The Finer Point of Laser Coding on Films: Higher Efficiency at Shorter Wavelengths

  • By Jon Hall
  • January 04, 2022
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In the third blog in this Flexible Film series, we covered “The Future of Flexible Films” and the evolution of multi-layer films into more sustainable packaging film offerings. In this blog I will provide guidance on achieving higher efficiency laser coding by using shorter laser wavelengths.

Multi-layer and the mono-films will require more than just new kinds of lasers. Having new levels of precision and control in the way the energy is delivered will be critical, as well. Some of the newer laser wavelengths are much shorter and so have higher energy levels which must be well controlled.

Fiber lasers have enabled many new applications for laser coding on films. Film compatibility has to do with how well the laser energy is absorbed by the film. When the absorption of the laser wavelength is efficient, then the film will typically code well. When the adsorption of the laser wavelength is not efficient, then heat is created in the process. This unwanted heat can degrade code quality as well as the overall film appearance.

Microns and light waves. There's more to it than you think

The fiber Laser has a wavelength of 1-micron and is well suited for many films. A UV laser has a wavelength of .355-micron (1/3 of the fiber wavelength) and can provide greater code quality for films which are more compatible with a shorter wavelength.

Assuming the same focal length lens value is used, the UV laser line width will be 1/10 of the Fiber laser linewidth and 1/30 of the CO2 Laser linewidth. The UV laser is much more capable of producing very crisp, very clear, small codes. This can especially be an advantage producing high quality, high readability 2D codes in small spaces or on small products.

Light waves with shorter wavelengths (higher frequencies) have more energy. So, UV laser energy at .335-micron is more energetic than Fiber laser energy at 1-micron, which is more energetic than CO2 laser energy at 10-microns. In fact, a UV laser with just a few watts of power can do jobs which would require 10-20-times the power (wattage) in a Fiber or CO2 laser (assuming all 3 wavelengths could mark the film).

More energy is good as it can improve code quality. However, this energy must be controlled such that it doesn’t adversely affect the functionality of the film. The shorter the wavelength, the more important it is to be able to control how the energy is delivered. This enables optimization of the energy characteristics for the specific attributes of the film.

If the laser output is not configurable based on the structure of the film, then there could be potential compromises in the films. Care needs to be taken (designed in) to control and apply this higher energy in a purely constructive manner. This capability is used to enhance code quality and to protect the barrier properties of the film.

In general, the better the understanding of the material science of the film, the better the prescribing of the optimum laser coding approach for this film. Even once the optimum laser technology / wavelength is identified, the ability to “fine tune” the laser parameters to the specific film will be what produces optimum coding. It takes both the right technology and the right technique / expertise to accomplish this. Having the flexible film supplier and laser supplier work together and collaborate upstream in the process can also provide some real benefits.

Always. Test. Your. Substrates.

Users have brought films to our Laser Sample Lab which other laser suppliers had compromised in the laser coding process. In most cases, our lab was able to fine-tune the laser characteristics to the specific film structure and produce codes without compromising any of the functionality of the film.

These film users initially pushed back saying they had already sampled with this same type of laser technology. We explained that while this type of laser was the right tool for the job, it also required some special knowledge and expertise to produce the desired results on their films. Producing high quality codes on flexible films is about understanding both sides of the equation, the laser side (energy delivery) as well as the film side (material reaction).

The first step is putting our Laser Sample Lab to work on your films. This is a process which should be conducted by experts familiar with laser/matter interactions and the pertinent material science. You will want a full validation of the laser application with the new film type(s) as a baseline for your records.

A complete report showing not only the code quality but also the maximum potential throughput, duty cycle, etc., at your full production parameters. You will also want evaluations performed with more non-traditional laser wavelengths, which could provide real advantages with this new material. As soon as new film, or similar film is available, have the laser lab begin evaluating the laser interaction.

Use the expertise of a real laser lab as an extension of your own engineering resources. Your engineers are going to be plenty busy introducing and testing new film types in production and determining the full compatibility with the existing equipment and production requirements.

And that's a wrap!

A wrap on the 4 part series focused on laser technology on film that is! As was highlighted in a previous blog, in the next 3 years, thousands of production lines will transition to new packaging films. It will be critical to ensure that your films have been validated early from a laser coding perspective. As the film suppliers may have minimum available bandwidth to address any potential issues when they are busy transitioning all these users / production lines to new films.

Let's start the dialogue. I hope you found these helpful to showcase options for coding onto your flexible film substrates.

As always, I invite you to connect with me on LinkedIn and reach out to me with any of your questions you might have. I also encourage you to review other content we have developed for you related to the laser journey.

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