JP5029266B2 - Driving method of liquid crystal display element - Google Patents

Description

  The present invention relates to a driving method of a liquid crystal display element that displays a color image by a plurality of display elements each including four pixels of three primary colors and white as one unit.

  Conventionally, a color liquid crystal display element (hereinafter, referred to as a three-color pixel display element) is configured to form one display element with pixels of three colors of red, green, and blue, and input red to define one color, In response to the gradation data of the three colors of green and blue, the data signals of the three colors of red, green and blue corresponding to the gradation data of the three colors are respectively applied to the pixels of the three colors of red, green and blue. It is driven by supplying.

  In order to display a bright image on the three-color pixel display element, for example, a plurality of pixels of four primary colors of red, green, and blue and white are alternately arranged in a matrix and are adjacent to each other. There has been proposed a liquid crystal display element that displays a color image by a plurality of display elements each including four pixels of red, green, blue, and white as one unit (see Patent Document 1).

  In this liquid crystal display element, one display element is composed of four color pixels in which white pixels are added to three color pixels of red, green, and blue, so that the screen can be brightened.

The liquid crystal display element in which one display element is constituted by pixels of four colors of red, green, blue, and white is based on the input gradation data of three colors of red, green, and blue. A bias value is determined by calculation from the gradation data of the minimum value of the gradation data, and the value is used as driving gradation data for the white pixel, and each of the input gradation data of three colors of red, green, and blue is used. By subtracting the gradation value of the drive gradation data of the white pixel, the drive gradation data of each of the three colors of red, green, and blue is obtained, and red, green, blue corresponding to these drive gradation data, respectively. And white color data signals are supplied to the four color pixels of red, green, blue and white, respectively (see Patent Document 2).
JP-A-1-259396 Japanese Patent Laid-Open No. 4-130395

  However, a liquid crystal display device that drives a liquid crystal display element (hereinafter referred to as a four-color pixel display element) in which one display element is configured by pixels of four colors of red, green, blue, and white by the above-described conventional driving method, A color image with good color reproducibility corresponding to the input gradation data of three colors of red, green and blue cannot be displayed.

  That is, in the liquid crystal display device that drives the four-color pixel display element by the conventional driving method, when the gradation values of the input three-color gradation data of red, green, and blue are different from each other, that is, the red, When the gradation data of the three colors of green and blue is data that defines an intermediate color obtained by mixing the three colors of red, green, and blue at different ratios, the display color by the four-color pixel display element is conventionally changed. A color shift occurs with respect to the display color of the three-color pixel display element.

  For example, the input gradation data of three colors of red, green, and blue are 64 gradation data having gradation values of 0 to 63, respectively, and the three-color pixel display element and the four-color pixel display element. When the luminance of each color pixel is proportional to the gradation value of the drive gradation data for driving these pixels, the red gradation of the input gradation data of three colors of red, green, and blue When the gradation value of the data is 47, the gradation value of the green gradation data is 29, and the gradation value of the blue gradation data is 15, the display chromaticity of one display element, that is, the x, y coordinate values. When the three-color pixel display element is driven by supplying three-color data signals corresponding to the three-color gradation data of red, green, and blue to the three-color pixels of red, green, and blue, respectively. X = 0.38 and y = 0.38, while the four-color pixel display element is driven in the conventional manner. When it is driven by law x = 0.35, a y = 0.36.

  As described above, the liquid crystal display device that drives the four-color pixel display element by the above-described conventional driving method displays when the input gradation data of the three colors of red, green, and blue is data that defines an intermediate color. A color shift occurs, and a color image with good color reproducibility corresponding to the input gradation data of three colors of red, green, and blue cannot be displayed.

An object of the present invention is to provide a driving method capable of displaying a liquid crystal display element, in which one display element is composed of pixels of three primary colors and white, with good color reproducibility.

According to a first aspect of the present invention, there is provided a driving method for a liquid crystal display element.
A color image is formed by a plurality of display elements in which a plurality of pixels of three primary colors and white are alternately arranged in a matrix, and four pixels of each of the three primary colors and white adjacent to each other are used as one unit. In a driving method of a liquid crystal display element that displays
Based on the input gradation data of the three primary colors,
The ratio of the luminance corresponding to the driving gradation data for driving these pixels with respect to the maximum gradation luminance of each of the three primary colors and the four colors of white, the luminance ratio,
When the maximum value of the absolute value of the difference in luminance rate between the pixels of the three primary colors for each of the plurality of display elements is the maximum luminance rate difference,
The luminance ratios of the four primary color pixels and the white color pixels for each of the plurality of display elements are set to arbitrary values predetermined according to the characteristics of the white pixels in the luminance ratios of the respective three primary color pixels. Add a luminance rate corresponding to the number of gradations other than the number of gradations corresponding to the maximum luminance rate difference of the luminance rate, and subtract the luminance rate of the white pixel from the added value, Four drive gradation data of three primary colors and white are set for each of the plurality of display elements, and the four color data signals corresponding to the drive gradation data are respectively set to the three primary colors and white 4 of the plurality of display elements. It supplies to the pixel of a color, It is characterized by the above-mentioned.

According to a second aspect of the present invention, there is provided a driving method for a liquid crystal display element.
Red, green, blue 及 plurality of pixels of four colors of the lightening is formed by arranging in a matrix alternately mutually adjacent said red, green, blue, and 1 unit of four pixels of each color one by one white In a driving method of a liquid crystal display element that displays a color image by a plurality of display elements,
Based on the input gradation data of red, green and blue,
The maximum gradation luminance of each of the red, green, blue and white pixels is _expressed as L _maxR , L _maxG , L _maxB , L _maxW ,
Luminances corresponding to the input three-color gradation data of red, green, and blue for each of the red, green, and blue pixels are represented by input data-corresponding luminances L _R , L _G , L _B ,
The red, green, and blue three color pixels each of the maximum gradation luminance _{L maxR, L maxG, L} the input to _maxB data corresponding luminance _{L R,} L G, the ratio _L R _{/ L} maxR of _{L B, L G} / L _maxG and L _B / L _maxB are input data corresponding luminance rates R _R , R _G , R _B , respectively.
The red for each of the plurality of display elements, green, the input data corresponding luminance of the pixels mutual three colors blue _{R R,} R G, the absolute value of the difference between _{R B | R R -R G |} , | R G −R _B |, | R _B −R _R | is the maximum luminance ratio difference d _max ,
The brightness corresponding to the drive gradation data for driving each of the red, green, blue and white pixels is set to drive data corresponding brightness L ′ _R , L ′ _G , L ′ _B , L ′. _W
The drive data-corresponding luminances L ′ _R , L ′ _G , L ′ _B , and L for the maximum gradation luminances L _maxR , L _maxG , L _maxB , and L _maxW of the pixels of the four colors of red, green, blue, and white, respectively. ′ _W ratios L ′ _R / L _maxR , L ′ _G / L _maxG , L ′ _B / L _maxB , L ′ _W / L _maxW are respectively set to drive data corresponding luminance rates R ′ _R , R ′ _G , R ′ _B , When R ′ _W ,
The drive data-corresponding luminance ratios R ′ _R , R ′ _G , R ′ _B , R ′ _W are
R ′ _R = R _R {1 + t (1−d _max )} − R ′ _W · L _maxW / (L _maxR + L _maxG + L _maxB )
R ′ _G = R _G {1 + t (1−d _max )} − R ′ _W · L _maxW / (L _maxR + L _maxG + L _maxB )
R ′ _B = R _B {1 + t (1−d _max )} − R ′ _W · L _maxW / (L _maxR + L _maxG + L _maxB )
However, t is a predetermined arbitrary value in the range of 0 or more and L _maxW / (L _maxW + L _maxG + L _maxB ) or less,
Driving gradation data of red, green, blue and white for each of the plurality of display elements set to a gradation value satisfying the above-mentioned, is generated, and the four colors corresponding to these driving gradation data are generated. A data signal is supplied to each of the pixels of four colors of red, green, blue and white of the plurality of display elements.

According to a third aspect of the present invention, in the method for driving a liquid crystal display element according to the second aspect,
In the liquid crystal display element, the luminance of each of the four colors of red, green, blue and white is proportional to the gradation value of the driving gradation data for driving these pixels, and the maximum gradation luminance of the white pixel L _maxW is, has red, green, three color pixels each maximum gradation luminance _L maxR _blue, L _MaxG, the sum and equal Shii characteristics of _{L maxB,}
The drive gradation data of four colors of red, green, blue and white for each of a plurality of display elements is
The gradation values of the input red, green, and blue color gradation data are the D _R , D _G , D _B , and the red, green, blue, and white driving gradation data gradation values. When D ′ _R , D ′ _G , D ′ _B , and D ′ _W ,
D ′ _R is a value obtained by _converting D _R {1 + t (1−d _max )} − C into an integer D ′ _G is a value obtained by converting D _G {1 + t (1−d _max )} − C into an integer D ′ _B is D _B {1 + t (1−d _max )} — value obtained by converting C to an integer D′ W is a value obtained by converting C to an integer, where t = 1 and C are D _R {1 + t (1−d _max )}, D _G { _{1 + t (1-d max} )}, when the smallest value among _{D B {1 + t (1} -d max)} and _{D min,} when the _{D min} is less than the maximum tone is an integer of the _{D min} When the D _min is equal to or greater than the maximum gradation, the maximum gradation value is set.
It is characterized in that it is set to each gradation value.

According to a fourth aspect of the present invention, in the liquid crystal display element driving method according to the second aspect,
In the liquid crystal display element, the luminance of each of the four colors of red, green, blue and white is proportional to the gradation value of the driving gradation data for driving these pixels, and the maximum gradation luminance of the white pixel L _maxW has a characteristic different from the sum of the maximum gradation luminances L _maxR , L _maxG , and L _maxB of the three pixels of red, green, and blue,
Drive gradation data of four colors of red, green, blue and white for each of the plurality of display elements is
The gradation values of the input red, green, and blue color gradation data are the D _R , D _G , D _B , and the red, green, blue, and white driving gradation data gradation values. When D ′ _R , D ′ _G , D ′ _B , and D ′ _W ,
D ′ _R is a value obtained by _converting D _R {1 + t (1−d _max )} − C ′ · L _maxW / (L _maxR + L _maxG + L _maxB ) into an integer D ′ _G is D _G {1 + t (1−d _max )} _{-C '· L maxW / (L} maxR + L maxG + L maxB) the integer value _{D' B} is _{D B {1 + t (1} -d max)} - C '· L maxW / (L maxR + L maxG + L maxB) D ′ _W is a value _{obtained by converting} C ′ to an integer. However, t = 1, C ′ is D _R {1 + t (1−d _max )} (L _maxR + L _maxG + L _maxB ) / L _maxW , D _{G {1 + t (1-} d max)} (L maxR + L maxG + L maxB) / L maxW, D B {1 + t (1-d max)} smallest among the _{(L maxR + L maxG + L} maxB) / L maxW When the threshold value is D ′ _min , when D ′ _min is less than the maximum gradation, the value obtained by _converting D ′ _min to an integer, and when D ′ _min is greater than or equal to the maximum gradation, the maximum gradation value is obtained. And
It is characterized in that it is set to each gradation value.

According to a fifth aspect of the present invention, in the liquid crystal display element driving method according to the second aspect,
In the liquid crystal display element, the luminance of each of the four colors of red, green, blue and white is expressed by a function other than the proportionality of the gradation value of the driving gradation data for driving these pixels, and the white pixel _Has a characteristic that is equal to the sum of the maximum gradation luminances L _maxR , L _maxG , and L _maxB of the pixels of the three colors red, green, and blue,
The drive gradation data of four colors of red, green, blue and white for each of a plurality of display elements is
The inputted red, green, and blue gradation data is D _R , D _G , D _B , and the red, green, blue, and white driving gradation data is D ′ _R , D ′ _G , When D ′ _B and D ′ _W ,
The red, converts green, three-color gray scale data _D R of _blue, D G, luminance respectively _{D B L R, L G,} the _{L B,}
L ′ _R / L _maxR = L _R {1 + t (1−d _max )} / L _maxR −C ″ · L _maxW / (L _maxR + L _maxG + L _maxB )
_{L 'G / L maxG = L} G {1 + t (1-d max)} / L maxG -C "· L maxW / (L maxR + L maxG + L maxB)
L ′ _B / L _maxB = L _B {1 + t (1−d _max )} / L _maxB −C ″ · L _maxW / (L _maxR + L _maxG + L _maxB )
L ′ _W / L _maxW = C ″
However, t = 1, C _{"is, L R {1 + t (} 1-d max)} (L maxR + L maxG + L maxB) / L maxR · L maxW, L G {1 + t (1-d max)} (L maxR + L _maxG + L _maxB ) / L _maxG · L _maxW , L _B {1 + t (1−d _max )} (L _maxR + L _maxG + L _maxB ) / L _maxB · L _maxW when D ″ _min When D ″ _min is 1 or less, a value obtained by _converting D ″ _min into an integer, and when D ″ _min is greater than 1, set to 1.
The red by each formula, green, blue and four colors of pixels each drive data corresponding luminance _{L 'R,} L' white _G, L _'B, L' seeking _W, these driving data corresponding luminance L _'R , L ′ _G , L ′ _B , and L ′ _W are set to gradation values obtained by inversely converting the gradation values.

  According to the driving method of the present invention, a color image with good color reproducibility can be displayed.

FIG. 1 is a configuration diagram of a liquid crystal display device, and this liquid crystal display device has a plurality of pixels 13R, 13G, 13B, and 13W (see FIG. 2) of four primary colors of red, green, and blue in additive color mixture and three colors of white. Based on the liquid crystal display elements 1 that are alternately arranged in a matrix and the input gradation data of the three primary colors (red, green, and blue), the four colors red, green, blue, and white are displayed. drive means 15 for generating gradation data, for driving the liquid crystal display device 1 with four pixels, and is configured by.

FIG. 2 is a cross-sectional view of a part of the liquid crystal display element 1. The liquid crystal display element 1 includes a pair of transparent substrates 2 and 3 that are arranged to face each other with a predetermined gap therebetween, and between these substrates 2 and 3. On the inner surface of one of the pair of substrates 2 and 3, for example, the opposite side to the observation side (upper side in the figure), and in the row direction (horizontal direction of the screen) and the column A plurality of transparent pixel electrodes 5 arranged in a matrix in the direction (vertical direction of the screen) and the inner surface of the other substrate, that is, the substrate 3 on the observation side, in the arrangement region of the plurality of pixel electrodes 5 It consists of a single film-like transparent counter electrode 6 formed correspondingly, and a pair of polarizing plates 11 and 12 disposed on the outer surfaces of the pair of substrates 2 and 3, respectively.

  The liquid crystal display element 1 is an active matrix liquid crystal display element using TFTs (thin film transistors) as active elements, and although not shown in FIG. 1, the liquid crystal display element 1 is formed on the inner surface of the opposite substrate 2 on which the plurality of pixel electrodes 5 are formed. , A plurality of TFTs arranged corresponding to the plurality of pixel electrodes 5, respectively, connected to these pixel electrodes 5, a plurality of scanning lines for supplying gate signals to the TFTs in each row, A plurality of data lines for supplying data signals to the TFT are provided.

The liquid crystal display element 1 displays an image by controlling the transmittance of light emitted from a surface light source (not shown) disposed on the side opposite to the observation side. The alignment state of the liquid crystal molecules in the liquid crystal layer 4 is changed by supplying the data signal, that is, by applying a voltage corresponding to the data signal between the electrodes 5 and 6 depending on the region facing the counter electrode 6. a plurality of pixels 13R for controlling the transmittance of light, 13G, 13B, 13W are formed.

  Of the plurality of pixels 13R, 13G, 13B, and 13W, 1/4 of the pixels 13R are red pixels including the red color filter 7R, and the other 1/4 of the pixels 13G are green color filters 7G. A green pixel having a color filter, and another 1/4 pixel 13B are a blue pixel having a blue color filter 7B, and the remaining 1/4 pixel 13W is a white pixel having no color filter. The plurality of pixels 13R, 13G, 13B, and 13W of the colors red, green, blue, and white are alternately arranged in a matrix.

  The color filters 7R, 7G, and 7B are formed on one of the pair of substrates 2 and 3, for example, on the inner surface of the observation side substrate 3, and further on the inner surface of the observation side substrate 3, the white pixel 13W. The colorless transparent film 8 for adjusting the thickness of the liquid crystal layer of the white pixel 13W to the same level as the thickness of the liquid crystal layers of the three colors red, green, and blue 13R, 13G, and 13B is provided. Is formed.

  The counter electrode 6 is formed on the color filters 7R, 7G, and 7B and the colorless transparent film 8, and the inner surfaces of the pair of substrates 2 and 3 respectively include the plurality of pixels. Alignment films 9 and 10 are provided so as to cover the electrode 5 and the counter electrode 6.

  The pair of substrates 2 and 3 are arranged to face each other with a predetermined gap therebetween, and a frame-shaped sealing material (a frame-like sealing material surrounding the screen region in which the plurality of pixels 13R, 13G, 13B, and 13W are arranged in a matrix shape). The liquid crystal layer 4 is sealed in a region surrounded by the sealing material between the substrates 2 and 3.

The liquid crystal display device 1, the liquid crystal layer 4 TN or STN type and the liquid crystal molecules are twisted in the liquid crystal molecules with respect to the substrate 2 side vertically into oriented so the vertical alignment type, thereby twisting the liquid crystal molecules horizontal alignment type has been oriented to the flat row with respect to the substrate 2 side without any bend alignment type to bend alignment of the liquid crystal molecules, or a ferroelectric or anti-ferroelectric liquid crystal display device, the pair The polarizing plates 11 and 12 are set so that the direction of the respective transmission axes is black or white when no voltage is applied between the electrodes 5 and 6 of the pixels 13R, 13G, 13B, and 13W. Has been placed.

  The liquid crystal display element 1 shown in FIG. 1 changes the alignment state of liquid crystal molecules by generating an electric field between the electrodes 5 and 6 provided on the inner surfaces of the pair of substrates 2 and 3, respectively. For example, comb-like first and second electrodes for forming a plurality of pixels are provided on the inner surface of one of the pair of substrates, and a horizontal electric field (direction along the substrate surface) is provided between these electrodes. A lateral electric field control type in which the alignment state of the liquid crystal molecules is changed by generating an electric field).

  The liquid crystal display element 1 displays a color image by a plurality of display elements 14 each including four pixels 13R, 13G, 13B, and 13W for each of the red, green, blue, and white colors adjacent to each other. .

  3 to 6 show pixel arrangement examples of the liquid crystal display element 1, respectively. In these drawings, a plurality of display elements 14 each including four pixels 13R, 13G, 13B, and 13W adjacent to each other are shown. Surrounded by bold lines.

  In the pixel arrangement example shown in FIG. 3, red, green, blue, and white pixels 13R, 13G, 13B, and 13W are arranged in the same order, for example, red pixel 13R, white pixel 13W, and green pixel 13G for each row. The blue pixels 13B are alternately arranged in the order, and for each row, a plurality of four pixels 13R, 13G, 13B, and 13W each having a red, green, blue, and white color adjacent to each other are arranged. A display element 14 is configured.

  In the pixel arrangement example shown in FIG. 4, the pixels 13R, 13G, 13B, and 13W of four colors of red, green, blue, and white are alternately arranged in each row, and the order of arrangement is different between the odd rows and the even rows. A plurality of display elements 14 composed of four pixels 13R, 13G, 13B, and 13W for each color of red, green, blue, and white adjacent to each other are configured for each row.

  In the pixel arrangement example shown in FIG. 5, pixels of two colors of four colors of red, green, blue, and white, for example, red pixels 13R and white pixels 13W are alternately arranged in an odd row, and even numbers are arranged. In a row, pixels of the other two colors among the four colors of red, green, blue and white, for example, a green pixel 13G and a blue pixel 13B are alternately arranged and arranged for every two adjacent rows. In addition, a plurality of display elements 14 composed of four pixels 13R, 13G, 13B, and 13W for each of the red, green, blue, and white colors in the two rows and two columns are configured.

  In the pixel arrangement example shown in FIG. 6, the red, green, blue, and white four-color pixels 13R, 13G, 13B, and 13W are alternately arranged in each row, and are arranged in an odd row and an even row. The odd-numbered pixel array and the even-numbered pixel array are shifted by ½ pitch in the row direction, and each row has red, green, blue and white adjacent to each other. A plurality of display elements 14 including four pixels 13R, 13G, 13B, and 13W for each color are configured.

  The pixel arrangement of the liquid crystal display element 1 is not limited to the arrangement shown in FIGS. 3 to 6, and four pixels 13R, 13G, 13B, and 13W for each of red, green, blue, and white adjacent to each other. As long as it is an array that constitutes one display element 14.

  Since this liquid crystal display element 1 comprises one display element 14 by the pixels 13R, 13G, 13B, and 13W of four colors of red, green, blue, and white, no white pixel is provided, and red, green, and blue Compared to a three-color pixel display element in which one display element is configured by three color pixels, the screen can be brightened.

  Next, a driving method of the liquid crystal display element 1 will be described. The liquid crystal display element 1 is divided into three levels of red, green, and blue of a video signal input from the outside by the driving means 15 shown in FIG. Based on the tone data, driving of the four colors red, green, blue and white for driving the pixels 13R, 13G, 13B and 13W of red, green, blue and white for each of the plurality of display elements 14 is performed. Gradation data is generated, and the four color data signals corresponding to the drive gradation data are respectively converted into the four color pixels 13R, 13G, 13B, and 13W of the plurality of display elements 14. It drives by supplying to each.

  The driving unit 15 supplies a gate signal for sequentially turning on the TFT to a plurality of scanning lines of the liquid crystal display element 1 and a data signal to the plurality of data lines of the liquid crystal display element 1. Four colors of red, green, blue and white for each of the plurality of display elements 14 of the liquid crystal display element 1 based on the data drive circuit 17 to be supplied and the gradation data of the three colors of red, green and blue of the video signal. A plurality of values corresponding to the voltage corresponding to the gate signal and the number of gradations of the drive gradation data of the four colors red, green, blue and white. The power supply unit 19 generates a voltage, and the controller 20 controls the scanning drive circuit 16, the data drive circuit 17, and the calculation unit 18.

Said video signal is a signal including a synchronization signal corresponding to an image to be displayed, the red that define a display color corresponding to each one of the display elements, green, and gray scale data of three colors of blue, the controller 20 Is input.

  The controller 20 separates the synchronization signal and the like from the video signal and supplies them to the scan drive circuit 16 and the data drive circuit 17, and also calculates the gradation data of the three colors red, green and blue. The circuit 18 is supplied to control the operation of these circuits.

  The calculation unit 18 performs a plurality of display elements of the liquid crystal display element 1 by calculation according to a predetermined calculation procedure based on gradation data of three colors of red, green, and blue input from the controller 20. The drive gradation data of four colors of red, green, blue and white for every 14 are generated, and the drive gradation data of four colors of red, green, blue and white are supplied to the data drive circuit 17.

  The scan driving circuit 16 sequentially supplies a gate signal having a voltage value generated by the power supply unit 19 to a plurality of scan lines of the liquid crystal display element 1 in accordance with a synchronization signal from the controller 20.

  The data driving circuit 17 selects voltages corresponding to the drive gradation data of the four colors red, green, blue and white from the arithmetic unit 18 from the power supply unit 19, and red, Data signals of four colors of green, blue and white are supplied to the plurality of data lines of the liquid crystal display element 1 in correspondence with the synchronization signal.

  That is, the driving unit 15 sequentially selects a plurality of pixel rows of the liquid crystal display element 1 by supplying gate signals to the plurality of scanning lines, and pixels of the pixels 13R, 13G, 13B, and 13W in the selected row. The four color data signals corresponding to the drive gradation data of four colors of red, green, blue and white for each of the plurality of display elements 14 generated in the calculation unit 18 are applied to the electrode 5. Supply through line and TFT.

  The driving gradation data of the four colors red, green, blue and white are calculated in the calculation unit 18 as follows based on the input gradation data of the three colors red, green and blue. Can be obtained.

  That is, the pixels 13R, 13G, 13B, and 13W corresponding to the maximum gradation luminance of the four colors of the pixels 13R, 13G, 13B, and 13W for each of the plurality of display elements 14 are driven. The luminance ratio corresponding to the driving gradation data is the luminance ratio, and the difference between the luminance ratios of the red, green, and blue pixels 13R, 13G, and 13B for each of the plurality of display elements 14 is absolute. When the maximum value among the values is the maximum luminance rate difference, the luminance rates of the four colors of pixels 13R, 13G, 13B, and 13W for each of the plurality of display elements 14 are The luminance ratio of each of the red, green, and blue pixels 13R, 13G, and 13B corresponds to the maximum luminance ratio difference of a set luminance ratio that is predetermined in accordance with the characteristics of the white pixel 13W. Tones other than the number of tones Adding the luminance factor of the rate of response, as from the added value becomes a value the less the luminance ratio of the white pixel 13W, the four-color driving gradation data is determined.

  Here, the maximum gradation luminance of the four colors 13R, 13G, 13B, and 13W of red, green, blue, and white is the gradation data of the maximum gradation value in each of the pixels 13R, 13G, 13B, and 13W. Data corresponding to (for example, input gradation data of three colors of red, green, and blue are 64 steps of data with gradation values of 0 to 63, respectively, gradation data of gradation value 63) This is the intensity of emitted light when a signal is supplied.

  In this driving method, the luminance ratio between the red, green, and blue pixels 13R, 13G, and 13B of the liquid crystal display element 1 is determined from the input red, green, and blue color gradation data. Based on the difference, driving gradation data of red, green, blue and white for each of the plurality of display elements 14 is generated by calculation, and the four color data signals corresponding to the gradation data are respectively generated. By supplying the red, green, blue, and white pixels 13R, 13G, 13B, and 13W respectively, the gradation values of the input red, green, and blue gradation data are different from each other. At this time, it is intended to reduce the color shift of the display color of the display element 14 with respect to the color determined by the gradation data of the three colors of red, green and blue.

  In this driving method, the driving gradation data of red, green, blue and white for each of the plurality of display elements 14 is the gradation value of the inputted gradation data of three colors of red, green and blue. And assigning the smallest value to the white driving gradation data among the values obtained by adding the number of gradations corresponding to the difference in luminance ratio between the three pixels 13R, 13G, and 13B of the three colors red, green, and blue, respectively. The values obtained by subtracting the number of gradations assigned to the white driving gradation data from the gradation values of the inputted three gradation data of red, green, and blue, respectively, are the red, green, and blue. Color drive gradation data is used.

  More specifically, the inputted gradation data of three colors of red, green, and blue determines data having a large gradation difference between these three colors, that is, the display color of one display element 14 is a dark color. When it is data, the drive gradation data of the four colors of red, green, blue and white is set so as to lower the luminance of the white pixel 13W, and the inputted three colors of red, green and blue are set. When the gradation data is data having a small gradation difference between these three colors, that is, data for determining the display color of one display element 14 to be a light color, the brightness of the white pixel 13W is increased. Drive gradation data of four colors of red, green, blue and white is generated.

  In order to generate drive gradation data of the four colors red, green, blue and white, in this drive method, the pixels 13R and 13G of the three colors red, green and blue are provided for each of the plurality of display elements 14. , 13B corresponding to the inputted red, green and blue gradation data for the maximum gradation luminance (data corresponding to the inputted red, green and blue gradation data). The luminance ratio corresponding to the input data, which is the ratio of the intensity of the emitted light when the signal is supplied), and the absolute value of the difference between the luminance ratios corresponding to the input data among the three color pixels 13R, 13G, and 13B. Find the maximum value of.

Here, the maximum gradation luminances of the four pixels 13R, 13G, 13B, and 13W of red, green, blue, and white are _represented by L _maxR , L _maxG , L _maxB , L _maxW , and red, green, and blue, respectively. the color of the pixel 13R, 13G, 13B of red, which is each of the input, green, input data corresponding luminance brightness corresponding to the gradation data of three colors of blue _{L R,} L G, when the _{L B,} wherein the maximum gray adjusting brightness _{L maxR, L maxG, L maxB} , wherein for _{L maxW} input data corresponding luminance _{L R,} L G, the input data corresponding luminance factor _R R is the ratio of _{L B, R G,} R _B are each _R R = L _R / L _maxR , R _G = L _G / L _{max G} , R _B = L _B / R _{max B} , and the input data corresponding luminance ratios R _R , R _G , of the three color pixels 13R, 13G, 13B R _B The maximum luminance ratio difference d _max is the maximum value among the absolute values of | R _R −R _G |, | R _G −R _B |, | R _B −R _R |.

Further, the red, green, four-color pixels 13R blue and white, 13G, 13B, 13W each of the driving grayscale data to the corresponding luminance drive data corresponding Luminance _{L 'R, L' G,} L 'B , L ′ _W , and the drive data-corresponding luminance for the maximum gradation luminances L _maxR , L _max G, L _maxB , and L _maxW of the four-color pixels 13R, 13G, 13B, and 13W of red, green, blue, and white, respectively. L ′ _R , L ′ _G , L ′ _B , L ′ _W ratios L ′ _R / L _maxR , L ′ _G / L _maxG , L ′ _B / L _maxB , L ′ _W / L _maxW When the ratios R ′ _R , R ′ _G , R ′ _B , and R ′ _W are set, the luminance ratio corresponding to the driving data of the pixels 13R, 13G, and 13B of three colors of red, green, and blue out of the luminance ratio corresponding to these driving data. _{R 'R, R' G,} R ' Each said input data corresponding luminance factor _R R _is, R G, the _{R B,} by adding the luminance ratio corresponding to the maximum brightness index difference _{d max,} and the drive data corresponding luminance factor R'W of the white pixel 13W Expressed by the subtracted value.

The luminance ratio corresponding to the maximum luminance ratio difference d _max is a set luminance ratio of an arbitrary value determined in advance according to the characteristics of the white pixel 13W in the range of 0 to L _maxW / (L _maxR + L _maxG + L _maxB ). (hereinafter, the setting luminance factor and t) to the input data corresponding luminance factor R _R, R _G, corresponding to the gradation number of the maximum brightness index difference d _max of the whole grayscale number R _B other multiplied by the number of gradations excluding the number of gradations, further wherein the input data corresponding luminance factor _{R R,} R G, a value obtained by multiplying the _{R B,} i.e. the input data corresponding luminance factor _{R R,} R G, the _{R B} This corresponds to a portion corresponding to the number of gradations other than the number of gradations corresponding to the number of gradations of the maximum luminance rate difference _{dmax in} the total number of gradations.

Also, the luminance rate of the white pixel 13W is the maximum floor of the white pixel 13W with respect to the sum of the maximum gradation luminances L _maxR , L _maxG , and L _maxB of the red, green, and blue pixels 13R, 13G, and 13B. This ratio is expressed by a value obtained by multiplying the ratio of the luminance adjustment L _maxW by the driving data corresponding luminance ratio R ′ _W of the white pixel 13W.

Therefore, in this driving method, based on the input gradation data of the three colors of red, green, and blue,
As described above, the maximum gradation luminance of each of the red, green, blue, and white pixels 13R, 13G, 13B, and 13W is _expressed as L _maxR , L _maxG , L _maxB , L _maxW ,
The red, green, three-color pixels 13R blue, 13G, 13B of red, which is of each of the input, green, input data corresponding luminance brightness corresponding to the gradation data of three colors of blue _{L R, L} G, L _B ,
The red, green, three-color pixels 13R blue, 13G, 13B of each of the maximum gradation luminance _{L maxR,} L _MaxG, the input data corresponding luminance to _{L maxB L R, L G,} the proportion of _{L B L} R / L _maxR , L _G / L _maxG , and L _B / R _maxB are set as input data corresponding luminance rates R _R , R _G , R _B , respectively.
The red for each of the plurality of display elements 14, green, three-color pixels 13R blue, 13G, the input data corresponding luminance factor of 13B mutual _{R R,} R G, the absolute value of the difference between _{R B | R R} -R _G |, | R _G -R _B |, | R _B -R _R | is the maximum luminance ratio difference d _max ,
The luminance corresponding to the driving gradation data for driving each of the pixels 13R, 13G, 13B, 13W of the four colors of red, green, blue, and white is represented by driving data corresponding luminance L ′ _R , L ′ _G. , L ′ _B , L ′ _W ,
Luminance L ′ _R , L ′ corresponding to the drive data with respect to the maximum gradation luminances L _maxR , L _maxG , L _maxB , L _maxW of the four pixels 13R, 13G, 13B, 13W of red, green, blue and white, respectively. _{G, L 'B, L'} W ratio _{L 'R / L maxR, L} ' of the _{G / L maxG, L 'B} / L maxB, L' W / L maxW each drive data corresponding luminance factor _{R 'R,} R ′ _G , R ′ _B , R ′ _W
The drive data-corresponding luminance ratios R ′ _R , R ′ _G , R ′ _B , R ′ _W are
R ′ _R = R _R {1 + t (1−d _max )} − R ′ _W · L _maxW / (L _maxR + L _maxG + L _maxB )
R ′ _G = R _G {1 + t (1−d _max )} − R ′ _W · L _maxW / (L _maxR + L _maxG + L _maxB )
R ′ _B = R _B {1 + t (1−d _max )} − R ′ _W · L _maxW / (L _maxR + L _maxG + L _maxB )
However, t is a predetermined arbitrary value in the range of 0 or more and L _maxW / (L _maxW + L _maxG + L _maxB ) or less,
Drive gradation data of four colors of red, green, blue and white for each of the plurality of display elements 14 set to a gradation value satisfying the above is generated.

That is, in this driving method, the driving data corresponding luminance ratio R ′ _R of the red pixel 13R is determined based on the input three-color gradation data of red, green, and blue, and the input data corresponding luminance of the red pixel 13R. It is equal to the difference between the product of the rate R _R and 1 + t (1−d _max ) and the value obtained by multiplying the drive data corresponding luminance rate R ′ _W of the white pixel 13W by L _maxW / (L _maxR + L _maxG + L _maxB ). , The driving data corresponding luminance ratio R ′ _G of the green pixel 13G is the product of the input data corresponding luminance ratio _{RG of the} green pixel 13G and 1 + t (1−dmax), and the driving data corresponding luminance ratio R of the white pixel 13W. ′ _W is equal to the difference between L _maxW / (L _maxR + L _maxG + L _maxB ), and the luminance ratio R ′ _B corresponding to the drive data of the blue pixel 13B is equal to the input of the blue pixel 13B. Data corresponding luminance factor and _{R B} and the product of the 1 + t (1-dmax) , the difference between the white pixel value obtained by multiplying _L maxW _/ a _{(L maxR + L maxG + L} maxB) the drive data corresponding luminance factor R _'W of 13W The gradation values of four colors of red, green, blue and white for each of the plurality of display elements 14 are set so as to be equal to each other, and driving gradation data of these gradation values are generated, respectively, Four-color data signals are supplied to the four-color pixels 13R, 13G, 13B, and 13W of the plurality of display elements 14, respectively.

(First embodiment)
A specific example of this driving method will be described. For example, the liquid crystal display element 1 has red, green, blue and white four-color pixels 13R, 13G, 13B, and 13W with luminances of these pixels 13R, 13G. , 13B, 13W, and the maximum gradation luminance L _maxW of the white pixel 13W is proportional to the gradation value of the driving gradation data for driving the pixels 13R, 13G, 13B of the three colors red, green, and blue. each maximum gradation luminance _{L maxR,} L _MaxG, if a device that is designed to have a sum and equal Shii characteristics of _{L maxB,} red for each of the plurality of display elements 14, green, four colors of blue and white The drive gradation data of
The gradation values of the inputted red, green and blue gradation data are the gradation values of the driving gradation data of four colors of D _R , D _G , D _B and red, green, blue and white. Is D ′ _R , D ′ _G , D ′ _B , D ′ _W ,
D ′ _R is a value obtained by _converting D _R {1 + t (1−d _max )} − C into an integer D ′ _G is a value obtained by converting D _G {1 + t (1−d _max )} − C into an integer D ′ _B is D _B {1 + t (1−d _max )} — a value obtained by converting C to an integer D ′ _W is a value obtained by converting C to an integer, where t = 1 and C are D _R {1 + t (1−d _max )}, D _G { _{1 + t (1-d max} )}, when the smallest value among _{D B {1 + t (1} -d max)} and _{D min,} when the _{D min} is less than the maximum tone is an integer of the _{D min} When the D _min is equal to or greater than the maximum gradation, the maximum gradation value is assumed.
Respectively.

Here, assuming that the input gradation data of the three colors red, green, and blue are, for example, 64 levels of data with gradation values of 0 to 63, the red, green, blue, and white 4 data. The maximum gradation luminance of each of the color pixels 13R, 13G, 13B, and 13W (luminance when a data signal corresponding to gradation data having a gradation value of 63 is supplied) L _maxR , L _maxG , L _maxB , and L _maxW are ,
L _maxR = 22 cd / m ²
L _maxG = 62 cd / m ²
L _maxB = 16 cd / m ²
L _maxW = 100 cd / m ²
It is.

That is, the maximum gradation luminances L _maxR , L _maxG , L _maxB , and L _maxW of the four color pixels 13R, 13G, 13B, and 13W of red, green, blue, and white are L _maxW = L _maxR + L _maxG + L _maxB There is a relationship.

  FIG. 7 shows the respective colors when data signals corresponding to the gradation data of the maximum gradation are supplied to the four color pixels 13R, 13G, 13B, and 13W of red, green, blue and white of the liquid crystal display element 1, respectively. The spectral characteristics of light of four colors of red, green, blue and white emitted from the pixels 13R, 13G, 13B and 13W are shown.

The luminance ratios R _R , R _G , R _B (R _R = L _R / L _maxR , R _G = L _G / L _maxG , R) of the red, green and blue pixels 13R, 13G, 13B _B = L _B / R _maxB ) means that the luminance of the four colors 13R, 13G, 13B, and 13W of the red, green, blue, and white of the liquid crystal display element 1 is determined by the pixels 13R, 13G, 13B, and 13W. When proportional to the gradation value of the drive gradation data for driving, it can be expressed by R _R = L _R / 63, R _G = L _G / 63, and R _B = L _B / 63.

Further, one of the four pixels 13R, 13G, 13B, and 13W of red, green, blue, and white constituting the one display element 14 corresponds to gradation data having a gradation value of 63. The display element 14 display chromaticity x, y (x coordinate value and y) when the data signal is supplied and the data signal corresponding to the gradation data of gradation value 0 is supplied to the other three color pixels. Coordinate value) is
A data signal corresponding to gradation data having a gradation value of 63 was supplied to the red pixel 13R, and a data signal corresponding to gradation data having a gradation value of 0 was supplied to the pixels 13G, 13B, and 13W of the other colors. When x = 0.56, y = 0.36
A data signal corresponding to gradation data having a gradation value of 63 was supplied to the green pixel 13G, and a data signal corresponding to gradation data having a gradation value of 0 was supplied to the pixels 13R, 13B, and 13W of the other colors. When x = 0.34, y = 0.54
A data signal corresponding to gradation data having a gradation value of 63 was supplied to the blue pixel 13B, and a data signal corresponding to gradation data having a gradation value of 0 was supplied to the pixels 13R, 13G, and 13W of other colors. When x = 0.16, y = 0.13
A data signal corresponding to gradation data having a gradation value of 63 was supplied to the white pixel 13W, and a data signal corresponding to gradation data having a gradation value of 0 was supplied to the pixels 13R, 13G, and 13B of other colors. When x = 0.31, y = 0.32.
It is.

On the other hand, the gradation values D ′ _R , the driving gradation data of the four colors red, green, blue and white for driving the red, green, blue and white pixels 13R, 13G, 13G and 13W. D ′ _G , D ′ _B and D ′ _W are as described above,
D ′ _R = D _R {1 + t (1−d _max )} − C integerized value D ′ _G = D _G {1 + t (1−d _max )} − C integerized value D ′ _B = D _B {1 + t (1-d _max )}-C integer value D ′ _W = Set to C integer value.

In this embodiment, since the maximum gradation value of the inputted three gradation data of red, green, and blue is 63, D _R {1 + t (1−d _max )}, D _G {1 + t ( 1−d _max )}, D _B {1 + t (1−d _max )}, the coefficient C corresponding to the smallest value D _min is C = D _min when the D _min is less than 63, When D _min is 63 or more, C = 63.

Also, the absolute value | R _R −R _G of the difference between the input data-corresponding luminance rates R _R , R _G , and R _B among the three colors of pixels 13R, 13G, and 13B in one display element 14. |, | R _G −R _B |, | R _B −R _R |, the maximum luminance rate difference d _max is the gradation value of the gradation data of the three colors red, green, and blue for the display element 14. _{D R,} D G, corresponding to the _{D B.}

When the gradation data of three colors of red, green, and blue for the one display element 14 is data that defines an intermediate color obtained by mixing the three colors of red, green, and blue at different ratios, for example, the red, green, the gradation value _D R of the gradation data of three colors of _blue, D G, is _{D B,} when _{D R = 47, D G =} 29, D B = 15, d max = 47 / 63-15 / 63 = 32/63.

Then, if the set luminance rate t of an arbitrary value determined in advance according to the characteristics of the white pixel 13W is, for example, t = 1,
D _R {1 + t (1-d _max )} = 47 {1 + 1 (1-32 / 63)} = 70.13
D _G {1 + t (1-d _max )} = 29 {1 + 1 (1-32 / 63)} = 43.27
D _B {1 + t (1-d _max )} = 15 {1 + 1 (1-32 / 63)} = 22.38
C = 22.38
It becomes.

That is, the red, green, gray-scale value _D R of the gradation data of three colors of _blue, D G, is _{D B,} D the red when _{R = 47, D G = 29} , D B = 15, green The gradation values D ′ _R , D ′ _G , D ′ _B , and D ′ _W of the drive gradation data of the four colors of blue and white are
D ′ _R = An integer value of 70.13-22.38 = 48
D ' _G = Integer value of 43.27-22.38 = 21
D ′ _B = 2.38-22.38 integerized value = 0
D ′ _W = 38 integer value = 22
It becomes.

The values of D ′ _R , D ′ _G , D ′ _B , and D ′ _R are integer values obtained by rounding off the values after the decimal point. It may be rounded down or rounded up.

Therefore, the drive data corresponding luminance L ′ _R , L ′ _G , L ′ _B , and L ′ _W of the four-color pixels 13R, 13G, 13B, and 13W of red, green, blue, and white are:
L ′ _R = 22 × 48/63 = 17 cd / m ²
L ′ _G = 62 × 21/63 = 21 cd / m ²
L ′ _B = 16 × 0/63 = 0 cd / m ²
L ′ _W = 100 × 22/63 = 35 cd / m ²
Thus, the chromaticities x and y of the display element 14 constituted by these four color pixels 13R, 13G, 13B, and 13W are x = 0.38 and y = 0.38.

The chromaticity of x = 0.38 and y = 0.38 is the red and green of one display element in a three-color pixel display element in which one display element is composed of pixels of three colors of red, green and blue. Chromaticity of display of the display element when the data signals corresponding to the gradation data of the three colors of red, green and blue are respectively 47, 29 and 15 are supplied to the pixels of three colors of blue and blue (see section problems to be solved invention) to be the same.

Here, red inputted, green, gray-scale value _D R of the gradation data of three colors of _blue, D G, is _{D B,} when _{D R = 47, D G =} 29, D B = 15 has been described in the gray scale display, the other gray scale display, i.e., the red, green, gray-scale value D _R of the gradation data of three colors of _blue, D _G, D _B are at different values other than 0, respectively On one occasion, and the red, green, gray-scale value D _R of the gradation data of three colors of _blue, D _G, the gradation value of one color grayscale data among the D _B is 0, the other two colors The chromaticity of intermediate color display when gradation values of gradation data are different from each other or the same value other than 0 is also three colors of red, green and blue constituting one display element of the three-color pixel display element. the pixel, the red input, green, the display elements is the same as the chromaticity when the supplied three-color data signals corresponding to the grayscale data of blue.

  Therefore, the display color of the display element 14 when the input gradation data of the three colors red, green, and blue is a data that defines an intermediate color is determined by the gradation data of the three colors red, green, and blue. This color has almost no color shift with respect to a predetermined color.

Further, when the gradation data of three colors of red, green, and blue for the one display element 14 is data that defines any one of red, green, and blue, for example, the three of red, green, and blue the gradation value _D R of the gradation data of _color, D G, is _{D B,} when the _{D R = 63, D G =} 0, D B = 0, d max = 63 / 63-0 / 63 = 63 / 63 = 1.

And if t = 1,
D _R {1 + t (1−d _max )} = 63 {1 + 1 (1-1)} = 63
_DG {1 + t (1- _dmax )} = 0 {1 + 1 (1-1)} = 0
D _B {1 + t (1-d _max )} = 0 {1 + 1 (1-1)} = 0
C = 0
So that
D ′ _R = 63
D ′ _G = 0
D ′ _B = 0
D ′ _R = 0
It becomes.

That is, the red, green, gray-scale value _D R of the gradation data of three colors of _blue, D G, is _{D B, D R = 63,} D G = 0, D B = the display element 14 when the 0 Of the red pixel 13R is the maximum gradation luminance L _maxR = 22 cd / m ² , and the chromaticities x and y are x = 0.56 and y = 0.36, and the red, green, blue The red color having no color deviation with respect to the color determined by the gradation data of the three colors is displayed.

Note that the red, green, gray-scale value _D R of the gradation data of three colors of _blue, D G, is _{D B,} when _{D R = 0, D G =} 63, D B = 0, the red, Green without any color deviation with respect to the color determined by the gradation data of three colors of green and blue is displayed. When D _R = 0, D _G = 0, and D _B = 63, the red, green, and blue colors are displayed. A blue color having no color shift with respect to the color determined by the gradation data of the three colors is displayed.

Further, when the gradation data of the three colors red, green, and blue for the one display element 14 is data defining white, that is, the gradation value D of the gradation data of the three colors red, green, and blue. _{R, D} G, is _{D B,} when the _{D R = 63, D G =} 63, D B = 63, is d max = 63 / 63-63 / 63 = 0.

And if t = 1,
_{D R {1 + t (1} -d max)} = 63 {1 + 1 (1-0)} = 126
D _G {1 + t (1-d _max )} = 63 {1 + 1 (1-0)} = 126
D _B {1 + t (1-d _max )} = 63 {1 + 1 (1-0)} = 126
C = 63
So that
D ′ _R = 63
D ′ _G = 63
D ′ _B = 63
D ′ _R = 63
It becomes.

That is, the red, green, gray-scale value _D R of the gradation data of three colors of _blue, D G, is _{D B, D R = 63,} D G = 63, D B = 63 the display element 14 when the _Are the maximum gradation luminances L _maxR (22 cd / m ² ), L _maxG (62 cd / m ² ), L _maxB (L _maxB ) of the pixels 13R, 13G, 13B, and 13W of the four colors red, green, blue, and white. 16 cd / m ² ), L _maxW (100 cd / m ² ), 22 + 62 + 16 + 100 = 200 cd / m ² , and chromaticity is x = 0.31, y = 0.32, and the red, green, blue A white color having no color shift with respect to the color determined by the gradation data of the three colors is displayed. The luminance (200 cd / m ² ) at the time of white display is 1.5 times the luminance of white display of the three-color pixel liquid crystal display element.

Note that the red, green, when the gradation value D _R of the gradation data of three colors of _blue, D _G, is D _B 0 respectively, the red, green, defined by the gradation data of three colors of blue displayed no black color shift with respect to the color, the gradation value D _R, D _G, D _B, respectively 0 or more, when the same value in the range of less than 63, the red, green, three colors of blue A gray color (intermediate color between white and black) with no color shift with respect to the color determined by the gradation data is displayed.

As described above, according to the driving method, when the input gradation data of three colors of red, green, and blue is data defining an intermediate color, that is, the gradation of the three colors of red, green, and blue. when the gradation value _D R _data, D G, is _{D B} is and different values other than 0, respectively, and the red, green, gray-scale value _D R of the gradation data of three colors of _{blue, D} G, gradation value of one color grayscale data among the D _B is 0, when the gradation value of the gradation data of the other two colors are different values or the same value other than 0, the red, green, The color shift of the display color of the display element 14 with respect to the color determined by the gradation data of three colors of blue is reduced, and 1 by the four colors 13R, 13G, 13B, and 13W of the red, green, blue, and white. The liquid crystal display element 1 constituting one display element 14 has excellent color reproducibility corresponding to the input gradation data of the three primary colors. Color images can be displayed.

In each of the above embodiments, the set luminance rate t having an arbitrary value determined in advance according to the characteristics of the white pixel 13W is set to t = 1, but this set luminance rate t is 0 or more and L _maxW / Any predetermined value in a range of (L _maxW + L _maxG + L _maxB ) or less may be used. By reducing the set luminance rate t, the luminance ratio between white and other colors in the intermediate color display is set to 3. The color ratio of the color pixel display element is made closer to the luminance ratio of the color pixel display element, and the color shift with respect to the color determined by the gradation data of the three colors of red, green, and blue can be further effectively reduced.

  For example, when the luminance ratio of white and yellow display of the three-color pixel display element is 1: 0.83, the white and yellow of the liquid crystal display element 1 when t = 1 in the driving method of the present invention. The luminance ratio of display is 1: 0.42, but when t = 0.5, the luminance ratio of white and yellow display is 1: 0.55. However, the brightness of white display is about 1.1 times that of the white display of the three-color pixel display element.

  Therefore, by reducing the set luminance rate t, the liquid crystal in which one display element 14 is configured by the three-color pixel display element and the four-color pixels 13R, 13G, 13B, and 13W of red, green, blue, and white. It is possible to almost eliminate the discomfort of the display color due to the difference in luminance ratio between the white color and the other color display with the display element 1.

Further, in the above embodiment, the smallest value D among the D _R {1 + t (1−d _max )}, D _G {1 + t (1−d _max )}, D _B {1 + t (1−d _max )}. the coefficient C corresponding to _min, the _D when _min is smaller than the maximum gradation (gradation value of 63 in the above embodiment) and _{C = D min,} when the _{D min} is equal to or greater than the maximum tone is C = 63 The coefficient C is equal to or less than D _min , D _R {1 + t (1−d _max )}, D _G {1 + t (1−d _max )}, D _B {1 + t (1−d _max )}. It may be an arbitrary value in a range equal to or larger than a value obtained by subtracting the maximum gradation value from the largest value D _{max of} .

  The coefficient C indicates that the pixel arrangement of the liquid crystal display element 1 is a white pixel 13W between the pixels of two colors among the pixels 13R, 13G, and 13B of three colors of red, green, and blue, that is, the center of the display element 14. Is preferably set to a value as large as possible, and by doing so, the brightness of white display is compared with the brightness of the pixels 13R, 13G, and 13B of three colors of red, green, and blue. To make the screen brighter.

Further, when the pixel array of the liquid crystal display element 1 is an array in which the white pixels 13W are located at the end of the display element 14, it is preferable to make the coefficient C as small as possible. It is possible to display a color image with better color reproducibility corresponding to the input gradation data of three colors of red, green, and blue. In this case, the coefficient C, the if D _max is greater than or equal to the maximum gray level of the gray scale data inputted to the value obtained by subtracting the maximum tone value from the D _min, when the D _min is less than the maximum tone is C = 0 may be set.

Further, in the above embodiment, the liquid crystal display element 1 supplies the luminances of the four colors of the pixels 13R, 13G, 13B, and 13W to the pixels 13R, 13G, 13B, and 13W. The maximum gradation luminance L _maxW of the white pixel 13W is proportional to the gradation value of the gradation data, and the maximum gradation luminance L of _each of the red, green, and blue pixels 13R, 13G, and 13B. _{maxR, L MaxG,} but applies when having a sum and equal Shii characteristics of L _maxB, the driving method of this invention can be the liquid crystal display device 1 is applied to a case having other properties .

(Second embodiment)
That is, the liquid crystal display element 1 has gradation data in which the luminance of each of the red, green, blue and white pixels 13R, 13G, 13B and 13W is supplied to these pixels 13R, 13G, 13B and 13W. And the maximum gradation luminance L _maxW of the white pixel 13W is the maximum gradation luminance L _maxR , L _maxG , of each of the red, green, and blue pixels 13R, 13G, 13B. When the characteristics differ from the sum of L _maxB , the gradation values D ′ _R , D ′ _G , D ′ _B , D ′ _W of the drive gradation data of the four colors red, green, blue and white are used. The
D ′ _R is a value obtained by _converting D _R {1 + t (1−d _max )} − C ′ · L _maxW / (L _maxR + L _maxG + L _maxB ) into an integer D ′ _G is D _G {1 + t (1−d _max )} _{-C '· L maxW / (L} maxR + L maxG + L maxB) the integer value _{D' B} is _{D B {1 + t (1} -d max)} - C '· L maxW / (L maxR + L maxG + L maxB) the integer value D, however _'W is C' values were integers of the, t = 1, C _{'is, D R {1 + t (} 1-d ma x) (L maxR + L maxG + L maxB) / L maxW}, _{D G {1 + t (1} -d max)} (L maxR + L maxG + L maxB) / L max W, D B {1 + t (1-d max)} (L maxR + L maxG + L maxB) / L most of _maxW small _{'When min,} and the _D' a have value _{D min} is _'integer values of _min, before Symbol _D' its _D if less than the maximum gradation _min is maximum gradation when the above said maximum gradation Value
Set the gradation value that satisfies the above.

  According to this embodiment, the inputted red, green, and blue color gradation data is determined by the gradation data of the red, green, and blue colors when the intermediate color is determined. The color shift of the display color of the display element 14 with respect to the color can be reduced, and a color image with good color reproducibility corresponding to the input gradation data of the three primary colors can be displayed on the liquid crystal display element 1 having the above characteristics. .

In this embodiment, the set luminance rate t of an arbitrary value determined in advance according to the characteristics of the white pixel 13W is set to t = 1, but this set luminance rate t is 0 or more and L _maxW / ( L _maxW + L _maxG + L _maxB ) Any predetermined value within the following range may be used.

(Third embodiment)
Further, the liquid crystal display element 1 has gradation data in which the luminance of each of the red, green, blue, and white pixels 13R, 13G, 13B, and 13W is supplied to the pixels 13R, 13G, 13B, and 13W. And the maximum gradation luminance _LmaxW of the white pixel 13W is the maximum gradation luminance L _{maxR of} each of the three colors 13R, 13G, and 13B of red, green, and blue. , _{L MaxG,} if you have a sum and equal Shii characteristics of _{L maxB,} the red, green, gray scale value _D of the driving gradation data for four colors of blue and white _{'R, D'} G, D ' _B , D ' _W
The red, converts green, three-color gray scale data _D R of _blue, D G, luminance respectively _{D B L R, L G,} the _{L B,}
L ′ _R / L _maxR = L _R {1 + t (1−d _max )} / L _{max R−} C ″ · L _maxW / (L _maxR + L _maxG + L _maxB )
_{L 'G / L maxG = L} G {1 + t (1-d max)} / L maxG -C "· L maxW / (L maxR + L maxG + L maxB)
L ′ _B / L _maxB = L _B {1 + t (1−d _max )} / L _{max B−} C ″ · L _maxW / (L _maxR + L _maxG + L _maxB )
L ′ _W / L _maxW = C ″
However, t = 1, C ″ is L _R {1 + t (1−d _max )} (L _maxR + L _maxG + L _maxB ) / L _maxR · L _maxW , L _G {1 + t (1−d _max )} (L _maxR + L _maxG + L _maxB ) / L _maxG · L _maxW , L _B {1 + t (1−d _max )} (L _maxR + L _maxG + L _maxB ) / L _maxB · L _maxW when D ″ _min , _D and rounding the _{min "min} is the value _D in the case of less than _1" value, before Symbol D _"min is 1 if greater than 1,
The red, green, blue and four colors of pixels each luminance _{L 'R,} L' white _G, L _'B, L' and _W calculated by the equations, these luminance _{L 'R, L' G,} L ′ _B and L ′ _W are respectively set as gradation values obtained by inverse conversion into gradation values.

  According to this embodiment, the inputted red, green, and blue color gradation data is determined by the gradation data of the red, green, and blue colors when the intermediate color is determined. The color shift of the display color of the display element 14 with respect to the color can be reduced, and a color image with good color reproducibility corresponding to the input gradation data of the three primary colors can be displayed on the liquid crystal display element 1 having the above characteristics. .

In this embodiment, the set luminance rate t of an arbitrary value determined in advance according to the characteristics of the white pixel 13W is set to t = 1, but this set luminance rate t is 0 or more and L _maxW / ( L _maxW + L _maxG + L _maxB ) Any predetermined value within the following range may be used.

1 is a configuration diagram of a liquid crystal display device. FIG. 3 is a cross-sectional view of a part of a liquid crystal display element. The figure which shows the pixel array example of the said liquid crystal display element. The figure which shows the other pixel arrangement example of the said liquid crystal display element. The figure which shows the other pixel arrangement example of the said liquid crystal display element. The figure which shows the other pixel arrangement example of the said liquid crystal display element. When a data signal corresponding to the gradation data of the maximum gradation is supplied to the four color pixels of red, green, blue and white of the liquid crystal display element, red, green, blue and white emitted from the pixels of each color FIG. 4 is a spectral characteristic diagram of light of four colors.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element, 13R ... Red pixel, 13G ... Green pixel, 13B ... Blue pixel, 13W ... White pixel, 14 ... Display element, 15 ... Drive means.

Claims (5)

A color image is formed by a plurality of display elements in which a plurality of pixels of three primary colors and white are alternately arranged in a matrix, and four pixels of each of the three primary colors and white adjacent to each other are used as one unit. In a driving method of a liquid crystal display element that displays
Based on the input gradation data of the three primary colors,
The ratio of the luminance corresponding to the driving gradation data for driving these pixels with respect to the maximum gradation luminance of each of the three primary colors and the four colors of white, the luminance ratio,
When the maximum value of the absolute value of the difference in luminance rate between the pixels of the three primary colors for each of the plurality of display elements is the maximum luminance rate difference
The luminance ratios of the four primary color pixels and the white color pixels for each of the plurality of display elements are set to arbitrary values predetermined according to the characteristics of the white pixels in the luminance ratios of the respective three primary color pixels. Add a luminance rate corresponding to the number of gradations other than the number of gradations corresponding to the maximum luminance rate difference of the luminance rate, and subtract the luminance rate of the white pixel from the added value, Four drive gradation data of three primary colors and white are set for each of the plurality of display elements, and the four color data signals corresponding to the drive gradation data are respectively set to the three primary colors and white 4 of the plurality of display elements. A driving method of a liquid crystal display element, characterized by being supplied to each color pixel. Red, green, blue 及 plurality of pixels of four colors of the lightening is formed by arranging in a matrix alternately mutually adjacent said red, green, blue, and 1 unit of four pixels of each color one by one white In a driving method of a liquid crystal display element that displays a color image by a plurality of display elements,
Based on the input gradation data of red, green and blue,
The maximum gradation luminance of each of the red, green, blue and white pixels is _expressed as L _maxR , L _maxG , L _maxB , L _maxW ,
Luminances corresponding to the input three-color gradation data of red, green, and blue for each of the red, green, and blue pixels are represented by input data-corresponding luminances L _R , L _G , L _B ,
The red, green, and blue three color pixels each of the maximum gradation luminance _{L maxR, L maxG, L} the input to _maxB data corresponding luminance _{L R,} L G, the ratio _L R _{/ L} maxR of _{L B, L G} / L _maxG and L _B / L _maxB are input data corresponding luminance rates R _R , R _G , R _B , respectively.
The red for each of the plurality of display elements, green, the input data corresponding luminance of the pixels mutual three colors blue _{R R,} R G, the absolute value of the difference between _{R B | R R -R G |} , | R G −R _B |, | R _B −R _R | is the maximum luminance ratio difference d _max ,
The brightness corresponding to the drive gradation data for driving each of the red, green, blue and white pixels is set to drive data corresponding brightness L ′ _R , L ′ _G , L ′ _B , L ′. _W
The drive data-corresponding luminances L ′ _R , L ′ _G , L ′ _B , and L for the maximum gradation luminances L _maxR , L _maxG , L _maxB , and L _maxW of the pixels of the four colors of red, green, blue, and white, respectively. ′ _W ratios L ′ _R / L _maxR , L ′ _G / L _maxG , L ′ _B / L _maxB , L ′ _W / L _maxW are respectively set to drive data corresponding luminance rates R ′ _R , R ′ _G , R ′ _B , When R ′ _W ,
The drive data-corresponding luminance ratios R ′ _R , R ′ _G , R ′ _B , R ′ _W are
R ′ _R = R _R {1 + t (1−d _max )} − R ′ _W · L _maxW / (L _maxR + L _maxG + L _maxB )
R ′ _G = R _G {1 + t (1−d _max )} − R ′ _W · L _maxW / (L _maxR + L _maxG + L _maxB )
R ′ _B = R _B {1 + t (1−d _max )} − R ′ _W · L _maxW / (L _maxR + L _maxG + L _maxB )
However, t is a predetermined arbitrary value in the range of 0 or more and L _maxW / (L _maxW + L _maxG + L _maxB ) or less,
Driving gradation data of red, green, blue and white for each of the plurality of display elements set to a gradation value satisfying the above-mentioned, is generated, and the four colors corresponding to these driving gradation data are generated. A driving method of a liquid crystal display element, wherein a data signal is supplied to each of four pixels of red, green, blue and white of the plurality of display elements. In the liquid crystal display element, the luminance of each of the four colors of red, green, blue and white is proportional to the gradation value of the driving gradation data for driving these pixels, and the maximum gradation luminance of the white pixel L _maxW is, has red, green, three color pixels each maximum gradation luminance _L maxR _blue, L _MaxG, the sum and equal Shii characteristics of _{L maxB,}
The drive gradation data of four colors of red, green, blue and white for each of a plurality of display elements is
The gradation values of the input red, green, and blue color gradation data are the D _R , D _G , D _B , and the red, green, blue, and white driving gradation data gradation values. When D ′ _R , D ′ _G , D ′ _B , and D ′ _W ,
D ′ _R is a value obtained by _converting D _R {1 + t (1−d _max )} − C into an integer D ′ _G is a value obtained by converting D _G {1 + t (1−d _max )} − C into an integer D ′ _B is D _B {1 + t (1−d _max )} — value obtained by converting C to an integer D′ W is a value obtained by converting C to an integer, where t = 1 and C are D _R {1 + t (1−d _max )}, D _G { _{1 + t (1-d max} )}, when the smallest value among _{D B {1 + t (1} -d max)} and _{D min,} when the _{D min} is less than the maximum tone is an integer of the _{D min} When the D _min is equal to or greater than the maximum gradation, the maximum gradation value is set.
The method for driving a liquid crystal display element according to claim 2, wherein the gradation values are set respectively. In the liquid crystal display element, the luminance of each of the four colors of red, green, blue and white is proportional to the gradation value of the driving gradation data for driving these pixels, and the maximum gradation luminance of the white pixel L _maxW has a characteristic different from the sum of the maximum gradation luminances L _maxR , L _maxG , and L _maxB of the three pixels of red, green, and blue,
The drive gradation data of four colors of red, green, blue and white for each of a plurality of display elements is
The gradation values of the input red, green, and blue color gradation data are the D _R , D _G , D _B , and the red, green, blue, and white driving gradation data gradation values. When D ′ _R , D ′ _G , D ′ _B , and D ′ _W ,
D ′ _R is a value obtained by _converting D _R {1 + t (1−d _max )} − C ′ · L _maxW / (L _maxR + L _maxG + L _maxB ) into an integer D ′ _G is D _G {1 + t (1−d _max )} _{-C '· L maxW / (L} maxR + L maxG + L maxB) the integer value _{D' B} is _{D B {1 + t (1} -d max)} - C '· L maxW / (L maxR + L maxG + L maxB) D ′ _W is a value _{obtained by converting} C ′ to an integer. However, t = 1, C ′ is D _R {1 + t (1−d _max )} (L _maxR + L _maxG + L _maxB ) / L _maxW , D _{G {1 + t (1-} d max)} (L maxR + L maxG + L maxB) / L maxW, D B {1 + t (1-d max)} smallest among the _{(L maxR + L maxG + L} maxB) / L maxW When the threshold value is D ′ _min , when D ′ _min is less than the maximum gradation, the value obtained by _converting D ′ _min to an integer, and when D ′ _min is greater than or equal to the maximum gradation, the maximum gradation value is obtained. And
The method for driving a liquid crystal display element according to claim 2, wherein the gradation values are set respectively. In the liquid crystal display element, the luminance of each of the four colors of red, green, blue and white is expressed by a function other than the proportionality of the gradation value of the driving gradation data for driving these pixels, and the white pixel maximum gradation luminance LmaxW of has red, green, three color pixels each maximum gradation luminance _L maxR _blue, L _MaxG, the sum and equal Shii characteristics of _{L maxB,}
The drive gradation data of four colors of red, green, blue and white for each of a plurality of display elements is
The inputted red, green, and blue gradation data is D _R , D _G , D _B , and the red, green, blue, and white driving gradation data is D ′ _R , D ′ _G , When D ′ _B and D ′ _W ,
The red, converts green, three-color gray scale data _D R of _blue, D G, luminance respectively _{D B L R, L G,} the _{L B,}
L ′ _R / L _maxR = L _R {1 + t (1−d _max )} / L _maxR −C ″ · L _maxW / (L _maxR + L _maxG + L _maxB )
_{L 'G / L maxG = L} G {1 + t (1-d max)} / L maxG -C "· L maxW / (L maxR + L maxG + L maxB)
L ′ _B / L _maxB = L _B {1 + t (1−d _max )} / L _maxB −C ″ · L _maxW / (L _maxR + L _maxG + L _maxB )
L ′ _W / L _maxW = C ″
However, t = 1, C _{"is, L R {1 + t (} 1-d max)} (L maxR + L maxG + L maxB) / L maxR · L maxW, L G {1 + t (1-d max)} (L maxR + L _maxG + L _maxB ) / L _maxG · L _maxW , L _B {1 + t (1−d _max )} (L _maxR + L _maxG + L _maxB ) / L _maxB · L _maxW when D ″ _min When D ″ _min is 1 or less, a value obtained by _converting D ″ _min into an integer, and when D ″ _min is greater than 1, set to 1.
The red by each formula, green, blue and four colors of pixels each drive data corresponding luminance _{L 'R,} L' white _G, L _'B, L' seeking _W, these driving data corresponding luminance L _'R 3. The method of driving a liquid crystal display element according to claim 2, wherein the gradation values are set to values obtained by inversely converting L ′ _G , L ′ _B and L ′ _W into gradation values.

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