Conductive inkjet ink

Abstract

To provide a conductive inkjet ink that realizes both of suppressing occurence of sheet attack, and improving dischargeability.SOLUTION: A conductive inkjet ink disclosed herein includes inorganic powder and three organic solvents. The first solvent has the viscosity of 5 mPa s or less and an SP value of 8 to 10 (cal / cm3)0.5. The second solvent has the viscosity of 10 to 100 mPa s and an SP value of 9 to 11 (cal / cm3)0.5. The third solvent has the viscosity of 3 mPa s or less and an SP value of less than 8 (cal / cm3)0.5. With respect to the total weight of the organic solvent, a content C1 (wt%) of the first solvent, the content C2 (wt%) of the second solvent, and the content C3 (wt%) of the third solvent satisfy the following formulas (1) to (3): 5≤C1≤75 (1) 20≤C2≤60 (2) 0.5 C2-10≤C3≤0.5 C2+10 (3).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to conductive inkjet inks. [Background technology]

[0002] Inkjet printing has traditionally been used as a printing method for printing images such as patterns and letters on a printing target. Because inkjet printing can print high-precision images on demand at low cost and with minimal damage to the printing target, its application to various fields has been considered. For example, in recent years, the use of inkjet printing has been considered for forming conductive films that constitute conductive circuit patterns (electrodes, etc.) of electronic components. By using inkjet printing, the variation in the thickness of the conductive film can be reduced compared to screen printing. Therefore, it is expected that inkjet printing will reduce the variation in the conductivity of the conductive film and enable the printing of finer conductive circuit patterns.

[0003] In the manufacture of such electronic components, for example, conductive inkjet ink (hereinafter also referred to as "conductive ink") is used, to which inorganic powder containing metal particles or the like is added as a conductive material. As an example of such a conductive ink, Patent Document 1 discloses a conductive ink containing nanometal powder such as silver or a silver-copper alloy. Furthermore, Patent Document 2 discloses a conductive ink containing metal oxide fine particles that are reduced by heat treatment, such as silver oxide, copper oxide, palladium oxide, nickel oxide, lead oxide, or cobalt oxide. In order to form an appropriate conductive circuit pattern by inkjet printing, for example, the conductive ink is required to have low viscosity and a high concentration of inorganic powder. The above-mentioned Patent Documents 1 and 2 propose technologies for achieving these inkjet suitabilities.

[0004] Furthermore, from the viewpoint of ensuring ejection properties during printing and conductivity after printing, conductive inks are also required to have stably dispersed inorganic powders. For example, Patent Document 3 discloses a technique of adding a first dispersant having only either an acidic adsorption group or a basic adsorption group, and a second dispersant having both an acidic adsorption group and a basic adsorption group, in order to improve the dispersibility of solid fine particles having a mixture of acid sites and basic sites on the surface.

[0005] Furthermore, in conductive inks, it is desirable to reduce the variation in the thickness of the conductive film from the viewpoint of reducing the variation in the conductivity of the conductive film and realizing a fine conductive circuit pattern. For example, Patent Document 4 discloses the addition of an organic solvent that increases the surface tension in order to reduce the wetting and spreading of a spacer particle dispersion printed by an inkjet device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2008-513565 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-216425 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-62871 [Patent Document 4] Japanese Patent Application Laid-Open No. 2008-111985 Summary of the Invention [Problem to be solved by the invention]

[0007] The manufacturing process of electronic components may include a step of printing a conductive circuit pattern on a substrate. In this printing step, for example, a conductive ink is printed on a green sheet made of ceramic powder (e.g., alumina powder) solidified with a binder resin. During this printing, it is preferable that the conductive ink has stable discharge properties. In addition, during this printing, it is also desirable to suppress the occurrence of sheet attack, in which the organic solvent in the conductive ink dissolves the binder resin in the green sheet.

[0008] Therefore, the present invention has been made in consideration of the above circumstances, and its object is to provide a conductive ink that suppresses the occurrence of sheet attack and improves ejection properties. [Means for solving the problem]

[0009] The conductive inkjet ink disclosed herein is used in the manufacture of electronic components. The conductive inkjet ink contains at least an inorganic powder and an organic solvent for dispersing the inorganic powder. The organic solvent has a viscosity of 5 mPa·s or less and a Hildebrand solubility parameter SP value of 8 (cal / cm 3 ) 0.5 ~10(cal / cm 3 ) 0.5 and a first solvent having a viscosity of 10 mPa·s to 100 mPa·s and an SP value of 9 (cal / cm 3 ) 0.5 ~11(cal / cm 3 ) 0.5 and a second solvent having a viscosity of 3 mPa·s or less and an SP value of 8 (cal / cm 3 ) 0.5 When the total weight of the organic solvents is taken as 100 wt %, the content C1 (wt %) of the first solvent, the content C2 (wt %) of the second solvent, and the content C3 (wt %) of the third solvent are expressed by the following formulas (1) to (3): 5≦C1≦75 (1) 20≦C2≦60 (2) 0.5·C2-10≦C3≦0.5·C2+10 (3) The present invention is characterized in that:

[0010] The conductive inkjet ink thus configured contains three types of organic solvents, each with a different viscosity and SP value. In this conductive inkjet ink, the content of each of the three types of organic solvents is set within the above-mentioned range. As a result, the conductive inkjet ink disclosed herein is able to both suppress the occurrence of sheet attack and improve ejection performance.

[0011] In a preferred embodiment of the conductive inkjet ink disclosed herein, the inorganic powder has an average particle size of 150 nm to 500 nm. In addition to the above-mentioned effects, this configuration can also achieve the long-term stability preferred for conductive inkjet inks.

[0012] In another preferred embodiment of the conductive inkjet ink disclosed herein, the inorganic powder comprises a metal powder having a true specific gravity of 11 or more. A conductive inkjet ink having such a configuration is suitable for producing a conductive film made of the metal. In the above embodiment, the metal powder may be tungsten powder. A conductive inkjet ink having such a configuration is suitable for producing a conductive film made of tungsten.

[0013] In another preferred embodiment, the conductive inkjet ink disclosed herein contains a cationic dispersant, and with this configuration, aggregation of inorganic particles can be suppressed via the cationic functional groups in the cationic dispersant.

[0014] In another preferred embodiment, the weight per unit volume of the conductive inkjet ink disclosed herein is 1.5 g / cm 3 ~3.0g / cm 3 , more preferably 1.5 g / cm 3 ~2.5g / cm 3In addition to the above-mentioned effects, this configuration can prevent the printing process from taking too long.

[0015] In another preferred embodiment of the conductive inkjet ink disclosed herein, the first solvent is composed of at least one of ethers and esters. The second solvent is composed of at least one of esters and alcohols. The third solvent is composed of a hydrocarbon compound. By using organic solvents having viscosities and SP values ​​within the above ranges composed of the above-mentioned solvents, the effects of the technology disclosed herein can be more effectively achieved.

[0016] In the above aspect, the first solvent may include at least one compound selected from the group consisting of glycol ether, glycol ether acetate, and terpineol derivative. The second solvent may include at least one compound selected from the group consisting of glycol ether acetate and monoterpene alcohol. The third solvent may include a linear alkane. This configuration can better achieve the effects of the technology disclosed herein. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an agitator / pulverizer used in the production of conductive ink. [Figure 2] 1 is an overall view schematically illustrating an example of an inkjet device. [Figure 3] FIG. 3 is a cross-sectional view schematically showing an inkjet head of the inkjet device in FIG. [Figure 4] FIG. 2 is a diagram showing the composition of the organic solvent of each sample in the test example. DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred embodiments of the technology disclosed herein are described below. Matters necessary for implementing the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. When a numerical range is described in this specification as "A to B (A and B are arbitrary numerical values)," this is the same as the general interpretation, meaning "A or more and B or less (including a range greater than A but less than B)."

[0019] 1.Conductive inkjet ink The conductive inkjet ink disclosed herein may contain, for example, (A) an inorganic powder, (B) a binder resin, (C) a dispersant, and (D) an organic solvent. Each component contained in the conductive inkjet ink disclosed herein will be described below.

[0020] (A) Inorganic powder The inorganic powder is a material that constitutes the main component (base material) of the printed layer (conductive circuit pattern) after firing. In the conductive ink disclosed herein, the inorganic powder may contain a metal powder as the main component. The metal powder may be composed of, for example, metal particles. The metal particles may be metal particles containing at least 95% or more, preferably 97% or more, and more preferably 99% or more metal elements. Elements other than metals that may be contained in the metal particles are unavoidable impurities that may be mixed in during the production of the metal particles, and are not particularly limited. Furthermore, depending on the type of metal, metal oxides produced by oxidation with oxygen in the atmosphere may be present on the particle surface of the metal particles.

[0021] Examples of metals that may be used to form the metal powder include tungsten (W), palladium (Pd), platinum (Pt), molybdenum (Mo), rhodium (Rh), cobalt (Co), nickel (Ni), iron (Fe), chromium (Cr), gold (Au), silver (Ag), copper (Cu), ruthenium (Ru), osmium (Os), and iridium (Ir).

[0022] The metal constituting the metal powder may have a true specific gravity of 11 or more (e.g., 15 or more). Examples of such metals include platinum group elements such as gold, platinum, palladium, rhodium, iridium, ruthenium, and osmium; and chromium group elements such as tungsten. In this specification, the term "true specific gravity" refers to the bulk specific gravity calculated using a chemical formula. Metal powders composed of metals with a true specific gravity of 11 or more tend to aggregate and settle more easily than other metal powders. Therefore, conductive inks containing such metal powders require ingenuity to improve their jetting properties and tend to have poor stability over time. However, the technology disclosed herein can suppress precipitation and aggregation even with metal powders with high true specific gravity. This can improve jetting properties and maintain stability over time. The metal powder may be composed of one type of metal or two or more types of metals.

[0023] Incidentally, some electronic components require plasma durability (e.g., electrostatic chucks, etc.). Such plasma-resistant electronic components use ceramic materials such as alumina and aluminum nitride as their base materials. In the manufacturing process of plasma-resistant electronic components, high-temperature firing at 1200°C or higher is performed to sinter the inorganic base material containing the ceramic material. As the conductive material for these plasma-resistant electronic components, high-melting-point metals having a melting point of 1200°C or higher (hereinafter simply referred to as "high-melting-point metals") such as tungsten, palladium, platinum, molybdenum, cobalt, nickel, iron, and chromium may be used (hereinafter simply referred to as "high-melting-point metals") to maintain the shape of the conductive circuit pattern during the high-temperature firing.

[0024] The metal powder is preferably composed of a high-melting-point metal with a true specific gravity of 11 or more. Using such a high-melting-point metal as a conductive material allows for the formation of a conductive circuit pattern that can maintain its shape even when exposed to high-temperature environments. Suitable examples of such high-melting-point metals include tungsten, palladium, and platinum. Tungsten, among others, not only has excellent chemical stability and a low volume resistivity ρV (Ω·cm), but is also inexpensive among high-melting-point metals. Therefore, using tungsten particles as the main component of the metal powder allows for the inexpensive production of high-quality plasma-resistant electronic components (such as electrostatic chucks).

[0025] The inorganic powder may contain inorganic particles other than metal powder as long as the effects of the technology disclosed herein are not impaired. Examples include ceramic particles such as ZrO2, Al2O3, Ag2O, Cu2O, PdO, NiO, and CoO. These ceramic particles have a higher melting point than general metal particles, so mixing them with metal powder can improve the heat resistance of the conductive circuit pattern.

[0026] When the inorganic powder contains inorganic particles other than metal powder, the content of the metal powder, when the total inorganic powder is taken as 100 wt%, is, for example, 70 wt% or more, preferably 80 wt% or more, more preferably 90 wt% or more, even more preferably 95 wt% or more, and particularly preferably 99 wt% or more. As the content of metal powder in the inorganic powder increases, the effects of stabilizing the conductive circuit pattern, reducing the volume resistivity ρV, and reducing manufacturing costs become greater. On the other hand, there is a tendency for deterioration in temporal stability due to aggregation and precipitation of the metal powder to occur. However, the conductive ink disclosed herein achieves favorable temporal stability, as shown in the test examples described below. Therefore, even when an inorganic powder containing 70 wt% or more of metal powder is used, deterioration in temporal stability due to aggregation and precipitation of the metal powder can be effectively prevented.

[0027] In order to properly exert the dispersibility-improving effect of the dispersant, it is preferable that the inorganic powder has a specific surface area of ​​at least a certain level. For example, the specific surface area of ​​the inorganic powder is 1.5 m 2 / g or more is preferable, and 2.0m 2 / g or more is more preferable, and 2.5m 2 On the other hand, if the specific surface area of ​​the inorganic powder is too large, aggregation of particles tends to occur. From this viewpoint, the specific surface area of ​​the inorganic powder is preferably 4.0 m 2 / g or less is preferable, and 3.5m 2 / g or less is more preferable, and 3.0m 2 / g or less is particularly preferred. Note that the "specific surface area" in this specification is the BET specific surface area measured based on the BET method specified in JIS Z8830:2013.

[0028] Furthermore, the particle size of the inorganic powder in the conductive ink is one of the factors that can affect the ejection properties and long-term stability. For example, if the particle size of the inorganic powder in the conductive ink is too large, the ejection orifices of the inkjet device may be clogged with the inorganic powder, significantly reducing the ejection properties. Therefore, the average particle size of the inorganic powder added to the inkjet ink is, for example, 500 nm or less, preferably 450 nm or less, more preferably 400 nm or less, even more preferably 350 nm or less, and particularly preferably 320 nm or less. On the other hand, if the particle size of the inorganic powder is too small, the long-term stability is likely to decrease due to particle aggregation. From this perspective, the average particle size of the inorganic powder is preferably 150 nm or more, more preferably 200 nm or more, and even more preferably 220 nm or more. Note that the "average particle size" in this specification refers to the average particle size measured by dynamic light scattering (DLS) method. The average particle size measured by DLS method can be measured in accordance with JIS Z 8828:2013.

[0029] The content of inorganic powder in the conductive ink is not particularly limited and can be adjusted appropriately depending on the printing purpose (e.g., the conductive circuit pattern to be formed). For example, as the content of inorganic powder in the conductive ink increases, it becomes easier to form a conductive circuit pattern of suitable thickness with fewer printing runs. From this perspective, when the entire conductive ink is taken as 100 wt%, the content of inorganic powder is preferably 30 wt% or more, and more preferably 35 wt% or more. On the other hand, as the content of inorganic powder decreases, stability over time and ejection properties tend to improve. From this perspective, when the entire conductive ink is taken as 100 wt%, the content of inorganic powder is preferably 80 wt% or less, more preferably 75 wt% or less, and particularly preferably 70 wt% or less.

[0030] (B) Binder resin The binder resin is an organic compound that fixes the inorganic powder to the substrate after the conductive ink is inkjet printed on the substrate. The conductive ink inkjet printed on the substrate is, for example, heated and dried on the substrate, and then subjected to a baking treatment. Therefore, it is preferable that the binder resin be one that completely disappears (burns out) during the baking treatment. For example, polyvinyl acetal resin, acrylic resin, etc. can be preferably used as the binder resin.

[0031] The conductive ink disclosed herein preferably contains a polyacetal resin as a binder resin. Polyvinyl acetal resin is, for example, a resin produced by acetalizing polyvinyl alcohol resin with an aldehyde. In addition to the aforementioned function of fixing inorganic powders to a substrate, polyvinyl acetal resins also have the function of dispersing in organic solvents and assisting the dispersant in suppressing the precipitation of metal powders. Furthermore, polyvinyl acetal resins can be appropriately configured to suppress sheet attack by, for example, adjusting the hydroxyl group content of the resin. Therefore, polyacetal resins are suitable as binder resins for the conductive ink disclosed herein. Suitable examples of polyvinyl acetal resins include polyvinyl butyral resins and polyvinyl formal resins.

[0032] The molecular weight of the binder resin can be adjusted as appropriate as long as it does not impair the effects of the technology disclosed herein. For example, if the average molecular weight of the binder resin is too small, the function of assisting the precipitation suppression effect tends to decrease. Therefore, the average molecular weight of the binder resin is set to 0.5 × 10 4 From the viewpoint of more effectively exhibiting the precipitation-inhibiting effect, the average molecular weight is 1.0 × 10 4 More than 2.0×10 is preferable. 4 More than 2.5 × 10 is more preferable. 4 More preferably, 3.0 x 10 4 The above is particularly preferable. On the other hand, if the average molecular weight of the binder resin is too large, the viscosity of the conductive ink increases, which may actually decrease the ink ejection properties. From this perspective, the upper limit of the average molecular weight of the binder resin is set to 30 × 10 4 From the viewpoint of ensuring favorable ejection properties, the upper limit of the average molecular weight is 20×10 4 Less than 10x10 is preferable. 4 Less than 5.0 x 10 is preferable. 4 The following is even more preferred. The average molecular weight of the binder resin and the dispersant described below can be measured by gel permeation chromatography (GPC), and the weight-based average molecular weight converted using a standard polystyrene calibration curve can be used. For such measurements, a GPC device (HLC-8320) manufactured by Tosoh Corporation can be used. Alternatively, the nominal value provided by the manufacturer or a value calculated based on the chemical formula can be used.

[0033] The glass transition temperature of the binder resin can be adjusted as appropriate as long as it does not impair the effects of the technology disclosed herein. For example, from the viewpoint of forming a dry film with excellent fixability, 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, the "glass transition point" refers to the glass transition temperature (Tg) determined by differential scanning calorimetry (DSC). Alternatively, a nominal value provided by a manufacturer or the like may be used.

[0034] The content of the binder resin can be adjusted as appropriate as long as it does not impair the effects of the technology disclosed herein. For example, when the entire organic vehicle of the conductive ink is taken as 100 wt%, the content of the binder resin may be, for example, 0.3 wt% or more, preferably 0.5 wt% or more, and more preferably 0.7 wt% or more. On the other hand, the content of the binder resin may be, for example, 5 wt% or less, preferably 3 wt% or less, more preferably 2 wt% or less, and even more preferably 1.5 wt% or less. In this specification, the term "organic vehicle" refers to, for example, a mixture of a binder resin, a dispersant, and an organic solvent in a conductive ink.

[0035] (C) Dispersant A dispersant is an organic compound that uniformly disperses inorganic particles in an ink and inhibits aggregation and sedimentation of the inorganic particles. The conductive ink disclosed herein may contain a cationic dispersant.

[0036] A cationic dispersant is a dispersant having a cationic functional group. The cationic dispersant adheres to the surface of metal particles via the cationic functional group, for example, and generates steric hindrance. This suppresses aggregation of the metal particles and ultimately improves the long-term stability of the conductive ink. For example, when the metal powder is composed of tungsten particles or molybdenum particles, the surfaces of these metal particles are oxidized by oxygen in the atmosphere and become weakly acidic. Therefore, the cationic dispersant easily adheres to the surfaces of these metal particles. Furthermore, even when the metal particles are composed of metal particles with few acid sites on their surfaces (e.g., noble metal particles), the cationic dispersant adheres to the surfaces of the metal particles, thereby improving the long-term stability of the conductive ink, as described above.

[0037] As the cationic dispersant, any cationic dispersant known in the art for 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 alkyl imidazolines. Note that one type of cationic dispersant may be used alone, or two or more types may be used in combination.

[0038] As the cationic dispersant, an amine dispersant can be preferably used. The amine dispersant is, for example, an organic compound having an amine group in the molecule. Among them, a chain-like amine dispersant having an amine group at at least one end can be preferably used. Suitable examples of such amine dispersants include fatty acid amine dispersants and polyester amine dispersants. Although not particularly limited, the average molecular weight of such amine dispersants is, for example, 1 × 10 3 ~5×10 4Specific examples of cationic dispersants that can be suitably used include Hypermer KD-1, Hypermer KD-2, and Hypermer KD-3 manufactured by Croda Japan Co., Ltd., and S-Leam AD Series (registered trademark) AD-508E manufactured by NOF Corporation.

[0039] The content of the cationic dispersant can be adjusted as appropriate as long as it does not impair the effects of the technology disclosed herein. For example, when the entire organic vehicle of the conductive ink is taken as 100 wt%, the content of the cationic dispersant is preferably 0.3 wt% or more, preferably 0.5 wt% or more, and more preferably 0.7 wt% or more, from the viewpoint of suppressing aggregation of metal particles in the conductive ink. On the other hand, the content of the cationic dispersant is preferably 5 wt% or less, preferably 3 wt% or less, and more preferably 2 wt% or less, from the viewpoint of forming a conductive film with appropriate conductivity by inkjet printing using the conductive ink.

[0040] Furthermore, when the total amount of dispersant contained in the conductive ink is taken as 100 wt%, the content of cationic dispersant is suitably set to 80 wt% or more, for example, 90 wt% or more, preferably 95 wt% or more, and the closer to 100 wt%, the better.

[0041] If necessary, the dispersant may also contain a nonionic dispersant. A nonionic dispersant is a dispersant that does not have a group that ionizes when dissolved in water. A nonionic dispersant is less likely to adhere to the surface of metal particles than a cationic dispersant. However, for example, when a cationic dispersant having a cationic functional group (e.g., an amine group) at one end adheres to the surface of a metal particle, a nonionic dispersant may adhere to the other end of the cationic dispersant. In this case, the cationic dispersant formed on the surface of the metal particle can strengthen steric hindrance. Therefore, the dispersant's effect of inhibiting aggregation of metal particles can be enhanced.

[0042] As for the nonionic dispersant, any known nonionic dispersant used for this type of application can be used without any particular limitation. Examples of such nonionic dispersants include ether-based dispersants, ester-based dispersants, ether-ester-based dispersants, and nitrogen-containing dispersants. Specific examples of nonionic dispersants include Hypermer KD-13 and Hypermer KD-14 manufactured by Croda Japan Co., Ltd., and Synperonic PE / L101 manufactured by Croda Co., Ltd.

[0043] The content of the nonionic dispersant can be adjusted as appropriate as long as it does not impair the effects of the technology disclosed herein. When the total amount of dispersant contained in the conductive ink is taken as 100 wt%, the content of the nonionic dispersant is suitably set to, for example, 20 wt% or less, preferably 10 wt% or less, and more preferably 5 wt% or less.

[0044] (D) Organic solvent The conductive ink disclosed herein contains an organic solvent. The organic solvent disperses the inorganic powder and can impart physical properties (e.g., viscosity) suitable for inkjet printing to the conductive ink. In the conductive ink disclosed herein, the organic solvent contains a first solvent, a second solvent, and a third solvent. The first solvent, the second solvent, and the third solvent each have a predetermined viscosity and SP value (solubility parameter). The viscosity (mPa·s) of the organic solvent can be, for example, a measured value obtained using a commercially available rheometer (see the test example below) or a nominal value provided by the manufacturer.

[0045] In this specification, the "SP value" of an organic solvent refers to the Hildebrand solubility parameter δ. The Hildebrand solubility parameter δ is calculated by using the three-dimensional vector (δD, δP, δH) of the Hansen solubility parameters and the following mathematical formula (X): δ 2 =δD 2 +δP 2 +δH 2 (X) The solubility parameter is a value specific to each compound. In the above formula (X), δD is a dispersion term, which indicates the action of, for example, van der Waals forces. δP is a polarization term, which indicates the action of, for example, dipole moments. δH is a hydrogen bond term, which indicates the action of, for example, hydroxyl groups. The unit of the three-dimensional vector (δD, δP, δH) of the Hansen solubility parameter is (J / cm) in the SI unit system. 3 ) 0.5 In this specification, the unit of the SP value is (cal / cm 3 ) 0.5 The unit of SP value is 1 (cal / cm 3 ) 0.5 ≒2.0455(cal / cm 3 ) 0.5 ; can be converted using the formula:

[0046] When the organic solvent is a mixed solvent, the overall SP value can be calculated based on the volume ratio of each organic solvent and the Hansen solubility parameter. For example, first, the following formulas (P) to (R) are used: δD all 2 = Σ((m i / d i ) / Σ(m i / d i )×δD i )···(P) δP all 2 = Σ((m i / d i ) / Σ(m i / d i )×δP i )···(Q) δH all 2 = Σ((m i / d i ) / Σ(m i / d i )×δH i )···(R) Based on this, the squared value of the Hansen solubility parameter (δD all 2 , δPall 2 , δH all 2 ) is calculated. Here, in the above formulas (P) to (R), d i is the specific gravity of organic solvent i, and m i is the mass fraction of organic solvent i, and δD i is the dispersion term of organic solvent i, and P i is the polarization term of organic solvent i, and δH i is the hydrogen bonding term of organic solvent i. Then, the following equation (S): δ all 2 =δD all 2 +δP all 2 +δH all 2 ···(S) Based on δ all 2 From this, the SP value of the entire organic solvent (δ all ) can be calculated.

[0047] The first solvent has a viscosity of 5 mPa·s or less and an SP value of 8 (cal / cm 3 ) 0.5 ~10(cal / cm 3 ) 0.5 The first solvent has the effect of, for example, reducing the viscosity of the conductive ink while realizing an appropriate SP value. Therefore, the first solvent can contribute to, for example, suppressing the occurrence of sheet attack. In addition, the first solvent can improve the stability of the conductive ink over time. The viscosity of the first solvent is, for example, 1 mPa·s or more, preferably 1.5 mPa·s or more, and more preferably 1.8 mPa·s or more. The SP value of the first solvent is 8.1 (cal / cm 3 ) 0.5 More than 9.5 (cal / cm 3 ) 0.5 It is recommended that the temperature be less than 9.3 (cal / cm 3 ) 0.5In a preferred embodiment, the viscosity of the first solvent is 2 mPa·s to 4.7 mPa·s, and the SP value of the first solvent is 8.3 (cal / cm 3 ) 0.5 ~9.0(cal / cm 3 ) 0.5 is.

[0048] The first solvent may be composed of, for example, at least one of ethers and esters. The first solvent may be, for example, a compound classified as an ether or an ester, having a viscosity of 5 mPa·s or less and a viscosity of 8 (cal / cm 3 ) 0.5 ~10(cal / cm 3 ) 0.5 and at least one compound having an SP value of . In this specification, "ethers" refers to a group of compounds having at least one ether bond (-C-O-C-) in the main chain (mother 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 explanation, compounds having multiple functional groups in one molecule are classified according to the IUPAC nomenclature. However, compounds having an ether bond and a hydroxyl group in one molecule are classified as ethers.

[0049] Examples of ethers used as the first solvent include glycol ethers. Examples of esters used as the first solvent include glycol ether acetates and terpineol derivatives. The first solvent preferably contains at least one compound selected from the group consisting of glycol ethers, glycol ether acetates, and terpineol derivatives.

[0050] As used herein, the term "glycol ether" refers to an aliphatic or alicyclic compound in which two hydroxyl groups are bonded to two different carbon atoms, and in which the hydrogen atoms of one or both of the two 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 the hydrogen of one hydroxyl group is substituted, and glycol dialkyl ethers in which both hydrogens of the two hydroxyl groups are substituted.

[0051] The structure of the glycol ether in the first solvent is represented by, for example, the following general formula (Chemical Formula 1). R1-(O-R2)mO-R3 (Chemical Formula 1) In the general formula (Chemical Formula 1), R1 and R3 are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms), R2 is a linear or branched alkylene group having 2 to 6 carbon atoms, and m is 1 to 3. In the general formula (Chemical Formula 1), examples of the alkyl group include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, n-pentyl group, isopentyl group, neopentyl group, and n-hexyl group. Examples of the alkylene group include an ethylene group, n-propylene group, n-butylene group, and n-pentylene group.

[0052] Examples of glycol ethers include alkylene glycol monoalkyl ethers, dialkylene glycol monoalkyl ethers, trialkylene glycol monoalkyl ethers, alkylene glycol dialkyl ethers, dialkylene glycol dialkyl ethers, trialkylene glycol dialkyl ethers, etc. In conductive inks, dialkylene glycol dialkyl ethers are preferably used from the viewpoint of achieving the desired SP value and viscosity, etc. Among these, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, etc. are preferably used.

[0053] In this specification, "glycol ether acetate" refers to a compound obtained by esterifying the above-mentioned glycol ether. In glycol ether acetate, for example, at least one of R1 and R3 in the above general formula (Chemical Formula 1) is an acyl group. In the above general formula (Chemical Formula 1), the acyl group is, for example, a straight-chain or branched-chain group having 1 to 6 carbon atoms. Examples of the acyl group include a methanoyl group, an ethanoyl group (acetyl group), a propanoyl group, a butanoyl group, a pentanoyl group, a hexanoyl group, and a benzoyl group.

[0054] Examples of glycol ether acetates include 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 (PGMEA), propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, butyl monoglycol acetate (BMGAC), and butyl diglycol acetate (BDGAC).

[0055] As used herein, the term "terpineol derivative" refers to a compound in which the terminal hydrogen atoms or hydroxyl groups of terpineol and dihydroterpineol (menthanol) are substituted with organic groups. It is known that terpineol and dihydroterpineol have isomers with different positions of the double bond and / or hydroxyl group. As long as the effects of the technology disclosed herein are achieved, any isomer may be used (the same applies hereinafter). The terpineol derivative as the first solvent may be, for example, a compound in which the hydroxyl group of terpineol or dihydroterpineol is ester-bonded to a fatty acid (R4-COOH). The fatty acid may be a lower fatty acid having 6 or less carbon atoms. R4 may be, for example, an alkyl group having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms). Such an alkyl group may be either linear or branched. Suitable examples of terpineol derivatives include dihydroterpinyl acetate (menthanol acetate), dihydroterpinyl propionate (menthanol propionate), and the like.

[0056] As the first solvent, for example, one or more organic solvents selected from the group consisting of diethylene glycol butyl methyl ether, BDGAC, and menthanol propionate can be preferably used.

[0057] The second solvent has a viscosity of 10 mPa·s to 100 mPa·s and an SP value of 9 (cal / cm 3 ) 0.5 ~11(cal / cm 3 ) 0.5 The second solvent can, for example, increase the viscosity of the conductive ink and provide it with an appropriate viscosity. Therefore, the second solvent can contribute to improving the ejection properties. In addition, the first solvent can improve the stability of the conductive ink over time. The SP value of the second solvent is, for example, 10 (cal / cm 3 ) 0.5 It is recommended that the temperature be less than 9.7 (cal / cm 3 ) 0.5 Preferably less than 9.5 (cal / cm 3 )0.5 In a preferred embodiment, the viscosity of the second solvent is 14 mPa·s to 79 mPa·s, and the SP value of the second solvent is 9.0 (cal / cm 3 ) 0.5 ~9.3(cal / cm 3 ) 0.5 is.

[0058] The second solvent may be composed of, for example, at least one of esters and alcohols. The second solvent may be, for example, a compound classified as an ester or alcohol, having a viscosity of 10 mPa·s to 100 mPa·s and a viscosity of 9 (cal / cm 3 ) 0.5 ~11(cal / cm 3 ) 0.5 and at least one compound having an SP value of . In this specification, "alcohols" refers to a group of compounds in which the hydrogen atoms of hydrocarbons are substituted with hydroxyl groups, and is represented by the general formula: R-OH. The second solvent may be a single solvent or a mixed solvent of two or more solvents.

[0059] Examples of esters used as the second solvent include glycol ether acetate, etc. Examples of alcohols used as the second solvent include aliphatic alcohols, monoterpene alcohols, etc. The second solvent preferably contains at least one compound selected from the group consisting of glycol ether acetates and monoterpene alcohols.

[0060] The structure of the glycol ether acetate in the second solvent is, for example, represented by the following general formula (Chemical Formula 2). R 11 -(OR 12 )nOR 13 ...(chemical 2) In the general formula (chemical formula 1), R 11 ,R 13 are each independently a hydrogen atom, an alkyl group, an alkoxy group, an acyl group, or an aryl group, and R11 ,R 13 At least one of R is an acyl group or a linear or branched alkyl group having 1 to 10 carbon atoms; 12 is a straight or branched alkylene group having 2 to 4 carbon atoms, and n is 1 to 4. In general formula (Chemical Formula 2), the alkyl group and alkylene group are, for example, the same as in general formula (Chemical Formula 1). The alkoxy group is, for example, a straight or branched alkylene group having 1 to 10 carbon atoms. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. Examples of the aryl group include a phenyl group, a benzyl group, and a tolyl group. A suitable example of the glycol ether acetate is 2,2,4-trimethyl-1,3-pentanediol 1-monoisobutyrate.

[0061] Examples of aliphatic alcohols include straight-chain or branched-chain aliphatic monoalcohols having 20 or less carbon atoms (preferably 4 to 12 carbon atoms, more preferably 6 to 10 carbon atoms). Suitable examples of such aliphatic monoalcohols include butanol, n-amyl alcohol, hexanol, heptanol, n-octanol, 2-ethylhexanol, isooctanol, nonanol, decanol, isoundecanol, lauryl alcohol, cetyl alcohol, and stearyl alcohol. Examples of monoterpene alcohols include terpineol and dihydroterpineol (menthanol).

[0062] As the second solvent, for example, one or more organic solvents selected from the group consisting of 2,2,4-trimethyl-1,3-pentanediol 1-monoisobutyrate and menthol can be preferably used.

[0063] The third solvent has a viscosity of 3 mPa·s or less and an SP value of 8 (cal / cm 3 ) 0.5The third solvent is an organic solvent having a viscosity of less than 5.0 (cal / cm). The third solvent can, for example, reduce the SP value of the conductive ink. Therefore, the third solvent can impart an appropriate SP value to the conductive ink and contribute to suppressing sheet attack. The viscosity of the third solvent may be, for example, 1 mPa·s or more, preferably 1.5 mPa·s or more, and more preferably 2.0 mPa·s or more. The SP value of the third solvent may, for example, be 5.0 (cal / cm). 3 ) 0.5 It is better to have more than 6.0 (cal / cm 3 ) 0.5 More than 7.0 (cal / cm 3 ) 0.5 In one preferred embodiment, the viscosity of the third solvent is 2.1 mPa·s to 2.6 mPa·s, and the SP value of the second solvent is 7.7 (cal / cm 3 ) 0.5 ~7.9(cal / cm 3 ) 0.5 is.

[0064] The third solvent may be composed of, for example, a hydrocarbon compound. The third solvent may be, for example, a hydrocarbon compound having a viscosity of 3 mPa·s or less and a viscosity of 8 (cal / cm 3 ) 0.5 The third solvent may be composed of at least one compound having an SP value of less than 0.05. In this specification, "hydrocarbon compound" refers to a compound composed of carbon atoms and hydrogen atoms. The hydrocarbon compound may be linear, branched, or cyclic. Examples of hydrocarbon compounds preferably used as the third solvent include linear alkanes, linear alkenes, and linear alkynes. The third solvent preferably contains a linear alkane. The third solvent may be a single solvent or a mixed solvent of two or more solvents.

[0065] The linear alkane used as the third solvent may be, for example, a linear alkane having 20 or less carbon atoms (preferably 10 to 16 carbon atoms). Suitable examples of the linear alkane include decane, undecane, dodecane, tridecane, tetradecane, etc. Among these, one or more organic solvents selected from the group consisting of, for example, tridecane and tetradecane may be preferably used as the third solvent.

[0066] In the conductive ink disclosed herein, when the total weight of the organic solvents is 100 wt %, the content C1 (wt %) of the first solvent, the content C2 (wt %) of the second solvent, and the content C3 (wt %) of the third solvent are expressed by the following formulas (1) to (3): 5≦C1≦75 (1) 20≦C2≦60 (2) 0.5·C2-10≦C3≦0.5·C2+10 (3) The content C1 can be set to 5 wt% to 75 wt%. The content C2 can be set to 20 wt% to 60 wt%. The content C3 can be set to (0.5 C2 - 10) wt% to (0.5 C2 + 10) wt%. However, the content C3 does not become 0 wt%. When the contents C1, C2, and C3 satisfy the above ranges, the SP value and viscosity of the entire organic solvent can be easily adjusted to a suitable range. In addition, the storage stability (e.g., stability over time) of the conductive ink can be improved. In a conductive ink containing an inorganic powder and three types of organic solvents in a predetermined ratio, it is possible to suppress the occurrence of sheet attack and improve the ejection properties.

[0067] Although not particularly limited, from the viewpoint of improving the ejection properties of the conductive ink, when the entire organic vehicle is taken as 100 wt%, the content of the organic solvent is, for example, 80 wt% or more, preferably 90 wt% or more, and more preferably 95 wt% or more.

[0068] (E) Other ingredients The conductive ink disclosed herein may further contain known additives that can be used in inkjet inks (e.g., conductive inkjet inks) to the extent that the effects of the technology disclosed herein are not impaired. Examples of such additives include resin components excluding the binder resin and dispersant described above; solvent components excluding the organic solvent described above; and the like. The conductive ink disclosed herein may also contain additives other than the resin components and solvent components described above. The types and amounts of such additives can be changed as appropriate based on conventionally known technical common sense and do not characterize the technology disclosed herein. Therefore, a description of these additives will be omitted here.

[0069] <Conductive ink properties> The viscosity of the conductive ink disclosed herein is not particularly limited as long as it can achieve the effects of the technology disclosed herein. The lower the viscosity of the conductive ink, the less likely the conductive ink is to adhere to the nozzles of an inkjet device, improving the dischargeability of the conductive ink. Furthermore, the lower the viscosity of the conductive ink, the lower the SP value of the conductive ink tends to be, which in turn can reduce the occurrence of sheet attack. From this perspective, the viscosity of the conductive ink is preferably 20 mPa·s or less, more preferably 17 mPa·s or less, and more preferably 15 mPa·s or less. On the other hand, the higher the viscosity of the conductive ink, the less likely the discharged ink will spread, reducing the occurrence of variations in the thickness of the conductive film. Furthermore, the higher the viscosity of the conductive ink, the less likely it is to splash from the nozzles of an inkjet device. From this perspective, the viscosity of the conductive ink is preferably 6 mPa·s or more. The ink viscosity is measured, for example, using a commercially available rheometer.

[0070] The SP value of the conductive ink disclosed herein is not particularly limited as long as it can realize the effects of the technology disclosed herein. The lower the SP value of the conductive ink, the lower the risk of dissolving or swelling the resin contained in the green sheet (substrate), and the more likely it is that sheet attack will be suppressed. On the other hand, the higher the SP value of the conductive ink, the more likely it is that the viscosity of the conductive ink can be increased. From this perspective, the SP value of the conductive ink is set to 8.0 (cal / cm 3 ) 0.5 ~8.5(cal / cm 3 ) 0.5 is preferable, and 8.22 (cal / cm 3 ) 0.5 ~8.46(cal / cm 3 ) 0.5 It is more preferable that the SP value of the conductive ink is, for example, the SP value of the entire organic solvent.

[0071] The weight per unit volume of the conductive ink disclosed herein is not particularly limited as long as it can achieve the effects of the technology disclosed herein. The weight per unit volume of the conductive ink is, for example, 1.5 (g / cm 3 )~3.0(g / cm 3 ) can be set. If the weight per unit volume of the conductive ink becomes too large, for example, there may be an increased risk of poor circulation of the conductive ink within an inkjet printing device. On the other hand, if the weight per unit volume of the conductive ink becomes too small, for example, the amount of solvent contained in the conductive ink increases accordingly. This may lead to, for example, an increase in the time it takes for the conductive ink to be absorbed into the sheet or an increase in the time it takes for the solvent to dry. Furthermore, the greater the amount of solvent, the more likely sheet attack may occur. From this perspective, the weight per unit volume of the conductive ink is set to 1.5 (g / cm 3 )~3.0(g / cm 3 ) (e.g., 2.0 (g / cm 3 )~2.5(g / cm 3 The weight per unit volume of the conductive ink can be measured, for example, by the procedure described in the test examples below.

[0072] 2. Conductive Ink Preparation Next, the procedure for preparing (manufacturing) the conductive ink disclosed herein will be described. The conductive ink disclosed herein is prepared by mixing the above-mentioned components and then crushing and dispersing the inorganic powder. FIG. 1 is a cross-sectional view that schematically shows an agitator / pulverizer used in manufacturing the conductive ink. Note that the following description shows an example of a means for preparing the conductive ink disclosed herein, and is not intended to limit the technology disclosed herein.

[0073] When manufacturing the conductive ink disclosed herein, first, the above-described components are weighed and mixed to prepare a slurry (including a paste and a suspension) that is a precursor of the ink. Then, using an agitator / miller 100 as shown in FIG. 1, the conductive ink is prepared by agitating the slurry and crushing the inorganic powder. Specifically, crushing beads (e.g., zirconia beads with an average particle size of 10 μm to 150 μm) are added to the slurry, and the slurry is then supplied into a stirring vessel 120 through a supply port 110. A shaft 134 having multiple stirring blades 132 is housed within the stirring vessel 120. One end of the shaft 134 is attached to a motor (not shown). By operating the motor, the shaft 134 is rotated, and the multiple stirring blades 132 agitate the slurry while sending it downstream in the liquid-feeding direction D. During this agitation, the inorganic powder is crushed by the crushing beads, and the finely divided inorganic powder is dispersed in the slurry.

[0074] The slurry sent downstream in the liquid sending direction D then passes through filter 140. As a result, the inorganic powder and crushing beads that were not atomized are collected by filter 140, and the conductive ink in which the inorganic powder is sufficiently dispersed is discharged from outlet 150. In this process, by adjusting the pore size of filter 140, the average particle size of the crushing beads, etc., it is possible to adjust the "average particle size of the inorganic powder" and the "specific surface area of ​​the inorganic powder" in the conductive ink to the desired range.

[0075] 3. Applications of conductive ink Next, applications of the conductive ink disclosed herein will be described. The conductive ink disclosed herein is used in the manufacture of electronic components. In this specification, "used in electronic components" not only refers to an embodiment in which the conductive ink disclosed herein is directly printed on the surface of an inorganic substrate, but also includes an embodiment in which the conductive ink is indirectly attached to the surface of an inorganic substrate via an intermediate material such as transfer paper.

[0076] (1) Printing Fig. 2 is a schematic overall view of an example of an inkjet device, and Fig. 3 is a schematic cross-sectional view of an inkjet head of the inkjet device shown in Fig. 2.

[0077] The conductive ink disclosed herein is printed on the surface of a printing target using an inkjet device 1 as shown in FIG. 2. The material and shape of the inorganic substrate W to be printed are not particularly limited, and any substrate that can be used as a substrate for general electronic components can be used without any particular restrictions. When using high-melting-point metals such as platinum powder, palladium powder, tungsten powder, or molybdenum powder as the inorganic powder for the conductive ink disclosed herein, it is particularly preferable to use an inorganic substrate W that has been fired at a high temperature of 1200°C or higher (for example, a green sheet made of alumina powder, aluminum nitride powder, etc.).

[0078] Next, the structure of the inkjet device 1 shown in Figure 2 will be described. The inkjet device 1 includes an inkjet head 10 that stores conductive ink. The inkjet head 10 is housed inside a print cartridge 40. The print cartridge 40 is inserted into a guide shaft 20 and is configured to reciprocate along the axial direction X of the guide shaft 20. Although not shown, the inkjet device 1 also includes a moving means for moving the guide shaft 20 in the vertical direction Y. This allows the inkjet device 1 to eject conductive ink onto a desired position on the inorganic substrate W.

[0079] The inkjet head 10 shown in FIG. 2 may be, for example, a piezoelectric inkjet head such as that shown in FIG. 3. This piezoelectric inkjet head 10 includes a storage section 13 for storing ink within a case 12, which is connected to a discharge section 16 via a liquid supply path 15. The discharge section 16 includes a discharge port 17 that opens to the outside of the case 12, and a piezoelectric element 18 is disposed opposite the discharge port 17. In this inkjet head 10, the piezoelectric element 18 is vibrated to discharge the ink from the discharge section 16 through the discharge port 17 toward the inorganic substrate W (green sheet) (see FIG. 2). The conductive ink disclosed herein exhibits excellent dischargeability and can be discharged with high accuracy over a long period of time. Therefore, the conductive ink disclosed herein achieves high productivity in printing patterns on the surface of the inorganic substrate W. Furthermore, the conductive ink disclosed herein exhibits excellent sheet attack suppression. Therefore, the conductive ink disclosed herein makes it possible to print precise patterns (images) on the surface of the inorganic substrate W. Furthermore, the conductive ink disclosed herein has excellent stability over time. Therefore, the conductive ink disclosed herein can provide the above-mentioned effects over a long period of time.

[0080] (2) Drying process Next, a drying process is performed in which the inorganic base material W (green sheet) with the ink attached thereto is heated at a predetermined temperature. This removes the organic solvent from the ink and forms a dry film on the inorganic base material W. The conductive ink disclosed herein contains the binder resin described above. This makes the conductive ink more likely to adhere to the surface of the inorganic base material W as a dry film. The heating temperature in the drying process is preferably set to a temperature (e.g., 50°C to 150°C, preferably 60°C to 80°C) at which the organic solvent is removed and the inorganic powder does not sinter.

[0081] (3) Firing The manufacturing method disclosed herein includes firing the inorganic substrate W after the formation of the dried film. This burns off organic components, including the binder resin, and sinters the inorganic powder, adhering to the surface of the inorganic substrate W. As a result, an electronic component having a conductive circuit pattern primarily composed of inorganic powder (e.g., metal powder) is manufactured. The firing temperature can be appropriately set depending on the type of inorganic powder (e.g., metal powder) contained in the conductive ink. For example, the firing temperature can be set to 500°C to 2000°C. Furthermore, when the metal powder is a high-melting-point metal, firing can be performed under conditions such that the maximum firing temperature is 1200°C or higher (preferably 1200°C to 2000°C, more preferably 1300°C to 1600°C). In this case, the metal powder does not melt during firing, preventing the conductive circuit pattern from losing its shape during firing. This ensures the reliable formation of electronic components having precise conductive circuit patterns.

[0082] [Test example] Test examples relating to the technology disclosed herein will be described below. Note that the following test examples are not intended to limit the technology disclosed herein. In the following test examples, "%" is by weight unless otherwise specified.

[0083] Preparation of Conductive Ink Twenty-seven types of conductive inks (Examples 1 to 17 and Comparative Examples 1 to 10) containing inorganic powder, binder resin, dispersant, and organic solvent were prepared. First, inorganic powder and organic vehicle (organic solvent, binder resin, and dispersant) were mixed in a weight ratio of 65:35 to prepare a slurry. The slurry was subjected to a crushing and dispersion process (rotation speed: 1500 rpm, mixing time: 4 hours) using crushing beads (zirconia beads with an average particle size of 100 μm), and then filtered under pressure to obtain a conductive ink. The proportions of each component in the organic vehicle (the proportions of organic solvent, binder resin, and dispersant, respectively, when the entire organic vehicle is taken as 100%) are shown in Tables 1 and 2. Table 1 lists information for Examples 1 to 17. Table 2 lists information for Comparative Examples 1 to 10. The materials used in preparing the conductive inks are described below.

[0084] (Inorganic powder) As an inorganic powder, it has a specific surface area of ​​2.9m 2 Tungsten (W) powder with a specific gravity of 19 / g was used.

[0085] (binder resin) As the binder resin, a polyvinyl acetal resin ("BL-5Z" by Sekisui Chemical Co., Ltd.) with a hydroxyl group content of 21 mol % and a weight average molecular weight of 32,000 was used.

[0086] (dispersant) As the dispersant, the following cationic dispersant was used. Dispersant C1: NOF Corporation, "Sleem AD Series (registered trademark) AD-508E" Dispersant C2: Hypermer KD-3 manufactured by Croda Japan Co., Ltd.

[0087] (organic solvent) Seven types of organic solvents were prepared as shown in Table 3. Tables 1 and 2 show the percentage (%) of the organic solvents used in each example, assuming the total organic solvents to be 100%. Table 3 lists the CAS number, viscosity (mPa·s), specific gravity, and boiling point (°C) of each organic solvent. Of the physical properties shown in Table 3, the specific gravity and boiling point of each organic solvent are the nominal values ​​of each manufacturer. The viscosity of each organic solvent shown in Table 2 was measured using a rheometer ("HAAKE MARS" manufactured by Thermo Fisher Scientific Co., Ltd.) (shear rate of the rheometer: 1000 s -1 ) is the measured value.

[0088] Table 4 shows the δD (J / cm) of each organic solvent. 3 ) 0.5 , δP(J / cm 3 ) 0.5 , δH(J / cm 3 ) 0.5 , δ(J / cm 3 ) 0.5 , and SP value (cal / cm 3 ) 0.5 Shows.

[0089] FIG. 4 shows the composition of the organic solvents in each sample in the test examples. In FIG. 4, the content C1 (%) of the first solvent, the content C2 (%) of the second solvent, and the content C3 (%) of the third solvent are plotted for each sample. At the top apex of the triangle shown in FIG. 4, the content C1 (%) of the first solvent is 100. At the left apex of the triangle shown in FIG. 4, the content C2 (%) of the second solvent is 100. At the right apex of the triangle shown in FIG. 4, the content C3 (%) of the third solvent is 100. The numbers attached to the "●" in the figure correspond to the numbers of the working examples, and the numbers attached to the "▲" correspond to the numbers of the comparative examples.

[0090] [Table 1]

[0091] [Table 2]

[0092] [Table 3]

[0093] [Table 4]

[0094] <Evaluation test> A. Weight per unit volume of conductive ink Using a micropipette capable of drawing up 5 ml at a time, 5 ml of each conductive ink was measured. The weight of the measured conductive ink was then measured. The weight obtained here was divided by the volume of the conductive ink (5 ml) to calculate the weight per unit volume of each conductive ink. The results are shown in Table 1.

[0095] B. SP value of conductive ink Using the composition ratio (%) of the organic solvents shown in Table 1 and the above formulas (P) to (S), the SP value (δ all The SP value (δ all ) and the SP value (cal / cm 3 ) 0.5 The results are shown in Table 1.

[0096] C. Seat attack Sheets A and B were prepared as green sheets for this test. A hot plate was heated to 30°C, and the porous alumina substrate and the green sheet were placed on the hot plate. Next, the organic solvent used to prepare the conductive ink was dripped onto each of the porous alumina substrate and the green sheet (amount dripped: 5 to 10 μL). Next, the absorption time of the organic solvent into the porous alumina substrate or the green sheet was measured. Here, the "absorption time" was the time from immediately after the organic solvent was dripped onto the porous alumina substrate or the green sheet until the gloss caused by the solvent disappeared over the entire surface of the dripped liquid. The disappearance of the gloss caused by the solvent was determined visually.

[0097] In evaluating sheet attack resistance, the absorption rate was calculated by dividing the absorption time by the weight of the organic solvent dropped. To eliminate variations due to differences in substrate lots, each calculated absorption rate was normalized by dividing it by the absorption rate when only organic solvent S11 was dropped. Next, the normalized absorption rate for the green sheet was divided by the normalized absorption rate for the porous alumina substrate to calculate the absorption rate ratio. This absorption rate ratio is shown in the corresponding column in Tables 1 and 2.

[0098] Furthermore, sheet attack resistance was evaluated based on this absorption rate ratio. If the impact of sheet attack on the green sheet becomes too great, the binder resin in the green sheet may swell, reducing the solvent absorption. Therefore, the absorption rate ratio may become smaller due to the impact of sheet attack. In this evaluation, an absorption rate ratio of 0.45 or more was rated as "○ (pass)" and an absorption rate ratio of less than 0.45 was rated as "× (fail)." The evaluation results are shown in the relevant columns in Tables 1 and 2.

[0099] Both Sheet A and Sheet B were prepared by applying a ceramic slurry consisting of alumina particles, binder, plasticizer, and organic solvent to a carrier substrate using the doctor blade method and then heating and drying. The binder contained in both Sheet A and Sheet B was polyvinyl acetal resin. The binder contained in Sheet A was "BM-1" manufactured by Sekisui Chemical Co., Ltd. The binder contained in Sheet B was a polyvinyl acetal resin with a different structure from the binder contained in Sheet A.

[0100] D. Viscosity The prepared conductive ink was kept at 25°C and the viscosity (mPa·s) of the conductive ink was measured using the rheometer described above. The shear rate of the rheometer was 1000 s -1 The viscosity was set at 6 mPa·s to 20 mPa·s and evaluated as "Good (excellent dischargeability)" when the measured viscosity was between 6 mPa·s and 20 mPa·s, and evaluated as "Poor dischargeability" when the measured viscosity was outside the above range. The results are shown in Tables 1 and 2.

[0101] E. Stability over time Portions of the prepared conductive ink were collected in three storage bottles, one of which was stored at 4°C, one at 25°C, and one at 60°C. After one week, the average particle size of each ink was measured using dynamic light scattering (DLS). In all three environments, an average particle size of 220 nm to 320 nm was evaluated as "Good" (excellent stability over time), and an average particle size outside this range was evaluated as "Poor stability over time." The results are shown in Tables 1 and 2.

[0102] F. Overall evaluation Based on the above evaluation tests, an overall evaluation of the conductivity of each example was made. If all the evaluation tests were evaluated as "Good", the sample was rated as "Good (pass)". If even one evaluation test was evaluated as "Poor", the sample was rated as "Poor (fail)". The results are shown in Tables 1 and 2.

[0103] As shown in Tables 1 and 2, the conductive inks of Examples 1 to 17 contained a first solvent, a second solvent, and a third solvent, and the content C1 (%) of the first solvent, the content C2 (%) of the second solvent, and the content C3 (%) of the third solvent were expressed by the following formulas (1) to (3): 5≦C1≦75 (1) 20≦C2≦60 (2) 0.5·C2-10≦C3≦0.5·C2+10 (3) This test example demonstrates that the conductive inks of Examples 1 to 17 both suppress the occurrence of sheet attack and improve the ejection properties. In addition, as shown in Tables 1 and 2, the conductive inks of Examples 1 to 17 were shown to have excellent stability over time.

[0104] While specific examples of the technology disclosed herein have been described above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Explanation of symbols]

[0105] 1. Inkjet device 10 Inkjet head 12 cases 13 Storage 15 Liquid transfer path 16 Discharge part 17 Outlet 18 Piezo element 20 Guide shaft 40 print cartridges 100 Stirring mill 110 Supply port 120 Stirring vessel 132 stirring blade 134 Shaft 140 filters 150 Outlet

Claims

1. 1. A conductive inkjet ink for use in the manufacture of electronic components, comprising: The composition contains at least an inorganic powder and an organic solvent for dispersing the inorganic powder, The organic solvent is The viscosity is 5 mPa·s or less, and the SP value, which is the Hildebrand solubility parameter, is 8 (cal / cm ３ ) ０．５ ~10(cal / cm ３ ) ０．５ a first solvent, The viscosity is 10 mPa·s to 100 mPa·s, and the SP value is 9 (cal / cm ３ ) ０．５ ~11(cal / cm ３ ) ０．５ a second solvent, The viscosity is 3 mPa·s or less, and the SP value is 8 (cal / cm ３ ) ０．５ a third solvent that is less than It contains When the total weight of the organic solvent is 100 wt %, the content C of the first solvent is １ (wt%) and the content C of the second solvent ２ (wt%) and the content C of the third solvent ３ (wt%) is expressed by the following formulas (1) to (3): 5≦C １ ≦75 (1) 20≦C ２ ≦60 (2) 0.5・C ２ -10≦C ３ ≦0.5・C ２ +10 (3) A conductive inkjet ink characterized by satisfying the above.

2. 2. The conductive ink-jet ink according to claim 1, wherein the inorganic powder has an average particle size of 150 nm to 500 nm.

3. The conductive inkjet ink according to claim 1 or 2, wherein the inorganic powder contains a metal powder having a true specific gravity of 11 or more.

4. The conductive ink-jet ink of claim 3 , wherein the metal powder is tungsten powder.

5. The conductive inkjet ink according to any one of claims 1 to 4, further comprising a cationic dispersant.

6. Weight per unit volume is 1.5 g / cm ３ ~3.0 g / cm ３ The conductive inkjet ink according to any one of claims 1 to 5, wherein

7. the first solvent is composed of at least one of ethers and esters, the second solvent is composed of at least one of an ester and an alcohol, The third solvent is composed of a hydrocarbon compound. The conductive inkjet ink according to any one of claims 1 to 6.

8. the first solvent contains at least one compound selected from the group consisting of glycol ether, glycol ether acetate, and terpineol derivatives; the second solvent includes at least one compound selected from the group consisting of glycol ether acetate and monoterpene alcohol; The third solvent comprises a linear alkane. The conductive inkjet ink according to claim 7.

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