| White light-emitting diodes (WLEDs) are receiving much attention by the general research workers, due to its advantage of less energy consumption, environment friendly, longer lifetime and higher efficiency. At present, the main technology measure to realize white light is phosphor-converted white LED (pc-WLED) by combing LED chip with the phosphors. Among them, the tricolor phosphor used in the pc-WLED could effectively improve the color rendering of LED on the premise of high luminous efficiency. The most common method to achieve white light LED is that ultraviolet (UV) LED chips stimulate red, green, blue (RGB) tricolor phosphor to realize white light. The emitting color of UV-LED is only determined by the ratios of phosphors. Therefore, there are the advantages of high color rendering index, light color and color temperature adjustable.This thesis focuses on the synthesis of copolymerization bonding and blending white-light polymer phosphors using the method of first covalently bonding after free radical copolymerization, and their luminescence properties were studied in detail, and the possibility of its application on the WLED was discussed. In this paper, the main research results are as follows:(1) The red, green and blue three color reacting Eu-complex, Gd-complex and Be-complex were synthesized. Using rare earth Eu3+ion as luminescence center,2-Thenoyltrifluoroacetone (TTA) as the first ligand,1,10-phenanthroline(Phen) as the coordinated ligand, Methyl methacrylate (MMA) as the active ligand, the red complex Eu(TTA)2(Phen)MAA was synthesized by covalently bonding metal ions and organic ligands. The emission peaks of the complex located at425,503,579,590, and612nm, and were corresponded to the emission of Eu3+ion. The CIE coordinates were calculated as (0.58,0.33) according to the emission spectra, and located at red region. Using rare earth Gd3+ion as coordinate center,2-(2-hydroxy phenyl)benzothiazole(BTZ) and Methyl methacrylate as organic ligands, the complex Gd(BTZ)(MAA) was synthesized. The maximum emission peak located at503nm, and the CIE coordinates were calculated as (0.24,0.57), which was ascribed to the green emission of the ligand BTZ. Using Be2+ion as coordinate center,2-(2-hydroxy phenyl)Benzothiazole(BTZ) and Methyl methacrylate as organic ligands, the complex Be(BTZ)(MAA) was synthesized. The maximum emission peak located at462nm, which is due to that the emission of ligand BTZ blue-shifted after coordination, and the CIE coordinates were calculated as (0.17,0.21), and located at blue region. Moreover, the decomposition temperature of three kinds of complexes respectively was208℃,198℃and326℃.(2) White-light copolymer phosphor PMEuGdBe was synthesized. Firstly, serial copolymers PMEuBe were prepared through free radical copolymerization of different feed ratios of Eu-complex, Be-complex monomers with methyl methacrylate (MMA). When the feed ratio of Eu/Be is1:1, the CIE coordinate was calculated as (0.38,0.23), which is closest to white-light region. Subsequently, a series of copolymers PMEuGdBe were prepared through copolymerization of different feed ratios of red, green, blue monomers with methyl methacrylate (MMA). The CIE coordinate was calculated as (0.34,0.33), located at white-light area, when the feed ratio of Eu/Gd/Be is1.5:15:2. The relative quantum yield (ηs) of the copolymer was calculated to be0.112. Moreover, the copolymer phosphor was disorder, and luminescent properties would be stable up to250℃, which was better thermal stability.(3) The influence of glass transition temperature Tg and luminescence properties of single copolymer owing to introduction of NVK was discussed. Taking for PMBe example, when the feed ratios of MMA/NVK are2.5, the Tg of the single copolymer PMBe is140.47℃, which is35℃higher than that of PMMA. The CIE coordinates of single copolymer PMN(0.1)Eu, PMN(0.0)Tb, PMN(0.3)Be were (0.56,0.32),(0.23,0.39) and (0.16,0.07), respectively, which were located at red, green, blue region.(4) The blended white-light copolymer phosphor was prepared. The results showed that when the three colors feed ratio was6.5:5.5:1, the CIE coordinate was calculated as (0.32,0.28), close to positive white light (0.33,0.33). The blended phosphor was not decomposed before228℃, and the glass transition temperature Tg was134.66℃,29℃higher than that of PMMA. |
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