JP2004300180A - Coating agent composition for conductive brush member, conductive brush raised fabric, conductive brush member, brush charging apparatus, cleaning apparatus and electrophotographic image-forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive brush member having uniform conductivity by coating a base fabric for a brush raised fabric using a specific coating agent composition for the conductive brush member. <P>SOLUTION: The coating agent composition for the conductive brush member comprises a polymer, an conductive compound and an aqueous medium. The viscosity is 3,000-100,000 mPa s and the thixotropic index is 1.5-10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a coating composition for a conductive brush member used for manufacturing a conductive brush member for a brush charging device, a cleaning device, and the like used in an electrophotographic image forming apparatus. More specifically, the present invention relates to a coating composition for a conductive brush member, which is applied to a base cloth constituting a conductive brush raising cloth to hold the brush bristles well.
Further, the present invention provides a conductive brush raising cloth obtained by using the coating composition for a conductive brush member, a conductive brush member including the conductive brush raising cloth, and the conductive brush member. The present invention relates to a brush charging device, a cleaning device, and an electrophotographic image forming apparatus including the same.
[0002]
[Prior art]
In electrophotographic image formation such as copying machines and printers, the surface of an electrostatic latent image carrier such as a photoconductor is charged by a charging device, and then the charged latent photoconductor is exposed to form an electrostatic latent image. The electrostatic latent image is formed on the surface of the photoreceptor, visualized by developing the electrostatic latent image with toner, and the visible image is transferred to a transfer material such as paper.
As a charging unit, a brush charging device has been awarded because it does not deteriorate the surface of the photoreceptor, generates very little ozone that adversely affects the human body, and has a simple structure.
In the brush charging device, a conductive brush member is fixed to a conductive support member, and the support member is connected to an applied potential to charge the brush. The conductive brush member is formed by applying a conductive resin to the other surface of a base cloth in which conductive fibers are planted on one surface (Patent Document 1), or a back coat agent is applied to a base cloth portion in which conductive fibers are planted. An impregnated one (Patent Document 2) is known.
[0003]
[Patent Document 1]
Japanese Utility Model Application Laid-Open No. 62-164357 [Patent Document 2]
JP-A-7-64372
However, some problems have been pointed out in the brush charging device currently used. That is, first, there is a problem that the conductivity is not uniform over the entire brush charging device. Second, problems such as brush bristles coming off the brush raising cloth and contaminating the inside of the electrophotographic image forming apparatus have been pointed out. For the former, attempts have been made to reduce the fluctuation of the resistance value of the conductive fibers used in the conductive brush member constituting the brush charging device, but no satisfactory results have been obtained. Also, no sufficient solution has been found for the latter problem. Further, in the manufacturing process, when hair breakage occurs in the step of cutting the base fabric having the brush bristles into a predetermined shape, the step of winding and fixing the base fabric of the predetermined shape around a shaft includes removing the brush bristles on the back surface. There is a problem that the contact resistance between the brush base cloth and the shaft becomes non-uniform.
Therefore, there is a need for a brush charging device that does not have these problems.
[0005]
[Problems to be solved by the invention]
The present inventors have conducted intensive studies on the conductive brush member constituting the brush charging device. As a result, in manufacturing the conductive brush member, the viscosity was 3,000 to 100,000 mPa · s, and the thixotropic index was 1 By coating the base fabric for a brush raising cloth using the coating composition for a conductive brush member of 0.5 to 10, a conductive brush member having uniform conductivity can be obtained. It has been found that a charging brush free from the above problems can be obtained by using a brush member, and the present invention has been completed.
[0006]
[Means for Solving the Problems]
A first aspect of the present invention is a conductive brush member containing a polymer, a conductive compound, and an aqueous medium, having a viscosity of 3,000 to 100,000 mPa · s and a thixotropy index of 1.5 to 10. The present invention relates to a coating composition.
The second aspect of the present invention relates to the coating composition for a conductive brush member according to claim 1, further comprising a thickener.
The third aspect of the present invention relates to the coating composition for a conductive brush member according to claim 1 or 2, further comprising non-conductive inorganic fine particles.
A fourth aspect of the present invention relates to a conductive brush raising cloth obtained by applying the coating composition for a conductive brush member according to any one of claims 1 to 3 to a base cloth.
A fifth aspect of the present invention relates to a conductive brush member provided with the conductive brush raising cloth according to claim 4.
A sixth aspect of the present invention relates to a brush charging device including the conductive brush member according to the fifth aspect.
A seventh aspect of the present invention relates to a cleaning device including the conductive brush member according to the fifth aspect.
An eighth aspect of the present invention relates to an electrophotographic image forming apparatus including the brush charging device according to the sixth aspect or the cleaning device according to the seventh aspect.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The coating composition for a conductive brush member of the present invention is obtained by dispersing 100 parts by weight of a polymer and 20 to 200 parts by weight of a conductive compound in an aqueous medium.
[0008]
The composition of the polymer that can be used is not particularly limited, but a preferred example is a copolymer of an aromatic vinyl monomer and a conjugated diene monomer. Specific examples thereof include a styrene-butadiene copolymer. There is no particular limitation on the monomer composition ratio or molecular weight of the copolymer. The polymer used in the present invention can be produced by a known method.
[0009]
Examples of the conductive compound include carbon black, carbon fiber, metal powder, metal whiskers, metal oxides, and semiconductor materials. By adjusting the amount of these conductive compounds, a desired resistance value can be obtained.
The compounding amount of the conductive compound is 20 to 200 parts by weight, preferably 50 to 150 parts by weight based on 100 parts by weight of the polymer. When the amount is less than the above lower limit, the conductivity is not sufficient. On the other hand, when the amount exceeds 200 parts by weight, it is difficult to uniformly apply the composition to the base fabric.
[0010]
Water and water-miscible organic solvents are used as the aqueous medium. Examples of the organic solvent miscible with water include alcohols such as methanol, ethanol, and propanol, and ketones such as acetone and methyl ethyl ketone. Water is preferably used from the viewpoint of economy and safety.
The amount of the aqueous medium is not particularly limited as long as it can be controlled within the specified range of the viscosity and the thixotropic index of the conductive brush member coating composition of the present invention, but is usually the solid content of the conductive brush member coating composition. The amount is such that the concentration is about 30 to 65% by weight.
[0011]
The viscosity of the coating composition for a conductive brush member of the present invention needs to be in the range of 3,000 to 100,000 mPa · s. When the viscosity is less than the above lower limit, when applied to the back surface of the raised cloth as the base cloth of the conductive brush member, the coating composition for the conductive brush member penetrates through the raised cloth and further to the upper part of the brush bristles due to surface tension. Things stick. As a result, adjacent brush bristles are adhered to each other, and the flexibility of the brush bristles is impaired, so that the brush charging is not performed smoothly, and also the conductivity of the brush member varies depending on the location of the brush member. On the other hand, if the upper limit is exceeded, it becomes difficult to apply the composition uniformly. As a result, a portion where the holding power of the brush bristles is insufficient and the brush bristles are detached. As a result, not only the brush is not smoothly charged, but also a problem that causes a variation in conductivity depending on the location of the brush member. is there. Preferably, the viscosity is in the range of 5,000 to 50,000 mPa · s. In order to adjust the viscosity of the conductive brush member coating composition to the above range, the concentration of the conductive brush member coating composition is adjusted, and the particles of the polymer particles constituting the conductive brush member coating composition are adjusted. Although there are methods such as adjusting the diameter, use of a thickener described later is preferred.
[0012]
As described above, in order to uniformly apply the coating composition for a conductive brush member, and to prevent the coating composition from adhering to the upper portion of the brush bristles, a certain viscosity is required. Uniform application becomes difficult. Therefore, the thixotropic index of the coating composition for a conductive brush member of the present invention must be in the range of 1.5 to 10.
When the thixotropy index is less than the lower limit, it is difficult to perform the application smoothly because the viscosity at the time of applying the coating composition for the conductive brush member is high, and it is difficult to apply the composition to a uniform thickness. On the other hand, if the upper limit is exceeded, it becomes difficult to apply the coating to a uniform thickness. In any case, the brush bristles cannot obtain a raised cloth held by the base cloth with a uniform holding force, causing the brush bristles to be detached during use of the conductive brush member, and the brush charging to be smooth. It is a cause that is not performed. The preferable range of the thixotropic index is 2.0 to 5.0. In order to adjust the thixotropic index of the coating composition for the conductive brush member to the above range, there is a method of adjusting the amount of the conductive compound, and the like.However, the use of a thickener and non-conductive inorganic fine particles described later is used. preferable.
[0013]
The coating composition for a conductive brush member of the present invention preferably further contains a thickener in addition to the polymer, the conductive compound and the aqueous medium. By including a thickener, the viscosity and thixotropic index can be easily controlled.
[0014]
The thickener is not particularly limited, but examples thereof include vinyl alcohol polymers such as polyvinyl alcohol and various modified products thereof; sodium polyacrylate, polyammonium ammonium, and acrylic acid-alkyl methacrylate copolymer. Polyacrylic acid polymer; saponified copolymer of vinyl acetate and acrylic acid, methacrylic acid or maleic anhydride; alkyl cellulose such as methyl cellulose, hydroxyalkyl cellulose such as hydroxyl ethyl cellulose, hydroxyl propoxyl methyl cellulose, alkyl hydroxy Cellulose derivatives such as alkylcellulose and carboxymethylcellulose; polyacrylamide, polyethylene oxide; polyalkylene glycol; polyvinylpyrrolidone; Rujon; alkyl starches, carboxymethyl starch, starch derivatives such as oxidized starch gum arabic, tragacanth; and the like can be given. Among these, use of carboxymethylcellulose, hydroxyethylcellulose, or an acrylic acid-alkyl methacrylate copolymer is preferred from the viewpoint of workability and the like.
[0015]
The amount of the thickener may be appropriately determined so as to obtain the desired viscosity and thixotropic index, but is usually 0.01 to 10 parts by weight, preferably 0.1 to 10 parts by weight, per 100 parts by weight of the polymer. It is in the range of 1 to 5 parts by weight. If the amount is outside the above range, the desired viscosity and thixotropy index cannot be obtained, and a coating film having a constant thickness may not be obtained from the coating composition for the conductive brush member.
[0016]
The thixotropic index can be easily controlled by introducing non-conductive inorganic fine particles into the coating composition for a conductive brush member of the present invention.
The non-conductive inorganic fine particles are not particularly limited as long as they are water-insoluble metal oxide fine particles, and examples thereof include sodium montmorillonite (aluminum silicate), silica, and bentonite.
The amount of the non-conductive inorganic fine particles is usually in the range of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the polymer.
[0017]
The coating composition for a conductive brush member of the present invention can be prepared by mixing the essential constituents of a polymer, a conductive compound and an aqueous medium by any method. From the viewpoint of ensuring the properties, it is preferable to prepare by mixing an aqueous dispersion of a polymer, an aqueous dispersion of a conductive compound and, if necessary, an aqueous medium.
[0018]
The aqueous dispersion of the polymer may be an emulsion or a dispersion. The solid concentration is not particularly limited, but is usually 30 to 55% by weight. The polymer emulsion and dispersion can be obtained by a known polymerization method or the like. Examples of the dispersion medium include water and an organic solvent miscible with water.
[0019]
The aqueous dispersion of the conductive compound can be obtained by dispersing the conductive compound in an aqueous medium by an appropriate method. Examples of the method of dispersion include a method of simultaneously stirring and dispersing media such as a ball mill and a bead mill, and a method of using rotating blades such as a disper.
The solid content concentration of the aqueous dispersion of the conductive compound is not particularly limited, but is usually 20 to 50% by weight. If the solid content is too low, it becomes difficult to impart a desired viscosity and a thixotropic index to the coating composition for the conductive brush member.
Examples of the aqueous medium include water and an organic solvent miscible with water, as in the preparation of the aqueous dispersion of the polymer.
[0020]
The method of mixing the aqueous dispersion of the polymer, the aqueous dispersion of the conductive compound, and the thickener and / or non-conductive inorganic fine particles used as necessary is not particularly limited, and they may be mixed in any order. Good.
In order to obtain a uniform coating composition for the conductive brush member, the mixing is preferably performed with stirring. Examples of the stirring method include a method using a rotary blade type stirrer.
[0021]
When using a water-soluble polymer compound as a thickener, which is an optional component, it is preferable to prepare by adding an aqueous dispersion of a polymer, an aqueous dispersion of a conductive compound, and a water-soluble polymer compound in this order. .
[0022]
The conductive brush raising cloth of the present invention is obtained by applying the coating composition for a conductive brush member of the present invention to the other surface of a raising cloth in which a conductive brush thread is planted on one surface of a base cloth. .
[0023]
The conductive brush yarn can be used without any particular limitation as long as it is conventionally used in this field. For example, it is a fiber having a thickness of 1 denier to 20 denier in which nylon is used as a base material, carbon is blended, and the volume resistivity is adjusted to 10 ⁴ to 10 ⁸ Ω · cm.
[0024]
The base fabric can also be used without particular limitation as long as it is conventionally used in this field, such as a polyester base fabric.
[0025]
The method for producing a raised cloth in which conductive brush yarn is planted on one surface of the base cloth is not particularly limited. For example, when forming a base cloth portion made of twill weave or the like of polyester yarn, a pile cloth is formed using conductive yarn, and a pile cloth is obtained by cutting the pile yarn between the two cloths. Can be.
[0026]
The method of applying the coating composition for the conductive brush member is not particularly limited, and a brush is applied to a brushed cloth using a flat brush, a roll brush, a sponge brush, or a roll coater using a doctor knife or the like. Examples of the method include a method of applying a brush cloth to a coating composition for a conductive brush member, a method of spraying a coating composition for a conductive brush member, and the like, in addition to a method and a paint roller coating method.
[0027]
The coating amount of the coating composition for the conductive brush member is usually 20 to 500 g, preferably 50 to 300 g per 1 m2 of the brushed cloth after drying. It is such an amount. If the amount of application is too small, the holding power for the brush bristles decreases. Conversely, if the coating amount is too large, the flexibility of the raising cloth is undesirably reduced.
[0028]
After the coating, the coating is left at room temperature or preferably dried by heating. The drying method and drying conditions (drying temperature, drying time, etc.) are not particularly limited, but it is usually preferable to dry at a temperature of from room temperature to 200 ° C. for 5 minutes to 24 hours, and particularly at a temperature of 50 to 120 ° C. It is desirable to heat and dry for 10 hours.
[0029]
The conductive brush member of the present invention is obtained by fixing the brush for the conductive brush member of the present invention to a conductive support member. The brush is charged by connecting this support member to the applied potential. At this time, the brush bristles and the conductive support member are electrically connected by the conductive compound contained in the coating composition for the conductive brush member.
[0030]
The method for fixing the raised cloth to the support member is not particularly limited, and examples thereof include a method using an adhesive or a pressure-sensitive adhesive, and a method for mechanically fixing with a screw or the like.
[0031]
For example, a conductive brush raising cloth is wound around a conductive metal core bar, and the raising cloth is bonded and fixed using a conductive adhesive. The length of the core is not particularly limited, but is usually 100 to 600 mm and a diameter of 2 to 50 mm.
[0032]
The brush charging device of the present invention includes the conductive brush member of the present invention. Further, the cleaning apparatus of the present invention is an apparatus for removing toner remaining on the surface of a photoreceptor without being transferred to a transfer material such as paper in an electrophotographic image forming apparatus. Of the conductive brush member.
[0033]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples. Parts and percentages in the examples are by weight unless otherwise specified.
[0034]
The method for preparing the conductive brush raising cloth and the method for evaluating the obtained characteristics are as follows.
(1) Preparation method of conductive brush raising cloth Volume obtained by spinning 6-nylon containing carbon into 6 denier on a base cloth formed by twill weaving a polyester fiber obtained by twisting two yarns having a thickness of 40. Conductive yarn having a specific resistance value of 10 ⁶ Ω · cm is planted by a W weaving method at a planting density of 6000 fibers / square inch to obtain a conductive brush raising cloth.
The coating composition for a conductive brush member was applied to the surface of the brushing cloth having no bristles with a roll coater so that the coating amount was 200 g in solid content per square meter of the brushing cloth. Dry for 8 hours in a dryer at 60 ° C. to obtain a conductive brush raising cloth.
The conductive brush raising cloth is cut into a ribbon having a width of 20 mm and a length of 400 mm such that the warp direction of the brush raising cloth is the longitudinal direction. The obtained ribbon-like raised cloth is wound at an angle of 30 ° with respect to the axial direction of the metal core (a metal rod made of SUS304 having a length of 250 mm and a diameter of 10 mm) and excluding a part of each 25 mm from both ends of the metal core. Then, the brushed cloth is bonded and fixed using a conductive adhesive. The outer diameter of the brush is shirred to 18 mm to prepare a brush. At this time, the distance from the center of the core bar to the tip of the brush bristles is 9 mm, and the distance from the surface of the core bar to the tip of the brush bristles is 4 mm.
(2) At a viscosity of 23 ° C., a BM type viscometer, rotor No. 4 at 12 rpm.
(3) Thixotropy index The value obtained by dividing the value of the viscosity measured at 12 rpm by the value of the viscosity measured at a rotation speed of 60 rpm by the same method as the viscosity measurement is defined as the thixotropic index.
(4) One terminal of the conductive resistance measuring device of the conductive brush member is connected to one end of the core of the brush, and the other end is connected to a copper metal plate (200 mm long, 5 mm wide, 0.1 mm thick). . At a distance of 8 mm in the radial direction from the center of the metal core, that is, at a distance of 3 mm from the surface of the metal core (at this time, since the length of the bristle is 4 mm from the surface of the metal core, a part of the copper metal plate is used. The copper metal plate is placed in a direction in which the axial direction of the metal core is perpendicular to the longitudinal direction of the copper metal plate, and the resistance value is measured. The outline of the measuring method is shown in FIG. This measurement is performed 40 times (the length of the core metal is 200 mm / the width of the copper metal plate is 5 mm) while being shifted by 5 mm in the axial direction, starting from one end of the core metal in the axial direction. The maximum value, the minimum value, and the average value are obtained for these 40 measurement values.
[0035]
Example 1
100 parts of ion-exchanged water, 30 parts of styrene, 60 parts of 1,3-butadiene, 3 parts of a nonionic surfactant (trade name “Emulgen 985” manufactured by Kao Corporation) and 2.75 parts of potassium peroxide are stirred and mixed. Thus, a monomer emulsion for polymerization was obtained. The monomer emulsion for polymerization was placed in a reactor, and the temperature was raised to 70 ° C. to start polymerization. One hour after the start of the polymerization, the temperature of the system was raised to 80 ° C., and then the polymerization was continued for 5 hours. The polymerization conversion was 98%. Next, after removing the residual monomer by a conventional method, the solid content concentration was adjusted to 40% to obtain a copolymer latex (1). The particle size of the latex was 0.185 μm.
To 45 parts of this copolymer latex (1) (in terms of solid content), 55 parts of an aqueous dispersion of carbon having a solid content of 35% and 0.5 part of carboxymethylcellulose were mixed to form a coating composition for a conductive brush member. The product (1) was obtained. The viscosity of this composition was 13,000 mPa · s, and the thixotropic index was 3.7.
A conductive brush member was prepared using this coating composition (1) for a conductive brush member, and the resistance was measured. The average value was 2.3 × 10 ⁵ Ω, and the maximum value was 4.5. × 10 ⁵ Ω, and the minimum value was 1.2 × 10 ⁵ Ω. That is, the ratio between the maximum value and the average value (maximum value / average value) is 1.96, and the ratio between the average value and the minimum value (average value / minimum value) is 1.92, both of which are single digits. The variation in resistance value was small.
In addition, when the raised cloth was observed, the coating agent did not penetrate into the raised portion.
[0036]
Example 2
To 55 parts of the copolymer latex (1) (in terms of solid content), 45 parts of the carbon dispersion liquid used in Example 1, 0.5 part of carboxymethylcellulose, and 0.5 part of silica fine particles (average particle diameter: 20 μm) were mixed. A coating composition (2) for a conductive brush member was obtained. The viscosity of this composition was 25,000 mPa · s, and the thixotropic index was 2.8.
Using this coating composition (2) for a conductive brush member, a conductive brush member was prepared and its resistance was measured. The average value was 4.3 × 10 ⁶ Ω, and the maximum value was 8.3. × 10 ⁶ Ω, and the minimum value was 9.8 × 10 ⁵ Ω. That is, the ratio between the maximum value and the average value (maximum value / average value) is 1.93, the ratio between the average value and the minimum value (average value / minimum value) is 4.39, and each is a single digit. The variation in resistance value was small.
When the brushed cloth was observed, the brushed portion did not penetrate the coating agent for the conductive brush member.
[0037]
Comparative Example 1
The latex obtained in Example 1 was adjusted to a solid content of 25%, and 45 parts of this latex (in terms of solid content) was mixed with 55 parts of an aqueous dispersion of carbon having a solid content of 35% to form a conductive brush member. Coating composition (3) was obtained. The viscosity of this composition was 700 mPa · s, and the thixotropy index was 1.1.
A conductive brush member was prepared using this coating composition (3) for a conductive brush member, and the resistance was measured. The average value was 4.7 × 10 ⁶ Ω, and the maximum value was 6.5 ×. 10 ⁶ Ω, and the minimum value was 2.2 × 10 ⁵ Ω. That is, the ratio between the maximum value and the average value (maximum value / average value) was 1.38, which was one digit, but the ratio between the average value and the minimum value (average value / minimum value) was as large as 21.36. It can be seen that there is a portion where the resistance value is low.
When the raised cloth was observed, it was found that the coating composition for the conductive brush member had penetrated into the raised portions, and the brush bristles were grouped.
[0038]
Comparative Example 2
A conductive brush member coating composition (4) was obtained in the same manner as in Example 2 except that 0.5 parts of silica fine particles were not added. The viscosity of this composition was 10,000 mPa · s, and the thixotropy index was 1.2.
A conductive brush member was prepared using this coating composition (4) for a conductive brush member, and the resistance was measured. The average value was 5.2 × 10 ⁵ Ω, and the maximum value was 8.5. × 10 ⁶ Ω, and the minimum value was 3.1 × 10 ⁴ Ω. That is, the ratio between the maximum value and the average value (maximum value / average value) is 16.35, and the ratio between the average value and the minimum value (average value / minimum value) is 16.77, which are both large, and the resistance value is large. You can see that it varies.
In addition, when the raised cloth was observed, it was observed that the coating composition for the conductive brush member penetrated into the raised portion, and the brush bristles were grouped.
[0039]
From the above results, the following can be understood.
The conductive brush (Comparative Example 1 and Comparative Example 2) obtained by using the coating composition for a conductive brush member whose viscosity and thixotropic index are out of the ranges specified in the present invention is a coating composition for a conductive brush member. Penetrated to the raised part or the tip of the brush, and grouped the brush bristles. For this reason, the conductivity varies depending on the location of the conductive brush. On the other hand, the conductive brush obtained by using the coating composition for a conductive brush member of the present invention exhibits uniform conductivity throughout the conductive brush.
[0040]
【The invention's effect】
According to the present invention, a conductive brush exhibiting uniform conductivity can be obtained by using the coating composition for a conductive brush member. Using this conductive brush, it is possible to obtain a brush charging device and a cleaning device having uniform conductivity and free from problems such as hair loss.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a method for measuring the conductivity of a conductive brush member.

Claims (8)

A coating composition for a conductive brush member comprising a polymer, a conductive compound and an aqueous medium, having a viscosity of 3,000 to 100,000 mPa · s and a thixotropy index of 1.5 to 10. The coating composition for a conductive brush member according to claim 1, further comprising a thickener. The coating composition for a conductive brush member according to claim 1, further comprising non-conductive inorganic fine particles. A conductive brush raising cloth obtained by applying the coating composition for a conductive brush member according to claim 1 to a base cloth. A conductive brush member comprising the conductive brush raising cloth according to claim 4. A brush charging device comprising the conductive brush member according to claim 5. A cleaning device comprising the conductive brush member according to claim 5. An electrophotographic image forming apparatus comprising the brush charging device according to claim 6 or the cleaning device according to claim 7.

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