KR20080054507A - Back light assembly, driving method of the same and display apparatus having the same - Google Patents

Abstract

A backlight assembly, a method of driving the backlight assembly, and a display device having the backlight assembly are provided to construct the backlight assembly such that each of sequentially driven light source units includes a white light source in addition to red, green and blue light sources to emit white light to thereby improve the luminance and contrast ratio of the display device. A backlight assembly(400) time-divides a unit frame into a plurality of fields respectively representing different colors and emits light. The backlight assembly includes a driving substrate(200) and light source units(300) arranged on the driving substrate. Each light source unit includes a red light source, a green light source, a blue light source and a white light source.

Description

BACK LIGHT ASSEMBLY, DRIVING METHOD OF THE SAME AND DISPLAY APPARATUS HAVING THE SAME}

1 is an exploded perspective view illustrating a display device according to an exemplary embodiment of the present invention.

2 is a perspective view showing the schematic structure of FIG.

3 is a cross-sectional view taken along line II ′ of FIG. 2.

4 is a timing diagram schematically illustrating a method of driving a light source unit illustrated in FIG. 1.

FIG. 5 is a timing diagram illustrating luminance during sequential driving of the display device illustrated in FIG. 1.

<Description of the symbols for the main parts of the drawings>

100: storage container 200: drive substrate

300: light source unit 330: phosphor

400: backlight assembly 500: display panel

600: display device

BL1: first blue light source BL2: second blue light source

The present invention relates to a backlight assembly, a driving method thereof, and a display device having the same, and more particularly, to a backlight assembly of a sequential driving method, a driving method thereof, and a display device having the same.

In general, a liquid crystal display device is a flat panel display that displays an image by using the light transmittance of the liquid crystal. The liquid crystal display includes a display panel for displaying an image using light and a backlight assembly for supplying light to the display panel.

Recently, a liquid crystal display device in which a color filter of a display panel is removed by using a light emitting diode (LED) with low power consumption and excellent light emission efficiency as a light source has been developed. Conventional liquid crystal displays use color filters to express colors by using spatial blending, while color filter-less (CFL) liquid crystal displays emit red, green, and blue light emitting diodes sequentially. Colors are expressed through mixed colors.

However, when the red, green, and blue light emitting diodes are sequentially driven on a line-by-line basis, color mixing occurs between the lines, thereby reducing color reproduction. In addition, in the sequential drive type display device, as the light emitting diodes are sequentially turned on instead of being turned on at the same time, problems of lowering of luminance and lowering of contrast ratio occur.

On the other hand, the recently developed Adobe RGB color space has a wide color reproduction area, and particularly, excellent color reproduction in the blue and green areas. When using the Adobe RGB color space, a liquid crystal display must support the wide color gamut of Adobe RGB to achieve accurate color images. However, although the color coordinates of the liquid crystal display device using the light emitting diode have excellent color reproducibility, there is a problem in that they do not completely cover the Adobe RGB color space.

Accordingly, the technical problem of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a backlight assembly for improving color reproducibility and brightness in a sequential driving method.

In addition, another object of the present invention is to provide a method of driving the above-described backlight assembly.

In addition, another object of the present invention is to provide a display device having the above-described backlight assembly.

In order to realize the above object of the present invention, a backlight assembly according to an embodiment emits light by time division of a unit frame into a plurality of fields displaying different colors, and is disposed on a driving substrate and the driving substrate, And a light source unit having a red light source, a green light source, a first blue light source, and a white light source.

According to another aspect of the present invention, there is provided a method of driving a backlight assembly, the method comprising: driving the red light source in a backlight assembly having a red light source, a green light source, a first blue light source, and a white light source; Driving the green light source, driving the first blue light source, and driving the white light source.

In order to realize the above object of the present invention, a display device according to an embodiment displays an image by time division of a unit frame into a plurality of fields displaying different colors, and a display panel for displaying an image, and driving. And a backlight assembly disposed on the substrate and the driving substrate, the backlight assembly having a light source unit consisting of a red light source, a green light source, a first blue light source, and a white light source.

According to such a backlight assembly, a driving method thereof, and a display device having the same, as the light source units sequentially driven emit white light by further including not only red, green, and blue light sources, but also white light sources, brightness and contrast of the display device are increased. The contrast ratio can be further improved.

Hereinafter, with reference to the accompanying drawings, it will be described in detail the present invention.

1 is an exploded perspective view illustrating a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the display device 600 includes a display panel 500 and a backlight assembly 400. The display device 600 is time-divided and driven to a plurality of fields in which one frame displays different colors to display a color image.

The display panel 500 is disposed above the backlight assembly 400 and displays an image using light supplied from the backlight assembly 400. The display panel 500 may include a first substrate 510, a second substrate 520 facing the first substrate 510, and a liquid crystal layer interposed between the first substrate 510 and the second substrate 520. 530 and a driving circuit 540 for driving the first substrate 510.

In detail, the first substrate 510 includes gate lines GL and data lines DL that intersect the gate lines GL, and the first substrate 510 is formed by the gate lines GL and the data lines DL. A plurality of pixel portions P are defined.

Each pixel portion P includes a switching element TFT electrically connected to the gate line GL and the data line DL, and a liquid crystal capacitor CLC and a storage capacitor CST connected to the switching element TFT. do. Each pixel portion P may include subpixels that display red, green, and blue adjacent to each other.

Meanwhile, the second substrate 520 of the present invention has a structure in which a color filter is not formed.

In the liquid crystal layer 530, the arrangement of the liquid crystals is changed by an electric field formed between the first substrate 510 and the second substrate 520. According to the arrangement change of the liquid crystal molecules, the display device 600 may display an image by adjusting the transmittance of light supplied from the backlight assembly 400.

The driving circuit unit 540 includes a data printed circuit board 548 for supplying a data driving signal to the display panel 500, a gate printed circuit board 544 for supplying a gate driving signal to the display panel 500, and a data printed circuit board. The data driving circuit film 546 connects 548 to the display panel 500, and the gate driving circuit film 542 connects the gate printed circuit board 544 to the display panel 500.

The backlight assembly 400 includes a storage container 100, driving substrates 200, and a light source unit 300.

The storage container 100 includes a bottom portion 110 and side portions 120 extending from an edge of the bottom portion 110 to form a storage space. The driving substrate 200 and the light source unit 300 are accommodated in the accommodation space. The storage container 100 is made of, for example, a metal having excellent strength and low deformation.

The light source units 300 are disposed on the driving substrates 200. For example, the driving substrates 200 may extend long in the longitudinal direction of the bottom portion 110. The driving substrates 200 may be electrically connected to an external power supply device (not shown) to supply power to the light source units 300, and may include signal wiring for supplying power.

A plurality of light source units 300 are disposed on the driving substrates 200. The light source units 300 may be arranged in a line along the arrangement direction of the gate lines GL of the display panel 500. The light source units 300 emit light of different colors corresponding to each field. For example, the light source units 300 may sequentially generate red light, green light, blue light, and white light corresponding to each field during one frame. The number of light source units 300 may be variously modified according to the size of the display panel 500 or the required luminance.

For example, the light source units 300 are spaced apart in a row on the driving substrate 200 to form a plurality of light source bars LB. From the first light source bar LB to the last light source bar LB, each of the light source bars LB sequentially emits red light, green light and blue light.

As such, as the light source units 300 sequentially emit light of different colors, the display device 600 may display a color image by using a temporal color mixing method without forming a color filter on the display panel 500. Can be.

2 is a perspective view showing the schematic structure of FIG. 3 is a cross-sectional view taken along line II ′ of FIG. 2.

1 and 2, the light source units 300 emit light of different colors corresponding to each field during one frame. To this end, each light source unit 300 includes a red light source RL, a green light source GL, a first blue light source BL1, and a white light source WL that emit light of different colors, and provide a time difference. During this period, red light, green light, blue light and white light are sequentially emitted.

The light source unit 300 may include a plurality of red light sources RL, green light sources GL, first blue light sources BL1, and white light sources WL, respectively. In one example, the light source unit 300 includes one red light source RL, two green light sources GL, one first blue light source BL1, and one white light source WL to increase luminance. can do. In the present embodiment, the red light source RL, the green light source GL, the first blue light source BL1 and the white light source WL may be arranged in various forms such as polygons.

For example, the light source units 300 may include a light emitting diode. That is, the light source units 300 may include a red light emitting diode, a green light emitting diode, and a blue light emitting diode. In the present embodiment, the red light source RL is a red light emitting diode, the green light source GL is a green light emitting diode, the first blue light source BL1 is a blue light emitting diode, and the white light source WL is coated with a phosphor. It may be a blue light emitting diode.

Accordingly, the light source units 300 drive the red light source RL to emit red light, drive the green light source GL to emit green light, and drive the first blue light source BL1 to emit blue light. Emitting white light by driving the white light source WL. In addition, the light source units 300 may simultaneously drive the red light source RL, the green light source GL, and the first blue light source BL1 to emit white light.

In detail, when the red light source RL is driven, the red light emitted from the light source unit 300 passes through the red pixel P_R to display a red image. When driving the green light source GL, the green light emitted from the light source unit 300 passes through the green pixel P_G to display a green image. When the first blue light source BL1 is driven, the blue light emitted from the light source unit 300 passes through the blue pixel P_B to display a blue image. In addition, the red, green, and first blue light sources and the white light sources RL, GL, BL1, and WL are simultaneously driven so that the white light emitted from the light source unit 300 is red, green, and blue pixels P_R, P_G, and P_B. ), White image is displayed.

As in the present exemplary embodiment, the red, green, and blue pixels P_R, P_G, and P_B of the display panel 500 are red, green, and blue light, respectively, and do not include a color filter. As such, the display device 600 displays the color image using light emitted from the light source unit 300 and emitted without passing through the color filter.

On the other hand, when the light emitted from the light source unit 300 passes through the color filter, the light emitted from the light emitting diode may be distorted in the original color by the intrinsic spectrum of the color filter. However, as in the present exemplary embodiment, as the display device 600 does not pass through the color filter and uses the light emitted from the light source unit as it is, the color reproduction region having a large area may be realized. For example, the display device 600 of the present invention can satisfy the Adobe RGB color space having excellent color reproduction capability of the green area in the blue area.

2 and 3, the red light source RL, the green light source GL, the first blue light source BL1, and the white light source WL are packaged to form a single multichip light source unit 300. Can be. The multichip light source unit 300 may include an insulation case 310, a red, green, first blue and white light sources RL, GL, BL1, and WL, and a protective layer 320.

The insulating case 310 is disposed on the driving substrate 200 and is made of an insulating resin material. Grooves may be formed in the upper center of the insulating case 310. Red, green, first blue and white light sources RL, GL, BL1, WL are disposed in the grooves to emit light. The passivation layer 320 covers and protects the red, green, first blue, and white light sources RL, GL, BL1, and WL. The passivation layer 320 may be made of, for example, a transparent silicone material.

 For example, the white light source WL may include the phosphor 330 directly coated on the emission surface of the second blue light source BL2 and the second blue light source BL2. In one example, the phosphor 330 may be a yellow phosphor. As such, the white light source WL is formed by coating a yellow phosphor on a blue light emitting diode, for example, to emit white light.

On the other hand, the light emitting area of the white light source WL in this embodiment is equal to the light emitting area of the red, green, and first blue light sources RL, GL, and BL1, or the red, green, and first blue light sources RL, It can be formed larger than the light emitting area of GL, BL1). As a result, the amount of white light emitted from the white light source WL can be increased. Accordingly, the overall brightness of the white light emitted from the light source unit 300 can be increased.

4 is a timing diagram schematically illustrating a method of driving a light source unit illustrated in FIG. 1.

2 and 4, one frame (1 FRAME) of the display device 600 may be time-divided into four fields R_F, G_F, B_F, and W_F. The display device 600 time-divides the unit frame into a red field (R_F) displaying red, a green field (G_F) displaying green, a blue field (B_F) displaying blue, and a white field (W_F) displaying white. To display a color image.

The light source units 300 emit light of different colors corresponding to each field. For example, the light source units 300 emit red light corresponding to the red field R_F, emit green light corresponding to the green field G_F, and emit blue light corresponding to the blue field B_F. And emit white light corresponding to the white field W_F. Meanwhile, the light emission order of the red light, the green light, and the blue light may be variously modified.

Specifically, first, the light source unit 300 emits red light by driving the red light source RL in the red field R_F. Next, the light source unit 300 emits green light by driving the green light source GL in the green field G_F. Subsequently, the light source unit 300 drives the first blue light source BL1 in the blue field B_F to emit blue light. Subsequently, the light source unit 300 emits white light by driving the red, green, first blue and white light sources RL, GL, BL1, and WL in the white field W_F. As such, the light source units 300 of the present invention may be sequentially driven in the order of R_G_B_W.

As in an embodiment of the present invention, the light source unit 300 simultaneously drives not only the red, green, and first blue light sources RL, GL, and BL1, but also the white light source WL in the white field W_F. It can emit light. Accordingly, the luminance of the white image displayed on the display device 600 may be increased.

FIG. 5 is a timing diagram illustrating luminance during sequential driving of the display device illustrated in FIG. 1.

1, 4, and 5, in general, in the display device 600 which is driven by a sequential driving method, a color break up (CBU) phenomenon in which colors of an image are separated into original colors occurs. Can be. In order to eliminate the CBU phenomenon, the four-field driving method of the R_G_B_W method including the white field (W_F) is applied last, it is possible to prevent color interference between the previous frame and the current frame. However, in the case of the four-field driving method, since the white luminance corresponds to only one field among the four fields, the luminance and contrast ratio (CR = W / B) of the display device 600 may drop.

According to the method of driving the light source unit 300, it is divided into a continuous driving method and a sequential driving method to compare and compare the luminance (Luminance: L) in each case. For reference, a white signal is input from the display panel 500, and white luminance of white light emitted by driving all of the red, green, and first blue light sources RL, GL, and BL1 for one frame is defined as W. In addition, although a black signal is input from the display panel 500 and the red, green, and first blue light sources RL, GL, and BL1 are continuously turned on, they are blocked by the liquid crystal layer 530 of the display panel 500. The black luminance in the case is defined as B.

First, the continuous driving method w_1 is a method in which the light source unit 300 simultaneously drives the red, green, and first blue light sources RL, GL, and BL1 to continuously emit white light for one frame. Although the white light continues to be emitted, the section that substantially affects the white luminance includes only the white field W_F, which is the moment when the white signal is received. Accordingly, the white luminance of the continuous drive system w_1 is W / 4. On the other hand, the black luminance of the continuous drive system w_1 is B. Accordingly, the contrast ratio of the display device 600 driven by the continuous driving method w_1 is W / 4B.

Next, the sequential driving method drives the red, green, and first blue light sources RL, GL, and BL1 sequentially, so that the light source unit 300 receives red light, green light, blue light, and white light for one frame. It releases sequentially. Such a sequential driving method may be divided into first and second sequential driving methods w_2 and w_3 according to the driving method of the light source unit 300 in the white field W_F.

The first sequential driving method w_2 drives the red, green, and first blue light sources RL, GL, and BL1 in the white field W_F to emit white light. In the case of the first sequential driving method w_2, the white luminance in the white field W_F into which the white signal is input is W / 4. On the other hand, the black luminance of the first sequential driving method w_2 is reduced by about half as compared with the case of the continuous driving method, and thus becomes B / 2. Accordingly, the contrast ratio of the display device 600 driven by the first sequential driving method w_2 is W / 2B.

As in one embodiment of the present invention, the second sequential driving method w_3 drives the red, green, first blue and white light sources RL, GL, BL1, WL in the white field W_F, thereby providing white light. Emits. As described above, when driving the red, green, and first blue light sources RL, GL, and BL1, the white luminance in the white field W_F can be increased to W / 2 by simultaneously driving the white light source WL. have. On the other hand, the black luminance of the second sequential driving method w_3 is increased to be 3B / 4 by the white light source WL than the first sequential driving method w_2 black luminance. Accordingly, the contrast ratio of the display device 600 driven by the second sequential driving method w_3 may be increased to 2W / 3B.

As such, since the display device 600 sequentially driven by R_G_B_W simultaneously drives the white light source WL in the white field W_F, the luminance and contrast ratio may be further improved. For example, the second sequential driving method w_3 may be applied to the display device 600 including the display panel 500 in an OCB (Optically Compensated Birefringence) mode. Accordingly, the contrast ratio of the display panel 500 in the OCB mode having a large amount of leakage light can be effectively improved.

As described above, since the light from the sequentially driven light source unit does not pass through the color filter and the spectrum of the light is not distorted, the display device can implement an image of a wide color reproduction region. In addition, in the case of a four-field sequential driving method including a white field, color breakup may be prevented, and color reproduction of the display device may be further improved.

On the other hand, as the light source unit includes a white light source that emits white light in the white field, the overall brightness and contrast contrast ratio of the display device can be further improved.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

Claims (9)

A backlight assembly emitting time by dividing a unit frame into a plurality of fields displaying different colors, A driving substrate; And And a light source unit disposed on the driving substrate, the light source unit having a red light source, a green light source, a first blue light source, and a white light source. The backlight assembly of claim 1, wherein the white light source comprises a second blue light source and a phosphor coated on the second blue light source. The backlight assembly of claim 2, wherein the phosphor is a yellow phosphor. The backlight assembly of claim 1, wherein an emission area of the white light source is greater than an emission area of the red, green, and first blue light sources. The backlight assembly of claim 1, wherein the red, green, first blue and white light sources are formed in a single package. A driving method of a backlight assembly having a red light source, a green light source, a first blue light source, and a white light source, Driving the red light source; Driving the green light source; Driving the first blue light source; And And driving the white light source. The method of claim 6, wherein the driving of the white light source comprises simultaneously driving the white light source and the red, green, and first blue light sources. The method of claim 6, wherein the white light source comprises a second blue light source and a phosphor coated on the second blue light source. A display apparatus for displaying an image by time-dividing a unit frame into a plurality of fields displaying different colors. A display panel displaying an image; And And a backlight assembly disposed on the driving substrate and having a light source unit comprising a red light source, a green light source, a first blue light source, and a white light source.

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