Filing in this space has historically been led by a small group of long-established glass manufacturers, including Corning, Schott, and Nippon Electric Glass, alongside DuPont and the Jenaer Glaswerk Schott / Carl Zeiss Foundation group. However, recent-year momentum data shows all of these historically dominant filers at zero filings in the latest tracked year, so current leadership by count does not equal current filing activity. Anyone assessing freedom to operate should weight older, still-active families more heavily than raw historical filing counts.

No — filing peaked in 2017 at 32 records and has trended flat to declining since, with the 2022 midpoint at 19. The most recent one to two years should be read with caution because publication typically lags filing by around 18 months, understating true recent activity. Even allowing for that lag, the multi-year direction from the 2017 peak is a genuine decline rather than a data artefact.

The United States is the largest receiving office in this dataset at 219 filings, followed by Japan at 130 and the EPO at 102, with China at 75 and 43 filings routed through the PCT system. This distribution reflects where the historical leaders in glass manufacturing have concentrated protection, so it is a reasonable starting map for competitive exposure, but it is not a substitute for a jurisdiction-specific novelty search in your target markets.

EP0172698A1, assigned to Owens-Illinois, covers a method of increasing the chemical durability of borosilicate glass tubing and hollow articles by adding a small volume of fluorine-containing gas to the inflating air during conventional tube-forming, reducing surface alkalinity by up to 70% or more. It is specific to a fluorine-gas treatment step applied during tube-forming, not to borosilicate glass compositions generally. New filings on different durability-improvement mechanisms, such as ion-exchange strengthening or surface coatings that do not rely on fluorine-gas inflation treatment, sit outside its literal scope, though a full claim-by-claim freedom-to-operate review is still advisable given its 1986 grant and long citation history in this corpus.

The IPC overlap data suggests several narrower branches carry comparatively lower claim density than the C03C core, including striae-control during melting, low-viscosity zirconium/lithium borosilicate formulations, porous antireflective surface layering, and specific process variants of fluorine-gas durability treatment and ion-exchange fast-cooling. These are not unclaimed spaces outright, but they show thinner overlap relative to the dominant composition claims, making them worth a closer prior-art search before committing R&D spend.