JP2957556B2 - Thermal fixing roll for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing roll for electrophotography, which is used in a fixing device of an electrophotographic apparatus and is used for fixing toner particles on a copy paper by fusing.

[0002]

2. Description of the Related Art Conventionally, as a heat fixing roll for electrophotography, a material having good releasability, for example, polytetrafluoroethylene (hereinafter, referred to as PTFE resin) is formed on a cylindrical metal core such as aluminum, iron, and stainless steel. Rolls coated with a fluororesin such as a copolymer of tetrafluoroethylene and perfluoroalkyl perfluorovinyl ether (hereinafter referred to as PFA resin) are used.

[0003] Such a heat fixing roll constitutes a fixing device by opposing pressure contact with a pressure roll coated with silicone rubber or fluorine rubber. Then, the copy paper is passed between the heated heat fixing roll and the pressure roll, and the powder toner image formed on the copy paper is melted by heat and pressure,
It is fixed on copy paper.

In the production of a heat fixing roll having a fluororesin coating layer, a powder or dispersion of a fluororesin is applied to the surface of a cored bar, fired at a temperature of 360 to 400 ° C. and fused. However, unevenness during coating remains and the thickness of the coating layer tends to be non-uniform. Such a variation in the thickness of the fluorine resin layer causes unevenness in the pressing force at the time of fixing the toner, and as a result, the quality of the fixed image is deteriorated. The surface was polished so as to have a predetermined thickness, and the surface smoothness was also increased.

[0005] However, such a heat fixing roll having a fluorine resin layer smoothed by surface polishing tends to cause deep scratches as the surface roughness decreases, so that it is difficult to clean the adhered toner. In other words, there is a problem that deterioration of image quality due to the offset phenomenon cannot be prevented. Therefore, a method of smoothing the surface using a pressure roll instead of surface polishing (Japanese Patent Laid-Open No. 57-43892) or a method of applying a fluororesin on a roller base material, smoothing the surface, and then melting the fluororesin A method of firing at the above temperature (JP-A-63-4287) has been proposed.

[0006]

The heat fixing roll whose surface has been smoothed by the conventional method as described above has the effect of improving the quality of a fixed image, but has an effect.
At the time of fixing the toner image, the phenomenon that the melted toner adheres to the heat fixing roll and transfers to the next copy paper to contaminate it, that is, the occurrence of the offset phenomenon has not yet been suppressed.

Generally, the offset phenomenon is roughly classified into what is called a high-temperature offset and what is called a low-temperature offset. The high-temperature offset is caused by the adhesion of the melted toner to the heat fixing roll, and the low-temperature offset is not melted. This is due to the toner particles adhering to the heat fixing roll, and is determined by the distribution state of the surface temperature of the heat fixing roll, the temperature drop during paper passing, the toner characteristics, and the like. Therefore, it is required for the heat fixing roll that the temperature at which the high-temperature offset occurs is high and the temperature at which the low-temperature offset occurs is low. However, the heat fixing roll obtained by these conventional methods has a high-temperature offset generation area and a low temperature. There is a problem that the offset generation area is close to the non-offset temperature area.

Accordingly, the present invention provides an improved electronic device which not only has a high quality of a fixed image but also has a wide non-offset temperature region in order to solve the above-mentioned problem of the offset resistance of the heat fixing roll according to the prior art. It was intended to provide a heat fixing roll for photography.

[0009]

An object of the present invention as described above is to provide a surface roughness Rz of 3.5 μm or less and a glossiness of 50 μm or less.
%, And a heat-fixing roll for electrophotography having a smooth fluorine resin layer having a contact angle of water of 115 ° or more on the surface. Further, the heat fixing roll of the present invention forms a dry film by applying a fluororesin dispersion liquid paint on the surface of the cored bar, and then presses a rotating pressure roll on the surface of the film to smooth the mirror surface. It is obtained by processing and then heat treating to fuse the coating.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The core used in the present invention is preferably in the shape of a hollow cylinder, and is preferably one in which a heating element for heating or the like can be mounted. The fluororesin paint applied on the cored bar is not particularly limited, but a PTFE resin, a PFA resin, or a mixture thereof dispersed in a liquid medium such as water is preferably used. Organic or inorganic fillers and the like can be blended in such paints as needed. Such fillers include, for example, fibrous or fine powder materials such as carbon, potassium titanate, metal oxides, ceramics, glass, and metals. Materials suitable for application can be selected and blended.

In general, it has been known that carbon blended in a surface resin layer of a fixing roll exhibits excellent static elimination characteristics when mixed in an amount of 3 to 8% by weight. Even if only a very small amount of 0.5 to 3% by weight, particularly about 0.5 to 1% by weight, which is much smaller than the carbon content of, is obtained, excellent static elimination properties can be exhibited.

Such a fluororesin paint is applied on a primer-coated hollow core metal by, for example, spray coating or the like, and dried at a temperature from room temperature to about 100 ° C. for 30 minutes to 1 hour. A coating is formed. Since the dried film of the fluororesin is not calcined and the particles of the fluororesin are merely overlapped, the surface has irregularities along the shape of the particles, and easily falls off when strongly rubbed. is there.

The surface of the dried fluororesin film thus formed on the core metal is subjected to a smoothing process. As such a smoothing process, a metal pressure roll having a mirror-finished surface is pressed against a rotating roll to be processed with a force of about 1 to 20 kgf, and is driven to rotate with respect to the roll to be processed.
A method of crushing a dry fluororesin film while moving a pressure roll from one end to the other end along the axis of the roll body to be processed, for example, at a speed of 2 cm / sec, and smoothing the surface to a mirror surface. Is used. According to this method, unlike the case where the fluorine resin layer melted by firing is smoothed,
Since smoothing can be easily performed with a remarkably low pressing force, inconveniences such as distorting the metal core do not occur.

The fluororesin dry film smoothed as described above is treated at a temperature of, for example, 360 to 400 ° C., for example, at 10 ° C.
By baking for about 1 minute to 1 hour, it is converted into a smooth and scratch-free fluorine resin layer. This resin layer has a matte appearance and a glossiness of less than 50%. Then, after sintering, the surface is polished, or the surface roughness is approximately the same as the resin layer according to the conventional method which is mirror-finished by roll pressing,
That is, 3.5-μm or less is realized in ten-point average roughness Rz.

A characteristic of the thus obtained heat fixing roll for electrophotography of the present invention is that the contact angle of water on the surface of the fluororesin layer is particularly large. That is, when a water drop is placed on the surface of the heat fixing roll for electrophotography of the present invention and its contact angle is measured, the fluororesin layer whose surface is smoothed by the conventional technique shows only a value of 110 ° or less. And has a very large contact angle of 115 ° or more.

As described above, the 10-point average roughness Rz is 3.
The heat fixing roll for electrophotography of the present invention having a characteristic of 5 μm or less, a glossiness of less than 50%, and a contact angle with water of 115 ° or more, is obtained by pressing and smoothing, baking and fusing. With a high density fluororesin layer,
It exhibits excellent performance such as no occurrence of offset phenomenon over a wide temperature range, excellent abrasion resistance and good durability.

[0017]

【Example】

Example 1 A primer (EK1909BKN, manufactured by Daikin Industries, Ltd.) was placed on a hollow metal core having a diameter of 30 mm and a length of 300 mm.
Is applied, and then a PTFE resin liquid (EDK manufactured by Daikin Industries, Ltd.)
4300 CRN). After drying at 80 ° C. for 30 minutes to form a fluororesin dry film, a metal pressing roll having a mirror surface is brought into contact with the roll to be processed with a pressing force of 6 kgf, and the pressing roll is rotated while rotating the roll to be processed. Was moved from one end to the other end along the axis of the roll to be processed at a speed of 2 cm / sec, so that the dried fluororesin film was mirror-finished. At this time, the 10-point average roughness Rz of the fluororesin dried film surface was 2 μm.

This was placed in a firing furnace having an atmosphere of 380 ° C. and fired for 30 minutes to produce a heat fixing roll having a 30 μm-thick fluorine resin layer. When the ten-point average roughness of the surface of the fluorine resin layer of the heat fixing roll thus obtained was measured, Rz was 2.0 μm.

A gloss meter (Nippon Denshoku Co., ND-K)
S, VG-107 type), and the glossiness of the surface of the fluororesin layer was measured at a light receiving angle of 75 ° with a halogen light of 580 to 600 nm, and found to be 9.1%. Furthermore,
A drop of water was placed on the surface of the fluororesin layer, and the angle of the water surface in contact with the surface was measured with a contact angle meter.
The value of ゜ was obtained.

Example 2 A heat fixing roll was prepared in the same manner as in Example 1 except that a coating material in which 0.75% by weight of carbon black was mixed in a PTFE resin solution (ED4300 CRN, manufactured by Daikin Industries, Ltd.) was applied. Was made. The 10-point average roughness Rz of the fluorine resin layer surface of this heat fixing roll is 2.0 μm, the glossiness is 4.2%, and the contact angle of water is 120 to 120 μm.
It was 126 ゜.

Example 3 A fixing roll was prepared in the same manner as in Example 1 except that a paint in which 3.0% by weight of tin oxide was mixed in a PTFE resin solution (ED4300 CRN, manufactured by Daikin Industries, Ltd.) was applied. Made. The surface of the fluorine resin layer of the heat fixing roll had a 10-point average roughness Rz of 2.0 μm, a gloss of 46.8%, and a contact angle of water of 118 to 124 °.

Comparative Example 1 A primer (EK19, manufactured by Daikin Industries, Ltd.) was placed on a hollow metal core having a diameter of 30 mm and a length of 300 mm.
09BKN), a PTFE resin solution (ED4300CRN, manufactured by Daikin Industries, Ltd.) was applied and dried at a temperature of 80 ° C. for about 30 minutes. Thereafter, it was baked at 380 ° C. for 30 minutes and polished with a No. 800 sandpaper to produce a heat fixing roll having a 30 μm-thick fluorine resin layer. 10 of the surface of the fluorine resin layer of the obtained heat fixing roll
The point average roughness Rz was 1.5 μm, and countless polishing scratches were visually confirmed. The glossiness of the surface was 65.7%, and the contact angle of water was 102 °.

Comparative Example 2 A heat fixing roll was produced in the same manner as in Comparative Example 1 except that 0.75% by weight of carbon black was mixed in a PTFE resin solution (ED4300 CRN, manufactured by Daikin Industries, Ltd.). The surface of the fluororesin layer of the obtained heat fixing roll had a 10-point average roughness Rz of 1.5 μm, a glossiness of 70.4%, and a contact angle of water of 104 to 106 °.

Comparative Example 3 A heat fixing roll was produced in the same manner as in Comparative Example 1 except that 3.0% by weight of tin oxide was mixed in a PTFE resin solution (ED4300 CRN, manufactured by Daikin Industries, Ltd.). The 10-point average roughness Rz of the surface of the fluororesin layer of the obtained heat fixing roll was 1.5 μm, and the glossiness was 65.1.
%, The contact angle of water was 98-102 °.

Comparative Example 4 A primer (EK19, manufactured by Daikin Industries, Ltd.) was placed on a hollow core metal having a diameter of 30 mm and a length of 300 mm.
09BKN), a PTFE resin solution (ED4300CRN, manufactured by Daikin Industries, Ltd.) was applied, and dried at a temperature of 80 ° C. for about 30 minutes. Thereafter, it is baked at 380 ° C. for 30 minutes, and the pressing roll having a mirror-finished surface is pressed at a pressure of about 40 kg to rotate the core metal, and while the fluorine resin surface is softened with a heat gun, the pressing roll is rotated at a speed of 2 cm / sec. By moving the roll from one end to the other end along the axis of the roll to be processed, a heat fixing roll having a fluorine resin layer having a thickness of 30 μm was manufactured.

The obtained heat fixing roll has a 10-point average roughness Rz of 1.95 μm on the surface of the fluororesin layer, a glossiness of the surface of 69.3%, and cloudy spots on all surfaces having a specular gloss. Was distributed. In addition, when observed with a microscope, many streaky scratches due to the pressing roll were confirmed. The contact angle of water was 104 to 106 °.

Comparative Example 5 A heat fixing roll was produced in the same manner as in Comparative Example 4, except that 0.75% by weight of carbon black was mixed in a PTFE resin solution (ED4300 CRN, manufactured by Daikin Industries, Ltd.). The 10-point average roughness Rz of the surface of the fluororesin layer of the obtained heat fixing roll was 1.9 μm, the glossiness was 73.6%, and the appearance was the same as Comparative Example 4. The contact angle of water was 106 to 108 °.

Comparative Example 6 A heat fixing roll was produced in the same manner as in Comparative Example 4, except that 3.0% by weight of tin oxide was mixed in a PTFE resin solution (ED4300 CRN, manufactured by Daikin Industries, Ltd.). The 10-point average roughness Rz of the surface of the fluorine resin layer of the obtained heat fixing roll was 1.9 μm, and the glossiness was 69.4.
%, And the contact angle of water was 101 to 104 °.

Test Example 1 Examples 1 to 3 and Comparative Example 1
Each of the heat fixing rolls of Nos. 6 to 6 was incorporated into a copying machine, and after heating to 240 ° C., the heater was turned off and the paper was passed.
The occurrence of the offset phenomenon of the copied image was observed until the temperature of the surface of the heat fixing roll gradually decreased to 130 ° C. Further, the charge amount at the initial stage and after 100 sheets were passed was measured using a Monroe surface electrometer. Tables 1 to 3 show these results.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

From these results, it can be seen that the heat fixing roll for electrophotography according to the present invention has good non-offset temperature range and good static elimination regardless of the presence of no filler, carbon or tin oxide. It turns out that the result is shown. In particular, from Tables 2 and 3, it is recognized that there is a remarkable difference in the static elimination effect regardless of the amount of the filler used, and that the characteristics of the filler are effectively exhibited in the present invention. I understand.

Next, a silicone oil having a viscosity of 100 cs at room temperature was kept at 200 ° C., and the heat-fixing rolls of Example 1 and Comparative Example 1 were immersed in the silicone oil, respectively. The heat fixing roll of Comparative Example 1 had a peeling of 10/100 in 216 hours and a peeling of 40/100 in 240 hours in the base line test. There was no peeling at all.

Further, when the heat fixing rolls of Example 2 and Comparative Example 2 were incorporated in a copying machine, and the abrasion due to the edge of the copying machine and the abrasion due to the separating claw were observed, in Example 2, the edge of the copying paper passed. The surface roughness of the part is initially Rmax
Is 2.5 μm, and after passing 30,000 sheets, Rmax is 3.2 μm,
In the portion where the separation claw comes into contact, Rmax is initially 3.0 μm.
m, after passing 30,000 sheets, Rmax was 1.8 μm. However, in Comparative Example 2, Rmax was initially 2.0 μm in the portion where the edge portion of the copy paper passed, and Rmax was found after passing 30,000 sheets.
max is 8 μm, and Rm is the initial value at the portion where the separation claw comes into contact.
a is 1.5 μm and Rmax is 5.5 after 30,000 sheets have passed.
μm, the heat fixing roll of Example 2 showed remarkably excellent wear resistance.

Examples 4 to 6 and Comparative Examples 7 and 8 All of Example 2 was carried out except that the amount of carbon black mixed in Example 2 was changed to 0.5% by weight, 1% by weight and 3% by weight. In the same manner as in the above, the heat fixing rolls of Examples 4 to 6 were manufactured. Heat fixing rolls of Comparative Examples 7 and 8 were produced in the same manner as in Comparative Example 2 except that the amount of carbon black mixed in Comparative Example 2 was changed to 3% by weight and 5% by weight.

Test Example 2 With respect to each of the heat fixing rolls of Examples 4 to 6 and Comparative Examples 7 and 8, the occurrence of an offset phenomenon in the copied image and the charge amount were examined in the same manner as in Test Example 1. Table 4 shows the results.

[0038]

[Table 4]

From the results shown in Table 4, it is clear that the heat fixing roll for electrophotography of the present invention has the same or better static elimination property than the conventional carbon content.

[0040]

The heat fixing roll for electrophotography of the present invention has a wide non-offset temperature range, has excellent abrasion resistance and durability against silicone oil, and has a filler for imparting conductivity. The effect is that the amount of the conductive filler is small and the production is easy.

Claims (1)

(57) [Claims] 1. A surface roughness Rz of 3.5 μm or less, a glossiness of less than 50%, and a contact angle of water of 115 ° or more.
A heat fixing roll for electrophotography, wherein a smooth fluorine resin layer is provided on the surface of a cored bar.