JPH0565873B2 - - Google Patents

Description

Detailed Description of the Invention (Object of the Invention) The present invention relates to a roller having an elastic layer made of silicone rubber sponge among the fixing rollers of electronic copying machines and other electrophotographic machines that use toner as a printing medium. The basic purpose is to provide a material that has excellent releasability to toner, low surface hardness, and good outer diameter accuracy. A second object of the present invention is to provide a silicone rubber sponge roller with a skin layer that has excellent outer diameter accuracy. A third object of the present invention is to provide a fluororesin-coated silicone rubber sponge roller with excellent outer diameter accuracy.

Regarding the above-mentioned fixing rollers for electrophotographic cameras, those in which the surface of the sponge rubber is coated with silicone rubber such as condensation type silicone rubber have been widely used, but in recent years, the surface layer of the sponge layer has been A roller with a thin so-called skin layer of about 0.2 mm has been developed. Such sponge rollers with a skin layer generally have a mold with a cylindrical wall on the inside, and the core metal is coated with unfoamed peroxide-vulcanized silicone rubber using an extruder or the like, and this coating is then It can be produced by inserting and fixing a core metal into a mold, and then heating and vulcanizing the coating and foaming it at the same time. The roller thus obtained has a thin skin layer of silicone sponge rubber and thus has a low surface hardness, which is advantageous in that a wide nip width can be formed between the pair of rollers during the fixing operation. Moreover, such a sponge roller with a skin layer is advantageous in that it requires fewer production steps and has lower production costs than a roller in which non-foamed silicone rubber is coated and layered on sponge rubber.

However, according to the above-mentioned known production method for a roller with a skin layer, it is very difficult to provide a roller with good outer diameter accuracy, and the produced roller has poor releasability with respect to toner during fixing work. It is also significantly inferior to the previous conventional multilayer silicone rubber roller.

Regarding the fixing effect in electrophotographic machines, it is well known that the accuracy of the outer diameter of the roller has a significant effect on the occurrence of paper wrinkles and offset. We suspected that the reason why the outer diameter accuracy of the sponge rollers with which the layers were formed was generally poor was due to the means for generating air bubbles. That is, according to the conventional technology, a foaming agent that reacts with heat is added to silicone rubber, and the foaming is performed simultaneously with the vulcanization of the silicone rubber by heat. Use vulcanized silicone rubber. Since condensation type and addition reaction type silicone rubbers are liquid, foaming begins as soon as the foaming agent is mixed in, and the bubbles expand over time, making it difficult to control the pore size and making it difficult to obtain a suitable sponge. be. Thus, by using peroxide vulcanized silicone rubber as the elastic material of the skin layer sponge roller according to the prior art,
Although it is possible to obtain a sponge-like material containing a sufficient number of air bubbles, due to the large molecular weight of the elastic material, it is difficult to orient the methyl groups in one direction on the surface of the roller, and the material is non-fluid. Therefore, it is difficult to add silicone oil to prevent offset in advance.

On the other hand, a roller with a silicone rubber sponge layer coated on the surface with a fluororesin has recently been proposed, but such a fluororesin-coated sponge roller is highly flexible and has better releasability to toner than the above-mentioned skin. This is because it is even better than a layered sponge roller. However, such a fluororesin-coated sponge roller has not yet been put into practical use because it has been extremely difficult to provide the above-mentioned fixing roller for an electronic copying machine with the necessary outer diameter accuracy. That is, according to the conventional proposal, a heat-shrinkable fluororesin tube is fitted into a sponge roller that has been ground and shaped to the required diameter.
This tube is fixed to the sponge layer by heating from the outside, or silicone rubber is injected between the fluororesin tube fitted on a sponge roller and the sponge layer, and the injected silicone rubber is vulcanized. The fluororesin tube is bonded to the sponge layer, but with the former method, it is difficult to shrink the entire circumference evenly, and with the latter method, the sponge layer deforms unevenly due to the injection pressure of silicone rubber, resulting in This is because only those with poor outer diameter accuracy can be obtained.

That is, the present invention aims to reduce the outer diameter required when producing a fixing roller that has both flexibility of the roller surface and good releasability for toner, such as a silicone rubber sponge roller with a skin or a silicone rubber sponge roller coated with a fluororesin. Its purpose is to provide a means to ensure accuracy.

(Structure of the Invention) FIG. 1 is a conceptual diagram of an example of an apparatus used to implement the method of the present invention, in order to explain the method. Referring to this FIG.
A method of producing a roller having a sponge layer by vulcanization molding an elastic material interposed between the cylindrical wall 11 and the cylindrical wall 11 has been conventionally known. contains microbubbles forcibly mixed into the outside of the mold 1, that is, in the illustrated example, in the liquid feed pipe 3 connected to the inside of the mold 1 through the through hole 13 of the end plate 12 of the mold 1. This is a method for producing a fixing roller for an electrophotographic machine, characterized in that a liquid addition reaction type silicone rubber 4 is injected into a mold 1. However, to prevent the generation of bubbles in the illustrated example, liquid addition reaction type silicone rubber is fed into the liquid feed pipe 3 and passed through at a slow speed, and high-pressure air is passed through the element filter 5 with fine bubbles provided in the liquid feed pipe 3. Alternatively, this is accomplished by releasing an inert gas under high pressure.

That is, according to the present invention, the elastic material charged into the mold contains air bubbles that are forcibly mixed in beforehand outside the mold, and the diameter and amount of the air bubbles are determined by the element filter 5.
By adjusting the average diameter of the bubbles, the amount of air supplied, or the mixing speed, it can be freely selected within a fairly wide range. Liquid addition reaction type silicone rubber is thus vulcanized and hardened in the mold, but since the time to complete vulcanization is relatively short, there are fewer bubbles escaping or merging and expanding, making it an excellent product. In addition to obtaining a sponge with soft elasticity,
A thin skin layer 8 (see FIG. 2) of about 0.1 to 0.2 mm is formed on the surface of the sponge layer 7 of the roller taken out from the mold. Skin layer 8 like this
The sponge roller has a large flexibility in its elastic part, so even if the inner surface of the cylindrical wall of the molding mold is formed into a drum shape or a knob shape, it is easy to pull out the molded product and remove it from the mold. or inverted crown type rollers can be easily obtained.

According to the above-mentioned conventional technology for producing a sponge roller with a skin layer, non-flowable peroxide vulcanized silicone rubber is used as the elastic material,
Since a foaming reaction takes place inside the mold, it was inevitable that the bubbles would expand unevenly when the mold was removed, resulting in uneven changes in roller diameter. According to the company, there are no such drawbacks. Furthermore, according to the prior art, since the molecular weight of the elastic material is relatively small, the orientation of the methyl groups during molding is good, and therefore the releasability of the roller surface of the molded product from the toner is very good. In addition to this, since the elastic material is liquid,
Because silicone oil can be added in advance for molding, even though the roller surface is formed by a thin skin layer, the separation is greater than that of a multi-layer roller coated with non-foamed silicone rubber as the surface layer. It is possible to provide products with significantly superior moldability.

In addition, according to the method of the present invention, a fluororesin tube is fitted to the cylindrical wall of a mold, and an elastic material made of liquid addition-reactive silicone rubber containing microbubbles forcibly mixed in outside the mold is placed in the mold. By injecting the silicone rubber into contact with the inner surface of the fluororesin tube and vulcanizing it, the silicone rubber in contact with the inner surface of the fluororesin tube becomes thin and bubble-free, similar to the case of the silicone rubber sponge roller with a skin layer described above. A skin layer 8 is generated, and as a result of this skin layer being adhered to the fluororesin tube, a sponge layer with high outer diameter accuracy is obtained, thus ensuring a fluororesin-coated silicone rubber roller with high outer diameter precision. It becomes possible to produce

Example 1 Liquid addition reaction silicone rubber (Shin-Etsu Chemical Co., Ltd.)
KE1330 manufactured by Co., Ltd.) is passed through the liquid sending tube 3 having a diameter of 50 mm at a flow rate of 25 ml/sec. Average pore diameter in liquid pipe 3 is 50μ
If a sintered metal element filter 5 having micropores of 1 is provided, and air is discharged at a pressure of 3 kg/cm ² through an air supply hose 6, countless microbubbles will be generated during the liquid supply. The cylinder wall 11 of the iron mold has an inner diameter of 25 mm and a length
250 mm, the inner surface roughness R _Z = 1μ, and the diameter of the core metal 2 inserted therein is 15 mm. Apply a primer to core metal 2 in advance. The elastic material containing air bubbles is injected into the mold 1 from the liquid feed pipe 3 through the through hole 13 and brought into contact with the cylindrical wall 11 . After injection is completed, heat the mold, perform a vulcanization reaction at 150℃ for 15 minutes, and remove the mold.The outer diameter is 25 mm, the length is 250 mm, the thickness of the sponge layer 7 is 5 mm, the thickness of the skin layer 8 is 0.2 mm, and the surface is A roller with roughness R _Z = 1μ is obtained.

Comparative Example 1 A stainless steel mandrel with the same diameter as in the above example was coated with peroxide-vulcanized silicone rubber (KE904 manufactured by Shin-Etsu Chemical Co., Ltd.) containing a foaming agent using an extruder, and heated and vulcanized. After foaming, the surface is ground to form a 4mm thick sponge layer. Next, this sponge layer was coated with addition reaction type silicone rubber (XE15-543 manufactured by Toshiba Silicone Rubber Co., Ltd.) that does not contain a foaming agent, heated and vulcanized, and the coated surface layer was ground to a thickness of 1 mm. , to obtain a multi-layer roller with sponge as the core layer.

Control example 2 A mandrel coated with the same foaming agent-containing silicone rubber as in control example 1 using an extruder was made with an inner diameter of 25 mm and a length of 370 mm.
The inner surface of the cylindrical wall is inserted into a mold made of iron polished to a roughness of R _Z = 1 μm, and heated and vulcanized to form a skin layer with a diameter of 25 mm, a length of 250 mm, and a thickness of approximately 0.2 mm. Get a sponge roller. The surface roughness of the skin layer is the same as in Example 1.

Comparing the values measured for Example 1 and Control Example below, in terms of surface roughness, Example 1 and Control Example 2 have R _Z = 1 μ, and Control Example 1
R _Z =3 to 5μ, and as for the surface hardness, Example 1 and Control Example 2 had an Asker hardness of 15°, whereas Control Example 1 had an Asker hardness of 30°.
Regarding the outer diameter accuracy, the difference in outer diameter between Example 1 and Control Example 1 is 0.1 mm or less, while that of Control Example 2 is 0.6 mm, which is a significant difference. Comparative Example 1 was the same as Example 1 when measured at room temperature, but when it was installed in an electronic copying machine and paper was fed, there was no paper wrinkles in Example 1, but in Control Example 1, the paper was often wrinkled. If you see paper wrinkles, it is control example 1.
It is thought that the outer diameter accuracy deteriorates due to temperature rise, which, together with the high surface hardness, affects the paper passing process. Regarding the occurrence of offset during sheet feeding and fixing, in Comparative Example 2 offset occurs after 2000 sheets, whereas in Example 1 and Control 1 no offset occurs even after 70000 sheets are exceeded. In the examples listed here, offset prevention oil is not added to the elastic material, but it is clear that the offset prevention effect is further improved by adding this oil.

Example 2 In Example 1 described above, a PFA tube (manufactured by Gunze Co., Ltd.) having a thickness of 50 μm, a length of 250 mm, and an outer diameter of 24 mm was fitted into the cylindrical wall 11 of the mold 1 in advance. Reference numeral 9 in FIG. 1 indicates this PFA tube. however,
The inner surface of the PFA tube 9 is prepared in advance with an etching solution (Tetra Etch, manufactured by Junkosha Co., Ltd.).
The mold 1, the mandrel 2, the liquid addition reaction type silicone rubber, the flow rate, the sintered metal element filter 5, and the pressure of the air released by the air supply hose 6 are the same as in Example 1 above.

(Effects of the Invention) Thus, according to the method of the invention, since the surface hardness of the roller is extremely low, comparable to that of a simple sponge rubber roller, it is possible to secure a large nip width for the roller, which is necessary to obtain a clear fixed image. A fixer for electrophotographic machines that maintains good cylindricity even when the temperature rises when using the roller, so there is no paper wrinkles when passing the paper, and it has extremely good releasability to toner, making it extremely effective in preventing offset. It is possible to produce rollers. Moreover, the method of this invention has a simpler process and lower production costs than a double-covered roller whose sponge feeding surface is coated with a non-foamed silicone rubber layer. However, with the conventional method, only extremely poor outer diameter precision could be obtained and it could not be put to practical use, but with the method of the present invention, it is possible to produce a roller with high outer diameter precision comparable to the multilayer roller shown in Comparative Example 1 above. This possibility is a remarkable effect of the method of this invention.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of an example of an apparatus used to carry out the method of this invention, Fig. 2 is a cross-sectional view perpendicular to the axis of a silicone rubber sponge roller with a skin layer produced by the method of this invention, and Fig. FIG. 2 is an axial cross-sectional view of a resin-coated silicone rubber sponge roller. 1 is a mold, 11 is a cylindrical wall, 12 is an end plate, 13 is a through hole, 2 is a mandrel, 3 is a liquid feed pipe, 4 is an elastic material, 5
1 is an element filter, 6 is an air pipe, 7 is a sponge layer, 8 is a skin layer, and 9 is a fluororesin coating.

Claims (1)

[Scope of Claims] 1. A mandrel is inserted and fixed in a mold having a cylindrical wall formed on the inner surface, and an elastic material of silicone rubber interposed between the mandrel and the cylindrical wall is vulcanized and molded to form a sponge layer. In the method for producing a roller having a roller for an electrophotographic camera, the elastic material is formed by injecting into the mold a liquid addition-reactive silicone rubber containing microbubbles that is forcibly mixed in outside the mold. Production method of fuser roller. 2. The method for producing a fixing roller for an electrophotographic apparatus according to claim 1, characterized in that the elastic material is brought into contact with the cylindrical wall. 3. The method for producing an electrophotographic fixing roller according to claim 1, characterized in that a fluororesin tube is fitted into the cylindrical wall and the elastic material is brought into contact with the inner surface of the fluororesin tube.