JP2005284056A - Liquid crystal display and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce lateral crosstalks, by driving a dummy pixel electrode provided at both sides of an effective display region at a gradation different from the effective display region. <P>SOLUTION: In a liquid crystal display using a TFD element, a plurality of the dummy pixel electrodes 80 are provided so as to make a vertical row on both sides of the effective display region V, respectively. Since each dummy pixel electrode 80 is covered with a black light shielding layer BM, an observer cannot see it, even if each dummy pixel electrode 80 is driven to display an image. When gray or the like is made the background color for displaying white or black rectangle, the dummy pixel electrode 80 is driven at gradation different from the gradation of the effective display region V by a first gradation control method. Thereby a gradation level can be prevented from concentrating on the same line to reduce the lateral crosstalks. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device and an electronic apparatus suitable for use in displaying various types of information.

  In a liquid crystal panel called a two-terminal element type active matrix or TFD (Thin Film Diode), a scanning line is provided on one of two substrates facing each other, and a signal line (data line) is provided on the other substrate. In addition, a pixel electrode is formed, and liquid crystal is sealed between both substrates. The other substrate is provided with an element having a nonlinear current-voltage characteristic, and the element is connected to the pixel electrode and the signal line, respectively.

  However, in such a TFD liquid crystal panel, when the level of the pixels included in one line is concentrated on a specific gradation during the display of one line (scanning line) on the display screen, the signal electrode is simultaneously formed. The potential of the line changes. This potential change propagates to each pixel through the scanning line, and causes horizontal crosstalk (hereinafter referred to as “lateral crosstalk”). Here, as described above, horizontal crosstalk means that on the display image, although the same gradation is displayed in the line where the pixel level is concentrated on a specific gradation and the line where the pixel level is not, This means that the display level is different.

  As this type of liquid crystal display device, for example, even when a charge / discharge driving method is used, a liquid crystal display device that improves contrast while eliminating crosstalk of the immediately preceding data has been proposed (for example, patents). Reference 1).

Japanese Patent Laid-Open No. 11-133377

  The present invention has been made in view of the above points, and an object thereof is to reduce lateral crosstalk.

  In one aspect of the present invention, a liquid crystal display device includes a plurality of signal lines, a plurality of pixel electrodes, and a plurality of switching elements connected to each of the signal lines and the pixel electrodes. A substrate, a second substrate having a plurality of scanning lines and facing the first substrate, a liquid crystal layer sandwiched between the first substrate and the second substrate, the scanning lines and the signal lines A driving circuit for driving the liquid crystal by supplying a signal to the plurality of pixel electrodes, wherein the plurality of pixel electrodes are arranged in the direction of extension of the scanning lines in the display region in which the display pixel electrodes and the display pixel electrodes are provided. And the light-shielded dummy pixel electrode is provided, and the drive circuit includes gradation control means for driving the dummy pixel electrode with a gradation value different from that of the display pixel electrode.

  The liquid crystal display device is an active matrix drive type liquid crystal display device having a switching element such as a so-called TFD or TFT (Thin Film Transistor). In this liquid crystal display device, the plurality of pixel electrodes include dummy pixel electrodes which are located at the end of the scanning line extending direction of the display area where the display pixel electrodes are provided and are shielded by a black light shielding layer or the like. In a preferred example, the dummy pixels may be provided on both sides of the display region in the extension direction of the scanning line. For this reason, even if an image is displayed by driving each dummy pixel electrode by the drive circuit, the image is covered with a black light shielding layer or the like and is not visible to the observer. The plurality of pixel electrodes include display pixel electrodes in addition to dummy pixels. Therefore, when the drive circuit drives the display pixel electrode, an image can be displayed in the area where the display pixel electrode is provided, that is, the effective display area.

  In particular, in this liquid crystal display device, the drive circuit includes gradation control means for driving the dummy pixel electrode with a gradation value different from that of the display pixel electrode. Thereby, gradation control can be performed so that the gradation level of the display pixel electrode does not concentrate on one gradation value, and lateral crosstalk can be reduced.

  In one aspect of the above-described liquid crystal display device, the gradation control unit may, for each of the plurality of scanning lines, provide a dummy pixel electrode corresponding to the scanning line with a gradation different from that of the display pixel electrode corresponding to the scanning line. Drive by value. Thereby, gradation control can be performed so that the gradation levels of the display pixel electrodes in each line are not concentrated on one gradation value, and lateral crosstalk can be reduced.

  In another aspect of the above-described liquid crystal display device, the gradation control unit may determine, for each of the plurality of scanning lines, an appearance probability of a gradation value that drives a plurality of display pixel electrodes corresponding to the scanning line. The gradation value for driving the dummy pixel electrode is determined.

  According to this aspect, the gradation control means can determine the gradation value for driving the dummy pixel electrode based on the appearance probability of the gradation value of the display pixel electrode during driving. Then, the drive circuit can drive the dummy pixel electrode with the determined gradation value. Thereby, gradation control can be performed so that the gradation levels of the display pixel electrodes in each line are not concentrated on one gradation value, and lateral crosstalk can be reduced.

  In another aspect of the above-described liquid crystal display device, the gradation control unit determines a gradation value having an appearance probability lower than a predetermined value as a gradation value for driving the dummy pixel electrode.

  According to this aspect, the gradation control means can determine the gradation value whose appearance probability is lower than the predetermined value as the gradation value for driving the dummy pixel electrode. Then, the drive circuit can drive the dummy pixel electrode with the determined gradation value. Thereby, gradation control can be performed so that the gradation levels of the display pixel electrodes in each line are not concentrated on one gradation value, and lateral crosstalk can be reduced.

  In another aspect of the liquid crystal display device, the driving circuit applies a voltage higher than the signal line connected to the display pixel electrode to the signal line connected to the dummy pixel electrode.

  According to this aspect, the drive circuit can apply a voltage higher than the signal line connected to the display pixel electrode to the signal line connected to the dummy pixel electrode during the line selection period. As a result, the spike waveform generated in the combined voltage waveform of the signal line and the scanning line, which causes horizontal crosstalk during the line selection period, can be made as small as possible. Therefore, even in a liquid crystal display device with a small number of dummy pixel electrodes, lateral crosstalk can be effectively reduced.

  In another aspect of the present invention, a liquid crystal display device includes a plurality of signal lines, a plurality of pixel electrodes, and a plurality of two-terminal elements connected to each of the signal lines and the pixel electrodes. One substrate, a second substrate having a plurality of scanning lines and disposed opposite to the first substrate, a liquid crystal layer sandwiched between the first substrate and the second substrate, the scanning lines and the signal A driving circuit that supplies a signal to a line to drive the liquid crystal, and the plurality of pixel electrodes are arranged in the direction in which the scanning lines extend in the display area in which the display pixel electrodes and the display pixel electrodes are provided. The driving circuit includes gradation control means for driving the dummy pixel electrode with a gradation value different from that of the display pixel electrode.

  The above liquid crystal display device is an active matrix drive type liquid crystal display device having a two-terminal element such as a so-called TFD. In this liquid crystal display device, the plurality of pixel electrodes include dummy pixel electrodes which are located at the end of the scanning line extending direction of the display area where the display pixel electrodes are provided and are shielded by a black light shielding layer or the like. For this reason, even if an image is displayed by driving each dummy pixel electrode by the drive circuit, the image is covered with a black light shielding layer or the like and is not visible to the observer. The plurality of pixel electrodes include display pixel electrodes in addition to dummy pixels. Therefore, when the drive circuit drives the display pixel electrode, an image can be displayed in the area where the display pixel electrode is provided, that is, the effective display area.

  In particular, in this liquid crystal display device, the drive circuit includes gradation control means for driving the dummy pixel electrode with a gradation value different from that of the display pixel electrode. Thereby, gradation control can be performed so that the gradation level of the display pixel electrode does not concentrate on one gradation value, and lateral crosstalk can be reduced.

  In addition, an electronic device including the above-described liquid crystal display device can be configured.

  The best mode for carrying out the present invention will be described below with reference to the drawings. In the following embodiments, the present invention is applied to a liquid crystal display device. In this embodiment, pixel electrodes that do not contribute to image display (hereinafter referred to as “dummy pixel electrodes”) are provided on both sides of the effective display area, and the dummy pixel electrodes are driven at a gradation different from that of the effective display area. . Alternatively, during the line selection period, a voltage higher than that of the data line connected to the pixel electrode in the effective display area is applied to the data line connected to the dummy pixel electrode to drive the dummy pixel electrode. Thereby, lateral crosstalk is reduced.

[Configuration of Liquid Crystal Display Device 100]
First, the configuration of the liquid crystal display device according to the embodiment of the present invention will be described. FIG. 1 is a plan view schematically showing a schematic configuration of a liquid crystal display device 100 of the present invention. In FIG. 1, the configuration of electrodes and wirings of the liquid crystal display device 100 is mainly shown as a plan view. Here, the liquid crystal display device 100 of the present invention is an active matrix driving method using a TFD element, and is a transflective liquid crystal display device. FIG. 2 is a schematic cross-sectional view along the cutting line AA ′ in the liquid crystal display device 100 of FIG.

  First, the cross-sectional configuration of the liquid crystal display device 100 taken along the cutting line A-A ′ will be described with reference to FIG. 2, and then the configuration of electrodes and wirings of the liquid crystal display device 100 will be described.

  In FIG. 2, the liquid crystal display device 100 includes an element substrate 92 and a color filter substrate 91 disposed so as to face the element substrate 92 with a frame-shaped seal member 3 interposed therebetween, and liquid crystal is sealed inside. Thus, the liquid crystal layer 4 is formed. A conductive member 7 such as a plurality of gold particles is mixed in the frame-shaped seal member 3.

  On the inner surface of the lower substrate 2, a scattering layer 9 having fine irregularities formed on the surface is formed. On the inner surface of the scattering layer 9, a reflective layer 5 having a predetermined thickness is formed for each subpixel SG. Each reflective layer 5 has a rectangular opening 20 (hereinafter also referred to as “transparent region”). Each reflective layer 5 can be formed of a thin film such as aluminum, an aluminum alloy, or a silver alloy. The opening 20 is formed so as to have an area of a predetermined ratio with respect to the total area of the sub-pixel SG for each sub-pixel SG arranged in a matrix in the vertical and horizontal directions on the inner surface of the color filter substrate 91.

  On the reflective layer 5 and between the sub-pixels SG, a black light-shielding layer BM is provided between the adjacent sub-pixels SG to prevent light from entering from one sub-pixel to the other sub-pixel. Is formed. The black light shielding layer BM can be made of a black resin material, for example, a black pigment dispersed in a resin. In the present invention, instead of this, an overlapping light shielding layer (not shown) formed by overlapping R, G, and B colored layers may be used.

  On the reflective layer 5 and the opening 20, colored layers 6R, 6G, and 6B made of any of the three colors R, G, and B are formed for each subpixel SG. A color filter is constituted by the colored layers 6R, 6G, and 6B. A pixel G indicates a region for one color pixel composed of R, G, and B sub-pixels SG. In the following description, when referring to a colored layer regardless of color, it is simply referred to as “colored layer 6”, and when referring to a colored layer by distinguishing colors, it is referred to as “colored layer 6R” or the like. Further, as shown in FIG. 2, the thickness of the colored layer 6 formed on the opening 20 is formed to be thicker than the thickness of the colored layer 6 formed on the reflective layer 5. Thus, the colored layer 6 is designed to exhibit a desired hue and brightness in the reflective display mode and the transmissive display mode, respectively.

  A protective layer 18 made of a transparent resin or the like is formed on the colored layer 6 and the black light shielding layer BM. The protective layer 18 has a function of protecting the colored layer 6 from corrosion and contamination caused by chemicals used during the manufacturing process of the color filter substrate 91 and the liquid crystal display device 100. On the surface of the protective layer 18, a transparent electrode (scanning electrode) 8 such as striped ITO (Indium-Tin Oxide) is formed. One end of the transparent electrode 8 extends into the seal member 3 and is electrically connected to the conducting member 7 in the seal member 3.

  On the other hand, the TFD element 21 and the pixel electrode 10 are formed on the inner surface of the upper substrate 1 for each subpixel. A protective layer 17 made of transparent resin or the like is formed on the inner surfaces of the TFD element 21 and the pixel electrode 10. Scan lines 31 are formed on the left and right peripheral edge portions on the inner surfaces of the upper substrate 1 and the protective layer 17. One end of the scanning line 31 extends into the seal member 3, and the scanning line 31 is electrically connected to the conduction member 7 in the seal member 3.

  An alignment film (not shown) is formed on the inner surface of the transparent electrode 8 of the lower substrate 2 and the inner surface of the protective layer 17 of the upper substrate 1. In order to keep the thickness of the liquid crystal layer 4 uniform between these alignment films, particulate spacers (not shown) are randomly arranged. As a material for the spacer, a material mainly composed of silica or resin is preferable.

  A retardation plate (¼ wavelength plate) 11 and a polarizing plate 12 are arranged on the outer surface of the lower substrate 2, and a retardation plate (¼ wavelength plate) on the outer surface of the upper substrate 1. 13 and a polarizing plate 14 are arranged. A backlight 15 is disposed below the polarizing plate 12. The backlight 15 is preferably a point light source such as an LED (Light Emitting Diode) or a linear light source such as a cold cathode fluorescent tube.

  The transparent electrode 8 of the lower substrate 2, that is, the scanning line of the lower substrate 2, and the scanning line 31 of the upper substrate 1 are vertically connected via the conductive member 7 mixed in the seal member 3.

  Now, when reflective display is performed in the liquid crystal display device 100 of the present embodiment, the external light incident on the liquid crystal display device 100 travels along the path R shown in FIG. That is, the external light incident on the liquid crystal display device 100 is reflected by the reflective layer 5 and reaches the observer. In this case, the external light passes through the region where the colored layer 6 is formed, is reflected by the reflective layer 5 below the colored layer 6, and passes through the colored layer 6 again to have a predetermined hue. And brightness. Thus, a desired color display image is visually recognized by the observer.

  On the other hand, when transmissive display is performed, the illumination light emitted from the backlight 15 travels along the path T shown in FIG. 2 and passes through the transmissive region, that is, the colored layer 6 on the opening 20 for observation. To the person. In this case, the illumination light has a predetermined hue and brightness by passing through the colored layer 6. Thus, a desired color display image is visually recognized by the observer.

  Next, with reference to FIG. 1, FIG. 3, and FIG. 4, the configuration of the electrodes and wirings of the element substrate 92 and the color filter substrate 91 of the present invention will be described. FIG. 3 is a plan view showing a configuration of electrodes, wirings, and the like of the element substrate 92 when the element substrate 92 is observed from the front direction (that is, the lower side in FIG. 2). FIG. 4 is a plan view showing the configuration of the electrodes of the color filter substrate 91 when the color filter substrate 91 is observed from the front direction (that is, the upper side in FIG. 2). In FIG. 3, the electrodes and wirings are formed on the back side in the observation direction, but are represented by solid lines for convenience of explanation. 3 and 4, other elements other than the electrodes and wiring are not shown for convenience of explanation.

  In FIG. 1, a region where the pixel electrode 10 of the element substrate 92 and the transparent electrode 8 of the color filter substrate 91 intersect constitute a sub-pixel SG which is the minimum unit of display. An area in which a plurality of subpixels SG are arranged in a matrix in the vertical direction and the horizontal direction of the drawing is an effective display area V (area surrounded by a two-dot chain line). In the effective display area V, images such as letters, numbers, and figures are displayed. Further, on both sides of the effective display region V, dummy pixel electrodes 80 corresponding to one to several rows are provided in the vertical direction, as shown in FIGS. Hereinafter, a region where the dummy pixel electrode 80 is provided is referred to as a “dummy pixel region 86” (a region surrounded by a broken line). The dummy pixel region 86 is covered with a black light shielding layer BM (not shown), but the black light shielding layer BM is omitted in this embodiment. For this reason, even if each dummy pixel electrode 80 is driven to display an image, the image is covered with the black light shielding layer BM and is not visible to the observer. Further, in FIGS. 1 and 3, an area defined by the outer periphery of the liquid crystal display device 100 and the effective display area V is a frame area 38 that does not contribute to image display. Of the pixel electrodes, an electrode other than the dummy pixel electrode may be referred to as a “display pixel electrode” to distinguish it from this.

[Electrode and wiring configuration]
First, with reference to FIG. 3, the structure of the electrode and wiring of the element substrate 92 will be described. The element substrate 92 includes a TFD element 21, a pixel electrode 10, a plurality of scanning lines 31, a plurality of data lines 32, a Y driver IC 33, an X driver IC 110, and a plurality of external connection terminals 35.

  On the projecting region 36 of the element substrate 92, a Y driver IC 33 and an X driver IC 110 are mounted, for example, via an ACF (Anisotropic Conductive Film). In FIG. 3, the direction from the side 92a on the projecting region 36 side of the element substrate 92 to the side 92c on the opposite side is defined as the X direction, and the direction from the side 92d to the side 92b is defined as the Y direction.

  A plurality of external connection terminals 35 are formed on the overhang region 36. Each input terminal (not shown) of the Y driver IC 33 and the X driver IC 110 is connected to the plurality of external connection terminals 35 through conductive bumps. The external connection terminal 35 is connected to a wiring board (not shown) such as a flexible printed board via ACF or solder. Thereby, for example, signals and power are supplied to the liquid crystal display device 100 from an electronic device such as a mobile phone or an information terminal.

  Output terminals (not shown) of the X driver IC 110 are connected to the plurality of data lines 32 through conductive bumps. On the other hand, the output terminal (not shown) of each Y driver IC 33 is connected to the plurality of scanning lines 31 via conductive bumps. Thus, each Y driver IC 33 outputs a scanning signal to the plurality of scanning lines 31, and the X driver IC 110 outputs a data signal to the plurality of data lines 32.

  The plurality of data lines 32 are linear wirings extending in the vertical direction on the paper surface, and are formed in the X direction from the overhang area 36 to the effective display area V. Each data line 32 is formed at a constant interval. Each data line 32 is connected to a plurality of TFD elements 21 at appropriate intervals, and each TFD element 21 is connected to a corresponding pixel electrode 10.

  The plurality of scanning lines 31 includes a main line portion 31a and a bent portion 31b that bends at substantially right angles to the main line portion 31a. Each main line portion 31 a is formed in the X direction from the overhanging region 36 in the frame region 38. Each main line portion 31a is formed substantially parallel to each data line 32 and at a predetermined interval. Each bent portion 31b extends in the Y direction to the inside of the seal member 3 located on the left and right in the frame region 38. The end portion of the bent portion 31 b is connected to the conductive member 7 in the seal member 3.

  Next, the configuration of the electrodes of the color filter substrate 91 will be described. As shown in FIG. 4, the color filter substrate 91 has stripe-shaped transparent electrodes (scanning electrodes) 8 formed in the Y direction. As shown in FIGS. 1 and 4, the left end portion or the right end portion of each transparent electrode 8 extends into the seal member 3 and is connected to the conduction member 7 in the seal member 3.

  FIG. 1 shows a state where the color filter substrate 91 and the element substrate 92 are bonded together via the seal member 3 as described above. As shown in the figure, each transparent electrode 8 of the color filter substrate 91 is orthogonal to each data line 32 of the element substrate 92 and overlaps the plurality of pixel electrodes 10 in a row in a plane. Thus, the region where the transparent electrode 8 and the pixel electrode 10 overlap constitutes the sub-pixel SG.

  Further, the transparent electrode 8 (that is, the scanning line on the color filter substrate 91 side) of the color filter substrate 91 and the scanning line 31 of the element substrate 92 alternately overlap between the left side and the right side as shown in the figure. The transparent electrode 8 and the scanning line 31 are vertically connected via the conductive member 7 in the seal member 3. That is, conduction between each scanning line of the color filter substrate 91 as the transparent electrode 8 and each scanning line 31 of the element substrate 92 is alternately realized between the left side and the right side as shown in the figure. Thereby, the transparent electrode 8 of the color filter substrate 91 is electrically connected to the Y driver ICs 33 located on the left and right sides of the paper via the scanning lines 31 of the element substrate 92.

[Drive circuit]
Next, a driving circuit of the liquid crystal display device 100 will be described. FIG. 5 schematically shows the configuration of the drive circuit of the liquid crystal display device 100. 5, the drive circuit of the liquid crystal display device 100 includes a scanning signal drive circuit 33a, a data signal drive circuit 110a, a timing signal generation circuit 51, and a conversion circuit 52. The timing signal generation circuit 51 outputs various timing signals for driving the illustrated components. These circuits are built in the X driver IC 110 and the Y driver IC 33.

  As described above, the liquid crystal display device 100 includes a plurality of scanning lines 31 extending in the row direction and a plurality of corresponding scanning electrodes 8 and a plurality of data lines extending in the column direction. 32. Hereinafter, for convenience of explanation, one scanning line 31 and one corresponding scanning electrode 8 are referred to as “scanning line 85”. At each intersection of the scanning line 85 and the data line 32, the TFD element 21 and the liquid crystal layer 4 are connected in series, whereby a pixel is formed at each intersection.

  The scanning signal driving circuit 33 a applies a scanning potential VA to the scanning line 85, and the data signal driving circuit 110 a applies a signal potential VB to the data line 32. The potentials VA and VB will be described with reference to FIG. First, a scanning potential VA as shown in FIG. 6A is applied to the scanning line 85. In each line selection period T, each scanning line 85 is sequentially selected, and a potential difference of ± Vsel with respect to a certain common potential VGND, that is, any potential having a voltage is applied. This voltage Vsel is called a selection voltage. Then, after the line selection period, any potential having a voltage of ± Vhld with respect to the common potential VGND is applied. Here, when the potential at the time of selection is VGND + Vsel, the potential of VGND + Vhld is applied, and when the potential at the time of selection is VGND−Vsel, the potential of VGND−Vhld is applied. This voltage Vhld is called a holding voltage. A period in which all the scanning lines 85 are selected in a round is called a field period. In the next field period, the scanning lines 85 are sequentially selected using a selection voltage having a characteristic opposite to that of the previous field period. Go.

  On the other hand, as shown in FIG. 6B, any potential having a voltage of ± Vsig with respect to the common potential VGND is applied to the data line 32. Here, when the potential applied to the scanning line 85 selected in a certain selection period is VGND + Vsel, VGND−Vsig is used as the on potential Von and VGND + Vsig is used as the off potential Voff. Further, when the potential applied to the scanning line 85 selected in a certain selection period is VGND−Vsel, VGND + Vsig is used as the on potential Von, and VGND−Vsig is used as the off potential Voff.

  That is, the waveform of the signal potential VB in each line selection period T is set according to the gradation of each pixel in the column related to the data line 32. First, the signal potential VB is set for each line selection period T. Are divided into an ON section and an OFF section, and are set to the ON potential Von in the ON section and to the OFF potential Voff in the OFF section. That is, the signal potential VB is pulse width modulated according to the gradation value. Then, the higher the gradation to be given to the pixel (the darker the normally white mode), the larger the proportion occupied by the ON section.

  Next, the interelectrode voltage VAB of the scanning line 85 and the data line 32 is indicated by a solid line in FIG. As shown in the figure, it can be seen that the absolute value of the interelectrode voltage VAB increases during the selection period of the pixel. Further, the liquid crystal layer voltage VLC applied to the liquid crystal layer 4 is indicated by hatching in FIG. When the liquid layer voltage VLC changes, the capacity formed by the liquid crystal layer 4 must be charged and discharged, so the liquid crystal layer voltage VLC changes in a transient response to the interelectrode voltage VAB. In FIG. 6C, the voltage VNL is the difference between the interelectrode voltage VAB and the liquid layer voltage VLC, that is, the terminal voltage of the nonlinear two-terminal element 21.

  An example of the signal potential VB in the present embodiment is shown in FIG. In FIG. 7A, the line selection period T includes an on section and an off section. Further, since the scanning potential VA is as shown in FIG. 6A, the interelectrode voltage VAB and the liquid layer voltage VLC are as shown in FIG. 7B.

  The conversion circuit 52 converts the color image signals R, G, and B input from the outside into data signals DR, DG, and DB. Specifically, when the color image signals R, G, and B are supplied, the conversion circuit 52 stores the color image signals R, G, and B in a line buffer (not shown) and converts the color image signals R, G, and B into the data signals DR, The data is converted into DG and DB and supplied to the data signal driving circuit 110a. Here, the gradation values of the respective colors of the color image signals R, G, and B are values in the range of “0” to “15”, and these are the gradation values within the line selection period T according to the table of FIG. Is converted to

  The conversion circuit 52 supplies a clock signal GCP (Gray Control Pulse) to the data signal driving circuit 110a. A method for generating the clock signal GCP will be described. In the conversion circuit 52, a basic clock signal that divides each line selection period T by “256” is generated. Next, this basic clock signal is counted by an 8-bit (maximum 255) counter, and when the count result reaches a predetermined value, one pulse of the clock signal GCP is output. This “predetermined value” corresponds to the gradation values (0, 13, 26,... 255) shown in FIG. Note that the counter value at which one pulse of the clock signal GCP is output is set so as to maintain linearity according to the gradation characteristics of the liquid crystal display device 100.

  In FIG. 8, if the gradation value is “0”, the width of the ON section is also “0”, and the entire section of the line selection period is the OFF section. As the gradation value increases, the proportion of the ON period (number of basic clock signals) increases. In the gradation value 15, the on section is set to “255”, and the entire section of the line selection period is the on section.

  Next, the configuration of the data signal driving circuit 110a will be described in detail with reference to FIG. The shift register 112 in the data signal driving circuit 110a is a shift register of “m / 3” bits (m is the number of data lines 32), and each time the pixel clock XSCL is supplied, the contents of each bit are adjacent to the right side. Shift to the bit you want. As shown in FIG. 10, the pixel clock XSCL is a signal that falls in synchronization with the timing at which the data signals DR, DG, and DB of each pixel are supplied. A pulse signal DX is supplied to the leftmost bit of the shift register 112. This pulse signal DX is a one-shot pulse signal that is generated when the output of the data signals DR, DG, and DB in the line selection period T from the conversion circuit 52 is started. Therefore, the signals S1 to Sm output from each bit of the shift register 112 are signals that are sequentially set to the H level exclusively for a time equal to the period of the pixel clock XSCL.

  The register 114 latches the data signals DR, DG, and DB by three pixels in synchronization with the rising edges of the output signals S1 to Sm of the shift register 112. The latch circuit 116 simultaneously latches the data signals stored in the register 114 in synchronization with the rising edge of the latch pulse LP. The waveform converter 118 converts the latched data signal into a signal potential VB as shown in FIG. 7A and applies it to the m data lines 32. That is, the output timing of the latch pulse LP becomes the start timing of the line selection period T.

  Next, a configuration example of the waveform converting unit 118 is shown in FIG. In FIG. 11, a counter 124 is a counter provided in common for all the data lines 32, and the count value is reset to “0” when the latch pulse LP rises, and the clock signal GCP is counted. The comparator 126 compares the data signals DR, DG, DB of each pixel latched by the latch circuit 116 with the count value of the counter 124. If the count value is less than the value of the data signal, the comparator 126 compares the data signal DR, DG, DB If the value is equal to or greater than the value of the data signal, an L level comparison signal CMP is output. The switch 122 selects the ON potential Von when the corresponding comparison signal CMP is at the H level, selects the OFF potential Voff when the corresponding comparison signal CMP is at the L level, and outputs the selected potential as the signal potential VB.

  FIG. 12 shows a driving waveform in gradation display in the liquid crystal display device 100. As described above, in the liquid crystal display device 100, gradation display is performed by pulse width modulation of the drive voltage applied to the liquid crystal layer 4. An example of driving waveforms for one line (1T) in the case of white display, gray display, and black display is shown in the upper part of FIG. In this example, it is assumed that the liquid crystal display device 100 is normally white.

  The scanning line driving waveform 61 is a pulse waveform applied to the scanning line 85 and defines the scanning potential VA. The data line drive waveform 62 is a pulse waveform applied to the data line 32 and defines the signal potential VB. As understood from FIG. 5, a potential difference between the scanning line 85 and the data line 32, that is, a potential between electrodes is applied to the liquid crystal layer 4. That is, the total voltage of the scanning line driving waveform 61 and the data line driving waveform 62, that is, the interelectrode voltage shown in the combined voltage waveform shown in the lower part of FIG. In the lower part of FIG. 12, a change in the actual voltage level of the liquid crystal layer 4 (liquid crystal layer voltage level) is shown as a liquid crystal layer voltage waveform 63. Since the liquid crystal layer 4 has a delay from the voltage application to the change in the orientation of the liquid crystal molecules, a transient response corresponding to the delay occurs, and the liquid crystal layer voltage waveform 63 shown in the lower part of FIG. 12 is applied to the liquid crystal layer 4. Will be. The gradation of the liquid crystal display device 100 changes according to the liquid crystal layer voltage level. Since the liquid crystal display device 100 of this example is normally white, when the liquid crystal layer voltage level is low, white display is performed, when the liquid crystal layer voltage level is high, black is displayed, and the middle is gray display (halftone display).

  As can be understood from the upper waveform in FIG. 12, the halftone level during gray display (halftone display) is controlled by the pulse width of the data line drive waveform 62. The data line driving waveform 62 is determined by the GCP described above. Therefore, by changing GCP, the pulse width of the data line drive waveform 62 changes, and as a result, the halftone level can be changed.

[Principle of horizontal crosstalk]
Next, lateral crosstalk will be described with reference to FIGS. FIG. 13 shows an equivalent circuit of one scanning line 85 of the liquid crystal display device 100. The liquid crystal layer 4 between the scanning line 85 and the data line 32 acts as a capacitance C between both electrodes. That is, in terms of electrical characteristics, a capacity C corresponding to the number of pixels of one line is connected in parallel between the scanning line 85 and the data line 32 for one specific line. Further, the resistance R resulting from the length of the scanning line 85 is connected in series with the parallel connection of these capacitors C. Thereby, a transient response occurs in the pulse waveform applied to the liquid crystal layer 4.

  FIG. 14 shows an equivalent circuit in specific lines X and Y of the liquid crystal display device 100, and a drive waveform and a composite voltage waveform applied thereto. In FIG. 14, the liquid crystal display device 100 shows a state where lateral crosstalk has occurred. The scanning line voltage and the signal line voltage are applied to the liquid crystal display device 100 so that the areas A and C have the same gray level and the area B has a white level. However, in actuality, due to the occurrence of lateral crosstalk, the gray level on the display image differs between area A and area C, which should have the same gradation level. At this time, even when the scanning line voltage and the signal line voltage are applied so that the area B is at the black level, the horizontal crosstalk is generated as described above.

  Specifically, an equivalent circuit of the line X is shown in the upper part of FIG. Since the area A is displayed at the same gradation level, each pixel of the line X is displayed at the same gradation level. In the drive waveform A at that time, a spike-like waveform (hereinafter referred to as a “spike waveform” for convenience of explanation) 66 is generated due to the resistance R and the capacitance C as shown in the figure, and the composite voltage waveform A is also generated. A corresponding spike waveform 68 is generated. This combined voltage waveform determines the gray level of the display pixels on the line X.

  On the other hand, for the line Y, the lower left drive waveform B is applied in the area B area, and the lower right drive waveform C is applied in the area C area. Therefore, compared with the case of the line X, the applied voltage is small in the area B where white display is performed, and as a result, the level of the spike waveform 67 generated in the drive waveform C is compared with the spike waveform 66 of the drive waveform A. Get smaller. Therefore, the spike waveform 69 in the combined voltage waveform BC of the line Y is larger than the spike waveform 68 in the combined voltage waveform A of the line X. As a result, in area C, the liquid crystal layer voltage level applied to the liquid crystal layer 4 is higher than in area A, and the display pixel becomes gray closer to black. That is, the gradations of area C and area A that are intended to display the same gray level are different. The above is the principle of occurrence of lateral crosstalk.

[How to reduce lateral crosstalk]
Next, with reference to FIG. 15 to FIG. 17, a method of reducing lateral crosstalk by the first and second gradation control methods of the present invention will be described.

(First gradation control method)
FIG. 15 and FIG. 16 are diagrams and graphs for explaining a method of reducing lateral crosstalk by the first gradation control method, respectively. In the liquid crystal display device 100 shown in FIG. 15, the black light shielding layer BM that covers the dummy pixel region 86 is omitted for convenience of explanation. The two types of graphs shown in FIG. 16 are graphs showing the appearance probability of the gradation of the pixel electrode 10 in a certain line in the effective display region V, respectively. A graph 87 shows an example of a graph that gradually peaks around the gradation value “32”. On the other hand, the graph 88 shows an example of a graph having a steep peak near the gradation value “13”. In FIG. 16, the horizontal axis indicates the gradation value of “64”, but this is merely an example, and the present invention can apply gradation values of “128”, “256”, and the like. it can.

  As described above, the horizontal crosstalk is generated because the spike waveform becomes large due to the gradation of pixels in a certain line being concentrated on one gradation. Therefore, basically, the lateral crosstalk can be reduced by controlling the gradation so that the gradation level of the pixels in a certain line is not concentrated on one gradation.

  In the first gradation control method, gradation control is performed so that the plurality of dummy pixel electrodes 80 provided on both sides of the effective display area V are driven at a gradation different from the gradation of the effective display area V. Thus, gradation control is performed so that the gradation levels of pixels in a certain line are not concentrated on one gradation, and lateral crosstalk is reduced.

  The first gradation control method will be described. For the liquid crystal display device 100 shown in FIG. 15, the scanning line voltage is set so that the areas A and C have the same gray level and the area B has the black level. And a signal line voltage is applied. For this reason, on the line X, the gradation corresponding to the specific gray is concentrated in the area A. Therefore, in the first gradation control method, a plurality of pixel electrodes 80 in the dummy pixel region 86 located on both sides of the area A, that is, a plurality of dummy pixel electrodes 80 corresponding to the area D-2 are arranged in the area A. It is driven with a gradation different from the gradation corresponding to the gray, for example, a gradation corresponding to black as shown in the figure. On the other hand, since the gradation corresponding to black is concentrated in the area B on the line Y, a plurality of dummy pixel electrodes 80 in the dummy pixel area 86 located on both sides of the area C, that is, the area D− The plurality of dummy pixel electrodes 80 corresponding to 1 are driven at a gradation different from the black gradation of the area B, for example, a prescribed gray gradation as shown in the figure.

  Here, referring to the graph shown in FIG. 16, when the gradation level of pixels in a certain line is concentrated on one gradation, the gradation at which the dummy pixel electrode 80 on that line is driven is determined. State.

  As shown in the graph 87, the first gradation control is performed by taking as an example a case where the gradation of the pixel electrode 10 on a certain line in the effective display region V gradually peaks near the gradation value “32”. In the method, it is preferable to drive the dummy pixel electrode 80 on the line with a gradation value with a low appearance probability. Specifically, as shown in the graph of FIG. 16, when a line having a certain appearance probability is set as the threshold value L1, in the first gradation control method, the dummy pixel electrode 80 on the line is set to be equal to or lower than the threshold value L1. Are driven at a gradation value of, i.e., a gradation value “13” or less, or a gradation value “51” or more. Note that the threshold L1 can be changed as needed.

  Further, as shown in the graph 88, when the gradation of the pixel electrode 10 on a certain line in the effective display area V has a steep peak near the gradation value 13, the first gradation control is performed. In the method, the dummy pixel electrode 80 on the line is basically driven with a gradation value equal to or lower than the threshold value L1 as described above. However, since the graph 88 has a sharp peak at the gradation value “13”, even if the dummy pixel electrode 80 on the line is driven at a gradation value equal to or less than “13” that is equal to or less than the threshold L1, the effective display area is displayed. It is not so different from the gradation value of the pixel electrode 10 in V. In such a case, in the first gradation control method, the dummy pixel electrode 80 on the line is changed from the gradation value “13” having the highest appearance probability to a predetermined gradation value (for example, the number of gradations “64”). Drive with gradation values shifted by 1/2 or 1/4).

  Thereby, in the effective display area V of the liquid crystal display device 100, it is possible to prevent the gradation levels from being concentrated on the same line, and to reduce the horizontal crosstalk.

  In the above description, as the number of dummy pixel electrodes 80 set for the liquid crystal display device 100 is larger, in other words, as the number of dummy pixel regions 86 is larger, the gradation level is concentrated on the same line. This can be prevented, and the effect of further reducing the lateral crosstalk can be obtained. However, if the number of set dummy pixel areas 86 is increased, the frame area 38 that does not contribute to the display is expanded correspondingly. Therefore, it is preferable to determine the number of dummy pixel regions 86 set for the liquid crystal display device 100 in relation to the desired effect of reducing the horizontal crosstalk.

(Second gradation control method)
FIG. 17 is a graph for explaining a method of reducing lateral crosstalk by the second gradation control method. FIG. 17A shows waveform diagrams of the scanning potential VA and the signal potential VB in the effective display area V. FIG. FIG. 17B shows waveform diagrams of the scanning potential VA and the signal potential VB in the dummy pixel region 86.

  In the second gradation control method, each pixel in the effective display region V is connected to each data line 32a connected to each dummy pixel electrode 80 in the dummy pixel region 86 shown in FIG. A voltage higher than the signal line voltage applied to each data line 32 (not shown) connected to the electrode 10 is applied to reduce lateral crosstalk.

  Specifically, as shown in FIG. 17A, each data line 32 connected to each pixel electrode 10 in the effective display area V has any voltage having ± Vsig with respect to the common potential VGND. Is applied. Therefore, in the second gradation control method, each data line 32a connected to each dummy pixel electrode 80 in the dummy pixel region 86 is connected to the common potential VGND as shown in FIG. Apply any high potential with a voltage of ± Vsig ± V1. As a result, the spike waveform generated in the combined voltage waveform can be made as small as possible (not shown), and lateral crosstalk can be effectively reduced even for a liquid crystal display device with a small number of dummy pixel electrodes 80 set.

(Modification)
In the above-described embodiment, the dummy pixel electrode regions 80 corresponding to one to several rows in the vertical direction, that is, the dummy pixel regions 86 are provided on both sides of the effective display region V, respectively. The horizontal crosstalk is reduced by the gradation control method. However, the present invention is not limited to this, and dummy pixel regions 86 are provided on either the left or right side of the effective display region V as shown in FIGS. 18A and 18B in accordance with various specifications of the liquid crystal display device. The lateral crosstalk may be reduced by the first or second gradation control method described above.

  Further, both the first gradation control method and the second gradation control method described above can be applied simultaneously.

  In the above embodiment, the present invention is applied to the transflective liquid crystal display device 100. However, the present invention is not limited to this, and the present invention can also be applied to a reflective or transmissive liquid crystal display device. In the above embodiment, the present invention is applied to the normally white liquid crystal display device 100. However, the present invention is not limited to this, and the present invention can also be applied to a normally black liquid crystal display device.

[Electronics]
Next, an embodiment in which the liquid crystal display device 100 according to the present invention is used as a display device of an electronic apparatus will be described.

  FIG. 19 is a schematic configuration diagram showing the overall configuration of the present embodiment. The electronic apparatus shown here includes the liquid crystal display device 100 and a control unit 410 that controls the liquid crystal display device 100. Here, the liquid crystal display device 100 is conceptually divided into a panel structure 403 and a drive circuit 402 composed of a semiconductor IC or the like. Further, the control means 410 includes a display information output source 411, a display information processing circuit 412, a power supply circuit 413, and a timing generator 414.

  The display information output source 411 includes a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), a storage unit such as a magnetic recording disk or an optical recording disk, and a tuning circuit that tunes and outputs a digital image signal. The display information is supplied to the display information processing circuit 412 in the form of an image signal of a predetermined format based on various clock signals generated by the timing generator 414.

  The display information processing circuit 412 includes various well-known circuits such as a serial-parallel conversion circuit, an amplification / inversion circuit, a rotation circuit, a gamma correction circuit, and a clamp circuit, and executes processing of input display information to obtain image information. Are supplied to the drive circuit 402 together with the clock signal CLK. The driving circuit 402 includes a scanning line driving circuit, a data line driving circuit, and an inspection circuit. The power supply circuit 413 supplies a predetermined voltage to each of the above-described components.

  Next, specific examples of electronic devices to which the liquid crystal display device 100 according to the present invention can be applied will be described with reference to FIG.

  First, an example in which the liquid crystal display device 100 according to the present invention is applied to a display unit of a portable personal computer (so-called notebook personal computer) will be described. FIG. 20A is a perspective view showing the configuration of this personal computer. As shown in the figure, the personal computer 710 includes a main body 712 having a keyboard 711 and a display 713 to which the liquid crystal display panel according to the present invention is applied.

  Next, an example in which the liquid crystal display device 100 according to the present invention is applied to a display unit of a mobile phone will be described. FIG. 20B is a perspective view showing the configuration of this mobile phone. As shown in the figure, the cellular phone 720 includes a plurality of operation buttons 721, a reception port 722, a transmission port 723, and a display unit 724 to which the liquid crystal display device 100 according to the present invention is applied.

  Electronic devices to which the liquid crystal display device 100 according to the present invention can be applied include a liquid crystal television, a viewfinder, in addition to the personal computer shown in FIG. 20A and the mobile phone shown in FIG. Type / monitor direct-view type video tape recorder, car navigation device, pager, electronic notebook, calculator, word processor, workstation, videophone, POS terminal, digital still camera, etc.

  Further, the present invention is not limited to a liquid crystal display device, but an electroluminescence device, an organic electroluminescence device, a plasma display device, an electrophoretic display device, and a device using an electron-emitting device (Field Emission Display and Surface-Conduction Electron-Emitter Display). The present invention can be similarly applied to various electro-optical devices such as the above.

The top view which shows the structure of the electrode and wiring of the liquid crystal display device which concern on this embodiment. The cross-sectional structure of a liquid crystal display device is shown. The top view which shows the structure of the electrode of an element substrate, wiring, etc. FIG. The top view which shows the structure of the electrode of a color filter board | substrate. An example of a driving circuit of a liquid crystal display device is shown. Waveform diagrams of the scanning potential VA, the signal potential VB, and the interelectrode voltage VAB are shown. The waveform diagram of the signal potential VB and the interelectrode voltage VAB is shown. The graph which shows the relationship between a gradation value and the pulse width of an ON area. The circuit diagram of a data signal drive circuit is shown. 3 shows a timing chart during driving of a liquid crystal display device. The circuit diagram of a waveform conversion part is shown. The wave form diagram which shows the drive waveform example of a different gradation level. An equivalent circuit for one line of a liquid crystal display device is shown. The figure explaining the generation | occurrence | production principle of horizontal crosstalk. The figure explaining the horizontal crosstalk reduction method by the 1st and 2nd gradation control method. The graph explaining the reduction method of the horizontal crosstalk by the 1st gradation control method. The wave form diagram explaining the reduction method of the horizontal crosstalk by the 2nd gradation control method. The figure explaining the horizontal crosstalk reduction method which concerns on a modification. 1 is a circuit block diagram of an electronic apparatus to which a liquid crystal display device of the present invention is applied. Examples of electronic devices to which the liquid crystal display device of the present invention is applied are shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper substrate, 2 Lower substrate, 3 Seal member, 6 Colored layer, 7 Conductive member, 8 Scan electrode, 10 Pixel electrode, 31 Scan line, 32, 32a Data line, 21 TFD element, 80 Dummy pixel electrode, 86 Dummy Pixel area, 91 color filter substrate, 92 element substrate, V effective display area, 100 liquid crystal display device

Claims (8)

A first substrate having a plurality of signal lines, a plurality of pixel electrodes, and a plurality of switching elements connected to each of the signal lines and each of the pixel electrodes;
A second substrate having a plurality of scanning lines and disposed opposite to the first substrate;
A liquid crystal layer sandwiched between the first substrate and the second substrate;
A driving circuit for supplying signals to the scanning lines and the signal lines to drive the liquid crystal,
The plurality of pixel electrodes include a display pixel electrode, and the dummy pixel electrode which is provided at a ridge in a direction in which the scanning line extends in a display area where the display pixel electrode is provided, and is shielded from light.
The liquid crystal display device, wherein the driving circuit includes gradation control means for driving the dummy pixel electrode with a gradation value different from that of the display pixel electrode.   The gradation control unit drives, for each of the plurality of scanning lines, a dummy pixel electrode corresponding to the scanning line with a gradation value different from that of the display pixel electrode corresponding to the scanning line. Item 2. A liquid crystal display device according to item 1.   For each of the plurality of scanning lines, the gradation control means is configured to drive the dummy pixel electrode based on the appearance probability of the gradation value that drives the plurality of display pixel electrodes corresponding to the scanning line. The liquid crystal display device according to claim 2, wherein the liquid crystal display device is determined.   The liquid crystal display device according to claim 3, wherein the gradation control unit determines a gradation value whose appearance probability is lower than a predetermined value as a gradation value for driving the dummy pixel electrode.   2. The liquid crystal display device according to claim 1, wherein the driving circuit applies a larger voltage to a signal line connected to the dummy pixel electrode than to a signal line connected to the display pixel electrode. .   6. The liquid crystal display device according to claim 1, wherein the dummy pixels are provided on both sides of the display region in the extending direction of the scanning lines. 7. A first substrate having a plurality of signal lines, a plurality of pixel electrodes, and a plurality of two-terminal elements connected to each of the signal lines and each of the pixel electrodes;
A second substrate having a plurality of scanning lines and disposed opposite to the first substrate;
A liquid crystal layer sandwiched between the first substrate and the second substrate;
A driving circuit for supplying signals to the scanning lines and the signal lines to drive the liquid crystal,
The plurality of pixel electrodes include a display pixel electrode, and the dummy pixel electrode which is provided at a ridge in a direction in which the scanning line extends in a display area where the display pixel electrode is provided, and is shielded from light.
The liquid crystal display device, wherein the driving circuit includes gradation control means for driving the dummy pixel electrode with a gradation value different from that of the display pixel electrode. An electronic apparatus comprising the liquid crystal display device according to claim 1.

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