Patent Application
20070262716
In the present invention, examples of the substrate include substrates of materials such as glass, quartz and ceramics, as well as any of these substrates on which a desired structure such as electrodes, an insulating film, a dielectric layer, a protective film and the like are formed.
A plurality of metal electrodes may be formed on the substrate in a predetermined direction. These metal electrodes can be formed by using various known materials through known methods in the corresponding field. With respect to the materials used for the electrodes, examples thereof include metal conductive materials such as Ag, Au, Al, Cu and Cr. With respect to the forming method of the electrodes, various conventionally known methods in the corresponding field may be used. For example, a thick-film forming technique such as printing may be used to form the electrodes, or a thin-film forming technique corresponding to a physical deposition method or a chemical deposition method may be used. As an example of the thick-film forming technique, a screen printing method is used. Examples of the physical deposition method as the thin-film forming technique include a vapor deposition method, a sputtering method and the like. Examples of the chemical deposition method include a thermal CVD method, a photo CVD method and a plasma CVD method.
The dielectric layer may be formed through processes in which a glass material is placed on a metal electrode and this is then fired. This dielectric layer is formed by applying a glass paste made from non-lead-type glass flit (glass powder), a binder resin and a solvent onto a substrate in a manner so as to cover the metal electrodes through a screen printing method, or by affixing a green sheet (un-sintered dielectric sheet) of non-lead-type glass powder thereto and firing the resulting substrate. Examples of glass materials used as the non-lead-type glass flit include B2O3—SiO2—ZnO-based glass, Bi2O3—B2O3—SiO2-based glass, B2O3—SiO2—Al2O3-based glass, ZnO—B2O3—SiO2—BaO-based glass, and any of the foregoing glass materials mixed with an alkali or alkali-earth oxide.
In the present invention, the dielectric layer may be formed by laminating a plurality of dielectric layers into, for example, double layers and triple layers. For example, in the case of forming the dielectric layer with a double layer structure, a first dielectric layer is formed with a film thickness of 12 μm or less and a second dielectric layer may be formed thereon with a film thickness of 13 μm or less.
The metal electrodes may be such that a Cr layer is formed on a substrate, a Cu layer is formed thereon, and a Cr layer is further formed thereon respectively through a vapor film-forming method, and a resist film is formed on the metal film with the three layers, and after having patterned the resist film by using a photolithographic technique, the metal film on unnecessary portions are removed by etching so that a metal electrode having a three-layer-structure of Cr—Cu—Cr is prepared.
The invention is explained in detail by the following embodiments with reference to the drawings. However, the present invention is not intended to be limited thereby, and various modifications may be made therein.
a) and 1(b) are explanatory diagrams that show a structure of a PDP manufactured by a manufacturing method of the present invention.
The PDP 10 is constituted by a substrate 11 on the front face side on which constituent elements that provide functions as the PDP are formed and a substrate 21 on the back face side. With respect to the substrate 11 on the front face side and the substrate 21 on the back face side, for example, a glass substrate, a quartz substrate and a ceramics substrate may be used.
Display electrodes X and display electrodes Y are placed with equal intervals in the horizontal direction on the inner side face of the substrate 11 on the front face side. All the gaps between the adjacent display electrodes X and display electrodes Y form display lines L. Each of the display electrodes X and Y is constituted by a transparent electrode 12 with a wide width, made of ITO, SnO2 or the like, and a bus electrode 13 with a narrow width, made of metal, such as Ag, Au, Al, Cu, Cr or a laminated body thereof (for example, Cr—Cu—Cr laminated structure), or the like. With respect to the display electrodes X and Y, in the case of Ag and Au, a thick-film forming technique such as screen printing may be used, and in the case of other materials, a thin-film forming technique such as a vapor method and a sputtering method and an etching technique may be used, so that the display electrodes having a desired number, thickness, width and intervals are formed.
The display electrodes X and Y may be made of only metal, such as Ag, Au, Al, Cu, Cr or a laminated body thereof. In such a case, preferably, the form of the metal electrode has a line pattern or a mesh pattern so that light from phosphor layers is effectively transmitted.
Here, in the present PDP, a PDP having a so-called ALIS structure, in which the display electrodes X and the display electrodes Y are placed with equal intervals, with all the gaps between the adjacent display electrodes X and display electrodes Y forming display lines L, is shown. However, the present invention may be applied even to a PDP having a structure in which paired display electrodes X and Y are placed with a gap (non-discharging gap) causing no discharge.
A dielectric layer 17 is formed on the display electrodes X and Y in a manner so as to cover the display electrodes X and Y. The dielectric layer 17 is formed by applying a glass paste made from non-lead-type glass flit, a binder resin and a solvent onto a substrate 11 on the front face side through a screen printing method and by firing the resulting substrate.
A protective layer 18 used for protecting the dielectric layer 17 from damage caused by collision of ions generated by a discharge upon displaying is formed on the dielectric layer 17. This protective film is made from MgO. The protective layer may be formed by using a known thin-film forming process in the corresponding field, such as an electron beam vapor deposition method and a sputtering method.
A plurality of address electrodes A are formed on the inner side face of the substrate 21 on the back face side in a direction crossing the display electrodes X and Y when viewed from above, and a dielectric layer 24 is formed so as to cover the address electrodes A. Each of the address electrodes A is used for generating an address discharge so as to select a light-emitting cell at an intersection with the Y electrode, and formed into a three-layer structure of Cr—Cu—Cr. The address electrodes A may be formed by using another material such as Ag, Au, Al, Cu, or Cr. In the same manner as the display electrodes X and Y, with respect to the address electrodes A, in the case of Ag and Au, a thick-film forming technique such as screen printing may be used, and in the case of the other materials, a thin-film forming technique such as a vapor method and a sputtering method and an etching technique may be used, so that the address electrodes having a desired number, thickness, width and intervals are formed. The dielectric layer 24 may be formed by using the same material and the same method as the dielectric layer 17.
A plurality of barrier ribs 29 having a stripe pattern are formed on the dielectric layer 24 between the adjacent address electrodes A. With respect to the shape of the barrier ribs 29, not limited to this shape, a mesh shape (box shape) in which discharge spaces are separated for each cell may be used. The barrier ribs 29 may be formed by using a method such as a sand blasting method, a printing method and a photo-etching method. For example, in the sand blasting method, after a glass paste, made from low-melting-point glass flit, a binder resin, a solvent and the like, have been applied to the dielectric layer 24 and dried thereon, cutting particles are blown onto the glass paste layer with a cutting mask having openings of the barrier rib pattern attached thereon, so that the glass paste layer exposed to the openings of the mask is cut; thus, the resulting layer is fired to form the barrier ribs. Moreover, in the photo-etching method, instead of cutting by the use of cutting particles, a photosensitive resin is used as the binder resin, and after exposing and developing processes by using a mask, the resulting layer is fired to firm the barrier ribs.
Phosphor layers of 28R, 28G and 28B having respective red (R), green (G) and blue (B) colors are formed on side faces and a bottom face of each of discharge spaces having a recess groove shape between the barrier ribs 29. Each of the phosphor layers 28R, 28G and 28B is formed through processes in which: a phosphor paste containing phosphor powder, a binder resin and a solvent has been applied to the discharge space having the recess groove shape between the barrier ribs 29 by using a screen printing method or a method using a dispenser, and after repeating this process for each of the colors, the resulting layers are fired. These phosphor layers 28R, 28G and 28B may also be formed through a photolithographic technique by using a sheet-shaped phosphor layer material (so-called green sheet) containing phosphor powder, a photosensitive material and a binder resin. In this case, a sheet having a desired color is affixed to the entire face of a display area on the substrate, and this is exposed and developed, and by repeating these processes for each of the colors, the phosphor layers of the respective colors are formed on the corresponding gaps between the barrier ribs.
The substrate 11 on the front face side on which these constituent elements have been formed and the substrate 21 on the back face side are placed face to face with each other so that the display electrodes X and Y cross the address electrodes A, and the peripheral portion is sealed so that a discharge space 30 surrounded by the barrier ribs 29 is filled with a discharge gas in which Xe, Ne and the like are mixed; thus, a PDP is manufactured. In this PDP, the discharge space 30, located each of the intersections between the display electrodes X and Y and the address electrodes A, forms one cell (unit light-emitting area) that is the minimum unit for display. One pixel is constituted by three cells of R, G and B.
The display electrodes X and Y are formed on the glass substrate 11 on the front face side. The display electrodes X (X electrodes) and the display electrodes Y (Y electrodes) have the same structure, that is, the structure in which bus electrodes 12 made of metal are formed on a transparent electrode 11.
The transparent electrode 11 is formed with a film thickness in a range from 500 to 2000 Å. The bus electrode 12 has a three-layer structure of Cr—Cu—Cr in which Cr has a film thickness in a range from 500 to 2000 Å, with Cu being formed with a thickness of about 3 μm. Therefore, the thickness TE of each of the display electrodes X and Y is in an approximate range from 3 to 4 μm. A dielectric layer 17 is formed on the display electrodes X and Y. The thickness TD of the dielectric layer 17 is about 20 μm.
a) and 3(b) are explanatory diagrams showing a first example of a manufacturing method of the substrate on the front face side.
The substrate on the front face side is manufactured in the following processes. First, a transparent conductive film, made of ITO, is formed on a glass substrate 11 by a method, such as a vapor deposition method and a sputtering method, and the transparent conductive film is patterned by using a photolithographic technique to prepare a transparent electrode 12. Then, a three-layer metal conductive film of Cr—Cu—Cr is formed on the transparent electrode 12 by using a method such as a vapor deposition method and a sputtering method, and a resist film is formed on the metal conductive film, and after the resist film has been patterned by using the photolithographic technique, unnecessary portions of the metal conductive film are removed by etching so that bus electrodes 13 are formed. In this manner, the display electrodes X and the display electrodes Y are simultaneously formed (see
Next, a glass paste (glass material), prepared by mixing a binder resin and a solvent with non-lead-based glass flit, is applied onto the glass substrate 11 so as to cover the display electrodes X and Y by using a screen printing method, and after this has been dried into a dried film, the glass substrate 11 is loaded into a firing furnace, and the dried film of the glass material is fired at a temperature in a range from 600 to 610° C. so that a dielectric film 17 is formed (see
Besides this method, the dielectric layer 17 may be formed by affixing a green sheet (un-sintered dielectric sheet) with which non-lead-based glass powder is mixed to the substrate 11 on the front face side, and by firing the resulting substrate.
As the non-lead-based glass flit, one of the following is used: B2O3—SiO2—ZnO-based glass, Bi2O3—B2O3—SiO2-based glass, B2O3—SiO2—Al2O3-based glass, ZnO—B2O3—SiO2—BaO-based glass, and any of the foregoing glass materials mixed with an alkali or alkali-earth oxide.
When the dried film of the glass material is fired, the glass material is fused. At this time, bubbles are generated in the glass material by an electrochemical reaction between the glass material and the bus electrodes 13 of metal. The generation of these bubbles is mainly caused by a chemical reaction between Cu and glass. Here, Cu is not directly made in contact with the glass material because it is sandwiched by Cr. However, in the case when the three-layer metal conductive film of Cr—Cu—Cr is etched by a wet-etching process or the like, Cu is exposed between Cr and Cr, and the exposed Cu comes into contact with the glass material to cause a reaction, with the result that bubbles are generated in the glass material.
In order to reduce the generation of these bubbles, the thickness of the bus electrode 13 that is a generation source of bubbles is made thinner. In particular, the thickness of Cu is made thinner. More specifically, as described earlier, the thickness of the bus electrode 13 is set to 6 μm or less, with the thickness of Cu being set to 3 to 4 μm.
Conventionally, low-melting point glass flit containing lead has been usually used as the glass material for the dielectric layer. In contrast, in recent years, from the viewpoint of reducing the environmental load, an attempt to use a non-lead-based glass material has been made. In the application of the non-lead-based glass material, however, the melting point (glass softening point) of the glass material becomes higher. For this reason, upon firing, the flowability in the glass deteriorates, making it difficult to release bubbles generated in the glass material when fired, to cause the bubbles to remain in the dielectric layer.
In order to easily release bubbles in the glass material, the film thickness of the dielectric layer 17 is made thinner. More specifically, as described above, the film thickness of the dielectric layer is set to 25 μm or less. With this arrangement, even when the flowability of the glass material is lowered because of the use of the non-lead-based glass material, generated bubbles are allowed to float and easily defoamed so that the bubbles in the dielectric layer 17 are reduced upon completion of the firing process.
In this manner, the thickness of the electrodes is made thinner to reduce the absolute amount of bubbles that are generated and the film thickness of the dielectric layer is also made thinner so as to easily release bubbles in the glass material so that bubbles in the dielectric layer 17 are reduced upon completion of the firing process. By reducing the bubbles in the dielectric layer 17, it becomes possible to prevent problems such as an insufficient insulation and a reduction in luminescence.
Here, the discharge voltage between the display electrodes relates to the film thickness of the dielectric layer. Moreover, the film thickness of the dielectric layer relates to the static capacitance of the dielectric layer. Furthermore, the static capacitance of the dielectric layer relates to the quantity of discharge between the display electrodes. Therefore, in an attempt to obtain an appropriate quantity of discharge by applying an appropriate discharge voltage across the display electrodes, the dielectric layer is preferably made so as to accumulate a charge of 0.2 nF or more per 1 cm2 thereof, in the case when the film thickness of the dielectric layer is set to 25 μm or less.
a) to 4(c) are explanatory diagrams that show a second example of the manufacturing method of the substrate on the front face side.
The dielectric layer may be formed by laminating a plurality of dielectric layers. For example, two layers or three layers of the dielectric layers may be formed. In the case when two layers of the dielectric layers are formed, for example, the first dielectric layer is formed with a film thickness of 12 μm or less, and the second dielectric layer may be formed thereon with a film thickness of 13 μm or less.
First, transparent electrodes 12 and bus electrodes 13 are formed on a glass substrate 11 on the front face side by using the same materials as those of the aforementioned first example through the same method (see
In the present example, the dielectric layer is formed through two-layer processes. In other words, a non-lead-based glass paste (softening point: about 600° C.) is applied onto a glass substrate 11 by using a screen printing method, and after this has been dried into a dried film, the glass substrate 11 is loaded into a firing furnace, and the dried film of the glass material is fired at a temperature in a range from 600 to 610° C. so that a first dielectric film 17a is formed with a thickness of 5 to 10 μm (see
At this time, upon firing the first dielectric layer 17a, since the first dielectric layer 17a is so thin that the first dielectric layer has a superior defoaming property. Moreover, upon firing the second dielectric layer 17b, since the second dielectric layer 17b is not made in contact with the bus electrodes, no electrochemical reaction takes place between the metal and glass to cause no generation of bubbles in the second dielectric layer. Therefore, it becomes possible to further reduce bubbles in the dielectric layer in comparison with the single-layer structure.
The following results are obtained by these Table and Graph. In other words, a dielectric layer is formed by affixing a green sheet with which non-lead-based glass powder is mixed to a glass substrate on which display electrodes are formed with a thickness of 3 to 4 μm, and by firing the resulting substrate in a range from 600 to 610° C., a dielectric layer is formed so that the dielectric layer after the firing process is allowed to have a film thickness of 20 μm. The Table and Graph indicate the relationship between the film thickness (μm) of the dielectric layer at this time and the number of bubbles (number). In the Graph, the solid line shows the number of bubbles having a size in a range from 5 to 10 μm in diameter, and the dot line shows the number of bubbles having a size of 10 μm or more in diameter.
As indicated by the Table and Graph, the following results are obtained:
(i) When the film thickness of the dielectric layer is 10 μm, the number of bubbles in a range from φ5 to 10 μm is “0”, and the number of bubbles of φ10 μm or more is also “0”.
(ii) When the film thickness of the dielectric layer is 20 μm, the number of bubbles in a range from φ5 to 10 μm is “2”, and the number of bubbles of φ10 μm or more is “0”.
(iii) When the film thickness of the dielectric layer is 25 μm, the number of bubbles in a range from φ5 to 10 μm is “10”, and the number of bubbles of φ10 μm or more is “3”.
(iv) When the film thickness of the dielectric layer is 35 μm, the number of bubbles in a range from φ5 to 10 μm is “58”, and the number of bubbles of φ10 μn or more is “7”.
(v) When the film thickness of the dielectric layer is 45 μm, the number of bubbles in a range from φ5 to 10 μm is “51”, and the number of bubbles of φ10 μm or more is “16”.
In the case when the display electrodes are formed with a thickness of 3 to 4 μm while the dielectric layer is formed with a film thickness of about 20 μm by using a non-lead-based glass material, it has been confirmed that no bubbles exist in the dielectric layer. When a panel is formed by using this structure, it has been confirmed that no problems such as an insufficient insulation and a reduction in luminescence arise.
As described above, in accordance with the present invention, the thickness of metal electrodes is made thinner (6 μm or less) and the film thickness of the dielectric layer is also made thinner (25 μm or less) so that it becomes possible to eliminate bubbles in the dielectric layer upon completion of the firing process. With this arrangement, even when a non-lead-based glass material is used as the material for the dielectric layer, problems with the panel, such as an insufficient insulation and a reduction in luminescence, can be prevented.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-135357 | May 2006 | JP | national |
