Short answer: judge an anti-reflective (AR) coating supplier less on the reflectance number in a brochure and more on whether the supplier can attach verifiable limits to that number — which standard edition, which measurement geometry, which durability sequence, and which usable coated area. In ophthalmic optics the reference point for AR and hydrophobic coatings on uncut finished lenses is ISO 8980-4, whose current edition (ISO 8980-4:2026, adopted in Europe as EN ISO 8980-4:2026) was published in 2026 and supersedes the 2006 edition. A supplier who can quote limits from that edition, run the tests it describes, and state exclusions can be contracted with; one who quotes a single reflectance figure without these qualifiers cannot.
Buyer brief: what you are actually buying
AR coating is a set of vacuum-deposited layers plus, in many products, a hydrophobic top layer. The purchase decision therefore has two separate risk surfaces:
- Optical performance — luminous reflectance (ρV) and mean reflectance (ρM) on the coated surface, measured by a defined spectrophotometric method.
- Durability and environmental behaviour — whether the stack stays bonded after rubbing plus environmental exposure, and whether the hydrophobic top layer still repels water.
These are different failure modes with different test procedures. Suppliers who conflate them ("our coating passes the ISO test") are usually quoting one clause and inheriting the credibility of the rest. Split your RFQ along the same two lines.
Note also the scope boundary: ISO 8980-4 does not cover the colour of the reflected light, and transmittance is handled by ISO 8980-3. If your product claim depends on residual-colour appearance or on luminous transmittance, those need separate evidence — they are not inside the AR-coating standard.
RFQ fields to fix before you compare suppliers
Write these into the RFQ so every quotation answers the same question. The values below are the ones published for ISO 8980-4:2026; confirm them against the copy of the standard your supplier declares, because the edition in force changes the durability sequence and adds hydrophobic testing.
| RFQ field | What to require | Reference point |
|---|---|---|
| Standard edition and clause set | State the exact edition the supplier tests to, and whether hydrophobic properties are in scope | ISO 8980-4:2026 replaces the 2006 edition; scope was expanded to include hydrophobic coatings |
| Coated usable area | Coated area diameter on uncut finished lenses | At least nominal diameter minus 4 mm (Clause 4.2) |
| Reflectance limits | ρV and ρM values the supplier commits to, per surface | Luminous reflectance below 2.5 % for any AR-coated surface (Clause 4.3); measured values may not exceed stated values by more than 20 % |
| Water repellency (if claimed) | Mean static contact angle on the front surface | At least 90° where hydrophobic performance is claimed (Clause 4.4) |
| Adhesion after durability sequence | Delamination observed on five consecutively tested lenses | No significant loss of adhesion; significant loss means more than 3 mm total delamination per surface, surfaces assessed separately (Clause 4.5) |
| Test timing and conditioning | Elapsed time after coating, storage temperature before test | At least 24 h after coating; lenses stored at 20 °C to 26 °C (Clause 5) |
Two details in the table do most of the contract work. The 20 % tolerance on stated reflectance means a brochure value is a commitment, not a target — press suppliers to state ρV and ρM in the specification rather than "typically around" language. The five-lens, both-surface durability rule means one good sample proves nothing; ask for the per-lens result table.
Supplier evidence to request
Ask for documents, not assurances. A realistic evidence pack for an AR coating supplier contains:
- Test report with the method parameters spelled out. For reflectance the 2026 edition expects a spectrophotometer with incident angle not larger than 17°, measurement from 380 nm to 780 nm, step width no more than 5 nm and spectral bandwidth no greater than 5 nm, and a calibration specimen of known refractive index with curvature within 0.50 D of the lens and no coating. A report that only says "reflectance measured" is unauditable.
- Contact-angle data with the measurement window. For hydrophobic claims, water droplets of 1 μl to 4 μl, measured 5 s to 30 s after transfer, at least three measurements per front surface, mean reported.
- Durability sequence description. Which environmental exposure, which rubbing tool and cloth preparation, how many cycles, and which zone was visually evaluated (the 2026 edition evaluates the central 20 mm zone).
- Declared conformity reference. Where the supplier claims compliance, the standard reference must appear on the package or in product documentation — so ask for the exact wording they print, plus a specimen of the label or datasheet.
- Substrate and process scope. Which lens materials, which base curves, which coating line. Coating performance is substrate-dependent; a report on one material is not evidence for another.
If a supplier cannot produce item 1 or item 3, treat the reflectance claim as marketing until a sample set is independently tested.
Capability and quality checks on the coating line
Documents describe the past. To judge reproducibility, look at how the supplier controls the process:
- In-line or lot-based reflectance monitoring. Ask what triggers a re-qualification of the coating run — chamber cleaning, target change, batch of consumables.
- Adhesion and appearance sampling frequency. A durability test performed once for a certification is not process control. Ask for the sampling plan across production lots.
- Handling between coating and assembly. Delamination and surface defects often appear downstream; ask how coated lenses are stored and protected before edging or mounting.
- Traceability from report to lot. Can the supplier map a test report to a production date range and to the material used?
For a parallel view of how to structure supplier scoring and qualification records generally, see our Supplier Evaluation section; the coating-specific point is that qualification must reference a test method, not a product family name.
Environmental limits and after-sales terms
The environmental sequence in the 2026 edition is stricter in scope than the withdrawn 2006 text described, and it is the part most often lost in translation into a purchase contract. Turn it into contractual language:
- Define the claim boundary. State that performance claims cover the coated area only (nominal diameter minus 4 mm on uncut finished lenses). Rejection of edge defects outside that zone needs its own clause.
- Exclude what the standard excludes. Reflected-light colour and transmittance sit outside ISO 8980-4; if you buy tinted or photochromic products, specify ISO 8980-3 evidence separately.
- Set the acceptance test at goods-in. Agree a sampling plan and the acceptance criteria (ρV limit, contact angle where claimed, delamination limit) so that a failed lot is a contractual non-conformity rather than a negotiation.
- Write the after-sales trigger. Define what counts as a coating complaint (field delamination, haze, loss of water repellency within a stated period) and what evidence the supplier must provide — batch, coating date, test record — before credit, rework or replacement is due.
- Pin the edition. Because ISO 8980-4:2026 replaces the 2006 edition and adds hydrophobic testing, a contract that says only "ISO 8980-4" is ambiguous across the transition. Name the edition and state how a future revision is handled.
Red flags and the limits of this checklist
Treat the following as reasons to hold an approval rather than to negotiate harder on price:
- A reflectance figure quoted without ρV/ρM definition, measurement geometry or per-surface basis.
- Durability evidence consisting of a single lens or a single accelerated test with no rubbing sequence.
- Hydrophobic claims without contact-angle data and without the measurement window.
- A declared standard reference that cannot be matched to a printed label or datasheet.
- Test reports older than the coating formulation currently offered, with no re-qualification record.
Limits of this checklist: it addresses AR and hydrophobic coating performance on spectacle lenses under ISO 8980-4. It does not establish whether a supplier is compliant — only a laboratory test on your substrate and geometry does that — and it does not cover coating performance for other optical products, where different standards and test sequences apply. Numerical limits quoted here are from the published 2026 edition; verify them against the standard text before you make them contractual obligations.
Sources
- ISO 8980-4:2006 (withdrawn) — scope and abstract: https://www.iso.org/standard/40122.html
- EN ISO 8980-4:2026 — scope, publication date 07 July 2026, clause-level requirements, test methods and annexes as summarised in the standards catalogue record: https://standards.iteh.ai/catalog/standards/cen/050b353f-1bb8-4cf6-b024-c17f9f72e548/en-iso-8980-4-2026