JP2008090623A - Display device, display device drive device, and drive method - Google Patents

Abstract

In a display device including a display panel and a touch panel, the position detection accuracy of the touch panel can be reduced by an induced voltage caused by polarity inversion of a counter electrode of the display panel, and the position detection period is lengthened. .
A touch panel drive circuit is provided that applies the same signal voltage as a common voltage, which is a signal voltage applied to a counter electrode, to a transparent conductive film of a touch panel during a display period and a non-display period of a display panel. Yes.
[Selection] Figure 1

Description

  The present invention relates to a display device including a touch panel that detects a position on a display surface that is touched by a pen, a finger, or the like, a display device drive device, and a drive method.

  2. Description of the Related Art Conventionally, a display device including a touch panel (touch sensor) that is an input device for detecting a position where a finger or a pen touches a display surface and transmitting a user's intention to an information processing system has been widespread. As a position detection method used for a touch panel, a capacitive coupling method, a resistive film method, an infrared method, an ultrasonic method, an electromagnetic induction / coupling method, and the like are known.

  For example, Patent Document 1 discloses a capacitive coupling touch sensor. Patent Document 2 discloses a display device including a resistive film type touch sensor.

  Generally, when a touch panel is used integrally with a display device, the touch panel is disposed on the front surface (observer side) of a display panel such as a liquid crystal panel.

  However, in this case, the touch panel receives noise from the display panel, and the position detection accuracy of the touch panel may decrease. The noise from the display panel includes, for example, an induced voltage generated in the transparent conductive film for position detection provided in the touch panel due to a common voltage applied to the counter electrode provided in the liquid crystal panel.

  For this reason, conventionally, when a capacitive coupling type touch sensor is disposed on a liquid crystal panel, a shield layer is disposed between the position detection transparent conductive film provided on the touch sensor and the liquid crystal panel. The sensor was restrained from being adversely affected by noise from the liquid crystal panel. Or the influence by the noise from a liquid crystal panel was suppressed by arrange | positioning the transparent conductive film for position detection of a touch sensor sufficiently away from the liquid crystal panel.

Further, in Patent Document 2, when the output change timing of the liquid crystal drive signal coincides with the timing of capturing the output data corresponding to the touch position with respect to the touch panel, the capturing of the output data according to the touch position is stopped, and at different timings. By capturing output data corresponding to the contact position, noise generated from the liquid crystal panel is prevented from being mixed into the output data.
JP 56-500230 A (publication date: February 26, 1981) JP-A-9-128146 (Publication date: May 16, 1997)

  However, in the conventional display device, the driving device and the driving method of the display device, a shield layer is provided between the touch sensor and the liquid crystal panel, or the transparent conductive film for position detection of the touch sensor is disposed away from the liquid crystal panel. If this happens, there is a problem that parallax increases. In addition, the transmittance may decrease due to the presence of the shield layer. Furthermore, there is a problem that the display device provided with the touch sensor becomes large and it is difficult to reduce the thickness.

  In the display device of Patent Document 2, when there is a possibility that the sampling clock of the touch panel and the output change timing of the liquid crystal drive signal are constantly monitored, and the liquid crystal drive signal output may be mixed into the touch panel signal as noise, It is necessary to provide a circuit for changing the sampling clock of the touch panel. For this reason, there is also a problem that the circuit configuration of the apparatus becomes complicated.

  In addition, the technique of Patent Document 2 is based on the premise that the generation of noise due to the liquid crystal drive signal occurs only during a limited period, and the generation of noise due to the liquid crystal drive signal occurs constantly. If this is the case, the effects of noise cannot be avoided. For example, as shown in FIG. 8, in a liquid crystal display device in which the polarity of the common voltage applied to the counter electrode of the display panel is inverted every horizontal synchronization period, when the capacitive coupling between the display panel and the touch panel is strong An induced voltage is generated in the transparent conductive film of the touch panel every time the polarity of the common voltage is reversed. For this reason, the technique of Patent Document 2 may not properly remove the influence of noise.

  Furthermore, in the technique of Patent Document 2, the position detection is performed only in a period in which the influence of noise on the position detection can be avoided, specifically, a period in which the output change timing of the liquid crystal drive signal does not coincide with the position data capture timing. . For this reason, the position detection period cannot be lengthened, and therefore the position detection accuracy may be lowered or the position detection response may be lowered.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a display device including a display panel and a touch panel, and the touch panel has an inductive voltage caused by polarity inversion of a counter electrode of the display panel. An object of the present invention is to provide a display device, a display device driving device, and a driving method capable of suppressing a decrease in position detection accuracy and extending a position detection period.

  In order to solve the above-described problem, the display device driving device of the present invention includes an optical modulation layer sandwiched between opposing insulating substrates and a plurality of pixels formed on one insulating substrate of the opposing insulating substrates. An electrode and a counter electrode formed on the other insulating substrate opposite to the plurality of pixel electrodes, and applying a voltage between the pixel electrode and the counter electrode In a drive device for a display device, comprising: a display panel that performs display by changing optical characteristics of the optical modulation layer; and a touch panel that is disposed on an observer side of the optical modulation layer and includes a transparent conductive film. Touch panel voltage application means for applying the same signal voltage as the common voltage applied to the counter electrode to the transparent conductive film of the touch panel during the display period and the non-display period. It is characterized in that.

  In the display device drive device of the present invention, it is preferable that the signal voltage applied to the transparent electrode film and the signal voltage applied to the counter electrode have the same waveform and phase. Here, the waveform is a form showing a change in voltage over time, and the phase means a relative shift at the same time for two waves having the same speed and frequency.

  In the display device drive device according to the present invention, the touch panel has a plurality of terminals electrically connected to the transparent conductive film and the touch panel voltage application unit at different locations on the surface of the transparent conductive film, respectively. Position detecting means for detecting the position of the contact point based on the detection result of the current flowing through each terminal when the contact point with respect to the transparent conductive film is formed by touching the transparent conductive film of the touch panel In addition, it is preferable that the position detection unit detects the position of the contact point during the display period and the non-display period. In addition, the said contact point is a position which the operator made pens, such as a finger and a stylus pen, contact the transparent conductive film of a touch panel, for example. Here, the stylus pen means a pen-type input device used for designating coordinates on a display screen in a PDA (Personal Digital Assistant) or the like.

  In the display device of the present invention, it is preferable to include a drive device for the display device.

  Further, in order to solve the above-described problem, the display device driving method of the present invention includes a plurality of optical modulation layers sandwiched between opposing insulating substrates and a plurality of insulating substrates formed on one of the opposing insulating substrates. A pixel electrode and a counter electrode formed on the other insulating substrate opposite to the plurality of pixel electrodes, and applying a voltage between the pixel electrode and the counter electrode. In the method of driving a display device, comprising: a display panel that performs display by changing the optical characteristics of the optical modulation layer, and a touch panel that is disposed on the viewer side of the optical modulation layer and has a transparent conductive film. During the display period and non-display period of the panel, the same signal voltage as the common voltage that is the signal voltage applied to the counter electrode is applied to the transparent conductive film of the touch panel.

  According to the above configuration, the same signal voltage as the common voltage that is applied to the counter electrode is applied to the transparent conductive film during the entire display period of the display panel and the non-display period. The potential of the transparent conductive film and the potential of the counter electrode are the same. In other words, since the same signal is input to the transparent conductive film and the counter electrode during the entire display period, no potential difference occurs between the transparent electrode film and the counter electrode. As a result, when position detection is performed based on a change in the surface charge of the transparent conductive film, an induced voltage generated due to, for example, polarity reversal or steep potential change of the counter electrode, which has been a hindrance to accurate position detection. Can be reduced during the entire display period of the display panel. Details will be described below.

  Usually, in the display period, a signal voltage that is inverted every horizontal synchronization period is applied to the counter electrode, so that an induced voltage is likely to occur between the transparent conductive film. This induced voltage becomes noise for position detection, and lowers the position detection accuracy. Therefore, conventionally, position detection has been performed during a non-display period in which the voltage applied to the counter electrode can be arbitrarily set. Specifically, the occurrence of the induced voltage is suppressed by applying a constant voltage or a signal voltage with a gradual change in potential to the counter electrode, thereby suppressing a decrease in position detection accuracy. However, in this configuration, since the position detection period is limited to the non-display period, the position detection period is shortened, and accurate position detection is difficult. In addition, the position detection response may be reduced. Further, a circuit for controlling the position detection period to a certain period is required, and the driving apparatus is complicated.

  On the other hand, according to the present invention, the potential of the counter electrode and the potential of the transparent conductive film of the touch panel are the same in all display periods of the display period and the non-display period. As a result, an induced voltage is unlikely to be generated in both the display period and the non-display period, and the position detection period can be made longer, so that position detection can be performed more accurately. Furthermore, since the position detection period is not limited and position detection is possible in the entire display period, it is possible to suppress a decrease in position detection response. In addition, since it is not necessary to limit the period for performing position detection to a certain period of all periods, for example, a non-display period or a period in which the potential change of the counter electrode is small, a circuit for controlling the position detection period is unnecessary. The drive device can be simplified.

  Therefore, in a display device including a display panel and a touch panel, it is possible to suppress a decrease in the position detection accuracy of the touch panel due to an induced voltage caused by polarity inversion of the counter electrode of the display panel, and the position detection period. It is possible to provide a display device, a driving device for the display device, and a driving method.

  In the display device drive device of the present invention, it is preferable that the polarity of the potential of the signal voltage applied to the counter electrode is inverted every horizontal synchronization period of the display panel.

  According to the above configuration, the signal voltage that is an example of the signal voltage suitable for the drive control of the display panel, which reverses the polarity of the potential of the signal voltage every horizontal synchronization period, is applied to the counter electrode. At this time, an induced voltage is likely to be generated due to polarity reversal. However, in the present invention, even if the polarity of the potential of the signal voltage is reversed, the same signal voltage as the signal voltage applied to the counter electrode is applied to the transparent conductive film. The polarity is reversed. As a result, even if the polarity of the potential of the signal voltage is reversed, a potential difference from the signal voltage of the transparent conductive film does not occur. Therefore, the deterioration of the display panel display quality is suppressed while the deterioration of the touch panel position detection accuracy is suppressed. can do.

  In the display device driving device according to the present invention, the position detection unit may form a current flowing through each terminal when a contact point with respect to the transparent conductive film is not formed and a contact point with respect to the transparent conductive film. It is preferable that the position of the contact point is detected based on a difference from the current flowing through each terminal when the contact is made.

  According to the above configuration, even when a current flows through each terminal when a contact point with respect to the transparent conductive film is not formed, the position can be accurately detected. Here, in the display device driving device of the present invention, since the transparent conductive film and the counter electrode of the touch panel have the same potential, the current flowing to the terminal when the contact point is not formed is zero in principle. obtain. However, in reality, a current may flow to the terminal due to a stray capacitance that is an intrinsic capacitance of the circuit itself. Even in this case, the position can be accurately detected by detecting the position based on the current difference. Here, the stray capacitance means an electrostatic capacity of wires and patterns for wiring, parts, and the like.

  In the display device drive device according to the present invention, a lead wiring that connects the terminal and the position detection unit and a shield wiring that covers an outer periphery of the lead wiring are provided, and the shield wiring is connected to the shield wiring. The same signal voltage as that applied to the counter electrode is preferably applied.

  According to the above configuration, it is possible to suppress the occurrence of parasitic capacitance between the shield wiring and the lead wire by applying the same signal voltage as that of the counter electrode to the shield wiring. This is based on the same principle as canceling the parasitic capacitance generated between the transparent conductive film of the touch panel and the counter electrode of the liquid crystal element by applying the same signal voltage to each. That is, the same signal voltage as that of the counter electrode is applied to the lead wire that is a path for applying the signal voltage to the transparent conductive film. Further, the same signal voltage as that of the counter electrode is applied to the shield wiring that has been a conventional ground (GND). By applying, parasitic capacitance generated between the shield wiring and the lead wire can be canceled. Therefore, more accurate position detection is possible.

  In the display device driving device according to the present invention, it is preferable that the transparent conductive film of the touch panel is formed between the opposing substrate and the insulating substrate provided with the counter electrode among the opposing insulating substrates.

  According to the above configuration, the transparent conductive film of the touch panel is close to the counter electrode of the display panel. Therefore, the generation of parasitic capacitance can be canceled more effectively, and more accurate position detection can be performed.

  As described above, the display device, the driving device and the driving method of the present invention are applied to the counter electrode with respect to the transparent conductive film of the touch panel during the display period and the non-display period of the display panel. Touch panel voltage application means for applying the same signal voltage as the common voltage as the signal voltage is provided.

  Therefore, in a display device having a display panel and a touch panel, the position detection accuracy of the touch panel can be reduced by an induced voltage caused by polarity inversion of the counter electrode of the display panel, and the position detection period is lengthened. It is possible to provide an obtained display device, a display device drive device, and a drive method.

[Embodiment 1]
An embodiment of the present invention will be described with reference to FIGS. 1 to 6 as follows. FIG. 2 is a perspective view illustrating a schematic configuration of the display panel 10 and the touch panel 20 provided in the display device 100 of the present embodiment.

  As shown in the figure, the display panel 10 includes two insulating substrates 1 and 6 arranged opposite to each other, a TFT array layer 2 provided on the insulating substrate 1 facing the insulating substrate 6, and an insulating substrate. 6, the color filter layer 5 provided on the surface facing the insulating substrate 1 and the counter electrode 4 as the counter electrode layer, and the optical modulation layer sandwiched between the TFT array layer 2 and the counter electrode 4 And a liquid crystal layer 3.

  The insulating substrates 1 and 6 are made of an insulating transparent material such as glass or plastic. Further, polarizing plates 51 and 52 are respectively provided on the outer surface side of the insulating substrates 1 and 6, that is, on the side opposite to the facing surface. The thickness of the insulating substrate 6 is, for example, not less than 0.2 mm and not more than 1.1 mm.

  A touch panel 20 having a touch panel substrate 21 and a transparent conductive film 22 is provided on the surface of the insulating substrate 6 opposite to the surface facing the insulating substrate 1.

  FIG. 3A is a block diagram showing the configuration of the display panel 10 and its driving device in the display device 100. As illustrated in FIG. 3A, the display device 100 includes a control circuit 11, a gradation reference voltage generation circuit 12, a source driver 13, a gate driver 14, a counter electrode drive circuit 15, and a position detection device 24. Although details will be described later, the position detection device 24 includes a position detection circuit 24a as a position detection unit and a touch panel drive circuit 24b as a touch panel voltage application unit.

  A predetermined signal such as a display video signal as data is supplied to the control circuit 11 via an external interface (I / F), and a horizontal synchronizing signal HSYC, a vertical synchronizing signal VSYC, and a clock signal CLK (pixel clock). Clock) or the like is input. The control circuit 11 generates various control signals based on the input display video signal, horizontal synchronization signal HSYC, vertical synchronization signal VSYC, clock signal CLK, and the like, and a gradation reference voltage generation circuit 12 and a source driver 13. To the gate driver 14 and the counter electrode drive circuit 15. When the video signal is analog, the clock signal CLK may be generated by a PLL circuit (Phase Locked Loop circuit) within the control circuit 11, for example.

  The gradation reference voltage generation circuit 12 generates a gradation display voltage and supplies it to the source driver 13.

  The source driver 13 supplies a data signal to each data signal line at a timing based on a control signal from the control circuit 11. The gate driver 14 supplies a scanning signal to each scanning signal line at a timing based on a control signal from the control circuit 11. The source driver 13 and the gate driver 14 are mounted or monolithically formed on the insulating substrate 1 of the display panel 10.

  The counter electrode drive circuit 15 controls the potential of the counter electrode 4 based on various control signals from the control circuit 11. In the display device 100, in order to prevent a DC voltage from being applied to the liquid crystal layer 3 of the display panel 10 and to reduce the breakdown voltage required for each driving IC of the source driver 13 and the gate driver 14. In addition, the polarity of the common voltage is reversed at regular intervals. Specifically, for example, inversion is performed every horizontal synchronization period (hereinafter referred to as “1H inversion”).

  Although details will be described later, in the display device 100, the same signal as the signal voltage applied to the counter electrode 4 is applied to the transparent conductive film 22 of the touch panel 20 during the display period and non-display period of image display. Is done. Specifically, the counter electrode drive circuit 15 controls the potential of the counter electrode 4 and supplies a counter electrode drive signal to the position detection device 24, and touches the touch panel via the touch panel drive circuit 23 b provided in the position detection device 24. The same signal as the signal voltage applied to the counter electrode 4 is applied to the 20 transparent conductive films 22.

  That is, in the display device 100 of the present embodiment, the control circuit 11 detects the position of the touch panel drive signal based on the input vertical synchronization signal VSYC, horizontal synchronization signal HSYC, and, if necessary, the clock signal CLK. Rather than being supplied directly to the device 24, the same signal as the counter electrode drive signal supplied to the counter electrode 4 through the counter electrode drive circuit 15 is supplied to the position detection device 24.

  FIG. 3B is a schematic diagram showing wiring of the display panel 10 of the present embodiment. As shown in FIG. 3B, the TFT array layer 2 in the display panel 10 includes a plurality of data signal lines SL1 to SLn (n is an arbitrary integer greater than or equal to 2) and each data signal line SL1 to SLn. A plurality of intersecting scanning signal lines GL1 to GLm (m is an arbitrary integer equal to or greater than 2) are provided, and a pixel 110 is provided at each intersection of the data signal lines SL1 to SLn and the scanning signal lines GL1 to GLm. It has been.

  FIG. 4 is an equivalent circuit diagram of each pixel 110 in the display panel. As shown in FIG. 4, each pixel 110 is provided with a switching element 16, a pixel electrode 17, and a counter electrode 4. The switching element 16 and the pixel electrode 17 are formed on the TFT array layer 2, and the counter electrode 4 is provided on the surface of the insulating substrate 6 facing the insulating substrate 1.

  As the switching element 16, for example, a TFT (thin film transistor) is used, the gate electrode of the switching element 16 is connected to the scanning signal line GLi (i is an arbitrary integer of 1 or more), and the source electrode is the data signal line SLj (j Is an arbitrary integer equal to or greater than 1, and the drain electrode is connected to the pixel electrode 17. The counter electrode 4 is connected to a common electrode line (not shown) common to all the pixels 110. Thereby, a pixel capacitor 18 is formed by the pixel electrode 17, the counter electrode 4, and the liquid crystal layer 3 between the electrodes.

  In each pixel 110, when the scanning signal line GLj is selected, the switching element 16 becomes conductive, and the signal voltage determined based on the display data signal input from the control circuit 11 to the source driver 13 The reference voltage generation circuit 12 and the source driver 13 apply the pixel capacitor 18 via the data signal line SLi. The pixel capacitor 18 ideally continues to hold the voltage at the time of shutoff while the selection period of the scanning signal line GLj ends and the switching element 16 is shut off.

  The position detection device 24 detects the position of the contact point based on currents flowing from a plurality of locations of the transparent conductive film 22, and details will be described later.

  Hereinafter, the touch panel 20 of the display device 100 of the present embodiment will be described in more detail. As shown in FIG. 2, the transparent conductive film 22 of the touch panel 20 is formed on the surface of the touch panel substrate 21 made of glass or transparent plastic, and an adhesive or the like is used on the observer side surface that is the outer surface of the display panel 10. It is mounted with a gap formed by direct adhesion or air layer. The transparent conductive film 22 is made of indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (NESA) formed by a well-known thin film forming technique such as sputtering. Pittburg Plate Glass's trade name), a transparent conductive film such as zinc oxide. Note that the material, film forming method, and film thickness of the transparent conductive film 22 are not particularly limited, and known materials and film forming methods can be used. However, in order to obtain the transparent conductive film 22 having good heat resistance and durability, it is preferable to form a film by sputtering using a target containing Mg.

  In the display device 100, no shield layer is provided between the counter electrode 4 and the transparent conductive film 22, and the distance between the counter electrode 4 and the transparent conductive film 22 is set to 2 mm or less. For this reason, the parallax is smaller than the conventional configuration in which a shield layer is provided between the counter electrode 4 and the transparent conductive film 22 or the configuration in which the space between the counter electrode 4 and the transparent conductive film 22 is increased. It has become. Note that not only the insulating substrate 6 but also the color filter layer 5, the polarizing plate 52, the phase difference plate (not shown) and the like are disposed between the counter electrode 4 and the transparent conductive film 22 as necessary. Since these thicknesses are small, the influence on parallax is small. Note that the effect of parallax can be sufficiently reduced by setting the distance between the counter electrode 4 and the transparent conductive film 22 to 2 mm or less.

  The transparent conductive film 22 may be disposed on the display panel 10 side, the touch panel substrate 21 may be disposed on the viewer side, and conversely, the touch panel substrate 21 may be disposed on the display panel 10 side. In any case, since the display panel 10 and the touch panel 20 can be manufactured separately and combined at the end, yield and production efficiency can be improved. Furthermore, when the touch panel substrate 21 is directly bonded to the display panel 10, since an interface with air is not formed between the two, reflection of external light that hinders display can be reduced. On the other hand, when the touch panel substrate 21 is mounted with a gap on the outer surface of the display panel 10, it is possible to prevent the display image from being disturbed due to the pressure applied by the formation of the contact point being directly applied to the display panel 10.

  Further, the transparent conductive film 22 may be directly formed on the outer surface of the insulating substrate 6 of the display panel 10. This configuration has an advantage that the thickness of the entire display device 100 can be reduced.

  Further, a protective layer made of an inorganic thin film such as SiO2 or SiNOx, a transparent resin coating, or a transparent resin film such as PET (Poly Ethylene Terephthalate) or TAC (Tri Acetyl cellulose) is provided on the surface of the transparent conductive film 22 on the viewer side. It may be formed. Furthermore, you may perform an antireflection process and / or antifouling process as needed.

  FIG. 5 is an explanatory diagram showing a schematic configuration of the touch panel 20, the position detection device 24, and the display panel. The display panel includes a TFT array layer 2 and a counter electrode 4 each formed on an insulating substrate. As shown in this figure, terminals 25 a to 25 d are provided at four corners of the transparent conductive film 22, respectively, and these terminals 25 a to 25 d are connected to terminals E 1 to E 1 of the position detection device 24 via lead wires 70. Each is connected to E4. The other ends of the terminals E1 to E4 are connected to current detection circuits 31a to 31d as detection circuits, respectively, and information on position detection is transmitted to the position detection circuit 24a.

  Then, the counter electrode driving signal supplied from the counter electrode driving circuit, that is, the AC voltage having the same homogenous potential as the signal supplied to the counter electrode 4 is used as a position detection signal as a touch panel driving circuit, terminals E1 to E4 and terminals It is supplied to the transparent conductive film 22 via 25a-25d. Thereby, since the potential difference between the transparent conductive film 22 and the counter electrode 4 is eliminated, the capacitance between the touch panel and the counter electrode between the transparent conductive film 22 and the counter electrode 4 can be zero in principle.

  In addition, although it is set as the structure provided with four terminals in the transparent conductive film 22 here, it is not restricted to this, If the number of terminals is at least two, the position between terminals can be calculated | required.

  When the surface of the transparent conductive film 22 or the protective layer provided on the observer side is touched with a pen or a finger, a contact point is formed on the transparent conductive film 22. When a contact point is formed on the transparent conductive film 22, the transparent conductive film 22 is capacitively coupled to a ground plane that is a ground. The capacitance is, for example, a combination of the capacitance between the protective layer and the transparent conductive film 22 and the impedance existing between the operator and the ground that is the ground.

  The electrical resistance value between the capacitively coupled contact portion and the four corner terminals of the transparent conductive film 22 is proportional to the distance between the contact portion and each terminal. Therefore, a current generally inversely proportional to the distance between the contact portion and each terminal flows through each terminal arranged at the four corners of the transparent conductive film 22. If the relative ratio of the magnitudes of these currents is detected, the position coordinates of the contact portion can be obtained.

  The position coordinate detection method will be described in more detail. The currents flowing through the terminals 25a to 25d arranged at the four corners of the transparent conductive film 22 by contact with a finger or the like are denoted by i1 to i4. Here, for the sake of simplicity, description will be made assuming that no current flows when no contact point is formed on the transparent conductive film 22, but as will be described later, when no contact point is actually formed. In addition, since a current flows through the stray capacitance, it is necessary to obtain a change (increase) in current due to the formation of the contact point in order to detect the position.

  The X coordinate and Y coordinate of the contact position with respect to the transparent conductive film 22 can be determined based on the following equations.

X = k1 + k2 · (i2 + i3) / (i1 + i2 + i3 + i4) (Formula 1)
Y = k1 + k2 · (i1 + i2) / (i1 + i2 + i3 + i4) (Formula 2)
Alternatively, the following calculation formula may be used.

X = k1 + k2 · [i2 / (i2 + i4) + i3 / (i1 + i3)] (Formula 3)
Y = k1 + k2 / [i1 / (i1 + i3) + i2 / (i2 + i4)] (Formula 4)
Here, X is the X coordinate of the contact position on the transparent conductive film 22, and Y is the Y coordinate of the contact position on the transparent conductive film 22. Further, k1 is an offset (0 when the output coordinate is the origin), and k2 is a magnification. k1 and k2 are constants that do not depend on the impedance of the operator.

  When the center of the position detection area is the origin, (Expression 1) to (Expression 4) can be expressed as (Expression 5) to (Expression 8), respectively.

X = k · (i2 + i3-i1-i4) / (i1 + i2 + i3 + i4) (Formula 5)
Y = k · (i1 + i2-i3-i4) / (i1 + i2 + i3 + i4) (Formula 6)
X = k · [(i2−i4) / (i2 + i4) − (i1−i3) / (i1 + i3)] (Formula 7)
Y = k · [(i1-i3) / (i1 + i3) + (i2-i4) / (i2 + i4)] (Formula 8)
Therefore, the contact position with respect to the transparent conductive film 22 can be obtained from the measured values of the currents i1 to i4 flowing through the four terminals 25a to 25d. In addition, when sufficient coordinate accuracy cannot be obtained only by the above calculation formula, higher-order correction calculation may be performed as necessary.

  In addition, a low-resistance conductive pattern is formed on the outer periphery of the position detection region of the transparent conductive film 22 for the purpose of adjusting the electric field distribution, and the terminals 25a to 25d formed on the transparent conductive film 22 and position detection are performed. A REIT line 70 for connecting the terminals E1 to E4 of the device 24 is formed. In addition, a shield wiring (not shown) is formed around the lead wire and the transparent conductive film 22 to cover the outer periphery thereof. Both the lead wire and the shield wiring are formed by a well-known thin film forming technique or thick film printing technique.

  In the display device 100 of the present embodiment, the counter electrode drive signal supplied from the counter electrode drive circuit, that is, the AC voltage having the same isotope potential as the signal supplied to the counter electrode 4 is also supplied to the shield wiring. The Thereby, in principle, the capacitance between the touch panel and the counter electrode between the shield wiring and the lead wire can be made zero.

  Next, the position detection device will be described with reference to FIG. The position detection device includes a position detection circuit 24a and a touch panel drive circuit, detects currents flowing from a plurality of terminals provided in the transparent conductive film, and detects changes in detected currents, specifically, currents due to formation of contact points. Based on this, position data of the contact point with respect to the transparent conductive film is generated. FIG. 6 is a block diagram illustrating a configuration example of the position detection circuit 24 a provided in the position detection device 24. As shown in this figure, the position detection circuit 24a includes current detection circuits 31a to 31d, detection filtering circuits 33a to 33d, sample hold circuits 34a to 34d, analog multiplexers 35, which are provided corresponding to the terminals E1 to E4, respectively. An A / D converter 36 and a processing device 37 are provided.

  The current detection circuits 31a to 31d detect currents flowing through the terminals E1 to E4 and output current signals to the detection filtering circuits 33a to 33d. More specifically, the current detection circuits 31a to 31d measure currents flowing between each of the four terminals E1 to E4 of the transparent conductive film 22 and the ground. Since an AC voltage for position detection is applied to the transparent conductive film 22, the current flowing through the terminals E1 to E4 due to contact with a finger or the like has an AC component.

  The current detection circuits 31a to 31d output current signals to the detection filtering circuits 33a to 33d during an arbitrary period (position detection period) in the display period and non-display period of image display. In the display device 100 according to the present embodiment, the capacitance between the touch panel and the counter electrode can be suppressed and accurate position detection can be performed in the display period and the non-display period as described above. It is possible to set the period, that is, the entire display period, and it is also possible to set the position detection period to an arbitrary period within the entire display period. In addition, in the period other than the position detection period, the output to the detection filtering circuits 33a to 33d is not performed.

  The detection filtering circuits 33a to 33d detect current signals input from the current detection circuits 31a to 31d. The detection filtering circuits 33a to 33d include, for example, a half-wave rectification circuit, a full-wave rectification circuit, or a synchronous detection circuit (with the frequency of the AC voltage generation circuit as a reference). The synchronous detection circuit has a higher frequency discrimination capability than the CR filter or the LC filter. The detection filtering circuits 33a to 33d perform filtering (band limitation) to remove various noises having frequencies different from the frequency of the AC voltage generation circuit from the frequency components included in the received noise cut current signal. .

  The signals output from the detection filtering circuits 33a to 33d are input to the sample and hold circuits 34a to 34d and held for a predetermined period. The sample hold circuits 34 a to 34 d send a signal held in synchronization with a hold signal supplied from the outside to the A / D converter 36 via the analog multiplexer 35. The analog multiplexer 35 and the A / D converter 36 are provided in common to the four sample hold circuits 34a to 34d.

  As described above, by providing the sample hold circuits 34a to 34d, the current signals of a plurality of channels (here, four channels) can be sequentially processed by using one A / D converter 36, thereby simplifying the configuration of the apparatus. And cost can be reduced. Further, by sharing the A / D converter 36, it is possible to reduce the variation between channels as compared with the case where the A / D converter 36 is provided for each channel, and the position detection accuracy can be improved.

  This sample hold operation is performed at a timing according to the hold signal supplied from the control circuit 11 to the sample hold circuits 34a to 34d. For example, the control circuit 11 generates the hold signal so that the sample hold operation is performed in synchronization with the vertical synchronization signal VSYC supplied to the display panel 10. If the conversion speed of the A / D converter 36 is sufficiently high, the sample hold circuits 34a to 34d may be omitted.

  The analog multiplexer 35 sends an output corresponding to the current signals from the four terminals E1 to E4 to the A / D converter 36. The A / D converter 36 generates a digitized current signal (digitized current data) and sends it to the processing device 37. Here, the digitized current data refers to data obtained by converting i1 to i4 in the above-described formulas 1 and 2 into DC voltage values and further digitizing them.

  Using these values, the processing device 37 obtains the coordinates X and Y of the contact point based on the above formulas 1 and 2, determines the input command by the operator who formed the contact point, and performs predetermined data processing, etc. I do. For example, the position coordinates of the contact position are detected based on the difference between the detection signal when nothing is in contact with the touch panel, that is, when the stylus is not in contact, and the detection signal when the stylus is in contact. The processing device 37 includes, for example, a car navigation device provided with the display device 100, a portable information terminal (PDA: Personal Digital Assistants, etc.), an ATM (Aautomated Teller Machine), a ticket vending machine, a game machine, a display device with various touch panels, etc. Alternatively, it is installed in various computers and executes data processing.

  The position data generated by the position detection device 24 is not limited to the above example. For example, the position detection device 24 may obtain XY coordinates using the digitized DC voltage value and output this as position data.

  Next, an image display operation and a position detection operation in the display device 100 will be described.

  FIG. 1 is a waveform diagram of a counter electrode drive signal, a touch panel drive signal, and a hold signal. In the display device 100 of this embodiment, the same signal voltage is always applied to the transparent conductive film and the counter electrode of the touch panel regardless of the display period / non-display period. A timing control signal for specifying a period during which the same signal voltage is applied to the electrodes is not necessary.

  As shown in FIG. 1, the counter electrode drive circuit 15 applies the counter electrode 4 to the counter electrode 4 based on the control from the control circuit 11 in the entire display period regardless of the display period / non-display period. The counter electrode drive signal is output so that the polarity of the applied potential is inverted every horizontal synchronization period. In the example of FIG. 1, the polarity is inverted between Va, which is a positive potential, and Vb, which is a negative potential. Here, the absolute values of Va and Vb (the absolute value of the difference between Va and Vb and the reference potential (ground potential)) may be the same or different. Further, the horizontal synchronization frequency and the vertical synchronization frequency are not particularly limited, but as an example, the horizontal synchronization frequency is 15.75 kHz (NTSC, EGA, QVGA) or 31.5 kHz (VGA, wide VGA), The vertical synchronization frequency is 60 Hz. The vertical blanking period is 1.14 ms, for example.

  In the display device 100 according to the present embodiment, the counter electrode drive signal is also output from the counter electrode drive circuit 15 to the position detection device 24 of the touch panel 20. As a result, the same potential as that applied to the counter electrode 4 is applied to the transparent conductive film 22 of the touch panel 20. That is, the waveforms applied to the counter electrode 4 and the transparent conductive film 22 of the touch panel 20 are the same waveform. As a result, the generation of parasitic capacitance between the counter electrode 4 and the transparent conductive film 22 can be suppressed.

  Accordingly, the counter electrode drive signal that is a signal applied to the counter electrode 4 and the touch panel drive signal that is a signal applied to the transparent conductive film 22 of the touch panel 20 during the entire period of the display period and the non-display period. Become the same potential, and there is no potential difference between the counter electrode 4 and the transparent conductive film 22.

  In the display device 100 according to the present embodiment, the counter electrode 4 and the transparent conductive film 22 of the touch panel 20 are at the same potential, so that the touch panel 20 has a potential difference due to the potential difference between the counter electrode 4 and the transparent conductive film 22. The induced voltage generated can be reduced to such an extent that the position detection accuracy is not lowered. In principle, the induced voltage can be reduced to zero as well as reduced. Therefore, position detection accuracy can be increased.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIG. FIG. 7 is a cross-sectional view showing a schematic configuration of a display device 100 according to another embodiment of the present invention. Configurations other than those described in the present embodiment are the same as those in the first embodiment. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are given the same reference numerals, and explanation thereof is omitted.

  Unlike the display device 100 of the first embodiment, the display device 100 of the present embodiment has a transparent conductive film 22 of a touch panel formed inside the display panel 10. Thus, the display device 100 is a display device 100 integrated with a touch panel / liquid crystal display device in which a touch panel is attached to the display panel 10.

  Specifically, the transparent conductive film 22 is formed between the color filter layer 5 and the counter electrode 4 in the insulating substrate 6 disposed on the viewer side of the insulating substrates 1 and 6 constituting the display panel 10. Has been. An overcoat layer 60 that electrically insulates each other is formed between the transparent conductive film 22 and the counter electrode 4. The material, thickness, and the like of the overcoat layer 60 are not particularly limited, and a general-purpose insulating material such as an oxide film such as silicon oxide is used.

  In the display device 100 of the present embodiment, the transparent conductive film 22 is formed close to the counter electrode 4 in the display panel 10, and the distance between the transparent conductive film 22 and the counter electrode 4 is the same as that of the first embodiment. The display device 100 is shorter. Therefore, the generation of parasitic capacitance can be more effectively canceled between the transparent conductive film 22 and the counter electrode 4.

  Note that although the case where an active matrix liquid crystal panel is used as the display panel 10 is illustrated in this embodiment, the display panel 10 used in this embodiment is not limited to this. Any display panel can be used as long as a common voltage with periodic inversion of polarity is applied to the counter electrode provided in the display panel 10. For example, instead of the liquid crystal layer (optical modulation layer) 3, an optical modulation layer made of a medium exhibiting electrophoretic properties may be used. That is, the display panel 10 may be a liquid crystal display panel or an electrophoretic display panel having an electrophoretic layer.

  In the present embodiment, the case where the potential of the counter electrode 4 is driven by line inversion (inversion every horizontal synchronization period) is mainly described. However, the present invention is not limited to this. For example, two-line inversion (2H inversion) ).

  In addition, the method of applying the same signal voltage to the transparent electrode film of the touch panel and the counter electrode of the display panel in the entire display period is not limited to the above embodiment, and in the display period, the transparent conductive film A touch panel applied to the transparent electrode film with respect to the counter electrode during a non-display period, while applying a signal voltage of a counter electrode drive signal applied to the counter electrode, for example, a signal voltage of a rectangular inversion signal There is also a method of applying a drive signal, for example, a signal voltage of a high frequency signal.

  In addition, the touch panel provided in the display device according to the present embodiment is not particularly limited as long as position detection is performed using a change in electrical characteristics due to contact with a finger or a pen.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be applied to a display device provided with a touch panel. For example, the present invention can be applied to a car navigation device, a portable information terminal (such as a PDA), an ATM, a ticket vending machine, various vending machines, and a game machine.

It is a wave form diagram of the signal regarding image display operation and position detection operation in the display of one embodiment of the present invention. It is a perspective view which shows schematic structure of the display panel with which the said display apparatus is equipped, and a touchscreen. (A) is a block diagram showing the configuration of a display panel and its driving device provided in the display device, and (b) is a schematic diagram showing wiring of the display panel. FIG. 2 is an equivalent circuit diagram of each pixel in a display panel provided in the display device. It is explanatory drawing which shows schematic structure of the touchscreen with which the said display apparatus is equipped, and a position detection apparatus. It is a block diagram which shows the structure of the position detection circuit with which the display apparatus concerning one Embodiment of this invention is equipped. It is sectional drawing which shows schematic structure of the display apparatus of other embodiment of this invention. It is explanatory drawing which showed the relationship between the electric potential of a counter electrode in the conventional display apparatus with a touch panel, and the induced voltage which arises in the transparent conductive film of a touch panel by the polarity reversal of the electric potential of this counter electrode.

Explanation of symbols

1 Insulating substrate 2 TFT array layer 3 Liquid crystal layer (optical modulation layer)
4 Counter electrode 5 Color filter layer 6 Insulating substrate 10 Display panel 11 Control circuit 12 Gradation reference voltage generation circuit 13 Source driver 14 Gate driver 15 Counter electrode drive circuit 16 Switching element 17 Pixel electrode 18 Pixel capacity 20 Touch panel 21 Touch panel substrate 22 Transparent Conductive film 24 Position detection device 24a Position detection circuit (position detection means)
23b Touch panel drive circuit (touch panel voltage application means)
25a to 25d Terminals 31a to 31d Current detection circuit 33a to 33d Detection filtering circuit 34a to 34d Sample hold circuit 35 Analog multiplexer 36 A / D converter 37 Processing device 40 Capacitor between touch panel and counter electrode 51 Polarizing plate 52 Polarizing plate 60 Overcoat Layer 70 Lead wire 100 Display device 110 Pixel E1-E4 terminal

Claims (9)

An optical modulation layer sandwiched between opposing insulating substrates; a plurality of pixel electrodes formed on one of the opposing insulating substrates; and the plurality of pixel electrodes on the other insulating substrate of the opposing insulating substrate A display panel that performs display by changing the optical characteristics of the optical modulation layer by applying a voltage between each of the pixel electrodes and the counter electrode,
In the driving device of the display device including the touch panel disposed on the viewer side of the optical modulation layer and having a transparent conductive film,
Touch panel voltage application means for applying the same signal voltage as the common voltage that is applied to the counter electrode to the transparent conductive film of the touch panel during the display period and the non-display period of the display panel. A driving device for a display device.   The display device driving device according to claim 1, wherein the signal voltage applied to the transparent electrode film and the signal voltage applied to the counter electrode have the same waveform and phase.   The display device drive device according to claim 1, wherein the polarity of the potential of the signal voltage applied to the counter electrode is inverted every horizontal synchronization period of the display panel. The touch panel includes a plurality of terminals electrically connected to the transparent conductive film and the touch panel voltage applying unit at different locations on the surface of the transparent conductive film, respectively.
A position detecting means for detecting a position of the contact point based on a detection result of a current flowing through each terminal when the contact point with respect to the transparent conductive film is formed by touching the transparent conductive film of the touch panel; The display device driving apparatus according to claim 1, wherein the position detection unit detects the position of the contact point during the display period and the non-display period.   The position detecting means is configured to detect a difference between a current flowing through each terminal when a contact point with respect to the transparent conductive film is not formed and a current flowing through the terminal when a contact point with respect to the transparent conductive film is formed. The display device driving apparatus according to claim 4, wherein the position of the contact point is detected based on the position. A lead wire connecting the terminal and the position detecting means;
And a shield wiring covering the outer periphery of the lead wiring,
The display device driving device according to claim 4, wherein the same signal voltage as that applied to the counter electrode is applied to the shield wiring.   The display device driving device according to claim 1, wherein the transparent conductive film of the touch panel is formed between an insulating substrate having a counter electrode among the opposing insulating substrates and the counter electrode. .   A display device comprising the drive device for the display device according to claim 1. An optical modulation layer sandwiched between opposing insulating substrates; a plurality of pixel electrodes formed on one of the opposing insulating substrates; and the plurality of pixel electrodes on the other insulating substrate of the opposing insulating substrate A display panel that performs display by changing the optical characteristics of the optical modulation layer by applying a voltage between each of the pixel electrodes and the counter electrode,
In a driving method of a display device including a touch panel disposed on an observer side of the optical modulation layer and having a transparent conductive film,
A display device driving method, wherein a signal voltage that is the same as a common voltage that is a signal voltage applied to the counter electrode is applied to the transparent conductive film of the touch panel.

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