Investigation of electrospray-deposited PEDOT:PSS thin film using an electrohydrodynamic jet printer for inverted QDLEDs

Journal of Materials Science: Materials in Electronics - In general, Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is spin-coated as a hole transport layer in multi-structured...     

Lewis Acid – Complexed Tetramethylene Biradicals Can Initiate the Thermal Copolymerization of Indene with Acrylonitrile

Summary To clarify the mechanism of the spontaneous copolymerization of styrene with acrylonitrile, the corresponding reaction of its analog, indene, was investigated. The spontaneous free radical copolymerization of indene with acrylonitrile was promoted by Lewis acids. Spontaneous copolymerization rates comparable to those of styrene with acrylonitrile were found. For indene, the Mayo [⁴+²] initiation mechanism, initially postulated for the spontaneous polymerization of styrene, cannot occur. Therefore the Flory mechanism, postulating a tetramethylene biradical initiating species, is proposed.     

Effect of small liquid crystal molecules on the driving voltage of cholesteric liquid crystal displays

In order to achieve a lower driving voltage of a cholesteric liquid crystal display (Ch-LCD) we formulated new nematic liquid crystal mixtures with dopants. The interesting thing is that the driving voltage is decreased more by adding the low molecular weight of liquid crystal materials in the cholesteric mixtures without decreasing its reflectivity. The cholesteric mixture is optimized by adding 20 wt% of CN-007 enough to drive the display, necessary for using a commercial STN driver. Homogeneous alignment layers provide a higher reflective panel because of stabilizing the planar texture of cholesteric liquid crystal, while homeotropic alignment layers provide a higher contrast ratio because of stabilizing focal-conic structure. The rubbing condition depending on the driving scheme also affects the panel properties. The combination of the panel structure and the process condition of cholesteric mixtures make the Ch-LCD high reflectivity and contrast ratio. Two 5.7 in. VGA monochromic cholesteric reflective liquid crystal displays with a high resolution like this folding type are demonstrated using a STN driver.     

Development of 3+2 dynamic drive scheme for cholesteric liquid crystal displays

In order to achieve fast driving for reflective cholesteric liquid crystal display (Ch-LCD) we have developed a novel 3+2 dynamic driving scheme (3+2 DDS), which uses 3 and 2 level driver ICs for row and columns, respectively. From the transient dielectric study, the selection period of around 1.0 ms/line showed the best contrast ratio at 30 °C in our system. The time of the homeotropic to transient planar state is strongly dependent on temperatures. The row driver IC has 3 level outputs of R_H, R_M (R_H/2), and R_L; 32, 16, and 0 V, respectively. And the outputs of the column driver IC are composed of 2 levels. We found that a preparation period of more than 40 times and an evolution period of around 40 times of the selection period are suitable. Also, we have accomplished a stable gray scale by using, as we call it, the pulse position modulation (PPM) in which the root mean square (RMS) value of the applied field during the evolution period does not change, even under cross-talk pulses. The driving condition made by PPM is more stable than that made by the usual PHM and PWM techniques. By adopting the 3+2 DDS, we have made 8.4 in. foldable VGA Ch-LCD (640×480×2) that shows an addressing speed of around 1.0 ms/line.