Radiation Curable Inkjet Inks for Flexibility and Scratch Resistance

The patent applies parameter changes by precisely controlling the ratio of polyfunctional to monofunctional monomers within specific ranges (polyfunctional: 5-50 wt%, monofunctional: 50-95 wt%). This optimized composition balance allows the ink to achieve both high scratch resistance through cross-linking and good flexibility by preventing excessive network rigidity, thereby resolving the contradiction between these two properties.

The patent uses composite materials by combining multiple types of monomers (polyfunctional acrylates, monofunctional acrylates, N-vinyl lactam) with specific glass transition temperatures. This composite monomer system creates a cured film that integrates both hard cross-linked structures for scratch resistance and softer segments for flexibility, eliminating the crack and peel problems associated with high polyfunctional monomer content.

The patent resolves this contradiction through parameter optimization by setting specific concentration ranges for different monomer types. The controlled presence of polyfunctional monomers (5-50 wt%) ensures adequate cross-linking density for fast curing, while the dominant monofunctional monomers (50-95 wt%) maintain chain flexibility, achieving both rapid curing and flexible cured films.

The patent applies local quality by incorporating N-vinyl lactam (10-30 wt%) which has specific local molecular structure characteristics. This component provides localized flexibility segments within the cross-linked network, allowing the material to maintain overall structural integrity for fast curing while having flexible regions that prevent cracking and enable bending.

The patent uses parameter changes by selecting monomers with appropriate molecular weights and structural characteristics. The chosen polyfunctional and monofunctional acrylates, along with N-vinyl lactam, have molecular structures that provide the required mechanical properties at lower viscosities compared to conventional high-Tg monomers, enabling jetting at moderate temperatures while maintaining scratch resistance and flexibility.

The patent applies the principle of flexible molecular structures by incorporating monomers that form flexible polymer chains in the cured film. This molecular-level flexibility allows the cured ink layer to bend without cracking while maintaining scratch resistance, and the low-Tg nature of these flexible structures keeps the uncured ink viscosity low for easy jetting without requiring high temperatures.

The patent extracts the harmful carboxy groups from the monomer composition while retaining the desired flexibility. Instead of using acrylic acid or carboxy-containing monomers that provide flexibility through hydrogen bonding but cause corrosion, the patent employs N-vinyl lactam and carefully selected acrylate monomers that achieve flexibility through different molecular mechanisms (lower Tg, flexible chain structures) without the corrosive carboxylic acid functionality.

The patent uses N-vinyl lactam as an intermediary component that mediates between the need for flexibility and the requirement for print head compatibility. This monomer provides flexible polymer segments in the cured film through its molecular structure without introducing corrosive functional groups, effectively replacing the role of carboxy-containing monomers while eliminating their harmful corrosion effects.