pressure sensor

Abstract

To provide a pressure sensitive sensor that can achieve a reduction in thickness and the number of components, and avoids the possibility that displacement between constituents occurs due to assembly.SOLUTION: A plurality of contact patterns 21, 51 and a plurality of wiring patterns 31, 61 connected with the contact patterns 21, 51, respectively, are formed on a substrate 10. A pressure-sensitive resistor 41 in which the value of resistance changes according to pressure is formed on the plurality of contact patterns 21, 51. A pattern 71 for conduction between contacts for establishing conduction between the plurality of contact patterns 21, 51 with the pressure-sensitive resistor 41 therebetween is formed at a position on the pressure-sensitive resistor 41 opposite to the plurality of contact patterns 21, 51, thereby constituting a pressure sensitive sensor 1-1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure sensor whose resistance value changes in response to a pressing force. [Background technology]

[0002] Conventionally, a pressure sensor whose resistance value changes depending on the pressing force has been configured, for example as shown in Patent Document 1, by stacking a lower circuit board with a lower electrode and an upper circuit board with an upper electrode via a spacer, with the upper and lower electrodes facing each other within an opening in the spacer, and pressing the upper circuit board on the back side of the upper electrode to lower it so that the upper electrode abuts against the lower electrode, and changing the resistance value between the upper and lower electrodes depending on the magnitude (contact area) of the abutment force (load). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-45629 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as mentioned above, conventional pressure sensors are constructed using two circuit boards and a spacer, which increases the number of parts and makes the product thicker.Furthermore, there is a risk that the position of the opening in the spacer or the upper electrode may become misaligned relative to the lower electrode due to misalignment when assembling the two circuit boards and the spacer.

[0005] The present invention has been made in consideration of the above points, and its purpose is to provide a pressure sensor that can reduce the number of parts and the thickness, and that does not have the risk of misalignment occurring between the components due to assembly. [Means for solving the problem]

[0006] The present invention is a pressure sensor in which the resistance value changes depending on the pressing force. Made of synthetic resin On the top surface of the board They are elongated rectangular and are arranged at a predetermined distance apart so that the opposing long sides are parallel to each other. R 1st, 2nd The contact pattern and the 1st, 2nd Connect to each contact pattern 1st, 2nd The wiring pattern is directly formed, 1st, 2nd On the top surface of the contact pattern of 1st, 2nd Contact pattern By forming the first and second contact patterns with an area larger than the combined area of ​​the first and second contact patterns, A pressure-sensitive resistor whose resistance value changes depending on pressure is directly laminated over the surface, having a surface rougher than the surface of the substrate the upper surface of the pressure-sensitive resistor 、 The aforementioned 1st, 2nd Opposite the contact pattern and covers the entire first and second contact patterns directly above it. In the position 1st, 2nd The contact patterns are directly laminated to form an inter-contact conductive pattern that provides electrical continuity between the contact patterns via the pressure sensitive resistor. According to the present invention, a pressure sensor can be constructed by forming various patterns on a single substrate, which reduces the number of components and the thickness. 1st, 2nd There is no risk of misalignment occurring between the contact patterns, pressure sensitive resistors, and contact conduction patterns due to assembly. Also, as usual 1st, 2nd Since no spacer is provided between the contact patterns, the resistance value begins to change with the application of only a light force, making it suitable for use as a pressure-sensitive sensor that requires a characteristic in which the resistance value begins to change with a light force and then changes further as the pressure increases. Furthermore, the electrical circuit of this pressure-sensitive sensor has a structure in which two resistances caused by pressure-sensitive resistors (their thicknesses) are connected in series, so the resistance value of the pressure-sensitive resistors can be easily increased, resulting in a pressure-sensitive sensor with high resolution. Also, because the pressure-sensitive resistor is thin, 1st, 2ndSince the contact pattern and the inter-contact conduction pattern are conductive only at the parts that face each other above and below (directly above and directly below) via the pressure-sensitive resistor (resistance value changes), the resistance value can be easily adjusted by adjusting the area and shape of each contact pattern, inter-contact conduction pattern, and pressure-sensitive resistor (for example, the resistance value increases when the opposing area of ​​the contact pattern and inter-contact conduction pattern is reduced).

[0008] In addition to the above features, the present invention also provides 1st, 2nd The contact pattern and 1st, 2nd The wiring pattern, the pressure-sensitive resistor, and the pattern for conducting electrical contacts between the contacts are all printed layers formed by being directly laminated on the substrate by printing. This allows various patterns to be formed easily and accurately on one substrate, reducing the number of parts, manufacturing costs, and thickness. 1st, 2nd There is no risk of misalignment occurring between the contact patterns, pressure sensitive resistors, and contact conduction patterns due to assembly. [Effects of the Invention]

[0009] According to the present invention, it is possible to reduce the number of parts and the thickness, and it is also possible to eliminate the risk of misalignment between the contacts due to assembly, thereby obtaining a pressure sensor with stable product characteristics. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic cross-sectional view of a pressure-sensitive sensor 1-1. [Figure 2] FIG. 2 is a schematic plan view of the pressure sensor 1-1. [Figure 3] FIG. 2 is an explanatory diagram of the operation of the pressure sensor 1-1. [Figure 4] FIG. 2 is a plan view showing a specific example of the pressure-sensitive sensor 1-1. [Figure 5] FIG. 2 is a schematic cross-sectional view of a pressure-sensitive sensor 1-2. [Figure 6] FIG. 2 is a schematic plan view of the pressure sensor 1-2. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 is a schematic cross-sectional view (a schematic cross-sectional view along the line AA in Fig. 2) of a pressure-sensitive sensor 1-1 according to a first embodiment of the present invention, and Fig. 2 is a schematic plan view of the pressure-sensitive sensor 1-1. As shown in these figures, the pressure-sensitive sensor 1-1 is configured by forming, on a substrate 10, a pair of first and second contact patterns 21, 51 and a pair of first and second wiring patterns 31, 61 connected to the first and second contact patterns 21, 51, respectively, a pressure-sensitive resistor (pressure-sensitive resistive layer, pressure-sensitive resistive pattern) 41 whose resistance value changes in response to pressure on the first and second contact patterns 21, 51, and forming, on the pressure-sensitive resistor 41, a contact-to-contact conduction pattern 71 that establishes conduction between the first and second contact patterns 21, 51 via the pressure-sensitive resistor 41, at a position facing the first and second contact patterns 21, 51. In the following explanation, "up" refers to the direction of looking from the substrate 10 toward the surface on which the first and second contact patterns 21, 51, etc. are formed, and "down" refers to the opposite direction, but this is not intended to limit the direction in which the pressure sensor 1-1 can be used.

[0012] Next, the configuration of the pressure-sensitive sensor 1-1 will be described together with the manufacturing method thereof. First, prepare the substrate 10. The substrate 10 is made of a flexible synthetic resin film, and in this example, a polyethylene terephthalate (PET) film is used.

[0013] Next, the first contact pattern 21 and the first wiring pattern 31, and the second contact pattern 51 and the second wiring pattern 61 are simultaneously formed on the substrate 10 by screen printing a conductive paste (silver paste in this example). The first and second contact patterns 21 and 51 are both elongated rectangular and formed to the same shape and dimensions, and are arranged a predetermined distance apart so that their opposing long sides are parallel to each other. The first and second wiring patterns 31 and 61 are linear and connected to the centers of the outer long sides of the first and second contact patterns 21 and 51, respectively. The first and second contact patterns 21 and 51 and the first and second wiring patterns 31 and 61 may have various other shapes. The first and second contact patterns 21 and 51 are preferably formed in positions where they can be simultaneously pressed by a pressing object such as a finger.

[0014] Next, a pressure-sensitive resistor 41 is formed on the substrate 10 by screen-printing carbon paste so as to cover the entire upper surfaces of the first and second contact patterns 21, 51 and parts of the first and second wiring patterns 31, 61 connected thereto. In this example, the pressure-sensitive resistor 41 is circular (it may have various other shapes) and is formed with an area larger than the combined area of ​​the first and second contact patterns 21, 51. The carbon paste is made of a conductive paint made by mixing a synthetic resin that remains flexible even when hardened, carbon powder, and a solvent.

[0015] Next, an inter-contact conductivity pattern 71 is formed on the upper surface of the pressure-sensitive resistor 41 by screen printing silver paste. In this example, the inter-contact conductivity pattern 71 is circular (it may have various other shapes), and is formed in a position directly above and facing the first and second contact patterns 21, 51, with the pressure-sensitive resistor 41 interposed therebetween, or more specifically, in a position directly above and covering the entire first and second contact patterns 21, 51. The inter-contact conductivity pattern 71 provides conductivity between the first and second contact patterns 21, 51 via the pressure-sensitive resistor 41.

[0016] The pressure-sensitive sensor 1-1 is completed by the above manufacturing method. Note that the above manufacturing procedure is only one example, and it goes without saying that various other manufacturing procedures may be used for manufacturing.

[0017] When a voltage is applied between the first and second wiring patterns 31 and 61 of the pressure-sensitive sensor 1-1 configured as described above, as shown in Figure 3, a current flows through the path of the first wiring pattern 31 ⇔ first contact pattern 21 ⇔ pressure-sensitive resistor 41 ⇔ inter-contact conductivity pattern 71 ⇔ pressure-sensitive resistor 41 ⇔ second contact pattern 51 ⇔ second wiring pattern 61.

[0018] In other words, the resistance value between the first and second wiring patterns 31 and 61 is 2R [Ω], which is twice the resistance value R [Ω] of the thickness of the pressure-sensitive resistor 41, assuming that the resistance values ​​of the first and second wiring patterns 31 and 61, the first and second contact patterns 21 and 51, and the pattern for inter-contact conductivity 71 are zero. Note that at least a portion of the pattern for inter-contact conductivity 71 must be located directly above the first contact pattern 21 and the second contact pattern 51 in order to be conductive to each other. Therefore, at least a portion of the pattern for inter-contact conductivity 71 must be located directly above each of the first contact pattern 21 and the second contact pattern 51, and this is the embodiment in which this is the case.

[0019] When the substrate 10 is placed on a base (not shown) and the inter-contact conductivity pattern 71 is pressed from above with a finger or a pressing object such as a key top, the flexible pressure-sensitive resistor 41 is compressed, its thickness is reduced, and the carbon particles in the pressure-sensitive resistor 41 come into strong contact with each other, increasing the contact area between the carbon particles. This reduces the resistance between the first contact pattern 21 and the inter-contact conductivity pattern 71 and the resistance between the inter-contact conductivity pattern 71 and the second contact pattern 51, i.e., the resistance between the first and second contact patterns 21 and 51. Meanwhile, as the pressure is gradually released, the thickness of the pressure-sensitive resistor 41 returns to its original thickness due to its elastic restoring force, and the resistance increases. In other words, the resistance between the first and second contact patterns 21 and 51 varies depending on the magnitude of the pressing force (pressing force), thereby obtaining different outputs corresponding to the pressing force and enabling the magnitude of the pressing force to be detected.

[0020] Incidentally, it is preferable that the resistance value when the pressure-sensitive resistor 41 is not pressed be larger, because this increases the range of change in resistance when it is pressed. In this pressure-sensitive sensor 1-1, as described above, the resistance value doubles because the electrical circuit passes through the pressure-sensitive resistor 41 twice in series, so the resistance value due to the pressure-sensitive resistor 41 can be easily increased, resulting in a pressure-sensitive sensor 1-1 with high resolution.

[0021] Of course, in the above pressure-sensitive sensor 1-1, it is more preferable to increase the resistance value by making the thickness of the pressure-sensitive resistor 41 thicker than the thickness of the first and second contact patterns 21, 51, but the present invention is not limited to this, and the thickness may be the same as or thinner than the thickness of the first and second contact patterns 21, 51.

[0022] Furthermore, because the thickness of the pressure-sensitive resistor 1 is thin, only the surface portion of the pressure-sensitive resistor 41 where the first contact pattern 21 (more precisely, including a portion of the first wiring pattern 31 connected thereto, but omitted from the following description) and the inter-contact conductivity pattern 71 vertically face (overlap) each other, and the surface portion of the pressure-sensitive resistor 41 where the second contact pattern 51 (more precisely, including a portion of the second wiring pattern 61 connected thereto, but omitted from the following description) and the inter-contact conductivity pattern 71 vertically face (overlap) each other. In this embodiment, because the first and second contact patterns 21 and 51 are smaller than the inter-contact conductivity pattern 71, only the portion of the pressure-sensitive resistor 41 directly above the surfaces of the first and second contact patterns 21 and 51 acts as a resistor. Therefore, if a high resistance value is desired, the resistance value can be increased by reducing the area of ​​at least one of the first and second contact patterns 21 and 51. In this case, it is preferable that the inter-contact conductivity pattern 71 be large enough to cover a wider area than the areas forming the opposing first and second contact patterns 21, 51, in order to reliably prevent printing errors from causing areas where the inter-contact conductivity pattern 71 does not face the first and second contact patterns 21, 51 vertically.

[0023] In other words, the first and second contact patterns 21, 51 and the contact-to-contact conductivity pattern 71 are conductive only at the portions that face each other vertically (directly above and directly below) via the pressure-sensitive resistor 41 (resistance value changes), so the resistance value can be easily adjusted by adjusting the area, shape and position of the first and second contact patterns 21, 51, the contact-to-contact conductivity pattern 71 and the pressure-sensitive resistor 41.

[0024] As described above, the resistance value of the pressure-sensitive sensor 1-1 is determined by the area of ​​the smaller pattern (first and second contact patterns 21, 51). However, as in this embodiment, the pattern (first and second contact patterns 21) printed directly on the substrate 10 is made smaller than the pattern (pattern 71 for inter-contact conductivity) printed on the pressure-sensitive resistor 41. This is because the pattern (first and second contact patterns 21, 51) formed on the substrate 10, which has a smooth surface, can be printed with higher accuracy than the pattern (pattern 71 for inter-contact conductivity) formed on the pressure-sensitive resistor 41, which has a rough surface, and it is expected that the accuracy of the resistance value, which is determined by the area of ​​the smaller pattern (first and second contact patterns 21, 51), can be further improved.

[0025] Furthermore, like this pressure-sensitive sensor 1-1, it is preferable that the pressure-sensitive resistor 41 be formed with an outer shape larger than the portion on the substrate 10 that forms the first and second contact patterns 21, 51, so as to reliably cover the first and second contact patterns 21, 51.

[0026] FIG. 4 is a plan view showing one specific example of a pressure-sensitive sensor 1-1. As shown in the figure, the substrate 10 is configured to include a sensor body forming portion 11 and an output lead portion 13 that is connected to the outer periphery of the sensor body forming portion 11 and extends in a strip shape. The sensor body forming portion 11 is printed with first and second contact patterns 21 and 51, a pressure-sensitive resistor 41, an inter-contact conduction pattern 71, and portions of the first and second wiring patterns 31 and 61 connected to the first and second contact patterns 21 and 51, respectively. The output lead portion 13 is printed with the remaining portions of the first and second wiring patterns 31 and 61, and output terminal patterns 33 and 63 are printed at their tips. This allows a voltage to be easily applied between the first and second contact patterns 21 and 51 to obtain an output.

[0027] Fig. 5 is a schematic cross-sectional view (sectional view taken along the line BB in Fig. 6) of a pressure-sensitive sensor 1-2 according to a second embodiment of the present invention, and Fig. 6 is a schematic plan view of the pressure-sensitive sensor 1-2. In the pressure-sensitive sensor 1-2 shown in these figures, parts that are the same as or correspond to those of the pressure-sensitive sensor 1-1 shown in Figs. 1 to 4 are given the same reference numerals (however, the reference numerals are given the suffix "-2"). Note that matters other than those described below are the same as those in the embodiment shown in Figs. 1 to 4.

[0028] The pressure-sensitive sensor 1-2 differs from the pressure-sensitive sensor 1-1 in that the first and second contact patterns 21-2, 51-2 are configured to be large enough to extend beyond the pressure-sensitive resistor 41-2 and the pattern for electrical continuity between contacts 71-2. As a result, the pressure-sensitive resistor 41-2 and the pattern for electrical continuity between contacts 71-2 cover part of the periphery (outer periphery) of the first and second contact patterns 21-2, 51-2.

[0029] That is, the pressure-sensitive resistor 41-2 does not need to cover the entire upper surface of the first and second contact patterns 21-2, 51-2, and in some cases may be configured to cover only a portion of the periphery of the first and second contact patterns 21-2, 51-2. In this way, the sizes and positions of the first and second contact patterns 21-2, 51-2, the pressure-sensitive resistor 41-2, and the inter-contact conductivity pattern 71-2 can be changed in various ways. Even when the pressure-sensitive sensor 1-2 is configured in this way, the functions and effects of the present invention can be achieved.

[0030] As described above, the pressure-sensitive sensor 1-1 (1-2) has, on the substrate 10 (10-2), a plurality of contact patterns 21, 51 (21-2, 51-2) and a plurality of wiring patterns 31, 61 (31-2, 61-2) connected to each of the contact patterns 21, 51 (21-2, 51-2), and a pressure-sensitive resistor 41 (41-2) whose resistance value changes depending on pressure is formed on the plurality of contact patterns 21, 51 (21-2, 51-2), and the pressure-sensitive resistor 41 (41-2) faces the plurality of contact patterns 21, 51 (21-2, 51-2) on the pressure-sensitive resistor 41 (41-2). Since the pressure-sensitive sensor 1-1 (1-2) is configured by forming an inter-contact conductivity pattern 71 (71-2) at a position where the pressure-sensitive resistor 41 (41-2) is interposed between the multiple contact patterns 21, 51 (21-2, 51-2), the pressure-sensitive resistor 41 (41-2) is interposed therebetween, the pressure-sensitive sensor 1-1 (1-2) can be configured simply by forming various patterns on a single substrate 10 (10-2), thereby reducing the number of parts and making the sensor thinner, and there is no risk of misalignment occurring between the multiple contact patterns 21, 51 (21-2, 51-2), the pressure-sensitive resistor 41 (41-2), or the inter-contact conductivity pattern 71 (71-2) due to assembly.

[0031] Furthermore, since there is no space between the multiple contact patterns using spacers as in the past, the resistance value begins to change with the application of only a light force, making it suitable for use as a pressure-sensitive sensor 1-1 (1-2) that requires a characteristic in which the resistance value begins to change with a light force and then changes further as the pressure increases.

[0032] Furthermore, as described above, the electrical circuit of this pressure-sensitive sensor 1-1 (1-2) has a structure in which two resistances due to the pressure-sensitive resistor 41 (41-2) are connected in series, so the resistance value due to the pressure-sensitive resistor 41 (41-2) can be easily increased, resulting in a pressure-sensitive sensor with high resolution.

[0033] Furthermore, the first and second contact patterns 21, 51 (21-2, 51-2), the first and second wiring patterns 31, 61 (31-2, 61-2), the pressure-sensitive resistor 41 (41-2), and the inter-contact conductivity pattern 71 (71-2) that constitute the pressure-sensitive sensor 1-1 (1-2) are formed by layering on the substrate 10 (10-2) by printing, so they can be formed easily and accurately in positions on a single substrate 10 (10-2), which also reduces the number of parts, manufacturing costs, and thickness. Furthermore, there is no risk of misalignment occurring between the first and second contact patterns 21, 51 (21-2, 51-2), the pressure-sensitive resistor 41 (41-2), and the inter-contact conductivity pattern 71 (71-2) during assembly.

[0034] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified in various ways within the scope of the claims and the technical concept described in the specification and drawings. Furthermore, any shape, structure, or material not directly described in the specification and drawings is within the scope of the technical concept of the present invention as long as it achieves the functions and effects of the present invention. For example, it goes without saying that various changes can be made to the shapes and positions of the substrate 10 (10-2), first contact pattern 21 (21-2), first wiring pattern 31 (31-2), pressure-sensitive resistor 41 (41-2), second contact pattern 51 (51-2), second wiring pattern 61 (61-2), and inter-contact conductivity pattern 71 (71-2).

[0035] In the above example, screen printing was used to form the various patterns, but other printing methods (e.g., offset printing, inkjet printing) or even pattern formation methods other than printing (e.g., etching) may be used. In the above embodiment, flexible substrates were used as the substrates 10 and 10-2, but rigid substrates may also be used.

[0036] The number of contact patterns may be three or more. Also, a separate insulating layer or insulating film may be placed on the inter-contact conduction pattern 71, and the pressing body may press from above.

[0037] Furthermore, the embodiments described above and shown in the drawings can be combined with each other as long as there is no contradiction in their purpose, configuration, etc. Furthermore, even a part of the description described above and the drawings can be an independent embodiment, and the embodiment of the present invention is not limited to a single embodiment combining the description described above and the drawings. [Explanation of symbols]

[0038] 1-1, 1-2 Pressure sensor 10,10-2 board 21,21-2 First contact pattern 31,31-2 First wiring pattern 41,41-2 Pressure-sensitive resistor 51,51-2 Second contact pattern 61,61-2 Second wiring pattern 71, 71-2 Conductive pattern between contacts

Claims

1. In a pressure sensor whose resistance value changes depending on the pressing force, First and second contact patterns, each having an elongated rectangular shape, are arranged at a predetermined distance apart so that opposing long sides are parallel to each other, and first and second wiring patterns connected to the first and second contact patterns, respectively, are directly formed on the upper surface of a single synthetic resin substrate; a pressure-sensitive resistor whose resistance value changes in response to pressure is formed by directly laminating it on the upper surfaces of the first and second contact patterns, the pressure-sensitive resistor being formed with an area larger than the combined area of ​​the first and second contact patterns, so as to cover the entire upper surfaces of the first and second contact patterns; A pressure-sensitive sensor characterized in that an inter-contact conductive pattern, which connects the first and second contact patterns via the pressure-sensitive resistor, is directly laminated on the upper surface of the pressure-sensitive resistor, which has a surface rougher than the surface of the substrate, in a position facing the first and second contact patterns and directly covering the entire first and second contact patterns.

2. 2. The pressure-sensitive sensor according to claim 1, A pressure-sensitive sensor characterized in that the first and second contact patterns, the first and second wiring patterns, the pressure-sensitive resistor, and the pattern for electrical conductivity between contacts are all printed layers formed by directly stacking them on the substrate by printing.

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