In producing TFT-LCD, as the glass size gets larger, conventional Spin Coaters can not meet its coating specification. The Slit Coater which coats the glass with PR(Photo Resist) by extrusion needs to be developed. The Slit Coater coats the glass with PR extruded through the slot die which is moved along the horizontal direction by the linear motor while floated by the air bearing to reduce the external disturbance effects. The purpose of this system is to coat the glass with the uniform thickness of 1.5㎛ with the maximum ±3% variation after volatilization of 88% of PR. The systematic error in thickness variation caused by the problems such as mechanical inaccuracy, efficiency of pump, stage flatness, linear motor velocity ripple, and setup skill, is reduced by controlling the velocity profile in y direction. Feedback control approach can not be applied because there is no on-line thickness measurement device. ILC(Iterative Learning Control), which is one of open loop control approaches, is applied to find the proper velocity profile. Because we can only measure the thickness after volatilization of PR, the conventional ILC approach requires too much time and too many iterations. Batch type ILC algorithm is developed to reduce the time and the number of iterations. To find the initial velocity profile based on the system model, we identified the system through experiments. The proposed method is applied to the Slit Coater and its feasibility is examined through experiments.
