JPH01300281A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent such phenomena as twinging of paper to a pressure roller and an offset, and blurring of a line image by forming a surface layer of one roller by an elastic body, adding a surface active agent of a fluorine compound into the elastic body, earthing a mandrel and quickening the attenuation of the potential. CONSTITUTION:The outside surface of a mandrel 1A having electric conductivity is covered with a resin layer 1B having a heat resistance and a mold releasing property of a PFA teflon resin, and with respect to a fixing roller 1, a pressure roller 3 is driven and rotated. As for the pressure roller 3, an elastic body layer 3B having a heat resistance and a mold releasing property such as silicone rubber, fluorine rubber, etc. is formed on a mandrel 3A having electric conductivity, and in this elastic body layer 3B, a surface agent 3B' of a fluorine compound is dispersed and contained, and its content percentage is set to 0.003-3wt.%. On the other hand, to a mandrel 3B of the pressure roller 3, a plate spring 15 comes into contact as a member having electric conductivity for a ground. In such a way, by suppressing an electrification of the pressure roller, twining of paper being an image carrying material, blurring of a line image, an offset of a toner, etc., are not generated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is utilized in the field of fixing technology in electrophotographic devices or electrostatic recording devices, and is particularly applicable to fixing images with unfixed toner images between a pair of rollers. The present invention relates to a fixing device that clamps and conveys a carrier material and fixes it under pressure.

[Prior Art] Conventionally, this type of fixing device includes a fixing roller and a pressure roller that is in pressure contact with the fixing roller and rotates as a result of the fixing roller.

The fixing roller is formed by coating a hollow core metal such as aluminum or iron with a layer of a material with good mold releasability such as PTFE, PFA, or silicone rubber. Further, the fixing roller is provided with a heater such as a halogen lamp, if necessary, to raise the temperature of the surface of the fixing roller to a temperature suitable for fixing. Further, in many cases, a sensor is used to control the surface temperature of the fixing roller to a set temperature.

Further, on the outer circumferential surface of the fixing roller, there are provided a xener for removing offset toner and paper dust, and a separating claw for preventing the image bearing material from being wrapped around the fixing roller.

On the other hand, the pressure roller is made of core metal such as iron or stainless steel.
The material is coated with an elastic layer having release properties such as silicone rubber. The pressure roller is pressed against the fixing roller by a spring or the like.

In this way, the image bearing material having the unfixed toner image is conveyed while being held under pressure by the fixing roller and the pressure roller, and the unfixed toner image is fixed under pressure.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional apparatus, when the paper serving as the image bearing material is passed through, the paper is charged to 2 kV or more due to frictional charging, for example, and as a result, the paper is There was a problem with it getting wrapped around the pressure roller. In addition, due to the electric field of the pressure roller, unfixed toner scatters and blurs the line image, and toner adheres to the surface of the constant zi roller, resulting in increased offset.

As a countermeasure to the above-mentioned problem, conventionally, a static elimination flange was brought into contact with a pressure roller to perform grounding static elimination.

However, this measure ``C'' cannot be said to be sufficient because the potential is only limited to about 1 to 2 kV, and the static elimination effect is limited, and an improvement has been desired.

[First Step to Solve the Problems] The present invention solves the above-mentioned problems and suppresses the charging of the pressure roller, thereby preventing wrapping of paper as an image bearing material, blurring of line images, and toner smearing. An object of the present invention is to provide a fixing device that does not generate offset or other problems.

In order to achieve the above object, the present invention provides a fixing device that pressurizes and fixes an unfixed toner image formed on an image bearing material 1- by sandwiching and conveying the image bearing material between a pair of rollers, at least one of the rollers. The roller has a surface layer consisting of an electrically conductive core metal and an elastic body, the elastic body containing between 0.003 and 3 percent of a fluorine-based surfactant, and the core metal is grounded via an electrically conductive member.

In addition, in order to achieve the item L1, in a fixing device that heats and fixes a toner image formed on an image carrier by sandwiching and conveying an image carrier between a pair of rollers, one of the rollers is The roller has an electrically conductive core and a surface layer of PFA covering the core; the other roller has a surface layer consisting of an electrically conductive core and an elastic body; The core bar is grounded via an electrically conductive member.

[Example] Hereinafter, the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a vertical cross-sectional view showing the general configuration of the fixing device of this embodiment. In the same figure, l is a fixing roller, and the fixing roller l is made of an aluminum, iron, stainless steel h9 electrically conductive core metal IA, and the outer surface of the core metal IA is coated with a resin layer IB having heat resistance and mold release properties of PFA. There is.

The fixed 6" roller l is pressed by a pressure roller 3 or a spring or the like (not shown) and rotates as a result of pressure. The pressure roller 3 is made of electrically conductive material such as iron or stainless steel. An elastic layer 3H having heat resistance and mold releasability such as silicone rubber or fluorine rubber is formed on F of the core bar 3A.This elastic layer 3B is coated with a fluorine-based surfactant 3B' or the like. It is dispersed and contained, and the content ratio is 0.00:3~3w
It is said to be L%.

Around the fixing roller l, there is a thermistor 4 that detects the temperature of the fixing roller l, a ripping claw 5 that separates the paper sheet 14, which is an image-bearing material, from the fixing roller l, and a parting claw 5 that contacts the fixing roller l and disassembles the surface of the fixing roller l. A cleaner 6 for cleaning the paper sheet 14, a human logite 11 for guiding the paper sheet 14 between the fixing roller l and the pressure roller 3, and the like are provided.

On the other hand, a plate spring 15 is in contact with the core metal 3B of the pressure roller 3 as an electrically conductive member for grounding.

The apparatus of this embodiment is composed of five or more parts, and after conducting experiments on each part under various conditions, a description will be given here showing specific numbers.

Experimental Example 1] The fixing roller L is 1325 mm in diameter, and the wall thickness is 1,8 mm.
A 25gm PFA coach ink is used on a 25mm aluminum cored pipe, and the pressure roller has a diameter of 10+nu.
A stainless steel core shaft with silicone rubber attached to the L end with a thickness of 5 mm was used. The hardness of this silicone rubber was 16° as a result of measuring a test piece based on the J15-A standard. Also, the surface of the fixing roller l
Heater 2 was controlled so that the temperature was around 0°C.

In the conventional example, the silicone rubber is the same as above, and the second
As shown by the broken line in the figure, the surface potential when used as a pressure roller is -2k due to friction with the paper serving as the paper sheet 14.
It becomes more than V. Therefore, in this experiment, fluorinated alkyl ester, which is a fluorine-based surfactant, was added to this silicone rubber at 0.00%. When the pressure was dispersed between f101wt$ and 0.3wL$, it was confirmed that the surface potential of the pressure roller 3 during sheet feeding decreased to below -1 kV, as shown by the solid line in FIG.

The solid line and the broken line shown in FIG. 2 show changes in the surface potential of the pressure roller over time, comparing changes in the surface potential of the pressure roller when one sheet is printed by the apparatus of the present invention and the conventional apparatus, respectively. As is clear from the figure, the effects of incorporating a fluorine-based surfactant into silicone rubber are: first, it can suppress the charging of the pressure roller due to friction between the paper and the pressure roller; The objective is to speed up the attenuation of the surface potential of the roller.

As a result, paper wrapping around the pressure roller no longer occurs, and the amount of toner accumulated in the cleaner 6 that is in contact with the fixing roller 1 is less than 1/10 compared to the conventional case, resulting in a reduction in offset. was confirmed. Furthermore, even when images are taken, blurring of line images no longer occurs.

The reason why a fluorine-based surfactant is used as a surfactant in the present invention is that it is more heat resistant than other surfactants. The surface temperature of the comb layer of the pressure roller is 110°C.
As a result, ordinary surfactants will decompose, or fluorine-based surfactants will not decompose and maintain their effectiveness.

Furthermore, in this experiment, we confirmed the static elimination effect of grounding the core metal of the pressure roller. As mentioned above, by mixing a fluorine-containing surfactant into the silicone rubber of the pressure roller, the frictional resistance of the silicone rubber decreases, and the cost of the band of the pressure roller also decreases. Therefore, it has been possible to reduce the offset by this alone, or by further grounding the core bar through an electrically conductive member, the amount of charge on the fixing roller can be further reduced, thereby reducing the offset.

Also, regarding the fixing roller, which is the other roller, PFA
By using a roller whose surface is coated with iron, it is possible to further prevent the toner from being offset to the fixing roller.

The following table shows PFA Teflon resin and PTFE for the fixing roller.
This is a comparison of actual prints to see the difference in anti-offset properties when used with a Teflon resin coating.

A in the table is a case where a fluorine-based surfactant is mixed into the silicone rubber of the pressure roller and the core of the pressure roller is grounded. B in the table is the case where ordinary silicone rubber was used for the pressure roller and it was not grounded.

Table Offset prevention (Note) 0. Δ and × are relative evaluations of anti-offset properties.

- As mentioned above, it is possible to further reduce the offset occurrence rate by mixing a fluorine-based surfactant into the pressure roller, grounding the core metal, and coating the surface of the ground roller with PFA. It is.

[Experimental Example 2] In the above-mentioned [Experimental Example 1], fluorinated alkyl ester was used as the fluorine-based surfactant, and in addition, perfluoroalkyl polyoxyethylene ethanol, perfluoroalkyl carboxylate, perfluoroalkylammonium, Perfluoroalkyl betaine, perfluoroalkyl amine oxide, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl phosphate ester, non-dissociable perfluoroalkyl compound, and EFTOll-EF122B manufactured by Mitsubishi Metals Corporation (product name)
hg.

It's also effective.

In addition, the dispersion ratio of the fluorine-based surfactant to the silicone rubber was set to 0.1wt$ in the above-mentioned [Experimental Example 1], or preferably between 0.003wt1 and 01wt$ (7). More preferably from 0.01wt$ to 0.1
wt,% is good.

The lower limit here was determined based on the effect of reducing surface tension, which is the main effect of surfactants. The reason for this is that the effects targeted by the present invention, which are the effects of lowering the surface potential and accelerating the attenuation of the surface potential, become more significant as the surface energy is lowered. Also, surface energy is correlated with surface tension. Therefore, based on FIG. 3, which shows the change in surface tension, the concentration required to obtain the desired effect of the present invention is determined.

For example, can it be said that an effect of 172 points or higher than the saturation level has a sufficient static elimination effect?
It can be seen that a surfactant concentration of about 1wt1 or more is sufficient. Furthermore, if 0.01wt1 or more is mixed, the surface tension will be lowered almost to its limit, and the static elimination effect will also reach its limit. Therefore, it is preferable to add the surfactant at a concentration of 0.003 wL$ or more, more preferably 0.01 wt$ or more.

Conversely, if too much surfactant is added, curing of the rubber will be inhibited, and this determines the upper limit of the amount added. From this, it has been found that the amount of surfactant to be added is preferably 0.0:Jwt$ or less, more preferably 0.1wt$ or less. In this case as well, by using a fixing roller whose surface was coated with PFA, it was possible to further reduce the occurrence of offset.

In addition, in this experimental example, if the ground of the pressure roller is applied to the core metal with a leaf spring, or if the bearing that receives the rotating shaft, which is a part of the core metal, is made of a material with a resistance of 1010 Ω・cm or less, the leaf spring can be used. It can be effectively used without setting up A7. Further, a bias voltage having a polarity opposite to the rubbing potential of the pressure roller may be applied to the bearing or the leaf spring to reduce the static elimination effect.

[Experimental Example 3] In the previous experimental example, a fluorine-based surfactant was added to the rubber of the pressure roller, and the surfactant may come off from the rubber after long-term use. For example, the above [Experiment Example 1]
However, when printing more than 100,000 sheets of 4-size paper, the surfactant tends to escape from the rubber, reducing the anti-offset and anti-wrapping effects.

Therefore, a fluorine-based surfactant was added to the silicone oil impregnated into the cleaning felt of the cleaner 6 as shown in Fig. 1, and the mixture was supplied to the surface of the pressure roller via the fixing roller. Good results were obtained that seemed to change the trend.

Specifically, a cleaner felt made of woven aromatic polyamide-imide fibers with a density of 0.15 g/cm:l was used with a thickness of 6 mm, a width of 10 [llff+], and a total length of 220 mm. In addition, dimethyl silicone oil (KF-96, 10,000c manufactured by Shin-Etsu Silicone Co., Ltd.)
s) was impregnated into this silicone oil, and 0.0.
0.6 g of fluorinated alkyl ester was added and applied to the fixing roller in an amount of about 0.5 mg per sheet of A4 size paper, and the felt was replaced after 4,000 sheets.

As a result, the surface potential of the pressure roller was maintained at 11 kV or more for more than 200,000 sheets, and the offset prevention effect and paper wrapping prevention effect were maintained.

In this case, a fluorinated alkyl ester may be used as the surfactant, or it may be selected from among the various fluorine-based surfactants listed in [Example 2] above.

Furthermore, the fluorine-based surfactant added to the silicone rubber of the pressure roller and the fluorine-based surfactant added to the silicone oil may be in a different combination.

In addition, the lower limit of the fluorine-based surfactant added to the silicone oil is 0, 11, for the same reason as the above experimental example.
13wt% or more, preferably 0.01
wL$ u)-Kayoi. Further, depending on the type of fluorine-based surfactant, the L limit may be determined depending on the type of fluorine-based surfactant that may cause gelation when added to silicone oil. 3w
Most fluorine-based surfactants did not gel silicone oils at t% or higher.

Furthermore, since fluorine-based surfactants are expensive, the less the better. In terms of effectiveness, a sufficient effect can be obtained even with 1wt, so for practical use it is preferably 0.00w
Between t% and 3wt1, more preferably 0.01wt$
This means that it should be between l wLX.

Alternatively, felt impregnated with silicone oil containing a fluorine surfactant may be brought into direct contact with the surface of the pressure roller 3. In this way, the fluorine-based surfactant can be efficiently supplied to the surface of the pressure roller. In this case as well, offset was further reduced by using a fixing roller whose surface was coated with PFA.

In the case of Ichikawa, including this experimental example, when the pressure roller has multiple rubber layers, it is sufficient to add the fluorine-based surfactant only to the outermost rubber layer. As a result, the amount of fluorine-based surfactant used can be small, making it possible to obtain the desired performance at low cost.

[Effects of the Invention] As described above, the present invention provides an apparatus for pressure-fixing an unfixed toner image formed on an image-bearing material by sandwiching and conveying the image-bearing material between a pair of rollers. The surface potential of the pressure roller is lowered by adding a fluorine-based surfactant to the surface layer of at least one roller with an elastic material and grounding the core metal. With,
Attenuation of that potential? This has the effect of preventing phenomena such as wrapping of paper around the pressure roller, offset, and blurring of line images. Furthermore,
It is possible to further prevent offset by aligning one of the rollers and the other roller whose surface is coated with PFA at M1. In addition, by applying a fluorine-based surfactant to the roller surface, it has become possible to further reduce offset products.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing an embodiment of the present invention;
The figure shows the surface of the pressure roller in one embodiment of the apparatus shown in Figure 1.
FIG. 3 is a diagram showing the change in potential, and is a diagram showing the low F of the surface tension due to the addition of a surfactant. 1.3...Roller (l...Fixing roller, 3...Pressure roller) 2...Heating means (heater) Crystal・・・・・・・・・Core 3B・・・・・・・・・Surface layer (elastic body) 3B′
......Fluorine-based surfactant 15...
・・・・・・Air conductive member (plate spring) 2nd
Figure passing period

Claims (5)

[Claims] (1) In a fixing device that pressurizes and fixes an unfixed toner image formed on an image carrier by sandwiching and conveying the image carrier between a pair of rollers, at least one of the rollers has an electrically conductive core metal. and an elastic body, the elastic body containing between 0.003 and 3 weight percent of a fluorine-based surfactant, and the core bar being grounded via an electrically conductive member. A fixing device characterized by: (2) The electrically conductive member is a bearing that receives the rotating shaft that is part of the core metal, and the bearing shall be made of a material with a volume resistance of 10 to the 10th power ohm-cm or less. The fixing device according to claim (1). (3) In a fixing device that heats and fixes a toner image formed on an image bearing material by sandwiching and conveying the image bearing material between a pair of rollers, one roller is connected to an electrically conductive core metal and the core. the other roller has a surface layer of PFA coated with gold; the other roller has a surface layer consisting of an electrically conductive core and an elastomer, the elastomer containing between 0.003 and 3 weight percent fluorine-based A fixing device containing a surfactant, wherein the core metal is grounded via an electrically conductive member. (4) The fixing device according to claim (3), wherein the surface layer of one roller is made of PFA Teflon resin. (5) A cleaning member is brought into contact with the surface layer of one roller, the cleaning member is impregnated with a fluorine-based surfactant, and the surfactant can be supplied to the surface of the other roller. The fixing device according to claim (3).