JPS6370880A - Fixing device - Google Patents

Abstract

PURPOSE:To increase the adhesive strength between inside elastic layers and sheath fluoroplastic layers and to improve durability by using the fluoroplastic of the same material quality to form the resin layers of an elastic rotating body for heating and elastic rotating body for pressing, disposing the fluoroplastic in an uncalcined state onto the elastic layers then calcining said layers to the crystal m.p. or above by heating. CONSTITUTION:This fixing device is constituted of a heating roller 1 which usually has a heating source H in the inside and contacts the unfixed toner image T deposited on transfer paper P and a press roller 10 which presses the transfer paper P deposited with the toner image. The heating roller 1 and the press roller 10 are made into the same constitution consisting of arbors 2, 12, the elastic layers 4, 14 and the resin layers 6, 16. A fluoroplastic dispersion or the like coated to a uniform film thickness forms a film-like resin film when heated to the glass transition point 327 deg.C of the crystal m.p. of; for example, the fluoroplastic, or above; therefore, the silicone rubber roller coated with the uncalcined fluoroplastic is heated to the crystal m.p. or above. The offset characteristic and the winding characteristic of the transfer material in particular are thereby improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device used in various image forming apparatuses such as electrophotographic copying machines, printers, etc., and particularly relates to a fixing device used in various image forming apparatuses such as electrophotographic copying machines, printers, and the like. In order to convey and fix a sheet-like transfer material, recording material, etc. at 1 tFa, an elastic rotating body for heating heated by a heat source has an elastic layer inside and a fluororesin layer is formed as a surface layer; The present invention relates to a fixing device having an internal elastic layer, a fluororesin layer formed as a surface layer, and a pressurizing elastic rotating body pressed against the heating elastic rotating body. The heating elastic rotating body and the pressing elastic rotating body are roller-shaped or belt-shaped.
It should be understood that the present invention will be described below mainly in relation to a fixing device in which both the heating elastic rotor and the pressurizing elastic rotor are roller-shaped; therefore, the present invention is not limited to this. I want to be

-BI LI! i.

Conventionally, in an image forming apparatus such as an electrophotographic copying apparatus, a fixing roller has to apply heat to an unfixed toner image on a transfer paper and convey the transfer paper to a predetermined path while preventing offset of the molten toner. These materials are required to have transportability, mold releasability, abrasion resistance, fixability, and durability under severe conditions.

In order to meet the above requirements, as illustrated in FIG.
An elastic rotating body for fixing having a structure in which an elastic layer 4a is provided on a core bar 2a, and a resin M6a is further formed on the upper surface of the elastic layer 4a;
In other words, a heating and pressing fixing roller 1a having elasticity has been proposed. In such a fixing roller 1a, an elastic layer 4a
is made of silicone rubber or fluororubber, and a fluororesin tube or a mixture of fluororesin and fluororubber is used as the resin layer 6a.

The biggest problem with the fixing roller having such a structure is a decrease in adhesive strength due to durability. In other words, after long-term use, the elastic layer 4a made of a rubber layer and the resin layer 6a will partially peel off, making it unusable. The limit for fixing 50,000 sheets, that is, for copying, was the limit.

The present inventors conducted numerous research experiments to improve the durability of an elastic rotating body that has a resin layer on an elastic layer, which has many advantages. It has been found that durability can be significantly improved by using an elastic rotating body formed by disposing it on an elastic layer and then heating and baking it above the crystallization point. As a result of further research experiments, we found that even if an elastic rotating body with such a configuration is used, if the fluororesin layers of the heating elastic rotating body and the pressing elastic rotating body are made of different materials, the elastic rotating body for heating It was found that frictional electrification easily occurs between the body and the pressurizing elastic rotating body, and offset and paper wrapping frequently occur.

Furthermore, research by the present inventors has shown that the maximum porosity and cracks of pores (voids) generated in the fluororesin layer of the heating elastic rotating body and the pressurizing elastic rotating body are related to fixing properties, mold releasability, offset properties, and durability. We found that it has a significant impact on gender, etc.

The present invention has been made based on this new knowledge.

Accordingly, the objects of the present invention are to improve the conveyance and fixing properties of a sheet-like conveyed object such as a sheet of paper, and to improve the stability of Jilt! It is an object of the present invention to provide a fixing device 2 which has not only improved properties, durability, and abrasion resistance, but also particularly improved offset properties and wrapping properties of a transfer material.

. The above object is achieved by the fixing device according to the present invention. In summary, the present invention provides an elastic rotating body for heating that is heated by a heat source and has an internal elastic layer and a fluororesin layer formed as a surface layer, and a heating elastic rotating body that is heated by a heat source and has an internal elastic layer and a fluororesin layer formed as a surface layer. In the fixing device, the fluororesin layer of the heating elastic rotating body and the pressing elastic rotating body are made of the same material. The fixing device is characterized in that it is formed by using the fixing device, disposing it on the elastic layer in an unfired state, and then heating and firing it above the crystal point.

In a preferred embodiment of the present invention, the elastic layer is formed of silicone rubber or fluorine rubber, and the fluororesin layers of the heating elastic rotor and the pressurizing elastic rotor are impermeable to liquid.
The resin layer of the heating elastic rotating body has a maximum porosity of 1.
0% or less, and the maximum porosity of the resin layer of the elastic rotating body for pressurizing is 15% or less, and at least the resin layer of the elastic rotating body for pressurizing has a discontinuous part where the crank is located on the first elastic layer side. However, the smooth surface portion is located on the front side.

1 Cliff 1 Next, the elastic rotating body according to the present invention will be explained in more detail with reference to the drawings.

FIGS. 1 and 2 show an embodiment in which a fixing device according to the present invention is implemented in a fixing device that heats and fixes a toner image in an electrophotographic copying device.

The fixing device, as schematically illustrated in FIG. Pressure roller 10 that presses the transfer paper P carrying the toner image
It consists of

The heating roller l and the pressure roller 10 have the same configuration,
Core metal 2.12. It consists of an elastic layer 4.14 and a resin layer 6.16.

The fixing device detects the surface temperature of the heating roller 1 and sets the surface temperature to an optimum temperature 1 for melting the toner, for example, 160°C to
A temperature detection control means G for controlling the temperature to 200° C., and an offset prevention liquid application means C for applying an offset prevention liquid such as silicone oil to the surface of the heating roller l and also cleaning the surface are provided.

The heating roller 1 includes a core metal 2 having good thermal conductivity such as aluminum,
An elastic layer 4 formed of silicone rubber on the core metal 2 (
In this embodiment, the layer thickness t1 is 0.3 mm to 0.8 mm, the rebound modulus is 65% to 85%), and the resin layer 6 formed on the elastic layer 4. The resin layer 6 is preferably made of PFA.
Resin (copolymer of tetrafluoroethylene resin/perfluoroalkoxyethylene resin), PTFE resin (tetrafluoroethylene resin), or other fluororesin, and in this example, the layer thickness tz
is 10 gm to 30 μm, and the membrane strength is 50 kg/crn' or more.

Regarding the pressure roller 10, the pressure roller lO has the same structure as the heating roller l, but the core bar 12 is made of stainless steel, iron, etc., and the thickness t3 of the silicone rubber elastic layer 14 is greater than tl. Thick.

For example, it is 4 mm to 10 mm, and its rebound modulus is 6.
The resin layer 16 is made of fluororesin such as PFA or PTFE, similar to the heating roller 1, but the layer thickness is 1.5% to 85%. According to the present invention, the resin layer 16 of the pressure roller 10 is thinner than the elastic layer 14 and has a thickness in the range of 5 m to 50 m, and has a film strength of 50 kg/cm or more. The same material as the resin layer of the heating roller l is selected.

The heating roller 1 and the pressure roller 10 are symmetrical, and preferably the heating roller 1 (or the pressure roller 1
0) had a slightly smaller diameter at the center in the axial direction than at both ends. It is considered to be the so-called reverse crown type.

Next, a method of manufacturing the heating roller 1 and the pressure roller 1O as described above will be further explained. First, a silicone rubber layer (thermal conductivity 1.4X10-' to 1.5X
1 0-3cal mcm/sec*crn
's °C) to produce a silicone rubber roller of a desired shape. Preferably, the silicone rubber roller is of a so-called inverted crown type, in which the center portion in the axial direction has a slightly smaller diameter than both end portions.

The surface of the silicone rubber roller is then roughened using any known means to have a surface profile of a predetermined roughness. In this way, the surface of the rubber roller roughened to a predetermined roughness is coated with unfired fluororesin, such as fluororesin in a dispersion state (fluororesin powder dispersed in water with a surfactant), enamel, or A powdered fluororesin is applied to a uniform thickness over the entire length of the rubber roller by spray coating, electrostatic coating, powder coating, or the like.

The fluororesin dispersion etc. coated to a uniform film thickness as described above becomes a film-like resin coating when heated above the glass transition point of 327°C, which is the crystalline melting point of the fluororesin. The silicone rubber roller coated with fluororesin needs to be heated to a temperature higher than the crystal melting point (327° C. or higher for PTFE and 306° C. or higher for PFA).

However, although silicone rubber itself has excellent rubber properties such as rebound modulus and compression set, when heated above 300°C, especially above 6306°C or 327°C, it causes smoke and depolymerization. This not only prevents the formation of a high-quality fluororesin layer, but also causes the silicone rubber itself to lose its rubber properties.

Therefore, in the present invention, the silicone rubber roller itself is heated at a low temperature (maximum 300°C or less) that does not cause smoke or depolymerization, while the fluororesin coating layer is heated at a temperature higher than its crystal melting point. A firing method that provides a high temperature state is preferred, more specifically, while rapidly cooling the rubber layer from inside the core metal.

A method of rapidly heating the unfired fluororesin on the surface, or a dielectric heating method that utilizes the fact that the dielectric loss tangent of the liquid fluororesin (dispersion) itself is larger than that of the rubber layer, etc., may be used.

Although these methods essentially form a thermal gradient in the silicone rubber in its thickness direction,
For unsintered fluororesin, the temperature is about 80℃, but for unsintered fluororesin, the temperature is higher than its crystal melting point (specifically, for PTFE, it is 340℃ or higher, which is 327℃ or higher).
380° C.) for about 5 to 10 minutes.

After performing the above baking, the roller is rapidly cooled.

Through this rapid cooling, the baked fluororesin surface layer on the silicone rubber roller, which exhibits resin properties such as a crystallinity of 95% or less, a tensile strength of 50 kg/cm or more, and a water contact angle of 100 degrees or more, forms a strong adhesive bond to the rubber roller. In the state
Moreover, it is formed sufficiently thick.

Therefore, in the heating roller 1 and pressure roller 10, the lower layer silicone rubber itself exhibits the desired rubber properties almost in the same way as before the resin layer was formed, and the surface fluororesin layer exhibits completely baked resin properties, The adhesion of these layers is strong.

As a result of research by the present inventors, the fluororesin layer 6.16 of the heating roller l and pressure roller 10 manufactured as described above
The outer surface of the resin layer is smoothed to provide a surface with good mold releasability, but as shown in FIGS. 5 and 6, due to manufacturing conditions, the side of the resin layer facing the elastic layer 4.14 has It was found that cracks indicated by the white parts occurred, and the size, shape, and amount of the cracks varied depending on the drying condition of the resin dispersion, the drying rate, or the surface condition of the adjacent lower layer. In the example, the drying rate of the dispersion was set at a temperature between 40 and 80°C and a humidity of 4.
When heat treatment was performed in an environment of 0 to 60%, the thickness D of the resin layer was 25 JLm, and the depth d was 8 to loJLm.
A crack was obtained.

Furthermore, according to research experiments conducted by the present inventors, the crack is
It has been found that this has the effect of improving the adhesive strength between the elastic layer and the resin layer in the elastic rotating body. In particular, since the pressure roller 10 is pressed against the heating roller 1 and rotates while being constantly deformed, it is necessary to strengthen the adhesive force between the resin layer and the elastic layer. Therefore, it is significant to form such cracks especially in the resin layer of the pressure roller IO.

In addition, if the resin layer is uniform without cracks, the volume resistance will be high, and there is a problem that the frictional electrification that occurs during transportation will increase the amount of dirt that adheres to the surface of the rotating body. The resin layer present has its volume resistivity reduced by an order of magnitude of 10'-102. Therefore, it has been found that it is possible to prevent the attachment of unnecessary deposits due to the additives and the generation of stains due to charging, which occur when the resistance is lowered by mixing additives into the resin layer.

In addition, the fluororesin layer produced according to the present invention has extremely fine pores (voids with an average pore diameter of 0.1 lm or less), and while the original fluororesin has a volume resistivity of 10111 Ωcm or more, In other words, it has been reduced by l O' to about 10 Ωam. The amount of voids mentioned above is regulated by the drying speed of the resin dispersion, and the more rapid the drying speed, the more they will occur, and the slower the drying speed, the less they will exist.According to research by the present inventors, the porosity of the voids in the heating roller 1 is It has been found that the porosity of the voids in the pressure roller 1o is preferably 15% or less at most. This is for the reasons described below.

As the elastic roller 1.10 has more voids, the amount of charge will decrease.
Even if the void is smaller than gm, some low-molecular components of silicone oil will penetrate into the void.According to experiments conducted by the present inventors, when the thickness of the rubber layer is 0.3~
When the diameter is about 0.8 mm, there is almost no effect on the outer diameter change due to the intrusion of oil even if 500,000 sheets are passed if the porosity is less than 10%, but when the porosity becomes about 15%, On the other hand, the pressure roller 10 has a smaller amount of oil intrusion than the heating roller l15.
Even if the porosity is on the order of %, there is no effect of oil intrusion, and furthermore, the elastic layer of the pressure roller 10 is made of thick rubber, so that changes in the outer diameter due to the amount of oil intrusion can be almost ignored.

In addition, in general, the pressure roller 10 has a thicker elastic layer than the heating roller 1, so it is easily charged. The charge of the charged pressure roller 10 tends to leak,
In particular, the amount of charge on the pressure roller 10 can be reduced.

As explained above, the roller 1 configured according to the present invention.
The fixing device using No. 10 has features that did not exist in the past. That is, heating and pressure rollers l and 10
Since the fluororesin is made of the same material as the surface layer, it is difficult to cause frictional charging between the rollers, and as mentioned above, if the present invention is applied, the fluororesin can be completely removed without thermal deterioration of the silicone rubber properties. Because it is fired, it has sufficient rebound resilience and allows the use of silicone rubber with low compression set.It is highly durable with excellent surface releasability, abrasion resistance, and sufficient elasticity. be. Moreover, even if the pressing force generated when fixing the toner image on the recording paper is concentrated between the silicone rubber layer and the fluororesin layer, the strength of the fluororesin layer is high and the adhesion between them is good, making it difficult to This kind of sudden peeling no longer occurs, and the number of sheets that can be used can be improved by several orders of magnitude.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

A silicone rubber layer (thermal conductivity 1.4
0-”1~1, 5X I O-'
cal mcm/sec conflict cr rn-m
℃) to produce a cylindrical silicone rubber roller. At this time, the silicone rubber layer had a thickness of 0.5 mm.

Next, the surface of the silicone rubber roller was ground using a grinding device to make it rough. In this way, unfired PTFE (tetrafluoroethylene resin) dispersion (Tetrafluoroethylene resin dispersion D-1 manufactured by Daikin Corporation) is uniformly sprayed over the entire length of the rubber roller on the roughened surface of the rubber roller. It was applied thickly.

The fluororesin dispersion coated to a uniform thickness as described above was fired in a dielectric heating device.

The dielectric heating device used has the configuration shown in FIG.
5 and the high frequency (950
A waveguide 106 that propagates waves (from MHz to 2450MHz), and a high frequency reflection plate 103 connected to the waveguide and made of metal on the inner surface.
An openable/closable resin container 102 having a
It also has an infrared lamp 111 with a reflective shade for external infrared heating.

Inside the resin container 102, a fan 100 that generates an air flow inside the hollow of the heating roller 1 and a fan 101 that generates an air flow inside the container 102 are provided so as to be rotatable by driving from a driving means outside the container. It will be done. This container has fulcrum 10
The upper and lower sides can be opened and closed with centering point 8, and the upper part has a handle 109, and the lower part has an arm 107 for positioning the flange IA of the roller l.
However, each is fixed.

The operation of drive means 104, magnetron 105, and infrared lamp 111 is controlled by control means 110.

Since the heating roller 1 has a silicone rubber layer 2 on its lower layer and a fluororesin dispersion on its surface, a large amount of high frequency waves are absorbed in the dispersion, which has a higher dielectric constant than the silicone rubber layer.

Therefore, fluororesin desversion is rapidly heated to a temperature of 340°C to 35°C by heating with high frequency, infrared rays, and constant temperature layer.
Heated to 0°C. At this time, the silicone rubber layer has a low high frequency absorption rate, so the temperature of the dispersion does not increase2.
It is heated to a temperature below about 80°C.

Although a thermal gradient is substantially formed in the silicone rubber in the thickness direction by such a method,
℃, but for unsintered fluororesin, the temperature is higher than its crystal melting point (specifically, for PTFE, the temperature is 340℃ to 38℃, which is 327℃ or higher).
A firing temperature of 0° C.) was applied for about 5 to 10 minutes.

After performing the above baking, the roller was rapidly cooled. As a result of this rapid cooling, the baked fluororesin surface layer 6, which exhibits resin properties such as a degree of crystallinity of 92%, a tensile strength of 120 kg/cm', and a contact angle with water of 110 degrees, is placed on the silicone rubber roller in a strong adhesion state to the rubber roller. It is sufficiently thick, and was formed with a thickness of 15 gm in this example. The final outer diameter of the heating roller 1 was 40 mm.

The same procedure as in Example 1 was carried out except that fluorine rubber was used instead of silicone rubber as the material for the inner elastic layer of the fork.
An internal elastic layer 4 is placed on the core bar 2 finished to 8.9m+n.
A heating roller 1 was manufactured by forming an outer covering resin layer 6.

As a result of experiments conducted by the present inventors, the elastic roller of this example also showed the same sticky notes as the elastic roller of Example 1.

11] Elastic pressure rollers 10 made of silicone rubber and fluoro rubber were respectively produced in the same manner as in Examples 1 and 2, except that an iron core bar 12 having an outer diameter of 27.86 mm was used. However, the thickness of the elastic layer 14 made of silicone rubber and fluorine rubber is 6 mm, and the fluororesin layer 16 serving as the outer covering is made of PTFE (tetrafluoroethylene resin) dispersion (manufactured by Daikin Corporation) like the heating roller 1. Tetrafluoroethylene resin dispersion D-1) PFA resin powder was applied to a thickness of 20 mm to form an elastic pressure roller with an outer diameter of 40 mm.

Internal elastic layer 14 on core bar 12. The method for forming the outer resin layer 16 was the same as in Examples 1 and 2 above.

As a result of experiments conducted by the inventors, the pressurized elastic roller l of this example
O also showed the same performance as the fixing elastic roller 1 of Examples 1 and 2.

Using the above fixing roller and pressure roller, a paper feeding durability test was conducted under the conditions of a paper feeding speed of 200 m/sec and a paper feeding number of 30 sheets/A4 min.

As a result of the test, no abnormality was observed in the pressure roller and fixing roller even after 300,000 sheets were passed through. Further, there was no occurrence of wrapping of the transfer paper around the roller due to charging.

When silicone rubber is used as the rubber layer, the rubber hardness is preferably 30 degrees or more and 80 degrees or less, elongation is 150% or more, and 100% elongation stress is 10 kg.
/crrf or more and has sufficient rubber elasticity.

In particular, the rebound modulus of the rubber layer is preferably 65 to 85% when the present invention is used in a fixing roller or the like.

In addition to the above embodiments, the present invention also provides a cleaning roller, g
It can also be used as a type I agent supply roller, etc.
It can also be belt-shaped as shown in the figure (
For example, an intermediate belt for simultaneous transfer and fixing).

In the fixing device of the present invention, as described above, the resin layers of the heating elastic rotating body and the pressing elastic rotating body are made of the same material of fluororesin, and the fluororesin is in an unfired state. In order to be disposed on the elastic layer and then heated and fired to a temperature above the crystal melting point,
This has the advantage of increasing the adhesion strength between the internal elastic layer and the outer fluororesin layer, improving durability, and eliminating the problem of the transfer material wrapping around the elastic rotating body.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of a fixing device according to the invention. FIG. 2 is a partially enlarged explanatory view of the fixing roller used in the apparatus shown in FIG. FIG. 3 is a sectional view of a conventional fixing roller. Figure i4 is a sectional view of an embodiment of a fixing roller manufacturing apparatus. FIG. 5 is a cross-sectional view of the resin layer for explaining cracks formed in the resin layer. FIG. 6 is an enlarged plan view of the resin layer viewed from the elastic layer side for explaining cracks formed in the resin layer. FIG. 7 is a sectional view of another embodiment of the elastic rotating body according to the present invention. l: Heating roller 4.14: Elastic layer 6.16: Covering resin layer 10: Pressure roller Fig. 1 Fig. 2 Fig. 3 a Fig. 4 Fig. 5 E, 14 Fig. 6

Claims (1)

[Scope of Claims] 1) An elastic rotating body for heating that is heated by a heat source and has an elastic layer inside and a fluororesin layer as a surface layer; form a layer,
In the fixing device having a pressure elastic rotor pressed against the heating elastic rotor, the fluororesin layers of the heating elastic rotor and the pressure elastic rotor are made of the same material, and A fixing device characterized in that it is formed by disposing an unfired state on an elastic layer and then heating and firing it above a crystal point. 2) The fluororesin layer of the heating elastic rotating body and the pressing elastic rotating body has fine pores with an average pore diameter of 0.1 μm or less, and the maximum porosity of the resin layer of the heating elastic rotating body is 10% or less. 2. The device according to claim 1, wherein the resin layer of the pressurizing elastic rotating body has a maximum porosity of 15% or less. 3) At least the resin layer of the pressurizing elastic rotating body has a discontinuous portion with cracks on the elastic layer side and a smooth surface portion on the front side. Equipment described in Section.