JP2006323266A - Conductive roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent or reduce a depression caused by a local pressing force. <P>SOLUTION: Resistance to a depression of a conductive elastic layer caused by a local pressing force can be significantly improved by implementing primary curing of an addition-cure conductive silicone rubber as a conductive elastic layer of a conductive roller under pressure. Since the resistance to a depression of a conductive elastic layer caused by a local pressing force is significantly improved in the conductive roller, the conductive roller can be obtained in which a depression is not caused or is reduced significantly compared to a conventional developing roller, even when it is in contact with a photosensitive drum and a blade for a long time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive roller having high resistance to a dent caused by local pressing and a measuring method thereof.

  Examples of the conductive roller of the electrophotographic non-magnetic one-component image forming apparatus include a charging roller, a developing roller, a toner supply roller, a transfer roller, and a toner cleaning roller. Among them, the developing roller is usually a rubber roller made of conductive rubber, and plays a role of developing the electrostatic latent image by transferring toner to the photosensitive drum. Silicone rubber is used for the elastic layer of the developing roller, and is in contact with a photosensitive drum and a blade for regulating toner. In particular, at night and on holidays when the machine is stopped, the same part of the developing roller is in contact with the photosensitive drum and blade for a long time and is pressed locally by these. As a result, a local dent is generated in the rubber roller. When such a dent occurs, toner is excessively applied to that portion, so that a dark streak appears in the copied image and the quality of the copied image is deteriorated.

  In order to prevent the occurrence of such a dent of the developing roller, Patent Document 1 describes an image forming apparatus capable of releasing the contact between the developing roller and the photosensitive drum. In this image forming apparatus, when the operation is not performed for a predetermined time or more, the contact between the developing roller and the photosensitive drum is automatically released. If such a mechanism is provided, it is considered that the occurrence of a dent in the developing roller is considerably prevented. However, if such a mechanism is incorporated, the machine becomes more complicated and the cost becomes higher.

  On the other hand, the test of the dent amount of the developing roller so far could only be evaluated with an image passed through after being left in the actual machine such as a printer for about one week. Further, although there is JIS K 6262 as a permanent strain test method, this test method could not measure the difference in the amount of dents due to local pressing.

JP2001-249541

  An object of the present invention is to provide a conductive roller in which dents caused by local pressing are prevented or reduced. Moreover, the objective of this invention is providing the measuring method of the amount of dents by the local press of a conductive roller.

  As a result of earnest research, the inventor of the present application conducted a primary curing of an addition-curing type conductive silicone rubber as a conductive elastic layer of a conductive roller under pressure. As a result, the inventors have found that the resistance to dents caused by a large pressing is significantly improved, and the present invention has been completed. Furthermore, the inventor of the present application has invented a measurement method that can accurately measure the resistance to a dent caused by local pressing.

  That is, the present invention provides a conductive roller having a cored bar and a conductive elastic layer, wherein the primary curing of the addition-curable conductive silicone rubber as the conductive elastic layer is performed under pressure. provide. The present invention also provides a conductive roller having a cored bar and a conductive elastic layer, and having a dent amount of local pressing after hanging a weight on the conductive elastic layer and hanging a weight of 5 μm or less. Furthermore, the present invention includes a cored bar and a conductive elastic layer, and the primary curing of the addition-curable conductive silicone rubber as the conductive elastic layer is performed under pressure, and a thread is applied to the conductive elastic layer. Provided is a conductive roller having a dent amount of local pressing after suspending a weight of 5 μm or less. Furthermore, the present invention hangs a weight on a conductive roller and suspends a weight, and measures a dent of a portion where the yarn is hung after a predetermined time has elapsed. To provide a method for measuring resistance.

  According to the present invention, a conductive roller having improved resistance to a dent in the conductive elastic layer caused by local pressing is provided. In the conductive roller according to the present invention, the resistance of the conductive elastic layer to the dent caused by local pressing is significantly improved. It is possible to obtain a conductive roller significantly reduced as compared with the developing roller. In addition, according to the method for measuring resistance to dents caused by local pressing of the conductive roller according to the present invention, resistance to dents caused by local pressing of the conductive roller can be easily and accurately measured. This is useful for developing rollers.

  The conductive roller of the present invention has a cored bar and a conductive elastic layer, and the conductive elastic layer is formed of an addition-curable conductive silicone rubber. Addition-curable conductive silicone rubber itself is well known in the field of rubber molded products, and various products are commercially available. Also in the present invention, various commercially available addition-curable conductive silicone rubbers can be used, and the kind thereof is not limited.

In the conductive roller of the present invention, the primary curing of the addition curing type conductive silicone rubber constituting the conductive elastic layer is performed under pressure. The primary curing means a process of first curing an uncured rubber after molding such as extrusion molding, and is usually a process subsequent to a molding process such as extrusion molding. During the production of the conductive roller of the present invention, primary curing is performed under pressure. By performing the primary curing under pressure, the crosslinking point of the addition reaction type conductive silicone rubber is surely crosslinked. As demonstrated in the examples described later, this is caused by local pressing of the obtained molded product. Resistance to dents is significantly improved. When primary curing of addition-curing type conductive silicone rubber is performed at normal pressure, the effect of significantly improving the resistance to dents cannot be obtained even at the same curing temperature. Even in the case of the peroxide-curing conductive silicone rubber, even if primary curing is performed under pressure, the effect of significantly improving the resistance to the dents cannot be obtained. The pressure at which the primary curing is performed is preferably 2 kgf / cm ² or more at a gauge pressure (hereinafter, unless otherwise specified, and unless the context clearly indicates otherwise) Preferably it is 4 kgf / cm ² or more. There is no particular upper limit to the pressure, but if too high a pressure is required, a large and robust facility is required, which increases the cost, so about 20 kgf / cm ² or less is usually appropriate. In addition, when using a general commercially available autoclave (steam kettle), the pressure is about 10 kg / cm ^{2 at the} maximum, and it is preferable to carry out under a high pressure. Pressurization can be carried out using any gas that does not react with rubber as a medium, and it is simple and preferable to use water vapor or air. In particular, water vapor is preferably used because it can be easily pressurized using a commercially available autoclave. it can.

  The temperature for primary curing is usually 50 ° C. or higher, preferably about 120 ° C. to 200 ° C. In addition, when pressurizing with water vapor in the autoclave, curing is performed at a temperature where the pressure is a saturated vapor pressure, but the temperature is preferably within the above range. The curing time is not particularly limited and is appropriately set according to the size of the conductive elastic layer to be formed, etc., but is usually 5 minutes or longer, and preferably about 10 minutes to 4 hours.

  The conductive roller manufacturing method of the present invention is characterized by the above-described primary curing method, and the conductive roller of the present invention can be manufactured by a manufacturing method similar to the conventional method except for the primary curing. That is, an uncured addition-curing type conductive silicone rubber layer is usually formed around the metal core by molding such as extrusion molding. This can be easily performed by a conventional method using a commercially available extruder or the like.

  Next, the above-described primary curing step is usually performed.

  Next, an aging process is usually performed. The conditions of the aging step are not particularly limited, but the primary cured conductive elastic layer is usually in air at 120 ° C. to 250 ° C., preferably 170 ° C. to 230 ° C., usually 1 hour to 48 hours, preferably It is performed by leaving for 4 to 24 hours.

  Next, if desired, a polishing step is performed to obtain the conductive roller of the present invention.

  The conductive roller of the present invention is not particularly limited as long as it is a conductive roller. However, as described above, the conductive roller is particularly effective in the case of a developing roller always in contact with a photosensitive drum or a blade for regulating toner. . That is, when the conductive roller of the present invention is a developing roller of an electrophotographic nonmagnetic one-component image forming apparatus, local dents caused by contact with the photosensitive drum or blade are prevented or significantly prevented. Therefore, the developing roller of the electrophotographic non-magnetic one-component image forming apparatus is a preferable example that makes good use of the characteristics of the present invention. Here, the “electrophotographic non-magnetic one-component image forming apparatus” is a method that uses only toner (one-component development method) without using a carrier for developing an electrostatic latent image on a photosensitive drum, and An image forming apparatus that does not have a magnet in the image forming apparatus, and is widely used as a recent small-sized copying machine or a small-sized printer, and includes a copying machine, a printer, a facsimile, and a combination machine thereof. .

  The primary curing of the addition-curing type conductive silicone rubber constituting the conductive elastic layer is performed under pressure, so that the amount of dents in the local press after hanging the weight on the conductive elastic layer and hanging the weight is 5 μm or less A conductive roller was provided. Accordingly, the present invention includes a conductive roller having a local pressing dent amount of 5 μm or less after a thread is hung on the conductive elastic layer and suspending the weight, a cored bar, and a conductive elastic layer. The primary curing of the addition curing type conductive silicone rubber as a layer is performed under pressure, and the conductive roller having a local pressing dent amount of 5 μm or less after a thread is hung on the conductive elastic layer and the weight is suspended is also included. provide. A conductive roller is particularly preferred in which the dent amount of local pressing after suspending a weight of 120 g or more and 300 g or less on a 1 mm diameter yarn for 24 hours is 5 μm or less. In addition, the measuring method of the amount of dents prescribed | regulated here is specifically described in the following Example.

  The present invention further provides a method for measuring the resistance to dents caused by local pressing of the conductive roller. In this method, a thread is hung on a conductive roller and a weight is hung, and after a predetermined time has elapsed, a dent in a portion where the thread is hung is measured. The thread may be a commercially available fishing line, octopus thread or the like, and its thickness can be appropriately selected according to the purpose of the test, but the diameter is usually 0.2 mm to 5 mm, preferably 0.2 mm to 2 mm. Moreover, string, a metal wire, such as a wire and a wire, are also included in the “thread” referred to in the present invention. The weight of the weight can be appropriately selected depending on the purpose of the test, and is usually about several tens to several kilograms, preferably several tens to several hundred grams. The test time can be appropriately selected according to the purpose of the test, and is usually several minutes to several tens of hours.

  Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited to the following examples.

(1) Manufacture of developing roller Addition-curing conductive silicone rubber (Toray Dow Corning Silicone (Toray Dow Corning Silicone) using a 50mm uniaxial bent silicone rubber extruder (Mitsuha Corporation) on a metal core with an outer diameter of 10mm Co., Ltd.) or peroxide-curing conductive silicone rubber (Toray Dow Corning Silicone Co., Ltd.) was extruded for comparison to obtain an uncured rubber roller.

  Next, primary curing was performed in a commercially available steam kettle. The pressure and temperature during curing are shown in Table 1 below. The primary curing time was 60 minutes for all rollers.

  For comparison, the rollers No. E and F were subjected to primary curing under normal pressure. This condition is shown in Table 2 below.

For comparison, the peroxide-curing conductive silicone rubber roller (Roller No. G) was first cured at a gauge pressure of 6 kgf / cm ² and a temperature of 165 ° C (same conditions as Roller No. A). It was.

  Next, aging was performed in a high-temperature furnace PHH-201 (Espec Corp.). The aging conditions were 200 ° C. and 6 hours.

  Next, polishing was performed using a rubber roller grinder MAC-600-TS (Mizuguchi Seisakusho Co., Ltd.) to obtain various developing rollers having a roller outer diameter of 20.00 ± 0.05 mm and a roller surface roughness Rz = 3 to 5 μm. .

(2) Measurement of resistance to dents due to local pressing of developing roller As shown in FIG. 1, a fishing line having a diameter of 1 mm was hung on the roller, a weight was hung on the lower part, and left for 24 hours. The weights of the weights were 60, 90, 120, 150, 210, 240, 300 and 480 gf. The position where the fishing line was applied was the position where the fishing line was first applied 20 mm from the end face of the roller rubber part, then moved at 10 mm intervals, and the position where the fishing line was applied up to 20 mm from the opposite end face (Fig. 1) ( When there was no longer a position to hook the fishing line, the same was done using the opposite side of the roller surface where the fishing line was hooked first). After 24 hours, the fishing line and load were released, and the position where the fishing line was applied was measured in the roller axis direction. The surface roughness was measured under the conditions shown in Table 3 using a surface roughness measuring device Surfcom 1400D (Tokyo Seimitsu Co., Ltd.).

  The test was performed three times for each load to see the accuracy of the data. In addition, the depression where the fishing line was depressed 3 μm or more was defined as a depression. Less than 3 μm was set to 0 because it cannot be read as a dent. The amount of dents was read from the roughness meter measurement chart where it was determined that the most of the dents where the fishing line was hung.

  The measurement results are shown in Tables 4 to 6 below. Tables 4, 5 and 6 show the first, second and third measurement results, respectively, and the numerical value in each table is the dent amount (μm). Moreover, the average value of the dent amount in each load was taken from three measurements, and the relationship between the dent amount and the load is shown in FIG.

  As is apparent from FIG. 2, when the addition curable conductive silicone rubber was used, the amount of dents decreased as the pressure during primary curing increased. In particular, Roller No. A and Roller No. E, Roller No. B and Roller No. F were each primarily cured at the same temperature, but were primarily cured under pressure. In the case of No. B, the amount of dents was smaller than that of roller No. E and roller No. F in which primary curing was performed at the same temperature under normal pressure. From this, it was clarified that what causes the effect of reducing the dent amount is the pressure at the time of primary curing. The peroxide curable silicone rubber roller No. G was primarily cured under the same pressure and temperature conditions as roller No. A. Roller No. A with a much larger dent than A and cured at normal pressure. The amount of dents was larger than E. From this, it was found that the addition reaction type silicone rubber is more effective in improving the resistance to the depression due to local pressing regardless of the pressure during curing than the peroxide curing type silicone rubber.

  From the above, it has been clarified that a conductive roller having improved resistance to dents due to local pressing can be obtained by the method of the present invention in which addition-curable conductive silicone rubber is primarily cured under pressure.

It is a figure for demonstrating the measurement of the tolerance with respect to the dent by the local press of the electroconductive roller of this invention employ | adopted in the Example. It is a figure which shows the relationship between the load of various developing rollers manufactured in the Example, and the amount of dents.

Claims (13)

  A conductive roller having a cored bar and a conductive elastic layer, wherein primary curing of addition-curable conductive silicone rubber as the conductive elastic layer is performed under pressure. The conductive roller according to claim 1, wherein the primary curing is performed under a gauge pressure of 2 kgf / cm ² or more. The conductive roller according to claim 2, wherein the primary curing is performed under a gauge pressure of 4 kgf / cm ² or more.   The conductive roller according to any one of claims 1 to 3, wherein the primary curing is performed under pressure with water vapor.   A conductive roller having a cored bar and a conductive elastic layer, and having a depression amount of a local pressure of 5 μm or less after a thread is applied to the conductive elastic layer and a weight is suspended.   6. The conductive roller according to claim 5, wherein the dent amount of local pressing after suspending a weight of 120 g or more and 300 g or less on a thread having a diameter of 1 mm for 24 hours is 5 μm or less.   After the core metal and the conductive elastic layer, the primary curing of the addition-curing type conductive silicone rubber as the conductive elastic layer is performed under pressure, and a weight is hung on the conductive elastic layer by applying a thread. A conductive roller having a dent of local pressing of 5 μm or less.   The conductive roller according to claim 7, wherein the amount of depression of local pressing after suspending a weight of 120 g or more and 300 g or less on a thread having a diameter of 1 mm for 24 hours is 5 μm or less. The conductive roller according to claim 7 or 8, wherein the primary curing is performed under a gauge pressure of 2 kgf / cm ² or more. The conductive roller according to claim 9, wherein the primary curing is performed under a gauge pressure of 4 kgf / cm ² or more.   The conductive roller according to claim 1, wherein the conductive roller is a developing roller.   A method for measuring resistance to a dent caused by local pressing of a conductive roller, comprising hanging a weight on a conductive roller and suspending a weight, and measuring a dent of a portion where the yarn is hung after a predetermined time has elapsed. The method of claim 12, wherein the conductive roller is a developing roller.

Images