러빙 처리된 폴리에스타이렌막표면에 있어서 표면액정배향에 관한 이방성분산력의 효과

서대식 崇實大學校 生産技術硏究所 1996 論文集 Vol.26 No.1

We have studied the effect of anisotropic dispersion force effects for surface alignment of liquid crystals (LCs) on rubbed polystyrene (PS) surfaces. We previously demonstrated that the nematic (N) LCs are shown to align in the direction perpendicular to the rubbing and polar anchoring strength is very weak compared to rubbed polyimide (PI) surfaces. In microphotographs of the textures, we obtained the NLCs are shown to align in both direction parallel and perpendicular to the rubbing for region up to medium rubbing, however to alina in the diretion perpendicular to the rubbing for strong rubbing region. We suggest that the anisotropic dispersion forceis very important rether than macro-surface groove effect to uniform alignment of LCs. We also observed the surface ordering of the NICs on rubbed PS surfaces for strong rubbing is disordered. We suggest that the low polarizaiton of the orientation surfaces is attributed to weak anchoring strength.

IPS-LCD의 전기광학 특성

서대식,최재학 崇實大學校 生産技術硏究所 1998 論文集 Vol.28 No.-

We have investigated the electro-optical characteriatics of in-plane switching (IPS) liquid crystal display (LCD) were investigated. The response time of photo-aligned IPS-LCD is fast compared with rubbing-aligned IPS-LCD on polyimide (PI) surface. The decay time ?? is decreased with increasing the azimuthal anchoring energy Aψdue to the steric interaction between the LC molecules and side chain of polymer. The viewing angle of IPS-LCD is increased by using phto-depolymerizatin method ; about ??70。 at all direction.

미선나무 葯培養에 의한 Callus 誘導에 관한 硏究

高大植,徐丙秀,李昌憲 全北大學校 1989 論文集 Vol.31 No.-

The study was carried out to investigate the optimal medium, time, auxin and combination for anthers culture of Abeliophyllum distichum. The obtained results are summarized as follow ; 1. Mid-November was the optimal time in callus induction from anther culture of Abeliophyllum distichum. 2. G.D. medium was more effective than M.S. or WPM medium, and NAA was more effective than IAA or IBA in callus induction from anther culture of Abeliophyllum distichum. 3. Callus were induced the most highly in NAA(0.5mg/ℓ)+BAP(0.5mg/ℓ) plused on G.D. medium. 4. Callus were not induced at all in no auxin medium of all.

때죽나무葉內 含有物質이 砂防草類의 發芽抑制에 미치는 影響

高大植,徐丙秀 全北大學校 1985 論文集 Vol.27 No.-

This study was carried out in order to investigate the germination inhibiting substance extracted from the leaves of 165 species belonging to 49 families, in Korea. Several grasses important for erosion control are used for germination testing. The results are summarized as follows; 1. Lettuce, radish and italianraygrass were used for germination testing. The extracts tested were obtained from 165 species. The extracts from Pinus densiflora, Pinus thunbergii, Abies holophylla, Chamaecyparis picifera, Salix koreansis, Prunus sargentii and Styrax japonica were more effective in inhibiting germination than others. 2. Several variation in the germination rate was observed. The extracts from leaves, which were harvested in the fall, inhibited the germination stronger than the ones of the spring. 3. Among the seven active species, Styrax japonica showed the strongest inhibiting effect, followed by Salix koreansis, Prunus sargentii, Abies holophylla, Chamaecyparis picifera, Pinusthunbergii and Pinus densiflora in ascending order. 4. In order to investigate the germination inhibitor of Styrax japonica leaves, solvent fractionation from these was undertaken, giving petroleum ether fraction and water fraction. The petroleum ether fraction was not effective. The effective water layer was column-chromatographied, combined with thin layer-chromatographying. The most effective germination inhibitor has Rf 0.72 in fraction Ⅲ of the column-chromatography with solvent of chloroform : MeOH(97 : 3, v/v). 5. In the germination testing with various concentrations of the effective substance, the germination of lettuce and Themeda japonica was fully inhibited at the level of 100ppm and 250ppm, respectively. 6. According to results of the physical and chemical analysis, the effective substance was proven belong to Ary-aliphatic alcohol. 7. The germination of several of soil conservation grass seeds are inhibited by water, ether and methanol extracts from Styrax japonica leaves, therefore it is supposed that the forest ecosystem and soil conditions, at treated or designated-land for erosion control, are disadvantageously effected by the formation of Styrax japonica community.

광분해법을 이용한 액정배향의 어닐링 효과에 대한 연구

김형규,서대식 崇實大學校 1999 論文集 Vol.29 No.1

We investigated the annealing effect on liquid crystal (LC) using the photo-depolymerization reaction in this study. For obliquely irradiating ultraviolet (UV) light on a polymer (PI) surface, pretilt angle shows to 0°and increased by annealing. The generated pretilt angle on rubbed PI surface was much higher than that on photo-aligned PI surface. It is attributed to the steric interaction and the number of LC molecular alignment on azimuthal direction. In addition, in case of obliquely irradiating UV light on a PI surface, it showed LC alignment to increase by annealing. It can be regarded due to the fact that the re-alignment of LC molecules is improved to residual polymer direction by annealing.

a-TN-LCD의 전기광학특성에 표면액정배향이 미치는 영향

황율연,이창훈,서대식,이보호 崇實大學校 生産技術硏究所 1996 論文集 Vol.26 No.2

The characteristics of the response time and the viewing angle on twisted nematic(TN)-liquid crystal display(LCD) and amorphous (a)-TN-LCD without rubbing were investigated. To measure the Tansmission-Voltage, response time, and viewing angle characteristics, we prepared three kinds of LC cells and then studied the surface liquid crystal alignment effect. It was found that the response time on a-TN-LCD was fast compared to the TN-LCD, and the weak anchoring strength was attributed to the fast response time on a-TN-LCD. Also, we obtained the wide viewing angle characteristics on-a-LCD. We suggest that the liquid crystal alignment effect on LCD device is very important for electro-optical characteristics.

가족성 고콜레스테롤혈증 유병자에서 HMG Co-A Reductasen Inhibitor 및 Bile Acid Resin의 투여로 인한 아킬레스건 황색종의 감소

채인호,한기훈,박영배,조주희,김효수,손대원,김철호,오병희,이명묵,최윤식,서정돈,이영우 대한순환기학회 1997 Korean Circulation Journal Vol.27 No.9

Effects of Surface Order Parameter on Polar Anchoring Energy in NLC on Weakly Rubbed Polyimide Surface

Seo, Dae-Shik The Korean Institute of Electrical and Electronic 1998 전기전자재료학회논문지 Vol.11 No.12

We have investigated the relationship between the polar anchoring energy and the surface order parameter in nematic liquid crystal (NLC), 4-n-pentyl-4-cyanobiphenyl (5CB), on the two kinds of the weakly rubbed polyimide (PI) surfaces. The observed polar anchoring energy of 5CB is approximately 2${\times}10^{-4}(J/m^2$) and then increases with increasing the rubbing strength (RS) on weakly rubbed surface (RS=57mm) with side chain at $30^{\circ}C$; same results are obtained on weakly rubbed PI surface without side chain. The surface order parameter of 5CB on rubbed PI surfaces increases with increasing the RS at a weak rubbing region. The surface order parameter of 5CB is strongly related to the characteristics of PI material. Consequently, we suggest that the polar anchoring energy of NLC is strongly attributed to the surface order parameter on rubbed PI surfaces.

Odd-even Effects on the Surface Anchoring Strength and the Pretilt Angle Generation in NLC on Rubbed Polythiophene Surfaces with Alkyl Chain Lengths

Seo, Dae-Shik The Korean Institute of Electrical and Electronic 1999 전기전자재료학회논문지 Vol.12 No.1

We have investigated that the high pretilt angle of the NLC, 4-n-pentyl-4-cyanobiphenyl (5CB), was observed on rubbed polythiophene (PTP) surfaces with alkyl chains with more than 10 carbon atoms; it is attributed to the surface-excluded volume effect by the alkyl chain lengths between the LCs and the PTP surfaces. Next, we investigated that the odd-even effect of the polar anchoring strength in 5CB on rubbed PTP surfaces with alkyl chain lengths has been successfully evaluated. The anchoring strength of 5CB for rubbed PTP surfaces with odd-number is weak compared with even-number up to the 6 carbon atoms in the alkyl chain; however, odd-number is strong compared with even-number above 7 carbon atoms. The weak anchoring strength of 5CB is approximately $1\times10^{-3} (J/m^2$) on rubbed PTP surface with 7 carbon atoms; it is relatively strong anchoring strength. Consequently, we conclude that the odd-even effects of the polar anchoring strength in NLCs are strongly related to the characteristics of the polymer and observed clearly for short alkyl chain lengths.

Odd-even effects of the polar an anchoring strength for nematic liquid crystal on polyimide Langmuir-Blodgett surfaces with alkyl chain lengths

Seo,Dae-Shik 崇實大學校 生産技術硏究所 1995 論文集 Vol.25 No.2

The odd-even effect of the alkyl chain length of rubbed polyimide (PI) Langmuir-Blodgett (LB) surfaces on the extrapolation length of 5CB has been successfully evaluated by measuring polar anchoring strength. The extrapolation length of 5CB for rubbed PI-LB surfaces with even numbers is small compared with odd numbers for alkyl chain lengths of greater than 7 carbons. The extrapolation length of 5CB on rubbed PI-LB surfaces with odd numbers increases gradually as the temperature increase but tends to diverge near the clearing temperature (T?=35,3℃). The extrapolation length diverges because of rapidly decreasing surface order near Tc. It is suggested that the polar anchoring strength on rubbed PI-LB surfaces with an even number is strong because of relatively high surface ordering caused by more crystalline surface. Finally, it is concluded that the odd-even effects of the polar anchoring strength in nematic liquid crystals (NLCs) are strongly related to the character of the polymer and observed clearly for long alkyl chain lengths.