Solvent-Free Curable Ink for High Refractive Index Optical Layers
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Solution Overview
Problem
The challenge lies in developing curable compositions for optical devices that have a high refractive index, are printable, and can be printed and cured to form articles with minimal light refraction at interfaces, while avoiding the use of solvents to maintain optical clarity and prevent drying defects.
Innovation Solution
The use of curable ink compositions comprising aromatic (meth)acrylates, multifunctional (meth)acrylates with heteroaromatic or fused aromatic groups, and a photoinitiator, which are inkjet printable, solvent-free, and have a viscosity suitable for printing at room temperature, forming a crosslinked (meth)acrylate-based layer with a refractive index of 1.55 or greater and optical clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If organic polymer films with limited refractive index range are used, then ease of processing and flexibility are maintained, but the ability to match refractive indices with other layers is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer by incorporating aromatic groups (such as phenyl, naphthyl, anthryl) and heteroatoms (such as sulfur, selenium, tellurium) into the polymer structure. This fundamentally alters the refractive index parameter of the material, enabling it to achieve higher refractive indices (1.6-1.8) while maintaining the processing characteristics of organic polymers through solution-based application methods.
Solution Approach 2:
The patent creates composite polymer materials by combining aromatic monomers with specific functional groups to achieve both high refractive index and desired mechanical properties. The composite structure incorporates heavy atoms (sulfur, selenium, tellurium) within the polymer backbone or side chains, achieving refractive index matching capabilities while retaining flexibility and processability.
2Adaptability or versatility
If layers with different refractive indices are adjacent, then device functionality is achieved, but light refraction at interfaces occurs
Solution Approach 1:
The patent enables precise control of the refractive index parameter by selecting specific aromatic monomers and functional groups, allowing the polymer layer to be tuned to match the refractive index of adjacent layers (such as inorganic barrier layers or other organic layers), thereby eliminating interface refraction while maintaining optical functionality.
3Ease of operation
If solvents are used in ink compositions, then printability is improved, but drying defects and reduced optical clarity occur
Solution Approach 1:
The patent extracts and eliminates the solvent component from the ink composition entirely, developing a solvent-free formulation that uses reactive monomers and oligomers with sufficiently low viscosity to be inkjet printable. This removal of solvent eliminates drying defects and maintains optical clarity while preserving printability through careful selection of low-viscosity aromatic monomers.
Solution Approach 2:
The patent changes the viscosity parameter of the ink composition by selecting specific low-viscosity aromatic monomers and controlling the molecular weight of oligomers, enabling solvent-free printability. The composition maintains viscosity within the inkjet printable range (10-1000 cP) without requiring solvent dilution, thereby avoiding drying defects.
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
These compositions enable the creation of thin, optically clear, and precise organic layers with high refractive indices, suitable for use in multilayer optical devices like OLEDs, with improved shelf life and surface smoothness, reducing the need for solvent-based drying processes and maintaining optical properties.
Implementation Method 1
curing the curable layer to form a cured organic layer
Data Source
AI summary
Curable ink compositions include at least one aromatic (meth)acrylate, at least one multifunctional (meth)acrylate with heteroaromatic groups, fused aromatic groups, heteroalkylene groups, or a group containing both heteroalkylene and aromatic groups, and a photoinitiator. The curable ink composition is Inkjet printable, having a viscosity of 30 centipoise or less at a temperature of from room temperature to 35° C., and is free from solvents. The ink composition, when printed and cured has a refractive index of 1.55 or greater, and is optically clear. The cured ink composition, when cured to a thickness of from 1-16 micrometers, has a surface roughness of less than or equal to 5 nanometers.