| Long afterglow luminescent material is capable of absorbing sunlight or ultraviolet ray and storing energy during the day, and releasing the energy in the form of visible light once the irradiation light is cut. From the perspective of three-color theory, any long-afterglow color can be obtained by mixing red, green and blue long-afterglow materials in proportion ratio. The existing rare earth long-afterglow materials are classified into blue, yellow-green and red luminescent materials. Among them, the brightness and afterglow time of the blue and yellow-green materials have been up to practical application, while the red long-afterglow phosphor is still under development. The red long-afterglow materials having been industrialized are sulfide and sulfur oxides. But the performance of the sulfides is much worse than those of the blue and green long-afterglow materials, and they are very unstable in air, because they can easily break down in the reaction with CO2 and H2O. This limits their further application. Although the sulfur oxides are stable, they have a much worse performance compared with the blue and yellow-green materials for afterglow time and brightness. So it is difficult for them to realize practical application. Therefore, to search and synthesize the red long-afterglow materials have become hot topics.In this thesis, a new idea of design and preparation of red long afterglow material was suggested. A red long-afterglow material which has a wide excitation spectrum was mixed with blue and green long-afterglow materials, the red luminescent materials can emit light with the excitation of the afterglow of the blue and green luminescent materials. Its emission time is determined by the afterglow time of the blue and green long-afterglow materials. Thus, full-color light-storage materials could be obtained indirectly.To practice the above idea, organic dye Rhodamine B (RB) and SrCaSi5N8:Eu2+ were used as the red fluorescent materials. The violet (PLP-6, (V)), blue (PLB-8B, (B)) or yellow green (PLO-8B, (G)) long afterglow materials were mixed with the red fluorescent materials with different mass ratios to made composite materials. Polymethyl methacrylate (PMMA), which is colorless, transparent and has good optical properties, was prepared by radical polymerization and was used as the carrier of the composite materials. A lamp was used to irradiate the mixtures, when the power is cut, the light color of the composites varied with the mass ratios. The properties of the composite materials were investigated.Rhodamine B's luminescence properties were found being influenced by its chemical environment strongly. In PMMA, it can be easy motivated by the yellow green light at 555 nm, and launch the orange ray at 580 nm. The excitation band of SrCaSi5N8:Eu2+ (R) extends from 300 nm to 550 nm, and it can be excited by blue-violet light in the visible region. Its main emission peak is at 628 nm. It almost can not launch afterglow.Results show that when G or B mixed with R, the mixtures could perform good afterglow properties. The light color varied from pink to orange and yellow according to the mass ratio. When the SrCaSi5N8:Eu2+ was coated on the surface of the blue (B),green (G) and purple (V) long afterglow material with PMMA as the carriers, the red afterglow could be observed obviously, and with the mixture proportion changing, the yellow, orange, pink, purple and other color lights were obtained. |
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