Field of invention:
The present invention relates to a plasma display panel (hereinafter referred to as PDP) and its driving method and more particularly related to a new PDP cell structure capable of providing higher brightness, improved luminous efficacy and applicable for making high picture quality flat panel displays.
Background of the invention:
In last few decades, proper attention has been paid to PDP development as a large size flat panel displays. PDP is composed of a matrix of discharge cells that are formed by partitions made by barrier ribs between a pair of glass substrates. Three color (Red, Blue and Green) phosphors are provided on the surface of the respective barrier ribs, and the cell volume is filled with a gas mixture (Ne+Xe). During PDP operation, the gas discharge takes place between electrodes in the cells that result in the generation of Vacuum Ultra Violet (VUV) photons with a wavelength of 147 nm and 173 nm. These phosphors absorb these VUV photons and emit visible light to display a picture including characters and graphics. Such PDPs are self-emitting type flat panel displays and have excellent characteristics such as large size, wide horizontal and vertical view-angle, slim look, lightweight etc. Thus, PDP is a prospective candidate in the competitive world of flat panel display devices. The drawback of the PDP is low luminous efficacy. At present various efforts are on to improve the luminous efficacy of PDP especially by cell structure modifications.
The conventional AC (Alternating Current) driven PDP possesses three-electrode structure on two glass plates forming front plate and back plate. The front plate has formed therein a plurality of pairs of display electrodes known as sustain and scan electrodes. These electrodes are formed of ITO (Indium-Tin-Oxide) material. The ITO electrode sheet resistance is decreased with the introduction of metal bus lines of electrically conducting material over the ITO electrodes. The display electrodes are covered with a transparent dielectric layer to limit the discharge current. A thin electron emissive layer is formed over the transparent dielectric layer to emit secondary electrons and to protect the transparent dielectric layer from sputtering by ion bombardment. The back plate has formed therein a plurality of address electrodes that are orthogonal to the display electrodes. A pair of sustain and scan electrodes along with an address electrode form a sub-pixel. A sub-pixel comprises of Red, Green or Blue color phosphor that make Red, Green or Blue sub-pixel respectively. A combination of Red, Green and Blue sub-pixels forms a pixel. The straight channel barrier ribs are formed on the back plate to create the discharge volume and also to separate different sub-pixels. The main co-planar discharge is created with the display electrodes by square pulse voltage. The VUV radiation produced in the discharge phenomenon excites the phosphor to emit visible light. This type of conventional AC POP is described in US Patent no. 5661500.
The luminous efficacy of an AC PDP depends on the four successive conversion factors. These are generation of VUV photons, capturing the VUV photon by phosphor layer, conversion of VUV to visible light and transmission of visible light. The conventional AC PDP suffers from drawback of low luminous efficacy and also the cross-talk problem between neighboring sub-pixels. The cross talk is defined as the leakage of discharge and VUV radiation over barrier rib from one sub-pixel to other neighboring sub-pixel that produce adverse effects in the un-addressed sub-pixel. To overcome this problem straight channel ribs are replaced by box shaped ribs having four walls to separate different sub-pixels by providing extra rib walls orthogonal to earlier straight channel barrier ribs existing on back plate. This rib structure comprises of straight ribs of first type and straight ribs of second type that are oriented orthogonal to the first type ribs with similar height and material. These ribs are formed with the increased phosphor area with two extra walls so that the light conversion efficiency is improved to increase the light output. The extra barrier wall between two discharge cells also minimizes the possibility of vertical cross talk. This type of rib structure is described in US patent no. 6,249264 and 6,683,589.
Further low VUV efficiency is also a considerable reason for low luminous efficacy in conventional AC PDP even with the box shaped rib structure. The VUV efficiency is low because most of the input power is wasted in ion heating. The conversion of electron energy to VUV radiation is also low. The transparency of the front plate structure consists of ITO and electrically conducting electrodes, transparent dielectric layer and electron emissive layer, are also a hindrance for low luminance efficacy with low brightness. With the presence of all these layers on the front plate the transparency of the front plate is reduced to 35-50%. Low luminous efficacy in the conventional PDPs contributes to high electrical power consumption for operation. The modification in the cell structure design effectively improves the luminous efficacy. In this invention the inventors propose a PDP cell structure that uses only back glass substrate while the front glass substrate was kept completely transparent for light to pass through.
Object of the invention:
It has already been proposed that luminous efficacy of the conventional AC driven PDP is low because of low brightness and high panel power consumption. The presence of electrode structure over the front glass plate creates opacity for light transmission and hence it is a major contributor for low panel brightness. About 35 - 50% of the visible light produced from phosphor excitation by VUV radiation is blocked by front plate structure.
The electrode separation between display electrodes is very short (~ 60-100 urn). Due to short gap, the length of positive column in the produced glow discharge is very short and even sometimes it is not present. The short positive column is responsible for low discharge efficiency or VUV output.
The front plate structure in the conventional PDP is formed with various rocesses such as ITO patterning, bus electrode printing and transparent
dielectric layer etc which often leads to pixel defects thus decreasing the yield of the manufacturing process. Hence there is always a requirement to minimize the front plate patterning processes. The removal of ITO material is required to reduce the panel capacitance for improved luminous efficacy and also to solve the problem of ITO leakage and electrode shorting during development process.
The principal object of the present invention is to provide a novel cell structure utilizing only back plate and keeping front plate completely free for light transmission.
Yet another object of the present invention is to increase the brightness by creating positive column discharge and providing front glass plate without any structure to block the light.
Yet another object of the present invention is to improve the luminous efficacy of the AC PDP.
Yet another object of the present invention is to remove subtractive patterning processes (e. g. photolithography) for ITO patterning on front plate and all other front plate processes are shifted to the back plate.
Statement of the invention:
Accordingly the invention provides a Plasma Display Panel comprising a pair of front and back glass substrates, and gas enclosed between the substrates, a plurality of address electrodes in first direction, plurality of pair of sustain (X) -scan (Y) display electrodes in second direction, a dielectric layer is provided to cover the plurality of address electrodes extending in first direction on back glass substrate, box shaped barrier rib structure having plurality of barrier ribs of first type in first direction parallel to address electrodes and plurality of barrier ribs of second type that are oriented in second direction orthogonal to the first type barrier ribs forming four wall structure on said dielectric layer to define a cavity where discharge takes place, the said cavity is covering the address electrode, the Red (R), Green (G) and Blue (B) phosphors emitting red , green and blue light respectively are provided to cover the cavity, which is characterized in that, front glass substrate is free from any kind of structure having no electrode or layer, back glass substrate is having plurality of pair of sustain (X) and scan (Y) display electrodes enclosed within barrier ribs of second type, the alternate barrier ribs of second type is having one sustain and two scan electrodes respectively, a separation between two adjacent scan electrodes forms the inter-pixel gap, the sustain discharge is created face-to-face between sustain and scan display electrodes separated by discharge space, sustain discharge remains floating in the discharge cavity and not diffusing towards the front glass substrate, the sustain (X)-scan (Y) display electrodes are covered with a dielectric layer at top of barrier ribs, the electron emissive layer is provided on the
inner walls of barrier ribs and/or on the phosphor, the X-Y-Y-X type driving scheme which is provided for line scanning for the PDP operation.
Brief description of Drawings:
Figure 1(a) illustrates the cross-sectional view of conventional AC PDP with straight barrier ribs
Figure 1(b) shows the top view of the conventional AC PDP structure shown in figure 1 (a).
Figure 2(a) shows the conventional AC PDP structure with box shaped ribs in the back plate replacing straight channel ribs.
Figure 2(b) shows the top view of the conventional AC PDP structure with box shaped ribs shown in figure 2(a).
Figure 3(a) illustrates the schematic view of new AC PDP structure according to the present invention.
Figure 3(b) shows the top view of the AC PDP structure according to the present invention.
Figure 4 (a) shows the X-Y-X-Y type driving scheme for AC PDP. Figure 4 (b) shows the X-X-Y-Y type driving scheme for AC PDP.
Figure 4 (c) shows the modified X-Y-Y-X type driving scheme of new AC PDP structure according to the present invention.
Figure 5(a) shows the cross sectional view of the back glass substrate with patterned address electrodes, formed layer of dielectric and layer of barrier rib material according to the present invention.
Figure 5(b) shows the cross sectional view of the barrier ribs along with grooves according to the present invention.
Figure 5(c) shows the cross sectional view of the barrier ribs with the filled dielectric layer, electrically conducting layer and a dielectric layer at top in the grooved spaces between barrier rib according to the present invention.
Figure 5(d) shows the cross sectional view of the deposited phosphor layer and electron emissive layer according to the present invention.
Detailed description of the invention with reference to drawings:
Before starting the detailed description of the present invention, it is necessary to discuss the conventional AC PDP for clear understanding of the present invention. Figure 1(a) illustrates the cross-sectional view of conventional AC PDP with straight barrier ribs and figure 1(b) shows the Red (R), Green (G) and Blue (B) pixel arrangement.
As in figure 1(a), the front glass substrate (1) and back glass substrate (2) are shown. In the front glass substrate (1), display electrodes are made of transparent ITO sheet (3). To reduce the resistance of the display electrode, opaque electrically conducting bus electrodes (4) are made over the ITO electrodes. The display electrode is covered with a transparent dielectric layer (5) to limit the discharge current. Then the electron emissive layer (6) is deposited over the transparent dielectric layer (5). On the back glass substrate (2), a plurality of address electrodes (7) are formed with one address electrode (7) is formed in each sub-pixel. The address electrodes (7) are covered with a dielectric layer (8) to limit the discharge current and for light reflection. The straight channel barrier ribs (9) are formed over the dielectric layer (8). The R (10a), G (10b), B (10c) phosphor layers are formed in the barrier rib (9) channel spaces.
Figure 1(b) shows the top view of the conventional PDP structure shown in figure 1(a). The Red (R) (11), Green (G) (12) and Blue (B) (13) sub-pixels are formed with the combination of front and back plate structure. One POP cell or sub-pixel comprises of one pair of display electrodes (3), (4) and an address electrode (7).
Figure 2(a) shows the conventional AC PDP structure utilizing box ribs on the back glass substrate (2) replacing straight channel ribs (9) as discussed in figure 1(a). Extra phosphor area enclosed in the rib walls (14) is utilized to enhance the brightness with same VUV to visible light conversion efficiency. The AC PDP structure shown in figure 2(a) consists of two glass substrates that enclose the gas for discharge. The front glass substrate (1) having display electrodes are made of transparent ITO sheet (3). To reduce the resistance of the display electrode, opaque electrically conducting bus lines (4) are made over the ITO electrodes (3). The display electrode is covered with a transparent dielectric layer (5) to limit the discharge current. Then the electron emissive layer (6) is deposited over the transparent dielectric layer (5). On the back glass plate (2), each sub-pixel comprises address electrode (7). The back plate comprising a plurality of address electrode (7) made of electrically conducting paste. The address electrode (7) is covered with a dielectric layer (8) to limit the discharge current and light reflection from the back plate. The box shaped barrier ribs are formed over the dielectric layer with straight barrier ribs (9), (14) crossing orthogonally. The R (10a), G (10b), B (10c) phosphor layers are formed in the area enclosed by four walls of the barrier ribs that define a discharge space/cavity.
Figure 2(b) shows the top view of the conventional AC PDP structure with box rib structure shown in figure 2(a). The Red (R) (11), Green (G) (12) and Blue (B) (13) sub-pixels are formed with the combination of front and back plate structure. One PDP cell or sub-pixel comprises of one pair of display electrodes (3), (4) and an address electrode (7).
Figure 3(a) illustrates the schematic view of new AC PDP structure according to the present invention. This AC PDP comprising of front (1) and back (2) glass substrates. The display electrodes are shifted from front glass substrate to the back glass substrate and there is no electrode or layer existing on the front glass substrate (1). The front glass substrate (1) is used to visualize the picture elements. The back plate comprising a plurality of address electrode (7) made of electrically conducting material in first direction and a plurality of pairs of display electrodes (16a, 16b) in second direction orthogonal to the address electrodes (7). The address electrodes (7) are covered with a dielectric layer (8) to limit the discharge current and increase the light reflection from the back glass substrate (2). The box shaped barrier ribs having four walls are formed over the dielectric layer (8) existing on back glass substrate (2). This rib structure comprises of ribs of first type (9) in first direction parallel to address electrodes (7) and ribs of second type (15a, 15b, 15c) that are oriented in second direction orthogonal to the first type ribs to form the box shaped barrier rib having four walls. The rib walls (9) enclose the address electrodes (7). The rib walls (15a, 15b, 15c) orthogonal to the rib walls (9) are enclosing a plurality of display electrodes (16a, 16b). A plurality of sustain display electrodes (16a) is formed therein known as X-electrodes. A plurality of two scan display electrodes (16b) is formed therein known as Y-electrodes after each X-electrode. To form the X and Y electrodes deep grooves are made in the barrier rib walls along with orthogonal oriented barrier rib (9) by single process. The height of the grooves is provided approximately equal to the barrier rib height and the plurality of barrier rib walls (15a, 15b, 15c) is formed.
One X-electrode is formed in the space between two consecutive barrier rib walls (15a). The scan display electrodes (16b) known as Y- electrodes are formed between the barrier rib walls (15b) and (15c) parallel to X-electrodes. The adjacent scan electrode (Y) is formed between barrier rib walls (15c) and (15b) also parallel to X-electrodes. At first, dielectric material is filled in the groove that creates a dielectric layer (17). The electrically conducting paste is filled in the top portion of the groove to make display electrodes (16a, 16b). Due to this there will be no possibility of formation of open lines in the electrode. These electrodes are covered with a dielectric layer (18) at top of barrier ribs to limit the discharge current. The dielectric layer (18) can be made of dark color to enhance the bright room contrast ratio. The thickness of the dielectric layer (18) is provided to satisfy the conditions such that it is equal or thicker than the mean free path of electrons/ions of the plasmas created in the discharge cavity and/or thick enough so that the sustain discharge does not diffuse to the front glass substrate and/or thicker than 10 urn. The width of the barrier rib (15c) defines the inter-pixel gap. The R (19a), G (19b), B (19c) phosphor layers are formed on the inner surface of the cavity formed between walls of barrier ribs (15a) and (15b). The height of the
phosphor at sidewalls is kept 10% - 90% of the height of the barrier ribs (9), (15a, 15b, 15c). The electron emissive layer (20) is deposited on the inner walls that may cover the phosphor area also. To create the VUV light through gas discharge, Ne+Xe gas mixture is enclosed between the front (1) and back glass substrate (2).
The Xenon excitation in the gas discharge generates VUV photons of two wavelengths 147 and 173 nm. Lifetime of the PDP can be enhanced as degradation of phosphor is minimized by providing an electron emissive layer (20) over phosphor layer (19a. 19b, 19c). Keeping in view of electron emissive layer coating over the phosphor layer, it is necessary to check the VUV transmission and absorption by the electron emissive layer. This may restrict the VUV radiation to excite the phosphor in order to emit visible light. The transmission of VUV radiation through the electron emissive layer is possible only when the energy of VUV photon is less than the band gap energy of electron emissive layer. Higher thickness of electron emissive layer over phosphor may also prevent the intensity of VUV wavelength. The 173 nm VUV photon is more useful because of its less energy loss for VUV to visible light conversion in comparison to 147 nm VUV photon. Both 173 nm and 147 nm VUV wavelengths can be used effectively by choosing proper thickness and band gap of electron emissive layer.
Figure 3(b) shows the top view of the PDP structure according to the present invention. This clarifies the orientation of plurality of display electrodes (16a, 16b) and plurality of address electrodes (7) placed orthogonal to the display electrodes in the pixels (11, 12, 13). The top of barrier rib walls that differentiates the R, G, and B sub-pixels is also visualized.
Figure 4(a) explains the driving scheme of the conventional AC PDP structures as shown in figures 1(a) and 2(a). In this conventional AC PDP structure alternate plurality of X and Y electrodes are formed at the front glass substrate so the X-Y-X-Y type driving scheme is applied. In the figure 4(a), total number of display electrode pairs is n and total number of address electrodes is m. This scheme has the disadvantage of higher X-Y capacitance that leads to high capacitive losses. To reduce the capacitive losses, an alternative X-X-Y-Y type driving scheme is used as shown in figure 4(b). This scheme has also the drawback of cross talk in straight rib structure (figure 1(a)) while in box shaped rib structure (figure 2(a)) the cross talk problem is reduced significantly. The driving scheme shown in figure 4(b) uses two common X electrodes that further can be reduced to one common X electrode to provide extra space and to reduce material quantity and its processing. The X-Y-Y-X driving scheme is possible due to low electrically conducting X and Y electrode resistance that is favorable for reduced resistive loss or electrode damage by excessive heating.
Figure 4(c) explains the X-Y-Y-X type driving scheme of the new AC PDP structure according to present invention. In this structure, the two scan electrodes (Y) (16b) are adjacent to each other. The sustain electrode (X) (16a) lies parallel to scan electrodes. Hence a plurality of two scan and one sustain electrode is
formed. The separation between two adjacent Y-electrodes forms the inter-pixel gap. The driving scheme proposed for scanning in the present invention is X-Y-Y-X type rather the conventional X-Y-X-Y type shown in figure 4(a) or X-X-Y-Y type shown in figure 4(b). In the figure 4(c), total number of display electrode pairs is 'n' and total number of address electrodes is 'm'. The X-electrodes (16a) are shorted and made common while the Y-electrodes (16b) are scanned sequentially from 1 to n. To generate discharge for sustaining illumination of each line (1 to n) in a display region, a plurality of scan (Y) and sustain (X) electrodes is formed in parallel to form electrode pairs and a plurality of address electrodes is formed with each address electrode disposed on each column (1 to m). The plasma display panel is driven by applying a scan pulse for line selection to the scan electrode in a specific order (from 1 to n) while applying an address pulse respectively to the address electrode according to display data in synchronization with the application of scan pulse. By the addressing, a proper wall charge is prepared in each cell on a line basis. Further strong discharge is created between X and Y electrodes of the addressed cell by applying sustain pulses of proper amplitude and frequency during the sustain period utilizing already present wall charges of address period, no discharge or illumination is created at un-addressed cells. This VUV radiation generated by sustain discharge is used to excite R, G, and B phosphors to emit visible light. The output luminance of the PDP can be increased by increasing the number of sustain pulses.
According to the present invention the display electrodes are made of electrically conducting material having much higher thickness in comparison to conventional structure (see figure 1(a)). Hence the electrode resistance R is reduced by 50-80% in comparison to conventional structure. The low resistance is favorable for reduced resistive heating (H=i2R), where H is the resistive heating and i is the current passing through the display electrode. Also, the voltage drop (i.R) across the display electrode will be low to improve its current carrying capability. The X-Y capacitance of the present electrode structure is also low because of reduced electrode area and large sustain gap in comparison to the conventional AC PDP having ITO electrodes (see figure 1(a)). Low X-Y capacitance leads to the low displacement current that results to low capacitive loss. The visible luminance or brightness of this PDP is high because of low loss of light at front plate and generation of long positive column discharge. The front plate is kept free from any structure or layer for efficient transmission of visible light. The main sustain discharge is initiated face-to-face between two display electrodes separated by discharge space that forms long path discharge column. The discharge remains floating in the discharge cavity and does not diffuse towards the front glass substrate to prevent VUV loss. The long positive column in the discharge is possible because of long discharge space. Due to large positive column or short negative glow region, the major part of the applied power is utilized to produce VUV production by electron excitation. The discharge space is large equal to the separation between two barrier rib walls having sustain (X) and scan (Y) electrodes respectively. This leads to higher sustain voltage requirement, but the applied voltage or power is efficiently used to produce VUV photons that after phosphor excitation generate visible light. To reduce the sustain voltage, a discharge triggering mechanism for creation of extra charges is beneficial.
Therefore present invented structure leads to improved luminous efficacy. As only one common X-electrode is formed for two different Y-electrodes, this may results in providing more space in the cell for adjusting PDP resolution and also to increase the visible luminance. Using this new cell structure, the luminance is enhanced by 10% to 60% as compared to the conventional structure.
As shown in figure 5(a)-(d), the process details for new cell structure development according to the present invention are given. At first the address electrodes (7) made of electrically conducting material are printed on the back glass substrate (2) (see figure 5(a)). A layer of dielectric material (8) is also printed over the address electrodes (7) for insulation and light reflection. The dielectric layer is also used to prevent address electrode deformation by absorbing the solvent from pastes for the address electrodes and the barrier rib. Further a thick layer (80 - 300 urn) of Barrier rib material (21) is coated over the dielectric layer (8).
The figure 5(b) shows cross-sectional view of the barrier ribs (15a, 15b, 15c) along with the grooves that are enclosing sustain and scan electrodes. The address electrodes (7) are formed by screen-printing or thick film photo process. The barrier ribs with embedded grooves (15a) - (15c) along with barrier ribs (9) are formed by patterning the barrier rib layer (21) by sand blasting or screen printing process printed over dielectric layer (8) in box shaped pattern. The groove depth is approximately equal to the barrier rib height (80 - 300 jam). The width of the barrier rib (15a) and (15b) is in the range of 10 - 300 (im and the width of the barrier rib (15c) that defines the inter-pixel gap can be in the range of 10 - 500 j^m. The barrier rib bottom width may be more than 10% to 50% of the width of the barrier rib top.
Figure 5(c) shows the cross-sectional view of the barrier ribs (9) with the filled dielectric paste in the grooved spaces provided with in barrier ribs which is filled with a dielectric layer (17) using screen-printing process. This dielectric layer (17) is subsequently dried and fired. Further electrically conducting paste is filled over the fired dielectric layer (17) using screen-printing process that forms the display electrodes (16a, 16b). The height of display electrodes is provided in the range of 10% to 90% of barrier rib height and width of display electrodes is equal to the separation between barrier ribs enclosing the same.
This electrically conducting electrode layer is again fired to make a solid electrode layer. Further a dielectric layer (18) is printed over the electrically conducting electrode for its insulation. This dielectric layer (18) can be black in color to enhance the bright room contrast ratio.
Figure 5(d) shows the cross-sectional view of back plate where the three color (R, G, B) phosphors (19a, 19b, 19c) are deposited by screen-printing process on the inner walls of the barrier rib cavity in the paste form so as to fill nearly 10% to 90% volume of the cavity and is deposited on the inner walls of the barrier rib cavity forming a layer of thickness 5-50 urn on the surface of cavity and up to height equal to 10% to 90% of the barrier rib height on the sidewalls. The

hosphor paste is fired to form a layer. In this process the volume of the phosphor paste is constant as it is determined by the volume of the cavity formed by barrier ribs. The composition of the phosphors is chosen such that on simultaneous excitation of the phosphors by the VUV gives white color. Then an electron emissive layer (20) of 10 - 800 nm thick is formed on the back glass substrate (2) at the walls of barrier ribs and/or over the phosphor layer using electron beam evaporation method or can be done by sputtering method that leads to higher lifetime for PDP. All the layers formed during the above processes can be provided by lamination method also.
The front and back glass substrates are joined using frit seal material (not shown) applied on front glass substrate (1). The Xe+Ne gas mixture is filled in the discharge spaces formed by barrier ribs between the front and back glass substrates.
The present invention provides an AC PDP having front glass substrate totally free from any electrode structure or layer. The Front plate can be used as color filter plate so that weight of PDP set can be reduced. Both the display and address electrodes exist on the back glass substrate. The present structure is able to provide high brightness and improved luminous efficacy. The present structure is cost effective because the ITO material and its processing are removed. Also the front and back glass substrate can be made of dissimilar glass materials with suitable thermal expansion coefficients and graded seals that make the PDP cost effective. This structure can be designed for different PDP resolutions such as SD, XGA, and HD etc with the optimization of cell dimensions.
To make this PDP functional, it is provided with the drive control system (not shown) consists of an analog-to-digital converter, a frame memory, a scan control portion, an X-electrode driving circuit, a Y-electrode driving circuit and an A-electrode driving circuit. The drive control system is electrically connected to the X, Y and A-electrodes via a flexible printed circuit board (not shown).
Although the invention has been described with reference to specific embodiments, this description is not meant to embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.

We Claim:
1) A Plasma Display Panel comprising
a pair of front and back glass substrates, and gas enclosed between the substrates, a plurality of address electrodes in first direction, plurality of pair of sustain (X) - scan (Y) display electrodes in second direction,
a dielectric layer is provided to cover the plurality of address electrodes extending in first direction on back glass substrate,
box shaped barrier rib structure having plurality of barrier ribs of first type in first direction parallel to address electrodes and plurality of barrier ribs of second type that are oriented in second direction orthogonal to the first type barrier ribs forming four wall structure on said dielectric layer to define a cavity where discharge takes place, the said cavity is covering the address electrode,
the Red (R), Green (G) and Blue (B) phosphors emitting red, green and blue light respectively are provided to cover the cavity,
wherein,
Front glass substrate is free from any kind of structure having no electrode or layer,
back glass substrate is having plurality of pair of sustain (X) and scan (Y) display electrodes enclosed within barrier ribs of second type, the alternate barrier ribs of second type is having one sustain and two scan electrodes respectively, a separation between two adjacent scan electrodes forms the inter-pixel gap,
the sustain discharge is created face-to-face between sustain and scan display electrodes separated by discharge space, sustain discharge remains floating in the discharge cavity and not diffusing towards the front glass substrate,
the sustain (X)-scan (Y) display electrodes are covered with a dielectric layer at top of barrier ribs,
the electron emissive layer is provided on the inner walls of barrier ribs and/or on the phosphor,
the X-Y-Y-X type driving scheme which is provided for line scanning for the POP operation.
2) The POP as claimed in claim 1, wherein, said dielectric layer above display
electrodes at the top of barrier rib is made to be,
a) equal or thicker than the mean free path of electrons/ions of the plasmas created in the discharge cavity and/or
b) thick enough so that the sustain discharge does not diffuse to the front glass
substrate and/or
c) thicker than 10 urn.

3) The PDP as claimed in claim 1, wherein, positive column is created by face-to-
face discharge between said scan and sustain electrodes separated by said
discharge space.
4) The PD0P as claimed in claim 1, wherein, said front glass substrate is having
no electrode structure, electrically conductive layer and dielectric layer.
5) The PDP as claimed in claim 1, wherein, the height of said sustain (X)-scan
(Y) display electrodes is provided in the range of 10% to 90% of barrier rib height
and width of said sustain (X) or scan (Y) display electrode is equal to the
separation between barrier ribs enclosing the same.
6) The PDP as claimed in claim 3 & 4, wherein, the luminance of the said PDP is
enhanced as compared to conventional structure PDP.
7) The PDP as claimed in claim 1, wherein, the three color (R, G, B) phosphors
are deposited on the inner walls of the barrier ribs of first and second type up to
height in the range of 10% to 90% of barrier rib height where the sustain and
scan electrodes are not existing.
8) The PDP as claimed in claim 1, wherein, dielectric layer at top of barrier ribs
can be made of dark color.
9) The PDP as claimed in claim 1, wherein, said front glass substrate and back
glass substrate can be made of dissimilar glass materials with suitable thermal
expansion coefficients and graded seals.

10) The PDP as claimed in claims 1 to 4, wherein X-Y-Y-X type driving scheme
for line scanning is provided having one common X-electrode for two different Y-
electrodes.
11) A Process for manufacturing AC PDP which comprises the following steps:

a) the address electrodes made by patterning of electrically conductive material
are provided on the back glass substrate in first direction,
b) a layer of dielectric material is provided over the address electrodes,
c) barrier ribs of first and second type are formed over the dielectric layer in box
shaped pattern on back glass substrate,
d) embedded grooved spaces are created within ribs of second type with one
groove between two consecutive barrier ribs and two grooves within next
consecutive barrier ribs alternatively which are separated by discharge space,
e) dielectric paste is filled in the grooved spaces provided within barrier ribs of
second type to form a dielectric layer,
f) electrically conductive paste is filled over the dielectric layer which forms the
sustain and scan display electrodes in the second direction orthogonal to
address electrodes within barrier ribs of second type on back glass
substrate,
g) a dielectric layer is formed over the electrically conductive electrodes,
h) the three color (R, G, B) phosphors are deposited on the inner walls of the on the barrier rib,
i) electron emissive layer is formed on the back plate and/or over the phosphor layer,
j) the front and back glass substrates are joined using frit seal material and Xe+Ne gas mixture is filled in the discharge spaces formed by barrier ribs between the front and back glass substrates to develop an AC PDP.
12) The process as claimed in claim 11, wherein, the groove depth is
approximately equal to the barrier rib height.
13) A Plasma Display Panel and a process for manufacturing PDP substantially
herein described with reference to the accompanying drawings.