KR20080068947A - Surface light source with electrode cells, and backlight unit having the same - Google Patents

Abstract

A surface light source and a backlight unit comprising the same are provided to enable local dimming, by which brightness of the backlight unit is locally controlled according to brightness of a screen of an LCD, thereby improving the image quality. A plurality of cell electrodes(310) are arranged in a matrix type. Each of the cell electrodes is electrically connected to at least one of adjacent cell electrodes by a connection wire(315). The cell electrodes on vertical lines, horizontal lines, or all lines of a matrix structure, which is constituted of the plurality of cell electrodes, are electrically connected to one another. Common electrodes(320) are electrically connected to the plurality of cell electrodes at both sides of the matrix structure. A discharge voltage is applied to the plurality of cell electrodes simultaneously through the common electrodes. The common electrodes are disposed above and below the matrix structure oppositely to each other.

Description

FIELD OF THE INVENTION A surface light source device having a cell electrode, and a backlight unit including the same.

1 is a perspective view showing an example of a surface light source device.

Figure 2 is a perspective view showing a flat surface light source device.

3 is a cross-sectional view taken along the line X-X 'of FIG.

4 is another sectional view taken along the line X-X 'of FIG.

5 is a cross-sectional view taken along line X-X 'of FIG. 2 again.

6 is a plan view showing an electrode for a surface light source including a cell electrode according to the present invention.

7 is an enlarged plan view of the cell electrode of FIG. 6;

8 is a plan view showing another surface light source electrode including a cell electrode according to the present invention.

9 is an enlarged plan view of the cell electrode of FIG. 8;

10 to 11 are plan views showing cell electrodes of a mesh pattern.

12 is a perspective view illustrating a surface light source device in which the cell electrode of FIG. 6 is formed.

FIG. 13 is a perspective view illustrating a surface light source device in which the cell electrode of FIG. 8 is formed. FIG.

14 is a perspective view showing another surface light source device in which a cell electrode is formed.

15 is a cross-sectional view showing a cell electrode of a multilayer structure.

16 is a schematic diagram of a surface light source device implementing local dimming by selective discharge.

17 is an exploded perspective view showing a backlight unit including the surface light source device of the present invention.

*** Explanation of symbols for the main parts of the drawing ***

200: surface light source device 210: first substrate

220: second substrate 230: sealing member

240: discharge space 250: partition

300: first electrode 310: cell electrode

315: connecting wire 320: common electrode

400: second electrode 410: cell electrode

420: electrode terminal

The present invention relates to a surface light source device, and more particularly, to a surface light source device having a plurality of cell electrodes capable of improving contrast by local dimming by selective discharge, and a backlight unit including the same.

The liquid crystal display displays an image by using electrical and optical characteristics of the liquid crystal. Liquid crystal displays have the advantages of being very small in volume and light in weight compared to cathode ray tubes (CRTs). As a result, they are widely used in portable computers, communication devices, liquid crystal television receivers, and aerospace industries. .

The liquid crystal display device includes a liquid crystal controller for controlling liquid crystal and a rear light source for supplying light to the liquid crystal. The liquid crystal controller includes a pixel electrode disposed on the first substrate, a common electrode disposed on the second substrate, and a liquid crystal interposed between the pixel electrode and the common electrode. The pixel electrode is formed in plural in correspondence with the resolution, and the common electrode is made of one and facing the pixel electrode. A thin film transistor (TFT) is connected to each pixel electrode to apply a pixel voltage having a different level, and a reference voltage of the same level is applied to the common electrode. The pixel electrode and the common electrode are made of a transparent material having conductivity.

Light supplied from the rear light source sequentially passes through the pixel electrode, the liquid crystal, and the common electrode. In this case, the display quality of the image passing through the liquid crystal largely depends on the luminance and luminance uniformity of the rear light source. In general, the higher the luminance and the uniformity of the luminance, the better the display quality.

Conventionally, the rear light source of the liquid crystal display is mainly used a cold cathode fluorescent lamp (CCFL) having a rod shape or a light emitting diode (LED) having a dot shape. Cold cathode ray tube lamp has the advantage of high brightness, long life, and very low heat generation compared to incandescent lamps. On the other hand, the light emitting diode has a high power consumption, but has an advantage of excellent brightness. However, cold cathode ray tube type lamps or light emitting diodes have poor brightness uniformity. Accordingly, a rear light source having a cold cathode ray tube lamp or a light emitting diode as a light source is an optical member such as a light guide panel (LGP), a diffusion member, a prism sheet, or the like to increase luminance uniformity. (optical member) is required. As a result, a liquid crystal display using a cold cathode ray tube lamp or a light emitting diode has a problem in that the volume and weight of the optical member are greatly increased.

As a back light source for a liquid crystal display, a flat fluorescent lamp (FFL) in the form of a flat plate has been proposed. Referring to FIG. 1, the conventional surface light source device 100 includes a light source body 110 and electrodes 160 provided on outer surfaces of both edges of the light source body 110. The light source body 110 includes first and second substrates disposed to face each other at predetermined intervals. A plurality of partitions 140 are disposed between the first and second substrates to partition the space between the first and second substrates into a plurality of discharge channels 120. A sealing member (not shown) is disposed between the edges of the first and second substrates to isolate the discharge channels 120 from the outside. Discharge gas is injected into the discharge space 150 inside the discharge channel.

In order to discharge-drive the surface light source device, an electrode is applied to the first substrate and the second substrate or one of the two substrates so that the electrodes have the same area per discharge channel in the form of a strip of strips or in the form of island electrodes. Therefore, when the surface light source device is driven using an inverter, all the front channels are discharged in the same manner.

The surface light source device maintains a constant level of luminance during driving. Although a dimming technique for varying the luminance of the surface light source device according to the screen information of the liquid crystal display has been proposed, a technique for locally controlling the luminance is not yet provided. When the surface light source device is driven only by on / off, power consumption increases, while the surface light source controls light transmission only in the liquid crystal part of the liquid crystal display in the continuous on state. In other words, it is difficult to realize high quality white contrast ratio.

In order to improve the image quality of the liquid crystal display device and to realize more clear and natural display quality, a technology for locally controlling the luminance of the surface light source device used as a backlight is required.

It is an object of the present invention to provide a novel surface light source device suitable for large area.

Another object of the present invention is to provide a surface light source device and a backlight unit capable of local luminance control.

The present invention provides a surface light source electrode including a plurality of cell electrodes arranged in a matrix form and electrically connected to each other, and at least one common electrode electrically connected to the plurality of cell electrodes.

In addition, the present invention provides a surface light source electrode comprising a plurality of cell electrodes arranged in a matrix form and electrically separated from each other, and an electrode terminal formed on one side of the cell electrode.

The cell electrode may include a plurality of fine wires in a stripe pattern or fine wires in a mesh pattern. Preferably, the cell electrode has a distance from an adjacent cell electrode smaller than the length or width of the cell electrode. The plurality of cell electrodes may be formed by printing a conductive material, or may be patterned on a transparent base layer to form a multilayer structure.

The present invention also includes a first electrode comprising a plurality of cell electrodes arranged in a matrix form and electrically connected to each other, and at least one common electrode electrically connected to the plurality of cell electrodes; The present invention provides a surface light source electrode including a plurality of cell electrodes arranged in a matrix and electrically separated from each other, and a second electrode including electrode terminals formed on one side of the plurality of cell electrodes.

The present invention also provides a light source body having a discharge space enclosed therein, a plurality of cell electrodes formed on one surface of the light source body, arranged in a matrix form and electrically connected to each other, and electrically connected to the plurality of cell electrodes. A first electrode including at least one common electrode, a plurality of cell electrodes formed on the other surface of the light source body, arranged in a matrix form and electrically separated from each other, and electrodes formed on one side of the cell electrode Provided is a surface light source device including a second electrode including a terminal.

The light source body may include a planar first substrate and a planar second substrate, wherein the first electrode is formed on an outer surface of the first substrate, and the second electrode is formed on an outer surface of the second substrate. In addition, the light source body may include a first substrate having a plurality of discharge channels and a flat plate type second substrate, and in this case, the first electrode may be formed on an outer surface of the first substrate or the second substrate. . The surface light source device of the present invention may further include a socket part for selectively applying a voltage to each cell electrode of the second electrode.

The present invention also provides a backlight unit including the surface light source device, a case accommodating the surface light source device, and an inverter for applying a discharge voltage to the cell electrode. In the surface light source device and the backlight unit of the present invention, a plurality of cell electrodes in a matrix form are formed on the surface of the light source body, and a discharge voltage is selectively applied to the cell electrodes to obtain locally controlled light emission characteristics. Accordingly, local dimming that partially controls the luminance of the surface light source can be performed according to the brightness of the image of the liquid crystal display, and more clear and natural image quality can be secured in the liquid crystal display. In particular, the surface light source device selectively emits light in association with the image signal of the liquid crystal display device, thereby remarkably improving the white contrast ratio and contrast.

2 is a perspective view showing a flat surface light source device 200 according to an embodiment of the present invention. The surface light source device 200 includes a planar first substrate 210 and a planar second substrate 220 having the same shape as the light source body.

The surface light source device has a sealed discharge space therein, and a flat electrode including a plurality of cell electrodes on one surface (for example, the surface 210 'of the first substrate) to cover the entire surface as described later. Is formed.

The first substrate 210 and the second substrate 220 is preferably a transparent thin glass substrate, each thickness is not particularly limited, but a thickness of about 1 ~ 2 mm, preferably 1 mm or less is appropriate. A fluorescent layer (not shown) may be applied to the inner surfaces of the first substrate 210 and the second substrate 220, and a reflective film (not shown) may be further formed on any one of the first substrate and the second substrate. The first substrate 210 and the second substrate 220 are opposed to each other at predetermined intervals, and as shown in FIG. 3, a sealing member 230, such as a frit, is inserted into the edge to seal the internal discharge space ( 240). Alternatively, as shown in FIG. 4, the edges of both substrates may be directly fused by heating to form a sealed internal discharge space 240.

The interior defined by the first substrate 210 and the second substrate 220 may form a discharge space 240 of one open structure. Alternatively, as shown in FIG. 5, a partition (or spacer) is illustrated. The discharge space 240 may be divided into a plurality of sub spaces by the reference numeral 250. The partitioned discharge space is advantageous for the divided driving of the surface light source device as described later. The partition wall 250 may be separately inserted between the first substrate 210 and the second substrate 220, or may be formed by molding one surface of the two substrates to partially protrude.

The gap between the first substrate 210 and the second substrate 220 is very small compared with the entire area of the substrate, so that it is very easy to inject the vacuum discharge and discharge gas into the internal discharge space. As the discharge gas, mercury, xenon, argon, neon, other inert gas, or a mixed gas thereof may be used.

The present invention proposes a new structure electrode in which cell electrodes are arranged in a matrix form for local brightness control of the planar surface light source device shown in FIG. Referring to FIG. 6, in the surface light source electrode 300 according to the exemplary embodiment of the present invention, a plurality of cell electrodes 310 are arranged in a matrix form, and each cell electrode is adjacent to at least one cell electrode. And is electrically connected through a connecting wire 315. As shown, the cell electrodes on the horizontal line are electrically connected to each other. Alternatively, the cell electrodes on the vertical line may be electrically connected to each other, or the entire cell electrodes may be electrically connected to each other.

Common electrodes 320 electrically connected to the cell electrodes are disposed at both sides of the matrix structure formed by the cell electrodes. The common electrode may be electrically connected to cell electrodes positioned at both sides thereof to simultaneously apply a discharge voltage to a plurality of cell electrodes. Unlike illustrated, the common electrode may be formed to face each other on the upper and lower portions of the matrix structure, and only one common electrode may be formed.

Although the shape of the cell electrode 310 is a quadrangular shape as shown in FIG. 7, it is suitable to form a matrix array, but the shape of the cell electrode 310 is not necessarily limited thereto. Each cell electrode preferably has a distance d ₂ between adjacent cell electrodes smaller than a length d ₁ of one side of the cell electrode. The cell electrode may be formed of a fine wire, and the wire pattern may be formed in a stripe shape, a mesh shape, and various other shapes. The spacing w ₁ between the wires constituting the cell electrode is preferably as small as possible, but preferably maintained so as to expose the light exit surface of the surface light source to a predetermined level or more, as described below.

The width of the wire can vary from a few micrometers to several millimeters depending on the size of the surface light source device. On the other hand, the width w ₂ of the common electrode 320 is preferably formed to be relatively thicker than the width of the wire constituting the cell electrode.

8 shows another surface light source electrode 400 according to the present invention. The plurality of cell electrodes 410 are arranged in a matrix form. Unlike the electrode of FIG. 6 described above, each cell electrode is electrically separated from an adjacent cell electrode, and an electrode terminal 420 is formed in contact with one side of the cell electrode 410. The electrode terminal 420 corresponds to an intermediate unit for applying a voltage to each cell electrode 410 independently. In order to apply a selective discharge voltage for each cell electrode 410 through the electrode terminal 420, an external socket part (not shown) may be formed to control a plurality of cell electrodes independently.

As illustrated in FIG. 9, the cell electrode 410 includes fine wires and has a rectangular shape. The length of the horizontal side d _a and the vertical side d _b may be the same or may be different from each other. Unlike the illustrated figure, the cell electrode 410 may be formed in the form of a circle, an ellipse, or another polygon.

The electrode terminal 420 formed to be in contact with one side of the cell electrode 410 is preferably formed in _a length (w _a , w _b ) larger than the gap w of the wire in terms of voltage application.

10 and 11 illustrate another form of the cell electrode of FIGS. 6 and 8 and include wires patterned in a mesh form.

6 and 8 may be used together to form the first electrode and the second electrode of the surface light source device, alternatively to the electrode portion of the surface light source device together with other flat electrodes. It may be. FIG. 12 illustrates the cell electrode 310 of FIG. 6 formed on one surface of the surface light source device 200 of FIG. 2, and FIG. 13 illustrates the surface of the surface light source device 200 of FIG. 8. The cell electrode 410 is formed. Electrodes on both surfaces of the surface light source device 200 may selectively discharge the space inside the surface light source device. For example, a voltage is generally applied to the interconnected cell electrodes 310 through the common electrode 320, but a separately controlled voltage is applied to the cell electrodes 410 that are separated from each other, so that the surface light source device is locally connected. Discharge occurs. That is, since independent discharge is possible for each cell electrode, local dimming is possible for each region of the surface light source device. This local dimming can not only control the luminance of the discharge space corresponding to one cell electrode, but also control the luminance of a predetermined region including the adjacent discharge space, and as a result, free luminance of each region of the surface light source device. Control is possible.

In the surface light source device according to the present invention, the cell electrode preferably has an open ratio of 60% or more for exposing the substrate to increase the transmittance of light emitted by the discharge from the discharge space inside the light source body. To this end, the cell electrode may be formed in an electrode pattern in the form of a stripe or a mesh, or a transparent electrode may be used.

Meanwhile, the cell electrode of the present invention can be applied not only to the flat surface light source device of FIG. 2 but also to the discharge channel type surface light source device of FIG. FIG. 14 schematically illustrates a cell electrode of the present invention formed on one surface of a surface light source device 100 having discharge channels formed on at least one substrate. Each discharge channel may emit light in a predetermined region by independent driving of the cell electrode.

In the present invention, a method of forming a cell electrode may be able to directly print a fine electrode pattern on the surface of the surface light source. Alternatively, it is also possible to form an electrode cell layer on which an electrode pattern is formed and attach it to the surface of the surface light source device. In the case of forming a plurality of cell electrodes in a single layer, as shown in FIG. 15, the base layer 340, the electrode pattern 310 of the cell electrode formed on the base layer, and the protective layer formed on the electrode pattern. It can be formed in a multilayer structure consisting of (350). It is preferable that the base layer and the protective layer are transparent to visible light. The cell electrode having a multilayer structure has an advantage of easily bonding with a substrate, securing durability of an electrode pattern, and forming electrode patterns of various types. As the base layer, a transparent polymer material may be used as a material resistant to thermal shock, and as the electrode pattern, a material having excellent conductivity having a resistance of 10 Ω or less of copper, silver, gold, aluminum, nickel, chromium, carbon series, or polymer series or the above It is possible to use a material in which the material is compounded. As the protective layer, a transparent polymer material resistant to thermal shock may be used.

The surface light source device according to the present invention can be selectively driven by dividing an internal discharge space into a plurality of discharge cells by using a plurality of cell electrodes in a matrix form. Therefore, independent discharge control is possible for a predetermined area inside the surface light source device, thereby realizing luminance control in various modes. For example, as illustrated in the schematic diagram of FIG. 16, dimming locally controlled by regions a, b, and c of the light exit surface of the surface light source is possible. Therefore, the luminance of the surface light source device may be locally controlled in conjunction with the image signal of the liquid crystal display device.

17 is an exploded perspective view showing a backlight unit including the surface light source device according to the present invention. As shown, the backlight unit includes a surface light source 200, upper and lower cases 1100 and 1200, an optical sheet 900, and an inverter 1300. The lower case 1200 includes a bottom portion 1210 and a plurality of sidewall portions 1220 extending to form an accommodation space from an edge of the bottom portion 1210 to accommodate the surface light source 200. The surface light source 200 is accommodated in the storage space of the lower case 1200.

The inverter 1300 is disposed on the rear surface of the lower case 1200 and generates a discharge voltage for driving the surface light source 200. The discharge voltage generated from the inverter 1300 is applied to the electrodes of the surface light source 200 through the first and second power lines 1352 and 1354, respectively. The optical sheet 900 may include a diffuser plate for uniformly diffusing the light emitted from the surface light source 200, a prism sheet for imparting linearity to the diffused light, and the like. The upper case 1100 is coupled to the lower case 1200 to support the surface light source 200 and the optical sheet 900. The upper case 1100 prevents the surface light source 200 from being separated from the lower case 1200.

Unlike the illustrated figure, the upper case 1100 and the lower case 1200 may be formed as one integrated case. On the other hand, the backlight unit according to the present invention may not include the optical sheet 900 because the brightness and luminance uniformity of the surface light source device is excellent.

Although described above with reference to preferred embodiments of the present invention, those skilled in the art or those skilled in the art without departing from the spirit and scope of the invention described in the claims to be described later Various modifications and variations can be made in the present invention without departing from the scope thereof.

According to the present invention, by selectively applying a voltage to the plurality of cell electrodes, a discharge can be selectively generated in the internal discharge space of the surface light source, thereby obtaining a light emission characteristic with locally controlled luminance. Therefore, local dimming is performed to locally control the brightness of the backlight according to the brightness of the screen of the liquid crystal display, thereby realizing a high quality image.

Claims (16)

A plurality of cell electrodes arranged in a matrix and electrically connected to each other; At least one common electrode electrically connected to the plurality of cell electrodes. Surface light source electrode. A plurality of cell electrodes arranged in a matrix and electrically separated from each other; An electrode terminal formed on one side of the cell electrode; Surface light source electrode. The surface light source electrode of claim 1 or 2, wherein the cell electrode comprises a plurality of fine wires in a stripe pattern. The surface light source electrode of claim 1 or 2, wherein the cell electrode comprises a fine wire of a mesh pattern. The surface light source electrode of claim 1 or 2, wherein the cell electrode has a distance from an adjacent cell electrode smaller than a length to a width of the cell electrode. The surface light source electrode of claim 1 or 2, wherein the plurality of cell electrodes are formed by printing a conductive material. The surface light source electrode according to claim 1 or 2, wherein the plurality of cell electrodes are patterned on the transparent base layer, and a multi-layer structure having a transparent protective layer formed on an upper surface thereof. A first electrode arranged in a matrix form and including a plurality of cell electrodes electrically connected to each other, and at least one common electrode electrically connected to the plurality of cell electrodes; Comprising a plurality of cell electrodes arranged in a matrix form and electrically separated from each other, and a second electrode including an electrode terminal formed on one side of the cell electrode Surface light source electrode. A light source body having a discharge space sealed therein; A first electrode formed on one surface of the light source body and arranged in a matrix form and including a plurality of cell electrodes electrically connected to each other, and at least one common electrode electrically connected to the plurality of cell electrodes; A second electrode including a plurality of cell electrodes formed on the other surface of the light source body and arranged in a matrix and electrically separated from each other, and an electrode terminal formed on one side of the cell electrode; Surface light source device. 10. The surface light source device according to claim 9, wherein the first electrode or the second electrode has an open ratio of 60% or more to expose the light source body. 10. The method of claim 9, wherein the light source body comprises a first flat plate and a second flat plate, the first electrode is formed on the outer surface of the first substrate, the second electrode on the outer surface of the second substrate Surface light source device, characterized in that formed. The surface light source device of claim 11, wherein a plurality of spacers are formed in a space between the first substrate and the second substrate. 12. The surface light source device according to claim 11, wherein the space between the first substrate and the second substrate is one open space. The surface light source of claim 9, wherein the light source body includes a first substrate having a plurality of discharge channels and a flat plate type second substrate, and the first electrode is formed on an outer surface of the first substrate or the second substrate. Device. The surface light source device of claim 9, further comprising a socket unit configured to selectively apply a voltage to each cell electrode of the second electrode. A light source body having a discharge space enclosed therein, a plurality of cell electrodes formed on one surface of the light source body and arranged in a matrix and electrically connected to each other, and at least one common electrode electrically connected to the plurality of cell electrodes A first electrode comprising an electrode; A surface light source device formed on the other surface of the light source body and including a plurality of cell electrodes arranged in a matrix and electrically separated from each other, and a second electrode including an electrode terminal formed on one side of the cell electrode; ; A case accommodating the surface light source device; And Including an inverter for applying a discharge voltage to the cell electrode Backlight unit.

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