Inkjet ink

Abstract

To provide an inkjet ink capable of suppressing both a coffee ring phenomenon during heating and drying and sheet attack on a lower layer during heating and drying.SOLUTION: There is provided an inkjet ink comprising a ceramic powder, a binder resin, a dispersant and an organic solvent which is at least one of a first organic solvent, which is 2-octyl propionate and a second organic solvent represented by the formula (2). (In the formula, A is a methylene group or an ethylene group and R1 is a hydrogen atom or a methyl group.) The second organic solvent is a saturated hydrocarbon having a vapor pressure at 20°C of 4 Pa or less. The value (Vs2 / Vp) obtained by dividing the volume ratio Vs2 of the second organic solvent to the total by the volume ratio Vp of the ceramic powder to the total is 1.5 or more.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Inkjet printing has been used for some time as a printing method for printing images such as patterns and letters on a printing target. Because inkjet printing can print highly accurate images on demand at low cost and with minimal damage to the printing target, its application to various fields has been considered. In recent years, the use of inkjet printing has been considered for forming conductive circuit patterns (wiring, electrodes, etc.) in the manufacture of electronic components.

[0003] In the manufacture of such electronic components, for example, conductive inkjet inks containing inorganic powders, such as metal particles, as conductive materials are sometimes used. Patent Document 1 discloses an example of such a conductive inkjet ink, which contains nanometal powders such as silver or silver-copper alloys. Patent Document 2 also discloses an ink containing metal oxide fine particles such as silver oxide, copper oxide, palladium oxide, nickel oxide, lead oxide, and cobalt oxide. Generally, to properly perform inkjet printing, a conductive ink is required to have low viscosity and a high concentration of inorganic powder. Patent Documents 1 and 2 above propose techniques for achieving these inkjet suitabilities.

[0004] Furthermore, in conductive inkjet inks, it is also necessary to stably disperse inorganic powders in order to ensure ejection properties during printing and conductivity after printing. For example, Patent Document 3 discloses a technique of adding a first dispersant having only either acidic adsorption groups or basic adsorption groups, and a second dispersant having both acidic adsorption groups and basic adsorption groups, in order to improve the dispersibility of solid fine particles (inorganic powders) having a mixture of acid sites and basic sites on the surface.

[0005] Patent Document 4 discloses a spacer particle dispersion containing spacer particles and a solvent mainly composed of an organic solvent, which is used to arrange the spacer particles at any position on a substrate using an inkjet device. This spacer particle dispersion is characterized by a surface tension of 30 to 65 mN / m. The publication also describes that, with this configuration, it is possible to provide a spacer particle dispersion that prevents droplets of the spacer particle dispersion ejected onto a substrate of a liquid crystal display device using an inkjet device from wetting and spreading, and that allows spacer particles to be selectively arranged at any position on the substrate, and 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 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] Among electronic components, there are multilayer products (e.g., multilayer ceramic capacitors (MLCCs)) that require high smoothness in the electrode and insulating layers. Such multilayer electronic components use ferroelectric ceramic materials such as barium titanate for the insulating layers and metal materials such as palladium and nickel for the electrode layers. In the manufacturing process for electrode and insulating layers, a ceramic layer is first formed on a plastic film, such as a PET film, whose surface has been treated to be smooth, using a ceramic slurry by a doctor blade method, screen printing, or other method. A metal layer is then formed on top of this using a metal slurry (paste), for example, by screen printing. Next, all printed materials are peeled from the PET film and laminated, followed by pressing and firing to form a multilayer electronic component. Here, a certain level of strength is required for the ceramic green sheets during the peeling process from the PET film. Therefore, there is a limit to how much the insulating (dielectric) layer thickness can be reduced.

[0008] Among ceramic particles, barium titanate, for example, has a high dielectric constant and is therefore used as a dielectric material, as mentioned above. Among metal particles, nickel, for example, is often used because it is chemically stable and relatively safe, has a low volume resistivity, and is inexpensive as a raw metal material. Currently, most MLCC manufacturers use a slurry in which barium titanate particles are dispersed in an organic solvent, and a paste in which nickel particles are dispersed in a highly viscous organic solvent, to manufacture laminated electronic components through the process mentioned above.

[0009] The inventors are investigating the formation of laminated components by alternately inkjet printing insulating and electrode layer patterns for electronic components, which require high smoothness, using a ceramic inkjet ink primarily composed of ceramic particles (e.g., ceramic particles that function as a dielectric, such as barium titanate particles) and a conductive inkjet ink primarily composed of nickel particles.The objective is to reduce the thickness of both the electrode and insulating layers, which has been difficult to achieve with the combination of green sheets and conductive pastes, as components become smaller and larger in capacity in MLCC manufacturing.

[0010] In order to achieve sufficiently thin layers in ceramic and conductive inkjet inks, it is necessary to smooth the surface of each layer. By smoothing both the ceramic and metal layers, it is possible to achieve miniaturization that was not possible with conventional screen printing methods, and high productivity that can be produced without peeling off the PET film.

[0011] Here, the inventors wanted to suppress the occurrence of the so-called coffee ring phenomenon during heat drying in order to obtain smoothness suitable for lamination when printing inkjet inks, as well as to suppress sheet attack on the underlying layer during heat drying. [Means for solving the problem]

[0012] The inkjet ink disclosed herein is an inkjet ink used in the manufacture of electronic components. The inkjet ink contains ceramic powder, a binder resin, a dispersant, and an organic solvent. The organic solvent contains a first organic solvent and a second organic solvent. The first organic solvent is The following formula (1): [ka] Solvent 1 shown in The following formula (2): [ka] (wherein A is a methylene group or an ethylene group, and R1 is a hydrogen atom or a methyl group) and solvent 2 shown in The second organic solvent is a saturated hydrocarbon having a vapor pressure of 4 Pa ​​or less at 20°C. The value (Vs2 / Vp) obtained by dividing the volume ratio Vs2 of the second organic solvent to the entire inkjet ink by the volume ratio Vp of the ceramic powder to the entire inkjet ink is 1.5 or more. This configuration can suppress the occurrence of the coffee ring phenomenon during heat drying, and can also suppress sheet attack on the lower layer during heat drying.

[0013] In a preferred embodiment of this inkjet ink, the ceramic powder has an average particle size of 10 nm or more and 400 nm or less, which allows the inkjet ink to print a film with desirable smoothness.

[0014] In another preferred embodiment of the ink-jet ink, the ceramic powder contains barium titanate powder. This configuration makes it possible to impart dielectric properties to a printed film of the ink-jet ink.

[0015] In another preferred embodiment of this inkjet ink, the volume ratio of the second organic solvent to the total volume of the first organic solvent and the second organic solvent is 5% to 25% by volume. This configuration allows the inkjet ink to achieve desirable smoothness in the printed film.

[0016] In another preferred embodiment of the ink-jet ink, the binder resin contains an acrylic resin. With this configuration, the sheet attack property of the ink-jet ink can be more effectively suppressed.

[0017] In another preferred embodiment of this inkjet ink, the saturated hydrocarbon is a linear alkane having a carbon number of 20 or less. With this configuration, the effects of the technology disclosed herein can be more effectively achieved. [Brief explanation of the drawings]

[0018] [Figure 1]FIG. 1 is a cross-sectional view of an agitator / pulverizer 100. As shown in FIG. [Figure 2] FIG. 2 is an overall view of the inkjet device 1. As shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the inkjet head 10. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the technology disclosed herein will be described. It should be noted that matters necessary for implementing the technology disclosed herein, 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. In this specification, the notation "P to Q" indicating a numerical range includes "P or more and Q or less," "more than P but less than Q," "more than P but Q or less," and "P or more and less than Q." In this specification, "R contains S as a major component" means that, when the entire R is 100% by mass, the S content 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).

[0020] <Inkjet ink> The inkjet ink (hereinafter simply referred to as "ink") disclosed herein may contain, for example, (A) ceramic powder, (B) binder resin, (C) dispersant, and (D) organic solvent. In the ink, for example, ceramic powder is dispersed in an organic vehicle component (a mixture of binder resin and organic solvent). Each component contained in the ink disclosed herein will be described below.

[0021] (A) Ceramic powder Ceramic powder is a material that constitutes a printed film on a substrate or a metal layer (for example, the electrode layer of a multilayer ceramic capacitor (MLCC)). Here, the "printed film" refers to a film-like substance (dried film) obtained by applying ink to a substrate and drying it, and is an unfired body. Ceramic powder is also a material that constitutes a fired film obtained by firing such a printed film.

[0022] The ceramic powder may contain, for example, ceramic particles as a main component. In addition to the ceramic that constitutes the ceramic particles, the ceramic particles may contain inevitable impurities that may be mixed in during the ceramic particle production process, etc. The ceramic powder may be composed of one type of ceramic powder or two or more types of ceramic powder.

[0023] The type of ceramic powder is not particularly limited, as long as it is appropriately selected depending on the function to be imparted to the fired film formed using the ink disclosed herein. The ceramic powder may, for example, be a ceramic powder that functions as a dielectric. This allows a dielectric ceramic layer (e.g., a dielectric layer of a multilayer ceramic capacitor (MLCC)) to be formed as an insulating layer on a substrate or a metal layer. Examples of ceramics that constitute the ceramic powder include metal oxides having a perovskite structure represented by ABO3, such as barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, zirconium titanate, zinc titanate, barium magnesium niobate, calcium zirconate, and barium zirconate titanate; titanium dioxide (rutile), titanium pentoxide, hafnium oxide, zirconium oxide, aluminum oxide, forsterite, niobium oxide, barium neodymium titanate, and rare earth element oxides. Among these, the ceramic may preferably be any one of barium titanate, strontium titanate, calcium zirconate, and barium titanate zirconate.

[0024] The particle size of the ceramic powder in the ink is one of the factors that affect, for example, the ejection performance, stability over time, and smoothness of the printed film. For example, from the viewpoint of preventing a decrease in the ejection performance of an inkjet device due to clogging of the ejection orifices with ceramic powder, the average particle size of the ceramic 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. Furthermore, from the viewpoint of improving the smoothness of the printed film, the average particle size of the ceramic powder is preferably 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 preventing particle aggregation and preventing a decrease in the ink's stability over time, the average particle size of the ceramic powder is, for example, 5 nm or more, preferably 10 nm or more, and more preferably 20 nm or more. Note that, in this specification, "average particle size" refers to the average particle size measured by dynamic light scattering (DLS) analysis. The average particle size based on the DLS method is measured in accordance with JIS Z 8828:2013.

[0025] The volume fraction of the ceramic powder in the ink is not particularly limited and can be set appropriately depending on the printing purpose. For example, as the volume fraction of the ceramic powder in the ink increases, a printed layer of suitable thickness can be formed with fewer printing iterations. From this perspective, when the entire ink is taken as 100% by volume, the volume fraction of the ceramic powder is generally 0.1% by volume or more, preferably 0.5% by volume or more, and more preferably 1% by volume or more. On the other hand, as the volume fraction of the ceramic powder decreases, stability over time, ejection performance, etc. tend to improve. From this perspective, when the entire ink is taken as 100% by volume, the volume fraction of the ceramic powder is generally 20% by volume or less, preferably 15% by volume or less, and more preferably 10% by volume or less.

[0026] The content of ceramic powder in the ink can be appropriately set depending on, for example, the desired thickness of the printed film. Here, when the total ink is taken as 100% by mass, the content of ceramic powder is preferably approximately 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 taken as 100% by mass, the content of ceramic powder is preferably, for example, 50% by mass or less, preferably 40% by mass or less, and more preferably 30% by mass or less. In one embodiment of the ink disclosed herein, when the total ink is taken as 100% by mass, the content of ceramic powder is preferably approximately 5% to 50% by mass, and preferably 10% to 30% by mass.

[0027] When using an ink containing the above-mentioned ceramic powder, for example, when the organic solvent volatilizes due to heat drying, a phenomenon known as the coffee ring phenomenon may occur in which the printed film accumulates on the outer periphery. This can result in the outer periphery of the printed film becoming thicker than the inner periphery, which can lead to insufficient smoothing of the film. Therefore, an ink composition that can suppress this phenomenon is required. In addition, when a green sheet is produced using an ink containing the above-mentioned ceramic powder (e.g., an ink for forming a dielectric layer) and then an ink containing a metal powder (e.g., an ink for forming an electrode layer) is printed on top of the green sheet, it is necessary to prevent the ink containing the metal powder from sheet attacking the ceramic powder green sheet.

[0028] In this regard, the inventors first considered using polyvinyl acetal resin A, which contains a relatively large number of hydroxyl groups, as the binder resin for the ceramic powder green sheet material and a highly polar solvent such as dimethyl sulfoxide (DMSO) as the organic solvent. The inventors then considered using polyvinyl acetal resin B, which contains a relatively small number of hydroxyl groups, as the binder resin for the metal powder ink material and a low-polarity solvent such as diethylene glycol butyl methyl ether as the organic solvent, so that the metal powder ink would not attack the ceramic powder green sheet. However, when printing an ink containing ceramic powder on top of a printed film of ink containing metal powder, it is necessary to use a solvent that does not dissolve both polyvinyl acetal resin A and polyvinyl acetal resin B.

[0029] An example of such a solvent is water. However, the ceramic powder described above is soluble in water, which can impair its properties (e.g., its dielectric properties). Alternatively, a solvent that selectively dissolves other resins (e.g., acrylic resins) but does not dissolve both polyvinyl acetal resin A and polyvinyl acetal resin B can be selected. However, even if sheet attack can be suppressed, there is still room for improvement in suppressing the coffee ring phenomenon. In other words, there has not previously been an ink that has sufficient sheet attack resistance against both a green sheet containing ceramic powder and a printed film of ink containing metal powder, and that can suppress the coffee ring phenomenon.

[0030] The inventors have conducted extensive research into ink containing ceramic powder to improve the smoothness of the ceramic layer by suppressing accumulation on the periphery of the layer pattern during heating and drying after printing, and by reducing sheet attack on the underlying layer (for example, the green sheet containing ceramic powder and the printed film of ink containing metal powder, as described above).

[0031] (B) Binder resin The binder resin is a component that fixes the ceramic powder on the substrate or metal layer after ink is inkjet printed on the substrate or metal layer. The ink inkjet printed on the substrate or metal layer is, for example, heated and dried, and then subjected to a firing process. Therefore, it is preferable that the binder resin be one that completely disappears (burns out) during the firing process. For example, a thermoplastic resin can be preferably used as the binder resin. As the thermoplastic resin, any conventionally known resin can be used without particular limitation, as long as it is soluble in the organic solvent used and thermally decomposes and burns out during the firing process. Among these, a thermoplastic resin whose basic skeleton is composed of oxygen (O), carbon (C), and hydrogen (H) is preferably used. Using a thermoplastic resin composed of such constituent elements can prevent the residue from remaining on the film after firing. Therefore, such a thermoplastic resin is preferable for better achieving the effects of the technology disclosed herein.

[0032] Suitable examples of binder resins include acrylic resins (including methacrylic resins) such as polymethyl methacrylate resin, polyethyl methacrylate resin, and polybutyl acrylate resin; polystyrene resins such as polystyrene and acrylonitrile-butadiene-styrene copolymer (ABS resin); polyolefin resins such as polyethylene, polypropylene, and cyclic olefin; polyvinyl acetate resin; polycarbonate resin; and polyurethane resin. Among these, acrylic resins (burnout temperature: 250°C), polystyrene resins (burnout temperature: 410°C), and polypropylene resins (burnout temperature: 445°C) are more preferably used. Furthermore, acrylic resins with lower burnout temperatures are more preferably used.

[0033] The weight-average molecular weight of the binder resin can be set as appropriate as long as it does not impair the effects of the technology disclosed herein. For example, from the viewpoint of appropriately suppressing the precipitation of the ceramic powder, the weight-average molecular weight of the binder resin is set to, for example, 0.5×10 4 It is recommended that the value is at least 1.0 x 10 4 More than 1.5 × 10 is preferable. 4More preferably, 2.0 x 10 4 On the other hand, from the viewpoint of maintaining the viscosity of the ink at an appropriate level and suppressing a decrease in the ejection properties, the weight average molecular weight of the binder resin is, for example, 10 × 10 4 It is recommended that the value is less than 9.0 x 10 4 The following is preferable: 8.0 x 10 4 Less than 7.0 x 10 is preferable. 4 The following is even more preferable. The weight-average molecular weight of the binder resin and dispersant is measured, for example, by gel permeation chromatography (GPC) and converted using a standard polystyrene calibration curve to obtain a weight-average molecular weight. For such measurements, a GPC device (HLC-8320) manufactured by Tosoh Corporation may be used. Alternatively, nominal values ​​from manufacturers of the resin binder and dispersant, or values ​​calculated based on their chemical formulas, may be used.

[0034] The glass transition temperature of the binder resin can be set 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 45°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.

[0035] The volume percentage of the binder resin in the ink can be set as appropriate as long as it does not impair the effects of the technology disclosed herein. For example, when the total volume of the ink is 100%, the volume percentage of the binder resin is approximately 0.3% to 3% by volume, and preferably 0.5% to 1.5% by volume.

[0036] (C) Dispersant The dispersant is a component that uniformly disperses ceramic particles in the ink and suppresses aggregation and sedimentation of the ceramic particles. To maximize the effectiveness of the dispersant, the ink disclosed herein preferably contains an anionic dispersant. The anionic dispersant is, for example, a dispersant having an anionic functional group. The anionic dispersant adheres to the surface of the metal particles via the anionic functional group, causing steric hindrance. This suppresses aggregation between ceramic particles, ultimately improving the long-term stability of the ink.

[0037] As the anionic dispersant, any of the conventionally known anionic dispersants used for this type of application can be used without any particular limitation. Examples of the anionic dispersant include carboxylic acid dispersants, phosphoric acid dispersants, and sulfonic acid dispersants. Carboxylic acid dispersants, for example, contain a carboxyl group (COO) in the molecule. - Phosphate-based dispersants are organic compounds that contain phosphonic acid groups (PO3 - group, PO3 2- Sulfonic acid dispersants are organic compounds that contain sulfonic acid groups (SO3 - group, SO3 2- Among them, as the anionic dispersant, a carboxylic acid dispersant (for example, a polymeric polycarboxylic acid dispersant) can be preferably used.

[0038] The anionic dispersant may have, for example, a main chain and a plurality of graft chains. The anionic dispersant may have an ionic group (e.g., a carboxyl group, a phosphonic acid group, or a sulfonic acid group) in the main chain and a polyoxyalkylene chain as a graft chain. Although not particularly limited, the weight-average molecular weight of the anionic dispersant may be, for example, 1×10 3 ~5×10 4 As a specific example of an anionic dispersant, SC-0708A of the Marialim (registered trademark) SC series manufactured by NOF Corporation is preferably used.

[0039] The volume percentage of the anionic dispersant in the ink can be set as appropriate as long as it does not impair the effects of the technology disclosed herein. For example, when the total volume of the ink is taken as 100 volume %, the volume percentage of the anionic dispersant is approximately 0.5 volume % to 5 volume %, and preferably 1 volume % to 3 volume %.

[0040] (D) Organic solvent The organic solvent disperses the ceramic powder and can impart fluidity suitable for inkjet printing to the ink. The organic solvent is required to have a surface tension suitable for improving the refillability of the inkjet ink, and also to be able to suppress the flow of the ink when the printed film is heated and dried after inkjet printing.

[0041] In the ink disclosed herein, the organic solvent may include a first organic solvent and a second organic solvent. The first organic solvent may, for example, increase the fluidity of the ceramic powder, contributing to thinner printed films and improving the ink's stability over time. The first organic solvent may, for example, be an organic solvent that selectively dissolves the resin binder. The first organic solvent may, for example, be an organic solvent that dissolves the binder resin contained in the ink disclosed herein but does not dissolve the binder resin contained in the green sheet containing the ceramic powder or the binder resin contained in the ink containing the metal powder. The first organic solvent is preferably, for example, an organic solvent that dissolves acrylic resin or celluloses but does not dissolve polyvinyl acetal resin (e.g., polyvinyl butyral resin).

[0042] The first organic solvent is, for example, at least one of solvent 1 and solvent 2. Solvent 1 is, for example, a compound represented by the following formula (1): [ka] Preferably, the compound is 2-octylpropionate as shown in the following formula:

[0043] Solvent 2 is, for example, a compound represented by the following formula (2): [ka] In formula (2), A is a methylene group or an ethylene group, and R1 is a hydrogen atom or a methyl group. Suitable examples of solvent 2 include 2,4-dimethyl-2-hexyl-1,3-dioxane and 2-hexyl-2-methyl-1,3-dioxolane.

[0044] The second organic solvent is a saturated hydrocarbon having a vapor pressure P of 4 Pa ​​or less at 20°C. The second organic solvent is, for example, an organic solvent that is less volatile than the first organic solvent. The evaporation rate of the second organic solvent is, for example, slower than that of the first organic solvent. Therefore, the second organic solvent can prevent the first organic solvent from excessively increasing the fluidity and dispersibility of the ceramic powder, contributing to the ceramic powder being appropriately dispersed in the ink. The vapor pressure P may be, for example, 3 Pa or less, or 2 Pa or less. On the other hand, the vapor pressure P may be, for example, 0.5 Pa or more, or 1 Pa or more. Although not particularly limited, the surface tension of the second organic solvent is, for example, 20 mN / m to 30 mN / m, and preferably 24 mN / m to 28 mN / m.

[0045] In this specification, the term "hydrocarbon compound" refers to a compound composed of carbon atoms and hydrogen atoms. The hydrocarbon compound used as the second organic solvent is, for example, a straight-chain alkane having 20 or less carbon atoms (preferably 10 to 16 carbon atoms) and having a vapor pressure P that satisfies the above-mentioned range. For example, tetradecane can be preferably used as such a straight-chain alkane.

[0046] From the viewpoints of increasing the solubility of the binder resin in the ink and reducing the sheet attack of the ink, the volume ratio of the first organic solvent to the total volume of the first organic solvent and the second organic solvent in the ink is, for example, 70% by volume or more, preferably 75% by volume or more, and more preferably 80% by volume. From the viewpoint of suppressing the coffee ring phenomenon, the volume ratio of the first organic solvent is, for example, 97% by volume or less, preferably 95% by volume or less, and more preferably 90% by volume or less.

[0047] From the viewpoint of suppressing the coffee ring phenomenon, the volume ratio of the second organic solvent to the total volume of the first organic solvent and the second organic solvent in the ink is, for example, 3% by volume or more, preferably 5% by volume or more, and more preferably 10% by volume or more. From the viewpoint of increasing the solubility of the binder resin in the ink and reducing the sheet attack property of the ink, the volume ratio of the second organic solvent is, for example, 30% by volume or less, preferably 25% by volume or less, and more preferably 20% by volume or less.

[0048] The value (Vs2 / Vp) obtained by dividing the volume ratio Vs2 of the second organic solvent to the total ink by the volume ratio Vp of the ceramic powder to the total ink is preferably 1.5 or more. By including the second organic solvent in the ink at a volume 1.5 times or more the volume of the ceramic powder, the ceramic powder can be appropriately dispersed in the ink. Furthermore, when the ink is heated and dried, the ceramic powder can be prevented from moving as the ink dries, thereby improving the smoothness of the printed film. From this perspective, the value (Vs2 / Vp) is preferably 1.6 or more, more preferably 1.8 or more. On the other hand, from the perspective of appropriately dispersing the ceramic powder in the ink, the value (Vs2 / Vp) is, for example, 5 or less, preferably 3 or less, and more preferably 2.7 or less.

[0049] As long as the effects of the technology disclosed herein are realized, the organic solvent may contain a third organic solvent that is not classified as either the first organic solvent or the second organic solvent. From the viewpoint of better realizing the effects of the technology disclosed herein, the first organic solvent and the second organic solvent account for 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.

[0050] Although there are no particular limitations, for example, from the viewpoint of improving the ejection properties of the ink, when the entire ink is taken as 100% by volume, the volume ratio 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.

[0051] (E) Other ingredients The inks disclosed herein may further contain known additives used in inkjet inks, provided that the effects of the technology disclosed herein are not impaired. The types and amounts of such additives can be appropriately changed based on conventionally known technical common sense, and do not characterize the technology disclosed herein. Therefore, a description thereof will be omitted here.

[0052] <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 the ceramic powder. FIG. 1 is a cross-sectional view of an agitator / pulverizer 100. Note that the following description shows an example of a means for preparing the ink disclosed herein and is not intended to limit the technology disclosed herein.

[0053] When producing the ink disclosed herein, first, the above-described components are weighed and mixed to prepare a slurry (including a paste and a suspension), which is a precursor of the ink. Then, the ink is prepared by stirring the slurry and crushing the ceramic powder using an agitator / miller 100 as shown in FIG. 1. For example, 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 to rotate the shaft 134, the multiple stirring blades 132 stir the slurry while sending it downstream in the liquid-feeding direction D. During this stirring, the ceramic powder is crushed by the crushing beads, and the atomized ceramic powder is dispersed in the slurry.

[0054] The slurry sent downstream in the liquid sending direction D then passes through filter 140. As a result, the ceramic powder, crushing beads, etc. that have not been atomized are collected in filter 140, and ink in which the ceramic powder is sufficiently dispersed is discharged from outlet 150. In this process, the average particle size, etc. of the ceramic powder can be adjusted to a desired range by appropriately adjusting the pore size of filter 140, the average particle size of the crushing beads, etc.

[0055] <Inkjet ink applications> Next, 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" not only refers to a case in which the ink is directly printed on the surface of an inorganic substrate, but also includes a case in which the ink is indirectly attached to the surface of an inorganic substrate via an intermediate material such as transfer paper, and a case in which the ink is printed on the surface of a layer previously formed on the surface of an inorganic substrate.

[0056] (1) Printing Fig. 2 is an overall view of the inkjet device 1. Fig. 3 is a cross-sectional view of the inkjet head 10. Ink is printed onto the surface of a printing target by the 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 those used as substrates for general electronic components can be used without particular limitation.

[0057] As shown in Fig. 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 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 enables the inkjet device 1 to eject ink onto a desired position on the inorganic substrate W.

[0058] The inkjet head 10 may be, for example, a piezoelectric inkjet head as shown in FIG. 3. The piezoelectric inkjet head 10 has a storage section 13 for storing ink in a case 12, and the storage section 13 is connected to a discharge section 16 via a liquid supply path 15. The discharge section 16 has a discharge port 17 that opens to the outside of the case 12, and a piezoelectric element 18 is arranged opposite the discharge port 17. In the inkjet head 10, the piezoelectric element 18 is vibrated to discharge the ink in the discharge section 16 from the discharge port 17 toward the inorganic substrate W (see FIG. 2). In this embodiment, the inorganic substrate W is a green sheet containing ceramic powder and a printed film (dried film) of ink containing metal powder provided on the surface of the green sheet.

[0059] (2) Drying process Next, a drying process is performed in which the inorganic substrate W with the ink attached thereto is heated at a predetermined temperature. This removes the organic solvent from the ink, forming a printed film (dried film) of the ink disclosed herein on the inorganic substrate W. The ink disclosed herein contains a first organic solvent and a second organic solvent having predetermined properties as organic solvents. By including the first organic solvent that selectively dissolves the resin in the ink, sheet attack on the underlying layer can be suppressed. In addition, the ceramic powder is appropriately dispersed in the ink. During the drying process, the first organic solvent, which has a relatively high relative volatilization rate, evaporates before the second organic solvent, which has a relatively low volatilization rate, in the ink attached to the inorganic substrate W. Therefore, the ceramic powder remains appropriately dispersed in the ink even during the drying process. This suppresses the coffee ring phenomenon that occurs when the ink dries. The heating temperature during the drying process can be set to a temperature (e.g., 50°C to 150°C) that removes the organic solvent but does not sinter the ceramic powder.

[0060] (3) Firing This manufacturing method includes firing the inorganic substrate W after the printing film is formed. This burns off the organic components, including the binder resin, and sinters the ceramic powder, causing it to adhere to the surface of the inorganic substrate W. As a result, an electronic component is manufactured having a fired film primarily composed of ceramic powder. The firing temperature can be set appropriately depending on, for example, the type of ceramic powder contained in the ink. For example, the firing temperature may be set to 500°C to 2000°C.

[0061] Next, test examples relating to the technology disclosed herein will be described. Note that the test examples shown below are not intended to limit the technology disclosed herein.

[0062] [Preparing materials] (ceramic powder) As the semilac powder, barium titanate powder with an average particle size of 0.10 μm was prepared.

[0063] (organic solvent) The following seven types of organic solvents were prepared. The physical properties of the following organic solvents are shown in Table 1. Among the physical properties shown in Table 1, the boiling point (boiling point under atmospheric pressure conditions) and vapor pressure at 20°C are nominal values ​​from each manufacturer. The surface tension of each organic solvent shown in Table 1 is a measured value measured for each organic solvent using a static surface tensiometer (DYNEMASTER DY-300, manufactured by Kyowa Interface Science Co., Ltd.). Among the physical properties listed in Table 1, the vapor pressure of organic solvent S2 and the vapor pressure of organic solvent S3 are not listed ("-").

[0064] Organic solvent S1: 2-Octylpropionate, "ORO-P" manufactured by Nippon Fragrance Pharmaceutical Co., Ltd., CAS No. "84782-03-6" Organic solvent S2: 2,4-Dimethyl-2-hexyl-1,3-dioxane, "2-OJK" manufactured by Nippon Fragrance Pharmaceutical Co., Ltd., CAS No. "6290-07-9" Organic solvent S3: 2-Hexyl-2-methyl-1,3-dioxolane, "2-OEK" manufactured by Nippon Fragrance Pharmaceutical Co., Ltd., CAS No. "937-94-0" Organic solvent S4: Diethylene glycol butyl methyl ether (Hisorb BDM), manufactured by Toho Chemical Industry Co., Ltd., CAS No. 7382-32-3 Organic solvent S5: 1-Octanol, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., CAS No. "111-87-5" Organic solvent S6: Tetradecane, manufactured by Kanto Chemical Co., Ltd., CAS No. "629-59-4" Organic solvent S7: 2,2,4-Trimethyl-1,3-pentanediol 1-monoisobutyrate, "NG-120" manufactured by Nippon Fragrance Pharmaceutical Co., Ltd., CAS No. "25265-77-4"

[0065] [Table 1]

[0066] (binder resin) The following four types of binder resins were prepared. Binder Resin B1: An acrylic resin with a weight-average molecular weight of 45,000 and a glass transition temperature of 48°C ("BR-105" manufactured by Mitsubishi Chemical Corporation) Binder Resin B2: An acrylic resin with a weight-average molecular weight of 50,000 and a glass transition temperature of 48°C ("BR-115" manufactured by Mitsubishi Chemical Corporation) Binder Resin B3: Acrylic resin with a weight-average molecular weight of 30,000 and a glass transition temperature of 75°C ("BR-113" manufactured by Mitsubishi Chemical Corporation) Binder resin B4: An acrylic resin with a weight-average molecular weight of 60,000 and a glass transition temperature of 50°C ("MH-0D041" manufactured by NOF Corporation)

[0067] (dispersant) An anionic dispersant ("SC-0708A" manufactured by NOF Corporation) was prepared as the dispersant.

[0068] [Ink preparation] Twelve types of ink were prepared, each containing a ceramic powder, a binder resin, a dispersant, and an organic solvent. First, a slurry was prepared by mixing the ceramic powder and an organic vehicle (organic solvent, binder resin, and dispersant) at a predetermined mass ratio. The resulting 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), followed by filtering under pressure to obtain an ink. The ceramic powder and dispersant used in each example were as described above. The organic solvent and binder resin used in each example are listed in the corresponding columns of Tables 2 and 3. Table 2 provides information on Examples 1 to 6. Table 3 provides information on Examples 7 to 12.

[0069] Regarding the ceramic powder and organic solvents, the values ​​listed in the "Percentage in ink (volume %)" columns in Tables 2 and 3 are the volume percentages of each component when the total volume of the ink is taken as 100%. A "-" in the column indicates that the corresponding component is not contained in the ink. Regarding the organic solvents, the values ​​listed in the "Percentage of first organic solvent in total organic solvents (volume %)" and "Percentage of second organic solvent in total organic solvents (volume %)" columns in Tables 2 and 3 are the volume percentages of the first organic solvent or the second organic solvent when the total volume of the organic solvents is taken as 100%. If the first organic solvent or the second organic solvent is not contained in the ink, a "-" is listed in the column. The numerical values ​​shown in the "Vs2 / Vp" column in Tables 2 and 3 are the ratios (Vs2 / Vp) of the volume fraction Vs2 of the second organic solvent when the entire ink is taken as 100% by volume, to the volume fraction Vp of the ceramic powder when the entire inkjet ink is taken as 100% by volume. If the ink does not contain the second organic solvent, "-" is shown in the corresponding column.

[0070] [Table 2]

[0071] [Table 3]

[0072] [Evaluation test] The following tests were carried out using the inks of each example. In Example 8, the binder resin was not soluble in the organic solvent, so the ink of this example could not be prepared. For this reason, evaluation tests were not carried out for Example 8. In Tables 2 and 3, a "-" in the "Printed film smoothness" and "Sheet attack" columns indicates that the corresponding evaluation test was not carried out.

[0073] A. Ink properties (A-1) Surface tension The surface tension (mN / m) of the ink in each example after preparation was measured using a static surface tensiometer (DYNEMASTER DY-300 manufactured by Kyowa Interface Science Co., Ltd.). The measurement results confirmed that the viscosity of the inks in Examples 1 to 7 and 9 to 12 was all between 25 mN / m and 35 mN / m. This indicates that the surface tension of the inks in Examples 1 to 7 and 9 to 12 was all within a preferred range.

[0074] (A-2) Viscosity After preparation, the ink viscosity (mPa·s) of each example was measured using a Brookfield DV-III ULTRA Spindle SC4-14 viscometer while maintaining the ink at 25°C. The Brookfield DV-III ULTRA Spindle SC4-14 viscometer was rotated at 10 rpm. The measurement results confirmed that the viscosities of the inks in Examples 1 to 7 and 9 to 12 were all 30 mPa·s or less. This indicates that the viscosities of the inks in Examples 1 to 7 and 9 to 12 were all within the preferred range.

[0075] (A-3) Average particle diameter The average particle size of the ceramic powder contained in each ink was measured using dynamic light scattering (DLS). The measurement results confirmed that the average particle size of the ceramic powder contained in the inks of Examples 1 to 7 and 9 to 12 was 20 nm to 320 nm. This shows that the average particle size of the ceramic powder contained in the inks of Examples 1 to 7 and 9 to 12 was within the preferred range.

[0076] (A-4) Stability over time After preparation, a portion of each ink was collected in two storage bottles, one of which was stored at 25°C and the other at 60°C. The average particle size of each ink was measured using dynamic light scattering (DLS) after 1 week, 2 weeks, 3 weeks, 4 weeks, and 8 weeks at 25°C and 60°C. Inks with an average particle size of 320 nm or less after at least 2 weeks were evaluated as having long-term stability. The results showed that Examples 1 to 7 and 9 to 12 all had long-term stability.

[0077] B. Printing test The following pattern printing tests and ejection tests were carried out using the inks of Examples 1 to 7 and 9 to 12.

[0078] (B-1) Pattern printing test The pattern forming ability of each ink was evaluated using an inkjet printer (Fujifilm Corporation: Material Printer DMP-2831). In this test, the inkjet printer's discharge 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 printed patterns were evaluated for the occurrence of the coffee ring phenomenon 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 in the center of each pattern, and the average value was obtained. The calculated values ​​obtained were calculated using the following formula (A): Maximum edge thickness / average center thickness<2 (A) Examples that satisfied the above criteria were evaluated as "○ (no coffee ring phenomenon)." On the other hand, examples that did not satisfy the above formula (A) were evaluated as "× (coffee ring phenomenon)." The results are shown in the "Uniformity of printed film" column in Tables 2 and 3.

[0079] (B-2) Discharge test Using the inkjet printer described above, the continuous and intermittent ejection performance (open time ejection performance) of each ink was evaluated. In the evaluation tests for both performances, each ink was printed as a film on the surface of an alumina substrate at 10 pL / dot and 1200 dpi. The ink ejection state was then visually observed using a camera attached to the inkjet printer.

[0080] (Continuous discharge performance) In the evaluation test for continuous ejection performance, it was evaluated whether the ink could be ejected continuously for 10 minutes. As a result, it was found that all of Examples 1 to 7 and 9 to 12 had continuous ejection performance.

[0081] (Intermittent discharge performance) The inks of each example were evaluated for intermittent ejection performance (open time ejection performance). In the evaluation test for intermittent ejection performance, after a 10-minute continuous ejection test, a 10-minute ejection stop period was set, and then an evaluation was made to see whether ejection was possible again. As a result, it was found that all of Examples 1 to 7 and 9 to 12 had intermittent ejection performance.

[0082] C. Seat attack resistance evaluation test The organic solvent contained in each ink was prepared and heated to 90°C, and polyvinyl acetal resin ("BL-5Z" manufactured by Sekisui Chemical Co., Ltd.) was dissolved therein at a concentration of 1 wt%. The solution was then cooled to 60°C. When the solution reached 60°C, the presence or absence of resin precipitation was visually observed. If resin precipitation was detected, the ink was evaluated as having no sheet attack properties. If resin precipitation was not detected, the ink was evaluated as having sheet attack properties. A similar test was also performed on another polyvinyl acetal resin ("BH-3" manufactured by Sekisui Chemical Co., Ltd.). Regarding the results of this test, in the "Sheet Attack Properties" column in Tables 2 and 3, inks that were evaluated as having no sheet attack properties for either of the two resins mentioned above were marked with "None," and inks that were evaluated as having sheet attack properties for at least one of the two resins mentioned above were marked with "Present."

[0083] Among Examples 1 to 12 shown in Tables 2 and 3, the inks of Examples 1 to 6 contain ceramic powder, a binder resin, a dispersant, and an organic solvent. In these inks, the organic solvent contains a first organic solvent and a second organic solvent. The first organic solvent is at least one of Solvent 1 and Solvent 2, each having a specific structure. The second organic solvent is a saturated hydrocarbon having a vapor pressure of 4 Pa ​​or less at 20°C. The value (Vs2 / Vp) obtained by dividing the volume fraction Vs2 of the second organic solvent to the entire inkjet ink by the volume fraction Vp of the ceramic powder to the entire inkjet ink is 1.5 or more. It was found that the inks of Examples 1 to 6 having such a configuration suppressed the coffee ring phenomenon and sheet attack.

[0084] The technology disclosed herein has been described above, but these are merely examples and do not limit the scope of the claims. Various modifications can be made to the technology disclosed herein without departing from the spirit of the technology.

[0085] The techniques disclosed herein include the techniques described in the following sections. Section 1: 1. An inkjet ink for use in the manufacture of electronic components, comprising: The ceramic powder includes a binder resin, a dispersant, and an organic solvent. wherein the organic solvent includes a first organic solvent and a second organic solvent, The first organic solvent is The following formula (1): [ka] Solvent 1 shown in The following formula (2): [ka] (wherein A is a methylene group or an ethylene group, and R1 is a hydrogen atom or a methyl group) and solvent 2 shown in At least one of the following is true: the second organic solvent is a saturated hydrocarbon having a vapor pressure of 4 Pa ​​or less at 20°C; an ink-jet ink, wherein a value (Vs2 / Vp) obtained by dividing a volume ratio Vs2 of the second organic solvent to the entire ink-jet ink by a volume ratio Vp of the ceramic powder to the entire ink-jet ink is 1.5 or more; Section 2: Item 2. The inkjet ink according to Item 1, wherein the ceramic powder has an average particle size of 10 nm or more and 400 nm or less. Section 3: Item 3. The inkjet ink according to item 1 or 2, wherein the ceramic powder includes barium titanate powder. Section 4: 4. The ink-jet ink according to any one of items 1 to 3, wherein the volume ratio of the second organic solvent to the total volume of the first organic solvent and the second organic solvent is 5% by volume to 25% by volume. Section 5: Item 5. The ink-jet ink according to any one of Items 1 to 4, wherein the binder resin includes an acrylic resin. Item 6: Item 6. The ink-jet ink according to any one of Items 1 to 5, wherein the saturated hydrocarbon is a linear alkane having 20 or less carbon atoms. [Explanation of symbols]

[0086] 1. Inkjet device 10 Inkjet head 12 cases 13 Storage 15 Liquid transfer path 16 Discharge part 17 Discharge port 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. An inkjet ink for use in the manufacture of electronic components, comprising: The ceramic powder includes a binder resin, a dispersant, and an organic solvent. wherein the organic solvent includes a first organic solvent and a second organic solvent, The first organic solvent is The following formula (1): 【Chemical 1】 Solvent 1 shown in The following formula (2): 【Chemistry 2】 (Wherein A is a methylene group or an ethylene group, R １ is a hydrogen atom or a methyl group) and solvent 2 shown in At least one of the following is true: the second organic solvent is a saturated hydrocarbon having a vapor pressure of 4 Pa ​​or less at 20°C; an ink-jet ink, wherein a value (Vs2 / Vp) obtained by dividing a volume ratio Vs2 of the second organic solvent to the entire ink-jet ink by a volume ratio Vp of the ceramic powder to the entire ink-jet ink is 1.5 or more;

2. 2. The ink-jet ink according to claim 1, wherein the ceramic powder has an average particle size of 10 nm or more and 400 nm or less.

3. The ink-jet ink of claim 1 or 2, wherein the ceramic powder comprises barium titanate powder.

4. 3. The ink-jet ink according to claim 1, wherein a volume ratio of the second organic solvent to a total volume of the first organic solvent and the second organic solvent is 5% by volume to 25% by volume.

5. The ink-jet ink according to claim 1 or 2, wherein the binder resin includes an acrylic resin.

6. The ink-jet ink according to claim 1 or 2, wherein the saturated hydrocarbon is a straight-chain alkane having 20 or less carbon atoms.

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