Julie Allen at EdisonReport.eu has a piece with a bit more background on “filament” style LED bulbs.  The key IP for the filament-style construction is held by EPISTAR:

LED Filaments are usually constructed by applying light emitting diodes on a transparent substrate, allowing light to be emitted from all sides. This omnidirectional light emission results in a higher energy efficiency level, as the light does not get “trapped” in the LED package itself. This increased efficiency of the LED filaments allows for more attractive light bulb shapes, without obstructive large heat sinks that limit application use. The traditional looking format improves the aesthetics of the light bulb in its application, especially for decorative use in chandeliers and other open fittings. EPISTAR holds key intellectual property regarding the LED filament technology used in making LED filament style lamps. This patent portfolio covers Taiwan, China, United States and Europe.

Dangoo has been at the forefront of developments in filament lamp technology since its inception, presenting their first solutions at the Hong Kong Light Fair in October 2012. Since then, manufacturing has been managed by Cosmoled, while Dangoo remained the exclusive reseller of the Cosmoled Filament lighting products. Today, Cosmoled has been granted licenses for the production of LED Filaments by EPISTAR.