By 2025, the global printing ink market had grown slowly to approximately USD 21.5 billion. Oil-based inks (including solvent-based variants) still hold the largest share, valued at around USD 14 billion. In the United States, for instance, oil-based inks still account for 41.12% of the market. Driven by growing demand for low-VOC formulations, water-based inks are conservatively estimated to have reached USD 9.7 billion, expanding at a steady CAGR of 3.0%. UV-curable inks (including UV-LED systems) are also on the rise, with the market now reaching USD 2.23 billion and an optimistic projected CAGR of around 5.5%.

The parallel growth of these three ink systems reflects a structural divergence in the printing industry, shaped by substrate diversification, tightening environmental regulations, and the push for higher throughput. Each ink system differs fundamentally in its film-formation mechanism — and those differences directly govern which tackifier resins belong in the formulation. Rosin-modified resins, terpene resins, and petroleum resins are the three principal tackifier resin families derived from natural or petrochemical sources. Their roles vary markedly across ink systems: in one context they may serve as the primary film-forming backbone; in another, as a secondary source of adhesion; and in yet another, only as functionalised derivatives that co-polymerise within a UV-curing network. This article maps out the specific functional roles and application characteristics of all three resin families across oil-based, water-based, and UV-curable ink systems.

Click to read “Ink Systems and Substrate Compatibility in Industrial Printing“

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Ink System Overview

— Oil-Based Inks & Solvent-Based Inks —

Oil-based inks remain a foundational system in conventional printing, particularly in offset lithography, newspaper printing, and paper-based packaging such as folding cartons and boards. Technically, the term refers to systems where mineral oils, vegetable oils, or high-boiling petroleum fractions serve as the main volatile component. Film formation relies on a combination of oxidative polymerisation, partial solvent evaporation, and absorption into the substrate. The characteristic properties are high viscosity, slow drying, good water resistance, and reasonable lightfastness — well suited to producing stable, durable prints on absorbent paper stocks.

By contrast, solvent-based inks use low-boiling organic solvents — alcohols (ethanol, isopropanol), esters, and ketones — as the primary volatile component; film formation depends almost entirely on rapid solvent evaporation. These are technically defined as systems in which organic solvents carry pigments or dyes dispersed in a solvent or solvent-borne polymer. Thanks to their fast drying, good wetting, and strong adhesion to non-absorbent substrates, solvent-based inks have been widely adopted for flexographic and gravure printing of flexible packaging, plastic films, aluminium foil, and outdoor signage, and have long dominated plastic packaging print.

Because the solvents in these inks are low-boiling, highly volatile organic compounds, the drying mechanism is a direct source of volatile organic compound (VOC) emissions. Regulatory and industry guidance documents in multiple countries classify the printing industry as a priority sector for VOC control. They note that solvent emissions from inks and coatings promote photochemical smog and secondary organic aerosol formation, and accordingly use legislation and technical guidelines to impose consumption caps, emission-concentration limits, and area-based usage constraints on printing inks, coatings, and adhesives — while also encouraging low-VOC formulations, waterborne conversion, and end-of-pipe abatement. Against this regulatory backdrop, solvent-intensive processes such as screen, gravure, and flexographic printing face continuing global pressure to reduce emissions and reformulate.

In ink technology, the two systems overlap but are distinct. Oil-based inks rely primarily on high-boiling mineral and vegetable oils; drying occurs through oxidative polymerisation, substrate absorption, and limited solvent evaporation — making them suitable for absorbent stocks such as paper. Solvent-based inks, by contrast, rely predominantly on low-boiling organic solvents and dry almost entirely by evaporation, giving them the surface adhesion needed for non-absorbent substrates like plastic films and metal foils. In practice, oil-based inks dominate offset printing of books, newspapers, and folding carton packaging, whilst solvent-based inks lead in flexible packaging and outdoor advertising — the two systems occupying fairly well-defined territories.

However, the heavy use of mineral oils and high-boiling petroleum fractions in oil-based ink formulations raises concerns about mineral oil hydrocarbon (MOSH/MOAH) migration in food packaging. European regulation of food contact materials (FCMs) has scrutinised MOSH/MOAH transfer to food, and some regulations and industry guidelines now require food packaging printers to prioritise low-migration inks, vegetable oil-based inks, and formulations with reduced mineral oil content — alongside stricter requirements for the barrier structure between the printed layer and the food. This has driven a reformulation trend towards vegetable oil-based, low-migration, and renewable-carbon ink systems.

The high viscosity and slow-drying nature of oil-based inks show up not only in industrial printing, but also in everyday writing instruments. Ballpoint pen inks are a direct consumer-facing parallel: because the oil-based ink is viscous, it spreads and penetrates paper only minimally, producing fine, sharp lines — though the overall tone tends towards deeper, more muted colours. Several Japanese stationery brands note in their product literature that oil-based ballpoints offer excellent water resistance and smear resistance, making them well suited for long-term records and formal signatures, but that they typically lag behind water-based and gel inks in colour vibrancy and writing smoothness. This consumer-level difference maps directly onto the fundamental contrast between the oil-based “high-viscosity vehicle + slow drying” paradigm and the water-based “low-viscosity, fast-penetrating film formation” paradigm.

The same vehicle-type contrast is visible in how the Japanese stationery market responds to colour. Water-based and gel-ink ballpoints are far more popular with everyday consumers and techo (planner/journal) enthusiasts — in note-taking, colour-coding, and decorative writing, neutral gel inks (ゲルインク) and water-based inks dominate shelves and online platforms, prized for their vivid colour, smooth writing feel, and wide colour range. Mitsubishi Pencil, for example, highlights that gel and water-based inks deliver smooth writing and excellent colour reproduction (書き味がなめらかで、発色がよい); Pilot markets its gel inks as combining the light, effortless feel of water-based inks with the water resistance of pigment inks. In consumer reviews, gel pens are frequently described as “incredibly smooth, with no bleed-through concern“, and are widely favoured for their rich, saturated colour. From a printing ink formulation perspective, this neatly illustrates how vehicle type and film-formation mechanism are decisive for colour rendering and ink film performance — oil-based vehicles lead in durability and water resistance, whilst water-based emulsion systems excel in colour vibrancy and coating flow. The same principle holds equally in industrial printing.

— Water-Based Inks —

Water-based inks use water as the primary evaporative medium. The film-forming resins are typically aqueous acrylic or waterborne polyurethane (PU) dispersions, supplemented by co-solvents, defoamers, wetting agents, and biocides. Unlike solvent-based inks, which rely on organic solvents to dissolve or swell the polymer, water-based inks achieve dispersion and film formation by introducing hydrophilic groups into the polymer backbone or by emulsion polymerisation, allowing the resin to exist as fine particles or a water-soluble species in the aqueous phase. During drying, as water evaporates, the latex particles come into contact and coalesce, ultimately forming a continuous resin film.

In terms of printability, water-based and solvent-based inks perform quite differently on porous versus non-absorbent substrates. On porous or absorbent materials — paper, board, and textiles — water-based inks generally deliver vivid colour and well-defined image gradation; solvent-based inks on fibrous substrates, by contrast, are more prone to deep penetration or show-through. On non-absorbent substrates such as plastic films, metals, and glass, solvent-based inks — with their stronger solvency and higher resin solids — typically yield sharper, more securely adhered ink films. This advantage is particularly pronounced on flexible packaging films such as BOPP and PET, whereas water-based inks in this segment depend heavily on specially engineered resin systems and surface pre-treatment.

In terms of drying speed and operational performance, solvent-based inks — driven by rapid evaporation of low-boiling solvents — generally dry faster than water-based inks and are thus better suited to high-speed gravure and flexo production. Water-based inks, because water evaporates more slowly, typically require longer drying tunnels or more powerful hot-air systems and are generally more suited to medium-speed presses. On the other hand, water-based inks have lower odour, lower VOC burden, and impose less demand on press-room ventilation, explosion-proofing, and exhaust treatment.

On durability, solvent-based inks generally offer superior water resistance, solvent resistance, and abrasion resistance, making them more suitable for demanding applications such as outdoor signage and industrial marking. Water-based inks are predominantly used in indoor packaging, corrugated board, labels, and short-life displays. To close this gap, water-based systems often require overlamination, varnishing, or crosslinking agents (such as waterborne two-component PU lacquers) to improve water, chemical, and weathering resistance — and are progressively replacing solvent-based inks in some of these segments.

— UV-Curable Inks —

UV-curable inks are typically composed of oligomers, reactive acrylate monomers, photoinitiators, pigments, and a small proportion of additives — a classic radiation-curing resin system. Under ultraviolet irradiation, the photoinitiator absorbs photons at a specific wavelength and generates free-radical or cationic reactive species, triggering chain polymerisation and crosslinking of the oligomer and acrylate double bonds. The liquid ink is converted into a crosslinked, three-dimensional polymer film within a matter of seconds. The oligomer forms the structural backbone, determining the hardness, flexibility, adhesion, and ageing resistance of the cured film; the reactive acrylate monomer acts both as a reactive diluent to adjust viscosity and as a co-reactant that is incorporated into the crosslinked network. This “photoinitiating — chain propagation — crosslinking” mechanism means UV-curable inks require virtually no solvent or water evaporation to dry; compared with conventional solvent-based inks, VOC emissions are negligible. The result is rapid curing with a significantly reduced environmental and workplace odour footprint.

Unlike solvent-based inks, UV systems replace most inert solvents with reactive monomers. Solvent volatilisation during curing is negligible, making VOC emissions extremely low — UV-curable technology is broadly regarded as one of the more environmentally responsible curing platforms in the printing industry. Research and industry reports note that UV inks cure instantaneously under UV light without solvent evaporation, reducing both air pollution and operator exposure, whilst also easing demands on factory ventilation and exhaust treatment, helping printers comply with increasingly stringent environmental regulations. Because curing takes place at ambient or moderately elevated temperatures, UV systems are particularly well suited to heat-sensitive substrates such as plastic films and composite materials — combining high throughput with the process advantage of low-temperature cure.

UV-curable inks are now widely used for printing and coating on a broad range of non-absorbent or low-absorbency substrates. In packaging and decoration, acrylate UV inks — valued for their fast cure and adaptability to low-surface-energy plastics — have found extensive application on PET, PP, PE, and PVC sheet and film for decorative laminates, labels, and packaging, though some low-surface-energy plastics still require surface pre-treatment to ensure adequate adhesion. In metal decoration, UV-curable inks and UV varnishes are applied to aluminium sheet and other metal substrates to produce highly abrasion-resistant, chemically resistant, high-gloss surfaces in short cycle times, making them suitable for metal cans and decorative metal components. On glass and other rigid non-absorbent surfaces — decorative glass, cosmetic bottles, electronic device housings — UV screen-printing inks and UV inkjet inks, when combined with appropriate primer and surface-tension management, can achieve high adhesion and fine pattern definition for high-value decoration and functional marking.

During UV printing, the moment ink is jetted or transferred onto a non-absorbent substrate it is struck by high-intensity UV radiation. The reactive monomer and oligomer crosslink almost instantly, “freezing” each droplet at the surface before significant flow or penetration can occur. This instant-cure characteristic ensures sharp image edges, controlled dot gain, and immediate entry into downstream finishing (lamination, die-cutting, hot-foil stamping, etc.) — substantially improving overall line efficiency. With the adoption of UV-LED and other next-generation curing sources, UV-curable inks continue to expand across labels, packaging, industrial print, and electronic materials, and are widely regarded as one of the key directions for future printing and coating technology.

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Applications of Rosin-Modified Resins, Terpene Resins, and Petroleum Resins in Different Ink Systems

Every ink system requires a film-formation mechanism through which the ink can adhere to the printed substrate. This section focuses on rosin-modified resins, terpene resins, and petroleum resins in their roles as tackifiers and binders in ink formulations.

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— Oil-Based Inks and Tackifier Resins —

In sheet-fed offset and publication printing, a tackifier resin serves as one of the principal binders, combining with vegetable oil or mineral oil to form the ink vehicle. The vehicle — comprising binder resin, drying oil or mineral oil, and additives — is responsible for wetting and encapsulating the pigment uniformly, and for imparting the correct viscosity, tack, flow, and drying behaviour to the ink. In offset oil-based inks, tackifier resins are typically drawn from rosin-modified resins, terpene resins, or petroleum resins; together with the drying oil, they govern the ink’s tack profile, emulsification behaviour, and transfer efficiency between blanket and substrate.

In offset oil-based inks, the tackifier resin first contributes pigment wetting and dispersion, ensuring that the pigment is distributed uniformly and stably throughout the oil vehicle to achieve adequate colour density and colour strength. The resin adsorbs onto pigment particle surfaces, improving pigment–vehicle compatibility and preventing flocculation and sedimentation, so that the ink retains a fine, homogeneous film even under high shear. In addition, the resin’s softening point and molecular weight influence the ink’s tack curve and rheological profile: higher softening-point resins generally improve the release of solvent or oil, produce a firmer dried film, and reduce back-trap and set-off at high press speeds. In the offset system, therefore, the tackifier resin is simultaneously a “pigment carrier” and the “core rheological control element” — decisive for both press performance and final gloss.

In gravure, flexographic, and screen-printing processes that use solvent-based inks, the choice of resin system directly affects compatibility, gloss, heat resistance, and substrate adhesion. In gravure printing, for instance, the organic solvent must first dissolve the resin to form a homogeneous fluid, allowing the resin to coat pigment particles uniformly and provide adequate wetting and flow. The interplay between solvent solvency, evaporation rate, resin polarity, and softening point collectively determines how the ink spreads, transfers, and dries within the engraved cells. In flexographic and screen systems, formulators choose from combinations of polyurethane, acrylic, polyamide, or modified rosin resins — depending on the target application — to balance solvent release, film flexibility, heat or chemical resistance, and high-gloss or matte finish.

— Water-Based Inks and Tackifier Resins —

Water-based inks use water as the primary evaporative medium. The principal binders are aqueous acrylic and waterborne polyurethane (PU) resins, supplemented by co-solvents, wetting agents, and defoamers, together providing pigment encapsulation and film formation. By introducing hydrophilic groups — carboxyl, sulphonate, or polyoxyethylene chains — into the polyurethane or acrylic backbone, and then neutralising to form ionic groups, these resins can be emulsified into stable aqueous dispersions or rendered partly water-soluble for use in coatings and ink systems. In PU–acrylic hybrid systems, the common approach is to first prepare a hydrophilic-group-bearing polyurethane prepolymer, then carry out acrylate emulsion polymerisation within its aqueous dispersion, yielding an interpenetrating or graft composite emulsion with improved film-formation characteristics and mechanical strength.

During emulsion polymerisation, the PU and acrylic monomers form monomer-containing micelles in the aqueous phase in the presence of an emulsifier or hydrophilic polymer (such as partially neutralised acrylic acid or PVA). Monomers polymerise within these micelles via free-radical emulsion polymerisation to generate polymer particles. The emulsifier or reactive surfactant adsorbs at the particle surface and stabilises particles against coalescence through electrostatic repulsion and steric hindrance, yielding a stable latex — typically in the 10–hundreds of nanometre particle-size range — that serves as the film-forming vehicle in water-based inks. Aqueous acrylic and PU emulsions further work in concert with dispersants to provide electrostatic stabilisation for the pigment, reducing flocculation and sedimentation and thus maintaining colour paste flow and colour uniformity throughout storage and printing.

By engineering the glass transition temperature (Tg), hard/soft segment ratio, and molecular weight, the latex particles are forced together as water evaporates and volume fraction increases, transitioning from isolated dispersion to a continuously packed structure. As the system temperature approaches or exceeds the polymer Tg, chain segments at the particle periphery gain sufficient mobility to interdiffuse and fuse at particle contact zones, eliminating interparticle boundaries and forming a continuous polymer film phase. This produces a resin film of measurable hardness and abrasion resistance on substrates such as paper and plastic film. During this process, coalescing aids (high-boiling glycol ethers or esters) can locally depress the resin Tg, helping particles fuse adequately at lower drying temperatures — a technique widely used in waterborne flexo and gravure inks to balance film formation and drying speed.

In water-based ink systems, tackifier resins work alongside the film-forming resins described above to govern ink transfer and ultimate adhesion. Typical tackifiers include rosin-modified resins, terpene resins, and their aqueous dispersions. These are generally converted by emulsification or neutralisation into water-borne resin dispersions and added as discrete “tackifier emulsions” to acrylic or PU systems, improving initial tack and peel strength on paper, corrugated board, and certain plastic films. In the formulation, such water-dispersed tackifiers improve ink wetting and anchoring on low-polarity or porous substrates — maintaining good dot-gain control and transfer efficiency even at high press speeds — whilst their softening point and addition level can be tuned to balance tack against cohesive strength, avoiding a film that is too soft and thus prone to poor abrasion resistance. Some hybrid tackifier dispersions — for instance, co-modified rosin or terpene resins with synthetic resins — are specifically designed for corrugated board and polyolefin substrates, boosting adhesion to polyolefinic (PO) surfaces and wet-resistance performance in both waterborne adhesives and inks. This “tackifier resin + waterborne film-forming resin” dual-resin architecture is becoming a common design approach in high-performance waterborne systems.

— UV-Curable Inks and Tackifier Resins —

UV-curable inks rely on UV-light-initiated polymerisation to form a film. The mechanism involves oligomers bearing unsaturated double bonds and reactive monomers undergoing a chemical transformation from monomer to polymer under the action of a photoinitiator. Upon UV irradiation, the photoinitiator absorbs energy at its specific wavelength and cleaves to generate free radicals or cations, which then drive chain initiation, propagation, and termination in rapid succession — crosslinking the prepolymer and reactive monomers into a three-dimensional polymer network within seconds, converting the liquid coating to a solid ink film. Compared with oil-based and water-based inks, the UV radiation in a UV-curable system can penetrate a certain depth into the wet ink layer, promoting near-simultaneous cure at both the surface and the bulk — yielding a highly crosslinked, dense, and abrasion-resistant film structure.

UV-curable inks are built on a backbone of oligomer resin plus reactive monomer. Commonly used systems include epoxy acrylates, polyurethane acrylates, and related UV resins. For UV-LED curing, the photoinitiator system must be selected for sensitivity to the narrow emission band of 365–395 nm, and the oligomer/monomer structure must be designed to overcome surface oxygen inhibition, ensuring complete cure and a tack-free continuous film even at lower irradiance and lower temperatures.

Compared with solvent-based inks, UV-curable inks form their film with virtually no reliance on volatile organic solvents. Instead, crosslinking polymerisation initiated by the photoinitiator generates new polymer resin in situ — classifying these inks as “high-solids, approaching 100% solids content, chemically cured film-forming systems.” In essence, this is “chemically driven drying initiated by light.” This mechanism substantially reduces VOC emissions and the energy demand of the drying section.

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Applications of Individual Tackifier Resin Types

— In Oil-Based Ink Systems —

In oil-based ink systems, the tackifier resin is one of the core components determining viscosity, gloss, adhesion, chemical resistance, and weathering resistance. Its fundamental function is to impart the correct surface tack and rheological behaviour to the ink. The three resin families discussed here — rosin-modified resins, petroleum resins, and terpene resins — differ significantly in polarity, glass transition temperature (Tg), molecular weight, and solubility. These structural differences are reflected directly in ink fluidity, the tack curve, film hardness and flexibility, and compatibility with different substrates (paper, plastic, metal). It is, in short, the choice of tackifier resin type that most defines the character of an oil-based ink.

Rosin-modified resins are the oldest and most widely used tackifier resins in oil-based inks — particularly offset inks. Typical product types include rosin-modified phenolic resins, maleic-modified rosin resins, and ester gum products such as glycerol esters and pentaerythritol esters of rosin. Japanese and European technical literature and patents explicitly identify rosin-modified phenolic resins as “primarily used as resin raw materials for offset inks in newspapers and magazines“, owing to their combination of excellent pigment wetting and dispersion, good solubility in aliphatic ink solvents, and tunable tack. By forming a lipophilic resin layer on pigment surfaces, these resins stabilise pigment dispersion in the oil vehicle, enabling high colour strength and uniform colour. The phenolic backbone contributes hardness and heat resistance; the rosin component provides flexibility and compatibility — together allowing offset inks to maintain fluidity, emulsification resistance, and abrasion resistance even at high press speeds. In low-viscosity, high-penetration newsprint ink systems, choosing a lower-softening-point, moderate-molecular-weight rosin-modified resin allows fine-tuning of the tack curve and flow, ensuring good penetration and set on newsprint whilst reducing common offset press faults such as plate filling and ink scumming — a point repeatedly emphasised in product specifications for rosin-phenolic resins aimed at newspaper and web-offset printing.

Unlike the higher-polarity, structurally “harder” rosin-modified resins, C5 and C9 petroleum resins are thermoplastic resins produced by polymerising cracked C5 or C9 fractions. Their viscosity contribution is moderate, but they offer an excellent cost-to-performance ratio for increasing tack and adjusting flow. European supplier literature notes that C5 aliphatic and C9 aromatic petroleum resins “possess notable tackifying properties and are suitable for coatings, printing inks, and adhesives requiring tack control,” with C9 aromatic resins — having higher polarity and aromaticity — showing the best compatibility with alkyd resins and oil vehicles. This makes C9 resins well suited as co-resins in oil-based industrial coatings and marking inks, where they improve pigment wetting, adhesion, and abrasion resistance.

C5 petroleum resins, by contrast, have lower polarity and a narrower compatibility window, and are better suited to cost-effective formulations aimed at improving flow and initial tack. In oil-based inks where cost is sensitive and extreme high-gloss is not required, C5 resins are often regarded as the “economy tackifier” — an advantage that becomes particularly pronounced when crude oil prices are low. In summary: rosin-modified resins lean towards colour strength, offset printability, and film-forming strength; C9 petroleum resins favour flow control and industrial protective performance; C5 resins favour economy and moderate tack. Each occupies a distinct formulation role rather than simply substituting for the others.

On pricing, the cost of C5 petroleum resin is driven primarily by upstream crude oil and cracking by-product prices — in particular, light naphtha and C5 fractions. When upstream feedstock prices are at relatively low levels, C5 petroleum resins maintain strong price competitiveness and are widely used in cost-sensitive sectors such as adhesives and inks. During 2024–2025, C5 petroleum resin prices in Asia were broadly in the range of USD 1,300–1,400 per tonne, fluctuating cyclically with upstream crude oil and synthetic resin demand — a clear reflection of their tight linkage to energy and petrochemical sentiment.

In the near term, any disruption or restriction to transit through the Strait of Hormuz would push up crude oil and light naphtha prices, with knock-on effects that transmit through to the production cost and market price of petroleum resins — placing upward pressure on C5 and C9 resin prices broadly. A short-lived disruption is more likely to produce sharp spike-type price swings; if instability persists for several months or longer, C5 and C9 petroleum resins could remain in an elevated price range for an extended period, with the increase passing through to downstream products including inks, coatings, and adhesives.

Against this backdrop, the traditional cost/moderate-tack advantage of C5 petroleum resins may face structural adjustment. C5/C9 petroleum resins are by-products of ethylene cracking units (raffinate and C9 fractions); their pricing is not only linked to crude oil but also deeply tied to ethylene cracker operating rates and the supply-demand balance for cracking by-products. If Strait of Hormuz tensions drive crude oil prices sharply higher, this may actually compress ethylene cracker margins, forcing petrochemical producers to reduce operating rates to protect profitability — thereby reducing C5/C9 feedstock availability. Conversely, if crude prices rise but downstream chemical (plastics) demand is weak, ethylene plants may run at low utilisation, leading to prolonged C5/C9 feedstock shortages. Geopolitical transmission to resin prices is therefore not a simple linear relationship; it operates through the complex chain of “crude oil price → cracking cost → unit utilisation → by-product yield.” Faced with this uncertainty, new formulation development in oil-based inks is accelerating towards higher solids content and lower solvent consumption, paired with higher-softening-point, narrower-molecular-weight-distribution synthetic resins or modified rosins — reducing dependence on highly volatile petroleum by-product feedstocks.

Unlike rosin-modified resins — which are built on an abietic acid skeleton — terpene resins have a saturated or partially saturated terpene carbon backbone. This gives them better colour stability and lower odour, providing a distinct advantage in high-quality ink formulations where hue and odour are tightly controlled.

In oil-based ink systems, the most notable performance characteristics of terpene resins are very high initial tack and excellent wetting of non-polar or low-polarity substrates — such as polyolefin films and wax-coated paper — attributable to their non-polar backbone and relatively low Tg. In solvent-based gravure and flexographic ink formulations, terpene-phenol resins — combining the low polarity of the terpene backbone with the polarity of phenol groups — show good solubility in a range of organic solvents (including aliphatic solvents and alcohols). They can be used in combination with polyamide, acrylic, or polyurethane resins to improve adhesion to polyolefin film substrates while also enhancing levelling and gloss. In high-end offset oil-based ink formulations, terpene resins are sometimes introduced to replace a portion of the rosin-modified resin, with the aim of improving roller affinity on high-speed presses and gloss and transfer efficiency on coated paper, while reducing the ageing resistance drawbacks associated with the abietic acid structure. In marking inks and contact-type printing (such as die stamps and hot-foil primer coatings), terpene resins are often the preferred tackifier, leveraging their high initial tack and good wetting of hard substrates such as metal and glass to provide adequate instant adhesion and film integrity.

— In Water-Based Ink Systems —

In water-based ink systems, the resin no longer forms the vehicle phase as an “oil + thermoplastic tackifier resin” combination. Instead, it forms a continuous and film-forming phase through aqueous dispersion or water solubility — typically a waterborne binder system comprising aqueous acrylic resin, waterborne polyurethane (PUD) dispersion, and tackifier resin (or its emulsion). Unlike oil-based systems that rely on oxidative film formation using mineral oil and drying oils, waterborne systems allow latex particles to approach, soften, and coalesce as water evaporates, optionally supplemented by self-crosslinking or reaction with a crosslinker such as an isocyanate, forming a continuous polymer film at ambient or mildly elevated temperature. The film-formation mechanism can be summarised as “water-evaporation-driven physical film formation with optional chemical crosslinking.” This architecture gives water-based inks a clear advantage in VOC control, suitability for flexo and gravure printing, and digital inkjet, but also imposes stricter demands on resin particle size distribution, Tg, hydrophilic/hydrophobic balance, and pH stability.

At the “backbone resin” level, acrylic emulsions are the most common primary resin in water-based inks. Their Tg, hard/soft segment ratio, and acid number directly determine drying speed, film strength, and adhesion to various substrates. Technical reviews note that acrylic emulsions are widely used as binders in waterborne flexographic inks because they offer good adhesion to paper and some treated plastic films, provide reasonably high gloss and water resistance, and are suited to high-speed flexo printing.

In recent resin technology developments, acrylic emulsions with “rheology-control (RC)” and “self-crosslinking” functionality have been used to improve the printability of water-based inks on non-absorbent films such as BOPP and PET, by incorporating alkali-soluble low-molecular-weight acrylic resin on the emulsion particle surface to give the wet ink near-Newtonian flow behaviour, enabling more consistent transfer and re-solubility in flexo and gravure printing. Waterborne polyurethane dispersions (PUDs), by contrast, place greater emphasis on flexibility, abrasion resistance, and chemical resistance. In flexible packaging, aqueous inkjet, and textile digital printing — where “soft handle + high durability” is required — PUDs are regarded as a step above standalone acrylic systems. The literature notes that waterborne polyurethane films are clearly superior to water-based acrylic and epoxy systems in abrasion resistance, water resistance, and chemical resistance; they therefore appear either as pure PUD or as acrylic–PU hybrid dispersions, used to improve the mechanical performance of digital inkjet, waterborne screen, and flexographic inks.

At the “tackifying and wetting” level, the third key resin family in waterborne systems comprises various modified rosin resins and their emulsions. Their role is both similar to and different from that of rosin tackifiers in oil-based systems: the similarity is that they still serve the important functions of pigment grinding/dispersion and tack adjustment; the difference is that they must first be made sufficiently hydrophilic and alkali-soluble — through maleation, acrylic modification, and esterification steps — so that they can exist stably in the aqueous phase.

For example, one study used acrylic-modified rosin–polyethylene glycol ester to prepare a high-solids waterborne ink binder, achieving low viscosity and high solids whilst exploiting the rosin backbone to improve affinity for paper and pigment, enhancing printability and film quality — regarded as a promising route to VOC-free waterborne binders. A related patent describes introducing maleic or fumaric acid onto the rosin molecule, followed by esterification with hydroxyl-bearing monomers (such as polyols or styrene–allyl alcohol copolymers), to produce a rosin-modified resin suited to aqueous grinding — used as a “grinding resin” and “vehicle resin” in water-based inks, combining high colour strength, fast drying, and good re-solubility.

Terpene resins can likewise be introduced into water-based ink systems through emulsification or alkali-soluble modification. Terpene-phenol resins, which contain phenolic hydroxyl groups, can be alkali-neutralised to form carboxylate salts or emulsified directly, then added to the formulation as an aqueous dispersion. In waterborne flexographic and gravure inks, they improve initial tack on polyolefin substrates (PP and PE) and supplement tack on paper. Compared with rosin-based emulsions, terpene resin emulsions typically offer better colour stability and lower odour. For food contact packaging inks, where low odour and compatibility with heat-seal layers are required, they represent a worthwhile alternative or complementary direction to rosin-based tackifier emulsions.

In flexographic and waterborne gravure formulations, the acrylic/PU backbone resins provide overall film strength and durability, whilst the rosin-based emulsion is focused more on improving pigment grinding efficiency, paper wetting, and “ink release and re-solubility” in high-line-count anilox applications — the three components forming a division of labour structured as “backbone resin (acrylic/PU) + functional rosin resin.”

Within this same context, C5 and C9 petroleum resins face a genuine chemical barrier in water-based ink systems. Because the petroleum resin backbone is non-polar hydrocarbon, it lacks the functional groups needed for neutralisation or emulsification, making it difficult to produce a stable aqueous dispersion directly. Conventional emulsification requires large amounts of surfactant, often resulting in poor emulsion stability and reduced water resistance of the formed film. That said, with recent advances in micro-emulsification technology, some specially modified petroleum resins can now be processed into nano-scale micro-emulsions using high-shear methods, retaining a degree of water resistance whilst providing excellent levelling. In addition, in waterborne systems that still contain a small amount of co-solvent, petroleum resins can participate in the formulation in dissolved form, contributing their low-cost tackifying advantage. Therefore, although the tackifying role in pure waterborne inks remains primarily the domain of modified rosin emulsions and terpene resin emulsions, C5/C9 petroleum resins are progressively expanding their application space through micro-emulsification and mixed-solvent system approaches.

Mirroring the division of labour in oil-based systems — where rosin-based resins govern colour strength and tack in offset inks, C5/C9 petroleum resins control flow and cost, and terpene resins boost initial tack on non-absorbent substrates — in water-based systems, acrylic resins lean towards film formation and optical performance; polyurethane dispersions towards flexibility and durability; modified rosin and rosin emulsions focus on pigment dispersion, paper wetting, and tack fine-tuning; terpene resin emulsions play a supplementary role in polyolefin adhesion and low-odour formulations; and C5/C9 petroleum resins are limited in application by their poor water-dispersibility. Together, these constitute a multi-resin platform distinctly different from UV and oil-based systems.

— In UV-Curable Ink Systems —

In UV-curable ink systems, the central mechanism is no longer the physical film formation of “drying oil + thermoplastic tackifier resin,” but rather a “chemically formed backbone” in which polymerisable oligomers and reactive monomers crosslink into a three-dimensional network via free-radical or cationic polymerisation under photoinitiator action. Technical documentation broadly identifies three principal oligomer systems for UV inks:

• Epoxy acrylate — after cure, delivers high film hardness and dense crosslinking; suited to UV offset and high-definition image reproduction.
• Polyester acrylate — valued for flexibility and good adhesion to paper and film; more appropriate for UV flexography and flexible substrates.
• Urethane acrylate — combines high adhesion, high toughness, and excellent fold resistance; widely used where “flexible yet abrasion-resistant” performance is required, such as flexible packaging, cigarette pack printing, and digital inkjet.

Compared with the physical drying of “oil + resin” in oil-based systems, the UV system crosslinks these acrylate oligomers and monomers under light to “generate new resin in situ.” The film-formation mechanism shifts fundamentally from “solvent evaporation + oxidative film formation” to “photo-initiated crosslinking polymerisation.”

From a tackifying and adhesion perspective, UV-curable systems carry little in the way of conventional non-reactive tackifier resins; nonetheless, different types of “tackifier resins” are introduced to address adhesion, wetting, and levelling challenges — though their category and role differ markedly from oil-based systems. On one hand, the oligomers in UV formulations themselves carry “backbone structures with adhesive function”: for example, polyester acrylate uses the polyester backbone to deliver strong interfacial interaction with plastic films, whilst urethane acrylate relies on flexible polyurethane segments to provide high adhesion and fold resistance. This “built-in tackification” is fundamentally different from the “externally added thermoplastic resin” approach in oil-based systems.

On the other hand, when improved wetting and initial tack are needed on difficult-to-adhere substrates (BOPP, PET, metal, glass), modified rosin resins or terpene resins are introduced in measured quantities as “reactive or semi-reactive tackifier resins.” Acrylate groups or double bonds are introduced via esterification, maleation, or similar reactions, enabling these resins to co-polymerise into the film during UV curing — a role distinctly different from their “inert thermoplastic resin” function in oil-based systems. Technical literature notes that functionalised rosin and terpene resins in UV inks not only contribute adhesion but also improve pigment wetting and levelling, and are particularly well suited to UV flexographic and UV inkjet systems on non-absorbent substrates such as plastic films, metals, and glass — compensating for adhesion shortfalls under solvent-free or low-solvent conditions. Of these, terpene–acrylate modified resins, with their light-coloured backbone and low odour, cause less interference with colour reproduction and final print appearance in UV inkjet and UV label inks, and are generally preferred by formulators over rosin-modified derivatives in high-quality colour printing applications.

Comparing traditional oil-based ink systems with UV-curable systems makes the differences in film-formation mechanism and functional positioning of rosin-modified resins, terpene resins, and petroleum resins much clearer:

• In oil-based ink systems: Rosin-modified resins dominate pigment dispersion and tack control in offset inks, serving as “structural backbone resins” that form the film jointly with drying oils. C5/C9 petroleum resins lean towards economical rheology and initial tack adjustment, improving abrasion resistance and adhesion in industrial protective coatings and marking inks. Terpene resins excel in high initial tack and wetting of non-absorbent substrates, making them suited to marking inks and premium offset formulations; their colour stability and low odour give them a distinctive position in high-quality colour printing and food-contact applications.
• In UV-curable ink systems: The corresponding tackifier resin types shift to: polymerisable backbone resins — typified by epoxy, polyester, and urethane acrylates — which govern crosslinked film formation and mechanical performance; functionalised tackifier resins — typified by modified rosin and terpene resins — which focus on compensating for insufficient wetting and adhesion on difficult substrates (plastics, metals) under solvent-free conditions; and conventional C5/C9 hydrocarbon resins, which — lacking polymerisable functional groups — can only be used in limited, specific scenarios for rheology adjustment or blended tackification, typically in concert with reactive systems to avoid adverse effects on cure shrinkage and crosslink density. This transition from “inert thermoplastic resin → polymerisable functional resin” is one of the most significant structural differences between UV-curable and oil-based inks at the tackification resin level.
• In water-based ink systems: Acrylic resins lean towards film formation and optical performance; polyurethane dispersions towards flexibility and durability; modified rosin/rosin emulsions focus on pigment dispersion, paper wetting, and tack fine-tuning; terpene resin emulsions play a supplementary role in polyolefin adhesion and low-odour formulations; C5/C9 petroleum resins are limited in application by their poor water dispersibility — together forming a multi-resin platform distinctly different from both UV and oil-based systems.