JP4708874B2 - Fixing unit pressure roller - Google Patents

Description

  The present invention relates to a roller for a fixing device of a heat fixing device used in an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic system.

  In order to save energy, a roller for a fixing unit of a heat fixing device used in an image forming apparatus such as a copying machine, a printer, or a facsimile has recently been used a thin hollow core metal roll having a heater inside. A system is adopted in which the rise time of the equipment is shortened by reducing the thickness.

  In addition, the surface of a thin belt made of a heat-resistant resin such as polyimide resin or metal is heated by an inner heater through a fixing belt provided with a release layer such as a fluororesin, and a toner image is formed on paper. There is also a method of fixing by heating. This method has an advantage that the rise time of the machine can be further shortened because a thin fixing belt having a small heat capacity is used.

  However, for quick start-up of the device, it is preferable to reduce the pressure roller of the fixing device from taking heat from the fixing roller and the fixing belt as much as possible during heat fixing. A low thermal conductivity pressure roller is used in which a silicone sponge layer having a low thermal conductivity is formed under the pressure roller and a thin fluororesin layer is provided on the outer surface thereof.

  As a silicone sponge under such a pressure roller, a method of forming a sponge layer by mixing liquid micro-resin pre-expanded resin microballoons is widely used from the viewpoint of stability of cell diameter and thermal conductivity. ing. This method has the advantage that the cell is stable because the resin microballoon has been thermally expanded in advance, and the porosity of the elastic layer can be controlled by the mixing ratio of the microballoon, so that stable thermal conductivity can be obtained. There is.

  However, if a roller with a single layer structure in which only a silicone rubber elastic layer containing a resin microballoon is provided on the outer peripheral surface of the core metal is used as a roller for a fixing device, the physical properties of the microballoon are very low. The strength of the roller is insufficient, cannot withstand the frictional force with the fixing belt and the frictional force with the paper, and the surface of the roller for the fixing device is destroyed immediately. For that purpose, a fluororesin layer is formed on the outer peripheral surface of the roller, or a fluororesin tube is put on to provide durability.

As a prior art of a fixing roller using an elastic layer containing a resin microballoon as a lower layer and provided with a fluororesin layer on its surface, an average particle diameter of 200 μm or less is added to 100 parts by weight of a thermosetting organopolysiloxane composition. A hollow filler is blended in an amount of 0.1 to 200 parts by weight, and a fluororesin layer is provided on the outer peripheral surface (see, for example, Patent Document 1), between a rubber layer containing an organic microballoon and a heat-resistant rubber layer In which a heat-resistant rubber layer containing a fluororesin is formed (see, for example, Patent Document 2), at least one rubber layer is formed on a base material, and the heat resistance of the fluororesin or polyimide resin is the outermost layer. In the rubber-covered roller on which the resin layer is formed, the rubber layer is composed of an organic microballoon and a rubber layer containing a supplement (see, for example, Patent Document 3). The pressure roller has an elastic layer containing dispersed voids formed by resin microballoons, and has a fluororesin and fluororubber release layer as the outermost layer (see, for example, Patent Document 4), at least on the support. A roller having an elastic layer, the elastic layer being formed by curing silicone rubber in which at least an already expanded resin microballoon is blended, and a roller having a fluororesin tube coated on the outer periphery or a roller coated with a fluororesin ( For example, see Patent Document 5).
Patent No. 3494039 (Claims, Claims 1 and 5) JP2000-230541 (Claims, Claims 1 and 4) JP 2001-295830 (Claims, Claims 5 and 6) JP 2002-148988 (Claims, Claims 1, 13) JP 2002-70838 (Claims, Claim 1, Paragraph 0004)

  However, as in the prior art described above, a silicon rubber layer is provided on the outer peripheral surface of the roller shaft, and a fluororesin layer is formed on the outer periphery, or a fluororesin tube is covered, and further, a fluororesin is coated. Has a problem that it is very difficult to firmly bond the fluororesin layer and the underlying silicone rubber elastic layer.

  For this purpose, a thin tube is molded in advance with a fluororesin, and the inner surface is formed into a layer that can be bonded by a strong alkaline chemical treatment or excimer laser treatment, and one or both of the inner surface of the fluororesin tube and the surface of the rubber elastic layer. A method is adopted in which an adhesive is applied to adhere the fluororesin tube to the rubber elastic layer. However, this method has a problem of lack of quality stability due to many bonding steps. Further, this method has a problem that the heat treatment of the treatment layer itself is inferior to that of fluororesin due to chemical treatment or excimer laser treatment on the inner surface of the tube, and if the roller is used for a fixing device at a high temperature for a long period of time, the treatment layer may be damaged. It was.

  In addition, after creating an elastic body containing resin microballoons, the surface is coated with fluororesin or fluororubber blended with fluororesin using the dipping method or spray method. In this method, the surface layer is vulcanized or cured to form a roller for a fixing device. However, in order to increase the adhesive force, this method does not provide a strong adhesive force even if a plurality of adhesive layers are provided. It could not withstand long-term use underneath.

  Further, blends of fluororesin and fluororubber are excellent in releasability, but this has a characteristic that the friction coefficient is very low. Therefore, when this is used as a pressure roller for a fixing device used for a fixing belt, there is a problem that slippage occurs between the pressure roller and the paper depending on the fixing conditions, and the conveyance speed changes. This slip changes depending on the type of paper and the environment, and in a high temperature and high humidity environment, the amount of water in the paper increases, so the water vaporizes due to heat during fixing and slipping is more likely to occur. there were.

  As an improvement measure for these problems, attempts have been made to suppress slip by reducing the influence of water vaporized by roughening the roller surface roughness, but in addition to the difficulty of making the surface roughness constant, Since the surface roughness may change due to wear during use of the roller, it is not an effective improvement measure.

  Recently, the development of toners with better releasability than before due to improvements in toner components has led to the use of highly releasable fluororesins and fluororubber materials containing fluororesins as the surface release layer. However, development of a fixing device in which toner does not adhere to the surface of the fixing device roller has been progressing for a long time. The purpose of this is to solve the problem of adhesion failure between the release layer and the paper, to solve the slip problem with paper, and because the price of fluororesin and fluororubber material containing fluororesin is very expensive, do not use fluororesin. The main purpose is to reduce the price of the fixing device. However, in reality, the problem of the reinforcing layer has not been solved by the improvement of the toner component.

  In view of the above circumstances, the present invention is free from the problem of adhesiveness to the underlying rubber elastic body, is excellent in slip resistance as a roller for a fixing device, has less hardness change and external shape change, and is a short process It is an object of the present invention to obtain a highly durable roller for a fixing device that can be manufactured by the above method.

The present invention cures a composition comprising a resin microballoon in which thermoplastic resin particles encapsulating liquid hydrocarbons encapsulated in a core metal outer peripheral surface and a polyhydric alcohol are blended in a liquid addition reaction type silicone rubber. A pressure roller of a fixing device (Claim 1), wherein a formed silicone rubber elastic layer is provided and a reinforcing layer made of 2 to 50 μm silicone rubber is provided on the surface thereof. 2. The pressure roller of the fixing device (Claim 2), the reinforcing layer, wherein the addition reaction-type silicone sponge composition containing the resin or the condensation reaction type silicone rubber composition containing the adhesive component is cured. The pressure roller of the fixing device according to claim 1, wherein the silicone rubber is a durometer, a type A hardness of 15 to 50 ° and a specific gravity of 1.4 or less. Claim 3).

  According to the present invention, since the silicone rubber layer is provided on the surface layer of the silicone sponge elastic body provided on the core metal peripheral surface of the roller for the fixing device such as a copying machine without using the fluororesin or the fluororesin film, Thus, the problem of poor adhesion between the lower layer silicone sponge rubber elastic body and the surface layer fluororesin or fluororesin film can be solved. In addition, since the lower silicon corn sponge layer is made of open cells, it is possible to prevent the roller from expanding due to heating during use. For this reason, such as a change in paper transport speed due to the expansion of the roller. Trouble can be prevented beforehand. Further, the toner can be stably fixed with little change in the hardness of the roller even after long-term use.

  FIG. 1 schematically shows the configuration of a fixing device 1 such as a copying machine. The fixing device 1 includes a fixing belt 2 and a pressure roller 3 that is in sliding contact with the fixing belt 2. The fixing belt 2 is a cylindrical sheet made of a heat-resistant resin film such as a metal thin plate or polyimide resin. The paper 5 on which the toner 4 is adhered in the form of characters, figures, etc. is supplied between the fixing belt 2 and the pressure roller 3, and is moved in the direction of the arrow 6 by the rotation of the pressure roller 3, and fixed in the meantime. The heater 7 of the belt 2 heats it, and the toner 4 is welded onto the paper 5.

  The pressure roller 3 forms one or more silicone sponge elastic layers 11 around the core metal 10. This silicone sponge elastic layer 11 is formed by curing a composition comprising a resin microballoon in which thermoplastic resin particles encapsulating liquid hydrocarbons are thermally expanded in advance and a polyhydric alcohol in liquid addition reaction type silicone rubber. Shall be. On the surface of the silicone rubber elastic layer 11, a reinforcing layer covered with a thin silicone rubber is formed.

  Here, the silicone sponge elastic layer 11 is a sponge elastic layer obtained by curing a composition comprising a resin microballoon in which thermoplastic resin particles encapsulating liquid hydrocarbons are thermally expanded in advance and a polyhydric alcohol in liquid addition reaction type silicone rubber. The reason for this is to make the elastic body into an open-cell type silicone sponge. Since the continuous foam type silicone sponge elastic layer can suppress thermal expansion due to heating when used as a roller for a fixing device, it is possible to suppress a change in paper conveyance speed due to thermal expansion of the roller. Moreover, it is possible to reduce the change in the hardness of the roller even during long-term use.

  On the silicone rubber elastic layer, a very thin silicone rubber reinforcing layer of 2 to 50 μm is provided. This reinforcing layer uses a low-viscosity liquid silicone rubber, or adjusts the viscosity by diluting with a solvent in a high-viscosity raw material, and forms a thin film on the elastic layer surface by the dipping method, spray coating method, It is formed by vulcanization and curing.

  In order to adhere the reinforcing layer to the surface of the silicone rubber elastic layer, it is necessary to provide an adhesive layer on the adhesive surface, but in order to stabilize the adhesion, an addition reaction type silicone rubber composition containing an adhesive component in advance or When a condensation reaction type silicone rubber composition containing an adhesive component is used, stable and strong adhesion can be obtained without providing an adhesive layer.

  The addition reaction type silicone rubber composition containing the above-mentioned adhesive component is generally called a thermosetting silicone adhesive, a silicone sealing material, or a potting material. TSE322 series, TSE325 series manufactured by GE Toshiba Silicone, It is a type of silicone rubber that self-adheres by adding an adhesive component to an addition reaction type series rubber such as X-32-1934 series manufactured by Shin-Etsu Chemical Co., Ltd. and heat curing. Further, the condensation reaction type silicone rubber composition containing an adhesive component is called a room temperature curable type silicone adhesive or a sealing agent. TSE382 series, TSE370 series, Shin-Etsu Chemical, manufactured by GE Toshiba Silicone Co., Ltd. It is represented by the KE45 series and KE42 series manufactured by Kogyo Co., Ltd., the SH780 series and SE9175 series manufactured by Toray Dow Corning Co., Ltd., and is a type of silicone rubber that cures and adheres at room temperature by a condensation reaction.

  The reinforcing layer is thin with a thickness of 2 to 50 μm. This thickness has a sufficient effect as a reinforcing layer for the fixing device. If the thickness of the reinforcing layer is less than 2 μm, it is difficult to form a uniform silicone rubber layer on the entire surface, and the crosslinking component in the silicone rubber is absorbed by the elastic body layer, causing partial curing failure. And a stable reinforcing layer is not formed. If the thickness of the reinforcing layer exceeds 50 μm, the surface hardness of the roller for the fixing device increases, which hinders the effect of using the low-hardness balloon sponge layer and greatly changes the thermal conductivity of the roller surface. The rise time of the fixing device and the fixed image may be affected.

  Further, the silicone rubber as the reinforcing layer of the fixing device roller of the present invention is preferably a low hardness silicone rubber so as not to hinder the low hardness of the fixing device roller. However, if silicone rubber with a JIS-A hardness of 15 ° or less is used, the surface will become sticky and the paper will wrap around the roller during fixing, so it cannot be used. It is preferable to use rubber having a JIS-A hardness of 15 to 50 °.

  Various fillers can be added to the silicone rubber used as the reinforcing layer to further increase the strength and impart electrical conductivity. However, if a large amount of the filler is added, the releasability as silicone rubber is reduced. For this reason, the toner tends to adhere to the surface. In addition, when a large amount of a filler having a specific gravity of silicone rubber of 1.40 or more is blended, toner adhesion is likely to occur and the roller for the fixing device may not be practically used.

  By adding a conductivity-imparting agent such as carbon black or metal powder to the silicone rubber elastic layer or silicone rubber reinforcing layer containing resin microballoons, the volume resistivity can be lowered, and charging of the fixing roller can be suppressed to improve image quality. Although it is possible to improve the paper passing property, the silicone rubber elastic layer containing the resin microballoon has a problem of strength, and the blending of a large amount of conductivity imparting agent may lead to a decrease in physical properties. It is preferable to add to the rubber reinforcing layer.

Example 1
As shown in FIG. 2, a metal core 32 having an outer diameter of 11 mm and an adhesive applied is mounted in a metal mold 33 having an inner diameter of 18.3 mm, and a liquid addition reaction is performed in the gap between the metal core 32 and the metal mold 33. Liquid addition reaction type in which 2.0 parts by weight of resin microball (Kema Nobel, trade name: EXPANSEL 092DE-120) previously heat-expanded and 100 parts by weight of silicone rubber are mixed with 8.0 parts of triethylene glycol A silicone rubber composition is injected from below the mold, and the mold is heated at 130 ° C. for 40 minutes to remove low molecular weight siloxane content, triethylene glycol, decomposition products of resin microballoons, and the like. A roller having an outer diameter of 18 mm formed on the outer periphery was obtained.

  A solution obtained by removing this from the mold and diluting an addition reaction type silicone rubber composition X-32-1934 (trade name of Shin-Etsu Chemical Co., Ltd.) containing an adhesive component with toluene on the silicone sponge elastic layer 34. Was coated by spray coating, and this was left at room temperature for 2 hours to remove toluene, and then heated in an oven at 100 ° C. for 4 hours to cure the silicone rubber, thereby forming a silicone rubber reinforcing layer having a thickness of 5 μm. The reinforcing layer had a hardness (durometer type A) of 35 ° and a specific gravity of 1.25. The fixing device roller had a roller surface hardness of 36 ° (Asker C hardness meter). This fixing device roller was used as a fixing device roller for a printer LBP 3000 manufactured by Canon Inc., and a paper passing test was conducted. As a result, there was no problem with 20,000 sheets.

(Examples 2 and 3)
In Example 2, a fixing roller was prepared in the same manner as in Example 1. In this case, the thickness of the silicone rubber reinforcing layer was set to 5 μm, and the others were the same as in Example 1. In Example 3, a fixing roller was prepared in the same manner as in Example 1. In this case, the thickness of the silicone rubber reinforcing layer was set to 50 μm, and the others were the same as in Example 1. When a paper passing test similar to that in Example 1 was performed, no unevenness of the fixed image or paper wrapping occurred up to 20,000 sheets, and there was no problem in use as a pressure roller.

(Comparative Example 1)
A core metal having an outer diameter of 11 mm coated with an adhesive is mounted in a mold having an inner diameter of 18.3 mm as shown in FIG. Liquid addition reaction type silicone rubber composition in which 2.0 parts by weight of resin micro balloon (Expancel 092DE-120) previously thermally expanded and 100 parts by weight of liquid addition reaction type silicone rubber are mixed with 8.0 parts of triethylene glycol. Was injected from below the mold, and the mold was heated at 130 ° C. for 40 minutes to remove low molecular weight siloxane content, triethylene glycol, resin microballoon degradation products, etc., and an open cell silicone sponge elastic layer was formed on the outer periphery. A roller for a fixing device having an outer diameter of 18 mm was obtained.

  This fixing roller has a roller surface hardness of 35 ° (Asker C hardness meter) and a roller surface thermal conductivity of 0.117 W / m. K, the specific gravity of the elastic layer was 0.62. When a sheet-passing test was conducted on the fixing device roller in the same manner as in Example 1, unevenness of the fixed image occurred on the 90th sheet. When the fixing roller was disassembled and the pressure roller surface was confirmed, the elastic surface was broken.

(Comparative Examples 2 and 3)
In Comparative Example 2, a fixing roller was prepared in the same manner as in Example 1. In this case, the thickness of the silicone rubber reinforcing layer was set to 1 μm, and the others were the same as in Example 1. In Comparative Example 3, the thickness of the silicone rubber reinforcing layer was set to 60 μm in the same manner as in Example 1, and the others were the same as in Example 1. Comparative Example 2 could not be used for the paper passing test because the silicone rubber partly had an uncured portion on the roller surface. Comparative Example 3 has a roller surface thermal conductivity of 0.136 W / m. The test was not conducted because the difference was found in the fixability of the first image of the sheet that passed through. The results of Examples 1 to 3 and Comparative Examples 2 and 3 are summarized in Table 1.

(Examples 4-7, Comparative Example 4)
On the silicone sponge elastic body molded in the same manner as in Example 1, the material of the paper cone rubber reinforcing layer was changed to obtain fixing rollers of Examples 4-6. Further, in Example 7, a surface reinforcing layer was formed on the elastic layer surface via an adhesive DY39-110A / B (manufactured by Toray Dow Corning Silicone Co., Ltd.) to obtain a roller for a fixing device. The silicone rubber material is as follows.

TSE322 GE Toshiba Silicone Co., Ltd. addition reaction type silicone rubber
TSE3221 GE Toshiba Silicone Co., Ltd. addition reaction type silicone rubber
KE45 Shin-Etsu Chemical Co., Ltd. Condensation reaction curable silicone rubber
KE1346 Shin-Etsu Chemical Co., Ltd. Addition reaction type silicone rubber
Does not contain wearing ingredients)
TSE325 TOSHIBA SILICON Co., Ltd., addition reaction type silicone A sheet-passing test was conducted using the fixing unit rollers of Examples 4-7 as the fixing unit roller of the same printer LBP 3000 as Canon Example 1. As a result, no fixed image unevenness or paper wrapping occurred up to 20,000 sheets of paper, and no problem occurred.

In Comparative Example 4, since the surface reinforcing layer having a hardness of 12 ° and a low hardness was used, the roller surface had adhesiveness, and the paper was wound around the fixing device roller in the first sheet of the paper passing test and could not be used. These results are summarized in Table 2.

(Comparative Examples 5 and 6)
On an open-cell silicone sponge elastic body molded in the same manner as in Comparative Example 1, an addition reaction type silicone rubber composition SE6746 (adhesive DY39-110A / B (manufactured by Toray Dow Corning Silicone Co., Ltd.)) Toray Dow Corning Silicone Co., Ltd.) was used to prepare a roller for fixing device of Comparative Example 5 by providing a silicone rubber reinforcing layer of 30 μm by the method of Example 1.

  In Comparative Example 5, the rubber of the reinforcing layer having a hardness of 60 ° was used, but the roller surface hardness became hard, and the nip width of the fixing device was measured. As a result, the nip width was 0.4 mm as compared with the roller of Example 1. It was confirmed that it was getting smaller. For this reason, there was a difference in the fixability of the first image of the paper passing, and the paper passing test was not performed.

In Comparative Example 6, a fixing roller was manufactured in the same manner as Comparative Example 5 using KE1367 (Shin-Etsu Chemical Co., Ltd.). Using this, a paper passing test was conducted in the same manner as in Example 1. As a result, stains appeared on the back side of the paper when about 20,000 sheets were passed. Then, when the surface of the pressure roller for the fixing device was confirmed, it was found that the toner was adhering, and this caused the backside of the paper to become dirty. At this point the test was stopped. This is considered to be due to the fact that the toner adheres due to insufficient releasability with respect to the toner due to the silicone rubber having a specific gravity of 1.47 and a large amount of filler. These results are summarized in Table 3.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory view of a fixing device using a fixing device roller according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory diagram illustrating a process for manufacturing a fixing device roller according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fixing device, 2 ... Fixing belt, 3 ... Pressure roller, 4 ... Toner, 5 ... Paper, 7 ... Heater, 10, 32 ... Core metal, 11, 34 ... Silicone sponge elastic layer, 33 ... Mold.

Claims (3)

On the outer peripheral surface of the cored bar, a resin microballoon in which thermoplastic resin particles encapsulating liquid hydrocarbons are previously thermally expanded and a polyhydric alcohol are mixed with a liquid addition reaction type silicone rubber is cured to form. A pressure roller for a fixing device, wherein a silicone rubber elastic layer is provided and a reinforcing layer made of silicone rubber of 2 to 50 μm is provided on the surface thereof. 2. The pressure roller for a fixing device according to claim 1, wherein the reinforcing layer is obtained by curing an addition reaction type silicone sponge composition containing an adhesive component or a condensation reaction type silicone rubber composition containing an adhesive component. The pressure roller of the fixing device according to claim 1 or 2, wherein the silicone rubber of the reinforcing layer is a silicone rubber having a durometer, a type A hardness of 15 to 50 °, and a specific gravity of 1.4 or less.

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