| 摘要: | 此研究目的為製作出具有高折射率光學性質的透明塊材或膜，其中氧化鈦本身具有高折射率(銳鈦相R.I=2.5)，適合被用來當作提升有機無機複合材料折射率中的無機添加材料。有機材料的部分為常被用作LED 封裝材料的環氧樹酯(R.I~1.51)。如果氧化鈦可以和樹酯混成為有機無機透明材料，便可以提高其應用價值。為了使混成材料的高折射率及穿透度等性質同時兼備的原則下，氧化鈦粒子大小必須有所控制( 10nm 以下)，粒子越大因散射效應會使穿透度越低。 在氧化鈦合成部分，是以四氯化鈦為前趨物在特定的酸鹼值下進行水解縮合，得到白色氫氧化鈦，經過去離子水清洗鹽類後，在酸性環境下進行解膠及結晶。解膠出來的粒子大小和溶膠濃度及解膠酸鹼值等有所關連，此研究第一步為嘗試找出分散在水中最小粒子的最佳條件。 要將氧化鈦和樹酯混合前必須將氧化鈦經過表面改質從水相轉到有機相，如此才有機會和樹酯相混合，因此改質方面我們嘗試葵胺等改質劑，最後能分散在氯仿中。另外也用具有官能基的矽烷類如MPS 及GPS 改質劑，最後能分散至醋酸乙酯。並進行下一步此分散液和環氧樹酯的混成。環氧樹酯實驗上用的是4221 及EP828 這兩種。 最後所做出的氧化鈦/環氧樹酯的厚膜是用MPS/GPS 改質的氧化鈦經過醋酸乙酯分散後和環氧樹酯4221 相混所做出。目前膜中經熱分析無機比例到達50wt%(估計之氧化鈦含量為45wt%)時之折射率接近1.7，約8 微米之膜在波長600nm 位置穿透度超過96%，此種具有高折射率的有機無機複合透明膜最大的缺點是用熱差分析的玻璃轉移溫度(Tg)不夠高，上述之膜之玻璃轉移溫度僅70oC，對於材料的應用將是一大限制。 The purpose of this research is the preparation of transparent thick film or monolith with high refractive index. Titanium oxide, with a reported refractive index of 2.5 for anatase, can be a suitable inorganic additive in improving the refractive index of organic-inorganic hybrid materials. Epoxy resin, which is in common use of LED’s encapsulation. If titanium oxide and epoxy could be composited into a transparent material, the resulting product would have wide applications. To achieve such hybrid material with high refractive index and good transparency, the particle size of titanium dioxide must be below 10 nm, for otherwise light scattering effect would dominate. For the synthesis of nano-sized titanium dioxide, tetrachloride (TiCl4) was used as a precursor, followed by hydrolysis and condensation reactions. After washed the white titanium hydroxide gel by water, peptization and crystallization took place in acidic condition. Since peptize size is strongly dependent on the solution concentration, pH and peptizing temperature, the first part of this research was finding the optimum experimental parameters to produce the smallest nano particles dispersible in water. To disperse titanium dioxide in organic solvent and resin, surface modification of the particles is pivotal. Two aliphatic amines, for instance, n-hexlamine and dodecylamine were modifying agents used in this study. After surface modification with these agents, titanium dioxide can be dispersed in chloroform. Concurrently, surface modification was done with functional silane, 3-(Trimethoxysilyl) propyl methacrylate (MPS) and 3-Glycidoxypropyl trimethoxysilane(GPS), allowing titanium dioxide to be dispersible in ethylacetate. Having successfully dissolved titanium dioxide, epoxy resin 4221 and EP828 were added. The as-synthesized TiO2/epoxy thick film is formed from MPS&GPS modified TiO2 and then dispersed in ethylacetate/epoxy 4221 mixture. From thermal gravimetric analysis (TGA), the 8 micron thick film contains up to 50 wt% inorganic material (approximately 45 wt% TiO2 estimated). In addition, the refractive index is measured to be up to 1.70, and it has over 96% transmittance at 600nm wavelength. Nonetheless, such tranparent thick film has a very low glass transition temperature (~70oC), resulting in limited applications. |
