JPH063398Y2 - Pressure roller for fixing - Google Patents

Description

[Detailed Description of the Invention] [Field of Use of the Invention] This invention is to impregnate a fixing roller of a heat fixing device in an electrostatic recording apparatus such as an electrophotographic copying machine, a computer OCR, and a facsimile with a silicone oil into a covering rubber layer. And a fixing pressure roller.

"Problems to be solved by conventional techniques and devices" Generally, in a heating and fixing device used in an electrophotographic copying machine, a recording material such as paper in which toner is electrostatically adsorbed on the surface between a heating roller and a pressure roller. By passing
The toner is heated and fixed on the recording medium by receiving heat and pressure from both rollers. A roller coated with heat resistant silicone rubber is generally used as the fixing pressure roller.

On the other hand, in heat fixing devices, sticky substances such as toner adhere to the surface of the heating roller (offset phenomenon)
To prevent this, silicone oil is generally applied to the surface as a release agent. Although the silicone rubber-fixing roller coated with silicone oil has sufficient releasability for toner, The silicone rubber layer swells due to oil, the outer diameter of the roller changes significantly, the strength decreases, and the adhesive strength with the roller core metal also decreases, resulting in uneven roller surface and uneven fixing. However, there are various problems such as the occurrence of wrinkles, the loss of roundness, wrinkles, curls, and curved feed on the recording paper, and the peeling of the silicone rubber from the core metal.

Therefore, in recent years, in order to improve such a problem, a so-called oilless fixing mechanism which does not supply silicone oil is used, and silicone oil is preliminarily added and impregnated with silicone oil to gradually exude the silicone oil during use. As a result, a method of maintaining the releasability of the toner is adopted.

As the silicone rubber in this case, since vulcanizable silicone rubber (HTV) itself has poor releasability, even if silicone oil is added, sufficient releasability cannot be obtained. Room temperature vulcanizing type silicone rubber (RTV) is used, but since this room temperature vulcanizing type silicone rubber has low strength, it can be used as a fixing pressure roller with a sufficient life due to abrasion of the recording material passing through. There was a problem of not having.

[Means for Solving Problems] In order to solve the above-mentioned conventional problems, this device has a viscosity of 50%.
The present invention proposes a fixing pressure roller in which the outer circumference of a cored bar 2 is covered with a rubber layer 3 made of an additive type liquid silicone rubber containing 3 to 20 parts of cs to 60,000 cs of dimethyl silicone oil.

"Function" Additive liquid silicone rubber (LSR) newly developed in recent years.
Is itself in the middle of HTVRTV in terms of strength, and in terms of releasability, it is also in the middle of HTV and RTV.
By adding silicone oil to the fixing pressure roller, the fixing pressure roller is superior in strength to RTV added with silicone oil, and in terms of releasability, superior to HTV in overall performance.

By blending 3 to 20 parts of dimethyl silicone oil having a viscosity of 50cs to 60,000cs into the rubber layer 3 of the LSR, the outer diameter shrinkage of the roller is suppressed, paper wrinkles and fixing unevenness are reduced, and the mold releasability is good. A roller is obtained.

"Embodiment" An embodiment of the present invention shown in the drawings will be described below.
The fixing pressure roller 1 has 3 to 20 dimethyl silicone oil having a viscosity of 50cs to 60,000cs on the outer periphery of the metal core 2.
It is formed by coating a rubber layer 3 made of partially added liquid silicone rubber (LSR, for example, SE6705 manufactured by Toray Silicone Co., Ltd.).

Additive type liquid silicone rubber (LSR) consists of two components, a base and a curing agent that are liquid at room temperature.When mixing these, add silicone oil and mix them together. A roller is molded by pouring into a mold and heating.

If a large amount of silicone oil is added, it will seep to the surface of the roller during use of the fixing roller and adhere to recording media such as paper.As the number of uses increases, the outer diameter of the roller will gradually decrease due to the loss of silicone oil. Become. And, in general, when the initial outer diameter is reduced by about 2.5% or more,
Since wrinkles are generated on the recording paper, or defects such as uneven fixing occur, which makes it unusable for use.To prevent this defect or delay its occurrence, use a silicone oil that suppresses the change in outer diameter of the roller to less than 2.5%. Needs to be added.

As the silicone oil, one having excellent stability at high temperature is preferable, and dimethyl silicone oil suitable for this condition is suitable. However, the viscosity is high or low depending on the size of the molecular weight. It is not preferable because the outer diameter shrinks quickly and in a short period of time, and conversely, when the viscosity is too high, the exudation from the rubber layer 3 is small and sufficient releasability cannot be obtained, which is not preferable.

Figure 2 shows the result of measuring the escape rate when the viscosity of the oil was changed. As is clear from this result, the escape rate increases as the viscosity decreases, especially 50
It can be seen that the ejection speed increases sharply when it becomes less than cs. Also,
It was confirmed that with a high-viscosity oil of 60,000 cs or more, excessive bleeding phenomenon appears on the surface of the rubber layer 3 and the moldability becomes extremely poor.

On the other hand, if the amount of oil to be added is too large, the strength of the rubber layer 3 will be reduced and the abrasion resistance will be poor, and if it is too small, the amount of oil that will exude will be insufficient and releasability will be poor. It is not preferable because it becomes worse and the life of the roller is shortened in any case.

FIG. 3 shows the results of measuring the removal rate from the rubber layer 3 when the addition amounts of dimethyl silicone oil and phenyl silicone oil were changed. It can be seen that the release rate increases with increasing amount and that the release rate of phenyl silicone oil is significantly higher than that of dimethyl silicone oil.

Furthermore, Fig. 4 shows the relationship between the addition amount and tensile strength when silicone oil is added to general HTV, LSR, and RTV. It can be seen that the strength decreases as the addition amount increases in all cases. . The broken line indicates the strength limit of the roll.

"Comparative Experimental Example" An actual pressure roller was prototyped by changing the addition amount of dimethyl silicone oil to the addition type liquid silicone rubber, and it was installed in a commercially available copying machine adjusted to a predetermined temperature and pressure and tested. The results shown in FIG. 5 were obtained.

The vertical axis in FIG. 5 is the achievement rate with 100% when the target number of copies is 200,000.

As a result, when the amount of oil added was 3 parts or less, the releasability was insufficient and the achievement rate was 80% or less, and when it was 20 parts or more, the outer diameter contraction due to the oil loss became remarkable and the wrinkle of the paper wrinkled. Outbreaks increased and the achievement rate was 80% or less.

From the above results, it was confirmed that the fixing roller made of the additive type liquid silicone rubber containing 3 to 20 parts of dimethyl silicone oil having a viscosity of 50 cs to 60,000 cs satisfies various conditions.

"Effect of device" As described above, according to this device, the outer periphery of the core metal is coated with the rubber layer made of the additive type liquid silicone rubber containing 3 to 20 parts of dimethyl silicone oil having a viscosity of 50cs to 60,000cs. As a fixing pressure roller, it is possible to obtain a pressure roller that is excellent in releasing property and abrasion resistance and has less wrinkles and uneven fixing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between oil viscosity and escape rate, and FIG. 3 is an oil addition amount and escape rate. 4 is a diagram showing the relationship between the amount of oil added and the tensile strength, and FIG. 5 is a diagram showing the results of experiments using a fixing roller molded by changing the amount of oil added. 1 ... Pressure roller for fixing, 2 ... Core metal, 3 ... Rubber layer.

Claims (1)

[Scope of utility model registration request] 1. A fixing pressure roller comprising a cored bar coated with a rubber layer made of an additive type liquid silicone rubber containing 3 to 20 parts of dimethyl silicone oil having a viscosity of 50 cs to 60,000 cs. .