.

  In addition, the initial 10 images (5 solid images and 5 halftone images) were output and judged according to the above criteria. Furthermore, about what was evaluation "(circle)", 10,000 standard charts which correspond to printing 20% were output by durability, and what was extracted for every 500 sheets was evaluated according to the above. The results are also shown in Table 3.

  The developing rollers of Examples 1 to 7 were able to produce developing rollers having a surface roughness Ra of 1.5 to 2.5 μm and a surface area ratio of 1.2 to 1.9. Also, good results were obtained in image evaluation.

  On the other hand, in Comparative Example 1, since carbon black having a high DBP absorption amount was used, the surface roughness Ra of the obtained developing roller was 1.4 to 1.5 μm, and the surface area ratio was 1.0 to 1. 1 compared with Examples 1 and 2. This is because the dispersion stability of the carbon black is poor due to the large DBP absorption amount of the carbon black, solvent shock occurs when the liquid B is added, the carbon black is re-agglomerated, and the thixotropy of the coating liquid is reduced. This is because the amount of polyurethane cross-linked resin particles held on the surface is reduced. Also, an image with sufficient density was not obtained in the image evaluation.

  In Comparative Example 2, since carbon black having a large primary particle diameter was used, the developing roller surface roughness Ra of the obtained developing roller was 1.6 to 1.7 μm, and the surface area ratio was 1.1 to 1.2. This is lower than in Examples 1 and 2. This is because the primary particle size of carbon black is large, so that the dispersion does not proceed sufficiently and the thixotropy of the coating liquid is reduced, so that the amount of crosslinked resin particles held on the roller surface is reduced. Also, an image with sufficient density was not obtained in the image evaluation.

  In Comparative Example 3, since carbon black having an alkaline pH was used, the developing roller surface roughness Ra of the obtained developing roller was 1.8 to 1.9 μm, and the surface area ratio was 1.1 to 1.2. Compared to Examples 1 and 2, it is lower. This is because the surface stability of the carbon black has changed, resulting in poor dispersion stability. When the B liquid is added, a solvent shock occurs, the carbon black re-aggregates, and the thixotropy of the coating liquid is reduced. This is because the amount of polyurethane resin particles held on the surface is reduced. Also in the image evaluation, slight unevenness was observed.

  In Comparative Example 4, since the B liquid was added to the A liquid at once, the surface roughness Ra of the developing roller of the obtained developing roller was 1.4 to 1.6 μm, and the surface area ratio was 1.1 to 1. 2 is lower than that of Examples 1 and 2. This is because the amount of polyurethane resin particles held on the roller surface is reduced because the carbon black is re-agglomerated by the solvent shock when the B solution is added and the thixotropy of the coating solution is reduced. Also, an image with sufficient density was not obtained in the image evaluation. Since the solvent shock occurred even when the addition time of the liquid B was 150 seconds, it was not used for forming the surface layer.

  In Comparative Example 5, since the addition speed of the B liquid with respect to the A liquid was 10 g / sec, the surface roughness Ra of the obtained developing roller was good at 1.8 to 1.9 μm, but the surface area ratio was 1.1 to 1.3, which is lower than that of Examples 1 and 2. This is because the addition speed of the liquid B is too fast and the influence of solvent shock appears, the carbon black is somewhat re-agglomerated, the thixotropy of the coating liquid is insufficient, and the polyurethane resin particles retained on the roller surface It is thought that the amount of Also in the image evaluation, slight unevenness was observed.

  In Comparative Example 6, since the particle diameter of the crosslinked resin particles was 2.4 μm, the surface roughness of the obtained developing roller was 1.3 to 1.4, and the surface area ratio was 1.0 to 1.2. Compared to Examples 1 and 2. This is because the roller surface could not be sufficiently roughened because the particle diameter of the crosslinked resin particles was small. Even in image evaluation, a sufficient density could not be obtained.

  In Comparative Example 7, since the particle diameter of the crosslinked resin particles is 35 μm, the surface roughness of the obtained developing roller is 2.6 to 2.7 and the surface area ratio is 2.1 to 2.4. Higher than 1 or higher. This is because the roller surface is greatly roughened because the particle diameter of the crosslinked resin particles is large. In the image evaluation, considerable density unevenness occurred.

It is the (a) perspective view and (b) sectional view of a conductive roller. It is a schematic diagram which shows the outline of a dispersing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive roller 2 Conductive core 3 Elastic body layer 4 Surface layer 5 Blade 6 Rotating shaft (disk)
7 Cylindrical container (vessel)
8 Tank 9 Pump 10, 11 Piping

Claims (3)

A conductive roller having a conductive rubber base layer on a conductive core metal and having a surface layer in which crosslinked resin particles are dispersed on the outermost surface,
The surface roughness Ra of the conductive roller is 1.5 to 2.5 μm, and
A conductive roller having a surface area ratio represented by the following formula (I) of 1.2 to 2.0.
Surface area ratio = S / S ₀ (I)
(In the formula, S is the measured surface area of the surface of the conductive roller, and S ₀ is the theoretical surface area when the surface of the conductive roller is an ideal plane.) The method for producing a conductive roller according to claim 1, comprising a conductive rubber base layer on a conductive metal core, and a surface layer in which crosslinked resin particles are dispersed on the outermost surface.
A method for producing a conductive roller, wherein the surface layer is formed by applying a surface layer coating solution prepared by the following steps to the conductive rubber base layer:
A step of dispersing 5 to 30% by mass of carbon black with respect to the resin for forming the surface layer in the resin material for forming the surface layer and the solvent mixture to obtain a liquid A;
A step of dispersing crosslinked resin particles having a particle diameter of 3 to 30 μm in a solvent at a concentration of 10 to 40% by mass to obtain a liquid B; and
In the liquid A being stirred, the addition rate is 1/200 or less of the B liquid amount per second, and the addition amount is 2 times or less in mass ratio (B / A) to the A liquid. Step of adding the B liquid.   Carbon black has a DBP absorption of 120 ml / 100 g or less, an average primary particle size of 0.03 μm or less, a pH of 8.0 or less, is powdery, and has a specific coloring power of carbon black. The method for producing a conductive roller according to claim 2, which is 90% to 150%.

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