Patent ID: 12242701

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Description will be given in the following order.1. Basic principle of touch detection method2. First embodimentAn example that touch sensor is provided in touch panel.An example that two kinds of detection electrodes having different shapes are provided.An example that sensitivity of detection electrode is constant regardless of scan electrode.3. Modification of first embodimentAn example that output adjustment circuit is provided.4. Second embodimentAn example that touch sensor is provided in touch panel.An example that two kinds of detection electrodes having different shapes are provided.An example that sensitivity of detection electrode varies according to scan electrode.5. Modification of second embodimentAn example that output adjustment circuit is provided.6. Third embodimentAn example that touch sensor is provided in touch panel.An example that detection electrodes having the same shape are provided.An example that fringe capacitance increases in predetermined detection electrode.7. Fourth embodimentAn example that touch sensor is provided in touch panel.An example that detection electrodes having the same shape are provided.An example that fringe capacitance is equal in all of detection electrodes.8. Fifth embodimentAn example that touch sensor is provided in liquid crystal display panel.An example that two kinds of detection electrodes having different shapes are provided.An example that sensitivity of detection electrode is constant regardless of scan electrode.9. Modification of fifth embodimentAn example that output adjustment circuit is provided.10. Sixth embodimentAn example that touch sensor is provided in liquid crystal display panel.An example that two kinds of detection electrodes having different shapes are provided.An example that sensitivity of detection electrode varies according to scan electrode.11. Modification of sixth embodimentAn example that output adjustment circuit is provided.12. Application examplesExamples that the liquid crystal display devices of the embodiments are applied to electronic devices.
[Basic Principle of Touch Detection Method]

First, the basic principle of a touch detection method used in a display device of an embodiment will be described below. This touch detection method is embodied as a touch sensor of an electrostatic capacitance type.FIG.1Aschematically illustrates the touch sensor.FIG.1Bschematically illustrates an equivalent circuit of the touch sensor illustrated inFIG.1Aand a peripheral circuit connected to the touch sensor. The touch sensor has a dielectric101and a pair of electrodes102and103disposed opposing to each other while sandwiching the dielectric101, and expressed as a capacitive element104in the equivalent circuit as shown inFIG.1B.

One end (electrode102) of the capacitive element104is connected to an AC signal source105. The other end (electrode103) of the capacitive element104is connected to a voltage detection circuit106and, further, is connected to a reference potential line108via a resistor107. The AC signal source105outputs an AC rectangular wave Sg of predetermined frequency (for example, a few kHz to tens kHz). The voltage detection circuit106detects a crest value of an input signal and, further, determines whether the touch sensor is touched with a finger or not on the basis of the detection voltage thereof. The reference potential line108is, for example, electrically connected to a member (for example, a ground layer of a printed board or a conductive casing) to which a potential as a reference of a circuit operation is applied in a device on which the touch sensor is mounted. When the reference potential line108is connected to the member, the potential in the reference potential line108is equal to that of the member (the reference potential). The reference potential is, for example, the ground potential.

In the touch sensor, when the AC rectangular wave Sg (Part (B) ofFIG.3) is applied from the AC signal source105to the electrode102, an output waveform (detection signal Vdet) as shown in Part (A) ofFIG.3appears.

In a state where the touch sensor is not touched with an object such as a finger (FIG.1A), as shown inFIG.1B, current Io according to the capacitance value of the capacitive element104flows in accordance with charging/discharging of the capacitive element104. The potential waveform at this time on the side of the electrode103of the capacitive element104becomes like a waveform Vo of Part (A) ofFIG.3, and is detected by the voltage detection circuit106.

On the other hand, in a state where the touch sensor is touched with an object such as a finger (FIG.2A), as shown inFIG.2B, a capacitive element109formed by the object such as the finger is added to the capacitive element104in series. In this state, currents I1and I2flow according to charging/discharging of the capacitive elements104and109, respectively. At this time, the potential waveform in the electrode103becomes, for example, a waveform V1of Part (A) ofFIG.3, and is detected by the voltage detection circuit106. The potential of the electrode103becomes a divided potential determined by the values of the currents I1and I2flowing in the capacitive elements104and109. Consequently, the waveform V1becomes a value smaller than the waveform V0in the non-contact state. After that, by the voltage detection circuit106, the detected voltage and predetermined threshold voltage Vthare compared with each other. When the detected voltage is equal to or less than the threshold voltage Vth, the non-contact state is determined. On the other hand, when the detected voltage is larger than the threshold voltage Vth, the contact state is determined. In such a manner, a touch is detected.

First Embodiment

FIG.4illustrates an example of a sectional configuration of a liquid crystal display device1according to a first embodiment of the invention. The liquid crystal display device1is a liquid crystal display device with a touch sensor. As a display element, a liquid crystal display element is provided. Further, on the surface of the liquid crystal display element, a touch sensor of the electrostatic capacitance type is provided separately from the liquid crystal display element.

The liquid crystal display device1has, for example, as illustrated inFIG.4, a liquid crystal display panel10, a touch panel20, a backlight30, and a peripheral circuit40. The touch panel20is disposed on the side of an observer (front) of the liquid crystal display panel10, and the backlight30is disposed on the rear side of the liquid crystal display panel10.

[Liquid Crystal Display Panel10]

The liquid crystal display panel10displays a video image by transmitting or modulating light from the lights source (backlight30) by changing arrangement of liquid crystal molecules. The liquid crystal display panel10is, for example, a transmission-type display panel in which a plurality of pixels11(refer toFIG.5) disposed in matrix are driven in accordance with a video signal40A. For example, as shown inFIG.5, the liquid crystal display panel10has a plurality of scan lines WSL1disposed as rows and a plurality of signal lines DTL disposed as columns. The plurality of pixels11are disposed in matrix in correspondence with intersections between the scan lines WSL1and the signal lines DTL. In the liquid crystal display panel10, further, for example, as shown inFIG.5, a plurality of common connection lines COM are disposed as rows. For example, each of the common connection lines COM is arranged for one row of pixels11.

Each pixel11includes, for example, as shown inFIG.5, a liquid crystal element12and a transistor13. One end of the liquid crystal element12is connected to the drain of the transistor13, and the other end of the liquid crystal element12is connected to the common connection line COM. The gate of the transistor13is connected to the scan line WSL1, and the source of the transistor13is connected to the signal line DTL. The liquid crystal element12modulates light passing therethrough in accordance with a state of electric field, and is provided in the liquid crystal display panel10. The internal configuration of the liquid crystal element12will be described in detail later. The transistor13is provided to drive the liquid crystal element12, and is structured by, for example, a TFT (Thin Film Transistor).

The liquid crystal display panel10has, for example, as illustrated inFIG.6, a liquid crystal layer130(display function layer), and a light-incidence-side substrate110and a light-outgoing-side substrate120which are disposed opposing to each other while sandwiching the liquid crystal layer130. The liquid crystal layer130modulates light according to the state of the electric field, thereby expressing the display function, and includes, for example, liquid crystal molecules in the transverse electric mode. Examples of liquid crystal molecules in the transverse electric mode include electric crystal molecules in the FFS (Fringe Field Switching mode) and liquid crystal molecules in the IPS (In-Plane Switching) mode.

The light-incidence-side substrate110is a transparent substrate disposed on the incident side (backlight30side) of light from the backlight30in the liquid crystal display panel10. The light-incidence-side substrate110has, for example, in order from the backlight30side, a polarizer111, a transparent substrate112, a plurality of common electrodes113, an insulation layer114, a plurality of pixel electrodes115, and an alignment film116. On the other hand, the light-outgoing-side substrate120is a transparent substrate disposed on the outgoing side (observer side) of light modulated by the liquid crystal layer130in the liquid crystal display panel10. The light-outgoing-side substrate120has, for example, in order from the liquid crystal layer130side, an alignment film121, a color filter122, a transparent substrate123, and a polarizer124. The color filter122may not be provided as necessary.

The liquid crystal element12corresponds to, for example, as shown by a broken line inFIG.6, a portion facing one pixel electrode115in the liquid crystal display panel10. The liquid crystal element12includes, for example, the transparent substrate112, the common electrode113, the insulation layer114, the pixel electrode115, the alignment film116, the liquid crystal layer130, the alignment film121, the color filter122, and the transparent substrate123in this order.

The polarizers111and124are a kind of an optical shutter, and transmit only light in a certain vibration direction (polarized light). The polarizers111and124are disposed in crossed nicols. For example, the polarizer111is disposed so that its transmission axis becomes parallel to the column direction, and the polarizer124is disposed so that its transmission axis becomes parallel to the row direction. With this configuration, the liquid crystal display panel10transmits or interrupts light emitted from the backlight30via the liquid crystal layer130.

The transparent substrates112and123are substrates, for example, plate glass transparent to visible light. In the transparent substrate112, for example, active drive circuits including the transistor, the signal line DTL, the scan line WSL1, and the common connection line COM are formed.

The common electrode113and the pixel electrode115are made of a material transparent to visible light, which can be, for example, ITO (Indium Tin Oxide). The common electrode113is the common connection line COM itself or a part of the common connection line COM. The plurality of common electrodes113have, for example, a band-like shape extending in the row direction and are disposed in parallel. The common electrode113functions, for example, as an electrode common to the pixels11by row. Incidentally, the plurality of common electrodes113may be integrated as a single plate-shaped electrode.

On the other hand, the plurality of pixel electrodes115are, for example, in lattice arrangement or delta arrangement on the transparent substrate112. The pixel electrode115functions as, for example, an electrode for each pixel11. The plurality of pixel electrodes115are, for example, disposed side-by-side via predetermined gaps on a region opposing one common electrode113. The electric field formed between the pixel electrode115and the common electrode113is directed in the transverse direction (row direction) in the region of the liquid crystal layer130. The insulation layer114is provided for insulation between the common electrode113and the pixel electrode115, and is made of, for example, SiO2or the like. The alignment films116and121are made of a high polymer material such as polyimide, and have the function of making the liquid crystal included in the liquid crystal layer130. The alignment films116and121are subjected to rubbing processes so that, for example, the rubbing directions thereof become parallel to the transmission axis of one of the polarizers111and124. For example, the rubbing directions of the alignment films116and121are parallel to the row direction (the extension direction of the common electrode113). The color filter122is provided to separate the color of light having passed through the liquid crystal layer130to, for example, three primary colors of red (R), green (G), and blue (B), or four colors of R, G, B, and white (W).

[Touch Panel20]

The touch panel20allows information to be entered by touching an image display face1A (the surface of the touch panel20) of the liquid crystal display device1with an object (i.e., an external proximity object). The object can be a finger, a pen, or other suitable member which is in contact with or in close to the image display face1A, for example. The touch panel20is provided separately from the liquid crystal display panel10and, for example, is attached to the surface of the liquid crystal display panel10via an adhesive (not shown) or the like. The touch panel20corresponds to an illustrative example of the above-described touch sensor of the electrostatic capacitance type, and detects the contact or non-contact state by XY (row/column) matrix.

FIG.7illustrates an example of the top face configuration of the touch panel20.FIG.8illustrates an example of a sectional configuration taken along line A-A of the touch panel20inFIG.7. For example, as shown inFIGS.7and8, the touch panel20has a scan-side substrate210and a detection-side substrate220which are disposed opposing to each other via an adhesion layer23.

The scan-side substrate210is a transparent substrate disposed on the side (the side of the liquid crystal display panel10) on which light from the liquid crystal display panel10is incident in the touch panel20. The scan-side substrate210has, for example, in order form the side of the liquid crystal display panel10, a transparent substrate21and a plurality of scan electrodes22. On the other hand, the detection-side substrate220is a transparent substrate disposed on the side (the observer side) from which light having passed through the touch panel20goes out. The detection-side substrate220has, for example, in order from the side of the liquid crystal display panel10, a transparent substrate24, a plurality of detection electrodes25(first detection electrodes), and a plurality of detection electrodes26(second detection electrodes).

In the touch panel20, for example, a capacitive element is structured by an adhesion layer23, the transparent substrate24, and the scan electrode22and the detection electrode25which are disposed opposing to each other via the adhesion layer23and the transparent substrate24. The capacitive element functions as the touch sensor of the electrostatic capacitance type in the touch panel20. In the touch panel20, the detection electrodes25and26may be formed on the top face (the surface of the touch panel20) of the transparent substrate24, or the under face of the transparent substrate24. In the case where the detection electrodes25and26are formed on the under face of the transparent substrate24, the capacitive element is structured by the adhesion layer23, and the scan electrode22and the detection electrodes25and26disposed opposing to one another via the adhesion layer23.

The transparent substrates21and24are substrates transparent to visible light, which can be, for example, light-transmission resin films. The scan electrode22and the detection electrodes25and26are made of a material transparent to visible light, which can be, for example, ITO.

The scan electrode22corresponds to one of electrodes of the electrostatic capacitance type touch sensor, and is electrically connected to a scan line WSL2(refer toFIG.4). The scan electrode22is formed, for example, in contact with the surface of the transparent substrate21. The plurality of scan electrodes22have, for example, a band-like shape extending in a row direction (first direction) and are disposed in parallel with each other. Each of the scan electrodes22extends, for example, in a direction parallel with the common electrode113in the liquid crystal display panel10. At one end of each scan electrode22, the connection pad22A to be connected to the peripheral circuit40is formed.

The detection electrode25corresponds to the other electrode of the touch sensor of the electrostatic capacitance type, and is electrically connected to a detection line DET (refer toFIG.4). The detection electrode25is, for example, formed in contact with the surface of the transparent substrate24. The plurality of detection electrodes25have a band-shape electrode part extending in a direction (for example, column direction) (second direction) crossing the extending direction of the scan electrodes22, and are disposed parallel with each other. The electrode part of the detection electrodes25faces any of the scan electrodes22. As shown inFIG.7, the detection electrode25has a plurality of projection parts25B coupled to the electrode part. The projection parts25B are disposed in, for example, a region facing the scan electrodes22. The projection part25B protrudes in a direction (for example, the row direction) crossing the extension direction of the electrode part and has, for example, a rod-like shape as shown inFIG.7. The detection electrode25has, for example, a comb-like shape formed by the electrode part, and the plurality of projection parts25B. The projection part25B does not always have to have the rod-like shape but may have, for example, as shown inFIG.9, an annular shape. Also, three projection parts25B may be provided in each region facing the scan electrode22as shown inFIG.7, or two projection parts25B may be provided in each region facing the scan electrode22as shown inFIG.10. At one end of each detection electrode25, a connection pad25A to be connected to the peripheral circuit40is formed. Preferably, the connection pads25A are disposed near one common side in the surface of the transparent substrate24. Where appropriate, the connection pads25A may be disposed dispersedly near a plurality of sides of the surface of the transparent substrate24.

The detection electrode26also corresponds to the other electrode in the capacitive element, and is electrically connected to a detection line DET (refer toFIG.4). The detection electrode26is formed in the same plane as that of the detection electrode25, and is formed in contact with, for example, the surface of the transparent substrate24. The plurality of detection electrodes26have a band-like shape extending in a direction (for example, the column direction) crossing the extension direction of the scan electrode22, and are arranged in parallel with each other. The detection electrode26faces any of the scan electrodes22. The detection electrode26is not provided with a structure similar to that of the projections25B. Therefore, the detection electrode26has a shape different from that of the detection electrode25. At one end of each detection electrode26, a connection pad26A to be connected to the peripheral circuit40is formed. Preferably, the connection pads26A are disposed close to one common side in the surface of the transparent substrate24together with the connection pads25A. Where appropriate, the connection pads26A may be disposed dispersedly near a plurality of sides of the surface of the transparent substrate24.

A line width of the detection electrode25is narrower than that of the detection electrode26in each of the electrode part and the projection part25B. In the detection electrode25, the electrode part has a line width of, for example, about 100 μm, and the projection part25B has a line width of, for example, about 10 μm. On the other hand, a line width of the detection electrode26is wider than that of the detection electrode25, and has, for example, a line width of about 500 μm.

The detection electrodes25and26are disposed so that at least one detection electrode25and one detection electrode26are provided just below a contact part between the object such as the finger or the pen and the image display face1A (for example, a part surrounded by a broken-line circle inFIG.7) when the object touches the image display face1A. That is, the detection electrodes25and26are disposed so that the gap between the neighboring detection electrodes25and26becomes smaller than the diameter of the contact part. Further, the detection electrodes25and26are formed so that, for example, when the image display surface1A is touched with the object such as the finger or the pen, a capacitance (capacitance C) formed between the detection electrode25and the object and a capacitance (capacitance D) formed between the detection electrode26and the object are almost equal to each other. To make the detection electrodes25and26easily satisfy such a condition, for example, as illustrated inFIGS.7,9, and10, preferably, the detection electrodes25and26are disposed alternately in the row direction. Also, for example, as illustrated inFIGS.7,9, and10, preferably, the projection parts25B of the detection electrode25are disposed closer to the adjacent detection electrode26as compared with the electrode parts of the detection electrode25. Further, for example, as illustrated inFIGS.7,9, and10, preferably, the area of a part facing one scan electrode22, of the detection electrode25and the area of a part facing one scan electrode22, of the detection electrode26are equalized to each other.

[Backlight30]

The backlight30illuminates the back of the liquid crystal display panel10, and has, for example, a light guide plate, a light source disposed on a side face of the light guide plate, and an optical element disposed on the top face (light outgoing face) of the light guide plate. The light guide plate guides light from the light source to the top face of the light guide plate, and, for example, has a shape formed in a predetermined pattern in one of the top face and the under face, and has the function of scattering light incident from the side face so as to uniform the light. The light source is a linear light source, and is made by, for example, an HCFL (Hot Cathode Fluorescent Lamp), CCFL, or a plurality of LEDs disposed linearly. The optical element is structured by, for example, stacking a diffuser, a diffusion sheet, a lens film, a polarization separation sheet, or the like.

[Peripheral Circuit40]

Next, circuits in the peripheral circuit40will be described with reference toFIG.4. The peripheral circuit40drives the liquid crystal display panel10and the touch panel20, and detects an output of the above-described touch sensor of the electrostatic capacitance type, for example. The peripheral circuit40is, for example, mounted on the light-incidence-side substrate110in the liquid crystal display panel10, or connected to a flexible print circuit board (FPC) connected to the liquid crystal display panel10and the touch panel20, for example. The peripheral circuit40has, for example, a video signal process circuit41(first drive section), a timing generation circuit42, a signal line drive circuit43, a scan line drive circuit44, a scan line drive circuit45(second drive section), and a detection circuit46(detection section).

The video signal process circuit41corrects, for example, the digital video signal40A which is input from the outside, converts the corrected video signal to an analog signal, and outputs the analog signal to the signal line drive circuit43. The timing generation circuit42controls, for example, so that the signal line drive circuit43and the scan line drive circuits44and45operate in conjunction with one another. The timing generation circuit42outputs, for example, a control signal42A to those circuits according to (synchronously with) a sync signal40B which is input from the outside.

The signal line drive circuit43applies an analog video signal (a signal potential corresponding to the video signal40A) input from the video signal process circuit41to signal lines DTL to write the analog video signal to the selected pixels11. The signal line drive circuit43, for example, outputs a signal potential corresponding to the video signal40A. The signal line drive circuit43, for example, performs frame inversion driving of writing a signal to the selected pixels11, by applying a signal potential, which inverts every frame period with respect to reference potential, to each of the signal lines DTL. The frame inversion driving is performed to suppress deterioration in the liquid crystal element12, and is used where appropriate. Further, the signal line drive circuit43, for example, also performs 1H inversion drive of writing a signal to the selected pixels11, by applying a signal potential, which inverts every 1H period with respect to the reference potential, to each of the signal lines DTL. The 1H inversion driving is performed to suppress occurrence of flicker in each frame due to inversion of the polarity of a voltage applied to the liquid crystal element12, and is used where appropriate. Here, the reference potential is a potential of the common connection line COM, and is, for example, a ground potential.

The scan line drive circuit44sequentially applies a selection pulse to a plurality of scan lines WSL1according to (synchronously with) input of the control signal42A to select a plurality of pixels11by desired unit. As the unit of selecting the pixels11, for example, as needed basis, various units may be selected such as one line or neighboring two lines. The selection of the pixels11may be, for example, sequential selection or random selection. The scan line drive circuit44outputs, for example, a voltage applied to turn on the transistor13and a voltage applied to turn off the transistor13.

The scan line drive circuit45sequentially applies a selection pulse to a plurality of scan lines WSL2according to (synchronously with) input of the control signal42A to select a plurality of scan electrodes22by desired unit. As the unit of selecting the scan electrodes22, for example, as needed basis, various units may be selected such as one line or neighboring two lines. The selection of the scan electrodes22may be, for example, sequential selection or random selection.

The scan line drive circuit45has, for example, as illustrated inFIG.11, a switching element45A connected to one end of the scan line WSL2. The other end of the scan line WSL2is electrically connected to the scan electrode22(the connection pad22A). One switching element45A is provided for each scan line WSL2, and has, for example, two input terminals. One input terminal of the switching element45A is, for example, connected to an AC signal source45B via a line L1. The AC signal source45B outputs an AC rectangular wave Sg of a predetermined frequency (for example, a few kHz to tens kHz). The other input terminal of the switching element45A is connected to, for example, a logic circuit45C via a line L2. The logic circuit45C outputs, for example, a predetermined fixed potential (for example, a potential in the range of 0V to 5V). The AC signal source45B and the logic circuit45C are, for example, connected to the reference potential line108or the like as illustrated inFIG.11. The reference potential line108is, for example, a line connected to the member which applies the potential as the reference of the circuit operation in the liquid crystal display device1. The scan line drive circuit45may be constructed by circuits different from those illustrated inFIG.11.

Next, the detection circuit46will be described. The detection circuit46detects the contact position of the object such as a finger, on the basis of a detection signals Vdetobtained from the plurality of detection electrodes25and26. More specifically, the detection circuit46detects whether the object such as the finger is in contact with the image display face1A or not, on the basis of the difference between the detection signal Vdetobtained from the detection electrode25and the detection signal Vdetobtained from the detection electrode26. When the difference is equal to or less than the predetermined threshold voltage Vth, the detection circuit46determines that the object is in contact with the image display face1A. When the difference exceeds the predetermined threshold voltage Vth, the detection circuit46determines that the object is not in contact with the image display face1A. When it is detected that the object such as the finger is in contact with the image display face1A, the detection circuit46executes the following process. Specifically, the detection circuit46calculates the position of contact of the object such as the finger in the image display face1A, on the basis of the timing of applying the selection pulse output from the scan line drive circuit45and the timing of detecting the difference which is equal to or less than the threshold voltage Vth.

The detection circuit46has, for example, as shown inFIG.12, a differential circuit50at an input stage. The detection circuit46has, for example, at the post stage of the difference circuit50, an operational amplifier51for amplifying a signal, a low pass filter (LPF)52, a high pass filter (HPF)53, a rectifying and smoothing unit54, and a comparator55. Two input terminals Tin1and Tin2of the difference circuit50are electrically connected to the detection electrodes25and26(the connection pads25A and26A). Therefore, to the input terminals Tin1and Tin2, the detection signal Vdetoutput from the detection electrode25and the detection signal Vdetoutput from the detection electrode26are input. The positive input terminal (+) of the operational amplifier51is connected to the output terminal of the difference circuit50, and the output terminal of the operational amplifier51is connected to the rectifying and smoothing unit54via the LPF52. To the LPF52, the HPF53is connected. The LPF52has a configuration that, for example, a resistor52R and a capacitor52C are connected in parallel. The HPF53has a configuration that, for example, a resistor53R and a capacitor53C are connected in series in the reference potential line108. The connection point between the LPF52and the HPF53is connected to the negative input terminal (−) of the operational amplifier51. The rectifying and smoothing unit54has, for example, a rectifying unit configured of a half-wave rectifier diode54D, and a smoothing unit obtained by connecting a resistor54R and the capacitor52C in parallel in the reference potential line108. The output terminal of the rectifying and smoothing unit54is connected to the positive input terminal (+) of the comparator55. The predetermined threshold voltage VII, is input to the negative input terminal (−) of the comparator55. The output terminal of the comparator55is connected to the output terminal Tout, and the output terminal Toutis connected to a not-shown computing circuit. Therefore, on the basis of a detection result (contact or non-contact) output from the output terminal Tout, a predetermined information process is performed by the computing circuit.

The detection circuit46having such a configuration operates as follows. The difference between the two detection signals Vdetinput to the input terminals Tin1and Tin2is calculated by the difference circuit50, and a signal (differential signal) obtained by the calculation is amplified by the operational amplifier51. After that, low frequency components of the signal pass through the LPF52, and high frequency components are removed by the HPF53. The AC components of low frequency having passed through the LPF52are subjected to half-wave rectification by the diode54D of the rectifying and smoothing unit54. After that, the resultant becomes a smoothed level signal, and the level signal is input to the comparator55. In the comparator55, the input level signal is compared with the threshold voltage Vth. When the level signal is equal to or less than the threshold voltage Vth, a touch detection signal is output from the comparator55. When the touch detection signal is input to the computing circuit, in the computing circuit, the touch position is calculated on the basis of the application timing of the selection pulse and the detection timing of the detection signal Vdetwhich is equal to or less than the threshold voltage Vth. Incidentally, the detection circuit46may be structured by circuits different from those shown inFIG.12.

[Operation]

An example of the operation of the liquid crystal display device1according to the present embodiment will now be described.

In the liquid crystal display device1, the signal potential corresponding to the video signal40A is applied to the signal lines DTL by the signal line drive circuit43, and the selection pulse according to the control signal42A is sequentially applied to the plurality of scan lines WSL1by the scan line drive circuit44. Consequently, a transverse electric field having a magnitude corresponding to the signal potential is applied on the pixel11unit basis to the liquid crystal layer130, and the liquid crystal molecules are aligned in a predetermined direction. Therefore, the light from the backlight30is modulated on the pixel11unit basis in the liquid crystal layer130in accordance with the alignment direction of the liquid crystal molecules. As a result, an image is displayed on the image display face1A.

In the liquid crystal display device1, further, the selection pulse is sequentially applied to the plurality of scan lines WSL2by the scan line drive circuit45. Thus, capacitive elements (corresponding to the capacitive elements104) each formed in the intersection part of the scan electrode22and the detection electrode25are sequentially changed/discharged, and the detection signal Vdetof the level based on the capacitance value of the capacitive element is output from each of the plurality of detection electrodes25. The outputs (detection signals Vdet) from the plurality of detection electrodes25are input to the detection circuit46. In a state where a finger of the user is not in contact with the surface of the touch panel20, the level of the detection signal V d et is almost constant.

When a finger of the user touches any place in the surface of the touch panel20, a capacitive element formed by the finger or the like (the capacitive element corresponding to the capacitive element109) is added to the capacitive element formed in the position where the finger or the like is touched. Consequently, the difference of the two detection signals Vdetoutput from the detection electrodes25and26when the selection pulse is applied to the scan electrode22corresponding to the touch position becomes smaller than the difference of the two detection signals V det output from the electrodes25and26when the selection pulse is applied to another place. In the detection circuit46, that difference is compared with the threshold voltage Vth. For example, when the difference is equal to or less than the threshold voltage Vth, it is determined that the finger or the like is in contact with the surface of the touch panel20. The contact position is determined from the application timing of the selection pulse and the detection timing of the detection signal Vdetwhich is equal to or less than the threshold voltage Vthin the detection circuit46.

Operation and Effects

Next, the operation and effects of the liquid crystal display device1according to the present embodiment will be described.

Generally, in a detection method of the electrostatic capacitance type, due to the principle of the method, when a finger or the like of the user touches the surface of the touch panel, the capacitive element formed by the finger or the like has to be added to the detection electrode provided in the touch panel. Thus, the detection electrode is provided on or near the surface of the touch panel, although external noise thereby easily enters the detection electrode. In particular, when the touch panel is used for a mobile device, the user holding the mobile device by his/her hand becomes an antenna and receives external noise, and the received noise enters the detection electrode via the hand of the user. When the noise enters the detection electrode, an output of the detection electrode (the value of the detection signal) fluctuates. Thus, contact/non-contact may be erroneously determined.

However, in the present embodiment, the two kinds of the detection electrodes25and26having different line widths are provided for the touch panel20, as one of the electrodes of the touch sensor of the electrostatic capacitance type used for detecting the contact/non-contact state. The detection electrodes25and26are disposed opposing to the scan electrode22via the predetermined gap. Thus, when voltage is applied between the scan electrode22and the detection electrodes25and26, for example, lines of electric force as illustrated inFIG.13are generated between the scan electrode22and the detection electrodes25and26. In the gap between the scan electrode22and the detection electrodes25and26, the lines of electric force extend almost straight. By the electric fields generated in the gap, a parallel plate capacitance C1is formed. On the other hand, around the gap between the scan electrode22and the detection electrodes25and26, the lines of electric force extend largely around the top face side of the detection electrodes25and26, and extend to the observer side more than the image display face1A with which a finger or the like comes in contact. By the round electric field, a fringe capacitance C2is formed.

Although the parallel plate capacitance C1and the fringe capacitance C2are formed for both of the detection electrodes25and26as described above, a region in which the parallel plate capacitance C1is formed in the detection electrode25having the narrower line width is smaller than that of the detection electrode26having the wider line width. That is, a value of the parallel plate capacitance C1in the detection electrode25is smaller than that in the detection electrode26. On the other hand, a size of a region in which the fringe capacitance C2is formed largely does not have the relation with the line width, and is proportional to the length of an edge of the detection electrodes25and26. For example, as shown inFIGS.7,9, and10, since the detection electrode25is provided with the projections25B, the edge of the detection electrode25is longer than that of the detection electrode26by the amount of the length of the edge included in the projection part25B. Consequently, the region in which the fringe capacitance C2is formed in the detection electrode25is wider than that of the detection electrode26by the amount of the length of the edge included in the projection part25B. Therefore, a rate of the fringe capacitance C2in the capacitance (total capacitance) obtained by adding the parallel plate capacitance C1and the fringe capacitance C2in the detection electrode25is larger than that in the detection electrode26.

It is now assumed that a finger or the like is brought close to the detection electrodes25and26and interrupts the electric field forming the fringe capacitance C2. Due to the interruption with the finger or the like, the fringe capacitance C2decreases, and, in association therewith, the total capacitance also decreases. A fluctuation rate (decrease rate) of the total capacitance in the detection electrode25is higher than that of the detection electrode26. Therefore, when the plurality of scan electrodes22are selected in desired unit, the signal level of the detection signal Vdetobtained from the detection electrode25fluctuates largely between the time when the finger or the like touches the image display face1A and the time when the finger or the like does not touch the image display face1A. On the other hand, the signal level of the detection signal Vdetobtained from the detection electrode26fluctuates only by a fluctuation amount smaller than the fluctuation amount in the detection electrode25, between the time when the finger or the like touches the image display face1A and the time when the finger or the like does not touch the image display face1A.

As described above, in the present embodiment, the sensitivity to touch of a finger or the like in the detection electrode25is higher than that in the detection electrode26. Further, the sensitivity to touch of a finger or the like in the detection electrode25is almost constant regardless of the scan electrode22. Similarly, the sensitivity to touch of a finger or the like in the detection electrode26is almost constant regardless of the scan electrode22. In other words, in the present embodiment, the detection electrodes25and26having different sensitivities to touch of a finger or the like are provided for the touch panel20.

Also, in the present embodiment, the detection electrodes25and26are formed so that, for example, when the object such as a finger or pen touches the image display face1A, the capacitance (capacitance C) formed between the detection electrode25and the object, and the capacitance (capacitance D) formed between the detection electrode26and the object, are almost equalized. In the present embodiment, for example, as shown inFIGS.7,9, and10, in the case where the detection electrodes25and26are disposed alternately in the row direction, or disposed so that the projections25B of the detection electrode25are closer to the neighboring detection electrode26more than the electrode parts of the detection electrode25, the capacitance C and the capacitance D are almost equalized. In the present embodiment, for example, as shown inFIGS.7,9, and10, also in the case where the area of the part facing one scan electrode22in the detection electrode25and the area of the part facing one scan electrode22in the detection electrode26are equalized, the capacitance C and the capacitance D are almost equalized.

Consequently, for example, sensitivity to external noise in the detection electrode25and that in the detection electrode26are almost equalized when the user becoming as an antenna and catching the external noise touches the panel with his/her finger and the external noise is transmitted to the touch panel20via the finger. In the case where the sensitivity to the external noise of the detection electrode25and the sensitivity to the external noise of the detection electrode26are equal to each other, the signal level of the external noise included in the detection signal Vdetobtained from the detection electrode25and that of the external noise included in the detection signal Vdetobtained from the detection electrode26are equal to each other. Therefore, for example, by calculating the difference between the detection signal Vdetobtained from the detection electrode25and that obtained from the detection electrode26, the external noise is eliminated from the detection signals.

Part (A) to Part (H) ofFIG.14illustrate an example of signal waveforms when the detection electrodes25and26have the configuration as illustrated inFIG.7,9, or10and when, in a state the touch panel20is touched with a finger, the plurality of scan lines WSL2are sequentially driven. In Parts (A) to (D) ofFIG.14, the number at the end of each of WSL2(1), WSL2(2), WSL2(3), and WSL2(4) indicates serial number (sequence number) of the scan line WSL2. The number at the end of each of DET(1) and DET(2) in Parts (F) and (G) ofFIG.14indicates serial number (sequence number) of the detection lines DET. In Parts (F) to (H) ofFIG.14, DET(1) corresponds to the detection line DET connected to the detection electrode25, and DET(2) corresponds to the detection line DET connected to the detection electrode26. Parts (F) to (H) ofFIG.14illustrate signal waveforms obtained when a finger touches a region opposing the crossing part of the first to third scan lines WSL2and the first and second detection lines DET.

It can be seen from Parts (F) and (G) ofFIG.14, that when the first to third scan lines WSL2are selected, the detection signal Vdetof the voltage Va is obtained from the first selection line DET, and the detection signal Vdetof a voltage Vb (>Va) is obtained from the second selection line DET. The reason why the signal level of the detection signal Vdetvaries between the first selection line DET and the second selection line DET is that the sensitivity to touch with a finger or the like in the detection electrode25connected to the first selection line DET is higher than that in the detection electrode26connected to the second selection line DET.

It can also be seen from Parts (F) and (G) ofFIG.14that, when the fourth scan line WSL2is selected, the detection signal Vdetof the voltage Vc is obtained from the selection line DET(1), and the detection signal Vdetof a voltage Vd (=Vc) is obtained from the selection line DET. The reason why the signal level of the detection signal Vdetof the first selection line DET and that of the second selection line DET are the same is that a finger does not touch a part just above the fourth scan line WSL2and the detection electrodes25and26are hardly influenced by the finger.

It can also be seen from Parts (E) to (G) ofFIG.14that noise having the same phase as that of external noise is included at almost the same level in the detection signal Vdetobtained from the first selection line DET and the detection signal Vdetobtained from the second selection line DET. The reason is that the sensitivity to the external noise in the detection electrode25connected to the first selection line DET and that in the detection electrode26connected to the second selection line DET are almost equal to each other.

It can be seen from Part (H) ofFIG.14that, by obtaining the difference between the detection signal Vdetobtained from DET(1) and the detection signal Vdetobtained from DET(2), a fluctuation component (Vb−Va) of the detection signal Vdetby touch of a finger is extracted. It can also be seen from Part (H) ofFIG.14that noise having the same phase as that of the external noise is eliminated from the detection signal Vdet.

From the above, by providing the two kinds of the detection electrodes25and26having the different sensitivities to the contact/non-contact state and having the almost equal sensitivities to the external noise, the external noise is eliminated from the detection signal Vdetonly by calculating the difference of the detection signals Vdet. Therefore, it is possible to eliminate the erroneous detection caused by the external noise.

Modification of First Embodiment

Modification 1

Although the case where one scan electrode22is connected to one scan line WSL2has been described in the foregoing embodiment, the plurality of neighboring scan electrodes22may be connected to one scan line WSL2. In such a case, as compared with the case where one scan electrode22is connected to one scan line WSL2, the signal level of the detection signal Vdetobtained from the detection electrodes25and26becomes higher. Incidentally, only by simply increasing the line width of the scan electrode22and the detection electrodes25and26, the signal level of the detection signal Vdetis made higher. However, in such a case, as described above, when the line width is increased, only the parallel plate capacitance C1increases, and the capacitance C and the capacitance D decrease. Therefore, the sensitivity to touch with a finger or the like decreases. On the other hand, as in the present modification, in the case of connecting the plurality of neighboring scan electrodes22to one scan line WSL2, not only the parallel plate capacitance C1but also the fringe capacitance C2increase, and the capacitance C and the capacitance D do not change. Thus, there is no possibility that the sensitivity to touch with a finger or the like decreases.

Modification 2

In the foregoing embodiment, the detection electrodes25and26are formed so that the capacitances C and D become almost equal to each other. However, for example, due to manufacture error or the like, there may be a case that the capacitances C and D are slightly different from each other. For example, in the case where the projection parts25B of the detection electrode25are eliminated and the detection electrode25is formed in a rod-like shape as illustrated inFIG.15, the capacitances C and D are largely different from each other. In the case where there is a difference between the capacitances C and D, the signal level of the external noise included in the detection signal Vdetobtained from the detection electrode25and that of the external noise included in the detection signal Vdetobtained from the detection electrode26become different from each other. Consequently, even if the difference between the detection signal Vdetobtained from the detection electrode25and the detection signal Vdetobtained from the detection electrode26is simply obtained, the external noise is not eliminated from the detection signal Vdet. Therefore, in the present modification, the case where there is a difference between the signal levels of external noises included in the detection signals Vdetis assumed, and means for correcting the difference is also provided.

For example, in the present modification, as illustrated inFIG.16, in the detection circuit46, an output adjustment circuit56is provided between the difference circuit50and the input terminals Tin1and Tin2. The output adjustment circuit56makes the signal level of the detection signal Vdetinput to the input terminal Tin1and the signal level of the detection signal Vdetinput to the input terminal Tin2equal to each other. Incidentally, it is assumed here that the detection electrode25is connected to the input terminal Tin1and the detection electrode26is connected to the input terminal Tin2.

Example of Using Operational Amplifier Whose Magnification is Adjustable

The output adjustment circuit56has, for example, two operational amplifiers56A and56B. The positive input terminal (+) of the operational amplifier56A is connected to the input terminal Tin′, and the output terminal of the operational amplifier56A is connected to one of input terminals of the difference circuit50. The negative input terminal (−) of the operational amplifier56A is connected to the output terminal of the operational amplifier56A, and the operational amplifier56A serves as a voltage follower. The positive input terminal (+) of the other operational amplifier56B is connected to the input terminal Tin2, and the output terminal of the operational amplifier56B is connected to the other input terminal of the difference circuit50. The negative input terminal (−) of the operational amplifier56B is connected to one end of each of a variable resistor56C and a fixed resistor56D which are connected in series, and the other end of each of the variable resistor56C and the fixed resistor56D which are connected in series are connected to the reference potential line108. A connection point between the variable resistor56C and the fixed resistor56D is connected to the output terminal of the operational amplifier56B. Therefore, the operation amplifier56A is a non-inversion amplifier.

The variable resistor56C in the output adjustment circuit56is adjusted, for example, as follows. First, a voltmeter is connected to two outputs of the output adjustment circuit56. Next, under environment where there is no external noise, in a state where the image display face1A is touched with a conductor to which a voltage source is connected (for example, a pseudo finger), a predetermined fixed voltage is applied to the scan line WSL2just below the conductor. Thus, the detection signals Vdetoutput from the detection electrodes25and26are input to the voltmeter via the output adjustment circuit56, and the voltage level of the input signal is displayed on the voltmeter. Next, the voltage of the conductor is set to a predetermined voltage value by using a voltage source, and the value of the variable resistor56C is adjusted while seeing display of the voltmeter so that the values of the detection signals Vdetobtained from the detection electrodes25and26become equal to each other.

As described above, in the present modification, the signal level of the detection signal Vdetinput to the input terminal Tin2is corrected by using the variable resistor56C whose resistance value is adjusted. After that, the difference between the corrected detection signal and the detection signal Vdetinput to the input terminal Tin2is obtained. Thereby, the external noise is eliminated from the detection signal Vdet. Therefore, it is possible to eliminate the erroneous detection caused by the external noise. Incidentally, the correction on the signal level of the detection signal Vdetmay be performed only on the detection signal Vdetinput to the input terminal Tin1, or may be performed on both of the detection signals Vdetinput to the input terminals Tin1and Tin2.

Example of Using Arithmetic Circuit

In the above-described modification, the output adjustment circuit56is structured by an analog circuit including the operational amplifier whose magnification is adjustable. The output adjustment circuit56may be structured by a digital circuit such as a ROM (Read-Only Memory) on which a program for correcting noise level is written. The program written on the digital circuit includes a correction formula for correcting the noise level.

When the signal level of the detection signal Vdetinput to the input terminal Tin1is Vin1, and that of the detection signal Vdetinput to the input terminals Tin2is set to Vin2, the correction formula is expressed, for example, by the following formulae (1) and (2).
Vc1=α×Vin1(1)
Vc1=Vin2(2)

In the above formulae, only Vin1is corrected. However, for example, as shown in the following formulae (3) and (4), only Vin2may be corrected. Also, both of them may be corrected.
Vc1=Vin1(3)
Vc1=(1/α)×Vin2(4)

A correction factor α in the correction formulae for correcting the noise level is set, for example, as follows. First, a voltmeter is connected to the detection line DET connected to the detection electrode25and the detection line DET connected to the detection electrode26. Next, under environment where there is no external noise, in a state where the image display face1A is touched with a conductor to which a voltage source is connected (for example, a pseudo finger), a predetermined fixed voltage is applied to the scan line WSL2just below the conductor. Thus, the detection signals Vdetoutput from the detection electrodes25and26are input to the voltmeter, and the voltage level of the input signal is displayed on the voltmeter. Next, the voltage of the conductor is set to a predetermined voltage value by using a voltage source, and the indication in the voltmeter at that time is read. After that, a ratio (Vy/(Vx−Vy)) between the voltage value Vx of the detection signal Vdetoutput from the detection electrode25and the voltage value Vy of the detection signal Vdetoutput from the detection electrode26is calculated. The ratio is set as the correction factor α.

As described above, in the present modification, the signal level of the detection signal Vdetinput to the input terminal Tin2is corrected by using the correction formula in which the value of the correction factor α is set. After that, the difference between the corrected detection signal and the detection signal Vdetinput to the input terminal Tin2is obtained. Thereby, the external noise is eliminated from the detection signal Vdet. Therefore, it is possible to eliminate the erroneous detection caused by the external noise. Incidentally, the correction on the signal level of the detection signal Vdetmay be performed only on the detection signal Vdetinput to the input terminal Tin1, or may be performed on both of the detection signals Vdetinput to the input terminals Tin1and Tin2.

Second Embodiment

FIG.17illustrates an example of the top face configuration of the touch panel20included in a liquid crystal display device according to a second embodiment of the invention. The liquid crystal display device of the second embodiment is different from the liquid crystal display device of the foregoing embodiment, in that a plurality of detection electrodes27are provided in place of the plurality of detection electrodes25, and a plurality of detection electrodes28are provided in place of the plurality of detection electrodes26in the touch panel20. In the following, the points different from the configuration of the foregoing embodiment will be mainly described, and description of the configuration common to that of the foregoing embodiment will not be repeated. In the following, the same reference numerals are designated to components common to those described above.

The detection electrode27corresponds to the other electrode in the touch sensor of the electrostatic capacitance type, and is electrically connected to the detection line DET. The detection electrode27is, for example, formed in contact with the surface of the transparent substrate24. The plurality of detection electrodes27have a band-shape electrode part extending in a direction (for example, the column direction) crossing the extending direction of the scan electrodes22, and are disposed parallel with each other. The electrode part of the detection electrodes27faces any of the scan electrodes22. As shown inFIG.17, the detection electrode27has a plurality of projection parts27B coupled to the electrode part. The projection parts27B are disposed in, for example, a region facing the scan electrodes22among the plurality of scan electrodes22. The projection part27B protrudes in a direction (for example, the row direction) crossing the extension direction of the electrode part, and has, for example, a rod-like shape as shown inFIG.17. The detection electrode27has, for example, a comb-like shape formed by the electrode part and the plurality of projection parts27B. The projection part27B does not always have to have the rod-like shape, but may have another shape. At one end of each detection electrode27, a connection pad27A which is to be connected to the peripheral circuit40is formed. Preferably, the connection pads27A are disposed near one common side in the surface of the transparent substrate24. Where appropriate, the connection pads27A may be disposed dispersedly near a plurality of sides of the surface of the transparent substrate24.

The detection electrode28also corresponds to the other electrode in the capacitive element, and is electrically connected to the detection line DET. The detection electrode28is formed in the same plane as that of the detection electrode27, and is formed in contact with, for example, the surface of the transparent substrate24. The plurality of detection electrodes28have a band-like shape extending in a direction (for example, the column direction) crossing the extension direction of the scan electrode22, and are arranged in parallel with each other. The detection electrode28faces any of the scan electrodes22. The detection electrode28also has, as illustrated inFIG.17, a plurality of projections28B coupled to the electrode part. The projections28B are disposed in regions facing the scan electrodes22which do not face the projections27B among the plurality of scan electrodes. That is, the projections27B and28B are provided in the regions facing the different scan electrodes22. Therefore, the detection electrode28has a shape different from that of the detection electrode27. For example, in the case where the projections27B are provided in the regions facing the odd-numbered scan electrodes22, the projections28B are provided in the regions facing the even-numbered scan electrodes22. For example, in the case where the projections27B are provided in the regions facing the even-numbered scan electrodes22, the projections28B are provided in the regions facing the odd-numbered scan electrodes22.

The projection part28B protrudes in a direction (for example, the row direction) crossing the extension direction of the electrode part, and has, for example, a rod-like shape as shown inFIG.17. The detection electrode28has, for example, a comb-like shape formed by the electrode part and the plurality of projection parts28B. In the detection electrode28, for example, the projection parts28B are disposed close to the projection parts27B so that the projection parts27B of the detection electrode27and the projection parts28B of the detection electrode28are disposed alternately in a direction (for example, the column direction) crossing the extension direction of the scan electrodes22. Preferably, the connection pads28A are disposed near one common side in the surface of the transparent substrate24together with the connection pads27A. Where appropriate, the connection pads28A may be disposed dispersedly near a plurality of sides of the surface of the transparent substrate24.

The line width of the detection electrode27may be equal to or different from that of the detection electrode28. In the case where the line width of the detection electrode27is equal to that of the detection electrode28, a region in which the fringe capacitance C2 is formed in the detection electrode27becomes wider than that in the detection electrode28by an amount of the length of the edge included in the projection part27B on the scan electrode22facing the projection part27B. In this case, when the scan electrode22facing the projection part27B is driven, the sensitivity to contact of a finger or the like of the detection electrode27is higher than that of the detection electrode28. When the line width of the detection electrode27is different from that of the detection electrode28, the region in which the fringe capacitance C2is formed in any of the detection electrodes27and28becomes wider by an amount of the difference between the length of the edge in the detection electrode27included on the scan electrode22facing the projection part28B and the length of the edge in the detection electrode28included on the scan electrode22facing the projection part28B. In this case, when the scan electrode22facing the projection part28B is driven, the sensitivity to contact of a finger or the like of the detection electrode27or28having the wider region in which the fringe capacitance C2is formed becomes higher. That is, in the present embodiment, the sensitivity to contact of a finger or the like, of the detection electrodes27and28varies depending on the scan electrode22.

Also, in the present embodiment, the detection electrodes27and28are disposed so that at least one detection electrode27and one detection electrode28are provided just below a contact part between the object such as a finger or pen and the image display face1A when the object touches the image display face1A. That is, the detection electrodes27and28are disposed so that the gap between the neighboring detection electrodes27and28becomes smaller than the diameter of the contact part. Further, the detection electrodes27and28are formed so that, for example, when the image display surface1A is touched with the object such as a finger or pen, capacitance (capacitance C) formed between the detection electrode27and the object, and capacitance (capacitance D) formed between the detection electrode28and the object, are almost equal to each other. In the present embodiment, for example, when the detection electrodes27and28are disposed alternately in the row direction as shown inFIG.17, the capacitances C and D are almost equal to each other. Also, in the present embodiment, for example, when the projection parts28B are disposed close to the projection part27B so that the projection parts27B and28B are alternatively disposed in a direction (for example, the column direction) crossing the extension direction of the scan electrode22as illustrated inFIG.17, the capacitances C and D are almost equal to each other. Further, in the present embodiment, for example, as shown inFIG.17, also in the case where the area of the part facing one scan electrode22in the detection electrode27and that of the part facing one scan electrode22in the detection electrode28are equal to each other, the capacitances C and D are substantially equal to each other.

Consequently, for example, the sensitivity to the external noise in the detection electrode27and that in the detection electrode28is almost equalized when the user becoming as an antenna and catching the external noise touches the panel with his/her finger and the external noise is transmitted to the touch panel20via the finger. In the case where the sensitivity to the external noise of the detection electrode27and the sensitivity to the external noise of the detection electrode28are equal to each other, the signal level of the external noise included in the detection signal Vdetobtained from the detection electrode27and that of the external noise included in the detection signal Vdetobtained from the detection electrode28are equal to each other. Therefore, for example, by calculating the difference between the detection signal Vdetobtained from the detection electrode27and that obtained from the detection electrode28, it is possible to eliminate the external noise from the detection signals.

Part (A) to Part (H) ofFIG.18illustrate an example of signal waveforms when the detection electrodes27and28have the configuration illustrated inFIG.17, and when, in a state where the touch panel20is touched with a finger, the plurality of scan lines WSL2are sequentially driven. In Parts (A) to (D) ofFIG.18, the number at the end of each of WSL2(1), WSL2(2), WSL2(3), and WSL2(4) indicates serial number (sequence number) of the scan line WSL2. The number at the end of each of DET(1) and DET(2) in Parts (F) and (G) ofFIG.18indicates serial number (sequence number) of the detection lines DET. In Parts (F) to (H) ofFIG.18, DET(1) corresponds to the detection line DET connected to the detection electrode27, and DET(2) corresponds to the detection line DET connected to the detection electrode28. Parts (F) to (H) ofFIG.18Fillustrate signal waveforms obtained when a finger touches the region opposing the crossing part of the first and second third scan lines WSL2and the first and second detection lines DET.

It can be seen from Part (F) ofFIG.18that, when the first scan line WSL2is selected, the detection signal Vdetof the voltage Va is obtained from the first selection line DET, and the detection signal Vdetof a voltage Vb (>Va) is obtained from the second selection line DET. It can be seen from Part (G) ofFIG.18that, when the second scan line WSL2is selected, the detection signal Vdetof the voltage Vb is obtained from the first selection line DET, and the detection signal Vdetof the voltage Va is obtained from the second selection line DET. The reason why the signal level of the detection signal Vdetvaries between the first selection line DET and the second selection line DET is that the sensitivity to touch with a finger or the like in the detection electrode27connected to the first selection line DET and that in the detection electrode28connected to the second selection line DET are different from each other.

It can also be seen from Parts (F) and (G) ofFIG.18that, when the third and fourth scan lines WSL2are selected, the detection signal Vdetof the voltage Vc is obtained from the selection line DET(1), and the detection signal Vdetof a voltage Vd (=Vc) is obtained from the selection line DET(2). The reason why the signal level of the detection signal Vdetof the first selection line DET and that of the second selection line DET are the same is that a finger does not touch the part just above the third and fourth scan lines WSL2, and the detection electrodes27and28are hardly influenced by the finger.

It can also be seen from Parts (E) to (G) ofFIG.18that noise having the same phase as that of the external noise is included at almost the same level in the detection signal Vdetobtained from the first selection line DET and the detection signal Vdetobtained from the second selection line DET. The reason is that the sensitivity to the external noise in the detection electrode27connected to the first selection line DET and that in the detection electrode28connected to the second selection line DET are almost equal to each other.

It can be seen from Part (H) ofFIG.18that, by obtaining the difference (the absolute value of the difference) between the detection signal Vdetobtained from DET(1) and the detection signal Vdetobtained from DET(2), a fluctuation component |Vb−Va| of the detection signal Vdetby touch of a finger is extracted. It can also be seen from Part (H) ofFIG.18that the noise having the same phase as that of the external noise is eliminated from the detection signal Vdet.

From the above, by providing the two kinds of the detection electrodes27and28having the different sensitivities to the contact/non-contact state and having the almost equal sensitivities to the external noise, the external noise is eliminated from the detection signal Vdetonly by calculating the difference of the detection signals Vdet. Therefore, it is possible to eliminate the erroneous detection caused by the external noise.

Modification of Second Embodiment

Modification 1

Although the case where one scan electrode22is connected to one scan line WSL2has been described in the foregoing embodiment, the plurality of neighboring scan electrodes22may be connected to one scan line WSL2. In such a case, as compared with the case where one scan electrode22is connected to one scan line WSL2, the signal level of the detection signal Vdetobtained from the detection electrodes27and28is made higher.

Modification 2

In the foregoing embodiment, the detection electrodes27and28are formed so that the capacitances C and D become almost equal to each other. However, for example, due to manufacture error or the like, there may be a case that the capacitances C and D are slightly different from each other. On the assumption of such a case, for example, the output adjustment circuit56as shown inFIG.16may be further provided as means for ensuring that the erroneous detection caused by the external noise is eliminated. With this configuration, the external noise is eliminated from the detection signal Vdetonly by calculating the difference between two signals output from the output adjustment circuit56. As a result, it is possible to eliminate the erroneous detection caused by the external noise.

Third Embodiment

FIG.19illustrates an example of the top face configuration of the touch panel20included in a liquid crystal display device according to a third embodiment of the invention. The liquid crystal display device of the third embodiment is different from the liquid crystal display device1of the foregoing embodiment, in that a plurality of detection electrodes29are provided in place of the plurality of detection electrodes25and26, and a plurality of scan electrodes31are provided in place of the plurality of scan-electrodes22in the touch panel20. In the following, the points different from the configuration of the foregoing embodiment will be mainly described, and description of the configuration common to that of the foregoing embodiment will not be repeated.

In the present embodiment, as one of electrodes in the touch sensor of the electrostatic capacitance type, only one kind of the detection electrode29is provided. That is, different from the first and second embodiments, the plurality of detection electrodes29having the same shape are provided as one of electrodes in the touch sensor. The detection electrode29is formed, for example, in contact with the surface of the transparent substrate24, and is electrically connected to the detection line DET. The plurality of detection electrodes29have a band-shape electrode part extending in a direction (for example, the column direction) crossing the extending direction of the scan electrodes31which will be described later, and are disposed parallel with each other. The detection electrode29faces any of the scan electrodes31. The detection electrode29is not provided with the structure which protrudes in the extending direction of the scan electrode31which will be described later. The detection electrode29has, for example, a rod-like shape. At one end of each detection electrode29, a connection pad29A which is to be connected to the peripheral circuit40is formed. Preferably, the connection pads29A are disposed near one common side in the surface of the transparent substrate24. Where appropriate, the connection pads29A may be disposed dispersedly near a plurality of sides of the surface of the transparent substrate24. The line widths of the detection electrodes29are, for example, equal to each other.

Also, in the present embodiment, the detection electrode29is disposed so that at least one detection electrode29is provided just below a contact part between an object such as a finger or pen and the image display face1A when the object touches the image display face1A. That is, the detection electrodes29are disposed so that the gap between the neighboring detection electrodes29becomes smaller than the diameter of the contact part. Further, the detection electrodes29are formed so that, for example, when the image display surface1A is touched with the object such as a finger or pen, capacitances formed between the detection electrodes29and the object are almost equal to each other. In the present embodiment, for example, when the detection electrodes29have the same line width as shown inFIG.19, the capacitances formed between the detection electrodes29and the object are almost equal to each other.

The scan electrode31corresponds to the other electrode in the electrostatic capacitance type touch sensor, and is electrically connected to the scan line WSL2. The scan electrode31is formed, for example, in contact with the surface of the transparent substrate21. The plurality of scan electrodes31have, for example, a band-shaped electrode part extending in the row direction, and are disposed in parallel with each other. The electrode parts of the scan electrodes31extend, for example, in a direction parallel with the common electrode113in the liquid crystal display panel10. At one end of each scan electrode31, the connection pad31A to be connected to the peripheral circuit40is formed.

For example, as illustrated inFIG.19, the scan electrode31is provided with a plurality of projection parts31B. The projection parts31B are provided in a region facing the predetermined detection electrodes29among the plurality of detection electrodes29, and protrude in the extension direction of the detection electrodes29. For example, the projection parts31B are provided in the region facing the odd-numbered detection electrodes29among the plurality of detection electrodes29disposed in parallel, or provided in the region facing the even-numbered detection electrodes29among the plurality of detection electrodes29disposed in parallel. That is, the projection parts31B do not face the predetermined detection electrodes in the plurality of detection electrodes29, and only the electrode parts of the scan electrodes31face. The scan electrode31is thick in the portion where the projection part31B is provided, and is narrow in the portion where the projection part31B is not provided. That is, the shape of the scan electrode31varies depending on the places (portions in the scan electrode31).

In the portion where the scan electrode31is thick, the edge included in the part facing to overlap the scan electrode31in the detection electrode29is long. Consequently, in the detection electrode29facing the projection part31B in the plurality of detection electrodes29, the rate of the fringe capacitance C2in the total capacitance is high. On the other hand, in the narrow portion in the scan electrode31, the edge included in the portion facing to overlap the scan electrode31in the detection electrode29is short. Therefore, in the detection electrode29which does not face the projection part31B in the plurality of detection electrodes29, the rate of the fringe capacitance C2in the total capacitance is low.

As described above, in the present embodiment, the sensitivity to touch of a finger or the like in the detection electrode29facing the projection part31B in the plurality of detection electrodes29is higher than that in the detection electrode29which does not face the projection part31B in the plurality of detection electrodes29. In other words, in the present embodiment, the detection electrodes29having the mutually-different sensitivities to touch of a finger or the like are provided for the touch panel20.

Consequently, for example, when the user serves as an antenna and catches external noise, and the user touches the panel with a finger and the external noise is thus transmitted to the touch panel20via the finger, the sensitivities to the external noise in the detection electrodes29are almost equalized. In the case where the sensitivities to the external noise in the detection electrodes29are equal to each other, the signal levels of the external noises included in the detection signals Vdetobtained from the detection electrodes29become equal to each other. Therefore, for example, by obtaining the difference between the detection signal Vdetobtained from the detection electrode29facing the projection part31B among the plurality of detection electrodes29and the detection signal Vdetobtained from the detection electrode29which does not face the projection part31B among the plurality of detection electrodes29, the external noise is eliminated from the detection signal.

From the above, in the present embodiment, by providing the two kinds of the detection electrodes29having the different sensitivities to the contact/non-contact state and having the almost equal sensitivities to the external noise, the external noise is eliminated from the detection signal Vdetonly by calculating the difference of the detection signals Vdet. Therefore, it is possible to eliminate the erroneous detection caused by the external noise.

Fourth Embodiment

FIG.20illustrates an example of the top face configuration of the touch panel20included in a liquid crystal display device according to a fourth embodiment of the invention. The liquid crystal display device of the fourth embodiment is different from the liquid crystal display device of the third embodiment, in that a plurality of scan electrodes32are provided in place of the plurality of scan electrodes31in the touch panel20of the third embodiment. In the following, the points different from the configuration of the foregoing embodiment will be mainly described, and description of the configuration common to that of the foregoing embodiment will not be repeated.

The scan electrode32corresponds to one of electrodes in the touch sensor of the electrostatic capacitance type, and is electrically connected to the scan line WSL2. The scan electrode32is formed, for example, in contact with the surface of the transparent substrate21. The plurality of scan electrodes32have, for example, a band-shape electrode part extending in the row direction, and are disposed parallel with each other. The electrode parts of the scan electrodes32extend in a direction parallel with the common electrodes113in the liquid crystal display panel10. At one end of each scan electrode32, a connection pad32A which is to be connected to the peripheral circuit40is formed.

For example, as illustrated inFIG.20, the scan electrode32is provided with a plurality of projection parts32B. The plurality of projection parts32B are provided so as to sandwich regions facing predetermined detection electrodes29among the plurality of detection electrodes29from the row direction, and extend in the extension direction of the detection electrodes29. The projection parts32B are provided in a region facing the odd-numbered detection electrodes29among the plurality of detection electrodes29disposed side-by-side, or in a region facing the even-numbered detection electrodes29among the plurality of detection electrodes29disposed side-by-side. That is, the detection electrodes29do not face the projection parts31B, but face only the electrode parts of the scan electrodes32. The scan electrode32is thick in the portion where the projection part32B is provided, and is narrow in the portion where the projection part32B is not provided.

To the detection electrode29sandwiched by the projection parts32B among the plurality of detection electrodes29, as compared with the detection electrode29which is not sandwiched by the projection parts32B among the plurality of detection electrodes29, the larger number of edges of the projection parts32B are adjacent. Consequently, in the detection electrode29sandwiched by the projection parts32B among the plurality of detection electrodes29, the rate of the fringe capacitance C2 in the total capacitance is high. On the other hand, in the detection electrode29which is not sandwiched by the projection parts32B among the plurality of detection electrodes29, the rate of the fringe capacitance C2 in the total capacitance is low.

As described above, in the present embodiment, the sensitivity to touch of a finger or the like in the detection electrode29which is sandwiched by the projection parts32B among the plurality of detection electrodes29is higher than that in the detection electrode29which is not sandwiched by the projection parts32B among the plurality of detection electrodes29. In other words, in the present embodiment, the detection electrodes29having the mutually-different sensitivities to touch of a finger or the like are provided for the touch panel20.

Consequently, for example, when the user serves as an antenna and catches the external noise, and the user touches the panel with a finger and the external noise is transmitted to the touch panel20via the finger, the sensitivities to the external noise in the detection electrodes29are almost equalized. In the case where the sensitivities to the external noise in the detection electrodes29are equal to each other, the signal levels of the external noises included in the detection signals Vdetobtained from the detection electrodes29become equal to each other. Therefore, for example, by obtaining the difference between the detection signal Vdetobtained from the detection electrode29sandwiched by the projection parts32B among the plurality of detection electrodes29and the detection signal Vdetobtained from the detection electrode29which is not sandwiched by the projection parts32B among the plurality of detection electrodes29, the external noise is eliminated from the detection signals.

From the above, in the present embodiment, by providing the two kinds of the detection electrodes29having the different sensitivities to the contact/non-contact state and having the almost equal sensitivities to the external noise, the external noise is eliminated from the detection signal Vdetonly by calculating the difference of the detection signals Vdet. Therefore, it is possible to eliminate the erroneous detection caused by the external noise.

Fifth Embodiment

Next, a liquid crystal display device2according to a fifth embodiment of the invention will be described. The liquid crystal display device2according to the present embodiment is, as in the first embodiment, a liquid crystal display device with a touch sensor. The liquid crystal display device2has, as a display element, a liquid crystal display element, and further includes a touch sensor of an electrostatic capacitance type on the inside of the liquid crystal display element. That is, the liquid crystal display device2has a liquid crystal display element of a touch sensor built-in type (in-cell type). The liquid crystal display device2has, for example, as illustrated inFIG.21, a liquid crystal display panel60, a backlight30, and a peripheral circuit40.

[Liquid Crystal Display Panel60]

The liquid crystal display panel60displays a video image by transmitting or modulating light from the light source (backlight30) by changing arrangement of liquid crystal molecules. The liquid crystal display panel60is, for example, a transmission-type display panel in which a plurality of pixels11disposed in matrix are driven in accordance with the video signal40A. As in the forgoing embodiments, for example, as shown inFIG.5, the liquid crystal display panel60has a plurality of scan lines WSL1disposed as rows, and a plurality of signal lines DTL disposed as columns. The plurality of pixels11are disposed in matrix in correspondence with intersections between the scan lines WSL1and the signal lines DTL. In the liquid crystal display panel60, further, for example, a plurality of common connection lines COM are disposed as rows. Each common connection line COM is disposed, for example, for the pixels11in each row, and is connected to a scan line drive circuit (common line drive circuit)47which will be described later.

The liquid crystal display panel60has, for example, as shown inFIG.22, a liquid crystal layer130(display function layer), and a light-incidence-side substrate110and a light-outgoing-side substrate120which are disposed opposing to each other while sandwiching the liquid crystal layer130. The light-incidence-side substrate110is a transparent substrate disposed on the incident side (backlight30side) of light from the backlight30in the liquid crystal display panel60. The internal configuration of the light-incidence-side substrate110is similar to that in the foregoing embodiments. On the other hand, the light-outgoing-side substrate140is a transparent substrate disposed on the outgoing side (observer side) of light modulated by the liquid crystal layer130in the liquid crystal display panel60. The light-outgoing-side substrate120has, for example, in order from the liquid crystal layer130side, an alignment film121, a color filter122, a transparent substrate123, an adhesion layer125, detection electrodes25and25, a transparent substrate24, and a polarizer124.

The color filter122may not be provided where appropriate. Also, as shown inFIG.23, the transparent substrate24may not be provided where appropriate. As shown inFIG.24, a stacked body including, in order from the side of the liquid crystal layer130, the adhesive layer125, the detection electrodes25and26, and the transparent substrate24may be provided on the top face (observer side) of the polarizer124. In any of the cases illustrated inFIGS.22,23, and24, the detection electrodes25and26are not exposed from the top face of the liquid crystal display panel60.

For example, as shown inFIGS.22,23, and24, the liquid crystal display panel60has a common electrode113as one of electrodes of the touch sensor of the electrostatic capacitance type, and does not have the scan electrode22in the first embodiment. As in the first embodiment, the liquid crystal display panel60has the detection electrode25as the other electrode of the touch sensor of the electrostatic capacitance type. Further, for example, as illustrated inFIG.22, the liquid crystal display panel60has, as a dielectric of the touch sensor of the electrostatic capacitance type, an insulating layer114, an alignment film116, the liquid crystal layer130, the alignment film121, the color filter122, the transparent substrate123, and the adhesive layer125. In the case where the liquid crystal display panel60has, for example, the configuration illustrated inFIG.24, the dielectric sandwiched by a pair of electrodes in the touch sensor of the electrostatic capacitance type has a configuration obtained by adding the polarizer124to the above-described configuration.

In the present embodiment, the common electrode113also serves as the scan electrode22of the foregoing embodiments, and is electrically connected to the common connection line COM. For example, the common electrode113is formed in contact with the surface of the transparent substrate112. The plurality of common electrodes113have, for example, a band-like shape extending in the row direction, and are disposed in parallel with each other. At one end of each common electrode113, the connection pad113A to be connected to the peripheral circuit40is formed (refer toFIG.25).

The detection electrodes25and26have configurations similar to those of the foregoing embodiments. That is, the shapes of the detection electrodes25and26are different from each other. For example, the projection part25B does not always have to have a rod-like shape as shown inFIG.25, but may have an annular shape as shown inFIG.26. Also, three projection parts25B may be provided in each region facing the scan electrode (common electrode)113as shown inFIG.25, or two projection parts25B may be provided in each region facing the scan electrode (common electrode)113as shown inFIG.27.

[Peripheral Circuit40]

In the present embodiment, the peripheral circuit40has the scan line drive circuit (common line drive circuit)47in place of the scan line drive circuit45. The scan line drive circuit47sequentially applies a selection pulse to the plurality of common connection lines COM according to (synchronously with) input of the control signal42A to sequentially select the plurality of common electrodes113on the basis of the common connection line COM. At the time of selecting the common electrode113, the scan line drive circuit47performs inversion driving of inverting a polarity of a voltage to be supplied to the common connection line COM at every predetermined cycle. For example, when the signal line drive circuit45performs 1H inversion driving, the scan line drive circuit47applies a potential, whose polarity relative to a reference potential becomes opposite to the polarity relative to the reference potential, of the signal line DTL to the common connection line COM corresponding to the selected pixels11selected by the scan line drive circuit44.

[Operation]

An example of the operation of the liquid crystal display device2according to the present embodiment will now be described.

In the liquid crystal display device2, the signal potential corresponding to the video signal40A is applied to the signal lines DTL by the signal line drive circuit43, and the selection pulse according to the control signal42A is sequentially applied to the plurality of scan lines WSL1by the scan line drive circuit44. Consequently, a transverse electric field having a magnitude corresponding to the signal potential is applied on the pixel11unit basis to the liquid crystal layer130, and the liquid crystal molecules are aligned in a predetermined direction. Therefore, the light from the backlight30is modulated on the pixel11unit basis in the liquid crystal layer130in accordance with the alignment direction of the liquid crystal molecules. As a result, an image is displayed on the image display face2A.

In the liquid crystal display device2, further, the selection pulse is sequentially applied to the plurality of common connection lines COM by the scan line drive circuit47. Thus, capacitive elements (capacitive elements corresponding to the capacitive elements104) each formed in the intersection part of the common electrode113and the detection electrode25are sequentially changed/discharged, and a detection signal Vdetof a level based on the capacitance value of the capacitive element is output from each of the plurality of detection electrodes25. The outputs (detection signals V det) from the plurality of detection electrodes25are input to the detection circuit46. In a state where a finger of the user is not in contact with the surface of the touch panel60, the level of the detection signal Vdetis almost constant.

When a finger of the user touches any place in the surface of the touch panel60, a capacitive element formed by an object such as the finger (a capacitive element corresponding to the capacitive element109) is added to the capacitive element formed in the position where the finger or the like is touched. Consequently, a value of the detection signal Vdetoutput from the detection electrode25when the selection pulse is applied to the common electrode113corresponding to the touch position becomes smaller than a value of the detection signal Vdetoutput when the selection pulse is applied to another place. In the detection circuit46, the detection signal Vdetis compared with a threshold voltage Vth. For example, when the detection signal Vdetis equal to or less than the threshold voltage Vth, it is determined that the finger of the user or the like is in contact with the surface of the touch panel60. The contact position is determined from the application timing of the selection pulse and the detection timing of the detection signal Vdetwhich is equal to or less than the threshold voltage Vthin the detection circuit46.

Effects

Next, the effects of the liquid crystal display device2according to the present embodiment will be described.

In the present embodiment, the two kinds of the detection electrodes25and26having different line widths are provided for the liquid crystal display panel60, as one of the electrodes of the touch sensor of the electrostatic capacitance type used for detecting the contact/non-contact state. The detection electrodes25and26are disposed opposing to the scan electrode (common electrode)113via a predetermined gap. Thus, when voltage is applied between the scan electrode (common electrode)113and the detection electrodes25and26, for example, lines of electric force as illustrated inFIG.28are generated between the scan electrode (common electrode)113and the detection electrodes25and26. In the gap between the scan electrode (common electrode)113and the detection electrodes25and26, the lines of electric force extend almost straight. By the electric fields generated in the gap, a parallel plate capacitance C1is formed. On the other hand, around the gap between the scan electrode113and the detection electrodes25and26, the lines of electric force extend largely around the top face side of the detection electrodes25and26, and extend to the observer side more than the image display face2A with which a finger or the like comes in contact. By the round electric field, a fringe capacitance C2is formed.

Although the parallel plate capacitance C1and the fringe capacitance C2are formed for both of the detection electrodes25and26, a region in which the parallel plate capacitance C1is formed in the detection electrode25having a narrower line width is smaller than that of the detection electrode26having a wider line width. That is, a value of the parallel plate capacitance C1in the detection electrode25is smaller than that in the detection electrode26. On the other hand, a size of a region in which the fringe capacitance C2is formed largely does not have the relation with the line width, and is proportional to the length of the edge of the detection electrodes25and26. For example, as shown inFIGS.25,26, and27, in the case where the detection electrode25is provided with the projection parts25B, the region in which the fringe capacitance C2is formed in the detection electrode25is wider than that of the detection electrode26by the amount of the length of the edge included in the projection part25B. Therefore, a ratio of the fringe capacitance C2in the capacitance (total capacitance) obtained by adding the parallel plate capacitance C1and the fringe capacitance C2in the detection electrode25is higher than that in the detection electrode26.

It is now assumed that a finger or the like is brought close to the detection electrodes25and26and interrupts the electric field forming the fringe capacitance C2. Due to the interruption with the finger or the like, the fringe capacitance C2decreases and, in association therewith, the total capacitance also decreases. A fluctuation rate (decrease rate) of the total capacitance in the detection electrode25is higher than that of the detection electrode26. Therefore, when the plurality of scan electrodes113are selected in desired unit, the signal level of the detection signal Vdetobtained from the detection electrode25fluctuates largely between the time when the finger or the like touches the image display face2A and the time when the finger or the like does not touch the image display face2A. On the other hand, the signal level of the detection signal Vdetobtained from the detection electrode26fluctuates only by a fluctuation amount smaller than the fluctuation amount in the detection electrode25, between the time when the finger or the like touches the image display face2A and the time when the finger or the like does not touch the image display face2A.

As described above, in the present embodiment, the sensitivity to touch of a finger or the like in the detection electrode25is higher than that in the detection electrode26. Further, the sensitivity to touch of a finger or the like of the detection electrode25is constant regardless of the scan electrode (common electrode)113. Similarly, the sensitivity of the detection electrode26is almost constant regardless of the scan electrode (common electrode)113. In other words, in the present embodiment, the detection electrodes25and26having different sensitivities to touch of a finger or the like are provided for the touch panel60.

Also, in the present embodiment, the detection electrodes25and26are formed so that, for example, when the object such as a finger or pen touches the image display face2A, the capacitance (capacitance C) formed between the detection electrode25and the object, and the capacitance (capacitance D) formed between the detection electrode26and the object, are almost equalized. In the present embodiment, for example, as shown inFIGS.25,26, and27, in the case where the detection electrodes25and26are disposed alternately in the row direction, or disposed so that the projection parts25B of the detection electrode25are closer to the neighboring detection electrode26more than the electrode parts of the detection electrode25, the capacitance C and the capacitance D are almost equalized. In the present embodiment, for example, as shown inFIGS.25,26, and27, also in the case where the area of the part facing one scan electrode22in the detection electrode25and the area of the part facing one scan electrode22in the detection electrode26are equalized, the capacitance C and the capacitance D are almost equalized.

Consequently, for example, sensitivity to external noise in the detection electrode25and that in the detection electrode26are almost equalized when the user becoming as an antenna and catching the external noise touches the panel with his/her finger and the external noise is transmitted to the liquid crystal display panel60via the finger. In the case where the sensitivity to the external noise of the detection electrode25and the sensitivity to the external noise of the detection electrode26are equal to each other, the signal level of the external noise included in the detection signal Vdetobtained from the detection electrode25and that of the external noise included in the detection signal Vdetobtained from the detection electrode26are equal to each other. Therefore, for example, by calculating the difference between the detection signal Vdetobtained from the detection electrode25and that obtained from the detection electrode26, the external noise is eliminated from the detection signals.

From the above, by providing the two kinds of the detection electrodes25and26having the different sensitivities to the contact/non-contact state and having the almost equal sensitivities to the external noise, the external noise is eliminated from the detection signal Vdetonly by calculating the difference of the detection signals Vdet. Therefore, it is possible to eliminate the erroneous detection caused by the external noise.

Modifications of Fifth Embodiment

Modification 1

Although the case where one common electrode113is connected to one common connection line COM has been described in the fifth embodiment, the plurality of neighboring common electrodes113may be connected to one common connection line COM. In such a case, as compared with the case where one common electrode113is connected to one common connection line COM, the signal level of the detection signal Vdetobtained from the detection electrodes25and26is made higher.

Modification 2

In the fifth embodiment, the detection electrodes25and26are formed so that the capacitances C and D become almost equal to each other. However, for example, due to manufacture error or the like, there may be a case that the capacitances C and D are slightly different from each other. Also, for example, in the case where the projection parts25B of the detection electrode25are eliminated and the detection electrode25is formed in a rod-like shape as illustrated inFIG.29, the capacitances C and D are largely different from each other. On the assumption of those cases, as means for ensuring that the erroneous detection caused by the external noise is eliminated, for example, the output adjustment circuit56as shown inFIG.16, may be further provided. With this configuration, the external noise is eliminated from the detection signal Vdetonly by calculating the difference between two signals output from the output adjustment circuit56. Therefore, it is possible to eliminate the erroneous detection caused by the external noise.

Sixth Embodiment

FIG.30illustrates an example of the top face configuration of the liquid crystal display panel60included in a liquid crystal display device according to a sixth embodiment of the invention. The liquid crystal display device according to the sixth embodiment is different from the configuration of the liquid crystal display device2according to the fifth embodiment, in that a plurality of detection electrodes27are provided in place of the plurality of detection electrodes25, and a plurality of detection electrodes28are provided in place of the plurality of detection electrodes26in the liquid crystal display panel60.

The detection electrodes27and28have configurations similar to those of the detection electrodes27and28in the second embodiment. That is, also in the sixth embodiment, the shapes of the detection electrodes27and28are different from each other. The sensitivity to touch of a finger or the like of the detection electrode27and that of the detection electrode28are different from each other depending on the scan electrode22. On the other hand, the sensitivity to external noise of the detection electrode27and that of the detection electrode28are almost equal to each other. Consequently, the external noise is removed from the detection signals Vdetonly by calculating the difference between the detection signals Vdet. Therefore, it is possible to eliminate the erroneous detection caused by the external noise.

Modifications of Sixth Embodiment

Modification 1

Although the case where one common electrode113is connected to one common connection line COM has been described in the sixth embodiment, the plurality of neighboring common electrodes113may be connected to one common connection line COM. In such a case, as compared with the case where one common electrode113is connected to one common connection line COM, the signal level of the detection signal Vdetobtained from the detection electrodes27and28is made higher.

Modification 2

In the sixth embodiment, the detection electrodes27and28are formed so that the capacitances C and D become almost equal to each other. However, for example, due to manufacture error or the like, there may be a case that the capacitances C and D are slightly different from each other. On the assumption of such a case, as means for ensuring that the erroneous detection caused by the external noise is eliminated, for example, the output adjustment circuit56as shown inFIG.16, may be further provided. With this configuration, the external noise is eliminated from the detection signal Vdetonly by calculating the difference between two signals output from the output adjustment circuit56. Therefore, it is possible to eliminate the erroneous detection caused by the external noise.

APPLICATION EXAMPLES

Hereinbelow, application examples of the display device with the touch sensor described in the foregoing embodiments and modifications will be described with reference toFIGS.31to35G. The display devices according to the foregoing embodiments and the modifications are applicable to electronic devices in all of fields such as a television apparatus, a digital camera, a notebook-sized personal computer, a portable terminal device such as a cellular phone, and a video camera. In other words, the display devices according to the embodiments and the modifications are applicable to electronic devices in all of fields, which display a video signal input from the outside or a video signal generated internally as an image or a video image.

Application Example 1

FIG.31illustrates the appearance of a television apparatus to which the display device according to any of the embodiments and the modifications is applied. The television apparatus has, for example, a video display screen300including a front panel310and a filter glass320. The video display screen300is structured by the display device according to any of the embodiments and the modifications.

Application Example 2

FIGS.32A and32Billustrate the appearance of a digital camera to which the display device according to any of the embodiments and the modifications is applied. The digital camera has, for example, a light emission unit410for flash, a display section420, a menu switch430, and a shutter-release button440. The display section420is structured by the display device according to any of the foregoing embodiments and the modifications.

Application Example 3

FIG.33illustrates the appearance of a notebook-sized personal computer to which the display device according to any of the foregoing embodiments and the modifications is applied. The notebook-sized personal computer has, for example, a body510, a keyboard520for operation of entering characters and the like, and a display section530for displaying an image. The display section530is structured by the display device according to any of the foregoing embodiments and the modifications.

Application Example 4

FIG.34illustrates the appearance of a video camera to which the display device according to any of the embodiments and the modifications is applied. The video camera has, for example, a body610, a lens620provided on the front face of the body610for photographing an object, a photographing start-stop switch630, and a display section640. The display section640is structured by the display device according to any of the embodiments and the modifications.

Application Example 5

FIGS.35A to35Gillustrate the appearance of a cellular phone to which the display device according to any of the embodiments and the modifications is applied. The cellular phone is obtained by, for example, coupling an upper-side casing710and a lower-side casing720via a coupling unit (hinge)730, and has a display740, a sub-display750, a picture light760, and a camera770. The display740or the sub-display750is structured by the display device according to any of the embodiments and the modifications.

The present invention has been described above with reference to the embodiments and their modifications and application examples. However, the invention is not limited to the embodiments, the modifications, and the application examples, but may be variously modified.

For example, although the case of using the transmission-type element as the liquid crystal display element has been described in the foregoing embodiments, the modifications, and the application examples, an element other than the transmission type, for example, a reflection-type element, may be used. In this case, the light source (backlight30) is eliminated, or the light source is disposed on the top face side of the liquid crystal display element.

Although the case of applying any of the foregoing embodiments, the modifications, and the application examples to the display device using the liquid crystal display element as the display element has been described, the foregoing embodiments, the modifications, and the application examples are also applicable to a display device using a display element other than the liquid crystal display element, such as an organic EL element.

The series of processes described in the foregoing embodiments, the modifications, and the application examples may be performed by hardware or software. In the case of performing the series of processes by software, a program configuring the software is installed in a general computer or the like. Such a program may be preliminarily recorded on a recording medium built in the computer.

The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2009-136507 filed in the Japan Patent Office on Jun. 5, 2009, the entire content of which is hereby incorporated by reference.

It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.