Ink composition, method for producing circuit board, and circuit board

Abstract

To reduce the viscosity of a copper formate ink having high viscosity for actual practical use by coating.SOLUTION: An ink composition comprising copper formate, an alkanolamine, and a solvent having two or more functional groups capable of forming a coordinate bond with copper formate in a molecular structure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an ink composition, a circuit board manufacturing method, and a circuit board. [Background technology]

[0002] An ink composition containing copper formate, aminodiol, and an alcohol having less than 10 carbon atoms is known as a conductive ink that can form a highly conductive copper film even when heated in the atmosphere (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-6903 Summary of the Invention [Problem to be solved by the invention]

[0004] However, copper formate ink has a high viscosity, and it is necessary to reduce the viscosity in order to actually apply it.

[0005] Therefore, at least one aspect of the problem to be solved by the present disclosure is to reduce the viscosity of an ink composition containing copper formate so that it can be used by coating. Note that, if a divisional application based on the present disclosure is filed, the problem that is obvious to a person skilled in the art and can be read from the embodiments and their explanations that are characteristic of the present disclosure and are described in the specification, drawings, etc. of the present disclosure may also be the problem to be solved by the divided invention. [Means for solving the problem]

[0006] In order to achieve the above object, the ink composition of the present disclosure contains copper formate, an alkanolamine, and a solvent having, in its molecular structure, two or more functional groups capable of forming a coordinate bond with the copper formate.

[0007] The circuit board manufacturing method of the present disclosure is a circuit board manufacturing method for manufacturing a circuit board having conductor wiring formed on an insulating substrate, and includes an ink ejection step of ejecting the above-mentioned ink composition from an inkjet printer head onto the insulating substrate, a first conductor layer formation step of heating the ejected ink composition to form a first conductor layer, and a second conductor layer formation step of performing a plating process on top of the first conductor layer to form a second conductor layer.

[0008] The ink composition has a first conductive layer formed by heating the ink composition ejected onto an insulating substrate made of any of polyimide, polyamide, polyethylene terephthalate, polyethylene naphthalate, polyether ether ketone, acrylonitrile butadiene styrene, polymethyl methacrylate, polystyrene, polyphenylene sulfide, polyvinyl chloride, epoxy resin, and glass epoxy resin, and a second conductive layer formed on the first conductive layer as a copper plating layer having a thickness greater than that of the first conductive layer, and the adhesion strength between the first conductive layer and the insulating substrate is 0.05 N / mm or more. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to obtain a copper formate ink with a liquid viscosity that allows it to be actually ejected from an inkjet nozzle, and it can be used in inkjet applications. [Brief explanation of the drawings]

[0010] [Figure 1] This is a schematic diagram showing the mechanisms of non-heated and heated inkjet nozzles. [Figure 2] FIG. 1 is a flowchart illustrating a process flow for manufacturing a circuit board according to the present disclosure. [Figure 3] FIG. 1 is a diagram showing the results of measuring the viscosity of a copper formate ink composition according to an example of the present disclosure. [Figure 4] FIG. 10 is a diagram showing the results of measuring adhesion strength based on the results of a peel test. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Copper formate ink> The ink composition of an embodiment of the present disclosure contains copper formate, an alkanolamine, and a solvent having, in its molecular structure, two or more functional groups capable of forming a coordinate bond with the copper formate.

[0012] Copper formate ink compositions have properties similar to dye inks when used to form metal films. In copper formate ink compositions, copper formate is dissolved in a solvent in an ionic state and reduced to zero-valent copper by heat treatment. This differs from the mechanism used in pigment-based metal nanoinks, where metal nanoparticles themselves are dispersed and the solvent is removed by heating, resulting in interparticle bonding.

[0013] Copper formate is based on Cu(HCOO)2 and may be its hydrate [Cu(HCOO)2·4H2O] or a copper formate complex coordinated with an alkanolamine. The content of copper formate (or its hydrate) may be 0.5% by weight or more and 80% by weight or less. More preferably, it may be 1% by weight or more and 50% by weight or less. An even more preferable range may be 5% by weight or more and 40% by weight or less. This is to ensure conductivity during copper thin film formation and to prevent the formation of aggregation and precipitates that make it difficult to create a uniform ink. It also enables inkjet ejection.

[0014] The alkanolamine forms a complex with copper formate and promotes its reduction to zero-valent copper through a reducing action. For example, the alkanolamine may contain at least one compound selected from the group consisting of 1-amino-2-propanol, 2-amino-1,3-propanediol, 1-3-diamino-2-propanol, 2-amino-1-butanol, 1-amino-2-butanol, and 2-aminoethanol.

[0015] The molar ratio of alkanolamine to copper formate may be, for example, 0.5 to 5.0 parts by weight of copper formate to alkanolamine, more preferably 1.0 to 3.0. In terms of weight percentage, the proportion of alkanolamine in the entire ink composition may be, for example, 1 to 85% by weight, more preferably 5 to 50% by weight, and even more preferably 10 to 30% by weight. This is because a low weight ratio makes it difficult to generate zero-valent copper, resulting in a decrease in sintered density and therefore affecting adhesion strength, while a high weight ratio affects the viscosity of the ink when made into ink.

[0016] <Viscosity of Inkjet Ink Composition> The technique of conducting a copper formate ink composition by thermal decomposition is known as a low-temperature sintering process, but when used as an inkjet ink composition, the viscosity of the copper formate ink composition is high, possibly due to the fact that it is a dye-based ink, making it difficult to eject by inkjet. Therefore, in order to eject a copper formate ink composition by inkjet, it is necessary to adjust the viscosity to a level that allows ejection.

[0017] Specifically, the viscosity of the ink composition is preferably 1 to 100 mPa·s at a measurement temperature of 25°C, as measured using an E-type viscometer or rheometer. It is even more preferably 1 to 50 mPa·s. Furthermore, these viscosities are preferably 1 to 100 mPa·s, and even more preferably 1 to 50 mPa·s, at a shear rate of 100 (1 / S) or higher. This is because these conditions are suitable for the environment in which ink is ejected from a non-heated inkjet nozzle; if the viscosity is too high, it becomes difficult for the ink to be ejected from the inkjet nozzle. Since the shear rate of ink flowing through the piping in an inkjet head is said to be about 10 (1 / S), a viscosity measured at a shear rate of 10 to 10,000 (1 / S) is a general guideline. Alternatively, it is 100 to 10,000 (1 / S).

[0018] Figure 1 is a simplified schematic diagram showing the workings of a non-heated inkjet nozzle and a heated (both thermal and bubble) inkjet nozzle. In this diagram, the non-heated inkjet nozzle is exemplified by a piezoelectric inkjet nozzle, nozzle A, which is equipped with a piezoelectric element 1. In addition to piezoelectric types, there are also continuous inkjet (CIJ) and super inkjet (SIJ) non-heated inkjet nozzles, but we will not explain these here. Nozzle B, which is a heated type, is equipped with a heater 2.

[0019] In Figure 1, a non-heating piezoelectric inkjet uses a piezoelectric element 1, which is a piezoelectric element, to eject ink. When a voltage is applied to the piezoelectric element, it deforms, allowing ink droplets to be forced out of the nozzle. On the other hand, a heated inkjet ejects ink droplets from the nozzle by generating boiling bubbles 3 in the ink when heated by a heater 2. Since each ink droplet is ejected based on this principle, a printing device using a non-heating inkjet printhead may be suitably used when the copper formate ink composition contains a large amount of organic solvent. On the other hand, a printing device using a heated inkjet printhead may also be used when the copper formate ink composition contains a large amount of water.

[0020] However, when high-viscosity ink is used in inkjet printheads, clogging can occur, or the ink can fail to eject. This problem can also occur with heated inkjet printheads. The reason this is particularly problematic with non-heated piezo-electric printheads is thought to be due to the small nozzle size and the principle that ink flows in response to pressure changes.

[0021] Furthermore, when the copper formate composition is used for inkjet ejection, it is necessary to prevent the copper composition from agglomerating during the solvent drying process and the baking process. To this end, the inventors focused on the solvent, conducted extensive research, and conducted experiments to select the solvent described below. As a result, the solvent was selected as follows. Examples of the experiments will be described later.

[0022] The solvent may contain a compound having an ethylene glycol skeleton, and may contain, for example, at least one selected from the group consisting of ethylene glycol, alkyl ether derivatives of ethylene glycol, more specifically ethylene glycol monoethyl ether, alkyl ester derivatives of ethylene glycol, diethylene glycol, alkyl ether derivatives of diethylene glycol, more specifically diethylene glycol monoethyl ether, alkyl ester derivatives of diethylene glycol, triethylene glycol, alkyl ether derivatives of triethylene glycol, alkyl ester derivatives of triethylene glycol, propylene glycol, alkyl ether derivatives of propylene glycol, and alkyl ester derivatives of propylene glycol.

[0023] Alternatively, the solvent may be ethanol.

[0024] The proportion of the solvent in the entire ink composition may be, for example, 1% by weight to 95% by weight, more preferably 50% by weight to 95% by weight, and even more preferably 70% by weight to 95% by weight. If the weight ratio is too low, the viscosity of the ink will increase, and if the weight ratio is too high, the amount of solvent remaining after solvent removal may affect the ink, leading to poor sintering.

[0025] In addition, appropriate stabilizers and other additives may be used. Although the copper formate ink composition of the present disclosure does not use a surfactant to adjust the viscosity to an appropriate range, the addition of a surfactant is not excluded as long as the viscosity can be maintained within the appropriate range.

[0026] <Circuit board manufacturing method> Next, the basic process flow of a circuit board manufacturing method using the copper formate ink composition of the present disclosure will be described with reference to the flowchart shown in FIG.

[0027] First, in step S100, an insulating substrate is prepared. This insulating substrate is an insulating substrate such as a flexible printed circuit board, and may be supplied in the form of a film, sheet, or roll. A primer layer may be formed on the surface of this insulating substrate for various purposes, such as improving the coatability of the ink composition or modifying the surface of the insulating substrate. The primer layer may generally be formed by applying a resin or an adhesion improver that improves the adhesion of ink containing a resin. Alternatively, instead of forming a primer layer, the insulating substrate surface may be subjected to plasma treatment, electron beam treatment, ultraviolet treatment, or the like.

[0028] The insulating substrate may be an organic substrate, such as a thermoplastic resin. Examples of the thermoplastic resin include polyesters such as polyimide, polyamide, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN), polyamide synthetic resins such as nylons (registered trademarks) identified as nylon 6,10 and nylon 4,6, resins such as polyether ether ketone, acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA), and polyvinyl chloride, epoxy resins, polystyrene, and polyphenylene sulfide (PPS). Examples of the organic-inorganic substrate may include an organic-inorganic composite material such as glass epoxy resin.

[0029] Other insulating substrates may also be used, such as inorganic substrates, such as ceramics, etc. Other organic substrates may also be used, such as polyvinylidene chloride, polyvinyl alcohol, styrene-acrylonitrile copolymer, polyethylene, styrene-vinyl acetate copolymer, polyacetal, cellulose acetate, polycarbonate, thermoplastic polyurethane, and polytetrafluoroethylene.

[0030] In some cases, the glass transition point of the material for the insulating substrate may be selected to be in the range of 20° C. to 250° C., 50° C. to 200° C., or 70° C. to 150° C. These temperature conditions depend on the material selected, taking into consideration that if the glass transition point is too low, distortion may occur in the insulating substrate when the ink composition is bonded to the insulating substrate, and if the glass transition point is too high, softening of the insulating substrate may be insufficient, resulting in reduced adhesion to the first conductor layer, which will be described later.

[0031] When the insulating substrate is provided as a film-like material, its thickness may be 5 μm to 3 mm, 12 μm to 1 mm, or 50 μm to 200 μm. The reasons for selecting these thicknesses include the fact that if the thickness is too thin, the strength may be insufficient and distortion may increase during the plating process, and if the thickness is too thick, the cost may increase and the volume and weight of the completed circuit board may increase.

[0032] Next, in step S101, the ink composition is applied in a wiring pattern using an inkjet printing device (ink application step), thereby forming an ink coating layer on the insulating substrate.

[0033] The diameter of a single ink droplet ejected from an inkjet nozzle of an inkjet printing device is, for example, within a range of 1 μm to 100 μm.

[0034] After the ink coating layer is formed, a drying step may be carried out to remove the solvent, etc. The drying step may be a heat treatment or a warm air treatment using a nitrogen or air flow, which leaves the ink composition on the insulating substrate.

[0035] Next, in step S102, the ink composition is heated to form a first conductor layer (first conductor layer forming step). As a result, copper formate contained in the ink coating layer is reduced by thermal decomposition, generating metallic copper (zero-valent copper), and the first conductor layer is formed.

[0036] The first conductor layer can be formed, for example, by heating at 100 to 200° C. for about 10 to 70 minutes.

[0037] Next, in step S103, copper plating is performed on the first conductor layer to form a second conductor layer of copper (second conductor layer forming step).

[0038] After the ink application process and drying process, a first conductor layer formation process is carried out, and the formed first conductor layer is plated (electrolytic plating or electroless plating). This deposits a plating metal (second conductor layer) on top of the first conductor layer. The plating method is similar to known plating processes using known plating solutions, and specifically may include electroless copper plating, electrolytic copper plating, etc.

[0039] Through the above steps, a circuit board can be manufactured in which copper wiring in a desired pattern is formed on an insulating substrate.

[0040] The adhesion strength between the first conductor layer of the circuit board manufactured in this manner and the insulating substrate may preferably be 0.05 N / mm or more, more preferably 0.15 N / mm or more, and even more preferably 0.3 N / mm or more.

[0041] Examples of the ink composition of the present disclosure and circuit boards manufactured by the circuit board manufacturing method using the ink composition are described below. In the examples, the viscosity of the ink composition was measured, and the adhesion strength between the first conductor layer and the second conductor layer of the manufactured circuit board and the insulating substrate was measured.

[0042] <Examples and Comparative Examples> Example 1 Five parts of copper formate tetrahydrate (Kanto Chemical Co., Ltd.) as copper formate, two parts of 1-amino-2-propanol (Tokyo Chemical Industry Co., Ltd.) as alkanolamine, and eight parts of ethylene glycol monoethyl ether as solvent were mixed in a container to obtain a deep blue liquid. No surfactant was included. Example 2 Three parts of copper formate tetrahydrate were mixed in a container as copper formate, two parts of 1-amino-2-propanol as alkanolamine, and five parts of ethylene glycol monoethyl ether as solvent to obtain a deep blue liquid. No surfactant was added. Example 3 A deep blue liquid was obtained by the same procedure as in Example 1, except that the solvent in Example 1 was changed from ethylene glycol monoethyl ether to diethylene glycol monomethyl ether. No surfactant was contained. Example 4 A deep blue liquid was obtained by the same procedure as in Example 2, except that the solvent in Example 1 was changed from ethylene glycol monoethyl ether to diethylene glycol monomethyl ether. No surfactant was contained. Example 5 A deep blue liquid was obtained by the same procedure as in Example 1, except that the solvent in Example 1, ethylene glycol monoethyl ether, was changed to ethylene glycol. No surfactant was contained. Example 6 A deep blue liquid was obtained by the same procedure as in Example 1, except that the solvent in Example 1 was changed from ethylene glycol monoethyl ether to ethanol. No surfactant was contained. (Comparative Example 1) As a hypothetical comparative example 1 corresponding to the example described in Patent Document 1, which is a conventional example, 4 parts of copper formate tetrahydrate, 4 parts of 3-dimethylamino-1,2-propanediol as an aminodiol, and 2 parts of 1,3-propanediol as an alcohol having less than 10 carbon atoms were mixed in a container to obtain a dark blue viscous body. (Comparative Example 2) As a hypothetical comparative example 2 corresponding to the example described in Patent Document 1, which is a conventional example, 4 parts of copper formate tetrahydrate, 4 parts of diethanolamine as an aminodiol, and 2 parts of 1,3-propanediol as an alcohol having less than 10 carbon atoms were blended in a container to obtain a dark blue viscous body. (Comparative Example 3) 16.8 parts of copper formate tetrahydrate as copper formate, 22.1 parts of 1,2-bis(2-aminoethoxy)ethane as an amine that is not an alkanolamine, 58.4 parts of ethylene glycol, and 2.7 parts of a surfactant were mixed in a container to obtain a dark blue liquid. Comparative Example 4 25.9 parts of copper formate tetrahydrate as copper formate, 34.0 parts of 1,2-bis(2-aminoethoxy)ethane as an amine that is not an alkanolamine, 35.9 parts of ethylene glycol, and 4.2 parts of a surfactant were blended in a container to obtain a dark blue liquid.

[0043] Here, in Examples 1 to 6, the compounding ratio of copper formate (A), alkanolamine (B), and solvent (C) in terms of concentration by weight % satisfies the following conditions. (A):20~40% by weight (B): 10~25% by weight (C):40~70% by weight However, the total amount of copper formate (A), alkanolamine (B), and solvent (C) is 100% by weight or less.

[0044] In addition, in Examples 1 and 3, the blending ratio of copper formate (A), alkanolamine (B), and solvent (C) in terms of concentration by weight % satisfies the following conditions. (A): 33~40% by weight (B): 12~19% by weight (C): 33~54% by weight However, the total amount of copper formate (A), alkanolamine (B), and solvent (C) is 100% by weight or less.

[0045] <Viscosity measurement> Figure 3 is a table showing the results of measuring the viscosity of the ink compositions of Examples 1 to 6 and Comparative Examples 1 to 4 using a rheometer at measurement temperatures of 25°C and 50°C to verify the ink fluidity and behavior under environmental conditions in which inkjet printing devices are generally used. The table shows the viscosity (mPa·s) at each shear rate (1 / s). With a rotational rheometer or E-type viscometer, a constant shear rate is applied to the sample to measure the shear stress. The ratio of shear stress to shear rate is the viscosity. ND indicates that the viscosity was too high to measure.

[0046] Note that heating to around 50°C is lower than the heating temperature used in thermal inkjet printers, which generally heat to temperatures of at least 100°C and up to around 300°C. A temperature of around 50°C is close to the temperature rise experienced inside the printer during operation.

[0047] As shown in Figure 3, at a measurement temperature of 25°C, Examples 1 to 4 had viscosities in the range of 24 to 53 mPa·s at least at all shear rates. Since the viscosity range was 1 to 100 mPa·s, all Comparative Examples showed viscosities of at least 280 mPa·s or higher, indicating that the viscosity was appropriately thickened to a level suitable for inkjet ejection. In particular, Examples 1 and 2 had a viscosity in the range of 24 to 29 mPa·s, which is more preferable in terms of viscosity. Furthermore, Example 5 also had a viscosity in the range of 1 to 100 mPa·s at shear rates of 10 (1 / S) or higher. Example 6 had a viscosity in the range of 1 to 100 mPa·s at shear rates of 100 (1 / S) or higher. Here, one guideline is to set the shear rate that simulates the behavior of ink when ejected from an inkjet head to 10 to 10,000 (1 / S) or 100 to 10,000 (1 / S), and the viscosities of Examples 5 and 6 meet this requirement. As in the Comparative Example, if the viscosity is high despite the increased shear rate, handling becomes more difficult.

[0048] At a measurement temperature of 50°C, the viscosity of Examples 1 to 4 further decreased to a range of 9 to 19 mPa·s due to softening caused by heating. In Example 5, the viscosity also decreased to a range of 22 to 23 mPa·s at shear rates of 10 (1 / S) or higher. In Example 6, the viscosity further decreased to a range of 0.4 to 5 mPa·s. In Comparative Examples 1 to 4, the viscosity also decreased considerably, but did not fall below 20 mPa·s. In particular, Comparative Examples 1, 2, and 4 did not even fall below 60 mPa·s. Even if the ink composition of Comparative Example 3 were to be used in inkjet printing, its viscosity would be too high to be measured at room temperature. In that case, the process load of filling the ink into the inkjet head would be high, and heating or some kind of idling time would be required, which would clearly affect the productivity of circuit boards.

[0049] Summarizing the results shown in Figure 3, it was found that at least Examples 1 to 4 were suitable as inkjet ink compositions because they had an appropriate viscosity even at room temperature and further decreased in viscosity at 50°C. Furthermore, Examples 5 and 6 also had viscosities in the range of 1 to 100 mPa s at shear rates of 10 (1 / S) or more and 100 (1 / S) or more.

[0050] <Adhesion strength measurement> Each of the copper formate ink compositions according to Examples 1 to 6 and Comparative Examples 1 to 4 was applied to an insulating substrate to form a first conductive layer, followed by electroless copper plating to form a second conductive layer. A peel test was then performed on the samples to measure the adhesion strength (N / mm). Because a high-viscosity ink composition was used for the comparative example, the samples used for the peel test were prepared by applying the ink composition to an insulating substrate and baking it without ejecting it from an inkjet head. The peel test, which was used to confirm the adhesion strength of the plating layer to the substrate, was conducted at a 90-degree angle in accordance with the U.S. UL standard, specifically the UL769F standard. The peel test involved multiple peeling attempts on multiple test piece widths.

[0051] 6 is a table showing the results of adhesion strength (N / mm) measurements from peel tests for Examples 1 to 6 and Comparative Examples 1 to 4, showing the average, maximum, and minimum values ​​from multiple peel tests, as well as plating suitability. Plating suitability refers to whether or not a plating layer, which is a second conductive layer, adheres to a first conductive layer formed by reducing an inkjet composition. Furthermore, the average adhesion strength is preferably 0.05 N / mm or greater, more preferably 0.15 N / mm or greater, and even more preferably 0.3 N / mm or greater.

[0052] 6, Examples 1 to 6 were all suitable for plating, with average adhesion strengths of 0.05 N / mm or more. On the other hand, for the comparative examples, Comparative Example 1 was suitable for plating and had a certain degree of adhesion strength, but Comparative Examples 2 to 4 had adhesion strengths so low that they were unmeasurable. For Comparative Example 2, adhesion of the plating layer was confirmed, so the plating suitability was rated as good.

[0053] From these results, it can be seen that the Examples met certain standards for ink viscosity and plating suitability, whereas the Comparative Examples did not meet the standards for either ink viscosity or plating suitability.

[0054] As described above, the copper formate ink composition of the present disclosure can have a liquid viscosity that allows it to be ejected from an inkjet nozzle for actual inkjet use.

[0055] The new technology of this disclosure can be realized in various other forms, and part of the content can be omitted, modified, or replaced within the scope of the gist of this disclosure. The embodiments and modifications shown in this disclosure are also within the scope and gist of this disclosure, and are treated as technologies that should be protected by the claims, and are equivalent or similar to them.

[0056] Additional notes regarding the embodiments of the present disclosure will be given below. [Note] (Appendix 1) An ink composition comprising copper formate, an alkanolamine, and a solvent having, in its molecular structure, two or more functional groups capable of forming a coordinate bond with the copper formate. (Appendix 2) Attachment 1. The ink composition according to claim 1, wherein the solvent has an ethylene glycol skeleton. (Appendix 3) 3. The ink composition according to claim 2, wherein the ink composition is used in an inkjet printing device. (Appendix 4) 4. The ink composition according to claim 3, wherein the ink composition is used in an application in which the ink composition is ejected onto an insulating substrate that is any one of polyethylene terephthalate, polyethylene naphthalate, polyimide, polystyrene, polyphenyl sulfide, epoxy resin, and glass epoxy resin. (Appendix 5) 5. The ink composition according to claim 4, wherein the solvent comprises at least one selected from the group consisting of ethylene glycol, alkyl ether derivatives of ethylene glycol, alkyl ester derivatives of ethylene glycol, diethylene glycol, alkyl ether derivatives of diethylene glycol, alkyl ester derivatives of diethylene glycol, triethylene glycol, alkyl ether derivatives of triethylene glycol, alkyl ester derivatives of triethylene glycol, propylene glycol, alkyl ether derivatives of propylene glycol, and alkyl ester derivatives of propylene glycol. (Appendix 6) Appendix 5. The ink composition according to Appendix 5, wherein the alkanolamine comprises at least one selected from the group consisting of 1-amino-2-propanol, 2-amino-1,3-propanediol, 1-3-diamino-2-propanol, 2-amino-1-butanol, 1-amino-2-butanol, and 2-aminoethanol. (Appendix 7) 7. The ink composition of claim 6, wherein the ink composition does not contain a surfactant. (Appendix 8) A circuit board manufacturing method for manufacturing a circuit board having conductor wiring formed on an insulating substrate, comprising: an ink ejection step of ejecting the ink composition described in Appendix 1 onto the insulating substrate from an inkjet printer head; a first conductor layer forming step of heating the ejected ink composition to form a first conductor layer; a second conductor layer forming step of forming a second conductor layer by plating on the first conductor layer. (Appendix 9) 8. The circuit board manufacturing method according to claim 7, wherein the insulating substrate is any one of polyethylene terephthalate, polyethylene naphthalate, polyimide, polystyrene, polyphenyl sulfide, epoxy resin, and glass epoxy resin. (Appendix 10) a first conductor layer formed by heating the ink composition according to Appendix 1 ejected onto an insulating substrate made of any one of polyimide, polyamide, polyethylene terephthalate, polyethylene naphthalate, polyether ether ketone, acrylonitrile butadiene styrene, polymethyl methacrylate, polystyrene, polyphenylene sulfide, polyvinyl chloride, epoxy resin, and glass epoxy resin; and a second conductor layer formed on the first conductor layer and having a thickness greater than that of the first conductor layer, the second conductor layer being a copper plating layer; A circuit board, wherein the adhesive strength between the first conductor layer and the insulating substrate is 0.05 N / mm or more. [Explanation of symbols]

[0057] A nozzle B nozzle 1 Piezo element 2 heaters 3. Bubbles

Claims

1. An ink composition comprising copper formate, an alkanolamine, and a solvent having, in its molecular structure, two or more functional groups capable of forming a coordinate bond with the copper formate.

2. The ink composition according to claim 1 , wherein the solvent has an ethylene glycol skeleton.

3. The ink composition of claim 2 , wherein the ink composition is used in an inkjet printing device.

4. The ink composition according to claim 3, which is used in an application in which it is discharged onto an insulating substrate made of any one of polyethylene terephthalate, polyethylene naphthalate, polyimide, polystyrene, polyphenyl sulfide, epoxy resin, and glass epoxy resin.

5. 5. The ink composition according to claim 4, wherein the solvent comprises at least one selected from the group consisting of ethylene glycol, alkyl ether derivatives of ethylene glycol, alkyl ester derivatives of ethylene glycol, diethylene glycol, alkyl ether derivatives of diethylene glycol, alkyl ester derivatives of diethylene glycol, triethylene glycol, alkyl ether derivatives of triethylene glycol, alkyl ester derivatives of triethylene glycol, propylene glycol, alkyl ether derivatives of propylene glycol, and alkyl ester derivatives of propylene glycol.

6. 6. The ink composition according to claim 5, wherein the alkanolamine comprises at least one selected from the group consisting of 1-amino-2-propanol, 2-amino-1,3-propanediol, 1-3-diamino-2-propanol, 2-amino-1-butanol, 1-amino-2-butanol, and 2-aminoethanol.

7. The ink composition of claim 6, which is surfactant-free.

8. A circuit board manufacturing method for manufacturing a circuit board having conductor wiring formed on an insulating substrate, comprising: an ink ejection step of ejecting the ink composition according to claim 1 from an inkjet printer head onto the insulating substrate; a first conductor layer forming step of heating the ejected ink composition to form a first conductor layer; a second conductor layer forming step of forming a second conductor layer by plating on the first conductor layer.

9. 8. The circuit board manufacturing method according to claim 7, wherein the insulating substrate is made of any one of polyethylene terephthalate, polyethylene naphthalate, polyimide, polystyrene, polyphenyl sulfide, epoxy resin, and glass epoxy resin.

10. a first conductor layer formed by heating the ink composition according to claim 1 ejected onto an insulating substrate made of any one of polyimide, polyamide, polyethylene terephthalate, polyethylene naphthalate, polyether ether ketone, acrylonitrile butadiene styrene, polymethyl methacrylate, polystyrene, polyphenylene sulfide, polyvinyl chloride, an epoxy resin, and a glass epoxy resin; a second conductor layer formed on the first conductor layer and having a thickness greater than that of the first conductor layer, the second conductor layer being a copper plating layer; A circuit board, wherein the adhesive strength between the first conductor layer and the insulating substrate is 0.05 N / mm or more.

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