JP6801193B2 - Organic NTC element - Google Patents

Description

The present invention relates to an organic NTC (negative semiconductor device) element, and more specifically, it is used for temperature detection of a battery of a mobile phone, a mobile communication device, a personal computer or the like, an IC of an electronic device, a transistor, a crystal transmitter, a liquid crystal display. It relates to an organic NTC element used for temperature compensation of a display or the like.

The organic NTC element has a negative temperature characteristic with respect to electrical resistance, and has a property that the electrical resistance decreases as the temperature rises. Utilizing such properties, organic NTC elements are widely used in temperature sensors and temperature compensation.
As a conventional NTC element thermistor, a composite oxide obtained by selecting two or more types of oxides of transition metals such as manganese, cobalt, nickel, iron, and copper and firing a raw material mixed in a predetermined ratio at a high temperature. Ceramics are known (Patent Document 1). However, since the production of this thermistor requires firing at a high temperature, there is a problem that the NTC element cannot be directly formed on the substrate, soldering is required, and the process becomes complicated.

To solve such a problem, an organic thermistor element using a conjugated conductive polymer that does not require high-temperature firing has been reported, but the electrical resistance and temperature dependence are uniquely dependent on the type and doping amount of the conjugated conductive polymer. Therefore, there is a problem that it is difficult to finely adjust the physical properties only with the conjugated conductive polymer (Patent Document 2).
On the other hand, it has been reported that a thin-film organic PTC element can be produced in cans and stools by applying a slurry obtained by dissolving and dispersing a conductive powder and a resin in a solvent. However, the PTC element becomes electric as the temperature rises. It is not suitable for temperature sensors because it has the property of increasing resistance (Patent Document 3).
In order to produce an organic NTC element in such a system, it is necessary to use a special carbon black that has undergone surface polymerization, which causes a problem that it is difficult to industrialize (Patent Document 4).

Japanese Unexamined Patent Publication No. 05-021209 Japanese Unexamined Patent Publication No. 03-211702 International Publication No. 2013/047122 Japanese Unexamined Patent Publication No. 63-11701

The problem to be solved by the present invention is to obtain an organic NTC element having good conductivity and sensitivity with good productivity by a simple method.

The present inventors have focused on solving such a problem by an organic NTC device having at least a pair of electrodes and having a thermistor layer containing hollow conductive particles and a binder resin in a specific ratio between the pair of electrodes. The present invention has been completed. The gist of the present invention is as follows.

[1] An organic NTC element having at least a pair of electrodes and having a thermistor layer between the pair of electrodes. The thermistor layer contains hollow conductive particles and a binder resin, and the ratio of the hollow conductive particles is the thermistor. layer 5 parts by mass or more, per 100 parts by 50 parts by Ri der hereinafter organic NTC element porosity of the hollow conductive particles Ru der least 50% by volume.

[2] The organic NTC device according to [1], wherein the average primary particle size of the hollow conductive particles is 20 nm or more and 5000 nm or less.

[3] The organic NTC device according to [1] or [2], wherein the hollow conductive particles are hollow conductive carbon particles.

[4] The organic NTC device according to any one of [1] to [3], which comprises a thermoplastic resin having a glass transition temperature of −50 ° C. or higher and 80 ° C. or lower in the binder resin.

[5] The organic NTC device according to any one of the thermistor layer and the electrode is Ru Oh on the same substrate surface [1] to [4].

[6] The organic NTC device according to any one of [1] to [5], wherein the B constant from 25 ° C. to 50 ° C. is 100 K or more and 10000 K or less.

The organic NTC element proposed by the present invention can easily obtain a thin film by a coating process, has good conductivity and sensitivity, and can be suitably used for inrush current control of a temperature sensor or a circuit.

It is sectional drawing which showed an example of the structure of the organic NTC element of this invention.

Hereinafter, an example of the embodiment of the present invention will be described.

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

1. 1. Organic NTC element The organic NTC element of the present invention is an organic NTC element having at least a pair of electrodes and having a thermistor layer between the pair of electrodes. The thermistor layer contains hollow conductive particles and a binder resin, and the hollow is formed. The proportion of the conductive particles is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the thermistor layer. As an example of a specific embodiment, as shown in FIG. 1, at least one pair of electrodes and a thermistor layer arranged between the electrodes are provided on the base material.
The mode of the element is roughly classified into a laminated type in which a thermistor layer is sandwiched between two flat electrodes and a flat type in which two flat electrodes and a thermistor layer are arranged in parallel on the same substrate surface. The flat type is preferable from the viewpoint that the size is small and the film can be made thinner.
In the case of the flat type, an electrode is formed by printing silver vapor deposition or silver ink on a film such as polyethylene terephthalate or polyimide as a base material or pasting silver foil or copper foil, and then a thermistor layer is formed on the base material between the electrodes. The method of applying the composition constituting the above is convenient and preferable.
In the present invention, an adhesion layer, a thermistor layer, a protective layer for protecting the electrodes, and the like may be provided in order to improve the adhesion to the base material.

In the organic NTC device of the present invention, the electric resistance at room temperature (25 ° C.) is preferably 10Ω or more and 50kΩ 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, when it is 50 kΩ or less, there is an effect that the heat generation of the element can be reduced.

In the organic NTC device of the present invention, it is important that the B constant is 100 K or more and 10000 K or less from 25 ° C. to 50 ° C. When the B constant is 100 K or more, sufficient accuracy can be exhibited when incorporated as a temperature sensor. On the other hand, when the current is 10,000 K or less, there is an effect that a sudden current fluctuation when incorporated in an electronic circuit can be suppressed. The B constant can be measured by the method described later.

In the organic NTC element of the present invention, the minimum radius (minimum allowable radius) when the element is bent is preferably larger than 0 mm and 150 mm or less. The minimum permissible bending radius is the smallest cylinder that can be wound by winding the organic NTC element around a cylinder with an arbitrary radius from 150 mm to 5 mm so that the base material layer is on the inside, without cracking or peeling. It can be determined by measuring the diameter.

Hereinafter, the thermistor layer, electrodes, and base material constituting the organic NTC device of the present invention will be described in detail.

2. 2. Thermistor layer In the thermistor layer used in the present invention, the thermistor layer contains hollow conductive particles and a binder resin, and the proportion of the hollow conductive particles is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the thermistor layer. It is a feature. When the proportion of the hollow conductive particles is 5 parts by mass or more, sufficient conductivity can be exhibited when the NTC element is used. On the other hand, when it is 50 parts by mass or less, sufficient temperature responsiveness can be exhibited when the NTC element is used.

It is important that the hollow conductive particles used in the present invention are hollow. Being hollow means having voids inside the particles, but the hollow conductive particles of the present invention preferably have a porosity of 50% by volume or more, preferably 55% by volume or more. More preferably.

The porosity was measured by the method described in JP2012-216537A. That is, as shown in FIG. 2 in the above publication, a tangent line (L) to the minimum value of the slope based on the pore distribution (integral curve) (L) obtained by the known Hg porosymometry measurement (mercury injection method). M) is drawn to obtain the branch point (P) between the tangent line (M) and the integral curve (L), and the pore volume smaller than the branch point is the intraparticle pore volume (cm ³ / g) (V). Defined as. The porosity can be calculated from the obtained amount of pores in the particles and the true density of graphite. As the true density of graphite used for the calculation, 2.26 g / cm ³ , which is the true density of general graphite, is used. The calculation formula is shown in Equation 1.

Equation 1
Porosity (%) = [Amount of pores in particles / {Amount of pores in particles + (1 / true density of graphite)}] x 100

Although the detailed mechanism is unknown, the hollow conductive particles have the effect of exhibiting NTC characteristics. It is presumed that the hollowness of the conductive particles increases the contribution of expansion and contraction to temperature, and the NTC characteristics are exhibited.
Examples of the hollow conductive particles used in the present invention include hollow carbon particles, hollow gold nanoparticles, and hollow silver nanoparticles. From the viewpoint of flexibility and availability of the hollow conductive particles, the hollow conductive carbon particles are used. preferable.
Examples of hollow carbon particles include Ketjen Black (manufactured by Lion Specialty Chemicals Co., Ltd.), Carbon Nano Balloon (manufactured by Toyohashi Campus Innovation Co., Ltd.), and Lignin Black (manufactured by Daio Paper Corporation).

The average primary particle size of the hollow conductive particles used in the present invention is preferably 20 nm or more and 5000 nm or less, more preferably 20 nm or more and 3000 nm or less, and further preferably 20 nm or more and 2000 nm or less. When the average primary particle size is 20 nm or more, NTC characteristics are exhibited. On the other hand, when it is 5000 nm or less, it is possible to prevent separation when the slurry is formed and to obtain a thin film NTC element having excellent smoothness. The average primary particle size can be measured by the arithmetic mean diameter obtained by observing with an electron microscope.

The binder resin used in the present invention preferably contains a thermoplastic resin. By using the thermoplastic resin, the elastic modulus of the resin decreases when the temperature rises, which has the effect of assisting the expansion of the hollow conductive particles. Examples of the thermoplastic resin include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, poly-1,4-cyclohexylene methylene terephthalate, polyethylene succinate, polybutylene succinate, polylactic acid, and Polyester-based resins such as poly-ε-caprolactam; polyethylene-based resins such as high-density polyethylene, low-density polyethylene, and linear polyethylene; ethylene-vinyl acetate copolymers and ethylene- (meth) acrylic acid copolymers, Ethylene- (meth) acrylic acid ester copolymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate-carbon monoxide copolymer, ethylene-vinyl acetate-vinyl chloride copolymer , And ethylene-based copolymers such as ethylene-α-olefin copolymers; acrylic copolymers such as methyl methacrylate and acrylonitrile-methyl acrylate copolymers; polypropylene-based resins; polybutene-based resins; polyamide-based resins; polyoxy Methylene-based resin; Polymethylpentene-based resin; Polypolyalcohol-based resin; Fluorine-based resin such as polytetrafluoroethylene and polyfluorinated vinyl acetate; Cellulous resin; Engineering plastics such as polyphenylene sulfide and polyparaphenylene terephthalamide; Super engineering plastics, etc. Can be mentioned. Among these, ethylene-based copolymers and acrylic-based resins are preferable.

The glass transition temperature of the thermoplastic resin used as the binder resin is preferably −50 ° C. or higher and 80 ° C. or lower, more preferably −30 ° C. or higher and 60 ° C. or lower, and further preferably −20 ° C. or higher and 50 ° C. or lower. When the glass transition temperature is −50 ° C. or higher, there is an effect that the electric resistance when incorporated as an organic NTC element is stable. On the other hand, when the glass transition temperature is 80 ° C. or lower, there is an effect of suppressing cracking and peeling of the thermistor layer. The glass transition temperature can be measured by a method according to JIS K 7121-1987.

The ratio of the binder resin to 100 parts by mass of the thermistor layer is 50 parts by mass or more and 95 parts by mass or less. Within this range, an element without cracking or peeling can be produced, and hollow conductive particles can also exert their functions.

In the present invention, in addition to the conductive particles and the binder resin, a dispersant, a cross-linking agent, a heat stabilizer, an antioxidant, from the viewpoint of stability, moldability, and conductivity within a range not deviating from the technical idea of the present invention. A third component such as a surfactant, an ionic liquid, or a semiconductor polymer may be added as a component of the thermista layer.

The method for forming the thermistor layer used in the present invention mainly includes the following three methods, but the method (1) by coating and drying is preferable because a thin-film organic NTC element can be easily obtained.
(1) Method of applying and drying a solution slurry containing hollow conductive particles and a binder resin (2) Method of melting and kneading hollow conductive particles and a binder resin and rolling to obtain a sheet (3) Binder resin A method of dispersing hollow conductive particles in a monomer that is a precursor of

The coating method in the coating step is not particularly limited as long as it can realize the required layer thickness and coating area. Examples of such coating methods include a gravure coater method, a small diameter gravure coater method, a reverse roll coater method, a transfer roll coater method, a kiss coater method, a dip coater method, a knife coater method, an air doctor coater method, a blade coater method, and a rod. Examples thereof include a coater method, a squeeze coater method, a cast coater method, a die coater method, a screen printing method, a spray coating method, and an inkjet method.

As the solvent of the solution slurry, water; an amide solvent such as N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide; an ether solvent such as tetrahydrofuran and dioxane; a ketone solvent such as acetone and methyl ethyl ketone. Solvents; lower alcohols such as ethanol and isopropyl alcohol; acetonitrile, glycols, glycerin, lactic acid esters and the like can be mentioned, but in terms of the environment, water alone or a mixed solvent of alcohol and water is preferable.

In the step of preparing the slurry, for example, a ball mill, a bead mill, a planetary ball mill, a vibrating ball mill, a sand mill, a colloid mill, an attritor, a roll mill, a high-speed impeller dispersion, a disperser, a homogenizer, a high-speed impact mill, an ultrasonic dispersion, a stirring blade, etc. The mechanical stirring method by the above can be mentioned.

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.

3. 3. Electrodes As the electrodes, known conductive materials can be preferably used. Examples of the form include a lump, a film, a linear, and the like, but the film is preferable in that both thinning and conductivity can be achieved.
Conductive materials include gold, silver, copper, iron, platinum, palladium, tin, lead, zinc, chromium, nickel, aluminum, magnesium, carbon, indium tin oxide (ITO), antimonz tin oxide (ATO), And zinc tin oxide (ZTO) and the like can be mentioned, but gold, silver, copper, aluminum, and carbon are preferable from the viewpoint of conductivity stability and contact resistance.

The thickness of the electrode is not particularly limited, but is particularly preferably 0.01 μm to 40 μm from the viewpoint of rigidity.

4. Base material In the present invention, it is preferable that the thermistor layer and the electrode are coated or vapor-deposited on the same base material. As the base material, a polyester resin film such as polyethylene terephthalate or polyethylene naphthalate, an imide resin film such as polyetherimide or polyimide, or a thin film glass is preferably used.
On the other hand, in the present invention, the thermistor layer can be formed by directly applying the composition constituting the thermistor layer between the electrodes without using a base material.

The thickness of the base material is not particularly limited, but is preferably 30 μm to 400 μm, particularly preferably 50 μm to 200 μm from the viewpoint of rigidity.

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

Generally, a "film" is a thin, flat product whose thickness 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 JISK6900), generally, "sheet" refers to a product that is thin by definition in JIS and whose thickness is generally small for its length and width. However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish between the two in the present invention, the term "film" is used to include the "sheet" and is referred to as the "sheet" in the present invention. Even if it is, it shall include "film".

Examples will be shown below and the present invention will be described in more detail. However, the present invention is not limited thereto, and various applications are possible without departing from the technical idea of the present invention.

<Measurement and evaluation method>
First, a method for measuring and evaluating various physical property values of the samples obtained in Examples and Comparative Examples will be described.

(1) Percentage of Hollow Conductive Particles The proportion of hollow conductive particles per 100 parts by mass of the thermistor layer was determined by dividing the solid content mass of the hollow conductive particles by the total solid content mass of the thermistor.

(2) Thickness of Organic NTC Element An unspecified 5 points were measured in the in-plane of the portion coated with the thermistor component with a dial gauge of 1/1000 mm, and the average value was taken as the thickness of the organic NTC element.

(3) Thickness of the thermistor layer In the produced organic NTC, the thickness of the thermistor layer is measured by unspecifiedly measuring 5 points in the plane of the portion coated with the thermistor component and subtracting the thickness of the base material from the average value. And said.

(4) Electrical resistance The distance between the electrodes of the organic NTC element was measured by a two-point method at room temperature of 25 ° C. to obtain electrical resistance.

(5) Conductivity The conductivity of the organic NTC element was evaluated according to the following criteria.
◯: The electrical resistance is 50 kΩ or less.
X: The electrical resistance exceeds 50 kΩ.

(6) B constant Organic NTC element is installed on a hot plate (manufactured by AS ONE Corporation; ND-2), the temperature is raised from 25 ° C to 50 ° C in 5 ° C increments, and the temperature is stabilized in each temperature range. The electrical resistance between the electrodes of the device was measured and plotted by the two-point method.
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 / 298.15)-(1 / 323.15)}
R ₂₅ : Electrical resistance at 25 ° C R ₅₀ : Electrical resistance at 50 ° C

(7) Sensitivity
The sensitivity of the organic NTC device was evaluated according to the following criteria.
◯: B constant from 25 ° C. to 50 ° C. is 100K or more and 10000K or less ×: B constant from 25 ° C. to 50 ° C. is less than 100K or more than 10000K (8) Minimum allowable bending radius The base material layer of the organic NTC element By winding the cylinder around a cylinder having an arbitrary radius from 150 mm to 5 mm so as to be inside, the minimum diameter of the cylinder that can be wound without cracking or peeling was determined.
(9) Flexibility The flexibility of the organic NTC device was evaluated according to the following criteria.
⊚: Minimum allowable bending radius is greater than 0 and less than 5 mm ◯: Minimum allowable bending radius is 5 mm or more and 150 mm or less ×: Minimum allowable bending radius exceeds 150 mm.

<Example 1>
(Thermistor precursor slurry)
As hollow conductive particles, 50 parts by mass of Ketjen Black Paste (manufactured by Lion Specialty Chemicals Co., Ltd .: Lion Paste W-311N, average primary particle size 40 nm, porosity 60% by mass) with a solid content of 16.5% by mass, and as a binder resin 50 parts by mass of acrylic resin latex (manufactured by Nippon Zeon Co., Ltd .: Nipol LX-852) having a solid content of 45% by mass was mixed to prepare a precursor slurry of a thermista.

(Preparation of base film with electrodes)
A polyethylene terephthalate film (manufactured by Mitsubishi Plastics: Diafoil T100-50) with a thickness of 50 μm was cut out as a base material to a size of 15 cm × 10 cm, and 15 cm × 2.5 cm aluminum tapes were attached in parallel to each of the two long sides, and a pair A base film with an electrode was obtained by producing the electrode of. At this time, the distance between the electrodes was 5 cm.

(Manufacturing of organic NTC elements)
An organic NTC device is obtained by pouring a thermistor precursor slurry between the electrodes of the above-mentioned base film with electrodes, applying the slurry uniformly using a # 16 bar coater, and drying in an oven at 50 ° C. for 5 minutes. It was. The evaluation results are shown in Table 1.

<Example 2>
Implemented except that Ketjen Black Paste with a solid content of 16.5% by mass (Lion Specialty Chemicals: Lion Paste W-356A, average primary particle size 34 nm, porosity 78% by volume) was used as the hollow conductive particles. The desired organic NTC element was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Comparative example 1>
As hollow conductive particles, 10 parts by mass of Ketjen Black Paste (manufactured by Lion Specialty Chemicals Co., Ltd .: Lion Paste W-311N, average primary particle size 40 nm, void ratio 60% by mass) with a solid content of 16.5% by mass, and as a binder resin An element was obtained in the same manner as in Example 1 except that 90 parts by mass of an acrylic resin latex (manufactured by Nippon Zeon Co., Ltd .: Nipol LX-852) having a solid content of 45% by mass was mixed to prepare a precursor slurry of a thermista. .. The evaluation results are shown in Table 1. The minimum allowable bending radius has not been measured because cracks and peeling have already occurred at the stage of manufacturing the element.

<Comparative example 2>
90 parts by mass of Ketjen Black Paste (manufactured by Lion Specialty Chemicals Co., Ltd .: Lion Paste W-311N, average primary particle size 40 nm, void ratio 60% by mass) with a solid content of 16.5% by mass as hollow conductive particles, and as a binder resin An element was obtained in the same manner as in Example 1 except that 10 parts by mass of an acrylic resin latex (manufactured by Nippon Zeon Co., Ltd .: Nipol LX-852) having a solid content of 45% by mass was mixed to prepare a precursor slurry of a thermista. .. The evaluation results are shown in Table 1.

<Comparative example 3>
8.25 parts by mass of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd .: Denka Black HS-100, average primary particle size 48 nm, porosity 22% by mass) is dispersed as conductive particles in 41.75 parts by mass of ion exchange resin. Subsequently, 50 parts by mass of an acrylic resin latex (manufactured by Nippon Zeon Co., Ltd .: Nipol LX-852) having a solid content of 45% by mass was mixed as a binder resin to prepare a slurry.
The obtained slurry was poured between the electrodes of the above-mentioned base film with electrodes, uniformly applied using a # 16 bar coater, and dried in an oven at 50 ° C. for 5 minutes to obtain an element. The evaluation results are shown in Table 1.

<Comparative example 4>
8.25 parts by mass of natural graphite as conductive particles (manufactured by Nippon Graphite Co., Ltd .: CBG-10, average primary particle size 40,000 nm, porosity 17% by volume) was dispersed in 41.75 parts by mass of an ion exchange resin, followed by As a binder resin, 50 parts by mass of an acrylic resin latex (manufactured by Nippon Zeon Co., Ltd .: Nipol LX-852) having a solid content of 45% by mass was mixed to prepare a slurry.
The obtained slurry was poured between the electrodes of the above-mentioned base film with electrodes, uniformly applied using a # 16 bar coater, and dried in an oven at 50 ° C. for 5 minutes to obtain an element. The evaluation results are shown in Table 1.

In Examples 1 and 2, NTC devices having excellent NTC characteristics were obtained.
On the other hand, in Comparative Example 1, since the amount of hollow conductive particles was small, the electric resistance was high and the element could not be used as an NTC element. In Comparative Example 2, since the amount of hollow conductive particles was too large, the sensitivity of the NTC element was low. In Comparative Examples 3 and 4, since the conductive particles were not hollow, the thermal expansion of the binder resin became predominant and the B constant became negative, and the NTC characteristics were not exhibited and the PTC characteristics were exhibited.

11: Base material 12: Electrode 13: Thermistor layer

Claims (6)

An organic NTC element having at least a pair of electrodes and having a thermistor layer between the pair of electrodes, wherein the thermistor layer contains hollow conductive particles and a binder resin, and does not contain an organic silicon compound polymer. An organic NTC element in which the proportion of hollow conductive particles is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the thermistor layer, and the void ratio of the hollow conductive particles is 50% by volume or more. The organic NTC device according to claim 1, wherein the average primary particle size of the hollow conductive particles is 20 nm or more and 5000 nm or less. The organic NTC device according to claim 1 or 2, wherein the hollow conductive particles are hollow conductive carbon particles. The organic NTC device according to any one of claims 1 to 3, wherein the binder resin contains a thermoplastic resin having a glass transition temperature of −50 ° C. or higher and 80 ° C. or lower. The organic NTC device according to any one of claims 1 to 4, wherein the thermistor layer and the electrode are on the same substrate surface. The organic NTC device according to any one of claims 1 to 5, wherein the B constant from 25 ° C. to 50 ° C. is 100 K or more and 10000 K or less.