Liquid crystal display device

Abstract

To provide a liquid crystal display device with which it is possible to improve display quality.SOLUTION: The liquid crystal display device includes: a first and a second substrate 10, 11; a liquid crystal layer 40 provided between the first and second substrates 10, 11; a common electrode 20 provided on the substrate 10 and provided in common to a plurality of pixels; an integrated circuit 12 that drives the common electrode 20; an FPC 13 connected to the integrated circuit 12; and a resistance element 23 provided to the FPC 13 and having one end which is connected to the common electrode 20 and the other end which is connected to a grounding terminal 24.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a liquid crystal display device. [Background technology]

[0002] Known liquid crystal display devices that can provide high contrast and a wide viewing angle include those that use an electric field that is approximately horizontal to a transparent substrate, i.e., liquid crystal display devices that operate in FFS (Fringe-Field Switching) mode or IPS (In-Plain Switching) mode.

[0003] For example, in an FFS mode liquid crystal display device, pixel electrodes to which display signals are supplied are formed on one of the two transparent substrates sandwiching a liquid crystal layer, and a common electrode is formed above the pixel electrodes via an insulating layer. The common electrode has multiple slits and is supplied with a common voltage.

[0004] When a DC voltage is continuously applied to the liquid crystal layer, impurity ions gather on one side of the electrode, preventing the liquid crystal display from being driven at the intended voltage, resulting in image retention and flicker. This reduces the display quality of the liquid crystal display. For this reason, liquid crystal display devices use AC drive, in which the electric field applied to the liquid crystal layer is reversed every unit time.

[0005] In FFS mode, the liquid crystal layer is driven by an electric field that passes from the pixel electrode through the slit in the common electrode and is applied to the common electrode. The path of the electric field is different between the layer structure on the pixel electrode side and the layer structure on the common electrode side. Charge accumulates at each interface when driven, but because the layer structures on the common electrode side and the pixel electrode side are different, the amount of accumulated charge differs.

[0006] Therefore, in FFS mode, even if the liquid crystal layer is driven with AC, if it is driven continuously, a direct current (DC) component occurs due to the difference (imbalance) in the charges stored on the common electrode side and the pixel electrode side, which can cause burn-in and flicker. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-217211 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a liquid crystal display device capable of improving display quality. [Means for solving the problem]

[0009] According to a first aspect of the present invention, there is provided a liquid crystal display device comprising first and second substrates, a liquid crystal layer provided between the first and second substrates, a common electrode provided on the first substrate and shared by a plurality of pixels, an integrated circuit for driving the common electrode, an FPC (Flexible Printed Circuit) connected to the integrated circuit, and a resistive element provided on the FPC and having one end connected to the common electrode and the other end connected to a ground terminal.

[0010] According to a second aspect of the present invention, there is provided a liquid crystal display device comprising first and second substrates, a liquid crystal layer provided between the first and second substrates, a common electrode provided on the first substrate and shared by a plurality of pixels, an integrated circuit for driving the common electrode, and a resistive element provided on the integrated circuit and having one end connected to the common electrode and the other end connected to a ground terminal.

[0011] According to a third aspect of the present invention, there is provided a liquid crystal display device comprising first and second substrates, a liquid crystal layer provided between the first and second substrates, a common electrode provided on the first substrate and shared by a plurality of pixels, an integrated circuit for driving the common electrode, an FPC connected to the integrated circuit, and a switching element provided on the FPC and having one end connected to the common electrode and the other end connected to a ground terminal, wherein the integrated circuit includes a driver for applying a common voltage to the common electrode and a control circuit, and the control circuit turns on the switching element while the driver is stopped operating.

[0012] According to a fourth aspect of the present invention, there is provided a liquid crystal display device comprising first and second substrates, a liquid crystal layer provided between the first and second substrates, a common electrode provided on the first substrate and shared by a plurality of pixels, an integrated circuit for driving the common electrode, and a switching element provided on the integrated circuit and having one end connected to the common electrode and the other end connected to a ground terminal, the integrated circuit including a driver for applying a common voltage to the common electrode and a control circuit, and the control circuit turning on the switching element while the driver is stopped operating.

[0013] According to a fifth aspect of the present invention, there is provided the liquid crystal display device according to the third or fourth aspect, wherein the control circuit turns off the switching element while the driver is operating.

[0014] According to a sixth aspect of the present invention, there is provided a liquid crystal display device according to any one of the first to fifth aspects, further comprising a plurality of pixel electrodes provided on the first substrate corresponding to the plurality of pixels, and an insulating layer provided on the plurality of pixel electrodes, wherein the common electrode is provided on the insulating layer and has slits arranged above each of the plurality of pixel electrodes.

[0015] According to a seventh aspect of the present invention, there is provided a liquid crystal display device according to any one of the first to fifth aspects, further comprising an insulating layer provided on the first substrate, and a plurality of pixel electrodes having slits provided on the insulating layer so as to correspond to the plurality of pixels, and the common electrode is provided between the first substrate and the insulating layer. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a liquid crystal display device capable of improving display quality. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic plan view of a liquid crystal display device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic plan view of the liquid crystal display device for explaining the common electrode and the wiring paths. [Figure 3] FIG. 3 is a cross-sectional view of the FPC shown in FIG. [Figure 4] FIG. 4 is a block diagram of a liquid crystal display device. [Figure 5] FIG. 5 is a circuit diagram of the pixel array shown in FIG. [Figure 6] FIG. 6 is a plan view of a pixel. [Figure 7] FIG. 7 is a cross-sectional view of the pixel taken along the line AA′ in FIG. [Figure 8] FIG. 8 is a timing chart illustrating the operation of the liquid crystal display device. [Figure 9] FIG. 9 is a block diagram of a liquid crystal display device according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a schematic plan view of a liquid crystal display device according to a third embodiment of the present invention. [Figure 11] FIG. 11 is a block diagram of a liquid crystal display device according to a fourth embodiment of the present invention. [Figure 12] FIG. 12 is a plan view of a pixel according to the fifth embodiment of the present invention. [Figure 13]FIG. 13 is a cross-sectional view of the pixel taken along the line AA′ in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions and proportions of each drawing are not necessarily the same as those of the actual drawing. Furthermore, even when the same parts are shown in different drawings, the dimensional relationships and proportions may be different. In particular, the following embodiments are illustrative of devices and methods for embodying the technical concept of the present invention, and the shape, structure, arrangement, etc. of the components do not specify the technical concept of the present invention. In the following description, elements having the same function and configuration are designated by the same reference numerals, and redundant description will be omitted.

[0019] [1] First embodiment [1-1] Configuration of the liquid crystal display device 1 The liquid crystal display device 1 according to this embodiment is a FFS (Fringe-Field switching) mode liquid crystal display device. The FFS mode is a method of switching homogeneously aligned liquid crystals using a fringe electric field.

[0020] 1 is a schematic plan view of a liquid crystal display device 1 according to a first embodiment of the present invention. The X direction in FIG. 1 is a direction along one side of the liquid crystal display device 1, and the Y direction is a direction perpendicular to the X direction.

[0021] The liquid crystal display device 1 includes a TFT substrate 10, a CF (color filter) substrate 11, and a liquid crystal layer sealed between the TFT substrate 10 and the CF substrate 11 with a sealant. The liquid crystal display device 1 also includes an integrated circuit (IC) 12 and a flexible printed circuit (FPC) 13.

[0022] The integrated circuit 12 is provided on the TFT substrate 10. The TFT substrate 10 is formed to be slightly larger in the Y direction than the CF substrate 11. The integrated circuit 12 is disposed in an area of ​​the TFT substrate 10 that extends beyond the CF substrate 11. The integrated circuit 12 is formed by an IC chip. The integrated circuit 12 includes a group of circuits that control the operation of the liquid crystal display device 1.

[0023] The FPC 13 is electrically connected to the integrated circuit 12. The liquid crystal display device 1 can be connected to an external device using the FPC 13. The FPC 13 is a type of printed circuit board and is also called a flexible printed circuit board. The FPC 13 is a film-like printed circuit board in which an electric circuit is formed on a substrate made of a thin, soft, insulating base film and a conductive metal laminated together. The FPC 13 includes a plurality of wirings (not shown).

[0024] The liquid crystal display device 1 has a display area 14 where an image is displayed. A plurality of pixels PX arranged in a matrix, a plurality of scanning lines, and a plurality of signal lines are arranged in the display area 14. The plurality of scanning lines are connected to an integrated circuit 12 via a plurality of wirings 15. The plurality of signal lines are connected to the integrated circuit 12 via a plurality of wirings 16. The plurality of wirings 15 and the plurality of wirings 16 are provided on a TFT substrate 10.

[0025] FIG. 2 is a schematic plan view of the liquid crystal display device 1 for explaining the common electrode 20 and wiring paths. The liquid crystal display device 1 includes a common electrode 20 provided in common to a plurality of pixels PX. The common electrode 20 has approximately the same area as the pixel array. In other words, the common electrode 20 is The common electrode 20 has an area equal to or slightly larger than the display area 14. The common electrode 20 is connected to the integrated circuit 12 via one or more wirings 21. The wirings 21 are provided on the TFT substrate 10.

[0026] Here, the common electrode 20 is electrically connected to the ground terminal 24 via a resistive element 23, not via the integrated circuit 12. Specifically, the FPC 13 includes the resistive element 23 and the ground terminal 24. The ground terminal 24 is a terminal to which a ground voltage Vss (0 V) is supplied. The ground voltage Vss is supplied from an external device to which the FPC 13 is connected. One end of the resistive element 23 is electrically connected to the common electrode 20 via wiring 22. The other end of the resistive element 23 is electrically connected to the ground terminal 24. In this specification, "grounded" has the same meaning as "ground voltage Vss is applied."

[0027] FIG. 3 is a cross-sectional view of the FPC 13 shown in FIG. 2. The FPC 13 includes a base film 13A, wiring layers 13B and 13C, and cover films 13D and 13E. The wiring layer 13B and the cover film 13D are laminated in this order on the base film 13A. The wiring layer 13C and the cover film 13E are laminated in this order below the base film 13A. The multiple layers constituting the FPC 13 are bonded together using an adhesive (not shown). The FPC 13 may include more wiring layers. The base film 13A and the cover films 13D and 13E are made of, for example, polyimide resin. The wiring layers 13B and 13C are provided with multiple wirings, a resistor element 23, and a ground terminal 24.

[0028] 4 is a block diagram of a liquid crystal display device 1. The liquid crystal display device 1 includes a pixel array 30, a gate driver (also referred to as a scanning line driving circuit) 31, a source driver (also referred to as a signal line driving circuit) 32, a common electrode driver (also referred to as a common electrode driving circuit) 33, a voltage generating circuit 34, and a control circuit 35. Although not shown, the liquid crystal display device 1 also includes a backlight disposed behind the pixel array 30.

[0029] The pixel array 30 includes a plurality of pixels PX arranged in a matrix. A plurality of scanning lines GL each extending in the X direction and a plurality of signal lines SL each extending in the Y direction are arranged in the pixel array 30. The pixels PX are arranged in the intersections of the scanning lines GL and the signal lines SL.

[0030] The gate driver 31 is electrically connected to the plurality of scanning lines GL. Based on a control signal sent from the control circuit 35, the gate driver 31 sends a scanning signal to the pixel array 30 to turn on / off the switching element included in the pixel PX.

[0031] The source driver 32 is electrically connected to a plurality of signal lines SL. The source driver 32 receives control signals and display data from the control circuit 35. The source driver 32 sends grayscale signals (drive voltages) corresponding to the display data to the pixel array 30 based on the control signals.

[0032] The common electrode driver 33 generates a common voltage Vcom and supplies the common voltage Vcom to the common electrode 20 in the pixel array 30 .

[0033] The voltage generating circuit 34 generates various voltages necessary for the operation of the liquid crystal display device 1 and supplies these voltages to the corresponding circuits.

[0034] The control circuit 35 comprehensively controls the operation of the liquid crystal display device 1. The control circuit 35 receives image data and control signals from the outside. The control circuit 35 generates various control signals based on the image data and sends these control signals to the corresponding circuits.

[0035] [1-2] Configuration of pixel array 30 Fig. 5 is a circuit diagram of the pixel array 30 shown in Fig. 4. The X direction in Fig. 5 is the row direction in which the scanning lines extend, and the Y direction is the column direction in which the signal lines extend.

[0036] A plurality of scanning lines GL1 to GLm and a plurality of signal lines SL1 to SLn are arranged in the pixel array 30. "m" and "n" are each an integer of 2 or greater.

[0037] Each pixel PX includes a switching element 36 and a liquid crystal capacitance Clc. The switching element 36 may be, for example, a thin film transistor (TFT), and may be an n-channel TFT. The source and drain of a transistor change depending on the direction of current flowing through the transistor. The following explanation focuses on an example of the connection state of a transistor. However, the source and drain are not fixed as their names suggest.

[0038] The source of the TFT 36 is connected to a signal line SL, its gate is connected to a scanning line GL, and its drain is connected to one electrode of a liquid crystal capacitor Clc. The liquid crystal capacitor Clc is composed of a pixel electrode, a common electrode, and a liquid crystal layer. A common voltage Vcom is applied to the other electrode of the liquid crystal capacitor Clc by a common electrode driver 33.

[0039] Fig. 6 is a plan view of the pixel PX, and Fig. 7 is a cross-sectional view of the pixel PX taken along line AA' in Fig. 6.

[0040] As described above, the liquid crystal display device 1 includes a TFT substrate 10 on which switching elements (TFTs) and pixel electrodes are formed, and a CF substrate 11 on which color filters are formed and which is disposed opposite the TFT substrate 10. Each of the TFT substrate 10 and the CF substrate 11 is made of a transparent and insulating substrate (for example, a glass substrate or a resin substrate).

[0041] The liquid crystal layer 40 is sandwiched and filled between the TFT substrate 10 and the CF substrate 11. Specifically, the liquid crystal layer 40 is sealed in a display area 14 surrounded by the TFT substrate 10, the CF substrate 11, and a sealing material (not shown). The sealing material is made of, for example, an ultraviolet curable resin, a thermosetting resin, or a UV / thermal curable resin, and is applied to the TFT substrate 10 or the CF substrate 11 in the manufacturing process and then cured by ultraviolet irradiation, heating, or the like.

[0042] The liquid crystal material constituting the liquid crystal layer 40 changes its optical properties as the orientation of the liquid crystal molecules is manipulated in response to an applied electric field. In this embodiment, a positive-type (P-type) nematic liquid crystal with positive dielectric anisotropy is used for the liquid crystal layer 40. In the initial state, the liquid crystal layer 40 is horizontally aligned (homogeneously aligned). When no voltage (no electric field) is applied, the liquid crystal molecules are aligned approximately horizontally with respect to the main surfaces of the substrates. When a voltage (electric field) is applied, the directors of the liquid crystal molecules tilt toward the direction of the electric field.

[0043] First, the configuration of the TFT substrate 10 side will be described. A TFT 36 is provided for each pixel PX on the liquid crystal layer 40 side of the TFT substrate 10. Although a cross-sectional configuration of the TFT 36 is omitted, a general TFT can be used for the TFT 36. The TFT 36 includes a gate electrode that functions as a scan line, a gate insulating film provided on the gate electrode, a semiconductor layer provided on the gate insulating film, and a source electrode and a drain electrode provided spaced apart from each other on the semiconductor layer.

[0044] Signal lines SL are provided on the TFT substrate 10. The signal lines SL are arranged in the same layer as the source electrodes of the TFTs.

[0045] An insulating layer 41 is provided on the TFTs 36 and the signal lines SL.

[0046] A pixel electrode 42 is provided on the insulating layer 41. The pixel electrode 42 extends in the Y direction. The pixel electrode 42 is provided for each pixel PX and has an area that covers approximately the entire pixel region. The pixel electrode 42 is electrically connected to the drain electrode of the TFT 36 via a contact (not shown).

[0047] An insulating layer 43 is provided on the pixel electrode 42 .

[0048] A common electrode 20 is provided on the insulating layer 43. The common electrode 20 is provided in common to a plurality of pixels PX. The common electrode 20 has a plurality of slits (also called openings) 44 for each pixel PX. In the present embodiment, a configuration in which four slits 44 are provided for each pixel PX is shown as an example. The number of slits 44 may be one, or two or more. The plurality of slits 44 are arranged above the pixel electrode 42. The plurality of slits 44 are arranged at equal intervals. The slits 44 extend in the Y direction, similar to the pixel electrode 42. The length of the slits 44 in the Y direction is set to be slightly shorter than the length of the pixel electrode 42 in the Y direction.

[0049] An alignment film 45 that controls the alignment of the liquid crystal layer 40 is provided on the common electrode 20 and the insulating layer 43. The alignment film 45 aligns the liquid crystal molecules horizontally in the initial state of the liquid crystal layer 40. The alignment film 45 is also rubbed so that the long axes of the liquid crystal molecules are oriented in the Y direction.

[0050] Next, the configuration of the CF substrate 11 side will be described.

[0051] A color filter 46 is provided on the CF substrate 11. The color filter 46 includes a red filter, a green filter, and a blue filter. Each pixel PX is provided with one of the red filter, the green filter, and the blue filter. A black matrix (not shown) is provided as a light-shielding layer at the boundary of the pixel PX.

[0052] An alignment film 47 that controls the alignment of the liquid crystal layer 40 is provided on the color filter 46. The alignment film 47 aligns the liquid crystal molecules horizontally in the initial state of the liquid crystal layer 40. The alignment film 47 is also rubbed so that the long axes of the liquid crystal molecules are oriented in the Y direction.

[0053] A polarizing plate (not shown) is provided on the TFT substrate 10 on the side opposite to the liquid crystal layer 40. A polarizing plate (not shown) is provided on the CF substrate 11 on the side opposite to the liquid crystal layer 40.

[0054] (Examples of materials) The scanning lines GL and the signal lines SL are made of, for example, any one of aluminum (Al), molybdenum (Mo), chromium (Cr), and tungsten (W), or an alloy containing one or more of these.

[0055] The common electrode 20 and the pixel electrodes 42 are made of a transparent electrode, for example, ITO (indium tin oxide).

[0056] The insulating layer 41 and the insulating layer 43 are made of a transparent insulating material, such as silicon nitride (SiN).

[0057] [1-3] Operation The operation of the liquid crystal display device 1 configured as above will now be described.

[0058] Fig. 8 is a timing chart illustrating the operation of the liquid crystal display device 1. Fig. 8 shows the waveforms of the scanning lines GL and the waveforms of the signal lines SL.

[0059] The gate driver 31 generates a gate signal that changes between voltage Vg1 and voltage Vg2. The voltage Vg1 is a low-level voltage, and the voltage Vg2 is a high-level voltage. For example, the voltage Vg1 is a positive voltage, and the voltage Vg2 is a negative voltage. The voltages Vg1 and Vg2 are set appropriately according to the specifications of the liquid crystal display device 1. The gate signal from the gate driver 31 is supplied to the gate of the TFT 36.

[0060] The source driver 32 generates a source signal that changes between voltage Vs1 and voltage Vs2. The voltage Vs1 is a low-level voltage, and the voltage Vs2 is a high-level voltage. For example, the voltage Vs1 is a positive voltage, and the voltage Vs2 is a negative voltage. The voltages Vs1 and Vs2 are set appropriately according to the specifications of the liquid crystal display device 1. The average voltage Vav in FIG. 8 is the average voltage (also referred to as an intermediate voltage) of the voltages Vs1 and Vs2. The source signal from the source driver 32 is supplied to the pixel electrode 42 via the TFT 36.

[0061] The common electrode driver 33 generates a common voltage Vcom and supplies the common voltage Vcom to the common electrode 20. The common voltage Vcom is used as a reference voltage and is higher than the voltage Vs1 and lower than the voltage Vs2. For example, the common voltage Vcom is lower than the average voltage Vav. For example, the common voltage Vcom is a negative voltage. The common voltage Vcom is set appropriately according to the specifications of the liquid crystal display device 1.

[0062] At time t0, the source driver 32 applies a voltage Vs2 to the signal line SL.

[0063] At time t1, the gate driver 31 applies a voltage Vg2 to the scanning line GL, which turns on the TFT 36 and applies the potential of the signal line SL to the pixel electrode 42.

[0064] At time t2, the gate driver 31 applies a voltage Vg1 to the scanning line GL, thereby turning off the TFT .

[0065] At time t3, the source driver 32 applies a voltage Vs1 to the signal line SL.

[0066] At time t4, the gate driver 31 applies a voltage Vg2 to the scanning line GL, which turns on the TFT 36 and applies the potential of the signal line SL to the pixel electrode 42.

[0067] At time t5, the gate driver 31 applies a voltage Vg1 to the scanning line GL, thereby turning off the TFT .

[0068] Thereafter, the liquid crystal display device 1 repeats the same operation as above. In this way, AC driving (also called inversion driving) of the liquid crystal display device 1 is realized. By performing AC driving, it is possible to suppress deterioration of the liquid crystal. The cycle of AC driving can be set arbitrarily.

[0069] Next, the alignment of the liquid crystal layer 40 will be described.

[0070] The off state is a state in which no electric field is applied to the liquid crystal layer 40, and the pixel electrode 42 is applied with the same common voltage Vcom as the common electrode 20, or with the ground voltage Vss (0 V). The on state is a state in which an electric field is applied to the liquid crystal layer 40, and the pixel electrode 42 is applied with a positive or negative voltage different from the common voltage Vcom.

[0071] In the off state, the liquid crystal molecules are set to their initial state, i.e., the long axes of the liquid crystal molecules are aligned in the Y direction, which is the same as the rubbing direction of the alignment film. In the off state, the liquid crystal display device 1 displays, for example, black.

[0072] In the on-state, an electric field indicated by the dashed arrow in FIG. 7 is applied to the liquid crystal layer 40. In a plan view, the liquid crystal molecules rotate in a direction oblique to the Y direction. This allows the liquid crystal display device 1 to control the amount of transmission of incident light. In other words, the transmittance of the liquid crystal display device 1 can be changed. In the on-state, the liquid crystal display device 1 displays color.

[0073] 2, in this embodiment, the common electrode 20 is connected to a ground terminal 24 via a resistive element 23. That is, the common electrode 20 is grounded via the resistive element 23.

[0074] While the common electrode driver 33 is not operating, charges accumulated on the common electrode 20 and on the interface of the common electrode 20 are discharged to the ground terminal 24 via the resistance element 23. "The common electrode driver 33 is operating" means that the common electrode driver 33 is applying the common voltage Vcom to the common electrode 20. "The common electrode driver 33 is not operating" means that the common electrode driver 33 is not applying the common voltage Vcom to the common electrode 20.

[0075] While the common electrode driver 33 is operating, the resistance element 23 functions to suppress current flow from the common electrode 20 to the ground terminal 24. The resistance value of the resistance element 23 is set based on the drive capability of the common electrode driver 33. The greater the drive capability of the common electrode driver 33, the greater the resistance value of the resistance element 23. The resistance element 23 is set to a relatively large resistance value so as to minimize interference with the voltage application operation of the common electrode driver 33 while the common electrode driver 33 is applying the common voltage Vcom to the common electrode 20.

[0076] 7, attention is focused on the path of the electric field applied to the liquid crystal layer 40. On the common electrode 20 side, there is an interface between the common electrode 20 and the alignment film 45, and an interface between the alignment film 45 and the liquid crystal layer 40. On the pixel electrode 42 side, there is an interface between the pixel electrode 42 and the insulating layer 43, an interface between the insulating layer 43 and the alignment film 45, and an interface between the alignment film 45 and the liquid crystal layer 40. Charge is accumulated at each interface when driven, but the layer structures on the common electrode 20 side and the pixel electrode 42 side are different, so the amount of accumulated charge differs.

[0077] A direct current (DC) component occurs due to an imbalance between the charge accumulated on the common electrode 20 side and the charge accumulated on the pixel electrode 42 side. The DC component is a constant DC voltage added to the AC voltage. The DC component causes burn-in and flicker.

[0078] However, in this embodiment, the charges accumulated in the layers provided on the TFT substrate 10 and at the interfaces between them can be discharged to the ground terminal 24 via the resistance element 23.

[0079] [1-4] Effects of the first embodiment In the first embodiment, the FFS mode liquid crystal display device 1 includes a TFT substrate 10, pixel electrodes 42 provided on the TFT substrate 10, and a common electrode 20 provided above the pixel electrodes 42. The common electrode 20 is connected to a ground terminal 24 via a wiring 22 and a resistor element 23, without going through an integrated circuit 12.

[0080] Therefore, according to the first embodiment, charges accumulated in the multiple layers provided on the TFT substrate 10 and at their interfaces can be discharged to the ground terminal 24 via the resistive element 23. This reduces the DC component generated in the liquid crystal display device 1, thereby reducing burn-in, flicker, and the like in the liquid crystal display device 1. This makes it possible to realize a liquid crystal display device that can improve display quality.

[0081] Furthermore, according to the configuration of the first embodiment, unnecessary charges accumulated in the liquid crystal display device 1 can be discharged more quickly using the resistive element 23 and the ground terminal 24.

[0082] Furthermore, the resistive element 23 and the ground terminal 24 are provided on the FPC 13 connected to the integrated circuit 12. This makes it possible to discharge unnecessary charges accumulated in the liquid crystal display device 1 without changing the configuration of the integrated circuit 12.

[0083] [2] Second embodiment In the second embodiment, a resistive element 23 is provided in the integrated circuit 12. Then, charges accumulated in the layers provided on the TFT substrate 10 and at the interfaces between them are discharged to a ground terminal via the resistive element 23.

[0084] 9 is a block diagram of a liquid crystal display device 1 according to a second embodiment of the present invention. The common electrode 20 is connected to a common electrode driver 33 via a wiring 21. The common electrode driver 33 supplies a common voltage Vcom to the common electrode 20 via the wiring 21.

[0085] The integrated circuit 12 includes a resistive element 23 and a ground terminal 24. The ground terminal 24 is a terminal to which a ground voltage Vss (0 V) is supplied. One end of the resistive element 23 is electrically connected to the wiring 21. The other end of the resistive element 23 is electrically connected to the ground terminal 24.

[0086] In the second embodiment, while the common electrode driver 33 is not operating, the charges accumulated on the common electrode 20 and the interface of the common electrode 20 are discharged to the ground terminal 24 via the resistance element 23. This reduces the DC component generated in the liquid crystal display device 1. As a result, burn-in, flicker, and the like in the liquid crystal display device 1 can be reduced.

[0087] [3] Third embodiment In the third embodiment, a switching element is used to switch the connection between the common electrode 20 and the ground terminal 24.

[0088] 10 is a schematic plan view of a liquid crystal display device 1 according to a third embodiment of the present invention. Like FIG. 2, FIG. 10 focuses on the common electrode 20.

[0089] The FPC 13 includes a switching element 25 and a ground terminal 24. One end of the switching element 25 is electrically connected to the common electrode 20 via a wiring 22. The other end of the switching element 25 is electrically connected to the ground terminal 24. The switching element 25 may be a field effect transistor (FET), a TFT, or the like. The switching element 25 is provided on wiring layers 13B and 13C of the FPC 13.

[0090] The switching operation of the switching element 25 is controlled by a control circuit 35. Specifically, a gate signal 26 is supplied from the control circuit 35 to the gate of the switching element 25. The control circuit 35 is included in the integrated circuit 12 of Fig. 10. Wiring for the gate signal 26 is provided within the FPC 13.

[0091] While the common electrode driver 33 is operating, the control circuit 35 turns off the switching element 25. This causes the common electrode driver 33 to apply the common voltage Vcom to the common electrode 20.

[0092] While the common electrode driver 33 is not operating, the control circuit 35 turns on the switching element 25. As a result, the electric charges accumulated in the common electrode 20 and the interface of the common electrode 20 are discharged to the ground terminal 24 via the switching element 25.

[0093] This reduces the DC component generated in the liquid crystal display device 1. As a result, burn-in, flicker, and the like in the liquid crystal display device 1 can be reduced.

[0094] In the above embodiment, the switching elements 25 are provided on the FPC 13, but the switching elements 25 may be provided somewhere along the wiring 22. For example, the switching elements 25 may be provided on the TFT substrate 10.

[0095] Furthermore, the above-mentioned resistive element 23 may be provided between the switching element 25 and the ground terminal 24. In this case, the resistive element 23 has the function of adjusting the current flowing between the common electrode 20 and the ground terminal 24.

[0096] [4] Fourth embodiment In the fourth embodiment, the switching element 25 and the ground terminal 24 are provided within the integrated circuit 12.

[0097] 11 is a block diagram of a liquid crystal display device 1 according to a fourth embodiment of the present invention. The common electrode 20 is connected to a common electrode driver 33 via a wiring 21.

[0098] The integrated circuit 12 includes a switching element 25 and a ground terminal 24. One end of the switching element 25 is electrically connected to the wiring 21. The other end of the switching element 25 is electrically connected to the ground terminal 24. A gate signal 26 is supplied to the gate of the switching element 25 from a control circuit 35.

[0099] While the common electrode driver 33 is operating, the control circuit 35 turns off the switching element 25. This causes the common electrode driver 33 to apply the common voltage Vcom to the common electrode 20.

[0100] While the common electrode driver 33 is not operating, the control circuit 35 turns on the switching element 25. As a result, the electric charges accumulated in the common electrode 20 and the interface of the common electrode 20 are discharged to the ground terminal 24 via the switching element 25.

[0101] This reduces the DC component generated in the liquid crystal display device 1. As a result, burn-in, flicker, and the like in the liquid crystal display device 1 can be reduced.

[0102] The above-mentioned resistive element 23 may be provided between the switching element 25 and the ground terminal 24 .

[0103] [5] Fifth embodiment The fifth embodiment is another example of the configuration of the pixel PX. In the fifth embodiment, the common electrode 20 is disposed on the lower side, and the pixel electrode 42 is disposed on the upper side.

[0104] Fig. 12 is a plan view of a pixel PX according to a fifth embodiment of the present invention, and Fig. 13 is a cross-sectional view of the pixel PX taken along line AA' in Fig. 12.

[0105] A common electrode 20 is provided on the insulating layer 41. The common electrode 20 has an area equal to or slightly larger than the display region 14. Unlike the first embodiment, the common electrode 20 does not have a slit.

[0106] A common electrode 20 and an insulating layer 43 are provided.

[0107] A pixel electrode 42 is provided on the insulating layer 43. The pixel electrode 42 extends in the Y direction. The pixel electrode 42 is provided for each pixel PX, and has an area that covers approximately the entire pixel region. The pixel electrode 42 has a plurality of slits (also called openings) 44. In this embodiment, a configuration in which the pixel electrode 42 has four slits 44 is shown as an example. The number of slits 44 may be one, or two or more. The multiple slits 44 are arranged at equal intervals. The slits 44 extend to near both ends of the pixel electrode 42 in the Y direction.

[0108] The pixel electrode 42 is electrically connected to the drain electrode of the TFT 36 via a contact (not shown). The common electrode 20 is provided with an opening (not shown) for passing the contact.

[0109] An alignment film 45 for controlling the alignment of the liquid crystal layer 40 is provided on the pixel electrodes 42 and the insulating layer 43 .

[0110] The other configurations are the same as those of the first embodiment. Furthermore, the second to fourth embodiments can also be applied to the fifth embodiment.

[0111] In each of the above embodiments, an FFS mode liquid crystal display device 1 has been described as an example, but this embodiment can also be applied to liquid crystal modes other than the FFS mode, such as IPS (In-Plane Switching) mode, Vertical Alignment (VA) mode, and TN (Twisted Nematic) mode.

[0112] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention. [Explanation of symbols]

[0113] 1...liquid crystal display device, 10...TFT substrate, 11...CF substrate, 12...integrated circuit, 13...FPC, 13A...base film, 13B, 13C...wiring layer, 13D, 13E...cover film, 14...display area, 15...wiring, 16...wiring, 20...common electrode, 21...wiring, 22...wiring, 23...resistance element, 24...ground terminal, 25...switching element, 26...gate signal, 30...pixel array, 31...gate driver, 32...source driver, 33...common electrode driver, 34...voltage generation circuit, 35...control circuit, 36...TFT, 40...liquid crystal layer, 41...insulating layer, 42...pixel electrode, 43...insulating layer, 44...slit, 45...alignment film, 46...color filter, 47...alignment film

Claims

1. first and second substrates; a liquid crystal layer provided between the first and second substrates; a common electrode provided on the first substrate and shared by a plurality of pixels; an integrated circuit provided on the first substrate and configured to drive the common electrode; a flexible printed circuit (FPC) connected to the integrated circuit; a resistive element provided on the FPC, the resistive element having one end connected to the common electrode and the other end connected to a ground terminal; Equipped with the FPC includes first and second insulating layers and a wiring layer provided between the first and second insulating layers; The wiring layer includes a plurality of wirings, the resistor element, and the ground terminal. LCD display device.

2. The resistor element is connected to the common electrode without passing through the integrated circuit. The liquid crystal display device according to claim 1 .

3. first and second substrates; a liquid crystal layer provided between the first and second substrates; a common electrode provided on the first substrate and shared by a plurality of pixels; an integrated circuit provided on the first substrate and configured to drive the common electrode; a flexible printed circuit (FPC) connected to the integrated circuit; a switching element provided on the FPC, the switching element having one end connected to the common electrode and the other end connected to a ground terminal; Equipped with the integrated circuit includes a driver that applies a common voltage to the common electrode and a control circuit; the control circuit turns on the switching element while the driver is not operating, the FPC includes first and second insulating layers and a wiring layer provided between the first and second insulating layers; The wiring layer includes a plurality of wirings, the switching element, and the ground terminal. LCD display device.

4. The switching element is connected to the common electrode without passing through the integrated circuit. The liquid crystal display device according to claim 3 .

5. The control circuit turns off the switching element while the driver is operating.

5. The liquid crystal display device according to claim 3 or 4.

6. a plurality of pixel electrodes provided on the first substrate so as to correspond to the plurality of pixels; an insulating layer provided on the plurality of pixel electrodes; Further comprising: The common electrode is provided on the insulating layer and has slits disposed above each of the plurality of pixel electrodes.

6. The liquid crystal display device according to claim 1.

7. an insulating layer provided on the first substrate; a plurality of pixel electrodes each having a slit, the pixel electrodes being provided on the insulating layer so as to correspond to the plurality of pixels; Further comprising: The common electrode is provided between the first substrate and the insulating layer.

6. The liquid crystal display device according to claim 1.

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