Why PFAS-free matters now
The European Chemicals Agency (ECHA) has proposed the most comprehensive restriction on per- and polyfluoroalkyl substances (PFAS) ever attempted. If adopted, the restriction will phase out PFAS across nearly all industrial applications in the EU, with limited time-bound derogations. For coating formulators and their OEM customers, this is not a distant regulatory exercise — it is an imminent supply-chain event that demands material substitution now.
PFAS compounds have been the backbone of low-surface-energy coatings for decades. In optical applications, fluorinated materials deliver the low refractive indices needed for the topcoat layers of anti-reflective stacks. The challenge has always been clear: how do you achieve RI values below 1.30 without fluorine chemistry?
How conventional AR coatings depend on PFAS
Traditional anti-reflective coatings achieve low reflection through a multi-layer stack of alternating high and low refractive index materials. The low-RI topcoat — typically the most critical optical layer — has historically relied on fluorinated polymers or fluorosilanes to reach RI values in the 1.30 to 1.38 range. These materials are classified as PFAS under the ECHA proposal.
Removing PFAS from just the topcoat is insufficient if the entire stack relies on fluorinated processing aids, surfactants, or intermediates. A truly PFAS-free AR system must be PFAS-free throughout — from synthesis to final cure.
Kriya's PFAS-free RI platform
Kriya Materials has developed a complete refractive index platform that is 100% PFAS-free, covering RI 1.16 to 2.00. This platform spans four chemistry families:
- Solvent sol-gel (RI 1.16 to 2.00) — cured at 200 to 700 degrees Celsius, suitable for glass and high-temperature-stable substrates
- 100% solids UV-curable (RI 1.34 to 1.65) — solvent-free formulations for R2R and nanoimprint lithography
- Solvent UV-curable hybrids (RI 1.35 to 1.95) — versatile multi-layer AR stacks via gravure, slot die, or spin coating
- Thermal-curable latex (RI 1.36 to 1.50) — broad compatibility with nearly any known application method
The key breakthrough is the overcoatable PFAS-free low-RI coating reaching RI 1.16 — a value previously achievable only with fluorinated chemistry. This enables full multi-layer AR stacks entirely free from PFAS, without sacrificing the optical performance that OEMs require.
Performance data on common substrates
Kriya's PFAS-free AR coatings have been validated on four polymer substrates commonly used in display, automotive, and consumer electronics applications:
| Substrate | Transmission (%) | Gain (%) | Haze (%) | Reflection avg (%) | Pencil hardness | Adhesion (%) |
|---|---|---|---|---|---|---|
| PET | 93.8 | +3.3 | 0.66 | 1.7 | 3H | 100 |
| PC | 95.1 | +3.1 | 0.06 | 1.3 | HB | 100 |
| PMMA | 96.2 | +2.2 | 0.76 | 1.4 | 4H | 100 |
| TAC | 96.3 | +2.3 | 0.16 | 1.4 | 3H | 100 |
Basecoat thickness approximately 3.0 micrometres, topcoat approximately 0.10 micrometres. Reflection further reducible via additional layers.
Application compatibility
The PFAS-free platform serves multiple application verticals without reformulation:
- Displays — anti-reflective films for LCD, OLED, and foldable displays. Multi-functional variants add anti-smudge, anti-static, or hardcoat properties to the AR stack. Explore display applications.
- Automotive — HUD anti-ghosting, LIDAR window AR, and interior decorative trims with optical windows for sensors. Explore automotive optics.
- AR/VR waveguides — high-RI core and low-RI cladding layers for diffractive waveguides. Explore waveguide applications.
Processing and integration
Kriya's PFAS-free coatings are compatible with all major wet-coating methods used in volume production:
- Spin coating for R&D and small-batch production
- Dip coating for cylindrical or complex geometries
- Roll-to-roll (R2R) gravure and slot-die for high-volume film production
- Spray coating for large-area substrates
The coatings integrate into existing production lines without equipment modification. Solvent systems are compatible with standard coating-line exhaust and recovery infrastructure. UV-curable grades eliminate solvent handling entirely.
Frequently asked questions
What RI range is available without PFAS?
RI 1.16 to 2.00, covering the full range needed for single-layer and multi-layer AR stacks. The low end (RI 1.16) was the most difficult to achieve without fluorine chemistry and represents a unique capability globally.
Can the low-RI coating be overcoated?
Yes. Unlike many low-RI materials that resist further coating adhesion, Kriya's LRI at RI 1.16 is fully overcoatable — enabling complex multi-layer stacks where the low-RI layer is not necessarily the topcoat. See the LRI coating page for details.
What is the timeline for EU PFAS restriction?
ECHA published the restriction proposal in early 2023, with RAC and SEAC opinions expected through 2025 to 2026. Adoption is anticipated in the 2025 to 2027 window, with transition periods of 18 months to several years depending on the application sector. The prudent approach is to qualify alternatives now rather than depend on derogation timelines.
How does wet-coat AR compare to vacuum-deposited AR?
Vacuum deposition (sputtering, evaporation) delivers excellent optical performance but is limited to rigid substrates and batch processing. Wet-coat AR — Kriya's approach — works on flexible polymer films, enables R2R processing, and reduces cost per square metre significantly. For polymer substrates like PET and TAC, wet-coat is the only practical path to volume.