KR100713891B1 - Backlight unit for LCD - Google Patents

Abstract

The present invention relates to a backlight unit for a liquid crystal display device which can be selectively used according to the luminance used by adding a side backlight to the direct backlight. The backlight unit according to the present invention includes a flat light guide plate for diffusing the incident light to uniformly irradiate the back of the liquid crystal panel; A first light source positioned on at least one side of the light guide plate to provide light to the light guide plate; A second light source positioned at a rear surface of the light guide plate to provide light to the light guide plate; And a transflective pattern layer positioned between the light guide plate and the second light source to change a traveling direction of light provided from the first and second light sources.

Description

Backlight unit for liquid crystal display {Backlight unit for LCD}

1 is a cross-sectional view of a backlight unit for a liquid crystal display device according to the present invention.

2 is a perspective view of a backlight unit according to the present invention;

Explanation of symbols on the main parts of the drawings

10: first light source 11: second light source

12: Light guide plate 13: transflective pattern layer

14: diffusion sheet 15: horizontal prism sheet

16: Vertical Prism Sheet 17: Pattern

The present invention relates to a backlight unit for a liquid crystal display device, and more particularly, to a backlight unit for a liquid crystal display device by adding a side type backlight to a direct type backlight and selectively using the same according to the luminance used.

In general, the liquid crystal display device displays an image using light supplied from the outside. Therefore, the conventional liquid crystal display device includes a backlight unit for supplying light to the liquid crystal display device. The backlight unit is divided into a side type and a direct type according to the light supply method. In the side type system, a lamp is installed outside the flat plate, and light incident from the lamp is supplied to the entire liquid crystal panel by a transparent light guide plate. The direct type method is a method of directly dimming the front of the liquid crystal panel by arranging a plurality of lamps on the back of the liquid crystal panel, and has a high luminance and a wide light emitting surface as compared to the side type method. Here, the direct type backlight unit does not need a light guide plate for converting the line light source of the lamp into a surface light source, and reflects the light emitted from the lamp and the plurality of lamps provided at the lower portion of the display surface to the display surface. It includes a reflective sheet to prevent the loss and the diffusion plate for emitting a uniform light by scattering the light on the upper portion of the lamp.

The direct type backlight unit having the configuration as described above is widely used in large liquid crystal display devices of 30 inches or more such as TVs because of high light utilization, simple handling, and no limitation on the size of the display surface. In this case, the backlight used in the TV has a brightness of 10000 cd / m ² to express a relatively high luminance. However, the backlight unit expressing such high brightness causes a large power loss when applied to a product using a TV and a monitor. In other words, when a monitor product capable of driving at a low luminance value, that is, a brightness of 5000 cd / m ² compared with a TV, is driven at the same high brightness as a TV, it consumes unnecessary power, and thus, the life of the product itself. Can be shortened. In order to solve the above problems, in Publication No. 1999-55686, there is proposed an automatic brightness adjustment device of the monitor that is equipped with a separate sensor to automatically adjust the brightness of the backlight. However, this is a single light source in the backlight unit for the monitor to optimally adjust the brightness of the backlight unit according to the surrounding environment, there is a limit to overcome the large luminance deviation between the monitor and the TV by using this.

Accordingly, the present invention was created to solve the problems inherent in the prior art as described above, and an object of the present invention is to provide a backlight unit for a liquid crystal display device which can be efficiently applied to a combined product of a TV and a monitor without losing power. In providing.

In order to achieve the above object, there is provided a backlight unit for a liquid crystal display device according to one aspect of the present invention: A backlight unit according to the present invention, a flat light guide plate for uniformly irradiating the back of the liquid crystal panel by diffusing the incident light ; A first light source positioned on at least one side of the light guide plate to provide light to the light guide plate; A second light source positioned at a rear surface of the light guide plate to provide light to the light guide plate; And a transflective pattern layer positioned between the light guide plate and the second light source to change a traveling direction of the light provided from the first and second light sources.

In the above configuration, the transflective pattern layer is attached to the lower part of the light guide plate, and a plurality of patterns are formed on the attached rear surface in the form of convex or concave lenses.

In the above configuration, the pattern has a size of 50um to 300um.

In the above configuration, the first light source maintains an OFF state while the second light source operates, and the second light source maintains an OFF state while the first light source operates.

In the above configuration, the first light source provides light from at least one side surface, and includes a light emitting diode (LED), a cold cathode discharge lamp (CCFL), an external electrode fluorescent lamp (External Electrode). Fluorescent Lamp (EEFL) or a combination of these.

In the above configuration, the second light source is one of an LED, a CCFL, an EEFL, an organic light emitting diode (OLED), or a combination thereof.

(Example)

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

1 is a cross-sectional view of a backlight unit for a liquid crystal display device according to the present invention.

As illustrated, the backlight unit according to the present invention includes a first and second light sources 10 and 11 used as a light source, a flat light guide plate 12 for diffusing light incident from the first and second light sources, A transflective pattern layer 13 attached to the rear surface of the light guide plate, a diffusion sheet 14 positioned on an upper surface of the light guide plate 12 and diffusing the light diffused by the light guide plate 12 again, and an upper surface of the diffusion sheet. Located in the vertical and horizontal prism sheet (15, 16) for condensing the light transmitted through the diffusion sheet 14 to the liquid crystal panel (not shown), and is located on the upper surface of the vertical and horizontal prism sheet, It consists of a protective sheet (not shown) that protects the sheets.

In the above configuration, the first light source 10 is a side light source for use as a light source for a monitor, and includes a fluorescent lamp for providing light from at least one side, preferably both sides, of the light guide plate. 12) and has a luminance of at least 5000 cd / m ² .

In addition, the second light source 11 is a direct type light source for use as a light source for a TV, and is disposed under the light guide plate to which the transflective pattern layer 13 is attached, and is composed of a plurality of fluorescent lamps connected in an array. And a luminance of at least about 10000 cd / m ² .

The semi-transmissive pattern layer 13 has a pattern on the back surface attached to the light guide plate 12 to transmit and reflect the light incident from the first and second light sources 10 and 11 so that the luminous efficiency of the backlight unit is achieved. To improve. Looking at this in detail with reference to Figure 2, Figure 2 shows a perspective view of the backlight unit according to the present invention, the semi-transmissive pattern layer 13 is attached to the lower surface of the light guide plate 12, attached to the light guide plate 12 The patterned back surface is provided with a plurality of patterns 17 in the form of convex or concave lenses. The pattern 17 formed in the form of such a convex and concave lens has a size of 50 um to 300 um and changes the direction of light provided from the first and second light sources. In other words, the pattern 17 changes the light path so that light incident from the side surface of the light guide plate 12 through the first light source is emitted from the upper surface of the light guide plate, thereby increasing luminance, and the light guide plate 12 through the second light source. Diffuse the light incident from the back of the to make the luminance distribution uniform. At this time, the semi-transmissive pattern layer 13 has a polarization function, and the polarization axis is in the same direction within a polarization axis of + 5 ° to -5 ° and a polarization axis of a polarizing film (not shown) positioned below the liquid crystal panel. Is adjusted. In addition, as described above, light incident by the first light source 10 may be reflected from the lower surface of the light guide plate 12 by the polarization function of the transflective pattern layer 13, and the second light source 20 Light may be incident on the lower surface of the light guide plate 12.

For reference, the convex or concave lens-shaped pattern 17 formed on the transflective pattern layer is formed by heat and pressure through the hot pressing or imprinting method of the bottom of the transflective pattern layer. do. Here, the hot pressing method means that a thin plate or a base material is placed between the hot plate and the plate, and the shape changes as the material softened by heat increases. And, imprinting (imprinting) is, after coating the UV curable resin on the object, and imprinted a predetermined pattern engraved in the master mold, it means to have a cured form by exposing the UV curable resin.

As described above, by simultaneously providing the first light source 10 of the backlight unit side type backlight for the liquid crystal display device and the second light source 11 of the direct type backlight according to the present invention, it is possible to efficiently use the product for both TV and monitor. Applicable In other words, when the product operates as a TV, the backlight unit according to the present invention can display a screen of high brightness by operating only the second light source 11. In addition, when the product operates as a monitor, the backlight unit according to the present invention can maintain the luminance appropriate to the monitor by operating only the first light source 10. Such an operation can prevent unnecessary power loss due to the use of the direct backlight when the product is operated for the monitor, and can extend the life of the backlight for the TV, that is, the second light source 11. In addition, the backlight unit according to the present invention may increase the luminous efficiency of the backlight unit itself by providing the transflective pattern layer 13 on the lower surface of the light guide plate 12. In the above, there is provided a trade-off for selectively driving one of the first and second light sources 10 and 11 in consideration of the life of the light source according to the operation of the monitor or the TV of the liquid crystal display device. The present invention is not limited thereto, and the first and second light sources 10 and 11 may be used to drive an optional one of the first and second light sources 10 and 11 during the monitor operation and to increase the luminance when the TV is operated. It is also possible to use a method of simultaneously driving.

According to the configuration as described above of the present invention, by using a different light source when implementing each function in the combined product of TV and monitor, it is possible to prevent the loss due to unnecessary power use, and also to The luminous efficiency is increased by changing the advancing direction.

While the invention has been shown and described with reference to certain preferred embodiments, the invention is not so limited, and the invention is not limited to the spirit and scope of the invention as set forth in the following claims. It will be readily apparent to those skilled in the art that these various modifications and variations can be made.

Claims (8)

In the backlight unit for a liquid crystal display device, A flat light guide plate for diffusing the incident light to uniformly irradiate the back of the liquid crystal panel; A first light source positioned on at least one side of the light guide plate to provide light to the light guide plate; A second light source positioned at a rear surface of the light guide plate to provide light to the light guide plate; And A transflective pattern layer positioned between the light guide plate and the second light source and having a plurality of patterns that refract light provided from the first light source to the light guide plate and diffuse light provided from the second light source. A backlight unit for a liquid crystal display device, characterized in that. The method of claim 1, The transflective pattern layer is attached to a lower portion of the light guide plate, and includes a polarization function. The method of claim 2, The transflective pattern layer is a backlight unit for a liquid crystal display device, characterized in that a plurality of patterns are formed on the back surface attached to the light guide plate as the pattern in the form of convex or concave lenses. The method of claim 3, wherein The pattern has a size of 50um ~ 300um backlight unit for a liquid crystal display device. The method according to any one of claims 1 to 4, Wherein the first light source maintains an OFF state while the second light source operates, and the second light source maintains an OFF state while the first light source operates. Backlight Unit. The method according to any one of claims 1 to 4, And the first and second light sources are selectively driven when relatively low luminance is required, and simultaneously driven when relatively high luminance is required. The method of claim 1, And the first light source is one of a light emitting diode, a cold cathode discharge lamp, an external electrode fluorescent lamp, or a combination thereof. The method of claim 1, And the second light source is one of LED, CCFL, EEFL, OLED, or a combination thereof.

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