JPH0752315B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, a printing machine, a facsimile machine, a printer, or a composite machine of these.

[Prior art]

Conventionally, in this type of device, a roller in which a core metal or a heat-resistant elastic body is coated with a fluorine resin such as tetrafluoroethylene resin (PTFE) or perfluoroalkoxyethylene resin (PFA) is known as a heating roller in contact with a toner image. A roller coated with a silicone rubber layer or a heat-resistant rubber layer such as silicone rubber or EPDM is used as a pressure roller that comes into pressure contact with the heating roller to increase the heating and pressing time of the toner image. A roller coated with a tube of a propylene oxide copolymer (FEP) is known.

However, since the upper and lower materials are not exactly the same, frictional charging between rollers is likely to occur, and offset or paper wrapping is likely to occur.

Therefore, in order to obtain the surface properties of the resin and the elasticity of the rubber, the applicant of the present application filed Japanese Patent Application No. 59-234780 (Japanese Patent Application Laid-Open No. 61-113083).
Although it was possible to obtain good fixability, releasability, and abrasion resistance, it is difficult to prevent triboelectrification because a highly insulating fluororesin is used for the surface layer. Atsuta

In most combinations using the heating roller and the pressure roller, it is difficult to control the charge amount of each of the heating roller and the pressure roller, and the charge amount toner and the like adhere to the roller surface. There was a problem that the change over time was large.

[Object of the Invention]

The present invention has been made to improve the above-mentioned drawbacks, having surface resin characteristics, and elasticity as a whole in a proper layer, fixing property, releasability, offset property, and durability are superior to conventional ones, An object of the present invention is to provide a fixing device having a pair of fixing rotators capable of controlling charging characteristics for a long period of time and suitable for high-speed copying and double-sided copying.

[Outline of the present invention]

In order to achieve the above object, the present invention provides a fluororesin layer in an unsintered state on a heat resistant elastic layer, and then heats and burns the fluororesin at a temperature higher than the crystal melting point to form a fluororesin layer on the elastic layer. And a second fixing roller, and a second fixing roller coated on the elastic layer with a fluororesin which has been previously processed into a sheet or tube shape.
A rotating body for fixing, wherein the second rotating body for fixing has a triboelectric charge amount larger than that of the first rotating body for fixing,
By using the fixing device that fixes the recording material carrying the unfixed image between the second fixing rotators, the charging characteristics can be controlled for a long period of time, and the good fixing property, releasability, offset property, and durability can be obtained. You can get sex.

〔Example〕

 The drawings are illustrations of an embodiment of the fixing device of the present invention.

In the figure, reference numeral 1 is a heating roller on the side in contact with the unfixed toner image, and 2 is a pressure roller rotating in pressure contact with the heating roller 1, both of which are examples of the fixing roller of the present invention. The specific configuration is as follows.

The heating roller 1 includes a relatively thin elastic layer 12 made of silicone rubber (a predetermined thickness within a range of 0.3 mm to 0.8 mm in this example), and an upper layer 13 thereof on a cored bar 11 having a good thermal conductivity such as aluminum. To P
Fluorine resin such as FA (copolymer of tetrafluoroethylene resin-perfluoroalkoxyethylene resin), PTFE (tetrafluoroethylene resin) is thinner than the elastic layer 12 (10 μm to 10 μm in this example).
It has a predetermined thickness within a range of 30 μm) as a resin layer. Similarly, the pressure roller 2 is provided with an elastic layer 22 which is thicker than the thickness of the silicone rubber elastic layer 12 and is relatively thick (a predetermined thickness in the range of 4 mm to 10 mm in this example) on a cored bar 21 of stainless steel, iron or the like. The upper layer thereof is made of a fluorine resin such as PFA or PTFE, which is thinner than the thick elastic layer 22 (in this example, a predetermined thickness within a range of 5 μ to 50 μ).

Reference numeral 3 is a heater such as a halogen lamp for heating the fixing roller from the inside, and the surface temperature of the fixing roller is the optimum temperature at which the toner can be always melted by the heater 3, the temperature detecting element 4, and the control means 31 (specifically, 160 to 200 ℃
℃) is maintained.

Reference numeral 5 denotes an offset prevention liquid application unit that also serves as a cleaning unit for applying an offset prevention liquid such as silicone oil to the surface of the fixing roller. The coating means 5 may be felt-like, but a web is used in this example. The web 51 containing the offset prevention liquid,
The heating roller 1 is brought into contact with the elastic pressing roller 52 such as silicone sponge, and a small amount of offset preventing liquid is applied to the surface of the heating roller 1. Further, the web 51 is gradually taken up from the supply roller 54 by the take-up roller 53, and the contact surface of the web with the heating roller 1 is sequentially known by the control means (not shown).

The recording paper P carrying the unfixed toner image T is fed to the entrance guide 6
The toner image T is permanently fixed to the recording paper P by passing between the roller pair 1 and 2 while being guided by the sheet.
The separation claw 41 that contacts the surface of the roller 1 is provided to separate the recording material from the surface 1 of the roller.

Here, the first fixing rotator is manufactured by the following manufacturing method.

A rubber roller having a desired shape is obtained by vulcanizing and molding a heat resistant rubber such as silicone rubber, fluorine rubber or EPDM on a core metal such as aluminum, iron or Sus. In this embodiment, silicone rubber having excellent rubber properties such as impact resilience and compression set is used. Fluorine resin such as PTFE or PFA is applied on the rubber roller by spraying, electrostatic coating, etc., and the lower rubber layer is maintained at a low temperature (about 280 ° C or less) below the heat resistant temperature of the rubber layer. The crystalline melting point of the fluororesin (327 ℃
The above-mentioned baking method that gives a high temperature is used to obtain a fixing rotator. Specifically, a method of heating the inside of the core bar from the outside with infrared rays while cooling the inside, a dielectric heating method that uses the difference in dielectric loss tangent between the rubber layer and the dispersion when using PTFE dispersion for the fluororesin, etc. Can be used.

On the other hand, for the second fixing rotor, a heat-shrinkable tube or sheet such as PFA or FEP in which a primer is applied on a rubber layer vulcanized and molded on a core metal and the adhesive surface is etched with sodium ammonium solution is used. Cover and heat to bond on rubber layer.

Alternatively, a method in which the above-mentioned tube or sheet is held on the inner wall of a mold, liquid silicone rubber is injected between the core metal and the tube or sheet, and the mixture is heated and vulcanized and molded can be used.

The first fixing rotary member manufactured as described above has extremely fine pores (average pore diameter of 0.1 μm or less), and the volume resistance is 10 ¹⁰ Ωcm compared to the volume resistance of genuine fluorine resin of 10 ¹⁸ Ωcm or more.
The degree and the 10th power of eight have also decreased.

Further, since the fluororesin of the second fixing rotary member is sufficiently heated and pressed in advance to be formed into a sheet or a tube, it has a large molecular weight and no pores. On the other hand, the first
The fixing rotator has a smaller molecular weight than the fluororesin used for the second fixing rotator, and has numerous fine pores. Therefore, the first fixing rotator has a characteristic that it is hard to be charged and its wear property is slightly inferior, and the second fixing rotator is easily charged and hardly wears.

Therefore, when the recording material is fixed between the first and second fixing rotators, the fluororesin layer on the surface of the first fixing rotator is more worn than the fluororesin layer on the surface of the second fixing rotator. Easy to do,
The surface is appropriately scraped due to abrasion with the second fixing rotator during durability, and the paper is cleaned by passing it through, so the surface condition is not contaminated with paper powder, toner, etc., and a new fluororesin surface is always maintained. . On the other hand, the second fixing rotator hardly wears and the surface property is smoother than that of the baked fluororesin surface, so that the paper powder, toner, etc. adhered to the second fixing rotator are used for the first fixing rotator. Since it is cleaned with a rotating body,
The second fixing rotator is also not contaminated with paper powder, toner, or the like.

In this way, since the first and second fixing rotators have the fluororesin surface which is not contaminated with toner, paper powder or the like for a long term durability, the charging characteristics can be stabilized for a long term. . At this time, as the first fixing rotary member, if the fluororesin is baked on the rigid body, the wear state of the fluororesin surface becomes uneven, and the above effect cannot be obtained unless the roller is made by baking the fluororesin on the elastic body. The sex is also inferior.

Here, the first fixing rotor is the heating roller 1 and the second fixing rotor is
When the fixing rotator is used as the pressure roller 2, the heating roller 1 is a combination of thin rubber and a low resistance fluororesin layer and is hardly charged during the fixing process. The pressure roller 2 is a combination of thick rubber and a high resistance fluororesin layer, and is charged to about -500V to -3000V during the fixing process. Therefore, when positively charged toner is used for the roller of this combination, the toner positively charged on the recording material is attracted by the negative charge of the pressure roller 2 during the fixing process, so that the toner is fixed without scattering. Further, since the heating roller 1 is hardly charged, the developer is hardly offset on the heating roller 1.

Conversely, when the second fixing rotary member is used as the heating roller 1 and the first fixing rotary member is used as the pressure roller 2, the heating roller 1 is a combination of thin rubber and a high resistance fluororesin layer, and the fixing process is performed. Sometimes it is slightly charged to -100V to 400V. The pressure roller 2 is a combination of thick rubber and a low resistance fluororesin layer and is negatively charged by several tens of volts. Therefore, when negatively charged toner is used for the roller of this combination, the roller is negatively charged on the recording material. The toner is not affected by the heating roller 1 and the pressure roller 2 during the fixing process, and is fixed on the recording material without scattering. Further, since the pressure roller 1 is slightly charged negatively, the developing material is hardly cut off to the heating roller 1.

Hereinafter, the experimental results with the above configuration will be described together with comparative examples.

As fixing roller 1, 25 μm PTFE on 0.5 mm silicon rubber
It has a resin layer, the outer diameter of the central part is 39.8 mm and both ends have an outer diameter of 39.8 mm.
A roller of mm + 100 μm (reverse crown amount of 100 μm) was used.

This roller was manufactured as shown below, and an aluminum core bar with a central diameter of 38.75 mm and a reverse crown amount of 100 μ was prepared as the core bar, and the surface was sandplasted to degrease / degrease.
After drying, wrap a silicone rubber sheet through the primer, press vulcanize at 150 ° C for 40 minutes, then
After secondary vulcanization at 00 ° C. for 2 hours, the rubber was uniformly ground to a thickness of 0.5 mm.

Next, apply a fluororesin discharge purgeon by a thickness of 25 μm by spray coating, and after drying the above, 260 on the rubber.
The resin was fired for 10 minutes by dielectric heating combined with infrared external heating so that 350 ° C was applied to the resin.

As the pressure roller 2, a roller having an outer diameter of 39.9 mm in which a 20 μm PFA resin layer was coated on 6 mm silicom rubber was used. The pressure roller was manufactured as shown below. The core metal has an outer diameter of 27.86m
Prepare an m core of iron, sandblast the surface, degrease and dry it, wrap a silicone rubber sheet through a primer, vulcanize the plate at 170 ° C for 30 minutes, then at 200 ° C for 1 hour. After secondary vulcanization, it was ground to a rubber thickness of 6 mm. Further, a primer was applied to this rubber roller, and a PFA sheet having a thickness of 20 μm was etched on the adhesive surface with a sodium ammonium solution, wound on a rubber roller, and heated to 200 ° C. for adhesion.

When the fixing device using the heating roller 1 and the pressure roller 2 formed in this way is incorporated into an electrophotographic apparatus using positively charged toner for durability, the charging amount of the heating roller 1 is 0 to 10 V in the initial stage. The charging amount of the pressure roller 2 is between -1500 and -2
Even after the endurance of 200,000 sheets, the charge amount between 000V was 0 to 5V for the heating roller 1 and -1300 to 1800V for the pressure roller 2, and the charge amount was almost unchanged. .

On the other hand, the offset amount was almost the same at the initial stage and at the time of running 200,000 sheets, and could be reduced to 1/10 or less of the conventional amount.

As a comparative example, a case where a silicone rubber roller is used on the pressure roller 2 side is shown. The initial charge amount was 0 to 10V for the heating roller 1 and -1300 to -1700V for the pressure roller 2, and the offset amount was about 1/10 of the conventional amount. After passing 200,000 sheets, the charge amount decreased between 0 to 5V for the heating roller 1 and -200 to -300V for the pressure roller 2, and the offset amount increased more than three times as compared with the initial amount. The pressure roller 2 was soiled with toner.

As another comparative example, when the surface layer of the heating roller 1 was coated with a heat shrinkable tube of PFA and the surface layer of the pressure roller 2 was coated with a heat shrinkable tube of FEP, durability was obtained.
Has a charge amount of -100 to -200V, and pressure roller 2 has a charge of -2000 to -2
It is charged to 500V and the offset amount is about 1/3 of the conventional value, but 2
After running 0,000 sheets, the heating roller 1 has a charge amount of -20 to -50V and the pressure roller 2 has a charge amount of -400 to -700V, and the offset amount is three times higher than the initial amount, which is the same as before. .

In this embodiment, the case where the positively charged toner is used has been described above. However, the negatively charged toner is not fired on the pressure roller 2 side using a tube or sheet-shaped molded fluororesin on the heating roller 1 side. By using a roller obtained by applying a fluororesin and baking it, the same effect as described above can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the charging property can be controlled for a long period of time, and the good fixing property,
It is possible to provide a fixing device having a fixing rotator, which has releasability, offset property, and durability and can always obtain a high-quality image without scattering.

[Brief description of drawings]

The drawings are explanatory views for explaining an embodiment of the fixing device of the present invention. 1 ... Heating roller 2 ... Pressure roller

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masaaki Sakurai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Michio Shigenobu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Masahiro Goto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-59-39372 (JP, A) JP-A-61-22377 (JP) , A) JP-A-53-144747 (JP, A)

Claims (1)

[Claims] 1. A first fixing device, comprising: forming a non-sintered fluororesin on a heat-resistant elastic material layer, and then heating and sintering the fluororesin to a crystal melting point or higher to form a fluororesin layer on the elastic upper layer. A rotating body and a second fixing rotating body in which an elastic body layer is coated with a fluororesin which has been previously processed into a sheet or tube shape, and the second fixing rotating body has the first fixing rotating body. A fixing device having a larger triboelectric charge amount than a rotating body and fixing a recording material carrying an unfixed image between the first and second fixing rotating bodies.