WO2025192095A1 - Two-component ink set, method for forming cured product, and product - Google Patents

Abstract

The present invention addresses the problem of providing: a two-component ink set which has a long pot life and can provide excellent film physical properties as an insulator used for an electronic component; a method for forming a cured product; and a product.　This inkjet two-component ink set is composed of at least ink A and ink B, the two-component ink set characterized in that the ink A contains at least a photocurable compound, the ink B contains at least a thermosetting compound, at least one of the ink A and the ink B contains a silica filler, and the silica filler is surface-modified.

Description

Two-component ink set, method for forming cured product, and product

The present invention relates to a two-component ink set, a method for forming a cured product, and a product. More specifically, it relates to an ink set that has a long pot life and can provide excellent film properties as an insulator for use in electronic components.

In recent years, there has been an increase in electronic devices and industrial equipment that require power electronics, which are relatively high-voltage or large-current power sources, such as EVs (electric vehicles) and drones. PCBs (Printed Circuit Boards), which provide the power for such equipment, are formed by etching the copper of copper plates or copper-clad laminates. Hereinafter, "PCB (Printed Circuit Board)" will be abbreviated to "PCB."

Generally, the layers formed to insulate and protect these wiring are formed by laminating and crimping prepregs containing glass fibers in the case of inner layer wiring in laminated boards. The outermost layers of single-layer boards, double-sided boards, and laminated boards are formed using solder resist as an insulating protective layer.

Here, PCBs that require large currents necessarily require a relatively large copper thickness. This is because thicker copper reduces wiring resistance and makes it possible to reduce the PCB size.

However, to provide insulation between wiring, it is necessary to completely fill the gaps between the tall, thick copper wiring. Conventional materials used as insulators, such as prepreg sheets and solder resist, often fail to completely fill the gaps between the thick copper wiring, resulting in voids, or the glass cloth that makes up the prepreg sheet can come into direct contact with the wiring, reducing reliability. Furthermore, liquid solder resist tends to thin at the edges of the wiring, creating unavoidable problems when it comes to ensuring reliable insulation.

Meanwhile, research and development is underway into the application of inkjet patterning in the manufacturing process of electronic devices such as FPCs (flexible printed circuit boards) and PCBs, and some of this has already been put to practical use.

The technology disclosed in Patent Document 1 uses a one-component inkjet composition consisting of a photocurable compound and a thermosetting compound, thereby improving the film properties after application of the composition.

Furthermore, the technology disclosed in Patent Document 2 uses a two-part inkjet composition consisting of a base agent and a curing agent, which has improved pot life and ejection stability, and aims to improve the film properties after curing.

However, there was still room for improvement in these technologies.

Japanese Patent Application Laid-Open No. 2016-204453 Japanese Patent Application Laid-Open No. 2018-203912

In Patent Document 1, the inkjet composition is a one-component type, so the ink has a short pot life and does not achieve sufficient inkjet ejection properties. Furthermore, because the ink contains a small amount of filler, when the inkjet composition is used as an insulating material, the physical properties of the insulating material do not achieve the desired properties.

When forming a cured film using an ink set, it is difficult to obtain a cured film with the excellent physical properties of high heat resistance, high durability, high strength, and low thermal expansion that are suitable for insulating materials that require thickness for electronic components, simply by improving the resin material. For this reason, the addition of inorganic materials is necessary.

However, it is difficult to stably eject ink compositions containing inorganic fillers using the inkjet method. For this reason, no technology has been disclosed to date that uses inkjet printing to incorporate inorganic fillers into inks such as those described above and form cured films with excellent film properties.

In Patent Document 2, an inkjet composition using a combination of a photocurable material and a thermosetting material contains a silica filler that is not surface-modified.

When considering the affinity between such silica fillers and ink solvents, the affinity between fillers themselves is higher than the affinity between the silica fillers and ink solvents. Therefore, interactions between particles can cause the fillers to aggregate, and structural viscosity can increase the viscosity of the ink, making it impossible to achieve stable inkjet ejection.

Furthermore, because the dispersion of fillers in inks containing photocurable or thermosetting materials is unstable, the silica filler settles over time, causing the components in the ink to separate. As a result, the ink's pot life is not long enough, and the state of the components in the ink is unstable.

Inkjet compositions containing silica fillers are unstable components in the ink, and are mixed on a substrate using an inkjet method. Cured films are then formed by UV curing and then thermal curing, but it has been difficult to obtain film properties suitable for insulating materials. Examples of film properties suitable for insulating materials include heat resistance, film strength, durability, thermal cycle suitability, thermal expansion coefficient, glass transition temperature, and toughness.

If the silica filler content in the inkjet composition is reduced to prevent the state of the ink components from becoming unstable, the desired thermal expansion coefficient, toughness, etc. cannot be achieved.

The present invention was made in consideration of the above problems and circumstances, and its objective is to provide a two-component ink set, a method for forming a cured product, and a product that has a long pot life and can produce a film with excellent physical properties as an insulator for use in electronic components.

The present inventors have conducted extensive research with reference to the prior art with the aim of easily forming an insulating material with excellent physical properties between thick copper wiring or on the surface of wiring by an inkjet process. As a result, they have found that the above-mentioned problems can be solved by incorporating a silica filler into one or both of the two inks in a two-component ink set consisting of ink A and ink B, each containing a photocurable compound, and have arrived at the present invention.
That is, the above-mentioned problems of the present invention are solved by the following means.

1. A two-component inkjet ink set consisting of at least ink A and ink B,
the ink A contains at least a photocurable compound,
the B ink contains at least a thermosetting compound,
At least one of the ink A and the ink B contains a silica filler, and
A two-component ink set, wherein the silica filler is surface-modified.

2. The two-component ink set described in item 1, wherein the silica filler has a polymerizable functional group.

3. The two-component ink set described in item 2, wherein the polymerizable functional group is a glycidyl group or a (meth)acrylic group.

4. The two-component ink set according to item 1, wherein both the ink A and the ink B contain a surface-modified silica filler.

5. The polymerizable functional group of the silica filler contained in the ink A is a (meth)acrylic group,
2. The two-component ink set described in 1, wherein the polymerizable functional group of the silica filler contained in the B ink is a glycidyl group.

6. A method for forming a cured product using the two-component ink set according to any one of items 1 to 5, comprising:
the A ink and the B ink constituting the two-component ink set are ejected from separate inkjet head nozzles to be applied onto a substrate and adhered thereto to form a coating film;
A method for forming a cured product, comprising irradiating the coating film with active energy rays to form the cured product.

7. A product having a cured resin composition,
6. A product characterized in that the cured product is a cured product consisting of components of the ink A and the ink B that constitute the two-component ink set described in any one of items 1 to 5.

8. The product of claim 7, wherein the product is a thick copper substrate.

The above-described means of the present invention can provide a two-component ink set that has a long pot life and can provide excellent film properties as an insulator for use in electronic components, a method for forming a cured product, and a product.
The mechanism by which the effects of the present invention are manifested or the mechanism of action is presumed as follows.

Either ink A or ink B, or both, that make up the two-component ink set of the present invention contain a surface-modified filler. Therefore, the two-component ink set of the present invention has the effect of improving the dispersion stability of the ink and reducing the viscosity of the ink compared to ink sets that contain fillers that are not surface-modified. It also has the effect of ensuring inkjet ejection stability, such as improving the ink landing accuracy and suppressing the generation of satellite droplets when ejecting ink.

These effects enable accurate and sufficient mixing of ink A and ink B on the substrate, and are thought to dramatically improve the physical properties of the cured film obtained by curing both inks. Furthermore, by surface-modifying the filler contained in the inks in the two-component ink set of the present invention, the dispersion stability of the filler is improved.

By improving the dispersion stability of the filler, even if the filler content in the ink is increased, the state of the components in the ink does not become unstable in an inkjet composition containing filler, as in the aforementioned Patent Document 2.

As a result of the above, it becomes possible to increase the filler content after mixing ink A and ink B. This makes it possible to reduce the thermal expansion coefficient and improve the toughness of the cured film.

In addition, the two-component ink set of the present invention has excellent inkjet ejection properties, resulting in excellent pattern accuracy. The A ink and B ink that make up the two-component ink set of the present invention are ejected by the inkjet method, land on a substrate, and are in a highly fluid state when mixed together. Furthermore, by irradiating both inks with UV light, the inks are able to flow until they are cured.

By ejecting both inks onto the substrate with high accuracy and mixing them, and then quickly curing them with UV light after they have landed and mixed, it is possible to form an insulating material with high pattern accuracy. It is also possible to form a cured film that excels as an insulating material.

For example, the technology disclosed in Patent Document 1 allows the ink to contain filler, but from the standpoint of thickness accuracy of the cured film, voids, and inkjet ejection properties, the lower the filler content, the better. Specifically, it describes that the filler content is preferably 5% by mass or less, and most preferably 0.5% by mass or less.

However, a cured film formed using an ink with such a low filler content does not have the excellent physical properties, such as a low thermal expansion coefficient, that would make it suitable for use as a planarization material for thick copper substrates.

Furthermore, in the technology disclosed in Patent Document 2, 10% by mass of silica filler is added to the ink, but this silica filler is not surface-modified. Furthermore, silica filler that is not surface-modified does not provide dispersion stability, resulting in thickening or aggregation/sedimentation, making it impossible to obtain a dispersion with excellent inkjet ejection properties.

It is possible to improve the inkjet ejection properties of inks with poor dispersibility by lowering their viscosity through heating. However, the landing accuracy of the ink is poor due to factors such as deflection of the ink when ejected, and poor landing accuracy deteriorates the mixing of the two liquids when using a two-liquid ink set. As a result, the physical properties of the cured film obtained by landing, mixing, and curing the inks in the two-liquid ink set are insufficient. Furthermore, problems arise such as the inability to mix the two liquids when the ink is scattered due to the generation of satellite droplets when ejecting the ink. As a result, the cured film formed using an ink set composed of inks to which non-surface-modified silica filler has been added does not have sufficient toughness.

In contrast, the surface-modified silica filler contained in either or both of the A and B inks that make up the two-component ink set of the present invention should be present in a larger amount, within the range that allows for inkjet ejection, resulting in excellent ink dispersibility. This results in excellent inkjet ejection properties and improved droplet landing accuracy. Improved droplet landing accuracy improves the mixing of the two components. Furthermore, because the amount of filler added can be increased while keeping the viscosity low, the glass transition temperature (Tg) can be maintained high and the thermal expansion coefficient can be reduced, resulting in high insulation resistance and excellent film toughness in the cured film after curing of the ink set.

From the above, it is believed that when the inkjet composition is cured, a cured film with a low coefficient of thermal expansion (CTE), a high glass transition temperature (Tg), high insulation resistance, and good film toughness can be obtained with good pattern accuracy. Furthermore, such a cured film is suitable for use as an insulating material that requires thickness for electrical materials, and is particularly suitable for insulating materials that require durability in harsh environments, such as those used in power electronics.

An example of a printing machine configuration An example of a schematic diagram of the structure of the glass epoxy substrate used to prepare the evaluation sample An example of a schematic diagram of an evaluation sample obtained by curing ink An example of a schematic diagram of a Teflon (registered trademark) plate evaluation sample

The two-component ink set of the present invention is a two-component ink set for inkjet printing composed of at least an A ink and a B ink, characterized in that the A ink contains at least a photocurable compound, the B ink contains at least a thermosetting compound, and at least one of the A ink and the B ink contains a silica filler, and the silica filler is surface-modified.
This feature is a technical feature common to or corresponding to each of the following embodiments (aspects).

In one embodiment of the present invention, it is preferable that the silica filler has a polymerizable functional group, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after ink set curing.

It is preferable that the polymerizable functional group is a glycidyl group or a (meth)acrylic group, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after curing of the ink set.

It is preferable that both the A ink and the B ink contain a surface-modified silica filler, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after ink set curing.

From the viewpoint of ink dispersibility and inkjet ejection properties, it is preferable that the polymerizable functional group of the silica filler contained in the ink A is a (meth)acrylic group, and that the polymerizable functional group of the silica filler contained in the ink B is a glycidyl group.

In the method of forming a cured product of the present invention, the ink A and the ink B that make up the two-component ink set are ejected from separate inkjet head nozzles. This extends the pot life of the two-component ink set.

Furthermore, the two-component ink set is applied to an object to be coated, forming a coating film, and the cured product is then formed by irradiating the coating film with active energy rays, resulting in a cured product with good pattern precision and excellent lamination suitability. In other words, the film obtained by laminating the ink composition can be made thicker, and it also effectively functions to flatten various components when used in electronic components, etc.

The product of the present invention is a product having a cured product of a resin composition, characterized in that the cured product is a cured product consisting of the components of the ink A and the ink B that make up the two-component ink set of the present invention. The two-component ink set of the present invention can be suitably used in the product of the present invention. Furthermore, the product can be suitably used on thick copper substrates.

The present invention, its components, and the embodiments and modes for implementing the invention are described in detail below. Note that in this application, the symbol "to" is used to mean that the numerical values before and after it are included as both the lower limit and upper limit.

The advantages and features provided by one or more embodiments of the present invention will be more fully understood from the following detailed description and the accompanying drawings, which are for illustrative purposes only and are not intended to define the limits of the present invention.

[Two-component ink set]
The two-component ink set of the present invention is a two-component ink set for inkjet printing composed of at least an A ink and a B ink, characterized in that the A ink contains at least a photocurable compound, the B ink contains at least a thermosetting compound, and at least one of the A ink and the B ink contains a silica filler, and the silica filler is surface-modified.

1. Overview The amount of surface-modified silica filler contained in ink A and/or ink B constituting the two-component ink set of the present invention is preferably as large as possible within the range that allows inkjet ejection.

The cured film formed by ink with a high filler content has excellent film properties, including a low thermal expansion coefficient, making it suitable for use as a planarization material for thick copper substrates.

Furthermore, surface-modified silica filler disperses easily in monomers, making it possible to obtain a dispersion with excellent inkjet ejection properties. Furthermore, cured films formed from inks containing surface-modified silica filler have sufficient toughness.

This improves the dispersibility and inkjet ejection properties of the A ink and B ink that make up the two-component ink set of the present invention, and also improves film properties such as film strength and thermal expansion coefficient after the ink set has cured.

Furthermore, because the ink set of the present invention is a two-component type, the A ink and B ink according to the present invention do not mix until they are ejected, for example, by an inkjet head. Therefore, there is an advantage in that the pot life of the A ink or B ink alone is longer than that of a one-component ink set.

2. Ink A The ink A according to the present invention contains at least a photocurable compound. It is preferable that the ink A contains a surface-modified silica filler. If the ink A does not contain a surface-modified silica filler, the ink B described below will contain a surface-modified silica filler. The ink A may also contain a filler other than the surface-modified silica filler. The ink A may also contain a thermosetting catalyst, a thermosetting agent, a photopolymerization initiator, a reactive diluent, and other components. The term "reactive" in the above "reactive diluent" includes both photoreactivity and heat reactivity.

(2.1) Photocurable compound Ink A according to the present invention contains at least a photocurable compound. This improves the pattern accuracy after application of the ink set, contributes to thickening of the film after curing of the ink set, and provides excellent flatness, improving lamination suitability.

"Photocurable compound" refers to a compound having a curable functional group, and is a compound that polymerizes (cures) when exposed to actinic rays such as ultraviolet light or electron beams. If the B ink according to the present invention, described below, contains a photocurable compound with a lower viscosity, the viscosity of the B ink will be lower. If the B ink contains a photocurable compound with a high glass transition temperature, the glass transition temperature of the cured film formed by curing an ink set containing the B ink will be higher.

The photocurable compound contained in Ink A according to the present invention is preferably a radically polymerizable compound.

Examples of photocurable compounds include curable compounds having a (meth)acryloyl group, curable compounds having a vinyl group, and curable compounds having a maleimide group. Furthermore, in addition to acrylics, cationic photocurable compounds such as alicyclic epoxy compounds and oxetane compounds can also be used as photocurable compounds contained in Ink A according to the present invention.

In this specification, a curable compound having a (meth)acryloyl group refers to a compound having at least one of a methacryloyl group and an acryloyl group. Furthermore, the term "(meth)acrylate" refers to acrylate or methacrylate. The term "(meth)acrylic" refers to acrylic or methacrylic.

From the viewpoint of forming a cured composition layer with even greater precision, it is preferable that the photocurable compound have a (meth)acryloyl group. Only one type of the photocurable compound may be used, or two or more types may be used in combination.

As the photocurable compound, a photocurable compound having one (meth)acryloyl group may be used, or a photocurable compound having two or more (meth)acryloyl groups may be used.

Examples of photocurable compounds having one (meth)acryloyl group include monofunctional compounds. Examples of photocurable compounds having two or more (meth)acryloyl groups include polyfunctional compounds.

Examples of polyfunctional compounds include (meth)acrylic acid adducts of polyhydric alcohols, (meth)acrylic acid adducts of alkylene oxide-modified polyhydric alcohols, urethane (meth)acrylates, and polyester (meth)acrylates.

Examples of the polyhydric alcohols include diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene glycol. Other examples include trimethylolpropane, cyclohexanedimethanol, tricyclodecanedimethanol, alkylene oxide adducts of bisphenol A, and pentaerythritol.

(Trifunctional or higher (meth)acrylic monomers)
At least one of the photocurable compounds contained in the ink A is a tri- or higher functional (meth)acrylic monomer, which is preferable from the viewpoints of printing precision and 3D formability, since this increases the UV curing speed.

Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, alkylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, trimethylolpropane tri((meth)acryloyloxypropyl)ether, alkylene oxide-modified isocyanuric acid tri(meth)acrylate, dipentaerythritol propionate tri(meth)acrylate, tri((meth)acryloyloxyethyl)isocyanurate, and sorbitol tri(meth)acrylate.

Examples of tetrafunctional (meth)acrylates include pentaerythritol tetra(meth)acrylate and sorbitol tetra(meth)acrylate. Other examples include ditrimethylolpropane tetra(meth)acrylate and dipentaerythritol propionate tetra(meth)acrylate.

Examples of pentafunctional (meth)acrylates include sorbitol penta(meth)acrylate and dipentaerythritol penta(meth)acrylate.

Examples of hexafunctional (meth)acrylates include dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate, and alkylene oxide-modified hexa(meth)acrylate of phosphazene.

(Commercially available)
Examples of commercially available photocurable compounds include monofunctional commercially available products such as "SR285" (tetrahydrofurfuryl acrylate) and "SR203" (tetrahydrofurfuryl methacrylate) manufactured by Sartomer, "A0144" (2-ethylhexyl acrylate) manufactured by TCI, "Light Acrylate PO-A" (phenoxyethyl acrylate) manufactured by Kyoeisha Chemical Co., Ltd., "Light Acrylate IB-XA" (isobornyl acrylate) manufactured by Kyoeisha Chemical Co., Ltd., "Light Ester IB-X" (isobornyl methacrylate) manufactured by Kyoeisha Chemical Co., Ltd., "Light Acrylate MPD-A" (3-methyl-1,5 pentanediol acrylate) manufactured by Kyoeisha Chemical Co., Ltd., and "Light Acrylate P2H-A" (phenoxydiethylene glycol acrylate) manufactured by Kyoeisha Chemical Co., Ltd. These can also be used as reactive diluents.

Other commercially available monofunctional products include Shin-Nakamura Chemical's "A-LEN-10" (ethoxylated o-phenylphenol acrylate) and "A-SA" (2-acryloyloxyethyl succinic acid).

Commercially available bifunctional products include, for example, Sartomer's "SR230" (diethylene glycol diacrylate), "SR212" (1,3-butylene glycol diacrylate), Shin-Nakamura Chemical's "A-HD-N" (1,6-hexanediol diacrylate), "A-NOD-N" (1,9-nonanediol diacrylate), "A-DOD-N" (1,10-decanediol diacrylate), "A-NPG" (neopentyl glycol diacrylate), and "A-200" (polyethylene glycol diacrylate), all manufactured by Miwon. These can also be used as reactive diluents.

Other commercially available bifunctional products include Sartomer's "SR833NS" (tricyclodecane dimethanol diacrylate) and "SR601J NS" (ethoxylated bisphenol A diacrylate). Other examples include Toagosei's "Aronix M-208" (bisphenol F EO-modified diacrylate).

Commercially available trifunctional products include, for example, Miwon's Miramer M300 (trimethylolpropane triacrylate) and Kyoeisha Chemical's Light Acrylate PE-3A (pentaerythritol triacrylate). Commercially available tetrafunctional products include, for example, Miwon's Miramer M410 (ditrimethylolpropane tetraacrylate) and Kyoeisha Chemical's Light Acrylate PE-4A (pentaerythritol tetraacrylate). Commercially available pentafunctional products include, for example, Shin-Nakamura Chemical's A-DPH (dipentaerythritol polyacrylate). Commercially available hexafunctional products include, for example, Kyoeisha Chemical's Light Acrylate DPE-6A (dipentaerythritol hexaacrylate).

(2.2) Filler The ink A according to the present invention preferably contains a surface-modified silica filler, which improves the dispersibility and inkjet ejection properties of the ink, and also improves the film properties such as film strength and thermal expansion coefficient after the ink is set and cured.

Ink A according to the present invention can use conventional fillers in addition to the surface-modified silica filler. Examples of conventional fillers include hollow silica, alumina, titanium oxide, aluminum hydroxide, and zinc oxide. Other examples include zirconium oxide, magnesium oxide, mica, bismuth oxychloride, talc, kaolin, barium sulfate, silicic acid anhydride, calcium carbonate, and magnesium carbonate. Other examples include magnesium silicate, aluminum silicate, magnesium aluminum silicate, silicon carbide, silicon nitride, boron nitride, glass powder, metal oxides, and metal powders. These fillers can be used alone or in combination.

(Surface modifier)
The silica filler surface-modified with a surface modifier comprises silica particles and chemical species derived from the surface modifier. The surface-modified silica particles may have the chemical species derived from the surface modifier on at least a portion of their surfaces.

Surface modification of silica filler can be carried out using known methods. For example, silica filler, surface modifier, and solvent can be mixed in a stirring mill, and then the solvent can be removed. Before mixing the silica filler, surface modifier, and solvent, the silica filler, surface modifier, and solvent can also be premixed to form a slurry.

One possible method for surface modifying fillers is to form a thin organic film on the filler surface by coating, but a more preferable method is to bond a surface modifier to the filler surface using a silane coupling agent.

Silane coupling agents include, for example, various alkyl silanes including methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, octadecyltrimethoxysilane, dimethyldimethoxysilane, octyltriethoxysilane, and n-octadecyldimethyl(3-(trimethoxysilyl)propyl)ammonium chloride; various fluoroalkyl silanes including trifluoromethylethyltrimethoxysilane and heptadecafluorodecyltrimethoxysilane; various amino group-containing silanes including N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane; and phenyltrimethoxysilane.

The average particle size of the filler is preferably within the range of 0.1 to 2 μm. More preferably, the average particle size is within the range of 0.1 to 1 μm, with a maximum average particle size of 2 μm. If the average particle size of the filler is smaller than 0.1 μm, the viscosity of the ink composition will be high and it will not be usable in inkjet printing. Furthermore, if the average particle size of the filler is larger than 2 μm, it may cause a deterioration in ejection stability, such as the accuracy of ink droplet placement. Furthermore, the filler will settle in the ink composition, and the filler and the resin components in the ink will easily separate within the tank containing the ink composition or within the inkjet head. Therefore, it will not be possible to apply a homogeneous ink composition.

In this specification, the average particle size is the particle size at 50% of the cumulative value in the particle size distribution on a volume basis, measured by laser diffraction/scattering. The average particle size can be measured, for example, using a laser diffraction/scattering particle size distribution measuring device: Zetasizer Nano S90 (manufactured by Malvern Instruments).

The weight-average molecular weight of the surface modifier is not particularly limited, but is preferably in the range of 1,000 to 50,000. The weight-average molecular weight of the surface modifier can be measured by gel permeation chromatography (GPC).

Surface modifiers can be used alone or in combination of two or more types. Furthermore, surface modifiers may be synthetic or commercially available.

The filler content is preferably 5% by mass or more, and more preferably 10% by mass or more, relative to 100% by mass of the ink A according to the present invention. This improves the ejection properties of the ink A. It is preferable that as much filler as possible be contained in the ink A, but if there is too much, the viscosity of the ink will become too high and it will not be possible to eject it by inkjet. Therefore, the filler content is preferably 40% by mass or less, and more preferably 30% by mass or less, relative to 100% by mass of the ink A according to the present invention.

(Polymerizable Functional Group)
In an embodiment of the present invention, it is preferable that the silica filler has a polymerizable functional group, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after curing of the ink set.

The silica filler according to the present invention is surface-modified with a surface modifier. There are no particular restrictions on the surface modifier, but it is preferable that the surface modifier be a surface modifier having a polymerizable functional group.

When the surface modifier is a silane coupling agent, examples of silane coupling agents having a polymerizable functional group include silane coupling agents having a vinyl group, glycidyl group, styryl group, methacryl group, or acrylic group.

Examples of silane coupling agents containing a vinyl group include vinyltrimethoxysilane and vinyltriethoxysilane. Examples of silane coupling agents containing a glycidyl group include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 3-glycidoxypropylmethyldimethoxysilane. Examples of other silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane. Examples of silane coupling agents containing a styryl group include p-styryltrimethoxysilane. Examples of silane coupling agents containing a methacryl group include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane. Examples of silane coupling agents containing an acrylic group include 3-acryloxypropyltrimethoxysilane.

It is preferable that the surface-modified silica filler according to the present invention has a polymerizable functional group, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after ink set curing.

It is preferable that the polymerizable functional group contained in Ink A according to the present invention is a glycidyl group, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after ink set curing. It is also preferable that the polymerizable functional group contained in Ink A according to the present invention is a (meth)acrylic group, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after ink set curing.

It is preferable that the polymerizable functional group is a glycidyl group or a (meth)acrylic group, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after curing of the ink set.

It is preferable that both the A ink and the B ink contain a surface-modified silica filler, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after ink set curing.

From the viewpoint of ink dispersibility and inkjet ejection properties, it is preferable that the polymerizable functional group of the silica filler contained in the ink A is a (meth)acrylic group, and that the polymerizable functional group of the silica filler contained in the ink B is a glycidyl group.

(Commercially available)
Commercially available surface-modified silica fillers according to the present invention include, for example, "SC2500-SEJ" (Admafine 0.5 μm, epoxy treatment) manufactured by Admatechs Co., Ltd. Other examples include "SC2300-SVJ" (Admafine 0.5 μm, vinyl treatment) and "SC2500-SXJ" (Admafine 0.5 μm, phenylamine treatment) manufactured by the same company. Other examples include "SC2500-SMJ" (Admafine 0.5 μm, methacrylic treatment) and "SC2500-SPJ" (Admafine 0.5 μm, phenyl treatment) manufactured by the same company.

(2.3) Thermosetting catalyst "Thermosetting catalyst" refers to a catalyst for controlling the heat-accelerated curing speed and curing temperature. When a thermosetting catalyst is contained in the A ink according to the present invention, for example, when an epoxy resin is used in the B ink according to the present invention, the thermosetting catalyst is used in an amount of 0.1 to 2.0 mass % relative to the epoxy resin, calculated after mixing of the two liquids. Furthermore, the thermosetting catalyst does not form the main skeleton and is not incorporated into the cured film formed by the ink set of the present invention, and therefore does not have a significant effect on the physical properties of the cured film.

In order to improve the pot life of the ink, the thermosetting catalyst can be mixed as a core material for microcapsules, or its catalytic action can be controlled by molecular modification so that catalytic action occurs at a certain temperature. It can also be contained in the A ink without being mixed into the B ink.

If the A ink contains a thermosetting catalyst, it is preferable that the B ink does not contain a thermosetting catalyst, as this promotes the curing reaction after the two inks are mixed and extends the pot life of the B ink.

Thermosetting catalysts used in the present invention include, for example, basic catalysts.

(Basic catalyst)
Examples of the basic catalyst include tertiary amines, tertiary amine salts, imidazole derivatives, phosphine compounds, phosphonium salts, etc. These basic catalysts may be used alone or in appropriate combination of two or more.

Examples of tertiary amines or tertiary amine salts include DBU (1,8-diazabicyclo(5,4,0)-undecene-7), DBN (1,5-diazabicyclo(4,3,0)-nonene-5), organic acid salts of DBU or DBN, 2,4,6-tris(dimethylaminomethyl)phenol, piperidine, N,N-dimethylpiperazine, triethylenediamine, benzyldimethylamine, and 2-(dimethylaminomethyl)phenol.

Examples of imidazole derivatives include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole.

Phosphine compounds and phosphonium salts include, for example, tributylphosphine, triphenylphosphine, benzyltriphenylphosphonium bromide, and ethyltriphenylphosphonium methanesulfonate. Other examples include tetraphenylphosphonium tetraphenylborate and tetra-n-butylphosphonium tetraphenylborate.

Among these, tertiary amines or tertiary amine salts, and imidazole derivatives are preferred from the standpoints of solubility, reactivity, and latency.

(Commercially available)
Examples of commercially available thermosetting catalysts include those classified as DBU, DBN, and imidazole.

Commercially available products classified as DBU include, for example, "U-CAT SA102" (2-ethylhexane salt of 1,8-diazabicyclo[5,4,0]undecene-7) manufactured by San-Apro Co., Ltd., "U-CAT SA1" (phenol salt of 1,8-diazabicyclo[5,4,0]undecene-7) manufactured by the same company, and "U-CAT SA603" (formate of 1,8-diazabicyclo[5,4,0]undecene-7) manufactured by the same company.
Examples of such products include "U-CAT SA810" (o-phthalate salt of 1,8-diazabicyclo[5,4,0]undecene-7) and "U-CAT SA506" (p-toluenesulfonate salt of 1,8-diazabicyclo[5,4,0]undecene-7) manufactured by the same company.

Commercially available products classified as DBN include, for example, "U-CAT 1102" (1,5-diazabicyclo[4.3.0]nonene-5, 2-ethylhexanoate) manufactured by San-Apro Co., Ltd.

Commercially available products classified as imidazoles include Shikoku Chemicals' "C11Z-A" (6-(2-(2-undecyl-1H-imidazol-1-yl)ethyl)-1,3,5-triazine-2,4-diamine), Shikoku Chemicals' "2MAOK-PW" (6-[2-(2-methyl-1H-imidazol-1-yl)ethyl]-1,3,5-triazine-2,4-diamine), Shikoku Chemicals' "1,2DMZ" (1,2-dimethylimidazole), Shikoku Chemicals' "2E4MZ" (2-ethyl-4-methylimidazole), Shikoku Chemicals' "1B2MZ" (1-benzyl-2-methylimidazole), Shikoku Chemicals' "1B2PZ" (1-benzyl-2-phenylimidazole), and Shikoku Chemicals' "2E4MZ-CN" (1-cyanoethyl-2-ethyl-4-methylimidazole).

(2.4) Heat Curing Agent The heat curing agent that can be contained in the ink A according to the present invention can be the same as the heat curing agent that can be contained in the ink B, which will be described later.

(2.5) Photopolymerization initiator Examples of photopolymerization initiators that can be contained in the ink A according to the present invention include photoradical polymerization initiators and photocationic polymerization initiators. There are no particular restrictions on the photopolymerization initiator, but it is preferable to use a photoradical polymerization initiator, and the photoradical polymerization initiators may be used alone or in combination of two or more types.

(Photoradical polymerization initiator)
The term "photoradical polymerization initiator" refers to a compound that generates radicals upon irradiation with light and initiates a radical polymerization reaction.

Examples of photoradical polymerization initiators include benzoin compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether; alkylphenone compounds such as 2-hydroxy-2-methyl-1-phenyl-propan-1-one; acetophenone compounds such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, and 1,1-dichloroacetophenone; and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane- aminoacetophenone compounds such as 1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, and N,N-dimethylaminoacetophenone; anthraquinone compounds such as 2-methylanthraquinone, 2-ethylanthraquinone, and 2-t-butylanthraquinone; 2,4-dimethylanthraquinone compounds such as 2,4-dimethylanthraquinone, ... Thioxanthone compounds such as thioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone; ketal compounds such as acetophenone dimethyl ketal and benzil dimethyl ketal; acylphosphine oxide compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; 1,2-octanedione, 1-[4-(phenylthio)-2-(o-benzoyloxime)], ethanol Examples of suitable oxime compounds include oxime ester compounds such as 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(o-acetyloxime); and titanocene compounds such as bis(cyclopentadienyl)-diphenyl-titanium, bis(cyclopentadienyl)-dichloro-titanium, bis(cyclopentadienyl)-bis(2,3,4,5,6-pentafluorophenyl)titanium, and bis(cyclopentadienyl)-bis(2,6-difluoro-3-(pyrrol-1-yl)phenyl)titanium.

The content of the photoradical polymerization initiator is preferably within the range of 1 to 10 mass% of the total amount of radical polymerization monomers contained in Ink A.

(Commercially available)
Examples of commercially available photopolymerization initiators include alkylphenone-based commercially available products and acylphosphine oxide-based commercially available products.

Commercially available alkylphenone products include IGM Resins' "Omnirad 369" (2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone), IGM Resins' "Omnirad 651" (2,2-dimethoxy-2-phenylacetophenone), IGM Resins' "Omnirad 184" (1-hydroxycyclohexyl-phenyl ketone), IGM Resins' "Omnirad 1173" (2-hydroxy-2-methyl-1-phenylpropanone), IGM Resins' "Omnirad 2959" (1-[4-(2-hydroxyethoxy )-phenyl]-2-hydroxy-methylpropanone), Omnirad 127 (2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one), Omnirad 907 (2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one), and Omnirad 379EG (2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one) manufactured by the same company.

Commercially available acylphosphine oxide products include "Omnirad TPO" (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide) manufactured by IGM Resins. Other examples include "Omnirad 819" (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) manufactured by the same company.

(Photocationic Polymerization Initiator)
A "cationic photopolymerization initiator" is a compound for photopolymerizing a cationically polymerizable monomer. Any known photoacid generator can be used as the cationic photopolymerization initiator. Examples of photoacid generators include compounds used in chemically amplified photoresists and cationic photopolymerization (see Organic Electronics Materials Research Group, "Organic Materials for Imaging," Bunshin Publishing (1993), pp. 187-192).

First, examples include B(C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , and CF ₃ SO ₃ ⁻ salts of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, and phosphonium. Second, examples include sulfonates that generate sulfonic acid. Third, examples include halides that photogenerate hydrogen halide. Fourth, examples include iron allene complexes.

Commercially available photocationic polymerization initiators include, for example, diaryliodonium or triallylsulfonium hexafluorophosphate, hexafluoroantimonate, or pentafluorophenylborate salts. These are commercially available under trade names such as Irgacure-261 (manufactured by BASF Japan), SP-150, SP-170 (all manufactured by ADEKA), PI2074, and UVI-6992 (manufactured by Dow Chemical).

The content of the above-mentioned photocationic polymerization initiator is preferably within the range of 1 to 10 mass% of the total amount of cationic polymerization monomers contained in Ink A.

(Photosensitizer)
A "photosensitizer" is an additive that absorbs light energy that cannot be excited by an initiator and transmits it to a photopolymerization initiator, thereby improving the polymerization rate, deep curing, and curing properties (adhesion, surface hardness, etc.).

Ink A of the present invention can also be used in combination with a photosensitizer to make the curing reaction more efficient.

Photosensitizers include, for example, amines such as triethanolamine, methyldiethanolamine, triisopropanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-dimethylamino)ethyl benzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, and 2-ethylhexyl 4-dimethylaminobenzoate, cyanine, phthalocyanine, merocyanine, porphyrin, spiro compounds, ferrocene, fluorene, fulgide, imidazole, perylene, phenazine, fluorene, fluorine ... Examples of photosensitizers include ethenothiazine, polyene, azo compounds, diphenylmethane, triphenylmethane, polymethine acridine, coumarin, ketocoumarin, quinacridone, indigo, styryl, pyrylium compounds, pyrromethene compounds, pyrazolotriazole compounds, benzothiazole compounds, barbituric acid derivatives, and thiobarbituric acid derivatives. Furthermore, compounds described in European Patent No. 568993, U.S. Patent Nos. 4,508,811 and 5,227,227, Japanese Patent Application Laid-Open Nos. 2001-125255 and 1999-271969 may also be used. The amount of photosensitizer used is preferably in the range of 0.01 to 10.00% by mass of the ink composition.

(2.6) Reactive Diluent A "reactive diluent" is a colorless, low-viscosity liquid that is added to a substance to reduce its viscosity and make it easier to handle. Ink A according to the present invention preferably contains a reactive diluent, which can reduce the viscosity of the ink A.

The purpose of adding a reactive diluent is to lower the viscosity of the ink to the point where it can be inkjet-ejected, but using a monomer with a high glass transition temperature is particularly preferable, as it can increase the glass transition temperature of the cured film.

Reactive diluents include, for example, photoreactive diluents and thermally reactive diluents. The photoreactive diluents may be, for example, the photocurable compounds described above, and the thermally reactive diluents may be, for example, the thermosetting compounds described below. These reactive diluents may be used alone or in combination of two or more.

The reason for using a photocurable compound and/or a thermosetting compound as described above is that after the ink set of the present invention is cured, the curable compound is fixed in the cured film and does not volatilize or bleed out. In particular, when a large amount of reactive diluent is used, the fluidity is lost after light irradiation, so a photocurable compound is preferred as the reactive diluent.

When a photocurable compound is used as the reactive diluent, there are no particular restrictions on the amount of reactive diluent that can be contained in Ink A, as long as the viscosity of Ink A can be adjusted to an optimum level. However, when a thermosetting compound is used as the reactive diluent, it is necessary to maintain UV curability to the extent that it loses fluidity when exposed to UV light. For this reason, there is an appropriate range for the amount of photocurable compound, and if it is too much, it is not desirable as the desired film properties will not be achieved after UV curing and thermosetting.

The amount of reactive diluent contained is determined taking into consideration the ink temperature and viscosity at which the ink can be ejected from the inkjet head, with the upper limit of the ink viscosity at 25°C being approximately 100 cp. The function of the reactive diluent is to lower the viscosity of the ink, so ink A with a viscosity of 30 cp or less is preferred, 15 cp or less is more preferred, and 10 cp or less is even more preferred.

Reactive diluents that can be contained in Ink A include low-viscosity photocurable compounds and low-viscosity thermosetting compounds, but photocurable compounds are preferred in consideration of their reactivity with thermosetting catalysts.

The reactive diluent content is preferably within the range of 1 to 70% by mass relative to 100% by mass of Ink A according to the present invention. A reactive diluent content of 1% by mass or more improves the compatibility of Ink A, allowing the components of Ink A to be dispersed uniformly. Furthermore, a reactive diluent content of 70% by mass or less provides the effect of improving heat resistance.

(Commercially available)
As commercially available reactive diluents, those listed as commercially available photocurable compounds described above and those listed as commercially available thermosetting compounds described below can be used.

(2.7) Other Components The ink A according to the present invention may contain other components, such as water, organic solvents, adhesion aids such as coupling agents, pigments, dyes, leveling agents, antifoaming agents, and polymerization inhibitors.

The water contained in Ink A according to the present invention is not particularly limited, and may be ion-exchanged water, distilled water, or pure water. However, it is preferable to keep the water content to 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.2% by mass or less, relative to 100% by mass of Ink A.

The organic solvent contained in Ink A according to the present invention is not particularly limited and can be any known organic solvent. However, the organic solvent content is preferably kept to 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, relative to 100% by mass of Ink A.

3. B Ink The B ink according to the present invention contains at least a thermosetting compound. The B ink preferably contains a surface-modified silica filler. If the B ink does not contain a surface-modified silica filler, the A ink contains a surface-modified silica filler. The B ink may also contain fillers other than the surface-modified silica filler. The B ink may also contain a thermosetting agent, a photo- and thermo-reactive compound, a photopolymerization initiator, a reactive diluent, and other components. The "reactive" in "reactive diluent" includes both photo-reactivity and heat-reactivity.

(3.1) Thermosetting Compound The term "thermosetting compound" refers to a compound having a curable functional group, which polymerizes (cures) when heat is applied.

As the thermosetting compound, an epoxy resin is preferably used. At least one of the thermosetting compounds contained in the B ink according to the present invention preferably has a cyclic structure. Furthermore, from the viewpoint of obtaining a cured film with a low coefficient of thermal expansion (CTE), it is preferable that at least one of the thermosetting compounds is an epoxy resin having a cyclic structure. One type of such thermosetting compound may be used alone, or two or more types may be used in combination.

In addition, a cured film can be formed by curing the ink set of the present invention using the curing of the epoxy resin, but a cured film can also be formed by using the curing reaction caused by adding a thermal radical polymerization initiator to an acrylic resin as a thermosetting compound.

Examples of thermosetting epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, and phenol novolac epoxy resins. Other examples include cresol novolac epoxy resins, biphenyl epoxy resins, aliphatic epoxy resins, and glycidyl amine epoxy resins. In particular, from the standpoint of heat resistance, it is preferable that the thermosetting epoxy resin be an epoxy resin with a cyclic structure other than an aliphatic type.

Among these, thermosetting epoxy resins that have aromatic rings, such as bisphenol A epoxy resin, phenol novolac epoxy resin, and cresol novolac epoxy resin, are more preferred from the standpoints of insulation properties and film strength. They are also more preferred from the standpoints of coefficient of thermal expansion (CTE), glass transition temperature (Tg), etc.

In particular, when using the above-mentioned thermosetting epoxy resin in combination with a photocurable compound such as (meth)acrylate, it is preferable to reproducibly obtain the desired film properties described above. Furthermore, it is preferable that the thermosetting epoxy resin be a novolac type or a bisphenol type.

(Novolac-type epoxy compound)
Examples of novolac epoxy compounds include phenol novolac epoxy compounds, cresol novolac epoxy compounds, biphenyl novolac epoxy compounds, trisphenol novolac epoxy compounds, and dicyclopentadiene novolac epoxy compounds.

(bisphenol-type epoxy compound)
Examples of bisphenol-type epoxy compounds include bisphenol A-type epoxy compounds and bisphenol F-type epoxy compounds, as well as 2,2'-diallyl bisphenol A-type epoxy compounds, hydrogenated bisphenol-type epoxy compounds, and polyoxypropylene bisphenol A-type epoxy compounds.

(Commercially available)
Examples of commercially available monofunctional thermosetting compounds include "Epogose 2EH" (2-ethylhexyl glycidyl ether) and "Epogose OCR" (glycidyl (2-methylphenyl) ether), both manufactured by Yokkaichi Chemical Co., Ltd. These can also be used as reactive diluents.

Commercially available bifunctional products include "Epogose HD (D)" (1,6-hexanediol diglycidyl ether) and "Epogose NPG (D)" (neopentyl glycol diglycidyl ether), both manufactured by Yokkaichi Synthetic Co., Ltd. Other examples include "Epogose BD (D)" (1,4-butanediol diglycidyl ether) and "DY-BP" (butyl glycidyl ether), both manufactured by the same company. These can also be used as reactive diluents.

Other commercially available bifunctional products include Nippon Steel Chemical's "YD-127" (bisphenol A type epoxy resin), ADEKA's "EP-4300E" (bisphenol A type epoxy resin), ADEKA's "EP-4520S" (bisphenol A type epoxy resin), ADEKA's "EP-4088L" (dicyclopentadiene type epoxy resin), ADEKA's "EP-3980S" (glycidylamine type epoxy resin), ADEKA's "ED-503G" (aliphatic epoxy resin), ADEKA's "ED-509S" (4-tert-butylphenyl glycidyl ether), and Mitsubishi Chemical's "JER828" (bisphenol A type epoxy resin). resin), the same company's "JER806" (bisphenol F type epoxy resin), the same company's "JER630" (glycidylamine type epoxy resin), the same company's "JER152" (phenol novolac type epoxy resin), the same company's "JER1032H60" (trisphenylmethane type epoxy resin), the same company's "JER604" (dimethyldiaminomethane type epoxy resin), DIC Corporation's "830-LVP" (bisphenol F type epoxy resin), the same company's "HP-7200" (dicyclopentadiene type epoxy resin), and Nagase ChemteX Corporation's "EX211" (neopentyl glycol diglycidyl ether).

(3.2) Heat Curing Agent The heat curing agent according to the present invention can be contained in either ink A or ink B to finally heat cure the thermosetting compound.

The heat curing agents contained in the B ink according to the present invention include types that cure at relatively low temperatures, such as aliphatic polyamines, polyaminoamides, and polymercaptans. Other types do not cure unless heated to high temperatures, such as aromatic polyamines, acid anhydrides, phenol novolac resins, and dicyandiamide. To obtain a cured film with high heat resistance, a low thermal expansion coefficient, a high glass transition temperature, and excellent film strength and insulation properties, a high-temperature heat curing agent is preferred.

Among the above heat curing agents, acid anhydrides are more preferred due to their high solubility in the epoxy resins and reactive diluents used in the ink materials. This results in a cured film with a low coefficient of thermal expansion (CTE), a high glass transition temperature (Tg), high insulation resistance, and good film toughness.

For example, solid materials such as dicyandiamide can precipitate even after dissolving, making it difficult to achieve inkjet suitability, such as ejection stability. Furthermore, solid materials may require heating to dissolve, which can shorten the ink's pot life.

(acid anhydride)
Examples of acid anhydrides include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, and dodecylsuccinic anhydride.Other examples include chlorendic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, methylcyclohexenetetracarboxylic anhydride, trimellitic anhydride, and polyazelaic anhydride.

(Thermal curing agents other than acid anhydrides)
As the heat curing agent other than the acid anhydride, for example, a phenolic compound or a modified polyamine compound such as an amine-epoxy adduct may be used, and other heat curing agents may also be used.

Phenol-based compounds include, for example, bis(4-hydroxyphenyl)-2,2-propane, 4,4'-dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,1-ethane, and bis(4-hydroxyphenyl)-1,1-isobutane. Other examples include polyhydric phenols such as bis(4-hydroxy-tert-butyl-phenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, and 1,5-dihydroxynaphthalene. Other examples include polyfunctional phenols such as phenol novolac resin, bisphenol novolac resin, and cresol novolac resin.

Instead of these polyhydric phenols, hydrogenated compounds in which hydrogen is added to some or all of the double bonds of the phenyl nucleus can also be used.

"Amine compound" refers to a compound containing one or more primary, secondary, or tertiary amino groups. Examples of amine compounds include aliphatic amines, alicyclic amines, aromatic amines, hydrazides, and guanidine derivatives.

Also usable are adducts such as epoxy compound-added polyamines (reaction products of epoxy compounds and polyamines) and Michael addition polyamines (reaction products of α,β-unsaturated ketones and polyamines). Also usable are adducts such as Mannich addition polyamines (condensation products of polyamines with formalin and phenols), thiourea addition polyamines (reaction products of thiourea and polyamines), and ketone-blocked polyamines (reaction products of ketone compounds and polyamines [ketimines]).

(Commercially available)
Examples of commercially available thermosetting agents include commercially available acid anhydrides such as "YH306" (methylbutenyltetrahydrophthalic anhydride) manufactured by Mitsubishi Chemical Corporation, "HN-2200" (methyltetrahydrophthalic anhydride), "HN-5500" (methylhexahydrophthalic anhydride) manufactured by Resonac Corporation, "MHAC-P" (methylnadic anhydride) manufactured by the same company, and "RIKACID TH" (tetrahydrophthalic anhydride) and "RIKACID HH" (hexahydrophthalic anhydride) manufactured by New Japan Chemical Co., Ltd.

Commercially available amine heat curing agents include ADEKA's "EH-105L" (aromatic polyamine) and Mitsui Fine Chemicals' "APB-N" (1,3-bis(3-aminophenoxy)benzene).

(Content)
The content of the heat curing agent is preferably in the range of 1 to 60% by mass, more preferably in the range of 5 to 60% by mass, and even more preferably in the range of 5 to 50% by mass, relative to 100% by mass of the B ink according to the present invention.

It is preferable that the thermosetting agent of the present invention be incorporated as a repeating unit in an appropriate ratio into the polymer chain of the thermosetting compound from the viewpoints of heat resistance, film strength, thermal expansion coefficient, glass transition temperature, and insulating properties.

Specifically, for example, if the thermosetting compound is an epoxy resin, the optimal ratio will vary depending on the compound used, but it is generally preferable to use a molar ratio of 0.1 to 1.5 equivalents of thermosetting agent to the epoxy equivalent, and it is even more preferable to use 0.8 to 1.2 equivalents. Note that the "epoxy equivalent" mentioned above is the molecular weight divided by the number of glycidyl groups.

If there is an excess of epoxy resin relative to the heat curing agent, the remaining epoxy resin may be a homopolymer of epoxy resin in which the heat curing agent is not incorporated into the repeating unit.

(3.3) Filler The B ink according to the present invention preferably contains a surface-modified silica filler. This significantly improves the dispersibility and inkjet ejection properties of the ink, and not only improves the accurate mixing of the two-component ink, printing precision, and 3D formability, but also dramatically improves the film properties after ink set curing, such as crack resistance, toughness, film strength capable of withstanding thermal cycles, and thermal expansion coefficient.

In the ink set according to the present invention, when the B ink does not contain a surface-modified silica filler, the A ink described above contains a surface-modified silica filler. The B ink according to the present invention may also contain a filler other than a surface-modified silica filler. Commercially available products may be used as the surface-modified silica filler.

The surface-modified silica filler and fillers other than said silica filler that can be contained in the ink B according to the present invention are the same as the surface-modified silica filler and fillers other than said silica filler that can be contained in the ink A described above.

(Polymerizable Functional Group)
The B ink according to the present invention preferably contains a surface-modified silica filler. When the B ink according to the present invention does not contain a surface-modified silica filler, the A ink described above contains a surface-modified silica filler. The surface modifier is not particularly limited, but is preferably a surface modifier having a polymerizable functional group B.

There are no particular restrictions on the method of surface modification using a surface modifier, but various known methods can be used.

If the B ink according to the present invention contains a surface-modified silica filler, it is preferable that the surface-modified silica filler have a polymerizable functional group, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after ink set curing.

The surface-modified silica filler contained in the B ink according to the present invention has a polymerizable functional group, and it is preferable that the polymerizable functional group is a glycidyl group, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after the ink set is cured. It is also preferable that the polymerizable functional group is a (meth)acrylic group, from the viewpoint of improving film properties such as film strength and thermal expansion coefficient after the ink set is cured.

It is preferable that the polymerizable functional group possessed by the surface-modified silica filler contained in the ink B according to the present invention is a glycidyl group, and that the polymerizable functional group possessed by the surface-modified silica filler contained in the ink A described above is a (meth)acrylic group. This improves the dispersibility and inkjet ejection properties of the ink.

(3.4) Photothermally Reactive Compound It is preferable that the B ink according to the present invention contains a photothermally reactive compound from the viewpoints of film toughness after curing of the ink composition, crack resistance, drill resistance, adhesion, and durability in a heat cycle test. The reason for improved film toughness is that having a photocurable functional group and a thermosetting functional group in the same molecule allows the photocurable compound and the thermosetting compound to be bonded together.

In this specification, a "photo-thermally reactive compound" refers to a compound having at least one photo-curable functional group and at least one thermo-curable functional group.

The photothermally reactive compound preferably has one or more (meth)acryloyl groups and one or more epoxy groups. Only one of the photothermally reactive compounds may be used, or two or more may be used in combination.

The photocurable compound and thermosetting compound according to the present invention are preferably contained as components different from the photo- and thermo-reactive compound.

Examples of photothermally reactive compounds include compounds having a (meth)acryloyl group and an epoxy group, partially (meth)acrylated epoxy compounds, and urethane-modified (meth)acrylic epoxy compounds.

(Compound having a (meth)acryloyl group and an epoxy group)
Examples of compounds having a (meth)acryloyl group and an epoxy group include glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether.

(Compound having an epoxy group)
Examples of epoxy compounds that can be used for the partially (meth)acrylated epoxy compound include novolac-type epoxy compounds and bisphenol-type epoxy compounds. The partially (meth)acrylated epoxy compound can be obtained, for example, by reacting an epoxy compound with (meth)acrylic acid in the presence of a catalyst according to a conventional method.

(Urethane-modified (meth)acrylic epoxy compound)
The urethane-modified (meth)acrylic epoxy compound can be obtained, for example, by the following method.

A polyol is reacted with a difunctional or higher isocyanate, and then the remaining isocyanate groups are reacted with a (meth)acrylic monomer having an acid group and glycidol. Alternatively, a difunctional or higher isocyanate may be reacted with a (meth)acrylic monomer having a hydroxyl group and glycidol without using a polyol. Alternatively, the above urethane-modified (meth)acrylic epoxy compound can also be obtained by reacting a (meth)acrylate monomer having an isocyanate group with glycidol.

Specifically, for example, 1 mole of trimethylolpropane and 3 moles of isophorone diisocyanate are reacted in the presence of a tin-based catalyst. The remaining isocyanate groups in the resulting compound are reacted with hydroxyethyl acrylate, an acrylic monomer containing a hydroxyl group, and glycidol, an epoxy containing a hydroxyl group. This produces the above-mentioned urethane-modified (meth)acrylic epoxy compound.

Polyols are not particularly limited, but examples include ethylene glycol, glycerin, sorbitol, trimethylolpropane, and (poly)propylene glycol.

The isocyanate is not particularly limited as long as it is difunctional or higher, and examples include isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, norbornane diisocyanate, tolidine diisocyanate, xylylene diisocyanate (XDI), hydrogenated XDI, lysine diisocyanate, triphenylmethane triisocyanate, tris(isocyanatophenyl)thiophosphate, tetramethylxylene diisocyanate, and 1,6,10-undecane triisocyanate.

From the standpoint of low viscosity, functioning as a reactive diluent, and improving the physical properties of the cured film, the photothermally reactive compound preferably includes glycidyl acrylate, glycidyl methacrylate, or 4-hydroxybutyl acrylate glycidyl ether, but from the standpoint of reactivity, 4-hydroxybutyl acrylate glycidyl ether is more preferred.

The content of the photothermally reactive compound is preferably 0.5% by mass or more relative to 100% by mass of the B ink according to the present invention, in order to further improve the physical properties of the cured film, particularly film toughness and crack resistance. It is more preferable that the content be within the range of 1 to 30% by mass.

If the content of the photothermally reactive compound is too low, the effect will not be obtained, and if the content of the photothermally reactive compound is too high, the flexibility will be too high, the thermal expansion coefficient will increase, and the glass transition temperature will decrease, which is undesirable.

(Commercially available)
Examples of commercially available photothermally reactive compounds include "4HBAGE" (4-hydroxybutyl acrylate glycidyl ether) manufactured by Mitsubishi Chemical Corporation, "G0497" (glycidyl acrylate) and "M0590" (glycidyl methacrylate) manufactured by TCI Corporation, "EA-1010LC" (bisphenol A glycidyl ether-containing epoxy acrylate) manufactured by Shin-Nakamura Chemical Co., Ltd., and "EBECRYL 3605" (epoxy resin half acrylate) manufactured by Daicel-Allnex Corporation.

(3.5) Photopolymerization Initiator As the photopolymerization initiator contained in the B ink according to the present invention, the same photopolymerization initiator as that contained in the A ink described above can be used.

(3.6) Reactive Diluent As mentioned above, a "reactive diluent" is a colorless, low-viscosity liquid that is added to a substance to reduce its viscosity and make it easier to handle. The B ink according to the present invention preferably contains a reactive diluent, which can reduce the viscosity of the B ink.

The purpose of adding a reactive diluent is to lower the viscosity of the ink to the point where it can be inkjet-ejected, but using a monomer with a high glass transition temperature is particularly preferable, as it can increase the glass transition temperature of the cured film.

Reactive diluents include, for example, photoreactive diluents and thermally reactive diluents. The photoreactive diluents may be, for example, the photocurable compounds described above, and the thermally reactive diluents may be, for example, the thermosetting compounds described above. These reactive diluents may be used alone or in combination of two or more.

The reason for using a photocurable compound and/or a thermosetting compound as described above is that after the ink set of the present invention is cured, the curable compound is fixed in the cured film and does not volatilize or bleed out. In particular, when a large amount of reactive diluent is used, the fluidity is lost after light irradiation, so a photocurable compound is preferred as the reactive diluent.

Furthermore, using a photocurable compound as the reactive diluent for the B ink is even more preferable, as it suppresses bleeding during printing, resulting in higher resolution and better 3D formability when laminating thick films.

The amount of reactive diluent contained is determined by the amount that adjusts the viscosity of the ink to approximately 100 cp at 25°C. Since the function of the reactive diluent is to lower the viscosity of the ink, it is preferable that the viscosity of the B ink be 30 cp or less, more preferably 15 cp or less, and even more preferably 10 cp or less.

When the reactive diluent content is 1% by mass or more relative to 100% by mass of the B ink according to the present invention, the viscosity-lowering effect is enhanced, and when it is 70% by mass or less, the content of the main ingredients, epoxy resin and thermosetting agent, can be ensured to be above a certain level. This allows for the desired film properties (thermal expansion coefficient, glass transition temperature, film strength, heat resistance, etc.). Therefore, the reactive diluent content in the B ink is preferably within the range of 1 to 70% by mass.

(3.7) Other Components The B ink according to the present invention may contain other components, such as water, organic solvents, adhesion aids such as coupling agents, pigments, dyes, leveling agents, antifoaming agents, and polymerization inhibitors.

Furthermore, the B ink according to the present invention may also contain a thermosetting catalyst, and may contain the same substances as those that can be contained in the A ink according to the present invention described above. However, since the pot life is longer when, for example, the epoxy resin, thermosetting catalyst, and thermosetting agent are not present in the same liquid, it is preferable that the B ink does not contain a thermosetting catalyst.

Therefore, it is preferable that the ink A according to the present invention contains a thermosetting catalyst while the ink B does not, in order to promote the curing reaction after the two inks are mixed together and to extend the pot life of the ink B.

The water contained in the B ink according to the present invention is not particularly limited, and may be ion-exchanged water, distilled water, or pure water. However, it is preferable to keep the water content to 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.2% by mass or less, relative to 100% by mass of the B ink.

The organic solvent contained in the B ink according to the present invention is not particularly limited and can be any known organic solvent. However, the organic solvent content is preferably kept to 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, relative to 100% by mass of the B ink.

[Method for forming a cured product using a two-component ink set]
In the method for forming a cured product of the present invention, the A ink and the B ink constituting the two-component ink set are ejected from separate inkjet head nozzles, thereby extending the pot life of the two-component ink set.

Extending the pot life improves ejection stability. The reason for improved ejection stability is that the ink's liquid properties are stable, which reduces fluctuations in ejection speed and suppresses the occurrence of nozzle gaps, bending, and satellites. High ink ejection stability prevents deterioration in ink landing accuracy during image formation, which in turn maintains the mixing of the two liquids, ensuring stable film properties for the cured film formed in subsequent processes.

Furthermore, the two-component ink set is applied to an object to be coated, forming a coating film, and the cured product is then formed by irradiating the coating film with active energy rays, resulting in a cured product with good pattern precision and excellent lamination suitability. In other words, the film obtained by laminating the ink composition can be made thicker, and it also effectively functions to flatten various components when used in electronic components, etc.

[Products having cured resin compositions]
The product of the present invention is a product having a cured product of a resin composition, wherein the cured product is a cured product consisting of the components of the ink A and ink B that constitute the two-component ink set of the present invention. The two-component ink set of the present invention has excellent 3D formability and is therefore suitable for forming thick insulating films, and can be used, for example, as an insulating material between electrodes in thick copper PCBs (printed circuit boards).

In particular, the cured product of the resin composition formed from the two-component ink set of the present invention has a low thermal expansion coefficient, a high glass transition temperature, and excellent film toughness, insulation resistance, and heat resistance, making it suitable for insulating film pattern formation processes that require thickness control. It can also be used favorably as a planarizing material for the insulating film between wiring on thick copper PCBs, which is increasingly required for power electronics PCBs. Furthermore, it can be used not only to planarize the inner layer thick copper circuits of such laminated PCBs, but also to provide insulating protection for the outer layer copper wiring of PCBs.

The thickness of the typical copper substrate used in conventional electronic components and other products is expected to be 70 μm or less. For example, by forming a hardened film that acts as an insulating resin layer, such as solder resist, on the metal wiring surface of such electronic components, the load on the electronic components, such as current, can be reduced.

In products such as electronic components for power electronics, it is expected that large currents will flow through them, so the thickness of the copper substrate used in such electronic components is different from normal thicknesses and is expected to be, for example, 140 μm or thicker. For this reason, the thickness of the hardened film formed on a normal copper substrate will be thicker.

In particular, it is extremely difficult to flatten thick copper of 210 μm or more, especially 300 μm or more, and currently there are no applicable insulating materials.

Furthermore, the thicker cured film, i.e., the cured product of the resin composition, is more susceptible to external loads. Specifically, the physical properties of the cured product are strongly affected by the thermal expansion coefficient and glass transition temperature, which can lead to problems such as cracks and reduced adhesion to thick copper substrates.

Therefore, there is a demand for products that have more reproducible and stable cured films than those produced by conventional methods, i.e., products that have cured resin compositions with extremely low thermal expansion coefficients and high glass transition temperatures.

In contrast, the cured product of the components of Ink A and Ink B that make up the inkjet-ejectable two-component ink set of the present invention has a thermal expansion coefficient that is significantly smaller than that of cured products of conventional inkjet-ejectable resin compositions, a high glass transition temperature, and excellent 3D formability. For this reason, it is suitable for flattening thick copper surfaces of 210 μm or more, particularly 300 μm or more, and can be used favorably in products such as electronic components.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

[1] Preparation and Evaluation of Inks [1-1] Preparation of Ink A Inks [A1] to [A10] were prepared using the components and ratios shown in Table I.

The ink components in Table I are as follows. The amounts of each component in Table I are expressed in mass %.

<Photocurable compound>
"SR833": Tricyclodecane dimethanol diacrylate (manufactured by Sartomer)
"M222": Dipropylene glycol diacrylate (manufactured by Miwon)
"M300": Trimethylolpropane triacrylate (manufactured by Miwon)
"A-HD-N": 1,6-hexanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)

<Filler>
"SPJ": Phenyl surface-treated silica (manufactured by Admatechs Co., Ltd.). Although "SPJ" is listed in Table I, it is actually the product name "SC2500-SPJ" (particle size 0.5 μm).
"SVJ": vinyl surface-treated silica (manufactured by Admatechs Co., Ltd.). Note that although "SVJ" is listed in Table I, it is actually the product name "SC2300-SVJ" (particle size 0.5 μm).
"SEJ": Epoxy surface-treated silica (manufactured by Admatechs Co., Ltd.). Note that although "SEJ" is listed in Table I, it is actually the product name "SC2500-SEJ" (particle size 0.5 μm).
"SMJ": Methacrylic surface-treated silica (manufactured by Admatechs Co., Ltd.). Note that although "SMJ" is listed in Table I, it is actually the product name "SC2500-SMJ" (0.5 μm).
"SO-C2": Silica (particle size 0.5 μm, manufactured by Admatechs Co., Ltd.)
<Thermosetting catalyst>
"SA102": DBU compound (thermal latent base generator, manufactured by San-Apro Co., Ltd.)
In Table I, "SA102" is written, but the product name is "U-CAT SA102"
・ "DICY7": Dicyandiamide (manufactured by Mitsubishi Chemical Corporation)
<Photopolymerization initiator>
"TPO": diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (manufactured by IGM Resins)
<Reactive diluent (photoreactive)>
"A-NPG": Neopentyl glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)

[1-2] Preparation of Ink B Inks [B1] to [B10] were prepared using the ingredients and ratios shown in Table II.

The ink components in Table II are as follows. The amounts of each component in Table II are expressed in mass %.

<Thermosetting compound>
・ "4300E": Bisphenol A type epoxy resin (manufactured by ADEKA Corporation)
In Table II, "4300E" is written, but the product name is "EP-4300E".
<Thermal curing agent>
"YH306": Methylbutenyltetrahydrophthalic anhydride (manufactured by Mitsubishi Chemical Corporation)
<Filler>
"SPJ": Phenyl surface-treated silica (manufactured by Admatechs Co., Ltd.). Although "SPJ" is listed in Table II, it is actually the product name "SC2500-SPJ" (particle size 0.5 μm).
"SVJ": vinyl surface-treated silica (manufactured by Admatechs Co., Ltd.). Note that although "SVJ" is listed in Table II, it is actually the product name "SC2300-SVJ" (particle size 0.5 μm).
"SEJ": Epoxy surface-treated silica (manufactured by Admatechs Co., Ltd.). Note that although "SEJ" is listed in Table II, it is actually the product name "SC2500-SEJ" (particle size 0.5 μm).
"SMJ": Methacrylic surface-treated silica (manufactured by Admatechs Co., Ltd.). Note that although "SMJ" is listed in Table II, it is actually the product name "SC2500-SMJ" (0.5 μm).
"SO-C2": Silica (particle size 0.5 μm, manufactured by Admatechs Co., Ltd.)
<Photothermally reactive compound>
"4HBAGE": 4-hydroxybutyl acrylate glycidyl ether (manufactured by Mitsubishi Chemical Corporation)
<Photopolymerization initiator>
"TPO" diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (manufactured by IGM Resins)
<Reactive diluent (photoreactive)>
"A-NPG": Neopentyl glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
"A-HD-N": 1,6-hexanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
"M222": Dipropylene glycol diacrylate (manufactured by Miwon)

[1-3] Preparation of Ink C Ink [C1] was prepared using the ingredients and proportions shown in Table III.

The ink components in Table III are as follows. The amounts of each component in Table III are expressed in mass %.

<Photocurable compound>
"SR833": Tricyclodecane dimethanol diacrylate (manufactured by Sartomer)
"A0144": 2-ethylhexyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)
<Thermosetting compound>
・ "4300E": Bisphenol A type epoxy resin (manufactured by ADEKA Corporation)
In Table III, "4300E" is written, but the product name is "EP-4300E".
<Thermal curing agent>
"YH306": Methylbutenyltetrahydrophthalic anhydride (manufactured by Mitsubishi Chemical Corporation)
<Photothermally reactive compound>
"4HBAGE": 4-hydroxybutyl acrylate glycidyl ether (manufactured by Mitsubishi Chemical Corporation)
<Thermosetting catalyst>
"SA102": DBU compound (thermal latent base generator, manufactured by San-Apro Co., Ltd.)
In Table III, "SA102" is written, but the product name is "U-CAT SA102".
<Photopolymerization initiator>
"TPO" diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (manufactured by IGM Resins)

[1-4] Evaluation of Dispersibility Each of the A inks and B inks was subjected to a dispersion treatment using an ultrasonic dispersion device (Ultrasonic Homogenizer, Model No. us-600CCVP, manufactured by Nippon Seiki Seisakusho Co., Ltd.) and transferred to a transparent container with a lid. The state of the dispersion of each of the A inks and B inks after the dispersion treatment was then visually observed and evaluated using the following three-level evaluation criteria. The evaluation results of the A ink are shown in Table IV, and the B ink are shown in Table V. Note that the dispersibility of the one-component C ink was not evaluated in particular because it does not contain a filler.

(Evaluation criteria)
3: The ink components are uniformly dispersed.
2: The ink components are dispersed almost uniformly, but a few aggregates are observed.
1: Solids have settled and the ink components are not uniformly dispersed.

[1-5] Evaluation of Sedimentation Property After the dispersion treatment, the dispersion liquid of each of the A inks and B inks used in the dispersibility evaluation was allowed to stand for one week, and then the state of the dispersion liquid was visually observed and evaluated according to the following three-level evaluation criteria.

(Evaluation criteria)
3: No sedimentation is observed in the dispersion.
2: A small amount of transparent supernatant was observed in the dispersion.
1: A transparent supernatant and a sediment were observed in the dispersion, and the two were clearly separated.

[1-6] Ink Pot Life Evaluation Each of the A inks, B inks, and C inks was sealed in a capped sample tube, which was then placed in an oven at 60°C and heated in the oven for 24 hours. The viscosity state of each of the A, B, and C inks before being placed in the oven was visually observed to determine how it changed after being heated in the oven, and evaluated using a three-level evaluation scale of "3,""2," and "1." The evaluation results for the A ink are shown in Table VI, those for the B ink in Table VII, and those for the C ink in Table VIII. "3" and "2" indicate no practical problems and are the pass criterion, while "1" indicates practical problems and is the fail criterion.

(Evaluation criteria)
3: There is no change in ink viscosity before and after heating in an oven.
2: The ink thickened before and after heating in the oven, but remained fluid in the heated state.
1: The ink completely gelled before and after heating in the oven, and had no fluidity.

[1-7] Printing method for print evaluation (print preparation)
Figure 1 shows an example of the configuration of a printing machine. Printing was performed using a serial printing type inkjet printer equipped with two inkjet heads in the layout shown in Figure 1. In Figure 1, "PS" refers to the printer stage, "S" refers to the substrate, "C" refers to the carriage, and "UV lamp" refers to a UV-LED irradiator manufactured by Phoseon Technology. Also, "H1" refers to inkjet head H1, and "H2" refers to inkjet head H2.

Phoseon 365nm UV-LED irradiators were mounted on both sides of carriage C, and inkjet heads H1 and H2 were Konica Minolta KM1024i series (nozzle pitch 360npi, 1024 nozzles, standard droplet size 30pL).

Ink was supplied from ink tanks (not shown) connected to inkjet heads H1 and H2. The flow path including the ink tanks was pressure-controlled (not shown) to form an appropriate meniscus.

As shown in Figure 1, printing is performed by scanning a carriage bidirectionally over the substrate, and after ink is ejected, a UV irradiator follows, allowing UV curing for each round trip scan.

After printing and scanning the required amount of image, the substrate S is fed out as appropriate to form the entire image. Note that Figure 1 is just an example, and the number and arrangement of inkjet heads may be changed as needed to suit the printing takt time and resolution.

The distance between inkjet head H1 and inkjet head H2 was 4 cm, and the distance between each inkjet head and the UV-LED irradiator was 10 cm.

(Outline of printing method)
After ink A and ink B were superimposed and ejected onto a glass epoxy substrate S _G , layer printing was performed by repeatedly exposing to UV light using a UV-LED irradiator. The image resolution was 1440 dpi in the main scanning direction (carriage movement direction) and 1440 dpi in the sub-scanning direction, and when producing a sample with a film thickness of 100 μm at a head nozzle resolution of 360 dpi, the image resolution was set to 1440 dpi using a four-pass method.

[2] Preparation and evaluation of glass epoxy substrate samples with cured films formed thereon [2-1] Preparation of glass epoxy substrate samples (preparation of evaluation sample [G1])
The glass epoxy substrate used to prepare the evaluation sample had the structure shown in Figure 2. Ink [A1] was used as the A ink constituting the ink set. Ink [B1] was used as the B ink constituting the ink set.

Inkjet head H1, which was connected to an ink cartridge filled with ink as shown in Figure 1, was filled with ink A, and inkjet head H2 was filled with ink B. At this time, the temperature, voltage, and drive waveform of the inkjet head were appropriately adjusted so that the droplet size of both ink A and ink B was 30 pL.

A 5cm x 5cm solid image was used to evaluate the physical properties of the printed material. The solid image was printed so that the ratio of the coverage rate of ink A to the coverage rate of ink B was 1:5, and the coverage rates of ink A and ink B were set so that when scanned four times (two round trips), i.e., four passes, a 1440 x 1440 dpi image was formed, resulting in a thickness of 100μm.

Furthermore, the coverage ratios of ink A and ink B were set so that when a 1440 x 1440 dpi image was formed using 8 (4 round trips), 12 (6 round trips), or 24 (12 round trips) scans, i.e., 8, 12, or 24 passes, the resulting thicknesses were 200 μm, 300 μm, or 400 μm.

Ink B was ejected immediately after ink A was ejected, mixing the two inks, and then the material was temporarily cured by UV exposure.

The head scanning speed was 300 mm/s, and the UV exposure amount per scan at this speed was 300 mJ/cm ² .

For samples with film thicknesses of 100 μm, 200 μm, 300 μm, and 400 μm, good pattern formation was achieved with an accuracy of ±200 μm on a 5 cm x 5 cm surface.

After printing was completed, the temperature was gradually raised from room temperature to 200°C over 30 minutes, and then the sample was treated at 200°C for 30 minutes to produce evaluation sample [G1] with film thicknesses of 100 μm, 200 μm, 300 μm, and 400 μm. Figure 3 is an example of a schematic diagram of the evaluation sample obtained by curing the ink.

(Preparation of evaluation samples [G2] to [G9])
The inks A and B constituting the ink set were changed to obtain the ink set combination shown in Table IX. Evaluation samples [G2] to [G9] were prepared in the same manner as evaluation sample [G1], except that the heating temperature, voltage, and printing ratio of the inkjet head were adjusted so that the laminate film thickness would be 100 μm, 200 μm, 300 μm, or 400 μm. Evaluation samples [G2] to [G9] were also prepared for film thicknesses of 100 μm, 200 μm, 300 μm, and 400 μm.

For evaluation samples [G2] to [G9] with thicknesses of 100 μm, 200 μm, 300 μm, and 400 μm, good pattern formation was achieved with an accuracy of ±200 μm on a 5 cm x 5 cm surface.

(Preparation of evaluation sample [G10])
The ink A and ink B constituting the ink set were changed to obtain the ink set combination shown in Table IX, and a solid image was printed so that the ratio of the coverage of ink A to the coverage of ink B was 1:1. Evaluation sample [G10] was prepared in the same manner as evaluation sample [G1], except that the heating temperature, voltage, and coverage of the inkjet head were adjusted so that the evaluation samples would be 100 μm, 200 μm, 300 μm, and 400 μm.

In this case, for the evaluation sample [G10], the image boundary was found to extend beyond the design value by more than 300 μm for a 5 cm x 5 cm size due to a deterioration in the landing accuracy of the ejected ink. This phenomenon worsened with each printing cycle.

Furthermore, for samples with a film thickness of 300 μm and 400 μm, droplets of ink [A10] stopped being ejected during the preparation of evaluation samples. This was because the filler in ink [A10] settled inside the head, causing clogging and preventing continuous ejection. As a result, it was not possible to prepare evaluation samples for evaluation sample [G10] with a film thickness of 300 μm and 400 μm.

(Preparation of evaluation sample [G11])
An attempt was made to prepare an evaluation sample [G11] using the one-component ink [C1], but the ink droplets stopped being ejected while adjusting the ink ejection conditions, and it was not possible to prepare the evaluation sample [G11].

[2-2] Evaluation of Glass Epoxy Substrate Samples [2-2-1] Crack Evaluation Each of the prepared evaluation samples with thicknesses of 100 μm, 200 μm, 300 μm, and 400 μm was heated from room temperature to 200°C over 30 minutes and then heat-treated at 200°C for 30 minutes. After that, each of the evaluation samples with thicknesses of 100 μm, 200 μm, 300 μm, and 400 μm was visually inspected for cracks and rated according to the following four-level evaluation criteria: "4,""3,""2," and "1." The evaluation results are shown in Table IX.

(Evaluation criteria)
4: No cracks were observed in any of the evaluation samples having thicknesses of 100 μm, 200 μm, 300 μm, and 400 μm.
3: No cracks were observed in the evaluation samples with film thicknesses of 100 μm, 200 μm, and 300 μm, but cracks were observed in the sample with a film thickness of 400 μm.
2: No cracks were observed in the evaluation samples with film thicknesses of 100 μm and 200 μm, but cracks were observed in the evaluation samples with film thicknesses of 300 μm and 400 μm.
1: No cracks were observed in the evaluation sample with a film thickness of 100 μm, but cracks were observed in the samples with film thicknesses of 200 μm, 300 μm, and 400 μm.

[2-2-2] Adhesion Evaluation A cross-cut tape peel test was conducted on 100 squares of each of the prepared evaluation samples with a film thickness of 200 μm, and the result was evaluated based on the number of remaining squares using the following three-level evaluation criteria of "3,""2," and "1." The evaluation results are shown in Table IX. "3" and "2" indicate no practical problems and are the pass evaluation criteria, while "1" indicates practical problems and is the fail evaluation criteria.

(Evaluation criteria)
3: There are 100 remaining squares.
2: The number of remaining squares is within the range of 90 to 99.
1: The number of remaining squares is within the range of 0 to 89.

[2-2-3] Solder Resistance Evaluation A 200 μm thick sample of each evaluation sample was immersed in a solder bath heated to 260°C for 60 seconds. The state of the cured film [α] formed on each 200 μm thick sample was then visually observed and evaluated using the following two-level evaluation criteria of "2" and "1." The evaluation results are shown in Table IX. A rating of "2" indicates no practical problems and is the pass rating, while a rating of "1" indicates practical problems and is the fail rating.

(Evaluation criteria)
2: No change in the cured film [α] before and after immersion in a solder bath heated to 260° C. for 60 seconds.
1: Lifting or peeling of the cured film [α] from the substrate _SG was observed before and after immersion for 60 seconds in a solder bath heated to 260°C.

[2-2-4] Evaluation results

[3] Preparation and Evaluation of Cured Film Samples [3-1] Preparation of Cured Film Sample Pieces for Evaluation [3-1-1] Preparation of Teflon (registered trademark) Plate Samples [Tef1] to [Tef10] The inks A and B constituting the ink set were changed to obtain the ink set combinations shown in Table IX. Teflon (registered trademark) plate samples [ _Tef1 ] to [Tef10] were prepared in the same manner as the preparation of evaluation sample [G1], except that a Teflon (registered trademark) plate Tef having a recess of 200 μm depth was used instead of the glass epoxy substrate _SG in the preparation of evaluation sample [G1].

[3-1-2] Preparation of cured film sample pieces for evaluation [T1] to [T10]
Then, the cured film [α] was isolated from each of the Teflon (registered trademark) plate samples [Tef1] to [Tef10], and the cured film [α] was cut into a length of 20 mm and a width of 2 mm to prepare cured film sample pieces for evaluation [T1] to [T10].

[3-1-3] Preparation of Cured Film Sample Piece for Evaluation [T11] An attempt was made to prepare a Teflon (registered trademark) plate sample [Tef11] using the one-component ink [C1], but ink droplets stopped being ejected while adjusting the ink ejection conditions. As a result, it was not possible to prepare the Teflon (registered trademark) plate sample [Tef11], and it was also not possible to prepare the cured film sample piece for evaluation [T11].

[3-2] Evaluation of Cured Film Sample Pieces for Evaluation The coefficient of thermal expansion (CTE) [ppm/°C] of the cured film sample pieces [T1] to [T10] was measured under the following measurement conditions using a thermal analyzer "SII TMA/SS7100" manufactured by Hitachi High-Tech Solutions Corporation. The glass transition temperatures (Tg) of the cured film sample pieces [T1] to [T10] were calculated from the inflection points of the coefficient of thermal expansion (CTE).

<Measurement conditions>
Heating start temperature: 30°C
Heating end temperature: 250°C
Temperature increase rate: 10°C/min
Atmosphere: Nitrogen

The coefficient of thermal expansion (CTE) below the glass transition temperature was calculated from the rate of dimensional change at sample temperatures between 40°C and 50°C.

[3-2-1] Evaluation of coefficient of thermal expansion (CTE) The measured coefficient of thermal expansion (CTE) was evaluated according to the following four-level evaluation criteria: "4,""3,""2," and "1." The evaluation results are shown in Table X.

(Evaluation criteria)
4: The coefficient of thermal expansion (CTE) is less than 61 ppm/°C.
3: The coefficient of thermal expansion (CTE) is 61 ppm/°C or more and less than 71 ppm/°C.
2: The coefficient of thermal expansion (CTE) is 71 ppm/°C or more and less than 81 ppm/°C.
1: The coefficient of thermal expansion (CTE) is 81 ppm/°C or more.

[3-3-2] Evaluation of Glass Transition Temperature (Tg) The calculated glass transition temperature (Tg) was evaluated according to the following four-level evaluation criteria: "4,""3,""2," and "1." The evaluation results are shown in Table X.

(Evaluation criteria)
4: The glass transition temperature (Tg) is 130°C or higher.
3: The glass transition temperature (Tg) is 110°C or higher and lower than 130°C.
2: The glass transition temperature (Tg) is 90°C or higher and lower than 110°C.
1: The glass transition temperature (Tg) is less than 90°C.

[3-2-3] Evaluation results

[4] Overall Evaluation As is clear from Tables IV to X, the Examples have a longer pot life than the Comparative Examples, and it is clear that excellent film properties can be obtained as an insulator for use in electronic components.

Although embodiments of the present invention have been described and illustrated in detail above, the disclosed embodiments have been made for purposes of illustration and example only and are not intended to be limiting. The scope of the present invention should be interpreted by the terms of the appended claims.

Although embodiments of the present invention have been described and illustrated in detail above, the disclosed embodiments have been made for purposes of illustration and example only and are not intended to be limiting. The scope of the present invention should be interpreted by the terms of the appended claims.

We can provide a two-component ink set, a method for forming a cured product, and a product that has a long pot life and can produce excellent film properties as an insulator for electronic components.

S _G Glass epoxy substrate H1, H2 Inkjet head C Carriage PS Print stage S Substrate α Hardened film T _ef Teflon (registered trademark) plate

Claims (8)

A two-component inkjet ink set comprising at least ink A and ink B,
the ink A contains at least a photocurable compound,
the B ink contains at least a thermosetting compound,
At least one of the ink A and the ink B contains a silica filler, and
A two-component ink set, wherein the silica filler is surface-modified. 2. The two-component ink set according to claim 1, wherein the silica filler has a polymerizable functional group. 3. The two-component ink set according to claim 2, wherein the polymerizable functional group is a glycidyl group or a (meth)acrylic group. The two-component ink set described in claim 1, characterized in that both the A ink and the B ink contain a surface-modified silica filler. the polymerizable functional group of the silica filler contained in the ink A is a (meth)acrylic group,
2. The two-constituent ink set according to claim 1, wherein the polymerizable functional group of the silica filler contained in the B ink is a glycidyl group. A method for forming a cured product using the two-component ink set according to any one of claims 1 to 5, comprising:
the A ink and the B ink constituting the two-component ink set are ejected from separate inkjet head nozzles to coat and adhere to an object to form a coating film;
A method for forming a cured product, comprising irradiating the coating film with active energy rays to form the cured product. A product having a cured product of a resin composition,
6. A product, wherein the cured product is a cured product made from components of the ink A and the ink B that constitute the two-component ink set according to claim 1. 8. The article of claim 7, wherein the article is a heavy copper substrate.