JPH03247662A - Pressure-sensitive and resistance-variable conductive composition - Google Patents

Abstract

PURPOSE:To obtain a composition containing an organic high polymer material, conductive material, semiconductor material, insulation material and organic solvent and capable of arbitrarily controlling relationship among pressure sensitive property, pressure force and resistance value and jointly having printability, coating property, etc. CONSTITUTION:The aimed composition containing an organic high polymer material, conductive material, semiconductor material having electric conductivity of <=1/100 based on the conductive material, insulating material and organic solvent and being 1-5000 poise in viscosity measured (at 25 deg.C, 5ppm, after 30sec.) by an EHD type viscometer. Graphite and titanium dioxide are used.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a pressure-sensitive resistance variable conductive composition that can be applied to printing, coating, etc. The present invention relates to a pressure-sensitive resistance change type conductive composition whose relationship with resistance value can be arbitrarily controlled.

<Prior Art> Materials having pressure-sensitive resistance change characteristics have been known.

For example, U.S. Patent No. 2,044,080 states:
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 disclosed in U.S. Pat. No. 3,806.471, which describes the use of various semiconductor materials, the binding of particulate materials together with binders, and the use of hysteresis phenomena. The use of spherical or granular materials to reduce the size and prevent wear is mentioned.

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, such powdered materials are used as is without a dispersion medium such as rubber, which may cause powder to fall off, and therefore the pressure-sensitive conductive material must be placed in a special container. There are disadvantages such as having to be accommodated.
In addition, in the invention of the above-mentioned US Pat. No. 3,806,471, an idea is made to bind the powdery material with a binder, but even with this invention, the flexibility of the material is insufficient.

JP-A-56-108279 discloses an invention in which the thickness of this binder is reduced to 25.4 μm or less. Further, an invention in which powder is confined within the cell spaces of a foam is disclosed in US Pat. No. 2,305,717. However, even with these inventions, falling off of powder cannot be completely prevented.

The problem of powder shedding is overcome by covering the faces of the foam cells with a coating containing conductive powder, as described, for example, in US Pat. No. 3,629,774. 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, a pressure-sensitive conductive elastic composition in which pressure-sensitive conductivity is imparted by blending a special conductive powder into an elastic material such as silicone rubber is disclosed in Japanese Patent Publication No. 56-9137. However, it is extremely difficult to impart properties such as printability, paintability, and coating properties to these elastomer compositions. It is difficult to achieve higher precision, thinner film, lighter weight, etc.

Therefore, it is desired to develop a pressure-sensitive resistance variable conductive material that has excellent pressure sensitivity and properties such as printability, paintability, and coating properties.

<Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned prior art, and its first purpose is to significantly reduce the It is an object of the present invention to provide a composition that exhibits a significant reduction in electrical resistance, whose resistance smoothly decreases with an increase in applied pressure, and which provides a pressure-sensitive conductor having desired pressure sensitivity.

A second object of the present invention is to provide a pressure-sensitive resistance variable conductive composition that can be used in printing, painting, coating, and the like.

<Means for Solving the Problems> The present invention comprises an organic polymer material, a conductive material, a semiconductor material and an insulating material having an electrical conductivity of 1/100 or less of the conductive material, and an organic solvent. The present invention provides a pressure-sensitive resistance change type conductive composition having a viscosity of 1 to 5000 voids as measured with an EHD viscometer (temperature 25° C., !5 rpm, after 30 seconds).

Preferably, the conductive material is graphite and the insulating material is titanium dioxide.

The present invention will be explained in detail below.

In the present invention, having printing characteristics refers to various thick film printing methods such as screen printing and gravure printing, various painting methods such as spraying, and various methods such as spray coating, spin code, roll coating, bar code, etc. This means that films can be formed and laminated using various printing methods, such as the coating method described above.

The organic polymeric material used as a binder in the present invention can be used in ordinary pressure-sensitive resistance variable conductive compositions, and the resulting pressure-sensitive resistance variable conductive composition has printing properties. It can be anything, but
For example, phenolic resin, area resin, melamine resin,
Furan resin, unsaturated polyester resin, epoxy resin,
Thermosetting resins such as silicone resins and polyurethane resins, thermoplastic resins such as vinyl chloride and vinyl acetate copolymers, vinyl chloride resins, vinylidene chloride resins, vinyl acetate resins, acrylic resins, styrene resins, and polyamide resins, nitrocellulose, Suitable examples include cellulose 8 conductors such as acetyl cellulose and ethyl cellulose, rubber conductors such as chlorinated rubber, hydrochloric acid rubber, and silicone rubber, and various modified forms of each of the above-mentioned rubbery elastic bodies. Among these, it is particularly preferable to use vinyl chloride/vinyl acetate copolymers and modified products thereof.

The conductive material used in the present invention may be any conductive material that is normally applied to pressure-sensitive resistance change type conductive compositions, and examples thereof include carbon, graphite, silver, nickel, Examples include copper, titanium carbide, mica whose surface is coated with a conductive material, and fibers. Among these, it is preferable to use graphite, and it is particularly preferable to use graphite in the form of scales, the size of which is about 3 to 8 μm.

Note that the electrical conductivity of graphite is anisotropic, with 10
It is in the range of 3 to 10°S-cm-'.

The semiconductor material and insulating material used in the present invention may be any material as long as it has an electrical conductivity of 17,100 or less of the above-mentioned conductive material, such as chromium sesquioxide, titanium dioxide, boron nitride, molybdenum disulfide, Inorganic substances such as magnesium, calcium carbonate, aluminum hydroxide, alumina, zinc white, clay, and talc, and benzoguanamine resin powder (e.g. Epostor manufactured by Nippon Shokubai Kagaku Co., Ltd.), which is an organic powder that does not dissolve in organic solvents.
Suitable examples include nylon resin spheres, silicone resin powder (eg Tospar manufactured by Toshi Silicone Co., Ltd.), rubber powder, polyethylene powder, and the like.

Semiconductor materials and insulating materials that have an electrical conductivity of 1/100 or less of the electrically conductive material are used when the electrical conductivity is 1710 that of the electrically conductive material.
This is because if it exceeds 0, pressure sensitivity will not be expressed.

A specific combination of a conductive material, a semiconductor material having an electrical conductivity of 17100 or less, and an insulating material includes, for example, graphite (electrical conductivity of 103 to 103).
10°S-cm-J and chromium sesquioxide (electrical conductivity 10
-" S -cm-' or less), graphite and titanium dioxide (electrical conductivity 10-5 to io-"s cm-'),
Graphite and boron nitride (electrical conductivity 10-” S-c
m-'), graphite and molybdenum disulfide (electrical conductivity 10-3 to 1o-lo-10S-'), graphite and magnesium oxide (electrical conductivity 10-'' S-am
-') Graphite and calcium carbonate (N vapor conductivity 10-13 S-cm-') Graphite and aluminum hydroxide (electrical conductivity 10-"SCm-'), graphite and alumina (electrical conductivity 10-"S-') cm
-'), graphite and zinc white (electrical conductivity 10-10
~10-10-15S'), graphite and clay (electrical conductivity 10''S-cm-'), and graphite and talc (electrical conductivity 10-''S-cm-').

In addition, silver (electrical conductivity 6.3X105SCm-'), the above semiconductor materials and insulating materials, nickel (electrical conductivity 1
．． 4X105Sam-') and the above semiconductor material and insulating material, copper (electrical conductivity 6.Ox 105S -cm-
') and the above semiconductor materials and insulating materials, aluminum (
Mica whose surface is coated with a conductive material (electrical conductivity 3.8X 105S-cm-') and the semiconductor and insulating materials, conductive Ceramic whisker material (electrical conductivity 10-'~10-2S-cm-'
) and the above-mentioned semiconductors and insulating materials.

In the present invention, the blending ratio of the organic polymer material, the conductive material, the semiconductor material, and the insulating material is not particularly limited, and the composition obtained by blending these three materials exhibits a pressure-sensitive resistance change. If so, it can be determined freely.

The pressure-sensitive resistance variable conductive composition of the present invention further contains an organic solvent for dissolving and dispersing each of the above-mentioned materials.

The organic solvent is useful for imparting printing properties to the composition of the present invention and for making the pressure sensitivity of the pressure-sensitive conductor obtained by forming the composition of the present invention into a film to any desired level. .

Examples of organic solvents used in the present invention include:
Aliphatic hydrocarbons such as industrial gasoline and kerosene, aromatic petroleum naphthas such as low-boiling aromatic petroleum naphtha and medium-boiling aromatic petroleum naphtha, aromatic hydrocarbons such as penzol, doluol, kijirole, and turchent naphtha, turpentine oil, Dipentene, terpene hydrocarbons such as pine oil, methylene chloride, trichlorethylene, perchlorethylene,
Chlorinated hydrocarbons such as orthodichlorobenzene, nitrated hydrocarbons such as 2-nitropropane, aliphatic alcohols such as methanol, ethanol, isopropanol, and imbutanol, ethylene glycol methyl ether, ethylene glycol monoethyl ether, ethylene glycol Monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, 1-butoxyethoxypropanol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, propylene glycol- Ether alcohols such as n-propyl ether and propylene glycol isopropyl ether, ethers such as dioxane, methyl acetate, ethyl acetate, isopropyl acetate, propylene glycol acetate monoester, propylene glycol acetate diester, 1-methoxy-2-propatol acetate, etc. acetic acid esters, cyclic esters such as propylene carbonate, ether esters such as ethylene glycol monomethyl acetate, ethylene glycol monoethyl acetate, ethylene glycol monobutyl acetate, diethylene glycol monoethyl acetate, and the various organic solvents listed above. A suitable example is a mixture. For example,

In the present invention, any organic solvent may be used as long as it is usable in consideration of the printing, painting, coating, etc. method and the volatilization rate of the organic polymer material (binder) and the solvent. Preferred is ethylene glycol monobutyl ether acetate.

The blending amount of the organic solvent is determined by measuring the viscosity of the pressure-sensitive resistance change type conductive composition of the present invention using an EHD type viscometer (temperature 25 ° C., 5 rpm).
pm, after 30 seconds) is within the range of 1 to 5000 poise.

Therefore, whatever compounds are used as organic polymer materials, conductive materials, semiconductor materials, and insulating materials,
Furthermore, the amount of organic solvent to be blended varies greatly depending on the blending ratio.

In addition, the composition of the present invention was measured with an EHD type viscometer (temperature 2
The viscosity (after 30 seconds at 5° C., 5 rpm, 30 seconds) must be between 1 and 5000 poise, because if the viscosity is less than 1 poise, the viscosity of the composition is too low to be practical; on the other hand, if it exceeds 5000 poise, This is because the viscosity of the composition is too high to be put to practical use.

The method for producing the pressure-sensitive resistance variable conductive composition of the present invention is not particularly limited, but includes, for example, an organic polymer material,
A conductive material, a semiconductor material, and an insulating material may be dissolved and dispersed in an organic solvent.

Since the pressure-sensitive resistance variable conductive composition of the present invention has printing properties, it is possible to produce a pressure-sensitive conductor by processing it by printing techniques such as printing, painting, and coating.

For various pressure-sensitive conductors, the slope of the straight line is called the "gradient" when the relationship is graphed with the logarithm of the resistance value on the vertical axis and the logarithm of the applied force on the horizontal axis (see Figure 1). ), in a normal pressure-sensitive conductor, the larger the absolute value of this gradient, the better the pressure-sensitivity. When a pressure-sensitive conductor is produced using the composition of the present invention, this gradient can be adjusted as desired, and the absolute value of the gradient can also be increased, so that it has excellent pressure sensitivity. I can do it.

<Example> EXAMPLES The present invention will be specifically explained below with reference to Examples.

(Example) A pressure-sensitive resistance variable conductive composition having the composition shown in Table 1 was prepared, and its viscosity was measured using an EHD viscometer. still,
The viscosity measurement conditions were a temperature of 25° C., 5 rpm, and 30 seconds.

Next, after printing these compositions on a 188 μm thick polyester film, a heat-drying treatment was performed to remove the solvent ethylene glycol monobutyl ether, and a 50 μm thick pressure-sensitive conductive film was printed on the polyester film. A body layer was formed. Place this on a flat comb-like electrode, add a parallel resistance of 50Ω to 100Ω, repeat pressurization and depressurization using a rod with a flat tip of 10mm in diameter, and adjust the relationship between resistance value and pressure. The slope was calculated using a logarithmic graph.

The results are shown in Table 1.

As is clear from Table 1, the composition of the present invention has printing properties, and when a pressure-sensitive conductor is prepared using the composition of the present invention, one having desired pressure sensitivity can be obtained.

<Effects of the Invention> The pressure-sensitive resistance variable conductive composition of the present invention can control the sensitivity and resistance value of a pressure-sensitive conductor produced using the composition.

Further, the pressure-sensitive conductor has little variation in sensitivity due to differences in the magnitude of applied force, and has linearity of sensitivity over a wide range of applied forces.

Furthermore, the pressure-sensitive conductor has the property of being able to withstand repeated pressurization and having a resistance value that smoothly decreases as the pressurizing force increases, so it is suitable for applications such as a pressurizing force conversion element or a variable resistor. It has excellent durability as a switch element operated by pressurization. It can also be used in a wide range of applications such as keychain switches, automatic door switches, various pressure contact switches, and other sensors.

In addition, since the pressure-sensitive conductor exhibits an inversely proportional relationship between the logarithm of the applied force and the logarithm of the resistance value, it can be applied as various sensors such as applied force detectors.

The pressure-sensitive resistance variable conductive composition of the present invention has properties such as printability, paintability, and coatingability, and can be printed into various shapes by using techniques such as screen printing.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the pressure applied to the pressure-sensitive conductor and the resistance value.

Claims (2)

[Claims] (1) Organic polymer material, conductive material, 1 of the conductive material
Contains a semiconductor material and an insulating material having an electrical conductivity of /100 or less, and an organic solvent, and has a viscosity of 1 when measured with an EHD type viscometer (temperature 25°C, 5 rpm, after 30 seconds).
A pressure-sensitive resistance change type conductive composition characterized by having a poise of 5000 to 5000 poise. (2) Claim 1, wherein the conductive material is graphite, and the semiconductor material and the insulating material are titanium dioxide.
The pressure-sensitive resistance change type conductive composition described in .