JP2022099136A - Ink for writing implements - Google Patents

Abstract

To provide an ink for writing implements, and writing implements using the ink for writing implements.SOLUTION: An ink for writing implements contains metal fine particles A, a polymer dispersant B, and a compound C having a metal adsorption group and a metal reduction group in the same molecule. The polymer dispersant B contains a constitutional unit derived from a monomer (b-1) having a carboxy group and a constitutional unit derived from a monomer (b-2) having a polyoxyalkylene group. The ink for writing implements has a content of the compound C of 3 mass% or more and 20 mass% or less and a content of the metal fine particles A of 5 mass% or more and 70 mass% or less. There are provided the ink for writing implements and writing implements using the ink for writing implements.SELECTED DRAWING: None

Description

The present invention relates to stationery ink and a writing tool using the writing tool ink.

Metal fine particles are expected to develop a wide range of industrial applications due to the variety of functions and physical properties exhibited by using metals in nano-sized particles.
As one of the industrial developments, the use of ink containing metal fine particles for printed electronics forming electronic devices and circuits by using printing technology is being studied.
For the design and trial production of electronic devices and circuits, it is required to form a conductive pattern by a simple method. As such a method, a writing tool filled with ink containing metal fine particles is used.
For example, Patent Document 1 describes a compound having a halogen in the molecule by ionic bonding for the purpose of providing a conductive pattern forming method capable of easily producing a conductive pattern and a writing tool for forming a conductive pattern used thereof. Described is a method for forming a conductive pattern in which an amount of conductive water-based ink not exceeding the absorption capacity of the porous base material is applied to the porous base material containing the above, and a writing tool filled with the conductive water-based ink used for the method. There is.

JP-A-2015-185212

In recent years, electronic devices have become familiar, and understanding of electronic devices and circuits is becoming more important even in educational settings. In addition, the development speed of electronic devices is accelerating, and prototyping is becoming more important. Demand for writing ink containing metal fine particles is increasing in various applications such as educational sites and prototyping. When creating a circuit as a prototype, the metal film forming the conductive wiring is required to have low resistance. Further, in prototyping, it is required to use a resin base material having low heat resistance such as vinyl chloride (PVC) as the base material. Sheet resistance (surface resistivity) is used as an index of electrical resistance of conductive wiring, but a writing tool that develops sheet resistance at a level that can be actually used even when dried at room temperature using a resin substrate with low heat resistance. Development of ink for use is required.
Ink for writing tools containing metal fine particles is also referred to as long-term storage stability (hereinafter, also referred to as "long-term storage stability") in which drawing blur is unlikely to occur when the ink is filled in the writing tool and stored for a long period of time and then used again. ) Is required to be excellent.
However, the reduction of sheet resistance and the long-term storage stability of the ink are in conflict with each other, and the technique of Patent Document 1 does not satisfy the requirements for achieving both the reduction of sheet resistance and the long-term storage stability.
It is an object of the present invention to provide a writing tool ink capable of forming a metal film having low sheet resistance even when dried at room temperature and having excellent long-term storage stability, and a writing tool using the writing tool ink. And.

The present inventors contain metal fine particles, a polymer dispersant, and a compound containing a metal adsorbing group and a metal reducing group in the same molecule, and the polymer dispersant is a structural unit derived from a monomer having a carboxy group. A predetermined range of the content of a compound containing a structural unit derived from a monomer having a polyoxyalkylene group and containing a metal adsorbing group and a metal reducing group in the same molecule in the writing instrument ink and the content of the metal fine particles. By doing so, it was found that the above problem can be solved.

That is, the present invention provides the following [1] and [2].
[1] An ink for writing utensils containing metal fine particles A, a polymer dispersant B, and a compound C containing a metal adsorbing group and a metal reducing group in the same molecule.
The polymer dispersant B contains a structural unit derived from a monomer (b-1) having a carboxy group and a structural unit derived from a monomer (b-2) having a polyoxyalkylene group.
The content of compound C is 3% by mass or more and 20% by mass or less.
An ink for writing tools having a content of metal fine particles A of 5% by mass or more and 70% by mass or less.
[2] A writing tool filled with the writing tool ink according to the above [1].

According to the present invention, there is provided a writing tool ink capable of forming a metal film having low sheet resistance even when dried at room temperature and having excellent long-term storage stability, and a writing tool using the writing tool ink. Can be done.

[Ink for writing tools]
The writing ink of the present invention is a writing tool ink containing metal fine particles A, a polymer dispersant B, and a compound C containing a metal adsorbing group and a metal reducing group in the same molecule, wherein the polymer dispersant B is used. , A structural unit derived from the monomer (b-1) having a carboxy group and a structural unit derived from the monomer (b-2) having a polyoxyalkylene group, and the content of the compound C is 3% by mass or more and 20% by mass or less. The content of the metal fine particles A is 5% by mass or more and 70% by mass or less.

According to the present invention, a metal film having low sheet resistance can be formed even when dried at room temperature, and long-term storage stability can be improved. The reason is not clear, but it can be considered as follows.
The writing ink of the present invention has metal fine particles dispersed in a medium by a polymer dispersant, and has an electrostatic action due to a monomer-derived structural unit having a carboxy group of the polymer dispersant and a polyoxyalkylene group. It is considered that the three-dimensional repulsive action derived from the monomer improves the dispersion stability of the metal fine particles and suppresses the aggregation of the metal fine particles. Further, it is considered that the compound containing the metal adsorbing group and the reducing group in the same molecule contained in the ink for writing tools of the present invention is concentrated in the ink film as the ink dries and joins the metal fine particles. As a result, sintering of metal fine particles proceeds rapidly even when dried at room temperature, and a metal film having low sheet resistance can be formed.
Further, in the writing tool ink of the present invention, as described above, the dispersion stability of the metal fine particles is improved, and the aggregation of the metal fine particles is suppressed even after the metal fine particles are stored in the writing tool for a long period of time. It is possible to maintain a finely dispersed state. As a result, it is considered that drawing blurring is less likely to occur even when the drawing is used again after long-term storage, and long-term storage stability is improved.

<Metallic particles A>
The metal (metal atom) constituting the metal fine particles A according to the present invention is a Group 4 transition metal such as titanium and zirconium, a Group 5 transition metal such as vanadium and niob, and a sixth group such as chromium, molybdenum and tungsten. Group 7 transition metals, Group 7 transition metals such as manganese, technetium and renium, Group 8 transition metals such as iron and ruthenium, Group 9 transition metals such as cobalt, rhodium and iridium, nickel, palladium and platinum. Group 10 transition metals such as copper, silver and gold, Group 12 transition metals such as zinc and cadmium, Group 13 metals such as aluminum, gallium and indium, germanium, etc. Examples include Group 14 metals such as tin and lead. As the metal constituting the metal fine particles, one kind may be used as a single metal, or two or more kinds may be used in combination as an alloy. Above all, from the viewpoint of reducing sheet resistance and improving long-term storage stability, it is preferably a transition metal of Group 4 to Group 11 in the 4th to 6th cycles, and more preferably copper, gold or silver. , Platinum, palladium and the like, more preferably containing at least one selected from gold, silver, copper and palladium, even more preferably containing at least one selected from gold, silver and copper, even more preferably. Is at least one selected from silver and copper, and even more preferably silver. The type of metal can be confirmed by high frequency inductively coupled plasma emission spectrometry.

The cumulant average particle size of the metal fine particles A in the ink for writing tools of the present invention is preferably 10 nm or more, more preferably 20 nm or more, still more preferably 20 nm or more, from the viewpoint of reducing sheet resistance and improving long-term storage stability. It is 30 nm or more, and preferably 100 nm or less, more preferably 80 nm or less, still more preferably 60 nm or less, still more preferably 50 nm or less. The cumulant average particle size is measured by the method described in Examples.

The content of the metal fine particles A in the ink for writing tools of the present invention is 5% by mass or more, preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30 from the viewpoint of reducing the sheet resistance. It is 70% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, and from the viewpoint of improving long-term storage stability, it is 70% by mass or less, preferably 67% by mass or less. It is more preferably 65% by mass or less, still more preferably 63% by mass or less.

<Polymer dispersant B>
In the present invention, the metal fine particles A are dispersed with a polymer dispersant B (hereinafter, also simply referred to as “dispersant B”). The dispersant B is a structural unit derived from a monomer (b-1) having a carboxy group and a polyoxyalkylene group from the viewpoint of improving the dispersion stability of the metal fine particles, reducing the sheet resistance, and improving the long-term storage stability. Containing a structural unit derived from the monomer (b-2) having.
The dispersant (B) can be obtained by copolymerizing a raw material monomer containing a monomer (b-1) and a monomer (b-2). The dispersant B may be a block copolymer, a random copolymer, or an alternate copolymer.

[Monomer having a carboxy group (b-1)]
The monomer (b-1) has a carboxy group, and at least a part of the carboxy group may form a salt.
Specific examples of the monomer (b-1) include unsaturated monocarboxylic acids such as (meth) acrylic acid, crotonic acid, and 2-methacryloyloxymethylsuccinic acid; maleic acid, itaconic acid, fumaric acid, citraconic acid, and the like. Examples thereof include unsaturated dicarboxylic acids. The unsaturated dicarboxylic acid may be anhydrous.
The monomer (b-1) may be used alone or in combination of two or more.
The monomer (b-1) is preferably at least one selected from (meth) acrylic acid and maleic acid from the viewpoint of improving the dispersion stability of the metal fine particles, reducing the sheet resistance, and improving the long-term storage stability. Is.
As used herein, the term "(meth) acrylic acid" means at least one selected from acrylic acid and methacrylic acid. "(Meta) acrylic acid" in the following is also synonymous.

[Monomer having a polyoxyalkylene group (b-2)]
The monomer (b-2) can introduce a polyoxyalkylene group as a side chain of the dispersant B, thereby improving the dispersion stability of the metal fine particles, reducing the sheet resistance, and providing long-term storage stability. It is thought that it can be improved.
Examples of the monomer (b-2) include polyalkylene glycol (meth) acrylate, alkoxypolyalkylene glycol (meth) acrylate, and phenoxyalkylene glycol (meth) acrylate. The monomer (b-2) may be used alone or in combination of two or more.
As used herein, "(meth) acrylate" is at least one selected from acrylates and methacrylates. The following "(meth) acrylate" is also synonymous.

The polyoxyalkylene group of the monomer (b-2) preferably contains a unit derived from an alkylene oxide having 2 or more and 4 or less carbon atoms, and more preferably at least one selected from a unit derived from ethylene oxide and a unit derived from propylene oxide. include.
The number of units derived from the alkylene oxide in the polyoxyalkylene group is preferably 2 or more, more preferably 5 or more, still more preferably 10 or more, and preferably 100 or less, more preferably 70 or less, still more preferably. It is 50 or less.
The polyoxyalkylene group may be a copolymer containing a unit derived from ethylene oxide and a unit derived from propylene oxide. The molar ratio [EO / PO] of the unit (EO) derived from ethylene oxide and the unit (PO) derived from propylene oxide is preferably 0.9 or more, more preferably 1 or more, still more preferably 1.1 or more. Then, it is preferably 9 or less, more preferably 6 or less, still more preferably 3 or less, still more preferably 2 or less.
The copolymer containing a unit derived from ethylene oxide and a unit derived from propylene oxide may be a block copolymer, a random copolymer, or an alternate copolymer.

The alkoxy group of the alkoxypolyalkylene glycol (meth) acrylate has preferably 1 or more and 8 or less carbon atoms.
Examples of the alkoxypolyalkylene glycol (meth) acrylate include methoxypolyalkylene glycol (meth) acrylate, ethoxypolyalkylene glycol (meth) acrylate, propoxypolyalkylene glycol (meth) acrylate, butoxypolyalkylene glycol (meth) acrylate, and octoxypoly. Examples thereof include alkylene glycol (meth) acrylate.

The monomer (b-2) is preferably a polyalkylene glycol (meth) acrylate and an alkoxypolyalkylene glycol (from the viewpoint of improving the dispersion stability of the metal fine particles, reducing the sheet resistance, and improving the long-term storage stability). At least one selected from (meth) acrylates, more preferably alkoxypolyalkylene glycol (meth) acrylates, and even more preferably methoxypolyalkylene glycol (meth) acrylates, ethoxypolyalkylene glycol (meth) acrylates, propoxypolyalkylenes. At least one selected from glycol (meth) acrylate, butoxypolyalkylene glycol (meth) acrylate, and octoxypolyalkylene glycol (meth) acrylate, more preferably octoxypolyalkylene glycol (meth) acrylate, and more. More preferably, it is octoxy (polyethylene glycol / polypropylene glycol) (meth) acrylate.

Specific examples of the commercially available monomer (b-2) include NK Ester AM-90G, AM-130G, AMP-20GY, NK Ester M-20G, and 40G of Shin Nakamura Chemical Industry Co., Ltd. 90G, 230G, etc., NOF Corporation's Blemmer PE-90, 200, 350, etc., Blemmer PME-100, 200, 400, 1000, 4000, etc., Blemmer PP-500, 800, etc. Examples thereof include Bremmer AP-150, 400, 550 and the like, Bremmer 50PEP-300, 50POP-800B, 43PAPE-600B and the like.

[Aromatic group-containing monomer (b-3)]
The dispersant B preferably further contains a structural unit derived from the aromatic group-containing monomer (b-3) from the viewpoint of improving the dispersion stability of the metal fine particles, reducing the sheet resistance, and improving the long-term storage stability. ..
The monomer (b-3) is preferably a vinyl monomer having an aromatic group having 6 or more and 22 or less carbon atoms, which may have a substituent containing a heteroatom, and more preferably a styrene-based monomer and a styrene-based monomer. One or more selected from aromatic group-containing (meth) acrylates. The molecular weight of the aromatic group-containing monomer is preferably less than 500.
Examples of the styrene-based monomer include styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), divinylbenzene and the like, but styrene and α-methylstyrene are preferable.
As the aromatic group-containing (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate and the like are preferable, and benzyl (meth) acrylate is more preferable.
The monomer (b-3) is preferably composed of styrene, α-methylstyrene, and benzyl (meth) acrylate from the viewpoint of improving the dispersion stability of the metal fine particles, reducing the sheet resistance, and improving the long-term storage stability. At least one selected, more preferably styrene.

The dispersant B is not limited to the structural unit derived from the monomer (b-1), the structural unit derived from the monomer (b-2), and the structural unit derived from the monomer (b-3), as long as the effect of the present invention is not impaired. It may contain a structural unit derived from another monomer. Examples of other monomers include (meth) acrylates having a hydrocarbon group derived from an aliphatic alcohol.
The (meth) acrylate having a hydrocarbon group derived from an aliphatic alcohol preferably has a hydrocarbon group derived from an aliphatic alcohol having 1 or more and 22 or less carbon atoms. For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, (Meta) acrylates having a linear alkyl group such as stearyl (meth) acrylate; isopropyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, isopentyl (meth) acrylate, isooctyl (meth) acrylate, (Meta) acrylate having a branched chain alkyl group such as isodecyl (meth) acrylate, isododecyl (meth) acrylate, isostearyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; alicyclic alkyl such as cyclohexyl (meth) acrylate. Examples thereof include (meth) acrylate having a group.

The content of each monomer in the raw material monomer at the time of producing the dispersant B (content as an unneutralized amount; the same applies hereinafter) or the content of the constituent unit derived from each monomer in the dispersant B is the dispersion of the metal fine particles. From the viewpoint of improving stability, reducing sheet resistance, and improving long-term storage stability, it is as follows.
The content of the monomer (b-1) is preferably 1% by mass or more, more preferably 1.5% by mass or more, still more preferably 2% by mass or more, still more preferably 2.5% by mass or more, and It is preferably 50% by mass or less, more preferably 30% by mass or less, still more preferably 10% by mass or less, still more preferably 5% by mass or less.
The content of the monomer (b-2) is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, still more preferably 60% by mass or more, and preferably 99. It is mass% or less, more preferably 98% by mass or less, still more preferably 95% by mass or less, still more preferably 90% by mass or less, still more preferably 80% by mass or less, still more preferably 70% by mass or less.
When the dispersant B contains a structural unit derived from the aromatic group-containing monomer (b-3), the content of the monomer (b-3) is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably. Is 20% by mass or more, preferably 60% by mass or less, more preferably 50.5% by mass or less, still more preferably 40% by mass or less.
The mass ratio of the content of the monomer (b-1) to the monomer (b-2) [monomer (b-1) / monomer (b-2)] is preferably 0.01 or more, more preferably 0.02 or more. , More preferably 0.03 or more, and preferably 1 or less, more preferably 0.5 or less, still more preferably 0.1 or less, still more preferably 0.07 or less, still more preferably 0.05. It is as follows.
The total content of the structural unit derived from the monomer (b-1) and the structural unit derived from the monomer (b-2) in the dispersant B is preferably 55% by mass or more, more preferably 60, from the same viewpoint as described above. By mass or more, more preferably 65% by mass or more, and preferably 100% by mass or less.

The dispersant B is preferably derived from (meth) acrylic acid and maleic acid as the monomer (b-1) from the viewpoint of improving the dispersion stability of the metal fine particles, reducing the sheet resistance, and improving the long-term storage stability. A structural unit and a structural unit derived from alkoxypolyalkylene glycol (meth) acrylate as the monomer (b-2), and more preferably at least one selected from (meth) acrylic acid and maleic acid as the monomer (b-1). At least one selected from a structural unit derived from, a structural unit derived from alkoxypolyalkylene glycol (meth) acrylate as the monomer (b-2), and styrene, α-methylstyrene, and benzyl (meth) acrylate as the monomer (b-3). Includes species-derived building blocks.
As the dispersant B, one synthesized by a known method may be used, or a commercially available product may be used. Examples of commercially available products of the dispersant B include DISPERBYK-190 and 2015 manufactured by BYK.

The number average molecular weight of the dispersant B is preferably 3,000 or more, more preferably 7,000 or more, still more preferably 10,000 or more, and preferably 100,000 or less, more preferably 70,000 or less. Below, it is more preferably 50,000 or less, still more preferably 40,000 or less. When the number average molecular weight of the dispersant B is in the above range, the adsorption force to the metal fine particles is sufficient and dispersion stability can be exhibited. The number average molecular weight is measured by the method described in Examples.

The acid value of the dispersant B is preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, still more preferably 15 mgKOH / g or more, and preferably 200 mgKOH / g or less, more preferably 100 mgKOH / g or less. It is more preferably 50 mgKOH / g or less, and even more preferably 30 mgKOH / g or less.
The acid value of the vinyl polymer can also be calculated from the mass ratio of the constituent monomers. It can also be obtained by a method of dissolving or swelling the polymer in an appropriate solvent and titrating it.

The present form of the dispersant B is a form in which the dispersant B is adsorbed on the metal fine particles, a form in which the metal fine particles are contained in the dispersant B (capsule), and a form in which the dispersant B is adsorbed on the metal fine particles. There is a form that is not. From the viewpoint of dispersion stability of the metal fine particles, a form in which the metal fine particles are contained in the dispersant B is preferable, and a state in which the metal fine particles are contained in the dispersant B is more preferable.

The content of the dispersant B in the writing instrument ink of the present invention is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, still more preferably 2% by mass. The above is even more preferably 2.7% by mass or more, and preferably 10% by mass or less, more preferably 7% by mass or less, still more preferably 5% by mass or less, still more preferably 4% by mass or less. ..

The mass ratio of the content of the metal fine particles A to the total content of the metal fine particles A and the dispersant B in the writing instrument ink of the present invention [metal fine particles A / (metal fine particles A + dispersant B)] is the dispersion stability of the metal fine particles. From the viewpoint of improving, reducing sheet resistance, and improving long-term storage stability, it is preferably 0.3 or more, more preferably 0.5 or more, still more preferably 0.7 or more, still more preferably 0.9. The above, and preferably 0.99 or less, more preferably 0.98 or less, still more preferably 0.97 or less.
The content mass ratio [metal fine particles A / (metal fine particles A + dispersant B)] is the metal fine particles A and dispersion measured by the method described in Examples using a differential thermal weight simultaneous measurement device (TG / DTA). Calculated from the mass of agent B.

<Compound C containing a metal adsorbing group and a metal reducing group in the same molecule>
The ink for writing utensils of the present invention contains a metal adsorbing group and a metal reducing group in the same molecule from the viewpoint of reducing sheet resistance and improving long-term storage stability (hereinafter, simply "compound C"). Also called).
The molecular weight of compound C is preferably 500 or less, more preferably 300 or less, still more preferably 150 or less, still more preferably 100 or less, from the viewpoint of reducing sheet resistance and improving long-term storage stability.
The metal adsorbing group of compound C includes a carboxy group, a sulfonic acid group, a phosphoric acid group, a hydroxy group, a thiol group, an amino group (-NH ₂ , -NHR, -NRR'), an imino group, and a functional group containing a halogen atom. Examples thereof include functional groups having a coordinating property with respect to metal fine particles such as. Among these, the metal adsorption group of compound C is preferably at least one selected from a carboxy group and an amino group, and more preferably a carboxy group.
Examples of the metal reducing group of the compound C include a functional group having an action of reducing a metal such as an aldehyde group, a hydroxy group, a primary amino group and a secondary amino group. Among these, the metal adsorbing group of compound C is preferably at least one selected from an aldehyde group and a hydroxy group, and more preferably an aldehyde group.
The compound C may be one functional group having both a function as a metal adsorbing group and a function as a metal reducing group, but the metal adsorbing group and the metal reducing group are different functional groups. Is preferable.

Specifically, the compound C is a monocarboxylic acid having an aldehyde group or a hydroxy group such as formic acid, glyoxylic acid, phthalaldehyde acid, and lactic acid; ethanolamine, N-methylethanolamine, N, N-dimethylethanolamine (2). -(Dimethylamino) ethanol), N, N-diethylethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, propanolamine, N, N-dimethylpropanolamine, butanolamine, alkanolamines such as hexanolamine, etc. Will be. Compound C can be used alone or in combination of two or more.
Compound C is preferably at least one selected from a monocarboxylic acid having an aldehyde group or a hydroxy group, and an alkanolamine, more preferably a monocarboxylic acid having an aldehyde group, and further preferably selected from formic acid and glyoxylic acid. At least one of these, more preferably formic acid.

The content of compound C in the ink for writing tools of the present invention is 3% by mass or more, preferably 5% by mass or more, more preferably 5% by mass or more, from the viewpoint of reducing sheet resistance and improving long-term storage stability. It is 7% by mass or more and 20% by mass or less, preferably 17% by mass or less, more preferably 15% by mass or less, still more preferably 13% by mass or less.

<Basic compound D>
The ink for writing tools of the present invention preferably further contains the basic compound D from the viewpoint of reducing sheet resistance and improving long-term storage stability.
Examples of the basic compound D include inorganic basic compounds other than compound C and organic basic compounds.
Examples of the inorganic basic compound include hydroxide salts, carbonates, and bicarbonates of alkali metals such as potassium, sodium, and lithium. Specific examples thereof include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogencarbonate and potassium hydrogencarbonate. Further, ammonia may be used.
Examples of the organic basic compound include alkylamines such as propylamine, butylamine, hexylamine, diethylamine, dipropylamine, dimethylethylamine, diethylmethylamine and triethylamine, ethylenediamine, triethylenediamine, tetramethylethylenediamine, diethylenetriamine, dipropylenetriamine and tri. Adicyclic amines such as (poly) alkylene polyamines such as ethylenetetramine and tetraethylenepentamine; alicyclic amines such as piperidine, pyrrolidine, N-methylpyrrolidin, morpholin; aniline, N-methylaniline, toluidine, anisidin, phenetidine and the like Aromatic amines; examples include organic amine compounds of aralkylamines such as benzylamine and N-methylbenzylamine.
Among these, the basic compound D is preferably an organic basic compound, more preferably an organic amine compound, and further preferably a fat, from the viewpoint of reducing sheet resistance and improving long-term storage stability. It is a group amine, more preferably an alkylamine, and even more preferably a propylamine.

The use equivalent ratio of the basic compound D represented by the following formula is preferably 0.1 or more, more preferably 0.3 or more, and further, from the viewpoint of reducing sheet resistance and improving long-term storage stability. It is preferably 0.5 or more, and preferably 2 or less, more preferably 1.5 or less, still more preferably 1 or less, still more preferably 0.8 or less, still more preferably 0.6 or less.
Equivalent ratio of basic compound D = [additional mass of basic compound D (g) / equivalent of basic compound D (g / mol)] / [additional mass of compound C (g) / equivalent of compound C (g) / Mol)]

<Water>
The writing instrument ink of the present invention preferably further contains water.
The content of water in the writing instrument ink of the present invention is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 5% by mass or more, from the viewpoint of reducing the sheet resistance and improving the long-term storage stability. 10% by mass or more, more preferably 13% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, still more preferably 50% by mass or less, still more preferably 40% by mass or less. It is even more preferably 30% by mass or less, and even more preferably 20% by mass or less.

Further, if necessary, the ink for writing tools of the present invention is a fixing aid such as a dispersion of polymer particles, a moisturizing agent, a wetting agent, a penetrant, a surfactant, a viscosity modifier, and a defoaming agent, which are usually used for inks. It can contain various additives such as agents, preservatives, antifungal agents, and rust preventives.

(Manufacturing ink for stationery)
The ink for writing tools of the present invention comprises a method of adding and mixing a dispersant B, a compound C, a basic compound D, water and various additives to metal fine particles prepared in advance by a known method, a metal raw material compound, and the like. It can be obtained by a method of mixing a reducing agent and a dispersant B to reduce the metal raw material compound or the like. Above all, from the viewpoint of reducing the sheet resistance and improving the long-term storage stability, after obtaining the metal fine particle dry powder containing the dispersant B in advance, compound C, if necessary, basic compound D, water and A method of adding and mixing various additives is preferable.
The dry metal fine particle powder is obtained by mixing a metal raw material compound, a reducing agent, and a dispersant B, reducing the metal raw material compound with the reducing agent to obtain a dispersion of metal fine particles dispersed with the dispersant B, and then obtaining the dispersion. It can be obtained by drying the dispersion of the metal fine particles by freeze-drying or the like.
The temperature of the reduction reaction is preferably 10 ° C. or higher, more preferably 20 ° C. or higher, still more preferably 30 ° C. or higher, and preferably 70 ° C. or lower, more preferably 60 ° C. or lower, still more preferably 50 ° C. or lower. It is preferable to carry out within the range. The reduction reaction may be carried out in an air atmosphere or in an inert gas atmosphere such as nitrogen gas.

The metal raw material compound is not particularly limited as long as it is a compound containing a metal constituting the above-mentioned metal fine particles A.
The reducing agent is not particularly limited, and either an inorganic reducing agent or an organic reducing agent can be used.
Examples of the organic reducing agent include alcohols such as ethylene glycol and propylene glycol; aldehydes such as formaldehyde, acetaldehyde and propionaldehyde; acids such as ascorbic acid and citric acid and salts thereof; ethanolamine, N-methylethanolamine, N, N-dimethylethanolamine (2- (dimethylamino) ethanol), N, N-diethylethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, propanolamine, N, N-dimethylpropanolamine, butanolamine, hexanolamine Alkanolamines such as alkanolamines, propylamines, butylamines, hexylamines, diethylamines, dipropylamines, dimethylethylamines, diethylmethylamines, alkylamines such as triethylamines, ethylenediamines, triethylenediamines, tetramethylethylenediamines, diethylenetriamines, dipropylenetriamines, triethylenetetramines, etc. , Alicyclic amines such as (poly) alkylene polyamines such as tetraethylenepentamine; alicyclic amines such as piperidine, pyrrolidine, N-methylpyrrolidin, morpholin; Group amines; examples include aralkylamines such as benzylamine and N-methylbenzylamine.
Examples of the inorganic reducing agent include borohydride salts such as sodium borohydride and ammonium borohydride; aluminum hydrides such as lithium hydride and aluminum potassium hydride; hydrazines such as hydrazine and hydrazine carbonate; hydrogen gas and the like. Can be mentioned.
The reducing agent may be used alone or in combination of two or more.

In the production of the ink for writing utensils of the present invention, from the viewpoint of removing impurities such as the unreacted reducing agent and the excess dispersant B that does not contribute to the dispersion of the metal fine particles A, the dispersion of the metal fine particles is used before freeze-drying. It may be purified.
The method for purifying the dispersion of metal fine particles is not particularly limited, and examples thereof include membrane treatment such as dialysis and ultrafiltration; and centrifugation treatment. Above all, membrane treatment is preferable, and dialysis is more preferable, from the viewpoint of efficiently removing impurities. Regenerated cellulose is preferable as the material of the dialysis membrane used for dialysis.
The molecular weight cut-off of the dialysis membrane is preferably 1,000 or more, more preferably 5,000 or more, still more preferably 10,000 or more, and preferably 100,000 or less, from the viewpoint of efficiently removing impurities. , More preferably 70,000 or less.

The viscosity of the writing instrument ink of the present invention at 25 ° C. is preferably 5 mPa · s or more, more preferably 10 mPa · s or more, still more preferably 20 mPa · s or more, still more preferably 25 mPa · s, from the viewpoint of storage stability. It is more preferably 50 mPa · s or less, more preferably 45 mPa · s or less, still more preferably 40 mPa · s or less, still more preferably 35 mPa · s or less. The viscosity of the ink can be measured by the method described in Examples using an E-type viscometer.
The pH of the writing instrument ink of the present invention at 20 ° C. is preferably 7.0 or higher, more preferably 7.2 or higher, still more preferably 7.5 or higher, from the viewpoint of storage stability. Further, from the viewpoint of member resistance and skin irritation, the pH is preferably 11 or less, more preferably 10 or less, still more preferably 9.5 or less. The pH of the ink can be measured by a conventional method.

[Stationery]
The writing tool of the present invention is filled with the writing tool ink.
In the present invention, the shape of the writing tool and the ink ejection mechanism are not particularly limited.
As a method of supplying ink to the pen tip portion of the tip of the writing tool of the present invention, (i) a method using a capillary phenomenon, (ii) a method using both gravity descent and a capillary phenomenon, and (iii) gravity descent. A method of adhering ink to the surface of a ball or the like can be mentioned. Examples of the writing tool using the method (i) include a marker (felt pen), a brush pen, a felt-tip pen, and the like. Examples of the writing tool using the method (ii) include a fountain pen and the like. Examples of the writing tool using the method (iii) include a ballpoint pen and the like. Above all, from the viewpoint of long-term storage stability, a writing tool using the capillary phenomenon of (i) is preferable.

Writing instruments that use capillarity are so-called marking pens, and guide ink from a batting-type or direct-liquid ink reservoir to the tip of the pen by capillarity. In the batting type, a batting containing ink (a storage body containing ink) is built in the writing tool body, and a pen tip is attached so as to come into contact with the batting. On the other hand, in the direct liquid type, the writing instrument main body is directly filled with ink.
As the shape of the pen tip of the writing tool using the capillary phenomenon, a marker type or a brush pen type is preferable, and a marker type is more preferable.
The marker core width of the marker type is preferably 0.5 mm or more, more preferably 1 mm or more, further preferably 3 mm or more, and preferably 60 mm or less, more preferably 40 mm or less, still more preferably 20 mm or less, still more. It is preferably 10 mm or less.

(Formation of metal film)
In the present invention, the method for forming a metal film preferably includes a step of applying ink on a base material using the writing tool and forming a metal film on the base material.
Examples of the base material used in the present invention include resins, papers, metal members, glass, ceramics, and composite materials thereof.
Examples of the resin base material include polyvinyl chloride (PVC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyimide (PI), polyamide (PA), polymethylmethacrylate (PMMA), polyethylene (PE), and polypropylene. Examples thereof include synthetic resin films such as (PP), polystyrene (PS), acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene copolymer (AS), and polycarbonate (PC).
Examples of the paper base material include coated paper (coated paper, art paper, etc.), uncoated paper, plain paper, kraft paper, synthetic paper, processed paper, paperboard, and the like.
Metal members include gold substrate, gold-plated substrate, silver substrate, silver-plated metal substrate, copper substrate, palladium substrate, palladium-plated metal substrate, platinum substrate, platinum-plated metal substrate, aluminum substrate, nickel substrate, nickel-plated substrate, tin substrate. , Metallic substrates such as tin-plated metal substrates or metal substrates; metal parts such as electrodes of electrically insulating substrates.
Among these, the base material is preferably at least one selected from a resin base material and a paper base material, more preferably a resin base material, and further preferably a synthetic resin film.

Since the present invention can form a good metal film even when dried at room temperature, it is possible to obtain a metal film having a low sheet resistance even when the heat resistant temperature of the substrate to be used is low. From this point of view, the heat resistant temperature of the substrate according to the present invention is preferably 130 ° C. or lower, more preferably 110 ° C. or lower, still more preferably 90 ° C. or lower, and preferably 50 ° C. or higher, more preferably 55 ° C. or lower. Above, more preferably 60 ° C. or higher. In the present invention, the heat resistant temperature of the base material means the upper limit temperature at which the physical properties of the base material can be maintained.
The thickness of the substrate according to the present invention is preferably 10 μm or more, more preferably 30 μm or more, still more preferably 50 μm or more, still more preferably 70 μm or more, and preferably 500 μm or less, more preferably 400 μm or less, further. It is preferably 300 μm or less, and even more preferably 200 μm or less.

The amount of the writing tool ink applied to the substrate is preferably 0.001 g or more, more preferably 0.005 g or more, still more preferably 0.007 g or more, and preferably 0.1 g per 100 cm ² of the substrate. Below, it is more preferably 0.07 g or less, further preferably 0.05 g or less, still more preferably 0.03 g or less.

In the present invention, from the viewpoint of reducing sheet resistance, it is preferable to apply the ink on the base material using the writing tool, and then evaporate and dry the medium in the ink film on the base material to perform sintering treatment.
The temperature of the sintering treatment is preferably lower than the temperature at which the base material is deformed, and from the viewpoint of ease of treatment, normal temperature (for example, 20 ° C. or higher and 35 ° C. or lower) is preferable.
The relative humidity of the surrounding environment of the sintering treatment is preferably 20% or more, more preferably 30% or more, further preferably 35% or more, and preferably 60% or less, more preferably 50% or less, still more preferable. Is less than 40%.
From the viewpoint of heat resistance of the base material and ease of treatment, the sintering treatment is preferably performed by storing at room temperature (for example, 20 ° C. or higher and 35 ° C. or lower).
The time of the room temperature treatment in the sintering treatment can be appropriately adjusted, but is preferably 1 hour or longer, more preferably 3 hours or longer, still more preferably 6 hours or longer, still more preferably 12 hours or longer, and It is preferably 36 hours or less, more preferably 24 hours or less.
The sintering treatment may be carried out under an air atmosphere or an inert gas atmosphere such as nitrogen gas, but when the substrate is a metal that is easily oxidized, it is under a nitrogen gas atmosphere. Is preferable.

The sintering treatment may be performed by heating the ink film on the base material, although it depends on the heat resistant temperature of the base material. As a result, the medium in the ink film can be rapidly evaporated and dried, and the metal fine particles can be further sintered to form a metal film having low sheet resistance.
The heating method is not particularly limited, and a method of heating by bringing a heater into contact with the surface of the base material opposite to the surface on which the ink film is formed, and a method of applying hot air to the ink film surface on the base material to heat the base material. Method, method of heating by bringing a heater close to the ink film surface on the base material, method of storing the base material on which the ink film is formed in a constant temperature device that can keep the temperature constant, high temperature steam at normal pressure or high pressure Examples thereof include a method of heating by steam curing using the ink.

The sheet resistance (surface resistivity) of the metal film according to the present invention is preferably 20 Ω / □ or less, more preferably 15 Ω / □ or less, still more preferably 10 Ω / □ or less, still more preferably 7 Ω / □ or less, still more. It is preferably 5 Ω / □ or less, more preferably 3 Ω / □ or less, and from the viewpoint of ease of processing, it is preferably 0.1 Ω / □ or more, more preferably 0.5 Ω / □ or more, still more preferably. It is 0.7Ω / □ or more. The surface resistivity is measured by the method described in Examples.

In the following synthesis examples, production examples, examples and comparative examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified.
Various physical properties were measured or calculated by the following methods.

(1) Number average molecular weight Mn of polymer dispersant B
Gel permeation chromatography method using a solution prepared by dissolving phosphoric acid and lithium bromide in N, N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively, as an eluent [GPC device (HLC) manufactured by Tosoh Corporation. -8320GPC), Tosoh Corporation column (TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guardcolumn Super AW-H), flow velocity: 0.5 mL / min], monodisperse polystyrene kit [PStQuickB] with a known molecular weight as a standard material. F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500), manufactured by Tosoh Corporation] Was measured using.
The measurement sample was prepared by mixing 0.1 g of polymer dispersant B in a glass vial with 10 mL of the eluent, stirring at 25 ° C. for 10 hours with a magnetic stirrer, and using a syringe filter (DISMIC-13HP PTFE 0.2 μm, Advantech Co., Ltd.). The one filtered by (manufactured by the company) was used.

(2) Content of metal fine particles A and content of polymer dispersant B in metal fine particle dispersion or writing instrument ink Differential thermal weight simultaneous measurement device (TG / DTA) "STA7200RV" (manufactured by Hitachi High-Tech Science Co., Ltd.) 10 mg of the sample was weighed in an aluminum pancell, the temperature was raised from 35 ° C. to 550 ° C. at a heating rate of 10 ° C./min, and the mass loss was measured under a nitrogen flow of 50 mL / min. The mass reduction from 35 ° C to 200 ° C is the mass of the solvent, the mass reduction from 200 ° C to 550 ° C is the mass of the polymer dispersant B, and the residual mass at 550 ° C is the mass of the metal fine particles A. The content of the metal fine particles A and the content of the polymer dispersant B in the body or writing instrument ink were calculated.

(3) Cumulant average particle size of metal fine particles A The particle size was measured by a dynamic light scattering method using a laser particle analysis system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.), and calculated by a cumulant method analysis. The measurement conditions were a temperature of 25 ° C., an angle of 90 ° between the incident light and the detector, and 100 times of integration, and the refractive index of water (1.333) was input as the refractive index of the dispersion solvent. For the measurement sample, weigh the sample into a screw tube (No. 5 manufactured by Marum Co., Ltd.), add water so that the solid content concentration becomes 5 × 10 ^-3 %, and use a magnetic stirrer at 25 ° C. 1 The one that was stirred for a time was used.

(4) Viscosity of ink for writing tools The viscosity of ink for writing tools at 25 ° C is measured by the E-type viscometer "TV-25" (manufactured by Toki Sangyo Co., Ltd., standard cone rotor 1 ° 34'x R24, rotation speed 50 rpm). Was measured using.

Synthesis Example 1 (Synthesis of Polymer Dispersant B1)
Put 100 g of 1,4-dioxane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) in a 1000 mL round-bottomed flask equipped with a thermometer, two dropping funnels with 100 mL nitrogen bypass, and a reflux device, and put it in an oil bath. After warming the internal temperature of the flask to 90 ° C., nitrogen bubbling was performed for 10 minutes. After that, as raw material monomers, 98% acrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) 3 g, octoxy (polyethylene glycol / polypropylene glycol) methacrylate (manufactured by Nichiyu Co., Ltd. "Blemmer 50 POEP-800B") 67 g, styrene. 30 g of (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 1.5 g of 3-mercaptopropionic acid (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) were dissolved in a polybeaker and dropped funnel (1). I put it in. Separately, add 20 g of 1,4-dioxane and 0.15 g of 2,2'-azobis (2,4-dimethylvaleronitrile) ("V-65" manufactured by Wako Pure Chemical Industries, Ltd., polymerization initiator) in a polybeaker. It was dissolved in and placed in the dropping funnel (2). Then, the mixture in the dropping funnel (1) and the dropping funnel (2) was simultaneously added dropwise to the flask over 90 minutes. Then, after raising the internal temperature in the flask to 90 degreeC, stirring was continued for another 1 hour. After that, it was cooled to room temperature, and then the rotation speed was adjusted to 50 rpm and the hot bath was adjusted to 80 ° C. using the rotary distillation apparatus "Rotary Evaporator N-1000S" (manufactured by Tokyo Rika Kikai Co., Ltd.), and the distillation was distilled off at a pressure of 100 tolls. Distillation was carried out until there was nothing left. Then, using a vacuum dryer "VO420" (manufactured by Advantech), the polymer dispersant B1 was dried at a temperature of 110 ° C. and a pressure of 40 tolls for 48 hours to obtain [acrylic acid / octoxy (polyethylene glycol / polypropylene glycol) methacrylate / Styrene] copolymer (acid value 23 mgKOH / g, Mn: 31,600) was obtained.

Comparative Synthesis Example 1 (Synthesis of Polymer Dispersant BC1)
In Synthesis Example 1, the raw material monomer was added to 70 g of octoxy (polyethylene glycol / polypropylene glycol) methacrylate (“Blemmer 50 POEP-800B” manufactured by Nichiyu Co., Ltd.) and 30 g of styrene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent). [Octoxy (polyethylene glycol / polypropylene glycol) methacrylate / styrene] copolymer (acid value: 0 mgKOH / g, Mn: 33,500) was obtained as the polymer dispersant BC1 in the same manner except for the modification.

Comparative Synthesis Example 2 (Synthesis of Polymer Dispersant BC2)
In Synthesis Example 1, the same applies except that the raw material monomer was changed to 3 g of 98% acrylic acid (manufactured by Fujifilm Wako Junyaku Co., Ltd., special grade reagent) and 97 g of styrene (manufactured by Fujifilm Wako Junyaku Co., Ltd., special grade reagent). As a polymer dispersant BC2, a [acrylic acid / styrene] copolymer (acid value: 23 mgKOH / g, Mn: 9,900) was obtained.

Example 1
[Manufacturing of dry metal fine particles]
(Step 1)
23 g of N, N-dimethylethanolamine (hereinafter referred to as "DMEA") as a reducing agent was placed in a 1000 mL glass beaker and heated to 40 ° C. in an oil bath while stirring with a magnetic stirrer.
Separately, put 140 g of silver nitrate as a metal raw material compound, 8 g of polymer dispersant B1 and 70 g of ion-exchanged water into a 100 mL beaker, and stir at 40 ° C. using a magnetic stirrer until it becomes visually transparent, and mix the mixture. Got
Then, the obtained mixture was placed in a 1000 mL dropping funnel, and the mixture was added dropwise to DMEA maintained at 40 ° C. over 30 minutes. Then, the reaction solution was stirred in an oil bath for 5 hours while controlling the temperature of the reaction solution to 40 ° C., and then air-cooled to obtain a dark brown dispersion containing dispersed silver fine particles.

(Step 2)
The entire amount of the dispersion obtained in step 1 is put into a dialysis tube (“Spectra / Pore 6” manufactured by REPLIGEN, dialysis membrane: regenerated cellulose, molecular weight cut-off (MWCO) = 50K), and the top and bottom of the tube are placed with a closer. Sealed. This tube was immersed in 5 L of ion-exchanged water in a 5 L glass beaker, and the water temperature was maintained at 20 to 25 ° C. and the mixture was stirred for 1 hour. Then, the operation of exchanging the entire amount of the ion-exchanged water every hour was repeated three times, and then stirring was continued for 48 hours to obtain a purified dispersion.
The mass ratio [metal fine particles A / (polymer dispersant B + metal fine particles A)] was calculated by the method using the above differential thermal weight simultaneous measurement device (TG / DTA).

(Step 3)
The purified dispersion obtained in step 2 was used in a freeze-dryer (manufactured by Tokyo Rika Kikai Co., Ltd., model: FDU-2110) attached with a dry chamber (manufactured by Tokyo Rika Kikai Co., Ltd., model: DRC-1000). Then, by freeze-drying under the drying conditions (freezing at −25 ° C. for 1 hour, decompression at −10 ° C. for 9 hours, depressurization at 25 ° C. for 5 hours, decompression degree 5 Pa), the metal fine particle dry powder 1 containing the polymer dispersant B1 was obtained. ..

[Manufacturing ink for stationery]
In a 2000 mL polyethylene beaker, 630 g of dry metal fine particle powder 1, diethylene glycol monoisobutyl ether (hereinafter referred to as "iBDG") (Nippon Embroidery Co., Ltd.) 50 g, ion-exchanged water 149 g, formic acid (Fuji Film Wako Pure Chemical Industries, Ltd.) Add 100 g of propylamine (special grade reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 70 g of propylamine (special grade reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 1 g of polyether-modified silicone surfactant "KF6011" (manufactured by Shin-Etsu Chemical Industries, Ltd.). The mixture was dispersed for 3 hours with an ultrasonic disperser (manufactured by Nippon Seiki Seisakusho Co., Ltd., model: US-3001) while stirring with a tick stirrer. Then, filtration was performed using a 5 μm disposable membrane filter (Minisalt manufactured by Sartorius) to obtain ink I-1 for writing tools.

[Creating a pen for writing tools]
5 g of ink for writing tools I-1 was put into an ink refill marker container (W-6 mm, manufactured by Holbein Art Materials Co., Ltd.), and the pen tip was filled with ink by pushing the pen tip downward to obtain a pen for writing tools. ..

[Manufacturing of printed matter]
Using the obtained pen for writing tools, the amount of ink applied to 100 cm ² of a soft PVC film (manufactured by 3M Co., Ltd., model number: IJ1220, usable temperature: -30 to 80 ° C) is 0.01 g. It was applied evenly. The substrate coated with this ink was stored for 24 hours in a constant temperature and high humidity room having a temperature of 25 ° C. and a relative humidity of 40% to form a metal film.

Examples 2 to 8, 10, 11, and Comparative Examples 5 to 8
Examples except that the amount of the metal fine particle dry powder 1, the type or amount of the compound C, the type or amount of the basic compound D, and the amount of the ion-exchanged water were changed so as to have the ink composition as shown in Table 1. Same as 1.

Example 9
The step 1 for producing the dry metal fine particle powder of Example 1 is changed to the following step 1', and the total amount of the dispersion obtained in the following step 1'is used in the step 2 for producing the dry metal fine particle powder of Example 1. And the metal fine particle dry powder 2 was obtained in the same manner as in Step 3. Next, in the same manner as in Example 1 except that the metal fine particle dry powder 2 was used instead of the metal fine particle dry powder 1, the writing tool ink I-9 was obtained, and then a writing tool pen using the ink was prepared. A metal film was formed.
(Step 1')
In a 1000 mL glass beaker, 10 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade) was put as a reducing agent, and the mixture was heated to 40 ° C. in an oil bath while stirring with a magnetic stirrer. Separately, in a 100 mL beaker, 88 g of copper sulfate, 8 g of polymer dispersant B1 and 70 g of ion-exchanged water were added as metal raw material compounds, and the mixture was stirred at 40 ° C. using a magnetic stirrer until it became visually transparent and mixed. Obtained liquid.
Then, the obtained mixed solution was put into a 1000 mL dropping funnel and added dropwise to DMEA maintained at 40 ° C. over 30 minutes. Then, the reaction solution was stirred in an oil bath for 5 hours while controlling the temperature of the reaction solution to 40 ° C., and then air-cooled to obtain a black dispersion containing dispersed copper fine particles.

Comparative Example 1
The same procedure as in Example 1 was carried out except that the polymer dispersant BC1 obtained in Comparative Synthesis Example 1 was used in place of the polymer dispersant B1 in the production of the dry metal fine particle powder of Example 1.

Comparative Example 2
The same procedure as in Example 1 was carried out except that the polymer dispersant BC2 obtained in Comparative Synthesis Example 2 was used in place of the polymer dispersant 1 in the production of the dry metal fine particle powder of Example 1.

Comparative Example 3
In the production of the writing ink of Example 1, the same procedure was used except that formic acid was replaced with propionaldehyde as a compound having no carboxy group, which is a metal adsorbing group.

Comparative Example 4
The same was applied in the production of the writing ink of Example 1 except that formic acid was replaced with acetic acid as a compound having no aldehyde group as a reducing group.

<Evaluation>
[Sheet resistance (surface resistivity)]
For the sheet resistance (surface resistivity) of each printed matter obtained in Examples and Comparative Examples, use a resistivity meter (main body: Lorester GP, four probe probe: PSP probe, both manufactured by Mitsubishi Chemical Analytech Co., Ltd.). Using the four-probe method, measurements were taken up to one digit after the minority point. The results are shown in Table 1. The lower the surface resistivity, the better the conductivity.

[Long-term storage stability]
Each writing instrument pen obtained in Examples and Comparative Examples was allowed to stand in a constant temperature and high humidity room having a temperature of 40 ° C. and a humidity of 50%. Then, every time it was stored for one day, it was drawn on a soft PVC sheet as a resin base material using a writing pen, and the day when cassoulet was first confirmed was recorded. The results are shown in Table 1. The longer it takes for cassoulet to be confirmed for the first time, the more stable it can be used for a long period of time.

From Table 1, it can be seen that Examples 1 to 11 can form a metal film having a low sheet resistance because the surface resistivity is low as compared with Comparative Examples 1 to 8, and are excellent in long-term storage stability.

According to the present invention, a metal film having a low sheet resistance can be formed, and an ink for a writing tool having excellent long-term storage stability can be obtained. The writing tool filled with the ink can be suitably used in various fields such as educational sites and prototyping.

Claims (9)

An ink for writing tools containing metal fine particles A, a polymer dispersant B, and a compound C containing a metal adsorbing group and a metal reducing group in the same molecule.
The polymer dispersant B contains a structural unit derived from a monomer (b-1) having a carboxy group and a structural unit derived from a monomer (b-2) having a polyoxyalkylene group.
The content of compound C is 3% by mass or more and 20% by mass or less.
An ink for writing tools having a content of metal fine particles A of 5% by mass or more and 70% by mass or less. The writing ink according to claim 1, wherein the compound C has a molecular weight of 500 or less. The ink for writing tools according to claim 1 or 2, wherein the metal adsorbing group of compound C is a carboxy group. The ink for writing tools according to any one of claims 1 to 3, wherein the metal reducing group of compound C is an aldehyde group. The ink for writing tools according to any one of claims 1 to 4, further comprising a basic compound D and having a usage equivalent ratio of the basic compound D represented by the following formula of 0.1 or more and 2 or less.
Equivalent ratio of basic compound D = [additional mass of basic compound D (g) / equivalent of basic compound D (g / mol)] / [additional mass of compound C (g) / equivalent of compound C (g) / Mol)] The ink for writing tools according to claim 5, wherein the basic compound D is an organic amine compound. The ink for writing tools according to any one of claims 1 to 6, wherein the metal constituting the metal fine particles A is at least one selected from silver and copper. The ink for a writing tool according to any one of claims 1 to 7, wherein the writing tool is a marker type or a brush pen type. A writing tool filled with the writing tool ink according to any one of claims 1 to 8.