JP2014228454A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensor capable of detecting a pressing force highly accurately.SOLUTION: A pressure sensor 1 includes at least one pressure sensitive cell 20 having a thin film transistor 30 and a strain gauge 40 electrically connected to the thin film transistor 30. The strain gauge 40 is provided on the upper side or on the lower side of the thin film transistor 30.

Description

  The present invention relates to a pressure sensor that detects pressing.

  A pressure-sensitive sensor unit is known in which a gap is formed by packing between a contact electrode connected to a thin film transistor and a conductive sheet, and the conductive sheet comes into contact with the contact electrode by pressing (for example, see Patent Document 1).

JP 2006-145318 A

  In the above technique, since the pressure is detected based on the presence or absence of contact between the conductive sheet and the contact electrode, it is impossible to grasp the degree of strength of the pressure. Further, since the thin film transistor and the contact electrode are provided on the same surface of the insulating substrate, the density of the contact electrode on the insulating substrate is limited. Therefore, there is a problem that it is difficult to detect the press with high accuracy.

  The problem to be solved by the present invention is to provide a pressure sensor capable of detecting a press with high accuracy.

  [1] A pressure sensor according to the present invention includes at least one pressure-sensitive cell having a thin film transistor and a strain gauge electrically connected to the thin film transistor, and the strain gauge is located above or below the thin film transistor. It is provided in.

  [2] In the above invention, the pressure sensor may further include an elastic member having an elastic modulus of 100 MPa or less, and the elastic member may be interposed between the thin film transistor and the strain gauge.

  [3] In the above invention, the strain gauge may be directly formed on the surface of the elastic member.

  [4] In the above invention, the pressure sensor may further include a resin substrate on which the strain gauge is formed, and the elastic member may be interposed between the thin film transistor and the resin substrate.

  [5] In the above invention, the pressure-sensitive cell further includes a fixed resistor that forms a bridge circuit together with the strain gauge, and the fixed resistor is provided on the same layer as the strain gauge. Also good.

  [6] In the above invention, the m × n pressure sensitive cells are arranged in m rows and n columns along the first and second directions, and in each of the pressure sensitive sensors, the source electrode of the thin film transistor or The strain gauge is connected to a drain electrode, and the pressure sensor interconnects the drain electrode or the source electrode of the thin film transistor of the n pressure-sensitive cells arranged in the second direction. M first wirings, n second wirings interconnecting gate electrodes of the thin film transistors of the m pressure-sensitive cells arranged along the first direction, and the first wirings And m sets of third and fourth wirings connected to the strain gauges of the n pressure-sensitive cells arranged along the direction of 2 or a bridge circuit including the strain gauges. .

  [7] In the above invention, the pressure sensor includes first voltage applying means for applying a voltage to the drain electrode or the source electrode of the thin film transistor via the first wiring, and the second wiring. The second voltage applying means for applying a voltage to the gate electrode of the thin film transistor and the potential difference between both ends of the strain gauge or the output of the bridge circuit are measured via the third and fourth wirings. And pressure detecting means for detecting the pressure applied to the pressure sensitive cell based on the measurement result.

  [8] In the above invention, the first voltage application unit can switch a connection destination in the m first wirings, and the second voltage application unit also includes the n number of the first voltage application units. It may be possible to switch the connection destination in the second wiring.

  According to the present invention, since the pressure is detected using the strain gauge, the degree of strength of the pressure can be grasped. In addition, since the strain gauge is provided on the upper side or the lower side of the thin film transistor, the strain gauge can be overlaid on the thin film transistor, and the strain gauge can be arranged at a high density without being limited by the thin film transistor. For this reason, it becomes possible to detect press with high precision.

FIG. 1 is an equivalent circuit diagram showing the overall configuration of the pressure sensor according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the pressure-sensitive cell in the first embodiment of the present invention. FIG. 3 is a plan view of the pressure-sensitive cell according to the first embodiment of the present invention. FIG. 4 is an equivalent circuit diagram of the pressure-sensitive cell shown in FIG. FIG. 5 is a cross-sectional view of a pressure-sensitive cell according to the second embodiment of the present invention. FIG. 6 is a cross-sectional view of a pressure-sensitive cell according to the third embodiment of the present invention. FIG. 7 is a cross-sectional view of a pressure-sensitive cell according to the fourth embodiment of the present invention. FIG. 8 is a cross-sectional view of a pressure-sensitive cell according to the fifth embodiment of the present invention. FIG. 9 is a cross-sectional view of a pressure-sensitive cell according to the sixth embodiment of the present invention. FIG. 10 is an equivalent circuit diagram of the pressure-sensitive cell shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<< first embodiment >>
FIG. 1 is an equivalent circuit diagram showing the overall configuration of the pressure sensor according to the first embodiment of the present invention.

  As shown in FIG. 1, the pressure sensor 1 in the present embodiment includes a sensing unit 10 having a plurality of (m × n in this example) pressure sensitive cells 20, a first scanning circuit 70, and a second scanning. The apparatus includes a circuit 80 and a pressure detection circuit 90, and detects the pressure applied to the sensing unit 10. The first scanning circuit 70 in the present embodiment corresponds to an example of the first voltage application unit in the present invention, and the second scanning circuit 80 in the present embodiment is an example of the second voltage application unit in the present invention. It corresponds to.

  The sensing unit 10 of the pressure sensor 1 is configured by forming m × n pressure-sensitive cells 20 (m and n are natural numbers) on a single insulating substrate 11, and this m × n. The n pressure sensitive cells 20 are arranged in a matrix of m rows and n columns along the Y direction and the X direction. For this reason, the pressure sensor 1 according to the present embodiment can detect the pressure applied to the sensing unit 10 with a surface resolution corresponding to the number of the pressure sensitive cells 20, so that the pressure can be detected with high accuracy. It has become. The Y direction in the present embodiment corresponds to an example of the first direction in the present invention, and the X direction in the present embodiment corresponds to an example of the second direction in the present invention.

  Below, the structure of the pressure sensitive cell 10 is demonstrated, referring FIGS.

  2 and 3 are a sectional view and a plan view of the pressure-sensitive cell according to the first embodiment of the present invention, and FIG. 4 is a circuit diagram showing an equivalent circuit of the pressure-sensitive cell shown in FIG.

  As shown in FIGS. 2 to 4, the pressure-sensitive cell 20 in this embodiment includes a thin film transistor (TFT) 30 and a strain gauge 40, and the strain gauge 40 is provided on the thin film transistor 30. Is formed.

  As shown in FIG. 2, the thin film transistor 30 includes a gate electrode 31, a gate insulating film 32, a semiconductor layer 33, a source electrode 34, a drain electrode 35, and a protective layer 36, which are sequentially formed on the insulating substrate 11. It is laminated and configured.

  The thin film transistor 30 shown in FIG. 2 has a so-called bottom gate / stagger type structure; however, the present invention is not particularly limited to this, and the top gate / stagger type, the bottom gate / planar type, or the top gate / planar type. It may have a mold structure.

  The insulating substrate 11 is, for example, a flexible film having a thickness of 18 μm or less and electrical insulation. Examples of the material constituting the insulating substrate 11 include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), and the like. By using such a flexible resin film as the insulating substrate 11, a flexible pressure sensor that can be attached to a curved surface can be obtained.

  The gate electrode 31 is formed by printing and curing a conductive ink on the surface of the insulating substrate 11. Examples of the conductive ink constituting the gate electrode 31 include those containing nano metal particles such as silver (Ag) and gold (Au).

  In place of the conductive ink, a conductive paste containing gold (Au), silver (Ag), carbon (C), etc., an organic resinate obtained by pasting an organometallic compound, or PEDOT (3,4-ethylenedioxythiophene) The gate electrode 31 may be formed using an organic conductive material such as).

  In addition, the manufacturing method of the gate electrode 31 is not particularly limited to the printing method, but by a sputtering method, a vacuum deposition method, a chemical vapor deposition method (CVD method), an electroless plating method, an electrolytic plating method, or a combination thereof, etc. The gate electrode 31 may be formed. In this case, as a material constituting the gate electrode 31, for example, chromium (Cr), titanium (Ti), copper (Cu), aluminum (Al), molybdenum (Mo), tungsten (W), nickel (Ni) ), Gold (Au), palladium (Pd), platinum (Pt), silver (Ag), tin (Sn), tantalum (Ta), or an alloy containing at least one of these.

  The gate insulating film 32 is formed by applying and curing a resin material on the surface of the insulating substrate 11 so as to cover the gate electrode 31. Examples of the resin material constituting the gate insulating film 32 include polyvinylphenol (PVP).

  The semiconductor layer 33 is formed by depositing an organic semiconductor on the gate insulating film 32 using a mask. Examples of the organic semiconductor constituting the semiconductor layer 33 include a low molecular material such as pentacene, a high molecular weight such as P3HT (poly- (3-hexylthiophene)) and F8T2 (poly (9,9-dioctylfluorene-co-bithiophene)). Examples thereof include molecular materials or carbon compounds having semiconductor characteristics such as carbon nanotubes and fullerenes. By forming the semiconductor layer 33 with such an organic semiconductor, a flexible pressure sensor that can be attached to a curved surface can be obtained.

  The manufacturing method of the semiconductor layer 33 is not particularly limited to vacuum vapor deposition, and the semiconductor layer 33 may be formed by using a sputtering method, a spin coating method, a chemical vapor deposition method, a printing method, or the like.

  The source electrode 34 is provided on the surface of the gate insulating layer 32 so as to partially cover the semiconductor layer 33. The drain electrode 35 is also provided on the surface of the gate insulating layer 32 so as to partially cover the semiconductor layer 33, and a predetermined interval is formed between the source electrode 34 and the drain electrode 35. The source electrode 34 and the drain electrode 35 are formed of the same material and manufacturing method as those of the gate electrode 31 described above.

  The protective layer 36 is formed by applying and curing a resin material on the gate insulating layer 32 and covers the semiconductor layer 33, the source electrode 34 and the drain electrode 35 on the gate insulating layer 32.

  As shown in FIGS. 2 and 3, the strain gauge 40 is provided on the protective layer 36 of the thin film transistor 30 so as to overlap the thin film transistor 30 in plan view. For example, the strain gauge 40 is formed by a semi-additive method or a full additive method. It is formed directly on the protective layer 36. The strain gauge 40 is composed of a metal foil film having a thickness of several μm mainly composed of copper (Cu) or aluminum (Al), and has a gauge grid 41 and a gauge tab 42 as shown in FIG. doing.

  The gauge grid 41 has a pattern in which fine lines are repeatedly folded at narrow intervals, and gauge tabs 42 a and 42 b are connected to both ends of the gauge grid 41. One gauge tab 42a is connected to the source electrode 34 of the thin film transistor 30 through a via hole 361 penetrating the protective layer 36, whereby the thin film transistor 30 is connected to the strain gauge 40 as shown in FIG. It is electrically connected to one end. On the other hand, the other end of the strain gauge 40 is grounded.

  The method for forming the strain gauge 40 is not particularly limited to the above, and for example, a sputtering method, a vacuum deposition method, a chemical vapor deposition method (CVD method), or the like may be used. Alternatively, the strain gauge 40 may be formed by directly printing the above-described conductive ink, conductive paste, organic resinate, organic conductive material, or the like on the protective layer 36. Further, the via hole 361 can be formed simultaneously with the strain gauge 40 by forming a through hole in the protective layer 36 by laser processing or the like before the strain gauge 40 is formed on the protective layer 36, for example. it can.

  Furthermore, an insulating layer 43 is laminated on the upper surface of the protective layer 36, and the insulating layer 43 covers the strain gauge 40. The insulating layer 43 is formed by applying a resin material on the upper surface of the protective layer 36 and curing it.

  The sensing unit 10 is configured by arranging the m × n pressure-sensitive cells 20 described above in a matrix. As shown in FIG. 1, in the sensing unit 10, m first wirings 12 are arranged side by side in the Y direction. The first wiring 12 is connected to the drain electrode 35 of the thin film transistor 30, and n pressure-sensitive cells 10 arranged along the X direction are connected to each other via the first wiring 12. Yes. Note that the first wiring 12 is not shown in FIGS. Further, the first wiring 12 may be connected to the source electrode 34 of the thin film transistor 30 and one end of the strain gauge 40 may be connected to the drain electrode 35 of the thin film transistor 30.

  The m first wirings 12 are connected to the first scanning circuit 70, and the first scanning circuit 70 applies a voltage to the drain electrode 35 of the pressure-sensitive cell 20 via the first wiring 12. The first scanning signal Va can be applied. Further, the first scanning circuit 70 can switch the connection destination among the m first wirings 12, and the first scanning circuit 70 performs the first scanning with respect to the m first wirings 12. Signals can be sequentially applied.

  In the sensing unit 10, n second wirings 13 are arranged in the X direction. The second wiring 13 is connected to the gate electrode 31 of the thin film transistor 30, and m pressure sensitive cells 20 arranged in the Y direction are connected to each other via the second wiring 13. Yes. Note that the second wiring 13 is not shown in FIGS.

  The n second wirings 13 are connected to the second scanning circuit 80, and the second scanning circuit 80 connects the gate electrode of the thin film transistor 30 of the pressure-sensitive cell 20 via the second wiring 13. A second scanning signal of voltage Vb can be applied to 31. Further, the second scanning circuit 80 can switch the connection destination among the n second wirings 13, and the second scanning signal is applied to the n second wirings 13. Can be sequentially applied.

  Therefore, the pressure sensor 1 of the present embodiment can individually apply scanning signals to all the pressure sensitive cells 20 provided in the sensing unit 10 by repeating the following operations. Thereby, the surface pressure applied to the sensing unit 10 can be ascertained by decomposing on the XY coordinate system.

That is, as shown in FIG. 1, with the first scanning circuit 70 is applied to the first scan signal Va _1, the second scanning circuit 80 a second scan signal Vb ₁ → Vb ₂ → · · · → Vb _n and switching, then, with the first scanning circuit 70 is applied to the first scan signal Va _2, the second scanning circuit 80 a second scan signal Vb ₁ → Vb ₂ → · · · → Vb _n and switch, with the ... first scanning circuit 70 is applied to the first scan signal Va _m, the second scanning circuit 80 a second scan signal Vb ₁ → Vb ₂ → · -Repeat the operation of switching to Vb _n .

  Further, the sensing unit 10 is provided with m sets of third and fourth wirings 14 and 15 connected to both ends of the strain gauge 40, via the third and fourth wirings 14 and 15. The n pressure sensitive cells 20 arranged in the X direction are connected to the voltage detection unit 91 of the pressure detection circuit 90. The voltage detector 91 can measure a potential difference between both ends of the strain gauge 40. Note that the third and fourth wirings 14 and 15 are not shown in FIGS.

  The measurement result of the voltage detection unit 91 is input to the calculation unit 92 of the pressure detection circuit 90. The calculator 92 calculates the pressure applied to the strain gauge 40 based on the potential difference of the strain gauge 40.

  As described above, in the present embodiment, since the pressure is detected using the strain gauge 40, the degree of pressure applied to the pressure sensitive cell 20 can be continuously grasped, and the output resolution can be increased. . Further, since the strain gauge 40 is provided on the upper side of the thin film transistor 30, the strain gauges 40 can be arranged at high density, and the surface resolution can be increased. Therefore, it becomes possible to detect a press with high accuracy.

  Moreover, in this embodiment, since a press is detected using the strain gauge 40, the gap required for the conventional structure which detects a press by the presence or absence of a contact becomes unnecessary, and the pressure sensor can be reduced in thickness. Specifically, since the strain gauge 40 is a metal layer having a thickness of several μm, the total thickness of the pressure-sensitive portion 10 can be set to 30 μm or less.

  Further, in the conventional structure, there is a possibility that the thin film transistor may be broken due to the transient current generated by the contact. However, in this embodiment, since the pressure is detected using the strain gauge 40, the failure of the thin film transistor can be suppressed.

  Furthermore, in this embodiment, the pressure sensitive range and sensitivity can be adjusted by changing the dimension of the strain gauge 40.

<< Second Embodiment >>
FIG. 5 is a cross-sectional view of a pressure-sensitive cell according to the second embodiment of the present invention.

  In this embodiment, the configuration of the pressure-sensitive cell 20B is different from that of the first embodiment, but the other configurations are the same as those of the first embodiment. Hereinafter, only the difference from the first embodiment in the pressure-sensitive cell 20B in the second embodiment will be described, and the same parts as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  As shown in FIG. 5, the pressure-sensitive cell 20 </ b> B in the present embodiment is different from the first embodiment in that a strain gauge 40 is provided below the thin film transistor 30.

  In the present embodiment, the strain gauge 40 is directly formed on the lower surface of the insulating substrate 11. One gauge tab 42 a of the strain gauge 40 is connected to the source electrode 34 of the thin film transistor 30 through a via hole 321 that penetrates the insulating substrate 11 and the gate insulating film 32.

  In the present embodiment, as in the first embodiment, since the pressure is detected using the strain gauge 40, the degree of pressure applied to the pressure sensitive cell 20B can be continuously grasped, and the output resolution is increased. be able to. In addition, since the strain gauge 40 is provided on the lower side of the thin film transistor 30, the strain gauges 40 can be arranged at high density, and the surface resolution can be increased. Therefore, it becomes possible to detect a press with high accuracy.

  Further, in the present embodiment, as in the first embodiment, the pressure is detected using the strain gauge 40, so that the pressure sensor can be reduced in thickness and the failure of the thin film transistor due to the transient current can be suppressed.

  Furthermore, in the present embodiment, the pressure sensitive range and sensitivity can be adjusted by changing the dimensions of the strain gauge 40, as in the first embodiment.

<< Third Embodiment >>
FIG. 6 is a cross-sectional view of a pressure-sensitive cell according to the third embodiment of the present invention.

  In the present embodiment, the configuration of the pressure-sensitive cell 20C is different from that of the first embodiment, but the other configurations are the same as those of the first embodiment. Hereinafter, only the difference from the first embodiment in the pressure sensitive cell 20C in the third embodiment will be described, and the same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

  As shown in FIG. 6, the pressure sensitive cell 20 </ b> C in the present embodiment is different from the first embodiment in that a resin substrate 44 is interposed between the strain gauge 40 and the thin film transistor 30.

  In this embodiment, the strain gauge 40 is formed on the resin substrate 44 by patterning the metal layer of the copper-clad laminate (CCL) into a predetermined shape. The strain gauge 40 is provided on the upper side of the thin film transistor 30 by laminating the resin substrate 44 on the protective layer 36 of the thin film transistor 30 through an adhesive. In this case, one gauge tab 42 a of the strain gauge 40 and the source electrode 34 of the thin film transistor 30 are connected via a via hole 441 that penetrates the resin substrate 44 and the protective layer 36.

  Although not particularly illustrated, the strain gauge 40 may be provided on the lower side of the thin film transistor 30 by laminating the resin substrate 44 on the lower surface of the insulating substrate 11 as in the second embodiment.

  In this embodiment, as in the first embodiment, since the pressure is detected using the strain gauge 40, the degree of pressure applied to the pressure sensitive cell 20C can be continuously grasped, and the output resolution is increased. be able to. Further, since the strain gauge 40 is provided on the upper side of the thin film transistor 30, the strain gauges 40 can be arranged at high density, and the surface resolution can be increased. Therefore, it becomes possible to detect a press with high accuracy.

  Further, in the present embodiment, as in the first embodiment, the pressure is detected using the strain gauge 40, so that the pressure sensor can be reduced in thickness and the failure of the thin film transistor due to the transient current can be suppressed.

  Furthermore, in the present embodiment, the pressure sensitive range and sensitivity can be adjusted by changing the dimensions of the strain gauge 40, as in the first embodiment.

<< Fourth embodiment >>
FIG. 7 is a cross-sectional view of a pressure-sensitive cell according to the fourth embodiment of the present invention.

  In the present embodiment, the configuration of the pressure-sensitive cell 20D is different from that of the first embodiment, but other configurations are the same as those of the first embodiment. Hereinafter, only the difference from the first embodiment will be described for the pressure-sensitive cell 20D in the fourth embodiment, and the same parts as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  As shown in FIG. 7, the pressure-sensitive cell 20 </ b> D in the present embodiment is different from the first embodiment in that an elastic member 60 is interposed between the strain gauge 40 and the thin film transistor 30.

  The elastic member 60 is a film-like elastomer having an elastic modulus (Young's modulus) of 100 MPa or less. Examples of the material constituting the elastic member include silicone rubber, urethane rubber, and acrylic rubber.

  The elastic member 60 is laminated on the protective layer 36 of the thin film transistor 30, and the strain gauge 40 is directly formed on the surface of the elastic member 60, so that the strain gauge 40 is provided on the upper side of the thin film transistor 30. In this case, one gauge tab 42 a of the strain gauge 40 and the source electrode 34 of the thin film transistor 30 are connected via a via hole 601 that penetrates the elastic member 60 and the protective layer 36.

  The elastic member 60 may be laminated on the thin film transistor 30 after the strain gauge 40 is formed on the surface of the elastic member 60. Although not particularly illustrated, the strain gauge 40 may be provided below the thin film transistor 30 by laminating the elastic member 60 on the lower surface of the insulating substrate 11 as in the second embodiment.

  In the present embodiment, as in the first embodiment, since the pressure is detected using the strain gauge 40, the degree of pressure applied to the pressure sensitive cell 20D can be continuously grasped, and the output resolution is increased. be able to. Further, since the strain gauge 40 is provided on the upper side of the thin film transistor 30, the strain gauges 40 can be arranged at high density, and the surface resolution can be increased. Therefore, it becomes possible to detect a press with high accuracy.

  Furthermore, in this embodiment, since the elastic member 60 provided between the strain gauge 40 and the thin film transistor 30 is easily deformed, the sensitivity of the strain gauge 40 is increased and the accuracy of pressure detection is further improved.

  Further, in the present embodiment, as in the first embodiment, the pressure is detected using the strain gauge 40, so that the pressure sensor can be reduced in thickness and the failure of the thin film transistor due to the transient current can be suppressed.

  In the present embodiment, as in the first embodiment, the pressure sensitive range and sensitivity of the strain gauge 40 can be adjusted by changing the dimensions of the strain gauge 40.

  Furthermore, in this embodiment, the pressure-sensitive range and sensitivity of the strain gauge 40 can be adjusted by changing the elastic modulus of the elastic member 60.

<< Fifth Embodiment >>
FIG. 8 is a cross-sectional view of a pressure-sensitive cell according to the fifth embodiment of the present invention.

  In the present embodiment, the configuration of the pressure-sensitive cell 20E is different from that of the first embodiment, but other configurations are the same as those of the first embodiment. Hereinafter, only the difference from the first embodiment in the pressure-sensitive cell 20E in the fifth embodiment will be described, and the same parts as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  As shown in FIG. 8, the pressure-sensitive cell 20 </ b> E in the present embodiment is different from the first embodiment in that a resin substrate 44 and an elastic member 60 are interposed between the strain gauge 40 and the thin film transistor 30.

  In this embodiment, similarly to the third embodiment, the strain gauge 40 is formed on the resin substrate 44 by patterning the metal layer of the copper-clad laminate (CCL) into a predetermined shape. On the other hand, the elastic member 60 described in the fourth embodiment is laminated on the protective layer 36 of the thin film transistor 30. Then, the strain gauge 40 is provided on the upper side of the thin film transistor 30 by laminating the resin substrate 40 on the elastic member 60. In this case, one gauge tab 42 a of the strain gauge 40 and the source electrode 34 of the thin film transistor 30 are connected via a via hole 442 that penetrates the resin substrate 44, the elastic member 60, and the protective layer 36.

  Alternatively, the elastic member 60 may be laminated on a copper-clad laminate, and the elastic member 60 may be attached to the protective layer 36 of the thin film transistor 30 after the strain gauge 40 is formed. Alternatively, the elastic member 60 and the resin substrate 44 may be laminated on the thin film transistor 30, and the strain gauge 40 may be directly formed on the resin substrate 44.

  Although not particularly illustrated, the strain gauge 40 may be provided below the thin film transistor 30 by laminating the elastic member 60 and the resin substrate 44 on the lower surface of the insulating substrate 11 as in the second embodiment.

  In this embodiment, as in the first embodiment, since the pressure is detected using the strain gauge 40, the degree of pressure applied to the pressure sensitive cell 20E can be continuously grasped, and the output resolution is increased. be able to. Further, since the strain gauge 40 is provided on the upper side of the thin film transistor 30, the strain gauges 40 can be arranged at high density, and the surface resolution can be increased. Therefore, it becomes possible to detect a press with high accuracy.

  Furthermore, in this embodiment, since the elastic member 60 provided between the strain gauge 40 and the thin film transistor 30 is easily deformed, the sensitivity of the strain gauge 40 is increased and the accuracy of pressure detection is further improved.

  Further, in the present embodiment, as in the first embodiment, the pressure is detected using the strain gauge 40, so that the pressure sensor can be reduced in thickness and the failure of the thin film transistor due to the transient current can be suppressed.

  In the present embodiment, as in the first embodiment, the pressure sensitive range and sensitivity of the strain gauge 40 can be adjusted by changing the dimensions of the strain gauge 40.

  Furthermore, in this embodiment, the pressure-sensitive range and sensitivity of the strain gauge 40 can be adjusted by changing the elastic modulus of the elastic member 60.

<< Sixth Embodiment >>
FIG. 9 is a cross-sectional view of a pressure-sensitive cell according to the sixth embodiment of the present invention, and FIG. 10 is an equivalent circuit diagram of the pressure-sensitive cell shown in FIG.

  In the present embodiment, the configuration of the pressure-sensitive cell 20F is different from that of the first embodiment, but other configurations are the same as those of the first embodiment. Hereinafter, only the difference from the first embodiment in the pressure-sensitive cell 20F in the sixth embodiment will be described, and the same parts as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  As shown in FIG. 10, the pressure-sensitive cell 20 </ b> F in the present embodiment is different from the first embodiment in that it includes a bridge circuit 50 in which a strain gauge 40 is incorporated.

  As shown in the figure, the bridge circuit 50 is configured by electrically connecting a first series circuit 51 and a second series circuit 52 in parallel. The first series circuit 51 is configured by electrically connecting a first fixed resistor 511 and a second fixed resistor 512 in series. The second series circuit 52 is configured by electrically connecting the strain gauge 40 and the third fixed resistor 521 in series.

  As shown in FIG. 9, the first fixed resistor 511 is directly provided on the protective layer 36 of the thin film transistor 30. The first fixed resistor 511 is formed by printing and curing a carbon paste, and is provided on the same layer as the strain gauge 40. Although not particularly illustrated, the second and third fixed resistors 512 and 521 are also directly formed on the protective layer 36 of the thin film transistor 30, and the entire bridge circuit 50 is provided on the protective layer 36. The first to third fixed resistors 511, 512, and 521 may be made of an insulating resin material or a conductive polymer material.

  The first connection point 531 of the bridge circuit 50 is connected to the source electrode 34 of the thin film transistor 30, and the second connection point 532 is grounded. On the other hand, the third connection point 533 of the bridge circuit 50 is connected to the voltage detection unit 91 via the third wiring 14, and the fourth connection point 534 is also connected to the voltage detection unit 91 via the fourth wiring 15. 91. In this embodiment, the voltage detection unit 91 of the pressure detection circuit 90 measures the output of the bridge circuit 50, and the calculation unit 92 detects the pressure applied to the pressure sensitive cell 20F based on this output. Note that the first wiring 12 may be connected to the source electrode 34 of the thin film transistor 30, and the first connection point 531 of the bridge circuit 50 may be connected to the drain electrode 35 of the thin film transistor 30.

  The first connection point 531 of the bridge circuit 50 is positioned between the first fixed resistor 511 and the strain gauge 40, and the second connection point 532 is connected to the second fixed resistor 512 and the third fixed resistor 512. The third connection point 533 is located between the fixed resistor 521 and the third connection point 533 is located between the first fixed resistor 511 and the second fixed resistor 512, and the fourth connection point. 534 is located between the strain gauge 40 and the third fixed resistor 521.

  Although not particularly illustrated, the strain gauge 40 may be provided on the lower side of the thin film transistor 30 by forming the bridge circuit 60 on the lower surface of the insulating substrate 11 as in the second embodiment. Although not particularly illustrated, the resin substrate 44 and the elastic member 60 may be interposed between the bridge circuit 50 and the thin film transistor 30 as in the third to fifth embodiments.

  In the present embodiment, as in the first embodiment, since the pressure is detected using the strain gauge 40, the degree of pressure applied to the pressure sensitive cell 20F can be grasped continuously, and the output resolution is increased. be able to. Further, since the strain gauge 40 is provided on the upper side of the thin film transistor 30, the strain gauges 40 can be arranged at high density, and the surface resolution can be increased. Therefore, it becomes possible to detect a press with high accuracy.

  Furthermore, in this embodiment, since the pressure applied to the pressure sensitive cell 20F is detected based on the output of the bridge circuit 50, the output resolution can be further increased.

  Further, in the present embodiment, as in the first embodiment, the pressure is detected using the strain gauge 40, so that the pressure sensor can be reduced in thickness and the failure of the thin film transistor due to the transient current can be suppressed.

  In the present embodiment, as in the first embodiment, the pressure sensitive range and sensitivity can be adjusted by changing the dimensions of the strain gauge 40.

  Furthermore, in this embodiment, the pressure-sensitive range and sensitivity can be adjusted by changing the dimensions of the fixed resistors 511, 512, and 521 of the bridge circuit 50.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Pressure sensor 10 ... Sensing part 11 ... Insulating substrate 12-15 ... 1st-4th wiring 20-20F ... Pressure sensitive cell 30 ... Thin-film transistor 31 ... Gate electrode 32 ... Gate insulating film 33 ... Semiconductor layer 34 ... Source Electrode 35 ... Drain electrode 36 ... Protective layer 40 ... Strain gauge 41 ... Gauge grid 42 ... Gauge tab 43 ... Insulating layer 44 ... Resin substrate 50 ... Bridge circuit 511 ... First fixed resistor 60 ... Elastic member 70 ... First scan Circuit 80 ... second scanning circuit 90 ... pressure detection circuit

Claims (7)

Comprising at least one pressure sensitive cell having a thin film transistor and a strain gauge electrically connected to the thin film transistor;
The pressure sensor, wherein the strain gauge is provided above or below the thin film transistor. The pressure sensor according to claim 1,
The pressure sensor further includes an elastic member having an elastic modulus of 100 MPa or less,
The pressure sensor, wherein the elastic member is interposed between the thin film transistor and the strain gauge. The pressure sensor according to claim 2,
The pressure sensor, wherein the strain gauge is directly formed on a surface of the elastic member. The pressure sensor according to claim 2,
The pressure sensor further includes a resin substrate on which the strain gauge is formed,
The pressure sensor, wherein the elastic member is interposed between the thin film transistor and the resin substrate. The pressure sensor according to any one of claims 1 to 4,
The pressure sensitive cell further has a fixed resistor that forms a bridge circuit with the strain gauge,
The pressure sensor, wherein the fixed resistor is provided on the same layer as the strain gauge. The pressure sensor according to any one of claims 1 to 5,
The m × n pressure-sensitive cells are arranged in m rows and n columns along the first and second directions,
In each of the pressure sensitive sensors, the strain gauge is connected to a source electrode or a drain electrode of the thin film transistor,
The pressure sensor is
M first wirings interconnecting the drain electrodes or the source electrodes of the thin film transistors of the n pressure-sensitive cells arranged along the second direction;
N second wirings interconnecting the gate electrodes of the thin film transistors of the m pressure-sensitive cells arranged along the first direction;
And m sets of third and fourth wirings connected to the strain gauges of the n pressure-sensitive cells arranged along the second direction or a bridge circuit including the strain gauges. A pressure sensor characterized by that. The pressure sensor according to claim 6,
The pressure sensor is
First voltage applying means for applying a voltage to the drain electrode or the source electrode of the thin film transistor via the first wiring;
Second voltage applying means for applying a voltage to the gate electrode of the thin film transistor through the second wiring;
Pressure for measuring the potential difference across the strain gauge or the output of the bridge circuit via the third and fourth wirings, and detecting the pressure applied to the pressure sensitive cell based on the measurement result A pressure sensor.

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