Ink, method for manufacturing ink, and method for manufacturing multilayer ceramic capacitor

Abstract

This ink contains metal nanoparticles and a solvent. At least a part of the surface of the metal nanoparticles is coordinated by a hydroxycarboxylic acid ligand, and the hydroxycarboxylic acid ligand includes a carboxyl group and at least one hydroxyl group.

Description

Ink, method for manufacturing ink, and method for manufacturing multilayer ceramic capacitor

[0001] The present invention relates to an ink, a method for manufacturing the ink, and a method for manufacturing a multilayer ceramic capacitor. This application claims priority to U.S. Provisional Application No. 63 / 262,177, filed October 6, 2021, the contents of which are incorporated herein by reference.

[0002] Multilayer ceramic capacitors (MLCCs) can utilize metal layers formed from sintered metal nanoparticles. Metal nanoparticles may also be used in a variety of other situations. For example, "Nickel Nanoparticles" describes a method for producing nickel nanoparticles.

[0003] Sophie Carenco; et al., “Controlled Design of Size-Tunable Monodisperse Nickel Nanoparticles” Chemistry of Materials, vol.22 No.4, 2010, pp1340-1349

[0004] As mentioned above, the conductive layer of the MLCC may be formed from metal nanoparticles. One possible method for depositing metal nanoparticles in the MLCC manufacturing process is to inkjet print an ink containing the metal nanoparticles onto a substrate, such as a ceramic tape. Such inks may also be used to deposit metal nanoparticles in any other suitable context to form any other suitable product.

[0005] However, formulating a metal nanoparticle ink suitable for inkjet deposition presents various challenges. For example, many metal nanoparticles, in their as-synthesized form, are not dispersible and / or stable in common inkjet solvent systems, such as propylene glycol butyl ether (PGBE). To aid in dispersing the metal nanoparticles in the solvent, organic polymers and / or ligands can be introduced as stabilizers during metal nanoparticle synthesis. However, the use of such organic moieties can increase the viscosity of the ink to values ​​that are unsuitable for inkjet printing. Polymers and other stabilizers can also increase the organic carbon content of the metal nanoparticles to inappropriate levels. For example, during the MLCC manufacturing process, a layer of metal nanoparticles may be sintered after deposition to bond the metal nanoparticles as a film. Inappropriate levels of organic stabilizers on the metal nanoparticles can result in the formation of insulating carbonaceous marks from the sintering process, which can degrade the performance of the resulting capacitor.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an ink in which metal nanoparticles are dispersed and which is suitable for inkjet printing.

[0007] An ink according to an embodiment of the present invention comprises metal nanoparticles and a solvent, wherein at least a portion of the surface of the metal nanoparticles is coordinated with a hydroxycarboxylic acid ligand, and the hydroxycarboxylic acid ligand comprises a carboxyl group and at least one hydroxyl group.

[0008] A method for producing ink according to an embodiment of the present invention includes the steps of: synthesizing metal nanoparticles; after synthesizing the metal nanoparticles, performing a ligand exchange / introduction reaction to bond hydroxycarboxylic acid ligands to at least a portion of the surface of the metal nanoparticles; and dispersing the metal nanoparticles having the hydroxycarboxylic acid ligands bonded to at least a portion of their surface in an ink solvent system, wherein the hydroxycarboxylic acid ligand comprises a carboxyl group and at least one hydroxyl group.

[0009] A method for manufacturing a multilayer ceramic capacitor according to an embodiment of the present invention is a method for manufacturing a multilayer ceramic capacitor having a plurality of layers, the method comprising the steps of inkjet printing an ink containing metal nanoparticles onto at least a portion of a substrate to obtain an ink layer, and sintering the ink layer to form an electrode layer, wherein at least a portion of the surfaces of the metal nanoparticles are coordinated by hydroxycarboxylic acid ligands, and at least a portion of the layers are formed from the ink containing the metal nanoparticles.

[0010] According to the present invention, it is possible to provide an ink in which metal nanoparticles are dispersed and which is suitable for inkjet printing.

[0011] FIG. 1 is a flow diagram illustrating an exemplary method for producing an ink containing metal nanoparticles. FIG. 2A shows an example of a transmission electron microscope (TEM) image of as-synthesized nickel nanoparticles. FIG. 2B shows an example of a transmission electron microscope (TEM) image of as-synthesized nickel nanoparticles. FIG. 2C shows an example of a transmission electron microscope (TEM) image of nickel nanoparticles after ligand exchange / incorporation. FIG. 3 shows as-synthesized metal nanoparticles in propylene glycol butyl ether (PGBE). FIG. 4 is a graph showing thermogravimetric analysis (TGA) results for as-synthesized metal nanoparticles. FIG. 5 is a graph showing TGA results for metal nanoparticles after ligand exchange / incorporation. FIG. 6 is an image showing an example dispersion of metal nanoparticles in PGBE after ligand exchange / incorporation. FIG. 7A shows a microscopic image of an inkjet-printed metal nanoparticle film printed using an example ink prepared with metal nanoparticles after ligand exchange / incorporation. FIG. 7B shows a microscopic image of an inkjet-printed metal nanoparticle film printed using an example ink prepared with metal nanoparticles after ligand exchange / incorporation. FIG. 8 shows a profilometer scan of the inkjet printed film shown in FIGS. 7A and 7B.

[0012] Disclosed are examples of inks having low viscosity suitable for inkjet printing, including dispersions of metal nanoparticles. One example provides an ink including metal nanoparticles having hydroxycarboxylic acid ligands coordinated to portions of their surfaces, and a solvent. The hydroxycarboxylic acid ligand includes at least one phenyl moiety, and the at least one phenyl moiety includes at least one hydroxyl group.

[0013] Another example provides a method for producing an ink containing metal nanoparticles. The method includes synthesizing metal nanoparticles and, after synthesizing the metal nanoparticles, performing a ligand exchange / introduction reaction to attach hydroxycarboxylic acid ligands to at least a portion of the surface of the metal nanoparticles. The hydroxycarboxylic acid ligands include at least one phenyl moiety, and the at least one phenyl moiety includes at least one hydroxyl group. The method further includes dispersing the metal nanoparticles having the hydroxycarboxylic acid ligands attached to a portion of their surface in an ink solvent system to produce an ink containing the metal nanoparticles.

[0014] This Summary is provided to introduce a selection of concepts in a simplified form that are further described in the Detailed Description. The Summary is not intended to identify key features or essential features of the claimed subject matter or to limit the scope of the claimed subject matter.

[0015] The ink of the present invention comprises metal nanoparticles, at least a portion of whose surface is coordinated with hydroxycarboxylic acid ligands.

[0016] The hydroxycarboxylic acid ligand contains a carboxyl group and at least one hydroxyl group. The inclusion of at least one hydroxyl group in the hydroxycarboxylic acid ligand can impart dispersibility to metal nanoparticles. Preferably, the hydroxycarboxylic acid ligand contains at least one phenyl moiety, which preferably contains at least one hydroxyl group. Such ligands may also be referred to as hydroxyphenylcarboxylic acids. Examples of hydroxycarboxylic acid ligands containing at least one phenyl moiety, which contains at least one hydroxyl group, include gallic acid, 4-hydroxybenzoic acid, and 3-(4-hydroxyphenyl)propionic acid. The use of a hydroxycarboxylic acid ligand as a ligand can improve the dispersibility and impart dispersion stability to metal nanoparticles. In particular, the use of a hydroxycarboxylic acid ligand containing at least one phenyl moiety, which contains at least one hydroxyl group, further improves the dispersion stability of metal nanoparticles, allowing the metal nanoparticles to be dispersed in an ink solvent system, thereby producing an ink suitable for inkjet printing.

[0017] Thus, embodiments are disclosed relating to the preparation, use, and formed films of inks containing metal nanoparticles having hydroxycarboxylic acid ligands coordinated to at least a portion of their surface. In some examples, the hydroxycarboxylic acid ligand comprises at least one phenyl moiety, and the at least one phenyl moiety comprises at least one hydroxyl group. Metal nanoparticles bound by hydroxycarboxylic acid ligands according to the disclosed embodiments can be highly dispersible in one or more inkjet printing solvent systems. In the present invention, the metal nanoparticles can comprise nickel nanoparticles. The inclusion of nickel nanoparticles can result in inks suitable for forming conductive layers of MLCCs. The diameter of the metal nanoparticles is preferably 2 nm to 80 nm. The diameter of the metal nanoparticles can be determined by calculating the approximate equivalent circle diameter of at least 50 particles using transmission electron microscope (TEM) images. Furthermore, inks according to the present disclosure can have low viscosities suitable for inkjet printing. According to the present disclosure, the metal nanoparticles can also have a relatively low organic carbon content, thereby avoiding the formation of inappropriate amounts of carbon residue during sintering of the printed metal layer.

[0018] The ink of the present invention contains a solvent (dispersion medium). The solvent may be a solvent commonly used in conductive pastes or a solvent commonly used in inkjet inks. Examples of the solvent include alcohol-based, ether-based, ester-based, and hydrocarbon-based solvents, as well as mixtures thereof. In particular, inkjet inks preferably contain propylene glycol butyl ether, propylene glycol methyl ether, terpineol, or dihydroterpineol acetate.

[0019] 1 is a flow diagram illustrating an exemplary method 100 for producing inks including metal nanoparticles according to the present disclosure. The method 100 includes synthesizing metal nanoparticles at 102. In some examples, the metal nanoparticles may include nickel nanoparticles, as shown at 104. In other examples, the metal nanoparticles may include any other suitable metal.

[0020] Any suitable synthesis can be used to form the metal nanoparticles. In one example, nickel nanoparticles can be prepared by the synthesis of nickel(acetylacetonate) with oleylamine and trioctylphosphine (TOP) at 220° C. ２ It was synthesized via the decomposition of a precursor, more specifically, nickel(acetylacetonate). ２ The nickel nanoparticles were prepared by mixing nickel nitrate, oleylamine, and TOP, degassing at 100°C, and then heating at 220°C for 2 hours in an inert atmosphere. This method for synthesizing nickel nanoparticles is described in more detail in Chem. Mater, 2010, 22, 1340 (although in this disclosure, the precursor amounts were modified to yield metal nanoparticles with diameters of at least 35 nm). In some instances, metal nanoparticles with diameters in the range of 40 nm to 50 nm were produced. This synthesis yields nickel nanoparticles bound by oleylamine and TOP ligands.

[0021] The resulting nickel nanoparticles were purified by centrifugation using acetone as an antisolvent. Purification yielded a black powder. Figures 2A and 2B show TEM images of the as-synthesized nickel nanoparticles. TEM analysis confirmed monodisperse nickel nanoparticles of approximately 45 nm. In contrast, Figure 2C shows a TEM image of nickel nanoparticles after ligand exchange / incorporation with 4-hydroxybenzoic acid. As explained in more detail below, the degree of dispersion of the nickel nanoparticles after ligand exchange / incorporation was increased relative to the nickel nanoparticles shown in Figures 2A and 2B. As a result, the nickel nanoparticles after ligand exchange / incorporation were less prone to clustering, either by aggregation or agglomeration, on the TEM grid compared to the as-synthesized nickel nanoparticles shown in Figures 2A and 2B.

[0022] The as-synthesized metal nanoparticles settle out of both polar and nonpolar solvents within minutes. Such metal nanoparticle solutions are unsuitable for use as inkjet inks due to the instability of the dispersion. For example, the as-synthesized nickel nanoparticles synthesized as described above could not be dispersed in ethanol and settled out in less than two minutes. The as-synthesized nickel nanoparticles were slightly soluble in common glycol ether ink solvents such as PGBE. A PGBE formulation containing 10 wt% as-synthesized nickel nanoparticles, when sonicated, resulted in a somewhat dark solution with undissolved particles, but completely settled out in less than 30 minutes. Figure 3 shows the condition of a PGBE formulation containing 10 wt% as-synthesized nickel nanoparticles after 7 days.

[0023] As-synthesized nickel nanoparticles in 30 wt % PGBE formed an unstable paste with a viscosity of 3,000 cP, which was too high for inkjet printing.

[0024] Therefore, to improve the stability and viscosity characteristics of inks made from metal nanoparticles, the method 100 includes performing a partial ligand exchange / incorporation reaction at 106 after synthesizing the metal nanoparticles. The ligand exchange reaction replaces the ligand used during the synthesis of the metal nanoparticles (e.g., oleylamine and / or TOP, for example) with another ligand or binds to the available, free surface of the metal nanoparticles. The ligand is selected to stabilize the metal nanoparticles in the ink solvent system and provide a viscosity suitable for inkjet printing. Furthermore, the ligand may also provide an appropriately low organic carbon content (e.g., less than 5 wt%) for the metal nanoparticles, which helps reduce the formation of carbon residue during sintering compared to other organic additives.

[0025] The ligand may comprise any suitable compound. Some examples of suitable ligands include phosphines, amines, thiols, alcohols, and carboxylic acids, including phenolic acids. Some carboxylic acids are particularly well suited for use as ligands in ligand exchange / incorporation. For example, carboxylic acids may not bind to metal nanoparticles as strongly as other ligands and may therefore be easier to remove during sintering without affecting the electronic properties of the film formed by the metal nanoparticles. In contrast, thiols may bind more strongly to metal nanoparticles, and sintering may result in the formation of residual metal sulfide phases that affect the conductivity of the formed film. As a more specific example, a hydroxycarboxylic acid ligand can be used, as shown at 107 in Figure 1. Such a ligand may include at least one phenyl moiety bearing a substituent hydroxyl group. As described in more detail below, such ligands may provide adequate dispersibility in inkjet solvent systems and a suitably low viscosity for inkjet printing, while providing a sufficiently low organic carbon content to avoid leaving harmful amounts of residual carbon after sintering.

[0026] The purified as-prepared nickel nanoparticles were collected in solid powder form and dispersed in ethanol, again forming a heterogeneous solution. Next, an excess amount of the ligand (hydroxycarboxylic acid ligand) for exchange was added and sonicated for 20 minutes. This was followed by stirring at 800 RPM for 90 minutes at room temperature to further promote ligand exchange / incorporation onto the nickel nanoparticle surface. The resulting ligand-exchanged / incorporated nickel nanoparticles were purified and the excess ligand was removed by centrifugation in hexane, resulting in a black powder solid. As introduced above, Figure 2C shows a TEM image of the ligand-exchanged / incorporated nickel nanoparticles. Compared to the as-synthesized nickel nanoparticles shown in Figures 2A and 2B, the ligand-exchanged / incorporated nickel nanoparticles have greater dispersibility and, as a result, are more uniformly distributed in Figure 2C.

[0027] [Example] The results of ligand exchange / introduction are listed in Table 1. 4-hydroxybenzoic acid, 3-(4-hydroxyphenyl)propionic acid, gallic acid, citric acid, and hexanoic acid were screened as ligands for ligand exchange / introduction (Table 1). For the hydroxycarboxylic acid ligands citric acid, 4-hydroxybenzoic acid, 3-(4-hydroxyphenyl)propionic acid, and gallic acid, a PGBE preparation containing 10 wt% nickel nanoparticles after ligand exchange / introduction yielded a nickel nanoparticle dispersion in which the nickel nanoparticles were well dispersed. It was confirmed that dispersibility can be achieved by using a ligand with a polar group in PGBE, a polar solvent. However, in dispersions using citric acid as a ligand, precipitation of the nickel nanoparticles was observed within about one day. In samples using gallic acid, a hydroxycarboxylic acid ligand containing at least one phenyl moiety substituted with at least one hydroxyl group, precipitation of the nickel nanoparticles occurred within less than two days after dispersion preparation. The 3-(4-hydroxyphenyl)propionic acid sample showed some separation and some settling of nickel nanoparticles approximately one week after dispersion preparation. The 4-hydroxybenzoic acid sample provided the best dispersion and stability (over one week) among the ligands tested. It was found that the dispersion stability of nickel nanoparticles was further improved by using a hydroxycarboxylic acid ligand containing at least one phenyl moiety, where the phenyl moiety contains at least one hydroxyl group. While the mechanism is unclear, it is speculated that the phenyl moiety in the hydroxycarboxylic acid increases the steric hindrance effect of the ligand on the nanoparticles. Furthermore, when hexanoic acid was used as the ligand, a PGBE preparation containing 10 wt% nickel nanoparticles after ligand exchange / incorporation was ultrasonically treated, resulting in a somewhat dark solution with undissolved particles, but complete precipitation occurred within 30 minutes. It was confirmed that the use of hexanoic acid, which has a nonpolar tail, as a ligand in PGBE, reduced dispersibility.Furthermore, as described in more detail below, Ni films have been successfully deposited by inkjet printing an ink containing nickel nanoparticles having 4-hydroxybenzoic acid coordinated to at least a portion of their surface.

[0028]

[0029] Using 4-hydroxybenzoic acid as the ligand, TGA of the nickel nanoparticles after ligand exchange / incorporation showed no detectable excess / uncoordinated / free ligand and less than a 1 wt% increase in organic carbon content. Figure 4 shows the TGA of an example of as-synthesized nickel nanoparticles. Figure 5 shows the TGA of an example of nickel nanoparticles after ligand exchange / incorporation. The initial gentle slope of each TGA graph is due to residual solvent leaving the sample. As explained in more detail below, the first peak in the weight first derivative is due to oleylamine and its derivatives and is not distinct from the ligand. The second peak in the weight first derivative is attributed to TOP.

[0030] In another study in which oleylamine was used to synthesize nickel nanoparticles, the second peak in the weight-first derivative did not appear without TOP. Thus, the first peak in the weight-first derivative at about 200-300°C was attributed to oleylamine, and the second peak at about 500°C was attributed to TOP. It has also been suggested in Chem. Mater, 2010, 22, 1340 and elsewhere that the signature of bound oleylamine may also include oleylamine derivatives, which are expected to have similar desorption temperatures.

[0031] The ligand-exchanged / loaded nickel nanoparticles were dispersed in PGBE at approximately 10 wt % and sonicated to obtain a uniform dispersion without particle settling. After 7 days or more, the nickel nanoparticles remained stable and did not produce a clear supernatant with settled nickel nanoparticles. Figure 6 shows the state of a PGBE formulation containing approximately 10 wt % ligand-exchanged / loaded nickel nanoparticles after aging for 7 days or more.

[0032] By introducing the ligand exchange / incorporation reaction after the synthesis of nickel nanoparticles, the nickel nanoparticles become dispersible and stable (for more than 7 days) in a common ink solvent (PGBE) with a high loading (e.g., 30 wt % or more), while the ink viscosity is suitable for inkjet printing (e.g., about 8 cP). Furthermore, the resulting nickel nanoparticles after ligand exchange / incorporation have been found to have a low organic carbon content (e.g., less than 5 wt %) suitable for the MLCC manufacturing process.

[0033] Thus, metal nanoparticles can be dispersed in an ink solvent system to produce an ink, as shown at 108 in FIG. 1 . As discussed above, a preparation containing 30 wt % as-obtained nickel nanoparticles and a PGBE formulation as an ink solvent system containing 30 wt % nickel nanoparticles after ligand exchange / incorporation resulted in viscosities of over 3000 cP and 8 cP, respectively (note that PGBE has a natural viscosity of 3 cP). As discussed above, the former viscosity is too high for inkjet printing, while the latter is suitable for inkjet printing. In other examples, inks containing ligand-exchanged metal nanoparticles as disclosed can have any other suitable viscosity. Suitable viscosities include those in the range of 7 cP to 20 cP.

[0034] Printing and application properties were evaluated for inks using the ligand species and solvents listed in Table 2. The ink was applied to a printed glass substrate at a resolution of 1200 dpi, with the ink ejection frequency varied between 236 Hz and 4724 Hz, for an effective application time of 3 minutes. For Comparative Example 1-1, which used ink containing as-synthesized nickel nanoparticles, nozzle-out occurred frequently, particularly in the low ink ejection frequency range. When nozzle-out occurred, the nozzle was cleaned while the printing and application properties were evaluated. On the other hand, for Examples 1-1 and 1-2, which used inks containing nickel nanoparticles that had been ligand-exchanged / introduced using hydroxyphenylcarboxylic acid as the ligand, the maximum number of nozzle-outs was about one, even at low ink ejection frequencies.

[0035]

[0036] In one experiment, films were prepared by inkjet printing a dispersion of ligand-exchanged / loaded nickel nanoparticles onto a glass substrate. Very thin, smooth films were obtained with high nickel loading densities. Figure 7A shows a microscopic image of a nickel nanoparticle film formed by inkjet printing an ink containing ligand-exchanged / loaded nickel nanoparticles. Figure 7B shows a close-up image of the nickel nanoparticle film shown in Figure 7A. The ink contained 30 wt. % ligand-exchanged / loaded nickel nanoparticles with 4-hydroxybenzoic acid ligands coordinated to at least a portion of their surface in a PGBE ink solvent system with 1% polyvinyl butyral (PVB) additive (viscosity of 8 cP).

[0037] Figure 8 shows a profilometer scan of the inkjet-printed nickel nanoparticle film shown in Figures 7A and 7B. The inkjet-printed nickel nanoparticle film with the ligand-exchanged / introduced nickel nanoparticles had a nickel density of 0.84 mg / cm by profilometry analysis. ２ , green density 4.9 g / cm ３ The film height was confirmed to be approximately 1.9 μm. The ink containing the ligand-exchanged / introduced metal nanoparticles for films formed by inkjet printing may be suitable for the fabrication of electrode layers of MLCCs.

[0038] That is, a method for manufacturing a multilayer ceramic capacitor according to an embodiment of the present invention is a method for manufacturing a multilayer ceramic capacitor having multiple layers, and includes the steps of inkjet printing an ink containing metal nanoparticles onto at least some of the substrates to obtain an ink layer, and sintering the ink layer to form an electrode layer. The sintering temperature may be any temperature at which the metal nanoparticles sinter together and the resulting electrode layer is conductive, and is preferably 200°C or higher, more preferably 300°C or higher, and even more preferably 400°C or higher. Furthermore, a multilayer ceramic capacitor of a desired size can be obtained by stacking multiple substrates and appropriately cutting them as needed. The step of stacking multiple substrates may be performed either before or after sintering the ink layer. This allows for the production of a multilayer ceramic capacitor in which at least some of the layers are formed from the ink containing the metal nanoparticles. When the metal nanoparticles contained in the ink are metal nanoparticles having hydroxycarboxylic acid ligands coordinated to at least a portion of the surface of the metal nanoparticles, as described above, the electrode layer of the multilayer ceramic capacitor can be suitably formed by inkjet printing.

[0039] Ink, ink manufacturing method, and multilayer ceramic capacitor manufacturing method according to embodiments of the present invention include the following: (1) An ink containing metal nanoparticles and a solvent, wherein at least a portion of the surface of the metal nanoparticles is coordinated by a hydroxycarboxylic acid ligand, and the hydroxycarboxylic acid ligand includes a carboxyl group and at least one hydroxyl group. (2) The ink according to (1), wherein the hydroxycarboxylic acid ligand includes at least one phenyl moiety, and the phenyl moiety includes at least one hydroxyl group. (3) The ink according to (1) or (2), wherein the hydroxycarboxylic acid ligand is a hydroxyphenyl carboxylic acid ligand. (4) The ink according to any one of (1) to (3), wherein the metal nanoparticles include nickel nanoparticles. (5) The ink according to any one of (1) to (4), wherein the metal nanoparticles have a diameter of 2 nm to 80 nm. (6) The ink according to any one of (1) to (5), wherein the hydroxycarboxylic acid ligand includes at least one of 4-hydroxybenzoic acid and 3-(4-hydroxyphenyl)propionic acid. (7) The ink according to any one of (1) to (6), wherein the solvent comprises propylene glycol butyl ether. (8) The ink according to any one of (1) to (7), wherein the ink is disposed on glass. (9) The ink according to any one of (1) to (8), wherein the metal nanoparticles comprise an organic carbon content of 5% by weight or less. (10) The ink according to any one of (1) to (9), wherein the ink comprises a viscosity of 7 cP to 20 cP. (11) The ink according to any one of (1) to (10), wherein the ink comprises 30% by weight or more of metal nanoparticles.(12) A method for producing ink, comprising the steps of: synthesizing metal nanoparticles; after synthesizing the metal nanoparticles, performing a ligand exchange / introduction reaction to bond a hydroxycarboxylic acid ligand to at least a portion of the surface of the metal nanoparticles; and dispersing the metal nanoparticles having the hydroxycarboxylic acid ligand bonded to at least a portion of their surface in an ink solvent system, wherein the hydroxycarboxylic acid ligand comprises a carboxyl group and at least one hydroxyl group. (13) The method for producing ink according to (12), wherein the hydroxycarboxylic acid ligand comprises at least one phenyl moiety, and the phenyl moiety comprises at least one hydroxyl group. (14) The method for producing ink according to (12) or (13), wherein the hydroxycarboxylic acid ligand is a hydroxyphenyl carboxylic acid ligand. (15) The method for producing ink according to any one of (12) to (14), wherein the step of synthesizing metal nanoparticles includes synthesizing nickel nanoparticles. (16) The method for producing ink according to any one of (12) to (15), wherein the metal nanoparticles have a diameter of 2 nm to 80 nm. (17) The method for producing an ink according to any one of (12) to (16), wherein the step of carrying out a ligand exchange / introduction reaction comprises bonding at least one of 4-hydroxybenzoic acid and 3-(4-(hydroxyphenyl)propionic acid to at least a portion of the surface of the metal nanoparticles. (18) The method for producing an ink according to any one of (12) to (17), wherein the step of dispersing the metal nanoparticles in the ink solvent system comprises dispersing the metal nanoparticles in a solvent system comprising propylene glycol butyl ether. (19) The method for producing an ink according to any one of (12) to (18), wherein the step of dispersing the metal nanoparticles in the ink solvent system comprises dispersing sufficient metal nanoparticles to provide a viscosity of 7 cP to 20 cP. (20) The method for producing an ink according to any one of (12) to (19), wherein the step of dispersing the metal nanoparticles in the ink solvent system comprises dispersing 30 wt % or more of the metal nanoparticles in the ink solvent system.(21) A method for manufacturing a multilayer ceramic capacitor having a plurality of layers, comprising: a step of inkjet printing an ink containing metal nanoparticles onto at least a portion of a substrate to obtain an ink layer; and a step of sintering the ink layer to form an electrode layer, wherein at least a portion of the surfaces of the metal nanoparticles are coordinated by hydroxycarboxylic acid ligands, and at least a portion of the layers are formed from the ink containing the metal nanoparticles.

[0040] It will be understood that the structures and methods described herein are provided by way of example and should not be considered in a limiting sense, as numerous variations, extensions, and omissions are contemplated. Any of the various operations of the methods described above may be performed in the order shown, in other orders, in parallel, or omitted. The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various structures, methods, properties, and other features disclosed herein, and any and all equivalents thereof.

Claims

1. 1. An ink comprising metal nanoparticles and a solvent, at least a portion of the surface of the metal nanoparticles is coordinated by hydroxycarboxylic acid ligands; the hydroxycarboxylic acid ligand comprises a carboxyl group and at least one phenyl moiety; the phenyl moiety contains at least one hydroxyl group; ink.

2. The ink of claim 1 wherein the hydroxycarboxylic acid ligand is a hydroxyphenylcarboxylic acid ligand.

3. The ink of claim 1 or 2, wherein the metal nanoparticles comprise nickel nanoparticles.

4. The ink according to any one of claims 1 to 3, wherein the metal nanoparticles have a diameter of 2 nm to 80 nm.

5. 5. The ink of claim 1, wherein the hydroxycarboxylic acid ligand comprises at least one of 4-hydroxybenzoic acid and 3-(4-hydroxyphenyl)propionic acid.

6. 6. An ink according to claim 1, wherein the solvent comprises propylene glycol butyl ether.

7. 7. The ink of claim 1, wherein the metal nanoparticles have an organic carbon content of 5% by weight or less.

8. The ink of any one of claims 1 to 7, wherein the ink has a viscosity of from 7 cP to 20 cP.

9. The ink of claim 1 , wherein the ink comprises 30% by weight or more of metal nanoparticles.

10. synthesizing metal nanoparticles; After synthesizing the metal nanoparticles, performing a ligand exchange / introduction reaction to attach hydroxycarboxylic acid ligands to at least a portion of the surface of the metal nanoparticles; dispersing the metal nanoparticles having the hydroxycarboxylic acid ligands bound to at least a portion of their surfaces in an ink solvent system; and the hydroxycarboxylic acid ligand comprises a carboxyl group and at least one phenyl moiety; The phenyl moiety contains at least one hydroxyl group How ink is made.

11. The method for producing an ink according to claim 10 , wherein the step of synthesizing metal nanoparticles includes synthesizing nickel nanoparticles.

12. The method for producing an ink according to claim 10 or 11, wherein the metal nanoparticles have a diameter of 2 nm to 80 nm.

13. 1. A method for manufacturing a multilayer ceramic capacitor having multiple layers, comprising: inkjet printing an ink comprising metal nanoparticles onto at least a portion of a substrate to obtain a layer of ink; sintering the layer of ink to form an electrode layer; and at least a portion of the surface of the metal nanoparticles is coordinated by hydroxycarboxylic acid ligands; At least a part of the layer is formed from an ink containing the metal nanoparticles. A method for manufacturing a multilayer ceramic capacitor.