JP2013230416A - Particle dispersant, particle dispersion ink, and conductive pattern formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle dispersant, a particle dispersion ink excellent in adhesion with a substrate and capable of forming a conductive pattern with sintering treatment, and a conductive pattern formation method.SOLUTION: A solid polymer compound that consists of a copolymer of a monomer selected from acrylic acid tetrahydrofurfuryl or methacrylic acid tetrahydrofurfuryl and a monomer having an adsorbent functional group that adsorbs the particle is made to a particle dispersant to disperse particles to a solvent. A particle dispersion ink contains the dispersant, which is sintered after applied on a substrate to form a conductive pattern.

Description

  The present invention relates to a metal particle dispersant for dispersing metal particles in a solvent, a metal particle-dispersed ink formed using the same, and a conductive pattern forming method.

  Conventionally, photolithography and etching are mainly used as means for forming a conductive pattern such as a wiring or an antenna on a base material, but there are many problems in terms of the number of process steps and material use efficiency. Manufacturing costs are high. In order to reduce such manufacturing costs, attempts have been made to form a conductive pattern using a printing method such as an inkjet printing method (see, for example, Patent Document 1).

  In the ink jet printing method, an ink that becomes a conductor by baking treatment after film formation is used. After the ink is printed on a substrate by the ink jet method, a conductive pattern is formed by drying and baking. When the ink jet printing method is used, the electrode pattern can be directly drawn, so that the material usage rate increases, and there is a possibility that the manufacturing process can be simplified and the cost can be reduced.

  As the ink used in the ink jet printing method, a so-called nano metal ink in which metal fine particles, particularly particles having a primary particle size of the order of nm is dispersed in a liquid is often used. In the nanometal ink, since the particle size of the metal fine particles is on the order of nm, the melting point is lower than that of the bulk body, the nanoparticles are fused at a firing temperature lower than the melting point of the bulk, and the electrode pattern becomes a conductor (for example Patent Document 2).

  In the nanometal ink, a dispersion stabilizer is provided around the fine metal particles so that the fine metal particles do not aggregate in the liquid. Since the dispersion stabilizer is an organic material, the dispersion stabilizer is removed by oxidation and decomposition by heating after applying the nanometal ink to the substrate and drying it. Furthermore, the metal particles are fused to each other to exhibit conductivity, and a conductive wiring corresponding to the coating pattern is formed. However, the adhesion to the substrate is not always sufficient. In order to solve this problem, a binder resin can be added to the ink. However, in this case, there is a problem that the binder resin becomes a factor that impedes conductivity.

  In addition, as a metal fine particle dispersing agent, the hyperbranched polymer which has an amino functional group or an imino functional group at the terminal is proposed (refer patent document 3). In this proposal, it is described that metal fine particles are prepared by reducing metal ions with a metal salt reducing agent in a state where the metal fine particle dispersant is added.

  In addition, metal fine particles are dispersed in the ethylenically unsaturated monomer by reducing the metal compound in a mixture of an aqueous metal compound solution, a liquid ethylenically unsaturated monomer and a pigment dispersant and then removing the aqueous phase. There has been proposed a method for producing a fine metal particle dispersion (see Patent Document 4). It is said that a conductive ink having good fluidity and stability can be obtained by using this metal fine particle dispersion.

Also, nano-shaped transition metal particles can be synthesized, separated, and reconstituted in an organic matrix by a process that includes adding an acrylate or methacrylate monomer or oligomer, or polyacrylate or polymethacrylate, and a reducing agent to an aqueous solution of a transition metal salt. A dispersion method has been proposed (see Patent Document 5). This technique is said to be useful as an IR absorber in architectural or automotive sheet glass.
However, in the prior art, it cannot be said that the adhesion to the substrate and the electrical conductivity are sufficient, and further improvement in characteristics is required.

  The present invention has been made in view of the above prior art, and has excellent adhesion to a substrate by using a metal particle dispersant that can favorably disperse metal particles such as metal nanoparticles and the metal particle dispersant. And it aims at providing the conductive pattern formation method using the metal particle dispersion ink which can form a conductive pattern by sintering processing (baking), and a metal particle dispersion ink.

As a result of intensive studies on the means for solving the above problems, the inventors of the present application are able to satisfactorily disperse metal particles, such as metal nanoparticles, in a solid polymer compound comprising a specific copolymer. It was found that the metal particle-dispersed ink using the ink adheres well to the substrate, exhibits conductivity by sintering treatment (firing), forms a conductive pattern, and can maintain the adhesion even after firing. The present invention has been reached.
That is, the above-mentioned problem is a metal particle dispersant for dispersing metal particles in a solvent, and the metal particle dispersant is tetrahydrofurfuryl acrylate represented by the following structural formula (I), or the following structural formula (II ), A solid polymer compound comprising a copolymer of a monomer selected from tetrahydrofurfuryl methacrylate and a monomer having an adsorptive functional group adsorbed on the metal particles. This is solved by a metal particle dispersant.

Further, the object is a metal particle-dispersed ink for forming a conductive pattern on a base material comprising metal particles, a solvent, and a metal particle dispersant, wherein the metal particle dispersant is claimed in claims 1 to 3. This is solved by a metal particle-dispersed ink, which is the metal particle dispersant described in any one of 5 above.
Moreover, the said subject has the process of apply | coating the metal particle dispersion ink of Claim 6 on a base material, and the process of expressing electroconductivity by sintering the ink apply | coated on the said base material, It is characterized by the above-mentioned. This is solved by the conductive pattern forming method.

The metal particle dispersant of the present invention includes a monomer selected from tetrahydrofurfuryl methacrylate represented by the structural formula (I) or tetrahydrofurfuryl acrylate represented by the structural formula (II), and the metal Since it is a solid polymer compound composed of a copolymer with a monomer having an adsorptive functional group that adsorbs to particles, metal particles such as metal nanoparticles can be well dispersed in a solvent.
In addition, if a metal particle-dispersed ink comprising metal particles, a solvent, and the metal particle dispersant of the present invention is used, the adhesion to the substrate is excellent, and conductivity is exhibited by sintering treatment (firing).
In addition, according to the conductive pattern forming method, which includes the step of applying the metal particle-dispersed ink on the substrate and the step of expressing the conductivity of the ink applied on the substrate by sintering, the conductive pattern is It is formed and adhesion can be maintained after firing.

  As described above, the metal particle dispersant in the present invention is a metal particle dispersant for dispersing metal particles in a solvent, and the metal particle dispersant is tetrahydrofurfuryl acrylate represented by the following structural formula (I). Or a solid polymer comprising a copolymer of a monomer selected from tetrahydrofurfuryl methacrylate represented by the following structural formula (II) and a monomer having an adsorptive functional group adsorbed on the metal particles. It is a molecular compound.

  The tetrahydrofurfuryl acrylate is sometimes referred to as “tetrahydrofurfuryl acrylate” or “acrylic acid (tetrahydrofuran) -2-ylmethyl”. In addition, tetrahydrofurfuryl methacrylate may be referred to as “tetrahydrofurfuryl methacrylate” or “methacrylic acid (tetrahydrofuran) -2-ylmethyl”.

The metal particle dispersant (abbreviation, “dispersant”) has good compatibility with a solvent described later, for example, a glycol-based, glycol ether-based or glycol ester-based organic solvent. Since the dispersant has an adsorptive functional group that adsorbs to the metal particles, it effectively adheres to the surface of the metal particles. At that time, the dispersant is a solid polymer compound and forms a self-supporting film alone. Is possible. In addition, the steric hindrance due to the tetrahydrofurfuryl group in the copolymer can prevent aggregation of metal particles and maintain dispersion stability. Moreover, the tetrahydrofurfuryl group in a dispersing agent (copolymer) has a high adhesion effect with a base material.
As described above, in order to function as a metal particle dispersant, it is necessary to have some adsorptivity to be adsorbed on metal particles. However, a monomer having such a functional group is a single monomer having a tetrahydrofurfuryl group. When copolymerized with the monomer, the polymer compound as the copolymer is adsorbed on the particle surface and has a high steric effect due to the polymer chain extending therefrom. Due to the steric hindrance of the polymer chain, the metal particles hardly aggregate in the metal particle dispersion.
Examples of the functional group having adsorptivity to the metal particles include a nitrogen-containing heterocyclic group and an ionic functional group. For introduction of these groups, a monomer having the corresponding group is selected and used, and tetrahydrofurfuryl acrylate represented by the above structural formula (I) or tetrahydrofurfur methacrylate represented by the above structural formula (II) is used. It is necessary to copolymerize with a monomer selected from furyl.
The ratio of each monomer in the copolymerization can be appropriately determined from the balance between the adsorptivity of the dispersant to the particles and the suppression of aggregation between the particles. Further, the means can be controlled by the charging ratio of each monomer at the time of polymerization.
The composition ratio (parts by weight) of each monomer [monomer selected from tetrahydrofurfuryl methacrylate or tetrahydrofurfuryl acrylate] and [monomer having an adsorptive functional group] in the copolymer is: It is preferable that it is 90: 10-99.9: 0.1.
In the case of a polymer compound that does not contain a monomer having an adsorptive functional group and is composed only of a monomer selected from tetrahydrofurfuryl methacrylate or tetrahydrofurfuryl acrylate, it can be adsorbed to metal particles. The aggregate of metal particles in the solvent cannot be crushed.
On the other hand, in the case of a polymer compound that does not contain a monomer selected from tetrahydrofurfuryl methacrylate or tetrahydrofurfuryl acrylate and only has a monomer having an adsorptive functional group, the attractive force between particles is inhibited. The steric hindrance is not obtained, and the particles reaggregate instantly.

Here, as a monomer which has a nitrogen-containing heterocyclic group which adsorb | sucks with respect to a metal particle, vinylpyrrolidone, vinylimidazole, acryloyl morpholine, acryloyl oxazolidinone, acrylate-N-succinimidyl etc. are mentioned.
A monomer having an ionic functional group is also preferably used. Such an ionic functional group is not limited as long as it has ionicity, and is selected from, for example, an amino group, a carboxyl group, a sulfo group (sulfonic acid group), and a phospho group (phosphonic acid group). A group is preferably selected.

The ionic functional group has a high adsorption effect on the surface of metal particles such as nano metal particles or the surface of the metal oxide film, and functions even when a small amount of metal particle dispersant is added. Examples of such a monomer having an ionic functional group include the following.
Examples of the monomer having an amino group include N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) ) Acrylate, N, N-dibutylaminoethyl acrylate, N, N-di-tert-butylaminoethyl acrylate, N-phenylaminoethyl methacrylate, N, N-diphenylaminoethyl methacrylate, aminostyrene, dimethylaminostyrene, N- Methylaminoethylstyrene, dimethylaminoethoxystyrene, diphenylaminoethylstyrene, N-phenylaminoethylstyrene, 2-N-piperidylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinyl 6-methylpyridine and the like.
As the monomer having a carboxyl group, (meth) acrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, cinnamic acid, crotonic acid, vinyl benzoic acid, 2-methacryloxyethyl succinic acid 2-methacryloxyethyl maleic acid, 2-methacryloxyethyl hexahydrophthalic acid, 2-methacryloxyethyl trimellitic acid, and the like.
Examples of the monomer having a sulfo group (sulfonic acid group) include vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, and 2-acrylamido-2-methylpropane sulfonic acid.
Examples of the monomer having a phospho group (phosphonic acid group) include (meth) acryloxypropylphosphonic acid.

As a solvent used when dispersing metal particles such as nano metal particles in a solvent using the metal particle dispersant of the present invention, from the viewpoint of the compatibility of the tetrahydrofurfuryl group in the copolymer constituting the dispersant. Glycol-based, glycol ether-based or glycol ester-based organic solvents are preferred. As described above, the tetrahydrofurfuryl group can prevent aggregation of particles due to the steric hindrance of the polymer chain in these solvents, and can maintain dispersion stability.
Examples of the glycol-based organic solvent include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol.
Examples of glycol ether organic solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethyl Butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol Mono butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, glycol ethers such as dipropylene glycol monopropyl ether.
Examples of the glycol ester organic solvent include glycol esters such as diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

  As a method of dispersing metal particles in a solvent using a metal particle dispersant, known stirring means such as a homogenizer, a ball mill, a sand mill, and an attritor can be applied. If necessary, mixing and stirring can be performed under conditions such as heating and applying ultrasonic vibration.

The metal particles dispersed in the solvent using the metal particle dispersant in the present invention are not particularly limited as long as they have conductivity, and may be nano-sized metal particles. Examples of such metal particles include copper (Cu), silver (Ag), aluminum (Al), and gold (Au). In particular, Cu is preferably used because it has a good balance between conductivity and cost.
When nano-sized metal particles are used, the particle size of the metal fine particles is on the order of nanometers. Therefore, the nanoparticles tend to fuse together at a firing temperature lower than the melting point of the bulk and become a conductor. Expected to be capable of forming a fine pattern when used, and having a relatively thick film having a higher metal concentration in the ink than that obtained from the reaction of the metal salt.

The metal particle-dispersed ink composed of the metal particle dispersant of the present invention, metal particles, and a solvent is useful as an ink for forming a conductive pattern on a substrate. The metal particle dispersant can be cast into a single solution on a base material and has excellent adhesion to the base material.
That is, the conductive pattern is formed by a step of applying a metal particle-dispersed ink on a substrate and a step of developing conductivity by sintering the ink applied on the substrate.
As an application means used in the step of applying the metal particle-dispersed ink on the substrate, an ink jet method is preferable in terms of direct patterning, but there is no particular limitation as long as it is a printing method using ink.

The sintering process is a process required to eliminate the metal particle dispersant adsorbed on the metal particle surface or the metal oxide film surface after removing the solvent, and to fuse the metal particles together to develop conductivity. is there. In order to fuse these metal particles, it is necessary to apply energy, and it is possible to apply thermal energy mainly, but there is no particular limitation.
For example, the sintering can be performed by light baking by light energy irradiation. In other words, the metal particles are fired at a room temperature to a low temperature by irradiation with light energy. The low temperature here refers to a temperature of about 200 ° C. or less at which the substrate is not damaged by heat. As the light source, known light irradiation means capable of applying energy, such as a xenon lamp, can be used. In addition, it is preferable to evaporate a solvent by preheating before light irradiation.
Further, the sintering can be performed by firing in an oxygen-free atmosphere. Due to the absence of oxygen, the fired metal is not oxidized and the conductivity is improved. As such an atmosphere, an atmosphere substituted with an inert gas such as nitrogen or argon is preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to the following Example. The parts used in the following examples are all parts by weight.

[Synthesis example of polymer compound (metal particle dispersant)]
(Examples 1-5)
In a reaction vessel equipped with a stirrer, thermometer and reflux condenser, 300 parts of ethanol was taken and heated to 60 ° C. under a nitrogen purge. Into this, a solution composed of monomers (monomer 1 and monomer 2) having the composition shown in Table 1 below and 1 part of azobisdimethylvaleronitrile as a polymerization initiator was dropped over 1 hour. Subsequently, stirring was continued for 5 hours at the same temperature to complete the reaction. When ethanol of the solvent was evaporated from the obtained resin solution with an evaporator, an elastic solid polymer (each polymer compound of Examples 1 to 5: metal particle dispersant) was obtained.
(Comparative Examples 1-4)
In the same manner as in the above Examples, each polymer compound of Comparative Examples 1 to 4 was obtained using one monomer (only monomer 1 or only monomer 2) shown in Table 1 below.

Before preparing the ink, as a preliminary experiment, using the polymer compounds obtained in Examples 1 to 5 and Comparative Examples 1 to 4, nano copper particles (QuantumSphere QSI-Nano Copper Powder) were used as solvents (diethylene glycol monobutyl ether acetate). In addition to the above, the mixture was stirred and mixed with a high-speed mixer (Primix Co., Ltd. Philmix), and the dispersibility was examined. As a result, those using the polymer compounds of Examples 1 to 5 all had good dispersion of the nanocopper particles, and the nanocopper particles did not aggregate. On the other hand, those using the polymer compounds of Comparative Examples 1 and 2 were poorly dispersed in the nano copper particles, and the particles immediately settled. In addition, those using the polymer compounds of Comparative Examples 3 and 4 immediately settled.
From these results, the following inks were prepared only by using the polymer compounds of Examples 1 to 5, and each ink was evaluated.

[Example of ink preparation]
(Examples 6 to 10)
According to the composition shown in Table 2 below, each metal particle dispersant synthesized in Examples 1 to 5 and nano copper particles (QuantumSphere QSI-Nano Copper Powder) were added to each solvent, and ultrasonic dispersion was performed for 10 minutes as a pre-dispersion. Then, the mixture was dispersed for 10 minutes with a high-speed mixer (Primics Co., Ltd. Philmix). The obtained slurry was passed through a 1 μm filter to remove coarse particles, thereby obtaining inks (Examples 6 to 10) having an average particle diameter shown in Table 2 below. In any of the inks, the copper particles were uniformly dispersed, and no abnormal aggregation state was observed even after being left standing.

[Formation of conductive thin film (conductive pattern) by sintering]
(Examples 11 to 15)
Next, the ink prepared in Examples 6 to 10 was spin-coated on a glass substrate, the solvent was evaporated on a hot plate at 120 ° C., and then introduced for 1 hour at 300 ° C. under introduction (flow) of nitrogen gas in an electric furnace. A conductive thin film (conductive pattern) was formed by heating and baking treatment (sintering treatment). The electrical resistance and film thickness of the heat-fired conductive thin film were measured, and the volume resistivity was calculated.
Moreover, peeling of the conductive thin film from the substrate was evaluated by a tape peeling test. In the tape peeling test, an adhesive tape (“CT24”: manufactured by Nichiban Co., Ltd .; width: 24 mm) was attached to the conductive thin film, and the presence or absence of peeling of the ink thin film was visually evaluated by peeling.
Table 3 shows the evaluation results of peeling of the conductive thin film by the volume resistivity and the tape peeling test.

[Example of formation of conductive thin film (conductive pattern) by light firing]
(Examples 16 to 20)
The inks of Examples 6 to 10 were spin-coated on a PET (polyethylene terephthalate) film, the solvent was evaporated on a hot plate at 120 ° C., and then irradiated with a xenon lamp for 1 minute (light baking by light energy irradiation). A conductive thin film (conductive pattern) was formed. The electrical resistance and film thickness of the photofired conductive thin film were measured, and the volume resistivity was calculated.
Moreover, the tape peeling test was implemented on the conditions similar to Examples 11-15, and peeling from the board | substrate of an electroconductive thin film was evaluated.
The results of peeling evaluation of the conductive thin film by the volume resistivity and the tape peeling test are shown in Table 4 below.

From the above evaluation results, the metal particle dispersant of the present invention can satisfactorily disperse metal particles such as metal nanoparticles, and the metal particle-dispersed ink prepared using the metal particle dispersant of the present invention has a substrate and A conductive thin film (conductive pattern) that exhibits excellent electrical conductivity is formed by sintering treatment such as heat firing or light firing, and maintains good adhesion to the substrate even after firing. I found out that
That is, a conductive ink can be formed by using the metal particle dispersant of the present invention. Wiring patterns of various electronic devices can be formed by a printing method using a conductive ink. In particular, when nano metal particles are used, a fine pattern can be formed. For example, if an ink jet method is adopted as a printing method, direct patterning is possible, and there is a possibility that the material usage rate can be improved, the manufacturing process can be simplified and the cost can be reduced.

JP 2008-60544 A Special table 2010-528428 gazette JP 2011-21122 A Japanese Patent No. 4636661 JP 2010-540769 A

Claims (9)

A metal particle dispersant for dispersing metal particles in a solvent, wherein the metal particle dispersant is tetrahydrofurfuryl acrylate represented by the following structural formula (I) or methacrylic acid represented by the following structural formula (II) A metal particle dispersant characterized by being a solid polymer compound comprising a copolymer of a monomer selected from tetrahydrofurfuryl and a monomer having an adsorptive functional group adsorbed on the metal particles .

  The composition ratio (parts by weight) of each monomer [monomer selected from tetrahydrofurfuryl methacrylate or tetrahydrofurfuryl acrylate] and [monomer having an adsorptive functional group] in the copolymer is as follows. 90: 10-99.9: 0.1, The metal particle dispersant according to claim 1.   The metal particle dispersant according to claim 1, wherein the adsorptive functional group is an ionic functional group.   The metal particle dispersant according to claim 3, wherein the ionic functional group is at least one group selected from an amino group, a carboxyl group, a sulfo group, and a phospho group.   The metal particle dispersant according to claim 1, wherein the metal particles are metal nanoparticles.   A metal particle-dispersed ink comprising a metal particle, a solvent, and a metal particle dispersant, and forming a conductive pattern on a substrate, wherein the metal particle dispersant is any one of claims 1 to 5. A metal particle-dispersed ink, characterized by being a metal particle dispersant.   A conductive pattern formation comprising: a step of applying the metal particle-dispersed ink according to claim 6 on a substrate; and a step of developing conductivity by sintering the ink applied on the substrate. Method.   The conductive pattern forming method according to claim 7, wherein the sintering is light baking by light energy irradiation.   The method for forming a conductive pattern according to claim 7 or 8, wherein the sintering is firing in an oxygen-free atmosphere.