KR101696470B1 - Edge type back light unit and liquid crystal display using the same - Google Patents

Abstract

The present invention relates to an edge type backlight unit, comprising: a plurality of unit cells divided in a horizontal direction and a vertical direction in a single light guide plate; A stationary frame for pressing side surfaces of the unit cells out of the unit cells; A point light source disposed outside the sub-unit cells so as to face side faces of the sub-unit cells; A light source driver for emitting the point light sources; And a local dimming control unit for controlling the light source driving unit in response to the local dimming signal.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an edge type backlight unit and a liquid crystal display device using the same,

The present invention relates to an edge type 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. BACKGROUND ART Liquid crystal display devices are widely used as portable computers such as notebook PCs, office automation devices, audio / video devices, indoor and outdoor advertisement display devices, and the like. The liquid crystal display 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 includes a direct type (backlight type) backlight unit 20 as shown in FIGS. 1 and 2 and an edge type (edge type or side light type) backlight unit 40 as shown in FIGS. 3 and 4, Respectively. The direct-type backlight unit 20 has a structure in which light emitting diodes (LEDs) 31 are evenly arranged on the entire screen under the liquid crystal display panel 10 as shown in Figs. 1 and 2, Local dimming can be easily implemented by turning on / off the LEDs 31 individually. 1, reference numeral 32 denotes a bottom cover 32 for supporting the LEDs 31 from below, reference numeral 33 denotes a diffusion plate, reference numeral 34 denotes a prism sheet, Respectively. However, since the direct-type backlight unit is required to uniformly place the LED array under the screen of the liquid crystal display panel 10, the number of necessary LEDs 31 increases in proportion to the size of the screen, resulting in an increase in manufacturing cost in case of a large screen. Also, since the direct-type backlight unit is disposed under the liquid crystal display panel 10, the thickness of the backlight unit 20 becomes thicker by the LED thickness, and further, the LEDs 31 and the diffuser plate 33, the thickness of the backlight unit 20 becomes thicker. Therefore, the direct-type backlight unit 20 has a high manufacturing cost and is difficult to design in a thin shape.

The edge type backlight unit 40 has the LEDs 41 disposed only on the edges of the liquid crystal display panel 40 of FIGS. 3 and 4 and converts the point light source into the surface light source by using the light guide plate 42, . The edge type backlight unit 40 has a lower manufacturing cost because the number of LEDs 41 required is smaller than that of the direct type backlight unit 20. [ Also, since the edge type backlight unit does not affect the thickness of the backlight unit, it is suitable for realizing slimness and light weight. However, the edge type backlight unit 40 is disadvantageous in that the light incident from the LEDs 41 in the light guide plate 42 is diffused and interfered with, thereby making local dimming difficult.

An object of the present invention is to provide an edge type backlight capable of local dimming, a liquid crystal display device capable of designing slim and lightweight using the backlight, and improving display quality.

The edge type backlight unit of the present invention includes a plurality of unit cells divided in the horizontal direction and the vertical direction in the single-layer light guide plate; A stationary frame for pressing side surfaces of the unit cells out of the unit cells; A point light source disposed outside the sub-unit cells so as to face side faces of the sub-unit cells; A light source driver for emitting the point light sources; And a local dimming control unit for controlling the light source driving unit in response to the local dimming signal.

A liquid crystal display device of the present invention includes a liquid crystal display panel and the edge type backlight unit disposed below the liquid crystal display panel.

The present invention can realize local dimming in an edge type backlight unit by dividing the single-layer light guide plate into a plurality of unit cells and propagating the light to total reflection in the unit cells of the lateral direction light-guiding channel and the vertical direction light- Therefore, the present invention can realize an ultra-thin backlight unit capable of local dimming and a liquid crystal display device including the same.

1 is a perspective view showing a conventional direct-type backlight unit.
2 is a cross-sectional view of the direct-type backlight unit shown in Fig.
3 is a perspective view showing a conventional edge type backlight unit.
4 is a sectional view of the edge type backlight unit shown in Fig.
5 is a block diagram illustrating a liquid crystal display device according to an embodiment of the present invention.
FIG. 6 is a perspective view showing the light guide plate shown in FIG. 5 in detail.
7 is a perspective view showing a unit cell of the light guide plate.
8 is a perspective view showing an example in which a fixing frame is assembled to side edges of the light guide plate shown in FIG.
9 is a sectional view showing an end face A of the light guide plate and the fixing frame in Fig.
10 is a sectional view showing a light guide plate, a fixed frame, and a bottom cover.
11 is a perspective view showing an example of the on / off operation of the light guide channel in the lateral direction in the light guide plate of the present invention.
12 is a plan view showing an example of the on / off operation of the light guide channel in the lateral direction in the light guide plate of the present invention.
13 is a perspective view showing an example of the on / off operation of the vertical light guide channel in the light guide plate of the present invention.
14 is a plan view showing an example of the on / off operation of the longitudinal light-guide channel in the light guide plate of the present invention.
FIG. 15 is a diagram showing an example in which luminance is increased by intersection of light propagated through a light guide channel in a horizontal direction and light propagated through a vertical light guide channel.
16 is a view showing the path of light propagating in total reflection in the light guide plate and the progress angle when the light guide plate of the present invention is viewed from above.
17 is a view showing the path of light propagating in total reflection in the light guide plate and the progress angle when the light guide plate of the present invention is viewed from the side.
18 is a view showing a phenomenon in which the light escapes to the outside of the channel when the interval between the unit cells in the light guide plate structure of the present invention is excessively large.
19 is a view showing a path through which light is propagated to total reflection in one channel when the interval between unit cells is optimized when the light guide plate of the present invention is viewed from above.
20 is a view showing an example in which when the gap between the unit cells is not optimized when the light guide plate of the present invention is viewed from above, the local dimming effect is reduced due to propagation of light from one channel to another channel due to total reflection failure.
21 and 22 are views showing an embodiment of a local dimming effect of the edge type backlight unit of the present invention.
23 and 24 are views illustrating dot patterns applied to the light guide plate 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.

5, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 10, a source driver 111 for driving data lines 14 of the liquid crystal display panel 10, A timing controller 110 for controlling the operation timings of the source driver 111 and the gate driver 112 for driving the gate lines 15 of the liquid crystal display panel 10, A light source driving units 103 and 104 for driving the LED arrays 101 and 102 of the edge type backlight unit and a local dimming control unit 113 for generating a local dimming signal LDIM, .

In the liquid crystal display panel 10, a liquid crystal layer is formed between two glass substrates. A plurality of data lines 14 and a plurality of gate lines 15 intersect the lower glass substrate of the liquid crystal display panel 10. The liquid crystal cells Clc are arranged in a matrix form in the liquid crystal display panel 10 by the intersection structure of the data lines 14 and the gate lines 15. [ The liquid crystal cell Clc connected to the data lines 14, the gate lines 15, the thin film transistor (TFT), and the thin film transistor TFT is connected to the lower glass substrate of the liquid crystal display panel 10, An electrode, and a storage capacitor Cst are formed. On the upper glass substrate of the liquid crystal display panel 10, 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 10, a polarizing plate is attached and an alignment film for forming a pre-tilt angle of the liquid crystal is formed on the inner surface in contact with the liquid crystal.

The source driver 111 latches the digital video data RGB input from the timing controller 110. The source driver 111 converts the digital video data RGB to positive / negative polarity analog data voltages using the positive / negative gamma compensation voltages under the control of the timing controller 110, .

The gate driver 112 sequentially supplies gate pulses (or scan pulses) synchronized with the analog data voltage to the gate lines 15 under the control of the timing controller 110.

The timing controller 110 receives digital video data RGB and timing signals Vsync, Hsync, DE and DCLK from an external SoC including a video source and outputs digital video data RGB to a source driver 111). The timing controller 110 generates timing control signals DDC and GDC for controlling the operation timings of the source driver 111 and the gate driver 112 based on the timing signals Vsync, Hsync, DE and DCLK Occurs.

The edge type backlight unit includes a light guide plate 100 divided into a single layer and LED arrays 101 and 102 disposed on the side edges of the light guide plate 100. [ In addition, the edge type backlight unit includes a plurality of optical sheets stacked between the light guide plate 100 and the liquid crystal display panel 10. The optical sheets include one or more prism sheets and one or more diffusion sheets to diffuse light incident from the light guide plate 100 and refract the path of light at an angle substantially perpendicular to the light incident surface of the liquid crystal display panel .

The light guide plate 100 is made of a dielectric material having a low absorption rate of light in a visible ray region such as polymethyl methacrylate (PMMA), polycarbonate (PC), and polyethylene terephthalate (PET) And a plurality of unit cells along the longitudinal direction y.

The LED arrays 101 and 102 include a first LED array 101 for emitting light to left and right sides of the light guide plate 100 along the longitudinal direction y, And a second LED array 102 for emitting light to the upper and lower sides. The first LED array 101 includes a plurality of LEDs serving as point light sources whose brightness is controlled individually and is disposed outside the side surface of the light guide plate 100 so as to face the upper and lower surfaces of the light guide plate 100, And is disposed outside the side surface of the light guide plate 100 so as to be opposed to any one of the side surfaces. The second LED array 102 may be disposed outside the side surface of the light guide plate 100 so as to be opposed to the left side surface and the right side surface of the light guide plate 100, The light guide plate 100 is disposed on the side of the light guide plate 100 so as to be opposed to either side of the light guide plate 100. Each of the LEDs of the first and second LED arrays 101 and 102 is independently controlled to emit light by the local dimming control. The number of LEDs of the first and second LED arrays 101 and 102 can be adjusted.

The first light source driving unit 103 adjusts a current applied to each of the LEDs of the first LED array 101 in response to the local dimming signal LDIM input from the local dimming control unit 113. The second light source driving unit 104 adjusts a current applied to each of the LEDs of the second LED array 102 in response to an input local dimming signal LDIM from the local dimming control unit 113.

The local dimming control unit 113 analyzes the luminance of the input image data RGB of one frame for each unit cell in the light guide plate 100 and outputs a local dimming signal for controlling the luminance of each block of the light guide plate 100 LDIM).

6 is a perspective view showing the light guide plate 100 in detail. 7 is a perspective view showing a unit cell of the light guide plate 100. FIG.

6 and 7, the light guide plate 100 includes a plurality of unit cells LGP11 to LGP33 that are divided into a horizontal direction x and a vertical direction y. 6 and 7, the light guide plate 100 is divided into 3x3, but the present invention is not limited thereto, and the light guide plate 100 is divided into ixj (each of i and j is a positive integer of 2 or more).

The unit cells LGP11 to LGP33 divide the light guide plate 100 into a light guide channel in the lateral direction (x) and a light guide channel in the vertical direction (y) so that local dimming is possible. For example, the eleventh to thirteenth unit cells LGP11 to LGP13 form a first lateral light guiding channel, and the twenty-first to thirteenth unit cells LGP21 to LGP23 form a second lateral light guiding channel do. And the 31st to 33rd unit cells LGP11 to LGP13 form a third lateral direction light guiding channel. The twelfth, twenty second, and thirty-second unit cells LGP12, LGP22, and LGP32 form the first longitudinal direction light-guiding channel, and the twelfth, twenty-second, and thirtieth unit cells LGP11, LGP21, Thereby forming a longitudinal light guiding channel. And the 13th, 23rd and 33th unit cells LGP13, LGP23, LGP33 form a third longitudinal light guide channel. The luminance of each of the unit cells LGP11 to LGP33 is represented by the sum of the light propagating in the lateral direction light-guiding channel and the light propagating in the longitudinal direction light-guiding channel. Accordingly, the present invention adjusts the luminance of each of the unit cells LGP11 to LGP33 by adjusting the LED current for irradiating the light to the lateral direction light-receiving channel and the LED current for illuminating the light-receiving channel for the vertical direction, thereby realizing local dimming have.

The unit cells LGP11 to LGP33 are rectangular parallelepipeds as shown in Fig. 7, and the lengths of the width a, the length b, and the height h can be designed as desired according to the purpose. If the interval between the unit cells LGP11 to LGP33 is too large, a strong bright line occurs. If the interval is smaller than the wavelength of light, a total reflection failure (FTIR) phenomenon occurs and the local dimming efficiency drops. Therefore, the interval g between the unit cells LGP11 to LGP33 is preferably not less than the wavelength of the light but not more than 100 mu m.

In order to maintain the gap g between the unit cells LGP11 to LGP33 at a constant value, a fixing frame 105 for fixing the outermost sides of the LGP 100 is required as shown in FIGS. The fixed frame 105 has a sectional structure that encloses the upper and lower outer edges of the outer unit cells LGP11 to LGP13, LGP21, LGP23 and LGP31 to LGP33 of the light guide plate 100 and the side surface thereof. The fixing frame 105 may be formed of a material suitable for reflecting light and enhancing the light efficiency incident on the light guide plate 100 and dissipating heat of the LED, for example, aluminum, copper, Is made of a metal having high reflectivity. A metal PCB (Printed Circuit Board) 106 on which the LED package 108 is mounted may be directly attached to the concave inner surface of the stationary frame 105 or may be attached through a thermal pad 109 serving as a thermal interface material . In addition to this LED fixing method, the metal PCB 106 and the fixing frame 105 can be fixed with a screw. The upper and lower ends of the fixed frame 105 press the upper and lower edges of the outer unit cells LGP11 to LGP13, LGP21, LGP23 and LGP31 to LGP33 of the light guide plate 100 to prevent the unit cells from flowing. 10, the bottom cover 107 is made of aluminum or an alloy thereof, and supports the unit cells LGP11 to LGP33 of the light guide plate 100 from below. Between the bottom cover 107 and the unit cells LGP11 to LGP33 of the light guide plate, a reflector (refer to FIG. 17) for reflecting the light incident on the back of the light guide plate toward the light guide plate is disposed. A fixing frame 105 is assembled to one side of the bottom cover 107. On the unit cells LGP11 to LGP33 of the light guide plate 100, the optical sheets and the liquid crystal display panel 10 are assembled. Therefore, the unit cells LGP11 to LGP33 of the light guide plate 100 can maintain the balance between the bottom cover 107 and the optical sheets.

In order to enhance the local dimming performance, the light propagated in the unit cells LGP11 to LGP33 must be diffused toward the unwanted light guide channel or propagated to the end of the channel without interfering with the light of the neighboring light guide channel. To this end, the present invention relates to a liquid crystal display (LCD) that is capable of performing total internal reflection (TIR) of light within unit cells LGP11 to LGP33 of a light-guiding channel, and to prevent light from being emitted to the outside between unit cells LGP11 to LGP33 (LGP11 to LGP33).

The unit cells LGP11 to LGP33 of the light guide plate 100 are disposed in the unit cells LGP11 to LGP33 of the light guide plate 100 to uniformly emit light propagated through the total reflection toward the optical sheets and the liquid crystal display panel 10. [ Fine dot patterns are formed on the bottom surface (or bottom surface) of the substrate. The shape of the dot pattern is V shape, hemispherical shape, etc., and the shape may be changed depending on the processing method. The dot pattern may be formed by a known method such as a v-cut method or a printing method. The v-cut method may be applied to a structure in which the light guide plate material is engraved by projecting convexly on the surface of the light guide plate material, or may be applied with a concave and fine structure. In the printing method, ink is printed on the surface of the light guide plate to form a dot pattern. A material such as a scattering agent or a diffusing agent may be added to the ink so as to more effectively diffuse the light. In general, materials such as SiO ₂ , Al ₂ O ₃ , TiO ₂ and the like may be added to the ink.

Since the edge type backlight unit of the present invention is located outside the outermost side of the light guide plate 100, if the density of the dot patterns is the same on all the surfaces of all the light guide plates, the distance from the light source decreases, The luminance of the unit cells LGP22 disposed at the center of the light guide plate 100 is smaller than the unit cells LGP11 to LGP13, LGP21, LGP23, and LGP31 to LGP33 arranged at the edges. Therefore, in order to uniformly distribute the luminance of the unit cells LGP11 to LGP33 of the light guide plate 100, it is necessary to design the density of the dot pattern to be higher toward the center of the light guide plate 100 as shown in FIG. 23 and FIG. In the following experimental example, the dot patterns are formed in the light guide plate as hemispherical dot patterns, and their densities are as shown in FIGS. 23 and 24. FIG. On the other hand, the density of the dot pattern can be adjusted to a value of one or more of the interval between the dot patterns and the size of the dot pattern.

11 and 12 are views showing examples of on / off operation of the lateral light guide channel in the light guide plate of the present invention.

11 and 12, when the LEDs facing the second lateral direction light-guiding channel among the LEDs of the second LED array 102 emit light, the twenty-first unit cells LGP21 of the second lateral direction light- Light is incident on the 23rd unit cell LGP23, and the light propagates to the total reflection (TIR) up to the end of the second lateral direction light-guiding channel. In order to select the first lateral directional light-guiding channel, if the LEDs facing the first lateral directional light-guiding channel are lit, light is totally reflected (TIR) in the unit cells LGP11 to LGP13 of the first lateral- It spreads to the end. In order to select the third lateral directional light guiding channel, when the LEDs facing the third lateral directional light guiding channel are lit, light is totally reflected (TIR) in the unit cells LGP31 to LGP33 of the third lateral direction light guiding channel, It spreads to the end.

13 and 14 are views showing an example of the on / off operation of the vertical light guide channel in the light guide plate of the present invention.

13 and 14, when the LEDs facing the second longitudinal light-guiding channel among the LEDs of the second LED array 102 emit light, the twelfth and thirty-second unit cells of the second longitudinal light- LGP12, and LGP32, and the light propagates to the total reflection (TIR) up to the end of the second vertical direction light-guiding channel. In order to select the first longitudinal direction light-guiding channel, if the LEDs opposed to the first longitudinal light-guiding channel emit light, the light is totally reflected (TIR) in the unit cells LGP11, LGP21 and LGP31 of the first longitudinal light- It propagates to the end of the channel. In order to select the third longitudinal direction light-guiding channel, if the LEDs facing the third longitudinal direction light-guiding channel are lit, the light is totally reflected (TIR) in the unit cells LGP13, LGP23, LGP33 of the third longitudinal light- It propagates to the end of the channel.

 As shown in FIG. 15, when the LEDs of the second and third longitudinal light-guiding channels are simultaneously emitted, the brightness of the twenty-second unit cell LGP22 where the light crosses is increased. For example, if the LEDs of the second and third longitudinal directional light-guiding channels emit light at a luminance of 50%, the twelfth, twenty-first, twenty-third, and thirty-second unit cells LGP12, LGP21, LGP23, LGP32 Is about 50%, and the brightness of the twenty-second unit cell LGP22 rises to 100% of the brightness.

FIGS. 16 to 19 are views showing total reflection of light propagated in the unit cells LGP11 to LGP33 of the light guide plate 100. FIG.

If the interval g between the unit cells LGP11 to LGP33 is optimized to be equal to or more than 100 占 퐉 of the wavelength of the light, as shown in FIG. 17, if the light is totally reflected within one channel without total internal reflection (FTIR) ) And propagated to the end of the channel.

The total reflection propagation of light in the light guide plate structure of the present invention will be described with reference to FIG. 17 using Snell's law.

17, it is assumed that light beams generated from the LEDs are incident on the unit cells LGP11 to LGP33 of the light guide plate 100 at an incident angle [theta] _i . The light is on the front of the unit in parallel with the light traveling direction cell (LGP11 ~ LGP33) side (see Figs. 12 and 14) of unit cells (LGP21) vertically has a reflection angle of θ _s, and the light traveling direction from the in (see Fig. 12 and 14) it has a reflection angle of θ _f. When the refractive index of the material constituting the light guide plate is n, θ _s and θ _f can be expressed as follows according to Snell's law with respect to θ _i .

In order to achieve local dimming, the total reflection always occurs at the side face with respect to all the incident angles &thetas; _i , and the total reflection should not occur at the front.

Substituting Equation (3) into Equations (1) and (2) and solving for the refractive index, the following results are obtained.

보다 클 경우 모든 θ_i에 대하여 옆면에서는 항상 전반사가 발생하고, 전면에서는 전반사가 발생하지 않는다. 일반적으로 사용되는 도광판 매질의 굴절율(PMMA의 굴절율 n = 1.489)은 수학식 4의 조건을 만족하므로 도 12 및 도 14에서 모든 θ_i에 대하여 옆면에서 전반사가 일어나고, 전면에서는 전반사가 일어나지 않게 된다.When the refractive index of the material constituting the light guide plate is

The total reflection always occurs on the side surface with respect to all the? _I , and the total reflection does not occur on the front surface. Since the index of refraction (PMMA refractive index n = 1.489) of the generally used light guide plate media satisfies the condition of Equation (4), the total reflection occurs on the side surface with respect to all the? _I in FIGS. 12 and 14, and the total reflection does not occur on the front surface.

When the interval between the unit cells LGP11 to LGP33 is excessively large, light is diffused out of the channel in a space g between the unit cells LGP11 to LGP33 as shown in Fig. 18, and a bright line is generated. When the unit cells LGP11 to LGP33 are completely attached to one body, the light in the light guide plate does not come out at all. In this case, since the unit cells LGP11 to LGP33 are not distinguished, Implementation is impossible. In the current light guide plate manufacturing process, since there is an average curvature of several hundreds of nm or more on the side surface of the unit cells LGP11 to LGP33, even if the unit cells LGP11 to LGP33 are mechanically completely in contact with each other, It is spread to the height of the curvature. If the interval between the unit cells LGP11 to LGP33 formed is equal to or greater than the wavelength of light, there is almost no light exiting from the channel because there is almost no total reflection defect (FTIR).

18 is a view showing a phenomenon in which the light escapes to the outside of the channel when the interval between the unit cells in the light guide plate structure of the present invention is excessively large. This phenomenon is irrelevant to the total reflection error (FTIR) and is a phenomenon that causes a bright line.

Total reflection does not occur at the total reflection critical angle? _C when the total reflection failure phenomenon occurs, and light can be emitted outside the channel between the unit cells LGP11 to LGP33 as shown in FIG. In this case, the local dimming effect is reduced because light is diffused to other light-guiding channels other than the desired light-guiding channel.

FIGS. 21 and 22 are views showing the result of an experiment of the local dimming effect of the edge type backlight unit of the present invention.

21 and 22, each thick dotted line disposed at the edge of the light guide plate corresponds to an LED. "LED ON" means the LEDs are ON, and "LED OFF" means the LEDs are OFF. The size of the light guide plate 100 is based on a 22 inch Full HD TV standard. The simulation conditions were 1 mm resolution and no diffuser sheet was applied. The height h of the unit cells is 3 mm, and the lengths a and b are 3 cm. The simulation was carried out with the gap g between unit cells being 10 탆. Actually, however, the unit gaps are not mechanically spaced. However, even if the unit cells are completely in contact with each other, an average interval is formed by the average curvature of the surface formed in the process of manufacturing the unit cell, without using the adhesive, and the interval is set to 10 mu m. The distance between the dot patterns is fixed to 1 mm and then the size of the dot pattern is adjusted as shown in FIGS. 23 and 24 so that the brightness of the entire screen of the light guide plate becomes uniform . In order to analyze the luminance of the screen more precisely, three water lines are selected in each of the horizontal and vertical directions, and the luminance according to the position on the water line is expressed by a graph.

The luminance graphs of FIGS. 21 and 22 are obtained from MATLAB by extracting data from an optical software ASAP (Advanced Systems Analysis Program) of Breault Research Organization. In each graph, the unit of the x-axis is mm, the total length of the light guide plate 100 is 540 mm, and the length is 300 mm. and the y-axis represents the luminance at each position. In order to easily see the luminance uniformity (the lowest luminance / the highest luminance), the value in the y-axis was set as the luminance ratio (luminance / highest luminance). Therefore, it is always larger than 0 and smaller than 1, and the minimum value on the y-axis determines the luminance uniformity.

Fig. 21 shows a simulation result when all the LEDs are lit. Bright lines are observed in the intervals between the unit cells, but when compared with specific numerical values, the brightness uniformity is not affected. The luminance uniformity (lowest luminance / highest luminance) of the above result is 50.6%. The luminance uniformity of the light guide plate actually commercialized is only about 20% when the diffusion sheet is not used, but is improved to about 80% when the diffusion sheet is used. Therefore, when the diffusion sheet is applied to the simulation result of FIG. 21, it is expected to be improved to at least 70% or more.

FIG. 22 shows a result obtained by emitting only some of the LEDs and confirming that the light propagates only along the desired lateral and longitudinal light-guiding channels. As can be seen from the simulation results of FIG. 22, the present invention implements a high level of local dimming in the edge type backlight unit. In the simulation results, it was confirmed that the light emitted from the LED is guided to only one light-guiding channel by using the total reflection effect, and that the brightest luminance appears at the portion where the horizontal and vertical channels overlap.

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: light guide plate 101, 102: LED array
105: fixed frame LGP11 to LGP33: unit cell of light guide plate

Claims (6)

A plurality of unit cells which are divided in the lateral direction and the longitudinal direction in the single-layer light guide plate and spaced apart from each other in the transverse direction by a predetermined distance from at least one neighboring transverse direction and spaced apart from each other in the longitudinal direction by a predetermined distance;
A stationary frame for pressing the side faces of the unit cells out of the unit cells together to maintain the predetermined spacing of the unit cells;
A point light source disposed outside the sub-unit cells so as to face side faces of the sub-unit cells;
A light source driver for emitting the point light sources; And
And a local dimming control unit for controlling the light source driving unit in response to the local dimming signal. The method according to claim 1,
The gap between the unit cells may be,
Wherein the wavelength of the light incident on the unit cell from the point light source is not less than 100 占 퐉. The method according to claim 1,
A bottom cover for supporting unit cells of the light guide plate in parallel below;
Further comprising optical sheets stacked on the light guide plate. A liquid crystal display panel; And
And an edge type backlight unit disposed below the liquid crystal display panel and irradiating light to the liquid crystal display panel,
In the edge type backlight unit,
A plurality of unit cells which are divided in a lateral direction and a longitudinal direction in the single-layer light guide plate and are spaced apart from each other by at least one neighboring in the transverse direction and spaced by a predetermined distance in the longitudinal direction from at least one neighboring in the longitudinal direction, A stationary frame for pressing the side faces of the cell units out of the cells to maintain the predetermined spacing of the cell units, a point light source disposed outside the cell units so as to face side faces of the cell units, And a local dimming control unit for controlling the light source driving unit in response to the local dimming signal. 5. The method of claim 4,
The gap between the unit cells may be,
Wherein a wavelength of light incident on the unit cell from the point light source is not less than 100 占 퐉. 5. The method of claim 4,
The edge type backlight unit includes:
A bottom cover for supporting unit cells of the light guide plate in parallel below;
Further comprising optical sheets stacked between the light guide plate and the liquid crystal display panel.

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