JP7248592B2 - Metal ink, method for producing metal ink, and method for producing substrate with metal pattern - Google Patents

Description

TECHNICAL FIELD The present invention relates to a metal ink containing a metal colloid, a method for producing the same, and a method for producing a substrate having a metal pattern using the metal ink.

A metal ink containing metal nanoparticles is used when forming a metal pattern such as a wiring pattern or a conductive layer of an electrode. A metal ink is applied to the surface of the substrate when forming the metal pattern. A resin film or the like is formed on the surface of the substrate (for example, Patent Document 1).

JP 2013-221058 A

If a metal pattern can be directly formed on a substrate made of various thermoplastic resins, the step of coating the substrate surface with a resin film can be omitted, which is convenient. However, many thermoplastic resins have low solvent resistance and are easily dissolved by the dispersion medium contained in the metal ink. When the base material is dissolved by the metal ink, the resistance increases, the accuracy of the metal pattern decreases, and the product fails. On the other hand, the use of a dispersion medium that does not dissolve the thermoplastic resin reduces the stability of the metal colloid in the metal ink.

One aspect of the present invention is a metallic ink for application onto a substrate to form a metallic pattern, comprising:
containing a metal colloid and a dispersion medium,
The base material contains a thermoplastic resin at least in a region where the metal pattern is formed,
The distance Dc of the Hansen solubility parameter between the dispersion medium and the metal colloid is 10 MPa ^0.5 or less,
It relates to a metallic ink, wherein the distance Ds of the Hansen solubility parameter between the dispersion medium and the thermoplastic resin is 10 MPa ^0.5 or more.

Another aspect of the present invention is a method for producing a metal ink that includes a metal colloid and a dispersion medium and is applied onto a substrate to form a metal pattern, comprising:
The base material contains a thermoplastic resin at least in a region where the metal pattern is formed,
Prepare the dispersion medium in which the distance Dc of the Hansen solubility parameter between the dispersion medium and the metal colloid is 10 MPa ^0.5 or less and the distance Ds of the Hansen solubility parameter between the dispersion medium and the thermoplastic resin is 10 MPa ^0.5 or more. and
and preparing a metal ink in which the metal colloid is dispersed in the dispersion medium.

Yet another aspect of the present invention comprises the step of applying a metal ink onto a substrate to form a metal pattern,
The base material contains a thermoplastic resin at least in a region where the metal pattern is formed,
The metal ink contains a metal colloid and a dispersion medium,
The distance Dc of the Hansen solubility parameter between the dispersion medium and the metal colloid is 10 MPa ^0.5 or less,
The present invention relates to a method for producing a substrate having a metal pattern, wherein the distance Ds of the Hansen solubility parameter between the dispersion medium and the thermoplastic resin is 10 MPa ^0.5 or more.

The high stability of the metal colloid in the metal ink can be ensured, and dissolution of the base material can be suppressed when the metal pattern is formed using the metal ink on the thermoplastic resin-containing region of the base material.

While the novel features of the present invention are set forth in the appended claims, the present invention, both as to construction and content, together with other objects and features of the present invention, will be further developed by the following detailed description in conjunction with the drawings. will be well understood.

Metal inks used for forming metal patterns need to ensure the stability (specifically, dispersion stability) of metal colloids in the metal ink. On the other hand, in the field of electronics, in recent years, techniques for forming wiring patterns on substrates made of thermoplastic resin using metallic ink have been studied. However, a dispersion medium that easily secures the stability of the metal colloid easily dissolves the thermoplastic resin. In the case of metal inks, it is also necessary to balance the affinity between the base material and the metal ink, the volatility of the dispersion medium contained in the metal ink, and the like.

A metal ink according to one aspect of the present invention is a metal ink that contains a metal colloid and a dispersion medium and is applied onto a substrate to form a metal pattern. The substrate contains a thermoplastic resin at least in the region where the metal pattern is to be formed. The Hansen Solubility Parameter (HSP) distance Dc between the dispersion medium and the metal colloid is 10 MPa ^0.5 or less, and the HSP distance Ds between the dispersion medium and the thermoplastic resin is 10 MPa ^0.5 or more. The solubility parameter represents a measure of affinity between substances, and HSP is represented by a three-dimensional vector of dispersion term dD, polarity term dP, and hydrogen bond term dH. Other aspects of the invention also include the use of the metallic inks described above for coating onto substrates to form metallic patterns.

A step of preparing such a metal ink in which the HSP distance Dc between the dispersion medium and the metal colloid is 10 MPa ^0.5 or less and the HSP distance Ds between the dispersion medium and the thermoplastic resin is 10 MPa ^0.5 or more. and a step of preparing a metal ink in which the metal colloid is dispersed in a dispersion medium. Yet another aspect of the invention includes a method for producing such a metallic ink.

Another aspect of the present invention includes a method of manufacturing a substrate having a metal pattern, comprising the step of applying a metal ink onto the substrate to form a metal pattern. Here, the substrate contains a thermoplastic resin at least in the region where the metal pattern is to be formed. A metal ink contains a metal colloid and a dispersion medium. The Hansen solubility parameter distance Dc between the dispersion medium and the metal colloid is 10 MPa ^0.5 or less, and the Hansen solubility parameter distance Ds between the dispersion medium and the thermoplastic resin is 10 MPa ^0.5 or more. Further, still another aspect of the present invention includes use of the metal ink in a method for manufacturing a substrate having a metal pattern.

According to the above aspect of the present invention, the HSP distance Dc between the dispersion medium and the metal colloid is 10 MPa ^0.5 or less, and the HSP distance Ds between the dispersion medium and the base material (specifically, thermoplastic resin) is 10 MPa. Adjust to ^0.5 or higher. As a result, high stability of the metal colloid in the metal ink can be ensured, and dissolution of the base material can be suppressed when the metal ink is applied onto the thermoplastic resin-containing region of the base material. By suppressing the dissolution of the base material (specifically, the thermoplastic resin) by the metal ink, it is possible to suppress an increase in the resistance of the metal pattern. Moreover, since the metal colloid in the metal ink is highly stable, the metal ink can be stably stored for a long period of time. The metal colloid usually contains metal particles and a dispersing agent coordinated to the metal particles. In the above aspect of the present invention, the distance Dc is calculated based on the HSP of the metal colloid. As a result, compared to the case of using the dispersant or the distance between the HSP of the organic group (hydrophobic group, etc.) with low affinity for the metal particles of the dispersant and the HSP of the dispersion medium, a dispersion medium suitable for metal colloids can be obtained. Since it can be selected with high accuracy, it is possible to ensure high stability of the metal colloid in the metal ink.

Note that the distances Dc and Ds can be obtained as follows.
First, a sediment and a supernatant liquid are collected by centrifuging the metal ink. The type and composition (in the case of a mixture, the mixing ratio) of the dispersion medium contained in the supernatant are determined by gas chromatography analysis. Then, from this type and composition, HSP calculation software HSPiP (available from HSP and HSPiP official sites) is used to obtain dispersion term dD, polarity term dP, and hydrogen bonding term dH of HSP of the dispersion medium.

The HSP of the sediment (metal colloid) and the base material (thermoplastic resin) can be obtained by testing the solubility in the 23 types of media shown in Table 1.

Specifically, HSP of metal colloid is obtained as follows. The above sediment is added to each medium shown in Table 1 so that the concentration becomes 0.1% by mass, and the mixture is stirred at room temperature (25° C.) for 10 minutes with a roller shaker. After stirring, the mixture is allowed to stand at room temperature (25° C.) for 1 hour. If the metal colloid is dispersed, it is scored as 1, and if it is precipitated, it is scored as 0. The HSP of each medium (that is, dD, dP and dH) is three-dimensionally plotted, a sphere called Hansen's melting sphere is created from the HSP distribution of the medium in which the metal colloid is dispersed, and the center coordinates of this sphere are be the HSP of the metal colloid.

The HSP of the substrate (thermoplastic resin) is determined as follows. 0.4 g of a small piece cut out from the substrate (at least the portion containing the region where the metal pattern is formed (the region containing the thermoplastic resin)) is put into 2 mL of each medium in Table 1, and is kept at room temperature (25°C) for 24 hours. put. After standing, the change in the small pieces was visually observed. If the small pieces were dissolved or cracked, the value was 1, and if there was no change in the small pieces, the value was 0. The HSP of each medium (that is, dD, dP and dH) is three-dimensionally plotted, and from the HSP distribution of the medium in which small pieces are dissolved or cracked, a sphere called Hansen's melting sphere is created, and the center of this sphere is Let the coordinates be the HSP of the substrate (thermoplastic resin).
The distance Dc (MPa ^0.5 ) is calculated from the respective HSPs of the dispersion medium and metal colloid obtained in this manner. Also, the distance Ds (MPa ^0.5 ) is calculated from the HSP of each of the dispersion medium and the substrate (thermoplastic resin).

The thermoplastic resin preferably contains at least one selected from the group consisting of polycarbonate resins, styrene resins, and polyester resins. Such thermoplastic resins are easy to mold and have high strength, so they are suitable as base materials for forming metal patterns. easy. According to the above aspect of the present invention, even when a metal ink is applied to a region of a substrate containing a thermoplastic resin, dissolution of the substrate (specifically, the thermoplastic resin) can be suppressed. can.

The distance Dc is preferably 8.6 MPa ^0.5 or less from the viewpoint of making it easier to ensure high stability of the metal colloid in the metal ink. Moreover, from the viewpoint of enhancing the sinterability of the coating film and easily suppressing an increase in the resistance value of the metal pattern, the distance Dc is preferably 3 MPa ^0.5 or more.

The distance Ds is preferably 15 MPa ^0.5 or less. In this case, high wettability of the metal ink to the substrate can be easily ensured, and repelling of the metal ink on the substrate can be suppressed.

The metal contained in the metal colloid is preferably at least one selected from the group consisting of silver, silver alloys, copper, and copper alloys. These metals have high conductivity and are suitable for forming metal patterns such as wiring patterns.

The metal colloid contains metal nanoparticles and a dispersing agent coordinated to the metal nanoparticles, and the average particle size of the metal nanoparticles is preferably 5 nm or more and 400 nm or less. When such a metal colloid is used, it becomes easier to ensure high stability (specifically, dispersion stability) of the metal nanoparticles in the metal ink. In addition, due to the nano-size effect of the metal nanoparticles, the metal ink is fused at a temperature lower than the melting point of the metal. It becomes easier to reduce the resistance of the pattern (metal film). In addition, since the sintering can be performed at a relatively low temperature, deterioration and deformation due to heat of the base material containing the thermoplastic resin can be suppressed.

The dispersant contained in the metal colloid preferably contains a _C4-16 alkylamine. In this case, since the metal film can be formed even under mild conditions, deterioration and deformation of the base material containing the thermoplastic resin can be suppressed.

In the following, the metal ink, its manufacturing method, and the manufacturing method of the substrate provided with the metal pattern will be described in more detail.

[Metal ink]
The metal ink contains a dispersion medium and a metal colloid dispersed in the dispersion medium. A metal colloid usually contains metal particles, and often contains metal particles and a dispersing agent coordinated to the metal particles. The metal ink can contain a polymerizable compound, a polymerization initiator, etc., in addition to these components. Moreover, the metal ink is preferably a firing-type metal ink that forms a metal pattern by firing a coating film formed by applying it to the surface of the base material.

(metal particles)
As the metal material forming the metal particles, a single metal, an alloy, or the like is used.
Typical metal elements, transition metal elements, etc. are mentioned as a metal element contained in a metal simple substance or an alloy. Examples of typical metal elements include Zn, Al, Ga, In, Ge, Sn, Pb, Sb, and Bi. Examples of transition metal elements include Ti, Zr, V, Cr, Mn, Fe, Ru, Co, Ni, Pd, Pt, Cu, Ag, and Au. The alloy preferably contains two or more of these metal elements. Al, Sn, Ti, Ni, Pt, Cu, Ag, Au, etc. are preferable as the metal element. Ag, Ag alloys, Cu, and Cu alloys are preferable as the metal material (metal contained in the metal colloid), and Ag and Ag alloys are particularly preferable. These metals have high conductivity and are suitable for forming metal patterns such as wiring patterns.

The metal ink may contain multiple types of metal particles of different materials. For example, the metal ink is composed of first metal particles made of Ag, Ag alloy, Cu, or Cu alloy, and a single metal other than Ag and Cu, or an alloy other than Ag alloy and Cu alloy, among the metals listed above. may be included in combination with the second metal particles. In this case, the ratio of the first metal particles to the total metal particles is preferably 80 mass % or more, and may be 80 mass % or more and 99 mass % or less, or 85 mass % or more and 99 mass % or less.

The average particle size of the metal particles is, for example, 5 nm or more and 1500 nm or less.
The metal ink preferably contains metal nanoparticles as the metal particles. Such metal ink is also called metal nanoink. When a metal colloid containing metal nanoparticles is used, the coating film of the metal ink formed on the substrate can be fired at a relatively low temperature due to the nanosize effect of the metal nanoparticles. can be easily reduced, and thermal deterioration and deformation of a substrate containing a thermoplastic resin can also be suppressed. The average particle size of the metal nanoparticles can be selected from the range of 5 nm or more and less than 1000 nm. The average particle size of the metal nanoparticles is preferably 5 nm or more and 500 nm or less (or 5 nm or more and 400 nm or less), more preferably 5 nm or more and 200 nm or less or 5 nm or more and 100 nm or less. By using metal nanoparticles having such an average particle size, it is possible to increase the contact between the metal nanoparticles and facilitate fusion between the metal nanoparticles even at a relatively low temperature. The conductivity of the metal pattern formed by this method tends to increase.

In the present specification, the average particle size is the particle size (D50) at 50% cumulative volume in the volume-based particle size distribution. The average particle size (D50) can be measured by a laser diffraction scattering method using a laser diffraction particle size distribution analyzer. In addition, the average particle diameter of the metal particles is the same area as the region surrounded by the outer edges of a plurality of (for example, 10) arbitrarily selected metal particles in a scanning electron microscope (SEM) photograph of the coating film of the metal ink. It may be calculated by obtaining and averaging the diameters of circles (equivalent circles) having .

The shape of the metal particles is not particularly limited, and may be spherical, ellipsoidal, polygonal columnar, polygonal pyramidal, flat (flake-like, scale-like, flake-like, etc.), or any shape similar thereto. may From the viewpoint of easily enhancing the contact between metal particles, a spherical shape, an elliptical shape, a flat shape, or a shape similar thereto is preferable.

As the metal particles, commercially available ones may be used, or those formed by evaporating a metal material may be used. Alternatively, metal particles produced by chemical reaction in a liquid phase or gas phase may be used.

(dispersant)
By using a dispersant, aggregation of metal particles in the metal ink can be suppressed, and the metal colloid can be stabilized in the metal ink. The dispersant may be added during preparation of the metal ink and coordinated with the metal particles, but is preferably coordinated with the metal particles prior to preparation of the metal ink. The dispersant may be mixed with the metal particles and heated if necessary to coordinate to the metal particles, or may be coordinated to the metal particles by using the dispersant in the process of preparing the metal particles.

As the dispersant, for example, an organic compound having a polar functional group that coordinates to the metal particles and an organic group that has a low affinity for the metal particles (for example, a hydrophobic organic group) is used. Polar functional groups include, for example, heteroatom-containing groups. Heteroatoms include, for example, nitrogen, sulfur, and/or oxygen atoms. Polar functional groups include, for example, amino groups, mercapto groups, oxygen-containing groups (eg, hydroxy groups (including phenolic hydroxy groups), carbonyl groups, ester groups, carboxy groups, etc.). The dispersant may contain one type of polar functional group, or may contain two or more types.

Among them, it is preferable to use an organic amine, which is a compound containing an amino group, from the viewpoint of room temperature stability. The organic amines may be primary amines, secondary amines, or tertiary amines. The organic amine may be either a cyclic amine or a chain amine. Primary amines (among them, primary chain amines) are preferred because they are easily coordinated with metal particles. Preferred examples of organic amines include alkylamines (n-butylamine, pentylamine, hexylamine, octylamine, decylamine, dodecylamine, myristylamine, etc.). C _4-16 alkylamines (for example, C _4-15 alkylamines) are preferred, and C _6-14 alkylamines or C _{8- 12-} alkylamines are more preferred. The use of such an amine enables formation of a metal film even under mild conditions, thereby suppressing deterioration and deformation of a base material containing a thermoplastic resin. Among them, amines with a small number of carbon atoms (e.g., _C4-10 alkylamines, preferably _C6-10 alkylamines, and more preferably _C8-10 alkylamines) have high reactivity. It is more advantageous in forming a metal film under the conditions.

The dispersant is preferably a low-molecular-weight compound (for example, a compound with a molecular weight of 500 or less) because it is preferably removed at an appropriate stage in the process of forming the metal pattern.

The amount of the dispersant (preferably the dispersant coordinated to the metal particles) contained in the metal ink is, for example, 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the metal particles. 3 parts by mass or more and 5 parts by mass or less, and more preferably 0.5 parts by mass or more and 5 parts by mass or less. When the amount of the dispersant is within this range, the metal particles can be easily stabilized in the metal ink, and the dispersant can be easily removed.

(dispersion medium)
As the dispersion medium, the HSP distance Dc between the dispersion medium and the metal colloid is 10 MPa ^0.5 or less, and the HSP distance Ds between the dispersion medium and the base material (thermoplastic resin) is 10 MPa ^0.5 or more. used. As such a medium, one that is liquid at room temperature (25° C.) is used. As the dispersion medium, one type of medium may be used alone, or two or more types of medium may be used in combination. When two or more media are used, the media may be selected and/or the ratio of each medium adjusted so that the HSP distance of the mixture of the two or more media is within the above range. As the medium, an organic medium is preferred.

The distance Dc should be 10 MPa ^0.5 or less (preferably 10.0 MPa ^0.5 or less). When the distance Dc exceeds 10 MPa ^0.5 , the stability of the metal colloid in the metal ink is greatly reduced. The distance Dc is preferably 9 MPa ^0.5 or less, more preferably 8.6 MPa ^0.5 or less. The distance Dc is, for example, 1 MPa ^0.5 or more, preferably 3 MPa ^0.5 or more, more preferably 4 MPa ^0.5 or more, and may be 4.5 MPa ^0.5 or more or 4.6 MPa ^0.5 or more. These upper and lower limits can be combined arbitrarily. When the distance Dc is within such a range, it becomes easier to ensure high stability of the metal colloid in the metal ink. The distance Dc is, for example, 1 MPa ^0.5 or more (or 3 MPa ^{0.5 or} more) 10 MPa ^{0.5 or} less, 1 MPa ^0.5 or more (or 3 MPa ^0.5 or more) 10.0 MPa ^0.5 or less, 1 MPa ^0.5 or more (or 3 MPa ^0.5 or more) 9 MPa ^0.5 or less, 1 MPa ^0.5 or more (or 3 MPa ^{0.5 or} more) 8.6 MPa ^0.5 or less, 4 MPa ^{0.5 or} more (or 4.5 MPa ^{0.5 or more} ) 10 MPa ^0.5 or less, 4 MPa ^{0.5 or} more (or 4.5 MPa 0.5 or more) 10.0 MPa ^0.5 or less, 4 MPa ^0.5 or more (or 4 .5 MPa ^{0.5 or} more) 9 MPa ^0.5 or less, 4 MPa ^0.5 or more (or 4.5 MPa ^{0.5 or} more) 8.6 MPa ^0.5 or less, 4.6 MPa ^0.5 or more and 10 MPa ^0.5 or less (or 10.0 MPa ^0.5 or less), or 4.6 MPa ^0.5 or more 9 MPa It may be ^0.5 or less (or 8.6 MPa ^0.5 or less).

The distance Ds may be 10 MPa ^0.5 or more (preferably 10.0 MPa ^0.5 or more). If the distance Ds is less than 10 MPa ^0.5 , the region of the substrate containing the thermoplastic resin will be dissolved. The distance Ds is, for example, 20 MPa ^0.5 or less, preferably 15 MPa ^0.5 or less, more preferably 13 MPa ^0.5 or less. When the distance Ds is in such a range, it is easy to ensure high wettability of the metal ink to the substrate, and it is possible to suppress the metal ink from being repelled on the substrate.

As for the dispersion medium (specifically, the medium described above), the specific type is not particularly limited as long as the distances Dc and Ds satisfy the above range, for example. Examples of dispersion media (specifically, the above media) include alcohols, ethers, esters, ketones, and hydrocarbons (alicyclic hydrocarbons, aromatic hydrocarbons, etc.).

The dD of HSP of the dispersion medium is, for example, 10 or more and 20 or less, preferably 13 or more and 19 or less, and more preferably 14 or more and 18 or less. dP is, for example, 10 or less, preferably 1 or more and 9 or less, and more preferably 2.5 or more and 8 or less (eg, 2.5 or more and 7.5 or less). dH is, for example, 20 or less, preferably 1 or more and 16 or less, and more preferably 3 or more and 15 or less. The HSP of the dispersion medium is not limited to such a range, but when each term is in such a range, it is easy to balance the distances Dc and Ds, and high dispersion stability of the metal particles and the base can be obtained. It is easy to obtain the effect of suppressing dissolution of the material.

When the metal ink is applied onto the base material, it is preferable that a coating film having a desired shape can be formed, and the dispersion medium quickly evaporates after the application. From such a viewpoint, the boiling point of the dispersion medium is, for example, 130° C. or higher and 280° C. or lower, preferably 150° C. or higher and 250° C. or lower. When the dispersion medium contains a plurality of media, the boiling point of at least one medium preferably falls within the above range, and the boiling points of all the media preferably fall within the above range.

The surface tension of the dispersion medium at 25° C. is preferably 20 mN/m or more and 40 mN/m or less, more preferably 25 mN/m or more and 40 mN/m or less. In this case, the applicability of the metal ink can be improved. Moreover, since excessive spreading of droplets is suppressed, a fine metal pattern can be formed.
In addition, in this specification, surface tension is calculated|required by the hanging drop method using a contact angle meter.

The proportion of the dispersion medium in the metal ink is preferably 25% by mass or more and 95% by mass or less, and may be 25% by mass or more and 90% by mass or less. When the proportion of the dispersion medium is within such a range, it is easy to disperse the constituent components such as the metal particles contained in the metal ink in the dispersion medium, and it is easy to ensure good coatability. Therefore, the metal ink is also suitable for jet coating (inkjet method, etc.).

(Polymerization-reactive compound)
A polymerizable compound may be selected according to the desired physical properties of the metal ink. A known polymerization-reactive compound can be used as long as it can be polymerized (including crosslinking and curing) by the action of an activated polymerization initiator to form a polymer. Examples of the polymerizable compound include precursors such as polymer raw materials such as monomers or oligomers in which several monomers are linked, and curable resins (photocurable resins, thermosetting resins, etc.) can also be used.

Curable resins include epoxy resins, acrylic resins, phenol resins, silicon resins, vinyl ester resins, vinyl ether resins, unsaturated polyester resins, diallyl phthalate resins, urethane resins, and the like.
A polymerizable compound may be used individually by 1 type, and may be used in combination of 2 or more types.

(Polymerization initiator)
The polymerization initiator may be selected depending on the desired physical properties of the metal ink, the type of the polymerizable compound, and the like. The polymerization initiator used is one that is activated by the action of heat and/or light to promote the polymerization of the polymerizable compound, and known polymerization initiators can be used. As the polymerization initiator, for example, a radical polymerization initiator, an ionic polymerization initiator, or the like is used. As the polymerization reaction initiator, other curing agents used in curable resins such as thermosetting resins and photocurable resins can also be used.
The polymerization initiators may be used singly or in combination of two or more.

(others)
The metal ink may contain known additives as necessary. For example, the metal ink may contain a binder (such as a resin binder), and when the metal ink contains a polymerization-reactive compound and a polymerization initiator, depending on the type of the polymerization-reactive compound, a curing accelerator, a reactive diluent , surface modifiers, and the like.

The viscosity of the metal ink at 25° C. is preferably, for example, 1 mPa·s or more and 10000 mPa·s or less. When the metal ink is applied onto the substrate by an inkjet method, it is preferable that the viscosity of the metal ink at 25° C. is 3 mPa·s or more and 300 mPa·s or less from the viewpoint of easily ensuring ejection performance from the nozzle.
In this specification, the viscosity is measured using an E-type viscometer at a rotational speed of 20 rpm.

The contact angle of the metal ink with respect to the substrate after the metal ink is applied on the substrate and left at 25° C. for 1 minute is preferably 5° or more and 30° or less, and 10° or more and 25° or less. is more preferable. Since the metal ink has a high affinity for the region containing the thermoplastic resin of the base material, the metal ink may spread too much on the base material. is suppressed from spreading too much. Moreover, excessive repelling of the metal ink on the substrate is also suppressed. Therefore, it becomes easy to form an elaborate metal pattern.

The contact angle can be measured from the lateral direction of the droplet using a contact angle meter (eg, DM-501 manufactured by Kyowa Interface Science Co., Ltd.). For example, the metal ink is applied on the substrate, and the contact angle of the metal ink to the substrate is measured after 1 minute at 25°C. The contact angle can be measured by observation from the side using a contact angle meter.

The surface tension of the metal ink is preferably 25 mN/m or more and 40 mN/m or less, more preferably 27 mN/m or more and 37 mN/m or less. When the surface tension is within this range, the metal ink is prevented from spreading too much, and the metal ink is also prevented from being repelled excessively, which is advantageous in obtaining an elaborate metal pattern.

Such a metal ink has high stability of the metal colloid in the metal ink, and can suppress dissolution of the base material when applied onto a region containing the thermoplastic resin of the base material. The base material may contain at least a thermoplastic resin in the area to which the metal ink is applied, and the area of the base material to which the metal ink is applied is preferably made of a thermoplastic resin.

The HSP dD of the thermoplastic resin (specifically, the area portion containing the thermoplastic resin of the substrate) is, for example, 15 or more and 25 or less, preferably 16 or more and 22 or less, and 17 or more and 19 or less. It is even more preferable to have dP is, for example, 0 or more and 20 or less, preferably 0 or more and 15 or less, and more preferably 0 or more and 11 or less. dH is, for example, 1 or more and 23 or less, preferably 1 or more and 15 or less, and more preferably 1 or more and 7 or less. Any combination of these dD, dP, and dH ranges can be used. The HSP of the thermoplastic resin (specifically, the area portion containing the thermoplastic resin of the substrate) is not limited to such a range, but when each term is within such a range, the distance It is easy to adjust Ds, and it is easy to obtain the effect of suppressing the dissolution of the base material (thermoplastic resin).

Examples of the thermoplastic resin contained in the substrate to which the metal ink is applied include polycarbonate resin, styrene resin (polystyrene (PS), acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), etc.), olefin resins, vinyl resins, acrylic resins, polyacetal resins, polyamide resins, polyester resins (that is, thermoplastic polyester resins), halogen-containing resins, polyphenylene ether resins, polyphenylene sulfide resins, and the like. Examples of polyester resins include aromatic polyesters (polyalkylene arylates (polyethylene terephthalate, polybutylene terephthalate, etc.), etc.). The substrate may contain one kind of these thermoplastic resins, or two or more kinds thereof. Among them, polycarbonate resins, styrene resins, and polyester resins are preferred. These thermoplastic resins are easy to mold and have high strength, so they are suitable as materials for base materials when forming metal patterns, but they are easily dissolved in dispersion media such as those used for metal inks. . In the present invention, dissolution of the base material (thermoplastic resin) can be suppressed even when the metal ink is applied to the area of the base material containing the thermoplastic resin.

[Method for producing metal ink]
The metal ink is prepared by preparing a dispersion medium having an HSP distance Dc of 10 MPa ^0.5 or less and an HSP distance Ds of 10 MPa ^0.5 or more, and preparing a metal ink in which a metal colloid is dispersed in the dispersion medium. and can be obtained by a manufacturing method comprising:

(Dispersion medium preparation step)
In this step, a dispersion medium used for preparing the metal ink is prepared. Specifically, a dispersion medium is prepared such that the distance Dc and the distance Ds are within the above ranges according to the respective HSPs of the thermoplastic resin contained in the metal colloid and the metal pattern forming region of the substrate. For example, the distance Dc and the distance Ds are adjusted by selecting the type of dispersion medium and/or adjusting the mixing ratio of a plurality of dispersion mediums. Further, the dispersion medium once determined may be prepared so that the distance Dc and the distance Ds are within the above range, and the dispersion medium is mixed by mixing a plurality of dispersion mediums according to the mixing ratio of the dispersion medium once determined. may be prepared.

By including a dispersing medium preparation step in the manufacturing method, it is possible to ensure high stability of the metal colloid in the obtained metal ink, and to apply the base material onto the thermoplastic resin-containing region of the base material. Dissolution of the material (thermoplastic resin) can be suppressed.

(Preparation process of metal ink)
In this step, it suffices if the metal ink in which the metal colloid is dispersed in the dispersion medium can be prepared. For example, a metal ink can be prepared by mixing the components of the metal ink (eg, metal particles and a dispersion medium). A known stirrer, mixer, or the like is used to more uniformly disperse the components.

The mixing order of the components is not particularly limited. For example, some ingredients may be premixed and the remaining ingredients may be added and mixed further. Each component may be added at once, or may be added in multiple portions. The dispersant may be added when mixing the metal particles and the dispersion medium, or may be mixed with the dispersion medium after being coordinated with the metal particles. The timing of adding other components (polymerization-reactive compound, polymerization initiator, and/or additives, etc.) is also not particularly limited.

In a preferred embodiment, the step of preparing the metal ink includes a step of coordinating a dispersant to metal particles to prepare a metal colloid, and a step of dispersing the metal colloid in a dispersion medium to obtain the metal ink.

In the step of preparing the metal colloid, for example, the dispersant can be coordinated to the metal particles by mixing the metal particles, the dispersant, and the liquid medium. If necessary, other components (such as additives (binders, etc.)) may be added in this step.

As the liquid medium, a medium (solvent) that is liquid at room temperature (25° C.) that dissolves the dispersant is preferable. The liquid medium may be selected according to the type of dispersant. As the liquid medium, aliphatic alcohols, aliphatic esters and the like are preferable, but not limited to these. The liquid medium may be used singly or in combination of two or more. Mixing may be performed under heating as needed. The produced metal colloid is separated from the liquid medium by centrifugation or the like and recovered.

In the step of obtaining the metal ink, a metal colloid and a dispersion medium are mixed. If necessary, other components (polymerization-reactive compound, polymerization initiator, and/or additives, etc.) may be added in this step. In order to more uniformly disperse the metal colloid in the dispersion medium, a known stirrer, mixer, or the like is used in this step.

[Method for producing substrate with metal pattern]
A method for manufacturing a base material having a metal pattern includes the step of applying a metal ink onto the base material to form a metal pattern. The metal pattern forming step can include a step of applying a metal ink to a substrate to form a coating film, and a step of baking the coating film to form a metal pattern (metal film). One aspect of the present invention also includes the use of the metallic ink described above in the present manufacturing method and the use of the metallic ink described above for coating onto a substrate to form a metallic pattern.

As mentioned above, the substrate contains a thermoplastic at least in the areas where the metallic ink is applied. It is preferable that at least the area of the base material to be coated with the metal ink is made of a thermoplastic resin. For example, the substrate may include a surface (or main surface) on which the metal ink is applied and a layer containing a thermoplastic resin in the vicinity thereof, or the entire substrate may contain a thermoplastic resin. . The base material may have a layer containing a thermoplastic resin over the entire surface (or main surface) of the base material on which the metal ink is applied, or may have it partially.

The material of the substrate for the layer containing the thermoplastic resin is not particularly limited, and examples thereof include glass, silicon, and/or cured resin.

(Metal pattern forming step)
(Coating film forming step)
In the coating film forming step, a metal ink is applied to the surface of the substrate. Application of the metal ink is not particularly limited, and can be performed by a known application method (spin coating, spray coating, blade coating, screen printing, inkjet, etc.). Moreover, the coating film may be a pattern film such as a wiring or hole-filling film, or may be a solid film.

The metal inks described above are suitable for non-contact jet coating (inkjet method, etc.) because of the high stability of the metal colloid in the metal inks. In addition, application by an inkjet method means non-contact jet application. Non-contact jet coating is a coating method that uses air pressure, spring elasticity, vibration of a piezo element (piezoelectric element), etc. to fly metal ink onto an ink adherend. Application is performed using a non-contact jet dispenser. Non-contact jet coating is also suitable for the formation of wiring patterns on the surface of three-dimensional objects, the production of multilayer substrates, and the like. Here, the three-dimensional structure refers to a material that serves as a base material for a circuit member having a three-dimensional structure.

(Drying process)
Prior to the baking step, the base material having the coating film obtained in the coating film forming step may be dried, if necessary. Drying conditions can be appropriately determined according to the constituent components of the metal ink. It is preferable to remove volatile components (dispersion medium, etc.) in the drying step.
The drying temperature is not particularly limited, and may be carried out at a temperature that can remove volatile components. The drying temperature is desirably lower than the firing temperature, which will be described later.

(Baking process)
In the baking step, the substrate having the coating film obtained in the coating film forming step is baked. The baking causes the metal particles contained in the coating film to fuse together, and the resistance of the obtained metal film can be greatly reduced. In the case of metal nanoparticles, due to the nano-size effect of the particles, they are fused at a temperature lower than the melting point of the metal, so even if the sintering is performed at a relatively low temperature, the effect of sufficiently reducing the resistance of the metal film can be obtained. .

Firing can be appropriately selected according to the type of metal of the metal particles, and may be performed, for example, at 50° C. or higher and 250° C. or lower, 100° C. or higher and 250° C. or lower, or 150° C. or higher and 250° C. or lower. A metal film can be formed even under mild conditions by using an amine having a small number of carbon atoms as a dispersant. In this case, the firing temperature is preferably 150° C. or lower (for example, 50° C. or higher and 150° C. or lower), and may be 100° C. or higher and 150° C. or lower.

Firing may be performed in the presence of a reducing agent, if desired.
Firing may be performed in an inert gas atmosphere or in the air.
The firing time is not particularly limited, but may be, for example, 5 minutes or more and 120 minutes or less.

When using a polymerization reaction initiator that is activated by the action of heat, it may be activated by heat applied in the drying step and/or the baking step to allow the polymerization of the polymerizable reactive compound to proceed. When using an initiator that is activated by the action of light as the polymerization initiator, it is preferable to irradiate the coating film with light at an appropriate stage from the formation of the coating film to the baking step. You may perform a drying process and/or a baking process under light irradiation.

[Example]
EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

<<Examples 1 to 10 and Comparative Examples 1 to 5>>
(1) Production of Metal Colloid 20 g of silver nitrate, 100 g of isobutanol, and 100 g of dodecylamine (dispersant) were mixed. The resulting mixture was heated to a temperature of 100° C. and refluxed for 5 hours. The solid content in the resulting mixture was collected by centrifugation. The recovered solid content was washed with methanol three times, and then centrifuged to recover silver nanoparticles with dodecylamine coordinated thereto. The mass ratio of the silver nanoparticles and the dodecylamine coordinated to the silver nanoparticles was 100:0.5.

A dispersion paste was prepared by dispersing the recovered silver nanoparticles in diethylene glycol monobutyl ether using a triple roll. The resulting dispersion paste was applied to a base material by spin coating, and SEM photographs of the silver nanoparticles were taken. In this captured image, the average particle size of the silver nanoparticles calculated by the method described above was about 40 nm.

(2) Preparation of metal ink The metal colloid containing silver nanoparticles recovered in (1) above was dispersed in the dispersion medium shown in Table 2 using a homogenizer, and then filtered using a disk filter with an opening of 1 μm. It was filtered and a metal ink was prepared. The concentration of metal colloid in the metal ink was set to 40% by mass.

(3) Evaluation The following evaluation was performed.
(a) Measurement of HSP and Calculation of Distances Dc and Ds Using the metal ink, the HSP of each of the dispersion medium and the metal colloid was determined according to the procedure described above. Table 2 shows the HSP of the dispersion medium. The metal colloid HSP had a dD of 19.5, a dP of 4.1, and a dH of 8.8.
In addition, a plate-like substrate (substrate A) made of polycarbonate resin (Panlite L-1225Y, manufactured by Teijin Limited) and an acrylonitrile styrene-butadiene resin (UMG ABS EX18A 11001, manufactured by UMG ABS) were formed. For each of the plate-shaped substrates (substrate B), the HSP was obtained by the procedure described above. Both substrates had a dD of 18.4, a dP of 10.1, and a dH of 2.4. HSPiP 4th Edition 4.1.07 was used as HSP calculation software.
Distances Dc and Ds were calculated from these HSPs.

(b) Dispersion stability After the metal ink was stored at 25°C for one month, the presence or absence of precipitation was visually observed and evaluated according to the following criteria.
A: Precipitation is not confirmed.
B: Precipitation is confirmed.

(c) Volume Resistivity A metal ink was applied to each of the substrates A and B using a bar coater, and heated and baked at 120° C. for 30 minutes using a blower dryer to form a metal pattern. The volume resistivity (μΩ·cm) of the formed metal pattern was measured by the four-terminal method using a resistivity meter (Mitsubishi Chemical Analytic Tech, Loresta).
Table 2 shows the evaluation results of (a) to (c).

As shown in Table 2, in the examples in which the HSP distance Dc was 10 MPa ^0.5 or less and the distance Ds was 10 MPa ^0.5 or more, high dispersion stability of the metal colloid could be secured. Also, the volume resistivity was lowered. It is considered that this is because the dissolution of the substrate by the metal ink was suppressed.

On the other hand, in Comparative Examples 1 and 2 in which the HSP distance Dc exceeded 10 MPa ^0.5 , precipitation was confirmed in the metal ink after storage, and the dispersion stability of the metal colloid was lowered. Moreover, in Comparative Examples 3 to 5, in which the distance Ds is less than 10 MPa ^0.5 , the volume resistivity was extremely large. It is considered that this is because the dissolution of the substrate became remarkable.

In the above examples, an example using a substrate containing a polycarbonate resin and a styrene resin was shown, but if the Dc and Ds of HSP are 10 MPa ^0.5 or less, a polyester resin (e.g., polybutylene terephthalate resin (e.g., It was also confirmed that the same or similar effects as those of the above examples can be obtained even when a base material containing other thermoplastic resin such as DURANEX 2002)) manufactured by Wintech Polymer Co., Ltd. is used.

While the invention has been described in terms of presently preferred embodiments, such disclosure is not to be construed in a limiting sense. Various alterations and modifications will no doubt become apparent to those skilled in the art to which the invention pertains after reading the above disclosure. Therefore, the appended claims are to be interpreted as covering all variations and modifications without departing from the true spirit and scope of the invention.

According to the metal ink according to the embodiment of the present invention, the dispersion stability of the metal colloid is high, and dissolution of the thermoplastic resin can be suppressed. Therefore, it is suitable for forming a metal pattern such as a wiring pattern on a substrate having a region containing a thermoplastic resin. Moreover, it can also be used for forming a wiring pattern on the surface of a three-dimensional model, manufacturing a multilayer substrate, and the like.

Claims (13)

A metal ink for forming a metal pattern by being applied onto a substrate,
containing a metal colloid and a dispersion medium,
The metal colloid contains metal particles made of silver or a silver alloy,
The dispersion medium contains at least one selected from the group consisting of alcohols, esters, and ethers,
The base material contains a thermoplastic resin at least in a region where the metal pattern is formed,
The distance Dc of the Hansen solubility parameter between the dispersion medium and the metal colloid is 8.6 MPa ^0.5 or less,
The distance Ds of the Hansen solubility parameter between the dispersion medium and the thermoplastic resin is 10.5 . A metal ink having a pressure of 0 MPa ^0.5 or more. 2. The metallic ink according to claim 1, wherein said thermoplastic resin includes at least one selected from the group consisting of polycarbonate resin, styrene resin, and polyester resin. 3. The metallic ink according to claim 1 , wherein the distance Dc is 3 ^MPa0.5 or more. The metal ink according to any one of claims 1 to 3 , wherein the distance Ds is 15 ^MPa0.5 or less. Any one of claims 1 to 4 , wherein the dispersion term dD of the Hansen solubility parameter of the dispersion medium is 10 or more and 20 or less, the polar term dP is 10 or less, and the hydrogen bonding term dH is 20 or less. A metal ink according to the above paragraph. The dispersion term dD of the Hansen solubility parameter of the thermoplastic resin is 15 or more and 25 or less, the polar term dP is 0 or more and 20 or less, and the hydrogen bonding term dH is 1 or more and 23 or less, claims 1 to 6. The metal ink according to any one of 5 . The metal colloid includes metal nanoparticles as the metal particles and a dispersant coordinated to the metal nanoparticles,
The metal ink according to any one of claims 1 to 6 , wherein the metal nanoparticles have an average particle size of 5 nm or more and 400 nm or less. 8. The metallic ink of Claim 7 , wherein the dispersant comprises a _C4-16 alkylamine. The metal ink according to any one of claims 1 to 8 , wherein the proportion of the dispersion medium in the metal ink is 25% by mass or more and 95% by mass or less. A method for producing a metal ink containing a metal colloid and a dispersion medium and applied onto a substrate to form a metal pattern, comprising:
The metal colloid contains metal particles made of silver or a silver alloy,
The dispersion medium contains at least one selected from the group consisting of alcohols, esters, and ethers,
The base material contains a thermoplastic resin at least in a region where the metal pattern is formed,
The distance Dc of the Hansen solubility parameter between the dispersion medium and the metal colloid is 8.6 MPa ^0.5 or less, and the distance Ds of the Hansen solubility parameter between the dispersion medium and the thermoplastic resin is 10 MPa . preparing the dispersion medium having a pressure of 0 MPa ^0.5 or higher;
and preparing a metal ink in which the metal colloid is dispersed in the dispersion medium. 11. The method for producing a metallic ink according to claim 10 , wherein the thermoplastic resin contains at least one selected from the group consisting of polycarbonate resin, styrene resin, and polyester resin. A step of applying a metal ink on the base material to form a metal pattern,
The base material contains a thermoplastic resin at least in a region where the metal pattern is formed,
The metal ink contains a metal colloid and a dispersion medium,
The metal colloid contains metal particles made of silver or a silver alloy,
The dispersion medium contains at least one selected from the group consisting of alcohols, esters, and ethers,
The distance Dc of the Hansen solubility parameter between the dispersion medium and the metal colloid is 8.6 MPa ^0.5 or less,
The distance Ds of the Hansen solubility parameter between the dispersion medium and the thermoplastic resin is 10.5 . A method for producing a substrate having a metal pattern, wherein the pressure is 0 MPa ^0.5 or more. 13. The method of manufacturing a substrate having a metal pattern according to claim 12 , wherein the thermoplastic resin includes at least one selected from the group consisting of polycarbonate resin, styrene resin, and polyester resin.