JP2012057991A - Pressure sensitive sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce changes of measurement results generated in accordance with dispersion in measurement results and measurement frequency of a pressure sensitive sensor.SOLUTION: Surfaces of conductive layers coating an electrode are smoothed by changing the size of silver particles to be used for the electrode in a tactile sensor to be used as a pressure sensitive sensor. Consequently, changes of contact areas of two conductive layers can be reduced in each application of pressure as long as the pressure to be applied is constant, and changes of surface roughness of these conductive layers corresponding to using frequency can be also reduced, so that the pressure sensitive sensor can reduce phenomena that dispersion is generated in measurement results in each application of pressure and measurement results are changed with the lapse of time in accordance with using frequency, and in its turn, can stably and accurately measure the pressure.

Description

  The present invention relates to a pressure-sensitive sensor that measures pressure.

  The pressure-sensitive sensor prints row electrodes at a constant width pitch, prints a column electrode at a constant width pitch, and a sheet-like substrate on one side on which a conductive layer is formed so as to cover the electrodes. And the other sheet-like base material on which the conductive layer is formed so as to cover the electrode, and the surfaces of the conductive layer are opposed to each other.

  In this type of pressure-sensitive sensor, when a load is applied to the laminated sheet-like base material, the conductive layers covered with the electrodes in the matrix come into contact with each other, and the resistance changes. Since the resistance value changes according to the magnitude of the pressure applied to the sheet-like base material, the magnitude of the pressure applied to the sheet-like base material is measured by detecting the change in the resistance value. be able to. The pressure-sensitive sensor is used, for example, to measure the uniformity of pressure applied to a paper feed roller of a printer, or to measure a seat pressure distribution when sitting on a chair or the like. As this type of pressure-sensitive sensor, for example, a pressure-sensitive sensor described in Patent Document 1 is known.

JP 2005-274549 A

  However, the pressure-sensitive sensor as described above has a problem that even if the same pressure is applied, the measurement result varies each time, or the measurement result changes with time depending on the frequency of use. .

  An object of the present invention is to solve such problems, and is to reduce variations in measurement results of pressure-sensitive sensors and changes in measurement results according to usage frequency.

  In order to solve the above problems, the present invention provides a sheet substrate on which a conductive layer is formed so as to cover a conductive electrode, and changes in resistance when pressure is applied to the sheet substrate. A first sheet-like base material in which a plurality of the electrodes are formed in a longitudinal shape with a predetermined interval along a first direction; and the first sensor A second sheet-like base material in which a plurality of the electrodes are formed in a longitudinal shape with a predetermined interval along a second direction intersecting the direction, and the first sheet-like base material Both of the surface of the conductive layer covering the electrode and the surface of the conductive layer covering the electrode of the second sheet-like substrate are smoothed.

  According to the present invention, the surface of the conductive layer covering the electrode of the first sheet-like substrate and the surface of the conductive layer covering the electrode of the second sheet-like substrate are smoothed. As long as the applied pressure is the same, the contact area between the conductive layer on the first sheet-like base material side and the conductive layer on the second sheet-like base material side may change each time the pressure is applied. Is small. Therefore, every time pressure is applied, there is little risk of variations in measurement results. In addition, since both the surface of the conductive layer covering the electrode of the first sheet-like substrate and the surface of the conductive layer covering the electrode of the second sheet-like substrate are smoothed, these conductive layers There is little possibility that the surface roughness of the material changes depending on the frequency of use. Therefore, there is little possibility that the measurement result will change over time according to the frequency of use. In this way, the pressure-sensitive sensor of the present invention can reduce changes in measurement results according to variations in measurement results and usage frequency.

  Moreover, in the pressure-sensitive sensor according to the present invention for solving the above-described problems, the surface roughness of the conductive layer covering the electrode of the first sheet-like substrate and the electrode of the second sheet-like substrate are covered. It is preferable that the surface roughness of the conductive layer is Ra = 1.0 μm or less.

  Furthermore, in the pressure-sensitive sensor according to the present invention for solving the above-mentioned problem, the electrode contains silver particles, and the silver particles contained in the electrode of the first sheet-like substrate and the second It is preferable that the average particle diameter of the silver particles contained in the electrode of the sheet-like substrate is in the range of 20 nm to 7 μm.

  Thus, the present invention can reduce changes in measurement results that can occur according to variations in the measurement results of the pressure-sensitive sensor and the measurement frequency.

It is a perspective view of a tactile sensor concerning an embodiment of the present invention, and shows the state where a part of one sheet-like base material was notched. (A) is a plan view showing one sheet-like substrate constituting a part of the tactile sensor shown in FIG. 1, and (b) is the other sheet-like substance constituting a part of the tactile sensor shown in FIG. It is the top view which showed the base material. (A) is a cross-sectional perspective view in a part of the tactile sensor shown in FIG. 1, (b) is a cross-sectional view of the main part of the tactile sensor shown in FIG. (A) is an expanded sectional view of an unused tactile sensor, (b) is an expanded sectional view of a tactile sensor used more than fixed frequency. It is a figure regarding the output reproducibility by the conventional tactile sensor. It is a figure regarding the output reproducibility by the tactile sensor of this invention.

  An embodiment according to a tactile sensor 1 as a pressure-sensitive sensor of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, the tactile sensor 1 according to this embodiment includes a sheet-like base material 10 and 20 having flexibility and a sheet-like base material 10 bonded so that the conductive portions face each other. And a connector 30 that can be connected to a power source (not shown). The sheet-like base materials 10 and 20 are used so as to face each other, and are pressure-sensitive sensors of a type that measure pressure by detecting a change in resistance that occurs when a load is applied.

  As shown in FIG. 1, FIG. 2A and FIG. 3, the first sheet-like base material 10 has a Y-axis on the film base 11 and on one side of the film base 11 (the surface inside the tactile sensor 1). A plurality of long electrodes 12 (more specifically, a long conductive portion having the electrode 12 and a first conductive layer 14 described later) provided along the direction, and one end of each of the plurality of electrodes 12 And a plurality of wirings 13 electrically connected to each other, and a plurality of terminals 16 to which ends of the plurality of wirings 13 are electrically connected.

  In the first sheet-like base material 10, the conductive portion extends in the longitudinal direction along the Y direction (corresponding to the first direction of the present invention), and a constant width pitch a (see FIG. 3B). )), A plurality of conductive portions are printed side by side. The conductive portion includes an electrode 12 and a first conductive layer 14 formed by applying a pressure-sensitive conductive ink containing conductive particles so as to cover the entire surface of the electrode 12. Yes. Hereinafter, in this specification, “electrode 12” is referred to as “row electrode 12”. Examples of the material used for the row electrode 12 include metal particles such as gold, silver, and copper, but are not limited thereto as long as they easily energize.

  As shown in FIGS. 1, 2 (b) and 3, the second sheet-like substrate 20 has a film substrate 21 and an X axis on one side of the film substrate 21 (the surface inside the tactile sensor 1). A plurality of long electrodes 22 (more specifically, a long conductive portion having the electrodes 22 and a second conductive layer 24 described later) provided along the direction, and one end of each of the plurality of electrodes 22 A plurality of wirings 23a electrically connected to each other, a plurality of wirings 23b electrically connected to the other end of each of the electrodes 22, and ends of the plurality of wirings 23a, And a plurality of terminals 26 to which ends of the plurality of wirings 23b are electrically connected.

  In the second sheet-like base material 20, the conductive portion extends in the longitudinal direction along the X direction (corresponding to the second direction of the present invention) substantially orthogonal to the row electrode 12, and the Y direction. A plurality of conductive parts are printed side by side at a constant width pitch a (see FIG. 3B). The conductive portion has an electrode 22 and a second conductive layer 24 formed by applying pressure-sensitive conductive ink containing conductive particles so as to cover the entire surface of the electrode 22. . Hereinafter, the “electrode 22” is referred to as a “column electrode 22” in the present specification. Examples of the material conductive particles used for the column electrode 22 include metal particles such as gold, silver, or copper, as in the case of the row electrode 12, but are not limited thereto as long as they easily energize.

  The first conductive layer 14 and the second conductive layer 24 both include conductive particles and a resin. Here, examples of the conductive particles include carbon black particles, metal particles such as gold, silver, and copper, alloy particles, and particles made of a resin whose surface is coated with a metal or alloy. The primary particle diameter of the conductive particles described above can be any value within the range of 20 nm to 40 nm.

  The metal particles contained in the row electrode 12 and the column electrode 22 preferably have an average particle diameter of 7 μm or less, more preferably a silver particle flake shape (abbreviated as silver flakes), an average particle diameter of 2 μm or less, or a sphere. Shaped silver particles (abbreviated as silver spheres) having an average particle size of 2.5 μm or less are used. When the metal particles contained in the row electrode 12 and the column electrode 22 are metal particles having a silver flake: average particle diameter of 2 μm or a silver sphere: average particle diameter of 2.5 μm, the first conductive layer 14 and the second conductive layer 14 The surface roughness (Ra) of the conductive layer 24 is about 0.6 μm (see Example 1 described later). Thus, the tactile sensor 1 according to this embodiment is characterized in that the surfaces of the first conductive layer 14 and the second conductive layer 24 are both smoothed.

  Next, the operation of the tactile sensor 1 will be described. In the state where the first sheet-like base material 10 and the second sheet-like base material 20 face each other as shown in FIG. 3A, no resistance is applied from the outside, the resistance value is infinite (that is, Insulated state). And if load F1 is added with respect to the 1st sheet-like base material 10 and the 2nd sheet-like base material 20, the conductive layer 14 and the conductive layer 24 will contact, and resistance value between both will become small. .

  As shown in FIG. 4A, the load is not necessarily limited to the load F1 in a direction substantially orthogonal to the sheet base material, and a shearing force F2 may be applied depending on the application. For example, when it is used to measure the pressure of a printer feed roller, a shearing force F2 is applied.

  By the way, silver particles having an average particle diameter of 8 μm and a maximum particle diameter of 12 μm are conventionally used for the electrodes of this type of tactile sensor, and pressure-sensitive conductive ink is placed on the electrodes made of the silver particles. The surface roughness of the conductive layer formed by coating was about Ra = 1.2 μm. A problem occurring in such a conventional tactile sensor will be described with reference to FIG.

  In the conventional unused tactile sensor, as shown in FIG. 4A, both the first conductive layer 140 and the second conductive layer 240 can be confirmed to have irregularities on the surface. This unevenness is caused by the pressure-sensitive conductive ink (first conductive layer 140 and second conductive layer 240) applied on the row electrode 120 and the column electrode 220 being in a liquid state, and thus the row electrode 120 and the column. It appears on the surface of the conductive layer under the influence of the unevenness of the electrode surface caused by the particle size of the silver particles used in the electrode 220. Even if a load is applied to such a conventional unused tactile sensor, the first conductive layer 140 of the first sheet-like substrate 100 and the second conductive layer 240 of the second sheet-like substrate 200 are used. The contact area between the two is relatively small because the protrusions on the surfaces contact each other.

  Further, if there are irregularities on the surfaces of the first conductive layer 140 and the second conductive layer 240, the first conductive layer 140 and the second conductive layer 140 and the second conductive layer 140 and the second conductive layer 140 and the second conductive layer 240 each time the load is applied. The position of contact with the conductive layer 240 slightly changes, and as a result, the measurement result may change each time the pressure is measured.

  Furthermore, when pressure is repeatedly applied to a conventional unused tactile sensor (when the tactile sensor is used more than a certain frequency), the irregularities on the surface of the conductive layer are crushed as shown in FIG. As a result, the contact area between the first conductive layer 140 of the first sheet-like substrate 100 and the second conductive layer 240 of the second sheet-like substrate 200 increases from the initial state, and both electrodes There was also a possibility that the resistance value between them would be small.

  In this regard, according to the tactile sensor 1 of the present embodiment, the surface of the first conductive layer 14 covered with the row electrodes 12 of the first sheet-like substrate 10, and the first The surface of the second conductive layer 24 covered with the column electrode 22 of the second sheet-like substrate 20 is smoothed. Therefore, as long as the pressure applied to the tactile sensor 1 is the same, the first conductive layer 14 of the first sheet-like substrate 10 and the second conductive layer 24 of the second sheet-like substrate 20 There is little possibility that the contact position will change. In addition, even when pressure is repeatedly applied (even if the tactile sensor 1 is used more than a certain frequency), the first conductive layer 14 of the first sheet-like base material 10 and the second sheet-like base material 20 There is little possibility that the contact area with the second conductive layer 24 will change. As a result, it is possible to reduce the fact that the measurement result changes each time the pressure is measured, and it is possible to obtain a stable measurement result even if the use frequency increases.

  The smoothing of the surface of the first conductive layer 14 and the surface of the second conductive layer 24 is used for the surface roughness of the row electrode 12 and the column electrode 22, that is, the row electrode 12 and the column electrode 22, respectively. For example, it can be realized by reducing the average particle size or the maximum particle size of the metal material.

  Next, examples of the tactile sensor according to the present invention will be described. First, a conventional tactile sensor will be described as a comparative example.

(Comparative Example 1)
The following were used about the electrode 120 and the electrode 220 in the conventional tactile sensor. Specifically, silver particles (for example, 5028 manufactured by DuPont) were used for the electrodes. Specifically, the silver particles have a structure of silver flakes: D50 = 8 μm (8 μm or less, 50% or more). The manufacturing method for the general configuration (sheet member, film base material, conductive layer) of the tactile sensor is omitted.

  In addition, the above-mentioned silver electrode, silver wiring, and silver terminal were formed by printing. The conductive layer 140 and the conductive layer corresponding to the conductive layer 240 are: bcetyl acetate: phenoxy resin (trade name PKHH manufactured by InChem): carbon black (trade name Vulcan XC-72R manufactured by CABOT): defoamer Kasei Co., Ltd. product name Disparon 1970) = 68.9: 25.5: 3.6: 2.0 The conductive ink obtained by blending was applied and dried. Here, the ratio of the phenoxy resin and carbon black in the conductive layer after drying is 14.2 parts by weight with respect to 100 parts by weight.

  Here, the output reproducibility of the conventional tactile sensor described in Comparative Example 1 will be described with reference to FIG. FIG. 5 shows the rate of change of the resistance value according to the number of times the tactile sensor is pressed. The horizontal axis represents the number of pressurizations, and the vertical axis represents the rate of change in resistance value. There are four types of measured data, and these indicate the resistance value at the left end, the center, and the right end of the sheet-like tactile sensor and the average value of the whole. The left end is indicated by a triangle, the center is indicated by a rectangle, the right end is indicated by a rhombus, and the overall average is indicated by a circle.

  As shown in FIG. 5, when the number of times of pressurization is less than 5, the rate of change increases rapidly each time the number of pressurizations is repeated. Specifically, the overall average change rate increases from 0% to about 5% or more during the number of pressurizations up to five. This indicates that the unevenness of the surface of the conductive layer of the tactile sensor is crushed and the contact area of the surface of the conductive layer is increased according to the number of times the tactile sensor is pressed, and the resistance value decreases accordingly.

  The rate of change of the resistance value is increased to about 20 times the pressure applied to the tactile sensor, and is steady after 20 times. This is because, after a certain number of times of pressurization (according to FIG. 5, the number of pressurizations is about 20), the unevenness of the surface of the conductive layer of the tactile sensor is flattened to some extent, and the contact area of the surface of the conductive layer is made constant to some extent. It is thought to be due to this.

  Thus, in order to obtain a certain resistance value using a tactile sensor with unevenness on the surface of the conductive layer, it is necessary to apply a certain amount of “break-in” pressure to crush the unevenness on the surface of the conductive layer. I understand. This not only reduces the reliability of the accuracy of resistance measurement, but also increases the number of pressurization times and costs associated with the replacement of the tactile sensor. .

  Therefore, the tactile sensor according to the present invention smoothes the unevenness of the surface of the conductive layer coated thereon by smoothing the electrode surface, and there is a significant difference in the rate of change in resistance value from the stage where the number of pressurizations is small. It is characterized by not appearing. Specifically, it is as in Example 1.

Example 1
The following were used about the electrode 12 and the electrode 22 in the tactile sensor of this invention. Specifically, fine silver (for example, CAT1648B-FS5 manufactured by Daiken Chemical Industry) was used for the electrode. Specifically, the fine silver includes silver flakes: D90 = 7 μm (7 μm or less 90% or more), D50 = 2.0 μm, silver spheres: D90 = 5 μm, D50 = 2.5 μm (5 μm or less 90% or more, 2 0.5 μm or less and 50% or more). The manufacturing method for the general configuration (sheet member, film base material, conductive layer) of the tactile sensor is omitted.

  In addition, the above-mentioned silver electrode, silver wiring, and silver terminal were formed by printing. The conductive layers corresponding to the first conductive layer 14 and the second conductive layer 24 were of the same composition as the conductive layer used in the above-described conventional tactile sensor.

  As described above, in the tactile sensor of the present invention, the size of the silver particles used for the electrodes was changed from the conventional average particle size of 8 μm to 2 μm or less. When silver particles having an average particle diameter of 2 μm are employed, the surface roughness (Ra) of the first conductive layer 14 and the second conductive layer 24 is approximately 0.6 μm, and silver particles having an average particle diameter of 8 μm are employed. As compared with the case (surface roughness Ra = 1.2 μm), the surface roughness is improved by about 50%. The surface roughness of the first conductive layer 14 and the second conductive layer 24 is preferably at least Ra = 1.0 μm or less.

  The output reproducibility of the tactile sensor of the present invention will be described with reference to FIG. FIG. 6 shows the change rate of the resistance value according to the number of pressurizations to the tactile sensor of the present invention. The horizontal axis represents the number of pressurizations, and the vertical axis represents the rate of change in resistance value. There are four types of measured data, and these indicate the resistance values at the left end, the center, and the right end of the sheet-like tactile sensor, and the average value of the whole, as in the comparative example of FIG. The left end is indicated by a triangle, the center is indicated by a rectangle, the right end is indicated by a rhombus, and the overall average is indicated by a circle.

  As shown in FIG. 6, since the rate of change in resistance value (overall average) when the number of pressurizations is less than 5 is about 3%, it is compared with the case of the conventional tactile sensor as shown in FIG. It can be seen that the rate of change decreases when the rate of change in resistance value when the number of times is less than 5 is about 5% or more.

  That is, by reducing the surface roughness of the electrodes 12 and 22 and smoothing, the surface roughness of the conductive layers 14 and 24 covered with the electrodes 12 and 22 can be reduced (ie, smoothed). Even in the initial stage where the number of pressures was small, the contact area of the surface of the conductive layer of the tactile sensor could be increased. As a result, the change rate of the resistance value of the tactile sensor can be reduced from the initial state where the number of pressurizations is small (for example, less than 5 times). In addition, even if the number of times of pressing is repeated (for example, 20 times or more), the irregularities on the surface of the conductive layer like the conventional tactile sensor are crushed according to the number of times of pressing, and the contact area changes successively. As a result, the rate of change in the resistance value of the tactile sensor can be reduced (about 3%). In other words, it can be said that the measurement error of the tactile sensor can be reduced.

  As described above, the tactile sensor described in the present embodiment opposes the sheet-like base materials 10 and 20 on which the conductive layers 14 and 24 are formed by applying the conductive ink to the electrodes 12 and 22 containing silver particles. And a tactile sensor of a type that causes a change in resistance when pressure is applied to the sheet-like base materials 10 and 20, and a plurality of electrodes 12 having a predetermined interval a along the X direction. A first sheet-like substrate 10 formed in a longitudinal shape, and a second sheet in which a plurality of electrodes 22 are formed in a longitudinal shape having a predetermined interval a along a Y direction substantially orthogonal to the X direction. And a substrate 20. Then, by changing the size of the silver particles used for the electrodes 12 and 22 from the conventional average particle diameter of 8 μm to 7 μm or less, the surface of the conductive layer covering the electrode 12 of the first sheet-like substrate and Any of the surfaces of the conductive layer covering the electrode 22 of the second sheet-like base material is smoothed. As a result, as long as the applied pressure is the same, the change in the contact area between the conductive layer on the first sheet-like substrate side and the conductive layer on the second sheet-like substrate side is reduced each time the pressure is applied. In addition, it is possible to reduce changes in the surface roughness of these conductive layers according to the frequency of use. Therefore, it is possible to reduce the occurrence of variations in the measurement results each time pressure is applied or the measurement results change over time according to the frequency of use, and to provide a pressure-sensitive sensor that can measure accurate pressure stably. be able to.

  In addition, this invention is not limited to the said embodiment and Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention. For example, in the above-described embodiments and examples, the row electrodes 12 and the column electrodes 22 are arranged so as to be substantially orthogonal to each other. However, the arrangement is not limited to this, and may be arranged in an intersecting manner.

  Moreover, in the said embodiment and Example, although the conductive layer is formed so that the whole surface of an electrode may be covered, it is not necessary to cover the whole surface of an electrode, and the conductive layer was formed so that it might laminate | stack on an electrode. It may be a thing.

DESCRIPTION OF SYMBOLS 1 Tactile sensor 10,100 First sheet-like base material 11,21 Film base material 12,120 Row electrode 13 Wiring 14,140 First conductive layer 16 Terminal 20,200 Second sheet-like base material 22,220 rows Electrodes 24, 240 Second conductive layer 30 Connector

Claims (3)

A pressure-sensitive sensor of a type in which a sheet base material on which a conductive layer is formed so as to cover an electrode having electrical conductivity is opposed and a change in resistance is caused when pressure is applied to the sheet-like base material. ,
A first sheet-like base material in which a plurality of the electrodes are formed in a longitudinal shape with a predetermined interval along a first direction;
A second sheet-like base material in which a plurality of the electrodes are formed in a longitudinal shape with a predetermined interval along a second direction intersecting the first direction,
Both the surface of the conductive layer covering the electrode of the first sheet-like base material and the surface of the conductive layer covering the electrode of the second sheet-like base material are smoothed. Pressure sensor. The surface roughness of the conductive layer covering the electrode of the first sheet-like substrate and the surface roughness of the conductive layer covering the electrode of the second sheet-like substrate are both Ra = 1.0 μm or less. The pressure-sensitive sensor according to claim 1. The electrode includes silver particles,
2. The average particle diameters of silver particles contained in the electrode of the first sheet-like substrate and silver particles contained in the electrode of the second sheet-like substrate are both in the range of 20 nm to 7 μm. Or the pressure-sensitive sensor of 2.