JP2019033172A - Organic ptc device and manufacturing method thereof - Google Patents

Abstract

To obtain an organic PTC device with good sensitivity in a wide temperature range and usable over a wide temperature range with a simple method with good productivity.SOLUTION: An organic PTC device including at least one pair of electrodes and a thermistor layer disposed between the electrodes, and the thermistor layer includes a crosslinked thermoplastic resin and conductive particles, and the crosslinked thermoplastic resin has a glass transition temperature of -150°C to 10°C, and the conductive particles have a thickness of 0.1 μm or more and 10 μm or less and has a circularity of 0.55 or more and 1.0 or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an organic PTC (Positive temperature coefficient) element, and more specifically, an organic PTC element used for a self-control heating cable, an overcurrent protection device, a contact control element, and the like, and a method for manufacturing the same It is about.

The organic PTC element has a positive temperature characteristic with respect to the electric resistance, and has a property that the electric resistance increases as the temperature increases. Utilizing such properties, organic PTC elements are widely used in self-control heating cables, overcurrent protection devices and the like.
NTC thermistors having a negative temperature characteristic with respect to electrical resistance are widely used as temperature sensors. However, NTC thermistors have high resistance at low temperatures, and have a problem that errors are large due to self-heating. Yes. On the other hand, the PTC thermistor has a low resistance in a low temperature range and a small self-heating. Therefore, when a PTC thermistor is used as a temperature sensor, it is expected that a low temperature range can be measured with high accuracy.
Known thermistors of conventional PTC elements include ceramic PTC (Patent Document 1) in which trace elements are doped in barium titanate, and polymer PTC (Patent Documents 2 and 3) in which conductive particles are mixed in a polyethylene resin. However, there has been a problem that it cannot be easily formed into a sheet in the coating / printing process.

  In order to solve such a problem, an organic thermistor element that can be produced in a coating step by dispersing conductive particles in a matrix resin such as polyester or polyvinylidene fluoride soluble in a solvent has been reported (Patent Documents 4 and 5). . However, since the change in electrical resistance is small except near the phase transition temperature of the matrix resin, there is a problem in that the measurable temperature range is narrow when used as a temperature sensor.

International Publication No. 2010/140653 Pamphlet JP-A-1-304704 Special table 2010-500454 gazette International Publication No. 2008/133073 Pamphlet JP 2005-54185 A

  The problem to be solved by the present invention is to obtain a PTC element that can be easily produced by a printing or coating process, has excellent conductivity and sensitivity, and has a wide measurable temperature range even when used as a temperature sensor. .

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have solved the problems and completed the present invention. That is, the gist of the present invention is as follows.

[1] An organic PTC element having at least a pair of electrodes and having a thermistor layer between the pair of electrodes,
The thermistor layer includes a crosslinked thermoplastic resin and conductive particles,
The thermoplastic resin crosslinked product has a glass transition temperature of −150 ° C. or more and 10 ° C. or less,
The conductive particles are organic PTC elements having an average particle diameter of 0.1 μm or more and 10 μm or less and a circularity of 0.55 or more and 1.0 or less.
[2] The organic PTC element according to [1], in which the crosslinked thermoplastic resin is 35 parts by mass or more and 65 parts by mass or less when the mass of the thermistor layer is 100 parts by mass.
[3] The organic PTC element according to [1] or [2], wherein the conductive particles are carbon-based particles.
[4] The organic PTC element according to any one of [1] to [3], wherein a resistance change rate every 5 ° C. from 25 ° C. to 50 ° C. is 12% to 200%.
[5] The organic PTC device according to any one of [1] to [4], wherein a B constant from 25 ° C. to 50 ° C. is 2500 K or more and 10,000 K or less.
[6] A temperature sensor using the organic PTC element according to any one of [1] to [5].
[7] The method for producing an organic PTC element according to any one of [1] to [5], wherein the thermistor layer is formed by printing or coating and drying.

  The organic PTC element proposed by the present invention has good conductivity and sensitivity. The organic PTC element can be manufactured with high productivity by a method such as a printing process or a coating process. Furthermore, this organic PTC element can be easily formed in various shapes by ink jet or plate printing, and can be used in a wide temperature range, so it is suitable for temperature sensor and inrush current control of circuits, etc. Can be used.

It is sectional drawing which showed an example of the structure of the organic PTC element of this invention. It is the top view which showed the electrode shape of the Example of the organic PTC element of this invention.

  Hereinafter, embodiments of the present invention will be described in detail. However, the contents of the present invention are not limited to the embodiments described below.

In the present invention, when expressed as “X to Y” (X and Y are arbitrary numbers), “X is preferably greater than X” and “preferably Y”, with the meaning of “X to Y” unless otherwise specified. It means “smaller”.
Further, in the present invention, when expressed as “X or more” (X is an arbitrary number), it means “preferably larger than X” unless otherwise specified, and “Y or less” (Y is an arbitrary number). ) Includes the meaning of “preferably smaller than Y” unless otherwise specified.

<Organic PTC element>
The organic PTC element of the present invention is an organic PTC element having at least a pair of electrodes and a thermistor layer between the pair of electrodes, wherein the thermistor layer comprises a thermoplastic resin crosslinked product and conductive particles. The thermoplastic resin crosslinked product has a glass transition temperature of −150 ° C. or more and 10 ° C. or less, the conductive particles have an average particle diameter of 0.1 μm or more and 10 μm or less, and 0.55 It is an organic PTC element having a circularity of 1.0 or more and less.

  The organic PTC element of the present invention is characterized by having good conductivity and good sensitivity in a wide temperature range. In general, the mechanism by which such an organic PTC element responds to temperature is considered to be mainly caused by the interval between conductive particles being expanded and contracted by the thermal response of an intervening matrix resin. However, conventional organic PTC elements use phase transition phenomena such as glass transition and crystal melting as a driving force that expands and contracts the matrix resin. There was a problem that the expansion and contraction was poor in a temperature range other than the temperature range, and the sensitivity was very low as a temperature sensor. The organic PTC element of the present invention can impart the above characteristics without using a phase transition phenomenon by using a thermoplastic resin crosslinked product having a low glass transition temperature and conductive particles having high dispersibility.

The organic PTC element of the present invention has at least a pair of electrodes, and a thermistor layer between the pair of electrodes. As its specific mode, it is roughly divided into a laminated type in which a thermistor layer is sandwiched between two planar electrodes and a planar type in which two planar electrodes and the thermistor layer are arranged in parallel on the same substrate surface. The flat type is preferable in that it has a small influence and can be made thinner.
In the case of the above flat type, silver deposition or silver ink is printed on a base film such as polyethylene terephthalate or polyimide, or an electrode is formed by pasting silver foil or copper foil, and then a thermistor is formed between the electrodes. A method of applying the composition is simple and preferred. In the present invention, an adhesion layer and a protective layer for protecting the thermistor layer and the electrode may be provided in order to improve the adhesion to the substrate film.
As an example of a specific aspect, as shown in FIG. 1, the substrate film has at least a pair of electrodes and a thermistor layer disposed between the electrodes. As an example of another aspect, there may be mentioned one in which a thermistor layer is disposed on a pair of comb-like electrode patterns provided on an insulating substrate shown in FIG.

A well-known electroconductive material can be used suitably for an electrode. Examples of the form include a lump, a film, a line, and the like, but a film is preferable from the viewpoint that both thinning and conductivity can be achieved.
Examples of conductive materials include gold, silver, copper, iron, platinum, palladium, tin, lead, zinc, chromium, nickel, aluminum, magnesium, carbon, indium tin oxide (ITO), antimony tin oxide (ATO), And zinc tin oxide (ZTO) etc. are mentioned. Among these, gold, silver, platinum, and carbon are preferable from the viewpoint of conductive stability and contact resistance.

  The thickness of the electrode is not particularly limited, but is preferably 0.01 μm to 40 μm from the viewpoint of rigidity, and the shape is comb-shaped, zigzag, spiral, etc. And from the viewpoint of reducing variation in elements.

In the present invention, the thermistor layer and the electrode are preferably formed on the same substrate. As the substrate, a polyester resin film such as polyethylene terephthalate or polyethylene naphthalate, an imide resin film such as polyetherimide or polyimide, a thin glass, or the like is preferably used.
On the other hand, in the present invention, the thermistor layer can be formed directly between the electrodes without using a substrate.

  The thickness of the substrate is not particularly limited, but is preferably 20 μm to 400 μm, particularly 50 μm to 200 μm from the viewpoint of rigidity.

  In the present invention, the form of the organic PTC element is not particularly limited, and includes a plate form, a sheet form, a film form, and other forms.

  In general, "film" refers to a thin flat product that is extremely small compared to its length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll (Japan) (Industrial standard JIS K6900), “sheet” generally refers to a product that is thin by definition in JIS and generally has a thickness that is small instead of length and width. However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.

  About the organic PTC element of this invention, it is preferable that the electrical resistance in room temperature (25 degreeC) is 10 ohms or more and 1000 kohms or less. When it is 10Ω or more, sufficient accuracy can be obtained when it is incorporated as a temperature sensor. On the other hand, the heat generation of the element can be reduced by being 1000 kΩ or less.

In the organic PTC element of the present invention, the rate of change in resistance every 5 ° C. from 25 ° C. to 50 ° C. is preferably 12% or more, and more preferably 15% or more. When it is 12% or more, for example, when used as a temperature sensor, temperature measurement becomes possible. On the other hand, the upper limit is preferably 200% or less, and more preferably 100% or less. When it is 200% or less, for example, when used as a temperature sensor, precise measurement is possible.
Here, the resistance change rate every 5 ° C. is calculated by the following equation.
Resistance change rate (%) = (Electric resistance at (T + 5) ° C./Electric resistance at (T) ° C.−1) × 100

In the organic PTC element of the present invention, the B constant from 25 ° C. to 50 ° C. is 2500 K or more and 10,000 K or less, preferably 2800 K or more and 8000 K or less, more preferably 3000 K or more and 6000 K or less. When the B constant is 2500 K or more, sufficient accuracy can be exhibited when the B constant is incorporated as a temperature sensor. On the other hand, when it is 10,000 K or less, rapid current fluctuation when incorporated in an electronic circuit can be suppressed.
Here, the B constant from 25 ° C. to 50 ° C. is calculated by the following equation.
B constant (K) = | {ln (R ₂₅ ) −ln (R ₅₀ )} / {(1 / 2298.15) − (1 / 323.15)} |
R ₂₅ : Electric resistance at 25 ° C. R ₅₀ : Electric resistance at 50 ° C.

The electrical resistance for obtaining the resistance change rate and the B constant is obtained by the following method.
An organic PTC element is installed on a hot plate (manufactured by ASONE; ND-2), heated from 25 ° C. to 50 ° C. every 5 ° C., and between the electrodes of the organic PTC element when stabilized in each temperature range The electrical resistance is measured and plotted by the two-point method.

A temperature sensor can be produced using the organic PTC element of the present invention.
In order to produce the temperature sensor of the present invention, lead portions such as lead wires and lead tabs are provided on the electrode portion of the organic PTC element, and additional layers such as a protective layer and an insulating layer are further provided. This is achieved by arraying.
In addition to these, attached circuits such as an AD conversion circuit and an amplifier circuit may be incorporated.

<Thermistor layer>
Hereinafter, the thermistor layer will be described.
The thermistor layer of the present invention includes a thermoplastic resin crosslinked product and conductive particles.

It is important that the crosslinked thermoplastic resin in the thermistor layer has a crosslinked structure. The crosslinked thermoplastic resin has an effect of physically retaining the shape. Furthermore, since there is also a function of fixing the conductive particles, the reproducibility (returnability) of the electrical resistance under the temperature rising / falling cycle is improved when the temperature is changed. Therefore, the PTC element of the present invention can be suitably used as a temperature sensor.
In the present invention, the thermoplastic resin cross-linked product is not particularly limited as long as it has a cross-linked structure. Preferably, the shear storage elastic modulus G ′ at 25 ° C. is 1 kPa or more from the viewpoint of the above properties.

  The thermoplastic resin crosslinked product in the thermistor layer has a glass transition temperature of −150 ° C. or higher and 10 ° C. or lower. More preferably, it is -150 degreeC or more and 0 degreeC or less, More preferably, it is -150 degreeC or less -10 degreeC or less. By having the glass transition temperature at −150 ° C. or higher, the reproducibility (returnability) of the electrical resistance of the organic PTC element under the temperature rising / falling cycle is improved. On the other hand, when the glass transition temperature is 10 ° C. or lower, a PTC element having good sensitivity is obtained. The glass transition temperature can be measured by a technique according to JIS K 7121-1987.

  As a thermoplastic resin that is a precursor of a crosslinked thermoplastic resin, the resin easily expands when it is used as a thermistor layer, the sensitivity is improved, and it is easy to dissolve in a solvent during the production of the thermistor layer. Poly fatty acid vinyl, polydimethylsiloxane, polyvinyl alcohol, polybutadiene, polybutene, polyethylene, polypropylene, polyvinylidene fluoride, polyvinyl fluoride, and the like are used, and two or more of these resins may be used. Among the resins listed above, polyacrylic acid ester, polydimethylsiloxane, and polybutadiene are preferably used because a crosslinked structure can be easily obtained.

  When the mass of the thermistor layer is 100 parts by mass, the thermoplastic resin crosslinked product is preferably 35 parts by mass or more and 65 parts by mass or less, more preferably 38 parts by mass or more and 63 parts by mass or less, and more preferably 40 parts by mass or more. 60 mass parts or less are still more preferable. By being 35 parts by mass or more, the mechanical characteristics of the thermistor layer are maintained. On the other hand, favorable electroconductivity can be hold | maintained because it is 65 mass parts or less.

  The conductive particles used in the present invention are not particularly limited as long as they are conductive particles. From the viewpoint of easy availability, carbon-based particles such as graphite, carbon black, carbon nanotube, and graphene; metal-based particles such as nickel powder, copper powder, and silver powder can be preferably used. Among these, carbon particles are preferred because they are difficult to precipitate when made into a paste. Further, among the carbon-based particles, graphite is preferable because it is easy to obtain a spherical material with good dispersibility.

It is important that the average particle size of the conductive particles used in the present invention is 0.1 μm or more and 10 μm or less. When the average particle size is 0.1 μm or more, there is an effect that the dispersion of the thermoplastic resin is uniformly dispersed in the crosslinked thermoplastic resin, and the sensitivity of the organic PTC element is improved. On the other hand, when the thickness is 10 μm or less, there is an effect of preventing liquid clogging and coating unevenness during the coating process.
Here, the average particle diameter is determined by the average value of the long diameters of 100 arbitrary conductive particles by SEM observation.

It is important that the average circularity of the conductive particles used in the present invention is 0.55 or more and 1.0 or less. When the average circularity is 0.55 or more, there is an effect that the sensitivity when the organic PTC is produced is uniformly dispersed in the crosslinked thermoplastic resin and the organic PTC is produced. Although there is no restriction | limiting in particular about an upper limit, 1.0 or less is preferable substantially.
Here, the circularity is obtained by image analysis of 100 arbitrary conductive particles by SEM observation. The circularity is calculated as follows.
Particle circularity = 4π × (particle projected area) / (particle projected circumference) ²

  The conductive particles are preferably 30 parts by mass or more and 60 parts by mass or less, more preferably 33 parts by mass or more and 55 parts by mass or less, and more preferably 35 parts by mass or more and 50 parts by mass when the mass of the thermistor layer is 100 parts by mass. The following is more preferable. The electroconductivity of a thermistor layer expresses because the ratio of the electroconductive particle which occupies for a thermistor layer is 30 mass parts or more. On the other hand, when the amount is 60 parts by mass or less, the sensitivity of the PTC element is improved.

  About the thermistor layer of the present invention, from the viewpoint of stability, moldability, and conductivity within the scope not departing from the technical idea of the present invention, in addition to the conductive particles and the crosslinked thermoplastic resin, a dispersant, a crosslinking agent, a thermal You may add 3rd components, such as a stabilizer, antioxidant, surfactant, and electroconductive imparting agent, as a component of the thermistor.

  The thermistor layer of the present invention can be formed by printing or coating and drying. Hereinafter, the formation method of the thermistor layer of this invention is demonstrated in detail.

  As a method for forming the thermistor layer in the present invention, since a thin organic PTC element can be easily obtained, the above thermoplastic resin or precursor thereof, conductive particles, and, if necessary, a solvent / plasticizer, etc. A method is selected in which a paste-like material to which is added is applied or printed and then dried and crosslinked and fixed.

Solvents added to the paste-like material include hydrocarbon solvents such as toluene and cyclohexane, ester solvents such as ethyl acetate and γ-butyrolactone, ketone solvents such as methyl ethyl ketone and cyclohexanone, N-methylpyrrolidone and dimethylacetamide. Examples include amide solvents, chlorinated solvents such as dichloromethane and chloroform, and suitable ones are selected according to the solubility of the thermoplastic resin used.
Moreover, when the viscosity of the said paste-form thing is low enough, it is not necessary to add a solvent.

  In the step of preparing the paste, for example, ball mill, bead mill, planetary mill, vibrating ball mill, sand mill, colloid mill, attritor, roll mill, high-speed impeller dispersion, disperser, homogenizer, high-speed impact mill, ultrasonic dispersion, stirring A mechanical stirring method using blades and the like can be mentioned, but it is preferable to select a planetary mill because it can be sufficiently kneaded and dispersed even under high viscosity.

  A method in the coating or printing process for forming the thermistor layer between the pair of electrodes is not particularly limited as long as it can realize a required layer thickness and coating area. Examples of such methods include gravure coater method, small diameter gravure coater method, reverse roll coater method, transfer roll coater method, kiss coater method, dip coater method, knife coater method, air doctor coater method, blade coater method, rod coater. Method, squeeze coater method, cast coater method, die coater method, screen printing method, spray coating method, and ink jet printing method.

  In the present invention, the thickness of the thermistor layer is not particularly limited, but is preferably 5 μm to 50 μm from the viewpoint of rigidity.

  As said drying process, it is preferable to dry at 20-100 degreeC for 1 hour. In the case of thermal crosslinking, a crosslinked structure of the thermoplastic resin is obtained by this drying step. On the other hand, in the case of UV crosslinking, it is preferable to perform UV irradiation after the drying step.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples, and various applications are possible without departing from the technical idea of the present invention.

<Measurement and evaluation method>
First, measurement methods and evaluation methods for various physical property values of samples obtained in Examples and Comparative Examples will be described.

(1) Average particle diameter and circularity of conductive particles The average particle diameter was determined by the average value of the major axis of 100 arbitrary conductive particles by SEM observation. The circularity was determined by image analysis of 100 arbitrary conductive particles by SEM observation. The calculation of the circularity is as follows.
Particle circularity = 4π × (particle projected area) / (particle projected circumference) ²

(2) Glass transition temperature Using a differential scanning calorimeter manufactured by PerkinElmer Co., Ltd., trade name “Pyris1 DSC”, according to JIS K7121, 10 mg of the thermoplastic resin in the thermistor layer was heated at a heating rate of 10 ° C./min. When the temperature is raised from −170 ° C. to 200 ° C. and held at 200 ° C. for 1 minute, then the temperature is lowered to −170 ° C. at a cooling rate of 10 ° C./min, and again when the temperature is raised to 200 ° C. at a heating rate of 10 ° C./min. The glass transition temperature was determined from the measured thermogram.

(3) Thickness of the organic PTC element With a dial gauge of 1/1000 mm, the in-plane of the portion where the thermistor component was applied was measured unspecified at five locations, and the average value was taken as the thickness of the organic PTC element.

(4) Thickness of the thermistor layer The thickness of the thermistor layer was measured by unspecifiedly measuring five in-plane areas of the coated portion of the thermistor component and subtracting the thickness of the substrate from the average value. It was.

(5) Electrical resistance The electrical resistance was measured by measuring the distance between the electrodes of the organic PTC element at room temperature of 25 ° C. by the two-point method.

(6) Conductivity The conductivity of the organic PTC element was evaluated according to the following criteria.
○: Electric resistance is 1000 kΩ or less.
X: Electric resistance exceeds 1000 kΩ.

(7) Electrical resistance change, B constant An organic PTC element was placed on a hot plate (ND-2, manufactured by AS ONE), and the temperature was increased from 25 ° C. to 50 ° C. every 5 ° C. and stabilized in each temperature range. The electrical resistance between the electrodes of the organic PTC element was measured by a two-point method.
The rate of resistance change every 5 ° C. was calculated by the following equation.
Resistance change rate (%) = (Electric resistance at (T + 5) ° C./Electric resistance at (T) ° C.−1) × 100

The B constant from 25 ° C. to 50 ° C. was calculated by the following formula.
B constant (K) = | {ln (R ₂₅ ) −ln (R ₅₀ )} / {(1 / 2298.15) − (1 / 323.15)} |
R ₂₅ : Electric resistance at 25 ° C. R ₅₀ : Electric resistance at 50 ° C.

(8) Sensitivity
The sensitivity of the organic PTC element was evaluated according to the following criteria.
○: B constant at 25 ° C. to 50 ° C. is 2500 K or more and 10000 K or less X: B constant at 25 ° C. to 50 ° C. is less than 2500 K or exceeds 10,000 K

(9) Shape stability
The shape stability of the organic PTC element was evaluated according to the following criteria.
○: The organic PTC element after the B constant measurement maintains the shape before the test.
X: The organic PTC element after a B constant measurement does not maintain the shape before a test.
(10) Returnability
The B constant measurement was performed five times, and the return property was evaluated by dividing the B constant (B ₅ ) measured for the fifth time by the B constant (B ₁ ) measured for the first time.
○: B ₅ / B ₁ is 0.6 or more.
X: B ₅ / B ₁ is less than 0.6.

<Example 1>
(Preparation of thermistor precursor)
50 mass% vinyl group-terminated polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., KE106F) as a thermoplastic resin, 45 mass% spherical graphite (manufactured by Nippon Graphite Co., Ltd., CGB-5), and 10 mass% methylcyclohexane as a solvent. Is stirred at 1500 rpm for 10 minutes with a self-revolving vacuum stirring and defoaming mixer (manufactured by EME, V-mini300), allowed to cool to room temperature, and then a curing agent (manufactured by Shin-Etsu Chemical Co., Ltd., CAT-106F) is 5% by mass. Was added, and the mixture was stirred at 1500 rpm for 3 minutes with a self-revolving vacuum stirring and defoaming mixer (manufactured by EME, V-mini300) to obtain a paste-like material serving as a thermistor precursor.

(Preparation of base film with electrode)
Use a # 10 bar coater with an ethanol solution (concentration 2.0 mass%) of polyvinylpyrrolidone (Nacalai Tesque, K-90) on a polyimide film (Ube Industries, Upilex-S 50S) having a thickness of 50 μm as a base material. Coated and crosslinked with a UV irradiation device.
On the surface of the obtained film, silver nanocolloid (manufactured by Mitsubishi Materials Kasei Co., Ltd., H-1) is printed in an interdigital shape as shown in FIG. 2 using an inkjet printer (manufactured by Seiko Epson Corporation, PX-1004). The base film with an electrode was produced by drying at 150 ° C. for 10 minutes.

(Production of organic PTC element)
An organic PTC element is manufactured by pouring the paste-like material, which is a thermistor precursor, with a thickness of 50 μm between the electrodes of the above-mentioned base film with electrodes and thermally crosslinking in an oven at 120 ° C. for 1 hour. did. The glass transition temperature of the crosslinked thermoplastic resin in the thermistor layer was −125 ° C. The evaluation results are shown in Table 1.

<Example 2>
A target organic PTC element was prepared in the same manner as in Example 1 except that cyclohexanone was not used as a solvent. The evaluation results are shown in Table 1.

<Example 3>
55% by mass of polyethylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., A-400) as a thermoplastic resin precursor, 45% by mass of spherical graphite (manufactured by Nippon Graphite Co., Ltd., CGB-5), and acetic acid as a solvent 10% by mass of butyl was stirred at 1500 rpm for 10 minutes in a self-revolving vacuum stirring defoaming mixer (manufactured by EME, V-mini300), allowed to cool to room temperature, and then a curing agent (manufactured by Nacalai Tesque, benzoyl peroxide) 0 0.5 mass% was added, and it stirred at 1500 rpm for 3 minutes with the self-revolving vacuum stirring deaerator mixer (the EME company make, V-mini300), and obtained the paste-form thing used as the precursor of a thermistor. Thereafter, an organic PTC element was produced by applying to a base film with an electrode in the same manner as in Example 1 and performing thermal polymerization and thermal crosslinking. The glass transition temperature of the crosslinked thermoplastic resin in the thermistor layer was −20 ° C. The evaluation results are shown in Table 1.

<Comparative Example 1>
50 mass% of vinyl group-terminated polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., KE106F) as a thermoplastic resin, 45 mass% of acetylene black (manufactured by Denka Kogyo Co., Ltd., HS-100) as a conductive resin, and 50 mass% of methylcyclohexane as a solvent. Is stirred at 1500 rpm for 10 minutes with a self-revolving vacuum stirring and defoaming mixer (manufactured by EME, V-mini300), allowed to cool to room temperature, and then a curing agent (manufactured by Shin-Etsu Chemical Co., Ltd., CAT-106F) is 5% by mass. Was added, and the mixture was stirred at 1500 rpm for 3 minutes with a self-revolving vacuum stirring and defoaming mixer (manufactured by EME, V-mini300) to obtain a paste-like material serving as a thermistor precursor. Thereafter, an organic PTC element was produced by applying to a base film with an electrode in the same manner as in Example 1 and performing thermal polymerization and thermal crosslinking. The evaluation results are shown in Table 1.

<Comparative example 2>
(Preparation of thermistor precursor)
72 mass% of vinyl group-terminated polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., KE106F) as a thermoplastic resin, 15 mass% of acetylene black (manufactured by Denka Kogyo Co., Ltd., HS-100), and 10 mass of methylcyclohexane as a solvent. Is stirred at 1500 rpm for 10 minutes in a self-revolving vacuum stirring and defoaming mixer (manufactured by EME, V-mini300), allowed to cool to room temperature, and then 7% by mass of a curing agent (manufactured by Shin-Etsu Chemical Co., Ltd., CAT-106F). Was added, and the mixture was stirred at 1500 rpm for 3 minutes with a self-revolving vacuum stirring and defoaming mixer (manufactured by EME, V-mini300) to obtain a paste-like material serving as a thermistor precursor. Thereafter, an organic PTC element was produced by applying to a base film with an electrode in the same manner as in Example 1 and performing thermal polymerization and thermal crosslinking. The evaluation results are shown in Table 1.

<Comparative Example 3>
An organic PTC element was produced in the same manner as in Example 1 except that scaly graphite (manufactured by Nippon Graphite Co., Ltd., J-CPB) was used instead of spherical graphite. The evaluation results are shown in Table 1.

<Comparative example 4>
An organic PTC element was produced in the same manner as in Example 1 except that the crosslinking agent was not added. The evaluation results are shown in Table 1.

In Examples 1 to 3, PTC elements having excellent electrical characteristics and sensitivity were obtained.
On the other hand, in Comparative Examples 1 and 2, since the conductive particles were too small, they easily aggregated, and good sensitivity as a temperature sensor could not be obtained. In Comparative Example 3, since the circularity of the conductive particles was low, aggregation was likely to occur, and good sensitivity as a temperature sensor could not be obtained. In Comparative Example 4, since the thermoplastic resin does not have a cross-linked structure, shape retention when the temperature was increased or decreased was insufficient.

  The organic PTC element of the present invention can be used for applications such as a self-control heating cable, an overcurrent protection device, and a contact control element that are conventionally known as PTC element applications. Further, since the organic PTC element of the present invention has a larger measurable temperature range than the conventional PTC element, its use is greatly expected in applications such as temperature compensation of a temperature sensor or humidity sensor, or temperature compensation of a semiconductor.

11: Base material 12: Electrode 13: Thermistor layer

Claims (7)

An organic PTC element having at least a pair of electrodes and having a thermistor layer between the pair of electrodes,
The thermistor layer includes a crosslinked thermoplastic resin and conductive particles,
The thermoplastic resin crosslinked product has a glass transition temperature of −150 ° C. or more and 10 ° C. or less,
The conductive particles are organic PTC elements having an average particle diameter of 0.1 μm or more and 10 μm or less and a circularity of 0.55 or more and 1.0 or less.   2. The organic PTC element according to claim 1, wherein the thermoplastic resin cross-linked product is 35 parts by mass or more and 65 parts by mass or less when the mass of the thermistor layer is 100 parts by mass.   The organic PTC element according to claim 1, wherein the conductive particles are carbon-based particles.   The organic PTC element according to any one of claims 1 to 3, wherein a rate of change in resistance every 5 ° C from 25 ° C to 50 ° C is 12% to 200%.   The organic PTC element according to any one of claims 1 to 4, wherein a B constant from 25 ° C to 50 ° C is 2500 K or more and 10,000 K or less.   The temperature sensor using the organic PTC element in any one of Claims 1-5.   The method for producing an organic PTC element according to claim 1, wherein the thermistor layer is formed by printing or coating and drying.

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