JPS63138703A - Ptc device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to electrical resistance elements, and in particular, the present invention relates to electrical resistance elements, in particular, the property that the electrical resistance rapidly increases in a relatively narrow temperature range as the temperature rises (PT
C characteristics (positive temperature)
The present invention relates to a resistive element having a PTC element, that is, a PTC element.

[Conventional technology]

Substances with PTC characteristics (PTC compositions) are self-contained substances based on Joule heat when a circuit containing a control element, a positive temperature coefficient thermistor (PTC therilster), a heat-sensitive sensor, a battery, etc. that stops generating heat when the heater reaches a certain temperature is short-circuited. It can be used as a circuit protection element, etc., in which the resistance value increases due to heat generation to limit overcurrent to a predetermined current or less, and on the other hand, the circuit returns to normal when the current is removed. Various materials have been developed as PTC compositions, including ceramic materials made by adding monovalent or trivalent metal oxides to B a T i O 3 and conductive materials added to polymers such as polyethylene. Examples include dispersed polymer-based radish.

Conventionally, as shown in FIG. 3, the PTC element 1 mainly consists of a polymer-based PTC composition 2, two metal electrode plates 3 sandwiching the composition, and leads (terminals) 4 connected to the electrode plates. Consisting of The method for manufacturing this PTC element is, for example, by first preparing a PTC composition, then thermocompressing electrodes such as rolled nickel foil onto the top and bottom of a film to form a laminate, and then applying the laminate to a predetermined shape. The PTC element is manufactured by cutting it to size and welding a lead plate to the electrode surface by spot welding, soldering, etc.

[Problem that the invention seeks to solve]

If the PTC composition is a polymer in which conductive particles such as carbon black are dispersed, the main component is an organic substance with no heat resistance, so a voltage exceeding the withstand voltage may be applied to the PTC element. Also, in conventional PTC devices, when exposed to temperatures well above the melting point of the polymer, the polymers in the PTC composition decompose, burn, or melt, causing the electrodes to touch each other and short circuit. As a result, there was a risk of serious failure in electronic equipment in which the PTC element was incorporated.

This invention was made based on the above background,
The purpose of this is to ensure that the PTC element does not cause short circuits even under severe conditions, such as when a voltage exceeding the withstand voltage of the PTC element is applied, a large current flows, and it is exposed to high temperatures. An object of the present invention is to provide a PTC element with high performance.

[Means for solving problems]

According to this invention, the above-mentioned stress is caused by two or more metal electrodes and a polymer-based PT disposed between the electrodes and electrically connected to each other.
C composition and an inter-electrode short-circuit prevention material disposed between the electrodes, and when a voltage is applied between the electrodes, the PTC
The solution is a PTC element that allows current to flow through the composition.

In a preferred embodiment of the present invention, the short-circuit prevention material can be a fibrous material such as a nonwoven fabric or a woven fabric, or an insulating inorganic material such as a mesh-like sheet.

This invention will be explained in more detail below.

Polymer-based PTC composition The PTC element used in the present invention usually consists of two or more electrodes and a polymer-based PTC composition electrically connected to the electrodes. This PTC composition includes, for example, a mixture of a polymer and conductive particles.

Polymers that can be used in this invention include polyethylene, polyethylene oxide, -4-polybutadiene, polyethylene acrylate, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, polyester, polyamide, polyether, Polycaprolactam, fluorinated ethylene-propylene copolymer,
Chlorinated polyethylene, chlorosulfonated ethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, styrene-acrylonitrile copolymer, polyvinyl chloride, polycarbonate, polyacetal, polyalkylene oxide, polyphenylene oxide, polysulfone, fluororesin, and the like There are at least two types of blend polymers selected from the following. In this invention, the type of polymer, composition ratio, etc. can be appropriately selected depending on desired performance, use, etc.

Furthermore, as the conductive particles dispersed in the polymer, particles of conductive substances such as carbon black, graphite, carbon powder, tin, silver, gold, and copper, and ceramic particles plated with silver or copper may be used. can. In preparing the PTC composition, in addition to the above-mentioned polymer and conductive particles, various additives can be mixed as necessary. Such additives include, for example, flame retardants such as antimony compounds, phosphorus compounds, chlorinated compounds, and brominated compounds, antioxidants, stabilizers, thermally conductive particles, and the like.

In the present invention, the PTC composition is prepared by blending and kneading raw materials, polymers, conductive particles, and other additives in predetermined proportions.

PTC Element The PTC element of this invention consists of the above-mentioned PTC composition and two or more electrodes in contact with it. The types of electrode materials that can be used here are metals that can be used as ordinary electrodes, such as nickel, cobalt, aluminum, chromium, tin, copper, silver, iron (stainless steel), etc. (including iron alloys such as steel),
These include zinc, gold, lead, and platinum. It is desirable that the shape, dimensions, etc. of the electrodes be appropriately selected depending on the use of the PTC element. In this invention, the electrode material may be annealed metal in addition to rolled metal foil. Here, annealing is performed by heating the metal to a predetermined temperature and then slowly cooling it. Annealing conditions such as heating rate, heating temperature, heating time, heating atmosphere, cooling rate, and cooling atmosphere are appropriately selected depending on the material of the metal to be heat treated.

Short-circuit prevention material In this invention, the short-circuit prevention material is disposed between electrodes, and when a high voltage is applied or exposed to high temperature,
Even if the polymer-based PTC composition burns, decomposes, or melts, it has the function of preventing the electrodes from coming into electrical contact with each other. The short-circuit prevention material is preferably an insulating inorganic material.

This short-circuit prevention material has a function of preventing the electrodes from electrically contacting each other, but the PTC composition electrically connects the electrodes. Therefore, this short circuit prevention material is PT
C Does not disturb the continuity of the composition. The shape of such a short-circuit prevention material is one having through holes such as a mesh shape or a fiber snout shape, and examples thereof include an insulating inorganic net, a nonwoven fabric, and a woven fabric. Preferred short-circuit prevention materials include the above-mentioned insulating inorganic materials having flexibility. This is because this material serves to separate the electrodes from each other even if the polymer melts at high temperatures and melts off the PTC element. It is desirable that the thickness of this short-circuit prevention material be changed appropriately depending on the thickness of the PTC element and the thickness of the PTC composition.Although the maximum thickness is limited to the thickness of the PTC element, at least A thickness of 10 μm is desirable. When the short-circuit prevention material has through holes, it is preferable that the total open area of the holes be as wide as possible. It connects P through its through hole.
This is because the continuity of the TC composition is maintained and current can flow through the PTC composition.

Method for manufacturing a PTC element An example of a method for manufacturing a PTC element of the present invention will be explained.

First, a PTC composition is prepared and molded into a predetermined size and shape. Next, a short-circuit prevention material is prepared, and if necessary, treated with a coupling agent to improve the adhesion between the PTC composition and the short-circuit prevention material. Next, in this invention, the PTC composition and the electrode are bonded. A laminate is formed by hot-pressing metal electrodes on the top and bottom of the obtained film-like PTC composition, and a laminate is formed by bonding the electrode plates and the PTC composition using a conductive adhesive. During this joining,
A short-circuit prevention material can be mixed into the PTC composition in advance, but it is also possible to layer a short-circuit prevention material on a film-like PTC composition and then hot-press metal electrodes on top and bottom of the short-circuit prevention material to form a laminate. Alternatively, a laminate can be formed by bonding the electrode plate, the PTC composition, and the short-circuit prevention material using a conductive adhesive. The latter method of simultaneous lamination is industrially efficient and advantageous. In addition, the electrode plate and the PTC composition may be bonded using a conductive adhesive.

A PTC element can be manufactured by cutting this laminate into a predetermined size and connecting lead wires to the electrode surfaces by spot welding, soldering, or the like. Figure 1 shows a PTC according to this invention.
An example of an element is shown. In this example, the short circuit prevention material is an inorganic woven fabric 5
The PTC composition is physically set.

In addition to the inorganic woven fabric in this example, the short-circuit preventing material may also be in the form of a mesh as shown in FIG.

A heat dissipation layer can also be provided on the entire outer surface of the PTC element or a part thereof. The heat dissipation layer made of a coloring material is, for example, P
It can be formed by coating or spraying a paint on the surface of the TC element. It is desirable to select a color, tone, etc. that has excellent heat dissipation. For example, there is a black coating film as a layer made of such a coloring material, and this black coating improves the heat dissipation effect by about 20%. The film thickness is PT
Various changes can be made depending on the use of the C element. As a heat dissipation layer made of an uneven film, there are a surface layer with a roughened surface, a rough plated layer, and the like. Surface roughening and plating can be carried out by conventional methods, and it is preferable to carry out the process under conditions that maximize the heat dissipation effect.

A coating film may also be formed on the outer surface of the PTC element using a resin such as an epoxy resin or a phenol resin. This resin preferably has insulation properties, more preferably PTC
This is a resin that has adhesive properties on the element surface. This coating film can be formed by, for example, spraying or dipping.

[For production]

Since this invention is configured as described above, it has the following effects.

When a voltage exceeding the withstand voltage of the PTC element is applied, when a large current flows due to a short circuit, or when exposed to an atmosphere with a temperature far exceeding the melting point of the polymer, PTC
The polymers of the TC composition burn, decompose, or melt. In this invention, the short-circuit prevention material is disposed between the electrodes, so that even if the polymer burns, decomposes, or melts, the electrodes do not come into contact with each other, thus preventing short circuits. In embodiments where the short-circuit prevention material is flexible, it has the advantageous function of opening the circuit.

〔Example〕 This invention will be specifically explained by way of example.

Example 1 A PTC composition having the following composition was prepared.

Weight% Polymer...High density polyethylene...
60 (manufactured by Toyo Soda Co., Ltd., Nipolon Hard 5100) Conductive particles...Carbon black...38 (
Manufactured by Asahi Carbon Co., Ltd., Asahi 55) Phenolic antioxidant 2
(Irganox 1010, manufactured by Ciba Geigy) These raw materials were kneaded to prepare a PTC composition, which was molded. This PTC composition and 5
Insert a glass cloth with a diameter of 0μ (opening area 5mm + square),
They were laminated and crimped using a hot press and cut into 110×10a pieces. Next, a PTC element was prepared by bonding leads to the electrodes.

A test was conducted by applying 300 V between the lead terminals of the obtained PTC element to burn and decompose the polymer component.

As a result, glass cloth remained between the electrodes, resulting in an insulating state.

Comparative Example 1 A PTC element was prepared and tested in the same manner as in Example 1, except that no glass cloth was used.

As a result, the polymer components burned, decomposed, and the electrodes touched each other and shorted. Resistance between leads is 2-10Ω
The value of

〔Effect of the invention〕

The PTC element of the present invention having the above-described configuration and functioning has the following effects.

As demonstrated in the examples, the PTC element of the present invention allows the PTC element to withstand applied voltages, currents, and
Even in an emergency when heat is applied, the electrodes do not come into contact with each other, making the PTC element insulating, and a highly reliable PTC element can be provided easily and at low cost.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a PTC element according to the present invention;
FIG. 2 is a perspective view showing an example of the short circuit prevention material according to the present invention;
FIG. 3 is a perspective view showing an example of a conventional PTC element. 1... PTC element, 2... PTC composition, 3...
Electrode, 4... Lead, 5... Inorganic short circuit prevention material, 6.
・Me-sauche type short circuit prevention material.

Claims (1)

[Claims] Consisting of one or more metal electrodes and a polymer-based PTC composition disposed between the electrodes and electrically connected, when a voltage is applied between the electrodes, the PTC composition 1. A PTC element through which a current can flow, characterized in that an inter-electrode short-circuit prevention material is disposed between the electrodes. 2. The PTC element according to claim 1, wherein the short circuit prevention material is an insulating inorganic material. 3. The PTC element according to claim 2, wherein the short-circuit prevention material is a mesh-like sheet. 4. The PTC element according to claim 2, wherein the short-circuit preventing material is a fibrous material. 5. The PTC element according to claim 4, wherein the short circuit prevention material is a nonwoven fabric or a woven fabric.