JP6155910B2 - Method for manufacturing tubular heating element - Google Patents

Description

  The present invention relates to a method for manufacturing a tubular heating element.

  The image forming apparatus transfers a toner image formed on a photoconductor to a recording medium such as plain paper, and heat-fuses the toner to fix the toner image on the recording medium, thereby forming an image on the recording medium. To do. The heat fusion is generally performed by a pressure member that presses the recording medium toward the fixing member and a fixing member that heats the recording medium. As the fixing member, a flexible tubular heating element (heating belt) is known.

  In the method of manufacturing the tubular heating element, a dope liquid containing polyamic acid and a conductive filler is applied to the inner peripheral surface of a cylindrical mold, an excitation coil is disposed on the outer peripheral surface side of the mold, and induction is performed. A method for producing a tubular heating element having a tubular heating layer composed of polyimide, by drying the coating film of the dope solution by heating the mold by heating, further imidizing polyamic acid by heating, As a method, a method using a cylindrical mold in which a specific plating process is performed on the outer peripheral surface and the inner peripheral surface is known (for example, see Patent Documents 1 and 2).

JP 2004-181731 A JP 2008-200939 A

  In the above method, the mold is heated by induction heating, and the coating film is heated by transferring the heat of the mold to the coating film in contact with the mold, so that the heat generating layer is formed. For this reason, the temperature difference in the thickness direction of a coating film arises in the coating film, such as the temperature of the surface of the metal mold | die side in a coating film is high, and the temperature of the surface inside a coating film or the other side is low. Therefore, the degree of drying in the thickness direction of the coating film varies, and the thickness uniformity of the heat generating layer and the uniformity of electrical resistance may be reduced.

  An object of this invention is to provide the manufacturing method of the tubular heating element excellent in the thickness of a heat-generating layer, and the uniformity of electrical resistance.

  A method of manufacturing a tubular heating element according to the present invention is a method of manufacturing a tubular heating element having a tubular heating layer, and a heat-resistant resin or a heat-resistant resin material and a conductive filler are provided on a peripheral surface of a cylindrical mold. An application of an exothermic layer material liquid containing a coating film to form a coating film, and an alternating current is passed through an excitation coil arranged in non-contact with the coating film on the outer peripheral side or inner peripheral side of the mold. And drying the coating film by induction heating. The conductive filler includes a metal filler.

  According to the present invention, not only the mold but also the metal filler in the coating film is heated by induction heating, so that the temperature difference in the thickness direction of the coating film is alleviated. Therefore, the present invention can provide a tubular heating element that is excellent in the thickness of the heat generating layer and the uniformity of electric resistance, compared to the method of drying the coating film by heat transfer from the mold by induction heating.

1A is a diagram schematically showing an example of a tubular heating element according to the present invention, and FIG. 1B is a longitudinal sectional view of the tubular heating element of FIG. 1A. It is a figure which shows roughly the state by which the exciting coil has been arrange | positioned at the outer peripheral side of a cylindrical metal mold | die. FIG. 3A is a diagram schematically showing how a conventional coating film is heated by induction heating, and FIG. 3B is a diagram schematically showing how the coating film in the present invention is heated by induction heating. . 4A is a schematic front view of an example of a fixing device having a tubular heating element as a heat generating belt in the present invention, and FIG. 4B is a schematic side view of the fixing device of FIG. FIG. 5 is a diagram schematically showing a configuration of an example of an image forming apparatus having the fixing device of FIG. 4.

  The manufacturing method of the tubular heating element according to the present invention includes the following first step and second step. The first step is to apply a heat generating resin or a heat generation layer material liquid (hereinafter also referred to as “dope liquid”) containing a heat resistant resin or a heat resistant resin material and a conductive filler to the peripheral surface of a cylindrical mold. It is a process of forming a coating film. In the second step, the excitation coil arranged in a non-contact manner with respect to the coating film on the outer peripheral side of the mold or the excitation coil arranged in a non-contact manner with respect to the coating film on the inner peripheral side of the mold In this process, an alternating current is applied and the coating film is dried by induction heating.

  An example of the tubular heating element manufactured by the present invention is shown in FIG. The tubular heating element 10 has a heating layer 12 and an electrode 14. The shape of the heat generating layer 12 is tubular. The heat generating layer 12 is configured by dispersing a conductive filler in a heat resistant resin such as polyimide. The conductive filler contains a metal filler. The shape of the electrode 14 is also tubular. The electrode 14 is disposed at the end of the outer peripheral surface in the axial direction of the heat generating layer 12. The electrode 14 is bonded to the outer peripheral surface of the heat generating layer 12 via, for example, a conductive adhesive 16.

[First step]
The coating film is formed by applying a dope solution to the peripheral surface of a cylindrical mold. A tubular coating film is formed by applying the dope solution. The cylindrical mold may be a mold that is heated by induction heating described later and has heat resistance that can withstand the heating. The material of the cylindrical mold preferably contains a magnetic material from the viewpoint of increasing the heating amount during induction heating. Examples of cylindrical mold materials include stainless steel, iron, nickel, copper, aluminum and zinc. Among them, iron is preferable from the viewpoint of further increasing the heating efficiency in induction heating because it causes hysteresis loss in induction heating.

  The dope solution may be applied to the inner peripheral surface of the cylindrical mold, or may be applied to the outer peripheral surface of the cylindrical mold. The coating film can be formed by a known method that can apply the material of the heat generating layer to the cylindrical mold, such as dip coating, spiral coating, and roll coating. The thickness of the coating film is determined according to the desired thickness of the heat generating layer 14, and is, for example, 50 to 150 μm in dry film thickness.

  The dope solution contains a heat resistant resin or a heat resistant resin material and a conductive filler. The heat-resistant resin is a heat-resistant resin that forms a film formed by induction heating described later, and is, for example, a thermosetting resin. One or more heat resistant resins may be used. Examples of the heat resistant resin include polyimide, polyamideimide, polyphenylene sulfide, polyarylate, polysulfone, polyethersulfone, polyetherimide, and polyetheretherketone.

  The heat-resistant resin material is a monomer, oligomer, or polymer that becomes the heat-resistant resin by induction heating described later. The heat resistant resin material is appropriately determined according to the type of the heat resistant resin. For example, when the heat resistant resin is polyimide, examples of the heat resistant resin material include polyamic acid. Polyamic acid is a polymer compound having a structure of a reaction product of diamine and tetracarboxylic dianhydride, for example, at least one aromatic diamine and at least one aromatic tetracarboxylic dianhydride, It is obtained by polymerizing in a solvent described later.

  Examples of the aromatic diamine include paraphenylene diamine, metaphenylene diamine, 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4 ′. -Biphenyl, 3,3'-dimethoxy-4,4'-biphenyl, 2,2-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 3,3'-diaminodiphenylmethane, 4,4'-diamino Diphenylmethane, 2,2-bis- (4-aminophenyl) propane, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfide, 4,4′-diaminodiphenyl Sulfide, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4 -Diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 1,3-bis (3-amino Phenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4 -Aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis (3-aminophenyl) 1,1,1,3,3,3-hexa Fluoropropane, 2,2-bis (4-aminophenyl) 1,1,1,3,3,3-hexafluoropropane Beauty 9,9-bis include (4-aminophenyl) fluorene.

  Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic acid dianhydride. Anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic Acid dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic acid dihydrate, 2,3,3 ′, 4 ′ -Benzophenone tetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (2,3-dicarboxy Phenyl) methane Anhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ) Ethane dianhydride, 2,2-bis [3,4- (dicarboxyphenoxy) phenyl] propane dianhydride, 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride, oxydiphthalic anhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) sulfoxide dianhydride, thiodiphthalic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 9,9-bis (3,4-di Carboxymethyl phenyl) fluorene dianhydride and 9,9-bis [4- (3,4'-dicarboxyphenoxy) phenyl] fluorene dianhydride are included.

  The conductive filler forms a conductive path during energization in the heat generating layer. The heat generating layer generates an amount of heat corresponding to the electric resistance generated during energization when energized. The conductive filler includes a metal filler. A metal filler heats the said coating film from the inside at the time of the induction heating mentioned later, relieves the temperature difference in the thickness direction of a coating film, and contributes to elimination of the dispersion | variation in the thickness of a heat generating layer.

  The lower limit value of the content of the metal filler in the dope liquid can be determined from the viewpoint of obtaining the effect of relaxing the temperature difference. From such a viewpoint, the content of the metal filler is preferably 20% by volume or more with respect to the heat resistant resin or the heat resistant resin material. Further, the content of the conductive filler in the dope liquid can be determined from the viewpoints of the coating property of the dope liquid and the strength of the tubular heating element provided by the resin (preventing cracking of the tubular heating element). From such a viewpoint, the content of the conductive filler is preferably 45% by volume or less with respect to the heat resistant resin or the heat resistant resin material.

  One or more metal fillers may be used. The particle shape of the metal filler is not particularly limited, and may be fibrous or granular. Furthermore, it is preferable that the metal filler is a magnetic material because the amount of heating during induction heating described later increases. Examples of the metal filler material include stainless steel, iron, nickel, copper and aluminum. Among these, stainless steel and iron are preferable from the viewpoint of further increasing the heating efficiency in induction heating as described above.

  In addition, the particle shape of the metal filler can be appropriately determined within a range where the effects of the present invention can be obtained. For example, the particle shape of the metal filler is fibrous, so that when the coating film is dried, the coating film is uniformly heated in both the surface direction and the thickness direction. It is preferable from the viewpoint of further improving the conductivity and the viewpoint of further improving the uniformity of conductivity of the tubular heating element. On the other hand, from the viewpoint of ensuring the smoothness of the heating element surface, a smaller aspect ratio is preferable. From the above viewpoint, the aspect ratio of the metal filler is preferably 1.5 to 15.0, and more preferably 2 to 8. Furthermore, from the above viewpoint, the diameter of the metal filler is preferably 0.5 to 30 μm, and the length of the metal filler is preferably 5.0 to 1000 μm.

  For the diameter and length of the metal filler, for example, the metal filler is photographed at 500 times using a scanning electron micrograph, and the diameter and length of at least 500 metal fillers are measured from the image captured by the scanner. It is calculated as an average value of the respective measured values obtained in this way. The aspect ratio of the metal filler is obtained by dividing the length (A) of the metal filler by the diameter (B) of the metal filler (A / B).

  The conductive filler may further contain a nonmetallic filler as long as the effects of the present invention are obtained. Examples of non-metallic fillers include carbon black, graphite and carbon fiber.

  The dope liquid may further contain a heat-resistant resin or a heat-resistant resin material and a material other than the conductive filler as long as the effects of the present invention are obtained. Other materials may be one kind or more. Examples of other materials include solvents, leveling agents and viscosity modifiers. Examples of solvents include amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone; γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone Cyclic ester solvents such as α-methyl-γ-butyrolactone; carbonate solvents such as ethylene carbonate and propylene carbonate; glycol solvents such as triethylene glycol; m-cresol, p-cresol, 3-chlorophenol, 4-chlorophenol Phenolic solvents such as; acetophenone; 1,3-dimethyl-2-imidazolidinone; sulfolane; and dimethyl sulfoxide. The content of the solvent in the dope solution can be appropriately determined from the viewpoint of improving the coating property of the dope solution.

[Second step]
An excitation coil is disposed in the mold on which the coating film is formed. FIG. 2 is a diagram schematically showing a state in which an exciting coil is arranged on the outer peripheral side of a mold on which a coating film is formed. A coating film 24 is formed on the outer peripheral surface of the cylindrical mold 22. On the outer peripheral side of the mold 22, an exciting coil 26 is disposed in a non-contact manner with respect to the coating film 24. A high frequency power supply 28 is connected to the excitation coil 26.

  A mold 22 is inserted in the exciting coil 26. The exciting coil 26 is arranged in non-contact with the coating film 24. Thus, the exciting coil 26 is disposed on the outer peripheral side of the mold 22. The shape of the exciting coil 26 is a spiral shape (string winding shape) in which the distance from the outer peripheral surface of the mold 22 or the surface of the coating film 24 to the exciting coil 26 is constant. Further, the exciting coil 26 protrudes from the end of the coating film 24 in the axial direction of the mold 22.

  If the distance between the exciting coil 26 and the outer peripheral surface of the mold 22 or the surface of the coating film 24 is too large, the coating film 24 is not heated sufficiently, and if it is too small, the exciting coil 26 contacts the coating film 24. 24 is easily damaged. From such a viewpoint, the interval is preferably 10 to 30 mm.

  The diameter of the wire constituting the exciting coil 26 can be appropriately determined within a range in which the effect of the present invention can be obtained, and is, for example, 3 to 10 mm. The pitch of the exciting coil 26 can also be appropriately determined within a range in which the effect of the present invention can be obtained, and is, for example, 15 to 100 mm. The “pitch of the excitation coil 26” is a distance between the centers of the adjacent wires. It is possible to adjust the amount of induction heating by the pitch. When the pitch is decreased, the heating amount is increased, and when the pitch is increased, the heating amount is decreased.

  By the way, at the end of the mold 22, heat radiation tends to occur from the beginning, and the temperature of the mold 22 tends to be low. From this point of view, the pitch of the exciting coil 26 may be constant, but as shown in FIG. 2, the end portion 241 of the coating film 24 is small and the other portion (center portion) of the coating film 24 is small. Then, it is preferable that it is large. That is, it is preferable that the exciting coil 26 has a small pitch portion 261 facing each of both end portions 241 and 241 of the coating film 24 and a large pitch portion 262 therebetween. Thereby, the state in which the drying of the end portion 241 is promoted as compared with the central portion of the coating film 24 is appropriately maintained, and the thickness of the coating film 24 can be made more uniform.

  The position of the small pitch portion 261 may be a position corresponding to the end portion 241 of the coating film 24 in the axial direction of the mold 22, and may not be the end of the exciting coil 24. The pitch of the small pitch portion 261 and the pitch of the large pitch portion 262 are both the desired mold temperature, the portion corresponding to the small pitch portion 261 (end portion 241), and the portion corresponding to the large pitch portion 262 (painting). It is determined as appropriate according to the desired temperature difference between the central portion of the membrane 24 and the like. The pitch may be determined in consideration of the outer diameter or inner diameter of the mold, the wall thickness, and the like, and is generally difficult to determine, but the pitch of the small pitch portion 261 is, for example, 5 to 30 mm, The pitch of the large pitch part 262 is, for example, 30 to 80 mm. The length of the end 241 in the axial direction of the mold 22 is preferably 20% or less of the total length of the coating film 24.

  An alternating current is supplied from the high frequency power supply 28 to the exciting coil 26 arranged as described above with respect to the mold 22. By this induction heating with an alternating current, the metal filler in the mold 22 and the coating film 24 generates heat, and the coating film 24 is heated and dried. The coating film 24 has lost its fluidity due to drying, and is fixed to the peripheral surface of the mold 22. The alternating current can be determined according to the temperature required for drying the coating film 24. The temperature required for drying the coating film 24 is, for example, 50 to 150 ° C. as the temperature of the mold 22 during induction heating. The high frequency power supply 28 is preferably used from the viewpoint of performing such desired heating. Here, “high frequency” means a frequency of 1 kHz or more.

  The power of the high-frequency current is appropriately determined according to the heating rate of the mold 22 or the coating film 24. For example, if the electric power is too large, heating of the coating film 24 is too strong, and foaming or bumping may occur in the coating film 24. If the electric power is too small, drying of the coating film 24 becomes insufficient, or Variations in the thickness of the coating film 24 may occur. From such a viewpoint, the power of the high-frequency current and the temperature increase rate are appropriately determined.

  A lower oxygen concentration in the induction heating atmosphere is preferable from the viewpoint of suppressing deterioration due to oxidation of the resin. From such a viewpoint, the oxygen concentration is preferably 200 ppm or less, and more preferably 100 ppm or less. The oxygen concentration can be lowered by a usual method such as deaeration or replacement.

  The humidity of the induction heating atmosphere is preferably as low as possible from the viewpoint of preventing hydrolysis of the heat-resistant resin material or the heat-resistant resin. From such a viewpoint, the relative humidity is preferably 50% or less, more preferably 40% or less in terms of relative humidity. The humidity can be adjusted by a known method such as degassing, replacement or drying of the atmospheric gas.

  The exciting coil may be disposed on the inner peripheral side of the mold, that is, inserted into the mold and disposed in a non-contact manner with respect to the coating film. When the coating film is formed on the outer peripheral surface of the mold and the exciting coil is disposed on the inner peripheral side of the mold, the exciting coil is prevented from coming into contact with the coating film and damaging the coating film. Even if the exciting coil is disposed on the opposite side of the coating film across the mold, the mold and the metal filler can be used as long as a desired condition is satisfied, for example, the distance between the mold and the exciting coil is within the above-described range. Both of them can be sufficiently heated by induction heating to properly dry the coating film.

  In addition, a helical excitation coil is preferable from the viewpoint of uniformly generating induction heating, but the shape of the excitation coil is such that an eddy current sufficient for heating the coating film can be generated in the mold and the metal filler. Good. For example, the coil diameter of the exciting coil may or may not be constant. The “coil diameter” is an outer diameter or an inner diameter in the shape of the exciting coil when the exciting coil is viewed along the axial direction. The shape of the exciting coil viewed along the axial direction may be non-circular or polygonal such as rectangular. Furthermore, the exciting coil may not protrude from the end of the coating film in the axial direction of the mold.

  In the second step, the coating film may be dried and fixed to the peripheral surface of the mold, but the coating layer may be further heated by induction heating to complete the heating layer. For example, in the case of a dope coating containing a polyamic acid solution, after heating and drying the coating by induction heating, the coating is further heated by induction heating to imidize the polyamic acid in the coating. It is possible to complete a heat generating layer made of polyimide. However, the further heating for completing the heat generating layer may not be the induction heating described above. Examples of heating methods other than induction heating include known heating methods such as warm air heating using a heated gas and heating using radiant heat from a heater.

[Other processes]
The said manufacturing method may further include other processes other than the 1st process mentioned above and the 2nd process in the range in which the effect of this invention is acquired. Examples of such other steps include a step of rotating a mold, a step of producing an electrode, and a step of producing a layer other than the heat generating layer.

  In the step of rotating the mold, at least during induction heating in the second step, the mold is rotated relative to the excitation coil with the mold axis as the rotation axis. In this step, the mold may be rotated, the excitation coil may be rotated, or both may be rotated. By this step, the coating film can be heated more uniformly in the circumferential direction of the coating film, which is preferable from the viewpoint of further suppressing variation in the thickness of the heat generating layer. From the viewpoint of obtaining the above effect, the rotational speed of the mold is, for example, in the case of a mold having a diameter of 30 mm, the peripheral speed of the mold with respect to the exciting coil is preferably 10 to 100 rpm, and preferably 15 to 50 rpm. More preferred.

  In the step of producing the electrode, for example, a known method for producing the electrode of the heat generating belt in the fixing device of the image forming apparatus can be employed. For example, the electrode can be produced by adhering a thin metal tube to the peripheral surface of the heat generating layer via a conductive adhesive as described above. Alternatively, the electrode can be manufactured by applying a conductive paste to the end of the peripheral surface of the heat generating layer 12.

  As the step of producing the other layer, for example, a known step of producing an intended layer on the peripheral surface of the tube can be employed. Examples of the intended layer include an insulating layer and a release layer that cover the surface of the heat generating layer. The insulating layer can be manufactured using the same material and the same method as the heat generating layer except that the conductive filler is not included. The release layer can be produced by a known method by using a resin material having high liquid repellency such as a fluororesin or silicone.

Next, features of the present invention will be described.
FIG. 3A is a diagram schematically showing a state when a coating film of a dope liquid containing a nonmetallic filler is heated by induction heating. FIG. 3B is a diagram schematically showing a state when a dope liquid containing a metal filler is heated by induction heating.

  When the coating film 34 of the dope liquid containing the nonmetallic filler 31 is dried by induction heating, the thickness of the coating film 34 may vary, and the coating film 34 may be warped. This is thought to be because, as shown by the arrows in FIG. 3A, the coating film 34 is heated by heat transfer from the mold 22 heated by induction heating, resulting in a temperature difference in the thickness direction of the coating film 34. It is done. The variation in the thickness of the coating film 34 and the occurrence of warping cause the variation in the thickness and the electric resistance of the heat-generating layer formed thereafter.

  On the other hand, when the coating film 24 of the dope liquid containing the metal filler 21 is dried by induction heating, the thickness variation and warpage of the coating film 24 as described above are suppressed. This is because, as shown by the arrows in FIG. 3B, not only the mold 22 but also the metal filler 21 is heated during induction heating, so that the temperature difference in the thickness direction of the coating film 24 is alleviated, and the coating film 24. Is considered to be more uniformly heated in the thickness direction. For this reason, since the variation in thickness and the variation in electrical resistance do not occur in the heat generation layer, a heat generation layer with excellent thickness and electrical resistance uniformity can be obtained.

  As described above, a dope solution containing a heat-resistant resin or a heat-resistant resin material and a metal filler is applied to the peripheral surface of a cylindrical mold, and the formed coating film is subjected to induction heating by an exciting coil. By drying, it is possible to obtain a tubular heating element that is excellent in the thickness of the heat generation layer and the uniformity of electrical resistance.

  In addition, as described above, since the temperature of the end portion of the mold becomes lower, the coating film drying speed varies. In this case, if the temperature of the end portion is made higher than the temperature of the central portion to promote drying of the end portion, the variation in the thickness of the coating film is further reduced. This further promotes the drying of the edges in the axial direction of the coating film, thereby further promoting the leveling of the coating film in the axial direction of the mold and further suppressing the variation in the thickness of the coating film in the axial direction. Because it is considered.

  For this reason, the exciting coil includes the two small pitch portions and the large pitch portion described above, and is arranged with respect to the coating film so that the small pitch portion faces each of both end portions of the coating film in the axial direction of the mold. It is even more effective from the viewpoint of obtaining a tubular heating element that is excellent in the thickness of the heating layer and the uniformity of electrical resistance.

  Furthermore, by applying an appropriate centrifugal force to the coating film of the dope solution, the thickness of the coating film in the circumferential direction of the mold can be made more uniform. Therefore, in the above-described second step, the tubular heating element having excellent uniformity of the thickness of the heat generation layer and the electric resistance is obtained by rotating the mold relative to the exciting coil with the mold axis as the rotation axis. From the viewpoint of obtaining the above, it is more effective.

  The tubular heating element manufactured by the above-described manufacturing method is used for use as a deformable heater. For example, in a fixing device or an image forming apparatus having the fixing device, the tubular heating element is preferably used as a heating belt of the fixing device.

[Fixing device]
FIG. 4A is a front view of an example of the fixing device, and FIG. 4B is a side view of the example of the fixing device. As shown in FIG. 4, the fixing device 60 includes a fixing roller 62, a heat generating belt 63, a pressure roller 64, and a power feeding device 65. The heat generating belt 63 corresponds to the tubular heat generating element described above.

  The fixing roller 62 includes a cylindrical cored bar 621 and a resin layer 622 disposed on the peripheral surface thereof. The outer diameter of the resin layer 622 is smaller than the inner diameter of the heat generating belt 63. The fixing roller 62 is disposed inside the heat generating belt 63. The fixing roller 62 is in contact with the inner peripheral surface of the heat generating belt 63 at a part in the circumferential direction of the heat generating belt 63.

  The pressure roller 64 includes a cylindrical cored bar 641 and a resin layer 642 disposed on the peripheral surface thereof. The pressure roller 64 is disposed to face the fixing roller 62 with the heat generating belt 63 interposed therebetween. The pressure roller 64 is disposed so that the outer peripheral surface of the heat generating belt 63 can be pressed toward the fixing roller 62. The pressure roller 64 can be normally arranged away from the heat generating belt 63.

  The resin layers 622 and 642 are, for example, a known resin layer or a layer formed by foaming a known resin. Examples of the resin include silicone rubber and fluororubber. At least one of the resin layers 622 and 642 has elasticity that deforms when pressed by the pressure roller 64.

  The pressure roller 64 may further have a release layer on the resin layer 642 having release properties with respect to the transfer material. This release layer is constituted by a fluorine-based tube or a fluorine-based coating. As the material for the release layer, the fluororesin described as the material for the release layer of the heat generating belt can be used. The thickness of the release layer is preferably 5 to 100 μm, for example.

  The power supply device 65 includes an AC power supply 651, a power supply member 652 that contacts the electrode 14, and a conductive wire 653 that connects the AC power supply 651 and the power supply member 652. The power supply member 652 is biased toward the electrode 14 by an elastic member (not shown) such as a plate spring or a coil spring. The power supply member 652 may be a member that slides with respect to the electrode 14 or may be a member that rotates. Examples of the power supply member 652 include a carbon brush made of a carbon-based material such as graphite or a copper-graphite composite material.

  The heat generating belt 63, the fixing roller 62, and the pressure roller 64 are all rotatable. Each may be independently rotatable, or the other may be rotated according to one rotatable.

  When the pressure roller 64 presses the outer peripheral surface of the heat generating belt 63 toward the fixing roller 62, a contact portion (nip portion) between the heat generating belt 63 and the pressure roller 64 is formed. The nip portion may be formed by depression of the fixing roller 62 or may be formed by depression of the pressure roller 64.

  In fixing the toner image, the rotation of each roller and the heat generating belt 63, the power supply to the heat generating belt 63, and the formation of the nip portion can be performed in the same manner as a known fixing device. The fixing device 60 may further have another configuration that the known fixing device has.

  Since the fixing device has the tubular heating element as a heating belt, the heating belt has a uniform electric resistance, so that uniform heating is possible. For this reason, it is possible to further reduce fixing unevenness.

[Image forming apparatus]
The image forming apparatus includes a photosensitive member, a charging device that charges the photosensitive member, an exposure device that irradiates the charged photosensitive member with light to form an electrostatic latent image, and supplies toner to the photosensitive member on which the electrostatic latent image is formed. A developing device for forming a toner image corresponding to the electrostatic latent image, a transfer device for transferring the toner image formed on the electrostatic latent image to the recording medium, and the above for fixing the toner image on the recording medium A fixing device. The “toner image” refers to a state where toner is gathered in an image form.

  An example of the image forming apparatus is shown in FIG. The image forming apparatus 1 includes an image reading unit 110, an image processing unit 30, an image forming unit 40, a paper transport unit 50, and a fixing device 60.

  The image forming unit 40 includes image forming units 41Y, 41M, 41C, and 41K that form images of toners of Y (yellow), M (magenta), C (cyan), and K (black). Since these have the same configuration except for the toner to be accommodated, the symbols representing the colors may be omitted hereinafter. The image forming unit 40 further includes an intermediate transfer unit 42 and a secondary transfer unit 43. These correspond to a transfer device.

  The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, and a drum cleaner 415. The photoreceptor drum 413 is, for example, a negatively charged organic photoreceptor. The surface of the photosensitive drum 413 has photoconductivity. The photoconductor drum 413 corresponds to a photoconductor. The charging device 414 is, for example, a corona charger. The charging device 414 may be a contact charging device that charges a contact charging member such as a charging roller, a charging brush, or a charging blade by contacting the photosensitive drum 413. The exposure apparatus 411 is composed of, for example, a semiconductor laser. The developing device 412 is, for example, a two-component developing type developing device.

  The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422 that presses the intermediate transfer belt 421 against the photosensitive drum 413, a plurality of support rollers 423 including a backup roller 423A, and a belt cleaner 426. The intermediate transfer belt 421 is an endless belt. The intermediate transfer belt 421 is looped around the plurality of support rollers 423. When at least one drive roller of the plurality of support rollers 423 rotates, the intermediate transfer belt 421 travels at a constant speed in the arrow A direction. The intermediate transfer belt 421 corresponds to an intermediate transfer member. The primary transfer roller 422 corresponds to a transfer member.

  The primary transfer roller 422 is disposed slightly downstream from the photosensitive drum 413 in the moving direction of the intermediate transfer belt 421. With this arrangement, the nip portion formed by the intermediate transfer belt 421 and the photosensitive drum 413 is formed slightly upstream from the nip portion formed by the intermediate transfer belt 421 and the primary transfer roller 422.

  The secondary transfer unit 43 has a plurality of support rollers 431 including an endless secondary transfer belt 432 and a secondary transfer roller 431A. The secondary transfer belt 432 is stretched in a loop by the secondary transfer roller 431A and the support roller 431. The fixing device is the fixing device 60 described above.

  The image forming apparatus 1 further includes an image reading unit 110, an image processing unit 30, and a paper transport unit 50. The image reading unit 110 includes a paper feeding device 111 and a scanner 112. The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, and a transport path unit 53. In the three paper feed tray units 51a to 51c constituting the paper feed unit 51, paper S (standard paper, special paper) identified based on basis weight, size, etc. is stored for each preset type. . The conveyance path unit 53 includes a plurality of conveyance roller pairs such as registration roller pairs 53a.

Image formation by the image forming apparatus 1 will be described.
The scanner 112 optically scans and reads the document D on the contact glass. Reflected light from the document D is read by the CCD sensor 112a and becomes input image data. The input image data is subjected to predetermined image processing in the image processing unit 30 and sent to the exposure device 411.

  The photosensitive drum 413 rotates at a constant peripheral speed. The charging device 414 uniformly charges the surface of the photosensitive drum 413 to a negative polarity. The exposure device 411 irradiates the photosensitive drum 413 with laser light corresponding to the input image data of each color component. Thus, an electrostatic latent image is formed on the surface of the photosensitive drum 413. The developing device 412 visualizes the electrostatic latent image by attaching toner to the surface of the photosensitive drum 413. In this way, a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 413.

  The toner image on the surface of the photosensitive drum 413 is transferred to the intermediate transfer belt 421 by the intermediate transfer unit 42. Transfer residual toner remaining on the surface of the photosensitive drum 413 after the transfer is removed by a drum cleaner 415 having a drum cleaning blade that is in sliding contact with the surface of the photosensitive drum 413.

  When the intermediate transfer belt 421 is pressed against the photosensitive drum 413 by the primary transfer roller 422, the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 421.

  On the other hand, the secondary transfer roller 431A is pressed against the backup roller 423A via the intermediate transfer belt 421 and the secondary transfer belt 432. Thereby, a transfer nip is formed. The sheet S passes through this transfer nip. The paper S is transported to the transfer nip by the paper transport unit 50. The correction of the inclination of the sheet S and the adjustment of the conveyance timing are performed by a registration roller unit provided with a registration roller pair 53a.

  When the sheet S is conveyed to the transfer nip, a transfer bias is applied to the secondary transfer roller 431A. By applying the transfer bias, the toner image carried on the intermediate transfer belt 421 is transferred onto the paper S. Transfer residual toner remaining on the surface of the intermediate transfer belt 421 is removed by a belt cleaner 426 having a belt cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 421.

  The sheet S on which the toner image is transferred is conveyed toward the fixing device 60 by the secondary transfer belt 432. The fixing device 60 heats and pressurizes the conveyed paper S at the nip portion. Thus, the toner image is fixed on the paper S. The paper S on which the toner image has been fixed is discharged out of the apparatus by a paper discharge unit 52 having a paper discharge roller 52a.

  Since the image forming apparatus includes the above-described tubular heating element as a heating belt, the sheet S is fixed in the surface direction of the sheet S by uniform electric resistance in the surface direction of the heating belt in fixing the toner image onto the recording medium. It is possible to heat uniformly. For this reason, occurrence of fixing unevenness is reduced, and a high-quality image can be stably formed over a long period of time.

  In addition, a sheet-like heating element is obtained by cutting the tubular heating element manufactured by the above manufacturing method along the axial direction of the tubular heating element. The sheet-like heating element has the characteristics of the thickness of the heating layer and the uniformity of electrical resistance in the tubular heating element described above, and other uses of the sheet-like heating element other than the above-described other heating belts It is possible to use it suitably.

  In the following, the invention will be described in more detail with reference to examples. By the description of these examples, the present invention is not construed as being limited.

[Example 1]
The following components were mixed in the following amounts with a revolutionary rotation type mixer (ARE-310: manufactured by Sinky Corporation) to prepare a heating layer dope solution. The aspect ratio of the following SMF 300 is 4.
Polyamic acid: U varnish S (manufactured by Ube Industries) 100 g
Stainless steel fiber: SMF300 (manufactured by JFE Steel) 30g
Silicone oil: FZ-2110 (Toray Dow Corning Co., Ltd.) 0.05g

  A circular tube made of SUS304 was prepared as a mold. This mold has an outer diameter of 30 mm and a length of 340 mm. By discharging the heating layer dope 1 from the dispenser while rotating the mold around the mold axis and moving the dispenser in parallel along the mold axial direction on the outer peripheral surface of the mold A coating film of a heating layer dope solution having a thickness of 600 μm was formed on the outer peripheral surface of the mold.

  Next, a string winding excitation coil was disposed on the outer peripheral side of the mold as a heating means for the mold and the coating film. The distance from the outer peripheral surface of the mold to the exciting coil was 10 mm. The number of turns of the coil was 12. The pitch of the exciting coil (distance between the centers of adjacent wires of the exciting coil in the axial direction of the mold) was adjusted so that the temperature of the mold became constant. That is, the pitch of the end portion of the exciting coil was adjusted to be narrower than 10 mm, and the pitch of the central portion of the exciting coil was adjusted to be wider as 30 mm. The “end portion” is a portion from the end of the exciting coil to the position of about 30 mm from the end of the coating film on the mold (see FIG. 2).

  Next, in order to suppress temperature unevenness at the time of heating, while rotating the mold in the circumferential direction at 20 rpm, the excitation coil has a frequency of 50 kHz in a nitrogen atmosphere with an oxygen concentration of 15 ppm or less and a relative humidity of 50% or less. A high frequency output of 10 kW was applied, and the mold surface temperature was raised from 25 ° C. to 60 ° C. in 0.5 minutes.

  Next, in the timer control and the PID control, the surface temperature of the mold is appropriately maintained, or while gradually heating, the surface temperature of the central part of the mold in the axial direction is increased to 100 ° C. over 1 hour, The coating film was dried. When the surface temperature of the central portion was 100 ° C., the surface temperature of the portion of the mold corresponding to the end portion in the axial direction was about 120 ° C. By this drying, the coating film was solidified in a tubular shape on the outer peripheral surface of the mold and fixed to the outer peripheral surface. The stainless fiber in the coating film was fixed in a state of being dispersed in the coating film.

  Next, using another heater arranged on the outer peripheral surface side of the mold, the temperature was gradually raised until the temperature reached on the outer peripheral surface of the mold reached 400 ° C., and the temperature reached 400 ° C. was maintained for 30 minutes. And heating operation was stopped and the metal mold | die was cooled to 25 degreeC. And the metal mold | die was taken out in air | atmosphere, the tubular polyimide composition was removed from the outer peripheral surface of the metal mold | die, and the heat generating belt comprised with the tubular heat generating layer in which the stainless fiber was disperse | distributed in the polyimide was obtained.

[Example 2]
A tubular heating belt was obtained in the same manner as in Example 1 except that stainless steel powder (SUS430L, aspect ratio: 1.2, manufactured by Daido Steel Co., Ltd.) was used instead of the stainless steel fiber.

[Comparative Example 1]
A tubular heating belt was obtained in the same manner as in Example 1 except that graphite fiber (XN-100, aspect ratio: 5, manufactured by Nippon Graphite Fiber Co., Ltd.) was used instead of stainless steel fiber.

[Comparative Example 2]
A tubular heating belt was obtained in the same manner as in Example 1 except that the heating method was changed from the induction heating to the heating by hot air.

[Comparative Example 3]
A tubular heating belt was obtained in the same manner as in Example 1 except that the heating method was changed from the induction heating to the heating by the halogen heater.

[Comparative Example 4]
Similar to Example 1 except that graphite powder (UP-10, aspect ratio: 2, manufactured by Nippon Graphite Industry Co., Ltd.) was used instead of stainless steel fiber, and the heating method was changed from induction heating to heating by a halogen heater. Thus, a tubular heat generating belt was obtained.

[Evaluation]
The following (1) to (3) were evaluated for each of the heat generating belts of Examples 1 and 2 and Comparative Examples 1 to 4.

(1) Film thickness deviation With an electromagnetic film thickness measuring machine (Fischer), the thickness of each heat generating belt (heat generating layer) is 80 points in total, 8 points in the circumferential direction of the heat generating belt and 10 points in the axial direction. The thickness (film thickness) was measured. Then, an average value tm of the thicknesses of the respective heat generating belts and a difference Δt (tmax−tmin) obtained by subtracting the minimum value tmin from the maximum value tmax of the thickness were calculated. Then, Δt was divided by tm, and a ratio Dt (%) of Δt to tm was calculated. The film thickness deviation was evaluated according to the following criteria.
◯: Dt is less than 0.8% Δ: Dt is 0.8% or more and less than 2.0% ×: Dt is 2.0% or more

(2) Resistance Deviation Low resistivity meter Loresta EP Probe (ASP) (Mitsubishi Chemical Analytech Co., Ltd.) produces 4 points in the circumferential direction of the heat generating belt and 5 points in the axial direction. The electric resistance value (Ω) of the belt was measured. And the electrical resistivity was computed from the following formula.
ρ = R × (S / L)
In the above formula, R represents an electric resistance value (Ω), L represents a current-carrying distance (cm), and S represents a current-carrying cross-sectional area (cm ² ).

Then, a difference ΔRs (Ω) obtained by subtracting the minimum value from the maximum value of the electric resistance value of each heating belt was calculated. Further, a difference ΔRe (Ω · cm) obtained by subtracting the minimum value from the maximum value of the electrical resistivity of each heating belt was calculated. Then, the resistance deviation of the surface resistance and the resistance deviation of the electrical resistivity were evaluated according to the following criteria.
(Surface resistance)
○: ΔRs is less than 0.05Ω Δ: ΔRs is 0.05Ω or more and less than 0.1Ω ×: ΔRs is 0.1Ω or more (electrical resistivity)
○: ΔRe is less than 0.1 Ω · cm Δ: ΔRe is 0.1 Ω · cm or more and less than 0.3 Ω · cm ×: ΔRe is 0.3 Ω · cm or more

(3) Appearance The film state of each heat generating belt was visually observed, and the appearance was evaluated according to the following criteria according to the number of cracks, film floats and wrinkles.
○: No crack, film float or wrinkle occurrence Δ: One or two cracks, film float or wrinkle occurrence ×: Three or more cracks, film float or wrinkle occurrence Evaluation results in the above examples and comparative examples Is shown in Table 1.

  As is clear from Table 1, in the heat generating belts of Example 1 and Example 2, good results were obtained in all of the film thickness deviation, resistance deviation and appearance. In the heat generating belts of Example 1 and Example 2, a metal (stainless steel) filler is used as the conductive filler. For this reason, the induction heating during drying of the coating film heats not only the mold but also the individual filler particles, and the difference between the internal temperature and the surface temperature of the coating film during drying is alleviated, resulting in film thickness deviation and resistance deviation. It is considered that good results were obtained.

  Moreover, at the time of drying of a coating film, the edge part of the coating film in an axial direction is heated at higher temperature, and the center part of the coating film is heated at lower temperature. For this reason, the coating film is heated at a temperature suitable for the ease of drying in the axial direction of the coating film, the uniformity of the coating film thickness in the axial direction is further improved, and the film thickness deviation and resistance deviation are good. It is thought that the result was obtained.

  Furthermore, heating is performed while rotating the mold when the coating film is dried. For this reason, it is thought that the uniformity of the thickness in the circumferential direction of the coating film was further improved, and good results were obtained in terms of film thickness deviation and resistance deviation.

  In particular, Example 1 shows better results. This is because the metal filler has an aspect ratio of 1.5 to 15.0, so the metal fillers are easily in contact with each other, so the heat transfer of the heat generating belt is improved, and the strength of the heat generating belt made of resin is increased. it is conceivable that.

  On the other hand, in the heat generating belt of Comparative Example 1, the conductive filler was a nonmetallic filler (graphite). For this reason, the filler does not sufficiently generate heat when the coating film is dried, and the effect of reducing the difference between the internal temperature and the surface temperature of the coating film during drying cannot be sufficiently obtained. It is considered that the results obtained in the evaluation of the deviation and the resistance deviation were not obtained in Comparative Example 1.

  Moreover, in the heat generating belt of Comparative Example 2, the heating method at the time of drying the coating film was heating with hot air. For this reason, it takes time until the temperature of the mold and the coating film rises, and since the temperature in the heating chamber rises uniformly, the heating of the coating film in the axial direction becomes uniform. It is considered that the effect of reducing the difference in the drying speed of the film was not sufficiently obtained, and the film thickness deviation, resistance deviation and appearance were insufficient.

  In the heat generating belts of Comparative Example 3 and Comparative Example 4, the heating method at the time of drying the coating film was heating with a halogen lamp. For this reason, since the coating film is dried from the surface and is heated by radiation, the heating is limited to the portion receiving the radiation, and the temperature in the mold and the heating chamber is not easily raised. It tends to be biased toward the outer peripheral surface. Therefore, the effect of making the thickness of the coating film uniform by rotating the mold, the effect of reducing the difference between the internal temperature and the surface temperature of the coating film during drying, the difference in the drying speed of the coating film in the axial direction It is considered that the effect of reducing the thickness was not sufficiently obtained, and the film thickness deviation, resistance deviation and appearance were insufficient.

  In induction heating, an alternating magnetic flux is generated along the axial direction of the mold. Therefore, for example, there is a possibility that the metal filler in the coating film may be affected by the alternating magnetic flux and oriented by increasing the frequency of the alternating current or using a magnetic metal filler as the metal filler. It is done.

  According to the present invention, the thickness of the heating layer in the tubular heating element and the dispersion of the filler in the heating layer are more uniformly controlled. Therefore, the present invention is expected to bring about further development of the use of the tubular heating element and further increase in demand for the tubular heating element.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Tubular heating element 12 Heat generating layer 14 Electrode 16 Conductive adhesive 21 Metal filler 22 Mold 24, 34 Coating film 26 Exciting coil 28 High frequency power supply 30 Image processing part 31 Non-metal filler 40 Image forming part 41Y, 41M , 41C, 41K Image forming unit 42 Intermediate transfer unit 43 Secondary transfer unit 50 Paper transport part 51 Paper feed part 51a, 51b, 51c Paper feed tray unit 52 Paper discharge part 52a Paper discharge roller 53 Transport path part 53a Registration roller pair 60 Fixing device 62 Fixing roller 63 Heat generating belt 64 Pressure roller 65 Power feeding device 110 Image reading unit 111 Paper feeding device 112 Scanner 112a CCD sensor 241 End portion 261 Small pitch portion 262 Large pitch portion 411Y Exposure device 412Y Developing device 413Y Photoconductor Ram 414Y Charging device 415Y Drum cleaner 421 Intermediate transfer belt 422 Primary transfer roller 423,431 Support roller 423A Backup roller 426 Belt cleaner 431A Secondary transfer roller 432 Secondary transfer belt 621, 641 Core metal 622, 642 Resin layer 651 AC power supply 652 Power supply member 653 Conductor D Document S Paper

Claims (4)

A method for producing a tubular heating element having a tubular heating layer,
A step of applying a heat generating layer material liquid containing a heat resistant resin or a heat resistant resin material and a conductive filler to the peripheral surface of a cylindrical mold to form a coating film;
Passing an alternating current through an excitation coil arranged in a non-contact manner with respect to the coating film on the outer peripheral side or inner peripheral side of the mold, and drying the coating film by induction heating,
The said conductive filler is a manufacturing method of a tubular heating element containing a metal filler. The excitation coil includes two small pitch portions with a smaller pitch of the excitation coil and a large pitch portion with a larger pitch between the small pitch portions,
2. The tubular heating element according to claim 1, wherein the exciting coil is disposed with respect to the coating film such that the small pitch portion faces both ends of the coating film in an axial direction of the mold. Manufacturing method.   The method for manufacturing a tubular heating element according to claim 1, further comprising a step of rotating the mold relative to the exciting coil with the axis of the mold as a rotation axis. The aspect ratio of the said metal filler is a manufacturing method of the tubular heating element as described in any one of Claims 1-3 which is 1.5-15.

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