Electrode for plasma display panel and method for manufacturing the same

Abstract: Electrode for a plasma display panel (PDP) in which an electrode having a high adhesive power is formed on a glass substrate of a color plasma display panel and a method for forming the same are disclosed, the electrode for the PDP including a metal ceramic thin film formed between the metal electrode and the dielectric substrate or a glass substrate; and the method including the steps of forming a metal ceramic thin film on a predetermined portion of the dielectric substrate, and forming an electrode having the same metal element as the metal ceramic thin film on the metal ceramic thin film.

Description: Field of the Invention The present invention relates to an electrode for a plasma display panel (PDP) in which an electrode having a high adhesive power is formed on a glass substrate of a color plasma display panel; and a method for forming the same. Discussion of the Related Art Fig. 1 is a cross-sectional view showing a structure of a conventional PDP. First, a pair of upper electrodes are formed on a front glass substrate 1, as shown in Fig. 1. Next, a dielectric layer 3 is formed over the pair of the upper electrodes 4 by employing a printing method and a protecting layer 2 is formed on the dielectric layer 3 by a deposition method. The pair of the upper electrodes 4 and the dielectric layer 3 and the protecting layer 2 constitute the upper structure. Secondly, on a back glass substrate 11, there is formed a lower electrode 12. Sidewalls 6 are formed in order to prevent crosstalk between the cell and an adjacent cell. And luminescent materials 8, 9, and 10 are formed on the both sides of each of the sidewalls and on the back glass substrate 11. The lower electrode 12, the sidewalls 6, and the luminescent materials 8, 9, and 10 constitute the lower structure. A non-active gas fills the space between the upper electrode 4 and the lower electrode 12 such that a discharge region 5 is formed. The operation of a general PDP will be explained. Referring to Fig. 1, a driving voltage is applied to the pair of the upper electrodes so that a surface discharge is generated in the discharge region 5, thereby generating ultraviolet 7. The ultraviolet 7 caused excites the luminescent materials 8, 9, and 10, which, thus, achieve color display. In other words, the space charge which is present in the discharge cell is traveled to cathode due to the driving voltage. And, the space charge collides with non-active mixed gas which is a penning mixed gas added to by xenon (Xe), and neon (Ne), helium (He) which is the main component of the mixed gas, such that the non-active gas is exited and that thus ultraviolet 7 of 147 nm is generated. Herein, when the non-active gas which fills the discharge cell, its pressure is 5.3 - 6.7 x 10 4 Nm -2 (400-500 torr). The ultraviolet generated collides with the luminescent material 8, 9, and 10 on the sidewalls 6 and the back glass substrate 11, thus forming a visible ray region. A conventional electrode of a PDP and a method for forming the same will be discussed with the accompanying drawings. Figs. 2a and 2b are cross-sectional views showing lower and upper substrates of a PDP according to a conventional method. As shown in Fig. 2a, for the lower substrate, a metal conductive material 30 such as nickel (Ni) or aluminum (Al) is formed on a back glass substrate 11 (dielectric substrate) by means of a printing technique. As shown in Fig. 2b, for the upper substrate, a copper (Cu) 35 used as an electrode is formed in a front glass substrate (dielectric substrate) (1). Cu, Ni, and Al have all a very low interfacial coherence with respect to glass. Thus, chromium (Cr) 40 is formed between glass and Cu 35, or between glass and Al 30 or Ni in order to maintain the coupling of the glass and the Cu 35, or that of the glass and the Al 30 or the Ni. Such a method is disclosed in JP 55102155. Referring to the forming process, a Cr thin film 40 is formed on the front glass substrate 1 of the PDP by means of a sputtering method in order to heighten the interfacial coherence. Then a Cu film (35) used as an electrode is formed on the Cr thin film 40. Next, another Cr thin film 40 is formed on the Cu film 35 in the same sputtering method in order to heighten the interfacial coherence. Finally, employing annealing, a glass is made to cover the entire surface of the front glass substrate 1 inclusive of the Cu film 35 and the Cr thin films 40. Like the glass substrate, a dielectric substrate is applied to the same manner as the glass substrate. In the same manner, there is formed the electrode on the front glass substrate 11 shown in Fig. 2a. A conventional electrode of a PDP and a forming method thereof have the following disadvantages. Since Cr is a pure metal, Cr has a poor interfacial coherence with respect to glass. Besides, in case glass is annealed at a high temperature, interfacial crack or foam is generated at the interface of the glass and the Cr due to their different expansions, and thus the discharge of the PDP becomes unstable and the life span of the PDP becomes shortened. Moreover, since the coupling is made by two metals that are Cu and Cr, that is, an electrode and an interfacial adhesives, sputtering process is carried out for the Cu and another sputtering process is also carried out for the Cr. Accordingly, the overall process is complicated. WO 95/00969 discloses an electrode structure for a plasma display panel having the features of the pre-characterising part of claim 1. SUMMARY OF THE INVENTION Accordingly it would be desirable to provide an electrode of a plasma display panel (PDP) that substantially obviates one or more of problems due to limitations and disadvantages of the related art. The invention provides an electrode structure for a plasma display panel as set out in claim 1 and a method of forming such an electrode structure as set out in claim 5. In a preferred embodiment of the present invention there is provided an electrode of a plasma display panel (PDP) in which, on a glass substrate of a color plasma display panel, there is formed an electrode having a high adhesive power for improving a discharge condition of a PDP and its life span and a forming method thereof. According to another embodiment there is provided a method for forming an electrode of a PDP in which a dielectric substrate and a metal electrode are formed, which includes the steps of forming a ceramic thin film on a predetermined portion of the dielectric substrate; and forming an electrode having the same metal element as the ceramic thin film on the ceramic thin film. Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS These and various other embodiments, features, and advantages of the present invention will be readily understood with reference to the following detailed description read in conjunction with the accompanying drawings, in which: Fig. 1 is a cross-sectional view showing a structure of a conventional PDP; Fig. 2a is a cross-sectional view showing a conventional electrode formed on a lower substrate of a PDP; Fig. 2b is a cross-sectional view showing a conventional electrode formed on an upper substrate of a PDP; Fig. 3a is a cross-sectional view showing an electrode formed on a lower substrate of a PDP according to a preferred embodiment of the invention; Fig. 3b is a cross-sectional view showing an electrode formed on an upper substrate of a PDP according to the preferred embodiment of the invention; Fig. 4a is a graph showing interfacial coherence with respect to temperatures according to an embodiment of the invention; Fig. 4b is a graph showing interfacial coherence with respect to thicknesses of a ceramic thin film; and Fig. 4c is a graph showing interfacial coherence with respect to bias voltages. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Figs. 3a and 3b are cross-sectional views showing electrodes formed on lower and upper substrates, respectively. In a PDP where a metal electrode is formed on a glass substrate or a dielectric substrate, a ceramic thin film containing the same metal element as the metal electrode is formed in order to heighten the interfacial coherence between the metal electrode and the glass substrate or a dielectric substrate. As shown in Figs. 3a and 3b, a ceramic thin film, which is an interfacial adhesive, is formed between the back glass substrate (dielectric substrate) 11 and the lower electrode 12 or between the front glass substrate 1 and the upper electrode 35. Referring to Fig. 3a, before a metal conductive material such as Ni or Al (30) used as an electrode is deposited on the back glass substrate 11 by employing a printing method, a thin film of a ceramic containing a metal, e.g. an aluminum nitride (Al x N) ceramic thin film or an aluminum oxide (Al x O) ceramic thin film 50 is formed by a reactive sputtering method. Referring to Fig. 3b, Cu 35 used as electrodes is formed over the front glass substrate 1 (or dielectric substrate). In this case, before the formation of the Cu film 35 used as the electrodes, either a copper nitride (Cu x N) ceramic thin film or a copper oxide (Cu x O) ceramic thin film 60 which has the same metal element as the Cu film 35 is formed to have a thickness of thousands of 10 -10 metres (Angstroms) by employing a reactive sputtering method Then the Cu film 35 is formed on the ceramic thin film 60. Next, another ceramic thin film 60 is formed on the Cu film 35. To explain more in detail the above-discussed process, in case a metal is formed to be used as electrodes, before a Cu film 35 is formed on the glass substrate 1, a copper nitride (Cu x N) ceramic thin film 60 is formed on the glass substrate 1 by employing a reactive sputtering method. Alternatively, a copper oxide (Cu x O) ceramic thin film 60 is formed on the glass substrate 1 by employing the same sputtering method. Thus, the reactive sputtering process is carried out only once on one metal, i.e., Cu. In other words, sputtering is applied to the Cu metal over a predetermined region of the glass substrate. Next, argon (Ar) and nitrogen (N) are injected in a predetermined ratio, or argon and oxygen (O) are injected to carry out the reactive sputtering, thereby forming the copper nitride ceramic thin film or the copper oxide ceramic thin film 60. Thereafter, if argon is injected, or if a reactive sputtering is subjected to only copper, the copper metal layer 35 is formed. Subsequently, argon and nitrogen are injected again in a predetermined ratio after a predetermined time, or argon and oxygen are injected appropriately to carry out another sputtering process so that a copper nitride ceramic thin film or a copper oxide ceramic thin film 60 is formed on the copper metal layer 35, thereby forming an electrode of a PDP. The conditions of the reactive sputtering are as follows: Driving pressure : 1.33 Nm -2 (10 m Torr) Discharge voltage : 450 V Discharge current : 100 mA Ratio of the reactive gases (N 2 /Ar) : 15% or more Deposition time : 10 - 20 minutes Substrate bias voltage : -100 V or less As shown in Figs. 4a through 4c, when the process is performed under the above-described conditions, the adhesive power is very good with regard to temperature, thickness of the ceramic thin film, and bias voltage. This process is applied to the front glass substrate 11, as well. The operation of a PDP formed by the above-described process is the same as that of a general PDP. The electrode of a PDP and the manufacturing method thereof have the followings advantages. Since the electrode of the PDP has a structure of ceramic thin film/metal/metal/ ceramic thin film, the interfacial adhesive power between the layers is improved, and interfacial flaking, interfacial crack, or interfacial foam is not generated when annealing is performed. Thus, discharge characteristics are improved, and the life span of a PDP is prolonged. Moreover, since a metal for interfacial adhesiveness is the same metal as a metal for an electrode when sputtering is carried out, or since only mood of the reactive gas is changed, the process of forming a ceramic thin film is simplified and the overall process of manufacturing a PDP is significantly simplified. It will be apparent to those skilled in the art that various modification and variations can be made in the electrode of a plasma display panel (PDP) of the present invention without departing from the scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims.

Claims: An electrode structure for a plasma display panel, comprising a metal electrode (30) formed on a dielectric or glass substrate (11), characterised in that : a thin film (50) of a ceramic compound including the same metal element as the electrode (30) is disposed between the electrode (30) and the substrate (11). The electrode structure of claim 1 wherein said ceramic thin film (50) is either a metal oxide ceramic thin film formed by oxidation of the metal element from which the metal electrode is formed or a metal nitride ceramic thin film formed by nitriding of the metal element from which the metal electrode is formed. The electrode structure of claim 1 wherein said metal electrode (30) is made of either copper or aluminium. A plasma display panel element comprising: a first structure according to any of claims 1 to 3 comprising a first metal electrode (35) disposed within a first dielectric substrate (1) and thin films (60) of a ceramic compound including the same metal element as the first electrode (35) disposed on both sides of the first electrode within the first substrate (1); and a second structure according to any of claims 1 to 3 comprising a second metal electrode (30) disposed upon a second dielectric substrate (11) and a thin film (50) of a ceramic compound including the same metal element as the second electrode disposed between the second substrate (11) and the second electrode (30). A method of forming an electrode structure on a dielectric substrate for use in a plasma display panel, characterised in that the method comprises the steps of: forming a thin film (50) of a ceramic compound including a metal element on a predetermined portion of the substrate (11); and forming an electrode (30) of the metal element on the ceramic thin film. The method of claim 5 further comprising the steps of: forming a further thin film (60) of the ceramic on the electrode (35); and covering the electrode (35) and the thin films with further dielectric substrate (1). The method of either of claims 5 or 6 wherein the electrode (30) and the thin film (50) or films (60) are formed by sputtering using a single metal target of the metal element. The method of either of claims 5 or 6 wherein at least one of the thin film (50) or films (60) is a metal nitride thin film formed by a reactive sputtering process employing a mixed gas containing argon and nitrogen in an appropriate ratio. The method of either of claims 5 or 6 wherein at least one of the thin film (50) or films (60) is a metal oxide thin film formed by a reactive sputtering process employing a mixed gas containing argon and oxygen in an appropriate ratio. The method of either of claims 5 or 6 wherein said electrode (30, 35) is made of either copper or aluminium. The method of either of claims 5 or 6 wherein said ceramic thin film (50) or films (60) are formed by selective reaction employing argon and nitrogen over copper or over aluminium, or argon and oxygen over copper or over aluminium. A method of manufacturing a lower substrate of a plasma display panel comprising the step of providing a dielectric substrate (11) and the steps of claim 5. A method of manufacturing an upper substrate of a plasma display panel comprising the step of providing a dielectric substrate (1) and the steps of claim 6.

Inventors: CHO JUNG SOO, KO JAE HYUN, LEE KI EN, PARK CHUNG HOO, RYU JEA HWA, CHO, JUNG SOO, KO, JAE HYUN, LEE, KI EN, PARK, CHUNG HOO, RYU, JEA HWA
Applicants: LG ELECTRONICS INC, LG ELECTRONICS INC.
Application year: 1997
Main classification: H01J17
IPC codes: H01J9, H01J17, H01J11