Gratings on glass surfaces
The newly developed method provides a faster and more efficient way for producing gratings - by ablation of small amounts of material - on glass surfaces. Thereby, the economic labeling of glass with patterns causing diffraction becomes possible. These patterns shimmer in different colors if observed from different angles.
Gratings with small distances between the lines produce a rainbow of colors via diffraction of light. This can be used to create aesthetic labels and give the marked product a unique characteristic. Until now, it was not possible - especially on glass - to produce these structures fast and efficiently enough. For contactless labeling of products, only laser ablation with pulsed lasers can be used. However, conventional laser procedures have specific disadvantages: glass hardly absorbs any light in the visible range, thus high pulse intensities have to be used. Due to the resulting small laser spots, only tiny areas can be processed per pulse. Plane structuring is therefore only possible using a scanner system. Even though the absorption of infrared light is higher and more powerful lasers are available, the longer wavelength results in low resolution of the generated structures - gratings with periods in the micrometer range are not possible. In contrast, excimer lasers combine several advantages for processing of glass surfaces: short wavelengths in the ultraviolet range are strongly absorbed by glass and plane beam profiles allow for parallel processing of larger areas. Established mask projection techniques can be used for micro-structuring. Mask projection however requires advanced optics and typically used amplitude masks lead to high light losses.
According to the above mentioned challenges, the aim of the inventors was to develop a method for fast and efficient micro structuring of glass. The developed process uses plane laser ablation by excimer lasers using low-loss optical components and methods. The whole beam profile of the laser is being used, resulting in higher throughput and increased efficiency and contrast. With the newly developed method it is possible to move the workpiece continuously, as needed in industrial production or processing. Laser pulses are triggered whenever the workpiece has moved by one or multiple periods of the desired grating. Additional beam steering devices, e.g. a scanner, are not required. If the grating has to be tilted towards the feed direction, only the increment between two pulses has to be adjusted to the line distance in feed direction. Optimally, the maximum repetition rate of the laser can be used. With this process, it is now possible to produce micrometer gratings on work piece surfaces - especially glass surfaces – within a very short time frame. The produced structure can fill a predefined shape. The resulting shape then appears intensely colorful, similar to what is known from holographic markings. Alternatively, it can be used to define the wavelength-dependent reflection or transmission of a surface.
- Efficient process with a simple setup
- High dispersion through microfine structures
- resulting in labels with brilliant color shimmer of high aesthetics
- High process speeds
- Structuring without (micro-)cracks
- Possibility to label plane and curved surfaces
- integrable into production lines
- Labelling of surfaces particularly glas or glas ceramics
- forgery-proof labeling
- micro- and nanostructuring of surfaces, e.g. modification of reflection and transmission
The method was successfully tested with different patterns on different surfaces:
- glass ceramics
Currently, the invention is being further developed in a Federal Ministry of Economics and Technology (BMWi)-funded project (WIPANO - funding focus "public research - further development of inventions"), with regard to industrial manufacturing processes.
J. Meinertz, T. Fricke-Begemann, J. Ihlemann:
Micron and sub-micron gratings on glass by UV laser ablation
Physics Procedia 41, 701 (2013)
J. Bekesi, J. Meinertz, P. Simon, J. Ihlemann:
Sub-500-nm patterning of glass by nanosecond KrF-excimer laser ablation
Applied Physics A 110, 17 (2013)
Dr. Markus Muchow
Patent Manager (Physics, Technology and Software)
Tel.: +49 (0) 551 30724 159