Effects of Pretilt Angle on Electro‐Optical Properties of π‐Cell LCDs

Abstract

High pretilt angle can help stabilizing the desired bend configuration of π‐cells but also changes the electro‐optical behaviors. We report here a study on how the pretilt angle affects the electro‐optical properties of π‐cells, including the critical voltages needed to stabilize the bend configuration, the minimum voltages needed to turn the π‐cells fully on, the cell gap required to produce the desired π phase retardation, the transmittance‐voltage curves, the response time, and the viewing angle characteristics. The results provide a guidance to construct π‐cells with various pretilt angles.

Measurement of the liquid crystal pretilt angle in cells with homogeneous and inhomogeneous liquid crystal director configuration

“…1). The bend cells are like the multidomain vertical alignment (MVA), optically compensated bend (OCB) cells described in [1][2][3]. The pretilt angle θ 0 varies in the range from 0°to 90°.…”

“…However they can appear during dynamic switching (e.g., OCB or pi cells [2,3]). Such configurations can be also created by using layered media that consist of alternating layers of birefringent material, e.g., birefringent polymeric LC material [13,14].…”

“…In many types of current liquid crystal displays (LCDs), tilted alignment combined with inhomogeneous liquid crystal (LC) director distribution is used [1][2][3]. It can improve the LCD speed of response or viewing angle range [4,5].…”

P‐123: Oblique Light Incidence onto Hybrid Aligned Nematic (HAN) Cells for Optical Compensators

“…In many types of to-date liquid crystal displays (LCD) tilted alignment and/or sophisticated configuration of the LC director is used (MVA, OCB et al [1][2][3]). Such cells as well as hybrid aligned nematic (HAN) cells [4,5] have such advantages as high speed of response, viewing angle range, low operating voltage [6][7][8][9][10][11].…”

Transient Response Characteristics of Polymer Stabilized Bend Alignment State of Nematic Liquid Crystal in Pi-Cell

“…However, it has been known that this method results in an increase in response time. 4) As an alternative approach, the polymer stabilization method has been proposed, in which the bend alignment is stabilized by forming a polymer network 5,6) or an aligned polymer wall 7) using the optical polymerization of UV-curable crystalline monomers, i.e., reactive mesogen molecules dissolved within the LC host. Using the polymer stabilization method, the LC can be stabilized in the bend state and remains in this state without the electric field because of the bulk anchoring of the LC at the surface of the bend polymer network formed by polymerization.…”