JPS6311668B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing roller that fixes a toner image to recording paper using the heat and/or pressure of the roller. 2. Description of the Related Art The fixing roller of the above type is well known and is used, for example, in electronic copying machines. In this type of fixing roller, the surface of a metal core member is coated with a layer having release properties in order to prevent offset and the like and obtain good fixing properties. However, the fixing roller is required to have good not only release properties but also good thermal conductivity and durability. In this case, durability includes the abrasion resistance and heat resistance of the surface layer itself, as well as the adhesion between the surface layer and the core member. A fixing roller that fully satisfies all of these requirements has not yet been realized, but as a fixing roller that can withstand use as a fixing roller, we have developed a core member coated with an elastomer such as silicone rubber, and a core member coated with fluororesin. One coated with a resin layer has been proposed. The former elastomer-coated fixing roller is
Its own hardness makes it difficult to withstand the effects of pressure and heat it undergoes during operation as a fuser roller, so fillers are added to achieve the desired hardness and depend on the type of filler added. As a result, wear resistance and heat resistance are enhanced. In this case, since the elastomer has a large elongation and is easily deformed, the filler can be easily mixed in, and the amount of the filler added can be increased. A fixing roller coated with an elastomer constructed in this manner is relatively inexpensive, but is slightly inferior in most aspects of mold releasability, thermal conductivity, and durability compared to a fixing roller coated with a resin layer. In particular, in terms of thermal conductivity, because the desired strength cannot be obtained unless the layer thickness of the elastomer is increased, the thermal conductivity is considerably poor and uneven fixing is likely to occur. On the other hand, the fixing roller coated with a resin layer has relatively good release properties, thermal conductivity, and durability.
In particular, the mold releasability is very good. This resin layer is made of trifluoride resin, tetrafluoride resin, or hexafluoride resin, but these resins are expensive. By the way, a fixing roller coated with a resin layer has a problem in that the adhesion between the core member and the resin layer is poor due to the resin having too good mold releasability, and the resin layer easily peels off from the core member. Conventionally, when coating a core member with resin, the resin is applied after etching the surface of the core member. At this time,
Unevenness is formed on the surface of the core member by etching, and the resin sinks into these irregularities even slightly.
Although a slight air pocket is formed in the recessed portion of the core member, the poor adhesion is somewhat alleviated. However, even with the fixing roller configured in this way,
If large pressure or high heat is applied to the roller, or if a blade for cleaning toner powder adhering to the fixing roller is brought into contact with the roller, the resin layer may peel off due to the mechanical friction of the blade. Sometimes it happens. Furthermore, if a suitable oil is applied to the roller to prevent toner from adhering to it, the oil may loosen the resin, which means that the oil may seep into the air pockets due to pinholes or uneven firing. This causes the resin layer to peel off. In order to improve the adhesion between the core member and the resin layer in order to solve this problem, the average surface roughness of the core member must be considerably increased. Usually, to obtain sufficient and effective adhesion, the average surface roughness of the core material is
Screw-shaped with a pitch of 100μ, and its surface roughness is 100μ
On the other hand, the thickness of the resin layer is also required to be 500μ or more. The surface roughness and the thickness of the resin layer are such that the surface of the core member has a large surface roughness because it is necessary for the surface of the applied resin layer to be in a mirror-like flat state with no unevenness in order to obtain good fixing properties. A layer thick enough to fill it up and create a mirror surface is required. However, increasing the thickness of the resin layer not only increases the cost since resin is expensive, but also adversely affects thermal conductivity. As described above, in the conventional fixing roller, the adhesion between the core member and the resin layer is in a contradictory relationship with cost and thermal conductivity, and the current situation is that one of them is sacrificed. Therefore, the surface roughness of the core member varies, and is rougher if adhesiveness is important, and finer if cost and thermal conductivity are important. Problems to be Solved by the Invention The present invention aims to sufficiently prevent peeling of the resin layer even if the resin layer of the fluororesin is made relatively thin, and also moderately deteriorates the resin's excellent mold releasability. An object of the present invention is to provide a fixing roller that has the following properties. Means for Solving the Problems The present invention achieves the above object by achieving an average roughness of 1μ to 20μ.
In a fixing roller formed by applying a resin layer of fluororesin to the surface of a metal core member whose surface has been processed so that carbon is added to the resin layer,
The amount of carbon added is 3% to 8% by weight, and the thickness of the resin layer is
This was achieved by having a thickness of 10μ to 40μ. The average roughness of 1μ to 20μ when processing the surface of a metal core member has a close relationship with the thickness of the resin layer of 10μ to 40μ, and if the average roughness is less than 1μ, the thickness of the resin layer will also be less than 10μ. Although it can be made thinner,
Even if carbon is mixed, sufficient adhesive strength cannot be obtained. Moreover, if the average roughness is larger than 20μ, the thickness of the resin layer becomes thicker than 40μ, resulting in high cost and poor thermal conductivity. In experiments, it has been found that a thickness approximately twice the surface roughness of the core member is satisfactory. The resin used is a fluororesin with good mold releasability. When the amount of carbon added is less than 3% to 8% by weight, a problem arises in that the wear resistance is poor, and when it is more than that, the ratio of carbon to resin appearing on the surface becomes too much. Changes properties and adversely affects mold releasability.
Moreover, the reinforcing effect of carbon is weakened, and adhesive strength cannot be obtained. Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings, but first an outline of a fixing device that can utilize the roller according to the present invention will be explained. In FIG. 1, a fixing roller 1 and a pressure roller 2 are shown.
The rollers 1 and 2 are brought into contact with each other along their longitudinal directions, and these rollers 1 and 2 are each driven to rotate in the direction of the arrow by a drive device (not shown). A heater 3 is disposed within the fixing roller 1, and this heater 3 serves to maintain the fixing roller within a predetermined temperature range. The pressure roller 2 is also provided with a heater if necessary. When recording paper 4 carrying a toner image is fed between rollers 1 and 2, the toner image is fixed on the recording paper by the action of heat from the rollers. In this case, if a so-called offset phenomenon occurs in which toner powder on the recording paper is transferred to the fixing roller, the next recording paper will be stained. Therefore, the surface of the fixing roller 1 is difficult for toner to adhere to, that is, it has excellent releasability. The material should be constructed of suitable materials. In order to more reliably reduce the above-mentioned offset phenomenon, an anti-offset liquid coating device is provided, and the coating device shown in FIG. It consists of an applicator roller 7 that comes into contact with the roller 1 and applies the prevention liquid to the roller 1, and a felt 8 that supplies the liquid 5 in the container to the applicator roller. The application roller is rotated following the fixing roller. The fixing roller 1 described above can be constructed according to the present invention. First, a specific example of the fixing roller 1 constructed according to the present invention will be described. The fixing roller 1 is composed of a core member 11 and a resin layer 12 coated on the surface of the core member, and the core member 11 is made of a material having excellent thermal conductivity such as aluminum, aluminum alloy, copper, or copper alloy. Preferably, it is made of a material. In order to clarify these configurations,
A method of manufacturing this fixing roller will be explained. First, the average roughness of the surface of the cylindrical core member 11 made of the above-mentioned material is set to 1μ to 20μ (second
figure). As a specific method for this, for example, the surface of the core member is subjected to mechanical processing such as sandblasting, knurling, and grooving with a lathe, or an anodized film or a hydrated alumina oxide film is formed on the surface. Next, a fluororesin having excellent mold releasability is applied to the surface of this roller core member 11 to form a resin layer 12. As the resin layer 12, fluororesins such as trifluoride, tetrafluoride, and hexafluoride, and copolymers of fluororesins and other resins, such as TFE, FEP, and PFA, are preferable. The thickness of the resin layer is 10μ to 40μ. In this case, according to the present invention, carbon having a higher specific gravity than the resin is added to the resin to be applied. In the case of the fixing roller, the amount of carbon added is 3 to 8 weight percent. In order to apply resin to the core member, powdered resin, resin dispersed in water, or resin powder mixed with a binder dispersed in a solvent can be applied by spraying, dipping, or brushing. Apply to the surface of the core member by an appropriate means. Note that if a primer or adhesive is applied to the core member before applying the resin, the resin can be firmly adhered to the core member. After coating the core member with resin, it is dried, then placed in a furnace and baked. Baking temperature is 300℃
The temperature should be ~450℃ and the baking time should be at least 5 minutes.
During this baking, the resin can be pressurized with a press roll if necessary. In this way, the resin is reliably embedded into the surface irregularities of the core member and is securely attached to the core member, which is convenient. After baking, the surface may be polished. When Teflon (trade name) is used as the fluororesin, its thickness is 10μ~
40μ and an average surface roughness of 1μ to 20μ, and especially polishing the surface after firing to an average roughness of 0.1μ to 30μ showed a remarkable effect on the copy finish. Fixing roller 1 configured by the above method
Not only is the core member 11 formed with unevenness and the resin is adhered to the core member 11 so as to bite into it, but also the above-mentioned carbon is added to the resin.
The resin is firmly adhered to the core member, and the peeling phenomenon of the resin layer 12 is reliably reduced. The reason why the amount of carbon added is determined as above is that if the amount of carbon is less than this amount, the resin layer will easily peel off from the core member, whereas if the amount of carbon is more than the above amount, the effect of carbon will cause the problem. This is because the releasability of the fixing roller decreases, causing the inconvenience of toner adhering to the roller. In this way, the resin layer 12 is difficult to peel off,
A fixing roller 1 with optimal mold releasability can be obtained. Furthermore, the addition of the above-mentioned carbon also improves the oil wettability of the roller surface. That is, the fluororesin has too good mold releasability when unfilled, so it completely repels oil and there is no oil application effect. Therefore,
When the mold releasability is slightly deteriorated with carbon, the carbon appearing on the roller surface becomes the core of oil adhesion and improves the wettability. Effects The fixing roller according to the present invention is configured as described above, and by adding carbon, the adhesive strength between the core member and the resin layer is significantly improved. This is because carbon has a higher specific gravity than resin, so when a resin containing carbon is applied to a metal core member, a large proportion of the resin sinks toward the side in contact with the core member. Therefore, it is presumed that the mold releasability of the resin deteriorates, and the resin blends into the core member and sufficiently penetrates into its unevenness, thereby increasing the adhesiveness between the resin layer and the core member. The inventor of the present invention conducted experiments on the release properties and durability of various fixing rollers based on the present invention. The durability of the fixing roller was evaluated from the peeling and abrasion of the resin layer depending on the number of sheets passed through the fixing roller. Furthermore, the releasing property was evaluated using the effective fixing temperature range from the temperature at which the toner is fixed to the hot offset temperature as a substitute characteristic. Experiment 1 Fixing roller according to the present invention (first experimental roller) Surface roughness of core member 1 μ to 3 μ Resin PFA Thickness of resin layer 10 μ to 30 μ Carbon (carbon powder) 3% by weight Conventional fixing roller (unfilled roller) Core Surface roughness of member: 1μ to 3μ Resin PFA Thickness of resin layer 10μ to 30μ Carbon Not filled Note that the fixing roller is coated with silicone oil. As a result of durability tests, the resin layer of the unfilled roller peeled off after passing approximately 100,000 sheets. In contrast, the first experimental roller showed no peeling of the resin layer even after passing 300,000 sheets. Furthermore, when a separating claw made of polyimide was brought into contact with the fixing roller of the above experimental device with a contact force of approximately 30 g/mm, the resin layer of the unfilled roller peeled off after approximately 30,000 sheets were passed through. However, the first experimental roller was 10
No peeling of the resin layer was observed even after 10,000 sheets were passed through the paper. Furthermore, as a result of a releasability experiment, the toner was fixed to both rollers without offset when the surface temperature of the fixing roller was approximately 150°C. When the surface temperature of the fixing roller was increased, the unfilled roller was approximately 170℃,
The first experimental roller experienced a hot offset when heated to approximately 195°C. This result is thought to be due to the above-mentioned wettability of the fixing roller coated with silicone oil. That is, it is thought that because the former has too good mold releasability, the silicone oil does not fit into the fixing roller and the mold releasability provided by the oil is weakened. Experiment 2 Fixing roller according to the present invention (second experimental roller) Surface roughness of core member 7μ to 8μ Resin PFA Thickness of resin layer 15μ to 30μ Carbon 5% by weight Conventional fixing roller (unfilled roller) Surface roughness of core member 7μ to 8μ Resin PFA Thickness of resin layer 15μ to 30μ Carbon Unfilled Fixing roller outside the present invention (multi-filled roller) Surface roughness of core member 7μ to 8μ Resin PFA Thickness of resin layer 15μ to 30μ Carbon (carbon Powder) 20% by weight The experiment was conducted using an oil application type fixing device and an oil-less type fixing device using a toner containing a component that provides the same effect as oil application. As a result of experiments, in the case of an oil-coated fixing device, the effective fixing temperature range of an unfilled roller is 150℃.
Same experiment as above at ~170 °C. Also, the second
With the experimental roller, good fixing was obtained without offset between 150°C and 190°C. Furthermore, the multi-filled roller had a temperature range of 150° C. to 160° C. and had extremely poor mold releasability. Next, in the case of the oil-less type fixing device, the unfilled roller had an effective fixing temperature range of 150°C to 190°C, but the paper was wrapped around the fixing roller violently, and the average was about 3 sheets per 10 sheets. was wrapped around. This wrapping is
This is due to the fact that fluororesin is easily charged due to friction with paper, and has a large resistance value that makes it difficult for the charge to escape, which causes the paper to be electrostatically attracted. For this reason, unfilled rollers had to be forcibly separated using separation claws. However, the roller made of 0% carbon had poor abrasion resistance, and after passing approximately 50,000 sheets, the roller wore out and became unusable. On the other hand, rollers filled with 5% carbon can be heated up to 150℃.
The effective fixing temperature range was 190°C. Furthermore, since the resistance value of the resin is lowered, the amount of electrical charge is reduced, and moreover, the electrical charge in the resin layer can easily escape to the ground via the carbon and core member, and because the amount of electrical charge is small, there is almost no paper wrapping. . The above experimental results are shown in the table below.
Note that ○ indicates good, △ indicates somewhat poor, and × indicates poor.

[Table] Experiment 3 This experiment was conducted in the following manner using a prototype FT-6600 PPC manufactured by Ricoh. The fixing roller has an aluminum core metal that is sandblasted to a surface roughness of 1μ and 20μ, and the core metal is made of PTFE with conductive carbon added.
were applied to a layer thickness of 30μ and 40μ, respectively, baked and polished to form rollers. Surface roughness 1μ and 20μ
On the other hand, a total of six fixing rollers were used in which the amount of carbon filling was 3, 5, and 8 weight percent. As a result, as shown in the following table, both durability and mold releasability were good.

[Table] Durability was determined by looking at wear and peeling of the separation claw.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of the present invention, and FIG. 2 is an enlarged sectional view of the fixing roller. 11... Core member, 12... Resin layer.

Claims (1)

[Scope of Claims] 1. A fixing roller comprising a fluororesin resin layer coated on the surface of a metal core member whose surface has been processed to have an average roughness of 1 μ to 20 μ, wherein the resin layer contains carbon. the amount of carbon added is 3% to 8% by weight, and the thickness of the resin layer is 10μ to 40μ
The fixing roller characterized in that: