High refractive index UV resins and monomers form a mature product line within the Trust series. With refractive indices covering the range of 1.575 to 1.635, this series offers material options for coating, bonding, lamination, and nanoimprint lithography processes in optoelectronic display and precision optics applications.
Product System and Technical Characteristics
The series is based on acrylate backbones, with refractive index enhancement achieved through the introduction of sulfur-containing or aromatic groups that possess high molar refraction, while maintaining good reactivity and process compatibility within the UV-curing system. Compared with silicone or epoxy systems, the acrylate system offers advantages in curing speed, film hardness, and adhesion to commonly used substrates.
In terms of product forms, we offer both resins and monomers:
High refractive index UV resins are prepolymer forms with high solid content and low volume shrinkage upon curing, suitable for coating and bonding applications that require a certain film thickness or structural strength.
High refractive index UV monomers are low-viscosity reactive diluents that can be used to adjust formulation viscosity, or applied alone as working fluids for nanoimprint lithography or UV transfer processes, facilitating the filling of fine mold structures.
For different process conditions, the series has been formulated with corresponding considerations:
Coating processes: Coating generally requires resins with good leveling and low viscosity to ensure uniform film thickness over large-area substrates. The corresponding resin grades have been optimized in terms of dilution ratio and wetting properties, achieving good spreading performance on common substrates such as PET, PC, and glass.
Bonding and lamination processes: Bonding applications require a balance between curing shrinkage and adhesion strength, while also considering adaptability to different material types. Selected grades in this series exhibit controlled volume shrinkage upon curing, making them suitable for precision bonding of optical components.
Nanoimprint and UV transfer: These processes demand high material fluidity and good release properties. Monomer products, with their low viscosity, can fully fill micro/nano structures of the mold during imprinting, and after curing they exhibit good demolding performance and high structural fidelity, suitable for replication of AR diffractive waveguide surface relief gratings, microlens arrays, and other microstructures.
Regarding curing conditions, the series products are compatible with various light sources (e.g., mercury lamps, LED) in production and accommodate a wide range of coating thicknesses. Adequate curing can be achieved under both thick coatings (tens to hundreds of micrometers) and thin coatings (sub-micron levels).
In addition, we also offer thermally cured solvent-based high refractive index optical resins. These products, with solvents as carriers, are suitable for irregularly shaped workpieces, three-dimensional structural parts, or substrates unsuitable for UV exposure. Through conventional thermal crosslinking curing, a refractive index as high as 1.645 can be obtained, and they offer better outdoor weatherability compared to UV-cured systems, making them suitable for outdoor or semi-outdoor optical devices with long service life requirements.
Typical Application Areas
The core value of high refractive index materials lies in shortening optical paths or enhancing light deflection capability through increased refractive index, thereby achieving higher optical efficiency within limited space.
Optical enhancement of microlens arrays for Micro OLED/LED
In Micro OLED and Micro LED display devices, microlens arrays (MLA) are used to improve light extraction efficiency. High refractive index materials are applied to fill or cover the microlens structures, reducing interfacial reflection losses by decreasing the refractive index difference between the lenses and the surrounding medium, allowing more light to be effectively extracted from the device. Such applications require the material to maintain high transparency (visible light transmittance generally above 90%) and low haze after curing to avoid contrast degradation.
FOV enhancement for AR surface relief gratings (diffractive waveguides)
In AR diffractive waveguides, the replication of surface relief grating structures is typically accomplished through nanoimprint lithography. High refractive index UV monomers serve as imprinting working fluids, filling the mold structure and curing to form the grating during the imprint process. The higher the refractive index of the grating material, the stronger the waveguide's ability to confine and deflect light, enabling a larger field of view (FOV) within the same physical dimensions while reducing light leakage and improving overall optical efficiency. Currently, grades with refractive indices above 1.60 in this series have been validated in practical applications, with some customers already using them in mass production processes for full-color diffractive waveguides.
Quality and Compliance
Products in this series undergo multi-dimensional testing throughout production, covering optical properties (refractive index, transmittance, haze), physical properties (adhesion, hardness, shrinkage), and chemical properties (solvent resistance, damp-heat aging resistance). All products comply with the latest environmental regulations including RoHS and PFAS, making them suitable for consumer electronics and exported products with clear material compliance requirements.