Omnidirectional LED Filament with Light Conversion Coating

The patent employs a composite structure consisting of a glass substrate coated with a metal reflective layer. The glass substrate provides excellent light transmission properties, while the metal reflective layer (such as aluminum or silver) deposited on its surface provides high thermal conductivity and reflects light that would otherwise be absorbed by the substrate, thereby solving both the light transmission and thermal management requirements simultaneously.

The invention applies different material properties to different regions of the substrate system. The glass substrate maintains its inherent light transmission properties in the light-emitting regions, while the metal reflective layer is strategically positioned to provide thermal conductivity and light reflection. This localized application of material properties allows the system to benefit from both glass and metal characteristics without the drawbacks of using either material alone.

The patent segments the LED filament into multiple independent LED chip units arranged along a flexible substrate. Each LED chip can be individually positioned to emit light in specific directions, and the flexible substrate allows the entire filament to be bent into configurations that achieve omnidirectional illumination. This segmentation approach enables complex lighting patterns using simpler, modular components rather than requiring multiple complete filament assemblies.

The invention extracts the phosphor conversion function from a bulk coating and implements it as a thin-film layer on the glass substrate. By using a thin-film phosphor coating rather than a thick mixture, the patent reduces the optical path length through the phosphor material, minimizing light absorption losses while still achieving effective wavelength conversion and wide-angle illumination. This extraction approach maintains the beneficial wide-angle emission while reducing optical efficiency degradation.