Laminated packaging materials that support product quality retention and long-term storage must provide protection against light induced degradation. Ultraviolet radiation, in particular, can damage packaged products and cause discoloration or changes in chemical composition.
For this reason, selecting coating materials with reliable UV blocking performance plays a critical role in increasing product value.
This article explains key performance criteria for UV blocking coating materials used in laminated packaging, along with processing considerations for practical application.
Performance Requirements for UV-Blocking Coatings
Target UV Blocking Ratio
UV blocking coating materials used for laminated packaging are specified according to the type of contents and the required shelf life. For sensitive products such as food, pharmaceuticals, and cosmetics, it is generally desirable to block more than 90 percent of ultraviolet light below 380 nm. In many cases, performance levels of 99 percent or higher are required.
Impact on Transparency and Evaluation Criteria
While achieving strong UV blocking performance is important, maintaining transparency as a core packaging function is equally critical. Additives such as UV absorbers or pigments may cause haze or yellowing in the coating layer, which can reduce product visibility.
In practical applications, strict criteria may be applied, such as a haze value below 1 percent and a color difference of 2 or less.
Stability and Boiling/Retort Resistance of the Coating Layer
When laminated packaging is used for applications involving boiling or retort processing, the stability of the UV blocking coating layer under severe conditions becomes a key evaluation factor. High temperature and high pressure environments may lead to issues such as delamination, bubble formation, significant discoloration, or reduced adhesion strength.
Accordingly, boiling resistance and retort resistance tests should be conducted to evaluate coating adhesion, durability, and changes in appearance in detail.
UV-Blocking Coatings by Dip Coating
What Is Dip Coating?
Dip coating is a method in which a substrate is immersed into a coating solution and withdrawn at a controlled speed to form a uniform thin film. Compared with spin coating or spray coating, dip coating enables uniform application over large surface areas and is particularly suitable for film and sheet materials.
Optimal Conditions for Uniform Coating by Dip Coating
When applying UV blocking coating materials to laminated films using dip coating, identifying optimal conditions for forming a uniform coating layer is essential. Adjustment of coating solution viscosity is the most fundamental factor for controlling film thickness.
In addition, maintaining constant coating and withdrawal speeds, along with appropriate temperature control of the coating equipment, helps achieve a uniform and defect free film.
Drying conditions, including temperature and duration, also influence solvent evaporation behavior and curing of the coating layer. These parameters must be optimized according to the substrate type and coating formulation to ensure stable coating quality.
Summary
Selecting UV blocking coating materials for laminated packaging is a critical process that directly affects product quality preservation and value enhancement.
This article discussed target UV blocking performance, evaluation criteria for maintaining transparency, and resistance to boil and retort processing. It also explained key considerations for achieving uniform coating through dip coating, as well as processing suitability for practical implementation.
By evaluating both performance requirements and process compatibility in an integrated manner, it becomes possible to select optimal coating materials for high performance laminated packaging.
Our company provides the development, rental, and contract coating of dip coating equipment designed with safety and reliability in mind. Please feel free to contact us for consultation.