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JP-7856409-B2 - Metallic ink for inkjet printers and inkjet recording method

JP7856409B2JP 7856409 B2JP7856409 B2JP 7856409B2JP-7856409-B2

Inventors

  • 大山 淳史

Assignees

  • キヤノン株式会社

Dates

Publication Date
20260511
Application Date
20211125

Claims (14)

  1. A metallic ink for inkjet printers containing flat metal particles and resin particles, The volume-based median diameter (DP50) of the aforementioned flat metal particles is 300 nm or more and less than 500 nm. The average thickness of the aforementioned flat metal particles is 50 nm or less. The content of the flat metal particles is 0.2% by mass or more and 10% by mass or less relative to the total mass of the inkjet metallic ink. The content of the resin particles is 0.2% by mass or more and 10% by mass or less relative to the total mass of the inkjet metallic ink. A metallic inkjet ink characterized in that the median diameter (DP50) of the flat metal particles based on volume / the median diameter (D50) of the resin particles based on volume is 4.0 or more and 20.0 or less .
  2. The metallic inkjet ink according to claim 1, wherein the volume-based median diameter (DP50) of the flat metal particles is 400 nm or less.
  3. The metallic ink for inkjet printers according to claim 1 or 2, wherein the volume-based median diameter (DP99) of the flat metal particles is 1 μm or less.
  4. The metallic ink for inkjet printers according to claim 3, wherein the volume-based median diameter (DP99) of the flat metal particles is 900 nm or less.
  5. The metallic ink for inkjet printers according to claim 3 or 4, wherein the volume-based median diameter (DP99) of the flat metal particles is 800 nm or more.
  6. The metallic ink for inkjet printers according to any one of claims 1 to 5, wherein the average thickness of the flat metal particles is 10 nm or more.
  7. The metallic ink for inkjet printers according to any one of claims 1 to 6, wherein the flat metal particles are aluminum particles.
  8. The metallic inkjet ink according to any one of claims 1 to 7, wherein the volume-based median diameter (D50) of the resin particles is 10 nm or more and 80 nm or less.
  9. The median diameter (DP99) of the aforementioned flat metal particles is 1 μm or less based on volume. The average thickness of the aforementioned flat metal particles is 10 nm or more. The metallic ink for inkjet according to claim 1 or 2, wherein the volume-based median diameter (D50) of the resin particles is 10 nm or more and 80 nm or less.
  10. The metallic ink for inkjet according to any one of claims 1 to 9, wherein the resin particles are polyester resin particles.
  11. The inkjet metallic ink according to any one of claims 1 to 10, wherein the inkjet metallic ink is an aqueous ink containing water.
  12. The metallic ink for inkjet printers according to any one of claims 1 to 11, wherein the flat metal particles are surface-treated with a phosphate compound.
  13. The metallic inkjet ink according to any one of claims 1 to 12, wherein the median diameter (DP50) of the flat metal particles based on volume / the median diameter (D50) of the resin particles based on volume is 5.0 or greater.
  14. An inkjet recording method for printing an image on a recording medium using an inkjet metallic ink according to any one of claims 1 to 13 .

Description

This invention relates to a metallic ink for inkjet printing. Furthermore, this invention relates to an inkjet recording method using the metallic ink. Traditionally, inks containing metallic pigments such as brass, aluminum, and silver have been used to create images with a metallic sheen in printed materials such as packaging, labels, and photographs. Analog printing techniques such as offset printing, screen printing, and gravure printing have been used to create such images. Other methods, such as foil stamping using metal foil, are also known. In recent years, with the development of digital printing technology, methods for forming images with metallic luster using inkjet technology have been proposed. Furthermore, from the perspective of environmental protection and human health safety, inkjet recording methods using water-based inks containing only small amounts of organic solvents are being developed. In the analog printing techniques described above, aluminum pigments, which have a flat, plate-like shape, have been used as one of the pigments capable of expressing metallic luster. Patent Document 1 is an example of applying a flat aluminum pigment to an inkjet recording method. Patent Document 1 aims to provide a high metallic mirror gloss, with specular gloss values of 200, 200, and 100 or higher at 20 degrees, 60 degrees, and 85 degrees, respectively. To achieve this, when the major axis on the plane of the flat metal particles is X, the minor axis is Y, and the thickness is Z, the 50% average particle diameter R50 of the equivalent circle diameter calculated from the area of the X-Y plane of the particles is 0.5 to 3 μm, and the condition R50/Z > 5 is satisfied. On the other hand, for metallic inkjet inks, a representative digital printing technology, there are also proposals to prepare and use granular metal nanoparticles, particularly silver nanoparticles, for printing in order to eject the ink from fine nozzles. Although a binder resin was used because metal nanoparticles could not be sufficiently adhered to the substrate (also called a recording medium), particularly non-absorbent substrates, sufficient metallic luster could not be obtained. To obtain sufficient metallic luster, Patent Document 2 proposes an inkjet ink containing metal nanoparticles and emulsion resin particles, wherein the average particle size of the metal nanoparticles and the average particle size of the emulsion resin particles are adjusted to a predetermined relationship. Japanese Patent Publication No. 2020-94217International Publication No. 2018/181080 The metallic inkjet ink of the present invention (hereinafter also simply referred to as "ink") contains flat metal particles and resin particles. <Flat metal particles> The plate-shaped metal particles used in this invention are particles made of metal that have a flat surface and a thin thickness in the direction intersecting the direction of the surface. In other words, they are flattened particles with a high aspect ratio, where the diameter of the circle-like part of the flat surface is large relative to the thickness. The pigments commonly found in inks are spherical. Furthermore, these pigments may adhere to the recording medium through penetration, physical adsorption, and chemical interactions, or they may have an auxiliary effect on adhesion to the recording medium, or they may have been processed to improve their adhesion. On the other hand, the flat metal particles contained in the metallic ink used in this invention have the characteristic of being less likely to exhibit adhesion to the recording medium due to their shape. In the present invention, a metallic ink containing resin particles and liquid is prepared to improve the fixation of the plate-shaped metal particles. Then, the metallic ink is ejected onto a liquid-absorbent recording medium, such as paper, using an inkjet method. The liquid in the metallic ink adhering to the recording medium is absorbed by the medium, causing the plate-shaped metal particles and resin particles to level on the recording medium. Because the resin particles have a smaller median diameter by volume than the plate-shaped metal particles, the plate-shaped metal particles are fixed onto the recording medium such that their planes are parallel to the surface of the recording medium. The size of the aforementioned flat metal particles can be measured and analyzed using a wet particle image analyzer (for example, product name: FPIA-3000, manufactured by Sysmex Corporation, or product name: IF-3200, manufactured by Jusco International, etc.). The sizes of the flat metal particles measured using the aforementioned apparatus, based on a volume-based particle distribution of the diameter equivalent to a circle on a flat surface, are described below at 50% integration (median diameter (DP50)) and 99% integration (median diameter (DP99)). The flat metal particles used in this invention preferably have a DP50 of less than 500 nm, an