Laser marking of ceramic materials, glazes, glass ceramics and glasses

Claim 1

A process for laser marking ceramic materials, glazes, glass ceramics and glasses that contain at least one radiation-sensitive additive effecting a change in color upon radiation in amounts from 0.01 to 30% by weight, based on said material, which process comprises utilizing a laser beam as radiation energy source which is either applied to, or focused on, the surface of the material to be marked in accordance with the form of the graphic symbols to be reproduced, such that a change in color of marked contrast and legible to the eye is induced at the irradiated areas and corresponding to the form of said graphic symbols, and without perceptible damage to the surface of the marked material, wherein the wavelength of said laser beam used as energy source is in the near UV and/or visible range and/or infra-red range, and the radiation-sensitive additive is an inorganic pigment selected from the group consisting of cobalt aluminates, chrome tin pink sphene, chrome tin orchid cassiterite, tin vanadium yellow, zirconium vanadium yellow, zirconium vanadium blue, zirconium preseodyme yellow, zirconium iron pink, the cadmium sulfoselenides and cadmium sulfides and the inclusion compounds containing them, copper-red, manganese pink, colcothar, the iron oxide brown pigments, iron-chrome-alumina spinels, manganese-alumina spinels, zinc-chrome spinels, iron-alumina spinels, zinc-iron spinels, nickel-iron spinels, manganese-chrome spinels, zinc-iron-chrome spinels, tin oxide, titanium dioxide and titanates.