inkjet ink

Abstract

Regarding ink, we provide a technology that reduces sheet attack on the ceramic layer while suppressing the occurrence of coffee rings and pinholes. [Solution] The ink disclosed herein is used in the manufacture of electronic components. In this ink, the organic solvent is a first organic solvent having a vapor pressure P1 at 20°C greater than 4 Pa ​​and less than or equal to 100 Pa, and a surface tension of 22 mN / m to 30 mN / m, and a second organic solvent having a vapor pressure P2 at 20°C of 4 Pa ​​or less, and a Fedors SP value of at least 8 (cal / cm²). 3 ) 1 / 2 The ink contains a second organic solvent. The organic solvent does not dissolve butyral resin containing 32 mol% or more hydroxyl groups in a temperature environment of 60°C or below. The ratio (Vs2 / Vp) of the volume percentage of nickel powder when the total ink is considered as 100 vol% to Vs2 of the total ink is 1.5 or greater.

Description

[Technical Field]

[0001] This disclosure relates to inkjet inks. [Background technology]

[0002] Inkjet printing has long been used as a printing method for drawing images such as patterns and characters onto a printing surface. Because inkjet printing allows for high-precision image printing at low cost and on demand, and causes minimal damage to the printing surface, its application in various fields is being explored. In recent years, the use of inkjet printing in forming conductive circuit patterns (wiring, electrodes, etc.) in the manufacturing of electronic components has been considered. The main objective is to achieve miniaturization and increased density of electronic components. For example, it is expected that the electrode layer and insulating layer in a laminate can be made thinner than those in a laminate produced using screen printing.

[0003] In the manufacture of such electronic components, conductive inkjet inks containing inorganic powders, such as metal particles, as conductive materials are sometimes used. One example of such a conductive inkjet ink is an ink containing nanometal powders, such as silver or silver-copper alloys, disclosed in Patent Document 1. Furthermore, an ink containing metal oxide fine particles, such as silver oxide, copper oxide, palladium oxide, nickel oxide, lead oxide, and cobalt oxide, is disclosed in Patent Document 2. Generally, for proper inkjet printing, conductive inks must have low viscosity and a high concentration of inorganic powders. Patent Documents 1 and 2 propose techniques for achieving these inkjet suitability requirements.

[0004] Furthermore, conductive inkjet inks require the stable dispersion of inorganic powders in order to ensure ejection performance during printing and conductivity after printing. For example, Patent Document 3 discloses a technique for improving the dispersibility of solid fine particles (inorganic powders) on which acidic and basic sites are mixed on the surface, by adding a first dispersant having only one of either an acidic adsorbent group or a basic adsorbent group, and a second dispersant having both an acidic adsorbent group and a basic adsorbent group.

[0005] Furthermore, Patent Document 4 discloses a spacer particle dispersion containing spacer particles and a solvent mainly composed of an organic solvent, which is used when arranging the spacer particles at arbitrary positions on a substrate using an inkjet device. This spacer particle dispersion is characterized by having a surface tension of 30 to 65 mN / m. The same publication states that with this configuration, it is possible to provide a spacer particle dispersion that prevents droplets of the spacer particle dispersion ejected onto the substrate of a liquid crystal display device using an inkjet device from wetting and spreading, and that allows for the selective arrangement of spacer particles at arbitrary positions on the substrate, as well as a liquid crystal display device using the spacer dispersion. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 2008-513565 [Patent Document 2] Japanese Patent Publication No. 2012-216425 [Patent Document 3] Japanese Patent Publication No. 2015-62871 [Patent Document 4] Japanese Patent Publication No. 2008-111985 [Overview of the project] [Problems that the invention aims to solve]

[0007] By the way, among electronic components, there are laminated products (e.g., multilayer ceramic capacitors (MLCC), etc.) that require high smoothness for electrode layers and insulating layers. In such laminated electronic components, ferroelectric ceramic materials such as barium titanate are used for the insulating layer, and metal materials such as palladium and nickel are used for the electrode layer. In the manufacturing process of the electrode layer and the insulating layer, first, a ceramic layer (e.g., insulating layer) is formed on a plastic film such as a PET film that has been processed to have a smooth surface by using a ceramic slurry and by methods such as the doctor blade method or the screen printing method. Then, a metal layer (e.g., electrode layer) is formed on it by using a metal slurry (paste), for example, by the screen printing method. Next, after laminating the green sheets obtained by peeling all the printed materials from the PET film, they are press-fired to form laminated electronic components. Here, in order to peel the above-mentioned layers from the PET film, it is necessary to impart appropriate strength to each green sheet. For this reason, for example, there is a limit to reducing the thickness of the layer provided on the PET film.

[0008] The inventor is considering forming laminated components by alternately inkjet printing the insulating layer pattern and the electrode layer pattern of the above-mentioned electronic components that require high smoothness using a ceramic inkjet ink mainly composed of barium titanate particles and a conductive inkjet ink mainly composed of nickel particles. The purpose is to simultaneously thin the electrode layer and the insulating layer, which was difficult with the combination of the green sheet and the conductive paste, while the miniaturization and large capacity of components are progressing in MLCC manufacturing. By smoothing both the electrode layer and the insulating layer, miniaturization that could not be achieved by the conventional screen printing method can be realized. In addition to this, for example, since it is not necessary to form each layer on the PET film, it is not necessary to peel the layer from the PET film, and productivity can be improved.

[0009] In order to achieve sufficient thinning in, for example, an electrode layer using a conductive inkjet ink, the conductive inkjet ink is required to be suitable for an inkjet head. In addition to this, after drying the printed conductive inkjet ink, it is necessary that the so-called coffee-ring phenomenon is suppressed, that there are no pinholes in the electrode layer, and that the conductive inkjet ink does not dissolve the insulating layer under the electrode layer constituted by the conductive inkjet ink. Here, the coffee-ring phenomenon refers to a phenomenon in which when the organic solvent volatilizes due to heating and drying after printing, nickel particles contained in the conductive inkjet ink accumulate on the outer peripheral portion, resulting in the thickness of the outer peripheral portion becoming larger than the thickness of the inner peripheral portion.

[0010] When a coffee-ring phenomenon occurs in an electrode layer formed using a conductive inkjet ink, for example, the electrode layer may not be sufficiently covered by an insulating layer provided on the surface of the electrode layer, and there is a possibility of a short circuit between the electrode layers. When pinholes occur in the coating film of the conductive inkjet ink after printing during the drying process, for example, there is concern that the insulating layer provided on the printed film (the dried film of the conductive inkjet ink) may dissolve the insulating layer provided under the printed film. Furthermore, if the conductive inkjet ink dissolves the underlying insulating layer (has sheet attack property with respect to the insulating layer), there is a possibility of a short circuit between the electrode layers.

[0011] However, conventionally, there has been no conductive inkjet ink that suppresses the occurrence of the coffee-ring phenomenon and the occurrence of pinholes while having low sheet attack property with respect to a ceramic layer.

[0012] The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for reducing the sheet attack property with respect to a ceramic layer while suppressing the occurrence of the coffee-ring phenomenon and the occurrence of pinholes in a conductive inkjet ink.

Means for Solving the Problems

[0013] The inkjet ink disclosed herein is used in the manufacture of electronic components. This inkjet ink comprises nickel powder, a binder resin, a dispersant, and an organic solvent. The organic solvent comprises a first organic solvent having a vapor pressure P1 greater than 4 Pa ​​and less than or equal to 100 Pa at 20°C, and a surface tension of 22 mN / m to 30 mN / m, and a second organic solvent having a vapor pressure P2 less than or equal to 4 Pa ​​at 20°C, and a Fedors SP value of at least 8 (cal / cm²). 3 ) 1 / 2 The ink contains a second organic solvent. The organic solvent does not dissolve butyral resin containing 32 mol% or more hydroxyl groups in a temperature environment of 60°C or below. The ratio (Vs2 / Vp) of the volume percentage of nickel powder Vp when the total ink volume is 100% is 1.5 or more. With this configuration, it is possible to reduce sheet attack on the ceramic layer while suppressing the occurrence of coffee rings and pinholes. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a cross-sectional view of the stirring and grinding machine 100. [Figure 2] Figure 2 is an overall view of the inkjet device 1. [Figure 3] Figure 3 is a cross-sectional view of the inkjet head 10. [Modes for carrying out the invention]

[0015] Embodiments of the technology disclosed herein will be described below. Matters other than those specifically mentioned herein but necessary for implementing the technology disclosed herein can be understood as design matters for those skilled in the art based on prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed herein and common technical knowledge in the relevant field. In this specification, the notation "P~Q" indicating a numerical range includes the cases of "P or more and Q or less", "greater than P and less than Q", "greater than P and less than or equal to Q", and "P or more and less than Q".

[0016] <Inkjet ink> The inkjet ink disclosed herein (hereinafter also simply referred to as "ink") may include, for example, (A) nickel powder, (B) a binder resin, (C) a dispersant, and (D) an organic solvent. In the ink, for example, the nickel powder is dispersed in an organic vehicle component (a mixture of the binder resin and the organic solvent). The components contained in the ink disclosed herein will be described below.

[0017] (A) Nickel powder Nickel powder is a material that constitutes a printed film on a substrate. Here, the substrate is preferably one whose surface is composed of a ceramic layer (for example, the insulating layer of a multilayer ceramic capacitor (MLCC)). Here, the "printed film" is a film-like material (dried film) obtained by applying ink to a substrate (in this case, the ceramic layer that constitutes the surface of the substrate) and drying it, and is an unfired body. Nickel powder is also a material that constitutes a fired body of the printed film (hereinafter also referred to as the "fired film") (for example, an electrode) obtained by firing such a printed film. In the ink disclosed herein, the nickel powder may contain nickel as a main component. Here, in this specification, "R contains S as a main component" means that when the total R (for example, the total nickel powder) is considered to be 100% by mass, the content of S (for example, nickel) is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more (the closer to 100% by mass, the better).

[0018] Nickel powder is composed of, for example, nickel particles. Nickel particles may contain nickel as well as unavoidable impurities that may be mixed in during the production process of the nickel particles. Nickel particles may be composed of pure nickel (Ni) or of a nickel alloy. Nickel particles may also be core-shell particles, which have a shell containing nickel as the main component on the surface of a core particle, which is a metal particle. "Nickel alloy" here refers to an alloy containing approximately 50% or more by mass, for example 60% or more by mass, preferably 70% or more by mass, more preferably 80% or more by mass, even more preferably 90% or more by mass, or 98% or less by mass or 95% or less by mass, when the entire alloy is considered as 100% by mass. Examples of nickel alloys include copper-nickel alloys and nickel-chromium alloys.

[0019] The particle size of nickel powder in ink is one of the factors that affect, for example, ejection performance, long-term stability, and the smoothness of the printed film. For example, from the viewpoint of suppressing a decrease in the ejection performance of an inkjet device due to clogging of the ejection port with nickel powder, the average particle size of nickel powder is, for example, 500 nm or less, preferably 450 nm or less, more preferably 400 nm or less, and even more preferably 350 nm or less. Also, from the viewpoint of improving the smoothness of the printed film, the average particle size of nickel powder is, for example, 320 nm or less, more preferably 300 nm or less, even more preferably 250 nm or less, and particularly preferably 200 nm or less. On the other hand, from the viewpoint of suppressing aggregation of particles and suppressing a decrease in the long-term stability of the ink, the average particle size of nickel powder is, for example, 5 nm or more, preferably 10 nm or more, and more preferably 20 nm or more. In this specification, "average particle size" refers to the average particle size based on the dynamic light scattering (DLS) method. The average particle size based on this DLS method is measured in accordance with JIS Z 8828:2013.

[0020] The average primary particle diameter of nickel powder is generally 5 nm to 100 nm. From the viewpoint of achieving a suitable ink viscosity while ensuring that the nickel powder is appropriately aggregated in the ink, the average primary particle diameter of the nickel powder is, for example, 10 nm or more, or 20 nm or more, preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more. From the viewpoint of suppressing excessive aggregation of nickel powder, the average primary particle diameter of the nickel powder is, for example, 90 nm or less, preferably 80 nm or less, and more preferably 70 nm or less. The "average primary particle diameter of nickel powder" is determined here by measuring the nickel powder dispersed in the dispersion medium using the dynamic light scattering method. "Dispersed in the dispersion medium" here means that each nickel particle exists individually in the dispersion medium, and that there are no aggregates formed by the aggregation of two or more nickel particles.

[0021] For measuring the average primary particle size, it is preferable to disperse nickel powder in a dispersion medium using methods such as ultrasonic treatment before measurement. A dispersant may be used as needed. Examples of dispersion media include isobornyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, butyl glycol acetate, butyl diglycol acetate, menthonol propionate, methanol, ethanol, propanol, isopropanol, butanol, n-amyl alcohol, hexanol, heptanol, n-octanol, 2-ethylhexanol, isooctanool, nonanol, decanol, isoundecanol, lauryl alcohol, cetyl alcohol, stearyl alcohol, and water.

[0022] The volume percentage of nickel powder in the ink is not particularly limited and can be set appropriately depending on the printing purpose. For example, as the volume percentage of nickel powder in the ink increases, a printed layer of a suitable thickness can be formed with fewer printing passes. From this viewpoint, when the total ink volume is 100%, the volume percentage of nickel powder is generally 0.1% or more, preferably 0.5% or more, and more preferably 1% or more. On the other hand, as the volume percentage of nickel powder decreases, the stability over time, ejection performance, etc. tend to improve. From this viewpoint, when the total ink volume is 100%, the nickel powder content is generally 20% or less, preferably 15% or less, and more preferably 10% or less.

[0023] The nickel powder content in the ink can be appropriately set, for example, according to the desired thickness of the printed film. Here, when the total ink is considered to be 100% by mass, the nickel powder content is generally 1% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, and particularly preferably 10% by mass or more. On the other hand, when the total ink is considered to be 100% by mass, the nickel powder content is, for example, 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, and particularly preferably 20% by mass or less. In one embodiment of the ink disclosed herein, when the total ink is considered to be 100% by mass, the nickel powder content is generally 5% to 30% by mass, and preferably 10% to 20% by mass.

[0024] (B) Binder resin The binder resin is a component that fixes nickel powder onto the substrate (in this case, the ceramic layer that makes up the surface of the substrate) after inkjet printing of the ink onto the substrate. The ink printed on the substrate is then subjected to a firing treatment, for example, after being heated and dried on the substrate. Therefore, it is preferable that the binder resin completely disappears (burns out) during the firing treatment. As the binder resin, polyvinyl acetal resin is preferably used, for example.

[0025] The ink disclosed herein preferably contains a polyacetal resin as a binder resin. A polyvinyl acetal resin is a resin produced, for example, by acetalizing a polyvinyl alcohol resin with an aldehyde. In addition to the above-described function of fixing nickel powder to a substrate, the polyvinyl acetal resin has a function of dispersing in an organic solvent and assisting the effect of suppressing precipitation of nickel powder by a dispersant. Further, in the polyvinyl acetal resin, for example, by adjusting the content of hydroxyl groups contained in the resin, a configuration suitable for suppressing the occurrence of sheet attack can be realized. Therefore, the polyacetal resin is suitable as a binder resin for the ink disclosed herein. Preferable examples of the polyvinyl acetal resin include, for example, polyvinyl butyral resin, polyvinyl formal resin, and the like.

[0026] The weight average molecular weight of the binder resin can be appropriately set as long as it does not inhibit the effects of the technology disclosed herein. For example, from the viewpoint of appropriately exhibiting the effect of suppressing precipitation of nickel powder, the weight average molecular weight of the binder resin is, for example, 0.5×10 4 or more, preferably 1.0×10 4 or more, more preferably 1.5×10 4 or more, and even more preferably 2.0×10 4 or more. On the other hand, from the viewpoint of maintaining the viscosity of the ink in an appropriate state and suppressing a decrease in ejection performance, the weight average molecular weight of the binder resin is, for example, 10×10 4 or less, preferably 7.5×10 4 or less, more preferably 5.0×10 4 or less, and even more preferably 4.5×10 4The following is even more preferable: The weight-average molecular weight of the binder resin and dispersant is, for example, the weight-based average molecular weight obtained by measuring by gel chromatography (GPC) and converting it using a standard polystyrene calibration curve. For such measurement, for example, a GPC instrument (HLC-8320) manufactured by Tosoh Corporation may be used. Alternatively, the nominal values ​​of the manufacturer or other relevant parties for the resin binder and dispersant, or values ​​calculated based on the chemical formula, may be used.

[0027] The glass transition temperature of the binder resin can be set as appropriate, as long as it does not hinder the effects of the techniques disclosed herein. For example, from the viewpoint of forming a dry film with excellent adhesion, the glass transition temperature of the binder resin is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. Such a glass transition temperature is, for example, 100°C or lower, preferably 90°C or lower, and more preferably 80°C or lower. In this specification, "glass transition temperature" refers to the glass transition temperature (Tg) based on differential scanning calorimetry (DSC). Alternatively, a nominal value from a manufacturer or the like may be used.

[0028] From the viewpoint of reducing sheet attack on the ceramic layer, it is preferable to use a polyvinyl acetal resin as the binder resin, which has lower polarity than the binder resin contained in the inkjet ink used to form the ceramic layer. In the polyvinyl acetal resin contained in the ink disclosed herein, the hydroxyl group content is generally less than 30 mol%. From the viewpoint of achieving suitable solubility in organic solvents described later, the hydroxyl group content is, for example, 28 mol% or less, preferably 25 mol% or less, more preferably 23 mol% or less, and even more preferably 22 mol% or less. Although not particularly limited, from the viewpoint of improving the adsorption of the binder resin to nickel powder, the hydroxyl group content is, for example, 10 mol% or more, preferably 15 mol% or more, and more preferably 19 mol% or more.

[0029] The hydroxyl group content in the binder resin is, in this context, the hydroxyl group content in the polyvinyl acetal resin, with the hydroxyl group content of the polyvinyl alcohol resin before acetalization with aldehydes being set to 100 mol%. For such hydroxyl group content, for example, the nominal value from the manufacturer may be adopted. Alternatively, the measured value obtained using the measurement method described in JIS K0070:1992 "Test methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiables of chemical products" may be adopted.

[0030] The volume percentage of the binder resin in the ink can be set appropriately, as long as it does not hinder the effects of the technology disclosed herein. For example, when the total ink volume is 100%, the volume percentage of the binder resin is generally 0.3% to 3%, and preferably 0.5% to 1.5%.

[0031] (C) Dispersant The dispersant is a component that uniformly disperses nickel particles in the ink and suppresses aggregation and sedimentation of the nickel particles. The ink disclosed herein preferably contains a cationic dispersant. The cationic dispersant is, for example, a dispersant having a cationic functional group. The cationic dispersant adheres to the surface of the nickel particles, for example, via the cationic functional group, causing steric hindrance. This suppresses aggregation of nickel particles and, consequently, improves the long-term stability of the ink.

[0032] As cationic dispersants, conventionally known cationic dispersants used in this type of application can be used without particular limitation. Examples of cationic dispersants include amine dispersants, imidazoline dispersants, and quaternary ammonium dispersants. Examples of amine dispersants include alkyl polyamine dispersants, polyalkylene polyamine dispersants, fatty acid amine dispersants, and polyester amine dispersants. Examples of imidazoline dispersants include alkylimidazolines. Note that cationic dispersants may be used alone or in combination of two or more types.

[0033] As a cationic dispersant, amine-based dispersants can be preferably used. Amine-based dispersants are, for example, organic compounds having an amine group in their molecule. Among these, chain-like amine-based dispersants having an amine group at least at one end are preferably used. Preferred examples of such amine-based dispersants include fatty acid amine-based dispersants and polyester amine-based dispersants. Although not particularly limited, the weight-average molecular weight of the amine-based dispersant is, for example, 1 × 10⁻⁶. 3 ~5×10 4 It is preferable to set it to this. Although not particularly limited, as a specific example of a cationic dispersant, HPA-N117 manufactured by Lubrizol Japan Co., Ltd. is preferably used.

[0034] The volume percentage of the dispersant in the ink can be set as appropriate, as long as it does not hinder the effects of the technology disclosed herein. For example, when the total ink volume is 100%, the volume percentage of the dispersant is generally 0.5% to 5%, and preferably 1% to 3%.

[0035] Furthermore, the dispersant may include a nonionic dispersant as needed. A nonionic dispersant is a dispersant that does not have a group that ionizes when dissolved in water. Nonionic dispersants are less likely to adhere to the surface of inorganic particles (in this case, nickel particles) compared to cationic dispersants. However, if a cationic dispersant having a cationic functional group (e.g., an amine group) at one end adheres to the surface of inorganic particles, a nonionic dispersant may adhere to the other end of the cationic dispersant. In this case, the steric hindrance can be strengthened by the cationic dispersant formed on the surface of the inorganic particles. Therefore, the effect of the dispersant in suppressing the aggregation of inorganic particles can be enhanced.

[0036] (D) Organic solvents Organic solvents can disperse nickel powder and impart fluidity and other properties to the ink suitable for inkjet printing. Organic solvents are required to have surface tension suitable for improving refillability as inkjet inks, as well as to suppress ink flow when the ink film is heat-dried after inkjet printing. The inventors focused on the evaporation rate of organic solvents. During heat drying, the organic solvent evaporates from the surface of the film exposed to air. However, the inventors' research revealed that, depending on the vapor pressure of the surrounding organic solvent, the evaporation rate is particularly high at the outer periphery of the film. From this, the inventors hypothesized that intra-film flow of the organic solvent occurs from the inner to the outer periphery of the film. Before the ink has fully dried, this flow is contained within the film, maintaining the homogeneity of the solids (in this case, nickel powder) within the film. However, as drying progresses, the flow of solids at the outer periphery stops before that at the inner periphery, causing the solids to accumulate at the outer periphery. This can impair the smoothness of the printed film.

[0037] In response to this, the inventor conceived of using a two-component organic solvent. These two components are a relatively low-volatility organic solvent and a relatively high-volatility organic solvent. The inventor's research revealed that by including a relatively low-volatility organic solvent, the ink simultaneously loses its fluidity throughout the entire ink film, as if it were a high-viscosity paste with a smooth print already applied. The low-volatility solvent is uniformly diffused and supplied within the film, thus suppressing the accumulation of solids at the outer periphery. In addition, from another perspective, some relatively low-volatility organic solvents, for example, have a molecular structure that makes them difficult to dissolve with the dispersant contained in the ink. Organic solvents that are difficult to dissolve with the dispersant are, for example, not compatible with nickel particles whose surfaces have been modified by the dispersant, and may separate from the nickel particles and accumulate in the ink. In the areas where the organic solvent accumulates, for example, nickel particles become less likely to be present, making it easier for pinholes to form in the printed film. In this regard, the inventors investigated a molecular structure for a relatively low-volatility organic solvent that is less polar than the organic solvent used in the ceramic layer, while also considering the sheet attack properties of the ink on the ceramic layer, and that is easily mutually soluble with the dispersant. As a result, by using an organic solvent whose Fedors SP value is within a predetermined range as a relatively low-volatility organic solvent, they obtained a combination of two organic solvents that suppresses the occurrence of the coffee ring phenomenon described above, suppresses the occurrence of pinholes, and reduces the sheet attack properties on the ceramic layer. It should be noted that the mechanism described above is based on the inventors' speculation, and there is no intention to limit the mechanism by which the effects of the technology disclosed herein are obtained.

[0038] The ink disclosed herein contains an organic solvent comprising a first organic solvent and a second organic solvent. The vapor pressures of the first and second organic solvents at 20°C are within a predetermined range. The vapor pressures of the organic solvents at 20°C may be the nominal values ​​of the manufacturers or other relevant parties.

[0039] The first organic solvent is, for example, an organic solvent whose vapor pressure P1 at 20°C is greater than 4 Pa ​​and less than or equal to 100 Pa, and whose surface tension is 22 mN / m to 30 mN / m (preferably 25 mN / m to 29 mN / m). The surface tension of the first organic solvent may be measured, for example, using a commercially available static surface tensimeter (the same applies to the surface tension of the second organic solvent described later). The first organic solvent can, for example, increase the fluidity of nickel powder and contribute to thinning the printed film. In addition, the first organic solvent may have the function of improving the long-term stability of the ink. The vapor pressure P1 is not particularly limited as long as it is within the above range, but may be, for example, 10 Pa or more. The vapor pressure P1 may be 90 Pa or less, or 80 Pa or less.

[0040] The boiling point BP1 of the first organic solvent under atmospheric pressure conditions is preferably approximately 150°C to 230°C. For example, when heating and drying the ink, from the viewpoint of making the first organic solvent more volatile, the boiling point BP1 is preferably 225°C or lower, and more preferably 220°C or lower. For example, when firing the printed film, from the viewpoint of improving the sinterability of nickel particles, the boiling point BP1 is, for example, 160°C or higher, preferably 170°C or higher, and more preferably 180°C or higher.

[0041] The first organic solvent may consist of at least one of the following: ethers, esters, and alcohols. The first organic solvent may consist of at least one compound classified as an ether, ester, or alcohol, having a vapor pressure P1 greater than 4 Pa ​​and less than or equal to 100 Pa, and a surface tension of 22 mN / m to 30 mN / m. In this specification, "ethers" refers to a group of compounds having at least one ether bond (-COC-) in the main chain (nucleus). In this specification, "esters" refers to a group of compounds having at least one ester bond (RC(=O)-O-R') in the main chain. In the following description, if a molecule has multiple functional groups, it will be classified according to IUPAC nomenclature. However, if a molecule has both an ether bond and a hydroxyl group, it is classified as an ether.

[0042] Examples of ethers used as the first organic solvent include glycol ethers. Examples of esters used as the first organic solvent include glycol ether acetates. Examples of alcohols used as the first organic solvent include aliphatic alcohols.

[0043] In this specification, "glycol ether" means an aliphatic or alicyclic compound in which two hydroxyl groups are bonded to two different carbon atoms, wherein one or two of the hydrogen atoms of the hydroxyl groups are substituted with a hydrocarbon group or a hydrocarbon group containing an ether bond. Glycol ethers include, for example, glycol monoalkyl ethers in which only one hydrogen atom of a hydroxyl group is substituted, and glycol dialkyl ethers in which both hydrogen atoms of the hydroxyl groups are substituted. As the glycol ether in the first organic solvent, for example, diethylene glycol butyl methyl ether, diethylene glycol diethyl ether, and the like can be preferably used.

[0044] In this specification, "glycol ether acetate" refers to a compound obtained by esterifying the glycol ether described above. For example, butyl monoglycol acetate (BMGAC) can be preferably used as the glycol ether acetate in the first organic solvent.

[0045] In this specification, "alcohols" refers to a group of compounds in which a hydrogen atom of a hydrocarbon is substituted with a hydroxyl group, and which are represented by the general formula: R-OH. As the alcohol in the first organic solvent, for example, 1-octanol, tetrahydrolinalool, and the like can be preferably used.

[0046] The second organic solvent has a vapor pressure P2 of 4 Pa ​​or less at 20°C and a Fedors SP value of at least 8 (cal / cm³). 3 ) 1 / 2This is a certain organic solvent. The second organic solvent can suppress the excessive increase in the fluidity and dispersibility of the nickel powder caused by the first organic solvent, and contribute to achieving an appropriate dispersion state of nickel powder in the ink. The vapor pressure P2 is, for example, 3 Pa or less, preferably 2 Pa or less, and more preferably 1 Pa or less. On the other hand, the vapor pressure P2 may be, for example, 0.01 Pa or more, or 0.05 Pa or more.

[0047] The Fedors SP value of the second organic solvent is, for example, 8 (cal / cm³). 3 ) 1 / 2 ~10 (cal / cm 3 ) 1 / 2 Preferably 8 (cal / cm²) 3 ) 1 / 2 ~9 (cal / cm 3 ) 1 / 2 More preferably 8 (cal / cm²) 3 ) 1 / 2 ~8.5 (cal / cm 3 ) 1 / 2 The SP value is a measure of the "ease of mixing" between the solid components of an ink and an organic solvent, for example. In this specification, "SP value" refers to the solubility parameter (SP) calculated using the method (Fedors method) described in RFFedors, Polymer Engineering Science, 14, p147 (1974). The SP value is unique to each compound. The SI unit of the SP value is (J / cm²). 3 ) 1 / 2 or (MPa) 1 / 2 However, in this specification, the conventionally used (cal / cm 3 ) 1 / 2 The SP value is used. The unit of the SP value is given by the following formula: 1 (cal / cm 3 ) 1 / 2 ≈2.05 (J / cm) 3 ) 1 / 2 ≈2.05 (MPa) 1 / 2 It can be converted using semicolons.

[0048] While not particularly limited, the surface tension of the second organic solvent is, for example, 25 mN / m to 29 mN / m, preferably 26 mN / m to 28 mN / m, and more preferably 27 mN / m to 28 mN / m.

[0049] The second organic solvent may consist of, for example, ethers. Examples of ethers used as the second organic solvent include glycol ethers. Diethylene glycol dibutyl ether is preferably used as the glycol ether used as the second organic solvent.

[0050] The boiling point BP2 of the second organic solvent under atmospheric pressure conditions is preferably higher than the boiling point BP1 of the first organic solvent under the same conditions. For example, from the viewpoint of suppressing the occurrence of the coffee ring phenomenon, the difference between the boiling points BP2 and BP1 is preferably 20°C or more, more preferably 30°C or more, and even more preferably 40°C or more. On the other hand, for example, from the viewpoint of properly volatilizing the second organic solvent during the heating and drying of the ink, the difference between the boiling points BP2 and BP1 is preferably 80°C or less, and even more preferably 70°C or less.

[0051] The boiling point BP2 of the second organic solvent under atmospheric pressure conditions is preferably approximately 230°C to 280°C. For example, when heating and drying the ink, from the viewpoint of making the second organic solvent more volatile, the boiling point BP2 is preferably 270°C or lower, and more preferably 260°C or lower. For example, when firing the printed film, from the viewpoint of improving the sinterability of nickel particles, the boiling point BP2 is preferably 235°C or higher, preferably 240°C or higher, and more preferably 245°C or higher.

[0052] In the ink disclosed herein, for example, the ratio (Vs2 / Vp) of the volume percentage Vs2 of the second organic solvent when the entire ink is considered as 100% by volume to the volume percentage Vp of nickel powder when the entire ink is considered as 100% by volume is preferably 1.5 or higher. By including the second organic solvent in the ink in a volume of 1.5 times or more relative to the volume of nickel powder, the nickel powder can be appropriately dispersed in the ink. During the heat drying of the ink, the movement of nickel powder as the ink dries can be suppressed, and consequently, the smoothness of the printed film can be improved. From this viewpoint, the ratio (Vs2 / Vp) is, for example, 2 or higher, preferably 5 or higher, more preferably 10 or higher, and even more preferably 15 or higher. On the other hand, from the viewpoint of appropriately dispersing the nickel powder in the ink, the ratio (Vs2 / Vp) is preferably less than 25, and even more preferably 23 or lower.

[0053] From the viewpoint of making the second organic solvent more easily volatilized during the heat drying of the ink, it is preferable that the volume ratio of the second organic solvent is smaller than that of the first organic solvent. In this case, when the total of the first and second organic solvents is 100% by volume, the volume ratio of the second organic solvent is, for example, less than 50% by volume, preferably 45% or less by volume, and more preferably 40% or less by volume. From the viewpoint of suppressing the occurrence of the coffee ring phenomenon and the occurrence of pinholes, when the total of the first and second organic solvents is 100% by volume, the volume ratio of the second organic solvent is, for example, 20% or more by volume, preferably 25% or more by volume, and more preferably 30% or more by volume.

[0054] While not specifically limited, the weighted average SP value of organic solvents is, for example, 8 (cal / cm³). 3 ) 1 / 2 ~9 (cal / cm 3 ) 1 / 2 (Preferably 8 (cal / cm³) 3 ) 1 / 2 ~8.5 (cal / cm 3 ) 1 / 2It is desirable that this be the case. In this context, "weighted average SP value of organic solvents" refers to the sum of the products of the SP value of each organic solvent contained in the ink and the composition ratio of each organic solvent (weighted average value).

[0055] Insofar as the effects of the technology disclosed herein are realized, the organic solvent may include a third organic solvent that is not classified as either the first or second organic solvent. From the viewpoint of better realizing the effects of the technology disclosed herein, the first and second organic solvents make up approximately 70% by volume or more of the total organic solvent, for example, 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more, even more preferably 95% by volume or more, particularly preferably 98% by volume or more, and the closer to 100% by volume, the better.

[0056] The organic solvent is preferably one that does not dissolve a butyral resin containing 32 mol% or more hydroxyl groups (e.g., polyvinyl butyral resin) in a temperature environment of 60°C or below. By having such characteristics, the organic solvent can reduce the sheet attack of the ink against the ceramic layer (e.g., an insulating layer containing a butyral resin containing 32 mol% or more hydroxyl groups).

[0057] While not particularly limited, for example, from the viewpoint of improving ink ejection performance, when the total ink volume is considered to be 100% by volume, the volume percentage of the organic solvent is, for example, 80% by volume or more, preferably 85% by volume or more, and more preferably 90% by volume or more.

[0058] (E) Other ingredients The inks disclosed herein may further contain known additives used in inkjet inks, to the extent that they do not impair the effects of the disclosed technology. The types of such additives, their amounts, etc., can be appropriately changed based on conventionally known common sense, and do not characterize the disclosed technology. Therefore, a detailed explanation is omitted here.

[0059] <Preparation of inkjet ink> Next, the procedure for preparing (manufacturing) the ink disclosed herein will be described. The ink disclosed herein is prepared by mixing the above-mentioned components and then crushing and dispersing nickel powder. Figure 1 is a cross-sectional view of the stirring and grinding machine 100. The following description is merely an example of a means for preparing the ink disclosed herein and is not intended to limit the technology disclosed herein.

[0060] In manufacturing the ink disclosed herein, first, a slurry (including paste and suspension), which is a precursor to the ink, is prepared by weighing and mixing the above-mentioned components. Then, the ink is prepared by stirring the slurry and crushing the nickel powder using a stirring and grinding machine 100 as shown in Figure 1. For example, after adding crushing beads (e.g., zirconia beads with an average particle size of 10 μm to 150 μm) to the slurry, the slurry is supplied from the supply port 110 into the stirring container 120. Inside the stirring container 120 is a shaft 134 having a plurality of stirring blades 132. One end of the shaft 134 is attached to a motor (not shown), and by operating the motor and rotating the shaft 134, the plurality of stirring blades 132 stir the slurry while sending it downstream in the liquid supply direction D. During this stirring, the nickel powder is crushed by the crushing beads, and the finely granulated nickel powder is dispersed in the slurry.

[0061] The slurry, which has been sent downstream in the liquid delivery direction D, then passes through the filter 140. As a result, nickel powder that has not been atomized, crushing beads, etc. are collected in the filter 140, and ink with sufficiently dispersed nickel powder is discharged from the outlet 150. In this process, the average particle size of the nickel powder can be adjusted to a desired range by appropriately adjusting the pore size of the filter 140, the average particle size of the crushing beads, etc.

[0062] <Applications of inkjet ink> Next, the applications of the ink disclosed herein will be described. The ink is used in the manufacture of electronic components. In this specification, "used in electronic components" includes not only the method of directly printing the ink onto the surface of an inorganic substrate, but also the method of indirectly adhering the ink to the surface of an inorganic substrate via an intermediate material such as transfer paper.

[0063] (1) Print Figure 2 is an overall view of the inkjet device 1. Figure 3 is a cross-sectional view of the inkjet head 10. The ink is printed onto the surface of the object to be printed by the inkjet device 1 as shown in Figure 2. The material and shape of the inorganic substrate W to be printed are not particularly limited, and any material commonly used as a substrate for electronic components can be used without particular restriction. In this embodiment, the inorganic substrate W may be an inorganic substrate with a ceramic layer on its surface, a ceramic green sheet, etc.

[0064] As shown in Figure 2, the inkjet device 1 includes an inkjet head 10 that stores ink. The inkjet head 10 is housed inside a print cartridge 40. The print cartridge 40 is inserted onto a guide shaft 20 and is configured to reciprocate along the axial direction X of the guide shaft 20. Although not shown in the figure, the inkjet device 1 also includes a moving mechanism for moving the guide shaft 20 in the vertical direction Y. This allows the inkjet device 1 to eject ink to a desired position on the inorganic substrate W.

[0065] For the inkjet head 10, for example, a piezo-type inkjet head as shown in Figure 3 may be used. The piezo-type inkjet head 10 is provided with a storage section 13 for storing ink inside the case 12, and the storage section 13 is in communication with the ejection section 16 via a liquid delivery path 15. The ejection section 16 is provided with an ejection port 17 that is open to the outside of the case 12, and a piezo element 18 is positioned opposite the ejection port 17. In the inkjet head 10, the ink inside the ejection section 16 is ejected from the ejection port 17 toward the inorganic substrate W (see Figure 2) by vibrating the piezo element 18.

[0066] (2) Drying treatment Next, the inorganic substrate W to which the ink is attached is subjected to a drying treatment by heating it at a predetermined temperature. This removes the organic solvent from the ink and forms a printed film (dried film) on the inorganic substrate W. The ink disclosed herein contains a first organic solvent and a second organic solvent having predetermined properties in a predetermined volume ratio, so that the nickel powder is in an appropriate dispersion state in the ink. Furthermore, during the drying treatment, in the ink attached to the inorganic substrate W, the first organic solvent, which has a relatively high vapor pressure (relatively low boiling point), volatilizes first, followed by the second organic solvent, which has a relatively low vapor pressure (relatively high boiling point). Therefore, even during the drying process, an appropriate dispersion state for the nickel powder is maintained in the ink. As a result, a printed film with improved smoothness can be obtained after drying. In addition, the second organic solvent, in terms of its molecular structure, has the property of being easily mutually soluble with the dispersant contained in the ink. Therefore, the second organic solvent and the nickel powder with the dispersant attached to its surface blend appropriately, which suppresses the separation of the second organic solvent in the ink. This suppresses the occurrence of pinholes in the ink coating or printed film applied on the inorganic substrate W. Furthermore, the organic solvent contained in the ink does not dissolve butyral resin containing 32 mol% or more hydroxyl groups in a temperature environment of 60°C or below. Therefore, the sheet attack properties of the ink on the inorganic substrate W are reduced. The heating temperature in the drying process can be set to a temperature at which the organic solvent is removed and sintering of the nickel powder does not occur (for example, 50°C to 150°C).

[0067] (3) Firing This manufacturing method includes firing the inorganic substrate W after the printed film has been formed. This process burns away the organic components, including the binder resin, while the nickel powder sinters and adheres to the surface of the inorganic substrate W. As a result, an electronic component having a fired film mainly composed of nickel powder is manufactured. The firing temperature is preferably set to, for example, 500°C to 2000°C.

[0068] Next, we will describe some test examples relating to the technology disclosed herein. Note that the following test examples are not intended to limit the scope of the technology disclosed herein.

[0069] [Prepare the materials] (Nickel powder) As the nickel powder, we prepared nickel powder with an average primary particle size of 60 nm.

[0070] (Organic solvents) The following seven types of organic solvents were prepared. The physical properties of the following organic solvents are shown in Table 1. Of the physical properties shown in Table 1, the SP values ​​were obtained using the Fedors method described above. The boiling points (boiling points under atmospheric pressure) and vapor pressures at 20°C shown in Table 1 are the nominal values ​​from each manufacturer. The surface tension of each organic solvent shown in Table 1 was measured for each organic solvent using a static surface tensimeter (DYNEMASTER DY-300, manufactured by Kyowa Interface Science Co., Ltd.).

[0071] • Organic solvent S1: Tetradecane, manufactured by Kanto Chemical Co., Ltd., CAS No. 629-59-4 • Organic solvent S2: Diethylene glycol butyl methyl ether (Hysolve BDM), manufactured by Toho Chemical Industry Co., Ltd., CAS No. 7382-32-3 • Organic solvent S3: Diethylene glycol dibutyl ether (Hysolve BDB), manufactured by Toho Chemical Industry Co., Ltd., CAS No. 112-73-2 • Organic solvent S4: Diethylene glycol diethyl ether (Hysolve EDE), manufactured by Toho Chemical Industry Co., Ltd., CAS No. 112-36-7 • Organic solvent S5: Methyl benzoate, manufactured by Tokyo Chemical Industry Co., Ltd., CAS No. 93-58-3 • Organic solvent S6: 2,2,4-Trimethyl-1,3-pentanediol 1-monoisobutyrate (NG-120), CAS No. 25265-77-4 • Organic solvent S7: Butyl benzoate, manufactured by Tokyo Chemical Industry Co., Ltd., CAS No. 136-60-7

[0072] [Table 1]

[0073] (Binder resin) The following binder resins were prepared. Polyvinyl acetal resin with 21 mol% hydroxyl groups and a weight-average molecular weight of 32,000 (manufactured by Sekisui Chemical Co., Ltd., "BL-5Z")

[0074] (Dispersant) As a dispersant, a cationic dispersant (HPA-N117, manufactured by Lubrizol Japan Co., Ltd.) was prepared.

[0075] [Ink preparation] Seven types of inks were prepared, each containing nickel powder, a binder resin, a dispersant, and an organic solvent. First, a slurry was prepared by mixing nickel powder and an organic vehicle (organic solvent, binder resin, and dispersant) in a predetermined mass ratio. This slurry was then subjected to a crushing and dispersion treatment using crushing beads (zirconia beads with an average particle size of 30 μm) (rotation speed: 1500 rpm, mixing time: 16 hours), and the ink was obtained by filter filtration under pressure. The organic solvents used in each example are shown in the corresponding column of Table 2. The nickel powder used in each example was the nickel powder described above. The binder resin used in each example was the binder resin described above. The dispersant used in each example was the cationic dispersant described above. The results of the evaluation of the inks 1 to 7 prepared in this test example are shown in Table 2.

[0076] Regarding nickel powder, the values ​​listed in Table 2 represent the content (mass%) when the total ink is considered to be 100% by mass. Regarding binder resin and dispersant, the values ​​listed in Table 2 represent the content (mass%) when the organic vehicle is considered to be 100% by mass. Regarding organic solvents, the values ​​listed in Table 2 represent the volume ratio of each organic solvent when the total organic solvent is considered to be 100% by volume. The values ​​listed in the "Vs2 / Vp" column of Table 2 represent the ratio (Vs2 / Vp) of the volume ratio of nickel powder when the total ink is considered to be 100% by volume, to the volume ratio of the organic solvent with a relatively high boiling point, Vs2, when the total ink is considered to be 100% by volume. Regarding organic solvents, the "weighted average SP value" listed in Table 2 is the sum of the products of the SP value of each organic solvent and the composition ratio of each organic solvent (weighted average value). Regarding the dispersant and nickel powder, the values ​​listed in the "Vcd / Vp" column of Table 2 represent the ratio (Vcd / Vp) of the volume percentage of the dispersant (Vcd) to the volume percentage of the nickel powder (Vp) when the total ink volume is set to 100%.

[0077] [Table 2]

[0078] [Evaluation Test] A. Ink characteristics (A-1) Viscosity The viscosity (mPa·s) of each ink sample was measured using a B-type viscometer (Brookfield, DV-III ULTRA spindle SC4-14) while maintaining the ink at 25°C. The rotor speed of the B-type viscometer was set to 10 rpm. The results are shown in Table 2. Here, inks with a viscosity of 30 mPa·s or less were evaluated as having appropriate viscosity for the inkjet head.

[0079] (A-2) Average particle diameter The average particle size of the particles contained in the ink was measured using dynamic light scattering (DLS). The results are shown in Table 2. In this study, inks with an average particle size of 20 nm to 320 nm were evaluated as having good dispersibility of nickel powder.

[0080] (A-3) Daily measurement (measurement of daily stability) After preparation, a portion of the ink was collected in two storage bottles. One bottle was stored at 25°C and the other at 60°C. The average particle size of each ink, stored at 1 week, 2 weeks, 3 weeks, 4 weeks, and 8 weeks, was measured using dynamic light scattering (DLS) spectroscopy. The results are shown in Table 2. Here, for both the 25°C and 60°C environments, an average particle size of 20 nm to 320 nm after 2 weeks was evaluated as "good long-term stability," while anything outside this range was evaluated as "poor long-term stability."

[0081] (A-4) Surface tension The surface tension (mN / m) of the inks was measured using the static surface tensimeter described above. Inks with a surface tension in the range of 25 (mN / m) to 35 (mN / m) were evaluated as having good surface tension. The results are shown in Table 2.

[0082] B. Evaluation of the coffee ring phenomenon The occurrence of the coffee ring phenomenon in ink was evaluated using an inkjet printer (Fujifilm Corporation: Material Printer DMP-2831). In this test, the inkjet printer's ejection frequency was set to 1 kHz, and four 2 mm x 2 mm patterns were solid-printed together on the surface of an alumina substrate. The occurrence of the coffee ring phenomenon was evaluated for the printed patterns using a surface roughness meter (Mitutoyo Corporation, "SURFTEST SV-3100"). Specifically, the film thickness was measured at three points on the edge of each pattern, and the maximum value was obtained. In addition, the film thickness was measured at three points on the center of each pattern, and the average value was obtained. The following formula (A) was used for the obtained calculated values: Maximum thickness at the edge / average thickness at the center < 2 (A) Examples that satisfied the above condition were evaluated as "none (no occurrence of coffee ring phenomenon)". On the other hand, examples that did not satisfy the above formula (A) were evaluated as "present (coffee ring phenomenon occurred)". The results are shown in Table 2.

[0083] C. Evaluation of pinhole occurrence Patterns were prepared using the same procedure as described in item B above. A laser microscope was used to evaluate the presence or absence of pinholes in these printed patterns. Here, the entire surface of each pattern was observed, and examples without pinholes were evaluated as "none (no pinholes)". On the other hand, examples with one or more pinholes were evaluated as "present (pinholes present)".

[0084] D. Evaluation of seat attack performance The organic solvent contained in the inks of each example was prepared and heated to 90°C. Polyvinyl butyral resin (Sekisui Chemical Co., Ltd.'s "BX-L") (a polyvinyl butyral resin containing 32 mol% hydroxyl groups and a weight-average molecular weight of 18,000) was dissolved in it at a concentration of 1% by weight. This solution was cooled to 60°C. When the solution temperature reached 60°C, the presence or absence of resin precipitation was visually observed. If resin precipitation occurred (i.e., the resin was not dissolved in the organic solvent at a temperature of 60°C), it was evaluated as "none (no sheet attack)". If no resin precipitation occurred, it was evaluated as "present (sheet attack present)". The results are shown in Table 2.

[0085] E. Overall Rating For inks that were evaluated as "none" for coffee ring phenomenon, pinhole occurrence, and sheet attack properties, they were evaluated as "○" because they solve the problems of the technology disclosed herein. For inks that were evaluated as "present" for any one of the coffee ring phenomenon, pinhole occurrence, or sheet attack properties, they were evaluated as "×" because they do not solve the problems of the technology disclosed herein. The results are shown in Table 2.

[0086] As shown in Table 2, the inks in Example 1 and Example 2 were evaluated as "none" for the occurrence of coffee rings, pinholes, and sheet attack. The inks in Example 1 and Example 2 contained nickel powder, binder resin, dispersant, and organic solvent. The organic solvent consisted of a first organic solvent with a vapor pressure P1 of more than 4 Pa ​​and less than or equal to 100 Pa at 20°C and a surface tension of 22 mN / m to 30 mN / m, and a second organic solvent with a vapor pressure P2 of 4 Pa ​​or less at 20°C and a Fedors SP value of at least 8 (cal / cm²). 3 ) 1 / 2 The ink contained a second organic solvent. The organic solvent was such that it did not dissolve butyral resin containing 32 mol% or more hydroxyl groups in an environment below 60°C. Furthermore, the ratio (Vs2 / Vp) of the volume percentage of the second organic solvent (Vs2) when the total ink volume is 100 vol. to the volume percentage of nickel powder (Vp) when the total inkjet ink volume is 100 vol. was 1.5 or greater.

[0087] The technologies disclosed herein have been described above, but these are merely examples and do not limit the scope of the claims. The technologies disclosed herein may be modified in various ways without departing from their essence.

[0088] The technologies disclosed herein include the technologies described in the following sections. Section 1: Inkjet ink used in the manufacture of electronic components, Nickel powder and Binder resin, Dispersant and Organic solvents and Includes, Here, The aforementioned organic solvent is A first organic solvent having a vapor pressure P1 at 20°C greater than 4 Pa ​​and less than or equal to 100 Pa, and a surface tension of 22 mN / m or more and less than or equal to 30 mN / m, The vapor pressure P2 at 20°C is 4 Pa ​​or less, and the Fedors SP value is at least 8 (cal / cm²). 3 ) 1 / 2A second organic solvent, Includes, A butyral resin containing 32 mol% or more of hydroxyl groups does not dissolve in a temperature environment of 60°C or below. An inkjet ink in which the ratio (Vs2 / Vp) of the volume percentage Vs2 of the second organic solvent when the entire inkjet ink is considered as 100% by volume, to the volume percentage Vp of the nickel powder when the entire inkjet ink is considered as 100% by volume, is 1.5 or greater. Section 2: The inkjet ink according to item 1, wherein the boiling point BP2 of the second organic solvent under atmospheric pressure conditions is higher than the boiling point BP1 of the first organic solvent under the same conditions, and the difference between the boiling points BP1 and BP2 is at least 20°C. Section 3: The inkjet ink according to claim 1 or 2, wherein the volume proportion of the second organic solvent is smaller than the volume proportion of the first organic solvent. Section 4: The inkjet ink according to any one of items 1 to 3, wherein when the sum of the first organic solvent and the second organic solvent is 100% by volume, the volume percentage of the second organic solvent is 20% by volume or more and less than 50% by volume. Section 5: The inkjet ink according to any one of claims 1 to 4, wherein the first organic solvent is at least one selected from the group consisting of ethers, esters, and alcohols. Item 6: The inkjet ink described in any one of items 1 to 5, wherein the second organic solvent is an ether. Section 7: The inkjet ink according to any one of items 1 to 6, wherein the average primary particle diameter of the nickel powder dispersed in a dispersion medium is 5 nm or more and 100 nm or less, as measured by dynamic light scattering. [Explanation of symbols]

[0089] 1. Inkjet device 10 inkjet heads 12 cases 13 Storage section 15. Fluid delivery routes 16 Discharge part 17 Discharge port 18 Piezo elements 20 Guide axis 40 Print Cartridges 100 Mixing and Grinding Machine 110 Supply port 120 stirring vessel 132 Agitator blades 134 shaft 140 filters 150 Outlet

Claims

1. Inkjet ink used in the manufacture of electronic components, Nickel powder and Binder resin and Dispersant and Organic solvents and Includes, Here, The aforementioned organic solvent is Vapor pressure P at 20°C １ A first organic solvent having a pressure greater than 4 Pa ​​and less than or equal to 100 Pa, and a surface tension of 22 mN / m or more and less than or equal to 30 mN / m, Vapor pressure P at 20°C ２ The pressure is 4 Pa ​​or less, and the Fedors SP value is at least 8 (cal / cm³). ３ ) １／２ A second organic solvent, Includes, A butyral resin containing 32 mol% or more of hydroxyl groups does not dissolve in a temperature environment of 60°C or below. An inkjet ink in which the ratio (Vs2 / Vp) of the volume percentage Vs2 of the second organic solvent when the entire inkjet ink is considered as 100% by volume, to the volume percentage Vp of the nickel powder when the entire inkjet ink is considered as 100% by volume, is 1.5 or more.

2. The inkjet ink according to claim 1, wherein the boiling point BP2 of the second organic solvent under atmospheric pressure conditions is higher than the boiling point BP1 of the first organic solvent under the same conditions, and the difference between the boiling point BP1 and the boiling point BP2 is at least 20°C.

3. The inkjet ink according to claim 1, wherein the volume proportion of the second organic solvent is smaller than the volume proportion of the first organic solvent.

4. The inkjet ink according to claim 3, wherein when the sum of the first organic solvent and the second organic solvent is 100% by volume, the volume percentage of the second organic solvent is 20% by volume or more and less than 50% by volume.

5. The inkjet ink according to claim 1, wherein the first organic solvent is at least one selected from the group consisting of ethers, esters, and alcohols.

6. The inkjet ink according to claim 5, wherein the second organic solvent is an ether.

7. The inkjet ink according to claim 1, wherein the average primary particle diameter of the nickel powder dispersed in a dispersion medium is 5 nm or more and 100 nm or less when measured by dynamic light scattering.

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