JPH0527620A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device which sufficiently secures the fusing of toner and has excellent glossiness and high color reproducibility, in an image after being fixed, without using releasing agent such as silicone oil, at all, or with using it a little even if it is used. CONSTITUTION:In the fixing device provided with an endless belt 15 wound on a fixing roller 10 and a carrying roller 14, and a fixing roller 20 in press- contact with the fixing roller 10 via the belt 15, and a heater on at least, one core part of the fixing rollers 10 and 20, elastic layers are provided on the outer peripheries of the fixing rollers 10 and 20, as a characteristic. On the other hand, the fixing roller 10 has the elastic layer thicker than that of the fixing roller 20, to obtain an excellent result. On the contrary, the former has the elastic layer of lower hardness than that of the elastic layer of the latter, to obtain an excellent result.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In the fixing process of toner images for electrophotography, heat roller fixing is the most common. In the recent electrophotographic process for handling color images, color reproducibility and glossiness of images after fixing are ensured and
It is required that the toner be sufficiently melted in order to ensure the transparency when the P transfer material is used. If the melting condition of the linear polyester toner that is widely used is set to the above-mentioned level, it is necessary to apply a large amount of low-viscosity silicone oil as a release agent as a prerequisite from the problem of high temperature offset. Has become.

[0003]

When a large amount of silicone oil is used in this way, problems such as spillage of silicone oil and adhesion of silicone oil to a transfer material occur. In particular, when OHP is used, since the transfer material is not impregnated with silicon oil, the user's hands are soiled with silicon oil, or the permeability of OHP itself is significantly reduced. For this problem, a general polyester toner, that is, a wax-based toner is adopted, but it is difficult to obtain a sufficient molten state under the present circumstances. Also,
As described above, the glossiness after fixing is often required for a color image, and in that case, as a means in that case, a large amount of a release agent is applied or a wax-based toner is used as described above. When using, the image once fixed is fixed again with the option unit.

The present invention solves such a problem of fixing by using no release agent such as silicone oil at all.
Even when used, it provides a fixing device with sufficient toner reproducibility in the image after fixing and excellent color reproducibility in toner fusion even with a slight use, and an image with good gloss as required for color images. The purpose is to achieve fixing with excellent transparency and color reproducibility especially when OHP is used.

[0005]

This object is achieved by the following technical means a, b, c or d.

(A) The endless belt is wound around one roller of a pair of rollers in a pressure-bonded state via a belt surface of the endless belt and a conveying roller located at a position separated by a predetermined distance. At least one of the pair of rollers is provided with a heater for heating, and a transfer material having an unfixed toner image of electrophotography passes through the pair of rollers and a part of the endless belt to transfer the toner. A fixing device for fixing onto a transfer material, wherein the endless belt has a structure in which a release agent layer is provided on a substrate, and elastic layers are provided on both outer peripheral surfaces of the pair of rollers. Fixing device.

(B) Both of the elastic layers have a thickness of 0.5.
The fixing device according to item a, wherein the fixing device has a thickness of 10 mm to 10 mm.

(C) The fixing device according to item a or b, wherein the thickness of the elastic layer is larger in the belt suspension side roller than in the pressure side roller.

(D) The fixing device according to item (a), item (b), or item (c) is characterized in that the hardness of the elastic layer is smaller in the belt suspension side roller than in the pressure contact side roller.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of Embodiment 1 of the present invention is shown in FIG. 1, the construction of Embodiment 2 is shown in FIG. 2, the construction of Embodiment 3 is shown in FIG. The present invention will be described with reference to sectional views, sectional views of the layer structure of the endless belt shown in FIGS. 5 and 6, and the graph shown in FIG. 7.

(Embodiment 1) A fixing roller having a core metal 11 as shown in FIG. 1, on which a heat-resistant synthetic rubber layer is concentrically provided as an elastic layer 12, and a heater 16 is provided at the center thereof. Ten
An endless belt 15 is wound between the fixing roller 10 and a conveying roller 14 provided at a specific distance. And
The endless belt is composed of a polyimide substrate 15A coated with a release layer 15C made of silicone rubber as shown in FIG. 5, or an elastic layer 15B sandwiched in the middle as shown in FIG. The thickness of the polyimide substrate 15A is preferably 10 to 100 μm, more preferably 25 to 75 μm. The silicon rubber layer is 50 to 300 μm. The fixing roller 20 is pressure-bonded to the fixing roller 10 via the endless belt 15. The fixing roller 20 is also provided with a heater 23 in the center thereof, a core metal 21 concentrically with the heater 23, and a heat-resistant synthetic rubber layer as an elastic layer 22 concentrically with the heater 23.

Then, the developed unfixed image in which the toner 52 is adhered onto the transfer material 51 is conveyed onto the entrance guide 17,
While being pressed by the fixing rollers 10 and 20 and the endless belt 15, it is sent in the direction of the arrow and passed through the guide 33 to complete the fixing to the outside of the conveying roller 14 and discharged and collected.

Silicon rubber is coated on the outer side of the endless belt 15 as a release agent layer 15C, and also serves as an elastic body.

Further, a sensor 13 as a temperature detecting means is provided in contact with a position where the endless belt 15 is not in contact with the outer peripheral surface of the fixing roller 10, and another fixing roller is provided.
A sensor 24 as a temperature detecting means is provided in contact with the outer peripheral surface of 20.

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

First, the viscosity-temperature characteristic curves of the linear polyester toner and the general polyester toner shown in the graph of FIG. 7 will be described.

In this graph, the vertical axis represents the viscosity in common logarithmic values in Poise units, and the horizontal axis represents the temperature. The linear polyester toner is shown by a solid line, and the 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, a glass transition state, and both toners are in a molten state when the temperature exceeds 100 ° C. And the optimum molten state has a viscosity of 5000
It's about Poise. As for the viscous state, although the heating temperature of a general polyester toner reaches 150 ° C., the linear polyester toner has a much lower temperature of 120 ° C.

Further, in the present invention, the endless belt 15 is interposed in comparison with the conventional fixing device in which the heat fixing is carried out by the nip of only the pair of rollers by the two fixing rollers. Since the time can be secured, the melting temperature can be expanded to a higher temperature than ever, and the heating area can be made much wider. In this heating region, the unfixed image is sufficiently melted by the toner obtained in a melted state at a low temperature such as linear polyester resin. The adhesive force between the toner 52 and the transfer material 51 in the molten state and natural cooling or the airflow from the cooling fan 32 applied from the back surface of the transfer material as in the third embodiment shown in FIG. The endless belt 15 is conveyed while being attached, and the temperature is lowered.

In this region, the toner 52 and the transfer material 51, which have been sufficiently cooled and have a large viscosity to be in a glass transition state, are
The endless belt 15 supported by the transport rollers 14 is peeled off from the endless belt 15. At this time, since the toner 52 is almost in the solidified glass transition state, the surface property of the belt 15 is maintained as it is, and a glossy surface close to a mirror surface is obtained. As described above, the toner 52 is solidified after it is sufficiently melted, so that color reproducibility by melting and mixing of a plurality of color toners is ensured, and the transparency when fixed on OHP or the like can be stably ensured. As described above, since the surface material forming the endless belt is a material such as silicone rubber which is a release agent, the release layer itself has elasticity as well as releasability. In addition to being able to realize the above, there is also a damper effect between the toner 52 and the endless belt 15, so even if a toner that easily melts at a relatively low temperature such as a linear polyester toner is used, does the offset state occur at all? However, even if it occurs, it is extremely small and can be kept at a level within a range where cleaning is possible.

At this time, since the elastic layer is provided on both of the pair of rollers, a buffering effect of the elastic layer acts on the molten toner coming out of the nip portion and the transfer agent supporting it. This prevents the occurrence of an offset state due to cohesive failure inside the molten toner layer. As for the thickness of the elastic layer of the roller, when the thickness t ₁ on the roller side on which the belt is hung is made thicker than the thickness t ₂ on the other side, the effect of preventing offset to the toner layer is further increased. In addition, the rubber hardness of the former roller and that of the latter roller are h ₁ and h _{2 respectively.}
In that case, h ₁ <h ₂ is more preferable because the effect of preventing offset is further increased.

Further, in the case of the fixing device using the endless belt 15, the heating value of the heater is controlled by matching the reading value of the sensor 24 as the temperature detecting means attached to the fixing roller 20 to be pressure-bonded with the reading value of the sensor 13. By doing so, it becomes possible to maintain the temperature of the fixing portion in a stable range.

(Embodiment 2) As shown in FIG. 2, the heater 16 is removed from the fixing roller 10 of Embodiment 1, and the roller 10 is composed of a core metal 11A at the central portion and an elastic layer 12A at the peripheral portion. Is.

Even in such a state, the temperature sensor 13
By controlling the heating state of the heater 23 by means of 24 and 24, it is possible to maintain the temperature of the fixing portion within a stable range. Since the elastic layer is provided on both the pair of rollers, cohesive failure does not easily occur inside the molten toner layer, and offset onto the endless belt 15 is prevented.

(Embodiment 3) As shown in FIG. 3, Embodiment 3 is different from Embodiment 1 in that it has an air suction guide 31 and a cooling fan 32.
A cooling device (30) is provided near the lower part of the guide (33) along the endless belt (15). Also in this case, cohesive failure is less likely to occur inside the molten toner layer as in Example 1. Then, the effect of preventing offset on the endless belt is achieved. Further, by controlling the heating states of the heaters 16 and 23 by the reading values of the sensors 13 and 24 as the temperature detecting means, it is possible to keep the temperature of the fixing portion within a stable range.

(Embodiment 4) In Embodiment 4, as shown in FIG. 4, a cooling device 30 is further provided near the lower end of the endless belt as compared with Embodiment 2. This also has the same effect as the third embodiment. That is, cohesive failure of the molten toner layer does not easily occur, offset is prevented, and fixing quality is significantly improved.

Even in the second and third embodiments having no cooling device, the transfer material 51 and the toner 52 are carried in a state of being in close contact with the surface of the endless belt 15 by the heating control of the heater by the temperature sensors 13 and 24 described above. The endless belt 15 is peeled off and collected very naturally at the end without being offset.

[0027]

EFFECTS OF THE INVENTION According to the present invention, a low temperature melting type toner does not cause the problem of transfer (offset) of the oil even if a releasing agent such as silicone oil is not used at all or even if it is used very little. By using, it was possible to sufficiently dissolve the toner and obtain a fixed image excellent in transparency and color reproducibility.

The transfer material at this time is not contaminated with silicone oil or the like. In addition, a gloss image required for a color image can be obtained at a sufficient level.

[Brief description of drawings]

1 is a sectional view of a first embodiment of the present invention. 2 is a sectional view of Embodiment 2 of the present invention. FIG. 3 is a sectional view of a third embodiment of the present invention. 4 is a sectional view of Embodiment 4 of the present invention. 5 and 6 are cross-sectional views of the layer structure of the endless belt. FIG. 7 is a toner viscosity-temperature characteristic curve.

[Explanation of symbols]

10,20… Fixing roller 11,21… Core metal 12,22… Elastic layer 13,24… Temperature detection sensor 14… Conveying roller 15… Endless belt 17… Inlet guide 30… Cooling device 31… Air suction duct 32… Cooling fan 33 ... Guide 51 ... Transfer material 52 ... Toner

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[Procedure amendment]

[Submission date] August 20, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a first embodiment of the present invention. Sectional view of.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a sectional view of a third embodiment of the present invention.

FIG. 4 is a sectional view of a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view of the layer structure of an endless belt.

FIG. 6 is a cross-sectional view of the layer structure of the endless belt.

FIG. 7 is a toner viscosity-temperature characteristic curve.

[Explanation of symbols] 10,20 Fixing roller 11,21 Core 12,22 Elastic layer 13,24 Temperature sensor 14 Transport roller 15 Endless belt 17 Entrance guide 30 Cooling device 31 Air suction duct 32 Cooling fan 33 Guide 51 Transfer material 52 toner

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 7]

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuhiko Tanaka             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company

Claims (4)

[Claims] 1. The endless belt is provided by being wound between one roller of a pair of rollers in a pressure-bonded state via a belt surface of the endless belt and a conveying roller located at a position separated by a predetermined distance, At least one of the pair of rollers,
A fixing device provided with a heater for heating, wherein a transfer material having an unfixed toner image for electrophotography passes through a pair of these rollers and a part of an endless belt to fix the toner on the transfer material. The fixing device is characterized in that the endless belt has a release agent layer on a substrate, and elastic layers are provided on the outer peripheral surfaces of both of the pair of rollers. 2. The elastic layers each have a thickness of 0.5 to 1
The fixing device according to claim 1, wherein the fixing device is 0 mm. 3. The fixing device according to claim 1, wherein the elastic layer has a thickness larger than that of the belt suspension side roller and that of the pressure contact side roller. 4. The fixing device according to claim 1, wherein the hardness of the elastic layer is smaller in the belt suspension side roller than in the pressure side roller.