Artículos de revistas
Asymmetric electrooptic reponse in a nematic liquid crystal
Autor
DASCALU , CONSTANTA
Institución
Resumen
SE HA OBTENIDO UNA RESPUESTA ELECTRO-ÓPTICA ASIMÉTRICA EN CRISTALES LÍQUIDOS NEMÁTICOS. LA CÉLULA HÍBRIDA DE CRISTAL LÍQUIDO FUE CONSTRUIDA UTILIZANDO UNA CONFIGURACIÓN ESTÁNDAR. UNO DE LOS ELECTRODOS ITO FUE CUBIERTO CON UNA PELÍCULA DELGADA DE MATERIAL ORGÁNICO PARA INDUCIR UNA ALINEACIÓN HOMEÓTROPA. EL OTRO ELECTRODO ITO FUE CUBIERTO CON UNA PELÍCULA DELGADA DE FOTOLÍMERO ANTERIORMENTE MEZCLADA CON UN ÁCIDO PARA FAVORECER LA EMISIÓN DE PROTONES. ESTOS CATIONES SON RESPONSABLES DEL PROCESO ELECTROQUÍMICO EN LC, CONDUCIENDO A UNA RESPUESTA ELECTRO-ÓPTICA ASIMÉTRICA QUE DEPENDE DE LA POLARIDAD DEL CAMPO ELÉCTRICO APLICADO. ESTE EFECTO ES ORIGINADO POR UN CAMPO INTERNO QUE CAMBIA EL UMBRAL EFECTIVO DEL VOLTAJE PARA LA REORIENTACIÓN DEL CRISTAL LÍQUIDO. DURANTE LA POLARIZACIÓN ANÓDICA, CONMUTACIÓN ÓPTICA SE INHIBE DEBIDO A QUE EL CAMPO EFECTIVO DISMINUYE ABAJO EL VALOR DEL UMBRAL. POR EL CONTRARIO, PARA LA POLARIZACIÓN OPUESTA EL CAMPO EFECTIVO ES SUFICIENTE PARA DETERMINAR UN ALINEAMIENTO HOMEÓTROPO.AbstractAN ASYMMETRIC ELECTROOPTIC RESPONSE IN NEMATIC LIQUID CRYSTAL (LC) HAS BEEN OBTAINED. THE LIQUID CRYSTAL HYBRID CELL WAS MADE BY USING A STANDARD CONFIGURATION. ONE OF THE ITO (INDIUM TIN OXIDE) ELECTRODES WAS COVERED WITH A SURFACTANT, WHICH INDUCES A HOMEOTROPIC ALIGNMENT. THE SECOND OF THE INDIUM TIN OXIDE ELECTRODES WAS COVERED BY A THIN LAYER OF PHOTOPOLYMER, WHICH WAS PREVIOUSLY MIXED WITH AN ACID, WHICH FAVOURS A PROCESS OF RELEASE OF PROTONS. SUCH CATIONS ARE RESPONSABLE OF ELECTROCHEMICAL PROCESS IN THE LC LEADING TO AN ASYMMETRIC ELECTROOPIC RESPONSE, WHICH DEPEND ON THE POLARITY OF THE APPLIED ELECTRIC FIELD. THIS FACT IS DUE TO AN INFERNAL FIELD, WHICH CHANGE EFFECTIVE VOLTAGE THRESHOLDS FOR THE REORIENTATION OF THE LIQUID CRYSTAL. DURING THE ANODIC POLARISATION, THE OPTICAL SWITCHING IS INHIBITED BECAUSE THE EFFECTIVE FIELD DECREASES BELOW THE THRESHOLD VALUE. ON CONTRARY FOR THE OPPOSITE POLARISATION THE EFFECTIVE FIELD IS ENOUGH TO DETERMINE A HOMEOTROPIC ALIGNMENT. AN ASYMMETRIC ELECTROOPTIC RESPONSE IN NEMATIC LIQUID CRYSTAL (LC) HAS BEEN OBTAINED. THE LIQUID CRYSTAL HYBRID CELL WAS MADE BY USING A STANDARD CONFIGURATION. ONE OF THE ITO (INDIUM TIN OXIDE) ELECTRODES WAS COVERED WITH A SURFACTANT, WHICH INDUCES A HOMEOTROPIC ALIGNMENT. THE SECOND OF THE INDIUM TIN OXIDE ELECTRODES WAS COVERED BY A THIN LAYER OF PHOTOPOLYMER, WHICH WAS PREVIOUSLY MIXED WITH AN ACID, WHICH FAVOURS A PROCESS OF RELEASE OF PROTONS. SUCH CATIONS ARE RESPONSABLE OF ELECTROCHEMICAL PROCESS IN THE LC LEADING TO AN ASYMMETRIC ELECTROOPIC RESPONSE, WHICH DEPEND ON THE POLARITY OF THE APPLIED ELECTRIC FIELD. THIS FACT IS DUE TO AN INFERNAL FIELD, WHICH CHANGE EFFECTIVE VOLTAGE THRESHOLDS FOR THE REORIENTATION OF THE LIQUID CRYSTAL. DURING THE ANODIC POLARISATION, THE OPTICAL SWITCHING IS INHIBITED BECAUSE THE EFFECTIVE FIELD DECREASES BELOW THE THRESHOLD VALUE. ON CONTRARY FOR THE OPPOSITE POLARISATION THE EFFECTIVE FIELD IS ENOUGH TO DETERMINE A HOMEOTROPIC ALIGNMENT.