WO1998026433A1

WO1998026433A1 - Overcurrent protective circuit element

Info

Publication number: WO1998026433A1
Application number: PCT/JP1996/003628
Authority: WO
Inventors: Kihachiro Nishiuchi; Taro Yamazaki
Original assignee: Otsuka Kagaku Kabushiki Kaisya
Priority date: 1995-06-14
Filing date: 1996-12-11
Publication date: 1998-06-18
Also published as: JPH099482A

Abstract

An overcurrent protective circuit element comprising a PTC conductive composition (1) and at least two electrodes (2) being in contact with the composition (1), wherein the electrodes (2) are composed of nickel foil. The contacting surface of each nickel foil with the composition is plated with nickel for roughening the surface. When the roughed nickel-plated electrodes (2) are used, the power loss of the circuit element can be reduced, because the resistance of the element becomes remarkably lower at a normal temperature as compared with an overcurrent protective element using simple metallic foil. When the temperature becomes higher, in addition, the resistance value of the element abruptly rises to a high value from the resistance value at the normal temperature so as to prevent current from becoming out of control.

Description

Description Overcurrent protection circuit element

Technical field>

The present invention relates to the field of conductive compositions exhibiting a positive temperature coefficient (PTC; positive temperature coefficient) (hereinafter referred to as “PTC conductive composition”), and in particular, to overcurrent using a PTC conductive composition. The present invention relates to a protection circuit element.

Background technology>

The PTC conductive composition, Y ₂ 0 ₃ or the like barium titanate was added small amount of (B a T i 0 ₃₎ or the like of the inorganic composition and the organic composition obtained by dispersing conductive particles in crystalline organic polymer one Matorittasu (For example, see Japanese Patent Application Laid-Open No. 46-27224).

Taking the organic composition as an example, while at a temperature lower than the crystal melting point of polymer matrix, the conductive particles exist only in the amorphous region of the polymer matrix and are connected to the conductive particles. Shows lower resistivity for electrons traveling through the chain. When the temperature rises and the polymer matrix begins to melt, the volume of the amorphous phase increases relative to the volume of the amorphous phase while maintaining the viscosity of the polymer matrix, so that the concentration of the conductive particles in the amorphous phase partially increases. Decreases, resulting in an increase in resistivity (positive temperature characteristic). As the temperature rises further, the viscosity of the polymer matrix decreases, and the conductive particles move freely around the entire amorphous state and rearrange to show sufficient conductivity (negative temperature characteristic) .

The positive temperature characteristic of the PTC conductive composition is generated in a temperature range where the polymer matrix starts to melt (referred to as switching temperature). By utilizing this positive temperature characteristic, the PTC conductive composition is Used for various resistance heating elements.

The basic literature on PTC conductive compositions is, for example, Polymer Engineering and 'Science, Vol. 13, No. 6 November, 1973. There is 322 publication. In the latter literature, PTC conductivity using carbon black as conductive particles and a crystalline thermoplastic polymer (eg, polyethylene, ethylenenoacrylate copolymer, polypropylene, polyvinylidene fluoride) as the polymer matrix A composition is disclosed.

However, since the volumetric change of the matrices due to temperature of the PTC conductive composition is large, when the temperature changes, the contact state and the arrangement state of the conductive particles in the matrix are changed. This tendency sometimes becomes more pronounced with repeated use, and as a result, the switching temperature changes, the desired characteristics are not exhibited, and the room temperature resistivity below the switching temperature deteriorates (increases). Therefore, there was a problem that the temperature of the element was increased, controllability was reduced, and fire occurred.

In addition, in a circuit element in which an electrode is brought into contact with such a conventional PTC conductive composition, the resistance value varies due to slight variations in film thickness in the manufacturing process, variations in dispersion of conductive particles, and variations in curing and drying conditions. In addition, there was a problem that the quality and characteristics were changed, many defects occurred, and the yield was poor.

Therefore, there is a difficulty in using it as a circuit element for a thermistor or the like, and in the past, it was only possible to develop a limited use of a planar heating element or the like (see Japanese Patent Application Laid-Open No. Hei 6-157787). .

However, circuit elements using PTC conductive compositions, such as ceramics, can be made small and thin, and have a large current capacity.For example, they can be incorporated inside the battery to prevent overdischarge of the battery. It is most suitable for the use to do. For this reason, attention has been paid recently, and the emergence of a device with stable operation is desired.

Accordingly, an object of the present invention is to provide a circuit element for overcurrent heating protection which exhibits a low resistivity at room temperature and has a good switching ratio.

Still another object of the present invention is to provide a circuit element for overcurrent heating protection that is stable against repeated use and has a PTC effect with good reproducibility. Invention disclosure>

An overcurrent protection circuit element of the present invention for achieving the above object is a overcurrent protection circuit element having a PTC conductive composition and at least two electrodes in contact with the PTC conductive composition. The electrode is a nickel foil, and the nickel foil is provided with a roughened nickel plating on a contact surface with the PTC conductive composition (Claim 1).

Further, the overcurrent protection circuit element of the present invention comprises: a PTC conductive composition; An overcurrent protection circuit element having two electrodes, wherein the electrode is a nickel foil, and a conductive thin film not exhibiting PTC characteristics is interposed between the nickel foil and the PTC conductive composition. The nickel foil may be provided with a roughened nickel plating on a contact surface with the conductive thin film (claim 2).

According to the overcurrent protection circuit element of the present invention, the use of the roughened nickel plating electrode significantly lowers the resistance at room temperature as compared with the conventional overcurrent protection circuit element using a simple metal foil. Power loss is reduced. In addition, when the temperature rises, the resistance value changes rapidly, indicating high resistance, and the difference from that at normal temperature is further increased, so that the effect of preventing current runaway increases. Therefore, the shape can be made thin.

In addition, it is possible to provide an overcurrent protection circuit element that has a stable resistance value change even when used for some time, so that it can be incorporated in various electric and electronic circuits requiring high reliability.

In particular, since the shape can be made into a thin compact, it can be easily incorporated into a primary battery or a secondary battery, and the battery circuit can be designed to be compact. Can be improved in reliability.

Since the overcurrent protection circuit element of the present invention is a protection circuit element that protects against overheating due to overcurrent, the resistance at room temperature must be lower than that of a normal heating element. The specific resistance of the overcurrent protection circuit element of the present invention at a normal temperature of 25 ° C. must be smaller than 10 Ω · cm, preferably smaller than 3 Ω · cm. To that end, the choice of the PTC conductive composition is not a matter of choice, and the choice of the electrode is a major factor. In the present invention, a nickel foil which has not been hitherto used and has been subjected to a roughened nickel plating is used. A nickel foil having a roughened nickel plating is, for example, a nickel foil having a thickness of about 10 to 300 μm, preferably about 15 to 80 μm, and having a nickel plating on one side and further having irregularities. It has been applied in the form of attachment.

Due to the irregularities, the surface feels uneven when touched, and is visually black. By using this treated electrode, the contact area between the PTC conductive composition and the electrode can be increased, and the adhesion is improved, so that an overcurrent protection circuit element with lower resistance than before can be obtained.

This roughened nickel plating means that a metal mesh, non-leaching metal, A resin sheet or the like used for clean printing is fixed in close contact, and nickel plating is applied by an electric plating method or a chemical plating method.

The porosity (the ratio of the area of the holes to the total area) of the wire mesh, punched metal, resin sheet used for screen printing, etc. may be adjusted in advance with ink or paint.

The electric plating method is performed by adjusting a bath of an aqueous solution of nickel sulfate, nickel chloride, or boric acid, or an aqueous solution of nickel sulfate, ammonium chloride, boric acid, or the like, and passing an electric current under acidic and predetermined temperature conditions. The chemical plating method uses a chemical plating bath containing a small amount of nickel sulfate, sodium hypophosphite, and in some cases, lactic acid, propionic acid, sodium citrate, sodium acetate, and sodium chloride. Perform under conditions.

After the construction, the wire mesh. It removes metal sheet, resin sheet used for screen printing, etc.

As a result, as shown in FIG. 2, fine irregularities adhere to the nickel foil surface, causing light to diffusely reflect. The pitch of the irregularities is determined by the pitch of the holes in the wire netting, bunching metal, resin sheet used for screen printing, and the like, and the pitch is 22〃m-5 mm. Preferably, 30 urn-850 m It is about. The depth of the unevenness is 2 to 15 m, preferably 3 to 8 zm, and more preferably about 5 μm. The overcurrent protection circuit element according to claim 2, wherein the conductive thin film does not show PTC characteristics, and the conductive thin film is made of a conductive material and a binder, and is coated on a PTC conductive composition or a nickel foil to form a thin film. Is preferable in order to obtain a low-resistance overcurrent protection circuit element (claim 3).

The conductive thin film having no PTC element used in the present invention is used to form a thin film such as a carbon paste, a graphite paste, a silver paste or the like usually used for a membrane switch or the like, and the thickness of the film is usually 1-3. 0〃m, preferably about 2 to 15 jam.

Due to the presence of this thin film, ohmic contact with the PTC conductive composition and nickel foil can be more easily realized, and it can be expected that the resistance of the overcurrent protection circuit element at room temperature can be reduced. Wherein the PTC conductive composition, Y ₂ 0 _3, etc. BAT i 0 ₃ was added in a small amount _{of, B a PbT i 0 3,} BaSrT i 0 3 or the like of the inorganic composition and the organic composition and the like. The organic composition is a composition in which conductive particles are dispersed in a thermoplastic resin, and exhibits a positive temperature coefficient (PTC) in a temperature range slightly lower than the crystalline melting point of the polymer (Claim 4). .

The thermoplastic resin includes, for example, polyolefins such as polyethylene and polypropylene, vinyl chloride, vinyl acetate, acrylic acid ester, ABS, polyamide, polyarylenes, PPS, PES.PEEK, polyoxymethylene, polyethylene terephthalate, Polyesters such as polybutylene terephthalate, wholly aromatic polyethylene, polycarbonates, polytetrafluoroethylene, polyvinylidene fluoride, a homopolymer selected from copolymers of thermoplastic resins and graft modified products thereof, or A mixture of two or more polymers can be provided. When polyolefins are used, the composition may be subjected to electron beam crosslinking.

The conductive particles are preferably made of one or more of conductive carbon black, which is an amorphous carbon particle, graphite, which is a crystalline carbon particle, expanded graphite, and fibrous graphite (claim 5). .

The conductive black is, for example, Ketchin black, acetylene black, furnace black or the like.

The graphite is, for example, spherical graphite, flake graphite, expanded graphite, fibrous graphite and the like. Expanded graphite is obtained by expanding the volume of graphite by heating graphite, and is usually used by being crushed to a particle size of about 2 to 100 m.鳞 Since graphite has a low bulk density and a small surface area, it has good dispersibility and wettability, and can obtain a very homogeneous PTC conductive composition, realizing a thin overcurrent protection circuit element. This can be expected.

The present invention comprises a mixture of one or more of these conductive particles, and the particle size of the conductive particles is about 0.1 m to 100 m, preferably about 0.3 m to 50 m. It is.

The conductive particles are obtained by cutting or crushing a carbon fiber shortly and graphitizing black. It may be lead (claim 6).

As the fibrous graphite particles used in the present invention, graphite whiskers are generally used, which is obtained by cutting or crushing a carbon fiber shortly and then graphitizing it in a non-oxidizing atmosphere at 200 ° C or more. is there. The graphite particles have a particle diameter of about 2 to 50 rn, and have a low resistance value and a small variation.

In the PTC conductive composition, it is preferable that part or all of the conductive particles be covered with another type of thermoplastic resin having a melting point different from that of the thermoplastic resin (claims 7 and 8).

The conductive coating is obtained by coating (encapsulating) conductive particles very thinly with a thermoplastic resin according to a known method (see Japanese Patent Application Laid-Open No. 6-157787). The capsule expands in volume by heating and has the effect of converting the PTC conductive composition into an insulator in a very short time.Also, even if the temperature changes mainly due to the surface tension of the encapsulating material, the Maintains shape and does not release conductive material. Therefore, by incorporating the PTC material into the force-pressing composition, superior temperature controllability and aging stability can be obtained as compared with the conventional PTC composition in which the PTC material is simply dispersed in a resin matrix. Therefore, it is expected that a highly reliable overcurrent protection circuit element whose resistance value change is stable even after use over time can be realized.

Specific examples of the encapsulating material include various soft resins, rubbers, elastomers, higher fatty acids, esters, and the like. Soft resins include, for example, silicone resin, polyester resin, fluorine resin, urethane resin, polyethylene resin, polypropylene resin, vinyl acetate resin, vinyl chloride resin, polystyrene resin, polyisoprene resin, and modification of the above resins. And copolymers. Examples of the rubber include fluorine rubber, silicone rubber, urethane rubber, acryl rubber, cyclized natural rubber, butadiene rubber, chloroprene rubber, butadiene latex, acrylonitrile butadiene rubber latex, and acrylic butadiene latex. Examples of the elastomer include polyester elastomer, urethane elastomer, and the like. The distribution ratio of the graphite particles and the encapsulating material is not particularly limited and is wide and can be appropriately selected from the range. However, the function required for the capsule (the function of sharpening the self-temperature control and the flow of current) Considering the function as a conductive material), it is necessary to add about 5 to 50 parts by weight, and preferably about 10 to 40 parts by weight, of the material for forming a forcepsel to 100 parts by weight of the conductive material. Is good. The encapsulation method is not particularly limited, and known methods can be applied. For example, (a) a method in which an encapsulating resin and graphite particles are melted or dispersed in an appropriate solvent and sprayed (b) A method of dissolving the encapsulated resin by heating, adding a conductive material to the mixture, kneading the mixture, and pulverizing the powder. The size of the capsule is not particularly limited, and may be appropriately selected depending on the purpose of use, the active ingredient, and the like. Usually, the particle size is about 1 m to 200 zm, preferably 5 ^ m-100 m. It should be about degree.

In the overcurrent protection circuit element according to claim 1 or 2, the PTC conductive composition may be one in which conductive particles are dispersed in a thermosetting resin (Claim 9).

Thermosetting resins are characterized by low thermal degradation even when temperature rises and falls repeatedly, and excellent reproducibility even when used repeatedly, so that excellent temperature controllability and stability over time can be obtained. In addition to the characteristics of the capsule composition, it can be expected to realize a highly reliable overcurrent protection circuit element having a stable resistance value change even after use over time.

The thermosetting resin preferably contains a thermosetting crosslinked polyorganosiloxane resin.

The thermosetting crosslinked polyorganosiloxane resin contains at least one or more substituent groups such as hydrogen, vinyl group, aryl group, hydroxyl group, alkoxy group having 1 to 4 carbon atoms, amino group, and mercapto group. There are straight silicone resins such as polydimethylsiloxane, polydiphenylsiloxane, polymethylphenylsiloxane, and straight silicone resins such as copolymers thereof, and polyacryloxyalkylalkoxysilane-based and polyvinylsilane-based resins. -Modified epoxy resin obtained by reacting epoxy resin with epoxy resin; polyester-modified silicone resin consisting of condensate of straight silicone resin with polybasic acid and polyhydric alcohol; condensation of straight silicone resin with fatty acid, polybasic acid and polyhydric alcohol Object or straight silicon resin Aruki' de modified silicone resin obtained by reacting Aruki' de resin, storage Amino resin such as melamine formaldehyde resin, urea formaldehyde resin, benzoguanamine, acetoguanamine, etc. Used as rubber, silicone resin, silicone adhesive, silicone coating.

In order to manufacture the overcurrent protection circuit element of the present invention, each step of (i) adjustment of the material, (ii) formation of the material and bonding with the electrode, and (Mi) shape adjustment are usually employed.

(i) Material adjustment

The adjustment of the material in the present invention is to adjust the PTC conductive composition. The PTC conductive composition can be adjusted, for example, by mixing a thermoplastic resin and conductive particles, heating the mixture, and kneading the mixture.

Also, conductive particles coated with a thermoplastic resin, for example, graphite particles coated with a thermoplastic resin, are mixed with a thermosetting resin, for example, a polyorganosiloxane resin, usually in a three-port unit for paint, It may be adjusted by coating.

At the time of adjustment, various additives such as a dispersant, a viscosity adjuster, and a stabilizer may be mixed and adjusted.

The electrodes are, as mentioned above, a wire mesh on the nickel foil surface. An etching metal, a resin sheet used for screen printing, or the like may be adhered and fixed, and a roughened nickel plating may be applied by an electric plating method or a chemical plating method, and the sheet may be peeled off.

Further, a material obtained by applying or printing a conductive thin film that does not exhibit the above-mentioned PTC characteristic on the roughened nickel plating surface and then drying it may be used.

(ϋ) Material formation and bonding with electrodes

The material may be formed by drying the sheet-like material obtained by extrusion molding, and then applying heat and pressure to the electrode and directly applying or printing the melted material on the electrode. To apply, the electrode may be applied with a roll, and for printing, for example, a screen printing method may be used.

The film thickness is not particularly limited, and is a force selected by the overcurrent protection circuit element to be obtained, usually about 10 to 250 m, preferably about 20 to 150 // m (after drying) Film thickness). In the case of a PTC conductive composition in which conductive particles are dispersed in a thermosetting resin (Claim 9), the material may be formed by coating or printing on the electrode itself and drying. To apply, the electrode may be applied with a roll, and for printing, for example, a screen printing method may be used. In the case of a relatively thick film, a polyorganosiloxane resin having no solvent may be used.

Regarding the bonding with the electrode, after drying, the coated surfaces are pressed together and heat-cured. C The heat-curing temperature is preferably as low as possible to prevent oxidation of the nickel foil.

(iii) Shape preparation

The shape is adjusted by appropriately cutting to the design dimensions required for the overcurrent protection circuit element.For example, when used inside a dry cell, a disk shape with holes as shown in Fig. 3 is used. To cut. Care is taken so that the electrodes do not touch each other during cutting.

FIG. 1 is a cross-sectional view showing the internal configuration of the overcurrent protection circuit element. (A) shows a case without a conductive thin film, and (b) shows a structure with a conductive thin film.

FIG. 2 is a cross-sectional view of a nickel foil subjected to roughening nickel plating.

FIG. 3 is an external perspective view showing the shape of the overcurrent protection circuit element used inside the dry battery.

FIG. 4 is a circuit diagram showing a method for measuring the resistivity of the overcurrent protection circuit element.

Hereinafter, the best mode for carrying out the present invention will be described in detail.

A. First, Examples and Comparative Examples in the case of using a PTC conductive composition in which conductive particles are dispersed in a thermoplastic resin will be described.

A resin sheet used for screen printing is closely adhered to one side of a nickel foil having a thickness of 20 μm and fixed, and nickel plating is performed by an electric plating method or a chemical plating method to perform a rough nickel plating.

The electroplating method is as follows: nickel sulfate 220-380 g. Nickel chloride 30-60 / boric acid 30-40 g aqueous solution of Z_g, nickel sulfate 150 / ammonium chloride 15 g /, Adjust the bath of an aqueous solution such as boric acid 15 gZ ^ to adjust pH Under the conditions of 4-5 and temperature of 40 ° C-55, a current of 18 AZ dm ^{2 in} current density is passed for a predetermined time. The chemical plating method is performed in a chemical plating bath containing a small amount of nickel sulfate 2 OgZ, sodium hypophosphite 10-25 g, and a small amount of lactic acid, propionic acid, sodium citrate, sodium acetate, and sodium chloride. H 4-6 or 8-9.5, temperature 30 ° C-90, for a predetermined time.

After plating, the wire mesh, punched metal, resin sheet used for screen printing, etc. are removed to obtain a roughly 5 m thick, one-side roughened nickel plating surface (Fukuda Metal Foil Powder) Industrial Co., Ltd.)

Example 1

Polyethylene resin (manufactured by Mitsui Petrochemical Industry Co., Ltd.) 45% by weight of graphite powder (manufactured by Nippon Power Ichibon Co., Ltd.) 35% by weight, and Kabuki Carbon (manufactured by Kanebo Co., Ltd.) 20% by weight The mixture was heated and kneaded by a kneading extruder and extruded into a sheet having a thickness of 200 m. This sheet is inserted between the roughened sides of the nickel plating roughened nickel foil, and heated at a pressure of about 10 O Kg / cm ^{2 at} a pressure of about 10 Kg / cm ² by a press machine having upper and lower heating press plates. C, thermocompression bonding for 5 minutes (see Fig. 1 (a)).

Example 2

Example 5 35% by weight of graphite resin (manufactured by Nippon Carbon Co., Ltd.) and 20% by weight of spherical carbon (manufactured by Kanebo Co., Ltd.) were added to 45% by weight of polypropylene resin (manufactured by Mitsui Petrochemical Industries, Ltd.). The mixture was heated and kneaded in the same manner and extruded into a sheet having a thickness of 200 μm. This sheet was inserted between the roughened sides of the nickel plating roughened nickel foil, and pressed with a pressure machine of about 10 O KgZcm ^{2 at} a pressure of about 10 O Og (Figure 1 (a)).

Example 3

45% by weight of the polyethylene resin used in Example 1 crushed with 45% by weight of carbon fiber and graphitized under a reducing atmosphere of about 900 ° C. (hereinafter referred to as “graphitized carbon fiber”) Then, 20% by weight of graphite powder was extruded into a sheet having a thickness of 200 m in the same manner as in Example 1.

This sheet was inserted between the roughened sides of the nickel plating roughened nickel foil, and heated at about 170 ° C. at a pressure of about 10 O KgZcm ² with a press machine provided with heating and pressing plates at the top and bottom. Thermocompression bonding was performed for 5 minutes (see Fig. 1 (a)).

Example 4

A vinylidene chloride resin was previously dissolved in 45% by weight of the polypropylene resin used in Example 2 with a mixed solvent of xylene and butyl acetate, and then graphitized carbon fibers were added thereto (about 20% by weight of the vinylidene chloride resin, The amount of graphitized carbon fiber was adjusted to about 80% by weight.) Mixed, cooled, dried under reduced pressure, and crushed and adjusted. 35% by weight of encapsulated graphitized carbon fiber, similarly encapsulated spherical carbon powder 20%. % By weight and extruded into a 200 m thick sheet as in Example 1.

Example 5

40% by weight of vinylidene chloride resin, 35% by weight of graphitized carbon fiber, and 25% by weight of encapsulated spherical carbon were heated and kneaded with a Banbury mixer, crushed, and extruded to a thickness of 200 m with an extruder. Extruded in one piece.

The sheet is inserted between the roughened sides of the nickel-plated roughened nickel foil, and is heated at a pressure of about 10 O Kg / cm ² by a press machine provided with a heating press plate on the upper and lower sides for about 17 times. Thermocompression bonding was performed at 0 ° C for 5 minutes (see Fig. 1 (a)).

Example 6

40% by weight of polypropylene resin used in Example 2, 25% by weight of encapsulated expanded graphite prepared in the same manner as in Example 4, 25% by weight of encapsulated graphite powder, and 10% by weight of ketchin black The mixture was kneaded in the same manner as in Example 5, and extruded into a sheet having a thickness of 200 m using an extruder.

Example 7 — Example 1 2

20% by weight of ketchin black and 55% by weight of spheroidal graphite (Mesocarbon manufactured by Osaka Gas Co., Ltd.) are mixed with 25% by weight of resin and appropriately kneaded with three rolls. A conductive paste was prepared.

This conductive paste was screen-printed and applied to the rough surface of the nickel plating roughened nickel foil used in Example 16 and dried to obtain a film having a thickness of about 1 Om. On this, a sheet prepared in the same manner as in Example 16 was heated and pressed in the same manner as in Example 1-6, with the sheet interposed between the coating films (see FIG. 1 (b)).

Comparative Example 1-Comparative Example 6

The sheets prepared in Examples 1 to 6 were interposed between two non-stick nickel foils (manufactured by Fukuda Metal Foil & Powder Co., Ltd.) having a thickness of 20 m. In the same manner, the thermocompression bonding was performed.

Comparative Example 7-Comparative Example 1 2

A conductive paste is applied to two unplated nickel foils having a thickness of 20 m in the same manner as in Example 7-12, dried, and the sheet prepared in Example 1_6 is sandwiched. It was heat-pressed.

Example 11 The resistance measurement of the example 11 and the comparative example 11 was performed by the circuit shown in FIG. 4, and the results are shown in Table 1.

Table 1 Example geometric ratio Comparative example Resistance ratio

(Roughened nickel plating) (No plating)

2 2 .0 2 4 .6

Sex 3 1. 8 3 4. 4

4 1 .7 4 3 .9 membrane 5 2 .1 5 4 .3

6 2. 2 6 4. 6

7.1 74.0

Denki 8.7 8 3.9

Sex 9.5 5 4.1

10. 4 1 0 3 .7

Membrane 1 1.8 1 1 4.0

A 12.8 1 24.0 Temperature 25 ° C, unit Ωcm According to Table 1, a nickel-plated element with rough nickel-plated nickel foil is simply nickel foil. It can be seen that the resistivity at room temperature (25 ° C) is on average about 60% lower than that of the element used in (1). Also, it can be seen that the resistivity of the device in which the conductive paste was sandwiched between the electrode and the PTC conductive composition was lower than that of the device in which the conductive paste was not sandwiched.

Overcurrent protection circuit device of the present invention does not change the resistance value from room temperature to around 9 0 ° C ± 5 ° C , 1 20 ° C ± 1 0 ° at least 1 0 ³ times more resistance value C around near It shows that the resistance change is stable even if the temperature rises and falls repeatedly.

B. Next, Examples and Comparative Examples in the case of using a PTC conductive composition in which conductive particles are dispersed in a thermosetting resin will be described.

First, a resin sheet used for screen printing is adhered and fixed to one side of a nickel foil having a thickness of 20 μm, and nickel plating is applied by an electric plating method or a chemical plating method to perform a rough nickel plating. The electroplating method is based on an aqueous solution of nickel sulfate 220-380 / ί, nickel chloride 30-600 / borate 30-40 gZ ^, nickel sulfate 150- / ί ヽ chloride ammonium 15 gZ_g A bath of an aqueous solution of boric acid 15 or the like is adjusted, and a current having a current density of 11 to 8 AZdm ² is passed under a condition of pH 4 to 5 and a temperature of 40 to 55 ° C for a predetermined time. The chemical plating method is as follows: Nickel sulfate 20 Sodium hypophosphite 10—25 g / ^, optionally, a small amount of lactic acid, propionic acid, sodium citrate, sodium acetate, and sodium chloride. 6 or 8-9.9.5, at a temperature of 30 ° C-90 ° C for a predetermined time.

After metal plating, the wire mesh, metal, metal sheet, resin sheet used for screen printing, etc. are removed to obtain a nickel-plated metal surface with a rough surface and a single-sided surface with a thickness of about 5 m (Fukuda Metal Co., Ltd.) Foil Powder Industry Co., Ltd.)

Example 13

Silicon rubber (manufactured by Dow Corning Co., Ltd. Q4) 35 A carbon fiber crushed to 35% by weight and graphitized in a reducing atmosphere at about 290 ° C (hereinafter referred to as “graphitized carbon fiber”) 50 By weight, 15% of graphite powder was roughly mixed in advance with a Shinagawa mixer, and then mixed with three rolls to prepare a PTC composition.

After applying this PTC composition to the roughened nickel foil on the roughened surface with an applicator so as to have a thickness of about 100 zm, another roughened nickel foil is coated on the roughened surface, and a heating press plate is applied. Then, the coated surfaces were combined by a press machine provided on the upper and lower sides, and pressed under a pressure of about 10 OKgZcm ² for about 1 hour and heat-pressed for 1 hour (see Fig. 1 (a)).

Example 14

35% by weight of silicone adhesive (Q9 manufactured by Die Corning Co.), 50% by weight of graphitized carbon fiber and 15% by weight of graphite powder were coarsely mixed in advance with a Shinagawa mixer, and then mixed in three holes. The PTC composition was prepared.

This PTC composition was applied to the rough surface of the roughened nickel foil over the entire surface so as to have a thickness of about 100 m, and then the rough surface of another roughened nickel foil was overlapped. The coated surfaces were combined using a press machine with upper and lower plates mounted on top and bottom, and heat-pressed at a pressure of about 10 OKg / cm ² at about 130 ° C for 1 hour (see Fig. 1 (a)). Polyethylene is charged and dissolved in a xylene / methanol mixed solvent before heating, and then graphitized carbon fiber is charged (about 20% by weight of polyethylene, 80% by weight of graphitized carbon fiber), cooled, and crushed and adjusted. 50% by weight of the encapsulated graphitized carbon fiber, 15% by weight of the similarly encapsulated graphite powder, and 35% by weight of the silicone rubber used in Example 13 were roughly mixed with a Shinagawa mixer beforehand. The PTC composition was prepared by mixing with this roll.

This PTC composition was applied to the rough surface of the roughened nickel foil over the entire surface so as to have a thickness of about 100 m, and then the roughened surface of another roughened nickel foil was overlaid and heated. The plates were heated and pressed at about 130 ° C for 1 hour at a pressure of about 10 O KgZcm ² , with the coated surfaces being combined by a press machine provided above and below (see Fig. 1 (a)).

Example 16

After dissolving vinylidene chloride by heating with a mixed solvent of xylene and butyl acetate, add expanded graphite powder (adjust to about 20% by weight of vinylidene chloride and 80% of expanded graphite powder) and dry by spray drying. Adjusted 15% by weight, Encapsulated graphitized carbon fiber adjusted in Example 15 25% by weight, same adjusted in Example 15 Forced graphite powder 15% by weight, used in Example 14 45% by weight of the silicone adhesive thus obtained was roughly mixed in advance with a Shinagawa mixer, and then mixed with three pieces of π-yl to prepare a pTC composition.

This PTC composition was applied to the rough surface of the roughened nickel foil over the entire surface so as to have a thickness of about 100 m, and then the roughened surface of another roughened nickel foil was overlaid and heated. The coated surfaces were combined with a press machine provided with 扳 on the top and bottom, and heated and pressed at about 130 ° C. for 1 hour at a pressure of about 10 O KgZcm ² (see Fig. 1 (a)).

Example 17

50% by weight of the silicone pressure-sensitive adhesive used in Example 14 was added to 25% by weight of the graphitized carbon fiber adjusted in Example 15; 15% by weight of the encapsulated graphite powder; and the force adjusted in Example 16 10% by weight of expanded graphite was roughly mixed in advance with a Shinagawa mixer, and then mixed with three rolls to prepare a PTC composition.

This PTC composition is applied to the rough surface of the roughened nickel foil over the entire surface so as to have a thickness of about 10 and then overlaid with another roughened nickel foil. The coating surfaces were combined using a press machine with upper and lower plates mounted on top and bottom, and heat-pressed at about 130 ° C for 1 hour at a pressure of about 10 OKgZcm ² (see Fig. 1 (a)).

Example 18-Example 22

60% by weight of spherical carbon (Belvar, manufactured by Kanebo Co., Ltd.), 20% by weight of spherical graphite (Mesocarbon, manufactured by Osaka Gas Co., Ltd.), 20% by weight of urethane resin, appropriately mixed with a solvent, and mixed with three rolls Thus, a conductive paste was prepared.

This conductive paste was screen-printed and applied to the roughened surface of the nickel plating roughened nickel foil used in Examples 13 to 17 and dried to obtain a film having a thickness of about 10 μm. Example 13 The PTC composition prepared in the same manner as in 3—17 was applied to the conductive paste surface with an applicator so as to have a thickness of about 100 mm, and then another roughened nickel foil was applied. superimposed conductive paste surface, the heated press plate in the form of combined in a press applying surface provided vertically, about 1 0 0 Kg / cm ² pressure of about 1 30 ° C, for 1 hour thermocompression bonding (Figure 1 ) See).

Comparative Example 13-Comparative Example 1

Example 13 A PTC composition prepared in the same manner as in Example 3-17 was coated on a non-plated nickel foil having a thickness of 20 zm (manufactured by Fukuda Metal Foil & Powder Co., Ltd.) for about 100 m. after coating with the applique Isseki one so that the thickness, overlapping the face of another nickel foil, in the form of combined application surface in a press provided with heated press plates above and below, a pressure of about 1 0 OKgZcm ² At about 130 ° (for 1 hour.

Comparative Example 1 8 Comparative Example 22

The conductive paste prepared in the same manner as in Example 18-22 was screen-printed on the non-plated nickel foil used in Comparative Example 13-17, and dried to about 10〃m. Was obtained.

Example 13 A PTC composition prepared in the same manner as in 3—17 was applied all over the conductive paste surface so as to have a thickness of about 100 μm, and then another nickel foil conductive paste was applied. The surfaces were overlapped, and the coated surfaces were combined by a press machine provided with a heated press plate on the upper and lower sides, and heat-pressed at a pressure of about 10 OKgZcm ² at about 130 ° C for 1 hour.

The resistances of Examples 13-22 and Comparative Examples 13-22 were measured using the circuit shown in Fig. 4. The results are shown in Table 2. Table 2

Temperature 25, unit Ω-cm

According to Table 2, the resistance of nickel-plated nickel-plated electrodes at room temperature (about 25 ° C) is higher than that of nickel-plated electrodes. You can see that the rate is on average 60% lower. Also, it can be seen that the resistivity of the device in which the conductive paste was sandwiched between the electrode and the PTC conductive composition was lower than that of the device in which the conductive paste was not sandwiched. Furthermore, a PTC composition in which graphite particles coated with a thermoplastic resin were dispersed in a thermosetting resin (Examples 15-17) was used. The graphite particles were simply dispersed in the thermosetting resin. It can also be seen that the resistivity was lower than that using the PTC composition (Examples 13 and 14).

Claims

The scope of the claims

1. An overcurrent protection circuit device having a PTC conductive composition and at least two electrodes in contact with the PTC conductive composition,

The electrode is a nickel foil,

An overcurrent protection circuit element, wherein the nickel foil has a roughened nickel plating on a contact surface with the PTC conductive composition.

2. An overcurrent protection circuit device having a PTC conductive composition and at least two electrodes,

The electrode is a nickel foil,

A conductive thin film that does not exhibit PTC characteristics is interposed between the nickel foil and the PTC conductive composition,

An overcurrent protection circuit element, wherein the nickel foil is provided with a roughened nickel plating on a contact surface with a conductive thin film.

3. The overcurrent protection circuit element according to claim 2, wherein the conductive thin film comprises a conductive substance and a binder, and is coated on the PTC conductive composition or nickel foil to form a thin film.

4. The overcurrent protection circuit element according to claim 1, wherein the PTC conductive composition has conductive particles dispersed in a thermoplastic resin.

5. The conductive particles

5. The overcurrent protection circuit element according to claim 4, comprising one or more of conductive carbon black, graphite, expanded graphite and fibrous graphite.

6. The conductive particles

5. The overcurrent protection circuit element according to claim 4, wherein the carbon fiber is made of graphite obtained by cutting or crushing a carbon fiber shortly and graphitizing it.

7. The overcurrent protection circuit element according to claim 4, wherein a part of the conductive particles is coated with another kind of thermoplastic resin having a melting point different from that of the thermoplastic resin.

8. All kinds of conductive particles have different melting point from the thermoplastic resin. 5. The overcurrent protection circuit element according to claim 4, wherein the element is covered with a conductive resin.

9. The overcurrent protection circuit element according to claim 1, wherein the PTC conductive composition has conductive particles dispersed in a thermosetting resin.

10. The overcurrent protection circuit element according to claim 9, wherein the conductive particles are made of one or more of conductive carbon black, graphite, expanded graphite, and fibrous graphite.

11. The overcurrent protection circuit element according to claim 9, wherein the conductive particles are graphite obtained by cutting or crushing a carbon fiber into a short length and graphitizing it.

12. The overcurrent protection circuit element according to claim 9, wherein a part of the conductive particles is coated with a thermoplastic resin.

13. The overcurrent protection circuit element according to claim 9, wherein all of the conductive particles are coated with a thermoplastic resin.