Plasma display panel

A plasma display panel (PDP) includes: a front substrate; a rear substrate disposed in opposition to the front substrate; first barrier ribs disposed between the front substrate and the rear substrate, defining discharge cells with the front substrate and the rear substrate, and formed of a dielectric material; front discharge electrodes disposed inside the first barrier ribs so as to surround the discharge cells; rear discharge electrodes disposed inside the first barrier ribs so as to surround the discharge cells, and spaced apart from the front discharge electrodes; phosphor layers disposed in the discharge cells; and a discharge gas deposited in the discharge cells. With respect to a longitudinal sectional view of the first barrier ribs, a virtual horizontal axis which extends from a lowermost portion of each of the rear discharge electrodes and is parallel to the front substrate intersects a lateral surface of the first barrier ribs at a certain position. An angle between a tangent line at the intersection of the horizontal axis and a lateral surface of the first barrier ribs, on one hand, and a virtual vertical axis orthogonal to the horizontal axis, on the other hand, ranges from 4° to 17°.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for PLASMA DISPLAY PANEL earlier filed in the Korean Intellectual Property Office on 20 Apr. 2004 and there duly assigned Serial No. 10-2004-0027158.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a plasma display panel (PDP) and, more particularly, to a PDP with a new structure.

2. Related Art

A device adopting a plasma display panel (PDP) has not only a large screen but also some excellent characteristics, such as high definition (HD), ultra-thin thickness, light weight, and wide viewing angle. Also, in comparison with other flat panel displays, the device including the PDP can be manufactured in a simple process can be easily fabricated in a large size, so that it has attracted much attention as the next generation of flat panel devices.

A PDP can be classified into a direct current (DC) PDP, an alternating current (AC) PDP, and a hybrid PDP according to the type of discharge voltage applied to it. The PDP can also be divided into an opposing discharge type PDP and a surface discharge type PDP according to the discharge structure. In recent years, an AC surface discharge type triode PDP has typically been used.

In the PDP, a considerable amount (about 40%) of visible rays emitted from phosphor layers are absorbed in scan electrodes, common electrodes, bus electrodes, a dielectric layer covering the electrodes, and a magnesium oxide (MgO) protective layer, which are disposed on a bottom surface of a front substrate. Thus, luminous efficiency is low.

Furthermore, when the surface discharge type triode PDP displays the same image for a long period of time, the phosphor layers are ion-sputtered due to charged particles of the discharge gas, thus causing a permanent image sticking.

SUMMARY OF THE INVENTION

The present invention provides a plasma display panel (PDP) with improved luminous efficiency.

According to an aspect of the present invention, there is provided a PDP including: a front substrate; a rear substrate disposed opposite to the front substrate; first barrier ribs which are disposed between the front substrate and the rear substrate for defining discharge cells with the front substrate and the rear substrate, and which are formed of a dielectric material; front discharge electrodes disposed inside the first barrier ribs so as to surround the discharge cells; rear discharge electrodes disposed inside the first barrier ribs so as to surround the discharge cells and spaced apart from the front discharge electrodes; phosphor layers disposed in the discharge cells; and a discharge gas which fills the discharge cells. From a longitudinal sectional view of the first barrier ribs, a virtual horizontal axis, which extends from a lowermost portion of each of the rear discharge electrodes and which is parallel to the front substrate, intersects a lateral surface of the first barrier ribs at a certain position. An angle between a tangent line at the intersection of the horizontal axis and the lateral surface of the first barrier ribs, on one hand, and a virtual vertical axis orthogonal to the horizontal axis, on the other hand, ranges from 4° to 17°.

The front discharge electrodes may extend in a given direction, and the rear discharge electrodes may extend in a direction which crosses the given direction in which the front discharge electrodes extend. Also, the front discharge electrodes and the rear discharge electrodes may extend in directions parallel to each other. The PDP of the present invention may further include address electrodes which extend in a direction which crosses the direction in which the front discharge electrodes and the rear discharge electrodes extend.

According to the present invention, an MgO protective layer is formed to a uniform thickness on the lateral surface of the first barrier rib, and a sustain voltage margin is sufficient. As a result, uniform plasma discharge occurs, thus improving discharge properties and luminous efficiency.

Also, surface discharge can be induced from all of the lateral surfaces of a discharge space so that the discharge surface can be greatly enlarged.

Furthermore, as discharge occurs from the lateral surfaces of the discharge cells and spreads toward the centers of the discharge cells, the discharge region notably increases, thus enabling efficient utilization of the entirety of the discharge cells. Accordingly, the PDP can be driven at a low voltage so that luminous efficiency is considerably enhanced.

In addition, because the PDP can be driven at a low voltage, even if a high-concentration Xe gas is used as a discharge gas, luminous efficiency improves.

Moreover, since an electric field caused by a voltage applied to the discharge electrode formed on the lateral surface of the discharge space crowds plasma into the center of the discharge space, even if discharge occurs for a long period of time, collision of generated ions with the phosphor layers due to the electric field is prevented. This inhibits the phosphor layers from being ion-sputtered, with the result that no permanent image sticking is caused.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is an exploded perspective view of a plasma display panel (PDP), and in particular a surface discharge type triode PDP. In the PDP100ofFIG. 1, a considerable amount (about 40%) of visible rays emitted from phosphor layers110are absorbed in scan electrodes106, common electrodes107, bus electrodes108, a dielectric layer109covering the electrodes106,107and108, and an MgO protective layer111, which are disposed on a bottom surface of a front substrate101. Thus, luminous efficiency is low.

Furthermore, when the surface discharge type triode PDP100displays the same image for a long period of time, the phosphor layers110are ion-sputtered due to charged particles of the discharge gas, thus causing permanent image sticking.

A plasma display panel (PDP) according to an exemplary embodiment of the present invention will now be described with reference toFIGS. 2 through 7.

FIG. 2is a cutaway exploded perspective view of a PDP according to an exemplary embodiment of the present invention, whileFIG. 3is a cross sectional view taken along lines III—III ofFIG. 2, andFIG. 4is a perspective view of discharge cells and electrodes shown inFIG. 2.

Referring toFIGS. 2 and 3, PDP200includes a front substrate201, a rear substrate202, address electrodes203, a dielectric layer204, first barrier ribs208, second barrier ribs205, front discharge electrodes206, rear discharge electrodes207, MgO layers209and phosphor layers210. The rear substrate202is disposed parallel and opposite to the front substrate201. The first barrier ribs208are disposed between the front substrate201and the rear substrate202, they define discharge cells220with the front and rear substrate201and202, and they are formed of a dielectric material. The front discharge electrodes206are disposed inside the first barrier ribs208so as to surround the discharge cells220. The rear discharge electrodes207are disposed inside the first barrier ribs208so as to surround the discharge cells220, and they are spaced apart from the front discharge electrodes206. The phosphor layers210are disposed in the discharge cells220, which are filled with a discharge gas (not shown).

In the exemplary embodiment of the present invention, since visible rays from the discharge cells220are transmitted through the front substrate201and then externally emitted, the front substrate201is formed of a material, such as glass, having good transmissivity. The front substrate201of the present invention transmits visible rays in the forward direction much better because it does not include scan electrodes, common electrodes, and bus electrodes, as compared with the front substrate of the PDP100. Therefore, if an image is embodied at the ordinary level of luminance, the scan electrodes106, common electrodes107and bus electrodes108are driven at a relatively low voltage so that luminous efficiency improves.

The first barrier ribs208disposed under the front substrate201define the discharge cells220, each of which corresponds to red, green or blue emitting sub-pixels that form one pixel. Also, the first barrier ribs208prevent generation of a misdischarge between the discharge cells220. As shown inFIG. 4, the first barrier ribs208are formed such that the discharge cells220are partitioned in a rectangular matrix shape.

The first barrier ribs208prevent an electrical short between the front discharge electrodes206and the rear discharge electrodes207and inhibit charged particles from directly colliding with the front discharge electrode206and the rear discharge electrode207, and damaging the same. The first barrier ribs208may be formed of a dielectric material, such as PbO, B2O3, or SiO2, which can accumulate wall charge by inducing charged particles.

As shown inFIG. 4, the front discharge electrodes206and the rear discharge electrodes207are disposed inside the first barrier ribs208such that the discharge cells220are surrounded. The front discharge electrode206and rear discharge electrode207are formed of a conductive metal, such as Al or Cu. Also, the front discharge electrodes206and rear discharge electrodes207are spaced apart from each other, and extend parallel to each other in a vertical direction relative to the front substrate201. In this case, the front discharge electrodes206and the rear discharge electrodes207are symmetric with respect to a virtual surface which is parallel to the front substrate201.

Also, when the distance between a scan electrode and an address electrode is small, address discharge is efficiently provoked. Accordingly, in the exemplary embodiment of the present invention, the rear discharge electrodes207act as scan electrodes because they are close to the address electrodes203, while the front discharge electrodes206act as common electrodes. However, even if address electrodes are not used, address discharge between the front discharge electrodes206and rear discharge electrodes207is enabled. Thus, the present invention is not limited to PDPs which include address electrodes. Although not shown in the drawings, if no address electrodes are formed, the rear discharge electrodes207extend in a direction so as to cross the direction in which the front discharge electrodes206extend.

The rear substrate202supports the address electrodes203and the dielectric layer204, and is typically formed of glass as the main element.

The address electrodes203are disposed on a front surface of the rear substrate202. The address electrodes203extend across the front discharge electrodes206and the rear discharge electrodes207.

The address electrodes203are used to generate address discharge, which facilitates sustain discharge between the front discharge electrodes206and the rear discharge electrodes207. More specifically, the address electrodes203aid in lowering the voltage at which sustain discharge begins. Address discharge refers to discharge induced between a scan electrode and an address electrode. Once the address discharge ends, positive ions are accumulated in the scan electrode, and electrons are accumulated in a common electrode, thereby facilitating sustain discharge between the scan electrode and the common electrode.

The dielectric layer204in which the address electrodes203are buried is formed of a dielectric material, such as PbO, B2O3, or SiO2, which prevents positive ions or electrons from colliding with and damaging the address electrodes203during discharge, and also induces charges.

The PDP200of the present invention may further include second barrier ribs205, which are disposed between the first barrier ribs208and the rear substrate202, and which define the discharge cells220together with the first barrier ribs208. AlthoughFIG. 2illustrates that the first barrier ribs208and the second barrier ribs205are partitioned in a matrix shape, the present invention is not limited thereto. As long as it is possible to form a plurality of discharge spaces, the first barrier ribs208and second barrier ribs205may have a variety of patterns. For example, the first barrier ribs208and second barrier ribs205may have not only open patterns, such as stripes, but also closed patterns, such as waffles, matrixes, and deltas. Also, in addition to the rectangular cross sections as in the present embodiment, closed barrier ribs may be formed such that the cross sections of discharge spaces are polygonal (e.g., triangular or pentagonal), circular, or elliptical. In the present embodiment of the present invention, the first barrier ribs208and the second barrier ribs205have the same shape, but may have different shapes.

As shown inFIG. 4, the phosphor layers210substantially form a planar top surface with the second barrier ribs205. Preferably, the phosphor layers210are coated on the lateral surfaces of the second barrier ribs205, and on the rear substrate202between the second barrier ribs205.

The phosphor layers210contain elements that absorb ultraviolet rays and emit visible rays. Namely, phosphor layers in a red emitting sub-pixel contain a fluorescent material such as Y(V,P)O4:Eu, phosphor layers in a green emitting sub-pixel contain a fluorescent material such as Zn2SiO4:Mn or YBO3:Tb, and phosphor layers in a blue emitting sub-pixel contain a fluorescent material such as BAM:Eu.

A discharge gas, for example, Ne, Xe, or a mixture thereof, is injected into the discharge cells220, and the discharge cells220are sealed. In the present invention, because the discharge surface can increase and discharge regions can be enlarged, the amount of generated plasma increases, thus enabling a low-voltage driving of the PDP200. Accordingly, even if high-concentration Xe gas is used as a discharge gas, the PDP200can be driven at a low voltage so that luminous efficiency is greatly enhanced. This solves the problems of a PDP which cannot be driven at a low voltage when a high-concentration Xe gas is used as a discharge gas.

At least the lateral surfaces of the first barrier rib208may be covered by the protective layer209, which is formed of MgO. The MgO layer209is not an indispensable element, but it prevents charged particles from colliding with and damaging the first barrier ribs208formed of a dielectric material, and it also emits a lot of secondary electrons during discharge.

The MgO layer209is typically formed using deposition methods after the first barrier ribs208are formed. It is possible to use non-vacuum deposition techniques, such as spray pyrolysis, but the MgO layer209is generally obtained by methods using MgO as a source. For instance, an MgO source is dissolved using e-beam methods and evaporated, or MgO is sputtered and deposited.

However, if the MgO layer209is deposited by emitting an MgO gas toward the front substrate201, since lateral surfaces208aof the first barrier ribs208are sloped downward as shown inFIG. 3, it is highly feasible that the MgO layer209formed on the lateral surfaces208aof the first barrier ribs208have a non-uniform thickness. Also, because the MgO may flow down the slopes of the lateral surfaces208of the first barrier ribs208, it is harder to obtain a uniform thickness of the MgO layer209. Therefore, in order to form the MgO layer209with a uniform thickness, the lateral surfaces208aof the first barrier ribs208should be appropriately formed.

In particular, portions of the lateral surfaces208a, on which concentrated discharge from the front discharge electrodes206and rear discharge electrodes207are projected, greatly affect the thickness of the MgO layer209. If the gradient of the lateral surface308ais too high as shown inFIG. 8, a difference occurs between the depths h1and h2of portions of a first barrier rib308that covers a front discharge electrode306and a rear discharge electrode307, respectively. As a result, the amount of wall charge accumulated on both of the electrodes306and307become different during discharge, thus inducing non-uniform discharge.

However, if the gradient of the lateral surface408ais too low, i.e., a minus value, as shown inFIG. 9, since the lateral surface408as of a first barrier rib408is blocked by a bottom surface408bof the first barrier rib408, no MgO layer is formed on the lateral surface408a. Even if the MgO layer209is deposited on the lateral surface408a, the MgO flow is downward so that it cannot be formed to a uniform thickness.

Accordingly, as described above, in order to deposit the MgO layer209with a uniform thickness, the shape of the first barrier rib208should be determined in consideration of positions of the front discharge electrodes206and rear discharge electrodes207, such that the lateral surfaces208ahave an appropriate gradient.

The present invention obtains such an appropriate shape of the lateral surface208aas to render uniform the thickness of the MgO layer209based on the rear discharge electrodes207on which discharge is concentrated, and the first barrier ribs208are formed at a relatively high gradient. Hereinafter, a lateral line208b(FIG. 5) of the lateral surface208awill be chiefly observed and described.

FIG. 5is a magnified longitudinal sectional view of a first barrier rib and an MgO layer shown inFIG. 2.

Referring toFIG. 5, from the longitudinal sectional view of the first barrier rib208, a virtual horizontal axis (x-axis), which extends from a lowermost portion207aof the rear discharge electrode207and is parallel to the front substrate201, is considered. The horizontal axis (x-axis) intersects the lateral line208bof the first barrier rib208at a first position P1. Also, a virtual vertical axis (y-axis), which is orthogonal to the horizontal axis (x-axis) at the first position P1, intersects the front substrate201at a second position P2. In this case, a tangent angle θ, between a tangent line T and the vertical axis (y-axis) at the first position P1becomes a parameter that represents the gradient of the lateral line208b.

FIG. 6is a graph of a sustain voltage margin with respect to a tangent angle, andFIG. 7is a graph of a thickness deviation of the MgO layer with respect to a tangent angle.

Referring toFIG. 6, when a tangent angle θ is 13°, the sustain voltage margin has a maximum of 15 V, and is generally distributed in a convex shape. When the tangent angle θ is less than 0° or more than 17°, the sustain voltage margin is greatly reduced. If an absolute value of the tangent angle θ is too great, a gradient is increased as much. This results in a difference between the depths H1and H2of portions of the first barrier rib208that cover the front and rear discharge electrodes206and207as described above. Consequently, the amount of wall charge accumulated on both of the electrodes206and207becomes different during discharge, thus causing non-uniform discharge.

InFIG. 7, the thickness deviation |A−B| of the MgO layer209refers to an absolute value of the difference between a thickness A of the MgO layer209, obtained at a third position (P3ofFIG. 5), and a thickness B of the MgO layer209, obtained at a fourth position (P4ofFIG. 5). Referring toFIG. 5, a virtual line which extends from a vertical center P5of the rear discharge electrode207and is parallel to the horizontal axis (x-axis) intersects the lateral line208bof the first barrier rib208at the third position P3. Also, a virtual line which extends from a vertical center P6of the front discharge electrode206and is parallel to the horizontal axis (x-axis) intersects the lateral line208bof the first barrier rib208at the fourth position P4.

Referring toFIG. 7, it can be observed that, as the tangent angle θ decreases, the thickness of the MgO layer209becomes more non-uniform, because the lateral line208bof the first barrier rib208is disposed in a more slanted orientation relative to the direction in which a MgO source is emitted. Particularly, when the tangent angle θ is less than 4°, the thickness deviation |A−B| of the MgO layer209increases. Accordingly, when the tangent angle θ is less than 4°, discharge is non-uniformly generated and discharge properties are degraded.

Therefore, it is concluded fromFIGS. 6 and 7that the tangent angle θ should range from 4° to 17° in order to obtain a sufficient sustain voltage margin and an MgO layer with a uniform thickness.

A method of driving the PDP200having the above-described structure will now be described.

At the outset, by applying an address voltage between the address electrodes203and the rear discharge electrodes207, address discharge is induced, with the result that one discharge cell220on which sustain discharge will be generated is selected.

Thereafter, if an alternating current (AC) sustain discharge voltage is applied between the front discharge electrode206and the rear discharge electrode207of the selected discharge cell220, sustain discharge is induced between the front discharge electrodes206and rear discharge electrodes207. As the energy level of a discharge gas excited by the sustain discharge is lowered, ultraviolet rays are emitted. Then, the ultraviolet rays excite the phosphor layer210coated inside the discharge cell220. As the energy level of the excited phosphor layer210is lowered, visible rays are emitted. The emitted visible rays form an image.

In the PDP100shown inFIG. 1, because sustain discharge is horizontally generated between the scan electrodes106and the common electrodes107, the discharge area is relatively narrow. On the other hand, in the PDP200of the present invention, sustain discharge is generated from all of the lateral surfaces that define the discharge cell220, and thus the discharge area is relatively wide.

Also, in the exemplary embodiment of the present invention, the sustain discharge is induced in the form of a closed curve along the lateral surfaces of the discharge cell220, and then gradually spread toward the center of the discharge cell220. Thus, the volume of a region where the sustain discharge occurs is increased. Moreover, even space charges of the discharge cell220, which are not conventionally utilized, contribute to luminescence. As a result, the luminous efficiency of the PDP200is enhanced.

Furthermore, in the PDP200of the present invention, as shown inFIG. 3, sustain discharge is generated only in portions defined by the first barrier ribs208. Accordingly, unlike in the PDP100, the ion-sputtering of the phosphor layers due to charged particles is prevented so that, even if the same image is displayed for a long period of time, no permanent image sticking is caused.