JP2003337492A - Image forming device and fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device using negative toner which can prevent calcium carbonate deposition and electrostatic offset of the toner even when transfer material containing calcium carbonate is allowed to pass through a fixing device. <P>SOLUTION: A fixing roller 1 is composed of a hollow mandrel 4, an insulating adhesive layer 2 and a release layer 3 consisting of an insulating PFA tube. A pressure roller 6 is composed of a mandrel 7, an elastic layer 8 made of conductive silicone rubber and a release layer 9 consisting of low-resistance PFA tube. A positive bias voltage is applied from an electric source 9 to the mandrel 7 of the pressure roller 6, a surface voltage of the pressure roller 6 is made to be 300 V and a surface voltage of the fixing roller 1 is made to be 100 V. Electric field between the fixing roller 1 and the pressure roller 6 is directed from the pressure roller 6 to the fixing roller 1, the negative toner 11 is pressed against the side of the transfer material P and the offset does not occur. In addition, calcium carbonate does not adhere to the fixing roller 1 and the pressure roller 6 because calcium carbonate is positive. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic type or electrostatic recording type image forming apparatus such as a copying machine or a printer, and a fixing apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, a heat-pressure fixing device is mainly used as a fixing device of an image forming apparatus. This heat and pressure fixing device includes a fixing roller as a fixing rotating body having a hollow core metal such as aluminum and a heater provided therein. Further, in order to improve the releasability of the fixing roller, those whose surface layer is coated with a tube of fluororesin or those whose surface is coated with fluororesin are used. The heat and pressure fixing device is further provided with a pressure roller as a pressure rotating body in which a rubber elastic layer is provided on a metal cored bar, and the surface layer thereof is covered with a fluororesin tube having good releasability. The pressure roller is in pressure contact with the fixing roller.

However, since the fluororesin-based resin has a high electric insulation property and is easily charged, when the transfer material carrying the unfixed toner passes between the fixing roller and the pressure roller, the unfixed toner is formed on the surface of the fixing roller. The phenomenon that some of the toner adheres from the transfer material (hereinafter referred to as “offset”) will occur. The offset unfixed toner may adhere to the transfer material that is sent next time and stain the transfer material.

In order to solve this, the fixing roller is cleaned by pressing a felt impregnated with silicone oil or an oil application member on the surface of the fixing roller. However, in recent years, these cleaning members tend not to be used due to the progress of material technology and cost.

In a fixing device which does not use this cleaning member, as disclosed in Japanese Patent Laid-Open No. 6-110350, as shown in FIG. 5, the uppermost layer of the pressure roller 106 is covered with a conductive layer 109. The core metal 107 of the pressure roller 106 is grounded via the diode 113, and a negative bias voltage is applied to the core metal 104 of the fixing roller 101 from the power supply 110. As a result, a repulsive electric field that attracts the negative toner 111, which is a negatively charged toner, to the transfer material P is generated, and the toner is prevented from being electrostatically offset on the fixing roller 101.

[0006]

However, when a negative bias voltage is applied to the core metal 104 of the fixing roller 101, the surface layer 103 of the fixing roller 101 is negatively charged.
Therefore, when a type containing calcium carbonate having a positive polarity is used as the filler in the transfer material P, many calcium carbonates in the transfer material P adhere to the surface layer 103 of the fixing roller 101. The adhesion of the calcium carbonate raises the surface potential of the fixing roller 101, greatly impairs the toner releasability of the surface layer 103 of the fixing roller 101, and further, the calcium carbonate adhered to the fixing roller 101 causes the transfer material P to pass through later. The upper negative toner 111 is the fixing roller 10.
In some cases, the negative toner 111 is offset to 1, and the offset negative toner 111 is again offset to the subsequent transfer material P to stain the image.

Therefore, the main object of the present invention is to provide an image forming apparatus using a negatively chargeable toner, even if a transfer material containing calcium carbonate is passed through a fixing device, the adhesion of calcium carbonate and electrostatic offset of the toner. It is an object of the present invention to provide an image forming apparatus using a negatively-chargeable toner that can prevent the above.

Another object of the present invention is, in a fixing device of an image forming apparatus using a negatively chargeable toner, even when a transfer material containing calcium carbonate is passed through the fixing device, the adhesion of calcium carbonate and the electrostatic charge of the toner are prevented. An object of the present invention is to provide a fixing device that can prevent offset.

[0009]

The above object can be achieved by an image forming apparatus and a fixing apparatus according to the present invention. In summary, the present invention includes a fixing rotator and a pressure rotator that is in pressure contact with the fixing rotator and rotates together with the fixing rotator. In an image forming apparatus having a fixing device for fixing the toner image on the transfer material as a permanent image by passing the placed transfer material, and heating and pressing, the fixing rotating body and the pressing rotating body have a positive polarity. Having a surface layer with a surface potential of
In the image forming apparatus, the absolute value of the surface potential of the pressing rotator is larger than the surface potential of the fixing rotator.

It is preferable that a positive bias voltage is applied to the pressing rotary member so that the absolute value of the surface potential on the pressing rotary member side becomes large. The fixing rotator has a hollow cored bar, an insulating adhesive layer on the cored bar, and a coating layer on the insulating adhesive layer, and the pressing rotator has a conductive elastic layer and a conductive layer. And a coating layer of It is preferable to have a cleaning member that comes into contact with the pressing rotary member. The cleaning member has a cleaning member that comes into contact with the pressing rotary member, and the cleaning member, the pressing rotary member, and the fixing rotary member are arranged in the cleaning member such that the absolute values of the surface potentials become larger in this order. It is preferable to apply a positive bias voltage.

According to another aspect of the present invention, there is provided a fixing rotator and a pressure rotator which is pressed against the fixing rotator and rotates together with the fixing rotator. In the fixing device for fixing the toner image as a permanent image on the transfer material by passing through the transfer material on which the toner image is formed and applying heat and pressure, the fixing rotating body and the pressing rotating body have a positive polarity. There is provided a fixing device characterized by having a surface layer having a surface potential of, and the absolute value of the surface potential of the pressing rotator is larger than that of the fixing rotator.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The image forming apparatus and fixing apparatus according to the present invention will be described below in more detail with reference to the drawings. In the embodiments described below, the present invention is described as being embodied in, for example, an electrophotographic image forming apparatus as shown in FIG. 4, but the present invention is not limited to this.

In FIG. 4, the electrophotographic image forming apparatus is
A photosensitive drum 21 which is an image carrier is rotatably provided, the photosensitive drum 21 is uniformly charged by a primary charger 22, and then an information signal is exposed by a light emitting element 23 such as a laser to electrostatically latent image. An image is formed and visualized by the developing device 24. Next, the visible image is transferred onto the transfer material P by the transfer charger 25 and further fixed by the fixing device 20 to obtain a permanent image. Further, the transfer residual toner on the photosensitive drum 21 is removed by the cleaning device 26.

Example 1 A first embodiment of the present invention will be described with reference to FIG.

The fixing device 20 of this embodiment includes a fixing roller 1 as a fixing rotary member and a pressure roller 6 as a pressing rotary member pressed against the fixing roller 1. The fixing roller 1 is composed of a hollow core metal 4, an insulating adhesive layer 2 provided thereon, and a release layer 3 as a surface layer provided thereon. In this embodiment, the release layer 3 is made of an insulating PFA tube as a coating layer and has a thickness of 30.
μm. The core metal 4 is made of aluminum and has a thickness of 1
It is 2 mm. A heater 5 is arranged inside the fixing roller 1. The fixing roller 1 is grounded via a cored bar 4.

A pressure roller 6 which rotates in pressure contact with the fixing roller 1.
Is composed of an aluminum cored bar 7, an elastic layer 8 of conductive silicon rubber provided on the cored bar 7, and a release layer 9 as a surface layer provided on the elastic layer 8 for enhancing the mold release property. The release layer 9 is made of a low resistance PFA tube as a coating layer and has a thickness of 50 μm.

In this embodiment, a DC bias voltage is applied from the power source 10 to the core metal 7 of the pressure roller 6. Its magnitude is 300V. At this time, the surface potential of the fixing roller 1 is 100 V and the surface potential of the pressure roller 6 is 300 V.
It is V.

When the transfer material P on which the negative toner 11 which is a negative charging toner is placed, passes between the fixing roller 1 and the pressure roller 6, the direction of the electric field between the fixing roller 1 and the pressure roller 6 is the pressure. Since it is generated in the direction from the roller 6 to the fixing roller 1, the negative toner 11 is pressed against the transfer material P side and remains on the transfer material P without being offset to the fixing roller 1 and the pressure roller 6.

A transfer material P containing a large amount of calcium carbonate
When calcium carbonate is used, calcium carbonate has a positive polarity, but since the surface potentials of the fixing roller 1 and the pressure roller 6 are positive, the calcium carbonate contained in the transfer material P is fixed to the fixing roller 1 and the pressure roller 6. It does not adhere to.

According to the experiments conducted by the present inventors, the pressure roller 6
The magnitude of the bias voltage applied to the
When the surface potential of the pressure roller 6 is higher than the surface potential of the fixing roller 1 by 100 V to 500 V, the electrostatic offset of the negative toner and the prevention of electrostatic attachment of calcium carbonate to the fixing roller 1 are most effective.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. The same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The fixing device 20 of the present embodiment is different from the fixing device of the first embodiment in that it further has a cleaning roller 12 as a cleaning member that contacts and rotates with the pressure roller 6. The cleaning roller 12 is a cylindrical roller made of aluminum or iron and has a diameter of 12 mm. When the negative toner 11 is electrostatically offset to the fixing roller 1,
The surface temperature of the pressure roller 6 is always lower than that of the fixing roller 1 due to its large heat capacity, and the negative toner 11 is affected by the temperature difference.
Moves from the fixing roller 1 to the pressure roller 6 having a low surface temperature. The cleaning roller 12, which rotates in contact with the pressure roller 6, has a lower surface temperature than that of the pressure roller 6. Therefore, the toner offset to the pressure roller 6 is further transferred to the cleaning roller 12, and the fixing roller 1 and the pressure roller 6 Are not polluted together. Further, the toner once taken into the cleaning roller 12 does not return from the cleaning roller 12 to the pressure roller 6 due to the binding force between the toners.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. The same members as those of the first and second embodiments are designated by the same reference numerals and the description thereof will be omitted.

In the fixing device 20 of the present embodiment, the cleaning roller 12 contacting and rotating with the pressure roller 6 is supplied from the power source 10 from the power source 10 in the same configuration as the fixing device of the second embodiment.
A bias voltage of 300 V is applied.

As a result, the magnitudes of the surface potentials of the fixing roller 1, the pressure roller 6, and the cleaning roller 12 are in the order of their absolute values.
2> Pressing roller 6> Fixing roller 1 in that order.

As a result, offset to the fixing roller 1 is prevented, and even if the negative toner adheres to the fixing roller 1, the offset toner moves from the fixing roller 1 to the pressure roller 6, and The pressure roller 6 moves to the cleaning roller 12. Therefore, stains due to redeposition on the transfer material P passing next by the offset toner do not occur.

[0027]

As is apparent from the above description, according to the image forming apparatus and the fixing device of the present invention, the fixing rotator and the pressing rotator have the surface layer having the positive surface potential,
Since the absolute value of the surface potential of the pressing rotary body is larger than that of the fixing rotary body, even if a transfer material containing calcium carbonate is passed through the fixing device, the adhesion of calcium carbonate and the toner Electrostatic offset can be prevented and a high quality image can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a fixing device according to a first exemplary embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a fixing device according to a second exemplary embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a fixing device according to a third exemplary embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing an embodiment of an electrophotographic image forming apparatus in which the present invention is embodied.

FIG. 5 is a schematic configuration diagram showing an example of a conventional fixing device.

[Explanation of symbols]

1 Fixing roller (Rotating body for fixing) 2 Insulation adhesive layer 3,9 Release layer (surface layer / coating layer) 4 Core bar for fixing roller 6 Pressure roller (rotating body for pressure) 7 Core for pressure roller 8 elastic layer 10 power supplies 11 Negative toner (negatively charged toner) 12 Cleaning roller (cleaning member) 20 Fixing device P transfer material

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H033 AA08 AA09 BA13 BA49 BA54                       BA55 BA59 BB00 BB04 BB29                 3J103 AA02 AA14 AA15 AA24 AA32                       AA33 AA51 BA03 BA41 BA46                       FA05 FA06 FA07 FA18 GA02                       GA57 GA58 GA66 HA03 HA04                       HA05 HA15 HA20 HA37 HA43                       HA53

Claims (6)

[Claims] 1. A transfer comprising a fixing rotator and a pressure rotator that is in pressure contact with the fixing rotator and rotates together, wherein a toner image composed of a negatively charged toner is placed between the rotators. In an image forming apparatus having a fixing device for fixing the toner image as a permanent image on the transfer material by passing a material through heating and pressing, the fixing rotating body and the pressing rotating body have a positive surface potential. An image forming apparatus having a surface layer having the surface potential of the pressure applying rotary member having a larger absolute value than the surface potential of the fixing rotating member. 2. The image forming apparatus according to claim 1, wherein a bias voltage having a positive polarity is applied to the pressing rotary body so that an absolute value of a surface potential on the pressing rotary body side becomes large. 3. The fixing rotator has a hollow core metal, an insulating adhesive layer on the core metal, and a coating layer on the insulating adhesive layer, and the pressure rotator has conductive elasticity. The image forming apparatus according to claim 2, further comprising a layer and a conductive coating layer. 4. The image forming apparatus according to claim 1, further comprising a cleaning member that comes into contact with the pressing rotary member. 5. A cleaning member, which comes into contact with the pressurizing rotary member, is provided so that the absolute value of each surface potential becomes larger in the order of the cleaning member, the pressurizing rotary member, and the fixing rotary member. The positive bias voltage is applied to the cleaning member.
Image forming device. 6. A transfer having a fixing rotator and a pressure rotator that is in pressure contact with the fixing rotator and rotates together, wherein a toner image composed of a negatively charged toner is placed between the rotators. In a fixing device for fixing the toner image as a permanent image on the transfer material by passing the material through heating and pressing, the fixing rotator and the pressing rotator have a surface layer having a positive surface potential. However, the fixing device is characterized in that the surface potential of the pressing rotary member has a larger absolute value than the surface potential of the fixing rotary member.