JPH0564351B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic copying machine, a facsimile machine,
This invention relates to a fixing device used in devices that use electrophotographic processes, such as printers.

[Prior art]

Conventionally, in copying machines and the like that use an electrophotographic process, it is necessary to fix the unfixed toner image formed on paper to make a permanent image, and the fixing methods include solvent fixing, pressure fixing, and heating. Fixation methods and the like are known.

However, the above solvent fixing method causes solvent vapor to scatter,
However, the pressure fixing method also has disadvantages such as poor fixing performance compared to other fixing methods, and pressure-sensitive toner is expensive, both of which are not widely used. The reality is that it has not been clarified.

Therefore, for fixing unfixed toner images, a heat fixing method is generally used in which the toner is melted by heating and adhered to the paper.

Conventionally, this heat-fixing method is a heat-roll method in which fixed pressure is applied between a pair of rolls (fixing roll and pressure roll), at least one of which is heated, and a sheet of paper carrying an unfixed toner image is inserted through it to perform fixing. This is because it has advantages over other heat fusing methods such as hot air fusing and oven fusing, such as lower power consumption, higher speed, and less risk of fire due to paper jams in the fusing section. Most widely used.

The above-mentioned fixing roll may be one in which the surface of a cylindrical core metal is coated with a heat-resistant resin such as polytetrafluoroethylene in a film thickness of several micrometers to several tens of micrometers, or one in which the surface of a cylindrical core metal is coated with a heat-resistant resin such as polytetrafluoroethylene, or one in which HTV silicone rubber (High
Temperature Vulcanization Silicone
Rubber), RTV silicone rubber (Room
Temperature Vulcanization Silicone Rubber)
A heat-resistant elastic material coated with a film thickness of about 300 μm is used, and one of the pressure rolls is a cylindrical core metal whose surface is coated with a certain width of contact when the above-mentioned fixing roll is brought into pressure contact. HTV silicone rubber, LTV silicone rubber (Low Temperature
Vulcanization silicone rubber), RTV silicone rubber, fluorocarbon rubber, and other heat-resistant elastic materials are used.

By the way, in the fixing roll coated with the above-mentioned heat-resistant resin, the resin film thickness is as thin as several μm to several tens of μm, so the toner image on the paper is crushed and smoothed during fixing, and the image after fixing is However, fixing rolls coated with a heat-resistant elastic material that do not have this drawback are mainly used.

However, in the fixing roll coated with this heat-resistant elastic material, the elastic layer is as thick as about 300 μm, and when the elastic layer is made of silicone rubber, its thermal conductivity is 4×10 ^-4 cal/cm. sec.℃, so it has the disadvantage that it takes a long time to raise the temperature of the circumferential surface of the fuser roll to the specified temperature, and when copying is performed continuously, the temperature of the circumferential surface of the fuser roll decreases. This had the disadvantage of causing poor fixing.

Therefore, a method has been adopted to improve the thermal conductivity of the elastic layer by kneading a thermally conductive substance such as metal powder or metal oxide inside the heat-resistant elastic body. In the case of a fixing device that does not use an inhibitor (for example, silicone oil), if the above-mentioned thermally conductive substance is kneaded into a heat-resistant elastic material, its release properties will deteriorate, and as a large number of copies are made, the surface of the fixing roll will become loose. There is a problem in that an offset phenomenon occurs in which toner adheres and once copied characters are retransferred to the next sheet of paper, significantly shortening the replacement life of the fixing roll.

Therefore, in order to improve mold releasability, as shown in Figure 1, a mold release material such as a fluorine-based coating material or silicone latex is applied to the surface of the elastic layer a, which is kneaded with a thermally conductive material, to a thickness of 5 μm to 100 μm. A fixing roll has been developed in which a thin film of RTV silicone rubber is formed on the surface of the elastic layer a to form an intermediate layer b, and a thin film layer c of methyl silicone varnish is formed on the surface of the intermediate layer b.

However, in the former case, since the adhesive strength between the elastic layer a and the intermediate layer b is weak, the intermediate layer b peels off after the number of copies exceeds 20,000, and the elastic layer a appears on the surface, and the toner However, in the latter case, since the elastic layer a and the intermediate layer b are made of similar materials, the adhesive strength between each layer is strong. , the abrasion resistance of the intermediate layer b is weak, and after the number of copies exceeds 50,000 copies, the intermediate layer b wears out together with the outermost thin film layer c, and the elastic layer a also appears on the surface, causing an offset phenomenon. It was hot.

[Purpose of the invention]

The present invention eliminates and improves the above-mentioned drawbacks of the prior art, and improves mold releasability and abrasion resistance by adding a thermally conductive substance as an elastic layer formed on the surface of the cylindrical core metal of the fixing roll. By using an excellent addition reaction type silicone rubber and using the same addition reaction type silicone rubber that does not contain the above additives as the thin film layer covering the surface, the adhesive strength between the elastic layer and the thin film layer can be increased. In addition, the abrasion resistance of the addition reaction type silicone rubber prevents abrasion of the thin film layer, and its releasability prevents toner adhesion and provides offset over a long period of time. It is an object of the present invention to provide a fixing device that does not cause such phenomena.

[Structure of the invention]

That is, the present invention provides a fixing device that fixes an unfixed toner image by inserting a sheet of paper on which an unfixed toner image is formed between a fixing roll and a pressure roll. By using a fixing roll in which an elastic layer made of an addition-reaction type silicone rubber containing a chemical substance and a thin film layer made of an addition-reaction type silicone rubber not containing the above-mentioned additives are sequentially formed, offset can be maintained over a long period of time. This prevents phenomena and poor fixing, thereby making it possible to obtain copies with stable image quality.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 2, the fixing device of the present invention includes a fixing roll 1 and a pressure roll 2.

First, the fixing roll 1 includes a cylindrical core metal 3 made of aluminum and rotatably supported in the direction of arrow A, and a cylindrical core metal 3 formed on the surface of the core metal 3, made of addition reaction type silicone rubber shown below. It is composed of an elastic layer 4 and a thin film layer 5.

That is, the elastic layer 4 is made of linear diorganopolysiloxane (25
300 parts by weight of crystalline silica (thermal conductive substance) with an average particle size of 2 μm, 5 parts by weight of diorganopolysiloxane with both ends of the molecular chain blocked, and a trace amount of a platinum compound (addition reaction catalyst) were added to The elastic material made of the mixture is coated on the surface of the core metal 3, which has been previously coated with a primer and fired, and then vulcanized.On the other hand, the thin film layer 5 is made by removing only the crystalline silica from the elastic material. The elastic layer 4 is diluted 10 times with a solvent, applied thinly onto the surface of the elastic layer 4 by spraying, and fired.

A Kortz lamp 6 for heating the fixing roll 1 is disposed within the core metal 3.

On the other hand, the pressure roll 2 is provided below the fixing roll 1, and is made of a cylindrical core bar 7 made of aluminum like the fixing roll 1, and a heat-resistant material made of HTV silicone rubber, which covers the surface of the core bar 7. The core bar 7 is rotatably supported by a bearing in the direction of arrow B as the fixing roll 1 rotates, and there is an elastic layer 8 between the fixing roll 1 and the pressure roll 2. Appropriate pressure is applied by a mechanism that is not connected.

To perform toe fixing using the fixing device of the present invention, as shown in FIG. Therefore, the unfixed toner is melted and poured into the fibers of the paper 9, cooled, and fixed.

At this time, since there is a thin film layer 5 made of addition reaction type silicone rubber with excellent release properties and abrasion resistance on the surface of the fixing roll 1, the toner does not adhere to the surface of the fixing roll 1 due to its action. There is no. Moreover, the thin film layer 5 is hard to wear out due to its abrasion resistance, and since it is formed of the same material as the elastic layer 4, it is firmly adhered to the elastic layer 4.
There is no possibility that the thin film layer 5 will peel off from the elastic layer 4 and the elastic layer 4 will appear on the surface.

Therefore, the offset phenomenon can be prevented for a long period of time. For example, when this fixing device is run using toner mixed with wax or the like and without using a release agent such as silicone oil, the number of copies is reduced. The offset phenomenon described above did not occur even after 150,000 sheets were printed.

In addition, in this device, since the elastic layer 4 of the fixing roll 1 contains crystalline silica, which is a thermally conductive substance, the surface temperature of the fixing roll 1 can be adjusted within about 60 seconds after turning on the switch. It was possible to raise the temperature to the required temperature, and its operability was significantly improved compared to the 110 seconds required by conventional equipment that did not take thermal conductivity into consideration.

Incidentally, even if the elastic layer 4 has good thermal conductivity, if the thin film layer 5 covering its surface is thicker than 30 μm, the thermal conductivity will decrease due to the presence of the thin film layer 5. is preferably about 5 μm to 30 μm.

Although silica is used as the thermally conductive material in this embodiment, it goes without saying that conventional metal powders, metal oxides, etc. may also be used.

〔Effect of the invention〕

As described above, the present invention provides an elastic layer made of an addition reaction type silicone rubber to which a thermally conductive substance is added, and a thin film made of an addition reaction type silicone rubber not containing the above additive, on the surface of a cylindrical core metal. Since a fixing roll in which layers are sequentially formed is used, it has various effects as shown below.

First of all, since a thermally conductive substance is added to the elastic layer, the thermal energy of the heater installed in the core metal can be transmitted to the surface of the fixing roll in a short time, reducing the waiting time after turning on the switch. In addition, even if copies are made continuously, the temperature of the circumferential surface of the fixing roll does not decrease, so there is no fear of defective fixing.

In addition, on the surface of the elastic layer, a thin film layer made of the same material as the elastic layer and having excellent releasability and abrasion resistance is formed, so that the toner on the paper does not adhere to the surface of the fixing roll. Furthermore, even after long-term use, the thin film layer does not wear out or peel off from the elastic layer, so the elastic layer does not appear on the surface of the fixing roll.

Therefore, the effects of the present invention are significant, such as being able to prevent the toner offset phenomenon that frequently occurs in conventional fixing devices and significantly extending the replacement life of the fixing roll.

[Brief explanation of the drawing]

FIG. 1 shows a side sectional view of a conventional fixing device.
FIG. 2 shows an embodiment of the present invention, and is a side sectional view of the fixing device of the present invention. Explanation of symbols, 1... Fixing roll, 2... Pressure roll, 3, 7... Core bar, 4... Elastic layer, 5... Thin film layer, 6
...Colts lamp, 8...Heat-resistant elastic layer, 9...Paper.

Claims (1)

[Claims] 1 In a fixing device that includes a fixing roll and a pressure roll that rotate while being pressed against each other, and fixes the unfixed toner image by inserting a sheet of paper on which an unfixed toner image is formed between these rolls, a cylindrical core A fixing roll is used in which an elastic layer made of addition-reaction silicone rubber to which a thermally conductive substance is added and a thin film layer made of addition-reaction silicone rubber not containing the above-mentioned additives are sequentially formed on the gold surface. A fixing device characterized by: