JP4354730B2 - Method for forming front electrode for plasma display panel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming bus electrodes on a front plate of a plasma display panel (PDP).
[0002]
[Prior art]
PDP is a next-generation display because it is self-luminous, can reduce power consumption, is thin and easy to enlarge, and has a simpler structure than a liquid crystal display (LCD). There is great demand for devices. However, under the present circumstances, the manufacturing cost of PDP is extremely high, which is a major obstacle to popularization as a display device for home use.
[0003]
For example, as shown in FIG. 1, the PDP includes a front plate (front substrate) 10 including a bus electrode (front electrode) 11, a transparent electrode 12, a transparent dielectric layer 13, and a protective layer 14, an address electrode (back electrode) 21, A back plate (rear substrate) 20 having a dielectric layer 22, a protective layer 23, a rib 24 and a fluorescent layer 25 (R, G, B) and electrodes 11, 12, and 21 provided on both substrates are fluorescent layers. Is arranged so as to face each other through 25 (See Patent Document 1) . Among these, the bus electrode 11 of the front plate 10 is required to have high blackness in addition to excellent conductivity. This is because, for example, if the bus electrode 11 has a metallic luster, it causes a reduction in the contrast of the PDP due to reflection toward the front plate 10 side.
[0004]
In order to reduce the price of the PDP, it is an urgent task to reduce the manufacturing cost, and among the plurality of manufacturing processes, the electrode forming process is the cause of the high cost along with the formation of the partition walls (ribs).
Conventionally, the bus electrode pattern has a predetermined thickness by applying a black photosensitive paste to the entire surface of the front plate, and further applying a photosensitive silver paste (for example, “DuPont” product name “Fordel®”). It is formed by photolithography, which is adjusted to be (5 to 10 μm), dried, and then exposed and developed according to the shape of the pattern.
[0005]
The reason why the two types of pastes are required in this way is that the black photosensitive paste can make the bus electrode black enough, but the conductivity is insufficient, while the photosensitive silver paste This is because although it is possible to improve the conductivity, it is difficult to achieve both conductivity and blackness, such as insufficient blackness.
The bus electrode pattern usually has a line width of several tens of μm and a pitch of about several hundreds of μm. Therefore, most of the black paste and silver paste applied to the entire surface of the front plate are exposed and exposed. The pattern forming material is wasted because it is washed and removed after the development process. In addition, since it is necessary to repeat the processes such as coating, exposure, and development in each of the black photosensitive paste and the photosensitive silver paste, a large cost is required for manufacturing the bus electrode. Furthermore, although both the photosensitive black paste and the silver paste are expensive and a process for recovering only silver from the discarded silver paste has been proposed, there is a problem that the cost for recovery is extremely high. .
[0006]
In addition, the manufacturing equipment used for pattern formation by the photolithography method is required to have extremely high accuracy and cleanliness, which is expensive and difficult to cope with an increase in the size of the PDP (upsizing screen). There is a problem. In addition, since a large amount of harmful waste liquid is generated during the development process, there is a problem in that the waste liquid is expensive to process.
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-245931
[0007]
[Problems to be solved by the invention]
As described above, the conventional bus electrode manufacturing process is extremely disadvantageous in terms of cost in terms of electrode forming material, forming method, forming equipment, etc., and these are one of the major factors that raise the manufacturing cost of the entire PDP. Yes.
Therefore, the present invention forms a bus electrode pattern easily, inexpensively, and with high accuracy while maintaining high blackness (contrast of the display surface) and conductivity (electrode conductivity). It is an object to provide a method that can do this.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have studied from various aspects, and as a result, have reached the method for forming the bus electrode of the front panel for the plasma display panel of the present invention.
That is, the present invention relates to the following bus electrode forming method for a plasma display panel front panel.
[0009]
1) A method for forming a front electrode for a plasma display panel, in which an electrode pattern is printed by an intaglio offset printing method,
(1) a step of transferring the conductive metal ink supplied to the pattern forming intaglio to a printing blanket;
(2) A step of transferring and laminating black ink containing a black metal oxide or / and a black composite alloy by intaglio offset printing on the conductive metal ink layer transferred onto the blanket,
(3) transferring the laminated ink from the blanket to a transparent substrate; and
(4) a step of firing the printed ink pattern as described above;
And the transition speed V in the step (1) ₁ (Mm / sec) and transition speed V in the step (2) ₂ (Mm / sec) as V ₁ ≦ V ₂ A method for forming a front electrode for a plasma display panel.
[0010]
2) Set the print pattern width in step (1) to W ₁ (Μm), and the laminated print pattern width in step (2) is W ₂ (Μm), 0.5 × W ₂ ≦ W ₁ ≦ W ₂ The method for forming a front electrode for a plasma display panel according to the above item 1), wherein the pattern is formed under the following conditions.
3) The conductive metal powder is one or more metal powders selected from the group consisting of silver, copper, gold, platinum, aluminum, nickel, iron and palladium, and the black metal oxide is ruthenium oxide. (RuO ₂ ), Manganese oxide (MnO), molybdenum oxide (MoO) ₂ ), Chromium oxide (Cr ₂ O _Three ), Copper oxide (CuO), titanium oxide (TiO), palladium oxide (PdO) and iron oxide (Fe ₂ O _Three 1) The method for forming a front electrode for a plasma display panel according to 1) or 2) above, which is one or more metal oxides selected from the group consisting of:
[0011]
4) The surface rubber layer of the blanket is made of silicone rubber, the JIS-A hardness is 20 to 80 °, and the surface roughness expressed by ten-point average roughness (Rz) is 0.01 to 3 μm. The method for forming a front electrode for a plasma display panel according to any one of items 1) to 3) above.
In the present invention, as described above, the conductive metal ink is transferred onto the printing blanket by the step (1) (first color), and then the black containing the black metal oxide by the step (2) thereon. The main feature is that the ink is layered (second color), and then the ink pattern that has been layered in the above step (3) is transferred to a transparent substrate such as a glass substrate. And the transition rate in steps (1) and (2) is V ₁ ≦ V ₂ With this relationship, the printability of the electrode pattern can be made extremely good.
[0012]
That is, according to the normal intaglio offset printing method, the black ink is transferred to the printing blanket as the first color and transferred to the transparent plate, and the conductive metal ink is transferred to the blanket as the second color and the 1 on the glass plate. However, in the present invention, the number of times of transfer onto the transparent plate is reduced compared to this forming method, so that a compact process design can be achieved and the productivity can be increased. This is extremely advantageous in terms of cost.
[0013]
In the present invention, the transition rate is V ₁ ≦ V ₂ This is because the first color is steadily transferred on the blanket first, and then the second color is easily transferred and laminated. The transition speed of the first color is usually about 5 to 200 mm / second, preferably about 10 to 100 mm / second. Exceeding this range makes it difficult for the conductive metal ink to transfer to the surface rubber layer of the blanket, and if it does not reach this range, the remaining part (dirt) of the non-painted area of the ink is also transferred, resulting in poor printing. Cause. Next, the transition speed of the second color is equal to or higher than the transition speed of the first color selected from the above range. If this transition rate is reversed (V ₁ > V ₂ ) When attempting to transfer the second color, the first color already transferred onto the blanket causes a reverse transition toward the intaglio, resulting in partial breaks and pinholes in the pattern formed on the blanket. .
[0014]
Further, since the first color ink is located inside the cell structure when the pattern is formed on the transparent substrate, an ink rich in conductive metal is printed in order to improve the conductivity as much as possible. In this case, the contrast is lowered because the metallic luster appears because the conductive metal is the main component. Therefore, the second color is printed as black as possible, and is laminated and printed on the first color. At this time, considering the accuracy of the printing press and the variation in the print pattern width, it is advantageous to make the line width of the first color ink narrower than the line width of the second color. For this purpose, the print pattern width in the step (1) is set to W. ₁ (Μm), and the laminated print pattern width in step (2) is W ₂ (Μm), 0.5 × W ₂ ≦ W ₁ ≦ W ₂ It is desirable to form a pattern according to the above conditions. Among these, W ₂ Is W as much as possible ₁ It is desirable that the line width be close to and the line width is too large. When the line width is too small, the electric resistance becomes high, resulting in a decrease in conductivity, and the power consumption of the PDP becomes large. Usually W ₂ Is preferably selected from the range of 40 to 150 μm.
[0015]
According to the present invention, since an electrode pattern is formed by a printing method, unlike the case of forming a pattern by a photolithography method, it is extremely simple, low-cost, and with high accuracy along with recent improvements in printing technology. Thus, pattern formation can be achieved.
In the present invention, an electrode pattern is formed by an intaglio offset printing method. In order to form a fine pattern of the bus electrode with high accuracy, it is necessary that the printing accuracy of the ink pattern is extremely high. Currently, various printing methods are known. However, according to the above printing method, the error is within ± 20 μm, preferably within ± 10 μm within an area of a 40-inch substrate (900 mm × 600 mm). It can be formed with high printing accuracy.
[0016]
In the intaglio offset printing method, the printing blanket used has a hardness (JIS A hardness) of 20 to 80 °, a surface roughness (10-point average roughness Rz) of 0.01 to 3 μm, and a surface rubber layer made of silicone Those provided with are preferably used. The thickness is usually selected from the range of 1 to 1500 μm.
In the method for forming a bus electrode of the front plate for PDP according to the present invention, the temperature for firing the printed pattern is preferably in the range of 200 to 700 ° C. By baking the said pattern at said temperature, the coupling | bonding between the laminated | stacked ink layers and the coupling | bonding to a transparent substrate can be strengthened, and electroconductive metal powder can be melt-bonded simultaneously. By electrically bonding the conductive metal powders, the conductivity of the bus electrode can be further improved.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a front panel for a plasma display panel according to the present invention, members used for forming the bus electrode, formation conditions, and the like will be described in detail.
[Ink for pattern printing]
In the present invention, the conductive metal ink used in the step (1) is prepared by mixing and dispersing conductive metal powder, resin and solvent.
[0018]
As the conductive metal powder, various conductive metal powders conventionally used for forming bus electrodes can be used, but in order to make the conductivity of the bus electrode more excellent, as described above. It is preferable to use a powder of at least one metal selected from the group consisting of silver, copper, gold, platinum, aluminum, nickel, iron and palladium.
The particle size of the conductive metal powder is preferably 0.05 to 20 μm. If the particle diameter exceeds 20 μm, the degree of flattening of the surface when the conductive powder deposit is pressure-bonded becomes small, and the flatness of the bus electrode may be lowered. Conversely, if the particle size is less than 0.05 μm, the conductivity of the finally obtained bus electrode may be reduced. Generally, by reducing the particle size of the conductive metal powder, it is possible to lower the melting temperature between metals, simplify the process, and further improve the conductivity significantly. it can.
[0019]
The thickness of the conductive metal powder is preferably adjusted so that the thickness of the metal film obtained by melt bonding after firing is 2 to 15 μm. When the thickness of the metal film after firing is less than 2 μm, disconnection is likely to occur, and the conductivity of the bus electrode may not be sufficient. On the other hand, the conductivity of the bus electrode is sufficient by setting the thickness of the fired metal film within the above range. Even if the thickness of the metal film after firing exceeds 15 μm, no particular effect is obtained from the viewpoint of the conductivity of the bus electrode. Rather, it may cause other problems such as a decrease in the flatness of the surface of the bus electrode.
[0020]
As the resin, various resins such as a thermosetting type, an ultraviolet curable type, and a thermoplastic type can be used. Examples of the thermosetting resin include polyester-melamine resin, melamine resin, epoxy-melamine resin, phenol resin, polyimide resin, and acrylic resin. Examples of the ultraviolet curable resin include acrylic resins. Examples of the thermoplastic resin include polyester resin, polyvinyl butyral resin, cellulose resin (such as ethyl cellulose), and acrylic resin.
[0021]
In the present invention, among these resins, in particular, it is completely CO2 by firing (for example, by firing at a high temperature of 400 ° C. or higher). ₂ And H ₂ It is preferable to use polyvinyl butyral resin that decomposes into O, cellulose resin (particularly ethyl cellulose), acrylic resin, or the like. These resins can be used alone or in a suitable mixture of two or more according to the printability.
The solvent is selected in consideration of the printability of the ink. When used for intaglio offset printing, the ink solvent directly contacts the surface rubber layer of the printing blanket, causing the surface rubber layer to swell and change its surface wetting characteristics. In general, if the solvent is small enough to swell the surface rubber layer, even if printing is repeated, the surface wettability of the printing blanket changes little and stable printing can be performed. Conversely, if the degree of swelling of the surface rubber layer is large, the surface wettability changes greatly by repeating printing, the line width of the pattern to be printed widens, and even fine stains on the surface of the printing plate The transfer stability and the transfer efficiency from the printing blanket to the substrate to be printed are reduced, resulting in a significant decrease in printing stability. Therefore, it is preferable that the degree of swelling is small, but considering the acceptability of the ink from the printing intaglio to the printing blanket, it is preferable that a certain degree of swelling occurs.
[0022]
In the present invention, the blending ratio in the conductive metal ink in the step (1) is determined in consideration of printability. For example, 100 parts by weight of resin, 400 to 2000 parts by weight of metal powder, and 100 to 500 parts by weight of solvent. The ratio of parts is preferred. The ink is produced by mixing and dispersing these blends using, for example, a three roll.
Next, the composition of the black ink in the step (2) contains a black metal oxide or / and a black composite alloy, and is set in consideration of the printability of the ink and the blackness after firing the ink. Is done. If the printability is low, it becomes impossible to form a fine and high-precision pattern suitable for the bus electrode. Further, when the blackness is low, the contrast of the PDP is lowered.
[0023]
The black metal oxide and the black composite alloy in the present invention may be any metal that is black at room temperature, does not change color even when fired at a temperature of 500 to 650 ° C. for 5 to 60 minutes, and does not decompose or sublime. . Examples of the black metal oxide include ruthenium oxide (RuO). ₂ ), Manganese oxide (MnO), molybdenum oxide (MoO) ₂ ), Chromium oxide (Cr ₂ O _Three ), Copper oxide (CuO), titanium oxide (TiO), palladium oxide (PdO) and iron oxide (Fe ₂ O _Three ) Or one or more metal oxides selected from the group consisting of: Examples of the black composite alloy include Cr—Co—Mn—Fe, Cr—Cu, Cr—Cu—Mn, Mn—Fe—Cu, Cr—Co—Fe, Co—Mn—Fe, and Co—Ni—. The 1 type (s) or 2 or more types selected from the group which consists of Cr-Fe and Cu-Fe-Cr can be mentioned.
[0024]
The black ink usually has a viscosity suitable for printing by dispersing the black metal oxide or / and the black composite alloy appropriately with a black pigment, dispersing the resin forming the ink (paste), and these. Prepared with the solvent to be adjusted. Examples of the black pigment include carbon black, titanium black, graphite, and other black pigments or dyes. Considering the printability of black ink, the particle diameter of the black metal oxide, composite alloy, and black pigment powder is preferably 0.05 to 20 μm. As the resin and the solvent for preparing the black ink, the same resin and solvent as in the conductive metal ink in the step (1) can be used at the same ratio.
[0025]
[Printing method of ink pattern]
In the present invention, as described above, by intaglio offset printing, the conductive metal ink is transferred onto the printing blanket by the step (1) (first color), and then the black metal oxide is oxidized by the step (2). And / or a black ink containing a black composite alloy is transferred and laminated (second color), and then the ink pattern laminated in the step (3) is transferred to a transparent substrate, and the step (1) and the step (2) The transition speed in the process is V ₁ ≦ V ₂ With this relationship, the electrode pattern is printed.
[0026]
In intaglio offset printing, printing accuracy can be further improved by providing a step of drying and then cooling the ink surface on the blanket for each transition between the steps (1) and (2). Here, the drying can be carried out, for example, by blowing hot air at 80 to 120 ° C. for about 5 to 30 seconds, and cooling can be carried out by blowing cold air at 10 to 15 ° C. for about 0.3 to 2 minutes.
When printing is repeated, it is preferable to evaporate and dry the solvent of the ink absorbed in the surface rubber layer by heating the surface rubber layer. The state of the surface rubber layer can be returned to the state before it is swollen with the solvent of the ink by transpiration and drying by heating.
[0027]
The transpiration of the solvent and the ease of drying vary depending on the heating temperature, the boiling point of the solvent of the ink, the thickness of the surface rubber layer, etc. However, it is usually effective if the heating temperature is 40 to 200 ° C. Transpiration and drying can be achieved. The heating / drying method is not particularly limited, and may be indirectly heated through a blanket cylinder, or may be directly heated by blowing hot air from the outside onto the surface rubber layer.
The surface temperature of the printing blanket is high after the heating / drying process. If printing is performed in this state, the surface rubber layer and the printing plate in contact with it will thermally expand. May decrease. Therefore, for example, cool air should be applied to the surface of the printing blanket so that the change in the surface temperature of the printing plate is within ± 1 ° C and the change in the surface temperature of the printing blanket (surface rubber layer) is within ± 5 ° C. It is preferable to perform a cooling process such as spraying, contacting the surface of the printing blanket with a member having a large heat capacity such as metal, or dissipating heat through the blanket cylinder.
[0028]
The present invention employs an intaglio offset printing method among conventionally known printing methods. Other printing methods, for example, screen printing methods, have a problem that when the line width of the pattern is less than 100 μm, it is impossible to faithfully reproduce the shape of the pattern, or disconnection occurs. There is also a problem that it is difficult to form. Further, in principle, the force applied to the central portion and the peripheral portion of the screen is different, and the amount of elongation is different, resulting in different pattern printing accuracy on the same back substrate. Therefore, the printing accuracy required for the bus electrode [error within ± 20 μm, preferably within ± 10 μm within the area of 40 inch substrate (900 mm × 600 mm)] cannot be sufficiently satisfied.
[0029]
Also, the direct printing method and the offset printing method produce a protruding portion of ink called a marginal zone around the pattern, so the resolution of the printing plate itself is low and it is extremely difficult to reproduce the pattern faithfully. is there. In addition, in the case of intaglio direct printing (gravure printing), a uniform printing pressure is applied to a glass substrate that is rigid and has uneven thickness due to the fact that the plate used for direct printing is a rigid member. There is a problem that transfer unevenness is likely to occur.
[0030]
In contrast to these printing methods, the intaglio offset printing method can freely control the film thickness of the pattern by changing the depth of the concave portion of the intaglio. In addition, by using a printing blanket with a surface rubber layer made of a material with low surface energy such as silicone rubber, the ink transferred from the printing plate (intaglio) to the printing blanket can be applied to rigid substrates. It is possible to transfer 100%.
In particular, in the present invention, since the intaglio offset printing method is adopted in the steps (1) and (2), the shape of the printed pattern can be made very good. Furthermore, since the cost required to form a pattern by the intaglio offset printing method is about 1/3 to 1/10 that of the photolithography method, the bus electrode of the front plate for PDP can be formed at a very low cost. can do.
[0031]
[Print blanket]
For the printing blanket used when the ink pattern is formed by the intaglio offset printing method, as described above, the hardness (JIS A hardness) is used as the printing blanket for the purpose of forming the ink pattern with high accuracy. A surface rubber layer having a surface roughness of 20 to 80 and a surface roughness (ten-point average roughness Rz) of 0.01 to 3 μm is provided, and the surface rubber layer is preferably made of silicone rubber.
[0032]
When the hardness of the surface rubber layer exceeds the above range, deformation of the surface rubber layer is difficult to occur during printing, and the acceptability of ink on the printing plate may be reduced. On the other hand, if the hardness of the surface rubber layer is below the above range, the degree of deformation of the surface rubber layer at the time of printing becomes large, which may cause a decrease in printing accuracy. The hardness of the surface rubber layer is particularly preferably 20 to 70 °, and more preferably 30 to 60 °, in the above range (JIS A hardness).
[0033]
The surface roughness of the surface rubber layer has a greater influence on the printed shape as the pattern to be printed is finer. When forming the bus electrode of the front plate for PDP, the line width required for the ink pattern is about several tens μm, more specifically about 20 μm. Therefore, the surface roughness of the surface rubber layer is the ink pattern. From the viewpoint of improving the printing shape of the ink, it is required that the 10-point average roughness (Rz) is 0.01 to 3 μm.
[0034]
If the 10-point average roughness (Rz) of the surface rubber layer exceeds the above range, the printed shape may be deteriorated, for example, the edge shape of the pattern may not be sharp. On the other hand, it is difficult to reduce the 10-point average roughness (Rz) of the surface rubber layer to be less than the above range, and the acceptability of the ink may be lowered if the surface roughness is extremely small. is there. The 10-point average roughness (Rz) of the surface rubber layer is more preferably 0.01 to 0.5 μm in the above range.
[0035]
The thickness of the surface rubber layer is set according to the degree of deformation during printing, and is usually set in the range of 1 to 1500 μm. When the thickness of the surface rubber layer is less than 1 μm, the surface rubber layer is hardly deformed during printing, and the ink acceptability of the printing plate may be lowered. On the other hand, if the thickness of the surface rubber layer exceeds 1500 μm, the degree of deformation of the surface rubber layer at the time of printing increases, which may cause a decrease in printing accuracy.
[0036]
As described above, silicone rubber is preferable as the material for forming the surface rubber layer, but any other material that does not easily swell with the solvent of the ink can be used. For example, acrylonitrile-butadiene rubber (NBR) can be used. , Acrylic rubber, fluororubber, chloroprene rubber (CR), polyvinyl chloride resin (PVC), and the like.
[Printing Intaglio]
In the present invention, the intaglio used in the intaglio offset printing method is not particularly limited, and conventionally known intaglio can be adopted. As the intaglio pattern, a pattern corresponding to a desired front electrode pattern for a plasma display panel is used.
[0037]
[Ink pattern firing conditions]
Conditions for firing the ink pattern are set appropriately according to the type of resin used in black ink (thermal decomposition temperature), type of conductive metal powder (melting point), etc., in accordance with conventional methods. However, from the viewpoint of improving the conductivity of the bus electrode, it is usually preferable to set the firing temperature in the range of 200 to 700 ° C.
When the firing temperature of the ink pattern is in the above range, the resin component in the ink pattern can be thermally decomposed almost completely, and fusion bonding of the conductive metal powder can be achieved. Therefore, the conductivity of the bus electrode can be made excellent while maintaining the blackness of the bus electrode surface on the entire surface of the front plate. The firing temperature of the ink pattern may be a temperature at which the resin of the ink is decomposed and the conductive metal powder is melted, but it is more preferably 400 to 600 ° C. in the above range.
[0038]
[Transparent substrate]
The transparent substrate used as the front plate for PDP is not particularly limited except that it has high transparency and heat resistance. For example, soda lime glass, low alkali glass, non-alkali glass, quartz glass, etc. A glass substrate is preferably used. The material of the transparent substrate is appropriately selected from the glass substrates and the like exemplified above according to various characteristics such as heat resistance, chemical resistance, and permeability.
[0039]
[Other members, etc.]
In the PDP front plate of the present invention, the black ink and conductive metal powder for forming the bus electrode and the transparent substrate serving as the base of the bus electrode are as described above, but other members (for example, transparent electrode) , Transparent dielectric layer, protective layer, etc.), its material, formation method and the like are not particularly limited in the present invention, and may be appropriately set and selected in accordance with a conventionally known PDP front plate.
[0040]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples.
Example 1
An intaglio offset printing method is adopted, and a conductive metal ink layer and black ink (on the surface thereof) are formed on the surface of a plasma display panel (PDP) front plate substrate (42-inch diagonal glass substrate) by the procedure described below. A front electrode for PDP was formed by laminating conductive paste ink).
[0041]
(1) Ink pattern printing
As black ink, 100 parts by weight of acrylic resin, 40 parts by weight of silver powder having an average particle size of 0.5 μm, black metal oxide having an average particle size of 0.9 μm [CI77428, pigment black 28, CuO, Cr ₂ O _Three 150 parts by weight and containing 20 parts by weight of glass frit having an average particle diameter of 1 μm are added to 50 parts by weight of butyl carbitol acetate (BCA) as a solvent, and mixed and dispersed by three rolls. What was produced was used.
[0042]
As the conductive metal ink, 100 parts by weight of acrylic resin, 1200 parts by weight of silver powder having an average particle diameter of 0.5 μm, and 20 parts by weight of glass frit having an average particle diameter of 1 μm were used as butyl carbitol acetate ( BCA) added to 50 parts by weight, mixed and dispersed with three rolls and used.
For the intaglio plate as a printing plate, a strip-shaped pattern (concave portion) having a line width of 70 μm, a line interval (pitch) of 360 μm, and a depth of 30 μm formed on a glass substrate was used for the first color. For the second color, a stripe-shaped pattern (concave portion) having a line width of 85 μm, a line interval (pitch) of 360 μm, and a depth of 30 μm was used.
[0043]
The printing blanket used was a silicone rubber [rubber hardness JIS A: 40 °, thickness: 300 μm, surface roughness (10-point average roughness Rz): 0.1 μm] as a surface rubber layer. As the silicone rubber, a room temperature curable addition type silicone rubber (product name “KE1600” manufactured by Shin-Etsu Chemical Co., Ltd.) was used. When printing the electrode pattern, in a clean room adjusted to a room temperature of 23 ° C. ± 1 ° C., first, the conductive metal ink filled in the first color intaglio was transferred onto the blanket at a speed of 50 mm / second (the blanket at this time). The line width above was 60 μm). Next, the surface was dried by blowing hot air of 100 ° C. for 20 seconds, and then cold treatment was performed by forcibly blowing cold air of 10 ° C. over the blanket surface for 5 minutes. The surface temperature of the blanket after cooling was in the range of room temperature + 3 ° C.
[0044]
The black ink filled in the intaglio for the second color was transferred at a speed of 80 mm / second onto the pattern of the conductive metal ink for the first color of the blanket. As a result, the line width on the blanket was 75 μm, and the second color was laminated with the pattern of the first color conductive ink completely covered. The laminated pattern surface was subjected to hot air drying and cooling treatment under the same conditions as before. After the cooling treatment, the target electrode pattern was printed by transferring the laminated pattern on the blanket to the glass substrate. At this time, the ink transferred onto the blanket was 100% completely transferred onto the glass substrate, and the printed pattern had a line width of 80 μm and a thickness (unfired) of 8 μm.
[0045]
According to this method, continuous printability was good, there was almost no change in shape, and no adverse effect on printing accuracy was observed. Moreover, since 100% of the ink was completely transferred to the glass substrate, the pattern shape after printing was very good and the film thickness was stable. As a result of performing the drying process and the cooling process, there was no problem that the printing accuracy was lowered even though the printing of the ink pattern was continuously repeated.
[0046]
(2) Printing pattern firing
The printed pattern was baked at 550 ° C. for 1 hour to completely decompose the resin component of the ink pattern and to melt bond the conductive metal powder. The thickness of the bus electrode (silver electrode) obtained by firing was 5 μm.
(3) Formation of transparent electrodes
By forming (etching) ITO (transparent electrode) on a glass substrate in advance by patterning (etching) with a sputter and photolithographic bath, forming a bus electrode, and then forming a transparent electrode, a transparent conductive layer and a protective layer according to a conventional method A front plate for PDP was obtained.
(4) Overall evaluation
In the front plate for PDP thus obtained, the printing accuracy of the bus electrode was able to keep the error within ± 10 μm within the area of the substrate (diagonal 42 inches). The range of this error was such that there was no problem in mounting the PDP. Further, the conductivity of the bus electrode was very good.
[0047]
The amount of ink used in the production of the front plate for PDP is very small compared to the case where, for example, a black photosensitive paste is applied to the entire surface of the front plate, and the cost of the material itself is low, Significant cost savings were achieved. Moreover, since there is no problem of waste liquid that occurs when adopting the photolithography method, and the printing equipment itself used for forming the ink pattern is also inexpensive, the cost for manufacturing the front plate for PDP could be kept extremely low. . Moreover, the obtained front plate for PDP has an ink pattern, so that the blackness of the bus electrode surface on the entire surface of the front plate is extremely high, and can exhibit a very high contrast when mounted on the PDP. It was.
[0048]
Comparative Example 1
A photosensitive paste ink (Dupont, “Fodel”) was uniformly applied to the front panel (42 inches diagonal) of the PDP by screen printing to a thickness of 10 μm. Here, first, a black photosensitive paste was applied and dried, and then a conductive photosensitive silver paste was applied to form two layers. Next, a striped electrode pattern was formed by exposure and development, and finally baked at 550 ° C. for 1 hour to form a silver electrode. Here, as in Example 1, the line width of the pattern was set to 80 μm and the pitch was set to 360 μm. After forming the bus electrode, a front electrode plate for PDP was obtained by forming a transparent electrode, a transparent conductive layer and a protective layer according to a conventional method.
[0049]
In the PDP front plate obtained in this way, the printing accuracy of the bus electrode is less than ± 3 μm within the area of the substrate for the front plate (diagonal 42 inches) because the photolithographic method was adopted. I was able to fit in. Further, the conductivity of the bus electrode was very good as in the case of Example 1. However, a large amount of silver waste liquid was generated during exposure / development of the bus electrode, and it was necessary to print two types of pastes, a black paste and a silver paste, in order to impart sufficient blackness to the bus electrode, etc. For this reason, the manufacturing cost of the front plate for PDP was 5 to 10 times that of Example 1.
[0050]
Comparative Example 2
Using the same conductive silver paste as in Example 1 on the front plate (42 inches diagonal) of the PDP, pattern printing was performed by screen printing with a line width of 80 μm and a pitch of 360 μm. According to this method, it was impossible to form a pattern with a stable line width, many breaks occurred, the printing accuracy was very poor, and the printing accuracy was ± 50 μm within a 42 inch plane. As a result, when the PDP is mounted, the electrode is displaced and it is difficult to put it to practical use.
[0051]
Comparative Example 3
In Example 1, pattern printing was performed in the same manner as in Example 1 except that the conductive ink of the first color was transferred onto the blanket at 50 mm / second and the black ink of the second color was transferred at 20 mm / second as the printing conditions. I did it. As a result, a part of the ink on the blanket transferred to the first color moved to the intaglio when transferring the second color, and many pinholes were generated, so that a good pattern could not be formed.
[0052]
【The invention's effect】
According to the present invention, the pattern of the front electrode for the plasma display panel can be formed with a highly accurate and stable resistance by the intaglio offset printing method. In addition, there is no generation of waste liquid as in the photolithography method, and the manufacturing facilities are inexpensive, and the manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of the structure of a PDP.
[Explanation of symbols]
10 Front plate
11 Front electrode / Bus electrode
12 ITO (transparent electrode)
30 Ink pattern
32 Conductive metal powder
33 Blanket for printing

Claims (4)

A method of forming a front electrode for a plasma display panel that prints an electrode pattern by an intaglio offset printing method,
(1) a step of transferring the conductive metal ink supplied to the pattern forming intaglio to a printing blanket;
(2) A step of transferring and laminating black ink containing a black metal oxide or / and a black composite alloy by intaglio offset printing on the conductive metal ink layer transferred onto the blanket,
(3) transferring the laminated ink from the blanket to a transparent substrate; and
(4) a step of firing the printed ink pattern as described above;
And the relationship between the transition speed V ₁ (mm / second) in the step (1) and the transition speed V ₂ (mm / second) in the step (2) is V ₁ ≦ V _2. A method for forming a front electrode for a plasma display panel. When the printing pattern width in the step (1) is W ₁ (μm) and the laminated printing pattern width in the step (2) is W ₂ (μm), 0.5 × W ₂ ≦ W ₁ ≦ W ₂ 2. The method of forming a front electrode for a plasma display panel according to claim 1, wherein the pattern is formed under conditions. The conductive metal powder is one or more metal powders selected from the group consisting of silver, copper, gold, platinum, aluminum, nickel, iron and palladium, and the black metal oxide is ruthenium oxide (RuO). ₂ ), manganese oxide (MnO), molybdenum oxide (MoO ₂ ), chromium oxide (Cr ₂ O ₃ ), copper oxide (CuO), titanium oxide (TiO), palladium oxide (PdO) and iron oxide (Fe ₂ O ₃₎ 3. The method of forming a front electrode for a plasma display panel according to claim 1, wherein the metal oxide is one or more metal oxides selected from the group consisting of: A surface rubber layer of the blanket is made of silicone rubber, has a JIS-A hardness of 20 to 80 °, and a surface roughness expressed by ten-point average roughness (Rz) of 0.01 to 3 μm. The method for forming a front electrode for a plasma display panel according to claim 1.

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