Patent Application
20050156523
This application claims priority to and the benefit of Korean Patent Application No. 10-2003-0093812, filed on Dec. 19, 2003, which is hereby incorporated by reference.
(a) Field of the Invention
The present invention relates to a plasma display panel (PDP), and more particularly, to a PDP having align marks structured so that they are not formed with defects. The present invention relates also to a method and apparatus for forming the align marks using an offset process.
(b) Description of the Related Art
A PDP is a display device that displays images by exciting phosphors using plasma discharge. Vacuum ultraviolet (VUV) rays emitted from plasma obtained by gas discharge excite phosphor layers. The phosphor layers then emit visible light forming images. With its potential for high resolution and large screen sizes, PDP technology may become the leading next-generation flat screen technology.
In the basic structure of the conventional PDP, address electrodes, barrier ribs, and phosphor layers are formed on a rear substrate, and display electrodes comprised of scan electrodes and sustain electrodes are formed on a front substrate. Each of the scan electrodes and sustain electrodes includes a transparent electrode made of a material having a degree of transmissivity (e.g., indium tin oxide), and a metal bus electrode.
The address electrodes and the display electrodes are covered by a first dielectric layer and a second dielectric layer, respectively. An MgO protective layer is formed on the second dielectric layer. A discharge cell is formed in a discharge space where the address electrodes intersect the display electrodes, and a discharge gas (typically a Ne-Xe compound gas) fills the discharge cells.
The scan electrodes are mounted opposite the sustain electrodes with predetermined discharge gaps between them. The discharge gaps correspond to centers of the discharge cells. The barrier ribs are formed in stripes in the same direction the address electrodes are formed such that the discharge cells are connected in this same direction.
Precise arrangement of the electrodes on the substrates is necessary to accurately align the substrates with each other. With the increased complexity of the transparent electrodes recently, it is increasingly important that the unit cells be properly aligned. Increasing panel size exacerbates the problem of deformation in the glass used in PDPs and in the transparent electrodes. This further complicates the alignment processes during PDP manufacture.
To perform alignment, align marks are formed on the substrates. The align marks may be formed simultaneously during the formation of the electrodes, dielectric layers, and other elements.
Screen printing and photolithography methods are used to form the bus electrodes. Lift-off and thin film methods can also be used to form the bus electrode. There is a recent preference to use offset printing.
The present invention can provide an align mark formation method and apparatus that may minimize the amount of align mark paste that is transferred, and may prevent deformation of the align marks during transfer onto a substrate.
It is another object of the present invention to provide a PDP having align marks in which defects in the formation and positioning of align marks are prevented to thereby ensure accurate alignment of the elements of the PDP.
A plasma display panel having a plasma discharge structure in a gap between a first substrate and a second substrate may include at least an align mark formed on a surface of the first substrate opposing the second substrate. The align mark may include a plurality of cavities.
The cavities may be arranged in a substantially uniform pattern with predetermined spaces between adjacent cavities. The spaces may be interconnected to form a lattice pattern.
In another aspect, an outer boundary of the align mark may be defined by an edge, and the cavities at the edge may be closed off by the edge. In yet another aspect, the cavities of the align mark are formed in a lattice pattern.
Each of the cavities may have a cross-sectional shape that is circular or polygonal.
The align marks may be formed using an offset printing process.
An align mark formation method using an offset printing process may include forming in a gravure a concavity in the shape of an align mark to be printed, and simultaneously forming a plurality of protrusions in the concavity. It may further include filling the concavity with a paste for aligning marks, transferring the paste to a printing blanket from the concavity, and transferring the paste to a substrate of a plasma display panel from the printing blanket.
The protrusions may be formed using an etching process. The gravure may be in the form of a plate or in the form of a cylinder.
An align mark formation apparatus may include a gravure having a concavity filled with a paste used to form align marks, a blanket for transferring the paste to a substrate, and a plurality of protrusions formed in the concavity of the gravure plate. The protrusions may have a cross-sectional shape that is circular or polygonal.
As shown in
Similarly, each of the sustain electrodes 13 may include a transparent electrode 13a made of a material such as ITO with a high transmissivity, and a bus electrode 13b made of metal. Thus the sustain electrode 13 may be conductive. The address electrodes 3 and the display electrodes 15 may be covered by a first dielectric layer 17 and a second dielectric layer 19, respectively. An MgO protective layer 21 may be formed on the second dielectric layer 19. Discharge cells may be formed in a discharge region and where the address electrodes 3 intersect the display electrodes 15. A discharge gas (typically an Ne-Xe compound gas) may fill the discharge cells.
As shown in
The align marks 24 may be formed using an electrode paste during the formation of bus electrodes or address electrodes. The align marks 24 may also be used as points of reference during exposure processes.
As shown in
As an example, the spaces may be interconnected and form a lattice pattern as shown in
Grooves may be formed in a gravure plate used in an offset process. After protrusions are formed in the grooves, the grooves may be filled with a paste and printing may be performed. This process may result in the cavities 24a. The cavities 24a may have a cross-sectional shape that is circular, square, rectangular, or the like.
In the first exemplary embodiment, the cavities 24a have a cross-sectional configuration that is square.
The align mark 24 may be interconnected along an edge. On a surface opposing the rear substrate 22, it may be possible for the align mark 24 to be completely interconnected without forming cavities.
As shown in
The cavities 25a may be formed having a cross-sectional shape that is, for example, square, triangular, and trapezoidal. The outer boundary of the align mark 25 may be defined by an edge, and the cavities 25a at these areas may be closed off by this edge.
As shown in
As shown in
Protrusions 40 may be formed in the concavity 33. The protrusions 40 may have a cross-sectional shape that is circular, square, rectangular, polygonal, or the like.
The concavity 33 and the protrusions 40 formed in the gravure plate 31 may be formed by an etching process. In such a case the steps involved may include deposition of a photoresist, exposure using a photomask, and developing. As shown in
As a result of this formation of the align mark concavity 33 including the protrusions 40 formed at predetermined intervals as described above, the paste 34 may fill between the protrusions 40 rather than within the entire area encompassed by the concavity 33. Hence, the amount of paste 34 required may be reduced by an amount equal to the volume occupied by the protrusions 40.
Next, the paste 34 filled in the concavity 33 may be transferred onto a printing blanket 35. When transferred onto the printing blanket 35, the resulting configuration of the paste 34 may be opposite to the shape of the concavity 33. Locations corresponding to where the protrusions 40 are formed in the concavity 33 may be indented.
Subsequently, the paste 34 transferred onto the printing blanket 35 from the concavity 33 may then be transferred onto a glass substrate 37. During this process, the paste 34 may be squeezed between the printing blanket 35 and the glass substrate 37. Nevertheless, the paste 34 may not undergo any significant outward deformation. This results from the relatively minimal use of the paste 34 as described above. The protrusions 40 thus may ensure that there are sufficient gaps in the paste 34 prior to transfer onto the printing blanket 35.
Thus, when the paste 34 is then transferred onto the glass substrate 37, the squeezing pressure applied to the paste 34 as a result of being pressed between the printing blanket 35 and the glass substrate 37 may be applied in an inward direction toward the gaps formed in the paste 34. This prevents an outwardly distorted formation of the align marks.
In the offset printing process, the align marks are typically formed during electrode formation. The paste may be transferred onto a cylindrically shaped blanket made of silicone rubber, and the blanket may contact the substrate and roll on it. Thus the paste may be transferred onto the substrate.
In the conventional process, with the pressure applied to the align marks in the direction of movement of the blanket, the align marks are not positioned correctly, and are frequently deformed.
However, with the use of the align mark formation method of the exemplary embodiment of the present invention described above, problems in position or formation of the align marks may not occur.
Following the transfer of the paste 34 onto the glass substrate 37, drying and firing of the paste 34 may be performed to thereby complete the formation of the align marks. The align marks may be formed at the same time electrode formation takes place as described above.
As shown in
As with the previous embodiment, an etching process may be performed on the surface of the gravure roll 39 to thereby form the concavities 38. A plurality of protrusions 41 may be formed in each of the concavities 38. The protrusions 41 may have a cross-section that is circular, square, rectangular, polygonal, or the like. The protrusions 41 may be formed at the same time as the concavities 38.
The concavities 38 may be filled with a paste 34. Next, a blade 32 may be used to remove excess portions of the paste 34 (e.g., overflow paste). Subsequently, the paste 34 filled in the concavities 39 may be transferred onto a printing blanket 35. The paste 34 may finally be transferred onto a glass substrate 37. Drying and firing may then be performed to complete the align marks.
Although embodiments of the present invention have been described in detail hereinabove, many changes may be made to the embodiments without departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2003-0093812 | Dec 2003 | KR | national |
