Abstract:
A liquid crystal display device includes a plurality of video signal lines that extends in columns in a display area, a plurality of inversion control signal line each supplied with an inversion control signal for controlling inversion, a first selector that selects one of a pair of amplifiers different in the polarity from each other to input signals corresponding to a pair of adjacent video signal lines on the basis of the inversion control signal, and a second selector that selects one of a pair of the corresponding adjacent video signal lines to input signals output from the pair of amplifiers on the basis of the inversion control signal, in which at least one of the signals to be supplied to the plurality of inversion control signal lines is a signal different from other signals.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority from Japanese application JP2012-090773 filed on Apr. 12, 2012, the content of which is hereby incorporated by reference into this application. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a liquid crystal display device. 
         [0004]    2. Description of the Related Art 
         [0005]    As a display device for an information communication terminal such as a computer or a television, a liquid crystal display device has been extensively used. The liquid crystal display device changes an electric field to change an orientation of a liquid crystal composition confined between two substrates, and controls the degree of transmission of a light transmitted through those two substrates and the liquid crystal composition to display an image. In order to change the electric field, the liquid crystal display device applies a voltage corresponding to a gradation value of each pixel to a pixel electrode through a pixel transistor of each pixel. 
         [0006]    The liquid crystal composition has a property that the orientation becomes fixed when a voltage of the same polarity continues to be applied to the liquid crystal composition for a long time, which results in a residual image phenomenon. Also, the transistor also has a property that a threshold value for rendering the transistor conductive becomes shifted when being continuously applied with a voltage of one polarity. For that reason, in the liquid crystal display device, it is general to display an image by so-called “inversion driving” which drives while inverting the polarity of electric charge. 
         [0007]    JP 2008-256811 A discloses a so-called dot inversion driving that prevents flicker. 
       SUMMARY OF THE INVENTION 
       [0008]    The inversion driving largely affects a power consumption of a panel by the driving method. Up to now, in the liquid crystal display device of a so-called IPS (in plane switching) system having pixel electrodes and a common electrode which is a counter electrode of the pixel electrodes on one substrate, line inversion driving that changes the potential of the common electrode has been mainstream. However, from the viewpoint of the power consumption, the dot inversion driving that conducts the inversion driving using the potential of a polarity different from that of up and down, left and right pixels is used without changing the potential of the common electrode. 
         [0009]    On the other hand, in particular, in order to improve the visibility in the liquid crystal display device of the middle and small sizes, a so-called “delta pixel array” in which pixels R (red), G (green), and B (blue) are arrange to form a triangle is frequently used. According to the present inventors&#39; study, in the delta pixel array, it is confirmed that an oblique stripe pattern is visually recognized when the dot inversion driving is applied.  FIGS. 15 and 16  illustrate a case in which monochromatic display of G (green) pixels is conducted and a case in which white display is conducted, in the dot inversion where the respective pixels are inverted every three horizontal synchronous periods, respectively. Also,  FIGS. 17 and 18  illustrate a case in which the monochromatic display of G pixels is conducted and a case in which the white display is conducted, in the dot inversion where the respective pixels are inverted every four horizontal synchronous periods, respectively. In any cases, one polarity is regularly arrayed, and the stripe pattern has been visually recognized. 
         [0010]    The present invention has been made under the above-mentioned circumstances, and an object of the present invention is to provide a liquid crystal display device in which no stripe pattern occurs in the dot inversion driving. 
         [0011]    According to the present invention, there is provided a liquid crystal display device, including a display area in which a plurality of pixels is arrayed; a plurality of video signal lines that extends in columns in the display area, and applies a video signal voltage based on a gradation value to the plurality of pixels; a plurality of inversion control signal lines each supplied with an inversion control signal for controlling inversion drive; a first selector that selects one of a pair of amplifiers different in the polarity from each other to input signals corresponding to a pair of adjacent video signal lines on the basis of the inversion control signal that is applied to one inversion control signal line among the plurality of inversion control signal lines; and a second selector that selects one of a pair of the corresponding adjacent video signal lines to input signals output from the pair of amplifiers on the basis of the inversion control signal of the one inversion control signal line, in which at least one of the signals to be applied to the plurality of inversion control signal lines is a signal different from other signals. 
         [0012]    Also, in the liquid crystal display device according to the present invention, the at least one signal is a signal different in cycle from the other signals. 
         [0013]    Also, in the liquid crystal display device according to the present invention, the at least one signal is a signal identical in cycle and different in phase from the other signals. 
         [0014]    Also, in the liquid crystal display device according to the present invention, a pixel array in the display area is a delta pixel array. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a diagram schematically illustrating a liquid crystal display device according to a first embodiment of the present invention; 
           [0016]      FIG. 2  is a plan view schematically illustrating a liquid crystal display panel of  FIG. 1 ; 
           [0017]      FIG. 3  is an enlarged view illustrating an arrangement of respective pixels and a state of electrodes on a TFT substrate in  FIG. 2 ; 
           [0018]      FIG. 4  is a diagram schematically illustrating a part of a circuit within a driver IC in  FIG. 2 ; 
           [0019]      FIG. 5  is a timing chart of control signals and video signals in  FIG. 4 ; 
           [0020]      FIG. 6  is a diagram illustrating the polarities of the respective pixels when a monochromatic display is conducted under a signal control in  FIG. 5 ; 
           [0021]      FIG. 7  is a diagram illustrating the polarities of the respective pixels when a white display is conducted under the signal control in  FIG. 5 ; 
           [0022]      FIG. 8  is a timing chart of control signals and video signals according to a second embodiment; 
           [0023]      FIG. 9  is a diagram illustrating the polarities of the respective pixels when a monochromatic display is conducted under a signal control in  FIG. 8 ; 
           [0024]      FIG. 10  is a diagram illustrating the polarities of the respective pixels when a white display is conducted under the signal control in  FIG. 8 ; 
           [0025]      FIG. 11  is a diagram schematically illustrating a part of a circuit within a driver IC according to a third embodiment; 
           [0026]      FIG. 12  is a timing chart of control signals and video signals according to a third embodiment; 
           [0027]      FIG. 13  is a diagram illustrating the polarities of the respective pixels when a monochromatic display is conducted under a signal control in  FIG. 12 ; 
           [0028]      FIG. 14  is a diagram illustrating the polarities of the respective pixels when a white display is conducted under the signal control in  FIG. 12 ; 
           [0029]      FIG. 15  is a diagram a case in which a monochromatic display of G (green) pixels is conducted in dot inversion where the respective pixels are inverted every three horizontal synchronous periods; 
           [0030]      FIG. 16  is a diagram a case in which a white display is conducted in dot inversion where the respective pixels are inverted every three horizontal synchronous periods; 
           [0031]      FIG. 17  is a diagram a case in which the monochromatic display of the G (green) pixels is conducted in the dot inversion where the respective pixels are inverted every four horizontal synchronous periods; and 
           [0032]      FIG. 18  is a diagram a case in which a white display is conducted in the dot inversion where the respective pixels are inverted every four horizontal synchronous periods. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    Hereinafter, first to third embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same or equivalent elements are denoted by identical symbols, and a repetitive description will be omitted. 
       First Embodiment 
       [0034]      FIG. 1  is a diagram schematically illustrating a liquid crystal display device  100  according to a first embodiment of the present invention. As illustrated in  FIG. 1 , the liquid crystal display device  100  includes an upper frame  110 , a lower frame  120 , and a liquid crystal display panel  200  fixed to be sandwiched between the upper frame  110  and the lower frame  120 . 
         [0035]      FIG. 2  is a plan view schematically illustrating the liquid crystal display panel  200  of  FIG. 1 . As illustrated in  FIG. 2 , the liquid crystal display panel  200  includes a thin film transistor substrate (hereinafter referred to as “TFT substrate”)  210  on which thin film transistors for applying a voltage corresponding to a gradation value to each of pixels  250  in a display area  215  are formed, a color filter substrate  220  on which a color filter of RGB is formed on each of the pixels  250 ; a liquid crystal composition not shown which is sealed between the TFT substrate  210  and the color filter substrate  220 , and changes brightness of each of the pixels  250  according to an orientation of the liquid crystal composition; video signal lines  400  through which a voltage corresponding to the gradation value is applied to the thin film transistor arranged in each of the pixels  250 ; and a driver IC (integrated circuit)  300  that drives each of the thin film transistors to hold the voltage corresponding to the gradation value applied to each of the video signal lines  400  in each of the pixels  250 . 
         [0036]      FIG. 3  is an enlarged view illustrating an arrangement of respective pixels and a state of electrodes on the TFT substrate  210 . As illustrated in  FIG. 3 , in one pixel  250  of RGB, a voltage for rendering a semiconductor film  252  conductive is applied to the semiconductor film  252  in the order from a higher scanning signal line  257 . As a result, the voltage corresponding to the gradation value applied to each video signal line  400  is applied and held into a drain line  256  and a pixel electrode  254 . A common electrode  258  that develops an electric field for orienting the liquid crystal component in cooperation with the pixel electrode  254  is formed into a planar shape expanding over an overall display area, and has a plurality of slender holes opened for each of the pixels  250 . Also, the respective pixels  250  of RGB are in a delta pixel array where the pixels of three colors of RGB are arrayed to form a triangle. 
         [0037]      FIG. 4  is a diagram schematically illustrating a part of a circuit within the driver IC  300  in  FIG. 2 . As illustrated in  FIG. 4 , the driver IC  300  includes data latch circuits  302  that hold display data corresponding to video signals  401  to  408  which are output to the video signal lines  400 , DAC (digital analog converter) circuits  306  that receive the outputs of the adjacent data latch circuits  302 , and convert digital data of the display data into drive voltages, first selectors  304  that are circuits that select and output any one of the adjacent DAC circuits according to alternating timing of control signals  321  to  324  which are supplied to inversion control signal lines  320 , positive amplifier circuits  308  that are buffer circuits for driving drive voltages generated by the DAC circuits  306  and amplifier circuits for positive poles of liquid crystal alternating, negative amplifier circuits  309  that are amplifier circuits for negative poles of liquid crystal alternating adjacent to the positive amplifier circuits  308  and paired with the positive amplifier circuits  308 , second selectors  310  that are circuits that receive drive voltages output from the amplifier circuits, and selectively output any one of two adjacent video signal output according to the alternating timings, and a control signal generator circuit  330  that receives a horizontal synchronous signal Hsync, and inverts the polarities of the control signals  321  to  324  on a horizontal synchronous signal Hsync basis. In the figure, the video signals  401  to  408  are supplied to the plurality of video signal lines  400 . The first selectors  304  and the second selectors  310  select paths A upon receiving a signal of high from the control signals  321  to  324 , and select paths B upon receiving a signal of low from the control signals  321  to  324 . The positive amplifier circuits  308  and the negative amplifier circuits  309  are pairs of amplifiers corresponding to the adjacent video signal lines  400 . 
         [0038]      FIG. 5  is a timing chart of the control signals  321  to  324  and the video signals  401  to  408  in  FIG. 4 . In the timing chart, a source signal is indicative of positive when the signal is higher than GND, and indicative of negative when the signal is lower than the GND. Also, a to x represent the respective horizontal synchronous periods. As illustrated in this timing chart, if the control signal  321  is high, the paths A are selected in the first selectors  304  and the second selectors  310 . As a result, for example, the video signal  401  becomes positive, and the video signal  402  becomes negative. Also, if the control signal  321  is low, the paths B are selected in the first selectors  304  and the second selectors  310 . As a result, for example, the video signal  401  becomes negative, and the video signal  402  becomes positive. The same is applied to the video signals  403  to  408 . 
         [0039]    In this embodiment, the respective four control signals  321  to  324  are signals inverted in polarity by the four horizontal synchronous signals Hsyn and different in phase from each other, and therefore become four pairs of the eight video signals  401  to  408 . Also, four line dot inversion in which the same positive and negative pattern is repeated is conducted every four lines on the screen. As a result, control can be conducted so that the alternating polarities on the screen are not visually recognized to be regularly arrayed. 
         [0040]      FIG. 6  is a diagram illustrating the polarities of the respective pixels when the monochromatic display is conducted in the driver IC  300  under the signal control of  FIG. 5 . In this embodiment, the color of the monochromatic display is “G (green)”, and the hatched pixels are “G” pixels which are display color. Also, in the G pixels, the positive pixels are each indicated by largely and thickly representing a character “+”. The “+” polarity of the G pixel is substantially irregularly arrayed, and the stripe pattern is not visually recognized. 
         [0041]      FIG. 7  is a diagram illustrating the polarities of the respective pixels when a white display is conducted in the driver IC  300  under the signal control in  FIG. 5 . In the case of the white display, because all of the pixels become in a high bright state, color coding display is not particularly conducted in the figure. In the figure, the “+” polarity is substantially irregularly arrayed, and the stripe pattern is not visually recognized. 
       Second Embodiment 
       [0042]    A liquid crystal display device according to a second embodiment of the present invention will be described. The configuration of the liquid crystal display device according to the second embodiment is identical with that of the liquid crystal display device according to the first embodiment illustrated in  FIGS. 1 to 4 , and a repetitive description will be omitted. In the liquid crystal display device according to the second embodiment, because the control signal generated by the control signal generator circuit  330  is different from that in the first embodiment, and therefore the polarities of video signals  421  to  428  are also different. 
         [0043]      FIG. 8  is a timing chart of the control signals  321  to  324  and the video signals  421  to  428  according to the second embodiment. As illustrated in the timing chart, the control signals  321  to  324  are inverted in polarity in the respective different cycles of the 4 to 7 horizontal synchronous periods Hsync. The video signals  421  to  428  are inverted in the polarity in response to the control signals  321  to  324  as illustrated in the timing chart. 
         [0044]      FIG. 9  is a diagram illustrating the polarities of the respective pixels when a monochromatic display is conducted in the driver IC  300  under the signal control in  FIG. 8 . As in  FIG. 6 , the color of the monochromatic display is “G (green)”, and the “G” pixels are hatched. As illustrated in the figure, the “+” polarity of the G pixel is substantially irregularly arrayed, and the stripe pattern is not visually recognized. 
         [0045]      FIG. 10  is a diagram illustrating the polarities of the respective pixels when a white display is conducted in the driver IC  300  under the signal control in  FIG. 8 . Similarly, in the figure, the “+” polarity is substantially irregularly arrayed, and the stripe pattern is not visually recognized. 
         [0046]    Thus, control can be conducted so that the alternating polarity is not regularly arrayed on the panel screen by changing the number of polarity inversions of the respective video signals  421  to  428 , and the power consumption can be reduced by expanding the polarity inversion period. 
       Third Embodiment  
       [0047]    A description will be given of a liquid crystal display device according to a third embodiment of the present invention. The configuration of the liquid crystal display device according to the third embodiment is identical with that of the liquid crystal display device according to the first embodiment illustrated in  FIGS. 1 to 3  except that a driver IC  600  is used in  FIG. 3 . 
         [0048]      FIG. 11  is a diagram schematically illustrating a part of a circuit within the driver IC  600 . The liquid crystal display device according to the third embodiment is different from that of the second embodiment in that there is provided a control signal generator circuit  630  that generates eight control signals  621  to  628  to be supplied to an inversion control signal line  620 . Also,  16  video signals  431  to  446  are output in correspondence with those eight control signals  621  to  628 . The other configurations are identical with those in the second embodiment, and therefore their description will be omitted. 
         [0049]      FIG. 12  is a timing chart of the control signals  621  to  628  and the video signals  431  to  446  according to the third embodiment. As illustrated in this timing chart, the control signals  621  to  628  are inverted in polarity in the respective different cycles of the second to ninth horizontal synchronous periods Hsync. The  16  video signals  431  to  446  are output in correspondence with those eight control signals  621  to  628  as shown in the timing chart. 
         [0050]      FIG. 13  is a diagram illustrating the polarities of the respective pixels when the monochromatic display is conducted in the driver IC  600  under the signal control in  FIG. 12 . As in  FIG. 6 , a color of the monochromatic display is “G (green)”, and the “G” pixels are hatched. As illustrated in the figure, the “+” polarity of the G pixels is substantially irregularly arrayed, and the stripe pattern is not visually recognized. 
         [0051]      FIG. 14  is a diagram illustrating the polarities of the respective pixels when a white display is conducted in the driver IC  600  under the signal control in  FIG. 12 . Also, in this figure, the “+” polarity is substantially irregularly arrayed, and the stripe pattern is not visually recognized. 
         [0052]    Thus, the number of combinations of the control conducted so that the alternating polarities are not regularly arrayed on the panel screen is increased more as the number of control signals is increased more, and the number of combinations of the control of the source signal is increased more. Therefore, the occurrence of the visual oblique stripe can be suppressed. 
         [0053]    In the above-mentioned respective embodiments, the delta pixel array is described. However, the above embodiments can be applied to vertical stripe array pixels and lateral stripe array pixels by appropriately selecting the period and the phase. 
         [0054]    Also, in the above-mentioned respective embodiments, the control signals of the same number as the number of kinds of the control signal lines are provided. However, the same control signal may be supplied to parts of the plurality of control signal lines to the extent where the oblique stripes cannot be visually recognized. 
         [0055]    While there have been described what are at present considered to be certain embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claim cover all such modifications as fall within the true spirit and scope of the invention.