The PVA mode was originally developed by
Samsung in 1996. It is characterized by multi-domain structures with
fringe-field effect. The electrodes are designed in a zigzag/cheveron
pattern, as show in the figure 1.
Figure 1. The
working principle of Patterned Vertical Alignment (PVA) mode.
In the off state, the LC molecules are
oriented perpendicularly to the substrate, as result, there is no
phase retardation and an excellent black state is obtained. In the
on state, the LC molecules will align perpendicular to the electric
field because of Δε < 0, consequently a multi-domain structure of LC
director configuration is obtained, which gives excellent viewing
angle. A PVA on-pixel texture under polarized microscope is shown in
figure 2, a retardation plate is inserted to distinguish the
director tilt direction. In the yellowish area, the director tilts
45 degrees upper left, and in the greenish area, the director tilts
45 degrees upper right.
On-pixels of PVA under polarized microscope. Retardation film is inserted.
Compared with IPS, PVA has higher peak contrast ratio because
of the good black state, however IPS usually has a better off axis
contrast ratio, figure 3 shows a comparison between PVA and S-IPS.
Figure 3. Viewing
angle performance comparison between PVA and IPS LCD.
Recent development of PVA mode has increased
the domain numbers from 4 to 8, so-called S-PVA, which further
increased the viewing angle performance. With Samsung's Dynamic
Capacitance Compensation (DCC) driving scheme, the response time can
be improved from 50ms to 8ms. Figure 4 shows the driving
scheme of the DCC II.