JP2002268423A - Fixing belt and image forming device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing belt which has moderate flexibility and has excellent releasability from toners, durability and traveling stability and an image forming device having the same at a low cost. SOLUTION: A base body of the fixing belt (1) successively having an elastic layer 3 consisting of heat resistant rubber and a surface layer 4 on the base body 2 is formed as (a) a sheet or endless belt composed of metallic materials, such as stainless steel and nickel, (b) a sheet or endless belt composed of heat resistant resins, such as polyimide and polyamide-imide, or (c) a laminated sheet or endless belt of (a) and (b) described above. The surface layer 3 is preferably composed of a fluororesin and the elastic layer 3 is preferably composed of silicon rubber having 3 to 35 wt.% iron oxide containing >=80% ferric oxide as a component.

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 an image forming apparatus such as a laser printer and a facsimile, and an image forming apparatus having the same.

[0002]

2. Description of the Related Art FIG. 9 is an explanatory view of a conventional electrophotographic image forming apparatus. 2. Description of the Related Art A conventional electrophotographic image forming apparatus 100, for example, a copying machine or a laser printer, includes a photosensitive drum 101 on which an electrostatic latent image is formed and a photosensitive drum 1.
01, a charging roll 102 for performing charging processing, an exposure unit 103 such as a laser scanning unit (not shown), a developing roll 104 for attaching toner to an electrostatic latent image on the photosensitive drum 101, and a DC to the charging roll 102. A power pack 105 for applying a voltage, a transfer roll 106 for transferring a toner image on the photosensitive drum 101 to a recording paper 107,
A cleaning device 108 for cleaning the photosensitive drum 101 after the transfer process, a surface voltmeter 109 for measuring the surface potential of the photosensitive drum 101, and a heat fixing roll 110 including a heat fixing roll 111 and a pressure roll 112 It is configured.

An image forming apparatus 1 using this electrophotographic method
00 is an exposure unit 1 after the photosensitive layer of the rotating photosensitive drum 101 is uniformly charged using the charging roll 102.
03, an electrostatic latent image is formed, and the electrostatic latent image is developed with toner to form a toner image. This toner image is transferred onto the recording paper 107, and the recording paper 1
07 is passed through a heat fixing device 110 including a heat fixing roll 111 and a pressure roll 112 to thermally fix the toner image.

In such a thermal fixing device of the image forming apparatus 100, for example, a fluorocarbon resin or the like coated on the outer peripheral surface of a core metal made of a hollow cylindrical body of metal such as aluminum to prevent toner from sticking is used. A fixing roller 111 having a surface layer provided thereon is used. In the fixing roller 111, a heater such as a halogen lamp is disposed along a rotation center line in a hollow portion of a cored bar, and the fixing roller is heated and fixed by radiant heat. The roll 111 is heated from the inside, and the heat fixing roll 111 and the pressure roll 11 are heated.
2, the toner adhering to the recording paper 107 is passed through the heat fixing roll 1
While being softened by the heat of 11, the pressure is applied to fix the recording paper.

In a conventional image forming apparatus such as a full-color copying machine or a laser printer, four color toners of red (magenta), blue (cyan), yellow (yellow), and black (black) are used. Are transferred onto the paper in a superimposed state. Therefore, when fixing these unfixed color toner layers, it is necessary to cause each toner layer to be colored in a transparent state by melting. Sufficient melting of the toner is also necessary for improving the transparency of the OHP film. Further, when the surface of the toner layer is roughened, the glossiness is reduced and the OHP film permeability is reduced, so it is necessary to smooth the surface of the toner layer,
Further, if the unfixed toner layer shifts during fixing,
Since the image becomes unclear, it is necessary to press the toner layer with a fixing member flexibly and uniformly to perform uniform fixing. As described above, the color toner is designed to exhibit a sharp melt material by lowering the softening temperature in order to ensure color development and OHP film permeability, so the color toner adheres to the surface of the fixing member. Offset is likely to occur. Therefore, in addition to heat resistance, the fixing member has flexibility,
Characteristics such as releasability from toner and durability are required.

However, a heat fixing roll having a fluororesin layer provided on a metal core (that is, a substrate) is excellent in releasability, but inferior in flexibility, elasticity, abrasion resistance and the like. Therefore, it cannot be applied to an image forming apparatus such as a full-color copying machine and a full-color laser printer.

Therefore, in order to impart flexibility to the surface layer of such a heat fixing roll, an elastic layer made of a heat-resistant rubber such as silicon rubber or fluorine rubber is provided on a cored bar (that is, a base). A provided heat-fixing roll has been proposed.

Although such heat-resistant rubber has both heat resistance and flexibility, it has a problem that the toner offset phenomenon is liable to occur due to insufficient release property from the toner. In addition, since these elastic layers have low wear resistance, their surfaces are worn or deteriorated, which may cause a problem in durability. As a general improvement method for such problems as toner release resistance and durability on the surface of the elastic layer, there is a method of applying silicone oil to the surface of the elastic layer made of silicone rubber. According to this method, the silicone rubber has a chemical structure similar to the silicone oil, so that the silicone oil is fully compatible with the surface of the elastic layer made of the silicone rubber.
The releasability of the surface of the fixing member, that is, the elastic layer made of silicon rubber is improved.

[0009]

However, the method of applying silicone oil, although initially effective, is not satisfactory, but is not sufficient, and the silicone oil is not limited to adapting to the surface of the elastic layer. There is a problem that the elastic layer is deteriorated due to swelling or permeation into the silicon rubber material, or the elastic layer is separated from the substrate. In addition, when silicone oil needs to be applied, the installation of the application device is required, which complicates the fixing device.
Therefore, there is a problem that the cost increases.

In order to avoid such a problem on the surface of the fixing member, recently, as disclosed in Japanese Patent Application Laid-Open No. 10-148988, an elastic layer made of heat-resistant rubber is provided on the base of the fixing member. A fixing device provided with a surface layer made of a fluororesin thereon has been proposed. However, JP
As shown in the example of Japanese Patent Application Publication No. 0-148988, when a tube of a fluororesin such as tetrafluoroethylene-hexafluoropropylene copolymer (FEP) is formed as a surface layer on an elastic layer made of silicone rubber. However, since there is a limit to the thinning of the tube processing, the flexibility of the underlying silicone rubber elastic layer is impaired. Therefore, according to such a fixing device, it is difficult to perform uniform fixing, and as a result, unevenness in gloss occurs on the toner surface, and unevenness occurs on the image on the OHP.

In recent color copiers and color printers, from the viewpoint of energy saving and ease of use by the user, it is required to shorten the start-up time (the time until fixing is possible). The development of components is under way. The reason is that, as described above, since sufficient fixing is required in color fixing, a wide nip needs to be formed, but in the case of color fixing using a roll-shaped fixing member, the nip is formed. This is because it is difficult to achieve both heat resistance and low heat capacity.

FIG. 10 is an explanatory view showing a use state of a conventional heat-fixing endless belt. As shown in FIG. 10, in the conventional image forming apparatus, the heating roll 11
5, a pair of parallel pressure rolls 116, 116 provided opposite thereto, and a heat-fixing endless belt which is in contact with the heating roll 115 and is rotatably provided by the pair of parallel pressure rolls 116, 116. A belt-type fixing unit 113 having a fixing unit 114 is used. In addition, there has been proposed a belt in which a rubber elastic layer made of an elastic material such as silicon rubber or fluorine rubber is provided on the base of the heat fixing endless belt 114.

In the case of a belt-shaped fixing member, the flexibility of the surface of the belt is important because the fixing member utilizes the bending of the belt. Therefore, as described in JP-A-10-148988, an elastic layer made of heat-resistant rubber such as silicon rubber is provided on a substrate, and an outermost layer made of a fluororesin, that is, a surface layer is formed thereon. In the oil-less fixing member, when the surface layer is formed of a belt, the flexibility of the fluororesin forming the surface layer becomes more important than that of the roller. That is, since the flexibility of the belt surface is largely caused by the thickness of the fluororesin layer of the surface layer, when the thickness of the fluororesin layer is increased and the flexibility of the belt surface is impaired, the uniformity of the toner is reduced. No fixing is performed, and as a result, an image having an uneven impression such as gloss is formed.

Unlike the fixing roll, the fixing belt can widen the nip width by making use of flexure. However, since the pressing force is weak, it is necessary to simply press the toner surface sufficiently to obtain a medium gloss image. However, it does not mean that the belt member should be soft.

In such a fixing belt, as a means for forming a thin film of a fluororesin as a surface layer thereof, there is a film forming means by a wet coating method such as spraying or dipping, and a dry coating method such as electrodeposition coating. There is also a film forming means by a construction method. Then, in such a fixing belt, after the fluororesin layer is applied on the heat-resistant rubber elastic layer such as silicon rubber, the fluororesin layer has sufficient releasability from toner, paper powder and the like. To do this, set the fluororesin layer to 300
It is indispensable to perform melting and firing at a high temperature of at least ℃.

However, such a fixing belt has the following problems. That is, (1) silicon rubber is
From around 250 ° C, heat resistance decreases and rubber characteristics such as hardness deteriorate more, so cracks and the like easily occur in the elastic layer of the fixing belt. (2) Elasticity composed of silicon rubber at high temperature Since volatiles are generated from the layer, it is easy for defects to be generated in the surface layer made of fluororesin, (3) Forming the surface layer made of fluororesin thin film on the elastic layer made of silicon rubber thin film, When this is fired and cooled, distortion occurs due to the difference in the coefficient of linear expansion of these thin films, and as a result, cracks are likely to occur in the surface layer,
There was such a problem.

Further, in such a fixing belt, the dimensional stability of the elastic layer made of a heat-resistant rubber such as silicon rubber in a state of being heated is reduced, so that the running stability of the fixing belt is reduced. There was a problem.

An object of the present invention is to solve such a problem. That is, the present invention has moderate flexibility,
Further, it is an object of the present invention to provide a low-cost fixing belt excellent in releasability from toner, durability and running stability, and an image forming apparatus having the same.

[0019]

According to a first aspect of the present invention, there is provided a fixing belt having a heat-resistant elastic layer and a releasable surface layer on a substrate in order. The base is (a) a sheet or an endless belt made of a metal material such as stainless steel or nickel; (b) a sheet or an endless belt made of a heat-resistant resin such as polyimide or polyamide imide; or (c) The fixing belt is a laminated sheet or an endless belt of (a) and (b).

According to a second aspect of the present invention, in the first aspect of the invention, the elastic layer is made of silicon rubber.

According to a third aspect of the present invention, in the first or second aspect, the elastic layer contains carbon fibers formed by a vapor phase growth method. .

According to a fourth aspect of the present invention, in the third aspect of the present invention, the carbon fiber is 2
It is a carbon fiber heat-treated at a high temperature of 200 to 3000 ° C.

According to a fifth aspect of the present invention, in the third or fourth aspect, the carbon fiber is contained in the elastic layer at a ratio of 3 to 10% by weight. It is.

According to a sixth aspect of the present invention, in the first aspect, the surface layer is made of a fluororesin, and the elastic layer contains 80% ferric oxide.
It is characterized by being made of silicon rubber having a constituent component of 1 to 35% by weight of iron oxide contained above.

The invention described in claim 7 is characterized in that, in the invention described in claim 5 or 6, the silicone rubber is a silicone rubber having a phenyl group introduced into a side chain. .

[0027] The invention described in claim 8 is the invention according to claims 5 to 5.
7. The invention according to any one of items 7 to 7, wherein the silicone rubber has a JIS A hardness of 5 to 60.

[0027] The invention described in claim 9 is the first invention.
8. In the invention described in any one of 8 above, the thickness of the surface layer is 3 μm or more and less than 30 μm.

The invention described in claim 10 is the first invention.
An image forming apparatus comprising the fixing belt according to any one of claims 1 to 9.

[0029]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a fixing belt according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of a bending test of the fixing belt.

In FIG. 1, reference numeral 1 denotes a fixing belt.
The fixing belt 1 has an elastic layer 3 on an endless belt-shaped base 2.
And a surface layer 4 in order. The base 2 is made of (a) a sheet or an endless belt made of a metal material such as stainless steel or nickel; (b) a sheet or an endless belt made of a heat-resistant resin such as polyimide or polyamide imide; It is constituted by the laminated sheet or the endless belt of (a) and (b).

According to the present invention, the base is made of (a) a sheet or an endless belt made of a metal material such as stainless steel or nickel, or (b) a sheet made of a heat-resistant resin such as polyimide or polyamideimide. An endless belt, or (c) a fixing belt formed of the laminated sheet or the endless belt of the above (a) and (b), so that the fixing belt has appropriate flexibility, and is excellent in durability and running stability. , And an image forming apparatus having the same can be provided at low cost.

The elastic layer 3 is preferably made of heat-resistant rubber such as silicone rubber, and the surface layer 4
Preferably, the fluororesin material is tetrafluoroethylene-hexafluoropropylene copolymer (FE
P), and a fluororesin such as tetrafluoroethylene-polyethylene fluorovinyl ether copolymer (PFA) and ethylene-tetrafluoroethylene copolymer (ETFE).

The elastic layer 3 preferably contains carbon fibers (hereinafter referred to as “carbon whiskers”) formed by a vapor phase growth method. The carbon fiber is preferably a carbon fiber heat-treated at a high temperature of 2200 to 3000 ° C. The carbon whiskers are preferably made of an elastic layer 3.
In a proportion of 3 to 10% by weight.

Conventionally, as a major factor for improving the characteristics of the fixing belt, there is thermal conductivity of the fixing belt. If the heat capacity or thermal conductivity due to the film thickness of the fixing belt is poor, the temperature of the surface of the fixing belt heated by the heating and heating unit does not quickly rise, and therefore, the temperature of the toner contacting the fixing belt is hardly softened. . Since rubber such as silicon rubber which forms the elastic layer has high heat insulating properties, and the fluororesin which forms the surface release layer also has heat insulating properties, these materials are disadvantageous in terms of thermal conductivity.
Furthermore, a major factor that affects the fixing characteristics of the fixing belt is the electrical conductivity of the film. When the toner adhered to the fixing belt is transferred to the transfer paper, if the fixing belt is easily charged with static electricity by a dielectric material, a phenomenon called a so-called electrostatic offset occurs in which the toner remains attracted by the static electricity.
This electrostatic offset has an effect on the dielectric constant of the entire fixing belt. However, since the dielectric constant can be reduced by including a conductive substance in the layer constituting the fixing belt, the conductive offset is contained in the layer. The filler is dispersed. It is known that the electrical conductivity and the thermal conductivity of a conductive material such as a metal or carbon have a certain correspondence between the electrical conductivity and the thermal conductivity.

Therefore, conventionally, in order to improve the heat conductivity and electric conductivity of the fixing belt, various heat conductive materials such as carbon black, metal, inorganic fine particles, graphite, and titanium whisker which has been subjected to conductive treatment are conventionally used. And the like are dispersed in a layer such as an elastic layer constituting the fixing belt. However, the thermal conductivity of carbon black, like its electrical conductivity, does not appear unless the carbon fine particles are linked in a chain (unless a so-called structure is formed). It is slightly different depending on conditions. Since metal or inorganic fine particles basically do not form a structure in an isolated dispersion system, their thermal conductivity greatly depends on the dispersion density of the fine particles, and therefore, several tens% is required to secure sufficient thermal conductivity. Was required. Therefore, the original elastic function of the elastic layer is impaired. Further, since graphite has remarkable anisotropy, if the amount of dispersion is small, uneven heat transfer occurs depending on the dispersion state, and therefore, distribution occurs in heat fixing. Therefore, graphite must be dispersed in a large amount as in the case of metal or inorganic fine particles in order to eliminate anisotropy, so that the function of elasticity is impaired. In addition, in graphite, planar bonding is dominant, and the coupling between planes is BandelWal.
Since the bonding force is weak due to the s-force bond and is chemically inert, the bond in rubber molecules such as silicone rubber was broken by oxygen in the atmosphere at a temperature of 300 ° C. or more.

However, when the carbon fibers formed by the vapor phase growth method, that is, the carbon whiskers are contained in the elastic layer of the fixing belt made of rubber such as silicone rubber as in the present invention, the carbon whiskers become Since the core generated by the vapor phase growth in the generation process is hollow, the core of this carbon whisker adsorbs oxygen in the elastic layer and reduces the contact between oxygen and rubber such as silicon rubber forming the elastic layer, Therefore, when the elastic layer 3 made of rubber such as silicon rubber contains carbon whiskers, oxidation deterioration of rubber such as silicon rubber is suppressed, and rubber heat resistance during film formation of the surface layer 4 is improved. Become.
Therefore, the elasticity of the elastic layer 3 can be maintained without increasing the amount of iron oxide added to the rubber such as silicon rubber that forms the elastic layer 3. Since the carbon whiskers have good thermal conductivity and good electrical conductivity, according to the heat fixing belt of the present invention, a good image can be obtained, and the electrostatic offset is prevented. be able to.

In the present invention, the carbon fibers are heat-treated at a high temperature of 2200 to 3000 ° C., more preferably 2800 to 3000 ° C. As described above, when the carbon fiber is a carbon fiber that has been subjected to a high-temperature heat treatment at a temperature of 2200 to 3000 ° C., its thermal conductivity is improved, so that a better image can be obtained. Further, in the present invention, the carbon fiber is preferably contained in the elastic layer 3 at a ratio of 3 to 10% by weight. When the content of the carbon fiber is less than 3% by weight, thermal conductivity is not sufficient, and when the content of the carbon fiber is 10% by weight or more, the moldability of the elastic layer 3 is reduced. And surface defects occur. As described above, according to the present invention, since the carbon fiber is contained in the elastic layer 3 at a ratio of 3 to 10% by weight, the heat conductivity is good, and the moldability is also good. In addition, a good image is obtained.

In the present invention, the surface layer 4 is preferably made of a fluororesin, and the elastic layer 2 is
Preferably, iron oxides 1 to 3 containing 80% or more of ferric oxide
It is composed of silicone rubber having 5% by weight as a component.

FIG. 3 is a graph showing the change in the peak of combustion decomposition of silicon rubber due to the addition of iron oxide measured by differential scanning calorimetry (DSC).
At 320 ° C. or higher, a peak of oxidative decomposition due to combustion of the silicon rubber is observed, and it is confirmed that when the added amount of iron oxide increases, the peak shifts to a higher temperature side and the heat resistance of the silicon rubber improves. This indicates that the addition of iron oxide to the silicon rubber elastic layer improves the chemical thermal stability of the silicon rubber.

The iron oxide used here was ferric oxide of 80%.
% Or more. When the content of ferric oxide is low, it becomes unstable because it contains ferrous oxide that oxidizes and burns at 200 ° C. or higher. When iron oxide having a low content of ferric oxide is added to the silicon rubber, the silicon rubber to which the iron oxide is added by melting and firing the fluororesin at least at 300 ° C. or more constituting the surface layer The situation of sustained combustion oxidation in the elastic layer is confirmed, and it becomes impossible to stably produce the fixing belt with predetermined characteristics. Therefore, if the ferric oxide is not iron oxide containing 80% or more, after adding these to the silicon rubber, it is impossible to carry out melting and firing of the fluororesin of at least 300 ° C. or more constituting the surface layer. The surface of the fixing belt cannot be made highly releasable.

FIGS. 4 and 5 are graphs showing changes in the hardness and compression set of the silicone rubber due to the addition of iron oxide at around 320 ° C. According to FIGS. With respect to hardness and compression set, the addition of iron oxide containing ferric oxide in an amount of 80% or more reduces the change in each physical property of the silicon rubber elastic body, and heats the resin to 300 ° C. or higher, which is the melting and firing temperature of the fluororesin. It can be seen that the thermal deterioration due to the heat is suppressed. Therefore, ferric oxide must be 80
% Is added to the silicon rubber elastic layer, the change in the silicon rubber characteristics is suppressed, and uniform fixing can be stably performed. In this case, the evaluation was made by preparing a rubber sample having a diameter of 29 mm and a height of 13 mm, and testing it.

FIG. 6 is a graph showing the change in weight of silicon rubber due to the addition of iron oxide at around 320 ° C. According to FIG. 6, iron oxide containing 80% or more of ferric oxide was added to silicon rubber. By doing so, it can be confirmed that the weight reduction of the fluororubber, that is, the reduction of volatile substances, is also caused by the melting and firing temperature of the fluororesin. Therefore, by adding iron oxide containing 80% or more of ferric oxide to the silicon rubber elastic layer, the amount of volatile substances generated from the silicon rubber elastic layer is suppressed, and surface defects of the upper fluororesin due to the volatile substances are reduced. Can also be suppressed.

FIG. 7 is a graph showing the difference in the linear expansion coefficient of silicon rubber due to the addition of iron oxide at around 320 ° C. According to FIG. 7, iron oxide containing 80% or more of ferric oxide contains silicon oxide. By adding to the rubber elastic layer,
It can be confirmed that the coefficient of linear expansion of the silicone rubber decreases. Therefore, by adding iron oxide at about 320 ° C. to the silicon rubber elastic layer, the strain between the fluororesin layer and the silicon rubber layer is alleviated during cooling after firing of the fluororesin layer, and the surface of the upper fluororesin layer is cooled. Cracks can also be suppressed.

FIG. 8 is a graph showing the difference in the dimensional change of silicon rubber due to the addition of iron oxide at around 320 ° C. According to FIG.
It can be confirmed that the dimensional change of the rubber due to the melting and firing temperature of the fluororesin is reduced by adding the iron oxide containing the above to the silicon rubber. Therefore 32
By adding iron oxide at about 0 ° C. to the silicone rubber elastic layer, the dimensions of the silicone rubber elastic layer are stabilized, and the driving stability of the belt is secured.

As described above, in the fixing belt of the present invention, by adding iron oxide containing at least 80% of ferric oxide to silicon rubber, the characteristics of the silicon rubber elastic layer can be stabilized and the surface layer can be made uniform. Although it becomes possible, if the amount of iron oxide added to the silicon rubber is too large, the dispersibility of the iron oxide decreases, so that the surface of the silicon rubber elastic layer before forming the fluororesin layer has defects. Therefore, defects remain on the surface of the fluororesin layer as the surface layer. If the amount of iron oxide added to the silicon rubber is too large, the film strength is reduced. Therefore, the necessary film strength can be secured by controlling the amount of iron oxide to be within 35% by weight. Therefore, the surface of the silicone rubber elastic layer before the formation of the fluororesin is uniform without any defects. However, when the addition amount of iron oxide is less than 11% by weight, the effect is small. Therefore, according to the present invention,
By setting the addition amount of iron oxide to 1 to 35% by weight, the characteristics of the silicone rubber elastic layer can be stabilized and the surface of the fixing belt can be made uniform, and a fixing belt having good durability can be obtained. .

The silicone rubber is preferably a silicone rubber having a phenyl group introduced into a side chain. Such a silicon rubber having a phenyl group introduced into its side chain is known, and in particular, when a silicon rubber in which at least one of its two side chains is a phenyl group is used, a general side rubber is used. The heat resistance is further improved by the antioxidant action of the phenyl group, as compared with silicone rubber having a dimethyl chain. Therefore, according to the present invention, by using a silicon rubber having a phenyl group introduced into a side chain, it is possible to further increase the firing temperature of the fluororesin constituting the surface layer, thereby constituting the surface layer. This makes it possible to improve the releasability of the fluororesin and shorten the baking time, thereby improving the margin for preparing the fixing belt.

JIS of silicone rubber constituting the elastic layer 3
A hardness is preferably 5 to 60. When the JIS A hardness of the silicone rubber is less than 5, the image is not glossy due to insufficient pressing of the toner, and when the JIS A hardness of the silicone rubber exceeds 60, the toner surface is retained and fixed. Is not uniform, and an image having an uneven toner surface is obtained. Therefore, the fixing belt of the present invention has the elastic layer 3
By setting the JIS A hardness of the silicone rubber constituting 5 to 5 to 60, a good image can be obtained.

The thickness of the surface layer 4 is preferably 3 μm.
m and less than 30 μm. If the thickness of the fluororesin constituting the surface layer exceeds 30 μm, the flexibility of the fixing belt surface is impaired, so that the toner is not uniformly fixed,
As a result, the image becomes non-uniform, and if the film thickness of the fluororesin constituting the surface layer is less than 3 μm, the durability decreases. Therefore, in the fixing belt of the present invention, by setting the thickness of the surface layer to 3 μm or more and less than 30 μm, uniform fixing can be performed, and durability is improved.

According to the present invention, there is provided an image forming apparatus having the fixing belt according to any one of claims 1 to 5,
It is possible to provide an image forming apparatus having a fixing belt having moderate flexibility, and excellent in releasability from toner, durability and running stability at low cost. And an image having a medium gloss due to sufficient pressure contact of the toner. Further, since the driving stability is excellent, it is possible to output a good fixed image for a long time without an oil application mechanism.

[0050]

Example 1 20% by weight of iron oxide containing 85% or more of ferric oxide (YELLOW49, manufactured by Toda Kogyo Co., Ltd.) is a well-known silicone rubber having a methyl side chain (hereinafter referred to as "the specification"). (Abbreviated as "silicon rubber") and stirred with a centrifugal stirrer to sufficiently disperse the iron oxide in the silicone rubber solution (JIS A hardness of the silicone rubber used here). Was 47 without iron oxide added.) This silicon rubber solution was coated on a belt-like stainless steel (SUS) substrate having a thickness of 40 μm to form a silicon rubber elastic layer having a thickness of 150 μm. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer was 53. Then, a coating film is formed by spray-coating tetrafluoroethylene-hexafluoropropylene copolymer (FEP) on the surface of the silicone rubber elastic layer, and subsequently, the coating film is baked at 320 ° C. for 30 minutes to have a thickness of 15 μm. By forming the surface layer, a fixing belt having a belt shape was obtained.

(Example 2) 35% by weight of iron oxide containing 100% or more of ferric oxide (manufactured by Toda Kogyo Co., Ltd., 100ED) was added to a silicon rubber solution, and the solution was stirred by a centrifugal stirrer. Iron was sufficiently dispersed in the silicone rubber solution (the JIS A hardness of the silicone rubber used here was 24 without iron oxide added). This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer was 31. Then, a coating film is formed by spray-coating tetrafluoroethylene-polyethylene fluorovinyl ether copolymer (PFA) on the surface of the silicone rubber elastic layer, and then the coating film is formed at 340 ° C. for 30 minutes.
By calcining for 15 minutes to form a surface layer having a thickness of 15 μm, a belt-shaped fixing belt was obtained.

Example 3 1% by weight of iron oxide containing 80% or more of ferric oxide was added to a silicon rubber solution, and this was stirred with a centrifugal stirrer to sufficiently add the iron oxide to the silicon rubber solution. (J of silicone rubber used here)
The ISA hardness was 24 without iron oxide added. ). This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer was 24. Then, FEP is spray-coated on the surface of the silicone rubber elastic layer to form a coating film.
By baking for 0 minutes to form a surface layer having a thickness of 15 μm, a belt-shaped fixing belt was obtained.

Example 4 28% by weight of iron oxide (160ED, manufactured by Toda Kogyo Co., Ltd.) containing 98.5% or more of ferric oxide was added to a silicone rubber solution, and this was stirred with a centrifugal stirrer. The iron oxide was sufficiently dispersed in the silicon rubber solution (the JISA hardness of the silicon rubber used here was 50 without iron oxide added). This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer was 60. Then, a coating film is formed by spray-coating FEP on the surface of the silicone rubber elastic layer, and then the coating film is baked at 340 ° C. for 30 minutes to form a coating film of 15 μm.
By forming a surface layer having a thickness of m, a belt-shaped fixing belt was obtained.

Example 5 3% by weight of iron oxide (KR370H, manufactured by Toda Kogyo Co., Ltd.) containing less than 98.5% of ferric oxide was added to a silicone rubber solution, and this was stirred with a centrifugal stirrer. The iron oxide was sufficiently dispersed in a silicon rubber solution (the silicon rubber used here had a JISA hardness of 5 without iron oxide added). This silicon rubber solution was coated on a belt-shaped SUS substrate having a thickness of 40 μm to form a silicon rubber elastic layer having a thickness of 150 μm. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer is 5
Met. Then, F is applied to the surface of the silicone rubber elastic layer.
An EP was spray-coated to form a coating film, and then the coating film was baked at 340 ° C. for 30 minutes to form a surface layer having a thickness of 15 μm, thereby obtaining a belt-shaped fixing belt.

(Example 6) 10% by weight of iron oxide (160ED, manufactured by Toda Kogyo KK) containing 98.5% or more of ferric oxide was added to a silicone rubber solution, and this was stirred with a centrifugal stirrer. The iron oxide was sufficiently dispersed in a silicon rubber solution (the JISA hardness of the silicon rubber used here was 24 without iron oxide added). This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer was 26. Then, the surface of the silicone rubber elastic layer is spray-coated with FEP to form a coating film. Subsequently, the coating film is baked at 320 ° C. for 30 minutes to obtain a coating film having a thickness of 28 μm.
By forming a surface layer having a thickness of m, a belt-shaped fixing belt was obtained.

Example 7 In the same manner as in Example 6, a silicone rubber solution was coated on a belt-like polyimide substrate to form a silicone rubber elastic layer. Then, a coating film is formed by spray-coating FEP on the surface of the silicone rubber elastic layer, and then the coating film is fired at 320 ° C. for 30 minutes to form a surface layer having a thickness of 3 μm. Fixing belt.

(Example 8) 10% by weight of iron oxide (160ED, manufactured by Toda Kogyo KK) containing 98.5% or more of ferric oxide was added to a solution of silicon rubber having a phenyl group introduced into a side chain. This was stirred with a centrifugal stirrer to sufficiently disperse the iron oxide in the silicon rubber solution (the JIS A hardness of the silicon rubber used here was 30 without iron oxide added). ). 40 μm of this silicone rubber solution
It was coated on a thick belt-shaped SUS substrate to form a 150 μm-thick silicon rubber elastic layer having phenyl groups introduced into side chains. JI of the silicon rubber elastic layer containing this iron oxide
The SA hardness was 30. Then, a coating film is formed by spray coating FEP on the surface of the silicone rubber elastic layer, and then the coating film is baked at 350 ° C. for 30 minutes to form a surface layer having a thickness of 15 μm. Fixing belt.

(Comparative Example 1) Silicone rubber solution of 40 μm
A 150 μm-thick silicon rubber layer was formed by coating on a thick belt-shaped SUS base (the JIS A hardness of the silicon rubber used here was 47 without iron oxide added). Then, F is applied to the surface of the silicone rubber elastic layer.
An EP was spray-coated to form a coating film, and then the coating film was baked at 320 ° C. for 30 minutes to form a surface layer having a thickness of 15 μm, thereby forming a belt-shaped fixing belt.

(Comparative Example 2) 20% by weight of iron oxide (KR370H, manufactured by Toda Kogyo KK) containing less than 5% of ferric oxide was added to a silicone rubber solution, and this was stirred with a centrifugal stirrer to give the oxidized solution. Iron was sufficiently dispersed in the silicone rubber solution (the JIS A hardness of the silicone rubber used here was 24 without iron oxide added). This silicon rubber solution was coated on a belt-shaped SUS substrate having a thickness of 40 μm to form a silicon rubber elastic layer having a thickness of 150 μm. Then, a FEP is spray-coated on the surface of the silicone rubber elastic layer to form a coating film.
By baking at 0 ° C. for 30 minutes to form a surface layer having a thickness of 15 μm, a belt-shaped fixing belt was obtained.

(Comparative Example 3) 40% by weight of iron oxide (160ED, manufactured by Toda Kogyo KK) containing 98.5% or more of ferric oxide was added to the silicone rubber solution, and this was stirred with a centrifugal stirrer. The iron oxide was sufficiently dispersed in a silicon rubber solution (the JISA hardness of the silicon rubber used here was 24 without iron oxide added). This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer was 32. Then, FEP is spray-coated on the surface of the silicone rubber elastic layer to form a coating film, and then the coating film is baked at 320 ° C. for 30 minutes to form a coating film having a thickness of 15 μm.
By forming a surface layer having a thickness of m, a belt-shaped fixing belt was obtained.

Comparative Example 4 0.5% by weight of iron oxide (160ED, manufactured by Toda Kogyo KK) containing 98.5% or more of ferric oxide
Was added to a silicon rubber solution, and the mixture was stirred with a centrifugal stirrer to sufficiently disperse the iron oxide in the silicon rubber solution (the JIS A hardness of the silicon rubber used here was that of iron oxide-free addition). 24 in the state.) This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. JIS of this silicon oxide elastic layer containing iron oxide
The A hardness was 24. Then, PFA is spray-coated on the surface of the silicone rubber elastic layer to form a coating film. Subsequently, the coating film is baked at 340 ° C. for 30 minutes to form a 15 μm thick surface layer, thereby forming a belt-like shape. Fixing belt.

(Comparative Example 5) 33% by weight of iron oxide (160ED, manufactured by Toda Kogyo KK) containing 98.5% or more of ferric oxide was added to a silicone rubber solution, and this was stirred with a centrifugal stirrer. The iron oxide was sufficiently dispersed in the silicon rubber solution (the JISA hardness of the silicon rubber used here was 50 without iron oxide added). This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer was 62. Then, a coating film is formed by spray-coating FEP on the surface of the silicone rubber elastic layer, and then the coating film is baked at 340 ° C. for 30 minutes to form a coating film of 15 μm.
By forming a surface layer having a thickness of m, a belt-shaped fixing belt was obtained.

(Comparative Example 6) 1% by weight of iron oxide (160ED, manufactured by Toda Kogyo KK) containing 98.5% or more of ferric oxide was added to a silicon rubber solution, and the solution was stirred by a centrifugal stirrer. The iron oxide was sufficiently dispersed in a silicon rubber solution (the JISA hardness of the silicon rubber used here was 2 without iron oxide added). This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer is:
It was 2. Then, a coating film is formed by spray-coating FEP on the surface of the silicone rubber elastic layer, and then the coating film is fired at 320 ° C. for 30 minutes to form a 15 μm thick surface layer, thereby forming a belt-like shape. Fixing belt.

(Comparative Example 7) 10% by weight of iron oxide (160ED, manufactured by Toda Kogyo KK) containing 98.5% or more of ferric oxide was added to a silicone rubber solution, and this was stirred with a centrifugal stirrer. The iron oxide was sufficiently dispersed in a silicon rubber solution (the JISA hardness of the silicon rubber used here was 24 without iron oxide added). This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer was 26. Then, a coating film is formed by spray-coating FEP on the surface of the silicone rubber elastic layer, and then the coating film is baked at 320 ° C. for 30 minutes to form a coating film having a thickness of 30 μm.
By forming a surface layer having a thickness of m, a belt-shaped fixing belt was obtained.

(Comparative Example 8) 1% by weight of iron oxide (160ED, manufactured by Toda Kogyo KK) containing 98.5% or more of ferric oxide was added to a silicone rubber solution, and this was stirred with a centrifugal stirrer. The iron oxide was sufficiently dispersed in a silicon rubber solution (the JISA hardness of the silicon rubber used here was 2 without iron oxide added). This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer is:
It was 2. Then, a coating film is formed by spray-coating FEP on the surface of the silicone rubber elastic layer, and then the coating film is fired at 320 ° C. for 30 minutes to form a surface layer having a thickness of 2 μm. Fixing belt.

The above Examples 1 to 8 and Comparative Examples 1 to 8
Evaluation of the belt-shaped fixing belt obtained in the above was as follows.

Obtained in Examples 1 to 8 and Comparative Examples 1 to 8
Image and durability using a belt-shaped fixing belt as a sample
The properties and releasability were evaluated. About the image
Indicates the visual evaluation of image uniformity and the gloss
The measurement and evaluation were carried out using a degree meter (incidence 60 °). More durable
As shown in Fig. 2, the test
Sheet 12 using a metal column 11 having a diameter of 15 mm.
Evaluation of abrasion while operating in reverse bending
The blade 13 against the test sheet 12 to perform
The evaluation was carried out while being performed. The test conditions are the test sheet
12 along the metal support 11 in the direction of the arrow twice / sec.
Run at speed. 15,000 bending / wear tests completed
After completion of the test, the test sheet of the portion where the blade 13 abuts
Using 12 surfaces, the releasability to color toner was evaluated.
Valued. That is, a surface pressure of 4 kg / cm ^Two , Linear velocity 50mm /
For testing color toner under the condition of seconds and temperature of 180 ℃
Heat and press between the sample of sheet 12 and paper,
Thereafter, the paper and the sample of the test sheet 12 were peeled off.
In the process, the toner and the sample of the test sheet 12
The release / wear condition (offset condition) was confirmed. For durability
Then, 20,000 bending / wear tests were also conducted.

The image uniformity, image glossiness, durability and releasability were evaluated according to the following evaluation criteria. (A) Image uniformity ；: Particularly good ○: Good △: Slight occurrence of abnormal image due to non-uniformity (no problem in practical use) ×: Abnormal image due to non-uniformity (pear surface-like rough image) (B) Image gloss ◎: Gloss 15% or more ；: Gloss 10% or more △: Gloss 10% or more (with unevenness) ×: Gloss less than 10% (c) Durability ；: 20,000 times No toner adhesion in repeated bending and abrasion tests of ○: No toner adhesion in 15,000 repeated bending and abrasion tests ×; Toner adhesion in 15,000 repeated bending and abrasion tests (d) Releasability ○: No belt abnormality × There is abnormal peeling of the surface layer. In the above evaluations (a) to (d), the samples that were evaluated as "x" in the evaluation process were abbreviated as "-" for the following evaluations. The evaluation results are shown in Table 1 below.

[0069]

[Table 1]

The overall evaluations of Examples 1 to 8 and Comparative Examples 1 to 8 are as follows.

[I] About Examples 1 to 8 (1) In Examples 1 to 8, the ratio of ferric oxide in iron oxide was large and the ratio of ferrous oxide was small, so that Even when added to the silicone rubber elastic layer, when the fluororesin of the surface layer is melted and fired, the combustion of iron oxide in the silicone rubber elastic layer does not occur, and the heat deterioration of the silicone rubber in the elastic layer is suppressed, and a stable fixing belt is formed. Fabrication could be performed.

(2) In Examples 4 and 5, since the hardness of the silicone rubber elastic layer is appropriate, the fixing belt surface can press the toner sufficiently and uniformly, and therefore, the uniformity and gloss of the image can be improved. Could be compatible. (3) In Examples 7 and 8, the film thickness of the fluororesin layer as the surface layer is appropriate, so that the fixing belt surface can uniformly press the toner without impairing the flexibility of the silicone rubber elastic layer. There was no problem in terms of durability.

(4) In Example 8, since a phenyl group was introduced into the side chain of the silicone rubber, there was a margin in terms of heat resistance in addition to the effect of improving the heat resistance of iron oxide.
Therefore, it is possible to raise the melting / firing temperature of the fluororesin layer, and to improve the releasability by shortening the fluororesin layer surface layer and shorten the firing time.

[II] Regarding Comparative Examples 1 to 8 (1) In Comparative Example 1, no iron oxide was added, and in Comparative Example 4, the amount of iron oxide added was insufficient. Of the silicone rubber elastic layer and the surface layer of the fluorine resin caused defects such as cracks, and the performance as a fixing belt could not be evaluated.

(2) In Comparative Example 2, since the ratio of ferric oxide in the iron oxide was small and the ratio of ferrous oxide having high reactivity was large, the silicon resin was melted and fired at the fluororesin surface layer. Ferrous oxide in the rubber elastic layer continuously burned, and it was difficult to produce a fixing belt. In the belt-shaped fixing belt thus obtained, the silicon rubber is embrittled by heat, and as a result, defects such as cracks occur in the silicon rubber elastic layer and the fluororesin surface layer. Performance could not be evaluated.

(3) In Comparative Example 3, although the heat resistance of the silicone rubber was increased by the addition of ferric oxide, aggregation was recognized due to poor dispersion of ferric oxide because the amount of addition was excessive. Therefore, defects due to unevenness occur on the surface of the silicone rubber elastic layer before spray coating with the fluororesin (FEP), whereby defects also occur on the fluororesin surface layer, image uniformity, image glossiness, and durability. There was a problem in the properties and peelability.

(4) In Comparative Example 5, since the hardness of the silicone rubber elastic layer was too high, uniform pressing was not performed with sufficient flexibility on the fixing belt surface, and the image was non-uniform. (5) In Comparative Example 6, since the hardness of the silicone rubber elastic layer was too low, the toner was not sufficiently pressed against the belt surface, resulting in an image with low gloss.

(6) In Comparative Example 7, the surface of the belt was uniform and excellent in releasability. However, since the thickness of the fluororesin as the surface layer was too large, the surface of the belt was insufficient. Uniform pressure contact was not performed due to flexibility, and the image was non-uniform. (7) In Comparative Example 8, the thickness of the fluororesin as the surface layer was small, and there was a problem in terms of releasability.

Example 9 1% by weight of a carbon whisker (hereinafter referred to as “high-temperature CW”) heat-treated at a high temperature (Glass Car VGCF manufactured by Nikkiso Co., Ltd.) was added as an additive to a silicone rubber solution, and this was centrifuged. The carbon whisker was sufficiently dispersed in the silicone rubber solution by stirring with a stirrer. The JIS A hardness of this silicone rubber was 5 as measured. This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. The JIS A hardness of the iron oxide-containing silicon rubber elastic layer is:
10, and the surface resistance (Ω) varied from 10 ⁵ to ⁸ . Then, PFA is spray-coated on the surface of the silicone rubber elastic layer to form a coating film. Subsequently, the coating film is baked at 340 ° C. for 30 minutes to be 15 μm
By forming a thick surface layer, a belt-shaped fixing belt was obtained.

(Examples 10 to 13) In the additives to be added to the silicone rubber solution, the addition ratio of high-temperature CW was set to 5% by weight and 10% by weight, and normal CW (hereinafter, referred to as "normal CW"). A belt-shaped fixing belt was produced in the same manner as in Example 9 except that the addition ratio of was 5% by weight and 10% by weight.

(Comparative Examples 9 to 13) In the additives to be added to the silicone rubber solution, the addition ratio of high-temperature CW was 1% by weight,
15% by weight, and the addition rate of CW is usually 1% by weight,
A belt-shaped fixing belt was obtained in the same manner as in Example 9 except that the amounts were 3% by weight and 15% by weight.

Comparative Example 14 A belt-shaped fixing belt was produced in the same manner as in Example 9 except that the additive added to the silicone rubber solution was changed to 30% by weight of iron oxide.

As described above, Examples 10 to 13 and Comparative Examples 9-1
In 3, the surface resistance (Ω) and the rubber hardness (JIS A hardness) were measured in the same manner as in Example 9. In addition, Examples 9 to
Image evaluation, electrostatic offset, image uniformity, and image glossiness of the belt-shaped fixing belts obtained in Comparative Example 13 and Comparative Examples 9 to 13 were evaluated.

The image evaluation and the electrostatic offset were evaluated according to the following evaluation criteria (e) and (f). The image uniformity and the image gloss were evaluated as follows.
The evaluation was made according to the evaluation criteria shown in the above (a) and (b). (E) Surface resistance (Ω) and rubber hardness (GIS A hardness) JI
Evaluation criteria of S) ；: variation in surface resistance is less than 10 ² , and
Rubber hardness is less than 60. Δ: variation in surface resistance is less than 10 ² , or
Rubber hardness is less than 60. ×: variation in surface resistance is 10 ² or more, or
Rubber hardness is 60 or more. (F) Electrostatic offset ；: No occurrence Δ: Slight occurrence ×: Many occurrence The measurement results and evaluation results are shown in Table 2 below.

[0085]

[Table 2]

As described above, Examples 14 to 25 and Comparative Examples 15 to
A comprehensive evaluation of 26 is as follows. The carbon whiskers CW of Examples 14 to 25 have good thermal conductivity and electric conductivity, so that even if they do not contain iron oxide, they have good image uniformity and image gloss, and the added amount is 10% or less. Is sufficient, so that an increase in rubber hardness due to an increase in the additive is suppressed, and consequently, good image uniformity and image gloss can be obtained. In particular, it can be seen that high-temperature-treated carbon whiskers (high-temperature CW) are more excellent in image uniformity, image gloss, and repetition durability. In Comparative Examples 15 to 26, when the content of iron oxide in carbon black or graphite was small, image uniformity was poor,
Further, even if the content is about 3 to 10%, the durability and the releasability cannot be sufficiently satisfied. From these facts, carbon whiskers, especially carbon whiskers of high temperature treatment (high temperature CW)
Indicates that a belt having excellent image quality and durability can be provided.

Example 14 5% by weight of high-temperature CW was added to a silicone rubber solution, which was stirred with a centrifugal stirrer.
The high temperature CW was sufficiently dispersed in the silicone rubber solution. This silicone rubber solution was coated on a 50 μm thick belt-like polyimide substrate to form a 150 μm thick silicone rubber elastic layer. Then, PFA is spray-coated on the surface of the silicone rubber elastic layer to form a coating film.
This coating film was fired at 340 ° C. for 30 minutes to form a surface layer having a thickness of 15 μm, thereby obtaining a belt-shaped fixing belt.

(Examples 15 to 19) In the additives to be added to the silicone rubber solution, the addition ratio of high-temperature CW was 5% by weight.
And the addition amount of iron oxide is 0.5% by weight, 1% by weight,
A belt-shaped fixing belt was obtained in the same manner as in Example 14, except that the amount was 3% by weight, 5% by weight, and 10% by weight.

(Examples 20 to 25) In the additives to be added to the silicone rubber solution, the addition rate of CW was usually 5% by weight.
And the addition amount of iron oxide is 0% by weight, 0.5% by weight,
A belt-shaped fixing belt was obtained in the same manner as in Example 14 except that the amounts were 1% by weight, 3% by weight, 5% by weight, and 10% by weight.

(Comparative Examples 15 to 20) In the additives to be added to the silicone rubber solution, the addition ratio of carbon black was fixed at 5% by weight, and the addition amount of iron oxide was 0% by weight and 0.5% by weight.
% By weight, 1% by weight, 3% by weight, 5% by weight and 10% by weight
A belt-shaped fixing belt was formed in the same manner as in Example 14 except that the above-mentioned was used.

Comparative Examples 21 to 26 In the additives to be added to the silicone rubber solution, the addition rate of graphite was fixed at 5% by weight, and the addition amount of iron oxide was 0%, 0.5% by weight, and 1% by weight. %, 3% by weight, 5% by weight and 10% by weight in the same manner as in Example 14 to obtain a belt-shaped fixing belt.

As described above, Examples 14 to 25 and Comparative Examples 15 to
The image uniformity, image glossiness, durability and releasability of the belt-shaped fixing belt obtained in No. 26 were evaluated. The image uniformity, image glossiness, durability and releasability were evaluated according to the following evaluation criteria (a) to (d). The measurement results and evaluation results are shown in Table 3 below.

[0093]

[Table 3]

As described above, Examples 14 to 25 and Comparative Examples 15 to
A comprehensive evaluation of 26 is as follows. That is, when carbon whiskers are added to the silicon rubber solution, the heat resistance is further improved even if the content of iron oxide is small, and when carbon whiskers treated at a high temperature are added to the silicon rubber solution, image uniformity and image The gloss was further improved. This is considered to be because the heat conductivity of the carbon whisker subjected to the high temperature treatment is better than that of the normal carbon whisker. Then, in the same manner as in Example 14, carbon black or fine graphite was added instead of carbon whiskers to form a belt. However, if no iron oxide entered, cracks occurred in the surface layer and the elastic layer during film firing. In addition, the film was prepared by adding iron oxide to prevent abnormal appearance during firing. However, in order to obtain a surface resistance of 10 5 Ω to 6 Ω equivalent to that of carbon whiskers, the amount of addition must be 20% or more. In addition, the film hardness was increased, the elasticity was lost, and the image fixing property was deteriorated.

[0095]

(1) According to the first aspect of the present invention,
Substrate, (a) stainless steel, sheet or endless belt made of metal material such as nickel, (b) polyimide or sheet or endless belt made of heat-resistant resin such as polyamideimide, or (c) (A) and (b) the fixing sheet is a laminated sheet or an endless belt, which has appropriate flexibility, and is excellent in durability and running stability;
In addition, an image forming apparatus having the same can be provided at low cost.

(2) According to the second aspect of the invention, since the elastic layer is made of silicon rubber, the heat resistance is good. (3) According to the third aspect of the invention, since the elastic layer contains carbon fibers formed by a vapor growth method, the rubber is suppressed from being oxidized and degraded, and the surface layer 4
Rubber heat resistance during film formation is improved. Therefore, the elasticity of the elastic layer can be maintained without increasing the amount of iron oxide added to the rubber such as silicon rubber forming the elastic layer. Since the carbon whiskers have good thermal conductivity and good electrical conductivity, according to the heat fixing belt of the present invention, a good image can be obtained, and the electrostatic offset is prevented. be able to.

(4) According to the fourth aspect of the invention, since the carbon fiber is a carbon fiber heat-treated at a high temperature of 2200 to 3000 ° C., the thermal conductivity is improved. The glossiness is improved, and a better image is obtained. (5) According to the fifth aspect of the invention, since the carbon fiber is contained in the elastic layer at a ratio of 3 to 10% by weight, the carbon fiber has good thermal conductivity and good moldability. Yes, and therefore a good image is obtained.

(6) According to the invention according to claim 6, the surface layer is made of a fluororesin, and the elastic layer is made of iron oxide containing 1 to 35% by weight of iron oxide containing 80% or more of ferric oxide. The silicon rubber elastic layer is not thermally degraded even under the conditions of melting and firing the fluororesin, so that a uniform surface layer free of crack bubbles and the like is formed of a fluororesin thin film. It is possible to form. Moreover, according to the invention of claim 2, it is possible to ensure both appropriate flexibility and high release surface properties,
Further, since the driving stability is excellent, it is possible to output a good fixed image for a long time without an oil application mechanism.

(7) According to the invention of claim 7, since the silicon rubber is a silicon rubber having a phenyl group introduced into the side chain, the firing temperature of the fluororesin constituting the surface layer can be further increased. Thereby, the releasability of the fluororesin constituting the surface layer can be improved and the firing time can be shortened, and the margin for preparing the fixing belt can be improved.

(8) According to the invention of claim 8, the JIS A hardness of the silicone rubber constituting the elastic layer is 5-6.
Since it is 0, the image is sufficiently glossy with sufficient pressure contact of the toner, and the toner surface is uniformly held and fixed, so that the toner surface is uniform. (9) According to the ninth aspect of the present invention, since the thickness of the surface layer is 3 μm or more and less than 30 μm, uniform fixing can be performed, and durability is improved.

(10) According to the tenth aspect of the present invention, since the fixing belt according to any one of the first to ninth aspects is provided, the fixing belt has an appropriate flexibility, and is separated from the toner. Image forming apparatus having a fixing belt with excellent performance, durability and running stability can be provided at low cost.
It is possible to achieve both a uniform image by uniform fixing of the toner and a medium gloss image by sufficient pressure contact of the toner. Further, since the driving stability is excellent, it is possible to output a good fixed image for a long time without an oil application mechanism.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fixing belt according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a bending test of a fixing belt.

FIG. 3 is a graph showing a change in a peak of combustion decomposition of silicon rubber due to addition of iron oxide measured by differential scanning calorimetry.

FIG. 4 is a graph showing the relationship between the amount of iron oxide added before and after firing at 320 ° C. and the rate of decrease in the hardness of silicon rubber.

FIG. 5 is a graph showing the relationship between the amount of iron oxide added at around 320 ° C. and the change in compression set of silicone rubber.

FIG. 6 is a graph showing the relationship between the amount of iron oxide added at about 320 ° C. and the weight reduction rate of silicon rubber.

FIG. 7 is a graph showing the relationship between the amount of iron oxide added before and after firing at 320 ° C. and the dimensional reduction rate of silicon rubber.

FIG. 8 is a graph showing the relationship between the amount of iron oxide added at about 320 ° C. and the linear expansion coefficient of silicon rubber.

FIG. 9 is an explanatory diagram of a conventional electrophotographic image forming apparatus.

FIG. 10 is an explanatory diagram showing a use state of a conventional heat-fixing endless belt.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing belt 2 Substrate 3 Elastic layer 4 Surface layer 11 Metal column 12 Test sheet 13 Blade

Continuing from the front page (72) Inventor Norihiko Yasue 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Toshiaki Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Koji Kamiya 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. 2H033 AA09 AA23 BA11 BA12 4J002 CP031 DA016 DE117 FA046 FD116 FD207 GQ00

Claims (10)

[Claims] 1. A fixing belt having a heat-resistant elastic layer and a releasable surface layer sequentially on a substrate, wherein the substrate comprises (a) a sheet or an endless belt made of a metal material such as stainless steel or nickel. (B) a sheet or endless belt composed of a heat-resistant resin such as polyimide or polyamide-imide, or (c) a laminated sheet or endless belt of (a) and (b) above. . 2. The fixing belt according to claim 1, wherein the elastic layer is made of silicone rubber. 3. The fixing belt according to claim 1, wherein the elastic layer contains carbon fibers formed by a vapor growth method. 4. The method according to claim 1, wherein said carbon fiber is 2200-3.
The fixing belt according to claim 3, wherein the fixing belt is a carbon fiber that has been subjected to a high-temperature heat treatment at a temperature of 000 ° C. 5. The fixing belt according to claim 3, wherein the carbon fiber is contained in the elastic layer at a ratio of 3 to 10% by weight. 6. The surface layer is made of a fluororesin,
2. The fixing belt according to claim 1, wherein the elastic layer is made of silicon rubber having 1 to 35% by weight of iron oxide containing 80% or more of ferric oxide. 7. The fixing belt according to claim 5, wherein the silicone rubber is a silicone rubber having a phenyl group introduced into a side chain. 8. The JIS A hardness of the silicone rubber is 5
The fixing belt according to any one of claims 5 to 7, wherein 9. The film thickness of the surface layer is 3 μm or more and 30 μm.
The fixing belt according to claim 1, wherein: 10. An image forming apparatus comprising the fixing belt according to claim 1.