JP2014032603A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of improving a sensing performance in a screen end part without reducing display performance.SOLUTION: The display device includes: a pixel circuit arranged in a matrix; and a plurality of sensor circuits for outputting voltage showing strength of combination of capacities between dielectric substances and detection electrodes arranged between rows of a plurality of pixel circuits. A plurality of detection electrodes arranged in a raw direction between the respective rows essentially consist of a plurality of first electrodes having a predetermined length and second electrodes shorter than the first electrodes which are arranged at least at one end part in the raw direction, and at least one of the second electrodes is electrically connected to an adjacent first electrode.

Description

  Embodiments described herein relate generally to a display device.

  Electronic devices such as mobile phones, personal digital assistants, and personal computers equipped with a display device having a touch panel function have been developed as a form of user interface. In an electronic device having such a touch panel function, it has been studied to add a touch panel function by separately attaching a touch panel substrate to a display device such as a liquid crystal display device or an organic EL display device.

  In recent years, thin films are formed of various materials on a transparent insulating substrate such as a glass substrate by CVD (Chemical Vapor Deposition) method, etc., and by repeating operations such as cutting and grinding, scanning lines and signal lines can be used. A technique for manufacturing an image reading device by forming a display element, an optical sensor element, or the like is being studied.

  Also, as a reading method of the image reading device, a conductive electrode is arranged in place of the optical sensor element, and so-called electrostatic detection is performed to detect information such as a finger on the panel surface by a capacitance change between the electrode and the finger. A technique for detecting a contact position by a capacitive method has been studied.

JP 2004-93894 A

  In the display device using the electrostatic capacity method, so-called in-cell technology in which a sensor function is incorporated in a display panel such as a liquid crystal has been actively developed. According to the in-cell technology, it is not necessary to attach a separately created touch panel to a liquid crystal or the like, so that it is possible to avoid an increase in thickness and weight of the entire electronic device. Furthermore, since there is no interface between the liquid crystal or the like and the touch panel, light reflection that tends to occur at the interface does not occur, which is excellent in terms of display quality.

  By the way, when realizing a touch panel function by incorporating a sensor function for detecting the contact position on the substrate constituting the display device, it is necessary to improve the sensing performance by suppressing the deterioration of the display performance. It is. However, the countermeasure for suppressing the deterioration in display performance may result in a decrease in sensing performance at the edge of the screen.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a display device that can improve the sensing performance at the edge of the screen without degrading the display performance.

  A display device according to one embodiment of the present invention outputs a voltage representing the strength of capacitive coupling between a dielectric circuit and a detection electrode, which is arranged between rows of pixel circuits arranged in a matrix and the plurality of pixel circuits. A plurality of sensor circuits, and the plurality of detection electrodes arranged along the row direction between the respective rows are arranged at a plurality of first electrodes having a predetermined length and at least one end in the row direction. The second electrode is shorter than the first electrode, and at least one second electrode is electrically connected to the adjacent first electrode.

1 is a schematic plan view illustrating a configuration of a display device of an embodiment mode. FIG. 6 is a diagram illustrating a cross section of a display device of an embodiment mode. The figure which shows the equivalent circuit of the sensor circuit in this Embodiment. 4 is a timing chart for explaining an example of a driving method of the display device according to the embodiment. FIG. 11 shows a pixel layout in a display device of an embodiment mode. The figure which shows typically the layout of the signal wire | line and detection electrode in the conventional display apparatus. FIG. 6 is a diagram schematically illustrating a layout of signal lines and detection electrodes in the display device of the present embodiment. The figure which shows typically the layout of the signal wire | line and the detection electrode in the display apparatus of the form of this Embodiment.

  Hereinafter, a display device and a display device driving method according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic plan view showing the configuration of the display device of the present embodiment.
The display device 1 according to the present embodiment includes a liquid crystal display panel PNL and a circuit board 60. One end of the flexible substrates FC1 and FC2 is electrically connected to the end of the liquid crystal display panel PNL. A circuit board 60 is electrically connected to the other ends of the flexible boards FC1 and FC2.

  The liquid crystal display panel PNL includes a display unit DYP composed of a plurality of pixels arranged in a matrix, and a scanning line driving circuit YD and a signal line driving circuit XD arranged around the display unit DYP. The circuit board 60 controls the display operation of the display device and also controls a sensor circuit (described later) provided in the liquid crystal display panel PNL. That is, the circuit board 60 outputs the video signal acquired from the external signal source SS to the liquid crystal display panel PNL. The circuit board 60 supplies a signal for operating the sensor circuit and outputs an output signal acquired from the sensor circuit to the control unit 65.

FIG. 2 is a diagram showing a cross section of the display device of the present embodiment.
The display device 1 according to the present embodiment includes a liquid crystal display panel PNL, a lighting unit, a frame 40, a bezel cover 50, a circuit board 60, and a protective glass PGL.

  The illumination unit is disposed on the back side of the liquid crystal display panel PNL. The frame 40 supports the liquid crystal display panel PNL and the illumination unit. The bezel cover 50 is attached to the frame 40 so as to expose the display unit DYP of the liquid crystal display panel PNL. The circuit board 60 is disposed on the back side of the frame 40. The protective glass PGL is fixed on the bezel cover 50 with an adhesive 70.

  The liquid crystal display panel PNL includes an array substrate 10, a counter substrate 20 disposed so as to face the array substrate 10, and a liquid crystal layer LQ sandwiched between the array substrate 10 and the counter substrate 20. The array substrate 10 includes a polarizing plate 10A attached to the main surface opposite to the liquid crystal layer LQ. The counter substrate 20 includes a polarizing plate 20A attached to the main surface opposite to the liquid crystal layer LQ.

The illumination unit includes a light source (not shown), a light guide 32, a prism sheet 34, a diffusion sheet 36, and a reflection sheet 38.
The light guide 32 emits light incident from the light source toward the liquid crystal display panel PNL. The prism sheet 34 and the diffusion sheet 36 are optical sheets disposed between the liquid crystal display panel PNL and the light guide 32. The reflection sheet 38 is disposed so as to face the main surface of the light guide 32 on the side opposite to the liquid crystal display panel PNL. The prism sheet 34 and the diffusion sheet 36 collect and diffuse the light emitted from the light guide 32.

  The protective glass PGL protects the display unit DYP of the liquid crystal display panel PNL from external impacts. The protective glass PGL can be omitted.

  Next, the display device shown in FIG. 1 will be described in detail.

  The liquid crystal display panel PNL has a structure in which a liquid crystal layer LQ is sandwiched between an array substrate 10 and a counter substrate 20 which are a pair of electrode substrates. The transmittance of the liquid crystal display panel PNL is controlled by the liquid crystal driving voltage applied to the liquid crystal layer LQ from the pixel electrode PE provided on the array substrate 10 and the common electrode CE provided on the counter substrate 20.

  In the array substrate 10, a plurality of pixel electrodes PE are arranged in a substantially matrix form on a transparent insulating substrate (not shown). In addition, a plurality of gate lines GL are arranged along the rows of the plurality of pixel electrodes PE, and a plurality of signal lines SL are arranged along the columns of the plurality of pixel electrodes PE.

  Each pixel electrode PE and common electrode CE are made of a transparent electrode material such as ITO (Indium Tin Oxide), for example, and are each covered with an alignment film AL. The pixel electrode PE and the common electrode CE constitute a liquid crystal pixel PX together with a pixel block that is a part of the liquid crystal layer LQ.

  A plurality of pixel switches SWP are arranged in the vicinity of the intersection position of the gate line GL and the signal line SL. Each pixel switch SWP is a thin film transistor (TFT), for example, and has a gate connected to the gate line GL, a source-drain path connected between the signal line SL and the pixel electrode PE, and a corresponding gate line GL. And the corresponding signal line SL and the corresponding pixel electrode PE are electrically connected.

Further, the array substrate 10 is provided with a sensor circuit 12, and a coupling pulse line CPL, a precharge gate line PGL, and a read gate line RGL for driving the sensor circuit 12 are formed of a plurality of pixel electrodes PE. Arranged along the line.
In the present embodiment, the signal line SL is also used as a precharge line PRL for supplying a signal for driving the sensor circuit 12 and a read line ROL. This detailed operation will be described later.

  The scanning line driving circuit YD supplies a gate voltage for turning on the pixel switch SWP (conducting the source-drain path) to the plurality of gate lines GL to sequentially drive the gate lines GL. Further, the scanning line driving circuit YD drives the sensor circuit 12 by driving the plurality of coupling pulse lines CPL, the plurality of precharge gate lines PGL, and the plurality of read gate lines RGL at a predetermined timing.

  The signal line drive circuit XD supplies a video signal from the signal line SL to the pixel electrode PE via the pixel switch SWP in which the source-drain path is conducted.

  A common electrode drive circuit (not shown) supplies the common voltage Vcom to the common electrode CE. The common electrode drive circuit reverses the polarity of the common voltage Vcom supplied to the common electrode CE as necessary, and changes the polarity of the voltage applied to the liquid crystal layer LQ so as to correspond to the polarity inversion method of the display device 1. Invert.

  The circuit board 60 includes a multiplexer MUX, a D / A converter DAC, an A / D converter ADC, an interface I / F, and a timing controller TCONT.

  The timing controller TCONT controls the operation of each unit mounted on the circuit board 60, the operation of the scanning line driving circuit YD, the signal line driving circuit XD, the common electrode driving circuit, and the sensor circuit 12.

  The digital video signal captured from the external signal source SS through the interface unit I / F is converted into an analog signal by the D / A conversion unit DAC and output to the signal line SL by the multiplexer MUX at a predetermined timing.

  An output signal from the sensor circuit 12 is supplied to the A / D converter ADC at a predetermined timing by the multiplexer MUX, converted into a digital signal, and supplied to the interface unit I / F. The interface unit I / F outputs the received digital signal to the control unit 65. The control unit 65 detects the presence / absence of contact and performs coordinate calculation based on the received digital signal, and detects the coordinate position where the fingertip, the pen tip, etc. are in contact.

FIG. 3 is a diagram showing an equivalent circuit of the sensor circuit 12 in the present embodiment.
The sensor circuit 12 includes a detection electrode 12E, a precharge line PRL, a readout line ROL, a precharge gate line PGL, a coupling pulse line CPL, a readout gate line RGL, a precharge switch SWA, a coupling capacitor C1, an amplification switch SWB, In addition, a read switch SWC is provided.

  The detection electrode 12E detects a change in the detection capacity due to the presence or absence of a contact body. The precharge line PRL supplies a precharge voltage to the detection electrode 12E. The read line ROL takes out the voltage of the detection electrode 12E. The precharge gate line PGL, the coupling pulse line CPL, and the readout gate line RGL supply signals for driving the operation of the sensor circuit 12.

  The precharge switch SWA is a switch for writing and holding a precharge voltage to the detection electrode 12E. The coupling capacitor C1 causes a voltage difference due to a change in the detection capacitance in the detection electrode 12E. The amplification switch SWB is a switch for amplifying a voltage difference generated in the detection electrode 12E. The read switch SWC is a switch for outputting and holding the amplified voltage difference to the read line ROL.

  The precharge line PRL and the read line ROL use a common line with the signal line SL. Since one sensor circuit 12 is arranged for the plurality of pixels PX, a part of the signal line SL is shared.

  The precharge switch SWA is, for example, a p-type thin film transistor, and has a gate electrode electrically connected to the precharge gate line PGL (or integrally formed) and a source electrode electrically connected to the precharge line PRL ( Alternatively, the drain electrode is electrically connected to the detection electrode 12E (or configured integrally).

  The amplification switch SWB is a p-type thin film transistor, for example, and has a gate electrode electrically connected (or integrally formed) with the detection electrode 12E and a source electrode electrically connected with the coupling pulse line CPL (or The drain electrode is electrically connected (or configured integrally) with the source electrode of the read switch SWC.

  The read switch SWC is, for example, a p-type thin film transistor, and the gate electrode is electrically connected to the read gate line RGL (or integrally formed), and the source electrode is electrically connected to the drain electrode of the amplification switch SWB. The drain electrode is electrically connected to the readout line ROL (or configured integrally).

  FIG. 4 is a timing chart for explaining an example of a driving method of the display device 1 according to the present embodiment.

  The precharge gate line drive waveform (precharge gate signal waveform) is applied to the precharge gate line PGL and input to the gate electrode terminal of the precharge switch SWA. As a result, the precharge voltage Vprc is written from the precharge line PRL to the detection electrode 12E through the precharge switch SWA at the timing when the precharge pulse is on level (low level).

  The coupling pulse line drive waveform is applied to the coupling pulse line CPL, and varies the potential of the detection electrode 12E through the coupling capacitor C1 depending on the presence or absence of a contact body. The detection electrode potential waveform indicates the potential fluctuation of the detection electrode 12E, and a voltage difference can be generated between the detection electrode potential (without a finger) and the detection electrode potential (with a finger).

  The voltage waveform between the gate and source (GS) of the amplification switch SWB indicates that the voltage difference generated at the detection electrode 12E is reflected in the difference in the operating point of the amplification switch SWB. There is a voltage difference between the gate-source (GS) voltage (without fingers) and the gate-source (GS) voltage (with fingers). The read gate line drive waveform is applied to the read gate line RGL and input to the gate electrode terminal of the read switch SWC.

  As a result, the potential after the fluctuation of the coupling pulse is output to the read line ROL via the amplification switch SWB and the read switch SWC at the timing when the pulse applied to the read gate line RGL is on level. The voltage waveform output to the read line ROL indicates this voltage fluctuation, and a voltage difference is generated between the output voltage (with a finger) and the output voltage (without a finger).

  When driving the sensor circuit 12, first, the timing controller TCON controls the scanning line driving circuit YD to set the voltage applied to the precharge gate line PGL to a low (L) level and to turn on the precharge switch SWA. The timing controller TCON controls the signal line drive circuit XD to apply a precharge voltage to the precharge line PRL, and applies a precharge voltage to the detection electrode 12E via the switch SWA.

  Next, after turning off the precharge switch SWA, the timing controller TCON controls the scanning line driving circuit YD to set the coupling pulse line CPL to the high (H) level. When the coupling pulse changes from the low level to the high level, the voltage is superimposed on the potential of the detection electrode 12E by the coupling capacitor C1. At this time, the magnitude of the voltage superimposed on the detection electrode 12E varies depending on the capacitance between the detection electrode 12E and the contact body.

  For example, when a finger, a pen tip, or the like is in contact with the counter substrate 20 above the detection electrode 12E, a capacitance is generated between the detection electrode 12E and the finger. When a fingertip, a pen tip, or the like is in contact with the detection electrode 12E, the magnitude of the voltage superimposed on the detection electrode 12E is smaller than when there is no fingertip, a pen tip, or the like.

  The on-resistance of the amplification switch SWB varies depending on the potential of the detection electrode 12E. In this embodiment, when the fingertip or the pen tip is in contact with the detection electrode 12E, the on-resistance of the amplification switch SWB is lowered, and the fingertip or the pen tip is in contact with the detection electrode 12E. If not, the on-resistance of the amplification switch SWB is relatively high.

  Next, the timing controller TCON controls the scanning line drive circuit YD to turn on the read switch SWC by setting the voltage of the read gate line RGL to a low level. When a fingertip or a pen tip is in contact with the detection electrode 12E, when the readout switch SWC is turned on, a coupling pulse is supplied to the readout line ROL via the amplification switch SWB and the readout switch SWC. Work in the direction

  Therefore, when the fingertip, the pen tip, or the like is in contact, the potential of the readout line ROL changes toward the coupling pulse potential. When the fingertip or the pen tip is not in contact, the change in the potential of the readout line ROL is smaller than when the fingertip or the pen tip is in contact.

  Therefore, the fingertip, the pen tip, etc. come into contact by detecting the output voltage difference between the output voltage (with a finger) and the output voltage (without a finger) when the output period Tread has elapsed since the read gate line RGL was turned on. It is possible to detect the position.

  FIG. 5 is a diagram showing a pixel layout in the display device of this embodiment. As shown in FIG. 5, every two adjacent pixel rows are arranged so that the pixels PX in each row face each other. Then, a required space is provided between the two pixel rows, and the sensor circuit 12 including the detection electrode 12E is formed in the space.

  One detection electrode 12E is arranged in a section extending over a plurality of pixels PX along the row direction. A precharge gate line PGL, a coupling pulse line CPL, and a read gate line RGL are arranged along the row direction. A signal line SL (also serving as a precharge line PRL and a read line ROL) is provided along the column direction of the pixels PX, and is connected to the precharge switch SWA and the read switch SWC, respectively.

  Thus, the reason why one detection electrode 12E is provided in the section extending over the plurality of pixels PX along the row direction is to detect a change in capacitance with the contact body (dielectric material) with high sensitivity. On the other hand, in order to detect a finger as a contact body, a required resolution (about 3 mm) is required. Therefore, there is an upper limit on the length of the detection electrode 12E. As the length of the detection electrode 12E, for example, a length of about 100 pixels can be set.

  FIG. 6 is a diagram schematically showing a layout of signal lines and detection electrodes in a conventional display device.

  In the conventional display device, the odd-numbered signal lines SL1, SL3,... Are electrically connected to the even-numbered detection electrodes 12E, and the even-numbered signal lines SL2, SL4,. 12E is electrically connected. Further, the length of the detection electrode 12E and the position where the detection electrode 12E is connected to the signal line SL are configured to be the same. Accordingly, the sensor electrodes 12E are arranged in a staggered manner for each row. Since the signal line SL has a function of supplying a signal for display to the pixel PX, the load connected to each signal line SL for operating the sensor detection circuit is the same. This is to avoid the deterioration of the display function.

  However, as a result of arranging the detection electrodes 12E in this way, as shown in FIG. 6, floating sensor electrodes 12E that are not connected to the signal lines SL and cannot be used as detection electrodes are formed at the left and right ends of the screen. It was. Therefore, at the left and right ends of the screen, the sensing performance is a factor that is lower than the center and upper and lower ends of the screen.

  FIG. 7 is a diagram schematically showing a layout of signal lines and detection electrodes in the display device of the present embodiment.

  In FIG. 7, floating sensor electrodes 12E that existed at the left and right ends of the screen are connected to sensor electrodes 12E that are adjacent in the left-right (row) direction. As a result, the dead zone of sensing at the left and right ends of the screen can be eliminated, and the capacitance formed by the finger and the sensor electrode 12E can be correctly captured at the left and right ends.

  FIG. 8 is a diagram schematically showing a layout of signal lines and detection electrodes in the display device according to the variation of the present embodiment.

  In FIG. 8, floating sensor electrodes 12E that existed at the left and right ends of the screen are connected to sensor electrodes 12E that are adjacent in the vertical (column) direction. As a result, the dead zone of sensing at the left and right ends of the screen can be eliminated, and the capacitance formed by the finger and the sensor electrode 12E can be correctly captured at the left and right ends.

  In this variation, a wiring region for connecting sensor electrodes 12E adjacent in the vertical (column) direction is required. Normally, since the upper and lower sensor electrodes 12E are not connected, the patterning with the connections shown in FIG. 8 is performed when designing the liquid crystal display panel PNL. For example, a wiring for connecting the sensor electrode 12E in the same layer may be provided, or a wiring for connection provided in a different layer may be connected via a contact hole. Note that if the size (width) of the wiring to be connected is large, the size of the electrode increases. For example, it is desirable that the size (width) is approximately the same as that of the signal line SL.

[Variations of this embodiment]
The above-described embodiment can be configured as various variations.

(1) Although the touch panel having an active sensor circuit has been described in the above-described embodiment, the active sensor circuit is not limited to the above-described configuration. The present invention can also be applied to a touch panel having a passive sensor circuit.

(2) The display device 1 according to the embodiment may be a liquid crystal display device that employs a display mode such as a TN (Twisted Nematic) mode, an IPS mode, or an OCB (Optically Compensated Bend) mode.

(3) The display device according to the above embodiment can be applied to a color display type and a monochrome display type display device.

(4) The sensor circuit 12 may omit the read switch SWC and the read gate line RGL. In that case, the drain electrode of the amplification switch SWB and the readout line ROL are electrically connected.

(5) The coupling pulse may not be supplied from the gate line GL. For example, a wiring parallel to the signal line SL may be added to form a coupling pulse line.

(6) The timing controller TCON is not limited to being provided on the circuit board 60, and may be provided externally or on the TFT substrate.

(7) The amplification switch SWB is not limited to the embodiment, and may be configured using an amplifier.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DYP ... display unit, PNL ... liquid crystal display panel, LQ ... liquid crystal layer, YD ... scan line drive circuit, XD ... signal line drive circuit, 10 ... array substrate, 12 ... sensor circuit, 12E ... detection electrode, 20 ... counter substrate, PX ... display pixel, PE ... pixel electrode, SWP ... pixel switch, CE ... common electrode, GL ... scan line, SL ... signal line, PGL ... precharge gate line, RGL ... read gate line, CPL ... coupling pulse line, ROL ... Read line, PRL ... Precharge line, SWA ... Precharge switch, C1 ... Coupling capacitor, SWB ... Amplification switch, SWC ... Read switch, TCON ... Timing controller, 100 ... Sensor, 110 ... Block.

Claims (6)

Pixel circuits arranged in a matrix,
A plurality of sensor circuits arranged between rows of the plurality of pixel circuits and outputting a voltage representing the strength of capacitive coupling between the dielectric and the sensing electrode;
The plurality of detection electrodes arranged in the row direction between the respective rows are more than the plurality of first electrodes having a predetermined length and the first electrode arranged at at least one end in the row direction. A short second electrode,
The display device, wherein the at least one second electrode is electrically connected to the adjacent first electrode.   The display device according to claim 1, wherein at least one of the second electrodes is electrically connected to a first electrode adjacent in a row direction.   The display device according to claim 1, wherein at least one of the second electrodes is electrically connected to a first electrode adjacent in a column direction.   4. The display device according to claim 2, wherein a connection line connecting the first electrode and the second electrode is formed in the same layer on the same substrate as the detection electrode. 5.   The display device according to claim 3, wherein the connection line connecting the first electrode and the second electrode is formed in a different layer on the same substrate as the detection electrode.   The display device according to claim 5, wherein the connection line has substantially the same size as a signal line that supplies a video signal to each of the plurality of pixels.

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