Whether to create a marketing effect aimed at attracting and engaging consumers or to provide labels or packaging with specific functionalities, inks represent powerful tools for differentiation.
Phosphorescent inks
When exposed to a light source (natural or artificial), phosphorescent inks store energy and release it as soon as the labels are placed in the dark. For maximum effect, it is recommended to print phosphorescent inks using screen printing. Their color range remains fairly limited and mainly includes whitish shades with green or fluorescent yellow tones.
Depending on the amount applied and the quality of the pigments used, the re-emission duration (also called afterglow) ranges from a few minutes for standard inks to several hours for applications more closely related to safety (transport, safety instructions, etc.).
Fluorescent inks
Activated by UV light from daylight or specific light sources (UV neon or black light), fluorescent inks create a bright fluorescent effect on the printed substrate.
Despite the strong visual impact they provide, fluorescent inks have two major drawbacks: they are difficult to dry during printing (whether water-based flexo or UV flexo), and their lightfastness is very low. This characteristic becomes particularly important when labels are exposed to light for prolonged periods, whether natural or artificial.
Thermochromic inks
At the crossroads between effect inks and functional inks, thermochromic inks change color according to temperature. There are two types of thermochromic inks:
Reversible thermochromic inks
Reversible thermochromic inks switch from one state to another depending on temperature variations (increase or decrease).
Very important: reversible thermochromic inks always change from colored to invisible when the temperature rises, whereas irreversible thermochromic inks change from invisible to colored. Reversible thermochromic inks are only available for high (>60°C) and very high temperatures (>100°C).
They allow consumers to identify an ideal consumption temperature (soft drinks, sparkling wines, etc.) or to indicate excessive temperatures in order to prevent burns (microwave-heated depilatory wax, hot beverages, baby bath water, etc.).
Irreversible thermochromic inks
Irreversible thermochromic inks permanently change color once the defined temperature threshold is exceeded.
They indicate that a product has exceeded a temperature limit that should not have been surpassed (technical equipment, pharmaceuticals, etc.). These inks can also be used for anti-counterfeiting purposes.
A reversible thermochromic ink will change color or reveal a message if a counterfeiter attempts to remove a label or open packaging using a high-temperature heat gun.
Although thermochromic inks can be printed in flexography, screen printing is recommended for optimal effect, particularly when masking text that must appear after a color change.
Accuracy ranges from +/- 1.5°C to +/- 2°C depending on suppliers and references.
The available color range is fairly limited, not to say basic. Shades are mainly blue, red, green, black or violet, and obtaining a specific Pantone is very difficult.
Scratch-off inks
Scratch-off inks have existed for many years and serve both marketing operations and security-oriented applications, particularly for masking personal data or identifiers.
They can be printed in water-based flexo, UV flexo, UV screen printing or offset (UV or conventional).
When masking text, a 2D code or a QR code, screen printing is strongly recommended to prevent readability under grazing light.
The color range is limited and mainly includes gold, silver or bronze.
Sterilization indicator inks
There are as many sterilization inks as sterilization processes:
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Steam sterilization (autoclave)
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Ethylene oxide sterilization
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Gamma ray sterilization
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Hydrogen peroxide sterilization
Sterilization inks indicate that specific packaging, instruments or medical devices have undergone sterilization and that the process is complete.
For each type of ink, several colors are usually available. The most common range from pink to brown for steam sterilization or from blue to brown for ethylene oxide gas sterilization.
These inks are almost exclusively printed in water-based flexography, with relatively heavy ink laydown to ensure a clear and unambiguous interpretation of the result.
Scented inks
They are more accurately described as scented varnishes, as these inks are mostly transparent or translucent.
Available mainly in water-based flexo or conventional offset, scented inks consist of varnish mixed with microencapsulated essential oils.
By rubbing or scratching with a fingernail, the microcapsules break and release the encapsulated fragrance. The scent does not diffuse spontaneously; mechanical action is required.
Virtually any fragrance can be microencapsulated: vanilla, chocolate, coffee, honey, orange, mint, rose, lavender, jasmine, monoï, thyme, rosemary, tomato, pineapple, curry, spices, etc.
Custom formulations can be developed based on specific perfumes or essential oils.
Scented inks allow packaging to feature a small label encapsulating the fragrance of the product inside (home fragrance, car air freshener, etc.), preventing tampering by consumers attempting to smell the product.
Security inks
To combat counterfeiting, various technical solutions exist, such as iridescent inks and anti-copy inks. These inks are mainly used on bank documents or items with monetary value (holiday vouchers, meal vouchers, gift vouchers, etc.).
Over the past decade, conductive inks have emerged to print specific RFID antennas where space constraints exist or where traditional RFID antennas cannot capture a required signal.