JP6946780B2 - Fixing roller, fixing device, and image forming device - Google Patents

Description

The present invention relates to a fixing roller, a fixing device, and an image forming device for fixing an unfixed toner image, which is used in a copying machine, a printer, a facsimile, etc. using an electrophotographic method.

As a fixing device used in various image forming devices such as a copying machine, a printer, a facsimile, or a multifunction device thereof, for example, a belt fixing method including a thin-walled fixing belt having a metal base material and an elastic rubber layer, or a film heating method. Fixing device is widely known.

The belt fixing type fixing device includes, for example, a fixing belt which is a fixing member, a pipe-shaped heat conductive member provided in the fixing belt, a heater such as a halogen heater for heating the fixing belt, a thermistor, and pressurization. It is configured to include a pressurizing roller as a member and a heat radiating member.

The fixing belt is made of, for example, a thin-walled and flexible endless belt-shaped member, and is rotatably provided. The thermistor is a temperature sensor provided in contact with the fixing belt and detecting the surface temperature of the fixing belt. Further, the pressure roller is a rotatable pressure member provided in contact with the fixing belt so as to form a fixing nip with the fixing belt. Further, the heat radiating member has a shape such as an arc shape in a cross-sectional view, and is provided so as to face a part of the outer peripheral surface of the fixing belt.

Further, the pressure roller used in the fixing device is, for example, a core metal which is a metal columnar member, an elastic layer provided on the outer peripheral surface of the core metal and made of a porous body or the like, and elasticity. It has a release layer provided on the outer peripheral surface of the layer and configured by using a resin.

In the process of image formation, heat is applied to the pressurizing roller used in the fixing device from the outside, and the pressurizing roller is gradually deteriorated by this heat, and an image abnormality such as uneven gloss may occur. In order to prevent deterioration of the pressurizing roller due to heat, a fixing device provided with a depressurizing mechanism on the fixing device side has been proposed, but there is a problem that the cost increases due to an increase in the number of parts. Further, for example, in order to improve the durability of the fixing roller used as a pressure roller, it has been proposed to fabricate a fixing roller using a porous body formed by a water foaming technique (for example, Patent Document 1). reference).

Japanese Unexamined Patent Publication No. 2013-164458

Patent Document 1 discloses that a fixing roller having excellent durability can be obtained by using a porous body formed by a water foaming technique as an elastic layer of the fixing roller. However, the porous body formed by the water foaming technique has a lower molecular weight and crosslink density of the materials constituting the porous body than the porous body formed by the chemical foaming technique, so that the compression set has a chemical permanent strain property. There is a problem that it may be lower than the porous body formed by the foaming technique.

Therefore, an object of the present invention is to pay attention to the above-mentioned problems and to provide a fixing roller, a fixing device, and an image forming device having high durability and good compression set.

In order to solve the above-mentioned problems, the fixing roller of the present invention includes a core metal and an elastic layer provided on the outer peripheral surface of the core metal, and the elastic layers have spherical shapes that partially overlap each other. It is characterized in that it is composed of a porous body having composite bubbles, which are bubbles, and silicone rubber particles dispersed in the porous body.

According to the fixing roller of the present invention, the core metal and the elastic layer formed on the outer peripheral surface of the core metal are provided, and the elastic layer is dispersed in a porous body having composite bubbles and a porous body. Since it is composed of silicone rubber particles, it is possible to obtain a fixing roller having high durability and good compression set.

It is sectional drawing which shows typically the fixing roller which concerns on one Embodiment of this invention. It is a figure which shows the arrow AA line cross section of the fixing roller shown in FIG. It is a figure which shows typically the elastic layer of the fixing roller shown in FIG. It is a schematic diagram which shows an example of the fixing device using the fixing roller which concerns on one Embodiment of this invention. It is a figure which shows typically the fixing belt in the cross section of the arrow BB line of the fixing device shown in FIG. It is a schematic block diagram which shows an example of the image forming apparatus using the fixing roller which concerns on one Embodiment of this invention. It is a figure which shows the analysis result of the size of the bubble contained in the elastic layer of the pressure roller in Example 1, Comparative Example 2, and Comparative Example 4.

[Fixing roller]
Next, the "fixing roller" according to the embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3. The pressurizing roller 10, which is a fixing roller according to the present embodiment, is used in an image forming apparatus using an electrophotographic method, and is used, for example, in a fixing apparatus 100 and an image forming apparatus 500, which will be described later.

As shown in FIG. 1, the pressure roller 10 which is a fixing roller is formed on the core metal 11, the elastic layer 12 provided on the outer peripheral surface of the core metal 11, and the outer peripheral surface of the elastic layer 12 in the paper passing region. It is provided with a surface release layer (release layer) 13 provided, and two grip layers 14 provided at portions outside the paper passing region at both ends of the pressure roller 10. The core metal 11, the elastic layer 12, the surface release layer 13, and the grip layer 14 are all cylindrical members. Further, as shown in FIG. 2, in the pressure roller 10, the outer peripheral surface of the elastic layer 12 and the outer peripheral surface of the grip layer 14 are flush with each other. In the pressure roller 10, the grip layer 14 is provided on the outer peripheral surface of the elastic layer 12, but may be provided on the outer peripheral surface of the core metal 11.

The core metal 11 is a metal cylindrical member. The metal used for the core metal 11 is not limited, but it is particularly preferable to use a highly rigid metal material such as stainless steel or carbon steel (for example, carbon steel pipe for machine structure (STKM material)). Further, the core metal 11 of the present embodiment can be formed in a hollow cylindrical shape with a wall thickness of, for example, 2 mm. In the pressure roller 10, the elastic layer 12 is provided on the outer peripheral surface of the core metal 11 and has heat insulating properties. Therefore, the core metal 11 may be made of a solid member. ..

The elastic layer 12 is composed of a porous body 12a having a composite bubble 12c and silicone rubber particles 12b dispersed in the porous body. FIG. 3 is a cross-sectional view schematically showing the elastic layer 12.

Here, the composite bubble is different from a single bubble (closed cell) in which each has an independent spherical shape, and as shown in FIG. 3, when the cross section of the porous body is observed, the spherical shape has a spherical shape. Refers to bubbles that partially overlap each other. The composite bubble can be easily distinguished from the single bubble by observing the cross section of the porous body with a microscope or the like.

The porous body 12a constituting the elastic layer 12 preferably has a thermal conductivity of 0.08 W / (m · K) to 0.2 W / (m · K), preferably 0.08 W / (m · K). It is more preferably ~ 0.15 W / (m · K), and even more preferably 0.08 W / (m · K) to 0.12 W / (m · K). By setting the thermal conductivity of the porous body 12a in an appropriate range, the heat insulating property of the pressure roller 10 can be improved and the durability can be improved.

Further, the porous body 12a constituting the elastic layer 12 preferably has a hardness of 20 to 60 (SRIS0101, Ascar C). By setting the hardness of the porous body 12a in an appropriate range, the durability of the pressure roller 10 can be enhanced.

The material constituting the porous body 12a is not particularly limited, and for example, a water-foamed silicone rubber formed by a water-foaming technique can be preferably used. Since the elastic layer 12 is formed of the porous body 12a, the pressure roller 10 can be provided with heat insulating properties, and heat transfer to the pressure roller 10 can be reduced. Therefore, it is possible to shorten the start-up time of the device provided with the pressurizing roller 10 (for example, the fixing device 100, the image forming device 500, etc., which will be described later) and save energy (for example, reduce the TEC value).

The bubbles in the water-foamed silicone rubber are so-called continuous foam type, which are connected by fine passages formed when water (and alcohol appropriately added to water) as a dispersion medium escapes from the molded body. It is a composite bubble in which spherical shapes partially overlap each other. As a result, the porous body formed by the water foaming technique has a high rate of continuous foaming. Further, by constructing the porous body 12a using water-foamed silicone rubber, sufficient durability, heat insulating property, and heat resistance can be obtained.

Further, in the elastic layer 12, it is preferable that the silicone rubber particles 12b are dispersed more on the surface layer side (for example, 50% of the surface layer side) in the thickness direction of the elastic layer 12 than on the core metal 11 side. The portion to which a load is particularly applied when the pressurizing roller is compressed (the portion subject to the stress of pressurization) is generally near the surface layer (particularly, the portion from the surface layer to the vicinity of 20% to 50% on the surface layer side). .. From the above, it is possible to increase the addition ratio of the silicone rubber particles 12b especially in the portion where the load is applied, which is more effective than the case where the same amount of the silicone rubber particles 12b is dispersed in the entire elastic layer 12. The compression set can be improved.

Further, the bubbles existing in the cross section obtained by cutting the porous body 12a preferably have a size (diameter dimension) in the range of 0.1 μm or more and 50 μm or less, and are 0.1 μm or more and 20 μm or less. Is more preferable, and 0.1 μm or more and 12 μm or less is further preferable. The cross section is, for example, a cross section obtained when the porous body 12a is cut in the axial direction of the pressure roller 10. By setting the size of the bubbles in an appropriate range, it is possible to reduce the bubble rupture in the porous body 12a and improve the durability of the pressure roller.

Further, the continuous foaming ratio of the porous body 12a is preferably 60% or more, more preferably 65% or more, and further preferably 70% or more. By setting the continuous foam ratio in an appropriate range, the air permeability of the porous body 12a can be improved, the influence on the pressure roller 10 when hot can be reduced, and the durability of the pressure roller 10 can be reduced. The sex can be improved. The method of calculating the continuous bubble ratio will be described later.

Further, among the bubbles existing in the cross section obtained by cutting the porous body 12a, the bubbles having a size of 5 μm or more and 10 μm or less are the most abundant when the bubbles having a size of 5 μm or more and 50 μm or less are fractionated every 5 μm. exist. As a result, the pressure stress received by the elastic layer 12 can be evenly dispersed, foam rupture in the porous body 12a can be reduced, and the durability of the pressure roller 10 can be improved. The method for measuring the number of bubbles will be described later.

Further, among the bubbles existing in the cross section obtained by cutting the porous body 12a, the ratio of the number of bubbles having a size of 10 μm or more and 20 μm or less is assumed to be 100 when the number of bubbles having a size of 5 μm or more and 10 μm or less is 100. Is preferably 45 or more, preferably 60 or more, and even more preferably 80 or more. By setting the ratio of the number of bubbles of 10 μm or more and 20 μm or less to an appropriate range, the stress of pressurization received by the pressurizing roller 10 can be more evenly dispersed, and the durability of the pressurizing roller 10 can be further enhanced. can.

The type of the silicone rubber particles 12b is not particularly limited as long as it is spherical and the number average particle size is 5 μm or less. When the diameter of the silicone rubber particles is larger than the diameter of the bubbles of the porous body, the strength of the pressure roller 10 using such an elastic layer 12 may decrease.

Further, the hardness of the silicone rubber particles 12b is preferably about the same as or slightly lower than that of the porous body 12a in order to obtain an appropriate hardness for the nip. The hardness is preferably 15 to 55 (SRIS0101, Ascar C).

The surface release layer 13 is a member for suppressing sticking of toner and smoothly separating the recording medium from the surface of the pressure roller 10 (improving the paper release property), and is a member of the elastic layer 12. It is provided on the outer peripheral surface in the paper passing area. The material constituting the surface release layer 13 is not particularly limited. For example, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), which is a material having good releasability and heat resistance. , Polytetrafluoroethylene (PTFE), or tetrafluoroethylene / hexafluoropropylene copolymer (FEP) can be preferably used.

The grip layer 14 is a member that suppresses the occurrence of slippage with the fixing belt 21. By providing the grip layer 14, slipping when the pressure roller 10 is driven can be suppressed, and the grip layer 14 can also secure a sufficient nip width with the fixing belt to improve the grip force. be able to. Thereby, good fixability can be obtained.

Further, as shown in FIG. 2, the grip layer 14 is provided at both ends of the pressure roller 10 outside the paper passing region. The material of the grip layer preferably has three characteristics: that it has a tack property to obtain a grip force, that it is an elastic body to form a nip portion, and that it has heat resistance to a fixing temperature. .. The material constituting the grip layer 14 is not particularly limited as long as it can suppress the occurrence of slippage with the fixing belt 21, and for example, a rubber material such as silicone rubber or fluororubber is preferably used. be able to.

Next, the porous body 12a constituting the elastic layer 12 will be described.

Generally, as a method for producing a porous body, a chemical foaming method in which a foaming agent is added to a porous body material to form a foamed structure, and a method of emulsifying water in a liquid silicone rubber and heating the water are used. A water foaming method is known in which a foamed structure is formed by volatilizing.

Of these, the porous body obtained by the chemical foaming method has a larger bubble size than the porous body obtained by the water foaming method. For this reason, when used as a fixing roller in an image forming apparatus, it may be difficult to apply a uniform pressure load to the toner, which may cause image unevenness and insufficient durability (hardness decrease, breakage, etc.). There is. On the other hand, in the water foaming method, fine bubbles can be uniformly formed. As a result, a uniform pressure load can be applied to the toner as compared with the case of using a porous body obtained by the chemical foaming method, and it is possible to make it easier to receive a pressure load from the outside evenly. Therefore, the durability of the roller can be improved.

The porous body 12a forming the elastic layer 12 of the present embodiment can be obtained, for example, by applying the water foaming method. Specifically, a water-foamed silicone composition is used, but the size of the bubbles existing in the cross section obtained when the finally formed porous body is cut is in the range of 0.1 μm or more and 50 μm or less. Moreover, it is preferable to stir the bubbles having a size of 5 μm or more and 50 μm or less so that the largest number of bubbles having a size of 5 μm or more and 10 μm or less are present when the bubbles have a size of 5 μm or more and 50 μm or less are fractionated every 5 μm.

More specifically, the elastic layer 12 described above can be obtained by, for example, the following method. First, a catalyst, a surfactant, and a cross-linking agent are mixed with a commercially available two-component liquid silicone rubber, and the silicone rubber particles are further dispersed. Next, a liquid silicone rubber in which silicone rubber particles are dispersed and a mixed solution in which additives, fillers, dispersants and the like are mixed with water to have a viscosity equivalent to that of the liquid silicone rubber are combined and stirred to form an emulsion composition. To prepare. At this time, alcohol may be added to water to which additives and the like are mixed, if necessary.

Liquid silicone rubber considering emulsifiable with water, it is preferable specific gravity used as the ^{1.00g / cm 3 ~1.05g / cm 3} .

Further, the addition ratio of the silicone rubber particles 12b to the liquid silicone rubber is preferably 1% by mass or more, more preferably 3% by mass or more, based on the external division with respect to the liquid silicone rubber. By setting the silicone rubber particles in the above range, good compression set can be obtained.

Further, the addition ratio of the silicone rubber particles 12b to the liquid silicone rubber can be about 10% by mass or less by external division with respect to the liquid silicone rubber, and more preferably 5% by mass or less. By setting the addition ratio of the silicone rubber particles in the above range, the liquid silicone rubber is easily emulsified and the processability is improved.

By setting the addition ratio of the silicone rubber particles 12b to an appropriate range, the compression set of the pressure roller 10 can be improved and the workability to the pressure roller 10 can be improved.

Here, the blending ratio of the liquid silicone rubber and the mixed solution differs depending on the desired porosity of the elastic layer 12. The porosity can be calculated by the following formula 1. The solid rubber in the formula 1 refers to a rubber having the same rubber material as the porous body and having no air bubbles.
Porosity (%) = (Relative density of porous material-Relative density of solid rubber) / Relative density of solid rubber x 100 ... (Equation 1)

For example, when the mixing ratio of the liquid silicone rubber and the mixed solution is 1: 1, the fine water in the emulsion in which the liquid silicone rubber and the mixed solution, which is the porous material, is mixed and becomes voids. Therefore, a porous body having a porosity of about 50% can be obtained. A homogenizer or, if necessary, a stirrer with ultrasonic treatment can be used to stir the emulsion. Further, as the stirring conditions of the emulsion, it is preferable to adjust various conditions such as the stirring means, the stirring time, and the stirring speed (for example, about 300 rpm to 1500 rpm) so that the bubble distribution satisfying the above conditions can be obtained.

Further, the method for forming the elastic layer 12 in which the silicone rubber particles 12b are more dispersed in the portion 50% on the surface layer side is not particularly limited. For example, a method of laminating two types of porous bodies, a method of using a plurality of filling nozzles, a method of unevenly distributing silicone rubber particles by centrifugation, and the like can be considered.

The method of laminating the two types of porous bodies is a method of laminating the porous body 12a containing the silicone rubber particles 12b and the porous body 12a not containing the silicone rubber particles 12b. In the method using a plurality of filling nozzles, for example, an emulsion composition containing the silicone rubber particles 12b and an emulsion composition not containing the silicone rubber particles 12b are injected into the mold of the elastic layer 12 using different filling nozzles and made porous. This is a method of forming a body 12a. The method of unevenly distributing the silicone rubber particles by centrifugation is a method of utilizing the difference in specific gravity between the silicone rubber particles 12b and the emulsion composition. Specifically, it is a method in which the silicone rubber particles are unevenly distributed on the surface layer side by injecting a porous material containing the silicone rubber particles 12b into the mold of the elastic layer 12 and then subjecting the porous material to centrifugation. By injecting the emulsion composition into the mold of the elastic layer 12 and then heating it, the silicone rubber is cured without evaporating the water content in the emulsion composition (primary heating).

The filling amount of the emulsion composition containing the silicone rubber particles can be, for example, in the range of 95 to 100% of the mold volume. Further, the primary heating can be performed in the range of, for example, 80 ° C. to 130 ° C., and the heating time can be about 30 minutes to 120 minutes. More preferable conditions are a filling rate of 98% to 100%, a heating temperature of 90 ° C. to 110 ° C., and a heating time of 60 minutes to 90 minutes.

Next, secondary heating is performed to remove water from the porous body after the primary heating. For example, the heating temperature can be 150 ° C. to 300 ° C., and the heating time can be 1 hour to 24 hours. More preferable conditions are a heating temperature of 200 ° C. to 250 ° C. and a heating time of 3 hours to 5 hours. By performing such secondary heating, water is removed from the porous body to form composite bubbles, and the final curing of the silicone rubber is completed.

Next, an example of a method of forming the pressure roller 10 using the elastic layer 12 will be described.

An adhesive such as a one-component thermosetting type is uniformly applied onto the molded elastic layer 12, and a tube made of PFA is further coated to form a surface release layer 13.

The grip layer 14 is formed outside the paper-passing region outside the surface release layer 13 from a portion about 1 mm to 15 mm outside the surface release layer 13 to the end of the elastic layer 12. Further, as a method of molding the grip layer 14, a method of coating the composition forming the grip layer 14 by a method such as spray coating, dip coating, roll coating, or the like and then drying it can be mentioned.

Further, the core metal 11 is inserted through the inner circumference of the elastic layer 12. From the above, the pressure roller 10 can be formed.

Next, a method for measuring the number of bubbles in the porous body (frequency for each bubble diameter dimension), the continuous bubble ratio, and the compression set will be described.

The method for measuring the number of bubbles in the porous body of the present embodiment is as follows. First, an image is taken of the porous body portion of the cross section of the pressure roller 10 with a laser microscope (LSM), an electron microscope (SEM), or the like. Next, for example, the image is binarized so that the porous body portion is white and the bubble portion is black. After extracting the bubble portion by the binarization treatment, the extracted bubbles are screened into each bubble diameter by using the opening treatment, which is one of the image processing methods, with the diameter dimension of each bubble as a component. By taking the difference between the results before and after each opening process, the number of pixels of the sifted component (bubble diameter) can be obtained. Further, in the above processing, it is preferable to determine the number of pixels from the porosity and the image magnification.

Further, by dividing the number of pixels of each screened component (bubble diameter) by the number of pixels of the component, the number of bubbles included in each diameter dimension range (the number of bubbles existing in each fractionated fraction). ), And the distribution of bubbles (frequency of bubbles for each bubble diameter) can be obtained. The number of bubbles in this embodiment can be calculated from the probability distribution obtained by the above method.

Next, a method of calculating the continuous bubble ratio will be described. This method is the method described in JP-A-2002-12696. First, the mass of the porous body cut out from the elastic layer 12 is measured. Next, after immersing the cut out porous body in methanol for 24 hours, water droplets on the surface of the porous body are lightly removed, and the mass is measured again. If it floats during immersion, the entire porous sample may be immersed by covering the upper surface of methanol with a metal mesh or the like. The mass ratio (mass increase ratio) of methanol immersed in the cut out porous body is defined as the continuous foaming ratio. That is, the continuous foam ratio can be calculated by the following formula 2.
Foam rate (%) = (mass after immersion-mass before immersion) / mass before immersion x 100 ... (Equation 2)

Next, a method for measuring the compression set will be described. The outer diameter of the pressure roller 10 is measured, the pressure roller 10 is sandwiched between two metal plates, and the pressure roller 10 is pushed in the radial direction to fix the pressure roller 10 so that the diameter is 30% of that before pushing. In that state, the pressure roller 10 is heated at 180 ° C. for 5 hours, and immediately after taking it out, the metal plate is removed to release the push, and 6 hours after the opening, the outer diameter of the pressure roller 10 is adjusted again. taking measurement. The restoration rate is calculated from the outer diameter dimensions before and after heating, and is used as the compression set. That is, the compression set can be calculated by the following equation 3.
Restoration rate (%) = (outer diameter before heating-outer diameter after heating) / (outer diameter before heating-outer diameter after pushing) x 100 ... (Equation 3)

According to the pressure roller 10 of the present embodiment, the core metal 11 and the elastic layer 12 formed on the outer peripheral surface of the core metal 11 are provided, and the elastic layer 12 is a porous body 12a having composite bubbles. , Silicone rubber particles 12b dispersed in the porous body 12a. As a result, high durability can be obtained by suppressing the rupture of air bubbles in the elastic layer 12 and further reducing the stress during hot weather due to the good air permeability. Further, the silicone rubber particles 12b dispersed in the porous body can impart cushioning property to the elastic layer 12 to improve the compressive strain property. This makes it possible to obtain a pressure roller 10 having high durability and good compression set.

[Fixing device]
Next, the "fixing device" according to the embodiment of the present invention will be described with reference to FIGS. 4 and 5. The fixing device 100 according to the present embodiment includes the pressure roller 10 described above, and is used in an image forming device using an electrophotographic method. Further, the fixing device 100 is used, for example, in the image forming device 500 described later.

As shown in FIG. 4, the fixing device 100 includes the above-mentioned pressure roller 10, a fixing belt 21, a heat conductive member 22, a halogen heater 23, a thermistor 24, a nip forming member 25, and a heat radiating member 26. , A lubricating sheet 27, a heat insulating material 28, and a holding member 29.

The pressure roller 10 is a pressure member that comes into contact with the fixing belt 21 to form a fixing nip N. As a result, the fixing nip N is formed at a position where the pressure roller 10 and the fixing belt 21 face each other.

The fixing belt 21 is made of a thin, flexible, endless belt-shaped member, and is rotatably provided.

The heat conductive member 22 is provided in the fixing belt 21. The heat conductive member 22 is a metal circular pipe-shaped member, and has an outer dimension smaller than the inner diameter of the fixing belt 21 (for example, about 1 mm smaller). As the material of the heat conductive member 22, a metal such as aluminum, iron, or stainless steel can be preferably used.

Further, the heat conductive member 22 is formed with a recess 22a at a position facing the fixing nip N. Further, in the recess 22a, the nip forming member 25, the mesh-shaped lubricating sheet 27 arranged between the fixing belt 21 and the nip forming member 25, and the bottom of the recess 22a and the nip forming member 25 are arranged. The heat insulating material 28 and the heat insulating material 28 are arranged. Further, inside the heat conductive member 22, a substantially T-shaped holding member 30 for supporting the nip forming member 25, the lubricating sheet 27, and the heat insulating material 28 is provided.

The halogen heater 23 is provided as a heat source for raising the temperature of the heat conductive member 22. As the heat source for raising the temperature of the heat conductive member 22, the halogen heater 23 may be used, but an IH (induction heating) method may be used, or a resistance heating element, a carbon heater, or the like may be used as the heat source.

The thermistor 24 is a temperature sensor provided in contact with the fixing belt 21 and detecting the surface temperature of the fixing belt 21.

The nip forming member 25 is made of an elastic body such as silicone rubber or fluororubber. Further, the nip forming member 25 is adapted to indirectly slide with respect to the inner surface of the fixing belt 21 via the lubricating sheet 27. The nip forming member 25 may be configured to slide directly on the inner surface of the fixing belt 21.

The heat radiating member 26 has an arcuate shape in cross-sectional view, and is provided so as to face a part of the outer peripheral surface of the fixing belt 21 as shown in FIG.

Next, the fixing belt 21 will be described with reference to FIG. FIG. 5 is a diagram schematically showing a cross section of the fixing belt 21 shown in FIG. 4 along the arrow BB.

The fixing belt 21 is a laminated body in which an elastic layer 21b and a release layer 21c are laminated in this order on a base material layer 21a, and the release layer 21c is a surface layer. The fixing belt 21 can have, for example, a thickness of 1 mm or less and a diameter of about 15 mm to 120 mm, and in the present embodiment, it is set to about 30 mm.

The base material layer 21a of the fixing belt 21 has a layer thickness of 30 μm to 50 μm, and is formed by using a metal material such as nickel or SUS or a resin material such as polyimide (PI).

The elastic layer 21b of the fixing belt 21 is formed for the purpose of giving flexibility to the surface of the fixing belt 21 in order to obtain a uniform image without uneven gloss. The thickness of the elastic layer 21b is preferably about 100 μm to 300 μm. Further, in consideration of heat resistance at the fixing temperature, silicone rubber, foamed silicone rubber, fluorosilicone rubber and the like can be preferably used as the material constituting the elastic layer 21b.

The materials constituting the release layer 21c of the fixing belt 21 are fluorinated ethylene resin (PTFE), tetrafluorinated ethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), and tetrafluorinated ethylene / six. Fluororesin such as fluorinated propylene copolymer (FEP), a mixture of these resins, or a heat-resistant resin in which these fluororesins are dispersed can be used.

According to the fixing device 100 of the present embodiment, the pressure roller 10 includes a core metal 11 and an elastic layer 12 formed on the outer peripheral surface of the core metal 11, and the elastic layer 12 has composite bubbles. It is composed of a porous body 12a and silicone rubber particles 12b dispersed in the porous body 12a. As a result, even when the fixing device 100 is used for a long period of time, the pressure roller 10 can maintain high durability and good compression set.

[Image forming device]
An "image forming apparatus" according to an embodiment of the present invention will be described with reference to FIG. The image forming apparatus 500 of the present embodiment utilizes an electrophotographic method and includes the fixing apparatus 100 described above.

FIG. 6 is a schematic configuration diagram showing an example of the entire image forming apparatus including the fixing roller according to the embodiment of the present invention. In the present embodiment, the image forming apparatus 500 includes an image forming unit for a tandem type color printer, but the image forming apparatus of the present invention may be a rotary type color printer or a monochrome printer. Further, the image forming apparatus is not limited to a printer, and various image forming apparatus such as a printer using an electrophotographic method, a copying machine, a facsimile, or a multifunction device thereof can be used.

Four toner bottles 102Y, 102M, 102C, and 102K corresponding to each color (yellow, magenta, cyan, and black) are detachably (replaceable) in the bottle accommodating portion 101 installed above the main body of the image forming apparatus 500. is set up. An intermediate transfer unit 85 is arranged below the bottle accommodating portion 101. Image-forming units 4Y, 4M, 4C, and 4K corresponding to each color (yellow, magenta, cyan, and black) are arranged side by side so as to face the intermediate transfer belt 78 installed in the intermediate transfer unit 85. Photoreceptor drums 5Y, 5M, 5C, and 5K are arranged in each image forming unit 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photoconductor drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing device 76, a cleaning unit 77, a static elimination unit, and the like are arranged, respectively. Then, each of the photoconductor drums 5Y, 5M, 5C, and 5K is rotated, and the following image forming process is performed on each of the photoconductor drums 5Y, 5M, 5C, and 5K, and each photoconductor drum 5Y, 5M is performed. Images of each color are formed on 5C and 5K. Here, the image forming process refers to a charging process, an exposure process, a developing process, a transfer process, and a cleaning process.

The image forming process for the photoconductor drums 5Y, 5M, 5C, and 5K will be described below. The photoconductor drums 5Y, 5M, 5C, and 5K are rotationally driven clockwise in FIG. 6 by a drive motor. Then, in the charging unit 75 (only those corresponding to the photoconductor drum 5K are shown in FIG. 6), the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K are uniformly charged (charging step). After being charged, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K are irradiated and exposed by the laser beam emitted from the exposed unit 40, and an electrostatic latent image corresponding to each color is formed (exposure step). The photoconductor drums 5Y, 5M, 5C, and 5K on which the latent image was formed have an electrostatic latent image formed by the developing device 76 (in FIG. 6, only those corresponding to the photoconductor drum 5K are coded). Toner development is performed to form a toner image of each color (development process).

Further, the toner image on the photoconductor drums 5Y, 5M, 5C, and 5K is transferred onto the intermediate transfer belt 78 by the intermediate transfer belt 78 and the primary transfer bias rollers 79Y, 79M, 79C, 79K (primary transfer). Process). By superimposing the toner image on the intermediate transfer belt 78 in this way and transferring the toner image, a color image is formed on the intermediate transfer belt 78.

After the transfer, the photoconductor drums 5Y, 5M, 5C, and 5K reach the cleaning unit 77, and the untransferred toner remaining on the surface of the photoconductor drums 5Y, 5M, 5C, and 5K is removed by the cleaning blade of the cleaning unit 77. It is collected mechanically (cleaning process). In FIG. 6, only those corresponding to the photoconductor drum 5K are designated by reference numerals. After that, the residual potential on the surface of the photoconductor drums 5Y, 5M, 5C, and 5K is removed by the static elimination unit. In this way, a series of image forming processes for the photoconductor drums 5Y, 5M, 5C, and 5K are completed.

Next, a series of transfer processes performed on the intermediate transfer belt 78 will be described.

The intermediate transfer unit 85 includes an endless intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, and a tension roller 84. It is composed of an intermediate transfer cleaning unit 80 and the like.

The intermediate transfer belt 78 is stretched and supported by the secondary transfer backup roller 82, the cleaning backup roller 83, and the tension roller 84, and is moved in the direction of the arrow in FIG. 6 by the rotational drive of the secondary transfer backup roller 82. The primary transfer bias rollers 79Y, 79M, 79C, and 79K form a primary transfer nip by sandwiching the intermediate transfer belt 78 between the photoconductor drums 5Y, 5M, 5C, and 5K, respectively. A transfer bias opposite to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. The intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nip between the intermediate transfer belt 78 and the photoconductor drums 5Y, 5M, 5C, and 5K. In this way, the toner images of each color on the photoconductor drums 5Y, 5M, 5C, and 5K are superimposed on the intermediate transfer belt 78, and the primary transfer is performed.

After the primary transfer, the intermediate transfer belt 78 reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 forms the secondary transfer nip so as to sandwich the intermediate transfer belt 78 with the secondary transfer roller 89. In the secondary transfer nip, the four-color toner images formed on the intermediate transfer belt 78 are transferred onto the conveyed recording medium P. After the transfer, the intermediate transfer belt 78 reaches the intermediate transfer cleaning unit 80, and the untransferred toner on the intermediate transfer belt 78 is collected. In this way, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

Here, the recording medium P conveyed to the position of the secondary transfer nip is conveyed from the paper feeding unit 50 arranged below the main body of the image forming apparatus 500 via the paper feeding roller 97 and the resist roller 98. It is a thing. That is, a plurality of recording media P such as transfer paper are stacked and stored in the paper feed unit 50. Then, when the paper feed roller 97 is rotationally driven in the counterclockwise direction in FIG. 6, the paper feed roller 97 is fed to the resist roller 98 in order from the highest recording medium P. The recording medium P conveyed to the resist roller 98 temporarily stops at the position of the roller nip of the resist roller 98 whose rotational drive has stopped. Then, the resist roller 98 is rotationally driven in time with the toner image on the intermediate transfer belt 78, so that the recording medium P is conveyed toward the secondary transfer nip. In this way, the toner image is transferred onto the recording medium P.

The recording medium P on which the color image is transferred by the secondary transfer nip is conveyed to the fixing device 100. Then, the recording medium P is heated and pressurized by the fixing belt 21 and the pressure roller 10 in the fixing device 100, and the toner image transferred to the surface is fixed on the recording medium P. After that, the recording medium P is discharged to the outside of the main body of the image forming apparatus 500 via the paper ejection roller 99, and is sequentially stacked on the stack portion 60.

As described above, the image formation on the recording medium P by the image forming apparatus 500 is completed.

Further, according to the image forming apparatus 500 of the present embodiment, the pressure roller 10 used in the fixing apparatus 20 includes a core metal 11 and an elastic layer 12 formed on the outer peripheral surface of the core metal 11. There is. Further, the elastic layer 12 is configured to have a porous body 12a having composite bubbles and silicone rubber particles 12b dispersed in the porous body 12a. As a result, even when the image forming apparatus is used for a long period of time, the pressure roller 10 can maintain high durability and good compression set.

In addition, the best configuration, method, and the like for carrying out the present invention are disclosed in the above description, but the present invention is not limited thereto. That is, although the present invention is particularly illustrated and described primarily with respect to a particular embodiment, it does not deviate from the scope of the technical idea and purpose of the present invention and has a shape relative to the embodiments described above. , Materials, quantities, and other detailed configurations can be modified by those skilled in the art.

Therefore, the description that limits the shape, material, etc. disclosed above is merely an example for facilitating the understanding of the present invention, and does not limit the present invention. Therefore, those shapes, materials, etc. The description by the name of the member which removes a part or all of the limitation such as is included in the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

(Example 1)
[Manufacturing of pressure roller]
First, a pressure roller was produced. As the core metal, an STKM material having a diameter dimension of φ24 mm, a wall thickness of 2 mm, and an axial length of 420 mm was used. Further, an elastic layer was formed on the outer circumference of the core metal with a wall thickness of 4 mm and an axial length of 330 mm. As the elastic layer, a water-foamed silicone manufactured by Toray Dow Corning having a hardness of 32 Hs (Asker C) and a specific gravity of 0.52 g / cm ^{3 was used as the porous body.} Further, in the elastic layer, silicone rubber particles were dispersed in an external division in an amount of 5% by mass with respect to the liquid silicone rubber used for the elastic layer. The average particle size of the number of silicone rubber particles was 2 μm, and the hardness was 30 Hs (Asker C).

Further, the elastic layer was produced by a casting method using two filling nozzles so that the silicone rubber particles were unevenly distributed on the surface layer side 50% in the thickness direction of the elastic layer more than on the core metal side. That is, a water-foamed emulsion containing 10% of silicone rubber particles is injected into the mold from the filling nozzle corresponding to the surface layer side, and water containing no silicone rubber particles is injected from the filling nozzle corresponding to the core metal side. The foamed emulsion was injected into the mold. As a result, an elastic layer in which 90% of the silicone rubber particles dispersed in the elastic layer was dispersed in a portion of 50% on the surface layer side was obtained. The ratio of the silicone rubber particles dispersed in the 50% portion on the surface layer side is referred to as "surface layer particle addition rate".

Further, in the paper-passing region, a PFA tube having a thickness of 30 μm is coated as a surface release layer, and Shin-Etsu Chemical is used as a material on the outer peripheral surface of the elastic layer outside the paper-passing region where both ends of the pressure roller are exposed. A grip layer was uniformly formed with a film thickness of 50 μm using a two-component liquid silicone rubber manufactured by Shin-Etsu Chemical Co., Ltd. From the above, the pressure roller of Example 1 was obtained.

[Confirmation of bubble shape, continuous bubble ratio, center value of bubble size, frequency for each bubble diameter dimension in elastic layer]
Next, the bubble shape, the rate of continuous bubbles, the center value of the size of the bubbles, and the frequency for each bubble diameter dimension in the elastic layer were confirmed.

The bubble shape in the elastic layer was confirmed by cutting the elastic layer and observing the obtained cut surface with a microscope. When the cut surface of the elastic layer was observed with a microscope, bubbles in which spherical shapes partially overlapped with each other were defined as "composite bubbles". Further, a shape other than the above (for example, a bubble that is communicated but the spheres of the bubbles do not overlap each other, or a bubble that has an independent sphere shape) is defined as "not a composite bubble". In this example, the bubbles in the elastic layer were composite bubbles.

Next, the continuous foam ratio was calculated. First, the mass of the porous body cut out from the elastic layer was measured. Next, after immersing the cut out porous body in methanol for 24 hours, water droplets on the surface of the porous body were lightly removed, and the mass was measured again. The mass ratio of methanol immersed in the cut out porous body was defined as the continuous foam ratio, and the continuous foam ratio (%) was calculated by the following formula 2.
Foam rate (%) = (mass after immersion-mass before immersion) / mass before immersion x 100 ... (Equation 2)
In this example, the foaming ratio of the elastic layer was 75%.

Next, the center value of the size (diameter dimension) of the bubble was calculated. In this example, the median value of the size of the bubbles in the elastic layer was 8 μm. The center value of the bubble size was the peak value of the distribution obtained in the confirmation of the frequency for each bubble diameter, which will be described later.

The frequency for each bubble diameter dimension was confirmed as follows. First, an image of the cross section of the pressure roller was taken, and the image was binarized. After extracting the bubble portion by the binarization treatment, the extracted bubbles were screened into each bubble diameter by using the opening treatment, which is one of the image processing methods, with the diameter dimension of each bubble as a component. By taking the difference between the results before and after each opening process, the number of pixels of the sifted component (bubble diameter) was obtained. Further, in the above processing, the number of pixels was determined from the porosity and the image magnification. By dividing this number of pixels by the number of pixels of the component (diameter dimension of each bubble), the number of bubbles included in each diameter dimension range (the number of bubbles existing in each fractionated fraction) can be found. The distribution of bubbles (frequency of bubbles for each bubble diameter) was determined. As a result, it was confirmed that the elastic body of Example 1 had a bubble frequency as shown by the solid line in the graph of FIG. 7.

The bubbles present in the cross section obtained by cutting the porous body had a size in the range of 0.1 μm or more and 50 μm or less. Further, when the bubbles having a size of 5 μm or more and 50 μm or less were fractionated every 5 μm, the most abundant bubbles were bubbles of 5 μm or more and 10 μm or less. Further, when the number of bubbles having a size of 5 μm or more and 10 μm or less was set to 100, the number ratio of bubbles having a size of 10 μm or more and 20 μm or less was 60.

(Example 2)
A pressure roller was produced by the same procedure as in Example 1 except that the dispersion amount of the silicone rubber particles was 1% by mass. In this example, the elastic layer had composite bubbles, the continuous bubble ratio was 75%, and the median size of the bubbles in the elastic layer was 8 μm. The bubble frequency shows the same distribution as in Example 1, and the bubble range, which is the most abundant when the bubbles having a size of 5 μm or more and 50 μm or less are fractionated every 5 μm, have a size of 5 μm or more and 10 μm or less. When the number of bubbles was 100, the ratio of the number of bubbles having a size of 10 μm or more and 20 μm or less was the same as in Example 1.

(Example 3)
A pressure roller was produced by the same procedure as in Example 1 except that the dispersion amount of the silicone rubber particles was 10% by mass. In this example, the elastic layer had composite bubbles, the continuous bubble ratio was 75%, and the median size of the bubbles in the elastic layer was 8 μm. The bubble frequency shows the same distribution as in Example 1, and the bubble range, which is the most abundant when the bubbles having a size of 5 μm or more and 50 μm or less are fractionated every 5 μm, have a size of 5 μm or more and 10 μm or less. When the number of bubbles was 100, the ratio of the number of bubbles having a size of 10 μm or more and 20 μm or less was the same as in Example 1.

(Example 4)
A pressure roller was produced by the same procedure as in Example 1 except that the dispersion amount of the silicone rubber particles was 5% by mass and the silicone rubber particles were dispersed in the entire elastic layer. In Example 4, an elastic layer in which 90% of the silicone rubber particles dispersed in the elastic layer was dispersed in a portion of 50% on the surface layer side was obtained. Further, in this example, the elastic layer had composite bubbles, the continuous bubble ratio was 75%, and the median size of the bubbles in the elastic layer was 8 μm. The bubble frequency shows the same distribution as in Example 1, and the bubble range, which is the most abundant when the bubbles having a size of 5 μm or more and 50 μm or less are fractionated every 5 μm, have a size of 5 μm or more and 10 μm or less. When the number of bubbles was 100, the ratio of the number of bubbles having a size of 10 μm or more and 20 μm or less was the same as in Example 1.

(Comparative Example 1)
A pressure roller was produced by the same procedure as in Example 1 except that an elastic layer was formed without adding silicone rubber particles. In this comparative example, the elastic layer had composite bubbles, the continuous bubble ratio was 75%, and the median size of the bubbles in the elastic layer was 8 μm. The bubble frequency shows the same distribution as in Example 1, and the bubble range, which is the most abundant when the bubbles having a size of 5 μm or more and 50 μm or less are fractionated every 5 μm, have a size of 5 μm or more and 10 μm or less. When the number of bubbles was 100, the ratio of the number of bubbles having a size of 10 μm or more and 20 μm or less was the same as in Example 1.

(Comparative Example 2)
A pressure roller was produced by the same procedure as in Example 1 except that a porous body having bubbles having a continuous foam ratio of 35% but not adjacent to each other was used for the elastic layer. In this comparative example, the elastic layer did not have composite bubbles, the continuous bubble ratio was 35%, and the median size of the bubbles in the elastic layer was 13 μm.

Further, when the bubble frequency was confirmed, it was confirmed that the elastic body of Comparative Example 2 had a bubble frequency as shown by the alternate long and short dash line in the graph of FIG. 7. The bubbles present in the cross section obtained by cutting the porous body had a size in the range of 0.1 μm or more and 50 μm or less. Further, when the bubbles having a size of 5 μm or more and 50 μm or less were fractionated every 5 μm, the most abundant bubbles were bubbles of 10 μm or more and 15 μm or less. Further, when the number of bubbles having a size of 5 μm or more and 10 μm or less was set to 100, the number ratio of bubbles having a size of 10 μm or more and 20 μm or less was 150.

(Comparative Example 3)
Same as Example 1 except that the elastic layer is formed by using a porous body having bubbles having a foaming ratio of 35% but not adjacent to the elastic layer without adding silicone rubber particles. A pressure roller was produced according to the procedure. In this comparative example, the elastic layer did not have composite bubbles, the continuous bubble ratio was 35%, and the median size of the bubbles in the elastic layer was 13 μm. The bubble frequency shows the same distribution as in Comparative Example 1, and the bubble range, which is the most abundant when the bubbles having a size of 5 μm or more and 50 μm or less are fractionated every 5 μm, have a size of 5 μm or more and 10 μm or less. When the number of bubbles was 100, the ratio of the number of bubbles having a size of 10 μm or more and 20 μm or less was the same as that of Comparative Example 2.

(Comparative Example 4)
A pressure roller was produced by the same procedure as in Example 1 except that chemically foamed silicone was used for the elastic layer. In this comparative example, the elastic layer did not have composite bubbles, the continuous bubble ratio was 20%, and the median size of the bubbles in the elastic layer was 100 μm.

Further, when the bubble frequency was confirmed, it was confirmed that the elastic body of Comparative Example 4 had a bubble frequency as shown by the broken line in the graph of FIG. The bubbles present in the cross section obtained by cutting the porous body had a size in the range of 0.1 μm or more and 50 μm or less. Further, when the bubbles having a size of 5 μm or more and 50 μm or less were fractionated every 5 μm, the most abundant bubbles were bubbles of 30 μm or more and 35 μm or less. Further, when the number of bubbles having a size of 5 μm or more and 10 μm or less was set to 100, the number ratio of bubbles having a size of 10 μm or more and 20 μm or less was 10.

[Performance evaluation of pressure roller]
Next, the performance of the pressure rollers produced in Examples and Comparative Examples was evaluated. Performance evaluation was performed using three indexes: workability, durability, and compression set.

The processability is evaluated in three stages. In the formation of the elastic layer, those that are easy to emulsify and disperse and are stable over time are marked with "○", and emulsification and dispersion take time or special dispersion is required. , Those that are unstable with time are marked with "Δ", and those that cannot be emulsified / dispersed are marked with “x”.

For durability, the produced pressure roller is used in an image forming apparatus to measure the hardness (shore hardness) before use, after pushing in 30%, heating at 180 ° C, and using for 300 hours under the condition of linear velocity of 250 mm / sec. Then, it was evaluated by observing the change in hardness and the presence or absence of damage to the pressure roller. When the change in hardness was 3 Hs or less and there was no damage to the pressure roller, it was evaluated as "◯", and in other cases, it was evaluated as "x".

The compression set was calculated by the following method. First, the outer diameter of the pressure roller was measured, and the pressure roller was sandwiched between two metal plates and pushed in the radial direction to fix the pressure roller so that the diameter was 30% of that before pushing. In this state, the pressure roller is heated at 180 ° C. for 5 hours, the metal plate is immediately removed after taking it out to release the push, and the outer diameter of the pressure roller 10 is measured again 6 hours after opening. bottom. The restoration rate was calculated from the outer diameter dimensions before and after heating and used as the compression set, which was calculated by the following formula 3.
Restoration rate (%) = (outer diameter before heating-outer diameter after heating) / (outer diameter before heating-outer diameter after pushing) x 100 ... (Equation 3)

Further, after heating the pressure roller under the above conditions, it was used in an image forming apparatus to confirm whether or not an abnormality such as image unevenness occurred in the formed image.

The evaluation is performed in 4 stages, and when the restoration rate is 7.0% or less and no abnormality occurs in the formed image in the compression set, the restoration rate is 7.1% or more. When 9.0% and no abnormality has occurred in the formed image, it is marked with "○", and the restoration rate is 9.1% to 15.0%, and the formed image has an abnormality. The case where there was no such thing was given as "Δ", and the case where the restoration rate was 15.1% or more or an abnormality occurred in the formed image was given as "x".

In addition, as a comprehensive evaluation, evaluation was performed on a four-point scale. If there are evaluation items of ◎ and there are no evaluation items below △, the overall evaluation is “◎”, if all the evaluation items are evaluated as “○”, the overall evaluation is “○”, and the evaluation items of “△” are Some items were given a comprehensive evaluation of "△", and those with evaluation items of "x" were given a comprehensive evaluation of "x".

Table 1 shows the properties of the elastic layer and the results of the above performance evaluation.

[Evaluation results]
Regarding workability, the pressure rollers of Examples 1, 2 and 4 and Comparative Examples 1 to 4 had good workability. Therefore, the pressure rollers of Examples 1, 2 and 4 and Comparative Examples 1 to 4 were judged as "◯". Further, the pressure roller of Example 3 had a slightly low processability because the addition ratio of the silicone rubber particles was high. Therefore, the pressure roller of Example 3 was judged as "Δ".

Regarding the durability, the pressure rollers of Examples 1 to 4 and Comparative Example 1 had a small change in hardness, and the pressure rollers were not damaged. Therefore, the pressure rollers of Examples 1 to 4 and Comparative Example 1 were judged as "◯". Further, the pressure rollers of Examples 2 to 4 had no damage to the pressure rollers, but the hardness change was larger than that of Examples 1 to 4. Therefore, the pressure rollers of Comparative Examples 2 to 4 were judged as "x", indicating that the durability was poor.

In Comparative Examples 2 and 3, when a porous body having a low continuous foam ratio was used for the elastic layer instead of the composite bubbles, the air permeability was low, the internal expansion during hot heat was large, the stress was large, and the bubbles were also broken. It was considered that the durability was low because it was easy to proceed and led to changes in hardness and breakage. Further, in Comparative Example 4, since the size of the bubbles was larger, it was considered that the bubble rupture was more likely to proceed, the hardness change was large, and the durability was low.

The pressure rollers of Examples 1 to 4 and Comparative Example 1 had good durability.

Regarding the compression set, the pressure rollers of Examples 1 and 3 had a low restoration rate in the compression set test, and no image abnormality occurred in the image formation after the compression set test. Therefore, the pressure rollers of Examples 1 and 3 were judged as "⊚". Further, the pressure rollers of Examples 2 and 4 and Comparative Example 4 had a higher restoration rate in the compression set in the compression set, but the restoration after the test was good. Therefore, the pressure rollers of Examples 2, 4 and Comparative Example 4 were judged as "⊚". In addition, no image abnormality occurred in the image formation after the compression set.

The pressure roller of Comparative Example 1 had a higher restoration rate in the compression set than that of the pressure roller of Example, and no image abnormality occurred in the image formation after the compression set. .. Therefore, the pressure roller of Comparative Example 1 was judged as "Δ". This is because the pressure roller of Comparative Example 1 has a high foaming ratio and good air permeability as compared with the pressure rollers of Comparative Examples 2 to 4, and therefore has higher durability than Comparative Examples 2 to 4. It was thought to be. It should be noted that the pressure roller of Comparative Example 1 is considered to have sufficient durability under conditions such as a monochrome image forming apparatus in which a threshold value for a glossy image is set widely or the usage environment is not strict. rice field. The pressure rollers of Comparative Examples 2 and 3 had a considerably high restoration rate in the compression set. In addition, no image abnormality occurred in the image formation after the compression set. Therefore, the pressure rollers of Examples 1 and 3 were judged as "x".

In terms of compression set, all of Examples 1 to 4 showed good results. Further, comparing Examples 1 to 3 and Comparative Example 1, since the restoration rate was lower in Examples 1 to 3 to which the silicone rubber particles were added, the silicone rubber particles were dispersed in the elastic layer. , It was shown that the compression set property is improved.

Further, in the pressure rollers of Examples 1 and 3 in which the silicone rubber particles were more dispersed within 50% on the surface layer side of the pressure roller, better compressive permanent strainability was exhibited. Further, when the addition ratios of the silicone rubber particles were compared, it was shown that as the addition ratio increased, the restoration rate decreased in the order of Example 2, Example 1, and Example 3. As a result, it was shown that in the range of 1 to 10% of the addition ratio of the silicone rubber particles, the higher the addition ratio, the better the compression set.

Further, when Example 1 and Comparative Example 2 and Comparative Example 1 and Comparative Example 3 were compared, Comparative Examples 2 and 3 having a low repetitive foam ratio had a considerably higher restoration rate and poor compression set. When the rate of continuous foaming is low as in Comparative Examples 2 and 3, that is, when the air permeability of the elastic layer is poor, the internal expansion during hot weather is large, the stress on the elastic layer is large, and foam rupture progresses. It was thought that it would be easier and the durability (change in hardness) and compression set would be worse.

Further, in Comparative Example 4, since the chemically foamed silicone was used, it was considered that the compressive permanent strain property was good due to the large molecular weight and the crosslink density of the porous body.

Regarding the comprehensive evaluation, it was judged that the pressure roller of Example 1, which showed good results in all of workability, durability, and compression set, was the best.

[Discussion of evaluation results]
As shown in [Evaluation Results], in the pressure rollers of Examples 1 to 4 which are exemplary embodiments of the present invention, it is possible to provide a fixing roller having high durability and good compression set. It has been shown. Further, it has been shown that in the fixing device and the image forming device using such a fixing roller, high durability and good compression permanent strain property can be obtained in the fixing roller.

10 Pressurizing roller (fixing roller)
100 Fixing device 500 Image forming device 11 Core metal 12 Elastic layer 13 Surface release layer (release layer)
14 Grip layer 12a Porous body 12b Silicone rubber particles 12c Composite bubbles

Claims (9)

A core metal and an elastic layer provided on the outer peripheral surface of the core metal are provided.
The elastic layer has a continuous foam ratio of 60% or more, and when the cut surface of the elastic layer is observed with a microscope, the elastic layer has a porous body having composite bubbles, which are bubbles in which spherical shapes partially overlap each other. , With silicone rubber particles dispersed in the porous body .
A fixing roller characterized in that the silicone rubber particles are dispersed more on the surface layer side in the thickness direction of the elastic layer than on the core metal side. A claim characterized in that the bubbles existing in the cross section obtained by cutting the porous body have a size in the range of 0.1 μm or more and 50 μm or less, and the continuous bubble ratio is 60% or more. Item 1. The fixing roller according to item 1. Bubbles existing in the cross section obtained by cutting the porous body have a size in the range of 0.1 μm or more and 50 μm or less, and bubbles having a size of 5 μm or more and 50 μm or less are fractionated every 5 μm. The fixing roller according to claim 1 or 2 , wherein the most bubbles having a size of 5 μm or more and 10 μm or less are present when the bubbles are formed. Among the bubbles existing in the cross section obtained by cutting the porous body, when the number of bubbles having a size of 5 μm or more and 10 μm or less is 100, the number ratio of the bubbles having a size of 10 μm or more and 20 μm or less is , The fixing roller according to any one of claims 1 to 3 , wherein the number is 50 or more. The fixing roller according to any one of claims 1 to 4 , wherein the porous body is made of water-foamed silicone rubber. The outermost layer is further provided with a release layer,
Claims 1 to 5 are characterized in that the release layer is composed of a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, polytetrafluoroethylene, or a tetrafluoroethylene / hexafluoropropylene copolymer. The fixing roller according to any one of the above items. The fixing roller according to any one of claims 1 to 6 , further comprising a grip layer made of an elastic body in a portion outside the paper passing region at both ends of the roller. A fixing device comprising the fixing roller according to any one of claims 1 to 7. An image forming apparatus comprising the fixing apparatus according to claim 8.

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