JPS6345111B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a fixing device that fixes a toner image on a supporting material by conveying the toner image supporting material with a pair of rollers. 2. Description of the Related Art The above-mentioned fixing devices are often used today to fix toner images formed on supporting materials such as paper in electrophotography and the like. In order to form a width in the supporting material conveyance direction in the nip formed by the roller pair, at least one of the roller pairs is provided with a surface layer of an elastic material such as silicone rubber, while a toner roller heated and melted is provided with a surface layer of an elastic material such as silicone rubber. In order to prevent the toner from adhering to the toner image surface of the roller pair, and to prevent the supporting material from becoming dirty (offset phenomenon) or being wrapped around the roller due to this, at least one roller of the roller pair, especially the side of the supporting material that is in pressure contact with the toner image surface, is It is common practice to coat the roller with an anti-offset (mold release) liquid such as silicone oil. Then, the offset prevention liquid soaks into the elastic material such as silicone rubber (rubber is impregnated with the liquid), causing it to expand.
It has a so-called swelling property, but when the surface layer of the elastic body swells with the anti-offset liquid in the above-mentioned fixing device, the nip width changes, the roller diameter increases, and the pressure at the nip and roller circumferential speed increase. Not only does this change the fixing properties of the toner image support material, but also uneven swelling occurs in the longitudinal direction of the roller, for example, when the diameter of one end of the roller becomes larger than the other. There is an inconvenience that wrinkles occur on the skin. In order to solve such inconvenience, Japanese Patent Application Publication No. 1973
As in the method described in Japanese Patent No. 46819, a method is known in which a silicone rubber roller is swollen with silicone oil in advance and then polished into a roller of a predetermined diameter. However, it takes a long time to saturate and swell a silicone rubber roller with silicone oil (generally about a month for a rubber layer several millimeters thick), and as a practical matter in terms of manufacturing costs, it is difficult to use a silicone rubber roller that remains unsaturated and swollen. However, in this case, if the applied oil has the same viscosity as the swelling oil, the swelling phenomenon will progress further in the applied oil, and the overall diameter of the roller will increase over a long period of use. , and/or an increase in the local diameter difference cannot be ignored. The main object of the present invention is to solve the above-mentioned disadvantages. The purpose of the present invention is to shorten the time required for impregnating an anti-offset liquid and to solve the problems that occur when a liquid of the same viscosity is used for impregnation and coating. The impregnation treatment is a heating impregnation treatment, and the viscosity of the anti-offset liquid for impregnation at room temperature is lower than the viscosity at room temperature of the anti-offset liquid for application in the coating means. As will be described later, the effects of the present invention are that impregnation treatment can be carried out in a short time and changes in the surface of the elastic body can be suppressed, thereby reducing manufacturing costs and achieving long-term use. Therefore, according to the present invention, the cost spent on the fixing device can be reduced;
It is possible to provide inexpensive and highly reliable equipment. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a heat roller type fixing device to which the present invention is applied. In the figure, 1 is a heat fixing roller, and a hollow roller 2 made of a material with good thermal conductivity such as aluminum or copper The roller had an outer diameter of 39 mm and had a releasable coating layer 3 made of heat-curable silicone rubber (KE860, manufactured by Shin-Etsu Chemical Co., Ltd.) with a thickness of 0.3 mm on the surface. A heating source 4 such as a halogen lamp is disposed inside the heating roller 1, and the heating roller 1 is heated by the heating source 4 and is heated by a temperature detecting element 5 such as a thermistor that is in contact with the surface of the heating roller. The surface of the third surface is maintained at a temperature of 170° C., which is the temperature at which the toner T is heated and melted and fixed onto the support paper C. Reference numeral 6 denotes a pressure roller, which has an outer diameter of 8 mm thick releasable coating layer 8 of heat-curable silicone rubber (KE-540 manufactured by Shin-Etsu Chemical Co., Ltd.) on a core metal 7 made of stainless steel or the like.
It is a 40mm roller. This rubber layer 8 has a hardness of 40 degrees, which is softer than the rubber layer 3 (hardness 60 degrees), and has a thicker rubber wall, making it suitable for forming the nip width between the rollers. However, it absorbs more oil than layer 3. Cheap. The heating roller 1 and the pressure roller 6 are pressed against each other by a pressure mechanism (not shown) during operation (during fixing processing) and rotate in the direction of the arrow, thereby pinching and pressing the toner image support paper C and conveying it in the direction of the arrow. However, when inactive, such as during standby, they are separated from each other and stop rotating. During the pressure contact, the layer 8 of the roller 6 is elastically deformed more than the layer 3 of the roller 1, forming a wide nip. Reference numeral 9 denotes a coating roller that applies offset prevention liquid (silicone oil) 0 to the surface of the silicone rubber layer 3 of the heating roller 1, and a core metal 1 made of stainless steel or the like.
The roller has an outer diameter of 25 mm and has a coating layer 11 of heat-vulcanized silicone rubber (KE-540, manufactured by Shin-Etsu Chemical Co., Ltd.) with a thickness of 6.5 mm on the roller. This rubber layer 11
The layer 3 is also softer than the layer 3, so that the rollers 1 and 9 can be brought into close contact with each other without any gaps, and the oil can be evenly applied to the roller 1. The offset prevention liquid 0 in the offset prevention liquid storage tank 12 flows through the heat-resistant felt 13 due to capillary action.
Then, after passing through the heat-resistant cloth 14, the application roller 1
0 and then applied from the rotating application roller 10 to the surface of the silicone rubber layer 3 of the heating roller 1. By adding this oil coating to the layer 3 having releasability, the effect of preventing toner from adhering to the roller 1 and wrapping of the paper C is greatly enhanced. The heat-resistant cloth 14 is in contact with the heat-resistant felt 13 and the application roller 10 only during operation, and is separated from both during standby. Reference numeral 15 denotes a guide plate for feeding the toner image supporting paper C into the nip between the rollers 1 and 6. The paper C is conveyed so that the supporting surface of the toner image T is pressed against the roller 1. Denoted at 16 and 17 are claws that separate the paper curled along the circumferential surface of the roller from the roller. Claws 16, 17
The tips of the rollers 1 and 6 are in light contact with the rollers 1 and 6, respectively. Note that the above fixing device has different widths (in the direction perpendicular to the paper conveyance direction, that is, in the longitudinal direction of the rollers 1 and 6,
It is capable of selectively fixing toner image supporting paper C of any width size), and one side edge parallel to the conveying direction of paper C of any width size is set at the corresponding side edge of rollers 1 and 6. It is transported so that it approximately matches the reference position that has been set. Alternatively, the paper C of any width size is conveyed so that its center line in the width direction substantially coincides with the center position of the rollers 1 and 6 in the longitudinal direction. Silicone oil O is applied to the peripheral surface area of the roller 1 against which the paper C is pressed.
is consumed by the paper C, but the oil O applied to the peripheral surface area of the roller where the paper C does not come into contact with the paper C is not consumed and remains in the same area of the roller 1, and when the paper C comes into contact with the same area and rotates It ends up being applied to the peripheral surface area of the roller 6 that is exposed to the surrounding area. Therefore, when fixing paper C of different width sizes as described above, if small-width paper is continuously fixed, silicone oil will seep into the peripheral surface area of the rollers 1 and 6 that are not in pressure contact with the paper, causing partial damage. When the diameters of the rollers 1 and 6 become larger (particularly the diameter of the roller 6 with the thicker rubber layer 8 becomes larger), when a larger size paper is to be subjected to the fixing process, wrinkles may appear on the paper. was traditionally hot. Further, although the oil O on the circumferential surface of the roller 1 that is in pressure contact with the paper C is consumed, it is not completely consumed and some amount remains. Some of this residue is also applied to roller 6 after paper C has passed through the nip. Conventionally, the rollers 1 and 6 have also swelled due to such oil O. In this embodiment, the offset prevention liquid used during operation, that is, the liquid O applied to the roller 1 through the members 13, 14, and 9, has a viscosity at room temperature.
300CS dimethyl silicone oil (KF96 manufactured by Shin-Etsu Chemical Co., Ltd., viscosity 300CS) was used. Also,
As the heating roller 1, on the core metal 2 with an outer diameter of 38.0 mm,
After applying a thin layer of primer and vulcanizing the heat-curable silicone rubber on top of it to form a rubber layer,
The rubber layer was ground to an outer diameter of 38.65 mm, and then immersed in dimethyl silicone oil (KF96 manufactured by Shin-Etsu Chemical Co., Ltd., viscosity 100 CS) heated to 180°C for 4 hours with a viscosity of 100 CS at room temperature. After swelling, it was polished to an outer diameter of 39.0 mm. In addition, a core metal 7 with an outer diameter of 24 mm is used as the pressure roller 6.
A thin layer of primer is applied on top, and the heat-curable silicone rubber is vulcanized on top to form a rubber layer with an outer diameter of approximately 37.8 mm, and then the viscosity at room temperature is
After swelling the above rubber layer by immersing it in 50CS dimethyl silicone oil (KF96 manufactured by Shin-Etsu Chemical Co., Ltd., viscosity 50CS) heated to 180℃ for 10 hours,
A piece polished to an outer diameter of 40.0 mm was used. In addition, as the application roller 9, a core metal 1 with an outer diameter of 12 mm is used.
A thin layer of primer is applied onto the 0, and the heat-curable silicone rubber is vulcanized on top of the primer to give an outer diameter of 23.2.
A rubber layer of approximately 1.0 mm in diameter is formed, and then the rubber layer is swollen by immersion in dimethyl silicone oil (KF96, manufactured by Shin-Etsu Chemical Co., Ltd., viscosity 50 CS) heated to 200°C for 8 hours with a viscosity of 50 CS at room temperature. After that, it was polished to an outer diameter of 25.0 mm. Using the fixing device with the above configuration, per sheet of B4 paper,
Applying the silicone oil (KF96, 300CS) at a rate of 4 x 10 ^-3 cc to heating roller 1, and maintaining the surface temperature of the heating roller at 170°C, 200,000 sheets were fixed, and 5,000 sheets were fixed. When A3 paper was fixed every time, good fixing was always obtained and the paper did not wrinkle. After fixing 200,000 sheets of B4 paper, the diameter of the heating roller is φ39.0, and the diameter of the pressure roller is 40.15 mm at the pressure contact part of B4 paper.B4
The paper non-contact part was 40.25 mm, and the coating roller diameter was φ25.1, which was slightly increased in diameter, but it was in a condition that could be used further without any practical problems. The experimental results are shown when the viscosity and temperature of the impregnating silicone oil (with the same polymer unit molecular structure) during pressure roll manufacturing were varied (the immersion time was 10 hours in both cases) using the same fuser configuration as above. Shown below. The fixing roller and application roller were manufactured under the above manufacturing conditions. In all experiments, B4 size paper (width 254mm) was continuously fixed at a speed of 13 sheets/minute, and every 5000 sheets, A3 size paper (width 297mm) was sampled to check for wrinkles on the A3 size paper. saw. The wrinkles are caused by the difference in circumferential speed in the axial direction due to the diameter of the rollers 1 and 6 in the B4 paper non-contacting part, especially the roller 6, which is easily impregnated with oil, being larger than the roller diameter of the B4 paper contacting part. This occurs due to the occurrence of

[Table] In the above table, the temperature of the silicone oil during application is the temperature of the oil applied to the surface of the heating roller 1, which is equal to the surface temperature of the roller 1. Now, from the above results, the viscosity at room temperature (25°C) of the impregnating silicone oil used for the swelling treatment of silicone rubber is higher than the viscosity at room temperature of the coating silicone oil applied to the roller during the fixing process. It can be seen that a large effect can be seen when the value is small. Furthermore, if in addition to this condition, the temperature of the silicone oil for impregnation during impregnation, that is, the swelling treatment, is higher than the temperature of the silicone oil for coating during application, the effect will be even higher; It is clear that even if the oil temperature is lower than the oil temperature during application, a sufficient effect can be obtained as long as the viscosity of the impregnating oil is lower than the viscosity of the coating oil at room temperature. As mentioned above, if the silicone rubber layer of the fuser roller is pre-impregnated with a silicone oil that has a lower viscosity than the silicone oil for coating at room temperature, the reason why the rubber layer of this roller is difficult to swell with the silicone oil for coating. can be considered as follows.
That is, low-viscosity silicone rubber is more easily impregnated into silicone rubber than high-viscosity silicone oil. In other words, although both have the same polymerized unit molecular structure, the low-viscosity one has a lower degree of polymerization than the high-viscosity one, and because it easily enters the rubber structure, a relatively large amount of silicone is absorbed in a relatively short period of time. Impregnated with rubber. Once the silicone rubber is impregnated with the above-mentioned low-viscosity silicone oil, even if the above-mentioned high-viscosity silicone oil is applied to the silicone rubber, the applied oil becomes difficult to impregnate. For this reason, the present invention can prevent the roller diameter from increasing. As shown in FIG. 2, if the viscosity of silicone oil is V (cs) and its absolute temperature is T (〓), then approximately the following relationship holds: logV=α·1/T+β. α is the same constant for oils of any viscosity, and β is a constant that differs for each oil. As can be seen, the viscosity is lower than that of silicone oil A (eg KF96, 300CS) at room temperature. Silicone oil B (e.g. KF96,
100CS), silicone oil C (e.g. KF96,
50CS), the viscosity is lower in the order of B and C than A even at the temperature of the surface of the fixing device roller. Therefore, even during the fixing process, the viscosity of the silicone oil impregnated into the heated silicone rubber layer of the roller is the same as the viscosity of the silicone oil applied to the same rubber layer when heated to the above rubber layer temperature. lower, so that the applied oil is also less likely to be impregnated into the rubber layer. Furthermore, as mentioned above, it is most preferable to impregnate silicone rubber with silicone oil at a temperature higher than the rubber layer temperature during fixing treatment, but as in the example above, the impregnation treatment is carried out at a temperature lower than the above temperature. You may also do this. However, even in this case, it is preferable that the impregnation treatment is carried out at a temperature such that the viscosity of the silicone oil for impregnation is equal to or lower than the viscosity (V ₀ Cs) of the silicone oil for coating on the surface of the rubber layer during the fixing treatment. (For example, in Figure 2, it is preferable to perform the impregnation treatment at t ₁ °C or higher for oil B and at t ₂ °C or higher for oil C.) On the other hand, the temperature of the silicone oil during the impregnation treatment (swelling treatment) is
Raising the temperature higher than 200°C is not preferable because it exceeds the heat resistance limit of the oil and accelerates its deterioration. Also,
Silicone oil with a viscosity lower than 10CS at room temperature (25℃) is thermally unstable, so silicone oil with a viscosity lower than 10CS at room temperature (25℃) is suitable for impregnation.
It is preferable to use 20CS or higher. Furthermore, a silicone rubber coated roller having a thickness thinner than the designed desired thickness is swollen with silicone oil as described above, and the coating layer is made thicker than the desired thickness, and then polished to the desired thickness. The effect increases. Experiments have shown that this is particularly effective when a silicone rubber coating layer having a thickness of 90% or less of the desired rubber thickness is swollen and then polished. As described above, according to the present invention, even if an anti-offset liquid is applied, the diameter of the elastic layer of the roller can be prevented from changing over time, and wrinkles in the toner image support material and changes in fixing performance can be prevented. In addition, since the roller can be manufactured in a short time, the manufacturing cost of the fixing device can be reduced, and various other useful effects can be obtained. Furthermore, although the embodiments have been described using a heat roller fixing device as an example, the present invention can also be applied to a pressure fixing device that uses an offset prevention liquid.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, and FIG. 2 is a graph for explaining the relationship between temperature and viscosity of silicone oil. 1 is a heat fixing roller, 3 is a silicone rubber layer,
6 is a pressure roller, 8 is a silicone rubber layer, 9 is a silicone oil application roller, and 11 is a silicone rubber layer.

Claims (1)

[Scope of Claims] 1 A pair of rollers, at least one of which has an elastic surface layer impregnated with an anti-offset liquid, and means for applying the anti-offset liquid to at least one of the pair of rollers. In a fixing device that fixes a toner image by conveying the toner image support material under pressure between a pair of rollers, the impregnation treatment of the surface layer of the elastic body is a heating impregnation treatment, and the offset prevention liquid for impregnation is heated at room temperature. A fixing device characterized in that the viscosity of the fixing device is lower than the viscosity of the anti-offset liquid used in the coating means at room temperature. 2. The fixing device according to claim 1, wherein the temperature of the anti-offset liquid for impregnation during the impregnation is set higher than the temperature of the anti-offset liquid for coating on the surface of the elastic body. 3. The fixing device according to claim 1 or 2, wherein the elastic surface layer is made of heat-curable silicone rubber.