JPH02158105A - Laminated type pressure sensitive material - Google Patents

Abstract

PURPOSE:To make it possible to form a material by a printing method and to prevent current conduction under the state wherein pressure is not applied positively even if a spacer and the like are not used when the material is applied for sensors, switches and variable resistors by laminating conductive compositions whose pressure sensitive resistance is changed and which have printing characteristics, and making the electric conductivity of the outermost layer smaller than the synthesized electric conductivity of the other layers. CONSTITUTION:On a base material 12 comprising an insulating material such as polyester, conductive composition whose pressure sensitive resistance is changed and which have printing characteristics are laminated by screen printing, and a first layer 14 is obtained. Then, conductive compositions whose pressure sensitive resistance is changed and which has printing characteristics are laminated on the first layer 14 by screen printing. Thus, a second layer 16 as an outermost layer having the electric conductivity smaller than the (synthesized) electric conductivity of the first layer 14 which is the layer other than the outermost layer is formed. The number of said laminated layers can be two or more and can be determined appropriately in correspondence with the intended applications and the like of the laminated type pressure sensitive material. With this constitution, insulation between the conductor and the laminated type pressure sensitive material when pressure is not applied is ensured, when various kinds of the conductors are brought into contact with the surface (outermost layer) and various kinds of elements and the like are formed. The change in electric resistance is large, and the pressure sensitive property is excellent.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention is directed to a pressure-sensitive resistance variable conductive composition (elastic conductor, elastic resistor, pressure-sensitive conductor, pressure-sensitive resistor) having printing properties. ). Specifically, it is a laminated type material with improved pressure resistance change characteristics, that is, pressure sensitivity (gradient), which is made by laminating a plurality of pressure-sensitive resistance change type conductive compositions using various printing methods such as screen printing. Regarding pressure materials.

<Prior art> Conductive particles such as metal powder with a diameter of about 0.5 to 1100 μ formed by various chemical, mechanical, electrical resistance, or gas phase decomposition methods are molded using various synthetic resins, etc. Various pressure-sensitive materials have been proposed, which are made of a pressure-sensitive resistance variable conductive composition mixed and dispersed in a rubber elastic body, and whose electrical resistance value changes when pressurized.

When applying such pressure-sensitive materials as conductive elastic bodies, pressure-sensitive resistors, various sensors and switches, etc., external metals (including graphite) are usually applied to the surface of the pressure-sensitive resistance variable conductive composition. It is used in contact with an external conductor such as
Conventional pressure-sensitive materials have a problem in that the electrical resistance of the contact portion between the external conductor and the pressure-sensitive material is low, and electricity is often applied even when no pressure is applied.

In order to solve this problem, we proposed a method of inserting spacers made of various insulating materials, and also
Various methods have been proposed, such as the method of inserting the rubber actuator disclosed in Japanese Patent No. 25.

However, each of the above-mentioned methods has drawbacks such as an increase in the number of parts and steps when applying the pressure-sensitive material to various uses, and an increase in cost when commercialized as a switch or the like.

In addition, as a method to solve the above problems,
JP-A-139989 also proposes a laminated pressure sensitive material in which pressure sensitive resistors are laminated. This method uses pressure-sensitive resistors using conductive particles with different particle densities, etc. by heat-pressing,
Lamination is performed by methods such as vulcanization adhesion of unvulcanized bodies, or methods using conductive adhesives mixed with conductive paints, adhesives, and metal powder.
It is glued to make a pressure-sensitive material.

However, the pressure sensitive material produced by this method has a large thickness as a whole. Moreover, when various adhesives are used, there is a problem that the presence of the adhesive layer impairs the pressure resistance change characteristics of the pressure sensitive material.

<Problems to be Solved by the Invention> An object of the present invention is to solve the problems of the prior art described above, and to provide a sensor, switch, etc. that can be produced by printing methods such as printing, painting, and coating. When applied to variable resistors, etc., it is possible to reliably prevent energization in an unpressurized state without using a spacer, etc., and the electrical resistance is significantly reduced by pressure compression. An object of the present invention is to provide a laminated pressure-sensitive material with excellent pressure sensitivity, whose electrical resistance value smoothly decreases as compression increases.

Means for Solving the Problems> In order to achieve the above object, the present invention comprises laminating at least two layers of pressure-sensitive resistance variable conductive compositions having printing properties, and the electrical conductivity of the outermost layer is To provide a laminated pressure-sensitive material having a composite electrical conductivity lower than that of other layers.

Hereinafter, a specific configuration of the present invention will be explained in detail.

The laminated pressure-sensitive material of the present invention is formed by laminating at least two layers of pressure-sensitive resistance variable compositions having printing properties.

Here, in the present invention, having printing characteristics means various thick film printing methods such as screen printing and gravure printing; various painting methods such as spraying; and spray coating, spin code, roll coating, bar code, etc. Various coating methods: This means that films can be formed and laminated by various printing methods such as:

The pressure-sensitive resistance variable conductive composition applied to the present invention is not particularly limited as long as it has the printing characteristics as described above.
Any known material that is commonly used as a pressure sensitive material can be used, for example, in Japanese Patent Application No. 62-2947 filed by the present applicant.
Preferred examples include pressure-sensitive resistance change type conductive compositions disclosed in various specifications such as No. 96.

Such a pressure-sensitive resistance variable conductive composition applied to the present invention basically contains an organic polymer material and a conductive material.

The organic polymer material used in the pressure-sensitive resistance variable conductive composition applied to the laminated pressure-sensitive material of the present invention can be applied to a normal pressure-sensitive resistance variable conductive composition, and the resulting pressure-sensitive Any resistance change type conductive composition can be applied as long as it has printing properties, such as phenol resin, area resin, melamine resin, furan resin, unsaturated polyester resin, epoxy resin, silicone resin, Thermosetting resins such as polyurethane resins; Thermoplastic resins such as vinyl chloride/vinyl acetate copolymers, vinyl chloride resins, vinylidene chloride resins, vinyl acetate resins, acrylic resins, styrene resins, polyamide resins: nitrocellulose, acetylcellulose, Suitable examples include cellulose derivatives such as ethyl cellulose; rubber derivatives such as chlorinated rubber, hydrochloric acid rubber, and silicone rubber; and various modified forms of each of the above-mentioned rubbery elastic bodies.

In particular, vinyl chloride/vinyl acetate copolymers and modified products thereof are preferably used.

As the conductive material used in the pressure-sensitive resistance variable conductive composition applied to the present invention, any conductive substance that is applied to a normal pressure-sensitive resistance variable conductive composition can be used, Examples include graphite, silver, nickel, copper, and mica whose surface is coated with a conductive material. Among them, graphite is suitably used, and particularly preferably, flake-like graphite with a size of about 6.0 μm is preferred.

The pressure-sensitive resistance variable conductive composition applied to the laminated pressure-sensitive material of the present invention may contain various semiconductor materials and insulating materials, if necessary.

As the semiconductor material and the insulating material, materials having an electrical conductivity of 1/100 or less of the above-mentioned conductive materials are preferable, and include chromium sesquioxide, titanium dioxide, boron nitride, molybdenum disulfide, magnesium oxide, calcium carbonate, and water. Preferred examples include aluminum oxide, alumina, zinc white, and clay talc.

The reason why it is preferable that the electrical conductivity of the semiconductor material and the insulating material is 1/100 or less of that of the above-mentioned conductive material is that the electrical conductivity of the semiconductor material and the insulating material is lower than that of the conductive material. This is because pressure sensitivity does not develop when the electrical conductivity exceeds 1/100 of the electrical conductivity.

The blending amounts of the organic polymer material, conductive material, and insulating material are not particularly limited. It can be freely determined within the range that indicates.

The pressure-sensitive resistance variable conductive composition applied to the laminated pressure-sensitive material of the present invention may contain various organic solvents, if necessary, in order to improve its printing characteristics.

Suitable organic solvents include, for example, aliphatic hydrocarbons such as industrial gasoline and kerosene; aromatic petroleum naphthas such as low-boiling aromatic petroleum naphthas and medium-boiling aromatic petroleum naphthas; penzole, doluol, and kijirole. Aromatic hydrocarbons such as , solvent naphtha; Terpene hydrocarbons such as turpentine oil, dipentene, and pine oil; Chlorinated hydrocarbons such as methylene chloride, trichlorethylene, perchlorethylene, orthodichlorobenzene; 2-nitropropane, etc. Nitrated hydrocarbons; methyl alcohol, ethyl alcohol, isopropyl alcohol,
Aliphatic alcohols such as isobutyl alcohol; Ether alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether; Ethers such as dioxane; Methyl acetate, ethyl acetate, isopropyl acetate Acetate esters such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl acetate ether, ethylene glycol monobutyl acetate, diethylene glycol monoethyl acetate, etc.; Further, mixtures of the various organic solvents mentioned above are preferably exemplified. Any usable solvent may be used, taking into account the lamination method such as printing, painting, coating, etc., and the volatilization rate of the organic polymer material and solvent, but ethylene is particularly preferred. Glycol monobutyl ether, acetic acid ethylene glycol monobutyl ether.

The laminated pressure-sensitive material of the present invention is formed by laminating at least two layers of such pressure-sensitive resistance variable conductive compositions, but in the present invention, pressure-sensitive resistance variable conductive compositions made of completely different materials are laminated. pressure-sensitive resistance change type conductive compositions, which are made of the same material but have different electrical conductivity by changing the content ratio of organic polymer material and conductive material, etc. The combination is completely arbitrary as long as the conductivity can be made smaller than the composite electrical conductivity of the other layers,
Various types are applicable.

Such a pressure-sensitive resistance change type conductive composition applied to the laminated pressure-sensitive material of the present invention may be manufactured by any known manufacturing method, and one example is: The conductive material, the electrically insulating material, and the organic polymer material may be dissolved and dispersed in a suitable solvent.

The laminated pressure-sensitive material of the present invention is obtained by laminating at least two layers of the pressure-sensitive resistance change type conductive composition having printing characteristics as described above by a printing method such as printing, encircling, coating, etc.
In addition, the electrical conductivity of the outermost layer is smaller than the combined electrical conductivity of the other layers.

Since the laminated pressure sensitive material of the present invention has the above structure, it can be laminated and created by a printing method, so it can be made thinner than conventional ones, and it also has electrical High degree of freedom in design. Furthermore, since the electrical conductivity of the outermost layer is lower than the composite electrical conductivity of the other layers,
When various types of conductors are brought into contact with the surface (outermost layer) to form various devices, the insulation between the conductor and the laminated pressure-sensitive material is ensured when no pressure is applied, and the electrical resistance is maintained when pressure is applied. It can be made to have excellent pressure sensitivity with a large change in resistance.

FIG. 1 shows an example of the laminated pressure sensitive material of the present invention.

The laminated pressure-sensitive material 10 shown in FIG. 1 has a first layer formed by laminating a pressure-sensitive resistance variable conductive composition having printing characteristics on a base material 12 made of an insulating material such as polyester by screen printing. 14, and then a pressure-sensitive resistance variable conductive composition having printing properties is laminated on this first layer 14 by screen printing to form the first layer 14 (other than the outermost layer).
Synthesis) Second layer 16 as the outermost layer with low electrical conductivity
That is.

The method of laminating each pressure-sensitive resistance variable conductive composition in the laminated pressure-sensitive material 10 of the present invention is not limited to screen printing, and any of the various printing methods described above are suitable. Applicable. Among these, screen printing, roll coating, etc. are particularly preferably applied because of their excellent productivity and ease of controlling the layer thickness of each layer. Further, if necessary, each layer may be laminated using a different printing method.

The number of laminated layers of the pressure-sensitive resistance variable conductive composition of the layered pressure-sensitive material of the present invention may be two or more, and may be appropriately determined depending on the intended use of the layered pressure-sensitive material.

In addition, when the number of laminated layers is 3 or more, if the electrical conductivity of the outermost layer is smaller than the combined electrical conductivity of each remaining layer, the remaining layers must have the same electrical conductivity.
The above layers may be stacked, and if the electrical conductivity of the outermost layer is smaller than the combined electrical conductivity of the remaining layers, layers having the same electrical conductivity as the outermost layer may be stacked other than the outermost layer.

The thickness of each layer in the laminated pressure-sensitive material of the present invention is not particularly limited, and is appropriately determined based on the electrical conductivity of each pressure-sensitive resistance variable conductive composition, the designed electrical resistance of the laminated pressure-sensitive material, and the like.

In the laminated pressure-sensitive material of the present invention, the electrical conductivity of the outermost layer (second layer 16 in the example shown in FIG. 1) is different from that of each of the remaining layers (
In the example shown in FIG. 1, it is smaller than the composite electrical conductivity of the first layer 14). By having such a structure, the laminated pressure sensitive material of the present invention can be used to form various elements etc. by bringing various conductors into contact with the surface (outermost layer).
The insulation between the conductor and the laminated pressure-sensitive material is ensured when no pressure is applied, and the electrical resistance changes significantly when pressure is applied, resulting in excellent pressure sensitivity.

In addition, for various pressure-sensitive materials, the logarithm of the resistance value is plotted on the vertical axis,
The slope of the straight line when graphing the change in logarithm of the applied force on the horizontal axis is called the "slope" (see Figure 2), and for normal pressure-sensitive materials, the larger the absolute value of this slope, the better. It has a high pressure sensitivity. Since the laminated pressure-sensitive material of the present invention has the above-described predetermined configuration, the absolute value of this gradient is also large, and it has excellent pressure sensitivity.

In the laminated pressure sensitive material of the present invention, the electrical conductivity of the outermost layer is smaller than the combined electrical conductivity of the remaining layers.

A method for adjusting the composite electrical conductivity of the outermost layer and the remaining layers is to use a pressure-sensitive resistance variable conductive composition made of completely different materials; A method using a pressure-sensitive resistance variable conductive composition in which the electrical conductivity is changed by changing the content ratio of the material;
Various known methods may be used, such as a method in which the electrical resistance is adjusted by changing the layer thickness, although the content ratios of the organic polymer material and the conductive material are exactly the same.

In this case, if the thickness of the outermost layer is made thinner, the electrical resistance tends to increase, so current leakage of the laminated pressure-sensitive material in the non-pressurized state can be reduced.

In the example shown in FIG. 1, the laminated pressure sensitive material 10 is produced by laminating it on a base material 12 made of polyester. is not limited to polyester, and various insulating materials such as various epoxy resins, melamine resins, acrylic resins, polyamide resins, polyimide resins, and vinyl chloride can be applied.

<Example> Hereinafter, the present invention will be explained in more detail by giving specific examples of the present invention.

Example 1 As shown in FIG.
124 parts by weight of titanium dioxide, 100 parts by weight of vinyl chloride/vinyl acetate copolymer, and 500 parts by weight of pressure-sensitive resistance variable conductive conductive material for printing obtained by dissolving and dispersing titanium dioxide in 500 parts by weight of ethylene glycol monobutyl ether. The composition A was laminated as the first layer 14 by screen printing and then dried by evaporating the solvent. Next, on this first layer 14, 43 parts by weight of graphite, 124 parts by weight of titanium dioxide, ioo parts by weight of vinyl chloride/vinyl acetate copolymer, and 475 parts by weight of ethylene glycol monobutyl ether acetate are dissolved and dispersed. The pressure-sensitive resistance variable conductive composition B obtained by this method is laminated as the second layer 16 by screen printing, and then the solvent is evaporated and dried to form the laminated layer of the present invention shown in FIG. A type pressure sensitive material 10 was obtained.

The thickness of each layer of the obtained laminated pressure sensitive material 10 is 20 μm.
The electrical conductivity of the second layer 16, which is the outermost layer, is 1 x 10
-'S -cm-' The first layer 14 which is the other layer
The (synthetic) electrical conductivity of was 1 x 1010-33-a.

The laminated pressure sensitive material 10 of the present invention created in this way,
After placing it on a flat comb electrode and applying a parallel resistance of 5 kΩ, pressure was repeatedly applied and depressurized using a rod with a flat tip having a diameter of 10 mm, and the characteristics were observed.

The relationship between the applied force and the electrical resistance of the obtained laminated pressure-sensitive material 1o is that as soon as pressurization starts, the electric resistance decreases smoothly and becomes conductive, and as soon as the pressurization is released, it immediately and smoothly decreases. It had excellent characteristics, with the resistance value returning to its original value.

Also, when I calculated the slope, the slope was -0.77 showed good pressure sensitivity.

[Example 2] Similarly to Example 1, 42 parts by weight of graphite was placed on a base material 12 made of a polyester film with a thickness of 188 μm.
124 parts by weight of titanium dioxide, 100 parts by weight of vinyl chloride/vinyl acetate copolymer, 473m! Pressure-sensitive resistance change type conductive composition C for printing obtained by dissolving and dispersing in 5 parts of acetic acid ethylene gelcol monobutyl ether was laminated as the first layer 14, the solvent was evaporated and dried, and then On this first layer 14, 49 parts by weight of graphite,
Pressure-sensitive resistance variable conductive composition for printing obtained by dissolving and dispersing 124 parts by weight of titanium dioxide, 100 parts by weight of vinyl chloride/vinyl acetate copolymer, and 468 parts by weight of acetic acid ethylene gelcol monobutyl ether. The material was laminated as the second layer 16 by screen printing, and the solvent was evaporated and dried to obtain the laminated pressure-sensitive material 10 of the present invention shown in FIG.

The thickness of each layer of the obtained laminated pressure sensitive material 10 was 20 um,
The electrical conductivity of the second layer 16, which is the outermost layer, is 7X10-'S.
-cm-', (synthesis) of the first layer 14 which is the other layer
The electrical conductivity was 7x10-'S-am-'.

The laminated pressure sensitive material 10 of the present invention created in this way,
Place it on a flat comb-like electrode as in Example 1, and
After applying a parallel resistance of It had an excellent property of quickly and smoothly returning to its original resistance value as soon as the pressure was released.

Further, the slope was -0.80, indicating good pressure sensitivity.

[Example 3] A first layer completely similar to the first layer 14 of Example 1 was laminated on the same base material as Example 1.

Next, on this first layer, a second layer completely similar to the second layer 16 of Example 1 was laminated in the same manner as in Example 1.

Further, on this second layer, a third layer that is exactly the same as the second layer 16 of Example 1 is laminated in the same manner as in Example 1, and the solvent is evaporated and dried to form a laminate of the present invention consisting of three layers. A type pressure sensitive material was obtained.

The thickness of each layer is 20 μm, and the electrical conductivity of the third layer, which is the outermost layer, is lXl0-'S-cm-'. The electrical conductivity was 3X10-'S-cm-'.

The laminated pressure sensitive material of the present invention produced in this way was placed on a flat comb electrode in the same manner as in Example 1, and a parallel resistance of 50Ω and Ω was added, and a flat tip with a diameter of 10 mm was When we repeatedly applied and released pressure with a rod having a It was found to have excellent properties including resistance.

Furthermore, the gradient was 10.82, indicating very good pressure sensitivity.

The electrical conductivity and gradient of each layer in each of the above examples are shown in Table 1 below.

[Comparative Examples 1 to 6] Various types of pressure-sensitive resistance change type conductive compositions for printing use that were used in Example 1 and had completely the same constituent materials as those used in Example 1, but with different composition ratios. Using a type conductive composition,
A laminated pressure-sensitive material was produced in the same manner as in Example 1, except that the printing order was changed.

In this way, each laminated pressure sensitive material was prepared with the electrical conductivity of the first layer and the second layer being the same, or with the electrical conductivity of the outermost layer being greater than the combined electrical conductivity of the remaining layers. Similar to 1, it was placed on a flat comb-like electrode, and a parallel resistance of 50 Ω was added, and then pressure was repeatedly applied and depressurized using a rod with a flat tip of 10 mm in diameter, and the characteristics were observed. The electrical resistance of the pressure-sensitive material also decreased as soon as pressure started, and returned to its original resistance value as soon as the pressure was removed, but the range of change was small.

Further, the electrical conductivity and gradient in each layer of each of the obtained laminated pressure-sensitive materials are shown in Table 1 below, but the absolute values of the gradients in all of them are small, and it cannot be said that they exhibit good pressure sensitivity.

[Comparative Examples 7 and 8] Various pressure-sensitive resistance variable conductive materials for printing were used in Example 1 and had the same constituent materials as the pressure-sensitive resistance variable conductive composition A, but with different composition ratios. A single-layer pressure-sensitive material was produced using the composition in the same manner as for the first layer 14 of Example 1.

The pressure-sensitive material thus prepared was placed on a flat comb-like electrode in the same manner as in Example 1, and a parallel resistance of 50Ω and Ω was added, and then a rod with a flat tip with a diameter of 10 mm was applied. After repeatedly applying pressure and removing pressure and observing the characteristics, we found that the electrical resistance of any pressure-sensitive material decreases as soon as pressure starts, and immediately returns to the original resistance value when the pressure is released, but the resistance The range of change in value was small.

The electrical conductivity and gradient of each pressure-sensitive material obtained are shown in Table 1 below.
However, the absolute value of the gradient is small in all cases, and it cannot be said that they exhibit good pressure sensitivity.

[Comparative Example 9] The first layer and the second layer were formed in exactly the same manner as in Example 3.

Next, a third layer was formed on the second layer in exactly the same manner as the first layer.

The thickness of each layer is 20μm, and the third layer is lX
l0-'S-cm-' The composite electrical conductivity of a 40 μm layer consisting of the first and second layers other than the outermost layer is 3X
10-'S-cm-'.

The laminated pressure sensitive material thus prepared was placed on a flat comb-like electrode in the same manner as in Example 1, and a parallel resistance of 50Ω and Ω was added to the electrode. When we repeatedly applied and removed pressure and observed its characteristics, we found that the electrical resistance decreased as soon as pressurization started, and immediately returned to its original resistance value when pressurization was released, but the range of change in resistance value was It was small.

Further, the slope of this comparative example was 10.70, which means that it cannot be said to have good pressure sensitivity.

Table <Effects of the Invention> Compared to conventional pressure-sensitive materials, the laminated pressure-sensitive material of the present invention has reliable insulation in an unpressurized state, and has a significant reduction in electrical resistance due to pressure compression. It has excellent pressure sensitivity, and the electrical resistance value smoothly decreases with increasing pressure and compression. Therefore, the laminated pressure-sensitive material of the present invention is very suitable and widely used in applied force conversion elements, variable resistors, various sensors, switches, and the like.

Further, the laminated pressure sensitive material of the present invention can be manufactured by printing methods such as printing, painting, coating, etc., so it is easy to manufacture and has a high degree of freedom in electrical design.

Moreover, when the laminated pressure-sensitive material of the present invention is applied to each of the above-mentioned elements, there is no need to use a spacer or the like for insulation, which is advantageous in terms of cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an example of the laminated pressure-sensitive material of the present invention. FIG. 2 is a graph for explaining the gradient of the pressure sensitive material. Explanation of symbols 10...Laminated pressure sensitive material, 12...Base material, 14...First layer, 16...Second layer, FIG, 2 LOG (pressure force) Hand thread filling (Spontaneous) January 26, 1999 Display of the case 1986 Patent Application No. 313600 2 Name of the invention Laminated pressure sensitive material 3 Relationship with the person making the amendment Patent applicant name Title (671) Yokohama Rubber Co., Ltd. 4, Agent Address: 101 Telephone: 864-4498 3-2-2 Iwamoto-cho, Chiyoda-ku, Tokyo Column 6 of "Detailed Description of the Invention" of the Specification, Contents of Amendment (1) Specification No. On page 13, line 8, the statement "has low electrical conductivity" is corrected to "has electrical conductivity lower than the electrical conductivity." (2) The statement "electrical conductivity is" in lines 17 to 18 of page 14 is corrected to "electrical conductivity is". (3) The description of "replacement" in line 741 and line 4 of page 16 will be corrected to "replacement". (4) The statement "49 parts by weight" on the 11th line of page 19 is corrected to "39 parts by weight." (5) r7xlo on page 20, lines 3 to 4
-' r5x the description of J! Correct to O-'J. (6) The statement "same as" on page 20, line 20 of the same document is amended to "similarly."

Claims (1)

[Claims] (1) At least two layers of pressure-sensitive resistance variable conductive compositions having printing properties are laminated, and the electrical conductivity of the outermost layer is
A laminated pressure-sensitive material characterized by a composite electrical conductivity lower than that of other layers.