JP2003323071A - Fixing roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing roller for heating which is coated with a fluorocarbon resin tube and is free from or almost free from crack defects although a PFA heat shrinkable tube having <20 μm thickness is used. <P>SOLUTION: The fixing roller has a roller body and a heat shrinkable tube covering the periphery of the roller body by heat shrinking. The heat shrinkable tube is made of a copolymer of tetrafluoroethylene and perfluoroalkylvinylether and has <20 μm average thickness. The transverse direction (TD) shrinkage rate of the tube at 200°C is ≥70% of the TD shrinkage rate at 300°C, and the TD shrinkage rate at 100°C is ≥20% of the TD shrinkage rate at 300°C. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing roller, and more particularly to a fixing roller for heating used in a toner image fixing unit of an electrophotographic image forming apparatus such as a copying machine, a facsimile, a laser beam printer.

[0002]

2. Description of the Related Art Generally, an electrophotographic image forming apparatus is
An electrostatic latent image forming unit for exposing the photosensitive drum based on predetermined image information to form an electrostatic latent image on the photosensitive drum, and toner from a developing roller to the electrostatic latent image formed on the photosensitive drum. A developing unit for supplying and adhering toner to form a toner image (visible image) corresponding to the electrostatic latent image, and a transfer unit for transferring the toner image formed on the photosensitive drum onto a recording sheet, A fixing unit is provided for firmly fixing the toner image transferred on the recording paper to the recording paper.

In the fixing unit, a recording paper carrying an unfixed toner image is inserted between a pressure roll and a heat fixing roll, and heat is applied from the heat fixing roll under pressure to fix the toner image on the recording paper. Is configured to let. Since the toner at the time of fixing has an adhesive property, the surface of the fixing roll in contact with the toner may be coated with a fluororesin having excellent toner releasability for the purpose of preventing the toner from adhering. It is commonly done.

Compared with the suspension coating method and the powder coating method, the coating with the fluororesin has fewer pinholes, is excellent in surface properties, and is excellent in withstand voltage. It is done using tubes.
That is, the fluororesin tube is fitted onto the fixing roller body, and this is fused at the same time as the heat shrinkage. As such a fluororesin tube, a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (PF
A) is preferably used.

By the way, the PFA heat-shrinkable tube currently mass-produced has a thickness of about 30 μm, and even a thin one has a thickness of about 22 to 25 μm.
There is nothing less than. If the thickness is thick as described above, the time from turning on the power of the electrophotographic image forming apparatus until the surface of the heating and fixing roll reaches a predetermined temperature, that is, the so-called warm-up time becomes long, and the power consumption also increases accordingly.
The coating type has a thickness of about 15 μm, and the warm-up time is satisfactory.

Therefore, from the viewpoint of shortening the warm-up time, it is desirable that the PFA heat-shrinkable tube having a thickness as thin as the coating type has a thickness of at least less than 20 μm, but a thickness of 20 μm obtained from the manufacturer.
When a fixing roller is manufactured using a PFA heat-shrinkable tube of less than m, defects such as cracks and wrinkles often occur in the obtained PFA heat-shrinkable tube layer. In particular, cracks are fatal to the fixing roller.

For this reason, Japanese Patent Application No. 2000-219482 (Japanese Patent Application Laid-Open No. 2002-4
No. 0851: Published on February 6, 2002), as a technology for preventing the generation of cracks in the heat-shrinkable tube, the heat-shrinkable tube is formed from a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether. An application has been made which is characterized in that the haze is 6% or less while the average thickness is less than 20 μm.

[0008]

According to the conventional patent application configured as described above, the above-described object can be achieved, but crack prevention measures from another viewpoint (factor) are desired. Has been done.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a PF having a thickness of less than 20 μm.
A heat-shrinkable tube is used, and a fixing roller for heating is coated with a fluororesin tube having few or no crack defects.

[0010]

[Means for Solving the Problems]
To achieve the object, the fixing roller according to the present invention is
According to claim 1, the roller body is provided with a heat-shrinkable tube whose outer periphery is covered by heat shrinkage, and the heat-shrinkable tube contains tetrafluoroethylene and perfluoroalkyl vinyl ether. Is characterized by having an average thickness of less than 20 μm and a circumferential shrinkage at 200 ° C. of 70% or more of the circumferential shrinkage at 300 ° C.

According to a second aspect of the present invention, a fixing roller comprises a roller body and a heat-shrinkable tube whose outer circumference is covered by heat shrinkage. The flexible tube is formed from a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, has an average thickness of less than 20 μm, and
The circumferential shrinkage at 100 ° C. is 20% or more of the circumferential shrinkage at 300 ° C.

According to a third aspect of the present invention, a fixing roller comprises a roller body and a heat-shrinkable tube whose outer circumference is covered by heat shrinkage. The flexible tube is formed from a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, has an average thickness of less than 20 μm, and
The circumferential shrinkage at 200 ° C is 70% or more of the circumferential shrinkage at 300 ° C, and the circumferential shrinkage at a temperature of 100 ° C is 2% of the circumferential shrinkage at 300 ° C.
It is characterized by being 0% or more.

[0013]

The present invention will be described in more detail below. FIG. 1 is a schematic sectional view of a heat fixing roller according to an embodiment of the present invention. As shown in FIG. 1, the heat fixing roller 10 has a cylindrical roller body 11 and a fluororesin tube layer 12 formed on the outer peripheral surface of the roller body 11 by heat contraction. A heating unit 13 such as a heater for heating the fixing roller is built in the roller body 11. The roller body 11 is made of metal such as aluminum or aluminum alloy.

The fluororesin tube layer 12 has a thickness of 20 μm.
Of the PFA heat-shrinkable tube of less than m, the TD shrinkage at 200 ° C. (shrinkage in the circumferential direction of the tube / TD:
transverse direction) is 70% or more of the circumferential shrinkage at 300 ° C, and TD at 100 ° C.
A shrinkage rate of 20% or more of the TD shrinkage rate at 300 ° C. is selected, and the heat shrinkable tube thus selected is fitted into the roller body 11 to cause heat shrinkage by heating, and at the same time, the roller body 11 It is fused to. Needless to say, this fluororesin tube layer 12
Form the outermost layer of the fixing roller 10.

The present inventors have established a thickness of 2 with Okura Industry Co., Ltd., located in Marugame City, Kagawa Prefecture, which is a manufacturer of heat-shrinkable resin tubes.
Have PFA heat-shrinkable tubes of less than 0 μm outsourced, fit these tubes on the fixing roller body, shrink and fuse to the roller body by heating to form the fluororesin tube layer 12, and to prevent crack defects The research was conducted on the occurrence. Here, the crack is defined as a minute break of the fluororesin tube layer 12 formed along the longitudinal direction of the fixing roller.

As a result of the above research, P having a thickness of less than 20 μm
In the FA heat-shrinkable tube, the temperature characteristic of the TD shrinkage (that is, the state of change in the TD shrinkage during heating) correlates with the occurrence of crack defects, and the TD shrinkage at a temperature of 200 ° C. is 300 ° C. 70% or more of the TD shrinkage,
And / or TD shrinkage at 100 ° C is 300 ° C
It has been found that the PFA heat-shrinkable tube having a TD shrinkage ratio of 20% or more can provide the fluororesin tube layer 12 with almost no cracks or no cracks.

As the heat-shrinkable tube used in the present invention, the predetermined PFA heat-shrinkable tube described above is fitted on the roller body 11 and charged into, for example, a hot air circulation furnace at 305 ° C. It can be manufactured by heat-shrinking and heat-sealing the heat-shrinkable tube.

[0018]

DESCRIPTION OF PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described below, but it goes without saying that the present invention is not limited thereto.

In the following examples, the temperature characteristics of the thickness and the heat shrinkage rate of the heat shrinkable tube were measured as follows.

First, the obtained PFA heat-shrinkable tube was cut into a ring shape having a width of 200 mm, and the thickness was measured. This thickness measurement was performed using a universal type film thickness meter LZ-200, which is a high-frequency film thickness meter manufactured by Kett Scientific. The surface roughness Ra of the tube at this time was 1.0 μm or less.

Next, the ring-shaped heat-shrinkable tube whose thickness was measured was measured with a caliper for the bending diameter and the length along the central axis direction. After that, put in a hot air circulation furnace that can be set from room temperature to 305 ° C, and set each temperature (100 ° C, 120
℃, 140 ℃, 160 ℃, 180 ℃, 200 ℃, 220
℃, 240 ℃, 260 ℃, 280 ℃, 300 ℃), leave for 3 minutes, take out after this, again measure the fold diameter and the length along the central axis direction with calipers, to each set temperature The heat shrinkage rate was calculated.

The shrinkage ratio is a value calculated by {(measured value before heating-measured value after heating) / measured value before heating} × 100. The shrinkage rate based on the fold diameter indicates the TD shrinkage rate, and the shrinkage rate along the central axis direction indicates the MD shrinkage rate (MD: machine direction).

Example 1: Outsourced to Okura Industry Co., Ltd. located in Marugame City, Kagawa Prefecture, and made of PFA (350J manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) and having a thickness of less than 20 μm.
A heat-shrinkable tube having an outer diameter of 60.3 mm was obtained. It was reported that these PFA heat-shrinkable tubes were manufactured through inflation molding.

First, the thickness and heat shrinkage of these PFA heat shrinkable tubes were measured. The measurement results for TD are shown in FIG. 2 and Table 1. The MD is shown in FIG. 3 and Table 2.

[0025]

[Table 1]

[0026]

[Table 2]

Next, an evaluation experiment on cracks of each PFA heat-shrinkable tube was conducted. In this evaluation experiment, the outer diameter is 6
The surface of the 0 mm aluminum (A5052) roller body was dry-blasted, and then the surface of the roller body was washed with a solvent. After cleaning, the surface of the roller body is coated with a primer for fluororesin paint (Mitsui DuPont Fluorochemicals P
R-902BN), and each PFA heat-shrinkable tube was fitted thereon. Hot-air circulation electric furnace (TABAI made SUPER-TEMP OVEN STPH-100) preheated to 380 ℃
The tube was heat-shrinked with respect to the roller body and fused to obtain a fixing roller. In this way, five fixing rollers were produced for one PFA heat-shrinkable tube.

Occurrence of cracks was visually determined by the obtained fixing roller. The determination result is also shown in Table 1 described above.

In Table 1, the mark ◯ indicates that no cracks were generated, and the mark x indicates that cracks were clearly generated.

From the results shown in Table 1, the present inventor has found that there is no correlation between the occurrence of cracks and the MD shrinkage, but the relationship between the occurrence of cracks and the temperature characteristics of TD shrinkage. In the fluororesin tube layer 12, the TD shrinkage at 200 ° C. is 70% or more of the TD shrinkage at 300 ° C., and / or 10
TD shrinkage at a temperature of 0 ° C is T at 300 ° C
If it is composed of a PFA heat-shrinkable tube having a D-shrinkage ratio of 20% or more, it hardly causes cracks.
I found that it does not occur at all.

That is, if the temperature characteristics of the TD shrinkage of the obtained PFA heat-shrinkable tube are measured in advance and it is confirmed that the above-mentioned conditions are satisfied, the PFA thus confirmed is confirmed. By forming the fluororesin tube layer 12 using a heat-shrinkable tube, the occurrence of cracks in the fluororesin tube layer 12 can be effectively suppressed.

Example 2 Similarly, a PFA heat-shrinkable tube having a thickness of less than 20 μm and an outer diameter of 30 mm was obtained from Okura Industry Co., Ltd. It was reported that these PFA heat-shrinkable tubes were manufactured through inflation molding, as in Example 1.

First, the thickness and heat shrinkage ratio of these PFA heat shrinkable tubes were measured. The measurement results are shown in FIG. 4 and Table 3 for TD. The MD is shown in FIG. 5 and Table 4.

[0034]

[Table 3]

[0035]

[Table 4]

Next, an evaluation experiment on cracks of each PFA heat-shrinkable tube was carried out. In this evaluation experiment, the outer diameter is 6
Evaluation was performed in the same procedure as in Example 1 in the case of 0.3 mm. Then, similarly, the occurrence of cracks was visually determined by the obtained fixing roller. The determination result is also shown in Table 3 described above.

As a result, even in the PFA heat-shrinkable tube having the outer diameter of 30 mm, the same result as in the PFA heat-shrinkable tube having the outer diameter of 60 mm could be obtained. This has nothing to do with the outer diameter of the tube.
It has been found that the temperature characteristics of D shrinkage ratio are defined.

[0038]

As described above, according to the present invention, a PFA heat-shrinkable tube having a thickness of less than 20 μm is used as the fluororesin tube layer, and the PFA heat-shrinkable tube has a TD shrinkage ratio at 200 ° C. , 70% or more of TD shrinkage at 300 ° C., and / or 10
By using the TD shrinkage percentage at 0 ° C. of 20% or more of the TD shrinkage percentage at 300 ° C., it is possible to provide a fixing roller having little or no crack defects.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a fixing roller of the present invention.

FIG. 2 is a diagram showing temperature characteristics of TD shrinkage in Example 1.

FIG. 3 is a diagram showing temperature characteristics of MD shrinkage in Example 1.

FIG. 4 is a diagram showing temperature characteristics of TD shrinkage in Example 2.

5 is a graph showing temperature characteristics of MD shrinkage in Example 2. FIG.

[Explanation of symbols]

11 ... roller body 12 ... Fluororesin (PFA) tube layer 13 ... Heating means

Claims (3)

[Claims] 1. A roller main body, and a heat-shrinkable tube whose outer circumference is covered by heat shrinkage, wherein the heat-shrinkable tube is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether. And having an average thickness of less than 20 μm, and 200
A fixing roller having a circumferential shrinkage at 70 ° C. of 70% or more of a circumferential shrinkage at 300 ° C. 2. A roller body, and a heat-shrinkable tube whose outer circumference is covered by heat shrinkage, wherein the heat-shrinkable tube is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether. And having an average thickness of less than 20 μm, and 100
A fixing roller having a circumferential shrinkage at 20 ° C. of 20% or more of a circumferential shrinkage at 300 ° C. 3. A roller main body, and a heat-shrinkable tube whose outer circumference is covered by heat shrinkage, wherein the heat-shrinkable tube is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether. And having an average thickness of less than 20 μm, and 200
The circumferential shrinkage at 70 ° C. is 70% or more of the circumferential shrinkage at 300 ° C., and the circumferential shrinkage at 100 ° C. is 20% or more of the circumferential shrinkage at 300 ° C. Fixing roller to do.