| Light emitting diode(LED) has attracted the favor of many manufacturers owing to the advantages of long lifetime, low energy consumption, and environmental-friendly characteristics. White light is a common and general light source, the research about the fluorescence transition substances is a hotspot in white light LED, so the studies on the phosphors in white light LED have theoretical significance, practical application value.In this article, the aim was to design and synthesize rare earth polymer-based light phosphors with high luminescent properties. White light polymer phosphors of blue and yellow composition, red, green and blue composition were synthesized using the technology route from complexes to polymerization.1. Quasi-white light polymer phosphor with blue and yellow composition was synthesized. With the Dy(Ⅲ) ion as the luminescent center, the Dy(Ⅲ) ion complex monomer was synthesized, then the polymer phosphor containing Dy(Ⅲ) ion was synthesized by copolymerizing the Dy(Ⅲ) complex monomer and polymer monomer. The results suggest that the Dy(Ⅲ) ion complex emitted characteristic peaks at480nm and572nm, separately; the CIE coordinates were calculated as (0.33,0.38) according to the fluorescence spectra, being located in the region of white light; compared with the Dy(Ⅲ) ion complex, the ratio of blue to yellow light changed in the copolymer containing Dy(Ⅲ) ion, gave the CIE coordinates of (0.31,0.33), being close to true white light point (0.33,0.33); however, showed much decreased quantum yield and fluorescence lifetime, which would limit the application in the luminescent materials.2. Two Eu-complexes and Tb-complexes monomers were synthesized. According to solubility, excitation wavelength, steric hindrance and luminescent properties, the complex monomer Eu(TTA)3(UA) with CIE value of (0.540,0.314) was screened as the red light moiety of white light; the complex Tb(2-ABA)3(UA)2with CIE value of (0.231,0.463) was screened as the green light moiety, for the subsequent polymerization of white light polymer phosphor.3. The singlet and triplet energy levels of the ligands of rare earth complexes were calculated with quantum chemistry by the Gussian03software package, coinciding well with the experimental values, proving the reliability of the calculation method. Furthermore, intramolecular energy transfer mechanism and processes were investigated on the basis of the matching degree between the lowest triplet energy level and resonance energy level, providing a new method for selecting the ligands of rare earth complexes with high luminescent properties. 4. With Be(Ⅱ) ion as luminescent center, blue light complex monomer Be(BTZ)(MAA) was synthesized. The complex was soluble in organic solvents, small in steric hindrance, excitation wavelength at365nm, the emission wavelength at about460nm. CIE coordinates were located at (0.161,0.054), being in the range of blue light. Therefore, the complex can be used as the blue light moiety of white light.5. Monochrome polymers were synthesized by a free radical copolymerization of polymer monomer with the red, green and blue complex monomers, separately. The results suggest that the complex monomers were bonded to the polymer chain and uniformly dispersed in the polymer matrix; red light and green light polymers maintained the luminescent properties of the complex monomers, while the excitation wavelength of blue light polymer had a blueshift of30nm; the CIE coordinates of red, green and blue polymers were calculated as (0.579,0.330),(0.262,0.554) and (0.157,0.067) respectively, and their luminescent intensity increased to1.69,11.53,10.57times that of the complex monomers, respectively.6. Blended-polymer phosphors. According to the colorimetric principle, the color scheme program was written on the basis of the coordinates and luminescent intensity. The blended ratios were calculated at different coordinates by the color program, and the blended-polymer phosphors were prepared by solvent blend. The results indicate that monochrome polymers kept their luminescent characteristics in the blend polymer; no energy transfer occurred between Eu(Ⅲ) ion and Tb(Ⅲ) ion; experimental values were in accordance with theoretical values for the CIE coordinates, indicating the feasibility and guidance of the color scheme.7. Copolymer phosphor. The copolymer phosphor was synthesized by copolymerizing the complex monomers and polymer momomer. The results suggest that quadripolymer kept the luminescent characteristics of red light and green light complex monomers, while blue light had a blue shift of30nm compared with blue light complex monomer; In addition, no energy transfer occurred between Eu(Ⅲ) ion and Tb(Ⅲ) ion in copolymer phosphor, which suggests that "diluting effect" of polymer matrix on complex monomers decreased and thus energy transfer was prevented; the experimental values was in good agreement with theoretical values for the CIE coordinates, once proving that the color scheme had the instruction function to the synthesis of copolymer phosphor. |
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