JPH07191567A - Thermopressure roller and fixing device - Google Patents

Abstract

PURPOSE:To provide a thermopressure roller having prescribed elastic force while excellently maintaining wear resistance to a separating pawl, etc., and the transmission responsiveness of heat from a core metal and not causing changes in a shape with lapse of time nor in characteristics. CONSTITUTION:The core metal 81 of a fixing roller is covered with silicone rubber 82 of about 100-500mum, desirably 200mum and moreover, it is covered with porous fluororesin 83 of about 10-200mum, desirably 50mum. Thus, micro surface hardness is suppressed lower than that in a conventional soft roller, so that the porous fluororesin 83 is closely stuck to the ruggedness of a transfer material 100 and toner 101 thereon as well, to sufficiently heat/melt the toner 101 and improve its fixing force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a thermal pressure roller for fixing toner and a transfer material in a copying machine, a printer, a facsimile and the like using electrophotography, and a fixing device using the same. .

[0002]

2. Description of the Related Art In a conventional fixing device, a fixing roller that contacts a surface of a transfer material on which a toner is placed and a pressure roller that applies a pressure to the roller are provided as a heat pressure roller. 10 by the heater installed inside
Generally, the toner is fixed to the transfer material by heat of about 0 to 200 ° C. and the pressure of the fixing roller and the pressure roller.

In this type of fixing device, the fixing roller is
A core metal such as iron or aluminum is used as a foundation of the structure, and a highly releasable material to which toner hardly adheres is applied onto the core. Examples of the highly releasable material include tetrafluoroethylene resin (hereinafter, PTFE) or tetrafluoroethylene perfluorovinyl ether copolymer (hereinafter, PF).
In many cases, the fluororesin represented by A) is coated alone or in combination. Further, as a means for improving the releasability, a mechanism for applying a releasing agent such as silicone oil to the roller has been devised.

The reason why the releasability of the roller is improved in this way is to prevent defects such as image loss and image stain. To prevent this, the toner fixed on the transfer material is It is also necessary to improve the fixing strength. That is, if the fixing force is weak, the toner is likely to be peeled off from the transfer material, and defects such as image loss and image smear occur as in the case where the releasability of the roller is lowered. Therefore, conventionally, as a means for improving the fixing force, an elastic body is provided between the core metal and the highly releasable material.

On the other hand, in the pressure roller, for the purpose of increasing the contact area with the fixing roller, an elastic body is coated on the core metal by about 1 to 10 mm, and the durability and the releasability are improved on it. Therefore, it is often coated with the same fluororesin as the fixing roller. In particular, the pressure roller is generally covered with PFA in a thickness of about 50 to 200 μm because it is easy and inexpensive to provide the fluororesin with a thickness.

As described above, the elastic body is used in the conventional heat and pressure roller, but in many cases, silicone rubber or fluororubber is used as the elastic body. In general comparison, silicone rubber is more advantageous than fluororubber in terms of workability, compression set, and cost, and is widely used. Further, the fluororubber has less swelling with oil and the like, and has a better releasability than silicone. However, it is a fluororubber, and its releasability is not sufficient as compared with a fluororesin.

[0007]

However, the above-mentioned conventional example has the following problems. First, in the fixing roller, the toner does not easily adhere, that is, the releasability is good, the fixing force of the toner on the transfer material is strong, and further, the transfer material, the oil applying mechanism, and the transfer material separating claw are used. Therefore, it is required that abrasion is unlikely to occur, and as described above, a fluororesin is often coated as the highly releasable material. However, in order to make use of the elastic force of the elastic layer for the purpose of improving the fixing force, the hardness of the resin is too high as compared with the elastic body, so the resin layer to be coated is thinned to about 10 to 50 μm. There is a need. As a result, the highly releasable layer, which is a fluororesin layer, is scraped by the friction of the transfer material, the oil application mechanism, the transfer material separating claw, etc. described above, and the elastic body layer is exposed relatively early, and the toner is transferred to the roller. The image was abnormal due to the adherence to the. Also, if the coating thickness of the elastic layer is made thicker than about 1 mm for the purpose of maintaining the elastic force, the heat transfer response from the core metal deteriorates, and it may not be suitable for high speed fixing. However, there has been a problem that the overshoot at the time of temperature adjustment is increased and the members around the heat pressure roller are deteriorated. Therefore, the soft roller having the above structure has a limit in improving the toner fixing force.

On the other hand, in the pressure roller, the fluororesin typified by PFA is often about 50 to 200 μm, which is thicker than the resin layer thickness of the fixing roller, and has excellent durability against abrasion. However, as described above, when the thickness of the silicone rubber generally used as an elastic body is set to about 1 to 10 mm, there is a phenomenon that a low molecular gas such as siloxane gas volatilizes and changes its shape with the lapse of time. Usually, both the fixing roller and the pressure roller are hourglass-shaped, and a difference in the diameter between the central portion and the end portion in the longitudinal direction, a so-called crown amount is often given around 100 μm, but the shape change of the roller due to volatilization of low-molecular gas Had a problem of causing a change in the amount of crown. The crown amount is given for the purpose of preventing the transfer material from wrinkling due to an appropriate pulling effect in the transfer material end direction, but in the pressure roller coated with PFA or the like, the free end is The outer diameter of the end portion of the roller is remarkably changed, and the crown amount is decreased with the lapse of time, causing an unpleasant phenomenon such as wrinkling of the transfer material.
In addition, in the silicone rubber, water (H ₂ O) released from the chemical bond is generated and stays in the rubber covered with PFA or the like to accelerate hydrolysis of the rubber and deteriorate the original properties of the rubber. I will let you. In this way, with the pressure roller,
Due to changes in shape and characteristics over time, wrinkles on the transfer material and changes in the physical properties of the rubber cause a decrease in the toner fixing force, and there is a problem that the life is short.

The present invention solves the above-mentioned problems, has a predetermined elastic force while maintaining good abrasion resistance against separation claws and the like, and heat transfer response from the cored bar. Thermal pressure roller that does not cause shape change and characteristic change,
It is also an object of the present invention to provide a fixing device including the same.

[0010]

SUMMARY OF THE INVENTION According to the present invention, the object of the present invention is, first of all, with respect to a thermal pressure roller, a thermal pressure of a fixing device for adhering hot melt toner onto a transfer material and fixing the toner by heat and pressure. In a roller, this is achieved by having an elastic silicone rubber on a core metal, and winding a porous fluororesin having a volume porosity of 20% or more on the rubber, and having an average pore diameter of 10 μm or less. It is achieved by

Next, the fixing device can be achieved by having a means for applying 1000 to 50000 cs of silicone oil as an offset preventive agent directly or indirectly to the heat and pressure roller having the above-mentioned structure.

[0012]

According to the present invention, a conventional silicone rubber is used for the elastic body, and a porous fluororesin having elastic force and gas permeability even though it is a fluororesin is used as the highly releasable material for the surface layer. Therefore, in the fixing roller, in addition to the elastic force of the silicone rubber, the elastic force of the porous fluororesin that can follow the fine irregularities of the transfer material and the toner improves the fixing force between the toner and the transfer material.

Further, in the pressure roller, due to the nature of the porous member that allows low-molecular siloxane gas and water vapor to pass through, unnecessary gas is evaporated from the entire roller surface, which causes uneven shape change over time and deterioration of rubber. Is suppressed.

Further, by applying silicone oil of 1000 to 50000 cs, which is a release agent, directly or indirectly to the fixing roller and the pressure roller, which are the heat pressure rollers, the pore diameter of the porous fluororesin is set to a predetermined value. By controlling the size of the rubber to prevent the oil from penetrating into the silicone rubber, the swelling phenomenon of the rubber is prevented.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1> First, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a schematic view of a copying machine according to this embodiment equipped with electrophotographic technology.

In the apparatus shown in FIG. 1, a document placed on the document table cover 1 and the platen glass 2 is illuminated by a document illumination lamp 3, and the respective reflection mirrors 4, 5, 6 and the lenses 7 and 8 are reflected. It is used and projected on the photoconductor 9. An electric charge is applied to the photoconductor 9 in advance by the charger 10. A transfer separation charger 1 is provided on the transfer material 100 conveyed from the paper feed deck 12 after being visualized by the developing device 11 to which the toner agent is attached.
The toner is fixed on the transfer material 100 by the fixing roller 51 and the pressure roller 52, and is output to the paper discharge tray 15.

FIG. 2 is a view for explaining the structure of a fixing device for fixing the toner on the transfer material in the above-mentioned electrophotographic copying machine or the like. The main components are a fixing roller 51 that fixes the toner to the transfer material and a pressure roller 52 that applies pressure to the transfer material and the toner by backup. Generally, the surface of the fixing roller 51 is heated to about 100 to 200 ° C. by a halogen heater 53 and a temperature adjusting thermistor (not shown). Further, for the purpose of cleaning the offset toner adhering to the fixing roller 51, a web 54 made of non-woven cloth and a web roller 55 for bringing the web 54 into contact with the fixing roller 51 are provided. As the cleaning means, there are various other methods such as a roller-shaped member or a lump-shaped member. Further, these cleaning means are equipped with a mechanism that is impregnated with silicone oil and applies to the oil as a release agent at the same time as the cleaning.

Further, an entrance guide 56 is attached so as to optimize the carry-in position when the transfer material is carried into the fixing roller 51 and the pressure roller 52, and a paper discharge guide 57 is provided even after the roller has entered. There is. An upper separating claw 58 is provided to prevent the transfer material from being wound around the fixing roller 51, and a lower separating claw 59 is provided on the pressure roller 52 side as well. Then, the blade 60 is brought into contact with the pressure roller 52 to prevent the paper powder of the transfer material, the mass of the molten toner, and the oil application unevenness in the case of having an oil application mechanism. The oil applying mechanism and the blade are members that can be attached to both the fixing roller 51 and the pressure roller 52.

3 (a) and 3 (b) are sectional views of the fixing roller 51 of the prior art. In the figure, a fixing roller 5 having a so-called hard roller without an elastic layer is provided.
1, the fixing roller 51 has a structure in which a core metal 61 made of iron or aluminum is used as a basis of the structure and a highly releasable layer 62 made of fluororesin or the like is coated on the order of 10 to 100 μm. The characteristic of the fixing roller 51 is advantageous in terms of material cost and production processing cost due to its simple structure, but since the hardness of the roller surface is high, the fixing force between the toner and the transfer material is weak and high-speed output is required. It is not suitable for medium and large size aircraft.

On the other hand, in the prior art, there is also a roller having an elastic layer between the cored bar and the highly releasable layer, that is, a so-called soft roller, and a fixing roller is shown in FIG. 4 (a).
It shows in (b). In the figure, the elastic layer 7 is formed on the core metal 71.
2 with a thickness of about 100 to 500 μm to form a highly releasable material 7
3 is covered by about 10 to 50 μm. Silicone rubber is often used for the elastic body in view of cost, workability, compression set and the like. A fluororesin typified by PTFE is often used as the highly releasable material, and it is often thinned to about 20 μm in order to utilize the elasticity of the elastic body.

FIGS. 5 and 6 schematically show the states of the above-mentioned conventional fixing roller, which is a hard roller and a soft roller, when passing through the transfer material. In FIG. 5, the hardness of the roller is high due to the configuration of the hard roller, it is difficult to contact the entire surface of the toner 101, and only the upper portion of the toner 101 is contacted. Therefore, the thermal conductivity to the toner is poor, and the toner is less likely to melt and stick to the transfer material so as to become entangled. Therefore, the fixing force of the toner is weak.

In the soft roller shown in FIG. 6, the hardness of the soft roller is lower than that of the hard roller due to its construction, and the unevenness of the transfer material and the unevenness of the toner can be effectively followed, and the toner is melted and the fixing force is increased. It is bigger than.

However, with a transfer material such as letterhead paper or Japanese paper, which has extremely severe surface irregularities, even the above soft roller cannot sufficiently exhibit its performance. For example, when a transfer material having a remarkably poor surface property such that the ten-point average roughness Rz exceeds 20 μm is used, even a soft roller has a resin layer with a microscopic high surface hardness, and therefore, a satisfactory fixing force cannot be obtained. I could not do it.

Therefore, in the present invention, FIGS. 7 (a) and 7 (b) are used.
In order to improve the fixing force, the structure as shown in FIG.
As shown in FIG.
0 to 500 μm, preferably about 200 μm is coated, and the porous fluororesin 83 is coated thereon to 10 to 200 μm, preferably about 50 μm. The porous fluororesin has pores formed by a stretching method.

FIG. 8 is a diagram showing the relationship between the volume porosity and the microscopic hardness of the roller surface. It can be seen that the phenomenon of roller hardness is remarkable when the porosity is about 20% or more. Due to this effect, as shown in FIG. 9, the toner fixing force is increased as the porosity is increased. However, the increase of the porosity is not only an advantage, but also the offset level indicating the degree of adhesion of the toner to the roller surface is deteriorated as shown in FIG. Offset refers to a phenomenon in which toner on a transfer material is peeled off by a fixing roller. In FIG. 10, a conventional fluororesin soft roller having a volume porosity of 0% is set as a reference level 100, and a level not usable is set as 50. Shows. Also in FIG.
As shown in (1), since the porosity of the porous fluororesin increases, the strength of the structure decreases, and the durability against abrasion by the transfer material, separation claws, etc. deteriorates. In FIG. 11, a conventional fluororesin soft roller having a volume porosity of 0% is shown as a reference level 100, and a level that cannot withstand use is shown as 50. From these experimental results, the porosity is 20.
% Or more, and preferably around 40% is a good condition for comprehensive evaluation.

By the way, if the volume porosity is the same, it can be seen that the change in the average pore diameter affects the offset level and the roller durability. FIG. 12 shows the offset level with respect to the average pore diameter.
It is shown as 0, and the level which cannot withstand use is shown as 50. The offset level changed drastically in the vicinity of 5 to 15 μm, which is the same as the toner particle size, and exceeded the use limit at approximately 20 μm or more. Further, FIG. 13 shows the roller durability with respect to the average pore diameter, and the average pore diameter is 1 μm.
The level of m is 100, and the level that cannot be used is 50
It is shown as. The average pore size is on the order of several tens of μm, which is also the limit of use. From these facts, the average pore size is 10 μm or less, and preferably 1 μm or less is the best condition in the comprehensive evaluation. It should be noted that the above result may be conditioned on the condition that the average pore size is approximately equal to or smaller than the toner particle size.

FIG. 14 is a diagram schematically showing the state of the fixing roller having the surface layer of the porous fluororesin according to the present invention when passing through the transfer material. The roller according to the present invention is also classified as a soft roller in the above-mentioned conventional technique, but since the microscopic surface hardness is suppressed to be lower than that of the conventional soft roller by using the porous material, the unevenness of the transfer material may be great. The toner adheres well to the toner on the transfer material, and the toner can be sufficiently heated and melted. As a result, the toner fixing force of the above-mentioned letterhead paper, Japanese paper, etc. is also improved, and the fixing roller has higher performance.

Table 1 compares the performance of the above-mentioned conventional hard roller and soft roller with the fixing roller coated with the porous fluororesin according to the present invention.
As described above, the toner of the present invention is excellent in the toner fixing force. Regarding the durability such as abrasion, there is not much difference in the basic surface layer components between the hard roller of the prior art, the soft roller and the roller of the present invention, so there is no significant difference. A hard roller with a highly releasable layer directly on the core is slightly superior,
A roller having an elastic layer other than the hard roller is, on the contrary, excellent in terms of dents due to careless contact with an object.

[0030]

[Table 1]

Further, there is a change in the image depiction ability. The roller of the present invention having a low microscopic surface hardness is faithful to the fine line reproducibility. On the other hand, with the hard roller, toner is scattered in the opposite direction of the transfer material traveling direction, and reproducibility is poor.

Further, the constitution of the present invention in which the roller surface is in contact with the entire surface of the toner on the transfer material further exerts the effect, and the density uniformity in solid black and high density halftone is also good with little feeling of roughness. An image is obtained.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. In addition, Example 1
The same parts as in FIG.

In the first embodiment, it has been explained that the present invention is an effective means for the fixing roller of the heat and pressure rollers that comes into direct contact with the toner. On the other hand, in the present embodiment, it will be described that the present invention is also effective for the pressure roller that is in pressure contact with the fixing roller among the thermal pressure rollers.

FIGS. 15 (a) and 15 (b) are sectional views showing a general pressure roller in the prior art.
1 to 10 m of elastic silicone rubber 112 on 1
m as a coating, and as a fluororesin layer 113, a PF
A is coated with about 50 to 200 μm. As described above, the silicone rubber is provided to increase the contact area involved in heat transfer in the contact with the fixing roller, and the PFA serves to maintain the releasability of the toner and prevent scraping of the transfer material. , Is provided for the purpose of preventing swelling of silicone rubber by oil.

Incidentally, the roller is often provided with a crown shape as shown in FIG. 16 as a means for preventing paper wrinkles of the transfer material. In FIG. 16, the dimensions in the radial direction are exaggerated in order to make the shape easy to understand.
Assuming that the outer diameters of the central portion and both end portions of the roller are DA, DB, and DC, respectively, the crown amount may be calculated as C = (DB + DC) / 2-DA as a convenient means of expressing the crown amount by a numerical value. Usually, this value is a small value of about 0 to 200 μm. However, when the transfer material is conveyed to the fixing device, if the transfer material passage positions of different sizes are all located on the front side or the back side, the above DB and DC may give different outer diameters. . At this time, it may be necessary to introduce an expression other than the above-mentioned arithmetic expression.

Here, as in the conventional case shown in FIGS. 15 (a) and 15 (b).
FIG. 17 is a graph showing changes in shape over time of the pressure roller shown in FIG. In FIG. 17, the horizontal axis represents the use time, and the crown amount C and the center outer diameter DA are plotted. With the conventional pressure roller, the outer diameter DA of the central portion hardly changes. However, it can be seen that the crown amount C decreases with time. This is because the outer diameters DB and DC at both ends are reduced, that is, what is called end thinning.
This factor is because the siloxane low molecule in the polysiloxane that constitutes the silicone rubber is dissociated from the bonded state, vaporized, and volatilized from the free end. The end of the roller is necessary to evaporate water, which promotes hydrolysis, in addition to the low molecular weight siloxane. It is not preferable to seal the ends in order to maintain the rubber physical properties as much as possible. Still, regarding the water content, it is still not enough to release only the end portion, and a structure that promotes further evaporation is desired.

Therefore, the above problem is solved by using the structure according to the present invention as shown in FIGS. 18 (a) and 18 (b). This figure is a cross-sectional view for explaining the coating structure of the pressure roller according to the present embodiment. The core metal 121 is coated with the silicone rubber layer 122 for about 1 to 10 mm, and the porous fluororesin 123 is coated thereon for 50 to 200 μm. Porous fluororesin has a volume porosity of 40%
And the average pore size is 1 μm. Under these conditions, low molecular weight siloxanes and water can pass through the porous fluororesin. FIG. 19 is a graph showing changes in the crown amount C and the central portion outer diameter DA after the time-dependent change under the above conditions. From FIG. 19, the outer diameter DA of the central portion gradually decreases, but the change in the crown amount C is slight and almost constant. This is because the central portion outer diameter DA is also becoming thinner at the same time as the end portion outer diameters DB and DC are becoming thinner. That is, according to the configuration of the present invention in which the siloxane low-content component is volatilized not only from the roller end portion but from the entire roller surface,
This is because even if the outer diameter changes over the entire roller, the crown amount acts to keep it substantially constant. The fluctuation of the outer diameter of the entire roller does not cause any problem when the pressure roller is driven by the fixing roller. Further, the contact area with the fixing roller and the contact pressure are small changes and have little influence. In addition, water that promotes hydrolysis is less likely to be constantly evaporated and accumulated, and the physical properties such as elastic force of the silicone rubber can be maintained for a long time.

FIG. 20 shows the relationship between the volume porosity and the amount of change in the crown amount. The higher the volume porosity, the more active the volatilization of siloxane low molecules and water, and the smaller the amount of change in the crown amount. In addition, FIG. 21 shows the changes over time in the average pore size and the crown amount. It can be seen that if the volume porosity is the same, the average pore size has little effect.

Table 2 compares the performance of the above-mentioned conventional resin-coated pressure roller and the pressure roller coated with the porous fluororesin according to the present invention. As described above, the central portion outer diameter DA changes as compared with the case of the conventional technique, but the crown amount is almost constant and paper wrinkles do not occur on the transfer material for a long time. Therefore, assuming that the occurrence of paper wrinkles is the life of the pressure roller, in the prior art, the life was about 500,000 μm, which was the output time corresponding to the number of continuously passed sheets, but according to the present embodiment, about 800,000 sheets are used. It is possible to continue functioning for a considerable continuous output time.

[0041]

[Table 2]

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 22 shows the case where the hot press roller of the present invention is used.
A fixing device provided with a mechanism of an oil-impregnated cleaning web that also serves to apply oil as a release agent and to clean offset toner on a roller. A fixing roller 80 of the present invention which is coated with a porous fluororesin and has a silicone rubber elastic body, and a pressure roller 120 of the present invention which is also coated with a porous fluororesin and has a silicone rubber elastic body, The cleaning web 54 and the web roller 55 are included. Here, a heat-resistant fiber is used as the web material, and dimethylpolysiloxane is used as the oil as a constituent component.
-50000 cs of silicone rubber oil is used.

FIG. 23 is a graph in which the amount of low-molecular siloxane passing through the porous fluororesin is plotted against the oil viscosity. As an experimental method, silicone rubber oil heated to about the fixing roller temperature is put into a container made of a porous fluororesin having a volume porosity of 20% or more and an average porosity of 10 μm or less according to the present invention, The amount of exudation was measured. According to this, it can be seen that the boundary of the seepage is around 1000 cs.

Therefore, if the silicone rubber oil of 1000 cs or more is applied, it is possible to construct a fixing device having an excellent releasability without causing the swelling phenomenon of the silicone rubber elastic body due to the exudation of the oil. Has become. In this embodiment, the web is used as the fixing roller to apply the oil, but the pressure roller can be installed and the oil applying mechanism may have a roller shape.
The same effect can be obtained by changing the shape part such as a lump. Of course, even when at least one of the fixing roller and the pressure roller is coated with the porous fluororesin according to the present invention, the above effect can be obtained.

[0046]

As described above, according to the present invention,
By using porous fluororesin for the surface layer of the fixing roller and the pressure roller, in the fixing roller, the microscopic hardness of the roller surface is reduced, the efficiency of heat transfer to the toner is improved, and the solidification of the toner and the transfer material. It becomes possible to strengthen the fit.

In the pressure roller, volatilization of low molecular weight siloxane is promoted from the inside of the silicone rubber which is an elastic body, the change of the crown amount is suppressed, and the durability against paper wrinkles is improved. At the same time, it becomes possible to evaporate the water inside the silicone rubber and play a role of preventing a change in physical properties.

Further, in applying the oil to the fixing roller and the pressure roller, by using 1000 to 50000 cs of silicone rubber oil, it is possible to suppress penetration of the roller into the silicone rubber which is an elastic body. .

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an electrophotographic copying machine according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a schematic configuration of a fixing device according to a first exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a fixing hard roller according to a conventional technique.

FIG. 4 is a diagram showing a configuration of a fixing soft roller in a conventional technique.

FIG. 5 is a diagram illustrating contact between a fixing hard roller and toner on a transfer material according to a conventional technique.

FIG. 6 is a diagram illustrating contact between a fixing soft roller and toner on a transfer material according to a conventional technique.

FIG. 7 is a diagram illustrating a configuration of a fixing roller according to the first exemplary embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between volume porosity and micro hardness of a roller surface.

FIG. 9 is a diagram showing a relationship between a volume porosity and a toner fixing force.

FIG. 10 is a diagram showing the relationship between volume porosity and offset level.

FIG. 11 is a diagram showing a relationship between volume porosity and roller durability level.

FIG. 12 is a diagram showing a relationship between an average pore diameter and an offset level.

FIG. 13 is a diagram showing the relationship between the average pore size and the durability level.

FIG. 14 is a diagram illustrating contact between a fixing roller and toner on a transfer material according to the first exemplary embodiment of the present invention.

FIG. 15 is a diagram showing a configuration of a pressure roller according to a conventional technique.

FIG. 16 is a diagram illustrating a roller crown amount.

FIG. 17 is a diagram showing the relationship between the use time of the conventional pressure roller and changes in the outer diameter of the central portion and the crown amount.

FIG. 18 is a diagram showing a configuration of a pressure roller according to a second embodiment of the present invention.

FIG. 19 is a diagram showing the relationship between the use time of the pressure roller of the present invention and changes in the outer diameter of the central portion and the amount of crown.

FIG. 20 is a diagram showing the relationship between the volume porosity and the amount of change in end outer diameter.

FIG. 21 is a diagram showing the relationship between the average porosity and the amount of change in the outer diameter of the end portion.

FIG. 22 is a schematic view of a fixing device including a roller and an oil applying mechanism of the present invention.

FIG. 23 is a diagram showing the relationship between oil viscosity and the amount of oil seeping out.

[Explanation of symbols]

 80 Fixing Roller Having Porous Fluorine Resin 82 Silicone Rubber Elastic Layer of Fixing Roller 83 Porous Fluorine Resin Layer of Fixing Roller 100 Transfer Material 101 Toner 120 Pressure Roller Having Porous Fluorine Resin 122 Silicone Rubber of Pressure Roller Elastic layer 123 Porous fluororesin layer of pressure roller

Claims (3)

[Claims] 1. A hot-pressing roller of a fixing device in which a hot-melt toner is adhered onto a transfer material and is fixed by heat and pressure, wherein an elastic silicone rubber is provided on a core metal, and a volume porosity is provided on the rubber. Of 20% or more is wrapped with a porous fluororesin. 2. The thermal pressure roller according to claim 1, wherein the average pore diameter is 10 μm or less. 3. A fixing device comprising means for applying 1000 to 50000 cs of silicone oil directly or indirectly as an offset preventive agent to the heat and pressure roller according to claim 1 or 2.