JP4446877B2 - Fixing roller and fixing device - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus of an electrophotographic system such as a copying machine, a facsimile machine, or a laser printer, and a fixing device used for melt-pressing unfixed toner on a sheet and fixing it to the sheet, and The present invention relates to a fixing roller used in a fixing device and a silicone rubber foam as a raw material thereof.

  Conventionally, as a fixing device of an electrophotographic image forming apparatus of an electrophotographic system, a so-called pair of rollers including a fixing roller having a built-in heat generation source and a pressure roller that presses the fixing roller with a predetermined pressure are provided. A roller structure is employed, and the fixing roller and the pressure roller are collectively referred to as a fixing roller.

  These fixing rollers are generally used in a state where they are pressed at a constant pressure at a high temperature of 180 to 200 ° C. in order to melt and press the unfixed toner onto the sheet. For this reason, the fixing roller is required to have a low coefficient of thermal expansion and low thermal degradation, and the surface friction force must be within a certain range in order to maintain a constant sheet conveyance capability. Is done.

  Further, in order to obtain a sheet conveying force, a high rubber elastic layer is provided on the surface of the pressure roller in order to secure a nip portion having a predetermined width at the rolling contact portion between the fixing roller and the pressure roller. Is required (see, for example, Patent Document 1).

  Therefore, conventionally, a fixing pressure roller provided with a silicone rubber-like elastic body having an open cell structure having a water absorption rate of 40% or more and an open cell rate of 90% or more on the outer periphery of a cylindrical metal core. Has been proposed.

This pressure roller for fixing has a continuous foam structure even under high temperatures, so that the internal steam escapes, the increase in the outer diameter of the roller due to thermal expansion and the decrease in the hardness of the foam are reduced, and a sufficient nip width It is said that the flexibility which can ensure is high (for example, refer patent document 2).
Japanese Patent Laid-Open No. 2002-6666 JP 2004-70159 A

  However, in the invention described in Patent Document 1, it is a main object of the invention to reduce the heat capacity of the rubber foam and thereby shorten the warm-up time. However, there is no recognition of the relationship between the thermal expansion coefficient of the rubber foam and the stable fixing operation.

  In the invention described in Patent Document 2, the rubber foam on the outer periphery of the fixing roller has an open cell structure of 90% or more, and further, the structure has a water absorption of 40% or more. The increase in roller outer diameter and the decrease in hardness due to thermal expansion are alleviated, thereby solving the problem of variation in the feed speed of the roller and stabilizing the fixing operation. Although it is common with this invention in the point which pays attention to the thermal expansion of a rubber foam, in order to obtain the desired rubber foam which has a 90% or more open-cell structure, it is necessary to perform foaming and hardening through three steps of heat treatments. In addition, it is difficult to produce a rubber foam in which the heating operation is complicated, the open cell structure is changed due to changes in heating conditions, and the thermal expansion is controlled to be constant.

  Accordingly, the present invention solves the above-mentioned problems of the prior art, and the temperature of the fixing roller is continuously increased from room temperature due to the synergistic effect of the reinforcing action and gas adsorption action of the porous filler having a pore volume of 0.3 ml / g or more. The present invention provides a silicone rubber foam having a small coefficient of thermal expansion even when the temperature is raised to the temperature during use, and a change in volume due to thermal expansion within a certain range, a fixing roller employing the silicone rubber foam, and the fixing It is an object of the present invention to provide a fixing device for an electrophotographic image forming apparatus incorporating a roller.

In order to achieve the above object, the present invention provides a fixing roller using a foam obtained by foaming and vulcanizing silicone rubber, wherein the silicone rubber foam according to claim 1 comprises : to 100 parts by weight of a silicone rubber compound, the pore volume 0.3 ml / g or more porous fillers containing 5 to 50 parts by weight, the thermal expansion coefficient of 5.1% or more and 6% or less der Resid silicone rubbers foam It is characterized by using.

The fixing roller using the silicone rubber foam according to claim 2 is characterized in that, in addition to the structure of claim 1, the porous filler is made of at least one of zeolite, silica, diatomaceous earth, and carbon. It is said.

A fixing roller using the silicone rubber foam according to claim 3 uses an organic azo compound as a foaming agent for the silicone rubber in addition to the structure of claim 1 or 2, and the organic azo compound is dimethyl -1,1′-azobis (1-cyclohexanecarboxylate).

According to a fourth aspect of the present invention, a fixing device in the electrophotographic image forming apparatus uses the fixing roller using the silicone rubber foam according to any one of the first to third aspects.

According to the fixing roller using the silicone rubber foam according to claim 1 or 2, it is possible to provide a fixing roller using a silicone rubber foam having a low coefficient of thermal expansion and little thermal deterioration. In addition, since the fixing roller is formed of such a silicone rubber foam, it is possible to maintain a stable sheet conveying capability during paper feeding and to provide a fixing roller that exhibits a good fixing operation.

According to the fixing roller using the silicone rubber foam according to claim 3, the fixing roller using the silicone rubber foam having a small coefficient of thermal expansion, high rubber elasticity and flexibility, and low thermal deterioration . Roller can provide. In addition, since the fixing roller is formed of such a silicone rubber foam, it is possible to maintain a stable sheet conveying capability during paper feeding and to provide a fixing roller that exhibits a good fixing operation.

According to the fixing device of an electrophotographic image forming apparatus according to claim 4, the constant wear roller is incorporated with silicone rubber foam according to claims 1 to 3, the sheet conveying during continuous operation It is possible to provide a fixing device for an electrophotographic image forming apparatus that has stable capability and extremely low occurrence of fixing failure.

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

  The foam base material obtained by foaming and vulcanizing the silicone rubber of the present invention is a vinyl group-containing dimethyl silicone raw rubber, a vinyl group-containing phenyl silicone raw rubber, a vinyl group-containing fluorosilicone raw rubber, or a modified product thereof as necessary. Further, reinforcing silica fillers such as fumed silica and precipitated silica are added.

  As the crosslinking agent for addition reaction used in the vulcanization treatment, organohydrogenpolysiloxane having two or more SiH groups in one molecule is used. As this organohydrogenpolysiloxane, linear, cyclic, molecular, Any of the branched structures may be used, and a known organohydrogenpolysiloxane can be used as a curing agent for the addition reaction curable silicone rubber composition. The compounding amount of the organohydrogenpolysiloxane is preferably 0.01 to 20 parts by mass with respect to 100 parts by mass of the organopolysiloxane as the silicone rubber compound component. In addition, the use of organic peroxide as a vulcanization aid is effective in improving physical properties such as rubber strength and strain. This includes benzoyl peroxide, bis 2,4 dichlorobenzoyl peroxide, and dicumyl peroxide. , Di-t-butyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane and the like. Further, non-reinforcing silica may be added to adjust the heat resistance improver and hardness.

  Furthermore, it is preferable to add a known platinum catalyst inhibitor such as methylvinylcyclotetrasiloxane, acetylene alcohols, siloxane-modified acetylene alcohol, hydroperoxide, etc. to the silicone rubber foam using a crosslinking reaction by this addition reaction.

  The addition reaction catalyst may be any conventionally known catalyst. Specifically, a platinum group metal simple substance and a compound thereof can be used. For example, particulate platinum metal adsorbed on a support such as silica, alumina or silica gel, platinous chloride, chloroplatinic acid, chloroplatinic acid hexahydrate complex with olefin or divinyldimethylpolysiloxane, chloroplatinic acid Examples thereof include platinum-based catalysts such as hexahydrate alcohol solutions, palladium catalysts, and rhodium catalysts. The addition amount of these catalysts is a catalyst amount and is usually used in the range of 1 to 1,000 ppm in terms of the amount of platinum-based metal, but preferably in the range of 10 to 500 ppm. If it is less than 1 ppm, the crosslinking reaction may not be sufficiently promoted and curing may be insufficient. Even if it is added in excess of 1,000 ppm, there is little influence on the reactivity and it is uneconomical.

  The blowing agent may be any conventionally known one, and specifically, an organic azo compound such as azodicarbonamide, azobis-isobutyronitrile is preferably used. In particular, dimethyl-1,1'-azobis (1-cyclohexanecarboxylate) can be preferably used, but is not limited thereto.

  When the amount of the porous filler used in the present invention is less than 5 parts by mass with respect to 100 parts by mass of the silicone rubber compound, a sufficient reinforcing action cannot be obtained, and the low thermal expansion coefficient cannot be maintained, and more than 50 parts by mass. Since the workability is deteriorated and the physical properties of the resulting silicone rubber are deteriorated, the amount is preferably 10 to 40 parts by mass.

  As the porous filler, for example, a mercury intrusion method or the like (an example of an apparatus used in this method is 0 when the integrated pore volume is measured by an automatic specific surface area measuring device “GEMINI 2375” (trade name, manufactured by Shimadzu Corporation). Any inorganic porous filler having a pore volume of 3 ml / g or more can be used. Specifically, ZEOSTAR “CA-100P”, which is a synthetic zeolite filler (trade name, manufactured by Nippon Kagaku Kogyo Co., Ltd.) And silica filler “SUNSPHERE H33” (trade name, manufactured by Asahi Glass Co., Ltd.).

  The foam formed by foaming and vulcanizing the silicone rubber of the present invention is filled with non-reinforcing silica such as pulverized quartz and diatomaceous earth, carbon black such as acetylene black, furnace black and channel black, and calcium carbonate as necessary. Additives, colorants, heat resistance improvers, flame retardant improvers, acid acceptors, heat conduction improvers, release agents, alkoxysilanes, diphenylsilanediols, carbon functional silanes, both end silanol group blocking low You may add dispersing agents, such as molecular siloxane.

  The silicone rubber compound for the present invention can be obtained by uniformly mixing the above-described components using a rubber kneader such as a two-roll, Banbury mixer, or dough mixer (kneader).

  The silicone rubber composition thus prepared can be easily foamed and cured by heating to obtain a silicone rubber foam characterized by having a coefficient of thermal expansion of 6% or less. The curing foaming method may be any method that can apply sufficient heat to the decomposition of the foaming agent and the vulcanization of the silicone rubber, and the molding method is particularly limited to continuous vulcanization by extrusion, pressing, injection molding, etc. Is not to be done. In this case, the heating temperature is preferably 100 to 500 ° C, particularly 200 to 400 ° C, and the heating time is preferably several seconds to 1 hour, particularly 10 seconds to 30 minutes. Moreover, you may carry out secondary vulcanization at 180-250 degreeC for about 1 to 10 hours as needed.

  Next, embodiments of the fixing roller and the fixing roller of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a configuration of an embodiment of a fixing roller, and FIG. 2 is a cross-sectional view of a main part when a pair of roller structures is used as a fixing roller.

  The basic configuration of the fixing roller A of the present invention is composed of a metal shaft 1 and a silicone rubber foam 2 on the outside thereof, which are arranged as shown in FIG. In order to improve the adhesion with the silicone rubber foam 2 prior to processing, the metal shaft body 1 in FIG. 1 is preferably cleaned with an organic solvent or the like to remove oil and then subjected to primer treatment. As the primer treatment, specifically, “Primer No. 101A / B” (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied and baked in an oven. It is not limited.

  The silicone rubber compound of the present invention and the metal shaft body are integrally extruded by an extrusion molding machine and then baked in an infrared oven to be cylindrically ground into a cylindrical shape as shown in the fixing roller embodiment of FIG. The outer diameter was polished with a board. As long as the metal shaft 1 and the silicone rubber foam 2 are in close contact with each other and a cylindrical appearance as shown in FIG. 1 is obtained, the method is not limited to this method, and the silicone rubber foam 2 Alternatively, a method may be used in which only foaming is first formed and then bonded to the metal shaft 1 later.

  The fixing roller A needs to be able to generate heat in order to melt and press the unfixed toner, and the metal shaft 1 used for the fixing roller A in FIG. 1 incorporates a heat source. Induction heating or the like is also used for heat generation of the fixing roller. In this case, the metal shaft 1 may be a solid metal rod. In the IH heating method, an IH coil for generating magnetic field lines is arranged around the metal shaft body 1.

  The pressure roller B in FIG. 2 plays a role of pressing the sheet against the fixing roller when the unfixed toner on the sheet is melt-pressed, and the pressure roller B itself may not have a heat generating function.

  When examining the occurrence of fixing failure when the fixing roller of the present invention is used, the fixing roller A and the pressure roller B created as described above are set on the upper side and the pressure roller B on the lower side. Applying enough pressure to ensure a nip with a predetermined width at the rolling contact, incorporating it into the actual fixing device with the configuration shown in Fig. 2, conducting a continuous print test of the dedicated pattern for evaluation, and evaluating the print quality by visual evaluation Did.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.
[Example 1]

  For 100 parts by mass of silicone rubber compound “KE-551U” (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), as a porous filler, ZEOSTER “CA-100P” (trade name, Nippon Chemical Industry Co., Ltd.), which is a synthetic zeolite filler. Co., Ltd.) 30 parts by weight, organohydrodiene polysiloxane 2 parts by weight, blowing agent dimethyl-1,1'-azobis (1-cyclohexanecarboxylate) 5 parts by weight, chloroplatinic acid as a catalyst, and silicone rubber blended A product was prepared. Also, a metal shaft (diameter 14 mm × 350 mm, SUS22 electroless nickel-plated) was washed with toluene, and “Primer No. 101A / B” as a primer (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) Apply.

  Further, the primer-treated metal shaft body was baked at a temperature of 180 ° C. for 30 minutes in a gear oven, cooled at room temperature for 30 minutes or more, and the primer-treated metal shaft body and the silicone rubber compound were combined. Then, it is integrally extruded by an extruder and fired in an IR furnace to form a sponge roll original. It was further baked for 7 hours at 200 ° C. in a gear oven, left at room temperature for 1 hour, then externally ground with a cylindrical grinder and stored in a constant temperature room at 20 ° C. The outer diameter of the product was measured for a total of three points, 10 mm from the center and the central part.

  The roll thus obtained was heated at 180 ° C. for 2 hours, and the product outer diameter when the product temperature was 180 ± 5 ° C. was measured in the same manner as at 20 ° C. Based on the data thus obtained, calculation was made using the following formula for calculating the coefficient of thermal expansion of the sponge layer at 20 to 180 ° C.

  Further, the pressure roller obtained as described above was incorporated into a fixing device, and in order to check whether or not fixing failure occurred, it was actually incorporated into an actual machine and 50000 printing was performed using A4 plain paper. Thereafter, the printing was evaluated visually using a dedicated evaluation pattern. ◎ is no problem, × is an occurrence of a serious problem such as fading or whiteout, ○ is an evaluation level that there is no problem with normal text printing, but there are some difficulties when printing graphs and photos Is shown.

  The pore volume of the filler was confirmed using an automatic non-surface area measuring device “GEMINI 2375” (trade name, manufactured by Shimadzu Corporation).

These data are shown in Table 1.
[Example 2]

A sponge roller was molded in the same manner as in Example 1 except that the porous filler of Example 1 was changed to 30 parts by mass of silica filler “SUNSPHERE H33” (trade name, manufactured by Asahi Glass Co., Ltd.). About the obtained roll, the thermal expansion coefficient and the fixability were confirmed in the same manner as in Example 1. These data are shown in Table 1.
[Example 3]

A sponge roller was molded in the same manner as in Example 1, except that 5 parts by mass of dimethyl-1,1′-azo-bisisobutylnitrile was used as the foaming agent in Example 1. About the obtained roll, the thermal expansion coefficient and the fixability were confirmed in the same manner as in Example 1. These data are shown in Table 1.
[Comparative Example 1]

  A sponge roller was molded in the same manner as in Example 1 except that the filler of Example 1 was changed to 30 parts by mass of the non-porous filler “SUNSPHERE NP-30” (trade name, manufactured by Asahi Glass Co., Ltd.). About the obtained roll, the thermal expansion coefficient and the fixability were confirmed in the same manner as in Example 1. These data are shown in Table 1.

  Examples 1 and 2 are cases where a porous filler having a pore volume of 0.3 ml / g or more and a dimethyl-1,1′-azobis (1-cyclohexanecarboxylate) foaming agent were used, and corresponded to claim 3. This is an example. The obtained fixing roll had a coefficient of thermal expansion of 6% or less, and the fixability evaluation using the dedicated evaluation pattern gave a very good fixability result.

  Example 3 is a case in which the foaming agent is a foaming agent generally used for foaming silicone rubber, and corresponds to claim 2. Although the thermal expansion coefficient of the fixing roll was slightly larger than those in Examples 1 and 2, 6% or less was obtained, and the results of the fixing property evaluation were generally good unless the conditions were such as graphs and photographic printing. From this result, it can be seen that the effect of the present invention can be obtained if a porous filler having a pore volume of 0.3 ml / g or more is contained.

  Comparative Example 1 is a case where dimethyl-1,1'-azobis (1-cyclohexanecarboxylate) is used as the non-porous filler having a pore volume of 0.05 ml / g and the foaming agent, which are not based on the present invention. The thermal expansion coefficient of the fixing roll was 7.5%, and occurrence of an event that could be a serious problem was observed, such as white spots observed during the fixing performance evaluation. From this result, it is understood that the desired effect cannot be obtained only by selecting the foaming agent, and it is effective to contain a porous filler having a pore volume of 0.3 ml / g or more.

FIG. 3 is a perspective view of a fixing roller embodiment of the present invention. It is a principal part cross-sectional view when it is set as a pair of roller structure as a fixing roller.

Explanation of symbols

1 Metal shaft body 2 Silicone rubber foam A Fixing roller B Pressure roller

Claims (4)

A fixing roller using a foamed product obtained by foaming and vulcanizing silicone rubber, wherein the silicone rubber contains 5 to 5 parts of a porous filler having a pore volume of 0.3 ml / g or more in 100 parts by mass of a silicone rubber compound. It contained 50 parts by weight, fixing roller, wherein the thermal expansion coefficient using a der Cie silicone rubbers foam 6% less than 5.1%. The fixing roller according to claim 1, wherein the porous filler is made of at least one of zeolite, silica, diatomaceous earth, and carbon. The organic azo compound is used as a foaming agent for the silicone rubber, and the organic azo compound is dimethyl-1,1'-azobis (1-cyclohexanecarboxylate). Fixing roller . Fixing device in an electrophotographic image forming apparatus using the constant wear rollers according to any one of claims 1 to 3.

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