JPH0594106A - Elastic roller - Google Patents

Abstract

PURPOSE:To produce the elastic roller which has a smooth surface and can uniformly fix a toner. CONSTITUTION:The siloxane of a low mol.wt. to be incorporated into an elastic material layer 4 consisting of silicone rubber is previously removed from the silicone rubber to decrease the content of the siloxane of the low mol.wt. of n<=20 expressed by -(Si(CH3)2-O)-n to <=0.01wt.%. Or the siloxane of the low mol.wt. is evaporated by heating the siloxane for a long period of time at a low temp. at the time of vulcanizing the silicone rubber. The siloxane of the low mol.wt. which is liable to evaporate at the time of forming a fluororesin film of the outermost layer 5 is prevented from existing therein in this way and, therefore, bubbles are not infiltrated into the outermost layer 5 and consequently, the generation of recessed parts in the outermost layer is obviated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller for a laser printer, an electronic copying machine or the like, and more particularly to a roller used in a toner fixing section.

[0002]

2. Description of the Related Art Conventionally, with the spread of electronic copying machines and laser printers, downsizing and weight reduction of equipment have been achieved. Correspondingly, the toner fixing portion of these equipments has also been downsized and low in hardness. Is required. The toner fixing unit is provided with a heating roller provided with a heater for melting the toner therein, and a pressure roller for pressing the sheet to the heating roller, and fixes the toner on the sheet. These fixing rollers have good thermal conductivity, heat resistance, and stability of paper passing, so a nip width must be secured, and a roller formed of a single layer of silicone rubber has a paper passing property, Satisfactory surface smoothness and durability were not obtained.

Therefore, there is used a roller having a multi-layer structure in which an elastic body is formed on a cored bar, and an outermost layer having good releasability from a toner having a small friction coefficient is provided on the elastic body. To make a roller with a multi-layered structure, a heat-shrinkable tube as the outermost layer is attached to the inside of a cylindrical mold, a cored bar is placed in the center, and liquid rubber is injected between the cored bar and the tube. There has been a method for producing by calcination and vulcanization for all (JP-A-1-219781, JP-A-1-278315, and JP-A-1-278316). However, when such a device is used, skill is required at the time of setting a mold and work efficiency is poor.

Further, after vulcanizing and adhering silicone rubber, fluororubber or the like to the core metal to form an elastic body, the surface is ground and a dispersion of fluororesin or the like is applied to the outermost layer through a primer, There has also been a method of forming a fluororesin layer having good releasability from the toner by firing. In particular, a roller that uses silicone rubber as the elastic body and has a fluororesin layer as the outermost layer has high image quality and good thermal response, so it has good fixing properties during continuous paper feeding, and also has durability, so it is often used. It had been.

[0005]

However, there are cases in which fine recesses are formed in the surface layer of the roller having the outermost fluororesin layer formed thereon. In the recessed portion, the toner did not fuse to the paper passing and a part of the copy was missing. Further, if the concave portion becomes larger, the separation claw that removes the paper passing on the roller from the roller may be caught in that portion and may damage the roller.

The present invention has been made to solve the above-mentioned drawbacks, and the outermost fluororesin layer surface layer has high smoothness, uniform toner fixing, and high-quality toner fixing can be obtained. Moreover, it is an object to provide an elastic roller having durability.

[0007]

In order to achieve the above object, an elastic roller of the present invention comprises an elastic layer made of silicone rubber on a core metal, and a fluororesin coated on the elastic layer. in the elastic roller having an outer layer, the silicone rubber is _{- (Si (CH 3) 2} -O) - n (n ≦ 20)
The content of the low molecular weight siloxane represented by is 0.01 weight percent or less.

[0008]

[Function] The content of low molecular weight siloxane contained in the silicone rubber forming the elastic layer is reduced. Since the low-molecular weight siloxane component, which is likely to be volatilized, is reduced in amount, the siloxane is not vaporized and mixed in the fluororesin layer as bubbles due to heating when forming the outermost fluororesin layer. Therefore, since there is no generation of low-molecular-weight siloxane that is mixed as bubbles in the fluororesin layer, a concave portion is not formed, and an elastic roller having a smooth surface layer can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the elastic roller of the present invention is applied to a heating roller of an electronic copying machine will be described with reference to the drawings. Figure 1
As shown in FIG. 3, the elastic roller 1 has an elastic layer 4 and an outermost layer 5 on a core metal 3 into which a heater 2 is inserted.

The cored bar 3 is selected from materials having good thermal conductivity for efficiently transmitting the heat of the heater 2 provided inside and good adhesion to the elastic body layer 4 provided on the outer periphery, such as iron and aluminum. To be done. The elastic body layer 4 provided on the cored bar 3 is formed of silicone rubber having good thermal conductivity and appropriate elasticity. The elastic layer 4 made of silicone rubber is formed on the cored bar 3 by applying a primer that promotes adhesion with the silicone rubber onto the cored bar 3 and winding unvulcanized silicone rubber, or by liquid at room temperature. Liquid silicone rubber such as condensation reaction type silicone rubber (RTV) or addition reaction type silicone rubber (LTV) is cast into a cylindrical mold and vulcanized at room temperature or by heating to be coaxial with the cylindrical mold. It may be provided on the outer periphery of the fixed core metal 3.

Further, the outermost layer 5 provided on the outer periphery of the elastic layer 4 is made of fluororesin. The fluororesin is heat resistant, does not deteriorate due to heat, and has a small friction coefficient, so that it has excellent releasability from the toner. Therefore, it is preferable as the outermost layer of the heating roller because of its excellent durability. Perfluoroalkoxy resin (PF
A resin) and polytetrafluoroethylene resin (PTF
E resin) is applied. These fluororesins are applied with dispersion dispersed in a solvent on the surface of the silicone rubber formed on the cored bar 3 and baked by heating to form the outermost layer 5 of the elastic roller 1.

The silicone rubber forming the elastic layer 4 of the elastic roller 1 is [-Si (CH ₃ ) ₂ -O].
-] X is a polydimethylsiloxane vulcanized to have a network structure and has rubber elasticity over a wider temperature range than other rubbers, but at the same time-(S
_{i (CH 3) 2 -O)} - containing low molecular weight siloxanes represented by _n. Such a siloxane has a lower molecular weight and is more likely to be vaporized, and is vaporized during heating during formation and during secondary vulcanization of the silicone rubber. Further, after that, the outermost layer 5 is vaporized even when it is formed by coating and baking the fluororesin dispersion, and is mixed into the fluororesin as bubbles.

The inventors of the present invention have found that when siloxane is mixed in the fluororesin as air bubbles, recesses are formed on the surface of the elastic roller, the toner fixing is not uniform, and high-quality copying is not performed. As a method of preventing the inclusion of air bubbles, there is a method of using a low amount of siloxane mixed in the raw material silicone rubber in advance, or a method of adjusting the heating during vulcanization of the silicone rubber.

As a method of selecting the silicone rubber as a raw material, the amount of low molecular weight siloxane which is mixed in the silicone rubber and which is easily vaporized at a low temperature is reduced. In particular,-(Si (C
The content of H ₃ ) 2-O) _-n in which n ≦ 20 of low molecular weight siloxane is 0.01 weight percent or less. By setting the content of siloxane of n ≦ 20 to 0.01% by weight or less, the formation of the concave portion in the outermost layer is eliminated.

More preferably, the outermost layer 5 does not have any recess by setting the content of siloxane with n ≦ 10 to 0.005% by weight or less. Further, as a method for adjusting the vulcanization heating of the silicone rubber, the secondary vulcanization heating is performed at a low temperature for a long time, and the low-molecular-weight siloxane that is easily vaporized during the vulcanization heating of the silicone rubber is vaporized and evaporated, It cures by increasing the degree of crosslinking of dithymel siloxane, which is the active ingredient of silicone rubber. The heating temperature and heating time differ depending on the thickness of the elastic layer and the outermost layer. It may be selected appropriately.

[0016] _{<Example> - (Si (CH 3)} 2 -O) - n n a
A silicone rubber having a low molecular weight siloxane content of ≤20 and a content of 0.01% by weight or less is formed to a thickness of 0.25 mm, and a fluororesin dispersion is applied so that the outermost layer has a thickness of 20 μm. After heating for an hour, an elastic roller was obtained. A good and smooth roller was obtained without the occurrence of roller recesses (depth of 200 μm or more).

As a comparative example, the content of-(Si (CH ₃ ) _2- O) _-n of low molecular weight siloxane of n≤20 is 0.05 to.
0.10 weight percent silicone rubber and 0.01
Similar elastic rollers were obtained with .about.0.05 weight percent silicone rubber. The defective fixing rates due to the generation of the concave portions of the roller were 20% and 5%, respectively. Further, a fluororesin was applied so that the elastic layer had a thickness of 0.5 mm and the outermost layer had a thickness of 20 μm, followed by heating and vulcanization at 200 ° C. for 20 hours. Siloxane is hardly detected at n ≦ 13. Similarly, a fluororesin was applied so that the elastic layer had a thickness of 0.25 mm and the outermost layer had a thickness of 20 μm, and then vulcanized by heating at 200 ° C. for 8 hours. The detected siloxane is hardly detected when n ≦ 13. The results are shown in Figure 2.

As a comparative example, a fluororesin was applied so that the elastic layer had a thickness of 0.5 mm and the outermost layer had a thickness of 20 μm.
It was heat vulcanized at 0 ° C. for 4 hours. Siloxane with n ≦ 13 was detected as shown in FIG. Similarly, the elastic layer is 0.25
After the fluororesin was applied so that the outermost layer had a thickness of 20 μm, the heat vulcanization was not performed. Siloxane with n ≦ 13 was detected as shown in FIG.

Thus, by prolonging the vulcanization time when the silicone rubber is vulcanized to form the elastic body, all the low molecular weight siloxanes that are easily vaporized in the silicone rubber are evaporated and vaporized. There is no low molecular weight siloxane that is vaporized during the formation of the fluororesin film as the outer layer, and therefore, bubbles are not mixed in the outermost layer. for that reason,
An elastic roller having a smooth surface can be obtained without forming a recess in the outermost layer.

[0020]

As is clear from the above description, according to the elastic roller of the present invention, the low molecular weight siloxane contained in the silicone rubber forming the elastic layer is removed from the silicone rubber in advance. Alternatively, since it is vaporized during vulcanization and evaporated from the roller, vaporized siloxane is not mixed as bubbles in the outermost fluororesin. For this reason, the toner is fixed uniformly on the surface without forming a recess in the outermost layer, so that an elastic roller having a long life can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an elastic roller of the present invention.

FIG. 2 is a diagram showing the amount of siloxane contained in one example shown in FIG.

[Explanation of symbols]

 1 ………… Elastic roller 3 ………… Core bar 4 ………… Elastic layer 5 ………… Outermost layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area // B29K 83:00

Claims (1)

[Claims] 1. An elastic roller having an elastic layer made of silicone rubber on a core metal and an outermost layer formed by coating a fluororesin on the elastic layer, wherein the silicone rubber is-(Si (CH ₃ ) An elastic roller characterized in that the content of low molecular weight siloxane represented by _2- O) _-n (n≤20) is 0.01% by weight or less.