JP3953873B2 - Method for forming electrode for plasma display panel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes a plasma display panel (hereinafter, referred to as PDP) relates to the technical field of, more particularly, to a method of forming electrodes for PDP.
[0002]
[Prior art]
In recent years, plasma display panels (hereinafter referred to as PDPs) are being used in various display devices due to their thin depth, light weight, clear display, and wide viewing angle. In general, a PDP has a structure in which a pair of electrodes regularly arranged on two opposing glass substrates are provided, and a gas mainly composed of neon, xenon, or the like is enclosed therebetween. Then, a voltage is applied between these electrodes, and discharge is generated in minute cells around the electrodes, thereby causing each cell to emit light for display. In particular, in order to display information, the regularly arranged cells are selectively discharged to emit light.
[0003]
Here, the configuration of the PDP will be described with reference to an example of the AC type PDP shown in FIG. FIG. 1 is a perspective view of a PDP configuration, but for the sake of clarity, the front plate (glass substrate 1) and the back plate (glass substrate 2) are shown separated from each other. As shown in the drawing, two glass substrates 1 and 2 are arranged in parallel and facing each other, and both are ribs (also referred to as barriers) 3 provided in parallel to each other on a glass substrate 2 serving as a back plate. By this, it is held at a constant interval. On the back side of the glass substrate 1 serving as a front plate, composite electrodes composed of a discharge sustaining electrode 4 made of a transparent electrode and a bus electrode 5 made of a metal electrode are formed in parallel to each other, covering the dielectric layer 6 is formed, and a protective layer 7 (MgO layer) is further formed thereon. Further, on the front side of the glass substrate 2 serving as the back plate, address electrodes 8 are formed in parallel with each other so as to be positioned between the ribs 3 so as to be orthogonal to the composite electrode. 9 is formed, and a phosphor 10 is provided so as to cover the wall surface of the rib 3 and the cell bottom surface. The rib 3 is for partitioning the discharge space, and each partitioned discharge space is called a cell or a unit light emitting region. The AC type PDP is a surface discharge type, and has a structure in which an AC voltage is applied between the composite electrodes on the front plate to discharge. In this case, since alternating current is applied, the direction of the electric field changes corresponding to the frequency. And the fluorescent substance 10 is light-emitted by the ultraviolet-ray which arises by this discharge, and an observer visually recognizes the light which permeate | transmits a front plate. The DC type PDP is different from the AC type in that the electrode has a structure not covered with a dielectric layer, but the discharge effect is the same.
[0004]
As a method for forming an electrode in the PDP as described above, there are the following two broad methods. That is, one is a method of forming a pattern by a screen printing method using a conductive thick film paste, and the other is a method for forming a pattern on a glass substrate by a vacuum deposition method, a sputtering method, a plating method or the like. A method of forming a conductive metal thin film and patterning it by photolithography is known. Among these, although the former screen printing method has an advantage that the electrodes can be formed relatively easily, there is a defect that the size and thickness of the electrodes vary depending on the manufacturing accuracy. It is difficult to form the electrodes as designed due to the distortion of the screen plate. Further, due to the size of the screen plate mesh and the processing accuracy of the emulsion, it is difficult to form fine electrodes having a line width of 100 μm or less without defects. On the other hand, the latter photolithography method is a method capable of forming electrodes with high accuracy, but has a drawback that the cost increases due to the main body of the film forming apparatus and its maintenance. In recent years, the resolution of display images has increased, and the electrode line width and pitch for display in the image display area tend to be reduced. Printing using a photosensitive conductive paste is performed by the screen printing method. After the process, a method for forming a precise predetermined dimension by a photolithography method is also performed.
[0005]
[Problems to be solved by the invention]
An example of the electrode for PDP is shown in FIG. 2 as a schematic plan view. The electrode for PDP is connected to the display unit electrode A in the image display region, the terminal unit electrode B connected to the connector outside the image display region and connected to the connector, and the connection unit connecting the display unit electrode and the terminal unit electrode. -It is comprised from the part electrode C. Generally, when a PDP electrode is formed by screen printing, a silver paste having a relatively low cost and good conductivity is used. It is efficient if all the electrodes A, B, and C can be printed with silver paste. However, when a silver paste is used for the terminal part electrode C, there is a problem in the chemical resistance of silver as an electrode, and there is a problem that a display defect is liable to occur due to silver migration. In order to solve this problem, the present applicant discloses in Japanese Patent Application Laid-Open No. 2001-357788 a PDP in which the electrode material of the terminal portion is gold that is excellent in conductivity and chemical resistance and has no problem of migration. is doing. Therefore, as shown in FIG. 2, first, the display portion electrode A and the lead portion electrode C are formed by the silver electrode 11 and connected to the silver electrode 11 extending into the terminal portion, and then the gold electrode 12 Thus, a PDP in which the terminal electrode B is formed has been used.
[0006]
As described above, when the display portion, the lead portion, and the terminal portion are formed of different electrode materials, it is necessary that the silver electrode portion and the gold electrode portion be in sufficient contact with each other. Has an overlap. However, new technical problems have arisen due to the overlapping of electrodes. FIG. 6 is an explanatory diagram of the electrode shape of the connection portion according to the prior art, FIG. 6A is a schematic cross-sectional view of the connection portion, and FIG. 6B is a schematic plan view of the connection portion. As shown in FIG. 6, the electrode 29 that is subsequently formed on the electrode 28 that is first formed on the glass substrate 27 is affected by the film thickness of the electrode 28 that is initially formed, and subsequently The thickness of the stepped portion of the portion 30 where the electrode 29 to be formed overlaps the electrode formed first becomes thin, or the shape of the edge 31 of the electrode to be formed subsequently deteriorates, reducing the reliability of the electrode There was a problem of letting.
[0007]
Accordingly, the present invention has been made to solve such problems. Its purpose is not or initially followed the formed electrode thin film thickness of the step portion and the electrode are overlapped to form, method of forming subsequently the electrode edge shape formed by favorable for PDP electrodes Is to provide.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problem, a method for forming an electrode for a plasma display panel according to the invention of claim 1 is formed on a substrate and is connected to the display unit electrode and the display unit electrode in the image display region, and displays an image. An electrode formed of a terminal part electrode for connecting to a connector outside the region, and a lead part electrode for connecting the display part electrode and the terminal part electrode, and the film thickness of the electrode formed first is subsequently formed In the method of forming an electrode for a plasma display panel that is thinned at the connection portion with a photosensitive conductive paste on the first electrode to be formed, pattern exposure is performed with a photomask having gradation, and development is performed. The electrode is formed by firing and reducing the film thickness at a predetermined portion of the connection portion.
[0009]
The method for forming an electrode for a plasma display panel according to claim 2 is a photomask having a gradation, wherein at least both ends of the electrode pattern width of the electrode connection portion are halftone. It is characterized by this.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0011]
FIG. 3 is an explanatory view of an embodiment of an electrode according to the method for forming an electrode for PDP of the present invention. An electrode 13 formed first as an electrode for PDP on a substrate (not shown) and an electrode formed subsequently. It is the plane schematic diagram which expanded 14 connection parts. As a substrate, a glass substrate is generally used. However, the electrode and the electrode forming method of the present invention are not necessarily limited to glass, and when applied to a portion that does not require the transparency of the substrate, a ceramic substrate. It is also possible to use it. FIG. 3 shows a case where the width of the electrode to be formed subsequently is slightly wider than the width of the electrode to be formed first, but each electrode width may be the same or either may be thicker. The thickness of the connection portion of the electrode 13 is reduced at the connection portion 15. The thickness of the connecting portion 15 is slightly different depending on the paste material of the electrode 13 and the electrode 14, paste printing conditions, etc., but is preferably about half of the thickness of the non-connecting portion, but is not limited thereto. The film thickness of the step portion of the electrode pattern edge is not reduced and the edge shape is not disturbed.
[0012]
FIG. 4 is an explanatory view of another embodiment of the electrode according to the method for forming a PDP electrode of the present invention. In the PDP electrode, the connection portion between the electrode 16 formed first and the electrode 17 formed subsequently is enlarged. It is a plane schematic diagram. In FIG. 4A, the thickness of the connection portion of the electrode 16 is the same as that of the non-connection portion in the central portion 18, but the thickness is reduced at both end portions 19 of the width of the electrode. It has a shape. In FIG. 4B, the thickness of the connecting portion of the electrode 20 is the same as that of the non-connecting portion up to about the middle of the center portion 22, but at both ends of the electrode width and the tip portion 23. The shape is reduced in film thickness. 4 (a) and 4 (b), the film thicknesses at least at both ends of the connection portion are slightly different depending on the paste material, paste printing conditions, etc. of each electrode, but are approximately half of the film thickness of the non-connection portion. However, the present invention is not limited to this, and the present invention can be applied to any film thickness where the thickness of the step portion of the electrode pattern edge does not become thin and the edge shape is not disturbed. Further, the width of both ends of the connecting portion may be a thickness that does not reduce the thickness of the stepped portion of the edge of the overlapped electrode pattern, and on one side, 1/3 to 1/3 of the width of the electrode formed first. About 1/5 is used. In FIG. 4, the electrode center portions 18 and 22 of the connection portion having the same film thickness as the non-connection portion absorb the alignment error in the length direction of the electrode when the electrodes to be formed subsequently are overlapped. The length of the center portion can be arbitrarily set within the range of the electrode length of the connection portion.
[0013]
In the present invention, the first electrode formed is preferably a silver electrode. When the silver electrode is formed of silver paste, it is preferable to use a photosensitive conductive silver paste. A silver paste can be applied. The photosensitive conductive silver paste can be formed on a glass substrate by methods such as screen printing, blade coating, roll coating, die coating, film transfer, and the like. The film thickness of the conductive conductive paste is preferably about 1 to 10 μm.
[0014]
When manufacturing the substrate constituting the PDP, it is preferable in the process that the electrode to be formed first is a display part electrode and a lead part electrode. An undercoat layer is provided on one surface of the glass substrate as required, and a photosensitive conductive paste is applied on the glass substrate by the above-described application method, dried, and then formed first with a gradation portion. Then, exposure is performed using a photomask having an electrode pattern to be developed, and development is performed to form a first electrode before firing composed of a display portion electrode and a lead portion electrode on a glass substrate.
[0015]
Since the photosensitive conductive paste is usually a negative type photocured by ultraviolet rays, the photomask of the electrode pattern to be formed first is a plane obtained by enlarging the electrode pattern portion of the photomask in FIG. As shown in the schematic diagram, only the portion where the film thickness of the electrode connecting portion is thinned is a gradation portion 26 through which ultraviolet rays are transmitted with a constant transmittance, and the normal electrode forming portion does not have a light shielding layer and the light transmitting portion 24 In other words, the non-electrode portion from which the conductive paste is removed by development is provided with a light shielding layer 25 that does not transmit exposure light. When the transmittance of exposure light in the light transmitting portion 24 of the photomask is 100%, the transmittance of the gradation portion 26 is about 20 to 80%. However, in order to widen the range of process conditions in the photolithography process. For the gradation portion, halftone having a transmittance of about 50% is preferable.
[0016]
Examples of the photomask having the above gradation include a silver salt emulsion mask and a chrome mask that can display gradation. For chrome masks with gradations, a photomask is formed by masking vapor deposition or masking sputtering, which partially controls the thickness of the light-shielding layer in time during film formation, or by partial half-etching after the light-shielding layer is formed To do. Since the optically black light shielding layer portion and the gradation portion are two stages, the photomask can be manufactured relatively easily.
[0017]
Next, alignment is performed on a connection portion of the first electrode before firing provided on the glass surface, and a terminal electrode as a subsequent electrode is formed. As described above, the terminal electrode is preferably a gold electrode because it is excellent in chemical resistance and does not have a display defect due to migration. When the gold electrode is formed from a gold paste, either a commonly used photosensitive gold paste or non-photosensitive gold paste can be used. In view of material cost and ease of forming process, it is preferable to form a pattern by screen printing using a non-photosensitive gold paste. The thickness of the gold paste after drying is preferably about 1 to 10 μm. After the gold paste pattern is formed, firing is performed at a paste firing temperature, and a display portion electrode and a lead portion electrode are made of silver and a terminal portion is made of gold on a glass substrate.
[0018]
Thereafter, according to a conventional method, for example, in the case of a PDP back plate, a dielectric layer is formed so as to cover the electrode, a rib is provided on the dielectric layer, a phosphor layer is formed between the ribs, A PDP back plate is formed.
[0019]
【Example】
In order to form the electrode of the back plate for PDP, a high-strain point glass (“PD200” manufactured by Asahi Glass Co., Ltd.) having a size of 1000 mm × 600 mm and a thickness of 2.8 mm was used as a glass substrate. Using a strike (DC206 manufactured by DuPont), solid printing was performed on a screen printing plate having an emulsion thickness of 10 μm (“ST400 mesh” manufactured by Tokyo Process Services Co., Ltd.) and dried at 80 ° C. for 30 minutes. . Next, in the pattern where the electrode line width of the display part and the lead part is 60 μm, both ends of the connection part with the terminal part are each 20 μm wide on one side, and the half level where the light transmittance is 50%. The film was exposed with a photomask having a tone and spray developed with a 0.4% sodium carbonate aqueous solution at a development pressure of 1.5 kgf / cm ² to form a silver electrode pattern. The thickness of the connecting portion was 8 μm at the center and the thickness of the non-connecting portion, and about 4 μm at both ends. Next, using a gold paste ("TR1451" manufactured by Tanaka Kikinzoku Co., Ltd.), a screen printing plate having an emulsion thickness of 10 [mu] m having a terminal electrode pattern ("ST400 mesh" manufactured by Sonocom Co., Ltd.). ) Was aligned with the silver electrode pattern formed first, screen printed, and dried at 120 ° C. for 30 minutes to form a gold electrode pattern having an electrode line width of 120 μm and a film thickness of 8 μm. In the silver electrode and the gold electrode connected at the terminal portion, the thickness of the stepped portion of the connecting portion was not thinned, and the edge shape was not disturbed. Next, it baked at 600 degreeC and the display part electrode, the lead part electrode, and the terminal part electrode were formed on the glass substrate.
[0020]
Next, a dielectric layer was formed to a thickness of 7 μm so as to cover the electrodes. Subsequently, the rib forming material is applied by a die coater, dried, and the rib forming material is cut by sand blasting through a mask made of a resist film provided on the rib forming material. Turned into Subsequently, the resist film was peeled off, and a substrate provided with an electrode layer, a dielectric layer, and ribs on a glass substrate was formed through a rib firing step.
[0021]
Next, as a post-process, a normal phosphor used for PDP is screen-printed and baked to form red, green, and blue phosphor layers between the ribs. Got.
[0022]
When this PDP back plate and a separately manufactured front plate were bonded and sealed to form a panel and image display was performed, a high-quality, high-definition image could be displayed.
[0023]
【The invention's effect】
The electrode for PDP by the method for forming the electrode for PDP of the present invention has excellent chemical resistance, no trouble due to silver migration, the film thickness of the stepped portion of the electrode connecting portion does not become thin, and the edge shape is Good electrode shape, suitable for high-quality, high-definition image display. In the method for forming a PDP electrode according to the present invention, high-definition electrodes having different film thicknesses are formed by a single exposure and development by using a photosensitive conductive paste and a photomask having gradation. There are advantages in terms of process and quality.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a configuration example of an AC type PDP. FIG. 2 is an explanatory view of a configuration example of an electrode pattern for a PDP. FIG. 3 shows an electrode shape according to the method for forming a PDP electrode of the present invention. Explanatory drawing [FIG. 4] Explanatory drawing which shows the other example of the electrode shape by the formation method of the PDP electrode of this invention [FIG. 5] The partial enlarged view of the photomask which has the gradation of this invention [FIG. 6] The electrode by a prior art Illustration of shape [Explanation of symbols]
1, 2 Glass substrate 3 Rib 4 Discharge sustaining electrode 5 Bus electrode 6, 9 Dielectric layer 7 Protective layer (MgO layer)
8 Address electrode 10 Phosphor layer 11 Silver electrode 12 Gold electrode 13, 16, 20, 28 First formed electrode 14, 17, 21, 29 Next formed electrode 15, 30 Port overlapped portion 18, 22 Connection portion Electrode center portion 19 both ends of electrode width of connection portion 23 both ends and tip portion of electrode width of connection portion 24 light transmission portion 25 light shielding layer 26 gradation portion 27 glass substrate 31 edge of electrode formed next Disorder

Claims (2)

A display unit electrode formed on the substrate and in the image display region; a terminal unit electrode connected to the display unit electrode and connected to the connector outside the image display region; and the display unit electrode and the terminal unit electrode In the method of forming an electrode for a plasma display panel, which is composed of lead electrodes connected to each other, and the film thickness of the first electrode formed is thin at the connection part with the electrode to be subsequently formed, the first electrode formed is exposed to light. The electrode is formed by pattern exposure using a conductive paste, pattern exposure with a photomask having gradation, development, and baking to reduce the film thickness at a predetermined portion of the connection portion. method of forming a pulp plasma display panel electrode. 2. The plasma display panel according to claim 1 , wherein the photomask having the gradation is a photomask in which at least both ends of the electrode pattern width of the electrode connection portion are half-tone. For forming an electrode.

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