JP2000200703A - Organic ptc thermistor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the resistance when an organic PTC thermistor is nonoperative, to improve peeling strength and to improve reliability by integrally forming electrodes installed on the surfaces of a thermistor element body with a conductive metal particles exposed to the surfaces of the thermistor element body. SOLUTION: In the organic PTC thermistor, a pair of electrodes 4 which are integrally formed with conductive metal particles 2 are installed by sandwiching a thermistor element body 3 where the conductive metal particles 2 are dispersed in polymer 1. The thermistor element body 3 may contain a low molecular weight organic compound and the low molecular weight organic compound may be an operating material. Nylon 12 or polyethylene oxido is desirable as the polymer. In the organic PTC thermistor, plating films which are integrally formed with the conductive metal particles 2 exposed to the surface of the thermistor element body 3 are made to be electrodes 4. Integrity means that an interface is not given between the conductive metal particles 2 and the electrodes 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive temperature coefficient of resistance (PTC).
The present invention relates to an organic PTC thermistor using a high molecular polymer, among PTC thermistors exhibiting high stivity, and a method for producing the same.

[0002]

2. Description of the Related Art As shown in FIG. 1, an organic PTC thermistor has an electrode 14 on the surface of a thermistor body 13 having a structure in which conductive particles 12 such as carbon black and metal are dispersed in a crystalline polymer 11. It is provided. In addition, an organic PT in which a low molecular organic compound such as a wax is contained in a polymer matrix, wherein the active substance is a low molecular organic compound.
C thermistors have also been proposed. Such organic PTC
Since the thermistor has a lower specific resistance at room temperature (non-operating specific resistance) than a conventional ceramic PTC thermistor, it is suitable for applications in which a large current flows, and can be miniaturized. (Maximum resistance / room temperature resistance) is known to have excellent characteristics.
The organic PTC thermistor can be used for, for example, a self-control type heater, a temperature detector, an overcurrent protection element, and the like.

[0003] As a method for providing an electrode on the body of the organic PTC thermistor, a method of pressing a metal foil (US Pat. No. 4,426,633) or a method of heat-sealing a reticulated metal (Japanese Patent Publication No. No. 2-160022) is widely known. However, when these crimping methods are used, the electrical contact between the element body and the electrode cannot be made uniform, so that the contact resistance of the electrode increases. Therefore, the resistance value during non-operation increases,
This is not preferable for applications in which a large current flows. This is because the surface of the conductive filler is covered with the polymer, and the insulating polymer is thinly present between the electrode and the conductive filler even when pressed as it is.

For this reason, in Japanese Patent Publication No. 4-44401, an electrode is formed by an electroplating method or a chemical plating method after a surface of a body is etched in advance to expose a conductive filler near the surface of the body. A method has been proposed. In this publication, a chromic acid mixed solution as an etching means,
Surface treatment with para-xylene, sandblasting,
Surface treatment with sandpaper is mentioned. However, the conductive fillers in the examples of the publication are all carbon black, and although there is a description of the effect of reducing the contact resistance value, there is no suggestion of the effect of preventing peeling. In addition, a strong adhesive effect cannot be expected without integration between the carbon black particles and the metal plating film. The electrodes of the thermistor element, which generate heat during operation and repeat expansion and contraction, are extremely easily peeled off because they are repeatedly subjected to severe tensile forces. In addition, an increase in the electric resistance value can be seen even without separation. Tokuho 4-4440
Patent Document 1 does not describe at all the effect of preventing the separation between the electrode and the PTC body. Actually, this can reduce the contact resistance of the electrode, but has a problem that the adhesion strength between the plating film and the element is insufficient and the electrode is easily peeled.

On the other hand, Japanese Patent Publication No. 4-3083
In the publication, in order to prevent peeling due to heat shock, the surface of the element body is etched, and then a plating film (electrode) is formed by an electroplating method or an electroless plating method, and the crystallization temperature of the crystalline polymer is increased. At the above-mentioned temperature, a method of applying pressure on the plating film has been proposed. However, the conductive filler in Examples and Comparative Examples of the publication is only carbon black, and there is no example of metal particles. In the specification, metal particles having a particle size of 20 μm or less and a length of 1 mm or less and an aspect ratio of 10
Although the above metal fibers are mentioned, carbon black is preferred, and no difference in effect is described. As described above, since the carbon black particles and the metal plating film are not integrated with each other, a sufficient separation preventing effect cannot be obtained even with such a treatment. Also, even if metal particles are used as the conductive filler, if the plating is performed as it is after etching, an oxide is present on the surface of the metal particles, and the metal particles and the plating film are hardly integrated,
Easy to peel off.

In Japanese Patent Application Laid-Open No. Sho 60-3881,
A method of forming an electrode by metal plating after enlarging the surface of a plastic PTC heating element surface has been proposed. It is said that this material has a larger electric capacity, is superior in corrosion resistance, and can be formed into a complicated shape as compared with an electrode made of silver paste or the like. As the enlargement process, a mechanical honing process by a sand blast method is mentioned. The gazette states that
The surface roughness of the PTC body was set to a center line average roughness Ra of 0.4.
It is described that the adhesive strength is improved by setting the Ra to 6 to 7 μm after the surface enlargement treatment from about μm. However, the conductive filler described in the publication is carbon black, and there is no mention of metal particles.

[0007] In the organic PTC thermistor, the element body undergoes significant thermal expansion during PTC operation, so that excessive stress is generated in the electrodes. Therefore, cracks occur in the electrodes due to the repetition of the PTC operation, or the electrodes are partially peeled off, which causes reliability problems such as an increase in electric resistance.

[0008] In order to improve the adhesive strength, porous metal foil used as an electrode has been widely used for a long time with copper-clad laminates and the like. PTC after expanding copper foil or Ni foil by chemical etching or plating
It has been proposed to crimp the body. U.S. Patent No. 4,
No. 689,475 describes an organic PTC thermistor having an electrode with a micro-rough surface. The electrode having the fine rough surface is a metal foil formed by electroplating, electrodeposition, or the like. Also in this specification, the effect of improving the adhesiveness of the electrode is described. This is due to the fact that PT
This is based on the anchor effect by thermocompression bonding of the C element. However, a metal foil having a specific rough surface capable of improving the adhesion and contact resistance of the electrode, particularly a Ni foil, is expensive, while a Cu foil is relatively inexpensive but has insufficient corrosion resistance. Further, according to the study of the present inventors, in the organic PTC thermistor, only a small number of conductive particles existing near the element body surface are exposed from the element body surface, and most of them have a thickness of several micrometer. It was found that it was coated with a high-molecular polymer of about a meter. For this reason,
In order to stably reduce the contact resistance, it is not sufficient to simply roughen the electrodes.

In US Pat. No. 4,444,708, two electrodes are covered with an amorphous high-conductivity rubber and embedded in a PTC material to improve the adhesion strength between the electrodes and the PTC material. Improvements have been made to improve the stability of the resistance value and the reliability. The amorphous high-conductivity rubber in the specification has non-PTC characteristics. In this specification, epichlorohydrin containing a large amount of carbon black is mentioned as a preferable example of the amorphous high conductivity rubber. The specification states that if necessary, the electrode surface may be formed in a projecting shape (for example, a minute projecting shape) to improve the contact resistance and the adhesive force. However, the specification does not disclose that the interface between the PTC material and the amorphous high-conductivity rubber may be etched. In a thermistor element having a configuration in which conductive particles are dispersed in a crystalline polymer, the conductive particles near the element surface are covered with the polymer as described above, so that the thermistor element and the electrode If the amorphous high-conductivity rubber described in the same specification is interposed between them, simply joining them together will increase the contact resistance.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable organic PTC thermistor having a low resistance value during non-operation, a high peel strength, and a high reliability. .

[0011]

This and other objects are achieved by any of the following configurations. (1) An organic PTC thermistor having a thermistor element having a structure in which conductive metal particles are dispersed in a high-molecular polymer, and an electrode provided on the surface of the thermistor element, wherein the electrode is a thermistor element An organic PTC thermistor integrally formed with the conductive metal particles exposed on the surface. (2) The organic PTC thermistor according to (1), wherein the thermistor body further contains a low molecular weight organic compound. (3) The organic PTC thermistor according to (1) or (2), wherein the electrode is a plating film. (4) The above (1), wherein the conductive metal particles are non-spherical.
The organic PTC thermistor according to any one of (1) to (3). (5) The organic positive temperature coefficient thermistor according to (4), wherein said conductive metal particles have spike-shaped protrusions. (6) The above (1) to (1), wherein the conductive metal particles are Ni.
The organic PTC thermistor according to any of (5). (7) The organic PTC thermistor according to any one of (1) to (6), wherein the conductive metal particles have an average particle size of 1 to 4 μm. (8) The organic PTC thermistor according to any one of (1) to (7), wherein the metal species of the conductive metal particles and the metal species of the electrode are the same. (9) A method for producing an organic PTC thermistor having a thermistor element having a configuration in which conductive metal particles are dispersed in a polymer and an electrode provided on the surface of the thermistor element, the method comprising: A selective removal step of selectively removing the high molecular polymer from the surface of the body to expose the conductive metal particles to the thermistor body surface; and forming an electrode integrally with the conductive metal particles exposed to the thermistor body surface. A method for producing an organic PTC thermistor, comprising: forming an electrode. (10) A method for producing an organic PTC thermistor having a thermistor element having a configuration in which conductive metal particles are dispersed in a high molecular polymer containing a low molecular organic compound, and an electrode provided on the surface of the thermistor element A selective removal step of selectively removing a high-molecular polymer and a low-molecular-weight organic compound from the surface of the thermistor body to expose conductive metal particles to the thermistor body surface; An electrode forming step of forming an electrode integrally with the conductive metal particles exposed to the substrate. (11) The method for producing an organic PTC thermistor according to the above (9) or (10), wherein a plating method is used in the electrode forming step. (12) The method for producing an organic PTC thermistor according to (11), wherein, in the electrode forming step, the thermistor body is electrolytically etched, and then an electrode is formed by an electroplating method. (13) In the selective removal step, any of plasma treatment, reactive ion etching, ultraviolet irradiation, exposure to an ozone-containing atmosphere, laser irradiation, reverse sputtering, sandblasting, organic solvent exposure, or organic solvent vapor exposure The method for producing an organic PTC thermistor according to any one of the above (9) to (12), wherein

[0012]

The organic PTC thermistor of the present invention has a thermistor element having a configuration in which conductive metal particles are dispersed in a polymer, and an electrode provided on the surface of the thermistor element. It is formed integrally with the conductive metal particles exposed on the thermistor body surface. The thermistor body may contain a low molecular weight organic compound, and the low molecular weight organic compound may be an active substance.

Such an organic PTC thermistor selectively removes a high molecular polymer and a low molecular weight organic compound on the surface of the thermistor body, and an oxide film of conductive metal particles exposed on the surface of the thermistor body by electrolytic etching. After forming a fresh surface by reducing / removing an electrode, and then forming an electrode by a plating method. Thereby, the electrodes are formed integrally with the conductive metal particles uniformly dispersed in the matrix resin.

As described above, by selectively removing the high molecular weight polymer and the low molecular weight organic compound on the thermistor body surface,
The contact resistance between the thermistor element and the electrode can be reduced to reduce the resistance value during non-operation. A physical removal method such as a sand blast method by preferably selectively removing a polymer or the like on the thermistor body surface by using plasma treatment, reactive ion etching, ultraviolet light, an ozone-containing atmosphere, or laser light. Compared with the case of using a wet etching method, there is substantially no adverse effect on the thermistor body, and the selectivity when etching a polymer or the like is good, so that reliability is high and non-operation An organic PTC thermistor having a low resistance value is obtained.

In the organic PTC thermistor of the present invention, since the electrodes are formed integrally with the conductive metal particles exposed on the surface of the thermistor body, the peel strength is increased, and the thermal expansion due to repetition of the operation is achieved. In addition, the electrode is not peeled off or cracked due to repeated shrinkage, the electrical resistance does not increase, and the reliability is high.

In Japanese Patent Publication No. Hei 4-44401, the electrodes are formed by plating, and the conductive particles are exposed. However, since the conductive particles are carbon black, they are integrally formed by plating. The electrode cannot be formed. For example, even if the surface roughness is increased, the conductive particles and the electrode metal are not integrated with each other, and there is a high possibility that the conductive particles are peeled off by a strong force, particularly a force of repeated thermal expansion and contraction.
Even if peeling does not occur, electrical contact becomes insufficient, not only the initial resistance value does not become sufficiently low, but also a phenomenon that the resistance value after repeated operation gradually increases, and the reliability decreases. In Japanese Patent Publication No. 4-44001, metal particles and metal fibers having a fiber length of 1 mm or less are mentioned as the conductive particles. However, as described above, the effect of preventing the separation between the electrode and the PTC body is completely eliminated. Not stated. In addition, even if metal particles are used as the conductive filler, if the plating is performed as it is after etching, an oxide is present on the surface of the metal particles, and the metal particles and the plating film are hardly integrated and easily peeled. . In addition, surface treatment using a mixed solution of chromic acid, para-xylene, or the like, or surface treatment using sandblasting or sandpaper is used as an etching means, but these methods have poor selectivity when etching a polymer.

This publication describes, as pretreatments for electroplating, surface oxidation with an ozone-containing gas and imparting hydrophilicity by plasma irradiation. However, the pretreatment of electroplating is a modification treatment of the surface to be plated, and only changes the surface at a depth of the order of submicrons, which is completely different from the selective removal treatment of the high molecular polymer in the present invention.

Further, Japanese Patent Application Laid-Open No. 63-321601 describes a method of forming an electrode on a roughened element body surface to strengthen the bonding of the electrode and improve the ohmic property. . In this publication, reverse sputtering and sand blast are mentioned as surface roughening means, and a sputtering method or an ion plating method is mentioned as an electrode forming method. However, the commonly used sandblasting method has poor selectivity when etching a crystalline polymer, and the reverse sputtering method also has poor selectivity compared to the reactive ion etching method.

[0019]

FIG. 2 shows an example of the structure of an organic PTC thermistor of the present invention. The organic PTC thermistor shown in FIG. 1 includes a thermistor element 3 having a configuration in which conductive metal particles 2 are dispersed in a high-molecular polymer (hereinafter, may be simply referred to as a polymer) 1 and a thermistor element 3 It has a pair of electrodes 4 provided so as to be sandwiched therebetween and formed integrally with the conductive metal particles 2. The thermistor body 3 may further contain a low molecular weight organic compound, and the low molecular weight organic compound may be an active substance. In this case, it is considered that each thermoplastic polymer matrix and each low-molecular organic compound have a sea-island structure in which they are independently dispersed.

The thermistor element The polymer and the low molecular weight organic compound used in the present invention are not particularly limited, and may be used without limitation as long as they can exhibit PTC characteristics when the conductive particles are dispersed to form an element.

When a high-molecular polymer is used as the active substance, a crystalline high-molecular polymer is used.

Examples of such a polymer include polyethylene, polyethylene oxide, t-4-polybutadiene, polyethylene acrylate, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer,
Polyester, polyamide, polyether, polycaprolactam fluorinated ethylene-propylene copolymer, chlorinated polyethylene, chlorosulfonated ethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, styrene-acrylonitrile copolymer, polyvinyl chloride, Examples thereof include polycarbonate, polyacetal, polyalkylene oxide, polyphenylene oxide, polysulfone, and fluororesin, and at least one of these may be used. Specifically, it may be appropriately selected according to the method of forming the electrodes, the required PTC thermistor characteristics, and the like.

Preferred specific examples of the polymer include nylon 12 and polyethylene oxide (PEO). Of these, polyethylene oxide is preferable when the operation is performed at a relatively low temperature of about 60 to 70 ° C, and nylon 12 is preferable when the operation is performed at a temperature of about 140 to 160 ° C. In particular, polyethylene oxide is preferred for the purpose of lowering the operating temperature.

The polyethylene oxide has a weight average molecular weight Mw of preferably 2,000,000 or more, more preferably 300,000,000 or more.
10,000 to 6 million. If Mw is too small, the viscosity at the time of melting will be too low, and the dispersibility of the conductive particles will deteriorate, making it difficult to lower the resistance at room temperature. Mw20
Polyethylene oxide having a melting point of 65 to 70
At about ° C, the density is about 1.15 to 1.22 g / cm ³ .

When polyethylene oxide is used as the polymer, it is preferable to further contain a water-insoluble polymer (polymer) and / or a water-insoluble low molecular weight organic compound. Thereby, the moisture resistance is greatly improved while substantially maintaining the excellent PTC characteristics.

The water-insoluble polymer has a water absorption (ASTM D570)
Is preferably 0.5% or less. Examples of such a material include thermoplastic polymers such as polyethylene, polystyrene, polymethyl methacrylate, polyvinyl chloride, and olefin copolymers, and thermoplastic elastomers. Among them, polyethylene, particularly low density polyethylene, is preferred.

The low density polyethylene has a density of 0.91
0 to 0.929 g / cm ³ . 0.93 density
Those having 0 to 0.941 g / cm ³ are called medium density polyethylene, and those having 0.942 g / cm ³ or more are called high density polyethylene. The low-density polyethylene is produced by a high-pressure method, that is, a high-pressure radical polymerization method of 1000 atm or more, and contains a long-chain branch in addition to a short-chain branch such as an ethylene group. High-density polyethylene is produced by coordination anion polymerization using a transition metal catalyst under medium or low pressure of several tens of atmospheres or less, and is linear. However, even when the α-olefin is copolymerized in the medium / low pressure method, short-chain molecules are introduced and the medium / low density polyethylene is obtained. Of these, those with low density are referred to as linear low density polyethylene.

The water-insoluble polymer used has a melt flow rate (MFR) defined by ASTM D1238 of 0.1 to 30.
g / 10 min, particularly preferably 1.0 to 10 g / 10 min. If it is higher than this, the melt viscosity is too low, making it difficult to make the dispersion of the conductive particles constant, and the variation in resistance value tends to be large. If it is lower than this, the melt viscosity is too high, and the chain structure of the conductive particles preferably used in the present invention is broken, and the rate of change in resistance tends to decrease.

The water-insoluble polymer is 2 even if only one kind is used.
More than one kind may be used in combination, but MFR 0.1 to 30
It is preferable to use only low density polyethylene of g / 10 min.

The weight ratio of the polyethylene oxide crystalline polymer to the water-insoluble polymer is 0.25 to 2.0, especially 1.0 to 1. 8 is preferable. If this ratio is too small and the amount of the water-insoluble polymer is too small, no improvement in moisture resistance can be seen. On the other hand, if this ratio is increased and the amount of the water-insoluble polymer is too large, it is not possible to obtain a sufficient increase in resistance at the melting point of polyethylene oxide.

The water-insoluble low molecular weight organic compound is not particularly limited as long as it has a molecular weight of up to about 1,000, preferably 200 to 800.
And those which are solid. The melting point mp of the low molecular weight organic compound is preferably from 40 to 100 ° C.

Examples of the wax include waxes (specifically, natural waxes such as petroleum waxes such as paraffin wax and microcrystalline wax, vegetable waxes, animal waxes, and mineral waxes), oils and fats ( Specific examples include fats or solid fats). Components of waxes and fats and oils include hydrocarbons (specifically, alkane linear hydrocarbons having 22 or more carbon atoms) and fatty acids (specifically, alkane linear hydrocarbons having 12 or more carbon atoms). Fatty acids), fatty acid esters (specifically, methyl esters of saturated fatty acids obtained from saturated fatty acids having 20 or more carbon atoms and lower alcohols such as methyl alcohol), fatty acid amides (specifically, oleic acid amide, Unsaturated fatty acid amides such as erucamide, aliphatic amines (specifically, aliphatic primary amines having 16 or more carbon atoms), higher alcohols (specifically, n-alkyl alcohols having 16 or more carbon atoms) ), But
These can be used alone or in combination as a low molecular weight organic compound.

As the water-insoluble low molecular weight organic compound, a wax or a compound having a functional group capable of hydrogen bonding, particularly a compound having a functional group capable of hydrogen bonding is preferable because a uniform mixed state can be obtained and the production is easy. When hydrocarbons, such as petroleum wax mainly composed of hydrocarbons, are used, uniform dispersion becomes difficult, and low-molecular compounds may be separated during press molding. Since those having a functional group capable of hydrogen bonding form a hydrogen bond with the ether oxygen of polyethylene oxide, the separation of low molecular weight compounds hardly occurs. Examples of the functional group capable of hydrogen bonding include an amino group, preferably a carbamoyl group and a hydroxyl group.

These low molecular organic compounds are commercially available, and commercially available products can be used as they are.

Examples of such a material include paraffin wax (eg, tetracosane C ₂₄ H ₅₀ ; mp 49-52).
° C., hexatriacontane C ₃₆ H _74; mp73 ℃, trade name HNP-10 (Nippon Seiro Co., Ltd.); mp75 ℃, HNP
-3 (manufactured by Nippon Seiro Co., Ltd .; mp 66 ° C., etc.), microcrystalline wax (for example, trade name Hi-Mic-1)
080 (manufactured by Nippon Seiro); mp83 ° C, Hi-Mic-
1045 (manufactured by Nippon Seiro); mp 70 ° C, Hi-Mic
2045 (manufactured by Nippon Seiro); mp 64 ° C, Hi-Mic
3090 (manufactured by Nippon Seiro); mp 89 ° C, shellac 10
4 (manufactured by Nippon Oil Refining Co., Ltd.); mp 96 ° C., 155 microwax (manufactured by Nippon Oil Refining Co., Ltd.); mp 70 ° C., etc.), fatty acids (for example, behenic acid (manufactured by Nippon Seika);
Stearic acid (manufactured by Nippon Seika); mp72 ° C, palmitic acid (manufactured by Nippon Seika); mp64 ° C, etc.), fatty acid ester (for example, arachiic acid methyl ester (manufactured by Tokyo Chemical Industry);
mp 48 ° C.), fatty acid amides (eg, oleic amide (Nippon Seika); mp 76 ° C.). Also, a compounded wax obtained by mixing a resin with paraffin wax, or a compounded wax mixed with a microcrystalline wax and having a melting point of 40 to 100 ° C. can be used.

The water-insoluble low molecular weight organic compounds may be used alone or in combination of two or more.

The mixing ratio of the polyethylene oxide crystalline polymer and the water-insoluble low-molecular-weight organic compound is 2 to 40% by weight, particularly 5 to 30% by weight of the water-insoluble low-molecular-weight organic compound per polyethylene oxide. Is preferred. If this ratio becomes too small and the amount of the water-insoluble low-molecular-weight organic compound becomes too small, no improvement in moisture resistance can be seen. If this ratio is increased and the amount of the water-insoluble low molecular weight organic compound becomes too large, a sufficient increase in the resistance at the melting point of polyethylene oxide cannot be obtained, and the strength of the device decreases.

Nylon 12 is a lactam polymer of 12-aminododecanoic acid, having a melting point of 177 ° C. and a density of 1.
It is preferably 0.3 g / cm ³ and Mw of 20,000 to 50,000.

As the fluorine resin, polyvinylidene fluoride is preferred. Polyvinylidene fluoride exhibits self-extinguishing properties. The self-extinguishing property is a property that, even after ignition, the fire extinguishes naturally when the flame is kept away. For this reason, polyvinylidene fluoride is suitable for applications in which ignition is possible.

Further, the thermistor element may use a low molecular weight organic compound as an active substance. Such a thermistor body includes a high-molecular polymer (thermoplastic polymer matrix), a low-molecular organic compound, and conductive metal particles.
By using a low molecular weight organic compound as the active substance, the hysteresis of the temperature-resistance curve is reduced as compared with the case where only the high molecular weight polymer is used. In addition, the operating temperature can be easily adjusted by using a low molecular weight organic compound having a different melting point, as compared with the case where the operating temperature is adjusted using the change in the melting point of the polymer. In the configuration using only the low molecular weight organic compound and the conductive particles, the shape of the element cannot be maintained when the device is operated due to the low melt viscosity of the low molecular weight organic compound. Flow due to melting of the molecular organic compound, deformation of the element, and the like can be prevented.

In this case, the thermoplastic polymer matrix may be either crystalline or amorphous, and is not particularly limited. However, it is preferable to use a polyolefin (including a copolymer) because good properties can be obtained.

Such a thermoplastic polymer matrix includes: i) a polyolefin (eg, polyethylene) ii) one or more olefins (eg, ethylene, propylene) and one or more polar groups Copolymers composed of monomer units derived from olefinically unsaturated monomers (e.g., ethylene-
Iii) vinyl halide and vinylidene polymers (eg, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride), iv) polyamides (eg, 12-nylon), v) Polystyrene, vi) polyacrylonitrile, vii) thermoplastic elastomer, viii) polyethylene oxide, polyacetal, ix) thermoplastically modified cellulose, x) polysulfones, xi) polyethyl acrylate, polymethyl (meth) acrylate and the like. Specifically, high-density polyethylene [for example, trade name Hyzex 2100JP (manufactured by Mitsui Petrochemical), trade name Marlex6003 (manufactured by Philips), trade name HY540 (manufactured by Nippon Polychem)
Etc.], low density polyethylene [for example, trade name LC500
(Manufactured by Nippon Polychem), trade name DYNH-1 (manufactured by Union Carbide), medium density polyethylene [for example, trade name 2604M (manufactured by Gulf), etc.], ethylene-ethyl acrylate copolymer [for example, trade name DPD616]
9 (manufactured by Union Carbide Co., Ltd.), ethylene-vinyl acetate copolymer [for example, LV241 (manufactured by Nippon Polychem), etc.], ethylene-acrylic acid copolymer [for example, EAA455 (manufactured by Dow Chemical), etc.], ionomer [For example, trade name Himilan 1555 (manufactured by DuPont-Mitsui Polychemicals) etc.], hexafluoroethylene-tetrafluoroethylene copolymer [for example,
Brand name FEP100 (manufactured by DuPont) or the like], polyvinylidene fluoride [for example, brand name Kynar461]
(Manufactured by Pemwald) and the like.

The weight average molecular weight Mw of such a thermoplastic polymer is preferably about 10,000 to 5,000,000.

One type of these thermoplastic polymers may be used, but it is preferable to use two or more types. When two or more thermoplastic polymer matrices having different melting points are used, the characteristic stability is greatly improved, the NTC phenomenon after resistance increase, hysteresis of a temperature-resistance curve, and unstable room temperature resistance are greatly improved, The room temperature resistance and a large resistance change during operation are stably maintained for a long period of time. In particular, the effect is remarkable in the high-temperature high-humidity acceleration test and the intermittent load test.
When the low-molecular-weight organic compound melts during operation, the rearrangement of the conductive particles dispersed in the low-molecular-weight organic compound may easily occur due to its low viscosity, but the melting point of the low-molecular-weight organic compound is relatively low. By using a polymer matrix with a close low melting point, the polymer matrix starts melting immediately after the low molecular weight organic compound is melted, the viscosity of the molten component increases, and the rearrangement of the conductive particles is suppressed, As a result, it is considered that the NTC phenomenon after the resistance increase and the hysteresis of the temperature-resistance curve are reduced. Also, by using a thermoplastic polymer matrix having a high melting point, the expansion of the entire system is suppressed, so that it is considered that a low room temperature resistance can be stably obtained over a long period of time.

The melting point of the thermoplastic polymer having a low melting point is at least 15 ° C., especially 20 to 30 ° C., higher than the melting point of the low molecular weight organic compound.
High is preferred. If the melting point of the low melting point thermoplastic polymer is higher than this, the polymer is unlikely to melt when the low molecular weight organic compound is melted, and the effect of increasing the viscosity of the molten component tends to be low. If the melting point of the low melting point thermoplastic polymer is lower than this, the rapid rise in resistance due to the melting of the low molecular weight organic compound tends to become slow. The melting point of the high melting point thermoplastic polymer matrix is 30 ° C. lower than the melting point of the low molecular weight organic compound.
As described above, it is particularly preferable that the temperature is higher by 40 to 110 ° C. If the melting point of the high melting point thermoplastic polymer is higher than this, the kneading temperature becomes high, so that the low molecular weight organic compound may be thermally degraded. If the melting point of the high melting thermoplastic polymer is lower than this,
It tends to be difficult to prevent the flow of the low molecular weight organic compound due to melting during operation, deformation of the elementary body, and the like. The difference between the melting point of the low melting point thermoplastic polymer and the melting point of the high melting point thermoplastic polymer is preferably 20 ° C. or more, particularly preferably 20 to 50 ° C. The melting point of the low melting point thermoplastic polymer matrix is usually preferably from 60 to 130 ° C. The melting point of a high melting thermoplastic polymer matrix is usually 80
It is preferable that it is -150 degreeC.

Further, a low-melting thermoplastic polymer matrix having a melt flow rate (MFF) defined by ASTM D1238.
R) is 1 to 20 g / 10 min, especially 1 to 10 g / 10 m
It is preferably in. MFR is 1-20g / 10mi
By using a polymer of n, the viscosity of the molten component when the low-molecular organic compound is melted (during operation) is increased and the rearrangement of the conductive particles is suppressed, so that the effect of stabilizing the characteristics is large. If the MFR is larger than this, it becomes difficult to sufficiently increase the viscosity of the molten component when the low-molecular-weight organic compound is melted, and the dispersion state of the polymer matrix, the low-molecular-weight organic compound, and the conductive particles tends to change. Tend.
If the MFR is smaller than this, the viscosity of the molten component at the time of melting the low molecular weight organic compound becomes too high, and it becomes difficult to obtain the effect of stabilizing the characteristics. In addition, the polymer matrix, the low molecular weight organic compound and the conductive particles Tends to be difficult to disperse.

The thermoplastic polymer matrix having a low melting point is preferably a low-density polyethylene or an olefin-based copolymer such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, polyethyl acrylate, or polymethyl (meth) acrylate. Polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, among which low density polyethylene is preferred.

As the high melting point thermoplastic polymer matrix, it is particularly preferable to use high-density polyethylene because it has an appropriate melting point and melt viscosity.

The high-density polyethylene has a melt flow rate (MFR) defined by ASTM D1238 of 3.0 g / 10
min or less, particularly preferably 1.5 g / 10 min or less. MF
If R is higher than this, the melt viscosity is too low, and the stability of the properties tends to be poor. Although there is no particular lower limit for the MFR,
Usually, it is about 0.1 g / 10 min.

Although three or more thermoplastic polymer matrices having different melting points may be used in combination, MFR of 3.0 g /
High density polyethylene less than 10min and MFR1-20g
It is preferable to use a low-density polyethylene or olefin copolymer of / 10 min, particularly preferably a low-density polyethylene.

The weight ratio of the high melting point thermoplastic polymer matrix to the low melting point thermoplastic polymer matrix is 1: 4.
９9: 1, particularly preferably 1: 3-8: 1.
With more low melting thermoplastic polymer matrix,
The stability of the initial resistance tends to decrease. If the amount of the low-melting-point thermoplastic polymer matrix is less than this, the NTC phenomenon after an increase in resistance tends to be observed, and the hysteresis of the temperature-resistance curve tends to increase.

The polymer matrix is preferably composed only of the above-mentioned thermoplastic resin (which may be crosslinked), but may contain an elastomer, a thermosetting resin or a mixture thereof in some cases. .

The low-molecular-weight organic compound as the active substance has a weight-average molecular weight of up to about 1,000, preferably 200 to 800.
There is no particular limitation as long as it is a crystalline substance of normal temperature (25 ° C.
And a solid at about the same temperature).

Examples of the low molecular weight organic compound include the same compounds as those described above as the water-insoluble low molecular weight organic compound used in combination with the polyethylene oxide. The low-molecular organic compound may be appropriately selected in consideration of the polarity of the polymer matrix in order to improve the dispersion of each component. Petroleum wax is preferred as the low molecular weight organic compound.

These low molecular organic compounds are commercially available, and commercially available products can be used as they are.

Considering the safety to the human body, the operating temperature is preferably 100 ° C. or lower. In this case, it is preferable to use a low molecular weight organic compound having a melting point mp of 40 to 100 ° C. preferable. Examples of such a compound include the same compounds as those described above as the water-insoluble low-molecular-weight organic compound used in combination with the polyethylene oxide.

One or more low-molecular organic compounds can be selected and used depending on the operating temperature and the like.

The weight of the low molecular weight organic compound is 0.2 to 4 times the total weight of the thermoplastic polymer matrix, especially 0.2 to 4 times.
It is preferably up to 2.5 times. When the mixing ratio is reduced and the amount of the low molecular weight organic compound is reduced, it becomes difficult to obtain a sufficient resistance change rate. Conversely, when the mixing ratio is increased and the amount of the low molecular weight organic compound is increased, when the low molecular weight compound is melted, the element body is greatly deformed, and mixing with the conductive particles becomes difficult.

The conductive particles used in the present invention are not particularly limited as long as they are metal, and may be used without limitation as long as they have the necessary conductivity and are integrated with the plating metal.

The conductive particles usable in the present invention include metal particles: Ni, Ti, Cu, Ag, Pd, Au, and Pt.
Metal coating particles: carbon black, Al ₂ O ₃ ,
What formed an Ag plating layer on particles such as TiO ₂ , Ba
A Pd plating layer formed on particles of TiO ₃ or the like; Metal fiber: Ni, Ti, Cu, Ag, Pd, Au, Pt, etc. having a length of 1 mm or less and an aspect ratio of 10 or more. At least one kind may be selected from these conductive particles or fibers. Specifically, it may be appropriately selected according to the method of forming the electrodes, the required PTC thermistor characteristics, and the like, but Ni is preferably used. Further, the metal type is the same as the metal type of the electrode. For example, when performing Ni plating, Ni is used as conductive particles.
The use of particles is preferable for integration.

The shape of the conductive particles is not particularly limited, and may be any of flakes, spheres, irregular shapes, etc., and is preferably non-spherical, particularly, for example, Japanese Patent Application Laid-Open No. 5-47503, US Pat. No. 5,378,407 and Japanese Patent Application No. Hei 8-
It is preferable to use a material having a spike-shaped protrusion as described in Japanese Patent No. 332979. When spike-like particles having a large number of projections are used, the peel strength increases. When using conductive particles having spike-like projections,
Due to the shape, a tunnel current easily flows, and a lower room temperature resistance than spherical conductive particles can be obtained. Also,
Since the distance between the conductive particles is larger than that of the spherical particles, a larger resistance change can be obtained during operation.

The conductive particles having spike-like projections
One and one are formed from primary particles having sharp projections, and a plurality of conical spike-shaped projections having a height of 1/3 to 1/50 of the particle diameter are formed on one particle (usually, 10 to 500)
It exists. The material is preferably a metal, particularly Ni or the like.

Such conductive particles may be powders in which one particle is present individually, but the primary particles are 10 to 10 particles.
It is preferable that about 1000 chains are connected in a chain to form secondary particles. Some primary particles may be present in the chain. An example of the former is a spherical nickel powder having spike-shaped protrusions, and the product name is INCO Type.
It is commercially available as e123 nickel powder (manufactured by Inco Corporation), has an average particle size of about ³ to 7 μm, an apparent density of about 1.8 to 2.7 g / cm ³ , and a specific surface area of 0.34.
~0.44m is about ² / g.

An example of the latter, which is preferably used, is a filamentous nickel powder, trade name IN
It is commercially available as CO Type 210, 255, 270, 287 nickel powder (manufactured by INCO), of which INCO Type 255, 287 is preferable.
The average particle size of the primary particles is particularly 0.5 to 4 μm.
m is preferable, and the apparent density is 0.3 to 1.0.
g / cm ³ and the specific surface area is about 0.4 to ^2.5 m ² / g.

The average particle size in this case is measured by the fish-sub-sieve method.

The preferred average particle size of the conductive metal particles varies depending on the type, shape, diameter measuring method and the like, but usually, relatively large particles of about 0.5 to 4 μm, especially about 1 to 4 μm are preferable. . Small spherical particles easily fall out of the resin matrix, and the peel strength is reduced.

The ratio (volume ratio) of the conductive particles in the element body is
What is necessary is just to determine appropriately so that the required PTC thermistor characteristics are obtained and the resistance value is sufficiently low during non-operation. The preferred ratio of the conductive particles {conductive particles / (polymer + conductive particles)} varies depending on various conditions such as the type and shape of the conductive particles, but is preferably 15 to 65% by volume, more preferably. 20 to 50% by volume. If the ratio of the conductive particles is too low, the resistance value of the elementary body increases,
This is not preferable for applications in which a large current flows. Also, it becomes difficult to form electrodes by electroplating. On the other hand, if the ratio of the conductive particles is too high, uniform dispersion becomes difficult when kneading the conductive particles with the polymer, and characteristics such as withstand voltage tend to deteriorate. In addition, PTC characteristics may not be exhibited.

The conductive particles preferably have a weight ratio of about 2 to 5 times the total amount of the polyethylene oxide crystalline polymer and the water-insoluble polymer and / or the water-insoluble low molecular weight organic compound. If the amount of the conductive particles is too small, the initial resistance during non-operation cannot be sufficiently reduced. On the other hand, when the amount of the conductive particles is too large, the rate of change in resistance from non-operation to operation is reduced, and kneading becomes difficult.

The weight of the conductive particles is preferably 1.5 to 5 times the total weight of the thermoplastic polymer matrix and the low molecular weight organic compound. When the mixing ratio is reduced and the amount of the conductive particles is reduced, the room temperature resistance during non-operation cannot be sufficiently reduced. Conversely, when the amount of the conductive particles is large, it is difficult to obtain a large rate of change in resistance, and it is difficult to achieve uniform mixing and to obtain stable characteristics.

Electrode The organic PTC thermistor of the present invention uses a plating film formed integrally with conductive metal particles exposed on the thermistor body surface as an electrode. “Integrally” means that there is no interface between the conductive metal particles and the electrode.

The type of plating metal used as the electrode material does not necessarily have to be the same as the metal type of the conductive metal particles, but is preferably the same type to ensure integration.

The thickness of the electrode is not particularly limited, but is usually about 10 to 300 μm.

It is preferable that at least half of the conductive particles integrated with the electrode are buried in the thermistor body, and the peel strength is affected by the size and shape of the buried portion.
In particular, it is preferable that the conductive metal particles are exposed from the surface of the thermistor body, that is, the surface of the polymer in a range of 10% or more and less than 50% of the particle size. If the exposed portion is smaller than this, it is difficult to form an electrode integrally, and it is difficult to sufficiently reduce the contact resistance between the thermistor element and the electrode, and the peel strength is also reduced.
On the other hand, if the exposed portion is larger than this, the conductive particles completely float from the polymer, so that the peel strength decreases and the electrode resistance increases. The conductive metal particles usually occupy 20 to 40% of the surface of the thermistor body.

The lower the resistance of the electrode, the better.
It is preferable that the resistance value hardly increases in a temperature range in which the C thermistor operates. That is, PT
When operating as a C thermistor, it is preferable that the resistance of the electrode be significantly lower than the resistance of the thermistor body. Specifically, at the PTC operating temperature, the resistance value of the electrode may be 1/100 or less of the resistance value of the thermistor body. In addition, during non-operation (25 ° C.), the resistance value of the electrode is preferably equal to or less than the resistance value of the thermistor body,
It is more preferably 1/10 or less. Here, the resistance value at PTC operating temperatures _{say, (R max + R 25)} / 2
Means R _max is the maximum resistance value when the temperature is raised, and R ₂₅ is the resistance value at 25 ° C.

Production of PTC Thermistor Element The thermistor element is usually produced by the following procedure.
First, a low molecular weight organic compound, conductive particles are added to a high molecular weight polymer, and the temperature is maintained at a temperature equal to or higher than the melting point or softening point of the polymer,
The mixture is sufficiently kneaded with a mill or a roll until the conductive particles are uniformly dispersed. Next, it is formed into a sheet or the like using an extrusion molding machine or a roll molding machine or the like, and is subjected to a crosslinking treatment as necessary, to obtain a thermistor body.

Further, an antioxidant can be mixed to prevent thermal deterioration of the high molecular weight polymer and the low molecular weight organic compound, and phenols, organic sulfurs, phosphites and the like are used.

Examples of the crosslinking method include radiation crosslinking, chemical crosslinking with an organic peroxide, and water crosslinking in which a silane coupling agent is grafted and a silanol group is condensed and reacted. Water crosslinking is preferred. In particular, vinyl groups or (meth)
It is preferable to carry out a cross-linking treatment with a silane coupling agent having an acryloyl group and an alkoxy group, especially a C = C bond-containing trialkoxysilane. As a result, the characteristic stability during storage and repetitive operation is significantly improved.

Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ- (meth) acryloxypropyltrimethoxysilane, γ- ( (Meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane and the like. Among them, vinyltrimethoxysilane and vinyltriethoxysilane are preferable.

The coupling treatment is preferably carried out in a kneaded mixture of the high molecular polymer, the low molecular organic compound, and the conductive particles, preferably 0.1 to 5 times the total weight of the high molecular polymer and the low molecular organic compound.
% By weight of a silane coupling agent is dropped, mixed well, and then water-crosslinked. When using a silane coupling agent having a vinyl group, 5 to 20% by weight of the coupling agent
Organic peroxides such as 2,2-di- (t-butylperoxy) butane, dicumyl peroxide, 1,1-
Di-t-butylperoxy-3,3,5-trimethylcyclohexane and the like are mixed together, and grafting is performed on an organic substance, that is, a high-molecular polymer and a low-molecular organic compound via a vinyl group. Then, after press-molding the kneaded material, a crosslinking treatment is performed in the presence of water. Specifically, a metal carboxylate such as dibutyltin dilaurate, dioctyltin dilaurate, tin acetate, tin octoate, or zinc octoate is used as a catalyst, and the molded body is immersed in warm water for 6 to 8 hours. Among them, dibutyltin dilaurate is preferably used as a catalyst. The crosslinking temperature is preferably lower than the melting point of the low molecular weight organic compound in order to enhance the stability of the characteristics such as the repetitive operation. After the crosslinking treatment, the formed body is dried to obtain a thermistor body.

Selective Removal Step After the thermistor body is manufactured, the high molecular polymer and the low molecular weight organic compound are selectively removed from the surface of the thermistor body to expose the conductive particles to the thermistor body surface. The reason for providing the selective removal step is as follows.

It is expected that the surface of the thermistor body manufactured by the above-described method is distributed depending on the mixing ratio of the conductive particles, the high molecular weight polymer, and the low molecular weight organic compound. However, according to the study of the present inventors, as described above, the conductive particles near the element body surface are covered with a thin film of a polymer (hereinafter, also referred to as a low molecular weight organic compound). I understood. Specifically, although it depends on the combination of the conductive particles and the polymer, the results of surface observation with a scanning electron microscope and measurement of the surface conductivity with an atomic force microscope show that the conductivity existing near the element body surface is high. It was found that at most about 90% of the particles were covered by a polymer layer having a thickness of about 0.1 to 3 μm.

When electrodes are formed on the surface of such a body,
The contact resistance between the electrode and the element body is significantly increased, which is not preferable. Therefore, in the present invention, a selective removal step is provided in order to remove the polymer film covering the conductive particles existing near the element body surface.

The removal depth of the polymer may be appropriately determined according to the combination of the conductive particles and the polymer so that the conductive particles are sufficiently exposed. As described above, the removal depth is preferably determined so that the conductive metal particles are exposed from the surface of the thermistor body within a range of 10% or more and less than 50% of the particle size. Is preferably 0.1 to 20 μm, more preferably 0.5 to 10 μm. If the depth of the selective removal is too shallow, the effect of the selective removal becomes insufficient. On the other hand, if the depth for selective removal is too deep, the conductive particles completely float from the polymer, which causes a decrease in electrode adhesion strength and an increase in electrode resistance.

The method used for the selective removal of the polymer is such that the combination of the two can be selectively removed from the thermistor body composed of the polymer and the conductive particles so as not to damage the thermistor body. The method may be appropriately selected in consideration of the method, and is not particularly limited. However, in the present invention, for example, a method described below is preferably used.

[0085] In the selective removal method This method utilizes a gas discharge plasma, to generate a gas plasma by introducing a discharge gas into the vacuum chamber was placed a thermistor body, it is produced by plasma ion bombardment and plasma The polymer is selectively removed by the active oxidizing gas. As the discharge gas, an inert gas such as Ar, an oxidizing gas such as oxygen, or a mixed gas thereof may be used, but a gas containing at least an oxidizing gas is preferably used. Specifically, a plasma treatment method, a reactive ion etching method, a reverse sputtering method, or the like may be used. In the reactive ion etching method, an oxidizing gas such as oxygen is used as a discharge gas, and in the reverse sputtering method, an inert gas such as Ar is used as a discharge gas. In both methods, an object to be etched is used as an electrode. On the other hand, unlike the reactive ion etching method and the reverse sputtering method, the plasma processing method is a method of simply exposing an etching target to a plasma atmosphere without using an etching target as an electrode.

The processing apparatus used for the plasma processing method is not particularly limited, but it is usually preferable to use a barrel type plasma processing apparatus. In a barrel-type plasma processing apparatus, unlike a reactive ion etching apparatus or a sputter etching apparatus used for a reverse sputtering method, a sample to be etched is not disposed on an electrode, but is exposed to plasma while being electrically insulated from the surroundings. You. Specifically, for example, the counter electrode is arranged in a quartz chamber. In this apparatus, first, after inserting a sample to be etched into the chamber, the inside of the chamber is evacuated to, for example, 10 Pa or less.
Next, a discharge gas containing an oxidizing gas such as oxygen is introduced into the chamber, and the pressure in the chamber is maintained at about 100 Pa by adjusting the pumping speed of the vacuum pump. In this state, plasma is generated by applying high frequency power to the electrodes. By heating the sample to about 100 ° C. during the etching, the etching time can be reduced to ３ or less.
The high-frequency power used for plasma excitation is not limited to the normally used frequency of 13.56 MHz, but may be any frequency that can generate plasma from a relatively low frequency of about 100 kHz to a microwave of about 2.45 GHz. An equivalent etching effect can be obtained.

The plasma processing method has a slightly lower etching rate than the reactive ion etching method or the reverse sputtering method. However, in the plasma processing method, since a high voltage for generating plasma is not directly applied to the sample, the plasma processing method cannot be used. The equipment is simple in configuration, capable of etching a large number of samples at the same time, easy to etch both sides of the sample at the same time, for example, continuously processing a sheet-shaped sample in a roll-up type. It is advantageous in that it is structurally easy. That is, the method using the plasma processing method is low in cost and has good productivity. on the other hand,
The reactive ion etching method is preferable in that it has excellent selectivity when etching a polymer as compared with the reverse sputtering method.

In the method using gas discharge plasma, it is possible to selectively remove the polymer on the surface of the elementary body from a few tens of seconds to a few tens of minutes to a depth of about 20 μm, depending on the composition of the polymer. It is possible.

UV irradiation and exposure to an ozone-containing atmosphere
By irradiating the thermistor body with the selective removal method utilizing at least one of the dew rays with ultraviolet light, the bonds between atoms in the polymer can be broken. If the ultraviolet irradiation is performed in an oxidizing atmosphere, the decomposed product can be oxidized and removed by a surrounding oxidizing gas. On the other hand, the polymer can also be removed by performing ultraviolet irradiation in an inert gas, followed by washing with water or etching. In addition,
The etching in this case may be performed using an organic solvent or the like.

Further, the polymer can be selectively removed by exposing the thermistor body to an atmosphere containing ozone having a strong oxidizing power and directly reacting the ozone with the polymer.

Further, it is also possible to use both ultraviolet irradiation and exposure to an ozone-containing atmosphere. In the combined method, bonds between atoms in the polymer are cut by irradiation with ultraviolet rays, and the bonds are strongly oxidized and removed by ozone.

The oxidizing atmosphere used for the ultraviolet irradiation method is not particularly limited, and may be, for example, air. Also,
The ozone concentration in the ozone-containing atmosphere used in each of the above methods is not particularly limited, and may be appropriately determined so as to obtain a necessary removal rate.

In the method using ultraviolet irradiation and the method of exposing to an ozone-containing atmosphere, the etching rate is slower than the method using gas discharge plasma, but the cost can be reduced because no vacuum device is used. It is also excellent in that a large area etching process can be performed. In addition, in the method using both the ultraviolet irradiation and the exposure to the ozone-containing atmosphere, an etching rate comparable to the method using gas plasma can be obtained. Specifically, for example, if a commercially available UV ozone cleaner is used, a maximum of 20 μm
Selective removal is possible to a certain depth. The UV ozone cleaner is a device that oxidizes oxygen in the air with ultraviolet rays at the same time as irradiating a sample with ultraviolet rays by an ultraviolet lamp, and reacts the generated ozone with the sample.

Selective Removal Method Using Laser Light Irradiation When a laser beam is irradiated to a thermistor body, the intermolecular bonds of the polymer are broken by strong photochemical excitation of the laser light, and the polymer is separated, decomposed, and scattered. By utilizing this, the polymer can be selectively removed from the element body surface. This method is generally called a laser ablation method, and is a type of photolytic removal processing. The etching rate is high for resins having relatively weak intermolecular bonds, and generally low for inorganic materials such as metals. It is excellent in selectivity when the polymer is selectively removed from the element body. Further, since there is almost no rise in the temperature of the element body during processing, high-quality processing is possible. Further, deep etching can be performed in a short time. In addition, a large area can be processed by scanning with a laser beam.

As the laser processing apparatus used in this method, an excimer laser processing apparatus is preferable. The excimer laser may be any of KrF, ArF, NeF, XeF and the like, and the same effect can be obtained in any case. The power of the excimer laser is not particularly limited, and may be appropriately determined depending on the combination of the polymer and the conductive particles, and is usually 0.1 to 6 J / cm ² as the energy density.
Degree, preferably about 0.5 to ⁴ J / cm ² .

The etching principle is different from that of the excimer laser, and the etching selectivity is inferior to the case of using the excimer laser.
Etching can also be performed with a laser or the like.

Selective Removal Method Using Sandblast By subjecting the thermistor body surface to sandblasting, the polymer in the vicinity of the body surface can be removed. However, this method is inferior in selectivity when selectively removing the polymer. Further, physical damage to the thermistor body and contamination with impurities may occur, which may cause deterioration of the thermistor characteristics.

Exposure to organic solvent or organic solvent vapor
By selectively exposing the thermistor element to an organic solvent or an organic solvent vapor, the polymer near the element surface can be removed. As the organic solvent, paraxylene, N-methyl-2-pyrrolidone, dichloroethane, N, N-dimethylformamide and the like can be used. However, this method makes it difficult to selectively remove the polymer. Further, since the infiltration of the etching solution into the element body is inevitable, the thermistor characteristics may be destabilized and reliability may be reduced.

In the selective removal step, it is preferable to use any of a plasma treatment method, a reactive ion etching method, ultraviolet irradiation, exposure to an ozone-containing atmosphere, and laser light irradiation.

Electrode forming step After the polymer is selectively removed, an electrode is formed on the surface of the thermistor body. The electrodes are formed by a plating method, preferably an electroplating method.

The electrode layer formed by electroplating is formed by using the thermistor element as a cathode and a metal plate as an anode. For a short time immediately after the start, the cathode and the anode are reversed and current is applied to the surface of the metal conductive particles. The oxide is reduced or dissolved. By performing the electrolytic etching in this manner, integration between the electrode and the conductive metal particles is ensured, and electrical connection and peeling prevention become effective. That is, a fresh metal surface is generated by reduction or partial dissolution, and there is no interface with the subsequently formed plating metal, so that integration is ensured. If the surface of the metal particles is slightly oxidized, it will be peeled off there.

Electrolytic etching is performed using the thermistor body from which the polymer has been selectively removed as an anode and a metal plate as a cathode.
The conditions of the electrolytic etching may be appropriately determined depending on the conductive metal particles, the polymer, and the like to be used.
° C, preferably 20 to 60 ° C, current density 0.2 to 10 A /
cm ² , preferably 0.5 to 5 A / cm ² for 0.5 to 10 minutes,
Preferably, it may be performed for 1 to 5 minutes. As the electrolyte, a plating solution for forming an electrode is usually used. The metal plate also usually uses a plating material (electrode material) for forming the electrode.

After the electrolytic etching, electrodes are formed preferably by an electroplating method.

Electroplating is performed using the thermistor body as a cathode and a metal plate as an anode. The plating conditions may be appropriately determined depending on the electrode material, conductive metal particles, polymer, and the like to be used. Usually, the plating bath temperature is 10 to 80 ° C., preferably 20 to 60 ° C., and the current density is 0.2 to 10 A / cm ^2. , Preferably 0.5 to 5 A / cm ² . The plating solution is usually
What is used may be used. The plating time is
The thickness may be appropriately determined according to the thickness of the electrode to be formed, but usually, it may be about 10 to 60 minutes. At the time of plating, the solution is preferably stirred.

It is preferable that the electrode has a uniform and fine crystal size. When the current density is small, precipitation occurs slowly, so that a large crystal is easily formed. Conversely, when plating is performed at a large current density, new crystals are formed one after another rather than one crystal grows, so that small crystals can be obtained. However, if the current density is too large, hydrogen is also generated at the same time as the deposition of metal, resulting in perforated plating or ragged plating. When the temperature of the plating bath is increased, large crystals tend to precipitate. Also,
In order to obtain a plating film having a uniform thickness, it is preferable to increase the conductivity of the plating bath.

[0106]

Example 1 An organic PTC thermistor sample was prepared according to the procedure shown below for Sample No. 101 .

Preparation of Thermistor Element High-density polyethylene (manufactured by Nippon Polychem, trade name HY540; MFR 1.0 g) as a high melting point polymer matrix
/ 10 min, melting point 135 ° C.), low-density polyethylene as a low-melting polymer matrix (manufactured by Nippon Polychem, trade name LC500; MFR 4.0 g / 10 min, melting point 106)
° C), paraffin wax (trade name: HNP-10, manufactured by Nippon Seiwa Co., Ltd., melting point: 75 ° C) as a low molecular organic compound, and filamentous nickel powder (INCO) as conductive particles.
(Trade name: Type 255 nickel powder). The filament-like powder is composed of particles formed by connecting particles having spike-like projections. The average particle size of the conductive particles is 2.2 to 2.8 μm, the apparent density is 0.5 to 0.65 g / cm ³ , and the specific surface area is 0.
68 m ² / g.

The weight ratio of the high-density polyethylene to the low-density polyethylene was set to 4: 1, nickel powder was added in an amount of 4 times the total weight, and the mixture was kneaded in a mill at 150 ° C. for 5 minutes. Then, paraffin wax having the same weight as the total weight of the high-density polyethylene and the low-density polyethylene, and nickel powder four times the weight of the wax were further added and kneaded. And, as a silane-based coupling agent, vinyltriethoxysilane (product name: KBE1003, manufactured by Shin-Etsu Chemical Co., Ltd.) of 0.5% by weight of the total weight of organic substances;
20% by weight of a silane coupling agent, 2,2-di- (t-butylperoxy) butane (manufactured by Kayaku Akzo, product name: Trigonox DT50) as an organic peroxide was dropped into the kneaded material. And kneaded for another 60 minutes.

The kneaded material was formed into a sheet having a thickness of 1 mm at 150 ° C. by a hot press. Then, the sheet was immersed in a 20% by weight emulsion water solution of dibutyltin dilaurate (manufactured by Tokyo Chemical Industry Co., Ltd.) and subjected to a crosslinking treatment at 65 ° C. for 8 hours. The crosslinked sheet was vacuum dried to obtain a sheet-like thermistor body having a thickness of 1 mm. The ratio of the conductive particles in the thermistor body was 35% by volume.

Selective Removal Step The thermistor body was irradiated with ultraviolet rays in an ozone-containing atmosphere using a UV ozone cleaner (VUM-3073-13-00, manufactured by Oak Manufacturing Co., Ltd.). This UV ozone cleaner is provided with four 40 W low-pressure mercury lamps, and has an effective irradiation area of 20 cm × 20 cm. The polymer was selectively removed from the thermistor body surface to a depth of about 10 μm by ultraviolet irradiation for 5 minutes and exposure to an ozone-containing atmosphere.

Scanning electron micrographs of the thermistor body surface before and after selective removal showed that the conductive particles near the body surface were thin film-like polymer and low molecular weight before the selective removal treatment. It covered the organic compound, and the conductive particles were exposed after the selective removal treatment. In addition, when the conductivity of the element body surface before and after the selective removal treatment was evaluated using the current application mode of the atomic force microscope, the element body surface before the selective removal treatment was almost insulated. Has significantly improved conductivity.

Electrode forming step As a plating solution, an aqueous solution containing 290 g / l of nickel sulfate, 50 g / l of nickel chloride and 40 g / l of boric acid was used.
The plating solution was used as an electrolytic solution, electrolytic etching was performed using the thermistor body from which the polymer and low molecular weight organic compound were selectively removed as an anode, and a nickel plate as a cathode. The conditions of electrolytic etching were as follows: liquid temperature 50 ° C., current density 0.5 A / cm ²
For 1 minute.

Then, electroplating was performed using the thermistor body from which the polymer and the like were selectively removed as a cathode and a nickel plate as an anode to form electrodes. Electroplating, liquid temperature 50 ℃,
The test was performed at a cathode current density of 5 A / cm ² for 20 minutes. Thus, a Ni plating layer having a thickness of 16 μm was formed as a metal electrode layer on the surface.

After the formation of the metal electrode layer, a disk having a diameter of 10 mm was punched out to obtain an organic PTC thermistor sample.

Sample No. 102 Sample No. 1 except that a metal plating electrode was formed in a plating bath using a sulfamic acid bath having a pH of 4.5 and a liquid temperature of 50 ° C.
Sample No. 102 was produced in the same manner as Sample No. 01.

Sample No. 103 (Comparative Example) Sample No. 10 except that the polymer was not selectively removed.
Sample No. 103 was prepared in the same manner as in No. 1.

Sample No. 104 (Comparative Example) The conductive particles were carbon black (Diablack (registered trademark) E, manufactured by Mitsubishi Kasei Kogyo KK) having an average particle diameter of 43 nm, and the compounding ratio was 100 parts by weight of the resin. Sample No. 1 was prepared in the same manner as Sample No. 101 except that 75 parts by weight was used.
04 was produced.

Sample No. 105 (Comparative Example) Sample No. 105 was prepared in the same manner as Sample No. 101 except that electrolytic etching was not performed before electroplating.

For each of the above samples, at 25 ° C. and 8 ° C.
The resistance value (initial resistance value) was measured at 5 ° C. Next, after repeating a cycle test in which heating and cooling were repeated between room temperature and 120 ° C. 1000 times, a resistance value (resistance value after the cycle test) was measured in the same manner. The resistance value was measured using a four-terminal method. Table 1 shows the results.

[0120]

[Table 1]

Table 1 clearly shows the effect of the present invention.
Comparing the initial resistance value at 25 ° C. and the resistance value after the cycle test, Sample Nos. 101 and 102 in which the polymer was selectively removed from the thermistor body surface were compared with Sample No. 103 in which the selective removal was not performed. It is significantly lower. In each sample, a sufficiently high resistance value was obtained at 85 ° C. As described above, the organic PTC thermistor manufactured by the method of the present invention has a sufficiently low initial resistance value and a high peel strength, so that the resistance value fluctuation due to the repetition of the PTC operation is so small as to be practically negligible. , Extremely reliable.

When carbon black was used as the conductive particles as in Sample No. 104, Sample N
In the case where no electrolytic etching was performed as in the case of o.105, the adhesion to the plating electrode was not sufficient, and the resistance value after repeated operation gradually increased, resulting in insufficient reliability.

The heating / cooling cycle described above heats the entire sample. Even when heating was performed by applying a current to the sample, the same result as in Table 1 was obtained after 1000 repetitions. .

Regarding the electrodes used for each of the above samples,
Resistance values in the range of 5 to 120 ° C were determined. Since the resistance value of the electrode alone cannot be measured directly, first, chemical plating is performed on the insulating substrate, an electroplating film is formed thereon, a Ni plating layer is formed, and a four-probe probe method is used. The specific resistance was measured. As a result, the specific resistance of the Ni plating layer was about 1 × 10 ⁻⁵ Ωcm, and no change in the specific resistance was observed between room temperature and 120 ° C. From the electrode resistance value and the resistance values of the samples shown in Table 1, the resistance value R ₂₅ at 25 ° C. and the resistance value at the PTC operating temperature Ｒ (R _max
+ R ₂₅ ) / 2}, it can be seen that the electrodes are all sufficiently lower than the thermistor body.

Example 2 Preparation of Sample No. 201 Thermistor Element As a crystalline polymer, polyethylene oxide (manufactured by Sumitomo Seika, weight average molecular weight of 4,300,000 to 4,800,
000, melting point 67 ° C) and a phenolic and organic sulfur-based antioxidant (Sumitomo Chemical, trade name Sumilyzer-B)
HT and TP-D) with 0.5 of polyethylene oxide
wt%, compatibilizer (Sumiedo 60, manufactured by Sumitomo Chemical)
0) was added to 5 wt% of polyethylene oxide, and 8
Kneaded at 0 ° C. for 10 minutes.

Next, the temperature of the mill was raised to 115 ° C., and a low-density polyethylene (manufactured by Nippon Polychem, trade name LC500, MFR = 4.0 g / 10 mi) was used as the water-insoluble polymer.
n, melting point 106 ° C.) 1.75 of polyethylene oxide
It was added by weight and kneaded for 5 minutes.

As the conductive particles, chain filamentous nickel powder (trade name: INCO, manufactured by Inco Corporation)
Type 255 nickel powder, average particle size 2.2-
2.8 μm, apparent density 0.5 to 0.65 g / cm ³ ,
A specific surface area of 0.68 m ² / g) was added in an amount of 4 times the total weight of polyethylene oxide and low-density polyethylene.
Kneading was performed at 115 ° C. for 60 minutes. The obtained kneaded material was molded by a press molding machine to obtain a sheet-shaped thermistor body having a thickness of 1 mm. The ratio of the conductive particles in the thermistor body was 35% by volume.

Selective Removal Step The thermistor body was set in a reactive ion etching type ashing apparatus and etched. O ₂ was used as a discharge gas, the discharge pressure was 20 Pa, the power density was 0.25 W / cm ² , and the discharge time was 2 minutes. As a result, the polymer from the thermistor body surface to a depth of about 10 μm was selectively removed.

Scanning electron micrographs of the thermistor body surface before and after the selective removal showed that the conductive particles near the body surface covered the thin film-like polymer before the selective removal treatment. Thus, the conductive particles were exposed after the selective removal treatment. In addition, when the conductivity of the element body surface before and after the selective removal treatment was evaluated using the current application mode of the atomic force microscope, the element body surface before the selective removal treatment was almost insulated. Has significantly improved conductivity.

Electrode forming step As a plating solution, an aqueous solution containing 80 g / l of copper sulfate, 180 g / l of sulfuric acid, and 0.06 ml / l of hydrochloric acid was used. The plating solution was used as an electrolytic solution, electrolytic etching was performed using the thermistor body from which the polymer was selectively removed as an anode, and a phosphor copper plate as a cathode. The electrolytic etching was performed at a liquid temperature of 25 ° C. and a current density of 0.5 A / cm ² for 1 minute.

Then, electroplating was performed using the thermistor body from which the polymer was selectively removed as a cathode and a phosphor copper plate as an anode to form electrodes. The electroplating was performed at a liquid temperature of 25 ° C. and a cathode current density of 0.5 A / cm ² for 30 minutes. Thus, a Cu plating layer having a thickness of 16 μm was formed as a metal electrode layer on the surface.

After forming the metal plating electrode layer, a disk having a diameter of 10 mm was punched out to obtain an organic PTC thermistor sample.

Sample No. 202 (Comparative Example) A sample was prepared in the same manner as in Sample No. 201 except that the polymer was not selectively removed and the metal electrode layer (Ni foil) was thermocompression-bonded to the element.
Sample No. 202 was produced.

Sample No. 203 The same Ni electrode as that of Sample No. 101 was used as the metal electrode layer.
Sample No. 203 was prepared in the same manner as in Sample No. 201 except that a plating layer was formed.

For each of the above samples, 25 ° C. and 1
At 90 ° C., the resistance value (initial resistance value) was measured. Next, after repeating a cycle test in which heating and cooling were repeated between room temperature and 200 ° C. 1000 times, a resistance value (resistance value after the cycle test) was measured in the same manner. The resistance value was measured using a four-terminal method. Table 2 shows the results.

[0136]

[Table 2]

Table 2 clearly shows the effect of the present invention.
That is, comparing the initial resistance value at 25 ° C. and the resistance value after the cycle test respectively, Sample No. 201 and No. 203 where the polymer was selectively removed were compared with Sample No. 202 where the selective removal was not performed. It is significantly lower. Further, the increase in the resistance value by the cycle test is smaller in sample No. 203 having a large anchor effect than in sample No. 201 in which the metal electrode layer is formed directly on the element body surface. This is considered to be due to stress absorption due to the spike-like Ni particles formed integrally with the electrode penetrating deep into the resin. As described above, the organic PTC thermistor manufactured by the method of the present invention has a sufficiently low initial resistance value, and the fluctuation of the resistance value due to the repetition of the PTC operation is so small as to be practically negligible.

The above-mentioned heating / cooling cycle is for heating the entire sample. Even when heating was performed by energizing the sample, the same result as in Table 2 was obtained after 1000 repetitions. .

When the specific resistance of the electrode used for each sample in Table 2 was measured in the same manner as in Example 1, the electrode resistance was estimated to be 1 × 10 ⁻⁵ Ω · cm as in Example 1, and It was found that the electrode resistance did not show temperature dependence. From this electrode resistance value and the resistance values of the samples shown in Table 2, 2
It can be seen that the resistance value R ₂₅ at 5 ° C. and the resistance value {(R _max + R ₂₅ ) / 2} at the PTC operating temperature are all sufficiently lower than those of the thermistor element.

Example 3 Polyethylene oxide (manufactured by Sumitomo Seika Chemical Co., Ltd., weight average molecular weight of 4,300,000 to 4,800,
Oleic acid amide (trade name: Neutron P, manufactured by Nippon Seika) as a low molecular weight water-insoluble organic compound, chain filamentous nickel powder (trade name: Type 255, manufactured by INCO) as conductive particles Nickel powder). The average particle size of the conductive particles is 2.2 to
2.8 μm, apparent density 0.5-0.65 g / cm ³ ,
The specific surface area is 0.68 m ² / g.

In polyethylene oxide, oleic amide was 20% by weight of polyethylene oxide, nickel powder was 4 times the weight of polyethylene oxide, and phenolic and organic sulfur-based antioxidants (Sumitomo Chemical Co., Ltd., trade names Sumilizer-BHT and TP-) D) was added by 0.5% by weight of polyethylene oxide and kneaded in a mill at 80 ° C. for 10 minutes. The obtained kneaded material was molded by a press molding machine to obtain a sheet-shaped thermistor body having a thickness of 1 mm. The ratio of the conductive particles in the thermistor body was 34% by volume.

Using this thermistor element, Example 2,
When selective removal was performed in the same manner as in Sample No. 201, the polymer was selectively removed from the thermistor body surface to a depth of about 10 μm. And sample No.20
An electrode was formed in the same manner as in No. 1 to obtain an organic PTC thermistor sample of Sample No. 301. Using this thermistor body, an electrode was formed in the same manner as in Example 2 and Sample No. 202 (Comparative Example).
The organic PTC thermistor sample of Comparative Example was used. In addition, using this thermistor body,
Selective removal was performed in the same manner as in No. 203, electrodes were formed, and an organic PTC thermistor sample of Sample No. 303 was obtained.

For each of the above samples, 25 ° C. and 1
At 90 ° C., the resistance value (initial resistance value) was measured. Next, after repeating a cycle test in which heating and cooling were repeated between room temperature and 200 ° C. 1000 times, a resistance value (resistance value after the cycle test) was measured in the same manner. The resistance value was measured using a four-terminal method. As a result, the organic PTCs of Sample Nos. 301, 302 (Comparative Example) and 303
Thermistors were sample Nos. 201 and 202, respectively.
(Comparative example), a result equivalent to 203 was obtained.

Example 4 The thermistor element used for Sample No. 101 was etched using a reactive ion etching type ashing apparatus. The discharge gas used was O ₂ or Ar, the discharge pressure was 20 Pa, the power density was 0.25 W / cm ² , and the discharge time was 1 minute. As a result, the polymer was selectively removed from the thermistor body surface to a depth of about 5 μm.
A scanning electron micrograph of the surface of the thermistor body when a reactive ion etching method using O ₂ is used;
Scanning electron micrographs of the thermistor body surface when using reactive ion etching method with a thin film were found. Before the selective removal treatment, the conductive particles near the body surface were thin film-like polymer. And the low molecular organic compound, and the conductive particles were exposed after the selective removal treatment. In addition, when the conductivity of the element body surface before and after the selective removal treatment was evaluated using the current application mode of the atomic force microscope, the element body surface before the selective removal treatment was almost insulated. Has significantly improved conductivity.

An organic PTC thermistor was prepared in the same manner as in Sample No. 101 except for the selective removal method, and the same measurement as in Example 1 was performed. As a result, a result equivalent to that of Sample No. 101 was obtained.

Example 5 Preparation of a Thermistor Element Polyvinylidene fluoride (PVDF: Kayner 71 manufactured by Elf Atochem North America, Inc., USA)
1) was prepared. A silane coupling agent (KBC100 manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 parts by weight of the polymer.
3) was added in an amount of 10 parts by weight.
5-dimethyl-2,5-di (t-butylperoxin)
Hexin-3 was added in an amount of 1 part by weight, and heated to 200 ° C. to obtain a graft resin using a twin screw extruder. Next, the spiked Ni powder was mixed with this graft resin so as to be 20% by volume of the whole, and kneaded for 1 hour at 200 ° C. The obtained kneaded material was molded by a press molding machine to obtain a sheet-shaped thermistor body having a thickness of 1 mm.

Selective Removal Step This thermistor body was set in a reactive ion etching type ashing apparatus and etched. O ₂ was used as the discharge gas, the discharge pressure was 20 Pa, the power density was 0.25 W / cm ² , and the discharge time was 1 minute. As a result, the polymer was selectively removed from the thermistor body surface to a depth of about 5 μm. Note that Ar gas is used as a discharge gas.
When etching was used, the etching rate was slightly reduced, but O ₂
The polymer was selectively removed almost in the same manner as in the case of using.

A scanning electron micrograph of the surface of the thermistor body before the selective removal, a scanning electron micrograph of the surface after selective removal using O ₂ as a discharge gas, and Ar using a discharge gas. Scanning electron micrograph of the one after the selective removal was performed, and the conductive particles near the elementary body surface covered the thin film polymer before the selective removal treatment, and after the selective removal treatment Had exposed conductive particles. In addition, when the conductivity of the element body surface before and after the selective removal treatment was evaluated using the current application mode of the atomic force microscope, the element body surface before the selective removal treatment was almost insulated. Has significantly improved conductivity.

Electrode Forming Step The electrode was formed in the same manner as in Sample No. 101. When the same measurement as in Example 1 was performed on the organic PTC thermistor sample thus manufactured, the resistance R ₂₅ at 25 ° C. was 9.5 mΩ, and the resistance R ₁₂₀ at 120 ° C. was ₁₃₀ MΩ.
Ω. For comparison, a sample was prepared by thermocompression-bonding a Ni foil directly to the thermistor body, and the resistance value was measured for this sample. R ₂₅ was 20 mΩ and R ₁₂₀ was 150 mΩ.
MΩ. For these samples, room temperature and 14
Cycle test of repeated heating and cooling between 0 ° C and 10 ° C
After repeating the test for 00 times, the resistance value was measured in the same manner. In the sample of the present invention, R ₂₅ and R ₁₂₀ were both +5 of the initial value.
While the rate of change was 0% or less, the electrode was completely peeled off in the comparative sample, making it impossible to evaluate the characteristics.

Example 6 Preparation of a Thermistor Element As a polymer, nylon 12 having a weight average molecular weight Mw of 30,000 was used.
(Melting point 180 ° C) and prepare filamentous nickel powder (Inco Typ.
e 255 nickel powder). The filament-like powder is composed of particles formed by connecting particles having spike-like projections. The particles having the spike-like projections have an average particle size of 2.2 to 2.8 μm.
m, apparent density is 0.5 to 0.65 g / cm ³ , and specific surface area is 0.68 m ² / g.

Next, conductive particles were added to the polymer and kneaded in a mill for 5 minutes while maintaining the temperature at 190 ° C. The obtained kneaded material was molded by a press molding machine to obtain a sheet-shaped thermistor body having a thickness of 1 mm. The ratio of the conductive particles in the thermistor body was 33% by volume.

Selective Removal Step This thermistor body was set in a reactive ion etching type ashing apparatus and etched. O ₂ was used as the discharge gas, the discharge pressure was 20 Pa, the power density was 0.25 W / cm ² , and the discharge time was 1 minute. As a result, the polymer was selectively removed from the thermistor body surface to a depth of about 5 μm. Note that Ar gas is used as a discharge gas.
When etching was used, the etching rate was slightly reduced, but O ₂
The polymer was selectively removed almost in the same manner as in the case of using.

A scanning electron micrograph of the surface of the thermistor element when the reactive ion etching method using O ₂ is used, and scanning of the surface of the thermistor element when the reactive ion etching method using Ar is used According to a scanning electron microscope photograph, the conductive particles near the surface of the element covered the thin film-like polymer before the selective removal treatment, and the conductive particles were exposed after the selective removal treatment. In addition, when the conductivity of the element body surface before and after the selective removal treatment was evaluated using the current application mode of the atomic force microscope, the element body surface before the selective removal treatment was almost insulated. Has significantly improved conductivity.

Electrode forming step The electrode was formed in the same manner as in Sample No. 101. The organic PTC thermistor sample thus prepared was subjected to the same measurement as in Example 1. The resistance R ₂₅ at 25 ° C. was 8.6 mΩ, and the resistance R ₁₂₀ at 120 ° C. was 110 MΩ.
Ω. For comparison, a sample in which a Ni foil was thermocompression-bonded directly to the thermistor body was prepared, and the resistance value was measured for this sample. R ₂₅ was ₂₅ mΩ and R ₁₂₀ was 120 mΩ.
MΩ. For these samples, room temperature and 14
Cycle test of repeated heating and cooling between 0 ° C and 10 ° C
After repeating the test for 00 times, the resistance value was measured in the same manner. In the sample of the present invention, R ₂₅ and R ₁₂₀ were both +5 of the initial value.
While the rate of change was 0% or less, the electrode was completely peeled off in the comparative sample, making it impossible to evaluate the characteristics.

Example 7 A thermistor element used for Sample No. 101 was replaced with a barrel type plasma processing apparatus (DE manufactured by Plasma System Co., Ltd.).
(S-106-254AEN) using the following procedure.
In this apparatus, a counter electrode is arranged in a cylindrical quartz chamber having a diameter of 25 cm and a length of 40 cm, and the sample to be etched is not arranged on the electrode as described above. First, after inserting the thermistor body into the chamber, the inside of the chamber was evacuated to 10 Pa or less. Then O
_2, and the pressure inside the chamber was kept at 100 Pa by adjusting the pumping speed of the vacuum pump. In this state, plasma was generated by applying high-frequency power of 13.56 MHz to 400 W to the electrodes, and the thermistor body was exposed to the plasma for 15 minutes. As a result, the polymer and the low molecular organic compound were selectively removed from the thermistor body surface to a depth of about 10 μm.

An organic PTC thermistor was manufactured in the same manner as in Sample No. 101 except that the thermistor element thus selectively removed was used, and the same measurement as in Example 1 was performed. A result equivalent to 101 was obtained.

Example 8 The thermistor body used for Sample No. 101 was etched by a laser ablation method using a KrF excimer laser having a wavelength of 248 nm. The energy density was ² J / cm ² , and the pulse irradiation frequency was 10 times. As a result, the polymer and the low molecular organic compound were selectively removed from the thermistor body surface to a depth of about 10 μm.

An organic PTC thermistor was manufactured in the same manner as in Sample No. 101 except that the thermistor element thus selectively removed was used, and the same measurement as in Example 1 was performed. A result equivalent to 101 was obtained.

Example 9 The thermistor element used for Sample No. 201 was etched by sandblasting to selectively remove the polymer from the thermistor element surface to a depth of about 10 μm. The selectivity for removing the polymer was lower than that of Sample No. 201.

An organic PTC thermistor was manufactured in the same manner as in Sample No. 201 except that the thermistor body thus selectively removed was used, and the same measurement as in Example 2 was performed. The same result as 201 was obtained.

Example 10 The thermistor body used for Sample No. 201 was exposed to para-xylene to remove about 10 μm from the surface of the thermistor body.
The polymer to a depth of m was selectively removed. Sample No.
The selectivity of polymer removal was lower than 201.

An organic PTC thermistor was prepared in the same manner as in Sample No. 201 except that the thermistor element thus selectively removed was used, and the same measurement as in Example 2 was performed. The same result as 201 was obtained.

[0163]

As described above, according to the present invention, it is possible to provide a highly reliable organic PTC thermistor having a low resistance value during non-operation, a high peel strength, and a high reliability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration example of a conventional organic PTC thermistor.

FIG. 2 is a schematic sectional view showing a configuration example of an organic PTC thermistor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High molecular polymer 2 Conductive metal particle 3 Thermistor element 4 Electrode 11 Crystalline high polymer 12 Conductive particle 13 Thermistor element 14 Electrode

Claims (13)

[Claims] 1. An organic PTC thermistor having a thermistor element having a configuration in which conductive metal particles are dispersed in a polymer and an electrode provided on the surface of the thermistor element, wherein the electrode is a thermistor. An organic PTC thermistor integrally formed with the conductive metal particles exposed on the element body surface. 2. The organic PTC thermistor according to claim 1, wherein said thermistor body further contains a low molecular weight organic compound. 3. The organic PTC thermistor according to claim 1, wherein said electrode is a plating film. 4. The organic PTC thermistor according to claim 1, wherein said conductive metal particles are non-spherical. 5. The organic positive temperature coefficient thermistor according to claim 4, wherein said conductive metal particles have spike-shaped projections. 6. The organic PTC thermistor according to claim 1, wherein said conductive metal particles are Ni. 7. The conductive metal particles have an average particle size of 1 to 4.
The organic PTC thermistor according to any one of claims 1 to 6, which has a diameter of µm. 8. The organic PTC thermistor according to claim 1, wherein the metal species of the conductive metal particles and the metal species of the electrode are the same. 9. A method for producing an organic PTC thermistor having a thermistor element having a structure in which conductive metal particles are dispersed in a high molecular polymer, and an electrode provided on the surface of the thermistor element, A selective removal step of selectively removing the high molecular polymer from the surface of the thermistor body to expose the conductive metal particles on the surface of the thermistor body; Having an electrode forming step of forming an electrode on the organic PT
Manufacturing method of C thermistor. 10. An organic PTC thermistor having a thermistor body having a structure in which conductive metal particles are dispersed in a high molecular polymer containing a low molecular weight organic compound, and an electrode provided on the surface of the thermistor body. A selective removal step of selectively removing the high molecular polymer and the low molecular weight organic compound from the surface of the thermistor body to expose conductive metal particles to the thermistor body surface; An electrode forming step of forming an electrode integrally with the conductive metal particles exposed on the body surface.
Manufacturing method of C thermistor. 11. The method for manufacturing an organic PTC thermistor according to claim 9, wherein a plating method is used in said electrode forming step. 12. The method of manufacturing an organic PTC thermistor according to claim 11, wherein, in said electrode forming step, electrodes are formed by electroplating after said thermistor body is electrolytically etched. 13. In the selective removal step, a plasma treatment method, a reactive ion etching method, an ultraviolet ray irradiation, an exposure to an ozone-containing atmosphere, a laser beam irradiation, a reverse sputtering method, a sandblasting method, an organic solvent exposure or an organic solvent vapor exposure. The method for producing an organic PTC thermistor according to claim 9, wherein the organic PTC thermistor is used.