The printing partner is responsible to ensure that Scantrust QR Codes (QR Codes + Secure Graphic) are printed correctly. Correct printing ensures that the codes can be easily scanned, and are recognized as authentic codes by the system. An inferior printing quality cannot be tolerated as it may result in QR Codes that are hard to scan during the authentication process, and/or that are not recognized as authentic. Scantrust works closely with Printing Partners to provide the support and knowledge required to ensure successful printing of Scantrust QR Codes.
'Image 1' below is an example of a high-quality print of a Scantrust QR Code: please note that for other printing techniques, the appearance of a high-quality print will vary. However, for all printing techniques, the following features are expected:
- Good contrast and crisp transitions in the QR Code
- The Secure Graphic contains a good balance of white and black and a high number of white/black transitions.
- The 12 small square markers around the Secure Graphic are neatly printed
- The marker at the bottom right contains a white center that can be clearly seen
It is acknowledged that not all printing techniques and substrates allow the level of precision showcased in 'Image 1' to be reached when printing the Scantrust QR Code. The intrinsic level of quality achievable by a particular printer, substrate (and in some cases finishing) combination is taken into account by the Scantrust Engineer during the calibration stage. The expected print quality level with tolerances are defined for each particular combination. From the calibration stage, as well as from prior experience with other printers using the same or comparable combinations, it is known that this print quality level can be reached and maintained.
Scantrust provides a Printer App to the printer which the printing operator should use as frequently as is reasonably possible to ensure a high and stable printing quality. The first function of the Printer App is to ensure that the codes are printed within the tolerance range, which is defined based on the results of the initial calibration phase. The printer is responsible for any codes not printed within the tolerance range. To ensure stable output within tolerance, the scans of all QA activities are saved in the Scantrust system and can give a detailed account of the variation during printing.
The following section reviews a subset of printing issues that may occur and which printers should be careful about.
Halftoning of Secure Graphic (All printing technologies)
Issue: Large information loss reduces ability to discriminate original from copies
Solution: Verify the prepress process and ensure QR Codes are integrated as TIF 1-bit images
Color Separation (All printing technologies)
Issue: The Secure Graphic is very light, there is low contrast; even if the information is still there; it will be harder to focus during authentication, scan quality can be affected
Solution: Verify the prepress process and ensure QR Codes are integrated as TIF 1-bit images. Check the color model in prepress.
Halo/Excessive Pressure (Flexo)
Issue: The white ridges along the borders of the black patches affect the quality assessment algorithms during QR Code scanning, which affects the scanning and can result in bad user experiences; it can also affect the Secure Graphic quality.
Solution: Control pressure of the plate across the full width of the plate to eliminate ridges; if possible add a black border around the QR Code to balance the pressure.
Issue: The black areas are not filled with ink. This affects the scanning experience.
Solution: Take standard procedural measures in normal printing environment to eliminate pinholing.
Too Low Ink Density (All printing technologies)
Issue: Secure Graphic is very light, low contrast; even if the information might still be there, it will be harder to focus and scan quality can be affected.
Solution: Increase amount of ink, or ink viscosity (offset); eventually run new printer calibration to determine other settings of Secure Graphic.
Excessive Dot Gain (All printing technologies)
Issue: Secure Graphic becomes saturated and the ability to authenticate is reduced.
Solution: Standard procedure to reduce dot gain.
Doubling (Offset printing)
Issue: Secure Graphic quality will be severely affected by doubling.
Solution: Standard procedure to eliminate doubling.
Feathering (Digital DoD)
Issue: Can affect the scanning and the authentication.
Solution: Standard procedure to eliminate feathering.
Design Issues (All printing technologies)
Issue: Affects Secure Graphic quality
Solution: Control PDF design carefully and make sure that no element has the risk to overlap the Secure Graphic and QR Code.
Excessive Variations of Ink Coverage / Dot Gain During Print Run (All printing technologies)
Issue: Affects Secure Graphic ability to discern originals from counterfeits
Solution: At the beginning of the print run, make sure that all imposition have the same ink coverage / same dot gain. Monitor all impositions throughout the print run.
The means to avoid variation of ink coverage during a print run or by imposition will vary depending on printing technology. They generally affect offset and flexo prints more frequently than digital prints.