A research team led by Chiye Shunichi, associate professor of production and environmental sciences at the Graduate School of Technology, Saitama University, Japan, recently established the adoption of Nd:YAG by using gold nanoparticles that emit red, blue, gold, and other color properties depending on the size of the diameter.钇·········································································································································· Marking techniques for writing words and symbols using laser irradiation have been widely used at present, but color markings are still the first in the world. Right-hand side figure of the Saitama University school emblem made with gold nanoparticle marking technology. The appearance is golden (Image provided by Associate Professor Chiye Shunichi, Saitama University)
The single-color (mainly black) marking technology based on laser irradiation has been widely used in the fields of canned food shelf life marking, writing of various bar codes, and computer keyboard key names and characters. Most of them are written using Nd:YAG lasers for surface oxidation, surface carbonization, removal of surface layers, and the formation of microcracks in the interior.
Professor Ikino, who hopes to use laser illumination to realize a color marking technique that can emit various colors, focuses on the fact that gold nanoparticles emit different colors due to their different sizes. As a gold nanoparticle, red is emitted when the diameter is 10 nm, and black and gold are respectively emitted when the diameter is 75 nm and 100 nm. Blue light is emitted between 10 nm and 75 nm. From this, it is inferred that since the surface plasma of the gold particle surface interacts with absorption and reflection of visible light, different colors are emitted depending on the diameter.
In order to produce gold nanoparticles capable of emitting a desired color, a solution containing gold colloidal particles is first coated on the glass surface and then dried to form a coating layer having a thickness of about 30 μm. The surface is irradiated with a Nd:YAG laser, and the medium near the gold colloidal particles is removed by evaporation, leaving the gold nanoparticles. With different laser irradiation conditions, gold nanoparticles first agglomerate and then melt, and large-diameter gold particles can be formed. By controlling the diameter of the gold nanoparticles, the desired color can be obtained.
As a Nd:YAG laser, the research team led by Prof. Ikeno used YVO4 (钇 vanadium oxygen) compounds instead of YAG. The laser power is 1.28 to 1.96 W, the laser wavelength is 1064 nm or 532 nm, and the laser scanning speed is 2.5 to 30 mm/s. The irradiation position was controlled using a shutter and Galvanometer Mirror. At the top of the galvanometer mirror, an optical system using an fθ lens (which can continuously focus the laser light on a straight line within a certain range) is arranged, and the laser light is written for scanning.
The laser marking technology based on laser irradiation is expected to be used for a wide range of applications such as marking on the surface of an automobile body and carrying out original designs on a watch dial. It is expected to generate a large number of uses such as its own unique designs that can meet individual customization needs.
About this technology, it is planned to be presented at the "Innovation Japan 2004" exhibition held for three days at the Tokyo International Forum Conference Building in Chiyoda-ku, Tokyo on September 28, 2004.
