Five Types of UV-Curable Adhesives

Reposted from: Adhesive Trading Platform News

　　UV adhesives can broadly be categorized into two main types: those with a substrate (such as tapes or double-sided adhesives) and those without a substrate (liquid adhesives). The latter cure upon exposure to UV light, while the former can have their adhesion enhanced or reduced by UV irradiation. UV‑de‑adhesive tapes, used for temporary protection or positioning, are in high demand in microelectronics and optoelectronics applications, such as wafer processing and touch‑screen glass manufacturing.

　　 UV pressure-sensitive adhesive (PSA)

　　Currently, pressure-sensitive adhesives (PSAs) are produced through solution coating, drying, and chemical reactions. Over 60% of the solvent must evaporate or be burned off, resulting in high emissions, a lengthy production process, and low efficiency; moreover, residual solvents and other harmful chemicals may remain in the final product. By contrast, PSA production using UV curing involves coating a solvent-free liquid formulation onto a substrate and then inducing photopolymerization with UV irradiation—eliminating the need for thermal curing ovens, simplifying the production line, ensuring an environmentally friendly process with near‑zero emissions, and significantly boosting production efficiency.

　　PSA products come in a wide variety of forms, ranging from decorative films and protective films to engineering‑grade structural tapes, with applications spanning advertising panels, electronic devices, and high‑end packaging boxes.

　　 UV composite adhesive

Food, beverages, and certain biopharmaceutical products require high-barrier flexible packaging, where the barrier properties of the packaging material directly determine and influence the shelf life. High-barrier packaging materials are typically produced by laminating plastic films with paper or metalized films, offering superior strength, excellent oxygen and moisture barrier performance, safety, hygiene, non-toxicity, and printability; they also withstand freezing temperatures and high heat up to 120°C. Currently, nearly all adhesives used in the flexible‑packaging industry are solvent-based, with solvent content exceeding 70%. The lamination process involves coating, solvent evaporation, lamination, storage, and curing—steps that not only pose fire and explosion hazards, generate substantial emissions, and result in lengthy production cycles with low efficiency, but also leave residual solvents in the composite film. During peak holiday periods, when demand for premium packaging is particularly strong and delivery deadlines are tight, many laminated films are shipped before the solvents have fully reacted and completely evaporated. Residual solvents and incompletely reacted chemical substances can leach into and contaminate food products, which remains a major reason why health‑related standards for numerous pharmaceutical and food packages continue to be unmet. Water‑based adhesives, while solvent‑free, suffer from slow drying, low production efficiency, and suboptimal bonding performance on plastics. Replacing solvent‑based adhesives with UV‑curable adhesives would not only dramatically boost production efficiency—reducing the typical several‑hour lamination process to just one minute—but also eliminate solvent emissions, harmful residues, and ensure that the finished composite film meets stringent health and hygiene requirements for food and pharmaceutical packaging. In contrast, traditional solvent‑based adhesives require several hours or even days for complete solvent evaporation, during which the work area must remain inaccessible. By contrast, using UV‑curable adhesives avoids these limitations: the adhesive can be applied to the substrate, allowed to self‑level, and then cured under ultraviolet light, leaving a tacky surface ready for immediate installation of PVC flooring. This approach significantly shortens the construction timeline and eliminates solvent emissions throughout the entire process, thereby preventing indoor air pollution.

　　UV architectural adhesive

　　Safety glass is primarily manufactured by bonding glass sheets together using polyvinyl butyral (PVB) interlayer film, a process that involves vacuum degassing and hot pressing, with a total production time of roughly ten-plus hours. Another method—producing laminated safety glass through edge sealing, resin injection, and curing under natural light for several tens of minutes to achieve photopolymerization—has been in use for quite some time; however, it remains a niche product, mainly serving the low‑end safety glass market. The primary reason this liquid‑bonding approach has yet to gain widespread acceptance is the insufficient performance of UV‑curable adhesives and the lack of reliable safety data. That said, UV adhesives are enjoying strong growth in the construction sector, with applications ranging from shop‑window displays and interior finishes to stained‑glass installations. As their performance continues to improve, UV‑based architectural adhesives are poised for significant expansion.

　　In recent years, the application of PVC stone‑plastic flooring has grown rapidly in China. The installation process involves first applying a uniform layer of adhesive to the substrate, followed by bonding the PVC floor tiles. PVC floor adhesives can be broadly classified into three main types: water‑based, solvent‑based, and reactive. Water‑based adhesives use water as the dispersing medium; they are non‑toxic and cost‑effective, but their water resistance is relatively poor—after immersion in water, their bond strength typically declines significantly, as seen with water‑borne acrylic esters. Solvent‑based adhesives are primarily polyvinyl acetate‑type and chloroprene rubber‑type formulations. Reactive adhesives include polyurethane‑based systems. All of these adhesive types require proper curing after application.

　　UV electronic adhesive

　　UV adhesives are already widely used in the electronics industry, for applications such as flex‑cable alignment, pin sealing, liquid‑crystal‑display panel fabrication, and mobile‑phone keypads. UV‑cured bonding has become an indispensable technology in electronic product manufacturing. With the trend toward thinner devices and the emergence of organic optoelectronic components and flexible, bendable display technologies, there is a growing demand for UV adhesives that are compatible with roll‑to‑roll processing. The advantages of UV curing—high efficiency, rapid cure, precise control, and on‑demand activation—will be fully realized.

　　UV optical adhesive

　　Touch screens currently represent the largest single application for UV optical adhesives. In touch‑screen assemblies, UV optical adhesives serve three key functions: bonding, enhancing light transmission, and improving impact resistance. They must meet stringent performance requirements, including color neutrality, weathering and environmental stability, electrical properties, and optical performance. The primary substrates involved in touch‑screen lamination include glass, ITO conductive layers, PET, PMMA, and PC. When sapphire is used as the cover glass, a higher‑refractive‑index UV adhesive is required to maximize light transmission. Today, both liquid (LOCA) and solid (OCA) optical adhesives are employed in touch‑screen applications. LOCA is dispensed using a dispensing robot, followed by lamination with a glass cover plate, leveling, and curing through the cover plate; it offers excellent filling capability and ease of application but necessitates post‑dispensing cleanup to remove excess adhesive. OCA, on the other hand, is a substrate‑free double‑sided pressure‑sensitive adhesive with release liners on both sides. During use, the lighter release liner is peeled off for initial lamination, then the heavier release liner is removed before bonding the second surface. Early touch‑screens utilized thermally curable liquid adhesives, which resulted in lengthy production cycles and low efficiency; these have now been entirely replaced by UV‑curable adhesives. However, current OCA products are still manufactured via conventional solvent‑based processes involving coating, drying, and thermal crosslinking, leading to long curing ovens and frequent defects caused by dust and other contaminants. Switching to a UV‑curing process would significantly boost production efficiency while reducing equipment investment and manufacturing costs.

　　UV medical adhesive

　　UV adhesives have significant growth potential in the medical field; for example, replacing conventional pressure-sensitive adhesives or tapes with UV-curable formulations can enable the development of a comprehensive product line.