JPH0376461B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device installed in a recording device such as an electrophotographic device or an electrostatic recording device. The present invention relates to a fixing device that extremely effectively prevents offset that occurs during processing or heating and pressure processing.

Conventionally, a method for preventing the offset phenomenon of rotating bodies such as rollers and belts used for fixing was disclosed in Japanese Patent Application Laid-open No. 1983
It is disclosed in Japanese Patent Application Laid-Open No. 55-55374 and Japanese Patent Application Laid-Open No. 1983-96970. A corotron applies a bias voltage of the same polarity as the fixing object supported by copy paper, such as a toner image, to a roller that contacts the image surface of the recording material, such as copy paper, or toner is applied to a roller on the opposite side of the toner image surface. It is known to apply a bias voltage of opposite polarity. In other words, in the conventional device, a charge is forcibly applied from the outside of the rotating body. When applying voltage using a corona charger such as a corotron, not only is the device larger, more complicated, and more costly, but if the corona charger becomes dirty, spark discharge and leaks are likely to occur, resulting in poor reliability and safety. Also, when applying with a bias roll,
The practical effect was small, and the bias roll was easily soiled, making it impractical.

The present invention satisfactorily improves the above-mentioned conventional drawbacks with a simple configuration.

The main object of the present invention is to extremely effectively prevent the offset phenomenon to the rotating body, and another object is to provide a fixing device that has stable fixing properties over a long period of time. The present invention applies a charging agent containing amino-modified silicone oil to the surface of the rotating body, thereby varying the frictional charging polarity of the rotating body, and offseting objects to be fixed such as toner and resin materials (coatings, etc.). This is to fundamentally prevent the cause from occurring.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is an explanatory diagram of an embodiment of the present invention. This figure shows a negative toner image T formed by electrophotography using a heat fixing device to a thickness of several tens of microns (usually 70 microns to
100μ) is fixed on plain paper P.

1 is a heating roller having a heating heater 3 such as a halogen heater inside, and a driving motor (not shown).
It rotates in the direction of the arrow in response to the driving force from. Reference numeral 2 denotes a pressure roller, which is brought into pressure contact with the heating roller 1 and rotates by sliding.

This heating roller 1 has a heat-resistant release resin layer ₁₁ such as tetrafluoroethylene resin on the outer peripheral surface of a hollow roller core ₁₂ made of metal such as aluminum, stainless steel, or copper.
It is 100μ thick.

The pressure roller 2 is rotatably supported by a bearing (not shown). The pressure roller 2 is pressed against the heating roller 1 by a known pressure means (not shown) at least during fixing, and the outer peripheral surface of the metal roller core ₂₂ is coated with an insulating elastic material such as silicone rubber, fluorosilicone rubber, or fluorosilicone rubber. The layer ₂₁ is relatively thick (approximately 1 mm or more). One purpose of this configuration is to secure a pressure contact area d with the heating roller.

A temperature sensing element 4 such as a thermistor or thermocouple is disposed in contact with the outer peripheral surface of the heating roller 1, and its detection signal is guided to a known control means (not shown) to control the temperature of the outer peripheral surface of the heating roller 1 ( Output of heater 3, or
By controlling the applied voltage, etc.), the toner image melting temperature is maintained.

Reference numeral 6 denotes a cleaning member for removing foreign matter such as offset toner and paper powder adhering to the heating roller surface from the roller surface.
The cleaning web ₆₁ is made of a heat-resistant nonwoven fabric (manufactured by Nippon Felt Industries Co., Ltd.) impregnated with silicone oil to prevent offset. The cleaning web 6 ₁ is an elastic pressing roller 6 ₃
It is in contact with the heating roller. Further, this web 6 ₁ is moved by a driven take-up roller 6 ₄ (not shown) from the supply roller 6 ₂ so as to change its contact position little by little, so that a new surface of the cleaning web 6 ₁ is always heated. It contacts the entire length of the roller 1 surface.

Separation claws 5 ₁ and 5 ₂ are used to reliably separate the plain paper P as a recording material after fixing from the surface of each roller. 7 is a heat-resistant nonwoven fabric impregnated with amino-modified silicone oil and is usually spaced slightly from the surface of the pressure roller. 8 is a supporting member for this purpose,
It is fixed to the substrate 9 of the device below the pressure roller 2.

When the copy switch is turned on, the heating roller 1 starts rotating and the pressure roller 2 starts rotating under pressure. By pressing and rotating, the insulating elastic layer of the pressure roller receives heat from the heating roller and expands, coming into contact with the heat-resistant nonwoven fabric impregnated with amino-modified silicone oil, and the amino-modified silicone oil is applied to the surface of the pressure roller. Granted. Pressure roller 2 after copying
shrinks again due to natural heat dissipation and separates from the heat-resistant nonwoven fabric. This can effectively prevent thermal deterioration of the amino-modified silicone oil.

The skeletal structure of this amino-modified silicone oil is shown below.

When the above amino-modified silicone oil is applied to the pressure roller, it will have a positive surface potential due to frictional charging with the plain paper P.

In the fixing device configured as shown above, the outer diameter is 60 mm.
A pair of rollers were brought into pressure contact with each other at a total pressure of 60 kg, and plain paper, Japanese Industrial Standard A3 size paper, was fixed at a speed of 23 sheets/min (roller peripheral speed 270 mm/sec). Using negatively charged toner (negative toner), 300 mg of toner was fixed on each sheet of A3 plain paper (the condition most likely to cause offset), and when amino-modified silicone oil was applied, it was found that The offset was reduced to less than 1/4 of that when methyl silicone oil was applied.
The surface potential of the pressure roller at this time was -6000V or more, which was tens of thousands of volts, when conventional silicone oil was applied.
During fixation, the polarity was reversed due to friction and the voltage was +2400V.

The above results suggest that the offset decreases due to the following factors. In other words, when transferring a positively charged latent image onto plain paper after developing it with negative toner,
Plain paper is given a positive charge and is transferred by electrostatic attraction with the negative toner. That is, it is important that the plain paper is positively charged at this point.
Thereafter, in the fixing process, when the plain paper P passes through the nip portion, it is charged by frictional separation between it and the pressure roller 2, and at this time, the amino-modified silicone oil acts and the pressure roller is highly charged positively. In other words, the plain paper P is negatively charged, which is opposite to the positive charge that should hold the negatively charged toner. The present inventors elucidated this phenomenon by considering that the offset is related not to the amount of charge but to the potential. In other words, when the same amount of charge is transferred, the pressure roller, which has a smaller capacitance than the paper, has a much higher potential on its surface than the paper, ignoring the charge on the back side of the paper. It exerts as large an electrostatic attraction force as possible on the negative toner on plain paper. In other words, during fixing, the negative toner is strongly held on the paper surface, thereby preventing offset.

Width 10 to examine the sustainability of the above effects
A heat-resistant non-woven fabric with a thickness of 2 mm and a thickness of 2 mm was provided over the entire length (320 mm) of the pressure roller, and the heat-resistant non-woven fabric was impregnated with 10 c.c. of amino-modified silicone oil. When we performed intermittent copying of one page per minute for 20,000 copies, we were able to confirm that the same effect as the above result was obtained even after 20,000 copies.

In addition, after uniformly applying 0.5 cc of amino-modified silicone oil to the surface of the pressure roller (removing the charging agent application members 6 and 7 shown in Fig. 1), intermittent copying similar to the above was performed for 2000 copies. Although the effect decreased slightly even after the 300° shift, we confirmed that the offset was reduced to 1/3 of that of the conventional method.

As is clear from the above, by applying amino-modified silicone oil to the rotating body that comes into contact with the surface of the recording material on the side opposite to the side on which the unfixed negative to-be-fixed object is fixed, it is more reliable than before. Better offset prevention can be achieved.

The amino-modified silicone oil may be applied via an application roller, or may be applied to the rotating body at predetermined rotational speeds using an eccentric cam for approaching and separating. Further, this amino-modified silicone oil may be impregnated and added into the surface layer of the rotating body in advance. Furthermore, when impregnated or added, the durability can be further improved by separating the rotating body from the heat source or heating roller during non-fixing periods using known means.

Of course, the present invention can be applied to any rotating body that comes into contact with a recording material and generates a frictional factor that offsets the fixing object (for example, one having an insulating layer thicker than the thickness of the recording material), and can also be applied to pressure fixing devices. It goes without saying that it can be done.

If this amino-modified silicone oil is used, offset can be prevented for a long period of time with just a small amount applied once for fixing thousands to tens of thousands of sheets, so it is inexpensive, does not require a complicated mechanism, and is extremely practical. It is something.

As described above, the present invention can effectively prevent offset on the surface of a rotating body over a long period of time by a simple method of applying amino-modified silicone oil to the surface of the rotating body.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention. 1 is a heating roller, 2 is a pressure roller, T is a toner image, P is plain paper, 7 is a heat-resistant nonwoven fabric, and 8 is a support member.

Claims (1)

[Claims] 1. A first rotating body that comes into contact with the object to be fixed;
A second rotating body that presses against the rotating body, and means for applying a positively charging agent to the second rotating body,
A fixing device that fixes an object to be fixed by nipping and conveying a supporting material supporting the object to be fixed which is negatively charged between the first and second rotary bodies, characterized in that the charging agent is amino-modified silicone oil. Fixing device.