JPH0325787B2 - - Google Patents

Description

Detailed Description of the Invention (Object of the Invention) The present invention relates to a toner image fixing roller for electronic copying machines, etc., which has a base layer made of silicone rubber coated with a surface layer of fluorine resin. The purpose is to provide a means for producing a toner image that is difficult to use and that can withstand many copying operations and still produce a clear toner image.

2. Description of the Related Art Conventionally, a fixing roller in which a thin surface layer of fluororesin is baked and coated on a base layer made of silicone rubber has been proposed and is known. Compared to silicone rubber, fluororesin has lower tackiness and has a higher ability to prevent offset of toner print images, and the use of a thin surface layer of fluororesin takes advantage of silicone rubber's excellent elasticity. It is.

Examples of such fluororesins include copolymers of tetrafluoroethylene and hexafluoropropylene (hereinafter referred to as FEP), polytetrafluoroethylene (hereinafter referred to as PTFE), and copolymers of tetrafluoroethylene and perfluoroalkyl perfluorovinylether. Combination (hereinafter referred to as PFA)
The fluororesin surface layers of the fixing rollers proposed so far are each made of a single substance of these materials, but almost none of them have been put into practical use.

Therefore, the inventors conducted additional tests on the fixing rollers proposed above, and found that each of them had the following significant drawbacks. That is, on top of the elastic layer described above
When coating FEP (melting point around 270℃), baking at around 290℃, which is slightly higher than the melting point, for 20 minutes to 1 hour will avoid deterioration of the silicone rubber of the elastic layer. Products tend to crack on the surface after firing, and
If a roller coated with FEP is used as a fixing roller in an electronic copying machine or the like, it will soften due to the high temperatures during operation and be easily damaged by paper separation claws, resulting in poor offset prevention properties. On the other hand, the surface layer is PFA (melting point 300-310℃) or PTFE.
(melting point around 343℃), 350 to 380℃
Because heat treatment is required at such high temperatures for 20 to 1 hour, deterioration of the silicone rubber base layer is unavoidable.

The present invention was made in order to eliminate the drawbacks of the above-mentioned known techniques in which a fluororesin film is formed on a silicone rubber base layer by firing.

(Structure of the Invention) To explain the present invention with reference to the drawings, the method for manufacturing a toner image fixing roller according to the present invention is characterized by the following features. In other words, 50 to 95 parts out of 100 parts to a base layer 2 of a constant thickness made of silicone rubber molded and coated on a core metal 1 of a constant diameter.
With FEP, a fluororesin composition with the remainder being PTFE is fired and coated at 280 to 300°C. After repeating this firing coating two or more times, the surface is polished to form multiple layers of fluororesin. A surface layer 3 having a constant thickness is formed on the base layer 2.

Some embodiments of this invention will be listed below, and in each embodiment, the mandrel 1 is made of aluminum, has a diameter d=37.94 mm, and a length 300 mm. Wall thickness t ₁ of base layer 2 made of silicone rubber after polishing = 1.0
mm. Further, after applying a primer (GL-E manufactured by Daikin Industries) on the base layer 2, a predetermined fluororesin composition is applied and baked at a predetermined temperature and for a predetermined time. The application and baking of this fluororesin composition was repeated a predetermined number of times in each cited example, and finally the peripheral surface was polished so that the diameter D of the product roll was 40.0 mm.

Example 1 A mixed solution of 70 parts of FEP (Teflon 120 manufactured by Mitsui Dupont Fluorochemicals) and 30 parts of PTFE (EK-4183GB manufactured by Daikin Industries) was used as a fluororesin composition. First, an undercoat was applied, and after baking at 290°C for 30 minutes, an intermediate coating was applied, and after baking again under the same conditions, a topcoat was applied, and after further baking under the same conditions, the peripheral surface was polished. That is, the surface layer 3 made of fluororesin in the finished product of the fixing roller consists of three layers, and the thickness of each layer is approximately 10 μm.
The wall thickness t ₂ of the entire surface layer 3 is 30μ.

Example 2 As a fluororesin composition, 55 parts of FEP (same as described in Example 1) and PTFE (same as described in Example 1) were used.
45 parts of the mixture was used. Undercoating, baking, topcoating, baking, and coating and baking were performed twice. However, since the amount of the fluororesin composition applied each time was larger than in Example 1, the diameter D of the product roll after polishing was the same as in Example 1, but the actual layer 3 consisted of two layers. The wall thickness of each layer is approximately 15μ. The firing conditions were 300°C and 20 minutes each time.

Example 3 A mixed solution of 95 parts of FEP (same as described in Example 1) and 5 parts of PTFE (same as described in Example 1) was used as a fluororesin composition. The number of times of coating and firing was 3 times as in Example 1, and the firing conditions each time were 280° C. for 1 hour. The thickness t ₂ of each layer and the entire surface layer 3 after firing is the same as in Example 1.

In this invention, the reason why the application and firing of the fluororesin composition is repeated multiple times to form the surface layer 3 is that the surface layer of the fluororesin obtained by one application and firing is coated with the fluororesin composition as shown in FIG. Many deep recesses K as shown in Fig. 3 occur, so when the circumferential surface is polished smooth to make the diameter uniform over the entire length of the roller, the recesses become cracks as shown in Fig. 3. If left as is, it is harmful to the offset prevention effect, but if the coating and firing of the fluororesin composition described above is repeated several times, and several layers are stacked, as shown in Figure 4, the higher the layer, the more the This is because the unevenness becomes shallower, and after polishing, a crack-free roller surface F as shown in FIG. 5 can be obtained. In the experience of the inventors, the coating and baking process takes 2 to 3
It has been found that the optimum polishing time is that a fluororesin surface layer with a thickness of about 30 μm and no cracks can be obtained after polishing.

According to this invention, as described above, 50 to 95 parts out of 100 parts to the base layer 2 of silicone rubber
A fluororesin composition consisting of FEP and the remainder PTFE.
The coating is fired at 270-310℃,
The melting point of FEP is around 270℃, and the melting point of PTFE is
Since the temperature is around 343°C, the composition is heated at 270 to 310°C.
If the FEP in the composition is calcined at
Since the molecule M, which has become a complete polymer of PTFE, does not reach the melting point, it is in a solid state and is evenly dispersed in the liquid phase of FEP. FIG. 6 schematically shows this state, and the surface layer 3 of the fluororesin formed by the method of this invention has PTFE molecules M after firing.
During FEP, they are bonded by intermolecular forces and evenly dispersed to form a composite, so even if the toner is heated to about 200°C during fixing, this composite will remain intact.
It is less likely to soften than FEP alone, and therefore less likely to be damaged during fixation. Further, at the above-mentioned firing temperature according to the method of the present invention, no deterioration occurs in the silicone rubber of the base 2, so that its good elasticity is not impaired in the slightest.

As mentioned above, the blending ratio of the fluororesin composition in this invention is 50 to 100 parts of FEP.
95 parts, and the remainder is PTFE. If the proportion of PTFE does not reach 5% of the composition, the surface layer 3 will soften when using a roller, resulting in poor trauma resistance, and the firing temperature will be significantly lower than the melting point of PTFE, resulting in PTFE If the ratio exceeds 50%, the formation of a film during firing will be poor, and although it will not soften during use, it will become more easily damaged.

In order to confirm the effect of the method of the present invention, the inventors investigated two cases in which the surface layer of the fluororesin was formed using a single compound such as FEP as in the prior art (Comparative Examples 1 and 2), and in the case in which the surface layer of the fluororesin was formed using a single compound such as FEP as in the prior art (Comparative Examples 1 and 2). Although the fluororesin layer is a composition consisting of multiple types of fluororesins, a comparative experiment was conducted for cases where the blending ratio requirements of this invention were not met (Comparative Examples 3 and 4). , these comparative examples are listed. However, for each of these comparative examples, the material, diameter d and length of the core 1, the material and wall thickness of the base layer 2,
t ₁ , the method of applying the single fluororesin or the fluororesin composition, the thickness t ₂ of the surface layer 3, and the diameter D of the product roll after polishing are the same as in each of the examples described above. Further, the materials of FEP and PTFE in the control example are the same as those described in each of the above-mentioned Examples.

Control Example 1 FEP alone was used as the material for the surface layer 3. The firing temperature was 290°C and the firing time was 30 minutes.

Control Example 2 PTFE alone was used as the material for the surface layer 3. The firing temperature was 380°C and the firing time was 30 minutes.

Control Example 3 As the material for the surface layer 3, a fluororesin composition consisting of 45 parts of FEP and 55 parts of PTFE was used. The number of times the composition was applied and fired and the firing conditions each time were the same as in Example 1 above.

Control Example 4 As a material for the surface layer 3, a fluororesin composition consisting of 97 parts of FEP and 3 parts of PTFE was used. The number of times the composition was applied and fired and the firing conditions each time were the same as in Example 1 above.

Below, the test results for each example and each control example listed above are described.
Since the cracks were not recognized, it was installed in the copying machine and
When we conducted a 50,000 sheet feeding test using 25 sheets, there was no offset, and the scratches on the roller surface caused by the separation claws were approximately 1 to 2 μm in depth, and clear images were obtained to the end. .

On the other hand, the one obtained in Control Example 1 had cracks on the surface layer, and was installed in a copying machine and
When we conducted a paper feeding test with 25 sheets, offset occurred after approximately 3,000 sheets, and the depth of the damage caused by the separation claws, etc.
It was about 5μ. The product obtained in Comparative Example 2 could not withstand the paper passing test from the beginning because the silicone rubber of the base layer was thermally degraded. Next, the material obtained in Control Example 3 was made from unmelted PTFE.
This is thought to be due to an excessive proportion of the surface layer, but the mechanical strength of the surface layer as a whole is insufficient, and when it was installed in a copying machine and a paper passing test was conducted at a rate of 25 sheets per minute, approximately 2000 sheets were damaged due to separation claws, etc. occurred, and its depth was approximately 5μ. In addition, the product obtained in Control Example 4 was installed in a copying machine and subjected to a paper passing test at a rate of 25 sheets per minute, which is thought to be due to the strong characteristics of FEP, which has a low softening point. The depth of the trauma caused by the separated nails, etc. is approximately 4μ.
It was hot.

(Effects of the Invention) Thus, according to the present invention, the silicone rubber that is the base layer of the roller does not deteriorate, so it has excellent elasticity, the surface layer of the fluororesin does not have any cracks, it is resistant to multiple trauma caused by separation nails, etc. It is possible to provide an excellent toner image fixing roller that can withstand repeated toner fixing operations and produce clear images.

[Brief explanation of drawings]

Fig. 1 is an axial sectional view of an example of a fixing roller manufactured by the method of the present invention, Fig. 2 is a sectional view of the surface layer after baking and formation on the base layer, and Fig. 3 is a sectional view of the surface layer of Fig. 2 after polishing. , FIG. 4 is a cross-sectional view of the case where the surface layer is formed into three layers in an embodiment of the method of the present invention, FIG. 5 is a cross-sectional view of the surface layer after polishing the peripheral surface of the surface layer of FIG. FIG. 2 is an enlarged cross-sectional view of the inside of the surface layer formed by the invention method. 1 is a core metal, 2 is a base layer, and 3 is a surface layer.

Claims (1)

[Claims] 1. 50 out of 100 parts for a base layer 2 of a constant thickness made of silicone rubber molded and coated on a core metal 1 of a constant diameter.
A fluororesin composition consisting of ~95 parts of a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP) and the remainder of polytetrafluoroethylene (PTFE) is fired and coated at 270 to 310°C, and this fired coating is applied to multiple layers. A method for manufacturing a toner image fixing roller, which comprises polishing the circumferential surface after repeating the process several times to form a surface layer 3 of a constant thickness on the base layer 2 with a plurality of layers made of fluororesin.