JPH03288164A - Fixing method - Google Patents

Abstract

PURPOSE:To prevent the offset phenomenon of toner which occurs by electrostatic cause by electrostatically charging a 1st roller which comes in contact with the toner in the same polarity as the electrostatically charged polarity of the toner at the time of fixing. CONSTITUTION:When the heating roller 11 and the pressing roller 12 of a fixing roller 10 are allowed to press-contact and rotate in directions shown by arrows (x) and (y) respectively at the time of fixing, the roller 11 is triboelectrified to be positive which is the same polarity as the toner 14 by the electrification rank of the coating materials 11c and 12c of both roller 11 and 12, and the roller 12 is triboelectrified to be negative. Therefore, the melt toner 14 having the positive polarity is electrostatically repulsed from the roller 11 which is electrostatically repulsed from the roller 11 which is electrostatically charged to be positive at the time of fixing and the toner 14 is electrostatically attracted to a sheet paper 13 side by dielectric polarization on the sheet paper 13 caused by a potential difference between both rollers 11 and 12. Thus, the offset phenomenon of the toner 14 which occurs by the electrostatic cause is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a fixing method for fixing a toner image on a support using a fixing roller in an image forming apparatus such as an electrophotographic apparatus.

(Prior Art) In an image forming apparatus such as a copying machine, in order to obtain a copied image from a document, a charging process and an exposure process are generally performed on the surface of a photoreceptor, which is a photoconductor, to create a photocopy image corresponding to the document image. Forms an electrostatic latent image. Next, a toner containing dye or colorant is applied to this electrostatic latent image, a development process is performed, the formed toner image is transferred to a support such as sheet paper, and the toner image is fixed on the support. to obtain a duplicate image. On the other hand, for the photoreceptor, a cleaning process and a static elimination process are performed after the transfer for the next image forming process.

As a method for fixing a toner image onto a support, a so-called heat roller fixing method has come into frequent use as image forming speeds have increased in recent years.

That is, in this heat roller fixing method, a support having a toner image is inserted between a pair of fixing rollers consisting of a heating roller and a pressure roller, and the toner is fixed under heat and pressure.

This heat roller fixing method has high thermal efficiency, little heat dissipation, and quick fixing, and is therefore considered to be an extremely efficient fixing method for increasing the image forming speed.

However, in this fixing method using a fixing roller,
Since the toner image comes into direct contact with the roller, a so-called offset phenomenon occurs in which molten toner is transferred to the roller surface.

For this reason, offset has conventionally been prevented by coating the roller surface with a material with excellent heat-resistant mold release properties, such as fluorocarbon resin, and further applying an anti-offset liquid such as silicone oil to the roller surface.

However, in such conventional offset prevention methods, no particular consideration has been given to the charging polarity of the human roller that comes into direct contact with the toner image, and the charging polarity due to friction with the support and pressure roller is negative. Therefore, if the charging polarity of the toner is positive, the toner will be electrostatically drawn toward the peat roller by the Coulomb force generated between it and the heat roller, resulting in an offset phenomenon. Ta.

(Problems to be Solved by the Invention) Conventionally, since the charge polarity of the heat roller that comes into contact with the toner image is negative, for toner with positive charge polarity,
Due to the Coulomb force that acts between the toner and the heat roller, the toner is pulled toward the heat roller, causing an offset phenomenon that degrades image quality and stains the image due to toner re-adhering to the fixing roller. there were.

SUMMARY OF THE INVENTION Therefore, the present invention aims to eliminate the above-mentioned problems by preventing the offset phenomenon caused by electrostatic causes, preventing offset/soto toward the fixing roller side regardless of the charging polarity of the toner, and achieving good fixing performance. The purpose is to provide a fixation method.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a first roller in contact with the toner of a fixing roller consisting of a first roller and a second roller to charge the toner. In this method, the support is charged to the same polarity as the fixing roller and then passed through the fixing roller.

Further, in order to solve the above problems, the present invention provides a first roller and a second roller such that the frictional charging polarity between the two rollers is the same as that of the first roller.
A method in which the first roller is made of a material that has the same polarity as the toner, the second roller is made of a material that has the opposite polarity to the toner, the tenth roller is charged to the same polarity as the toner, and the support is inserted through the fixing roller. be.

(Function) According to the above-mentioned means, the Coulomb force of the present invention works to repel each other between the toner and the heat roller during fixing, and the toner is not electrostatically transferred to the formation roller side. It is possible to prevent the toner offset phenomenon caused by the toner, and form a good image with good fixing properties. Moreover, by the above means, the first and second rollers can be easily set to the predetermined polarity required to prevent offset by simply rotating the first and second rollers in contact with each other without using a charging device or other charge applying device. It can be triboelectrically charged, has good fixing properties, and can easily form good images.

(Example) Embodiment 1 will be described below using FIGS. 1 and 2.

A fixing roller 10 provided at a fixing position of an image forming apparatus main body (not shown) includes a heat roller 1 which is a first roller.
1, and a pressure roller 12 which is a second roller that rotates in pressure contact with the heat roller 11. This heat roller 11 has a built-in heater 11b in the hollow part of a first roll base 11a made of an aluminum tube with a diameter of 24 mm, and a heater 11b on its surface.
, after covering with a cylindrical polyester sulfon film (manufactured by Sumitomo Chemical Co., Ltd.) with a thickness of 0.5 [mff1],
First coating material 11 heat-shrinked at 0 ['C] for 30 [minutes]
coated with C. Further, the pressure roller 12 has a heat-resistant silicone rubber layer 12a on the outer periphery of the metal roller core.
second roll base 1 with a diameter of 24 mm
2b was covered with a cylindrical tetrafluoroethylene and ethylene copolymer film (manufactured by Unitika) with a diameter of 25 [aa+] and a thickness of 0.5 [mml], and then heated at 160 [℃] for 15 [minutes]. A heat-shrinked second covering material 12c is also covered. Note that 13 is a sheet of paper that is a support on which a toner image using positive polarity toner 14 is formed.

Then, the heat roller 11 and pressure roller 12 of the fixing roller 10 obtained in this way are moved by the arrows X, respectively, during fixing.
When pressed and rotated in the direction of the arrow y, both rollers 11.
Due to the charging sequence of the 12 coating materials 11c and 12C, the heat roller 11 is tribo-electrified to the same positive polarity as the toner 14, and the pressure roller 12 is tribo-charged to the negative polarity. Therefore, during fixing, the fused positive polarity toner 14 electrostatically repels the positively charged heat roller 11 and is not transferred to the heat roller 11 side. Moreover, the toner 14 is electrostatically attracted to the sheet paper 13 due to the dielectric polarization within the sheet paper 13 caused by the potential difference between both rollers lL12, and the offset phenomenon is more effectively prevented.

In addition, such a fixing roller 10 was attached to a Toshiba copying machine "RheoDry 2810J", modified so that the control temperature of the heat roller 11 could be made variable, and used as an evaluation machine to determine the offset during fixing using positively charged toner. When the test was conducted, as shown in Table 1, no toner offset phenomenon was observed up to the control temperature of the heat roller 11 of 240 [''C], and good images were obtained.

Next, Examples 2 to 10 will be described.

Examples 2 to 10 are obtained by changing the first coating material and/or the second coating material in Example 1,
The rest is the same as in Example 1.

That is, in Examples 2 and 3, polymethylpentene and heat-resistant nylon 66 were used as the first coating material 11C on the surface of the heat roller 11 in the first example. In Examples 4 to 6, the first covering material 11C in the first example is polyether sulfon, polymethylpentene, or heat-resistant nylon 66, and the surface of the pressure roller 12 in the first example is second covering material 12c of
Both are copolymers of tetrafluoroethylene and hexafluoropropylene. In Examples 7 and 8, the first coating material 11C in the first embodiment was made of polymethylpentene and heat-resistant nylon 66, and the second coating material in the first embodiment was
Both of the covering materials 12c are made of a copolymer of polyethersulfone and polysulfone. Example 9 is
The first covering material 11c in Example 1 was made of polytetrafluoroethylene, and the second covering material 12c was made of isoprene polymer. In Example 10, the first coating material 11c in Example 1 was made of a copolymer of tetrafluoroethylene and 67-fluorinated propylene, and the second coating material 12c was made of a copolymer of polyethersulfone and polysulfone. It is something.

Then, in the same manner as in Example 1, an offset test was conducted using a copying machine manufactured by Toshiba ``RheoDry 2810J'', and as shown in Table 1, no toner offset phenomenon was observed in any of the cases.

However, in Examples 2 to 8, the charging polarity of the heat roller is positive, so positively charged toner is used, and in Examples 9 and 10, the charging polarity of the heat roller is negative. A negatively charged toner was used. The charging polarity of the heat roller was confirmed by frictionally charging the films each consisting of the first coating material and the second coating material, and measuring the charging polarity using a contact potential difference measuring device.

(Margin below) For comparison, when negative polarity toner was fixed using the RheoDry 2810J using the fixing rollers of Examples 9 and 10, the control temperature of the heat roller was 220.
At [°C], an offset occurred in both cases.

In this way, the coating materials 11C and 12C of the heat roller 11 and pressure roller 12 are selected such that their frictional charging series makes the heat roller 11 have the same polarity as the toner 14, and both rollers 11 and 12 are rotated under pressure. In the above-mentioned embodiment, it is possible to easily obtain a predetermined charging polarity by simply rubbing both rollers 11 and 12 without using any electrification device such as a charger. During fixing, the Coulomb force generated between the fused toner 14 and the heat roller 11 acts in the direction of repelling each other, so the toner 14 is not transferred to the heat roller 11, and the electrostatic It is possible to prevent the toner offset phenomenon caused by various causes, obtain good fixing, and improve image quality. In addition, the offset toner on the heat roller 11 may be transferred to the sheet paper 13 or the pressure roller 12 again, causing staining of the image, or the sheet paper 13 may be wrapped around the fixing roller 10 due to the adhesion of the toner 14. There is no fear.

Note that the present invention is not limited to the above-mentioned embodiments, but can be modified in various ways. For example, a voltage application means such as a charger may be used to charge the first roller to the same polarity as the toner. However, if frictional charging is performed by rotation of the first roller and the second roller as in the embodiment, the voltage application means is not required. Furthermore, the materials for the first coating material and the second coating material may be any material as long as they take into account the charging series so as to obtain a predetermined charging polarity and have good heat-resistant mold release properties. The materials of the first and second roll bases are also not limited to aluminum alloy, iron, stainless steel, ceramics, etc. Further, the structure of both rollers is arbitrary, and as long as the first roller is charged to the same polarity as the toner, it may be a single layer, or the structure of the first roller may be a single layer. To improve the performance, a primer layer made of a mixture of a roll base material and a coating material may be provided.

[Effects of the Invention] According to the present invention as described above, during fixing, the first roller in contact with the toner is charged to the same polarity as the toner, and there is a repulsion between the toner and the first straw. Since the mutual Coulomb force acts, the toner is not electrostatically transferred to the first roller side, and the toner offset phenomenon due to electrostatic causes can be prevented. Therefore, regardless of the charge polarity of the toner, an offset phenomenon does not occur, and good fixation is obtained and image quality is improved, and it is possible to prevent image staining due to staining of the fixing roller and wrapping of the support.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention, with FIG. 1 being a sectional view and FIG. 2 being a partially enlarged explanatory view. 10... Fixing roller, 11... Heat roller, 11
c...first covering material, 12...pressure roller 12C.
...Second covering material, 13... Sheet paper 14... Toner

Claims (2)

[Claims] (1) In a method of fixing by inserting a support on which a powder toner image is formed between a pair of fixing rollers consisting of a first roller and a second roller that rotate in pressure contact with each other, contacting the toner. A fixing method characterized in that a first roller is charged to the same polarity as the toner, and the support is inserted between the fixing rollers. (2) The first roller and the second roller are arranged such that the frictional charging series between both rollers is such that the first roller has the same charging polarity as the toner and the second roller has the opposite charging polarity to the toner. 2. The fixing method according to claim 1, wherein the first roller is made of a material and is charged to the same polarity as the toner by rubbing both rollers.