JP4957597B2 - Sensing circuit, driving method thereof, display device, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply constitute a sensing circuit. <P>SOLUTION: The sensing circuit 40 is provided with: an amplification transistor 41 which outputs a detection current according to gate potential; a reset transistor 42 which is provided between a gate of the amplification transistor 41 and a power line 20 and becomes an on state according to a reset signal RES supplied via a first control line 10; a reference capacity element 44 which is provided between the first control line 10 and the gate of the amplification transistor 41; a capacitance detection element 45 one terminal of which is connected to the gate of the amplification transistor 41 and to the other terminal of which predetermined potential Vx is supplied; and a selection transistor 43 which is provided between the amplification transistor 4l and a detection line 21 and becomes an on state according to a selection signal SEL via a second control line 11. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a sensing circuit that detects a change in capacitance, a driving method thereof, a display device, and an electronic apparatus.

A display device having a sensing circuit that detects a change in capacitance is known. For example, the technique described in Patent Document 1 incorporates a sensing circuit in a liquid crystal display device. In this sensing circuit, a reference capacitor and a capacitance detection element are connected in series, the connection point is connected to the gate of the amplification transistor, and a detection current corresponding to the gate potential is passed through the amplification transistor. Then, a change in capacitance of the capacitance element is taken out as a change in detection current.
JP 2007-48275 A

By the way, in the sensing circuit, it is necessary to reset the gate potential of the amplification transistor to a predetermined potential every time sensing is performed. For this reason, in the conventional sensing circuit, a reset voltage is supplied to the gate of the amplification transistor via the reset transistor, separately from the power supply of the amplification transistor. In addition, a reference voltage is supplied to one terminal of the reference capacitor, and a common potential supplied to the counter electrode of the liquid crystal display device is supplied to one terminal of the capacitance element.
In order to supply various voltages in this way, it is necessary to form a plurality of wirings, which causes a problem that the structure of the sensing circuit becomes complicated. The common potential is a voltage used for AC driving of the liquid crystal, and the polarity needs to be inverted at a predetermined cycle. For this reason, since the sensing cycle is synchronized with the liquid crystal display, there is a problem that the sensing cycle cannot be made independent of the liquid crystal display cycle.
The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to reduce the number of wirings and to freely set the sensing cycle.

  In order to solve this problem, a sensing circuit according to the present invention includes a first transistor (for example, a diagram) in which a power supply line is electrically connected to one electrode and a detection current corresponding to a gate potential is output from the other electrode. 2 shown in FIG. 2) and a second transistor (for example, for example) that is provided between the gate of the first transistor and the power supply line and is turned on in response to a reset signal supplied to the gate through the first control line. 42) shown in FIG. 2, a reference capacitor provided between the first control line and the gate of the first transistor, and one terminal electrically connected to the gate of the first transistor, A capacitance detection element to which a predetermined potential is supplied to a terminal, and a selection signal provided between the other electrode of the first transistor and the detection line and supplied to the gate via the second control line On state and That the third transistor (e.g., 43 shown in FIG. 2) and a.

  According to the present invention, since the voltage supplied through the power supply line is used to reset the gate potential of the first transistor, it is not necessary to prepare a special power supply for resetting, and the number of wirings for supplying the power is reduced. Can be reduced. In addition, since one terminal of the reference capacitor is connected to the first control line and performs a sensing operation by a reset signal, it is not necessary to provide a dedicated power source for the reference capacitor, and the number of wirings for supplying this can be reduced. . Therefore, the configuration of the sensing circuit can be greatly simplified. In addition, if the predetermined potential supplied to the other terminal of the capacitance element is a fixed potential, the gate potential of the first transistor does not fluctuate in a predetermined cycle. In addition, since it is not necessary to perform sensing in synchronization with the image display cycle of the display device, sensing can be performed as necessary, or sensing can be performed with a longer cycle. As a result, power consumption can be reduced.

Here, the reference capacitance is preferably a parasitic capacitance generated between the gate and the drain of the second transistor. In this case, since it is not necessary to build a reference capacitor as an element, the configuration of the sensing circuit can be further simplified.
The first to third transistors are formed by the same process, and include a semiconductor layer, a gate oxide film, and a gate wiring. The reference capacitor uses the semiconductor layer as one electrode, and the gate wiring Is preferably used as the other electrode. In this case, a reference capacitor is formed, but since it can be formed by the same process as the first to third transistors, the manufacturing cost can be reduced.

  Next, a display device according to the present invention includes a pixel electrode, a common electrode, and a plurality of pixel circuits having a liquid crystal to which an electric field generated between the pixel electrode and the common electrode is applied, and the sensing circuit described above. The capacitance detection element includes a first electrode formed simultaneously with the pixel electrode, a second electrode formed simultaneously with the common electrode, and an electric field generated between the first electrode and the second electrode. And the liquid crystal to be added. According to the present invention, when the electrical state between the first electrode and the second electrode (for example, the distance (gap length) between the first electrode and the second electrode) changes, the capacitance detection element Since the capacitance value changes, this can be detected when a person touches it. As a more specific aspect of the present invention, a display device in which the liquid crystal included in the pixel circuit is sandwiched between the pixel electrode and the common electrode, or the pixel electrode and the common electrode are formed in separate layers. And the liquid crystal included in the pixel circuit is disposed in a region different from a region between the layer including the pixel electrode and the layer including the common electrode, and the pixel electrode and the common electrode are the same A display device in which the liquid crystal formed in the layer and included in the pixel circuit is included in a layer different from the layer can be exemplified.

  Next, an electronic apparatus according to the present invention preferably includes the display device described above. Such electronic devices include personal computers, mobile phones, portable information terminals, touch panels, and the like.

  Next, a driving method of the sensing circuit according to the present invention is a method of driving the above-described sensing circuit, and supplies the reset signal for turning on the second transistor to the first control line in a reset period. Then, the selection signal for turning off the third transistor is supplied to the second control line, and the reset signal for turning off the second transistor in the sensing period following the reset period is supplied to the first control line. And supplying the selection signal for turning off the third transistor to the second control line and supplying the reset signal for turning off the second transistor in a reading period following the sensing period. Supplying to the first control line, supplying the selection signal for turning on the third transistor to the second control line. To. According to the present invention, when the level of the reset signal changes during the sensing period, the reference capacitor functions as a coupling capacitor, and the gate potential of the first transistor changes. Since this change is determined according to the capacitance value of the reference capacitance and the capacitance value of the capacitance detection element, it is possible to detect a change in the capacitance value of the capacitance detection element.

  Further, it is preferable that the detection line is precharged to a predetermined potential during part or all of the reset period and the sensing period. In the reading period, the detection current flows into the detection line through the third transistor. For this purpose, the third transistor needs to be surely turned on. According to the present invention, since the potential of the detection line is precharged before the reading period starts, the third transistor can be reliably turned on.

<1. Embodiment>
FIG. 1 is a block diagram showing a configuration of a liquid crystal display device according to an embodiment of the present invention. The liquid crystal display device 500 includes a display area A and sensing areas B1 and B2 provided around the display area A. The sensing areas B1 and B2 are non-display areas where no image is displayed. In the display area A, a plurality of scanning lines 30, a plurality of data lines 31, and a plurality of pixel circuits P are arranged corresponding to the intersections thereof. The pixel circuit P includes a transistor 33, a pixel electrode 34, a counter electrode (common electrode) 36 to which a common potential Vcom is supplied, and a liquid crystal 35 sandwiched between the pixel electrode 34 and the counter electrode 36. The transistor 33 is constituted by a TFT (Thin Film Transistor), the gate thereof is connected to the scanning line 30, the drain is connected to the data line 31, and the source is connected to the pixel electrode 34. An electric field (electric field in the thickness direction of the liquid crystal) generated between the pixel electrode 34 and the counter electrode 36 is applied to the liquid crystal 35.

  The Y driver 100 generates a scanning signal for sequentially selecting the plurality of scanning lines 30 and supplies it to each pixel circuit P. The scanning signal is a pulse having a width corresponding to one horizontal scanning period (1H) from the first timing of one vertical scanning period (1F), and is supplied to the scanning line 30 in the first row. Thereafter, this pulse is sequentially shifted and supplied to each scanning line 30 as a scanning signal. On the other hand, the X driver 200 supplies a data signal having a magnitude corresponding to the gradation to be displayed to each of the pixel circuits P located on the selected scanning line 30.

Next, a plurality of sensing circuits 40 are arranged in the sensing areas B1 and B2. The sensing circuit 40 detects a change in capacitance and is driven by the drive circuit 300.
FIG. 2 shows a circuit diagram of the sensing circuit 40. The sensing circuit 40 includes an amplification transistor 41, a reset transistor 42, and a selection transistor 43. These transistors are composed of TFTs similarly to the transistor 33 of the pixel circuit P described above, and are formed by the same process.

A reset signal RES is supplied to the gate of the reset transistor 42 via the first control line 10. The drain of the reset transistor 42 is connected to the power supply line 20, and the source thereof is connected to the gate of the amplification transistor 41. The voltage VRH is supplied to the power line 20.
The drain of the amplification transistor 41 is connected to the power supply line 20, and the source thereof is connected to the drain of the selection transistor 43. The source of the selection transistor 43 is connected to the detection line 21, and the selection signal SEL is supplied to the gate of the selection transistor 43 via the second control line 11.
A reference capacitance element 44 is provided between the gate of the amplification transistor 41 and the first control line 10. Furthermore, one terminal of the capacitance detection element 45 is connected to the gate of the amplification transistor 41, and a predetermined potential Vx is supplied to the other terminal. In this example, the predetermined potential Vx is a fixed potential different from the common potential Vcom. Therefore, even if the common potential Vcom is changed by AC driving, the potential of the amplification transistor 41 does not change, and sensing can be performed independently of the image display. In addition, since it is not necessary to perform sensing in synchronization with the image display cycle of the display device, sensing can be performed as necessary, or sensing can be performed with a longer cycle. As a result, power consumption can be reduced.

Next, the operation of the sensing circuit 40 will be described with reference to FIGS. The sensing circuit 40 operates with the reset period Tres, the sensing period Tsen, and the readout period Tout as one unit.
First, in the reset period Tres, the level of the reset signal RES becomes VD, and the reset transistor 41 is turned on. At this time, the selection signal SEL is at a low level, and the selection transistor 43 is turned off. Then, as shown in FIG. 4, the potential of the gate of the amplification transistor 41 is reset to the power supply potential VRH.

  Next, in the sensing period Tsen following the reset period Tres, the level of the reset signal RES changes from VD to GND (= 0V). Then, as shown in FIG. 5, the reset transistor 42 is turned off. Since the first control line 10 is connected to one electrode of the reference capacitor element 44, the reference capacitor element 44 functions as a coupling capacitor, and the gate potential of the amplification transistor 41 changes when the level of the reset signal RES changes. .

Here, if the capacitance value of the reference capacitance element 44 is Cr, the capacitance value of the capacitance detection element 45 is Cs, and the potential change of the first control line 10 is ΔVgate (= VD), the gate potential of the amplification transistor 41 The change ΔV is given by the following equation (1). However, the parasitic capacitance is ignored.
ΔV = ΔVgate * Cr / (Cr + Cs) (1)
From equation (1), if the capacitance value Cs of the capacitance detection element 45 is large, the change ΔV due to capacitive coupling is small, and conversely, if the capacitance value Cs is small, the change ΔV is large. Therefore, the capacitance change of the capacitance detection element 45 can be reflected in the gate potential.

Next, in the reading period Tout, the selection signal SEL changes from the low level to the high level. Then, the selection transistor 43 is turned on as shown in FIG. As a result, a detection current Idet corresponding to the gate potential of the amplification transistor 41 flows through the detection line 21.
By the way, it is preferable to precharge the potential of the detection line 21 to the precharge potential Vpre prior to the read period Tout in order to surely turn on the selection transistor 43 in the read period Tout. In this example, as shown in FIG. 3, the reset period Tres and the sensing period Tsen are set as a precharge period Tpre, and the precharge potential Vpre is supplied to the detection line 21 during the period.

  Here, the change of the electrostatic capacitance by the electrostatic capacitance detection element 45 will be described with reference to FIG. As shown in FIG. 7, the capacitance detecting element 45 is configured by sandwiching a liquid crystal 35 between a first electrode 45a and a second electrode 45b. In a state where a human finger is not touched, the first electrode 45a and the second electrode 45b are parallel as shown in FIG. 5A, but when the liquid crystal display device 500 is pressed with the finger, the second electrode 45b is bent. The distance between the first electrode 45a and the second electrode 45b is shortened. For this reason, when a person presses the liquid crystal display device 500 with a finger, the capacitance value Cs of the capacitance detection element 45 increases. In this way, a change in capacitance is detected.

  Further, the reference capacitor element 44 of this example is configured by using a semiconductor layer 47 as one electrode, using a gate wiring 48 as the other electrode, and sandwiching a gate oxide film 49 therebetween. The semiconductor layer 47, the gate wiring 48, and the gate oxide film 49 are formed by the same process as the other transistors 41 and 42. Therefore, a special process is not required for forming the reference capacitor element 44, and the manufacturing cost can be reduced.

  Incidentally, the reference capacitance element 44 may be provided between the first control line 10 and the gate of the amplification transistor 41. Parasitic capacitance resulting from the structure is attached between the gate and drain of the reset transistor 42 and between the gate and source. Therefore, the parasitic capacitance of the reset transistor 42 may be used as the reference capacitance element 44 as in the sensing circuit 40 ′ illustrated in FIG. 8. In this case, as shown in FIG. 7, the reference capacitor element 44 does not have to be built in, so that the structure can be further simplified.

  In the above-described embodiment, the fixed potential different from the common potential Vcom is set as the predetermined potential Vx. However, this may be modified so that the common potential Vcom is set as the predetermined potential Vx. That is, the second electrode 45b and the counter electrode (common electrode) 36 may be electrically connected. This form may be a form in which the common potential Vcom is changed (common modulation drive), and the common potential Vcom may be a fixed potential at least during the sensing period Tsen. In these embodiments, the common electrode to which the second electrode 45b is electrically connected is a liquid crystal display device that drives liquid crystal in a transverse electric field mode such as an FFS (Fringe Field Switching) method or an IPS (In-Plane Switching) method. It is good also as a form which adopted the common electrode. In this mode, an electric field (lateral electric field) generated between the pixel electrode and the common electrode is applied to the liquid crystal.

  FIG. 9 is a cross-sectional view showing a structural example of the FFS mode. However, the illustration of the amplification transistor and the reference capacitance element is omitted. As in this example, in the FFS mode, the pixel electrode 81 and the common electrode 82 are formed in separate layers, and the liquid crystal 35 is a region 83 between the layer including the pixel electrode 81 and the layer including the common electrode 82. It is arranged in a different area. The region 83 is also a region between the layer including the first electrode (capacitive electrode) 91a and the layer including the second electrode 91b. The first electrode 91a is connected to the source 94s of the reset transistor 94 (that is, the gate of the amplification transistor).

  In this example, a color filter 92 and a black matrix 93 overlap the pixel electrode 81 and the first electrode 91a. The reason why the black matrix 93 is used is to block unnecessary light from the sensing circuit. Also in this example, when a person presses the liquid crystal display device 501 with a finger, the capacitance value Cs of the capacitance detection element 91 changes, so that a change in capacitance can be detected. In the IPS mode, the pixel electrode and the common electrode are formed in the same layer, and the liquid crystal 35 is included in a layer different from this layer.

  In the above-described embodiment, the drive circuit 300 is provided to drive the sensing circuit 40. However, if it is allowed to execute sensing in synchronization with image display, sensing is performed as shown in FIG. The selection signal SEL and the reset signal RES supplied to the circuit 40 may be generated by the Y driver 101 (the liquid crystal display device 501). To obtain this configuration, the number of shift registers included in the Y driver 100 is increased by one to make the Y driver 101, and the selection signal SEL and the reset signal RES are generated based on the shift signal output from the first stage or the last stage. You just have to do it.

  FIG. 11 is a circuit diagram of the liquid crystal display device 501. However, the illustration of the X driver 200 is omitted. The liquid crystal display device 501 includes a sensor X driver 301, a Y driver 101, an N−1 row L column pixel circuit P arranged in the display area A, and N−1 + L pieces arranged in the sensing area B1 or B2. The sensing circuit 40 is provided. In the sensing region B1, L sensing circuits 40 are arranged in the row direction (Nth row), and in the sensing region B2, the remaining N-1 sensing circuits 40 are arranged in the column direction (L + 1th column). In the following description, “unit circuit” is used as a general term for the pixel circuit P and the sensing circuit 40.

  The sensor X driver 301 is provided at a position facing the display area A across the sensing area B1, and supplies the selection signal sel to each of the L second control lines 11. The Y driver 101 is provided at a position facing the sensing area B2 across the display area A, and sequentially shifts the same pulse as the scanning signal in the liquid crystal display device 500 to each of the N scanning lines 30. Is supplied as a reset signal to each of the N-1 first control lines 10 as a scan signal. That is, the pixel circuit P and the sensing circuit 40 operate with the same shift pulse.

  The data line 31 and the Nth scanning line 30 (for the L sensing circuits 40 in the sensing area B1) are arranged so as not to cross each other. In addition, the detection lines 21 for the N-1 sensing circuits 40 in the sensing area B2 and the detection lines 22 for the L sensing circuits 40 in the sensing area B1 are arranged so as not to intersect the scanning lines 30. Has been.

  In each of the unit circuits (L sensing circuits 40) in the Nth row, the scanning line 30 is connected to the gate of the reset transistor 42 and one electrode of the reference capacitance element 44, and the second control line 11 is connected to the selection transistor 43. The detection line 22 connected to the gate and common to the unit circuit in the Nth row is connected to the source of the selection transistor 43. Note that the liquid crystal display device 501 does not precharge the detection lines 22.

  On the other hand, in each of the unit circuits (N−1 sensing circuits 40) in the L + 1 column, the scanning line 30 common to the unit circuits in the same row is connected to the gate of the selection transistor 43, and is common to the unit circuits in the same row. The first control line 10 is connected to the gate of the reset transistor 42 and one electrode of the reference capacitor 44, and the detection line 21 common to the unit circuits in the (L + 1) th column is connected to the source of the selection transistor 43. That is, the N−1 sensing circuits 40 are selected by the same selection signal SEL as the pixel circuit P. In the liquid crystal display device 501, the potential of the detection line 21 is precharged to the precharge potential Vpre.

  Next, the operation of the liquid crystal display device 501 will be described with reference to FIG. As shown in the drawing, in one horizontal scanning period (1H) in which the data signal (DATA) is supplied to the pixel circuit P in the nth row, the selection signal SEL [1] to [N] among the selection signals SEL [1] to [N]. Only n] becomes a high level, and in the next one horizontal scanning period, only the selection signal SEL [n + 1] among the selection signals SEL [1] to [N] becomes a high level. That is, the levels of the selection signals SEL [1] to [N] are cyclically and exclusively high level in units of one horizontal scanning period.

  Further, as shown in the figure, in one horizontal scanning period (1H) in which the data signal (DATA) is supplied to the pixel circuit P in the n-th row, among the reset signals RES [1] to [N−1]. The level of only the reset signal RES [n + 2] becomes VD, and the level of only the reset signal RES [n + 1] among the reset signals RES [1] to [N−1] becomes VD in the immediately preceding horizontal scanning period. In the immediately preceding one horizontal scanning period, only the level of the reset signal RES [n] among the reset signals RES [1] to [N−1] is VD. That is, the levels of the reset signals RES [1] to [N−1] are cyclically and exclusively VD in units of one horizontal scanning period.

  As shown in the figure, the selection signal SEL [n] supplied to the nth scanning line 30 and the reset signal RES [n + 2] supplied to the n + 2th scanning line 30 are the same. However, the reset signal RES [N] does not exist, the selection signal SEL [N−1] is the same as the reset signal RES [1], and the selection signal SEL [N] is the same as the reset signal RES [2]. Therefore, one horizontal scanning period following one horizontal scanning period in which the level of the reset signal RES [N−1] is VD (one horizontal scanning immediately before one horizontal scanning period in which the level of the reset signal RES [1] is VD). In the period), the level of any reset signal RES does not become VD, and the sensing circuit 40 that reaches the reset period Tres in this period is not included in the unit circuit in the (L + 1) th column.

  As is clear from the above, the unit circuit (N−1 sensing circuits 40) in the (L + 1) th column reaches the reset period Tres cyclically and exclusively in units of one horizontal scanning period, and the unit circuit in the Nth row. The (L sensing circuits 40) reach the reset period Tres when the selection signal SEL [N] becomes low level.

  When the reset signal RES [n] changes from the high level to the low level, the unit circuit (sensing circuit 40) in the nth row L + 1 column reaches the sensing period Tsen, and the selection signal SEL [n] changes from the low level to the high level. Then, the reading period Tout is reached. That is, the unit circuit (N−1 sensing circuits 40) in the L + 1th column reaches the sensing period Tsen and the reading period Tout cyclically and exclusively in units of one horizontal scanning period. The operation of the sensing circuit 40 in each period is as described above. Therefore, the detection current Idet (Vs) from the N−1 sensing circuits 40 flows cyclically and exclusively through the detection line 21 in units of one horizontal scanning period. Note that the precharge period Tpre for each of the N−1 sensing circuits 40 is a period before the readout period Tout for the sensing circuit 40, and the N−1 sensing circuits 40 include the precharge period Tpre. This is a period after the readout period Tout for the sensing circuit 40 that reaches the readout period Tout immediately before the sensing circuit 40.

  On the other hand, as shown in the figure, when the selection signal SEL [N] is at a high level, when one horizontal scanning period is equally divided into L as one unit period, the selection signal sel is used in one unit period (1h). If only the selection signal sel [m] among [1] to [L] is at a high level, only the selection signal sel [m + 1] is selected from the selection signals sel [1] to [L] in the next one unit period. Become high level. That is, the unit circuit (L sensing circuits 40) in the Nth row reaches the sensing period Tsen when the selection signal SEL [N] becomes high level, and one unit in the period when the selection signal SEL [N] is high level. The reading period Tout is exclusively reached in units of periods. Since the operation of the sensing circuit 40 in each period is as described above, the detection current Idet (Vs) from the L sensing circuits 40 is supplied to the detection line 22 during the period in which the selection signal SEL [N] is at a high level. It flows exclusively in units of one unit period.

  The liquid crystal display device 501 may be modified so that the sensing area B2 is arranged between the Y driver 101 and the display area A, or the sensing area B1 is arranged between the X driver 200 and the display area A. It is good also as a form. In the latter case, it is preferable to employ an X driver having the functions of the X driver 200 and the sensor X driver 301 instead of the X driver 200.

  Next, the relationship between the sensing circuit 40 and the image displayed in the display area A will be described with reference to FIG. In this example, menu buttons are displayed in the individual areas Q1 and Q2 inside the end of the display area A. The user can input an instruction to the apparatus by depressing the menu button. The individual area Q1 is arranged close to the sensing area B1 where the sensing circuit 40 is arranged. Here, when the user presses the individual area Q1 with a finger, the surrounding area is dented, and in conjunction therewith, the capacitance value Cs of the capacitance detection element 45 formed in the sensing circuit 40 in the sensing area B1 is calculated. Change. Therefore, it is possible to detect which individual area Q1 the user touches with a finger.

  When the sensing circuit 40 is formed in the display area A, the aperture ratio is reduced. However, if the sensing circuit 40 is formed in the sensing areas B1 and B2, there is no such inconvenience. Of course, the sensing circuit 40 may be formed inside the display area A if the decrease in the aperture ratio is allowed. The sensing areas B1 and B2 in which the sensing circuit 40 is formed are formed along the edge of the display area A, and the capacitance detecting element 45 changes its capacitance when the gap length of the cell gap changes. Therefore, even if the user does not press the sensing areas B1 and B2 directly, this can be detected.

  FIG. 14 illustrates another mode in which the sensing circuit 40 is arranged. In FIG. 14A, a sensing area B1 is formed along the lower side of the display area A, and the sensing circuit 40 is arranged there. In this case, it is preferable to arrange the X driver 200 along the upper side opposite to the lower side where the sensing region B1 is arranged. When the X driver 200 is arranged in this way, it is not necessary to arrange the data line 31 across the sensing circuit 40, so that the wiring layout can be simplified.

  14B, the sensing area B3 may be formed along the upper side of the display area A, and the sensing area B1 may be formed along the lower side of the display area A. Further, as shown in FIG. 14C, the sensing areas B1, B2, and B3 may be arranged along the lower side, the right side, and the upper side of the display area A, respectively. Furthermore, as shown in FIG. 14D, the sensing areas B1, B2, B3, and B4 may be arranged along the four sides of the display area A, respectively.

<2. Application example>
Next, electronic equipment using the liquid crystal display device according to the present invention will be described. FIG. 15 is a perspective view showing a configuration of a mobile personal computer adopting the liquid crystal display device 500 or 501 as a display unit. The personal computer 2000 includes a liquid crystal display device 500 or 501 as a display unit and a main body 2010. The main body 2010 is provided with a power switch 2001 and a keyboard 2002. Menu buttons 2020, 2030, and 2040 are displayed on the liquid crystal display device 500 or 501. Various programs can be assigned to these menu buttons. For example, an e-mail can be assigned to the menu button 2020, a browser can be assigned to the menu button 2030, and drawing software can be assigned to the menu button 2040. Even if the user does not operate the keyboard 2002, the user can activate desired software simply by touching the menu button.

  FIG. 16 shows a configuration of a mobile phone to which the liquid crystal display device 500 or 501 according to the embodiment is applied. A cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and a liquid crystal display device 500 or 501 as a display unit. By operating the scroll button 3002, the screen displayed on the liquid crystal display device 500 or 501 is scrolled. Menu buttons 3010 and 3020 are displayed on the liquid crystal display device 500 or 501. For example, when the user touches the menu button 3010, the phone book is displayed, and when the user touches the menu button 3020, the telephone number of the mobile phone is displayed.

  FIG. 17 shows a configuration of a personal digital assistant (PDA) to which the liquid crystal display device 500 or 501 according to the embodiment is applied. The information portable terminal 4000 includes a plurality of operation buttons 4001, a power switch 4002, and a liquid crystal display device 500 or 501 as a display unit. When the power switch 4002 is operated, menu buttons 4010 and 4020 are displayed. When the menu button 4010 is pressed, the address book is displayed, and when the menu button 4020 is pressed, the schedule book is displayed.

  The electronic apparatus to which the electro-optical device according to the present invention is applied includes those shown in FIGS. 15 to 17, a digital still camera, a television, a video camera, a car navigation device, an electronic notebook, electronic paper, a calculator, Examples thereof include a word processor, a workstation, a video phone, a scanner, a copying machine, a video player, and a device equipped with a touch panel.

  The sensing circuit 40 described above is formed on the same plane on which the pixel circuit P in the display area A is formed. Good. Further, the sensing circuit 40 may be provided inside the display area A. Even in these cases, the number of wirings can be reduced by combining the wiring for supplying a potential to one electrode of the reference capacitance element 44 by the first control line 10 and the wiring for supplying the reset signal RES to the gate of the reset transistor 42. The effect is not impaired.

It is a block diagram which shows the structure of the liquid crystal display device which concerns on embodiment of this invention. It is a circuit diagram which shows the structure of a sensing circuit. It is a timing chart which shows operation | movement of a sensing circuit. It is explanatory drawing which shows operation | movement of the sensing circuit in a reset period. It is explanatory drawing which shows operation | movement of the sensing circuit in a sensing period. It is explanatory drawing which shows operation | movement of the sensing circuit in a read-out period. It is sectional drawing which shows the structure of an electrostatic capacitance detection element. It is a circuit diagram which shows the other example of a sensing circuit. It is sectional drawing which shows the structural example of the form of a FFS system. It is a block diagram which shows the other structural example of a liquid crystal display device. It is a circuit diagram of another example of composition. It is a timing chart which shows operation of other examples of composition. It is explanatory drawing for demonstrating the relationship between the image displayed on a sensing circuit and a display area. It is explanatory drawing for demonstrating the other relationship of the image displayed on a sensing circuit and a display area. It is a perspective view which shows the specific form of the electronic device which concerns on this invention. It is a perspective view which shows the specific form of the electronic device which concerns on this invention. It is a perspective view which shows the specific form of the electronic device which concerns on this invention.

Explanation of symbols

500, 501 ... Liquid crystal display device, A ... Display area, B1-B4 ... Sensing area, Q1-Q4 ... Individual area, 40, 40 '... Sensing circuit, 41 ... Amplifying transistor, 42, 94 ... ... reset transistor, 43 ... selection transistor, 44 ... reference capacitance element, 45, 91 ... capacitance detection element, RES ... reset signal, SEL ... selection signal, 10 ... first control line, 11 ... ... second control line, 20 ... power supply line, 21,22 ... detection line, Tres ... reset period, Tsen ... sensing period, Tout ... readout period, Tpre ... precharge period.

Claims (10)

A first transistor that has a power line electrically connected to one electrode and outputs a detection current corresponding to the gate potential from the other electrode;
A second transistor provided between the gate of the first transistor and the power supply line and turned on in response to a reset signal supplied to the gate through the first control line;
A reference capacitor provided between the first control line and the gate of the first transistor;
A capacitance detecting element having one terminal electrically connected to the gate of the first transistor and a predetermined potential supplied to the other terminal;
A third transistor provided between the other electrode of the first transistor and the detection line and turned on in response to a selection signal supplied to the gate through the second control line;
Sensing circuit provided.   The sensing circuit according to claim 1, wherein the reference capacitance is a parasitic capacitance generated between a gate and a drain of the second transistor. The first to third transistors are formed by the same process, and include a semiconductor layer, a gate oxide film, and a gate wiring.
The reference capacitor uses the semiconductor layer as one electrode and the gate wiring as the other electrode.
The sensing circuit according to claim 1. A plurality of pixel circuits having a pixel electrode, a common electrode, and a liquid crystal to which an electric field generated between the pixel electrode and the common electrode is applied;
A sensing circuit according to any one of claims 1 to 3,
The capacitance detection element includes a first electrode formed simultaneously with the pixel electrode, a second electrode formed simultaneously with the common electrode, and an electric field generated between the first electrode and the second electrode. Including the liquid crystal to be added,
A display device characterized by that.   The display device according to claim 4, wherein the liquid crystal included in the pixel circuit is sandwiched between the pixel electrode and the common electrode. The pixel electrode and the common electrode are formed in separate layers,
The liquid crystal included in the pixel circuit is disposed in a region different from a region between the layer including the pixel electrode and the layer including the common electrode.
The display device according to claim 4. The pixel electrode and the common electrode are formed in the same layer,
The liquid crystal included in the pixel circuit is included in a layer different from the layer.
The display device according to claim 4.   An electronic apparatus comprising the display device according to claim 4. A driving method of a sensing circuit according to any one of claims 1 to 3,
During the reset period,
Supplying the reset signal for turning on the second transistor to the first control line, and supplying the selection signal for turning off the third transistor to the second control line;
In the sensing period following the reset period,
Supplying the reset signal for turning off the second transistor to the first control line, and supplying the selection signal for turning off the third transistor to the second control line;
In the readout period following the sensing period,
Supplying the reset signal for turning off the second transistor to the first control line, and supplying the selection signal for turning on the third transistor to the second control line;
Driving method of sensing circuit. The sensing circuit driving method according to claim 9, wherein the detection line is precharged to a predetermined potential in part or all of the reset period and the sensing period.

Images