Patent Application
20080085423
The accompanying drawings illustrate example implementations and, along with the description, serve to explain principles of this disclosure.
The thickness ratios of the layers shown in
As shown in
The front substrate 110 is prepared by machining a glass for a display substrate, using milling and cleaning. The transparent electrodes 120a and 130a are formed in accordance with a photo-etching process using a sputtering process or a lift-off method using a CVD process. The bus electrodes 120b and 130b are made of silver (Ag). A black matrix may be formed on the sustain electrode pairs. The black matrix may be made of a material including a glass exhibiting a low melting point and a black pigment.
The dielectric layer 140, which is an upper dielectric layer, is formed over the front substrate 110 provided with the transparent electrodes and bus electrodes. The upper dielectric layer 140 is made of a transparent glass having a low melting point. The protect layer 150 is formed over the upper dielectric layer 140, using a magnesium oxide. The protect layer 150 functions to protect the upper dielectric layer 140 from an impact of positive (+) ions during an electrical discharge, while functioning to increase the emission of secondary electrons.
The glass composition of the upper dielectric layer 140 includes 10 to 60 mol % of Bi2O3 (bismuth oxide), 5 to 40 mol % of CuO (cupric oxide), and 15 to 40 mol % of B2O3 (boric oxide). The glass composition may further include at least one of 0 to 10 mol % of SiO2 (silicon dioxide), 0 to 30 mol % of ZnO (zinc oxide), or 0 to 35 mol % of BaO (barium oxide) to improve fluidity. Further, the glass composition may further include at least one of 0 to 10 mol % of MgO (magnesium oxide), SrO (strontium oxide) or CaO (calcium oxide), at least one of 0 to 10 mol % of Al2O3 (aluminum oxide) or La2O3 (lanthanum oxide), and 0 to 10 mol % of R2O. The R2O can be at least one selected from Li2O (lithium oxide), Na2O (sodium oxide), or K2O (potassium oxide).
The Bi2O3 added in the amount of 10 to 60 mol % serves as a glass forming agent, and functions to reduce a softening temperature, and increase a thermal expansion coefficient and a dielectric constant. Thus, the Bi2O3 is added in the appropriate composition ratio. The CuO added in the amount of 5 to 40 mol % functions to ensure the fluidity which may lack in the glass composition containing the Bi2O3 by reducing the glass transition temperature. Furthermore, the B2O3 added in the amount of 15 to 40 mol % is usually added as a flux to facilitate a solid-state reaction. The improvement in a glass forming ability elevates the glass transition temperature. The B2O3 is therefore added in the appropriate composition ratio.
The BaO added in an amount of 0 to 35 mol % is an alkaline earth oxide that serves as a network modifier. When a certain amount of BaO is added, it functions to reduce the glass transition temperature. When an excessive amount of BaO is added, however, it causes crystallization. The MgO, SrO or CaO added in an amount of 0 to 10 mol % is added to control properties, such as the glass transition temperature, thermal expansion coefficient, softening temperature, and yellowing phenomenon. The ZnO added in an amount of 0 to 30 mol % functions to reduce the thermal expansion coefficient and glass transition temperature, while increasing the glass forming ability. The ZnO also functions to absorb orange light generated by the discharge of Ne (neon) among the discharge gases injected into the inner space of the PDP, thereby preventing the degradation of a chromaticity property of the PDP.
The SiO2 added in an amount of 0 to 10 mol % is added to prevent crystallization. The R2O added in an amount of 0 to 10 mol % is an alkaline earth oxide that serves as a network modifier. When a certain amount of R2O is added, it functions to reduce the glass transition temperature. When an excessive amount of R2O is added, it causes devitrification. The R2O is thus added in the above-mentioned appropriate composition ratio. The R2O can be selected from Li2O, Na2O, or K2O. Additionally, 0 to 10 mol % of Al2O3 or La2O3 may be further added to help mixing of the powders among the glass compositions or printing, and prevent crystallization.
The protect layer 150 is formed on the dielectric layer 140 having the above-mentioned composition using MgO.
The PDP of
Barrier ribs 240 are formed on the white dielectric layer 230 such that each barrier rib 240 is arranged between the adjacent address electrodes 220. For the same reason as the white dielectric layer 230, the barrier ribs 240 can be prepared by using a parent glass, having the same composition and composition ratio of the dielectric composition, used for the dielectric layer 140 formed over the front substrate 110. The glass composition included in the barrier ribs 240 may further include 10 to 20 mol % of TiO2, which is a filler, and a high refractive material at the same time. Additionally, a sealing part (not shown) for sealing the front substrate 110 and back substrate (210) can make use of a material having the same composition as the above-mentioned dielectric layer or barrier ribs.
Red (R), green (G), and blue (B) phosphor layers 250 are formed between each adjacent barrier rib 240.
Discharge cells are defined in regions where the address electrodes 220 on the back substrate 210 intersect the display electrodes 120 and 130 on the front substrate 110.
When an address voltage is applied between one address electrode 220 and one display electrode 120 or 130, an address discharge occurs in the associated cell, so that a wall voltage is generated in the cell. A sustain voltage is subsequently applied to the display electrodes 120 and 130, a sustain discharge occurs in the cell, at which the wall voltage has been generated. Vacuum ultraviolet rays generated in accordance with the sustain discharge excite the phosphors in the associated cell, so that the phosphors emit light. Thus, visible rays are emitted through the transparent front substrate 110, and an image is displayed on the PDP.
Examples of glass compositions for the dielectric layer of the PDP are described below.
Table 1 below shows specific examples (Ex. 1 to 15) of glass compositions. In Table 1, “×” represents no fluidity in the glass composition, “Δ” represents insufficient fluidity in the glass composition, and “◯” represents sufficient fluidity ensured in the glass composition.
In the examples 1-15 of Table 1, the glass composition was prepared by mixing the constituent components in accordance with the compositions shown in each example, respectively. The glass composition thus prepared was melted in an electric furnace at 1250° C. The melted mixture was quickly cooled in the drying process using a twin roll. The quickly cooled mixture was crushed using a disk mill, and further grinded using a dry mill to prepare glass powder having a particle size of 1 to 1.5 μm. The glass transition temperature (Tg) of the glass powder was measured, and the result showed that a stable glass transition temperature in the range of 330 to 386° C. could be obtained. The glass transition temperature defines the heat resistance of a polymer. Thus, having a high glass transition temperature means that the polymer is not easily melted.
The fluidity was measured at a temperature in the range of 440 to 480° C., and, as a result, the glass composition prepared according to the disclosed compositions in Examples 7, 13 and 15 showed a stable fluidity. Therefore, the glass powder prepared with the above-mentioned composition and a vehicle were mixed, and the mixture was utilized in dielectric layers, barrier ribs and sealing parts of the PDP. As a result, the stability was ensured in that a low curing temperature of 480° C. or lower was possible, and, at the same time, cracks did not generate at the parts where the mixture was used.
An example method for manufacturing a PDP will now be described. First, transparent electrodes and bus electrodes are formed on a front substrate. The front substrate is prepared by milling and cleaning a glass or a soda-lime glass for a display substrate. The transparent electrodes are formed, using ITO or SnO2, in accordance with a photo-etching method using a sputtering process or a lift-off method using a CVD process. The bus electrodes are formed, using a material such as silver (Ag), in accordance with a screen printing method or a photosensitive paste method. A black matrix may be formed on the sustain electrode pairs. The black matrix may be formed, using a low-melting-point glass and a black pigment, in accordance with a screen printing method or a photosensitive paste method.
Thereafter, a dielectric, which is an upper dielectric layer, is formed over the front substrate provided with the transparent electrodes and bus electrodes. The formation of the dielectric layer may be achieved by laminating the above mentioned dielectric material in accordance with a screen printing method or a coating method, drying and curing the laminated layer. The curing process can be performed at a curing temperature of 480° C. or lower. The dielectric material may be applied in a form of a paste.
The dielectric material mixed with the above-mentioned composition ratio is melted at high temperatures (S220). The melted mixture is quickly cooled by immersing in water having room temperature or using a dry twin roll, followed by grinding the cooled mixture using a mill (S230). If necessary, the dielectric material may be mixed with a filler and dried to prepare a parent glass powder. The filler may further include at least one substance of cordierite (2MgO.2Al2O3.5SiO2), zircon (ZrSiO4), baddeleyite (ZrO2), or B-eucryptite (Li2O—Al2O3—SiO2) in an amount of 0 to 20 parts by weight based on the 100 parts by weight of the glass composition.
Thereafter, a paste is formed by mixing 70 to 90 wt % of the parent glass powder prepared as mentioned above and 10 to 30 wt % of a vehicle (S240). The vehicle may be a mixture of 0 to 15 wt % of a binder, 0 to 80 wt % of a solvent and 0 to 5 wt % of a dispersant to help mixing of the powders or printing. As the solvent, alcohols, glycols, propylene glycol ethers, propylene glycol acetates, ketones, BCA, xylene, terpineol, texanol, water, or the like can be used. As the dispersant, acryl-based dispersants having a high dispersing effect are mainly used. These materials are then coated (S250). For example, the paste may be applied to a surface of a substrate to coat the surface using a screen printing method or other method. Once coated, the pasted is dried and cured (S260) at a temperature of 480° C. or lower to form the upper dielectric layer.
A protect layer is then deposited over the upper dielectric layer. The formation of the protect layer may involve depositing a magnesium oxide, etc. in accordance with an electron beam deposition process, a sputtering process, or an ion plating process.
Meanwhile, address electrodes are formed on the back substrate. The back substrate is prepared by milling and cleaning a glass or a soda-lime glass for a display substrate. The address electrodes are formed, using silver (Ag), in accordance with a screen printing method, a photosensitive paste method, or a photo-etching method. The photo-etching method is carried out after completion of a sputtering process. A dielectric, which is a lower dielectric layer, is then formed over the back substrate provided with the address electrodes. The composition of the lower dielectric layer is the same as described above, and its formation is the same as that of the upper dielectric layer. It is preferred that the lower dielectric layer exhibit white, in order to achieve an enhancement in the brightness of the PDP.
Thereafter, barrier ribs are formed to separate discharge cells from one another. The material of the barrier ribs includes a parent glass and a filler. The specific composition is the same as described above, and its formation is the same as the formation of the dielectric.
A black top material is coated over the barrier rib material. The black top material includes a solvent, inorganic powder, and an additive. The inorganic powder includes glass frits and a black pigment. The layers of the barrier rib material and black top material are patterned, to form the barrier ribs and black tops.
The patterning process involves masking, light exposure, and development. That is, a mask is arranged to cover regions corresponding to the address electrodes, and a light exposure is subsequently carried out. When development and curing processes are sequentially carried out, only the light-exposed portions of the barrier rib material layer and black top material layer remain. Thus, the barrier ribs and black tops are formed. When a photoresist material is contained in the black top material, it is possible to more easily achieve the patterning of the barrier rib and black top materials. When the barrier rib and black top materials are simultaneously cured, the binding force between the parent glass of the barrier rib material and the inorganic powder of the black top material increases. In this case, accordingly, an enhancement in durability is expected.
Thereafter, phosphors are coated over the surfaces of the lower dielectric layer facing discharge spaces and the side surfaces of the barrier ribs. The coating of the phosphors is carried out such that R, G, and B phosphors are sequentially coated in each discharge cell. The coating is carried out using a screen printing method or a photosensitive paste method.
Subsequently, an upper panel is assembled to a lower panel, such that the barrier ribs are interposed between the upper and lower panels. The upper and lower panels are then sealed. The space between the upper and lower panels is then evacuated, to remove impurities from the space. A discharge gas is then injected into the space. The materials of the sealing part used for sealing the upper and lower panels are as described above.
In some implementations, the lower dielectric layer material and the barrier rib material can be laminated into a green sheet. The green sheet may have a first layer including the lower dielectric layer material and a second layer including the barrier rib material. Each material may be materials for the above-mentioned dielectric and barrier rib. The second layer is patterned into the barrier ribs, thus it contains a photoresist component.
The green sheet is formed over the back substrate formed with address electrodes, and light exposure and development is carried out on the green sheet. At this time, the second layer is patterned into the barrier rib. When the lower dielectric layer and the barrier rib are simultaneously cured at a temperature lower than 480° C., the binding force between the lower dielectric layer and the barrier rib increases. An enhancement in durability is therefore expected.
Various modifications and variations can be made in the example implementations described and shown, and other implementations are within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0098326 | Oct 2006 | KR | national |
