Light Prints Innovation - A complete photonics solution for print
Visit Hamamatsu Photonics at Future Print Tech 2023 (table 1)
Attend our talk on the 8 th of November (11.45am-12.00pm)
In recent years, with the constant evolution of applications, technologies and regulations, the printing market has increased its demands for higher speeds, higher quality and higher value. Along with our customers, Hamamatsu Photonics has come across a number of challenges and have aimed to solve them with our decades of accumulated photonics experience. Hamamatsu has developed a complete proposal for innovative printing using an array of optical technologies for a variety of printing applications.
Electrostatic Countermeasures
Controlling the substrates going through a printer can cause the build-up of static electricity, which can cause a variety of headaches for end users, each of which can significantly affect the quality of their product. Charged surfaces attract dust and other sections of charged material, which can cause problems with misprinting and paper alignment. In addition, depositing ink onto a charged surface can affect particle adhesion and affect the quality of the print.
Hamamatsu’s Photoionizers use low-energy, “soft” X-rays to remove electrons from stable atoms to create positive ions, with the electrons then combining with other stable atoms to create negative ions. These ions are then attracted to the substrates’ charged surface and combine to cancel it out, with the remainder of the ions then returning to their natural neutral state. This means that there is no danger of accidentally creating a second charge imbalance as a result of the neutralisation process.
In addition to being able to completely neutralise the target, the Photoionizer has some other features that make it particularly suitable for the printing market when compared to other existing technologies, such as corona treatment. The first of these reverts back to the earlier comment regarding dust. These sources require no airflow, nor do they create any during the irradiation process, which means no dust is moved through the printer as a result of the process. In addition to this, there is no regular maintenance required to keep the high performance of the product.
Finally, then the system can also work in special environments such as those using inert gases.
This process can be used at both the beginning and the end of the printing process, to prepare substrates for printing and then again at the end before the printed product is removed for packing and shipment.
UV Printing
Once the substrate has been prepared it is moved through to the ink deposition stage. For some applications, the conventional drying of water-based inks are too energy-intensive, in which case UV-cured inks can be used as an alternative in a world where energy efficiency and environmental impact are of increasing importance. Whilst halide lamps have been an industry staple for many years, UV-LED technologies have improved significantly to be very competitive for many printing applications and can be used to print on a variety of materials including paper, film and timber. The UV light creates chemical bonds between monomers in the printer inks, creating strong bonds and by extension, strong prints.
UV-LED lamps are often used for two different sections of the print. Firstly, after each initial printhead, a lower-powered UV-LED is used to “pin” the deposited ink in place as it moves through the printer. This pinning process holds the ink in place without completely drying the ink to allow further layers to be printed. After all inks have been printed, a higher power UV-LED is used to “deep cure” the ink to finalise the print ready for post-processing.
There are a few key parameters that UV-LED manufacturers decide on when designing these kinds of sources. Firstly, the amount of dose reaching the target – this is done by either increasing the power of the lamp or by increasing the size of the LED window, both of which require more power and cooling to perform efficiently. Air-cooling is generally preferred due to the lower costs involved, but water cooling is necessary for the highest powers and doses to maintain performance. In addition, if the cooling system does not cool the LEDs evenly, there can be nonuniformities in the print due to differences in the performance. To combat this Hamamatsu have developed their ThoMaS system, which includes a double-walled structure to prevent the buildup of heat across the LED window, and a customised heat sink. Using these technologies it is expected that the next generation of products can either reduce size to a half of the current design but maintain performance, or keep the current size and add significant performance benefits.
In addition to the ThoMaS system, Hamamatsu has also developed a proprietary Nitrogen inserting system, HANCE. Nitrogen can be used in front of a UV-LED window to prevent oxygen from inhibiting the UV light and reducing performance. In addition, it can act as barrier to unwanted contaminants.
The HANCE system has been developed to minimise the Nitrogen used during the inerting process to help reduce size and cost whilst maintaining performance.
Velocity vector and temperature distribution (Typ.)
New type heat sink Conventional heat sink
Surface Modification & Matting
Once the main print process has been completed, Excimer light can be used to further modify the final results of the print. Using very low wavelength UV light, this technology enhances or changes the characteristics of materials by altering the compositions and structures of the surface materials.
Excimer light sources can be used for applications such as matting, which is achieved by this surface modification technique. After varnish is applied (but before the varnish is cured), excimer light is used to irradiate it, modifying the surface and creating a matting effect. With this end users can control how glossy their final product is.
Hamamatsu’s excimer lamps are unique in a couple of ways that maximise their effectiveness for these kinds of applications. Firstly, the flat shape of the lamp means that throughout the entire exposure period of the excimer light, a uniform amount of power is deposited. By using Radio Frequency discharge, we can emit a uniform and stable output in a dust-free process. These minimise the damage and problems caused whilst maximizing the performance of the print process and helping to increase print speeds.
Light Level Control
Whilst curing inks and varnishes it is important that UV-LED light sources are outputting the correct amount of light to complete the curing process, otherwise, the end product will be poor and customers will be dissatisfied. Using our decades of expertise in light detection, Hamamatsu’s highly precise power meters allow the control of light levels from UV-LED light sources and Excimer light sources. The proprietary solid-state devices give highly reproducible measurements and allows accurate management and digitization of the light hitting the target, allowing customers to vary the degree of surface modification to their materials.
When used in combination, photonics solutions can be used to increase the performance and quality of the printing process, allowing customers to reduce their energy used whilst increasing the throughput of their machines. Hamamatsu looks to work closely with our customers to develop solutions that fit their individual circumstances – for more information and to arrange a discussion with one of our experts, reach out via email to info@hamamatsu.co.uk, or call us at 01707 294 888.