JP2004021327A - Display device with touch sensor and positional data forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device with a touch sensor and a positional data forming method for reducing parallax more than by conventional device, and requiring no complicated circuit configuration. <P>SOLUTION: This display device 20 with the touch sensor has a display panel 10 having an electrode 5, a position detecting transparent conductive film 7 and a detecting circuit. This display device with the touch sensor forms an electric field in the position detecting transparent conductive film 7 by generating induced voltage in the position detecting transparent conductive film 7 by impressing periodically changing oscillating voltage on the electrode 5, and forms positional data on a contact point based on an electric current change caused by forming the contact point in the position detecting transparent conductive film 7. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a display device with a touch sensor that can detect a position on a display surface touched by a pen, a finger, or the like, and a position data generation method.
[0002]
[Prior art]
The touch sensor is an input device for detecting the position of a place where a finger or a pen makes contact. As a position detection method, a capacitance coupling method, a resistance film method, an infrared method, an ultrasonic method, an electromagnetic induction / coupling method, and the like are known.
[0003]
When the touch sensor is used integrally with the display device, for example, the touch sensor is arranged on the front surface (observer side) of an image display unit such as a liquid crystal panel. In this case, there is a problem that the touch sensor receives noise from the image display unit and the position detection accuracy of the touch sensor is reduced. The noise from the image display unit includes, for example, an induced voltage generated in the position detecting transparent conductive film included in the touch sensor due to a common voltage applied to the counter electrode included in the liquid crystal panel. To remove this noise, a detection circuit for detecting the contact position calculates the contact position after subtracting a signal corresponding to the induced voltage from the detected signal.
[0004]
Japanese Patent Publication No. 56-500230 discloses a touch sensor of a capacitive coupling type. Conventionally, when a capacitive touch sensor is disposed on a liquid crystal panel, a shield layer is disposed between the liquid crystal panel and the position detecting transparent conductive film provided in the touch sensor. It was suppressed from being adversely affected by noise from the panel. Further, the transparent conductive film for detecting the position of the touch sensor is disposed sufficiently far from the liquid crystal panel, thereby also suppressing the influence of noise from the liquid crystal panel.
[0005]
Japanese Patent Application Laid-Open No. 9-128146 discloses a display device having a resistive touch sensor. In this publication, the timing at which output data is taken in from the touch sensor is changed so that noise generated from the liquid crystal panel is not mixed into the output data.
[0006]
Further, as a method of avoiding noise caused by a display signal, a method of detecting the position of a touched place during a blanking period in which there is no display signal is also used.
[0007]
[Problems to be solved by the invention]
However, when a shield layer is provided between the touch sensor and the liquid crystal panel, and / or when the position detecting transparent conductive film of the touch sensor is arranged sufficiently far from the liquid crystal panel, there is a problem that parallax increases. . In addition, the transmittance between the display surface of the liquid crystal panel and the viewer may be reduced. Further, there is a problem that a display device provided with a touch sensor becomes large and it is difficult to reduce the thickness.
[0008]
In the display device disclosed in Japanese Patent Application Laid-Open No. 9-128146, the interval between sampling clocks of the touch sensor is not constant, and the interval between input / display varies. Therefore, the user of the touch sensor feels uncomfortable.
[0009]
When the influence of noise is avoided by performing position detection during the blanking period, detection is performed during the vertical blanking period because the horizontal blanking period does not have enough time to perform noise avoidance processing. There is a need. To perform position detection during the vertical blanking period, when the liquid crystal is driven at, for example, 60 Hz, the sampling interval is 16.7 ms. This interval is too slow for the user of the touch sensor to input the contact position smoothly. Further, in order to realize the method of performing position detection during the blanking period, it is necessary to know the drive timing of the liquid crystal panel, so that a separate circuit for obtaining a timing signal is required. Therefore, there is a problem that the circuit of the device is complicated.
[0010]
The present invention has been made in view of the above problems, and a main object of the present invention is to provide a display device with a touch sensor that has a smaller parallax than the related art and does not require a complicated circuit configuration, and a position data generation method. Is to provide.
[0011]
[Means for Solving the Problems]
The display device with a touch sensor of the present invention is disposed on a display medium layer, an observer side of the display medium layer, and an electrode for driving the display medium layer, and disposed on an observer side of the electrode. A display panel having an insulating layer, a transparent conductive film for position detection arranged to face the electrode via the insulating layer, and a change in current flowing from a plurality of locations of the transparent conductive film for position detection. And generating an electric field in the transparent conductive film for position detection by applying an oscillating voltage that changes periodically to the electrode to generate an induced voltage in the transparent conductive film for position detection. Then, position data of the contact point is generated based on the current change caused by forming the contact point in the transparent conductive film for position detection, thereby solving the above-described problem.
[0012]
It is preferable that the induced voltage is a pulse wave having a maximum value and / or a minimum value periodically.
[0013]
Preferably, the oscillation voltage is a voltage used to drive the display medium layer.
[0014]
The display panel may be a liquid crystal panel, and the vibration voltage may be a voltage whose polarity is periodically inverted.
[0015]
The liquid crystal panel may be an active matrix type liquid crystal panel, and the electrode may be a transparent counter electrode.
[0016]
A distance between the electrode and the transparent conductive film for position detection may be about 1 mm or less.
[0017]
The frequency of the pulse wave may be about 40 kHz.
[0018]
The method of generating position data of a contact point according to the present invention is a method of generating position data of a contact point with respect to a position detecting transparent conductive film arranged to face an electrode via an insulating layer. Generating an electric field in the position detecting transparent conductive film by applying an oscillating voltage that changes periodically to generate an induced voltage in the position detecting transparent conductive film; and Generating the position data of the contact point based on the current change caused by forming the contact point on the contact point, thereby solving the above-mentioned problem.
[0019]
It is preferable to use an electrode used for driving a display medium layer included in a display panel as the electrode.
[0020]
The oscillating voltage is preferably a voltage used for driving a display medium layer included in a display panel.
[0021]
Hereinafter, the operation of the present invention will be described.
[0022]
A display device with a touch sensor according to the present invention includes a display panel having electrodes, a transparent conductive film for position detection, and a detection circuit. In the display device with the touch sensor of the present invention, an induced voltage is generated in the transparent conductive film for position detection by applying a periodically changing vibration voltage to the electrode, and an electric field is generated in the transparent conductive film for position detection. The method is characterized in that position data of a contact point is generated based on a current change caused by forming the contact point on the transparent conductive film for position detection.
[0023]
The display device with a touch sensor of the present invention generates position data of a contact point with the position-detecting transparent conductive film by positively utilizing an induced voltage that has been conventionally considered to be noise. Specifically, an induced voltage is generated in the transparent conductive film for position detection by applying a periodically changing vibration voltage to the electrode, and an electric field is generated in the transparent conductive film for position detection. Position data of the contact point is generated based on a current change caused by forming the contact point on the transparent conductive film for position detection.
[0024]
Therefore, it is not necessary to increase the distance between the position detecting transparent conductive film and the electrode. Further, there is no need to provide a shield layer between the display panel and the position detecting transparent conductive film. As a result, it is possible to provide a display device with a touch sensor that can be reduced in thickness and has small parallax. Furthermore, in order to detect a contact position, instead of using a voltage specifically applied to the position detecting transparent conductive film, an induced voltage generated by a periodically changing vibration voltage applied to the electrode is used, No complicated circuit is required, and power consumption is not increased. In addition, as such an oscillating voltage, a voltage inherently provided in a display panel for driving a display medium layer can be used. Furthermore, since it is not necessary to separately apply an AC voltage to the transparent conductive film for position detection, power can be saved.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a display device with a touch sensor of the present invention will be described with reference to the drawings.
[0026]
FIG. 1 schematically shows a configuration of a display device with a touch sensor 20 according to an embodiment of the present invention.
[0027]
The display device with a touch sensor 20 includes the display panel 10, the transparent conductive film 7 for position detection, and a detection circuit (not shown in FIG. 1).
[0028]
The display panel 10 is disposed at least on the display medium layer 4, on the viewer side of the display medium layer 4, and on the viewer side of the transparent counter electrode 5 for driving the display medium layer 4. And an insulating layer (dielectric layer) 6 disposed. The position detecting transparent conductive film 7 is disposed so as to face the transparent counter electrode 5 via the insulating layer 6 provided in the display panel 10. The detection circuit detects a change in current flowing from a plurality of portions of the position detecting transparent conductive film 7.
[0029]
The display device with a touch sensor 20 generates an induced voltage in the transparent conductive film 7 for position detection by applying an oscillating voltage that changes periodically to the transparent counter electrode 5, and generates an electric field in the transparent conductive film for position detection. The main feature is that the position data of the contact point is generated based on a change in current generated and generated by forming the contact point on the transparent conductive film for position detection.
[0030]
In a conventional display device with a touch sensor, the induced voltage generated in the position-detecting transparent conductive film by applying a common voltage to the transparent counter electrode is considered to be noise for the touch sensor. Therefore, in order to suppress the generation of the induced voltage in the transparent conductive film for position detection, a sufficient distance is provided between the transparent conductive film for position detection and the transparent counter electrode. Alternatively, a shield layer is disposed between the position detecting transparent conductive film and the transparent counter electrode. Alternatively, as described above, in the detection circuit for detecting the contact position, the contact position is calculated after subtracting the signal corresponding to the induced voltage from the detected signal.
[0031]
On the other hand, in the display device with a touch sensor 20 of the present embodiment, the position data of the contact point with respect to the position detecting transparent conductive film 7 is generated by positively utilizing the induced voltage which is conventionally considered to be noise. I do. Therefore, it is not necessary to increase the distance between the position detecting transparent conductive film 7 and the transparent counter electrode 5. Further, there is no need to provide a shield layer between the display panel 10 and the position detecting transparent conductive film 7. As a result, it is possible to provide a display device with a touch sensor that can be reduced in thickness and has small parallax.
[0032]
Further, in order to detect the contact position, instead of using a voltage specially applied to the position detecting transparent conductive film 7, an induced voltage generated by a periodically changing vibration voltage applied to the transparent counter electrode 5 is generated. Use. Therefore, a complicated circuit is not required and power consumption does not increase. In addition, as such an oscillating voltage, a voltage inherently provided in a display panel for driving a display medium layer can be used. Further, it is not necessary to separately apply an AC voltage to the position detecting transparent conductive film 7.
[0033]
Hereinafter, a specific example of the display device with a touch sensor 20 will be described with reference to FIG. In the following description, a case where a liquid crystal panel is used as the display panel 10 will be exemplified.
[0034]
When a liquid crystal panel is used as the display panel 10, for example, as shown in FIG. 1, the display panel 10 further includes, in addition to the insulating layer 6, the transparent counter electrode 5, and the display medium layer 4 including a liquid crystal material, It further includes an active matrix substrate 8 and a first polarizing plate 1 arranged so as to face the transparent counter electrode 5 with the display medium layer 4 interposed therebetween. In the active matrix substrate 8, a TFT array 3 is formed on a main surface of a substrate 2 formed of a transparent material such as glass or plastic, and pixel electrodes (not shown) are arranged in a matrix.
[0035]
The insulating layer 6 is, for example, a counter substrate such as a glass substrate or a plastic substrate, and may further include a color filter and a second polarizing plate as needed. Further, the color filter and the second polarizing plate may be arranged on the observer side of the position detection transparent electrode 7. The preferred thickness of the insulating layer 6 may be such that it can generate a sufficiently large induced voltage in the transparent electrode 7 for position detection.
[0036]
A specific preferable thickness of the insulating layer 6 depends on the dielectric constant of a material included in the insulating layer. As will be described later, in order to generate a sufficiently large induced voltage in the position detecting transparent electrode 7, the capacitance of the capacitor formed from the position detecting transparent conductive film 7, the opposing transparent electrode 5, and the insulating layer between them is required. Is preferably about 200 pF or more. Therefore, for example, when a glass substrate is used for the insulating layer of a 3.7-type liquid crystal panel, the thickness of the glass substrate is preferably set to be more than 0 mm and 1.1 mm or less. At present, a glass substrate having a thickness of 0.4 mm or more is used. When the size of the liquid crystal panel is larger than 3.7 inches, the capacitance of the capacitor can be increased to about 200 pF or more even if the thickness of the glass substrate is larger than 1.1 mm.
[0037]
In addition, a protective layer may be formed on the outermost surface of the display device 20 on the viewer side.
[0038]
The liquid crystal panel is generally AC driven. This is because the life of the liquid crystal layer is shortened when a DC voltage is applied to the liquid crystal layer. Therefore, a voltage whose positive and negative polarities are periodically inverted is applied to the transparent counter electrode 5 as a common voltage.
[0039]
FIG. 2A is a diagram illustrating an example of a temporal change of a common voltage applied to the transparent counter electrode 5 of the display panel 10. The vertical axis indicates the potential of the transparent counter electrode 5, and the horizontal axis indicates time. Here, the case of line inversion driving is illustrated, but the present invention is not limited to this.
[0040]
As shown in FIG. 2A, the common voltage has its positive and negative polarities inverted every horizontal period, and the absolute value of the positive voltage value is equal to the absolute value of the negative voltage value. . In the display device 20 with a touch sensor, this common voltage becomes an oscillating voltage for generating an induced voltage in the transparent conductive film 7 for position detection.
[0041]
FIG. 2B shows a temporal change of the induced voltage generated in the position detecting transparent conductive film 7 when the common voltage shown in FIG. 2A is applied to the transparent counter electrode 5. The vertical axis indicates the potential of the transparent conductive film 7 for position detection, and the horizontal axis indicates time. This induced voltage is a pulse wave synchronized with the voltage change of the transparent counter electrode 5 shown in FIG. 2A and having a maximum value or a minimum value every horizontal period. The maximum value or the minimum value appears, for example, at a period of about 40 kHz. The induced voltage shown in FIG. 2B is sufficiently higher than, for example, an induced voltage generated by a display signal voltage supplied to the active matrix substrate 8 or the like.
[0042]
By generating the induced voltage shown in FIG. 2B in the transparent conductive film 7 for position detection, an electric field having a small gradient is formed substantially uniformly in the transparent conductive film 7 for position detection.
[0043]
In the position detecting transparent conductive film 7, for example, position detecting electrodes are formed at four corners. When a protective layer is provided on the outermost surface on the observer side of the display device with a touch sensor 20, the surface of the protective layer is touched with a pen or a finger, so that a contact point is formed on the position-detecting transparent conductive film 7. It is formed. When a contact point is formed on the position detecting transparent conductive film 7, the position detecting transparent conductive film 7 is capacitively coupled to the ground (ground plane). This capacitance is, for example, the sum of the capacitance between the protective layer and the position-detecting transparent conductive film 7 and the capacitance existing between the person and the ground.
[0044]
The electric resistance value between the capacitively coupled contact portion and the electrodes at the four corners of the transparent conductive film 7 for position detection is proportional to the distance between the contact portion and each electrode. Therefore, a current proportional to the distance between the contact portion and each electrode flows through the four corner electrodes of the position detecting transparent conductive film 7. By detecting the magnitude of these currents, the position coordinates of the contact portion can be determined.
[0045]
In a conventional display device with a touch sensor, by applying a predetermined AC voltage to the transparent conductive film for position detection using an oscillation circuit, an electric field with a small gradient is formed substantially uniformly in the transparent conductive film for position detection, The contact position was detected. On the other hand, in the display device with a touch sensor 20 according to the present embodiment, as described above, the position detecting transparent conductive film 7 is induced by the vibration voltage applied to the transparent counter electrode 5, and the position detecting transparent conductive film 7 is used. An electric field having a small gradient is formed substantially uniformly in the transparent conductive film 7. Further, position data of a contact point is generated based on a change in current generated from a change in an electric field generated in the transparent conductive film 7 for position detection.
[0046]
That is, in the display device 20 with a touch sensor, the position data of the contact point is generated using the induced voltage that has not been effectively used conventionally. Therefore, an oscillation circuit, which has been conventionally required for applying an AC voltage to the position detecting transparent conductive film 7, is not required, so that power consumption can be reduced as compared with the related art. Conventionally, the above-described induced voltage was considered to be noise. To suppress the generation of the induced voltage, a shield layer was provided between the transparent counter electrode 5 and the position detecting transparent conductive film 7. And / or the distance between the transparent counter electrode 5 and the position-detecting transparent conductive film 7 is increased, but this is not necessary in the display device 20 with a touch sensor.
[0047]
In the display device with a touch sensor, a pseudo capacitor is formed between the position-detecting transparent conductive film 7 and the opposing transparent electrode 5 using an insulating layer (dielectric layer) such as a glass substrate and an air layer. As described above, in the present embodiment, the induced voltage is used for position detection. For example, when the display panel is a 3.7-type display panel (the diagonal length of the display surface is 3.7 inches), the display panel is sufficiently large. In order to generate an induced voltage, the capacitance of the capacitor is preferably 200 pF or more.
[0048]
For example, assuming that the liquid crystal panel 10 is a 3.7-type liquid crystal panel, a glass substrate having a thickness of 0.7 mm is arranged between the transparent counter electrode 5 and the transparent conductive film 7 for position detection. When a gap of an air layer having a thickness of 0.1 mm is provided between the transparent electrode 7 and the film 7, the distance between the transparent counter electrode 5 and the transparent conductive film 7 for position detection is 0.8 mm, and the capacitance of the capacitor is 192 pF.
[0049]
When the distance between the transparent counter electrode 5 and the position detecting transparent conductive film 7 is 0.8 mm as described above, for example, when a voltage having an amplitude of 4.9 V shown in FIG. It was measured that an induced voltage having an amplitude of 0.65 V as shown in FIG. 2B was generated in the position detecting transparent conductive film 7. The magnitude of the induced voltage is sufficient for performing the position detection of the present embodiment.
[0050]
On the other hand, in the conventional display device with a touch sensor, in order to suppress the generation of the induced voltage, the distance between the transparent counter electrode and the position detecting transparent conductive film is reduced so that the capacitance of the capacitor is reduced. I was taking it big.
[0051]
For example, assuming that the liquid crystal panel is of a 3.7 type, a 0.7 mm glass substrate is disposed between the transparent counter electrode and the transparent conductive film for position detection, and the liquid crystal panel is placed between the glass substrate and the transparent conductive film for position detection 7. In the case where a gap of an air layer having a thickness of 0.5 mm is provided, the distance between the transparent counter electrode and the transparent conductive film for position detection is 1.2 mm, and the capacitance of the capacitor is 62.5 pF. A distance equivalent to the distance between the transparent counter electrode and the position detecting transparent conductive film was required between the resistive film and the counter transparent electrode of the conventional resistive display device with a touch sensor. .
[0052]
As described above, in the display device 20 with a touch sensor, the distance between the opposing transparent electrode 5 and the position detecting transparent conductive film 7 can be, for example, 1 mm or less. Since the position 5 and the position detecting transparent conductive film 7 can be brought close to each other, parallax can be reduced.
[0053]
In the above description, the case where the induced voltage is generated using the common voltage applied to the opposing transparent electrode 5 has been described, but the voltage applied to the opposing transparent electrode 5 to generate the induced voltage is not limited to this. .
[0054]
For example, an oscillating voltage for generating an induced voltage in the position detecting transparent conductive film 7 may be applied to the opposed transparent electrode 5 separately from the common voltage. FIG. 2C shows this specific example. The vertical axis indicates the potential of the opposing transparent electrode 5 and the horizontal axis indicates time. One cycle of the potential of the opposing transparent electrode 5 shown in FIG. ₁ And period T ₂ And
[0055]
In the case of FIG. 2C, a period in which the opposing transparent electrode 5 is used as a display common electrode (display mode) and a period in which the induced voltage is generated in the position detection transparent conductive film 7 (position detection mode). And are switched. Period T ₁ And period T ₂ Respectively correspond to the position detection mode and the display mode.
[0056]
The electrodes at the four corners of the position-detecting transparent conductive film 7 are each connected to a detection circuit, which will be described later, using a switching circuit including a transistor, a diode, and the like. Period T ₁ And period T ₂ Are alternately switched by using this switching circuit, for example. Period T ₁ During the period, the electrodes at the four corners of the position detecting transparent conductive film 7 are connected to the detection circuit, respectively, and the period T ₂ During the period, the electrodes at the four corners of the position detection transparent conductive film 7 are not connected to the detection circuit.
[0057]
First, period T ₁ In the position detection mode, an oscillating voltage having a predetermined amplitude is applied to the opposing transparent electrode 5 to generate an induced voltage having a predetermined amplitude in the transparent conductive film 7 for position detection. This period T ₁ During the period, the electrodes at the four corners of the position detecting transparent conductive film 7 are respectively connected to a detection circuit described later, and the detection circuit generates position data of the contact point.
[0058]
On the other hand, period T ₂ In the display mode, when a common voltage of a predetermined magnitude is applied and the common voltage oscillates as described above, an induced voltage is generated in the position detecting transparent conductive film 7, but the period T ₂ During this period, the electrodes at the four corners of the position detecting transparent conductive film 7 are not connected to the detection circuit, so that the induced voltage does not affect the detection accuracy of the contact position. Note that, as shown in FIG. ₂ If a constant voltage is applied to the opposing transparent electrode 5 during this period, no induced voltage is generated in the transparent conductive film 7 for position detection, so that the switching circuit can be omitted.
[0059]
Next, with reference to FIG. 3, the basic principle of the position detection method based on the capacitance coupling method employed in the present invention will be briefly described. As shown in FIG. 3, alternating voltages of the same homologous potential are applied to the four corner electrodes of the transparent conductive film 7 for position detection, and the current flowing through the four corners of the transparent conductive film 7 for position detection by contact with a finger or the like Each of i ₁ , I ₂ , I ₃ , And i ₄ And
[0060]
In FIG. 3, AC voltages having the same homologous potential are applied from the four corner electrodes of the transparent conductive film 7 for position detection. The induced voltage is not a voltage applied by a circuit or the like, but an induced voltage generated by an oscillating voltage applied to the transparent counter electrode 5.
[0061]
The X coordinate and the Y coordinate of the contact position with respect to the position detecting transparent conductive film 7 can be determined based on the following equation.
[0062]
X = k ₁ + K ₂ ・ (I ₂ + I ₃ ) / (I ₁ + I ₂ + I ₃ + I ₄ (Equation 1)
Y = k ₁ + K ₂ ・ (I ₁ + I ₂ ) / (I ₁ + I ₂ + I ₃ + I ₄ (Equation 2)
[0063]
Here, X is the X coordinate of the contact position on the transparent conductive film 7 for position detection, and Y is the Y coordinate of the contact position on the transparent conductive film 7 for position detection. Also, k ₁ Is the offset, k ₂ Is the magnification. k ₁ And k ₂ Is a constant independent of human impedance.
[0064]
Therefore, the contact position with respect to the position detecting transparent conductive film 7 is determined by i flowing through the four electrodes. ₁ , I ₂ , I ₃ , And i ₄ Can be determined from the measured values of
[0065]
In the above description, the case where the display panel 10 is a liquid crystal panel, and particularly, the case where the liquid crystal panel is an active matrix type liquid crystal panel is exemplified, but the display panel 10 used in the present embodiment is not limited to this. Any display panel can be used as long as a periodically changing vibration voltage is applied to the transparent counter electrode included in the display panel. Here, the oscillation voltage applied to the transparent counter electrode is preferably a voltage used to drive the display medium layer. The oscillating voltage is required to generate an induced voltage in the transparent conductive film for position detection. If the oscillating voltage is a common voltage used to drive the display medium layer, a common voltage is applied to the transparent counter electrode. In addition, there is no need to separately apply a voltage for generating an induced voltage. Therefore, the power supply circuit can be prevented from having a complicated configuration as compared with the conventional display device, and the power consumption can be prevented from increasing.
[0066]
The electrode that generates an induced voltage in the position detecting transparent conductive film 7 is not limited to the transparent counter electrode 5 described above. However, when a plurality of electrodes to which different vibration voltages are applied are opposed to the position detecting transparent conductive film 7, the electric field between these electrodes and the position detecting transparent conductive film 7 becomes non-uniform, and the position detecting accuracy is reduced. May decrease. Therefore, at least the entire area of the position detecting transparent conductive film 7 for detecting the contact position is so set that a uniform electric field can be generated between the electrode for generating the induced voltage and the position detecting transparent conductive film 7. It is preferable that the transparent conductive film 7 for position detection and an electrode for generating an induced voltage are provided so as to face each other.
[0067]
Next, a configuration of a detection circuit included in the display device with a touch sensor 20 will be described. The detection circuit detects a change in current flowing from a plurality of locations of the position detecting transparent conductive film 7 and generates position data of a contact point with the position detecting transparent conductive film 7 based on the detected change in current.
[0068]
FIG. 4 is a block diagram illustrating an example of the detection circuit 50. The detection circuit 50 illustrated in FIG. 4 includes four current change detection circuits 31. The four current change detection circuits 31 are connected to the four corner electrodes of the position detecting transparent conductive film 7, respectively. I have. The number and arrangement of the electrodes provided on the position detecting transparent conductive film 7 are not limited thereto.
[0069]
The current change detection circuit 31 measures a current flowing between each of the four electrodes of the position detecting transparent conductive film 7 and the ground. Since the above-described induced voltage is applied to the transparent conductive film 7 for position detection, a current flowing through each electrode due to contact with a finger or the like has an AC component.
[0070]
The output of the current change detection circuit 31 is subjected to amplification and band-pass filtering by the analog signal processing circuit 32. The output of the analog signal processing circuit 32 is detected by a detection filtering circuit 33.
[0071]
The detection filtering circuit 33 performs filtering to remove various noises included in the received signal. Conventionally, an induced voltage (for example, FIG. 2B) generated in the position detecting transparent conductive film by a voltage applied to the transparent counter electrode was considered to be noise. Therefore, a signal corresponding to the induced voltage was included in the noise to be deleted by the detection filtering circuit.
[0072]
On the other hand, in the detection circuit of the present embodiment, since the induced voltage is positively used for detecting the position of the contact point, the detection filtering circuit 33 does not delete the signal corresponding to the induced voltage. Therefore, the detection filtering circuit 33 of the present embodiment does not include a circuit for deleting a signal corresponding to the induced voltage.
[0073]
The output from the detection filtering circuit 33 is input to the noise canceling DC conversion circuit 34. The noise elimination DC circuit 34 converts the output of the detection filtering circuit 33 into DC, and generates a signal having a value proportional to the current flowing through each electrode. The noise elimination DC circuit 34 converts the detected current value into a voltage value, amplifies the voltage value, generates the signal, and sends the signal to the A / D converter 36 via the analog multiplexer 35.
[0074]
In the conventional noise elimination DC circuit, the signal (voltage value) received from the detection filtering circuit has a signal corresponding to the induced voltage deleted. Therefore, the signal received from the detection filtering circuit does not have the induced voltage shown in FIG. 2B, for example, and has a waveform that changes continuously with time. Therefore, the conventional noise canceling DC circuit continuously inputs the voltage value having the continuously changing waveform to the A / D converter via the analog multiplexer.
[0075]
On the other hand, in the present embodiment, the signal (voltage value) received from the detection filtering circuit 33 has the induced voltage shown in FIG. 2B superimposed thereon, for example, as shown in FIG. It has a discontinuous waveform. For this reason, when the signal detected by the noise canceling DC circuit is continuously input to the A / D converter via the analog multiplexer as in the related art, the signal fluctuates even when the contact position is not input. Therefore, the contact position cannot be accurately detected. FIG. 6A is a diagram illustrating an example of a temporal change of a signal (voltage value) received by the noise elimination DC circuit 34 from the detection filtering circuit 33. The vertical axis indicates the potential, and the horizontal axis indicates time.
[0076]
Therefore, in the detection circuit 50 of the present embodiment, as shown in FIG. 5, a capacitor is provided in an amplification circuit included in the noise canceling DC conversion circuit 34. For example, when the induced voltage is a pulse wave having a maximum value or a minimum value at a period of 40 kHz, it is preferable to provide a capacitor having a capacitance of several hundred nF. By providing the capacitor, the current value detected when the induced voltage is present and the current value detected when the induced voltage is not present are averaged, as shown in FIG. A DC voltage is applied to the / D converter 36. The position of the contact point is determined based on the difference between the value of the DC voltage obtained when the contact point is not formed on the transparent conductive film 7 for position detection and the value of the DC voltage obtained when the contact point is formed. Is required.
[0077]
The analog multiplexer 35 receiving the above signal from the noise canceling DC conversion circuit 34 sends out the outputs from the four electrodes to the A / D converter 36. The A / D converter 36 generates a digitized position signal (position data) and sends it to the processing device 37. The position data referred to here is the value of i in Equations 1 and 2 described above. ₁ , I ₂ , I ₃ , And i ₄ Is converted to a DC voltage value, and these are further digitized. The processing device 37 obtains the coordinates X and Y based on the expressions 1 and 2 using these values, determines an input command by the operator who has formed the contact point, and performs predetermined data processing and the like. The processing device 37 is mounted in, for example, a portable information terminal (PDA), an ATM, a ticket vending machine, or various computers equipped with the display device of FIG. 1 and executes data processing.
[0078]
The position data generated by the detection circuit 50 is not limited to the above example. For example, the detection circuit 50 may obtain the XY coordinates using the digitized DC voltage value and output this as position data.
[0079]
【The invention's effect】
According to the present invention, it is possible to provide a display device with a touch sensor that is thin, has small parallax, and does not require a complicated circuit configuration, and a position data generation method.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating a configuration of a display device with a touch sensor according to an embodiment of the present invention.
FIG. 2A is a diagram illustrating an example of a time change of a common voltage applied to a transparent counter electrode of a display panel, and FIG. 2B is a diagram illustrating a common voltage shown in FIG. FIG. 7C is a diagram showing a time change of an induced voltage generated in the position detecting transparent conductive film when the common voltage applied to the transparent counter electrode is constant when a common voltage applied to the transparent counter electrode is constant. FIG. 5 is a diagram illustrating an example of a temporal change of an applied voltage.
FIG. 3 is a diagram for briefly explaining a basic principle of a position detection method by an electrostatic capacitance coupling method employed in the present invention.
FIG. 4 is a block diagram illustrating an example of a detection circuit.
FIG. 5 is a diagram illustrating an amplifier circuit included in the noise canceling DC conversion circuit.
FIG. 6A is a diagram illustrating an example of a time change of a signal received by a noise canceling DC circuit from a detection filtering circuit, and FIG. 6B is a diagram illustrating a time change of a DC voltage applied to an A / D converter; It is a figure showing an example.
[Explanation of symbols]
1 First polarizing plate
2 Glass substrate
3 TFT array
4 Display media layer
5 Transparent counter electrode
6 Insulation layer
7 Transparent conductive film for position detection
8 Active matrix substrate
10 Display panel
20 Display device with touch sensor
31 Current change detection circuit
32 analog signal processing circuit
33 Detection and filtering circuit
34 Noise canceling DC circuit
35 Analog Multiplexer
36 A / D converter
37 Processing equipment
50 detection circuit

Claims (10)

A display medium layer, disposed on the viewer side of the display medium layer, and an electrode for driving the display medium layer, and a display panel having an insulating layer disposed on the viewer side of the electrode.
Via the insulating layer, a transparent conductive film for position detection arranged to face the electrode,
A detection circuit that detects a change in current flowing from a plurality of locations of the position detection transparent conductive film,
By generating an induced voltage in the transparent conductive film for position detection by applying an oscillating voltage that changes periodically to the electrode, an electric field is generated in the transparent conductive film for position detection,
A display device with a touch sensor, which generates position data of the contact point based on the current change caused by forming a contact point on the transparent conductive film for position detection. The display device with a touch sensor according to claim 1, wherein the induced voltage is a pulse wave having a maximum value and / or a minimum value periodically. The display device with a touch sensor according to claim 1, wherein the vibration voltage is a voltage used for driving the display medium layer. The display device according to claim 3, wherein the display panel is a liquid crystal panel, and the oscillating voltage is a voltage whose polarity is periodically inverted. The display device according to claim 4, wherein the liquid crystal panel is an active matrix liquid crystal panel, and the electrodes are transparent counter electrodes. The display device with a touch sensor according to claim 1, wherein a distance between the electrode and the transparent conductive film for position detection is about 1 mm or less. The display device with a touch sensor according to claim 2, wherein a frequency of the pulse wave is about 40 kHz. A method for generating position data of a contact point with respect to a position detection transparent conductive film arranged to face an electrode via an insulating layer,
By applying an oscillating voltage that changes periodically to the electrode, generating an induced voltage in the transparent conductive film for position detection, and generating an electric field in the transparent conductive film for position detection,
Generating the position data of the contact point based on the current change caused by forming the contact point on the transparent conductive film for position detection. The position data generation method according to claim 8, wherein an electrode used to drive a display medium layer included in a display panel is used as the electrode. The position data generation method according to claim 8, wherein the vibration voltage is a voltage used to drive a display medium layer included in a display panel.

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