Print Quality Assessment of QR Code Elements Achieved by the Digital Thermal Transfer Process

Area of Science:

• Printing Technology
• Packaging Science
• Information Technology

Background:

• European Regulation (EU) 2025/40 mandates modern packaging solutions, including the use of QR codes.
• QR codes, defined in ISO/IEC 18004:2024, are replacing linear barcodes on packaging and personal documents.
• Implementation of QR codes in printing systems requires further research, particularly for high-precision applications.

Purpose of the Study:

• To investigate the feasibility of producing QR code elements using digital foil printing.
• To determine the optimal UV varnish thickness for achieving high-quality QR code reproduction.
• To assess the impact of element size and UV coating thickness on QR code readability.

Main Methods:

• A hybrid printing process combining drop-on-demand UV inkjet and thermal foil transfer was employed.
• MGI JETvarnish 3DS digital machine used to apply UV varnish coatings of 7, 14, and 21 µm.
• Analysis of QR code element quality (square profiles and surface definition) for various element sizes (0.06 cm² to 16 cm²).

Main Results:

• Imprint quality was suboptimal for the smallest QR code elements (0.1 cm and 0.25 cm base lengths) with 7 µm UV coating.
• Increasing UV varnish thickness to 14 µm (2 drops) and 21 µm (3 drops) significantly improved reproduction stability and uniformity.
• The highest technical precision and most stable, even reproduction were achieved with a 21 µm UV varnish thickness.

Conclusions:

• Digital foil printing is a viable technique for producing high-precision QR codes on packaging.
• Optimal UV varnish thickness is crucial for ensuring the quality and readability of printed QR codes.
• A UV varnish thickness of 21 µm provides the best results for digital foil printing of QR codes.