JP2005148461A - Developing roller and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller capable of making a toner layer uniform in thickness to obtain an excellent image having no density unevenness. <P>SOLUTION: When the developing roller is made to enter a latent image carrier by 20 to 70 μm, the gap between the developing roller and latent image carrier is ≤3 times as large as the size of a toner particle in use and the length of the gap in a longitudinal direction is ≥2 times as large as the gap quantity. Further, the conditions are met at any angle of rotation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing roller used in an image forming apparatus such as an electrophotographic copying apparatus, a printer, or an electrostatic recording apparatus, and relates to a developing roller that achieves a high-quality image without density unevenness.

  A number of rollers such as a charging roller, a developing roller, and a transfer roller are used in copying machines, printers, and the like that are electrophotographic apparatuses.

  FIG. 1 shows a schematic configuration diagram of the image forming apparatus. 2. Description of the Related Art Image forming apparatuses such as copiers and printers are rotating drum type / transfer type electrophotographic apparatuses, 1 is a latent image carrier (photosensitive drum) as an image carrier, and has a predetermined peripheral speed in the clockwise direction. Rotation driven with (process speed). The photosensitive drum 1 is uniformly charged at a predetermined polarity and potential (-600 V in this embodiment) by a charging roller 2 to which a charging bias is applied from a power source E1 as a charging means during its rotation process, and then exposed. The system 3 receives negative image exposure (analog exposure of the original image, digital scanning exposure) corresponding to the target image information, and an electrostatic latent image of the target image information is formed on the peripheral surface.

  Subsequently, the electrostatic latent image is developed as a toner image by a toner developing method using a developing roller 4 of a reverse developing method using minus toner. Then, the toner image is fed to the transfer portion between the photosensitive drum 1 and the transfer roller as the transfer means 5 from a paper supply means (not shown) at a predetermined timing, and the power supply E2 is supplied to the transfer roller 5. Then, a transfer bias of about +2 to 3 KV is applied, and the toner image that has been reversely developed on the surface of the photosensitive drum 1 is sequentially transferred onto the transfer material P.

  The transfer material P that has received the transfer of the toner image is separated from the surface of the photosensitive drum 1 and is introduced into fixing means (not shown) to undergo image fixing processing. The surface of the photosensitive drum 1 after the transfer of the toner image is subjected to a removal process of adhering contaminants such as transfer residual toner by the cleaning unit 6 to be cleaned and repeatedly used for image formation.

  In recent electrophotographic apparatuses, a one-component developing apparatus is often used as the main body is downsized. As a one-component developing system using a one-component developer, a toner carrier is applied by applying a thin coating on the toner carrier at the same time that the toner particles are charged by friction between the toner regulating member and toner particles and friction between the developing roller and toner particles. And the latent image carrier are conveyed to a development area facing each other, the electrostatic latent image on the latent image carrier is developed, and visualized as a toner image.

  The one-component development method does not require carrier particles such as glass beads, iron powder, and ferrite, unlike the two-component development method, so that the development device itself can be reduced in size and weight. Furthermore, since the two-component development method needs to keep the toner concentration in the developer constant, a device for detecting the toner concentration and supplying a necessary amount of toner is necessary, which leads to an increase in size and weight of the developing device. In this respect as well, the one-component development method is advantageous for reduction in size and weight.

  The one-component development method is roughly divided into a magnetic one-component development method using a magnetic toner containing a magnetic material in the toner and a non-magnetic one-component development method using no magnetic material. A non-magnetic one-component developing method that can use toner is used.

  In general, in the non-magnetic one-component developing method, toner is supplied onto the toner carrier by an elastic roller in contact with the toner carrier, and then the toner is applied thinly on the toner carrier by the toner regulating member and at the same time the toner regulation The toner particles are charged by friction with the member and friction with the toner carrier.

  However, the non-magnetic one-component development method may have inferior charge imparting property to the toner as compared with the two-component development method using a mixture of carrier and toner. This is because the two-component development method has a large surface area of the carrier, which is a charge imparting member for the toner, and therefore the friction frequency with the toner is large, and a stable charge can be imparted to the toner. This is because, in the developing method, the toner regulating member, which is a charge imparting member, and the surface of the toner carrier are small, and there may be toner that is not sufficiently rubbed with these members.

  Therefore, when the nonmagnetic one-component developing method is used, it is necessary to uniformly form a thin toner layer having a uniform and constant charge on the developing roller. When the surface of the developing roller is too smooth, a sufficient toner thin layer cannot be formed, and when it is too rough, it is difficult to form a uniform toner thin layer.

Various improvements on these problems have been proposed. Patent Document 1 describes the surface roughness of the developing roller, the elastic modulus of the surface layer, and the like. Patent Document 2 discloses a developing roller in which a filtered center line average waviness is defined.
Japanese Patent Laid-Open No. 10-268643 JP 2001-1000051 A

  However, the above conventional example has the following problems.

  In the case of Japanese Patent Laid-Open No. 2001-100512, no measures are taken against local undulations on the surface of the developing roller, and it is very difficult in terms of manufacturing method to make the filtered centerline average undulations 1.5 μm or less. Is.

  Similarly, in the case of Japanese Patent Laid-Open No. 10-268643, no measures are taken against local undulations on the surface of the developing roller, and means for achieving this configuration is complicated and expensive.

  Accordingly, the object of the present invention is not only to have a good developing characteristic in the early stage of use of the developing roller by forming a uniform toner thin layer on the surface of the developing roller, but also after the endurance of paper passing and in a harsh environment. Another object of the present invention is to provide a developing roller capable of performing stable development even after being left for a long time, an electrophotographic process cartridge having the developing roller, and an electrophotographic image forming apparatus.

  The present invention can solve the above problems by providing the following configuration.

  (1) A visible image is formed by forming a thin layer of toner on the surface and bringing it into contact with a latent image holding member holding an electrostatic latent image such as a photosensitive drum, and attaching the toner to the latent image of the latent image holding member. In the contact-type developing roller for forming the toner, when the developing roller is inserted into the cylindrical body by 20 to 70 μm, the maximum gap between the developing roller and the cylindrical body is not more than three times the toner particle size used. Development roller.

  (2) A visible image is formed by forming a thin layer of toner on the surface and bringing it into contact with a latent image holding member holding an electrostatic latent image such as a photosensitive drum, and attaching the toner to the latent image of the latent image holding member. In the contact-type developing roller for forming a toner image, when the developing roller is inserted into the latent image carrier 20 to 70 μm, the maximum gap between the developing roller and the latent image latent image carrier is less than three times the used toner particle size. There is a developing roller.

  (3) The developing roller according to (1) or (2), wherein a gap in the longitudinal direction of the maximum gap is at least twice as large as a gap in the roller radial direction.

  (4) In the developing roller, the developing roller, the cylindrical body, and the latent image carrier may satisfy any one of (1), (2), and (3) regardless of the rotation angle. roller.

  (5) The development according to any one of (1) to (4), wherein an elastic body is disposed around the conductive shaft body, and at least one resin layer is disposed on the outer periphery of the elastic body. roller.

  (6) By forming a thin layer of toner on the surface and bringing it into contact with a latent image carrier holding an electrostatic latent image, such as a latent image carrier, and attaching the toner to the latent image of the latent image carrier An image forming apparatus comprising a developing roller for forming a visible image, wherein the developing roller according to any one of (1) to (5) is used.

  According to the present invention, the following effects can be obtained.

  When the developing roller of the present invention is used in an image forming apparatus such as an electrophotographic copying apparatus, a printer, or an electrostatic recording apparatus, a uniform thin toner layer can be formed on the surface of the developing roller. In addition to having good development characteristics in the initial stage, stable development can be performed even after paper passing durability or after being left in a harsh environment for a long time, achieving a high-quality image. It has become possible to provide a developing roller that can be developed, an electrophotographic process cartridge and an electrophotographic image forming apparatus having the developing roller.

  According to the configuration of the conductive roller according to the above means for solving the problems, there are the following actions.

  A thin layer of toner is formed on the surface and brought into contact with a latent image holding body holding an electrostatic latent image such as a photosensitive drum, and a visible image is formed by attaching the toner to the latent image of the latent image holding body. By using a developing roller in which the maximum clearance between the developing roller and the cylindrical body is less than three times the particle size of the toner used when the developing roller enters the cylindrical body by 20 to 70 μm in the contact type developing roller. It is possible to form a uniform toner thin layer on the surface of the developing roller, which not only has good developing characteristics in the initial stage of use of the developing roller, but also after the endurance of paper passing and in harsh environments for a long time. The inventors have found that stable development can be performed even after being left standing, and have reached the present invention.

  The developing roller of the present invention has a form as shown in FIG. As shown in FIG. 2, the developing roller has a structure in which a conductive elastic body is provided around the shaft body and one or more surface layers are provided. When the developing roller is intruded into the cylindrical body by 20 to 70 μm. The developing roller is such that the maximum gap between the developing roller and the cylindrical body is not more than three times the toner particle size used.

  When this maximum gap is 3 times or more of the toner particle size, the friction between the toner regulating member and the toner particles and the friction between the developing roller and the toner particles are not sufficiently performed, so that a sufficient charge cannot be given to the toner. At the same time, the toner cannot be conveyed to the latent image carrier. Even when the maximum gap is 3 times or less of the toner particle size, a local gap is also formed when the length of the gap in the longitudinal direction is 2 times or less of the maximum gap, and sufficient charge is similarly applied to the toner. At the same time, the toner cannot be conveyed to the latent image carrier.

  A schematic diagram of the measurement method of the gap is shown in FIG. For example, when intruding 30 μm, the developing roller is allowed to stand for 24 hours in an environment of 23 ° C. and 50% humidity, and rollers 9 having an outer diameter 60 μm smaller than the average outer diameter of the developing roller are placed on both sides of the developing roller. It was set aside and a 1 kg load was applied to both ends of the metal core and pressed against the cylindrical body 8 having a diameter of 30 mm. Next, from the side of this apparatus, the gap a and the gap length b (FIG. 5) were measured using a non-contact laser length measuring machine. Here, the average outer diameter of the developing roller means that the developing roller is left for 24 hours in a temperature of 23 ° C. and a humidity of 50%, and the pitch is 10 mm from the end using a non-contact laser length measuring machine in the same environment. The average value of the measured values was taken as the average outer diameter. Further, with respect to the gap amount in the circumferential direction of the developing roller, the gap amount was measured by the same method after rotating every three degrees. Further, the cylindrical body used here is not particularly limited as long as the material has such a hardness that the cylindrical body is not deformed when a developing roller such as iron, aluminum, titanium, copper, and nickel enters 20 to 70 μm.

  The conductive shaft 4b used in the present invention is a cylinder having a carbon steel alloy surface subjected to industrial nickel plating having a thickness of 5 μm. Other examples of the material constituting the conductive metal core include, for example, metals such as iron, aluminum, titanium, copper and nickel, alloys such as stainless steel, duralumin, brass and bronze containing these metals, carbon black, A known material exhibiting rigidity and conductivity, such as a composite material in which carbon fibers are hardened with plastic, can also be used. Moreover, as a shape, it can also be set as the cylindrical shape which made the center part the cavity other than column shape.

  The conductive elastic body may be in the form of a foam or a solid.

  Materials that can be used as the elastic body used here are ethylene propylene rubber (EPDM), isoprene rubber (IR), styrene rubber (SBR), butadiene rubber (BR), nitrile rubber (NBR), butyl rubber (IIR), silicone Examples include rubber (Q), chloroprene rubber (CR), chlorosulfonated polyethylene (CSM), acrylic rubber (ACM), hydrin rubber (ECO), polysulfide rubber (T), and fluoro rubber (FKM). It can also be used in combination with more than one type. Further, these materials can be used after imparting conductivity. Furthermore, a foaming agent, a balloon, etc. can be added and used for these materials. In the case of using a liquid material, a roller shape can be obtained by injecting a liquid conductive material on the shaft into a mold and crosslinking the conductive material by applying heat in the mold.

  In addition to the materials used for the elastic body listed above, the materials used for the surface layer disposed outside the conductive elastic body include urethane resin, epoxy resin, diallyl phthalate resin, polyethylene resin, polycarbonate resin Fluorine resin, polypropylene resin, urea resin, melamine resin, silicon resin, polyester resin, styrene resin, acrylic resin, vinyl acetate resin, phenol resin, polyamide resin, fiber resin, vinyl chloride resin, silicone resin, etc. These can be used in combination of two or more. Further, these materials can be used after imparting conductivity. It is also possible to form a surface layer by coating these materials.

  In addition, as a method of making these materials conductive, there are a method of adding an ionic conductive substance by an ionic conduction mechanism to the above material and a method of making the material conductive by adding a conductivity imparting agent by an electronic conduction mechanism to the material, Either one or two types can be used in combination.

Examples of the conductivity-imparting agent based on the ion conduction mechanism include LiCF ₃ SO ₃ , NaClO ₄ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , NaSCN, KSCN, NaCl, etc. Group 1 metal salts, NH ₄ Cl, NH ₄ Ammonium salts such as SO ₄ , NH ₄ NO ₃ , etc., salts of Group 2 metals of the periodic table such as Ca (ClO ₄ ) ₂ , Ba (ClO ₄ ) ₂ , these salts and 1,4-butanediol, ethylene Complexes of polyhydric alcohols such as glycol, polyethylene glycol, propylene glycol, polypropylene glycol and their derivatives, salts thereof and ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether, etc. Monoo Complexes with water, cationic surfactants such as quaternary ammonium salts, anionic surfactants such as aliphatic sulfonates, alkyl sulfate esters and alkyl phosphate esters, amphoteric surfactants such as betaines You can list the agent. These conductivity-imparting agents based on the ion conduction mechanism can be used alone or in combination of two or more in the form of powder or fiber.

  As the conductivity imparting agent by the electronic conduction mechanism, carbon-based materials such as carbon black and graphite, metals or alloys such as aluminum, silver, gold, tin-lead alloy, copper-nickel alloy, zinc oxide, titanium oxide, aluminum oxide, Examples thereof include metal oxides such as tin oxide, antimony oxide, indium oxide, and silver oxide, and materials obtained by applying conductive metal plating such as copper, nickel, and silver to various fillers. These conductivity-imparting agents based on the electronic conduction mechanism can be used alone or in combination of two or more in the form of powder or fiber.

  In addition, as means for forming a surface layer on the elastic body, there are the following. First, when the material constituting the surface layer is made into a paint, it is dispersed using a conventionally known dispersion apparatus using beads such as a sand mill, paint shaker, dyno mill, pearl mill or the like. The obtained coating material for forming the surface layer is applied to the surface of the conductive elastic body by a spray coating method, a dipping method, a roll coater method or the like. In the present invention, since the surface of the developing roller is preferably uniformly rough, dipping is particularly preferably used.

  The thickness of the surface layer is preferably 5 to 500 μm, particularly 10 to 30 μm. If the thickness is too small, low molecular weight components in the base layer may ooze out and contaminate the photoreceptor, and if it is too thick, the developing roller will become hard and cause fusing.

  In the present invention, toner particles on the surface of the developing roller can be easily conveyed by dispersing fine particles having a mass average particle diameter of 1 to 20 μm in the surface layer formed as described above. The toner can be conveyed to the development area. Examples of the fine particles used for such purpose include plastic pigments such as polymethyl methyl methacrylate fine particles, silicone rubber fine particles, polyurethane fine particles, polystyrene fine particles, amino resin fine particles, and phenol resin fine particles. Methyl acid fine particles and silicone rubber fine particles are preferred. These fine particles are preferably added in the range of about 3 to 50% by weight of the surface layer.

  When the conductive roller is used as a developing roller by using the materials and conductive substances as described above, the resistance value is preferably 1E3 to 1E10Ω when a voltage of 100 V is applied to the roller. It is desirable to make it 1E4 to 1E7. If the resistance value is smaller than 1E3Ω, the current flows too much and an appropriate amount of toner does not get on the developing roller. On the other hand, when the value is larger than 1E10Ω, there is a problem that the current hardly flows to the roller and the density does not come out. Also, with respect to the resistance in the longitudinal direction and the circumferential direction, it is better that the resistance unevenness is small, and when the resistance is locally small and large, high-definition image quality is caused by the same reason as described above or local development failure. Difficult to get.

  As shown in FIG. 4, the resistance value of the conductive roller is such that the conductive roller is pressed against the metal drum with a load of 500 g applied to both ends of the shaft, and the roller is rotated at 60 rpm. A resistance value was calculated by applying a voltage of 200 V to the shaft of the roller and measuring the value of the current flowing through the conductive roller.

  The Asker C hardness of the conductive roller formed as described above is preferably 60 ° or less. If the Asker C hardness exceeds 60 °, the toner is melted on the surface of the developing roller or the photosensitive drum due to friction between the developing roller and the photosensitive drum, which is not preferable. The “Asker C hardness” is the hardness of a roller measured using an Asker C-type spring rubber hardness tester (manufactured by Kobunshi Keiki Co., Ltd.) in accordance with Japan Rubber Association standard SRIS0101. The measured value is 30 seconds after the hardness tester is brought into contact with a roller left in a humid (23 ° C., 55% RH) environment for 12 hours or more with a force of 10 N. However, when the hardness is 10 ° or less, the material itself has a large compression set, or wear due to durability increases, which is not preferable.

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

[Example 1]
As the core, a SUS core was plated with nickel, further coated with a primer, and then baked at 150 ° C. for 30 minutes. Next, the metal core is placed in the metal mold, the metal mold is heated at 120 ° C. for 5 minutes, and the vinyl group is terminated at 100 phr with respect to polydimethylsiloxane, 15 phr of polydimethylsiloxane containing silicon-hydrogen bonds, 50 phr of silica, Carbon black (10 phr) was added and well dispersed, and injected into a cavity formed in the mold.

  Subsequently, the silicone rubber was cured by heating at 120 ° C. for 5 minutes, and after cooling, the elastic layer was provided on the outer periphery of the cored bar by demolding. After polishing the roller provided with an elastic layer, add 5 phr of MDI, 30 phr of carbon black and 10 phr of urethane resin particles to 100 phr of polyol, adjust to a 15% solution with respect to polyol using methyl ethyl ketone, and dip it into the elastic layer. After coating and drying the solvent at room temperature for 5 hours, a developing roller was obtained by heating at 170 ° C. for 60 minutes. The obtained developing roller was allowed to stand for 24 hours under a temperature of 23 ° C. and a humidity of 50%, and then measured in a pitch of 10 mm from the end using a non-contact laser length measuring machine in the same environment to obtain an average outer diameter.

  Also, after leaving the developing roller at a temperature of 23 ° C. and a humidity of 50% for 24 hours, a roller 9 having an outer diameter of 60 μm smaller than the average outer diameter of the developing roller is set on both sides of the developing roller. A 1 kg load was applied to the cylindrical body 8 having a diameter of 30 mm, and the gap a and the gap length b (FIG. 5) were measured from the side of the apparatus using a non-contact laser length measuring machine. As a result of the measurement, a was 10 μm and b was 26 μm.

Next, using a toner having a toner particle diameter of 7 μm, image evaluation was performed using a Canon color leather beam printer [Example 2]
The same procedure as in Example 1 was performed except that the grindstone used for polishing was changed. As a result of the measurement, a was 18 μm and b was 10 μm.

[Example 3]
The same procedure as in Example 1 was conducted except that the grindstone used for polishing was replaced and the toner particle diameter of the used toner was changed to 10 μm. As a result of the measurement, a was 25 μm and b was 40 μm.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that the grindstone used for polishing was changed. As a result of the measurement, a was 27 μm and b was 49 μm.

[Comparative Example 2]
The same procedure as in Example 1 was performed except that the grindstone used for polishing was changed. As a result of the measurement, a was 34 μm and b was 25 μm.

[Comparative Example 3]
The same procedure as in Example 1 was conducted except that the grindstone used for polishing was replaced and the toner particle diameter of the used toner was changed to 10 μm. As a result of the measurement, a was 26 μm and b was 79 μm.

  The results are shown in Table 1. O in the density unevenness portion indicates that there is no density unevenness, Δ indicates that there is a little density unevenness, and x indicates that the density unevenness is clearly recognized.

1 is a schematic diagram of an image forming apparatus showing an embodiment of the present invention. Side surface sectional drawing of the developing roller which shows embodiment of this invention Schematic of a device that measures the resistance value of the developing roller Schematic of the device that measures the gap between the developing roller and the cylinder Schematic of the gap (enlarged view of the contact portion between the developing drum and the cylindrical body in FIG. 4)

Explanation of symbols

1 Latent image carrier (photosensitive drum)
2 Charging means (charging roller)
3 Exposure system 4 Developing means (developing roller)
4a Elastic body 4b Core metal (shaft)
4c Surface 5 Transfer means (transfer roller)
6 Cleaning means 7 Metal drum 8 Cylindrical body 9 Rollers E1, E2, E3 Power supply for bias application

Claims (6)

  A thin layer of toner is formed on the surface and brought into contact with a latent image holding body holding an electrostatic latent image such as a photosensitive drum, and a visible image is formed by attaching the toner to the latent image of the latent image holding body. A developing roller characterized in that, when the developing roller is inserted into the cylindrical body by 20 to 70 μm, the maximum gap between the developing roller and the cylindrical body is not more than three times the toner particle size used.   A thin layer of toner is formed on the surface and brought into contact with a latent image holding body holding an electrostatic latent image such as a photosensitive drum, and a visible image is formed by attaching the toner to the latent image of the latent image holding body. In the contact-type developing roller, when the developing roller enters the latent image carrier 20 to 70 μm, the maximum gap between the developing roller and the latent image latent image carrier is less than three times the toner particle size used. A developing roller.   3. The developing roller according to claim 1, wherein a gap in the longitudinal direction of the maximum gap is at least twice as large as a gap in the roller radial direction.   4. The developing roller according to claim 1, wherein the developing roller, the cylindrical body, and the latent image carrier are rotated at any angle.   The developing roller according to claim 1, wherein an elastic body is disposed around the conductive shaft body, and at least one resin layer is disposed on an outer periphery of the elastic body.   A thin layer of toner is formed on the surface and brought into contact with a latent image carrier holding an electrostatic latent image, such as a latent image carrier, and the toner is attached to the latent image of the latent image carrier to thereby form a visible image. 6. An image forming apparatus comprising a developing roller to be formed, wherein the developing roller according to claim 1 is used.

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