JP6795826B1 - Overcurrent protection element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overcurrent protection element having a PTC characteristic having a high basic current value and which can be easily and inexpensively manufactured. The disclosed overcurrent protection elements include poly (3-alkylthiophene) represented by the formula (1), poly (3,4-methylenedioxythiophene), and poly (3,4-ethylenedioxy). It contains either oxythiophene) or poly (2-benzothiophene) and either persulfate or ferric salt. [Chemical formula 1] In the formula (1), R1 is an alkyl group having 1 to 18 carbon atoms. [Selection diagram] None

Description

The present invention has a PTC (Positive temperature coefficient) characteristic in which the electrical resistance rapidly increases when a predetermined temperature (hereinafter referred to as “trip” temperature) is exceeded, and overcurrent protection protects the circuit from inrush current and overcurrent. Regarding the element, in particular, it relates to an overcurrent protection element made of an organic conductor.

Conventionally, a conductor obtained by annealing a poly (3-alkylthiophene) obtained by chemically oxidatively polymerizing 3-alkylthiophene having an alkyl group having 1 to 18 carbon atoms at a temperature of 0 ° C. or lower is known. This conductor has a PTC characteristic in which the conductivity rapidly decreases in a temperature range exceeding the melting point of around 190 ° C. (see, for example, Patent Document 1). Hereinafter, this technique will be referred to as a first conventional example.

式（３）において、Ｒ_２、Ｒ_３はそれぞれ独立して水素原子又は炭素数１〜８のアルコキシ基、マロン酸基を表している。 Further, conventionally, the copolymer that can be used as an overcurrent protection element has a poly (3,4-ethylenedioxythiophene) residue unit represented by the formula (2) of 99.99 to 80 mol%. Some polythiophene derivatives represented by (3) have a residue unit of 0.01 to 20 mol% (see, for example, Patent Document 2). Hereinafter, this technique will be referred to as a second conventional example.

In the formula (3), R ₂ and R ₃ independently represent a hydrogen atom, an alkoxy group having 1 to 8 carbon atoms, and a malonic acid group, respectively.

式（４）において、Ｒ_４、Ｒ_５、Ｒ_６及びＲ_７はそれぞれ独立して水素原子又は炭素数１〜１６の炭化水素基を表している。Ｒ_４とＲ_５又はＲ_６とＲ_７はそれぞれ互いに連結して環状構造を形成してもよい。 Further, conventionally, the copolymer that can be used as an overcurrent protection element includes a repeating unit derived from the thiophene-3,4-bissulfonic acid ester represented by the formula (4) and a repeating unit represented by the formula (5). Some include repeating units derived from 3,4-ethylenedioxythiophene (see, for example, Patent Document 3). Hereinafter, this technique will be referred to as a third conventional example.

In formula (4), R ₄ , R ₅ , R ₆ and R ₇ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 16 carbon atoms. R ₄ and R ₅ or R ₆ and R ₇ may be connected to each other to form an annular structure.

式（６）において、Ｒ_８、Ｒ_９はそれぞれ独立して炭素数１〜１２のアルキル基を表している。また、式（７）において、Ｒ_１０〜Ｒ_１５はそれぞれ独立して水素原子又は炭素数１〜３の炭化水素基を表している。Ｒ_１１とＲ_１２又はＲ_１４とＲ_１５はそれぞれ互いに連結して環状構造を形成してもよい。 Further, conventionally, the copolymer that can be used as an overcurrent protection element includes a repeating unit derived from 3,4-bis (carbamoyloxy) thiophenes represented by the formula (6) or the formula (7). Some include a repeating unit derived from 3,4-ethylenedioxythiophene represented by the formula (5) (see, for example, Patent Document 4). Hereinafter, this technique will be referred to as a fourth conventional example.

In formula (6), R ₈ and R ₉ each independently represent an alkyl group having 1 to 12 carbon atoms. Further, in the formula (7), R _{10 to} R ₁₅ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. R ₁₁ and R ₁₂ or R ₁₄ and R ₁₅ may be connected to each other to form an annular structure.

式（６）において、Ｒ_８、Ｒ_９はそれぞれ独立して炭素数１〜１２のアルキル基を表している。また、式（７）において、Ｒ_１０〜Ｒ_１５はそれぞれ独立して水素原子又は炭素数１〜３の炭化水素基を表している。Ｒ_１１とＲ_１２又はＲ_１４とＲ_１５はそれぞれ互いに連結して環状構造を形成してもよい。
また、式（８）において、Ｒ_１６、Ｒ_１７はそれぞれ独立して水素原子、ヒドロキシ基、カルボキシ基を表している。Ｒ_１６、Ｒ_１７のうち、一方が水素原子の場合、他方は水素原子以外のヒドロキシ基、又はカルボキシ基を表している。 Further, the conventional overcurrent protection element includes a repeating unit derived from 3,4-bis (carbamoyloxy) thiophenes represented by the formula (6) or the formula (7) and a repeating unit represented by the formula (5). Some include a copolymer (A) containing a repeating unit derived from 3,4-ethylenedioxythiophene, and a polythiophene composition containing the phenols (B) represented by the formula (8) (eg,). , Patent Document 5). Hereinafter, this technique will be referred to as a fifth conventional example.

In formula (6), R ₈ and R ₉ each independently represent an alkyl group having 1 to 12 carbon atoms. Further, in the formula (7), R _{10 to} R ₁₅ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. R ₁₁ and R ₁₂ or R ₁₄ and R ₁₅ may be connected to each other to form an annular structure.
Further, in the formula (8), R ₁₆ and R ₁₇ independently represent a hydrogen atom, a hydroxy group, and a carboxy group, respectively. When one of R ₁₆ and R ₁₇ is a hydrogen atom, the other represents a hydroxy group other than a hydrogen atom or a carboxy group.

Japanese Patent No. 3270959 (Claim 1, paragraph 0020) Japanese Unexamined Patent Publication No. 2012-255049 (Claim 1, Claim 3) JP-A-2014-43500 (Claim 1, Claim 4, Claim 6) Japanese Patent No. 6015243 (Claim 1, Claim 3) Japanese Patent No. 60152444 (Claim 1, Claim 6)

Although the first conventional example has PTC characteristics, it seems difficult to put it into practical use as an overcurrent protection element because the basic current value is low. In this respect, the second to fifth conventional examples solve the problem of the first conventional example that the basic current value is low. However, since the second to fifth conventional examples are all copolymers or contain copolymers, it is necessary to synthesize a polymer. Further, in the second to fifth conventional examples, it is necessary to design the distribution ratio according to the PTC characteristics at the stage of synthesizing the polymer. Therefore, in the second to fifth conventional examples, it seems that the overcurrent protection element cannot be manufactured easily and inexpensively.

The present invention has been made in view of the above circumstances, and an example of the problem is to solve the above-mentioned problems, and provides an overcurrent protection element capable of solving these problems. The purpose is to do.

式（１）において、Ｒ_１は、炭素数１〜１８のアルキル基である。 In order to solve the above problems, the overcurrent protection element according to the invention according to claim 1 includes poly (3-alkylthiophene) represented by the formula (1) and poly (3,4-methylenedioxythiophene). ), Poly (3,4-ethylenedioxythiophene) or poly (2-benzothiophene), and either a persulfate or a ferric salt.

In formula (1), R ₁ is an alkyl group having 1 to 18 carbon atoms.

Further, the invention according to claim 2 is related to the overcurrent protection element according to claim 1, and is characterized by further containing a carbon filler.

The invention according to claim 3 relates to the overcurrent protection element according to claim 1 or 2, the poly (3-alkylthiophene), the poly (3,4-methylenedioxythiophene), and the poly. The ratio of (3,4-ethylenedioxythiophene) or the poly (2-benzothiophene) is characterized by being 1: 3 to 3: 1.

Further, the invention according to claim 4 relates to the overcurrent protection element according to any one of claims 1 to 3, and the persulfate is any one of ammonium persulfate, potassium persulfate or sodium persulfate. , The ferric salt is characterized by being either ferric sulfate, ferric chloride or ferric toluene sulfonate.

According to the present invention, since the basic current value is high, it can be put into practical use as an overcurrent protection element, and since it is not necessary to synthesize a polymer, it can be easily and inexpensively manufactured.

It is a figure which shows an example of the composition of the overcurrent protection element which concerns on Example and the comparative example, the resistance value at the time of measurement, the type of an element, and the presence or absence of a PTC phenomenon. It is a circuit diagram which shows an example of the circuit diagram of the measuring apparatus for measuring the characteristic of the overcurrent protection element which concerns on Example and comparative example. It is a graph which shows an example of the resistance value characteristic with respect to the temperature of the overcurrent protection element which concerns on Example 5. FIG.

An object of the present invention is to provide an overcurrent protection element having a PTC characteristic having a high basic current value and which can be easily and inexpensively manufactured. The present inventors have completed the present invention as a result of diligent studies to achieve this object. Hereinafter, modes for carrying out the present invention will be described.

The overcurrent protection element of the present invention includes poly (3-alkylthiophene) represented by the formula (1), poly (3,4-methylenedioxythiophene), poly (3,4-ethylenedioxythiophene) or It contains either poly (2-benzothiophene) and either a persulfate or a ferric salt. Further, a carbon filler may be further contained in order to improve the characteristics of the overcurrent protection element.

式（１）において、Ｒ_１は、炭素数１〜１８のアルキル基である。 <Poly (3-alkylthiophene)>
The poly (3-alkylthiophene) constituting the overcurrent protection element of the present invention is represented by the formula (1).

In formula (1), R ₁ is an alkyl group having 1 to 18 carbon atoms.

The poly (3-alkylthiophene) constituting the overcurrent protection element of the present invention is particularly a polymer having 6 or more carbon atoms in the alkyl group, that is, poly (3-hexylthiophene) {P3HT: Poly (3-hexylthiophene). )}, Poly (3-heptylthiophene), Poly (3-octylthiophene), Poly (3-nonylthiophene), Poly (3-decylthiophene), Poly (3-undecylthiophene), Poly (3-dodecylthiophene) ), Poly (3-tridecylthiophene), Poly (3-tetradecylthiophene), Poly (3-pentadecylthiophene), Poly (3-hexadecylthiophene), Poly (3-heptadecylthiophene), Poly (3) -Octadecylthiophene) is preferred. This is because these polymers are soluble in organic solvents such as toluene and chloroform, have excellent crystallinity, and have high crystallinity, so that they have high electron mobility and stable PTC characteristics. ..

In the present invention, the method for producing poly (3-alkylthiophene) is not particularly limited, but for example, a known chemical oxidation polymerization method, CH direct arylation polymerization method, or electrolytic polymerization method is used. Can be done.

For example, the chemical oxidative polymerization of P3HT is as follows. First, the polymerization solvent is dissolved in an organic solvent to prepare a catalyst solution having a concentration of 0.5 mol, and then the mixture is sufficiently stirred. Next, only 200 mg of 3-hexylthiophene monomer is added to this catalyst solution, and the reaction is carried out in a constant temperature bath while stirring for a predetermined time. After this reaction, the black powdery polymerization product is put into 500 ml of methanol as a precipitant together with the catalyst solution, and the mixture is stirred for 30 minutes. As the organic solvent, for example, toluene, chloroform and the like are preferable.

Further, as the polymerization solvent, for example, general ones such as persulfate and ferric salt can be used. Examples of the persulfate include ammonium peroxodisulfate {(NH ₄ ) ₂ S ₂ O ₈ }, potassium peroxodisulfate (K ₂ S ₂ O ₈ ), sodium peroxodisulfate (Na ₂ S ₂ O ₈ ), and the like. is there. Examples of the ferric salt include ferric sulfate {Fe ₂ (SO ₄ ) ₃ }, ferric chloride (FeCl ₃ ), and ferric toluene sulfonate (C ₂₁ H ₂₁ FeO ₉ S ₃ ). And so on.

The electrolytic polymerization of P3HT is as follows. After dissolving 0.1 mol of 3-hexylthiophene monomer in an organic solvent, a potential of 2-5 V is applied at room temperature for several minutes together with 0.1 mol of supporting electrolyte.

As the organic solvent, for example, toluene or chloroform is preferable because it is stable under electrolytic conditions and it is necessary to dissolve not only the monomer but also the supporting electrolyte at a high concentration (for example, 0.1 mol / liter or more). Further, as the supporting electrolyte, for example, n-dodecylbenzenesulfonic acid or the like is preferable. As the working electrode, for example, one made of tin-doped indium oxide (ITO: Indium Tin Oxide) or the like is preferable. On the other hand, as the counter electrode, one made of platinum (Pt) or the like is preferable. The polymerization time is preferably about 3 minutes.

Further, in the present invention, as the poly (3-alkylthiophene), a commercially available product synthesized by using the above-mentioned known polymerization method may be used. For example, as a commercially available product of P3HT polymerized by the CH direct arylation polymerization method, there is a product manufactured by Tokyo Chemical Industry Co., Ltd. (product code P2513).

<Polythiophene>
In the present invention, examples of polythiophene other than poly (3-alkylthiophene) include poly (3,4-methylenedioxythiophene), poly (3,4-ethylenedioxythiophene), and poly (3,4-dimethyl). Thiophene), poly (3,4-diethylthiophene), poly (3,4-dibutylthiophene), poly (3-methoxythiophene), poly (3,4-dimethoxythiophene), poly (3-ethoxythiophene), poly (3-Methyl-4-methoxythiophene), poly (3-methyl-4-butoxythiophene), poly (3-methyl-4-octyloxythiophene), poly (3-methyl-4-lauryloxythiophene), poly (3-Methyl-4-cetyloxythiophene), poly {R, S-3,4- (1'-hydroxymethyl) ethylenedioxythiophene}, poly (3,4-ethyleneoxythithiophene), poly (iso) Benzothiophene) {poly (2-benzothiophene)} and the like. Of these, poly (3,4-methylenedioxythiophene), poly (3,4-ethylenedioxythiophene) or poly (isobenzothiophene) {due to their high conductivity, workability and industrial availability. Poly (2-benzothiophene)} is particularly preferred.

In the present invention, for example, the method for producing poly (3,4-ethylenedioxythiophene) {PEDOT: Poly (3,4-ethylenedioxythiophene)} is not particularly limited, but for example, known chemical oxidation weight. Legal, CH direct arylation polymerization methods or depolymerization methods can be used. Further, in the present invention, PEDOT may use a commercially available product synthesized by using such a known polymerization method. Commercially available products include, for example, those manufactured by TDA Research, which are dispersed in an organic solvent.

<Manufacturing method of complex>
The method for producing the composite constituting the overcurrent protection element of the present invention is not particularly limited, and examples thereof include the methods (a) and (b) shown below.

(A) First, 40 mg of P3HT and 40 mg of ferric chloride (FeCl ₃ ) are dissolved in 2 ml of chloroform, respectively. Next, these three types of solutions and the solution in which PEDOT is dispersed are weighed in predetermined amounts to form a complex at a predetermined ratio. In this case, a carbon filler may be further added.

(B) First, 0.1 mol of 3-hexylthiophene monomer and 0.1 mol of 3,4-ethylenedioxythiophene monomer are dissolved in an organic solvent, and then 0.1 to 0.2. A potential of 2-5 V at room temperature is applied with the molar supporting electrolyte for several minutes to produce a mixture of P3HT and PEDOT in a ratio of 1: 1.

As the organic solvent, for example, toluene, chloroform and the like are preferable. Further, as the supporting electrolyte, for example, n-dodecylbenzenesulfonic acid or the like is preferable. As the working electrode, for example, one made of ITO or the like is preferable. On the other hand, as the counter electrode, one made of platinum (Pt) or the like is preferable. The polymerization time is preferably about 3 minutes.

Next, 40 mg of the above mixture and 40 mg of ferric chloride (FeCl ₃ ) are dissolved in 2 ml of chloroform, respectively. Then, each of these three kinds of solutions is weighed in a predetermined amount to form a complex at a predetermined ratio. In this case, a carbon filler may be further added.

In the complex produced by the method shown in (a) or (b) above, 70 to 20% by weight of poly (3-alkylthiophene), 20 to 70% by weight of PEDOT, and persulfate or ferric salt. Any of them is preferably 5% by weight. When a carbon filler is added, it is preferably 5 to 10% by weight. In particular, the ratio of poly (3-alkylthiophene) to PEDOT is from 3: 1 to 1: 3, preferably 1: 1. Both poly (3-alkylthiophene) and PEDOT are π-conjugated polythiophene compounds, but poly (3-alkylthiophene) alone has an excessively low basic current value as an overcurrent protection element. On the other hand, although PEDOT has excellent conductivity, it is insoluble in a solvent (particularly water) by itself, so that it is not stably dispersed in the solvent, has low crystallinity, and polymerizes directly from the monomer into a thin film. Is difficult.

Therefore, by mixing PEDOT with poly (3-alkylthiophene), the present inventors sufficiently connect the conductive paths of PEDOT, improve the conductivity, increase the basic current value, and obtain desired PTC characteristics. I thought that it would be possible to design the overcurrent protection element shown.

In addition, some carbon fillers have high conductivity and high mechanical strength. Therefore, it is considered that the overcurrent protection element can be imparted with conductivity and mechanical strength by adding a carbon filler to the mixture of poly (3-alkylthiophene) and PEDOT.

Due to the nature of the overcurrent protection element, heating and natural cooling are repeated, but the resistance value characteristics during heating (when the temperature rises) and the resistance value characteristics during natural cooling (when the temperature drops) are almost the same. It is preferable that there is no so-called hysteresis. In this respect, in the present invention, since the mixing ratio of poly (3-alkylthiophene) and PEDOT can be easily controlled, the specific heat of the entire overcurrent protection element can be reduced, and the above-mentioned hysteresis can be improved. It is considered to be. Since the ratio of the carbon filler added to the composite can be controlled, it is considered that the specific heat of the entire overcurrent protection element is reduced and the performance is improved.

Further, ferric chloride (FeCl ₃ ), of course, functions as a polymerization catalyst when polymerizing poly (3-alkylthiophene) and PEDOT, but remains to impart conductivity to the complex as an auxiliary. It also functions as an electron-accepting molecule (dopant).

Based on the above, by mixing poly (3-alkylthiophene), which is commercially available and industrially easy to handle, and PEDOT, and further mixing ferric chloride (FeCl ₃ ), it is possible to adjust the temperature according to the application. It is considered that the trip temperature, the amount of change, and the basic current value can be set, and an overcurrent protection element exhibiting desired PTC characteristics can be designed. Further, it is considered that the desired conductivity and mechanical strength can be imparted to the overcurrent protection element by controlling the ratio of adding the carbon filler to this composite.

In addition, those having both the function of a polymerization catalyst and the function of an electron-accepting molecule (dopant) include persulfate and ferric salt. Examples of the persulfate include ammonium peroxodisulfate {(NH ₄ ) ₂ S ₂ O ₈ }, potassium peroxodisulfate (K ₂ S ₂ O ₈ ), sodium peroxodisulfate (Na ₂ S ₂ O ₈ ), and the like. is there. As ferric salts, in addition to the above ferric chloride (FeCl ₃ ), for example, ferric sulfate (Fe ₂ (SO ₄ ) ₃ }, ferric toluene sulfonate (C ₂₁ H ₂₁ FeO ₉₎ There are S ₃ ) and so on.

<Overcurrent protection element>
The overcurrent protection element of the present invention comprises the above-mentioned composite of the present invention.
The method for manufacturing the overcurrent protection element of the present invention is not particularly limited, but includes, for example, the methods (c) and (d) shown below.

(C) The above (a) or (b) is contained in a container having a width of 6 mm, a length of 8 mm, and a height of 7 mm, which has an open upper part and is provided with a pair of electrodes at a distance of 5 mm at the bottom. The composite produced by the method shown in the above is filled and dried to obtain a container-type element.

(D) The composite produced by the method shown in (a) or (b) above is applied to the surface of the base material and dried to obtain a cast film type device.

The base material is not particularly limited, and examples thereof include a plastic sheet, a plastic film, a non-woven fabric, and a glass plate. The coating method is not particularly limited, and examples thereof include spin coating, wire coating, bar coating, roll coating, plate coating, curtain coating, screen printing, and the like. The heating conditions for drying are not particularly limited, but are preferably 50 to 120 ° C., which are not affected by thermal deterioration.

The present inventors presume that the overcurrent protection element made of the composite of the present invention exhibits PTC characteristics by the mechanism shown below. That is, at normal temperatures such as room temperature, poly (3-alkylthiophene) is in a crystalline form in which conductive particles such as dopants are in electrical contact with each other to form a low resistance network.

Poly (3-alkylthiophene) or consumed above-described structure portions power internally excessive current flow (I 2 ^R) is the other component constituting the overcurrent protection element mounted device abnormality When the temperature of the overcurrent protection element itself rises due to a sudden rise in the ambient temperature due to heating, the movement of the side chain of the poly (3-alkylthiophene) gradually increases. Then, when the temperature of the structural portion exceeds the trip temperature, the crystal structure in the poly (3-alkylthiophene) changes to a non-crystal structure.

At this time, the π-conjugated system of poly (3-alkylthiophene) (arrangement in which single bonds and double bonds are alternately arranged) is distorted and the conductive path is shortened (first phenomenon). At the same time, due to the movement of the side chain of the poly (3-alkylthiophene), the poly (3-alkylthiophene) melts and expands to increase its volume, so that conductive particles such as dopants become poly (3). -Separation from alkylthiophene) destroys the low resistance network (second phenomenon). As a result of the synergistic action of the first and second phenomena, the resistance value of the overcurrent protection element increases non-linearly, which is more than cubed higher than the normal resistance value. Transition (trip) to the resistance state.

By increasing the resistance value of the overcurrent protection element, the amount of current flowing through the circuit incorporating the overcurrent protection element is stable and suppressed to a low value when a problem such as an overcurrent or a sudden rise in ambient temperature occurs. Therefore, the circuit can be protected. This change in resistance value, that is, trip, can be used as a signal source for notifying the control system that the circuit and the device in which the circuit is incorporated are overheated.

The high resistance state of the overcurrent protection element is maintained for a while, but when the defect is resolved and the circuit is re-powered and the composite in the overcurrent protection element is cooled, poly (3-alkylthiophene) Recrystallization occurs. As a result, the overcurrent protection element returns to a low resistance state in the circuit, and the device in which the circuit is incorporated returns to the normal operation.

Based on speculation about the above mechanism, it seems that the trip temperature can be set by changing the length of the side chain that affects the motility of the side chain of poly (3-alkylthiophene). For example, instead of poly (3-hexylthiophene) having 6 carbon atoms in the side chain, poly (3-octylthiophene) having 8 carbon atoms in the side chain or poly (3-octylthiophene) having 12 carbon atoms in the side chain ( It is considered that the trip temperature can be shifted to the higher temperature side by using 3-dodecylthiophene) as compared with the case of using poly (3-hexylthiophene).

The obtained overcurrent protection element has a high basic current value at room temperature around 25 ° C., exhibits a constant resistance value as low as that of other conductors, and the electric resistance rapidly increases when the temperature exceeds a predetermined temperature. It is suitably used as an overcurrent protection element having PTC characteristics.

Hereinafter, examples of the present invention will be described in more detail, but the following examples do not have properties that limit the present invention, and may be appropriately modified and carried out within a range that can be adapted to the gist of the above and the following. It is possible, and they are all within the technical scope of the invention.

Examples (1-5) and Comparative Examples (1-2)
(composition)
An example of the composition of each overcurrent protection element of the examples and comparative examples produced this time is shown on the left side of FIG. In PEDOT and P3HT,% means the ratio of each other in% by weight. Further, in ferric chloride (FeCl ₃ ) and the carbon filler, ◯ indicates that the substance is contained, and × indicates that the substance is not contained.

(Measuring method)
FIG. 2 shows an example of a circuit diagram of a measuring device for measuring the characteristics of the overcurrent protection element according to the examples and the comparative examples. This measuring device is a regulated DC power supply (manufactured by Kikusui Electronics Co., Ltd., model number: 7325), two thermocouples (both manufacturing company and model number unknown), and two carbon film resistors (both manufacturing company and model number unknown). ) And a data logger (manufactured by Hioki Electric Co., Ltd., model number: 8420).

The element 1 which is the first overcurrent protection element and the resistor 1 which is the first carbon film resistor are connected in series, and the element 2 which is the second overcurrent protection element and the resistor 2 which is the second carbon film resistor are connected in series. Was connected in series. These were connected in parallel, and a DC voltage of 5 V was applied to both ends thereof by a regulated DC power supply. The types of the elements 1 and 2 are both container types manufactured by the method (c) of the above-mentioned manufacturing method of the overcurrent protection element.

Each resistance value of the resistors 1 and 2 is determined in each of the voltage dividing states of the corresponding elements 1 and 2. Specifically, the voltage dividing ratio of the element 1 and the resistor 1 and the voltage dividing ratio of the element 2 and the resistor 2 are both set to be 1: 1 with respect to the applied DC voltage of 5 V, or the element 1 is set in the heating process. And, assuming that the voltage dividing on the element 2 side becomes high, each resistance value of the resistors 1 and 2 is set to a slightly higher value. Each resistance value of resistors 1 and 2 was measured using a circuit element measuring instrument (manufactured by Hioki Electric Co., Ltd., model number: 3531).

Next, the element 1 and the element 2 are placed in an oven toaster (manufactured by Zojirushi Corporation, model number: ET-VA22), and then the first thermocouple, the thermocouple 1, is placed in the vicinity of the element 1. At the same time, a thermocouple 2 which is a second thermocouple was placed in the vicinity of the element 2.

The data logger captures the DC voltage 5V supplied by the regulated DC power supply on channel Ch1, captures the voltage signal generated on both ends of the resistor 1 on channel Ch3, and captures the voltage signal generated on both ends of the resistor 2 on channel Ch5. .. Further, the data logger captures the voltage signals generated at both ends of the thermocouple 1 on the channel Ch4, and captures the voltage signals generated at both ends of the thermocouple 2 on the channel Ch6.

In the experiment, an oven toaster was operated to heat the temperature measured by thermocouples 1 and 2, respectively, connected to channels Ch4 and Ch6 of the data logger from room temperature to 200 degrees Celsius. After that, the power of the oven toaster was turned off and left. The elements 1 and 2 were covered with a heat-resistant sheet to prevent direct irradiation of infrared rays generated in the toaster oven.

(result)
The right side of FIG. 1 shows the resistance value at the start of measurement and the presence or absence of the PTC phenomenon of the overcurrent protection element alone manufactured this time. The resistance value at the start of measurement represents the resistance value measured when the entire measurement circuit is placed in the oven toaster and the measurement is started.

In the PTC phenomenon column, ○ indicates that the PTC phenomenon was observed for the corresponding overcurrent protection element, ◎ indicates that a good PTC phenomenon was observed for the corresponding overcurrent protection element, and × indicates that a good PTC phenomenon was observed for the corresponding overcurrent protection element. It indicates that the PTC phenomenon was not observed for the corresponding overcurrent protection element.

Of Examples 1 to 5, in Examples 1 to 3, although the resistance value increased in the heating process, the resistance value did not decrease sufficiently in the cooling process, so that there was hysteresis, but the PTC phenomenon was observed. It was judged. Further, in Examples 1 to 3, those having high resistance at the start of measurement were observed. On the other hand, in Examples 4 and 5, a good PTC phenomenon was observed, and the resistance at the start of measurement was relatively low. FIG. 3 is a graph showing an example of resistance value characteristics with respect to temperature of the overcurrent protection element (element 2) according to the fifth embodiment. In this graph, the solid line is the characteristic when the temperature rises, and the broken line is the characteristic when the temperature falls. As can be seen from this graph, there is almost no hysteresis. On the other hand, in Comparative Examples 1 and 2, not only a sufficient PTC phenomenon was not observed, but also the resistance at the start of measurement was high.

Claims (4)

Poly (3-alkylthiophene) represented by the formula (1) and any of poly (3,4-methylenedioxythiophene), poly (3,4-ethylenedioxythiophene) or poly (2-benzothiophene). An overcurrent protection element comprising a heel and either a persulfate or a ferric salt.

In formula (1), R ₁ is an alkyl group having 1 to 18 carbon atoms. The overcurrent protection element according to claim 1, further comprising a carbon filler. The ratio of the poly (3-alkylthiophene) to any of the poly (3,4-methylenedioxythiophene), the poly (3,4-ethylenedioxythiophene) or the poly (2-benzothiophene) is The overcurrent protection element according to claim 1 or 2, wherein the ratio is 1: 3 to 3: 1. The persulfate is either ammonium persulfate, potassium persulfate or sodium persulfate, and the ferric salt is either ferric sulfate, ferric chloride or ferric toluenesulfonate. The overcurrent protection element according to any one of claims 1 to 3, wherein the overcurrent protection element is characterized.

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