KR20070001620A - Back light unit - Google Patents

Abstract

A back light unit is provided to reduce a gap between a diffusion plate and a lamp by reducing a brightness peak value of the central axis of a lamp by forming a resin at the center axis of the lamp, thereby realizing a slim back light unit. A lamp(4) has a resin applied on a surface at the central axis of the lamp along a length direction of the lamp, wherein the resin disperses light. A diffusion plate(2) is placed on the lamp for diffusing light received from the lamp. A plurality of optical sheets(5) are placed on the diffusion plate for changing a path of light entered from the diffusion plate into a direction vertical to a liquid crystal panel(10).

Description

Backlight Unit

1 is a view showing a conventional liquid crystal display device.

FIG. 2 is a diagram illustrating luminance of the backlight unit illustrated in FIG. 1.

3 is a diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a cross-sectional view showing in detail the lamp shown in FIG.

5 is a cross-sectional view illustrating the lamp illustrated in FIG. 3.

<Description of Symbols for Main Parts of Drawings>

2 diffuser 3 bottom cover

4, 34 lamp 5 optical sheets

7: reflector 9: wire

10 liquid crystal display panel 17 glass tube

19: inert gas 20: top case

21: cathode 23: phosphor

25: electronic

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a backlight unit capable of slimming the thickness.

In general, the liquid crystal display device has a trend that the application range is gradually widened due to the characteristics such as light weight, thin, low power consumption. In accordance with this trend, liquid crystal displays are used in office automation equipment, audio / video equipment, and the like. In such a liquid crystal display device, a transmission amount of a light beam is adjusted according to a signal applied to a plurality of control switches arranged in a matrix to display a desired image on a screen.

Since the liquid crystal display is not a self-luminous display, a separate light source such as a back light is required.

The backlight includes a direct type and an edge type according to the position of the light source. The edge type backlight is provided with a light source at one edge of the liquid crystal display, and irradiates the liquid crystal display panel with light incident from the light source through the light guide plate and the plurality of optical sheets. In the direct type backlight, a plurality of light sources are disposed directly below the liquid crystal display, and light incident from the light sources is irradiated onto the liquid crystal display panel through the diffusion plate and the plurality of optical sheets. Light sources used for backlights include a cold cathode fluorescent lamp (CCFL) and a light emitting diode (LED).

Recently, the direct type backlight having higher luminance, light uniformity and color purity than the edge type is being used more mainly in LCD TV.

Referring to FIG. 1, a conventional liquid crystal display device includes a liquid crystal display panel 10 for displaying an image, a top case 20 disposed on the liquid crystal display panel 10, and a liquid crystal display panel 10. And a direct type backlight unit which is disposed on the rear surface of the panel) and irradiates light to the liquid crystal display panel 10.

In the liquid crystal display panel 10, a plurality of data lines and a plurality of scan lines are arranged to cross each other, and liquid crystal cells are arranged in an active matrix form between the upper and lower substrates to display an image.

The backlight unit includes a lamp 4, a bottom cover 3, a reflecting plate 7, a diffusion plate 2, a plurality of optical sheets 5, and a wire 9.

The lamps 4 are cold cathode fluorescent lamps (CCFLs), and a plurality of lamps are arranged in a row. Here, the wire 9 is connected to an external power source for driving the lamp 4.

The bottom cover 3 includes a bottom surface and a side surface, and a reflection plate 7 is accommodated therein.

The optical sheets 5 include a diffusion sheet and a prism sheet to uniformly irradiate the light incident from the diffusion plate 2 to the entire liquid crystal display panel 10 and to bend the path of the light in a direction perpendicular to the display surface. It increases the brightness in front of the display surface.

The diffusion plate 2 is positioned on the lamp 4 and includes a plurality of beads in a polymethylmethacrylate (PMMA), and scatters the light incident from the lamp 4 using the beads to disperse the liquid crystal display panel 10. In the display surface of b), there is no difference in luminance where the lamp 4 is located and where it is not.

As described above, the conventional backlight unit has a problem that the luminance difference Δ1 between the lamps 4 is large as shown in FIG. 2. In order to solve this problem, the gap between the lamp 4 and the diffuser plate 2 is reduced by measuring the brightness on one lamp and lowering the maximum peak brightness at the brightness having a normal distribution based on the lamp central axis. However, in spite of this research, the conventional backlight unit had to sufficiently secure the gap g1 between the lamp 4 and the diffuser plate 2 in order to eliminate the luminance difference between the lamps 4, which resulted in the liquid crystal display device. It became a factor which thickened the whole thickness t1.

Accordingly, an object of the present invention is to provide a backlight unit that can reduce the thickness by forming a resin on the surface of the lamp.

In order to achieve the above object, the backlight unit according to the present invention comprises a lamp formed on the surface of the resin scattering light along the longitudinal direction on the central axis, and a diffusion plate positioned on the lamp to diffuse the light from the lamp; And optical sheets positioned on the diffusion plate and converting light incident from the diffusion plate in a direction perpendicular to the liquid crystal display panel.

The resin is formed long on the upper surface of the lamp along the longitudinal direction of the lamp.

According to the present invention, a backlight unit includes a lamp including a tube having a roughness on at least a portion of the upper part, a diffuser plate positioned on the lamp to diffuse light from the lamp, and a diffuser plate positioned on the diffuser plate from the diffuser plate. Optical sheets for converting the incident light to the liquid crystal display panel in a direction perpendicular to the liquid crystal display panel.

Roughness formed in the tube of the lamp is formed long on the outer surface of the tube along the longitudinal direction of the lamp.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

A preferred embodiment of the present invention will be described with reference to FIGS. 3 to 5.

Referring to FIG. 3, the backlight unit according to the exemplary embodiment of the present invention forms a stripe (or strip) -shaped resin 37 in the longitudinal direction of the lamp 34 at the center of the lamp 34.

The liquid crystal display device according to the present invention includes a liquid crystal display panel 10 for displaying an image, a top case 20 disposed on the liquid crystal display panel 10, and a liquid crystal display panel disposed on a rear surface of the liquid crystal display panel 10. It is composed of a direct type backlight unit for irradiating light to the display panel 10.

In the liquid crystal display panel 10, a plurality of data lines and a plurality of scan lines are arranged to cross each other, and liquid crystal cells are arranged in an active matrix form between the upper and lower substrates. Further, pixel electrodes and a common electrode for applying an electric field to each of the liquid crystal cells are formed in the liquid crystal display panel. Thin film transistors (TFTs) for switching data voltages to be applied to the pixel electrodes are formed at intersections of the plurality of data lines and the plurality of scan lines. Gate drive integrated circuits and data drive integrated circuits are electrically connected to the liquid crystal display panel through a tape carrier package (TCP).

The backlight unit includes a lamp 34, a bottom cover 3, a reflecting plate 7, a diffusion plate 32, a plurality of optical sheets 5, and a wire 9.

The lamps 34 are cold cathode fluorescent lamps (CCFLs), and a plurality of lamps 34 are arranged in a row. Here, the wire 9 is connected to an external power source for driving the lamp 34.

Referring to the driving principle of the lamp 34, as shown in FIG. 4, when the voltage is supplied to the electrode of the lamp 34, the electrons 25 protrude from the cathode 21 and the inert gases inside the glass tube 17. It collides with (19), and the electrons 25 increase exponentially. Current flows through these electrons 25, and the inert gas 19 is excited by the electrons 25 emitted from the cathode 21 to emit ultraviolet rays as radiant energy, which is the inner wall of the glass tube 17. It collides with the phosphor 23 applied to the film to emit visible light.

Here, a band-shaped resin 37 is formed on the surface of the lamp 34 in the longitudinal direction along the center of the lamp 34 as shown in FIGS. 3 and 5. In the conventional backlight unit, if the gap between the lamp and the diffusion plate is reduced to slim, the luminance peak value appears in a band shape at the center of the lamp 34, thereby degrading the image quality. In order to prevent this, in the present invention, the resin 37 is formed on the central axis of the lamp 34 to scatter light emitted to the central axis of the lamp 34 to relatively lower the luminance at the center of the lamp 34. The central axis of the lamp 34 is located at the top of the lamp 34 closest to the image display surface. This resin 37 serves to lower the peak value in the central axis of the lamp 34 by scattering light from the lamp 34. The resin 37 may be made of polymethylmethacrylate (PMMA), polycarbonate, acryl, or the like, and a plurality of beads may be mixed to increase acid loss.

Accordingly, since the lamp 34 according to the present invention can scatter light from the central axis of the lamp 34 than the conventional backlight unit, the distance between the lamp 34 and the diffuser plate 2 can be reduced. As a result, it is possible to reduce the thickness of the entire liquid crystal display device to implement a slim liquid crystal display device.

The bottom cover 3 includes a bottom surface and a side surface, and a reflection plate 7 is accommodated therein.

The optical sheets 5 include a diffusion sheet and a prism sheet to uniformly irradiate the light incident from the diffusion plate 2 to the entire liquid crystal display panel 10 and to bend the path of the light in a direction perpendicular to the display surface. It serves to increase the luminance in front of the display surface.

The diffusion plate 2 is positioned on the lamp 34 and includes a plurality of beads in polymethylmethacrylate (PMMA), and scatters the light incident from the lamp 4 using the beads to disperse the liquid crystal display panel 10. In the display surface of b), there is no difference in luminance where the lamp 4 is located and where it is not.

On the other hand, it is also possible to scatter the light generated from the lamp 34 by forming a roughness on the surface of the lamp tube without applying resin to the surface of the lamp 34.

As described above, the backlight unit according to the present invention may lower the luminance peak value of the center of the lamp by forming a resin on the center axis of the lamp. Accordingly, the backlight unit according to the present invention can reduce the distance between the diffusion plate and the lamp can implement a slim backlight unit.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (6)

A lamp having a resin formed on at least a portion of the upper portion A diffusion plate positioned on the lamp to diffuse light from the lamp; And optical sheets positioned on the diffuser plate and converting light incident from the diffuser plate in a direction perpendicular to the liquid crystal display panel. The method of claim 1, And the resin is formed on the outer surface of the lamp along the longitudinal direction of the lamp. The method of claim 1, The resin is a backlight unit, characterized in that it comprises any one of polymethylmethacrylate (PMMA), polycarbonate (acryl). The method of claim 1, The resin unit comprises a plurality of beads. A lamp comprising a tube having a roughness on at least a portion of the upper portion, A diffusion plate positioned on the lamp to diffuse light from the lamp; And optical sheets positioned on the diffuser plate and converting light incident from the diffuser plate in a direction perpendicular to the liquid crystal display panel. The method of claim 5, The roughness formed in the tube of the lamp is formed on the outer surface of the tube long along the longitudinal direction of the lamp.

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