Let's 'spot the differences' together! These 'four major aspects' help you fully understand the similarities and differences between toner and inkjet technologies!

Comparison and Analysis of Several Printing ConsumablesFor simplicity, the evaluation below will focus on four aspects: their interaction with label substrates, the appearance of printed products, durability, and sustainability.Interaction with Label SubstratesWhen evaluating the interaction of toner and inkjet inks with different substrates, we considered the ink adhesion and pigment penetration. Adhesion determines whether and how the printed image is fixed on the substrate, while pigment penetration indicates whether the pigment in toner or ink infiltrates the substrate. In the evaluation, maximum ink adhesion should be sought while pigment penetration should be minimized. The main reasons are: (1) color penetration has negative effects on color depth, dot shape, and dot size; (2) color penetration leads to inefficient use of pigments, meaning more ink or toner is required to achieve the same color depth.(1) Paper MaterialsSince dry toner has good chemical affinity with paper or paper coatings, adhesion is strong without needing a coating. In dry and liquid toners, pigment molecules are encapsulated in high polymer resins, and these pigment particles are too large to penetrate the fibers of uncoated paper, and even less so into coated paper fibers. However, the polyethylene resin in liquid toner (electronic ink) is less compatible chemically with paper or paper coatings, and because the carrier liquid dissolved in the resin still needs to evaporate, the adhesion of liquid toner (electronic ink) is somewhat affected. Therefore, compared with dry toner, liquid toner (electronic ink) does require a coating, not to prevent pigment penetration, but to improve adhesion. Notably, applying a uniform coating on natural paper for liquid toner (electronic ink) to ensure even adhesion remains a significant challenge.To ensure reliable inkjet quality, inkjet inks need to have low viscosity, typically maintaining printhead temperatures at 45℃ to ensure low viscosity (usually 4–17 mPa·s). UV inkjet inks have a viscosity about six times lower than commonly used UV flexo inks, making them more likely to penetrate paper fibers. This is why inkjet printing requires a coating to prevent pigment penetration.Regarding adhesion, water-based inks typically do not require a coating because the components encapsulating the pigments are more chemically compatible with paper or paper coatings. However, to prevent pigment penetration and dot gain, a coating may still be needed. For UV inkjet printing, the entire ink layer must remain on the substrate surface for complete curing, and any ink that penetrates the substrate cannot be adequately exposed to UV light, resulting in ineffective curing. Providing printed products with uncured substances is cumbersome for label printing companies and may cause a series of problems. Therefore, when printing on porous paper substrates, a coating should be used to ensure proper curing ability and adhesion.(2) Synthetic MaterialsCurrently, no pigment can penetrate synthetic substrates, so pigment penetration is not an issue for any of the consumables discussed above.Dry toner has good chemical affinity for synthetic substrates, so adhesion is generally not a problem. However, for liquid toner (electronic ink), adhesion is somewhat affected since the carrier liquid dissolved in the resin still needs to evaporate, so liquid toner (electronic ink) printing requires a coating.The adhesion of UV inkjet inks depends on the relative balance between the ink and the substrate surface energy. The higher the surface energy of the substrate compared to the ink's surface energy, the better the wettability. Good wettability is crucial for achieving strong adhesion. Synthetic substrates generally have lower surface energy, so for certain combinations of substrates and inks, a coating or corona treatment is needed to increase the substrate's surface energy and improve adhesion, although this may impact gloss uniformity and image quality.Since synthetic substrates are waterproof, water-based inks remain on the substrate surface after evaporation. This can be achieved in two ways: using inks containing polymers to form a polymer film after water evaporation, providing good adhesion, or using a polymer coating compatible with the ink pigment.The interactions of dry toner, liquid toner, UV inkjet, and water-based inkjet with label paper and synthetic substrates are compared in Table 1.

Appearance PerceptionDepending on different printing applications, functionality or aesthetic considerations may dominate. The following discussion is limited to image quality, glossiness, tactile feel, and opacity.(1) Image QualityImage quality is a relatively complex concept, and explaining all its aspects is time-consuming. From the perspective of precise dot placement and dot size control, dry toner and wet toner (electronic ink) printing can create more image details at the same (original) resolution compared to UV inkjet and aqueous inkjet, and the printing process is more consistent and controllable.(2) Glossiness on Matte MaterialsThe high viscosity of dry toner and wet toner (electronic ink) results in medium gloss (satin/silk matte). UV inkjet inks have low viscosity, which allows the ink to self-level, forming an extremely smooth surface with high gloss. On the other hand, aqueous inkjet, whether with or without a primer, will have a gloss level equivalent to that of the substrate because the amount of ink remaining on the substrate surface is insufficient to affect gloss.(3) Tactile Feel (3D Texture)The possibility of achieving a 3D texture largely depends on the thickness of the printed image layer. The image layer produced by UV inkjet has an average thickness of about 6 μm, allowing for pronounced texture. Dry toner produces an image layer with an average thickness of about 4 μm (the white ink layer is usually thicker); although thinner than UV inkjet layers, it is sufficient to produce some subtle 3D texture. Wet toner (electronic ink) and aqueous inkjet produce image layers that are too thin to create any 3D textural effect.(4) OpacityThe opacity of a color is determined by the pigment concentration (amount of pigment) and pigment particle size, in which dry toner performs well in both aspects. For white, higher opacity is better. Dry toner combines the highest pigment amount with the largest pigment particle size, so the opacity of white in One Pass printing is usually higher than that of white in flexographic printing. The pigment particle size in wet toner is similar to dry toner, but its concentration is lower (the carrier liquid reduces concentration), resulting in lower opacity. Of course, depending on the machine structure, wet toner (electronic ink) printers can apply multiple layers of toner to achieve better opacity, but this reduces printing speed, lowering productivity, and increases production costs due to additional service fees for multiple toner layers.For UV inks used in One Pass high-speed inkjet, the pigment particle size must be small enough to avoid nozzle clogging, and the ink viscosity required by the nozzle limits the maximum pigment amount, resulting in low opacity. The viscosity of aqueous inkjet inks is lower than that of UV inks, so the single-layer white ink opacity in aqueous inkjet is also relatively low.In contrast, for colors other than white, opacity should be minimized. The smaller the pigment particles and the lower the pigment content, the more transparent the color. Transparency can also be optimized according to the image layer thickness, with thinner layers being better.The comparison of the appearance perception of dry toner, wet toner, UV inkjet, and aqueous inkjet prints is shown in Table 2.

Weather Resistance of Printed MaterialsIdeally, the colors of labels are required to last as long as possible on shelves and during use. Therefore, according to the intended use, printed materials should be able to withstand scratching and abrasion, heat, water, and chemical corrosion.(1) Scratch and Abrasion ResistanceThe lower the surface energy of the material, the higher its scratch resistance. The thicker the image layer, the lower the scratch resistance. Depending on the thickness of the image layer, if dry toner and UV inkjet ink are to perform the same, dry toner and wet toner (electronic ink) image layers are more easily scratched because the surface energy of UV inkjet ink is lower than that of dry and wet toner. In this case, applying a UV varnish on the surface of toner-printed materials can give them the same scratch resistance as UV inkjet prints. Water-based inkjet prints demonstrate the best scratch resistance; however, since their image layers are very thin, the scratch resistance of the underlying substrate also has some effect on the final printed result.(2) Heat ResistanceThe images of dry toner and wet toner (electronic ink) are polymers fused to the substrate, so when heated, they can melt again. Thermal lamination can remedy this issue. Both UV inkjet and water-based ink inks are heat-resistant, with UV inkjet ink forming fully cured polymers with high melting points, while water-based inks, due to the low concentration of polymers on the substrate surface, will not melt or become sticky when exposed to heat.(3) Water ResistanceComponents in dry toner or UV inkjet inks do not have chemical affinity to water, thus they have good water resistance. For wet toner (electronic ink), since a water-based primer is usually used in printing and such primers are not water-resistant, it may peel off. To make water-based inkjet labels waterproof, a primer that reduces or inhibits the hydrophilicity of the pigments, such as a primer containing calcium salts, must be used.(4) Chemical ResistanceCrosslinking usually provides strong chemical resistance, which explains why UV inkjet inks have stronger chemical resistance compared to toner, as most of the resins in toner are not crosslinked. Applying chemical-resistant overlaminates can remedy this issue. The chemical resistance of water-based inks is due to the absence of any components in the ink that have affinity for chemical solvents.A comparison of the weather resistance of dry toner, wet toner, UV inkjet, and water-based inkjet printed materials is shown in Table 3.

Sustainability of Printed ProductsLike other industries, the printing industry also faces environmental pressures for sustainable development. How do different digital printing technologies perform in terms of chemical waste generation, operator convenience, and food compliance? Here is a detailed analysis.(1) Chemical WasteDry toner electrostatic imaging printing and water-based inkjet printing share a common feature: they do not produce any hazardous chemical waste. In contrast, UV inkjet printing, due to the ink residue in its cartridges and the use of cleaning agents during the printing process, must be safely handled according to the instructions on the safety data sheets. As for wet toner (electronic ink) printing, most of the carrier liquid is collected in the printer during printing and treated as chemical waste, while some evaporates into the production environment, and some remains in the printed materials, eventually also evaporating from the material.(2) Operator ConvenienceBoth toner printing and UV inkjet printing produce ozone during the discharge and curing processes. Ozone is a potentially toxic substance, but its concentration is well below the safety threshold. Proper ozone filtration devices can effectively reduce any odor or harmful substances, such as the built-in ozone filter in Xeikon CX series equipment, which can effectively remove harmful substances and odors, making the printing process odorless. Additionally, during UV inkjet printing operations, operators must also ensure protection from UV light exposure.Regarding volatile organic compounds (VOCs), wet toner (electronic ink) electrostatic printing generates VOCs as the carrier liquid evaporates. Water-based inkjet inks contain humectants, some of which are VOCs. Dry toner, having no additives, rarely produces VOCs.The sustainability comparison of dry toner, wet toner, UV inkjet, and water-based inkjet printed products is shown in Table 4.

ConclusionAs discussed above, it is evident that label printing is not a one-size-fits-all solution. For example, alcoholic beverage labels do not necessarily require chemical resistance, while industrial, pharmaceutical, and cosmetic labels need good chemical resistance. Pharmaceutical labels require particularly precise printing, whereas food labels should prioritize food safety. In short, the most suitable technology depends on the application of the product, and label printing companies can selectively choose appropriate digital label printing equipment based on their specific products.With printing becoming increasingly short-run, automated workflows can enhance productivity, which is exactly the advantage of digital printing. Since each technology has its own pros and cons, ideally, several or all of these technologies should be combined to form a hybrid printing technique, thereby maximizing their respective advantages and features.