Liquid crystal display

Abstract

A segmented-pixel liquid crystal display has a plurality of pixels of which each has three sub-pixels 10 a - 10 c, namely one middle and two side sub-pixels, arranged next to one another in the column or row direction. The sub-pixels 10 a - 10 c have different brightness levels when the pixel as a whole is in a given middle halftone state, and the middle sub-pixel 10 a has the highest brightness level. This eliminates unnaturalness as is conventionally produced when an image with a straight border is displayed, and further improves the gamma characteristic.

1 . A liquid crystal display having a plurality of pixels arrayed in a matrix, each pixel having a plurality of electrodes for applying an electric field to a liquid crystal layer,
 wherein, each pixel has at least three sub-pixels, said at least three sub-pixels having at least two different brightness levels when the pixel as a whole is in a given middle halftone state, and   wherein, of said at least three sub-pixels, one having a highest brightness level is called a bright sub-pixel and at least two others are called dim sub-pixels,
 one of the dim sub-pixels is located at one end of the pixel, 
 another of the dim sub-pixels is located at an opposite end of the pixel, and 
 the bright sub-pixel is located between said one an another of the dim sub-pixels. 
   
   
   
       2 . The liquid crystal display according to  claim 1 , wherein said one and another of the dim sub-pixels have an identical brightness level. 
   
   
       3 . The liquid crystal display according to  claim 1 ,
 wherein a ratio of an aperture area of the bright sub-pixel to a total aperture area of the dim sub-pixels is in a range from 1:1 to 1:4.   
   
   
       4 . The liquid crystal display according to  claim 1 ,
 wherein a ratio between aperture areas of said one and another of sub-pixels is in a range from 1:1 to 1:4.   
   
   
       5 . The liquid crystal display according to  claim 1 ,
 wherein said at least three sub-pixels each have
 a liquid crystal capacitance between a sub-pixel electrode and an common electrode disposed opposite each other across the liquid crystal layer and 
 an auxiliary capacitance between an auxiliary capacitance electrode electrically connecting to the sub-pixel electrode and an auxiliary capacitance common electrode disposed opposite the auxiliary capacitance electrode and connecting to an auxiliary capacitance conductor, 
   wherein a single electrode is shared as the common electrodes of said at least three sub-pixels, and   wherein at least two different auxiliary capacitance conductors are provided one for the bright sub-pixel and another for the dim sub-pixels.   
   
   
       6 . The liquid crystal display according to  claim 5 ,
 wherein an insulating layer is interposed between the auxiliary capacitance electrode and the auxiliary capacitance common electrode.   
   
   
       7 . The liquid crystal display according to  claim 5 , the liquid crystal display further having
 scanning lines extending in the row direction,   signal lines extending in the column direction, and,   for each pixel, at least two switching devices provided one for the bright sub-pixel and another for the dim sub-pixels, the switching devices connecting to a scanning line and a signal line each common to the three sub-pixels of the pixel,   wherein the switching devices are turned on and off by a scanning signal voltage supplied to the common scanning line and, when the switching devices are on, a display signal voltage is supplied from the common signal line to the sub-pixel electrode and the auxiliary capacitance electrode of each of the bright and dim sub-pixels, and   wherein, after the switching devices are turned off, auxiliary capacitance common voltages at the auxiliary capacitance common electrodes of the bright and dim sub-pixels vary such that variations in the auxiliary capacitance common voltages as defined by directions and degrees in which the auxiliary capacitance common voltages vary differ between the bright sub-pixel and the dim sub-pixels.   
   
   
       8 . The liquid crystal display according to  claim 7 ,
 wherein the switching devices are TFTs, and these TFTs are formed with a single semiconductor layer.   
   
   
       9 . The liquid crystal display according to  claim 5 ,
 wherein the auxiliary capacitance common voltages invert polarities thereof periodically.   
   
   
       10 . The liquid crystal display according to  claim 9 ,
 wherein the auxiliary capacitance common voltage applied to the auxiliary capacitance common electrode of the bright sub-pixel and the auxiliary capacitance common voltage applied to the auxiliary capacitance common electrodes of the dim sub-pixels are 180 degrees out of phase with each other.   
   
   
       11 . The liquid crystal display according to  claim 10 ,
 wherein the auxiliary capacitance common voltage applied to the auxiliary capacitance common electrode of the bright sub-pixel and the auxiliary capacitance common voltage applied to the auxiliary capacitance common electrodes of the dim sub-pixels have an equal amplitude.   
   
   
       12 . The liquid crystal display according to  claim 9 ,
 wherein, between every two mutually adjacent signal lines, display signal voltages applied thereto have opposite polarities and, between every two pixels mutually adjacent in the row direction, the auxiliary capacitance electrodes and the auxiliary capacitance common electrodes of the bright and dim sub-pixels are disposed in reversed patterns.   
   
   
       13 . The liquid crystal display according to  claim 5 ,
 wherein the scanning lines are laid between mutually adjacent pixels, and, in each pixel, the two auxiliary capacitance conductors are laid parallel to the scanning lines.   
   
   
       14 . The liquid crystal display according to  claim 13 ,
 wherein a conductor electrode via which the display signal voltage is supplied to the sub-pixel electrode of the bright sub-pixel crosses the two auxiliary capacitance conductors.   
   
   
       15 . The liquid crystal display according to  claim 1 ,
 wherein the sub-pixel electrodes of said at least three sub-pixels are separate from one another.   
   
   
       16 . The liquid crystal display according to  claim 1 ,
 wherein the sub-pixel electrodes of said one and another of side sub-pixels are continuous with each other.   
   
   
       17 . The liquid crystal display according to  claim 1 ,
 wherein a metal layer is formed under a contact hole via which a conductor electrode via which the display signal voltage is supplied connects to a sub-pixel electrode, with an insulating layer interposed between the metal layer and the contact hole.   
   
   
       18 . The liquid crystal display according to  claim 13 ,
 wherein the two auxiliary capacitance conductors are laid between the sub-pixels.