10-06-2021 дата публикации
Номер: US20210171786A1
The present invention relates to a process for the preparation of thin silver nanoparticle layers, which are produced directly on a substrate as part of a coating or printing process. The layers show different colours in transmittance and reflectance. The layers do not show the typical conductivity of metallic layers, since the particles are essentially discrete particles which are not sintered. The invention further relates to decorative and security elements. When the layers are applied over a security element, such as a hologram, the obtained products show also different colours in reflection and transmission, an extremely bright optically variable image (OVD image) and high purity and contrast. Depending on the thickness of the layer a more or less intensive metallic aspect appears. 1. A method for forming a silver nanoparticles-containing layer on a substrate , the method comprising:A) optionally forming an optically variable device (OVD) on a discrete portion of the substrate;B) applying a composition on at least part of the substrate, optionally on at least part of the OVD obtained in step A), or both, to obtain a coating; andC) exposing the coating to heat, irradiating the coating with electromagnetic radiation, or both, to form a highly reflective layer comprising silver nanoparticles, b1) a silver metal precursor,', 'b2) an acid,', 'b3) optionally a solvent,', 'b4) an optionally substituted polyhydric phenol, and', 'b5) optionally a polymeric binder., 'wherein the composition comprises2. The method according to claim 1 , wherein the silver metal precursor is selected from the group consisting of:{'sup': 11', '11, 'sub': 1', '8, 'a compound of formula RC(═O)OAg, wherein Ris a C-Calkyl group, wherein part of the hydrogen atoms may be replaced by F and/or Cl,'}{'sup': 12', '13', '12', '13, 'sub': 1', '8, 'a compound of formula RC(═O)CH═C(—OAg)—R, wherein Rand Rare independently of each other a C-Calkyl group, wherein part of the hydrogen atoms may be replaced ...
Подробнее