Patent Application
20110102399
The present invention relates to an AC surface discharge-type plasma display panel used for a display device and also relates to a method for manufacturing the panel.
An AC surface discharge-type plasma display panel, which has become dominance in plasma display panel (hereinafter simply referred to as a panel), has a front plate and a back plate oppositely disposed with each other and a plurality of discharge cells therebetween. The front plate has a glass front substrate, display electrode pairs each of which formed of a pair of a scan electrode and a sustain electrode, a dielectric layer and a protective layer that cover them. The back plate has a glass back substrate, data electrodes, a dielectric layer that covers the electrodes, barrier ribs, and phosphor layers. The front plate and the back plate are oppositely disposed and sealed with each other so that the display electrode pairs are located orthogonal to the data electrodes. The discharge space formed between the two plates is filled with discharge gas. The discharge cells are formed at which the display electrode pairs face the data electrodes. In the panel with the structure above, a gas discharge is generated in each discharge cell to excite phosphors of red, green, and blue. Color display is thus attained.
Each of the scan electrodes and the sustain electrodes is formed in a manner that, for example, a bus electrode of a narrow stripe is disposed on a transparent electrode of a wide stripe. To form the transparent electrode, for example, a thin film of indium tin oxide (ITO) formed on the front substrate by sputtering undergoes patterning by a photolithography method so as to be formed into a stripe shape. To form the bus electrode, paste of silver (Ag) is printed into a stripe shape on the transparent electrode and then fired (for example, see patent literature 1). However, to form an indium-tin-oxide (ITO) thin film by sputtering, it needs a vacuum device and an exposure device, that is, a large production facility is required. Besides, the forming process above has a problem of low productivity and high cost.
To address the problems above, some methods for forming a transparent electrode have been introduced. For example, a dispersion liquid containing particles of metal chosen from indium (In), tin (Sn), antimony (Sb), aluminum (Al), and zinc (Zn) is applied and fired to form a transparent electrode (for example, see patent literature 2).
However, compared to a thin film of indium-tin-oxide (ITO) formed by sputtering, the aforementioned transparent electrodes formed by firing a dispersion liquid containing particles of metal have some defects: poor mechanical strength, being easily peeled-off, and being easily damaged. Therefore, simply employing the aforementioned material, instead of ITO film, has considerably decreased the yield.
The plasma display panel of the present invention has a scan electrode, which contains a first bus electrode and a first transparent electrode, and a sustain electrode, which contains a second bus electrode and a second transparent electrode, on the front substrate. The first bus electrode and the second bus electrode are disposed on the front substrate. The first transparent electrode is disposed on the front substrate so as to cover at least a part of the first bus electrode. The second transparent electrode is disposed on the front substrate so as to cover at least a part of the second bus electrode.
Employing the structure above allows a panel to have a low-cost transparent electrode without decrease in yield.
Exemplary embodiments of the present invention will be described hereinafter with reference to the accompanying drawings.
Front plate 20 has glass-made front substrate 21, display electrode pairs 24 formed of scan electrodes 22 and sustain electrodes 23, black stripes 25, dielectric layer 26, and protective layer 27. On front substrate 21, display electrode pairs 24, each of which is a pair of scan electrode 22 and sustain electrode 23, are formed in parallel with each other. Besides, black stripe 25 is formed between adjacent display electrode pairs 24. Although
Dielectric layer 26 is formed so as to cover display electrode pairs 24 and black stripes 25, and protective layer 27 is formed over dielectric layer 26.
Back plate 30 has glass-made back substrate 31, data electrodes 32, base dielectric layer 33, barrier ribs 34, and phosphor layers 35. On back substrate 31, a plurality of data electrodes 32 are formed in parallel with each other. Base dielectric layer 33 is formed so as to cover data electrodes 32, and grid-like barrier ribs 34 are formed on base dielectric layer 33. In addition, phosphor layers 35 of red, green, and blue are formed on the surface of base dielectric layer 33 and on the side surface of barrier ribs 34.
Scan electrode 22 has opaque first bus electrode 22a and transparent first transparent electrode 22b. First bus electrode 22a is formed of black layer 22c and conductive layer 22d. Similarly, sustain electrode 23 has second bus electrode 23a and second transparent electrode 23b. Second bus electrode 23a is formed of black layer 23c and conductive layer 23d. Hereinafter, first bus electrode 22a and second bus electrode 23a are simply referred to as bus electrode 22a and bus electrode 23a, respectively; first transparent electrode 22b and second transparent electrode 23b are referred to as transparent electrode 22b and transparent electrode 23b, respectively.
Black layers 22c, 23c are disposed for making bus electrodes 22a, 23a look black, respectively, when panel 10 is seen from the display surface side. The black layers are formed of a black material, for example, having ruthenium oxide (RuO2) as the main component and are formed into a narrow stripe shape on front substrate 21. Conductive layers 22d, 23d enhance conductivity of bus electrodes 22a, 23a. Conductive layers 22d, 23d are formed in a manner that paste containing silver is printed on black layers 22c, 23c and then fired.
Black stripes 25 are disposed for making the display surface look black when panel 10 is seen from the display surface side. Black stripes 25 are formed of, for example, a black material containing ruthenium oxide (RuO2) as the main component and are disposed on front substrate 21.
Transparent electrodes 22b and 23b are disposed not only for generating a strong electric field and accordingly generating a discharge in the discharge space, but also for drawing light generated from phosphor layers 35 outside panel 10. Transparent electrodes 22b and 23b are formed in a manner that a dispersion liquid containing particles of metal or particles of metal oxide is printed into a wide stripe shape so that transparent electrode 22b covers at least a part of bus electrode 22a; similarly, transparent electrode 23b covers at least a part of bus electrode 23a. After that, the applied dispersion liquid is fired in an oxidizing atmosphere.
Next, the manufacturing method of panel 10 will be described.
As the first step of manufacturing front plate 20, glass-made front substrate 21 undergoes alkali cleaning. After that, precursors 22cx, 23cx for black layers 22c, 23c and precursor 25x for black stripe 25 are formed on front substrate 21. The precursors above are made of black layer paste containing ruthenium oxide (RuO2) and black pigment as the main component, an organic component, and an inorganic component, such as glass frit.
The “precursor” termed in the present invention is the applied paste for structure member, such as black layer paste, that undergoes a thermal process until reaching a state where an organic component originally contained in the paste has been removed and an inorganic component does not melt.
Precursors 22cx, 23cx, and 25x are formed by heretofore known technique, such as screen printing and photolithography. After that, as shown in
Next, as shown in
Next, transparent electrodes 22b and 23b are formed. First, dispersion liquid containing any one of the following particles with an average particle diameter of 5-100 nm is prepared:
In the embodiment, the dispersion liquid is formed in a manner that particles of indium (In)-tin (Sn) alloy with an average particle diameter of 10 nm is dispersed at a concentration of 12 wt % into an organic solvent with dispersant. In the embodiment, decahydronaphthalene is used for the organic solvent. Instead, for example, the followings can be employed: nonpolar solvent, such as toluene, xylene, benzene, tetradecane; aromatic hydrocarbon group; long-chain alkane, such as hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, octadecane, nonadecane, eicosane, trimethylpentane; and cyclic alkane, such as cyclohexaane, cycloheptane, cyclooctane.
Next, as shown in
After that, as shown in
In this way, after bus electrodes 22a, 23a are formed, transparent electrodes 23a, 23b are formed so as to cover at least a part of bus electrodes 22a, 22b, respectively. This reduces the risk that the transparent electrodes are peeled off or damaged in the forming process of the bus electrodes. Transparent electrodes are thus formed with the use of a dispersion liquid containing particles of metal or particles of metal oxide.
Next, the precursor of the dielectric layer is formed, by printing or other heretofore known technique, on front substrate 21 on which scan electrodes 22, sustain electrodes 23, and black stripes 25 have been formed. The precursor of the dielectric layer is fired, so that dielectric layer 26 with a thickness of 20 to 50 μm is formed.
The dielectric paste formed in the embodiment contains dielectric glass having the following composition: 34.6 wt % boron oxide (B2O3), 1.4 wt % silicon oxide (SiO2), 27.6 wt % zinc oxide (ZnO), 3.3 wt % barium oxide (BaO), 25 wt % bismuth oxide (Bi2O3), 1.1 wt % aluminum oxide (Al2O3), 4.0 wt % molybdenum oxide (MoO3), and 3.0 wt % tungsten oxide (WO3). The softening point of the dielectric glass is about 570° C. Next, the precursor of the dielectric layer is formed by applying dielectric paste, by die coating, onto front substrate 21 having scan electrodes 22, sustain electrodes 23, and black stripes 25 thereon. The precursor of the dielectric layer is then fired at about 590° C., so that dielectric layer 26 with a thickness of about 40 μm is formed.
Instead of the dielectric paste above, for example, a dielectric paste containing dielectric glass that has a softening point of 520° C. to 590° C. and contains some of the followings can be used: boron oxide (B2O3), silicon oxide (SiO2), zinc oxide (ZnO), bismuth oxide (Bi2O3), aluminum oxide (Al2O3), molybdenum oxide (MoO3), tungsten oxide (WO3), cerium oxide (CeO), alkaline-earth metal oxide, and alkali metal oxide.
As shown in
In the embodiment, transparent electrodes 22b and 23b are formed of indium tin oxide (ITO) with the use of particles of indium (In)-tin (Sn) alloy, but it is not limited thereto. For example, the transparent electrodes may be formed of a tin oxide (SnO2) film with the use of particles of tin (Sn). As still another possibility, the transparent electrodes may be formed of a zinc oxide (ZnO) film with the use of particles of zinc (Zn).
In the embodiment, after precursors 22cx, 23cx, 22dx, and 23dx for black layers 22c, 23c, conductive layers 22d, 23d are fired, wet layers 22bx and 23bx are formed and fired, but it is not limited thereto. For example, scan electrodes 22 and sustain electrodes 23 may be formed in a manner that, after precursors 22cx, 23cx, 22dx, and 23dx are formed and then further wet layers 22bx and 23bx are formed on the precursors, the precursors 22cx, 23cx, 22dx, 23dx, wet layers 22bx, 23bx are fired at the same time.
Next, the method for manufacturing back plate 30 will be described.
First, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
A red phosphor may be formed of, for example, (Y, Gd) BO3:Eu, (Y, V) PO4:Eu. A green phosphor may be formed of, for example, Zn2SiO4:Mn, (Y, Gd) BO3:Tb, (Y, Gd) Al3(BO3)4:Tb. A blue phosphor may be formed of, for example, BaMgAl10O17:Eu, Sr3MgSi2O8:Eu.
Front plate 20 and back plate 30 are oppositely disposed so that display electrode pairs 24 are positioned orthogonal to data electrodes 32. The two plates are sealed with low-melting glass at the peripheries outside the image display area where the discharge cells are formed. After that, the discharge space inside the plates is filled with discharge gas containing xenon. Panel 10 is thus completed.
According to the embodiment, transparent electrodes 22b, 23b are formed in a manner that a dispersion liquid containing particles of metal, such as indium (In) and tin (Sn), is applied into a wide stripe shape so that transparent electrode 22b covers at least a part of bus electrode 22a; similarly, transparent electrode 23b covers at least a part of bus electrode 23a, and then fired in an oxidizing atmosphere. In the next step that follows above, dielectric layer 26 is formed so as to cover transparent electrodes 22b and 23b by die coating. The structure further reduces the risk of damage and peel-off of transparent electrodes 22b and 23b even when they have insufficient mechanical strength.
Besides, in the embodiment, transparent electrodes 22b and 23b are formed in a manner that a dispersion liquid containing indium (In)-tin (Sn) alloy particles with an average diameter of 10 nm is printed and then fired at a high temperature of 500° C. Such formed transparent electrodes 22b, 23b not only have low resistance, high transmittance, but also keep an intimate contact with front substrate 21 and bus electrodes 22a, 23a. This is considered that the firing process at high temperatures allows the particles to be expanded during the change from indium (In) to indium oxide (In2O3), enhancing the contact between the particles and between the particles and the substrate.
Besides, according to the embodiment, transparent electrodes 22b and 23b are formed of metal particles with an average particle diameter of 5 to 100 nm. Particles with an average particle diameter smaller than 5 nm easily causes reaction of the particles to the dielectric glass, and at the same time, easily causes a crack at the stepped section between the transparent electrodes and silver (Ag)-contained bus electrodes 22a, 23a. On the other hand, particles with an average particle diameter greater than 100 nm easily cause clogging in the minute nozzle of the inkjet printer. Besides, if the average particle diameter becomes excessively large, the contact area between the particles after the firing process decreases, resulting in increased sheet resistance.
According to the embodiment, a dispersion liquid containing particles of metal is printed into stripes by inkjet printing. The inkjet printing described above allows the patterning process to be completed with high dimensional accuracy and the least wasted dispersion liquid.
The amount of dispersion liquid can be further reduced by adding a twist to the shape of a transparent electrode, which is described below.
Scan electrode 52 has bus electrode 22a and transparent electrode 52b. Similarly, sustain electrode 53 has bus electrode 23a and transparent electrode 53b. Each of display electrode pairs 54 is formed of scan electrode 52 and sustain electrode 53.
Transparent electrodes 22b, 23b are formed in a manner that a dispersion liquid containing particles of metal, such as indium (In) and tin (Sn), is applied into a wide stripe shape so that transparent electrode 22b covers at least a part of bus electrode 22a; similarly, transparent electrode 23b covers at least a part of bus electrode 23a, and then fired in an oxidizing atmosphere. Transparent electrodes 52b, 53b of the embodiment, as shown in
Scan electrode 82, which is formed on front substrate 81 that constitutes front plate 80, has bus electrode 22a and transparent electrode 82b. Similarly, sustain electrode 83 has bus electrode 23a and transparent electrode 83b. Each of display electrode pairs 84 is formed of scan electrode 82 and sustain electrode 83.
Transparent electrodes 82b, 83b are formed in a manner that a dispersion liquid containing particles of metal, such as indium (In) and tin (Sn), is applied into a wide stripe shape so that transparent electrode 82b covers at least a part of bus electrode 22a; similarly, transparent electrode 83b covers at least a part of bus electrode 23a, and then fired in an oxidizing atmosphere. Transparent electrodes 82b, 83b of the third exemplary embodiment, as shown in
Transparent electrodes 92b, 93b are formed in a manner that a dispersion liquid containing particles of metal, such as indium (In) and tin (Sn), is applied into a wide stripe shape so that transparent electrode 92b covers at least a part of bus electrode 92a; similarly, transparent electrode 93b covers at least a part of bus electrode 93a, and then fired in an oxidizing atmosphere. Transparent electrodes 92b, 93b of the embodiment, as shown in
The panel of the fourth exemplary embodiment differs from that of the third exemplary embodiment in that the section between oppositely disposed scan electrode 92 and sustain electrode 93, i.e., discharge gap 99 is formed by bus electrodes 92a, 93a.
In general, the distance of a discharge gap significantly affects discharge characteristics of the discharge cell. Large variations in distance of a discharge gap due to poor dimensional accuracy in printing a transparent electrode increase variations in discharge characteristics between discharge cells. This can cause unevenness to the display surface. According to the fourth exemplary embodiment, however, bus electrodes 92a and 93a are formed by photolithography with high, dimensional accuracy. This allows variations in distance of discharge gap 99 to be decreased, thereby suppressing variations in discharge characteristics between discharge cells.
As described above, transparent electrode 92b is formed so as to cover at least a part of bus electrode 92a, and similarly, transparent electrode 93b is formed so as to cover at least a part of bus electrode 93a. In the forming process above, it is preferable that each width of transparent electrodes 92b and 93b overlapped with bus electrodes 92a and 93a, respectively, should be at least half each width of transparent electrodes 92b, 93b and should be smaller than each width thereof. That is, the following relation should preferably be satisfied:
½W≦D<W, where, W represents the width of bus electrode 92a (93a); D represents an overlapped width between transparent electrode 92b (93b) and bus electrode 92a (93a).
If transparent electrodes 92b, 93b are formed so as to completely cover bus electrodes 92a, 93a, silver particles as the material of bus electrodes can undergo insufficient sintering in the firing process of bus electrodes 92a, 93a. To avoid the problem, overlapped width D should preferably be smaller than width W of bus electrode 92a (93a). On the other hand, if overlapped width D is smaller than half width W of bus electrode 92a (93a), contact resistance between bus electrode 92a (93a) and transparent electrode 92b (93b) increases, resulting in impaired image display quality due to an excessive increase in resistance value of scan electrode 92 and sustain electrode 93. Therefore, it is not preferable that overlapped width D is determined to be smaller than half width W of bus electrode 92a (93a).
Although the “teeth” of the “comb” shape, as shown in
Besides, specific values seen in the description of the first through fourth embodiments are cited merely by way of example. They should be optimally determined according to, for example, specifications of a panel.
The manufacturing method above allows the transparent electrodes to be formed, without decrease in yield, by firing a dispersion liquid containing particles of metal or particles of metal oxide. This provides a panel with low-cost transparent electrodes. It is therefore useful for manufacturing a panel and a method for manufacturing thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-170072 | Jun 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/002984 | 6/29/2009 | WO | 00 | 2/17/2010 |
