Yohei Nakanishi

40.1: A New MVA-LCD by Polymer Sustained Alignment Technology

A new MVA-LCD using Polymer Sustained Alignment technology (PSA-LCD) has been developed. This technology can realize a stable alignment with protrusion free structure by polymer sustainment. PSA-LCD has established high brightness, high contrast ratio and fast response speed.

23.1: Fast-Switching LCD with Multi-Domain Vertical Alignment Driven by an Oblique Electric Field

We have developed a novel fast-switching LCD with multidomain vertical alignment driven by an oblique electric field. The oblique electric field is applied between comb-shaped source electrodes and comb-shaped common electrodes on a TFT substrate and an ITO electrode on a CF substrate covering the entire display area. The ITO electrode is covered by a dielectric layer. The LCD has a wide viewing range (>160°), a high contrast ratio (>250:1) and fast response times even in black-and-white (13 ms (rise), 4 ms (decay)), and gray-scale (<17 ms) switching. The LCD has no problems with electrostatic charge, disclination, or slow gray-scale switching.

Relation between Monomer Structure and Image Sticking Phenomenon of Polymer-Sustained-Alignment Liquid Crystal Displays

We investigated the image-sticking phenomenon of polymer-sustained-alignment liquid crystal displays (PSA-LCDs) by the evaluation of residual DC and the difference in tilt angle. Experimental results indicate that the difference in tilt angle affects the image sticking of PSA-LCDs more than the residual DC. We also found that the difference in tilt angle is strongly dependent on the chemical structure of the monomer that forms the polymer layer between the alignment layer and the liquid crystal layer by photopolymerization.

Relationship between Concentration of Initiator and Image-Sticking Phenomenon of Polymer-Sustained-Alignment Liquid Crystal Displays

We investigated the image-sticking phenomenon of polymer-sustained-alignment liquid crystal displays (PSA-LCDs). According to our experimental results, the image-sticking level of PSA-LCDs depends on the concentration of the photoinitiator in the liquid crystal of PSA-LCDs and the best concentration of the photoinitiator was zero. We found that polymerization of the monomer occurs without the photoinitiator, and clarified the mechanism of polymerization.

Vertically Aligned TFT-LCDs

Fujitsu has developed several types of vertically aligned TFT-LCD: with protrusion; with photo-alignment; and with comb-shaped electrodes. The protrusion-type TFT-LCD has the best balance of specifications and is in mass- production. It has a transmittance of 5% for a 15-inch XGA LCD, a response of 25 ms (τon + τoff), and a contrast ratio of over 400. The photo-aligned type gives highest transmittance (7.5%) with dual domains. The lamp for UV irradiation can be a tube type and non-polarized UV is possible. We think it is a good candidate for notebook-type applications. The comb-shaped electrode type has the fastest response of better than 17 ms for any gray-scale switching. We think it is a good candidate for video applications.

Polymer layer and tilt angle of polymer-sustained-alignment liquid crystal displays

We determined the tilt angle of polymer-sustained-alignment liquid crystal displays (PSA-LCDs) through experiments and simulations of the polar angle of the director of LC molecules. We clarified that LC molecules are anchored by the polymer layer as they polymerize and stack on the surface of the alignment layer with UV irradiation. Anchored LC molecules at the surface of the polymer layer align unanchored LC molecules of PSA-LCDs. The tilt angle of LC molecules at the surface of the polymer is identical to the polar angle of LC molecules at the same surface when a voltage is applied and UV is irradiated in the PSA process. By checking the tilt angle of PSA-LCDs, the thickness of the polymer can be estimated. We investigated the relationship between the thickness of the polymer and the concentration of the monomer or photoinitiator in the LC material.