JP2012243232A - Touch panel device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a touch panel device which prevents malfunction in a capacitance type touch panel caused by noise radiated from a liquid crystal display device.SOLUTION: In a touch panel device, after displaying an initial correction image data 26, a touch panel control unit 11 performs an initial correction of a touch panel 2, and a capacity detection unit 13 stores a parasitic capacitance detected at an electrode 12 as a reference value in a reference value storing unit (step S2). A control unit 1 displays on a display unit 3 a start-up image to be displayed on an LCD 21 at starting up (step S3), and lights a back light 23 (step S4).

Description

  The present invention relates to a touch panel device using a capacitive touch panel.

In recent years, many PDAs (Personal Digital Assistants) and mobile phones using a touch panel have been seen. In particular, mobile phones equipped with capacitive touch panels are attracting attention. As a touch panel device used for this type of mobile phone, for example, those described in Patent Document 1 and Patent Document 2 are known. The liquid crystal display device with a touch panel described in Patent Document 1 shifts to a power save mode without detecting contact for a predetermined time in order to prevent a change in parasitic capacitance caused by turning off an LCD (Liquid Crystal Display) during power save. When doing so, it is described that only the backlight is turned off while the LCD is turned on.
On the other hand, in Patent Document 2, the display immediately below the electrode is set to a fixed color at the timing of sampling the signal of the electrode of the capacitive touch panel. Accordingly, it is described that variations in parasitic capacitance during scanning are suppressed.

Japanese Patent No. 42237741 Japanese Patent No. 4453710

  A capacitive touch panel calculates the increase in capacitance that occurs when a conductor such as a finger is in proximity, based on the parasitic capacitance that exists between the transparent sensor electrode and the object surrounding the electrode. It is a sensor that detects operation. The capacitive touch panel is a system in which a plurality of electrodes having a width sufficiently smaller than the width of a finger to be touched are arranged, and the contact position is calculated from the distribution of the amount of change in capacitance detected by each electrode. Setting the detected parasitic capacitance to the reference capacitance of the sensor electrode is called initial correction.

  In the initial correction, the parasitic capacitance that has the greatest influence on the reference value of the parasitic capacitance is the parasitic capacitance generated between the display device such as an LCD disposed in the immediate vicinity of the touch panel. Image display on the LCD is performed by turning on / off the transistor arranged for each pixel and supplying a voltage to the liquid crystal molecules. However, when the transistor is turned on, the parasitic capacitance of the LCD transistor increases.

  FIG. 4 is a graph of the detected parasitic capacitance when the initial correction is performed by the conventional touch panel device. In the initial correction, the parasitic capacitance of the first to nth electrodes is acquired, and the value is used as a reference for the sensor capacitance. The parasitic capacitance of each electrode varies, but here, description will be given focusing on one electrode.

  As shown in FIG. 4, when the LCD is not lit, since the transistor of the LCD is not turned on, the detected parasitic capacitance is small. Therefore, the capacitance of the sensor electrode also becomes a small value and is initially corrected as a reference capacitance. When the LCD is turned on here, the TFT is turned on and the parasitic capacitance increases. Thereby, the capacitance of the electrode increases even though the touch panel is not touched. When this change in capacitance exceeds the finger contact determination threshold, there is a problem that the device operates even when it is not operated. Even when the contact determination value is not exceeded, the profile of the reference capacitance of each sensor electrode changes. In that case, the increase in capacitance due to finger contact cannot be acquired correctly, leading to an error in coordinate accuracy. For this reason, an increase in parasitic capacitance caused by LCD image display is determined as an increase in capacitance due to finger contact, leading to a malfunction.

  Incidentally, although the capacitive touch switch device described in Patent Document 1 described above can prevent malfunction due to driving of the LCD, power consumption increases because the LCD is continuously displayed even during power saving control such as a standby state. It has a problem.

  The touch switch detection device described in Patent Document 2 needs to synchronize the display on the LCD and the signal detection on the touch panel, and has a problem that the device becomes complicated.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a touch panel device that can prevent malfunction due to LCD driving without increasing the power consumption without complicating the configuration. .

  The touch panel device according to the present invention includes a capacitive touch panel, a display unit including a transmissive LCD and a backlight, a control unit that controls the capacitive touch panel, the display unit, and an activation unit that activates the control unit. When the control unit is activated by the activation unit, the control unit displays an initial image on the transmissive LCD, performs initial correction of the capacitive touch panel, and then turns on the backlight. Control is performed.

According to the above configuration, the parasitic capacitance of the sensor electrode can be acquired as a reference capacitance with a display close to actual use, and the user of the touch panel device does not show the initial correction screen for acquiring the reference capacitance, Initial correction equivalent to the actual use state is possible.
Furthermore, in the touch panel device of the present invention, the initial image is a white screen or a screen in which white and black are alternately displayed for each pixel of the transmissive liquid crystal. The initial correction value can be acquired.

  According to the present invention, the capacitive touch panel has a simpler configuration than the prior art, and can prevent malfunction due to a parasitic capacitance change of the LCD without increasing current consumption.

The block diagram which shows schematic structure of the touchscreen apparatus which concerns on Embodiment 1 of this invention. Graph of detected parasitic capacitance when initial correction is performed with LCD on in touch panel device according to Embodiment 1 of the present invention Control flow chart of touch panel device according to embodiment 1 of the present invention Graph of detected parasitic capacitance when initial correction is performed on a conventional touch panel device

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments for carrying out the invention will be described in detail with reference to the drawings.

(Embodiment 1)
First, initial correction of the capacitive touch panel will be described. FIG. 1 is a block diagram showing a schematic configuration of a touch panel device according to Embodiment 1 of the present invention.

  In FIG. 1, the touch panel device of the present embodiment includes a control unit 1, a capacitive touch panel 2, a display unit 3, an activation unit 4, and a storage unit 5. Further, the capacitive touch panel 2 includes a touch panel control unit 11 and a sensor unit including n sensor electrodes 12, and the display unit 3 includes a transmissive LCD 21, a display driving circuit 22, a backlight 23, and a backlight. A drive circuit 24 is provided.

  The touch panel control unit 11 includes a capacity detection unit 13, a correction unit 14, a reference value holding unit 15, and a coordinate calculation unit 16.

The activation unit 4 is for activating the touch panel device, and specifically, for example, depressing an activation button or turning on the power. When the touch panel device is activated, the control unit 1 causes the transmissive LCD 21 to display the initial correction image data 26 of the touch panel.
The initial correction image data 26 is image data to be displayed on the transmissive LCD 21 when initial correction is performed. When the initial correction image data 26 is displayed, since the backlight is not turned on, it does not appear to the user that the initial correction image data 26 is displayed. In this state, the control unit 1 instructs the touch panel control unit 11 to perform initial correction of the touch panel.

  The control unit 1 performs lighting control of the capacitive touch panel and the display unit that constitute the touch panel device. The sensor electrode 12 is disposed on the front surface of the display unit, and is made of a conductor because the capacitance needs to change when a conductor such as a finger comes close. The capacitance detection unit 13 is connected to the sensor electrode 12, acquires the capacitance of the sensor electrode 12 as a voltage, and converts it into a digital value. The correction unit 14 is a block that acquires the capacitance value of each sensor electrode acquired by the capacitance detection unit 13 as a reference value and records it in the reference value holding unit. The coordinate calculation unit 16 compares the capacitance of each sensor electrode 12 acquired by the capacitance detection unit 13 with a reference value. If there is a change amount greater than or equal to a predetermined value with respect to the reference value, the contact of the object is detected. It is a block that determines that there was. When it is determined that there is a finger, the coordinates of the contact position are calculated from the capacitance distribution of the sensor electrode 12.

  FIG. 2 is a graph of the detected capacity when the initial correction is performed with the LCD 21 turned on. In the initial correction, the parasitic capacitance of the first to nth electrodes is acquired, and the value is used as a reference for the sensor capacitance. The parasitic capacitance of each electrode varies, but in FIG. 2, attention is paid to one electrode for simplification.

  As shown in FIG. 2, when the initial correction is performed while the LCD 21 is lit, the capacitance detection unit 13 detects the parasitic capacitance when the transistor of the LCD 21 is ON, and the reference value holding unit 15 Hold as value. As a result, the increase in capacitance due to finger contact can be acquired correctly, and normal contact detection becomes possible.

  FIG. 3 shows a control flowchart of the touch panel device according to Embodiment 1 of the present invention. The operation of the touch panel device according to the first embodiment will be described with reference to FIG. When the touch panel device is activated by the activation unit 4, first, the control unit 1 displays the initial correction image data 26 of the touch panel on the LCD 21 (step S1). At this stage, the backlight 23 is not turned on, and the display contents are not visible to the user. The initial correction image data 26 is preferably in a display state in which the parasitic capacitance is most easily detected from the LCD 21. Although the display pattern in which the parasitic capacitance is the largest differs depending on the LCD driving method, an example is black and white alternate display for each pixel.

  After displaying the initial correction image data 26, the touch panel control unit 11 performs initial correction of the touch panel 2, and the capacitance detection unit 13 holds the parasitic capacitance detected from the electrode 12 as a reference value in the reference value holding unit. (Step S2). The control unit 1 displays an activation image to be displayed at the time of activation on the LCD 21 on the display unit 3 (step S3), and turns on the backlight 23 (step S4).

  As described above, according to the touch panel device of the present embodiment, the parasitic capacitance of the sensor electrode can be acquired as the reference capacitance with a display close to actual use, and the user of the touch panel device can acquire the reference capacitance in the initial stage. Initial correction equivalent to the actual use state is possible without showing the correction screen.

  The lighting timing of the backlight 23 may be provided with a predetermined wait time (waiting time), or may be turned on upon receiving an initial correction completion notification from the touch panel control unit 1.

  Alternatively, the control sequence may be such that after starting image data 27 is displayed first, the backlight is once turned off, the correction image is displayed and initial correction processing is performed, and the backlight is turned on again.

  INDUSTRIAL APPLICABILITY The present invention has an effect of preventing malfunction due to an LCD without increasing power consumption and without complicating the configuration, and is applicable to an electronic device using a touch panel such as a PDA or a mobile phone. Is possible.

DESCRIPTION OF SYMBOLS 1 Control part 2 Touch panel 3 Display part 4 Starting part 5 Memory | storage part 11 Touch panel control 12 Sensor electrode 13 Capacity | capacitance detection part 14 Correction | amendment part 15 Reference value holding | maintenance part 16 Coordinate calculation part 21 Transmission type LCD
22 Display Drive Circuit 23 Backlight 24 Backlight Drive Circuit 26 Initial Correction Image Data 27 Startup Image Data

Claims (2)

A capacitive touch panel having sensor electrodes;
A display unit comprising a transmissive liquid crystal and a backlight;
The capacitive touch panel, a control unit that controls the display unit, and an activation unit that activates the control unit,
When the control unit is activated by the activation unit, after the initial correction image is displayed on the transmissive liquid crystal, the controller performs initial correction to acquire the parasitic capacitance of the sensor electrode of the capacitive touch panel, Next, a control for turning on the backlight is performed. The touch panel device according to claim 1, wherein the initial correction image is a white screen or a screen that alternately displays white and black for each pixel of the transmissive liquid crystal.

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