JPH10254263A - Belt for fixing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the waiting time on speeding-up of fixing, making a high speed copying possible, and quickening the temp. rising rate to the fixing temperature by composing a electromagnetic induction heat generating metallic layer generating heat by the eddy current loss on the surface of a heat resistance plastic tube shape substrate. SOLUTION: As for this belt, the electromagnetic induction heat generating metallic layer 12 generating heat by the eddy current loss is formed on the surface of the heat resistance plastic tube shape substrate 11. Moreover, the electromagnetic induction heat generating metallic layer 12 is heated by adopting a high frequency coil that a parting layer consisting of fluorinated resin, and silicone rubber of a RTV type or the LTV type is composed thereon, and making the eddy current generated in the material namely, the electromagnetic induction heat generating metallic layer 12 becomes a heating body. When performing the induction heating with use of this belt for fixing, the temp. on the fixing surface held in contact with the toner image, can be raised up to the heat resisting temp. of the heat resistance plastic 11 of the substrate, consequently, the speed up of the copying by increasing paper passing speed can be made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to a fixing belt used in a fixing unit of an image forming apparatus such as a laser beam printer and a facsimile, and more particularly, to a fixing belt for heating a toner image by an induction heating method and fixing the toner image on a transfer material.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, a laser beam printer, and a facsimile, at the final stage of printing and copying, a toner image formed on a transfer material such as transfer paper is heated and melted to be transferred. Established on wood. For example, in an electrophotographic copying machine, a latent image carrier (eg,
A process of forming an electrostatic latent image by performing image exposure on a photosensitive drum), a process of attaching a developer (toner) to the electrostatic latent image to form a visible image (toner image), a process of forming a toner image on a transfer paper Is transferred through a step of transferring the transfer paper from the photosensitive drum and a step of fixing the unfixed toner image on the transfer paper by a method such as heating. Generally, colored resin particles composed of a colorant such as carbon black and a binder resin are used as the toner.

As a fixing method, a heat fixing method is generally used, and a heat roller fixing method as shown in FIG. 1 has been widely used. In the heat roller fixing method, a heater 2
Are arranged, and a pair of rollers including a heat roller (fixing roller) 1 and a rubber roller (pressing roller) 5 whose outer periphery is covered with rubber or resin having good release properties are pressed against each other, and the toner image 3 is formed between the rollers. The toner is heated and melted by passing the formed transfer paper 4 to fuse the toner onto the transfer paper. The heat roller 1 is usually heated to a temperature higher than the melting temperature of the binder resin of the toner. The heat roller fixing method is suitable for high-speed operation because the entire heat roller is maintained at a predetermined temperature during operation of the apparatus, but has a drawback that the waiting time at the time of startup is long. . That is,
At the start of the operation of the apparatus, a heating time is required for raising the temperature of the heat roller to a predetermined temperature, and a relatively long waiting time occurs between the time when the power is turned on and the time when the apparatus becomes operable. In addition, since the entire heat roller must be heated, power consumption is large.

Therefore, in recent years, as shown in FIG. 2, a fixing method has been proposed in which the toner on the transfer paper is heated by a heater through a thin tube-shaped endless belt. In this endless belt fixing method, the fixing belt 6 is used.
And the rubber roller 10 are pressed against each other, and the transfer paper 9 on which the toner image 8 is formed is passed during this time. At this time, the toner is heated by the heater 7 and fused on the transfer paper. In this fixing method, since the toner is heated substantially directly by a heater only through a thin film-like fixing belt, after the power is turned on, the heating unit reaches a predetermined temperature in a short time, and The waiting time at the time of introduction becomes almost zero. Further, in this fixing method, since only a portion necessary for fixing is heated, there is an advantage that power consumption is small.

However, since the endless belt fixing method employs a heating method using a heater in the same manner as the heat roller fixing method, the amount of heat dissipation is still large, and the heater temperature needs to be fixed for sufficient fixing. It was necessary to set the temperature considerably higher than the temperature and to slow down the transfer paper passing speed (paper passing speed) to provide a sufficient fixing time. On the other hand, in recent years, with the demand for high-speed copying and printing, it is necessary to increase the paper passing speed.
There is a need to raise the heater temperature much more than before. However, when the temperature of the heater is increased, there arises a problem that the heat capacity of the heater is exceeded, or the heat resistant temperature of the resin stay for fixing the heater is exceeded. Therefore,
In the endless belt fixing method, as long as the heater heating method is adopted, there is a limit in increasing the paper passing speed.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power-saving type fixing belt which has a high fixing speed, enables high-speed copying, has a high temperature rising speed to a fixing temperature, and has a short waiting time. Is to provide. The present inventors have conducted intensive studies to overcome the problems of the prior art. The present inventors have conceived of a fixing belt formed by the following method. The fixing belt can be heated by generating an eddy current in the electromagnetic induction heat generating metal layer by high frequency magnetic flux by a high frequency induction heating method using a high frequency coil. That is, the electromagnetic induction heat-generating metal layer serves as a heating element. When induction heating (electromagnetic heating: IH) is performed using this fixing belt, the temperature of the fixing surface in contact with the toner image can be raised to the heat-resistant temperature of the heat-resistant base material.
The speed of copying can be increased by increasing the paper passing speed.

In order to realize high-speed copying, the heater system must be heated to a temperature considerably higher than the fixing temperature in the case of the heater system. Since the (electromagnetically induced heat-generating metal layer) is close to the fixing portion, the temperature of the heating element can be made almost the same as the fixing temperature. In addition, due to heat generated by electromagnetic induction, the time until temperature rise can be shortened as compared with the conventional case. The present invention has been completed based on these findings.

[0008]

Thus, according to the present invention, an electromagnetic induction heat-generating metal layer which generates heat by eddy current loss is formed on the surface of a heat-resistant plastic tubular base. A fixing belt is provided.

According to the present invention, the following preferred embodiments are provided. (1) The fixing belt described above, wherein the electromagnetic induction heat-generating metal layer is a single layer or a plurality of layers formed of nickel, a nickel alloy, iron, an iron alloy, cobalt, or a cobalt alloy. (2) The fixing belt described above, wherein the thickness of the electromagnetic induction heat generating metal layer is larger than the depth of the skin effect determined by the frequency of the eddy current and the electromagnetic induction heat generation metal material. (3) The fixing belt as described above, further comprising a release layer made of fluororesin or RTV type or LTV type silicone rubber on the electromagnetic induction heat generating metal layer. (4) The fixing belt described above, wherein a heat-resistant elastomer layer is further formed on the electromagnetically induced heat-generating metal layer. (5) Fluororesin or RTV type or LT on electromagnetic induction heat generating metal layer via heat resistant elastomer layer
The above fixing belt further comprising a release layer made of V-shaped silicone rubber. (6) A fixing device including the fixing belt, and an electromagnetic induction heating coil disposed inside the fixing belt.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a heat-resistant plastic tube-shaped substrate is used as a substrate of a fixing belt. As the heat-resistant plastic, those having a melting point or a decomposition temperature equal to or higher than the fixing temperature can be used. Specific examples include polyimide, polyamideimide, polyether sulfone, polyphenylene sulfide, polyether ether ketone, and polybenzimidazole. So-called super engineering plastics.

Although the thickness of the tubular substrate is not particularly limited, it is usually 10 to 1000 in consideration of rigidity and elasticity.
μm, preferably 20-500 μm, more preferably 3 μm
It is desirable that the thickness be about 0 to 100 μm. The outer diameter of the tubular substrate can be appropriately determined depending on the size of the fixing device, but is usually 15 to 150 mm, preferably 20 to 150 mm.
It is about 100 mm. The length of the tubular substrate can be appropriately determined according to the size of a transfer material such as transfer paper.

In the present invention, an electromagnetic induction heat-generating metal layer that generates heat due to eddy current loss is formed on the surface of a heat-resistant plastic tubular substrate. Generally, when a conductive object to be heated such as a metal is put in a coil and an alternating current is applied to the coil, an eddy current flows through the object due to an electromagnetic induction action. Induction heating (Induction H)
eating; IH). In the high-frequency induction heating, a high-frequency coil is used to generate an eddy current in an object to be heated by high-frequency magnetic flux to heat the object. An induction heating coil is arranged near (in most cases) the fixing belt of the present invention, and alternating current is supplied, or in the case of direct current power, the ON / OF of a switch is repeated in an inverter circuit, and the alternating current is applied. When the current is converted into electric power and the current is intermittently applied, the eddy current is generated in the electromagnetically induced heat-generating metal layer, induced by the change in the magnetic field lines. Electromagnetically induced heat-generating metals have high resistance,
In practice, eddy currents do not flow smoothly and most of the electrical energy provided by the coils is converted to heat. This is called heat generation due to eddy current loss. As the electromagnetic induction heat generating metal, nickel, nickel alloy, iron, iron alloy, cobalt, cobalt alloy and the like are preferable. Among these, nickel and nickel alloys are particularly preferable in terms of heat generation and cost.

As a method of forming an electromagnetically induced heat-generating metal layer on the surface of a heat-resistant plastic tubular base,
There is also a method of attaching a thin layer of the metal (a metal foil or a thin sheet-like material) to a tubular substrate, but a method of forming a plated layer of the metal on the surface of the tubular substrate involves forming a metal layer having a uniform thickness. It is preferable because it can be easily formed. The electromagnetically induced heat-generating metal layer can be provided on the inner surface or outer surface of the heat-resistant plastic tubular substrate. However, since the metal layer serves as a heating element, it is preferably disposed on the outer surface near the fixing surface. Further, the metal layer may be formed on the entire surface of the tubular substrate, but may not necessarily be formed on the entire surface of the tubular substrate as long as the metal layer has a width suitable for the size of a transfer material such as transfer paper. Good. The metal layer may be a single layer, or may be a multilayer of two or more layers.

The upper limit of the thickness of the electromagnetic induction heat generating metal layer is as follows:
Although not particularly limited, it is desirable that the thickness is usually 1000 μm or less, preferably 500 μm or less, from the viewpoint of cost and thermal conductivity. The electromagnetic induction heat-generating metal layer is induced by a change in high-frequency magnetic flux, and becomes a heating element when an eddy current flows. Therefore, the lower limit of the thickness of the electromagnetically induced heat-generating metal layer is set to the depth of the skin effect determined by the frequency of the eddy current and the material of the metal layer because heat is generated by effectively consuming the alternating magnetic field generated by the high-frequency current. That is, it is preferable that the thickness is larger than the penetration depth.

The penetration depth is a thickness at which the eddy current near the surface of the metal layer becomes 1 / e, that is, a thickness necessary for attenuating the magnetic flux density by about 63%.
%. That is, when the thickness of the metal layer is thinner than the penetration depth, the magnetic flux generated by the applied high frequency is hardly consumed and penetrates. The thickness of the metal layer is preferably at least a penetration depth defined by the material. To consume nearly 100% of the applied magnetic flux, it is more preferable that the metal layer be somewhat thicker.

Regarding the material of the electromagnetic induction heat generating metal layer,
As a means to increase the resistance of the skin resistance itself in order to efficiently generate heat, one of the methods is to use nickel, a nickel alloy such as a nickel-chromium alloy, iron, an iron alloy such as permalloy or stainless steel, which constitutes the metal layer. And so on. In the present invention, a nickel-iron alloy (iron content: 10 to 30%) is particularly preferable from the viewpoint of the calorific value and the industrial viewpoint.
For example, in the case of iron (25%) / nickel (remainder) alloy,
The penetration depth is about 40 μm. Further, as a conductive material for induction heating, which is most industrially used, in the case of an iron-chromium alloy (equivalent to SUS430), the penetration depth is 400 μm.
m.

At the time of electroplating or chemical plating, a phosphoric acid compound is added to a bath to form a phosphorus eutectoid plating, for example,
Ni-P and Fe-P plating can be obtained. By adding a carboxylic acid compound, carbon eutectoid plating, for example,
Ni-C and Fe-C plating can be obtained. By adding a boron compound such as aminoborane, boron eutectoid plating, for example, Ni-B or Fe-B plating can be obtained. These can increase the skin resistance while almost maintaining the original magnetic properties and mechanical properties of the metal material, and are very effective for the use of the present invention.

When there is a further conductive metal layer inside the conductive metal layer, the inner metal layer functions as an electromagnetic shielding layer. Therefore, if the conductive metal layer is thick, magnetic flux reaches the outer metal layer contributing to heat generation. Attenuate. Therefore, the inner metal layer is preferably thin. For example, in the case of nickel, the magnetic flux density is attenuated to about 80% when the thickness near the surface is 100% when the thickness is 10 μm. If the material is coated with a material having sufficient elongation and low magnetic permeability, the attenuation rate is considered to decrease, and a thickness design according to the magnetic permeability of the material is required. Therefore, as in the present invention, it is preferable to use an organic material having a low magnetic permeability and a very high electric resistance, that is, a heat-resistant plastic as the tubular substrate.

When an electromagnetically induced heat-generating metal layer is formed on the surface of a heat-resistant plastic tubular substrate by plating, (1) after the surface of the tubular substrate is subjected to surface treatment by chemical etching or the like, (2) A thin alloy plating layer is formed by phosphorus eutectoid plating, carbon eutectoid plating, boron eutectoid plating, and the like. (3) An electromagnetic induction heat generating metal layer of a desired thickness is further formed thereon by electroplating or chemical plating. Preferably, it is formed. According to this method, the skin resistance can be increased, and the plating layer can be firmly adhered to the tubular substrate.

On the electromagnetically induced heat-generating metal layer, a fluororesin or RTV is used to improve the releasability of the toner.
It is preferable to provide a release layer made of a silicone rubber of a mold or LTV type. Examples of the fluorine resin include tetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer. The thickness of the release layer is usually about 10 to 50 μm. FIG. 3 shows a heat-resistant plastic tubular base 1.
1 is a cross-sectional view of a fixing belt having a laminated structure in which an electromagnetic induction heat-generating metal layer 12 is formed on a surface and a fluororesin layer is further formed thereon.

It is preferable to form a heat-resistant elastomer layer on the electromagnetically induced heat-generating metal layer. The presence of the elastomer layer increases the heat capacity. The one with larger heat capacity
Since the temperature retention of the fixing belt after the temperature rise is good, it is advantageous to speed up the fixing. As the heat-resistant elastomer, fluorine rubber or silicone rubber excellent in heat resistance is preferable. The thickness of the heat-resistant elastomer layer is usually less than 1.0 mm, preferably about 0.1 to 0.9 mm. When the releasability of the heat-resistant elastomer layer is insufficient, it is preferable to further form a release layer similar to that described above thereon. The induction heating coil is usually arranged inside the fixing belt. Therefore, according to the present invention, there is provided a fixing device including the fixing belt and the electromagnetic induction heating coil disposed inside the fixing belt. If necessary, the induction heating coil may be arranged close to the outside of the fixing belt.

[0022]

EXAMPLES Preferred embodiments of the present invention will now be described more specifically with reference to examples and comparative examples.

Example 1 Using a polyimide varnish (Pyre ML varnish manufactured by IST), a thickness of 5 was obtained by an ordinary method.
A polyimide tube having a thickness of 0 μm and an outer diameter of 27.6 mm was prepared. Next, an electromagnetic induction heat generating metal layer (electromagnetic induction layer) was formed on the outer surface of this polyimide tube by the following steps. (1) A polyimide tube was immersed in a 20 g / liter sodium hydroxide solution at 90 ° C. for 5 minutes to perform chemical etching. (2) After washing the polyimide tube with water, it is 160 ° C in air.
At a temperature of. (3) Electroless nickel plating was performed by the following method. The polyimide tube was immersed in an aqueous acidic palladium solution to adsorb palladium as a catalyst core. Next, it is immersed in an electroless nickel plating solution and nickel-P (10%) having a thickness of about 1 μm is formed on the surface of the polyimide tube.
An alloy plating layer was formed. (4) Electric nickel plating was performed by the following method. A Watts bath nickel solution was used as an electric nickel plating bath. The polyimide tube on which the nickel-P alloy plating layer was formed was immersed in a nickel solution of a Watt bath, and subjected to eddy electrolysis at 45 ° C. and a cathode current density of 25 A / dm ² for 30 minutes. As a result, a nickel film having a thickness of about 200 μm was formed. Next, a primer for rubber (DY39012, manufactured by Dow Corning Toray Co., Ltd.) was applied on the nickel film of the polyimide tube, and after drying, silicone rubber (KE7016U, manufactured by Shin-Etsu Silicone) was press-molded and coated. After grinding the coated rubber layer to adjust the thickness to 0.8 mm, a fluororesin paint (manufactured by Daikin, product number EK-4300) is spray-coated thereon, followed by drying and firing to obtain a thickness of 20 μm. Was formed. In this way, a fixing belt in which the electromagnetic induction heat-generating metal layer (plated layer), the heat-resistant elastomer layer, and the fluororesin layer were formed on the surface of the polyimide tube was obtained.

Comparative Example 1 A fixing belt having a heat-resistant elastomer layer and a fluororesin layer formed thereon was prepared in the same manner as in Example 1 except that no plating layer was formed on the outer surface of the polyimide tube of Example 1. Created.

<Evaluation of fixing speed> LBP manufactured by Canon Inc.
The fixing unit of A404P was taken out, the fixing belt was replaced with the fixing belt obtained in Example 1, and an electromagnetic induction heating coil was arranged in the fixing belt instead of the heater. On the other hand, a copying machine NP-4335 manufactured by Canon Inc.
Then, an appropriate pattern was copied, and an A4 sheet on which an unfixed toner image was formed was taken out. A large number of transfer sheets on which the unfixed toner image was formed were prepared. An alternating current was passed through the coil for electromagnetic induction heating, and the fixing belt was heated with an electric power of 100 W to adjust the surface temperature to 170 ° C. The transfer paper on which the unfixed toner image was formed was passed through the fixing unit one by one and fixed. At this time, the number of rotations of the fixing belt was changed, and the maximum number of sheets that could be fixed in one minute was evaluated. For comparison, the fixing speed of the fixing belt of Comparative Example 1 was evaluated. In the fixing belt of Comparative Example 1, the temperature was raised using an alumina heater attached to the apparatus.
The surface temperature was adjusted to 170 ° C. with an electric power of 100 W. The fixing property was evaluated based on the following fixing evaluation method. As a result, as shown in Table 1, in the fixing belt of Comparative Example 1, the decrease in lightness was reduced to the level of × at eight copies per minute, whereas in the fixing belt of Example 1, The level of ○ was maintained even with 12 copies per minute.

<Evaluation Method of Fixing Property> The fixing property was evaluated by placing a silver paper 15 on a fixed image (toner image) of a transfer paper 14 as shown in FIG.
A weight 16 of 00 g was placed and rubbed five times. The lightness of the fixed image before and after the rubbing was measured with a color difference meter, the degree of decrease in the lightness was calculated, and evaluated according to the following criteria. ◎: Lightness reduction is within 25%, ○: Lightness reduction is more than 25%, 50% or less, ×: Lightness reduction is more than 50%.

[0027]

[Table 1]

[0028]

According to the present invention, the fixing speed is high, high-speed copying is possible, and the temperature rising speed up to the fixing temperature is high.
A power saving type fixing belt with a short waiting time is provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a conventional heat roller fixing method.

FIG. 2 is an explanatory diagram of a conventional endless belt fixing method.

FIG. 3 is an explanatory diagram of a laminated structure of an example of a fixing belt of the present invention.

FIG. 4 is an explanatory diagram of a method for evaluating fixability.

[Description of Signs] 1: Hero tora (fixing roller) 2: Heater 3: Toner 4: Transfer paper 5: Pressing roller 6: Fixing belt 7: Heater 8: Toner 9: Transfer paper 10: Pressing roller 11: Tubular substrate 12: Electromagnetically induced heat-generating metal layer 13: Fluororesin layer 14: Transfer paper 15: Silbon paper 16: Weight

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshihiko Takiguchi 1-3-1 Shimaya, Konohana-ku, Osaka-shi, Osaka Sumitomo Electric Industries, Ltd. Osaka Works

Claims (1)

[Claims] 1. A fixing belt comprising: a heat-resistant plastic tubular substrate having an electromagnetically induced heat-generating metal layer which generates heat due to eddy current loss formed on a surface thereof.