JPS58129712A - Pressure sensitive conductive switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-sensitive conductive switch that is incorporated into electronic equipment such as a keyboard switch, and particularly relates to a pressure-sensitive conductive switch that is used by being incorporated into electronic equipment, such as a keyboard switch, and particularly relates to a pressure-sensitive conductive switch that is used by being incorporated into an electronic device such as a keyboard switch. Related to piezoconductive switches.

Traditionally, keyboard switch dojis, for example, Fig. 1 △
And as shown in Figure B, a substrate 1 such as a pudding board
A comb-shaped electrode [El
, El are formed, and then a conductive silicone rubber 5, which pigments carbon, is placed at a position opposite to these comb-shaped electrodes El, El, and held by, for example, a die 17 and a flam-shaped rubber cover 6. Characterized.

However, in such a switch, the comb-shaped electrode IE
Gold plating 4.4 is used to form I % E +, which increases the cost, and since carbon is used as the face of the conductive silicone rubber, there is a risk of carbon scattering during operation and short circuits. There was a drawback.

In addition, as shown in FIG. 2, a conductive resin film 8.8 is printed on the surface of a polyester or polyurethane film lx 7.7, electrodes [2, E2 are formed thereon, and adhesive and hot Electrode E2.9 is formed using a melt agent or prepreg. A switch having a structure in which E2 is separated is also known.

However, in a switch with such a structure, although it has the advantage of being easy to maintain an airtight state inside, it uses an air cap (g), in other words, it cannot be moved easily. IIJ
Since the ON/OFF operation of the switch is performed depending on the amount, there is a drawback that the wear and tear on the electrodes [2, [2] increases considerably.

Furthermore, as shown in FIG. 3, a switch (so-called solid switch) having a structure in which a pressure-sensitive conductive rubber seal 1-11 is arranged between the comb-shaped electrodes IE 3 and 1-3 arranged on the substrate 10J- is also known. However, although this switch does not cause wear and tear on the electrodes, it has many disadvantages as described below.

(-In other words, (1) It is necessary to select the characteristic category such as anisotropy or isotropy for the pressure-sensitive conductive rubber sheet.

(2) Since the pressure-sensitive S-conductive rubber sheet is an elastic body, it is difficult to fix it to a printed circuit board.

(3) The contact resistance at the joint between the rubber sheet and the electrode varies depending on the joining method, making it difficult to obtain stable switch characteristics.

In addition, as the conductive layer 1 in this pressure-sensitive keyboard switch, silver powder, silver-nickel powder, nickel powder, copper powder, graphite powder, conductive carbon, conductive glass beads, etc. have traditionally been used. However, all of these have the disadvantage that the conductive region is not specified and it is difficult to obtain stable characteristics.

That is, FIG. 4 shows a composition in which a conductive pigment using nickel powder is dispersed in a binder, and a composition in which a conductive pigment using conductive glass beads is dispersed in a binder, respectively, after being coated and dried. This is a graph showing the resistance value of the conductive film (distance between electrodes Q, 3 mm, width 1°5 mm). However, as long as there is a binder function that binds the conductive pigments closely together (in the appropriate content range indicated by the arrow in Figure 4), the resistance value is the lowest, and outside this range, the resistance value increases significantly. I come to do it. .

By the way, as shown in FIG.
113 is dispersed in the rubber-like elastic body 14 at a high concentration. l T
- When pressure is applied to the conductive substrate 12 side as shown, the conductive pigment in this direction approaches and contacts the phase H, but the conductive pigment in the direction perpendicular to this almost never approaches. 1) It exhibits electrical conductivity in the thickness direction (anisotropic pressure-sensitive film).

The conditions for setting the amount of conductive pigment to be mixed in order to obtain a pressure-sensitive conductive rubber exhibiting a predetermined conductivity are: ■ degree of dispersion of the pigment, ■ thickness of the skin, ■ curing and drying conditions, and ■ the ink. The optimum content that exhibits anisotropic pressure-sensitive characteristics must be determined by considering all factors such as viscosity, ■ composition of ink, ■ material of conductive substrate, and ■ method of electrode construction. was extremely complex and difficult.

However, as shown in FIG. 6, in a switch having a structure in which electrodes E4' and E4 are provided on both sides of the pressure-sensitive conductive rubber seats 1 to 15, the resistance value Rp between both electrodes is calculated by the following formula % (Formula %) <However, Rpo is the resistance value of the pressure-sensitive film, PSE+i is the resistance value of the contact part between the upper electrode [4 and the pressure-sensitive conductive rubber sheet 15, and R3E7 is the resistance value of the pressure-sensitive conductive rubber sheet 1 between 4 and the pressure-sensitive conductive rubber sheet 1. ~1
The resistance of the contact portion between 5 and 5 is expressed as 1+tf).

Here, during the sedimentation of R13 (1, R8E2, fI''+#113, the pigments 13 come close to each other or come into contact with each other, resulting in a fairly low resistance and not being affected much by the pressing force).
It is necessary to disperse the conductive pigment so that R3E1 changes in thickness due to the pressure applied, but this is a difficult problem because, as mentioned above, there are many conditions for determining the optimum content of the pigment. A-).

In other words, if the content of conductive pigment is too low, it will pass through when not in operation (OFF), and if it is too small or combed, the resistance value will show an infinite value even when in operation (ON). j,
J: It will not work, or it will require an extremely large pressurizing force to work.

In this way, if conventional conductive pigments are used as they are, it is difficult to make the distribution uniform and the conditions are complicatedly interrelated, making it difficult to obtain a switch with stable characteristics. I was at work.

Furthermore, when using room-temperature curable silicone rubber as the rubber-like elastic body (1), metal powders such as lead, tin, antimony, bismuth, sulfur, phosphorus, nitrogen-based compounds, amine compounds, and phosphorus-containing silane coupling may be used. Pigments treated with coating agents, certain ditanes, and higher fatty acids may become so-called catalyst poisons, and may also cause spontaneous vulcanization, severely limiting the combinations that can be used. There were also some difficulties.

The present defender has carried out intensive research to eliminate these conventional drawbacks, and has discovered a pressure-sensitive section consisting of a pair of electrodes and a sensing section that is interposed between these electrodes and is actuated in response to an external action. In the conductive switch, the sensitive part is
A pressure-sensitive conductor with good 0N-OFF characteristics is formed by using at least b metal powder on the surface of which an insulating film is formed as a pigment, and an ink containing this pigment, a rubber-like elastic body, and a solvent. It was found that the switch can be turned on by 19.

The present invention has been made based on this knowledge, and is directed to a pressure-sensitive conductive switch consisting of a pair of electrodes and a sensing section that is interposed between these electrodes and is actuated in response to an external action.
), and the sensitive part is formed of at least one type of metal powder with an insulating film formed on the surface, and an ink containing this pigment, a rubber bullet, and a solvent. A pressure sensitive conductive switch is provided.

It is not necessarily clear why metal powder with such an insulating film exhibits electrical conductivity, but when metal powder comes into contact with the metal powder through a thin insulating film formed on its surface, it is deposited due to the Hall effect. This is thought to be due to the occurrence of low conductivity.

In other words, the nickel powder with an insulating film or the zinc powder with an oxide film, which has been applied to the method described later, is filled into an acrylic resin cylinder with an inner diameter of 10 mm and a height of 10 mm. When measuring resistance by inserting cylindrical electrodes from both ends of a cylinder and applying a load between the two electrodes, the resistance becomes infinite when the load is small, but as the load increases, it becomes conductive.

This simply means that when the metal powders are in contact with each other, they are insulated by the insulating film on their surfaces, and when pressure is applied, the metal powders come close to each other, separating the films formed on their respective surfaces. This means that a bridge conduction occurs with a distance of 1!11, which is enough to suppress the Hall effect.

In addition, if some kind of base metal powder is used as a pigment, the resistance value in the direction perpendicular to the pressure direction increases because the base metal powder always forms an oxide film naturally on the surface. There is a possibility that the OFF characteristics will improve, but the thickness of the oxide film formed on such base metal powder is not constant, and the particle size is distributed over a wide range, so it is unlikely that the characteristics will be stable. It's impossible to get a keyboard switch.

In the present invention, since the metal powder is coated with an insulating film, no conduction occurs in a direction perpendicular to the direction of pressurization, and excellent ON-OFF characteristics can be achieved.

The present invention will be described below based on embodiments shown in the drawings.

The pressure-sensitive conductive switch of the present invention includes, for example, a pair of electrodes E, 5, [5 disposed close to each other on a printed circuit board 16, as shown by Δ in FIG. 7, and a conductive ink interposed between these electrodes. It consists of a sensitive part 17 which is formed by screen printing and operates in response to external pressure, and a conductive layer 18 provided thereon, and the conductive ink can maintain a conductive state based on the ball effect when pressurized. It is obtained by blending and dispersing a metal powder pigment on the surface of which an insulating film of a certain thickness is formed, for example, in an ink base such as room temperature curable silicone rubber. Reference numeral 19 is a metal powder pigment, and 20 is a room temperature curable silicone rubber.

FIG. 7B shows another type of embodiment, in which the electrode F5 is placed on the conductive substrate 16J=, the sensitive part 17 is formed thereon, and then the other electrode is placed on the conductive substrate 16J=. Electrode [5 (Ards electrode) is formed.

-19- When pressure is applied from the outside in the direction of the arrow to the sensitive part 17, the matrix of the silicone rubber 20 containing the metal powder pigment is compressed, and at this time, the distance between adjacent pigments becomes closer, for example In the case of zinc powder, it comes into contact with other pigments across the thickness of the insulating film on the surface. Of course, in the case of nickel powder as well, it comes into contact with other adjacent pigments across the insulating film coated on its surface. In this way, conduction occurs when adjacent faces 1 come close to each other and have a distance sufficient to produce a Hall effect across the films formed on their respective surfaces.

When the pressure applied to the sensitive part 17 is removed, the pigments are separated from each other due to the restoring force of the silicone rubber 20, resulting in a non-conducting state.

Here, the metal powder that becomes the pigment of the conductive ink forming the sensitive part 17 is selected from the following points: ease of acquisition, economic efficiency, stability of properties, necessity of secondary processing, and compatibility with the ink base. It is suitable to use zinc powder and nickel powder either alone or in combination.

-1 and - It is suitable for the above-mentioned zinc powder to have an average particle diameter of 2 to 15 μN and an insulating film of about 50 to 500, such as lead oxide, formed on its surface. ing.

Furthermore, the nickel powder has an average particle size of about 2 to 7 μm, and an insulating film of nickel oxide or other inorganic film, resin film, or elastomeric composition such as silicone rubber is formed on the surface of the nickel powder, with a thickness of 50 to 500 μm. The one shown is suitable. In addition, when using niratar powder and zinc powder together, it is desirable that the average particle size of the former is larger than the average particle size of the latter.

If the thickness of the insulating film is thinner than the above range, there is a risk that conduction will occur even when no pressure is applied, whereas if it is thicker than the above range, there is a risk that there will be no conduction even when pressure is applied. The optimal value for the thickness of the nickel powder insulating film is difficult to determine unambiguously because it is correlated with other conditions, but the range determined experimentally is 50 to 500.
The thickness of the person is suitable.

In addition, when using nickel powder, if the weight ratio of the insulating film to the entire metal powder exceeds 8% by weight, it becomes difficult to mix it into the ink base.
However, it is preferable that it does not contain 0 weight %).

Note that better results can be obtained when zinc powder and nickel powder are used in combination than when used alone. Using zinc powder and nickel powder (1), pressing force 2, Okg/'
When manufacturing a keyboard switch that operates from 1 to 1 with l: A or less, it is desirable that the blending ratio of both sides be in the range of 5 to 20% by weight of curved lead powder and 80 to 95% by weight of nickel powder. , if the amount of nickel powder is less than this, 2
, even when a pressure of 0 kg/c+ is applied, there may be no conduction, and conversely, if too much chive/fur flour is used, conduction may occur even under no load.

In addition, as a pressure-sensitive conductive ink, it can be used for adhesion to electrodes!
Alternatively, when considering the workability of pressure-sensitive conductive ink during printing, it is desirable to select an ink base so that the coating film exhibits the following characteristics. That is, to -1 - (1) There is no small bottle.

(2) Form a film as thick as possible.

(3) Contains an xr-lastomer composition or silicone rubber that is not corroded by solvents.

(4) Pigment sedimentation is performed so that the particles of the face fl near the upper electrode become more attractive.

etc.

In the pressure-sensitive conductive switch of the present invention, in which the sensitive part is formed using the conductive ink formulated as described above, when pressure is applied to the sensitive part from the outside, the conductive pigment (metal powder) is contained. The rubber bullet +171 ~ lix is compressed, and a state occurs in which pigments η adjacent to each other in the pressing direction approach each other and come into contact with each other across the insulating film on the surface. In such a state, conduction occurs due to the ball effect, and when the pressure is removed, the pigment phase is separated by the restoring force of the rubber-like elasticity 71 to the ricks, resulting in a non-conduction state.

Next, examples will be described.

Example 1 Preparation of nickel powder) Nickel powder (manufactured by Inco Co., Ltd. #255), silicone rubber
Toshiba Silicone XE13-009>, Kijiroll, Coupling agent (Plain Act 41B manufactured by Aji no Rustic)
were mixed as shown in Table 1 and kneaded using three rolls to obtain five types of treated nickel powders with trial numbers @1-A to 1-E.

Table 1 (Adjustment of conductive pigment) Sample numbers 1-Δ to 1-E treated nickel powder (paste) and fumed silica (AE manufactured by Nippon Aerosil Co., Ltd.)
RO8I L#200) and zinc powder (F manufactured by Honjo Chemical Company)
5000) were prepared by blending according to Table 216, respectively, and mixed and granulated using a high-speed mixer to obtain conductive face 1.

After passing the pigments listed in table 2 through a 300 mesh sieve,
Heat vulcanization was carried out at 150°C for 2 hours, and then stirred with a high-speed mixer to crush some of the congealed powder.
It was passed through a 00 Metsushiko sieve to make a powder.

Incidentally, the smoke nbo series jy was blended to improve the strength during film formation.

(Feeling 1 - Adjustment of conductive ink) Conductive pigments 2-A to 2- adjusted according to the blending ratio in Table 2
F and silicone rubber (Toshiba silicone product X61.3-
009), cambling agent (K 13 manufactured by Shin-Etsu Chemical Co., Ltd.)
M 503 ) and a hydrocarbon solvent (Via IIm manufactured by Nippon Oil Net 1) were adjusted at the compounding ratio shown in Table 3, and 1 g of conductive ink was prepared using d1.

Table 3 The conductive inks obtained in the following were mixed in a high-speed millimeter to give a screen printable 2000 to 300.
What is the viscosity of 0 poise?

Note that the viscosity was adjusted by diluting it with Vialom.

(Formation of a pressure-sensitive conductive switch) Switches A and 13 having the same structure as the pressure-sensitive conductive switch shown in FIGS. 7A and 7B were manufactured using the pressure-sensitive conductive ink adjusted in the above manner.

Switch Δ was manufactured by the following method.

First, use silver resin ink (Tokuriki Kagakusha MPS-105).
200 pieces on paper funol board 1-, thickness 100μ
Print using the screen of electrode []・l, IE5
At predetermined intervals (formation 1), heat curing treatment is performed at 150° C. for 2 hours.

Next, each ink shown in Table 3 was printed across these ten electrodes using a 200mm thick screen with a thickness of 120μ, and then heated and cured! II! Perform llj1.
Finally, a conductive paste using conductive glass beads (S 5000-84 manufactured by Toshiba Ba 1T Nirei Co., Ltd.) is coated and baked on one part of the glass to form a C-conductor layer, thereby forming a pressure-sensitive conductive switch.

Note that the switch electrodes rE5, E! i is width 1.5mm, + width 20-30μ, distance between electrodes (ρ)
Q, 3 mm, and the thickness of the sensitive part is 30 to 7011 mm. Σ, switch B was also manufactured with the same dimensions as the switch Δ using the same monthly yield.

Switch special +! 1 is shown in Table 4.

= 19- Table 1 20- However, non-operating resistance: resistance between electrodes at voltage 100 V electrode gap: 120μ Load pressure crab 3. OX3. Example 2 (Preparation of conductive pigment) Niracle powder, coupling agent, silicone rubber and solvent were treated in the usual manner using the formulation shown in Table 5. The solid content of conductive 1 Hi 1 face diagonal is 4'4.

Table 5 Next, 30 parts by weight of zinc powder (manufactured by Honjo Chemical Co., Ltd. F5000) and 20 parts by weight of fumed silica were mixed with stirring, and 100 parts by weight of the conductive pigment described in L were combined and thoroughly kneaded. The mixture was granulated and dried in a dryer at 150°C for 2 hours.

(Adjustment of pressure-sensitive conductive ink) The above pigments were mixed in proportions of 70.75.80.
Kneaded with silicone rubber (XF 13-009 manufactured by Toshiba Silicone Co., Ltd.) to a concentration of 85.90% and 95% by weight,
I added 1 liter of pressure-sensitive conductive ↑ No. 1 ink.

Using the pressure-sensitive conductive zeolite ink obtained in Example 1, a switch 13 having the same structure as the switch shown in 3 was produced in the same manner as in Example 1.

141 2.0 kg/cJ pressure strip of the switch
When operating (ON) and when not operating +1i'
A resistance vessel of r (0′F ) was measured.

11111 results are shown in Figure 8.

From the graph in FIG. 8, the pigment content of the pressure-sensitive conductive ink that forms the Ff area is 78 to 855 in the case of △.
In the case of B, it is 70-E30%, and it can be seen that △ requires a larger amount of face than the mouth.

Therefore, the optimum range that satisfies both of these is the range of 78 to 82% by weight. .

In addition, in this example, the formulation of a3 (,1j electric face H) was 8
In the range of 0 to 90%/]"+3, consideration must be given to eliminating the occurrence of pinholes as much as possible, such as increasing the thickness of the sensitive part or reducing the The diameter of the pinhole - 2: J
- It is desirable that consideration be given to the 4F so that the sword can be used in a more personable manner.

Example 3 After premixing each component of Composition C in Table 6, the components were kneaded four times using three rolls to form C conductive bamboo face, and a pressure-sensitive conductive ink using zinc powder alone was prepared.

Table 6 Using this conductive 1'4 ink, a switch 2 having the same structure as the switch shown in FIG.
/I - Chi △ and switch B in the same figure [switch 1 shown in 3 - horizontal)^ is l! I81 was built.

The Mj t'l of the broken switch was accepted on the 7th table.

As shown in Table 7, when zinc alone is used as the pigment, the operating pressure is 6 degrees higher than that of b when using nil powder. Is this an insulating film on the particle surface of the ilF lead particle? P9 <, a skeleton particle phase! It is considered that the pressure required to make conduction based on the Hall effect 111 by bringing the i close together is large.

In addition! Since the insulating film on the surface of the IF lead particles causes voltage breakdown under high applied voltage, it is practically desirable to use the voltage within a few volts.

In addition, the content of l1li lead was 80 to 9 in the experiment.
5) The pressure-sensitive conductive ink having the composition shown in Table 6 is suitable for the range of ■φ%, and the resistance of the pressure-sensitive conductive ink with the composition shown in Table 6 has a resistance of 10" Ω or more when not in operation (when there is no single layer) at a distance of 120μ between the inner electrodes. It was confirmed that the insulation resistance can be reduced by 1.

In the present invention, a sensitive part formed between a pair of electrodes is placed in a conductive pigment ink base made of a small metal powder having an insulating film on the surface. Appropriately distributed pressure-sensitive guidance? Since it is formed using six rS bamboo inks, it can respond with high sensitivity and fidelity during the desired operation, and also has stable recovery properties.

Note that the pressure-sensitive conductive switch of the present invention has a digitizer, =1
It can be used as a switch for Octa, I, and various other electronic devices.

[Brief explanation of the drawing]

Figure 1 △ is a sectional view of the main part of a conventional pressure-sensitive S-electric switch, Figure B is a sectional view taken along line B-B in Figure 1 △, Figures 2 and 3
Figure 4 is a cross-sectional view of a conventional pressure-sensitive conductive switch, Figure 4 is a graph showing the relationship between the content of nickel powder pigment and conductive glass tin, and the electrical resistance value. 1 no run no 1 ((Ω'II7+ time〈△) and square charge time (
13) A sectional view of the main part showing the behavior of the pigment, Figure 6 is the thickness I
A pair of electric conductors 1 are installed in the direction of J. Cross-sectional views C and ΔliL of the pressure-sensitive conductive switch show a counter-electrode structure, and 3 shows a ground-electrode structure.Furthermore, FIG. This is a graph showing: 1.10.12... Substrate 2... Copper foil 3... Chive 9 Lumetsu 1 Gold plating 7... ...... Poly 1-Stel or polyurethane film 11 ~ ';1... Comb-shaped electrode 8 ...... Conductive resin film 11.15
...Feeling J ■ Conductive T! 1 rubber seam 1~-27- 13... Conductive f1 face size 1/I...
......Rubber-like elastic body 16...
...Princess 1 to board 17...
・Sensitive part 18・・・・・・・・・Electrical polishing layer 19・・・・・・・・・Metal powder pigment fee
1 Yamasa − =28=

Claims (1)

[Scope of Claims] (1) A pressure-sensitive conductive switch comprising a pair of electrodes and a sensitive part interposed between these electrodes and actuated in response to an external action, wherein the sensitive part is provided with an insulating film on the surface. 1. A pressure-sensitive conductive switch, characterized in that it is formed from an ink containing at least one type of metal powder formed by a pigment as a pigment, the pigment, a rubber-like elastic body, and a solvent. (2) The pressure-sensitive conductive switch according to claim 1, wherein at least one of the pigments is made of zinc powder. (3) The pressure sensitivity according to claim 1 or 2, characterized in that at least one kind of pigment is zinc powder, and the thickness of the insulating film formed on the surface is 50 to 500 mm. conductive switch. (4) The pressure-sensitive conductive switch according to any one of claims 1 to 3, wherein 90% or more of the total amount of zinc powder has an average particle size in the range of 2 to 15 μm. (5) The pressure-sensitive conductive switch according to claim 1, wherein at least one of the pigments is made of nickel powder. (6) At least one type of pigment is nickel powder, and the surface thereof is coated with an insulating film consisting of an oxide film, an inorganic film, a resin film, a lastmer composition film, etc. A pressure-sensitive conductive switch according to item 1 or 5. (7) At least one type of pigment is nickel powder, and the total thickness of the insulating film consisting of an oxide film, an inorganic film, a resin film, or an Ex1 to F composition film formed on the surface is 50 to 500 A pressure-sensitive conductive switch according to claim 5 or 6, characterized in that: (8) The pressure-sensitive conductive switch according to claim 6 or 7, wherein the average particle size of the nickel powder is in the range of 2 to 7 microns. (9) The pressure-sensitive conductive switch according to any one of claims 1 to 8, wherein the pigment is formed from zinc powder and nickel powder. (10) The pressure-sensitive conductive switch according to any one of claims 1 to 9, wherein the average particle size of the pigment zinc powder is smaller than that of the nickel powder. (11) The pressure-sensitive conductive switch according to claim 1, wherein the rubber-like elastic body is made of silicone rubber. (12) The pressure-sensitive conductive switch according to any one of claims 1 to 11, wherein the sensitive portion is formed by screen printing on a conductive substrate on which electrodes are formed.