JPH0157791B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fixing device for an electrophotographic copying machine. Electrophotographic copying machines can be roughly divided into two types, wet-type electrophotographic copying machines and dry-type electrophotographic copying machines, depending on the difference in development method. Conventionally, each method has the following drawbacks regarding fixing. be. (1) Disadvantages of wet-type electrophotographic copying machines When fixing a wet-developed image, if the developer solvent (for example, Isopar: trade name) evaporates on the fixing object, for example, transfer paper, the fixing will actually fail. The resin contained in the toner adheres to the transfer paper together with carbon and is fixed. Therefore, the technical point is how quickly the solvent can be evaporated and dried. Therefore, various studies have been made so far, and as a result, a fixing device having a structure as shown in FIGS. 1 and 2 has been commercialized. However, in the example shown in the figure, the temperature of the hot plate is controlled at 190°C ± 10°C based on the temperature rise of the fixing hot plate 1, the copy speed, the amount of solvent attached, etc., and the heater H is 700W, which is the power of the entire copier 1/2 of power consumption
The current situation is that an equivalent amount of electricity is spent on fusing, and even then, the fusing is not completed completely and the paper is ejected onto the tray unfixed, leaving marks from the knurling of the paper ejection roller and unfixed paper. , problems such as dirt on the back of the transfer paper occur after the second sheet is ejected. Therefore, in order to prevent these problems, a fixing roller 2 was installed on the hot plate 1.
If the transfer paper S is brought into contact with the fixing roller 2 and the transfer paper S is passed between them, offset development will occur via the fixing roller 2. Therefore, as shown in the figure, the fixing roller 2 has to be kept out of contact with the transfer paper S. However, even with non-contact, a part of the image may rub against the fixing roller 2 and an abnormal image may occur due to fluctuations such as curling of the transfer paper S or slight timing deviation during conveyance. There is. Therefore, the fixing roller 2 is knurled to minimize rubbing against the image. However, even if the knurling process is performed, as shown in Figure 3, the surface of the convex part is flat and 350 to 400 μm wide, and the adhered toner T is offset to the image, making it impossible to complete the process. No, no. Furthermore, from the standpoint of fixing efficiency, it is desirable that the transfer paper S be in complete contact with the heating plate 1, but for the above-mentioned reasons, the fixing roller 2 is not in contact with the heat plate 1, and when the transfer paper S is conveyed, Because it temporarily contacts the hot plate 1 or is transported floating, the heat conduction efficiency is poor and the evaporation efficiency of the solvent is reduced.
Documents with a lot of black solid areas, especially those with a lot of black solid areas at the leading edge, transfer paper that is difficult to penetrate with solvent (so-called second original), or transfer paper made of transparent film for overhead projectors are particularly prone to unfixing. There are many cases where this happens. Therefore, until now, various measures have been tried to prevent the above-mentioned drawbacks. For example, there are examples of fixing rollers made of materials to which toner does not easily adhere (Teflon, silicone rubber, etc.), but none of them have been able to completely solve the problem of offset development. Currently, there is no means of fixation. (2) Disadvantages of dry-type electrophotographic copying machines There are various methods for fixing dry-developed images, such as heated rollers, hot plates, flashes, ovens, and infrared heaters, each of which has its own advantages and disadvantages. However, the mainstream is the heated roller method. An outline of the fixing device according to this method is shown in FIG. The biggest drawback of this system is offset, and in order to avoid this development, silicone oil 3 is applied as a release agent to the fixing roller 2, and its release effect prevents offset development. However, by applying the silicone oil 3 as described above, for example, the transfer paper S is also uniformly coated with the silicone oil 3, making it difficult to write with water-based ink, a ballpoint pen, etc. when adding notes after copying. It was hot. On the mechanical side, due to creep development due to the characteristics of silicone oil, the entire interior of the machine became sticky with silicone oil, and scattered toner and carrier powder adhered thereto, making the interior of the machine extremely dirty. Furthermore, fixing roller 2' is coated with silicone oil.
Even if offset development can be prevented, especially for documents with a lot of solid black at the tip, the toner melts during fixation and has an adhesive effect, so if a roller with poor release properties is used, the transfer paper may wrap around or , when passing between the fixing rollers, it becomes charged due to friction and winding occurs. As a means to prevent this, a separation claw 4 is provided, but this claw mechanism complicates the machine, takes up space, and becomes an obstacle to miniaturization, and the toner that accumulates on the separation claw 4. Due to this, abnormal images occurred. SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device for an electrophotographic copying machine that can eliminate the above-mentioned drawbacks of wet-type and dry-type electrophotographic copying machines. The present invention will be explained in detail below. The fixing device according to the present invention has a surface that contacts an unfixed toner image on an object to be fixed,
A fixing rotary body having a microscopic irregularity in which grains with particle diameters of 10 to 500 μm equivalent are densely arranged, and a fixing object that is held in a fixed position relative to the fixing rotary body while also being able to slide between the two. The present invention is characterized in that it includes an auxiliary feeding means for assisting the conveyance of the object to be fixed in the discharge direction without causing the problem, and a heat source for heating the unfixed toner image. The invention is based on the following facts. Transfer paper (excluding those with smooth surfaces such as films)
Even if the surface is fairly smooth, there are always unevenness in the fibers, and toner adheres to the tips of the unevenness, and the larger the gap between the unevenness, the more
The amount of toner adhesion decreases, and the efficiency of toner transfer from the photoreceptor to the transfer paper decreases. Furthermore, according to what we have confirmed through experiments, the gap between unevenness is
When it is 10 to 50 μm or more, it becomes extremely small. or,
Depending on the type of transfer paper, some have good black solid uniformity and others have poor black solid uniformity, and when observing and measuring each surface with a microscope or surface roughness meter, it is found that black solid uniformity is poor. The more uneven the surface of the transfer paper becomes, the more uneven the surface of the transfer paper becomes. That is, if the unevenness of the transfer paper is large, the transfer rate will decrease, and if the unevenness is small, the transfer rate will be good. Based on the above, the above-mentioned transfer paper with large surface irregularities can be replaced with the above-mentioned fixing roller, for example, with irregularities of 10 μm or more, a heat-resistant material, and more preferably, a fixing roller made of a low surface energy material. They came up with the idea that the drawbacks of the prior art described above could be overcome by configuring the following, and when they put this idea into practice, they were able to obtain the desired results. Examples will be described below. Example 1 (see FIGS. 5 to 7). This embodiment is suitable for a fixing device of a wet-type electrophotographic copying machine. In FIG. 5, reference numeral 5 indicates a fixing roller as a rotating body for fixing, and its surface portion has a structure as shown in FIG. 6 when enlarged. Referring to FIG. 6, the surface portion has a three-layer structure including a glass bead layer _50B , a binding layer _50K , and a support layer _50S . Specifically, the glass bead layer _50B has a particle size of 10~
It consists of 50 _G glass beads with a size of about 500 μm. Although the shape does not necessarily have to be spherical, it is preferable to minimize the exposed area (convex portion). Further, although the figure shows them as being uniformly arranged in one layer, in reality they tend to have a certain distribution and are likely to be in two or three layers. However, considering the heat conduction of the fixing roller using heat, it is ideal to configure it with one layer. In addition to glass, the material is thermally stable (for example, does not melt at 300℃)
It is best to select materials that have low surface energy. A sphere coated with fluorine-based resin may also be used. Next, the binding layer _50K functions to bind the cylindrical support layer _50S and the glass beads _50G . Therefore, for example, the support layer 50
This is not necessary if 50 _G of glass beads are directly embedded in _S. The properties required of the material constituting the _50K binding layer include thermal stability such as not changing at temperatures above 200°C, impact resistance, and solvent resistance (chemical stability). Specifically, a phenolic resin solution (2% solids added to ethanol) was used. The curing temperature was 150°C and it took 3 hours. In addition to the above materials, epoxy resins, modified silicone resins, and other resins that have heat resistance of 200° C. or higher and are chemically stable can all be used. Next, the materials constituting the support layer _50S are as follows:
Generally, metals with good thermal conductivity are suitable.
The size of the specific heat is determined depending on the purpose, such as the size of the specific heat, depending on the configuration of the device, but Al was used in the experiment due to cost considerations. Next, as for the manufacturing method of the fixing roller 5, first, an Al cylinder as the support layer _50S is prepared, the above phenol resin solution is applied to it by a dipping method, and then the above glass beads _50G are applied. After sprinkling and pre-drying, it was cured at 150°C for 3 hours and then left to cool naturally. In addition, in the above, a spray gun may be used in addition to the depping method, and a highly volatile solvent other than ethanol may be used as the solvent. Also, in the above, glass beads 5
Since 0 _G has charging characteristics, electrodeposition can also be used by utilizing this. Now, returning to FIG. 5, the lower half of the fixing roller 5 is surrounded by a hot plate 6 that is curved to match the curvature of the roller. This is because the fixing roller 5 is covered as much as possible in order to improve heat conduction efficiency. A heater H is provided inside the hot plate 6 to heat the unfixed toner image. The gap between the hot plate 6 and the outer periphery of the fixing roller 5 is set to about 0.05 to 0.2 mm, and there is no contact between the two. During fixing, the transfer paper S passes between the heating plate 6 and the fixing roller 5, but at this time, there must be no slippage between the transfer paper S and the fixing roller 5; Slip must occur between S and heat 6. For this reason, the hot plate 6 not only supplies heat, but also functions as an auxiliary feeding means for conveying the transfer paper S, which is the object to be fixed, in the discharge direction indicated by the arrow. When the fixing performance according to the prior art shown in FIGS. 1 and 2 was compared with the fixing performance according to the embodiment shown in FIG. 5, the following results (Table 1) were obtained.
In addition, in the conventional technology, the heating plate 1 and the fixing roller 2
The gap is 1.5±0.2mm, and the heater is set to 700W.

[Table] 〓◎……Extremely good fixing property〓

Claims (1)

[Scope of Claims] 1. A fixing rotating body whose surface that comes into contact with an unfixed toner image on an object to be fixed has a micro-asperity shape in which particles with a particle diameter of 10 to 500 μm are densely arranged; an auxiliary feeding means for assisting in conveying the object to be fixed in a discharge direction while holding the object at a fixed position relative to the fixing rotating body and preventing slippage between the two; and heating the unfixed toner image. 1. A fixing device for an electrophotographic copying machine, characterized in that it has a heat source, etc. for fixing the image.