JP2006301506A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent sounding generated in a display device equipped with a panel, having a common electrode driven at a predetermined frequency, such as a liquid crystal panel, and a flat plate member disposed separated by at a certain space from the panel, as a touch panel. <P>SOLUTION: A display device is equipped with a panel having a common electrode layer to which a voltage which changes at a predetermined frequency is applied and a flat plate member disposed at a certain space from the panel, to which a sounding improvement signal, of which the voltage changes in synchronization with the change of the voltage applied to the common electrode layer, is applied. The device comprises the electrode layer, a sounding improvement signal generating part, a switching means 90, a first signal line, and a second signal line. The switch means 90 comprises a first transistor connected to the positive supply and a second transistor connected to the negative supply, when the electrical connection of the sounding improvement signal generating part and the electrode layer is set in a conduction state. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device, and more specifically, is suitable for a liquid crystal display device in which, for example, a touch panel is opposed to a liquid crystal panel with a predetermined gap.

  In a liquid crystal display device that performs line inversion driving, for example, in the case of a display device in which a touch panel is installed on the display surface side of a liquid crystal panel, there is a problem that a sound that causes discomfort to humans occurs. The present inventors paid attention to this problem, and as a result of intensive studies, the cause was considered as follows. In other words, the surface of the liquid crystal panel (the surface of the polarizing plate) and the back surface of the touch panel facing the liquid crystal panel are charged for some reason, and this is caused by the vibration caused by the electric field generated by the electrodes of the liquid crystal panel. It is done.

The principle will be described in detail below with reference to the drawings. For example, paying attention to an arbitrary point a on the back surface of the touch panel 1 as shown in FIG. 14 and a point b on the surface of the liquid crystal panel 2 facing the point a, the charge charged at the point a of the touch panel 1 is qa, If the electric charge charged at the point b of the panel 2 is qb, the forces Fa and Fb acting on these electric charges qa and qb, respectively, can be obtained from the following equations. (In the description, as the force component (and the electric field component), only the component in the stacking direction of the liquid crystal panel and the touch panel is considered.)
Fa = qa × Ea
Fb = qb × Eb
Ea is the electric field strength at point a, and Eb is the electric field strength at point b.

Here, the electric field intensity Ea at point a is obtained by the following equation. (Strictly speaking, there are electric field components due to signals applied to the upper and lower electrodes of the touch panel and the pixel electrodes or segment electrodes of the liquid crystal panel, but these electric field strengths are at a constant frequency that causes noise. (In most cases, there are no fluctuations, so we have omitted it here.)
Ea = Ecoma (t) + Eqa + Eqb
Note that Ecoma (t) is due to driving of the liquid crystal panel (counter electrode) among electric field components at point a (function of time), and Eqa is due to electric charge qa among electric field components at point a. , Eqb is due to the electric charge qb among the electric field components at the point b.

  Here, Ecoma (t) is an electric field generated by a counter electrode signal (hereinafter referred to as a COM signal) applied to the counter electrode. Since the potential of the COM signal varies with the driving frequency, the value of Ea is constant. Instead, it fluctuates with the driving frequency component, and therefore Fa also fluctuates with the driving frequency. The same applies to the force Fb acting on the point b of the panel.

Further, considering the entire back surface of the touch panel, if the total charge on the back surface of the touch panel is Qtp, it is considered that Qtp, that is, the force Ftp acting on the entire surface of the back surface of the touch panel also varies. Similarly, when the total charge on the entire panel surface is Qlc, the force Flc acting on the entire panel surface is also considered to vary.
That is, if Ea and Eb are constant, the force acting on Qtp and Qlc is constant, so that vibration of the panel and touch panel does not occur. However, since Ea and Eb vary with the driving frequency as described above, the panel surface or touch panel It is thought that the back surface vibrates at the same frequency as the drive frequency, shaking the space between the panel and the touch panel, and generating noise.

  The following methods can be considered as a method for reducing and reducing such noise.

  First, the liquid crystal panel drive frequency that causes sound generation is increased or decreased so that it is out of the human audible frequency range or is difficult to hear. However, increasing the drive frequency leads to an increase in power consumption, and in the case of a liquid crystal display device, increasing the drive frequency shortens the charging time for the liquid crystal. Problems such as occurrence occur. Further, when the drive frequency is lowered, there is a problem of occurrence of flicker.

  Further, a method for preventing the fluctuation component itself of the Coulomb force on the panel surface from being generated by using a DC drive as the drive signal is also conceivable. However, in order to set the drive signal to DC drive, the output voltage of the source is increased by that amount, so it is necessary to use a high breakdown voltage product for the source driver, resulting in a problem of increased power consumption.

  Furthermore, a method of preventing sound generation by eliminating the air layer between the liquid crystal panel and the touch panel by sticking the surface of the touch panel to the surface of the liquid crystal panel with glue or the like is also considered. It is done. However, when a touch panel or the like is directly attached to the panel surface, there are display quality problems due to peeling on the adhesive surface and a problem that the attaching operation is difficult.

  In addition, a method of suppressing the charging of the panel surface and the back surface of the touch panel as much as possible so that vibration due to Coulomb force does not occur is conceivable. However, in order to prevent electrification, it is necessary to carry out the static elimination work while managing the charge amount with a static elimination blower, etc., and the equipment for managing the decrease in productivity due to the time spent on the static elimination work and the charge amount There is an investment problem.

  In addition, a method may be considered in which the distance between the panel and the touch panel facing it is increased and the Coulomb force is reduced to suppress the occurrence of vibration, or even if it vibrates, the sound due to the vibration of air cannot be heard. However, in order to increase the distance in this way, there is a problem that the dimension in the thickness direction of the display device must be increased.

  In addition, the thing of patent document 1 place is well-known as what solves the influence on the position detection accuracy by the noise around a touch panel (resistive film tablet apparatus). Patent Document 1 discloses that a transparent electrode layer is formed on the outer surface of a touch panel, and the transparent electrode layer is grounded. In addition, in the thing of this patent document 1, since electrification is suppressed in the back surface (surface which formed the transparent electrode layer) of a touch panel, it is effective with respect to the sound by the vibration of the back surface of this touch panel. You might also say that. However, when another member is further added to the back surface of the transparent electrode, it is considered that the above-described sounding occurs due to charging of the member.

  As described in Patent Document 2, in order to prevent vibration of the optical sheet disposed in the gap between the liquid crystal panel and the backlight, the gap between the liquid crystal panel and the backlight or the back side of the backlight is transparent. An electrode sheet is arranged and a voltage that changes the driving frequency of the liquid crystal panel in synchronization with the opposite phase is applied to the transparent electrode sheet. In the one described in this Patent Document 2, the periodic fluctuation of the electric field in the optical sheet generated based on the periodic potential change of the common electrode layer of the liquid crystal panel due to the voltage supplied to the transparent electrode sheet. Therefore, it is considered that a certain effect can be expected in preventing the vibration of the optical sheet. However, such a transparent sheet is disposed on the back side of the liquid crystal panel, and it is considered that the effect of preventing the sounding phenomenon in the touch panel located on the display surface side of the liquid crystal panel as described above is poor. . Further, when this transparent electrode sheet is disposed in the gap between the backlight and the liquid crystal panel, there is a problem that the light use efficiency is lowered due to the presence of an air layer between the transparent electrode sheet and the backlight.

  Further, in view of the problem of the sounding phenomenon in a liquid crystal display device having a touch panel and a liquid crystal panel, the present inventors generate a signal based on a drive signal for a common electrode layer of the liquid crystal panel as in Japanese Patent Application No. 2003-400385. A means for applying a sound improvement signal that generates an electric field that changes the period of the periodic electric field to the electrode layer of the touch panel is proposed.

  The touch panel of this liquid crystal display device has a pair of electrode layers facing each other with a predetermined gap, and a position touched by the user by detecting an electrical change that occurs between the pair of electrode layers when the user touches the touch panel. And a touch panel controller for detecting. The sound improvement signal is applied to at least one of the pair of electrode layers of the touch panel. Here, the liquid crystal display device includes a sound generation improvement signal generation unit that generates the sound generation improvement signal, and a switch that switches electrical connection between the sound improvement signal generation unit and the electrode layer between a conductive state and a disconnected state. Means, a first signal line for electrically connecting the switch means and the sound generation improvement signal generator, a second signal line for electrically connecting the switch means and the electrode layer, and the switch And a third signal line for electrically connecting the means and the touch panel controller. Then, the switch means makes the first signal line and the second signal line conductive, and disconnects the second signal line and the third signal line, so that the sound generation improvement signal generation unit The generated sound improvement signal is supplied to the touch panel, and the first signal line and the second signal line are disconnected, and the second signal line and the third signal line are conductive. Thus, the touch panel controller can detect the position touched by the user. Further, the switching between the conductive state and the disconnected state by the switch means is performed based on the switching signal generated by the switching signal generation unit.

  Here, as the switch means, as shown in FIG. 15, the first signal line 101 (sound improvement signal generation circuit 81) and the second signal line 102 (touch panel 1) are brought into a conductive state and a disconnected state. In order to switch, a P-channel MOS transistor 92a (hereinafter referred to as “PMOS”) and an N-channel MOS transistor 92b (hereinafter referred to as “NMOS”) that are electrically connected in parallel to the first signal line 101 and the second signal line 102, respectively. ")") And a means to adopt. That is, the source electrodes of the PMOS 92a and the NMOS 92b are connected to the first signal line 101, the drain electrodes of the PMOS 92a and the NMOS 92b are connected to the second signal line 102, and one of the gate electrodes of the PMOS 92a and the NMOS 92b is connected to the first signal line 101. The switching signal generator 94 is connected and the other gate electrode is connected to the switching signal generator 94 via a NOT gate.

However, when the PMOS 92a and the NMOS 92b as described above are employed, as shown in FIG. 15, when the PMOS 92a is a positive power source and the NMOS 92b is grounded, the sound generation improvement signal generator 81 and the electrode layer of the touch panel 1 are used. The positive component of the sound improvement signal is supplied to the electrode layer of the touch panel 1 via the second signal line 102 when the electrical connection to the touch panel is made conductive, but the negative component of the sound improvement signal is the touch panel. It is not supplied to one electrode layer. That is, the signal from which the negative component has been deleted in the sound improvement signal is transmitted to the electrode layer of the touch panel 1, and the effect of improving sound is not sufficiently obtained.
Actual Kaihei 7-20623 JP 2004-184885 A

  Accordingly, the present invention provides a sound generated in a display device including a panel having a common electrode that is driven at a predetermined frequency, such as a liquid crystal panel, and a flat plate member that is disposed with a certain gap from the panel, such as a touch panel. It is an object to more reliably prevent the problem.

  The present invention has been made to solve the above problems, and a display device according to the present invention includes a panel having a common electrode layer to which a voltage changing at a predetermined frequency is applied, and a predetermined gap with the panel. A display device comprising a flat plate member disposed, wherein a sound improvement signal whose voltage changes in synchronization with a change in voltage applied to the common electrode layer is applied, and the flat plate member and the panel An electrode layer arranged to be substantially parallel to the electrode layer, a sound generation improvement signal generation unit that generates the sound improvement signal applied to the electrode layer, and an electrical connection between the sound improvement signal generation unit and the electrode layer Switch means for switching the electrical connection between a conductive state and a disconnected state, a first signal line for electrically connecting the switch means and the sound improvement signal generating unit, and the switch means and the electrode layer are electrically connected. A second signal line that is electrically connected, and the switch means outputs a positive component of the sound improvement signal when the electrical connection between the sound improvement signal generator and the electrode layer is in a conductive state. A first transistor connected to a positive power supply to supply to the second signal line, and a second transistor connected to the negative power supply to supply a negative component of the sound improvement signal to the second signal line. It is characterized by.

  The display device according to the present invention is a display device including a panel having a common electrode layer to which a voltage changing at a predetermined frequency is applied, and a flat plate member disposed with a predetermined gap from the panel. A sound improvement signal that changes in voltage is applied to the common electrode layer to generate an electric field that changes a period of change in electric field generated by applying a voltage that changes at a predetermined frequency, and the flat plate An electrode layer disposed so as to be substantially parallel to the panel-like member and the panel, a sound generation improvement signal generation unit that generates the sound improvement signal applied to the electrode layer, the sound improvement signal generation unit, and the Switch means for switching electrical connection with the electrode layer between a conductive state and a disconnected state, a first signal line for electrically connecting the switch means and the sound improvement signal generating unit, and the switch And a second signal line for electrically connecting the electrode layer and the switch means when the electrical connection between the sound improvement signal generating unit and the electrode layer is made conductive. A first transistor connected to a positive power supply to supply a positive component of the sound improvement signal to the second signal line, and a negative power supply to supply a negative component of the sound improvement signal to the second signal line. And a second transistor to be connected.

In the display device according to the present invention having the above-described configuration, the electric field generated based on the common electrode layer of the panel can be canceled by the electric field generated by the electrode layer to which the sound improvement signal is applied. For this reason, for example, even when the surfaces facing the flat plate member and the panel are charged, the Coulomb force of the charged flat plate member and the surface of the panel can be suppressed. The vibration of the member can be suppressed, and the phenomenon of sounding can be avoided.
Particularly, since the switch means includes the first transistor connected to the positive power source and the second transistor connected to the negative power source as described above, the sound generation improvement signal generating unit and the electrode layer When the electrical connection is in the conductive state, the positive and negative components of the sound improvement signal can be supplied to the electrode layer, so that the effect of sound improvement is more reliably exhibited.

  In addition, the display apparatus according to the present invention can be suitably used for a flat plate member that is disposed on the display surface side of the panel with a predetermined gap from the panel. That is, when the above-described sounding is generated on the display surface side of the panel, it is more prone to give the user unpleasant feeling than when the sounding is generated on the back surface side.

  In particular, a first electrode layer, and a touch panel including a second electrode layer disposed to face the first electrode layer on the display surface side of the panel with respect to the first electrode layer, In the display device provided, it is preferable to adopt a configuration in which the electrode layer is at least one of the first electrode layer and the second electrode layer.

  Thus, by using the conventional touch panel as it is by using it as an electrode layer for applying a sound improvement signal to the first electrode layer or the second electrode layer of the conventional touch panel, the first electrode layer Alternatively, the display device according to the present invention can be obtained only by changing the electrical control of the second electrode layer.

  In addition, when the configuration including the touch panel as described above is adopted, an electrical change generated between the first electrode layer and the second electrode layer is detected by touching the touch panel by the user. And a touch panel controller for detecting a position touched by the user, and a third signal line for electrically connecting the touch panel controller and the switch means, wherein the switch means is connected to the touch panel controller and the sound. A touch panel controller switch unit that switches an electrical connection with an electrode layer to which an improvement signal is applied between a conductive state and a disconnected state, and the switch unit is configured to be connected to the first electrode layer by touching the touch panel by the user; When an electrical change occurring between the second electrode layer is detected, the first transistor and the second transistor are detected. A transistor disconnects the electrical connection between the first signal line and the second signal line, and the touch panel controller switch unit electrically connects the second signal line and the third signal line. Is preferably provided so as to be in a conductive state.

  As a result, when the user touches the touch panel, the electrode layer is disconnected from the audible noise improvement signal generation unit and connected to the touch panel controller by the switch means, and the touch panel controller detects the position touched by the user. be able to.

  Further, when the configuration including the touch panel controller as described above is adopted, a switching signal generation unit that generates a switching signal transmitted from the switch means to the first transistor, the second transistor, and the touch panel controller switch unit. And the switching signal generation unit is connected to the first electrode layer and / or the second electrode layer, and the first electrode layer and the first electrode generated when the user touches the touch panel It is preferable that the switching signal is generated based on an electrical change occurring between the two electrode layers.

  Accordingly, when the user touches the touch panel, the switching signal generation unit generates a switching signal based on an electrical change that occurs between the first electrode layer and the second electrode layer of the touch panel. When the signal is transmitted to the first transistor and the second transistor of the switch means and the touch panel controller switch unit, the electrode layer of the touch panel is disconnected from the sound improvement signal generation unit and is in a conductive state with the touch panel controller. Thus, the touch panel controller can detect the position touched by the user.

  Further, when the configuration including the touch panel controller as described above is employed, the electrical change that occurs between the first electrode layer and the second electrode layer when the switch means touches the touch panel by the user. Is not detected for a predetermined time, the first transistor and the second transistor make the electrical connection between the first signal line and the second signal line conductive, and the touch panel controller switch unit However, it is preferable that the electrical connection between the second signal line and the third signal line is cut off.

  Thereby, the user does not touch the touch panel, that is, in the non-use state of the touch panel, the electrode layer is in a conductive state with the sound improvement signal generation unit and disconnected from the touch panel controller by the switch means, A sound improvement signal from the sound improvement signal generation unit is supplied to the electrode layer, and sound generation can be prevented.

  Thus, when the structure which makes an electrode layer and a sound improvement signal generation part a conduction | electrical_connection state in the non-use state of a touch panel is employ | adopted, the said switch means is a said 1st transistor, a 2nd transistor, and a touch panel controller. A switching signal generating unit that generates a switching signal to be transmitted to the switch unit, and the switching signal generating unit is configured such that the first transistor and the second transistor are connected to the first signal line every predetermined time. So that the electrical connection between the second signal line and the second signal line is made conductive, and the touch panel controller switch unit generates a switching signal for making the electrical connection between the second signal line and the third signal line conductive. And is connected to the first electrode layer and / or the second electrode layer, and is generated when the user touches the touch panel. The first transistor and the second transistor are connected to the first signal line and the second signal line based on an electrical change that occurs between the first electrode layer and the second electrode layer. The touch panel controller switch unit is provided so as to generate a switching signal that makes the electrical connection between the second signal line and the third signal line conductive. preferable.

Thereby, when the user touches the touch panel, the switching signal generation unit is connected to the sound improvement signal generation unit based on an electrical change that occurs between the first electrode layer and the second electrode layer of the touch panel. A switching signal for generating a disconnection state with the electrode layer and a conduction state between the electrode layer and the touch panel controller is generated, and the switching signal is transmitted to the first transistor, the second transistor, and the touch panel controller switch unit of the switch means. Thus, the electrode layer of the touch panel is in a disconnected state with the sound improvement signal generation unit and in a conductive state with the touch panel controller, and the touch panel controller can detect the position touched by the user.
When a predetermined time elapses, the switching signal generator makes the electrical connection between the first signal line and the second signal line conductive, and the electrical connection between the second signal line and the third signal line. Since the switching signal for making the electrical connection in the conductive state is generated, it is in a conductive state with the sound improvement signal generation unit and is disconnected from the touch panel controller, and the sound improvement signal from the sound improvement signal generation unit is It can be supplied to the electrode layer to prevent noise.

Embodiments of a liquid crystal display device according to embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of the liquid crystal display device of this embodiment. FIG. 2 is a schematic perspective view for schematically explaining the liquid crystal display device of the embodiment. FIG. 3 is a schematic explanatory view for explaining the relationship between the voltage applied to each electrode layer and the electric field in the flat plate member in the liquid crystal display device of the embodiment, and (a) is a counter electrode layer of the liquid crystal panel. Relationship between voltage (vertical axis) applied to (common electrode layer) and time (horizontal axis), (b) Relationship between voltage (vertical axis) applied to the back side electrode layer of the touch panel and time (horizontal axis) , (C) shows the relationship between the electric field (vertical axis) and time (horizontal axis) in the flat plate member. FIG. 4 is a schematic block diagram of the liquid crystal display device of the embodiment, and FIG. 5 is a schematic block diagram for explaining details of the switching control unit in the liquid crystal display device of the embodiment. These are the schematic block diagrams for demonstrating the detail of the sound improvement signal switch part in the liquid crystal display device of the Example. FIG. 7 is a schematic block diagram for explaining details of a switching signal generation unit in the liquid crystal display device of the embodiment. FIG. 8 is a schematic block diagram of an analog switch used in the liquid crystal display device of the embodiment, and FIG. 9 is a simplified diagram of the entire circuit when the analog switch is used. FIG. 10 is a block diagram of switch means of the liquid crystal display device of the embodiment. FIG. 11 is a schematic cross-sectional view of the liquid crystal display device of this embodiment. FIG. 12 is a schematic perspective view for schematically explaining a liquid crystal display device according to another embodiment of the present invention. FIG. 13 is a schematic explanatory view for explaining the relationship between the voltage applied to each electrode layer and the electric field in the flat plate member in the liquid crystal display device of the embodiment, and (a) is a counter electrode layer of the liquid crystal panel. Relationship between voltage (vertical axis) applied to (common electrode layer) and time (horizontal axis), (b) Relationship between voltage (vertical axis) applied to the back side electrode layer of the touch panel and time (horizontal axis) , (C) shows the relationship between the electric field (vertical axis) and time (horizontal axis) in the flat plate member.

  In the liquid crystal display device of this embodiment, the touch panel 1 is arranged with a predetermined gap on the surface (surface on the display surface side) of the liquid crystal panel 2.

  In the present embodiment, the liquid crystal panel 2 is the same as the conventionally known one. That is, as shown in FIG. 1, the liquid crystal panel 2 includes a first transparent substrate 26 and a second transparent substrate 22 disposed closer to the display surface than the first transparent substrate 26. A liquid crystal 24 is sealed between the pair of transparent substrates 22 and 26. The first transparent substrate 26 may be hereinafter referred to as a “back side substrate”, and the second transparent substrate 22 may be referred to as a “front side substrate”.

  Electrode layers 23 and 25 (a pixel electrode layer and a counter electrode layer (common electrode layer)) are laminated on the front side substrate 22 and the back side substrate 26, respectively. The liquid crystal panel 2 includes polarizing plates 21 and 27 bonded to the surface of the front substrate 22 (surface on the display surface side) and the back surface of the back substrate 22 (surface opposite to the display surface), respectively. It has. A common electrode signal whose voltage changes at a predetermined frequency is applied to the counter electrode layer 23. Further, the display device of this embodiment includes a common electrode signal generation circuit 81 for applying a common electrode signal to the counter electrode layer 23. (See Figure 4)

  In the present embodiment, the touch panel 1 has the same structure as a conventionally known touch panel. That is, as shown in FIG. 1, the touch panel 1 includes a first sheet material 14, a first electrode layer 13 formed by being laminated on the surface of the first sheet material 14, and the first electrode layer. 13 includes a second electrode layer 12 disposed so as to be opposed to 13 with a predetermined gap, and a second sheet material 11 formed by laminating the second electrode layer 12 on the back surface. The first sheet material 14 is a “back side sheet material”, the first electrode layer 13 is a “back side electrode layer”, the second electrode layer 12 is a “front side electrode layer”, and the first The second sheet material 11 may be referred to as a “surface side substrate” hereinafter.

  At least the surface side sheet material 11 of the pair of sheet materials 11 and 14 is composed of a flexible member, and when the user touches the touch panel 1, the surface side sheet material 11 bends to the back side, A pair of electrode layers 12 and 13 are provided in contact with each other at a location touched by the user. In addition, the touch panel 1 includes a transparent plate material 15 disposed on the back surface of the back surface side sheet material 14. That is, in this embodiment, the polarizing plate 21 on the surface side of the liquid crystal panel 2 and the transparent plate material 15 of the touch panel 1 are arranged so as to face each other with a predetermined gap.

  The display device of this embodiment is provided so that a voltage (sounding improvement signal) that changes in synchronization with the change of the voltage of the common electrode signal can be applied to the back surface side electrode layer 13 of the touch panel 1. Here, a sound improvement signal is applied to the back electrode layer 13 by the common electrode signal generation circuit 81 via the switch means 90, and this sound improvement signal is a change in the voltage of the common electrode signal. And the same voltage level as the voltage of the common electrode signal (see FIG. 3). In the present invention, the common electrode signal generation circuit 81 constitutes a sound improvement signal generation unit, but a sound improvement signal generation circuit may be provided separately. Further, the above sound generation improvement signal can be applied to the front surface side electrode layer 12, and furthermore, a desired voltage can be applied to both the front surface side electrode layer 12 and the back surface side electrode layer 13. Is within the intended range.

  In addition, the display device according to the present embodiment detects an electrical change that occurs between the pair of electrode layers 12 and 13 of the touch panel 1 when the user touches the touch panel 1 as described above, and the user touches the touch panel 1. A touch panel controller 82 for detecting the position is provided (see FIG. 4). The touch panel controller 82 is electrically connected to the pair of electrode layers 12 and 13 of the touch panel 1 via the switch means 90.

  The switch means 90 switches the electrical connection between the common electrode signal generation circuit 81 and the back side electrode layer 13 of the touch panel 1 between a conductive state and a disconnected state, and at the same time, the touch panel controller 82 and the back side electrode layer 13 of the touch panel 1. The switching control unit 91 that switches the electrical connection between the switching state to the conductive state and the disconnected state, and the switching signal generation unit 94 that generates a switching signal to be supplied to the switching control unit 91 are provided.

  The common electrode signal generation circuit 81 is connected to the switching control unit 91 of the switch means 90 by the first signal line 101, and the back-side electrode layer 13 of the touch panel 1 switches the switch means 90. The touch panel controller 82 is connected by the control unit 91 and the second signal line 102, the touch panel controller 82 is connected by the switching control unit 91 of the switch means 90 and the third signal line 103, and the switching control unit 91 is connected with the switching signal. By the switching signal from the generation unit 91, the second signal line 102 is in a conductive state with the first signal line 101 and disconnected from the third signal line 103, or the second signal line 102 is switched to the first signal line 102. The two signal lines 101 are switched between two states that are disconnected from the first signal line 101 and in a conductive state with the third signal line 103.

  In addition, as shown in FIG. 5, the switching control unit 91 switches the electrical connection between the common electrode signal generation circuit 81 and the back-side electrode layer 13 of the touch panel 1 between a conductive state and a disconnected state. Unit 92 and a touch panel controller switch unit 93 that switches the electrical connection between the touch panel controller 82 and the back electrode layer 13 of the touch panel 1 between a conductive state and a disconnected state.

  As shown in FIG. 5, the sound generation improvement signal switch unit 92 is configured to switch the first signal line 101 and the second signal line 102 in order to switch the first signal line 101 and the second signal line 102 between a conductive state and a disconnected state. P-channel MOS transistor (hereinafter referred to as “PMOS”) 92 a and N-channel MOS transistor (hereinafter referred to as “NMOS”) 92 b electrically connected in parallel to the respective signal lines 102. Here, the source electrodes of the PMOS 92 a and the NMOS 92 b are connected to the first signal line 101, and the drain electrodes of the PMOS 92 a and the NMOS 92 b are connected to the second signal line 102. Further, the gate electrode of the NMOS 92b is connected to the switching signal generation unit 94, and the gate electrode of the PMOS 92a is connected to the switching signal generation unit 94 via a NOT gate (see FIG. 6). Both the PMOS 92a and the NMOS 92b are in a conductive state, and both are provided in a disconnected state.

  Further, when the PMOS 92a of the sound improvement signal switching unit 92 is connected to a positive power source and the NMOS 92b is connected to a negative power source, and the electrical connection between the common electrode signal generating unit 81 and the back side electrode layer 13 is made conductive. In addition, a positive component of the common electrode signal is supplied to the back side electrode layer 13 through the PMOS 92a, and a negative component of the common electrode signal is supplied to the back side electrode layer 13 through the NMOS 92b (FIG. 5 and FIG. 6).

  The touch panel controller switch unit 93 also includes a PMOS (not shown) and an NMOS (not shown) electrically connected in parallel to the third signal line 103 and the second signal line 102, respectively. The PMOS and NMOS of the touch panel controller switch unit 93 have substantially the same configuration as that of the sound improvement signal switch unit 92, but the PMOS gate electrode is connected to the switching signal generation unit 94 via a NOT gate, and the NMOS. The gate electrode is connected to the switching signal generator.

  Furthermore, the switching signal generation unit 94 of the switch means 90 is connected to the surface side electrode layer 12 of the touch panel 1, and an electrical change that occurs in the surface side electrode layer 12 when the user touches the touch panel 1. When detected, a switching signal (such that the electrical connection between the common electrode signal generation circuit 81 and the back-side electrode layer 13 is cut off and the electrical connection between the touch panel controller 82 and the back-side electrode layer 13 is turned on ( In the following description, the TPC on signal may be generated, and the TPC on signal may be supplied to the switching control unit 91.

  The switching signal generation unit 94 is connected to the surface-side electrode layer 12 via the switching control unit 91, and the TPC on signal generated when the user touches the touch panel 1 as described above. Is supplied to the switching control unit 91, the switching control unit 91 disconnects the electrical connection between the switching signal generation unit 94 and the surface side electrode layer 12, and the touch panel controller 82 and the surface side electrode layer 12 are disconnected. It is provided so as to make the electrical connection conductive.

  Further, the switching signal generation unit 94 and the common electrode signal generation circuit 81 and the back-side electrode when the electrical change that occurs between the electrode layers 12 and 13 of the touch panel 1 due to the user touching the touch panel 1 is not detected for a predetermined time. A switching signal (hereinafter sometimes referred to as a “COM ON signal”) is generated so that the electrical connection with the layer 13 is in a conductive state and the electrical connection between the touch panel controller 82 and the back-side electrode layer 13 is in a disconnected state. The COM on signal is provided to the switching control unit 91.

  Further, when the switching signal generation unit 94 supplies the COM ON signal to the switching control unit 91 as described above, the switching control unit 91 establishes an electrical connection between the switching signal generation unit 94 and the surface side electrode layer 12. The electrical connection between the touch panel controller 82 and the surface side electrode layer 12 is provided in a disconnected state.

  Here, as shown in FIG. 7, the switching signal generation unit 94 is connected to a trigger signal generation circuit 95 that periodically generates a trigger signal. When the trigger signal is received, a COM ON signal is transmitted as a switching signal. In addition, when there is no trigger signal and a signal (position detection signal) is received from the surface side electrode layer 12 of the touch panel 1, a TPC on signal is transmitted.

  The switching control unit 91 can be configured by two analog switches, for example, and the configuration will be described more specifically with reference to FIGS. 8 to 10. When an analog switch as shown in FIG. 8 is used, X-COM, Y-COM, Z-COM of one analog switch, and Y-COM of another analog switch are respectively connected to the electrode layer 12 of the touch panel 1. , 13. Also, one analog switch 1X, 1Y, 1Z and another analog switch 1Y are connected to the touch panel controller 82, respectively. Further, 0X and 0Z of one analog switch are connected to the common electrode signal generation circuit 81, respectively. In addition, 0Y of one analog switch and 0Y of another analog switch are connected to the input side of the switching signal generation unit 94, respectively. In addition, analog switches A, B, and C are connected to the output side of the switching signal generator 94.

  When the switching signal from the switching signal generation circuit 94 is LOW, X-COM and 0X, Y-COM and 0Y, and Z-COM and 0Z are in a conductive state, while the switching signal is generated. When the switching signal from the circuit 94 is HIGH, X-COM and 1X, Y-COM and 1Y, and Z-COM and 1Z become conductive.

  A simplified circuit diagram of the above configuration is shown in FIG. 9, and more specifically, a configuration as shown in FIG. 10 is obtained. In the example shown in FIG. 10, the positive power source connected to the analog switch is 5V, and the negative power source is −4V. In FIG. 10, what is described as TC4053BP is an analog switch, and what is described as TC74HC02P is a switching signal generation unit 94.

  The liquid crystal display device according to the present embodiment having the above-described configuration can be configured by the same members as those of the conventional liquid crystal display device only by changing the electrical control of the electrode layer 13 of the touch panel 1.

In the liquid crystal display device of this embodiment, the electric field generated based on the voltage of the common electrode signal applied to the counter electrode layer 23 of the liquid crystal panel 2 is periodic, but the change in the voltage of the common electrode signal By applying a voltage that changes in synchronization with the frequency to the back-side electrode layer 13 of the touch panel 1, the electric field due to the voltage of the common electrode signal can be canceled. For this reason, for example, the surface of the liquid crystal panel 2 or the touch panel 1 Since the Coulomb force acting on the charged electric charge can be suppressed even when the back surface of the liquid crystal is charged, the vibration of the liquid crystal panel 2 and the touch panel 1 can be suppressed, and the phenomenon of sounding can be avoided. Is possible.
In particular, the liquid crystal display device according to the present embodiment can supply not only the positive component of the common electrode signal but also the negative component to the electrode layer of the touch panel, so that it is possible to avoid the sounding phenomenon more accurately. .

The theory of avoiding this sounding phenomenon will be specifically described below with reference to FIG.
First, paying attention to an arbitrary point c on the back surface (of the transparent plate 15) of the touch panel 1 and a point d on the surface (of the polarizing plate 21) of the liquid crystal panel 2 opposite thereto, the charge charged at the point c is represented by qc, When the charge charged at the point d is qd, the forces Fc and Fd acting on qc and qd can be obtained by the following equations. (In the description, as the force component (and the electric field component), only the component in the stacking direction of the liquid crystal panel 2 and the touch panel 1 is considered.)
Fc = qc × Ec
Fd = qd × Ed
Note that Ec is the electric field strength at point c, and Ed is the electric field strength at point d.

Here, the electric field intensity Ec at the point c is obtained by the following equation. (Strictly speaking, the electric field strength includes electric field components due to the voltage of a signal applied to the pair of electrode layers of the touch panel 1 and the pixel electrode or segment electrode of the liquid crystal panel 2, but these cause noise. (Since there is almost no change at a certain frequency, it is omitted here.)
Ec = Ecomc (t) + Eqc + Eqd-Etpd (t) (1) Equation Ecomc (t) is driven by the liquid crystal panel 2 (counter electrode layer 23) among electric field components at point c. Eqc is the charge qc of the electric field component at point c, Eqd is the charge qd of the electric field component at point c, and Etpc (t) is the point c. This is due to the voltage of the back-side electrode layer 13 of the touch panel 1 among the electric field components in FIG.

Here, when no voltage is applied to the back surface side electrode layer 13 of the touch panel 1, Etpd becomes 0. Therefore, Ecomc (t) varies with the drive frequency component due to the COM signal that varies with the drive frequency as in the prior art. , Fc also changes at this drive frequency, but in Example 1, since a voltage synchronized with the change in the voltage of the common electrode signal is applied to the back surface side electrode layer 13 of the touch panel 1, at the point c. Since the component in which the electric field strength Ec changes with time decreases, the change in Fc with time decreases. The level of the signal amplitude (AC voltage value) applied to the transparent electrode 13 of the touch panel 1 is determined based on the positional relationship between the back surface of the touch panel 1, the counter electrode layer 23, and the back surface side electrode layer 13 of the touch panel 1. It is also possible to eliminate the temporal change of the intensity Ec. This can be considered similarly for the force Fd acting on the charge at the point d.
Since the same change in electric field strength occurs at other points on the back surface of the touch panel 1 (transparent plate material 15), the total charge on the back surface of the touch panel 1 (transparent plate material 15) is Qtp. That is, it is considered that the force Ftp acting on the entire surface is also unlikely to change, and similarly, when the total charge amount on the entire surface of the liquid crystal panel 2 is Qlc, the force Flc acting on the entire panel surface is also unlikely to change.

  As described above, since the temporal changes in the forces Ftp and Flc acting on the back surface of the touch panel 1 and the surface of the liquid crystal panel 2 can be reduced, the vibration of the space between the touch panel 1 and the liquid crystal panel 2 is eliminated. The phenomenon of sounding can be avoided.

  In the above embodiment, the common electrode signal generated by the common electrode signal generation circuit 81 is supplied to the switch means. However, the present invention is not limited to this, and for example, as shown in FIGS. In addition, the present invention also includes a sound improvement signal generating circuit 84 that applies a predetermined process to the common electrode signal to generate a sound improvement signal and applies the sound improvement signal to the back-side electrode layer 13. Within the intended range. In this illustrated example, the sound improvement signal generation circuit 84 generates a sound improvement signal whose voltage changes at a frequency that is an integral multiple (for example, four times) the frequency of the common electrode signal. An improvement signal is applied to the back side electrode layer 13 of the touch panel 1. Thereby, since the change of the electric field intensity on the back surface of the touch panel 1 and the surface of the liquid crystal panel 2 is not a constant frequency change, the phenomenon of sounding can be avoided. That is, for example, when a voltage of 10 kHz is applied to the counter electrode layer 23 and a voltage of 40 kHz is applied to the back electrode layer, the electric field in the transparent plate 15 is as shown in FIG. Although the change at a constant frequency does not occur and the change of the electric field is considered to be involved in the vibration to the flat plate member within a very short time, the vibration due to this electric field is outside the audible region (40 kHz). , Not recognized by people.

  In addition, a voltage synchronized with the same phase as the liquid crystal drive is applied to the electrode layer so that a voltage is applied so as to generate an electric field that changes the period of the periodic electric field generated based on the common electrode layer, Although the description has been given above of the case where the voltage of an integral multiple of the liquid crystal driving frequency is applied so that the vibration of the liquid crystal panel is out of the audible region, the present invention is not necessarily limited to these methods. Absent.

  Further, in the above embodiment, the desired voltage for suppressing sound generation applied to the electrode layer is the same voltage as the common electrode signal, but the desired voltage for suppressing sound generation is It is also possible to apply a voltage different from the voltage level of the common electrode signal. In this case, it is preferable to further include the sound improvement signal generating circuit.

1 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment of the present invention. It is a schematic perspective view for demonstrating schematically the liquid crystal display device of the Example. It is typical explanatory drawing for demonstrating the relationship between the voltage applied to each electrode layer, and the electric field in a flat member in the liquid crystal display device of the Example, (a) is a counter electrode layer (common electrode layer) of a liquid crystal panel (B) is the relationship between the voltage (vertical axis) applied to the back side electrode layer of the touch panel and the time (horizontal axis), (c) Indicates the relationship between the electric field (vertical axis) and time (horizontal axis) in the flat plate member. It is a schematic block diagram in the liquid crystal display device of the Example. The schematic block diagram for demonstrating the detail of the switching control part in the liquid crystal display device of the Example is shown. The schematic block diagram for demonstrating the detail of the sound improvement signal switch part in the liquid crystal display device of the Example is shown. It is a schematic block diagram for demonstrating the detail of the switching signal production | generation part in the liquid crystal display device of the Example. The schematic block diagram of the analog switch used in the liquid crystal display device of the embodiment is shown. It is a simplified diagram of the entire circuit when the analog switch is used. It is a block diagram of the switch means of the liquid crystal display device of the embodiment. 1 is a schematic cross-sectional view of a liquid crystal display device of the same embodiment. It is a schematic perspective view for demonstrating schematically the liquid crystal display device of the other Example of this invention. It is typical explanatory drawing for demonstrating the relationship between the voltage applied to each electrode layer, and the electric field in a flat member in the liquid crystal display device of the Example, (a) is a counter electrode layer (common electrode layer) of a liquid crystal panel (B) is the relationship between the voltage (vertical axis) applied to the back side electrode layer of the touch panel and the time (horizontal axis), (c) Indicates the relationship between the electric field (vertical axis) and time (horizontal axis) in the flat plate member. The schematic sectional drawing of the liquid crystal display device of a prior art example is shown (however, detailed illustration of a touch panel is abbreviate | omitted). The schematic block diagram of the analog switch used in the other liquid crystal display device which is a comparative example is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Touch panel 11, 14 Sheet material 12, 13 Transparent electrode 15 Transparent board material 2 Liquid crystal panel 21, 27 Polarizing plate 22, 26 Substrate 23, 25 Electrode 81 Common electrode signal generation circuit 82 Touch panel controller 90 Switch means 91 Switching control part 92 Sound Signal switch unit 93 Touch panel controller switch unit 94 Switching signal generation unit

Claims (7)

A display device comprising a panel having a common electrode layer to which a voltage changing at a predetermined frequency is applied, and a flat plate member disposed with a predetermined gap from the panel,
An electrode layer disposed so as to be substantially parallel to the flat plate member and the panel while applying a sound improvement signal whose voltage changes in synchronization with a change in voltage applied to the common electrode layer ,
A sound improvement signal generating unit that generates the sound improvement signal applied to the electrode layer,
Switch means for switching electrical connection between the sound generation improvement signal generator and the electrode layer between a conductive state and a disconnected state;
A first signal line for electrically connecting the switch means and the sound improvement signal generating unit;
And a second signal line for electrically connecting the switch means and the electrode layer,
The switch means is connected to a positive power supply so as to supply a positive component of the sound improvement signal to the second signal line when the electrical connection between the sound improvement signal generator and the electrode layer is made conductive. And a second transistor connected to a negative power source for supplying a negative component of the sound improvement signal to the second signal line. A display device comprising a panel having a common electrode layer to which a voltage changing at a predetermined frequency is applied, and a flat plate member disposed with a predetermined gap from the panel,
The common electrode layer is applied with a sound improvement signal whose voltage changes so as to generate an electric field that changes the period of change of the electric field generated when a voltage changing at a predetermined frequency is applied. An electrode layer disposed so as to be substantially parallel to the member and the panel;
A sound improvement signal generating unit that generates the sound improvement signal applied to the electrode layer,
Switch means for switching electrical connection between the sound generation improvement signal generator and the electrode layer between a conductive state and a disconnected state;
A first signal line for electrically connecting the switch means and the sound improvement signal generating unit;
And a second signal line for electrically connecting the switch means and the electrode layer,
The switch means is connected to a positive power supply so as to supply a positive component of the sound improvement signal to the second signal line when the electrical connection between the sound improvement signal generator and the electrode layer is made conductive. And a second transistor connected to a negative power source for supplying a negative component of the sound improvement signal to the second signal line. The display device according to claim 1 or 2,
A touch panel including a first electrode layer, and a second electrode layer disposed so as to face the first electrode layer on the display surface side of the panel with respect to the first electrode layer;
The display device, wherein the electrode layer is at least one of the first electrode layer and the second electrode layer. The display device according to claim 3,
A touch panel controller that detects an electrical change that occurs between the first electrode layer and the second electrode layer when a user touches the touch panel, and detects a position touched by the user; and A third signal line for electrically connecting the touch panel controller and the switch means;
The switch means includes a touch panel controller switch unit that switches electrical connection between the touch panel controller and the electrode layer to which the sound improvement signal is applied between a conductive state and a disconnected state,
The switch means detects the electrical change that occurs between the first electrode layer and the second electrode layer when a user touches the touch panel, and the first transistor and the second transistor Cuts off the electrical connection between the first signal line and the second signal line, and the touch panel controller switch unit establishes an electrical connection between the second signal line and the third signal line. A display device provided to be in a conductive state. The display device according to claim 4,
The switch means includes a switching signal generation unit that generates a switching signal to be transmitted to the first transistor, the second transistor, and the touch panel controller switch unit.
The switching signal generation unit is connected to the first electrode layer and / or the second electrode layer, and the first electrode layer and the second electrode layer generated when the user touches the touch panel. The display device is provided so as to generate the switching signal based on an electrical change occurring between the display device and the display device. The display device according to claim 4 or 5,
When the switch means does not detect an electrical change occurring between the first electrode layer and the second electrode layer due to a user touching a touch panel for a predetermined time, the switch means and the second transistor And the transistor makes the electrical connection between the first signal line and the second signal line conductive, and the touch panel controller switch unit electrically connects the second signal line and the third signal line. A display device, characterized in that it is provided so as to disconnect the general connection. The display device according to claim 6,
The switch means includes a switching signal generation unit that generates a switching signal to be transmitted to the first transistor, the second transistor, and the touch panel controller switch unit.
The switching signal generator
At predetermined time intervals, the first transistor and the second transistor make electrical connection between the first signal line and the second signal line conductive, and the touch panel controller switch unit It is provided so as to generate a switching signal that makes the electrical connection between the signal line and the third signal line conductive.
And it is connected to the 1st electrode layer and / or the 2nd electrode layer, and it arises between the 1st electrode layer and the 2nd electrode layer which arise when a user touches the touch panel. Based on the electrical change, the first transistor and the second transistor disconnect the electrical connection between the first signal line and the second signal line, and the touch panel controller switch unit A display device, characterized in that it is provided so as to generate a switching signal that makes electrical connection between the signal line and the third signal line conductive.