| 摘要 |
The invention relates to special types of printing which make it possible to produce a distinctive image from metal monocrystals in the body of a non-absorbent sheet material, which image is capable of protecting against counterfeiting. The production of such an image involves introducing materials for the formation of monocrystals from a solution into a sheet material and acting on the aforesaid materials with pulses of laser radiation via set points on the surface of the sheet material. For the purposes of introducing the solution into a non-absorbent sheet material which does not have pores or capillaries, a surfactant is additionally added to the solution. The solution is then applied in an even layer to the non-absorbent surface of the sheet material, and the film which forms on the surface of the solution is cured, thus enclosing the solution between the sheet material and the cured film. When the solution situated underneath the film is acted on with pulses of laser radiation, at each point at which such action is carried out a protective gaseous medium is produced underneath the cured film in the region of the laser spot, in which gaseous medium the metal is reduced to pure metal with the formation of clusters which are introduced into the sheet material via the channel formed by the laser beam. In the channel, a high concentration of clusters is produced which are scattered at high speed onto the walls of the channel and melted to form a liquid substrate, producing metal seeds upon cooling which grow and form monocrystals that are integral with the sheet material. The distinctiveness of an image made up of monocrystals produced in the body of a sheet material is increased if the surface of the material to which the solution is applied is ribbed rather than smooth, having parallel lines embedded therein which collectively form a diffraction grating. |
