KR100823189B1 - Light emission device and liquid crystal display device using the same as back light unit - Google Patents

Abstract

A light emitting device and a liquid crystal display device having the same are provided to effectively radiate heat from a vacuum chamber by arranging a heat delivery medium inside the vacuum chamber. A light emitting device includes a first and second substrates(12,14), an electron emission unit(110), a fluorescent layer, an anode electrode, and a heat delivery medium(20). The first and second substrates are opposed to each other to form a vacuum chamber. The electron emission unit is arranged on an inner surface of the first substrate. The fluorescent layer is formed on an inner surface of the second substrate and emits light using electrons, which are emitted from the electron emission unit. The anode electrode is formed on one surface of the fluorescent layer. The heat delivery medium absorbs and radiates the heat from the vacuum chamber. The second substrate is divided into effective and non-effective regions. The heat delivery medium is formed on the non-effective region.

Description

LIGHT EMISSION DEVICE AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME AS BACK LIGHT UNIT}

1 is a cross-sectional view of a light emitting device according to an embodiment of the present invention.

2 is a cross-sectional view of a light emitting device according to another embodiment of the present invention.

3 is an exploded perspective view schematically illustrating a light emitting device according to another embodiment of the present invention.

4 is a partially cutaway perspective view of a light emitting device including an FEA type electron emission device.

FIG. 5 is a partial cross-sectional view of the light emitting device shown in FIG. 4.

6 is an exploded perspective view of a liquid crystal display device using a light emitting device as a backlight unit.

FIG. 7 is a partially cutaway perspective view of the liquid crystal panel assembly shown in FIG. 6.

8 is a block diagram of a configuration for driving a liquid crystal display device.

The present invention relates to a light emitting device and a liquid crystal display using the same as a backlight unit, and more particularly, to a heat dissipation structure of a light emitting device.

Recently, a liquid crystal display device, which is a type of flat panel display device, has been widely used in place of a cathode ray tube. The liquid crystal display has a characteristic of changing the amount of light transmission for each pixel by using the dielectric anisotropy of the liquid crystal whose twist angle changes according to the applied voltage.

Such a liquid crystal display device basically includes a liquid crystal panel assembly and a backlight unit positioned at the rear of the liquid crystal panel assembly to provide light to the liquid crystal panel assembly. The liquid crystal panel assembly receives light emitted from the backlight unit and transmits or blocks the light by the action of the liquid crystal layer to realize a predetermined image.

The backlight unit may be classified according to the type of light source, and one of them is a cold cathode fluorescent lamp (CCFL). Since the CCFL is a line light source, the light generated from the CCFL can be evenly distributed toward the liquid crystal panel assembly through optical members such as a diffusion sheet, a diffusion plate, and a prism sheet.

However, in the CCFL method, since the light generated by the CCFL passes through the optical member, considerable light loss occurs, and power consumption is high because the light must be emitted at a high intensity from the CCFL in consideration of the light loss. In addition, the CCFL method is difficult to apply to a large liquid crystal display device of 30 inches or more because it is difficult to large area structure.

As a conventional backlight unit, a light emitting diode (LED) method is known. A plurality of LEDs are usually provided as a point light source, and are combined with optical members such as a reflective sheet, a light guide plate, a diffusion sheet, a diffusion plate, and a prism sheet to constitute a backlight unit. This LED method has the advantages of fast response speed and excellent color reproducibility, but has a disadvantage of high price and large thickness.

As such, the conventional backlight unit has respective problems according to the type of light source. In addition, since the conventional backlight unit is always turned on at a constant brightness when the liquid crystal display is driven, it is difficult to meet the image quality improvement required for the liquid crystal display.

For example, when the liquid crystal panel assembly displays an arbitrary screen including a bright portion and a dark portion in accordance with an image signal, the backlight unit displays the liquid crystal panel pixels portion displaying the bright portion and the liquid crystal panel pixels displaying the dark portion. If the light of different intensity is provided to the part, it is possible to realize a screen having excellent dynamic contrast.

However, the above-described backlight unit cannot implement the above functions, and thus the conventional liquid crystal display device has a limitation in increasing the dynamic contrast ratio of the screen.

On the other hand, a field emission display device (FED, hereinafter referred to as FED) which displays by using an electron emission characteristic by an electric field is known, and a study for using this FED as a backlight unit of a liquid crystal display device is known. Development is in progress.

The FED is basically provided in a vacuum container composed of a first substrate, a second substrate and a sealing member, an electron emission unit including an electron emission portion and driving electrodes, provided on one surface of the first substrate, and provided on one surface of the second substrate, It consists of a light emitting unit comprising a layer and an anode electrode.

The electron emission unit emits electrons for each pixel according to a driving signal applied to the driving electrodes, and the anode electrode receives a direct current voltage of thousands of volts to accelerate the electrons to the fluorescent layer, and the accelerated electrons are the fluorescent layer of the corresponding pixel. Emit light.

In order to use the FED as a backlight unit, a higher luminance is applied to the anode electrode because the luminance of the screen must be increased than when the FED is used as the display device. Accordingly, the FED generates a lot of heat due to the increase in the amount of emission currents of the electron emission portion.

If such heat is not emitted to the outside and accumulated in the FED, there is a problem in that the lifetime of the electron-emitting part is decreased, and the luminance of the FED is decreased to function as a light emitting device. Although a separate cooling fan may be used for heat dissipation, the thickness of the FED increases due to the cooling fan.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a light emitting device having a heat dissipation structure capable of efficiently removing internal heat without increasing the thickness.

In addition, another object of the present invention is to provide a liquid crystal display device which can implement excellent screen quality by increasing the dynamic contrast ratio of the screen by employing the light emitting device as a backlight unit.

In order to achieve the above object, a light emitting device according to an embodiment of the present invention is disposed opposite to each other to constitute a vacuum container, a first substrate and a second substrate, an electron emission unit provided on an inner surface of the first substrate, the second A fluorescent layer formed on an inner surface of the substrate and emitting light by electrons emitted from the electron emitting unit, an anode formed on one surface of the fluorescent layer, and a heat transfer medium positioned inside the vacuum container to absorb and emit heat The second substrate is divided into an effective region where actual light is emitted and an invalid region located outside the effective region, and the heat transfer medium is formed on the side of the invalid region.

In addition, the heat transfer medium may be made of a refrigerant injected into the chamber.

In addition, the vacuum container may include a sealing member formed along an edge between the first substrate and the second substrate, and the chamber may be formed by a partition wall positioned inside the sealing member.

In addition, the partition wall may vertically connect the first substrate and the second substrate.

In addition, the partition wall may be formed in a closed curve along the sealing member.

In addition, the partition wall may be formed on any one of the first substrate and the second substrate.

In addition, the refrigerant may include an ethylene-based material such as ethylene glycol.

In addition, the electron emission unit may include a cathode electrode, a gate electrode, and an electron emission portion connected to the cathode electrode, which are formed along a direction crossing each other with an insulating layer interposed therebetween.

In addition, the electron emission unit may include at least one of a carbon-based material and a nanometer size material.

In addition, the light emitting device according to the embodiment of the present invention can be used in the liquid crystal display as a backlight unit. Accordingly, the liquid crystal display according to the exemplary embodiment of the present invention includes a liquid crystal panel assembly having a plurality of pixels in a row direction and a column direction, and the light emitting device positioned behind the liquid crystal panel to function as a backlight unit. .

In addition, the light emitting device may have a smaller number of pixels than the liquid crystal panel assembly in the row direction and the column direction, and may emit light of different intensity for each pixel.

In addition, the light emitting device may express a gray level of 2 to 8 bits for each pixel.

In addition, the fluorescent layer may be formed of a white fluorescent layer, or may be formed of a red, green, and blue fluorescent layer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like elements throughout the specification.

1 is a cross-sectional view of a light emitting device according to an embodiment of the present invention.

Referring to FIG. 1, the light emitting device 100A includes a first substrate 12 and a second substrate 14 disposed to face each other at predetermined intervals. The sealing member 16 is disposed at the edge of the first substrate 12 and the second substrate 14 to bond the two substrates, and thus the first substrate 12, the second substrate 14, and the sealing member 16. ) Constitutes a vacuum vessel. The inner space of the vacuum vessel is evacuated to a vacuum of approximately 10 ⁻⁶ Torr.

The sealing member 16 is made of frit glass in the form of a bar, or the glass frame provided between the first substrate 12 and the second substrate 14 and the glass frame are both. It may be made of frit glass bonded to a substrate.

The electron emission unit 110 is disposed on the inner surface of the first substrate 12 of the vacuum vessel, and the light emitting unit 120 is disposed on the inner surface of the second substrate 14 of the vacuum vessel. Spacers 18 are disposed between the light emitting units 120 to maintain a gap between the first substrate 12 and the second substrate 14.

In addition, a heat transfer medium 20 for removing heat generated from the electron emission unit 110 and the light emitting unit 120 is formed in the vacuum container.

The second substrate 14 may be divided into an effective area A in which light is actually emitted and an invalid area NA located at an outer side of the effective area A. The heat transfer medium 20 may be an invalid area NA. ) Side. The heat transfer medium 20 is irrelevant to the state of a solid, liquid, or the like as long as it can absorb heat inside the vacuum vessel and release it to the outside.

In addition, the heat transfer medium 20 may be formed locally at the non-effective area NA, or may be formed surrounding the effective area A. FIG.

In addition, a diffusion plate 22 may be formed on the outer surface of the second substrate 14 to disperse the light emitted from the light emitting unit 120.

Heat absorbed by the heat transfer medium 20 may be discharged to the outside through a heat sink (not shown) positioned at the rear surface of the first substrate 12.

2 is a cross-sectional view of a light emitting device according to another embodiment of the present invention, Figure 3 is an exploded perspective view schematically showing a light emitting device according to another embodiment of the present invention.

2 and 3, the heat transfer medium may include, for example, a refrigerant 24 injected into the chamber 23 inside the vacuum container.

The chamber 23 may be formed by a partition 26 positioned inside the sealing member 16. The partition wall 26 is configured to vertically connect the first substrate 12 and the second substrate 14 to form a chamber 23 together with the sealing member 16. As such, when the partition wall 26 connects the first substrate 12 and the second substrate 14, there is an advantage that the spacer 26 may maintain a gap between the two substrates 12 and 14.

In addition, the partition wall 26 may be formed in a closed curve along the sealing member 16, as shown in FIG. 3.

In addition, the partition wall may be formed only on one of the first substrate 12 and the second substrate 14 inside the sealing member 16 to form a chamber together with the one substrate. That is, the partition wall may be variously modified if it can form a chamber into which the refrigerant can be injected.

The partition wall 26 may be made of a glass material like the sealing member 16, but may be made of a metal or an alloy having good thermal conductivity.

In addition, the refrigerant 24 filled in the chamber 23 discharges heat generated in the vacuum container to the outside through a heat sink (not shown). This refrigerant 24 may comprise an ethylene-based material such as ethylene glycol.

4 is a partially cutaway perspective view of a light emitting device including an FEA type electron emission device, and FIG. 5 is a partial cross-sectional view of the light emitting device shown in FIG. 4.

The light emitting device 100 includes an electron emitting unit consisting of an electron emitting device, which may be classified into a method using a hot cathode and a cold cathode according to the type of electron source. Can be.

Herein, an electron emission device using a cold cathode is referred to as a field emitter array (FEA) type, surface-conduction emission (SCE), or "SCE". ), Metal-insulator-metal (MIM) type and metal-insulator-semiconductor (MIS) type There is this.

The light emitting device 100 according to the embodiment of the present invention includes, for example, an electron emission unit made of an FEA type electron emission device.

4 and 5, the electron emission unit 110 may include cathode electrodes 28 formed in a stripe pattern along one direction (y-axis direction in FIG. 4) of the first substrate 12 and an insulating layer. Gate electrodes 32 formed in a stripe pattern along a direction orthogonal to the cathode electrode 28 (in the x-axis direction in FIG. 4) with an interposed portion 30 interposed therebetween, and electrons electrically connected to the cathode electrode 28. Discharge portions 34.

The gate electrodes 32 may receive scan signals to function as scan electrodes, and the cathode electrodes 28 may receive data signals to serve as data electrodes.

Electron emitters 34 are formed in the cathode electrode 28 at each intersection of the cathode electrode 28 and the gate electrode 32. Openings 301 and 321 corresponding to the electron emission portions 34 are formed in the insulating layer 30 and the gate electrodes 32 so that the electron emission portions 34 are exposed on the first substrate 12. do.

In the above-described structure, one intersection region of the cathode electrode 28 and the gate electrode 32 may correspond to one pixel region of the light emitting device, or two or more intersection regions may correspond to one pixel region of the light emitting device. In the second case, two or more cathode electrodes 28 and two or more gate electrodes 32 corresponding to one pixel area may be electrically connected to each other to receive the same driving voltage.

The electron emission part 34 is made of materials that emit electrons when an electric field is applied in a vacuum, such as a carbon-based material or a nanometer (nm) size material. The electron emission part 34 may include, for example, carbon nanotubes, graphite, graphite nanofibers, diamonds, diamond-like carbons, fullerenes (C ₆₀ ), silicon nanowires, or a combination thereof. The method of manufacturing the electron emission part 34 may include screen printing, direct growth, chemical vapor deposition, or sputtering.

On the other hand, the electron emission portion may be formed of a tip structure having a pointed tip mainly made of molybdenum (Mo) or silicon (Si).

Next, the light emitting unit 120 provided on the second substrate 14 includes a fluorescent layer 36 and an anode electrode 38 positioned on one surface of the fluorescent layer 36. The fluorescent layer 36 may be formed of a white fluorescent layer or a combination of red, green, and blue fluorescent layers. In the figure, the first case is illustrated.

The white fluorescent layer may be formed on the entirety of the second substrate 14, or may be divided and positioned in a predetermined pattern such that one white fluorescent layer is positioned in each pixel area. The red, green, and blue fluorescent layers may be divided and positioned in a predetermined pattern in one pixel area.

The anode electrode 38 may be formed of a metal film such as aluminum (Al) covering the surface of the fluorescent layer 36. The anode 38 is an acceleration electrode for attracting an electron beam, and is applied with a high voltage (a positive DC voltage of approximately several thousand volts) to maintain the fluorescent layer 36 in a high potential state. The luminance of the screen is increased by reflecting the visible light emitted toward the first substrate 12 toward the second substrate 14.

In the above configuration, when a predetermined driving voltage is applied to the cathode electrodes 28 and the gate electrodes 32, an electric field is formed around the electron emission section 34 in the pixel region where the voltage difference between the two electrodes is greater than or equal to the threshold. Electrons are emitted. The emitted electrons are attracted by the high voltage applied to the anode electrode 38 and collide with the corresponding fluorescent layer 36 to emit light. The emission intensity of the pixel-specific fluorescent layer 36 corresponds to the electron beam emission amount of the pixel.

In the driving process as described above, heat generated from the electron emission unit and the light emitting unit is discharged to the outside through the refrigerant and the heat sink.

The light emitting devices 100A and 100B of the above-described embodiments may be used as backlight units of the liquid crystal display device described below.

6 is an exploded perspective view of a liquid crystal display device using a light emitting device as a backlight unit, and FIG. 7 is a partially cutaway perspective view of the liquid crystal panel assembly illustrated in FIG. 6.

Referring to FIG. 6, the liquid crystal display 200 according to the exemplary embodiment of the present invention may include a liquid crystal panel assembly 210 having arbitrary pixels in a row direction and a column direction, and a rear side of the liquid crystal panel assembly 210. Positioned to provide light to the liquid crystal panel assembly 210.

The light emitting device 100 according to the embodiment of the present invention has a smaller number of pixels than the liquid crystal panel assembly 210 along the row direction and the column direction, so that one pixel of the light emitting device 100 has two or more liquid crystal panel assemblies 210. ) Corresponds to pixels.

Here, the row direction may be defined as one direction of the liquid crystal display 200, for example, the horizontal direction (the x-axis direction in FIG. 6) of the screen implemented by the liquid crystal panel assembly 210, and the column direction may be the liquid crystal display ( Another direction of 200 may be defined as, for example, a vertical direction (y-axis direction in FIG. 6) of a screen implemented by the liquid crystal panel assembly 210.

In this case, the cathode electrode 28 of the light emitting device 100 may be formed in parallel with the column direction, and the gate electrode 32 of the light emitting device 100 may be formed in parallel with the row direction.

The number of pixels of the liquid crystal panel assembly 210 and the number of pixels of the light emitting device 100 along the row direction are referred to as M and M ', respectively, and the number of pixels and the light emitting device 100 of the liquid crystal panel assembly 210 along the column direction. If the number of pixels of N and N 'are respectively, the number of pixels (resolution) of the liquid crystal panel assembly 210 can be expressed as M × N, and the number of pixels (resolution) of the light emitting device 100 is M' × N '. Can be expressed as

In this case, M and N representing the number of pixels of the liquid crystal panel assembly 210 may be defined as an integer of 240 or more, respectively, and M 'and N' representing the number of pixels of the light emitting device 100 may be any one of 2 to 99. Can be defined as an integer.

According to the above-described configuration, the light emitting device 100 may increase the dynamic contrast ratio of the screen by providing light having different intensity to the pixels of the liquid crystal panel assembly 210 corresponding to each pixel.

Referring to FIG. 7, the liquid crystal panel assembly 210 is a liquid crystal injected between a transparent third substrate 42 and a fourth substrate 44 and a third substrate 42 and a fourth substrate 44 disposed to face each other. Layer 46; Pixel electrodes 48 and switching elements 50 are formed on an inner surface of the third substrate 42, and a common electrode 52 is formed on an inner surface of the fourth substrate 44.

On the outer surface of the third substrate 42 and the fourth substrate 44, a pair of polarizing plates 54 and 56 having polarization axes orthogonal to each other are positioned, and the alignment layers 58 are disposed to face each other with the liquid crystal layer 46 therebetween. Is done.

A plurality of gate lines 60 transmitting a gate signal (scan signal) and a plurality of data lines 62 transmitting a data signal are formed on an inner surface of the third substrate 42. The gate lines 60 are located next to each other along the row direction, and the data lines 62 are located next to each other along the column direction.

One pixel electrode 48 is positioned for each sub-pixel and is connected to the gate line 60 and the data line 62 through the switching element 50.

The color filter 64 is disposed between the fourth substrate 44 and the common electrode 52. The color filter 64 is composed of red, green, and blue filters corresponding to one sub-pixel, and three sub-pixels in which three filters of red, green, and blue are located constitute one pixel.

When the switching element 50 is turned on in the liquid crystal panel assembly 210 having the above-described configuration, an electric field is formed between the pixel electrode 48 and the common electrode 52, and the electric field is positioned in the liquid crystal layer 46 by the electric field. The twist angle of the liquid crystal molecules is changed. The liquid crystal panel assembly 210 implements a predetermined color image by controlling the amount of light transmission by adjusting the twist angle of the liquid crystal molecules for each sub-pixel.

8 is a block diagram of a configuration for driving a liquid crystal display device.

Referring to FIG. 8, the liquid crystal display of the present exemplary embodiment is connected to the liquid crystal panel assembly 210, the gate driver 212 and the data driver 214 connected to the liquid crystal panel assembly 210, and the data driver 214. And a gray voltage generator 216, a light emitting device 100, and a signal controller 218 for controlling them.

The liquid crystal panel assembly 210 includes a plurality of signal lines G ₁ -G _n , D ₁ -D _m , and a plurality of pixels PX connected to the signal lines and arranged in a substantially matrix form when viewed in an equivalent circuit. ). The signal lines G ₁ -G _n and D ₁ -D _m are a plurality of gate lines G ₁ -G _n for transmitting a gate signal (also called a “scan signal”), and a plurality of data lines for transmitting a data signal. (D ₁ -D _m ).

Each pixel PX, for example, the i-th (i = 1,2, ... n) gate line G _i and the j-th (j = 1,2, ... m) data line D _j The pixel 211 connected to includes a switching element Q connected to the signal lines G _i and D _j , a liquid crystal capacitor Clc, and a storage capacitor Cst connected thereto. Holding capacitor Cst can be omitted as needed.

The switching element Q is a three-terminal element such as a thin film transistor, which is provided on the lower substrate (not shown) of the liquid crystal panel assembly 210, the control terminal of which is connected to the gate line G _i , and the input terminal is connected to the data. It is connected to the line D _j , and the output terminal is connected to the liquid crystal capacitor Clc and the storage capacitor Cst.

The gray voltage generator 216 generates two sets of gray voltages (or a set of reference gray voltages) related to the transmittance of the pixel PX. One of the two sets has a positive value for the common voltage Vcom, and the other set has a negative value.

A gate driver 212, the gate lines of the liquid crystal panel assembly _{(210) (G 1 -G n} ) and is connected to the gate turn-on voltage (Von) and the gate line Gate a gate signal which is a combination of a turn-off voltage (Voff) (G ₁ -G _n ).

The data driver 214 is connected to the data lines D ₁ -D _m of the liquid crystal panel assembly 210, selects a gray voltage from the gray voltage generator 216, and uses the data line D ₁ -D as a data signal. _m ). However, when the gray voltage generator 216 provides only a predetermined number of reference gray voltages instead of providing all of the voltages for all grays, the data driver 214 divides the reference gray voltages and thus the gray voltages for all grays. Generate and select the data signal from it.

The signal controller 218 controls the gate driver 212, the data driver 214, the light emitting device controller 220, and the like. The signal controller 218 receives input image signals R, G, and B and an input control signal for controlling the display thereof from an external graphic controller (not shown).

The input image signals R, G, and B contain luminance information of each pixel PX, and luminance has a predetermined number, for example, 1024 (= 2 ¹⁰ ), 256 (= 2 ⁸ ), or 64 ( = 2 ⁶ ) There are grays. Examples of the input control signal include a vertical sync signal Vsync, a horizontal sync signal Hsync, a main clock MCLK, and a data enable signal DE.

The signal controller 218 properly processes the input image signals R, G and B based on the input image signals R, G and B and the input control signal according to the operating conditions of the liquid crystal panel assembly 210, and controls the gate. After generating the signal CONT1 and the data control signal CONT2, the gate control signal CONT1 is sent to the gate driver 212, and the data control signal CONT2 and the processed image signal DAT are transmitted to the data driver. Export to 214. In addition, the signal controller 218 transmits the gate control signal CONT1, the data control signal CONT2, and the processed image signal DAT to the light emitting device controller 220.

The light emitting device 100 includes a light emitting device controller 220, a column driver 222, a scan driver 224, and a display unit 226.

The display unit 226 includes a plurality of scan lines S ₁ -S _p for transmitting scan signals, a plurality of column lines C ₁ -C _q for transferring column signals, and a plurality of light emitting pixels EPX. . Each of the plurality of light emitting pixels EPX is positioned in a region defined by scan lines S ₁ -S _p and column lines C ₁ -C _q intersecting the scan lines. Scan lines S ₁ -S _p are connected to scan driver 224, and column lines C ₁ -C _q are connected to column driver 222. In addition, the scan driver 224 and the column driver 222 are connected to the light emitting device controller 220 and operate according to a control signal of the light emitting device controller 220.

The plurality of scan lines S ₁ -S _p are scan electrodes of the above-described light emitting device, and the column lines C ₁ -C _q are data electrodes.

The light emitting device controller 220 generates and transmits a scan driver control signal CS for controlling the scan driver 224 using the gate control signal CONT1. A column driver control signal CC is generated using the data control signal, and a column signal CLS corresponding to the image signal DAT is generated. The generated column driver control signal CS and the column signal CLS are transmitted to the column driver 222. The light emitting device controller 220 generates luminance information for each pixel of the light emitting device 100 from the image signal DAT of one frame, and generates a column signal CLS according to the generated luminance information.

The scan driver 224 sequentially applies a scan signal having a predetermined pulse to the scan lines S ₁ -S _p based on the received scan driver control signal. The column driver 222 applies a driving voltage corresponding to the color signal to each column line C ₁ -C _q according to the input column driver control signal.

By the above-described configuration, the display unit 226 of the light emitting device 100 receives a driving signal synchronized with the image signal and emits light of an appropriate intensity according to the luminance information of each pixel, which is transmitted to the liquid crystal panel assembly 210. to provide. Each of the light emitting pixels EPX of the light emitting device display unit 226 may be driven so that gray scale representation of 2 to 8 bits is possible.

As a result, when the liquid crystal panel assembly 210 displays a screen having different brightness for each position, the light emitting device 100 provides strong light to the pixels of the liquid crystal panel assembly 210 displaying the bright portion, and the dark portion. Weak light may be provided to a portion of the pixels of the liquid crystal panel assembly 210 that displays. In addition, the light emitting pixels of the light emitting device 100 corresponding to the pixels of the liquid crystal panel assembly 210 displaying black may be turned off.

As a result, the liquid crystal display 200 of the present exemplary embodiment may improve the dynamic contrast of the screen through the above-described process.

As described above, the liquid crystal display 200 according to the exemplary embodiment of the present invention uses the light emitting device 100 having the above-described configuration as a backlight unit, and thus, when compared to the conventional CCFL and LED backlight units, Has an advantage.

Since the light emitting device according to the embodiment of the present invention is a surface light source, it does not require a plurality of optical members used in the CCFL type and the LED type backlight unit. Therefore, the liquid crystal display according to the exemplary embodiment of the present invention has almost no light loss generated through the optical member, and does not have to emit excessive intensity light in consideration of the light loss, thereby obtaining excellent efficiency with low power consumption.

In addition, the light emitting device according to the embodiment of the present invention can reduce the cost according to not using the optical member, the manufacturing cost is lower than the LED type backlight unit. In addition, since the light emitting device according to the embodiment of the present invention is easily enlarged, the light emitting device may be easily applied to a large liquid crystal display of 30 inches or more.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

The light emitting device according to the embodiment of the present invention has a heat transfer medium such as a refrigerant inside the vacuum container even when used for high brightness, such as a backlight unit, thereby efficiently dissipating heat inside the vacuum container while maintaining a constant thickness. have.

In addition, the light emitting device according to the embodiment of the present invention does not need a separate cooling fan and is compactly formed as a whole, and can improve the lifespan of the electron emission unit due to an increase in heat radiation efficiency.

In addition, the liquid crystal display according to the exemplary embodiment of the present invention using the light emitting device as the backlight unit may increase the dynamic contrast ratio of the screen to improve display quality, reduce power consumption, and facilitate enlargement.

Claims (17)

A first substrate and a second substrate disposed opposite to each other to constitute a vacuum container; An electron emission unit provided on an inner surface of the first substrate; A fluorescent layer formed on an inner surface of the second substrate and emitting light by electrons emitted from the electron emission unit; An anode formed on one surface of the fluorescent layer; And Heat transfer medium located inside the vacuum vessel to absorb and release heat Including; The second substrate is divided into an effective area where actual light is emitted and an invalid area located outside the effective area, And the heat transfer medium is formed on the ineffective region side. The method of claim 1, And the heat transfer medium comprises a refrigerant injected into the chamber. The method of claim 2, The vacuum container includes a sealing member formed along an edge between the first substrate and the second substrate, The chamber is a light emitting device formed by a partition wall located inside the sealing member. The method of claim 3, And the partition wall vertically connects the first substrate and the second substrate. The method of claim 4, wherein The partition wall forms a closed curve along the sealing member. The method of claim 3, The partition wall is formed on any one of the first substrate and the second substrate. The method of claim 2, The refrigerant includes an ethylene-based material. The method of claim 1, The electron emission unit, A cathode electrode and a gate electrode formed in a direction crossing each other with an insulating layer interposed therebetween; And An electron emission unit connected to the cathode electrode; Light emitting device comprising a. The method of claim 8, The light emitting device of claim 1, wherein the electron emission unit comprises at least one of a carbon-based material and a nanometer-sized material. A liquid crystal panel assembly having a plurality of pixels along the row direction and the column direction; And A light emitting device positioned behind the liquid crystal panel assembly and functioning as a backlight unit; The light emitting device, A first substrate and a second substrate disposed opposite to each other to constitute a vacuum container; An electron emission unit provided on an inner surface of the first substrate; A fluorescent layer formed on an inner surface of the second substrate and emitting light by electrons emitted from the electron emission unit; An anode formed on one surface of the fluorescent layer; And A heat transfer medium located inside the vacuum vessel to absorb and release heat; The second substrate is divided into an effective area where actual light is emitted and an invalid area located outside the effective area, And the heat transfer medium is formed on the ineffective region side. The method of claim 10, And the heat transfer medium comprises a refrigerant injected into the chamber. The method of claim 11, The vacuum container includes a sealing member formed along an edge between the first substrate and the second substrate, And the chamber is formed by the sealing member and a partition wall positioned inside the sealing member. The method of claim 11, The refrigerant includes an ethylene-based material. The method of claim 10, The light emitting device, And a smaller number of pixels in the row direction and the column direction than the liquid crystal panel assembly, and emit light of different intensity for each pixel. The method of claim 14, The light emitting device is a liquid crystal display device to represent the gray level of 2 to 8 bits (bit) for each pixel. The method of claim 10, The liquid crystal display device in which the said fluorescent layer consists of a white fluorescent layer. The method of claim 10, And a fluorescent layer comprises a red, green, and blue fluorescent layer.

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