JP2006186268A - Thermistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermistor in which a sufficiently small room temperature resistance value is maintained even after receiving heating history in a reflow process etc. while using an organic material as a thermistor element body. <P>SOLUTION: The thermistor 10 comprises a pair of facing electrodes 2 and 3, and the thermistor element body 1 which is arranged between the pair of electrodes 2 and 3 and contains a cured material of a cured resin composition comprising a heat-curing resin and conductive particles. A glass transition temperature of the cured material of the thermistor 10 is 110°C or below. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermistor using an organic material as a thermistor body.

  A thermistor using a material composed of a polymer layer and conductive particles dispersed therein as a thermistor body is generally referred to as an organic thermistor, and its resistance value increases rapidly as the temperature rises. Those having a PTC (Positive Temperature Coefficient) characteristic may be referred to as an organic positive temperature coefficient thermistor. Such thermistors are used in devices such as overcurrent / heat protection elements, self-control heating elements, temperature sensors and the like.

As the organic thermistor, for example, an organic thermistor using a material in which conductive particles are dispersed in an epoxy resin, which is a thermosetting resin, is used as a thermistor element (Patent Document 1).
International Publication No. 2004/086421 Pamphlet

  However, the conventional organic thermistor has a problem that the room temperature resistance value is greatly increased due to the thermal history received during the reflow process for mounting on the substrate than before the thermal history is received. When the room temperature resistance value increases, it becomes difficult to function as a thermistor.

  Accordingly, an object of the present invention is to provide a thermistor capable of maintaining a sufficiently low room temperature resistance value even after receiving a thermal history in a reflow process or the like while using an organic material as a thermistor body. To do.

  The present inventors have intensively studied to solve the above problems, and the inventors of the present invention are that the increase in the room temperature resistance value after receiving the thermal history is greatly influenced by the glass transition temperature of the cured product constituting the thermistor body. I found. As a result of further investigation based on this finding, the present invention has been completed.

  That is, the present invention comprises a thermistor body including a pair of opposed electrodes, a cured product of a curable resin composition disposed between the pair of electrodes and containing a thermosetting resin and conductive particles, A thermistor having a glass transition temperature of 110 ° C. or lower.

  The thermistor of the present invention has a sufficiently low room temperature even after receiving a thermal history in a reflow process or the like because the cured product of the thermosetting resin in the thermistor body has a glass transition temperature in the specific range. The resistance value can be maintained.

  The glass transition temperature of the cured product is preferably 20 ° C. or higher. Thereby, the rate of change in resistance value (resistance rate of change) when the thermistor body is heated from room temperature to high temperature can be particularly increased.

  The thermosetting resin preferably contains an epoxy resin and a curing agent thereof. Thereby, the room temperature resistance value after receiving the thermal history can be kept lower.

  Furthermore, it is more preferable that the total average molecular weight of the epoxy resin and the curing agent thereof is 300 to 1000. By setting it as such a specific average molecular weight, the room temperature resistance value after receiving a thermal history can be kept still lower.

  The epoxy resin includes at least one of a plurality of glycidyl ether groups, a divalent group represented by the following general formula (11), (12), (13), or (14) and a divalent alicyclic group. It is preferable that the polyepoxy compound which has one partial structure is included. This makes it particularly easy to adjust the glass transition temperature of the cured product to the specific range.

式（１１）、（１２）、（１３）及び（１４）中、ａ、ｂ、ｃ及びｄはそれぞれ独立に１〜２０の整数を示す。

In formulas (11), (12), (13) and (14), a, b, c and d each independently represent an integer of 1 to 20.

  The curing agent combined with the epoxy resin preferably contains an acid anhydride, and more preferably contains an acid anhydride represented by the following chemical formula (21), (22), (23) or (24). This makes it particularly easy to adjust the glass transition temperature of the cured product to the specific range.

式（２１）中、Ｒ^１は炭素数４〜２０の炭化水素基を示す。

In formula (21), R ¹ represents a hydrocarbon group having 4 to 20 carbon atoms.

式（２２）中、Ｒ^２は炭素数１〜２０の炭化水素基を示し、ｐは１〜３の整数を示し、同一分子中の複数のＲ^２は同一でも異なっていてもよい。

In Formula (22), R ² represents a hydrocarbon group having 1 to 20 carbon atoms, p represents an integer of 1 to 3, and a plurality of R ² in the same molecule may be the same or different.

式（２３）中、Ｘは炭素数４以上の２価の炭化水素基を示し、ｑは１〜２０の整数を示す。

In the formula (23), X represents a divalent hydrocarbon group having 4 or more carbon atoms, and q represents an integer of 1 to 20.

式（２４）中、Ｚは炭素数２以上の２価又は３価の有機基を示し、ｒは２又は３を示す。

In formula (24), Z represents a divalent or trivalent organic group having 2 or more carbon atoms, and r represents 2 or 3.

  According to the present invention, there is provided a thermistor capable of maintaining a sufficiently low room temperature resistance value even after receiving a thermal history in a reflow process or the like while using an organic material as a thermistor body.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a perspective view schematically showing a preferred embodiment of a thermistor according to the present invention. The thermistor 10 shown in FIG. 1 is provided in close contact with each electrode between a pair of electrodes 2 and 3 arranged so as to face each other, and between the electrodes 2 and 3, and has a positive resistance-temperature characteristic. And a thermistor body 1 having a substantially rectangular parallelepiped shape as a whole. The thermistor 10 may be further provided with a lead (not shown) electrically connected to the electrode 2 and a lead (not shown) electrically connected to the electrode 3 as necessary. . The thermistor 10 can be suitably used as an overcurrent / heat protection element, a self-control heating element, a temperature sensor, or the like.

  The electrode 2 and the electrode 3 are formed of a conductive material that functions as an electrode of the thermistor. The material constituting the electrodes 2 and 3 is preferably made of a metal such as nickel, silver, gold, or aluminum, or carbon. The thickness is preferably 1 to 100 μm, and more preferably 1 to 50 μm from the viewpoint of weight reduction of the thermistor. Further, the shape and the material of the lead are not particularly limited as long as they have electrical conductivity capable of discharging or injecting charges from the electrode 2 and the electrode 3 to the outside.

  The thermistor body 1 is formed of a cured product of a curable resin composition containing a thermosetting resin and conductive particles dispersed therein, and the glass transition temperature of the cured product is 110 ° C. or less. . In order to keep the room temperature resistance value after the reflow process lower, the glass transition temperature is more preferably 100 ° C. or less, and further preferably 90 ° C. or less. Moreover, it is preferable that the glass transition temperature of the said hardened | cured material is 20 degreeC or more, It is more preferable that it is 25 degreeC or more, It is still more preferable that it is 30 degreeC or more. If the glass transition temperature is less than 20 ° C., the resistance value during PTC operation tends to be small, and the resistance change rate tends to be small. If the resistance change rate is too small, the operation as a thermistor becomes difficult.

  Here, the “glass transition temperature” is measured using a suggested scanning calorimeter (DSC). For example, when the calorific value and the endothermic amount of the cured product are measured in a temperature range from room temperature or lower to 200 ° C. under an inert gas atmosphere such as helium at a temperature rising rate of 10 ° C./min. In the DSC curve (horizontal axis: temperature), the straight line equidistant in the vertical axis direction from the two straight lines obtained by extending the baseline on the low temperature side and the high temperature side of the glass transition region, and the DSC curve in the glass transition region The temperature of the intersection can be the glass transition temperature. In addition, the glass transition temperature of the hardened | cured material which comprises the thermistor element | base_body 1 is a temperature derived from the glass transition of the polymer layer (parts other than electroconductive particle) in hardened | cured material normally.

  As a method of setting the glass transition temperature of the cured product to 110 ° C. or lower, as described later, a method using a thermosetting resin having a specific structure (including a crosslinkable compound (polyepoxy compound, etc.) having a specific structure) A method using a crosslinkable resin, a method using a curing agent having a specific structure, a method of adding a plasticizer that changes the glass transition temperature in a thermosetting resin, a method of optimizing curing conditions, etc. Is mentioned.

  The thermistor body 1 preferably has a thickness of 0.2 to 1.0 mm. When the thickness of the thermistor body layer 1 is less than 0.2 mm or more than 1.0 mm, the variation in the room temperature resistance value tends to increase. When the thermistor body layer 1 has a thickness of less than 0.2 mm, a short circuit occurs and a normal room temperature resistance value tends not to be obtained.

  The thermosetting resin contains a crosslinkable resin such as an epoxy resin, a phenol resin, an unsaturated polyester resin, a urea resin, a melamine resin, a furan resin, and a polyurethane resin, and these curing agents. In addition, this hardening | curing agent may react with a crosslinkable resin etc., may comprise a part of crosslinked structure in hardened | cured material, and may act as a catalyst of hardening reaction. Alternatively, it may act as a catalyst and constitute a part of the crosslinked structure.

  Especially as a thermosetting resin, the epoxy resin composition containing an epoxy resin and its hardening | curing agent is preferable.

  In the present invention, the epoxy resin means a resin composed of a single or plural kinds of polyepoxy compounds having a plurality of epoxy groups. Examples of the polyepoxy compound include polyglycidyl ethers of polyhydric phenols such as bisphenol A, bisphenol F, bisphenol AD, catechol, resorcinol, and tetramethylbiphenyl, alkylene oxide adducts of bisphenol compounds, glycerin, and polyalkylene glycols. Examples thereof include polyglycidyl ethers of polyhydric alcohols, polyglycidyl esters of polycarboxylic acids such as phthalic acid and terephthalic acid.

  Examples of the polyepoxy compound in the epoxy resin include a soft segment composed of a linear divalent polyoxyalkylene group represented by the general formula (11), (12), (13) or (14), and a divalent compound. Those having at least one of the alicyclic structures consisting of these alicyclic groups are preferred. By using a polyepoxy compound having a soft segment or an alicyclic structure, it becomes particularly easy to adjust the glass transition temperature of the cured product to the specific range.

  As the soft segment, in addition to the above polyoxyalkylene group, a linear divalent organic compound derived from polyalkylene, polysiloxane, aliphatic acid, polybutadiene, butadiene-acrylonitrile copolymer, polybutylene, polyurethane, etc. Groups.

  Examples of the polyalkylene include polyethylene and polypropylene, and examples of the polysiloxane include polydimethylsiloxane.

The polyepoxy compound having a polyoxyalkylene group is preferably a polyglycidyl ether of an alkylene oxide adduct of a bisphenol compound. Preferable specific examples of such a polyepoxy compound include those represented by the following general formula (1) or (2). In formulas (1) and (2), L ¹ and L ^{2 each} represent a divalent organic group, and n ¹ , n ² , n ^3, and n ⁴ each independently represent an integer of 1 or more. n ¹ , n ² , n ³ and n ⁴ are preferably 1 to 20, and more preferably 1 to 10.

L ¹ and L ² are preferably divalent groups represented by the following chemical formula (31), (32) or (33).

As the above polyepoxy compound having a soft segment, a compound represented by the following general formula (1a), wherein L ¹ in the above formula (1) is a divalent group represented by the above formula (31) Is particularly preferred.

  As a suitable example of the polyepoxy compound having other soft segments, a rubber-modified epoxy resin obtained by a reaction of a carboxyl group of a butadiene-acrylonitrile copolymer (acrylonitrile-butadiene rubber) and an epoxy group of a polyepoxy compound, Epoxy-modified poly-silicone having an epoxy group at the end, poly-epoxy compound obtained by reaction of amino-modified poly-silicone and polyepoxy compound, poly-polyester obtained by reaction of isocyanate group in polyurethane prepolymer and hydroxyl group in polyepoxy compound An epoxy compound etc. are mentioned.

  In the polyepoxy compound having an alicyclic structure, the alicyclic group is a cyclic divalent organic group mainly composed of saturated hydrocarbons, and different atoms such as an oxygen atom, a nitrogen atom and a sulfur atom are included in the ring. Those including atoms and those partially having an unsaturated bond are also included. Moreover, this alicyclic group may have a substituent. In order to increase the flexibility of the cured product, the alicyclic group is preferably a divalent group consisting of a cyclohexane ring, a cyclopentane ring or a dicyclopentadiene ring, and a divalent group consisting of a cyclohexane ring or a cyclopentane ring. The group is particularly preferred.

  Specific examples of suitable polyepoxy compounds having an alicyclic structure include those represented by the following chemical formula (3), (4), (5), (6), (7) or (8). It is done. Among these, the polyepoxy compound represented by the formula (3), (4) or (5) is particularly preferable.

  The epoxy resin preferably contains a polyepoxy compound having a soft segment or an alicyclic structure in an amount of 10 to 100% by mass, more preferably 15 to 95% by mass, based on the entire epoxy resin. The content ratio of the polyepoxy compound having a soft segment or an alicyclic structure is optimized within the above range, and further, by appropriately selecting the type of curing agent to be combined therewith, the cured product usually has a glass transition temperature of 110 ° C. or lower. be able to.

  Examples of the curing agent used in combination with the epoxy resin include acid anhydrides, aliphatic polyamines, aromatic polyamines, polyamides, polyphenols, polymercaptans, tertiary amines, and Lewis acid complexes. Of these, acid anhydrides are preferred. When an acid anhydride is used, the initial room temperature resistance value of the thermistor tends to be lowered and the rate of change in resistance tends to be higher than when an amine-based curing agent such as an aliphatic polyamine is used.

  As the acid anhydride, an acid anhydride represented by the general formula (11), (12), (13) or (14) is preferable. Thereby, moderate flexibility is provided to the cured product, and the durability of the thermistor 1 is improved.

  Examples of the acid anhydride represented by the general formula (11) include dodecenyl succinic anhydride, and examples of the acid anhydride represented by the general formula (12) include methyltetrahydrophthalic anhydride. Examples of the acid anhydride represented by the formula (13) include polyadipic acid anhydride, polyazeline acid anhydride, polysebacic acid anhydride, poly (ethyloctadecanedioic acid) anhydride, and poly (phenylhexadecanedioic acid) anhydride. Examples of the acid anhydride represented by the general formula (14) include ethylene glycol bisanhydro trimellitate and glycerol tris anhydro trimellitate.

  Other suitable specific examples of the acid anhydride include, in addition to the above, 2,4-diethylglutaric anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, phthalic anhydride, succinic anhydride Acid, trimetic anhydride, pyromellitic anhydride, methyl nadic anhydride, maleic anhydride, benzophenone tetracarboxylic anhydride, endomethylenetetrahydrophthalic anhydride, methylendomethylenetetrahydrophthalic anhydride, methylbutenyltetrahydrophthalic anhydride, methyl Examples include cyclohexene dicarboxylic acid anhydride alkylstyrene-maleic anhydride copolymer, ethylene glycol bistrimellitate, chlorendic anhydride, and tetrabromophthalic anhydride.

  Among these, since it is easy to set the glass transition temperature of the cured product to 110 ° C. or less, as the acid anhydride, dodecenyl succinic anhydride, polyadipic acid anhydride, polyazelinic acid anhydride, polysebacic acid anhydride , Poly (ethyloctadecanedioic acid) anhydride, poly (phenylhexadecanedioic acid) anhydride, 2,4-diethylglutaric anhydride, ethylene glycol bisanhydro trimellitate and glycerol tris anhydro trimellitate At least one acid anhydride selected from the above is preferably used. Furthermore, among these, dodecenyl succinic anhydride is preferable.

  In an epoxy resin composition, the above acid anhydrides can be used alone or in combination.

  What is necessary is just to determine suitably the content rate of the hardening | curing agent in a thermosetting resin according to the kind etc. of a crosslinkable compound or a hardening | curing agent. For example, when an acid anhydride is combined with the epoxy resin as a curing agent, the equivalent ratio to the epoxy group in the epoxy resin is 0.5 to 1.5, more preferably 0.8 to 1.2. It is more preferable to contain a curing agent in a content ratio. When the equivalent ratio of the curing agent is less than 0.5 or more than 1.5 with respect to the epoxy group, the unreacted epoxy group and acid anhydride group increase, and the mechanical strength of the thermistor body decreases. Or the resistance change rate of the thermistor tends to decrease.

  When the thermosetting resin is an epoxy resin composition containing an epoxy resin and a curing agent thereof, the total average molecular weight of the epoxy resin and the curing agent is preferably 300 to 1000, and preferably 300 to 650. More preferred. Thereby, hardened | cured material becomes what has moderate flexibility and the durability with respect to a heat history is further improved.

  The glass transition temperature of the cured product can also be adjusted by adding an additive such as a reactive diluent or a plasticizer in the thermosetting resin. As the reactive diluent, a monoepoxy compound is preferred particularly when combined with an epoxy resin. Monoepoxy compounds include n-butyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, p-sec-butylphenyl glycidyl ether, glycidyl methacrylate, tertiary carboxylic acid A glycidyl ester etc. are mentioned. The plasticizer is preferably a polyhydric alcohol such as polyethylene glycol or propylene glycol.

  The thermosetting resin may further contain other components, for example, thermoplastic resins, low molecular organic compounds such as waxes, fats and oils, fatty acids, and higher alcohols, if necessary. The thermoplastic resin may be dissolved in the thermosetting resin or may be dispersed in a particulate state.

  The conductive particles are not particularly limited as long as they are electrically conductive particles. For example, carbon black, graphite, metal particles of various shapes, or ceramic conductive particles can be used. Examples of the metal material of the metal particles include copper, aluminum, nickel, tungsten, molybdenum, silver, zinc, cobalt, and copper powder subjected to nickel plating. Examples of the material for the ceramic conductive particles include TiC and WC. These conductive particles can be used alone or in combination of two or more.

  As the conductive particles, metal particles are particularly preferable. When metal particles are used as the conductive particles, the resistance change rate of the thermistor can be maintained sufficiently large, and the room temperature resistance value can be further reduced. For example, it is suitable when the thermistor of the present invention is used as an overcurrent protection element. It is. Further, among the metal particles, nickel particles are particularly preferable from the viewpoint of chemical stability such as being hardly oxidized.

  The shape of the conductive particles is not particularly limited, and examples thereof include a spherical shape, a flake shape, a fiber shape, and a rod shape, and those having spike-like protrusions on the surface of the particles are preferable. By using conductive particles having spike-like protrusions, a tunnel current easily flows between adjacent particles, so that the room temperature resistance value can be further lowered while sufficiently ensuring the resistance change rate of the thermistor. Further, since the distance between the centers of the particles can be increased as compared with the spherical particles, a larger resistance change rate can be obtained. Furthermore, the variation in the room temperature resistance value of the thermistor can be reduced compared to the case where fibrous particles are used.

The conductive particles having spike-like protrusions may be powders in which primary particles are dispersed individually, but about 10 to 1000 primary particles are connected in a chain to form filamentary secondary particles. Is preferred. Further, the material is preferably a metal, and more preferably a material mainly composed of nickel. Furthermore, the conductive particles preferably have a specific surface area of 0.3 to 3.0 m ² / g and an apparent density of 3.0 g / cm ³ or less. Here, the “specific surface area” means a specific surface area determined by a nitrogen gas adsorption method based on the BET single point method.

  The average particle size of the primary particles of the conductive particles is preferably 0.1 to 7.0 μm, and more preferably 0.5 to 5.0 μm. Here, the average particle size of the primary particles is a value measured by the Fischer sub-sieving method.

  Examples of commercially available conductive particles having spike-shaped protrusions include “INCO Type 210”, “INCO Type 255”, “INCO Type 270”, “INCO Type 287” (all manufactured by INCO, trade name), etc. Is mentioned.

  The content ratio of the conductive particles in the thermistor body is preferably 5 to 90% by mass, and more preferably 60 to 80% by mass based on the whole thermistor body. When the content ratio of the conductive particles is less than 50% by mass, it tends to be difficult to obtain a low room temperature resistance value, and when it exceeds 90% by mass, it tends to be difficult to obtain a large resistance change rate.

  The thermistor 10 includes, for example, a resin composition layer forming step in which a resin composition layer made of a curable resin composition containing a thermosetting resin and conductive particles is formed on a first conductor foil to obtain a laminate. A laminating step of laminating the second conductor foil or another laminate on the laminate so as to sandwich the resin composition layer by a pair of opposing conductor foils, and heating the sandwich And a curing step of curing the curable resin composition and a cutting step of cutting the cured sandwiched material into a predetermined shape and size to obtain a thermistor.

  The curable resin composition used in the resin composition layer forming step can be obtained by mixing the above-described constituent components using devices such as various stirrers, dispersers, and mills. At this time, in order to lower the viscosity, an organic solvent such as alcohol or acetone or a solvent such as a reactive diluent is added to the curable resin composition to form a mixed solution, which is used to form a resin composition layer. May be. Although mixing time is not specifically limited, Usually, each component can be uniformly dissolved or dispersed by mixing for 10 to 30 minutes. Moreover, although mixing temperature is not specifically limited, 100-150 degreeC is preferable. The mixed curable resin composition or mixed solution is preferably defoamed under vacuum in order to remove bubbles mixed in during mixing.

  By applying the curable resin composition or the mixed solution on the conductor foil, a laminated body in which the resin composition layer is formed on one surface of the conductor foil is obtained. When the mixed solution is used, it is preferable to remove the solvent by heating the resin composition layer.

  Subsequently, in the laminating step, the second conductive foil or other laminate is laminated on the resin composition layer so that the resin composition layer is sandwiched between a pair of opposing conductor foils, and the sandwiched article is obtain. At this time, it is preferable to pressurize the whole so that the conductor foil and the resin composition layer are in close contact with each other.

  In the curing step, the sandwich is heated at a predetermined temperature for a predetermined time so that the curable resin composition forming the resin composition layer is sufficiently cured. The heating conditions at this time may be appropriately set so that curing proceeds sufficiently and the glass transition temperature of the cured product is 110 ° C. or lower, depending on the type of curing agent and the like. For example, when an acid anhydride is used as a curing agent, curing can usually proceed sufficiently by heating at 80 to 200 ° C. for 30 to 600 minutes. In addition, you may perform this hardening process, applying a pressure, and in this case, you may perform the said lamination process and hardening process simultaneously or continuously.

  Then, in the cutting step, the thermistor 10 can be obtained by cutting the sandwiched product obtained by curing the curable resin composition into a desired shape (for example, 3.6 mm × 9 mm) by punching or the like. The punching can be performed by a method usually used for obtaining a thermistor, such as a cat press.

  Furthermore, if necessary, a thermistor having a lead can be produced by bonding the lead to the surfaces of the electrodes 2 and 3 made of a conductive foil.

  The thermistor 10 can be obtained by, for example, a method of preparing a sheet-like thermistor body and forming a conductor layer on both surfaces of the sheet-like thermistor body instead of the above-described manufacturing method. In this case, the sheet-like thermistor element is cured between the pair of opposing releasable support sheets and the curable resin composition is cured, and then the support sheet is peeled off. Can be produced. Examples of the method for forming the conductor layer in this method include plating, application of a metal paste, sputtering, and vapor deposition.

  The thermistor described above can maintain a sufficiently low room temperature resistance even after the reflow process. The thermistor is also excellent in other characteristics required for the thermistor, such as a low initial resistance value and a large resistance change rate.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

(Example 1)
An epoxy resin “EP-4005” (trade name, manufactured by Asahi Denka Co., Ltd., epoxy equivalent 510 g / eq.) Composed of a mixture of a polyepoxy compound (methyltetrahydrophthalic anhydride) represented by the following chemical formula (22a), and the above chemical formula From an epoxy resin “EP-4080S” (trade name, manufactured by Asahi Denka Co., Ltd., epoxy equivalent 205 g / eq.) Composed of a polyepoxy compound represented by (4) and an acid anhydride represented by the following chemical formula (9) Curing agent “B570” (trade name, manufactured by Dainippon Ink & Chemicals, Inc., acid anhydride equivalent 168 g / eq.), “PN-40J” (trade name, manufactured by Ajinomoto Co., Inc.) as a curing accelerator, Filamentous nickel powder (“Type 255 nickel powder” (trade name), manufactured by INCO, average particle size 2.2 to 2.8 μm, apparent density 0.5 to 0.6) g / cm ^3, by mixing the specific surface area 0.68m ² / g), to prepare a curable resin composition.

  In the preparation of the curable resin composition, first, the epoxy resins “EP-4005” and “EP4080S” are mixed so that the weight ratio is 70:30, and the curing agent is added to the entire epoxy resin. A mixture containing 53% by mass of (B570) and 1% by mass of a curing accelerator (PN-40J) was stirred using a stirrer. Then, the conductive particles were added to the mixture in such an amount that it would be 75% by mass with respect to the entire curable resin composition containing the conductive particles, and further stirred to obtain a curable resin composition. .

  The curable resin composition obtained above was applied on a nickel foil to a thickness of 0.5 mm to form a resin composition layer, and another nickel foil was placed thereon. And it hardened | cured by the heating in oven set to 130 degreeC, and the clamping thing by which the thermistor element body was clamped by two nickel foils was obtained. The obtained sandwich was punched into a 3.6 × 9.0 mm shape to obtain a thermistor.

  The cured product in the thermistor body formed by curing is subjected to DSC under the conditions where the measurement temperature range is room temperature (or 0 ° C.) to 200 ° C., the heating rate is 10 ° C./min, and the measurement atmosphere is He = 50 mL / min. When measured, the glass transition temperature was 45 ° C.

In order to give a thermal history assuming the reflow process to the obtained thermistor, the thermistor is heated from room temperature to 200 ° C. while being heated at a rate of 3 ° C./min in the thermostat, and then the temperature is lowered at the same rate. While cooling. At this time, the resistance value of the thermistor was measured by a four-terminal method to obtain a temperature-resistance curve. From the obtained temperature-resistance curve, the initial room temperature resistance value of the thermistor is 1.0 × 10 ⁻³ Ω (resistivity: 6.5 × 10 ⁻³ Ωcm), and the resistance change rate value is 10 digits or more. It was confirmed that. Moreover, the room temperature resistance value after the heat history by said heating and cooling was 4.0 * 10 < ^-3 > (omega ^| ohm) (low efficiency: 2.6 * 10 ^<-2 > (omega ^| ohm) cm), and was maintaining the low level.

(Example 2)
The same as in Example 1 except that the weight ratio of the epoxy resins “EP-4005” and “EP-4080S” was 70:30 and the curing agent “B570” was 38% by mass with respect to the total epoxy resin. A curable resin composition was prepared and a thermistor using the curable resin composition was prepared.

  It was 30 degreeC when the glass transition temperature of the hardened | cured material in the thermistor body formed by hardening was measured like Example 1. FIG.

About the obtained thermistor, when the temperature-resistance curve was obtained like Example 1, the initial room temperature resistance value of the thermistor was 1.0 * 10 < ^-3 > (ohm) (resistivity: 6.5 * 10 < ^-3 > (omega ^| ohm) cm). The resistance change rate value was 10 digits or more. Moreover, the room temperature resistance value after a thermal history was 3.0 * 10 < ^-3 > (omega ^| ohm) (resistivity: 1.9 * 10 ^<-2 > (omega ^| ohm) cm), and was maintaining the low level.

(Example 3)
As the epoxy resin, only the epoxy resin “BPO20E” (trade name, manufactured by Shin Nippon Chemical Co., Ltd., epoxy equivalent of 315 g / eq.) Composed of the polyepoxy compound represented by the above chemical formula (1) is used, and the curing agent “B570” is epoxy. A curable resin composition and a thermistor using the same were prepared in the same manner as in Example 1 except that the amount was 53% by mass based on the resin.

  When the glass transition temperature of the cured product in the thermistor body formed by curing was measured in the same manner as in Example 1, it was 60 ° C.

About the obtained thermistor, when the temperature-resistance curve was obtained like Example 1, the initial room temperature resistance value of the thermistor was 1.0 * 10 < ^-3 > (ohm) (resistivity: 6.5 * 10 < ^-3 > (omega ^| ohm) cm). The resistance change rate value was 10 digits or more. Moreover, the room temperature resistance value after the thermal history was 2.0 × 10 ⁻³ Ω (resistivity: 1.3 × 10 ⁻² Ωcm), and maintained a low level.

(Example 4)
As epoxy resin, “BPO20E” and “E850” (trade name, manufactured by Dainippon Ink & Chemicals, Inc., epoxy equivalent 190 g / eq.) Which is a bisphenol A type epoxy resin were used at a weight ratio of 70:30, and cured. A curable resin composition and a thermistor using the same were prepared in the same manner as in Example 1 except that the agent “B570” was changed to 60% by mass with respect to the entire epoxy resin.

  It was 80 degreeC when the glass transition temperature of the hardened | cured material in the thermistor body formed by hardening was measured like Example 1. FIG.

About the obtained thermistor, when the temperature-resistance curve was obtained like Example 1, the initial room temperature resistance value of the thermistor was 1.0 * 10 < ^-3 > (ohm) (resistivity: 6.5 * 10 < ^-3 > (omega ^| ohm) cm). The resistance change rate was an 8-digit value. Moreover, the room temperature resistance value after the thermal history was 9.0 × 10 ⁻³ Ω (resistivity: 5.8 × 10 ⁻² Ωcm), and the low level was maintained.

(Example 5)
Curing was carried out in the same manner as in Example 1 except that “BPO20E” and “E850” were used at a weight ratio of 20:80 as the epoxy resin and the curing agent “B570” was 80% by mass with respect to the entire epoxy resin. Preparation of a functional resin composition and production of a thermistor using the same.

  It was 110 degreeC when the glass transition temperature of the hardened | cured material in the thermistor body formed by hardening was measured like Example 1. FIG.

About the obtained thermistor, when the temperature-resistance curve was obtained like Example 1, the initial room temperature resistance value of the thermistor was 1.0 * 10 < ^-3 > (ohm) (resistivity: 6.5 * 10 < ^-3 > (omega ^| ohm) cm). ) The resistance change rate was a 7-digit value. Moreover, the room temperature resistance value after the thermal history was 5.0 × 10 ⁻² Ω (resistivity: 3.3 × 10 ⁻² Ωcm), and the low level was maintained.
(Example 6)
Only "E850" is used as an epoxy resin, and dodecenyl succinic anhydride "Licacid DDSA" (trade name, manufactured by Shin Nippon Chemical Co., Ltd., acid anhydride equivalent 266 g / eq.) Is used as a curing agent in an amount of 140% by mass. In the same manner as in Example 1, a curable resin composition was prepared and a thermistor was prepared using the same.
It was 40 degreeC when the glass transition temperature of the hardened | cured material in the thermistor body formed by hardening was measured like Example 1. FIG.
About the obtained thermistor, when the temperature-resistance curve was obtained like Example 1, the initial room temperature resistance value of the thermistor was 1.0 * 10 < ^-3 > (ohm) (resistivity: 6.5 * 10 < ^-3 > (omega ^| ohm) cm). ) The resistance change rate was a 7-digit value. Moreover, the room temperature resistance value after the thermal history was 3.0 × 10 ⁻³ Ω (1.9 × 10 ⁻² Ωcm), and the low level was maintained.

(Comparative Example 1)
As the epoxy resin, only “E850” is used, the curing agent “B570” is 88% by mass with respect to the epoxy resin, and the conductive particles are 60% by mass with respect to the entire curable resin composition including the conductive particles. In the same manner as in Example 1, a resin composition was prepared and a thermistor using the resin composition was prepared.

  It was 120 degreeC when the glass transition temperature of the hardened | cured material in the thermistor body formed by hardening was measured like Example 1. FIG.

About the obtained thermistor, when the temperature-resistance curve was obtained like Example 1, the initial room temperature resistance value of the thermistor was 3.0 * 10 < ^-3 > (ohm) (resistivity: 1.9 * 10 ^<-2 > (omega ^| ohm) cm). The resistance change rate had a number of 10 ⁶ digits. Moreover, the room temperature resistance value after the thermal history was 2.4 × 10 ⁻¹ Ω (resistivity: 1.56 Ωcm), which was a remarkably large value.

(Comparative Example 2)
The preparation and use of the curable resin composition were the same as in Example 1 except that only “EP-4080S” was used as the epoxy resin and the curing agent “B570” was 85% by mass with respect to the epoxy resin. The thermistor was prepared.

  It was 120 degreeC when the glass transition temperature of the hardened | cured material in the thermistor body formed by hardening was measured like Example 1. FIG.

About the obtained thermistor, when the temperature-resistance curve was obtained like Example 1, the initial room temperature resistance value of the thermistor was 4.0 * 10 < ^-3 > (ohm) (resistivity: 2.6 * 10 ^<-2 > (omega ^| ohm) cm). The resistance change rate was a 6-digit value. Moreover, the room temperature resistance value after the thermal history was 1.5 × 10 ⁻¹ Ω (resistivity: 0.97 Ωcm), which was a remarkably large value.

(Comparative Example 3)
As epoxy resin, “E850” and “EP-4005” were used at a weight ratio of 97: 3, and the curing agent “B570” was changed to 87% by mass with respect to the total epoxy resin, as in Example 1. Then, preparation of a curable resin composition and production of a thermistor using the same were performed.

  When the glass transition temperature of the cured product in the thermistor body formed by curing was measured in the same manner as in Example 1, it was 115 ° C.

About the obtained thermistor, when the temperature-resistance curve was obtained like Example 1, the initial room temperature resistance value of the thermistor was 3.0 * 10 < ^-3 > (ohm) (resistivity: 1.9 * 10 ^<-2 > (omega ^| ohm) cm). The resistance change rate value was a 7-digit value. Moreover, the room temperature resistance value after the thermal history was 1.2 × 10 ⁻¹ Ω (resistivity: 0.78 Ωcm), which was a remarkably large value.

As shown in Table 2, the thermistors of Comparative Examples 1 to 3 in which the glass transition temperature of the cured product in the thermistor body exceeds 110 ° C. have a remarkable room temperature resistance value after receiving a thermal history assuming a reflow process. It increased to a large value of 1 × 10 ⁻¹ or more. On the other hand, the thermistors of Examples 1 to 6 in which the glass transition temperature of the cured product in the thermistor body is 110 ° C. or lower are not significantly increased in room temperature resistance even after receiving a thermal history, and are low. The room temperature resistance value was maintained. In Table 2, the value of the average molecular weight indicates the value of the average molecular weight of the entire epoxy resin and curing agent used for preparing the curable resin composition.

It is a perspective view which shows typically one Embodiment of the thermistor by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Thermistor body, 2, 3 ... Electrode, 10 ... Thermistor.

Claims (7)

A pair of opposing electrodes, and a thermistor body including a cured product of a curable resin composition disposed between the pair of electrodes and containing a thermosetting resin and conductive particles,
The thermistor whose glass transition temperature of the said hardened | cured material is 110 degrees C or less.   The thermistor of Claim 1 whose glass transition temperature of the said hardened | cured material is 20 degreeC or more.   The thermistor of Claim 1 or 2 in which the said thermosetting resin contains an epoxy resin and its hardening | curing agent.   The thermistor of Claim 3 whose average molecular weight of the whole of the said epoxy resin and the said hardening | curing agent is 300-1000. The epoxy resin is at least one of a plurality of glycidyl ether groups, a divalent group represented by the following general formula (11), (12), (13) or (14) and a divalent alicyclic group. The thermistor of Claim 3 or 4 containing the polyepoxy compound which has a partial structure.

[In the formulas (11), (12), (13) and (14), a, b, c and d each independently represents an integer of 1 to 20. ]   The thermistor as described in any one of Claims 3-5 in which the said hardening | curing agent contains an acid anhydride. The thermistor as described in any one of Claims 3-5 in which the said hardening | curing agent contains the acid anhydride represented by following Chemical formula (21), (22), (23) or (24).

[In the formula (21), R ¹ represents a hydrocarbon group having 4 to 20 carbon atoms. ]

[In Formula (22), R ² represents a hydrocarbon group having 1 to 20 carbon atoms, p represents an integer of 1 to 3, and a plurality of R ² in the same molecule may be the same or different. ]

[In formula (23), X shows a C4 or more bivalent hydrocarbon group, q shows the integer of 1-20. ]

[In the formula (24), Z represents a divalent or trivalent organic group having 2 or more carbon atoms, and r represents 2 or 3. ]

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