Heating roller

Abstract

To provide a heating roller whose resistance can be reduced, whose sufficient performance can be maintained over a long term and whose warming-up time can be shortened.SOLUTION: In the heating roller 100, a conductive layer 1 of a heating resistor is laminated on a cylindrical metal roller 3 via an insulating layer 2, and power is supplied to the heating resistor to generate heat. The heating resistor contains at least a predetermined amount of multi-walled carbon nanotubes, a predetermined amount of a silica-containing epoxy resin, and a predetermined amount of an organic metal compound, and the organic metal compound is at least one compound selected from the group consisting of an organic metal chelate compound and a metal alkoxide containing at least one metal selected from the group consisting of titanium, zirconium, and aluminum.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat-generating roller used in a fixing device mounted in an image forming apparatus such as a copying machine, a printer, or a facsimile machine. [Background technology]

[0002] In electrophotographic image forming devices such as copiers, printers, and facsimiles, thermal fixing devices are widely used as fixing devices for fixing unfixed toner images transferred to recording materials (hereinafter also referred to as "paper") onto the paper. Conventionally, thermal fixing devices have frequently used a heat roller type in which a pressure roller is pressed against a heated fixing roller, and the recording material is sandwiched and conveyed between the two rollers while the toner is heated and melted to fix the unfixed toner image. Another type is called belt fixing, which uses a release layer on the surface of a 100 μm-thick polyimide film, for example, and heats the belt from the inside with a heating roller. The belt is then pressed against a pressure roller to fix the toner.

[0003] Due to recent environmental regulations and growing awareness of environmental protection, various image forming devices are required to reduce power consumption. One measure to achieve this is an on-demand system, in which the heater of the fixing device is energized only when paper is being fed to perform the fixing operation, and is not energized (preheating is not performed) at other times.

[0004] In such a power-saving image forming apparatus, the surface temperature of the fixing roller must quickly reach a set temperature (generally about 180° C.) during image formation, and a fast start-up time for the fixing device is required.

[0005] Conventional fuser rollers are thin-walled, hollow-pipe metal rollers with a heater such as a halogen lamp installed inside, which generates heat to heat the entire roller. However, there is an air layer between the roller base and the lamp, and heat is transferred to the fuser roller by radiation, resulting in poor heating efficiency.

[0006] On the other hand, there has been active technological development in the past regarding a fixing method in which a heat generating layer such as an electric resistor is provided on the inner peripheral surface of the fixing roller via an insulating layer, and this is used to generate heat, as this fixing device is capable of shortening the start-up time by approximately 20 to 30% compared to the halogen lamp method because heat is transferred by thermal conduction rather than radiation.

[0007] For example, Patent Document 1 discloses an insulating layer provided on the inner surface of the core metal of a heat roller, on which a heat-generating layer is formed from a material with PTC characteristics (the characteristic of a conductor whose resistance value increases with increasing temperature). Patent Document 2 also discloses a technology in which conductive fibers and carbon nanotubes are mixed as the material for the heat-generating layer. Patent Document 3 also proposes a heat-generating layer that mixes metal powder and carbon nanotubes. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-134126 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-37213 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-133673 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the case of the heating layer of Patent Document 1, it was difficult to find a material with PTC characteristics around 190°C suitable for fixing. Furthermore, in the heating layer of Patent Document 2, the conductive fiber is a mixture of graphite fiber and carbon black or CNT, but the resistance value of the heating layer changes depending on the environmental humidity due to the moisture absorption of carbon black in high humidity. Therefore, the inventors have confirmed that mixed heating layers cannot be used due to their different heat generation rates. Patent Document 3 also proposes mixing metal powder with CNT. However, it was not possible to uniformly disperse multiple materials with different specific gravities to obtain a uniform coating, and the resistance value on the heating roller could not be made uniform. The inventors speculate that uneven dispersion caused the uneven heat generation. An example is also described in which CNT alone is blended at 30 (VOL%) as a conductive filler, but those skilled in the art will recognize that dispersion is difficult.

[0010] The present invention has been made in consideration of the above circumstances, and its purpose is to provide a heat-generating roller that can have low resistance, maintain sufficient performance for a long period of time, and shorten the warm-up time. [Means for solving the problem]

[0011] That is, according to the present invention, the following heating roller is provided. [1] A heating roller in which a conductive layer of a heating resistor is laminated on a cylindrical metal roller via an insulating layer, and power is supplied to the heating resistor to generate heat, wherein the heating resistor contains at least multi-walled carbon nanotubes, a silica-containing epoxy resin, and an organometallic compound, and the organometallic compound is at least one compound selected from the group consisting of organometallic chelate compounds and metal alkoxides containing at least one metal selected from the group consisting of titanium, zirconium, and aluminum, and the coating film of the conductive layer after drying contains 25% by mass or more and 65% by mass or less of the multi-walled carbon nanotubes, 30% by mass or more and 70% by mass or less of the silica-containing epoxy resin, and 1.5% by mass or more and 14% by mass or less of the organometallic compound, and the ratio of the multi-walled carbon nanotubes to the silica-containing epoxy resin is in the range of 2.5:7.5 to 7:3, and the ratio of the silica-containing epoxy resin to the organometallic compound is in the range of 5:1 to 20:1. [2] The heating roller according to [1], wherein the multi-walled carbon nanotubes have an average length of 5 μm or more and 900 μm or less. [3] The heating roller according to [1] or [2], wherein the conductive layer has a dried coating film containing 34% by mass or more and 60% by mass or less of multi-walled carbon nanotubes. [4] The heating roller according to any one of [1] to [3], wherein the surface resistance of the heating resistor is 1.5 Ω / sq or more and 100 Ω / sq or less. [5] The heating roller according to any one of [1] to [4], wherein the time required for the surface temperature of the heating roller to reach 200°C from 25°C is 30 seconds or less. [6] The heating roller according to any one of [1] to [5], wherein the conductive layer has a thickness of 1 μm or more and 100 μm or less. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a heat roller that can have a low resistance, can maintain sufficient performance for a long period of time, and can shorten the warm-up time. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a cross-sectional view illustrating an example of a heating roller according to the present embodiment. [Figure 2] 1 is a schematic diagram illustrating an example of an image forming apparatus using a heating roller according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0015] <Heating roller> As shown in Fig. 1, the heating roller 100 according to this embodiment has a conductive layer 1 of a heating resistor laminated on a cylindrical metal roller 3 via an insulating layer 2, and power is supplied to the heating resistor to generate heat. In the heating roller 100 shown in Fig. 1, the conductive layer 1 of the heating resistor is laminated on the inner surface of the metal roller 3 via the insulating layer 2, but this is not limiting. The conductive layer 1 of the heating resistor may also be laminated on the outer surface of the metal roller 3 via the insulating layer 2. In the technical field, carbon nanotubes (hereinafter also referred to as "CNTs") refer to carbon materials with a cylindrical graphene structure. The inventors of the present invention have conducted extensive research into heat-generating materials, which have many problems, and have finally developed a heat-generating material with high stability in both resistance and dispersibility. The heat-generating resistor, which serves as a conductive layer, contains at least multi-walled carbon nanotubes, a silica-containing epoxy resin, and an organometallic compound. The dried coating of the conductive layer contains 25% to 65% by mass of the multi-walled carbon nanotubes, 30% to 70% by mass of the silica-containing epoxy resin, and 1.5% to 14% by mass of the organometallic compound. The ratio of the multi-walled carbon nanotubes to the silica-containing epoxy resin is in the range of 2.5:7:5 to 7:3, and the ratio of the silica-containing epoxy resin to the organometallic compound is in the range of 5:1 to 20:1. According to this embodiment, it is possible to provide a heat-generating roller that can achieve low resistance, maintain sufficient performance for a long period of time, and shorten the warm-up time. Furthermore, it is possible to improve upon the problems of conventional heat-generating materials, such as resistance stability due to humidity and high-temperature resistance, as well as high durability due to no resistance change during continuous use. Furthermore, by obtaining a heat-generating material with a fast temperature rise rate, which was the ultimate goal, it is possible to eliminate the need for standby heating, a major issue for image forming devices, and contribute to energy conservation. From the viewpoint of warm-up time, it is preferable that the time required for the surface temperature of the heating roller 100 to reach 200° C. from 25° C. be 30 seconds or less.

[0016] <Metal roller> The metal roller 3 is basically the same as a conventionally known shaft, and is solid or hollow and cylindrical. It is made of metal such as iron, aluminum, stainless steel, or brass. The metal roller 3 is also called a "core metal" and has good thermal conductivity.

[0017] <Insulating layer> The insulating layer 2 is a layer that exists between the metal roller 3 and the conductive layer 1, and its purpose is to prevent current from flowing through the metal roller 3. It is preferable to use a material with excellent electrical insulation properties, such as polyamide resin, polyimide resin, polycarbonate resin, or polyacetal resin, for the insulating layer 2. As a coating method, a method can be used in which the resin is dissolved in an organic solvent such as N-methylpyrrolidone and then coated by a conventionally known method, such as spray coating or dipping.

[0018] <Conductive layer> The conductive layer 1 generates heat due to resistance loss when current is applied from power supply electrodes (not shown) at both ends of the heating roller 100. The conductive layer 1 in this embodiment contains at least multi-walled carbon nanotubes, silica-containing epoxy resin, and an organometallic compound. Furthermore, since the conductive layer 1 in this embodiment does not contain any fillers other than carbon material, the resistance value is uniform regardless of the coating direction. Furthermore, the high concentration of CNTs enables low resistance. The average thickness of the conductive layer 1 is preferably in the range of 1 μm to 100 μm, and more preferably 8 μm to 80 μm. If the average thickness exceeds the upper limit, the resistance value will not decrease beyond a certain level, which is wasteful. On the other hand, if the average thickness is below the lower limit, it is difficult to form a uniform film, resulting in uneven coating loss after drying, making it difficult to control the resistance value and causing temperature unevenness. The conductive layer 1 can be formed by preparing a coating composition for the heating resistor, applying the coating composition, and drying it. As the coating method, a conventionally known method such as spray coating or dipping can be used.

[0019] The surface resistance of the conductive layer 1 (heat-generating resistor) is preferably 1.5 Ω / sq to 100 Ω / sq, more preferably 3 Ω / sq to 40 Ω / sq. If the surface resistance exceeds the upper limit, the resistance is too high and it tends to take a long time to increase the temperature. On the other hand, if the surface resistance is below the lower limit, the resistance tends not to decrease below a certain level due to the characteristics of the paint. Furthermore, because the heating area of ​​the heating roller varies depending on the required paper size, and the voltage or power limits that can be supplied to the heating roller of an image forming device vary depending on the model, it is more preferable to maintain the target surface resistance within a range of ±5% Ω / sq. Exceeding this range increases the resistance and prolongs the temperature rise time. On the other hand, a lower resistance results in a larger current flow and increased power consumption, making the heating roller less energy-efficient. For example, with an A4 landscape paper size, a 300mm inter-electrode distance, a 100V input voltage, a 1,200W power consumption limit, and an iron metal roll (0.5mm thick, 45mm outer diameter), a surface resistance of 3.8 Ω / sq. ±5% for the conductive layer 1 allows for stable temperature rise with a constant power consumption. Furthermore, with an input voltage of 200V under these conditions, a surface resistance of 15.4 Ω / sq. ±5% allows for stable temperature rise with a constant power consumption. Furthermore, for example, in the case of an A4 portrait paper size, an inter-electrode distance of 230 mm, an input voltage of 200 V, a power consumption limit of 800 W, and a metal roll made of iron (thickness 0.5 mm, outer diameter Φ45 mm), a surface resistance value of the conductive layer of 32 Ω / sq ±5% enables a stable temperature rise with a constant power consumption. The change in resistance value of the conductive layer 1 due to moisture absorption is preferably 5% or less, and more preferably 1% or less. If the change in resistance value exceeds the above amount, when used in a humid environment, the resistance value will increase and the temperature rise rate will slow down. Furthermore, when the moisture is removed by heating, the temperature rise rate will return to normal, and this will cause variations in the control of the temperature rise time due to moisture absorption. The conductive layer 1 used in the heating roller 100 according to this embodiment is not affected by moisture absorption because none of the materials used are hygroscopic.

[0020] <Silica-containing epoxy resin> In the coating composition for the heating resistor used in this embodiment, the silica-containing epoxy resin is preferably a mixture of a silicone resin having at least one silicon-containing group and an epoxy resin.

[0021] The silicone resin having a silicon-containing group is preferably a silicone resin having at least one silicon-containing group selected from the group consisting of an alkoxysilyl group, an alkoxysilylene group, and a siloxane bond. The silicone resin having a silicon-containing group is preferably formed by addition polymerization of a vinyl monomer having an alkoxysilyl group or an alkoxysilylene group.

[0022] Examples of epoxy resins include glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, alicyclic epoxy resins, modified epoxy resins obtained by modifying these epoxy resins with at least one selected from alkylphenols and fatty acids, alkylphenyl glycidyl ethers (e.g., reaction products of alkylphenols and epichlorohydrin), and alkylphenol novolac type epoxy resins (e.g., reaction products of novolac type alkylphenol resins and epichlorohydrin).

[0023] The content of the silica-containing epoxy resin in the coating film of the conductive layer 1 after drying must be 30% by mass or more and 70% by mass or less, preferably 30% by mass or more and 65% by mass or less, more preferably 35% by mass or more and 62% by mass or less, and even more preferably 40% by mass or more and 60% by mass or less. If the content exceeds the upper limit, the multi-walled CNT content in the coating film will be low, which may result in insufficient conductivity and increased resistance. On the other hand, if the amount range is below the lower limit, sufficient coating film strength may not be obtained, and the multi-walled CNTs may not be stably fixed in the coating film.

[0024] <Organometallic compounds> Examples of organometallic compounds include water-soluble organometallic chelate compounds or metal alkoxides containing metal components such as titanium, zirconium, and aluminum. By using this organometallic compound, the multi-walled CNTs can be stably fixed to the heating roller.

[0025] The content of the organometallic compound in the coating film of the conductive layer 1 after drying must be 1.5% by mass to 14% by mass, preferably 1.5% by mass to 13% by mass, more preferably 2% by mass to 12% by mass, and even more preferably 4% by mass to 6.5% by mass. If the content exceeds the upper limit, the presence of components other than the required amount may relatively reduce the coating film strength, and the increased amount of excess material may tend to reduce conductivity and increase manufacturing costs. On the other hand, if the amount range is below the lower limit, crosslinking may be insufficient, resulting in insufficient coating film strength and inability to stably fix multi-walled CNTs in the coating film, which may tend to reduce conductivity.

[0026] The ratio of silica-containing epoxy resin to organometallic compound in the coating film after drying of the conductive layer 1 must be in the range of 5:1 to 20:1, more preferably 6:1 to 18:1, and even more preferably 8:1 to 12:1. If there is too much silica-containing epoxy resin, the coating film will not have sufficient strength, making it difficult to stably fix the multi-walled CNTs in the coating film. Furthermore, if there is too much organometallic compound, the presence of components other than the required amount may relatively reduce the coating film strength and increase production costs.

[0027] <Multi-walled carbon nanotubes> The average length of the multi-walled carbon nanotubes is usually preferably 1 μm or more and 900 μm or less. When used as a constituent material of this embodiment, the average length of the multi-walled CNTs is more preferably 5 μm or more and 300 μm or less from the viewpoint of dispersibility, and is particularly preferably 5 μm or more and 200 μm or less (more preferably 5 μm or more and 50 μm or less) from the viewpoint of being able to further reduce the surface resistivity of the coating film formed. If the average length of the multi-walled CNTs is below the lower limit, sufficient conductivity may not be obtained, and the resistance value of the heating roller may increase. Furthermore, if the average length of the multi-walled CNTs exceeds the upper limit, uneven dispersion may occur, and the resistance value of the heating roller may not be stable.

[0028] The content of multi-walled CNTs must be 25% by mass or more and 65% by mass or less, preferably 29% by mass or more and 65% by mass or less, and more preferably 34% by mass or more and 60% by mass or less. By keeping the content of multi-walled CNTs within this range, the multi-walled CNTs can be more stably dispersed. If the content of multi-walled CNTs is too low, sufficient conductivity may not be obtained, and the resistance value of the heating roller may increase. On the other hand, if the content of multi-walled CNTs is too high, aggregation and viscosity increase may occur, which may slightly reduce the physical properties of the formed coating film, such as strength and conductivity.

[0029] The ratio of multi-walled carbon nanotubes to silica-containing epoxy resin in the coating film after drying of the conductive layer 1 must be in the range of 2.5:7.5 to 7:3, preferably in the range of 3:7 to 7:3, and more preferably in the range of 3.5:6.5 to 6.5:3.5. If there are too many multi-walled carbon nanotubes, sufficient coating strength may not be obtained, and the multi-walled CNTs may not be stably fixed in the coating film. Furthermore, if there is too much silica-containing epoxy resin, the multi-walled CNT content in the coating film may be too low, resulting in insufficient conductivity and an increase in resistance.

[0030] <Dispersant> The dispersant is a component for dispersing multi-walled CNTs in a liquid medium. Examples of dispersants that can be used include anionic, cationic, nonionic, or amphoteric surfactants, polymer dispersants, and cellulose derivatives. Among these, it is preferable to use at least one of polymer dispersants and cellulose derivatives as the dispersant.

[0031] Examples of cellulose derivatives include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and metal salts thereof. Among these, carboxymethyl cellulose and carboxymethyl cellulose sodium salt are preferred. Furthermore, it is preferable that the viscosity of a 1% by mass aqueous solution of the cellulose derivative is 20 mPa·s or more and 500 mPa·s or less, and that the degree of etherification is 0.5 or more and 0.9 or less. The use of such a cellulose derivative can improve the dispersion of multi-walled CNTs and storage stability.

[0032] The polymer dispersant is preferably a modified polyester polymer, a polymer having structural units derived from (meth)acrylonitrile and structural units derived from (meth)acrylic acid, or a polyurethane polymer having a polycaprolactone chain. The polymer dispersant is also preferably a polymer having functional groups at least partly neutralized with an alkali.

[0033] <Other additives> The conductive layer 1 of this embodiment may further contain additives or resins. Examples of additives include dyes, pigments, UV absorbers, light stabilizers, antioxidants, leveling agents, antifoaming agents, preservatives, mildew inhibitors, photopolymerization initiators, and other pigment dispersants. Examples of resins include polyolefin resins, polyhalogenated olefin resins, polyester resins, polyamide resins, polyimide resins, polyether resins, polyvinyl resins, polystyrene resins, polyvinyl alcohol resins, polymethacrylate resins, polyurethane resins, polyepoxy resins, polyphenol resins, polyurea resins, and polyethersulfone resins.

[0034] <Image forming device> FIG. 2 shows an image forming apparatus using the heating roller 100 according to this embodiment. 2, the image forming apparatus 200 includes a heating roller 100, a fixing belt 5, a fixing roller 6, a cleaning roller 7, a separation plate 8, and a pressure roller 9. The heating roller 100 is provided with a temperature control member 101. The fixing belt 5 is heated by a heating roller 100. The temperature of the heating roller 100 is controlled by a temperature control member 101. A fixing nip portion N is provided between the fixing roller 6 and the pressure roller 9. The transfer material P onto which the toner image T has been transferred is transported to the fixing nip portion N provided between the fixing roller 6 and the pressure roller 9 and thermally fixed. Dirt on the surface of the fixing roller 6 is cleaned by a cleaning roller 7. A separation plate 8 prevents the transfer material P from wrapping around the fixing roller 6.

[0035] 1 has been described using the heating roller 100 in which an insulating layer 2 is provided on the inside of the metal roller 3 and a conductive layer 1 is provided thereon, but the present invention is not limited to this. For example, the present invention may be adopted in a fixing roller in which a release layer is provided on the conductive layer 1 as disclosed in Patent Document 2, a heat-generating belt for belt fixing as also disclosed in Patent Document 3, or a planar or linear heating element made of a heat-resistant insulating material such as a metal flat plate or rod-shaped ceramic. [Example]

[0036] The present invention will be described in more detail below using examples, although the technical scope of the present invention is not limited to these examples.

[0037] <Examples 1 to 3 and Comparative Examples 1 to 3: Methods for Making Heating Rollers> A polyimide resin (trade name "U Imide Varnish AR" manufactured by Unitika Co., Ltd.) diluted with NMP (N-methylpyrrolidone) was applied multiple times using a spray painter to form an insulating layer on the inner surface of an iron core with a roller diameter of 45 mm, an inner diameter of 44 mm, and a length of 400 mm, creating a 40 μm-thick coating. After application, the coating was heated to approximately 300°C to complete imidization. Next, seven types of conductive layers were created, each with a different mass percentage of CNTs in the dried coating, as shown in Table 1 below. Specifically, in Example 1, 30 parts by mass of a polymer dispersant (trade name "TEGO Dispers 670" manufactured by Evonik Co., Ltd., solids content 40%) was dissolved in 64 parts by mass of propylene glycol monomethyl ether. 12 parts by mass of multi-walled CNTs with an average length of 10 μm and an average thickness of 50 nm were added to the solution, and the mixture was stirred and homogenized using a dissolver to create a slurry. This slurry was dispersed in a bead mill using glass beads (φ1.0 mm) as the crushing media at 300 rpm for 60 minutes to obtain a CNT dispersion. Next, 30 parts by mass of the resulting CNT dispersion, 6 parts by mass of a silica-containing epoxy resin (a mixture of acrylic silicone resin and epoxy resin), and 0.6 parts by mass of an organometallic compound (aluminum monoacetylacetonate bisethylacetoacetate) were mixed to obtain a coating composition for forming a conductive layer. This coating composition was applied multiple times using a spray coater to produce a 60 μm thick conductive layer. Next, power supply electrodes were provided on both ends of the roller, which can be formed using metal foil, conductive paste, etc. Here, silver paste was dispensed from the nozzle of a dispenser, and the electrodes were prepared at a distance of 300 mm.

[0038] <Examples 4 to 6 and Comparative Examples 4 to 6> Conductive layers were prepared in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3 using the blending amounts shown in Table 1, except that the multi-walled CNTs were changed to have an average length of 100 μm and an average thickness of 8 nm.

[0039] <Comparative Example 7> Except for changing to a polyimide resin (product name "U-Varnish-S", manufactured by UBE Corporation), conductive layers were prepared in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3, using the blending amounts shown in Table 1. However, a good coating film could not be prepared, and the resistance value could not be measured.

[0040] [Table 1]

[0041] <Method for measuring dispersibility> Dispersibility was evaluated by leaving the mixture for a certain period of time after dispersion and then visually inspecting the surface after painting, according to the following evaluation criteria. ○: No abnormalities. △: The surface is slightly rough. ×: Aggregation occurs and the surface becomes rough.

[0042] <How to measure resistance> The surface resistance was calculated by measuring the resistance between the power supply electrodes using a HIOKI RM3544 resistance meter and calculating the surface resistance from the aspect ratio of the distance between the electrodes and the circumferential distance. The surface resistance of the conductive layer was evaluated according to the following evaluation criteria. ◯: The surface resistance is within the range of 3 Ω / sq to 40 Ω / sq. ×: The surface resistance is less than 3 Ω / sq or more than 40 Ω / sq.

[0043] <Method for measuring the time it takes for heat to reach 200°C> A voltage of 100 V is applied to the electrodes on both ends of the roll to supply power. The roll surface temperature was measured using a thermograph manufactured by Testo, and the time it took for the average temperature within a 250 mm range at the center of the roll to reach 200°C was measured using a stopwatch. The measurement started at 25°C, and if the initial temperature was other than 25°C, it was measured by converting it from the temperature rise trend. The emissivity of the thermograph was determined to be 0.45 after correlating it with a contact thermometer in advance. The heat generation area of ​​the heating roller used as an example here is 300 mm from the center of the roll width, and the effective heat generation range is 250 mm from the center.

[0044] Looking at the results in Table 1, Comparative Examples 1 and 4, which contain small amounts of CNT, have good dispersibility but low resistance and take a long time to heat up. Conversely, Comparative Examples 2 and 5, which contain 70% CNT by mass, have poor dispersibility and aggregation, resulting in uneven coating and uneven temperature distribution on the roller surface, making them unsuitable for practical use. Furthermore, Comparative Examples 3 and 6, which contain large amounts of organometallic compound, have good dispersibility but low resistance and take a long time to heat up. Looking at both the dispersibility and resistance characteristics of Examples 1 to 6 and Comparative Examples 1 to 6, it can be seen that a particularly preferable CNT amount is between 34% and 60% by mass. [Explanation of symbols]

[0045] 1...Conductive layer 2...Insulating layer 3...Metal roller 100...heating roller 101...Temperature control member 5...Fuser belt 6...Fuser roller 7...Cleaning roller 8...Separator plate 9...Pressure roller N: Fixing nip P...Transfer material T...Toner image 200...Image forming apparatus

Claims

1. 1. A heating roller comprising a cylindrical metal roller on which a conductive layer of a heating resistor is laminated via an insulating layer, and which generates heat by supplying power to the heating resistor, wherein the heating resistor contains at least multi-walled carbon nanotubes, a silica-containing epoxy resin, and an organometallic compound, and the organometallic compound is at least one compound selected from the group consisting of organometallic chelate compounds and metal alkoxides, which contain at least one metal selected from the group consisting of titanium, zirconium, and aluminum, and a coating film of the conductive layer after drying contains 25% by mass or more and 65% by mass or less of the multi-walled carbon nanotubes, 30% by mass or more and 70% by mass or less of the silica-containing epoxy resin, and 1.5% by mass or more and 14% by mass or less of the organometallic compound, and the ratio of the multi-walled carbon nanotubes to the silica-containing epoxy resin is in the range of 2.5:7.5 to 7:3, and the ratio of the silica-containing epoxy resin to the organometallic compound is in the range of 5:1 to 20:

1.

2. 2. The heating roller according to claim 1, wherein the multi-walled carbon nanotubes have an average length of 5 [mu]m or more and 900 [mu]m or less.

3. The heating roller according to claim 1 , wherein the conductive layer contains 34% by mass or more and 60% by mass or less of multi-walled carbon nanotubes in a coating film after drying.

4. 2. The heating roller according to claim 1, wherein the surface resistance of the heating resistor is 1.5 Ω / sq or more and 100 Ω / sq or less.

5. 2. The heating roller according to claim 1, wherein the time required for the surface temperature of the heating roller to reach 200[deg.] C. from 25[deg.] C. is 30 seconds or less.

6. 6. The heating roller according to claim 1, wherein the conductive layer has a thickness of 1 [mu]m or more and 100 [mu]m or less.

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