The response time of the vertically aligned in-plane-switching (VA-IPS) mode with respect to different driving voltages is studied. It is found that the rising time, Ton, is highly related to the square of the electric field between the inter-digit electrodes. Since the dielectric torque exerted on the liquid crystal molecules is proportional to the square of the electric field, one can say that it basically dominates the Ton of the VA-IPS mode. However, there’s evidence showing that the total torque perceived by the LC molecules is not simply caused by the voltage applied to the inter-digit electrodes, but also by the flexoelectricity originating from the splay deformation between the electrodes. This leads to the phenomenon that Ton doesn’t monotonically decrease with the increasing dielectric torque.