Krainer Sarah, Smit Chris, Hirn Ulrich
Institute of Paper, Pulp and Fiber Technology, TU Graz Inffeldgasse 23 8010 Graz Austria
CD Laboratory for Fiber Swelling and Paper Performance Inffeldgasse 23 8010 Graz Austria.
RSC Adv. 2019 Oct 7;9(54):31708-31719. doi: 10.1039/c9ra04993b. eCollection 2019 Oct 1.
In this study, we investigated the effect of liquid viscosity and surface tension for inkjet printing on porous cellulose sheets. We used five model liquids, representing the operational field of an industrial high speed inkjet printer, as specified by Ohnesorge- and Reynolds number. Drops with 30 pl and 120 pl drop size were jetted with a commercial HSI printhead. We printed on four uncoated papers representing the most relevant grades on the market in terms of hydrophobisation and surface treatment. We are presenting a quantitative analysis of viscosity and surface tension on the print outcome, evaluating dot size, liquid penetration (print through) and surface coverage of the printed dots. The most important finding is that for liquids within the jetting window the variation of the liquid viscosity typically has a 2-3 times higher impact on the print outcome than variation of the liquid surface tension. Increased viscosity in all cases reduces dot area, liquid penetration and liquid surface coverage. Surface tension plays a smaller role for liquid spreading and penetration, except for hydrophobised substrates, where both are reduced for higher surface tension. Interestingly, higher surface tension consistently increases liquid surface coverage for all papers and drop sizes. A detailed analysis on the competing effect of dot spreading and liquid penetration is presented, in terms of viscosity, surface tension and surface coverage of the liquid.
在本研究中，我们调查了喷墨打印在多孔纤维素片材上时液体粘度和表面张力的影响。我们使用了五种模型液体，这些液体代表了工业高速喷墨打印机的操作范围，由奥内佐格数和雷诺数规定。用商业热转印喷墨打印头喷射出体积为30皮升和120皮升的墨滴。我们在四种未涂布纸张上进行打印，这些纸张代表了市场上在疏水化和表面处理方面最相关的等级。我们对粘度和表面张力对打印结果的影响进行了定量分析，评估了墨滴尺寸、液体渗透（渗印）和打印墨滴的表面覆盖率。最重要的发现是，对于处于喷射窗口内的液体，液体粘度的变化对打印结果的影响通常比液体表面张力的变化高2至3倍。在所有情况下，粘度增加都会减小墨滴面积、液体渗透和液体表面覆盖率。表面张力对液体铺展和渗透的作用较小，但对于疏水化基材除外，在疏水化基材上，较高的表面张力会使两者都降低。有趣的是，对于所有纸张和墨滴尺寸，较高的表面张力始终会增加液体表面覆盖率。本文针对液体的粘度、表面张力和表面覆盖率，对墨滴铺展和液体渗透的竞争效应进行了详细分析。
