Light emission device including a heat dissipation plate and a thermal diffuser plate

A light emission device and a display device using the light emission device as a light source are provided. The light emission device includes first and second substrates facing each other, an electron emission unit located on an inner surface of the first substrate, a phosphor layer located on an inner surface of the second substrate and adapted to be excited by electrons emitted from the electron emission unit, an anode electrode located on the phosphor layer, a heat dissipation plate located at a side of the first substrate, and a thermal diffuser plate located on the second substrate and thermally coupled to the heat dissipation plate. The thermal diffuser plate is configured to transmit light emitted by the phosphor layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2006-0055456 filed on Jun. 20, 2006 in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emission device and a display device using the light emission device as a light source.

2. Description of Related Art

A liquid crystal display (LCD), which is a flat panel display device, displays an image by varying a light transmission amount at each pixel using a dielectric anisotropy property of liquid crystal that varies in a twisting angle according to a voltage applied.

The liquid crystal display includes a liquid crystal (LC) panel assembly and a backlight unit for emitting light toward the liquid crystal panel assembly. The liquid crystal panel assembly receives light emitted from the backlight unit and selectively transmits or blocks the light using a liquid crystal layer.

The backlight unit is classified according to a light source into different types, one of which is a cold cathode fluorescent lamp (CCFL). The CCFL is a linear light source that can uniformly emit light to the liquid crystal panel assembly through an optical member such as a diffusion sheet, a diffuser plate, and/or a prism sheet.

However, in the backlight unit employing the CCFL, since the CCFL emits the light through the optical members, there may be a light loss. Considering the light loss, the intensity of the light emitted from the CCFL must be increased. Therefore, the power consumption of the backlight unit employing the CCFL increases. In addition, since the backlight unit employing the CCFL cannot be large-sized due to its structural limitation, it cannot be applied to a large-sized liquid crystal display over 30-inch.

A backlight unit employing light emitting diodes (LEDs) is also well known. The LEDs are point light sources that are combined with optical members such as a reflection sheet, a light guiding plate (LGP), a diffusion sheet, a diffuser plate, a prism sheet, and/or the like, thereby forming the backlight unit. The LED type backlight unit has fast response speed and good color reproduction. However, the LED is costly and increases an overall thickness of the liquid crystal display.

As described above, the conventional backlight units have their inherent problems. In addition, the conventional backlight units must maintain a predetermined brightness when the liquid crystal display is being driven. Therefore, it is difficult to improve the display quality to a sufficient level.

SUMMARY OF THE INVENTION

In exemplary embodiments according to the present invention, a light emission device that can effectively dissipate heat generated from a substrate on which a light emission unit is disposed, is provided. Such light emission device can be used as a backlight unit.

In exemplary embodiments according to the present invention, a display device that can improve a display quality by enhancing the dynamic contrast by employing the light emission device as a light source, is also provided. The display device may be a liquid crystal display, and the light source may be a backlight unit for the liquid crystal display.

According to an exemplary embodiment of the present invention, a light emission device is provided. The light emission device includes a first substrate having a first side and a second side opposite the first side; a second substrate having a first side and a second side opposite the first side, the first sides of the first and second substrates facing each other; an electron emission unit located on the first side of the first substrate; a phosphor layer located on the first side of the second substrate and adapted to be excited by electrons emitted from the electron emission unit; an anode electrode located on the phosphor layer; a heat dissipation plate located at the second side of the first substrate; and a thermal diffuser plate located on the second substrate and thermally coupled to the heat dissipation plate, the thermal diffuser plate being configured to transmit light emitted by the phosphor layer.

The thermal diffuser plate may extend to the first substrate and the heat dissipation plate may be located on an outer surface of the thermal diffuser plate at the first substrate.

The thermal diffuser plate may have a light transmissivity of at least 80%.

The thermal diffuser plate may be transparent.

The thermal diffuser plate may be formed of a ceramic material.

The ceramic material may include at least one of aluminum oxide or titanium oxide.

The heat dissipation plate may include a material selected from the group consisting of Al, Ag, Cu, Au, Pt, and an alloy thereof.

The heat dissipation plate may include a base and a plurality of heat dissipation fins located on the base and spaced apart from each other.

The heat dissipation plate may be thermally coupled to a circuit unit to dissipate heat generated from the circuit unit.

The electron emission unit may include a cathode electrode and a gate electrode insulated from each other and crossing each other, and electron emission regions electrically connected to the cathode electrode.

The electron emission regions may include at least one of a carbon-based material or a nanometer-sized material.

In another exemplary embodiment, a display device is provided. The display device includes a display panel having a plurality of pixels arranged in rows and columns; and a light emission device disposed behind the display panel and configured to function as a light source for the display device. The light emission device includes: a first substrate having a first side and a second side opposite the first side; a second substrate having a first side and a second side opposite the first side, the first sides of the first and second substrates facing each other; an electron emission unit located on the first side of the first substrate; a phosphor layer located on the first side of the second substrate and adapted to be excited by electrons emitted from the electron emission unit; an anode electrode located on the phosphor layer; a heat dissipation plate located at the second side of the first substrate; and a thermal diffuser plate located on the second substrate and thermally coupled to the heat dissipation plate, the thermal diffuser plate being configured to transmit light emitted by the phosphor layer.

The thermal diffuser plate may be formed of a ceramic material.

The light emission device may have a plurality of pixels arranged in rows and columns, the number of the pixels of the light emission device being less than that of the pixels of the liquid crystal panel assembly and the pixels of the light emission device are adapted to emit lights having different light intensities.

The light emission device may be adapted to represent a gray of 2-8 bits for each pixel.

The phosphor layer may be a white phosphor layer or may include red, green and blue phosphor layers.

DETAILED DESCRIPTION

When a liquid crystal panel assembly is used to display an image having a bright portion and a dark portion in response to an image signal, it will be possible to realize an image having a more improved dynamic contrast if the backlight unit can emit lights having different intensities to pixels for the dark portion and pixels for the bright portion of the liquid crystal panel assembly. Similarly, the dynamic contrast can be improved for any display device having a separate light source, if the light source can emit lights having different intensities to dark and bright portions of a display panel (e.g., non-self emissive type display panel) in the display device.

However, conventional backlight units cannot achieve the above function and thus there is a limit to improving the dynamic contrast of the image displayed by the liquid crystal display.

In exemplary embodiments according to the present invention, a field emission display (FED) that is capable of displaying an image using an electron emission property in response to an electric field, is used as the backlight unit of the liquid crystal display.

A typical field emission display includes a vacuum envelope having front and rear substrates and a sealing member, an electron emission unit provided on the first substrate and having electron emission regions and driving electrodes, and a light emission unit provided on the second substrate and having a phosphor layer and an anode electrode.

The electron emission regions emit electrons in response to driving signals. The anode electrode receives a positive DC voltage of thousands of volts to accelerate the electrons to the phosphor layers, thereby exciting the phosphor layers of target pixels.

In order to use the FED as the backlight unit, in one embodiment, a higher positive voltage is applied to the anode electrode to increase the brightness compared with a case where the FED is used as a display device. That is, the backlight unit must provide a brightness higher than 10,000 cd/m2. Therefore, when the FED is used as the backlight unit, a relatively large amount of heat is generated in the FED. When the generated heat is not dissipated to an external side but accumulated in the FED, the substrates may be damaged and the driving error may occur.

In order to dissipate the heat generated from a circuit unit arranged on the rear substrate, a cooling fan or a heat dissipation plate is typically installed near the rear substrate. However, the heat generated from the front substrate is generally not effectively dissipated.

FIG. 1is a sectional view of a light emission device according to an embodiment of the present invention.

Referring toFIG. 1, a light emission device100A of this exemplary embodiment includes first and second substrates12and14facing each other with a distance or interval (e.g., a predetermined distance) between them. A sealing member (or sealer)16is provided at the peripheries of the first and second substrates12and14to seal them together and thus form a vacuum envelope. The interior of the sealed vessel is exhausted to be kept to a degree of vacuum of about 10−6Torr.

An electron emission unit110for emitting electrons is provided on an inner surface of the first substrate12, and a light emission unit120for emitting the visible light is provided on an inner surface of the second substrate14. Spacers18are arranged between the electron emission unit110and the light emission unit120to maintain a gap (e.g., a predetermined gap) between the first and second substrates12and14.

A heat dissipation plate20is formed on the first substrate12. A thermal diffuser22that is adapted to transmit the light emitted from the light emission unit120is formed on an outer surface of the second plate14. A connecting member (or connector)24is disposed between the heat dissipation plate20and the thermal diffuser plate22for the thermal conduction between them.

The heat dissipation plate20includes a base201contacting the first substrate12and a plurality of heat dissipation fins202arranged on the base201and spaced apart from each other. The heat dissipation fins202increase the contact area of the heat dissipation plate20with the outside air.

The heat dissipation plate20may be formed of Al, Ag, Cu, Pt, or any combination thereof.

The heat dissipation plate20is connected (or thermally coupled) to a circuit unit (not shown) for supplying electric power to the electron emission unit110and the light emission unit120, so as to dissipate heat generated from the circuit unit.

The thermal diffuser plate22transmits (or transfers) the heat generated from the light emission unit120to the heat dissipation plate20. Since the thermal diffuser plate22is formed on the outer surface of the second substrate14formed on the screen (i.e., light emitting side of the light emission device), the thermal diffuser plate22is designed to transmit light. For example, the thermal diffuser plate22may be transparent or substantially transparent.

The thermal diffuser plate22may be formed of a ceramic material such as aluminum oxide (Al2O3), titanium oxide (TiO2), or a combination thereof.

The thermal diffuser plate22may have a light transmissivity of 80% or more in one embodiment. When the light transmissivity is less than 80% in one embodiment, the light loss increases. In this case, power consumption increases to compensate for the light loss.

The connecting member (or connector)24connects (couples or thermally couples) the heat dissipation plate20to the thermal diffuser plate22. The connection member24may contact an outer surface of the sealing member16or be spaced apart form the sealing member16. The connecting member24may be formed of any material (or materials) that can transmit heat. For example, the connecting member24may be formed of a material identical to that of the heat dissipation plate20or the thermal diffuser plate22.

FIG. 2is a partially broken, exploded perspective view of the light emission device shown inFIG. 1, andFIG. 3is a partial sectional view taken along a line III-III of the light emission device shown inFIG. 2.

The light emission device has the electron emission unit110having an array of electron emission elements. Generally, the electron emission elements are classified into those using hot cathodes as an electron emission source, and those using cold cathodes as the electron emission source.

There are several types of cold cathode electron emission elements, including Field Emitter Array (FEA) elements, Surface Conduction Emitter (SCE) elements, Metal-Insulator-Metal (MIM) elements, and Metal-Insulator-Semiconductor (MIS) elements.

The light emission device100A of this embodiment includes an electron emission unit having an array of FEA elements.

Referring toFIGS. 2 and 3, the electron emission unit110includes cathode electrodes26arranged in a stripe pattern running in a direction (i.e., in a direction of a y-axis inFIG. 2) on the first substrate12, gate electrodes30arranged in a stripe pattern running in a direction (i.e., in a direction of an x-axis inFIG. 2) crossing the cathode electrodes26at a right angle, an insulation layer28interposed between the cathode electrodes26and the gate electrodes30, and electron emission regions32electrically connected to the cathode electrodes26.

The gate electrodes30function as scan electrodes for receiving scan signals while the cathode electrodes26function as data electrodes for receiving data signals.

Openings281and301corresponding to the respective electron emission regions32are formed through the insulation layer28and the gate electrodes30, respectively, at crossing areas of the cathode and gate electrodes26and30to expose the electron emission regions32.

One crossing area of the cathode and gate electrodes26and30may correspond to one pixel area of the light emission device. Alternatively, two or more crossing areas of the cathode and gate electrodes26and30may correspond to one pixel area of the light emission device. In this case, according to one embodiment, two or more first electrodes26and/or two or more gate electrodes30that correspond to one pixel area are electrically connected to each other to receive a common driving voltage.

The electron emission regions32are formed of a material that emits electrons when an electric field is applied thereto under a vacuum atmosphere, such as a carbon-based material or a nanometer-sized material. For example, the electron emission regions32can be formed of carbon nanotubes, graphite, graphite nanofibers, diamonds, diamond-like carbon, C60, silicon nanowires or a combination thereof. The electron emission regions32can be formed, for example, through a screen-printing process, a direct growth, a chemical vapor deposition, or a sputtering process.

Alternatively, the electron emission regions can be formed to have a tip structure formed of a Mo-based or Si-based material.

The light emission unit120includes a plurality of phosphor layers34and an anode electrode36. The phosphor layers34may be white phosphor layers or a combination of red, green and blue phosphor layers. The former is shown inFIG. 2, for example.

The white phosphor layer may be formed on an entire surface of the second substrate14or formed in a pattern (e.g., a predetermined pattern) having a plurality of sections each corresponding to one pixel area. The red, green and blue phosphor layers, for example, may be formed in a predetermined pattern in one pixel area.

The anode electrode36covers the phosphor layers34, an may be formed of metal such as Al. The anode electrode36is an acceleration electrode that receives a high voltage to maintain the phosphor layer34at a high electric potential state. The anode electrode36functions to enhance the brightness by reflecting the visible light, which is emitted from the phosphor layers34toward the first substrate12, to the second substrate14.

When driving voltages are applied to the cathode and gate electrodes26and30, an electric field is formed around the electron emission regions32at pixel areas where a voltage difference between the cathode and gate electrodes26and30is higher than a threshold value, thereby emitting electrons from the electron emission regions32. The emitted electrons are accelerated by the high voltage applied to the anode electrode36to collide with the corresponding phosphor layer34, thereby exciting the phosphor layer34. A light emission intensity of the phosphor layer34at each pixel corresponds to an electron emission amount of the corresponding pixel.

In the above-described driving process, heat generated from the electron emission unit110is directly dissipated through the first substrate12and the heat dissipation plate20. Heat generated from the light emission unit120is dissipated through the second substrate14, the thermal diffuser plate22, the connecting member24, and the heat dissipation plate20.

FIG. 4is a sectional view of a light emission device according to another embodiment of the present invention. In this embodiment, parts identical to those of the foregoing embodiment are assigned with like reference numerals.

Referring toFIG. 4, a light emission device100B includes a thermal diffuser plate38that is continuously formed on an entire outer surface of the vacuum envelope. That is, the thermal diffuser plate38is formed on the first and second substrates12and14and the sealing member16. The heat dissipation plate20is formed on an outer surface of the thermal diffuser plate38at the first substrate12. According to this embodiment, the heat dissipation plate20directly contacts (or is directly connected to) the thermal diffuser plate38without using any connecting member (or connector). In this case, the light emission device manufacturing process can be simplified.

The light emission devices100A and100B of the foregoing embodiments can be used as a backlight unit for a liquid crystal display.

FIGS. 5 and 6show a liquid crystal display according to an embodiment of the present invention.

Referring toFIG. 5, a liquid crystal display200of this embodiment includes a liquid crystal (LC) panel assembly210having a plurality of pixels arranged in rows and columns and a light emission device (backlight unit)100for emitting light toward the liquid crystal panel assembly210. The light emission device100can be the light emission device100A ofFIG. 1or the light emission device100B ofFIG. 4.

In one embodiment, the number of pixels of the light emission device100is less than that of the liquid crystal panel assembly210so that one pixel of the light emission device100corresponds to two or more pixels of the liquid crystal panel assembly210.

The rows are defined in a horizontal direction (i.e., a direction of an x-axis inFIG. 6) of a liquid crystal display region (e.g., a screen or display area of the liquid crystal panel assembly52). The columns are defined in a vertical direction (i.e., a direction of a y-axis inFIG. 6) of the liquid crystal display region (e.g., the screen of the liquid crystal panel assembly52).

In one embodiment, the cathode electrodes26of the light emission device are arranged along a column direction (i.e., direction of the columns) and the gate electrodes30of the light emission device100(100A or100B) are arranged along a row direction (i.e., a direction of the rows).

When the number of pixels arranged along a line of the liquid crystal panel assembly210is M and the number of pixels arranged along a column of the liquid crystal panel assembly210is N, the resolution of the liquid crystal panel assembly210can be represented as M×N. When the number of pixels arranged along a line of the backlight unit (light emission device)100is M′ and the number of pixels arranged along a column of the light emission device100is N′, the resolution of the light emission device100can be represented as M′×N′.

In this embodiment, the number of pixels M can be defined as a positive number greater than or equal to 240 and the number of pixels N can be defined as a positive number greater than or equal to 240. The number of pixels M′ can be defined as one of the positive numbers ranging from 2 to 99, and the number of pixels N′ can be defined as one of the positive numbers ranging from 2 to 99.

The pixels of the light emission device100provide different intensities of light to the corresponding pixels of the liquid crystal panel assembly210, thereby enhancing the dynamic contrast of the screen.

Referring toFIG. 6, the liquid crystal panel assembly210includes third and fourth substrates42and44facing each other and a liquid crystal layer46disposed between the third and fourth substrates42and44. Pixel electrodes48and switching elements50are formed on an inner surface of the third substrate42and a common electrode52is formed on an inner surface of the fourth substrate44.

A pair of polarizers54and56are respectively disposed on outer surfaces of the third and fourth substrates42and44. Orientation layers58are disposed to face each other with the liquid crystal layer46interposed therebetween.

A plurality of gate lines60for transmitting gate signals and data lines62for transmitting data signals are formed on the inner surface of the third substrate42. The gate lines60are arranged in parallel with each other along the rows, and the data lines62are arranged in parallel with each other along the columns.

The pixel electrodes48are formed, such that each pixel electrode corresponds to one sub-pixel. The pixel electrodes48are connected to the gate lines60and the data lines62through the respective switching elements50.

A color filter64is disposed between the fourth substrate44and the common electrode52. The color filter64includes red, green and blue filters, each sub-pixel corresponding to one of the red, green or blue filter. Three sub-pixels where the red, green and blue filters are arranged define one pixel.

When the switching elements50are turned on, an electric field is formed between the pixel electrodes48and the common electrode52to change twisting angles of the liquid crystal molecules of the liquid crystal layer46. By controlling the twisting angle of each sub-pixel, an amount of the light transmission is controlled to realize a color image (e.g., a predetermined color image).

FIG. 7is a block diagram of a driving part of the liquid crystal display according to an embodiment of the present invention.

Referring toFIG. 7, the driving part of the liquid crystal display includes gate and data drivers212and214connected to the liquid crystal panel assembly210, a gray voltage generator216connected to the data driver214, and a signal controller218for controlling the drivers as well as the light emission device100.

When the liquid crystal panel assembly210is viewed as an equivalent circuit, the liquid crystal panel assembly210includes a plurality of signal lines and a plurality of pixels PX arranged in rows and columns and connected to the signal lines. The signal lines include a plurality of gate lines G1-Gnfor transmitting gate signals (or scan signals) and a plurality of data lines D1-Dmfor transmitting data signals.

Each pixel, e.g., a pixel54connected to an ith(i=1, 2, . . . n) gate line Giand a jth(j=1, 2, . . . m) data line Dj, includes a switching element Q connected to the ithgate line Giand the jthdata line Dj, and liquid crystal and sustain capacitors Clc and Cst. In another embodiment, the sustain capacitor Cst may be omitted.

The switching element Q is a 3-terminal element such as a thin film transistor formed on a lower substrate (shown inFIG. 6) of the liquid crystal panel assembly210. That is, the switching element Q includes a control terminal connected to the gate line Gi, an input terminal connected to the data line Dj, and an output terminal connected to the liquid crystal and sustain capacitors Clc and Cst.

In one embodiment, the gray voltage generator216generates two sets of gray voltages (or two sets of reference gray voltages) related to the transmissivity of the first pixels PX. One of the two sets has a positive value with respect to a common voltage Vcom and the other has a negative value.

The gate driver212is connected to the gate lines G1-Gn of the liquid crystal panel assembly210to apply a scan signal that is a combination of a gate-on-voltage Von and a gate-off-voltage Voff to the gate lines G1-Gn.

The data driver214is connected to the data lines Di-Dmof the liquid crystal panel assembly210. The data driver214selects a gray voltage from the gray voltage generator216and applies the selected gray voltage to the data lines D1-Dm. However, when the gray voltage generator216does not provide all of the voltages for all of the grays but provides only a number (e.g., a predetermined number) of reference gray voltages, the data driver214divides the reference gray voltages, generates the gray voltages for all of the grays, and selects a data signal from the gray voltages.

The signal controller218controls the gate driver212, the data driver214and the backlight unit controller220. The signal controller218receives input image signals R, G and B and an input control signal for controlling the display of the image from an external graphic controller (not shown).

The input image signals R, G and B have luminance information of each pixel PX. The luminance has a number (e.g., a predetermined number) of grays (e.g., 1024 or 256 gray levels in the gray scale). The input control signal may include one or more of a vertical synchronizing signal Vsync, a horizontal synchronizing signal Hsync, a main clock signal MCLK, or a data enable signal DE.

The signal controller218properly processes the input image signals R, G and B in response to the operating condition of the liquid crystal panel assembly210with reference to the input control signal and generates a gate control signal CONT1and a data control signal CONT2. The signal controller218transmits the gate control signal CONT1to the gate driver212. The signal controller218transmits the data control signal CONT2and the processed image signal DAT to the data driver214. The signal controller218further transmits the gate control signal CONT1, the data control signal CONT2, and the processed image signal DAT to the backlight unit controller220.

The light emission device100includes a backlight unit controller220, a column driver222, a scan driver224, and a display unit226.

The display unit226of the light emission device100includes a plurality of scan lines S1-Spfor transmitting scan signals, a plurality of column lines C1-Cq, and a plurality of light emission pixel EPX. Each light emission pixel EPX is disposed at a crossing area between the scan lines S1-Spand the column lines C1-Cq. The scan lines S1-Spare connected to the scan driver224and the column lines C1-Cqare connected to the column driver222. The scan and column drivers224and222are connected to the backlight unit controller220to operate in response to the control signal from the backlight unit controller220.

In one embodiment, the scan lines S1-Spcorrespond to the scan electrodes of the light emission device and the column lines C1-Cqcorrespond to the data electrodes of the light emission device.

The backlight unit controller220generates a scan driver control signal CS for controlling the scan driver224using the gate control signal CONT1. The scan driver control signal CS is transmitted to the scan driver224. The backlight unit controller220generates a column driver control signal CC using the data control signal CONT2. The backlight unit controller220generates a column signal CLS corresponding to the image signal DAT. The column driver control signal CC and the column signal CLS are transmitted to the column driver222. The backlight unit controller220generates luminance information for each pixel of the light emission device100from the image signal DAT of one frame. The column signal CLS is generated according to the luminance information.

The scan driver224sequentially applies scan signals each having a pulse (e.g., a predetermined pulse) to the scan lines S1-Spaccording to the scan driver control signal CS inputted thereto. The column driver222receives the column driver control signal CC and the column signal CLS, and applies a driving voltage corresponding to the received column driver control signal CC and the column signal CLS to the column lines C1-Cq.

By the above described structure, the display unit226of the light emission device100receives a driving signal synchronized with an image signal and emits light having a proper intensity according to the luminance information of each pixel. The emitted light is transmitted to the liquid crystal panel assembly210. In one embodiment, each light emission pixel EPX of the display unit226may be driven to represent a gray of 2-8 bits.

Therefore, when the liquid crystal panel assembly210displays an image having bright and dark portions, the light emission device100provides a light having a relatively high intensity to pixels corresponding to the bright portion and provides a light having a relatively low intensity to pixels corresponding to the dark portion. The pixels of the light emission device100, which correspond to pixels of the liquid crystal panel assembly210for displaying a black color, may be turned off.

As a result, a dynamic contrast of the liquid crystal display may be improved by the above-described process.

The liquid crystal display200using the light emission device100as a backlight unit has the following features that may be advantageous when compared with a case where a CCFL or LED type backlight unit is used.

Since the light emission device is a surface light source, there is no need to use optical members that were used in the CCFL or LED type backlight unit. Therefore, the light loss that was caused by the optical members can be significantly reduced and thus there is less need or no need to increase the light intensity. As a result, the power consumption can be reduced.

In addition, since no optical member is used in the light emission device of exemplary embodiments according to the present invention, the manufacturing cost can be reduced. The manufacturing cost of the light emission device in exemplary embodiments of the present invention is lower than that of the LED type backlight unit. Furthermore, since a large size light emission device can be easily made, it can be effectively applied to a large-sized liquid crystal display above 30-inch.

Even when the light emission device in exemplary embodiments of the present invention is used as a high luminance device such as the backlight unit, the thermal diffuser plate provided on the first substrate and configured to transmit light, effectively dissipates the heat generated from the light emission unit through the heat dissipation plate without blocking the light and thus the temperature of the second substrate on which the light emission unit is formed can be reduced to be lower than 50° C.

In addition, since the light emission device in exemplary embodiments of the present invention still has the heat dissipation plate that has been conventionally used, there is no need to install additional heat dissipation unit.

Since the dynamic contrast of the liquid crystal display using the light emission device as the backlight unit can be enhanced, the display quality can be improved and the power consumption can be reduced. In addition, the liquid crystal display having a large size can be made more easily.

Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concept taught herein still fall within the spirit and scope of the present invention, as defined by the appended claims and their equivalents.

By way of example, while the display device in exemplary embodiments has been described primarily in reference to a liquid crystal display, the invention is not limited thereto. The exemplary embodiments are fully applicable to any display device that uses the light emission device as a light source.