JP2017116820A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of flicker to improve display quality.SOLUTION: A liquid crystal display according to one embodiment comprises: a first substrate including pixel electrodes that are provided respectively for pixels arranged in a display area and a common electrode that faces the pixel electrodes; a second substrate that faces the first substrate; a liquid crystal layer that is encapsulated between the first substrate and the second substrate; and a driver that supplies a voltage to the common electrode. The common electrode includes a first electrode and a second electrode that is closer to an edge part of the display area than the first electrode. In displaying an image in the display area, the driver supplies, to the first electrode, a first voltage that changes with the lapse of time and supplies, to the second electrode, a second voltage different from the first voltage.SELECTED DRAWING: Figure 4

Description

  Embodiments described herein relate generally to a liquid crystal display device.

  An IPS (In-Plane-Switching) mode liquid crystal display device in which a pixel electrode and a common electrode are arranged on one substrate is known. In a FFS (Fringe Field Switching) mode liquid crystal display device which is a kind of IPS mode, a pixel electrode and a common electrode are opposed to each other with an insulating layer interposed therebetween. In addition, in an FFS mode liquid crystal display device, there is an AC driving method for supplying an AC signal to a pixel electrode.

  When the AC driving method is employed, flicker that causes the display image to flicker may occur. In general, the flicker becomes conspicuous with the passage of time after power is supplied to the liquid crystal display device. Further, flicker tends to be generated at the edge and the center of the display area.

JP 2009-282332 A JP 2002-358056 A JP 2010-243968 A

  An object of one embodiment of the present disclosure is to provide a liquid crystal display device that can suppress generation of flicker and improve display quality.

  A liquid crystal display device according to an embodiment includes a first substrate including a pixel electrode provided for each pixel arranged in a display region and a common electrode facing the pixel electrode, and a second substrate facing the first substrate. And a liquid crystal layer sealed between the first substrate and the second substrate, and a driver for supplying a voltage to the common electrode. The common electrode includes a first electrode and a second electrode closer to the edge of the display region than the first electrode. The driver supplies a first voltage that changes over time to the first electrode, and supplies a second voltage different from the first voltage to the second electrode when displaying an image in the display area.

FIG. 1 is a perspective view illustrating a schematic configuration of the liquid crystal display device according to the first embodiment. FIG. 2 is a diagram showing a schematic equivalent circuit of the liquid crystal display device according to the first embodiment. FIG. 3 is a diagram schematically illustrating an example of a cross section of the liquid crystal display device according to the first embodiment. FIG. 4 is a plan view schematically showing the shape of the common electrode according to the first embodiment. FIG. 5 is a plan view illustrating a part of a common electrode configured by segments. 6 is an enlarged view of the boundary between the first electrode and the second electrode in the common electrode shown in FIG. FIG. 7 is a diagram schematically showing a part of a cross section of the display panel taken along line VII-VII in FIG. FIG. 8 is a graph obtained by measuring the degree of flicker in the FFS mode liquid crystal display device. FIG. 9 is a diagram illustrating the cause of occurrence of flicker. FIG. 10 is a waveform diagram showing an example of control of the first voltage and the second voltage. FIG. 11 is a waveform diagram showing another control example of the first voltage and the second voltage. FIG. 12 is a waveform diagram showing still another control example of the first voltage and the second voltage. FIG. 13 is a plan view schematically showing the shape of the common electrode according to the second embodiment. FIG. 14 is a waveform diagram illustrating a control example according to the second embodiment of the first voltage, the second voltage, and the third voltage. FIG. 15 is a plan view schematically showing the shape of the common electrode according to the third embodiment. FIG. 16 is a plan view schematically showing the shape of the common electrode according to the fourth embodiment. FIG. 17 is an enlarged view showing the boundary between the first electrode and the second electrode according to the fifth embodiment. FIG. 18 is a diagram schematically showing a part of a cross section of the display panel taken along line XVII-XVII in FIG.

Several embodiments will be described with reference to the drawings.
It should be noted that the disclosure is merely an example, and those skilled in the art can easily conceive of appropriate changes while maintaining the gist of the invention are naturally included in the scope of the present invention. In addition, the drawings may be schematically represented in comparison with actual modes in order to clarify the description, but are merely examples, and do not limit the interpretation of the present invention. In each drawing, the reference numerals may be omitted for the same or similar elements arranged in succession. In addition, in the present specification and each drawing, components that perform the same or similar functions as those described above with reference to the previous drawings are denoted by the same reference numerals, and redundant detailed description may be omitted.

  In each embodiment, a transmissive liquid crystal display device including a backlight is disclosed as an example of a liquid crystal display device. However, each embodiment does not preclude the application of the individual technical ideas disclosed in each embodiment to other types of display devices. As another type of display device, for example, a liquid crystal display device having a reflective function of reflecting external light and using the reflected light for display is assumed.

(First embodiment)
FIG. 1 is a perspective view showing a schematic configuration of a liquid crystal display device 1 according to the first embodiment. The liquid crystal display device 1 can be used for various devices such as a smartphone, a tablet terminal, a mobile phone terminal, a personal computer, a television receiver, an in-vehicle device, a game machine, and a wearable terminal.

  The liquid crystal display device 1 includes a display panel 2, a backlight 3, a driver IC 4 that drives the display panel 2, a control module 5 that controls operations of the display panel 2 and the backlight 3, and the display panel 2 and the backlight 3. Flexible circuit boards FPC1 and FPC2 for transmitting a control signal to.

  In the present embodiment, a first direction X and a second direction Y are defined as shown in FIG. The first direction X is a direction along the short side of the display panel 2, for example. The second direction Y is a direction along the long side of the display panel 2, for example. In the illustrated example, the directions X and Y intersect perpendicularly to each other, but the directions X and Y may intersect at other angles.

  The display panel 2 includes a first substrate SUB1, a second substrate SUB2 facing the first substrate SUB1, and a liquid crystal layer (a liquid crystal layer LC described later) disposed between the first substrate SUB1 and the second substrate SUB2. I have. The display panel 2 has a display area DA (active area) for displaying an image. The display panel 2 includes, for example, a plurality of pixels PX arranged in a matrix in the first direction X and the second direction Y in the display area DA.

  The backlight 3 is opposed to the first substrate SUB1. For example, the driver IC 4 is mounted on the first substrate SUB1. However, the driver IC 4 may be mounted on the control module 5 or the like. The flexible circuit board FPC1 connects the first substrate SUB1 and the control module 5. The flexible circuit board FPC 2 connects the backlight 3 and the control module 5.

  FIG. 2 is a diagram showing a schematic equivalent circuit of the liquid crystal display device 1. The liquid crystal display device 1 includes a gate driver GD, a source driver SD, a scanning line G, and a signal line S. The scanning line G is connected to the gate driver GD. The signal line S is connected to the source driver SD and intersects each scanning line G.

  Each scanning line G extends in the first direction X and is arranged in the second direction Y in the display area DA. Each signal line S extends in the second direction Y and is aligned in the first direction X in the display area DA. Each scanning line G and each signal line S are formed on the first substrate SUB1.

  In the example of FIG. 2, a region defined by each scanning line G and each signal line S corresponds to one subpixel SPX. For example, one pixel PX includes sub-pixels SPX that display red (R), green (G), and blue (B). The pixel PX may further include a subpixel that displays white, or may include a plurality of subpixels corresponding to the same color. In the present disclosure, the subpixel SPX may be simply referred to as a pixel.

  Each subpixel SPX includes a switching element SW, a pixel electrode PE, and a common electrode CE. The switching element SW, the pixel electrode PE, and the common electrode CE are also formed on the first substrate SUB1 like the scanning line G and the signal line S. The switching element SW and the pixel electrode PE are provided for each pixel PX. The switching element SW is a thin film transistor, for example, and is electrically connected to the scanning line G, the signal line S, and the pixel electrode PE. The common electrode CE is formed over the plurality of subpixels SPX and is opposed to the pixel electrodes PE of these subpixels SPX.

  The driver IC 4 includes a common electrode driver 40 that supplies a voltage to the common electrode CE. In the present embodiment, the common electrode driver 40 changes the voltage supplied to the common electrode CE according to the count value of the counter 50. For example, the counter 50 counts the time from when power supply to the liquid crystal display device 1 is stopped to when it is restarted. As another example, the counter 50 may count the time from when the backlight 3 is turned off to when it is next turned on. The counter 50 is provided, for example, in the liquid crystal display device 1 and includes a battery, and can operate while power supply to the liquid crystal display device 1 is stopped. However, the counter 50 may be provided in an electronic device in which the liquid crystal display device 1 is mounted. In this case, by receiving power supply from the electronic device, the counter 50 can be operated regardless of whether or not power is supplied to the liquid crystal display device 1.

  The gate driver GD sequentially supplies a scanning signal to each scanning line G. The source driver SD selectively supplies a video signal to each signal line S. When a scanning signal is supplied to the scanning line G connected to a certain switching element SW and a video signal is supplied to the signal line S connected to the switching element SW, a voltage corresponding to the video signal is applied to the pixel electrode PE. To be applied. At this time, due to the electric field generated between the pixel electrode PE and the common electrode CE, the alignment of the liquid crystal molecules in the liquid crystal layer LC changes from the initial alignment state where no voltage is applied. By such an operation, an image is displayed in the display area DA.

  FIG. 3 is a diagram schematically showing an example of a cross section of the liquid crystal display device 1 in the display area DA. The cross section shown in this figure focuses on one subpixel SPX. In the example of FIG. 3, the first substrate SUB1 includes a first insulating substrate 10, a first insulating layer 11, a second insulating layer 12, a third insulating layer 13, a first alignment film 14, and a pixel electrode PE. And a common electrode CE and a signal line S.

  The first insulating substrate 10 has a first surface 10A facing the second substrate SUB2 and a second surface 10B facing the backlight 3 described above. The first insulating layer 11 is formed on the first surface 10A. The signal line S is formed on the first insulating layer 11. The second insulating layer 12 covers the first insulating layer 11 and the signal line S. The common electrode CE is formed on the second insulating layer 12. The third insulating layer 13 covers the common electrode CE. The pixel electrode PE is formed on the third insulating layer 13. The first alignment film 14 covers the pixel electrode PE and the third insulating layer 13.

  The pixel electrode PE has a slit ST. The pixel electrode PE and the common electrode CE are formed of a transparent conductive material such as indium tin oxide (ITO), for example. A storage capacitor for holding charges is formed between the pixel electrode PE and the common electrode CE.

  The second substrate SUB2 includes a second insulating substrate 20, a light shielding layer 21, a color filter 22, an overcoat layer 23, and a second alignment film 24. The second insulating substrate 20 has a first surface 20A facing the first substrate SUB1, and a second surface 20B opposite to the first surface 20A. The light shielding layer 21 is formed on the first surface 20A and partitions the sub-pixel SPX. The color filter 22 is also formed on the first surface 20A and is colored in a color corresponding to the sub-pixel SPX. The overcoat layer 23 covers the color filter 22. The second alignment film 24 covers the overcoat layer 23. A liquid crystal layer LC including liquid crystal molecules is formed between the first alignment film 14 and the second alignment film 24.

  A first optical element OD1 including a first polarizing plate PL1 is disposed on the second surface 10B of the first insulating substrate 10. On the second surface 20B of the second insulating substrate 20, the second optical element OD2 including the second polarizing plate PL2 is disposed. The polarization axes (or absorption axes) of the first polarizing plate PL1 and the second polarizing plate PL2 are orthogonal to each other.

  Note that the structure shown in FIG. 3 is applicable to a liquid crystal display device according to an FFS mode, which is a kind of IPS mode. In this mode, the liquid crystal layer LC is driven mainly using a so-called lateral electric field (an electric field substantially parallel to the main surface of the substrate or a fringe electric field) generated between the pixel electrode PE and the common electrode CE.

  Subsequently, the common electrode CE will be described. FIG. 4 is a plan view schematically showing the shape of the common electrode CE according to the present embodiment. As shown in this figure, the common electrode CE is formed over the entire surface of the display area DA. The common electrode CE and the display area DA are surrounded by the seal material SL. The sealing material SL is disposed between the first substrate SUB1 and the second substrate SUB2, and bonds the first substrate SUB1 and the second substrate SUB2 together. The above-described liquid crystal layer LC is sealed between the first substrate SUB1 and the second substrate SUB2 by the sealing material SL.

  The common electrode CE includes a first electrode E1 and a second electrode E2. In the example of FIG. 4, the first electrode E1 has a rectangular shape, and the second electrode E2 has a rectangular frame shape surrounding the first electrode E1. Therefore, the second electrode E2 is located closer to the edge of the display area DA and the seal material SL than the first electrode E1. For example, the width W of the second electrode E2 is constant over the entire circumference. However, the width W may be different depending on the position. As an example, the width W is 1 mm or more, preferably 5 mm or more.

  The first electrode E1 is not limited to a rectangular shape, and at least a part thereof may be a curved shape. The second electrode E2 is not limited to the rectangular frame shape, and at least a part of the inner periphery and the outer periphery may be curved.

  The first electrode E1 and the second electrode E2 are electrically connected to the common electrode driver 40. The common electrode driver 40 supplies a common voltage Vcom to the first electrode E1 and the second electrode E2. In the following description, the common voltage Vcom supplied to the first electrode E1 is referred to as a first voltage V1, and the common voltage Vcom supplied to the second electrode E2 is referred to as a second voltage V2.

  In FIG. 4, each of the 1st electrode E1 and the 2nd electrode E2 is represented as a continuous electrode which spreads uniformly. However, the first electrode E1 and the second electrode E2 may be a set of a plurality of segments having a predetermined size.

  FIG. 5 is a plan view illustrating a part of the common electrode CE configured by segments. In this example, the first electrode E1 and the second electrode E2 are configured by a rectangular segment SG. The segments SG constituting the first electrode E1 are electrically connected to each other. The segments SG constituting the second electrode E2 are electrically connected to each other. The segment SG constituting the first electrode E1 and the segment SG constituting the second electrode E2 are not electrically connected.

  The segments SG are arranged in a matrix along the first direction X and the second direction Y, for example. The segment SG is not limited to a rectangular shape, and may be another shape such as a parallelogram. The segment SG can be formed of a transparent conductive material such as ITO.

  FIG. 6 is an enlarged view showing the boundary between the first electrode E1 and the second electrode E2 in the common electrode CE shown in FIG. A slit-shaped gap GP is formed between the first electrode E1 and the second electrode E2. That is, the first electrode E1 and the second electrode E2 are physically and electrically disconnected. For example, the gap GP overlaps the light shielding layer 21 in a plan view as illustrated.

  FIG. 7 is a diagram schematically showing a part of a cross section of the display panel 2 along the line VII-VII in FIG. The first electrode E1 and the second electrode E2 are both formed on the second insulating layer 12. The gap GP passes between two subpixels SPX adjacent in the first direction X or the second direction Y (between the two pixel electrodes PE).

  For example, when the source driver SD supplies an AC video signal to the signal line S, flicker that causes the display image in the display area DA to blink may occur. FIG. 8 is a graph obtained by measuring the degree of flicker in the FFS mode liquid crystal display device as in the present embodiment. The horizontal axis is the elapsed time [min] from the start of power supply to the liquid crystal display device, and the vertical axis is the flicker value [%, FMA]. FMA is an abbreviation for Flicker Modulation Amplitude and represents the degree of flicker. Since the backlight is turned on at the start of power supply, the horizontal axis is also the elapsed time since the backlight is turned on.

  The measurement was performed near the center and the periphery of the display area DA. R1 in FIG. 8 is a measurement result near the center, and R2 is a measurement result near the periphery. The vicinity of the center of the display area DA is an area where the resistance of the liquid crystal layer LC is high, and the vicinity of the periphery of the display area DA is an area where the resistance of the liquid crystal layer LC is lower (than the vicinity of the center).

  As can be seen from the measurement results R1 and R2, the flicker value increases with time in both the vicinity of the center and the vicinity of the periphery. At the beginning of the measurement, there was no significant difference between the flicker values near the center and the periphery, but the difference became larger as time passed. When a sufficient amount of time has elapsed from the start of power supply, these flicker values have a certain difference and stabilized at a predetermined value.

  One consideration of the cause of such flicker will be described with reference to FIG. The left waveform in the figure shows the relationship between the AC voltage Vsig supplied to the pixel electrode and the common voltage Vcom supplied to the common electrode in a state where flicker is not generated, and the right waveform is in the state where flicker is generated. The relationship between AC voltage Vsig and common voltage Vcom is shown. Here, it is assumed that the common voltage Vcom is constant.

  As soon as power supply to the liquid crystal display device is started, the amplitude center C of the AC voltage Vsig and the common voltage Vcom coincide with each other as shown on the left waveform. On the other hand, when a certain amount of time has elapsed since the start of power supply, it has been found that the amplitude center C of the AC voltage Vsig and the common voltage Vcom are shifted as shown in the waveform on the right side.

  The state in which this deviation occurs corresponds to a state in which a DC component corresponding to the difference ΔV between the amplitude center C and the common voltage Vcom is applied between the pixel electrode and the common electrode. Since the potential difference between the pixel electrode and the common electrode changes depending on whether the polarity of the AC voltage Vsig is positive or negative, flicker is generated according to the AC frequency. Although FIG. 9 shows an example in which the amplitude center C is shifted in the positive direction with respect to the common voltage Vcom, flicker occurs in the same manner even when the amplitude center C is shifted in the negative direction.

  In the present embodiment, flicker is suppressed by changing the common voltage Vcom supplied to the common electrode CE over time. Further, by making the first voltage V1 supplied to the first electrode E1 different from the second voltage V2 supplied to the second electrode E2, the difference in the degree of flicker according to the position is absorbed, which is suitable for the entire display area DA. To suppress flicker.

  Specifically, the first voltage V1 is changed over time so that the amplitude center of the alternating voltage Vsig of the pixel electrode PE facing the first electrode E1 matches the first voltage V1. Further, the second voltage V2 is changed over time so that the amplitude center of the alternating voltage Vsig of the pixel electrode PE facing the second electrode E2 matches the second voltage V2.

  The first voltage V1 and the second voltage V2 do not have to coincide with the amplitude center of the AC voltage Vsig. Even in this case, flicker can be reduced by changing the first voltage V1 and the second voltage V2 so as to approach at least the amplitude center. Further, the amplitude center of the AC voltage Vsig of each pixel electrode PE facing the first electrode E1 may vary depending on the position in the display area DA. Therefore, a voltage at which flicker is preferably suppressed in the entire region overlapping with the first electrode E1 may be specified by experiment or simulation, and the first voltage V1 may be controlled to the specified voltage. The second voltage V2 can be similarly controlled.

Hereinafter, control examples of the first voltage V1 and the second voltage V2 will be described with reference to FIGS.
FIG. 10 is a waveform diagram showing one control example of the first voltage V1 and the second voltage V2. In the conventional example, the common voltage Vcom is constant at V0. In the example of FIG. 10, both the first voltage V1 and the second voltage V2 decrease with time.

  Specifically, the first voltage V1 is the first initial value Vi1 at the start of power supply to the liquid crystal display device 1, decreases linearly with time, and eventually stabilizes at the first convergence value Vs1. The second voltage V2 is the second initial value Vi2 when power supply to the liquid crystal display device 1 is started. The second voltage V2 decreases linearly with the passage of time and eventually stabilizes at the second convergence value Vs2.

  In the example of FIG. 10, the initial values Vi1 and Vi2 are the same. The convergence values Vs1 and Vs2 are different values, and Vs1 <Vs2. The first voltage V1 is smaller than the second voltage V2 at any time except for the beginning of power supply (V1 <V2). Further, the gradient at which the second voltage V2 decreases is smaller than the gradient at which the first voltage V1 decreases. Such waveforms of the first voltage V1 and the second voltage V2 are set in advance in a memory accessible by the common electrode driver 40, for example. The specific waveforms of the first voltage V1 and the second voltage V2 may be determined as appropriate so that the flicker in each time phase is suitably suppressed.

  Although FIG. 10 shows an example in which the first voltage V1 and the second voltage V2 are decreased with the passage of time, the first voltage V1 and the second voltage V2 may be increased with the passage of time. In this case, Vs1> Vs2, and V1> V2 except at the beginning of power supply. The rise and fall of these voltages are determined according to whether the amplitude center described above shifts in the positive direction or the negative direction with time.

  Note that the relationship of | Vs1 |> | Vs2 | and | V1 |> | V2 | holds true regardless of whether the first voltage V1 and the second voltage V2 rise or fall. The gradient at which the second voltage V2 changes is smaller than the gradient at which the first voltage V1 changes.

  FIG. 11 is a waveform diagram showing another control example of the first voltage V1 and the second voltage V2. This example is different from the example shown in FIG. 10 in that the first voltage V1 and the second voltage V2 change in a curved shape. When the flicker value changes in a curved line as shown in FIG. 8, flicker can be more suitably suppressed by changing the first voltage V1 and the second voltage V2 in a curved line in accordance with this. As in the example of FIG. 10, the first voltage V1 and the second voltage V2 may increase with time.

  FIG. 12 is a waveform diagram showing still another control example of the first voltage V1 and the second voltage V2. In this example, waveforms are shown in the case where power supply (or backlight lighting) and stop to the liquid crystal display device 1 are repeated. Specifically, power supply to the liquid crystal display device 1 is started at timing T1, stopped at timing T2, restarted at timing T3, stopped at timing T4, and restarted at timing T5.

  The first voltage V1 and the second voltage V2 are lowered in the period (T1-T2, T3-T4, T5-) during which the power is supplied to the liquid crystal display device 1 as in the example of FIG. If the power supply stop time is short, the influence at the time of the previous power supply is not sufficiently eliminated, and there is a possibility that a large flicker occurs from the time of restarting the power supply. Therefore, in the example of FIG. 12, the first initial value Vi1 and the second initial value Vi2 are dynamically determined according to the previous power supply stop time.

  Assume that the period P1 from timing T2 to T3 is sufficiently long, while the period P2 from timing T4 to T5 is short. In this case, as shown in FIG. 12, the common electrode driver 40 sets (resets) the first initial value Vi1 and the second initial value Vi2 at the timing T3 to predetermined values as in the example of FIG. On the other hand, the common electrode driver 40 sets the first initial value Vi1 and the second initial value Vi2 at the timing T5 to values smaller than the example in FIG. 10 (values having large absolute values). The first initial value Vi1 and the second initial value Vi2 can be determined using, for example, a predetermined calculation formula or table and the count value of the counter 50 described above.

  Further, the first initial value Vi1 and the second initial value Vi2 may be determined in consideration of not only the previous power supply stop time but also the previous power supply time. For example, the first initial value Vi1 and the second initial value Vi2 may be increased (the absolute value is decreased) as the previous power supply time is shorter. Further, only one of the first initial value Vi1 and the second initial value Vi2 may be determined according to the previous power supply stop time or the previous power supply time.

  As described above, in the present embodiment, the common electrode CE is divided into the first electrode E1 and the second electrode E2, and different voltages are supplied to the electrodes E1 and E2. Accordingly, it is possible to supply an appropriate voltage according to the position of the display area DA to the common electrode CE, and it is possible to suitably suppress the occurrence of flicker over the entire display area DA.

  Specifically, the first voltage V1 supplied to the first electrode E1 and the second voltage V2 supplied to the second electrode E2 are changed over time. Thereby, the flicker which becomes large with progress of time can be suppressed more suitably.

When the first voltage V1 and the second voltage V2 are made different, an electric field is generated between the first electrode E1 and the second electrode E2. When this electric field acts on the liquid crystal layer LC, the display can be affected. However, in the present embodiment, as shown in FIG. 6, the light shielding layer 21 overlaps the gap GP between the first electrode E1 and the second electrode E2. Therefore, even if the electric field acts on the liquid crystal layer LC, the influence on the display due to this can be prevented or reduced.
In addition to these, various suitable effects can be obtained from this embodiment.

(Second Embodiment)
A second embodiment will be described. In the present embodiment, another configuration that can be applied to the common electrode CE is disclosed. Structures not particularly mentioned are the same as those in the first embodiment.

  FIG. 13 is a plan view schematically showing the shape of the common electrode CE according to the present embodiment. The common electrode CE includes a third electrode E3 in addition to the first electrode E1 and the second electrode E2. The third electrode E3 is disposed between the first electrode E1 and the second electrode E2. In the example of FIG. 13, the first electrode E1 has a rectangular shape, the third electrode E3 has a rectangular frame shape surrounding the first electrode E1, and the second electrode E2 has a rectangular frame shape surrounding the third electrode E3. . For example, the width of the second electrode E2 and the width of the third electrode E3 are constant over the entire circumference. However, these widths may differ depending on the position. As an example, the combined width W of the second electrode E2 and the third electrode E3 is 1 mm or more, preferably 5 mm or more.

  The first electrode E1 is not limited to a rectangular shape, and at least a part thereof may be a curved shape. Further, the second electrode E2 and the third electrode E3 are not limited to the rectangular frame shape, and at least a part of the inner periphery and the outer periphery may be curved.

  In FIG. 13, each of the electrodes E <b> 1 to E <b> 3 is represented as a continuous electrode that extends uniformly. However, each of the electrodes E1 to E3 may be a set of a plurality of segments having a predetermined size, for example, as shown in FIG.

  Each of the electrodes E1 to E3 is electrically connected to the common electrode driver 40. The common electrode driver 40 supplies the first voltage V1 to the first electrode E1, supplies the second voltage V2 to the second electrode E2, and supplies the third voltage V3 to the third electrode E3.

  FIG. 14 is a waveform diagram illustrating an example of control of the first voltage V1, the second voltage V2, and the third voltage V3. The first voltage V1 and the second voltage V2 are the same as in the example of FIG. The third voltage V3 is the third initial value Vi3 at the start of power supply to the liquid crystal display device 1, decreases linearly with the passage of time, and eventually stabilizes at the third convergence value Vs3.

  In the example of FIG. 14, the initial values Vi1, Vi2, Vi3 are the same. The convergence values Vs1, Vs2, and Vs3 are different values, and Vs1 <Vs3 <Vs2. The third voltage V3 is greater than the first voltage V1 (V3> V1) and smaller than the second voltage V2 (V3 <V2) at any time except for the beginning of power supply. Such waveforms of the voltages V1 to V3 are set in advance in a memory accessible by the common electrode driver 40, for example. The specific waveforms of the voltages V1 to V3 may be determined as appropriate so that the flicker in each time phase is suitably suppressed.

  Although FIG. 14 shows an example in which the voltages V1 to V3 are decreased with the passage of time, the voltages V1 to V3 may be increased with the passage of time. The relationship of | Vs1 |> | Vs3 |> | Vs2 | and | V1 |> | V3 |> | V2 | is established regardless of whether the voltages V1 to V3 rise or fall. In addition, the gradient in which each of the voltages V1 to V3 decreases or increases is the largest at the first voltage V1, the second largest at the third voltage V3, and the smallest at the second voltage V2.

  Each of the voltages V1 to V3 may change in a curved line as in the example of FIG. The initial values Vi1 to Vi3 may be determined dynamically based on the previous power supply stop time or the previous power supply time, as in the example of FIG.

  If the common electrode CE is divided into three as in the present embodiment, flicker can be suppressed more accurately. If the common electrode CE is divided into four or more, not limited to three, flicker can be more accurately suppressed.

(Third embodiment)
A third embodiment will be described. In the present embodiment, still another configuration that can be applied to the common electrode CE is disclosed. Structures not particularly mentioned are the same as those in the above-described embodiments.

  FIG. 15 is a plan view schematically showing the shape of the common electrode CE according to the present embodiment. Similar to FIG. 13, the common electrode CE includes a first electrode E1, a second electrode E2, and a third electrode E3. The first electrode E1 has a rectangular shape. The third electrode E3 surrounds the three sides of the first electrode E1, but does not surround the lower side ES in the drawing. The second electrode E2 surrounds the three sides of the third electrode E3, but does not surround the lower end of the third electrode E2 in the drawing and the side ES of the first electrode E1.

  The side ES is adjacent to, for example, a region where the driver IC 4 is mounted on the first substrate SUB1. This region is a non-opposing region (wiring region) where the first substrate SUB1 and the second substrate SUB2 do not face each other.

With the configuration of the present embodiment, the common electrode driver 40 and the electrodes E1 to E3 can be easily connected. That is, with the configuration of FIG. 13, it is necessary to devise a wiring for connecting the first electrode E1 and the common electrode driver 40 so as not to contact the second electrode E2 and the third electrode E3. . On the other hand, in the configuration of FIG. 15, the common electrode driver 40 and the side ES can be connected without requiring any special device. Similarly, the third electrode E3 can be easily connected to the common electrode driver 40 as compared with the configuration of FIG.
As shown in FIG. 4, in the common electrode CE that does not include the third electrode E3, one side of the first electrode E1 may not be surrounded by the second electrode E2.

(Fourth embodiment)
A fourth embodiment will be described. In the present embodiment, still another configuration that can be applied to the common electrode CE is disclosed. Structures not particularly mentioned are the same as those in the first embodiment.

  FIG. 16 is a plan view schematically showing the shape of the common electrode CE according to the present embodiment. The common electrode CE in this figure includes a plurality of first electrodes E1 extending in the second direction Y and a plurality of second electrodes E2 extending in the second direction Y. The first electrode E1 and the second electrode E2 are arranged in the first direction X.

  Specifically, one second electrode E2 is arranged at the left end and the right end in the drawing, and the first electrodes E1 are arranged between the second electrodes E2. Each first electrode E1 and each second electrode E2 are connected to a common electrode driver 40. However, the number of the first electrode E1 and the second electrode E2 shown in the figure is an example, and these may be increased or decreased as appropriate.

  The common electrode CE configured as described above can be used for a liquid crystal display device having a touch panel function, for example. That is, if the detection electrode facing the common electrode CE is formed on the outer surface of the second substrate SUB2 or a separate substrate, the display area DA is based on the change in capacitance formed between the common electrode CE and the detection electrode. It is possible to detect an object such as a user's finger that is close to the object.

  FIG. 16 shows an example in which the first electrode E1 and the second electrode E2 extend in the second direction Y and are aligned in the first direction X. However, these electrodes extend in the first direction X and extend in the second direction Y. You may line up.

(Fifth embodiment)
A fifth embodiment will be described. As described above in the first embodiment, in the common electrode CE shown in FIGS. 4 and 16, when the first voltage V1 and the second voltage V2 are different, an electric field is generated between the first electrode E1 and the second electrode E2. When this electric field acts on the liquid crystal layer LC, the display can be affected. In the common electrode CE shown in FIGS. 13 and 15, similar electric fields are generated between the first electrode E1 and the third electrode E3 and between the second electrode E2 and the third electrode E3. In the present embodiment, a configuration for suitably preventing the influence of such an electric field on display is disclosed.

  Assume that the present embodiment is applied to the common electrode CE shown in FIG. 4 or FIG. FIG. 17 is an enlarged view showing the boundary between the first electrode E1 and the second electrode E2. FIG. 17 differs from FIG. 6 in that a shield electrode SE that overlaps the gap GP in plan view is provided.

  FIG. 18 is a diagram schematically showing a part of a cross section of the display panel 2 taken along line XVII-XVII in FIG. The shield electrode SE is formed on the same layer as the pixel electrode PE, that is, on the third insulating layer 13. Although not shown in FIG. 18, the shield electrode SE is covered with the first alignment film 14. For example, the shield electrode SE is formed of the same transparent conductive material as the pixel electrode PE. 17 and 18, the width of the light shielding layer 21 is larger than the width of the shield electrode SE, and the shield electrode SE completely overlaps the light shielding layer 21 in plan view.

  The shield electrode SE is electrically connected to, for example, the driver IC 4. The driver IC 4 supplies the voltage Vse to the shield electrode SE. For example, if the liquid crystal display device 1 is in the normally black mode, the voltage Vse may be the same as the voltage during black display applied to the pixel electrode PE. The voltage Vse may be the first voltage V1, the second voltage V2, or an intermediate value between the first voltage V1 and the second voltage V2.

  Since the electric field formed between the first electrode E1 and the second electrode E2 is prevented by the shield electrode SE, the influence on the liquid crystal layer LC can be reduced or prevented. Even when the shield electrode SE cannot completely prevent the electric field, the light shielding layer 21 prevents the influence on the display. Thus, with the configuration of the present embodiment, it is possible to prevent the display quality from being deteriorated due to the potential difference between the first voltage V1 and the second voltage V2.

  17 and 18, the present embodiment has been described with respect to the common electrode CE shown in FIG. 4 or FIG. 16, but between the first electrode E1 and the third electrode E3 shown in FIGS. 13 and 14. A shield electrode SE may be provided between the second electrode E2 and the third electrode E3.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

For example, in the first embodiment, an example in which the first voltage V1 and the second voltage V2 are changed over time has been described. However, it is not necessary to change only the first voltage V1 and change the second voltage V2. In the second embodiment and the third embodiment, it is not necessary to change only the first voltage V1 and the third voltage V3 and change the second voltage V2.
The configurations disclosed in the embodiments can be combined as appropriate.

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 2 ... Display panel, 3 ... Back light, 4 ... Driver IC, 21 ... Light shielding layer, 40 ... Common electrode driver, 50 ... Counter, SUB1 ... 1st board | substrate, SUB2 ... 2nd board | substrate, LC ... Liquid crystal layer, DA ... display region, PX ... pixel, PE ... pixel electrode, CE ... common electrode, SL ... sealing material, E1 ... first electrode, E2 ... second electrode, E3 ... third electrode, V1 ... first voltage , V2 ... second voltage, V3 ... third voltage.

Claims (10)

A first substrate comprising a pixel electrode provided for each pixel arranged in the display area, and a common electrode facing the pixel electrode;
A second substrate facing the first substrate;
A liquid crystal layer sealed between the first substrate and the second substrate;
A driver for supplying a voltage to the common electrode;
With
The common electrode includes a first electrode and a second electrode closer to the edge of the display area than the first electrode,
The driver supplies a first voltage that changes over time to the first electrode and displays a second voltage different from the first voltage to the second electrode when displaying an image in the display area.
Liquid crystal display device. The driver lowers or raises the first voltage from a first initial value over time;
The liquid crystal display device according to claim 1. The driver lowers or raises the second voltage from a second initial value over time with a slope smaller than the first voltage;
The liquid crystal display device according to claim 2. The driver resets the first voltage to the first initial value and resets the second voltage to the second initial value when restarted after power supply to the liquid crystal display device is stopped;
The liquid crystal display device according to claim 3. The driver determines at least one of the first initial value and the second initial value according to a time during which power supply to the liquid crystal display device is stopped;
The liquid crystal display device according to claim 4. The second electrode surrounds the first electrode;
The liquid crystal display device according to claim 1. The first electrode has a rectangular shape,
The second electrode surrounds the first electrode except at least one side of the first electrode;
The liquid crystal display device according to claim 1. The common electrode further includes a third electrode disposed between the first electrode and the second electrode,
The driver supplies a third voltage different from the first voltage and the second voltage to the third electrode when displaying an image in the display region.
The liquid crystal display device according to claim 6 or 7. The second substrate includes a light shielding layer that overlaps with a gap between the first electrode and the second electrode in plan view.
The liquid crystal display device according to claim 1. The pixel electrode is disposed between the common electrode and the liquid crystal layer,
The first substrate further includes a shield electrode disposed in the same layer as the pixel electrode,
The shield electrode overlaps with the gap between the first electrode and the second electrode in a plan view;
The liquid crystal display device according to claim 1.

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