Dong-Mee Song

Photochemistry of chalcone and the application of chalcone-derivatives in photo-alignment layer of liquid crystal display

Abstract We synthesized chalcone derivatives and introduced them as a side chain unit in the backbone of polyimide for photo-alignment layers. The rate of photoreaction was followed by the disappearance of the CCCO bond in the chalcone moiety using UV–visible spectroscopy. The absorption peak at around 340 nm decreased significantly in less than a few minutes at room temperature. We studied the effect of the length of alkyl chain in chalcone derivatives and found that the alignment properties are very much dependent on the chain length.

Simple method for measuring the high pretilt angle of nematic liquid crystals

Pretilt angle measurable by using the conventional crystal rotation method is limited to about 0°–20° and 70°–90°. We propose a method by which we can measure the pretilt angle by using the crystal rotation method even if the pretilt angle is between 20° and 70°. In this method, the determination of a pretilt angle is achieved by finding the rotation angles where transmittances are maximum and minimum in the periodic transmittance characteristics obtained with the variation of rotation angle.

The characteristics of polyimide photoalignment layer with chalcone derivatives produced by linear polarized UV light

The photoalignment of liquid crystal (LC) molecules located onto polyimide films with chalcone derivatives using linearly polarized UV (LPUV) light is investigated. The LPUV light irradiation generated dimerization products of the chalcones followed by isomerization of the chalcone derivatives. The alignment directions of LC molecules were either homeotropic or planar with respect to plane of polyimide film, depending upon the alkyl chain length attached on the chalcones.

Photochemical Behavior of Chalcone and the Photo-Alignment of Liquid Crystal with Chalcone Derivatives

The photoisomerization behavior of benzylidene-acetophenones known as chalcones, was studied. We synthesized the chalcone derivatives that have ether groups at 4 and 4′ positions. Due to the electron donating ability of the ether oxygen, the bond order of the single bond between two phenyl ring of the chalcone strengthened, which eventually increased the rotational barrier of the single bond. The rotational barrier of the single bond is about 20-22 kcal/mole. Photo-irradiation with the 365 nm light monotonously decreases the 340 nm peak. However, the photo-irradiation with 254 nm light induce two competing processes and produced rather complicated absorption profile.

Application of Photo-Alignment Technique through the Modification of the Polyimide Surface with Chalcone Derivatives to Vertically Aligned LCD

Abstract The photo-alignment with the linear-polarized UV (LP-UV) light was applied to the surface modified polyimide film with chalcone derivatives for the vertical alignment of liquid crystal molecules. The LP-UV light irradiation caused either dimerization or isomerization of chalcone derivatives. The long alkyl-chains attached on the chalcone derivatives were aligned homeotropically and so are LC-molecules.

Study of the Photo-Alignment using Photo-Sensitive Polyimide (PI) Containing Chalcone Moiety

Abstract Photosensitive polyimide containing chalcone moiety as a photoalignment layer in LCD is synthesized. Chalcone monomer is prepared through Williams reaction and DOCDA-DAP is polymerized via one-step imidization followed by introducing the prepared chalcone moiety. The solution and film of the photosensitive polyimide are irradiated with UV light and characterized by UV-vis. and FT-IR spectroscopies.

COMPLEXATION OF AROMATIC MOLECULES WITH NEW CALIXARENE DERIVATIVES CONTAINING TWO ARYL SULFIDE RINGS

The cuplike structure of calix[4]arenes is one of the most attractive features, which has been observed both in the solid state and in solution. The newly synthesized 5,11,17,23-tetrakis(3-mercaptopropyl)calix[4]arene (1) and 25,26,27,28-tetrakis(5-mercaptopenthoxy)calix[4]arene containing aryl sulfide rings (2), have four alkyl thiol linkages, which allow the calixarenes to attach onto the gold surface. Surface plasmon resonance (SPR) spectroscopy allows us to monitor the binding of calixarene derivatives on the gold surface. The 1 and 2 bind very effectively on the gold surface and self-assembled layers of 1 and 2 produce significant change in SPR signals in 30 min. Calixarenes layers are used as platforms for molecular recognition, where complementary binding sites are easily and selectively introduced. The aromatic molecules used in this study are anthracene, pyrene, coronene and rubrene. The host-guest properties of these aromatic molecules and the calixarene cavity exhibit selectivity of these aromatic molecules. The anthracene, pyrene and coronene have moderate binding affinity to the cavity, and the rubrene does not bind at all.

Photo-Curable Cholesteric Liquid Crystal Film for Application in the Liquid Crystal Display

The cholesteric filters can improve the efficiency of light use when it is applied to a reflective mode. They reflect circularly polarized incident light of the same handedness as the cholesteric helix and transmit the one having the opposite handedness. The transmission bandwidth depends on the helical pitch. In order to widen the bandwidth, we synthesized new cholesteric liquid crystal molecules containing the active reaction moeity to UV light and investigated the various UV treatment methods to broaden the bandwidth of the cholesteric filters. There was appears that the band broadened about 200 nm by using the photo-mask. It is caused of a factor as a consequence of UV-curing when the cholesteric pitch changes locally by using the mask.

38.3: Photochemical Reaction on the Polymer Layer for Liquid Crystal Display

Polyimide containing the chalcone moiety is expected to show the high photodimerization rate and stable alignment characteristics. We introduced the chalcone moiety as a side chain into the polyimide backbone to apply to the photo-alignment layer. The photochemical reaction with the tilted incident light produced out-of -the plane orientation of chalcone side chain. The orientation effects align the LC in LCD, which possesses the various pretilt angles depending on the length of side chains.

Application of photo-alignment technique for low pretilt angle liquid crystal cell

Abstract The photosensitive PI film composing of DOCDA/DAP-Chalcone [5-2,5-dioxotetrahydrofuryl]-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride/1,4-diaminopheno1/4-n-propyl-4-(3-propylene hydroxide) chalcone] induces orientation of liquid crystal alignment perpendicular to the polarization direction. The pretilt angle of liquid crystal was about 1°. It will be applied to the ferroelectric liquid crystal display.