JP4589137B2 - How to apply fine particles - Google Patents

Description

  The present invention relates to a method for applying fine particles that can be suitably used for manufacturing a conductive roll used in a process cartridge, an electrophotographic apparatus, and the like.

  Conventionally, a number of methods are known as electrophotographic methods. In general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the latent image is formed with toner. It is developed to make a visible image, and if necessary, the toner image is transferred to a transfer material such as paper, and then the toner image is fixed on the transfer material such as paper by heat and pressure to obtain a copy. is there. In addition, toner particles that are not transferred onto the transfer material but remain on the photoconductor are removed from the photoconductor by a cleaning process.

  Conventionally, a corona charger has been used as a charging device for electrophotography. In recent years, contact charging devices have been put to practical use instead. This is intended for low ozone and low power, and among them, a roller charging method using a conductive roller as a charging member is particularly preferably used from the viewpoint of charging stability.

  In roller charging, a conductive elastic roller is brought into pressure contact with a member to be charged, and a voltage is applied thereto to charge the member to be charged.

  Specifically, since charging is performed by discharging from a charging member to an object to be charged, charging is started by applying a voltage higher than a certain threshold voltage. For example, when a charging roller is pressed against an organic photoreceptor (OPC photoreceptor) having a thickness of 25 μm, the surface potential of the photoreceptor rises if a voltage of about 640 V or more is applied. Beginning and thereafter, the photoreceptor surface potential increases linearly with a slope of 1 with respect to the applied voltage. Hereinafter, this threshold voltage is defined as the charging start voltage Vth.

  That is, in order to obtain the photoreceptor surface potential Vd required for electrophotography, the charging roller requires a DC voltage higher than Vd + Vth, which is more than necessary. A method of charging by applying only the DC voltage to the contact charging member in this way is called DC charging.

  However, in DC charging, the resistance value of the contact charging member fluctuates due to environmental fluctuations, etc., and Vth fluctuates when the thickness of the surface of the photoconductor changes due to the photoconductor being scraped. In some cases, it is difficult to control to a desired value.

  For this reason, as a method for further uniformizing the charging, for example, an AC in which a voltage obtained by superimposing an AC component having a peak-to-peak voltage of 2 × Vth or more on a DC voltage corresponding to a desired Vd is applied to the contact charging member. A charging method is used. This is for the purpose of smoothing the potential due to AC, and the potential of the charged body converges to Vd, which is the center of the peak of the AC voltage, and is not affected by disturbances such as the environment. In recent years, contact charging has been widely used in which a roller-shaped charging member is brought into contact with an image carrier to charge the surface of the image carrier. The contact charging member has advantages such as a simple structure and a very small generation amount of ozone.

  As the conductive member for contact charging, a structure is known in which a conductive seamless tube is covered on the outer periphery of a conductive metal core to form a surface layer. Patent Document 1 discloses a conductive member in which an iron core is inserted into a multilayer seamless tube having a layer structure having different conductivity, and a method for manufacturing the same.

  However, a thermoplastic resin is used for the surface layer of the conductive roll obtained by such a method, and when the crosslinking density of the thermoplastic resin is low and the surface hardness is not sufficient, depending on the state of use, Toner, external additives, and photoconductor shavings may adhere to the surface and cause image defects.

  As means for solving this, Patent Document 2 proposes a method of reducing and smoothing the surface roughness (Rz; ten-point average roughness). Here, a resin component containing at least a fluorine-modified acrylate resin and a fluorinated olefin resin and / or a non- (fluorine-modified) acrylate resin is used.

  However, when a seamless tube based on a thermoplastic elastomer is produced, because of the softness of the characteristics, simply reducing the surface roughness (Rzjis; 10-point average roughness) and smoothing it results in adhesion of the shaving powder on the photoreceptor. It was not sufficient to improve image defects.

  On the other hand, in Patent Document 3, as another means for preventing toner and external additives from adhering to the roll surface, cleaning is performed by pressing a sponge, a brush or a blade against a charging roller with an appropriate pressing pressure, and charging capability. A method of maintaining the above has been proposed.

  However, in the configuration as described above, in the case of a blade, a container for storing exclusive removal toner is required, which may limit the miniaturization of the apparatus. In the case of a sponge or brush, the amount of toner confined in bubbles When the amount exceeds a certain amount, there is a problem that the cleaning ability is lowered and the adhesion preventing effect is reduced.

  Therefore, Patent Document 4 proposes a method of reducing the adhesion of toner and external additives by applying various inorganic compounds on the roller surface and improving the surface property of the roller.

As a method for applying the powder to the surface of the member, a method of directly coating the powder on the surface of the member or a method of spraying the powder onto the surface of the member with air is known. In addition, as a method for applying powder (lubricant) to the developing sleeve, in Patent Document 5, the powder supplied to the application member such as an application roller is moved to the application member, and further, a grinder or the like is used. A powder coating method is disclosed in which the powder on the surface is uniformly regulated by the regulating means.
Japanese Patent Laid-Open No. 1993-96648 JP 2000-137369 A JP-A-6-149020 JP 2002-31958 A JP 2003-57941 A

  However, when the method of directly spraying the powder onto the surface of the member or the method of spraying the powder onto the surface of the member with air is used for powder coating on the conductive roll for charging, unevenness due to coating tends to occur. The effect of preventing adhesion of toner or the like over the whole is reduced. Furthermore, when the method of leveling the powder supplied to the surface of the member and forming a uniform powder layer on the surface of the member is used for powder application to the conductive roll, the material of the member used for leveling the powder Depending on the structure, the leveling effect may not be sufficient, and the surface of the conductive roll may be damaged.

  Accordingly, an object of the present invention is to provide a coating method that can uniformly apply powder (fine particles) to the entire surface of a conductive roll used as a charging member. A further object of the present invention is to provide a process cartridge for an electrophotographic apparatus using a conductive roll produced by such a coating method as a charging member. Another object of the present invention is to provide an electrophotographic apparatus using a conductive roll produced by such a coating method as a charging member.

The coating method according to the present invention is a coating method for coating fine particles on the surface of a conductive roll having a cored bar and an elastic layer provided on the cored bar.
Supplying inorganic fine particles to at least a part of the surface of the conductive roll;
A step of wiping member made of a fiber by relatively sliding, securing the inorganic fine particles supplied to the surface to the surface with respect to the inorganic fine particles is supplied electrically conductive surface of the roll,
Have
The diameter of the fibers of the wiping member is 5 μm or less, and the inorganic fine particles have an average particle size of 0.01 μm or more and less than 4.0 μm as measured by a laser light scattering method, and the conductive roll of the wiping member This is a fine particle coating method characterized in that the pressing pressure on the surface is 0.02 kg / cm ² or more and less than 0.2 kg / cm ² .

The process cartridge according to the present invention at least integrally supports an electrophotographic photosensitive member and a charging member that is disposed in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage. In process cartridges that are detachable,
The process cartridge is characterized in that the charging member is made of a conductive roll having fine particles on the surface by the above-described coating method.

An electrophotographic apparatus according to the present invention includes an electrophotographic photosensitive member, a charging member that is disposed in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage, an exposure unit, a developing unit, and a transfer unit. In the device
The charging member is composed of a conductive roll having fine particles on the surface by the coating method described above.
This is an electrophotographic apparatus.

  According to the coating method of the present invention, adhesion of toner, external additives, and the like to the roll surface is reduced, and further, image defects due to adhesion of scraping powder on the photoreceptor are prevented, and charging is performed well from the beginning to the end of the usage period. An electrically conductive roll can be obtained. Furthermore, it is possible to maintain a desired charging function with high durability by incorporating a conductive roll having an anti-adhesion effect by applying fine particles on the surface as a charging member into an electrophotographic apparatus.

  In the coating method of the present invention, fine particles (powder) for obtaining an adhesion preventing effect are supplied to at least a part of the surface of the conductive roll, and then the wiping member is slid with respect to the surface of the conductive roll. In this way, the fine particles are uniformly distributed and fixed.

This wiping member can be made of fibers having a thickness of (diameter) of 5 μm or less and having various structures in which a wiping surface is formed from a cloth satisfying desired physical properties such as mechanical strength for wiping.

  The structure of the conductive roll used in the coating method of the present invention is not particularly limited, but it is seamless made of an elastic body containing a thermoplastic elastomer in order to uniformly and firmly fix various powders having an adhesion preventing effect. A conductive roll having a tube is preferred.

  Any thermoplastic elastomer may be used as long as it can be extruded. Specifically, styrene-butadiene-styrene (SBS) and styrene-butadiene-styrene water additive (SEBS), polyethylene, polypropylene , Saturated polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyether, polyamide, polycarbonate, polyacetal, acrylonitrile butadiene styrene, polystyrene, high impact polystyrene (HIPS), polyurethane, polyphenylene oxide, polyvinyl acetate, polyvinyl fluoride Vinylidene chloride, polytetrafluoroethylene, acrylonitrile-butadiene-styrene resin (ABS), acrylonitrile-ethylene / propylene Rubber - styrene resins (AES) and acrylonitrile - acrylic rubber - styrene resins and acrylic resins such as styrene resin (AAS), vinyl chloride resin, vinylidene chloride resin, the resin and copolymers and the like are preferable.

  The seamless tube for the conductive roll is obtained by, for example, kneading a conductive pigment such as thermoplastic elastomer and carbon black together with necessary additives, then pelletizing, and then forming the resulting pellet into a seamless tube by an extruder. Obtainable. Then, the formed seamless tube can be coated on a support member such as a core bar to obtain a conductive roll.

  The fine particles may be any material as long as they can be attached to the surface of the conductive roll to obtain an adhesion preventing effect such as toner, and the desired function as a charging member of the conductive roll can be obtained by applying fine particles. Fine particles made of various inorganic compounds can be used. Furthermore, fine particles made of layered compounds such as hydrotalcite, molybdenum disulfide, tungsten disulfide, boron nitride, silicon nitride, bentonite, zeolite, and carbon are more easily formed on the surface of the conductive roll. preferable. That is, in the present invention, since a powder coating film is formed by a dry method, a layered compound having a layered structure and less coating unevenness is considered to be more preferable.

  A layered compound is a general term for a material in which atoms that are strongly bonded two-dimensionally form a plate-like layer and these layers are stacked to form a crystal.

  As the particle diameter of the coated powder, an average particle diameter measured by a laser light scattering method is preferably 0.01 μm or more and less than 4 μm. If the particle size is larger than 4 μm, it is difficult to fix on the roller surface, the adhesion preventing effect is reduced, and problems such as image unevenness also occur. Further, when the particle size is smaller than 0.01 μm, it becomes difficult to apply uniformly and the roller surface is damaged.

  Various application methods can be selected, but there is a method in which powder is adsorbed on an adhesive roller, a conductive roll is brought into direct contact with the fine particle adhesion surface of the adhesive roller, the adhesive roller is rotated, and uniform application is performed. It is effective.

  The diameter of the fiber which the wiping member which is a member which rubs a roll surface has is 5 micrometers or less. Use of fibers larger than 5 μm is not preferable because the roll surface is damaged regardless of the pressing pressure. In addition, image defects due to non-uniformity of the inorganic compound on the roll surface also occur. A wiping member can be formed by forming a wiping surface from a cloth made of such ultrafine fibers, and the thickness of the cloth is preferably 0.2 to 5 mm. Note that the wiping member may be used in a form in which a wiping surface is formed by supporting the wiping member with an appropriate base as necessary and covering the surface of the base with this cloth.

  Specific examples of the type of fiber include viscose, acetate, nylon, vinylon, polyacrylonitrile, polyvinyl chloride, polyester, polyethylene, polypropylene, polyurethane, and polychlore. Among these, polyester fiber having high heat resistance and high wear resistance is considered preferable.

The pressing force of the wiping member on the roll surface is preferably 0.02 kg / cm ² or more and less than 0.2 kg / cm ² . If the pressing pressure is less than 0.02 kg / cm ² , the lump or layer of the applied powder is not crushed even if it takes time, and it becomes difficult to rub the inorganic compound uniformly on the roller surface. On the other hand, if it is 0.2 Kg / cm ² or more, rubbing unevenness due to strong contact with the roller surface will occur.

  As a method for measuring the pressing force of the wiping member, a push-pull gauge can be directly pressed against the member and visually confirmed. The physical property value of the roll surface after application is preferably 65 ° to 135 ° in water contact angle. In the case of hydrophobic powder, the powder is not completely fixed when it is larger than 135 °, and in the case of hydrophilic powder, the powder is not completely fixed when it is smaller than 65 °. Even in this case, the effect of reducing adhesion is reduced.

By incorporating a conductive roll having fine particles (powder) coated on the surface thereof as a charging member by the coating method according to the present invention, an electrophotographic apparatus having improved charging performance durability can be assembled. As the electrophotographic apparatus, the electrophotographic photosensitive member, disposed in contact with the electrophotographic photosensitive member, a charging member for charging the electrophotographic photosensitive member by applying voltage, an exposure means, it is configured to have a developing means and transfer means Can do. Further, these members are provided so as to be replaceable with respect to the apparatus main body. For example, at least the electrophotographic photosensitive member and the charging member are integrally supported, and can be attached to and detached from the electrophotographic apparatus main body as a process cartridge. A structure incorporated in a photographic apparatus may be used. The process cartridge may further include at least one of a developing unit and a cleaning unit. FIG. 2 schematically shows an outline of the electrophotographic apparatus when the process cartridge is incorporated. The process cartridge 21 in this example is incorporated at a predetermined position facing the peripheral surface of the photoconductor 13, a charging roller 11 connected to the power supply 12, a portion for taking in light from exposure means for performing image exposure 14, and a built-in part. A developing device 15 having a toner supply roller for supplying toner to the surface of the photosensitive member, a portion for moving the toner image to the transfer material 17 by the transfer device 16 on the main body side, and a cleaning device 19 are disposed, and these are supported integrally. Have a structure. The attachment / detachment of the process cartridge to / from the main body device is achieved by a known structure with respect to the device main body rail 20. The transfer material 17 to which the toner image is applied is heated and fixed via a fixing roller 18.

  Hereinafter, although an example etc. are given and explained, the present invention is not limited to an example. The average particle size of the fine particles (powder) was determined by laser light scattering measurement. A laser light scattering particle size distribution meter (ELS-800 manufactured by Otsuka Electronics Co., Ltd.) was used as a measuring device.

(Reference Example 1)
(Formation of coated tube for conductive roll)
60 parts by weight of styrene-based thermoplastic elastomer SEBC (styrene content 20% by weight) [melting point 100 ° C., MFR 5.6 g / 10 min (230 ° C., 2.16 Kg)] as a material for the outer layer of the coated tube, impact resistance 40 parts by weight of polystyrene, 30 parts by weight of acidic carbon black, 10 parts by weight of magnesium oxide, 1 part by weight of calcium stearate, kneaded at 180 ° C. for 30 minutes using a pressure kneader, cooled and ground by a pulverizer, Pelletized with a single screw extruder.

  For the tube inner layer, 100 parts by weight of thermoplastic polyurethane elastomer (TPU) is added with 16 parts by weight of carbon black, 20 parts by weight of conductive titanium oxide, 10 parts by weight of magnesium oxide, and 1 part by weight of calcium stearate. And kneaded at 180 ° C. for 15 minutes, and pelletized in the same process as the material of the outer layer.

  Using the above pellets, after extrusion molding with a two-color extruder equipped with a die with an inner diameter of φ18.0 mm and a point with an outer diameter of φ16.5 mm, through a sizing and cooling process, the inner diameter φ11.5 mm, the thickness of the surface layer It was molded into a seamless tube having a two-layer structure of 100 μm and an inner layer thickness of 400 μm.

(Core metal)
The core metal was prepared by extruding an iron material into a bar material having a diameter of about 5 mm by cutting and cutting it to a length of 242 mm, and then applying chemical plating to the thickness of about 3 μm.

(Formation of foamed elastic layer on the outer periphery of the cored bar)
Ethylene-propylene-diene rubber (EPDM) is blended with carbon black, paraffinic plasticizer, vulcanizing material, and foaming agent, and the mixed mixture has an inner diameter of 4.5 mm and an outer diameter of 11.5 mm by an extrusion molding machine. Foam-molded into a hose shape (hose-like foamed elastic layer with an inner diameter of 4.5 mm and an outer diameter of 11.5 mm), a cored bar is inserted into the center hole of this hose-like material, and a foamed elastic layer is placed on the outer periphery A coated mandrel was obtained.

  Furthermore, the seamless tube obtained previously was further coated on the foamed elastic layer on the core metal to produce a conductive roll.

Example 1
Hydrotalcite having an average particle size of 0.4 μm was used as the coating powder, and the powder was applied to the outer peripheral surface of the conductive roll prepared in Reference Example 1 with an adhesive roller.

While rotating the conductive roll at 700 rpm, the wiper member was pressed with a sponge roller wrapped with a thin cloth made of 2 μm polyester fiber so that a load of 0.03 kg / cm ² was applied, and the wiper member was 600 mm in the longitudinal direction of the roller. By reciprocating for 12 seconds at a speed of / sec, a conductive roll having hydrotalcite fixed on the entire roller surface as shown in FIG. 1 was obtained.
(Example 2)
The hydrotalcite having an average particle diameter of 0.4 μm was applied in the same procedure as in Example 1, a thin cloth made of 2 μm polyester fiber was used as the wiping member, and the wiping member was rotated at 700 rpm while rotating the conductive roll at 0 rpm. A conductive roll fixed with hydrotalcite was obtained by pressing and reciprocating for 12 seconds so that a load of 0.06 kg / cm ² was applied.
(Example 3)
The hydrotalcite having an average particle diameter of 0.4 μm was applied in the same procedure as in Example 1, a thin cloth made of 2 μm polyester fiber was used as the wiping member, and the wiping member was rotated at 700 rpm while rotating the conductive roll at 0 rpm. A conductive roller fixed with hydrotalcite was obtained by pressing and reciprocating for 12 seconds so that a load of .18 kg / cm ² was applied.
Example 4
The hydrotalcite having an average particle size of 0.02 μm was applied in the same procedure as in Example 1, a thin cloth made of 4 μm polyester fiber was used as the wiping member, and the wiping member was rotated 0 at 700 rpm while rotating the conductive roll at 700 rpm. A conductive roll fixed with hydrotalcite was obtained by pressing and reciprocating for 12 seconds so that a load of 0.06 kg / cm ² was applied.
(Example 5)
In the same procedure as in Example 1, molybdenum disulfide having an average particle diameter of 0.4 μm was applied, a thin cloth made of 4 μm polyester fiber was used as the wiping member, and the wiping member was rotated at 700 rpm while rotating the conductive roll at 0 rpm. A conductive roll fixed with molybdenum disulfide was obtained by pressing and reciprocating for 12 seconds so that a load of 0.06 kg / cm ² was applied.
(Example 6)
Zeolite having an average particle diameter of 3.2 μm was applied in the same procedure as in Example 1, a thin cloth made of 4 μm polyester fiber was used as the wiping member, and 0.06 Kg was applied to the wiping member while rotating the conductive roll at 700 rpm. A conductive roll fixed with zeolite was obtained by reciprocating for 12 seconds while applying a load of / cm ² .

(Comparative Example 1)
The hydrotalcite having an average particle diameter of 0.4 μm was applied in the same procedure as in Example 1, a thin cloth made of 2 μm polyester fiber was used as the wiping member, and the wiping member was rotated at 700 rpm while rotating the conductive roll at 0 rpm. The conductive roll fixed with hydrotalcite was obtained by pressing and reciprocating for 12 seconds so that a load of 0.01 kg / cm ² was applied.
(Comparative Example 2)
The hydrotalcite having an average particle diameter of 0.4 μm was applied in the same procedure as in Example 1, a thin cloth made of 2 μm polyester fiber was used as the wiping member, and the wiping member was rotated at 700 rpm while rotating the conductive roll at 0 rpm. A conductive roll fixed with hydrotalcite was obtained by pressing and reciprocating for 12 seconds so that a load of .25 kg / cm ² was applied.
(Comparative Example 3)
The hydrotalcite having an average particle diameter of 0.4 μm was applied in the same procedure as in Example 1, a thin cloth made of 8 μm polyester fiber was used as the wiping member, and the wiping member was rotated 0 at 700 rpm while rotating the conductive roll at 700 rpm. A conductive roll fixed with hydrotalcite was obtained by pressing and reciprocating for 12 seconds so that a load of 0.06 kg / cm ² was applied.
(Comparative Example 4)
In the same procedure as in Example 1, silica having an average particle diameter of 8.9 μm was applied, a thin cloth made of 2 μm polyester fiber was used as the wiping member, and 0.06 Kg was applied to the wiping member while rotating the conductive roll at 700 rpm. A conductive roll fixed with silica was obtained by pressing and reciprocating for 12 seconds so that a load of / cm ² was applied.
(Comparative Example 5)
In the same procedure as in Example 1, silica having an average particle diameter of 0.005 μm was applied, a thin cloth made of 2 μm polyester fiber was used as the wiping member, and 0.06 Kg was applied to the wiping member while rotating the conductive roll at 700 rpm. A conductive roll fixed with silica was obtained by pressing and reciprocating for 12 seconds so that a load of / cm ² was applied.

  For the evaluation of the image, an electrically conductive roll obtained in the process cartridge (Q5949X) shown in FIG. 2 was incorporated as a charging roller using an LBP main body (HP Laser Jet 1320), and 3000 images were intermittently output. The presence / absence of an image defect due to adhesion was confirmed. In addition, unevenness due to coating and scratches on the roller surface were also confirmed. The results are shown in Table 1.

As described above, an inorganic compound having an average particle diameter of 0.01 μm or more and less than 4.0 μm as measured by a laser light scattering method is applied to the roll surface, and the member for rubbing the inorganic compound on the roll surface is a fiber of 5 μm or less. A conductive roll coating method characterized in that, when forming a layer, the inorganic compound is coated with a pressing force of the member to the roll surface of 0.02 kg / cm ² or more and less than 0.2 kg / cm ^2. Further, it was verified that the adhesion of the toner and the external additive was reduced, and it was difficult for image defects due to adhesion of the photoconductor scraping powder to occur.

It is a block diagram of the electroconductive roller apply | coated in this invention. It is a figure which shows typically the structure of the electrophotographic apparatus which comprises a process cartridge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive base | substrate 2 Elastic layer 3 Conductive coating layer 3 (a) Inner layer 3 (b) Outer layer 3 (c) Powder layer 11 Conductive roll 12 Power supply 13 Photoconductor 14 Image exposure 15 Developer 16 Transfer device 17 Transfer material 18 Fixing device 19 Cleaning device 20 Apparatus body rail 21 for mounting process cartridge Process cartridge

Claims (4)

In a coating method for coating fine particles on the surface of a conductive roll having a cored bar and an elastic layer provided on the cored bar,
Supplying inorganic fine particles to at least a part of the surface of the conductive roll;
A step of wiping member made of a fiber by relatively sliding, securing the inorganic fine particles supplied to the surface to the surface with respect to the inorganic fine particles is supplied electrically conductive surface of the roll,
Have
The diameter of the fibers of the wiping member is 5 μm or less, and the inorganic fine particles have an average particle size of 0.01 μm or more and less than 4.0 μm as measured by a laser light scattering method, and the conductive roll of the wiping member The method of applying fine particles, wherein the pressure on the surface of the substrate is 0.02 kg / cm ² or more and less than 0.2 kg / cm ² . In a process cartridge which is at least integrally supported by an electrophotographic photosensitive member and a charging member which is disposed in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage, and is detachable from the main body of the electrophotographic apparatus. ,
A process cartridge, wherein the charging member comprises a conductive roll having fine particles on the surface by the coating method according to claim 1. The process cartridge according to claim 2 , further comprising at least one of a developing unit and a cleaning unit. In an electrophotographic apparatus having an electrophotographic photosensitive member, a charging member that is disposed in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage, an exposure unit, a developing unit, and a transfer unit.
The charging member comprises a conductive roll having fine particles on the surface by the coating method according to claim 1.
An electrophotographic apparatus characterized by that .

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