KR20160091855A - Back light unit and liquid crystal display using the same - Google Patents

Abstract

The present invention relates to an edge-type backlight unit and a liquid crystal display using the same. The backlight unit includes a first light source opposed to one side of a first light guide plate, a second light source opposed to the other side of the first light guide plate, a second light guide plate arranged under the first light guide plate, a third light source provided under the first light guide plate and opposed to one side of the second light guide plate, and a fourth light source provided under the first light guide place and opposed to the other side of the second light guide plate. The first and second light guide plates are provided on bottom surfaces thereof with fine patterns to increase surface uniformity of light. The second light guide plate is provided under the first light guide plate so that the central portion of the second light guide plate overlaps the central portion of the first light guide plate. The first and second light guide plates are integrated with each other in the form of one light guide plate. Block division patterns are arranged on at least one among top and bottom surfaces of the integrated light guide plates corresponding to the boundary between division areas of light emitting areas. The block division pattern includes any one among an intaglio pattern, an embossment pattern, and an intaglio-embossment pattern deeper than or higher than the fine patterns. The height of the block division pattern is lower than a thickness of each of the first and second light guide plates.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY USING THE SAME [0002]

The present invention relates to a backlight unit capable of local dimming and a liquid crystal display using the same.

BACKGROUND ART [0002] Liquid crystal display devices are becoming increasingly widespread due to features such as light weight, thinness, and low power consumption driving. This liquid crystal display device is used as a portable computer such as a notebook PC, an office automation device, an audio / video device, and an indoor / outdoor advertisement display device. A transmissive liquid crystal display device that occupies most of the liquid crystal display device controls an electric field applied to the liquid crystal layer to modulate light incident from the backlight unit to display an image.

The image quality of the liquid crystal display device depends on the contrast characteristics. The method of modulating the light transmittance of the liquid crystal layer by controlling the data voltage applied to the liquid crystal layer of the liquid crystal display panel has a limitation in improving the contrast characteristic. In order to improve the contrast characteristic, a backlight dimming control method for adjusting the luminance of the backlight unit according to an image has been developed, which dramatically improves the contrast characteristic. The backlight dimming control method may reduce the power consumption by adaptively adjusting the brightness of the backlight unit according to the input image. The backlight dimming method includes a global dimming method for adjusting the brightness of the entire display surface and a local dimming method for locally adjusting the brightness of the display surface. The global dimming method can improve the dynamic contrast measured between the previous frame and the next frame. The local dimming method can improve the static contrast which is difficult to improve by the global dimming method by locally controlling the brightness of the display surface within one frame period.

The backlight unit is divided into a direct type and an edge type. The direct-type backlight unit has a structure in which light emitting diodes (hereinafter referred to as "LEDs") are uniformly arranged on the bottom of a liquid crystal display panel, and LEDs are individually turned on / off . However, the direct-type backlight unit requires a large number of LEDs and requires an LED driver circuit for each LED package in order to individually control each of the LEDs. In addition, since the direct-type backlight unit has to be sufficiently long in distance between the LED packages and the diffusion plate in order to make the point light source appear as a planar light source, the thickness thereof is inevitably large.

The edge type backlight unit arranges the LEDs only at the edge of the liquid crystal display panel and converts the point light source into the surface light source by using the light guide plate to diffuse the light to the entire screen. The edge type backlight unit has a lower manufacturing cost than the direct type backlight unit because the required number of LEDs and the LED driving circuit are small. Further, since the edge type backlight unit is thinner and lighter than the direct-type backlight unit, the edge type backlight unit is suitable for realizing a slim and lightweight liquid crystal display device. However, the edge type backlight unit is disadvantageous in that the light incident from the LEDs in the light guide plate interferes with and diffuses in the light guide plate, which makes local dimming difficult.

For example, as shown in FIG. 1, only the first and second target blocks 13a and 13d in the edge-type backlight where the LEDs 11u, 11b, 11l, and 11r are disposed at the upper and lower left and right edges of the light guide plate 12, The upper-side LED 11u and the lower-left LED 111 which are orthogonal to the target blocks 13a and 13d are turned on. In this case, the light generated from the upper end LED 11u is totally reflected in the light guide plate 12 and propagated to the lower end of the light guide plate 12, and the light generated from the left end LED is totally reflected in the light guide plate 12, (12). Therefore, in addition to the first and second target blocks 13a and 13d, the undesired blocks 13b and 13c also appear bright, and due to the diffusion of light in the light guide plate 12 as shown in FIG. 2, 13d and a wide portion 14 including the periphery thereof are bright, and it is difficult to realize accurate local dimming.

SUMMARY OF THE INVENTION The present invention provides a backlight unit capable of designing slim and lightweight and realizing accurate local dimming, and a liquid crystal display using the backlight unit.

The backlight unit of the present invention includes: a first light source facing one side of the first light guide plate; A second light source facing the other side of the first light guide plate; A second light guide plate disposed below the first light guide plate; A third light source facing the one side of the second light guide plate below the first light guide plate; And a fourth light source facing the other side of the second light guide plate below the first light guide plate. Fine patterns for increasing the surface uniformity of light are disposed on the lower surfaces of the first and second light guide plates. The second light guide plate is disposed below the first light guide plate so that the center portion of the second light guide plate overlaps the center portion of the first light guide plate, and the first and second light guide plates are integrated into one light guide plate. The block division pattern is disposed at a portion corresponding to the divisional region boundary of the light emitting regions on at least one of the upper surface and the lower surface of the integrated light guide plate. Wherein the block dividing pattern is formed of one of an engraved pattern, an embossed pattern, and a negative ambience pattern that is deeper or higher than the fine patterns, and the height of the block divided pattern is smaller than the thickness of each of the first and second light guide plates.

The liquid crystal display of the present invention includes the backlight unit.

The present invention realizes a slim and lightweight backlight unit and a liquid crystal display device using a backlight unit having a stepped light guide plate, and realizes accurate local dimming.

FIGS. 1 and 2 are views showing optical interference and diffusion effects of a conventional edge type backlight unit.
3 is a block diagram showing a liquid crystal display device according to an embodiment of the present invention.
4 is a perspective view showing a light guide plate and a light source of a backlight unit according to the first embodiment of the present invention.
5 is a cross-sectional view of a backlight unit according to the first embodiment of the present invention.
6 is a plan view of the backlight unit according to the first embodiment of the present invention.
7 is a graph showing the results of an experiment of a local dimming operation of the backlight unit according to the first embodiment of the present invention.
8 is a cross-sectional view of a backlight unit according to a second embodiment of the present invention.
9 is a sectional view of a backlight unit according to a third embodiment of the present invention.
FIG. 10 is a sectional view showing the light guide plate shown in FIGS. 4 to 9 in detail.
11 is a cross-sectional view of a backlight unit according to a fourth embodiment of the present invention.
12 is a view showing a manufacturing method of the light guide plate shown in FIG.
13 is a cross-sectional view of a backlight unit according to a fifth embodiment of the present invention.
14 is a cross-sectional view of a backlight unit according to a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The component names used in the following description are selected in consideration of ease of specification, and may be different from actual product names.

3, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 100, a source driver 102 for driving data lines DL of the liquid crystal display panel 100, A timing controller 101 for controlling the source driver 102 and the gate driver 103 for driving the gate lines GL of the liquid crystal display panel 100, A light source driving unit 105 for driving light sources of the backlight unit 200, and a local dimming control unit 104 for controlling local dimming.

In the liquid crystal display panel 100, a liquid crystal layer is formed between two glass substrates. A plurality of data lines DL and a plurality of gate lines GL are crossed on the lower glass substrate of the liquid crystal display panel 100. [ The liquid crystal cells are arranged in a matrix form in the liquid crystal display panel 100 by the intersection structure of the data lines DL and the gate lines GL. Data lines DL, gate lines GL, thin film transistors (hereinafter referred to as "TFTs"), pixel electrodes of liquid crystal cells connected to TFTs, And a storage capacitor are formed.

On the upper glass substrate of the liquid crystal display panel 100, a black matrix, a color filter, and a common electrode are formed. The common electrode is formed on the upper glass substrate in a vertical electric field driving method such as a TN (Twisted Nematic) mode and a VA (Vertical Alignment) mode, and a horizontal electric field such as IPS (In Plane Switching) mode and FFS (Fringe Field Switching) Is formed on the lower glass substrate together with the pixel electrode in the driving method. On the upper glass substrate and the lower glass substrate of the liquid crystal display panel 100, a polarizing plate is attached and an alignment film for forming a pretilt angle of liquid crystal is formed on the inner surface in contact with the liquid crystal.

The pixel array of the liquid crystal display panel 100 and the light emitting surface of the backlight unit 200 opposed thereto are virtually divided into a plurality of blocks for local dimming. Each of the blocks includes i x j (i and j are positive integers of 2 or more) pixels and a backlit light emitting surface for irradiating the pixels with light. Each of the pixels includes subpixels of three or more primary colors, and the subpixel includes a liquid crystal cell Clc.

The timing controller 101 receives timing signals Vsync, Hsync, DE, and DCLK from an external system board and supplies digital video data RGB to the source driver 102. The timing signals Vsync, Hsync, DE and DCLK include a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal DE and a dot clock signal DCLK. The timing controller 101 generates timing control signals DDC for controlling the operation timings of the source driver 102 and the gate driver 103 based on the timing signals Vsync, Hsync, DE, DCLK from the external system board. , GDC). The system board or the timing controller 101 inserts an interpolation frame between the frames of the input video signal input at a frame frequency of 60 Hz and multiplies the source timing control signal DDC and the gate timing control signal GDC to generate 60 × N (N is a positive integer equal to or greater than 2) Hz to the frame frequency of the source driver 102 and the gate driver 103. [

The timing controller 101 supplies the digital video data RGB of the input image input from the external system board to the local dimming control unit 104 and the digital video data R ' G'B ') to the source driver 102.

The source driver 102 latches digital video data (R'G'B ') under the control of the timing controller 101. The source driver 102 converts the digital video data R'G'B 'into a positive / negative polarity analog data voltage using the positive / negative gamma compensation voltages and supplies the converted data to the data lines DL .

The gate driver 103 includes a shift register, a level shifter for converting an output signal of the shift register into a swing width suitable for driving the TFT of the liquid crystal cell, and an output buffer. The gate driver 103 sequentially outputs gate pulses (or scan pulses) having a pulse width of about one horizontal period, which are composed of a plurality of gate drive integrated circuits. The gate pulse is sequentially supplied to the gate lines GL in synchronization with the data voltage supplied to the data lines DL.

The backlight unit 200 is disposed below the liquid crystal display panel 100. The backlight unit 200 includes a plurality of light sources individually controlled for each block by the light source driver 105 to uniformly irradiate light to the liquid crystal display panel 100. The backlight unit 200 is implemented as an edge type backlight unit capable of local dimming. The backlight unit 200 includes the light guide plate structure as shown in FIGS. 4 to 14 and the light sources disposed on the sides of the light guide plate. The light sources of the backlight unit 200 include a plurality of LEDs (Light Emitting Diodes).

The light source driving unit 105 individually controls the light sources of the backlight unit 200 by a pulse width modulation (PWM) whose duty ratio is variable according to the dimming value BLdim inputted from the local dimming control unit 104 . The pulse width modulation signal PWM controls the ratio of lighting and lighting of the light sources, and the duty ratio% thereof is determined according to the dimming value (BLdim) output from the local dimming control unit 104. [ The micro control unit (MCU) of the light source driving unit 105 lights the light sources of the backlight unit 200 on a block-by-block basis by an SPI (Serial Peripheral Interface) method.

The local dimming control unit 104 analyzes the digital video data (RGB) input from the timing controller 101 on a block-by-block basis, and calculates a representative value of each block. The representative value for each block can be calculated as an average value of an input image or an average picture level (APL). The average value of the input image is the average value of the highest values among the RGB values of the pixel and the average image level APL is the average value of the luminance values Y of the pixels. The local dimming control unit 104 maps the representative value for each block to a predetermined dimming curve to output a dimming value BLdim for each block of the backlight unit 200 and outputs the digital video data RGB inputted from the timing controller 101. [ Thereby compensating for pixel data to be displayed on the liquid crystal display panel 100. FIG. The local dimming control unit 104 codes the dimming value (BLdim) for each block into data of the SPI format and supplies the data to the microcontrol unit (MCU) of the light source driving unit 105.

4 to 7 show a backlight unit according to the first embodiment of the present invention.

4 to 7, the backlight unit of the present invention includes a first light guide plate 210, a second light guide plate 220 disposed below the first light guide plate 210, and a second light guide plate 220 disposed on both sides of the first light guide plate 210 The first and second LED arrays 202a and 202b and the third and fourth light source arrays 202c and 202d disposed on both sides of the second light guide plate 220. [

The first and second light guide plates 210 and 220 include transparent resins such as PC (Polycarbonate), PMMA (Polymethacrylamide), and COP (Cyclo-olefin-polymer).

A first LED array 202a is disposed on the upper side of the first light guide plate 210 and a second LED array 202b is disposed on the lower side of the first light guide plate 210. [ As shown in FIG. 6, the first LED array 202a illuminates the upper side of the first light guide plate 210 to illuminate the uppermost first blocks BL1 during local dimming. The second LED array 202b illuminates the lower side surface of the first light guide plate 210 as shown in FIG. 6 to illuminate the fourth blocks BL4 at the lowest level during local dimming.

6) of the second light guide plate 220 is substantially the same as that of the first light guide plate 210 and the vertical length of the second light guide plate 220 (the y- Is smaller than that of the first light pipe 210. The second light guide plate 220 is disposed below the first light guide plate 210 so that the central portion of the second light guide plate 220 is overlapped with the central portion of the first light guide plate 210. The third LED array 202c is disposed below the first light guide plate 210 so as to face the upper side surface of the second light guide plate 220. [ As shown in FIG. 6, the third LED array 202c illuminates the upper side surface of the second light guide plate 220 to illuminate the second blocks BL2 disposed at the upper end of the central block rows at the time of local dimming. The fourth LED array 202d illuminates the lower side surface of the second light guide plate 220 to illuminate the third blocks BL3 disposed at the lower end of the central block light illumination during local dimming.

The backlight unit of the present invention includes a plurality of optical sheets 230 disposed between the liquid crystal display panel 100 and the first light guide plate 210 and a cover bottom (not shown) disposed below the light guide plates 210 and 220 (Not shown).

The optical sheets 230 include one or more prism sheets and one or more diffusion sheets to diffuse the light incident from the diffusing plate and to reflect the light traveling path of light at an angle substantially perpendicular to the light incident surface of the liquid crystal display panel. . The optical sheets 230 may include a dual brightness enhancement film (DBEF).

The cover bottom is disposed below the light guide plates 210 and 220 to support the entire backlight unit 200 from below and protect the backlight unit from external shocks and vibrations.

The present invention drives the first and second LED arrays 202a and 202b to selectively turn on the first and fourth blocks according to the input image and to drive the third and fourth LED arrays 202c and 202d And selectively illuminates the second and third blocks according to the input image to implement local dimming. FIG. 7 is a diagram showing a local dimming test result of the backlight unit 200 of FIGS. As can be seen from FIG. 7, the present invention can realize precise local dimming by selectively illuminating only the target block using the edge-type backlight unit 200.

8 is a cross-sectional view of a backlight unit according to a second embodiment of the present invention.

8 is different from the backlight unit of the first embodiment in that the first light guide plate 210 is divided into a plurality of upper light guide plates 211 to 213 and the second light guide plate 220 is divided into a plurality of lower light guide plates (221, 222), and the other configurations are substantially the same.

A first LED array 202a is disposed on the upper side of the first upper light guide plate 211. [ As shown in FIG. 6, the first LED array 202a illuminates the side surface of the first upper light guide plate 211 to illuminate the uppermost first blocks BL1 during local dimming. And a second LED array 202b is disposed on a lower side surface of the second upper light guide plate 212. [ The second LED array 202b illuminates the lower side surface of the second upper light guide plate 212 as shown in FIG. 6 to illuminate the lowermost fourth blocks BL4 during local dimming. The third upper light guide plate 213 is disposed between the first and second upper light guide plates 211 and 212 and overlaps with the lower light guide plates 221 and 222. The lower surface of the third upper light guide plate 213 is not formed with a fine pattern for refracting the liquid crystal display panel 100 toward the liquid crystal display panel 100 to increase the surface uniformity of light incident on the liquid crystal display panel 100 as shown in FIG. The third upper light guide plate 213 transmits light from the lower light guide plates 221 and 222 toward the optical sheets 230 and the liquid crystal display panel 100.

The horizontal lengths (the length in the x-axis direction in FIG. 6) of the lower light guide plates 221 and 222 are substantially the same as those of the upper light guide plates 211 to 213, (The length in the y-axis direction in Fig. 6) is smaller than the sum of the vertical lengths of the upper light guide plates 213. [ The first and second lower light guide plates 221 and 222 are disposed under the third upper light guide plate 213. The third LED array 202c is opposed to the upper side surface of the first lower light guide plate 221. As shown in FIG. 6, the third LED array 202c illuminates the upper side of the first lower light guide plate 221 to illuminate the second blocks BL2 during local dimming. The fourth LED array 202d faces the lower side surface of the second lower light guide plate 222. [ The fourth LED array 202d illuminates the lower side surface of the second light guide plate 220 to illuminate the third blocks BL3 at the time of local dimming.

The reflectors may be coated on the divided surfaces 214 of the upper light guide plates 211 to 213 and the divided surfaces 223 of the lower light guide plates 221 and 222, respectively. The reflector reflects light that can be diffused into neighboring blocks to increase the brightness of the blocks that are turned on during local dimming and to block the diffusion of light between the blocks.

9 is a sectional view of a backlight unit according to a third embodiment of the present invention.

9, a plurality of first block dividing patterns 215 are formed on the first light guide plate 210, and a plurality of first block dividing patterns 215 are formed on the second light guide plate 220 as compared with the backlight unit of the first embodiment described above. The two-block division pattern 224 is different from the one that has been emplaced, and the other structures are substantially the same.

The first block dividing patterns 215 are formed on the upper surface 210u, the lower surface 210b or the upper surface 210u and the lower surface 210b of the first light guide plate 210 in a negative angle, The first block dividing patterns 215 have a cross section such as a triangle (or prism), a hemispherical (or lenticular), or a square (or a ractangle). The first block dividing patterns 215 are located at the boundary between the blocks and the boundary between the upper light guide plates shown in FIG. 8 to block the diffusion of light between the blocks and to enhance the straightness of the light.

The second block dividing patterns 224 are formed on the upper surface 220u, the lower surface 220b or the upper surface 220u and the lower surface 220b of the second light guide plate 220 in a negative angle, The second block dividing patterns 224 have a cross section such as a triangle (or prism), a hemispherical (or lenticular), a square (or a ractangle), or the like. The second block dividing patterns 215 are positioned at the boundary between the blocks and the boundary between the lower light guide plates shown in FIG. 8 to block the diffusion of light between the blocks and to enhance the straightness of the light.

In each of the embodiments, the block portions BL1 and BL2 that are not overlapped with the second light guide plate (or the lower light guide plates) on the lower surface 210b of the first light guide plate 210 (or the upper light guide plates) Fine patterns are formed to refract the light toward the panel 100 to increase the surface uniformity of light incident on the liquid crystal display panel 100. The fine patterns are formed on the entire lower surface 220b of the second light guide plate 210 facing the second and third blocks BL2 and BL3.

Each of the first light guide plate 210 (or the upper light guide plates) and the second light guide plate 220 (or the lower light guide plates) may be formed in the form of a flat plate or a wedge plate. Each of the first light guide plate 210 (or the upper light guide plates) and the second light guide plate 220 (or the lower light guide plates) has a thickness H between 0.5 mm and 4 mm as shown in FIG. The block dividing patterns 224 have a depth (or height) between 10 mu m and 300 mu m. The fine patterns formed on the lower surfaces 210b and 220b of the light guide plates 210 and 220 have a depth (or height) between 5 and 200 mu m. The depth (or height) of the fine patterns is smaller than that of the block division patterns 224. [

11 is a cross-sectional view of a backlight unit according to a fourth embodiment of the present invention. In the following embodiments, elements substantially the same as those of the above-described embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted.

11, the backlight unit of the present invention includes an integrated light guide plate 300, first and second light source arrays 202a and 202b disposed on both sides of the upper portion of the integrated light guide plate 300, And third and fourth light source arrays 202c and 202d disposed on both sides.

The integrated light guide plate 300 includes transparent resins such as polycarbonate (PC), polymethacrylamide (PMMA), and cyclo-olefin-polymer (COP). A manufacturing method of the integrated light guide plate 300 will be described later with reference to FIG.

The integrated light guide plate 300 has a structure in which the first light guide plate 210 (or the upper light guide plates) and the second light guide plate 220 (or the lower light guide plate) are bonded to each other and has a step therebetween. The upper portion of the integrated light guide plate 300 has a larger area than the lower portion. The lower portion of the integrated light guide plate 300 protrudes downward from the central portion of the light guide plate 300.

As shown in FIG. 6, the first LED array 202a irradiates light on one side of the upper side of the integrated light guide plate 300 to illuminate the uppermost first blocks BL1 during local dimming. As shown in FIG. 6, the second LED array 202b irradiates light on the other side of the upper side of the integrated light guide plate 300 to illuminate the lowermost fourth blocks BL4 during local dimming.

As shown in FIG. 6, the third LED array 202c illuminates the lower side of the integrated light guide plate 300 to illuminate the second blocks BL2 during local dimming. The fourth LED array 202d illuminates the other end of the lower end of the integrated light guide plate 300 to illuminate the third blocks BL3 during local dimming.

12 is a view showing a manufacturing method of the integrated light guide plate 300. FIG.

Referring to FIG. 12, a method for manufacturing a light guide plate of the present invention fabricates a pattern mold 401 having an engraved pattern. The engraved pattern of the pattern mold 401 has an inverted form of the lower protrusion of the integrated light guide plate 300.

In the method for manufacturing a light guide plate of the present invention, a liquid light guide plate resin (301) is applied to a pattern mold (401). The light guide plate resin contains a photoinitiator and a photo-binder. The method of manufacturing a light guide plate of the present invention is characterized in that after the transparent plate material 501 is pressed on the light guide plate resin 301 applied to the pattern mold 401, ultraviolet or infrared light is transmitted through the transparent plate material 501 to the light guide plate resin Thereby inducing curing of the light guide plate resin 301. [ Finally, the method of manufacturing a light guide plate of the present invention separates the pattern mold 401 and the transparent plate 501 from the integrated light guide plate 300.

13 is a cross-sectional view of a backlight unit according to a fifth embodiment of the present invention.

The backlight unit shown in FIG. 13 differs from the backlight unit according to the fourth embodiment in that the integrated light guide plate 300 is divided into a plurality of light guide plates 301 to 304, and the other structures are substantially the same. Each of the divided surfaces 305 of the light guide plates 301 to 304 may be coated with a reflector.

14 is a cross-sectional view of a backlight unit according to a sixth embodiment of the present invention.

The backlight unit shown in Fig. 14 is different from the backlight unit according to the fourth embodiment in that a plurality of block dividing patterns 306 are formed in the integrated light guide plate 300, and the other structures are substantially the same.

The block dividing patterns 306 are formed on the upper face 300u, the lower face 300b or the upper face 300u and the lower face 300b of the integrated light guide plate 300 in a negative angle, The block dividing patterns 306 have a cross section such as a triangular (or prism), hemispherical (or lenticular), rectangular (or ractangle), or the like. The block dividing patterns 306 are positioned at the boundary between the blocks and at the boundary between the light guide plates shown in FIG. 13 to block the diffusion of light between the blocks and increase the straightness of the light.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the 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.

100: liquid crystal display panels 202a to 202d: LED array
210 to 213, 220 to 222, and 300: a light guide plate

Claims (4)

A first light source facing one side of the first light pipe;
A second light source facing the other side of the first light guide plate;
A second light guide plate disposed below the first light guide plate;
A third light source facing the one side of the second light guide plate below the first light guide plate; And
And a fourth light source facing the other side of the second light guide plate below the first light guide plate,
Fine patterns for increasing the surface uniformity of light are arranged on the lower surfaces of the first and second light guide plates,
The second light guide plate is disposed below the first light guide plate so that a central portion of the second light guide plate overlaps with a central portion of the first light guide plate, the first and second light guide plates are integrated into one light guide plate,
The block dividing pattern is disposed at a portion corresponding to the boundary of the divided regions of the light emitting regions on at least one of the upper surface and the lower surface of the integrated light guide plate,
Wherein the block dividing pattern is formed of one of an engraved pattern, an embossed pattern, and a minuscule pattern that is deeper or higher than the fine patterns, and the height of the block divided pattern is smaller than the thickness of each of the first and second light guide plates Backlight unit. The method according to claim 1,
Wherein the integrated light guide plate has a step structure between the first light guide plate and the second light guide plate. A liquid crystal display device in which a light emitting surface of a pixel array and a backlight unit of a liquid crystal display panel are virtually divided into a plurality of blocks for local dimming,
The backlight unit includes:
A first light source facing one side of the first light pipe;
A second light source facing the other side of the first light guide plate;
A second light guide plate disposed below the first light guide plate;
A third light source facing the one side of the second light guide plate below the first light guide plate; And
And a fourth light source facing the other side of the second light guide plate below the first light guide plate,
Fine patterns for increasing the surface uniformity of light are arranged on the lower surfaces of the first and second light guide plates,
The second light guide plate is disposed below the first light guide plate so that the center portion of the second light guide plate overlaps the center portion of the first light guide plate, the first and second light guide plates are integrated into one light guide plate,
The block dividing pattern is disposed at a portion corresponding to the boundary of the divided regions of the light emitting regions on at least one of the upper surface and the lower surface of the integrated light guide plate,
Wherein the block dividing pattern is formed of one of an engraved pattern, an embossed pattern, and a minuscule pattern that is deeper or higher than the fine patterns, and the height of the block divided pattern is smaller than the thickness of each of the first and second light guide plates Liquid crystal display device. The method of claim 3,
Wherein the integrated light guide plate has a step structure between the first light guide plate and the second light guide plate.

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