KR100912695B1 - Backlight unit of liquid crystal display device - Google Patents

Abstract

The present invention relates to a backlight unit of a liquid crystal display device which increases the light incidence efficiency by increasing the light incidence efficiency by forming the incident surface of the light guide plate thicker than the emission surface, and at the same time reduces the thickness and weight of the light guide plate. And a light guide plate having a light incident surface thicker than an exit surface, a light source unit configured at one side of the light guide plate to arrange a plurality of green, blue and red light emitting diodes to emit light, and fixing the light source unit to emit light from the light source unit. And a reflecting plate configured to condense the light in one direction, and a reflecting plate configured to reflect the light leaking out to the opposite side of the liquid crystal panel.

LGP, LED, Housing, Reflector, Backlight

Description

Backlight unit of liquid crystal display device

1 is a view for explaining the structure of a typical backlight assembly

2 is a perspective view showing a backlight unit using a conventional fluorescent lamp

3 is a cross-sectional view showing a backlight unit of a conventional liquid crystal display device.

4 is a plan view of a backlight unit using a conventional LED lamp

5 is a perspective view showing the overall configuration of a liquid crystal display device in the present invention;

6 is a cross-sectional view illustrating a backlight unit of a liquid crystal display according to a first embodiment of the present invention.

7A to 7D are cross-sectional views illustrating various forms of the light guide plate of FIG. 6.

8 is a cross-sectional view illustrating a backlight unit of a liquid crystal display according to a second exemplary embodiment of the present invention.

Explanation of symbols for the main parts of the drawings

61 light guide plate 62 LED lamp

63 housing 64 reflector plate

65: PCB Board

The present invention relates to a backlight unit of a liquid crystal display device, and more particularly to a backlight unit of a liquid crystal display device suitable for increasing color mixing efficiency.

CRT (Cathode Ray Tube), one of the commonly used display devices, is mainly used for monitors such as TVs, measuring devices, information terminal devices, etc., but the miniaturization of electronic products due to the weight and size of CRT itself It was unable to actively respond to the demand for weight reduction.

Therefore, in the trend of miniaturization and light weight of various electronic products, CRT has a certain limit in weight and size, and is expected to be replaced. Liquid crystal display (LCD) and gas discharge using electro-optic effects Plasma Display Panel (PDP) and Electro Luminescence Display (ELD) using the electroluminescent effect, among others, are being actively studied for the liquid crystal display device.

In order to replace the CRT, a liquid crystal display device having advantages such as small size, light weight, and low power consumption has recently been developed to be able to perform a sufficient role as a flat panel display device. As used in monitors and large information display devices, the demand for liquid crystal display devices continues to increase.                         

The liquid crystal display may be classified into a liquid crystal panel displaying an image and a driving unit for applying a driving signal to the liquid crystal panel. The liquid crystal panel may include first and second glass substrates bonded to each other with a predetermined space, and It consists of the liquid crystal layer injected between the 1st, 2nd glass substrate.

The first glass substrate (TFT array substrate) may include a plurality of gate lines arranged in one direction at a predetermined interval, a plurality of data lines arranged at regular intervals in a direction perpendicular to the gate lines, A plurality of pixel electrodes formed in a matrix form in each pixel region defined by crossing a gate line and a data line, and a plurality of thin films which are switched by signals of the gate line to transfer the signal of the data line to each pixel electrode Transistors are formed.

The second glass substrate (color filter substrate) includes a black matrix layer for blocking light in portions other than the pixel region, an R, G and B color filter layer for expressing color colors, and a common electrode for implementing an image. Is formed.

The first and second glass substrates are bonded to each other by a seal material having a predetermined space by a spacer and having a liquid crystal injection hole, so that the liquid crystal is injected between the two substrates.

On the other hand, since most of the liquid crystal display devices are light-receiving elements that display an image by controlling the amount of light source coming from the outside, a separate light source, that is, a backlight, is required for irradiating light to the liquid crystal panel. It is divided into edge type and direct type according to the location where the lamp unit is installed.                         

The light source includes EL (Electro Luminescence), LED (Light Emitting Diode), CCFL (Cold Cathode Fluorescent Lamp), HCFL (Hot Cathode Fluorescent Lamp), etc., especially long life, low power consumption and thin can be formed. CCFL is widely used in large color TFT LCDs.

The CCFL method uses a fluorescent discharge tube in which mercury gas containing argon, neon, or the like is sealed at a low pressure in order to use a penning effect. Electrodes are formed at both ends of the tube, and the cathode is formed in a wide plate shape.When voltage is applied, as in the sputtering phenomenon, charged particles in the discharge tube collide with the plate-shaped cathode to generate secondary electrons, which excite surrounding elements to excite the plasma. Form.

These elements emit strong ultraviolet light, which in turn excites the phosphor, causing the phosphor to emit visible light.

In the double-edge method, the lamp unit is installed on the side of the light guide plate for guiding the light, and the lamp unit covers a lamp emitting light, a lamp holder inserted at both ends of the lamp to protect the lamp, and an outer circumferential surface of the lamp, and one side It is provided with a lamp reflector plate fitted to the side of the light guide plate to reflect the light emitted from the lamp toward the light guide plate.

The edge method in which the lamp unit is installed on the side of the light guide plate is applied to a relatively small liquid crystal display device such as a monitor of a laptop computer and a desktop computer, and has good uniformity of light and a long service life. It is advantageous to thin the liquid crystal display device.

On the other hand, the direct method began to develop mainly as the size of the liquid crystal display device became larger than 20 inches, and arranged a plurality of lamps in a row on the lower surface of the diffusion plate to direct light directly to the front of the liquid crystal panel. will be.

The direct method is mainly used for a large screen liquid crystal display device requiring high luminance because the light utilization efficiency is higher than that of the edge method.

However, the liquid crystal display device adopting the direct method is used as a large monitor or a television, which takes longer to use than a laptop computer, and because the number of lamps is larger, the failure and life of the lamp in the direct method than the edge method. It is more likely that a lamp that will not turn on appears.

In the direct method, because a plurality of lamps are installed on the bottom of the screen, for example, due to the life and failure of the lamp, if one lamp does not light up, the part where the lamp does not light up becomes significantly darker than the other part. The part will appear immediately on the screen.

For this reason, since the lamp is frequently replaced in the direct method, the lamp unit should be easily disassembled and assembled.

As described above, the liquid crystal display device uses a liquid crystal to control the amount of light transmitted through the screen, and uses the light to determine the contrast and the color of the screen.

For example, the viewing angle of which the image quality varies greatly depending on the angle of view of the screen, the transmittance according to the projection light emitting display, and the transmitted light pass through the color filter to display the colors of red (R), green (G), and blue (B). These include color reproducibility depending on how much they are reproduced, luminance representing the contrast of the image, and afterimages in which the traces of the image remain long when the same image is continued for a long time.

Currently, liquid crystal displays are expanding from display of portable products to monitors for desktop PCs and home TVs. Although the liquid crystal display has the physical advantages of light and thin, the color reproducibility and luminance, among the above characteristics, are particularly weak compared to the CRT.

Conventional LCD monitors have 40-50% color reproducibility compared to the NTSC system adopted by the National Television System Committee for color television broadcasting. Could meet.

However, in the case of a TV which is attracting attention as a market for a new liquid crystal display device, it is required to develop a liquid crystal display device capable of realizing color reproducibility of CRT level or higher.

A typical multi-color liquid crystal display device is largely composed of a liquid crystal panel, a backlight, and a color filter. That is, by using a backlight composed of a three-wavelength fluorescent lamp as a light source, the white light emitted from the color filter is separated into three colors of red, green, and blue in the color filter, and then added and mixed again to realize various colors.

The color of the light source is determined by chromaticitycordinates determined by the International Lighting Commission. That is, after calculating tristimulus values X, Y and Z from the spectra of an arbitrary light source, color coordinates x, y and z of red, green and blue are obtained from the tristimulus values using the transformation matrix. Subsequently, when the x, y values of red, green, and blue are expressed in Cartesian coordinates, a horn-shaped spectral trajectory is drawn, which is called a CIE chromaticity diagram. All common light sources have their color coordinates inside these horseshoe shapes.

In this case, a triangular region formed by each color coordinate of red, green, and blue becomes a color reproduction region, and as the triangle region becomes larger, color reproducibility is increased. Color reproducibility depends on color purity and luminance, and color reproducibility increases as color purity and luminance increase.

Here, the tristimulus values X, Y, and Z represent weights of individual color-matching functions close to a spectrum, and particularly Y represents a stimulus value for brightness.

On the other hand, the color temperature of the white color based on the color change of the light emitted according to the temperature of the heat source is called the color temperature, the color temperature on the monitor is represented by three, that is, 9300K, 6500K and 5000K.

The closer the color temperature is to 9000K, the more white is added to the blue color. If the color temperature is 6500K, the red color is added to the white. If the color temperature is 5000K, the color becomes neutral. The color temperature is obtained from the color coordinates (x, y) of white. As the color temperature is around 9000K, the European broadcasting union (EBU) standard can be satisfied.

In the case of the liquid crystal display device described above, the emission spectrum of the backlight is combined with the transmission spectrum of the color function and the color filter to determine tristimulus values for each wavelength of the visible light region. Correlation between extremes should be adjusted accordingly. That is, in order to optimize color reproducibility and color temperature, the emission spectrum of the backlight should be changed, and the transmission spectrum of the color filter should be adjusted to maximize the emission efficiency correspondingly.

If a white, blue, green, and red LEDs must be used at the same time, many application problems occur. In particular, when using blue, green, and red LEDs at the same time, it is difficult to apply them realistically because of a technical problem of gathering different colors coming out according to the position of each LED to make white.

Therefore, in order to realize white light, it is required that all three wavelengths of one LED emit light with a predetermined intensity or more.

As such, there is an urgent need for the development of a backlight capable of utilizing the advantages of the backlight of the SMD (Surface Mounting Device) LED of the mobile phone, which is not only small and cold, but also has a small power consumption.

Meanwhile, the configuration of a general backlight assembly is as follows.

1 is a view for explaining the structure of a general backlight assembly.

As shown in FIG. 1, the fluorescent lamp 1, the light guide plate 2, the diffusion material 3, the reflection plate 4, the diffusion plate 5, the prism sheet 6, and the like are constituted.

First, when the voltage is applied to the fluorescent lamp 1, residual electrons present in the fluorescent lamp 1 move to the anode, and the moving residual electrons collide with argon (Ar) to excite argon to proliferate cations, The multiplying cations collide with the cathode to release secondary electrons.

When the discharged secondary electrons flow through the tube to initiate discharge, the flow of electrons by the discharge collides with, and ionizes, the mercury vapor to emit ultraviolet rays and visible light, and the emitted ultraviolet rays excite the phosphor coated on the inner wall of the lamp. It emits visible light and emits light.

Subsequently, the light guide plate 2 is a wave guide for injecting the light emitted from the fluorescent lamp 1 into the surface to emit a surface light source to the top, and has excellent light transmittance. PMMA (Poly Methyl Meth Acrylate) ) Resin is used.

Factors related to light incidence efficiency of the light guide plate 2 include light guide plate thickness versus lamp diameter, the distance between the light guide plate and the lamp, the shape of the lamp reflector, and the like. In general, the fluorescent lamp 1 is thicker than the center of the light guide plate 2. By inclining in the direction, the light incidence efficiency is increased.

The light guide plate 2 of the backlight unit for an LCD includes a printing light guide plate, a V-cut light guide plate, and a scattering light guide plate.

Subsequently, the diffusion material 3 is composed of Si0 ₂ , particles, PMMA, solvent, and the like. At this time, the Si0 ₂ particles described above are used for light diffusion and have a porous particle structure. PMMA is also used to attach Si0 ₂ particles to the lower surface of the light guide plate 2.

The diffusion material 3 is applied to the lower surface of the light guide plate in the form of a dot, and the area of the dot is gradually increased in order to obtain a uniform surface light source on the light guide plate 2. That is, the area ratio occupied by the dot per unit area is smaller in the one closer to the fluorescent lamp 1, and the area ratio occupied by the dot per unit area is larger in the far side from the fluorescent lamp 1.

In this case, the shape of the dot may have various shapes. If the area ratio of the dots per unit area is the same, the same brightness effect may be obtained on the light guide plate regardless of the shape of the dot.

Subsequently, the reflector 4 is installed at the rear end of the light guide plate 2 so that the light emitted from the fluorescent lamp 1 is incident into the light guide plate 2.

The diffusion plate 5 is installed on the light guide plate 2 to which the dot pattern is applied to obtain uniform luminance according to a viewing angle. As the material of the diffusion plate 5, PET or PC (Poly) is used. Carbonate) resin is used, and the upper part of the diffusion plate 5 has a particle coating layer that serves as a diffusion.

Subsequently, the prism sheet 6 is to increase the front luminance of the light that is transmitted through the diffusion plate 5 and reflected. The prism sheet 6 allows only the light of a specific angle to pass therethrough and the light incident at the remaining angle. Total internal reflection occurs and returns back to the bottom of the prism sheet 6. As described above, the returning light is reflected by the reflecting plate 4 attached to the lower part of the light guide plate 2.

The backlight assembly configured as described above is fixed to the mold frame, and the display unit disposed on the upper surface of the backlight assembly is protected by the top chassis, and the top chassis and the mold frame are coupled while receiving the backlight assembly and the display unit therebetween.

Hereinafter, a backlight unit of a conventional liquid crystal display device will be described with reference to the accompanying drawings.

2 is a perspective view illustrating a backlight unit using a conventional fluorescent lamp.

As shown in FIG. 2, the fluorescent lamp 11 is coated on the inner surface to emit light, and the fluorescent lamp 11 is fixed, and the light emitted from the fluorescent lamp 11 is oriented in one direction. A lamp housing 12 for condensing the light, a light guide plate 13 for supplying the light emitted from the fluorescent lamp 11 to the liquid crystal panel side of the upper part of the backlight, and a light guide plate 13 which is attached to the lower part of the light guide plate 13 and leaks out to the opposite side of the liquid crystal panel. A reflector 14 for reflecting light to the light guide plate 13, a diffuser plate 15 positioned above the light guide plate 13 to uniformly diffuse the light emitted from the light guide plate 13, and the diffuser plate 15. A prism sheet 16 positioned above and condensing the light diffused from the diffusion plate 15 to a liquid crystal panel, and a protection provided at the upper portion of the prism sheet 16 to protect the prism sheet 16. The seat 17 and the components It consists of a main support (18) that secure.

In the backlight unit configured as described above, the light emitted from the fluorescent lamp 11 is focused on the light incident surface of the light guide plate 13, and then passes through the light guide plate 13 through the diffuser plate 15 and the prism sheet 16 to the liquid crystal panel. Delivered.

However, as described above, the backlight unit using the conventional fluorescent lamp has low color reproducibility due to the light emission characteristics of the light source itself. In addition, it is difficult to obtain a high brightness backlight unit due to constraints of the size and capacity of the fluorescent lamp.

On the other hand, in recent years, the backlight unit has been used as a function for reading information displayed on the screen of a liquid crystal display in a dark place, but recently, the light guide plate has been formed thinner due to various requirements such as design, low power, and thinning. In addition to the ability to express various colors, technologies for reducing power consumption using LEDs (Light Emitting Diodes) are being made.

3 is a cross-sectional view illustrating a backlight unit of a conventional liquid crystal display device.

As shown in FIG. 3, a flat light guide plate 21 formed on a rear surface of a liquid crystal panel (not shown), and an LED lamp 23 including red LEDs, green LEDs, and blue LEDs on one side of the light guide plate 21. ), A housing 22 for fixing the LED lamp 23 and condensing the light emitted from the LED lamp 23 in one direction, and a lower end of the light guide plate 21 to the opposite side of the liquid crystal panel. It comprises a reflecting plate 24 for reflecting the light leaking out, and a PCB substrate 25 to which the LED lamp 23 is attached.

The housing 22 is made of Al to condense the light emitted from the plurality of LED lamps 23, which are point light sources, by condensing light.

The LED lamp 23 is divided into a body portion 23a and a light emitting portion 23b.

On the other hand, the housing 22 is configured to surround the light emitting portion 23a of the LED lamp 23 arranged on the PCB substrate 25.

In the case of performing a display in the liquid crystal display device using the backlight unit configured as described above, the light emitted from the LED lamp 23 is incident on the light guide plate 21 and scattered in the light guide plate 21 to emit white light. The liquid crystal panel is illuminated by emitting the light to the entire surface of 21).

The white light incident on the liquid crystal panel is modulated according to the alignment of the liquid crystal material and is transmitted through the color filter of the opposing substrate to output a color image.                         

4 is a plan view of a backlight unit using a conventional LED lamp.

As shown in FIG. 4, the LED lamp 23 including the red LED 23a, the green LED 23b, and the blue LED 23c and the light emitted from the LED lamp 23 are evenly distributed on the liquid crystal panel. It consists of a flat light guide plate 21 to make.

As such, monochromatic light of R, G, and B is emitted from the LED lamp 23 to emit white light by using the LED lamp 23 as a light source. However, in the region "a" of the light guide plate 21, A portion 20 in which the light emitted by the LED lamp 23 does not overlap is generated to produce a uniform white light, and R, G from the LED lamp 23 in the "b" region of the light guide plate 21 is generated. , The emitted monochromatic light of B can be mixed to make uniform white light.

Thus, the backlight unit uses only half of the light guide plate 21 far from the LED lamp 23 by forming a light spot on the light guide plate 21 to effectively use only the "b" region of the light guide plate 21.

That is, as described above, the backlight unit of the conventional liquid crystal display device uses only two light guide plates 21 to overlap two light guide plates having the same size.

However, in the backlight unit of the conventional liquid crystal display device as described above, there are the following problems.

That is, the light guide plate for mixing light emitted from the red, green, and blue LEDs emitting three primary colors of additive mixed color is formed in a flat plate shape, thereby increasing weight and thickness, lowering light incidence efficiency, and inferior color mixing efficiency.

The present invention has been made to solve the above-mentioned problems, the liquid crystal made to increase the light receiving efficiency by increasing the light incident efficiency by forming the incident surface of the light guide plate thicker than the exit surface, and at the same time reduce the thickness and weight of the light guide plate It is an object of the present invention to provide a backlight unit of a display device.

The backlight unit of the liquid crystal display according to the present invention for achieving the above object is a light guide plate formed on the rear surface of the liquid crystal panel and the incident surface is formed thicker than the exit surface, and is configured on one side of the light guide plate, a plurality of green, blue, A red light emitting diode is arranged to emit light, a housing for fixing the light source and condensing the light emitted from the light source in one direction, and a lower portion of the light guide plate to emit light leaking out to the opposite side of the liquid crystal panel. Characterized in that it comprises a reflecting plate for reflecting.

Here, the housing is made of Al.

In addition, the light guide plate is formed in a shape where the upper surface is horizontal and the lower surface corresponding thereto becomes thinner from the incident surface to the exit surface.

In addition, the light guide plate is formed in a shape where the lower surface is horizontal and the upper surface corresponding thereto becomes thinner from the entrance surface to the exit surface.

In addition, the light guide plate is formed in a shape in which the thickness becomes thinner from the entrance surface to the exit surface while having a predetermined slope on the upper surface and the lower surface.                     

In addition, the light guide plate has a horizontal shape where the upper surface is horizontal and the lower surface has a thickness thinner from the entrance surface to the exit surface. The first light guide plate and the lower surface are horizontal and the upper surface is thinner from the entrance surface to the exit surface. Two light guide plates overlap each other.

According to another exemplary embodiment of the present invention, a backlight unit of a liquid crystal display device includes a main light guide plate formed on a rear surface of a liquid crystal panel and having an entrance surface thicker than an exit surface, and a bottom side of the main light guide plate and having an entrance surface thicker than an exit surface. A sub-light guide plate, a light source unit arranged on one side of the sub-light guide plate and arranged with a plurality of green, blue and red light emitting diodes to emit light, and a housing for fixing the light source unit and condensing the light emitted from the light source unit in one direction And a reflector configured to reflect light leaking out to the opposite side of the liquid crystal panel.

Here, the reflecting plate is composed of two reflecting plates.

In addition, the said reflecting plate uses what coated Ag with Al.

Hereinafter, the backlight unit of the liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings.

5 is a perspective view showing the overall configuration of a liquid crystal display device in the present invention.

As shown in Fig. 5, a shield case 31 made of metal for forming the upper frame and a display window 32 for determining an effective screen of the liquid crystal display module are formed.

The liquid crystal panel 33 formed below the shield case 31 and the display window 32 is a TFT or color filter made of a thin layer such as a source / drain electrode, a gate electrode or an amorphous silicon layer between two glass substrates. Etc. are laminated.

A drain circuit board 34, a gate circuit board 35, and an interface circuit board 36 are formed on the liquid crystal panel 33. Furthermore, joiners 37 and 38 for connecting the circuit boards are formed. 39). These circuit boards 34, 35, 36 are fixed to the shield case 31 via the insulating sheet 40.

On the other hand, the light shielding space 51 is provided below the liquid crystal panel 33 through the rubber cushion 50, and the diffusion plate 52 and the prism sheet 53 are provided. The diffuser plate 52 has a function of diffusing light generated from a light guide plate described later to obtain uniform planar light, and the prism sheet 53 is used to increase the luminance in the front direction.

A light guide plate 54 is provided below the prism sheet 53, and a light emitting lamp unit 55 is provided at two sides of the light guide plate 54.

In addition, a reflecting plate 56 is provided below the light guide plate 54 to reflect light incident from the light emitting lamp unit 55 into the light guide plate 54 toward the direction of the liquid crystal panel 33. have.

In addition, a lower case 57 having an opening 58 is provided below the reflecting plate 56.

Although not shown in the drawing, the light emitting lamp unit 55 has a housing for condensing light emitted from the light emitting lamp in one direction.

6 is a cross-sectional view illustrating a backlight unit of a liquid crystal display according to a first embodiment of the present invention.

As illustrated in FIG. 6, the light guide plate 61 is formed on the rear surface of the liquid crystal panel 33 (FIG. 5) and the incident surface is thicker than the emission surface, and is configured on one side of the light guide plate 61. The LED lamp 62 which emits light by arranging red light emitting diodes in one dimension, and the housing which fixes the LED lamp 62 and condenses the light emitted from the LED lamp 62 in one direction ( 63) and a reflecting plate 64 configured to reflect the light leaking out to the opposite side of the liquid crystal panel.

The LED lamp 62 is attached to and arranged on the PCB board 65.

In addition, the housing 63 is configured to surround the light emitting portions of each light emitting diode arranged on the PCB substrate 65, and is made of Al.

In the case of performing a display in the liquid crystal display device using the backlight unit configured as described above, when each light emitting diode of the LED lamp 62 emits light, the green light emitted from the green, blue, and red light emitting diodes of the LED lamp 62 is emitted. , Blue light, and red light are incident on the incident surface of the light guide plate 61, and are mixed by scattering in the light guide plate 61 to emit white light to the entire surface of the light guide plate 61 to illuminate the entire liquid crystal panel. .

The white light incident on the liquid crystal panel is modulated according to the alignment of the liquid crystal material and is transmitted through the color filter of the opposing substrate to output a color image.

Here, the housing 63 receives a point light source emitted from each light emitting diode and converts the light into a line light source.

Meanwhile, in the present invention, the PCB substrate 65 to which the LED lamp 62 is attached may be disposed in a direction perpendicular to the light guide plate 61 without being disposed in a direction parallel to the light guide plate 61.

7A to 7D are cross-sectional views illustrating various forms of the light guide plate of FIG. 6.

First, FIG. 7A illustrates a first form of the light guide plate 61 in which the upper surface is horizontal, and the lower surface corresponding thereto is formed to become thinner from the entrance surface to the exit surface so that the entrance surface is thicker than the exit surface. .

Subsequently, FIG. 7B illustrates a second shape of the light guide plate 61 in which the lower surface is horizontal, and the upper surface corresponding thereto is formed to become thinner from the entrance surface to the exit surface, whereby the entrance surface is thicker than the exit surface. .

Subsequently, FIG. 7C illustrates a third embodiment of the light guide plate 61 in which the incidence surface is thicker than the emission surface by forming the upper surface and the lower surface in a form in which the thickness becomes thinner from the entrance surface to the exit surface with a constant slope.

7D shows a light guide plate 61 having a fourth shape of the light guide plate 61 formed so that two light guide plates overlap, that is, a first light guide plate 61 of the first shape as shown in FIG. 7A, and a second light guide plate 61 as shown in FIG. 7B. ) Is formed on the upper portion, and the light guide plate having the third form is shown.

8 is a cross-sectional view illustrating a backlight unit of a liquid crystal display according to a second exemplary embodiment of the present invention.

As shown in FIG. 8, the main light guide plate 71 is formed on the rear surface of the liquid crystal panel (33 of FIG. 5) and the incident surface is thicker than the emission surface, and the incident surface is formed below the main light guide plate 71. A sub light guide plate 72 formed thicker than a surface; and an LED lamp 73 configured to emit light by forming a plurality of green, blue, and red light emitting diodes one-dimensionally on one side of the sub light guide plate 72; Fixing the LED lamp 73 and at the same time, the housing 74 for condensing the light emitted from the LED lamp 73 in one direction, and the light leaking to the opposite side of the liquid crystal panel formed on the lower end of the main light guide plate 71 And first and second reflecting plates 75 and 76 which reflect the light.

The LED lamps 73 are attached to and arranged on the PCB board 77.

In addition, the second reflector 77 has a reflective effect by using an Ag-coated material made of Al.

In addition, the housing 75 is configured to surround the light emitting portions of each light emitting diode arranged on the PCB substrate 78, and is made of Al.

In the case of performing display in the liquid crystal display device using the backlight unit configured as described above, when each light emitting diode of the LED lamp 73 emits light, the light emitted from each light emitting diode enters the sub light guide plate 72. By scattering in the sub light guide plate 72, white light is emitted to the incident surface of the main light guide plate 71, and the white light is emitted from the entire surface of the main light guide plate 71 to illuminate the entire liquid crystal panel. do.

In this case, since the incident surfaces of the main LGP 71 and the sub LGP 72 are formed to be thicker than the emission surface, the light incidence efficiency can be increased, thereby reducing the thickness and weight of the conventional LGP 71.

The white light incident on the liquid crystal panel is modulated according to the alignment of the liquid crystal material and is transmitted through the color filter of the opposing substrate to output a color image.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

As described above, the backlight unit of the liquid crystal display according to the present invention has the following effects.

That is, by forming the incident surface of each light guide plate thicker than the exit surface, the light incidence efficiency can be increased to increase the color mixing efficiency, and the thickness and weight of the light guide plate can be reduced.

Claims (9)

delete delete delete delete delete delete A light source unit which emits light by arranging a plurality of green, blue and red light emitting diodes; A sub light guide plate that receives green, blue, and red light emitted from the light source and emits white light through scattering and color mixing therein, and the incident surface is thicker than the emission surface; A main light guide plate in which white light emitted from the sub light guide plate is incident and irradiated uniformly to the rear surface of the liquid crystal panel, and the incident surface is thicker than the exit surface; A housing for fixing the light source and condensing the light emitted from the light source in one direction; And a reflector configured to reflect the light leaking out to the opposite side of the liquid crystal panel, the backlight unit of the main light guide plate. The backlight unit of claim 7, wherein the reflecting plate comprises two reflecting plates. 8. The backlight unit of claim 7, wherein the reflector is coated with Al by Ag.

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