JPH01168761A - Pressure-sensitive, variable-resistance conductive composition - Google Patents

Abstract

PURPOSE:To obtain the title compsn. which is excellent in resistance to repeated pressure applications; exhibits resistance values smoothly decreasing in accordance with an increase in applied pressure and is suited for use in an applied pressure-sensing element, a variable resistor, a pressure-actuated switching element having excellent durability, etc., by compounding predetermined amts. of graphite and Cr2O3 with an org. polymeric material. CONSTITUTION:100 pts.wt. org. polymeric material (A) as a binder, such as a vinyl chloride-vinyl acetate copolymer, is compounded with 40-180 pts.wt. graphite (B) as a conductive material, such as scaly graphite, having a size of, e.g., about 6.0mum and 110-340 pts.wt. Cr2O3 (C) as an insulating material, pref. having a particle size of 0.1-0.3mum, the sum of B+C being 280-390 pts.wt. Optionally, further, ethylene glycol monobutyl ether and/or ethylene glycol monobutyl ether acetate (D) is added thereto and blended.

Description

DETAILED DESCRIPTION OF THE INVENTION ■ Industrial Application Field The present invention relates to a pressure-sensitive resistance change type conductive composition that can be applied to printing, painting, coating, etc. More specifically, it relates to a pressure-sensitive resistance change type conductive composition that can be applied to printing, painting, coating, etc. The present invention also relates to a pressure-sensitive resistance change type conductive composition in which the applied force and the resistance value are inversely proportional.

■ Prior art and its problems Materials having pressure-sensitive resistance change characteristics have been known for a long time. For example, U.S. Patent No. 2,044°080 discloses that Granulated Carbon
It has been disclosed that the resistance of a conductive material sandwiched between electrodes decreases when the material is compressed. A similar example is U.S. Patent No. 3,806,4
No. 71 also discloses the use of various semiconductor materials, the fact that particulate materials are held together by a binder, and the use of spherical or granular materials to reduce the bisteresis phenomenon and prevent wear. It describes how to use it.

Further, US Pat. No. 3,710,050 discloses an invention in which 20 to 50% of rubber powder is added to conductive powder to bring out the pressure-sensitive conductivity of the powder.

In these examples, the powder or material is used as it is without using a dispersion medium such as rubber, so there are drawbacks such as the pressure-sensitive conductive material having to be stored in a special container. In the invention disclosed in the above-mentioned US Pat. No. 3,806,471, an idea was made to bind the powdery material with a binder, but the flexibility of the material was insufficient. JP-A-56-108279 discloses an invention in which the J diameter of this binder is made 25.4μ or less. Further, although an invention for trapping powder in the cell spaces of a foam is disclosed in US Pat. No. 2,305,717, this invention cannot completely prevent the powder from falling off.

The problem of powder parentage is, for example, U.S. Patent No. 3,629.77.
As described in the specification of No. 4, this problem can be solved by covering the surface of the cells of the foam with a coating film containing conductive powder. However, the range of change in the resistance value of the pressure-sensitive conductor obtained by this technique is small. That is, the resistance value itself when released is not sufficiently high, and the ratio of the resistance value when released to the resistance value when pressurized is small, so it is not preferable as a switch element, for example.

In addition, pressure-sensitive conductive elastic compositions in which pressure-sensitive conductivity is imparted by blending special conductive powder with elastic materials such as silicone rubber are disclosed in Japanese Patent Publication No. 56-9137, etc.; It is extremely difficult to impart properties such as printing, painting, and coating to body compositions, and there are limits to the precision, thinning, and weight reduction of switch elements and electronic components, and excellent pressure sensitivity is extremely difficult. The emergence of a pressure-sensitive resistance variable conductive material that has the characteristics of printing, painting, coating, etc. has been desired.

■ Purpose of the Invention The purpose of the present invention is to provide a method that shows a significant reduction in electrical resistance due to pressurization compared to the electrical resistance when not pressurized, and that the resistance decreases smoothly as the pressurizing force increases. It is an object of the present invention to provide a composition that provides a pressure-sensitive conductive material that provides a pressure-sensitive conductive material.

Another object of the present invention is to provide a pressure-sensitive resistance variable conductive composition that can be applied to printing, painting, coating, etc.

■ Structure of the Invention The first aspect of the present invention contains 40 to 180 parts by weight of graphite and 110 to 340 parts by weight of chromium sesquioxide with respect to 100 parts by weight of an organic polymer material, and the graphite and the chromium sesquioxide Provided is a pressure-sensitive resistance variable conductive composition characterized in that the total amount is 280 to 390 parts by weight.

A second aspect of the present invention contains 40 to 180 parts by weight of graphite, 110 to 340 parts by weight of chromium sesquioxide, and an organic solvent based on 100 parts by weight of the organic polymer material, and the total of the graphite and the chromium sesquioxide 280~3
Provided is a pressure-sensitive resistance variable conductive composition characterized in that the amount is 90 parts by weight.

Here, a pressure-sensitive resistance variable conductive composition in which the organic polymer material is a vinyl chloride/vinyl acetate copolymer is preferable.

Further, a pressure-sensitive resistance change type conductive composition in which the organic solvent is ethylene glycol monobutyl ether and/or acetic acid ethylene glycol monobutyl ether is preferable.

The configuration of the present invention will be explained in detail below.

The organic polymer material used as a binder in the present invention is, for example, a thermosetting resin such as a phenol resin, a urea resin, a melamine resin, a furan resin, an unsaturated polyester resin, an epoxy resin, a silicone resin, a polyurethane resin, or a chlorinated resin. Vinyl resin, vinylidene chloride resin, vinyl acetate resin, acrylic resin, styrene resin, thermoplastic resin such as polyamide resin, cellulose derivatives such as nitrocellulose, acetylcellulose, ethylcellulose, chlorinated rubber,
Examples include rubber derivatives such as hydrochloric acid rubber and silicone rubber, but any material that can be printed, painted, coated, etc. may be used, but vinyl chloride/vinyl acetate copolymer is particularly preferred. .

Graphite is used as a conductive material in the present invention. Particularly preferred is flaky graphite having a size of about 6.0 microns. The blending amount of graphite is in the range of 40 parts by weight to 180 parts by weight, more preferably in the range of 45 parts by weight to 110 parts by weight, based on 100 parts by weight of the organic polymer material of the binder.

If it is less than 40 parts by weight, it will only exhibit an insulating state with no resistance change due to pressurization, and if it exceeds 180 parts by weight, the resistance change due to pressurization will be too rapid and it will become a pressure-sensitive resistance change type.
This is because there is no j.

Chromium sesquioxide is used in the present invention as an insulator. Chromium sesquioxide is preferably in the form of particles. The blending amount of chromium sesquioxide is 10% of the binder resin.
The range is from 110 parts by weight to 340 parts by weight, more preferably from 225 parts by weight to 325 parts by weight of chromium sesquioxide having a particle size of about 0.1 to 0.3 microns.
It is sufficient to mix parts by weight.

When the amount of chromium sesquioxide is less than 110 parts by weight,
This is because the resistance change due to pressurization is too rapid and it cannot become a pressure-sensitive resistance change type, and if it exceeds 340 parts by weight, it only shows an insulating state with no resistance change due to pressurization.

Further, the total amount of graphite and chromium sesquioxide is 280 to 390 parts by weight based on 100 parts by weight of the organic polymer material. This is because even if it is less than 280 parts by weight or more than 390 parts by weight, it cannot become a pressure-sensitive resistance variable type.

The solvent used in the second aspect of the present invention includes:
For example, aliphatic hydrocarbons such as industrial gasoline and kerosene, aromatic petroleum naphthas such as low-boiling aromatic petroleum naphtha, medium-boiling aromatic petroleum naphtha, aromatic carbonization such as penzol, doluol, xylogol, and solvent naphtha. hydrogen, turpentine,
Terpene hydrocarbons such as dipentene and pine oil, chlorinated hydrocarbons such as methylene chloride, trichloroethylene, perchlorethylene, orthodichlorobenzene, 2
-Nitrated hydrocarbons such as nitropropane, aliphatic alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol methyl ether, diethylene glycol monomethyl ether, etc. Ether alcohols such as butyl ether, ethers such as dioxane, acetic esters such as methyl acetate, ethyl acetate, isopropyl acetate, ethylene glycol monomethyl acetate, ethylene glycol monoethyl acetate, ethylene glycol monobutyl acetate, diethylene glycol monoethyl acetate, etc. Examples include ether ester.

Any usable solvent may be used, taking into account printing, painting, coating, etc. methods and the volatilization rate of the binder and solvent, but particularly preferred are ethylene glycol monobutyl ether and/or acetic acid ethylene glycol monobutyl ether. It is. ' The pressure-sensitive resistance variable conductive composition of the first aspect of the present invention may be produced by any method, but one example is as follows:
The composition of the second aspect of the present invention, in which graphite as a conductive material, chromium sesquioxide as an electrically insulating material, and an organic polymer binder are dissolved and dispersed in a suitable solvent, is applied onto a substrate such as a polyester film. It is obtained by evaporating the solvent at . The base material to be used is not limited to polyester film, but any material suitable for printing, painting, and coating may be used.

In the pressure-sensitive resistance change type conductive composition of the present invention, it is possible to control the rate of change in resistance (hereinafter sometimes referred to as sensitivity) with respect to applied force by changing the ratio of graphite and chromium sesquioxide. .

■　Example A more specific explanation will be given below with reference to Examples.

(Example 1) 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 52 parts by weight of graphite (size approximately 6.0μ), 320 parts by weight of chromium sesquioxide, 115 parts by weight of ethylene glycol monobutyl ether acetate, 485 parts by weight of ethylene glycol monobutyl ether After printing a printing ink composition consisting of parts by weight on a polyester film with a thickness of 188 microns, heat drying is performed to remove the solvents ethylene glycol monobutyl ether acetate and ethylene glycol mobutyl ether, and the thickness A pressure-sensitive resistance variable conductive composition having a pressure-sensitive conductor layer of 70 microns was obtained. This composition was placed on a flat comb electrode, and its properties were observed by repeatedly applying and removing pressure using a rod with a flat tip having a diameter of 10 mm.

The characteristics are shown in Figure 1. The upper curve of the hysteresis curve is the pressure measurement, and the lower curve is the reduced pressure measurement (the same applies to FIGS. 1 to 7 below).

As shown in Figure 1, the relationship between pressurization force and resistance is such that as soon as pressurization starts, the resistance drops smoothly and becomes conductive, and when pressurization is released, it immediately and smoothly returns to its original resistance value. , and the pressurizing force and resistance value show an almost inversely proportional relationship.

Moreover, this state did not change even after repeated pressurization with a rod 1 million times.

It can be seen that the composition of the present invention has excellent durability against repeated pressurization and release.

(Example 2) Printing ink consisting of 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 41 parts by weight of graphite, 330 parts by weight of chromium sesquioxide, 90 parts by weight of ethylene glycol monobutyl ether acetate, and 510 parts by weight of ethylene glycol monobutyl ether. After printing the composition on a polyester film with a thickness of 188 microns, a heat-drying process was performed to remove the solvent ethylene glycol monobutyl ether acetate and ethylene glycol monobutyl ether, and a pressure-sensitive conductor layer with a thickness of 70 microns was formed. A pressure-sensitive resistance variable conductive composition having the following properties was obtained. This composition was placed on a flat comb electrode, and its properties were observed by repeatedly applying and removing pressure using a rod having a flat tip with a diameter of 10 ma+.

The characteristics are shown in Figure 2.

As shown in Figure 2, the relationship between pressurizing force and resistance is such that as soon as pressurization starts, the resistance drops smoothly and becomes conductive, and when pressurization is released, it immediately and smoothly returns to its original resistance value. to return to.

(Example 3) Printing ink composition consisting of 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 180i graphite, rtxli parts of chromium sesquioxide, 420 parts by weight of ethylene glycol monobutyl ether acetate, and 180 parts by weight of ethylene glycol monobutyl ether. After printing on a polyester film with a thickness of 188 microns, a heat-drying process is performed to remove the solvent ethylene glycol monobutyl ether acetate and ethylene glycol monobutyl ether, resulting in a pressure-sensitive conductor layer with a thickness of 70 microns. A pressure-sensitive resistance variable conductive composition was obtained. This composition was placed on a flat comb electrode, and its properties were observed by repeatedly applying and removing pressure using a rod with a flat tip having a diameter of 10 mm.

The characteristics are shown in Figure 3.

As shown in Figure 3, the relationship between pressurization force and resistance is such that as soon as pressurization starts, the resistance drops smoothly and becomes conductive, and when pressurization is released, it immediately and smoothly returns to its original resistance value. to return to.

(Comparative Example 1) A printing ink composition obtained by dissolving and mixing 100 parts by weight of vinyl chloride/vinyl acetate copolymer and 250 parts by weight of graphite in 600 parts by weight of ethylene glycol monobutyl ether acetate was applied to a polyester film with a thickness of 188 microns. After printing on the surface, a heating drying treatment was carried out to remove ethylene glycol monobutyl ether acetate to obtain a composition with a dry film thickness of 70 microns. This composition was placed on a flat comb electrode, and its properties were observed by repeatedly applying and removing pressure using a rod with a flat tip having a diameter of 10 mm.

The characteristics are shown in Figure 4.

In this comparative example, as is clear from the relationship graph of pressurized Kerr resistance in Figure 4, when pressurization starts, the resistance suddenly drops and becomes conductive, and when pressurization is released, the resistance value sharply increases. This results in an insulating state, and the variable pressure sensitive resistance type of the present invention cannot be realized.

(Comparative Example 2) A printing ink composition similar to Comparative Example 1 was prepared by dissolving and mixing 100 parts by weight of vinyl chloride/vinyl acetate copolymer and 400 parts by weight of chromium sesquioxide in 600 parts by weight of ethylene glycol monobutyl ether. A composition with a dry film thickness of 70 microns was prepared using the method, and the same characteristics as in Comparative Example 1 were observed.

The characteristic +'L is shown in FIG.

In this comparative example, as is clear from the relationship graph of pressurized Kerr resistance in Figure 5, the resistance value does not change at all even when pressurization starts and remains in an insulated state, and even when pressurization is released, the resistance value remained unchanged and remained insulated.

(Comparative Example 3) 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 227 parts by weight of graphite, 36 parts by weight of chromium sesquioxide, 540 ff of ethylene glycol monobutyl acetate
lffi part, ethylene glycol monobutyl ether 6
After printing the printing ink composition consisting of 0 parts by weight on a polyester film with a thickness of 188 microns, a heat drying treatment was performed to remove the solvent ethylene glycol monobutyl ether acetate and ethylene glycol monobutyl ether, and the film had a thickness of 70 microns. A micron composition was obtained. This composition was placed on a flat comb electrode, and its properties were observed by repeatedly applying and removing pressure using a rod with a flat tip having a diameter of 10 mm.

The characteristics are shown in Figure 6.

As shown in FIG. 6, the relationship between the pressurizing force and the resistance is such that when pressurization starts, the resistance drops rapidly and becomes conductive, and when pressurization is released, the resistance value sharply increases and becomes insulated. The sensitivity of the composition in this example is closer to Comparative Example 1 than to Examples 1 and 3. Therefore, the composition in this example cannot be used as the pressure-sensitive resistance variable type of the present invention.

(Comparative Example 4) Printing ink consisting of 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 35 parts by weight of graphite, 360 parts by weight of chromium sesquioxide, 60 parts by weight of ethylene glycol monobutyl ether acetate, and 540 parts by weight of ethylene glycol monobutyl ether. After printing the composition on a polyester film with a thickness of 188 microns, a heat drying treatment was performed to remove the solvents ethylene glycol monobutyl ether acetate and ethylene glycol mobutyl ether to obtain a composition with a thickness of 70 microns. Ta.

This composition was placed on a flat comb electrode with a diameter of 10III.
Pressure was repeatedly applied and depressurized using a rod with a flat tip of m, and the characteristics were observed.

The characteristics are shown in Figure 7.

In this comparative example, as is clear from the relationship graph of pressurized Kerr resistance in FIG. 7, even when pressurization starts, the resistance does not change much and remains in an insulated state, and the sensitivity is low. Furthermore, even when the pressure was removed, the resistance value remained unchanged and remained in an insulated state. The composition in this example cannot be used as the pressure-sensitive resistance variable type of the present invention.

■ Effects of the Invention The pressure-sensitive resistance variable conductive composition of the present invention has the property of being able to withstand repeated pressurization and smoothly decreasing its resistance value as the pressurizing force increases. Suitable for uses such as the body.

Furthermore, the pressure-sensitive resistance variable conductive composition of the present invention has If as an element of a switch operated by pressurization in terms of durability.
kt'.

Further, the pressure-sensitive resistance variable conductive composition of the present invention exhibits an inversely proportional relationship between applied force and resistance value, and can be applied as various sensors such as applied force detectors.

Furthermore, the pressure-sensitive resistance variable conductive composition of the present invention can be used for printing,
It has application properties such as painting and coating, and can be printed into various shapes by using techniques such as screen printing.

The present invention is a keyboard switch, an automatic door switch,
Can be widely used as various pressure contact switches and other sensors.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the characteristics of the composition of Example 1. FIG. 2 is a graph showing the characteristics of the composition of Example 2. FIG. 3 is a graph showing the characteristics of the composition of Example 3. FIG. 4 is a graph showing the characteristics of the composition of Comparative Example 1. FIG. 5 is a graph showing the characteristics of the composition of Comparative Example 2. FIG. 6 is a graph showing the characteristics of the composition of Comparative Example 3. FIG. 7 is a graph showing the characteristics of the composition of Comparative Example 4. F I G, 1 force Od force (to 9) F I G, 2 shi, pressure (to 9) FIG, 3 force ro μ force (to 9) FIG, 4 karo 1 eka (to 9) F I G , 5 calo/I force (in 9) FIG, 6 calo, pressure (in 9)

Claims (5)

[Claims] (1) 40 to 180 parts by weight of graphite and 110 to 340 parts by weight of chromium sesquioxide to 100 parts by weight of organic polymer material
1. A pressure-sensitive resistance variable conductive composition, characterized in that the graphite and the chromium sesquioxide contain 280 to 390 parts by weight in total. (2) The pressure-sensitive resistance variable conductive composition according to claim 1, wherein the organic polymer material is a vinyl chloride/vinyl acetate copolymer. (3) 40 to 180 parts by weight of graphite and 110 to 340 parts by weight of chromium sesquioxide for 100 parts by weight of organic polymer material
1. A pressure-sensitive resistance change type electrically conductive composition containing 280 to 390 parts by weight of the graphite and the chromium sesquioxide. (4) The pressure-sensitive resistance variable conductive composition according to claim 3, wherein the organic polymer material is a vinyl chloride/vinyl acetate copolymer. (5) The pressure-sensitive resistance variable conductive composition according to claim 3 or 4, wherein the organic solvent is ethylene glycol monobutyl ether and/or acetic acid ethylene glycol monobutyl ether.