JPH01243401A - Pressure sensitive variable resistance type conductive composition - Google Patents

Abstract

PURPOSE:To obtain a pressure sensitive conductor excellent in repetitive durability, by containing graphite, titanium dioxide and organic polymer binder of specified weight ratios respectively. CONSTITUTION:For 100 pts.wt. of organic polymer material, the following are contained; 30-160 pts.wt. of graphite and 50-150 pts.wt. of titanium dioxide, in the manner that the sum total of graphite and titanium is made 170-200 pts.wt. By changing the ratio of graphite and titanium dioxide in this manner, the rate of change of resistance with respect to applied pressure can be controlled. Thereby, an applied pressure converting element or a variable resistor being excellent in the durability for the repletion of pressure applying and releasing, and having characteristics wherein the resistance value smoothly decreases in accordance with the increase of applied pressure, can be obtained.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a pressure-sensitive resistance change type conductive composition that has properties such as printing, painting, and coating, and more specifically, a composition that exhibits high resistance or insulation when no pressure is applied. , relates to a pressure-sensitive resistance change type conductive composition that exhibits low resistance or conductivity when pressurized.

■Prior Art Materials having such pressure-sensitive resistance change characteristics have been known for a long time. For example, U.S. Pat. No. 2,044,080 describes granulated carbon (:a
An invention has been disclosed in which, when a conductive material such as (rbon) is sandwiched between electrodes and the material is compressed, the resistance value of the material decreases. A similar example is U.S. Pat.
．． No. 806.471 also discloses the use of various semiconductor materials, the fact that particulate materials are held together by a binder, the spherical or granular shape to reduce the bisteresis phenomenon and to prevent wear. The use of substances is mentioned. Furthermore, U.S. Patent No. 3,
No. 710゜050 specifies that conductive powder contains 20 to 50%
An invention has been disclosed in which rubber powder is added to bring out the pressure-sensitive conductivity of the powder.

In these examples, the powdered 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 housed 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 powder and granules together with a binder, but the flexibility of the material was insufficient.

JP-A-56-108279 discloses an invention in which the thickness of this binder is made 25.4 microns or less. Furthermore, 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 shedding can be solved, for example, in US Pat.
29,774, by covering the cell surfaces of the foam with a coating 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 open is not sufficiently high, and the ratio of the resistance value when open to the resistance value when pressurized is small, so it is not preferable as a switch element, for example.

In addition, pressure-sensitive conductive elastomer compositions in which special conductive powder is blended with an elastic material such as silicone rubber to impart pressure-sensitive conductivity are disclosed in Japanese Patent Publication No. 56-9187, etc., but these It is extremely difficult to impart properties such as printing, painting, and coating to elastic body compositions, and there are limits to the precision, thinning, and weight reduction of switch elements and electronic components, and it is difficult to achieve excellent sensibility. There has been a desire for the emergence of a pressure-sensitive resistance change type conductive material that has both pressure resistance and properties such as printing, painting, and coating.

■Object of the Invention The object of the present invention is to provide a method in which the electrical resistance is significantly reduced by pressurization compared to the electrical resistance when the pressure is not compressed, and the resistance is smoothed by increasing the pressurizing force. An object of the present invention is to provide a pressure-sensitive resistance variable conductive composition that provides a pressure-sensitive conductive body with reduced printing, painting, coating, etc. characteristics.

Another object of the present invention is to provide a pressure-sensitive resistance variable conductive composition that provides a pressure-sensitive conductive body with excellent durability against repeated pressurization and release.

(2) Structure of the Invention The present invention relates to a pressure-sensitive resistance variable conductive composition having properties as a printing ink, paint, or coating material.

The pressure-sensitive resistance change type conductive composition of the present invention contains graphite as a conductive material, titanium dioxide as an electrically insulating material, and an organic polymer binder, and more preferably in a suitable solvent. If it is dissolved and dispersed in the liquid, it becomes a composition that is excellent for printing, painting, coating, etc.

For example, it can be formed into a film by coating it on a base material such as a polyester film and evaporating the solvent.

In the pressure-sensitive resistance change type conductive composition of the present invention, the rate of change in resistance (hereinafter sometimes referred to as sensitivity) against applied pressure can be controlled by changing the ratio of graphite and titanium dioxide.

Examples of the organic polymer material (binder) used in the present invention include thermosetting resins such as phenol resins, urea resins, melamine resins, furan resins, unsaturated polyester resins, epoxy resins, silicone resins, polyurethane resins, and chlorinated resins. Thermoplastic resins such as vinyl resin, vinylidene chloride resin, vinyl acetate resin, acrylic resin, styrene resin, polyamide resin, cellulose derivatives such as nitrocellulose, acetylcellulose, and ethylcellulose, rubber derivatives such as chlorinated rubber, hydrochloric acid rubber, silicone rubber, etc. For example,

In the present invention, any material may be used as long as it can be printed, painted, coated, etc., but it is particularly preferable to use vinyl chloride/vinyl acetate copolymer and modified products thereof.

Graphite is preferred as the conductive material used in the present invention. Particularly preferred is flaky graphite having a size of about 6.0 microns.

The blending amount of graphite is from 30 parts by weight to 16 parts by weight per 100 parts by weight of the organic polymer material (binder resin).
The range is 0 parts by weight, more preferably 33 parts by weight to 148 parts by weight.

The insulator used in the present invention is preferably titanium dioxide. The amount of titanium dioxide to be blended is in the range of 50 parts by weight to 150 parts by weight per 100 parts by weight of the organic polymer material (binder resin), and more preferably the particle size is about 0.1 to 0.3 microns. The one is good.

The total amount of graphite as a conductive material and titanium dioxide as an insulating material is preferably in the range of 170 to 220 parts by weight. This is less than 170 parts by weight or 2
If it exceeds 20 parts by weight, a pressure-sensitive resistor type cannot be obtained.

Examples of the solvent used in the present invention include industrial gasoline, aliphatic hydrocarbons such as kerosene, aromatic petroleum naphthas such as low-boiling aromatic petroleum naphtha, medium-boiling aromatic petroleum naphtha, penzole, doluol, and kijirole. , aromatic hydrocarbons such as solvent naphtha, turpentine oil, dipentene,
Terpene hydrocarbons such as pine oil, chlorinated hydrocarbons such as methylene chloride, trichlorethylene, perchlorethylene, orthodichlorobenzene, nitrated hydrocarbons such as 2-nitropropane, methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl Aliphatic alcohols such as alcohol, ether alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, ethers such as dioxane, methyl acetate, ethyl acetate, isopropyl acetate, etc. Examples include ether esters such as acetic acid ester, ethylene glycol monomethyl acetate, ethylene glycol monoethyl acetate, ethylene glycol monobutyl acetate, and diethylene glycol monoethyl acetate.

However, the present invention is not limited to printing,
Any usable solvent may be used, taking into account the method of painting and coating and the volatilization rate of the binder and solvent, but ethylene glycol monobutyl acetate is particularly preferred.

The base material used in the present invention includes printing, painting,
Any material suitable for coating may be used.

(2) Examples Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples.

(Example 1) A printing ink composition containing 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 50 parts by weight of graphite, 134 parts by weight of titanium dioxide, and 504 parts by weight of ethylene glycol monobutyl ether acetate was applied to a polyester film having a thickness of 188 microns. After printing on the film, a heat-drying treatment was performed to remove the solvent ethylene glycol monobutyl ether acetate, thereby obtaining a pressure-sensitive resistance variable conductive composition having a pressure-sensitive conductor layer with a 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 of the pressure-sensitive resistance variable conductive composition in this example are as follows:
As shown in the figure. This figure 1 shows the relationship between pressurization force and resistance; as soon as pressurization starts, the resistance drops smoothly and becomes conductive, and when pressurization is released, it immediately and smoothly returns to the original resistance value. The condition is shown.

Furthermore, this state did not change even when the rod was repeatedly pressurized 1 million times, indicating that the composition of the present invention has excellent durability against repeated pressurization and release. .

(Example 2) A printing ink composition containing 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 33 parts by weight of graphite, 146 parts by weight of titanium dioxide, and 497 parts by weight of ethylene glycol monobutyl ether acetate was applied to a polyester film having a thickness of 188 microns. After printing on the film, a heat-drying treatment was performed to remove the solvent ethylene glycol monobutyl ether acetate, thereby obtaining a pressure-sensitive resistance variable conductive composition having a pressure-sensitive conductor layer with a 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 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) The same method as in Example 1 was prepared from a printing ink composition containing 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 148 parts by weight of graphite, 58 parts by weight of titanium dioxide, and 547 parts by weight of ethylene glycol monobutyl ether acetate. A composition having a dry film thickness of 7.degree. microns was prepared using the same method as in Example 1, and its properties were observed using the same method as in Example 1. .

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 225 parts by weight of graphite in 580 parts by weight of ethylene glycol monobutyl ether acetate was applied to a polyester film with a thickness of 188 microns. After printing on top, a heating drying treatment was performed to remove ethylene glycol monobutyl ether acetate, yielding 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 pressure-sensitive resistance variable type of the present invention cannot be achieved.

(Comparative Example 2) The same method as in Comparative Example 1 was prepared from a printing ink composition obtained by dissolving and mixing 100 parts by weight of vinyl chloride/vinyl acetate copolymer and 170 parts by weight of titanium dioxide in 480 parts by weight of ethylene glycol monobutyl ether acetate. dry film thickness 70
A micron composition was prepared and the same characteristics as Comparative Example 1 were observed.

The characteristics are shown in Figure 5.

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 remains unchanged. The value did not change and remained in an insulating state.

(Comparative Example 3) The same method as in Comparative Example 1 was prepared from a printing ink composition containing 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 198 parts by weight of graphite, 20 parts by weight of titanium dioxide, and 569 parts by weight of ethylene glycol monobutyl ether acetate. 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 characteristics are shown in Figure 6. FIG. 6 shows the relationship between the pressurizing force and the resistance. When pressurization starts, the resistance rapidly drops to a conductive state, and when the pressurization is released, the resistance value sharply increases to an insulating state.

The sensitivity of the composition in this example is closer to Comparative Example 1 than to Examples 1.2 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) The same method as in Comparative Example 1 was prepared from a printing ink composition containing 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 19 parts by weight of graphite, 157 parts by weight of titanium dioxide, and 490 parts by weight of ethylene glycol monobutyl ether acetate. 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 characteristics are shown in Figure 7.

In this comparative example, as is clear from the relationship graph of pressurized resistance in FIG. 7, even when pressurization starts, the resistance value changes only slightly, and its sensitivity is also very small. 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.

■Description of Effects The pressure-sensitive resistance variable conductive composition of the present invention has the property of withstanding repeated pressurization and smoothly decreasing its resistance value as the pressurizing force increases, and can be used as a pressurizing force converting element or Suitable for applications such as variable resistors.

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.

Moreover, 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]

All of the drawings are relationship diagrams between pressure and resistance values to show pressure-sensitive characteristics. Figures 1, 2 and 3 are graphs showing the properties of the compositions in Examples 1.2 and 3, respectively. FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are graphs showing the characteristics of the compositions in Comparative Examples 1.2.3 and 4, respectively. FIG, 1 Add F power (to 9) FIG, 2 KaOg force (to 9) FIG, 3 Pressure power (to 9) FIG, 4 Calo pressure (to 9) FIG, 5 force OLE force (to 9) FIG, 6 Calo I5 Power (Ni9)

Claims (5)

[Claims] (1) It contains 30 to 160 parts by weight of graphite and 50 to 150 parts by weight of titanium dioxide with respect to 100 parts by weight of the organic polymer material, and the total of the graphite and titanium dioxide is 170 to 220 parts by weight. A pressure-sensitive resistance variable conductive composition. (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) Contains 30 to 160 parts by weight of graphite, 50 to 150 parts by weight of titanium dioxide, and an organic solvent to 100 parts by weight of the organic polymer material, and the total of the graphite and titanium dioxide is 170 to 220 parts by weight. A pressure-sensitive resistance variable conductive composition characterized by the following. (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 acetic acid ethylene glycol monobutyl ether.