JPH0572934A - Fixing device - Google Patents

Abstract

(57) [Summary] [Objective] To provide a fixing device having excellent releasability even after long-term use. A fixing device that inserts an image carrier on which an unfixed toner image is placed between a pair of rotating members, and heats and pressurizes the toner image to permanently fix the toner image on the image carrier.
The fixing device is characterized in that a layer of PFA resin having an end group of —CF ₃ is formed on the surface of the other rotating body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for permanently fixing an unfixed toner image on an image bearing member (paper sheet) by heating and pressing.

[0002]

2. Description of the Related Art Conventionally, a fixing device having a pressure roller and a fixing roller is constructed as shown in FIG. PFA, PTF on cored bar 11 made of metal such as iron and aluminum
The fixing roller 1 provided with the release layer 12 made of fluororesin such as E is heated from the inner surface by the heater 3. The surface temperature of the fixing roller 1 is detected by the temperature sensor 4, the output signal of the sensor 4 is input to a temperature controller (not shown), and the temperature controller controls ON / OFF of the heater 3 to maintain a constant surface temperature. It Metal core 2
1, the pressure roller 2 provided with the elastic layer 22 is pressed against the fixing roller 1 by a biasing means (not shown), and as the fixing roller 1 rotates in the arrow direction, the pressure roller 2 also moves in the arrow direction. Rotate to. An unfixed toner image 6 is carried on the paper sheet 5, and as the paper sheet 5 is moved in the direction of the arrow, it is inserted into the nip portion formed by the fixing roller 1 and the pressure roller 2 to form the toner image 6. Is permanently fixed to the paper sheet 5 by heating and pressurizing action.

The release layer 12 prevents a so-called offset phenomenon in which the toner image 6 is transferred to the fixing roller 1 and stains the subsequent image, but the electrostatic charge peculiar to the toner image 6 (see FIG. 2). If the negative polarity), use the power supply 7
By applying a bias voltage having the same polarity as the toner image to the cored bar 11, the offset phenomenon can be prevented more reliably.

[0004]

However, in the above-mentioned conventional example, the release layer 12 is locally damaged and the releasability is lowered, and the toner image 6 adheres to the release layer 12 to stain the subsequent image. Problems such as peeling may occur. This is because there is a portion (leak site) where electricity is easily passed inside the release layer 12 which originally has a high insulation property, and the surface of the release layer 12 is caused by Joule heat generated by current concentration. It is thought that this is due to breakage and a decrease in releasability. As a substance that contributes to the formation of leak sites, an acid fluoride group (-CO
It is considered that there is F), free fluorine ions are supplied from here, and a conduction path is formed under the electric field by the power supply 7.
Further, the thermal stability of the terminal group was not sufficient, and the acid fluoride group (—COF) was hydrolyzed to generate an acid, which caused clouding on the surface of the release layer 12 to lower the releasability. ..
It is considered that these deterioration phenomena of the release layer 12 are accelerated by high temperature gas such as steam generated when the paper sheet 5 is inserted.

An object of the present invention is to solve the problems of the release layer on the roller surface as described above, and to provide a fixing device excellent in releasability even after long-term use.

[0006]

According to the present invention, an image carrier on which an unfixed toner image is placed is inserted between a pair of rotating members, and the toner image is heated and pressed on the image carrier. In the fixing device for permanent fixing, a PFA resin layer having a terminal group of —CF ₃ is formed on the surface of at least one of the rotating bodies. By forming this PFA resin layer, generation of free fluorine ions is prevented, leak sites are prevented from occurring, damage to the release layer is prevented, and offset phenomenon and image peeling are prevented. Furthermore,
The present invention provides a good releasing layer having good thermal stability and free from deterioration of releasing property such as clouding.

The PFA resin layer according to the present invention has a wall thickness of 10 to 10.
100 μm is preferable, and more preferably 30 to 60 μm.
Is. Further, the PFA resin layer may contain a reinforcing material such as whiskers, if necessary.

The present invention can be applied to a known fixing device except for the resin layer, and not only a roller type heating / pressurizing type fixing device shown in the following examples,
It can be applied to a belt type fixing device or a pressure fixing type fixing device.

[0009]

Embodiment 1 FIG. 1 is a longitudinal sectional view of a main portion of a first embodiment of the present invention. The same reference numerals as those used above indicate the same members. 12 'is a PFA resin layer end groups consisting -CF _3, core metal 11 a method or PFA tube is baked formed by spray coating on the core metal 11
It may be formed by a method of covering the upper surface. The core metal 11 and P
An adhesive or the like may be interposed between the FA resin layers 12 '.

An example of a PFA resin having an end group of --CF ₃ is Teflon PFA450HP, a trade name of Mitsui DuPont Fluorochemical Co., Ltd., and the conventional end group is --COF.
As shown in the table below, the amount of eluted fluorine ions is smaller than that of Teflon PFA350J under the trade name of Mitsui DuPont Fluorochemical Co., Ltd.

[0011]

[Table 1] PFA resin layer 1 in this way end groups consisting -CF ₃
By disposing 2 ′ on the surface of the fixing roller 1 ′, even if a potential difference is applied between the fixing roller 1 ′ and the pressure roller 2 by the power source 7, the free ions are generated inside the PFA resin layer 12 ′. Since the probability of occurrence of leak sites is greatly reduced, the conventional PFA resin layer 12 having an end group of -COF is used.
The phenomenon of the local decrease in releasability that has occurred in 1) is drastically reduced.

(Experimental Example 1) The fixing roller 1'has a thickness of 3
mm P made of aluminum with a thickness of 50 μm on an aluminum cored bar 11
A roller having an outer diameter of 30.0 mm was prepared by coating and firing a tube 12 'made of FA450HP. As the pressure roller 2, a release layer 22 made of silicon rubber (volume resistivity 10 ¹² Ω · cm) having an Asker C hardness of 40 ° is formed on an iron cored bar 21 having a diameter of 16.0 mm to form an outer diameter of 30.0 mm. And prepared the roller. When both were pressed at a total pressure of 10.0 kgw, a nip having a width of 4.0 mm was formed. The fixing roller 1 was driven at an outer peripheral speed of 100.0 mm / sec, and the plain paper 5 carrying the unfixed toner image 6 was inserted between the fixing roller 1 ′ and the pressure roller 2 to obtain a fixed image. .. At this time, the toner 6 is a one-component magnetic toner using a styrene / butadiene copolymer as a binder and has a volume average particle size of 6
The one having an intrinsic charge amount of μm of −10 μc / gr was used. Also, the plain paper 5 is composed mainly of cellulose and has a basis weight of 75 gr.
/ M ² paper was used. The power supply 7 applies a potential difference of 1500 V between the fixing roller 1 ′ and the pressure roller 2, and the core metal 11 of the fixing roller 1 ′ is arranged to be negative with respect to the core metal 21 of the pressure roller 2. Has been done.

When the surface of the fixing roller 1'was observed after a paper feed test of 50,000 sheets was conducted with the above configuration, there was no local damage to the release layer 12 '. When printing was performed in that state, no abnormal image was generated.

As a reference experiment, as shown in FIG. 3, the release layer 12 was subjected to a 50,000-sheet passing test with the same configuration as above except that the release layer 12 was made of a tube made of PFA350J. Toner was locally adhered to the upper part, and the size thereof was a circle with a diameter of 0.2 mm and 1 mm, and two sizes were formed on the fixing roller 1. When printing was performed in this state, the image of the portion corresponding to the toner adhesion portion on the fixing roller 1 was peeled off from the print, and a circular defect was generated on the print.

Embodiment 2 FIG. 4 shows a longitudinal sectional view of the essential parts of a second embodiment of the present invention. The same reference numerals as those used above indicate the same members. 2 'is a pressure roller, and arranged a release layer 23 made of PFA resin having a -CF ₃ in end groups on the surface, 22' conductive silicon rubber (volume resistivity 10 ³ Ω · cm ) Etc. are elastic layers. Compared to the pressure roller 2 of the first embodiment, the pressure roller 2 ′ of this embodiment has a release layer 23 on the surface thereof, and the release property is not impaired even after long-term use. This is a preferred embodiment when performing double-sided printing in which the toner images 6 are formed on both sides of the paper sheet 5.

That is, when the surface layer of the pressure roller 2 is formed by using the conventional PFA resin having --COF at the end group, pressure is applied at the position corresponding to the leak site of the release layer 12 of the fixing roller 1. When the PFA layer on the surface of the roller 2 is damaged and the releasability is lowered, local toner adhesion occurs on the surface of the pressure roller 2, and when fixing double-sided printing,
The image on the first surface facing the pressure roller 2 is the pressure roller 2.
May be stripped by. On the other hand, as in the present embodiment, as the release layer 23 of the pressure roller 2 ′, the end group is-
When a PFA tube made of PFA resin containing CF ₃ is used, no leak site from the fixing roller 1 through the pressure roller 2 ′ is generated, and free ions generated in the release layer 11 of the fixing roller 1 are also pressure roller. Since the electric field is suppressed by the insulating action of the 2'release layer 23, the movement of ions in the release layer 11 is also suppressed, and as a result, the release layer 11 itself is prevented from being damaged. No abnormal images occur when printing on both sides. It should be noted that it is possible to use a PFA tube having --CF ₃ as an end group for the release layer of the fixing roller 1, but as far as the result of a paper passing test of about 200,000 sheets shows, the cost is low. -COF for various end groups
It was found that the resulting satisfactory utility in combination with a PFA tube 23 having a -CF ₃ in the release layer 11 and the end groups consisting PFA tube having.

By using a conductive material as the elastic layer 22 'of the pressure roller 2'as shown in this embodiment, the offset of the toner image 6 on the fixing roller 1 can be effectively prevented. The magnitude of the voltage of the power source 7 is smaller than that of (Experimental Example 1), and about 500 V is sufficient, which is also advantageous in that the occurrence of local leak sites can be reduced.

Embodiment 3 FIG. 5 is a vertical sectional view of the essential parts of a third embodiment of the present invention. The same reference numerals as those used above indicate the same members. This embodiment has the same configuration as that of the first embodiment shown in FIG. 1 except that the power supply 7 is omitted. That is, the gist of the present invention is to fix the fixing roller 1 ′.
The core metal 11 and the core metal 21 are both grounded as in the present embodiment, without being limited to the power supply 7 for positively applying a potential difference between the core metal of the pressure roller 2 and the fixing device having the diodes. The present invention can also be applied to fixing devices that are used. That is, since the release layer 12 ′ of the fixing roller 1 ′ is generally subjected to peeling charge by contact with the paper sheet 5, the release layer 12 ′.
Is placed under the action of an electric field. Therefore, in the case of the conventional PFA resin having --COF in the terminal group, which is likely to generate free ions in the release layer, a leak site is generated in the release layer due to long-term use, and the release of the corresponding surface site is caused. The moldability was sometimes degraded. Further, a gas such as water vapor contained in the paper sheet 5 or the like reacts with -COF of the terminal group to cause clouding on the surface, which may lower the releasability. When the release layer 12 ′ made of PFA having —CF ₃ in the terminal group is used as in this example, the occurrence of leak sites and the occurrence of clouding are significantly reduced, so that stable release properties can be obtained for a long period of time. There is an effect that can be maintained.

[0019]

As described above, --CF ₃ is added to the terminal group.
By forming the PFA resin having the above as the surface layer of the fixing roller or the pressure roller, it is possible to obtain a fixing device having excellent releasability even after long-term use.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part of a first embodiment of the present invention.

FIG. 2 is a vertical sectional view of a conventional fixing device.

FIG. 3 is a vertical cross-sectional view of a main part of a conventional fixing device.

FIG. 4 is a longitudinal sectional view of a main part of a second embodiment of the present invention.

FIG. 5 is a vertical cross-sectional view of a main part of a third embodiment of the present invention.

[Explanation of symbols]

 1, 1'Fixing roller 2, 2'Pressure roller 3 Heater 4 Temperature sensor 5 Paper sheet 6 Toner 7 Power supply 11 Core metal 12, 12 'Release layer 21 Core metal 22, 22' Elastic layer 23 Release layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yasumasa Otsuka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (2)

[Claims] 1. A fixing device which inserts an image carrier carrying an unfixed toner image between a pair of rotating bodies and heats and pressurizes the toner image to permanently fix the toner image on the image carrier. PF to the square rotating surface of the end groups consisting -CF ₃
A fixing device having a resin layer A formed thereon. 2. The fixing device according to claim 1, further comprising means for applying a potential difference between the pair of rotating bodies.