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.

Challenge

Gratings with small distances between the lines cause a diffractive effect and thus shimmer in different colors. 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 several specific disadvantages: glas absorbs hardly 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 on resting workpieces using a scanner. Even though the absorption of infrared light is higher and more powerful lasers are available, the higher wavelength results in lowered 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 glas surfaces: short wavelengths in the ultraviolet range are well absorbed by glas and plane beam profiles allow for parallel processing of larger areas. Common 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.

Our Solution

According to the above mentioned challenges, the aim of the inventors was to develop a method for fast and efficient microstructuring of glass.
The developed process uses plane laser ablation by excimer lasers, however, with low-loss optical components and methods. The whole beam profile of the laser is being used, resulting in higher laser output and increased efficiency and contrast. With the newly developed method it is now 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 devises that create a relative movement between the laser and the workpiece, 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 maximal repetition rate of the laser can be used.
With this process, it is now possible to produce gratings on a micrometer scale within a very short time frame on workpiece surfaces - especially glass surfaces. The produced structure can fill a predefined shape. The resulting shape then appears colorful and shimmering, similar to what is known from holographic markings. Alternatively, it can be used to define the wavelength-dependent reflection or transmission of a surface.

A micrometer scaled grating on a glass surfaces causes diffraction and creates a colorful and shimmering structure. (Source: Dr. Jürgen Ihlemann, LLG)

Advantages

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

Applications

Labelling of surfaces particularly glas or glas ceramics
forgery-proof labeling
micro- and nanostructuring of surfaces, e.g. modification of reflection and transmission

Development Status

The method was successfully tested with different patterns on different surfaces:

glas
glas ceramics
plastics

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.

Patent Status

DE patent granted: DE102015216342B3
EP patent application disclosed: EP3341153A1
US patent application disclosed: US2018236596A1
CN patent application disclosed: CN107921579A
KR patent application disclosed: KR20180098217A

Patent Applicant: Laser-Laboratorium Göttingen e.V.

References

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)

Contact

Dr. Ireneusz Iwanowski
Patent Manager (Physics, Technology and Software)
E-Mail: iiwanowski(at)sciencebridge.de
Tel.: +49 (0) 551 30724 153
Ref: MM-1773-LLG
www.sciencebridge.de