Search

US-12624236-B2 - Inkjet inks for opaque printed images

US12624236B2US 12624236 B2US12624236 B2US 12624236B2US-12624236-B2

Abstract

An inkjet ink, including (A) a resin, which is (A1) a terpene resin or (A2) a terpene phenol resin, (B) a solvent system including (B1) a volatile organic solvent having a boiling point of less than 100° C., and (C) silver nanoparticles. A printed article, including a substrate, and an opaque film disposed on the substrate. The opaque film is formed from the inkjet ink.

Inventors

  • Yuta Matsumoto
  • Tomohide Yoshida

Assignees

  • KAO CORPORATION

Dates

Publication Date
20260512
Application Date
20210331

Claims (19)

  1. 1 . An inkjet ink, comprising: (A) a resin, which is (A1) a terpene resin or (A2) a terpene phenol resin; (B) a solvent system comprising (B1) a volatile organic solvent having a boiling point of less than 100° C.; and (C) silver nanoparticles, wherein the silver nanoparticles (C) are in a dispersion with a dispersant, and wherein the dispersant is a styrene/(poly)alkylene glycol (meth)acrylate/acrylic acid copolymer.
  2. 2 . The inkjet ink of claim 1 , wherein the resin (A) is present in an amount of 0.1 to 5 wt. %, based on a total weight of the inkjet ink.
  3. 3 . The inkjet ink of claim 1 , wherein the resin (A) is the terpene resin (A1).
  4. 4 . The inkjet ink of claim 3 , wherein the terpene resin (A1) is a homopolymer made from α-pinene.
  5. 5 . The inkjet ink of claim 1 , wherein the resin (A) is the terpene phenol resin (A2).
  6. 6 . The inkjet ink of claim 5 , wherein the terpene phenol resin (A2) has a hydroxyl value of 10 to 80 mgKOH/g.
  7. 7 . The inkjet ink of claim 1 , wherein the volatile organic solvent (B1) is present in an amount of 50 to 95 wt. %, based on a total weight of the inkjet ink.
  8. 8 . The inkjet ink of claim 1 , wherein the volatile organic solvent (B1) is an alcoholic solvent.
  9. 9 . The inkjet ink of claim 1 , wherein the volatile organic solvent (B1) is ethanol.
  10. 10 . The inkjet ink of claim 1 , wherein the volatile organic solvent (B1) is a ketone solvent.
  11. 11 . The inkjet ink of claim 1 , wherein the volatile organic solvent (B1) is methyl ethyl ketone.
  12. 12 . The inkjet ink of claim 1 , wherein the solvent system (B) further comprises (B2) a glycol ether.
  13. 13 . The inkjet ink of claim 1 , wherein the silver nanoparticles (C) are present in an amount of 0.5 to 15 wt. %, based on a total weight of the inkjet ink.
  14. 14 . The inkjet ink of claim 1 , wherein the silver nanoparticles (C) have an average particle size of less than 100 nm.
  15. 15 . The inkjet ink of claim 1 , further comprising (D) an alkanolamine, wherein the alkanolamine (D) is present in an amount of 0.1 to 10 wt. %, based on a total weight of the inkjet ink.
  16. 16 . The inkjet ink of claim 15 , wherein the alkanolamine (D) is at least one selected from the group consisting of ethanolamine, propanolamine, isopropanolamine, diethanolamine, and triethanolamine.
  17. 17 . The inkjet ink of claim 1 , further comprising (E) a silicone acrylate copolymer, wherein the silicone acrylate copolymer (E) is present in an amount of up to 5 wt. %, based on a total weight of the inkjet ink.
  18. 18 . A printed article, comprising: a substrate; and an opaque film disposed on the substrate, wherein the opaque film is formed from the inkjet ink of claim 1 .
  19. 19 . A method of forming an opaque printed image on a substrate, comprising: applying the inkjet ink of claim 1 onto the substrate with a thermal inkjet printhead; and drying the inkjet ink, thereby converting the inkjet ink into an opaque film forming the opaque printed image.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a National Stage entry under 35 U.S.C. § 371 of PCT/US2021/025065, filed on Mar. 31, 2021. The entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to inkjet inks, specifically inkjet inks that include (A) a resin, which is (A1) a terpene resin or (A2) a terpene phenol resin; (B) a solvent system containing (B1) a volatile organic solvent having a boiling point of less than 100° C.; and (C) silver nanoparticles. Discussion of the Background The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention. Thermal inkjet (TIJ) printing is a desirable technology for printing, coding, and marking as it offers high print resolutions at lower costs than competing technologies in the field, such as continuous inkjet methods. In thermal inkjet printing processes, the print cartridges contain a series of tiny chambers, each containing a heater, which produce ink droplets from thermal vaporization of an ink solvent. In the jetting process, a resistor is heated rapidly to produce a vapor bubble (hence the phrase “bubble jet”), which subsequently ejects a droplet from the orifice. This process is extremely efficient and reproducible and modern TIJ printheads for industrial graphics applications are capable of generating uniform drops of 4 pL or smaller in volume at frequencies of 36 kHz or greater. Yet, providing readable images on dark colored substrates poses a significant challenge for inkjet ink printing. Traditionally, opaque pigmented inks (e.g., white or yellow pigmented inks) have been used to provide contrast on dark colored substrates. The pigments used in these inks, such as titanium oxide, need to be of large particle size on the order of about 200 nm or larger, and must be applied to the dark surface in high density to achieve adequate legibility (i.e., adequate opacity). As a result, opaque pigmented inks are prone to settling, leading to poor shelf-life, clogging of the inkjet nozzles, and defective jetting. Opaque pigmented inkjet inks thus typically require inkjet printers fitted with a mechanical mechanism (e.g., shaking or stirring mechanisms) for keeping the pigment suspended throughout the printing operation. The open atmosphere print head design (the nozzle orifices are open to atmosphere and there is no valve seal at the orifice to allow ink pressurization) of thermal inkjet printheads further exacerbates the issue of nozzle clogging, where decap time (print idle time) causes premature drying of ink in and around the nozzles. Solvent losses due to prolonged exposure to air within an uncapped printhead results in clogging/plugging of printhead nozzles and unreliable ink jetting and image quality erosion over time. SUMMARY OF THE INVENTION In view of the forgoing, there is a need for inkjet inks that are capable of providing legible (opaque) images on dark colored substrates, perform under extended decap conditions, and have robust running stability—i.e., are not prone to settling during printing operations-without the need for special mechanical mechanisms for achieving adequate particle suspension. Accordingly, it is one object of the present invention to provide novel inkjet inks that meet these criteria. It is another object of the present disclosure to provide novel printed articles which contain an opaque film, formed from the inkjet inks, disposed on a substrate. It is another object of the present disclosure to provide novel methods of forming an opaque printed image on a substrate by applying the inkjet inks onto the substrate and drying the inkjet ink, thereby converting the inkjet ink into an opaque film forming the opaque printed image. These and other objects, which will become apparent during the following detailed description, have been achieved by the inventors' discovery that silver nanoparticles can be stably suspended in an inkjet ink without settling, and after being applied to a substrate surface, drying of the inkjet ink and coalescence of the silver nanoparticles provides opaque printed images of excellent legibility. Further, reliable ink jetting at extended decap times is possible when the inkjet ink is also formulated with specific resins and volatile organic solvents. Thus, the present invention provides: (1) An inkjet ink, comprising: (A) a resin, which is (A1) a terpene resin or (A2) a terpene phenol resin;(B) a solvent system comprising (B1) a volatile organic solvent having a boiling point of less than 100° C.; and(C) silver nanoparticles. (2) The inkjet ink of (1), wherein the res