A New Coating Configuration With Two Tapered Phosphor Layers Lamination

Main indicators of high quality light sources are the luminous efficiency of the device, the spatial uniformity of correlated color temperature(CCT) and light spot intensity, while the phosphor coating structure is the important influencing factors of these three indicators. However, even if advanced structural concepts and preparation methods of phosphor layer are employed, currently available white light pc-LEDs still show low uniformity spatial ratio of yellow light and blue light, thus unable to satisfy the performance demand of high quality light sources. Therefore, to improved spatial spot light color uniformity of pc-LEDs devices, this paper simulated the photon transmission process by using the self-developed phosphor layer optical model, researching how structure parameters influenced the device’s performance of photometry and colorimetry. Then, we optimized the design of coating structure, and proposed a new coating configuration method to excellently improve CCT, finally verified it by experiment.First, this paper followed the widely used Monte Carlo method to model the phosphor coating structure, optimizing the inverse problem solving method to effectively control the theoretical error under the condition of limited calculation. Through strictly deducing the rotation matrix in the transformation of a three dimensional coordinate system, this paper simplified the dealing process of scattering vector, reduced the judgments times of scattering angle, and finally enhanced the efficiency of scattering calculations.Based on this model, the simulated result of the conventional spherical crown coating structure proved that the physical defect of color nonuniformity is due to the distribution characteristic mismatch of converted yellow light and scattered blue light. Emitted blue rays excessively focused on the central normal axis, leading to a result that the CCT at central region was too high, but the one at the margins is relatively low, i.e. spot blue heart phenomenon. It is consistent with experimental phenomena that the light spot was blue in the center but yellow in the ring. Therefore, this paper presented a new idea of phosphor coated structure design to match the intensity angles of blue light and yellow light.Originated from this philosophy, we designed a new double conical coating configuration with two tapered phosphor layers lamination. This configuration redistributed forward-scattering blue rays that emergent angles overly focused on small-angle laser by introducing total reflection and resorption mechanisms, thus the small angle laser light and large angle emitted light in edge area are treated differently, which will achieve a better response to the distribution about yellow and blue ray.Placed the new double conical phosphor layer laminated structure and the traditional spherical cap structure at the same related color temperature region 4470K for comparison. Simulated data showed new laminated structure spatially correlated color temperature deviation (-90 degree to 90 degree CCT deviation) is 280.8K, compared with traditional spherical cap structure of 1046K decreased 71.5%. The spot blue heart phenomenon has been overcome, and the ratio deviation of yellow light weight to blue is reduced in spatial, which indicate distribution characteristics of emergent functions of Blue rays matching yellow.Finally, this paper implements two kinds of structure by widely used dispensing technology, namely the new double conical phosphor layer laminated structure and the traditional spherical cap structure, then test the two structures of the same equivalent color temperature region 4800K. of photometry and colorimetric parameters. Test data: compared to conventional spherical cap structure with novel laminated structure ACCT respectively, for traditional structure, with a deviation of 715K, for novel lamination structure, with a deviation of 205.2K, the ACCT reduce 71.3%; At driving current of 250mA, for traditional structure, with luminous flux of 581m and luminous efficiency of 601m/W, respectively for novel lamination structure, with luminous flux of 671m luminous efficiency of 65.41m/W, the luminous flux increase 15.6% and the luminous efficiency increase 9%. A new double conical laminated structure not only has better lighting and suitable for mass production...