Liquid crystal display device having gate sharing structure and method of driving the same

The present application claims the benefit of Korean Patent Application No. 10-2013-0008571 filed in Korea on Jan. 25, 2013, which is hereby incorporated by reference for all purposes as if fully set forth herein.

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device having less power consumption and a gate sharing structure and a method of driving the same.

2. Discussion of the Related Art

The LCD device as a display device is driven by using optical anisotropy and polarization properties of liquid crystal molecules. The LCD device is widely used for a display part of mobile electronic equipments, a monitor of computers and televisions.

The liquid crystal molecules have a definite alignment direction as a result of their thin and long shapes. The alignment direction of the liquid crystal molecules can be controlled by application of an electric field across the liquid crystal molecules. As the intensity or direction of the electric field is changed, the alignment of the liquid crystal molecules also changes.

The LCD device includes two substrates respectively including an electric field generating electrode and a liquid crystal layer therebetween. The alignment of the liquid crystal molecules are changed by an electric field between the electrodes such that images can be displayed by controlling light transmissivity.

The LCD device includes an array substrate, a color filter substrate and a liquid crystal layer interposed therebetween. The array substrate may include a pixel electrode and TFT, and the color filter substrate may include a color filter layer and a common electrode. The LCD device is driven by an electric field between the pixel electrode and the common electrode resulting in excellent properties of transmittance and aperture ratio. However, since this LCD device uses a vertical electric field, the LCD device has a bad viewing angle.

An in-plane switching (IPS) mode LCD device may be used to resolve the above-mentioned limitations. The related art IPS mode LCD device includes a color filter substrate, an array substrate facing the color filter substrate, and a liquid crystal layer interposed therebetween. Both common and pixel electrodes for driving the liquid crystal layer are formed on the array substrate such that a horizontal electric field is induced between the pixel and common electrodes. Since the liquid crystal molecules are driven by the horizontal electric field, the IPS mode LCD device has improved viewing angle. However, the IPS mode LCD device has disadvantages in the aperture ratio and the transmittance.

To overcome the disadvantages of the IPS mode LCD device, a fringe field switching (FFS) mode LCD device is introduced. Hereinafter, the related art FFS mode LCD device is explained.

FIG. 1 is a schematic view of the related art FFS mode LCD device, and FIG. 2 is a circuit diagram of pixels in the related art FFS mode LCD device.

Referring to FIGS. 1 and 2 , in the related art FFS mode LCD device, a plurality of data lines DL 1 to DL 10 and a plurality of gate lines GL 1 to GL 4 are formed to cross each other. A plurality of pixels R 11 to R 43 , G 11 to G 43 and B 11 to B 43 are defined by the plurality of data lines DL 1 to DL 10 and the plurality of gate lines GL 1 to GL 4 .

Each of the plurality of pixels R 11 to R 43 , G 11 to G 43 and B 11 to B 43 includes a thin film transistor (TFT) Tr, a storage capacitor Cst and a liquid crystal capacitor CLC. The liquid crystal capacitor CLC includes a pixel electrode (not shown) and a common electrode Vcom. The pixel electrode is electrically connected to the TFT.

The plurality of pixels R 11 to R 43 , G 11 to G 43 and B 11 to B 43 are arranged in a stripe shape.

For example, the pixels arranged along a vertical direction include the same color filter, e.g., red color filter, and different color filters, e.g., red, green and blue color filters, are alternately arranged in the pixels along a horizontal direction.

In this pixel structure, the TFT in one pixel of vertically adjacent two pixels is electrically connected to the gate line between the vertically adjacent two pixels. Accordingly, an area for the TFT is required in each of the pixels R 11 to R 43 , G 11 to G 43 and B 11 to B 43 . As a result, the aperture ratio and the transmittance of the pixels are decreased by the region for the TFT.

Namely, although the FFS mode LCD device has been developed to overcome the disadvantages, e.g., the aperture ratio and the transmittance, of the IPS mode LCD device, there still are disadvantages in the aperture ratio and the transmittance.

Accordingly, the present invention is directed to an LCD device and a method of driving the same that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. These and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, the present invention provides a liquid crystal display device including gate lines extending on a substrate; data lines crossing the gate lines to define a plurality of pixels; a thin film transistor in each pixel; and a liquid crystal capacitor in each pixel region, an electrode of the liquid crystal capacitor is connected to the thin film transistor, wherein the thin film transistors of a ( 2 a −1)th pixel and a ( 2 a )th pixel in a ( 2 b )th pixel column share a ( 2 a )th gate line, and the thin film transistors in a ( 2 a )th pixel and a ( 2 a +1)th pixel in a ( 2 b +1)th pixel column share a ( 2 b +1)th gate line, and wherein each of a and b is a positive integer.

In another aspect of the present invention, the present invention provides a method of driving a liquid crystal display device, which includes first to fourth gate lines, first to seventh data lines crossing the first to fourth gate lines to define 18 pixels arranged in a 3*6 matrix; a thin film transistor in each pixel; first to third color filters corresponding to each pixel; and a liquid crystal capacitor in each pixel region, an electrode of the liquid crystal capacitor is connected to the thin film transistor, wherein the thin film transistors of a ( 2 a −1)th pixel and a ( 2 a )th pixel in a ( 2 b )th pixel column share a ( 2 a )th gate line, and the thin film transistors in a ( 2 a )th pixel and a ( 2 a +1)th pixel in a ( 2 b +1)th pixel column share a ( 2 b +1)th gate line, wherein the thin film transistors of a ( 2 c −1)th pixel and a ( 2 c )th pixel in a ( 2 d −1)th pixel row share a ( 2 c )th data line, and the thin film transistors of a ( 2 c )th pixel and a ( 2 c +1)th pixel in a ( 2 d )th pixel row share a ( 2 c +1)th data line, wherein one of the first to third color filters are arranged in a zigzag shape in two adjacent pixel columns, and the first to third color filters are alternately arranged in each pixel row, and wherein each of a, b, c and d is a positive integer, the method comprising: applying a first gate signal into the second gate line; applying a high-gray data signal into the third and fourth data lines and a low-gray data signal into the first, second and fifth to seventh data lines; applying a second gate signal into the third gate line; and applying a high-gray data signal into the second and fifth data lines and a low-gray data signal into the first, third, fourth, sixth and seventh data lines.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a schematic view of the related art FFS mode LCD device.

FIG. 2 is a circuit diagram of pixels in the related art FFS mode LCD device.

FIG. 3 is a circuit diagram of pixels in an LCD device according to the present invention.

FIG. 4 is a schematic plan view of a pixel arrangement in an LCD device according to a first embodiment of the present invention.

FIG. 5 is a schematic plan view of a pixel arrangement in an LCD device according to a second embodiment of the present invention.

Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings.

FIG. 3 is a circuit diagram of pixels in an LCD device according to the present invention.

Referring to FIG. 3 , in the LCD device of the present invention, first to third gate lines GL 1 , GL 2 and GL 3 and first to third data lines DL 1 , DL 2 and DL 3 are formed on a substrate (not shown). The gate lines GL 1 to GL 3 and the data lines DL 1 to DL 3 cross each other to define first to fourth pixels P 1 , P 2 , P 3 and P 4 . The first to fourth pixels P 1 to P 4 are arranged in a 2*2 matrix shape.

Each of the first to fourth pixels P 1 to P 4 includes a thin film transistor (TFT) Tr, a storage capacitor Cst and a liquid crystal capacitor CLC. The liquid crystal capacitor CLC includes a pixel electrode (not shown) and a common electrode Vcom. The pixel electrode is electrically connected to the TFT.

In addition, the LCD device includes first to third color filters, e.g., red, green and blue color filters. The first to third color filters correspond to each pixel.

In this instance, two adjacent pixels along a direction of the data line DL 1 to DL 3 share one of the gate line GL 1 to GL 3 . In FIG. 3 , the second and fourth pixels P 2 and P 4 share the second gate line GL 2 . Namely, the LCD device has a gate-sharing configuration.

In addition, two adjacent pixels along a direction of the gate line GL 1 to GL 3 share one of the data line DL 1 to DL 3 . In FIG. 3 , the first and second pixels P 1 and P 2 share the second data line DL 2 .

FIG. 4 is a schematic plan view of a pixel arrangement in an LCD device according to a first embodiment of the present invention.

Referring to FIG. 4 , in the LCD device according to the first embodiment of the present invention, first to tenth data lines DL 1 to DL 10 and first to fifth gate lines GL 1 to GL 5 are formed on the substrate (not shown). The first to tenth data lines DL 1 to DL 10 and the first to fifth gate lines GL 1 to GL 5 cross each other to define 36 pixels. However, the numbers of the gate lines, the data lines and the pixels are not limited thereto.

In addition, the LCD device includes first to third color filters, i.e., red, green and blue color filters. The red, green and blue color filters correspond to each pixel such that red pixels R 11 to R 13 , R 21 to R 23 and R 31 to R 33 , green pixels G 11 to G 13 , G 21 to G 23 and G 31 to G 33 , and blue pixels B 11 to B 13 , B 21 to B 23 and B 31 to B 33 are defined.

In a pixel row along a direction of the gate line, the red pixel, the green pixel and the blue pixel are alternately arranged. In a pixel column along a direction of the data line, one of the red, green and blue pixels are continuously arranged. In other words, the pixels are arranged in a stripe shaped.

In the LCD device, adjacent pixels share the gate line, and adjacent pixels share the data line. As a result, an area for the TFT is reduced in comparison to the related art LCD device such that the aperture ratio and the transmittance in the pixel are improved.

In more detail, the TFTs Tr (of FIG. 3 ) of a ( 2 a −1)th pixel and a ( 2 a )th pixel in a ( 2 b )th pixel column share a ( 2 a )th gate line, and the TFTs Tr (of FIG. 3 ) in a ( 2 a )th pixel and a ( 2 a +1)th pixel in a ( 2 b +1)th pixel column share a ( 2 b +1)th gate line. (Each of “a” and “b” is a positive integer.) In FIG. 4 , the TFT Tr of the green pixel G 11 , e.g., the first pixel in the second pixel column, and the TFT Tr of the green pixel G 21 , e.g., the second pixel in the second pixel column, share the second gate line GL 2 . In addition, the TFT Tr of the blue pixel B 21 , e.g., the second pixel in the third pixel column, and the TFT Tr of the blue pixel B 31 , e.g., the third pixel in the third pixel column, share the third gate line GL 3 .

On the other hand, the thin film transistors Tr of a ( 2 c −1)th pixel and a ( 2 c )th pixel in a ( 2 d −1)th pixel row share a ( 2 c )th data line, and the thin film transistors of a ( 2 c )th pixel and a ( 2 c +1)th pixel in a ( 2 d )th pixel row share a ( 2 c +1)th data line. (Each of “c” and “d” is a positive integer.) In FIG. 4 , the TFT Tr of the red pixel R 11 , e.g., the first pixel in the first pixel row, and the TFT Tr of the green pixel G 11 , e.g., the second pixel in the first pixel row, share the second data line DL 2 . In addition, the TFT Tr of the green pixel G 21 , e.g., the second pixel in the second pixel row, and the TFT Tr of the blue pixel B 21 , e.g., the third pixel in the second pixel row, share the third data line DL 3 .

For example, the TFT Tr of the red pixel R 11 in the first pixel column and the first pixel row is electrically connected to the first gate line GL 1 and the second data line DL 2 , and the TFT Tr of the red pixel R 21 in the first pixel column and the second pixel row is electrically connected to the third gate line GL 3 and the first data line DLL The TFT Tr of the green pixel G 11 in the second pixel column and the first pixel row is electrically connected to the second gate line GL 2 and the second data line DL 2 , and the TFT Tr of the green pixel G 21 in the second pixel column and the second pixel row is electrically connected to the second gate line GL 2 and the third data line DL 3 . The TFT Tr of the blue pixel B 11 in the third pixel column and the first pixel row is electrically connected to the first gate line GL 1 and the fourth data line DL 4 , and the TFT Tr of the blue pixel B 21 in the third pixel column and the second pixel row is electrically connected to the third gate line GL 3 and the third data line DL 3 .

When the full white image (full color image) is displayed with the above LCD device, the power consumption is substantially equal to the related art LCD device.

However, when one color image, e.g., a red image, is displayed, the power consumption of the above LCD device is increased.

For example, in the related art LCD device having the pixel arrangement in FIG. 1 , a high-gray data signal is applied into the first, fourth and seventh data lines DL 1 , DL 4 and DL 7 for every gate lines GL 1 to GL 4 to display the red image.

However, in the LCD device having the pixel arrangement in FIG. 3 , the number of the data lines, where the high-gray data signal should be applied, is changed with respect to the gate lines.

Namely, when the gate signal is applied to the second gate line GL 2 , the high-gray data signal is applied into two data lines, i.e., the fourth and fifth data lines DL 4 and DL 5 , to drive two red pixels R 12 and R 22 . In this instance, the low-gray data signal is applied into other data lines, i.e., the first to third and sixth to tenth data lines DL 1 to DL 3 and DL 6 to DL 10 . On the other hand, when the gate signal is applied to the third gate line GL 3 , the high-gray data signal is applied into four data lines, i.e., the first, second, seventh and eighth data lines DL 1 , DL 2 , DL 7 and DL 8 , to drive four red pixels R 21 , R 23 , R 31 and R 33 . In this instance, the low-gray data signal is applied into other data lines, i.e., the third to sixth, ninth and tenth data lines DL 3 to DL 6 , DL 9 and DL 10 .

As explained above, the high-gray data signal is applied to two data lines when the second gate line GL 2 is selected, while the high-gray data signal is applied to four data lines when the third gate line GL 3 is selected. Namely, in the LCD device in FIG. 3 , with respect to the gate lines, the number of the data lines, where the high-gray data signal is applied, is changed.

Accordingly, the power consumption for an amplifier (not shown) amplifying the output signal of the data driving circuit (not shown) is increased.

Consequently, the aperture ratio and the transmittance of the LCD device in FIG. 3 are improved in comparison to the related art LCD device by sharing the gate line and the data line. However, the number of the data lines, where the high-gray data signal should be applied, is changed with respect to the selected gate line, there is a disadvantage in the power consumption.

FIG. 5 is a schematic plan view of a pixel arrangement in an LCD device according to a second embodiment of the present invention. The above problem can be overcome in the LCD device having the pixel arrangement in FIG. 5 .

Referring to FIG. 5 , in the LCD device according to the second embodiment of the present invention, first to tenth data lines DL 1 to DL 10 and first to fifth gate lines GL 1 to GL 5 are formed on the substrate (not shown). The first to tenth data lines DL 1 to DL 10 and the first to fifth gate lines GL 1 to GL 5 cross each other to define 36 pixels. However, the numbers of the gate lines, the data lines and the pixels are not limited thereto.

In addition, the LCD device includes first to third color filters, i.e., red, green and blue color filters. The red, green and blue color filters correspond to each pixel such that red pixels R 11 to R 13 , R 21 to R 23 and R 31 to R 33 , green pixels G 11 to G 13 , G 21 to G 23 and G 31 to G 33 , and blue pixels B 11 to B 13 , B 21 to B 23 and B 31 to B 33 are defined.

In a pixel row along a direction of the gate line, the red pixel, the green pixel and the blue pixel are alternately arranged. In a pixel column along a direction of the data line, two different pixels are alternately arranged. For example, in a first pixel column, the red pixels R 11 and R 31 are arranged in a first pixel row and a third pixel row, and the blue pixels B 21 and B 41 are arranged in a second pixel row and a fourth pixel row. Namely, the red pixels R 11 and R 31 and the blue pixels B 21 and B 41 are alternately arranged. In a second pixel column, the green pixels G 11 and G 31 and the red pixels R 21 and R 41 are alternately arranged. In a third pixel column, the blue pixels B 11 and B 31 and the green pixels G 21 and G 41 are alternately arranged.

In other words, in two adjacent pixel columns, one of the red, green and blue pixels are arranged in a zigzag shape, and the other two of the red, green and blue pixels are alternately arranged in another zigzag shape.

In the LCD device, adjacent pixels share the gate line, and adjacent pixels share the data line. As a result, an area for the TFT is reduced in comparison to the related art LCD device such that the aperture ratio and the transmittance in the pixel are improved.

In more detail, the TFTs Tr (of FIG. 3 ) of a ( 2 a −1)th pixel and a ( 2 a )th pixel in a ( 2 b )th pixel column share a ( 2 a )th gate line, and the TFTs Tr (of FIG. 3 ) in a ( 2 a )th pixel and a ( 2 a +1)th pixel in a ( 2 b +1)th pixel column share a ( 2 b+ 1 )th gate line. (Each of “a” and “b” is a positive integer.) In FIG. 5 , the TFT Tr of the green pixel G 11 , e.g., the first pixel in the second pixel column, and the TFT Tr of the red pixel R 21 , e.g., the second pixel in the second pixel column, share the second gate line GL 2 . In addition, the TFT Tr of the green pixel G 21 , e.g., the second pixel in the third pixel column, and the TFT Tr of the blue pixel B 31 , e.g., the third pixel in the third pixel column, share the third gate line GL 3 .

On the other hand, the thin film transistors Tr of a ( 2 c −1)th pixel and a ( 2 c )th pixel in a ( 2 d −1)th pixel row share a ( 2 c )th data line, and the thin film transistors of a ( 2 c )th pixel and a ( 2 c +1)th pixel in a ( 2 d )th pixel row share a ( 2 c +1)th data line. (Each of “c” and “d” is a positive integer.) In FIG. 5 , the TFT Tr of the red pixel R 11 , e.g., the first pixel in the first pixel row, and the TFT Tr of the green pixel G 11 , e.g., the second pixel in the first pixel row, share the second data line DL 2 . In addition, the TFT Tr of the red pixel R 21 , e.g., the second pixel in the second pixel row, and the TFT Tr of the green pixel GB 21 , e.g., the third pixel in the second pixel row, share the third data line DL 3 .

For example, the TFT Tr of the red pixel R 11 in the first pixel column and the first pixel row is electrically connected to the first gate line GL 1 and the second data line DL 2 , and the TFT Tr of the red pixel R 21 in the second pixel column and the second pixel row is electrically connected to the second gate line GL 2 and the third data line DL 3 . The TFT Tr of the green pixel G 11 in the second pixel column and the first pixel row is electrically connected to the second gate line GL 2 and the second data line DL 2 , and the TFT Tr of the green pixel G 21 in the third pixel column and the second pixel row is electrically connected to the third gate line GL 3 and the third data line DL 3 . The TFT Tr of the blue pixel B 11 in the third pixel column and the first pixel row is electrically connected to the first gate line GL 1 and the fourth data line DL 4 , and the TFT Tr of the blue pixel B 21 in the first pixel column and the second pixel row is electrically connected to the third gate line GL 3 and the first data line DL 1 .

In the LCD device including the above pixel arrangement, the number of the data lines, where the high-gray data signal is applied, is constant such that the increase of the power consumption is not generated.

For example, when the gate signal is applied to the second gate line GL 2 , the high-gray data signal is applied into three data lines, i.e., the third, fourth and ninth data lines DL 3 , DL 4 and DL 9 , to drive three red pixels R 21 , R 12 and R 23 . In this instance, the low-gray data signal is applied into other data lines, i.e., the first, second, fifth to eighth and tenth data lines DL 1 , DL 2 , DL 5 to DL 8 and DL 10 . On the other hand, when the gate signal is applied to the third gate line GL 3 , the high-gray data signal is applied into three data lines, i.e., the second, fifth and eighth data lines DL 2 , DL 5 , DL 8 , to drive three red pixels R 31 , R 22 , R 33 . In this instance, the low-gray data signal is applied into other data lines, i.e., the first, third, fourth, sixth, seventh, ninth and tenth data lines DL 1 , DL 3 , DL 4 , DL 6 , DL 7 , DL 9 and DL 10 .

An exemplary driving method of the LCD device including the pixel arrangement in a pixel group PG of FIG. 5 is explained.

Four gate lines GL 1 to GL 4 and seven data lines DL 1 to DL 7 are formed to define 18 pixels in a 3*6 matrix. The 18 pixels in the 3*6 matrix form the pixel group PG.

In the pixel group PG, when the gate signal is applied to the second gate line GL 2 in the pixel group PG, the high-gray data signal should be applied into the third and fourth data lines DL 3 and DL 4 to drive two red pixels R 21 and R 12 . In this instance the low-gray data signal is applied into the first, second and fifth to seventh data lines DL 1 , DL 2 and DL 5 to DL 7 . In addition, when the gate signal is applied to the third gate line GL 3 in the pixel group PG, the high-gray data signal should be applied into the second and fifth data lines DL 2 and DL 5 to drive two red pixels R 31 and R 22 . In this instance, the low-gray data signal is applied into the first, third, fourth, sixth and seventh data lines DL 1 , DL 3 , DL 4 , DL 6 and DL 7 .

As explained above, the high-gray data signal is applied to two data lines both when the second gate line GL 2 is selected and when the third gate line GL 3 is selected. Namely, in the LCD device in FIG. 5 , the number of the data lines, where the high-gray data signal is applied, is not changed.

Accordingly, the power consumption for an amplifier (not shown) amplifying the output signal of the data driving circuit (not shown) is not increased.

As a result, the LCD device has advantages in the aperture ratio and the transmittance without increase of the power consumption.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.