JPS60140280A - Preventing method of offset of toner - Google Patents

Abstract

PURPOSE:To prevent toner from sticking on a roller surface by impressing a heat fixing roller with a bias potential which has the same polarity with a toner potential. CONSTITUTION:When the fixing roller 7 is impressed during toner heating with the bias potential having the same polarity with unfixed toner through a metallic piece 11, a negative potential is developed at a ''Teflon'' layer 8. Therefore, toner with the negative potential is repelled to prevent the toner from sticking on the surface of the fixing roller 7. Further, even when oil for offsetting is used, the staining of a form and the formation of black stripes due to the oil are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an electronic copying machine, in which when an unfixed toner image fed from a transfer machine is fixed by a heat fixing roller, the toner adheres to the surface of the roller. 2. This invention relates to a method for preventing toner offset.

<Prior Art> As shown in FIG. 1, the heat fixing device of an electronic copying machine includes an upper heat fixing roller 2 whose surface is coated with Teflon and a lower heat fixing roller 2 whose surface is coated with silicone rubber, and an upper heat fixing roller 1 coated with silicone. It consists of a device 3 for supplying a desiliconizing agent such as oil, a cleaning blade 4 made of Teflon rubber, etc., and a paper separation claw 5 for cleaning toner adhering to the roller l and uniformly applying the oil. .

Transfer paper 6 having an unfixed toner image is transferred to fixing rollers 1 and 2.
When passing through the transfer paper, the toner is heated and melts, permanently fixing it on the transfer paper. However, during the charging, exposure, development, transfer, and peeling processes up to the formation of an unfixed toner image, the toner takes on a negative potential (or positive potential), whereas the upper heating fixing roller 1 is different from the lower heating fixing roller 2. , the cleaning blade 4, the separating claw 5, and the transfer paper 6, and as shown in FIG. Therefore, when the potential of the fixing roller I becomes opposite to the potential of the toner, the toner adheres to the surface of the roller during fixing.

Therefore, conventionally, in order to prevent the toner from adhering to the fixing roller l, an oil supply device 3 applies silicone oil, which is a desilicon release agent, to the surface of the fixing roller l. However, in order to obtain sufficient effect with this method, approximately 20
It is necessary to apply oil of f/10,000 sheets or more,
Application of such a large amount of oil has the disadvantage that too much oil accumulates at the tip of the separating claw 5 for separating the vapor from the fixing roller 1, and the oil stains the edges of the paper. On the other hand, experiments have shown that in order to eliminate this drawback, it is necessary to keep the amount of oil applied to ff: 6f710,000 sheets or less.
If the amount of oil applied to the roller is reduced, the amount of toner adhering to the surface of the roller will increase, resulting in the formation of black streaks of toner on the paper image.

<Purpose> The present invention has been made in view of such conventional problems, and
The purpose is to provide a toner offset prevention method that prevents toner from adhering to the roller surface by applying a bias potential of the same polarity as the toner potential to the heat fixing roller. be.

<Example> The present invention will be explained in detail below.

FIG. 8 is a sectional view of the upper heating fixing roller.

The main body of the fixing roller 7 is made of metal, and the surface is further coated with Teflon 8, and both ends thereof are rotatably supported by a bearing sleeve 9 and a bearing 10.

Reference numeral 11 denotes an elastic metal piece for supplying bias potential, one end of which contacts the end of the fixing roller 7, that is, the metal portion, and the other end connected to the bias potential supply source 12.

The offset prevention method of the present invention includes applying a bias potential of the same polarity as the potential of the unfixed toner to the fixing roller rough via the metal piece 11 by the bias potential supply source 12 when fixing the toner by heating.
For example, if the toner potential is negative, a negative bias potential is also applied to the fixing roller 7. When a negative potential is applied to the fixing roller 7, the P portion in the figure is the fourth
As shown in the figure, an electrostatic electrode is formed in the Teflon layer 8, and a negative potential appears on the surface of the layer. Therefore, the surface of the Teflon layer of the upper heat fixing roller 7 has a frictional potential generated by the friction of the lower heat fixing roller, that is, the second
By applying a negative bias potential that exceeds the potential vA shown in the figure, all the toner at the negative potential is repelled and it is possible to prevent toner from adhering to the roller surface.

By the way, without applying silicone oil as a silicon release agent to the upper heating fixing roller 7 and without heating the roller, the black solid A4
When a total of 10 copies are made, the offset toner on the roller surface collected by the cleaning blade 4 is about 12, but when a bias potential of -500V is applied to the fixing roller 7, the offset toner is about 0.8F, -1000.
It can be seen that the offset toner decreases by about 0.6 f at V and about 0.4 f at -2000 V, indicating that it is sufficiently effective.

Furthermore, if the fixing roller 7 is coated with silicone oil of about 4f/10,000 sheets, that is, the amount of oil that does not accumulate on the separation claw 5, and +200■ is applied to the roller, about 500 copies will be made. When a ground potential was applied to the roller, black streaks of toner were generated which affected the image, and black streaks of toner were generated after approximately 2000 copies were made.

On the other hand, when 300V was applied to the roller, there was no toner smudge even after 400'00 copies were made.
I am convinced that the effect is remarkable.

Particularly when used in combination with a slight amount of oil coating, toner offset can be effectively prevented at a low bias potential.

<Effects> As explained in detail above, the toner offset prevention method according to the present invention applies a bias potential of the same polarity as the toner potential to the heating fixing roller. It is possible to prevent toner from adhering, prevent paper from becoming stained by offset oil, and prevent black streaks from occurring due to toner, making it possible to perform high-quality copies.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the heat fixing device, Fig. 2 is a diagram showing the state of frictional charging of the upper heat fixing roller, Fig. 3 is a sectional view of the upper heat fixing roller used in the method of the present invention, and Fig. 4 is an enlarged view of the same main part. 7tri upper heating fixing roller, 8 is Teflon layer, ■ is metal piece, 12 is bias potential supply source agent, patent attorney Yoshihiko Fuku (and 2 others) # & 2
figure

Claims (1)

[Claims] ■ A toner offset prevention method characterized by applying a bias potential of the same polarity as the toner potential to a heating fixing roller that fixes an unfixed toner image to prevent toner from adhering to the roller surface.