Liquid crystal(LC) materials with 1,3,2-dioxaborinane group have been synthesized and their physical properties have been investigated to get new LC mixtures. The test LC samples were made up of a base LC material doped with 5, 10, 15, 20, and 25 % of each compound in weight, We have measured optical and dielectric anisotropy, nematic-isotropic phase transition temperature, and threshold voltages as a function of doping concentration. From our measurements, it is found that each compound has different properties compared with other ones. So, these results would contribute to development of new LC mixtures for LCD applications.
INTRODUCTIONThe application range of supertwisted nematic(STN) liquid crystal displays (LCDs) span from low information content displays such as mobile telephone Downloaded by [University of Windsor] at 20:09 18 November 2014 320/[754] MOOJONG LIM et 01. and pagers to high resolution display such as PDA's, notebook PC's and monitors. In order to achieve better applications. it is essential to synthesize new LC single compounds with suitable properties. During the past 70 years, attempts to optimize the physical properties of polar nematogens for LCDs[ 11 have been concerned themselves with varying the rings in the core['], the terminal substituents[3] and the central linkages[4]For good quality of LCD applications, high contrast ratio, wide temperature range of nematic phase, low driving voltage, and high duty ratio, etc. are required. These characteristics are strongly related to the basic physical properties of each LC single compound. The basic physical properties are An, AE, and TNI etc. Furthermore, it is essential to characterize the properties of newly developed LC materials before applying to the LCDs.In this study, the properties of newly synthesized LC single compounds were investigated by measuring several physical quantities. And for these materials, some suggestions were made, in the area of blending new LC mixtures, for high quality LCD applications.
EXPERIMENTALThe LC single materials with 1,3,2-dioxaborinane group (boroxane compounds) used in this study are listed in Table I . From this table, we know that Bxl and Bx2 (or Bx3 and Bx4) have same structures but different terminal fbnctional groups(-CN or -F), but Bxl and Bx3 (or Bx2 and Bx4) have different central linkage groups. In order to investigate the physical properties of these materials, the changes of optical anisotrapy (And), dielectric anisotropy (AE), nematic-isotropic phase transition temperature (TN), threshold voltage (V,,,) and duty ratio (Nl&) were measured as a tinction of doping ratio(5, 10. 5, 20, and 25 % in weight) in base material, which is blended with three single LC compounds as shown in Table 2. Since these three single compounds have very low optical and dielectric anisotropy(see Table 3), the measured properties of LC materials with boroxane compounds are not influenced by base material. All
