JP6256177B2 - LCD with touch panel - Google Patents

Description

  The present invention relates to a liquid crystal display device with a touch panel, and relates to a liquid crystal display device including a touch panel with reduced peripheral noise and high detection accuracy.

  A touch panel that detects a touch by an indicator such as a finger and specifies the coordinates of the touch position is an excellent input means and is widely used. Generally, a touch panel includes a touch screen that generates a signal corresponding to a touch position and a detection device that identifies a touched position coordinate based on a signal from the touch screen. Detection type touch panels have been commercialized.

  As one of such capacitive touch panels, there is a projected capacitive touch panel (see, for example, Patent Document 1). This projected capacitive touch panel can detect a touch even when the front side of the touch screen is covered with a protective plate such as a glass plate having a thickness of several millimeters. Such a touch screen is excellent in robustness, can detect a touch even when wearing a glove, and has a feature that it has a long life because it does not have a movable part.

  The projected capacitive touch panel is a detection electrode for detecting capacitance on a touch screen, and the row direction electrode formed in the row direction is insulated from the column direction electrode formed in the column direction. They are placed across the membrane. Based on the detection result of the touch capacitance, which is the capacitance formed between the row direction electrode, the column direction electrode, and the indicator, the touch position of the indicator is calculated as coordinates on the touch screen and output. .

  These row-direction electrodes and column-direction electrodes are formed of fine metal wires that are continuous in a zigzag shape, and electrically connect a plurality of metal wires to be used as row-direction bundle wires, column-direction bundle wires, There are known ones in which a row direction electrode and a column direction electrode are formed by using a transparent conductive film such as ITO.

  When using this projected capacitive touch panel, a touch screen is usually disposed on the surface of the liquid crystal display device. In the liquid crystal display device, coupling noise is generated from the source wiring, the gate wiring, and the like at the time of driving, and the operation of the touch panel may become unstable due to the coupling noise. In order to solve such a problem, the timing when the gate driver IC and the source driver IC are not driven, that is, the gap time during which the rewrite is performed once from the upper end to the lower end of the liquid crystal screen and the next rewrite cycle is started. A method of measuring capacitance during the vertical blanking period has been proposed (see, for example, Patent Document 2).

JP 2010-61502 A JP 2008-165434 A

  However, even if the source wiring and gate wiring coupling noise generated when driving the liquid crystal display device is removed, the backlight light source installed on the back of the liquid crystal display panel in the liquid crystal display device. Noise from a drive current itself or a drive current supply circuit such as a certain LED or CCFL is generated and becomes detection noise of the touch panel. Therefore, even if the touch position is detected in the vertical blanking period of the liquid crystal driving blanking period, there is a problem that the influence of noise due to the driving of the light source of the backlight cannot be prevented.

  Furthermore, in recent years, with the aim of thin and light touch screens, an on-cell touch panel in which touch screen detection wiring is directly formed on the surface of the color filter substrate of the liquid crystal display panel, and the inner surface of the array substrate and color filter substrate of the liquid crystal display panel In-cell type touch panels in which detection wiring is formed are being studied. In such touch panels, the distance from the backlight light source to the detection electrode is shortened, and the influence of noise caused by driving the backlight light source is reduced. Has the problem of becoming more prominent.

  The present invention has been made to solve such a problem, and an object of the present invention is to obtain a liquid crystal display device including a touch panel that prevents noise generated when driving a light source of a backlight and has high touch coordinate detection accuracy. And

The liquid crystal display device with a touch panel according to the present invention includes a plurality of row-direction electrodes extending in the row direction, a plurality of column-direction electrodes extending in the column direction, and a capacitance obtained from the row-direction electrodes and the column-direction electrodes. A touch panel, a liquid crystal display panel, a liquid crystal display panel, and a touch coordinate calculation circuit that calculates touch coordinates by an indicator based on a detection result of the capacitance detection circuit A liquid crystal display device having a backlight on the back surface portion, an overlapping period of a liquid crystal drive stop period corresponding to a vertical blanking period of the liquid crystal display panel and a light source drive stop period of the backlight , and a horizontal blanking period in the overlapping period of the light source drive halt period of the corresponding liquid crystal drive stop period and the backlight, you and performs the capacitance detection of the touch panel.

  Since the liquid crystal display device with a touch panel according to the present invention detects touch coordinates during the period in which the driving of the liquid crystal display panel and the driving of the light source of the backlight are both stopped, the noise accompanying the driving of the liquid crystal display panel and the light source device The influence on the capacitance detection of the touch panel can be prevented, and a liquid crystal display device with a touch panel with high touch coordinate detection accuracy can be obtained.

It is a top view which shows the structure of the touch screen which concerns on Embodiment 1 of this invention. It is a perspective sectional view showing the composition of a part of the touch screen according to Embodiment 1 of the present invention. It is a block diagram which shows the drive of the liquid crystal display device with a touchscreen which concerns on Embodiment 1 of this invention. It is a timing chart which shows operation | movement of the liquid crystal display device with a touchscreen which concerns on Embodiment 1 of this invention. It is a timing chart which shows operation | movement of the liquid crystal display device with a touchscreen which concerns on Embodiment 2 of this invention. It is a timing chart which shows operation | movement of the liquid crystal display device with a touchscreen which concerns on Embodiment 3 of this invention. It is a timing chart which shows operation | movement of the liquid crystal display device with a touchscreen which concerns on Embodiment 3 of this invention.

    In the description of the embodiments and the respective drawings, the same reference numerals denote the same or corresponding parts.

  In the embodiment of the present invention, the touch screen refers to a position sensor that outputs a signal corresponding to the contact position by the contact of an indicator such as a finger, and the touch panel refers to the touch screen and an output from the touch screen. An input device mainly composed of a detection device that identifies position coordinates based on signals.

Embodiment 1 FIG.
<Structure of liquid crystal display device>
The configuration of the touch screen 1 included in the touch panel 10 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view of a touch screen 1 according to an embodiment of the present invention, and FIGS. 2A and 2B are perspective views showing a part of the touch screen 1 according to an embodiment of the present invention.

  As shown in FIG. 1, the touch screen 1 has a plurality of columns extending in the column direction (y direction in FIG. 1) and repeatedly arranged in the row direction (x direction in FIG. 1) at a predetermined interval. A direction electrode 2 and a plurality of row direction electrodes 3 extending in the row direction (x direction) orthogonal to the column direction electrode 2 and repeatedly arranged in the column direction (y direction) at a predetermined interval are provided. Yes. The column-direction electrode 2 and the row-direction electrode 3 are connected in pairs by the column-direction electrode connection wiring 4 and the row-direction electrode connection wiring 5 respectively (five in FIG. 1). A row direction detection bundle electrode 7 (all of which are surrounded by a one-dot chain line) is formed.

  The column direction electrode 2 and the row direction electrode 3 constituting the column direction detection bundle electrode 6 and the row direction detection bundle electrode 7, respectively, are formed of metal thin metal wires having a width of several μm, and in FIG. The electrode 2 and the row direction electrode 3 are shown as straight lines, but may be formed in a zigzag shape. A column-direction electrode 2 and a row-direction electrode 3 made of thin metal wires bent in a zigzag are connected by a column-direction electrode connection wiring 4 and a row-direction electrode connection wiring 5, respectively. The detection bundle electrode 7 is configured. The column direction detection bundle electrode 6 and the row direction detection bundle electrode 7 are formed via an insulating film, and are arranged so as to intersect three-dimensionally without being in electrical contact with each other. The column direction detection bundle electrode 6 and the row direction detection bundle electrode 7 are drawn on the touch screen 1 by the lead wiring 8 and are connected to the outside by the connection terminal 9.

  Next, the layer structure of the touch screen 1 will be described with reference to FIG. In the touch screen 1, a column-direction detection bundle electrode 6 made of an opaque and highly conductive metal material made of aluminum or the like is formed on the back surface of a transparent substrate (base substrate) 12 made of a transparent glass material or a transparent resin. Further, a transparent interlayer insulating film 13 made of a silicon nitride film is formed so as to cover the column direction detecting bundle electrode 6 on the back surface of the base substrate 12, and the row direction detecting bundle made of a metal material such as aluminum is formed on the interlayer insulating film 13. A wiring 7 is formed.

  In the present embodiment, the column direction detection bundle wiring 6 is formed on the back surface of the base substrate 12 and the row direction detection bundle wiring 7 is formed through the interlayer insulating film 13. The configuration with the direction detection bundle wiring 7 may be reversed. Also, a protective film 14 made of silicon nitride or the like can be formed on the row direction detection bundle wiring 7 formed in the interlayer insulating film 13. Further, in the present embodiment, silicon nitride is used for the interlayer insulating film 13 and the protective film 14, but silicon oxide, an organic resin film, or the like can be used.

  In the present embodiment, as shown in FIG. 2A, the configuration in which each detection bundle wiring is formed on the back surface of the base substrate 12 is used. As shown, the column direction detection bundle wiring 6, the interlayer insulating film 13, and the row direction detection bundle wiring 7 are formed on the surface of the base substrate 12, and the protective glass 16 is pasted on the surface via the adhesive layer 15. You can also. By making the protective glass 16 have a thickness of about several millimeters, the touch screen 1 having excellent robustness can be obtained.

  In the present embodiment, as described above, the column direction electrode 2 and the row direction electrode 3 are drawn in a straight line, but a thin metal wire bent zigzag can be used. On the liquid crystal display panel to which the touch screen 1 is attached, pixels for liquid crystal display are arranged in the column direction and the row direction. Therefore, when the column direction electrode 2 and the row direction electrode 3 are formed of straight metal thin lines, optical interference may occur with the pixel arrangement of the liquid crystal display panel, and moire (interference fringes) may occur. However, when the row direction electrode 2 and the column direction electrode 3 are inclined by 45 degrees from the row direction and the column direction to form an oblique zigzag, the occurrence of moire can be reduced.

<Driving of LCD with touch panel>
FIG. 3 is a block diagram showing driving of the liquid crystal display device with a touch panel according to Embodiment 1 of the present invention. In this embodiment, the touch screen 1 has W column (1), Wx (2)... Wx (m) m column direction detection bundle wires 6, Wy (1), Wy (2),. -It has n row direction detection bundle wirings 7 of Wy (n).

  As a detection method of the touch screen 1, a self-capacitance detection method for detecting an electrostatic capacitance formed between each of the column direction detection bundle wiring 6 and the row direction detection bundle wiring 7 and an indicator such as a finger, There is a mutual capacitance detection method for detecting the amount of change due to the proximity of the indicator of the interelectrode capacitance (mutual capacitance) between the direction detection bundle wiring 6 and the row direction detection bundle wiring 7. The invention can be applied. Therefore, in this embodiment, a case where a mutual capacitance detection method capable of simultaneous detection of multiple points is used will be described. Accordingly, in the description of the touch screen 1 so far, it has been referred to as a column direction detection bundle wiring 6 and a row direction detection bundle wiring 7 because of its structural features. The direction detection bundle wiring 6 may be called a sense electrode, the row direction detection bundle wiring 7 may be called an excitation electrode, and the capacitance detection circuit may be called a mutual capacitance detection circuit 21.

  From the excitation electrode driver circuit 20, excitation pulses (charge / discharge pulses) of a predetermined voltage are sequentially applied to Wy (1), Wy (2)... Wy (n) which are the excitation electrodes 7. That is, the excitation electrode driver circuit 20 applies excitation pulses while sequentially scanning each excitation electrode 7 (Wy (1), Wy (2)... Wy (n)). Here, among the excitation electrodes 7, the excitation electrodes 7 other than the electrode selected and applied with the excitation pulse are fixed to the GND potential, for example.

  The charge / discharge current to the mutual capacitance between the selected excitation electrode 7 and each sense electrode 6 is measured by the mutual capacitance detection circuit 21 and integrated over a predetermined time, and then A / D converted and selected. A mutual capacitance detection value between the excitation electrode 7 and each sense electrode 6 is input to the touch coordinate calculation circuit 22. Here, the integral value of the charge / discharge current to the mutual capacitance by the mutual capacitance detection circuit 21 represents the amount of charge charged / discharged with respect to the mutual capacitance, and this charge amount is proportional to the mutual capacitance. By detecting the integrated value of the charge / discharge current (the amount of charge accompanying charge / discharge), the change in mutual capacitance can be detected.

  By repeating the application of excitation pulses to each excitation electrode 7 a predetermined number of times, the average value of the integral values is obtained, and further the digital filter processing is performed, thereby improving the detection S / N ratio.

  Thus, after applying the excitation pulse to the selected excitation electrode 7, a series of processes such as integrating the charge / discharge current and averaging the detection values of the mutual capacitance are performed on the selected excitation electrode 7. By switching while sequentially scanning, all interelectrode capacitances (mutual capacitances) formed by each excitation electrode 7 and each sense electrode 6 can be measured (in this embodiment, m × n static capacitances). Capacitance detection value).

  In the touch coordinate calculation circuit 22, based on the digital mutual capacitance detection value input from the mutual capacitance detection circuit 21, it is determined whether or not there is a touch with an indicator such as a finger, and the touch coordinates when it is determined that there is a touch. Calculation is performed, and touch coordinate data is transmitted to the outside.

  The detection control circuit 23 controls scanning of the excitation electrode 7 by the excitation electrode driver circuit 20, excitation pulse application timing, mutual capacitance charge / discharge current integration timing by the mutual capacitance detection circuit 21, and the like.

  In the present invention, the change in mutual capacitance due to touch on the touch screen is measured at the timing when both the driving of the liquid crystal display panel and the driving of the backlight are stopped, and the driving of the liquid crystal display panel and the backlight is performed. It will be described in detail after the outline. In this specification, as described above, a target touched by an indicator such as a finger is referred to as a touch screen 1, and the touch screen 1 is provided with an excitation electrode driver circuit 20, a mutual capacitance detection circuit 21, a touch. The peripheral circuit including the coordinate calculation circuit 22 and the detection control circuit 23 is referred to as the touch panel 10.

  On the other hand, the liquid crystal display panel 30 is formed with a plurality of gate wirings extending in the row direction and a plurality of source wirings extending in the column direction on a glass substrate (array substrate). A TFT (thin film transistor) which is a switching element is formed in the portion. A counter substrate on which a color filter (CF) and a black matrix (BM) are formed is disposed opposite to the array substrate, and a liquid crystal material is sandwiched between these substrates to form a liquid crystal display panel 30.

  In driving the liquid crystal display panel 30, the gate lines are sequentially scanned, a gate signal output from the gate driver circuit 31 is applied, and the TFTs connected to the corresponding gate lines are turned on. The source driver circuit 32 develops an image signal for one line input from the outside in units of pixels in the row direction, performs D / A conversion, and applies it to each source wiring as an applied voltage to the liquid crystal material. This operation can be performed while sequentially scanning each gate wiring to display on the front surface of the liquid crystal display panel 30. Such a driving method of the liquid crystal display panel is generally called line sequential driving and is controlled by the display control circuit 33.

  On the side surface of the backlight 40 installed on the back surface of the liquid crystal display panel 30, for example, an LED array 41 in which a plurality of LEDs are arranged in the column direction is provided as a light source. A drive current is supplied to each LED of the LED array 41 by an LED drive circuit 42. In addition, a dimming level adjustment signal is sent to the lighting control circuit 43, and the supply timing of the LED drive current to each LED is controlled based on the signal.

<Driving timing of LCD with touch panel>
Based on FIG. 4, the drive timing of the touch panel, the liquid crystal display panel 30, and the backlight 40 of the liquid crystal display device with a touch panel of the present embodiment will be described. FIG. 4 is a timing chart showing the operation of the liquid crystal display device with a touch panel according to Embodiment 1 of the present invention.

  From the top of FIG. 4, the gate wiring of the liquid crystal display panel is sequentially scanned, and the vertical synchronization signal VD which is a signal indicating the timing of rewriting one screen and the next one screen, and the gate wiring are sequentially scanned. A horizontal synchronizing signal HD that is a signal indicating the timing of switching each gate wiring one by one, an image signal effective period signal DENA that indicates a rewriting period of an image displayed on the screen, and a period during which a display image is written on the liquid crystal display panel Liquid crystal display panel driving signal, LED driving current applied to turn on the LED constituting the backlight 40, and excitation pulse signal for detecting the touch position of the touch screen are shown. The timing for integration and A / D conversion is represented by A / D conversion timing indicated by arrows.

  The vertical synchronization signal VD indicates the rewriting timing of one screen, and the entire image is rewritten in each display frame period (j), (J−1), and (J + 1). Generally, the display frame period (j) is 1/60 second or less.

  The horizontal synchronization signal HD indicates a timing for selecting one gate line in a case where all the gate lines are sequentially selected to form one display frame period. Therefore, the pulse-like horizontal synchronization signal HD is applied for the number of gate lines in one display frame period.

  The image signal effective period signal DENA controls the timing of the image signal applied to the liquid crystal display panel. The gap period of the image signal effective period signal DENA is called a vertical blanking period, which is a period during which no image signal is applied to the liquid crystal display panel. A liquid crystal display panel drive signal is applied to the liquid crystal display panel based on the video signal effective period signal DENA. Accordingly, since the liquid crystal display panel drive signal is applied to the liquid crystal display panel after receiving the image signal effective period signal DENA and after a certain process, it is delayed for a certain period from the vertical blanking period which is the gap period of the image signal effective period signal DENA. The liquid crystal display panel drive period begins.

  Lighting / non-lighting of the LED, which is the light source of the backlight 40, is controlled by application / non-application of the LED drive current. The lighting timing of the LED may be a period during which an image is displayed on the liquid crystal display panel 30. In this embodiment, since the liquid crystal drive stop period and the light source drive stop period, which is a non-lighting period of the LED, are set as much as possible, the light source drive period for applying the LED drive current for turning on the LED is the liquid crystal drive period. However, it is also possible to set a part of the light source driving period so as to overlap with the liquid crystal driving stop period.

  However, in the present invention, since the excitation pulse signal of the touch panel 10 is applied at the timing when the liquid crystal drive stop period and the light source drive stop period overlap, the mutual capacitance is detected and the touch coordinates are detected. It is essential that the start / stop period and the light source drive stop period have overlapping timings.

  When the image signal effective period signal DENA described so far is applied, the display control circuit 33 causes the liquid crystal drive stop period to be provided corresponding to the vertical blanking period as shown in FIG. The driver circuit 32 is controlled. Also, the lighting control circuit 43 that controls the LEDs has the LED array 41 of the backlight 40 from the LED drive circuit 42 so that the liquid crystal drive stop period corresponding to the vertical blanking period overlaps the light source drive stop period that is a non-lighting period of the LED. Control is performed so as to provide a period during which the drive current to each LED is stopped.

  That is, the lighting control circuit 43 supplies a drive current to each LED constituting the LED array 41 and turns on the backlight 40 at a timing delayed from the vertical synchronization signal VD by a predetermined period via the LED drive circuit 42. Subsequently, during a period overlapping with the liquid crystal drive stop period, the supply of drive current is stopped and the backlight 40 is turned off.

  In the touch panel 10, the excitation electrode driver circuit 20 uses the excitation electrode Wy (1), the excitation electrode driver circuit 20 during the period where the liquid crystal drive stop period and the light source drive stop period overlap, that is, the period during which both the liquid crystal display panel 30 and the backlight 40 are stopped. Wy (2)... Wy (n) is sequentially applied with an excitation pulse signal (mutual capacitance charge / discharge pulse), and the mutual capacitance between the excitation electrode 7 and each sense electrode 6 to which the excitation pulse signal is applied. The charge / discharge current is integrated by the mutual capacitance detection circuit 21 and A / D converted to obtain each mutual capacitance detection value.

  At this time, the timing of A / D conversion is indicated by “↑” at the bottom of FIG. In the liquid crystal drive stop period corresponding to the vertical blanking period, the mutual capacitance detection including A / D conversion corresponding to the excitation pulse signal sequentially applied to the excitation electrode 7 is repeated, and between all the excitation electrodes 7 and the sense electrodes 6 is repeated. The detection result of mutual capacitance (m × n) is obtained.

  As described above, the mutual capacitance detection of the touch screen 1 is performed in a period in which the liquid crystal drive stop period and the light source drive stop period overlap, that is, in a period in which the drive of the liquid crystal display panel 30 and the LED constituting the backlight 40 is stopped. Therefore, it is possible to prevent the integration result of the mutual capacitance detection circuit 21 seen when the liquid crystal display panel is driven or the LED is driven, that is, the occurrence of noise appearing in the detection result, and improve the touch coordinate detection accuracy. Can be made.

  The mutual capacitance of the touch screen 1 constituting the touch panel 10 is detected by sequentially selecting the excitation electrodes 7 and performing line sequential detection for detecting the mutual capacitance of each sense electrode 6. This detection method is highly common in control method with the liquid crystal display panel 30 that performs line-sequential driving in which gate wiring is sequentially selected, voltage is applied to each source electrode, and voltage is applied to the liquid crystal material. Therefore, a part of the detection control circuit 23 and the display control circuit 33 can be shared due to the common driving method between the liquid crystal display panel 30 and the touch screen 1, and the circuit configuration can be simplified. It also has the feature that it can.

  The touch panel 10 has been described so as to obtain the mutual capacitance detection results between all the excitation electrodes 7 and all the sense electrodes 6 of the touch screen in one liquid crystal drive stop period corresponding to the vertical blanking period. It is also possible to adopt a configuration in which all mutual capacitances are detected over a liquid crystal drive stop period corresponding to a plurality of vertical blanking periods as long as the problem of response (response speed) does not occur.

Embodiment 2. FIG.
In the present embodiment, the basic configuration and drive timing are the same as those in the first embodiment, but by adjusting the lighting period of the LEDs that constitute the LED array 41 that is the light source of the backlight 40, the liquid crystal display The display brightness of the panel 30 is adjusted.

  FIG. 5 is a timing chart showing the operation of the liquid crystal display device with a touch panel according to the second embodiment of the present invention. The brightness of the LEDs constituting the backlight 40 is adjusted by the light source driving period. Specifically, among the three types of dimming levels shown in FIG. 5, the light source driving period is the longest and brightest at the dimming level “maximum”. As the dimming level is changed from “medium” to “low”, the light source driving period becomes shorter and the display becomes darker.

  When the light source drive period is the longest, in other words, when the light source drive stop period is the shortest, the dimming level is maximized, and the touch panel detection timing matches the overlap period of the light source drive stop period and the liquid crystal drive stop period at this time Set.

  When the dimming level of the liquid crystal display panel (brightness of the backlight 40) is adjusted by adjusting the lighting period of the LEDs constituting the LED array 41 in accordance with an external dimming level adjustment signal, the dimming level is maximum. PWM (Pulse Width Modulation) dimming is performed by extending the light source drive stop period before, after, or both. FIG. 5 shows an example in which light control is performed by extending the light source drive stop period backward.

  In this way, the period during which the touch position of the touch panel is detected is set in accordance with the overlap period between the liquid crystal drive stop period and the light source drive stop period at the maximum dimming level. The light source drive stop period at the maximum light level is extended before, after, or both. As a result, it is possible to prevent noise seen in the integration result of the mutual capacitance detection circuit, which is seen with the driving of the liquid crystal display panel and the light source, and the touch coordinate detection accuracy can be improved.

Embodiment 3 FIG.
In the first and second embodiments, the touch panel is detected during the overlap period of the liquid crystal drive stop period and the light source drive stop period corresponding to the vertical blanking period that is the gap period of each display frame period. In this embodiment, when rewriting the screen by sequentially selecting gate wirings, a period until a certain gate wiring is selected and the next gate wiring is selected, that is, a gap period of the horizontal synchronization signal HD is displayed on the display line. The detection operation of the touch panel 10 is performed using the period Th, which is called a period Th, and the period during which the liquid crystal driving is stopped is present.

  FIG. 6 is a timing chart showing the operation of the liquid crystal display device with a touch panel in the present embodiment. The vertical synchronization signal VD, the liquid crystal display panel drive signal, the LED drive current, the touch panel drive timing, the horizontal synchronization signal HD, LED The three light control levels are shown.

  As in the first embodiment, as shown in FIG. 6, the liquid crystal provided in the period in which the liquid crystal drive stop period and the light source drive stop period corresponding to the vertical blanking period overlap, that is, the gap period between the screen rewriting periods. The excitation electrode driver circuit 20 excites a predetermined number of times for each of the excitation electrodes Wy (1), Wy (2)... Wy (n) while the display panel and the LED drive are both stopped. A pulse signal (mutual capacitance charge / discharge pulse) is applied, the charge / discharge current for the mutual capacitance between the excitation electrode 7 and the sense electrode 6 is integrated by the mutual capacitance detection circuit 21, and the result is A / D converted to each A mutual capacitance detection value is obtained.

  In the present embodiment, the mutual capacitance is not only detected in the period in which the liquid crystal drive stop period and the light source drive stop period corresponding to the vertical blanking period overlap, but also in the period corresponding to the horizontal synchronization signal HD. The difference is in the detection.

  FIG. 7 is an enlarged view of a period surrounded by a broken-line circle described in the timing chart showing the horizontal synchronization signal HD in FIG. FIG. 7 is a timing chart showing the operation of the liquid crystal display device with a touch panel according to the third embodiment. In the present embodiment, the touch panel detection operation is performed even during the period in which the liquid crystal display panel drive and the LED drive are simultaneously stopped corresponding to the display line period Th in the liquid crystal display panel drive period. is there. In other words, the lighting control circuit 43 responds to a signal for instructing the dimming level from the outside, for example, with the integer multiple a of the display line period Th (in FIG. 6, an example of a = 8 being shown) as the dimming period unit. The LED drive circuit 42 applies an LED drive current for switching between the lighting period and the extinguishing period of the LED array 41.

  In the present embodiment, as shown in the lower part of FIG. 6, the dimming level of the LED is adjusted by changing the ratio between the lighting period and the extinguishing period of the dimming period unit (a = 8). As a specific example shown in FIG. 6, when the dimming level is maximum, the lighting period is 6 × Th and the extinguishing period is 2 × Th. When the dimming level is medium, both the lighting period and the extinguishing period are 4 × Th. When the dimming level is low, the dimming level of the LED is adjusted by setting the lighting period to 2 × Th and the extinguishing period to 6 × Th.

  FIG. 7 shows a timing chart of the liquid crystal display device corresponding to the display line period Th. As shown in FIG. 6 and FIG. 7, when the dimming level is maximum (when the LED drive stop period is the shortest), the LED drive stop period is 2 × Th, during which the image signal effective period signal DENA and The corresponding liquid crystal display panel drive signal can be adjusted, and the liquid crystal drive stop period and the light source drive stop period overlap. In this overlap period, an excitation pulse is applied from the excitation electrode driver circuit 20 to the excitation electrode 7, and the charge / discharge current for the mutual capacitance between the excitation electrode 7 and the sense electrode 6 is integrated by the mutual capacitance detection circuit 21 to detect the mutual capacitance. A value can be obtained.

  As described above, in the present embodiment, the liquid crystal drive stop period and the light source drive stop period overlap not only in the period corresponding to the vertical blanking period but also in the period corresponding to a part of the horizontal blanking period. Thus, the touch panel 10 is detected during the overlapping period of the liquid crystal drive stop period and the light source drive stop period.

  In the case of a liquid crystal display device in which the TFT is made of amorphous silicon, the mobility of the TFT as a switching element is not sufficient, and the writing time of the liquid crystal display panel is relatively long. However, the liquid crystal drive stop period cannot be ensured sufficiently long, and the liquid crystal drive stop period corresponding to the vertical blanking period alone may be insufficient as the detection period of the touch panel 10.

  In such a case, not only the liquid crystal drive stop period corresponding to the vertical blanking period, but also a liquid crystal drive stop period provided in a period corresponding to a part of the horizontal blanking period can be used as a detection period of the touch panel 10. Even if the liquid crystal drive stop period corresponding to the vertical blanking period cannot be extended due to insufficient writing ability of the TFT to the liquid crystal display panel, the detection period can be secured, and the liquid crystal display It is possible to reduce the occurrence of noise appearing in the mutual capacitance detection result associated with the panel drive or LED drive.

  Further, even when the number of excitation electrodes 7 and sense electrodes 6 on the touch screen 1 is large and the detection period of the touch panel 10 is insufficient in the liquid crystal drive stop period corresponding to the vertical blanking period, the horizontal blanking period is also supported. By using the liquid crystal drive stop period, the detection period can be secured, and the occurrence of noise appearing in the mutual capacitance detection result can be reduced.

  In the present embodiment, dimming control of the backlight is performed in units of the display line period Th. The display line period Th is equivalent to the period for selecting each gate line of the line sequential drive (drive for sequentially selecting the gate lines) of the liquid crystal display panel 30, and therefore has high affinity with the liquid crystal display panel 30 and lighting control. A part of the circuit 43 and the display control circuit 33 can be easily shared, and the circuit configuration can be simplified.

  In the embodiment of the present invention, the LED array 41 is used as the light source of the backlight 40. However, other light sources such as CCFL (Cold Cathode Fluoresent Lamp) and organic EL (Organic Electro Luminescence) are used. However, it can be used similarly.

  Further, in the embodiment of the present invention, the column direction electrode 2 and the row direction electrode 3 on the touch screen 1 are each configured by mesh wiring made of a fine metal wiring material, and the electrode shape is rectangular. However, the present invention is not limited to these, and for example, a transparent conductive film can be used, and the electrode can be used in various shapes such as a diamond-shaped chain shape that is usually used. .

1 touch screen, 2 column direction electrode, 3 row direction electrode, 4 column direction electrode connection wiring, 5 row direction electrode connection wiring, 6 column direction detection bundle electrode (sense electrode), 7 row direction detection bundle electrode (excitation electrode) 8) Lead wiring, 9 connection terminals, 10 touch panel, 12 base substrate, 13 interlayer insulating film, 14 protective film, 15 adhesive layer, 16 protective glass, 20 excitation electrode driver circuit, 21 mutual capacitance detection circuit, 22 touch coordinate calculation Circuit, 23 detection control circuit, 30 liquid crystal display panel, 31 gate driver circuit, 32 source driver circuit, 33 display control circuit, 40 backlight, 41 LED array, 42 LED drive circuit, 43 lighting control circuit, VD vertical synchronization signal, HD Horizontal sync signal, DENA image signal effective period signal.

Claims (9)

A plurality of row direction electrodes extending in the row direction;
A plurality of column direction electrodes extending in the column direction;
A capacitance detection circuit that detects a capacitance obtained from the row direction electrode and the column direction electrode;
A touch coordinate calculation circuit that calculates a touch coordinate by an indicator based on a detection result of the capacitance detection circuit;
A liquid crystal display panel, and a liquid crystal display device having a backlight on the back portion of the liquid crystal display panel,
The liquid crystal drive stop period corresponding to the vertical blanking period of the liquid crystal display panel and the overlap period of the light source drive stop period of the backlight, and the liquid crystal drive stop period corresponding to the horizontal blanking period and the light source drive of the backlight A liquid crystal display device with a touch panel, wherein capacitance detection of the touch panel is performed in an overlapping period with a stop period.   The liquid crystal display device with a touch panel according to claim 1, wherein the liquid crystal drive stop period is a liquid crystal drive stop period that stops based on an image signal effective period signal of the liquid crystal display panel.   3. The liquid crystal display device with a touch panel according to claim 1, wherein the capacitance detection circuit detects a mutual capacitance that is an interelectrode capacitance between the plurality of row direction electrodes and the plurality of column direction electrodes. The capacitance detection circuit includes an excitation electrode driver circuit that sequentially applies excitation pulses for charging and discharging the mutual capacitance to a plurality of the row direction electrodes,
4. A mutual capacitance detection circuit that detects the mutual capacitance by integrating the charge / discharge current of the mutual capacitance over a predetermined period through each of the plurality of column direction electrodes. The liquid crystal display device with a touch panel as described. Dimming level adjustment of the liquid crystal display panel is performed by adjusting the lighting period of the backlight,
The adjustment of the lighting period of the backlight is that the light source driving stop period of the backlight is expanded or contracted before or after in time, or both. Liquid crystal display with touch panel. An integral multiple (a times) of the interval between horizontal synchronizing signals of the liquid crystal display panel is set as a unit time for adjusting the ratio between the lighting period and non-lighting period of the backlight, and the non-lighting period is defined as the interval between horizontal synchronizing signals. 6. The liquid crystal display device with a touch panel according to claim 5 , wherein backlight dimming is performed as an integral multiple (b times) of the above (where a> b).   7. At least a part of the plurality of row direction electrodes and the plurality of column direction electrodes are formed on an outer surface of a color filter substrate constituting the liquid crystal display panel. 2. A liquid crystal display device with a touch panel according to item 1.   8. At least a part of the plurality of row direction electrodes and the plurality of column direction electrodes are formed on inner surfaces of two substrates constituting the liquid crystal display panel. A liquid crystal display device with a touch panel according to claim 1. In the display frame period of the liquid crystal display panel, switching the backlight on / off is repeated a plurality of times, and the dimming level adjustment of the liquid crystal display panel is performed by changing the ratio of the lighting period and the non-lighting period,
9. The capacitance detection of the touch panel is performed in an overlapping period of a liquid crystal drive stop period corresponding to the horizontal blanking period and a non-lighting period that is a light source drive stop period. A liquid crystal display device with a touch panel as described in 1.

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