JP2000155489A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fixing device and an image forming device which can prevent the occurrence of crack and which can perform good paper ejection in an OHP by improving the followup ability between a surface layer resin and a lower layer elastic body layer. SOLUTION: This fixing device has the roller pair of a fixing roller and a pressure roller rotatably disposed while the rollers are brought into press- contact with each other, holds and carries a recording material having an unfixed image at a press-contact part formed by the roller pair, so that the unfixed image on the recording material is thermally fixed. In this case, the fixing roller is formed by calcining the elastic body layer 2 of >= 1 mm and the resin from 20 μm to 50 μm on the surface of the layer 2, the coefficient of linear expansion of the layer 2 of 150 deg.C is within 2.7 times as that of the resin layer of 150 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device suitable for heat fixing used in electrophotography, electrostatic recording and magnetic recording, and an image forming apparatus using a toner for developing an electrostatic image.

[0002]

2. Description of the Related Art Conventionally, electrophotography has been disclosed in U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910.
As described in Japanese Patent Application Publication No. JP-B-43-24748 and Japanese Patent Publication No. 43-24748, generally, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means. Forming and then developing the latent image with toner,
Using a direct or indirect means as necessary, after transferring the toner image to a transfer material such as paper, fixing by heating, pressure, heating and pressurizing or solvent vapor, etc. to obtain a copy, and The toner remaining on the photoreceptor without being transferred is cleaned by various methods, and the above steps are repeated.

Further, a general method of forming a full-color image will be described. The photosensitive member of a photosensitive drum is uniformly charged by a primary charger, and image exposure is performed by a laser beam modulated by a magenta image signal of a document. To form an electrostatic latent image on the photosensitive drum, and develop the electrostatic latent image by a magenta developing device having magenta toner to form a magenta toner image. Next, the magenta toner image developed on the photosensitive drum by the transfer charger is transferred to the conveyed transfer material using direct or indirect means.

On the other hand, the photosensitive drum after the development of the electrostatic latent image is neutralized by a static eliminator, cleaned by a cleaning unit, and charged again by a primary charger. A cyan toner image is formed and the cyan toner image is transferred to a transfer material on which the magenta toner image has been transferred.
The same procedure is performed in the same manner as for the black color to transfer the four color toner images to the transfer material. A full-color image is formed by fixing the transfer material having the four color toner images by the action of heat and pressure by a fixing roller.

[0005] In recent years, such devices have begun to be used not only as office work copiers for copying original manuscripts, but also as printers as personal computer outputs or personal copies for individuals.

[0006] In addition to such fields represented by laser beam printers, the development of plain paper faxes using a basic engine has been rapidly developing.

For this reason, smaller, lighter, faster, higher image quality, and higher reliability have been strictly pursued, and machines have become simpler in various aspects. . As a result, the performance required of the toner has become higher, and if the performance of the toner cannot be improved, a better machine cannot be realized. Further, in recent years, demands for color copying have been rapidly increasing along with various copying needs, and further higher image quality, higher resolution, etc. are desired in order to more faithfully copy original color images. From these viewpoints, the toner used in the color image forming method needs to have good meltability and color mixing when heat is applied thereto, and has a low softening point and a low melt viscosity. It is preferable to use a toner having a high melting property.

That is, by using such a sharp melt toner, the color reproduction range of a copy can be widened and a color copy faithful to the original image can be obtained.

However, such a color toner having a high sharp melt property generally has a high affinity with a fixing roller, and tends to be easily offset to the fixing roller during fixing.

Particularly, in the case of a fixing device in a color image forming apparatus, since a plurality of toner layers of magenta, cyan, yellow, and black are formed on a transfer material, offset tends to occur particularly due to an increase in toner layer thickness. It is in.

Conventionally, for the purpose of preventing the toner from adhering to the surface of the fixing roller, for example, the roller surface is formed of a material having excellent releasability from the toner, such as silicone rubber or fluorine rubber, and the surface of the roller is prevented from being offset and the roller surface is formed. In order to prevent fatigue of the roller, the surface of the roller is coated with a thin film of a liquid having high releasability such as silicone oil or fluorine oil. At this time, a material having good compatibility with the release agent and the roller surface is selected. However, this method is extremely effective in preventing toner offset, but has a problem that a fixing device is complicated because a device for supplying an anti-offset liquid is required. Needless to say, this oil application causes delamination between the layers constituting the fixing roller, and consequently has a disadvantage that the life of the fixing roller is shortened. As a transfer material for fixing a toner image using these fixing devices, generally, various papers, coated paper,
A plastic film or the like is used. In particular, the necessity of a transparency film (OHP) using an overhead projector for presentation has recently attracted attention. Especially, in OHP, unlike paper, copy OH obtained at present because of low oil absorption capacity
For P, stickiness due to oil application is inevitable, and there is still a large problem in the quality of the obtained image. In addition, there is a large possibility that silicone oil and the like will evaporate due to heat and contaminate the inside of the machine, and problems such as processing of collected oil will occur. Therefore, instead of using a silicone oil supply device, instead of supplying the anti-offset liquid during heating from the toner, a method of adding a release agent such as low molecular weight polyethylene or low molecular weight polypropylene to the toner is proposed. Have been. However, if a large amount of such an additive is added in order to obtain a sufficient effect, filming on the photoreceptor and contamination of the surface of the toner carrier such as a carrier or a sleeve are performed, and an image is deteriorated, which is a practical problem. Become. Therefore, a small amount of a release agent is added to the toner to the extent that the image is not deteriorated, and a small release oil is supplied or the offset toner is wound up using a device such as a web-like member or a cleaning pad. It is common to use a cleaning device together.

It is known to include wax as a release agent in a toner. For example, Japanese Patent Publication No. 52-3304
JP, JP-B-52-3305, JP-A-57-5-5
The technology is disclosed in 2574 and the like.

Further, JP-A-3-50559, JP-A-2-79860, JP-A-1-109359, JP-A-62-14166, and JP-A-61-27
3554, JP-A-61-94062, JP-A-61-138259, JP-A-60-25236
No. 1, Japanese Unexamined Patent Publication No. 60-252360, Japanese Unexamined Patent Publication No.
Japanese Patent Application Laid-Open No. 0-217366 discloses a technique for containing waxes.

By using such a toner containing wax in the toner, it is possible to prevent offset without applying a release agent to the roller surface as in the prior art, and therefore, the material on the surface of the fixing roller can be prevented. Are no longer limited to those that are particularly familiar with the release agent. That is, in the case of the conventional sharp melt toner, silicone rubber or fluorine rubber is used for the roller surface, but these have problems in abrasion resistance, strength, etc., and when the number of copies increases, the surface is scratched. And the image was defective. Thus, by using such a wax-containing toner, it has become possible to use a fluorine-based resin having further excellent abrasion resistance and releasability for the surface layer of the roller.

However, the use of such a fixing roller in which the surface of the fluororesin is coated and baked causes the following problems.

Since the surface of such a fluororesin sintering roller is harder than a conventional roller having an elastic layer on the surface, the amount of deformation of the surface of the fixing roller is smaller than that of the elastic layer roller, and the recording material is discharged in the discharge direction. In the figure, the fluororesin sintering roller was higher. If the discharge direction is higher, gloss unevenness may appear on the image, or the recording material may wind around the fixing roller depending on the type of the recording material. Particularly, in the case of fixing an OHP film, it is necessary to perform fixing at a lower speed in order to improve the transparency, so that it has become easier to wind around the fixing roller. Therefore, an elastic layer is provided below the fluororesin layer on the surface to increase the thickness, which softens the fixing roller, and increases the amount of deformation to stably discharge the paper downward from the horizontal direction. Was doing.

However, when the fixing roller having such a configuration is used, the surface resin cannot follow the elastic layer due to the difference in linear expansion coefficient between the lower elastic layer and the surface resin layer.
When the number of copies increases and the surface resin deteriorates, cracks occur in the surface resin, resulting in image defects.
This was more likely to occur when the thickness of the lower elastic layer was increased.

[0018]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides a fixing device that does not cause cracks in the surface resin of the fixing roller and an image forming apparatus using the fixing device. With the goal.

[0019]

The above object is achieved by the following means.

That is, the first aspect of the present invention has a roller pair of a fixing roller and a pressure roller which are rotatably disposed while being in pressure contact with each other, and has an unfixed image at a pressure contact portion formed by the roller pair. In a fixing device in which a recording material is nipped and conveyed to heat and fix an unfixed image on the recording material, the fixing roller includes an elastic layer of 1 mm or more, and a resin of 20 μm to 50 μm on a surface of the elastic layer. The elastic layer has a linear expansion coefficient at 150 ° C. of 1
The present invention proposes a fixing device characterized by being within 2.7 times the linear expansion coefficient at 50 ° C.

According to a second aspect of the present invention, there is provided a roller pair of a fixing roller and a pressure roller which are rotatably disposed while being in pressure contact with each other, and a non-fixed image is formed at a pressure contact portion formed by the roller pair. In a fixing device that heats and fixes an unfixed image on a recording material by nipping and transporting the recording material, the fixing roller includes an elastic layer having a thickness of 1 mm to 3 mm, and a resin is baked on the surface of the elastic layer. Molded and the thickness of the resin layer is 60
The present invention proposes a fixing device having a thickness of from 100 μm to 100 μm.

According to a third aspect of the present invention, there is provided a recording roller having a pair of a fixing roller and a pressure roller which are rotatably disposed while being in pressure contact with each other, and having an unfixed image at a pressure contact portion formed by the roller pair. In a fixing device that heats and fixes an unfixed image on the recording material by nipping and conveying the material, the fixing roller includes an elastic layer having a thickness of 1 mm or more, and a surface having a thickness of 20 μm.
m is formed by firing a resin having a thickness of 50 μm to 50 μm, and a linear expansion coefficient between the elastic body layer and the resin layer between the linear expansion coefficient of the elastic body at 150 ° C. and the resin layer at 150 ° C. A fixing member having at least one elastic layer having a coefficient, wherein the linear expansion coefficient at 150 ° C. of an adjacent inner layer is within 2.7 times the linear expansion coefficient at 150 ° C. of an adjacent outer layer. A device is proposed.

According to a fourth aspect of the present invention, there is provided a roller pair of a fixing roller and a pressure roller which are rotatably disposed while being pressed against each other, and a non-fixed image is formed at a pressure contact portion formed by the roller pair. In a fixing device that heats and fixes an unfixed image on a recording material by nipping and conveying the recording material, the fixing roller has an elastic layer of 1 mm or more, and a surface of the elastic layer having a thickness of 20 mm or more.
A resin having a hardness of 75 ° according to JIS-A standard is formed by baking a resin having a thickness of 50 μm to 50 μm, and between the elastic layer and the resin layer.
A fixing device having at least one elastic layer as described above is proposed. In the first aspect, preferably, the elastic layer has a linear expansion coefficient of 4.0 × 10E at 150 ° C. ^-4 cm / cm · ° C. or less, and preferably in the third aspect, the coefficient of linear expansion at 150 ° C. of the elastic layer away from the resin layer is 150 ° C. 2.7 times or more and 3.4 times or less, and the coefficient of linear expansion of the elastic layer adjacent to the resin layer is within 4.0 × 10E ⁻⁴ cm / cm · ° C.

In the present invention, by setting the relationship between the resin layer and the elastic layer as described above, it is possible to improve the followability between the surface resin and the lower elastic layer, to prevent the occurrence of cracks and to prevent OHP. This makes it possible to perform excellent paper discharge.

[0025]

According to a first aspect of the present invention, there is provided a roller pair of a fixing roller and a pressure roller which are rotatably disposed while being pressed against each other, and a pressing portion formed by the roller pair. In the fixing device, the recording material having the unfixed image is nipped and conveyed to heat and fix the unfixed image on the recording material. In the fixing device, the fixing roller has an elastic layer of 1 mm or more and a surface of the elastic layer. When the resin of 20 μm to 50 μm is fired and molded, and the coefficient of linear expansion at 150 ° C. of the elastic layer is within 2.7 times the linear expansion coefficient of the resin layer at 150 ° C., the surface layer resin and the lower layer elastic The ability to follow the body layer can be improved, cracks can be prevented from occurring, and good OHP paper discharge can be achieved.

FIG. 1 is a sectional view showing an example of a fixing roller used in the fixing device of the present invention.

The fixing roller according to the first aspect of the present invention has a surface layer 1 provided on a metal core 3 via an elastic layer 2 as shown in FIG.

Examples of the core metal 3 include aluminum and iron, and the thickness is preferably in the range of 1 to 10 mm.

As the elastic layer 2, HTV silicone rubber,
LTV silicone rubber and the like, the thickness of which is 1 mm
A range of not less than 3 mm or less is preferable.

As the surface layer 1, tetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PF)
A) and the like.
mm or less, the thickness of the surface layer 1 is 20 μm to 50 μm.
Is important. If the thickness of the surface layer 1 is less than 20 μm, unevenness of the surface layer 1 is likely to appear, and the surface property of the roller is deteriorated, resulting in a defective image. However, there are problems such as deterioration of the image quality and an increase in the cost of the roller, which is not preferable.

In this case, it is important that the coefficient of linear expansion of the elastic layer 2 at 150 ° C. is within 2.6 times the coefficient of linear expansion of the resin layer of the surface layer 1 at 150 ° C.

Further, according to the second aspect of the present invention, there is provided a roller pair of a fixing roller and a pressure roller which are rotatably disposed while being pressed against each other, and a non-fixed portion is formed by a pressure contact portion formed by the roller pair. In a fixing device in which a recording material having an image is nipped and conveyed to heat and fix an unfixed image on the recording material, the fixing roller has an elastic layer of 1 mm to 3 mm, and a resin is applied to the surface of the elastic layer. When the resin layer is formed by baking and the thickness of the resin layer is 60 μm to 100 μm, the thermal expansion of the lower elastic layer can be suppressed by the surface layer resin. Becomes possible.

Next, the second invention of the present invention is the case where the thickness of the elastic layer 2 of the fixing roller is 1 mm to 3 mm. In this case, it is important that the thickness of the resin layer of the surface layer 1 is 60 to 100 μm. It is. If the thickness of the surface layer 1 is less than 60 μm, the thermal expansion of the lower elastic layer 2 cannot be suppressed, and
Crack cannot be prevented. The thickness of the surface layer 1 is 100
If it exceeds μm, there is a problem that heat conduction becomes poor and heat supply from the inside becomes poor.

Further, according to the third aspect of the present invention, there is provided a roller pair of a fixing roller and a pressure roller which are rotatably disposed while being in pressure contact with each other. In a fixing device for carrying out heat fixing of an unfixed image on the recording material by nipping and conveying the recording material having a landing image,
The fixing roller is formed by firing an elastic layer having a thickness of 1 mm or more and a resin having a thickness of 20 μm to 50 μm on the surface of the elastic layer, and a temperature of 150 ° C. between the elastic layer and the resin layer.
Has at least one elastic layer having a linear expansion coefficient between the linear expansion coefficient of the resin layer and the linear expansion coefficient of the resin layer at 150 ° C., and the linear expansion coefficient of the adjacent inner layer at 150 ° C. When the coefficient of linear expansion at 150 ° C. is set to 2.7 times or less, the followability between the surface resin and the lower elastic layer can be improved, cracks can be prevented from occurring, and good OHP paper can be discharged. .

It is important that the coefficient of linear expansion at 150 ° C. of the resin layer of the surface layer 1 is 2.7 times or less. Elastic layer 2
1. The linear expansion coefficient at 150 ° C. of the resin layer of the surface layer 1 is 2.
If it exceeds 7 times, cracks occur in the surface layer 1, which is not preferable.

The thickness of the elastic layer 2 of the fixing roller is 1 m.
In the case of m to 3 mm, it is important that the thickness of the resin layer of the surface layer 1 is 60 to 100 μm. The thickness of the surface layer 1 is 6
If the thickness is less than 0 μm, thermal expansion of the lower elastic layer 2 cannot be suppressed, and cracks in the surface layer 1 cannot be prevented. On the other hand, if the thickness of the surface layer 1 exceeds 100 μm, there is a problem that heat conduction is deteriorated and heat supply from the inside is deteriorated.

FIG. 3 shows another example of the fixing roller. In this example, the surface layer 1 is provided on the cored bar 3 via the lower elastic layer 4 and the intermediate elastic layer 5 as elastic layers. It is provided. Two or more elastic layers may be provided.

In this case, the core metal 3 and the surface layer 1 of the fixing roller
The same material as that in the case of FIG. 1 is used.
Examples of the lower elastic body 4 include fluorine rubber and silicone rubber. FIG. 2 is a cross-sectional view showing another example of the fixing roller.

As shown in FIG. 2, the fixing roller of the third invention has a surface layer 1 provided on a cored bar 3 as an elastic layer via a lower elastic layer 4 and an intermediate elastic layer 5. The intermediate elastic layer 5 may be two or more layers.

As the material of the core metal 3 and the surface layer 1 of the fixing roller, the same material as the fixing roller of FIG. 1 is used.

The material of the lower elastic layer 4 is, for example, fluorine rubber or silicone rubber. The intermediate elastic layer 5 is, for example, a mixture of fluorine rubber and PFA, FEP, or the like.

In this case, the thickness of the lower elastic layer 4 is 1 mm.
The thickness of the intermediate elastic layer 5 is preferably in the range of 10 μm to 100 μm.

In this case, the thickness of the surface layer 1 is 20 μm.
A resin having a thickness of about 50 μm is baked and molded.

The coefficient of linear expansion at 150 ° C. of the intermediate elastic layer 5 has a coefficient of linear expansion between the lower elastic layer 4 and the resin layer of the surface layer 1 at 150 ° C. It is important that the coefficient of linear expansion of the lower elastic layer 4 at 150 ° C. is within 2.6 times the linear expansion coefficient of the adjacent outer elastic layer 5 at 150 ° C.

Further, according to the fourth aspect of the present invention, there is provided a roller pair of a fixing roller and a pressure roller which are rotatably disposed while being in pressure contact with each other, and the pressure contact portion formed by the roller pair is undetermined. In a fixing device for carrying out heat fixing of an unfixed image on the recording material by nipping and conveying the recording material having a landing image,
The fixing roller is formed by firing an elastic layer having a thickness of 1 mm or more and a resin of 20 μm to 50 μm on the surface of the elastic layer, and a hardness between the elastic layer and the resin layer according to JIS-A standard. By having at least one elastic body layer of 75 ° or more, the followability between the surface resin and the lower elastic body layer can be improved, cracks can be prevented from being generated, and good OHP paper can be discharged.

According to a fifth aspect of the present invention, in the first to fourth aspects, the elastic layer has a temperature of 150 ° C.
Has a linear expansion coefficient of 4.0 × 10E ⁻⁴ cm / cm · ° C.
Within this range, it is possible to improve the followability between the surface resin and the lower elastic body layer, to prevent the occurrence of cracks and reduce the OH
Good discharge of P is possible.

According to a sixth aspect of the present invention, in the second to fourth aspects, the elastic layer has a temperature of 150 ° C.
Is from 2.7 times to 3.4 times the linear expansion coefficient of the resin layer at 150 ° C., and 4.0 ×
When the temperature is within 10E ⁻⁴ cm / cm · ° C., the followability between the surface resin and the lower elastic layer can be improved, and the occurrence of cracks can be prevented and the OHP can be discharged well.

The fixing device of the present invention can be applied to a fixing device of a conventional image forming apparatus.

As an example of such an image forming apparatus, FIGS. 3 to 5 show a full-color copying machine having a plurality of optical scanning means. FIG. 3 is a sectional view of a full-color copying machine, and FIG.
5 is an enlarged view of the image forming unit, and FIG. 5 is an enlarged view of the fixing unit in FIG.

First, a full-color copying machine will be briefly described with reference to FIGS.

As shown in FIG. 3, around an electrophotographic photosensitive member (hereinafter referred to as a "photosensitive drum") as a latent image carrier, an image forming stay as an image forming means having a developing device and the like is provided. An image on the photosensitive drum formed at each of the image forming stations is provided with a recording material such as a sheet of paper (hereinafter referred to as transfer paper) on a conveying means which moves and passes adjacent to the photosensitive drum. ) Is transferred to P.

Above the image forming station, there is provided a reader unit for reading a document by a photoelectric conversion element such as a CCD.

As shown in FIG. 4, photosensitive drums 1a, 1b, 1c, and 1d are provided at image forming stations Pa, Pb, Pc, and Pd for forming images of magenta, cyan, yellow, and black, respectively. Each photosensitive drum is rotatable in the direction of the arrow. further,
Around each photosensitive drum 1a, 1b, 1c, 1d, a charger 12a, 12b, 12c, 12d, a laser scanning unit, developing devices 2a, 2b, 2c, 2d, and a cleaner 4
a, 4b, 4c, and 4d are sequentially arranged along the rotation direction of the photosensitive drum, and a transfer section 3 is arranged below each photosensitive drum. The transfer unit 3 includes a transfer belt 31 serving as a recording material conveying unit common to each image forming station.
And transfer chargers 3a, 3b, 3c, 3d.

In the copying machine as described above, FIGS.
The transfer paper P supplied from a paper feed cassette 61 as a recording material supply means is supported on a transfer belt 31 and conveyed to each image forming station, and contains wax of each color formed on each photosensitive drum. The toner images are sequentially transferred.

When the transfer step is completed, the paper P is separated from the transfer belt 31 and is conveyed to the fixing device 5 by the conveyer belt 62 serving as recording material guiding means.

The fixing device 5 includes, as shown in detail in FIG.
A fixing roller 51 rotatably disposed as a fixing rotating body.
A pressure roller 52 serving as a pressure rotating body that rotates while being pressed against the fixing roller 51;
4 and 55 are provided.

The fixing roller 51 has a structure in which a lower layer made of HTV (high temperature vulcanization type) silicone rubber is coated on a core metal of aluminum or iron, and the outer surface thereof is coated with a fluororesin layer using an adhesive. I have. Materials such as tetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer (PFA) are used for the surface fluororesin layer. Since the surface is softer when using a roller coated with these than the shape, the roller surface can be more closely adhered to the toner image and good fixability can be obtained. In addition, the use of these fluororesin coating rollers enables lower cost production and cost reduction as compared with conventional silicone rubber and fluororubber rollers.

Heaters 56 and 57 such as halogen lamps are provided inside the fixing roller 51 and the pressure roller 52, respectively. (However, in some cases, the halogen heater 57 is not provided inside.) Thermistors 58 and 59 are disposed so as to be in contact with the fixing roller 51 and the pressing roller 52, respectively, and are connected via a temperature control circuit. Heater 5
6. The temperature of the surfaces of the fixing roller 51 and the pressure roller 52 is adjusted by controlling the voltage to the heater 57.

Further, a cleaning device 54 is attached to the fixing roller 51, and the cleaning device 54 cleans the toner and the like offset on the fixing roller 51.

The cleaning device 54 includes a cleaning web 54 a made of a belt-shaped heat-resistant nonwoven fabric, and a pressing roller 5 for pressing the cleaning web 54 a against the fixing roller 51.
4b, an unwinding roller 54c for unwinding a new cleaning web 54a, and a winding roller 54d for gradually winding the cleaning web 54a having a reduced cleaning ability due to the adhesion of toner and the like. The cleaning device 54 is provided upstream of the thermistor 58 in the rotation direction of the fixing roller 51 so as to prevent the offset toner from adhering to the thermistor 58 and causing a detection failure in the thermistor 58.

As a method for winding the cleaning web 54a, when it is determined that a predetermined number of copies have been made from the counter, a solenoid (not shown) is turned on and the one-way clutch is operated, so that a predetermined amount of the web is wound in a direction opposite to the rotation of the roller. I have. By taking up in the opposite direction, the cleaning web 54a is prevented from being taken up in the roller rotation direction.

The pressing roller 52 is also provided with the fixing roller 5.
A cleaning device 55 including a cleaning web 55a, a pressing roller 55b, an unwinding roller 55c, a take-up roller 55d, and the like similar to the first cleaning device 54 is attached, and the toner adhered to the pressure roller 52 via the fixing roller 51. Cleaning has been done. (However, the pressure roller cleaning 55 may not be provided.)

In this state, when the transfer paper P is conveyed, the fixing roller 51 and the pressure roller 52 rotate, and when the recording material P passes between the fixing roller 51 and the pressure roller 52, Then, the unfixed toner image on the paper surface is melted and fixed by applying pressure and heating at a substantially constant pressure and temperature, and a full-color image is formed on the recording material P. The transfer paper P on which the image has been fixed is separated by the separation claw 68 and discharged out of the apparatus.

Hereinafter, the present invention will be described more specifically with reference to examples.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a sectional view of a fixing roller embodying the present invention, and Table 1 shows an experimental result using the fixing roller of this embodiment.

In this embodiment, the occurrence of cracks is prevented by setting the ratio of the coefficient of linear expansion between the surface resin layer and the lower resin layer within a predetermined range. First, the fixing roller used in this embodiment will be described with reference to FIG. The fixing roller used in this embodiment is formed by forming an HTV silicone rubber on a 5 mm Al core metal to a thickness of 0.5 to 3.5 mm, and then applying a powder coating of a PFA resin to a thickness of about 20 to 50 μm thereon and firing. The outer diameter was 40 mm. Here, regarding the lower layer HTV silicone rubber, the coefficient of linear expansion at 150 ° C. is changed to 3 to 5 × 10 E ⁻⁴ by changing the amount of the filler.
The one adjusted to cm / cm · ° C. was used. The pressure roller is 1mm HTV silicone rubber on a 5mm Al core.
And a roller having a 50 μm PFA tube formed thereon. Table 1 shows the results of examining the OHP sheet discharge performance and the occurrence of cracks by applying a pressure of 40 kg to these fixing roller and pressure roller.

First, regarding the paper discharge property of OHP, Y, M,
OH made of 100 μm PET for each of C and Bk toners
The unfixed toner image formed on P is fixed at a fixing temperature of 150.
The OHP was conveyed to the above-mentioned fixing device rotating at a fixing speed of 30 mm / sec at a fixing temperature of 30 ° C., and the discharge direction of OHP after fixing was examined.
As a result, if the thickness of the lower elastic layer of the fixing roller was smaller than 1 mm, the OHP was wound around the fixing roller, and good discharge was not performed. In addition, the thickness of the lower rubber of the pressure roller is set to 1
The same result was obtained even if the thickness was smaller or larger than 1 mm, and the thickness of the lower elastic layer of the fixing roller was required to be 1 mm or more in order to discharge OHP satisfactorily. Next, the state of occurrence of cracks was examined by changing the linear expansion coefficient of the lower elastic layer of the fixing roller. As a measurement method, a heat cycle test was repeated in which the power was turned on, the temperature was controlled at a temperature of 150 ° C. for 30 minutes, and then cooled for 90 minutes. As a result, when the thickness of the lower elastic layer of the fixing roller is 1 mm or more, no crack occurs when the linear expansion coefficient of the lower elastic layer at 150 ° C. becomes smaller than 2.7 times the linear expansion coefficient of the surface resin layer. It became clear.

The fixing temperature, speed, and pressure in the present embodiment vary depending on the toner used and the mechanical configuration, and are not necessarily limited to these values. In this embodiment, a fixing roller whose surface layer is baked with a PFA resin is used. However, the same effect can be obtained by coating and baking PTFE or FEP with a spray or the like.

[0070]

[Table 1]

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a sectional view of a fixing roller embodying the present invention, and Table 2 shows an experimental result using the fixing roller of this embodiment.

In this embodiment, cracks are prevented from occurring when the ratio of the coefficient of linear expansion between the surface resin layer and the lower resin layer is out of a predetermined range. First, the fixing roller used in this embodiment will be described with reference to FIG. The fixing roller used in this embodiment has a linear expansion coefficient of the lower elastic layer at 150 ° C. of at least 2.6 times the linear expansion coefficient of the surface resin layer, and the thickness of the surface resin layer is changed from 20 to 100 μm. .
The same pressure roller as that used in the first embodiment is used.
Table 2 shows the results of an experiment performed under the same conditions as in the above.

In Table 2, when the linear expansion coefficient of the lower layer at 150 ° C. is 2.7 to 3.4 times the linear expansion coefficient of the surface resin layer, cracks tend to occur when the thickness of the lower elastic layer is increased. However, if the surface resin layer is thickened at that time, cracks will not occur because the surface resin can suppress deformation due to thermal expansion. As the region, the thickness of the lower elastic layer is 1 m.
When the thickness is in the range of m to 3 mm, the thickness of the surface resin layer is adjusted to 60 to 10 mm.
When the thickness is set to 0 μm, no crack occurs. The thicker the surface resin, the more effective it is against cracks,
The thickness is preferably up to 100 μm from the viewpoint of heat conduction and manufacturing problems.

By doing so, the same as in the first embodiment, O
There is no HP winding and cracks can be prevented from occurring.

This embodiment is further effective when used when the coefficient of linear expansion of the elastic layer at 150 ° C. is 2.7 or less of the coefficient of linear expansion of the resin layer at 150 ° C.

[0077]

[Table 2]

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a sectional view of a fixing roller embodying the present invention, and Table 3 shows an experimental result using the fixing roller of this embodiment.

In this embodiment, the occurrence of cracks when the ratio of the coefficient of linear expansion between the surface resin layer and the lower resin layer is out of a predetermined range is prevented. First, the fixing roller used in this embodiment will be described with reference to FIG. In this embodiment, the thickness of the lower elastic body is 1 mm or more, and the linear expansion coefficient of the lower elastic layer at 150 ° C. is 2.6 of the linear expansion coefficient of the surface resin layer.
In order to prevent cracking with a fixing roller having a thickness of 50 μm or less and a surface resin layer having a thickness of 50 μm or more, the linear expansion coefficient of the surface resin layer and the linear expansion coefficient of the lower elastic layer between the surface resin layer and the lower elastic layer are reduced. At least one elastic layer having a linear expansion coefficient between them is used. Here, the intermediate elastic layer used in the present embodiment is an elastic layer in which fluorine rubber and a surface PFA resin are mixed.

Table 3 shows the results of a heat cycle test performed using this fixing roller in the same manner as in Examples 1 and 2.
As shown in Table 3, the intermediate elastic layer was formed to a thickness of 0.01 mm to 0.1 mm.
mm, the surface resin layer 20 to 50
Even when the lower elastic layer was 1 mm or more and the linear expansion coefficient between the surface resin layer and the lower elastic layer was 2.7 times or more and 3.4 times or less, cracks could be prevented.

In this embodiment, a mixed elastic body of fluorine rubber and a surface PFA resin is used as the intermediate elastic body layer, but the present invention is not limited to this, and similar results can be obtained by using only the elastic body. The kind of the elastic body is not necessarily limited to fluororubber, and the same effect can be obtained with another elastic body such as silicone rubber as long as it has a linear expansion coefficient between the lower elastic body and the surface resin layer. Further, in the present embodiment, fluorine rubber and PFA resin were used as the intermediate elastic body,
The resin is not necessarily limited to this, and PTFE, P
Similar effects can be obtained with FA and the like. In this embodiment, one intermediate elastic layer is used. However, the same effect can be obtained by providing a plurality of intermediate elastic layers.

This embodiment is further effective when used when the coefficient of linear expansion of the elastic layer at 150 ° C. is 2.7 or less of the coefficient of linear expansion of the resin layer at 150 ° C.

[0084]

[Table 3]

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to Table 4.

Table 4 shows the results of experiments using the fixing roller of this embodiment.

In this embodiment, cracks are prevented from occurring when the ratio of the coefficient of linear expansion between the surface resin layer and the lower elastic layer is out of a predetermined range. In this embodiment, an intermediate elastic layer is provided between the surface resin layer and the lower elastic layer as in the third embodiment, but in this embodiment, the hardness of the intermediate elastic layer is changed. That is the difference. First, the fixing roller used in this embodiment will be described. In this embodiment, the thickness of the lower elastic body is 1 mm or more, the linear expansion coefficient of the lower elastic layer at 150 ° C. is 2.7 times or more the linear expansion coefficient of the surface resin layer, and the thickness of the surface resin layer is 50 μm or less. In order to prevent the fixing roller from cracking, an elastic layer having a predetermined hardness or more is provided between the surface resin layer and the lower elastic layer. Here, as the intermediate elastic layer used in the present embodiment, an elastic layer in which fluorine rubber and a surface PFA resin were mixed was used, and a fixing roller in which the hardness of the fluorine rubber was changed was prepared and an experiment was performed. In the present embodiment, fluorine rubbers having different hardnesses were prepared by changing the amount of the inorganic powder as a vulcanizing material, and a fixing roller was obtained. Table 4 shows the results of the heat cycle test performed in the same manner as in Examples 1, 2, and 3. As shown in Table 4, the fluorine rubber hardness of the intermediate elastic layer was measured in accordance with JIS.
0.01 mm to 0.1 m by making -A 75 ° or more
m, surface resin layer 20 to 50 μm, lower elastic layer 1 m
m and the linear expansion coefficient of the surface resin layer and the lower elastic layer was 2.7 times or more and 3.4 times or less. In this example, a mixed elastic body of fluoro rubber and a surface PFA resin was used as the intermediate elastic body layer. However, the present invention is not limited to this. Similar effects can be obtained. The type of the elastic body is not necessarily limited to fluororubber. Further, in this embodiment, fluorine rubber and PFA resin are used as the intermediate elastic body. However, the resin is not necessarily limited to this, and the same effect can be obtained with PTFE, PFA, or the like. In this embodiment, one intermediate elastic layer is used. However, the same effect can be obtained by providing a plurality of intermediate elastic layers.

The present embodiment is further effective when used when the coefficient of linear expansion of the elastic layer at 150 ° C. is 2.7 or less of the coefficient of linear expansion of the resin layer at 150 ° C.

[0089]

[Table 4]

[0090]

As described above, according to the present invention,
An object of the present invention is to provide a fixing device capable of improving the followability between the surface resin and the lower elastic layer, preventing the occurrence of cracks, and enabling excellent OHP discharge.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a fixing roller used in a fixing device of the present invention.

FIG. 2 is a cross-sectional view illustrating another example of a fixing roller used in the fixing device of the present invention.

FIG. 3 is a schematic sectional view of a conventional full-color copying machine.

FIG. 4 is a schematic sectional view of a conventional full-color copying machine.

FIG. 5 is a schematic sectional view of a fixing device in a conventional full-color copying machine.

Claims (7)

[Claims] An image forming apparatus comprising: a roller pair of a fixing roller and a pressure roller rotatably disposed while being in pressure contact with each other; and pressing and conveying a recording material having an unfixed image at a pressure contact portion formed by the roller pair. In the fixing device for performing heat fixing of the unfixed image on the recording material, the fixing roller is formed by firing an elastic layer having a thickness of 1 mm or more and a resin of 20 μm to 50 μm on the surface of the elastic layer, and A fixing device, wherein a linear expansion coefficient of the elastic layer at 150 ° C. is within 2.7 times a linear expansion coefficient of the resin layer at 150 ° C. And a roller pair of a fixing roller and a pressure roller which are rotatably disposed while being pressed against each other, and press-convey a recording material having an unfixed image at a pressure contact portion formed by the roller pair. In the fixing device for performing the heat fixing of the unfixed image on the recording material by heating, the fixing roller may be 1 mm to 3 mm.
And an elastic layer formed by baking a resin on the surface of the elastic layer, and having a thickness of 60 μm to 100 μm. 3. A recording medium having an unfixed image is nipped and conveyed by a pressing portion formed by a pair of a fixing roller and a pressing roller rotatably disposed while being pressed against each other. In the fixing device for performing heat fixing of the unfixed image on the recording material, the fixing roller is formed by firing an elastic layer having a thickness of 1 mm or more and a resin of 20 μm to 50 μm on the surface of the elastic layer, and Having at least one elastic layer having a linear expansion coefficient between the linear expansion coefficient of the elastic body at 150 ° C. and the linear expansion coefficient of the resin layer at 150 ° C. between the elastic layer and the resin layer; And one of the adjacent inner layers
The linear expansion coefficient at 50 ° C is 150 ° C of the adjacent outer layer.
2. The fixing device according to claim 1, wherein the linear expansion coefficient is 2.7 times or less. 4. A roller pair of a fixing roller and a pressure roller, which are rotatably disposed while being pressed against each other, and press-conveys a recording material having an unfixed image at a pressure contact portion formed by the roller pair. In the fixing device for performing heat fixing of the unfixed image on the recording material, the fixing roller is formed by firing an elastic layer having a thickness of 1 mm or more and a resin of 20 μm to 50 μm on the surface of the elastic layer, and A fixing device comprising at least one elastic layer having a hardness of 75 ° or more in JIS-A standard between the elastic layer and the resin layer. 5. The fixing device according to claim 1, wherein a linear expansion coefficient of the elastic layer at 150 ° C. is within 4.0 × 10 E ⁻⁴ cm / cm · ° C. 6. An elastic layer 150 separated from a resin layer.
The linear expansion coefficient at 150 ° C. is 2.7 to 3.4 times the linear expansion coefficient of the resin layer at 150 ° C., and the elastic layer adjacent to the resin layer has a linear expansion coefficient of 4.0 × 10E.
^4. The fixing device according to claim 3, wherein the temperature is within ^-4 cm / cm.degree. 7. An image forming apparatus comprising the fixing device according to claim 1. Description: