Patent Application
20190278202
The present invention relates to an electrophotographic rotatable pressing member to be used in a fixing device configured to nip, convey, and heat a recording material, and a method of manufacturing the electrophotographic rotatable pressing member. The present invention also relates to a fixing device.
In an electrophotographic image forming apparatus, a heat fixing device is used as a device configured to fix an unfixed toner image formed on a recording material onto the recording material. The heat fixing device includes a heating member and an electrophotographic rotatable pressing member arranged so as to be opposed to the heating member. The heat fixing device is configured to convey the recording material by rotation of the heating member and the electrophotographic rotatable pressing member while fixing a toner onto the recording material with heat from the heating member and a pressure caused by pressure contact between the heating member and the electrophotographic rotatable pressing member.
The electrophotographic rotatable pressing member includes a substrate and an elastic layer. The substrate gives stiffness sufficient for withstanding the pressure contact with the heating member. The elastic layer gives elasticity required for forming a nip portion. Further, a surface layer made of a fluorine resin for giving toner releasability may be formed on the elastic layer.
In International Publication No. WO2016/009527, there is described an invention which has an object to provide a pressurizing member capable of achieving, at a high level, both reduction in warm-up time and suppression of generation of creases extending in a circumferential direction. In this case, the warm-up time refers to a time period for raising the temperature of a nip portion to a temperature required for fixing a toner in order to reduce power consumption in a fixing device.
In International Publication No. WO2016/009527, there is described that the above-mentioned object can be achieved by the following configuration. That is, there is provided a pressurizing member including a substrate, an elastic layer formed on an outer side of the substrate, and a surface layer containing a fluorine resin formed on the elastic layer. The surface layer is fixed to the elastic layer under a state of being extended in a longitudinal direction, and the elastic layer has a hollow part ratio of from 20 vol % to 60 vol % or less. The pressurizing member has E(MD)/E(ND) being larger than 1.0, where E(ND) represents an elastic modulus of the elastic layer in a thickness direction, and E(MD) represents an elastic modulus of the elastic layer in a longitudinal direction. Further, there is disclosed that the above-mentioned physical properties are obtained by the elastic layer in which hollow parts are dispersed, the hollow parts being formed by evaporating water in a silicone rubber in which needle-shaped fillers are arranged in the longitudinal direction and water is dispersed.
One embodiment of the present invention is directed to providing an electrophotographic rotatable pressing member being capable of reducing the warm-up time and having further durability, and a method of manufacturing the electrophotographic rotatable pressing member.
Further, another embodiment of the present invention is directed to providing a fixing device capable of stably providing a high-quality electrophotographic image. According to one embodiment of the present invention, there is provided an electrophotographic rotatable pressing member, including: a substrate; and an elastic layer formed on the substrate, the elastic layer containing a silicone rubber and a needle-shaped filler dispersed in the silicone rubber, and having hollow parts, when cutting the elastic layer along a cross section including a center axis of the substrate in a longitudinal direction of the electrophotographic rotatable pressing member, and a total of each sectional area of the hollow parts in a unit area A2 of a cross-sectional surface is defined as A1, a standard deviation of an area ratio A1/A2 is 0.08 or less.
According to another embodiment of the present invention, there is provided a method of manufacturing an electrophotographic rotatable pressing member, the electrophotographic rotatable pressing member including: a substrate; and an elastic layer formed on the substrate, the elastic layer containing a silicone rubber and a needle-shaped filler dispersed in the silicone rubber and having hollow parts, the method including: dispersing the needle-shaped filler and a water-containing gel in a liquid silicone rubber to obtain an emulsion-like liquid composition; filling the emulsion-like liquid composition into a cavity formed between an outer peripheral surface of the substrate and an inner peripheral surface of a tubular mold, the substrate being held by a substrate-holder arranged at each end of the tubular mold; crosslinking and curing the liquid silicone rubber by heating without causing the emulsion-like liquid composition in the cavity to flow, to thereby obtain a cured product; and removing water from the cured product.
According to yet another embodiment of the present invention, there is provided a fixing device, including: an electrophotographic rotatable pressing member of the present invention; and a heating member arranged so as to be opposed to the electrophotographic rotatable pressing member.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
The inventors of the present invention have confirmed presence or absence of durability at a higher level in an electrophotographic rotatable pressing member including the elastic layer disclosed in International Publication No. WO2016/009527, in which hollow parts formed by evaporating water in a silicone rubber containing needle-shaped fillers and dispersed water are dispersed. Specifically, the inventors of the present invention mounted the electrophotographic rotatable pressing member on a fixing device under a state in which a pressurizing force with respect to a heating member is set to be higher than a normal pressurizing force and subjected the fixing device to a test (hereinafter referred to as “severe durability test”) in which a large number of electrophotographic images were continuously output. As a result, in the electrophotographic rotatable pressing member after being subjected to the severe durability test, there were cases in which some parts in which the hardness of a surface changed by 5% or more as compared to an initial value. Specifically, there were cases in which some parts in which a change ratio of the hardness as compared to an initial hardness was more than 5%.
The inventors of the present invention have made investigations of the reason that the hardness of the surface significantly changed in some parts of the pressurizing member disclosed in International Publication No. WO2016/009527 when the pressurizing member was subjected to the severe durability test. In the process of the investigations, observation was made on the elastic layer including the parts in which the hardness changed. As a result, it has been found that, in the parts in which the hardness changed, rubber skeletons supporting the hollow parts in the elastic layer were fractured, and further the fracture of the rubber skeletons was caused by the fact that the rubber skeletons were thinner than in the parts in which the rubber skeletons were not fractured.
In view of the foregoing, as the reason that there are parts including thin rubber skeletons and portions including thick rubber skeletons in the elastic layer, the inventors of the present invention have discussed the following. The method of manufacturing the pressurizing member disclosed in International Publication No. WO2016/009527 includes, as a production process of the elastic layer, a first step of filling an emulsified liquid silicon rubber mixture containing needle-shaped fillers and dispersed water into a mold for molding, then sealing the mold for molding, and heating and curing the liquid silicone rubber mixture in the mold for molding, and a second step of further heating the cured silicone rubber removed from the mold for molding to remove water finely dispersed in the cured silicone rubber, to thereby form a porous silicon rubber elastic layer.
In the first step, in the sealed mold for molding, the liquid silicone rubber mixture basically was not to flow, but actually, the liquid silicone rubber mixture leaked from the mold for molding in some cases. When the leakage of the liquid silicone rubber mixture from the mold for molding was recognized, the rubber skeletons in the elastic layer obtained through the second step significantly varied in thickness. In view of the foregoing, the inventors of the present invention have discussed the following. When the liquid silicone rubber mixture flows in the sealed mold for molding, the emulsified state of the liquid silicone rubber mixture is disrupted, and a water-containing gel in the liquid silicone rubber mixture is aggregated, resulting in variation in thickness of the rubber skeletons in the elastic layer to be obtained.
That is, an emulsified liquid has a thermodynamically unstable non-equilibrium system. Therefore, when the liquid silicone rubber mixture flows in the mold for molding at the time of being cured, disruption of the emulsified state proceeds due to a shearing force caused by the flow of the liquid silicone rubber mixture, and the water-containing gel dispersed in the liquid silicone rubber mixture is aggregated. When the liquid silicone rubber mixture is cured under a state in which the water-containing gel is aggregated, hollow parts are formed at positions where the water-containing gel was present in the elastic layer of the electrophotographic rotatable pressing member. Therefore, it is thought that the hollow parts are formed under a state of being aggregated to cause uneven distribution of the hollow parts in the elastic layer.
Based on the above-mentioned discussion, the inventors of the present invention have made an attempt to reduce the flow of the liquid silicone rubber mixture in the mold for molding at a higher level when the liquid silicone rubber mixture in the mold for molding is cured in the first step. Specifically, the inventors of the present invention have improved a sealing property of the mold for molding.
As a result, it has been found that, in the obtained electrophotographic rotatable pressing member, the hollow parts were remarkably uniformly distributed in the elastic layer, and a partial change in hardness is less liable to occur even after long-term use.
When the hollow parts are uniformly distributed in the elastic layer, the distances between the adjacent hollow parts become substantially uniform as compared to the case in which the distribution of the hollow parts is non-uniform. Therefore, it is considered that, when the elastic layer of the electrophotographic rotatable pressing member is pressurized in the fixing device, the number of portions in which large stress is concentrated becomes small, and thus fracture of the rubber skeletons forming the hollow parts is effectively suppressed.
Hitherto, in the case of considering durability of the electrophotographic rotatable pressing member, which is related to fracture of the rubber skeletons in the elastic layer in which the hollow parts are formed by evaporating water in a silicone rubber containing needle-shaped fillers and dispersed water, the uniformity of distribution of the hollow parts in the elastic layer has not been considered. In view of the foregoing, the inventors of the present invention used, as an indicator for representing the uniformity of distribution of the hollow parts, a standard deviation of a ratio (hereinafter sometimes simply referred to as “area ratio”) of a total area of the hollow parts per unit area in a cut surface obtained by cutting the elastic layer of the electrophotographic rotatable pressing member along a cross section including a center axis of the substrate. As the standard deviation of the area ratio is smaller, the distribution of the hollow parts in the elastic layer is more uniform.
Now, a fixing device and an electrophotographic rotatable pressing member according to an embodiment of the present invention are specifically described.
(1) Fixing Device
The fixing device according to the present invention is not limited to this embodiment, and is applicable also to a heat-roll type fixing device using a halogen heater as a heat source and to a fixing device employing an induction heating (IH) system configured to cause a member itself to generate heat by energizing a coil, which are generally used.
In
The film guide member 1 is, for example, a molded product made of a heat-resistant resin such as polyphenylene sulfide (PPS) or a liquid crystal polymer.
The heater 2 has a configuration in which a heat generating resistor is arranged on a ceramic substrate. The heater 2 illustrated in
The film 3 is, for example, a composite layer film in which a surface layer is applied to a surface of a base film. In order to reduce a heat capacity to improve a quick start property of a heating device, a total thickness of the film 3 is preferably set to be 500 μm or less.
As a material for the base film, there may be used: resins, such as polyimide (PI), polyamide-imide (PAI), polyether ether ketone (PEEK), and polyethersulfone (PES); and alloys or metals, such as stainless steel (e.g., SUS304) and nickel.
As a material for the surface layer, there may be used fluorine resin materials, such as polytetrafluoroethylene (PTFE), a tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer (PFA), and a tetrafluoroethylene-hexafluoropropylene copolymer (FEP).
An elastic layer containing a cured silicone rubber and an adhesive layer may be formed between the base film and the surface layer.
The electrophotographic rotatable pressing member 4 is arranged so as to be opposed to a lower surface of the heater 2 and is brought into pressure contact with the heater 2 through intermediation of the film 3.
The electrophotographic rotatable pressing member 4 is pressurized to the surface protective layer 2d of the heater 2 through intermediation of the film 3 with a predetermined pressurizing force by a predetermined pressurizing mechanism (not shown). An elastic layer 4b of the electrophotographic rotatable pressing member 4 is elastically deformed in accordance with the pressurizing force, and a nip portion N having a predetermined width required for heat fixing of an unfixed toner image T is formed between the surface of the electrophotographic rotatable pressing member 4 and the surface of the film 3. The pressurizing force is appropriately set based on the type and size of a sheet being a product target, the type of a toner, and the configuration of the fixing device. A general pressurizing force is set to be from about 10 kgf to about 70 kgf.
A recording material P being a material to be heated is introduced into the nip portion N, and through the recording material P being held and conveyed, the recording material P is heated.
The electrophotographic rotatable pressing member 4 receives a drive force from a drive source M transmitted through a gear (power transmission mechanism) (not shown) and is driven to rotate in a counterclockwise direction of the arrow “b” at a predetermined rotational peripheral speed.
When the electrophotographic rotatable pressing member 4 is driven to rotate in the counterclockwise direction of the arrow “b” at the time of implementation of image formation, the film 3 is rotated in a direction of the arrow “a” in association with the rotation of the electrophotographic rotatable pressing member 4.
(2) Layer Configuration of Electrophotographic Rotatable Pressing Member 4
The substrate 4a is made of a metal such as iron, aluminum, or nickel, or an alloy, for example, stainless steel. When the electrophotographic rotatable pressing member 4 is mounted on the fixing device, the electrophotographic rotatable pressing member 4 is pressurized under a state in which shaft portions of the substrate 4a at both ends in which the elastic layer 4b is not formed are held by substrate-holders. Therefore, the substrate 4a is required to have strength sufficient for withstanding the pressurizing force, and hence iron or stainless steel is preferably used. Further, parts of the surface of the substrate 4a on which the elastic layer 4b is formed are generally subjected to adhesion treatment. As the adhesion treatment, physical treatment such as blasting or F-polishing and chemical treatment such as oxidation treatment, primer treatment, or coupling agent treatment may be performed alone or in combination.
(3) Elastic Layer 4b of Electrophotographic Rotatable Pressing Member 4
The elastic layer 4b forming the electrophotographic rotatable pressing member 4 contains a cured silicone rubber and needle-shaped fillers 4b1 dispersed in the cured silicone rubber. Further, the elastic layer 4b contains hollow parts 4b2. In a cut surface obtained by cutting the elastic layer 4b along a cross section “b” including a center axis of the substrate 4a in a longitudinal direction of the electrophotographic rotatable pressing member 4, a standard deviation of an area ratio A1/A2 is 0.08 or less, where A1 represents a total of each sectional area (hereinafter sometimes referred to as “hollow part area”) of the hollow parts 4b2 in a unit area of the cross section “b” being the cut surface in the longitudinal direction of the electrophotographic rotatable pressing member 4, and A2 represents the unit area of the cross section “b”.
When the standard deviation is 0.08 or less, the plurality of hollow parts 4b2 in the elastic layer 4b are uniformly present. Therefore, variation in thickness of the rubber skeletons in the elastic layer 4b is suppressed, and variation in strength of the rubber skeletons in the elastic layer 4b is suppressed. Therefore, it is considered that, even under pressurization, a stress is less liable to be concentrated on a part of the elastic layer 4b, and partial fracture of the rubber skeletons forming the hollow parts 4b2 is suppressed.
A lower limit value of the standard deviation is not particularly limited but is practically 0.01 or more. The standard deviation can be set to be 0.08 or less by controlling (suppressing), to a high degree, the flow of an emulsion-like liquid silicone rubber mixture containing needle-shaped fillers and a dispersed water-containing gel (described later) in a mold for molding at the time of being cured.
The elastic layer 4b is formed of a single layer. The thickness of the elastic layer 4b is not particularly limited as long as the thickness falls within a range capable of forming the nip portion N having a desired width but is preferably 2 mm or more and 5 mm or less.
(3-1) Base Polymer
A base polymer of the elastic layer 4b contains a cured product of an addition-curable liquid silicone rubber. The addition-curable liquid silicone rubber is an uncrosslinked silicone rubber containing organopolysiloxane (A) having an unsaturated aliphatic group, for example, a vinyl group and organopolysiloxane (B) having a Si—H group (hydrosilyl group). When the Si—H group is added to an unsaturated bond of the unsaturated aliphatic group by heating, a crosslinking reaction proceeds. Further, through appropriate adjustment of the amounts of the organopolysiloxane (A) having an unsaturated aliphatic group and the organopolysiloxane (B) having a Si—H group, a base polymer having a desired hardness can be obtained.
The hardness of the elastic layer 4b is measured based on “Vulcanized Rubber and Thermoplastic Rubber—Method of Determining Hardness—Third Section: Durometer Hardness” stipulated under “Japanese Industrial Standards (JIS)K 6253-3:2012” and is preferably 20 degrees or more and 80 degrees or less.
The addition-curable liquid silicone rubber generally contains a platinum compound as a catalyst for accelerating a crosslinking reaction. Further, the addition-curable liquid silicone rubber can be regulated for flowability within a range of not impairing the object of the present invention. Further, in the present invention, the elastic layer 4b may contain a filler or a filling material other than the needle-shaped fillers 4b1 in the present invention, and a compounding agent as known means for solving the problem without departing the scope of the feature of the present invention.
(3-2) Needle-Shaped Filler 4b1
It is preferred that the content ratio of the needle-shaped fillers 4b1 be 2 vol % or more and 15 vol % or less with respect to the elastic layer 4b. When the content ratio of the needle-shaped fillers 4b1 is set to be 2 vol % or more, the effect of suppressing circumferential creases can be obtained. Further, when the content ratio of the needle-shaped fillers 4b1 is set to be 15 vol % or less, the elastic layer 4b can be easily molded. Further, when the content ratio of the needle-shaped fillers 4b1 is set to be 15 vol % or less, an excessive decrease in elasticity of the elastic layer 4b can be avoided, and the nip portion N of the electrophotographic rotatable pressing member 4 in the fixing device can be easily ensured.
As a material for the needle-shaped fillers 4b1, a material having a large ratio of a length L to a diameter D, that is, a large aspect ratio as illustrated in
As specific examples of the needle-shaped fillers 4b1, there are given pitch-based carbon fibers, PAN-based carbon fibers, glass fibers, and other inorganic whiskers. The needle-shaped fillers 4b1 having, as a more specific shape, an average diameter D of 5 μm or more and 11 μm or less, an average length L of 50 μm or more and 1,000 μm or less, and an aspect ratio of 5 or more and 120 or less in
The aspect ratio of the needle-shaped fillers 4b1 can be determined through use of the following expression based on the average length and the average diameter of the needle-shaped fillers 4b1.
Aspect ratio=Average length/Average diameter
In the following, description is made of a specific method of calculating an aspect ratio when the needle-shaped fillers 4b1 are carbon fibers. First, a sample cut out from the elastic layer 4b is fired at 700° C. for 1 hour in a nitrogen gas atmosphere to calcify and remove a silicone rubber component. Thus, the needle-shaped fillers 4b1 in the sample can be taken out. The content ratio of the needle-shaped fillers 4b1 in the elastic layer 4b can be determined by determining a volume of the needle-shaped fillers 4b1 taken out from the sample. Further, an aspect ratio of the needle-shaped fillers 4b1 can be determined through use of the above-mentioned expression by randomly selecting 100 or more needle-shaped fillers 4b1 and measuring an average length and average diameter thereof with an optical microscope. In this embodiment, the aspect ratio of the needle-shaped fillers 4b1 is represented by a value obtained by rounding off the first decimal place of the value obtained from the above-mentioned expression.
The step of forming the elastic layer 4b containing the needle-shaped fillers 4b1 includes, for example, a first step of curing an emulsion-like liquid silicone rubber mixture containing the needle-shaped fillers 4b1 and the water-containing gel in a sealed mold for molding and a second step of removing water from the cured product. In the first step, when the liquid silicone rubber mixture flows in the sealed mold for molding, the needle-shaped fillers 4b1 serve as cores, and the water-containing gel is easily aggregated. As a result, the hollow parts 4b2 present in the elastic layer 4b obtained through the second step are liable to be non-uniformly distributed. That is, as the amount of the needle-shaped fillers 4b1 in the rubber composition is larger, the standard deviation of the area ratio A1/A2 is liable to increase, where A1 represents the hollow part area in the cut surface obtained by cutting the elastic layer 4b along the cross section including the center axis of the substrate 4a, and A2 represents the unit area.
(3-3) Hollow Part 4b2
The elastic layer 4b of the electrophotographic rotatable pressing member 4 contains the hollow parts 4b2 in order to decrease the heat conductivity of the elastic layer 4b. That is, when the heat conductivity of the electrophotographic rotatable pressing member 4 is suppressed, escape of heat from the heating member to the substrate 4a is suppressed to improve a temperature increase speed of the heating member, with the result that the warm-up time can be reduced. The hollow parts 4b2 in the elastic layer 4b in the present invention are dispersed so that the standard deviation of the area ratio A1/A2 is 0.08 or less, where A1 represents the hollow part area in the cut surface obtained by cutting the elastic layer 4b along the cross section “b” including the center axis of the substrate 4a, and A2 represents the unit area.
The standard deviation of the area ratio A1/A2 can be determined as follows. First, the elastic layer 4b of the electrophotographic rotatable pressing member 4 is cut out by 3 mm each in the circumferential direction and in the longitudinal direction of the electrophotographic rotatable pressing member 4 as illustrated in a sample 4bs represented by the shaded area of
Therefore, it is considered that the difference is easily exhibited when the dispersion of the hollow parts 4b2 is evaluated based on the standard deviation of the area ratio A1/A2. Binarization is performed by Otsu's discriminant analysis method. The obtained binarized image is segmentalized to a size of 53 μm square. The obtained segmentalized images are each determined for the hollow part area A1 and the unit area A2, and each area ratio A1/A2 is calculated. The reason for setting the unit area for segmentalizing the binarized image to 53 μm square is that, during the investigations of the inventors of the present invention, the standard deviation of a ratio (area ratio) of the hollow part area with respect to the unit area of 53 μm square was found to be satisfactorily correlated to the results of presence or absence of a change in hardness after the severe durability test of the electrophotographic rotatable pressing member.
A standard deviation of the sample 4bs is calculated based on the obtained area ratio A1/A2. When the hollow parts 4b2 are non-uniformly distributed, the number of the segmentalized images each having a large hollow part area and the number of the segmentalized images each having a small hollow part area are both large, and hence a standard deviation obtained by measuring a large number of segmentalized images becomes large. Meanwhile, when the hollow parts 4b2 are uniformly distributed, the number of the segmentalized images each having a large hollow part area and the number of the segmentalized images each having a small hollow part area are both small, and hence a standard deviation obtained by measuring a large number of segmentalized images becomes small.
Calculation of a standard deviation of the area ratio A1/A2 is performed with respect to the sample 4bs obtained from six positions of the elastic layer 4b. The samples 4bs are cut out from a total of six positions of the elastic layer 4b, the six positions including, when a total axial length of the elastic layer 4b is represented by L1, two positions of 0.1 L1 from both ends and one position of 0.5 L1 being the center, and three positions different from the above-mentioned positions by 180° in the circumferential direction. In the electrophotographic rotatable pressing member 4 of the present invention, all the standard deviations of the area ratios A1/A2 obtained from the samples 4bs cut out from the six positions become 0.08 or less.
When, in the standard deviations of the area ratios A1/A2 obtained from the samples 4bs cut out from the six positions of the elastic layer 4b of the electrophotographic rotatable pressing member 4, the standard deviation of the area ratio A1/A2 is larger than 0.08 even at one position, a change in hardness in that position of the elastic layer 4b becomes large. As a result, when the electrophotographic rotatable pressing member 4 having changed hardness is used in the fixing device, sheet creases are liable to occur at the time of sheet passage. Therefore, the electrophotographic rotatable pressing member 4 including the elastic layer 4b in which the standard deviation of the area ratio A1/A2 is larger than 0.08 even at one position has unsatisfactory durability, and the member needs to be frequently replaced.
Further, it is preferred that the elastic layer 4b have a hollow part ratio of 20 vol % or more and 60 vol % or less. When the hollow part ratio is 20 vol % or more, the above-mentioned effect of sufficiently reducing the warm-up time can be obtained. Even when an attempt is made to form the elastic layer 4b having a hollow part ratio of more than 60 vol %, it may be difficult to mold the elastic layer 4b. When the elastic layer 4b has a high hollow part ratio, the warm-up time can be reduced, and hence the hollow part ratio is more preferably 40 vol % or more and 60 vol % or less.
The hollow part ratio of the elastic layer 4b can be determined as follows. First, the elastic layer 4b is cut at any position through use of a razor to obtain an evaluation sample. The obtained evaluation sample is measured for a volume at 25° C. by an immersion specific gravity measuring device (product name: SGM-6 manufactured by Mettler Toledo International Inc.) (hereinafter this volume is represented by “Vail”). Next, the evaluation sample subjected to volume measurement is heated at 700° C. for 1 hour in a nitrogen gas atmosphere through use of a thermogravimetric measurement device (product name: TGA851e/SDTA manufactured by Mettler Toledo International Inc.), to thereby decompose and remove a silicone rubber component. A reduction amount of weight in this case is represented by Mp. When inorganic fillers are contained in the elastic layer 4b in addition to the needle-shaped fillers 4b1, a residue obtained after decomposition and removal of the silicone rubber component contains the needle-shaped fillers 4b1 and the inorganic fillers in a mixed state.
A total volume of the needle-shaped fillers 4b1 and the inorganic fillers at 25° C. is measured in this state by a dry-process automatic densitometer (product name: AccyPyc 1330-1 manufactured by Shimadzu Corporation). Volume measurement is performed ten times for each replacement of nitrogen gas, and an arithmetic average thereof is represented by Va.
A hollow part ratio of the evaluation sample can be determined from the following expression based on the above-mentioned values. Calculation is performed with the density of the silicone rubber component being 0.97 g/cm3 (hereinafter the density is represented by “ρp”).
Hollow part ratio (vol %)=[{Vall−(Mp/ρp+Va)}/Vall]×100
The hollow part ratio described in this embodiment is defined as follows. That is, any portions are cut out from five positions to obtain evaluation samples, and an average value of hollow part ratios determined from the evaluation samples is defined as the hollow part ratio of the elastic layer 4b.
It is preferred that the hollow part 4b2 in the elastic layer 4b have such a diameter that, when the elastic layer 4b is cut in a thickness direction with a razor, 80% or more of the number of the hollow parts 4b2 appearing on the cut surface falls within a range of 5 μm or more and 30 μm or less. Here, the diameter of the hollow part 4b2 is obtained by observing the cross section “b” being the cut surface at an accelerating voltage of 3 kV and a magnification of 100 times through use of a scanning electron microscope (SEM) (product name: XL30 SFEG manufactured by Philips Inc.), binarizing the cross section “b” through use of image analysis software (product name: Image-Pro Plus 5.0 J manufactured by Media Cybernetics Inc.), and defining, as the diameter of the hollow part 4b2, a half of a total value of the maximum length and the minimum length of the diameter of the hollow part 4b2. The hollow part 4b2 has a diameter as small as 30 μm or less. Therefore, at the time of passage of a sheet for printing a second surface in duplex printing, an image defect is less liable to occur on an image printed on a first surface of the sheet that is brought into contact with a pressure roller.
(4) Surface Layer 4c
In order to give releasability to the electrophotographic rotatable pressing member 4, the surface layer 4c formed of a fluorine-containing resin tube may be formed on the elastic layer 4b.
As a material for the surface layer 4c, a fluorine-containing resin is used from the viewpoint of releasability for the recording material P at the time of image printing. As specific examples of the fluorine-containing resin, there are given a tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer (PFA), polytetrafluoroethylene (PTFE), and a tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Further, two or more kinds of the materials listed above may be blended to be used, and additives may be added.
The thickness of the surface layer 4c is not particularly limited as long as the thickness falls within a range capable of giving sufficient releasability to the electrophotographic rotatable pressing member 4 but is preferably 20 μm or more and 50 μm or less.
(5) Method of Manufacturing Electrophotographic Rotatable Pressing Member 4
The manufacturing method described below enables the electrophotographic rotatable pressing member 4 to be obtained, the electrophotographic rotatable pressing member 4 including the elastic layer 4b in which the hollow parts 4b2 are dispersed, the hollow parts 4b2 being formed by evaporating water in a silicone rubber containing the needle-shaped fillers 4b1 and dispersed water.
(i) Preparation Step of Liquid Composition for Forming Elastic Layer 4b
In a method of forming the elastic layer 4b containing the hollow parts 4b2 according to the present invention, an emulsion-like liquid composition containing a water-containing gel, an addition-curable liquid silicone rubber, and the needle-shaped fillers 4b1 is used.
The water-containing gel, the addition-curable liquid silicone rubber, and the needle-shaped fillers 4b1 are mixed and stirred through use of a known filler mixing and stirring unit, for example, a planetary universal mixing and stirring machine, thereby being capable of preparing an emulsion-like liquid composition in which the needle-shaped fillers 4b1 and the water-containing gel are dispersed in the addition-curable liquid silicone rubber.
A cured product of a composition in which water is finely dispersed is formed through use of the emulsion-like liquid composition containing the water-containing gel, and then dehydrated, thereby being capable of obtaining the elastic layer 4b containing the fine hollow parts 4b2 as illustrated in
As the water-containing gel, a gel obtained by swelling a water-absorbing polymer and clay mineral through introduction of water can be used. The water-containing gel dispersed in the emulsion-like liquid composition has a diameter of about 1 μm or more and about 30 μm or less and is less liable to inhibit the alignment of the needle-shaped fillers 4b1. Therefore, the elastic layer 4b having a high hollow part ratio and containing the needle-shaped fillers 4b1 aligned highly can be formed.
Meanwhile, when a liquid composition containing hollow particles (having a diameter of about 40 μm), for example, resin balloons is injected into a mold for cast molding, instead of the water-containing gel, to form an elastic layer, in the case in which shells of the hollow particles flow in a cavity of the mold for cast molding, the alignment of the needle-shaped fillers 4b1 is inhibited. Therefore, it is difficult to form an elastic layer that satisfies both a high hollow part ratio and high alignment of the needle-shaped fillers 4b1.
Further, even when an elastic layer is formed by injecting a liquid composition containing a foaming agent for forming hollow parts into a mold for cast molding, the alignment of the needle-shaped fillers 4b1 is disturbed at the time of foaming of the foaming agent, and hence it is difficult to align the needle-shaped fillers 4b1 in the longitudinal direction.
Of the water-containing gel, as the water-absorbing polymer, there are given a polymer, a copolymer, or a crosslinked product of acrylic acid, methacrylic acid, and metal salts thereof. Of those, an alkali metal salt of polyacrylic acid and a crosslinked product thereof (product name: RHEOGIC 250H manufactured by Toagosei Co., Ltd.) can be suitably used, and can easily be obtained in an industrial manner. Further, clay mineral having a thickening effect and swollen with water is suitable for preparing a liquid composition for forming the emulsion-like elastic layer 4b. As a thickening agent containing such clay mineral, there is given “BEN-GEL W-200U” (product name) manufactured by Hojun Co., Ltd.
The emulsion-like liquid composition may contain a platinum compound serving as a catalyst for accelerating a crosslinking reaction, a filler, a filling material, and a compounding agent.
Further, the liquid composition may be prepared by mixing and stirring after adding an emulsifier and a viscosity modifier as necessary. As an additive for emulsification, there is given a surfactant, for example, nonionic surfactant (sorbitan fatty acid ester (product name: IONET HLB4.3 manufactured by Sanyo Chemical Industries, Ltd.)).
The hollow part ratio of the elastic layer 4b of the electrophotographic rotatable pressing member 4 can be produced by adjusting the content of the water-containing gel in the liquid composition for forming the elastic layer 4b. A specific method of adjusting the hollow part ratio is described below. The density of the water-containing gel and the density of the addition-curable liquid silicone rubber are both 1.0 g/cm3. Further, the density of the needle-shaped fillers 4b1 is 2.2 g/cm3 when the needle-shaped fillers 4b1 are pitch-based carbon fibers used in an Example described later. Based on those values, the amount of the water-containing gel is regulated so that the content ratio of the water-containing gel with respect to the total volume of the liquid composition to be used for forming the elastic layer 4b becomes 20 vol % or more and 60 vol % or less. The volume of the hollow parts in the elastic layer 4b after dehydration is substantially the same as that of the water-containing gel in the liquid composition. Therefore, the elastic layer 4b having a hollow part ratio of 20 vol % or more and 60 vol % or less can be produced by setting the volume of the water-containing gel with respect to the total volume of the liquid composition within the above-mentioned range.
(ii) Forming Step of Layer of Liquid Composition
This step is specifically described with reference to
First, in order to improve shape transferability at the time of molding, the tubular mold 7 is decompressed through two horizontal holes 13 formed on the tubular mold 7 to bring the surface layer 4c into close contact with an inner wall of the tubular mold 7.
Then, in the mold in which the substrate 4a is held by the substrate-holders 5 and 6 set at both ends of the tubular mold 7, the liquid composition of the present invention prepared in the above-mentioned step (i) is filled into the cavity 9 formed between the outer peripheral surface of the substrate 4a and the inner peripheral surface of the tubular mold 7 through the communication path 11. At this time, bubble catching can be reduced at the time of cast molding involving injecting the liquid composition by mounting a decompressor, for example, an aspirator (not shown) at the end of the communication path 10 to bring the inside of the cavity 9 into a decompressed state. When bubble catching is reduced, the flow of the liquid composition at the time of thermal expansion in a step (iii) described later can be reduced, and hence the progress of demulsification is suppressed to obtain uniform distribution of the hollow parts 4b2. As a result, the standard deviation of the area ratio A1/A2 becomes small, where A1 represents the hollow part area in the cut surface obtained by cutting the elastic layer 4b of the present invention along the cross section including the center axis of the substrate 4a, and A2 represents the unit area. It is necessary to set the decompression in the cavity 9 to be lower than that for close adhesion between the surface layer 4c and the tubular mold 7 so as to keep a state in which the surface layer 4c and the tubular mold 7 are brought into close contact with each other also at the time of injection of the liquid composition.
(iii) Crosslinking and Curing Step of Silicone Rubber Component
Next, the cavity 9 filled with the liquid composition is sealed by closing the communication paths 10 and 11 that have been opened as flow passages for cast molding with a screw, a ball valve, and the like so that the liquid composition does not flow out. In this state, the liquid composition is heated at a temperature less than the boiling point of water, for example, at 60° C. or more and 90° C. or less for 5 minutes to 120 minutes to cure the silicone rubber component being the base polymer of the elastic layer 4b.
The mold to be used in the step (iii) of the electrophotographic rotatable pressing member 4 has a seal structure for implementing high-level sealing. Therefore, the liquid silicone rubber can be crosslinked and cured by heating to provide a cured product without causing the liquid composition in the cavity 9 to flow. In the case in which the cavity 9 is not sealed at a high level in spite of the fact that the cavity 9 is sealed, when the pressure in the mold is increased due to thermal expansion of the liquid composition at the time of heating, the liquid composition leaks to flow outside the mold through fitting portions between the tubular mold 7 and the substrate-holders 5 and 6, resulting in disruption of the emulsified state of the liquid composition. Therefore, the seal structure for implementing high-level sealing is required.
Specifically, as illustrated in
Each of the O-rings 8 is held by the tubular mold 7 under a state of projecting outside from a tapered surface of the tubular mold 7 of the fitting portion between the tubular mold 7 and the substrate-holder 5 or 6. The groove 12 is formed with a curvature in a groove depth direction in a circumferential shape in the fitting portion between the substrate-holder 5 or 6 and the tubular mold 7 in conformity with the shape of the O-ring 8 arranged in the tubular mold 7.
It is preferred that the depth of the groove 12 have a value of 20% or more and 100% or less with respect to an amount (projection amount) by which the O-ring 8 projects from the tapered surface of the tubular mold 7. With this depth of the groove 12, the contact area in which the O-ring 8 and the groove 12 are opposed to each other can be prevented from becoming excessively small. Further, it is possible to prevent a situation in which the O-ring 8 and the groove 12 are not brought into pressure contact with each other to make it difficult to perform high-level sealing. Further, it is preferred that the curvature of the groove 12 be set to be smaller than that of a cross section of the O-ring 8. With this curvature of the groove 12, the O-ring 8 is easily crushed into a shape in conformity with the groove 12 when the tubular mold 7 and the substrate-holders 5 and 6 are fitted with each other. Therefore, high-level sealing can be reliably achieved.
(iv) Demolding Step
The addition-curable liquid silicone rubber in the liquid composition is crosslinked and cured in the step (iii), and then the mold is appropriately cooled with water or air, to thereby demold the cured product. Alternatively, the electrophotographic rotatable pressing member 4 may be demolded after the elastic layer 4b is formed in the step (v).
(v) Dehydration Step
Water is removed from the cured product of the liquid composition laminated on the substrate 4a by heating treatment to form the hollow parts 4b2. As the heating treatment condition, it is desired that a temperature be 100° C. or more and 250° C. or less, and a heating time be 1 hour to 5 hours. The step (v) may be performed before or after the step (iv).
(vi) Lamination Step of Surface Layer 4c
As described above, the surface layer 4c can be laminated by a method involving fixing and arranging the fluorine-containing resin tube in the mold for cast molding in advance and subjecting the liquid composition to cast molding. Alternatively, the surface layer 4c can be laminated also by a method involving forming the elastic layer 4b, covering the elastic layer 4b with the fluorine-containing resin tube, and bonding and fixing the fluorine-containing resin tube to the elastic layer 4b with an adhesive.
According to one embodiment of the present invention, an electrophotographic rotatable pressing member in which hardness is less liable to change from an initial state even after long-term use can be obtained.
Further, according to another embodiment of the present invention, a method of manufacturing an electrophotographic rotatable pressing member in which hardness is less liable to change from an initial state even after long-term use can be obtained. According to still another embodiment of the present invention, a fixing device capable of stably providing a high-quality electrophotographic image can be obtained.
Materials used in each of the following Examples are described.
(Substrate 4a)
As the substrate 4a, a substrate made of iron (having a diameter of 24.5 mm and a length of a forming region of the elastic layer 4b of 330 mm) was used.
(Base Polymer)
As the base polymer of the elastic layer 4b, an addition-curable liquid silicone rubber having a viscosity of 10 Pa·s at a shearing speed of 10 (l/s) in an environment of 25° C. was used.
(Water-Containing Gel)
As the water-containing gel, a water-containing gel, which was prepared by adding 99 parts by mass of ion-exchange water to 1 part by mass of a thickening agent (product name: “BEN-GEL W-200U” manufactured by Hojun Co., Ltd.) containing, as a main component, sodium polyacrylate and smectite-based clay mineral and sufficiently stirring and swelling the mixture, was used.
(Needle-Shaped Filler 4b1)
As the needle-shaped fillers 4b1, the following four kinds of fibrous materials were used.
1. Pitch-based carbon fiber, product name: GRANOC Milled Fiber XN-100-05M (manufactured by Nippon Graphite Fiber Co., Ltd.); fiber diameter: 9 μm, fiber length: 50 μm, aspect ratio: 6, density: 2.2 g/cm3, hereinafter referred to as “100-05M”.
2. Pitch-based carbon fiber, product name: DIALEAD K223HM (manufactured by Mitsubishi Plastics, Inc.); fiber diameter: 11 μm, fiber length: 200 μm, aspect ratio: 18, density: 2.2 g/cm3, hereinafter referred to as “K223HM”.
3. PAN-based carbon fiber, product name: TORAYCA Milled Fiber MLD-300 (manufactured by Toray Industries, Inc.); fiber diameter: 7 μm, fiber length: 130 μm, aspect ratio: 19, density: 1.8 g/cm3, hereinafter referred to as “MLD-300”.
4. Glass fiber, product name: EFH150-01 (manufactured by Central Glass Co., Ltd.); fiber diameter: 11 μm, fiber length: 150 μm, aspect ratio: 14, density: 2.6 g/cm3, hereinafter referred to as “150-01”.
(Surface Layer 4c)
As the surface layer 4c, a PFA tube having a thickness of 40 μm and an outer diameter of 29.0 mm was used. As the PFA tube, the following commercially available product was used.
<product name: Teflon (trademark) PFA 451HP-J (manufactured by Du Pont-Mitsui Fluorochemicals Co., Ltd.), hereinafter referred to as “451HP-J”>
An uncrosslinked addition-curable liquid silicone rubber being the base polymer, “100-05M” being the needle-shaped fillers 4b1, and a water-containing gel were stirred at a rotation number of a stirring blade of 80 rpm for 30 minutes through use of a universal mixing and stirring machine (product name: T.K. HIVIS MIX Model 2P-1 manufactured by Primix Corporation) to prepare an emulsion-like liquid composition. In this case, the uncrosslinked addition-curable liquid silicone rubber and the needle-shaped fillers 4b1 were blended so that the content ratio of the needle-shaped fillers 4b1 was 15 vol % as shown in Table 1.
In order to obtain the configuration as illustrated in
Next, decompression was performed with a unit (not shown) through the horizontal holes 13 to bring the PFA tube into close contact with an inner wall of the tubular mold 7. After that, the liquid composition prepared in advance was injected into the cavity 9 through the communication path 11 to fill the cavity 9 with the liquid composition. In this state, the communication path 11 was sealed with a screw (not shown), and the communication path 10 was sealed with a ball valve (not shown).
As the O-ring 8, a ring having a diameter in cross section of 3.5 mm was used and held in the groove of the tubular mold 7 so as to project from the tapered surface of the tubular mold 7. The curvature of each of the grooves 12 formed in the substrate-holders 5 and 6 was set to be round so as to draw an arc having a radius of 2 mm in conformity with the shape of the O-ring 8. Further, the depth of the groove 12 is set to be 60% with respect to the projection amount of the O-ring 8 from the tapered surface of the tubular mold 7.
Next, the mold having the liquid composition sealed therein was heated at 90° C. for 1 hour in a hot-air oven to crosslink and cure the silicone rubber in the liquid composition. After the mold was cooled, the substrate-holders 5 and 6 were removed from the tubular mold 7. The cured product in the tubular mold 7 was heated at 130° C. for 4 hours and then 200° C. for 4 hours in the hot-air oven to evaporate water in the cured silicone rubber layer. Thus, the elastic layer 4b formed of a single layer containing the needle-shaped fillers 4b1 and the dispersed hollow parts 4b2 was formed. Finally, an unnecessary end portion was cut to provide an electrophotographic rotatable pressing member No. A-01.
The standard deviation of the area ratio A1/A2 was 0.08, where A1 represents the hollow part area in the cut surface obtained by cutting the elastic layer 4b of the obtained electrophotographic rotatable pressing member No. A-01 along the cross section “b” including the center axis of the substrate 4a, and A2 represents the unit area. Further, the hollow part ratio of the elastic layer 4b of the electrophotographic rotatable pressing member No. A-01 was 60 vol %.
The standard deviation of the area ratio A1/A2 of the electrophotographic rotatable pressing member No. A-01 was measured through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. A-01. The standard deviation was measured as follows. The samples 4bs, each having a size of 3 mm in a long axis direction of the elastic layer 4b and a size of 3 mm in a circumferential direction thereof, were cut out from a total of six positions of the elastic layer 4b, the six positions including two positions of 33 mm from both ends and one position of 165 mm being the center with respect to a length of 330 mm of the elastic layer 4b and three positions different from the above-mentioned positions by 180° in the circumferential direction, and as described in the section “(3-3) Hollow part 4b2”, the standard deviation of the area ratio A1/A2 in the cross section “b” was calculated, where A1 represents the hollow part area and A2 represents the unit area. Of the standard deviations of the area ratios A1/A2 of the six samples 4bs, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. A-01.
An electrophotographic rotatable pressing member No. A-02 was obtained under the same condition as that of Example A-1 except that, when the same liquid composition as that of Example A-1 was injected into the cavity 9 through the communication path 11, the cavity 9 was filled with the liquid composition after the cavity 9 was decompressed through use of a decompressor (product name: VUH07-66A manufactured by Nihon Pisco Co., Ltd.) mounted at the end of the communication path 10.
The standard deviation of a hollow part area ratio was measured in the same manner as in Example A-1 through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. A-02. Of the standard deviations, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. A-02.
An electrophotographic rotatable pressing member No. A-03 was obtained under the same condition as that of Example A-1 except that substrate-holders having no groove 12 were used as the substrate-holders 5 and 6.
The standard deviation of the area ratio A1/A2 was measured in the same manner as in Example A-1 through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. A-03. Of the standard deviations, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. A-03.
An uncrosslinked addition-curable liquid silicone rubber being the base polymer, “K223HM” being the needle-shaped fillers 4b1, and a water-containing gel were mixed, being stirred at a rotation number of a stirring blade of 80 rpm for 30 minutes through use of a universal mixing and stirring machine (product name: T.K. HIVIS MIX Model 2P-1 manufactured by Primix Corporation) to prepare an emulsion-like liquid composition. In this case, the uncrosslinked addition-curable liquid silicone rubber and the needle-shaped fillers 4b1 were blended so that the content ratio of the needle-shaped fillers 4b1 was 7 vol % as shown in Table 1.
Except for the foregoing, an electrophotographic rotatable pressing member No. B-01 was obtained under the same condition as that of Example A-1. The elastic layer 4b of the obtained electrophotographic rotatable pressing member No. B-01 had a hollow part ratio of 40 vol %.
The standard deviation of the area ratio A1/A2 was measured in the same manner as in Example A-1 through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. B-01. Of the standard deviations, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. B-01.
An electrophotographic rotatable pressing member No. B-02 was obtained under the same condition as that of Example B-1 except that, when the same liquid composition as that of Example B-1 was injected into the cavity 9 through the communication path 11, the cavity 9 was filled with the liquid composition after the cavity 9 was decompressed through use of a decompressor (product name: VUH07-66A manufactured by Nihon Pisco Co., Ltd.) mounted at the end of the communication path 10.
The standard deviation of the area ratio A1/A2 was measured in the same manner as in Example A-1 through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. B-02. Of the standard deviations, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. B-02.
An electrophotographic rotatable pressing member No. B-03 was obtained under the same condition as that of Example B-1 except that substrate-holders having no groove 12 were used as the substrate-holders 5 and 6.
The standard deviation of the area ratio A1/A2 was measured in the same manner as in Example A-1 through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. B-03. Of the standard deviations, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. B-03.
An uncrosslinked addition-curable liquid silicone rubber being the base polymer, “MLD-300” being the needle-shaped fillers 4b1, and a water-containing gel were stirred at a rotation number of a stirring blade of 80 rpm for 30 minutes through use of a universal mixing and stirring machine (product name: T.K. HIVIS MIX Model 2P-1 manufactured by Primix Corporation) to prepare an emulsion-like liquid composition. In this case, the uncrosslinked addition-curable liquid silicone rubber and the needle-shaped fillers 4b1 were blended so that the content ratio of the needle-shaped fillers 4b1 was 2 vol % as shown in Table 1.
Except for the foregoing, an electrophotographic rotatable pressing member No. C-01 was obtained under the same condition as that of Example A-1. The elastic layer 4b of the obtained electrophotographic rotatable pressing member No. C-01 had a hollow part ratio of 20 vol %.
The standard deviation of the area ratio A1/A2 was measured in the same manner as in Example A-1 through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. C-01. Of the standard deviations, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. C-01.
An electrophotographic rotatable pressing member No. C-02 was obtained under the same condition as that of Example C-1 except that, when the same liquid composition as that of Example C-1 was injected into the cavity 9 through the communication path 11, the cavity 9 was filled with the liquid composition after the cavity 9 was decompressed through use of a decompressor (product name: VUH07-66A manufactured by Nihon Pisco Co., Ltd.) mounted at the end of the communication path 10.
The standard deviation of a hollow part area ratio was measured in the same manner as in Example A-1 through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. C-02. Of the standard deviations, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. C-02.
An electrophotographic rotatable pressing member No. C-03 was obtained under the same condition as that of Example C-1 except that substrate-holders having no groove 12 were used as the substrate-holders 5 and 6.
The standard deviation of the area ratio A1/A2 was measured in the same manner as in Example A-1 through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. C-03. Of the standard deviations, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. C-03.
An uncrosslinked addition-curable liquid silicone rubber being the base polymer, “150-01” being the needle-shaped fillers 4b1, and a water-containing gel were stirred at a rotation number of a stirring blade of 80 rpm for 30 minutes through use of a universal mixing and stirring machine (product name: T.K. HIVIS MIX Model 2P-1 manufactured by Primix Corporation) to prepare an emulsion-like liquid composition. In this case, the uncrosslinked addition-curable liquid silicone rubber and the needle-shaped fillers 4b1 were blended so that the content ratio of the needle-shaped fillers 4b1 was 4 vol % as shown in Table 1.
An electrophotographic rotatable pressing member No. D-01 was obtained under the same condition as that of Example A-1 except that, when the liquid composition prepared as described above was injected into the cavity 9 through the communication path 11, the cavity 9 was filled with the liquid composition under a state in which the cavity 9 was decompressed in advance through use of a decompressor (product name: VUH07-66A manufactured by Nihon Pisco Co., Ltd.) mounted at the end of the communication path 10. The elastic layer 4b of the obtained electrophotographic rotatable pressing member No. D-01 had a hollow part ratio of 30 vol %.
The standard deviation of the area ratio A1/A2 was measured in the same manner as in Example A-1 through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. D-01. Of the standard deviations, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. D-01.
An electrophotographic rotatable pressing member No. D-02 was obtained under the same condition as that of Example D-1 except that substrate-holders having no groove 12 were used as the substrate-holders 5 and 6.
The standard deviation of the area ratio A1/A2 was measured in the same manner as in Example A-1 through use of an electrophotographic rotatable pressing member obtained by the same manufacturing method as that for the electrophotographic rotatable pressing member No. D-02. Of the standard deviations, the maximum value was shown in Table as the standard deviation of the electrophotographic rotatable pressing member No. D-02.
It was confirmed that, in each of Comparative Examples, the liquid composition flowed at the time of heating and crosslinking and slightly leaked through a clearance between the O-ring 8 and the tubular mold 7 or between the O-ring 8 and the substrate-holder 5 or 6.
<<Evaluation of Electrophotographic Rotatable Pressing Member>>
The obtained electrophotographic rotatable pressing member was measured for hardness at the same positions as the six positions from which the samples were cut out for measuring the standard deviation of the area ratio A1/A2 through use of a hardness tester (product name: Durometer Type E, 1 kgf, manufactured by Kobunshi Keiki Co., Ltd.)
After that, the manufactured electrophotographic rotatable pressing member was mounted on the fixing device illustrated in
Then, a severe durability test was performed through continuous sheet passage. After the passage of 100,000 sheets, the electrophotographic rotatable pressing member was removed from the fixing device, and the six positions measured for hardness before the severe durability test were similarly measured for hardness. Of the hardness change ratios after the severe durability test in the case of setting the hardness before the severe durability test at each of the six positions to 100%, the maximum hardness change ratio was shown in Table 1 as the hardness change ratio in the severe durability test.
The hardness change ratio was calculated by the following expression.
Hardness change ratio={(Hardness after severe durability test-Hardness before severe durability test)/Hardness before severe durability test}×100
The present invention has been described by means of exemplary embodiments so far. However, the present invention is not limited to those embodiments. The present invention can be modified and changed variously within the scope and the gist thereof.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-063793 | Mar 2017 | JP | national |
This application is a divisional application of U.S. patent application Ser. No. 15/926,028, filed Mar. 20, 2018, which claims the benefit of Japanese Patent Application No. 2017-063793, filed on Mar. 28, 2017. Both prior applications are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15926028 | Mar 2018 | US |
| Child | 16426498 | US |
