The trend is flat to declining rather than active. Filings rose from zero in 2017 to a peak of 11 families in 2022, and the midpoint of the whole 2015–2026 series is that same 2022 figure, which is the statistical signature of a field that has already crested. The most recent one to two years will look artificially low because publication lags filing by roughly 18 months, but the shape of the rise-then-plateau predates that lag effect and is a genuine finding, not a cut-off artefact. New filers should expect to be working into occupied claim space rather than an expanding frontier.

C08L (polymer compositions) and C08G (condensation polymers) carry almost all the weight, appearing in 44 and 30 of the 44 tracked families respectively. H01L (semiconductor devices) appears in only 13, and shaping/layering classes like B29C and B32B barely register at 2 each. This means the inventive core of most filings is the resin chemistry itself, with electronic encapsulation or composite integration treated as an applied use case rather than the subject of the primary claim.

Start with the C08L and C08G classifications, since every family in this corpus touches the former and most touch the latter — that is where the dense prior art sits. The most-cited records, including the ternary benzoxazine-epoxy-phenolic systems and the epoxy-mercaptan curable liquid compositions, are older filings that still shape citation patterns in this space, so they are worth checking even though they predate the 2015 window. Only after clearing the resin-composition layer does it make sense to check the thinner H01L device-integration layer.

USH1405H1 is a statutory invention registration from Shell Oil Company, published in 1995, covering an epoxy resin composition with a finely dispersed elastomeric block copolymer phase made by a specific emulsification process — non-polar solvent dispersal followed by gradual polar solvent addition, yielding rubber particles of 0.05–0.20 microns. It blocks that particular combination of copolymer structure, emulsification method and particle-size range, not epoxy-elastomer blends generally. A formulation using a different dispersal method, a different block chemistry, or particle sizes outside that stated range sits outside its literal claim scope, though it remains a relevant citation for anyone patenting rubber-toughened epoxy systems.

The European Patent Office leads with 8 of the tracked filings, ahead of the United States at 7, Japan at 6, China at 5, the PCT route at 4, and the United Kingdom at 3. No single office accounts for even a fifth of total filings, so this is not a US-centric or China-centric art in the way many polymer technologies are. A clearance or filing strategy built around only one or two jurisdictions would miss a meaningful share of the documented activity.