JP2008058466A - Method for manufacturing electrifying roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably manufacturing an electrifying roller over a long period of time outputting a good image without an image failure even when used in an electrophotographic apparatus using only DC voltage for voltage applied to the electrifying roller. <P>SOLUTION: The method for manufacturing the electrifying roller is provided with; (1) a process for preparing a supporting body or a supporting body with one layer or more of coating layer, (2) a primary dispersion process adjusting primary dispersion liquid in which conductive particles are dispersed into solvent with a ratio of ≥70 to ≤800 mass parts for 100 mass parts of binding resin material (A), (3) a secondary dispersion process adjusting secondary dispersion liquid in which the conductive particles are dispersed with a ratio of 10 to 60 mass parts for total of 100 mass parts of the binding resin materials (A) and (B), and (4) a process forming a coating layer that becomes an outermost surface layer by coating the secondary dispersion liquid on the supporting body or on the coating layer provided on the supporting body and curing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a charging roller (conductive member) used in an image forming apparatus employing an electrophotographic system such as a printer, a facsimile machine, and a copying machine.

  An image forming apparatus employing an electrophotographic system, that is, an electrophotographic apparatus, generally includes an electrophotographic photosensitive member, a charging unit, an exposure unit, a developing unit, and a transfer unit. Among them, as the charging means, a method of charging the surface of the photoconductor by applying a voltage (a DC voltage or a voltage obtained by superimposing an AC voltage on a DC voltage) to a charging member placed in contact with or close to the surface of the electrophotographic photosensitive member. Many things are adopted.

  Here, as a voltage to be applied to the charging member (such as a charging roller), a method in which an AC voltage is superimposed on a DC voltage may increase the size and cost of the electrophotographic apparatus and increase the power consumption. In addition, the durability of the charging member and the electrophotographic photosensitive member may be reduced due to a large amount of ozone generated due to the use of alternating current. Therefore, from these viewpoints, it is preferable that the voltage applied to the charging member is only a DC voltage.

  However, when only the DC voltage is applied to the charging member, the above problem does not occur, but the charged potential on the surface of the charged object becomes uneven and minute streak-like image defects are likely to occur. In some cases, it was difficult to obtain uniform charging. Further, there has been a problem that the charging member is easily energized and deteriorated due to continuous use, and the resistance of the charging member is likely to increase (charge up), and the charged potential of the surface of the charged object is lowered accordingly.

Further, in an image forming apparatus using a contact-type charging method, there is a problem in that unevenness of image density or the like occurs due to charging failure due to contamination (developer surface adhesion) of a charging member.
As described above, in the charging method in which only the DC voltage is applied to the charging member, the influence of dirt on the charging member tends to appear as an image defect compared to the charging method in which the voltage in which the AC voltage is superimposed on the DC voltage is applied. It was.

In order to solve such a problem of the charging member in which the applied voltage is only a DC voltage, a technique for obtaining uniformity of charging property and resistance by using conductive particles has been proposed (Patent Literature). 1).
In addition, when manufacturing a charging member, there is a technology aimed at obtaining high dispersibility by increasing the dispersion share and efficiency of the material by increasing the number of dispersers and the number of processes used in the material dispersion process of the charging member. It has been proposed (see Patent Document 2).
Japanese Patent Laid-Open No. 06-250494 JP 2004-22158 A

  However, in the technique described in Patent Document 1, since the conductive particles having a small particle size have a large surface energy, the cohesive force between the particles is strong and a secondary aggregate such as a structure structure is often formed. . Accordingly, as a result, it is not easy to uniformly disperse the charging member material, and micro resistance unevenness is likely to occur, and it may be difficult to obtain resistance uniformity.

  In the technique described in Patent Document 2, when dispersion processing is performed with a strong share in order to obtain high dispersibility, the dispersion liquid (charging member material) is suddenly released from the share at the end of the dispersion process. It was. For this reason, repulsion of the material of the charging member is likely to occur due to this reaction, and there is a problem that, for example, the dispersion state of the conductive particles becomes unstable and the stability of the dispersion liquid is poor.

The present invention has been made in view of the situation as described above, and is a method for manufacturing a charging roller (conductive member) used in an electrophotographic apparatus in which a voltage applied to a charging member is only a direct current voltage. The present invention relates to a method of manufacturing a charging roller in which conductive particles are uniformly dispersed. In addition, the present invention provides a method for producing a charging roller that can easily disperse particles uniformly, does not cause microscopic resistance unevenness, and can provide resistance uniformity and hardly generate defective charging, thereby outputting a good image. The purpose is to provide.
Another object of the present invention is to provide a method for producing a charging roller in which the dispersion of conductive particles in the coating layer is stable for a long period of time.

The above problem can be solved by having the following configuration.
1. In a method for manufacturing a charging roller having a support and one or more coating layers on the support,
(1) preparing a support or a support having one or more coating layers;
(2) Primary in which conductive particles having a ratio of 70 parts by mass or more and 800 parts by mass or less are dispersed in 100 parts by mass of the binder resin material (A) in a solvent containing the binder resin material (A). A primary dispersion step of adjusting the dispersion;
(3) The binder resin material (B) and the solvent are added to the primary dispersion, and the conductive particles are 10 parts by mass or more and 60 parts by mass with respect to 100 parts by mass of the total amount of the binder resin materials (A) and (B). A secondary dispersion step of adjusting the secondary dispersion dispersed so as to have a ratio of less than or equal to parts by mass;
(4) A step of forming a coating layer serving as the outermost surface layer by applying a secondary dispersion on the support or a coating layer provided on the support and curing the coating.
A method of manufacturing a charging roller, comprising:

2. 2. The method for producing a charging roller according to 1 above, wherein the conductive particles are dispersed using a bead mill in at least one of the steps (2) and (3).
In addition, "the ratio of the conductive particles to 100 parts by mass of the binder resin material (A)" in the step (2) and "conductivity to 100 parts by mass of the total amount of the binder resin materials (A) and (B)" in the step (3). The “ratio of conductive particles” represents the ratio of conductive particles based on the amounts of the binder resin materials (A) and (B) converted into solid content, respectively.

  According to the manufacturing method of the present invention, even in a charging roller in which conductive particles are dispersed in a coating layer, the particles can be easily dispersed uniformly, and micro resistance unevenness does not occur. Can get. In addition, it is possible to provide a charging roller that is unlikely to cause charging failure and can output a good image without image defects. Furthermore, it is possible to provide a method for manufacturing a charging roller in which the dispersion of conductive particles in the material constituting the coating layer is stable for a long time.

1. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a method for manufacturing a charging roller having a support and a coating layer such as an elastic layer on the support in this order, and includes the following steps.
(1) A step of preparing a support or a support having one or more coating layers.
(2) Primary in which conductive particles having a ratio of 70 parts by mass or more and 800 parts by mass or less are dispersed in 100 parts by mass of the binder resin material (A) in a solvent containing the binder resin material (A). A primary dispersion step of adjusting the dispersion.
(3) The binder resin material (B) and the solvent are added to the primary dispersion, and the conductive particles are 10 parts by mass or more and 60 parts by mass with respect to 100 parts by mass of the total amount of the binder resin materials (A) and (B). A secondary dispersion step of adjusting a secondary dispersion dispersed so as to have a ratio of less than or equal to parts by mass.
(4) The process of forming the coating layer used as an outermost surface layer by apply | coating a secondary dispersion liquid on the said support body or the coating layer provided on the support body, and making it harden | cure.

  First, in step (1), a support or a support having one or more coating layers is prepared. As the support, a commercially available product may be purchased and used as it is, or a support may be prepared in advance according to the shape and size of the charging roller that is finally required. The support having one or more coating layers may be formed, for example, by adhering or coating a sheet-shaped or tube-shaped layer formed in advance to a predetermined film thickness, or by electrostatic spray coating. Alternatively, a coating method such as dipping coating may be used. Moreover, after forming a layer roughly by extrusion molding, the method of adjusting the shape of a layer by grinding | polishing etc. may be used, and the method of hardening and shaping | molding material to a predetermined shape within a type | mold may be used.

  Next, in step (2), a primary dispersion containing at least a solvent, a binder resin material (A), and conductive particles is prepared. At this time, the ratio of the conductive particles in the primary dispersion is 70 parts by mass or more and 800 parts by mass or less with respect to 100 parts by mass (in terms of solid content) of the binder resin material (A). Dispersed in the primary dispersion. When the ratio of the conductive particles is less than 70 parts by mass with respect to 100 parts by mass of the binder resin material (A), the total amount of the conductive particles is small, so the process (2) and the next process (3) are performed in two stages. It becomes impossible to disperse the conductive particles stably. On the other hand, when the ratio of the conductive particles exceeds 800 parts by mass with respect to 100 parts by mass of the binder resin material (A), the dispersibility of the conductive particles is deteriorated and excellent dispersibility is obtained even in the secondary dispersion step. Can not be. In addition, you may use a solvent and binder resin material (A) individually or in combination of multiple types, respectively.

  In the step (2), the ratio of the conductive particles to 100 parts by mass of the binder resin material (A) in the primary dispersion is preferably 100 parts by mass or more and 700 parts by mass or less, and 200 parts by mass or more and 650 parts by mass. More preferably, it is more preferably 300 parts by mass or more and 600 parts by mass or less. When the ratio of the conductive particles is within these ranges, the conductive particles can be dispersed with better dispersibility in the primary dispersion step.

  Thereafter, in step (3), the binder resin material (B) and a solvent are further added to the primary dispersion to adjust the secondary dispersion. In this secondary dispersion, the conductive particles are uniformly dispersed. At this time, the ratio of the conductive particles in the primary dispersion is 10 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass (solid content conversion) of the binder resin materials (A) and (B). Yes, the conductive particles are dispersed in the secondary dispersion. When the ratio of the conductive particles is less than 10 parts by mass with respect to 100 parts by mass of the total amount of the binder resin materials (A) and (B), the total amount of conductive particles is reduced, and the charging roller after manufacture is sufficient. It cannot be charged. On the other hand, when the ratio of the conductive particles exceeds 60 parts by mass with respect to 100 parts by mass of the total amount of the binder resin materials (A) and (B), stable and uniform dispersibility of the conductive particles in the secondary dispersion liquid. You will not be able to get.

  The ratio of the conductive particles to 100 parts by mass of the total amount of the binder resin materials (A) and (B) is preferably 15 parts by mass or more and 55 parts by mass or less, and preferably 20 parts by mass or more and 50 parts by mass or less. More preferably, it is more preferably 25 parts by mass or more and 45 parts by mass or less. When the ratio of the conductive particles is within these ranges, the conductive particles can be dispersed with better dispersibility in the secondary dispersion step.

  The solvent added to the primary dispersion in step (3) may be the same or different type of solvent contained in the primary dispersion in step (2). Do not use the one that impairs the function of the binder resin and solvent. The binder resin material (A) may be the same material as the binder resin material (B) or a different material. Preferably, at least a part of the binder resin material (B) is made of a material that reacts and cures with the binder resin material (A) in the subsequent step (4). For example, even if all of the binder resin material (B) is made of a material that reacts and cures with the binder resin material (A), a part of the binder resin material (B) is bound to the binder resin material (A ) And may be made of a material that cures.

  In the steps (2) and (3), conventionally known solution dispersing means such as a ball mill, a sand mill, a paint shaker, a dyno mill and a pearl mill can be used as a method for dispersing the conductive particles in the dispersion. In the present invention, among these dispersers, it is preferable to use a bead mill that can continuously perform the step of dispersing conductive particles, has an appropriate dispersion share, and can easily change the share.

  FIG. 5 shows an example of a bead mill used in the production method of the present invention. The bead mill container 21 has a supply port 22 for supplying a dispersion (primary dispersion, secondary dispersion) and a discharge port 23 for discharging the dispersion from which beads are separated after dispersion. A stirring blade 24 is provided inside the container, and the dispersion liquid 25 and the beads 26 are stirred and mixed to disperse the conductive particles in the dispersion liquid. The dispersion liquid and the beads are mixed in the container 21, but the dispersed liquid is separated by a bead separation screen (not shown) provided inside the mill and dispersed. Only the liquid passes through the inside of the screen and flows out from the discharge port 23. In this manner, the dispersion may be continuously dispersed while continuously circulating in the bead mill. Further, without providing the supply port 22 and the discharge port 23, a closed type bead mill may be used to perform dispersion mixing for a predetermined time in a batch manner. The outer wall of the bead mill container is provided with a cooling jacket (not shown) to which a refrigerant supply port and a discharge port are attached so that the bead mill container can be controlled to a predetermined temperature.

  The circulation type bead mill may be either a vertical type or a horizontal type, for example, Imex Visco Mill Series, Ashizawa Star Mill, System ZETA, Shinmaru Enterprises Dino Mill, Dries Velke DCP Pearl Mill, Mitsubishi Heavy Industries, Ltd. There are diamond fine mills and the like, but the above type of bead mill is not limited to these models.

  Thereafter, in step (4), the secondary dispersion is applied and cured on the support or the support having one or more coating layers to form a coating layer that becomes the outermost surface layer on the support. . As a coating method, electrostatic spray coating, dipping coating, or the like can be performed. Moreover, as for the curing conditions, preferable conditions (curing time and curing temperature) can be appropriately selected according to the type of the binder resin.

Here, the present inventor has clarified that the following effects can be obtained by using the production method of the present invention by intensive studies.
Generally, the dispersibility of conductive particles and functional particles used as a material constituting the charging roller greatly contributes to the uniformity of charging of the charging roller used in the image forming apparatus. When the dispersibility of the conductive particles is inferior, the uniformity of the resistance is not sufficient, and it becomes difficult to obtain the uniformity of charging. In addition, the dispersion state of the conductive particles and the contact state between the conductive particles also affect the deterioration due to energization. If the dispersibility of the conductive particles is poor, the deterioration of the energization tends to occur. For this reason, it is very important to improve the dispersibility of the conductive particles. If the dispersibility of the conductive particles is improved, it is considered that the resistance does not increase even when the charging roller is continuously used (continuous energization).

  In order to improve the dispersibility of the conductive particles in this way, it is preferable to disperse the particles until they become primary particles. However, since the conductive particles have a strong cohesive force between the particles, the particles have a strong share of a certain level or more. It is necessary to break strong aggregates formed between them. However, after the dispersion process is performed with a strong share, the dispersion liquid is suddenly released from the share when the dispersion process is terminated. Therefore, the reaction is likely to cause re-aggregation of the particles and the dispersion state of the conductive particles is unstable. It will become.

  Therefore, in the production method of the present invention, the ratio of the binder resin material and the solvent to the conductive particles is increased stepwise through the primary dispersion step and the secondary dispersion step, thereby being selective for the dispersion of the conductive particles. Can disperse dispersed energy. As a result, a dispersion liquid in which conductive particles are uniformly dispersed can be obtained. In addition, since the ratio of the conductive particles in the dispersion is high, the achieved uniform dispersed state of the conductive particles is maintained as it is once, and the conductive particles are conductive in the dispersion and in the coated layer after the dispersion process. Particles can exist in a stable dispersion state. As described above, according to the manufacturing method of the present invention, a conductive member excellent in charging stability / durability can be stably manufactured for a long period of time. For this reason, not only can the charging uniformity of the charging roller after manufacture be improved, but also resistance change can be suppressed, and when this charging member is used in an image forming apparatus, a very excellent image can be obtained. it can.

  For example, FIG. 1 shows an image forming apparatus using the conductive member of the present invention as a charging roller. When a voltage is applied to the charging roller, a discharge occurs in a minute space between the charging roller and the photoconductor, and the surface of the photoconductor is charged. The charging roller manufactured according to the present invention does not have a developing and independent cleaning means as shown in FIG. 1, and an image forming apparatus adopting a so-called cleaner-less system in which toner remaining on the photosensitive member after transfer is collected by the developing means. It is extremely effective for printing multiple sheets.

Next, a schematic configuration of the image forming apparatus of the present invention will be described.
2. Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus provided with a charging roller of the present invention. The image forming apparatus of this example is a reversal developing method using transfer type electrophotography, and a developing and cleaning method (cleanerless).

  Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member as an image carrier, which is driven to rotate at a predetermined peripheral speed (process speed) in the direction of an arrow. Reference numeral 2 denotes a charging roller as charging means for the electrophotographic photosensitive member, which is brought into contact with the electrophotographic photosensitive member 1 with a predetermined pressing force. Here, the electrophotographic photosensitive member to be brought into contact with the charging roller manufactured in the present invention is not particularly limited. In this example, the charging roller 2 is driven to rotate at the same speed as the electrophotographic photosensitive member 1.

  A predetermined DC voltage (in this case, -1180 V) is applied to the charging roller 2 from the charging bias application power source S1, so that the surface of the electrophotographic photosensitive member 1 has a predetermined polarity potential (dark part potential -400 V). ) Is uniformly charged by a contact charging method or a DC charging method.

  Reference numeral 3 denotes exposure means, for example, a laser beam scanner. The surface L of the electrophotographic photosensitive member is set to the potential of the exposure bright portion (bright portion potential −120 V) by performing exposure L corresponding to the target image information by the exposure unit 3 on the charging processing surface of the electrophotographic photosensitive member 1. ) Is selectively lowered (attenuated) to form an electrostatic latent image.

  Reference numeral 4 denotes a reversal developing unit, which selects a toner (negative toner) that is charged (development bias of −350 V) with the same polarity as the charging polarity of the electrophotographic photosensitive member in the exposed bright portion of the electrostatic latent image of the electrophotographic photosensitive member. The electrostatic latent image is visualized as a toner image. In the figure, 4a is a developing roller, 4b is a toner supply roller, and 4c is a toner layer thickness regulating member.

  Reference numeral 5 denotes a transfer roller as transfer means, which is brought into contact with the electrophotographic photosensitive member 1 with a predetermined pressing force to form a transfer portion, and the electrophotographic photosensitive member is rotated in the forward direction with the rotation of the electrophotographic photosensitive member. It rotates at the same peripheral speed as the peripheral speed. Further, a transfer voltage having a polarity opposite to the charging polarity of the toner is applied from the transfer bias applying power source S2. The transfer material P is fed at a predetermined control timing from a paper feed mechanism unit (not shown) to the transfer unit. The back surface of the fed transfer material P is charged to a polarity opposite to the charging polarity of the toner by the transfer roller 5 to which a transfer voltage is applied, so that the toner image on the electrophotographic photosensitive member 1 is transferred to the transfer material at the transfer portion. Electrostatic transfer to P.

  The transfer material that has received the transfer of the toner image at the transfer unit is separated from the electrophotographic photosensitive member, introduced into a toner image fixing unit (not shown), subjected to a toner image fixing process, and output as an image formed product. . In the case of the double-sided image formation mode or the multiple image formation mode, the image formed product is introduced into a recirculation conveyance mechanism (not shown) and reintroduced into the transfer unit.

  Residues on the electrophotographic photosensitive member such as transfer residual toner are charged to the same polarity as the charging polarity of the electrophotographic photosensitive member by the charging roller 2. Then, the transfer residual toner reaches the developing means 4 through the exposure portion, and is electrically collected in the developing device by the back contrast, thereby achieving development and cleaning (cleanerless).

  In this example, the electrophotographic photosensitive member 1, the charging roller 2, and the developing means 4 are integrally supported, and the process cartridge 6 is detachable from the main body of the image forming apparatus. At this time, the developing means 4 may be a separate body.

3. Charging roller (charging member)
An example of the charging roller manufactured by the manufacturing method of the present invention has a roller shape as shown in FIG. 2, and is composed of a support 2a and an elastic layer 2b integrally formed on the outer periphery thereof as a coating layer. In the case of this charging roller, the outermost coating layer is the elastic layer 2b, and this elastic layer 2b can be formed by the steps (2) to (4) of the present invention.

  Another structural example of the charging member of the present invention is shown in FIG. As shown in FIG. 3, the charging member may be a two-layer coating layer composed of an elastic layer 2b and a surface layer 2c (FIG. 3A), or from the elastic layer 2b, the resistance layer 2d, and the surface layer 2c. 3 layers (FIG. 3B) may be formed. Alternatively, the second resistance layer 2e may be provided between the resistance layer 2d and the surface layer 2c, and four or more layers may be formed on the support 2a (FIG. 3C). In the case of these charging rollers, the outermost coating layer is the surface layer 2c, and this surface layer 2c can be formed by the steps (2) to (4) of the present invention.

(Support)
The support 2a used in the present invention can be a round bar made of a metal material such as iron, copper, stainless steel, aluminum, and nickel. Furthermore, these metal surfaces may be plated for the purpose of providing rust prevention and scratch resistance, but it is necessary not to impair the conductivity.
· If the coating layer is composed of two or more layers <br/> less, the coating layer and the elastic layer 2b of the case composed of two or more layers, the configuration of the surface layer 2c (outermost surface layer).

(Elastic layer)
The elastic layer 2b has appropriate conductivity and elasticity in order to supply power to the electrophotographic photosensitive member as a member to be charged and to ensure good uniform adhesion to the electrophotographic photosensitive member 1. In order to ensure uniform adhesion between the charging roller 2 and the electrophotographic photosensitive member 1, the elastic layer 2b is preferably polished so that the central portion is thickest and narrows toward both ends, so-called crown shape. Since the charging roller 2 that is generally used is in contact with the electrophotographic photosensitive member 1 by applying a predetermined pressing force to both ends of the support 2a, the pressing force at the central portion is small and increases at both ends. Yes. For this reason, there is no problem as long as the straightness of the charging roller 1 is sufficient, but if it is not sufficient, density unevenness may occur in the images corresponding to the center and both ends. The crown shape is formed to prevent this.

  Specific elastic layer materials constituting the elastic layer 2b include, for example, natural rubber, ethylene propylene rubber (EPDM), styrene butadiene rubber (SBR), silicone rubber, urethane rubber, epichlorohydrin rubber, isoprene rubber (IR), butadiene rubber. Synthetic rubbers such as (BR), nitrile butadiene rubber (NBR) and chloroprene rubber (CR), as well as polyamide resins, polyurethane resins and silicone resins can be mentioned.

  In a charging roller that applies a direct current voltage only to charge the object to be charged, in order to achieve charging uniformity, in particular, a medium resistance polar rubber (for example, epichlorohydrin rubber, NBR, CR, urethane rubber, etc.) It is preferable to use a polyurethane resin as an elastic material. These polar rubbers and polyurethane resins are considered to have a slight conductivity due to moisture and impurities in the rubber and resin as carriers, and these conduction mechanisms are considered to be ionic conduction.

When the elastic layer is produced without adding conductive particles to the material of the elastic layer, the obtained charging roller has a high resistance value in a low temperature and low humidity environment (L / L). Specifically, there are some which become 10 ¹⁰ Ωcm or more. For this reason, a high voltage must be applied to the charging roller, which is not preferable in practice. Therefore, the conductivity is adjusted by appropriately adding the conductive particles having the above-described electronic conductive mechanism and the conductive particles having the ionic conductive mechanism so that the resistance value of the charging roller is less than 10 ¹⁰ Ωcm in the L / L environment. Need to do. In general, conductive particles having an ionic conduction mechanism have a small effect of reducing the resistance value, and the effect is particularly small in an L / L environment. Therefore, the resistance (conductivity) may be adjusted by adding conductive particles having an electronic conductive mechanism in addition to conductive particles having an ionic conductive mechanism.

This conductivity is a conductive agent having an electron conduction mechanism such as carbon black, graphite and a conductive metal oxide in an elastic layer material such as rubber, or a conductive agent having an ion conduction mechanism such as an alkali metal salt or a quaternary ammonium salt. It can control by adding suitably.
The elastic layer 2b may be a foam formed by foaming using these elastic materials.

(Surface layer)
Since the surface layer 2c constitutes the outermost surface of the charging roller and comes into contact with the photoreceptor to be charged, it is not preferable for the material configuration to contaminate the photoreceptor. Also, those having good surface releasability are preferable, and a binder resin can be used as a specific main material of the surface layer.

  As the binder resin for the surface layer 2c, fluorine resin, polyamide resin, acrylic resin, polyurethane resin, silicone resin, butyral resin, styrene-ethylene-butylene-olefin copolymer (SEBC), and olefin-ethylene-butylene-olefin copolymer A polymer (CEBC) etc. are mentioned. As the binder resin in the present invention, a fluororesin, an acrylic resin, a silicone resin and the like are particularly preferable. These resins can be used alone or in combination of two or more.

  As the binder resin material (A) in the primary dispersion step and the binder resin material (B) in the secondary dispersion step, the above-mentioned resins can be used. For example, as the two-component urethane resin, the main agent When a surface layer is formed by reacting (polyol) with a curing agent (isocyanate), the binder resin material (A) contains a main agent and the binder resin material (B) contains a curing agent in order to suppress the reaction during dispersion. It is particularly preferable to use it.

  For the purpose of reducing the static friction coefficient to these binder resins, solid lubricants such as graphite, mica, molybdenum disulfide and fluororesin powder, or fluorosurfactants, wax, silicone oil, etc. may be added. Good.

  Various conductive particles can be used for the surface layer 2c. Examples of the conductive particles include metal oxide conductive particles, metal conductive particles, carbon black, and carbon conductive particles.

Examples of the metal oxide conductive particles include zinc oxide, tin oxide, indium oxide, titanium oxide (titanium dioxide, titanium monoxide, etc.), iron oxide, aluminum oxide, and the like.
Some metal oxide-based conductive particles exhibit sufficient conductivity by themselves. In order to make the conductivity of the particles sufficient, a dopant may be added to these particles. In general, it is considered that surplus electrons are generated due to the presence of metal oxide lattice defects to exhibit conductivity, and formation of lattice defects is promoted by addition of a dopant, and sufficient conductivity can be obtained. For example, aluminum is used as a dopant for zinc oxide, antimony is used as a dopant for tin oxide, and tin is used as a dopant for indium oxide. Moreover, when obtaining the electroconductivity of titanium oxide, what coated electroconductive tin oxide on titanium oxide etc. can be mentioned.

Furthermore, what coated the carbon black on the silica etc. are mentioned. Examples of carbon black include acetylene black, furnace black, and channel black. Examples of the carbon conductive particles include graphite, carbon fiber, activated carbon, charcoal and the like.
Examples of the metal conductive particles include silver, copper, nickel, and zinc.
In the present invention, in order to obtain a desired electric resistance, the above various conductive particles may be used alone or in combination of two or more.

  The average particle size of the conductive particles is preferably 1.0 μm or less. If the average particle diameter exceeds 1.0 μm, pinhole leakage may easily occur when pinholes exist on the photosensitive drum, which is not preferable. Further, when the specific gravity of the conductive particles is heavy, if the average particle diameter exceeds 1.0 μm, the dispersion stability of the dispersion liquid may be deteriorated, and it is not preferable because it tends to settle in the dispersion liquid.

These conductive particles may be subjected to surface treatment, modification, introduction of functional groups, coating, and the like. The resistance value of the surface layer is preferably 10 ⁴ to 10 ¹⁵ Ωcm. Moreover, it is preferable that thickness is 1-500 micrometers. In particular, the thickness is preferably 1 to 50 μm.

-When a coating layer consists of one layer The description about the said elastic layer and surface layer is description when a coating layer consists of two or more layers. When the coating layer is composed of one layer, the elastic layer is the outermost surface layer, so that the structure of the elastic layer is the structure of the surface layer.

  When dispersing the conductive particles, various dispersants can be added in order to obtain more uniform and stable dispersion. There are no particular limitations on the type of dispersant used, and not only one type but also several types of dispersants can be used in combination. In particular, it is preferable to use a dispersant in the primary dispersion step because the dispersion uniformity and stability of the conductive particles can be more easily obtained.

  The solvent used in the primary dispersion and the secondary dispersion may be any solvent that can dissolve the binder material. Examples of the solvent include alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and dimethyl sulfoxide. Sulfoxides, ethers such as tetrahydrofuran, dioxane and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, and aliphatic halogenated carbonization such as chloroform, ethylene chloride, dichloroethylene, carbon tetrachloride and trichloroethylene Examples thereof include hydrogen and aromatic compounds such as benzene, toluene, xylene, ligroin, chlorobenzene, and dichlorobenzene.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Example 1)
A charging roller as a charging member was manufactured by the manufacturing method of the present invention in the following manner.

(Formation of elastic layer)
Epichlorohydrin rubber (Epichromer CG102, manufactured by Daiso Corporation) 100 parts by mass Quaternary ammonium salt (Adekasizer LV70, manufactured by Asahi Denka Kogyo Co., Ltd.) 2 parts by mass Calcium carbonate (Nanox # 30, manufactured by Maruo Calcium Co., Ltd.) 90 parts by mass Zinc oxide (Huxitec Co., Ltd.) Product: 2 types of zinc oxide) 5 parts by mass of zinc stearate (Zinc stearate manufactured by Nippon Oil & Fats Co., Ltd.) 1 part by mass of carbon black (Chiest G-SO manufactured by Tokai Carbon Co.)

  The above materials were kneaded for 10 minutes in a closed mixer adjusted to 60 ° C. Thereafter, 15 parts by mass of a plasticizer (Dai Nippon Ink Co., Ltd., Polycizer P202) was added to 100 parts by mass of epichlorohydrin rubber, and the mixture was further kneaded for 20 minutes with a closed mixer cooled to 20 ° C. to prepare a raw material compound. In this compound, 100 parts by mass of raw material epichlorohydrin rubber, 1.2 parts by mass of sulfur as a vulcanizing agent (Sulfax PMC, manufactured by Tsurumi Chemical Co., Ltd.), dibenzothiazyl sulfide (Ouchi Shinsei Chemical) as a vulcanization accelerator 1 part by mass of Noxeller DM) and 1 part by mass of tetramethylthiuram monosulfide (Noxeller TS manufactured by Ouchi Shinsei Chemical Co., Ltd.) were added. Then, it knead | mixed for 10 minutes with the 2-roll machine cooled to 20 degreeC. The obtained compound is molded by an extrusion molding machine so as to form a roller around a φ6 mm stainless steel support, heated and steam vulcanized, and then polished to an outer diameter of φ8.5 mm. Got. The roller length was 230 mm.

(Adjustment of surface layer material (coating layer material))
Then, the material shown below was stirred using the mixer and the mixed solution was produced.
Acrylic polyol solution (PLACCEL DC2016, solid content: 70 wt%, manufactured by Daicel Chemical Industries, Ltd.) (binder resin material (A)) 143 parts by mass (solid content equivalent: 100 parts by mass)
Carbon black (MA-100 manufactured by Mitsubishi Chemical Corporation) (conductive particles) 70 parts by mass Methyl isobutyl ketone (solvent) 239 parts by mass.

  Next, this mixed solution was disk-disclosed using a bead mill disperser (Ultra Visco Mill manufactured by IMEX Co., Ltd.) filled with glass beads having an average particle diameter of 0.8 mm as a medium at a filling rate of 80% with respect to the volume of the container. Circulation operation was performed at a peripheral speed of 10 m / s and a processing speed of 200 ml / min for 6 hours, and dispersion treatment was performed to prepare a primary dispersion (primary dispersion step).

Next, 452 parts by mass of the above dispersion and the following materials were stirred using a mixer to prepare a mixed solution.
Isocyanate A (IPDI) (manufactured by Degussa VESTANAT B1370, solid content: 60 wt%) (binder resin material (B)) 32 parts by mass (solid content equivalent 19 parts by mass)
Isocyanate B (HDI) (Duranate TPA-B80E manufactured by Asahi Kasei Chemicals Corporation, solid content: 80 wt%) (binder resin material (B)) 48 parts by mass (solid content equivalent: 38 parts by mass)
PMMA particles (MBX-8 manufactured by Sekisui Plastics Co., Ltd.) 30 parts by mass modified dimethyl silicone oil (SH28PA manufactured by Toray Dow Corning Silicone)
0.5 part by mass Methyl isobutyl ketone (solvent) 243 parts by mass.

Next, the mixed solution was mixed with a bead mill disperser (Ultra Visco Mill manufactured by IMEX Co., Ltd.) filled with glass beads having an average particle diameter of 0.8 mm as a medium at a filling rate of 80% with respect to the volume of the container. A circulation operation was performed for 2 hours at a speed of 6 m / s and a processing speed of 600 ml / min, and dispersion treatment was performed to prepare a secondary dispersion (secondary dispersion step).
This secondary dispersion was applied on the elastic layer by dipping and cured by heating at 160 ° C. for 60 minutes to form a surface layer having a film thickness of 15 μm to obtain a roller-shaped charging roller. .

“Evaluation of stability of dipping coating solution over time (viscosity measurement)”
The viscosity of the coating solution for dipping (secondary dispersion) produced by this method was measured on the first day of production and 7 days after production. The viscosity was measured at 60 rpm with a No. 1 rotor using a Bismetron viscometer (VDA-L type) manufactured by Shibaura System. The results are shown in Table 1.

"Evaluation of image when only DC voltage is applied to charging roller"
In the L / L environment (temperature 15 ° C./humidity 10%), the halftone in the L / L environment (temperature 15 ° C./humidity 10%) is mounted on the electrophotographic image forming apparatus (LASER SHOT LBP-2510 manufactured by Canon Inc.) shown in FIG. An image was output. The applied voltage (only DC voltage) was adjusted so that the surface potential (dark portion potential) VD of the electrophotographic photosensitive member charged by the charging roller was around −400V. About the halftone image obtained in this way, the output image was visually evaluated. The results are shown in Table 1. In addition,
A is a very good image. B is a good image. C is a slight streak-like defect in a halftone image. D is a noticeable image defect of a streak.

"Measurement of roller resistance of charging roller"
Further, before starting the image evaluation, the roller resistance of the charging roller was measured by the method shown in FIG. In the figure, 2 is a charging roller, 11 is a cylindrical electrode made of stainless steel, 12 is a resistor, and 13 is a recorder. The pressing force between them is the same as that of the image forming apparatus used (9.8 N / m ² ), and the resistance value when -200 V is applied from the external power source S3 is measured. The results are shown in Table 1.

  Each of the above evaluations (viscosity measurement, image evaluation, roller resistance measurement) was carried out on the charging roller produced using the dipping coating solution on the first day of production and 7 days after production.

(Example 2)
In the primary dispersion step, a primary dispersion was prepared in the same manner as in Example 1 except that 7 parts by weight of a dispersant (CEFKA4050 manufactured by Fuka Additives Co., Ltd.) was newly used as a material. In addition, the material for the secondary dispersion described in Example 1 was added to 459 parts by mass of the primary dispersion. Each evaluation was performed in the same manner as in Example 1 for this charging roller. The results are shown in Table 1.

(Example 3)
Example 1 except that in the primary dispersion step, the material carbon black (MA-100 manufactured by Mitsubishi Chemical Corporation: conductive particles) was 400 parts by mass and the dispersant (EFKA 4050 manufactured by Fuka Additives) was 40 parts by mass. The primary dispersion was prepared in the same manner as described above. Further, a charging roller was produced in the same manner as in Example 2 except that 144 parts by mass of the primary dispersion and the following materials were used to adjust the secondary dispersion.
Acrylic polyol solution (PLACCEL DC2016, solid content: 70 wt%, manufactured by Daicel Chemical Industries, Ltd.) (Binder resin material (B)) 118 parts by mass (solid content equivalent 83 parts by mass)
Isocyanate A (IPDI) (manufactured by Degussa VESTANAT B1370, solid content: 60 wt%) (binder resin material (B)) 32 parts by mass (solid content equivalent 19 parts by mass)
Isocyanate B (HDI) (Duranate TPA-B80E manufactured by Asahi Kasei Chemicals Corporation, solid content: 80 wt%) (binder resin material (B)) 48 parts by mass (solid content equivalent: 38 parts by mass)
PMMA particles (MBX-8 manufactured by Sekisui Plastics Co., Ltd.) 30 parts by mass modified dimethyl silicone oil (SH28PA manufactured by Toray Dow Corning Silicone)
0.5 parts by mass Methyl isobutyl ketone (solvent) 243 parts by mass This charging roller was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
In the primary dispersion step, the same procedure as in Example 1 was conducted except that the material carbon black (manufactured by Mitsubishi Chemical Corporation, MA-100) was 800 parts by mass, and the dispersant (EFKA 4050, EFKA Additives Co., Ltd.) was 80 parts by mass. A primary dispersion was prepared. Further, a charging roller was produced in the same manner as in Example 2 except that the secondary dispersion was adjusted using 110 parts by mass of the primary dispersion and the following materials.
Acrylic polyol solution (PLACEEL DC2016, manufactured by Daicel Chemical Industries, Ltd.) (Binder resin material (B)) 130 parts by mass isocyanate A (IPDI) (VESTANAT B1370, solid content: 60 wt% manufactured by Degussa) (Binder resin material (B)) 32 parts by mass (solid content equivalent 19 parts by mass)
Isocyanate B (HDI) (Duranate TPA-B80E manufactured by Asahi Kasei Chemicals Corporation, solid content: 80 wt%) (binder resin material (B)) 48 parts by mass (solid content equivalent: 38 parts by mass)
PMMA particles (MBX-8 manufactured by Sekisui Plastics Co., Ltd.) 30 parts by mass modified dimethyl silicone oil (SH28PA manufactured by Toray Dow Corning Silicone)
0.5 parts by mass Methyl isobutyl ketone (solvent) 243 parts by mass This charging roller was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
Subsequently, the materials shown below were stirred using a mixer to prepare a mixed solution.
Acrylic polyol solution (PLACCEL DC2016, solid content: 70 wt%, manufactured by Daicel Chemical Industries, Ltd.) (binder resin material (A)) 143 parts by mass (solid content equivalent: 100 parts by mass)
Carbon black (MA-100 manufactured by Mitsubishi Chemical Corporation) (conductive particles) 70 parts by mass Isocyanate A (IPDI) (VESTANAT B1370 manufactured by Degussa, solid content: 60 wt%) (Binder resin material (A)) 32 parts by mass ( Solid content equivalent 19 parts by mass)
Isocyanate B (HDI) (manufactured by Asahi Kasei Chemicals Corporation DURANATE TPA-B80E, solid content: 80 wt%) (binder resin material (A)) 48 parts by mass (solid content equivalent 38 parts by mass)
PMMA particles (MBX-8 manufactured by Sekisui Plastics Co., Ltd.) 30 parts by mass modified dimethyl silicone oil (SH28PA manufactured by Toray Dow Corning Silicone)
0.5 part by mass Methyl isobutyl ketone (solvent) 239 parts by mass.

  Next, the mixed solution was mixed with a bead mill disperser (Ultra Visco Mill manufactured by IMEX Co., Ltd.) filled with glass beads having an average particle diameter of 0.8 mm as a medium at a filling rate of 80% with respect to the volume of the container. A circulation operation was performed for 6 hours at a speed of 10 m / s and a processing speed of 200 ml / min to carry out a dispersion treatment.

Next, 532.5 parts by mass of the above dispersion and the following materials were stirred using a mixer to prepare a mixed solution.
PMMA particles (MBX-8 manufactured by Sekisui Plastics Co., Ltd.) 30 parts by mass Methyl isobutyl ketone (solvent) 243 parts by mass.

  Next, the mixed solution was mixed with a bead mill disperser (Ultra Visco Mill manufactured by IMEX Co., Ltd.) filled with glass beads having an average particle diameter of 0.8 mm as a medium at a filling rate of 80% with respect to the volume of the container. A circulation operation was performed for 2 hours at a speed of 6 m / s and a processing speed of 600 ml / min to carry out dispersion processing. This dispersion solution was applied on a support by a dipping method and cured by heating at 160 ° C. for 60 minutes, and an elastic layer having a film thickness of 15 μm was formed to obtain a charging roller. The charging roller was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
In the primary dispersion step, the material carbon black (MA-100 manufactured by Mitsubishi Chemical Corporation) is 60 parts by mass, and in the secondary dispersion step, the secondary dispersion is added to 442 parts by mass of the primary dispersion. A charging roller was produced in the same manner as in Example 1 except that 10 parts by mass of black was added. The charging roller was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
In the primary dispersion step, the material carbon black (MA-100 manufactured by Mitsubishi Chemical Corporation) is 900 parts by mass, the dispersant is 90 parts by mass, the primary dispersion is 107 parts by mass, and the secondary dispersion step is performed using the following materials. A charging roller was produced in the same manner as in Example 2 except that the above was performed.
Acrylic polyol solution (PLACCEL DC2016, solid content: 70 wt%, manufactured by Daicel Chemical Industries, Ltd.) (Binder resin material (B)) 132 parts by mass (solid content equivalent: 92 parts by mass)
Isocyanate A (IPDI) (manufactured by Degussa VESTANAT B1370, solid content: 60 wt%) (binder resin material (B)) 32 parts by mass (solid content equivalent 19 parts by mass)
Isocyanate B (HDI) (Duranate TPA-B80E manufactured by Asahi Kasei Chemicals Corporation, solid content: 80 wt%) (binder resin material (B)) 48 parts by mass (solid content equivalent: 38 parts by mass)
PMMA particles (MBX-8 manufactured by Sekisui Plastics Co., Ltd.) 30 parts by mass modified dimethyl silicone oil (SH28PA manufactured by Toray Dow Corning Silicone)
0.5 parts by mass Methyl isobutyl ketone (solvent) 243 parts by mass The charging roller was evaluated in the same manner as in Example 2, and the results are shown in Table 1.

  From the results of the Examples, it can be seen that the viscosity of the secondary dispersion is low both on the first day of production and after 7 days of the charging roller by using the production method of the present invention. Further, it can be seen that the charging roller has an appropriate roller resistance, and in most cases, the image evaluation on the first day and after the seventh day is “A”.

1 is a schematic configuration diagram of an image forming apparatus including a charging roller manufactured by a manufacturing method of the present invention. It is the schematic showing an example of the charging roller manufactured with the manufacturing method of this invention. It is the schematic showing another example of the charging roller manufactured with the manufacturing method of this invention. It is the schematic showing the resistance measuring apparatus of a charging roller. It is the schematic showing an example of the bead mill used with the manufacturing method of this invention.

Explanation of symbols

1: Image carrier (electrophotographic photosensitive member)
2: Charging member (charging roller)
3: Image exposure means 4: Development means 5: Transfer means (transfer roller)
6: Cleaning means S1, S2, S3: Bias application power supply P: Transfer material 11: Cylindrical electrode (metal roller)
12: Fixed resistor 13: Recorder

Claims (2)

In a method for manufacturing a charging roller having a support and one or more coating layers on the support,
(1) preparing a support or a support having one or more coating layers;
(2) Primary in which conductive particles having a ratio of 70 parts by mass or more and 800 parts by mass or less are dispersed in 100 parts by mass of the binder resin material (A) in a solvent containing the binder resin material (A). A primary dispersion step of adjusting the dispersion;
(3) The binder resin material (B) and the solvent are added to the primary dispersion, and the conductive particles are 10 parts by mass or more and 60 parts by mass with respect to 100 parts by mass of the total amount of the binder resin materials (A) and (B). A secondary dispersion step of adjusting the secondary dispersion dispersed so as to have a ratio of less than or equal to parts by mass;
(4) A step of forming a coating layer serving as the outermost surface layer by applying a secondary dispersion on the support or a coating layer provided on the support and curing the coating.
A method of manufacturing a charging roller, comprising:   The method for manufacturing a charging roller according to claim 1, wherein the conductive particles are dispersed using a bead mill in at least one of the steps (2) and (3).

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