JP5976367B2 - Conductive metal paste - Google Patents

Description

  The present invention relates to a conductive metal paste, and more particularly to a paste used for forming a metal wiring or a conductive film by a screen printing method.

  Conventionally, it is known to use a so-called screen printing method for forming a metal wiring or a conductive film in a manufacturing process of an electronic device. In the screen printing method, a screen plate is placed facing a substrate made of glass, silicon, or the like, and a conductive metal paste is applied to the substrate surface through an opening pattern formed in the screen plate, whereby the substrate surface is coated. A conductive metal paste corresponding to the opening pattern is printed. Then, by firing the printed conductive metal paste, the dispersing agent that covers the surface of the metal fine particles of the conductive metal paste is detached, and the metal fine particles are sintered together to obtain a conductive metal wiring.

  By the way, in recent years, in order to improve the performance of electronic devices, further reduction in resistance of metal wiring is required. A method for further reducing the resistance of metal wiring is known, for example, from Patent Document 1. In this case, a conductive metal paste containing both metal fine particles and a metal filler as a metal solid content and further containing a varnish-like resin that prevents dripping and bleeding is used, and this conductive metal paste is applied to the substrate surface, for example, 1 μm. It is made to apply with the above thickness. When the conductive metal paste is applied to a thickness of 1 μm or more, depending on the substrate surface state, dripping and bleeding cannot be completely prevented, and the adhesion of the metal wiring to the substrate after firing is reduced. To do. From this, it is conceivable to increase the amount of additive such as the varnish-like resin.

  Here, generally, when a polar solvent having a high viscosity is used and the amount of additive added is increased, the viscosity of the conductive metal paste increases, and the conductive metal paste cannot be uniformly applied to the substrate surface. On the other hand, if the metal solid content concentration is lowered, the viscosity of the conductive metal paste can be lowered, but the thickness of the metal wiring after firing is reduced. Therefore, in order to increase the additive amount while maintaining the metal solid content concentration high, it is effective to use a low polarity solvent having a viscosity lower than that of the polar solvent. However, many additives such as the varnish-like resin are usually polar, and it is difficult to sufficiently dissolve such polar additives in a low-polar solvent. For this reason, since the occurrence of sagging or bleeding cannot be reliably suppressed when the conductive metal paste is applied thickly, it is difficult to form a metal wiring having a target line width or film thickness. Further, since it is difficult to uniformly introduce more varnish-like resin into the paste, there is a problem that the adhesion between the fired metal wiring and the substrate is lowered.

International Publication No. 2002/035554

  In view of the above points, the present invention can surely suppress the occurrence of sagging or bleeding when a conductive metal paste is applied thickly on the substrate surface, and has excellent adhesion between the fired metal wiring and the substrate. It is an object of the present invention to provide a conductive metal paste that can be obtained.

  In order to solve the above problems, the conductive metal paste of the present invention is a conductive metal paste comprising a low-polarity solvent, metal fine particles whose surface is coated with a dispersant, and a polyimide varnish. It further comprises a fatty acid amide.

  According to the present invention, a low polarity solvent having a lower viscosity than that of a polar solvent is used as a solvent. Therefore, even when the amount of added polyimide varnish is increased while maintaining a high concentration of metal fine particles, which are metal solids, conductivity is increased. Metal paste can be applied uniformly. Here, since the polyimide varnish has polarity, it is difficult to dissolve the polyimide varnish in a low polarity solvent.

  Therefore, the conductive metal paste of the present invention further contains a fatty acid amide as a surfactant. When the hydrophilic group of the fatty acid amide is directed to the polyimide varnish and the hydrophobic group is directed to the low polarity solvent, the low polarity solvent and the polyimide varnish are emulsified (emulsified). Thereby, a sufficient amount of polyimide varnish can be dissolved in the low polarity solvent. Therefore, even if the conductive metal paste is applied thickly on the surface of the substrate, the occurrence of sagging and bleeding can be suppressed. Further, combined with the effect that the metal solid content concentration can be kept high as described above, a thick metal wiring can be formed, and the resistance of the metal wiring can be reduced. Furthermore, excellent adhesion between the fired metal wiring and the substrate can be obtained.

  As the metal fine particles, those having an average particle diameter in the range of 1 nm to 50 nm can be used. When the average particle diameter is less than 1 nm, the amount of the dispersant adsorbed on the surface of the metal fine particles increases with the increase in the specific surface area, so that the detachment of the dispersant becomes insufficient during firing, and the resistance of the metal wiring The problem that the value becomes high occurs. On the other hand, when the average particle diameter exceeds 50 nm, there arises a problem that the dispersibility of the metal fine particles in the conductive metal paste is lowered.

  In the present invention, as the fatty acid amide, methylene bis stearic acid amide, methylene bis palmitic acid amide, methylene bis behenic acid amide, hexamethylene bis stearic acid amide, ethylene bis stearic acid amide, ethylene bis behenic acid amide, ethylene From bis-12-hydroxystearic acid amide, trimethylene 1,3 bis stearic acid amide, tetramethylene bis stearic acid amide, distearyl sebacic acid amide, distearyl adipic acid amide, ethylene bisoleic acid amide and xylylene bis stearic acid amide At least one selected can be used alone or in combination.

  In the present invention, if the polyimide varnish is imide ring-closed, the solubility of the polyimide varnish in the low polarity solvent may be further enhanced.

  In the present invention, it is preferable to further include polyamide. According to this, the polyamide crosslinks to the metal fine particles, and the thixotropic property can be further enhanced. Even when the conductive metal paste is applied at high speed, dripping and bleeding can be prevented.

  In addition, as a dispersing agent which coat | covers the metal fine particle surface, it is preferable to use at least any one among a C6-C18 fatty acid and a C6-C18 aliphatic amine. In the case of fatty acids and aliphatic amines having less than 6 carbon atoms, there is a problem that the dispersibility of the metal fine particles in the conductive metal paste is lowered. On the other hand, in fatty acids and aliphatic amines having 19 or more carbon atoms, the elimination of fatty acids and aliphatic amines from the surface of metal fine particles becomes insufficient during firing, and the resistance of the metal wiring after firing increases (conductivity decreases). ) May occur.

  In the present invention, as the low polarity solvent, at least one liquid hydrocarbon selected from octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, toluene, xylene, cyclododecane, cyclododecene, octylbenzene, and dodecylbenzene is used alone. Or in combination.

  In the present invention, a metal filler having an average particle diameter of 1 to 20 μm may be further included. In this case, when the total of the metal filler and the metal fine particles is 100% by weight, the ratio of the metal filler is preferably in the range of 50 to 95% by weight. If the ratio of the metal filler is less than 50% by weight, it is difficult to increase the thickness of the metal wiring printed by the screen printing method. Furthermore, even if the thickness of the metal wiring can be increased. In this case, the detachment of the dispersant from the surface of the metal fine particles becomes insufficient during firing, resulting in an increase in resistance of the metal wiring after firing. On the other hand, if the ratio of the metal filler exceeds 95% by weight, there is a problem that the sintering of the metal fillers through the metal fine particles becomes insufficient and the resistance of the metal wiring after firing becomes high.

In the present invention, it is preferable that a silane coupling agent is adsorbed on the surface of the metal fine particles coated with the dispersant . As the silane coupling agent, aminoalkyltrialkoxysilane can be used. According to this, the adhesiveness between the metal wiring after baking and the substrate surface can be further improved.

  The metal used in the present invention is composed of at least one metal selected from Ag, Au, Cu, Ni, Pd, In, Sn, Rh, Ru, Pt, In, and Sn, or at least two of these metals. It is an alloy and can be appropriately selected depending on the purpose and application.

  Hereinafter, the conductive metal paste according to the embodiment of the present invention will be described using an Ag paste as an example. The Ag paste of the present embodiment includes a low polarity solvent, Ag fine particles whose surface is coated with a dispersant, a polyimide varnish, and a fatty acid amide as a surfactant.

  As the Ag fine particles, those having an average particle diameter in the range of 1 nm to 50 nm can be used. As a brand name of a commercial product, Ag nano metal ink Ag1T and Au1T (made by ULVAC, Inc.) can be mentioned, for example. When the average particle diameter is less than 1 nm, the specific surface area increases and the amount of the dispersant covering the surface of the Ag fine particles increases, so that the detachment of the dispersant becomes insufficient during firing, and the resistance value of the Ag wiring is high. The trouble that becomes. On the other hand, when the average particle diameter exceeds 50 nm, there arises a problem that the dispersibility of Ag fine particles in the Ag paste is lowered.

  As the dispersant for coating the Ag fine particle surface, it is preferable to use at least one of a fatty acid having 6 to 18 carbon atoms and an aliphatic amine having 6 to 18 carbon atoms. In the case of fatty acids or aliphatic amines having less than 6 carbon atoms, there is a problem that the dispersibility of Ag fine particles in the Ag paste is lowered. On the other hand, in the case of a fatty acid or aliphatic amine having 19 or more carbon atoms, the detachment of the fatty acid or aliphatic amine from the surface of the Ag fine particles becomes insufficient during firing, resulting in a problem that the resistance value of the Ag wiring film increases.

  As the fatty acid, for example, carboxylic acid can be used. Specifically, C6 hexanoic acid, 2-ethylbutyric acid, neohexanoic acid (2,2-dimethylbutyric acid); C7 heptanoic acid, 2-methylhexanoic acid, cyclohexanecarboxylic acid; C8 Octanoic acid, 2-ethylhexanoic acid, neooctanoic acid (2,2-dimethylhexanoic acid); Nonanoic acid having 9 carbon atoms; Decanoic acid having 10 carbon atoms, neodecanoic acid (2,2-dimethyloctanoic acid); At least one selected from the group consisting of undecanoic acid of 12 carbons; dodecanoic acid having 12 carbon atoms; tetradecanoic acid having 14 carbon atoms; and palmitic acid having 16 carbon atoms; and stearic acid, oleic acid, linoleic acid, and linolenic acid having 18 carbon atoms. They can be used alone or in combination.

  Examples of the aliphatic amine include hexylamine, cyclohexylamine and aniline having 6 carbon atoms; heptylamine having 7 carbon atoms; octylamine having 8 carbon atoms; 2-ethylhexylamine; nonylamine having 9 carbon atoms; decylamine having 10 carbon atoms. At least one selected from dodecylamine having 12 carbon atoms and tetradodecylamine having 14 carbon atoms can be used alone or in combination.

  As the polyimide varnish, it is preferable to use a imide ring closed ring (for example, a ring closing rate of 40% or more). According to this, the solubility of the polyimide varnish with respect to a low polarity solvent can further be improved. Moreover, since the polyimide varnish is excellent in heat resistance, it does not deteriorate even if the applied Ag paste is baked at a temperature of 200 ° C. or higher, for example.

  Examples of the fatty acid amide include methylene bis stearic acid amide, methylene bis palmitic acid amide, methylene bis behenic acid amide, hexamethylene bis stearic acid amide, ethylene bis stearic acid amide, ethylene bis behenic acid amide, and ethylene bis-12. -Selected from hydroxystearic amide, trimethylene 1,3 bis stearic amide, tetramethylene bis stearic amide, distearyl sebacic amide, distearyl adipic amide, ethylene bisoleic amide and xylylene bis stearic amide At least one kind can be used alone or in combination. As a brand name of a commercial product, DISPARLON A603-10X, A603-20X, 6900-10X, 6900-20X, PFA-131 (made by Enomoto Kasei Co., Ltd.) can be mentioned, for example. In addition, the manufacturing method of fatty acid amide is disclosed by Unexamined-Japanese-Patent No. 11-293158, for example.

  Moreover, it is preferable to adsorb | suck a silane coupling agent to the surface of Ag microparticles | fine-particles. As the silane coupling agent, for example, those having an amino group and an alkoxy group such as aminoalkyltrialkoxysilane such as aminopropyltrimethoxysilane and aminopropyltriethoxysilane can be used. According to this, when the applied Ag paste is baked, the alkoxy group is hydrolyzed to become an OH group, and this OH group undergoes dehydration condensation, whereby excellent adhesion to the substrate surface can be obtained, while an amino group Binds strongly to the metal surface. As a result, excellent adhesion can be obtained between the metal wiring after firing and the substrate surface. Furthermore, since the amino group is strongly bonded to the metal surface in this way, dripping and bleeding of the Ag paste can be effectively suppressed in combination with the action of the polyimide varnish.

  As the low polarity solvent, for example, at least one liquid hydrocarbon selected from octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, toluene, xylene, cyclododecane, cyclododecene, octylbenzene, dodecylbenzene alone or They can be used in combination.

  The Ag paste of the present embodiment can further include an Ag filler having an average particle diameter in the range of 1 μm to 20 μm. In this case, when the total of the Ag fine particles and the Ag filler is 100% by weight, the ratio of the Ag filler is preferably in the range of 50 to 95% by weight. When the ratio of the Ag filler is less than 50% by weight (the ratio of the Ag fine particles is 50% by weight or more), it may be difficult to increase the film thickness of the Ag wiring obtained by the screen printing method to, for example, 10 μm or more. Further, even if the thickness of the Ag wiring can be increased, desorption of the dispersant from the surface of the Ag fine particles becomes insufficient during firing, and the resistance of the Ag wiring after firing may increase. On the other hand, when the ratio of Ag filler exceeds 95% by weight (when the ratio of Ag fine particles is 5% by weight or less), the sintering of Ag fillers through Ag fine particles becomes insufficient, and the resistance of Ag wiring after firing becomes low. The trouble of becoming high arises.

  Polyamide can further be included in the Ag paste of this embodiment. This polyamide crosslinks to the Ag fine particles to impart thixotropic properties to the Ag paste. Therefore, combined with the action of the silica, the thixotropic properties of the Ag paste can be enhanced. As the polyamide, at least one polyamide wax synthesized by a known method such as polycondensation of dibasic acid and diamine, polycondensation of dibasic acid derivative or dimer acid and diamine, or ring-opening polymerization of lactam is used alone. Or in combination. As a brand name of a commercial product, DISPARLON 3900EF (made by Enomoto Kasei Co., Ltd.) can be mentioned, for example.

  As the metal, in addition to the above Ag, for example, at least one metal selected from Au, Cu, Ni, Pd, Rh, Ru, Pt, In and Sn, or an alloy composed of at least two of these metals is used. Depending on the purpose and application, it can be appropriately selected. Hereinafter, a method for producing a conductive metal paste will be described by taking an example of producing an Ag paste as an example.

  First, a dispersion liquid of Ag fine particles having an average particle diameter of 1 nm to 50 nm is placed in a glass container, and a solvent such as toluene is removed using an evaporator. As a result, Ag fine particles whose surface is coated with at least one of the fatty acid having 6 to 18 carbon atoms and the aliphatic amine having 6 to 18 carbon atoms are obtained.

  In addition, when making a silane coupling agent adsorb | suck to Ag fine particle surface, a silane coupling agent is added and stirred to Ag fine particle with an average particle diameter of 1 nm-50 nm. Then, a polar solvent such as acetone is added to the agitated material to precipitate Ag fine particles, and the supernatant liquid is discharged by decantation or the like (hereinafter, this operation is referred to as “cleaning step”). This washing process is repeated a plurality of times, the solvent is removed, and Ag fine particles having the silane coupling agent adsorbed on the surface are obtained.

  Next, Ag fine particles obtained as described above, an imide ring-closed polyimide varnish, a fatty acid amide, and a low polarity solvent composed of hydrocarbon are blended at a predetermined ratio. In this case, the proportion of Ag fine particles is 60 to 90 wt%, the proportion of polyimide varnish is 0.4 to 1.6 wt%, the proportion of fatty acid amide is 0.5 to 3.0 wt%, and the proportion of low polarity solvent is It is preferable to be within the range of 5 to 30% by weight. Then, an Ag paste is obtained by kneading the above blended material with a three-roll mill.

  In addition, when apply | coating Ag paste by the thickness of 10 micrometers or more, you may mix | blend Ag filler with an average particle diameter of 1-20 micrometers with the said Ag microparticles | fine-particles as Ag solid content. In this case, when the total of the Ag filler and the Ag fine particles is 100% by weight, the ratio of the Ag filler is preferably in the range of 50 to 95% by weight. Moreover, if the polyamide is blended at a ratio of 0.2 to 4% by weight, the thixotropic property of the Ag paste can be further enhanced.

  Since the Ag paste of the present embodiment described above uses a low polarity solvent having a viscosity lower than that of a polar solvent as a solvent, the addition of polyimide varnish while maintaining a high Ag solid content concentration (concentration of Ag fine particles and Ag filler). Even if the amount is increased, the Ag paste can be applied uniformly. Here, since the polyimide varnish has polarity, it is difficult to dissolve the polyimide varnish in a low polarity solvent.

  Therefore, the Ag paste of this embodiment further contains a fatty acid amide as a surfactant. The hydrophilic group of this fatty acid amide is directed to the polyimide varnish and the hydrophobic group is directed to the low polarity solvent, so that the low polarity solvent and the polyimide varnish are emulsified (emulsified), and a sufficient amount of the polyimide varnish is dissolved in the low polarity solvent. it can. Therefore, even if the Ag paste is applied thickly on the substrate surface, the occurrence of dripping or bleeding can be reliably suppressed. Combined with the effect of increasing the amount of added polyimide varnish while keeping the Ag solid content concentration high as described above, the thickness of the Ag wiring after firing can be increased, and the resistance of the Ag wiring can be reduced. Can be realized. Furthermore, excellent adhesiveness is obtained between the Ag wiring after firing and the substrate.

Examples of the present invention will be described below.
Example 1
Ag fine particles having an average particle diameter of 4 nm (trade name “Ag Nanometal Ink Ag1T” manufactured by ULVAC, Inc.) are placed in a glass container, and toluene as a solvent is distilled off using an evaporator to form Ag fine particles (hereinafter “Ag fine particles”). 1 ”). 50 parts by weight of the Ag fine particles 1, 0.5 parts by weight of fatty acid amide (trade name “DISPARLON A603-10X” manufactured by Enomoto Kasei), and 1.0 part of polyimide varnish (trade name “Composeran H800” manufactured by Arakawa Chemical) 11.5 parts by weight of parts by weight and dodecylbenzene were blended. And what was mix | blended was knead | mixed with a 3 roll mill, and Ag paste was obtained. The obtained Ag paste was printed on the surface of the glass substrate by a screen printing method and baked at 230 ° C. for 20 minutes. No sagging or bleeding was observed in the printed Ag paste. As a result of performing a grid eye tape peeling test on the fired Ag wiring, it was confirmed that no peeling of the Ag wiring was seen and excellent adhesion to the glass substrate was obtained. The thickness of the Ag wiring after firing was 3 μm, the line width was 100 μm, and the specific resistance was 16 μΩ · cm, and it was confirmed that the resistance of the Ag wiring can be reduced.

(Example 2)
25 parts by weight of the Ag fine particles 1 obtained in Example 1 above, 25 parts by weight of Ag filler having an average particle diameter of 2.1 μm (trade name “Silcoat AgC-2011” manufactured by Fukuda Metal Foil Powder Industry), fatty acid amide (Enomoto) 0.5 parts by weight of Kasei's trade name “DISPARLON A603-10X”, 1.0 part by weight of polyimide varnish (trade name “COMPOCELAN H800” by Arakawa Chemical), and 10.5 parts by weight of dodecylbenzene did. Then, in the same manner as in Example 1, the above blended material was kneaded by a three-roll mill to obtain an Ag paste, and this Ag paste was applied to the surface of the glass substrate by a screen printing method and printed. Bake for minutes. As in Example 1, the printed Ag paste did not sag or bleed, and no Ag wiring peeling after firing was observed. The thickness of the Ag wiring after firing was 10 μm, the line width was 100 μm, and the specific resistance was 14 μΩ · cm. It was confirmed that the resistance of Ag wiring with a narrow wiring width can be reduced.

(Example 3)
15 parts by weight of Ag fine particles 1 obtained in Example 1 above, 35 parts by weight of Ag filler (trade name “Silcoat AgC-2011” manufactured by Fukuda Metal Foil Powder Industry), fatty acid amide (trade name “DISPARLON manufactured by Enomoto Kasei) 0.53 parts by weight of A603-10X "), 1.0 part by weight of polyimide varnish (trade name" COMPOCERAN H800 "manufactured by Arakawa Chemical), and 9.5 parts by weight of dodecylbenzene. Then, in the same manner as in Example 1 above, the blended material was kneaded by a three-roll mill to obtain an Ag paste, and this Ag paste was applied to the surface of the glass substrate by a screen printing method and printed, at 230 ° C. for 30 minutes. Baked. As in Example 1, the printed Ag paste did not sag or bleed, and no Ag wiring peeling after firing was observed. The thickness of the Ag wiring after firing was 17 μm, the line width was 100 μm, the specific resistance was 12 μΩ · cm, and it was confirmed that the resistance of Ag wiring can be reduced.

Example 4
5 parts by weight of Ag fine particles 1 obtained in Example 1 above, 45 parts by weight of Ag filler (trade name “Silcoat AgC-2011” manufactured by Fukuda Metal Foil Powder Industry), fatty acid amide (trade name “DISPARLON manufactured by Enomoto Kasei) 0.53 parts by weight of A603-10X "), 1.0 part by weight of polyimide varnish (trade name" COMPOCERAN H800 "manufactured by Arakawa Chemical Co., Ltd.), and 8.5 parts by weight of dodecylbenzene. Then, in the same manner as in Example 1 above, the blended material was kneaded by a three-roll mill to obtain an Ag paste, and this Ag paste was applied to the surface of the glass substrate by a screen printing method and printed, at 230 ° C. for 30 minutes. Baked. As in Example 1, the printed Ag paste did not sag or bleed, and no Ag wiring peeling after firing was observed. The thickness of the Ag wiring after firing was 20 μm, the line width was 100 μm, and the specific resistance was 10 μΩ · cm, and it was confirmed that the resistance of the Ag wiring can be reduced.

(Example 5)
5 parts by weight of Ag fine particles 1 obtained in Example 1 above, 45 parts by weight of Ag filler (trade name “Silcoat AgC-2011” manufactured by Fukuda Metal Foil Powder Industry), fatty acid amide (trade name “DISPARLON manufactured by Enomoto Kasei) 0.5 parts by weight of A603-10X "), 1.0 part by weight of polyimide varnish (trade name" COMPOSELLAN H800 "manufactured by Arakawa Chemical), and 0.6 parts of polyamide (trade name" DISPARLON 3900EF "manufactured by Enomoto Kasei) Part by weight and 7.9 parts by weight of dodecylbenzene were blended. Then, in the same manner as in Example 1 above, the blended material was kneaded by a three-roll mill to obtain an Ag paste, and this Ag paste was applied to the surface of the glass substrate by a screen printing method and printed, at 230 ° C. for 30 minutes. Baked. As in Example 1, the printed Ag paste did not sag or bleed, and no Ag wiring peeling after firing was observed. The thickness of the Ag wiring after firing was 22 μm, the line width was 100 μm, the specific resistance was 11 μΩ · cm, and it was confirmed that the resistance of the Ag wiring can be reduced.

(Example 6)
5 parts by weight of Ag fine particles 1 obtained in Example 1 above, 45 parts by weight of Ag filler (trade name “Silcoat AgC-2011” manufactured by Fukuda Metal Foil Powder Industry), fatty acid amide (trade name “DISPARLON manufactured by Enomoto Kasei) 0.5 parts by weight of A603-10X ”), 1.0 part by weight of polyimide varnish (trade name“ COMPOSELLA AA ”manufactured by Arakawa Chemical Co., Ltd.) and 0 polyamide (trade name“ DISPARLON 3900EF ”manufactured by Enomoto Kasei) .6 parts by weight and 7.9 parts by weight of dodecylbenzene were blended. Then, in the same manner as in Example 1 above, the blended material was kneaded by a three-roll mill to obtain an Ag paste, and this Ag paste was applied to the surface of the glass substrate by a screen printing method and printed, at 230 ° C. for 30 minutes. Baked. As in Example 1, the printed Ag paste did not sag or bleed, and no Ag wiring peeling after firing was observed. The thickness of the Ag wiring after firing was 23 μm, the line width was 100 μm, and the specific resistance was 10 μΩ · cm, and it was confirmed that the resistance of the Ag wiring can be reduced.

(Example 7)
10 g of aminopropyltriethoxysilane was added to 100 g of Ag fine particles (trade name “Ag nanometal ink Ag1T” manufactured by ULVAC, Inc.) and stirred at 25 ° C. for 12 hours. To this stirred mixture, 500 g of acetone is added to precipitate Ag fine particles, and the “washing step” in which the supernatant is discharged by decantation or the like is repeated a plurality of times to obtain Ag fine particles adsorbed on the surface (hereinafter “Ag fine particles”). 2 ”). 5 parts by weight of the Ag fine particles 2 thus obtained, 45 parts by weight of Ag filler (trade name “Silcoat AgC-2011” manufactured by Fukuda Metal Foil Powder Industry), and fatty acid amide (trade name “DISPARLON A603 manufactured by Enomoto Kasei) -10X "), 0.5 parts by weight of the ring-closed polyimide varnish (trade name" COMPOSELLA AA "manufactured by Arakawa Chemical), and polyamide (trade name" DISPARLON 3900EF "manufactured by Enomoto Chemical). 6 parts by weight and 7.9 parts by weight of dodecylbenzene were blended. Then, in the same manner as in Example 1 above, the blended material was kneaded by a three-roll mill to obtain an Ag paste, and this Ag paste was applied to the surface of the glass substrate by a screen printing method and printed, at 230 ° C. for 30 minutes. Baked. As in Example 1, the printed Ag paste did not sag or bleed, and no Ag wiring peeling after firing was observed. The thickness of the Ag wiring after firing was 24 μm, the line width was 100 μm, the specific resistance was 9 μΩ · cm, and it was confirmed that the resistance of the Ag wiring can be reduced.

(Example 8)
2.5 parts by weight of Ag fine particles 2 obtained in Example 7 above, 47.5 parts by weight of Ag filler (trade name “Silcoat AgC-2011” manufactured by Fukuda Metal Foil Powder Industry), fatty acid amide (manufactured by Enomoto Kasei) 0.5 parts by weight of the trade name “DISPARLON A603-10X”, 1.0 part by weight of the closed polyimide varnish (trade name “COMPOSELLA AA” manufactured by Arakawa Chemical), and polyamide (trade name “DISPARLON 3900EF manufactured by Enomoto Kasei) ]) And 0.6 parts by weight of dodecylbenzene. Then, in the same manner as in Example 1 above, the blended material was kneaded by a three-roll mill to obtain an Ag paste, and this Ag paste was applied to the surface of the glass substrate by a screen printing method and printed, at 230 ° C. for 30 minutes. Baked. As in Example 1, the printed Ag paste did not sag or bleed, and no Ag wiring peeling after firing was observed. The thickness of the Ag wiring after firing was 24 μm, the line width was 100 μm, and the specific resistance was 10 μΩ · cm, and it was confirmed that the resistance of the Ag wiring can be reduced.

Next, a comparative example for the above embodiment will be described.
(Comparative Example 1)
An Ag paste was obtained in the same manner as in Example 6 except that the fatty acid amide and the polyimide varnish were not included. In the same manner as in Example 1, the obtained Ag paste was applied onto the surface of the glass substrate by a screen printing method, printed, and baked at 230 ° C. for 30 minutes. Unlike the above examples, dripping and bleeding were noticeably generated in the printed Ag paste. Moreover, as a result of performing a grid eye tape peeling test on the fired Ag wiring, peeling of the Ag wiring was observed, and it was confirmed that the adhesion between the Ag wiring and the substrate was low. The fired Ag wiring had a film thickness of 14 μm, a line width of 100 μm, and a specific resistance of 11 μΩ · cm.

(Comparative Example 2)
An attempt was made to obtain an Ag paste in the same manner as in Example 7 except that the fatty acid amide was not included, but the polyimide varnish could not be dissolved in dodecylbenzene, and a uniform Ag paste could be produced. There wasn't.

(Comparative Example 3)
An Ag paste was obtained in the same manner as in Example 7 except that Ag fine particles were not included. In the same manner as in Example 1, the obtained Ag paste was applied onto the surface of the glass substrate by a screen printing method, printed, and baked at 230 ° C. for 30 minutes. The printed Ag paste did not sag or bleed, and as a result of performing a cross-cut eye tape peeling test on the fired Ag wiring, no peeling of the Ag wiring was observed. The film thickness of the Ag wiring after firing was 14 μm and the line width was 100 μm, but the specific resistance was greatly increased to 47 μΩ · cm. From this, it was found that the resistance of the Ag wiring cannot be reduced.

Claims (8)

A conductive material comprising a low polarity solvent, metal fine particles coated with a dispersant having at least one of a fatty acid having 6 to 18 carbon atoms and an aliphatic amine having 6 to 18 carbon atoms in the fatty acid portion, and a polyimide varnish. Metal paste,
The average particle diameter of the metal fine particles is in the range of 1 nm to 50 nm,
A conductive metal paste further comprising a fatty acid amide as a surfactant.   The fatty acid amide is methylene bis stearic acid amide, methylene bis palmitic acid amide, methylene bis behenic acid amide, hexamethylene bis stearic acid amide, ethylene bis stearic acid amide, ethylene bis behenic acid amide, ethylene bis-12-hydroxy. At least one selected from stearic acid amide, trimethylene 1,3 bis stearic acid amide, tetramethylene bis stearic acid amide, distearyl sebacic acid amide, distearyl adipic acid amide, ethylene bisoleic acid amide and xylylene bis stearic acid amide The conductive metal paste according to claim 1, wherein:   The conductive metal paste according to claim 1 or 2, wherein the polyimide varnish is ring-closed with an imide.   The conductive metal paste according to any one of claims 1 to 3, further comprising polyamide.   The low-polarity solvent is composed of at least one liquid hydrocarbon selected from octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, toluene, xylene, cyclododecane, cyclododecene, octylbenzene, and dodecylbenzene. The conductive metal paste according to any one of claims 1 to 4. Conductive metal paste according to any one of claims 1 to 5, characterized in that the average particle size further comprises a metal filler is 1 to 20 [mu] m.   7. The conductive metal paste according to claim 6, wherein the metal filler is in the range of 50 to 95% by weight when the total of the metal filler and the metal fine particles is 100% by weight. The conductive metal paste according to any one of claims 1 to 7, wherein a silane coupling agent is adsorbed on a surface of the metal fine particles coated with the dispersant .