JP2021044308A - Conductive film forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive film forming method capable of easily forming a conductive film having a low electric resistance by using a copper fine particle dispersion liquid. SOLUTION: The conductive film forming method includes a step of forming a liquid film 3 made of a copper fine particle dispersion liquid on a base material 1, and drying the liquid film 3 to put a film-like aggregate 4 on the base material 1. The step of forming, the step of immersing the agglomerate 4 on the base material 1 in the pretreatment liquid 5, the step of removing the liquid 51 on the agglomerate 4, and the step of firing the agglomerate 4 on the base material 1. The steps of forming the conductive film 2 are provided in this order. The dispersant is an organic compound having at least one acidic functional group or a salt thereof. The pretreatment liquid 5 is an aqueous solution that dissolves a dispersant, and contains one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid as solutes. .. As a result, the dispersant contained in the aggregate 4 and not contributing to the adhesion to the base material 1 is removed by using the pretreatment liquid 5. [Selection diagram] Fig. 2

Description

The present invention relates to a conductive film forming method for forming a conductive film on a substrate.

Conventionally, a method of forming a conductive film (conductive film) on a substrate by using a copper fine particle dispersion liquid (copper nanoink) containing copper fine particles (copper nanoparticles) in a dispersion medium has been known (for example). , Patent Document 1). In this method, a liquid film of a copper fine particle dispersion liquid is formed on a substrate, and the liquid film is dried to form a copper fine particle layer. The copper fine particle layer is light-fired by irradiation with light to form a conductive film.

Further, it is known that a copper fine particle dispersion liquid used for forming a conductive film is blended (see, for example, Patent Document 2).

Further, a method of forming a conductive film on a substrate by heat firing a copper fine particle layer is also known.

However, in the above-mentioned method, when a base material having low heat resistance (low heat resistance base material) is used, it is necessary to bake the copper fine particle layer with a small amount of energy. In such a case, firing may not proceed sufficiently and a conductive film having low electrical resistance may not be formed.

U.S. Patent Application Publication No. 2008/0286488 Japanese Patent No. 5088760

The present invention solves the above problems, and an object of the present invention is to provide a conductive film forming method capable of easily forming a conductive film having a low electric resistance by using a copper fine particle dispersion liquid.

The conductive film forming method of the present invention is a method of forming a conductive film on a base material, in which a step of forming a liquid film composed of a copper fine particle dispersion liquid on the base material and a step of drying the liquid film to form a film. A step of forming the shape-like aggregate on the base material, a step of immersing the agglomerate on the base material in the pretreatment liquid, a step of removing the liquid on the agglomerate, and a step on the base material. The steps of firing the aggregate to form a conductive film are included in this order, and the copper fine particle dispersion liquid includes copper fine particles, a dispersion medium, and a dispersant for dispersing the copper fine particles in the dispersion medium. The dispersant is an organic compound having at least one acidic functional group or a salt thereof, and the pretreatment solution is an aqueous solution for dissolving the dispersant, which is citric acid, formic acid, oxalic acid, or adipic acid. It is characterized by containing one or more acids selected from the group consisting of dihydrazide and p-toluenesulfonic acid as solutes.

The conductive film forming method of the present invention is a method of forming a conductive film on a base material, in which a step of forming a liquid film composed of a copper fine particle dispersion liquid on the base material and a step of drying the liquid film to form a film. A step of forming the shape-like agglomerates on the base material, a step of immersing the agglomerates on the base material in a pretreatment solution, a step of immersing the agglomerates on the base material in water, and the like. The step of removing the liquid on the aggregate and the step of firing the aggregate on the base material to form a conductive film are included in this order, and the copper fine particle dispersion liquid includes copper fine particles, a dispersion medium, and the like. The dispersant has a dispersant for dispersing the copper fine particles in the dispersion medium, the dispersant is an organic compound having at least one acidic functional group or a salt thereof, and the pretreatment solution contains the dispersant. It is a soluble aqueous solution, and may be characterized by containing one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid as solutes.

The conductive film forming method of the present invention is a method of forming a conductive film on a base material, in which a step of forming a liquid film composed of a copper fine particle dispersion liquid on the base material and a step of drying the liquid film to form a film. A step of forming the shape-like aggregate on the base material, a step of immersing the agglomerate on the base material in the first pretreatment solution, and a step of immersing the agglomerate on the base material in the second pretreatment solution. The step of immersing, the step of removing the liquid on the aggregate, and the step of firing the aggregate on the base material to form a conductive film are included in this order, and the copper fine particle dispersion liquid is a copper fine particle. The dispersant is an organic compound having at least one acidic functional group or a salt thereof, which comprises a dispersion medium and a dispersant for dispersing the copper fine particles in the dispersion medium. The treatment liquid is an aqueous solution that dissolves the dispersant, and contains one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid as solutes. The second pretreatment liquid is an aqueous solution that dissolves the dispersant, and is a solute of one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipate dihydrazide and p-toluenesulfonic acid. The solute may be different from the solute of the first pretreatment liquid.

The conductive film forming method of the present invention is a method of forming a conductive film on a base material, in which a step of forming a liquid film composed of a copper fine particle dispersion liquid on the base material and a step of drying the liquid film to form a film. A step of forming the shape-like agglomerates on the base material, a step of immersing the agglomerates on the base material in the first pretreatment solution, and a step of immersing the agglomerates on the base material in the second pretreatment solution. A step of immersing the aggregate on the substrate, a step of immersing the aggregate on the substrate in water, a step of removing the liquid on the aggregate, and a step of firing the aggregate on the substrate to form a conductive film. The steps are carried out in this order, the copper fine particle dispersion having copper fine particles, a dispersion medium, and a dispersant for dispersing the copper fine particles in the dispersion medium, and the dispersant is at least one acidic. An organic compound having a functional group or a salt thereof, the first pretreatment solution is an aqueous solution for dissolving the dispersant, and is a group consisting of citric acid, formic acid, oxalic acid, adipate dihydrazide and p-toluenesulfonic acid. The second pretreatment liquid, which contains one or more acids selected from the above as a solute, is an aqueous solution for dissolving the dispersant, and is a citric acid, formic acid, oxalic acid, adipate dihydrazide and p-toluenesulfone. It may be characterized in that it contains one or more acids selected from the group consisting of acids as solutes, and the solutes are different from the solutes of the first pretreatment liquid.

According to the conductive film forming method of the present invention, the dispersant contained in the agglomerates and not contributing to the adhesion to the substrate is removed by using the pretreatment liquid, so that the copper fine particles of the agglomerates are fired by the dispersant. It is possible to form a conductive film having a low electric resistance on the base material with a smaller firing energy than when the pretreatment liquid is not used, because the firing of the agglomerates is promoted.

FIG. 3 is a cross-sectional configuration diagram of a conductive film on a substrate formed by the conductive film forming method according to the embodiment of the present invention. (A) to (f) are cross-sectional configuration views showing the conductive film forming method according to the first embodiment of the present invention in chronological order. (A) to (g) are sectional views showing the conductive film forming method according to the 2nd Embodiment of this invention in chronological order. (A) to (g) are cross-sectional configuration views showing the conductive film forming method according to the third embodiment of the present invention in chronological order. (A) to (h) are sectional views showing the conductive film forming method which concerns on 4th Embodiment of this invention in chronological order.

(First Embodiment)
The conductive film forming method according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2 (a) to 2 (f). As shown in FIG. 1, the conductive film forming method of the present embodiment is a method of forming the conductive film 2 on the base material 1.

As shown in FIG. 2A, first, a liquid film 3 made of a copper fine particle dispersion liquid is formed on the base material 1. The base material 1 is a support for supporting the conductive film, and is, for example, polyethylene terephthalate (PET) formed into a film. The base material 1 may be made by molding soda glass into a plate shape.

The copper fine particle dispersion liquid has a copper fine particle 31, a dispersion medium, and a dispersant for dispersing the copper fine particle 31 in the dispersion medium. The liquid film 3 on the base material 1 is formed by, for example, a printing method. In the printing method, a copper fine particle dispersion liquid is used as an ink for printing, a predetermined pattern is printed on the base material 1 by a printing apparatus, and a liquid film 3 of the pattern is formed.

The copper fine particles 31 include nanoparticles having a median diameter (D50) of 1 nm or more and less than 100 nm. Therefore, this copper fine particle dispersion is also called copper nanoink. The copper fine particle dispersion liquid may contain copper fine particles on the order of μm in addition to copper nanoparticles (copper nanoparticles).

The dispersion medium is a liquid that disperses the copper fine particles 31, and is, for example, a protic and aprotic dispersion medium or an aprotic polar dispersion medium having a relative permittivity of 30 or more.

The protic and aprotic dispersion medium is a linear or branched alkyl compound or alkenyl compound having one hydroxyl group and having 5 or more and 30 or less carbon atoms. This protic and aprotic dispersion medium may have 1 or more and 10 or less ether bonds, and may have 1 or more and 5 or less carbonyl groups.

Examples of such a protonal dispersion medium include 3-methoxy-3-methylbutanol, triethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monohexyl ether, and ethylene glycol mono-. Examples include, but are not limited to, tert-butyl ether, 2-octanol, and the like.

Further, the protic and aprotic dispersion medium may be a linear or branched alkyl compound or alkenyl compound having 2 or more and 6 or less hydroxyl groups and having 2 or more and 30 or less carbon atoms. This protic and aprotic dispersion medium may have 1 or more and 10 or less ether bonds, and may have 1 or more and 5 or less carbonyl groups.

Examples of such a protic dispersion medium include 2-methylpentane-2,4-diol, ethylene glycol, propylene glycol, 1,5-pentanediol, diethylene glycol, triethylene glycol, glycerin, sorbitol and the like. , Not limited to these.

Examples of the aprotic polar dispersion medium having a relative permittivity of 30 or more include propylene carbonate, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphoramide, N-methylpyrrolidone, N-ethylpyrrolidone, and nitrobenzene. , N, N-diethylformamide, N, N-dimethylacetamide, furfural, γ-butyrolactone, ethylenesulfite, sulfolane, dimethylsulfoxide, succinonitrile, ethylene carbonate and the like, but are not limited thereto.

These polar dispersion media may be used alone or in admixture of two or more.

The dispersant is an organic substance, which is an organic compound having at least one acidic functional group or a salt thereof. The acidic functional group of the dispersant is an acidic, that is, a functional group having a proton donating property, for example, a phosphoric acid group, a phosphonic acid group, a sulfonic acid group, a sulfate group and a carboxyl group. The molecular weight of the dispersion medium is preferably 200 or more and 100,000 or less.

One kind of dispersant may be used alone, or two or more kinds of dispersants may be mixed and used. When the copper fine particle dispersion is a highly viscous paste, the need for a dispersant is reduced, but the dispersant is also used in such a case.

Then, as shown in FIG. 2B, the liquid film 3 is dried, and a film-like aggregate 4 (dry aggregate) is formed on the base material 1. For example, the liquid film 3 on the base material 1 is dried by warming the base material 1 having the liquid film 3 or blowing warm air on the liquid film 3.

Then, as shown in FIG. 2C, the agglomerates 4 on the base material 1 are immersed in the pretreatment liquid 5.

The pretreatment liquid 5 is an aqueous solution that dissolves a dispersant, and contains one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide, and p-toluenesulfonic acid as solutes. ..

Then, as shown in FIG. 2 (d), the aggregate 4 on the base material 1 is taken out from the pretreatment liquid 5, and as shown in FIG. 2 (e), the liquid 51 on the aggregate 4 is removed. The liquid. The component of the liquid 51 is mainly the pretreatment liquid 5. In the present embodiment, the liquid 51 on the aggregate 4 is removed by applying an air flow to the aggregate 4 on the base material 1. The liquid 51 may be removed by ejecting nitrogen gas onto the agglomerate 4. Even if the liquid 51 is dried, the water content in the liquid 51 only evaporates, so that the liquid 51 is not removed. The liquid 51 may be attached to the back surface of the base material 1 on which the aggregate 4 is not formed.

Then, the agglomerates 4 on the base material 1 are fired, and as shown in FIG. 2 (f), the conductive film 2 is formed (firing step). In this firing step, the agglomerates 4 are irradiated with light and light-fired. Light firing is performed in the atmosphere at room temperature. The light source used for light firing is, for example, a xenon lamp. A laser device may be used as the light source. In the light firing, the copper fine particles 31 in the aggregate 4 are necked (bonded between particles) and adhere to the base material 1.

In the firing step, the agglomerates 4 may be thermally fired. In the heat firing, the agglomerates 4 on the base material 1 are heated in an inert atmosphere or a reducing atmosphere. For example, the agglomerate 4 is heated and fired in a furnace in a nitrogen atmosphere. In the heat firing, the copper fine particles 31 in the agglomerate 4 are necked (bonded between particles) and adhere to the base material 1.

The energy for firing the agglomerates 4 is set so as not to damage the base material 1. In the conductive film forming method of the present embodiment, by having a step (pretreatment step) using the pretreatment liquid 5, firing of the agglomerates 4 is promoted, and the base material 1 requires less energy than in the case without the step. The above aggregate 4 is fired to form a conductive film 2 on the base material 1.

The promotion of firing of the agglomerates 4 in the conductive film forming method of the present embodiment will be described. Of the dispersants in the copper fine particle dispersion, some are bound to the surface of the copper fine particles 31, and most of them contribute to the dispersion of the copper fine particles 31 as a steric hindrance to particle aggregation in the dispersion medium. (See FIG. 2 (a)).

When the liquid film 3 made of the copper fine particle dispersion liquid is dried, the dispersion medium in the liquid film 3 evaporates, and the copper fine particles 31 and the dispersant remain on the base material 1. The copper fine particles 31 of the aggregate 4 adhere to the base material 1 by the dispersant which is an organic substance (see FIG. 2B).

Dispersants that do not contribute to the adhesion to the substrate 1, that is, most of the dispersants that contributed to the dispersion as steric hindrance in the dispersion medium, are unnecessary in the agglomerates 4 and hinder the firing of the agglomerates 4. It remains in the formed conductive film and increases the electrical resistance.

On the other hand, the dispersant bonded to the surface of the copper fine particles 31 is bound to such an extent that it does not flow out of the copper fine particles 31 even when washed with water due to its acidic functional group. Further, since the portion other than the acidic functional group of the dispersant, which is an organic substance, is more hydrophobic, it contributes to the fact that the dispersant does not flow out even when washed with water. The dispersant, which is an organic substance, flows out when washed with acetone or alcohol, which is an organic solvent.

The reason why the film-like aggregate 4 is not peeled off from the base material 1 by a normal handling operation is that the dispersant remains in the aggregate 4. Therefore, in order to promote the firing of the agglomerates 4 on the base material 1, the dispersant bonded to the surface of the copper fine particles 31 should be left as much as possible, and the other dispersants should be washed away as much as possible. The agglomerates 4 on the material 1 do not peel off, and the firing of the agglomerates 4 is promoted.

Since the dispersant is an organic substance having an acidic functional group, there may be an option of immersing the aggregate 4 in an aqueous solution of an acid or a basic compound to wash it away. However, it has been experimentally found that when a strong acid or a basic compound is used, the dispersant bonded to the surface of the copper fine particles 31 can also be removed. For example, when dilute sulfuric acid is used, it is difficult to control the time for immersing the aggregate 4 so that the copper fine particles 31 do not peel off from the base material 1. Further, when a weak alkali such as amine is used, there is a case where it remains in the conductive film 2 and promotes corrosion. The inventor of the present application has found the right acid by conducting a number of experiments. These are citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid.

The concentration of the acid in the pretreatment liquid 5 and the time for immersing the agglomerates 4 in the pretreatment liquid 5 are set so that the dispersant bonded to the surface of the copper fine particles 31 of the agglomerates 4 on the base material 1 is left as much as possible. It is desirable to set the other dispersants to be washed away. When the solute of the pretreatment liquid 5 is selected from citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid, such setting is facilitated.

In the aggregate 4 formed on the base material 1, the copper fine particles 31 are covered with the dispersant contained in the copper fine particle dispersion liquid. When the firing energy is sufficiently large, the dispersant covering the copper fine particles 31 is decomposed by the firing energy. However, when the firing energy is kept small, the dispersant covering the copper fine particles 31 is not decomposed by the firing energy and hinders the firing of the copper fine particles 31.

After the agglomerates 4 on the base material 1 are immersed in the pretreatment liquid 5, the liquid 51 adheres to the agglomerates 4 (see FIG. 2D). The liquid 51 is a pretreatment liquid 5 containing a dispersant that has flowed out of the agglomerate 4. Then, the liquid 51 on the aggregate 4 is removed (see FIG. 2E). That is, the dispersant is removed together with the pretreatment liquid 5.

According to the conductive film forming method according to the first embodiment, the dispersant contained in the agglomerates 4 and not contributing to the adhesion to the base material 1 is removed by using the pretreatment liquid 5, so that the agglomerates 4 The copper fine particles 31 are less likely to be hindered by the dispersant, the firing of the agglomerates 4 is promoted, and the electrical resistance is low on the substrate 1 with less firing energy than when the pretreatment liquid 5 is not used. The film 2 can be formed.

(Second embodiment)
The conductive film forming method according to the second embodiment of the present invention will be described with reference to FIGS. 1 and 3 (a) to 3 (g). As shown in FIG. 1, the conductive film forming method of the present embodiment is a method of forming the conductive film 2 on the base material 1. The conductive film forming method of the present embodiment has the same steps as those of the first embodiment, and after the step of immersing the agglomerates 4 on the base material 1 in the pretreatment liquid 5, the agglomerates 4 are immersed in water. It further has a step of dipping. In the present embodiment, the same reference numerals are given to the parts equivalent to those in the first embodiment. In the following description, detailed description of the same steps as in the first embodiment will be omitted.

As shown in FIG. 3A, first, a liquid film 3 made of a copper fine particle dispersion liquid is formed on the base material 1.

The copper fine particle dispersion liquid has a copper fine particle 31, a dispersion medium, and a dispersant for dispersing the copper fine particle 31 in the dispersion medium.

The dispersant is an organic compound having at least one acidic functional group or a salt thereof.

Then, as shown in FIG. 3B, the liquid film 3 is dried, and a film-like aggregate 4 (dry aggregate) is formed on the base material 1.

Then, as shown in FIG. 3C, the agglomerates 4 on the base material 1 are immersed in the pretreatment liquid 5.

The pretreatment liquid 5 is an aqueous solution that dissolves a dispersant, and contains one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide, and p-toluenesulfonic acid as solutes. ..

Then, as shown in FIG. 3D, the agglomerates 4 on the base material 1 are immersed in water 6.

Then, as shown in FIG. 3 (e), the aggregate 4 on the base material 1 is taken out from the water 6, and as shown in FIG. 3 (f), the liquid 61 on the aggregate 4 is removed. The component of the liquid 61 is substantially water 6. In the present embodiment, the liquid 61 on the agglomerates 4 is removed by applying an air stream to the agglomerates 4 on the base material 1. The liquid 61 may be removed by ejecting nitrogen gas onto the agglomerate 4. Even if the liquid 61 is dried, the water content in the liquid 61 only evaporates, so that the liquid 61 is not removed.

Then, the agglomerates 4 on the base material 1 are fired to form the conductive film 2 as shown in FIG. 3 (g) (firing step).

The energy for firing the agglomerates 4 is set so as not to damage the base material 1. In the conductive film forming method of the present embodiment, by having the steps using the pretreatment liquid 5 and the water 6, the firing of the agglomerates 4 is promoted, and the firing of the agglomerates 4 is promoted, and the substrate 1 is subjected to a smaller energy than in the case without these steps. The agglomerates 4 of the above are fired to form a conductive film 2 on the base material 1.

The promotion of firing of the agglomerates 4 in the conductive film forming method of the present embodiment will be described. This embodiment is the same as that of the first embodiment up to the step of immersing the aggregate 4 on the base material 1 in the pretreatment liquid 5 (see FIGS. 3A to 3C). After the agglomerates 4 on the base material 1 are immersed in the pretreatment liquid 5, the pretreatment liquid 5 is attached to the agglomerates 4. The pretreatment liquid 5 contains a dispersant that has flowed out of the agglomerates 4. Then, the agglomerate 4 to which the pretreatment liquid 5 is attached is immersed in water 6 (see FIG. 3D). The pretreatment liquid 5 adhering to the agglomerate 4 and the dispersant contained in the pretreatment liquid 5 diffuse into the water 6. Then, the aggregate 4 on the base material 1 is taken out from the water 6 (see FIG. 3 (e)), and the liquid 61 on the aggregate 4 is removed (see FIG. 3 (f)). That is, the agglomerates 4 immersed in the pretreatment liquid 5 are washed with water 6.

According to the conductive film forming method according to the second embodiment, the dispersant contained in the aggregate 4 and not contributing to the adhesion to the base material 1 is removed by using the pretreatment liquid 5 and the water 6. The copper fine particles 31 of the agglomerate 4 are less likely to be hindered by the dispersant, the firing of the agglomerate 4 is promoted, and the firing energy on the substrate 1 is smaller than that in the case where the pretreatment liquid 5 and water 6 are not used. It is possible to form a conductive film 2 having a low electrical resistance.

(Third Embodiment)
The conductive film forming method according to the third embodiment of the present invention will be described with reference to FIGS. 1 and 4 (a) to 4 (g). As shown in FIG. 1, the conductive film forming method of the present embodiment is a method of forming the conductive film 2 on the base material 1. The conductive film forming method of the present embodiment has the same steps as those of the first embodiment, and is different in that two-step pretreatment is performed using two types of pretreatment liquids. In the present embodiment, the same reference numerals are given to the parts equivalent to those in the first embodiment. In the following description, detailed description of the same steps as in the first embodiment will be omitted.

As shown in FIG. 4A, first, a liquid film 3 made of a copper fine particle dispersion liquid is formed on the base material 1.

The copper fine particle dispersion liquid has a copper fine particle 31, a dispersion medium, and a dispersant for dispersing the copper fine particle 31 in the dispersion medium.

The dispersant is an organic compound having at least one acidic functional group or a salt thereof.

Then, as shown in FIG. 4B, the liquid film 3 is dried, and a film-like aggregate 4 (dry aggregate) is formed on the base material 1.

Then, as shown in FIG. 4C, the agglomerates 4 on the base material 1 are immersed in the first pretreatment liquid 5.

The first pretreatment liquid 5 is an aqueous solution that dissolves a dispersant, and contains one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide, and p-toluenesulfonic acid as solutes. contains.

Then, as shown in FIG. 4D, the aggregate 4 on the base material 1 is immersed in the second pretreatment liquid 7.

The second pretreatment liquid 7 is an aqueous solution that dissolves the dispersant, and contains one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid as solutes. It is contained and its solute is different from that of the first pretreatment liquid 5. That is, the solute options of the second pretreatment liquid 7 include the same options as the first pretreatment liquid 5, and the solute selection is different from that of the first pretreatment liquid 5. Formaldehyde may be added to the solute options of the second pretreatment liquid 7.

Then, as shown in FIG. 4 (e), the aggregate 4 on the base material 1 is taken out from the second pretreatment liquid 7, and as shown in FIG. 4 (f), the liquid 71 on the aggregate 4 is removed. Will be removed. The component of the liquid 71 is substantially the second pretreatment liquid 7. In the present embodiment, the liquid 71 on the aggregate 4 is removed by applying an air flow to the aggregate 4 on the base material 1. The liquid 71 may be removed by ejecting nitrogen gas onto the agglomerate 4. Even if the liquid 71 is dried, the water content in the liquid 71 only evaporates, so that the liquid 71 is not removed.

Then, the aggregate 4 on the base material 1 is fired, and as shown in FIG. 4 (g), the conductive film 2 is formed (firing step).

The energy for firing the agglomerates 4 is set so as not to damage the base material 1. In the conductive film forming method of the present embodiment, by having the steps using the first pretreatment liquid 5 and the second pretreatment liquid 7, the firing of the agglomerates 4 is promoted, which is smaller than the case without those steps. The agglomerates 4 on the base material 1 are fired by energy, and the conductive film 2 is formed on the base material 1.

The promotion of firing of the agglomerates 4 in the conductive film forming method of the present embodiment will be described. This embodiment is the same as that of the first embodiment up to the step of immersing the aggregate 4 on the base material 1 in the first pretreatment liquid 5 (see FIGS. 4A to 4C). After the agglomerates 4 on the base material 1 are immersed in the first pretreatment liquid 5, the first pretreatment liquid 5 is attached to the agglomerates 4. The first pretreatment liquid 5 contains a dispersant that has flowed out of the agglomerates 4. Then, the aggregate 4 to which the first pretreatment liquid 5 is attached is immersed in the second pretreatment liquid 7 (see FIG. 4D). The dispersant contained in the first pretreatment liquid 5 and the first pretreatment liquid 5 adhering to the agglomerates 4 diffuses into the second pretreatment liquid 7. Further, the dispersant remaining in the aggregate 4 and not contributing to the adhesion to the base material 1 flows out into the second pretreatment liquid 7. Then, the aggregate 4 on the base material 1 is taken out from the second pretreatment liquid 7 (see FIG. 4 (e)), and the liquid 71 on the aggregate 4 is removed (see FIG. 4 (f)).

According to the conductive film forming method according to the third embodiment, the dispersant contained in the aggregate 4 and not contributing to the adhesion to the base material 1 uses the first pretreatment liquid 5 and the second pretreatment liquid 7. The copper fine particles 31 of the aggregate 4 are less likely to be hindered by the dispersant, the firing of the aggregate 4 is promoted, and the first pretreatment liquid 5 and the second pretreatment liquid 7 are used. It is possible to form the conductive film 2 having a low electric resistance on the base material 1 with a smaller firing energy than in the case where it is not used.

(Fourth Embodiment)
The conductive film forming method according to the fourth embodiment of the present invention will be described with reference to FIGS. 1 and 5 (a) to 5 (h). As shown in FIG. 1, the conductive film forming method of the present embodiment is a method of forming the conductive film 2 on the base material 1. The conductive film forming method of the present embodiment has the same steps as those of the third embodiment, and further includes a step of immersing the aggregate 4 in water after the two-step pretreatment. In the present embodiment, the same reference numerals are given to the parts equivalent to those in the third embodiment. In the following description, detailed description of the same steps as in the third embodiment will be omitted.

As shown in FIG. 5A, first, a liquid film 3 made of a copper fine particle dispersion liquid is formed on the base material 1.

The copper fine particle dispersion liquid has a copper fine particle 31, a dispersion medium, and a dispersant for dispersing the copper fine particle 31 in the dispersion medium.

The dispersant is an organic compound having at least one acidic functional group or a salt thereof.

Then, as shown in FIG. 5B, the liquid film 3 is dried, and a film-like aggregate 4 (dry aggregate) is formed on the base material 1.

Then, as shown in FIG. 5C, the agglomerates 4 on the base material 1 are immersed in the first pretreatment liquid 5.

The first pretreatment liquid 5 is an aqueous solution that dissolves a dispersant, and contains one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide, and p-toluenesulfonic acid as solutes. contains.

Then, as shown in FIG. 5D, the agglomerates 4 on the base material 1 are immersed in the second pretreatment liquid 7.

The second pretreatment liquid 7 is an aqueous solution that dissolves the dispersant, and contains one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid as solutes. It is contained and its solute is different from that of the first pretreatment liquid 5. That is, the solute options of the second pretreatment liquid 7 include the same options as the first pretreatment liquid 5, and the solute selection is different from that of the first pretreatment liquid 5. Formaldehyde may be added to the solute options of the second pretreatment liquid 7.

Then, as shown in FIG. 5 (e), the agglomerates 4 on the base material 1 are immersed in water 6.

Then, as shown in FIG. 5 (f), the aggregate 4 on the base material 1 is taken out from the water 6, and as shown in FIG. 5 (g), the liquid 62 on the aggregate 4 is removed. The component of the liquid 62 is approximately water 6. In the present embodiment, the liquid 62 on the agglomerates 4 is removed by applying an air stream to the agglomerates 4 on the base material 1. The liquid 62 may be removed by ejecting nitrogen gas onto the agglomerate 4. It should be noted that even if the liquid 62 is dried, the water content in the liquid 62 only evaporates, so that the liquid 62 is not removed.

Then, the agglomerates 4 on the base material 1 are fired to form the conductive film 2 as shown in FIG. 5 (h) (firing step).

The energy for firing the agglomerates 4 is set so as not to damage the base material 1. In the conductive film forming method of the present embodiment, by having the steps using the first pretreatment liquid 5, the second pretreatment liquid 7, and water 6, the firing of the agglomerates 4 is promoted, and there is no such step. The agglomerates 4 on the base material 1 are fired with less energy, and the conductive film 2 is formed on the base material 1.

The promotion of firing of the agglomerates 4 in the conductive film forming method of the present embodiment will be described. This embodiment is the same as the third embodiment up to the step of immersing the aggregate 4 on the base material 1 in the second pretreatment liquid 7 (see FIGS. 5A to 5D). After the agglomerates 4 on the base material 1 are immersed in the second pretreatment liquid 7, the second pretreatment liquid 7 is attached to the agglomerates 4. The second pretreatment liquid 7 contains a dispersant that has flowed out of the aggregate 4. Then, the agglomerate 4 to which the second pretreatment liquid 7 is attached is immersed in water 6 (see FIG. 5 (e)). The second pretreatment liquid 7 adhering to the agglomerate 4 and the dispersant contained in the second pretreatment liquid diffuse into the water 6. Then, the aggregate 4 on the base material 1 is taken out from the water 6 (see FIG. 3 (e)), and the liquid 62 on the aggregate 4 is removed (see FIG. 3 (f)). That is, the agglomerates 4 immersed in the second pretreatment liquid 7 are washed with water 6.

According to the conductive film forming method according to the fourth embodiment, the dispersants contained in the aggregate 4 and not contributing to the adhesion to the base material 1 are the first pretreatment liquid 5, the second pretreatment liquid 7, and water. Since it is removed using No. 6, the copper fine particles 31 of the agglomerate 4 are less likely to be hindered by the dispersant, the firing of the agglomerate 4 is promoted, and the first pretreatment liquid 5 and the second pretreatment liquid are removed. A conductive film 2 having a low electric resistance can be formed on the base material 1 with a smaller firing energy than when 7 and water 6 are not used.

The selection of the first to fourth embodiments described above and the selection of the pretreatment liquid (pretreatment liquid 5, the first pretreatment liquid 5 and the second pretreatment liquid 7) are appropriately performed. If the firing energy is too small, the conductive film 2 is not formed, and if it is too large, the base material 1 is damaged. The electrical resistance of the conductive film 2 is affected by the firing energy, the type of pretreatment liquid, and the presence or absence of a step of immersing in water. The electric resistance of the conductive film 2 should be low. Therefore, the index for selection is the electrical resistance of the conductive film 2 to the firing energy allowed for the substrate 1. When there are a plurality of options for obtaining the conductivity (reciprocal of electrical resistance) required for the conductive film 2, a simpler step (embodiment) is desirable. In the case of thermal firing, the higher the firing temperature, the greater the firing energy applied to the aggregate 4, and in the case of light firing, the greater the irradiation energy, the greater the firing energy applied to the aggregate 4.

As an example of the present invention, a conductive film was formed on a substrate by using a conductive film forming method having a step using a pretreatment liquid. Further, as a comparative example, it was tested whether or not a conductive film was formed on the substrate with the same firing energy (firing temperature or irradiation energy) as in the examples without using the pretreatment liquid.

A copper fine particle dispersion (copper nanoink) having copper fine particles, a dispersion medium, and a dispersant was prepared. Copper fine particles (copper nanoparticles) having a median diameter (D50) of about 40 nm were used. The concentration of the copper fine particles was 40% by mass (mass%). Diethylene glycol monobutyl ether was used as the dispersion medium. The dispersion medium does not affect the firing of the agglomerates because the liquid film made of the copper fine particle dispersion liquid is dried and does not remain in the agglomerates. The dispersant was added in an amount of 8% by mass based on the weight of the copper fine particles. As the dispersant, a phosphoric acid ester (manufactured by BYK-Chemie, trade name "DISPERBYK (registered trademark) -111") was used. The dispersant having an acidic functional group is not limited to a phosphoric acid ester because it dissolves in a pretreatment liquid containing an acid. As a base material, soda glass having a thickness of 30 mm square and a thickness of 0.5 mm was used.

A copper fine particle dispersion was applied to this substrate by a spin coating method to form a liquid film having a film thickness of 1.0 μm. Then, the base material was placed on a hot plate at 80 ° C., the liquid film was dried, and a film-like aggregate was formed on the base material. The dispersion medium evaporates and the agglomerates have copper microparticles and a dispersant.

A 2% by weight aqueous citric acid solution was used as the pretreatment liquid. The base material having the agglomerates was immersed in the pretreatment liquid for 15 seconds.

Then, the base material having the agglomerates was taken out from the pretreatment liquid and immersed in water for 10 seconds. Then, the base material having the agglomerates was taken out from the water, and nitrogen gas was blown toward the agglomerates to remove the liquid on the agglomerates.

Then, the agglomerates on the substrate were heat-fired. An infrared heating type furnace was used for the heat firing. A substrate on which aggregates were formed was placed in a furnace, the temperature was raised at 250 ° C./min in a nitrogen atmosphere, and the firing temperature was maintained for 10 minutes. The firing temperature was set to three conditions of 150 ° C., 180 ° C., and 200 ° C.

At any firing temperature, a conductive film (copper film) was formed on the substrate. The sheet resistance (electrical resistance) of the formed conductive film was measured by the four-probe method. Sheet resistance is specified in Japanese Industrial Standard JIS C 5600: 2006 "Basic Terminology of Electrical Technology". When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 79 kΩ / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 7Ω / □. When the firing temperature was 200 ° C., the sheet resistance of the conductive film was 0.4 kΩ / □. The higher the firing temperature, the lower the sheet resistance of the conductive film.

A 2% by weight aqueous solution of formic acid was used as the pretreatment liquid. In the pretreatment, the base material on which the agglomerates were formed was immersed in the pretreatment liquid for 15 seconds. Then, the base material having the agglomerates was taken out from the pretreatment liquid, and nitrogen gas was blown toward the agglomerates to remove the liquid on the agglomerates. That is, the step of immersing in water was not carried out. Other conditions were the same as in Example 1.

At any firing temperature, a conductive film (copper film) was formed on the substrate. When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 48 kΩ / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 17Ω / □. When the firing temperature was 200 ° C., the sheet resistance of the conductive film was 36 Ω / □. The difference in sheet resistance of the conductive film when the firing temperature is 180 ° C. and 200 ° C. is estimated to be within the range of variation. Since there is little merit of setting the firing temperature to 200 ° C., the case where the firing temperature is 200 ° C. is omitted in some of the following examples.

A 2% by weight aqueous solution of oxalic acid was used as the pretreatment liquid. Other conditions were the same as in Example 2. That is, the step of immersing in water was not carried out.

At any firing temperature, a conductive film (copper film) was formed on the substrate. When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 963 Ω / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 1.4Ω / □. When the firing temperature was 200 ° C., the sheet resistance of the conductive film was 1.0 Ω / □. The difference in sheet resistance of the conductive film when the firing temperature was 180 ° C. and 200 ° C. was a slight difference. When the calcination temperature is 180 ° C., it is presumed that the agglomerates are sufficiently calcinated.

Two-step pretreatment was performed. A 2% by weight aqueous citric acid solution was used as the first pretreatment liquid. A 2% by weight aqueous solution of formic acid was used as the second pretreatment liquid. In the pretreatment, the base material on which the agglomerates were formed was immersed in the first pretreatment liquid for 15 seconds. Then, the base material having the aggregate was taken out from the first pretreatment liquid and immersed in the second pretreatment liquid for 15 seconds. Then, the base material having the agglomerates was taken out from the second pretreatment liquid, and nitrogen gas was blown toward the agglomerates to remove the liquid on the agglomerates. Other conditions were the same as in Example 2. That is, the step of immersing in water was not carried out.

At any firing temperature, a conductive film (copper film) was formed on the substrate. When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 59Ω / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 0.9Ω / □. When the firing temperature was 200 ° C., the sheet resistance of the conductive film was 2Ω / □. Compared with Example 2 (one-step pretreatment), the sheet resistance of the conductive film was lowered by performing the two-step pretreatment.

Two-step pretreatment was performed. A 2% by weight aqueous citric acid solution was used as the first pretreatment liquid. A 2% by weight aqueous solution of oxalic acid was used as the second pretreatment liquid. Other conditions were the same as in Example 4.

At any firing temperature, a conductive film (copper film) was formed on the substrate. When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 2.3 kΩ / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 0.8 Ω / □. When the firing temperature was 200 ° C., the sheet resistance of the conductive film was 0.7Ω / □.

The pretreatment was set to one stage. As the pretreatment liquid, an aqueous solution in which 1% by weight of citric acid and 1% by weight of formic acid were mixed was used. Other conditions were the same as in Example 2.

When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 6 kΩ / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 26 kΩ / □. The difference in sheet resistance of the conductive film when the firing temperature is 150 ° C. and 180 ° C. is estimated to be within the range of variation.

As the pretreatment liquid, an aqueous solution in which 1% by weight of citric acid and 1% by weight of oxalic acid were mixed was used. Other conditions were the same as in Example 6.

When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 1 to 400 Ω / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 0.9Ω / □. When the firing temperature was 200 ° C., the sheet resistance of the conductive film was 0.7Ω / □.

As the pretreatment liquid, an aqueous solution in which 0.7% by weight citric acid, 0.7% by weight formic acid, and 0.7% by weight oxalic acid were mixed was used. Other conditions were the same as in Example 6.

When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 3Ω / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 0.9Ω / □.

As the pretreatment liquid, an aqueous solution in which 1% by weight of formic acid and 1% by weight of oxalic acid were mixed was used. Other conditions were the same as in Example 6.

When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 2Ω / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 7Ω / □.

As in Example 3, a 2% by weight aqueous oxalic acid solution was used as the pretreatment liquid. Other conditions were the same as in Example 1. That is, unlike Example 3, the step of immersing in water was carried out.

When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 13Ω / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 1.5Ω / □. When the firing temperature was 200 ° C., the sheet resistance of the conductive film was 0.8 Ω / □. Compared with Example 3, when the firing temperature was 150 ° C., the sheet resistance of the conductive film was lowered by the step of immersing in water. When the firing temperatures were 180 ° C. and 200 ° C., the sheet resistance of the conductive film was equivalent to that of Example 3. When the firing temperatures are 180 ° C. and 200 ° C., it is presumed that the agglomerates were sufficiently fired even without the step of immersing in water.

As in Example 6, an aqueous solution in which 1% by weight of citric acid and 1% by weight of formic acid were mixed was used as the pretreatment liquid. Other conditions were the same as in Example 1. That is, unlike Example 6, the step of immersing in water was carried out.

When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 0.7 to 7.6 Ω / □. No significant difference in sheet resistance of the conductive film was observed by the step of immersing in water as compared with Example 6. It is presumed that the effect of the pretreatment liquid was sufficient.

As in Example 7, an aqueous solution in which 1% by weight of citric acid and 1% by weight of oxalic acid were mixed was used as the pretreatment liquid. Other conditions were the same as in Example 1. That is, unlike Example 7, the step of immersing in water was carried out.

When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 12Ω / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 0.8 Ω / □. When the firing temperature was 200 ° C., the sheet resistance of the conductive film was 0.5Ω / □. Compared with Example 7, the sheet resistance of the conductive film was lowered by the step of immersing in water.

As in Example 8, an aqueous solution in which 0.7% by weight citric acid, 0.7% by weight formic acid, and 0.7% by weight oxalic acid were mixed was used as the pretreatment liquid. Other conditions were the same as in Example 1. That is, unlike Example 8, the step of immersing in water was carried out.

When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 69Ω / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 0.9Ω / □. No significant difference in sheet resistance of the conductive film was observed by the step of immersing in water as compared with Example 8. It is presumed that the effect of the pretreatment liquid was sufficient.

As in Example 9, an aqueous solution in which 1% by weight of formic acid and 1% by weight of oxalic acid were mixed was used as the pretreatment liquid. Other conditions were the same as in Example 1. That is, unlike Example 9, the step of immersing in water was carried out.

When the firing temperature was 150 ° C., the sheet resistance of the conductive film was 6Ω / □. When the firing temperature was 180 ° C., the sheet resistance of the conductive film was 1.0 Ω / □. No significant difference in sheet resistance of the conductive film was observed by the step of immersing in water as compared with Example 9. It is presumed that the effect of the pretreatment liquid was sufficient.

(Comparative Example 1)
Neither the step of immersing in the pretreatment liquid nor the step of immersing in water was carried out. Other conditions were the same as in Example 1. When the firing temperature was 150 ° C., 180 ° C., and 200 ° C., no conductive film was formed. When the firing temperature was further increased, the sheet resistance of the conductive film was on the order of kΩ / □ at 250 ° C. and 8 to 9Ω / □ at 300 ° C. It was found that a high temperature, that is, a large firing energy is required for firing the agglomerates without the step of using the pretreatment liquid.

As a base material, a 30 mm square, 50 μm thick PET (polyethylene terephthalate) film (manufactured by Toray Industries, Inc., trade name “Lumilar® T60”) was used instead of soda glass. A copper fine particle dispersion was applied to this base material to form a liquid film having a film thickness of 0.5 μm. The firing of the agglomerates was light firing instead of thermal firing. A xenon flash lamp was used as a light source for light firing. The irradiation time was 1.0 ms, and the irradiation energy was 1.2 J / cm ² , 1.4 J / cm ² , and 1.7 J / cm ² . Other conditions were the same as in Example 1. That is, a step of immersing in water using a 2% by weight aqueous citric acid solution as the pretreatment liquid was also carried out.

In the case of any irradiation energy, a conductive film (copper film) was formed on the base material. When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 30 kΩ / □. When the irradiation energy was 1.4 J / cm ² , the sheet resistance of the conductive film was 0.4 Ω / □. When the irradiation energy was 1.7 J / cm ² , the sheet resistance of the conductive film was 0.3 Ω / □.

A 2% by weight aqueous solution of formic acid was used as the pretreatment liquid. The step of immersing in water was not carried out. Other conditions were the same as in Example 15.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 0.6 Ω / □. When the irradiation energy was 1.4 J / cm ² , the sheet resistance of the conductive film was 0.4 Ω / □.

A 2% by weight aqueous solution of oxalic acid was used as the pretreatment liquid. Other conditions were the same as in Example 16. That is, the step of immersing in water was not carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 80 Ω / □. When the irradiation energy was 1.4 J / cm ² , the sheet resistance of the conductive film was 0.5 Ω / □. When the irradiation energy was 1.7 J / cm ² , the sheet resistance of the conductive film was 0.4 Ω / □.

As the pretreatment liquid, a 2% by weight aqueous solution of adipic acid dihydrazide was used. Other conditions were the same as in Example 16. That is, the step of immersing in water was not carried out.

When the irradiation energy was 1.2 J / cm ^2, no conductive film was formed. That is, the irradiation energy was insufficient. When the irradiation energy was 1.7 J / cm ² , the sheet resistance of the conductive film was 1.1 Ω / □.

Two-step pretreatment was performed. A 2% by weight aqueous citric acid solution was used as the first pretreatment liquid. A 2% by weight aqueous solution of formic acid was used as the second pretreatment liquid. Other conditions were the same as in Example 18. That is, the step of immersing in water was not carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 2.4 Ω / □. Compared with Example 16 (one-step pretreatment), the sheet resistance of the conductive film was lowered by performing the two-step pretreatment.

Two-step pretreatment was performed. A 2% by weight aqueous citric acid solution was used as the first pretreatment liquid. A 2% by weight aqueous solution of oxalic acid was used as the second pretreatment liquid. Other conditions were the same as in Example 19.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 26 Ω / □. Compared with Example 17 (one-step pretreatment), the sheet resistance of the conductive film was lowered by performing the two-step pretreatment.

Two-step pretreatment was performed. A 2% by weight aqueous citric acid solution was used as the first pretreatment liquid. As the second pretreatment liquid, a 2% by weight aqueous solution of adipic acid dihydrazide was used. Other conditions were the same as in Example 19.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 48 kΩ / □. A conductive film was formed with a small irradiation energy of ^{1.2 J / cm 2 as} compared with Example 18 (one-step pretreatment).

The pretreatment was set to one stage. As the pretreatment liquid, an aqueous solution in which 1% by weight of citric acid and 1% by weight of formic acid were mixed was used. Other conditions were the same as in Example 16. That is, the step of immersing in water was not carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 20 kΩ / □.

As the pretreatment liquid, an aqueous solution in which 1% by weight of citric acid and 1% by weight of oxalic acid were mixed was used. Other conditions were the same as in Example 22.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 74 kΩ / □.

As the pretreatment liquid, an aqueous solution in which 0.7% by weight citric acid, 0.7% by weight formic acid, and 0.7% by weight oxalic acid were mixed was used. Other conditions were the same as in Example 22.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 47 kΩ / □.

As the pretreatment liquid, an aqueous solution in which 1% by weight of formic acid and 1% by weight of oxalic acid were mixed was used. Other conditions were the same as in Example 22.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 25 kΩ / □.

As in Example 16, a 2% by weight aqueous solution of formic acid was used as the pretreatment liquid. Other conditions were the same as in Example 15. That is, unlike Example 16, the step of immersing in water was carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 0.8 Ω / □. Compared with Example 16, the sheet resistance of the conductive film was lowered by the step of immersing in water.

As in Example 17, a 2% by weight aqueous solution of oxalic acid was used as the pretreatment liquid. Other conditions were the same as in Example 15. That is, unlike Example 17, the step of immersing in water was carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 1.2 Ω / □. Compared with Example 17, the sheet resistance of the conductive film was lowered by the step of immersing in water.

Two-step pretreatment was performed. Similar to Example 20, a 2% by weight aqueous citric acid solution was used as the first pretreatment liquid. A 2% by weight aqueous solution of oxalic acid was used as the second pretreatment liquid. Other conditions were the same as in Example 15. That is, unlike Example 20, the step of immersing in water was carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 23 Ω / □. Compared with Example 20, the sheet resistance of the conductive film was slightly lowered by the step of immersing in water.

The pretreatment was set to one stage. As in Example 22, an aqueous solution in which 1% by weight of citric acid and 1% by weight of formic acid were mixed was used as the pretreatment liquid. Other conditions were the same as in Example 15. That is, unlike Example 22, the step of immersing in water was carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 7 kΩ / □. Compared with Example 22, the sheet resistance of the conductive film was lowered by the step of immersing in water.

As in Example 23, an aqueous solution in which 1% by weight of citric acid and 1% by weight of oxalic acid were mixed was used as the pretreatment liquid. Other conditions were the same as in Example 15. That is, unlike Example 23, the step of immersing in water was carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 4 Ω / □. Compared with Example 23, the sheet resistance of the conductive film was lowered by the step of immersing in water.

As in Example 24, an aqueous solution containing 0.7% by weight of citric acid, 0.7% by weight of formic acid, and 0.7% by weight of oxalic acid was used as the pretreatment liquid. Other conditions were the same as in Example 15. That is, unlike Example 24, the step of immersing in water was carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 0.9 Ω / □. Compared with Example 24, the sheet resistance of the conductive film was lowered by the step of immersing in water.

As in Example 25, an aqueous solution in which 1% by weight of formic acid and 1% by weight of oxalic acid were mixed was used as the pretreatment liquid. Other conditions were the same as in Example 15. That is, unlike Example 25, the step of immersing in water was carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 0.9 Ω / □. Compared with Example 25, the sheet resistance of the conductive film was lowered by the step of immersing in water.

A 2 wt% p-toluenesulfonic acid aqueous solution was used as the pretreatment liquid. Other conditions were the same as in Example 16. That is, the step of immersing in water was not carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 580 kΩ / □.

Two-step pretreatment was performed. A 2% by weight aqueous citric acid solution was used as the first pretreatment liquid. A 2% by weight aqueous formaldehyde solution was used as the second pretreatment liquid. Other conditions were the same as in Example 19. That is, the step of immersing in water was not carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 26 kΩ / □. Compared with Example 19 (the second pretreatment liquid was an aqueous solution of formic acid) and Example 20 (the second pretreatment liquid was an aqueous solution of oxalic acid), the sheet resistance of the conductive film was higher.

Two-step pretreatment was performed. A 2% by weight aqueous citric acid solution was used as the first pretreatment liquid. A 2% by weight p-toluenesulfonic acid aqueous solution was used as the second pretreatment liquid. Other conditions were the same as in Example 19. That is, the step of immersing in water was not carried out.

When the irradiation energy was 1.2 J / cm ² , the sheet resistance of the conductive film was 27 kΩ / □. Compared with Example 19 (the second pretreatment liquid was an aqueous solution of formic acid) and Example 20 (the second pretreatment liquid was an aqueous solution of oxalic acid), the sheet resistance of the conductive film was higher.

(Comparative Example 2)
Neither the step of immersing in the pretreatment liquid nor the step of immersing in water was carried out. Other conditions were the same as in Example 15. Irradiation energy ^{1.2J / cm 2, 1.4J / cm} 2, the case of 1.7 J / cm ^2, the conductive film was not formed. When the irradiation energy was further increased, the PET film as a base material was damaged at ^{2.0 and J / cm 2.} Without the step of using the pretreatment solution, the agglomerates could not be fired with a small amount of energy that did not damage the PET film.

The present invention is not limited to the configuration of the above embodiment, and various modifications can be made without changing the gist of the invention. For example, in the third embodiment and the fourth embodiment, after taking out from the first pretreatment liquid, the liquid on the aggregate may be removed and then immersed in the second pretreatment liquid. Further, in the step of immersing the aggregate on the base material in the pretreatment liquid, the pretreatment liquid may be applied or sprayed to the agglomerate to bring the aggregate into a state of being immersed in the pretreatment liquid (first pretreatment). The same applies to the treatment liquid and the second pretreatment liquid).

1 Base material 2 Conductive film 3 Liquid film 31 Copper fine particles 4 Aggregates 5 Pretreatment liquid, 1st pretreatment liquid 6 Water 7 2nd pretreatment liquid

Claims (4)

A conductive film forming method for forming a conductive film on a substrate.
A process of forming a liquid film composed of a copper fine particle dispersion on a substrate, and
A step of drying the liquid film to form a film-like aggregate on the base material, and
The step of immersing the aggregate on the base material in the pretreatment liquid and
The process of removing the liquid on the aggregate and
A step of calcining the aggregate on the base material to form a conductive film is provided in this order.
The copper fine particle dispersion liquid has copper fine particles, a dispersion medium, and a dispersant for dispersing the copper fine particles in the dispersion medium.
The dispersant is an organic compound having at least one acidic functional group or a salt thereof.
The pretreatment liquid is an aqueous solution that dissolves the dispersant, and contains one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid as solutes. A method for forming a conductive film, which comprises the above. A conductive film forming method for forming a conductive film on a substrate.
A process of forming a liquid film composed of a copper fine particle dispersion on a substrate, and
A step of drying the liquid film to form a film-like aggregate on the base material, and
The step of immersing the aggregate on the base material in the pretreatment liquid and
The step of immersing the aggregate on the substrate in water and
The process of removing the liquid on the aggregate and
A step of calcining the aggregate on the base material to form a conductive film is provided in this order.
The copper fine particle dispersion liquid has copper fine particles, a dispersion medium, and a dispersant for dispersing the copper fine particles in the dispersion medium.
The dispersant is an organic compound having at least one acidic functional group or a salt thereof.
The pretreatment liquid is an aqueous solution that dissolves the dispersant, and contains one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid as solutes. A method for forming a conductive film, which comprises the above. A conductive film forming method for forming a conductive film on a substrate.
A process of forming a liquid film composed of a copper fine particle dispersion on a substrate, and
A step of drying the liquid film to form a film-like aggregate on the base material, and
The step of immersing the aggregate on the base material in the first pretreatment liquid and
A step of immersing the aggregate on the base material in the second pretreatment liquid, and
The process of removing the liquid on the aggregate and
A step of calcining the aggregate on the base material to form a conductive film is provided in this order.
The copper fine particle dispersion liquid has copper fine particles, a dispersion medium, and a dispersant for dispersing the copper fine particles in the dispersion medium.
The dispersant is an organic compound having at least one acidic functional group or a salt thereof.
The first pretreatment liquid is an aqueous solution that dissolves the dispersant, and is a solute of one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid. Contains as
The second pretreatment liquid is an aqueous solution that dissolves the dispersant, and is a solute of one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipate dihydrazide and p-toluenesulfonic acid. A method for forming a conductive film, which is contained as a solute and whose solute is different from that of the first pretreatment liquid. A conductive film forming method for forming a conductive film on a substrate.
A process of forming a liquid film composed of a copper fine particle dispersion on a substrate, and
A step of drying the liquid film to form a film-like aggregate on the base material, and
The step of immersing the aggregate on the base material in the first pretreatment liquid and
A step of immersing the aggregate on the base material in the second pretreatment liquid, and
The step of immersing the aggregate on the substrate in water and
The process of removing the liquid on the aggregate and
A step of calcining the aggregate on the base material to form a conductive film is provided in this order.
The copper fine particle dispersion liquid has copper fine particles, a dispersion medium, and a dispersant for dispersing the copper fine particles in the dispersion medium.
The dispersant is an organic compound having at least one acidic functional group or a salt thereof.
The first pretreatment liquid is an aqueous solution that dissolves the dispersant, and is a solute of one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipic acid dihydrazide and p-toluenesulfonic acid. Contains as
The second pretreatment liquid is an aqueous solution that dissolves the dispersant, and is a solute of one or more acids selected from the group consisting of citric acid, formic acid, oxalic acid, adipate dihydrazide and p-toluenesulfonic acid. A method for forming a conductive film, which is contained as a solute and whose solute is different from that of the first pretreatment liquid.

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