JPH04273275A - Method and device for fixing - Google Patents

Abstract

PURPOSE:To offer a stable fixing device for sufficiently securing the melting of toner and to obtain excellent glossiness and high color reproducibility, on an image after being fixed, and accurate temp. detecting performance by never using the releasing agent of silicone oil, etc., or using it a little if it is used. CONSTITUTION:In the fixing device, an endless belt 15 wound on a fixing roller 10 and a carrying roller 11, a fixing roller 20 press-contacting with the fixing roller 10 via the belt 15, the outer periphery of the fixing roller 10 of a position where the belt 15 of the fixing roller 10 does not exist, and a sensor 13 as a temp. detecting means are provided, and the heating state of a heating roller attached to, at least, one of the fixing rollers 10 and 20 is controlled with the reading values of the sensors, to achieve an aim.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to means for preventing offset transfer and dirt transfer of a fixing device in electrophotography, means for preventing malfunctions due to sensor dirt, and means for eliminating lack of gloss in color images.

0002

2. Description of the Related Art In the fixing process of electrophotographic toner images, hot roller fixing is the most common. In recent years, in the electrophotographic process that handles color images, it is necessary to ensure the color reproducibility and glossiness of the image after fixing, and to
In order to ensure transparency when using a P transfer material, it is required to melt the toner sufficiently. When using linear polyester toner, which is widely used in general, and adjusting its melting conditions to the above-mentioned level, it becomes necessary to apply a large amount of low-viscosity silicone oil as a release agent due to the problem of high-temperature offset. It has become.

0003

Problems to be Solved by the Invention When a large amount of silicone oil is used as described above, problems such as spillage of the silicone oil and adhesion of the silicone oil to the transfer material occur. Particularly when using an OHP, since the transfer material is not impregnated with silicone oil, the silicone oil may stain the user's hands or significantly reduce the permeability of the OHP itself. To solve this problem, toners using general polyester, that is, wax-based toners, have been used, but at present it is difficult to obtain a sufficient melting state. Furthermore, as mentioned above, color images often require gloss after fixing, and in that case, within the scope of the prior art, the only means to achieve this are to apply a large amount of release agent as mentioned above, or to apply a general release agent. When using a polyester toner, that is, a wax toner, an image that has been fixed once is fixed again using an optional unit.

In order to avoid such trouble, an endless belt is placed between one of the pair of fixing rollers and a separately provided conveyance roller, and the developed transfer material is passed between the pair of fixing rollers and the endless belt. This gives the molten toner a cooling chance to solidify on the transfer paper, but it is necessary to set the temperature of the pair of fixing rollers and the belt, and the temperature of the conveying roller portion appropriately. In order to achieve this, it is necessary to install accurate temperature sensors in important parts to detect the temperature and control heating based on the temperature. However, if the temperature sensor is directly applied to the belt, the image quality may be impaired, or dust or toner may adhere to the sensor due to peeling, etc., causing the sensor to malfunction, making it impossible to perform satisfactory control.

The present invention solves these fixing problems and eliminates the use of a mold release agent such as silicone oil at all.
To provide a fixing device that ensures sufficient toner melting in the image after fixing even if only a small amount is used, and has excellent color reproducibility in toner melting, and furthermore, provides an image with good gloss as required for color images. The purpose is to achieve fixing with excellent transparency and color reproducibility, especially when using an OHP.

[0006]

[Means for Solving the Problem] This object is achieved by the following technical means a, b, or c.

(a) The endless belt is wound between one roller of a pair of rollers in a crimped state through the belt surface of the endless belt and a conveying roller located a certain distance apart, and the A pair of rollers and an endless belt are heated and a transfer material having an unfixed electrophotographic toner image is passed between the pair of rollers and along the outer peripheral surface of the endless belt, thereby transferring the toner onto the transfer material. The endless belt is provided with a layer of a release agent on the substrate to facilitate peeling, and the belt is fixed at a position of the pair of rollers on which the belt is stretched, where the belt does not contact. A sensor is brought into contact with the outer circumferential surface of the toner to detect the temperature of the outer circumferential surface, and the heating amount is controlled to an appropriate amount so that the toner melts and solidifies appropriately and does not cause image contamination, sensor contamination, or offset transfer. Fixation method.

(b) The endless belt is provided so as to be wound between one of the pair of rollers that are pressed together via the belt surface of the endless belt and a conveyance roller that is located a certain distance apart. , at least one of the pair of rollers is provided with a heater for heating, and a transfer material having an unfixed electrophotographic toner image passes through the pair of rollers and a part of the endless belt to remove the toner. The fixing device fixes the image onto the transfer material, and the endless belt has a layer of release agent on the base, and the endless belt has a layer of release agent on the base, and the roller on the heating side on which the belt is stretched is located at a position where the belt does not contact. A fixing device characterized in that a temperature detection means is provided in contact with an outer peripheral surface.

(c) The fixing device according to item (b), wherein the heating control of the heater is performed based on the value read by the temperature detection means.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a first embodiment of the present invention will be explained with reference to the sectional view of FIG.

(Embodiment 1) As shown in FIG. 1, a fixing device has a core bar 11, a heat-resistant synthetic rubber layer is provided concentrically thereon as an elastic layer 12, and a heater 16 is provided in the center of the core bar 11. An endless belt 15 is wound between the roller 10 and a conveying roller 14 provided at a specific distance from the fixing roller 10. The endless belt is composed of a polyimide base coated with a release layer made of silicone rubber. The thickness of the polyimide substrate is preferably 10 to 100 μm, and 20 to 50 μm.
μm is more preferable. In addition, the silicone rubber layer is 50 to 3
00 μm. A fixing roller 20 is pressed against the fixing roller 10 via the endless belt 15. The inclination angle of the line connecting the pair of roller axes formed by both fixing rollers 10 and 20 with respect to the vertical line is 5 to 5.
It is kept at 45℃. The fixing roller 20 also has a heater 23 disposed in the center, a core metal 21 concentrically therewith, and a lining layer of heat-resistant synthetic rubber as an elastic layer 22 concentrically provided on the outside.

The developed unfixed image with the toner 52 attached to the transfer material 51 is conveyed onto the entrance guide 17, and is sent in the direction of the arrow while being pressed by the fixing rollers 10, 20 and the endless belt 15, and the guide 33, and is discharged and collected after completion of fixing outside the conveying roller 14.

A cooling device 30 consisting of an air suction duct 31 and a cooling fan 32 is provided below the fixing rollers 10 and 20, adjacent to a guide provided between the endless belt 15 and the conveying roller 14.

The outer side of the endless belt 15 is coated with silicone rubber as a mold release agent, and also serves as an elastic body.

Further, a sensor 13 as a temperature detecting means is provided in contact with the outer peripheral surfaces of the fixing roller 10 and the conveying roller 14 at a position where the endless belt 15 is not in contact with them. This sensor 13 is suitably a contact type thermistor or thermocouple.

Next, the operation of the fixing device 1 constructed as described above will be described.

First, the viscosity-temperature characteristic curves of the linear polyester toner shown in FIG. 2 and a general polyester toner, that is, a wax toner will be explained.

In this graph, the viscosity is scaled by a common logarithmic value in poise units on the vertical axis, and the temperature is scaled on the horizontal axis. Linear polyester toner is shown by a solid line, and general polyester toner is shown by a chain line. Both toners have a high viscosity of about 100,000 poise near 100°C, that is, are in a glass transition state, and when the temperature exceeds 100°C, both toners become molten. The optimum melt state is when the viscosity is about 5000 poise. and,
Although the heating temperature of conventional polyester toner reaches 150°C, linear polyester toner has a much lower temperature of 120°C.
℃ is sufficient.

Furthermore, compared to the conventional fixing device that performs thermal fixing by a nip between only a pair of rollers, the present invention uses an endless belt 15, which reduces the temperature drop until peeling. Since time can be secured, the melting temperature can be increased higher than before, allowing a much wider heating area. In this heating region, the unfixed image is sufficiently melted by toner, such as linear polyester resin, which can be obtained in a molten state at a low temperature. The adhesive force between the toner 52 and the transfer material 51 in the molten state and the cooling fan 32 applied from the back side of the transfer material
Due to the air flow, the transfer material 51 and toner 52 are conveyed while remaining attached to the endless belt 15, and the temperature is lowered by the temperature of the belt itself and the cooling effect of the air flow.

In this region, the toner 52 and the transfer material 51 have been sufficiently cooled, their viscosity has increased, and they have entered a glass transition state.
is peeled off from the endless belt 15 at the end of the endless belt 15 supported by the conveyance roller 14. At this time, toner 5
Since the belt 2 is almost in a solidified glass transition state, the surface properties of the belt 15 are maintained as they are, and a glossy surface close to a mirror surface can be obtained. In this way, since the toner 52 is solidified after being sufficiently melted, color reproducibility by melting and mixing a plurality of color toners is ensured, and transparency when fixed on an OHP or the like can also be stably ensured. Here, as mentioned above, the surface material constituting the endless belt 15 is a material such as silicone rubber which is a mold release agent, so the mold release layer itself has elasticity as well as mold releasability, so that uniform heating and application of the toner can be achieved. In addition to being able to realize the pressure, there is also a damper effect between the toner 52 and the base of the endless belt 15, so even if toner that easily melts at a relatively low temperature, such as linear polyester toner, is used, no offset occurs. It can be kept to a level that can be cleaned, either not at all, or at a very small level if it occurs.

[0021]Furthermore, temperature control is performed by contacting the sensor 13 as a temperature detection means provided along the outer circumferential surface of the fixing roller 10 and the conveying roller 14 on the side on which the endless belt 15 is stretched, which does not correspond to the belt conveying path. However, an advantage that cannot be overlooked is that the surface of the endless belt 15 is not damaged by the sensor 13 at all. Conversely, only on the surface of the endless belt 15 is the belt and the toner 5
Since there is contact with the sensor 13 and the toner does not go around to the back surface, there is no possibility that the toner 52, dust, etc. will adhere to the sensor 13 and cause a detection failure. Therefore, as shown in the comparative example in FIG. 3, the sensor 13 is brought into direct contact with the endless belt to detect the temperature, and the belt may be damaged, resulting in poor image quality, or the sensor surface may be soiled with toner or scraped dirt. This method is much more effective than the method that caused malfunctions in temperature detection.

Furthermore, in the case of a fixing device using the endless belt 15, the temperature of the fixing part is likely to be affected by the state of the cooling device 30, but the temperature of the fixing portion is likely to be affected by the temperature of the fixing roller 20. By controlling the heating of the heater in conjunction with the reading value of the sensor 13, it becomes possible to maintain the temperature of the fixing portion within a stable range.

[0023]

[Effects of the Invention] According to the present invention, a low-temperature melting toner can be produced without the use of a release agent such as silicone oil, or even if it is used in a very small amount, without causing the transfer (offset) problem of the oil. By using the toner, it has become possible to sufficiently dissolve the toner and obtain a fixed image that is excellent in transparency and color reproducibility and has no scratches on the image surface.

[0024]The transfer material at this time is not contaminated by silicone oil or the like. Furthermore, it has become possible to obtain glossy images of a sufficient level required for color images.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention. Figure 2 shows the viscosity-temperature characteristic curve of toner. FIG. 3 is a cross-sectional view of a comparative example.

[Explanation of symbols]

10, 20...Fixing roller
11, 21...Core metal 12, 22...Elastic body layer 13
…Temperature detection sensor 14…Conveyance roller
15...Endless belt 17...Entrance guide
30...Cooling device 31...Air absorption duct
32...Cooling fan 33...Guide
51... Transfer material 52... Toner

Claims (3)

[Claims] 1. The endless belt is wound between one roller of a pair of rollers that are in contact with each other through the belt surface of the endless belt and a conveyance roller that is located a certain distance apart, and the The rollers and the endless belt are heated and a transfer material having an unfixed electrophotographic toner image is passed between the pair of rollers and along the outer circumferential surface of the endless belt, thereby transferring the toner onto the transfer material. In this fixing method, a layer of a release agent is provided on the base of the endless belt to facilitate peeling, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt, and a layer of a release agent is provided on the base of the endless belt. The fixing device is characterized in that a sensor is brought into contact with the outer circumferential surface to detect the temperature of the outer circumferential surface, and the heating amount is controlled to an appropriate amount for proper toner melting and coagulation and no image contamination, sensor contamination, or offset transfer. Method. 2. The endless belt is provided so as to be wound between one roller of a pair of rollers that are in contact with each other via the belt surface of the endless belt and a conveyance roller that is located a certain distance apart, At least one of the pair of rollers is provided with a heater, and a transfer material having an unfixed electrophotographic toner image passes through the pair of rollers and a part of the endless belt, thereby transferring the toner to the transfer material. The endless belt is a fixing device for fixing onto a material, and the endless belt has a layer of a release agent on the base, and the belt is placed on the outer circumferential surface of the heating side roller at a position where the belt does not come into contact with the roller. A fixing device characterized in that it is provided with a temperature detecting means in contact with the device. 3. The fixing device according to claim 2, wherein heating of the heater is controlled based on the value read by the temperature detection means.