具獨立可調變控制驅動波形之噴墨驅動系統設計

Abstract

本論文研製之一個在最近的很多工業領域或是學術研究，噴墨技術被運用在很多領域裡頭發展，像是顯示器領域，半導體領域等。尤其是使用壓電式噴墨頭為基礎的相關衍生應用，針對其中特別有運用利基的課題進行相關的研究與投入，像是顯示器的彩色濾光片，金屬線路的形成，液晶的填入，以及未來著眼的軟性顯示器之連續製程等等。 最近綜觀噴墨技術的發展，不只是縮小噴墨的墨滴的技術數個微微公升（pico-liter）而已，具有多功, 可調變性控制的驅動技術，以及及時的觀測系統亦被積極的開發與投入，其將決定並提升噴墨系統的能力與可靠度。尤其存在這系統中的基礎元件噴頭製造上的變異，所衍生諸多噴墨孔所行程墨滴的不均一性問題，將造成工業應用領域的限縮。本論文將提及一種驅動控制墨滴變異的方法，將噴墨頭中的各個噴孔施以獨立的驅動波形，讓每一個噴孔所形成的墨滴皆可以把變異控制在最佳值,，並以控制方法, 補償噴孔製造差異，以及高頻高壓操作下的種種環境條件之落差，我們將其稱之為一個具有獨立可調整驅動波形的電路設計(Addressable Waveform Trimming Circuit, AWTC)，本設計包含有驅動每一個獨立噴孔的高電壓驅動電路，並將其時序控制單元設計並置入FPGA中；具有一個類比數位轉換的驅動電壓迴授機制，在噴墨的調校過程中監控施於每一個噴孔的電壓；另外及時的觀墨量測系統，其將追蹤每一顆墨滴形成的狀態，並適時的改變驅動的條件，讓每一個噴孔能夠輸出優良且均一的墨滴品質。 讓噴墨在工業應用中，落實可量產性是我們想要著力的點。以顯示器之噴墨工業應用來說，據統計需要降低墨滴的變異至±2%才有實施的機會。本論文探討噴墨技術即時高精密控制與多工獨立驅動方法，電路設計特徵為開放式可任意調變波形, 除將其噴孔與噴孔間的噴墨行為之變異縮至最小，並使在工業應用上能廣泛的適用各種不同機制驅動的壓電式噴墨頭，在噴墨頭製造時所存在的噴孔特性差異之等效電容性負載變異，可以自主回饋修正驅動條件，並建立相關的最佳化控制邏輯。

Definitely the ink-jet fabrication is an expectable technology in the fields of display and semiconductors, especially the applications in the fabrication of color filters, the forming of metal circuits, the dispensing of liquid crystal, and the further continuous manufacture of flexible displays etc. Recently, inkjet printing technologies have been rapidly developing and are not only for the diminished size of the drops to the pico-liter, the multiplex driving scheme, or for the real-time observation technology which led to the improvement of the inkjet printing performance, and which realized the pixel-to-pixel control. In this thesis, an electrical controller is designed to differentiate the waveform for each nozzle synchronously, to compensate jetting disturbance for the nozzle cell deformation and pressure drag loss during inkjet firing at high voltage, and for a high frequency named addressable waveform trimming circuit (AWTC). The controller is composed of a high voltage control block which drives each nozzle, an FPGA chip to multiplex the high voltage output, an A/D converter which transfers an analog signal into a digital signal and then into FPGA, a differential signal input to FPGA as feedback to correct analog output, which gives a real-time tracking of jetting quality to verify the nozzle-to-nozzle variation. For dynamic feedback of the drop variation in real jetting, this AWTC accepts correction signals by a machine vision system synchronously with the firing trigger in order to analyze the individual captured images. The contribution of this work is to improve the nozzle jetting performance which is capable handled within minimum jetting droplet variation between nozzle to nozzle in a print head. In industry applications, this ink-jet driving technical can be suitable for the extensive piezoelectric print-heads, and create the logic of the driving waveform of droplet size modulation of inkjet printing technology.