JPS5933924B2 - pressure sensitive resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure sensitive resistor exhibiting stable electrical properties.

Conventionally, conductive metal particles are mixed with an elastic polymer, and then molded.
There are known pressure-sensitive resistors that are cross-linked and have a volume resistivity in an insulating region in their natural state, which changes to a conductive region by deformation such as applying pressure (Japanese Patent Publication No. 40-24061, 49-114798, Japanese Unexamined Patent Publication No. 46-6179).

There are also methods of coating conductive metal particles used in pressure-sensitive resistors with silver or the like (Japanese Patent Publication No. 47-3019), methods of treating the particle surface with a semiconductor, or making the interface between the metal particles and the elastic polymer body loose. Method (Japanese Patent Application Laid-Open No. 49-114798)
etc. are also publicly known. In addition, the present inventors have determined that the bond between metal particles and rubber is not a strong bond that causes stress concentration at the interface and large changes due to repeated pressurization, but rather a bond that improves dispersibility and avoids stress concentration. He discovered that bonding is good for pressure-sensitive resistors, and has already applied for a patent (patent application 1972-
42028, 51-61630, 51-75077
). The present invention improves the dispersibility of the metal into the elastic body by interposing a compound with hardness between that of the metal and the elastic polymer at the interface between the metal and the elastic polymer, thereby reducing stress on the metal. This aims to provide a pressure-sensitive resistor whose electrical properties change little with repeated pressurization by indirectly transmitting the pressure, and also aims to achieve a large change in resistance value with smaller pressure. It is. According to the present invention, polyvinyl alcohol or its copolymer (Λ, 5-norbornene-2-alkyl ester (0COORI, R4 is Cl
A ring-opened (co)polymer (2) of (showing the above alkyl group),
The partially saponified product (C) (part of the main chain?, a polymer compound containing a unit represented by C=C0), the ring-opening of 2,3 monoanhydride carboxy 5-norbornene (1>I' \ 0) ( Co)polymer (g), its hydrate (g) (H in part of the main chain).

(a polymer compound containing a unit represented by OO-L3),
2-tri ring-opened copolymer (F') and its derivative 6 (
-X or ゛-゛-T5》fu. ．． ．． ．． At least one polymer compound selected from the group consisting of polymeric compounds containing the following units, or a combination of at least one of the above compounds and a silane coupling agent is interposed at the interface between the metal particle surface and the elastic body. .

It has been found that by interposing these compounds between the surface of the metal particles and the interface of the elastic body, the dispersibility of the metal particles into the elastic body is improved, and changes in electrical properties due to repeated pressurization and aging can be reduced. Ta.

In the present invention, it is preferable to use a method in which the specific compound used as a surface treatment agent for conductive metal particles is diluted with a solvent, added to the conductive metal particles, and then the solvent is removed.

The amount of the surface treatment agent added is 0.1 to the conductive metal particles.
0.1 to 3 volume fraction) (when combined with a silane coupling agent, the total amount is suitably 0.2 to 6 volume fraction (approximately 1 liter).

If the amount added is less than 0.1 volume fraction (4), the effect will be insufficient, and if it is added more than 3 volume fraction (4), the effect will be reduced. A good pressure-sensitive resistor can be obtained by mixing 8 to 40 volume fractions of the conductive particles obtained in this way into an elastic polymer material and crosslinking the material after applying a magnetic field if necessary. Obtainable.

Elastic bodies that can be used in the present invention include, for example, polybutadiene rubber, styrene-butadiene rubber, butadiene-acrylonitrile rubber, acrylic rubber, polychloroprene rubber,
Examples include polyisoprene rubber, ethylene-propylene rubber, silicone rubber, and polypentenamyl rubber.

As is widely known, conductive metal particles that can be used in the present invention include nickel, copper, aluminum, silver, tin, cobalt,
Examples include iron and alloys containing iron.

The shapes of these metal particles may be spherical, dendritic, petal-like, etc., and this does not prevent the use of fillers such as silica, silicate, calcium carbonate, and carbon black in combination. The polyvinyl alcohol or copolymer thereof used in the present invention can be obtained by saponifying a (co)polymer of vinyl formate, vinyl acetate, vinyl propionate, etc., and increasing the degree of saponification to 20% or more. . Particularly suitable are completely or partially saponified products of polyvinyl acetate or vinyl acetate copolymers; for example, Dupont's "Elvanol" has more than a dozen types with saponification degrees ranging from 43% to 100%, and there are many others. There are commercially available products, all of which can be used in the present invention. Ring opening (co) of 5-norbornene-2-alkyl ester used in the present invention
Polymer 8 can be easily obtained using organic aluminum and tungsten halide as a catalyst.

The ring-opened (co)polymer 8 includes, for example, a copolymer with a rubber having a double bond, a copolymer with a norbornene derivative substituted with a substituent containing a polar group such as a thalol group, a cyclo Copolymers with cycloalkenes such as benzene, etc. These ring-opened (co)polymers are treated with alkali,
The alkyl ester group can be easily converted into a carboxyl group by subsequent acid treatment (0. The ring-opened (co)polymer of 2,3-carboxy anhydride-5-norbornene used in the present invention has ( Copolymers with norbornene derivatives containing units of -C-C→(7V-,o) and substituted with other substituents such as esters, nitrile, chloro groups, copolymers with citaloalkenes, double bonds Examples include copolymers with rubber containing (c).

In addition, these ring-opened (co)polymers can be easily converted into hydrates [
F] can be made. The ring-opened (co)polymer of 2-trichlorosilyl-5-norbornene that can be used in the present invention is obtained in the same manner as the ring-opened (co)polymer of 5-norbornene-2-alkyl ester (g); Derivative 0 can be easily obtained by treating the (co)polymer with pyridine and water or with CH(0CH3)3.

The treatment of the conductive metal particle surface with the above-mentioned specific compound or the combination of the above-mentioned specific compound and a silane coupling agent is not intended to firmly bond the conductive metal particle and the elastic body, but rather to It is important that a specific compound having a hardness intermediate between that of the metal particles and the elastic body is present at the interface between the metal particles and the elastic body.

The silane coupling agent used in the present invention is generally Rl
It is represented by Si(R2)3.

Here, R1 represents an organic functional group having an alkylchlor group, a vinyl group, a meta-acroxy group, an epoxy group, a mercapto group, an amino group, a peroxy group, etc., and R2 represents an alkoxy group, an acetyl group, an alkylperoxy group, or an alkylperoxy group. and is generally easily hydrolyzed. For example, gammachloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris(betamethoxyethoxy)silane, gammamethacroxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyl-trimethoxy Silane, γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, gamma-mercaptopropyltrimethoxysilane, vinyltriacetoxysilane, gammaaminopropyltristoxysilane, N-beta(aminoethyl)-gammaaminopropyl-tri Examples include methoxysilane, vinyltristacyalbutylperoxysilane, etc., and silane coupling agents having a vinyl group, a metataloxy group, or a peroxy group as a functional group are particularly preferred. The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples unless it goes beyond the gist of the present invention.

Example 1 Ethylene-vinyl alcohol copolymer (sample A) (GM-14 manufactured by Nippon Gosei Kagaku Co., Ltd.) 29 was dissolved in ethanol 100me.
Carbonyl non-nickel 382 with a particle size of 1 to 3μ dissolved in
．． 79 and dried under reduced pressure at 70° C. for 2 hours to obtain surface-treated nickel particles.

Surface-treated nickel particles 186.39, addition-type silicone rubber (KEl3OOT manufactured by Shin-Etsu Chemical) 719, and crosslinking agent for silicone rubber 7.19 were mixed in a Brabender for 5 minutes, and molded in a mold with a thickness of 1, I left it for a day. Molding/
The crosslinked sheet was heat-treated in a constant temperature box at 130° C. for 30 minutes, and a sample was cut into a 1c1L circular shape. (Sample 1)
As Comparative Sample 1, a pressure-sensitive resistor was obtained in exactly the same manner as in Example 1 except that surface-untreated Nickel 186 and 39 were used in place of the surface-treated Nickel in Example 1.

Next, as sample 2, ethylene-vinyl alcohol copolymer (GM-14 manufactured by Nippon Gosei Kagaku Co., Ltd.) 19 and vinyltrimethoxysilane 1! 1 was dissolved in ethanol 507ne, mixed with carbonyl nickel 191.3y having a particle size of 1 to 3 μm, and dried at 70° C. under reduced pressure for 2 hours to obtain surface-treated nickel particles. Sample 2 was obtained in exactly the same manner as Sample 1 using the nickel particles. While applying pressure to Samples 1 and 2 and Comparative Sample 1 thus obtained, the electrical resistance was measured, and the relationship between pressure and volume resistivity was determined.

The force required for the volume resistivity to become 103Ωα, P*Kf
/Clt was used as a measure of the electrical properties of the pressure sensitive resistor. The sample was pressurized 104 times to (P'l'+1)Kf/Clt, and P3 at that point was determined and shown in Table 1.

In addition, each sample was left at 70° C. and 80% humidity for one month, and the temperature was determined in the same manner as shown in Table 1. Example 2 Methyl 5-norbornene 2-carboxylate Ring-opening polymerization was carried out using tungsten hexachloride and paraaldehyde as catalysts and butene-1 as a molecular weight regulator.

Yield of the obtained polymer: 100%, 31°C [η] = , 0
．． 9, the vitrification temperature was 61°C and the temperature was 61°C.

(Sample B-1) 5-norbornene-2-carboxylic acid methyl ester 50f! and reprecipitation purified rubber of styrene-butadiene rubber (Japan Synthetic Rubber JSRl5OO) 50
9 was ring-opening copolymerized in a cyclobenzene solution.

30℃ The yield was 100%, [η], 1.4.

(Sample B-2) 59 of Sample B-1 was mixed with 1007ne of benzene and 10d of 10% sodium hydroxide, and the sample B-1 was hydrolyzed for 5 hours under reflux.

1% sulfuric acid was added to the reaction system to precipitate the reaction product, washed with ethanol and water, and then dried under reduced pressure. The degree of saponification was confirmed to be 30% by titration with aqueous potassium. (Sample C-1) 29 pieces each of the obtained samples B-1, B-2, and C-1 were each dissolved in 100 ml of chloroform and divided into two equal parts.

The solution 50T1Le was added to reduced copper particles 3109 having a particle size of about 70 tur1, mixed, and then dried at room temperature under reduced pressure. Each of these samples was mixed with 619 addition-type silicone rubber (KEl3OOT manufactured by Shin-Etsu Chemical Co., Ltd.) and 7 g of its crosslinking agent using a Brabender for 5 minutes, molded on a 1-thick mold, and left at room temperature for 2 days. and cross-linked. Circular samples with a cross-section of 1 d were cut out from these crosslinked sheets and tested in the same manner as in Example 1. The results are shown in Table 2. Also,
As Comparative Sample 2, the reduced copper particles used in Example 2 were used as they were in the same manner as in Example 2 to obtain a circular sample, and the results are also listed in Table 2. Next, divide the remaining solution into two equal parts, 50ml each.
N-beta(aminoethyl)-gammaaminopropyltrimethoxysilane 19 was added to e, and the mixture was added to reduced copper particles 3109 having a particle size of about 70 μm, mixed, and then dried at 100° C. under reduced pressure.

The copper particles thus obtained were measured in exactly the same manner as described above, and the results are shown in Table 2. Example 3 5-norbornene-2-carboxylic acid methyl ester 95
9 and 2,3 monocarboxylic anhydride-5-norbornene (1)
V-0)59 was ring-opening copolymerized in dichloroethylene using triethylaluminum, tungsten hexachloride, and paraaldehyde as catalysts.

The yield was 99 cm, and the vitrification temperature was 63°C. (Sample D-
1) Take 29 samples of sample D-1 and dissolve them in 50 d of benzene.
Add 10 d of 10% potassium and react under reflux for 1 hour.
Methanol was added to obtain sample E-1. Furthermore, 5-
Trichlorosilyl-2-norbornene (') 0151
3) 5y and 5-cyano-2-norbornene 4〉J-6”
') 959 was subjected to ring-opening copolymerization in dichlorobenzene using triisobutylaluminum, tungsten hexachloride, and paraaldehyde as catalysts and 1-butene as a molecular weight regulator.

Ethyl orthoformate CH (0C25
) 33y, stirred, and poured into methanol to prepare sample G.
-1 was obtained. The yield was 100%, and [η] in toluene at 30°C was 0.55.

The obtained samples D-1, E-1, and G-1 were each 0.2
1) Take 0.5g, 19, 31) 5g, toluene 50
Nickel metal particles with a particle size of about 40μ 15
11 and the toluene was removed under reduced pressure at 70°C.

Claims (1)

[Claims] 1. Polyvinyl alcohol or copolymer thereof (A), 5.
- Ring-opened (co)polymer of norbornene-2-alkyl ester (B), partially saponified product thereof (C), ring-opened (co)polymer of 2,3-anhydride carboxy-5-norbornene (D)
, its hydrate (E), ring-opened (co)polymer of 2-trichlorosilyl-5-norbornene (F) and its derivative (
A pressure-sensitive resistor characterized by using conductive metal particles surface-treated with at least one selected from G) or a compound (A to G) and a silane coupling agent. 2. Claim 1, characterized in that conductive metal particles surface-treated with a ring-opening polymer (B) of 5-norbornene-2-alkyl ester and a silane coupling agent having an amino group are used. pressure sensitive resistor.