JP2008216741A - Heating body, and image heating device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating body used for an image heating device, and capable of reducing an excessive temperature rise in an area where a recording material does not pass through. <P>SOLUTION: The image heating device is configured to include a flexible member 11, the heating body 1 for heating the flexible member, and a backup member 13 that forms a nip part between the heating body and the flexible member, and to heat the recording material P carrying the toner image T at the nip part while holding and conveying the recording material P. The heating body 1 is used for the image heating device, and the heating body 1 includes a heat generating body 4 and a heat-conductive anisotropic layer 5 containing filler having heat-conductive anisotropy via an insulating layer 3 in a direction orthogonal to the recording material conveying direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heating body suitable for use in an image heating and fixing apparatus (fixing device) mounted on an image forming apparatus such as an electrophotographic copying machine and an electrophotographic printer, and an image heating apparatus having the heating body.

  As an image heating fixing device (fixing device) mounted on an image forming apparatus such as an electrophotographic copying machine or a printer, there is a film heating type. A film heating type fixing device includes a heater having a heater on a ceramic substrate, a flexible fixing film that moves while contacting the heater, a pressure roller that forms a nip portion with the heater via the fixing film, There are some that have Patent Document 1 and Patent Document 2 describe this type of fixing device. The recording material carrying the unfixed toner image is heated while being nipped and conveyed by the nip portion of the fixing device, whereby the toner image on the recording material is heated and fixed on the recording material. This fixing device has an advantage that the time required for starting energization of the heater and raising the temperature to the fixable temperature is short. Therefore, a printer equipped with this fixing device can shorten the time (FPOT: first printout time) after the print command is input until the first image is output. This fixing device also has an advantage that power consumption during standby for waiting for a print command is small.

  By the way, when a small-size recording material is continuously printed at the same print interval as a large-size recording material with a printer equipped with a fixing device using a flexible fixing film, the area where the recording material of the heater does not pass (non-paper passing) It is known that the temperature of the region) rises excessively. When the temperature of the non-sheet passing region of the heater is excessively high, there is a possibility that the heater is locally damaged by heat.

Therefore, the applicant of the present invention has a configuration in which a heat conduction anisotropic layer made of a graphite material having heat conduction anisotropy is provided on the substrate surface for the purpose of alleviating excessive temperature rise in the non-sheet passing region of the heater. A heater was proposed (Patent Document 3).
JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP 2003-7435 A

  The present invention is a further development of the above prior art. An object of the present invention is to provide a heating body used in an image heating apparatus, which can alleviate excessive temperature rise in an area through which a recording material does not pass, and an image heating apparatus having the heating body.

  The configuration for achieving the above object includes a flexible member, a heating body that heats the flexible member, and a backup member that forms a nip portion across the heating body and the flexible member, A heating element used in an image heating apparatus that heats a recording material carrying a toner image in the nip portion while nipping and conveying the recording material. In a direction perpendicular to the recording material conveyance direction, the heating element and the heat conduction member sandwich an insulating layer. And a thermally conductive anisotropic layer containing a filler having anisotropy.

  Moreover, the structure for achieving the said subject is a flexible member, the heating body which heats the said flexible member, and the backup member which forms a nip part on both sides of the said heating body and the said flexible member, and In the image heating apparatus that heats while sandwiching and transporting a recording material carrying a toner image at the nip portion, the heating body generates heat with an insulating layer sandwiched in a direction perpendicular to the recording material transport direction. And a heat conduction anisotropic layer containing a filler having heat conduction anisotropy.

  According to the present invention, it is possible to provide a heating body that is a heating body used in an image heating apparatus and can alleviate an excessive temperature rise in a region through which a recording material does not pass, and an image heating apparatus having the heating body.

  The present invention will be described with reference to the drawings.

(1) Example of Image Forming Apparatus FIG. 9 is a structural model diagram of an example of an image forming apparatus in which the image heating apparatus according to the present invention can be mounted as an image heating fixing apparatus. This image forming apparatus is a laser beam printer that forms an image on a recording material (for example, recording paper, OHP sheet, etc.) using an electrophotographic image forming system.

  An image forming apparatus A shown in this embodiment includes a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 101 as an image carrier. The photosensitive drum 101 is rotatably supported by an image forming apparatus main body B that constitutes a casing of the image forming apparatus A, and is rotationally driven in a direction of an arrow at a predetermined process speed by a driving unit (not shown). Around the photosensitive drum 101, a charging roller (charging means) 102, a laser exposure device (exposure means) 103, a developing device (developing means) 105, a transfer roller (transfer means) 106, and a cleaning device are arranged along the rotation direction. (Cleaning means) 107 are arranged in that order.

  During the rotation operation, the outer peripheral surface (surface) of the photosensitive drum 101 is uniformly charged to a predetermined potential and polarity by the charging roller 102. Then, the surface of the photosensitive drum 101 is scanned and exposed from the laser exposure device 103 to the laser L based on target image information through the mirror 104 and the like. As a result, the charge at the exposed portion is removed, and an electrostatic latent image (electrostatic image) corresponding to the image information is formed on the surface of the photosensitive drum 101. The electrostatic latent image is developed using toner (developer) by a developing device 105 having a developing roller 105a. In other words, the developing device 105 applies a developing bias to the developing roller 105 a and attaches toner to the electrostatic latent image on the surface of the photosensitive drum 101. Thereby, the electrostatic latent image is visualized (visualized) as a toner image (developed image).

  On the other hand, the recording material P is fed from the feeding cassette 108 by the feeding roller 109 at a predetermined timing, and the recording material P is transferred to the transfer nip Tn between the photosensitive drum 101 and the transfer roller 106 by the transport roller 110. Be transported. The recording material P is nipped and conveyed by the transfer nip Tn, and a transfer bias is applied to the transfer roller 106 in the conveyance process. As a result, the toner images on the surface of the photosensitive drum 101 are sequentially transferred onto the recording material P.

  The recording paper P carrying an unfixed toner image at the transfer nip Tn is separated from the surface of the photosensitive drum 101 and conveyed to the image heating and fixing device 112 along the conveyance guide 111. The fixing device 112 applies heat and pressure to the unfixed toner image on the recording material P to heat and fix the unfixed toner image on the recording material P. The recording material P that has exited the fixing device 112 is transported to the discharge roller 114 by the transport roller 113, and is discharged to the discharge tray 115 on the apparatus main body B by the discharge roller 114.

  The surface of the photosensitive drum 101 after the transfer of the toner image is subjected to removal of adhering matter such as transfer residual toner by a cleaning blade 107a of the cleaning device 107, and used for the next image formation.

(2) Fixing Device FIG. 1 is a schematic cross-sectional view of an example of the fixing device 112. FIG. 2 is a schematic longitudinal sectional view of the fixing device 112. FIG. 3 is a view of the fixing device 112 as viewed from the recording material introduction side. The fixing device 112 is a film heating type device.

  In the following description, with respect to the fixing device or the members constituting the fixing device, the longitudinal direction is a direction orthogonal to the recording material conveyance direction on the surface of the recording material. The short side direction is a direction parallel to the recording material conveyance direction on the surface of the recording material. The width is a dimension in the recording material conveyance direction.

  The fixing device 112 shown in this embodiment includes a ceramic heater 1 as a heating body, a fixing film 12 as a flexible member, a stay 11 as a guide member, and a pressure roller 13 as a backup member. . The film 12, the stay 11, and the pressure roller 13 are all elongated members in the longitudinal direction.

2-1) Structure of stay and fixing film The stay 11 is formed in a cross-sectional saddle shape using a predetermined material having heat resistance and rigidity. Both ends of the stay 11 are supported by a device frame (not shown) of the fixing device 112 via flanges (not shown) that restrict the movement of the film 11 in the longitudinal direction. A groove 11a is formed in the center of the short side of the lower surface of the stay 11, and the heater 1 is held in the groove 11a. The film 12 is formed endless (cylindrical) by a heat resistant film. The film 12 is externally fitted to the stay 11 with a sufficient circumference. A lubricant (not shown) is interposed between the inner peripheral surface of the film 12 and the outer peripheral surface of the stay 11. This reduces the sliding resistance of the film 12 that rotates while contacting the outer peripheral surface of the stay 11.

2-2) Configuration of Pressure Roller The pressure roller 13 includes a cored bar 13a and an elastic layer 13b provided around the cored bar 13a. A release layer (not shown) may be provided around the elastic layer 24b. The pressure roller 13 is arranged in parallel with the film 12 below the film 12. The pressure roller 13 is rotatably supported at both ends of a core bar 13a by a device frame (not shown) via bearings 21L and 21R. Both ends of the stay 11 are pressed against the pressure roller 13 by a pressure spring (not shown) as pressure means through a flange. As a result, the pressure roller 13 has a predetermined width necessary for heating and fixing the unfixed toner image T on the recording material P with the film 12 sandwiched between the outer peripheral surface (front surface) of the pressure roller 13 and the heater 1. A nip portion N (fixing nip portion) is formed.

2-3) Configuration of Ceramic Heater FIG. 4 shows an example of the heater 1. 4A is a structural model diagram of the heater 1 on the heating element 4 side, and FIG. 4B is an enlarged cross-sectional view of the heater 1.

  The heater 1 shown in the present embodiment has a ceramic substrate 2 elongated in the longitudinal direction as a heater substrate (heating body substrate). As will be described later, the substrate 2 is configured as an integral ceramic substrate by heat-pressing the insulating layer 3 and the heat conduction anisotropic layer 5 after extrusion. In the substrate 2, a heat conduction anisotropic layer 5 is provided on the back surface (surface on the nip portion N side) of the insulating layer 3, and heat is generated on the surface of the insulating layer 3 (surface opposite to the nip portion N). The body 4, the conductive parts 6-1 and 6-2, the electrode part 7, and the heating element protective layer 8 are provided.

  The insulating layer 3 is preferably made of a material having heat resistance, electrical insulation, low heat capacity, and high rigidity, and examples thereof include aluminum nitride. Further, as other material of the insulating layer 3, silicon carbide and aluminum oxide are preferably used, and a metal plate such as SUS may be subjected to an insulation treatment. In this embodiment, the insulating layer 3 was manufactured using aluminum nitride which is a material having heat resistance, electrical insulation, low heat capacity, and high rigidity. The outer dimensions of the insulating layer 3 are a longitudinal length of 270 mm, a width of 8.75 mm, and a thickness of 0.6 mm.

  The heat conduction anisotropic layer 5 is also preferably made of a material having heat resistance, low heat capacity, and high rigidity, like the insulating layer 3. In this embodiment, the external dimensions of the heat conduction anisotropic layer 5 are made of, for example, aluminum nitride as a base material, and a filler having a large heat conduction anisotropy is added to give the heat conduction anisotropy. . The outer dimensions of the thermally conductive anisotropic layer 5 were the same as the outer dimensions of the insulating layer 3. An acicular filler is added as the filler. The thermally conductive anisotropic layer 5 is preferably composed of a thermally conductive anisotropic layer containing pitch-based carbon fibers as needle-like fillers. There are roughly two types of carbon fibers, PAN-based and pitch-based, but pitch-based carbon fibers having a high heat-resistant temperature are suitable for adding to the ceramic material and allowing it to exist after firing. Here, the longitudinal direction of the heat conduction anisotropic layer 5 is added to the heat conduction anisotropic layer 5 by adding 50 vol% of carbon fiber having a fiber length of 500 μm and a heat conductivity λ in the major axis direction of 500 W / mK. Was able to be 300 W / mK.

  Examples of the heating element 4 include resistance-heating elements such as silver palladium (Ag · Pb) and Ta 2 N. The heating element 4 can be provided by applying a pattern on the surface of the insulating layer 3 by screen printing or the like. In this example, silver palladium (Ag · Pb) was applied as a heating element 4 by pattern printing or the like. The dimensions of the heating element 4 were 225 mm in the longitudinal direction, 2 mm in width, and 10 μm in thickness, and two were formed in parallel along the longitudinal direction of the insulating layer 3. The heating element 4 is slightly shorter than the length of the substrate 2 and has a length sufficient for heating and fixing the unfixed toner image T carried by the recording material P. Further, by forming and using two heating elements 4 in parallel along the longitudinal direction of the insulating layer 3, a single power connector (not shown) that supplies current to the heating element 4 can be integrated into one, reducing costs and saving space. Can be realized.

  The electrode part 7 connected to the power connector, the two conductive parts 6-1 connecting the electrode part 7 and the heating element 4, and the conductive part 6-2 connecting the heating elements 4 are made of a conductive material such as Ag. Used as a paste. The paste can be formed by pattern coating on the surface of the insulating layer 3 by screen printing or the like.

  The protective layer 6-1 protects the heating element 4 from mechanical destruction and chemical erosion, and maintains the electrical insulation so that the heating layer 4 is covered with a material such as glass. It is preferable to provide on the surface.

  Accordingly, the heater 1 has a heat conduction anisotropic layer 5 containing a heating element 4 and a filler having heat conduction anisotropy across the insulating layer 3 in a direction (longitudinal direction) perpendicular to the conveyance direction of the recording material P. And have. The surface of the thermally conductive anisotropic layer 5 is a sliding surface that moves while the inner peripheral surface (inner surface) of the film 12 is in contact therewith.

2-4) Manufacturing Method of Ceramic Substrate FIG. In FIG. 5, the conceptual diagram of the extrusion process of two ceramic substrates A and B and those adhesion processes is shown.

  In step A, an aluminum nitride paste is kneaded alone and extruded into a plate shape. Appropriate amounts of water, binder, dispersant, and lubricant were added to the aluminum nitride paste and kneaded under reduced pressure. In step B, carbon fiber is combined with an aluminum nitride paste, kneaded, and extruded into a plate shape in a primary orientation in the molded body. At this time, since the carbon fibers are oriented and dispersed along the extrusion direction of the substrate, the carbon fibers have high heat conduction characteristics in the extrusion direction.

  Here, as a more specific shape, the needle-shaped filler can be exemplified by those having a minor axis length of 5 to 15 μm and a major axis length (average length) of about 50 μm to 1 mm. Since the carbon fiber itself has a high thermal conductivity in the longitudinal direction, the effect as a filler is hardly exhibited unless the carbon fiber has a certain length. On the other hand, when a carbon fiber longer than the above length is used, the fiber length is less effective due to breakage or wear during kneading or extrusion molding, so the above fiber length is an effective length.

  Moreover, the thermal conductivity λ of the pitch-based carbon fiber shows a high value of 500 to 600 W / mK in the major axis direction.

  FIG. 6 shows the relationship between the addition rate of carbon fiber having a fiber length of 500 μm and a thermal conductivity λ in the major axis direction of 500 W / mK and the thermal conductivity λ in the longitudinal direction. Here, the relationship between the addition rate of carbon fiber and the thermal conductivity λ is compared under the condition of using aluminum nitride having a thermal conductivity λ of 100 W / mK after firing. As shown in FIG. 6, when the carbon fiber content exceeds 30 vol%, the continuous arrangement of the carbon fibers in the longitudinal direction is promoted and the thermal conductivity λ tends to increase significantly (λ ≧ 100 W / mK). . The carbon fiber content can be set in a range that can promote the continuous arrangement of the carbon fibers in the longitudinal direction. Therefore, if the carbon fiber content is in the range of 10 vol% to 70 vol%, the continuous arrangement of the carbon fibers in the longitudinal direction can be promoted, and the thermal conductivity λ can be increased. That is, the heat conductive anisotropic layer 5 may contain 10 vol% to 70 vol% filler.

  When A, B, and two extrusion moldings are finished, each substrate is dried, a solvent is applied to the adhesive surface, and thermocompression bonding is performed.

  Thereafter, a degreasing process is performed at 1000 ° C. for 1 hour, and further, a baking process is performed at 1600 ° C. for 2 hours, so that the insulating layer 3 whose surface is aluminum nitride and the back surface is carbon fiber longitudinally oriented anisotropically. An integral ceramic substrate 2 made of the conductive layer 5 is formed.

  Next, the heating element 4, the conductive portions 6-1 and 6-2, the electrode portion 7, and the protective layer 8 are formed on the surface of the aluminum nitride insulating layer 2 by screen printing.

(3) Heat Fixing Operation of Fixing Device When the driving gear G (FIG. 3) provided at the end of the core bar 13a of the pressure roller 13 is rotationally driven by the fixing motor M, the pressure roller 13 is moved in the direction of the arrow. Rotate to. Due to the rotation of the pressure roller 13, a rotational force acts on the film 12 by the frictional force between the surface of the pressure roller 13 and the outer peripheral surface (surface) of the film 12 at the nip portion N. The rotational force of the film 12 causes the inner surface of the film 12 to slide in close contact with the surface of the thermally conductive anisotropic layer 5 of the substrate 2 of the heater 1 at the nip N, while the pressure roller 13 rotates in the direction of the arrow around the stay 11. It is driven to rotate at the same peripheral speed as the rotational peripheral speed.

The CPU 31 (FIG. 4) as the control means turns on the triac 32 as the energization control means. Thereby, electricity is supplied from the AC power supply 33 to the electrode portion 7 of the heater 1 through the power supply connector. The heater 1 is energized to one heating element 4 from the electrode part 7 through the conductive part 6-1, and the other heater 4 is energized via the conductive part 6-2, so that the entire area of the heater 4 generates heat. Raise the temperature. The temperature of the heater 1 is detected by a temperature detection element 14 (FIG. 1) such as a thermistor as temperature detection means provided on the surface of the protective layer 8.
The temperature detection element 14 is a small-size sheet passing through a small-size (minimum size) recording material within a large-size sheet passing region through which a large-size (maximum size) recording material P used in the image forming apparatus passes. Arranged in the area. That is, the temperature detection element 14 is disposed in a region through which recording materials P of all sizes used in the image forming apparatus pass. Here, when a small-size recording material passes through the large-size sheet passing area, the outside of the small-sized sheet passing area becomes a non-sheet passing area. The CPU 31 takes in an output signal (temperature detection signal) S1 (FIG. 1) of the temperature detection element 14 after A / D conversion. Then, based on the output signal S1 from the temperature detection element 14, the electric power supplied to the heater 1 by the triac 32 is controlled by phase control or wave number control, etc., and the temperature control of the heater 1 is performed. That is, the CPU 31 increases the temperature of the heater 1 when the temperature detected by the temperature detection element 14 is lower than a predetermined set temperature (target temperature), and lowers the temperature of the heater 1 when higher than the set temperature. By controlling, the heater 1 is kept at the set temperature.

  The recording material P carrying the unfixed toner image T is introduced into the nip portion N in a state where the temperature of the heater 1 rises to the set temperature and the rotational peripheral speed of the film 12 is stabilized by the rotation of the pressure roller 13. . Then, the recording material P is nipped and conveyed through the nip portion N together with the film 12. In the conveying process, the heat of the heater 23 is applied to the unfixed toner image T of the recording material P through the film 12 and the nip pressure by the nip portion N is applied, so that the unfixed toner image T is recorded on the recording material P. The surface is fixed by heating. The recording material P that has exited the nip portion N is separated from the surface of the film 12 and discharged from the fixing device 112 by the transport roller 15 (FIG. 1).

(4) Experimental Example The temperature distribution in the longitudinal direction of the heater 1 used in the fixing device 112 of this embodiment was measured. In the temperature distribution measurement, a plurality of thermocouples are arranged along the longitudinal direction between the heater 1 and the stay 11 in the fixing device 112, and a predetermined number of small-sized recording materials are continuously introduced into the nip portion. The temperature of the heater 1 is detected by each thermocouple.

  Further, for comparison with the heater 1 of the present embodiment, in a fixing device having a conventional heater, a predetermined number of small-sized recording materials are continuously introduced into the nip portion under the same conditions as the fixing device 112 of the present embodiment. The temperature distribution in the longitudinal direction of the heater 1 was measured. The measurement of the temperature distribution is the same as that of the fixing device 112 of this embodiment. The conventional heater has a substrate made of an aluminum nitride insulating layer, and the thickness of the substrate is equal to the sum of the insulating layer 3 and the heat conduction anisotropic layer 5 of the heater 1 of this embodiment. A heating element, an electrode part, and a conductive part were provided on the back surface of the substrate, and a glassy protective layer having the same thickness as that of the heat conduction anisotropic layer 5 of the heater 1 of this example was provided. . In the conventional heater, the length and width of the substrate and the pattern of the heating element, the electrode part, and the conductive part are the same as those of the heater 1 of this embodiment.

  In the fixing device of this embodiment and a fixing device having a conventional heater, a B5 envelope transfer material is used as the small-size recording material P, and the temperature of the small-size sheet passing region (FIG. 7) through which the transfer material passes. A predetermined number of transfer materials were continuously passed through the nip portion so that the ink was sufficiently saturated. In this case, the outside of the small size paper passing area is the non-paper passing area within the range of the large size paper passing area. FIG. 7 shows the relationship among the heater 1, the large size sheet passing area, the small size sheet passing area, and the non-sheet passing area. FIG. 8 shows the measurement results of the temperature from the center of the small-size sheet passing area and the non-sheet passing area temperature in the heater when the transfer material is passed through the nip portion. Table 1 shows the temperature at the center of the sheet passing area and the temperature of the thermal peak (maximum temperature at the end of the transfer material) in the heater of each fixing device at that time.

  In FIG. 8, the vertical axis represents temperature (° C.), and the horizontal axis represents the distance (mm) in the longitudinal direction of the nip portion from the center of the sheet passing area. In FIG. 8, the vicinity of 91 mm on the horizontal axis is the end of the transfer material. The broken line shows the temperature distribution on the surface of the heater of the conventional product (surface opposite to the nip portion), and the solid line shows the temperature distribution on the surface of the heater 1 (surface opposite to the nip portion) of this embodiment.

  As shown in Table 1, the temperature of the thermal peak in the heater 1 of this example was reduced by 26 ° C. compared to the conventional heater. Therefore, as in the heater 1 of this embodiment, the anisotropic heat conduction is realized by configuring the heat conduction anisotropic layer 5 having excellent heat conduction characteristics in the longitudinal direction and the insulating layer 3 as an integrated ceramic substrate 2. The thermal peak at the end of the transfer material can be effectively mitigated as compared with a conventional heater without a conductive layer. That is, heat can be effectively released from the portion where the thermal peak is generated in the longitudinal direction of the heater 1, and the local thermal deterioration of the components (heater 1, stay 11, fixing film 12, pressure roller 13) / The occurrence of destruction can be reduced.

  Another example of the heater will be described.

  In the present embodiment, the same members / portions as those of the heater 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The same applies to Example 3.

  FIG. 10 shows an example of the heater 1 according to this embodiment. 10A is a structural model diagram of the heater 1 on the side of the heating element 4, and FIG. 10B is an enlarged cross-sectional view of the heater 1.

  In the heater 1 shown in this embodiment, aluminum oxide is used for the material of the insulating layer 3 of the ceramic substrate 2 as the heater substrate and the base material of the heat conduction anisotropic layer 5. The thermal conductivity λ of aluminum oxide is as low as about 25 W / mK compared to aluminum nitride (100 W / mK). Therefore, in the heater 1 of the present embodiment, the surface on which the heating element 4 is formed and the surface on which the heat conduction anisotropic layer 5 is formed have a reverse relationship with the heater 1 of the first embodiment. In other words, the heating element 4, the conductive portions 6-1 and 6-2, the electrode portion 7, and the protective layer 8 are provided on the separation surface of the insulating layer 3, and the heat conduction anisotropic is provided on the surface of the insulating layer 3. A conductive layer 5 is provided. Therefore, the surface of the protective layer 8 becomes a sliding surface that moves while the inner surface of the fixing film 12 contacts. Further, when aluminum oxide is used, there is an advantage that the substrate 2 can be manufactured at a lower cost than in the case of aluminum nitride.

  The outer dimensions of the insulating layer 3 are a longitudinal length of 270 mm, a width of 8.75 mm, and a thickness of 0.6 mm. The external dimensions of the thermally conductive anisotropic layer 5 are the same size as the insulating layer 3. And the board | substrate 2 is comprised as an integrated ceramic board | substrate by heat-pressing the insulating layer 3 and the heat conductive anisotropic layer 5 after extrusion molding using the same manufacturing method as Example 1. FIG. Here, the longitudinal direction of the heat conduction anisotropic layer 5 is added to the heat conduction anisotropic layer 5 by adding 50 vol% of carbon fiber having a fiber length of 500 μm and a heat conductivity λ in the major axis direction of 500 W / mK. Was able to be 150 W / mK.

  Further, as the heating element 4, silver palladium (Ag · Pb), which is a resistance heating element, was pattern-coated on the surface of the insulating layer 3 of the substrate 2 by screen printing or the like. The dimensions of the heating elements 4 were 225 mm in length in the longitudinal direction, 2 mm in width, and 10 μm in thickness, and two were arranged in parallel along the longitudinal direction of the insulating layer 3.

  The conductive portions 6-1 and 6-2 and the electrode portion 7 were subjected to pattern coating on the surface of the insulating layer 3 by screen printing of Ag paste. The protective layer 8 was formed of a vitreous protective layer having high slidability in consideration of sliding with the film 11.

  The same experiment as in Example 1 was performed on a fixing device having the heater 1 of this example and a fixing device having a conventional heater. That is, a B5 envelope transfer material is used as the small size recording material P, and a predetermined number of transfer materials are continuously passed through the nip portion so that the temperature of the small size paper passing region through which the transfer material passes is sufficiently saturated. I let you. FIG. 11 shows the measurement results of the temperature from the center of the small-size sheet passing area and the non-sheet passing area temperature in the heater when the transfer material is passed through the nip portion. Table 2 shows the temperature at the center of the sheet passing region and the temperature of the thermal peak (transfer material end portion maximum temperature) in the heater of each fixing device at that time.

  In FIG. 11, the vertical axis represents temperature (° C.), and the horizontal axis represents the distance (mm) in the longitudinal direction of the nip portion from the center of the sheet passing area. In FIG. 11, the vicinity of 91 mm on the horizontal axis is the end of the transfer material. The broken line shows the temperature distribution on the surface of the heater of the conventional product (surface opposite to the nip portion), and the solid line shows the temperature distribution on the surface of the heater 1 (surface opposite to the nip portion) of this embodiment.

  As shown in Table 2, the temperature of the thermal peak in the heater 1 of this example was 18 ° C. lower than that of the conventional heater. Therefore, also in the heater 1 of this embodiment, the heat conduction anisotropic layer 5 and the insulating layer 3 having excellent heat conduction characteristics in the longitudinal direction and the insulating layer 3 are configured as an integral ceramic substrate 2, thereby providing the heat conduction anisotropy. The thermal peak at the end of the transfer material can be more effectively mitigated than a conventional heater without a layer. That is, heat can be effectively released from the portion where the thermal peak is generated in the longitudinal direction of the heater 1, and the local thermal deterioration of the components (heater 1, stay 11, fixing film 12, pressure roller 13) / The occurrence of destruction can be reduced.

  Another example of the heater will be described.

  FIG. 12 shows an example of the heater 1 according to this embodiment. 12A is a structural model diagram of the heater 1 on the heating element 4 side, and FIG. 12B is an enlarged cross-sectional view of the heater 1.

  The heater 1 shown in this embodiment has a thermally conductive anisotropic layer 5 elongated in the longitudinal direction as a heater substrate. This heat conduction anisotropic layer 5 uses aluminum nitride as a base material. Then, a glass layer is provided as the insulating layer 3 on the back surface of the thermally conductive anisotropic layer 5, and the heating element 4, the conductive portions 6-1 and 6-2, and the electrode portion 7 are formed on the back surface of the insulating layer 3. The protective layer 8 is provided. Therefore, the surface of the protective layer 8 becomes a sliding surface that moves while the inner surface of the fixing film 12 contacts.

  The external dimensions of the thermally conductive anisotropic layer 5 are a longitudinal length of 270 mm, a width of 8.75 mm, and a thickness of 0.6 mm. Here, the longitudinal direction of the heat conduction anisotropic layer 5 is added to the heat conduction anisotropic layer 5 by adding 50 vol% of carbon fiber having a fiber length of 500 μm and a heat conductivity λ in the major axis direction of 500 W / mK. Was able to be 300 W / mK. The outer dimensions of the insulating layer 3 were a longitudinal length of 270 mm and a width of 8.75 mm, and the thickness was made thinner than the thickness of the heat conduction anisotropic layer 5.

  The pattern of the heating element 4, the conductive portions 6-1 and 6-2, the electrode portion 7 and the protective layer 8 formed on the back surface of the insulating layer 3 are the same as those in the first embodiment.

  The same experiment as in Example 1 was performed on a fixing device having the heater 1 of this example and a fixing device having a conventional heater. The results are shown in Table 3.

  As shown in Table 3, the temperature of the thermal peak in the heater 1 of this example was lowered by 22 ° C. compared to the conventional heater. Accordingly, the heater 1 of this embodiment also has the heat conduction anisotropic layer 5 having excellent heat conduction characteristics in the longitudinal direction, so that the end portion of the transfer material is more than the conventional heater without the heat conduction anisotropic layer. The thermal peak of can be effectively relaxed. That is, heat can be effectively released from the portion where the thermal peak is generated in the longitudinal direction of the heater 1, and the local thermal deterioration of the components (heater 1, stay 11, fixing film 12, pressure roller 13) / The occurrence of destruction can be reduced.

Cross-sectional model diagram of an example of a fixing device Longitudinal cross section model of fixing device The fixing device 112 is viewed from the recording material introduction side. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure showing the heater which concerns on Example 1, Comprising: (a) is a structural model figure by the side of the heat generating body of a heater, (b) is an expanded horizontal sectional view of a heater. Explanatory drawing showing the manufacturing method of a ceramic substrate A graph showing the relationship of the thermal conductivity of the anisotropic thermal conduction layer to the carbon fiber addition rate A diagram showing the relationship among a heater, a large-size sheet passing area, a small-size sheet passing area, and a non-sheet passing area The figure showing the measurement result of the temperature from the paper passing area center of the small size paper passing area and the non-paper passing area temperature in the heater according to the first embodiment and the conventional heater Configuration model diagram of an example of an image forming apparatus FIG. 5 is a diagram illustrating a heater according to a second embodiment, where (a) is a structural model diagram of the heater on the heating element side, and (b) is an enlarged cross-sectional view of the heater. The figure showing the measurement result of the temperature from the sheet passing area center of the small size sheet passing area and the non-sheet passing area temperature in the heater according to the second embodiment and the conventional heater. FIG. 5 is a diagram illustrating a heater according to a third embodiment, where (a) is a structural model diagram of the heater on the heating element side, and (b) is an enlarged cross-sectional view of the heater.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ceramic heater, 2 ... Ceramic substrate, 3 ... Insulating layer, 4 ... Heating element, 5 ... Heat conduction anisotropic layer, 12 ... Fixing film, 13 ... Pressure roller, 112 ... Fixing device, N ... Nip part

Claims (16)

  A flexible member, a heating member that heats the flexible member, and a backup member that forms a nip portion between the heating member and the flexible member, and carries a toner image at the nip portion. Heating element used in an image heating apparatus that heats while sandwiching and conveying a material, and includes a heating element and a filler having thermal conductivity anisotropy across an insulating layer in a direction orthogonal to the recording material conveyance direction A heating body comprising a conductive anisotropic layer.   The heating body according to claim 1, wherein the substrate and the thermally conductive anisotropic layer are formed as an integral ceramic substrate.   2. The heating element according to claim 1, wherein the thermal conductivity anisotropic layer has a thermal conductivity λ in a direction orthogonal to a recording material conveyance direction of λ ≧ 100 W / mK.   2. The heating body according to claim 1, wherein the thermally conductive anisotropic layer contains a filler having a thermal conductivity λ of λ ≧ 300 W / mK.   The heating body according to claim 4, wherein the heat conduction anisotropic layer contains 10 vol% to 70 vol% of the filler.   The heating body according to claim 4 or 5, wherein the filler is a needle-like filler.   The heating element according to claim 6, wherein an average length of the needle-like filler is 50 μm to 1 mm.   The heating body according to claim 6 or 7, wherein the acicular filler is pitch-based carbon fiber. A flexible member; a heating member that heats the flexible member; and a backup member that forms a nip portion between the heating member and the flexible member. In an image heating apparatus that heats while holding and transporting a recording material to be carried,
The heating element includes a heating element and a heat conduction anisotropic layer containing a filler having heat conduction anisotropy with an insulating layer interposed therebetween in a direction orthogonal to the conveyance direction of the recording material. Heating device.   The image heating apparatus according to claim 9, wherein the insulating layer and the thermally conductive anisotropic layer are formed as an integral ceramic substrate.   The image heating apparatus according to claim 9, wherein the thermal conductivity anisotropic layer has a thermal conductivity λ in a direction orthogonal to a recording material conveyance direction of λ ≧ 100 W / mK.   The image heating apparatus according to claim 9, wherein the thermally conductive anisotropic layer contains a filler having a thermal conductivity λ of λ ≧ 300 W / mK.   13. The image heating apparatus according to claim 12, wherein the thermally conductive anisotropic layer contains 10 vol% to 70 vol% of the filler.   The image heating apparatus according to claim 12, wherein the filler is a needle-like filler.   The image heating apparatus according to claim 14, wherein an average length of the needle-like filler is 50 μm to 1 mm.   The image heating apparatus according to claim 14, wherein the needle-like filler is pitch-based carbon fiber.