Pressure-sensitive sensor

The present invention relates to a pressure sensitive sensor used in an input device included in various electronic devices.

Various pressure-sensitive sensors having a resistor and an electrode as components are known, and an example thereof is shown in FIG. The pressure-sensitive sensor 1 comprises an elastically deformable conductive contact (resistor) 2 formed in a convex shape such as a dome shape or a hemisphere, and a pair of electrodes 3 provided on the circuit board B at intervals. Have. In this pressure-sensitive sensor 1, when the conductive contact 2 is pressed, the top 2b of the curved surface 2a of the conductive contact 2 comes into contact with the circuit board B between the pair of electrodes 3, and then the electrodes 2a are deformed. The pair of electrodes 3 conducts when they come into contact with 3, and the contact area with respect to the electrodes 3 gradually increases while the curved surface 2a is deformed, so that the resistance value between the pair of electrodes 3 changes.

In such a pressure-sensitive sensor 1, the relationship between the pressing load or pressing stroke (hereinafter collectively referred to as pressing pressure) on the conductive contact 2 and the resistance value that changes accordingly is not necessarily linear and is in the initial stage of pressing. In this case, the change in the contact area between the electrode 3 and the conductive contact 2 is large, whereas the change in the contact area is small in the later stage of pressing. Therefore, as shown in FIG. 16, the resistance value is large in the initial stage of pressing. There was a relationship that it decreased and the change in resistance value gradually became smaller in the latter half of pressing. Therefore, it is necessary to make a correction for linearly matching the pressing force and the output corresponding to the pressing force, and its control is complicated. As a technique for solving this problem, there is a pressure-sensitive sensor described in Japanese Patent Application Laid-Open No. 2001-006906 (Patent Document 1).

<p num="0004"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2001-006906</text></patcit></p>

<p num="0005"> The pressure-sensitive sensor described in Japanese Patent Application Laid-Open No. 2001-006906 is provided with a protruding portion at the tip of the conductive contact to alleviate a rapid increase in the contact area with the electrode at the initial stage of pressing. However, since such a protruding portion is locally greatly deformed when pressed, its durability tends to be low. In addition, since the protruding portion is deformed by a relatively light load, the load increases sharply in the latter half of the pressing, and it is easy to feel a sense of discomfort when pressing.</p><p num="0006"> The present invention has been made to solve the above problems. That is, it is an object of the present invention to provide a pressure sensitive sensor whose resistance value characteristic to pressure is close to linear.</p>

<p num="0007"> In order to achieve the above object, a contact portion made of a resistor having a predetermined conductive resistance, a pair of electrodes provided in isolation from each other on a circuit board with which the contact portion contacts, and an elastic pressing body formed in a convex shape. The pressure-sensitive sensor has a pressure-sensitive sensor in which the contact portion and the pair of electrodes come into contact with each other when the elastic pressing body is pressed, and the contact area thereof changes to change the resistance value between the pair of electrodes. Provided is a pressure-sensitive sensor that suppresses a decrease in resistance value with respect to a unit pressing force in the initial stage of pressing against a pressing body and promotes a decrease in resistance value with respect to a unit pressing force in a later stage of pressing.</p><p num="0008"> Regarding the pressure-sensitive sensor that senses the pressure change by changing the contact area between the contact part and the electrode by the pressure change on the elastic pressing body, the decrease in the resistance value with respect to the unit pressing force is suppressed at the initial stage of pressing the elastic pressing body. Therefore, in other words, since the degree of change in which the resistance value decreases as the pressing pressure changes is suppressed, the change in the resistance value at the initial stage of pressing can be reduced. Therefore, it is possible to improve the defect of the prior art in which the resistance value changes significantly at the initial stage of pressing, and to make the relationship between the pressing pressure at the initial stage of pressing and the output based on the change in resistance value close to linear. In addition, since the decrease in resistance value with respect to the unit pressing force was promoted in the latter stage of pressing the elastic pressing body, in other words, the degree of change in which the resistance value decreased as the pressing force changed was promoted. The decrease in resistance value can be increased. Therefore, it is possible to improve the defect of the prior art in which the resistance value is hard to change in the latter stage of pressing, and to make the relationship between the pressing pressure and the output based on the resistance value change close to linear. Therefore, the relationship between the pressing force and the output based on the change in the resistance value can be made close to linear in the entire pressing range from the initial pressing period to the late pressing period.</p><p num="0009"> The pressure-sensitive sensor may have a surface shape in which the contact area with the circuit board gradually changes in the process from the initial stage of pressing to the latter stage of pressing. In order for the elastic pressing body to have a surface shape in which the contact area with the circuit board gradually changes in the process from the initial pressing period to the late pressing period, in other words, there is no change point that abruptly changes the pressing force. The shape of the elastic pressing body can be a convex shape such as a dome shape, a substantially hemispherical shape, or a substantially conical shape. This is because such a shape does not suddenly change the normal direction of the outer surface. Since the contact area with the circuit board is gradually changed, in other words, the surface shape does not have a change point where the pressing force changes suddenly, so that the pressing feeling does not feel uncomfortable and the operation feeling against pressing is excellent. It is preferable in that it is. Further, the larger the pressing force, the larger the contact area with the circuit board, which can cause a monotonous change. On the other hand, in a shape having a protruding portion protruding from the tip of the conductive contact, the normal direction suddenly changes at the boundary between the main body and the protruding portion. In this shape, the protruding portion is locally greatly deformed at the initial stage of pressing, and the load suddenly increases (that is, the pressing pressure changes rapidly) in the latter half of the pressing, and it is easy to feel a sense of discomfort when pressing.</p><p num="0010"> The shape of the pair of electrodes can be a characteristic shape. More specifically, the outer edges (opposing edges) of the pair of electrodes facing each other have a chevron having a top that first contacts the contact portion, a valley shape that occurs at both ends of the chevron shape, and a valley shape that rises diagonally from the valley shape. It can be a pressure-sensitive sensor in which the oblique shape appears as a continuous shape.</p><p num="0011"> Since a chevron having a top that first contacts the contact portion is provided on the opposite edge, the change in the conductive path that occurs according to the change in the contact region between the electrode and the contact portion at the initial stage of pressing when the electrode contacts the contact portion is conductive. Can be made difficult to rise. Further, since the valleys formed at both ends of the chevron are provided on the opposite edges, the tendency of conductivity accompanying the conversion from the initial pressing stage to the later pressing stage can be changed. Furthermore, since an oblique shape that rises diagonally from the valley shape is provided, the change in the conductive path that occurs according to the change in the contact area between the electrode and the contact portion in the later stage of pressing when the electrode contacts the contact portion can be easily increased in conductivity. Can be made to. Since these shapes are continuously represented, the relationship between the pressing force and the resistance value is brought closer to a linear shape, and a part of the curve showing the relationship between the pressing force and the resistance value is formed from the approximate straight line as an ideal linear line. It is possible to prevent it from coming off significantly.</p><p num="0012"> The slope from the valley to the slope can be made gentler than the slope from the valley to the mountain. In other words, since the angle of the chevron inclined surface is steep, the contact area between the conductive contact and the electrode in the width direction of the electrode is located at the initial stage of pressing when the contact area between the conductive contact and the circuit board changes significantly with respect to the pressing. The spread can be suppressed and the change in resistance value can be effectively reduced. On the other hand, since the slope from the valley shape to the chevron shape is gentle, the contact area between the conductive contact and the electrode expands in the width direction of the electrode at the later stage of pressing when the change in the contact area between the conductive contact and the circuit board is small with respect to the pressing. Can be promoted to effectively increase the decrease in resistance value. Therefore, as a whole, the relationship between the pressing force and the resistance value can be made closer to linear.</p><p num="0013"> The contact portion can be formed on the surface of the elastic pressing body. If the contact portion is formed on the surface of the elastic pressing body formed in a convex shape, the contact area with the circuit board can be increased as the pressing force is larger, and the contact portion can be formed on the surface of the elastic pressing body. By forming the conductive portion, an elastic pressing body having a contact portion can be easily manufactured from synthetic rubber, a thermoplastic elastomer, or the like.</p><p num="0014"> The contact portion can be formed of a resistor provided on the resin film. Even if the pressure-sensitive sensor is configured to press the resin film with the elastic pressing body, the resin film is deformed along the elastic pressing body, so that the contact area with the pair of electrodes can be changed. In such a configuration, since the contact portion is formed on the resin film, patterning can be easily performed by a method such as printing. Therefore, there is a degree of freedom to flexibly realize arbitrary resistance value characteristics. Further, since the contact portion provided on the resin film comes into contact with the pair of electrodes, the elastic pressing body formed in a convex shape can be used as an insulator. Therefore, since various materials can be selected, it is easy to adjust the physical properties of the elastic pressing body, and it is possible to have desired pressing characteristics and durability.</p><p num="0015"> An insulating portion can be provided in the area of the contact portion. Since the insulating portion is provided in the region of the contact portion, it is possible to suppress a large decrease in the resistance value. Therefore, the degree to which the resistance value is lowered can be suppressed.</p><p num="0016"> The resistor may have a plurality of conductive regions in which the resistance value decreases in the radial direction from the center of the circle. Since the contact portion is made of a resin film provided with a circular resistor, and the resistor has a plurality of conductive regions in which the resistance value decreases in the radial direction from the center of the circle, printing on the resin film is performed. The contact portion can be easily manufactured by the above.</p>

<p num="0017"> According to the pressure-sensitive sensor of the present invention, the change in resistance value with respect to the change in pressing force can be made close to linear. In addition, it has an excellent feeling of operation against pressing. Further, the strict accuracy of the alignment between the contact portion and the electrode is not required, and the tolerance is high.</p>

<figref num="1">It is a schematic view of the pressure sensitive sensor according to one embodiment, FIG. 1 (A) is a sectional view thereof, and FIG. 1 (B) is a plan view showing an electrode.</figref><figref num="2">FIG. 5 is a plan view showing a change in the contact area of the contact portion per unit pressing force with respect to the circuit board when the contact portion is pressed with a constant pressing force.</figref><figref num="3">It is a top view of one electrode.</figref><figref num="4">It is a top view which shows the change of the contact area between the contact part and the circuit board which occur on the electrode provided on the circuit board, FIG. 4 (A) shows the initial stage of pressing, and FIG. 4 (B) shows the late stage of pressing.</figref><figref num="5">It is a schematic diagram of the pressure-sensitive sensor of the modified example, FIG. 5 (A) is a front view thereof, and FIG. 5 (B) is a diagram showing the contact between the electrode and the contact portion.</figref><figref num="6">It is a schematic view of the pressure-sensitive sensor which is another embodiment, FIG. 6A is a sectional view thereof, and FIG. 6B is a plan view showing an electrode.</figref><figref num="7">It is a bottom view which shows the contact part of the pressure sensitive sensor shown in FIG.</figref><figref num="8">It is a graph which shows the relationship between the pressing force of the pressure sensitive sensor shown in FIG. 6 and the resistance value.</figref><figref num="9">Yet another embodiment is a schematic view of the pressure sensitive sensor, FIG. 9 (A) is a sectional view thereof, and FIG. 9 (B) is a plan view showing an electrode.</figref><figref num="10">It is a bottom view which shows the contact part of the pressure sensitive sensor shown in FIG.</figref><figref num="11">It is a top view which shows the electrode used in the experimental example.</figref><figref num="12">It is a top view which shows another electrode used in an experimental example.</figref><figref num="13">It is a top view which shows still another electrode used in an experimental example.</figref><figref num="14">It is a graph which shows the relationship between the pressing force of the pressure-sensitive sensor shown in Samples 1 to 3 and a resistance value.</figref><figref num="15">It is the schematic sectional drawing which shows the conventional pressure sensitive sensor.</figref><figref num="16">It is a graph which shows the relationship between the pressing force of a conventional pressure-sensitive sensor and a resistance value.</figref>

The present invention will be described in more detail based on embodiments. The parts common to each of the following embodiments are designated by the same reference numerals, and duplicate description will be omitted. In addition, duplicate explanations will be omitted for common materials, manufacturing methods, working effects, and the like.

<u style="single">First Embodiment [Figs. 1 to 4]</u>:: The pressure-sensitive sensor 11 described in this embodiment is shown in FIG. The pressure-sensitive sensor 11 is insulated from each other by a contact portion 12 made of a resistor having a predetermined conductive resistance, an elastic pressing body 18 having the contact portion 12 on the surface, and a circuit board B in which the contact portion 12 is in contact. It has a pair of provided electrodes 13, and when the elastic pressing body 18 is directly or indirectly pressed, the contact portion 12 comes into contact with the pair of electrodes 13 and their contact areas change. Then, the resistance value between the pair of electrodes 13 is changed.

The elastic pressing body 18 is formed of an elastic body, and its surface is a contact portion 12. The convex shape (hemispherical shape) is formed so that the larger the pressing force, the larger the contact area with the circuit board B on which the electrode 13 is provided. FIG. 2 shows a change in the contact area of the contact portion 12 per unit pressing force with respect to the circuit board B when the elastic pressing body 18 is pressed with a constant pressing force. For example, when the elastic pressing body 18 is pressed and a constant pressing force is applied from the state where the contact area with the circuit board B is indicated by P1, the contact area changes to P2 and the contact area is further constant. When is applied, the contact area changes to P3, and when a constant pressing force is applied, the contact area changes to P4. Similarly, the change is P5 P6 P7. As described above, in the present embodiment, the rate of change in the contact area between the elastic pressing body 18 and the circuit board B is gradually reduced.

The elastic pressing body 18 integrated with the contact portion 12 is a resistor, but it is not an insulator, and needs to have enough conductivity to conduct by contacting a pair of electrodes 13. Therefore, such an elastic pressing body 18 is a mixture of an elastic conductive polymer, an elastic body such as synthetic rubber, natural rubber, or a thermoplastic elastomer with a conductive medium, or such an elastic body having a metal film or conductivity. It can be formed of a conductive film such as a coating film.

For the pair of electrodes 13, use a conductive ink containing conductive particles such as silver or carbon printed and formed by a method such as a screen printing method, or a printed circuit board formed by etching a copper foil to form a pattern. It is characterized by the shape of the opposing edges 14, which are the outer edges facing each other. An enlarged view of one electrode 13 is shown in FIG. The facing edge 14 of the electrode 13 is a series of a chevron 15 having a top portion 15a that first contacts the contact portion 12, a trough 16 generated at both ends of the chevron 15, and a slant 17 rising diagonally from the trough 16. Appears as a bird wing shape. Since the outer edge of the electrode 13 other than the facing edge 14 does not affect the contact region with the contact portion 12, it can have an arbitrary shape. In FIG. 1, it is formed as three sides of a rectangle.

A wiring (not shown) leading to the outside is connected to the pair of electrodes 13. Comparing the conductivity of the contact portion 12 and the pair of electrodes 13, it is required that the contact portion 12 has a higher resistance. Preferably, the resistance value is 10.³The difference may be more than double, and more preferably, the resistance value of the contact portion 12 is 1 to 10.⁵(Ω / )<u style="single">so</u>Yes, there are 10 pairs of electrodes^-4It is preferably (Ω / ) or less. From this point of view, it is preferable to use a conductive material containing carbon particles for the contact portion 12, and it is preferable that the pair of electrodes are made of a metallic material such as copper foil or plating.

The contact state between the contact portion 12 and the electrode 13 when the elastic pressing body 18 is pressed will be described with reference to FIG. The concentric circles shown in FIG. 4 are the same as the concentric circles shown in FIG. 2, and show the contact region between the contact portion 12 and the circuit board B, which changes depending on the degree to which the elastic pressing body 18 is pressed. When the elastic pressing body 18 is pressed, the contact portion 12 comes into contact with the circuit board B from the top 12a of the contact portion 12, then the contact portion 12 contacts the circuit board B in the state of P1, and then the contact portion 12 comes into contact with the circuit board B. The contact area changes, such as contacting with P2, then contacting with P3, and then contacting with P4. In the initial process of pressing, which changes from the state of P1 to the state of P4, the contact area between the contact portion 12 and the circuit board B is (P1) (P1 + P2) as shown in FIG. 4 (A). (P1 + P2 + P3) (P1 + P2 + P3 + P4), the contact area does not change uniformly, but the contact area increases at first, and then gradually decreases. Become.

On the other hand, the contact area between the contact portion 12 and the electrode 13 is a small portion including the top portion 15a of the chevron 15 of the electrode 13 in the state of P1, and the contact area thereof is small. Even in the state of P2 below, the contact area between the contact portion 12 and the electrode 13 is reduced by making contact only at the chevron 15 portion of the electrode 13. After that, even in the process of changing from P2 to P3 and from P3 to P4, by gradually contacting the chevron 15 part of the electrode 13 toward the base, the increase in the contact area of the chevron 15 in the height direction is small. On the other hand, the increase in the contact area of the chevron 15 in the width direction increases, and the total increase in the contact area between the contact portion 12 and the electrode 13 is about the same.

Further, the resistance value is examined by paying attention to the contact boundary between the contact portion 12 and the electrode 12 and the distance between the electrodes 13 at the boundary. In other words, the distance between the boundary between the contact portion 12 in the Y direction of FIG. 4, that is, the width direction of the electrode 13 and the pair of electrodes 13 in the X direction of FIG. 4, that is, the separation direction of the pair of electrodes 13. The part surrounded by and is considered as a conductive path. Then, in the initial change of pressing from P1 to P4, since the inclined surface 15b of the chevron 15 is steep, the conductive path in the X direction changes to be longer, and the conductive path in the Y direction almost increases. Change so as not to. Therefore, in this change from P1 to P4, the increase in the ease of conducting as a conductive path is small.

In the later stage of pressing, it changes from P4 to P5, P6, and P7, but in this process, the contact area of the contact portion 12 with respect to the circuit board B does not change so much, and is compared with the degree of change in pressing pressure. The degree of increase in the contact area between the contact portion 12 and the circuit board B becomes small. As shown in FIG. 4B, the contact region between the contact portion 12 and the electrode 13 in this process is such that the contact portion 12 is formed in the oblique 17 portion that rises diagonally from the valley 16 portion of the electrode 13. It changes to make contact in sequence. Therefore, the degree of increase in the contact area between the contact portion 12 and the electrode 13 is about the same.

On the other hand, looking at the conductive path, in the late pressing change from P4 to P7, the conductive path in the X direction gradually shortens as the oblique shape 17 rises, and in the Y direction. In the conductive path of No. 1, the increase in the contact area between the contact portion 12 and the circuit board B is small. In this change from P4 to P7, the increase in the ease of conduction as a conductive path is large, especially due to the shortening of the conductive path in the X direction, and the change in resistance value in the process of change is large. ing.

From the above, comparing the initial stage of pressing and the latter stage of pressing with respect to the change in pressing pressure, the length of the conductive path is rapidly increased at the initial stage of pressing, and the width of the conductive path is gradually increased to reduce the change in resistance value and obtain high resistance. There is. On the other hand, in the latter stage of pressing, the length of the conductive path is gradually shortened, the width of the conductive path is made as long as possible, and the change in resistance value is made large to reduce the resistance. In this way, the change in resistance value with respect to pressing force can be made linearly closer to the resistance value characteristic of a general electrode in which the opposing edges 14 of the pair of electrodes 13 are parallel to each other.

By the way, in the concentric circles shown in FIG. 2, the contact area increases significantly at first, and then the contact area increase rate gradually decreases. By increasing the contact area per unit pressing force in this way, the strictness of accuracy regarding the alignment between the contact portion 12 and the electrode 13 can be relaxed. Therefore, the pressure-sensitive sensor with high tolerance for misalignment can be obtained.

The rubber switch type pressure-sensitive sensor 11 using the contact portion 12 on the surface of the convex elastic pressing body 18 does not need to bend the resin film and feels lighter to press than the membrane type described later. Tend to be. In addition, it has a simple structure, is inexpensive, and can be easily manufactured.

<u style="single">Second Embodiment [Fig. 5]</u>:: The pressure sensor 21 of this embodiment is shown in FIG. The pressure-sensitive sensor 21 has a contact portion 22 different from that of the pressure-sensitive sensor 11 described in the previous embodiment.

The contact portion 22 in the present embodiment does not have the entire convex surface of the elastic pressing body 18 that is pressed and contacts the circuit board B as a resistor, but has two hole-shaped insulating portions in the vicinity of the contact center. 22a is provided. More specifically, the insulating portion 22a is the surface of the elastic pressing body 18, and a virtual line connecting the tops 15a of the chevron 15 of the pair of electrodes 13 when the elastic pressing body 18 is brought into contact with the circuit board B is formed. Two are formed at the upper and lower positions sandwiched between them. The shape of the insulating portion 22a has an outer shape along the virtual line on the virtual line side, and on the opposite side of the virtual line, when the contact portion 22 is pressed and comes into contact with the top portion 15a of the electrode 13. It has an outer shape substantially equivalent to the outer shape of the contact area between the contact portion 22 and the circuit board B.

By forming the contact portion 22 provided with the two hole-shaped insulating portions 22a, the conductive path at the time of pressing is narrowed and high resistance is obtained. That is, since the width of the conductive path is small, it is possible to suppress a large decrease in the resistance value. Even if such a contact portion 22 is used, the resistance value characteristic works to be close to linear, and the resistance value characteristic based on the shape of the opposite edge 14 of the electrode 13 can be finely adjusted.

<u style="single">Third Embodiment [Figs. 6 to 8]</u>:: The pressure sensor 31 of this embodiment is shown in FIG. Unlike the pressure sensor 11 shown in the above embodiment, the pressure sensor 31 uses a membrane contact at the contact portion. That is, a resin film 39 separated from the circuit board B is provided, and a contact portion 32 having a predetermined pattern formed of a resistor is formed on the surface of the resin film 39 at a position facing the electrode 3. Then, the resin film 39 is pressed from the upper surface by the elastic pressing body 38, and the resin film 39 is deformed along the elastic pressing body 38 to bring the contact portion 32 into contact with the electrode 3.

As shown in FIG. 7, the contact portion 32 is composed of a circular resistor 34, and four regions are continuously formed concentrically around the pressing center. These four regions are the second region 34b, the third region 34c, and the fourth region 34d in order from the central first region 34a to the outside. Needless to say, the resistor 34 has conductivity to the extent that conduction between the electrodes 3 is achieved. The first region 34a to the third region 34c are formed in a network pattern, with the first region 34a being the coarsest, the second region 34b, and the third region 34c being finer in that order. In addition, the fourth region 34d is formed by solid (filling).

Assuming that the resistance values (surface resistivity) of the first region 34a to the fourth region 34d are R1 to R4, respectively, there is a relationship of R1&gt; R2&gt; R3&gt; R4, and the resistance value of the first region 34a is the highest, and the fourth region 34a. The resistance value of region 34d is the lowest. With this relationship, it is possible to suppress the decrease in the resistance value at the initial stage of pressing and promote the decrease in the resistance value at the latter stage of pressing, and it is possible to make the change in the resistance value with respect to the pressing pressure close to linear.

Further explaining, the initial resistance is high because the resistance value of the first region 34a is high. However, if it is formed as a circular pattern having a uniform resistance value, the resistance value curve as shown by the broken line L1 in FIG. 8 continues, whereas in the present embodiment, the first region 34a is switched to the second region 34b. Then, the slope becomes large again and becomes the curved part of L2, approaching a straight line. Similarly, by switching to the L3 curve in the third region 34c and the L4 curve in the fourth region 34d, the curve changes linearly as a whole. The resistance value curve given as the prior art has a form in which all the regions are formed in the same pattern as the first region.

Since the elastic pressing body 38 does not function as a contact portion, it is sufficient to use an elastic conductive polymer, an elastic body such as synthetic rubber, natural rubber, or a thermoplastic elastomer. The membrane-type pressure-sensitive sensor 31 using a membrane contact for the contact portion 32 has the following advantages as compared with the rubber switch-type pressure-sensitive sensor 11. In the membrane type, since the contact portion 32 is formed on the resin film, patterning can be easily performed by a method such as printing. Therefore, there is a degree of freedom to flexibly realize arbitrary resistance value characteristics.

The pressure sensor 31 of the present embodiment can be changed as follows. For the first region 34a to the fourth region 34d, each region may be solidly formed by using conductive inks having different resistance values. Further, in the first region 34a to the fourth region 34d, the resistance value can be changed by changing the film thickness of the conductive ink to be printed. More specifically, the first region can be made into a thin film, and the film thickness can be gradually increased in the second region, the third region, and the fourth region. Even in this way, the relationship between the resistance values in each region can be the relationship of R1&gt; R2&gt; R3&gt; R4, suppressing the decrease in the resistance value at the initial stage of pressing and promoting the decrease in the resistance value in the latter stage of pressing. Can be made to.

Fourth Embodiment<u style="single">[Fig. 9, Fig. 10]</u>:: The pressure sensor 41 of this embodiment is shown in FIG. This pressure sensor 41 uses a membrane contact for the contact portion, but its shape is different from that of the pressure sensor 31 shown in the previous embodiment. Further, as the electrode, the bird wing-shaped electrode 13 of the pressure sensor 11 is used.

As shown in FIG. 10, the contact portion 42 is provided with an insulating portion 42a in a part formed of a circular resistor 44. The shape of the insulating portion 42a is the same as the shape when the insulating portion 22a of the pressure sensor 21 is in contact with the circuit board B, and is the top of the chevron 15 of the pair of electrodes 13 on the surface of the resin film 49. Two are formed at the upper and lower positions across the virtual line connecting 15a, and the virtual line side has an outer shape along the virtual line, and the opposite side to the virtual line is concentric with the outer shape of the resistor 44. It has the outer shape of. The elastic pressing body 38 is the same as the elastic pressing body 38 of the pressure sensor 31, and may be an elastic body.

<u style="single">Example</u>:: Sample 1: A circuit board having a pair of electrodes formed of a copper foil having a thickness of 35 μm was prepared. The electrode shape is the shape shown in FIG. The contact part is made of silicone rubber with hardness A50 (JIS K6253 standard) and molded into a convex shape (hemispherical shape) with a diameter of 1.5 mm, and carbon is formed on the surface of this convex shape so that the film thickness is 10 μm. Manufactured by applying paste.

Sample 2 (Comparative example): The shape of the electrode was the same as that of Sample 1 except that the shape shown in FIG. Sample 3 (Comparative example): The shape of the electrode was the same as that of Sample 1 except that the shape was shown in FIG. In FIGS. 11 to 13, the electrode is designated by reference numeral 43, and the contact portion is in contact with the circuit board B. The contact area of the contact portion in a certain state is indicated by the symbol P.

Evaluation methods: The resistance value between the pair of electrodes with respect to the pressing stroke (pressing pressure) when the contact portion was pressed against the circuit board was measured. The origin of the pressing stroke was set to the measurement point immediately before the measurement point where the resistance value became 2000Ω or less (measurement point from 10 kΩ to the insulated state).

Evaluation results: Figure 14 shows the relationship between the pressing stroke and the resistance value for Samples 1 to 3. Comparing Sample 1 with a bird wing-shaped electrode facing edge and Sample 2 with a linear electrode, the initial resistance value change is small, and the resistance value gradually decreases in the latter half, approaching linear characteristics. You can see that. On the other hand, it can be seen that the resistance value of sample 2 decreased significantly at the initial stage of pressing, and the change in resistance value almost disappeared in the latter half. Furthermore, although the initial resistance value change of sample 3 was smaller than that of sample 2, there was almost no change in resistance value in the latter stage of pressing as in sample 2.

From the above, the electrode shape of sample 1 has a relatively small change in resistance value in the initial stage of pressing and a large change in resistance value in the latter stage of pressing as compared with the electrode shapes of sample 2 and sample 3, so that the resistance value with respect to the pressing stroke I was able to make the change more linear.

The pressure-sensitive sensor shown in the above-described embodiments and examples is an example of the present invention, and is not limited to these embodiments, and the shape, material, manufacturing method, etc. of each member are not limited to these embodiments. It includes a modified form of. For example, the contact portion 42 of the pressure-sensitive sensor 41 of the fourth embodiment can be formed in a solid shape like the contact portion 12 of the pressure-sensitive sensor 11 of the first embodiment, and various changes can be made.

1 Pressure sensor (conventional technology) 2 Conductive contacts 2a curved surface 2b top 3 electrodes 11 Pressure sensor (1st embodiment) 12 contacts 12a top 13 electrodes 14 Opposing edge 15 Yamagata 15a top 15b slope 16 Tanigata 17 diagonal 18 Elastic pressing body 21 Pressure sensor (second embodiment) 22 Contact 22a Insulation part 28 Elastic press 31 Pressure sensor (third embodiment) 32 contacts 34 resistor 34a 1st area 34b second area 34c Third area 34d 4th area 38 Elastic press 39 Resin film 41 Pressure sensor (4th embodiment) 42 contacts 42a Insulated part 44 resistor B circuit board