KR20050040020A - Back light assembly and the liquid crystal display device using it - Google Patents

Abstract

The present invention relates to a direct type backlight assembly and a liquid crystal display device having the same, and more particularly, to a direct type backlight assembly and a liquid crystal display device having the same, which can secure the uniformity of brightness while minimizing its thickness. .

According to an aspect of the present invention, there is provided a backlight assembly comprising: a light source for generating light from a flat plate; A reflection plate positioned below the light source; A first diffuser plate positioned above the light source to diffuse light; And a second diffuser plate which adheres to the first diffuser plate to make the luminance uniform. The liquid crystal display according to the present invention includes the backlight assembly.

The present invention has the effect of minimizing the thickness while securing the overall luminance uniformity by using the diffusion plate, thereby reducing the thickness of the liquid crystal display device, and diffusing without adding a separate diffusion sheet to secure the luminance uniformity. Since the plate itself is implemented, the manufacturing cost can be reduced.

Description

Back light assembly and the liquid crystal display device using it}

The present invention relates to a direct type backlight assembly and a liquid crystal display device having the same, and more particularly, to a direct type backlight assembly and a liquid crystal display device having the same, which can secure the uniformity of brightness while minimizing its thickness. .

Recently, with the development of the electronics industry, display devices, which have been limitedly used for TV CRTs, have been widely used in personal computers, notebooks, wireless terminals, automobile dashboards, electronic displays, etc. As a result, the importance of the next generation display device that can process and implement this is increasing.

Such next-generation display devices should be able to realize light and small size, high brightness, large screen, low power consumption and low price. And various flat panel display devices such as a vacuum fluorescent display (VFD) have been studied, and one of them has recently attracted attention.

The liquid crystal display device is superior in resolution to other flat panel display devices, and exhibits characteristics such that the response speed is faster than that of a CRT when a moving image is realized.

In addition, the liquid crystal display device has excellent characteristics such as high brightness, high contrast, low power consumption, and so is used in a wide range of fields such as a desktop computer monitor, a notebook computer monitor, a TV receiver, a vehicle-mounted TV receiver, and navigation.

In general, a liquid crystal display device is formed by arranging two substrates having electrodes formed on one side thereof so that the surfaces on which the two electrodes are formed face each other, injecting a liquid crystal material between the two substrates, and then applying voltage to the two electrodes. By moving the liquid crystal molecules by the electric field is a device that represents the image by the transmittance of light that varies accordingly.

Since the liquid crystal display does not emit light by itself, light is supplied from a backlight assembly attached to a rear surface of the liquid crystal display panel to display an image.

The backlight assembly is classified into a direct method and an edge method according to the position of the light source.

The direct method is a method of directly dimming the entire surface of the panel by placing a light source under the liquid crystal display panel. Compared to the edge method, the direct light method has advantages in that a plurality of light sources can be used to secure a high luminance. Has the disadvantage of being non-uniform.

1 is a cross-sectional view showing the structure of a conventional direct backlight assembly.

Unless otherwise specified, the portion where the lamp is positioned in the completed liquid crystal display device is referred to as the lower portion, and the portion in which the liquid crystal display panel is positioned as an upper portion.

Referring to FIG. 1, the backlight assembly 100 may include a lamp 130 that generates light, a reflector plate 140 disposed below the lamp 130, and a diffuser plate 120 positioned above the lamp 130. ), A diffusion sheet 110 placed on the diffusion plate 120 and a mold frame 150 for storing them.

The mold frame 150 is formed in a box shape of a rectangular parallelepiped having an upper surface opened.

An accommodation space having a predetermined depth is formed inside the mold frame 150, and a step for sequentially receiving the diffusion plate 120 and the diffusion sheet 110 is formed at an upper end of the side wall constituting the accommodation space.

The reflective plate 140 is installed along the inner surface of the storage space of the mold frame 150, and a plurality of lamps 130 are installed on the reflective plate 140.

In addition, the diffusion plate 120 and the diffusion sheet 110 are sequentially received in the stepped portion formed at the upper side end of the mold frame 150.

In this case, a predetermined space (hereinafter, light guide area) is formed between the lamp 130 and the diffusion plate 120.

As shown in FIG. 1, forming a light guiding region between the lamp 130 and the diffuser plate 120 widens the irradiation range of the light generated from the lamp 130 so as to extend the front of the diffuser plate 120. This is to guide the incident to the area.

In this case, a part of the light generated radially from the lamp 130 is incident directly to the diffusion plate 120, and part of the light is reflected toward the diffusion plate 120 through the reflection plate 140. In addition, the light incident on the diffusion plate 120 is diffused and emitted to have a wide range of angles.

On the other hand, the diffusion sheet 110 placed on the diffusion plate 120 serves to diffuse to uniformize the brightness of the light emitted from the diffusion plate 120 toward the liquid crystal display panel.

However, the conventional direct backlight assembly 100 described above has a luminance of light emitted from the light emitting region (hereinafter, A region) of the lamp 130 as shown in the luminance distribution curve 160 shown in FIG. 1. It is relatively higher than the luminance of the light emitted from the lamp and the area between the lamps (hereinafter, B area). Thus, luminance unevenness occurs between the A area and the B area.

In order to solve this problem, the light guide area of the direct type backlight assembly 100 is extended to increase the distance between the lamp 130 and the diffuser plate 120. As such, when the light guiding region is extended, the light irradiation area of the lamp 130 is widened, and the light guide area is wider and incident on the diffuser plate 120.

As a result, the amount of light incident on the region B increases, thereby reducing the difference in the amount of light incident on the region A and the region B, thereby making the luminance distribution uniform.

However, when the light guide area is extended to form a large distance between the lamp 130 and the diffuser plate 120, the thickness of the direct backlight assembly 100 is not only thickened, but as the light guide area is expanded, the lamp is increased. The irradiation distance of the light generated from the 130 is increased, and thus the overall luminance of the liquid crystal display is reduced.

The present invention provides a direct type backlight assembly and a liquid crystal display device having the same, which can secure luminance uniformity by dividing a diffusion plate for light diffusion and luminance uniformity into two layers in a backlight assembly of a liquid crystal display device.

In order to achieve the above object, the backlight assembly includes a light source for generating light from a flat plate; A reflection plate positioned below the light source; A first diffuser plate positioned above the light source to diffuse light; And a second diffuser plate which adheres to the first diffuser plate to make the luminance uniform.

In addition, in order to achieve the above object another liquid crystal display device according to the present invention, in the liquid crystal display device having a diffusion plate and a liquid crystal panel on the direct type backlight, the diffusion plate is composed of two and at least one diffusion plate is It is characterized in that the amount of emitted light is different depending on the position.

At this time, the at least one diffusion plate in the two diffusion plates is characterized by having a different haze, transmittance.

The diffusion plate may be a combination of a diffusion plate having a differential thickness.

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

2 is an exploded perspective view schematically illustrating a liquid crystal display having a backlight assembly according to the present invention.

Referring to FIG. 2, the liquid crystal display 290 includes a liquid crystal display panel assembly 270 for displaying an image and a direct type backlight assembly 200 for supplying light to the liquid crystal display panel assembly 270. .

The liquid crystal display panel assembly 270 includes a liquid crystal display panel 271, a data printed circuit board 278, a gate printed circuit board 274, a data tape carrier package 277, and a gate tape carrier package 275. .

The liquid crystal display panel 271 includes a TFT substrate 272, a color filter substrate 273 positioned on the TFT substrate 272, and a liquid crystal (not shown) injected between the two substrates.

A thin film transistor (not shown) that performs a switching role is formed in the TFT substrate 272, a gate line is connected to a gate electrode of each thin film transistor, a data line is connected to a source electrode, and a drain electrode. The pixel electrode is formed.

The data line and the gate line are electrically connected to the data printed circuit board 278 and the gate printed circuit board 274 through the data tape carrier package 277 and the gate tape carrier package 275.

Therefore, when the data and gate printed circuit boards 278 and 274 receive electrical signals from the outside, the data and gate printed circuit boards 278 and 274 drive and drive the liquid crystal display panel assembly 270. The driving signal and the timing signal for controlling the control signal are transmitted to the gate line and the data line through the data tape carrier package 277 and the gate tape carrier package 275.

The color filter substrate 273 is formed with an RGB pixel which is a color pixel for displaying an image. Therefore, the light transmitted through the liquid crystal is expressed in a predetermined color through the RGB pixel.

In addition, a common electrode is formed on an entire surface of the color filter substrate 273. Accordingly, when a voltage is applied to the liquid crystal display panel 271, an electric field is formed between the common electrode and the pixel electrode of the thin film transistor to change the arrangement of liquid crystals therebetween.

The direct backlight assembly 200 includes a lamp 230 generating light, a reflecting plate 240 positioned below the lamp 230, and a diffuser plate 220 positioned above the lamp 230. 221 and a mold frame 250 for receiving them.

In addition, a middle chassis 260 is provided to press the upper and lower middle chassis 260 to interview the diffusion plates 220 and 221 to fix the diffusion plates 220 and 221 to the mold frame 250. 280 covers the effective display area of the liquid crystal display panel 290 so that the inner wall contacts the outer wall of the mold frame 250.

The diffusion plates 220 and 221 are formed of two layers having haze formed therein, and a lower diffuser plate 220 through which light generated from a lamp is incident and diffused, and the diffusion plate. And an upper diffuser plate 221 for allowing the light to be incident on the liquid crystal display panel with uniform luminance.

At this time, the haze and the transmittance of the upper diffusion plate 221 according to the position is different, or the thickness is formed differently according to the position of the upper diffusion plate 221 to increase the uniformity of the brightness of the lamp 230 and the diffusion plate ( Since the distances 220 and 221 can be reduced, a thin backlight assembly can be manufactured.

Here, the haze serves to improve the uniformity of the light by diffusing the light.

3 is a view showing a cross-sectional view of a direct type backlight assembly as an embodiment according to the present invention.

Referring to FIG. 3, the direct type backlight assembly 300 includes a lamp 330 for generating light, a reflecting plate 340 positioned under the lamp 330, and a lower diffusion positioned above the lamp 330. The plate 320 includes an upper diffusion plate 310 placed on the lower diffusion plate 320, and a mold frame 350 for storing them.

The mold frame 350 is formed in a box shape of a rectangular parallelepiped having an upper surface opened. A storage space having a predetermined depth is formed inside the mold frame 350, and a stepped portion in which the lower diffusion plate 320 and the upper diffusion plate 310 are sequentially seated is formed at an upper end of the side wall constituting the storage space. . The mold frame 350 for accommodating the lamp 330, the reflector 340, and the diffuser plates 310 and 320 is presented as an embodiment of the present invention, and other types of frames may be applied to the mold.

The reflective plate 340 is installed along the inner surface of the storage space of the mold frame 350, and a plurality of lamps 330 are installed on the reflective plate 340. In this case, opposite ends of the lamp 330 may be coupled to the lamp holders 231 in FIG. 2 to stably fix the plurality of lamps 330 to the upper portion of the reflective plate 340.

The lamp 330 has an effective light emitting area C and an invalid light emitting area D. FIG. The effective light emitting area C is an area where light is generated substantially, and represents a central portion of the lamp 330, and the invalid light emitting area D is coupled to the lamp holder 231 in FIG. 2. 330 is shown at both ends, and substantially no light is generated in this region.

Meanwhile, the lower diffusion plate 320 and the upper diffusion plate 310 are sequentially received in the stepped portion formed at the upper end of the sidewall of the mold frame 350.

In this case, a predetermined space is formed between the lamp 330 and the lower diffuser plate 320, and the light guide in which light generated from the lamp 330 is guided to the lower diffuser plate 320 is formed. Area.

A portion of the light emitted radially from the lamp 330 is incident directly to the lower diffuser plate 320, and a portion of the light is reflected toward the lower diffuser plate 320 by the reflector 340, so that the lower diffuser plate 320 is disposed. Incident).

The lower diffusion plate 320 serves to diffuse the light incident from the lamp 330 to be emitted at a wide range of angles.

In this case, the lower diffuser plate 320 is divided into a region in which the amount of incident light is large and a region in which the incident light is partially small.

That is, the area C corresponding to the lamp 330 of the lower diffuser plate 320 has a relatively large amount of light incident from the lamp 330, and is disposed between the lamp 330 and the lamp 330. The corresponding area D has a relatively small amount of light incident from the lamp 330.

As such, the light diffused non-uniformly from the lower diffuser plate 320 has a uniform luminance while passing through the upper diffuser plate 310.

The upper diffusion plate 310 is formed of a combination of a plurality of diffusion plates (H1, H2, H3 .....) having different haze and transmittance.

In this case, the plurality of diffusion plates forming the upper diffusion plate 310 pass through the upper diffusion plate 310 in combination with a diffusion plate having an appropriate haze and transmittance according to the luminance distribution of light passing through the lower diffusion plate 320. The emission amount of light is made constant so as to have a uniform luminance.

Preferably, the upper diffuser plate 310 uses a diffuser plate having a high haze and low transmittance in a C region having a relatively high light emission amount corresponding to the lamp 330, and the lamp 330 and the lamp 330. Correspondingly, in the D region where the light emission amount is relatively small, a diffuser plate having a low haze and a high transmittance is used to make the light emission amount constant and suppress luminance unevenness as a whole.

 That is, by successively passing through the upper and lower diffusion plates 310 and 320, the difference in the amount of light emitted between the C region and the D region is more finely adjusted, so that the overall luminance uniformity of the liquid crystal display 290 is maintained. The castle can be secured.

Therefore, luminance uniformity can be secured without using a separate diffuser sheet, and the backlight assembly can be thinned.

4 is a cross-sectional view of a direct backlight assembly according to another embodiment of the present invention.

Referring to FIG. 4, the direct type backlight assembly 400 includes a lamp 430 for generating light, a reflecting plate 440 disposed below the lamp 430, and a lower portion positioned above the lamp 430. The diffusion plate 420 includes an upper diffusion plate 410 disposed above the lower diffusion plate 420, and a mold frame 450 for storing the diffusion plate 420.

The mold frame 450 is formed in a box shape of a rectangular parallelepiped having an upper surface opened. A storage space having a predetermined depth is formed inside the mold frame 450, and a stepped portion in which the lower diffuser plate 420 and the upper diffuser plate 410 are sequentially seated is formed at an upper end of the side wall constituting the storage space. . The mold frame 450 for accommodating the lamp 430, the reflector plate 440, and the diffuser plates 410 and 420 is presented as an embodiment of the present invention, and other types of frames may be applied to the mold.

The reflective plate 440 is installed along the inner surface of the storage space of the mold frame 450, and a plurality of lamps 430 are provided on the reflective plate 440. In this case, opposite ends of the lamp 430 may be coupled to the lamp holders 231 in FIG. 2 to stably fix the plurality of lamps 430 to the upper portion of the reflector 440.

The lamp 430 has an effective light emitting area C and an invalid light emitting area D. FIG. The effective light emitting area C is an area where light is generated substantially, and represents a central portion of the lamp 430, and the invalid light emitting area D is coupled to the lamp holder 231 of FIG. 430 is shown at both ends, and substantially no light is generated in this region.

Meanwhile, the lower diffusion plate 420 and the upper diffusion plate 410 are sequentially received in the stepped portion formed at the upper end of the sidewall of the mold frame 450.

In this case, a predetermined space is formed between the lamp 430 and the lower diffuser plate 420, and the light guide is configured to guide light generated from the lamp 430 to the lower diffuser plate 420. Area.

A portion of the light emitted radially from the lamp 430 is incident directly to the lower diffuser plate 420, and a portion of the light emitted from the lamp 430 is reflected toward the lower diffuser plate 420 by the reflector plate 440, and thus the lower diffuser plate 420. Incident).

The lower diffuser plate 420 forms the same haze and transmittance, and serves to diffuse the light incident from the lamp 430 to be emitted at a wide range of angles.

In this case, the lower diffuser plate 420 is divided into a region having a large amount of incident light and a region having a small amount of incident light.

That is, the region C corresponding to the lamp 430 of the lower diffuser plate 420 has a relatively large amount of light incident from the lamp 430, and the region D corresponding between the lamp and the lamp. Relatively little amount of light incident from the lamp 430 is.

As such, the light diffused non-uniformly from the lower diffuser plate 420 has a uniform luminance while passing through the upper diffuser plate 410.

Here, the upper diffusion plate 410 is made of the same material as the lower diffusion plate 420, and is made of a combination of diffusion plates (T1, T2, T3 ...) different in thickness depending on the position.

That is, the lower diffuser plate 420 is divided into a region having a large amount of incident light and a region having a small amount of incident light, and a region C corresponding to the lamp 430 of the lower diffuser plate 420. ) Has a relatively large amount of light incident from the lamp 430, and a region D corresponding between the lamp 430 and the lamp 430 has a relatively small amount of light incident from the lamp 430. .

Accordingly, the light having non-uniform brightness through the lower diffuser plate 420 is changed by the upper diffuser plate 410 having a differential thickness arranged according to the light projection amount, thereby resulting in uneven luminance. Will compensate.

At this time, as described above, the plurality of diffusion plates constituting the upper diffusion plate 410 are combined with the diffusion plate having a thickness that is differentiated according to the luminance distribution of the light passing through the lower diffusion plate 420. The output quantity of light passing through) is made constant so as to have a uniform luminance.

Preferably, the upper diffuser plate 410 lowers the transmittance by using a diffuser plate having a relatively thick thickness for the C region in which light output is relatively high corresponding to the lamp 430, and the lamp 430 and the lamp Corresponding to 430, the D region having a relatively small amount of light emission is used to increase the transmittance by using a relatively thin diffuser plate, so that the total amount of light emission is constant and the luminance unevenness is suppressed.

 Therefore, by successively passing through the upper and lower diffusion plates 410 and 420, the difference in the amount of light emitted between the C region and the D region is more finely adjusted to ensure overall luminance uniformity of the liquid crystal display. can do.

As such, luminance uniformity may be secured without using a separate diffuser sheet, thereby making the backlight assembly thin.

As described above, when the upper diffuser plate is formed, a passage distance through which light incident to the C region of the upper diffuser plate passes through the diffuser plate is longer than a passage distance of light incident to the D region. Therefore, the amount of reduction of light passing through the C region is greater than the amount of reduction of light passing through the D region.

Therefore, even though the incidence of light incident from the lamp into the upper diffusion plate corresponding to the C region and the D region is different from each other, the emission amount of the light emitted from the diffuser plate is substantially the same. That is, the overall luminance of the light emitted from the diffusion plate is maintained in a uniform state.

Although the present invention has been described in detail through specific embodiments, it is intended to specifically describe the present invention, and the backlight assembly and the liquid crystal display device having the same according to the present invention are not limited thereto. It is apparent that modifications and improvements are possible by those skilled in the art.

According to the present invention, the thickness of the liquid crystal display device can be minimized while the overall brightness uniformity can be minimized by using a diffusion plate composed of two layers in the backlight assembly of the liquid crystal display device.

In addition, the present invention is implemented by using the diffusion plate itself without adding a separate diffusion sheet in order to ensure the uniformity of the brightness has the effect of reducing the manufacturing cost.

1 is a cross-sectional view showing the structure of a conventional direct type backlight assembly.

2 is an exploded perspective view schematically showing a liquid crystal display device having a backlight assembly according to the present invention;

3 is a cross-sectional view of a direct backlight assembly according to one embodiment of the present invention.

4 is a cross-sectional view of a direct backlight assembly according to another embodiment of the present invention.

<Description of Signs of Major Parts of Drawings>

200, 300, 400: backlight assembly 221, 310, 410: upper diffusion plate

220, 320, 420: lower diffuser 230, 330, 430: lamp

340, 440: reflector 250, 350, 450: mold frame

260: middle chassis 270: liquid crystal display panel assembly

271: liquid crystal display panel 272: TFT substrate

273: color filter substrate 274: gate printed circuit board

275: Gate Tape Carrier Package

277: data tape carrier package

278: data printed circuit board 280: top chassis

290 liquid crystal display device

Claims (8)

A light source for generating light from the flat plate; A reflection plate positioned below the light source; A first diffuser plate positioned above the light source to diffuse light; And a second diffuser plate which adheres to the first diffuser plate to make the luminance uniform. The method of claim 1, And the light source comprises a plurality of lamps on a flat plate. The method of claim 1, And the first diffusion plate is made of a material having the same haze and transmittance. The method of claim 1, The second diffuser plate is a backlight assembly, characterized in that consisting of a combination of the differential haze, the diffusion plate having a transmittance. The method of claim 1, And said second diffuser plate comprises a combination of diffuser plates having the same haze and of different thicknesses. In a liquid crystal display device having a diffusion plate and a liquid crystal panel on a direct backlight, The diffusion plate is composed of two, the at least one diffusion plate is characterized in that the amount of light transmitted through the different position according to the liquid crystal display device. The method of claim 6, And at least one diffuser plate in the two diffuser plates has differential haze and transmittance. The method of claim 6, And the diffusion plate is a combination of a diffusion plate having a differential thickness.