KR20060000814A - Back light unit of liquid crystal display device - Google Patents

Abstract

The present invention relates to a backlight unit of a liquid crystal display device for supplying light having uniform luminance to the entire area of the liquid crystal panel, wherein the backlight units according to the present invention are different from each other so as to correspond to the entire surface of the panel on which an image is displayed. A plurality of lamps arranged at intervals and emitting light; A reflector for reflecting light propagating to the back of the lamp in the panel direction; An optical member diffusing and condensing the light irradiated from the lamp and incident on the panel; It is configured to include an inverter for driving the lamp.

Description

BACK LIGHT UNIT OF LIQUID CRYSTAL DISPLAY DEVICE}

1 is a cross-sectional view showing a liquid crystal display device to which a conventional direct type backlight unit is applied.

2 is a plan view showing the arrangement of the lamp in a typical direct backlight unit;

FIG. 3 is an exemplary diagram showing luminance distributions for respective regions of a liquid crystal panel according to the lamp arrangement of FIG. 2; FIG.

4 is a cross-sectional view showing a backlight unit of a liquid crystal display device according to the present invention;

5 illustrates an arrangement of lamps according to the invention.

FIG. 6 is an exemplary diagram illustrating luminance distribution for each region of a liquid crystal panel according to the lamp arrangement of FIG. 5; FIG.

*** Description of the symbols for the main parts of the drawings ***

244: reflecting plate 245: diffusion plate

246: optical sheet 247: lamp

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit of a liquid crystal display device, and more particularly, to a backlight unit of a liquid crystal display device capable of supplying uniform luminance to a liquid crystal display panel. It is about.

In today's information society, display is more important as a visual information transmission medium. In order to occupy a major position in the future, display needs to satisfy requirements such as low power consumption, thinning, light weight, and high quality.

The display itself has a cathode ray tube (CRT), an electroluminescent element (EL), a light emitting diode (LED), a vacuum fluorescence display (VFD), an electric field It can be divided into a light emitting type such as a field emission display (FED), a plasma display panel (PDP), and a non-light emitting type which does not emit light such as a liquid crystal display.

A liquid crystal display device displays an image by using optical anisotropy of liquid crystal. Plasma display panels or electric fields are not only small in view of conventional CRTs, but also smaller than CRT tubes having the same average power consumption. Along with the emission display, it is recently attracting attention as a next generation display device.

In general, a liquid crystal display device is a flat panel display device that can display a desired image by separately supplying data signals according to image information to pixels arranged in a matrix form, and adjusting light transmittance of the pixels. to be.                         

Accordingly, the LCD device includes a liquid crystal panel in which pixels are arranged in a matrix; A driving unit for driving the pixels is provided.

The liquid crystal panel includes a thin film transistor array substrate and a color filter substrate bonded together so that the same cell-gap is maintained to face each other, and the color filter substrate and the thin film transistor array substrate. It consists of a liquid crystal layer formed in the cell-gap of.

The liquid crystal display device is a transmissive display device, and a desired image is displayed on a screen by adjusting the amount of light passing through the liquid crystal layer by refractive index anisotropy of liquid crystal molecules. Accordingly, the liquid crystal display device includes a backlight unit for supplying light to the liquid crystal layer for displaying an image, and the backlight unit is provided with a lamp that is a light source for emitting light. In general, the backlight unit may be classified into two types.

First, an edge-type backlight unit is provided on the side of the liquid crystal panel to provide light to the liquid crystal layer. Second, the lamp is provided on the rear side of the liquid crystal panel to provide light directly to the front of the liquid crystal panel. It is a direct backlight unit.

The side type backlight unit may be installed on the side of the liquid crystal panel to supply light to the liquid crystal layer through the reflecting plate and the light guide plate. Therefore, since the thickness can be made thin, it is mainly used for the notebook etc. which are manufactured with thin thickness. However, in the side type backlight unit, since the lamp emitting light is located on the side of the liquid crystal panel, it is difficult to apply to a large area liquid crystal panel, and it is difficult to obtain high luminance because light loss occurs through the light guide plate. Therefore, there is a problem that it is not suitable for the large-area liquid crystal panel for televisions, which has been in the spotlight recently.

On the other hand, in the direct type backlight unit, since the light emitted from the lamp is directly supplied to the liquid crystal layer, and there is no loss of light due to the light guide plate, it is possible to provide sufficient luminance to a large area liquid crystal panel. It is mainly used to make.

1 is a cross-sectional view of a liquid crystal display device to which a conventional direct type backlight unit is applied.

As shown in the figure, the liquid crystal display device 1 is bonded so that the first substrate 10a and the second substrate 10b facing each other have a predetermined interval, and the first substrate 10a and the second substrate ( A liquid crystal panel 10 having a liquid crystal layer (not shown) formed in a space between the portions 10b), a backlight unit 40 provided on a rear surface of the liquid crystal panel 10, and a driver 50 for driving the liquid crystal panel 10. It is composed of

Although not shown in the drawing, a plurality of gate lines that are uniformly spaced apart laterally and a plurality of data lines that are regularly spaced apart longitudinally intersect each other on the first substrate 10a, and the gate line and the data line cross each other. Pixels are provided in these intersecting regions. The pixels are individually provided with a switching element such as a thin film transistor and a pixel electrode.

Red, green, and blue color filters are formed on the second substrate 10b to display various color images by mixing red, green, and blue light passing through the red, green, and blue color filters. In addition, a black matrix is formed in a net shape to prevent light leakage from being formed outside the color filters.

The second substrate 10b is provided with a common electrode to form an electric field in the liquid crystal layer together with the pixel electrode of the first substrate 10a, thereby changing the light transmittance of the liquid crystal layer, thereby providing the backlight unit 40. The light supplied from the image is displayed.

The backlight unit 40 emits light and supplies a plurality of lamps 47 to supply light to the front of the liquid crystal panel 10, and a reflector 44 reflecting light emitted from the lamp 47 to improve light efficiency. ), A diffusion plate 45 for diffusing the light emitted from the lamp 47 and incident on the liquid crystal panel 10, and re-diffusing light diffused by the diffusion plate 45, And an optical sheet 46 incident on the liquid crystal panel 10.

The reflector plate 44 provided on the rear surface of the lamps 47 reflects the light emitted from the rear surface of the lamps 47 toward the diffuser plate 45 to reduce the loss of light and to the diffuser plate 45. Improve the uniformity of the incident light.

The driver 50 is largely divided into a gate driver and a data driver. The gate driver applies a gate low voltage and a gate high voltage to the gate lines to activate the pixels, and the data driver applies image information to the pixels through the data lines.

Outside the liquid crystal panel 10, the driver 50, and the backlight unit 40, various structures are provided to protect and fasten the liquid crystal panel 10, the driver 50, and the backlight unit 40. The bottom cover 52 protects the lower portion of the backlight unit 40, supports the liquid crystal panel 10, the driver 50, and the backlight unit 40 under the liquid crystal display device 1. The upper case 51 compresses the edge region of the liquid crystal panel 10 to fix the liquid crystal panel 10 and is coupled to the side surface of the lower case 52. Internal accessories are protected by the fastening of the upper case 51 and the lower cover 52.

As described above, the direct type backlight unit is mainly used in large-area liquid crystal panels, which are being produced in recent years, and are used to obtain brighter brightness even in small and medium-area liquid crystal panels. The direct type backlight unit has a merit of obtaining clear image quality through high luminance by supplying light of a lamp directly to the front of the liquid crystal panel.

2 is a plan view showing the arrangement of a lamp in a general direct type backlight unit.

Referring to FIG. 2, the backlight unit includes a plurality of lamps 147 emitting light and a reflecting plate 144 under the lamps 147.

The lamps 147 are arranged at regular intervals ΔL1 and are disposed to correspond to the entire surface of the liquid crystal panel (not shown). Therefore, light of uniform brightness must be supplied to the entire liquid crystal panel. However, the light emitted from the lamps 147 and supplied to the front of the liquid crystal panel is not uniform. As shown in FIG.

FIG. 3 is an exemplary diagram illustrating a luminance distribution appearing for each region of a liquid crystal panel according to the lamp arrangement of FIG. 2.

Referring to FIG. 3, luminance distributions of upper, middle, and lower regions of the liquid crystal panel corresponding to the lamps of FIG. 2 are illustrated. As shown, the central region of the liquid crystal panel has the highest luminance, and the luminance is lowered toward the upper region and the lower region, respectively. This is because the number of lamps arranged to the left and right in the center area of the liquid crystal panel is larger than that of the lower area and the upper area, so that light from a relatively large number of lamps is concentrated, while the lower area and the upper area of the liquid crystal panel are relatively This is because light emitted from a small number of lamps is concentrated.

Therefore, when light is supplied from lamps arranged at uniform intervals as in the related art, a luminance difference is generated according to regions in the liquid crystal panel, which may result in deterioration of image display quality of the liquid crystal display device.

Accordingly, the present invention has been devised to solve the above-described problems, and an object of the present invention is to provide a liquid crystal display for supplying light having the same brightness over the entire area of the liquid crystal panel by flexibly adjusting the arrangement interval of the lamps. It is to provide a backlight unit of the device.

The backlight unit of the liquid crystal display device for achieving the above object of the present invention comprises a plurality of lamps arranged at different intervals so as to correspond to the entire surface of the panel on which the image is displayed; A reflector for reflecting light propagating to the back of the lamp toward the panel; An optical member diffusing and condensing the light irradiated from the lamp and incident on the panel; It is configured to include an inverter for driving the lamp.

4 is a cross-sectional view illustrating a backlight unit of a liquid crystal display according to the present invention.

Referring to FIG. 4, the backlight units are arranged at different intervals, and reflect light emitted from the lamps 247 and the plurality of lamps 247 for emitting light to supply light to the front of the liquid crystal panel, thereby improving light efficiency. The reflection plate 244 to be improved, the diffusion plate 245 for diffusing the light emitted from the lamp 247 and entering the liquid crystal panel, and the light diffused by the diffusion plate 245 The optical sheet 246 is incident to the liquid crystal panel.

The reflector plate 244 provided on the rear surface of the lamps 247 reflects the light exiting the rear surface of the lamps 247 toward the diffusion plate 245 to reduce the loss of light and to the diffusion plate 245. Improve the uniformity of the incident light.

The optical sheet 246 is composed of a diffusion sheet and a prism sheet. The diffusion sheet disperses the light incident through the diffusion plate 245, thereby preventing the light from being partially concentrated to cause stains in the image displayed on the liquid crystal panel, and the prism sheet is the light incident from the diffusion sheet. By condensing the angle of the light vertically, the light is uniformly distributed on the entire surface of the liquid crystal panel.

Cold cathode fluorescent lamp (CCFL) or external electrode fluorescent lamp (EEFL) may be used as the lamps 247.

Although not shown in the drawing, the backlight unit is provided with an inverter unit for supplying power for driving the lamps 247. The inverter applies a high voltage to turn on the lamp 247, and applies a tube current to the lamp 247 to adjust the amount of light emitted.

On the other hand, the lamps 247 provided between the reflecting plate 244 and the diffusion plate 245 are not arranged at a uniform interval, but are arranged to have a different distance from each other.

5 is an exemplary view showing an arrangement of lamps according to the present invention.

Referring to FIG. 5, the lamps 347 are arranged at different intervals, and a rear surface of the lamps 347 is provided with a reflecting plate 344 for increasing light efficiency.

The lamps 347 are arranged to correspond to the front surface of the liquid crystal panel. The lamps 347 are arranged at both edges of the liquid crystal panel and the gap ΔL11 between the lamps 347 arranged in the center area of the liquid crystal panel. The interval ΔL11 between the 347 is different from each other. That is, the distance ΔL11 between the lamps 347 is narrowed from the center area of the liquid crystal panel to both edge areas. As described above, by arranging the lamps 347 corresponding to the edge regions of the liquid crystal panel with a small interval, many lamps 347 can be arranged in a limited space, thereby increasing the amount of light irradiated to the edge regions. have.

FIG. 6 is an exemplary diagram illustrating luminance distribution for each region of a liquid crystal panel according to the lamp arrangement of FIG. 5. As illustrated, images displayed in the upper region, the lower region, and the center region of the liquid crystal panel have similar luminance distributions. . Therefore, it is possible to supply light having uniform luminance over the entire liquid crystal panel.

As described above, the backlight unit of the liquid crystal display according to the present invention controls the unbalance of the amount of light irradiated to the liquid crystal panel due to the different intervals between the lamps, thereby supplying light of uniform luminance to all regions of the liquid crystal panel. Degradation of the image quality of the liquid crystal display device can be prevented.

Claims (6)

A panel on which an image is displayed; A lamp that emits light and supplies light to the panel; And And an optical member for diffusing and condensing the light irradiated from the lamp to be incident on the panel, wherein the lamps are arranged at different intervals and equalize the luminance of the entire panel. The backlight unit of claim 1, wherein the lamp is a cold cathod electrode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL). The method of claim 1, wherein the optical member A diffuser plate for diffusing light; And And an optical sheet for re-diffusing light diffused by the diffusion plate, condensing light, and entering the panel. The backlight unit of claim 1, wherein a corresponding interval of arrangement of lamps decreases from the center area to the edge area of the panel. The backlight unit of claim 1, further comprising a reflector for reflecting light traveling toward the rear surface of the lamp toward the panel. The backlight unit of claim 1, further comprising an inverter configured to drive the lamp to emit light.

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