JPS5838974A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent on offset, toner image scattaring and to maintain excellent fixability for duration by using a rotating body having a layer which is approximately the same or the same in the sequence of frictional charging series in the sequence of frictional charging series of unfixed images. CONSTITUTION:A fixing roller 1 is provided with a coating layer 11 wherein PE is coated on a steel roller by a melt spraying method in order to be made coincident with the essential component of toners and toner images. A steel roller is used for a press roller 2. Since the PE of roughly the same sequence in frictional charging series as the low density PE which is the essential component of the toner images, the electrostatic charging on the surface of the fixing roller can be made roughly equal to the electrostatic charging of the toner. Therefore, the adhesive power of the toner images to the surface of the fixing roller is prevented highly and offset and the disturbance in the toner images are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device having a rotating body used in a fixing process for contacting a support material supporting an unfixed image and fixing the unfixed image to the support material.

Conventionally, when an unfixed image is formed using, for example, an electrophotographic copying machine, the unfixed image is supported by a support material that supports it by electrical attraction. The method of fixing this unfixed image to the support material is mainly based on heating.
It can be roughly divided into those that rely on pressure, and those that use a contact type roller pair are often used for fixing.

A support material such as a sheet of paper that supports such an unfixed image, for example, a toner image, comes into contact with an object, thereby separating the object and the support material.
The toner image may become triboelectrically charged.

On the other hand, in conventional fixing devices that use heat or pressure,
A toner image offset phenomenon often occurs, and various methods have been taken to solve this problem, but they are still incomplete.

For example, in a fixing device that has a metal roller, when ordinary toner is used, the toner easily has a mirroring force on the metal surface due to its own electric charge.
As a result, the toner image is drawn to the surface of the metal roller, causing disturbance and offset of the toner image.

On the other hand, even when the fixing roller is made of a dielectric material such as plastic, there is no effect of mirroring force, and repeated friction causes offset and toner image disturbance. This is mainly due to the fact that the toner adheres electrostatically due to frictional charging of the insulating roller.

Such frictional charging of the insulating roller may exceed 1000 V in surface potential depending on the material of the fixing head roller, resulting in severe disturbance of the toner image.

Further, although a device has been provided in which the amount of charge accumulated due to frictional charging is removed using a static eliminator, this not only complicates the entire device, but also disturbs the toner image during the static neutralization operation, and the degree of this is rather poor. This becomes a big drawback.

The present invention has been made in view of the above-mentioned drawbacks.Secondly, the present invention focuses on the above-mentioned problems and drawbacks as the origin of the offset phenomenon.

This offset phenomenon occurs when the adhesion force between the toner image and the supporting material becomes smaller than the adhesion force between the toner image and a contact rotating body such as a fixing roller. It has been confirmed that this problem occurs when the toner image scatters and adheres to the surface of the fixing roller just before being fixed by the nipping portion (or pressure contact portion) of the fixing roller. Furthermore, it was confirmed that the main cause of this phenomenon is the adhesion force due to electrostatic attraction generated between the toner image and the fixing roller. The present invention has been made in consideration of the above-mentioned contents, and focuses on the unfixed image and the fixing device.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of a pressure fixing device to which the present invention is applicable. In FIG. 1, 1 is a fixing roller, and 2 is a suppression roller, which are each rotatably supported by side plates 3 and 4 which are rotatably connected to each other by an axis OK. In order to pressurize the roller pair 1.2, the side plates 3 and 4 are equipped with p-ra pair 1.
, 2 is provided with a bolt 5 on the side opposite to the narrow opening, and a pressure device including a compression spring 6 provided between the bolt head and the side plate 3, and the elastic force of the spring 6 causes the roller 1.2 to be pressed. Pressure contact. The linear pressure between p-j-1 and p-2 at that time is about 10 to 20 gin.6. The roller 1 is rotationally driven by an electric motor via a gear train (not shown), and the roller 2 is driven to rotate by frictional force. The paper P supporting the toner image, such as photosensitive paper or transfer paper, is placed so that the toner image surface is in pressure contact with the roller 1. The toner image is fixed to the paper P under pressure by the splash 6).

The toner used herein was mainly composed of low-density polyethylene, a resin containing high-density polyethylene, and further mixed with i-gnetite for imparting magnetism. The main component of the toner image is polyethylene.

On the other hand, the fixing roller 1 is provided with a ridge 11 made of a steel roller coated with polyethylene by thermal spraying to match the toner and the main components of the toner image. P-Lar manufactured by Ichito Kogyo was used.

Therefore, since polyethylene, which has approximately the same rank in the triboelectrification series as low-density polyethylene, which is the main component of the toner image, is provided on the surface of the fixing roller, the charge on the surface of the fixing roller can be made almost equal to the charge on the toner. Therefore, the adhesion of the toner image to the surface of the fixing roller is highly prevented.
Offset and toner image disturbance can be prevented.

The material for the surface of the fixing roller may contain a small amount of impurities and unreacted substances during resin production, and may also contain a conductive substance such as an antistatic material mixed therein in order to reduce the resistivity of the resin. is a further preferred embodiment.

Further, it is preferable that the coating layer 11 is coated with a low-resistivity substance such as a monofatty polyamine to slightly lower the electrical resistance value, since the accumulated charge is more appropriately corrected. .

The steel roller may be coated with polyethylene by other techniques such as a high-temperature solution method, a fluidized dipping method, and a dispersion method.

Although it is difficult to directly measure the magnitude of frictional charging between the toner and the fixing roller, its value can be evaluated by the following experiment. The toner is solidified by heating and pressurizing, and the solidified toner 8 is attached to a support 17 as shown in FIG. On the other hand, a sheet 9 made of the same material as the coating layer of the fixing roller is fixed on a base 10, and a support 7 holding solidified toner 8 is moved in the direction of the arrow with a periodic amplitude of 50 to 100 times per minute. 50w! 9) Slide back and forth on the top. At this time, the surface voltage due to frictional electrification generated on the sheet 9 is measured by a surface electrometer 12 attached to a potential globe 11. The measured surface potential oscillates in accordance with the reciprocating period of the support, as shown in FIG. 3, and this indicates the potential distribution on the surface of the sheet.

Now, the envelope line (indicated by the broken line) of this potential waveform shows that for the toner mainly composed of polyethylene in this example, the maximum value of the surface potential for the polyethylene sheet is +8 as shown in Figure 3-1.
For 0v1 Teflon sheet, Figure 3 - Sunotoku Max - 20
0V, while for nylon sheet +1 as shown in Figure 6-C.
It became more than 000V.

When such an experiment was conducted using various sheets, it was found that the fixing roller materials of polyethylene, Teflon, and vinyl chloride, which were effective in preventing offset and image disturbance in the experiment, all had surface voltages in absolute value, and the offset and image Adhesive forces other than the above-mentioned electrostatic attraction force are also involved in the disturbance of the toner, but in particular, the flow of air generated when the toner image is sandwiched and pressed between the fixing rollers is also involved.

For this reason, it is preferable that the toner image also has a certain degree of attractive force that resists the air flow. In this example, the toner image has a frictional charging system that is in a higher or lower order than that of the fixing roller, and the toner image is within the range that ensures that the toner image is held on the support material, and the friction between the suppression roller and the fixing roller is It is sufficient that the triboelectrification series is approximately the same or has a relation that allows the toner image to be held on the support material. - For example, if the toner is negative and the back side of the support material is positive, the four-see potential on the side in contact with the toner image is negative, the opposing p-see potential is positive, and the amount of charge on the toner image is greater than that of the toner image. It is preferable that the amount of electric charge on the roller is small.

In another embodiment, a toner containing polyethylene as a main component is used, and a rotating body whose surface is covered with PrFE and vinyl chloride, which are close to polyethylene in the triboelectric charging system, is used as described above. A high degree of offset prevention effect and toner image disturbance prevention effect was obtained.

As described above, the present invention includes a rotating body having layers that are in the order of triboelectrification before and after or in the same order of triboelectrification as the unfixed image, so that offset can be prevented for a long time.
It is possible to prevent the toner image from scattering, maintain excellent fixing properties, and obtain excellent images.

The present invention is particularly effective for pressure fixing type fixing devices, but it can also be applied to rollers and belt-shaped rotating bodies of heat fixing devices, pressure rollers, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of one embodiment of the present invention and an explanatory diagram of the surface potential of the second embodiment. 1 is a fixing roller, 2 is a suppression roller, T is a toner, P
is paper, and 11 is a covering layer.

Claims (1)

[Claims] A fixing device characterized by having a rotating body having layers that are before and after or in the same triboelectrification series order of the main and -components constituting an unfixed image.