JP6079434B2 - Conductive copper ink composition - Google Patents

Description

  The present invention relates to a conductive copper ink composition. More specifically, the present invention relates to a conductive copper ink composition for forming a copper film by heating after coating or printing.

  Conventionally, as a method of forming a copper electrode and a copper wiring on a substrate, an electronic component, etc., after plating copper on the substrate, an electronic component, masking this with a photoresist or the like, and etching away the unmasked copper Have been widely used. However, this method is suitable for forming highly conductive fine wiring, but has a problem that the number of processes is large and copper resources are wasted.

  In addition to the above method, a method of forming an electrode or an electric wiring by heating after applying or printing a conductive ink on a substrate is also widely used. In this method, the number of processes is small, and metal resources are also effectively used. As metals, silver, aluminum and the like have been put into practical use and widely used. Many of these inks use fine metal particles, and the fine particles are aggregated and fused by heating to form electrodes and wiring. Inks have also been developed that use copper, a metal resource richer than silver. For example, an ink containing copper-based nanoparticles and a thermosetting resin (see Patent Documents 1 and 2), an ink containing copper nanoparticles and silver nanoparticles (see Patent Document 3), metallic copper particles, copper formate, and alkanolamine. Ink is included (see Patent Documents 4 and 5). These inks contain fine particles of metal such as copper, but the fine particles of metal are expensive and have a problem in industrial use in large quantities.

  In view of this, inks using an inexpensive copper salt that becomes a metal by heating in an inert gas or in hydrogen have been proposed. A method of heating an ink containing organic acid copper and a polyhydric alcohol to 165 ° C. or more (see Patent Documents 6, 7, 8, 9), and a method of heating an ink composed of alkanolamine and copper formate to 100 to 400 ° C. (patent Many proposals such as References 10 and 11) have been made.

  However, these inks require a high temperature of 165 ° C. or higher in an inert gas to convert the copper salt into metallic copper, and hydrogen is required at a low temperature of 150 ° C. or lower. A high temperature of 165 ° C. or higher is not suitable for a resin substrate such as PET that is widely used, and the use of hydrogen is disadvantageous industrially because a special explosion-proof device is required.

  Therefore, 150 ° C. can be applied to a resin substrate such as PET in an inert gas such as nitrogen without using expensive copper metal particles, using an inexpensive raw material such as a copper salt, and without using hydrogen. Development of an ink that forms a metal film by the following heating is desired.

JP 2011-142052 A JP 2009-99561 A JP 2011-44509 A JP 2012-131894 A JP 2012-131895 A JP-A-1-168865 JP-A-1-168866 JP-A-1-168867 Japanese Patent Laid-Open No. 1-168868 JP 2010-242118 A JP 2012-112022 A

  The present invention has been made in view of the above-described problems, and its purpose is to form a copper metal film even when heated at 150 ° C. or less in an inert gas such as nitrogen using an inexpensive copper salt as a raw material. And it is providing the electroconductive copper ink composition from which the film | membrane becomes high electroconductivity (low resistance).

  As a result of intensive studies on the ink composition for forming a copper film, the present inventor has found that an ink composition comprising copper formate, dimethylaminoethanol, formic acid, and water has a metallic copper film even when baked at 150 ° C. under nitrogen. The inventors have found a new fact that the film can be formed and the film has high conductivity (low resistance), and has completed the present invention.

  That is, the present invention is a conductive copper ink composition as shown below.

  [1] A conductive copper ink composition containing copper formate, dimethylaminoethanol, formic acid and water.

  [2] The conductive copper ink composition according to [1], further including a polyvalent carboxylic acid.

  [3] The conductive copper ink composition according to [2], wherein the polyvalent carboxylic acid is at least one selected from the group consisting of oxalic acid, citric acid, malic acid, tartaric acid, malonic acid, and succinic acid.

  [4] The conductive copper ink composition according to any one of [1] to [3], further including cyclohexylamines.

  [5] The conductive copper ink composition according to [4], wherein the cyclohexylamine is at least one selected from the group consisting of cyclohexylamine, dimethylcyclohexylamine, and diaminocyclohexane.

  [6] The conductive copper ink composition according to any one of [1] to [5], wherein the amount of copper formate in the conductive copper ink composition is 1 to 40% by weight.

  [7] The conductive copper ink composition according to any one of the above [1] to [6], wherein the amount of dimethylaminoethanol exceeds 5 mol times with respect to copper formate.

  [8] The conductive copper ink composition according to any one of [1] to [7], wherein the amount of formic acid is equal to or less than an equimolar amount of dimethylaminoethanol.

  [9] The conductive copper ink composition according to any one of [1] to [8], wherein the amount of water is 4 mol times or more and 25 mol times or less of copper formate.

  [10] The conductive copper ink composition according to any one of [1] to [9], wherein the conductive copper ink is heated to form a metallic copper film at an oxygen concentration of 10% or less.

  [11] The conductive copper ink composition according to any one of the above [1] to [10], which is heated to a temperature of 100 to 160 ° C. to form a metallic copper film after being applied to the substrate.

  The conductive copper ink composition of the present invention is extremely useful industrially because it can form a wiring with few steps and can form a fine wiring at a low temperature in the production of an electronic device such as a printed wiring board and a solar cell. .

  The essential components of the conductive copper ink composition of the present invention are copper formate, dimethylaminoethanol, formic acid and water.

  In the conductive copper ink composition of the present invention, copper formate generates metallic copper by heating. The copper formate to be used is not particularly limited, and copper formate (I) and copper formate (II) which are generally distributed industrially can be used. For copper formate, an anhydrous salt or a hydrated salt may be used.

  In the conductive copper ink composition of the present invention, dimethylaminoethanol is used to decompose copper formate at a low temperature. A mixture of dimethylaminoethanol and copper formate is stable at room temperature and easily decomposes at 150 ° C. or lower when heated. Moreover, dimethylaminoethanol having a boiling point as low as 133 ° C. is volatilized even at a temperature of 150 ° C. or lower and does not remain in the metal copper film. There is no restriction | limiting in particular in the dimethylamino ethanol to be used, The cheap product currently distribute | circulated industrially can be used.

  In the conductive copper ink composition of the present invention, formic acid acts as a regulator of the volatilization rate of dimethylaminoethanol and a reducing agent of the copper salt. There is no restriction | limiting in particular in the formic acid to be used, The thing generally distribute | circulated industrially can be used.

  In the conductive copper ink composition of the present invention, water acts as a dimethylaminoethanol volatilization rate, a copper salt reduction rate regulator, and a copper salt solubilizer.

  In the conductive copper ink composition of the present invention, a polyvalent carboxylic acid can be contained. In the conductive copper ink composition of the present invention, the polyvalent carboxylic acid means a carboxylic acid having two or more carboxyl groups. By containing the polyvalent carboxylic acid, the metal copper film can be made dense and the adhesion to the substrate can be improved. Examples of the polyvalent carboxylic acid that can be contained include oxalic acid, citric acid, malic acid, tartaric acid, malonic acid, succinic acid, and the like, and oxalic acid and / or citric acid from the viewpoint of the conductivity of the resulting copper metal film. Acid is particularly preferred.

  The conductive copper ink composition of the present invention can contain cyclohexylamines. By containing cyclohexylamines, a uniform film can be formed on a resin substrate such as polyethylene terephthalate (PET). Examples of cyclohexylamines include cyclohexylamine, dimethylcyclohexylamine, diethylcyclohexylamine, and dicyclohexylamine. Among these, cyclohexylamine and dimethylcyclohexylamine are particularly preferable. Cyclohexylamine and dimethylcyclohexylamine are easily volatilized by heating and do not remain in the formed metallic copper film.

  In the conductive copper ink composition of the present invention, the amount of copper formate is preferably 1 to 40% by weight, more preferably 5 to 30% by weight, and particularly preferably 8 to 20% by weight from the viewpoint of the viscosity of the obtained ink. .

  In the conductive copper ink composition of the present invention, the amount of dimethylaminoethanol is preferably more than 5 mole times with respect to copper formate from the viewpoint of the stability of the resulting ink, more than 5 mole times and more than 20 mole times. The following are particularly preferred:

  In the conductive copper ink composition of the present invention, the amount of formic acid is preferably equal to or less than an equimolar amount of dimethylaminoethanol from the viewpoint of uniform application of the resulting ink to a resin substrate, and is preferably less than 0.1 mol per 1 mol of dimethylaminoethanol. 15-0.7 mol is preferable.

  In the conductive copper ink composition of the present invention, the amount of water is preferably 4 mol times or more and 25 mol times or less, more preferably 4 mol times or more of copper formate from the viewpoint of uniform application of the obtained ink to the resin substrate. 20 mol times or less are preferable.

  In the conductive copper ink composition of the present invention, when a polyvalent carboxylic acid is contained, the content is made 0.1% by weight or less of the ink composition from the viewpoint of the conductivity of the obtained metallic copper film. Is preferred.

  In the conductive copper ink composition of the present invention, when cyclohexylamines are added, the molar amount is preferably equal to or less than that of dimethylaminoethanol from the viewpoint of the heating temperature when forming the obtained metal copper film.

  The conductive copper ink composition of the present invention may contain alcohol. Alcohol can adjust the viscosity of the conductive ink, can suppress the volatilization of amine, and can improve the adhesion to the substrate. The alcohol is not particularly limited, and those generally added to the ink can be used. For example, monoalcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol, octanol, cyclohexanol, terpineol; ethylene glycol, propylene glycol And polyhydric alcohols such as butanediol, glycerin and sorbitol; ether alcohols such as diethylene glycol, dipropylene glycol, methoxyethanol, ethoxyethanol and butoxyethanol;

  The conductive copper ink composition of the present invention can contain additives such as anticorrosives, solvents, thickeners and surfactants. As these additives, those commonly used can be used, and there is no particular limitation. Anticorrosives are effective in suppressing copper oxidation after forming a copper film and copper wiring, and solvents, thickeners, and surfactants can improve ink application and stability.

  After apply | coating the electroconductive copper ink composition of this invention to a board | substrate, a metal copper film | membrane can be formed by heating. There is no restriction | limiting in particular in the board | substrate to be used, For example, resin, ceramics, glass, paper, etc., such as PET, polyethylene naphthalate (PEN), polycarbonate (PC), a polyimide, nylon, an epoxy, etc. are mentioned.

  The heating temperature at the time of heating is preferably 100 to 160 ° C., more preferably 120 to 150 ° C. from the viewpoint of decomposition of copper formate and damage to the substrate.

  When heating, it is preferable to carry out in an inert gas such as nitrogen gas. Even if oxygen is present, the metal copper film and the copper wiring can be formed. However, when heated in an inert gas atmosphere containing less oxygen, a highly conductive metal copper film can be formed. A preferable oxygen concentration is 10% or less, and 2% or less is particularly preferable.

  Since the conductive copper ink composition of the present invention has high conductivity, it is suitably used for copper films for forming wirings such as printed wiring boards and solar cells, and is expected to have effects such as enabling fine wiring. it can. It can also be applied to a transparent conductive film such as a touch panel.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In order to simplify the notation, the following abbreviations were used.

FA: formic acid,
CF: Copper (II) formate
DMAE: Dimethylaminoethanol MDEA: Methyldiethanolamine CHA: Cyclohexylamine DMCHA: Dimethylcyclohexylamine DIW: Deionized water OA: Oxalic acid CA: Citric acid Example 1
1 g of CF (6.5 mmol), 8 g of DMAE (90 mmol), 1 g of FA (22 mmol), and 2 g of DIW (111 mmol) were mixed to prepare a blue uniform liquid conductive copper ink. As a result of TG-DTA analysis in which the temperature of the ink was increased at a rate of 10 ° C./min in a nitrogen stream, the ink decomposition end temperature was 145 ° C.

  When this ink was applied to glass and heated at 150 ° C. for 10 minutes in a nitrogen stream having an oxygen concentration of 2%, a metallic copper film was formed on the glass. When the sheet resistance of the formed copper film was measured by a four-terminal method and the film thickness was measured by a step meter, the volume resistance was 20 μΩ · cm, which was excellent in conductivity.

Comparative Example 1
1 g of CF (6.5 mmol), 10.6 g of DMAE (119 mmol), and 0.4 g of DIW (22 mmol) were mixed to prepare a blue uniform liquid conductive copper ink. As a result of TG-DTA analysis in which the temperature of the ink was increased at a rate of 10 ° C./min in a nitrogen stream, the ink decomposition end temperature was 157 ° C.

  When this ink was applied to glass and heated at 150 ° C. for 10 minutes in a nitrogen stream having an oxygen concentration of 2%, a blue copper salt film remained on the glass because no formic acid was used. Generated.

Comparative Example 2
1 g of CF (6.5 mmol), 9.6 g of DMAE (108 mmol), and 0.4 g of FA (8.7 mmol) were mixed to prepare a conductive copper ink. Since water was not used, crystals were deposited when this ink was allowed to stand.

Comparative Example 3
1 g of CF (6.5 mmol), 8 g of MDEA (67 mmol), 1 g of FA (22 mmol), and 2 g of DIW (111 mmol) were mixed to prepare a blue uniform liquid conductive copper ink. As a result of TG-DTA analysis in which the temperature of the ink was increased at a rate of 10 ° C./min in a nitrogen stream, the ink decomposition end temperature was 167 ° C.

  When this ink was applied to glass and heated at 150 ° C. for 10 minutes in a nitrogen stream having an oxygen concentration of 2%, methyl diethanolamine was used instead of dimethylaminoethanol, and a blue copper salt film remained on the glass. A partially black film was produced.

Example 2
0.9 g CF (5.9 mmol), 2.7 g DMAE (30 mmol), 0.46 g FA (10 mmol), 0.6 g DIW (33 mmol) were mixed. When 2 g of CHA (20 mmol) and 0.005 g of CA (0.03 mmol) were further mixed with this liquid, it could be uniformly applied to the polyimide sheet. When this polyimide sheet was heated at 160 ° C. for 10 minutes in a nitrogen stream having an oxygen concentration of 0.2%, a metal copper film was formed on the polyimide sheet.

Example 3
0.9 g CF (5.9 mmol), 2.7 g DMAE (30 mmol), 0.92 g FA (20 mmol), 0.6 g DIW (33 mmol), 1 g DMCHA (7.8 mmol), 0.01 g A conductive copper ink mixed with OA (0.11 mmol) was prepared. When this ink was applied to a polyimide sheet, it could be applied uniformly. When this polyimide sheet was heated at 160 ° C. for 10 minutes in a nitrogen stream having an oxygen concentration of 0.2%, a metal copper film was formed on the polyimide sheet.

Example 4
Conductive copper mixed with 0.9 g CF (5.9 mmol), 2.7 g DMAE (30 mmol), 0.23 g FA (5 mmol), 0.5 g DIW (28 mmol), 1 g CHA (10 mmol) An ink was prepared. Furthermore, an ink to which 0.005 g of CA (0.03 mmol) was added was prepared and applied to an A-PET (Amorphous Polyethylene Terephthalate) sheet. The copper metal film heated for 1 hour at 135 ° C. in a nitrogen stream with an oxygen concentration of 0.1% did not peel even in a tape peeling test using a cellophane tape.

Claims (11)

A conductive copper ink composition comprising copper formate, dimethylaminoethanol, formic acid and water. Furthermore, the electroconductive copper ink composition of Claim 1 containing polyhydric carboxylic acid. The conductive copper ink composition according to claim 2, wherein the polyvalent carboxylic acid is at least one selected from the group consisting of oxalic acid, citric acid, malic acid, tartaric acid, malonic acid, and succinic acid. The conductive copper ink composition according to claim 1, further comprising cyclohexylamines. The conductive copper ink composition according to claim 4, wherein the cyclohexylamine is at least one selected from the group consisting of cyclohexylamine, dimethylcyclohexylamine, and diaminocyclohexane. The conductive copper ink composition according to claim 1, wherein the amount of copper formate in the conductive copper ink composition is 1 to 40% by weight. The electroconductive copper ink composition according to any one of claims 1 to 6, wherein the amount of dimethylaminoethanol exceeds 5 mole times with respect to copper formate. The conductive copper ink composition according to claim 1, wherein the amount of formic acid is equal to or less than equimolar amount of dimethylaminoethanol. The amount of water is 4 mol times or more and 25 mol times or less of copper formate, The electroconductive copper ink composition in any one of Claims 1-8. The conductive copper ink composition according to any one of claims 1 to 9, wherein the conductive copper ink is heated to form a metal copper film at an oxygen concentration of 10% or less. The conductive copper ink composition according to claim 1, wherein the metal copper film is formed by heating at a temperature of 100 to 160 ° C. after being applied to the substrate.