JP7537836B2 - Vital Sensor - Google Patents

Description

The present invention relates to a vital sensor.

Pulse wave sensors are known that detect pulse waves generated when the heart pumps blood. One example is a pulse wave sensor that is provided with a pressure-receiving plate that is a strain-generating body supported so that it can flex under the action of an external force, and a piezoelectric conversion means that converts the flexure of the pressure-receiving plate into an electrical signal. In this pulse wave sensor, the flexible area of the pressure-receiving plate is formed in a dome shape that is a convex curved surface facing outward, and a pressure detection element is provided on the inner surface of the apex of the pressure-receiving plate as the piezoelectric conversion means (see, for example, Patent Document 1).

JP 2002-78689 A

However, there is a demand for a vital sensor that can measure not only pulse waves but also the direction of blood vessel expansion and contraction.

The present invention has been made in consideration of the above points, and aims to provide a vital sensor that can detect the expansion and contraction directions of blood vessels in addition to pulse waves.

This vital sensor is a vital sensor that monitors blood flow, and has a strain gauge arranged on the strain gauge, which has three or more resistors, and when the direction in which blood vessels extend at the measured site is defined as a first direction and the direction perpendicular to the first direction is defined as a second direction, the strain gauge is attached to the measured site so that at least three resistors are positioned differently in the first direction and differently in the second direction.

The disclosed technology can provide a vital sensor that can detect the direction of blood vessel expansion and contraction in addition to pulse waves.

1 is a plan view illustrating a vital sensor according to a first embodiment; FIG. 1 is a diagram (part 1) illustrating a schematic diagram of a state in which the vital sensor according to the first embodiment monitors the blood flow of a subject. FIG. 2 is a second diagram illustrating the manner in which the vital sensor according to the first embodiment monitors the blood flow of a subject. FIG. 2 is a plan view of the vicinity of one resistor of the strain gauge according to the first embodiment. 2 is a cross-sectional view of the vicinity of one resistor of the strain gauge according to the first embodiment. FIG. 10 is a plan view illustrating a vital sensor according to a first modified example of the first embodiment; FIG. FIG. 11 is a plan view of the vicinity of one resistor of a strain gauge according to a second modified example of the first embodiment. 11 is a cross-sectional view of the vicinity of one resistor of a strain gauge according to a second modified example of the first embodiment. FIG. FIG. 11 is a plan view (part 1) of the vicinity of one resistor of a strain gauge according to a third modified example of the first embodiment. FIG. 13 is a second plan view of the vicinity of one resistor of the strain gauge according to the third modified example of the first embodiment; FIG. 13 is a plan view (part 3) of the vicinity of one resistor of the strain gauge according to the third modification of the first embodiment; FIG. 4 is a plan view (part 4) of the vicinity of one resistor of the strain gauge according to the third modified example of the first embodiment;

Below, a description of the embodiment of the invention will be given with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicated explanations may be omitted.

First Embodiment
[Vital Signs Sensor]
Fig. 1 is a plan view illustrating a vital sensor according to a first embodiment. Referring to Fig. 1, the vital sensor 1 has a strain body 10 that is attached to a measurement site of a subject, and a strain gauge 100 that is disposed on the strain body 10.

The flexure body 10 is, for example, rectangular in plan view. The size of the flexure body 10 can be, for example, about 10 mm in length × 15 mm in width × 0.1 mm in thickness. The material of the flexure body 10 can be, for example, SUS (stainless steel), copper, aluminum, etc.

The strain gauge 100 has a first resistor 130 ₁ , a second resistor 130 ₂ , and a third resistor 130 ₃ that serve as sensing parts on a substrate 110. The first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ have, for example, the same shape in a plan view. Here, the same shape also includes shapes that are arranged in rotational symmetry.

The first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ are arranged on the substrate 110 with their respective longitudinal directions (grid direction, which will be described later) facing the same direction. In Fig. 1 , the grid direction is the X direction, and the grid width direction perpendicular to the grid direction is the Y direction. The direction perpendicular to the X direction and the Y direction (thickness direction of the strain body 10) is the Z direction.

The first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ are located at different positions in the grid direction and at different positions in the direction perpendicular to the grid direction. The position of each resistor refers to the position of the center of gravity of the region of the substrate 110 where the resistor is formed (hereinafter, referred to as the resistor forming region) in a plan view. In other words, the X and Y coordinates of the centers of gravity of the resistor forming regions of the first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ are all different.

The first resistor ₁₃₀₁ , the second resistor ₁₃₀₂ , and the third resistor ₁₃₀₃ are arranged, for example, at regular intervals in the grid direction. That is, for example, the distance in the X direction between the first resistor ₁₃₀₁ and the second resistor ₁₃₀₂ is equal to the distance in the X direction between the first resistor ₁₃₀₁ and the third resistor ₁₃₀₃ .

The first resistor ₁₃₀₁ , the second resistor ₁₃₀₂ , and the third resistor ₁₃₀₃ are arranged at regular intervals in a direction perpendicular to the grid direction, for example. In other words, for example, the distance in the Y direction between the first resistor ₁₃₀₁ and the second resistor ₁₃₀₂ is equal to the distance in the Y direction between the first resistor ₁₃₀₁ and the third resistor ₁₃₀₃ .

The spacing (distance) between each resistor refers to the spacing (distance) between the centers of gravity of the resistor formation areas of each resistor when viewed in a plane. Furthermore, equal distances includes cases where the shorter distance is 90% or more of the longer distance.

The second resistor ₁₃₀₂ and the third resistor ₁₃₀₃ are disposed facing each other in a direction oblique to the grid direction, sandwiching the first resistor _1301. Here, "the second resistor ₁₃₀₂ and the third resistor ₁₃₀₃ are disposed facing each other, sandwiching the first resistor ₁₃₀₁ " means that a straight line connecting the center of gravity of the resistor formation region of the second resistor ₁₃₀₂ and the center of gravity of the resistor formation region of the third resistor ₁₃₀₃ passes through any part of the first resistor ₁₃₀₁ in a plan view.

Figures 2 and 3 are schematic diagrams showing how the vital sensor according to the first embodiment monitors the blood flow of a subject. Figure 2 shows a schematic diagram of a blood vessel 800 contracting, and Figure 3 shows a schematic diagram of a blood vessel 800 expanding. Arrow B in Figures 2 and 3 indicates the direction in which the blood vessel 800 extends at the measurement site of the subject, and is also the direction in which blood flows.

The vital sensor 1 is a sensor that monitors blood flow, and is attached to the subject's wrist, for example, so that the underside of the strain body 10 contacts the subject's radial artery. In other words, the part of the subject to be measured is, for example, the subject's wrist.

The flexure body 10 is attached to the measurement site of the subject so that the first resistor _130-1 , the second resistor _130-2 , and the third resistor _130-3 are positioned differently in the direction of arrow B in which the blood vessel extends, and are positioned differently in the direction perpendicular to arrow B. The flexure body 10 is attached to the measurement site of the subject so that, for example, the X direction, which is the grid direction, coincides with the direction of arrow B. In other words, the flexure body 10 is attached to the measurement site of the subject so that, for example, the first resistor _130-1 , the second resistor _130-2 , and the third resistor _130-3 are arranged with the grid direction facing the direction of arrow B.

2 and 3, the vital sensor 1 is enlarged for convenience, but the vital sensor 1 is sized so that the first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ are all located on the blood vessel 800. In the strain gauge 100, the size of each resistor forming region may be, for example, about 0.3 mm square.

When the strain body 10 is attached to the measurement site of the subject, for example, the first resistor _130-1 is placed near the center line of the blood vessel 800 with the grid direction facing the direction of arrow B. The second resistor _130-2 is placed on one side of the first resistor _130-1 in the direction of arrow B (the X-side in Figs. 2 and 3) and on one side in the direction perpendicular to the arrow B (the Y-side in Figs. 2 and 3).

The third resistor ₁₃₀₃ is disposed on the other side of the first resistor ₁₃₀₁ in the direction of arrow B (the X+ side in FIGS. 2 and 3) and on the other side in the direction perpendicular to the arrow B (the Y+ side in FIGS. 2 and 3). In other words, the second resistor ₁₃₀₂ and the third resistor ₁₃₀₃ are disposed opposite each other in a direction oblique to the direction of arrow B, sandwiching the first resistor ₁₃₀₁ therebetween.

The first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ are arranged, for example, at regular intervals in the grid direction. Also, the first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ are arranged, for example, at regular intervals in a direction perpendicular to the grid direction.

The blood vessel 800 repeatedly contracts and expands in response to the pulse wave. The vital sensor 1 is attached to the measurement site of the subject so that the first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ are positioned differently in the direction of arrow B and in a direction perpendicular to arrow B. Therefore, the vital sensor 1 can detect the pulse wave based on the changes in the output of the first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ , and can detect the fluctuation in the blood flow rate in the blood vessel 800 and the expansion and contraction directions of the blood vessel 800.

In addition, because the vital sensor 1 monitors blood flow using a strain gauge, it can be an inexpensive wearable vital sensor compared to optical sensors that utilize changes in the absorption characteristics of oxygenated hemoglobin in blood vessels, or expensive and bulky optical fiber FBG sensors (Fiber Bragg Grating sensors). In particular, when a Cr mixed-phase film, as described below, is used for each resistor, it is possible to realize an inexpensive, small, and highly accurate wearable vital sensor.

The strain gauge 100 will be described in detail below. Note that the first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ may be collectively referred to as resistors 130 unless there is a particular need to distinguish between them.

Figure 4 is a plan view of the vicinity of one resistor of the strain gauge according to the first embodiment. Figure 5 is a cross-sectional view of the vicinity of one resistor of the strain gauge according to the first embodiment, showing a cross section along line A-A in Figure 4. With reference to Figures 1, 4, and 5, the strain gauge 100 has three sets including resistors 130, wiring 140, electrodes 150, and cover layers 160, which are arranged on one substrate 110. However, unlike Figure 1, three strain gauges each having one set including resistors 130, wiring 140, electrodes 150, and cover layers 160 on one substrate 110 may be arranged on the strain generating body 10. Note that in Figure 4, for convenience, only the outer edge of the cover layer 160 is shown by a dashed line. The cover layer 160 may be provided as necessary.

4 and 5, for convenience, the side of the strain gauge 100 on which the resistor 130 of the substrate 110 is provided is referred to as the upper side or one side, and the side on which the resistor 130 is not provided is referred to as the lower side or the other side. Also, the surface on which the resistor 130 of each part is provided is referred to as the one side or upper surface, and the surface on which the resistor 130 is not provided is referred to as the other side or lower surface. However, the strain gauge 100 can be used upside down or placed at any angle. Also, a planar view refers to viewing an object from the normal direction of the upper surface 110a of the substrate 110, and a planar shape refers to the shape of the object viewed from the normal direction of the upper surface 110a of the substrate 110.

The substrate 110 is a flexible member that serves as a base layer for forming the resistor 130 and the like. There are no particular limitations on the thickness of the substrate 110, and it can be selected appropriately depending on the purpose, but it can be, for example, about 5 μm to 500 μm. In particular, a thickness of 5 μm to 200 μm is preferable in terms of the transmission of strain from the surface of the strain generator that is joined to the lower surface of the substrate 110 via an adhesive layer or the like, and dimensional stability against the environment, and a thickness of 10 μm or more is even more preferable in terms of insulation.

The substrate 110 can be formed from an insulating resin film such as PI (polyimide) resin, epoxy resin, PEEK (polyether ether ketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, LCP (liquid crystal polymer) resin, polyolefin resin, etc. Note that a film refers to a flexible material with a thickness of about 500 μm or less.

Here, "formed from an insulating resin film" does not prevent the base material 110 from containing fillers, impurities, etc. in the insulating resin film. The base material 110 may be formed from an insulating resin film containing fillers such as silica or alumina.

_{Examples of materials other than resin for the base material 110 include crystalline materials such as SiO2, ZrO2 (including YSZ), Si, Si2N3, Al2O3 ( including sapphire ) ,} ZnO, perovskite ceramics ( _CaTiO3 , _BaTiO3 ), and amorphous glass. Metals such as aluminum, aluminum alloys (duralumin), and titanium may also be used as the material for the base material 110. In this case, for example, an insulating film is formed on the metal base material 110.

The resistor 130 is a thin film formed in a predetermined pattern on the substrate 110, and is a sensing part that generates a resistance change when strained. The resistor 130 may be formed directly on the upper surface 110a of the substrate 110, or may be formed on the upper surface 110a of the substrate 110 via another layer. For convenience, the resistor 130 is shown in FIG. 4 with a dark matte pattern.

The resistor 130 has multiple elongated portions arranged at regular intervals with their longitudinal direction in the same direction (the direction of line A-A in Figure 4 (X direction)), and the ends of adjacent elongated portions are alternately connected, so that the resistor 130 is folded back in a zigzag pattern as a whole. The longitudinal direction of the multiple elongated portions is the grid direction, and the direction perpendicular to the grid direction is the grid width direction (the direction perpendicular to line A-A in Figure 4 (Y direction)).

One end in the longitudinal direction of the two elongated portions located at the outermost sides in the grid width direction is bent in the grid width direction to form respective ends _130e1 and _130e2 in the grid width direction of the resistor 130. The respective ends _130e1 and _130e2 in the grid width direction of the resistor 130 are electrically connected to the electrodes 150 via the wiring 140. In other words, the wiring 140 electrically connects the respective ends _130e1 and _130e2 in the grid width direction of the resistor 130 to the respective electrodes 150.

The resistor 130 can be formed, for example, from a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 130 can be formed from a material containing at least one of Cr and Ni. An example of a material containing Cr is a Cr mixed phase film. An example of a material containing Ni is Cu-Ni (copper-nickel). An example of a material containing both Cr and Ni is Ni-Cr (nickel-chromium).

Here, the Cr mixed phase film is a film in which Cr, CrN, Cr ₂ N, etc. are mixed together. The Cr mixed phase film may contain inevitable impurities such as chromium oxide.

The thickness of the resistor 130 is not particularly limited and can be appropriately selected depending on the purpose, but can be, for example, about 0.05 μm to 2 μm. In particular, a thickness of 0.1 μm or more is preferable in that the crystallinity of the crystals constituting the resistor 130 (for example, the crystallinity of α-Cr) is improved. Furthermore, a thickness of 1 μm or less is even more preferable in that film cracks caused by internal stress of the film constituting the resistor 130 and warping from the substrate 110 can be reduced. The width of the resistor 130 can be optimized for the required specifications such as resistance value and lateral sensitivity, and can be, for example, about 10 μm to 100 μm, taking into consideration measures against disconnection.

For example, when the resistor 130 is a Cr mixed phase film, the stability of the gauge characteristics can be improved by making the main component α-Cr (alpha chromium), which is a stable crystal phase. In addition, by making the resistor 130 mainly composed of α-Cr, the gauge factor of the strain gauge 100 can be set to 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be set within the range of -1000 ppm/°C to +1000 ppm/°C. Here, the main component means that the target substance accounts for 50% by weight or more of the total substance constituting the resistor, but from the viewpoint of improving the gauge characteristics, it is preferable that the resistor 130 contains α-Cr at 80% by weight or more, and more preferably at 90% by weight or more. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

Furthermore, when the resistor 130 is a Cr mixed-phase film, the Cr mixed-phase film preferably contains 20% by weight or less of CrN and Cr ₂ N. By containing 20% by weight or less of CrN and Cr ₂ N in the Cr mixed-phase film, a decrease in the gauge factor can be suppressed.

In addition, the ratio of _Cr2N in CrN and _Cr2N is preferably 80% by weight or more and less than 90% by weight, and more preferably 90% by weight or more and less than 95% by weight. When the ratio of _Cr2N in CrN and _Cr2N is 90% by weight or more and less than 95% by weight, the decrease in TCR (negative TCR) becomes more significant due to the _Cr2N having semiconducting properties. Furthermore, by reducing the ceramicization, brittle fracture is reduced.

On the other hand, if a small amount of _N2 or atomic N is mixed into or present in the film, it will escape to the outside of the film due to the external environment (for example, a high temperature environment), causing a change in the film stress. By creating chemically stable CrN, it is possible to obtain a stable strain gauge without generating the unstable N mentioned above.

The wiring 140 is formed on the substrate 110 and is electrically connected to the resistor 130 and the electrode 150. The wiring 140 has a first metal layer 141 and a second metal layer 142 laminated on the upper surface of the first metal layer 141. The wiring 140 is not limited to being linear, and can be in any pattern. The wiring 140 can also be of any width and length. For convenience, in FIG. 4, the wiring 140 and the electrode 150 are shown with a matte pattern that is thinner than the resistor 130.

The electrodes 150 are formed on the substrate 110 and are electrically connected to the resistor 130 via the wiring 140, and are formed, for example, in a substantially rectangular shape wider than the wiring 140. The electrodes 150 are a pair of electrodes for outputting the change in resistance value of the resistor 130 caused by strain to the outside, and for example, lead wires for external connection are joined to the electrodes 150.

The electrode 150 has a pair of first metal layers 151 and a second metal layer 152 laminated on the upper surface of each of the first metal layers 151. The first metal layers 151 are electrically connected to the ends 130e _-1 and 130e- ₂ of the resistor 130 via the first metal layers 141 of the wiring 140. The first metal layers 151 are formed in a substantially rectangular shape in a plan view. The first metal layers 151 may be formed to have the same width as the wiring 140.

Note that although the resistor 130, the first metal layer 141, and the first metal layer 151 are given different reference numbers for convenience, they can be formed integrally from the same material in the same process. Therefore, the resistor 130, the first metal layer 141, and the first metal layer 151 have approximately the same thickness. Also, although the second metal layer 142 and the second metal layer 152 are given different reference numbers for convenience, they can be formed integrally from the same material in the same process. Therefore, the second metal layer 142 and the second metal layer 152 have approximately the same thickness.

The second metal layers 142 and 152 are formed from a material with a lower resistance than the resistor 130 (the first metal layers 141 and 151). There are no particular limitations on the material of the second metal layers 142 and 152, as long as it is a material with a lower resistance than the resistor 130, and it can be appropriately selected according to the purpose. For example, when the resistor 130 is a Cr mixed phase film, the material of the second metal layers 142 and 152 can be Cu, Ni, Al, Ag, Au, Pt, etc., or an alloy of any of these metals, a compound of any of these metals, or a laminated film in which any of these metals, alloys, and compounds are appropriately laminated. There are no particular limitations on the thickness of the second metal layers 142 and 152, and it can be appropriately selected according to the purpose, but it can be, for example, about 3 μm to 5 μm.

The second metal layers 142 and 152 may be formed on a portion of the upper surface of the first metal layers 141 and 151, or may be formed on the entire upper surface of the first metal layers 141 and 151. One or more other metal layers may be laminated on the upper surface of the second metal layer 152. For example, the second metal layer 152 may be a copper layer, and a gold layer may be laminated on the upper surface of the copper layer. Alternatively, the second metal layer 152 may be a copper layer, and a palladium layer and a gold layer may be sequentially laminated on the upper surface of the copper layer. By making the top layer of the electrode 150 a gold layer, the solder wettability of the electrode 150 can be improved.

In this way, the wiring 140 has a structure in which the second metal layer 142 is laminated on the first metal layer 141 made of the same material as the resistor 130. Therefore, the resistance of the wiring 140 is lower than that of the resistor 130, and the wiring 140 can be prevented from functioning as a resistor. As a result, the accuracy of strain detection by the resistor 130 can be improved.

In other words, by providing wiring 140 with a lower resistance than resistor 130, the actual sensing area of strain gauge 100 can be limited to the local area where resistor 130 is formed. This improves the accuracy of strain detection by resistor 130.

In particular, in a highly sensitive strain gauge with a gauge factor of 10 or more that uses a Cr mixed phase film as the resistor 130, making the wiring 140 less resistant than the resistor 130 and limiting the actual sensing area to the local area where the resistor 130 is formed has a significant effect on improving strain detection accuracy. In addition, making the wiring 140 less resistant than the resistor 130 also has the effect of reducing lateral sensitivity.

The wiring pattern of the wiring 140 and the position of each electrode 150 can be set as appropriate. For example, the electrodes 150 connected to each resistor may be arranged in a row at a predetermined position.

The cover layer 160 is formed on the substrate 110, covers the resistor 130 and the wiring 140, and exposes the electrode 150. A part of the wiring 140 may be exposed from the cover layer 160. By providing the cover layer 160 that covers the resistor 130 and the wiring 140, mechanical damage to the resistor 130 and the wiring 140 can be prevented. Furthermore, by providing the cover layer 160, the resistor 130 and the wiring 140 can be protected from moisture and the like. The cover layer 160 may be provided so as to cover the entire portion except for the electrode 150.

The cover layer 160 can be formed from an insulating resin such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, or composite resin (e.g., silicone resin, polyolefin resin). The cover layer 160 may contain a filler or pigment. There is no particular limit to the thickness of the cover layer 160 and it can be appropriately selected depending on the purpose, but it can be, for example, about 2 μm to 30 μm.

To manufacture the strain gauge 100, first, a substrate 110 is prepared, and a metal layer (for convenience, referred to as metal layer A) is formed on the upper surface 110a of the substrate 110. Metal layer A is a layer that is ultimately patterned to become resistor 130, first metal layer 141, and first metal layer 151. Therefore, the material and thickness of metal layer A are the same as those of resistor 130, first metal layer 141, and first metal layer 151 described above.

Metal layer A can be formed, for example, by magnetron sputtering using a raw material capable of forming metal layer A as a target. Instead of magnetron sputtering, metal layer A may also be formed using reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or the like.

From the viewpoint of stabilizing the gauge characteristics, it is preferable to vacuum-deposit a functional layer of a predetermined thickness as a base layer on the upper surface 110a of the substrate 110, for example, by conventional sputtering, before depositing the metal layer A.

In this application, the functional layer refers to a layer that has the function of promoting the crystal growth of at least the upper layer, metal layer A (resistor 130). The functional layer preferably also has the function of preventing oxidation of metal layer A due to oxygen and moisture contained in the substrate 110, and the function of improving adhesion between the substrate 110 and metal layer A. The functional layer may also have other functions.

The insulating resin film constituting the substrate 110 contains oxygen and moisture, and since Cr forms a self-oxidized film, particularly when the metal layer A contains Cr, it is effective for the functional layer to have the function of preventing oxidation of the metal layer A.

The material of the functional layer is not particularly limited as long as it has the function of promoting the crystal growth of at least the upper layer, the metal layer A (resistor 130), and can be appropriately selected according to the purpose. For example, Cr (chromium), Ti (titanium), V (vanadium), Nb (niobium), Ta (tantalum), Ni (nickel), Y (yttrium), Zr (zirconium), Hf (hafnium), Si (silicon), C (carbon), Zn (zinc), Cu (copper), Bi (bismuth), etc. Examples of the metal include one or more metals selected from the group consisting of ruthenium (Ru), iron (Fe), molybdenum (Molybdenum), tungsten (W), ruthenium (Ru), rhodium (Rh), rhenium (Rhenium), osmium (Os), iridium (Ir), platinum (Pt), palladium (Pd), silver (Ag), gold (Au), cobalt (Co), manganese (Mn), and aluminum (Al), an alloy of any of the metals in this group, or a compound of any of the metals in this group.

Examples of the alloy include FeCr, TiAl, FeNi, NiCr, CrCu, etc. Examples of the compound include TiN, _TaN , _Si3N4 , _TiO2 , _Ta2O5 , _{SiO2 ,} etc.

When the functional layer is made of a conductive material such as a metal or alloy, the thickness of the functional layer is preferably 1/20 or less of the thickness of the resistor. In this range, the crystal growth of α-Cr can be promoted, and a part of the current flowing through the resistor can be prevented from flowing through the functional layer, which would reduce the sensitivity of strain detection.

When the functional layer is made of a conductive material such as a metal or alloy, it is more preferable that the thickness of the functional layer is 1/50 or less of the thickness of the resistor. In this range, the crystal growth of α-Cr can be promoted, and it is further possible to prevent a portion of the current flowing through the resistor from flowing through the functional layer, which would otherwise reduce the sensitivity of strain detection.

When the functional layer is made of a conductive material such as a metal or alloy, it is even more preferable that the thickness of the functional layer is 1/100 or less of the thickness of the resistor. In this range, it is possible to further prevent a portion of the current flowing through the resistor from flowing through the functional layer, thereby reducing the strain detection sensitivity.

When the functional layer is made of an insulating material such as an oxide or nitride, the thickness of the functional layer is preferably 1 nm to 1 μm. This range promotes the crystal growth of α-Cr and allows the functional layer to be easily formed without cracking.

When the functional layer is made of an insulating material such as an oxide or nitride, it is more preferable that the thickness of the functional layer is 1 nm to 0.8 μm. This range promotes the crystal growth of α-Cr and makes it easier to form the functional layer without cracking.

When the functional layer is made of an insulating material such as an oxide or nitride, it is even more preferable that the thickness of the functional layer is between 1 nm and 0.5 μm. This range promotes the crystal growth of α-Cr and makes it easier to form the functional layer without cracking.

The planar shape of the functional layer is patterned to be approximately the same as the planar shape of the resistor shown in FIG. 4, for example. However, the planar shape of the functional layer is not limited to being approximately the same as the planar shape of the resistor. If the functional layer is formed from an insulating material, it does not have to be patterned to be the same as the planar shape of the resistor. In this case, the functional layer may be formed in a solid shape at least in the area where the resistor is formed. Alternatively, the functional layer may be formed in a solid shape over the entire top surface of the substrate 110.

In addition, when the functional layer is made of an insulating material, the functional layer is formed relatively thick, at a thickness of 50 nm to 1 μm, and formed in a solid shape, thereby increasing the thickness and surface area of the functional layer, and therefore heat generated by the resistor can be dissipated to the substrate 110. As a result, the deterioration of measurement accuracy due to self-heating of the resistor can be suppressed in the strain gauge 100.

The functional layer can be formed in a vacuum by conventional sputtering, for example, using a raw material capable of forming the functional layer as a target and introducing Ar (argon) gas into a chamber. By using conventional sputtering, the functional layer is formed while etching the upper surface 110a of the substrate 110 with Ar, so that the amount of the functional layer formed can be minimized and the effect of improving adhesion can be obtained.

However, this is just one example of a method for forming the functional layer, and the functional layer may be formed by other methods. For example, a method may be used in which the upper surface 110a of the substrate 110 is activated by plasma treatment using Ar or the like before forming the functional layer, thereby improving adhesion, and then the functional layer is vacuum-formed by magnetron sputtering.

There are no particular restrictions on the combination of the material of the functional layer and the material of the metal layer A, and they can be selected appropriately depending on the purpose. For example, it is possible to use Ti as the functional layer and form a Cr mixed phase film with α-Cr (alpha chromium) as the main component as the metal layer A.

In this case, for example, the metal layer A can be formed by magnetron sputtering using a raw material capable of forming a Cr mixed phase film as a target and introducing Ar gas into a chamber. Alternatively, the metal layer A can be formed by reactive sputtering using pure Cr as a target and introducing an appropriate amount of nitrogen gas together with Ar gas into a chamber. In this case, the ratio of CrN and Cr 2 N contained in the Cr mixed phase film and the ratio of Cr ₂ N in CrN and Cr ₂ N can be adjusted by changing the amount and pressure (nitrogen partial pressure) of the _nitrogen gas introduced or by adjusting the heating temperature by providing a heating process.

In these methods, the growth surface of the Cr mixed-phase film is determined by the functional layer made of Ti, and a Cr mixed-phase film can be formed that is mainly composed of α-Cr, which has a stable crystal structure. In addition, the Ti that constitutes the functional layer diffuses into the Cr mixed-phase film, improving the gauge characteristics. For example, the gauge factor of the strain gauge 100 can be set to 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be set within the range of -1000 ppm/°C to +1000 ppm/°C. Note that when the functional layer is formed from Ti, the Cr mixed-phase film may contain Ti and TiN (titanium nitride).

When metal layer A is a Cr mixed phase film, the functional layer made of Ti has all of the following functions: promoting crystal growth of metal layer A, preventing oxidation of metal layer A due to oxygen and moisture contained in the base material 110, and improving adhesion between the base material 110 and metal layer A. The same applies when Ta, Si, Al, or Fe is used as the functional layer instead of Ti.

In this way, by providing a functional layer below the metal layer A, it is possible to promote crystal growth in the metal layer A, and to produce a metal layer A consisting of a stable crystalline phase. As a result, the stability of the gauge characteristics of the strain gauge 100 can be improved. In addition, the material constituting the functional layer diffuses into the metal layer A, thereby improving the gauge characteristics of the strain gauge 100.

Next, the second metal layer 142 and the second metal layer 152 are formed on the upper surface of the metal layer A. The second metal layer 142 and the second metal layer 152 can be formed, for example, by a photolithography method.

Specifically, first, a seed layer is formed by, for example, sputtering or electroless plating so as to cover the upper surface of metal layer A. Next, a photosensitive resist is formed over the entire upper surface of the seed layer, and is exposed and developed to form openings that expose the areas in which second metal layer 142 and second metal layer 152 are to be formed. At this time, the pattern of second metal layer 142 can be formed into any shape by adjusting the shape of the openings in the resist. For example, a dry film resist can be used as the resist.

Next, for example, the second metal layer 142 and the second metal layer 152 are formed on the seed layer exposed in the opening by electrolytic plating using the seed layer as a power supply path. The electrolytic plating method is advantageous in that it has high tact and can form low-stress electrolytic plating layers as the second metal layer 142 and the second metal layer 152. By making the thick electrolytic plating layer low-stress, it is possible to prevent warping of the strain gauge 100. The second metal layer 142 and the second metal layer 152 may also be formed by electroless plating.

Then, the resist is removed. The resist can be removed, for example, by immersing it in a solution that can dissolve the resist material.

Next, a photosensitive resist is formed on the entire upper surface of the seed layer, and is exposed and developed to be patterned into a planar shape similar to that of the resistor 130, wiring 140, and electrode 150 in FIG. 4. For example, a dry film resist can be used as the resist. Then, the resist is used as an etching mask to remove the metal layer A and the seed layer exposed from the resist, forming the resistor 130, wiring 140, and electrode 150 in the planar shape of FIG. 4.

For example, unnecessary portions of the metal layer A and the seed layer can be removed by wet etching. If a functional layer is formed below the metal layer A, the functional layer is patterned by etching into the planar shape shown in FIG. 4, similar to the resistor 130, the wiring 140, and the electrode 150. At this point, a seed layer is formed on the resistor 130, the first metal layer 141, and the first metal layer 151.

Next, the second metal layer 142 and the second metal layer 152 are used as an etching mask to remove the unnecessary seed layer exposed from the second metal layer 142 and the second metal layer 152, thereby forming the second metal layer 142 and the second metal layer 152. Note that the seed layer directly below the second metal layer 142 and the second metal layer 152 remains. For example, the unnecessary seed layer can be removed by wet etching using an etching solution that etches the seed layer but does not etch the functional layer, resistor 130, wiring 140, and electrode 150.

Thereafter, as necessary, a cover layer 160 that covers the resistor 130 and wiring 140 and exposes the electrodes 150 is provided on the upper surface 110a of the substrate 110, thereby completing the strain gauge 100. The cover layer 160 can be produced, for example, by laminating a semi-cured thermosetting insulating resin film on the upper surface 110a of the substrate 110 so as to cover the resistor 130 and wiring 140 and expose the electrodes 150, and then heating and curing the film. The cover layer 160 may also be produced by applying a liquid or paste-like thermosetting insulating resin to the upper surface 110a of the substrate 110 so as to cover the resistor 130 and wiring 140 and expose the electrodes 150, and then heating and curing the resin.

First Modification of the First Embodiment
In the first modification of the first embodiment, an example of a vital sensor including a strain gauge in which the arrangement of resistors is different from that in the first embodiment is shown. Note that in the first modification of the first embodiment, the description of the same components as those in the already described embodiments may be omitted.

Fig. 6 is a plan view illustrating a vital sensor according to Modification 1 of the first embodiment. Referring to Fig. 6, the vital sensor 1A differs from the vital sensor 1 in that the strain gauge 100 is replaced with a strain gauge 100A. The strain gauge 100A differs from the strain gauge 100 in that a fourth resistor ₁₃₀₄ and a fifth resistor ₁₃₀₅ are added. The fourth resistor ₁₃₀₄ and the fifth resistor ₁₃₀₅ are arranged with the grid direction facing the X direction.

The fourth resistor ₁₃₀₄ is located at the same position in the grid direction as the second resistor ₁₃₀₂ , and at the same position in the direction perpendicular to the grid direction as the third resistor _1303. The fifth resistor ₁₃₀₅ is located at the same position in the grid direction as the third resistor ₁₃₀₃ , and at the same position in the direction perpendicular to the grid direction as the second resistor _1302. The fourth resistor ₁₃₀₄ and the fifth resistor ₁₃₀₅ are disposed opposite each other in a direction oblique to the grid direction, with the first resistor ₁₃₀₁ in between.

In this way, by adding the fourth resistor ₁₃₀₄ and the fifth resistor ₁₃₀₅ , outputs can be obtained from the fourth resistor ₁₃₀₄ and the fifth resistor ₁₃₀₅ , so that when the vital sensor 1A is attached to the measurement site of the subject, the detection accuracy of the pulse wave, fluctuations in the blood flow rate in the blood vessels, and the expansion and contraction directions of the blood vessels can be improved.

<Modification 2 of the First Embodiment>
In the second modification of the first embodiment, an example of a vital sensor including a strain gauge in which the structure of each resistor is different from that in the first embodiment is shown. Note that in the second modification of the first embodiment, the description of the same components as those in the already described embodiment may be omitted.

Figure 7 is a plan view of the vicinity of one resistor of a strain gauge according to the second modification of the first embodiment. Figure 8 is a cross-sectional view of the vicinity of one resistor of a strain gauge according to the second modification of the first embodiment, showing a cross-section along line B-B in Figure 7. With reference to Figures 7 and 8, the strain gauge 100B has a substrate 110, a resistor 230 (multiple resistance portions 231 and 232), and multiple electrodes 251 and 252.

The strain gauge 100B has three sets including a resistor 230 and electrodes 251 and 252, which are arranged on one substrate 110. In each set including a resistor 230 and electrodes 251 and 252, the resistor 230 is arranged at the same position as the first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ in Fig. 1. However, three strain gauges each having one set including a resistor 230 and electrodes 251 and 252 on one substrate 110 may be arranged on the strain generating body 10.

The resistor 230 is formed on the substrate 110 and is a sensing part whose resistance value changes continuously in response to strain. The resistor 230 may be formed directly on the upper surface 110a and the lower surface 110b of the substrate 110, or may be formed on the upper surface 110a and the lower surface 110b of the substrate 110 via another layer.

The resistor 230 includes a plurality of resistive sections 231 and 232 laminated via the base material 110, which is an insulating layer. For convenience, the resistive sections 231 and 232 are shown in FIG. 7 with a matte finish.

The multiple resistance sections 231 are thin films arranged in the Y direction at a predetermined interval on the upper surface 110a of the substrate 110 with their longitudinal direction facing the X direction. The multiple resistance sections 232 are thin films arranged in the X direction at a predetermined interval on the lower surface 110b of the substrate 110 with their longitudinal direction facing the Y direction. However, the multiple resistance sections 231 and the multiple resistance sections 232 do not need to be orthogonal in a plan view, as long as they intersect. The resistor 230 is formed, for example, from the same material as the resistor 130.

The width of the resistor 230 is not particularly limited and can be selected appropriately depending on the purpose, but can be, for example, about 0.1 μm to 1000 μm (1 mm). The pitch between adjacent resistors 230 is not particularly limited and can be selected appropriately depending on the purpose, but can be, for example, about 1 mm to 100 mm. Note that although six resistor portions 231 and ten resistor portions 232 are shown in Figures 7 and 8, in reality, about several hundred to several tens of thousands of resistor portions 231 and 232 are provided.

The electrodes 251 extend from both ends of each resistor portion 231 on the upper surface 110a of the base material 110, and are formed in a generally rectangular shape wider than the resistor portion 231 in a plan view. The electrodes 251 are a pair of electrodes for outputting the change in resistance value of the resistor portion 231 caused by the pressing force to the outside, and are connected to, for example, a flexible board or a lead wire for external connection. The upper surface of the electrode 251 may be covered with a metal that has better solderability than the electrode 251. Note that, although the resistor portion 231 and the electrode 251 are given different reference numerals for convenience, the two can be integrally formed from the same material in the same process.

The electrodes 252 extend from both ends of each resistor portion 232 on the lower surface 110b of the substrate 110, and are formed in a generally rectangular shape wider than the resistor portion 232 in a plan view. The electrodes 252 are a pair of electrodes for outputting the change in resistance value of the resistor portion 232 caused by the pressing force to the outside, and are connected to, for example, a flexible board or lead wire for external connection. The upper surface of the electrode 252 may be covered with a metal that has better solderability than the electrode 252. Note that, although the resistor portion 232 and the electrode 252 are given different reference numerals for convenience, the two can be integrally formed from the same material in the same process.

In addition, a through-hole that penetrates the base material 110 may be provided, and the electrodes 251 and 252 may be concentrated on the upper surface 110a side or the lower surface 110b side of the base material 110.

A cover layer (insulating resin layer) may be provided on the upper surface 110a of the substrate 110 so as to cover the resistor portion 231 and expose the electrode 251. Also, a cover layer (insulating resin layer) may be provided on the lower surface 110b of the substrate 110 so as to cover the resistor portion 232 and expose the electrode 252. By providing a cover layer, mechanical damage to the resistor portions 231 and 232 can be prevented. Also, by providing a cover layer, the resistor portions 231 and 232 can be protected from moisture and the like. The cover layer may be provided so as to cover the entire portion except for the electrodes 251 and 252.

In strain gauge 100B, when resistance portion 231 and/or resistance portion 232 are distorted by pressure due to blood flow, the resistance value between a pair of electrodes connected to the distorted resistance portion (resistance portion 231 and/or resistance portion 232) changes continuously according to the magnitude of the strain. Therefore, by monitoring the change in the resistance value detected from each electrode 251 and 252, it is possible to know the XY coordinates of the position where pressure due to blood flow is detected, the magnitude of the pressure, and the changes therein.

In addition, since blood vessels are thin and branch toward the ends, changing the flow of blood, a resistor that faces only in one longitudinal direction may not provide sufficient sensitivity. By having a lattice-shaped resistor 230 like the strain gauge 100B, pulse wave information can be obtained regardless of the branching of blood vessels, their thickness, or whether the blood vessels are expanding or contracting, making it possible to realize a vital sensor with higher accuracy.

<Modification 3 of the First Embodiment>
In the third modification of the first embodiment, another example of a vital sensor including a strain gauge in which the structure of each resistor is different from that in the first embodiment is shown. Note that in the third modification of the first embodiment, the description of the same components as those in the embodiments already described may be omitted.

Figure 9 is a plan view (part 1) of the vicinity of one resistor of a strain gauge according to the third modification of the first embodiment. Referring to Figure 9, the strain gauge 100C has a substrate 110, a resistor 330, and electrodes 351 and 352.

The strain gauge 100C has three sets including a resistor 330 and electrodes 351 and 352, which are arranged on one substrate 110. In each set including a resistor 330 and electrodes 351 and 352, the resistor 330 is arranged at the same position as the first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ in Fig. 1. However, three strain gauges each having one set including a resistor 330 and electrodes 351 and 352 on one substrate 110 may be arranged on the strain generating body 10.

The resistor 330 is patterned in a circular spiral shape in a plan view. The resistor 330 is a single continuous pattern connecting the electrodes 351 and 352, but for convenience, the portion from the electrode 351 to the folded portion 335 where the pattern is folded back is referred to as the first resistive wiring 331, and the portion from the folded portion 335 to the electrode 352 is referred to as the second resistive wiring 332. Note that in FIG. 9, for convenience, the first resistive wiring 331, the second resistive wiring 332, and the folded portion 335 are shown with different matte patterns.

In the resistor 330, the first resistive wiring 331 extends from the electrode 351 and is patterned in a circular spiral shape in a clockwise direction from the outer periphery to the center, and reaches the folded portion 335. The second resistive wiring 332 extends from the folded portion 335 and is patterned in a circular spiral shape in a counterclockwise direction from the center to the outer periphery, and reaches the electrode 352.

The first resistive wiring 331 and the second resistive wiring 332 are arranged alternately in principle. That is, except for a portion near the folded portion 335, the first resistive wiring 331 is always adjacent to the second resistive wiring 332, and the first resistive wiring 331 is always adjacent to the second resistive wiring 332. Except for a portion near the folded portion 335, the first resistive wirings 331 and the second resistive wirings 332 are never adjacent to each other. The resistor 330 is formed, for example, from the same material as the resistor 130.

When the strain body 10 is subjected to blood pressure, tensile and compressive strain distribution occurs concentrically from the center of the strain body 10. Therefore, by providing the resistor 330 in a circular spiral shape along the concentric circle, it is possible to detect strain around the entire circumference of the concentric circle, and even slight strain caused by blood pressure can be detected efficiently.

Figure 10 is a plan view (part 2) of the vicinity of one resistor of a strain gauge according to the third modification of the first embodiment. Referring to Figure 10, the strain gauge 100D has a substrate 110, a resistor 430, and electrodes 451 and 452.

The strain gauge 100D has three sets including a resistor 430 and electrodes 451 and 452, which are arranged on one substrate 110. In each set including a resistor 430 and electrodes 451 and 452, the resistor 430 is arranged at the same position as the first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ in Fig. 1. However, three strain gauges each having one set including a resistor 430 and electrodes 451 and 452 on one substrate 110 may be arranged on the strain generating body 10.

The resistor 430 is patterned into a square spiral shape in a plan view. In the resistor 430, the first resistive wiring 331, the second resistive wiring 332, and the folded portion 335 of the resistor 330 are replaced with the first resistive wiring 431, the second resistive wiring 432, and the folded portion 435. In addition, the electrodes 351 and 352 are replaced with the electrodes 451 and 452.

In this way, the resistor is not limited to a circular spiral shape, but may be a rectangular spiral shape like resistor 430. Alternatively, the resistor may be a spiral shape other than circular or rectangular. In these cases, the same effect is achieved as when resistor 330 is arranged in a circular spiral shape.

Figure 11 is a plan view (part 3) of the vicinity of one resistor of a strain gauge according to the third modification of the first embodiment. Referring to Figure 11, strain gauge 100E differs from strain gauge 100C in that resistor 330B and electrodes 351B and 352B are added. Resistor 330B is a circular spiral pattern arranged outside resistor 330 in plan view.

In resistor 330B, first resistive wiring 331B extends from electrode 351B and is patterned in a circular spiral shape in a clockwise direction from the outer periphery to the center, and reaches folded-back portion 335B. Second resistive wiring 332B extends from folded-back portion 335B and is patterned in a circular spiral shape in a counterclockwise direction from the center to the outer periphery, and reaches electrode 352B. Resistor 330 and resistor 330B are arranged in a roughly concentric shape.

The strain gauge 100E has three sets including resistors 330 and 330B, electrodes 351 and 352, and electrodes 351B and 351B, which are arranged on one substrate 110. In each set including resistors 330 and 330B, electrodes 351 and 352, and electrodes 351B and 351B, the resistors 330 and 330B are arranged at the same positions as the first resistor 130 ₁ , the second resistor 130 ₂ , and the third resistor 130 ₃ in Fig. 1. However, three strain gauges each having one set including resistors 330 and 330B, electrodes 351 and 352, and electrodes 351B and 351B may be arranged on the strain generating body 10 on one substrate 110.

In this way, each resistor may include resistor 330 with a circular spiral pattern and resistor 330B with another circular spiral pattern arranged to surround resistor 330 in a planar view. In this case, resistor 330 and resistor 330B can form a half-bridge circuit. As a result, the output from the resistor can be doubled, allowing blood flow to be detected with high accuracy. Note that a resistor with a circular spiral pattern similar to resistors 330 and 330B may also be arranged on the underside of strain generating body 10. In this case, a full-bridge circuit can be formed in combination with resistors 330 and 330B on the upper side.

Figure 12 is a plan view (part 4) of the vicinity of one resistor of a strain gauge according to the third modification of the first embodiment. Referring to Figure 12, strain gauge 100F differs from strain gauge 100D in that resistor 430B and electrodes 451B and 452B are added. Resistor 430B is a square spiral pattern arranged outside resistor 430 in plan view.

In resistor 430B, first resistive wiring 431B extends from electrode 451B and is patterned in a square spiral shape clockwise from the outer periphery to the center, and reaches folded-back portion 435B. Second resistive wiring 432B extends from folded-back portion 435B and is patterned in a square spiral shape counterclockwise from the center to the outer periphery, and reaches electrode 452B. Resistor 430 and resistor 430B are arranged approximately concentrically.

In this way, resistors 430 and 430B with a rectangular spiral pattern may be arranged in a double configuration. In this case, the same effect as when resistors 330 and 330B with a circular spiral pattern are arranged in a double configuration is achieved. Note that resistors with a rectangular spiral pattern similar to resistors 430 and 430B may also be arranged on the underside of strain body 10. In this case, a full bridge circuit can be formed in combination with resistors 430 and 430B on the upper side.

Although the preferred embodiments have been described above in detail, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

1, 1A vital sensor, 10 strain body, 100, 100A, 100B, 100C, 100D, 100E, 100F strain gauge, 110 base material, 110a top surface, 110b bottom surface, 130, 230, 330, 330B, 430, 430B resistor , 130 ₁ first resistor, 130 ₂ second resistor, 130 ₃ third resistor, 130 ₄ fourth resistor, 130 ₅ fifth resistor, 130e ₁ , 130e ₂ termination, 140 wiring, 141, 151 1 metal layer, 142, 152 Second metal layer, 150, 251, 252, 351, 351B, 352, 352B, 451, 451B, 452, 452B electrode, 160 cover layer, 231, 232 resistor portion, 331, 331B, 431, 431B first resistor wiring, 332, 332B, 432, 432B: second resistance wiring, 335, 335B, 435, 435B: folded portion

Claims (14)

A vital sensor for monitoring blood flow,
A strain body attached to a measurement site of a subject;
A strain gauge disposed on the strain body,
The strain gauge has three or more resistors,
When a direction in which the blood vessel extends at the measurement site is defined as a first direction and a direction perpendicular to the first direction is defined as a second direction,
The vital sensor, wherein the strain generating element is attached to the measurement site such that at least three of the resistors are different in position in the first direction and different in position in the second direction. The vital sensor according to claim 1, wherein the strain generating body is attached to the measurement site such that at least three of the resistors are spaced at regular intervals in the first direction and the second direction. At least three of the resistors are
A first resistor;
a second resistor disposed on one side of the first resistor in the first direction and on one side of the first resistor in the second direction when the strain generating body is attached to the measurement portion;
a third resistor that is disposed on the other side of the first resistor in the first direction and on the other side of the second direction when the strain generating body is attached to the measurement portion,
The vital sensor according to claim 1 , wherein the second resistor and the third resistor face each other with the first resistor therebetween. At least three of the resistors are
a fourth resistor disposed on the other side of the second resistor in the second direction when the strain generating body is attached to the measurement portion, and a fifth resistor disposed on one side of the third resistor in the second direction,
The vital sensor according to claim 3 , wherein the fourth resistor and the fifth resistor face each other with the first resistor therebetween. At least three of the resistors are
a first resistor, a second resistor, and a third resistor arranged with the grid direction facing the same direction;
the first resistor, the second resistor, and the third resistor are positioned differently in a grid direction and in a direction perpendicular to the grid direction,
The vital sensor according to claim 1 , wherein the second resistor and the third resistor face each other with the first resistor therebetween. At least three of the resistors are
Further including a fourth resistor and a fifth resistor arranged with their grid directions facing the same direction,
the fourth resistor is located at the same position as the second resistor in a grid direction and at the same position as the third resistor in a direction perpendicular to the grid direction,
the fifth resistor is located at the same position as the third resistor in the grid direction and at the same position as the second resistor in the direction perpendicular to the grid direction,
The vital sensor according to claim 5 , wherein the fourth resistor and the fifth resistor face each other with the first resistor therebetween. The vital sensor according to claim 5 or 6, wherein the strain generating body is attached to the measured part so that the grid direction of the first resistor, the second resistor, and the third resistor is arranged in the first direction. Each of the resistors includes a plurality of first resistor portions arranged in parallel with a longitudinal direction of the resistor in the first direction when the strain generating body is attached to the measurement portion, and a plurality of second resistor portions arranged in parallel with a longitudinal direction of the resistor in the second direction,
The vital sensor according to claim 1 , wherein the first resistor portion and the second resistor portion are disposed via an insulating layer. The vital sensor according to any one of claims 1 to 4, wherein each of the resistors is spiral-shaped. The vital sensor according to claim 9, wherein each of the resistors includes a resistor having a spiral pattern and another resistor having a spiral pattern arranged to surround the resistor having the spiral pattern in a plan view. The vital sensor according to claim 1 , wherein the resistor is formed from a film containing Cr, CrN, and Cr ₂ N. The vital sensor according to any one of claims 1 to 11, having a gauge factor of 10 or more. 13. The vital sensor according to claim 1, wherein the resistor contains 20% by weight or less of CrN and _Cr2N . The vital sensor according to claim 13 , wherein a ratio of said Cr ₂ N in said CrN and said Cr ₂ N is equal to or greater than 80% by weight and less than 90% by weight.

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