JP2014224834A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device in which a touch panel is hardly influenced by noises generated when a liquid crystal panel is driven.SOLUTION: The display device includes a liquid crystal panel 14 and a touch panel 12 disposed on a top surface side of the liquid crystal panel 14. The liquid crystal panel 14 includes a pair of substrates 18, 20, a liquid crystal layer 26 sealed between the pair of substrates 18, 20, a conductive layer 30 formed on one of the pair of substrates 18, 20, and a capacitor 36 connected to the conductive layer 30. The conductive layer 30 is formed on the substrate 20 of the pair of substrates 18, 20, which is located close to the touch panel 12. The conductive layer 30 overlaps the entire liquid crystal layer 26 when viewed from the front of the liquid crystal panel 14. The capacitor 36 is connected at one terminal to the conductive layer 30 and grounded at the other terminal.

Description

  The present invention relates to a display device having a touch panel function.

  In recent years, display devices having a touch panel function have been proposed. In order to realize the touch panel function, for example, it is necessary to provide a separate touch panel in addition to the display panel. In this case, the thickness of the display device becomes large. Therefore, it has been studied to reduce the thickness of the display device. For example, Japanese Patent Laying-Open No. 2011-70092 (Patent Document 1) discloses a liquid crystal display device in which a touch panel is incorporated in a liquid crystal panel.

JP 2011-70092 A Japanese Patent Laid-Open No. 7-294953

  In the liquid crystal display device described in Patent Document 1, a touch panel is disposed in a liquid crystal panel. Therefore, there is no shield between the touch panel and the liquid crystal panel. As a result, the touch panel does not operate normally due to the influence of noise generated when driving the liquid crystal panel.

  An object of the present invention is to provide a display device in which a touch panel can be hardly affected by noise generated when a liquid crystal panel is driven.

  The display device of the present invention includes a liquid crystal panel and a touch panel disposed on a surface side of the liquid crystal panel, and the liquid crystal panel includes a pair of substrates, a liquid crystal layer sealed between the pair of substrates, A conductive layer formed on one of a pair of substrates; and a capacitor connected to the conductive layer, wherein the conductive layer is formed on a substrate located on the touch panel side of the pair of substrates, The conductive layer overlaps the entire liquid crystal layer when the liquid crystal panel is viewed from the front, and the capacitor has one end connected to the conductive layer and the other end grounded.

  The display device of the present invention can make the touch panel less susceptible to noise generated when driving the liquid crystal panel.

FIG. 1 is a cross-sectional view showing an example of a schematic configuration of a display device as a first embodiment of the present invention. FIG. 2 is a plan view illustrating an example of a schematic configuration of a liquid crystal panel included in the display device illustrated in FIG. 1. FIG. 3 is a cross-sectional view showing another example of the schematic configuration of the display device as Application Example 1 of the first embodiment of the present invention. FIG. 4 is a cross-sectional view showing another example of a schematic configuration of a display device as an application example 2 of the first embodiment of the present invention. FIG. 5 is a cross-sectional view showing an example of a schematic configuration of a liquid crystal panel included in a display device as a second embodiment of the present invention. FIG. 6 is a cross-sectional view showing an example of a schematic configuration of the capacitor shown in FIG. FIG. 7 is a cross-sectional view showing another example of the schematic configuration of the capacitor shown in FIG. FIG. 8: is sectional drawing which shows an example of schematic structure of the display apparatus as the application example 2 of the 2nd Embodiment of this invention. FIG. 9 is a block diagram showing an example of a schematic configuration of a display device as a third embodiment of the present invention. FIG. 10 is a graph showing the relationship between noise and time constant.

  A display device according to an embodiment of the present invention includes a liquid crystal panel and a touch panel disposed on a surface side of the liquid crystal panel, and the liquid crystal panel is sealed between a pair of substrates and the pair of substrates. A liquid crystal layer; a conductive layer formed on one of the pair of substrates; and a capacitor connected to the conductive layer, wherein the conductive layer is a substrate located on the touch panel side of the pair of substrates. The conductive layer overlaps the entire liquid crystal layer when the liquid crystal panel is viewed from the front, and the capacitor has one end connected to the conductive layer and the other end grounded (first Constitution).

  In the first configuration, the conductive layer is formed on the substrate located on the touch panel side among the pair of substrates. The conductive layer overlaps the entire liquid crystal layer when the liquid crystal panel is viewed from the front. One end of the capacitor is connected to the conductive layer, and the other end of the capacitor is grounded. Thereby, a conductive layer can be utilized as a shield. As a result, the touch panel can be made less susceptible to noise generated when driving the liquid crystal panel. Note that that one end of the capacitor is connected to the conductive layer includes that one electrode of the capacitor is a conductive layer. Further, the phrase “a liquid crystal panel has a capacitor” includes that a member connected to the liquid crystal panel has a capacitor.

  The second configuration is a configuration in which the capacitor includes the conductive layer in the first configuration. In such a configuration, a capacitor can be easily realized.

  According to a third configuration, in the first configuration, the liquid crystal panel further includes a wiring portion connected to the conductive layer, and one end of the capacitor is connected to the wiring portion. In such a configuration, it is possible to ensure a degree of freedom in designing the capacitor arrangement.

  A fourth configuration further includes a pair of conductive films formed on one of the pair of substrates and an insulating film disposed between the pair of conductive films in the third configuration, and the pair of conductive films The capacitor is realized by the insulating film. In such a configuration, a capacitor can be formed by utilizing a thin film forming technique.

  A fifth configuration includes the thin film transistor formed on one of the pair of substrates in the fourth configuration, and a short-circuit portion that short-circuits the source electrode and the drain electrode of the thin film transistor, and one of the pair of conductive films Is the gate electrode of the thin film transistor, and the other is the short circuit portion. In such a configuration, a capacitor can be formed by using a thin film transistor forming technique.

  A sixth configuration is a configuration in which, in any one of the first to fifth configurations, the cutoff frequency of the RC circuit realized by including the capacitor is set to be equal to or lower than the drive frequency of the touch panel. In such a configuration, the touch panel is hardly affected by noise.

  A seventh configuration is a configuration in which, in the sixth configuration, the cutoff frequency is set to 70% or less of the drive frequency. In such a configuration, the touch panel is less susceptible to noise.

  The eighth configuration is a configuration in which, in any one of the first to seventh configurations, the liquid crystal panel is a display panel for displaying an image.

  A ninth configuration is a switch liquid crystal panel in which, in any one of the first to seventh configurations, the liquid crystal panel realizes a parallax barrier. In such a configuration, a stereoscopic display device can be realized.

  Hereinafter, more specific embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated. Note that, in the drawings referred to below, the configuration is shown in a simplified or schematic manner, or some components are omitted for easy understanding of the description. Further, the dimensional ratio between the constituent members shown in each drawing does not necessarily indicate an actual dimensional ratio.

[First Embodiment]
With reference to FIG.1 and FIG.2, the display apparatus 10 as the 1st Embodiment of this invention is demonstrated. The display device 10 is a display used for, for example, a mobile phone, a portable information terminal, a game machine, a digital camera, a printer, a car navigation, an information home appliance, and the like. As shown in FIG. 1, the display device 10 includes a touch panel 12 and a liquid crystal panel 14.

  The touch panel 12 is a capacitive touch panel, for example. The touch panel 12 is disposed so as to overlap the substrate 20 of the liquid crystal panel 14. A controller (not shown) is connected to the touch panel 12. The controller controls the touch panel 12.

  The liquid crystal panel 14 is a display panel that displays an image. The liquid crystal panel 14 is provided with a driver 16. The driver 16 drives the liquid crystal panel 14. The driver 16 may be provided separately from the liquid crystal panel 14.

  The liquid crystal panel 14 includes a pair of substrates 18 and 20. These substrates 18 and 20 are non-alkali glass substrates, for example.

  A pixel electrode 22 is formed on the substrate 18. The pixel electrode 22 is, for example, an indium tin oxide film.

  A counter electrode 24 as a conductive layer is formed on the substrate 20. The counter electrode 24 is, for example, an indium tin oxide film. The counter electrode 24 overlaps the entire liquid crystal layer 26 described later when the liquid crystal panel 14 is viewed from the front. In other words, the counter electrode 24 is formed over the entire display area of the liquid crystal panel 14.

  A liquid crystal layer 26 exists between the pair of substrates 18 and 20. The liquid crystal layer 26 is sealed between the pair of substrates 18 and 20 by a seal member 28. The operation mode of the liquid crystal is an operation mode in which a drive voltage is applied in the vertical direction.

  As shown in FIG. 2, the liquid crystal panel 14 is provided with a wiring portion 30. The wiring unit 30 electrically connects the counter electrode 24 and the driver 16.

  The wiring part 30 includes, for example, a lead wiring 32 formed on the substrate 18 and a seal member 28. The lead wiring 32 is, for example, molybdenum, aluminum, titanium, tantalum, silver, or the like. The lead wiring 32 has a large resistance due to, for example, a narrow frame of the liquid crystal panel 14. Therefore, for example, it is necessary to appropriately select the wiring material, the wiring width, etc., and reduce the resistance of the lead-out wiring 32.

  The seal member 28 includes, for example, conductive particles. Thereby, the sealing member 28 has conductivity. The counter electrode 24 and the lead wiring 32 are electrically connected via the seal member 28.

  An electrode 34 is formed on the substrate 18. The electrode 34 is, for example, an indium tin oxide film. Thereby, the capacitor 36 is realized by the counter electrode 24, the electrode 34, and the liquid crystal layer 26 positioned therebetween. One electrode of the capacitor 36 is realized by the counter electrode 24.

  The electrode 34 is grounded. As a method of grounding the electrode 34, for example, there is a method of connecting the electrode 34 and the ground line of the driver 16 or the like.

  In such a display device 10, one electrode of the capacitor 36 is realized by the counter electrode 24, and the other electrode (electrode 34) of the capacitor 36 is grounded. Thereby, the counter electrode 24 can be used as a shield. As a result, it becomes difficult for the touch panel 12 to be affected by noise generated when the liquid crystal panel 14 is driven.

  The capacity of the capacitor 36 is set in consideration of the cutoff frequency of the RC circuit realized by the capacitor 36 and the wiring unit 30. The cut-off frequency is set to be equal to or lower than the drive frequency of the touch panel 12, and is preferably set to be 70% or lower of the drive frequency of the touch panel 12. Thereby, for example, even when the drive frequency of the touch panel 12 changes due to a temperature change or the like, the touch panel 12 becomes less susceptible to noise.

[Application 1 of the first embodiment]
In the first embodiment, the operation mode of the liquid crystal is the operation mode in which the drive voltage is applied in the vertical direction. However, in this application example, the operation mode of the liquid crystal is the operation mode in which the drive voltage is applied in the horizontal direction. Yes. In the display device 38 of this application example, as shown in FIG. 3, the common electrode 40 for driving the liquid crystal is formed on the substrate 18. In this application example, the shield layer 42 for removing static electricity formed on the substrate 20 functions as a conductive layer.

[Application 2 of the first embodiment]
In the display device 44 of this application example, as shown in FIG. 4, the counter electrode 24 and the driver 16 are connected by a wiring 46 such as an FPC (Flexible Printed Circuits). A capacitor 48 is provided on the wiring 46. Thus, one end of the capacitor 48 is connected to the counter electrode 24, and the other end of the capacitor 64 is grounded via the ground line of the driver 16.

[Second Embodiment]
In the present embodiment, as shown in FIG. 5, the capacitor 50 is provided on the substrate 18. The capacitor 50 is provided on the lead wiring 32.

  The capacitor 50 can be formed using a thin film transistor. In the example shown in FIG. 6, a capacitor 50 using a bottom gate type thin film transistor is shown.

  In the example shown in FIG. 6, the gate electrode 52 is formed on the substrate 18. The gate electrode 52 is, for example, a metal film such as tantalum, molybdenum, aluminum, or titanium.

  A gate insulating film 54 is formed on the gate electrode 52. The gate insulating film 54 is, for example, a silicon nitride film.

  An amorphous silicon film 56 is formed on the gate insulating film 54. The amorphous silicon film 56 is formed, for example, by laminating an intrinsic amorphous silicon film and a conductive amorphous silicon film.

  On the amorphous silicon film 56, a source electrode 58, a drain electrode 60, and a short-circuit portion 62 that short-circuits these electrodes 58 and 60 are formed. For example, when the source electrode 58 and the drain electrode 60 are patterned, the short-circuit portion 62 can be formed by not removing the metal film positioned between the electrodes 58 and 60. The short circuit part 62 is formed at a position overlapping the gate electrode 52. The source electrode 58, the drain electrode 60, and the short circuit part 62 are metal films, such as aluminum and titanium, for example.

  The source electrode 58, the drain electrode 60, and the short circuit portion 62 are covered with a protective film 64. The protective film 64 is, for example, a silicon oxide film.

  In the example illustrated in FIG. 6, the gate insulating film 54 is disposed between the short-circuit portion 62 and the gate electrode 52. The capacitor 50 is realized by the short-circuit portion 62, the gate electrode 52, and the gate insulating film 54.

  In such a display device, the capacitor 50 can be formed on one substrate 18 by using a thin film transistor manufacturing technique. As a result, the capacitor 50 can be easily formed.

[Application 1 of the second embodiment]
In the second embodiment, the capacitor 50 using a bottom gate type thin film transistor is employed. However, for example, as shown in FIG. 7, a capacitor 50 using a top gate type thin film transistor may be employed.

  In the example shown in FIG. 7, a polysilicon film 66 is formed on the substrate 18. A gate insulating film 54 is formed on the polysilicon film 66. A gate electrode 52 is formed on the gate insulating film 54. On the gate electrode 52 and the gate insulating film 54, a first protective film 64a is formed. A source electrode 58 and a drain electrode 60 are connected to the polysilicon film 66. On the first protective film 64a, a short-circuit portion 62 that short-circuits the source electrode 58 and the drain electrode 60 is provided. The source electrode 58, the drain electrode 60, and the short circuit part 62 are covered with the second protective film 64b. In the example illustrated in FIG. 7, the capacitor 50 is realized by the gate electrode 52, the short-circuit portion 62, and the first protective film 64 a.

[Application Example 2 of Second Embodiment]
As shown in FIG. 8, in this application example, the driver 16 is provided outside the liquid crystal panel 14. The driver 16 and the lead wiring 32 are connected by an FPC 68. A capacitor 70 is provided on the FPC 68. One end of the capacitor 70 is connected to the counter electrode 24 via the FPC 68, the lead wiring 32, and the seal member 28. The other end of the capacitor 70 is connected to the ground line of the driver 16, for example.

[Third Embodiment]
In the first and second embodiments, the case where the liquid crystal panel is a display panel has been described. However, the liquid crystal panel is not limited to a display panel that displays an image. For example, the liquid crystal panel may be a switch liquid crystal panel capable of realizing a parallax barrier.

  The case where the liquid crystal panel is a switch liquid crystal panel will be described with reference to FIG. The display device 72 of the present embodiment includes a touch panel 12, a switch liquid crystal panel 74, and a display panel 76. In the display device 72, a stereoscopic image can be shown to the observer by using a parallax barrier realized in the switch liquid crystal panel 74.

  The display panel 76 may be, for example, a liquid crystal panel, a plasma display panel, or an organic EL panel. One end of a capacitor 80 is connected to a wiring part 78 that connects the switch liquid crystal panel 74 and the driver 16. The other end of the capacitor 80 is grounded. The resistor 82 that realizes the RC circuit together with the capacitor 80 is, for example, the resistance of the wiring part 78 itself.

  In the display device 72 shown in FIG. 9, the relationship between the time constant of the RC circuit and noise was examined. The result is shown in FIG. As is clear from FIG. 10, it can be confirmed that the noise decreases as the time constant increases.

  As mentioned above, although embodiment of this invention has been explained in full detail, these are illustrations to the last and this invention is not limited at all by the above-mentioned embodiment.

10: Display device, 12: Touch panel, 14: Liquid crystal panel, 16: Driver, 18: Substrate, 20: Substrate, 24: Counter electrode (conductive layer), 26: Liquid crystal layer, 28: Seal member, 30: Wiring part, 36: capacitor, 42: shield layer (conductive layer), 52: gate electrode (conductive film), 54: gate insulating film (insulating film), 58: source electrode, 60: drain electrode, 62: short circuit part, 64a: first 1 Protective film (insulating film), 74: Switch liquid crystal panel

Claims (9)

LCD panel,
A touch panel disposed on the surface side of the liquid crystal panel,
The liquid crystal panel is
A pair of substrates;
A liquid crystal layer sealed between the pair of substrates;
A conductive layer formed on one of the pair of substrates;
A capacitor connected to the conductive layer,
The conductive layer is formed on the touch panel side of the pair of substrates,
The conductive layer overlaps the entire liquid crystal layer when the liquid crystal panel is viewed from the front,
One end of the capacitor is connected to the conductive layer, and the other end is grounded.   The display device according to claim 1, wherein the capacitor is realized including the conductive layer. The liquid crystal panel further includes a wiring portion connected to the conductive layer,
The display device according to claim 1, wherein one end of the capacitor is connected to the wiring portion. A pair of conductive films formed on one of the pair of substrates;
An insulating film disposed between the pair of conductive films,
The display device according to claim 3, wherein the capacitor is realized by the pair of conductive films and the insulating film. A thin film transistor formed on one of the pair of substrates;
A short-circuit portion for short-circuiting the source electrode and the drain electrode of the thin film transistor,
The display device according to claim 4, wherein one of the pair of conductive films is a gate electrode of the thin film transistor and the other is the short-circuit portion.   The display device according to claim 1, wherein a cutoff frequency of an RC circuit realized including the capacitor is set to be equal to or lower than a driving frequency of the touch panel.   The display device according to claim 6, wherein the cutoff frequency is set to 70% or less of the driving frequency.   The display device according to claim 1, wherein the liquid crystal panel is a display panel that displays an image.   The display device according to claim 1, wherein the liquid crystal panel is a switch liquid crystal panel that realizes a parallax barrier.

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