JP2005133832A - Conductive roller and core bar used in the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive roller and a core bar used in the same capable of coping with the fluctuation of the resistance of the roller with the lapse of time, which can not be improved only by using a coating layer. <P>SOLUTION: In this conductive roller comprising the core bar and the coating layer 4 formed on an outer periphery of the core bar, the core bar is composed of a cylindrical conductive sleeve 3, a pair of left and right insulating bearings 3 for closing both end openings of the sleeve 3, and a conductive shaft 1 inserted between both bearings 2 for coaxially rotating the sleeve 3 and the bearing 2, and the sleeve 3 and the shaft 1 are connected by an electric resistor 5 having specific electric resistance. This core bar is used in the conductive roller. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a conductive roll such as a charging roll used in an electrophotographic apparatus such as a copying machine, a printer, and a facsimile, and a core bar used therefor.

  In general, copying by an electrophotographic copying machine such as a printer is performed as follows. In other words, a document image is formed as an electrostatic latent image on a photosensitive drum that rotates about its axis, and a toner image is formed by adhering toner to the image. Then, the toner image is transferred to a copy sheet for copying. is there. In this case, in order to form an electrostatic latent image on the surface of the photosensitive drum, the surface of the photosensitive drum is charged in advance, and a document image is projected onto the charged portion via the optical system, and is exposed to light. For example, an electrostatic latent image is formed by canceling the charging of the portion. As a method for charging the surface of the photosensitive drum prior to the formation of the electrostatic latent image, recently, there is a method (contact charging method) in which a charging roll, which is a kind of conductive roll, is brought into direct contact with the surface of the photosensitive drum. It has been adopted.

In addition to the charging roll, the conductive roll used in the electrophotographic apparatus such as the printer includes a developing roll and a transfer roll. And as these conductive rolls, for example, a roll having a multilayer structure in which an outer peripheral surface of a metal core made of a metal is coated with a conductive resin layer or rubber layer is generally used. (For example, refer to Patent Document 1).
JP-A-5-297710

  Many of the current conductive rolls including the above-described rolls are made of an electronic conductive agent such as carbon black or an ionic conductive agent such as quaternary ammonium added to the coating layer forming material such as the resin layer or the rubber layer. Thus, the electrical characteristics of the roll itself are appropriately adjusted. Then, by appropriately adjusting the type of each conductive agent and the amount of the conductive agent, or by appropriately changing the configuration of each layer, resistance fluctuations that occur over time due to the use environment and use conditions of the roll can be suppressed. The problem is not to occur.

However, the conductive roll whose electric characteristics are adjusted by the conductive agent in the coating layer has a limit in the solution in the coating layer in the following cases (A) or (B).
(A) Increase in the amount of conductive agent used against electrical deterioration due to long-term use.
(B) Overcoming environmental dependence in systems based on ionic conduction.

  That is, in the case of the above (A), although there is an advantage that the durable life of the roll is extended when the amount of the conductive agent used is increased, there is a possibility that the initial electrical characteristics may not be satisfied. Moreover, the increase in the amount of the conductive agent leads to the generation of bloom and the cost increase. On the other hand, in the case of (B), since the ionic conductive agent alone has a large environmental dependency on the temperature and humidity, in order to eliminate this, usually, it is used together with an electronic conductive agent such as carbon black. However, if an electronic conductive agent is used until the environmental dependency is overcome, there is a risk of demerits in workability.

  In addition, as described above, the current conductive roll has an electric resistance value set by the coating layer formed on the outer periphery of the core metal, so the electric resistance is adjusted after the product (roll) is completed. It is impossible to do. For this reason, when the resistance fluctuation of the roll becomes remarkable due to long-term use or the like, usually, there is no choice but to discard and replace it with a new one.

  The present invention has been made in view of such circumstances, and provides a conductive roll capable of coping with fluctuations in roll resistance that occurs over time, which cannot be improved only by a coating layer, and a core metal used therefor. Objective.

  In order to achieve the above object, the present invention provides a conductive roll comprising a metal core and a coating layer formed on the outer periphery thereof, wherein the metal core includes a cylindrical conductive sleeve, A pair of left and right insulative bearings that block the opening at both ends of the sleeve, and a conductive shaft that passes through both the bearings and rotates the sleeve and the bearing coaxially, and the sleeve and the shaft have a predetermined electric resistance. A conductive roll connected by an electric resistor having the above is defined as a first gist, and a core metal used for the conductive roll is defined as a second gist.

  That is, the present inventors have intensively studied to solve the above problems. In the course of that research, I recalled that the core of the roll was involved in the resistance adjustment of the roll. That is, the resistance adjustment of the roll is conventionally performed only by the coating layer, and the cored bar part was hardly involved, but by improving the configuration of the cored bar part, it cannot be improved only by the coating layer, We thought that it would be possible to cope with roll resistance fluctuations that occur over time. As a result of repeated research on the cored bar portion, a cylindrical conductive sleeve, a pair of left and right insulating bearings that block the opening at both ends of the sleeve, and the sleeve and the bearing are coaxially rotated through the both bearings. When a current is supplied from the shaft end when the core is formed by the conductive shaft and the sleeve and the shaft are connected by an electric resistor having a predetermined electric resistance, Since the current limited by the electric resistor flows to the sleeve, it was found that the resistance value of the entire roll can be adjusted by appropriately setting the resistance value of the electric resistor, and the present invention has been achieved. did.

  As described above, the conductive roll of the present invention includes a cylindrical conductive sleeve having a cylindrical shape, a pair of left and right insulating bearings that block the opening at both ends of the sleeve, and the sleeve passing through both the bearings. The conductive shaft that rotates the bearing coaxially is formed, and the sleeve and the shaft are connected by an electric resistor having a predetermined electric resistance. Thereby, the resistance value of the whole roll can be determined arbitrarily, and it is possible to cope with the roll resistance fluctuation that occurs with time, which cannot be improved only by the coating layer formed on the outer periphery of the cored bar.

  In particular, when the electrical resistor is provided in an integrated state with the insulating bearing, the configuration of the cored bar is simplified, and the electrical resistor is less likely to be disconnected. Better.

  In addition, if the electric resistor has a structure in which the resistance value can be varied, it is possible to easily cope with environmental changes and deterioration with time of the roll resistance, and it is easy to keep the resistance value constant. It becomes.

  The core metal used for the conductive roll can be appropriately limited in current depending on the characteristics of the electric resistor, so that it can be used not only for a normal conductive roll, but particularly for the coating layer alone. Suitable for use in conductive rolls, which are not likely to cause resistance fluctuations over time.

  Next, embodiments of the present invention will be described in detail.

  The electroconductive roll of this invention is equipped with the special metal core and the coating layer 4 formed in the outer periphery, as shown, for example in FIG. The metal core includes a cylindrical conductive sleeve 3, a pair of left and right insulating bearings 2 that closes the openings at both ends of the conductive sleeve 3, and the conductive sleeve 3 and the insulating bearing 2 that are inserted through the both bearings 2. And the conductive sleeve 3 and the conductive shaft 1 are connected to each other by soldering or the like by an electric resistor 5 having a predetermined electric resistance. . As described above, the conductive sleeve 3 and the conductive shaft 1 are electrically connected via the electrical resistor 5.

  The conductive shaft 1 is not particularly limited, and examples thereof include a nonmagnetic metal shaft made of stainless steel, aluminum, iron or the like.

  The pair of insulative bearings 2 is not particularly limited as long as both ends of the above-described conductive sleeve 3 can be closed and the end of the conductive shaft 1 can be inserted and fixed. For example, a circular lid provided with a hole for inserting and fixing the conductive shaft 1 in the center can be used. In addition, the material for forming the insulating bearing 2 is not particularly limited, and among them, polypropylene, polytetrafluoroethylene (PTFE), engineering plastic, and the like are preferable because of excellent strength and insulating properties.

  As the conductive sleeve 3, for example, a cylindrical body made of a metal such as aluminum, nickel, titanium, iron, copper, etc., having a uniform thickness and excellent rigidity is used.

  The electrical resistor 5 that connects the conductive sleeve 3 and the conductive shaft 1 is not particularly limited. For example, as shown in FIG. 1, a coil-shaped one formed of a copper wire or the like is used. And commercially available resistors. The electrical resistor 5 may be connected in a manner as shown in the figure, for example, a gap formed inside the conductive sleeve 3 (a gap between the conductive sleeve 3 and the conductive shaft 1). ) May be provided with an electrical resistor 5 to couple them together. By the way, when the electrical resistor 5 is provided in an integrated state with the insulating bearing 2 unlike FIG. 1, the configuration of the cored bar can be simplified and the electrical resistor 5 is disconnected. It becomes difficult and becomes superior in terms of durability. Here, the term “integrated” means that the insulating bearing 2 itself has a function as an electric resistor, in addition to the case where the electric resistor 5 is bonded or embedded in the insulating bearing 2. This includes cases where

  Further, if the electrical resistor 5 can be exchanged with other electrical resistors having different resistance values as required, it can cope with the environmental change and deterioration with time of the roll resistance, and as a result, the life of the roll. Can be extended more. Furthermore, it is preferable that the electrical resistor 5 has a structure in which the resistance value can be varied because it can easily cope with environmental changes and the like. As such a thing, the thing of a structure as shown in FIG. 2 is mention | raise | lifted, for example. That is, in the drawing, 5a, 5b, and 5c are electric resistors having different resistance values, respectively, and one end thereof is electrically connected to the conductive shaft 1 and integrated with the insulating bearing 2. The conductive sleeve 3 is installed in the internal space. Then, the conductive shaft 1 is rotated by clicking with respect to the conductive sleeve 3, and the one having the most suitable resistance value among the three types of electric resistors (5a, 5b, 5c) interlocked therewith is selected. By making contact with the contact 3a formed on the inner peripheral surface of the conductive sleeve 3 (which can be confirmed by a clicking sound or the like), a roll having a desired electric resistance can be obtained.

The material of the coating layer 4 formed on the outer periphery of the special core metal as described above is not particularly limited. For example, acrylonitrile-butadiene rubber (NBR), epichlorohydrin rubber, acrylic rubber, ethylene-propylene- Rubbers such as diene rubber (EPDM), hydrogenated acrylonitrile-butadiene rubber (H-NBR), styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), natural rubber (NR), and polyamide resins , Fluororesin, acrylic resin, melamine resin, phenol resin, epoxy resin, urethane resin, silicone resin and the like, and these may be used alone or in combination of two or more. Also, for imparting conductivity, carbon black, graphite, potassium titanate, iron _{oxide, c-TiO 2, c-} ZnO, c-SnO 2, an ion conductive agent (quaternary ammonium salt, borate, surfactant A conventionally known conductive agent such as an agent is appropriately added to the material. Furthermore, if necessary, a foaming agent, a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, a processing aid, oil, and the like may be added as appropriate.

  The conductive roll of the present invention can be produced, for example, as follows. That is, first, as shown in FIG. 1, a metal core is manufactured from a conductive shaft 1, a pair of insulating bearings 2, a conductive sleeve 3, and an electrical resistor 5. On the other hand, the tube which becomes the coating layer 4 is prepared by preparing the material of the coating layer 4 and extruding it using an extruder, heat-treating at 160 to 200 ° C. for about 1 to 2 hours, and vulcanizing. Is made. And after apply | coating an adhesive agent to the outer peripheral surface of the said metal core as needed, the metal core is press-fitted in the said tube, and the outer periphery of a metal core is coat | covered with the said tube, The target electroconductive roll is carried out. Can be obtained.

  The conductive roll can also be produced as follows. That is, first, after producing a cored bar with components excluding the electric resistor 5, an adhesive is applied to the outer peripheral surface as necessary. Next, the material of the coating layer 4 is extruded together with the core metal, the coating layer (unvulcanized) is rubbed onto the core metal, and the coating layer (unvulcanized) together with the core metal is 1-2 at 160 to 200 ° C. The coating layer 4 is formed on the outer periphery of the cored bar by heat treatment for about an hour and vulcanization. And finally, the electrical resistance body 5 is attached as shown in FIG. 1, and the target electroconductive roll is obtained.

  Further, in addition to the above-described extrusion molding, the coating layer 4 is, for example, dissolved in an organic solvent such as MEK and dispersed with a sand mill or the like to form a coating liquid, which is a roll coating method. It can also be formed by applying to the outer peripheral surface of the cored bar by spray coating method, dipping method, etc., drying, and then heat vulcanizing under predetermined conditions.

  In the conductive roll of the present invention thus obtained, the dimensions of the core metal are not particularly limited. Usually, the conductive shaft has a diameter of 5 to 8 mm, the inner diameter is 11 to 15 mm, and the thickness is 0. The one constituted by a conductive sleeve of about 3 to 1.5 mm is used. Further, the thickness of the coating layer formed on the outer periphery of the core metal is not particularly limited, but is usually set in a range of 0.3 to 1.5 mm, preferably in a range of 0.5 to 1.2 mm. Is within.

  In the conductive roll of the present invention, for example, electrical deterioration caused by long-term energization or the like can be dealt with by replacing the electrical resistor connecting the conductive sleeve and the conductive shaft with one having a low resistance value. can do. Further, for example, in the case where the amount of the conductive agent used in (A) is increased as described in the above section [Problems to be solved by the invention], the electrical resistance of the coating layer is made as low as possible. In addition, by combining variable electric resistors and setting the resistance value to be high at the initial stage and gradually changing the resistance value, the same resistance value as that at the initial stage can be maintained. Furthermore, the environmental dependency in the system of (B), which mainly uses ionic conduction, described in the same column can be determined by combining temperature sensitive electric resistors or by setting multiple resistors with different resistance values. It can be overcome by switching to. That is, in a low-temperature and low-humidity environment, the resistor is replaced so as to reduce the resistance value of the electric resistor. Conversely, in a high-temperature and high-humidity environment, the resistor is replaced so as to increase the resistance value. By doing so, a constant roll resistance can be maintained, and the uneven density of the printed image can be suppressed.

  Moreover, since the conductive roll of the present invention has the greatest feature in the configuration of the cored bar, the coating layer formed on the outer periphery of the cored bar is not particularly limited, and is further shown in FIG. It is not limited to such a single layer structure. Therefore, if necessary, the covering layer may have a laminated structure of two or more layers.

  The conductive roll of the present invention can be suitably used as a charging roll for OA equipment such as an electrophotographic copying machine, a printer, and a facsimile machine, as well as a developing roll and a transfer roll.

  Next, examples will be described together with comparative examples.

(Preparation of coating layer material)
Epichlorohydrin rubber 100 parts by weight (hereinafter abbreviated as “parts”), alkyltrimethylammonium perchloride 1 part, silica 50 parts, sulfur 2 parts, dibenzothiazole disulfide 5 parts, zinc oxide 10 parts, stearic acid 1 part was blended and kneaded using a roll to prepare a coating layer material.

[Preparation of conductive roll]
SUM22 shaft (diameter 6 mm, length 293 mm), aluminum sleeve (inner diameter 12 mm, length 273 mm, thickness 1 mm), a pair of polypropylene circular bearings (diameter 6 mm), and copper electrical resistor (0.8 MΩ) And a cored bar as shown in FIG. 1 was produced using these. The electrical resistor was connected to the shaft and the sleeve by soldering. On the other hand, the coating layer material prepared as described above was extruded using an extruder, heat treated at 180 ° C. for 1 hour, and vulcanized to produce a tube having a thickness of 1 mm. And after apply | coating an adhesive agent to the outer peripheral surface of the said metal core, the metal core is press-fitted in the said tube, and the outer periphery of a metal core is coat | covered with the said tube, The intended electroconductive of single layer structure A roll was obtained (see FIG. 1).

When a voltage of −300 V is applied to the conductive roll of the example obtained as described above in a normal temperature and normal humidity (23 ° C., 53% RH) environment, the resistance value at that time is 1.0 × 10. ⁶ Ω was shown. When this roll was incorporated in an electrophotographic printer as a charging roll and images were taken out, no image unevenness was found. On the other hand, when the resistance value was measured in a low-temperature and low-humidity (15 ° C., 10% RH) environment, the resistance value was less than 1.0 × 10 ⁶ Ω. The resistance value could be set to 1.0 × 10 ⁶ Ω by replacing with a low resistance one (0Ω). On the other hand, when the resistance value was measured in a high temperature and high humidity (32 ° C., 85% RH) environment, the resistance value exceeded 1.0 × 10 ⁶ Ω. The resistance value could be set to 1.0 × 10 ⁶ Ω by replacing it with a high resistance (1 MΩ). Then, using the roll set in this way so as to conform to each environmental condition, and by outputting an image according to the above method, it was possible to output an image without unevenness regardless of the environmental condition. .

  A conductive roll was produced in accordance with Example 1 using a core bar in which three types of electric resistors (0Ω, 0.8 MΩ, and 1 MΩ) were switchable as shown in FIG. And this electroconductive roll was able to respond to an environmental change etc. more easily than Example 1 since the result similar to Example 1 was obtained, and an electrical resistor can be switched freely. .

[Comparative example]
A metal shaft (manufactured by SUM22) made of a solid body having a diameter of 6 mm was used as the core metal. Except this, it carried out similarly to Example 1, and obtained the conductive roll of single layer structure.

When a voltage of −300 V is applied to the conductive roll of the comparative example obtained as described above in a low temperature and low humidity (15 ° C., 10% RH) environment, the resistance value at that time is 1.0 × 10 ^6. Ω was shown. When this roll was incorporated in an electrophotographic printer as a charging roll and images were taken out, no image unevenness was found. However, when the resistance value was measured in a normal temperature and normal humidity (23 ° C., 53% RH) environment, the resistance value at that time was 1.7 × 10 ⁵ Ω, and the high temperature and high humidity (32 The resistance value was 3.5 × 10 ⁴ Ω when the test was performed under the environment of (° C., 85% RH). Therefore, when this roll was used and images were taken out under normal temperature and normal humidity and high temperature and high humidity environments, image unevenness occurred.

It is sectional drawing which shows an example of the electroconductive roll of this invention. It is sectional drawing (sectional drawing of an axial center) which shows the other example of the electroconductive roll of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive shaft 2 Insulating bearing 3 Conductive sleeve 4 Covering layer 5 Electrical resistor

Claims (4)

  A conductive roll provided with a cored bar and a coating layer formed on the outer periphery thereof, wherein the cored bar has a cylindrical conductive sleeve, and a pair of left and right insulating bearings that block the opening at both ends of the sleeve. A conductive shaft for inserting the both bearings and coaxially rotating the sleeve and the bearing, and the sleeve and the shaft are connected by an electric resistor having a predetermined electric resistance. A conductive roll.   The conductive roll according to claim 1, wherein the electric resistor is provided in an integrated state with the insulating bearing.   The conductive roll according to claim 1 or 2, wherein the electrical resistor has a structure in which a resistance value thereof is variable.   A cored bar used for the conductive roll according to any one of claims 1 to 3.