JPH0764419A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device in which the surface of a member in contact with a toner image is smooth. CONSTITUTION:The mold releasing layer 1 of a heat roller 5 is coated with a tetrafluoroethylene, which is a fluororesin, and a perfluoroalklyl perfluoro vinyl ether (PFA), and its surface is polished after the formation of the coating, so as to smooth the surface to provide a surface roughness with a center line average roughness Ra of 0.2mum or less and a filtered center line waviness WCA of 0.1mum or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device of an image forming apparatus such as a copying machine, a printer and a facsimile, which uses electrophotography, and more particularly to a surface roughness of a member in contact with a toner image. is there.

[0002]

2. Description of the Related Art Conventionally, a heat roller fixing device has been used in an electrophotographic copying machine. The heat roller fixing device is shown in FIG.
As shown in, the heating roller 5 heated by the heater 3
And a pressure roller 6 rotatably pressed against the heating roller 5, and the heating roller 5 and the pressure roller 6 cooperate with each other to form a nip portion for nip-conveying the recording material. There is.

In such a fixing device, when an image is formed on the recording material 8, the unfixed toner image 7 corresponding to the original image is first formed on the recording material 8, and the unfixed toner image 7 is formed. The recording material 8 is sent toward the fixing device. The recording material 8 sent is guided to the nip portion. As the recording material 8 passes through the nip portion, the unfixed toner image 7 on the recording material 8 is heated and pressed and fixed on the recording material 8 as a permanent image.

However, in the above fixing device, when a transparent sheet for an overhead projector (OHP) or the like is used as a recording material, the transparency of the OHP transparent sheet lowers the rigidity of the recording material. Adhesion with the roller is improved, and unevenness occurs depending on the surface roughness of the heating roller. As a result, when this transparent sheet is projected by OHP, there is a problem that black spots, streaks, or unevenness occur on the projected image due to the unevenness of the surface, especially in the concave portion, and the image quality is deteriorated.

Further, when a line image is formed on an OHP transparent sheet and is fixed by using a heating roller having a poor surface roughness, irregularities on the surface of the heating roller, particularly convex portions, are line toners on the OHP transparent sheet. When the image is crushed, the line width of the crushed part becomes wider, and the line width becomes uneven, resulting in a problem that the image quality is deteriorated.

As a fixing device for solving such a problem, there is a fixing device proposed in Japanese Utility Model Application No. 61-164992. In this fixing device, the above problem is solved by using a heating roller whose center line average roughness Ra of the heating roller surface is a certain value or less.

[0007]

However, in the above-mentioned conventional example, in order to improve the problem due to the unevenness of the portion in contact with the toner image, as in the conventional example, the surface of the member (heating roller in the conventional example) in contact with the toner image is Centerline average roughness R
Even if a is less than a certain value, if the waviness of the surface of the member in contact with the toner image is large, the cross-sectional shape of the surface of the member in contact with the toner image becomes uneven. There was a problem that the problem could not be improved.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a fixing device capable of preventing an image defect due to unevenness of the surface of a member in contact with a toner image.

[0009]

SUMMARY OF THE INVENTION According to the present invention, the above-mentioned object is to fix a toner image formed on a recording material while conveying the toner image at a pressure contact portion of two members arranged to face each other. In the fixing device of the forming device, of the above two members,
The surface roughness of the member in contact with the toner image is the center line average roughness R
When a is 0.2 μm or less, the filtered center line waviness W _CA is 0.1.
This can be achieved by setting the center line average roughness Ra to be 0.2 μm or less and the filtered wave maximum waviness W _{CM to} be 1 μm or less.

[0010]

According to the present invention, in a fixing device for fixing a toner image formed on a recording material while carrying a narrow pressure at a nip portion formed by two members arranged to face each other, , The surface roughness of the member in contact with the toner image is such that the center line average roughness Ra is 0.2 μm or less, the filtered center line waviness W _CA is 0.1 μm or less, or the center line average roughness Ra is
Is 0.2 μm or less and the maximum waviness W _CM of the filter is 1 μm or less, the surface of the member contacting the toner image has a smooth cross-sectional shape, and after fixing when a recording material such as a transparent sheet for OHP is used. Improve image defects

[0011]

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 FIG. In FIG. 1, 5 is a heating roller, 3 is a heater as a heat generating means, 2 is a core metal, and aluminum (Al) is used in this embodiment. Reference numeral 1 denotes a release layer, which is formed by coating a fluororesin such as tetrafluoroethylene and perfluoroalkylperfluorovinylether (PFA) in this embodiment. 6 is a pressure roller, 2 is a core metal, 4 is an elastic layer, and PF
A tube is used. After the coat is formed on the surface of the release layer of the heating roller, the surface roughness is reduced by polishing so that the center line average roughness Ra is 0.2 μm or less and the filtered center line waviness W _CA is 0.1 μm or less. And the surface of the heating roller is smoothed.

Table 1 summarizes the results of experiments conducted on the level of problems when a transparent sheet for OHP or the like is used as a recording material due to the difference in surface roughness of the surface of the heating roller.
Is.

[0014]

[Table 1]

The heating roller in this embodiment is No.
1, No. 2 and the conventional heating roller is No. 2. 3, N
o. 4, No. It is 5. No. In the heating roller of No. 3 and N0.5, the center line average roughness Ra is N in this embodiment.
o. The same as the heating roller of No. 2 but 0.2 μm, but the filtered center line waviness W _CA is larger than that of the heating roller of this embodiment,
Therefore, the level of surface irregularities is also poor. For this reason, in No. 1, No. With the heating roller of No. 2, defects due to surface irregularities are not seen in the image after fixing. However, no. Even if the center line average roughness is 0.1 μm as in the heating roller of No. 4, if the waviness component is large, the defect level of the image after fixing becomes worse.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. The description of the same parts as those in the first embodiment will be omitted.

In this embodiment, a PFA tube is used as the release layer on the surface of the heating roller. The surface of the PFA tube is formed smooth when the tube is formed. However, when the PFA tube is coated on the heating roller core metal, the surface roughness of the surface layer of the heating roller core metal is affected. For this reason, if the surface layer of the cored bar has a waviness component or the like, the waviness component or the like appears on the surface of the PFA tube on the surface layer of the heating roller. Therefore, if the surface roughness of the core metal surface is poor, unevenness appears on the surface of the heating roller after coating the PFA tube. Therefore, when an OHP transparent sheet or the like is used as a recording material, the image after fixing has a problem. Will occur. On the other hand, when the surface of the heating roller coated with the PFA tube is polished to make the surface smooth, unevenness in the film thickness of the PFA tube layer occurs depending on the surface roughness of the core metal surface. For this reason, at the convex portion on the surface of the cored bar, the film thickness of the PFA tube layer becomes thin, so that the potential on the surface of the heating roller cannot be held and the offset deteriorates.

Therefore, in this embodiment, since the surface roughness of the heating roller core metal is reduced by polishing or cutting to reduce the surface roughness and then the PFA tube is formed by coating, the surface roughness of the heating roller surface is Ra 0.2 μm or less. , W _CA 0.1 μm
It is smooth as below. Therefore, when a recording material such as a transparent sheet for OHP is used, the problem of the image after fixing can be improved. Moreover, in this embodiment, a constant film thickness can be obtained without the PFA tube being partially thinned.

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

FIG. 3 is a schematic sectional view of a tensionless film heating type fixing device. In FIG. 3, 11 is
It is a horizontally long stay made of heat-resistant resin, and serves as an inner surface guide member of the heat-resistant film 12 described later and a reinforcing member (holder) for supporting a heating body described later.

The heating element is provided on the lower surface side of the resin stay 11 having a laterally long rigidity, high heat resistance, and heat insulation whose longitudinal direction is the cross direction of the heat resistant film (direction perpendicular to the running direction of the heat resistant film 12). The heater substrate 13 is integrally attached and supported along the longitudinal direction, and the heating element 9 applied to the heater substrate 13.

The heating element 9 is made of an electric resistance material such as Ag / Pd (silver palladium) along the substantially central portion of the lower surface of the heater substrate 13 and has a thickness of about 10 μm, a width of 1 to 3 mm, and a longitudinal width of about 200 to 300 mm. Is coated by screen printing or the like, and a glass layer 14 for insulation and protection is provided thereon. Further, PFA, PTFE or the like may be further coated on this to reduce friction with the heat resistant film 12.

The endless heat-resistant film 12 is fitted onto the stay 11 including the heating element, and the inner circumference of the endless heat-resistant film 12 and the stay 1 including the heating element.
The outer peripheral length of 1 is larger than that of the film 12 by, for example, about 3 mm. Therefore, the film 12 is loosely fitted to the stay 11 including the heating element with a sufficient peripheral length. The film 12 has a total thickness of 100 μm or less, preferably 40 μm or less and 20 μm or more, in order to reduce the heat capacity and improve the quick start property, or a single layer having heat resistance, releasability, strength, durability, or the like, or Use a composite layer film.

Further, in FIG. 3, reference numeral 6 denotes a pressure roller (pressure contact roller, backup roller) as a rotating body which drives the film 12 by forming a nip portion with the film 12 sandwiched between the heating body and the center. It is composed of a shaft 2 and an elastic layer 4 which is a rubber elastic body having a good releasability such as a silicone rubber which is sheathed on the shaft 2. The left and right end portions of the central shaft 2 are freely rotatable on left and right bearing members (not shown). Bearings are supported.

In the apparatus of this embodiment as described above, the heat-resistant film 12 is formed by sequentially forming the primer layer and the releasability on the base of the polyimide film, and the release layer as the surface layer of the heat-resistant film is formed. , PFA, polytetrafluoroethylene (PTFE), or other fluororesin is used, and is formed by a dipping coat or the like.

Usually, when the release layer is formed by the dipping coating method, due to fluctuations in pulling rate, viscosity of the solution, etc.
After the dipping coat is formed, the surface of the release layer becomes uneven, and when an OHP transparent sheet or the like is used as a recording material, a problem occurs in the image after fixing.

However, in this example, the surface roughness of the heat-resistant film was smooth so that the center line average roughness Ra was 0.2 μm or less and the maximum wave undulation W _CM was 1.0 μm or less. Since such a surface is used, it is possible to improve the problem of the image after fixing when a transparent sheet for OHP or the like is used as a recording material.

Table 2 summarizes the experimental results of the difference in the defect level of the image after fixing depending on the surface roughness of the heat-resistant film surface.

[0029]

[Table 2]

No. 1 in this embodiment. 1, No. With the heat-resistant film of No. 2, there is no image defect after fixing,
No. 3, No. 4, No. As with the heat-resistant film of No. 5, as the unevenness level of the film surface deteriorated, the defect level of the image after fixing also deteriorated.

[0031]

As described above, according to the present invention,
In a fixing device of an image forming apparatus, which fixes a toner image formed on a recording material at a nip portion formed by two members arranged to face each other with a narrow pressure, the toner image is in contact with the toner image. Regarding the surface roughness of the member, the centerline average roughness Ra is 0.2 μm or less, the filtered centerline waviness W _CA is 0.1 μm or less, or the centerline average roughness Ra is 0.2.
Since the maximum waviness of filtered wave W _CM is set to be 1 μm or less at the surface of a member, the surface of the member in contact with the toner image is sufficiently smooth, and the problem of the image after fixing when a recording material such as a transparent sheet for OHP is used occurs. There is an effect that can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a fixing device according to a first exemplary embodiment of the present invention.

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

FIG. 3 is a schematic configuration diagram of a fixing device according to a third exemplary embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a fixing device in a conventional example.

[Explanation of symbols]

 5 heating roller (member in contact with toner image) 6 pressure roller (member in contact with toner image) 7 toner 8 recording material 12 heat resistant film (member in contact with toner image)

Claims (3)

[Claims] 1. A fixing device for an image forming apparatus, wherein a toner image formed on a recording material is fixed while being conveyed under a narrow pressure at a pressure contact portion of two members arranged to face each other. Regarding the surface roughness of the member in contact with the toner image, the center line average roughness Ra is 0.2 μm or less, and the filtered center line waviness W _CA
Is 0.1 μm or less, or the center line average roughness Ra is 0.2
A fixing device characterized in that the maximum waviness of filtered wave W _CM is 1 μm or less at μm or less. 2. The fixing device according to claim 1, wherein the member in contact with the toner image is a roller. 3. The fixing device according to claim 1, wherein the member in contact with the toner image is a film.