Heater, heating device, ceramic material, and method for manufacturing ceramic component

Abstract

A heater (22) includes a base material (22a) and a ceramic composition (22d) provided on the base material, wherein the ceramic composition generates heat when a voltage is applied. The ceramic composition includes a plurality of aggregates (22f) formed by an aggregation of semiconductor crystal grains containing barium and titanium, and metal elements (22g) present at grain boundaries of the aggregates, the aggregates being linked together in a state in which the metal elements are necked.

Description

Heater, heating device, ceramic material, and method for manufacturing ceramic parts

[0001] This disclosure relates to heaters, heating devices, ceramic materials, and methods for manufacturing ceramic components.

[0002] Electrophotographic copiers and printers are equipped with a heating device that heats and fixes the toner image formed on the recording material. One type of heating device is a film heating system, which includes a heater with a heating element on a ceramic or metal substrate, a fixing film that moves in contact with the heater, and a pressure roller that forms a nip portion with the heater via the fixing film.

[0003] In such a heating device, when narrow recording material (hereinafter referred to as small-size paper) is printed continuously, a phenomenon occurs in which the temperature of the area in the longitudinal direction of the fixing nip section through which the paper does not pass (hereinafter referred to as the non-paper-passing area) gradually rises (hereinafter referred to as the non-paper-passing area temperature rise).

[0004] As a configuration to suppress the temperature rise of the non-paper-passing section, a semiconductorized barium titanate (BaTiO) is used. ３ A heater has been proposed that utilizes the positive temperature resistance characteristic (PTC characteristic; hereinafter referred to as PTC characteristic) of a sintered body of barium titanate (see Patent Document 1). More specifically, Patent Document 1 proposes a configuration in which an elongated plate-shaped barium titanate sintered body (hereinafter referred to as a plate-shaped sintered body) with the axial direction of the fixing film as the longitudinal direction is used, and a pair of current-carrying electrodes are provided on this plate-shaped sintered body. The plate-shaped sintered body is then heated by passing current between the electrodes.

[0005] Japanese Patent Application Publication No. 5-19652

[0006] However, in reality, manufacturing ceramic components that meet the design requirements while possessing the aforementioned PTC properties proved extremely difficult. For example, the barium titanate would react with other materials during the manufacturing process, resulting in the loss of the PTC properties.

[0007] Therefore, the object of this disclosure is to provide a heater, a heating device, a ceramic material, and a method for manufacturing ceramic parts having PTC characteristics.

[0008] One aspect of the present disclosure is a heater comprising a substrate and a ceramic composition provided on the substrate, wherein the ceramic composition generates heat when a voltage is applied to the ceramic composition, the heater comprising a plurality of aggregates formed by the aggregation of semiconductor crystal grains containing barium and titanium, and metal elements present at the grain boundaries of the aggregates, wherein the aggregates are connected to each other in a state in which the metal elements are necked.

[0009] One aspect of the present disclosure is a ceramic material comprising a sintered body in the form of secondary particles in which semiconductor crystal grains containing barium and titanium are bonded together, and a metal element.

[0010] One aspect of the present disclosure is a method for manufacturing a ceramic part, comprising the steps of coating the ceramic material onto a substrate and firing the ceramic material coated onto the substrate.

[0011] According to this disclosure, it is possible to provide a heater having PTC characteristics, a heating device, a ceramic material, and a method for manufacturing ceramic parts.

[0012] Other features and advantages of this disclosure will become apparent from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are given the same reference numeral.

[0013] This is a schematic diagram of an image forming apparatus according to an embodiment of the present disclosure. This is a cross-sectional view of a heating device. This is an exploded perspective view of a film assembly unit used in the heating device. This is a front view of the heating device. This is an exploded perspective view of a heater. This is a perspective view of a heater. This is a cross-sectional view of the heater along line a in Figure 5B. This is a cross-sectional view of the heater along line b in Figure 5B. This is a plan view of the heater. This is a diagram showing the state of barium titanate in secondary particulate form before firing. This is a diagram showing the state of barium titanate in secondary particulate form after firing. This is a diagram showing the state of a resistance heating element. This is a schematic diagram of a resistance heating element. This is an enlarged view of field A in Figure 7A. This is a schematic diagram showing the state of necking of metal particles in field B in Figure 7C. This is a diagram showing the resistance temperature characteristics of a heater according to Example 1. This is a diagram showing a plate-shaped sintered body of a heater according to Comparative Example 1. This is an exploded perspective view of a heater according to Comparative Example 1. This is a perspective view of a heater according to Comparative Example 1. This is a diagram showing the state of cross-sectional SEM observation of the mixed powder of sample 1 according to Comparative Example 4, showing the state near the press surface. This figure shows the cross-sectional SEM observation results of the mixed powder of sample 1 according to Comparative Example 4, where the PTC particles are in a fractured state. This figure shows the cross-sectional SEM observation results of the resistance heating element according to Comparative Example 4.

[0014] The embodiments of this disclosure will be described below. Note that the embodiments described below are illustrative, and for example, those skilled in the art may modify the detailed configurations as appropriate without departing from the spirit of this disclosure.

[0015] <Example 1> (Image Forming Apparatus) Figure 1 is a cross-sectional view of a laser printer 100 as an image forming apparatus using electrophotographic recording technology. The laser printer 100 is configured to transfer a toner image formed by an image forming unit 101 to a recording material P, and to transfer the toner image (image) transferred on the recording material to a recording medium P by heating and pressurizing it with a heating device 9.

[0016] More specifically, the image forming unit 101 is equipped with a scanner unit 3 as an exposure device. When the laser printer 100 receives a print command, the scanner unit 3 emits laser light L corresponding to the image information. The photoreceptor 1, which has been charged to a predetermined polarity by the charging roller 2, is scanned by the aforementioned laser light L, thereby forming an electrostatic latent image on the surface of the photoreceptor 1 corresponding to the image information. Subsequently, the developer 4 supplies toner to the photoreceptor 1 to develop the electrostatic latent image, forming a toner image on the photoreceptor 1 corresponding to the image information. The toner image that reaches the transfer position formed by the photoreceptor 1 and the transfer roller 5 due to the rotation of the photoreceptor 1 in the direction of arrow R1 is transferred to the recording material P supplied from the cassette 6 by the pickup roller 7 as a feeding unit. The surface of the photoreceptor 1 that has passed the transfer position is cleaned by the cleaner 8.

[0017] The recording material P onto which the toner image has been transferred is subjected to heat and pressure by the heating device 9 for fixing. After that, the recording material P is discharged into the output tray 11 by the output roller 10.

[0018] (Heating device) Next, the heating device 9 will be described using Figures 2 to 4. Figure 2 is a schematic cross-sectional view of the heating device 9 of this embodiment. Figure 3 is an exploded perspective view of the film assembly unit 20 used in the heating device, and Figure 4 is a front view of the heating device. The heating device 9 employs a tensionless type film heating method. In the heating device 9 of the tensionless type film heating method, an endless belt-shaped (for example, cylindrical) heat-resistant film is used. At least a portion of the circumference of the film is always tension-free (no tension is applied), and the film is configured to be rotationally driven by the rotational driving force of the pressurizing body.

[0019] More specifically, as shown in Figure 2, the heating device 9 comprises a cylindrical film 23, a heater 22 which is a heating element, and a pressure roller 30 which is a pressurizing member that forms a fixing nip portion N with the heater 22 via the film 23. The fixing nip portion N is a pressing portion that heats the toner image on the recording material P between the heater 22 and the pressure roller 30 via the film 23. In addition, sliding grease 60 is applied to the inner surface of the film 23 to improve sliding properties with the heater 22.

[0020] The reinforcing member 24 is made of a metal such as iron, and the biasing force from the pressure spring 45 (see Figure 4), which acts as a biasing member, presses the heater 22 toward the pressure roller 30 via the film guide 21. The reinforcing member 24 is also a member that maintains its strength so as not to deform significantly even when subjected to the pressure that presses the pressure roller 30 to form the fixing nip portion N. The film guide 21 is a support member that supports the heater 22 and also functions as a guide that guides the rotation of the film 23. The film guide 21 is a molded product of a heat-resistant resin such as PPS (polyphenylene sulfite) or liquid crystal polymer. In Example 1, PPS was used. The pressure roller 30 receives power from the motor M via a gear (not shown) and rotates in the direction of arrow b. As the pressure roller 30 rotates, the film 23 rotates in the direction of arrow a. That is, the film 23, which is the fixing film, is configured to be movable while heat from the heater 22 is transferred to it.

[0021] The heater 22 comprises a substrate 22a, a resistive heating element 22d, a conductive pattern 22c, and a glass coating layer 22e. The substrate 22a is an elongated plate-shaped member made of ceramic. The resistive heating element 22d is configured to generate heat when an electric current is passed through it, and the conductive pattern 22c is provided on both the front and back surfaces in the thickness direction of the resistive heating element 22d. Furthermore, the glass coating layer 22e is configured to cover and protect the surfaces of the substrate 22a, the resistive heating element 22d, and the conductive pattern 22c.

[0022] Furthermore, a thermistor 25, which is a temperature sensing element, is in contact with the surface of the substrate 22a opposite to the surface that contacts the film guide 21 (i.e., the surface facing the film guide 21). The current supplied to the resistive heating element 22d is controlled according to the temperature detected by the thermistor 25.

[0023] The thickness of the film 23 is preferably 20 μm to 100 μm in order to ensure good thermal conductivity. The film 23 is preferably a composite layer film in which a release layer 23b is coated on the surface of a film base layer 23a. The film base layer 23a may be a single-layer film made of a material such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether), or PPS, or a material such as PI (polyimide), PAI (polyamide-imide), PEEK (polyetheretherketone), or PES (polyethersulfone). The release layer 23b may be made of PTFE, PFA, FEP (tetrafluoroethylene-perfluoroalkyl vinyl ether), etc. Furthermore, a film in which a pure metal or alloy such as SUS, Al, Ni, Cu, Zn, etc., which have high thermal conductivity is used as the base layer, and the release layer is coated with the aforementioned coating treatment or covered with a fluororesin tube is also suitable.

[0024] In Example 1, the film base layer 23a was made of PI with a thickness of 60 μm, and the release layer 23b was coated with PFA with a thickness of 12 μm, taking into consideration both wear of the release layer 23b due to paper feeding and thermal conductivity. The outer diameter of the film 23 was 18 mm and the longitudinal length was 240 mm.

[0025] The pressure roller 30, which acts as a pressurized rotating body, comprises a core metal 30a made of a material such as iron or aluminum, an elastic layer 30b made of a material such as silicone rubber, and a release layer 30c made of a material such as PFA. In Example 1, the outer diameter of the pressure roller 30 was 20 mm, the thickness of the elastic layer 30b was 3.5 mm, the thickness of the release layer 30c was 30 μm, and the longitudinal length of the elastic layer 30b and the release layer 30c was 230 mm.

[0026] The pressure roller 30 receives power from the motor M via a gear (not shown) and rotates in the direction of arrow b. The recording material P is gripped and conveyed by the nip section N, and the toner image T on the recording material P is heated and fixed to the recording material P. The recording material P that has passed through the nip section N is conveyed to the paper output tray 11.

[0027] Next, we will explain with reference to the exploded perspective view in Figure 3. As shown in Figure 3, when assembling the film assembly unit 20 of the heating device 9, first the film guide 21 and the reinforcing member 24 are fitted together, and then the film 23 is fitted onto the outer circumference of the film guide 21 and the reinforcing member 24 with some circumferential clearance. In the following explanation, the axial direction of the cylindrical shape of the film 23 will be referred to as the longitudinal direction.

[0028] The reinforcing members 24 protrude from both ends of the film 23, and flange members 26 are fitted to each end to assemble the whole into a film assembly unit 20. The power supply terminals of the heater 22 also protrude from one end of the film 23, and a power supply connector 27 is fitted to them. The power supply connector 27 makes contact with the electrode portion of the heater 22 with contact pressure, creating a power supply path. The heater clip 28 is formed from a metal plate bent into a U shape and has spring properties.

[0029] Next, we will explain with reference to the front view in Figure 4. The flange member 26 restricts the longitudinal movement of the rotating film 23 and restricts the position of the film 23 while the heating device 9 is in operation.

[0030] The film assembly unit 20 is positioned opposite the pressure roller 30. Its movement in the left-right direction in the figure is restricted by the frame side plate 42, while its movement in the up-down direction is freely movable, supported by the top plate side housing 41 of the heating device 9. A pressure spring 45 is mounted in a compressed state on the top plate side housing 41 of the heating device 9. The pressing force of the pressure spring 45 is received by both ends of the reinforcing member 24 via the flange member 26, causing the reinforcing member 24 to be pressed towards the pressure roller 30, and the entire film assembly unit 20 to be pressed towards the pressure roller 30.

[0031] A bearing member 31 is provided so as to pivotally support the core bar of the pressure roller 30. The bearing member 31 receives the pressing force from the film assembly unit 20 via the pressure roller 30. In order to rotatably support the core bar of the pressure roller 30, which reaches a relatively high temperature, a material having heat resistance and excellent slidability is used for the bearing. The bearing member 31 is attached to a bottom housing 43 of the heating device.

[0032] (Heater) Next, materials, a manufacturing method and the like constituting the heater 22 will be described with reference to FIGS. 5A to 8. FIG. 5A is an exploded perspective view of the heater 22 with the protective layer 22e removed, and FIG. 5B is a perspective view of the heater 22 with the protective layer 22e removed. FIG. 5C is a cross-sectional view in the short-side direction of the heater 22 taken along line a shown in FIG. 5B, FIG. 5D is a cross-sectional view in the longitudinal direction of the heater 22 taken along line b shown in FIG. 5B, and FIG. 5E is a plan view of the heater 22 as viewed from the surface side of the substrate 22a on which the protective layer 22e is provided.

[0033] In the present embodiment, the substrate 22a is a ceramic substrate, and the type of ceramic is not particularly limited, and may be appropriately selected in consideration of necessary mechanical strength, a coefficient of linear expansion matching the formation of the heating element, ease of obtaining plate materials on the market, and the like. In addition, the thickness of the substrate 22a may be determined in consideration of strength, heat capacity, and heat dissipation performance. When the thickness of the substrate 22a is small, the heat capacity is small, which is advantageous for quick start, but when the thickness is too small, the problem of distortion tends to easily occur during heat molding of the heating element. Conversely, when the thickness of the substrate 22a is large, it is advantageous in terms of distortion during heat molding of the heating element, but when the thickness is too large, the heat capacity is large, which is disadvantageous for quick start.

[0034] A preferable thickness of the substrate 22a is 0.3 mm to 2.0 mm when considering the balance of mass productivity, cost, and performance. In Embodiment 1, an alumina substrate having a width of 10 mm, a length of 270 mm, and a thickness of 1 mm is used as the substrate 22a.

[0035] Next, the feeding electrode 22b and the conductive pattern 22c will be described. The feeding electrode 22b and the conductive pattern 22c shown in FIG. 5A are mainly composed of silver (Ag), platinum (Pt), gold (Au), silver-platinum (Ag-Pt) alloy, silver-palladium (Ag-Pd) alloy, etc., and are formed by applying a paste, which is a mixture of a conductive component, a glass component and an organic binding component, by screen printing and then calcining the paste. In Example 1, a paste for feeding electrodes and conductive patterns, which uses silver as the conductive component and is mixed with a glass component and an organic binding component, is used. The feeding electrode 22b and the conductive pattern 22c are provided for the purpose of feeding power to the resistance heating element 22d, and their respective resistance values are sufficiently lower than the resistance value of the resistance heating element 22d.

[0036] As shown in FIG. 5A, the conductive pattern 22c-1, the resistance heating element 22d described later, the conductive pattern 22c-2, and the feeding electrode 22b are sequentially printed and calcined from the ceramic substrate 22a side to form the layered structure. After printing, the feeding electrode 22b and the conductive pattern 22c are formed through drying at 180° C. and calcination at 600° C.

[0037] As shown in FIG. 5A, for the conductive patterns 22c-1 and 22c-2, along the longitudinal direction of the heater 22, the length of the portion indicated as the heating region length w is set to 220 mm. Further, along the lateral direction of the heater 22, the length of the portion indicated as the heating region width s is set to 7 mm. A rectangular region having the two sides of the heating region length w and the heating region width s described above serves as the heating region.

[0038] On the other hand, the resistance heating element 22d described later has a width of 7 mm and a length of 221 mm. As shown in the cross-sectional view of FIG. 5C, the width thereof is the same as the 7 mm length of the portion indicated as the heating region width s of the conductive patterns 22c-1 and 22c-2 described above. However, in terms of length, the length of the portion indicated as the heating element extended length x is set to be 1 mm longer than the 220 mm length of the portion indicated as the heating region length w of the conductive patterns 22c-1 and 22c-2. This is aimed at preventing contact between the conductive patterns 22c-1 and 22c-2 by providing the portion indicated as the heating element extended length x, as shown in the cross-sectional view of FIG. 5D.

[0039] Next, the resistive heating element 22d as a ceramic composition will be explained in detail. The resistive heating element 22d is obtained by printing a resistive heating element paste, which is a mixture of a conductive component, a glass component, and an organic binder component, onto a substrate 22a, and then firing it. When the resistive heating element paste is fired, the organic binder component burns away, leaving the conductive component and the glass component, thus forming a heating element 22d containing the conductive component and the glass component. In Example 1, a sintered body of semiconducting barium titanate in the form of secondary particles was used as the main component of the conductive component.

[0040] Here, using Figures 6A and 6B, a method for producing a sintered body of semiconducting barium titanate in secondary particulate form will be explained. First, a powder made primarily of barium titanate, with the addition of rare earth elements necessary for semiconductivity and sifter elements necessary for shifting the Curie temperature, is pre-calcined at a relatively low temperature of around 1000°C. The powder obtained in this process is called calcined powder, and raw material powder is prepared by grinding and classifying this calcined powder to an average particle size of 1 to 2 μm.

[0041] In Example 1, erbium (Er) was used as the rare earth element, added at a weight ratio of 0.3 wt% of the raw material powder. Lead (Pb) was used as the sifter element, added at a weight ratio of 21 wt% of the raw material powder, and the Curie temperature was shifted from 120°C, the literature value for barium titanate, to 225°C. The Curie temperature is generally defined as the temperature at which the resistance value is twice the resistance value at room temperature (25°C), and this definition is followed here as well. In addition, the Curie temperature sifter element may be an element other than lead (Pb), such as bismuth (Bi) or calcium (Ca). Furthermore, a very small amount (about 150 ppm) of manganese (Mn) was added to adjust the resistance value of the semiconductorized barium titanate sintered body. It is known that the resistance value increases as the amount of Mn increases.

[0042] Furthermore, the rare earth element may be lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), or holmium (Ho). Further, the additive for making the material semiconducting may be niobium (Nb), antimony (Sb), or tantalum (Ta). In addition, the shifter may be not only a shifter element, but also bismuth sodium titanate ((Bi ０．５ Na ０．５ )TiO ３ ), bismuth potassium titanate ((Bi ０．５ K ０．５ )TiO ３ ), sodium niobate (NaNbO ３ ), bismuth ferrite (BiFeO ３ ), or a perovskite-type metal oxide such as these, or bismuth titanate (Bi ４ Ti ３ O １２ ), or a Bi-layered structure oxide such as this, and these may also be used in combination. This makes it possible to obtain a raw material powder for heaters having PTC characteristics with a high Curie temperature.

[0043] It is preferable to configure a heater having PTC characteristics by producing a raw material powder or sintered body that does not use lead for the shifter, as this reduces the environmental load. The preferred content of lead (Pb) contained in the raw material powder or sintered body is less than 1000 ppm. The technology described in the present specification can contribute to the realization of a sustainable society such as a decarbonized / circular society.

[0044] Polyvinyl alcohol (PVA), used as a binder to hold the raw material powders together, is dispersed in a solvent such as water to form a slurry, which is then granulated into secondary particles by spray drying. The secondary particles shown in Figure 6A are obtained by passing the spray-dried granulated powder through sieves with mesh sizes of 38 μm and 45 μm to classify it into particles of 38-45 μm. Figure 6B shows the sintered body after placing the granulated powder in an alumina crucible and firing it at 1300°C for 1 hour. The sintered body shrinks in particle size by approximately 16% due to firing. Because the contact surfaces of adjacent secondary particles are bonded together in this obtained sintered body of secondary particles, it is crushed using a mortar and pestle to extract isolated secondary particles. Subsequently, the secondary particles are passed through sieves with mesh sizes of 32 μm and 38 μm to remove fine powder and irregularly shaped large particles generated by crushing, classifying them into approximately spherical secondary particles of 32-38 μm.

[0045] The secondary particle size after firing can be controlled by the particle size of the raw material powder, slurry concentration, spray nozzle type, and spraying conditions during spray drying, as well as the heat treatment time, heat treatment temperature, and heat treatment profile during firing. Experimental results showed that when the average particle size of the primary particle was between 0.5 μm and 30 μm, the average particle size of the secondary particle after firing was between 1 μm and 200 μm. Example 1 described above shows an example of these conditions.

[0046] The barium titanate sintered body in the form of secondary particles became semiconducting through the firing process described above, and further transformed into a state in which PTC properties are exhibited by the formation of particle interfaces between primary particles. This PTC property allows for the acquisition of self-temperature control characteristics near the Curie temperature. The semiconducting barium titanate sintered body in the form of secondary particles exhibiting PTC properties obtained in this way will be referred to as PTC particles 22f below.

[0047] Furthermore, the PTC particles 22f can also be described as aggregates formed by the aggregation of semiconductor crystal grains (primary particles) containing barium (Ba) and titanium (Ti), and these semiconductor crystal grains are bonded together by sintering to form secondary particles. In addition, the semiconductor crystal grains are compounds having a perovskite-type crystal structure. Moreover, it is desirable that the aggregates contain 1 part by weight or less of rare earth elements when the semiconductor crystal grains are measured in 100 parts by weight, and that at least one of the Curie temperature shifter elements is contained in a molar ratio of 25% or less relative to the semiconductor crystal grains.

[0048] In this disclosure, the term "perovskite-type crystal structure" refers to a metal oxide having a perovskite-type structure (also called a perovskite structure), which is ideally a cubic structure, as described in the Iwanami Dictionary of Physics and Chemistry, 5th Edition (published by Iwanami Shoten on February 20, 1998). Metal oxides having a perovskite-type structure are generally ABO ３ It is represented by the chemical formula ABO3. In perovskite-type metal oxides, elements A and B each occupy specific positions in the unit cell called A-sites and B-sites in ionic form. For example, in a cubic crystal unit cell, element A is located at the vertices of the cube, and element B is located at the body center. Element O occupies a face-centered position in the cube as an oxygen anion. The A-site element is 12-coordinate, and the B-site element is 6-coordinate. If elements A, B, and O are slightly coordinate-shifted from their symmetrical positions in the unit cell, the unit cell of the perovskite-type structure is distorted, resulting in crystal systems such as tetragonal, rhombohedral, and orthorhombic. Although the chemical formula for perovskite-type metal oxides is generally represented as ABO3, in reality, due to volatilization during calcination and errors in compositional analysis, the ratio of A-site elements, B-site elements, and oxygen elements in the entire metal oxide is not necessarily 1:1:3. Even in such cases, as long as the oxide has a perovskite-type structure as its main phase, it is included within the scope of this disclosure.

[0049] In this disclosure, the perovskite type crystal structure is ABO ３ Although it is expressed by the chemical formula, elements A and B are not limited to just one element, such as barium titanate (BaTiO ３ ) and bismuth sodium titanate ((Bi０．５ Na ０．５ )TiO ３ ), bismuth potassium titanate ((Bi ０．５ K ０．５ )TiO ３ ), sodium niobate (NaNbO ３ ), bismuth ironate (BiFeO ３ It may also be a solid solution with other substances, or a mixed crystal.

[0050] Furthermore, as described above, when the granulated powder was placed in an alumina crucible and fired, a reaction sometimes occurred between the contact surface between the crucible and the granulated powder near the bottom of the crucible's inner surface after firing. As a result, problems such as deformation of the crucible's bottom surface or some of the granulated powder close to the contact surface with the crucible being altered and firmly adhering to the crucible occurred. Therefore, Figure 6B shows the portion where no reaction with the crucible occurred and the firing process was completed successfully, and in Example 1, PTC particles 22f from this portion were used.

[0051] Furthermore, in the example shown in Figure 6B above, the granulated powder was fired at 1300°C to create a sintered body. However, it is preferable that the firing temperature for creating this sintered body be in the range of 1250°C to 1360°C. This is because, while the grain growth of primary particles accelerates from 1250°C, at temperatures above 1360°C the granulated powder becomes more prone to reacting with the crucible and setter used during firing.

[0052] Next, the obtained PTC particles 22f were made into a paste for screen printing onto a ceramic substrate 22a. This paste is a ceramic material for manufacturing a resistive heating element 22d as a ceramic component. The main components of the paste are a solvent, glass frit and organic binders, PTC particles 22f, and metal particles 22g to connect the PTC particles 22f together and form a current path. Since PTC particles 22f (semiconductorized barium titanate) are classified as N-type semiconductors, it is necessary to select materials so that the interface between the PTC particles 22f and the metal particles 22g becomes an ohmic contact. For example, noble metals such as gold (Au), silver (Ag), and palladium (Pd) are known to form a large barrier at the interface. On the other hand, base metals such as zinc (Zn), tin (Sn), nickel (Ni), and aluminum (Al) are known to produce an ohmic contact.

[0053] Therefore, in Example 1, a mixture of silver and zinc in a weight ratio of 8:1 was used as 22g of metal particles. That is, the above 22g of metal particles was configured to contain base metal elements. Furthermore, the PTC particles 22f and the metal particles 22g were blended in a weight ratio of 10:1. A weight ratio in the range of 11:1 to 9:1 was considered optimal. If the amount of PTC particles 22f was greater than this weight ratio, the amount of metal particles 22g became insufficient, and conductive paths between the PTC particles 22f were not formed, resulting in poor conductivity. Conversely, if the amount of PTC particles 22f was reduced, the amount of metal particles 22g became excessive, and conductive paths were formed only by the metal particles 22g, resulting in the loss of PTC characteristics.

[0054] Using the paste described above, the ceramic substrate 22a was coated by screen printing, followed by drying at 180°C and firing at 600°C to form the resistance heating element 22d. Here, by setting the firing temperature to 600°C, which is lower than the firing temperature of 1300°C used when producing the PTC particles 22f, no reaction occurred between the PTC particles 22f and the ceramic substrate 22a (alumina), and good PTC properties could be maintained.

[0055] In other words, in this embodiment, the PTC particles 22f contained in the paste are semiconducting. Therefore, in the secondary firing process in which the screen-printed paste is fired, it is sufficient to solidify the paste and fire it at a temperature necessary to neck the metal particles contained in the paste, as will be described later. That is, it is sufficient to fire it at a temperature at which the metal particles 22g, which act as binders connecting the PTC particles 22f, melt. The firing temperature during paste firing (secondary firing temperature) is usually set in the range of 150°C to 850°C depending on the type of substrate used for the paste, but this temperature range is lower than the temperature range that semiconducts barium titanate (primary firing temperature). By firing the paste at a lower temperature range, it is possible to prevent the PTC particles 22f from reacting with the substrate 22a. In this embodiment, a ceramic substrate (ceramic base material) 22a is used as the base material in order to minimize the reaction with the PTC particles 22f. However, the invention is not limited to this, and for example, a metal substrate (metal base material) with an insulating layer formed on it may be used as the base material, and the above paste may be applied to this insulating layer to form the resistive heating element 22d as the ceramic composition part.

[0056] Figures 7A to 7D illustrate how PTC particles 22f are connected by metal particles (metal elements) 22g. Figure 7A shows a scanning electron microscope (SEM) view of a portion of the resistance heating element 22d. Figure 7B is a schematic diagram of Figure 7A, showing how PTC particles 22f (aggregates) are connected by metal particles 22g. As shown by the conductive paths indicated by the arrows in Figure 7B, conductive paths are formed to pass through the PTC particles 22f, allowing the resistance heating element 22d to exhibit PTC properties. Figure 7C is a magnified view of field A in Figure 7A, showing that sintering of the metal particles 22g (metal elements) has progressed due to the firing process, resulting in a necked state. Figure 7D is a schematic diagram showing the necked state of metal particles 22g located in field B of Figure 7C, indicating that sintering has progressed between multiple metal particles 22g, causing the particles to form a neck shape and connect to each other.

[0057] In this way, by connecting multiple metal particles 22g together through necking during firing, a stable conductive path is ensured. As a result, even when a large current of around 10A (amperes) is passed through the heater 22, no malfunctions such as sparks occur at the connection point in field A, and stable electrical heating becomes possible. The state of this conductive path can also be observed by splitting the heater 22 and observing the fracture surface with a SEM, or, in more detail, by cutting out the resistive heating element 22d using FIB processing (focused ion beam processing) and observing its surface with a transmission electron microscope (TEM).

[0058] Next, the protective layer 22e will be explained in detail. As shown in Figure 5E, the protective layer 22e covers the entire resistive heating element 22d and conductive pattern 22c, excluding the power supply electrode 22b, protecting them and ensuring insulation and sliding properties between them and the film 23.

[0059] Glass and PI (polyimide) are preferred materials from the viewpoint of heat resistance, and if necessary, a heat-conducting filler with insulating properties may be mixed in. In Example 1, glass was used as the protective layer 22e. The type of glass should be selected to match the recommended firing temperature of the metal particles 22g used in the resistance heating element 22d. The protective layer 22e was formed by coating the glass paste with screen printing, then drying at 180°C and firing at 600°C.

[0060] (Electrical Characteristics of the Heater) Figure 8 shows the resistance-temperature characteristics of the heater 22 in Example 1. In Example 1, the thickness of the resistance heating element 22d relative to the ceramic substrate 22a is 500 μm. The resistance values ​​between the two power supply electrodes 22b shown in Figures 5A to 5E were measured while the heater 22 was placed in a constant temperature bath and the temperature was changed. The resistance values ​​increased sharply from around the Curie temperature of 225°C, indicating that the PTC characteristic was manifesting.

[0061] Furthermore, the withstand voltage characteristics of the heater 22 were also measured. The measurement method involved energizing the heater 22 alone and gradually increasing the applied voltage. The voltage at which the heater 22 overheated and destroyed was measured, exceeding the maximum resistance point shown in Figure 8. As a result, it was found that the withstand voltage of the heater 22 in Example 1 is approximately 170V.

[0062] Next, the configurations of other examples and comparative examples will be described, and finally, the effects will be explained in summary. Note that the image forming apparatus and heating apparatus other than the heater 22 in the other examples and comparative examples will be the same as in Example 1, so their descriptions will be omitted.

[0063] <Example 2> Example 2 is a modified version of Example 1 in which the thickness of the resistive heating element 22d of the heater 22 is changed to 300 μm. Since the resistance value of the heater 22 decreases due to the reduction in thickness compared to Example 1, the resistance value was increased by slightly increasing the Mn content in the raw material powder of the PTC particles, and adjusted to have a resistance value equivalent to that of Example 1. The withstand voltage decreased by the amount that the thickness was reduced to 3 / 5 compared to Example 1, becoming 102 V.

[0064] <Example 3> Example 3 is a modified version of Example 1 in which the thickness of the resistive heating element 22d of the heater 22 is changed to 1000 μm. The other configurations are the same as in Example 1. As the resistance of the heater 22 increases due to the increased thickness compared to Example 1, the resistance was reduced by slightly decreasing the Mn content in the raw material powder of the PTC particles, and adjusted to have a resistance equivalent to that of Example 1. The withstand voltage increased by the amount that the thickness doubled compared to Example 1, reaching 340 V.

[0065] <Example 4> Example 4 is a modified version of Example 1 in which the thickness of the resistive heating element 22d of the heater 22 is changed to 600 μm. The other configurations are the same as in Example 1. As the resistance of the heater 22 increases due to the increased thickness compared to Example 1, the resistance was reduced by slightly decreasing the Mn content in the raw material powder of the PTC particles, and adjusted to have a resistance equivalent to that of Example 1. The withstand voltage increased by 6 / 5 times compared to Example 1, becoming 204 V.

[0066] <Example 5> Example 5 is a modified version of Example 1 in which the thickness of the resistive heating element 22d of the heater 22 is changed to 200 μm. The other configurations are the same as in Example 1. As the thickness is reduced compared to Example 1, the resistance of the heater 22 decreases. Therefore, the resistance is increased by slightly increasing the Mn content in the raw material powder of the PTC particles, and the resistance is adjusted to be equivalent to that of Example 1. The withstand voltage decreased by the amount that the thickness was reduced to 2 / 5 compared to Example 1, becoming 68 V.

[0067] <Comparative Example 1> As shown in Figures 9A to 9C, Comparative Example 1 uses a configuration of multiple plate-shaped sintered bodies 22h and a heat transfer plate 22k as the heater 22. The plate-shaped sintered body 22h shown in Figure 9A was formed by press-molding a powder with a slightly reduced Mn content compared to the raw material powder used in Example 1, and firing it at 1300°C. Its size is 7 mm wide, 22 mm long, and 1 mm thick. The surface and back surface (not shown) of the plate-shaped sintered body 22h are equipped with electrodes 22i, which consist of a Ni layer and an Ag layer of overcoat electrodes laminated on top of the Ni layer for the purpose of ohmic contact. As shown in Figure 9B, ten of these are arranged in the longitudinal direction to form a heating element with the same length as Example 1, 220 mm long and 7 mm wide. Furthermore, two electrode plates 22j made of stainless steel (SUS) with a thickness of 0.1 mm were prepared and sandwiched between the surface and back surface of the ten plate-shaped sintered bodies 22h. This was integrated with the heat transfer plate 22k as shown in Figure 9C to complete the heater 22. The heat transfer plate 22k was made of an aluminum nitride substrate with a width of 10 mm, a length of 270 mm, and a thickness of 0.6 mm. The plate-shaped sintered body 22h had a thickness of 1 mm. Since the resistance value of the heater 22 increased due to the increased thickness compared to Example 1, the resistance value was reduced by slightly decreasing the Mn content in the raw material powder, and the resistance value of the heater 22 was adjusted to be the same as that of Example 1.

[0068] The heater 22 can generate heat from the plate-shaped sintered body 22h by applying a voltage between the two electrode plates 22j. Furthermore, by making the surface of the heat transfer plate 22k opposite to the surface in contact with the electrode plates 22j the sliding surface with the film 23, the heat from the plate-shaped sintered body 22h is transferred to the film 23 via the heat transfer plate 22k. In addition, since aluminum nitride is an insulator, the heat transfer plate 22k can ensure insulation between the electrode plates 22j and the film 23.

[0069] <Comparative Example 2> Comparative Example 2 differs from Example 1 in that the step of preparing PTC particles 22f in the preparation of the resistance heating element was omitted. In preparing the resistance heating element according to Comparative Example 2, first, a calcined powder was prepared by grinding and classifying the raw material powder of the PTC particles 22f used in Example 1, i.e., barium titanate as the main component, with 0.3 wt% Er and 21 wt% Pb added by weight ratio of the raw material powder, to an average particle size of 1 to 2 μm. This raw material powder was dispersed in terpineol, a solvent, to form a paste, which was printed onto the alumina substrate used in Example 1 with a width of 7 mm, a length of 220 mm, and a thickness of 500 μm, and then fired at 1300°C. As a result, a reaction occurred between the contact surface of the alumina substrate and the raw material powder, causing deformation of the alumina substrate along its entire length. Furthermore, the raw material powder near the contact surface with the alumina substrate was altered, and countless cracks also occurred near the surface of the raw material powder. As a result, the resistive heating element 22d prepared in Comparative Example 2 could not generate heat when energized.

[0070] <Comparative Example 3> In Comparative Example 3, instead of bonding the PTC particles 22f together with metal particles 22g by a firing process as in Example 1, we attempted to bond the metal particles 22g by crushing them with a pressing process. Solder particles with a particle size of 10 μm and mainly composed of tin were prepared as the metal particles 22g, and the PTC particles 22f from Example 1 and the solder particles were mixed in a weight ratio of 10:1. This mixed powder was applied to the alumina substrate used in Example 1 to a width of 7 mm, a length of 220 mm, and a thickness of 500 μm (hereinafter referred to as Sample 1). In a part of the area where the mixed powder was applied, the mixed powder and the alumina substrate were sandwiched between cylindrical metal with a diameter of Φ15 mm from the thickness direction of the alumina substrate, and pressed at 50 MPa.

[0071] Figures 10A and 10B show the cross-sectional SEM observation results of the mixed powder of sample 1 after press processing. Figure 10A shows the area near the press surface of the mixed powder of sample 1, and it can be seen that the PTC particles 22f are crushed in a straight line (planar) on the press surface. Furthermore, it can be seen that the pressure applied in the pressing direction causes the PTC particles 22f inside the film of the mixed powder to push against each other, and the PTC particles 22f are densely packed together without gaps, accompanied by the crushing of the outer periphery of the PTC particles 22f. If a large amount of fine powder is present on the outer periphery of the PTC particles 22f due to this crushing, a large contact resistance will occur between the fine powders themselves, or between the fine powders and the PTC particles 22f, leading to poor conductivity. In addition, it can be observed that large cracks have occurred inside the PTC particles 22f, which may lead to poor conductivity of the PTC particles 22f themselves. Furthermore, Figure 10B shows that the secondary particles of the PTC particles 22f had broken down into primary particles. When the secondary particles break down in this way, not only is it impossible to obtain PTC characteristics, but it is also thought that the conductivity of the PTC particles 22f themselves cannot be obtained. On the other hand, cracks also occurred in the alumina substrate due to localized pressing. Thus, the resistive heating element 22d made in Comparative Example 3 could not generate heat when energized.

[0072] <Comparative Example 4> Comparative Example 4 is an example in which metal particles 22g become liquid when PTC particles 22f reach the Curie temperature. Sample 1, the same as that used in Comparative Example 3, was placed on a hot plate and heated to 225°C, the Curie temperature of PTC particles 22f. The solder particles used in sample 1 began to melt at around 190°C and became liquid at 225°C. At that time, the liquid solder particles began to aggregate due to surface tension and formed large spherical shapes. Figure 11 shows the cross-section of sample 1 observed by SEM after heating sample 1 to 225°C and then cooling. It can be seen that solder particles with a particle size of 10 μm, which were dispersed among the PTC particles 22f with a particle size of 32 to 38 μm, melted and aggregated as described above, and precipitated near the surface of the film as huge solder balls 22l with a particle size of about 200 μm. One drawback of the metal particles 22g becoming liquid is that proper conductive paths between the PTC particles 22f cannot be obtained, resulting in poor conductivity. Alternatively, conductive paths formed by localized aggregation of metal particles 22g near the surface of the film may be created, resulting in the formation of very low-resistance conductive paths that do not involve the PTC particles 22f. As a result, the resistance heating element 22d fabricated in Comparative Example 4 could not generate heat through current.

[0073] The heater according to this embodiment aims to suppress the heating of the non-paper-passing section by its self-temperature control characteristics near the Curie temperature. Therefore, it is necessary to obtain an appropriate conductive path at the Curie temperature. From this perspective, it is considered necessary that the melting point of the metal particles 22g be at least higher than the Curie temperature of the PTC particles 22f.

[0074] Furthermore, indium-gallium (In-Ga) alloy, which is in a liquid state at room temperature, is also known as an electrode material that can achieve ohmic contact with a plate-shaped sintered body of barium titanate having PTC properties. When a liquid indium-gallium alloy is mixed with PTC particles 22f and applied to a substrate, aggregation of the indium-gallium alloy occurs, similar to the solder particle experiment, and it is thought that a suitable conductive path cannot be obtained.

[0075] (Evaluation) Each of the heaters 22 of Examples 1 to 5 above was incorporated into the heating device 9 and its performance was evaluated. As mentioned above, the heaters 22 of Comparative Examples 2 to 4 could not be evaluated because a suitable conduction path could not be obtained, and they did not generate heat when energized.

[0076] As a condition for performance evaluation, 100V was applied to the heater 22 to heat it up. The laser printer 100 was operated with the peripheral speed of the pressure roller 30 set to 250 mm / s, and A5 size (148 mm x 210 mm) recording material P was printed at 50 ppm. During this process, the quick start evaluation, the fixing performance on the 50th sheet evaluation, and the effect of suppressing the temperature rise of the non-paper-feeding area on the 50th sheet evaluation were performed. For the quick start evaluation, printing was started from a state where the heating device 9 had cooled to room temperature of 23°C, and the time from when the heating device 9 started up until the toner image T was properly fixed to the recording material P by the heating device 9 and discharged into the output tray 11 was evaluated. For the fixing performance on the 50th sheet evaluation, the temperature detected by the thermistor 25 (hereinafter referred to as the temperature control temperature) was set to several levels, and the temperature control temperature at which proper fixing was performed was investigated. To evaluate the effect of suppressing the temperature rise of the non-paper-feeding portion of the 50th sheet, the surface temperature of the film 23 corresponding to the non-paper-feeding portion of the A5-sized recording material P was monitored using a radiation thermometer.

[0077] Table 1 summarizes the performance evaluation results for Examples 1 to 5, in which the thickness of the resistance heating element 22d was varied. For each evaluation item, ◎ indicates that the performance is sufficient, ○ indicates that it is not sufficient but within an acceptable range, △ indicates that it does not meet the required performance but may be usable, × indicates that it is unusable, and - indicates that it cannot be evaluated.

[0078] Regarding the withstand voltage, as mentioned above, Example 5 had a withstand voltage of 68V, which was insufficient with the applied voltage of 100V used in the performance evaluation conditions described above, resulting in destruction. Therefore, for Example 5, the other evaluation items could not be evaluated. On the other hand, all configurations other than Example 5 had a withstand voltage exceeding 100V, so the heater 22 could be heated with an applied voltage of 100V.

[0079] Regarding the evaluation of the quick start, the configuration of Example 2, in which the resistive heating element 22d has a thin thickness of 300 μm, performed best, and the performance deteriorated as the thickness increased. One possible reason for this is simply that the heat capacity increases as the thickness increases, thus worsening the start-up performance.

[0080] The second reason is thought to be that as the thickness increases, a heat distribution occurs inside the resistive heating element 22d, causing a pinch effect where the center of the resistive heating element 22d becomes hotter and more resistant than the Curie temperature, resulting in a concentration of the electric field. In other words, as shown in the cross-sectional view of the heating device 9 in Figure 2, the heat from the resistive heating element 22d is transferred to the pressure roller 30 via the protective layer 22e and the film 23. Furthermore, on the opposite side, the heat is transferred to the substrate 22a and the film guide 21, causing the center of the resistive heating element 22d to become hot. Once the pinch effect occurs, the area near the center of the resistive heating element 22d remains highly resistant, resulting in a prolonged state where not much power is supplied. Therefore, it is necessary to wait for the high temperature near the center of the resistive heating element 22d to transfer to the surface over time, until the surface of the film 23 reaches a printable temperature. As a result, in Example 3, where the pinch effect is considered to be significant, it took 13 seconds.

[0081] For quick starts, the faster the target time, the better, and a time in the 5-second range is considered sufficient. Therefore, Example 2 was marked with ◎, Example 1 with ○, and Example 4 (7 seconds) and Example 3 (13 seconds) with △.

[0082] For the 50th print's fixation performance evaluation, an A5-sized recording material P was printed at high speed at 50 ppm at a room temperature of 23°C. As a result, the surface temperatures of the film 23 and pressure roller 30 were cooled, as shown in Figure 2. This led to a more pronounced heat distribution and pinch effect within the resistance heating element 22d. Consequently, in Example 3, even when the temperature control temperature was set to the Curie temperature of 225°C, the fixation process was not successful. Even when set higher than 225°C, the resistance heating element 22d remained in a high-resistance state, preventing power from being supplied and thus failing to improve fixation performance. On the other hand, in Example 2, because the resistance heating element 22d was thin at 300 μm, a heat distribution within the resistance heating element 22d was less likely to occur, and a good fixation process was achieved at a temperature control temperature of 195°C. Furthermore, in Examples 1 and 4, the thickness of the resistance heating element 22d was 500 μm and 600 μm, respectively, which was thicker than in Example 2. However, in Example 1, a good result was obtained with a temperature control temperature of 200°C, and in Example 4, the fixing treatment could be performed at 215°C, just below the Curie temperature.

[0083] As for the target temperature for temperature control, lower temperatures are more desirable. Examples 1 and 2, which were below 200°C, were marked with ◎, Example 4, which was below the Curie temperature of 225°C, was marked with ○, and Example 3, which was higher than the Curie temperature of 225°C, was marked with △.

[0084] Regarding the effect of suppressing the temperature rise of the non-paper-passing section at the 50th sheet, in all of Examples 1 to 4, it was measured that the surface temperature of the film 23 saturated at 235°C due to the self-temperature control characteristics of the resistance heating element 22d.

[0085] Finally, a similar evaluation was performed on the configuration of Comparative Example 1. As shown in Figures 9A and 9B, the configuration of Comparative Example 1 has a plate-shaped sintered body 22h with a thickness of 1000 μm, making it prone to pinch effects. Furthermore, it uses two SUS electrode plates 22j with a thickness of 0.1 mm and an aluminum nitride substrate with a thickness of 0.6 mm as a heat transfer plate. As a result, a significant heat distribution occurred within the heater 22 due to the increased heat capacity and the increased contact thermal resistance between these components. Consequently, the quick start evaluation result was 16 seconds, which was worse than that of Example 3. Furthermore, regarding the fixing performance evaluation for the 50th sheet, it was found that the temperature control temperature needed to be 225°C or higher, similar to Example 3, and good fixing performance could not be obtained. The evaluation result of the effect of suppressing the temperature rise of the non-paper-feeding part for the 50th sheet was similar to that of Examples 1 to 4, and it was measured that the surface temperature of the film 23 was saturated at 235°C.

[0086] From the above results, it was found that a configuration like that of Example 1 or Example 2 is particularly desirable for a heating device 9 that can cope with the increased processing speed of printers in recent years. Furthermore, it was found that a thickness of 500 μm or less is desirable for the resistance heating element 22d.

[0087] Furthermore, the heater 22 in Examples 3 and 4 may also be configured to include, for example, a power supply electrode 22b, a conductive pattern 22c, a resistive heating element 22d made of a conductive component that does not cause pinch effects, such as silver-palladium (Ag-Pd) or ruthenium oxide (RuO2), and a protective layer 22e, separately on the back surface of the substrate 22a. In this way, the energization state to the resistive heating elements 22d on the front and back surfaces of the substrate 22a can be controlled from the viewpoint of quick start, fixing performance, and suppression of temperature rise in non-paper-passing areas, and energization can be performed individually or simultaneously.

[0088] In the embodiments described above, a ceramic component was constructed using a sintered body in which PTC particles 22f are connected by metal particles 22g (metal elements), and this ceramic component was used as a resistance heating element 22d. However, the ceramic component is not limited to this and can also be used, for example, in a safety device that automatically shuts off the power supply when the temperature exceeds a certain level. Furthermore, although described as a comparative example above, the ceramic material containing PTC particles 22f and metal particles 22g may be shaped using press molding. For this reason, the ceramic material containing PTC particles 22f and metal particles 22g for manufacturing the ceramic component does not necessarily have to be in paste form, but may be in powder form. In addition, the disclosures described in the embodiments described above may be combined in any way.

[0089] (Summary) [Configuration 1] A heater comprising a base material and a ceramic composition provided on the base material, wherein the ceramic composition generates heat when a voltage is applied to the ceramic composition, wherein the ceramic composition comprises a plurality of aggregates formed by the aggregation of semiconductor crystal grains containing barium and titanium, and metal elements present at the grain boundaries of the aggregates, wherein the aggregates are connected to each other in a state in which the metal elements are necked.

[0090] [Configuration 2] The heater according to Configuration 1, wherein the aggregate is a secondary particle formed by the semiconductor crystal grains bonding together by sintering.

[0091] [Configuration 3] The heater according to Configuration 1 or 2, wherein the semiconductor crystal grains are a compound having a perovskite-type crystal structure.

[0092] [Configuration 4] The heater according to any one of Configurations 1 to 3, wherein the metal element contains a base metal element.

[0093] [Configuration 5] The heater according to any one of Configurations 1 to 4, wherein the metal element has a melting point higher than the Curie temperature of the aggregate.

[0094] [Configuration 6] The heater according to any one of Configurations 1 to 5, wherein the aggregate contains 1 part by weight or less of a rare earth element when the semiconductor crystal grains are 100 parts by weight.

[0095] [Configuration 7] The heater according to any one of Configurations 1 to 6, wherein the aggregate contains at least one of the Curie temperature shifter elements in a molar ratio of 25% or less with respect to the semiconductor crystal grains.

[0096] [Configuration 8] The heater according to any one of Configurations 1 to 7, wherein the average particle size of the semiconductor crystal grains is 0.5 μm or more and 30 μm or less, and the average particle size of the aggregate is 1 μm or more and 200 μm or less.

[0097] [Configuration 9] The heater according to any one of Configurations 1 to 8, wherein the thickness of the ceramic composition based on the substrate is 500 μm or less.

[0098] [Configuration 10] The heater according to any one of Configurations 1 to 9, wherein the base material is a ceramic base material.

[0099] [Configuration 11] The heater according to any one of Configurations 1 to 10, wherein the base material is configured by forming an insulating layer on a metal base material, and the ceramic composition is formed on the insulating layer.

[0100] [Configuration 12] A heating device comprising: a heater according to any one of Configurations 1 to 11; a support member for supporting the heater; a fixing film that is movable while heat from the heater is transferred to it; and a pressing member that forms a pressing portion between itself and the heater via the fixing film for heating a toner image on a recording medium.

[0101] [Configuration 13] A ceramic material comprising a sintered body in the form of secondary particles in which semiconductor crystal grains containing barium and titanium are bonded together, and a metal element.

[0102] [Configuration 14] The ceramic material according to Configuration 13, wherein the metal element is a base metal element.

[0103] [Configuration 15] A method for manufacturing ceramic parts, comprising the steps of: coating a ceramic material described in Configuration 13 or 14 onto a substrate; and firing the ceramic material coated on the substrate.

[0104] [Configuration 16] The method for manufacturing ceramic parts according to Configuration 15, wherein the firing temperature when firing the ceramic material is lower than the firing temperature when creating the sintered body.

[0105] This disclosure can be used in methods for manufacturing heaters, heating devices, ceramic materials, and ceramic components.

[0106] The present invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are attached to make the scope of the invention public.

[0107] This application claims priority based on Japanese Patent Application No. 2025-040376 filed on 13 March 2025 and Japanese Patent Application No. 2026-018405 filed on 6 February 2026, and all of the contents of those applications are incorporated herein by reference.

[0108] 22: Heater / 22a: Substrate (ceramic substrate) / 22d: Ceramic composition (resistive heating element) / 22f: Aggregate (PTC particles) / 22g: Metal element (metal particles)

Claims

1. A heater comprising a base material and a ceramic composition provided on the base material, wherein the heater generates heat when a voltage is applied to the ceramic composition, the ceramic composition comprising a plurality of aggregates formed by the aggregation of semiconductor crystal grains containing barium and titanium, and metal elements present at the grain boundaries of the aggregates, wherein the aggregates are connected to each other in a state in which the metal elements are necked.

2. The heater according to claim 1, wherein the aggregate is a secondary particle formed by the semiconductor crystal grains bonding together by sintering.

3. The heater according to claim 1 or 2, wherein the semiconductor crystal grains are a compound having a perovskite-type crystal structure.

4. The heater according to any one of claims 1 to 3, wherein the metal element contains a base metal element.

5. The heater according to any one of claims 1 to 4, wherein the metal element has a melting point higher than the Curie temperature of the aggregate.

6. The heater according to any one of claims 1 to 5, wherein the aggregate contains 1 part by weight or less of a rare earth element when the semiconductor crystal grains are 100 parts by weight.

7. The heater according to any one of claims 1 to 6, wherein the aggregate contains, with respect to the semiconductor crystal grains, at least one of the Curie temperature shifter elements in a molar ratio of 25% or less.

8. The heater according to any one of claims 1 to 7, wherein the average particle size of the semiconductor crystal grains is 0.5 μm or more and 30 μm or less, and the average particle size of the aggregate is 1 μm or more and 200 μm or less.

9. The heater according to any one of claims 1 to 8, wherein the thickness of the ceramic composition based on the substrate is 500 μm or less.

10. The heater according to any one of claims 1 to 9, wherein the substrate is a ceramic substrate.

11. The heater according to any one of claims 1 to 10, wherein the substrate is configured by forming an insulating layer on a metal substrate, and the ceramic composition is formed on the insulating layer.

12. A heating device comprising: a heater according to any one of claims 1 to 11; a support member for supporting the heater; a fixing film that is movable while heat from the heater is transferred to it; and a pressing member that forms a pressing portion between itself and the heater via the fixing film for heating a toner image on a recording medium.

13. A ceramic material comprising a sintered body in the form of secondary particulate matter in which semiconductor crystal grains containing barium and titanium are bonded together, and a metallic element.

14. The ceramic material according to claim 13, wherein the metal element is a base metal element.

15. A method for manufacturing a ceramic part, comprising the steps of: coating a ceramic material according to claim 13 or 14 onto a substrate; and firing the ceramic material coated on the substrate.

16. The method for manufacturing a ceramic part according to claim 15, wherein the firing temperature when firing the ceramic material is lower than the firing temperature when creating the sintered body.

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