JP3506629B2 - Organic positive temperature coefficient thermistor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a temperature sensor or an overcurrent protection element and has a PTC (positive temperature coefficient) whose resistance value increases as temperature rises.
organic positive temperature coefficient thermistor having a characteristic of resistivity.

[0002]

2. Description of the Related Art Organic positive temperature coefficient thermistors in which conductive particles are dispersed in a crystalline thermoplastic polymer are known in the art, and are described in US Pat. No. 3,243,753 and US Pat.
No. 351882 specification and the like. It is considered that the increase in the resistance value is because the crystalline polymer expands with the melting and cuts the conductive path of the conductive fine particles.

The organic positive temperature coefficient thermistor can be used for a self-regulating heating element, an overcurrent protection element, a temperature sensor and the like. The characteristics required for these are that the room temperature resistance value during non-operation is sufficiently low, that the rate of change between the room temperature resistance value and the resistance value during operation is sufficiently large, and the change in resistance value due to repeated operation is small. To be

In order to satisfy such required characteristics, an organic positive temperature coefficient thermistor has been proposed which uses a low molecular weight organic compound such as wax and uses a thermoplastic polymer as a matrix as a binder. As such an organic positive temperature coefficient thermistor, for example, polyisobutylene / paraffin wax / carbon black system (F. Bueche, J. Appl. Phy
s., 44 , 532, 1973), styrene-butadiene rubber / paraffin wax / carbon black system (F.Bueche, J.Poly)
mer Sci., 11 , 1319, 1973), low density polyethylene / paraffin wax / carbon black system (K.Ohe et al., Jpn.
J.Appl.Phys., 10 , 99, 1971). In addition, Japanese Examined Japanese Patent Sho
No. 23, Japanese Examined Patent Publication No. 7-109786, No. 7-48396, JP-A-62-5118
No. 4, No. 62-51185, No. 62-51186, No. 62-51187, JP-A No. 1-231284, No. 3-132001, No. 9-27383, No. 9-694.
Each publication of No. 10 also discloses a self-temperature control heating element, a current limiting element and the like using an organic positive temperature coefficient thermistor using a low molecular weight organic compound. In these cases, it is considered that the resistance value increases due to the melting of the low molecular weight organic compound.

When a low molecular weight organic compound is used as a working substance,
In general, since the crystallinity is higher than that of a polymer, there is an advantage that the rising is steep when the resistance is increased by the temperature rise. In addition, since the polymer is easy to take a supercooled state,
Normally, a hysteresis is shown such that the temperature at which the resistance value decreases at the time of temperature decrease becomes lower than the temperature at which the resistance value increases at the time of temperature increase, but this hysteresis can be suppressed by using a low molecular weight organic compound. Furthermore, by using low molecular weight organic compounds having different melting points, the temperature at which the resistance increases (operating temperature) can be easily controlled. In the case of a polymer, the melting point and the operating temperature can be changed by the difference in the molecular weight and the degree of crystallinity and the copolymerization with the comonomer, but at that time, it is necessary to change the crystal state. PTC
The characteristics may not be obtained.

However, in the organic positive temperature coefficient thermistor disclosed in the above document, since carbon black or graphite is used as the conductive particles, both low initial (room temperature) resistance and large resistance change rate are not achieved at the same time. . Jpn.J.Ap
pl.Phys., 10 , 99, 1971 has a resistivity value (Ω · cm) of 10 ⁸
An example of double increase is shown, but the specific resistance value at room temperature is 1
It is very high at 0 ⁴ Ω · cm, which is not practical for use in overcurrent protection devices and temperature sensors. Further, the increase in the resistance value (Ω) or the specific resistance value (Ω · cm) in other documents is in the range of 10 times or less to 10 ⁴ times, and the room temperature resistance is not sufficiently low.

Further, when a thermoplastic polymer is used for the matrix, it softens and flows at its melting point, so that the dispersion state of the system changes, especially when it is exposed to a high temperature, and there is a problem that the characteristics are not stable.

On the other hand, organic positive temperature coefficient thermistors using a low molecular weight organic compound and a thermosetting polymer as a matrix are disclosed in JP-A-2-156502, JP-A-2-230684 and JP-A-3-132001,
It is disclosed in each publication of the above-mentioned 3-205777. However, these also use carbon black or graphite as the conductive particles, and the rate of change in resistance is as low as one digit or less, and the room temperature resistance is not low enough at around 1 Ω · cm. It is not compatible with the rate of change.

Further, organic positive temperature coefficient thermistors composed of only thermosetting polymers and conductive particles without using low molecular weight organic compounds have been disclosed in JP-A-55-68075, JP-A-58-34901 and JP-A-63-63. 1
70902, JP-A-2-33881, JP-A-9-9482, JP-A-10-4002, and U.S. Pat. No. 4,966,729. Also in these, since carbon black or graphite is used as the conductive particles, there is no example in which the room temperature resistance of 0.1 Ω · cm or less and the resistance change rate of 5 digits or more are made compatible. In addition, in general, there is no composition having a clear melting point in the composition of only thermosetting polymer and conductive particles, so the rise of resistance in the temperature-resistance characteristic becomes slow, especially in the application of overcurrent protection element and temperature sensor. In many cases, satisfactory characteristics are not obtained.

In the conventional organic positive temperature coefficient thermistor including the above-mentioned ones, carbon black and graphite have been often used as conductive particles. However, when the filling amount of carbon black is increased in order to lower the initial resistance value, it is sufficient. There is a drawback that a resistance change rate cannot be obtained, and a low initial resistance and a large resistance change rate cannot both be achieved. In addition, although there is an example in which general metal particles are used as the conductive particles, it is similarly difficult to achieve both a low initial resistance and a large resistance change rate.

As a method of solving the above-mentioned drawbacks, a method of using conductive particles having spike-like protrusions has been disclosed. Japanese Unexamined Patent Publication (Kokai) No. 5-47503 discloses an organic positive temperature coefficient thermistor composed of a crystalline polymer, specifically polyvinylidene fluoride and conductive particles having spike-like protrusions, specifically spiked Ni powder. Has been done. Further, US Pat. No. 5,378,407 also discloses a filament-shaped Ni having spike-like protrusions, and a polyolefin, an olefin-based copolymer, or a fluoropolymer. However, with these materials, although the effect of achieving both a low initial resistance and a large resistance change is improved, the point of hysteresis is insufficient because a low molecular weight organic compound is not used as an operating material, and especially in the case of temperature sensors. Not suitable for use. In addition, if the resistance is increased during operation and heating is further performed, the resistance value decreases with increasing temperature.
There is a problem of showing a gative temperature coefficient of resistivity). The above publication and the above specification do not suggest the use of low molecular weight organic compounds.

Further, Japanese Patent Laid-Open Nos. 5-198403 and 5-198403,
Japanese Unexamined Patent Publication No. 198404 discloses an organic positive temperature coefficient thermistor obtained by mixing a thermosetting resin and conductive particles having spike-like protrusions, and a resistance change rate of 9 digits or more is obtained. However, if the filler filling amount is increased to lower the room temperature resistance value, a sufficient resistance change rate cannot be obtained,
It is difficult to achieve both low initial resistance and large resistance change. Further, since it is composed of the thermosetting resin and the conductive particles, the rise of resistance is not sufficiently steep. It should be noted that the above publication also does not suggest the use of low molecular weight organic compounds.

[0013]

DISCLOSURE OF THE INVENTION It is an object of the present invention that room temperature resistance is sufficiently low, resistance change rate during operation and non-operation is large, temperature-resistance curve hysteresis is small, and NTC characteristics after resistance increase. It is an object of the present invention to provide an organic positive temperature coefficient thermistor which is not seen, whose operating temperature can be easily adjusted, and whose characteristic stability is high.

[0014]

The above object is achieved by the present invention described below. (1) A thermosetting polymer matrix, a low molecular weight organic compound, and conductive particles having spike-shaped protrusions are included,
The melting point of the low molecular weight organic compound is 40 to 100 ° C.,
The weight of the conductive particles is 1.5 to 5 times the total of the thermosetting polymer matrix and the low molecular weight organic compound, and the weight of the low molecular weight organic compound is the thermosetting polymer matrix. The organic positive temperature coefficient thermistor has an initial resistance of 8.2 × 10 ⁻³ Ω or less and a resistance change rate of 8 digits or more. (2) The organic positive temperature coefficient thermistor according to (1), wherein the low molecular weight organic compound has a molecular weight of 4,000 or less. (3) The organic positive temperature coefficient thermistor according to (1) or (2) above, wherein the low molecular weight organic compound is a petroleum wax or a fatty acid. (4) The organic positive temperature coefficient thermistor according to any one of (1) to (3), wherein the thermosetting polymer matrix is any one of epoxy resin, unsaturated polyester resin, polyimide, polyurethane, phenol resin, and silicone resin. . (5) The organic positive temperature coefficient thermistor according to any one of the above (1) to (4), wherein the conductive particles having the spike-like protrusions are connected in a chain.

[0015]

In the present invention, since the conductive particles having the spike-like protrusions are used, the tunnel current easily flows due to the shape, and the room temperature resistance lower than that of the spherical conductive particles can be obtained. Further, since the distance between the conductive particles is larger than that of the spherical particles, a larger resistance change can be obtained during operation.

In the present invention, a PTC (positive temperature coef) which contains a low-molecular organic compound and whose resistance increases with temperature rise due to melting of the low-molecular organic compound
ficient of resistivity),
The hysteresis of the temperature-resistance curve becomes smaller than that in the case of operating by melting the crystalline thermoplastic polymer.
Further, as compared with the case where the operating temperature is adjusted by utilizing the change in melting point of the polymer, the operating temperature can be easily adjusted by using a low molecular weight organic compound having a different melting point.
Also, unlike the case of using thermosetting polymer as the working substance,
The resistance rises sharply during operation.

Further, in the present invention, a thermosetting polymer is used as the matrix. In the present invention, the large volume expansion accompanied with the melting of the low molecular weight organic compound is used to obtain a large resistance change during operation.However, in the configuration of only the low molecular weight organic compound and the conductive particles, the low molecular weight organic compound is melted. Due to its low viscosity, the shape of the device cannot be maintained when it is operated. for that reason,
It is necessary to disperse the low molecular weight organic compound and the conductive particles in the matrix polymer in order to prevent the flow of the low molecular weight organic compound due to melting during operation and the deformation of the device. When a thermoplastic polymer is used as the matrix polymer, the polymer melts above the melting point, so that there is a problem particularly in high temperature stability. In the present invention, the thermosetting polymer is used as the polymer matrix, and the low molecular organic compound and the conductive particles are dispersed in the insoluble and infusible three-dimensional network matrix. Compared with, the characteristic stability is greatly improved, and the low room temperature resistance and the large resistance change during operation are stably maintained for a long period of time.

Further, when a thermoplastic polymer matrix is used, when the resistance is increased and further heating is performed, the NTC phenomenon in which the resistance value decreases as the temperature rises is exhibited. Further, during cooling, the resistance decreases from a temperature higher than the melting point of the low molecular weight organic compound, and the hysteresis of the temperature-resistance curve is large.
The recovery of the resistance value at a temperature higher than the set temperature can be a serious problem especially when used as a protective element.
The NTC phenomenon is also a phenomenon that can be seen in a system using a thermoplastic polymer and conductive particles, and the conductive particles are rearranged in a matrix in a molten state by continuing to flow an electric current after the resistance increases, and the resistance is increased. Is expected to decrease. The same reason can be considered that the resistance value decreases from the temperature higher than the operating temperature during heating during cooling. In the present invention, by using the insoluble and infusible thermosetting polymer matrix, the above-mentioned drawbacks, that is, the NTC phenomenon after the increase in resistance and the hysteresis of the temperature-resistance curve are significantly improved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The organic positive temperature coefficient thermistor of the present invention comprises a thermosetting polymer matrix, a low molecular weight organic compound,
It contains conductor particles having spike-like protrusions.

The thermosetting polymer matrix is not particularly limited, but epoxy resin, unsaturated polyester resin, polyimide, polyurethane, phenol resin, silicone resin are preferably used.

The epoxy resin is a glycidyl ether type resin represented by bisphenol A, which is obtained by curing (cross-linking) an oligomer (molecular weight of several hundreds to 10,000) having a reactive epoxy group at the terminal with various curing agents. It is classified into glycidyl ester type, glycidyl amine type, and alicyclic type. Depending on the application, a trifunctional or higher-functional polyfunctional epoxy resin can also be used. In the present invention, of these, it is preferable to use the glycidyl ether type, especially the bisphenol A type. The epoxy equivalent of the epoxy resin used is 1
It is preferably about 00 to 500. The curing agent is classified into a polyaddition type, a catalyst type, and a condensation type according to the reaction mechanism. In the polyaddition type, the curing agent itself adds to an epoxy group or a hydroxyl group, and examples thereof include polyamine, acid anhydride, polyphenol, polymercaptan, and isocyanate. The catalyst type serves as a polymerization catalyst for epoxy groups, and examples thereof include tertiary amines and imidazoles. The condensation type cures by condensation with a hydroxyl group, and examples thereof include a phenol resin and a melamine resin.
In the present invention, as the curing agent for the bisphenol A type epoxy resin, it is preferable to use a polyaddition type, particularly a polyamine type and an acid anhydride. The curing conditions may be appropriately determined.

Such epoxy resin and curing agent are commercially available, and examples thereof include Epicoat (resin) manufactured by Yuka Shell Epoxy Co., Epicure, Epomate (curing agent), Araldite manufactured by Ciba Geigy.

The unsaturated polyester resin is obtained by dissolving unsaturated dibasic acid or a polyester mainly composed of dibasic acid and polyhydric alcohol (molecular weight of about 1000 to 5000) in a vinyl monomer having a function of crosslinking. It is obtained by curing an organic peroxide such as benzoyl peroxide as a polymerization initiator. If necessary, a polymerization accelerator may be used in combination for curing. As the raw material of the unsaturated polyester used in the present invention, maleic anhydride is used as the unsaturated dibasic acid,
Fumaric acid is preferable, phthalic anhydride is used as the dibasic acid,
Isophthalic acid and terephthalic acid are preferred, and propylene glycol and ethylene glycol are preferred as the polyhydric alcohol. Styrene, diallyl phthalate and vinyltoluene are preferable as the vinyl monomer. The blending amount of the vinyl monomer may be appropriately determined, but is usually about 1.0 to 3.0 mol per 1 mol of the fumaric acid residue. Also,
Known polymerization inhibitors such as quinones and hydroquinones are added for the purpose of preventing gelation in the synthesis step and controlling the curing characteristics. The curing conditions may be appropriately determined.

Such unsaturated polyester resins are commercially available, for example, Epolac manufactured by Nippon Shokubai, Polyset manufactured by Hitachi Chemical, Polylite manufactured by Dainippon Ink and Chemicals, and the like.

Polyimides are roughly classified into condensation type and addition type depending on the production method, but addition polymerization type bismaleimide type polyimides are preferred. Bismaleimide type polyimides are homopolymerized, reacted with other unsaturated bonds, subjected to Michael addition reaction with aromatic amines or with dienes.
It can be cured by using the Diels-Alder reaction. In the present invention, a bismaleimide-based polyimide resin obtained by the addition reaction of bismaleimide and aromatic diamines is particularly preferable. Examples of aromatic diamines include diaminodiphenylmethane. The synthesizing / curing conditions may be appropriately determined.

Such polyimides are commercially available,
For example, there are imidaloy manufactured by Toshiba Chemical Co., Ltd. and kelimide manufactured by Ciba Geigy.

Polyurethane is obtained by polyaddition reaction of polyisocyanate and polyol. The polyisocyanate includes an aromatic type and an aliphatic type, but an aromatic type is preferable, and 2,4- or 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate and the like are preferably used. Polyols include polyether polyols such as polypropylene glycol, polyester polyols and acrylic polyols, with polypropylene glycol being preferred.
The catalyst may be an amine type (a tertiary amine type such as triethylenediamine and an amine salt), but it is preferable to use an organometallic type catalyst such as dibutyltin dilaurate or stannas octoate. In addition, a cross-linking agent such as polyhydric alcohol and polyvalent amine may be used together as an auxiliary material. The synthesis / curing conditions may be appropriately determined.

Such polyurethane is commercially available, for example, Sumitomo Bayer Urethane Co., Ltd.
There are NP series manufactured by Mitsui Toatsu Chemicals, and Coronate manufactured by Nippon Polyurethanes.

Phenolic resins are obtained by reacting phenol with an aldehyde such as formaldehyde, and are roughly classified into novolac type and resol type depending on the synthesis conditions.
The novolac type produced under an acidic catalyst is cured by heating with a crosslinking agent such as hexamethylenetetramine, and the resol type produced under a basic catalyst is cured by itself or in the presence of an acid catalyst. Either may be used in the present invention. The synthesis / curing conditions may be appropriately determined.

Such phenolic resins are commercially available, for example, Sumicon manufactured by Sumitomo Bakelite Co., Standlight manufactured by Hitachi Chemical, Tecolite manufactured by Toshiba Chemical Co., and the like.

The silicone resin is composed of repeating siloxane bonds and is mainly obtained by hydrolysis or polycondensation of organohalosilane, and also alkyd modification, polyester modification, acrylic modification, epoxy modification,
Modified silicone resins such as phenol-modified, urethane-modified, melamine-modified, etc., silicone rubber obtained by crosslinking linear polydimethylsiloxane and its copolymer with organic peroxide, etc., room temperature curable (RTV) condensation and addition type There are silicone rubber and the like.

Such silicone resins are commercially available, for example, various silicone rubbers manufactured by Shin-Etsu Chemical, Toray Dow Corning, Toshiba Silicone, silicone resins and the like.

The thermosetting resin to be used can be appropriately selected according to the desired performance and application, but among them, epoxy resin and unsaturated polyester resin are preferably used. Further, it may be a polymer obtained by reacting two or more kinds with each other.

The polymer matrix is preferably composed of only the thermosetting resin as described above, but may optionally contain an elastomer, a thermoplastic resin or a mixture thereof.

The low molecular weight organic compound used in the present invention has a molecular weight of up to about 4,000, preferably up to about 1,000.
More preferably, it is not particularly limited as long as it is a crystalline substance of 200 to 800, but a substance which is solid at room temperature (a temperature of about 25 ° C.) is preferable.

Examples of the low molecular weight organic compound include waxes (specifically, petroleum waxes such as paraffin wax and microcrystalline wax, natural waxes such as plant wax, animal wax, and mineral wax),
Fats and oils (specifically, fats or solid fats)
and so on. The components of wax and fats and oils include hydrocarbons (specifically, alkane-based straight chain hydrocarbons having 22 or more carbon atoms) and fatty acids (specifically, alkane-based straight chain hydrocarbons having 12 or more carbon atoms). Fatty acid), fatty acid ester (specifically, saturated fatty acid methyl ester obtained from saturated fatty acid having 20 or more carbon atoms and lower alcohol such as methyl alcohol), fatty acid amide (specifically, oleic acid amide, Unsaturated fatty acid amides such as erucic acid amide), aliphatic amines (specifically, aliphatic primary amines having 16 or more carbon atoms), higher alcohols (specifically, n-alkyl alcohols having 16 or more carbon atoms) ), Chlorinated paraffin, etc., which can be used alone or in combination as a low molecular weight organic compound. The low molecular weight organic compound may be appropriately selected in consideration of the polarity of the polymer matrix in order to improve the dispersion of each component.
As the low molecular weight organic compound, petroleum wax and fatty acid are preferable.

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

In the present invention, the operating temperature is preferably 100.
Since the purpose is a thermistor having a temperature of not higher than 0 ° C, it is preferable to use a low molecular weight compound having a melting point mp of 40 to 100 ° C. Examples of such materials include paraffin wax (eg, tetracosane C ₂₄ H
₅₀ ; mp 49 to 52 ° C., hexatriacontane C
₃₆ H ₇₄ ; mp 73 ° C., trade name HNP-10 (manufactured by Nippon Seiro Co., Ltd.); mp 75 ° C., HNP-3 (manufactured by Nippon Seiro Co., Ltd.); mp
66 ° C.), microcrystalline wax (for example, trade name Hi-Mic-1080 (manufactured by Nippon Seiro Co., Ltd.);
mp83 ° C, Hi-Mic-1045 (manufactured by Nippon Seiro Co., Ltd.); mp70 ° C, Hi-Mic2045 (manufactured by Nippon Seiro Co., Ltd.); mp64 ° C, Hi-Mic3090 (manufactured by Nippon Seiro Co., Ltd.); mp89 ° C, serrata 104 ( Nippon Petroleum Refining Co., Ltd .; mp96 ° C., 155 Microwax (Nippon Petroleum Refining Co., Ltd.); mp70 ° C.), fatty acids (eg, behenic acid (Nippon Seika); mp81 ° C., stearic acid (Nippon Seika) Mp72 ° C, palmitic acid (Nippon Seika);
mp64 ° C, etc.), fatty acid ester (for example, arachidic acid methyl ester (manufactured by Tokyo Kasei); mp48 ° C, etc.),
There are fatty acid amides (for example, oleic acid amide (Nippon Seika); mp 76 ° C.). There is also polyethylene wax (for example, Mitsui High Wax 110 (trade name, manufactured by Mitsui Petrochemical Industry Co., Ltd .; mp 100 ° C.)). Also,
A blended wax obtained by blending paraffin wax with a resin or a blended wax mixed with microcrystalline wax and having a melting point of 40 to 100 ° C. can be preferably used.

The low molecular weight organic compounds may be used alone or in combination of two or more depending on the operating temperature and the like.

The weight of the low molecular weight organic compound used is preferably 0.2 to 4 times, more preferably 0.2 to 2.5 times the total weight of the thermosetting polymer matrix (including a curing agent etc.). . If this mixing ratio becomes small and the amount of the low molecular weight organic compound becomes small, it becomes difficult to obtain a sufficient resistance change rate. On the contrary, when the mixing ratio becomes large and the amount of the low molecular weight compound increases, the element body is largely deformed when the low molecular weight compound melts, and it becomes difficult to mix with the conductive particles.

The conductive particles having spike-like projections used in the present invention are formed of primary particles each having sharp projections, and have a height of 1/3 to 1/50 of the particle diameter. There are multiple cone-shaped spike-shaped protrusions of one particle (usually 1
0 to 500) exist. The material is metal,
Ni or the like is particularly preferable.

Such conductive particles may be powders in which one particle and one particle are individually present, but the primary particles are 10 to 10.
It is preferable that about 1000 particles are connected in a chain to form secondary particles. Some of the chain-like particles may have primary particles. An example of the former is a spherical nickel powder having spike-shaped protrusions, which has a trade name of INCO Type.
e 123 Nickel powder (manufactured by Inco), having 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.
It is about 0.44 m ² / g.

Further, as the latter example which is preferably used,
There is a filamentary nickel powder, trade name IN
CO Type 210, 255, 270, 287 Ni
It is commercially available as Kelpowder (manufactured by Inco).
Of these, INCO Type 255 and 287 are preferable.
The average particle size of the primary particles is preferably 0.1
μm or more, more preferably 0.5 or more and 4.0 μm or less
It is degree. Of these, the average particle size of the primary particles is 1.0
Above 4.0μm is most preferable, and the average particle size is
50% by weight or less of 0.1 μm or more and less than 1.0 μm
You may mix. The apparent density is 0.3 to 1.0.
g / cm³Degree, specific surface area 0.4-2.5m ²/ G
is there.

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

Such conductive particles are described in JP-A-5-47503 and US Pat. No. 5,378,407.

In addition to the conductive particles having spike-like protrusions, carbon black, graphite, carbon fiber, conductive particles for auxiliary conductivity are also used.
Metal-coated carbon black, graphitized carbon black, carbon-based conductive particles such as metal-coated carbon fibers, spherical, flake-shaped, fibrous, etc. metal, different metal-coated metal (silver-coated nickel, etc.) particles, tungsten carbide, nitriding Ceramic-based conductive particles of titanium, zirconium nitride, titanium carbide, titanium boride, molybdenum silicide, etc., and conductive potassium titanate whiskers described in JP-A Nos. 8-31554 and 9-27383. May be added. Such conductive particles are preferably 25% by weight or less of the conductive particles having spike-shaped protrusions.

The weight of the conductive particles used is preferably 1.5 to 5 times the total weight of the thermosetting polymer matrix and the low molecular weight organic compound (the total weight of the organic components including the curing agent etc.). If this mixing ratio becomes small and the amount of conductive particles becomes small, it becomes impossible to sufficiently lower the room temperature resistance during non-operation. On the other hand, when the amount of the conductive particles is large, it becomes difficult to obtain a large rate of resistance change, and it becomes difficult to uniformly mix the particles, and it becomes difficult to obtain stable characteristics.

Next, a method of manufacturing the organic positive temperature coefficient thermistor of the present invention will be described. First, a predetermined amount of a thermosetting resin before curing, a curing agent, etc., a low molecular weight organic compound and conductive particles having spike-like protrusions are mixed and dispersed to form a paint. Mixing / dispersion may be carried out by a known method, and various stirrers, dispersers, mills, paint roll machines and the like are used.
If air bubbles are mixed in during mixing, vacuum degassing is performed. Various solvents such as aromatic hydrocarbons, ketones and alcohols may be used for adjusting the viscosity. This is poured between metal foil electrodes of nickel, copper or the like, or a sheet formed by coating such as screen printing is cured under a predetermined heat treatment condition of a thermosetting resin. At this time, there is also a method in which pre-curing is performed at a relatively low temperature and then main curing is performed at a high temperature. Alternatively, a conductive paste or the like may be applied to a sheet obtained by curing only the mixture into a sheet to form an electrode. The obtained sheet molded body is punched into a desired shape to form a thermistor element.

Further, the organic thermistor of the present invention may be mixed with various additives as long as the characteristics of the present invention are not impaired. For example, an antioxidant can be mixed in order to prevent thermal deterioration of the polymer matrix and the low molecular weight organic compound, and phenols, organic sulfurs, phosphites (organic phosphorus) are used.

Further, as a good heat conductive additive, Japanese Patent Laid-Open Publication No. Sho 5
7-12061, silicon nitride, silica, alumina, clay (mica, talc, etc.), Japanese Patent Publication No. 7-
Silicon, silicon carbide, silicon nitride, beryllia, selenium described in Japanese Patent No. 77161, JP-A-5-217
Inorganic nitrides, magnesium oxide and the like described in Japanese Patent No. 711 may be added.

To improve durability, Japanese Patent Laid-Open No. 5-2261
Titanium oxide, iron oxide, zinc oxide, silica, magnesium oxide, alumina, chromium oxide, barium sulfate, calcium carbonate, calcium hydroxide, lead oxide described in JP-A-6-68963. Inorganic solid having a high relative dielectric constant, specifically, barium titanate, strontium titanate, potassium niobate or the like may be added.

To improve the withstand voltage, Japanese Patent Laid-Open No. 7438/1992.
Boron carbide and the like described in Japanese Patent Publication No. 3 may be added.

To improve the strength, Japanese Patent Laid-Open No. 5-74603
The hydrated alkali titanate described in JP-A-8-17563 and the titanium oxide, iron oxide, zinc oxide, silica and the like described in JP-A-8-17563 may be added.

As a crystal nucleating agent, JP-B-59-10553
Alkali halide, melamine resin described in JP-A-6-76511, benzoic acid, dibenzylidene sorbitol, metal benzoate described in JP-A-6-76511, and JP-A-7-6864. Talc, zeolite, dibenzylidene sorbitol, sorbitol derivative (gelling agent) described in JP-A-7-263127, asphalt, and bis (4-t-butylphenyl) sodium phosphate are added. Good.

As an arc control agent, Japanese Patent Publication No. 4-2
Alumina, magnesia hydrate described in Japanese Patent No. 8744, metal hydrate described in JP-A No. 61-250058, silicon carbide and the like may be added.

As a metal damage inhibitor, JP-A-7-6864 is known.
Irganox MD1024 described in Japanese Patent Publication No.
(Manufactured by Ciba Geigy) or the like may be added.

Further, as a flame retardant, JP-A-61-239
Diantimony trioxide and aluminum hydroxide described in Japanese Patent No. 581, magnesium hydroxide described in JP-A-5-74603, and further 2,2-bis (4-hydroxy-3,5-). Organic compounds (including polymers) containing halogen such as dibromophenyl) propane and polyvinylidene fluoride (PVDF), phosphorus-based compounds such as ammonium phosphate and the like may be added.

Besides these, zinc sulfide, basic magnesium carbonate, aluminum oxide, calcium silicate, magnesium silicate, aluminosilicate clay (mica, talc, kaolinite, montmorillonite, etc.), glass powder, glass flakes, glass fiber , Calcium sulfate, etc. may be added.

These additives are a polymer matrix,
It is preferably 25% by weight or less based on the total weight of the low molecular weight organic compound and the conductive particles.

The organic positive temperature coefficient thermistor of the present invention has a low initial resistance of 8.2 × 10 ⁻³ Ω or less when not operating,
The room temperature specific resistance value is about 10 ^-2 Ω · cm, the resistance rises sharply during operation, and the resistance change rate from non-operation to operation is as large as eight digits or more.

[0061]

EXAMPLES Examples of the present invention will be shown below together with comparative examples to specifically describe the present invention. <Example 1> Bisphenol A type epoxy resin (made by Yuka Shell Epoxy Co., Ltd. as a thermosetting polymer matrix,
Trade name Epicoat 801), modified amine-based curing agent (Yukaka Shell Epoxy Co., trade name Epomate B002), paraffin wax as a low molecular weight organic compound (Nippon Seiwa Co., trade name HNP-10, melting point 75 ° C.), Filamentous nickel powder (manufactured by INCO, trade name Type 255 nickel powder) was used as the conductive particles. The average particle diameter 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.

20 g of bisphenol A type epoxy resin,
Modified amine hardener 10g, paraffin wax 15g
(0.5 times the total weight of the epoxy resin and the curing agent), 180 g of nickel powder (4 times the total weight of the organic components) and 20 ml of toluene were mixed for about 10 minutes with a centrifugal disperser. Then, apply the obtained mixture in paint form on one side of the Ni foil electrode with a thickness of 30 μm, sandwich it with another Ni foil electrode, sandwich it with a brass plate, and use a spacer to make a total thickness of 1
mm, and heated and cured at 80 ° C. for 3 hours while being pressed by a hot press. The sheet-like cured product to which this electrode was thermocompression-bonded was punched out into a disc having a diameter of 1 cm to obtain an organic positive temperature coefficient thermistor element. A schematic cross-sectional view of this thermistor element is shown in FIG.
Shown in. As shown in FIG. 1, the thermistor element is Ni
A thermistor body 12, which is a sheet-shaped cured product containing a low molecular weight organic compound, a polymer matrix, and conductive particles, is sandwiched between electrodes 11 formed of foil.

This element was heated and cooled from room temperature (25 ° C.) to 120 ° C. at 2 ° C./min in a constant temperature bath, and the resistance value was measured at a predetermined temperature by the 4-terminal method to obtain a temperature-resistance curve. It was The result is shown in FIG.

Initial room temperature resistance (25 ° C.) is 8.2 × 10 ^-3
Ω (6.4 × 10 ^-2 Ω · cm), the melting point of the wax was around 75 ° C., and the resistance value rapidly increased, and the resistance change rate was 10 digits or more. After the resistance increased, even if heating was further continued up to 120 ° C., no decrease in resistance (NTC phenomenon) was observed. Further, the temperature-resistance curve during cooling did not change much from that during heating, and the hysteresis was sufficiently small.

Example 2 An unsaturated polyester resin (manufactured by Nippon Shokubai, trade name G) as a thermosetting polymer matrix
-110AL), benzoyl peroxide (manufactured by Kayaku Akzo, trade name Cadox B-75W) as an organic peroxide, and behenic acid (manufactured by Nippon Seika, melting point 81) as a low molecular weight organic compound.
C), and the same filamentary nickel powder as in Example 1 as conductive particles (manufactured by INCO, trade name Type 255).
Nickel powder) was used.

Unsaturated polyester resin 30 g, benzoyl peroxide 0.3 g, behenic acid 15 g, nickel powder 1
80 g and 20 ml of toluene were mixed by a centrifugal disperser for about 10 minutes. Then, the obtained paint mixture is applied to a thickness of 30 μm.
After applying it to one side of the Ni foil electrode, sandwich it with another Ni foil electrode, sandwich it with a brass plate to a total thickness of 1 mm using a spacer, and press it with a heat press machine at 80 ° C
It was heat-cured for 30 minutes. The sheet-like cured product to which this electrode was thermocompression-bonded was punched out into a disc having a diameter of 1 cm to obtain an organic positive temperature coefficient thermistor element. And the temperature of this element −
The resistance curve was obtained in the same manner as in Example 1. This result is shown in Figure 3.
Shown in.

Initial room temperature resistance (25 ° C.) is 5.0 × 10 ⁻³
Ω (3.9 × 10 ^-2 Ω · cm), the resistance value drastically increased near the melting point of behenic acid of 81 ° C., and the resistance change rate was 8 digits or more. After the resistance increased, even if heating was further continued up to 120 ° C., almost no decrease in resistance (NTC phenomenon) was observed. Further, the temperature-resistance curve during cooling did not change much from that during heating, and the hysteresis was sufficiently small at about 10 ° C. Hysteresis is the temperature −
The tangent line of the curve before and after the operation on the resistance curve graph is drawn, and the intersection is taken as the operating temperature. Similarly, the operating temperature is calculated from the temperature-resistance curve when the temperature drops, and the difference between the operating temperature (absolute value) ) Is the hysteresis degree.

Example 3 In Example 1, instead of the bisphenol A type epoxy resin and the modified amine type curing agent as the thermosetting polymer matrix, polyamino bismaleimide prepolymer (manufactured by Ciba-Geigy, trade name Kelimide B601) was used. 20 g, dimethylformamide 10
A thermistor element was manufactured in the same manner as in Example 1 except that it was cured at 150 ° C. for 1 hour and 180 ° C. for 3 hours using g, and was evaluated in the same manner. The result was obtained.

Example 4 In Example 1, 30 g of polyurethane (Nippon Polyurethane Industry Co., Ltd., trade name Coronate) was used as the thermosetting polymer matrix instead of the bisphenol A type epoxy resin and the modified amine type curing agent.
A thermistor element was manufactured in the same manner as in Example 1 except that the above was used and cured at 100 ° C. for 1 hour. As a result, the same results as those of the thermistor element in Example 1 were obtained.

Example 5 In Example 1, as the thermosetting polymer matrix, 30 g of a phenol resin (Sumitomo Bakelite, trade name Sumicon PM) was used instead of the bisphenol A type epoxy resin and the modified amine type curing agent.
A thermistor element was manufactured in the same manner as in Example 1 except that the above was used for curing for 3 hours at 120 ° C., and the same evaluation was performed. As a result, the same result as that of the thermistor element in Example 1 was obtained.

Example 6 In Example 1, as the thermosetting polymer matrix, 30 g of silicone rubber (Toshiba Silicone, trade name TSE3221) was used instead of the bisphenol A type epoxy resin and the modified amine type curing agent.
A thermistor element was manufactured in the same manner as in Example 1 except that the above was used and cured at 100 ° C. for 1 hour. As a result, the same results as those of the thermistor element in Example 1 were obtained.

Comparative Example 1 A thermistor element was manufactured in the same manner as in Example 1 except that paraffin wax was not used and nickel powder was added in an amount of 4 times the total weight of the epoxy resin and the curing agent. Then, the temperature-resistance curve of this device was obtained in the same manner as in Example 1. The result is shown in FIG.

The initial room temperature resistance (25 ° C.) of this element is 8.8 × 10 ⁻³ Ω (6.9 × 10 ⁻² Ω · cm) and 80 ° C.
The resistance gradually increased from before and after, and no clear transition temperature was obtained. At 180 ° C., the resistance value was 13Ω, and the resistance change rate was as small as 3.2 digits.

Comparative Example 2 Carbon Black (Tokai Carbon, trade name Toka Black # 4500; average particle size 6)
Example 1 except that 0 nm, a specific surface area of 66 m ² / g) was used as the conductive particles and 0.3 times the total weight of the epoxy resin, the curing agent and the paraffin wax was blended.
A thermistor element was prepared in the same manner as in, and evaluated in the same manner.

The initial room temperature resistance (25 ° C.) of this element is 7.2 Ω (56.5 Ω · cm), and the melting point of the wax is 75 ° C.
The resistance value increased in the vicinity, and the resistance change rate was 2.5 digits.

When the amount of the carbon black compounded was increased to 0.5 times the weight of the mixture, the room temperature resistance could be lowered, but the resistance change rate was further reduced. From this, the effect of the conductive particles having spike-like protrusions is clear.

[0077]

According to the present invention, the room temperature resistance is sufficiently low,
The organic material has a high rate of change in resistance between operating and non-operating conditions, a small hysteresis in the temperature-resistance curve, no NTC characteristics after increasing resistance, easy adjustment of operating temperature, and high characteristic stability. A positive temperature coefficient thermistor can be provided.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an organic positive temperature coefficient thermistor element.

2 is a temperature-resistance curve of the thermistor element of Example 1. FIG.

3 is a temperature-resistance curve of the thermistor element of Example 2. FIG.

4 is a temperature-resistance curve of the thermistor element of Comparative Example 1. FIG.

[Explanation of symbols]

11 electrodes 12 Thermistor body

Claims (5)

(57) [Claims] 1. A thermosetting polymer matrix, a low-molecular weight organic compound, and conductive particles having spike-shaped protrusions, wherein the low-molecular weight organic compound has a melting point of 40 to 100 ° C., and the weight of the conductive particles. Is 1.5 to 5 times the total of the thermosetting polymer matrix and the low molecular weight organic compound, and the weight of the low molecular weight organic compound is 0.2 of the weight of the thermosetting polymer matrix. An organic positive temperature coefficient thermistor having an initial resistance of 8.2 × 10 ⁻³ Ω or less and a resistance change rate of 8 digits or more. 2. The low molecular weight organic compound has a molecular weight of 4,0.
The organic positive temperature coefficient thermistor according to claim 1, which is not more than 00. 3. The organic positive temperature coefficient thermistor according to claim 1, wherein the low molecular weight organic compound is a petroleum wax or a fatty acid. 4. The organic positive temperature coefficient thermistor according to claim 1, wherein the thermosetting polymer matrix is any one of epoxy resin, unsaturated polyester resin, polyimide, polyurethane, phenol resin and silicone resin. 5. The organic positive temperature coefficient thermistor according to claim 1, wherein the conductive particles having the spike-shaped protrusions are connected in a chain.