JPH08335439A - Cathode of dc type plasma display panel and its formation - Google Patents

Abstract

PURPOSE: To provide a cathode in which conductivity is excellent, deterioration resulting from spatter at a discharge time is reduced, and the life thereof is long. CONSTITUTION: The cathode 4 of a DC type plasma display panel has a upper and lower double structure composed of a lower layer 4a made of low resistant conductive material and an upper layer 4b made of high spattering resistant conductive material. Excellent conductivity is secured by the lower layer 4a, and simultaneously electrode deterioration resulting from spattering at a discharge time is prevented by the upper layer 4a. Utilizing a photolithography method in the forming process of the lower layer 4a and the upper layer 4b, a fine and thick electrode required for securing a resistant value as a cathode is formed with high precision.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC type plasma display panel (hereinafter referred to as PDP) which is a self-luminous type flat display using gas discharge, and more specifically, a cathode of the DC type PDP and a method for forming the same. It is about.

[0002]

2. Description of the Related Art In recent years, research on colorization of flat displays has been actively conducted, but PDPs are regarded as the most promising as large-sized ones. DC type PD
Since P has a simpler structure than the AC type PDP and is relatively easy to manufacture, it has been noted as being extremely advantageous for increasing the size.

FIG. 1 shows an example of the configuration of a conventional DC PDP. As shown in the figure, this DC type P
In DP, a flat front plate 1 made of a glass plate or the like
The rear plate 2 and the rear plate 2 are arranged in parallel and opposite to each other, and both of them are held at a constant interval by the cell barrier 3 provided therebetween. Further, a cathode 4 is formed on the back side of the front plate 1, and an anode 5 is formed on the front side of the back plate 2 so as to be orthogonal to the cathode 4. Further, the front plate 1 and the back plate 2 are connected to each other. A phosphor 7 is provided on the wall surface of the cell barrier 3 in each cell 6 as a display element including the cell barrier 3. In this DC type PDP, the cathode 4
A predetermined voltage is applied from a DC power supply between the anode 5 and the anode 5 to form an electric field, so that discharge is performed inside each cell 6. Then, the phosphor 7 of the rear plate 2 is caused to emit light by the ultraviolet rays generated by this discharge, and the observer visually recognizes this light transmitted through the front plate 1.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the C-type PDP, a thick film electrode of Ni, Al or the like is generally used as its cathode. That is, since the electrode resistance required for the cathode is 100 μm width and 300Ω per 1000 mm length, the Ni electrode has a resistance of 20 to 30 μm.
An Al electrode having a high resistivity requires a thickness of 50 to 100 μm. However, when the Al electrode is used, there is a problem that it is difficult to form a thin electrode thick by printing or the like, and it is also difficult to etch and embed glass or the like. When using a Ni electrode, N in the Ni paste is used.
If the i particles are made finer, the electrical resistance increases, so there is a problem that it is difficult to make the wires thinner (for example, 50 μm width).

Further, in the DC type PDP, since the electrodes are exposed, there is a problem that positive ions collide with the cathode during the discharge and are sputtered. Particularly, Ni is inferior in the sputtering resistance, so that harmful Hg is added. There is a problem that it has a long life. Further, as the electrode material, Au and Ag which are mainly used for the electrode terminal portion can be used, but as the cathode material of the DC type PDP, they are not used because they have poor sputtering resistance like Ni. Is.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a cathode of a DC type PDP which is excellent in conductivity and has reduced deterioration due to sputtering during discharge. And also to provide a method for forming the cathode.

[0007]

In order to achieve the above object, the cathode of a DC type PDP according to the present invention comprises a lower layer made of a low resistance conductive material and an upper layer made of a conductive material having high sputtering resistance. It is characterized in that it is composed of an upper and lower two-layer structure.

In the method of forming a cathode having the above-mentioned structure, when forming a cathode having a two-layer structure on a substrate, a lower layer made of a low resistance conductive material is formed on the substrate, and then the lower layer is formed on the lower layer. The feature is that an upper layer made of a conductive material having high sputtering resistance is formed.

[0009]

In the cathode having the above-mentioned structure, the lower layer ensures good conductivity, and the upper layer serves to prevent electrode deterioration due to sputtering during discharge.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

2 and 3 show a DC type PDP according to the present invention.
3 is a cross-sectional view showing an example of the cathode of FIG. As shown in these figures, a cathode 4 having a two-layer structure is formed on a substrate such as glass as the front plate 1. In the embodiment shown in FIG. 2, the lower layer 4a and the upper layer 4b are simply laminated. In the configuration,
In the embodiment shown in FIG. 3, the upper layer 4b covers the lower layer 4a. The lower layer 4a is made of a low resistance conductive material, and the upper layer 4b is made of a conductive material having high sputtering resistance. As the low resistance conductive material, Ag, A
u, Ni, etc. can be used, and Al, Cr, Ta, W, etc. can be used as the conductive material having high sputtering resistance.

The above-mentioned two-layer cathode 4 can be obtained by forming the lower layer 4a on the substrate to be the front plate 1 and then forming the upper layer 4b so as to overlap the lower layer 4a. The lower layer 4a and the upper layer 4b. Each can be formed in various ways.
A specific example of the forming method will be described below.

(Specific Example 1) Here, a procedure for forming a lower layer of a cathode on a substrate to be a front plate will be described with reference to FIG.

The substrate for forming the cathode may be any one which is chemically stable on a flat surface or a curved surface, and a glass substrate, a resin substrate or the like is conceivable. In this embodiment, a glass substrate is used and before use It was cleaned and annealed. In addition, for the purpose of improving printing quality, a glass paste is applied as a base layer on a glass substrate by a screen printing method,
The front plate 1 was dried and then baked.

First, the front plate 1 pretreated as described above.
The conductive paste is thick-film printed on the top by a screen printing method and dried, and then the paste is fired to form the conductive paste shown in FIG.
The conductive film 11 is formed as shown in FIG. This conductive film 1
1 is a lower layer 4a of the cathode 4 which is patterned by an etching process in a later step. As the material of the conductive paste, low resistance conductive materials such as Au, Ag and Ni are used, and Au and Ag are preferably used among them.

Taking Au as an example, after the Au printing paste for etching is thick-film printed by the screen printing method, 17
The conductive film 11 having a thickness of about 2 μm could be formed by drying at 0 ° C. for 30 minutes and further baking at 580 ° C. for 8 minutes. In some cases, the steps of thick film printing and drying of the conductive paste may be repeated several times to increase the film thickness of the conductive film 11. In this case, the film thickness increases in proportion to the number of prints. 1 if the conductive paste is Ag
After screen-printing twice, drying is performed at 170 ° C for 30 minutes and baking is performed at 580 ° C for 8 minutes.
The conductive film 11 having a thickness of μm could be formed.

Next, as shown in FIG. 4B, a liquid photosensitive resin 12 is applied onto the conductive film 11 and dried. As a coating method, spin coating, roll coating,
Any method may be used as long as it is a method for coating a liquid material such as blade coating, reverse coating, spraying or dipping. Further, the photosensitive resin 12 does not have to be liquid, and a film resist can be used. When a film resist is used, it may be directly attached on the conductive film 11 using a laminator.

Then, as shown in FIG.
The photosensitive resin 12 is exposed through the light-shielding mask 13 in which the pattern of FIG. When the photosensitive resin 12 was a film-shaped resist, the pattern resolution was better when heat treatment was performed at 70 to 90 ° C. for about 5 to 15 minutes to accelerate curing of the exposed portion after exposure.

Then, as shown in FIG. 4D, pattern development of the photosensitive resin 12 is performed. Specifically, when the photosensitive resin 12 is a positive type, the exposed portion is chemically dissolved, and when the negative type is used, an unexposed portion is chemically dissolved with a dedicated developing solution. The photosensitive resin 12 is pattern-developed. Then, after finishing the developing process, the photosensitive resin 12 is cured by heat treatment. As a result of this curing treatment, the adhesiveness between the conductive film 11 and the photosensitive resin 12 is increased, and it is possible to prevent the etching failure that occurs during the etching treatment in the subsequent process. This heat treatment is not always necessary depending on the photosensitive resin.

Subsequently, the patterned photosensitive resin 1
The conductive film 11 is chemically etched using 2 as a mask to form a lower layer 4a of the cathode 4 as shown in FIG. After finishing the etching process, cleaning and drying were performed.

When a paste material containing Au as a main component is used for the conductive film 11, iodine, potassium iodide and water are mixed at a ratio of 1: 2: 5 (% by weight), respectively. Was good. Conductive film 11
When the thickness is 2 μm, the etching processing time is 90 to 1
A predetermined cathode pattern could be created in 50 seconds. Further, it was most preferable to use a mixed solution prepared by adding at least one organic solvent selected from alcohol, glycol, glycerin, ether, ketone and ester to the mixed solution. The addition of this organic solvent is characterized by suppressing the precipitation of iodine. That is, iodine is likely to precipitate in the iodine / potassium iodide aqueous solution, and when iodine is deposited on the conductive film 11, etching failure occurs at that portion, but the solubility of iodine in the organic solvent is higher than that in water. Since it was large, the precipitation of iodine could be significantly suppressed even if the addition amount was 10% or less by volume.

When a paste material containing Ag as a main component is used as the conductive film 11, it can be etched by using either an aqueous solution of nitric acid or ferric nitrate having a concentration of 25% (weight%) or more. However, especially when the first stage etching treatment with nitric acid was performed for 1 minute or less and then the second stage etching was performed with the ferric nitrate aqueous solution, the electrode processing accuracy was the best. The reason is Ag by nitric acid
When the paste is etched, hydrogen gas is generated, and the etching does not proceed at the portion where the generated gas adheres to the conductive film 11, which easily causes etching defects.
This is because the ferric nitrate aqueous solution does not generate gas, but the surface stains remaining on the conductive film 11 act as an etching mask and easily cause etching defects. Therefore, the finest processing was possible when the surface stains on the conductive film 11 were first cleaned with nitric acid as the first step and then etched with the ferric nitrate aqueous solution as the second step.

By the way, when the conductive film 11 is chemically etched as described above, the residue may not be completely removed depending on the material of the conductive paste, and sufficient line insulation may not be achieved. In such a case, after the etching step and before the photosensitive resin 12 is peeled off, the residue can be removed by performing sandblasting using this as a mask. For example, when a paste material containing Ag as a main component is used as the conductive film 11, the line resistance after patterning by chemical etching was about several MΩ, but brown fused alumina # 1000, injection pressure 2.5 kg / cm ² , distance between nozzle and substrate 150 mm, scan speed 4800
When sandblasting was performed under the condition of mm / sec, the residue was removed, and sufficient line insulation could be secured.

After the conductive film 11 is subjected to etching treatment or after further sandblasting treatment, the photosensitive resin 12 is peeled off, and the substrate is washed and dried as shown in FIG. 4 (f). The lower layer 4a of the cathode 4 processed into a predetermined pattern was formed.

(Specific Example 2) In the formation example 1, instead of chemically etching the conductive film 11, sandblasting is performed. That is, the pattern-developed photosensitive resin 12 was cured by heat treatment, sandblasting was performed using the cured photosensitive resin 12 as a mask, and patterning was performed by removing unnecessary portions of the conductive film 11. When the conductive film 11 is Ag (about 5 μm thick), brown fused alumina # 1000 is used as the abrasive, the ejection pressure is 2.5 kg / cm ² , the distance between the nozzle and the substrate is 150 mm,
The sandblasting treatment was performed under the condition of the scanning speed of 4800 mm / sec. Then, the photosensitive resin 12 is peeled off,
The substrate was washed and dried to form the lower layer 4a of the cathode 4 processed into a predetermined pattern.

(Specific Example 3) Here, the procedure for forming the upper layer so as to overlap the lower layer of the already formed cathode will be described with reference to FIG.

First, as shown in FIG. 5A, a layer of photosensitive resin 21 is formed on the front plate 1 on which the lower layer 4a of the cathode 4 is formed. When the liquid photosensitive resin 21 is used, it is applied and then dried. The coating method may be any method such as spin coating, roll coating, blade coating, reverse coating, spraying or dipping as long as it is a method for coating a liquid material. Further, the photosensitive resin 21 does not need to be liquid,
A film resist can also be used.

After that, as shown in FIG.
The photosensitive resin 21 is exposed through the light-shielding mask 22 on which the pattern of FIG. When the photosensitive resin 21 was a film-like resist, the pattern resolution was better when heat treatment was performed at 70 to 90 ° C. for about 5 to 15 minutes to accelerate curing of the exposed area after exposure.

Next, as shown in FIG. 5C, pattern development of the photosensitive resin 21 is performed to form a recess 21a for filling the conductive paste in a later step. Specifically, when the positive type is used as the photosensitive resin 21, the exposed part is chemically dissolved, and when the negative type is used, the unexposed part is chemically dissolved with a dedicated developer. The photosensitive resin 21 is pattern-developed. After finishing the development process,
The photosensitive resin 21 is cured by heat treatment. By thus sufficiently curing the photosensitive resin 21, a stable resin film can be obtained even in the subsequent process.

Subsequently, as shown in FIG. 5D, the conductive paste 23 is applied to the concave portion 21a formed in the photosensitive resin 21.
Embed and dry. As a material for the conductive paste 23, a conductive material having high sputtering resistance such as Al, Cr, Ta, and W is used. To fill the conductive paste 23, first, the paste is placed on one end of the substrate, and a spatula made of resin, metal or ceramic, a blade or a doctor is scanned to scrape the paste. The conductive paste 23 was dried at 120 to 200 ° C. for about 10 to 60 minutes.
The embedding of the conductive paste 23 does not have to be completed in one procedure, and may be repeated several times. this is,
This is because volume contraction occurs as the conductive paste 23 dries.

After the conductive paste 23 is dried, the photosensitive resin 21 is peeled from the substrate by using a dedicated peeling liquid. When the photosensitive resin 21 is a film resist, an alkaline stripping solution, that is, an aqueous solution of sodium hydroxide, potassium hydroxide, monoethanolamine, or ammonia water was used. In the peeling process of the photosensitive resin 21, there is a problem that the filled conductive paste 23 is also peeled together with the photosensitive resin 21 depending on the type of the conductive paste 23 used. Therefore, the peeling step of the photosensitive resin 21 is omitted for this kind of conductive paste. However, in this case, excess conductive paste left on the upper surface of the photosensitive resin 21 when the conductive paste 23 is filled is wiped off with a cloth soaked with an organic solvent such as acetone, or It was necessary to remove the upper surface of the resin 21 by polishing. Such cleaning of the upper surface of the photosensitive resin 21 may be effective not only when the peeling step of the photosensitive resin 21 is omitted, but also when the photosensitive resin 21 is peeled as described above. That is, this is a case where the surplus conductive paste 23 remains near the boundary surface of the recess 21 a and the surplus conductive paste 23 hinders the peeling of the photosensitive resin 21. Therefore, if the excess conductive paste 23 is removed and the boundary surface of the recess 21a is cleaned, the peeling process of the photosensitive resin 21 can be performed without delay.

After filling the conductive paste 23 as described above, the photosensitive resin 21 is peeled off or the photosensitive resin 2 is removed.
1 is placed in a firing furnace to fire the conductive paste 23 to form a cathode 4 having a structure in which an upper layer 4b is simply laminated on a lower layer 4a as shown in FIG. 5 (e). Formed. The firing temperature was 580 ° C., and the treatment time was about 10 minutes. Even when the peeling step of the photosensitive resin 21 was omitted as described above, the photosensitive resin 21 could be burned off in the firing step of the conductive paste 23.

When the photosensitive resin 21 is exposed in the above process, a light-shielding mask having a pattern wider than the lower layer 4a is used to form the recess 21a having a width wider than the lower layer 4a. Therefore, by filling the recess 21a with the conductive paste 23 and drying it, the cathode 4 having a structure in which the upper layer 4b covers the lower layer 4a can be formed as shown in FIG.

(Specific Example 4) Here, another procedure for forming the upper layer so as to overlap the lower layer of the already formed cathode will be described with reference to FIG.

First, a conductive paste is thick-film printed on the front plate 1 having the lower layer 4a of the cathode 4 formed thereon by a screen printing method and dried, and then the paste is fired to form the paste shown in FIG.
A conductive film 31 is formed as shown in FIG. This conductive film 31 is patterned by a sandblasting process in a later step to become the upper layer 4b of the cathode 4. As a material for the conductive paste, a conductive material having high sputtering resistance such as Al, Cr, Ta, and W is used.

Next, as shown in FIG. 6B, a liquid photosensitive resin 32 is applied on the conductive film 31 and dried. As a coating method, spin coating, roll coating,
Any method may be used as long as it is a method for coating a liquid material such as blade coating, reverse coating, spraying or dipping. Further, the photosensitive resin 32 does not need to be in a liquid state, and a film resist can be used. When a film resist is used, it may be directly attached on the conductive film 31 using a laminator.

Then, as shown in FIG. 6C, the cathode 4
The photosensitive resin 32 is exposed through the light-shielding mask 33 on which the pattern of FIG. When the photosensitive resin 32 was a film-like resist, the pattern resolution was better when heat treatment was performed at 70 to 90 ° C. for about 5 to 15 minutes to accelerate curing of the exposed portion after exposure.

Next, as shown in FIG. 6D, pattern development of the photosensitive resin 32 is performed. Specifically, when the positive type is used as the photosensitive resin 32, the exposed part is chemically dissolved, and when the negative type is used, the unexposed part is chemically dissolved with a dedicated developer. The photosensitive resin 32 is pattern-developed. Then, after finishing the developing process, the photosensitive resin 32 is cured by heat treatment. As a result of this hardening treatment, the adhesiveness between the conductive film 31 and the photosensitive resin 32 is increased, and it is possible to prevent grinding defects that occur during the sandblasting process in the subsequent step. This heat treatment is not always necessary depending on the photosensitive resin.

Subsequently, the patterned photosensitive resin 3
Sandblasting is performed using 2 as a mask to remove unnecessary portions of the conductive film 32, and the upper layer 4b of the cathode 4 is formed as shown in FIG. 6 (e). The conductive film 32 is made of Al (about 5 μm
m thick), brown fused alumina # 100 as abrasive
No. 0, jet pressure 2.5 kg / cm ² , distance between nozzle and substrate 150 mm, scan speed 4800 mm / sec
Sand blasting treatment was performed under the conditions of. After that, the photosensitive resin 32 is peeled off, and the substrate is washed and dried to obtain the structure shown in FIG.
As shown in (f), the cathode 4 having a structure in which the upper layer 4b was simply laminated on the lower layer 4a was formed.

When the photosensitive resin 32 is exposed in the above step, by using a light-shielding mask having a pattern wider than the lower layer 4a, the pattern of the photosensitive resin 32 is wider than the lower layer 4a. It is formed. Therefore, by performing sandblasting using the patterned photosensitive resin 32 as a mask, the cathode 4 having a structure in which the upper layer 4b covers the lower layer 4a as shown in FIG. 3 can be formed.

[0041]

As described above, the DC according to the present invention
The cathode of the type PDP has a two-layer structure of a lower layer made of a low resistance conductive material and an upper layer made of a conductive material having high sputtering resistance, so that good conductivity can be secured by the lower layer and the upper layer can be Since the electrode deterioration due to sputtering at the time of discharge is prevented, it is possible to provide a long-life cathode having no problem in conductivity and reduced electrode deterioration.

Further, in the method of forming the cathode according to the present invention, since the photolithography method is used in the steps of forming the lower layer and the upper layer of the cathode, the thin and thick electrode necessary to secure the resistance value as the cathode is used. Can be formed with high accuracy.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a conventional DC type plasma display panel.

FIG. 2 is a sectional view showing an embodiment of a cathode of a DC type plasma display panel according to the present invention.

FIG. 3 is a sectional view showing another example of the same.

FIG. 4 is a process drawing for explaining a method of forming a lower layer of a cathode.

FIG. 5 is a process drawing for explaining one method of forming the upper layer of the cathode.

FIG. 6 is a process drawing for explaining another method of forming the upper layer of the cathode.

[Explanation of symbols]

1 Front Plate 4 Cathode 4a Lower Layer 4b Upper Layer 11 Conductive Film (Low Resistance Conductive Material) 12 Photosensitive Resin 21 Photosensitive Resin 21a Recess 23 Conductive Paste (Conductive Material with High Sputtering Resistance) 31 Conductive Film (Resistance) Conductive material with high sputtering properties) 32 Photosensitive resin

Claims (11)

[Claims] 1. A cathode of a DC type plasma display panel, which has a two-layer structure of a lower layer made of a low resistance conductive material and an upper layer made of a conductive material having high sputtering resistance. 2. The cathode of a DC type plasma display panel according to claim 1, wherein the lower layer is one of Ag, Au and Ni. 3. The cathode of a DC type plasma display panel according to claim 1, wherein the upper layer is any of Al, Cr, Ta and W. 4. When forming a cathode having an upper and lower two-layer structure on a substrate, a lower layer made of a low resistance conductive material is formed on the substrate, and then a conductive material having high sputtering resistance is formed on the lower layer. Forming a cathode upper layer of a DC type plasma display panel. 5. The method according to claim 4, wherein the lower layer is formed by the following steps. (1) A step of forming a conductive film on the substrate by applying a paste of a low-resistance conductive material as a thick film on the substrate and then drying and firing the conductive paste, (2) the conductivity A step of forming a layer of a photosensitive resin on the film, (3) a step of exposing the photosensitive resin through a light-shielding mask on which a cathode pattern is arranged, and then performing pattern development of the photosensitive resin,
(4) A step of patterning the conductive film by chemical etching using the patterned photosensitive resin as a mask, (5) A step of peeling the patterned photosensitive resin. 6. The method according to claim 5, further comprising a step of performing sandblasting to remove etching residues after the step (4). 7. The method according to claim 4, wherein the lower layer is formed by the following steps. (1) A step of forming a conductive film on the substrate by applying a paste of a low-resistance conductive material as a thick film on the substrate and then drying and firing the conductive paste, (2) the conductivity A step of forming a layer of a photosensitive resin on the film, (3) a step of exposing the photosensitive resin through a light-shielding mask on which a cathode pattern is arranged, and then performing pattern development of the photosensitive resin,
(4) A step of patterning the conductive film by sandblasting using the patterned photosensitive resin as a mask, and (5) a step of peeling the patterned photosensitive resin. 8. The method according to claim 4, wherein the upper layer is formed by the following steps. (1) a step of forming a photosensitive resin layer on a substrate on which a lower layer of the cathode is formed, (2) exposing the photosensitive resin through a light-shielding mask having a cathode pattern, and then performing pattern development. Forming a recess on the lower layer, (3)
A step of embedding a paste of a conductive material having a high sputtering resistance in the recesses of the photosensitive resin and then drying the conductive paste; (4) a step of peeling the photosensitive resin; (5) the conductivity Step of firing the paste. 9. The method according to claim 8, wherein the light-shielding mask used in the step (2) is a light-shielding mask having a pattern wider than the lower layer. 10. The method according to claim 4, wherein the upper layer is formed by the following steps. (1) After applying a paste of a conductive material having high sputtering resistance as a thick film on the substrate on which the lower layer of the cathode is formed,
Drying and baking the conductive paste to form a conductive film on the substrate, (2) forming a photosensitive resin layer on the conductive film, and (3) arranging a cathode pattern. Exposing the photosensitive resin through the light-shielding mask, and then developing the pattern of the photosensitive resin; (4) patterning the conductive film by sandblasting using the patterned photosensitive resin as a mask. (5) A step of peeling the patterned photosensitive resin. 11. The method according to claim 10, wherein the light-shielding mask used in the step (3) is a light-shielding mask having a pattern wider than the lower layer.