JP2912441B2 - Manufacturing method of heating roller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a heating roller used in a fixing device in an electrophotographic apparatus using a dry toner such as a laser printer or a copying machine.

2. Description of the Related Art A laser printer as an electrophotographic apparatus irradiates a laser beam from a laser optical system 3 onto a photoreceptor belt 2 charged by a charging charger 1 as shown in an example in FIG. An electrostatic latent image is formed, and the electrostatic latent image is developed by a developing unit 4 to become a visible image. The visible image is fed from a paper feed cassette 5 and sent at a timing by a registration roller 6. The transferred image is transferred to the transferred transfer paper 7 by the transfer charger 8, and further, a visible image (unfixed toner) on the transfer paper 7 is transferred.
Is fixed by passing through a fixing device 9, and thereafter, the transfer paper 7 is discharged to a paper discharge unit 10.
On the other hand, the residual charge is removed from the photosensitive belt 2 after the transfer by the charge removing device 11, and the residual toner is removed by the cleaning device 12.

The fixing device 9 used in the laser printer includes a heating roller 14 having a built-in heater 13 as shown in FIG.
A pressure roller 16 which is pressed against the heating roller 14 by a pressure spring 15;
Is passed through the nip between the rollers 14 and 16 so that the toner can be fixed. Here, reference numeral 17 denotes a separation claw, and reference numeral 18 denotes a cleaning pad.

In general, a laser printer uses a charged toner, and has a property that the charged toner easily adheres to the charged toner by an electrostatic force. Therefore, the heating roller 14 used in the fixing device 9 is charged. Therefore, toner offset is likely to occur. Incidentally, usually, the heating roller 14
Is set at 160 to 180 ° C. when paper is not passed, the nip width at that time is 2.5 to 4 mm, and the linear velocity is 47 to 51 mm / s.

Therefore, conventionally, in order to prevent the toner from being offset to the heating roller, a resin layer having good releasability is formed on a core metal serving as the original shape of the roller, and then baked. It has been proposed to manufacture a heating roller by reheating at a temperature near the melting point of the resin (JP-A-61-141472).

[Problems to be Solved by the Invention] However, in the case of the above-mentioned method of manufacturing a heating roller, in order to increase the crystallinity of the surface layer and improve the releasability, the melting point (about 300 ° C.) ) There is a problem that re-heating must be performed for one hour in the vicinity.

In view of the above, the present invention makes it possible to suppress the magnitude of the charging of the heating roller to a small value, to prevent the PFA from deteriorating without causing thermal degradation of the PFA, and to obtain a good image without offset. Such a heating roller can be manufactured without performing heating for a long time.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a fixing device in which an unfixed toner is fixed on a transfer sheet by rotating while being pressed against a pressure roller. In the method of manufacturing the heating roller used in the apparatus, a layer made of a releasable resin is formed on the surface of the pipe-shaped core by baking, and then the releasable resin layer is polished, After heating the cored bar having the resin layer formed thereon to a temperature of 340 to 400 ° C.
A method for manufacturing a heating roller, comprising re-baking for 5 to 20 minutes.

[Function] By adding a short-time re-firing step, the fluffing of the surface of the releasable resin layer after polishing is eliminated, and the magnitude of the electrostatic negative charge is suppressed to a value close to zero.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

1 and 2 show one embodiment of the present invention.
In the method of manufacturing the heating roller 14 used in the fixing device 9 shown in FIG. 4, first, a PFA (PFA) is formed on the surface of a pipe-shaped core metal 19 made of aluminum or an aluminum alloy whose surface is blasted with regular or irregular particles. A releasable resin layer 20 mainly composed of (perfluoroalkoxy) resin is formed by coating (firing step I), and then the surface of the releasable resin layer 20 after firing is coated with R _Z (10-point average roughness). Then, polishing is performed to 2 μm or less (polishing step II). Further, the release resin layer 20
Is heated until the temperature reaches 340 to 400 ° C. (heating step III), and then refired for 5 to 20 minutes (refire step IV).

When performing the above-mentioned manufacturing process, specifically, the furnace temperature is set so that all the rollers in the furnace can be refired at 360 to 380 ° C., which is highly effective, for 10 minutes or more. At this time, since the set temperature and the baking time vary depending on the size of the furnace and the number of rollers to be put into the furnace, the number of rollers is determined in advance, the roller temperature in the furnace is measured, and the setting conditions are determined. This is due to the overshoot with respect to the temperature setting inside the furnace, the difference in temperature distribution due to the location of the furnace (the temperature distribution differs between the center and the periphery),
This is because it is necessary to determine the set temperature and the sintering time in consideration of the temperature decrease due to the heat taken by the roller when the roller is inserted.

In the present invention, as described above, the heating roller 14 is heated by reheating and heating for a short time at a temperature that does not cause thermal degradation of the releasable resin layer 20 and at a temperature that can efficiently eliminate the fuzz on the surface. Since the roller 14 is manufactured, electrostatic offset of the toner can be prevented. That is, the third
As shown in the figure, in the initial streaking, the charged toner 21 is attracted by charging the fixing roller 14,
It is conceivable that this is caused by offsetting to the fixing roller 14 without fixing to the transfer paper 7. In FIG. 3, F ₁
Force the toner 21 is to fixed to the transfer sheet 7, F ₂ binding force between the toner 21 particles, the force F ₃ is the toner 21 tries Kuttsuko the fixing roller 14, F ₄ is the fixing roller 14 and the toner Indicates the electrostatic force between 21 particles. To prevent offset,
Although not may be reduced to F ₃ and F _4, F ₃ Where by material of the fixing roller 14 and the toner 21 (releasability) is large, the surface layer material PFA quite releasability of the fixing roller 14 is well And no further improvement is possible. On the other hand, F ₄ because those generated due to charging large heat roller 14 to bring about the time and the sheet passing time of the pressure roller, be varied by changing the surface property of the fixing roller 14 It is possible. Therefore, as described above, by performing refiring, the surface property can be changed, and the charging potential can be suppressed to a small value. The following table shows the results of experiments performed to evaluate toner offset based on the relationship between the refiring temperature and the refiring time in the above manufacturing process. In the table below, the charging potential of the heating roller means the roller rotation (non-paper passing).
The charging potential at this time is a stable potential value. The mark ◎ indicates that no offset occurs, the mark こ と indicates that almost no offset occurs, the mark △ indicates that slight offset occurs, and the mark x indicates that offset occurs. In this connection, current heating roller; if (after firing PFA resin, R _Z 2 [mu] m obtained by polishing below), charge potential -180～280 [V], ○ pencil hardness of at least HB, releasability 、, the offset evaluation is XX.

As a result of the above experiment, if the temperature at the time of refiring is 400 ° C. or higher, the releasability decreases due to the thermal degradation of PFA, and not only is it easy to offset, but also from the pencil hardness test, the strength reduction and peeling degree The decline was seen. On the other hand, if the temperature is lower than 340 ° C., the fluffing of the surface after polishing cannot be eliminated unless re-firing takes a considerable time. The offset could not be prevented. Therefore, the range suitable for refiring considering toner offset and pencil hardness is 340 ° C. for 5 minutes to 400 minutes.
It is in the range of 20 minutes at ° C.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the scope of the present invention.

[Effects of the Invention] As described above, according to the method for manufacturing a heating roller of the present invention, a releasable resin layer is formed on the surface of a cored bar by firing and polished, and then refired for 5 to 20 minutes. As a result, the magnitude of the charging of the heating roller can be reduced,
In addition, since it does not cause thermal deterioration of the release resin layer and does not impair the releasability, it is possible to obtain a good image without offset by using it incorporated in a fixing device. Demonstrates excellent effects.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process chart showing a method for manufacturing a heating roller of the present invention,
FIG. 2 is a cross-sectional view of a heating roller, FIG. 3 is a schematic diagram showing the principle of toner offset, FIG. 4 is a schematic diagram showing an example of a laser printer, and FIG. 5 is a schematic diagram of a fixing device. 7 ... transfer paper, 14 ... heating roller, 16 ... pressure roller,
19: core metal, 20: release resin layer, 21: toner.

Continuation of front page (58) Fields investigated (Int. Cl. ⁶ , DB name) B29D 31/00 G03G 15/20 B32B 31/26

Claims (3)

(57) [Claims] In a method of manufacturing a heating roller used in a fixing device configured to fix unfixed toner to transfer paper by rotating while pressing against each other with a pressure roller, a pipe-shaped cored bar is provided. On the surface, a layer made of a release resin is formed by firing, then the release resin layer is polished, and further, the core metal on which the release resin layer is formed is treated with 34
A method for manufacturing a heating roller, comprising heating to a temperature of 0 to 400 ° C. and re-baking for 5 to 20 minutes. 2. The method for manufacturing a heating roller according to claim 1, wherein the surface of the polishing roller is made to have a surface roughness R _Z (10-point average roughness) of 2 μm or less during the polishing. 3. The method for manufacturing a heating roller according to claim 1, wherein the release resin contains a PFA resin as a main component.