JP2007036045A - Ptc element and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PTC element excellent in withstand voltage characteristics and a method for manufacturing the PTC element. <P>SOLUTION: The PTC element 1 is provided with a first element 2, a second electrode 4, and a PTC element assembly L 5 disposed between the first electrode 2 and the second electrode 4. The PTC element assembly L5 has a first PTC region 6 and a second PTC region 8 containing a resin and conductive particles, and an intermediate region 10 sandwiched between the first PTC region 6 and the second PTC region 8. The intermediate region 10 is extended in a direction with which an arrow A direction that is the disposition direction of the first electrode 2, the PTC element assembly L5, and the second electrode 4. In addition, the intermediate region 10 has a value of resistance higher than those of the first PTC region 6 and the second PTC region 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a PTC element and a method for manufacturing a PTC element.

As a conventional PTC element, for example, as described in Patent Document 1, a PTC element body (organic positive temperature characteristic composition) obtained by dispersing conductive particles in a resin is sandwiched between electrodes. .
JP-A-5-021207

  In the PTC element body included in the PTC element described in Patent Document 1, there may be a case where a region where the conductive particles are aggregated is formed due to dispersion dispersion of the conductive particles at the time of manufacture or air mixing. When the PTC element body in which such a region is formed is used for a PTC element, a conductive path is established through the region, which may cause a problem that a withstand voltage characteristic of the PTC element is deteriorated.

  Therefore, an object of the present invention is to provide a PTC element having good withstand voltage characteristics and a method for manufacturing the PTC element.

  A PTC element according to the present invention includes a pair of electrodes disposed in a state of being opposed to each other, and a PTC element body disposed between the pair of electrodes and having a positive resistance temperature characteristic. The PTC element body includes a plurality of PTC regions including a resin and conductive particles, and an intermediate region sandwiched between the PTC regions and extending in a direction intersecting with the arrangement direction of the pair of electrodes and the PTC element body. The intermediate region has a higher resistance value than the PTC region.

  The PTC element of the present invention includes a pair of electrodes and a PTC element body sandwiched between the electrodes. An intermediate region is formed in the PTC element, and this intermediate region has a high resistance value. By providing such a high resistance region in the PTC body, the construction of the conductive path can be suppressed.

  By the way, in order to suppress the construction of the conductive path, it is conceivable to cover the surface of the PTC element body with a high-resistance film or the like. However, in this case, the high-resistance film is damaged by the electrode disposed on the PTC element body, and the construction of the conductive path may not be sufficiently suppressed. On the other hand, in the PTC element body included in the PTC element of the present invention, the intermediate region is located between the PTC region and the PTC region. Therefore, the intermediate region is not damaged by the electrode. Therefore, the construction of the conductive path can be reliably suppressed. As a result, a PTC element with good withstand voltage characteristics can be obtained.

  The intermediate region contains a resin as a main component, and it is preferable that the resin contained in the intermediate region and the resin contained in the PTC region have the same components. In this case, the intermediate region including the resin composed of the same component and the PTC region can be easily joined. As a result, it is possible to obtain a PTC element in which the bonding state between the intermediate region and the PTC region is good.

  Moreover, it is preferable that the surface which contacts a PTC element | base_body among the surfaces of an electrode is roughened. In this case, when the electrode is disposed on the PTC element body, fine convex portions formed on the surface of the electrode enter the surface of the PTC element body. Therefore, the bonding strength of the electrode with respect to the PTC element body can be improved.

  A method of manufacturing a PTC element according to the present invention includes a pair of electrodes arranged in a state of being opposed to each other, a PTC element body disposed between the pair of electrodes, and having a positive resistance temperature characteristic. A first step of preparing a plurality of PTC substrates including a resin and conductive particles, and a predetermined surface of at least one PTC substrate among the plurality of PTC substrates. And a second step of forming a high resistance region having a higher resistance value than the PTC base material, and a plurality of PTC base materials are stacked so that the high resistance region is positioned between them, thereby forming a PTC body. A third step of forming a body, a fourth step of arranging a pair of electrodes so as to sandwich the PTC molded body in the stacking direction of the PTC substrate, and a PTC molding after arranging the pair of electrodes And a fifth step of cross-linking the body. .

  In this manufacturing method, after the high resistance region is formed on a predetermined surface of the PTC substrate, the PTC substrate is overlapped so that the high resistance region is located between the PTC substrate and the high resistance region. It will be sandwiched between the materials. Thus, by providing the high resistance region between the PTC base material and the PTC base material, the construction of the conductive path can be reliably inhibited. As a result, a PTC element with good withstand voltage characteristics can be obtained.

  Moreover, it is preferable that a 2nd process forms a high resistance area | region by heating a PTC base material and raising the resin contained in the said PTC base material on a predetermined | prescribed surface. In this case, since the high resistance region can be formed by heating the PTC substrate, the high resistance region can be easily formed.

  Moreover, it is preferable that a 2nd process forms a high resistance area | region using resin from which a component differs from resin contained in a PTC base material.

  Moreover, it is preferable that a 2nd process etches the predetermined surface of a PTC base material, and removes electroconductive particle. In this case, since a new material is not required for forming the high resistance region, the high resistance region can be formed at low cost.

  A PTC element according to the present invention is disposed between a first electrode and a second electrode disposed in a state of facing each other, between the first electrode and the second electrode, and has a positive resistance. A PTC element body having temperature characteristics, wherein the PTC element body includes a resin and conductive particles, and includes a first PTC region bonded to the first electrode, a resin and conductive particles, and a second A second PTC region joined to the electrode, an intermediate region located between the first PTC region and the second PTC region and having a higher resistance value than the first PTC region and the second PTC region; It is characterized by having.

  The PTC element body of the present invention has a high-resistance intermediate region. Since the intermediate region is located between the first PTC region and the second PTC region, the intermediate region is not damaged by the first electrode and the second electrode arranged on the surface of the PTC element. Therefore, the construction of the conductive path can be reliably inhibited. Therefore, a PTC element with good withstand voltage characteristics can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a PTC element with a favorable withstand voltage characteristic and a PTC element can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  FIG. 1 is a cross-sectional view of a PTC element according to this embodiment. As shown in FIG. 1, the PTC element 1 includes a first electrode 2 and a second electrode 4 that are a pair of electrodes, and a PTC element body L5.

  The first electrode 2 and the second electrode 4 are arranged in a state of facing each other. Each of the first electrode 2 and the second electrode 4 has electron conductivity. Of the surfaces of the first electrode 2 and the second electrode 4, the surfaces 2a and 4a in contact with the PTC element body L5 are It is roughened. More specifically, the 1st electrode 2 and the 2nd electrode 4 consist of Cu foil which gave Ni or Ni plating. The 1st electrode 2 and the 2nd electrode 4 are exhibiting the shape of a flat plate, and the surface 2a of the 1st electrode 2 and the surface 4a of the 2nd electrode 4 have nodules (unevenness difference is about 5-15 micrometers). A large number of portions from the middle part to the base part are constricted with respect to the head part. This nodule has entered the surface of the PTC element body L5. A lead (not shown) is connected to the first electrode 2 and the second electrode 4. It is possible to discharge or inject electric charges from the first electrode 2 and the second electrode 4 to the outside through the connected leads.

  A PTC element body L5 having a positive resistance temperature characteristic is disposed between the first electrode 2 and the second electrode 4. The PTC element body L5 has a first PTC region 6, a second PTC region 8, and an intermediate region 10. The first PTC region 6 and the second PTC region 8 each contain a resin and conductive particles. More specifically, the first PTC region 6 and the second PTC region 8 are mainly composed of linear low-density polyethylene as a thermoplastic resin and filament-like particles made of nickel as conductive particles. It is said. The first PTC region 6 is bonded to the first electrode 2, and the second PTC region 8 is bonded to the second electrode 4.

  Note that the resin contained in the first PTC region 6 and the second PTC region 8 may not be thermoplastic. That is, it may be a thermosetting resin, or may be a crystalline resin or an amorphous resin.

  Here, a crystalline resin means a resin whose melting point can be observed by ordinary thermal analysis measurement, and an amorphous resin means a resin whose melting point cannot be observed even by ordinary thermal analysis measurement. Say. Examples of the amorphous resin include olefin polymers, halogen polymers, polystyrene, epoxy resins, unsaturated polyester resins, diallyl phthalate resins, phenol resins, thermosetting polyimide resins, and melamine resins.

  Examples of the olefin-based polymer include polyolefins such as polyethylene, ethylene-vinyl acetate copolymer or polyalkyl acrylate such as polyethyl acrylate, polyalkyl (meth) acrylate such as polymethyl (meth) acrylate, or copolymers thereof.

  Examples of the halogen-based polymer include fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, and copolymers thereof, polyvinyl chloride, polyvinylidene chloride, chlorinated polyvinyl chloride, chlorinated polyethylene, or chlorinated polypropylene. Or chlorine-type polymers, such as these copolymers, etc. are mentioned.

  These can be used alone or in combination of two or more. Among these, it is preferable to use an olefin polymer, more preferably polyethylene, and particularly preferably linear low density polyethylene.

  Further, the conductive particles contained in the first PTC region 6 and the second PTC region 8 are not particularly limited as long as they have electronic conductivity. For example, carbon black, graphite, metal particles of various shapes or Ceramic conductive particles can be used. These can be used alone or in combination of two or more.

  Among these, it is preferable to use conductive metal particles particularly in applications where low room temperature resistance and a sufficient resistance change rate are required, such as overcurrent protection elements. As the conductive metal particles, copper, aluminum, nickel, tungsten, molybdenum, silver, zinc, cobalt, or the like is used, and it is particularly preferable to use silver or nickel. Further, the shape may be a spherical shape, a flake shape or a rod shape, and those having spike-like projections on the surface are preferable.

  Such conductive metal particles may be a powder in which each individual particle (primary particle) exists individually, but these primary particles are linked in a chain to form filamentary secondary particles. More preferably, the material is nickel. A PTC element in which such particles are uniformly dispersed in a polymer matrix has high reliability for repeated operation and long-term storage.

  An intermediate region 10 is formed between the first PTC region 6 and the second PTC region 8. The intermediate region 10 is sandwiched between the first PTC region 6 and the second PTC region 8, and an arrow A indicating the arrangement direction of the first electrode 2, the PTC element body L 5, and the second electrode 4. It extends in the direction that intersects. The intermediate region 10 includes a resin as a main component, and the resin has the same component as the resin included in the first PTC region 6 and the second PTC region 8. More specifically, linear low density polyethylene used in the first PTC region 6 and the second PTC region 8 is also used in the intermediate region 10. The ratio of the amount of linear low density polyethylene contained in the intermediate region 10 to the amount of all components in the intermediate region 10 is included in the first PTC region 6 with respect to the amount of all components in the first PTC region 6. Greater than the proportion of the amount of the linear low density polyethylene to be added, and the amount of the linear low density polyethylene contained in the second PTC region 8 relative to the amount of all the components of the second PTC region 8. Greater than percentage. By setting such a ratio, the intermediate region 10 has a higher resistance value than the first PTC region 6 and the second PTC region 8.

  Then, with reference to FIGS. 1-3, the manufacturing method of the PTC element 1 which has the structure mentioned above is demonstrated. FIG. 2 is a flowchart for explaining the manufacturing method of the PTC element according to this embodiment. FIG. 3 is a view for explaining the method for manufacturing the PTC element according to the present embodiment.

  First, a PTC base material is prepared (step S101). In preparing the PTC base material, the PTC base material such as linear low-density polyethylene and filamentary particles made of nickel are weighed so as to have a predetermined ratio, and then the components are mixed and kneaded. To prepare. And the adjusted kneaded material is put into an extruder to make a rod-like lump. This rod-shaped lump is cut into a predetermined width and subjected to a molding process such as press molding to obtain a sheet-like PTC substrate.

  Next, a high resistance region having a resistance value higher than that of the PTC substrate is formed on the obtained sheet-like PTC substrate (step S103). The high resistance region is formed by heating a sheet-like PTC substrate with a hot plate or the like. The linear low density polyethylene contained in the PTC base material has a lower melting point than other components contained in the PTC base material. Therefore, when the PTC base material is heated, linear low-density polyethylene emerges on the surface of the PTC base material. This raised linear low density polyethylene becomes a high resistance region. Thus, the high resistance region can be formed by an easy method such as heating the PTC substrate. The heating position with respect to the PTC substrate is adjusted so that the linear low-density polyethylene is raised on a predetermined surface of the PTC substrate. Here, the predetermined surface refers to one main surface of the sheet-like PTC base material.

  Next, as shown in FIG. 3, two PTC base materials S1 each formed with a high resistance region R1 are overlapped so that the high resistance region R1 is positioned therebetween to obtain a PTC laminate G5 ( Step S105). That is, the two PTC base materials S1 are overlapped so that the main surfaces of the high resistance region R1 face each other. The PTC laminate G5 thus obtained is cut into a desired size (step S107), and a PTC molded body that becomes the PTC element body L5 is obtained.

  Next, the first electrode 2 and the second electrode 4 are provided on the surface of the PTC molded body so as to sandwich the PTC molded body in the stacking direction of the PTC base material (step S109). These electrodes are joined to the PTC compact by hot pressing. At this time, since the nodules of the first electrode 2 and the second electrode 4 enter the surface of the PTC molded body, the first electrode 2 and the second electrode 4 must be reliably bonded to the PTC molded body. Can do.

  Next, an electron beam is irradiated to the PTC molded body to which the first electrode 2 and the second electrode 4 are joined. When irradiated with an electron beam, the linear low-density polyethylene contained in the PTC molded product is crosslinked. By cross-linking the linear low-density polyethylene, the PTC molded body having high fluidity is cross-linked to become a PTC element body L5 having elasticity (step S111). As a result, the PTC base material S1 located on the first electrode 2 side becomes the first PTC region 6, the PTC base material S1 located on the second electrode 4 side becomes the second PTC region 8, and the high resistance region R 1 becomes the intermediate region 10. In this way, the PTC element 1 including the first electrode 2, the second electrode 4, and the PTC element body L5 is manufactured.

  As described above, the PTC element 1 according to this embodiment includes the PTC element body L5 sandwiched between the first electrode 2 and the second electrode 4. The PTC element body L5 has a high-resistance intermediate region 10 between the first PTC region 6 and the second PTC region 8. By having the high-resistance intermediate region 10, the construction of the conductive path can be suppressed. In addition, by setting the position of the intermediate region 10 between the first PTC region 6 and the second PTC region 8, the intermediate region 10 can be prevented from being damaged by the first electrode 2 and the second electrode 4. Therefore, the construction of the conductive path can be reliably suppressed. As a result, a PTC element 1 with good withstand voltage characteristics can be obtained.

  Further, since the intermediate region 10 is mainly composed of linear low density polyethylene contained in the first PTC region 6 and the second PTC region 8, the first PTC region 6 and the second PTC region 8 are included. And the familiarity with the intermediate region 10 is improved. As a result, it is possible to obtain the PTC element 1 in which the bonding state between the first PTC region 6 and the second PTC region 8 and the intermediate region 10 is good.

  In addition, since the surfaces 2a and 4a of the first electrode 2 and the second electrode 4 in contact with the PTC element body L5 are roughened, the first electrode 2 and the second electrode 4 with respect to the PTC element body L5. It is possible to improve the bonding strength.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment.

  For example, in the above embodiment, the resin contained in the first PTC region 6 and the second PTC region 8 is used for the intermediate region 10. Alternatively, a resin having a component different from that of the resin contained in the first PTC region 6 and the second PTC region 8 may be used for the intermediate region 10. The intermediate region 10 may be made of a resin contained in the first PTC region 6 and the second PTC region 8 and a resin having a component different from that of the resin. In these cases, the high resistance region to be the intermediate region 10 is formed by applying, evaporating, or laminating the above-described resin on the PTC base material.

  Moreover, in the said embodiment, the high resistance area | region used as the intermediate | middle area | region 10 is formed by heating a PTC base material and making linear low density polyethylene stand out on one main surface of a PTC base material. did. Alternatively, the high resistance region serving as the intermediate region 10 may be formed by etching one main surface of the PTC base material to remove the conductive particles. In this case, linear low density polyethylene remains on one main surface of the PTC substrate after etching, and this linear low density polyethylene becomes a high resistance region. Therefore, since no new material is required to form the high resistance region, the high resistance region can be formed at low cost.

  In the above embodiment, two PTC base materials each having a high resistance region are overlapped to obtain a PTC laminate, but at least one of the two PTC base materials to be overlapped is obtained. It is sufficient that a high resistance region is formed. Further, the number of PTC base materials may be three or more.

  Further, the cross-sectional shape of the PTC element 1 is not limited to that shown in FIG. 1 of the above embodiment, and may be as shown in FIGS. 4A and 4B, for example. The PTC element 20 shown in FIG. 4A has a first electrode 22, a second electrode 24, a first PTC region 26, a second PTC region 28, and an intermediate region 30, and these Corresponds to the first electrode 2, the second electrode 4, the first PTC region 6, the second PTC region 8, and the intermediate region 10 in the PTC element 1. The PTC element 40 shown in FIG. 4B has a first electrode 42, a second electrode 44, a first PTC region 46, a second PTC region 48, and an intermediate region 50. Corresponds to the first electrode 2, the second electrode 4, the first PTC region 6, the second PTC region 8, and the intermediate region 10 in the PTC element 1.

  Here, with respect to the PTC element of the present invention, the following experiment was conducted in order to confirm the effect that the withstand voltage characteristic is improved.

  That is, a plurality of types of PTC elements having different structures were prepared, and the withstand voltage characteristics were examined. An Example is a PTC element which has the same structure as the PTC element 1 of this embodiment, Comprising: It manufactures according to the manufacturing process shown by FIG. In the step of preparing the sheet-like PTC base material, press molding was performed so that the thickness of the PTC base material was 0.8 mm. Moreover, in the process of providing the 1st electrode 2 and the 2nd electrode 4 in a PTC molded object, the hot press was performed twice.

  In contrast, the PTC element of Comparative Example 1 was obtained by cutting one sheet-like PTC base material into a desired size, and sandwiching the cut piece between a pair of electrodes and performing two hot presses. Is. The PTC element of Comparative Example 2 is obtained by stacking two sheet-like PTC base materials and cutting them to a desired size, and then subjecting the cut pieces to a pair of electrodes and performing two hot presses. In Comparative Example 1 and Comparative Example 2, the heat treatment using a hot plate or the like is not performed on the PTC substrate before cutting. That is, both the PTC elements of Comparative Example 1 and Comparative Example 2 do not have a high resistance region. In addition, the sheet-like PTC base material used by the comparative example 1 and the comparative example 2 is manufactured similarly to the sheet-like PTC base material used by the Example.

  Ten pieces of the three types of PTC elements thus manufactured were prepared, and the withstand voltage value was measured. The measurement results are shown in FIG. In each of the example, comparative example 1 and comparative example 2, there were some of the 10 prepared that had substantially the same withstand voltage value, so the number of points on the graph was 10 or less, respectively. Yes.

  The withstand voltage value of the PTC element of Comparative Example 1 was about 30V or more. The withstand voltage value of the PTC element of Comparative Example 2 was about 32V or more. On the other hand, the withstand voltage value of the PTC element of the example was about 44V or more.

  Thus, the withstand voltage value of the example according to the present invention is higher than that of Comparative Example 1 and Comparative Example 2. Therefore, the effectiveness of the present invention that the withstand voltage characteristic is good was confirmed.

It is sectional drawing which shows the PTC element which concerns on this embodiment. It is a flowchart for demonstrating the manufacturing method of the PTC element which concerns on this embodiment. It is a figure for demonstrating the manufacturing method of the PTC element which concerns on this embodiment. It is sectional drawing which shows the modification of the PTC element which concerns on this Example carrying. It is a graph which shows the result of the experiment which investigates the pressure | voltage resistance of a PTC element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... PTC element, 2 ... 1st electrode, 4 ... 2nd electrode, 6 ... 1st PTC area | region, 8 ... 2nd PTC area | region, 10 ... Middle area | region, L5 ... PTC element | base_body, R1 ... High resistance Area, S1 ... PTC substrate.

Claims (8)

A pair of electrodes arranged in opposition to each other;
A PTC element body disposed between the pair of electrodes and having a positive resistance temperature characteristic,
The PTC element body includes a plurality of PTC regions including a resin and conductive particles, and an intermediate region sandwiched between the PTC regions and extending in a direction intersecting with an arrangement direction of the pair of electrodes and the PTC element body. , And
The intermediate region has a higher resistance value than the PTC region.   The PTC element according to claim 1, wherein the intermediate region contains a resin as a main component, and the resin included in the intermediate region and the resin included in the PTC region have the same components.   3. The PTC element according to claim 1, wherein a surface of the electrode in contact with the PTC element body is subjected to a rough surface treatment. 4. A method of manufacturing a PTC element comprising: a pair of electrodes arranged in a state of being opposed to each other; and a PTC element body disposed between the pair of electrodes and having a positive resistance temperature characteristic. And
A first step of preparing a plurality of PTC substrates containing a resin and conductive particles;
A second step of forming, on a predetermined surface of at least one of the plurality of PTC substrates, a high resistance region having a higher resistance value than the PTC substrate;
A third step of stacking the plurality of PTC base materials so that the high resistance region is located therebetween, and forming a PTC molded body that becomes the PTC base body;
A fourth step of arranging the pair of electrodes so as to sandwich the PTC molded body with respect to the stacking direction of the PTC base material;
After arranging the pair of electrodes, a fifth step of crosslinking the PTC molded body;
A method for producing a PTC element, comprising:   The said 2nd process forms the said high resistance area | region by heating the said PTC base material and making resin contained in the said PTC base material stand out on the said predetermined | prescribed surface, The said high resistance area | region is formed. Manufacturing method of the PTC element.   5. The method of manufacturing a PTC element according to claim 4, wherein in the second step, the high resistance region is formed using a resin having a component different from that of the resin contained in the PTC base material.   The said 2nd process forms the said high resistance area | region by etching the predetermined surface of the said PTC base material, and removing the said electroconductive particle, The manufacture of the PTC element of Claim 4 characterized by the above-mentioned. Method. A first electrode and a second electrode arranged facing each other;
A PTC element body disposed between the first electrode and the second electrode and having a positive resistance temperature characteristic,
The PTC element body includes a first PTC region including a resin and conductive particles and bonded to the first electrode; and a second PTC region including the resin and conductive particles and bonded to the second electrode. A PTC region; and an intermediate region located between the first PTC region and the second PTC region and having a higher resistance value than the first PTC region and the second PTC region. The PTC element characterized by the above-mentioned.

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