JP2003076167A - Fixation belt and image forming device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation belt which can uniformly fix images without generating any image defect for a long period and an image forming device which has the fixation belt. SOLUTION: A fixation belt 10 which has an elastic layer 2 formed on a base 1 and a release layer 3 formed on the elastic layer 2 is characterized by that the universal hardness HU (N/mm<2> ) of its top surface side is <35 and the plastic hardness HUplast (N/mm<2> ) is larger than the universal hardness. The HU and HUplast are prescribed in the German standards DIN 50359-1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing belt and an image forming apparatus having the fixing belt. More specifically, the present invention relates to a fixing belt for fixing an unfixed toner image on a recording medium by heating and pressurizing it, and an image forming apparatus having the fixing belt. Regarding the device.

[0002]

2. Description of the Related Art FIG. 3 is an illustration of a conventional electrophotographic image forming apparatus. A conventional electrophotographic image forming apparatus 100, such as a copying machine and a laser printer, includes a photosensitive drum 101 and a photosensitive drum 1 on which an electrostatic latent image is formed.
01, a charging roll 102 for performing a charging process, an exposure unit 103 such as a laser beam, a developing roll 104 for adhering toner to an electrostatic latent image on the photoconductor drum 101, and a DC voltage for applying a DC voltage to the charging roll 102. Power pack 1
05, the toner image on the photosensitive drum 101 is recorded on the recording paper 107
Transfer roller 106 for performing transfer processing on the surface, a cleaning device 108 for cleaning the photoconductor drum 101 after the transfer processing, a surface potential meter 109 for measuring the surface potential of the photoconductor drum 101, and a heat fixing roll 111 and a pressure roll. The thermal fixing device 110 is composed of 112.

Image forming apparatus 1 using this electrophotographic system
In 00, the photosensitive layer of the rotating photosensitive drum 101 is uniformly charged by using a charging roll 102, and then exposed by an exposing means 103 such as a laser beam to form an electrostatic latent image. The image is developed with toner to form a toner image, the toner image is transferred onto a recording paper 107, and the recording paper 107 is passed through a heat fixing device 110 including a heat fixing roll 111 and a pressure roll 112. It is configured to thermally fix the toner image.

In the heat fixing device of the image forming apparatus 100 as described above, for example, the outer peripheral surface of the cored bar made of a hollow cylinder made of metal such as aluminum is coated with a fluororesin or the like to prevent adhesion of toner. A heat fixing roll 111 provided with a releasing layer is used. The heat fixing roll 111 has a heater such as a halogen lamp arranged along the rotation center line in the hollow portion of the cored bar and is heated by the radiant heat. The fixing roll 111 is heated from the inside, and the heating fixing roll 111 and the pressure roll 11 are heated.
By passing the recording paper 107 between the heat fixing roll 1 and the recording paper 107,
While being softened by the heat of 11, pressure is applied to fix the recording paper.

The heat fixing roll 111 provided with a fluororesin layer on the core metal is excellent in releasability but inferior in flexibility and elasticity, so that a full color copying machine requiring gloss, It cannot be applied to image forming apparatuses such as full-color laser printers. In conventional image forming apparatuses such as full-color copying machines and laser printers, red (magenta), blue (cyan), yellow (yellow),
Black (black) color toners of four colors are used, and the toners of these colors are transferred to the paper surface in a superposed state. Therefore, when fixing these unfixed color toners, it is necessary to uniformly mix them in a molten state so as to wrap them around the surface of the heat fixing roll. Therefore, one of the properties required for the surface of the fixing member (roll, belt) is flexibility.

Conventionally, in order to impart flexibility to the surface of the fixing roll, an elastic layer such as silicone rubber or fluororubber is provided on the silicone rubber roll (a rubber material in consideration of releasability and durability rather than the base rubber is used). There is a fixing roll provided with (use). However, in the fixing roll having such an elastic layer, the thickness of the elastic layer cannot be increased beyond a certain value in order to prevent the warm-up time from becoming long.
The heat fixing roll is suitable for speeding up fixing because it has characteristics such as keeping the whole heat roll at a predetermined temperature and having a large heat capacity, but heats the heat roll to a predetermined temperature. Takes quite some time,
Therefore, there is a problem that power consumption increases.

Therefore, in recent years, activities for energy saving have become active in the field of image processing. As a result of such activities, a belt fixing device has been proposed in which a toner on a transfer target is heated by a heater via a film-shaped fixing endless belt capable of shortening the rising time. FIG. 4 is an explanatory view showing a usage state of a conventional fixing endless belt. As shown in FIG. 4, in the conventional image forming apparatus, a heating roll 115, a pair of parallel pressure rolls 116 provided opposite to the heating roll 115,
A belt fixing device 113 having a fixing endless belt 114 that is in contact with the heating roller 115 and is rotatably provided by a pair of parallel pressure rollers 116 and 116 is used. There is also proposed a fixing endless belt provided with a rubber elastic layer made of an elastic material such as silicone rubber or fluororubber on the substrate (not shown). According to this belt fixing device, the fixing endless belt is wound around the fixing roll and the heating roll and rotated, and the pressure roll is pressed against the fixing roll via the fixing endless belt. Here, when the fixing roll is rotationally driven and the fixing belt rotates in the same direction, the heating roll and the pressure roll also rotate. In this case, each part of the fixing belt is heated by the heating roll before reaching the nip, and the heated part softens and heats the toner image in advance, and then the recording material passes through the nip to fix the toner image. I do.

In this belt fixing device, the fixing belt in the form of a thin film is directly heated, and the heating section reaches a predetermined temperature in a short time after the power is turned on. Therefore, the waiting time after the power is turned on is considerably reduced. You can Further, since only the necessary portion is heated, there is an advantage that power consumption is small. In the case of a fixing belt, the above-mentioned rubber material in consideration of releasability and durability is directly formed on the substrate. However, it has the same problems as described below.

The surface of a conventional fixing belt (silicon rubber,
Fluorine rubber and the like) are excellent in flexibility, but the toner releasing property is insufficient, so that the toner offset phenomenon is likely to occur. Further, since these rubber elastic layers have low wear resistance, the surface is severely worn and deteriorated. For these problems, there is a method of applying a silicone-based lubricating oil to the surface of the fixing roll and the fixing belt. However, although this oil application method is initially effective, it is not sufficient, and this oil causes a new problem of swelling of the rubber material. Further, the mechanism for applying the oil (including the application amount control mechanism) and the replenishment of the oil also have the drawbacks of user maintenance load and high cost, and therefore fixing without using oil is required.

Recently, it has been proposed that a rubber elastic layer is provided on the base of a fixing belt, and a release material such as fluororesin is coated on the rubber elastic layer. However, when the release material is coated, the flexibility, which is an important characteristic of the surface described above, tends to decrease. Problems in this case include non-uniformity of the image and poor transparency of the image on the OHP sheet. Therefore, as a means to avoid these,
It is important to consider a coating method and a coating material that do not impair the flexibility of the elastic layer as much as possible, and a surface hardness characteristic value at the time of coating. The conventional means are shown below.

1) Prior Art 1 Japanese Unexamined Patent Publication No. 10-198201 discloses a fixing belt having a laminated structure in which a heat-resistant elastomer layer is provided on the outer peripheral surface of a thin-walled tubular substrate, and a fluororesin layer is further provided thereon. Although the soft index S is defined and the allowable range of the thickness of the substrate, the thickness of the outer surface layer, and the soft index S is described, the hardness of the fluororesin layer (outer surface layer) is not taken into consideration. Not paid. 2) Prior Art 2 Japanese Patent No. 3000516 defines the flexural modulus of toner / polyimide substrate / heat resistant elastic layer / surface layer resin,
The surface hardness according to JIS K6301 is specified, the thermal conductivity and thickness of the heat resistant elastic layer are specified, and the linear pressure is specified. What is the "universal hardness" and "plastic hardness"? No consideration is given.

By the way, while the purpose of fixing the toner in the image formation is to fix the toner to the recording material, it is also to form the visible image by coloring the toner. A general black-and-white image has almost no problems relating to color development, but in order to obtain a particularly high image quality in a full-color image, the color development problem is very important. In image formation using a full-color copying machine, four types of toners of cyan, magenta, yellow, and black are used, toner images of respective colors are sequentially formed, and then heat-melted to form a secondary color or a tertiary color. Color reproduction is performed to form a full-color image. At that time, for example, when a secondary color is obtained by superimposing two types of toner, the color difference from the actually obtained secondary color is determined by the light transmittance of the toner layer. That is, when voids or the like exist inside the toner layer, light scattering is caused, and when unevenness exists on the toner image surface, irregular reflection hinders color development. Therefore, it is important that the toner is uniformly melted and fixed at the time of fixing. For uniform fixing, it is necessary for the fixing belt of the fixing device to have elasticity so as to surely contact the unevenness of the toner. Such "elasticity" is ensured, for example, by coating the elastic layer of the heat-resistant elastomer on the substrate and then coating the outermost layer of the heat-resistant resin, or by blending the heat-resistant elastomer in the outermost layer. .

As described above, in the electrophotographic image forming apparatus, particularly in the full-color copying machine in which the image quality is important, the outermost layer of the fixing belt is used in terms of releasability, heat resistance, and mechanical durability. Materials are fluororubber, silicone rubber,
Although it is limited to materials such as fluororesin, each of those materials actually has some problems.

That is, the fluororubber has the following problems. The fluororubber crosslinks the main chain by adding a crosslinking agent to the fluororesin and heats it into a rubber, but unreacted functional groups and the crosslinking agent remain in the fluororubber, and as a result, the surface energy is reduced. Get higher When this kind of fluororubber is used for the outermost layer of the fixing belt, it is impossible to secure releasability from the toner because of high surface energy. Therefore, a releasing agent such as silicone oil is supplied to the surface of the fixing belt which is in direct contact with the unfixed toner image to form a releasing agent layer between the unfixed toner image and the surface of the fixing belt. A method has been adopted that facilitates image separation. However, the release agent adheres to the transfer body carrying the toner image at the time of fixing. As a result, there is a problem in that the surface of a transfer body such as paper or OHP film becomes sticky and tapes cannot be attached. Further, since it is necessary to attach a release agent supply device to the fixing device, downsizing of the fixing device can be achieved. There is a problem that it goes against cost reduction. Therefore, the outermost layer of the fixing belt, while ensuring durability against friction,
It is an important issue to reduce the amount of the release agent supplied to the fixing roll member or to secure the releasability of the toner in a state where it is rarely used.

Silicon rubber has the following problems. At the beginning of use of the fixing belt, the free oil contained in the silicone rubber exudes to the surface of the outermost layer of the fixing belt, so it is not necessary to apply a release agent. However, as the oil is used, exudation of the free oil disappears and the releasability drops sharply. On the other hand, if the release agent is supplied to the outermost layer of the fixing belt made of silicone rubber, another problem occurs that the silicone rubber swells and the strength decreases. Also, the durability against friction is generally inferior to that of fluororubber.

The fluororesin has the following problems. Since the fluororesin has a low surface energy and does not have a reactive functional group, it has a good mold release property, and therefore, it is almost unnecessary to apply a mold release agent. Also,
Fluororesin is excellent in mechanical strength and generally good in durability. However, since the fluororesin itself has a remarkably high rigidity, even if an elastic layer is interposed between the base of the fixing belt and the outermost layer, the surface of the outermost layer made of the fluororesin will be affected by the unevenness of the toner image. It cannot be sufficiently deformed, and it becomes difficult to bring the outermost layer into uniform contact with the toner image. As a result, the toner is crushed before being melted in the heat fixing step, and the toner image cannot be fixed uniformly. This is a factor that impairs the suitability for high image quality.

[0017]

SUMMARY OF THE INVENTION The present invention aims to solve such problems. That is, an object of the present invention is to provide a fixing belt that can be fixed uniformly without causing image defects for a long period of time, and an image forming apparatus having the fixing belt.

[0018]

In order to achieve the above-mentioned object, an elastic layer is formed on a substrate, and a release layer is further formed on the elastic layer. In the fixed belt, the surface side has a universal hardness; HU (N / mm ² ) smaller than 35, and a plastic hardness; HU _plast (N / mm ² ) larger than the universal hardness. Is a fixing belt.
However, HU and HU _plast are defined by the following equations.

[Formula 4] F F HU = ─────────────────── (1) A (h) 26.43 · h ²

[Equation 5] 4 · sin (a / 2) A (h) = ─────────── ・ h ² (2) cos ² (a / 2)

[6] _{F max HU plast = ────────── (3} ) 26.43 · h r 2 In Formula (1) ~ (3), a (°) , the pyramidal penetration It is the angle (136 °) of the facing faces of the body, and F
Is the test force (N), h (mm) is the indentation depth when the test force is applied, and h _r (mm) is h-F
It is the h coordinate value of the h axis intersection of the tangents at the (h _max , F _max ) point of the curve.

According to a second aspect of the present invention, in a fixing belt in which an elastic layer is formed on a substrate, the surface side has a universal hardness; HU (N / mm ² ) is smaller than 35, and , Plastic hardness; HU _plast (N / mm ² )
Is larger than the universal hardness described above. However, the HU and HU _plast are
It is defined by the formula described in claim 1 above.

According to a third aspect of the invention, in a fixing belt in which an elastic layer is formed on a substrate, and a surface-modified release layer is further formed on the elastic layer, the surface of the fixing belt is formed. Side, universal hardness; HU (N / mm ² ) is smaller than 35, and plastic hardness; HU _plast (N /
mm ² ) is larger than the universal hardness described above. However, the HU and HU
_plast is defined by the formula described in claim 1 above.

According to a fourth aspect of the present invention, an elastic layer is formed on the substrate, a release layer is formed on the elastic layer, and a metal thin film or metal oxide is further formed on the release layer. In the fixing belt on which the thin film is formed,
A fixing belt having a universal hardness; HU (N / mm ² ) smaller than 35, and a plastic hardness; HU _plast (N / mm ² ) larger than the universal hardness. However, the HU and HU _plast are defined by the formula described in claim 1 above.

According to a fifth aspect of the present invention, there is provided a fixing belt in which an elastic layer is formed on a substrate, and a metal thin film or a metal oxide thin film is further formed on the elastic layer.
Universal hardness on the surface side; HU (N / mm ² )
Is less than 35 and plastic hardness; HU _plast (N
/ Mm ² ) is larger than the universal hardness described above. However, the HU and HU
_plast is defined by the formula described in claim 1 above.

The invention described in claim 6 is from claim 1
An image forming apparatus comprising the fixing belt according to any one of 5 above as a charging unit, an exposing unit, a developing unit, a transferring unit and / or a fixing unit.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partially enlarged sectional view of a fixing endless belt showing an embodiment of the present invention, and
Fig. 2 shows the test force (N) and the indentation depth h when the test force is applied.
It is a graph which shows the relationship with (mm).

In FIG. 1, 10 is a fixing belt. In the fixing belt 10, the elastic layer 2 is formed on the base 1, and the release layer 3 is further formed on the elastic layer. Universal hardness on the surface side of this fixing belt; H
U (N / mm ² ) is smaller than 35, and plastic hardness; HU _plast (N / mm ² ) is larger than the universal hardness. However, the HU and HU _plast are defined by the following formula (such HU and HU _plast
Is described in German standard DIN 50359-1. ).

[Formula 7] F F HU = ─────── = ─────────── (1) A (h) 26.43 · h ²

[Equation 8] 4 · sin (a / 2) A (h) = ─────────── ・ h ² (2) cos ² (a / 2)

Equation 9] _{F max HU plast = ─────────── (3} ) 26.43 · h r 2 In Formula (1) ~ (3), a (°) is pyramidal It is the angle (136 °) of the facing surfaces of the penetration body, and F
Is the test force (N), h (mm) is the indentation depth when the test force is applied, and h _r (mm) is h-F
It is the h coordinate value of the h axis intersection of the tangents at the (h _max , F _max ) point of the curve.

The h-F curve is shown in FIG. 2, for example. In Figure 2, is an h-F curve when weighted load from 0 to F _max, is followed by load to 0 from F _{ma x} is h-F curve when the Joni and , Are tangents at the (h _max , F _max ) point of the hF curve.

Further, according to the present invention, (a) in a fixing belt having an elastic layer formed on a substrate, the universal hardness; HU (N / mm ² ) on the surface side is smaller than 35, and Fixing belt (not shown) having a plastic hardness of HU _plast (N / mm ² ) higher than the universal hardness, (b) an elastic layer is formed on the substrate, and a surface modification is performed on the elastic layer. In a fixing belt having a release layer subjected to quality treatment, the surface side thereof has a universal hardness; HU (N / mm ² ) of less than 35 and a plastic hardness; HU _plast (N / mm ² ) Having a hardness larger than the universal hardness (not shown), (c) an elastic layer is formed on the substrate, a release layer is formed on the elastic layer, and further on the release layer. A fixing plate with a metal thin film or metal oxide thin film formed on In bets, of the surface side, the universal hardness; HU (N / mm ²⁾ is smaller than 35, and plastic ^{_{hardness; HU plast (N / mm 2}} )
A fixing belt (not shown) having a hardness greater than the universal hardness, (d) an elastic layer is formed on the substrate, and
In a fixing belt having a metal thin film or a metal oxide thin film formed on the elastic layer, the surface side has a universal hardness; HU (N / mm ² ) of less than 35, and
A fixing belt (not shown) having a plastic hardness; HU _plast (N / mm ² ) larger than the universal hardness may be used. However, HU and HU _plast are defined by the formulas described above.

In the present invention, a substrate, an elastic layer, a release layer,
As the surface-modified release layer, metal thin film or metal oxide thin film, for example, the following are used. (1) Stainless steel seamless belt having a substrate thickness selected from 30 μm, 40 μm, 60 μm, etc., thickness 30 μm, 40 μm
A nickel seamless belt selected from m, 60 μm, etc., a polyimide seamless belt selected from thicknesses of 50 μm, 100 μm, 200 μm, etc., and a seamless belt made of these materials. (2) Elastic layer hardness (JIS K 6301) is 5 degrees, 15 degrees, 25
An elastic layer made of silicone rubber selected from degrees, 35 degrees, 45 degrees, etc. and / or a thickness selected from 10 μm, 50 μm, 100 μm, 200 μm, etc., and
Hardness (JIS K6301) is 5 degrees, 15 degrees, 25 degrees,
An elastic layer made of fluororubber selected from 35 degrees, 45 degrees, and / or a thickness selected from 10 μm, 50 μm, 100 μm, 200 μm, and the like. (3) P having a release layer thickness selected from 10 μm, 20 μm, 50 μm, etc.
TFE, PFA, FEP, PFA / FEP blend, E
A surface layer made of a fluororesin such as TFE. (4) Release layer subjected to surface modification Release layer subjected to surface modification treatment by UV ozone treatment, plasma treatment, EB treatment or the like. (5) Metal thin film or metal oxide thin film Metal film of aluminum, silver, gold, chromium or the like, or Al
A metal oxide thin film formed by vacuum deposition or sputtering with a metal oxide such as ₂ O ₃ .

The specific examples of the substrate, the elastic layer, the release layer, the surface-modified release layer, the metal thin film or the metal oxide thin film are merely examples. Therefore, the present invention
Other than the specific examples of the substrate, the elastic layer, the release layer, the surface-modified release layer, the metal thin film or the metal oxide thin film as long as the object of the present invention is not impaired.

In the present invention, the substrate, the elastic layer, the release layer, the surface-modified release layer, the metal thin film and the metal oxide thin film are the "universal hardness; HU ( N / mm ² ) ”and“ plastic hardness; HU
_plast (N / mm ² ) ”.
Further, in the present invention, the substrate, the elastic layer, the release layer,
A primer may be applied between the surface-modified release layer, the metal thin film, and the metal oxide thin film, if necessary.

The fixing belt of the present invention may be an image forming apparatus having these as a charging means, an exposing means, a developing means, a transferring means and / or a fixing means.

According to the present invention, the toner has elasticity required for fixing the toner and also has an ability to suppress scratches caused by the toner and foreign matters, which may cause image defects for a long period of time. Therefore, it is possible to provide a fixing belt capable of uniformly fixing.

Further, according to the present invention, the toner has elasticity necessary for fixing the toner and also has an ability to suppress scratches caused by the toner and foreign matters, which causes image defects for a long period of time. It is possible to provide an image forming apparatus that forms a stable electrophotographic image without causing any trouble.

[0034]

[Example] (Example 1) Using a polyimide resin, a diameter of 6
After forming a belt-shaped substrate having a thickness of 0 mm, a surface length of 315 mm and a film thickness of 50 μm, an elastic layer having a layer thickness of 200 μm is formed on the substrate by using silicon rubber, and a PTFE resin is further coated on the elastic layer. A release layer having a layer thickness of 10 μm was formed using the above to obtain a fixing belt. The fixing belt thus obtained was cut into a test piece to obtain sample A, and the HU
And HU _plast are commercially available testers: Fisherscope H-100 (this tester has a test load of 0.4 to 100).
It is possible to measure up to 0 mN. ), A test load of 30
It was measured at 0 mN. At this time, since the rigidity of the fixing belt is weak, the fixing belt was cut into a sheet shape, adhered and cured on BK7 glass to be reinforced, and then measured. The measurement results were as follows. HU = 1.11 mN (HU <35) HU _plast = 2.21 mN (HU <HU _plast )

(Comparative Example 1) A belt-shaped substrate having a diameter of 60 mm, a surface length of 315 mm and a film thickness of 50 μm was formed using a polyimide resin, and then an elastic layer having a layer thickness of 30 μm was formed on the substrate using silicon rubber. Then, a release layer having a layer thickness of 4 μm was formed on the elastic layer using FEP resin to obtain a fixing belt. The fixing belt thus obtained was cut out into a test piece to prepare a sample B, and its HU and HU _plast were measured in the same manner as in Example 1. The measurement result is
It was as follows. HU = 6.102 mN (HU <35) HU _plast = 5.989 mN (HU> HU
_plast )

(Example 2) A belt-shaped substrate having a diameter of 60 mm, a surface length of 315 mm and a film thickness of 50 μm was formed using a polyimide resin, and then an elastic layer having a layer thickness of 200 μm was formed on the substrate using silicon rubber. After forming, a fixing belt was obtained. The fixing belt thus obtained was cut out into a test piece to give a sample C, and its HU and HU _plast were measured in the same manner as in Example 1. The measurement results were as follows. HU = 1.31 mN (HU <35) HU _plast = 2.35 mN (HU <HU _plast )

COMPARATIVE EXAMPLE 2 A belt-shaped substrate having a diameter of 60 mm, a surface length of 315 mm and a film thickness of 50 μm was formed using a polyimide resin, and then an elastic layer having a layer thickness of 10 μm was formed on the substrate using silicon rubber. After forming, a fixing belt was obtained. The fixing belt thus obtained was cut out into a test piece to obtain a sample D, and its HU and HU _plast were obtained in Example 1.
It measured similarly to. The measurement results were as follows. HU = 335.6mN (HU> 35) HU _plast = 734.6mN (HU <HU
_plast )

Example 3 A belt-shaped substrate having a diameter of 60 mm, a surface length of 315 mm and a film thickness of 50 μm was formed using a polyimide resin, and an elastic layer having a layer thickness of 200 μm was formed on the substrate by using silicon rubber. Then, a release layer having a layer thickness of 10 μm is formed on the elastic layer using PFA resin, and the surface of the release layer is further irradiated with ultraviolet rays by a low-pressure ultraviolet device of 5 mW / cm ² for 5 minutes. After a minute, the surface modification layer was added to obtain a fixing belt. The fixing belt thus obtained was cut into a test piece to obtain a sample E.
And HU _plast were measured as in Example 1. The measurement results were as follows. HU = 1.33 mN (HU <35) HU _plast = 2.65 mN (HU <HU _plast )

Comparative Example 3 A belt-shaped base having a diameter of 60 mm, a surface length of 315 mm and a film thickness of 50 μm was formed using a polyimide resin, and then an elastic layer having a layer thickness of 10 μm was formed on the base using silicon rubber. Then, a release layer having a layer thickness of 10 μm is formed on the elastic layer using PFA resin, and the surface of the release layer is further irradiated with ultraviolet rays by a low-pressure ultraviolet device of 5 mW / cm ² for 5 minutes. After a minute, the surface modification layer was added to obtain a fixing belt. The fixing belt thus obtained was cut into a test piece to give a sample F, and its HU and HU _plast were measured in the same manner as in Example 1. The measurement results were as follows. HU = 44.7 mN (HU> 35) HU _plast = 56.1 mN (HU <HU _plast )

Example 4 A belt-shaped substrate having a diameter of 60 mm, a surface length of 315 mm and a film thickness of 50 μm was formed using a polyimide resin, and then an elastic layer having a layer thickness of 150 μm was formed on the substrate using silicon rubber. Then, a release layer having a layer thickness of 10 μm is formed on the elastic layer by using a PTFE resin, and a wear layer having a thickness of 0.05 μm is sputtered on the release layer with an alumina thin film. To form a fixing belt. The fixing belt thus obtained was cut into a test piece to give a sample G, and its HU and HU _plast were measured in the same manner as in Example 1. The measurement results were as follows. HU = 2.11 mN (HU <35) HU _plast = 2.21 mN (HU <HU _plast )

(Comparative Example 4) A belt-shaped substrate having a diameter of 60 mm, a surface length of 315 mm and a film thickness of 50 μm was formed by using a polyimide resin, and an elastic layer having a layer thickness of 10 μm was formed on the substrate by using silicon rubber. Then, a release layer having a layer thickness of 10 μm is formed on the elastic layer using PFA resin, and a wear layer having a thickness of 0.05 μm is sputtered with an alumina thin film on the release layer. To form a fixing belt. The fixing belt thus obtained was cut into a test piece to give a sample H, and the HU and H
U _plast was measured as in Example 1. The measurement results were as follows. HU = 45.7 mN (HU <35) HU _plast = 57.1 mN (HU <HU _plast )

The image evaluation results of the fixing belts obtained in Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1 below.
In Table 1, ◯ and × indicate the following. ◯: HU <35 and HU <HU in the test results
Satisfies _plast x; HU <35 and HU <HU in the above test results
What doesn't satisfy _plast

[0043]

[Table 1]

[0044]

(1) According to the invention described in claims 1 to 5, it has elasticity necessary for fixing the toner and also has an ability to suppress scratches caused by the toner and foreign matters. For these reasons, it is possible to provide a fixing belt capable of fixing uniformly without causing image defects for a long period of time. (2) According to the invention described in claim 6, it has elasticity necessary for fixing the toner and also has an ability to suppress scratches caused by the toner and foreign matters, and for that reason, for a long period of time. An image forming apparatus capable of forming a stable electrophotographic image without causing image defects can be provided.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of a fixing endless belt showing an embodiment of the present invention.

[Fig. 2] Test force (N) and indentation depth h when the test force is applied
It is a graph which shows the relationship with (mm).

FIG. 3 is an explanatory diagram of a conventional electrophotographic image forming apparatus.

FIG. 4 is an explanatory view showing a usage state of a conventional heat fixing endless belt.

[Explanation of symbols]

1 base 2 elastic layer 3 Release layer 10 fixing belt

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tokuhiko Yasuse             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Minoru Matsuo             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 2H033 BA12 BE00

Claims (6)

[Claims] 1. An elastic layer is formed on a substrate, and further,
In a fixing belt having a release layer formed on the elastic layer, the surface side has a universal hardness; HU (N / mm
² ) is less than 35 and plastic hardness; HU _plast
A fixing belt characterized in that (N / mm ² ) is larger than the universal hardness. However, the HU and HU
_plast is defined by the following equation. [Formula 1] F F HU = ─────── ＝ ────────── (1) A (h) 26.43 · h ² [Formula 2] 4 · sin (a / 2 ) A (h) = ─────────── ・ h ² (2) cos ² (a / 2) [ _Equation 3] F _max HU _plast = ────────── ( 3) 26.43 · h _r ² in formula (1) ~ (3), a (°) is an angle of facing surfaces of penetration of pyramid (136 °), F
Is the test force (N), h (mm) is the indentation depth when the test force is applied, and h _r (mm) is h-F
It is the h coordinate value of the h axis intersection of the tangents at the (h _max , F _max ) point of the curve. 2. A fixing belt having an elastic layer formed on a substrate, wherein the surface side has a universal hardness of HU.
(N / mm ² ) is smaller than 35, and plastic hardness;
A fixing belt having a HU _plast (N / mm ² ) larger than the universal hardness. However, the HU
And HU _plast are defined by the formulas set forth in claim 1 above. 3. An elastic layer is formed on a substrate, and further,
In a fixing belt having a surface-modified release layer formed on the elastic layer, the surface side has a universal hardness; HU (N / mm ² ) of less than 35 and a plastic hardness. A fixing belt having HU _plast (N / mm ² ) larger than the universal hardness. However,
The HU and HU _plast are defined by the formula recited in claim 1 above. 4. A fixing belt in which an elastic layer is formed on a substrate, a release layer is formed on the elastic layer, and a metal thin film or a metal oxide thin film is further formed on the release layer. At its surface side, universal hardness; HU (N /
mm ² ) is smaller than 35 and has a plastic hardness; HU
A fixing belt having a _plast (N / mm ² ) larger than the universal hardness. However, the HU and HU _plast are defined by the formula described in claim 1 above. 5. An elastic layer is formed on the substrate, and further,
In a fixing belt having a metal thin film or a metal oxide thin film formed on the elastic layer, the surface side has a universal hardness; HU (N / mm ² ) of less than 35, and
A fixing belt having a plastic hardness; HU _plast (N / mm ² ) larger than the universal hardness. However, the HU and HU _plast are defined by the formula described in claim 1 above. 6. An image forming apparatus comprising the fixing belt according to claim 1 as a charging unit, an exposing unit, a developing unit, a transferring unit and / or a fixing unit.