A Multimode-Type Transflective Liquid Crystal Display Using the Hybrid-Aligned Nematic and Parallel-Rubbed Vertically Aligned Modes

Song

Symp Digest of Tech Papers

et al. 2013

Self Cite

In this work we propose a liquid crystal mode in which vertically-aligned negative nematic liquid crystals are switched on by applying a fringe electric field. In the proposed mode, vertically-aligned negative liquid crystals can be switched on by the vertical as well as in-plane components of an applied fringe field so that high transmittance can be achieved. By fabricating a test cell, we experimentally obtained a transmittance of 33.7 %, which is 8.7 % higher than a homogeneously-aligned fringe field switching cell using positive liquid crystals. Author KeywordsLiquid crystals; high transmittance; fringe field switching; vertical alignment Objective and BackgroundThe performance of liquid crystal displays (LCDs) has been greatly improved and this has led to the wide usage of LCDs for applications such as smart phones, monitors, tablet PCs, TVs, etc. LCDs for these applications require high display performances, such as a high contrast ratio, wide viewing angle, fast response, and high transmittance. In particular, high transmittance is required because the aperture ratio can be reduced as the pixel size decreases for ultrahigh resolution [1,2].Several LC modes including in-plane switching (IPS) [3][4][5], fringe-field switching (FFS) [6][7][8], and vertical alignment (VA) [9,10] modes have been in competition with each other in the LCD market [11,12]. Among these modes, the IPS and FFS modes provide wide viewing angle. The rubbing process is used in these modes to align the LC molecules homogeneously. However, the LC molecules may not be perfectly aligned along the rubbing direction. Moreover, use of cotton in the rubbing process can cause defects in the alignment layer [13]. These may result in light leakage in the dark state.On the other hand, the rubbing process is not required in the VA mode. The VA mode has the merit of a superior dark state because the LCs are vertically-aligned thereby giving it a much higher contrast ratio than homogeneously aligned LCs. Various type of VA modes have been proposed to reduce the response time [14,15]. Although in-plane switching of vertically-aligned positive LCs can provide fast response, it suffers from low transmittance because only a small portion of LCs can be switched on by applying an in-plane electric field.In this paper we propose a liquid crystal mode in which vertically-aligned negative nematic liquid crystals are switched on by applying a fringe electric field. Vertically-aligned negative liquid crystals can be switched on by the vertical as well as in-plane components of the applied fringe field so that a high transmittance can be obtained. Mode configuration and operation principleThe equipotential lines in the cell structures for the IPS and FFS modes are shown in Fig.1. In an IPS cell, the pixel and common electrodes are placed alternately on the bottom substrate. The inplane component of the electric field is dominant between adjacent pixel electrodes, whereas the vertical component is dominant above the pixel \electrodes. In a FFS cell, in whic...

Section: Objective and Backgroundmentioning

confidence: 99%

mentioning

confidence: 99%

P.103: High Transmittance LC Mode Based on Fringe Field Switching of Vertically‐Aligned Negative LCs

Song

Symp Digest of Tech Papers

et al. 2013

Self Cite

“…In the recent years, homeotropic alignment of liquid crystals or vertical orientation has got worldwide applications in liquid crystal displays. [3][4][5] Mainly, the vertical orientation of liquid crystals is used in reverse-mode polymer-dispersed liquid crystal (R-PDLC) displays. This particular kind of PDLC device becomes transparent during OFF state and light scattering during ON state; thus operating opposite to the normal-mode PDLCs.…”

Section: Introductionmentioning

confidence: 99%

Surfactant-doped reverse-mode polymer-dispersed liquid crystal display with enhanced properties

et al. 2015

In this article, a nonionic surfactant Brij30 has been used to vertical align the negative anisotropic liquid crystal. The surfactant is further used in reverse-mode polymer-dispersed liquid crystal display to enhance the electrooptical properties. This work shows an enhancement of contrast ratio simply with the addition of surfactant. In addition, contact angle and surface free energies have been determined to judge the role of surfactant in control of surface orientation of liquid crystal molecules.

Journal of Applied Physics

“…Vertical alignment (VA)-type nematic modes 1 were denominated by the initially vertical LC alignment, and an in-plane switching (IPS) mode 2,3 was designated by the orientation of LC movement due to the direction of the electric field, and twisted nematic mode (TN) 4 refers to the initially twisted LC state, etc. [5][6][7][8][9][10][11] Among the various LCD modes, TN electro-optical mode has many merits, 12 such as a simple manufacturing process and high light efficiency. Therefore, it has been used widely in a range of small size display applications.…”

Section: Introductionmentioning

confidence: 99%

Electro-optical characteristics of two domain normally black-electrically controlled birefringence mode

Son

et al. 2013

A normally black ECB mode with two domains is presented to improve the low contrast ratio of the conventional, normally white, electrically controlled birefringence [ECB] and gray inversion of twist nematic [TN] modes. This system requires a λ/2 plate to compensate for optical phase retardation at the liquid crystal layer, and a good dark state is then obtained under no-field, indicating a high contrast ratio. The two domain structure to improve the gray inversion was obtained using the ion beam alignment technique. The simulated and measured results showed that the proposed mode can improve the gray inversion and contrast ratio considerably, compared to the TN mode and normally white ECB mode.