JP2003098819A - Developing roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing roller for improving wear resistance to a developer, without enhancing the hardness of the roller and small in irregularity of the electrical resistance and a developing device, using the developer roller. SOLUTION: In the developing roller provided with a proper conductive shaft and a conductive elastic layer formed on the outer periphery of the shaft, and supplying the developer on the latent image retaining body surface and visualizing the electrostatic image of a latent image holding body surface by carrying the developer on the surface, forming the thin film and rotating, to be brought into contact with or neared to a latent image-retaining body in this state, the conductive elastic layer is formed of a silicone rubber and a rubber composition which contains one or more kinds of rubbers other than the silicone rubber, and the rubber composition is manufactured by a method for kneading the silicone rubber previously kneaded with a conductive agent and the rubber other than the silicone rubber previously kneaded with a conductive agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roller and a developing device, and more particularly, to a surface of a latent image carrier such as a photosensitive drum in an electrophotographic device such as a copying machine, a facsimile, a printer or an electrostatic recording device. The present invention relates to a developing roller for visualizing the electrostatic latent image held on the developing roller and a developing device equipped with the developing roller.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic developing device such as a copying machine or a printer, a one-component toner (developer) is supplied to a latent image holding member such as a photoconductor holding an electrostatic latent image.
A pressure developing method is known as an image forming method for visualizing the toner by attaching the toner to the latent image (US Pat. No. 3,152).
No. 012 specification, No. 3731146 specification). In this pressure development method, a developing roller carrying a toner is brought into contact with a latent image carrier (photoconductor) carrying an electrostatic latent image to adhere the toner to the latent image on the surface of the latent image carrier. The image is formed by means of the above-mentioned method. Therefore, it is necessary to form the developing roller with a conductive elastic body having conductivity and elasticity. That is, in this pressure developing method, for example, as shown in FIG. 1, between the toner application roller 5 for supplying toner and the latent image holder (photoconductor) 6 holding the electrostatic latent image, The developing roller 1 is disposed, and the developing roller 1, the latent image carrier 6 and the toner applying roller 5 rotate in the directions of the arrows in the drawing, so that the toner 7 is applied to the surface of the developing roller 1 by the toner applying roller 5. And the toner is adjusted to a uniform thin film by the stratifying blade 8.
Then, in this state, the developing roller 1 rotates in contact with the latent image holding member 6, whereby the toner formed in a thin layer adheres to the latent image on the latent image holding member 6 from the developing roller 1 and the latent image holding member 6 is rotated. The image is made visible. Reference numeral 9 in the drawing denotes a transfer unit, which transfers a toner image onto a recording medium such as paper. Further, 10 is a cleaning unit,
The cleaning blade 11 removes the toner remaining on the surface of the latent image carrier 6 after transfer.

In the developing device using such a pressure developing method, the developing roller 1 has to rotate while maintaining a state of being in close contact with the latent image holding member 6, and therefore, FIG.
As shown in the schematic cross-sectional view of FIG. 1, a conductive agent is mixed with elastic rubber or foam such as silicone rubber, acrylonitrile butadiene rubber, ethylene propylene rubber, polyurethane rubber, etc. on the outer periphery of the shaft 2 made of a good conductive material such as metal. In this structure, the conductive elastic layer 3 made of a conductive elastic body having conductivity is formed. In addition, toner 7
In order to control the chargeability and adhesion to the latent image carrier 6
A coating layer 4 made of resin or the like is provided on the surface of the conductive elastic layer 3 in order to control the frictional force with the stratifying blade 8 or to prevent the latent image holding body from being contaminated by the elastic body.

When the electrostatic latent image is developed by the pressure developing method using such a developing roller, it is not used for the development and remains at the end portion of the developing roller to cause friction with the accumulated toner. As a result, the end surface of the developing roller is abraded, and this abrasion causes a defective image and causes the durability of the developing roller to be reduced. Therefore, if the hardness of the roller surface is increased to improve the abrasion resistance of the developing roller, when the electrostatic latent image is developed by the pressure developing method, the developing roller and the latent image holding member such as the photosensitive drum are Since the contact area is small, good development may not be possible. If the hardness of the roller surface is too high, the latent image carrier may be damaged. Further, if the hardness of the developing roller is too high, the developer may be overloaded with the layer regulating blade that is in contact with the developing roller and may be damaged. As a means for solving such a problem, it is effective to lower the friction between the developing roller and the developer by lowering the friction coefficient of the elastic layer of the developing roller. Silicone rubber is suitable as a material for forming the elastic layer in terms of lowering friction, but silicone rubber has problems that mechanical properties are low and cost is high. In order to solve such a problem, it is effective to use a blend of an organic rubber having a high mechanical property and a cost lower than that of a silicone rubber, and a silicone rubber. However, since the dispersed state of the conductive agent is different between the silicone rubber and the other rubber, when the roller is formed of a blend of the silicone rubber and the other rubber, the electric resistance varies. Therefore, there is a problem that a good image cannot be obtained when this roller is mounted on the image forming apparatus as a developing roller and printed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to improve the abrasion resistance to a developer without increasing the hardness of the roller.
Another object of the present invention is to provide a developing roller having a small variation in electric resistance and a developing device equipped with the developing roller.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that a conductive elastic layer made of a specific rubber material is formed on the outer circumference of a shaft having good conductivity. It has been found that it is possible to obtain a developing roller which has improved wear resistance to a developer and has a small variation in electric resistance without increasing the hardness of the roller. The present invention has been completed based on such findings. That is, the present invention comprises (1) a shaft having good conductivity and a conductive elastic layer formed on the outer periphery of the shaft, and a developer is carried on the surface to form a thin film thereof. In this state, the developer is supplied to the surface of the latent image holding member by rotating in contact with or in close proximity to the latent image holding member holding the electrostatic image on the surface of the latent image holding member. In the developing roller for visualizing, the conductive elastic layer is formed of a rubber composition containing silicone rubber and one or more rubbers other than silicone rubber, and the rubber composition is preliminarily conductive with silicone rubber in which a conductive agent is kneaded in advance. A developing roller manufactured by a method of kneading an agent with a rubber other than the silicone rubber, (2) the content of the silicone rubber in the total amount of the silicone rubber and the other rubber 5 to 90 mass% The developing roller according to (1) above, (3) rubber other than silicone rubber is urethane rubber, polybutadiene rubber, natural rubber, isoprene rubber, styrene butadiene rubber, nitrile rubber, ethylene propylene rubber, acrylic rubber, The developing roller according to (1) or (2) above, which is one or more selected from epichlorohydrin rubber and chloroprene rubber, and the elastic layer is a non-foamed elastic layer or a foamed elastic layer, and (4) a developing roller. The developing roller according to any one of (1) to (3) above, wherein a coating layer is formed on the surface of the elastic layer.
(5) The resin constituting the coating layer is at least one selected from melamine resin, phenol resin, alkyd resin, fluororesin resin and polyamide resin (1)
To the developing roller according to any one of (4) to (6), and (6) a latent image holding member capable of holding an electrostatic latent image on the surface thereof, and rotating in contact with or in proximity to the surface of the latent image holding member. A developing roller provided, and a developer is carried on the surface of the developing roller to form a thin film thereof, and the developer is supplied to the surface of the latent image holding member to form the surface of the latent image holding member. In the developing device for visualizing the electrostatic image of, the above-mentioned (1) is used as the developing roller.
To provide a developing device characterized by using the developing roller according to any one of (5) to (5).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the developing roller of the present invention, as shown in FIG. 2, for example, a conductive elastic layer 3 is formed on the outer periphery of a good conductive shaft 2, and the surface of the conductive elastic layer 3 is formed as needed. To form the coating layer 4. As the shaft 2, any one can be used as long as it has good conductivity, but normally, a metal such as a metal core made of a solid metal body or a metal cylindrical body hollowed out inside is used. A manufactured shaft is used. Examples of the metal shaft include a steel material such as sulfur free-cutting steel plated with zinc or the like, and a shaft made of aluminum, stainless steel, phosphor bronze, or the like. The conductive elastic layer 3 is formed of a rubber composition containing silicone rubber and one or more rubbers other than silicone rubber. This rubber composition is produced by a method of kneading a silicone rubber in which a conductive agent is previously kneaded and a rubber other than the silicone rubber in which a conductive agent is previously kneaded. As the silicone _{rubber, - (SiR 2 -O-SiR} 2 -
O-SiR ₂ -O) _n - in (wherein, R represents a a methyl group, a vinyl group, a phenyl group, a trifluoropropyl group.
n is the number of repetitions. It is preferable that the structure represented by () is a basic molecular structure. As rubbers other than silicone rubber, urethane rubber, polybutadiene rubber, natural rubber, isoprene rubber, styrene butadiene rubber, nitrile rubber, ethylene propylene rubber, ethylene propylene ethylene rubber, acrylic rubber, epichlorohydrin rubber, chloroprene rubber, butyl rubber, ethylene propylene Examples include diene rubber and the like. In the present invention, urethane rubber, polybutadiene rubber, natural rubber,
Isoprene rubber, styrene butadiene rubber, nitrile rubber, ethylene propylene rubber, acrylic rubber, epichlorohydrin rubber and chloroprene rubber are preferred. The content of the silicone rubber is preferably 5 to 90% by mass in the total amount of the silicone rubber and the other rubber,
80 mass% is more preferable.

The conductive agent added to the rubber material to make the elastic layer conductive is conductive powder or an ion conductive substance. Examples of the conductive powder include conductive carbon such as Ketjen Black EC and acetylene black, SAF, ISAF, HAF, FEF, GPF and SR.
Carbon for rubber such as F, FT, MT, carbon for ink (ink) that has been subjected to oxidation treatment, pyrolytic carbon, natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper Metals and metal oxides such as silver and germanium, and conductive polymers such as polyaniline, polypyrrole and polyacetylene. Among them, carbon black is inexpensive and whose conductivity can be easily controlled with a small amount. As the ion conductive material, sodium perchlorate, lithium perchlorate, calcium perchlorate, inorganic ionic conductive materials such as lithium chloride, further modified aliphatic dimethyl ammonium ethosulfate, stearyl ammonium acetate,
Examples thereof include organic ionic conductive substances such as lauryl ammonium acetate, octadecyl trimethyl ammonium perchlorate and tetrabutyl ammonium borofluoride. The conductive powder is 1 part with respect to 100 parts by mass of the rubber material.
It is preferably used in the range of ˜50 parts by mass, particularly 5 to 40 parts by mass. The ion conductive substance is suitably used in the range of 0.01 to 5 parts by mass, and particularly 0.05 to 2 parts by mass with respect to 100 parts by mass of the rubber material. The amount of the conductive agent added to the silicone rubber and the amount of the conductive agent added to the other rubber may be distributed according to the usage ratio of the rubber. In addition, when forming a coating film layer described below on the outer side of the elastic layer, the coating film layer may contain a conductive agent.

It is preferable to adjust the volume resistivity of the conductive elastic layer to a range of 10 ³ to 10 ¹⁰ Ω · cm, particularly 10 ⁴ to 10 ⁸ Ω · cm by adjusting the addition amount of the conductive agent. In addition to the above-mentioned conductive agent, other rubber additives such as conventionally known fillers and cross-linking agents can be appropriately added to the conductive elastic layer, if necessary. The hardness of this conductive elastic layer is 35-80 °, especially 40 for Asker C type.
It is preferably in the range of ˜75 °. This hardness is 80
If the temperature exceeds 50 °, the developing roller becomes hard and the contact area with image formation becomes small, so that good image formation may not be possible, and the developer may be damaged and the latent image carrier or the layering blade may be damaged. Toner sticking or the like occurs, which causes a defective image. On the other hand, if the hardness is too low, friction with the latent image carrier or the layering blade becomes large, and image defects such as jitter may occur. In the developing roller of the present invention, the elastic layer may be a non-foamed elastic layer or a foamed elastic layer. When forming a foamed elastic layer, a foaming agent is added to the rubber composition. As the foaming agent, for example,
Sulfonyl hydrazides such as p, p′-oxybis (benzenesulfonyl hydrazide) (OBSH), benzenesulfonyl hydrazide and toluenesulfonyl hydrazide, azo compounds such as azodicarbonamide (ADCA) and azobisisobutyronitrile, N, N′- Dinitrosopentamethylene tetramine, N, N'-dimethyl-N,
Organic foaming agents such as nitroso compounds such as N'-dinitrosoterephthalamide; inorganic foaming agents such as sodium bicarbonate and ammonium bicarbonate. OB among these
SH, ADCA, or a foaming agent using these in combination is preferable. The amount of foaming agent added is 1 with respect to 100 parts by mass of rubber.
-10 parts by mass is preferable, and 3-8 parts by mass is particularly preferable. The foaming agent can reduce its particle size as much as possible.
It is preferable for reducing the size of foam cells. The particle diameter of the foaming agent is preferably 10 μm or less, particularly preferably 5 μm or less. The foaming agent may be added to the silicone rubber and / or other rubber together with the conductive agent in advance, or may be added when kneading the silicone rubber and the other rubber.

The material for the elastic layer includes, in addition to a conductive agent and a foaming agent added as necessary, a vulcanizing agent, a vulcanization accelerator such as zinc white, stearic acid, a conductivity imparting agent, a softening agent, etc. It is prepared as a composition containing the additive of. The elastic layer is formed by vulcanizing and molding the elastic layer material on the surface of the core material by means of injection molding, extrusion molding, press molding or the like. The additive may be added to the silicone rubber and / or other rubber together with the conductive agent in advance, or may be added when kneading the silicone rubber and the other rubber. It is preferable that the additive is added to each of the silicone rubber and the other rubber in advance, and the amount of the additive to be added to the silicone rubber and the amount of the additive to be added to the other rubber are different depending on the usage ratio of the rubber. Allot it.

In the developing roller according to the present invention, in order to control the chargeability and adhesion to the developer, to control the frictional force between the developing roller and the latent image holding member and the layer regulating member, or to make the conductive material conductive. A coating layer is preferably provided on the roller surface in order to prevent contamination of the latent image carrier by the elastic layer. The coating layer is formed by applying a coating material in the form of a coating on the surface of the elastic layer and then drying at room temperature or at a temperature of about 50 to 170 ° C. As the coating material, an aqueous conductive coating material using a water-soluble or water-dispersible material as a matrix component, and an organic solvent (alcohol solvent such as methanol, ketone solvent such as methyl ethyl ketone, aromatic solvent such as toluene) as a matrix component There is an oily conductive paint that uses a soluble material. Examples of the matrix component of the water-based conductive paint include acrylic resin, polyester resin, polyurethane resin, vinyl acetate resin, isoprene rubber latex, butadiene rubber latex, chloroprene rubber latex and the like. As the matrix component of the oil-based conductive paint, soluble copolymer nylon, alkyd resin, melamine resin,
Examples thereof include polyester resin, silicone resin, urethane resin, acrylic urethane resin, fluororesin and phenol resin. The thickness of this coating layer is preferably 1 to 100 μm. If desired, these resins may include a charge control agent,
Various additives such as lubricants, conductive agents, and other resins can be contained. In the developing roller of the present invention, the volume resistivity of this coating layer is preferably 10 ⁷ to 10 ¹⁶ Ω · cm, and particularly preferably 10 ⁹ to 10 ¹⁴ Ω · cm.

The developing roller of the present invention is used by being incorporated in a developing device such as an electrophotographic apparatus. For example, as shown in FIG. 1, a toner applying roller 5 for supplying toner and a static roller. The developing roller of the present invention is disposed as the developing roller 1 between the photosensitive drum (latent image holding member) 6 holding the electrostatic latent image, and the toner 7 is carried by the toner applying roller 5, and the layering blade 8 is used. To form a uniform thin layer, and toner is further supplied from this thin layer to the photosensitive drum (latent image carrier) 6 to form a photosensitive drum (latent image carrier).
Toner is attached to the electrostatic latent image 6 to visualize the latent image. The details of the developing device shown in FIG. 1 have been described in the above-mentioned prior art, and will be omitted. The image forming apparatus equipped with the developing roller of the present invention is not limited to the one shown in FIG. 1, and a developer is carried on the surface to form a thin layer of the developer. Any material may be used as long as it forms a visible image on the surface of the image forming body by supplying a developer to the surface of the image forming body in contact with or close to the surface of the image forming body. For example, paper sheets such as paper and OHP paper are used as the image forming body, and the developer carried on the developer carrying body is made to fly directly through the holes formed in the control electrode to directly form the image on the paper or OHP paper. It may be formed.

As the developer carried on the developing roller of the present invention, a non-magnetic one-component toner is preferably used, but a magnetic type one-component developer can also be used.
For example, the developing roller and the developing device of the present invention can be preferably used even when black-and-white images are printed using a magnetic one-component toner.

[0014]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples. [Example 1] Carbon 6 was added to 20 parts by mass of silicone rubber.
A mass A (phr), a vulcanizing agent (peroxide) 0.3 mass parts (phr), stearic acid 1 mass part and zinc white 1 mass part were added and kneaded to obtain a composition A. In addition, 55 parts by mass of butadiene rubber and 25 parts by mass of liquid isoprene rubber,
24 parts by mass of carbon (phr), 1.2 parts by mass of vulcanizing agent (peroxide), 4 parts by mass of stearic acid and 4 parts by mass of zinc white were added and kneaded to obtain a composition B. The composition A and the composition B were blended with a roller, the obtained rubber composition was cast into a mold, and cured under vulcanization conditions of 150 ° C. for 1 hour, and the diameter of the outer circumference of the metal shaft was 20 m.
A roller having a conductive elastic layer of m and a length of 398 mm was obtained. Next, as a resin for forming the coating layer, epoxy-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd., silicone epoxy varnish ES1004, solid content 50% by mass) and melamine resin (manufactured by Dainippon Ink and Super Beckamine L-14).
5-60, solid content 60% by mass), and epoxy-modified silicone and melamine resin are used in a solid content weight ratio of 50/50.
Was mixed with a mixed solvent in which methyl ethyl ketone and toluene were mixed at a mass ratio of 9/1. Further, to 100 parts by mass of this mixture, 30 parts by mass of carbon black (manufactured by Mikuni dye company, carbon black # 220, solid content 40% by mass) previously dispersed in a solvent was added and dispersed as a conductive agent. A paint having a solid content of 25% by mass was prepared. The above roller was immersed in this coating material, pulled up, and heated at 110 ° C. for 4 hours to prepare a developing roller having a cured coating layer.

Example 2 In Example 1, 35 parts by weight of butadiene rubber (phr) and 40 parts of silicone rubber were used.
A developing roller was obtained in the same manner as in Example 1 except that the amount was changed to parts by weight (phr). [Comparative Example 1] Silicone rubber 20
Vulcanizing agent (peroxide) 0.2 parts by mass (ph)
r) was added and kneaded to obtain a composition C. Further, 55 parts by mass of butadiene rubber and 25 parts by mass of liquid isoprene rubber, 1.3 parts by mass (phr) of a vulcanizing agent (peroxide),
5 parts by mass of stearic acid and 5 parts by mass of zinc white were added and kneaded to obtain a composition D. Composition C, composition D, and 30 parts by mass of carbon (phr) were blended with a roller, and then a developing roller was obtained in the same manner as in Example 1. [Comparative Example 2] In Comparative Example 1, 35 parts of butadiene rubber was used.
Parts by weight (phr), 40 parts by weight of silicone rubber (ph)
A developing roller was obtained in the same manner as Comparative Example 1 except that the developing roller was changed to r). With respect to the developing rollers of Examples and Comparative Examples thus produced, each characteristic was measured by the following methods, and these developing rollers were mounted on a printer for printing and image evaluation was performed. The results are shown in Table 1.

(1) Asker C hardness Measured according to JIS K6301. (2) Electric resistance of roller and dispersion of resistance 4.9 N each on both ends of the produced developing roller and metal drum
In the state where the roller-shaped toner carrier and the metal drum were rotated by applying pressure, the electric resistance of the roller-shaped toner carrier was measured at 72 points by applying a voltage of 10 V between the roller-shaped toner carrier and the metal drum. The electrical resistance is the average of the measured values, and the variation in resistance is
The difference between the logarithm of the maximum resistance and the logarithm of the minimum resistance within one rotation of the roller was used. (3) Image test The developed developing roller was mounted on a commercially available LBP (laser beam printer), a halftone image was printed, and the image condition was visually checked. When the image was good, the image was good, and the image was good. If not, it was marked as x.

[0017]

[Table 1]

[0018]

The developing roller of the present invention has improved wear resistance to a developer and reduced variation in electric resistance without increasing the hardness of the roller, and is excellent over a long period of time. An image can be surely obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an image forming apparatus equipped with a developing device of the present invention.

FIG. 2 is a schematic sectional view showing an example of a developing roller of the present invention.

[Explanation of symbols] 1: Developing roller 2: Shaft 3: Conductive elastic layer 4: coating layer 5: Toner application roller 6: Latent image holder (photoreceptor) 7: Toner 8: Stratified blade 9: Transfer unit 10: Cleaning section 11: Cleaning blade

Claims (6)

[Claims] 1. A shaft comprising a highly conductive shaft and a conductive elastic layer formed on the outer periphery of the shaft, wherein a developer is carried on the surface to form a thin film thereof, and in this state, the surface is formed. Development in which the electrostatic image on the surface of the latent image carrier is visualized by supplying the developer to the surface of the latent image carrier by rotating in contact with or close to the latent image carrier that holds the electrostatic image on the surface of the latent image carrier. In the roller, the conductive elastic layer is formed of a rubber composition containing silicone rubber and one or more rubbers other than the silicone rubber, and the rubber composition is prepared by previously kneading the conductive agent with the silicone rubber. A developing roller manufactured by a method of kneading a rubber other than silicone rubber. 2. The developing roller according to claim 1, wherein the content of the silicone rubber is 5 to 90% by mass in the total amount of the silicone rubber and the other rubber. 3. The rubber other than silicone rubber is one selected from urethane rubber, polybutadiene rubber, natural rubber, isoprene rubber, styrene butadiene rubber, nitrile rubber, ethylene propylene rubber, acrylic rubber, epichlorohydrin rubber and chloroprene rubber. The developing roller according to claim 1, wherein there are two or more kinds, and the conductive elastic layer is a non-foamed elastic layer or a foamed elastic layer. 4. The developing roller according to claim 1, wherein the developing roller has a coating layer formed on the surface of an elastic layer. 5. The developing roller according to claim 1, wherein the resin constituting the coating layer is at least one selected from melamine resin, phenol resin, alkyd resin, fluororesin resin and polyamide resin. 6. A latent image holding member capable of holding an electrostatic latent image on the surface thereof, and a developing roller arranged so as to rotate in contact with or close to the surface of the latent image holding member, In a developing device for carrying a developer on the surface of a developing roller to form a thin film thereof and supplying the developer to the surface of the latent image carrier to visualize an electrostatic image on the surface of the latent image carrier, A developing device using the developing roller according to claim 1 as a developing roller.