# US 2023/0057712 A1 · Ink containing fine metal particles

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- Number: US 2023/0057712 A1
- Document ID: US20230057712A1
- Status: Published application
- Kind: A1
- Application number: 17/788,535
- Filed: 2020-12-24
- Published: 2023-02-23
- Earliest claimed: 2019-12-27
- Assignees: Kao Corporation
- Applicants: Kao Corporation
- Inventors: Tomohide YOSHIDA; Kosuke MUTO
- Web page: https://patentgrep.com/patent/US20230057712A1

## CPC

- C09D 11/107: from unsaturated acids or derivatives thereof
- C09D 11/38: characterised by non-macromolecular additives other than solvents, pigments or dyes
- B41M 5/00: Duplicating or marking methods; Sheet materials for use therein (by using light-sensitive materials G03; electrography, magnetography G03G {; repeatedly usable boards or tablets for writing or drawing B43L1/00})
- C09D 11/106: containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- C09D 11/326: characterised by the pigment dispersant
- C09D 11/52: Electrically conductive inks
- B41M 5/0023: {Digital printing methods characterised by the inks used (inks per se C09D11/00)}
- B41M 7/009: {using thermal means, e.g. infrared radiation, heat}
- C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)
- B41M: PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING, (correction of typographical errors B41J; processes for applying transfer pictures or the like B44C1/16; fluid media for correction of typographical errors by coating C09D10/00; printing textiles D06P)

## Abstract

A metal fine particle-containing ink that contains metal fine particles dispersed therein with a polymer dispersant, a low-molecular weight carboxylic acid and an aqueous solvent, wherein the polymer dispersant contains a constitutional unit derived from an acid group-containing monomer; a content of the low-molecular weight carboxylic acid C in the ink is not less than 1% by mass and not more than 15% by mass. A boiling point (C) of the low-molecular weight carboxylic acid and a boiling point (D) of the aqueous solvent satisfy the following relational formula (I); and an acid dissociation exponent pKa (C) of the low-molecular weight carboxylic acid and an acid dissociation exponent pKa (B) of an acid group in the polymer dispersant satisfy the following relational formula (II): boiling point (C)>boiling point (D) (I), and pKa (C)<pKa (B) (II).

## Claims

### Claim 1

A metal fine particle-containing ink, comprising:
metal fine particles (a) dispersed therein with a polymer dispersant B,
a low-molecular weight carboxylic acid C, and
an aqueous solvent D, in which
wherein:
the polymer dispersant B comprises a constitutional unit derived from an acid group-containing monomer (b-1);
a content of the low-molecular weight carboxylic acid C in the ink is not less than 1% by mass and not more than 15% by mass;
a boiling point (C) of the low-molecular weight carboxylic acid C and a boiling point (D) of the aqueous solvent D satisfy the following relational formula (1); and
an acid dissociation exponent pKa (C) of the low-molecular weight carboxylic acid C and an acid dissociation exponent pKa (B) of an acid group in the polymer dispersant B satisfy the following relational formula (II),
boiling point (C)>boiling point (D) (I), and
pKa (C)<pKa (B) (II).

### Claim 2 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein the low-molecular weight carboxylic acid C comprises an aldehyde group.

### Claim 3 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein the boiling point (D) of the aqueous solvent D as measured under 1 atm is not higher than 150° C.

### Claim 4 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein the aqueous solvent D is at least one compound selected from the group consisting of acetone, ethanol, and ethyl acetate.

### Claim 5 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein a metal constituting the metal fine particles (a) is silver.

### Claim 6 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein the low-molecular weight carboxylic acid C is at least one compound selected from the group consisting of formic acid and glyoxylic acid.

### Claim 7 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein the acid dissociation exponent pKa (B) of the acid group in the polymer dispersant B is not less than 2 and not more than 5.5.

### Claim 8 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein the polymer dispersant B is a water-soluble vinyl polymer that comprises the constitutional unit derived from the acid group-containing monomer (b-1).

### Claim 9 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein the boiling point (C) of the low-molecular weight carboxylic acid C as measured under 1 atm is higher than 100° C. and not higher than 250° C.

### Claim 10 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein the acid dissociation exponent pKa (C) of the low-molecular weight carboxylic acid is not less than 1.5 and not more than 4.5.

### Claim 11 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein an average particle size of the metal fine particles (a) in the metal fine particle-containing ink is not less than 5 nm and not more than 100 nm.

### Claim 12 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein a content of the metal in the metal fine particle-containing ink is not less than 1% by mass and not more than 70% by mass.

### Claim 13

(canceled)

### Claim 14 (depends on 1)

A method for producing a printed material, comprising:
applying the metal fine particle-containing ink of claim 1 onto a printing substrate to form a metal coating film of the ink on the printing substrate under ordinary-temperature environmental conditions, thereby obtaining the printed material.

### Claim 15 (depends on 14)

The method for producing a printed material according to claim 14, wherein a sintering atmosphere upon forming the metal coating film is an atmosphere of air.

### Claim 16 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein a mass ratio of the low-molecular weight carboxylic acid C to the metal [low-molecular weight carboxylic acid C/metal] in the metal fine particle-containing ink is not less than 0.05 and not more than 1.

### Claim 17 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein a mass ratio of the low-molecular weight carboxylic acid C to the aqueous solvent D [low-molecular weight carboxylic acid C/aqueous solvent D] in the metal fine particle-containing ink is not less than 0.1 and not more than 0.7.

### Claim 18 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein a difference Δbp(C−D) between the boiling point (C) and the boiling point (D) is not less than 0.5° C. and not more than 70° C.

### Claim 19 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein s difference ΔpKa(B−C) between the acid dissociation exponent pKa (B) of the acid group in the dispersant B and the acid dissociation exponent pKa (C) of the low-molecular weight carboxylic acid is not less than 0.1 and not more than 2.0.

### Claim 20 (depends on 1)

The metal fine particle-containing ink according to claim 1, wherein the dispersant B is a water-soluble vinyl polymer comprising the constitutional unit derived from the acid group-containing monomer (b-1) and a constitutional unit derived from a polyalkylene glycol segment-containing monomer (b-2).