CN100445819C - Liquid crystal display with low color cast and driving method thereof - Google Patents

Abstract

A liquid crystal display includes a plurality of scan lines, a plurality of data lines, pixels, a first switch circuit, and a second switch circuit. The plurality of scanning lines comprise an Nth scanning line and an N +1 th scanning line, wherein N is a positive integer. The pixel comprises a first sub-pixel and a second sub-pixel. The first switch circuit is coupled to the nth scan line and the (N + 1) th scan line, and the first switch circuit is used for controlling the second sub-pixel. The second switch circuit is coupled to the Nth scan line and is used for controlling the first sub-pixel. Wherein the pixel is used for displaying one of red, green, blue or white.

Description

Liquid crystal display with low color shift and its driving method

technical field

The present invention relates to a liquid crystal display and its driving method, in particular to a low color shift liquid crystal display and its driving method.

Background technique

With the thinner display trend, liquid crystal displays are currently widely used in various electronic products such as mobile phones, notebook computers, and color TV sets. However, in a traditional color liquid crystal display, a pixel is only provided with one driving voltage within a frame period (Frame Period), so that the corresponding liquid crystal presents a specific angle of inclination, which results in color changes as the viewer's viewing angle changes. offset. Figure 1 shows the equivalent circuit of a known pixel, which is arranged at the intersection of the Mth data line and the Nth scanning line, and this equivalent circuit includes a thin film transistor T ₁₁ , a liquid crystal capacitor C _LC , and a storage capacitor C _ST . As shown in FIG. 1 , the pixel is controlled by the thin film transistor _T11 so that the pixel is only provided with one driving voltage within a frame time.

FIG. 2 shows a plot of the transmittance (Transmittance) versus the driving voltage of a known liquid crystal display under different viewing angles (θ). FIG. 3 shows the plot of the transmittance of a known liquid crystal display against the gray level (Gray Level) under different viewing angles (θ). It can be seen from FIG. 2 and FIG. 3 that under the same driving voltage or the same gray scale, different viewing angles will result in different transmittances, and thus color shift will appear when displaying images. Therefore, how to improve the color shift phenomenon to improve the image quality of the liquid crystal display is one of the subjects that the industry is dedicated to.

Contents of the invention

In view of this, the object of the present invention is to provide a liquid crystal display with improved color shift and its driving method, which can effectively reduce the color shift phenomenon and improve the image quality of the display.

According to the purpose of the present invention, a liquid crystal display is proposed, which includes a plurality of scan lines, a plurality of data lines, pixels, a first switch circuit, and a second switch circuit. The plurality of scan lines includes an Nth scan line and an N+1th scan line, where N is a positive integer. The pixel includes a first sub-pixel and a second sub-pixel. The first switch circuit is coupled to the Nth scan line and the N+1th scan line, and the first switch circuit is used to control the second sub-pixel. The second switch circuit is coupled to the Nth scan line, and the second switch circuit is used to control the first sub-pixel. Wherein the pixel is used to display one of red, green, blue, or white, wherein the first switch circuit includes: a first transistor, including a first gate, a first source and a first drain, and the first gate is controlled by the Nth scanning line, and the first source is coupled to the Mth data line; and the second transistor includes a second gate, a second source and a second drain, and the first source is coupled to the Mth data line; The second gate is controlled by the N+1 scan line, the second source is coupled to the first drain, and the second drain is coupled to the second sub-pixel, when the first When the transistor and the second transistor are turned on at the same time, a sub-pixel voltage transmitted by the Mth data line is output to the second sub-pixel through the first transistor and the second transistor.

According to the purpose of the present invention, a method for driving a liquid crystal display is also proposed, the liquid crystal display includes a plurality of data lines, a plurality of scanning lines and pixels, and these scanning lines include the Nth scanning line and the N+1th scanning line , N is a positive integer, the data lines include the Mth data line, M is a positive integer, the pixel includes a first sub-pixel and a second sub-pixel, and the first sub-pixel and the second sub-pixel are arranged on the first sub-pixel Between N scan lines and the N+1th scan line, and the first sub-pixel and the second sub-pixel are arranged on the same side of the M-th data line, the method includes the following steps: The first pulse signal and the second pulse signal are generated on the first scanning line within a time period, and the second pulse signal has a duration; the third pulse signal and the fourth pulse signal are generated on the second scanning line within the frame time ; within the duration, when the second pulse signal overlaps with the third pulse signal, the second subpixel voltage of the Mth data line is transmitted to the second subpixel; during the duration, When the second pulse signal and the third pulse signal do not overlap, the first sub-pixel voltage of the Mth data line is transmitted to the first sub-pixel.

In order to make the above-mentioned purpose, features, and advantages of the present invention more comprehensible, a preferred embodiment will be described in detail below together with the accompanying drawings.

Description of drawings

FIG. 1 is an equivalent circuit diagram of a known pixel.

FIG. 2 is a plot of the transmittance versus driving voltage of a known liquid crystal display under different viewing angles.

FIG. 3 is a plot of the grayscale versus driving voltage of a known liquid crystal display under different viewing angles.

FIG. 4 is an equivalent circuit diagram of a pixel of a liquid crystal display according to a preferred embodiment of the present invention.

FIG. 5 illustrates a method for driving pixels of a liquid crystal display according to a preferred embodiment of the present invention.

FIG. 6A is a block diagram of a first circuit for driving data lines in a preferred embodiment of the present invention.

FIG. 6B is a block diagram of a second circuit for driving the data lines of the preferred embodiment of the present invention.

FIGS. 7A-7D illustrate the layout configuration diagrams of the first sub-pixel and the second sub-pixel according to the preferred embodiment of the present invention.

[Description of main component labels]

P: pixel

SP1: First sub-pixel

SP2: Second sub-pixel

S1: first switch circuit

S2: Second switch circuit

C _LC , C _LC1 , C _LC2 : LCD capacitors

C _ST , C _ST1 , C _ST2 : storage capacitors

T ₁₁ , T ₄₁ , T ₄₂ , T ₄₃ : thin film transistors

600: The first value lookup table

610: The second value lookup table

640: First gamma circuit

650: second gamma circuit

630, 650: data driver

Detailed ways

Please refer to FIG. 4 , which shows an equivalent circuit diagram of a pixel of a liquid crystal display according to a preferred embodiment of the present invention. The pixel P is disposed at the intersection of the M th data line and the N th scan line, and the pixel P includes a first sub-pixel SP1 and a second sub-pixel SP2 , a first switch circuit S1 , and a second switch circuit S2 . The first sub-pixel SP1 is equivalent to the liquid crystal capacitor C _LC1 and the storage capacitor C _ST1 , and the second sub-pixel SP2 is equivalent to the liquid crystal capacitor C _LC2 and the storage capacitor C _ST2 .

The first switch circuit S1 includes thin film transistors T ₄₂ and T ₄₃ , and the second switch circuit S2 includes thin film transistors T ₄₁ . The thin film transistor _T41 includes a first gate, a first source and a first drain. The first gate is controlled by the Nth scan line, the first source is coupled to the Mth data line, and the first drain is coupled to the first sub-pixel SP1. The thin film transistor _T42 includes a second gate, a second source and a second drain. The second gate is controlled by the N scan line and the second source is coupled to the M data line. The thin film transistor _T43 includes a third gate, a third source and a third drain. The third gate is controlled by the N+1th scan line, the third source is coupled to the second drain, and the third drain is coupled to the second sub-pixel SP2.

Therefore, when the thin film transistor _T42 and the thin film transistor _T43 are turned on at the same time, the sub-pixel voltage V1 is transmitted to the first sub-pixel SP2 from the Mth data line. And when the thin film transistor _T41 is turned on and the thin film transistor _T43 is not turned on, the sub-pixel voltage V2 is transmitted from the Mth data line to the first sub-pixel SP1.

Please refer to FIG. 4 and FIG. 5 at the same time. FIG. 5 illustrates a method for driving pixels of a liquid crystal display according to a preferred embodiment of the present invention. As shown in Figure 5, the voltage level of the Nth scanning line has a duration b and a duration d maintained at a high level within a frame time, and the duration d includes time d1 and time d2, the N+th scan line The voltage level of one scan line is high level during time d1 and low level during time d2. Therefore, the sub-pixel voltage V1 is provided to the first sub-pixel SP1 and the second sub-pixel SP2 respectively at time d1, and the sub-pixel voltage V2 is only provided to the first sub-pixel SP1 at time d2. At this time, the first sub-pixel SP1 is driven by the sub-pixel voltage V2 and the second sub-pixel SP2 is driven by the sub-pixel voltage V1, so that the total charging time of the first sub-pixel SP1 is d1+d2 and the total charging time of the second sub-pixel SP2 is only d1.

Because the viewing angle characteristics of the pixel P are the accumulation and average of the viewing angle characteristics of the first sub-pixel SP1 and the second sub-pixel SP2. By properly designing the arrangement of the liquid crystal molecules of the first sub-pixel SP1 and the second sub-pixel SP2, the viewing angle characteristics thereof can complement each other, thereby reducing the color shift caused by different viewing angles. In addition, the data lines in this embodiment are driven in a Dot Inversion mode. However, other modes such as frame inversion (Frame Inversion), column inversion (Row Inversion) and row inversion (Column Inversion) are also applicable to this embodiment.

Please refer to FIG. 6A , which is a partial block diagram of a first driving circuit for driving data lines in this embodiment. As shown in FIG. 6A , its circuit block diagram includes a first value lookup table 600 , a second value lookup table 610 and a data driver 620 . The first value look-up table 600 is used to output the first sub-pixel data value D61 for controlling the first sub-pixel SP1 according to the original pixel data D60, and the second value look-up table 610 is used to output the first sub-pixel data value D61 for controlling the second sub-pixel SP1 according to the original pixel data D60. The second sub-pixel data value D62 of the sub-pixel SP2, and the data driver 620 are used to output corresponding to the first sub-pixel SP1 and the second sub-pixel SP2 respectively according to the first sub-pixel data value D61 and the second sub-pixel data value D62 The sub-pixel voltage V1 and the sub-pixel voltage V2 are sent to the Mth data line. The sub-pixel voltage V1 and the sub-pixel voltage V2 are respectively controlled through different first value look-up tables 600 and second value look-up tables 610, so that there are two sets of voltages inside the pixel P, so that each gray scale can be optimally designed To achieve the best display effect.

When the corresponding sub-pixel voltage V1 and sub-pixel voltage V2 are selected for each gray scale, the present embodiment obtains the optimized viewing angle characteristics for each gray scale through a trial-and-error method. . Furthermore, in the case of certain gray scales such as bright state, the sub-pixel voltage V1 can also be designed to be equal to the sub-pixel voltage V2, so that the loss of transmittance can be avoided.

Please refer to FIG. 6B , which is a block diagram of a second circuit for driving data lines in this embodiment. As shown in FIG. 6B , its circuit block diagram includes a first gamma circuit 630 , a second gamma circuit 640 and a data driver 650 . The first gamma circuit 630 is used to generate a first set of gamma voltages V63 corresponding to the first sub-pixel SP1, and the second gamma circuit 640 is used to generate a second set of gamma voltages V64 corresponding to the second sub-pixel SP2, And the data driver 650 is used to output the sub-pixel voltage V1 and the sub-pixel voltage V2 corresponding to the first sub-pixel SP1 and the second sub-pixel SP2 to the Mth data lines. Similarly, the above effects achieved by using different first value lookup tables 600 and second value lookup tables 610 can also be achieved through different first gamma circuits 630 and second gamma circuits 640, and will not be repeated here. .

Please refer to FIGS. 7A-7D at the same time, which are diagrams showing various layout configurations of the first sub-pixel SP1 and the second sub-pixel SP2 in this embodiment. The arrangement shown in FIG. 7A is a top-down arrangement, the arrangement shown in FIG. 7B is a left-right arrangement, the arrangement shown in FIG. 7C is a staggered arrangement, and the arrangement shown in FIG. 7D is a triangular left-right arrangement. In addition, since the total charging time of the second sub-pixel SP2 in this embodiment is less than the total charging time of the first sub-pixel SP1, the layout area of the first sub-pixel SP1 is configured to be larger than the layout area of the second sub-pixel SP2 to avoid the second The charging time of the sub-pixel SP2 is insufficient, and the preferred layout area ratio of the first sub-pixel SP1 and the second sub-pixel SP2 is about 9:1˜5:5.

In this embodiment, a pixel is divided into a first sub-pixel and a second sub-pixel, and the two sub-pixels of this pixel can be driven by two different voltages through different driving methods, resulting in two different liquid crystal tilt angles, The optical effects of the display domains of the two sub-pixels are mutually compensated. Taking Multi-Domain Vertical Alignment liquid crystal display as an example, the known four display domains can be changed into eight display domains to compensate Brightness difference, its viewing angle effect will be better than known liquid crystal displays using four display domains. Taking a transflective liquid crystal display as an example, the pixels in the reflective area and the transmissive area can be driven by two different voltages, so that the optical effects of the reflective area and the transmissive area can be matched. Taking Twisted Nematic LCD as an example, the color shift caused by different viewing angles can also be reduced by increasing the number of regions.

In summary, although the present invention has been disclosed above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make various modifications without departing from the spirit and scope of the present invention. Changes and modifications, so the protection scope of the present invention should be defined by the scope of the appended claims.

Claims (8)

1. A liquid crystal display, comprising: A plurality of scan lines, including the Nth scan line and the N+1th scan line, where N is a positive integer; Multiple data lines, including the Mth data line, where M is a positive integer; A pixel includes a first sub-pixel and a second sub-pixel, the first sub-pixel and the second sub-pixel are both arranged between the Nth scanning line and the N+1th scanning line, and the first subpixel The pixel and the second sub-pixel are arranged on the same side of the Mth data line; a first switch circuit coupled to the Nth scan line and the N+1th scan line, the first switch circuit is used to control the second sub-pixel; and a second switch circuit coupled to the Nth scan line, the second switch circuit is used to control the first sub-pixel; Wherein the pixel is used to display one of red, green, blue, or white, Wherein the first switch circuit includes: The first transistor includes a first gate, a first source and a first drain, the first gate is controlled by the Nth scan line, and the first source is coupled to the Mth data line; and The second transistor includes a second gate, a second source and a second drain, the second gate is controlled by the N+1 scan line, and the second source is coupled to the first drain connected, and the second drain is coupled to the second sub-pixel, when the first transistor and the second transistor are turned on at the same time, a sub-pixel voltage transmitted by the Mth data line is passed through the second A transistor and the second transistor output to the second sub-pixel. 2. The liquid crystal display according to claim 1, wherein a layout area ratio of the first sub-pixel to the second sub-pixel is about 9:1˜1:1. 3. The liquid crystal display according to claim 1, wherein a layout area of the first sub-pixel is larger than a layout area of the second sub-pixel. 4. The liquid crystal display according to claim 1, further comprising: a first look-up table, configured to output a first sub-pixel data value for controlling the first sub-pixel according to the original pixel data; a second lookup table, configured to output a second sub-pixel data value for controlling the second sub-pixel according to the original pixel data; and The data driver is coupled to the data lines, and is used to respectively output the first sub-pixel corresponding to the first sub-pixel and the second sub-pixel according to the first sub-pixel data value and the second sub-pixel data value. The pixel voltage and the second sub-pixel voltage. 5. The liquid crystal display according to claim 1, further comprising: a first gamma circuit, configured to generate a first set of gamma voltages corresponding to the first sub-pixel; a second gamma circuit, configured to generate a second set of gamma voltages corresponding to the second sub-pixel; and The data driver is coupled to the data lines, and is used to respectively output the first sub-pixel corresponding to the first sub-pixel and the second sub-pixel according to the first set of gamma voltages and the second set of gamma voltages voltage and the second sub-pixel voltage. 6. A method for driving a liquid crystal display, the liquid crystal display comprising a plurality of data lines, a plurality of scanning lines and pixels, the scanning lines comprising the Nth scanning line and the N+1th scanning line, where N is a positive integer, The data lines include the Mth data line, M is a positive integer, the pixel includes a first sub-pixel and a second sub-pixel, and the first sub-pixel and the second sub-pixel are arranged on the Nth scanning line and the Between the N+1th scanning line, and the first subpixel and the second subpixel are arranged on the same side of the Mth data line, the method includes the following steps: generating a first pulse signal and a second pulse signal on the first scanning line within a frame time, and the second pulse signal has a duration; generating a third pulse signal and a fourth pulse signal on the second scanning line within the frame time; During the duration, when the second pulse signal overlaps with the third pulse signal, the second subpixel voltage of the Mth data line is transmitted to the second subpixel; During the duration, when the second pulse signal and the third pulse signal do not overlap, the first sub-pixel voltage of the Mth data line is transmitted to the first sub-pixel. 7. The method according to claim 6, further comprising the steps of: generating a first look-up table for outputting a first sub-pixel data value for controlling the first sub-pixel according to the original pixel data; generating a second look-up table for outputting a second sub-pixel data value for controlling the second sub-pixel according to the original pixel data; and A data driver is configured, the data driver is coupled to the data lines, and is used to respectively output data corresponding to the first sub-pixel and the second sub-pixel according to the first sub-pixel data value and the second sub-pixel data value. The first sub-pixel voltage and the second sub-pixel voltage. 8. The method according to claim 6, further comprising the steps of: generating a first set of gamma voltages corresponding to the first sub-pixel; generating a second set of gamma voltages corresponding to the second sub-pixel; and A data driver is configured, the data driver is coupled to the data lines, and is used to respectively output corresponding to the first sub-pixel and the second sub-pixel according to the first group of gamma voltages and the second group of gamma voltages The first sub-pixel voltage and the second sub-pixel voltage.

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