JP2013120361A - Charging member, and method for manufacturing charging member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily provide a charging member in which a discharging surface of the charging member does not deteriorate even if it is used for a long period of time, and which maintains stable charging properties.SOLUTION: In a charging member, a conductive support, and a conductive base layer 2 provided on the outer periphery of the conductive support are included, and the conductive base layer 2 has, on its surface, insulating projections 3 derived from particles. In the stepped portions between the insulating projections 3 and the conductive base layer 2, non-adhesive fine powder 4 is held, and the fine powder 4 has its number average particle diameter smaller than that of the particles.

Description

  The present invention relates to a charging member and a manufacturing method thereof.

The charging member used in electrophotography may gradually change its electric resistance by applying a direct current over a long period of time. Further, since the surface of the charging member is exposed to the discharge itself or ozone or nitrogen oxide generated along with the discharge, the surface state thereof changes with time. When the surface state changes with time, horizontal streaky charging unevenness or the like occurs in the electrophotographic image.
Patent Document 1 discloses that a powder is applied to the surface of the charging member in order to improve the charging of the charging member. Patent Document 2 discloses a method of fixing a protrusion made of powder on the surface of a charging member.

Japanese Patent Laid-Open No. 03-103878 JP 04-116673 A

  However, the method of Patent Document 1 still has room for improvement in order to suppress the temporal change in the surface state of the charging member. That is, the charging member according to Patent Document 1 has a small amount of powder that can be held on the surface itself, and also has a small powder holding force. For this reason, changes in the surface state of the charging member could not be sufficiently suppressed due to long-term use.

  Further, in the configuration in which the powder described in Patent Document 2 is only fixed on the surface of the charging member, only one layer of powder can be fixed on the surface of the charging member. Therefore, it has been difficult for the surface of the charging member to hold a sufficient amount of powder on the surface to suppress changes in the surface state even when exposed to discharge or discharge products.

  There are also known charging members in which convex portions are formed on the surface layer by roughening particles, but it is not possible to hold a large amount of fine powder with such convex portions, and the convex tip is also a conductive surface layer. It acts as an initial discharge surface. Therefore, even if fine powder is held, if it has been used for a long period of time, the discharge product may adhere to the convex tip that is the discharge point, and the charging characteristics may change.

In the prior art, there has not been known a configuration aiming at stable durability by sufficiently holding fine powder in a gap between protrusions firmly fixed on the surface of the charging member.
An object of the present invention is to provide a charging member that hardly changes the surface state of the charging member even after long-term use and maintains stable charging performance, and a method for manufacturing the charging member.

According to the present invention, it has a conductive support and a conductive base layer provided on the outer periphery of the conductive support, and the conductive base layer has insulating protrusions derived from particles on its surface. A non-adhesive fine powder is held at a step portion between the insulating protrusion and the surface of the conductive base layer, and the fine powder has a number average particle size. A charging member smaller than the number average particle diameter of the particles is provided.
According to the present invention, the step of dispersing the particles in a curable liquid to form a coating liquid;
Applying the coating solution to the conductive base layer;
Impregnating the conductive base layer with the applied coating liquid;
Curing the impregnated curable liquid to fix the particles to the conductive base layer to create protrusions;
There is provided a method for producing a charging member, comprising a step of holding non-adhesive fine powder having a number average particle size smaller than the number average particle size of the particles at a step portion between the protrusion and the surface of the conductive base layer. The

  According to the present invention, it is possible to obtain a charging member in which the surface state hardly changes even after long-term use, and stable charging performance is maintained.

The schematic showing the cross section of one Embodiment of the charging member of this invention is shown. (A) shows a transverse section of the charging member, and (b) shows a longitudinal section of the charging member. 1 is a schematic view of an image forming apparatus according to the present invention. 1 is a schematic view of a color image forming apparatus according to the present invention. The schematic explanatory drawing of the measuring method of charging member electric resistance concerning the present invention is shown. The schematic explanatory drawing of the charging member surface which concerns on this invention is shown. The schematic diagram of the coating apparatus used for formation of protrusion on the charging member according to the present invention is shown. The schematic explanatory drawing of operation | movement of the coating apparatus in the coating process of the charging member which concerns on this invention is shown. The schematic explanatory drawing of the bearing part of the charging member coating apparatus which concerns on this invention is shown. 1 is a schematic cross-sectional view of a charging member including a coated coating film according to the present invention. The schematic of the base layer surface before making the charging member which concerns on this invention hold | maintain a fine powder is shown.

<Charging member>
Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 shows a schematic view of the charging member of the present invention. FIG. 1A shows a schematic cross-sectional view of the charging member of the present invention, and FIG. 1B shows a schematic cross-sectional view of the charging member of the present invention. The charging member of the present invention has a conductive base layer 2 on the outer periphery of a conductive support 1, and has insulating protrusions 3 derived from particles on the surface of the conductive base layer 2. Further, non-adhesive fine powder 4 having a number average particle size smaller than the number average particle size of the particles is held at the step portion between the protrusion 3 and the surface of the conductive base layer 2.

FIG. 5 shows an enlarged view of the vicinity of the surface of the charging member of the present invention. 5A is a schematic enlarged view of the vicinity of the surface of the charging member of the present invention as viewed from the vertical direction, and FIG. 5B is a schematic enlarged view of a cross section of the vicinity of the surface of the charging member of the present invention. It is.
Protrusions 3 are randomly fixed on the surface of the conductive base layer 2, and fine powder 4 is held in a gap formed by the protrusions 3 and the conductive base layer 2. With respect to the electrophotographic photosensitive member, a discharge is generated from the surface of the conductive base layer 2, and the charge moves through the gaps in the fine powder 4 to the photosensitive member to charge the photosensitive member.

The charging member of the present invention includes a conductive support, a conductive base layer provided on the outer periphery of the conductive support, a protrusion fixed on the surface of the conductive base layer, and a protrusion and the surface of the conductive base layer. It consists of fine powder held at the step.
Hereinafter, a member formed of a conductive support and a conductive base layer before fixing the protrusions is referred to as a “conductive base layer member”. Further, a member in which the protrusion is fixed to the conductive base layer member and fine powder is not held is simply referred to as “base layer”.

<Protrusions>
The protrusions are present at a predetermined density on the surface of the conductive base layer so as to keep a constant distance between the photoreceptor and the surface of the conductive base layer.
The shape of the protrusion is more preferably spherical. When it is spherical, it is possible to increase the area of both the surface of the photoconductor, which is the surface to be charged, and the surface of the conductive base layer, which is the discharge surface, when contacting the photoconductor. Is possible. That is, since the contact area to the photoconductor and the fixed area to the conductive base layer are small compared to the same size cylinder or cuboid protrusion, the area not charged is preferable. The spherical protrusion is preferable because it can be formed by a simple manufacturing method even on the surface on which the protrusion is manufactured. That is, if the protrusions are manufactured using spherical particles, the spherical particle diameter, the height of the protrusions, the width of the protrusions, and the distance between the photoreceptor and the surface of the conductive base layer can be easily controlled.

  The distance between the photoreceptor and the surface of the conductive base layer is preferably 2 μm or more and 100 μm or less, more preferably 3 μm or more and 30 μm or less. Therefore, the average height of the protrusions is also preferably 2 μm or more and 100 μm or less, and particularly preferably 3 μm or more and 30 μm or less. When the height 3a of the protrusion shown in FIG. 10B is 2 μm or more and 100 μm or less, the distance between the photoreceptor and the surface of the conductive base layer becomes a stable region against discharge, and a uniform charged state by good discharge Is preferable. Moreover, since it becomes easy to hold | maintain non-adhesive fine powder as height is 2 micrometers or more and 100 micrometers or less, there exists an effect which prevents dissipation of fine powder. When the average height of the protrusions is 2 μm or more, the holding power of the fine powder is not lowered, and the fine powder is not scattered by continuous use. When the height of the protrusion is 100 μm or less, the discharge start voltage required for charging does not increase, and charging does not become difficult.

  The width 3b of the protrusion is also preferably 2 μm or more and 100 μm or less which is the same as the height of the protrusion. If the width 3b of the protrusion is 2 μm or more and 100 μm or less which is the same as the height 3a of the protrusion, the discharge will not be disturbed to cause unevenness, and the contact pressure between the charging member and the photosensitive member will be sufficiently supported and not damaged. This is preferable because non-adhesive fine powder is retained. When the width of the protrusion is 100 μm or less, the protrusion portion is not charged and does not appear as uneven charging on the image. On the other hand, when the width of the protrusion is 2 μm or more, the protrusion becomes too sharp and there is no fear that the photoconductor will be damaged and scraped, or that the strength of the protrusion itself becomes too small and the protrusion may be damaged and removed. .

  The ratio of the area covered by the protrusions to the surface area of the base layer (hereinafter also referred to as “protrusion density”) is preferably 0.03 times or more and 0.9 times or less, and particularly preferably 0.06 times or more and 0.6 times or less. . If the projection density is within this range, fine powder can be held for a long time while performing stable discharge. When the protrusion density is 0.03 times or more, the holding power of the fine powder is lowered, and the fine powder is not scattered by continuous use. When the protrusion density is 0.9 times or less, the surface area that can be discharged is reduced, and the charging ability is not lowered. The protrusion density (area ratio) indicates the area occupied by the protrusions 3 with respect to the total area of the base layer in the image observed from the direction perpendicular to the surface of the base layer as shown in FIG.

  The arrangement of the protrusions may be regular or irregular in positional relation on the surface of the conductive base layer, but is preferably irregular to the extent that there is no local protrusion. That is, a distribution in which the distance between the protrusions is a natural distribution is preferable. If the arrangement of the protrusions is regular, there is a possibility that a pattern resulting from the protrusions may remain in the charging of the photosensitive member, which is not preferable. The method for forming the protrusions is not particularly problematic as long as the protrusions are distributed irregularly on the surface of the conductive base layer. Preferably, a method of fixing particles for a spherical projection material on the surface of the conductive base layer is preferable. At that time, a formation method is preferred in which the particles are overlapped so as not to generate protrusions twice the diameter of the particles.

  As a method for forming such protrusions, there is a method in which spherical particles are attached to a conductive base layer coated with an adhesive, and then the attached particles are fixed. More preferably, the conductive base layer is coated with a coating liquid in which particles are dispersed in a curable liquid, and then the curable liquid is sufficiently impregnated in the conductive base layer. In this method, the particles are fixed to the conductive base layer by curing. By using this method, there is no fear that the protrusions overlap each other in two steps to make a protrusion having a height higher than the surroundings, and the protrusions of random arrangement can be uniformly formed by a simple method.

Measuring method of protrusion size (height, width)
1) Air blow the surface of the charging member to remove fine powder.
2) Take an image of the protrusion with Hitachi FE-SEM (S-4800). The protrusions image the surface of the charging member in a direction perpendicular to the surface of the conductive base layer and a tilt angle of 50 to 70 ° from the surface.
3) For each photograph, for the 10 randomly selected protrusions, the maximum and minimum diameters on the image are measured, and the average value is taken as the diameter.
(The image is introduced into an image processing apparatus (for example, an image analysis apparatus “Luzex III” manufactured by Nireco) and analyzed).
4) Average the diameter of 10 pieces to obtain the particle size of the protrusion.
If the particle size of the protrusion obtained from the image photographed in the vertical direction and the particle diameter of the protrusion obtained from the image photographed with a tilt angle are not the same, it is determined that the protrusion is not spherical, and the vertical The direction shooting value is the protrusion width, and the tilt shooting value is the protrusion height. When the particle size of the protrusion obtained from the image photographed in the vertical direction is the same as the particle diameter of the protrusion obtained from the image photographed with the tilt angle, the height and width of the protrusion are the same value. .
5) The SEM photographing magnification is a magnification in which the average particle diameter of the target protrusion falls within the range of 2 to 10% with respect to the maximum width of the SEM image.

<Protrusion-forming particles>
The average particle size of the particles used in the present invention is preferably 2 μm or more and 100 μm or less, more preferably 3 μm or more and 30 μm or less. When the average particle size is 2 μm or more and 100 μm or less, the height 3a of the protrusion shown in FIG. 10B is 2 μm or more and 100 μm or less, and the distance between the photoreceptor and the surface of the conductive base layer is stable against discharge. This is preferable because a uniform charge state by good discharge can be obtained. If the average particle diameter is 2 μm or more and 100 μm or less, the width 3b of the protrusion is also 2 μm or more and 100 μm or less, and the contact pressure between the charging member and the photosensitive member is sufficiently supported without obstructing discharge and causing unevenness. This is preferable because the non-adhesive fine powder is retained without being damaged. Moreover, since it becomes easy to hold | maintain non-adhesive fine powder as the average particle diameter of particle | grains is 2 micrometers or more and 100 micrometers or less, there exists an effect which prevents dissipation of fine powder. When the average particle diameter of the particles is 2 μm or more, the height of the protrusion becomes too small, the holding power of the fine powder is lowered, and the fine powder is not scattered by continuous use. Further, if the average particle size is 2 μm or more, the projections are too sharp and there is no risk of scratching and scratching the photoreceptor, and there is no risk that the projections will be too weak and damaged. . When the average particle size is 100 μm or less, the height of the protrusion becomes too large, the discharge start voltage necessary for charging becomes large, and charging does not become difficult.

Further, when the average particle size is 100 μm or less, the protruding portion is not charged and does not appear as uneven charging on the image.
The particle size distribution of the particles is preferably small. A small particle size distribution is preferable because the height of the formed protrusions becomes uniform, the discharge distance is kept uniform, and the charged state becomes uniform.
The average particle diameter of the particles can be determined by a pore electrical resistance method using, for example, a Coulter Multisizer manufactured by Beckman Coulter, Inc.

Below, the specific example of the particle size measurement of the particle | grains in this invention is shown.
0.1 to 5 ml of a surfactant (alkylbenzene sulfonate) is added to 100 to 150 ml of the electrolyte solution, and 2 to 20 mg of particles to be measured are added thereto. The electrolytic solution in which the particles are suspended is dispersed for 2 minutes with an ultrasonic disperser, and 0.3 to 64 μm on the basis of volume using an aperture that is appropriately matched to the resin fine particle size such as 17 μm or 100 μm by a Coulter counter multisizer. Measure the particle size distribution, etc. The number average particle diameter is obtained by computer processing of data measured under these conditions.

  It is more preferable that the particles used for forming the protrusions used in the present invention have a more nearly spherical shape. Specifically, by using particles whose average circularity is 0.95 or more and whose circularity standard deviation is less than 0.040, the size of the protrusions becomes uniform, and more uniform charging characteristics. Can be obtained. The circularity in the present invention can be determined by measuring the particle shape using, for example, a flow type particle image analyzer FPIA-2000 manufactured by Sysmex Corporation. That is, a value obtained by dividing the total circularity of all the measured particles by the total number of particles is defined as the average circularity.

The circularity of each particle is obtained as follows. First, particles are photographed, and the obtained image is converted into a binary image to obtain a projection image. From there, the perimeter of the projected image of the particle and the projected area are obtained. Next, assuming a circle having the same area as the projected area, the circumference of the circle is obtained. Finally, the ratio of the circumference of the circle to the circumference of the projection image is obtained, and this is used as the circularity.
Here, “particle projection area” is the area of the binarized particle image, and “perimeter of the particle projection image” is defined as the length of the contour line obtained by connecting the edge points of the particle image. .

  In addition, "FPIA-2000" which is a measuring apparatus used in the present invention uses the following calculation method in calculating the average circularity and the circularity standard deviation after calculating the circularity of each particle. The calculation method is based on the circularity obtained from the particles, and the circularity of 0.400 to 1.000 is divided into 61 divided ranges at intervals of 0.010, and the average is calculated using the center value and frequency of the dividing points. Calculate the circularity. “Dividing a circularity of 0.400 to 1.000 into 61 divided ranges at 0.010 intervals” means 0.400 or more and less than 0.410, 0.410 or more and less than 0.420 ... 0.990 or more It means dividing into less than 1.000 and 1.000.

  There is very little error between the average circularity value calculated by this calculation method and the average circularity value calculated by the above-described calculation formula that directly uses the circularity of each particle, and can be substantially ignored. Degree. For this reason, in the present invention, for the reason of handling data such as short-circuiting of the calculation time and simplification of the calculation formula, the concept of the calculation formula that directly uses the circularity of each particle described above is used. This modified calculation method is used.

The circularity in the present invention is an index indicating the degree of unevenness of particles, and is 1.000 when the particles are completely spherical, and the circularity becomes smaller as the surface shape becomes more complicated.
As a specific measuring method, 10 ml of ion-exchanged water from which impure solids have been removed in advance is prepared in a container, and a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant therein, followed by further measurement. Add 0.02 g of sample and disperse uniformly. As a means for dispersion, an ultrasonic disperser “UH-50 type” (manufactured by SMT Co., Ltd.) equipped with a 5φ titanium alloy chip as a vibrator is used, and a dispersion for measurement is performed using a dispersion treatment for 5 minutes. To do. In that case, it cools suitably so that the temperature of this dispersion may not be 40 degreeC or more. The obtained dispersion of particles is put into FPIA-2000, and the number of particles of 1000 or more is measured, and the average circularity is obtained.

As particles for generating protrusions, insulating particles are used. By using insulating particles, the protrusions derived from the particles are made insulating. By making the protrusions insulative, the conductive base layer surface of the charging member and the surface of the photosensitive member at the nip between the charging member and the photosensitive member are suppressed while preventing current leakage at the contact portion between the protrusion and the photosensitive member. Can be stably maintained at a distance suitable for discharge.
Examples of such particles include various inorganic powders, organic powders, and polymer powders. In terms of material, it is necessary that the charging member and the photosensitive member have such strength that they are not deformed or collapsed by contact, rotation, or friction. Specific examples include cross-linked acrylic resin particles, cross-linked styrene resin particles, and zeolite.

<Conductive support>
The conductive support 1 is a cylinder having a surface of carbon steel alloy plated with nickel having a thickness of 5 μm. As a material constituting the conductive support, a known material that is rigid and exhibits conductivity can be used.
<Conductive base layer>
In the present invention, a conductive base layer is provided under the protrusion. First, the conductive base layer 2 is formed on the outer periphery of the conductive support 1. The conductive base layer 2 is made of a conductive elastic body. The conductive elastic body is formed by mixing a conductive agent and a polymer elastic body.

<Polymer elastic body>
Specific examples of the polymer elastic body include the following. Epichlorohydrin rubber; EPM (ethylene propylene rubber); EPDM (ethylene propylene diene rubber); norbornene rubber; NBR (nitrile rubber); chloroprene rubber; natural rubber; isoprene rubber; butadiene rubber; styrene-butadiene rubber; Polyethylene; Urethane rubber; Styrenic block copolymer (SBS (styrene-butadiene-styrene-block copolymer), SEBS (styrene-ethylenebutylene-styrene-block copolymer), etc.); Silicone rubber.

<Conductive agent>
Examples of the conductive agent include an ionic conductive agent and an electronic conductive conductive agent. A combination of several types of ionic conductive agents and several types of electronic conductive agents may be used.
(1) Ionic conductive agent Examples of the ionic conductive agent include perchlorates such as LiClO ₄ and NaClO ₄ and quaternary ammonium salts. These can be used alone or in combination of two or more.
(2) Electronic conductive agent Specific examples of the electronic conductive material include the following (A) to (K).
(A) Metallic powders and fibers such as aluminum, palladium, iron, copper, and silver.
(A) Carbon powder such as carbon black and graphite.
(C) Metal powder.
(D) Metal oxides such as titanium oxide, tin oxide, and zinc oxide.
(E) Metal compound powders such as copper sulfide and zinc sulfide.
(F) Adhering the surface of suitable particles to tin oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, chromium, cobalt, iron, platinum, rhodium by electrolytic treatment, spray coating, and mixed shaking Powder.
(G) Carbon powders such as acetylene black, ketjen black, PAN (polyacrylonitrile) -based carbon, and pitch-based carbon.
(H) A combination of two or more selected from the groups (a) to (ki) above.

<Amount of conductive agent>
The amount of the conductive agent is such that the volume resistivity of the conductive elastic body is in the middle resistance region (volume resistivity is 1 × 10 ² to 1 × 10 ⁷ Ω · cm) in each of the following three environments. Is preferred.
Low temperature and low humidity (L / L) environment (temperature 15 ° C., relative humidity 10%).
Normal temperature and humidity (N / N) environment (temperature 23 ° C., relative humidity 55%).
-High temperature and high humidity (H / H) environment (temperature 30 ° C, relative humidity 80%).

<Method for measuring volume resistivity of conductive base layer>
The volume resistivity of the conductive elastic body is determined by the following method.
After forming into a sheet with a thickness of 1 mm, platinum is vapor-deposited on both sides to produce an electrode and a guard electrode. And the voltage of 200V is applied between both electrodes using the microammeter (ADVANTEST R8340A ULTRA HIGH RESISTANCE METER Co., Ltd. product), and the electric current 30 seconds after is measured. The volume resistivity is calculated from the measured value, the film thickness, and the electrode area.

  By setting the volume resistivity of the conductive elastic body within the above numerical range, when it is used as a charging member, even if there is a pinhole in the photoconductor that is an image carrier, a large current flows into the pinhole at once. The phenomenon of concentrating and making the hole larger is avoided. In addition, it is possible to effectively suppress a phenomenon in which a current does not flow in a place other than a hole and a black band is formed on a high-definition halftone image and a portion where a charged potential is insufficient can be visually recognized. Furthermore, it is possible to avoid a phenomenon in which the applied voltage drops in the conductive base layer, and the required discharge current cannot be obtained and the photosensitive member cannot be uniformly charged to a desired potential.

<Other additives>
Other additives such as plasticizers, fillers, vulcanizing agents, vulcanization accelerators, anti-aging agents, scorch preventing agents, dispersants and mold release agents are added to the conductive elastic body as necessary. It is also preferable.

<Method for forming conductive base layer>
Examples of the method for forming the conductive base layer include known methods such as extrusion molding, injection molding, and compression molding by mixing the raw materials for the conductive elastic body. The conductive base layer may be produced by directly forming a conductive elastic body on the conductive support, or the conductive elastic body formed into a tube shape may be coated on the conductive support. . Note that the surface may be polished and the shape may be adjusted after the production of the conductive base layer.

  The shape of the conductive base layer is so that the contact nip width between the finished charging member and the photosensitive member is as uniform as possible in the longitudinal distribution of the charging member, so that the shape of the central portion of the conductive base member on the photosensitive member side is from the end. Is also preferably convex toward the photoreceptor. When the charging member has a roller shape, the charging member preferably has a crown shape in which the diameter of the central portion of the roller is larger than the diameter of the end portion. Further, since the contact nip width of the completed charging member is uniform, it is preferable that the conductive base layer member has a small deflection.

<Asker C hardness of conductive base layer member>
The Asker C hardness of the conductive base layer member is preferably 85 ° or less. Since a nip between the charging member and the photosensitive member can be secured, charging is stabilized. The Asker C hardness is a hardness measured using an Asker C spring rubber hardness tester (manufactured by Kobunshi Keiki Co., Ltd.) in accordance with the Japan Rubber Association standard SRIS0101. The value according to the present invention is measured 30 seconds after the hardness meter is brought into contact with the surface of the conductive base layer portion of the conductive base layer member left in an N / N environment for 12 hours or more with a force of 10 N. Value.

  In order to adjust Asker C hardness, a plasticizer may be added to the conductive elastic body. The amount is preferably 1 part by mass or more, more preferably 3 parts by mass or more. As the plasticizer, for example, an ester-based polymer plasticizer such as a copolymer of sebacic acid and propylene glycol can be used. The conductive base layer is bonded to the conductive support through an adhesive as necessary. In this case, the adhesive is preferably conductive. In order to make it conductive, the adhesive may have the above-described conductive agent. Examples of the binder of the adhesive include resins such as a thermosetting resin and a thermoplastic resin, and known adhesives such as urethane, acrylic, polyester, polyether, and epoxy can be used.

<Electric resistance of conductive base layer member>
The electric resistance of the conductive base layer member is preferably 1 × 10 ⁴ Ω or more in the H / H environment and 1 × 10 ⁸ Ω or less in the L / L environment. In an N / N environment, it is preferably 2 × 10 ⁴ Ω or more and 6 × 10 ⁷ Ω or less. It is preferable to set the electric resistance in the L / L environment to be equal to or less than the above value because charging potential unevenness due to variation in the position of the member resistance is less likely to occur. Further, it is preferable that the resistance in a high-temperature and high-humidity environment is larger than the above range because even if there is a pinhole in the photoconductor, the applied current does not leak and the uneven density of charging does not appear on the halftone image.
When the conductive base layer is not in a roller shape, it is represented by a resistance per 1 cm ² .

The electrical resistance of the conductive base layer member was measured as follows.
That is, as shown in FIG. 4, the resistance is measured when energized while contacting a cylindrical metal 32 having the same curvature as that of the photosensitive member under the same stress as that in the usage state when used in an image forming apparatus. In FIG. 4A, 33 a and 33 b are bearings fixed to weights, and apply stress that pushes the conductive base layer member 40 to both ends of the conductive support 1 vertically downward. A columnar metal 32 is located in a vertically downward direction of the conductive base layer member 40 in parallel with the conductive base layer member 40. Then, the conductive base layer member 40 is pressed against the columnar metal 32 as shown in FIG. 4B while rotating the columnar metal 32 by a driving device (not shown). The cylindrical metal 32 is rotated at the same rotational speed as the photosensitive drum in use, and the DC voltage −200 V is applied from the power source 34 while the conductive base layer member 40 is driven to rotate, and the current flowing out from the cylindrical metal 32 Is measured with an ammeter A. The electrical resistance of the conductive base layer member 40 is calculated from the applied voltage and the measured current at this time. In the following examples, a force of 5 N was applied to both ends of the shaft to contact a metal cylinder having a diameter of 30 mm, and the metal cylinder was rotated at a peripheral speed of 150 mm / s.

<Surface roughness of conductive base layer>
The surface roughness of the conductive base layer is preferably small. As for the surface roughness of the base layer, Rz (10-point average roughness) is preferably 7 μm or less, particularly 5 μm or less, and more preferably 4 μm or less. If the surface roughness is small, a step between the protrusion and the surface of the conductive base layer is secured, and the ability to hold fine powder is also maintained.
As a surface roughness measuring apparatus, a surf coder SE3400 manufactured by Kosaka Laboratory was used, and a diamond contact needle having a tip radius of 2 μm was used. The measurement conditions were based on JIS B0601: 1982, the measurement speed was 0.5 mm / s, the cut-off frequency λc was 0.8 mm, the reference length was 0.8 mm, and the evaluation length was 8.0 mm.

<Method for producing protrusion>
The outline of the coating apparatus used for the elastic roller manufacturing method of this invention is shown to Fig.6 (a). The conductive base layer member 40 to be coated is fixed to the coating apparatus by upper and lower bar bearings 35 and 36. The bearings 35 and 36 are positioned in parallel with the actuator 13 of the coating apparatus, and are held with respect to the support column 37 via a base 38 and an upper plate 39. The bearing has a cylindrical shape with substantially the same thickness as that of the conductive base layer member 40. A coating ring 14 is fixed to the actuator 13 and can move in parallel with the axis of the conductive base layer member 40.

The coating liquid 17 sucked up from the coating liquid tank 16 by the piston of the coating liquid supply controller 15 is supplied to the coating ring 14 through the flexible tube 19.
The actuator 13 and the coating liquid supply controller 15 are controlled by the computer 21 and are operated by adjusting the respective operation timings.

  FIG. 6B is an enlarged schematic cross-sectional view of the vicinity of the coating ring. The coating liquid 17 is supplied to the coating ring 14 through the flexible tube 19, becomes a rotationally symmetric flow while passing through the slits arranged concentrically inside the ring, and is discharged from the ring nozzle 23, and is a conductive base layer member. It is applied to the surface of 40 conductive base layers 2. The material of the coating ring 14 is SUS304, and the surface is finished with a smoothness of Ra (arithmetic mean roughness) = 0.1 μm or less. The conductive base layer member 40 is held by bearings 35 and 36 above and below the core metal (conductive support) 1.

The operation of the coating apparatus in the coating process will be described with reference to FIG. In FIG. 7, a flexible tube or the like is omitted. First, the upper bearing 35 to which the weight 24 is fixed is pulled up, the conductive base layer member 40 is set on the lower bearing 36 (a), and then the upper bearing 35 is lowered to fix the conductive base layer member 40 to the coating apparatus. (B). Next, as shown in (c), the head of the actuator to which the coating ring 14 is fixed is moved upward so that the ring nozzle of the coating ring comes to a position between the conductive base layer member 40 and the upper bearing. Move the actuator head. Hereinafter, the entire portion in which the coating ring and the head of the actuator are fixed to each other and operate integrally is referred to as a coating head 25.
Then, while controlling and discharging the coating liquid, the coating head 25 is lowered at a controlled speed as shown in FIGS. When the coating is completed, as shown in (f), the upper bearing is raised and the conductive base layer member on which the coating film is formed is taken out.

  FIG. 9A shows a schematic view of a cross section of the charging member including the coating film applied in FIG. As shown in FIG. 9 (a), the resin particles that become the protrusions are present in a state of being dispersed in the curable liquid immediately after coating, but as the curable liquid is gradually absorbed by the conductive base layer, The head begins to appear (b). In addition, the resin particles that form protrusions in the process of absorbing the curable liquid into the conductive base layer move slightly with respect to each other, and are uniformly and randomly dispersed so as not to overlap. When the curable liquid is completely absorbed by the conductive base layer (c), the resin particles that form the protrusions are randomly and uniformly dispersed and attached to the surface of the conductive base layer. At this stage, the resin particles are also slightly impregnated with the curable liquid, and at the time of subsequent curing, the curable liquid soaked into the conductive base layer and the curable liquid soaked into the resin particles are bonded by curing, so that the protrusions are formed. Bonds strongly to the conductive base layer. In the formation of the protrusion by this method, there is an advantage that the protrusion and the conductive base layer can be firmly bonded by the interpolymer network to form a strong protrusion.

  Prior to the start of coating, a small amount of coating liquid may be discharged from the coating nozzle while rotating the upper and lower bearings, so that the liquid level of the coating nozzle is evenly conditioned. As shown in FIG. 8A, the upper and lower bearings preferably have an edge at the portion E that contacts the roller. By using the edge, adhesion between the end portion of the conductive base layer member and the bearing is further increased, and the coating liquid can be prevented from penetrating into the gap between the bearing and the conductive base layer member. It is preferable that the upper and lower bearing surfaces are subjected to water / oil repellent treatment so that the coating is difficult to adhere to. Examples of the water / oil repellent finishing method include coating with various fluorine-containing compounds and coating with a silicone compound. Also, as shown in FIG. 8 (b), the coating is started from above the boundary B between the conductive base layer member and the upper bearing, and the non-uniformity of the coating film at the start of coating is applied to the surface of the conductive base layer. It is also possible not to leave it. In this case, as shown in FIG. 8C, FIG. 8D, FIG. 8E, and FIG. 8F, it is possible to use a cap that can replace the tip of the bearing on the roller side. When coating is performed using a cap, it is preferable that the cap has a greater affinity with the coating solution (a smaller contact angle) because the uniformity of the coating film is improved. Examples of the shape of the cap include a cylindrical cap such as 26 and 27, and a cup-shaped cap such as 28 and 29.

  The film thickness of the coating film applied to the conductive base layer member is 1 mm or less, more preferably 200 μm or less, and still more preferably 60 μm or less. If it is too thick, the ultraviolet rays do not reach the deep part of the ultraviolet curable resin, so that curing failure occurs, and it becomes impossible to form a layer with the ultraviolet curable resin. The film thickness is adjusted by controlling the viscosity and discharge speed of the UV curable paint and the moving speed of the coating head. When it is desired to increase the film thickness, it is preferable to increase the viscosity, to increase the discharge speed, and to decrease the moving speed of the coating head. Conversely, when it is desired to reduce the film thickness, it is preferable to reduce the viscosity, the discharge speed is preferably low, and the movement speed of the coating head is preferably high.

The material that fixes the particles to the conductive base layer to form the protrusions is a curable liquid. The liquid is a liquid molecule that is polymerized by crosslinking with heat, ultraviolet light, visible light, electron beam, or other radiation.
Examples of the curable liquid include isocyanate compounds and vinyl polymerizable monomers. In view of the strength of fixing the protrusion, an acrylic ultraviolet polymerizable monomer is particularly preferable. An acrylic UV-polymerizable monomer is preferable because it can reduce the viscosity and is excellent in the dispersibility of the resin particles serving as protrusions and in controlling the thickness of the coating film.

  Examples of the isocyanate compounds include hexamethylene diisocyanate isocyanate compounds, diphenylmethane diisocyanate isocyanate compounds, toluene diisocyanate isocyanate compounds, and isophorone diisocyanate isocyanate compounds. The isocyanate compound preferably has a functional group of 2 or more functional groups, more preferably 3 or more functional groups. Furthermore, the isocyanate group is preferably blocked with a blocking agent. Blocking with a blocking agent is preferable because it can suppress changes in the properties of the paint due to the influence of water. Furthermore, the isocyanate compound is preferably water-soluble or water-dispersible. The water dispersibility is preferable because the surface potential is stable when the paint is used, and the change in the properties of the paint is small even when left for a long period of time.

Specific examples of the (meth) acrylic ultraviolet curable monomer include the following compounds. As monofunctional methacrylate, methoxydiethylene glycol methacrylate, β-methacryloyloxyethyl hydrogen phthalate, β-methacryloyloxyethyl hydrogen succinate, 3-chloro-2-hydroxypropyl methacrylate, stearyl methacrylate, isobornyl methacrylate, isostearyl methacrylate, Methoxypolyethylene glycol methacrylate. As monofunctional acrylates, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, β-acryloyloxyethyl hydrogen succinate, isobornyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, isostearyl acrylate, phenoxy polyethylene glycol acrylate. As bifunctional methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, 2-hydroxy 1,3 -Dimethacryloxypropane, 2,2-bis [4- (methacryloxyethoxy) phenylpropane], 2,2-bis [4- (methacryloxydiethoxy) phenylpropane], ethoxylated cyclohexanedimethanol dimethacrylate, ethoxylated Bisphenol A acrylate, tricyclodecane dimethanol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate , Polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate. As bifunctional acrylates, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate, 2,2-bis [4- (acryloxy-diethoxy) phenyl] propane, 2-hydroxy, 1-acryloxy 3-methacryloxypropane, ethoxylated cyclohexanedimethanol diacrylate, ethoxylated bisphenol A diacrylate, dioxane glycol diacrylate, tricyclodecane dimethanol diacrylate, 1,9-nonanediol diacrylate, 1,10-decanediol Diacrylate, propoxylated ethoxylated bisphenol A diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate. Trimethylolpropane trimethacrylate as a trifunctional methacrylate. As trifunctional acrylates, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, ethoxylated glycerin triacrylate, ethoxylated isocyanuric acid triacrylate, ε-caprolactone modified tris- ( -Acryloxyethyl) isocyanurate. As tetrafunctional acrylate, tetramethylol methane tetraacrylate, ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate.
In addition, various modified monomers and oligomers can be used. Examples of the modifying group include a urethane group, an epoxy group, an ether group, an ester group, a carbonate group, a dimethyl silicone group, and a phenyl silicone group.

  A photopolymerization initiator is added to the ultraviolet curable coating. A conventionally well-known thing can be used as a photoinitiator. Furthermore, various conductive agents and leveling agents may be mixed in the paint. Examples of the leveling agent include silicone oil.

<Ultraviolet curable coating solution>
In order to prepare an ultraviolet curable coating solution, an ultraviolet curable monomer, a photopolymerization initiator, and particles for forming protrusions are mixed and dispersed by a known method to prepare a coating for forming protrusions. Examples of known dispersion methods include the following (a) to (c).
(A) Agitating and dispersing device such as a rotating blade rotated by a motor or a homogenizer. (A) A fine orifice dispersing device that disperses pigment by colliding with accelerated paint. (C) A conventionally known dispersing device using beads such as a sand mill, a paint shaker, a dyno mill, and a pearl mill.

  After the protrusions are cured with the ultraviolet curable resin as described above, another curing means may be added. That is, it is preferable that the curing by exposure to ultraviolet rays by the ultraviolet irradiation means is only temporary curing for maintaining the positional relationship between the protrusions and the conductive base layer, and the final curing is performed in a subsequent step. Examples of the final curing means include thermal curing and electron beam curing in an inert atmosphere.

<Non-sticky fine powder>
The non-adhesive fine powder exists while being held in a gap formed by the protrusion and the surface of the conductive base layer, and plays a role of protecting the discharge surface of the surface of the conductive base layer from damage due to discharge. Non-adhesive means the difficulty of adhering when the fine powder contacts the solid surface. When the non-adhesiveness is small (high adhesiveness), the fine powder adheres to the surface of the conductive base layer of the base layer without any gap, and it is not preferable because it covers the discharge surface of the charging member and is difficult to discharge.

  The primary particle diameter of the fine powder is preferably smaller than the particle diameter for forming the protrusions. If the fine powder is too large, it is difficult to hold it between the protrusions, which is not preferable. The surface area of the fine powder is preferably large. When the surface area per unit mass of the fine powder is small, the effect of preventing the fine powder from being exposed to the discharge product instead of the surface of the conductive base layer and exposing the conductive base layer to deteriorate is less preferable.

Measuring method of primary particle size of fine powder
1) Air blow the surface of the charging member and transfer the fine powder to the conductive carbon sheet.
2) Take an image with Hitachi FE-SEM (S-4800). Taken in a direction perpendicular to the conductive carbon sheet.
3) For 10 randomly selected fine powders, the maximum and minimum diameters on the image are measured, and the average value is taken as the diameter.
(The image is introduced into an image processing apparatus (for example, image analysis apparatus Luzex III manufactured by Nireco) and analyzed)
4) The number average particle diameter of 10 fine particles is averaged to calculate the number average particle diameter of the fine powder, which is the primary particle diameter of the fine powder.
5) The SEM photographing magnification is a magnification in which the average particle diameter of the target fine powder falls within the range of 2 to 10% with respect to the maximum width of the SEM image.

The surface area can be measured by the BET method.
The measurement of the BET specific surface area is performed using a known apparatus such as a degassing apparatus Bacuprep 061 (manufactured by Micromesotech) or a BET measuring apparatus Gemini 2375 (manufactured by Micromesotech). The BET specific surface area in the present invention is a value of a one-point method BET specific surface area. Specifically, the procedure is as follows.

  After measuring the weight of the empty sample cell, the sample to be measured is filled so as to fall between 0.01 and 0.002 g. Further, the sample cell filled with the sample is set in the degassing apparatus, and degassing is performed at room temperature for 3 hours. After completion of degassing, the mass of the entire sample cell is measured, and the accurate mass of the sample is calculated from the difference from the empty sample cell. Next, empty sample cells are set in the balance port and analysis port of the BET measuring apparatus. A dewar bottle containing liquid nitrogen is set at a predetermined position, and P0 is measured by a saturated vapor pressure (P0) measurement command. After the P0 measurement is completed, the sample cell prepared for degassing is set in the analysis port, and after inputting the sample mass and P0, the measurement is started by the BET measurement command. After that, the BET specific surface area is automatically calculated.

Specifically, the fine powder material includes the following (a) to (ku).
(A) Metallic powders such as aluminum, palladium, iron, copper and silver. (A) Carbon powder such as carbon black and graphite. (C) Metal oxides such as silica, alumina, titanium oxide, tin oxide and zinc oxide. (D) Metal compound powders such as copper sulfide, zinc sulfide, calcium carbonate, barium sulfate, titanium nitride, copper sulfide and the like. (E) Appropriate treatment of tin oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, chromium, cobalt, iron, lead, platinum, rhodium, carbon on the surface of suitable particles, spray coating, mixing Powder attached by shaking. (F) Carbon powders such as acetylene black, ketjen black, PAN (polyacrylonitrile) -based carbon, and pitch-based carbon. (G) Polymer particles such as melamine, acrylic, urethane, styrene, PTFE (polytetrafluoroethylene). (H) Double oxides such as mica, hydrotalcite, zeolite and smectite.

In particular, an oxide such as silica or tin oxide is preferable, and the oxide may have conductivity. Since the oxide is already oxidized by oxygen, it is more resistant to oxidation by ozone or the like due to discharge than a non-oxide material. Therefore, when the non-adhesive fine powder is an oxide, the properties of the fine powder hardly change even when exposed to electric discharge, so that the good performance of the charging member is maintained for a long time.
The primary particle diameter of the fine powder is preferably 5 nm to 300 nm, more preferably 7 nm to 200 nm, and still more preferably 10 nm to 100 nm.

The surface area of the fine powder is preferably 5 m ² / g to 1500 m ² / g, more preferably 10 m ² / g to 1000 m ² / g, and still more preferably 15 m ² / g to 800 m ² / g.
The fine powder has an appropriate fluidity and is held in the gap between the protrusion and the conductive base layer. When the fine powder is held in a gap formed by the conductive base layer and the protrusion on the surface of the base layer, it is preferable that the fine powder adheres to each other or the conductive base layer and the protrusion and does not lose fluidity. As for the fluidity, the Carr's fluidity index is preferably 40 or more and 98 or less. When the fluidity is small, it is preferable that when the fine powder is held on the charging member, the fine powder is tightly packed and solidified in the gap between the protrusion and the conductive base layer, and the discharge gap is crushed and becomes unchargeable. Absent. On the other hand, if the fluidity is too high, the powder cannot be retained, and the fine powder will dissipate immediately after the charging member is used, which is not preferable.

The measurement of Carr's fluidity index is described in detail in Japanese Patent Publication No. 51-14278, and is not particularly limited, but in the present invention, it is measured by the following method.
That is, using a powder tester P-100 (manufactured by Hosokawa Micron Corporation), parameters of repose angle, degree of compression, degree of aggregation, and spatula angle are measured. The values obtained for each were applied to Carr's liquidity index table (Chemical Engineering. Jan. 18.1965), converted into each index of 25 or less, and the sum of the indices determined from each parameter was used as the liquidity index. calculate.

An example of a method for measuring each parameter is shown below.
(1) Angle of repose 150 g of fine powder is passed through a mesh having an opening of 710 μm, and the fine powder is deposited on a circular table having a diameter of 8 cm. At this time, it is deposited to such an extent that fine powder overflows from the end of the table. The angle formed between the ridgeline of the fine powder deposited on the table at this time and the circular table surface is measured with a laser beam. This is the angle of repose.

(2) Compressibility From the loosely packed bulk density (relaxed apparent specific gravity, “A”) and the tapping bulk density (hardened apparent specific gravity, “P”), the compressibility can be obtained by the following equation.
Compressibility (%) = 100 (PA) / P
As for the apparent specific gravity, for example, 150 g of fine powder is gently poured into a cup having a diameter of 5 cm, a height of 5.2 cm, and a capacity of 100 ml. Then, when the measurement cup is filled with fine powder, the surface of the fine powder is ground, and the specific gravity of the fine powder filled in the cup is calculated from the amount of fine powder filled in the cup and the capacity of the cup. .
For the apparent apparent specific gravity, for example, add the attached cap to the measuring cup used at the loose apparent specific gravity, fill the cup with fine powder, tap the cup 180 times, remove the cap when tapping is completed, and pile up the cup. Grind any excess fine powder that has become. And it calculates | requires by calculating the specific gravity of the fine powder with which the cup is filled from the quantity of the fine powder with which the cup is filled, and the capacity | capacitance of a cup. Both apparent specific gravity values are inserted into the above formula to determine the degree of compression.

(3) Spatula angle Place a 3 cm x 8 cm spatula in contact with the bottom of a 10 cm x 15 cm bat, and deposit fine powder on the spatula. At this time, the fine powder is deposited so as to rise on the spatula. Thereafter, the bat alone is gently lowered, and the inclination angle of the fine powder side surface remaining on the spatula is measured with a laser beam. Then, after applying an impact once with a shocker attached to the spatula, the spatula angle is measured again. The average of this measured value and the measured value before giving an impact is defined as a spatula angle.

(4) Aggregation degree A sieve is set on the vibration table in the order of openings of 250 μm, 150 μm, and 75 μm from the top. The vibration amplitude is set to 1 mm, the vibration time is set to 20 seconds, and 5 g of fine powder is gently put on and vibrated. After the vibration stops, measure the weight remaining on each sieve. The weight of the fine powder remaining on each sieve is applied to the following formula, and each value of a, b, and c is obtained from each formula. The sum of a, b, and c is defined as the degree of aggregation (%).
a = (amount of toner remaining on upper screen) ÷ 5 (g) × 100
b = (amount of toner remaining on the middle screen) ÷ 5 (g) × 100 × 0.6
c = (amount of toner remaining on the lower screen) ÷ 5 (g) × 100 × 0.2
The sum of the indices ((1) + (2) + (3) + (4)) in the parameters (1), (2), (3), and (4) above is the Carr's liquidity index.

As the surface treatment agent, an alkoxysilane coupling agent and a fluoroalkylalkoxysilane coupling agent are particularly preferable as a coupling agent (a central element such as silicon, titanium, aluminum and zirconium is not particularly selected).
Examples of coupling agents include silane coupling agents and titanate coupling agents.
Examples of the silane coupling agent include isobutylsilane, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, and benzyldimethyl. Chlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilyl mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilamen, dimethyldi Ethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyl Rutetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and 2-12 siloxane units per molecule, each containing a hydroxyl group bonded to each silicon atom in the terminal unit Dimethylpolysiloxane.

Carr's fluidity index is controlled by the degree of surface treatment.
If the amount of fine powder retained is small, the effect of preventing the fine powder from being exposed to the discharge product instead of the conductive base layer and the conductive base layer from being exposed and deteriorated is not preferable. On the other hand, if the holding amount is too large, the discharge gap is crushed and charging becomes impossible.
The amount of fine powder retained is 4 or more and 4000 or less when expressed by the ratio of the surface area of the fine powder held to the surface area of the conductive base layer member (in the case of a roller, diameter × circumference × rubber surface length). Preferably, it is 10 or more and 3000 or less, more preferably 100 or more and 800 or less.

The method for holding the fine powder may be any method as long as the fine powder is uniformly held on the surface of the charging member.
In the present invention, while the base layer is first rotated at a peripheral speed of 200 mm / s, fine powder is applied to a regenerated cellulose cloth having a thickness of 5 mm and pressed against the base layer to hold the fine powder on the conductive base layer. .
In addition, there are a method in which fine powder and gas are mixed and sprayed onto the base layer, and a slurry in which fine powder is dispersed in a liquid is applied to the base layer, followed by drying to remove the liquid and hold it.

The mass of the charging member before and after holding is measured, and the holding amount is obtained by subtracting the mass before holding from the mass after holding.
As another method of obtaining the holding amount, there is a method of sucking out fine powder on the surface of the charging member using a vacuum cleaner equipped with a filter. The retention amount is obtained by calculating the difference between the mass of the fine powder sucked by the vacuum cleaner and trapped by the filter and the mass of the base layer sucked and no longer containing fine powder.
According to the present invention, it is possible to apply a large amount without compressing the fine powder by holding the fine powder in the gap between the protrusions.
In this configuration, the surface of the conductive base layer to be discharged is always at a position away from the photoconductor, and is protected by fine powder, so that it is difficult to be exposed to attacks from discharge products and the like, and charging is stable even after repeated use. There is an effect that. Furthermore, since the fine powder is held without being compressed and there is a gap in the portion where the fine powder is held, there is also an effect of not inhibiting the discharge from the surface of the base layer.

In addition, since the projection surrounds the fine powder and can prevent the fine powder from diffusing, the charging characteristics through the fine powder layer hardly change even when used for a long time, and stable charging can be performed. .
Further, according to the method for producing a charging member of the present invention, it is possible to easily form protrusions caused by particles firmly bonded to the surface of the conductive base layer, and stable charging can be achieved by holding fine powder. It is possible to easily create a charging member capable of performing the above.
Furthermore, when the charging member is regenerated, there is an effect that the charging member can be easily regenerated by simply removing the fine powder and replacing it with a new fine powder.

<Manufacture of conductive base layer member>
The following materials were mixed and kneaded with an open roll for 20 minutes.

  Next, the following materials were further added and kneaded with an open roll for 15 minutes.

出来上がった未加硫ゴム組成物を、実施例１の導電性基層用未加硫ゴム組成物とした。

The finished unvulcanized rubber composition was used as the unvulcanized rubber composition for the conductive base layer of Example 1.

The obtained unvulcanized rubber composition for the conductive base layer was coaxially formed on the outer periphery of a cored bar (diameter 6 mm, length 252 mm) coated with a polyester adhesive at a thickness of about 10 μm by extrusion molding using a crosshead. Were simultaneously extruded into a cylindrical shape having a diameter of 10 mm.
After vulcanization at 160 ° C. for 40 minutes in a hot air furnace, both ends of the rubber part were cut to make the axial width of the conductive base layer part 228 mm. Thereafter, the surface of the conductive base layer portion was polished with a rotating grindstone to obtain a crown-shaped conductive base layer member having an end diameter of 8.4 mm and a central diameter of 8.6 mm.

<Manufacture of base layer (state with protrusions fixed)>
The following materials were put in a light shielding bottle and stirred for 30 minutes with a paint shaker to obtain an ultraviolet curable coating solution.

  The obtained conductive base layer member was set in the apparatus shown in FIG. 6 which was left in an air environment of normal temperature and normal humidity (N / N) environment (temperature 23 ° C., relative humidity 55%). Further, the ultraviolet curable coating liquid was put into the coating liquid tank 18 of the apparatus. Next, in accordance with the procedure described in <Method for producing protrusions>, an ultraviolet curable coating solution was applied to the conductive base layer member. After coating, it was left in an N / N environment for 10 minutes, and only the liquid component in the ultraviolet curable coating solution was soaked into the conductive base layer.

The coated conductive base layer member was set in an ultraviolet post-irradiation device (not shown), and a low-pressure mercury lamp having a central wavelength of 254 nm was uniformly irradiated for 2 minutes at an illuminance of 1000 mW / cm ² while rotating the roller. Thus, the base layer 1 of Example 1 was obtained. The manufacturing conditions are as follows.
Coating speed (coating head descending speed): 100 mm / s
Coating liquid supply rate: 45 μl / s
The size (height, width) and density of the protrusions of the obtained base layer were measured by the methods described above. The results are shown in Table 1.

<Base layer 2>
A base layer 2 was obtained under the same production conditions as those of the base layer 1 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 7 parts by mass.
<Base layer 3>
A base layer 3 was obtained under the same production conditions as those of the base layer 1 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion-forming particles was changed to 2 parts by mass.

<Base layer 4>
A base layer 4 was obtained under the same production conditions as those of the base layer 1 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 1 part by mass.
<Base layer 5>
The diameter of the spherical cross-linked acrylic resin balls as the forming particles for protrusions was changed to 2 μm, and the supply rate of the coating liquid was changed to 10 μl / s in order to adjust the protrusion density to be the same as in Example 1. A base layer 5 was obtained under the same production conditions as in the base layer 1 except that.

<Base layer 6>
A base layer 6 was obtained under the same production conditions as those for the base layer 5 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion-forming particles was changed to 2 parts by mass.
<Base layer 7>
A base layer 7 was obtained under the same production conditions as those for the base layer 5 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion-forming particles was changed to 1 part by mass.

<Base layer 8>
The diameter of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 3 μm, and the supply rate of the coating liquid was changed to 15 μl / s in order to adjust the protrusion density to be the same as in Example 1. Except for the above, base layer 8 was obtained under the same production conditions as base layer 1.
<Base layer 9>
A base layer 9 was obtained under the same production conditions as those of the base layer 8 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 2 parts by mass.

<Base layer 10>
A base layer 10 was obtained under the same production conditions as those of the base layer 8 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 1 part by mass.
<Base layer 11>
The diameter of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 20 μm, and the blending amount was changed to 2 parts by mass. Further, a base layer 11 was obtained under the same production conditions as those of the base layer 1 except that the supply rate of the coating solution was changed to 90 μl / s in order to adjust the protrusion density to be the same as in Example 1.

<Base layer 12>
The diameter of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 30 μm, and the supply speed of the coating liquid was changed to 145 μl / s in order to adjust the protrusion density to be the same as in Example 1. A base layer 12 was obtained under the same production conditions as in the base layer 1 except for the above.
<Base layer 13>
A base layer 13 was obtained under the same production conditions as those for the base layer 12 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion-forming particles was changed to 2 parts by mass.

<Base layer 14>
A base layer 14 was obtained under the same production conditions as those of the base layer 12 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 1 part by mass.
<Base layer 15>
The diameter of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 35 μm, and the supply speed of the coating liquid was changed to 180 μl / s in order to adjust the protrusion density to be the same as in Example 1. A base layer 15 was obtained under the same production conditions as in the base layer 1 except for the above.

<Base layer 16>
A base layer 16 was obtained under the same production conditions as those of the base layer 15 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 2 parts by mass.
<Base layer 17>
A base layer 17 was obtained under the same production conditions as those for the base layer 15 except that the blending amount of the spherical crosslinked acrylic resin balls as the protrusion forming particles was changed to 1 part by mass.

<Base layer 18>
The material of the protrusion forming particles was changed. A base layer 18 was obtained under the same production conditions as those for the base layer 8 except that the spherical cross-linked acrylic resin balls were changed to spherical cross-linked styrene resin balls (trade name: SBX-3SS, manufactured by Sekisui Plastics Co., Ltd.).
<Base layer 19>
The material of the protrusion forming particles was changed. A base layer 19 was obtained under the same production conditions as those for the base layer 9 except that the spherical cross-linked acrylic resin balls were changed to spherical cross-linked styrene resin balls (trade name: SBX-3SS, manufactured by Sekisui Plastics Co., Ltd.).

<Base layer 20>
The material of the protrusion forming particles was changed. A base layer 20 was obtained under the same production conditions as those of the base layer 12 except that the spherical cross-linked acrylic resin balls were changed to spherical cross-linked styrene resin balls (trade name: SBX-30SS, manufactured by Sekisui Plastics Co., Ltd.).
<Base layer 21>
The material of the protrusion forming particles was changed. A base layer 21 was obtained under the same production conditions as the base layer 13 except that the spherical cross-linked acrylic resin ball was changed to a spherical cross-linked styrene resin ball (trade name: SBX-30SS, manufactured by Sekisui Plastics Co., Ltd.).

<Base layer 22>
The material of the protrusion forming particles was changed. Manufacturing conditions similar to those of the base layer 8 except that the spherical crosslinked acrylic resin balls were changed to spherical porous zeolite particles (trade name: Ryukyu Light, manufactured by Ecowell Co., Ltd.) and adjusted to an average particle size of 3 μm. Thus, the base layer 22 was obtained.
<Base layer 23>
The material of the protrusion forming particles was changed. Manufacturing conditions similar to those of the base layer 9 except that the spherical crosslinked acrylic resin balls were changed to spherical porous zeolite particles (trade name: Ryukyu Light, manufactured by Ecowell Co., Ltd.) and adjusted to an average particle size of 3 μm. Thus, the base layer 23 was obtained.

<Base layer 24>
The material of the protrusion forming particles was changed. Production conditions similar to those of the base layer 12 except that the spherical crosslinked acrylic resin balls were changed to spherical porous zeolite particles (trade name: Ryukyu Light, manufactured by Ecowell Co., Ltd.) and adjusted to an average particle size of 30 μm. Thus, the base layer 24 was obtained.
<Base layer 25>
The material of the protrusion forming particles was changed. Manufacturing conditions similar to those of the base layer 13 except that the spherical crosslinked acrylic resin balls were changed to spherical porous zeolite particles (trade name: Ryukyu Light, manufactured by Ecowell Co., Ltd.) and adjusted to an average particle size of 30 μm. Thus, the base layer 25 was obtained.

<Base layer 26>
Preparation of outermost surface layer coating liquid 1 part by mass of dimethyldimethoxysilane was blended with 100 parts by mass of silica powder (Reosil QS-10, manufactured by Tokuyama Corporation). The mechanomicros (manufactured by Nara Seisakusho Co., Ltd.) was charged while operating at a vessel rotational speed of 200 rpm / minute (hereinafter: rpm) and a rotor rotational speed of 2000 rpm, and kneaded for 15 minutes while maintaining 70 ° C. Next, 100 parts by mass of carbon black (trade name: MA100, manufactured by Mitsubishi Chemical Corporation, 1.5% volatile content) as a conductive material was added to the silica powder, and kneaded for 100 minutes while maintaining 70 ° C. The obtained conductive composite particles 1 had a specific surface area of 140 m 2 / g and a DBP oil absorption of 90 cm 3/100 g.

  1056 parts by mass of lactone-modified acrylic polyol (trade name: Plaxel DC2016, manufactured by Daicel Chemical Industries, Ltd.) was dissolved in 2304 parts by mass of methyl isobutyl ketone (MIBK) to obtain a solution having a solid content of 22% by mass. It mixed with the ratio shown in the following table | surface with respect to 200 mass parts of this acrylic polyol solution, and the compounding liquid was obtained.

  30 liters of the above blended solution was put into a stainless steel cylindrical container having a diameter of 30 cm, and the stirring blade was rotated at 300 rpm and stirred for 30 minutes. 30 liters of this dispersion was circulated and dispersed in a 2 liter horizontal bead mill filled with 80% glass beads with a diameter of 0.8 mm. It was dispersed for 8 hours while rotating at a peripheral speed of 8 mm / s, a circulation rate of 2 liters / minute, and a temperature of the outer wall of the mill of 22 ° C. Thereafter, spherical crosslinked acrylic resin balls (trade name: MBX-10SS, manufactured by Sekisui Plastics Co., Ltd.) having an average particle diameter of 10 μm are placed in a circulating bead mill tank at 10.10 parts by mass with respect to 200 parts by mass of the acrylic polyol solution. It mix | blended so that it might become 5 mass parts. Furthermore, it was dispersed for 4 hours while rotating at a peripheral speed of 3 mm / s, a circulation rate of 2 liters / minute, and a temperature of the outer wall of the mill of 22 ° C. After dispersion, the liquid was taken out and the viscosity was measured. The viscosity of the paint was 12.0 mPa · s under an environment of 23 ° C.

This coating liquid was put into a coating tank for dip coating, and was slowly circulated for 12 hours. When the liquid was stabilized, coating was continued on the conductive base layer member used in Example 1 while continuing circulation and overflow. At that time, the lowering speed is 30 mm / s, and after stopping for 4 seconds at the lowest point, the position of the charging member is set so that the initial speed is 25 mm / s and the final speed (speed at which the lower end is applied) is 2 mm / s. The workpiece was moved up and down with a linear velocity gradient. Thus, the coating was performed so that the film thickness of the outermost surface layer was substantially uniform in the upper and lower portions in the coating state of the charging member.
Thereafter, it was air-dried at 23 ° C. for 30 minutes, dried in a clean oven at 80 ° C. for 30 minutes, and then dried in an oven at 160 ° C. for 60 minutes.
In this way, the base layer 26 was obtained.

<Base layer 27>
In the production process of the base layer 26, a base layer 27 was obtained in the same manner as the base layer 26, except that a spherical crosslinked acrylic resin ball (trade name: MBX-10SS, manufactured by Sekisui Chemical Co., Ltd.) was not blended.
<Base layer 28>
The conductive base layer member itself used in Example 1 was used as the base layer 28.
Table 5 shows a list of base layers.

<Fine powder>
100 g of fumed silica having a primary particle size of 20 nm (trade name: Aerosil 90, manufactured by Nippon Aerosil Co., Ltd.) and 10 g of isobutyltrimethoxysilane (trade name: AY43-048, manufactured by Toray Dow Corning Silicone) as a silane coupling agent Surface treatment was performed to obtain fine powder 1 having a primary particle size of 20 nm and a Carr fluidity of 90.

  Furthermore, fine powders 2 to 18 were obtained by adjusting the treatment amount of the silane coupling agent and the primary particle diameter of the raw material silica in a timely manner. Increasing the throughput of the silane coupling agent also increases the Carr's fluidity index, and decreasing the throughput of the silane coupling agent decreases the Carr's fluidity index.

  Further, conductive tin oxide powder having a primary particle size of 20 nm was designated as fine powder 19, and conductive zinc oxide powder having a primary particle size of 50 nm was designated as fine powder 20. Further, the insulating titanium oxide powder having a primary particle diameter of 20 nm was used as fine powder 21, the insulating alumina powder having a primary particle diameter of 100 nm was used as fine powder 22, and the crosslinked melamine resin powder having a primary particle diameter of 0.2 μm was used as fine powder 23. In addition, hydrotalcite powder having a primary particle size of 0.5 μm was fine powder 24, PTFE powder having a primary particle size of 20 nm was fine powder 25, and rosin powder having a primary particle size of 0.5 μm was fine powder 26.

The non-stickiness of each fine powder was examined. Non-adhesive evaluation was judged by whether each fine powder was pressed against an acrylic plate at a pressure of 100 g / cm 2 for 1 minute and then remained when 20 m / s of air was sprayed. That is, a product in which the lump of fine powder disappeared by air blowing was designated as “O” (non-adhesive), and a fine powder in which the lump remained was designated as “X” (adhesive).
Table 6 shows a list of fine powders.

<Example 1>
Fine powder 1 was held on the base layer 1 to obtain a charging member of Example 1.
In the present invention, while the base layer is rotated at a peripheral speed of 200 mm / s, the fine cellulose powder is applied to the regenerated cellulose cloth piled up to a thickness of 5 mm and pressed against the base layer to hold the fine powder on the conductive base layer. It was. The pressing stress was 0.5 N / cm ² and the pressing time was 20 seconds. The amount of fine powder retained was adjusted by adjusting the amount of fine powder applied to the regenerated cellulose cloth.

<Evaluation of charging member>
<Image forming apparatus>
FIG. 2 shows an electrophotographic image forming apparatus using a charging member 6 as an embodiment of a charging member according to the present invention as a charging roller. The photosensitive drum 5 as an image carrier is primarily charged by the charging roller 6 while rotating in the direction of the arrow, and then an electrostatic latent image is formed by the exposure light 11 from an exposure unit (not shown). The developer in the developer container 31 is carried on the surface of the developing roller 12 while being rubbed and charged between the developing roller 12 and the developing blade 30 and conveyed to the surface of the photosensitive drum 5. As a result, the electrostatic latent image is developed and a toner image is formed.

The toner image is transferred to the recording medium 7 between the transfer roller 8 and the photosensitive drum 5, and then fixed by the fixing unit 9. The toner remaining on the surface of the photoreceptor 5 without being transferred is collected by the cleaning blade 10.
Voltages are applied to the developing roller 12, the charging roller 6, the transfer roller 8, and the like from power sources 18, 20, and 22, respectively, of the image forming apparatus.

Here, a DC voltage is applied to the charging roller 6 from the power supply 20. By using a DC voltage as the applied voltage, there is an advantage that the cost of the power supply can be kept low. There is also an advantage that no charging noise is generated.
The absolute value of the DC voltage to be applied is preferably the sum of the discharge start voltage of air and the primary charging potential of the surface of the member to be charged (photosensitive member surface). Usually, the discharge start voltage of air is about 600 to 700 V, and the primary charging potential of the photoreceptor surface is about 300 to 800 V. Therefore, the specific primary charging voltage is preferably 900 to 1500 V.

  Further, the electrophotographic image forming apparatus according to the present invention may be a color electrophotographic image forming apparatus provided with four members for image formation as shown in FIG. While the recording medium 7 moves in the direction of the arrow, the toner image is exposed between the photosensitive drum 5d and the transfer roller 8d, between the photosensitive drum 5c and the transfer roller 8c, between the photosensitive drum 5b and the transfer roller 8b, and between the photosensitive drum 5b and the transfer roller 8b. Transfer is performed sequentially between the body drum 5a and the transfer roller 8a. The toner image transferred to the recording medium 7 is fixed in the fixing unit 9. The charging rollers 6a, 6b, 6c, and 6d charge the photosensitive drums 5a, 5b, 5c, and 5d, respectively. In order to form a color electrophotographic image, toners of four colors of cyan, yellow, magenta and black are usually used. The four color toners may be transferred to the recording medium 7 in any order.

<Image evaluation>
The electrophotographic laser printer is for A4 portrait output, and an electrophotographic laser printer with a recording medium output speed of 160 mm / s and an image resolution of 600 dpi was prepared.
The photoreceptor is a reversal development type photosensitive drum in which an aluminum cylinder is coated with an OPC layer having a thickness of 22 μm, and the outermost layer is a charge transport layer using a modified polyarylate resin as a binder resin.

  The toner is made by polymerizing a random copolymer of styrene and butyl acrylate containing a charge control agent and a pigment mainly with wax, further polymerizing a thin polyester layer on the surface, and externally adding silica fine particles, etc., glass transition temperature 63 ° C., mass This is a polymerized toner having an average particle size of 6.5 μm.

<Initial image evaluation>
The charging member according to this example was mounted on the electrophotographic laser printer. The electrophotographic laser printer was placed in an N / N environment for 12 hours, and then an image was output in the N / N environment. A primary charging voltage of −1150 V was applied to the charging roller. As an image pattern, a halftone pattern (an image in which a horizontal line having a width of 1 dot and an interval of 2 dots is drawn in the direction perpendicular to the rotation direction of the photosensitive member) is used.

<Initial black potty rank>
The initial black spot rank was evaluated based on how the black spots caused by the protrusions blocking the laser beam appeared on the image. The more difficult the black spots are seen, the better the image and the higher the numerical value of the rank.

<Surface potential / rank>
Next, the surface potential after charging of the photoreceptor of the electrophotographic laser printer was measured, and the surface potential rank was evaluated. The photoreceptor surface potential is about the value obtained by subtracting the discharge start voltage in the air from the absolute value of the charging voltage. The charging capability of the charging member increases as the surface potential of the photoreceptor increases, and the rank value increases.

<Initial leak rank>
Further, a pinhole empty photoconductor for making a pinhole leak by making a small hole was prepared, and the initial leak crank of each charging member was evaluated using the pinhole empty photoconductor.
The pinhole empty photoconductor was prepared by making a hole perpendicular to the OPC layer of the photoconductor using a precision drill. The hole penetrated the OPC layer and reached the underlying aluminum cylinder. There were two types of holes with diameters of 0.5 mm and 0.3 mm. The holes of each size were randomly arranged on the surface of the OPC, and a total of 10 holes were formed with 5 pieces having a diameter of 0.5 mm and 5 pieces having a diameter of 0.3 mm.

  This pinhole empty photoconductor was incorporated into the electrophotographic laser printer, a halftone image was output, and the charging member of each example was evaluated. If there is a pinhole in the photoconductor, the electric charge easily flows from the charging member to the aluminum cylinder through the pinhole, the supply of the electric charge in the portion without the pinhole is insufficient, and a black band is easily generated on the halftone image. Become. The larger the pinhole size, the easier it is for the charge to flow in and black spots are more likely to occur. As the charging member, it is better that a black belt is hardly generated on the halftone image even if a pinhole is present.

<Early fine powder retention amount evaluation Maximum retention amount rank>
The retention amount when the charging member held the fine powder to the maximum was measured, and the maximum retention amount rank was evaluated.
In the charging member of the present invention, it is possible to protect the discharge surface of the charging member due to durability when a larger amount of fine powder is retained. The larger the holding amount, the better the maximum holding amount rank.

<Durable image evaluation durability rank>
Next, the state of occurrence of charging horizontal streaks when the charging member was repeatedly used was investigated, and the durability rank of the charging member was evaluated.
Using the electrophotographic laser printer, after continuously outputting 3000 patterns in which a horizontal line having a width of 2 dots and an interval of 98 dots is drawn in an N / N environment, the halftone image is output in the same environment. A pattern was output. Then, the roller was taken out, high pressure ion exchange water was sprayed with a high pressure water washer to wash the roller, and high pressure dry air was blown to drain the water. The cleaned roller was left in an N / N environment for 12 hours, and then the initial amount of fine powder held was maintained at the same amount as the initial value. The roller holding the fine powder was again left in the N / N environment for 12 hours, and then the initial image output, the 3000 sheet durable output, and the final halftone image output were performed again. As an evaluation standard of this example, it was observed how many times the above-mentioned durability was performed and when the last image was printed, horizontal streak-like image unevenness was observed on the halftone image.

実施例１の帯電部材は４回の耐久と再生を繰り返しても横スジ状の画像ムラの発生は無かった。横スジ状の画像ムラ評価ランクは５であった。

The charging member of Example 1 did not cause horizontal streak-like image unevenness even after repeated durability and reproduction four times. The horizontal streak-like image unevenness evaluation rank was 5.

<Evaluation of durable fine powder retention rate change rate Fine powder retention rate change rate rank>
In the durability test, the rate of change in fine powder retention before and after the first durability test was measured. A charging member that does not easily change the amount of fine powder retained even after performing an endurance test is easier to maintain chargeability and is a better charging member. The fine powder retention rate change rate rank was set according to the ratio of the fine powder retention amount after durability to the fine powder retention amount before durability. The measurement of the amount of fine powder retained after durability was in accordance with the initial evaluation of the amount of fine powder retained.

[Example 2 to Example 12]
The test was performed by changing the protrusion density of the conductive base layer and the amount of fine powder retained. All were rechargeable charging members. Table 13 below shows combinations of conductive base layer and fine powder.

表１３に記載の実施例の評価結果を表１４に示す。

Table 14 shows the evaluation results of the examples described in Table 13.

[Example 13 to Example 25]
The test was conducted by changing the size of the protrusions of the conductive base layer, the density of the protrusions, and the amount of fine powder retained. When the size of the protrusion was less than 3 μm or larger than 30 μm, a slight horizontal stripe-like image unevenness appeared after reproduction. Other charging members could be recycled and used repeatedly. Table 15 below shows combinations of conductive base layer and fine powder.

表１５に記載の実施例の評価結果を表１６に示す。

The evaluation results of the examples described in Table 15 are shown in Table 16.

[Example 26 to Example 67]
The test was performed by changing the material of the fine powder to be held to conductive tin oxide. When the size of the protrusion was less than 3 μm or larger than 30 μm, a slight horizontal stripe-like image unevenness appeared after reproduction. Other charging members also had the same tendency as when the fine powder was silica, and could be regenerated and used repeatedly. Table 17 below shows combinations of conductive base layer and fine powder.

表１７に記載の実施例の評価結果を表１８に示す。

The evaluation results of the examples described in Table 17 are shown in Table 18.

[Example 68 to Example 80]
The test was performed by changing the fluidity of the fine powder to be retained by the coupling agent treatment. When the amount of the coupling agent added in Example 1 was increased, the fluidity was improved, and when the amount was decreased, the fluidity was lowered. When the size of the protrusion was less than 3 μm or larger than 30 μm, a slight horizontal stripe-like image unevenness appeared after reproduction. Further, when the Carr's fluidity index is less than 40, a slight horizontal stripe-like image unevenness appears after reproduction. Other charging members could also be recycled and used repeatedly. Table 19 below shows combinations of conductive base layer and fine powder.

表１９に記載の実施例の評価結果を表２０に記載する。

The evaluation results of the examples described in Table 19 are shown in Table 20.

[Example 81 to Example 102]
The test was conducted by changing the flowability and the fine powder diameter of the fine powder to be held. When the size of the protrusion was less than 3 μm or larger than 30 μm, a slight horizontal stripe-like image unevenness appeared after reproduction. Further, when the Carr's fluidity index is less than 40, a slight horizontal stripe-like image unevenness appears after reproduction. Further, when the fine powder diameter was larger than 0.5 times the protrusion, a slight horizontal stripe-like image unevenness appeared after reproduction. Other charging members could also be recycled and used repeatedly. Table 21 below shows combinations of conductive base layer and fine powder.

表２１に記載の実施例の評価結果を表２２に示す。

Table 22 shows the evaluation results of the examples described in Table 21.

[Example 103 to Example 113]
The test was conducted by changing the fluidity and material of the fine powder to be retained. Further, the evaluation was performed by changing the material of the protrusion.
When PTFE (polytetrafluoroethylene) particles having a Carr's fluidity index of 10 were used, horizontal streak-like image unevenness appeared after reproduction. Other charging members could also be recycled and used repeatedly. Table 23 below shows combinations of conductive base layer and fine powder.

Although PTFE is non-tacky, it tends to agglomerate and is slightly inferior in fluidity, and Carr's fluidity index is small. Therefore, it is considered that aggregates are likely to adhere to the discharge surface of the charging member surface, causing horizontal streaks after regeneration.
Also, non-adhesive fine powder of melamine resin generated horizontal streaks due to regeneration after endurance. Compared with silica, conductive tin oxide, conductive zinc oxide, and insulating titanium oxide having the same amount of fine powder retention, the number of times of repeated use is small. This is presumably because the melamine resin is not an oxide, and fine powder deteriorates due to oxidation by the discharge during durability, and is fixed to the surface of the charging member, thereby reducing the discharging ability of the charging member.

表２３に記載の実施例の評価結果を表２４に示す。

Table 24 shows the evaluation results of the examples described in Table 23.

[Comparative Example 1]
The base layer 26 was used as the charging member of Comparative Example 1 as it was. This was evaluated in the same manner as in Example 1.
[Comparative Example 2]
The fine powder 1 was held with respect to the base layer 26 so that the area ratio of the fine powder holding amount was 2. Thus, a charging member of Comparative Example 2 was obtained. This was evaluated in the same manner as in Example 1.
[Comparative Examples 3 to 6]
With respect to the base layer 26, the charging member of Comparative Example 2 was changed to a fine powder material, a fine powder diameter, and a fine powder holding amount to hold the fine powder, and the charging member of Comparative Example 3 to Comparative Example 6 was obtained. Table 25 shows the changed fine powder material, fine powder diameter, and fine powder retention. These charging members were evaluated in the same manner as in Example 1.

[Comparative Example 7]
The base layer 1 was used as a charging member as it was. This was used as the charging member of Comparative Example 7. This was evaluated in the same manner as in Example 1.
[Comparative Example 8]
The base layer 11 was used as a charging member as it was. This was used as the charging member of Comparative Example 8. This was evaluated in the same manner as in Example 1.
[Comparative Example 9]
The base layer 27 was used as a charging member as it was. This was used as the charging member of Comparative Example 9. This was evaluated in the same manner as in Example 1.

[Comparative Example 10]
The fine powder 1 was held with respect to the base layer 27 so that the area ratio of the fine powder holding amount was 2. Thus, a charging member of Comparative Example 10 was obtained. This was evaluated in the same manner as in Example 1.
[Comparative Example 11]
The fine powder 24 was held with respect to the base layer 27 so that the area ratio of the fine powder holding amount was 2. Thus, a charging member of Comparative Example 11 was obtained. This was evaluated in the same manner as in Example 1.
[Comparative Example 12]
The fine powder 31 was held with respect to the base layer 1 so that the area ratio of the fine powder holding amount was 30. Thus, a charging member of Comparative Example 12 was obtained. This was evaluated in the same manner as in Example 1.
[Comparative Example 13]
The fine powder 31 was held with respect to the base layer 11 so that the area ratio of the fine powder holding amount was 30. Thus, a charging member of Comparative Example 13 was obtained. This was evaluated in the same manner as in Example 1.
[Comparative Example 14]
The fine powder 31 was held with respect to the base layer 26 so that the area ratio of the fine powder holding amount was 2. Thus, a charging member of Comparative Example 14 was obtained. This was evaluated in the same manner as in Example 1.
[Comparative Example 15]
The fine powder 31 was held with respect to the base layer 27 so that the area ratio of the fine powder holding amount was 2. Thus, a charging member of Comparative Example 15 was obtained. This was evaluated in the same manner as in Example 1.

[Comparative Example 16]
The base layer 28 was used as a charging member as it was. This was used as the charging member of Comparative Example 16. This was evaluated in the same manner as in Example 1.
[Comparative Example 17]
The fine powder 1 was held with respect to the base layer 28 so that the area ratio of the fine powder holding amount was 2. Thus, a charging member of Comparative Example 17 was obtained. This was evaluated in the same manner as in Example 1.
[Comparative Example 18]
The fine powder 31 was held with respect to the base layer 28 so that the area ratio of the fine powder holding amount was 2. Thus, a charging member of Comparative Example 8 was obtained. This was evaluated in the same manner as in Example 1.

The configuration of the comparative example is listed in Table 25 below.
Table 26 shows the evaluation results of the comparative examples as a list.
When no fine powder was used, clear horizontal streaks were generated in the image after durability, and the evaluation rank was 1. In addition, when a charging member having no protrusion was used, a severe horizontal streak-like image defect occurred after durability.

DESCRIPTION OF SYMBOLS 1 ............ Electroconductive support body 2 ............ Conductive base layer 3 ............ Projection 4 ............ ..Fine powder

Claims (4)

Having a conductive support and a conductive base layer provided on the outer periphery of the conductive support;
The conductive base layer is a charging member having insulating projections derived from particles on its surface,
Non-adhesive fine powder is held at the step portion between the insulating protrusion and the surface of the conductive base layer, and the fine powder has a number average particle size smaller than the number average particle size of the particles. A charging member.   The charging member according to claim 1, wherein the number average particle diameter of the particles is 3 μm or more and 30 μm or less.   The charging member according to claim 1, wherein the fine powder has a Carr's fluidity index of 40 or more and 98 or less. A step of dispersing particles in a curable liquid to form a coating liquid;
Applying the coating solution to the conductive base layer;
Impregnating the conductive base layer with the applied coating liquid;
Curing the impregnated curable liquid to fix the particles to the conductive base layer to create protrusions;
And a step of holding non-adhesive fine powder having a number average particle size smaller than the number average particle size of the particles at a step portion between the protrusion and the conductive base layer. .

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