KR100766927B1 - Light emitting device and liquid crystal display with the light emitting device as back light unit - Google Patents

Abstract

A light emitting device and an LCD using the light emitting device as a backlight unit are provided to increase a static contrast ratio of the LCD and improve image quality by dividing a light emitting device screen into a plurality of areas and independently controlling the light intensity for each divided area. A first substrate(12) and a second substrate(14) are disposed to face each other, and form a vacuum container. An electron emission assembly is provided on the first substrate, and includes a plurality of electron emission units the electron emission amounts of which are controlled independently. A light emission assembly is placed at one surface of the second substrate. Each of the electron emission units includes first electrodes(24) formed in one direction of the first substrate, electron emitting parts electrically connected to the first electrodes, and second electrode(28) including a mesh portion(30) placed on an upper portion of the first electrodes and the electron emitting parts and including a plurality of electron beam path holes, and a support portion(32) fixed on the first substrate and supporting the mesh portion.

Description

Light emitting device and liquid crystal display using the light emitting device as a backlight unit {LIGHT EMITTING DEVICE AND LIQUID CRYSTAL DISPLAY WITH THE LIGHT EMITTING DEVICE AS BACK LIGHT UNIT}

1 is a partially exploded perspective view of a light emitting device according to an embodiment of the present invention.

2 is a partial plan view of an electron emission assembly of a light emitting device according to an embodiment of the present invention.

3 is an enlarged perspective view of the electron emission unit illustrated in FIG. 1.

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

5 is a partially enlarged cross-sectional view illustrating a second electrode and a second wiring part of a light emitting device according to an exemplary embodiment of the present invention.

6 is an exploded perspective view of a liquid crystal display according to an exemplary embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a light emitting device that emits light using an electron emission characteristic by an electric field, and a liquid crystal display device using the light emitting device as a backlight unit.

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

The liquid crystal display basically includes a liquid crystal panel assembly and a backlight unit for providing light to the liquid crystal panel assembly, and the liquid crystal panel assembly receives the light emitted from the backlight unit and transmits the light through the action of the liquid crystal layer. By blocking, a predetermined image is realized.

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

Accordingly, recently, a field emission type backlight unit that emits light using electron emission characteristics by an electric field has been proposed as a backlight unit to replace the CCFL method and the LED method. The field emission type back light unit is a surface light source, has the advantage of low power consumption, large size, and does not require a complicated optical member.

However, the conventional backlight units including the field emission type backlight unit have a problem that it is difficult to meet the image quality improvement required for the liquid crystal display because the entire screen is always turned on at a constant brightness when the liquid crystal display is driven.

For example, when the liquid crystal panel assembly displays an arbitrary screen including a bright portion and a dark portion according to an image signal, the backlight unit applies light of different intensities to the region displaying the bright portion and the region displaying the dark portion. If it is provided, it is possible to display a screen having excellent dynamic contrast.

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

Accordingly, an object of the present invention is to provide a field emission type light emitting device capable of dividing a screen into a plurality of regions and independently controlling the light emission intensity for each divided region.

Another object of the present invention is to provide a liquid crystal display that can improve the dynamic contrast ratio of a screen by using the above-described light emitting device as a backlight unit.

In order to achieve the above object, the present invention,

An electron emission assembly composed of a first substrate and a second substrate disposed opposite to each other and constituting a vacuum container, a plurality of electron emission units provided on the first substrate and having an independently controlled amount of electron emission, and one surface of the second substrate A light emitting assembly positioned at the first electrode, wherein each of the electron emission units is formed along one direction of the first substrate, electron emission portions electrically connected to the first electrodes, and the first electrodes; Provided is a light emitting device including a second electrode positioned above the electron emission parts and forming a plurality of electron beam through holes.

The electron emitters may be positioned on side surfaces of the first electrode along the length direction of the first electrodes, and may include at least one of a carbonaceous material and a nanometer size material.

The electron emission assembly may include a first wiring portion connecting with first electrodes of electron emission units arranged along one direction of a first substrate, and second electrodes of electron emission units arranged along a direction orthogonal to the one direction. And a second wiring portion to be connected with them.

The second electrode may include a mesh part positioned on the first electrodes and the electron emission parts to form a plurality of electron beam through holes, and a support part fixed on the first substrate to support the mesh part.

The support part may be provided at two edges of the mesh part facing along the length direction of the second wiring part, and may be fixed on the second wiring part through a conductive adhesive layer.

In addition, the present invention, in order to achieve the above object,

A liquid crystal display device including a light emitting device having the above-described configuration and a liquid crystal panel assembly positioned in front of the light emitting device to receive light emitted from the light emitting device to display an image.

The liquid crystal panel assembly forms a plurality of pixels along the row direction and the column direction, and the light emitting device forms a smaller number of pixels than the liquid crystal panel assembly along the row direction and the column direction.

When the liquid crystal panel assembly forms M pixels in a row direction and N pixels in a column direction, M and N may be defined as an integer of 240 or more. When the light emitting device forms M 'pixels along the row direction and N' pixels along the column direction, M 'and N' may be defined as any integer of 2 to 99.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a partially exploded perspective view of a light emitting device according to an embodiment of the present invention, and FIG. 2 is a partial plan view of an electron emission assembly of a light emitting device according to an embodiment of the present invention.

1 and 2, the light emitting device 10 according to the present exemplary embodiment includes a first substrate 12 and a second substrate 14 that are disposed to face each other in parallel at predetermined intervals. Sealing members (not shown) are disposed at the edges of the first substrate 12 and the second substrate 14 to bond the two substrates, and the internal space is evacuated with a vacuum of approximately 10 ⁻⁶ Torr to form the first substrate 12. ), The second substrate 14 and the sealing member constitute a vacuum container.

The first substrate 12 and the second substrate 14 have an effective area contributing to the actual visible light emission inside the sealing member, and an invalid area surrounding the effective area. The effective region of the first substrate 12 is provided with an electron emission assembly 16 for emitting electrons using an electric field, and the effective region of the second substrate 14 has a light emitting assembly 18 for emitting visible light by electrons. Is provided.

In the present embodiment, the electron emission assembly 16 is composed of a plurality of electron emission units 20, and each electron emission unit 20 is independently controlled in the amount of electron emission.

3 is an enlarged perspective view of the electron emission unit illustrated in FIG. 1, and FIG. 4 is a partially enlarged cross-sectional view of a light emitting device according to an exemplary embodiment.

Referring to FIGS. 3 and 4, the electron emission unit 20 is formed in a stripe pattern along one direction (the x-axis direction of the drawing) of the first substrate 12 and is electrically connected by the connection part 22 at at least one end thereof. First electrodes 24 connected to each other, electron emitters 26 provided on side surfaces of the first electrodes 24, and first electrodes 24 and electron emitters 26. And a second electrode 28 having a mesh shape to form the electron beam through hole 281.

The first electrode 24 functions as a cathode electrode for supplying current to the electron emission section 26, and the second electrode 28 forms an electric field around the electron emission section 26 due to the voltage difference from the cathode electrode. Function as a gate electrode to induce electron emission.

One end or both ends of the first electrodes 24 are connected to the connection part 22 to receive a corresponding driving voltage through the connection part 22. In FIG. 3, the connection part 22 is positioned at both ends of the first electrodes 24.

The electron emission parts 26 are positioned at both edges of the first electrode 24 along the length direction of the first electrodes 24. The electron emission part 26 may be formed to contact the side surface of the first electrode 24, or may be positioned to cover the entire side surface and a portion of the upper surface of the first electrode 24. In the figure, the first case is illustrated.

The electron emission unit 26 may be formed of materials emitting electrons when a electric field is applied in a vacuum, such as a carbon-based material or a nanometer (nm) size material. The electron emitter 26 may include, for example, carbon nanotubes, graphite, graphite nanofibers, diamonds, diamond-like carbons, C ₆₀ , silicon nanowires, or mixtures thereof. Chemical vapor deposition or sputtering may be applied.

The second electrode 28 is positioned above the first electrodes 24 and the electron emission parts 26 to support the mesh part 30 forming the plurality of electron beam through holes 281 and the mesh part 30. And a support part 32 fixed on the first substrate 12. The support part 32 may be fixed on the first substrate 12 through an adhesive layer (not shown), and may be positioned at two edges facing each other of the mesh part 30.

Referring back to FIGS. 1 and 2, the electron emission units 20 of the above-described configuration are positioned side by side at an arbitrary distance from each other in the effective area of the first substrate 12. In addition, wiring portions for applying a driving voltage to the first electrodes 24 and the second electrode 28 of the electron emission unit 20 are positioned between the electron emission units 20.

On the first substrate 12, the first wiring part 34 connected to the connection parts 22 is formed along one direction (the x-axis direction of the drawing) of the first substrate 12, and the electrons are positioned along this direction. The first electrodes 24 of the emission units 20 are electrically connected. A second wiring portion 36 is formed along the direction orthogonal to the first wiring portion 34 (y-axis direction in the drawing) to be connected to the support portion 32 of the second electrode 28, and is positioned along this direction. The second electrode 28 of the electron emission units 20 is electrically connected to each other.

In this case, the supporting part 32 of the second electrode 28 is provided only at two edges facing along the longitudinal direction of the second wiring part 36 so as not to contact the first wiring part 34. Likewise, the electrical connection between the support part 32 and the second wiring part 36 may be made through the conductive adhesive layer 38.

By the above-described configuration, one electron emission unit 20 in which the first wiring part 34 and the second wiring part 36 intersect serves as one pixel of the light emitting device 10.

1 and 4, the light emitting assembly 18 includes a fluorescent layer 40 and an anode electrode 42 positioned on one surface of the fluorescent layer 40. The fluorescent layer 40 may be formed of a white fluorescent layer or a combination of red, green, and blue fluorescent layers. In the drawing, a white fluorescent layer is positioned in the entire effective region of the second substrate 14.

The anode electrode 42 may be formed of a metal film such as aluminum covering the surface of the fluorescent layer 40. The anode 42 is an acceleration electrode for attracting an electron beam, and is applied with a high voltage of about thousands of volts to maintain the fluorescent layer 40 in a high potential state, and the first substrate 12 of visible light emitted from the fluorescent layer 40. The brightness of the screen is increased by reflecting the visible light emitted toward the second substrate 14.

Spacers (not shown) are disposed between the first substrate 12 and the second substrate 14 to support the compressive force applied to the vacuum container and to keep the two substrates at a constant distance.

The light emitting device 10 having the above-described configuration is driven by supplying a predetermined voltage to the first wiring portions 34, the second wiring portions 36, and the anode electrode 42 from outside the vacuum container. In this case, a positive voltage of thousands of volts is applied to the anode electrode 42, and a driving voltage is selectively applied to the first wiring parts 34 and the second wiring parts 36 to be turned on / off for each electron emission unit 20. Independently control the amount of off and electron emission.

For example, when voltages having different magnitudes are applied to the first wiring part 34 and the second wiring part 36 with respect to any one electron emission unit 20, the first electrode 24 and the second electrode 28 are applied. An electric field is formed around the electron emission portion 26 by the voltage difference of the electrons, and electrons (denoted by e ⁻ in FIG. 4) are emitted therefrom, and the emitted electrons are passed through the electron beam through holes (2) of the second electrode 28. 281) and attracted to the anode voltage to collide with the corresponding fluorescent layer 40 region to emit light.

In this process, the cathode voltage applied to the first electrode 24 may be set to a range of 0V or several to several tens of volts, and the gate voltage applied to the second electrode 28 may be to several to several tens of volts greater than the cathode voltage. Can be set. Meanwhile, the electron emitters 26 belonging to one electron emission unit 20 emit electrons at the same time. However, in FIG. 4, some of the electron emitters 26 are shown as electrons for convenience.

As described above, the light emitting device 10 according to the present exemplary embodiment may divide the screen of the light emitting device 10 into a plurality of areas by the above-described structure and driving method, and emit visible light having different intensities for each divided area. Therefore, the light emitting device 10 of the present embodiment effectively contributes to increasing the dynamic contrast ratio of the screen of the liquid crystal display when applied to the backlight unit of the liquid crystal display described below.

6 is an exploded perspective view of a liquid crystal display according to an exemplary embodiment of the present invention using the light emitting device having the above-described configuration as a backlight unit.

Referring to FIG. 6, the liquid crystal display device 50 according to the present exemplary embodiment includes a liquid crystal panel assembly 52 having arbitrary pixels in a row direction and a column direction, and is positioned behind the liquid crystal panel assembly 52 so that the liquid crystal panel assembly ( 52, a light emitting device 10 that provides light. Any known liquid crystal panel assembly may be applied to the liquid crystal panel assembly 52, and the light emitting device 10 of the above-described embodiment functions as a backlight unit.

An optical member (not shown), such as a diffusion plate or a diffusion sheet, may be disposed between the liquid crystal panel assembly 52 and the light emitting device 10 as necessary.

The row direction may be defined as one direction of the liquid crystal display 50, for example, a horizontal direction of a screen implemented by the liquid crystal display 50, and the column direction may be different from that of the screen implemented by the liquid crystal display 50. One direction, for example, may be defined as the vertical direction of the screen implemented by the liquid crystal display device 50.

In particular, in the present embodiment, the light emitting device 10 forms a smaller number of pixels than the liquid crystal panel assembly 52 along the row direction and the column direction so that one pixel of the light emitting device 10 has two or more liquid crystal panel assemblies 52. To correspond to the pixels. Here, one pixel of the light emitting device 10 is defined as one electron emission unit 20 and a corresponding light emitting assembly 18 region.

If the number of pixels of the liquid crystal panel assembly 52 in the row direction and the number of pixels of the liquid crystal panel assembly 52 in the column direction are M and N, respectively, M and N may be defined as an integer of 240 or more. If the number of pixels of the light emitting device 10 in the row direction and the number of pixels of the light emitting device 10 in the column direction are M 'and N', respectively, M 'and N' are any integer of 2 to 99. Can be defined as

The light emitting device 10 having the above-described configuration provides light of different intensities to the pixel group of the liquid crystal panel assembly 52 corresponding to each pixel during driving. In the driving process of the light emitting device 10, a light emitting device controller (not shown) generates luminance information for each pixel of the light emitting device 10 from an image signal of one frame, and according to the generated luminance information, the electron emission unit 20 Generating a driving signal, and the electron emitting unit 20 emits a predetermined amount of electrons in accordance with the corresponding driving signal to emit light of an appropriate intensity for each pixel.

At this time, each pixel of the light emitting device 10 is preferably driven so that the gray scale representation of 2 to 8 bits.

Therefore, when the liquid crystal panel assembly 52 displays a screen of different brightness for each position, the light emitting device 10 provides strong light to the pixel group of the liquid crystal panel assembly 52 displaying a bright portion, and displays a dark portion. The liquid crystal panel assembly 52 may provide weak light to the pixel group. In addition, a specific pixel of the light emitting device 10 corresponding to the pixel group of the liquid crystal panel assembly 52 displaying black may be turned off.

As a result, the liquid crystal display device 50 according to the present exemplary embodiment may improve the dynamic contrast of the screen and realize a clearer picture quality.

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 present invention can divide the screen of the light emitting device into a plurality of areas and control the light emission intensity independently for each divided area, thereby increasing the dynamic contrast ratio of the liquid crystal display device and providing a clearer picture quality. Can be. In addition, the liquid crystal display according to the present invention using the above-described light emitting device as a backlight unit can reduce the power consumption of the backlight unit to lower the overall power consumption, and can be easily manufactured with a large display device of 30 inches or more.

Claims (13)

A first substrate and a second substrate which are disposed to face each other and constitute a vacuum container; An electron emission assembly provided on the first substrate and composed of a plurality of electron emission units in which an electron emission amount is independently controlled; And A light emitting assembly positioned on one surface of the second substrate, Each of the electron emission units, First electrodes formed along one direction of the first substrate; Electron emission parts electrically connected to the first electrodes; And A second electrode disposed on the first electrodes and the electron emission parts and including a mesh part forming a plurality of electron beam through holes, and a support part fixed on the first substrate and supporting the mesh part; Light emitting device comprising a. The method of claim 1, The light emitting device of claim 1, wherein the electron emission unit includes a connection part disposed at an end of the first electrodes to electrically connect the first electrodes. The method of claim 1, The light emitting device of the electron emitting portion is located on the side of the first electrode along the longitudinal direction of the first electrode. The method of claim 1, The light emitting device of claim 1, wherein the electron emission parts include one of a carbonaceous material and a nanometer size material. The method of claim 1, The electron emission assembly, A first wiring portion connected to the first electrodes of the electron emission units arranged along one direction of the first substrate; And a second wiring portion connected to the second electrodes of the electron emission units arranged along a direction orthogonal to the one direction. delete The method of claim 5, And a support part provided at two edges of the mesh part facing each other along the length direction of the second wiring part and in contact with the second wiring part. The method of claim 7, wherein And a conductive adhesive layer positioned between the support portion and the second wiring portion. The method of claim 1, The light emitting assembly, A fluorescent layer formed on one surface of the second substrate; And A light emitting device comprising an anode of a metal formed on the surface of the fluorescent layer. The light emitting device according to any one of claims 1 to 5 and 7 to 9; And A liquid crystal panel assembly positioned in front of the light emitting device to receive light emitted from the light emitting device to display an image Liquid crystal display comprising a. The method of claim 10, The liquid crystal panel assembly forms a plurality of pixels along a row direction and a column direction, And the light emitting device forms a smaller number of pixels than the liquid crystal panel assembly along the row direction and the column direction. delete The method of claim 11, The light emitting device forms M 'pixels along the row direction and N' pixels along the column direction, The liquid crystal display device wherein M 'and N' are an integer of any one of 2 to 99.

Images