高固含量膠體流動性之研究

Abstract

近年來，印刷電子的技術被廣泛利用在各個領域上。印刷電子是利用不同的印刷方式，將功能性墨水或膠體印製在不同基材上，形成各式電子元件與線路。為了提升特定性質，如導電性、機械強度等，會在溶劑或樹脂內加入不同種類的顆粒以達到需求，但加入越多顆粒會導致膠體的黏度大幅上升，且由於顆粒間彼此的凡得瓦力過大，容易造成顆粒間團聚，使得流動性不佳，影響印刷的品質。 本論文主要探討如何提升膠體固含量至90 wt% (~80 vol%)，並且在提升膠體固含量的同時，使膠體在低剪切速率下黏度低於100 Pa·s，以提升未來印刷電子上之應用。首先，為了使顆粒可以均勻地混入樹脂中，我們利用三滾筒以物理方式給予適當剪切應力以避免顆粒團聚。接著，透過整合Sudduth model以及Krieger-Dougherty equation來預測在已知的二氧化矽粒徑分布下，不同固含量之膠體的黏度性質，並預測出最適顆粒大小與比例來達到最大堆積密度。利用球磨技術縮小顆粒粒徑，並在經過計算後將大小兩種粒徑分布以4:1的比例進行混合，可以使最大填充密度達到90 wt%。總而言之，本研究提出了一種製備具有良好流動性的高固含量膠體之方法，並且透過建立模型來預測出在已知粒徑分布下之顆粒最密堆積以及懸浮液在不同固含量下之黏度變化，同時針對兩種粒徑分布找出一最佳比例來獲得顆粒間的最密堆積。

In recent years, printed electronics have been widely used in various fields. The printed electronics use different printing methods to print functional inks or paste on different substrates to form various electronic components and circuits. To enhance the specific properties of the printed patterns, such as conductivity, mechanical strength, different kinds of particles are added to the solvent to reach the requirements. However, higher solid fraction will significantly increase the viscosity of the paste. Also, due to the higher van der Waals force between particles, particles are prone to aggregate, which will cause poor flowability and affect the quality of printing. In this study, high solid fraction colloid with great flowability is formulated for the future applications on printed electronics. First, three-roll milling is used to well-disperse particles into the resin without aggregation by applying appropriate shear stress. Then, the Sudduth model and Krieger-Dougherty equation are integrated to predict the viscosity of different solid fraction colloids under the existing particle size distribution. To obtain different sizes of particles, ball-milling is used to reduce the particle size. The packing density is enhanced by adjusting the ratio of particles with different particle size distribution. In summary, this study provides a method to formulate high solid fraction colloids with good flowability. By building the model, the maximum packing density with known particle size distribution and the viscosity of suspension with different solid fraction can be predicted. The optimal ratio of two different particle size distributions can also be obtained to get the maximum packing density.