KR20100080750A - Back light unit comprising light guide panel - Google Patents

Abstract

PURPOSE: By keeping the existing edge type backlight unit outfitting point and existing direct type back light unit outfitting point the backlight unit including the light guide plate obtains the excellent applicability. CONSTITUTION: A light guide plate(20) comprises a plurality of fractional areas divided with a plurality of light incoming areas(22) and plurality of reflecting bodies(24). It is arranged so that a plurality of LED groups be corresponded to a plurality of fractional areas. Fractional areas are divided by the arrangement of matrices including a plurality of rows and heats. Each of fractional areas comprises the light incoming area and reflecting body. The light incoming area is perpendicularly formed about the upper side photometric section of the light guide plate.

Description

BACK LIGHT UNIT COMPRISING LIGHT GUIDE PANEL}

The present invention relates to a backlight unit, and more particularly, to a backlight unit having a slim structure and suitable for local dimming of a large liquid crystal display (LCD).

Conventionally, Cold Cathode Fluorescent Lamps (CCFLs) have been mainly used as backlight sources for LCDs. However, since the cold cathode fluorescent lamp uses mercury gas, it is not environmentally friendly and has disadvantages such as slow response speed, low color reproducibility, and coarse structure.

On the other hand, an LED (Light Emitting Diode) has the advantage of being environmentally friendly, good response speed and color reproducibility, and the implementation of a relatively compact backlight unit. Accordingly, development, research, and manufacture of a backlight unit using LED as a backlight light source of an LCD instead of a conventional cold cathode fluorescent lamp is increasing.

Such a backlight unit is classified into an edge type and a direct type according to the LED position as a light source. The edge type backlight unit has a structure in which an LED is positioned on a side of the light guide plate, and light enters through the side of the light guide plate, and the light is sufficiently mixed in the light guide plate and then emitted through the upper surface of the light guide plate toward the LCD panel located above. In addition, the direct type backlight unit has a structure in which LEDs as light sources are positioned directly under the LCD panel, and light generated from the LEDs is directed to the LCD panel through various optical sheets or optical panels. Edge type backlight unit is mainly used for backlighting of small LCD, and direct type backlight unit is limited to backlighting of large LCD such as TV.

Meanwhile, local dimming techniques have been developed to more vividly display images displayed on LCDs such as large TVs. Local dimming is a technique of dividing an LCD panel into a plurality of regions and individually adjusting the backlight luminance value in each division region according to the gray level value of each division region. The technique using a backlight unit using LED as a light source for local dimming of LCD is disclosed, for example, in Korean Patent No. 10-0780187. However, due to the characteristics of local dimming, which individually adjusts the backlight luminance value per division region, only the direct type backlight unit is limitedly used in the LCD.

Conventional direct backlight unit requires a long optical distance between the object and the object in order to sufficiently mix the light (R, G, B) of different wavelengths, such a long optical distance of the backlight unit This causes the thickness and the thickness of an apparatus such as an LCD, including the same, to increase. Therefore, there is a need in the art for the replacement or improvement of the direct type backlight unit which hinders the slimming of the device by the long optical distance.

Accordingly, the technical problem of the present invention is to provide a backlight unit capable of implementing local dimming of a large liquid crystal display (LCD) while having a slim structure by greatly reducing the optical distance.

According to an aspect of the present invention, there is provided a local dimming backlight unit of an LCD including: a light guide plate including a plurality of divided regions arranged in a matrix over an entire area; A plurality of LED groups evenly disposed in the divided regions, each of the plurality of divided regions including a light incident portion, a reflecting portion on an inclined surface inclined upward from a lower portion of the light incident portion, and the light guide plate; And a light emitter on an upper surface of the LED group, wherein each of the plurality of LED groups is disposed adjacent to a light receiver of each of the divided regions.

According to one embodiment, the light incident portions of the divided regions are preferably arranged at regular intervals along the longitudinal direction of the plate. Preferably, the light incidence portion of each of the divided regions is in a vertical plane perpendicular to the light exit portion. The reflector preferably includes an uneven reflection pattern formed on the inclined surface. Each of the plurality of LED groups preferably includes a blue LED, a green LED, and a red LED. Preferably, a planar portion is formed between the reflecting portion and the light incident portion of the divided regions adjacent to each other among the divided regions.

According to the present invention, it is possible to implement an excellent and slim backlight unit having the advantages of the existing edge type backlight unit and the advantages of the existing direct type backlight unit. In particular, the present invention implements local dimming of a large LCD, which was not possible with an edge type backlight unit, and at the same time significantly reduces the optical distance required for color mixing of light, thereby realizing an LCD having a minimum thickness.

1 is a cross-sectional view showing a backlight unit according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a part of the backlight unit shown in FIG. 1; FIG.
Figure 3 is a plan view showing a light guide plate with an LED according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to ensure that the spirit of the present invention can be fully conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a cross-sectional view illustrating a backlight unit according to an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of a portion of FIG. 1.

As shown in FIG. 1, the backlight unit of the present embodiment includes a plurality of LEDs 10 and a light guide plate 20. In addition, the backlight unit includes a diffusion sheet 30 disposed above the light guide plate 20 to diffuse light, and a prism sheet 40 disposed above the diffusion sheet 30 to collect a light. Include.

In this case, the diffusion sheet 30 and / or prism sheet 40 may be omitted, and other optical sheets or optical panels may be further disposed. That is, the arrangement of the optical sheet or the optical panel including the diffusion sheet and / or prism sheet may be variously changed and is not intended to limit the present invention.

1 and 2, the light guide plate 20 is formed of a light transmissive plate, more preferably, a transparent material plate, and includes the bottom, top, and side surfaces of the plate as a whole. A light exit portion 21 is provided that emits light entering the plate in the form of surface light over the entire top surface of the plate. In addition, the backlight unit of this embodiment corresponds to the plurality of light incidence portions 22 and the plurality of light incidence portions 22 on the bottom of the plate, unlike the existing direct type backlight unit in which the bottom of the light guide plate constitutes a single light incidence portion. A plurality of reflecting portions 24 are formed. Accordingly, in the backlight unit, the light exit part 21 forms one light exit area over the entire top surface of the plate, and the plurality of light incident parts 22 and the plurality of reflectors 24 over the entire bottom surface of the plate. A plurality of light-reflecting regions defined by the above are formed.

In the present embodiment, the plurality of light incidence portions 22 are arranged at regular intervals along the longitudinal direction X of the plate at the bottom of the plate. In addition, each of the plurality of light incident parts 22 is configured as a vertical plane perpendicular to the light exit part 21. In addition, the plurality of reflecting portions 24 are formed of an inclined surface that intersects the vertical surface of the light output portion 21 and is inclined upwardly from the vertical surface. In addition, the reflector 24 located in one light-reflecting region extends obliquely toward the light-receiving portion 22 of the other light-reflecting region adjacent thereto. The planar portion 23 may be formed between the reflector 24 and the light incident portion 22 positioned in different areas adjacent to each other.

A plurality of LEDs 10 including at least red, blue, and green (R, G, B) LEDs may be disposed adjacent to the individual light incident portions 22. Light entering the inside of the plate from the plurality of LEDs 10 through the light incidence part 22 may continue to progress laterally, and further, may be sufficiently mixed while being reflected upward by the reflecting part 24. . Therefore, the part of the light guide plate including one light incident portion 22 adjacent to the plurality of LEDs 10 and one reflecting portion 24 corresponding thereto is a function similar to the light guide plate of the existing edge type backlight unit by itself. can do.

In addition, the reflector 24 includes an uneven reflection pattern 242 formed on its inclined surface. The shape of the reflective pattern 242 is not limited to that shown in the drawings and may have various shapes. In addition, the light reflection by the reflector 24 may be mainly performed by total internal reflection due to a difference in refractive index between the light guide plate and the outside air, and thus, the reflection pattern may be omitted. It may also be considered to form a separate reflective film on the inclined surface instead of the reflective pattern.

Referring to FIG. 2, the operation of the light guide plate 20 described above will be described. Light of different wavelengths generated from the plurality of LEDs 10 (only one is shown) enters through the light incidence part 22 of the bottom of the plate and is laterally oriented. Proceed to At this time, the distance traveled in the lateral direction provides an optical distance or a part of the distance that the light of different wavelengths are mixed.

 Then, the light propagated in the lateral direction is reflected by the reflecting portion 24 and directed to the light emitting portion 21 on the upper surface of the plate. In this case, the distance between the reflector 24 and the light emitter 21 also becomes part of the optical distance where light of different wavelengths is mixed. In addition, since the inclined surface of the reflector 24 is provided with a concave-convex reflection pattern 242, according to the critical angle principle, the reflector 24 can reflect light more effectively and more upwards.

The operation of the light guide plate 20 described above is not limited to one region of the light guide plate, but is performed over the divided regions of the light guide plate 20. Therefore, the light guide plate 20 and the backlight unit including the same according to the present exemplary embodiment divide the LCD panel (not shown) into a plurality of regions, and the backlight luminance value of each divided region according to the gray level value of the divided region. Can be suitably used for local dimming of the LCDs to adjust them individually.

3 is a plan view illustrating a light guide plate 20 disposed with a plurality of LEDs 10.

Referring to FIG. 3, the light guide plate 20 is divided into a plurality of regions A1, A2, A3, A4, A5, A6, A7, A8, and A9 along the longitudinal direction X and the width direction Y. . The division is performed by a plurality of light incidence portions 22 and a plurality of reflection portions 24 (see FIGS. 1 and 2) formed at predetermined intervals on the bottom surface of the light guide plate 20, whereby the plurality of divided regions Are arranged in a matrix. In one divided area, the individual light incidence portions 22 are provided with red, green and blue (R, G, B) LEDs 10 on one strip 10 '. The strip 10 ′ may additionally be equipped with white or other colored LEDs. In each of the regions, the plurality of R, G, and B LEDs 10 adjacent to the light incidence part 22 are arranged at regular intervals along the width direction (Y).

Each divided area in FIG. 3 may correspond to a divided area for local dimming of the LCD panel. Therefore, local dimming of the LCD panel can be implemented by driving the red LED, the green LED, and the red LED individually or simultaneously for each divided region of the light guide plate 20. In the local dimming implementation, the R, G, and B light entering the light guide plate 20 through the light incidence part 22 progress in the lateral direction and are uniformly mixed while being reflected by the reflecting part 24. It is emitted through the light exit portion 21 (see FIGS. 1 and 2).

1 and 2, it can be seen that the light receiving part 22 of the light guide plate 20 adjacent to the LED 10 is located not only on the bottom of the plate but also on the side of the light guide plate. According to an aspect of the present invention, unlike the conventional edge type backlight unit, the light incidence part 22 which is located only at the side of the light guide plate is extended to various positions of the bottom of the light guide plate, and the plurality of light incidence parts 22 and the reflector 24 are formed on the bottom of the light guide plate. ) Together. For that reason, the light incident portion 22 and the reflector 24 formed on the bottom of the light guide plate are mainly described above, and the importance of the light incident portion on the side of the light guide plate is not relatively small.

20: Light guide plate 21: light emitting part
22: light incident part 24: reflecting part

Claims (4)

A light guide plate including a plurality of divided regions divided by a plurality of light incident parts and a plurality of reflecting parts;
A plurality of LED groups disposed to correspond to the plurality of divided regions;
And said partitions are partitioned into an array of matrices comprising a plurality of rows and a plurality of columns. The method according to claim 1, wherein each of the plurality of partitions,
A light incident part perpendicular to the top light exit part of the light guide plate, on which one of the plurality of LED groups is disposed;
And a reflecting unit present on an inclined surface inclined toward the upper side from a lower part of the light incident unit. The backlight unit for local dimming of the large area LCD of claim 2, wherein the reflector comprises an uneven reflection pattern. The backlight unit of claim 1, wherein each of the plurality of LED groups comprises a blue LED, a green LED, and a red LED.

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