Direct Laser Interference Patterning of Nickel Molds for Hot Embossing of Polymers

Rank, Andreas; Kunze, Tim; Hoffmann, Tina; Lasagni, Andrés Fabían

doi:10.1002/adem.201600068

Cited by 12 publications

(8 citation statements)

References 21 publications

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“…It should be pointed out that the presented results add to the research presented by other authors and continue to prove DLIP as a rapid patterning technique which is compatible with materials conventionally used in production of anti-counterfeiting security tags, i.e. nickel foil and plastics used for thermal embossing 26 , 48 .…”

Section: Discussionsupporting

confidence: 73%

“…0.36 J/cm 2 was used for DLIP with a laser of 1064 nm wavelength and 10 ps pulse duration 47 . Using longer pulses of 6 ns and 1053 nm wavelength, 2.2 J/cm 2 fluence was selected by 48 . It was also demonstrated that using a reasonable pulse overlap one can make the grating continuous—557 mJ/cm 2 fluence and 95% overlap led to deepest structures in 26 .…”

Section: Discussionmentioning

confidence: 99%

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Dot-Matrix Hologram Rendering Algorithm and its Validation through Direct Laser Interference Patterning

Tamulevičius¹,

Juodėnas²,

Klinavičius³

et al. 2018

Sci Rep

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The fight against forgery of valuable items demands efficient and reasonably priced solutions. A security tag featuring holographic elements for anti-counterfeiting is one of them. However, the content and colours of a diffraction image that would be seen by an observer are often counterintuitive in the design stage. Here, we propose an original algorithm based on the conical diffraction formalism, which can be used to describe the variations of a diffraction image with respect to all aspects of observation. We validate the output of the algorithm by comparing it to test holograms, which we have produced by employing direct laser interference patterning (DLIP) in electrochemically grown nickel foil. We have employed a motorized femtosecond laser system to micro-machine arrays of 65 µm × 65 µm sized diffraction gratings with a defined orientation and pitch on the order of 1 µm. Based on completed diffraction efficiency measurements, we determined optimal ablation parameters, i.e. 57.4 mJ/cm2 fluence per pulse and 1100 pulses/pixel. Furthermore, we show how accurate the proposed algorithm is through measured diffraction spectra as well as captured diffraction images of test holograms produced using the obtained parameters. Finally, we showcase anti-counterfeiting tag prototypes with complex holographic effects, i.e. colour reconstruction, animation effects, and image multiplexing. The proposed algorithm can severely shorten the time between design and production of a holographic tag, especially when realizing it via a competitive origination technology—DLIP.

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Section: Discussionsupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Dot-Matrix Hologram Rendering Algorithm and its Validation through Direct Laser Interference Patterning

Tamulevičius¹,

Juodėnas²,

Klinavičius³

et al. 2018

Sci Rep

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show abstract

“…2. As expected, the structure depths in the stamps as well as in the PET foils increases with the number of laser pulses [16,18] . It can also be observed that the stamps produced with one and two laser pulses have a similar structure depth than the corresponding imprinted PET, which confirms the proper pattern transfer.…”

Section: Stamps and Imprints Topographysupporting

confidence: 80%

Fast and cost effective fabrication of microlens arrays for enhancing light out-coupling of organic light-emitting diodes

et al. 2019

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The efficiency of organic light-emitting diodes (OLEDs) deposited on flat substrates is strongly limited by the total internal reflection at the air-substrate interface. An effective strategy to reduce the amount of substrate modes and enhance the light out-coupling into the air is attaching a microlens array (MLA) on the external surface of OLEDs. In this study, polymeric MLA with periods between 1.2 µm and 2.0 µm are patterned by plate-to-plate nano-imprint lithography using metallic stamps structured by direct laser interference patterning. When MLA with a spatial period of 2.0 µm and a structure depth of 200 nm are employed on red, green and blue OLEDs, the external quantum efficiency is increased to 11.4%, 6.6% and 12.7%, respectively, due to a reduction of internally reflected radiation at the air-MLA-glass interfaces.

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“…Former studies about DLIP of metallic surfaces, utilizing ns‐pulsed laser irradiation, showed a limitation in the feasible maximal structure depth up to values of approximately 0.2 times the spatial pitch ( Λ ), especially for pitches below 2 μm . This effect was explained due to the significant decrease of the temperature difference between interference maxima and minima positions, since the heat provided by the laser has enough time to diffuse to the minima by thermal conduction.…”

Section: Introductionmentioning

confidence: 99%

Large Area One‐Step Fabrication of Three‐Level Multiple‐Scaled Micro and Nanostructured Nickel Sleeves for Roll‐to‐Roll Hot Embossing

2017

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Direct laser interference patterning enabled the fabrication of three level multiple-scaled microstructures on nickel surfaces using infrared picosecond laser pulses. While the largest spatial period (1.5 to 5.7 mm) could be controlled by adjusting the angle between the interfering laser beams and the laser wavelength, low and high spatial frequency laser induced periodic surface structures with pitches of approximately 800 nm and 160 nm, respectively, were also observed. Using a set of optimized processing parameters, large area Ni-sleeves were treated. These sleeves were later employed in preliminarily investigations of roll-to-roll high throughput hot-embossing of polymer foils.

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Direct Laser Interference Patterning of Nickel Molds for Hot Embossing of Polymers

Cited by 12 publications

References 21 publications

Dot-Matrix Hologram Rendering Algorithm and its Validation through Direct Laser Interference Patterning

Dot-Matrix Hologram Rendering Algorithm and its Validation through Direct Laser Interference Patterning

Fast and cost effective fabrication of microlens arrays for enhancing light out-coupling of organic light-emitting diodes

Large Area One‐Step Fabrication of Three‐Level Multiple‐Scaled Micro and Nanostructured Nickel Sleeves for Roll‐to‐Roll Hot Embossing

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