JP5625994B2 - Bending sensor - Google Patents

Description

  The present invention relates to a bending sensor capable of measuring the degree of bending (curvature) of an object surface.

  A conventional bending sensor has a rod shape as described in Patent Document 1, for example, and detects whether or not the rod is bent. Specifically, as shown in FIG. 16 (a), two bars (the metal bar 11 and the metal bar 12) are overlapped, and the difference in distortion generated in the two bars when bent is detected. . For example, as shown in FIG. 16B, when the bending sensor is bent so as to have a convex shape to the left, the metal rod 11 located on the left side extends, and conversely, the metal rod 12 located on the right side contracts, Changes in electrical resistance corresponding to these strains were detected to measure the bending of the bars.

JP-A-6-18206

  However, the conventional bending sensor has a problem that it can detect only simple information as to whether or not the bar is bent. For example, as shown in FIGS. 16C and 16D, when the bar AB is bent so as to be convex leftward, it is bent at a position close to the end A of the bar (FIG. 16C). It was not possible to distinguish whether it was bent near the end B of the rod (FIG. 16D). Further, as shown in FIG. 16 (e), when the S-shaped curve is bent at two places, the distortion is canceled out, so that an erroneous detection result indicating that it is straight is obtained. As described above, the conventional bending sensor has a problem that the detection result is not reliable. In other words, the conventional bending sensor has almost no spatial resolution with respect to the bending state, and therefore there is a problem that it is impossible to determine how the rod is bent.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A bending sensor according to this application example includes a first thin film transistor and a second thin film transistor on a flexible substrate, and the substrate includes a flexible region and a non-flexible region. The thin film transistor and the second thin film transistor form a differential transistor pair, wherein the first thin film transistor is formed in a flexible region and the second thin film transistor is formed in a non-flexible region.
Since the thin film transistor can be formed in units of micrometers, according to this configuration, a bending sensor having a very high spatial resolution of several micrometers can be realized.

Application Example 2 In the bending sensor according to the application example, the bending sensor further includes a fifth thin film transistor and a sixth thin film transistor, and the fifth thin film transistor and the sixth thin film transistor form a current mirror pair, It is preferable that the fifth thin film transistor can be electrically connected, and the second thin film transistor and the sixth thin film transistor can be electrically connected.
According to this configuration, since the thin film transistor group constitutes a current mirror type differential amplifier circuit, it is possible to read the bending state (curvature) as a potential difference and accurately measure them.

Application Example 3 The bending sensor according to the application example further includes a first power source, a second power source, and a seventh thin film transistor, wherein the first thin film transistor and the second thin film transistor are connected to the first power source, The fifth thin film transistor and the sixth thin film transistor are preferably connected to the seventh thin film transistor, and the seventh thin film transistor is preferably connected to the second power source.
According to this configuration, since the seventh thin film transistor can be a constant current source, signal amplification related to bending is linear, and a potential proportional to bending stress can be accurately measured.

Application Example 4 The bending sensor according to the application example further includes a first selection circuit along the first direction, and a plurality of first thin film transistors are formed along the first direction. It is preferable that the selection circuit can select in the first direction.
According to this configuration, since a plurality of first thin film transistors for detecting bending are arranged in the first direction and individually selected, the spatial distribution of the bending in the first direction can be measured. Therefore, even if the bending degree is a plurality of places along the first direction, the bending degree can be quantitatively and accurately measured as a function of the place.

Application Example 5 In the bending sensor according to the application example described above, the bending sensor according to the application example further includes a second selection circuit along a second direction intersecting the first direction, and a plurality of first thin film transistors are provided along the second direction. Preferably, it is formed and can be selected in the second direction by the second selection circuit.
According to this configuration, since a plurality of first thin film transistors for detecting bending are arranged in the second direction and individually selected, the spatial distribution of the bending in the second direction can be measured. Therefore, even if the bending degree is a plurality of places along the second direction, the bending degree can be quantitatively and accurately measured as a function of the place.

Application Example 6 The bending sensor according to the application example further includes a third thin film transistor and a fourth thin film transistor, the third thin film transistor being disposed between the first thin film transistor and the fifth thin film transistor, The four thin film transistors are preferably disposed between the second thin film transistor and the sixth thin film transistor, and the third thin film transistor and the fourth thin film transistor are preferably controlled by the second selection circuit.
According to this configuration, since the third thin film transistor and the fourth thin film transistor function as a part of the selection circuit in the second direction, it is possible to prevent the information on the bending state in the second direction from interfering. .

Application Example 7 In the bending sensor according to the application example described above, the second thin film transistor operates as a reference transistor, and compares the electrical characteristics of the first thin film transistor and the electrical characteristics of the second thin film transistor to detect the bending condition. It is preferable to do.
According to this configuration, the bending property is measured by comparing the electrical characteristics of the first thin film transistor located in the flexible region with the electrical characteristics of the second thin film transistor located in the non-flexible region. Accurate measurement.

Application Example 8 In the bending sensor according to the application example described above, it is preferable that an equalize circuit is provided between the drain of the fifth thin film transistor and the drain of the sixth thin film transistor.
According to this configuration, when the measurement of the bending state is sequentially and spatially repeated, the output potential can be reset between each measurement, so that accurate measurement can be realized quickly.

Application Example 9 In the bending sensor according to the application example, it is preferable that the fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are N-type, and the second power source is a negative power source.
According to this configuration, a bending sensor can be realized with an N-type thin film transistor.

Application Example 10 In the bending sensor according to the application example, it is preferable that the fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are P-type, and the second power source is a positive power source.
According to this configuration, a bending sensor can be realized with a P-type thin film transistor.

Application Example 11 In the bending sensor according to the application example, it is preferable that a fixing plate harder than the substrate is bonded to the substrate in the non-flexible region.
According to this configuration, it is possible to easily create a flexible region and a non-flexible region using a flexible substrate.

1 is a perspective external view schematically showing a bending sensor according to Embodiment 1. FIG. FIG. 3 is a diagram for explaining the measurement principle of the bending sensor according to the first embodiment. FIG. 3 illustrates a circuit of a bending sensor according to the first embodiment. FIG. 3 is a diagram for explaining a timing chart of a bending sensor according to the first embodiment. FIG. 3 is a diagram illustrating a planar layout of a detection circuit of a bending sensor according to the first embodiment. FIG. 3 is a diagram illustrating a part of a cross section of the bending sensor according to the first embodiment. The figure explaining the relationship between the thickness of a fixed plate in a flexible area | region, and distance. The figure explaining the relationship between the deflection | deviation of the fixing plate in a flexible area | region, and distance. (A); The figure showing the state which applied the downward load to the bending sensor of the comparative example, (b); The figure showing the state which applied the downward load to the bending sensor of Embodiment 1. FIG. 6 illustrates a circuit of a bending sensor according to a second embodiment. FIG. 6 is a diagram for explaining a timing chart of a bending sensor according to a second embodiment. The figure explaining the circuit of the bending sensor concerning the modification 1. FIG. The figure explaining the circuit of the bending sensor concerning the modification 2. The figure explaining the plane layout of the detection circuit of the bending sensor concerning the modification 3. FIG. The figure explaining the plane layout of the detection circuit of the bending sensor concerning the modification 4. FIG. The figure explaining the conventional bending sensor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scales are different for each layer and each member so that each layer and each member can be recognized on the drawing.

(Embodiment 1)
"Bending sensor overview"
FIG. 1 is a perspective external view schematically showing a bending sensor according to the present embodiment. Hereinafter, the outline of the bending sensor will be described first with reference to FIG.

  The bending sensor 1 according to the present embodiment is formed on a flexible substrate 2 such as a soft plastic film. The substrate 2 has a non-flexible region 21 and a flexible region 22. The flexible region 22 has flexibility as the name indicates, and the flexible substrate 2 is used as it is. The non-flexible region 21 does not have flexibility and usually has a fixed shape. In the present embodiment, a hard fixing plate 7 is fixed to a part of the back surface of the substrate 2, and the substrate 2 is not bent at that portion to form a non-flexible region 21. A plurality of N-type first thin film transistors TN1 (i, j) (see FIG. 3) are arranged in a matrix in the flexible region 22 to form the detection circuit 3. On the other hand, the non-flexible region 21 is provided with an N-type second thin film transistor TN2 (see FIG. 3) and constitutes a part of the output circuit 4. The first thin film transistor TN1 (i, j) and the second thin film transistor TN2 form a differential transistor pair. The second thin film transistor TN2 operates as a reference transistor, and compares the electrical characteristics of the first thin film transistor TN1 (i, j) with the electrical characteristics of the second thin film transistor TN2, thereby comparing the first thin film transistor TN1 (i, j). Detects the degree of bending of the part where is placed.

  The plurality of first thin film transistors TN <b> 1 (i, j) arranged in the detection circuit 3 are sequentially selected by the first selection circuit 51 and the second selection circuit 61 arranged on the outer periphery of the detection circuit 3. One side of the substrate 2 is defined as a first direction (a direction parallel to the x axis and a row direction), and another direction intersecting (substantially orthogonal to) the first direction is a second direction (parallel to the y axis). The first selection circuit 51 and the first processing circuit 52 are formed along the first direction outside the detection circuit 3, and the second selection circuit 61 and the second processing circuit 52. The processing circuit 62 is formed along the second direction outside the detection circuit 3. A plurality of first thin film transistors TN1 (i, j) are formed along the first direction and selected by the first selection circuit 51 in the first direction. Similarly, a plurality of first thin film transistors TN <b> 1 (i, j) are formed along the second direction and selected by the second selection circuit 61 in the second direction. The first thin film transistors TN1 (i, j) arranged in a matrix are sequentially selected in this way, and their electrical characteristics are compared with the electrical characteristics of the second thin film transistor TN2 each time, thereby measuring the surface distribution related to the bending state. Is done.

"Measurement Principle"
FIG. 2 is a diagram for explaining the measurement principle of the bending sensor according to the present embodiment. Hereinafter, the principle of measuring the degree of bending will be described with reference to FIG.

  FIG. 2 shows a state in which a thin film transistor formed on a plastic film changes electrical characteristics according to the curvature of the film. The thin film transistor is formed on the film surface. When the film surface is curved so as to have a convex shape with respect to the source / drain direction of the thin film transistor, the thin film transistor is subjected to tensile stress in the source / drain direction and suffers from an elongation strain. On the other hand, when the film surface is curved so as to be concave, the thin film transistor is subjected to compressive stress in the source / drain direction and suffers from shrinkage. The on-characteristics of the transistor change depending on the strain applied. In FIG. 2, the strain applied to the transistor is shown on the x-axis, and the change rate of the on-current at that time is shown on the y-axis. A triangular solid line indicates a characteristic change of the N-type thin film transistor, and a square broken line indicates a characteristic change of the P-type thin film transistor.

In an N-type thin film transistor, the on-current increases when the thin-film transistor receives a tensile stress in the source / drain direction, and the on-current decreases when the thin-film transistor receives a compressive stress. In contrast, in a P-type thin film transistor, the on-current decreases when the thin film transistor is subjected to a tensile stress in the source / drain direction, and the on-current increases when it receives a compressive stress. The increase / decrease amount of the on-current has a linear relationship with the distortion amount. Therefore, if the amount of change in on-current is detected when the film is bent, the amount of strain ε _T that the thin film transistor suffers at that time can be known. On the other hand, the following relational expression holds between the strain amount ε _T covered by the thin film transistor and the curvature radius R _F of the curved film.

ここで、ｄ_Tは薄膜トランジスター層の厚み、ｄ_Fはフィルムの厚み、Ｙ_Tは薄膜トランジスター層のヤング率、Ｙ_Fはフィルムのヤング率である。数式１を用いると、歪み量ε_Tが分かれば、その場に於けるフィルムの曲率半径Ｒ_Fが定まる。こうして面状に分布した第一薄膜トランジスターＴＮ１（ｉ，ｊ）のオン電流を調べれば、曲がり具合の面分布を計測出来る事になる。具体的には第一薄膜トランジスターＴＮ１（ｉ，ｊ）が配置された各点に於ける曲率半径Ｒ_Fijが定まる事になる。

Here, d _T is the thickness of the thin film transistor layer, d _F is the thickness of the film, Y _T is the Young's modulus of the thin film transistor layer, and Y _F is the Young's modulus of the film. Using Equation 1, if the amount of distortion ε _T is known, the curvature radius R _F of the film in the field can be determined. By examining the on-current of the first thin film transistor TN1 (i, j) distributed in a planar manner in this way, the surface distribution of the bending state can be measured. Specifically, the radius of curvature R _{Fij at} each point where the first thin film transistor TN1 (i, j) is arranged is determined.

  As shown in FIG. 2, since the amount of change with respect to the on-current distortion is small, in this embodiment, the reference transistor (second thin film transistor TN2) and the first thin film transistor TN1 (i, j) that do not receive bending stress. And the difference between the two is differentially amplified, and the amount of bending (the radius of curvature Rij) is measured.

"circuit"
FIG. 3 is a diagram for explaining a circuit of the bending sensor according to the present embodiment. Hereinafter, the circuit of the bending sensor will be described with reference to FIG.

  As shown in FIG. 1, the bending sensor 1 includes a detection circuit 3, an output circuit 4, a first selection circuit 51, a first processing circuit 52, a second selection circuit 61, and a second processing circuit 62. In the detection circuit 3, first thin film transistors TN1 (i, j) are arranged in a matrix of M rows and N columns. M and N are integers of 1 or more (1 ≦ i ≦ M, 1 ≦ j ≦ N). The first selection circuit 51 selects one specific row line from the M row lines R (i) in the first direction. Therefore, the first selection circuit 51 is also a row selection circuit. For the first selection circuit 51, a shift register or a decoder is used. The first processing circuit 52 processes the selection signal from the first selection circuit 51 so as to be suitable for measurement. Specifically, a level shifter for converting the selection potential and a buffer for selecting a row line stably at high speed are provided. The second selection circuit 61 selects one specific column line from the N column lines C (j) in the second direction. Therefore, the second selection circuit 61 is also a column selection circuit. For the second selection circuit 61, a shift register or a decoder is used. The second processing circuit 62 processes the selection signal from the second selection circuit 61 so as to be suitable for measurement. Specifically, a level shifter for converting the selection potential and a buffer for selecting the column line stably at high speed are provided.

Returning to FIG.
In addition, the second processing circuit 62 includes column selection transistors TN3 (j) and TN4 (j). The output circuit 4 amplifies the electrical state of the first thin film transistor TN1 (i, j) and outputs it as LDOUT and XLDOUT. Among these circuits, the detection circuit 3 and the output circuit 4, and the column selection transistors TN3 (j) and TN4 (j) in the second processing circuit 62 are formed of thin film transistors. In this embodiment, in addition to these, the first selection circuit 51, the first processing circuit 52, the second selection circuit 61, and the second processing circuit 62 are also formed of thin film transistors (N-type and P-type) having a CMOS configuration. However, circuits other than the column selection transistors TN3 (j) and TN4 (j) in the first selection circuit 51, the first processing circuit 52, the second selection circuit 61, and the second processing circuit 62 are external silicon IC chips. May be formed.

The first thin film transistor TN1 (i, j) and the second thin film transistor TN2 positioned in the i row and j column form a differential transistor pair and are arranged symmetrically with each other. That is, the drains of both transistors are connected to the first power source and are arranged in parallel with the power source. The first power source is a positive power source _Vdd . In addition, as for the source and drain of the N-type thin film transistor, the higher the potential becomes the drain, and the lower the potential becomes the source. In FIG. 3, the source and drain of each thin film transistor is indicated by s and d, respectively. The gate of the first thin film transistor TN1 (i, j) is connected to the row line R (i) of the i-th row, and a selection signal or a non-selection signal is supplied. The reference signal V _ref is supplied to the gate of the second thin film transistor TN2.

The bending sensor 1 further includes a fifth thin film transistor TN5 and a sixth thin film transistor TN6, and the fifth thin film transistor TN5 and the sixth thin film transistor TN6 form a current mirror pair. In the current mirror pair, the sources of both transistors are connected in common, and the same potential is applied to the gate, so that the drain potential of both transistors is somewhat _higher during saturation operation (V _ds > V _gs −V _th > 0). Even though they are different, they are transistor pairs that carry the same current.

The bending sensor 1 further includes a seventh thin film transistor TN7. The seventh thin film transistor TN7 is a current source transistor. A current source transistor is a transistor that performs a saturation operation and always supplies a constant current even if the drain potential slightly varies. The source of the fifth thin film transistor TN5 and the source of the sixth thin film transistor TN6 are connected to the drain of the seventh thin film transistor TN7, and the source of the seventh thin film transistor TN7 is connected to the second power source. The second power source is a negative power source V _ss . The first control signal Cnt1 is supplied to the gate of the seventh thin film transistor TN7. Since the fifth thin film transistor TN5 and the sixth thin film transistor TN6 always pass the same current and the seventh thin film transistor TN7 supplies a constant current, the fifth thin film transistor TN5 and the sixth thin film transistor TN6 always have the same current (the seventh Half of the current through the thin film transistor TN7).

  The third thin film transistor TN3 (j) and the fourth thin film transistor TN4 (j) located in the jth column are column selection transistors. That is, the third thin film transistor TN3 (j) is disposed between the first thin film transistor TN1 (i, j) and the fifth thin film transistor TN5, and the first thin film transistor TN1 (i, j) and the fifth thin film transistor TN5. Can be electrically connected. The source of the third thin film transistor TN3 (j) is connected to the drain of the fifth thin film transistor TN5, and the drain of the third thin film transistor TN3 (j) is connected to the source of the first thin film transistor TN1 (i, j). As a result, when a selection signal (high potential signal) enters the j-th column line C (j), the first thin film transistor TN1 (i, j) and the fifth thin film transistor TN5 are electrically connected. Conversely, when a non-selection signal (low potential signal) enters the column line C (j), the first thin film transistor TN1 (i, j) and the fifth thin film transistor TN5 are electrically insulated. Similarly, the fourth thin film transistor TN4 (j) is disposed between the second thin film transistor TN2 and the sixth thin film transistor TN6, and can electrically connect the second thin film transistor TN2 and the sixth thin film transistor TN6. . The source of the fourth thin film transistor TN4 (j) is connected to the drain of the sixth thin film transistor TN6, and the drain of the fourth thin film transistor TN4 (j) is connected to the source of the second thin film transistor TN2. As a result, when the selection signal (high potential signal) is input to the column line C (j), the second thin film transistor TN2 and the sixth thin film transistor TN6 are electrically connected. Further, when a non-selection signal (low potential signal) enters the column line C (j), the second thin film transistor TN2 and the sixth thin film transistor TN6 are electrically insulated. The selection signal or non-selection signal supplied to the column line C (j) level-shifts the output from the second selection circuit 61 as necessary, and the output from the level shifter is reinforced by a buffer. That is, the third thin film transistor TN3 and the fourth thin film transistor TN4 are controlled by the second selection circuit 61.

Detection result from the output circuit 4, the drain potential V ₆ of the sixth thin film transistor TN6 is output as LDOUT, drain potential V ₅ of the fifth thin film transistor TN5 is output as XLDOUT.

"Measurement method"
FIG. 4 is a diagram for explaining a timing chart for driving a circuit when the bending state is measured by the bending sensor according to the present embodiment. Hereinafter, a measurement method using a bending sensor will be described with reference to FIG.

First, prior to measurement, the potential value of V _ref at the time of measurement is determined. As described above, the bending sensor 1 includes the electrical characteristics of the second thin film transistor TN2 that is located in the non-flexible portion and serves as the reference transistor, and the electrical characteristics of the plurality of first thin film transistors TN1 (i, j) located in the flexible portion. By comparing the characteristics with each other, the degree of bending of the portion where the first thin film transistor TN1 (i, j) is located is detected. On the other hand, a thin film transistor generally has slightly different electrical characteristics for each transistor. In order to correct this, the value of V _ref is determined in order to cancel out the variation of each transistor arranged in the detection circuit 3. Specifically, the bending sensor 1 is installed on a flat surface so that the detection circuit 3 is flat. In this state, each first thin film transistor TN1 (i, j) is selected (the row line R (i) is set to the selection signal potential H ₁ and the column line C (j) is set to the selection signal potential H ₂ ), and the LDOUT output is output. And the value of V _ref for each first thin film transistor TN1 (i, j) are determined so that the output of XLDOUT becomes equal to the output of XLDOUT (V ₅ = V ₆ ). V _ref is a value close to the selection signal potential H ₁ supplied to the row line R (i). If the selection potential to be taken by V _ref when selecting the first thin film transistor TN1 (i, j) is H _rij , this is expressed by the following equation.

検出回路３が平坦時に、総ての第一薄膜トランジスターＴＮ１（ｉ，ｊ）に対してＶ₅＝Ｖ₆となる様にＨ_rij（又はθ_ij）を定め、まずこれを外部コントローラーに設けられて居る不揮発メモリーに記憶する。その後に検出回路３を対象物の表面に合わせ、表面の曲がり具合を計測する。

When the detection circuit 3 is flat, H _rij (or θ _ij ) is determined so that V ₅ = V ₆ for all the first thin film transistors TN1 (i, j). Store it in non-volatile memory. Thereafter, the detection circuit 3 is aligned with the surface of the object, and the degree of bending of the surface is measured.

  At the time of measurement, an external controller supplies appropriate signals and power to the first selection circuit 51, the first processing circuit 52, the second selection circuit 61, the second processing circuit 62, and the like. As a result, the following signals shown in FIG. 4 are supplied to each row line, column line, and output circuit 4.

Row lines R (1) to R (M) are alternately selected one by one. Normally, selection is made in order from the first row line R (1) to the Mth row line R (M) of the last row. A selection signal potential (high potential) H ₁ is selectively supplied to the row line, and a non-selection signal potential (low potential) L is supplied when not selected. The non-selection signal potential L is a potential close to the negative power supply potential V _ss or V _ss and is clearly lower than the high potential. For example, L = V _ss = 0V (ground potential). The selection signal potential is, for example, H ₁ = 5.4V.

In a period in which one row line is selected, column lines (C (1) to C (N)) are alternately selected one by one. Normally, the selection is made in order from the first column line C (1) to the Nth column line C (N) of the last column. A selection signal potential (high potential) H ₂ is selectively supplied to the column line, and a non-selection signal potential (low potential) L is supplied when not selected. The non-selection signal potential L is a potential close to the negative power supply potential V _ss or V _ss and is clearly lower than the high potential. For example, L = V _ss = 0V (ground potential). The selection signal potential is, for example, H ₂ = 7.0V.

In this way, a specific one is selected from the plurality of first thin film transistors TN1 (i, j). At that time, a selection potential H _rij suitable for the selected first thin film transistor TN1 (i, j) is read from the nonvolatile memory and set to V _ref . Selection potential H _rij first TFT TN1 (i, j) so is set as the output voltage if the flat is V ₅ = V _6, V ₅ to the reading the value of V _6, selected It can be seen how the first thin film transistor TN1 (i, j) is bent. For example, if the selected portion is bent in a convex shape, the potential of LDOUT (V ₆ ) is lowered and the potential of XLDOUT (V ₅ ) is raised, so that the value of V ₅ -V ₆ becomes positive. On the other hand, if the selected portion is bent in a concave shape, the potential of LDOUT (V ₆ ) becomes high and the potential of XLDOUT (V ₅ ) becomes low, so the value of V ₅ -V ₆ becomes negative.

"how to use"
When using the bending sensor, a preparation period and a measurement period may be provided. The preparation period is a period in which measurement is repeated at a low frequency in preparation for the measurement period. During the measurement period, the bending sensor repeats measurement with high frequency. For example, when wearing a bending sensor and using it as a motion capture to analyze a specific motion (for example, baseball swing), it is a preparation period until the motion to be analyzed (swing) starts, and the motion to be analyzed is performed. The measured period is the measurement period. Alternatively, when the bending sensor is applied to a display device having image storage characteristics (for example, an electronic book having an electrophoretic display or a cholesteric liquid crystal display), the image storage period is set as a preparation period, and the measurement is performed immediately before the image rewriting period. Period.

  The bend sensor performs a measurement operation in the preparation period and the measurement period by the method described in the section “Measurement Method” above, but the measurement frequency is different. In the preparation period, the number of measurements performed within a unit time is small, and this is large in the measurement period. A period in which all the measurement cells arranged in M rows and N columns (TN1 (i, j) are arranged in the measurement cells in i row and j column) are selected as a frame period, and one frame is measured. When the time from one period to the next frame period is the standby period, the measurement frequency is the reciprocal of the sum of the frame period and the standby period (1 / (frame period + standby period)). That is, the measurement frequency in the measurement period is made larger than the measurement frequency in the preparation period. As an example, in the measurement period, the standby period is set to zero, and the frame frequency (reciprocal of the frame period) and the measurement frequency are matched. On the other hand, the standby period in the preparation period is a relatively long time of several milliseconds or more (for example, 1 second), and the measurement frequency in the preparation period is made to substantially coincide with the reciprocal of the standby period.

  By providing such a preparation period and a measurement period, power consumption can be reduced during the preparation period, and time resolution can be maximized during the measurement period. Here, the frame period is the same in both the preparation period and the measurement period, and the standby period is changed. However, the present invention is not limited to this, and the frame period may be changed between the preparation period and the measurement period. That is, the measurement frequency in the measurement period may be increased by setting the clock frequency in the measurement period higher than the clock frequency in the preparation period.

"Transistor size and driving conditions"
Next, referring to FIG. 3, conditions for realizing high-sensitivity and high-performance measurement will be described. Hereinafter, the first thin film transistor TN1 (i, j) is abbreviated as TN1. Similarly, the second thin film transistor TN2 to the seventh thin film transistor TN7 are also abbreviated. H _rij and θ _ij are also abbreviated as H _r and θ. Note that represents a drain potential of TN3 at V _3, represented by _7, V the drain potential of V _4, TN7 the drain potential of TN4.

Since TN1 and TN2 are differential input pairs, nonlinear operation such as saturation operation is desirable. TN3 and TN4 are column selection transistors, and linear operation is desirable from the viewpoint of widening the output potential range. Therefore, for TN3 and TN4, V _ds is as small as possible, V ₃ ? V ₅ and V _4? V ₆ is desirable. TN5 and TN6 must be in saturation with the current mirror pair. Further, since TN7 is a current source transistor, it must be operated in an arrow-saturated manner.

  First, the symbol of Equation 3 is used to express the current equation of the transistor.

ここでＷはトランジスターチャンネル形成領域の幅、Ｌはトランジスターチャンネル形成領域の長さ、Ｃ_oxは単位面積当たりのゲート絶縁膜容量、μは移動度である。すると、飽和特性の近似式は数式４で表される。

Here, W is the width of the transistor channel formation region, L is the length of the transistor channel formation region, C _ox is the gate insulating film capacitance per unit area, and μ is the mobility. Then, the approximate expression of the saturation characteristic is expressed by Expression 4.

又、線型特性の近似式は数式５で表される。

Further, the approximate expression of the linear characteristic is expressed by Expression 5.

本実施形態では薄膜トランジスターのしきい値電圧をＶ_thで表し、薄膜トランジスター間のＶ_th変動は僅かであると近似する。即ち、ＴＮ１からＴＮ７のＶ_thは総て等しいと近似する。又、Ｖ_thは正であるとし、全体の電流（ＴＮ７の電流）を２Ｉとする。まず、ＴＮ１からＴＮ７のＺをＺ₁からＺ₇で表し、これらを数式６の関係とする。

In this embodiment, the threshold voltage of the thin film transistor is represented by V _th , and it is approximated that the V _th variation between the thin film transistors is slight. That is, it is approximated that V _{th of} TN1 to TN7 are all equal. Further, it is assumed that V _th is positive, and the entire current (current of TN7) is 2I. First, represent the Z from TN1 TN7 from Z ₁ in Z _7, these are the relationship in Equation 6.

数式６が満たされていると、曲げによるＴＮ１の電流変化をゲート電位の変化と見なした際に、ＴＮ１の見なしゲート電位とＶ_refとの差は線型増幅されて出力される。以下、各トランジスターに求められる駆動条件を検討する。

When Expression 6 is satisfied, when a change in the current of TN1 due to bending is regarded as a change in the gate potential, the difference between the assumed gate potential of TN1 and _Vref is linearly amplified and output. Hereinafter, driving conditions required for each transistor will be examined.

  (1) TN1 is preferably saturated. Therefore, it is desirable that the saturation conditions represented by Expression 7 and Expression 8 are satisfied.

その結果、ＴＮ１のドレイン電流は次式となる。

As a result, the drain current of TN1 is given by

  (2) Saturation operation is desirable for TN2. Therefore, it is desirable that the saturation condition represented by Expression 10 and Expression 11 is satisfied.

その結果、ＴＮ２のドレイン電流は次式となる。

As a result, the drain current of TN2 is as follows.

  (3) TN3 is preferably linear. Therefore, it is desirable that the linear condition expressed by Equation 13 is satisfied.

その結果、ＴＮ３のドレイン電流は次式となる。

As a result, the drain current of TN3 is as follows.

  (4) TN4 is preferably linear. Therefore, it is desirable that the linear condition expressed by Equation 15 is satisfied.

その結果、ＴＮ４のドレイン電流は次式となる。

As a result, the drain current of TN4 is given by

  (5) It is desirable that TN5 operates in saturation. Therefore, it is desirable that the saturation condition expressed by Equation 17 is satisfied.

その結果、ＴＮ５のドレイン電流は次式となる。

As a result, the drain current of TN5 is as follows.

  (6) It is desirable that TN6 operates in saturation. Therefore, it is desirable that the saturation condition expressed by Equation 19 and Equation 20 is satisfied.

その結果、ＴＮ６のドレイン電流は次式となる。

As a result, the drain current of TN6 is as follows.

  (7) It is desirable for TN7 to perform a saturation operation. Therefore, it is desirable that the saturation condition expressed by Equation 22 be satisfied.

その結果、ＴＮ７のドレイン電流は次式となる。

As a result, the drain current of TN7 is as follows.

ここで、数式２２を満たす為に、数式２４とする。

Here, in order to satisfy Expression 22, Expression 24 is used.

δは例えば０．１Ｖ程度で、容易に飽和条件を満たすには１Ｖ程度未満が理想である。

For example, δ is about 0.1 V, and ideally less than about 1 V in order to easily satisfy the saturation condition.

  Next, in order to satisfy Expressions 13 and 15, Expression 25 is used.

これにより、少なくとも数式２６と数式２７とが満たされる様になる。

As a result, at least Expressions 26 and 27 are satisfied.

  From Equation 23 relating to TN7 and Equation 16 relating to TN4, the following equation is obtained.

この数式２８に数式２４と数式２５とを適応すると、次の様になる。

Applying Equation 24 and Equation 25 to Equation 28 yields the following.

数式２９の右辺に関しては、数式３０を考慮する。

For the right side of Equation 29, Equation 30 is considered.

ここで数式３１とする。

Here, Equation 31 is used.

こうすれば、数式３２が得られる。

In this way, Expression 32 is obtained.

即ち、ＴＮ４はゲート電圧がＶ_th＋１Ｖ以上ならば、線型動作する。更に、ＴＮ４での電位降下を確実に０．１Ｖ未満と小さくし、ＴＮ４を線型動作させる為には、概ね次式が満たされれば良い。

That is, TN4 operates linearly when the gate voltage is V _th + 1V or higher. Furthermore, in order to reliably reduce the potential drop at TN4 to less than 0.1 V and to operate TN4 in a linear manner, the following expression should be satisfied.

数式３３は数式３４と変形される。

Equation 33 is transformed to Equation 34.

この場合、数式３５の関係が得られる。

In this case, the relationship of Formula 35 is obtained.

即ち、明らかに線型条件（数式１５）は満たされる。

That is, the linear condition (Formula 15) is clearly satisfied.

  Next, the configuration is determined to satisfy all desirable conditions. Equation (36) is obtained for Equation (23) relating to TN7 and Equation (21) relating to TN6.

こうすると、数式２１と数式２３とから数式３７が得られる。

In this way, Expression 37 is obtained from Expression 21 and Expression 23.

  Next, Equation 38 is given to Equation 9 relating to TN1 and Equation 18 relating to TN5.

こうすると、数式３９が得られる。

In this way, Equation 39 is obtained.

ＴＮ７とＴＮ４の議論（数式２８から数式３５までの議論）により、数式４０と数式４１で表される関係になっている。

Based on the discussion of TN7 and TN4 (discussions from Equation 28 to Equation 35), the relationship is expressed by Equation 40 and Equation 41.

数式３９に数式４１を代入し、数式３７と連立させると、数式４２と数式４３の解が得られる。

By substituting Equation 41 into Equation 39 and simultaneously with Equation 37, the solutions of Equation 42 and Equation 43 are obtained.

  From Equation 12 regarding TN2 and Equation 21 regarding TN6, Equation 44 is obtained.

数式４４に数式３７と数式４０とを代入すると、数式４５が得られる。

Substituting Equation 37 and Equation 40 into Equation 44 yields Equation 45.

  The following shows how to satisfy each of the conditions that should be satisfied in order to realize high-sensitivity and high-performance measurement.

  Equation 7 as a preferred condition: Equation 7 is obtained from Equation 41 and Equation 42.

  Formula 10 as a suitable condition: Formula 10 is expressed by Formula 46 from Formula 40 and Formula 44.

Formula 8 as a preferred condition: Formula V is positively satisfied if Formula 47 holds because V _th is positive.

Formula 11 as a preferred condition: Formula 11 is positively satisfied if Formula 48 holds because V _th is positive.

  Formula 13 and Formula 15 as preferred conditions: Formula 13 and Formula 15 are satisfied by Formula 24 and Formula 34.

  Formula 17 as a preferred condition: Formula 17 is expressed by Formula 46 from Formula 42 and Formula 43.

  Formula 19 as a preferred condition: Formula 19 is expressed by Formula 49 from Formula 42 and Formula 45.

ここで、数式５０とする。

Here, Formula 50 is assumed.

こうすると、好適条件としての数式１９は、数式５１と記載し直される。

In this way, Equation 19 as the preferred condition is rewritten as Equation 51.

  Formula 22 as a preferred condition: Formula 24 to Formula 22 are expressed as Formula 52.

これに数式４３を適応すると、数式２２は、数式５３となる。

When Formula 43 is applied to this, Formula 22 becomes Formula 53.

数式２４により、これは、数式５４を意味する。

By equation 24 this means equation 54.

  Now, the relationship of Equation 55 is assumed.

すると、数式４３と数式４２とから、数式５６が得られる。

Then, the mathematical formula 56 is obtained from the mathematical formula 43 and the mathematical formula 42.

即ち、ＴＮ１とＴＮ５、ＴＮ７にはほぼ均等なドレイン電圧が印可される。同様にＴＮ２、ＴＮ６、ＴＮ７にもほぼ均等なドレイン電圧が掛かる。尚、この際に数式２４と数式５５とにより、数式５７の関係となる。

That is, substantially equal drain voltages are applied to TN1, TN5, and TN7. Similarly, substantially equal drain voltages are applied to TN2, TN6, and TN7. At this time, the relation of Expression 57 is established by Expression 24 and Expression 55.

In summary, the potential relationship is such that the formula 55, the formula 24, the formula 25, the formula 57, the formula 50, and the formula 51 are satisfied. As an example, V _th = 1.5V, δ = 0.3V, γ = 0.1V, V _dd = 5.4V, H ₁ = 5.4V, H ₂ = 7V, H ₃ = 1.8V , H _r = 5.4 ± θV, and 0 ≦ θ <1.5V.

  Regarding the transistor size, Expression 6 and Expression 34, Expression 36, Expression 38 to Expression 58 are used.

この様な電気関係とトランジスターサイズとを採用する事で、高感度で正確な計測が実現する。

By adopting such electrical relationship and transistor size, highly sensitive and accurate measurement is realized.

"Planar layout"
FIG. 5 is a diagram for explaining a planar layout of the detection circuit of the bending sensor according to the present embodiment. Hereinafter, the planar layout of the detection circuit will be described with reference to FIG.

  In the detection circuit 3, TN1 (i, j) are arranged in a matrix. The source s of TN1 (i, j) located in i row and j column is connected to the first column line CL (j) of the j column, and the drain d is connected to the second column line CR (j) of the j column. The gate G is connected to the i-th row line R (i). The first column line CL (j) and the second column line CR (j) of the j-th column are wired in parallel in the first direction, and each of TN3 (j) (see FIG. 3) is outside the detection circuit 3. Connected to the drain and Vdd (see FIG. 3). The i-th row line R (i) is wired in parallel in the second direction, and is connected to the first processing circuit 52 (see FIG. 1) outside the detection circuit 3.

  The channel formation region of TN1 (i, j) is arranged in parallel to the first column line CL (j) and the second column line CR (j). That is, the source / drain direction of TN1 (i, j) is parallel to the first column line CL (j) and the second column line CR (j). Between the first thin film transistors adjacent in the second direction (y-axis direction), a linear cut 31 along the first direction (x-axis direction) enters the substrate 2. In other words, the cut 31 and the source / drain direction of TN1 (i, j) are parallel. The bending sensor 1 detects the degree of bending with respect to the first direction. The electrical characteristics of the thin film transistor are affected both when it is bent parallel to the source / drain direction and when it is bent perpendicularly to the source / drain direction. In FIG. 5, since the linear cut line 31 is provided along the first direction, the first thin film transistor is not subjected to the bending stress from the second direction and mainly receives the bending stress from the first direction. receive. For this reason, there is no interference of bending stress from the second direction, and highly accurate measurement is possible.

  In FIG. 5, the cut line 31 draws a gentle curve, but the shape is not limited as long as the adjacent first thin film transistors are mechanically separated from each other, and the straight line may be a straight line. Alternatively, the cut line 31 may have a plurality of holes opened along the first direction.

“Cross-section of fixed plate”
FIG. 6 is a diagram for explaining a part of a cross section of the bending sensor according to the present embodiment. FIG. 7 is a diagram for explaining the relationship between the thickness of the fixing plate and the distance in the flexible region. Further, FIG. 8 is a diagram for explaining the relationship between the deflection of the fixing plate and the distance in the flexible region. Here, the cross-sectional shape of the fixing plate in the flexible region will be described with reference to FIGS. 6, 7, and 8.

  6 is a cross-sectional view taken along the line A-A 'of FIG. In the bending sensor 1, the back surface of the substrate 2 is fixed by a fixing plate 7 in a non-flexible region 21. The fixing plate 7 is made of a strong plastic having a good appearance such as an ABS resin (copolymer synthetic resin of acrylonitrile, butadiene, and styrene) and is hardly bent. On the other hand, the substrate 2 is a polyester film having a thickness of 100 micrometers and is highly flexible. Circuits and wirings are formed by thin film transistors on the surface of the substrate 2, but there is a slight possibility that these are destroyed at the boundary between the flexible region 22 and the non-flexible region 21. In order to avoid this completely (almost 100%), the fixing plate 7 is formed so as to protrude into the flexible region 22, and its thickness is gradually reduced in the flexible region 22. By doing so, the reliability of the circuit and wiring is remarkably increased. The following will discuss how the shape of the fixed plate 7 can be realized to realize a highly reliable bending sensor 1.

As shown in FIG. 6, the fixed plate 7 in the flexible region 22 has a cross-sectional width that widens from the lower side to the upper side, and the width is maximized on the upper surface of the fixed plate 7. That is, with respect to the x-axis direction, the thickness of the fixed plate 7 in the flexible region 22 is the origin O (the fixed plate 7 begins to decrease in thickness at the boundary between the flexible region 22 and the non-flexible region 21). It becomes thinner as you move away from the position. Hereinafter, what kind of function is preferable when the thickness t (x) of the fixing plate 7 in the flexible region 22 is expressed as a function of the distance x from the origin O will be described. That is, as a preferred example, a form in which the thickness is expressed by a linear expression of a distance, a form expressed by a square root, and a form expressed by a cubic root are shown. When the width W _H of the fixing plate 7 in the flexible region 22 is the same, it can withstand the strongest load and the most flexible is the form of the primary formula, and stress is applied in the flexible region 22. It is shown that the shape of the square root is uniformly received by the entire fixed plate 7, the shape of the cubic root is the same in the entire fixed plate 7 in the flexible region 22, and the like.

(Preferred Example 1) Form in which thickness is expressed by linear expression of distance In the first specific example, the thickness t (x) of the fixing plate 7 in the flexible region 22 has a linear relationship with respect to the distance x. Yes, it is described by Equation 59.

ここでＷ_Hは可撓領域２２に於ける固定板７の幅であり、αは傾斜パラメーター、可撓領域２２に於ける固定板７の厚さは原点Ｏ（ｘ＝０）にてｔ₀であり、先端（エッジ、ｘ＝Ｗ_H）にてｔ_E＝αｔ₀である。図７には実線Ｌにて数式５９にて表される距離（ｘ／Ｗ_H）と厚み（ｔ（ｘ）／ｔ₀）との関係を、α＝０．２として描いてある。可撓領域２２に於いて、固定板７の厚みが距離の一次関数で表され、原点から離れるに従って線型に薄くなっているのが分かる。

Here, W _H is the width of the fixed plate 7 in the flexible region 22, α is the inclination parameter, and the thickness of the fixed plate 7 in the flexible region 22 is t ₀ at the origin O (x = 0). And t _E = αt ₀ at the tip (edge, x = W _H ). In FIG. 7, the relationship between the distance (x / W _H ) and the thickness (t (x) / t ₀ ) represented by the mathematical formula 59 with a solid line L is depicted as α = 0.2. In the flexible region 22, it can be seen that the thickness of the fixed plate 7 is expressed by a linear function of the distance, and becomes thinner linearly as the distance from the origin is increased.

  When the load F is applied to the fixed plate 7 in the flexible region 22 perpendicularly (parallel to the z-axis), it is approximated that the load is concentrated on the tip, and is derived from the moment balance. The equation is Equation 60.

尚、ここでＲは可撓領域２２に於ける固定板７がたわんだ際の曲率半径、ｚは可撓領域２２に於ける固定板７のｚ方向へのたわみ量、Ｅは固定板７のヤング率、Ｌ_Hは固定板７の長さである。数式６０に対する境界条件は、数式６１である。

Here, R is a radius of curvature when the fixing plate 7 bends in the flexible region 22, z is a deflection amount in the z direction of the fixing plate 7 in the flexible region 22, and E is the amount of bending of the fixing plate 7. The Young's modulus, L _H is the length of the fixed plate 7. The boundary condition for Equation 60 is Equation 61.

数式６０を数式６１の元に解くと、数式６２の解が得られる。

Solving Equation 60 based on Equation 61 yields the solution of Equation 62.

これが可撓領域２２に於ける固定板７に荷重Ｆが垂直に加えられた際の、距離（ｘ）とたわみ（ｚ（ｘ））との関係である。図８にこの関係を、α＝０．２として、縦軸を規格化されたたわみ量（ｚ（ｘ）／（ＦＷ_H ³／（ＥＬ_Hｔ₀ ³）））で、横軸を規格化された距離（ｘ／Ｗ_H）として、実線Ｌにて描いてある。荷重Ｆに対し、可撓領域２２に於ける固定板７が優れた柔軟性を有している事が判る。可撓領域２２に於ける固定板７の端部に於けるたわみｚ_Eは、数式６２でｘ＝Ｗ_Hと置いて、数式６３となる。

This is the relationship between the distance (x) and the deflection (z (x)) when the load F is vertically applied to the fixed plate 7 in the flexible region 22. FIG. 8 shows this relationship, with α = 0.2, the vertical axis is normalized deflection (z (x) / (FW _H ³ / (EL _H t ₀ ³ ))), and the horizontal axis is normalized. The drawn distance (x / W _H ) is depicted by a solid line L. It can be seen that the fixing plate 7 in the flexible region 22 has excellent flexibility with respect to the load F. Bending z _E is at the end of the in the fixing plate 7 in the flexible area 22, at the x = W _H in the formula 62, the formula 63.

又、可撓領域２２に於ける固定板７の上での曲げ応力σは、固定板７の歪みをεとして、数式６４で表される。

Further, the bending stress σ on the fixed plate 7 in the flexible region 22 is expressed by Expression 64, where ε is the strain of the fixed plate 7.

この式から曲げ応力が最大となるのは、ｘ＝（１−２α）／（１−α）・Ｗ_Hで、０≦α＜０．５の時に、数式６５となる。

From this equation, the maximum bending stress is x = (1-2α) / (1-α) · W _H , and Equation 65 is obtained when 0 ≦ α <0.5.

可撓領域２２に於ける固定板７をなす材料の曲げ強さ（国際標準化機構のＩＳＯ１７８が定め、三点曲げ試験から得られる曲げ強さ）をσ_bとすると、σ_Maxがσ_bよりも小さくなる条件（数式６６）を満たしている限り、可撓領域２２に於ける固定板７は破断しない。

Assuming that the bending strength of the material forming the fixing plate 7 in the flexible region 22 (the bending strength obtained from the three-point bending test defined by ISO 178 of the International Organization for Standardization) is σ _b , σ _Max is greater than σ _b As long as the condition for decreasing (Equation 66) is satisfied, the fixing plate 7 in the flexible region 22 does not break.

従って、可撓領域２２に於ける固定板７は、使用時に想定される荷重の線密度（Ｆ／Ｌ_H）と可撓領域２２に於ける固定板７の曲げ強さσ_bとを元に、数式６６を満たす様に幅Ｗ_Hや原点Ｏに於ける厚みｔ₀、傾斜パラメーターαを定める。或いは、使用時に想定される最もきつい曲率半径をＲ（Ｍ）_inとし、それが曲げ応力の最大になる場所での曲率半径に一致しても可撓領域２２に於ける固定板７が破断しない条件とする。曲げ応力が最大になる場所での可撓領域２２に於ける固定板７の厚みをｔ_Mとして、σ_Maxがσ_bよりも小さくなる条件は、数式６７である。

Therefore, the fixing plate 7 in the flexible region 22 is based on the linear density (F / L _H ) of the load assumed at the time of use and the bending strength σ _b of the fixing plate 7 in the flexible region 22. The width _WH , the thickness t _{0 at} the origin O, and the inclination parameter α are determined so as to satisfy Formula 66. Alternatively, even if the hardest radius of curvature assumed at the time of use is R (M) _in and matches the radius of curvature at the place where the bending stress is maximum, the fixing plate 7 in the flexible region 22 does not break. Condition. The condition for σ _Max to be smaller than σ _b, where t _M is the thickness of the fixed plate 7 in the flexible region 22 at the place where the bending stress is maximized, is Equation 67.

従って、数式６７を満たす様に厚みｔ₀と傾斜パラメーターαとを定める。即ち、可撓領域２２に於ける固定板７の先端での厚みｔ_E＝αｔ₀を、数式６７を満たす様にすると、使用時に可撓領域２２に於ける固定板７が破断することはない。本実施形態では、可撓領域２２に於ける固定板７はＡＢＳ樹脂からなり、そのヤング率はＥ＝２０００ＭＰで、曲げ強さはσ_b＝５０ＭＰａである。使用時に想定される最もきつい曲率半径は１０ｍｍであるので、先端での厚みは、数式６７に従って、０．２５ｍｍ未満でなければならない。実際には、ｔ₀＝１ｍｍでα＝０．２、先端部の厚みは０．２ｍｍ、Ｗ_H＝５ｍｍであったので、数式９を満たしているにのみならず、曲率半径を８ｍｍに小さくされるまで可撓領域２２に於ける固定板７は破断しない様にされている。尚、可撓領域２２を強く屈曲させて、その結果として可撓領域２２に於ける固定板７がたわみ、可撓領域２２に於ける固定板７での最小曲率半径が８ｍｍ未満になった際に破断が生ずる恐れのある位置はおおよそ、ｘ＝０．８８９Ｗ_Hである。

Therefore, the thickness t ₀ and the inclination parameter α are determined so as to satisfy Expression 67. That is, if the thickness t _E = αt ₀ at the tip of the fixing plate 7 in the flexible region 22 is set so as to satisfy Expression 67, the fixing plate 7 in the flexible region 22 will not break during use. . In the present embodiment, the fixing plate 7 in the flexible region 22 is made of ABS resin, the Young's modulus is E = 2000 MP, and the bending strength is σ _b = 50 MPa. Since the tightest radius of curvature assumed during use is 10 mm, the thickness at the tip should be less than 0.25 mm according to Equation 67. Actually, since t ₀ = 1 mm, α = 0.2, the tip thickness was 0.2 mm, and W _H = 5 mm, not only the expression 9 was satisfied, but also the curvature radius was reduced to 8 mm. The fixing plate 7 in the flexible region 22 is not broken until it is done. When the flexible region 22 is strongly bent, as a result, the fixing plate 7 in the flexible region 22 bends and the minimum radius of curvature at the fixing plate 7 in the flexible region 22 becomes less than 8 mm. The position where breakage may occur is approximately x = 0.889 _WH .

When 0.5 ≦ α <1, the bending stress is maximized at x = 0, and the value σ _Max and the curvature radius R ₀ are expressed by Formula 68, respectively.

使用時に想定される最も厳しい荷重線密度（Ｆ／Ｌ_H）や最もきつい曲率半径をＲ（Ｍ）_inに対して、数式６９を満たす様にＷ_Hやｔ₀を定める。

W _H and t ₀ are determined so that the most severe load line density (F / L _H ) and the tightest radius of curvature assumed at the time of use are satisfied with respect to R (M) _{in so as} to satisfy Expression 69.

例えば先と同じＡＢＳ樹脂で可撓領域２２に於ける固定板７を作成し、同じ最小曲率半径を想定すると、数式１１に則り、ｔ₀＜０．５ｍｍとする。

For example, if the fixed plate 7 in the flexible region 22 is made of the same ABS resin as before, and the same minimum curvature radius is assumed, t ₀ <0.5 mm is satisfied according to Equation 11.

(Preferred example 2) Form in which the thickness is expressed by the square root of the distance In the second specific example, the thickness t (x) of the fixing plate 7 in the flexible region 22 has a square root relationship with respect to the distance x. Yes, expressed as Equation 70.

図７には点線ＳＲにて数式１２にて表される距離（ｘ／Ｗ_H）と厚み（ｔ（ｘ）／ｔ₀）との関係を描いてある。固定板７の厚みが距離の平方根に比例して薄くなり、取り分け、先端（ｘ＝Ｗ_H）付近で急にではあるが、なめらかに薄くなっているのが分かる。

FIG. 7 shows the relationship between the distance (x / W _H ) and the thickness (t (x) / t ₀ ) represented by Equation 12 with a dotted line SR. It can be seen that the thickness of the fixing plate 7 is reduced in proportion to the square root of the distance, and in particular, it is abruptly thinned near the tip (x = W _H ).

  When the load F is applied to the fixed plate 7 in the flexible region 22 perpendicularly (parallel to the z-axis), it is approximated that the load is concentrated on the tip, and is derived from the moment balance. The equation is Equation 71.

境界条件は具体例１と同じで、数式６１にて与えられる。数式７１を数式６１の元に解くと、数式７２の解が得られる。

The boundary condition is the same as in the first specific example and is given by the mathematical formula 61. When Formula 71 is solved based on Formula 61, a solution of Formula 72 is obtained.

これが可撓領域２２に於ける固定板７に荷重Ｆが垂直に加えられた際の、距離（ｘ）とたわみ（ｚ（ｘ））との関係で、図８にこの関係を点線ＳＲにて描いてある。荷重Ｆに対し、可撓領域２２に於ける固定板７が柔軟性を有している事が判る。可撓領域２２に於ける固定板７の端部に於けるたわみｚ_Eは、数式７３で表される。

This is the relationship between the distance (x) and the deflection (z (x)) when the load F is vertically applied to the fixed plate 7 in the flexible region 22, and this relationship is shown by the dotted line SR in FIG. It is drawn. It can be seen that the fixing plate 7 in the flexible region 22 has flexibility with respect to the load F. The deflection z _E at the end of the fixed plate 7 in the flexible region 22 is expressed by Equation 73.

又、可撓領域２２に於ける固定板７の上での曲げ応力σは数式７４となる。

Further, the bending stress σ on the fixed plate 7 in the flexible region 22 is expressed by Equation 74.

曲げ応力は可撓領域２２に於ける固定板７の幅方向で均一となる。即ち、幅方向の特定の位置で破断し易い様な事はなくなる。曲げセンサー１の使用時に可撓領域２２を屈曲させると、可撓領域２２の屈曲に伴う応力が発生し、その応力の一部を可撓領域２２に於ける固定板７が曲げ応力として受け持つことになるが、それが可撓領域２２に於ける固定板７上で均一になる。換言すれば、可撓領域２２に於ける固定板７の特定箇所に応力が集中する事がなくなるので、その意味から曲げセンサー１の機械的耐久性が向上することになる。可撓領域２２に於ける固定板７が曲げ応力で破断されない条件は、数式７５である。

The bending stress is uniform in the width direction of the fixing plate 7 in the flexible region 22. That is, it is not easy to break at a specific position in the width direction. If the flexible region 22 is bent when the bending sensor 1 is used, a stress accompanying the bending of the flexible region 22 is generated, and a part of the stress is handled by the fixing plate 7 in the flexible region 22 as a bending stress. However, it becomes uniform on the fixing plate 7 in the flexible region 22. In other words, stress does not concentrate on a specific portion of the fixing plate 7 in the flexible region 22, so that the mechanical durability of the bending sensor 1 is improved in that sense. The condition that the fixing plate 7 in the flexible region 22 is not broken by the bending stress is Expression 75.

使用時に想定される最も厳しい荷重線密度（Ｆ／Ｌ_H）に対して、数式７５を満たす様にｔ₀やＷ_Hを定める。厚みが距離に対して平方根の関係にある場合、最も曲がりにくい点はｘ＝０であるから、ｘ＝０に於ける曲率半径Ｒ₀を用いて、Ｒ₀＝Ｒ（Ｍ）_inとされた時に、ｘ＝０に於ける曲げ応力σ₀が曲げ強さσ_bよりも小さく、数式７６を満たせば、曲げセンサー１が屈曲されても可撓領域２２に於ける固定板７は破断しない。

T ₀ and W _H are determined so as to satisfy Expression 75 with respect to the most severe load line density (F / L _H ) assumed at the time of use. When the thickness has a square root relationship with respect to the distance, the most difficult point to bend is x = 0. Therefore, using the radius of curvature R ₀ at x = 0, R ₀ = R (M) _in . Sometimes, if the bending stress σ ₀ at x = 0 is smaller than the bending strength σ _b and satisfies the mathematical expression 76, the fixing plate 7 in the flexible region 22 does not break even if the bending sensor 1 is bent.

即ち、使用時に想定される最もきつい曲率半径Ｒ（Ｍ）_inに対して、数式７６を満たす様にｔ₀を定める。例えば先と同じＡＢＳ樹脂で可撓領域２２に於ける固定板７を作成し、同じ最小曲率半径を想定すると、数式７６に則り、ｔ₀＜０．５ｍｍとすれば、使用時に可撓領域２２に於ける固定板７が破断する恐れはない。この場合、非可撓領域２１に於ける固定板７は１ｍｍ以上の厚みを持たせ、原点Ｏで階段状に厚みを減じてｔ₀とし、非可撓領域２１では固定板７の厚みをｔ₀から距離の平方根に比例して薄くして行く。

That is, t ₀ is determined so as to satisfy Expression 76 with respect to the tightest radius of curvature R (M) _in assumed at the time of use. For example, if the fixing plate 7 in the flexible region 22 is made of the same ABS resin as described above and the same minimum curvature radius is assumed, the flexible region 22 can be used at the time of use if t ₀ <0.5 mm in accordance with Equation 76. There is no fear that the fixing plate 7 in the case breaks. In this case, the fixing plate 7 in the non-flexible region 21 has a thickness of 1 mm or more, and the thickness is reduced to t ₀ in a step shape at the origin O. In the non-flexible region 21, the thickness of the fixing plate 7 is set to t. Decrease in proportion to the square root of the distance from ₀ .

  It should be noted that when the fixing plate 7 in the flexible region 22 is made of plastic, it is difficult to accurately process the thickness into the relationship of the square root expressed by Formula 70. In this case, it can be approximated by the linear relationship shown in the first preferred embodiment. That is, Formula 77 is used.

一例として、α＝０．３９５とした際のたわみを図８の実線Ｌ２にて描く。実線Ｌ２と点線ＳＲとが良く一致している事が判る。この線型近似で、曲げ応力は可撓領域２２に於ける固定板７の幅方向でほぼ均一となり、厚みが線型関係の時の効果に加え、平方根の時と同様な効果が期待でき、更に製造加工も容易になる。

As an example, the deflection when α = 0.395 is drawn by a solid line L2 in FIG. It can be seen that the solid line L2 and the dotted line SR are in good agreement. With this linear approximation, the bending stress becomes substantially uniform in the width direction of the fixed plate 7 in the flexible region 22, and in addition to the effect when the thickness is linear, the same effect as when the square root can be expected, and further manufacturing Processing is also easy.

(Preferred example 3) Form in which thickness is expressed by cube root of distance In the third specific example, the thickness t (x) of the fixing plate 7 in the flexible region 22 has a cubic root relationship with respect to the distance x. Yes, it is described as Formula 78.

図７には一点鎖線ＣＲにて数式７８にて表される距離（ｘ／Ｗ_H）と厚み（ｔ（ｘ）／ｔ₀）との関係を描いてある。固定板７の厚みが距離の立方根に比例して薄くなり、取り分け、先端（ｘ＝Ｗ_H）付近で急にではあるが、なめらかに薄くなっているのが分かる。

FIG. 7 shows the relationship between the distance (x / W _H ) and the thickness (t (x) / t ₀ ) represented by the mathematical expression 78 with a one-dot chain line CR. It can be seen that the thickness of the fixing plate 7 is reduced in proportion to the cube root of the distance, and in particular, it is abruptly thinner near the tip (x = W _H ).

  When the load F is applied to the fixed plate 7 in the flexible region 22 perpendicularly (parallel to the z-axis), it is approximated that the load is concentrated on the tip, and is derived from the moment balance. The equation is Equation 79.

この場合、曲率半径は距離ｘに依存せず、一定となる。即ち可撓領域２２に於ける固定板７の何処も同じ曲率半径を有しながら均一に変形する。可撓領域２２の固定板７を屈曲させた際に、固定板７は可撓領域２２内で同一の曲率半径で綺麗に曲がる事になる。即ち、可撓領域２２の曲げに対する耐久性を向上させる事ができる。境界条件は具体例１と同じで、数式６１にて与えられる。数式７９を数式６１の元に解くと、数式８０の解が得られる。

In this case, the radius of curvature does not depend on the distance x and is constant. That is, the fixed plate 7 in the flexible region 22 is uniformly deformed while having the same radius of curvature. When the fixing plate 7 in the flexible region 22 is bent, the fixing plate 7 bends neatly with the same radius of curvature in the flexible region 22. That is, durability against bending of the flexible region 22 can be improved. The boundary condition is the same as in the first specific example and is given by the mathematical formula 61. Solving Equation 79 based on Equation 61 yields the solution of Equation 80.

これが可撓領域２２に於ける固定板７に荷重Ｆが垂直に加えられた際の、距離（ｘ）とたわみ（ｚ（ｘ））との関係で、図８にこの関係を一点鎖線ＣＲにて描いてある。荷重Ｆに対し、可撓領域２２に於ける固定板７が柔軟性を有している事が判る。可撓領域２２に於ける固定板７の端部に於けるたわみｚ_Eは、数式８１である。

This is the relationship between the distance (x) and the deflection (z (x)) when the load F is applied to the fixed plate 7 in the flexible region 22 vertically. This relationship is shown in FIG. It is drawn. It can be seen that the fixing plate 7 in the flexible region 22 has flexibility with respect to the load F. The deflection z _E at the end of the fixed plate 7 in the flexible region 22 is expressed by Equation 81.

又、可撓領域２２に於ける固定板７の上での曲げ応力σは数式８２となる。

Also, the bending stress σ on the fixed plate 7 in the flexible region 22 is expressed by Equation 82.

即ち、ｘ＝０にて歪みも曲げ応力も最大となる。可撓領域２２に於ける固定板７が曲げ応力で破断されない条件は、数式８３である。

That is, the strain and the bending stress are maximized when x = 0. The condition that the fixing plate 7 in the flexible region 22 is not broken by the bending stress is Expression 83.

使用時に想定される最も厳しい荷重線密度（Ｆ／Ｌ_H）に対して、数式８３を満たす様にｔ₀やＷ_Hを定める。厚みが距離に対して立方根の関係にある場合、屈曲時に最も破断しやすい点はｘ＝０であるから、Ｒ₀＝Ｒ（Ｍ）_inとされた時に、ｘ＝０に於ける曲げ応力σ₀が曲げ強さσ_bよりも小さく、数式８４を満たせば、曲げセンサー１が屈曲されても可撓領域２２に於ける固定板７は破断しない。

T ₀ and W _H are determined so as to satisfy Expression 83 with respect to the most severe load line density (F / L _H ) assumed at the time of use. When the thickness has a cubic root relationship with the distance, the point that is most likely to break during bending is x = 0. Therefore, when R ₀ = R (M) _in , the bending stress σ at x = 0 is set. _{If 0} is smaller than the bending strength σ _b and the mathematical expression 84 is satisfied, the fixing plate 7 in the flexible region 22 is not broken even if the bending sensor 1 is bent.

即ち、使用時に想定される最もきつい曲率半径Ｒ（Ｍ）_inに対して、数式８４を満たす様にｔ₀を定める。例えば先と同じＡＢＳ樹脂で可撓領域２２に於ける固定板７を作成し、同じ最小曲率半径を想定すると、数式８４に則り、ｔ₀＜０．５ｍｍとすれば、使用時に可撓領域２２に於ける固定板７が破断する恐れはない。この場合、非可撓領域２１に於ける固定板７は１ｍｍ以上の厚みを持たせ、原点Ｏで階段状に厚みを減じてｔ₀とし、非可撓領域２１では固定板７の厚みを距離の立方根に比例して薄くして行く。

That is, t ₀ is determined so as to satisfy Formula 84 for the tightest radius of curvature R (M) _in assumed at the time of use. For example, when the fixing plate 7 in the flexible region 22 is made of the same ABS resin as described above and the same minimum curvature radius is assumed, the flexible region 22 can be used at the time of use if t ₀ <0.5 mm according to Formula 84. There is no fear that the fixing plate 7 in the case breaks. In this case, the fixing plate 7 in the non-flexible region 21 has a thickness of 1 mm or more, the thickness is reduced in a stepped manner at the origin O to t _0, and in the non-flexible region 21, the thickness of the fixing plate 7 is the distance. Decrease in proportion to the cube root.

  Incidentally, when the fixing plate 7 in the flexible region 22 is made of plastic, it is difficult to process the thickness into the cubic root relationship represented by the mathematical expression 78 accurately. In this case, it can be approximated by the linear relationship shown in the first preferred embodiment. That is, Formula 85 is used.

一例として、α＝０．５８とした際のたわみを図８の実線Ｌ３にて描く。実線Ｌ３と一点鎖線ＣＲとが良く一致している事が判る。この線型近似で、可撓領域２２に於ける固定板７の曲率半径はほぼ均一となり、厚みが線型関係の時の効果に加え、立方根の時と同様な効果が期待でき、更に製造加工も容易になる。

As an example, the deflection when α = 0.58 is drawn by a solid line L3 in FIG. It can be seen that the solid line L3 and the alternate long and short dash line CR are in good agreement. With this linear approximation, the radius of curvature of the fixed plate 7 in the flexible region 22 is almost uniform, and in addition to the effect when the thickness is linear, the same effect as that of the cubic root can be expected, and the manufacturing process is also easy become.

  FIG. 9 is a cross-sectional view for explaining the effect of the present embodiment, in which (a) shows a state in which a downward load is applied to the bending sensor of the comparative example, and (b) shows a downward load on the bending sensor of the present embodiment. Represents the state with.

  In the bending sensor 1 of the comparative example shown in FIG. 9A, the fixing plate 7 is provided only in the non-flexible region 21. In contrast to this comparative example, the bending sensor 1 of the present embodiment shown in FIG. 9B is provided with a fixing plate 7 that gradually becomes thinner with respect to the distance from the origin in the flexible region 22. In the bending sensor 1 of the comparative example, as shown in FIG. 9A, when the flexible region 22 is bent into a convex shape, the corners of the fixing plate 7 are difficult to bend into the flexible region 22 and are extremely strong locally. A biting pressure P is applied to the substrate 2. In FIG. 9, the strength of the biting pressure P is expressed by the length of the arrow, and the range covered by the biting pressure P is expressed by the width of the arrow (therefore, mathematically, the product of the length and width of the arrow). (The value of this product is the same in FIG. 9 (a) and FIG. 9 (b)). On the other hand, in the bending sensor 1 of this embodiment, as shown in FIG. 9B, even if the flexible region 22 is bent into a convex shape, the fixing plate 7 in the flexible region 22 is a surface. A wide and weak biting pressure P is applied to the substrate 2. For this reason, in the bending sensor 1 of the comparative example, there is a slight possibility that the circuit and wiring on the substrate 2 are affected by the biting pressure P and the characteristics are changed. In the bending sensor 1, the possibility of such a situation is almost zero due to the biting pressure P. Furthermore, in the width direction of the flexible region 22, the fixing plate 7 decreases in thickness as it moves away from the origin O, so that almost no biting pressure P is generated at the tip (edge) of the fixing plate 7, and It is possible to completely prevent (almost 100%) the adverse effects of the circuit and wiring accompanying the stress concentration. A strong biting pressure may damage the circuit or wiring (there may be a crack in the circuit or wiring, causing the wiring to break). As well as improving the mechanical reliability during use.

"Bending sensor manufacturing method"
In the bending sensor 1, a thin film circuit is formed on a flexible plastic film substrate 2. Here, a manufacturing method of the bending sensor 1 will be described. Specifically, the bending sensor 1 is manufactured by peeling the thin film circuit first formed on the glass substrate and transferring it to a plastic film.

  As a 1st process, a peeling layer is provided on the glass substrate used as a manufacturer board | substrate. The release layer is a hydrogenated amorphous silicon film having a thickness of about 50 nm. After forming a silicon oxide film serving as a base insulating film on the release layer, a thin film circuit including a thin film transistor is manufactured. For the thin film circuit, a known low temperature process polycrystalline silicon thin film transistor manufacturing method is applied. Specifically, a laser-crystallized polycrystalline silicon semiconductor layer is provided on the base insulating film, and then a gate insulating layer using a silicon oxide film and a metal obtained by adding an additive to aluminum or aluminum are used. Create a gate electrode. In addition, a first interlayer insulating layer using a silicon oxide film, a source contact and a drain contact using aluminum or a metal obtained by adding an additive to aluminum, a second interlayer insulating layer using a polyimide resin (protective film) Then, an electrode terminal (mounting terminal) using indium tin oxide (ITO) is created.

  Next, as a second step, a temporary adhesive is applied to the surface of the thin film circuit, and the manufacturer substrate is attached to the temporary transfer substrate. As a temporary adhesive, what mixed polyvinyl pyrrolidone resin in order to give water solubility to acrylic resin is used. The temporary transfer substrate is a smooth glass substrate.

  Next, as a third step, the manufacturer substrate is removed and the thin film circuit is transferred to a temporary transfer substrate. As a method for removing the manufacturer's substrate, laser light is irradiated from the back of the manufacturer's substrate to weaken the adhesive force inside or at the interface of the release layer, and then the manufacturer's substrate and the temporary transfer substrate are peeled off. By doing so, the thin film circuit is transferred to the temporary transfer substrate.

  Next, in a fourth step, the peeling layer remaining on the back surface of the thin film circuit is removed, and charges existing on the back surface of the thin film circuit are removed using, for example, an ionizer. In this way, it is possible to remove a certain amount of peeling electrification and frictional electrification with air during drying.

  Next, as a fifth step, the back surface of the thin film circuit is attached to the first surface side of the plastic film using a permanent adhesive made of, for example, an acrylic resin. As the plastic film, a polyester film such as polyethylene naphthalate (PEN: Polyethylene naphthalate) can be used.

  After affixing the plastic film, as a sixth step, the fixing plate 7 is attached to the place to be the non-flexible region 21 on the second side of the plastic film (the side opposite to the first side) using a permanent adhesive. Glue. This permanent adhesive may be the same as or different from the permanent adhesive used in the fifth step, but is a material that does not dissolve in the solvent that dissolves the temporary adhesive. Before and after the fixing plate 7 is bonded, the cut line 31 is formed by using laser processing or the like. Since these operations are performed with the temporary transfer substrate attached, even if the substrate 2 has flexibility, it is easy to handle and the bending sensor 1 can be manufactured without difficulty.

  Next, as a seventh step, the temporary transfer substrate is removed using a solvent (in this case, water) that dissolves the temporary adhesive. Thereafter, the temporary adhesive is washed away.

  Next, as an eighth step, a mounting operation is performed. First, tape wiring is mounted on mounting terminals provided in the non-flexible region 21. In this case, an anisotropic conductive paste or an anisotropic conductive film (these are collectively referred to as an anisotropic conductive adhesive) is disposed between the mounting terminal and the tape wiring, and both are adhered. The tape wiring is connected to an external controller provided outside the bending sensor 1. Thus, the bending sensor 1 is completed.

  In addition to the plastic film described above, the substrate 2 may be a thin metal foil having a thickness of about 50 to 500 micrometers, or a thin glass having a thickness of about 10 to 200 micrometers. The manufacturing method may also be a method in which a thin film circuit is formed on a thick glass and then the glass is thinned, or a thin film circuit is directly formed on a plastic film or metal foil. In the case of direct formation, an amorphous silicon thin film transistor, an oxide thin film transistor using an oxide containing zinc or tin as a semiconductor layer, or the like can be used.

As described above, according to the bending sensor 1 according to the present embodiment, the following effects can be obtained.
Since the bending sensor 1 is composed of thin film transistors such as the first thin film transistor formed in the flexible region 22 and the second thin film transistor formed in the non-flexible region 21, the spatial resolution can be extremely high. it can.

  In addition, since the fifth thin film transistor and the sixth thin film transistor are provided and these form a current mirror pair and can be connected to the first thin film transistor and the second thin film transistor, the degree of bending (curvature) can be accurately measured. .

  In addition, since the first power supply, the second power supply, and the seventh thin film transistor are provided, and the seventh thin film transistor can be a constant current source, the signal amplification related to the bending becomes linear, and the potential proportional to the bending stress can be accurately measured. .

  In addition, since a plurality of first thin film transistors for detecting bending are arranged in the first direction and individually selected, the spatial distribution of the bending in the first direction can be measured. Therefore, even when the bending degree is a plurality of places along the first direction, the bending degree can be accurately measured.

  In addition, since a plurality of first thin film transistors for detecting bending are arranged in the second direction and individually selected, the spatial distribution of the bending in the second direction can be measured. Therefore, even if the bending degree is a plurality of places along the second direction, the bending degree can be accurately measured.

  Further, since the third thin film transistor and the fourth thin film transistor function as a part of the selection circuit in the second direction, it is possible to prevent the information on the bending state in the second direction from interfering.

In addition, the bending characteristics are measured by comparing the electrical characteristics of the first thin film transistor located in the flexible region 22 with the electrical characteristics of the second thin film transistor located in the non-flexible area 21, so that the bending condition can be accurately determined. It can be measured.
In addition, since the fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are N-type and the second power source is a negative power source, a bending sensor is used with an N-type thin film transistor without using a P-type thin film transistor. 1 can be realized.

(Embodiment 2)
"Equalization circuit is arranged"
FIG. 10 is a diagram for explaining a circuit of a bending sensor according to the second embodiment. FIG. 11 is a diagram for explaining a timing chart for driving a circuit when the bending state is measured by the bending sensor according to the second embodiment. Hereinafter, the bending sensor according to the present embodiment will be described. In addition, about the component same as Embodiment 1, the same number is attached | subjected and the overlapping description is abbreviate | omitted.

  This embodiment (FIG. 10) is different from the first embodiment (FIG. 3) in that an equalize circuit is provided between the drain of the fifth thin film transistor TN5 and the drain of the sixth thin film transistor TN6. Accordingly, the precharge period is provided in the selection period in the timing chart (FIG. 11) as compared with the timing chart (FIG. 4) of the first embodiment. Other configurations are almost the same as those of the first embodiment.

As shown in FIG. 10, in this embodiment, an eighth thin film transistor TN8 is provided in the output circuit 4 as an equalizing circuit. One of the source and drain of TN8 is connected to the drain of TN5 and becomes XLDOUT, and the other is connected to the drain of TN6 and becomes LDOUT. The second control signal Cnt2 is supplied to the gate of TN8. In order to shorten the precharge period (the first half of the selection period), it is desirable that the on-current of TN8 be large. Therefore, the transistor size of TN8 should be the same as that of TN3 or TN4 (Z ₃ = Z ₄ = Z ₈ ) is preferred.

Next, a circuit driving method of the bending sensor 1 will be described with reference to FIG. When a specific one is selected from a plurality of first thin film transistors arranged in a matrix, the first half of the selection period precharges the potential V ₅ of XLDOUT and the potential V _{6 of} LDOUT to V _dd for selection. Measure the bend in the second half of the period. The first control signal Cnt1 becomes a low potential L (V _ss ) in the first half of the selection period and becomes a high potential H _{3 in} the second half of the selection period. The potential value of H ₃ is as discussed in the first embodiment. The second control signal Cnt2 is a signal that is complementary to the first control signal Cnt1 and has a different potential amplitude. That is, the second control signal Cnt2 becomes the high potential H _{4 in} the first half of the selection period and becomes the low potential L (V _ss ) in the second half of the selection period. In order to realize high-speed measurement, the potential value of H ₄ is preferably high. For example, it is desirable to use H _{2 as} discussed in the first embodiment. In this way, TN7 is turned off in the first half of the selection period, TN8 since turned on, can be equal to the potential V ₆ potential V ₅ and LDOUT of XLDOUT to V _dd. After the outputs become equal, the bending state is measured in the second half of the selection period, so one measurement and the next measurement (for example, measurement of TN1 (i, j) and measurement of the next TN1 (i, j + 1)) The previous measurement result (measurement result of TN1 (i, j)) no longer interferes with the subsequent measurement result (measurement result of TN1 (i, j + 1)) (measurement to eliminate interference when these interfere) The time will be long), and accurate measurement can be performed quickly.

As described above, according to the bending sensor 1 according to the present embodiment, the following effects can be obtained in addition to the effects of the first embodiment.
Since the equalizer circuit is provided, the output potential can be reset between each measurement when the measurement of the bending state is repeated sequentially in space and time. As a result, accurate measurement can be realized quickly.

  The present invention is not limited to the above-described embodiment, and various changes and improvements can be added to the above-described embodiment. A modification will be described below.

(Modification 1)
"The circuit is formed by PMOS"
FIG. 12 is a diagram for explaining a circuit of a bending sensor according to the first modification. Hereinafter, a bending sensor according to this modification will be described. In addition, about the component same as Embodiment 1, the same number is attached | subjected and the overlapping description is abbreviate | omitted.
This modified example (FIG. 12) differs from the first embodiment (FIG. 3) in the conductivity type of the thin film transistor that constitutes the circuit of the bending sensor 1. Other configurations are almost the same as those of the first embodiment.

In the first embodiment, the circuit of the bending sensor 1 (the detection circuit 3, the output circuit 4, and the column selection transistor of the second processing circuit 62) is configured using an N-type thin film transistor. These circuits are configured using thin film transistors TP1 (i, j) to TP7. In this case, the first power source is the negative power source V _ss and the second power source is the positive power source V _dd . The source and drain of the P-type thin film transistor is the source having the higher potential and the drain having the lower potential. In FIG. 12, the source and drain are indicated by s and d for reference. As a P-type thin film transistor, poly (9,9-dioctylfluorene-cordithiophene) (F8T2), poly (3-hexylthiophene) (P3HT), poly [5,5′-bis (3-dodecyl) is used as a semiconductor layer. -Tinyl) -2,2′-bithiophene] (PQT-12), PBTTT, organic thin film transistors using organic materials such as pentacene can be used.

The transistor size is the same as in the first embodiment. The driving method is the same as in FIG. 4 of the first embodiment, but so-called high potentials such as H ₁ , H ₂ , H ₃ , and H _r are changed so that the negative absolute value with respect to the low potential L becomes large. Note that the threshold voltage V _th of the P-type thin film transistor is negative. Specifically, Formula 57 is changed to Formula 86.

ＴＰ１（ｉ，ｊ）のゲートに接続するｉ行目の行線ＸＲ（ｉ）は、非選択期間にＶ_ddとし、選択期間には、数式８７とする。

The i-th row line XR (i) connected to the gate of TP1 (i, j) is set to V _dd during the non-selection period and Formula 87 is used during the selection period.

ｊ列目の列線ＸＣ（ｊ）は、非選択期間にＶ_ddとし、選択期間には数式８８とする。

The column line XC (j) of the j-th column is set to V _dd during the non-selection period and Formula 88 during the selection period.

電流源トランジスターＴＰ７のゲートに入る第一制御信号ＸＣｎｔ１は、非計測期間にＶ_ddとし、計測期間には数式８９とする。

The first control signal XCnt1 entering the gate of the current source transistor TP7 is set to V _dd during the non-measurement period and is represented by Equation 89 during the measurement period.

第二薄膜トランジスターＴＰ２のゲートに入力するＸＶ_refは、非計測期間にＶ_ddとし、計測期間には数式９０とする。

XV _ref input to the gate of the second thin film transistor TP2 is set to V _dd during the non-measurement period and Formula 90 during the measurement period.

従って、例えば、Ｖ_th＝−１．５Ｖとして、δ＝−０．３Ｖ、γ＝−０．１Ｖとし、Ｖ_dd＝５．４Ｖ、Ｈ₁＝０Ｖ、Ｈ₂＝−１．６Ｖ、Ｈ₃＝３．６Ｖ、Ｈ_r＝０±θＶ、−１．５Ｖ＜θ≦０Ｖとする。ここでのＨ₂やＨ_rの様に、負電圧を準備するのが困難な場合、総ての電位が正になる様にＶ_ddとＶ_ssを一定量ずらしても良い。例えば、上記例で全体を１．６Ｖずらして、Ｖ_dd＝７．０Ｖ、Ｖ_ss＝Ｈ₁＝１．６Ｖ、Ｈ₂＝０Ｖ、Ｈ₃＝５．２Ｖ、Ｈ_r＝１．６±θＶ、−１．５Ｖ＜θ≦０Ｖとしても良い。

Thus, for example, V _th = −1.5 V, δ = −0.3 V, γ = −0.1 V, V _dd = 5.4 V, H ₁ = 0 V, H ₂ = −1.6 V, H ₃ = 3.6 V, H _r = 0 ± θV, −1.5 V <θ ≦ 0 V. When it is difficult to prepare a negative voltage like H ₂ and H _r here, V _dd and V _ss may be shifted by a certain amount so that all potentials become positive. For example, in the above example, the whole is shifted by 1.6 V, V _dd = 7.0 V, V _ss = H ₁ = 1.6 V, H ₂ = 0 V, H ₃ = 5.2 V, H _r = 1.6 ± θV , −1.5V <θ ≦ 0V.

  As described above, according to the bending sensor 1 according to this modification, the bending sensor 1 can be realized by using a P-type thin film transistor without using an N-type thin film transistor.

(Modification 2)
“A form in which the circuit is formed of PMOS and an equalize circuit is arranged”
FIG. 13 is a diagram for explaining a circuit of a bending sensor according to the second modification. Hereinafter, a bending sensor according to this modification will be described. In addition, about the same component as Embodiment 1 thru | or 2, the same number is attached | subjected and the overlapping description is abbreviate | omitted.
This modified example (FIG. 13) differs from the second embodiment (FIG. 10) in the conductivity type of the thin film transistor that constitutes the circuit of the bending sensor 1. Other configurations are almost the same as those of the second embodiment.

In the first embodiment, the circuit of the bending sensor 1 (the detection circuit 3, the output circuit 4, and the column selection transistor of the second processing circuit 62) is configured using an N-type thin film transistor. These circuits are configured using thin film transistors TP1 (i, j) to TP8. That is, the P-type eighth thin film transistor TP8 is added to the first modification. TP8 is arranged as an equalize circuit between the drain of the fifth thin film transistor TP5 and the drain of the sixth thin film transistor TP6. As in the first modification, the first power source is the negative power source V _ss , the second power source is the positive power source V _dd , and the threshold voltages V _th of the eight types of P-type thin film transistors are negative.

The transistor size is the same as in the first and second embodiments. The driving method is the same as in FIG. 11 of the first embodiment, but as in the first modification, so-called high potentials such as H ₁ , H ₂ , H ₃ , H ₄ , and H _r have a negative absolute value with respect to the low potential L. Change the way. V _dd , V _ss , H ₁ , H ₂ , H ₃ , and H _r are the same as those in the first modification, and are determined so as to satisfy Expression 90 from Expression 86. The second control signal XCnt2 input to the gate of TP8 is a signal that is complementary to the first control signal XCnt1 and has a different potential amplitude. That is, the second control signal XCnt2 becomes H _{4 in} the first half of the selection period of TP1, and becomes V _{dd in} the second half of the selection period. In order to realize high-speed measurement, the absolute value of H ₄ with respect to V _dd (| H ₄ −V _dd |) is preferably higher. For example, H _{2 of} Modification 1 is desirable.

  As described above, according to the bending sensor 1 according to this modified example, the bending sensor 1 can be realized by a P-type thin film transistor and the equalization circuit is provided. Therefore, the bending state is sequentially measured spatially and temporally. When repeated, the output potential can be reset between each measurement. Therefore, accurate measurement can be realized quickly.

(Modification 3)
"Form in which a cut is formed in the vicinity of the first thin film transistor"
FIG. 14 is a diagram for explaining a planar layout of the detection circuit of the bending sensor according to the third modification. Hereinafter, a bending sensor according to this modification will be described. In addition, about the component same as Embodiment 1, the same number is attached | subjected and the overlapping description is abbreviate | omitted.
This modified example (FIG. 14) differs from the first embodiment (FIG. 5) in the size and position of the cut. Other configurations are almost the same as those of the first embodiment.

  In the first embodiment shown in FIG. 5, the cut line 31 is relatively large, and is between the second column line CR (j) and the first column line CL (j + 1) connected to the adjacent first transistor (measurement of the jth column). Between the cell and the measurement cell in the j + 1-th column). On the other hand, in this modification, as shown in FIG. 14, a relatively small cut 31 is provided in the vicinity of the first thin film transistor (in the measurement cell). The purpose of the cut 31 is to prevent stress interference from the lateral direction, but if this is large, the strength of the bending sensor 1 may be insufficient. Therefore, if microfabrication is possible, it is desirable to provide in the vicinity of the first thin film transistor (in each measurement cell) as shown in this modification. In this way, accurate bending measurement is realized while maintaining the strength of the bending sensor 1. If one elongated cut 31 along the measurement direction (in this case, the first direction, the x-axis direction) is provided in the measurement cell, it is from the other direction (in this case, the second direction, the y-axis direction). Interference can be prevented. In order to surely prevent interference, as shown in FIG. 14, it is ideal to provide two elongated cuts 31 along the measurement direction and to form a first thin film transistor between them.

(Modification 4)
"Form in which cuts are formed along the second direction"
FIG. 15 is a diagram for explaining a planar layout of a detection circuit of a bending sensor according to Modification 4. Hereinafter, a bending sensor according to this modification will be described. In addition, about the component same as Embodiment 1, the same number is attached | subjected and the overlapping description is abbreviate | omitted.
This modification (FIG. 15) differs from the first embodiment (FIG. 5) in the measurement direction of bending. Other configurations are almost the same as those of the first embodiment.

  In the first embodiment shown in FIG. 5, the source / drain direction of the first thin film transistor TN1 and the direction of the elongated cut 31 are parallel to the first direction (x-axis direction), and the bending in the first direction is measured. In this modification, the source / drain direction of the first thin film transistor TN1 and the direction of the elongated cut 31 are parallel to the second direction (y-axis direction), and the bending in the second direction is measured. In the first embodiment (FIG. 5), since the source / drain direction is parallel to the first column line CL and the second column line CR, the semiconductor film must be bent 90 ° at two locations, A relatively large area was required. On the other hand, in this modification, since the source / drain direction is perpendicular to the first column line CL and the second column line CR, the semiconductor film is a straight line, and each measurement cell is relatively small. That is, the spatial resolution can be increased. Further, since the stress interference from the x-axis direction is eliminated by the cut line 31, high-accuracy measurement is possible.

(Modification 5)
“Mode 1 with variable measurement frequency”
In the modified example 5, the measurement frequency is variable according to the situation. Hereinafter, a method for using the bending sensor according to this modification will be described. In addition, about the component same as Embodiment 1, the same number is attached | subjected and the overlapping description is abbreviate | omitted.
This modification is different from the “usage method” described in the first embodiment in that the measurement frequency is variable. Other configurations are almost the same as those of the first embodiment.

  In the first embodiment, the measurement frequency has fixed values for the preparation period and the measurement period. On the other hand, in the present modification, the measurement frequency in the preparation period or the measurement period is increased or decreased depending on the situation. As an example, even if the measurement frequency of the preparation period enters the measurement period, it continues in the initial stage, and the measurement frequency is increased when bending is detected. For example, when a bending sensor is applied to a flexible electronic book, it is measured infrequently until the user starts a page turning operation, and if the bending sensor detects bending as the operation starts, Bending is measured at a frequency to detect what action the user is actually trying to do. Alternatively, the measurement frequency is increased when the bending time change is severe, and the measurement frequency is decreased when the bending time change is small. For example, when a bending sensor is used as a motion capture, the measurement frequency is increased or decreased according to the operation speed of the analysis target. Taking baseball swing as an example, the operation speed is slow from the stage where the bat is set up to the takeback, so the measurement frequency during the measurement period is slowed down to about 10 Hz, and the operation is performed from the takeback to the end of the swing. Since the speed is high, the measurement frequency in the measurement period is increased to about 100 Hz.

By making the measurement frequency variable in this way, power saving is realized, wasteful information is reduced, and measurement with high time resolution becomes possible.
(Modification 6)
“Mode 2 with variable measurement frequency”
In the modified example 6, the measurement frequency is variable according to the purpose. Hereinafter, a method for using the bending sensor according to this modification will be described. In addition, about the component same as Embodiment 1, the same number is attached | subjected and the overlapping description is abbreviate | omitted.
This modification differs from the “usage method” described in the first embodiment in that the measurement frequency is variable according to the purpose. Other configurations are almost the same as those of the first embodiment.

  In the first embodiment, the measurement frequency has fixed values for the preparation period and the measurement period. On the other hand, in the present modification, the measurement frequency in the preparation period or the measurement period is increased or decreased according to the measurement object and the measurement purpose. That is, the measurement frequency is reduced when the time change related to the bending of the measurement object is predicted to be moderate, and the measurement frequency is increased when the time change is predicted to be severe. For example, when the bending sensor is used as a motion capture, if the bending change is severe in a short time such as baseball swing, the measurement frequency in the measurement period is increased to about 100 Hz. On the other hand, when it changes slowly over a long period of time as in the analysis of Japanese dance, the measurement frequency is slowed down to about 1 Hz.

  In this way, by adjusting the measurement frequency of the bending sensor according to the application, time followability can be expanded, and various operations and changes can be measured with one bending sensor.

  In the above description, the preparation period and the measurement period have been provided, but the preparation period is not essential and can be omitted.

  DESCRIPTION OF SYMBOLS 1 ... Bending sensor, 2 ... Board | substrate, 3 ... Detection circuit, 4 ... Output circuit, 7 ... Fixed board, 21 ... Non-flexible area | region, 22 ... Flexible area | region, 31 ... Break, 51 ... First selection circuit, 52 ... First processing circuit 61... Second selection circuit 62.

Claims (8)

Flexible with and the first TFT and the second TFT and the third TFT and the fourth TFT and fifth TFT sixth thin film transistor on a substrate, a having,
The substrate includes a flexible region and a non-flexible region;
The first thin film transistor and the second thin film transistor form a differential transistor pair,
The first thin film transistor is formed in the flexible region, the second thin film transistor is formed in the non-flexible region ,
The second thin film transistor operates as a reference transistor;
Compare the electrical characteristics of the first thin film transistor and the electrical characteristics of the second thin film transistor, detect the bending state,
The third thin film transistor is disposed between the first thin film transistor and the fifth thin film transistor;
The fourth thin film transistor is disposed between the second thin film transistor and the sixth thin film transistor;
The third thin film transistor and the fourth thin film transistor are controlled by a second selection circuit,
Wherein the fifth thin film transistor and the sixth thin film transistor sensor bending, characterized in that that have no current mirror pair. Furthermore, a first power source, a second power source, and a seventh thin film transistor are provided,
The first thin film transistor and the second thin film transistor are connected to the first power source,
The fifth thin film transistor and the sixth thin film transistor are connected to the seventh thin film transistor,
The bending sensor according to claim 1 , wherein the seventh thin film transistor is connected to the second power source. A first selection circuit is provided along the first direction,
Wherein with the first thin film transistor is formed in plural along the first direction, by the first selection circuit, as claimed in claim 1 or 2, characterized in that it can be selected in the first direction Bending sensor. With the first two selection circuits along a second direction crossing the first direction,
Wherein with the first thin film transistor is formed in plural along the second direction, said by the second selection circuit, the bending sensor according to claim 3, characterized in that can be selected by the second direction . Bending sensor according to any one of claims 1 to 4, characterized in that comprises an equalizing circuit between the drains of said sixth thin film transistor of the fifth thin film transistor. The fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are N-type,
The bending sensor according to claim 2 , wherein the second power source is a negative power source. The fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are P-type,
The bending sensor according to claim 2 , wherein the second power source is a positive power source.   The bending sensor according to any one of claims 1 to 10, wherein a fixing plate that is harder than the substrate is bonded to the substrate in the non-flexible region.

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