Kwon, Yang Ho (1410 Jinhyeung Apt. 279-4 Dongseohag-Dong Wansan-Gu Junju-Si Jun Ra Buk Do 560-120, KR)
Kang, Gil Young (206-906, Hannuri Tawoon Goa-Myun Gumi-Si Kyung Sang Buk Do 730-810, KR)
Kwon, Yang Ho (1410 Jinhyeung Apt. 279-4 Dongseohag-Dong Wansan-Gu Junju-Si Jun Ra Buk Do 560-120, KR)
Background Art Fig. 1 illustrates a schematic partial sectional view for explaining a structure of a conventional plasma display panel of a alternative-current, surface-discharge type. As shown in Fig. 1, the plasma display panel comprises a front substrate 1 wherein the front substrate is provided with a front electrode group consisting of an X electrode 3 and an Y electrode 4 as transparent electrodes such as ITO in common, bus electrodes 3a and 4a as metal electrodes such as Ag formed on the X electrodes 3 and the Y electrodes 4, black stripes 10 formed between each pair of the X electrodes 3 and the Y electrodes 4, and a dielectric layer 6 and a protective layer 6a formed thereon. And a rear substrate 2 faced
parallel to the front substrate 1 is provided with address electrodes 5 as data electrodes, a dielectric layer 7 and a phosphor pattern 9 of three different color phosphors formed between barrier ribs 8.
In an illustrative method of driving the plasma display panel, one frame is divided into a plurality of subframes and each subframe is divided into a reset period, an address period and a sustain period, with different sustain periods set in each subframe, thus, a gray scale display of an image screen is obtained by combining each subframe.
During the reset period, a write pulse is applied to the X electrodes 3 connected commonly to each other in order to equalize or initialize discharge conditions in all cells of the panel, thereby totally discharging all cells. A sustain pulse is applied to the Y electrodes 4 in order to sustain the discharge and then an erasure pulse is applied to the commonly connected X electrodes 3 in order to erase wall charges accumulated on the dielectric layers 6 and 7.
During the address period, wall charges are accumulated on the front dielectric layer 6 of cells to be displayed by applying data pulses to the address electrodes 5 in order to selectively address cells to be displayed depending on inputted image data and sequentially applying scan pulses to the Y electrodes 4. Then, by applying alternately the sustain pulses to the X electrodes 3 and 5 the Y electrodes 4, sustain discharge is produced in only the cells which were addressed during the address period, that is, which had a wall charge accumulated thereon.
In the reset period and the address period in the course of displaying one subframe as discussed above, the address electrodes 10 5 are maintained at the reference level, that is, a ground level, equal to that of the X electrodes 3 and the Y electrodes 4 of the front electrode group, as the result of which space charges and wall charges are generated, thereby to facilitate writing and erasing operations necessary for electric discharge.
15 Alternatively, in the sustain period, the address electrodes 5 may be maintained at a high impedance, not at the ground level and, at this time, a voltage is induced to the address electrodes 5 by the space charges formed on the front electrode group. As a matter of convenience, a floated address voltage is referred to as an 20 induced voltage. During the sustain discharge, the induced address
voltage to be maintained at the ground level may cause the instability of the sustain discharge. Therefore, in a surface discharge structure of a plasma display panel, the induced sustain voltage is typically maintained at the high impedance.
SUMMARY OF THE INVENTION In such structure of the conventional plasma display panel, since the thickness of the dielectric layer 6 on the metal electrodes 3a and 4a and the black stripes 10 is thinner than that of the dielectric layer 6 on the X electrodes 3 and the Y electrodes 4, electrostatic capacitances on the metal electrodes 3a and 4a and the black stripes 10 becomes higher. Thus, due to a field spreading effect that each electric field does not become concentrated on each discharge space and becomes spreaded to adjoining cells, there are problems that discharging efficiency decreases and probability of cross-talk becomes higher. In order to solve such problems, a stepped dielectric structure, in where one more layer of the dielectric layer is formed on the metal electrodes 3a and 4a, is proposed by Pioneer Co., Ltd. However, such a structure still has a danger such as cross-talk by intersection with barrier ribs in a vertical direction.
Accordingly, in order to solve the above discussed problems, an object of the present invention is to provide a plasma display panel in which each electric field can be concentrated on each discharge space and field spreading to exert 5 an influence on adjoining cells can be prevented.
In order to accomplish the object, in accordance with a first embodiment of the present invention, a plasma display panel for preventing field spreading is presented, in which comprises a plurality of front electrode groups consisting of an X electrode 10 and an Y electrode formed on the rear surface of a front substrate, black stripes formed at the exterior of the X electrodes and the Y electrodes, metal electrodes formed on each of the X electrodes and the Y electrodes, address electrodes formed on the interior surface of a rear substrate faced parallel 15 to the front substrate so as to form a plurality of cells for discharge-by-display in each region crossing with each of the front electrode groups, dielectric layers formed on the front electrode groups and the address electrodes, respectively, and a phosphor pattern formed on the rear dielectric layer between 20 barrier ribs, said plasma display panel being characterized in
that said dielectric layer comprises dielectric layers of a low dielectric constant with the relative dielectric constant of 6 to 10 formed on at least the upper surfaces of the black stripes and dielectric layers of a high dielectric constant with the relative dielectric constant of 13 to 17 formed on portions except the dielectric layers of a low dielectric constant.
The dielectric layers of a high dielectric constant may be formed only on upper surfaces of the X electrodes and the Y electrodes except those of the metal electrodes, and said dielectric layers of a low dielectric constant may be formed on each upper surface between the metal electrodes on the X electrodes and the metal electrodes on the Y electrodes over each upper surface of the black stripes. That is, it is to print on the metal electrodes and the black stripes with a material of a lower dielectric constant than that of dielectric layers on the X electrodes, and the Y electrodes, of ITO in order to prevent field spreading.
BRIEF DESCRIPTION OF DRAWINGS Fig. 1 illustrates a schematic partial sectional view for explaining a structure of a conventional plasma display panel.
Fig. 2 illustrates a schematic partial sectional view of a front substrate of a plasma display panel for preventing field spreading in accordance with one embodiment of the present invention.
5 Fig. 3 illustrates a schematic partial sectional view of a front substrate of a plasma display panel for preventing field spreading in accordance with another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 10 Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
A structure of the plasma display panel according to one embodiment of the present invention is shown in Fig. 2 as a schematic partial sectional view similar to Fig. 1.
15 Even in Fig. 2 as shown in Fig. 1, a plasma display panel of the present invention for preventing field spreading comprises a plurality of front electrode groups consisting of an X electrode 3 and an Y electrode 4 formed on the rear surface of a front substrate 1, black stripes 10 formed at the exterior of the X 20 electrodes 3 and the Y electrodes 4, metal electrodes 3a and 4a formed on each of the X electrodes 3 and the Y electrodes 4, and dielectric layers 11 and 12 formed thereon by printing.
A rear substrate is not shown in Figs. 2 and 3, but a rear substrate 2, as shown in Fig. 1, may be employed in the present 5 invention which comprises address electrodes 5 formed on the interior surface of the rear substrate 2 faced parallel to the front substrate 1 so as to form a plurality of cells for display by discharge in each region crossing with the front electrode groups, dielectric layer 7 formed on the address electrodes 5, 10 respectively, barrier ribs 8 formed at a constant distance and a phosphor pattern 9 formed on the rear dielectric layer 7 between the barrier ribs 8.
In accordance with one embodiment of the present invention in the plasma display panel of such a structure, the dielectric 15 layers 12 of a low dielectric constant, which has the relative dielectric constant of 6 to 10, are formed on the upper surfaces of the black stripes 10, as shown in Fig. 2, and the dielectric layers 11 of a high dielectric constant, which has the relative dielectric constant of 13 to 17, are formed on portions except the 20 dielectric layers 12 of a low dielectric constant.
In general, where an electric field or flux density passes through a boundary surface of two dielectrics (each dielectric constant: el, #2) in contact with each other at an incidence angle 01 from one dielectric and flows into the other dielectric at an angle #2, the following relationships are established. That is: each each vertical component of each electric flux density D1 and D2 before and after the boundary surface is identical at both side of the boundary surface, i. e., D1n=D2n or D1cos #1=D2cos #2; (2) each component of each electric field E1 and E2 parallel with the boundary surface is identical at opposite sides of the boundary surface, i. e., Elt=E2t or E1sin #1=E2sin #2; From the relation of D1= e lE1 and D2= e 2E2, tan #1/tan #2 = #1/#2; an electric field or flux density is refracted at the boundary surface largely toward the dielectric with the higher dielectric constant (since, if #2>#1, #2>#1); (5) an electric flux density is high in a dielectric with a high dielectric constant, and the strength of an electric field is low in a dielectric with a high dielectric constant, i. e., D2>D1 and
E>E2 (since, if #2>#1, #2>#1).
Meanwhile, tubes, which consist of electric fluxes diverging from the circumference of minute area JS of a surface of the charged conductor within a dielectric, are called electric power tubes. Particularly among the electric power tubes, a tube which charge within JS is a unit value (l [C]) is called a Faraday tube. The characteristics of the Faraday tube are as follows: 09 the number of electric fluxes within a Faraday tube is constant; zu there are positive and negative unit charges at the opposite ends of a Faraday tube; p a Faraday tube is continuous at points of no true charge; T a density of a Faraday tube is identical to a density of the electric flux.
In addition, an energy of an electric field per a unit volume in a dielectric of a dielectric constant e is as the following equation, i. e., W = E#D/2 = e E2/2 = D 2/2 e.
From the above-described relations, each electric flux density becomes higher, and each electric field weaker, in the dielectric layers 11 of a high dielectric constant, and contrariwise in the dielectric layers 12 of a low dielectric constant.
Thus, each electric flux density and each electric field 5 are changed according to the present invention, and therefore each electric field is concentrated on each discharge space, thereby preventing decrease in discharging efficiency and danger such as cross-talk.
In an embodiment as shown in Fig. 3, the dielectric layers 10 11 of a high dielectric constant having the relative dielectric constant of 13 to 17 are formed only on upper surfaces of ITO electrodes of the X electrodes 3 and the Y electrodes 4 except those of the metal electrodes 3a and 4a and between the X electrodes 3 and the Y electrodes 4. And, said dielectric layers 15 12 of a low dielectric constant having the relative dielectric constant of 6 to 10 are formed on each upper surface of the metal electrodes 3a and 4a on the X electrodes 3 and the Y electrodes 4 and on each upper surface of the black stripes 10, and between the black stripes 10 and the metal electrodes 3a and 4a.
20 Even in case of such a structure, as in Fig. 2, each electric flux density becomes higher, and each electric field weaker, in the dielectric layers 11 of a high dielectric constant, and contrariwise in the dielectric layers 12 of a low dielectric constant, so that each electric flux density and each electric 5 field are changed and therefore each electric field is concentrated on each discharge space, thereby preventing decrease in discharging efficiency and excluding danger such as cross-talk.
Here, the upper surfaces mean exposed surfaces during manufacturing, and will be lower surfaces on the drawings.
10 In the above-description, two types of embodiments are illustrated and explained, but the dielectric layers 12 of a low dielectric constant are formed on at least the upper surfaces of the black stripes 10 separating cells and the dielectric layers 11 of a high dielectric constant are formed on portions on at least 15 upper surfaces of ITO electrodes of the X electrodes 3 and the Y electrodes 4 except those of the metal electrodes 3a and 4a, thereby creating the above-describing effect of the present invention. The dielectric layers 12 of a low dielectric constant can be expanded onto the upper surfaces of the metal electrodes 3a 20 and 4a, and the present invention can be also applied to other types of plasma display panels.
By forming dielectric layers 12 of a low dielectric constant on at least the upper surfaces of the black stripes 10 separating cells and dielectric layers 11 of a high dielectric 5 constant on at least upper surfaces of ITO electrodes of the X electrodes 3 and the Y electrodes 4 except those of the metal electrodes 3a and 4a, there are effects such that each electric field can be concentrated on each discharge space and field spreading to exert an influence on adjoining cells can be 10 prevented, according to the constructions and their acting effects of the plasma display panel for preventing field spreading in the above preferred embodiments of the present invention.
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