Plasma display panel (PDP) having electromagnetic wave shielding electrodes

A PDP that can significantly improve light emitting efficiency and light transmission includes a new discharge cell structure and electromagnetic wave shielding electrodes that replace the function of an electromagnetic wave shielding filter includes: a transparent front substrate; a rear substrate arranged in parallel to the front substrate; a plurality of front barrier ribs, consisting of a dielectric material, and arranged between the front substrate and the rear substrate to define discharge cells together with the front substrate and the rear substrate; a front discharge electrode and a rear discharge electrode, separated from each other, and arranged in the front barrier rib to surround the discharge cell; at least one electromagnetic wave shielding electrode, arranged in front of and separated from the front discharge electrode, and surrounding the discharge cell; a plurality of rear barrier ribs arranged between the front barrier ribs and the rear substrate; a fluorescent layer arranged in a space defined by the rear barrier ribs; and a discharge gas arranged within the discharge cells.

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 HAVING ELECTROMAGNETIC WAVE SHIELDING ELECTRODES earlier filed in the Korean Intellectual Property Office on 20 Apr. 2004 and there duly assigned Serial No. 2004-27142.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a Plasma Display Panel (PDP), and more particularly, to a PDP having an electromagnetic wave shielding electrode.

2. Description of the Related Art

A PDP includes a front case having a peripheral unit to define a window, an electromagnetic wave shielding filter to cover the window, a conductive filter holder fixed to a coupling boss of the front case by a screw to press the electromagnetic wave shielding filter onto the front case, a PDP on the rear of the filter holder, including a front panel and a rear panel, a chassis to support the PDP, connecting cables mounted on the rear of the chassis, connecting the PDP to a driver to drive the PDP, and a rear case to couple with the front case to form a case to the rear of the chassis. A thermal conductive sheet is interposed between the PDP and the chassis.

In an alternative type three electrode surface discharge PDP, the front panel includes a front substrate, sustaining electrode pairs including Y electrodes and X electrodes formed on the rear surface of the front substrate, a front dielectric layer to cover the sustaining electrode pairs, and a protective film to cover the front dielectric layer. Each of the Y electrodes and the X electrodes includes transparent electrodes formed of ITO and bus electrodes formed of a high conductivity metal. The bus electrodes are connected to a connecting cable located on the left and right sides of the PDP.

The rear panel includes a rear substrate, address electrodes crossing the sustaining electrode pairs on the front surface of the rear substrate, a rear dielectric layer to cover the address electrodes, barrier ribs to define discharge cells formed on the rear dielectric layer, and a fluorescent layer in each of the discharge cells. The address electrodes are connected to connecting cables located in the upper and lower parts of the PDP.

The electromagnetic wave shielding filter includes a central unit facing the window, and a peripheral unit surrounding the central unit. A conductive mesh layer to shield electromagnetic waves is formed in the central unit, and a metal layer to electrically connect the conductive mesh layer to the conductive filter holder is formed in the peripheral unit. The conductive mesh layer is formed on a transparent substrate and covered by a planarized layer, and a near infrared shielding layer is formed on the planarized layer. Electromagnetic energy trapped by the conductive mesh layer is transferred to the rear of the PDP via the metal layer and the conductive filter holder or discharged to the outside of the PDP.

However, the above plasma display device has a low brightness problem due to the absorption of visible light emitted from the fluorescent layer in the discharge cells, by the sustaining electrode pairs that cause the discharge, the front dielectric layer, and the protective layer on the rear surface of the front substrate through which the light must pass, and the electromagnetic wave shielding filter that has low transmission of light in front of the rear panel.

Also, in the PDP, all of the sustaining electrode pairs except the bus electrodes have to be formed of ITO electrodes, which have a high resistance, to transmit the visible light generated by the discharge cells, since the sustaining electrode pairs that cause the discharge are located on the rear surface of the front substrate, thereby increasing driving voltage. Also, the voltage drop of the ITO electrodes can cause non-uniform images in a large panel.

Also, in the PDP, the discharge occurs at the rear of the protective film in the discharge cells, since the electrodes that cause the discharge are formed on the rear surface of the front substrate through which the visible light is transmitted. This causes a drop in light emitting efficiency. Also, there is a problem of a permanent latent image due to ion sputtering on the fluorescent layer by charged particles of the discharge gas.

Also, a plasma display device having above structure is expensive to manufacture, since the electromagnetic wave shielding filter and the filter holder must be manufactured separately and then attached to the front case.

Also, in a plasma display device having above structure, a space is formed between the electromagnetic wave shielding filter and the PDP due to the thickness of the conductive filter holder. Heat generated by the PDP builds up in this space, because air circulation is blocked by the conductive filter holder. Paths for ventilation can be formed by modifying the shape of the conductive filter holder, but since the gap (the thickness of the conductive filter holder) between the electromagnetic wave shielding filter and the PDP is very small, it is difficult to provide sufficient heat discharge by air circulation.

Also, the conductive mesh layer reduces light transmission and brightness ratio by absorbing or diffracting a portion of the visible light generated by the discharge cells, since the electromagnetic wave shielding filter in front of the PDP includes the conductive mesh layer.

Also, the contrast ratio of the PDP is lowered since the PDP does not include a device for absorbing external light. Accordingly, a clear image can not be displayed. To solve these problems, an additional device for absorbing the external light can be applied to the PDP, but this requires an additional process and cost.

SUMMARY OF THE INVENTION

The present invention provides a PDP that can solve the problems of non-uniform images, a permanent latent image, and lowering of the contrast ratio of the PDP, and can significantly improve discharge efficiency, opening ratio, transmission of light, and heat radiation efficiency.

According to an aspect of the present invention, a PDP is provided comprising: a transparent front substrate; a rear substrate arranged in parallel to the front substrate; a plurality of front barrier ribs, formed of a dielectric material, are arranged between the front substrate and the rear substrate to define discharge cells together with the front substrate and the rear substrate; a front discharge electrode and a rear discharge electrode, separated from each other, are arranged in the front barrier rib to surround the discharge cell; at least one electromagnetic wave shielding electrode, arranged in front of and separated from the front discharge electrode, and surrounding the discharge cell; a plurality of rear barrier ribs arranged between the front barrier ribs and the rear substrate; a fluorescent layer arranged in each space defined by the rear barrier ribs; and a discharge gas arranged within the discharge cells.

The at least one electromagnetic wave shielding electrode is preferably arranged in the front barrier ribs.

The at least one electromagnetic wave shielding electrode is preferably arranged on the rear of the front substrate and covered by the front barrier ribs.

The at least one electromagnetic wave shielding electrode is preferably of a dark color.

The at least one electromagnetic wave shielding electrode is preferably electrically connected to an external conductive member of the PDP.

The external conductive member preferably comprises a chassis adapted to support the PDP from the rear of the PDP.

The PDP preferably further comprises a near infrared ray shielding layer affixed to the front substrate.

The front discharge electrodes preferably extend in one direction and the rear discharge electrodes extend to cross the front discharge electrodes in the discharge cells.

The PDP further preferably comprises address electrodes, wherein the front discharge electrodes and the rear discharge electrodes extend in one direction and wherein the address electrodes extend to cross the front discharge electrodes and the rear discharge electrodes.

The address electrodes are preferably arranged between the rear substrate and the fluorescent layers, and a dielectric layer is preferably located between the address electrodes and the fluorescent layers.

The front discharge electrodes and the rear discharge electrodes each preferably have a ladder shape, and at least the side surface of the front barrier ribs is preferably covered by a protective film.

The front barrier ribs and the rear barrier ribs preferably comprise a single unit.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is an exploded perspective view of a PDP. Referring toFIG. 1, the PDP includes a front case10having a peripheral unit11to define a window12, an electromagnetic wave shielding filter100to cover the window12, a conductive filter holder20fixed to a coupling boss13of the front case10by a screw23to press the electromagnetic wave shielding filter100onto the front case10, a PDP200on the rear of the filter holder20, including a front panel210and a rear panel220, a chassis30to support the PDP200, connecting cables31and32mounted on the rear of the chassis30, connecting the PDP200to a driver (not shown) to drive the PDP200, and a rear case40to couple with the front case10to form a case5to the rear of the chassis30. As depicted inFIG. 4, a thermal conductive sheet230is interposed between the PDP200and the chassis30.

FIG. 2is a cutaway exploded perspective view of part of an alternative type three electrode surface discharge PDP. Referring toFIG. 12, the front panel210and the rear panel220of the alternative type three electrode surface discharge PDP200is depicted. The front panel210includes a front substrate211, sustaining electrode pairs214including Y electrodes212and X electrodes213formed on the rear surface211aof the front substrate211, a front dielectric layer215to cover the sustaining electrode pairs214, and a protective film216to cover the front dielectric layer215. Each of the Y electrodes212and the X electrodes213includes transparent electrodes212band213bformed of ITO and bus electrodes212aand213aformed of a high conductivity metal. The bus electrodes212aand213aare connected to a connecting cable31located on the left and right sides of the PDP200.

The rear panel220includes a rear substrate221, address electrodes222crossing the sustaining electrode pairs214on the front surface221aof the rear substrate221, a rear dielectric layer223to cover the address electrodes222, barrier ribs224to define discharge cells226formed on the rear dielectric layer223, and a fluorescent layer225in each of the discharge cells. The address electrodes222are connected to connecting cables32located in the upper and lower parts of the PDP200.

The electromagnetic wave shielding filter100, as depicted inFIGS. 3 and 3A, includes a central unit110facing the window12, and a peripheral unit120surrounding the central unit110. A conductive mesh layer111to shield electromagnetic waves is formed in the central unit110, and a metal layer121to electrically connect the conductive mesh layer111to the conductive filter holder20is formed in the peripheral unit120. As depicted inFIG. 4, the conductive mesh layer111is formed on a transparent substrate113and covered by a planarized layer112, and a near infrared shielding layer101is formed on the planarized layer112. Electromagnetic energy trapped by the conductive mesh layer111is transferred to the rear of the PDP200via the metal layer121and the conductive filter holder20or discharged to the outside of the PDP200.

However, the above plasma display device, as depicted inFIG. 4, has a low brightness problem due to the absorption of visible light emitted from the fluorescent layer225in the discharge cells226, by the sustaining electrode pairs214that cause the discharge, the front dielectric layer215, and the protective layer216on the rear surface211aof the front substrate211through which the light must pass, and the electromagnetic wave shielding filter100that has low transmission of light in front of the rear panel220.

Also, in the PDP200, all of the sustaining electrode pairs214except the bus electrodes have to be formed of ITO electrodes, which have a high resistance, to transmit the visible light generated by the discharge cells226, since the sustaining electrode pairs214that cause the discharge are located on the rear surface211aof the front substrate211, thereby increasing driving voltage. Also, the voltage drop of the ITO electrodes can cause non-uniform images in a large panel.

Also, in the PDP200, the discharge occurs at the rear of the protective film216in the discharge cells226, since the electrodes that cause the discharge are formed on the rear surface211aof the front substrate211through which the visible light is transmitted. This causes a drop in light emitting efficiency. Also, there is a problem of a permanent latent image due to ion sputtering on the fluorescent layer by charged particles of the discharge gas.

Also, a plasma display device having above structure is expensive to manufacture, since the electromagnetic wave shielding filter100and the filter holder20must be manufactured separately and then attached to the front case10.

Also, in a plasma display device having above structure, a space S is formed between the electromagnetic wave shielding filter100and the PDP200due to the thickness of the conductive filter holder20. Heat generated by the PDP200builds up in this space S, because air circulation is blocked by the conductive filter holder20. Paths for ventilation can be formed by modifying the shape of the conductive filter holder20, but since the gap (the thickness of the conductive filter holder20) between the electromagnetic wave shielding filter100and the PDP200is very small, it is difficult to provide sufficient heat discharge by air circulation.

Also, the conductive mesh layer111reduces light transmission and brightness ratio by absorbing or diffracting a portion of the visible light generated by the discharge cells, since the electromagnetic wave shielding filter100in front of the PDP200includes the conductive mesh layer111.

Also, the contrast ratio of the PDP200is lowered since the PDP200does not include a device for absorbing external light. Accordingly, a clear image can not be displayed. To solve these problems, an additional device for absorbing the external light can be applied to the PDP, but this requires an additional process and cost.

A plasma display panel (PDP) according to a first embodiment of the present invention will now be described in detail with reference to theFIGS. 5 through 8.

Referring toFIG. 5, the plasma display device comprises a front case10which includes a window12and a peripheral unit11, a PDP400which includes a front panel410and a rear panel420and is located on the rear of the front case10, a chassis30that supports the PDP400, connecting cables31and32that connect the PDP400to a circuit substrate (not shown) and are located on the rear of the chassis30, a connecting boss9and a screw8which couple the chassis30to the front case10, and a case5composed of a rear case40and the front case10as a single body, wherein the rear case40is located on the rear of the chassis30and is coupled to the front case10.

As depicted inFIG. 8, a thermal conductive sheet230is interposed between the PDP400and the chassis30.

As is easily seen by comparingFIG. 1andFIG. 5, a plasma display device having the PDP400according to a first embodiment of the present invention does not include an electromagnetic wave shielding filter100and a filter holder20. This saves cost and time for manufacture and assembly. However, the PDP400according to the first embodiment of the present invention does include an element to shield electromagnetic waves generated during operation, which will be described later.

Now, the PDP400according to an embodiment of the present invention will be described in detail.

Referring toFIG. 6, the PDP400according to the first embodiment of the present invention comprises a front panel410and a rear panel420. The front panel410includes a transparent front substrate411and the rear panel420includes a rear substrate421parallel to the front substrate411.

The front panel410comprises: front barrier ribs424formed of dielectric, located on the rear surface of the front substrate411, to define discharge cells426together with the front substrate411and the rear substrate421; front discharge electrode413and rear discharge electrode412separated from each other and located in the front barrier rib424to surround the discharge cell426; an electromagnetic wave shielding electrode414located between the front substrate411and the front discharge electrode413in the front barrier ribs424, and separated from the front discharge electrode413; a protective film416to cover a side surface424f,which can be formed as necessary, of the front barrier ribs424; and a near infrared ray shielding layer403formed on the front surface411aof the front substrate411.

The rear panel420comprises a rear substrate421; address electrodes422on the front surface421aof the rear substrate421, crossing the front discharge electrodes and the rear discharge electrodes, and extending over the discharge cells426aligned in a row; a dielectric layer423to cover the address electrodes422; rear barrier ribs415formed on the dielectric layer423; and fluorescent layer425arranged in a space defined by the rear barrier rib415.

The front panel410and the rear panel420are sealed by a coupling member such as frit (not shown), and the inside of the discharge cells426is filled with a discharge gas selected from the group consisting of Ne, He, and Ar or a mixture of those gases. The discharge gas can include approximately 10% Xe.

The front substrate411and the rear substrate421are generally formed of glass, and the front substrate411is preferably formed of a material having a high light transmission. The rear surface411bof the front substrate411that defines the discharge cells426does not include the sustaining electrode pairs214, the front dielectric layer215covering the sustaining electrode pairs214, the protection film216covering the front dielectric layer215, and the electromagnetic wave shielding filter100which has a light transmission of approximately 40–50%. Therefore, unlike the conventional alternate type three electrode surface discharge PDP, the front visible light transmission is significantly increased, since the visible light emitted from the fluorescent layers425of the discharge cells426passes through only the front substrate411, which has high light transmission, and the near infrared shielding layer403.

Also, in order to increase the brightness of the PDP400, a reflection layer (not shown) can be formed on the upper surface421a of the rear substrate421or the upper surface423aof the dielectric layer423, or a light reflecting material can be included in the dielectric layer423, to reflect visible light generated by the fluorescent layers425forward.

In an alternate type three electrode surface discharge PDP, the front discharge electrodes413and the rear discharge electrodes412are ITO electrodes, which have a relatively high resistance, to increase light transmission. However, in the present embodiment, the material for forming the front discharge electrodes413and the rear discharge electrodes412can be formed of materials having high electrical conductivity like Ag, Cu, Cr, or a composite of these materials without needing to consider the light transmission.

The front barrier ribs424are formed of dielectric and protect the front discharge electrodes413, the rear discharge electrodes412, and the electromagnetic wave shielding electrode414from damage by charged particles during discharge. The front barrier ribs424, formed of a dielectric; also prevent direct electrical connection between the front discharge electrodes413, the rear discharge electrodes412, and the electromagnetic wave shielding electrode414. The dielectric also generates a wall charge by inducing charged particles during discharge, and the wall charge helps the discharge between the front discharge electrodes413and the rear discharge electrodes412. Dielectrics that can perform above function can comprise PbO, B2O3, or SiO2.

The front barrier ribs424are formed to define the discharge cells426together with the front substrate411and the rear substrate421on the rear surface of the front substrate411. InFIG. 6, the front barrier ribs424are depicted to define the discharge cells426as a matrix shape, but are not limited thereto and can be formed in a honeycomb shape or a delta shape. Also, inFIG. 6, the cross-section of the discharge cells426is rectangular, but is not limited thereto and can be shaped in a triangle, a polygon such as a pentagon, a circle, or an oval.

The front discharge electrode413, the rear discharge electrode412, and the electromagnetic wave shielding electrode414that surround the discharge cell426are disposed in the front barrier rib424. Also, referring to the magnified portion inFIG. 6, to locate the front discharge electrodes413, the rear discharge electrodes412, and the electromagnetic wave shielding electrode414in the front barrier ribs424, a first front barrier rib layer424ais formed on the rear surface411bof the front substrate411and the electromagnetic wave shielding electrode414is formed on the first front barrier rib layer424a. A second front barrier rib layer424bis formed on the electromagnetic wave shielding electrode414to cover the electromagnetic wave shielding electrode414, and the front discharge electrodes413are formed on the second front barrier rib layer424b. Afterward, a third front barrier rib layer424cis formed on the front discharge electrodes413to cover the front discharge electrodes413, and the rear discharge electrodes412are formed on the third front barrier rib layer424c.A fourth front barrier rib layer424dis formed on the rear discharge electrodes412to cover the rear discharge electrodes412. Each of the first through the fourth front barrier rib layers424athrough424dcan be formed in more than two layers if necessary (for example, to make a thick layer).

As depicted inFIGS. 6 and 6A, at least a portion of the side surface424fof the front barrier ribs424is preferably covered by the protective film416, and the protective film416is preferably formed of MgO. The protective film416protects the front discharge electrodes413, the rear discharge electrodes412, the electromagnetic wave shielding electrode414, and the front barrier ribs424, and also aids discharge through effective emission of secondary electrons. Referring to the magnified drawing of the front barrier ribs424inFIGS. 6 and 6A, the protective film416can be formed by deposition, and the protective film416can also be formed on the rear surface424eof the front barrier ribs424and the rear surface411bof the front substrate411during the deposition of the protective film416. However, the protective film416formed on the rear surface424eof the front barrier ribs424and the rear surface411bof the front substrate411does not adversely affect the performance of the PDP of the present embodiment.

The rear barrier ribs415can be formed on the dielectric layer423, and can be formed of glass containing elements such as Pb, B, Si, Al and O, and when necessary, a filler such as ZrO2, TiO2, and Al2O3and a pigment such as Cr, Cu, Co, Fe, and TiO2. The rear barrier ribs415can be formed of the same material as the front barrier ribs424.

The rear barrier ribs415secure a space for locating the fluorescent layer425, define the discharge cells426, and prevent cross talk between discharge cells. Also, together with the front barrier ribs424, they resist the negative pressure generated by the vacuum (for example, 0.5 atm) of a discharge gas filling the space between the front panel410and the rear panel420. The rear barrier ribs415can include a reflection material so that the visible light generated by the discharge cell can be reflected forward. The fluorescent layers425of red, green and blue can be located in the space defined by the rear barrier ribs415, and the fluorescent layers425are sectioned by the rear barrier ribs415.

The fluorescent layer425is formed by drying and sintering a fluorescent paste applied on the front surface423aof the dielectric layer423and the side surface415aof the rear barrier ribs415, and is a mixture of solvent, a binder, and a red, green, or blue light emitting fluorescent material. The red light emitting fluorescent material can be a material such as Y(V,P)O4:Eu, the green light emitting fluorescent material can be materials such as ZnSi04:Mn, YBO3:Tb, and the blue light emitting fluorescent material can be a material such as BAM:Eu.

InFIGS. 7 and 7A, the front discharge electrodes413, the rear discharge electrodes412, the electromagnetic wave shielding electrode414, and the discharge cells426according to the first embodiment are depicted. InFIGS. 7 and 7A, the front discharge electrodes413and the rear discharge electrodes412extend along the x axis parallel to each other, and the address electrodes422extend along the y axis to cross the front discharge electrodes413and the rear discharge electrodes412in the discharge cells426.

On the other hand, it is preferable that the addressing discharge occurs between the rear discharge electrode412and the address electrode since the distance between the rear discharge electrode and the address electrode is shorter than the distance between the front discharge electrode and the address electrode. The rear discharge electrode412is preferably a common electrode and the front discharge electrode413is preferably a scan electrode, but the present invention is not limited thereto.

The electromagnetic wave shielding electrode414is located in front of the front discharge electrodes413, and it is not necessarily located in the front barrier ribs424as depicted inFIG. 6. The locations of the electromagnetic wave shielding electrode414will be described later.

The width414wof the electromagnetic wave shielding electrode414is preferably greater than the widths413wand412wof the front discharge electrodes413and the rear discharge electrodes412. In this manner, the electromagnetic waves generated at the front discharge electrodes413and the rear discharge electrodes412can be shielded readily. However, the width414wof the electromagnetic wave shielding electrode414is not necessarily greater than the widths413wand412wof the front discharge electrodes413and the rear discharge electrodes412, while still shielding the electromagnetic waves within the permissible electromagnetic wave generation range. Also, the width414wof the electromagnetic wave shielding electrode414is preferably large enough to simultaneously cover the front discharge electrodes413a1and413a2located sequentially along a row of the discharge cells426and adjacent to each other in the front barrier ribs424, and to cover the rear discharge electrodes412a1and412a2extending sequentially parallel to the front discharge electrodes413and adjacent to each other in the front barrier ribs424from the front surface of the front discharge electrodes413and the rear discharge electrodes412, but the present invention is not limited thereto.

Also, the electromagnetic wave shielding electrode414can be formed separately along the light emitting cells of the x axis as the front discharge electrodes413and the rear discharge electrodes412depicted inFIG. 7However, in this case also, an additional electrical conductor to the electromagnetic wave shielding electrode414or a plurality of grounding conductors is required for migration of free electrons in the electromagnetic wave shielding electrode414. The concept of the present invention includes one or more electromagnetic wave shielding electrodes414in front of the front discharge electrodes413, in order to perform the electromagnetic wave shielding function. Generation of the electromagnetic waves, migration of the free electrons, and the grounding in relation to the electromagnetic wave shielding electrode414will be described later.

The operation of the PDP400having above structure will now be described. The operation of the PDP400described herewith is only illustrative, and therefore the present invention is not limited thereto.

When applying an address voltage between the address electrodes422and the rear discharge electrodes412from an external power source, a discharge cell426to be illuminated is selected, and then wall charges accumulate on the side surface of the barrier rib where the rear discharge electrodes412of the selected discharge cells426are located. Afterward, when a high voltage pulse is applied to the front discharge electrodes413and a relatively low voltage pulse (generally it can be a ground voltage, but is not limited thereto) is applied to the rear discharge electrodes412, the wall charges migrate due to the potential voltage difference generated between the front discharge electrodes413and the rear discharge electrodes412. A plasma is generated by the collision of the migrating wall charges with atoms of the discharge gas in the discharge cells. A discharge is easily initiated at points where the front discharge electrodes413and the rear discharge electrodes412are close to each other, since a relatively strong electric field is formed at these points. Unlike the alternate type three electrode surface discharge PDP200in which the discharge occurs mainly on the rear of the front dielectric layer215, that is, on the rear surface216aof the protective film216, in the case of the present embodiment, the amount of the discharge is significantly increased since the discharge occurs in the surrounded side surface of the discharge cells426where the front discharge electrode413and the rear discharge electrodes412are located. Also, when the voltage between the front discharge electrodes413and the rear discharge electrodes412is maintained for a defined period of time, the electric fields formed on the side surfaces of the discharge cells426are concentrated on the center of the discharge cells426. Accordingly, the discharge region is greater than that of the previously described PDP, and accordingly, the amount of ultraviolet radiation generated by the discharge is increased. Also, ion sputtering to the fluorescent layers425is prevented, since the discharge occurs from the surrounding area toward the center of the discharge cells426, blocking the migration of ions colliding with the fluorescent layers425.

When the voltage difference between the front discharge electrodes413and the rear discharge electrodes412after discharging is lower than the discharge voltage, no further discharge occurs, but a space charge and a wall charge are formed in the discharge cells426. When applying an opposite voltage to the pulse voltage initially applied to the front discharge electrodes413and the rear discharge electrodes412, a discharge occurs again by reaching the firing voltage with the aid of the wall charge. By applying the pulse voltage alternately to the front discharge electrodes413and the rear discharge electrodes412, the discharge is continued. Ultraviolet rays generated by the discharge excite fluorescent molecules of the fluorescent layers425by colliding with the fluorescent layers425. When the excited fluorescent molecules fall from a higher energy level to a lower energy level, visible light is generated. Some of the visible light proceeds forward and the rest displays an image after reflecting from the dielectric layer423, the rear barrier ribs415, or the rear substrate421. A predetermined color image can be displayed when the red, green, or blue light fluorescent material is coated in each discharge cell of the unit pixels that form a color image.

The principle of generating an electromagnetic wave and the function of the electromagnetic wave shielding electrode414will now be described with reference toFIG. 7.

As described above, a pulse voltage that can cause a discharge, the magnitude and polarity of which can change according to time, is applied between the front discharge electrodes413and the rear discharge electrodes412. The magnitude and direction of the electric field generated by the front discharge electrodes413and the rear discharge electrodes412can also change according to time, with changes in the pulse voltage. Also, when the magnitude and direction of the electric field change according to time, as can be verified by Maxwell's equations, an magnetic field is induced. The magnetic field also changes according to time since the rate of change of the electromagnetic field is not constant. When the electromagnetic waves are irradiated by the PDP, they can cause malfunctions of other electronic devices, and are also harmful to the human body. When an electromagnetic wave shielding electrode414formed of a conductive material is located in front of the front discharge electrodes413, the electromagnetic waves generated between the front discharge electrodes413and the rear discharge electrodes412move free charges in the electromagnetic wave shielding electrode414. This reduces the electromagnetic waves as their energy is consumed in moving the free charges. In addition, electromagnetic waves generated by the circuit unit, which controls, transforms, and amplifies the voltages applied to the PDP, located on the rear of the chassis, can also be shielded by the electromagnetic wave shielding electrode414by the same principle as described above.

The contribution of the electromagnetic wave shielding electrode414to the increase in light transmission and heat radiation characteristics will now be described with reference toFIG. 8.

As seen inFIG. 4, the transmission of visible light in the PDP200is significantly reduced by the conductive mesh layer111which blocks a portion of the visible light emitted from the discharge cells226, since the electromagnetic wave shielding filter100having the conductive mesh layer111is located in front of the PDP200.

However, in the PDP400of the present embodiment, the electromagnetic wave shielding electrode414can act as the electromagnetic wave shielding filter100without blocking the visible light from the fluorescent layers425since the electromagnetic wave shielding electrode414is formed in the front barrier ribs424together with the front discharge electrodes413and the rear discharge electrodes412.

Also, unlike the PDP200, since the PDP400according to the present embodiment does not have a space formed by the electromagnetic wave shielding filter100and the filter holder20, heat generated by the PDP400is not trapped but is instead easily released to the outside. Also, the electromagnetic wave shielding electrode414can dissipate heat generated by the PDP400since the electromagnetic wave shielding electrode414generally has a high thermal conductivity and is grounded to a relatively low temperature conductive member outside the PDP400. The grounding of the electromagnetic wave shielding electrode414will be described later.

The contribution of the electromagnetic wave shielding electrode414to the improvement of contrast ratio will now be described with reference toFIG. 9. The PDP200has a low contrast ratio since external light Vi from an external light source enters the PDP200and can not be efficiently absorbed but is reflected forward. However, in the first embodiment of the present invention, the reduction of contrast ratio by light reflection can be prevented by making the electromagnetic wave shielding electrode414a dark color to easily absorb external light Vi and prevent reflection.

A modified version of PDP from the first embodiment of the present invention will now be described, focusing on the features which differ from the first embodiment, with reference toFIG. 10. In the modified version of PDP500, the electromagnetic wave shielding electrode414is not located in front barrier ribs524but on the rear surface411bof the front substrate411, covered by front barrier ribs524. As can be seen in the magnified drawing of the front barrier ribs524inFIG. 10, the front barrier ribs524include the electromagnetic wave shielding electrode414on the rear surface411bof the front substrate411, a first front barrier rib layer524aformed on a rear surface of the front substrate411to cover the electromagnetic wave shielding electrode414, and the front discharge electrodes413on the first front barrier rib layer524a. A second front barrier rib layer524bis formed on the front discharge electrodes413to cover the front discharge electrode413, and the rear discharge electrode412is formed on the second front barrier rib layer524b. Afterward, a third front barrier rib layer524cis formed on the rear discharge electrodes412to cover the rear discharge electrodes412.

In the modified version of the first embodiment of the present invention, as can be seen from the process for forming the front barrier rib524, the process for forming the fourth front barrier rib layer524dis omitted, thereby reducing processing and manufacturing costs. Each of the first through third front barrier rib layers524a,524b, and524ccan include more than two layers (for example, to make a thick layer) as necessary.

The electromagnetic wave shielding electrode414can be formed in a variety of locations beside that of the modified version of the present invention. For example, after forming a hollow portion (not shown) on a location where the front barrier rib of the rear surface of the front substrate is formed, and an electromagnetic wave shielding electrode is formed in the hollow portion, the front barrier rib can be formed on the electromagnetic wave shielding electrode. Also, after forming the electromagnetic wave shielding electrode414on the front surface of the front substrate, the electromagnetic wave shielding electrode414can be covered by a planarizing material having good light transmission. Also, after forming the electromagnetic wave shielding electrode414on the front surface of the front substrate, the electromagnetic wave shielding electrode414can be covered by the near infrared ray shielding layer403. Also, after forming the electromagnetic wave shielding electrode414on the front surface of the near infrared ray shielding layer403, the electromagnetic wave shielding electrode414can be covered by an additional planarizing layer. After forming the electromagnetic wave shielding electrode414on the front surface of the front substrate411, the electromagnetic wave shielding electrode414can be covered by an optical film such as a light reflection film as well as the near infrared ray shielding layer. Also, after forming the electromagnetic wave shielding electrode414on the front surface of the optical film, the electromagnetic wave shielding electrode414can be covered by a planarizing layer. Accordingly, the location of the electromagnetic wave shielding electrode414is not limited to the embodiment of the present invention.

Grounding of the electromagnetic wave shielding electrode414according to the present invention will now be described with reference toFIG. 11. A grounding conductor for migration of free charges from the PDP400to the outside is preferably included in the PDP400since the electromagnetic wave shielding electrode414shields the electromagnetic waves generated at the PDP400by the movement of the free charges. In this reason, the electromagnetic wave shielding electrode414needs to be grounded by electrically connecting a conductive grounding cable33to the electromagnetic wave shielding electrode414in the PDP400, and connecting the grounding cable33to the chassis30formed of a conductive member and located outside of the PDP400.

However, connecting the grounding cable33to a conductive member is not limited to the chassis30. That is, for grounding the electromagnetic wave shielding, the grounding cable33can be electrically connected to the case5outside of the PDP400, or to a grounding unit (not shown) of the circuit unit to the rear of the chassis30. Also, the electromagnetic wave shielding electrode414can be grounded by electrically connecting the grounding cable33to the conductive connecting boss9and a screw8which couple the chassis30to the front cabinet10. The conductive member is not limited to the above description, and grounding can be achieved by connecting the grounding cable33to any conductive member outside the PDP400.

A second embodiment of the present invention will now be described, focusing on the features which differ from the first embodiment, with reference toFIGS. 12 and 13.

In the second embodiment, the address electrodes of the first embodiment do not exist, but instead, as can be seen inFIG. 13, front discharge electrodes613extend along the x axis and rear discharge electrodes612extend along the y axis to cross the front discharge electrodes613at discharge cells626.

The operation of a PDP600according to the second embodiment will now be described, focusing on the differences from the first embodiment. In the second embodiment, unlike the first embodiment, addressing discharge occurs when a voltage is applied to the front discharge electrodes613and the rear discharge electrodes612, and a wall charge accumulates on the side surface of the discharge cells626. That is, the addressing discharge which occurred between the address electrodes and the rear discharge electrodes in the first embodiment, occurs between the front discharge electrodes613and the rear discharge electrodes612. Therefore, the discharge cell626to be discharged is selected and then the sustaining discharge occurs in the discharge cell626. So, the PDP600can display an image in this process.

Referring toFIG. 14, a third embodiment will now be described, focusing on the features which differ from the first embodiment. The PDP700of the third embodiment has a single combined barrier rib724instead of the front barrier rib424and the rear barrier rib415of the PDP400in the first embodiment. The combining the front barrier rib424and the rear barrier rib415to a single unit does not imply that the barrier rib724is formed by a single process, but rather that the front barrier rib424and the rear barrier rib415can not be separated without breaking since they are bonded by an adhesive. To manufacture the single combined barrier rib724, referring to the magnified drawing inFIG. 14, a rear barrier unit724bof the barrier rib724is formed on the front surface421a of the rear substrate421. After arranging a paste that contains fluorescent material in a space defined by the rear barrier rib unit724b, the paste is dried and sintered.

Afterward, a first barrier rib layer724cis formed on the rear barrier rib unit742bof the barrier rib724, the rear discharge electrode412is formed on the first barrier rib layer724c,a second barrier rib layer724dis formed to cover the rear discharge electrode412, the front discharge electrode413is formed on the second barrier rib layer724d,and a third barrier rib layer724eis formed to cover the front discharge electrode413. Then, the electromagnetic wave shielding electrode414is formed on the third barrier rib layer724e,and the electromagnetic wave shielding electrode414is covered by a fourth barrier rib layer724f.Each of the rear unit742bof the barrier rib724and the first through fourth barrier rib layers724c,724d,724e,and724fcan include more than two layers (for example, to make a thick layer) as necessary.

After forming the barrier rib724by the above method, the protective film416is formed on a front unit724aof the barrier rib724on which at least the electromagnetic wave shielding electrode414, the front discharge electrode413, and the rear discharge electrode412are formed. The protective film416can also be formed on the upper surface425aof the fluorescent layer425and the front surface724gof the barrier rib724. However, forming the protective film416on the upper surface425aof the fluorescent layer425and the front surface724gof the barrier rib724does not adversely affect the operation of the PDP700. On the contrary, the protective film416on the upper surface425aof the fluorescent layer can increase the emission of secondary electrons when discharging and prevent degradation of the fluorescent layer.

On the other hand, from the above descriptions, it is clear that the barrier ribs of the first embodiment, the modified version of the first embodiment, the second embodiment, and the third embodiment of the present invention can be formed in a single unit.

The present invention provides the following advantages.

First, the PDP according to the present invention employs a structure where discharge electrodes are formed in the barrier ribs surrounding the discharge cells, unlike a conventional PDP in which the sustaining electrode pairs are formed on the front panel of the PDP. This structure needs no dielectric layer or protective film on the front panel of the PDP through which visible light is transmitted. Also, no electromagnetic wave shielding filter is needed in front of the PDP, since an electromagnetic wave shielding electrode is located in front of the front discharge electrode. Accordingly, the PDP according to the present invention has improved light transmission, since the visible light emitted from the fluorescent layers in the discharge cells only passes through the front substrate and a near infrared absorbing layer, and not through the omitted layers which all have bad light transmission.

Second, in a conventional PDP, the majority of the sustaining electrode pairs (except the bus electrodes) have to be formed of ITO, which has a high resistance, to allow visible light from the florescent layers in the discharge cells to pass, since the sustaining electrode pairs that cause discharge are located on the rear surface of the front substrate. Therefore, there are problems of increased operating voltage and non-uniform images on a large panel, due to the voltage drop of the ITO electrodes. However, in the present invention, the discharge electrodes can be formed of a material having high electrical conductivity, since the discharge electrodes are located in the barrier ribs, thereby solving above problems.

Third, a conventional PDP has low light emitting efficiency since discharge initiates on the rear of the protective film and diffuses in the discharge cells since the sustaining electrode pairs that cause discharge are located on the rear surface of the front substrate. Also, there is the problem of a permanent latent image due to ion sputtering of charged particles of a discharge gas by an electric field after long use. However, the present invention solves the ion sputtering problem, since the discharge initiates from the entire side surfaces that surround the discharge cells and diffuses toward the center.

Fourth, a conventional PDP is expensive and time consuming to manufacture, since the electromagnetic wave shielding filter and the filter holder have to be coupled to the front case after manufacturing them separately. However, in the present invention, the function of the electromagnetic wave shielding filter is replaced by the electromagnetic wave shielding electrode, removing the need for the electromagnetic wave shielding filter and the filter holder, and that the electromagnetic wave shielding electrode is formed integral with the PDP, thereby reducing manufacturing cost.

Fifth, the present invention solves the problem of dissipating heat from the space formed by the thickness of the filter holder between the electromagnetic wave shielding filter and the conventional PDP, thereby increasing the heat radiation efficiency of the PDP.

Sixth, the dark colored electromagnetic wave shielding electrode absorbs external light without reflecting it, thereby increasing the contrast ratio.