Optically Clear Adhesive Curing Under Ink Steps
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current optically clear adhesives face challenges in curing under light-obscuring ink steps in display applications, leading to issues like yellow mura and light leakage, and existing solutions either compromise adhesion, require additional equipment, or struggle with depth of cure, especially in complex constructions like in-cell displays.
Innovation Solution
A composition of free-radically polymerizable acrylate or meth(acrylate) functional group oligomers, trialkyl borane complex initiator, photoacid generator, and photosensitizer, which is activated by actinic radiation to cure the adhesive both under and above the ink step, maintaining optical clarity and adhesion without the need for excessive heat or complex alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a light obscuring ink step is used, then cosmetic appearance is improved, but UV light transmission is blocked causing insufficient cure under the ink step
Solution Approach 1:
The patent divides the curing process into two segments: UV irradiation for surface cure and thermal initiation for subsurface cure under the ink step. This segmentation allows each method to address its optimal zone, with UV handling the transparent areas and thermal handling the obscured areas, thereby resolving the contradiction between cosmetic appearance and cure completeness.
Solution Approach 2:
The patent incorporates a thermal initiator that remains dormant during UV curing and activates later through thermal energy. This preliminary action allows the adhesive to be positioned and initially cured by UV light while the thermal initiator waits to activate subsequently, ensuring complete cure under the ink step without compromising the cosmetic appearance achieved by the ink step.
2Strength
If pre-curing is performed prior to lamination, then adhesion performance is improved, but coating defects and light leakage occur
Solution Approach 1:
The patent employs periodic action by implementing a two-stage curing process: first UV irradiation for initial set and positioning, then thermal activation for complete cure. This periodic approach prevents the defects associated with premature single-stage curing, as the adhesive remains processable during UV exposure and only fully cures after lamination is complete, eliminating picture framing and light leakage issues.
3Reliability
If thermal initiator is used for secondary cure, then cure under ink step is achieved, but additional equipment and high temperatures are required
Solution Approach 1:
The patent merges UV photopolymerization and thermal free-radical polymerization into a single adhesive system. The composition contains both photoinitiator and thermal initiator components that work in sequence, combining the advantages of both curing methods while eliminating the need for separate equipment. The UV lamp provides initial cure and the same processing system provides thermal activation, reducing device complexity.
Solution Approach 2:
The patent creates a multi-functional adhesive composition that responds to both UV light and thermal energy. The single composition performs multiple functions: it cures under UV exposure for surface areas, remains stable during lamination, and completes curing under thermal activation for areas under the ink step. This universality eliminates the need for multiple specialized materials and equipment.
4Reliability
If side irradiation is used to cure under ink step, then some cure is achieved, but alignment precision and depth of cure are insufficient
Solution Approach 1:
The patent uses thermal energy as an intermediary to achieve cure under the ink step. Instead of attempting to direct UV light from the side through alignment-sensitive paths, the thermal initiator is activated by heat that penetrates the ink step. This intermediary thermal activation mechanism eliminates the need for precise alignment while achieving sufficient depth of cure through the adhesive layer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures reliable curing of optically clear adhesives under ink steps, preventing defects like yellow mura and light leakage, while maintaining high optical clarity and adhesion, even in complex display constructions, without exposing the display to high temperatures or requiring additional equipment.
Implementation Method 1
a free-radically polymerizable acrylate or meth(acrylate) functional group oligomer, a trialkyl borane complex initiator, a photoacid generator, and a photosensitizer. The viscosity of the composition immediately after mixing and a viscosity of the composition about 24 hours after mixing changes by less than about 10%.
Implementation Method 2
a photoacid generator, and a photosensitizer
Implementation Method 3
a free-radically polymerizable acrylate or meth(acrylate) functional group oligomer, a trialkyl borane complex initiator
Data Source
AI summary
The present invention is an optically clear adhesive composition including a free-radically polymerizable acrylate or meth(acrylate) functional group oligomer, a trialkyl borane complex initiator, a photoacid generator, and a photosensitizer. A viscosity of the composition immediately after mixing and a viscosity of the composition about 24 hours after mixing changes by less than about 10%.