What Are UV/EB Cured Resins?
UV/EB Cured Resin is a generic term for resins in which monomers and oligomers polymerize and cure from a liquid to a solid state when irradiated with ultraviolet rays of 200 to 400 nm in wavelength.
The resins polymerize instantly and cures in a few seconds when irradiated with UV light. Therefore, they are highly efficient and do not require the application of heat, making them energy-efficient.
Although organic solvents were used in the past as the mainstay of UV cured resins, recently, solvent-free and water-based resins have been developed, making them more friendly to humans and the earth.
In addition, because of the simplicity of curing by simply irradiating with ultraviolet light and the beautiful luster after curing, they are also used for general purposes such as DIY, homemade accessories, and miscellaneous goods.
Uses of UV/EB Cured Resin
UV/EB Cured Resins are used in a wide range of fields from daily life to industrial applications. Familiar applications include printing on POP, direct mail, food labels, and clear files.
The resins are suitable for printing on plastic film and cardboard, where heat-drying ink is not suitable. They are also used as coatings for wood and plastics.
In recent years, they are often used to prevent scratches on smartphones, tablet devices, and automobile exterior materials.
In the industrial field, they are utilized as adhesives for electronic components, encapsulants for liquid crystal panels, and resist materials for base formation.
Principle of UV/EB Cured Resin
UV/EB Cured Resins contain 1-5% by weight of a photoinitiator that generates radicals and cations upon UV irradiation. Since the reaction mechanism differs depending on the type of photoinitiator, resins can be divided into two major types: radical-curing type and cationic-curing type.
1. Radical Curable Type
Radicals are generated from the initiator by the energy of UV light, and unsaturated groups such as acrylate, methacrylate, and vinyl ether undergo radical polymerization and cure. Since there are many resins and monomers that can be used, various properties such as hardness, chemical resistance, and contamination resistance can be imparted depending on the coating design.
The majority of these resins are radical cured resins because of their fast curing speed and relatively low cost.
2. Cationic Curable Type
Cationic curable resins use iodonium salts or sulfonium salts as initiators. When the initiator is irradiated with ultraviolet light, an acid is generated, which acts as a catalyst for cationic polymerization of cyclic ethers and vinyl ethers, resulting in curing.
Since curing shrinkage can be reduced, the adhesion of the coating can be improved. However, the degree of freedom of design is not high, so it is difficult to control the characteristics.
Types of UV/EB Cured Resins
UV/EB Cured Resins are broadly classified into three categories according to the presence or absence of a solvent and the type of solvent. The most common type is solvent-based.
In recent years, in response to the needs of the times, such as VOC (Volatile Organic Compounds) regulations, solvent-free types and water-based resins that use water as a solvent have been attracting attention.
1. Solvent-Based Resins
Solvent-based resins are easy to handle and provide a uniform coating thickness. Grades containing silicone-based inorganic components are also available to withstand outdoor use.
2. Solventless Resins
Since they do not contain organic solvents, these resins have almost no odor and can suppress the generation of VOCs, making them friendly to both workers and the global environment. Another advantage is that there is no need to volatilize organic solvents, simplifying the production line.
Some base materials are denatured by solvents, so solventless types are chosen.
3. Water-Based Resins
As with the solventless type, this type does not contain organic solvents. The main applications are in the construction field, such as on-site installation of floor surfaces and coating of polyvinyl chloride flooring materials, where the generation of VOCs is a major disadvantage. They also have the advantage of greater strength and chemical resistance than conventionally used waxes.
Other Information on UV/EB Cured Resin
Additives for UV/EB Cured Resin
UV/EB Cured Resins are produced by mixing monomers, oligomers, photoinitiators, and solvents. In addition to these, various additives can be added to improve reactivity by resins, adhesion between the coating film and the substrate, hardness of the resin, stain resistance, water resistance, dispersibility, etc.
Examples of additives include polymerization inhibitors, pigments, leveling agents, etc. The composition of the resin is adjusted according to the purpose and application.