How to ensure the quality of QR code printing in the era of "digital tags"?
On September 8th, the National Health Commission and the State Administration for Market Regulation jointly issued the Announcement on the Implementation of Digital Labels for Prepackaged Foods (No. 5 of 2025). This announcement further elaborates on the requirements for "digital labels" in the "General Rules for Pre packaged Food Labeling of National Food Safety Standards" (GB7718-2025).
Digital tags "are display methods that use information technology such as QR codes. When consumers scan the QR code of the digital tag, they can understand the tag information through mobile devices such as smartphones.
At present, the QR code on product packaging has become an important link connecting consumers, enterprises, and regulatory authorities. How to ensure the quality, speed, aesthetics, and traceability of printed QR codes is a crucial issue that printing enterprises must pay attention to in production.
Key elements of QR code design
A good QR code design is a prerequisite for perfectly printing QR codes. In the design process, it is necessary to comprehensively consider the characteristics of the QR code and its printing suitability.
01size
ISO/IEC 18004 standard: The international standard for QR codes, which specifies the size, error tolerance, and encoding method of QR codes.
Module Size: A QR code is composed of several "grid modules", and the size of each module determines the final size of the entire QR code.
It is generally recommended that the module size be no less than 0.25mm to obtain clear and recognizable details at 300dpi or higher resolution. The common problem is that the design size is too small. The recommended printing size is>20mm * 20mm, and it should be adjusted according to the usage scenario.
02
Resolution and clarity
Recommended printing resolution: The common digital printing resolution is 150-300dpi. The higher the DPI value, the clearer the details of the QR code. In compact situations, increasing resolution can better ensure scanning efficiency.
03
Reasonable use of colors
QR code scanning relies on color difference recognition, and the code color should be darker than the background (black is preferred) to avoid light colors (such as white background and white code). When using color, ensure that the code has sufficient contrast with the background. Colors that are too similar are difficult to recognize in low light.
04
Printing materials and processes
Material types: Paper, plastic, adhesive labels, metal, etc. Different materials can have different effects on the clarity of QR codes.
Post production processes such as lamination, hot stamping, and polishing may cause QR code reflection, color difference, or loss of details, so testing and adjustment are required during the design phase.
05
Manage content capacity
Too much content makes the QR code too encrypted and difficult to read. When carrying a large amount of information, prioritize using live code over static code.
Key points of QR code printing control
QR code printing mainly adopts inkjet printing, which can achieve variable data processing functions that traditional printing does not have, and can better complete the printing of QR codes. Compared with electrostatic imaging digital printing technology and direct imaging technology of printing machines, inkjet printing has its unique advantages in speed, cost, and quality.
01
Adjust the moisture content of the paper
If the moisture content of the paper is not adjusted properly, it is possible that the variable QR code that has just been printed can be recognized by the QR code reading device, but after being left to dry, the diffusion of ink and the shrinkage of the paper can cause deformation of the text and image, thereby affecting the recognition of the QR code reading device.
02
Ensure smooth operation of the paper
The distance between the paper and the nozzle is generally about 2mm, but sometimes due to the unstable tension of the roll paper or the inability to control the flatness of the paper within the appropriate range on the single sheet paper feeding platform, the distance between the paper and the nozzle may change during the printing process, resulting in the occurrence of two-dimensional code blurring, breakage, or scratching. To avoid this situation, it is advisable to choose high-quality paper as much as possible. Before printing, the paper should be flattened to remove powder and hair from the surface and reduce the roughness of the paper. At the same time, the paper can be moderately stretched during the printing process to further improve the flatness of the paper. Especially when the paper passes through the nozzle, it should not shake and the distance from the nozzle should be constant to ensure that the printed QR code does not float on the surface of the paper.
03
Adjust parameters when the substrate changes
Due to the fact that QR codes can be printed on various substrates, when the substrate changes, it is necessary to take samples for testing, analyze the surface characteristics of the substrate, and adjust technical parameters such as printing resolution and nozzle temperature to meet production requirements.
04
Ensure overlay error
Mainly refers to colored QR codes. When printing, it is necessary to ensure that the QR code is neat and clear. Usually, we stipulate that the maximum value of the overprint error (the overprint error between the main color tone and the image) should be less than or equal to 0.4 times the nominal width of the narrowest line barcode. If the overprinting is not accurate, the QR code will be difficult to recognize during scanning. Inaccurate QR code printing can also seriously affect production efficiency. Some advanced equipment can fully meet the standards in this regard, while some technologically backward equipment, such as those with unstable overprinting, is recommended to use monochrome printing for QR codes.
05
The printing speed should not be too high
If a rotary inkjet printer equipped with a nozzle or coding system is used to print QR codes, in order to ensure the printing accuracy of the QR code and improve the detection accuracy of the subsequent detection device, the printing speed of the rotary inkjet printer should be controlled at 40-80m/min, otherwise it may cause an increase in product scrap rate. The nozzle resolution should be adjusted to 600dpi × 300dpi, and it is best to use disposable or new nozzles.
06
Control the ink volume well
The thickness of the ink layer should ideally be less than 0.1mm, otherwise it may affect the normal reading of the QR code due to the stripes and spaces being on different scanning planes. To ensure a sufficiently thin ink layer, ink with good uniformity and diffusion should be selected, and attention should be paid to the matching between the ink and the substrate. In addition, because the fluidity and other properties of ink are closely related to the ambient temperature, the ink volume needs to be adjusted according to the ambient temperature. It should be noted that after drying, the dryness of the QR code should reach over 90% and ensure that the dried QR code does not have a "tail".
07
Prevent content loss
Omitting content during printing can cause scanning difficulties. In printing, due to reasons such as paper, it is easy to cause defects in printed patterns. For patterns like QR codes that appear slightly fragmented, careful inspection should be carried out during printing to avoid such situations.
08
Other precautions
When printing QR codes in bulk, it is best to scan the code with a QR code reading device first, and then proceed with mass production after testing. After printing is completed, it should be stored as flat as possible to avoid distortion of the printed material.
The above are the precautions to be taken during the QR code printing process, which are also the key points of daily quality management for digital printing enterprises.