scholarly journals Physical Properties of Thermally Crosslinked Fluorinated Polyimide and Its Application to a Liquid Crystal Alignment Layer

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3903
Author(s):  
Jong-Soo Ahn ◽  
Su-Hong Park ◽  
Na-Yeon Kwon ◽  
Min-Ju Cho ◽  
Sang-Hyon Paek ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
High Performance ◽  
Mechanical Analysis ◽  
Alignment Layer ◽  
Polyamic Acid ◽  
Fluorinated Polyimide ◽  
Ring Opening Reaction ◽  
Epoxy Ring Opening ◽  
Good Potential ◽  
Direct Current Voltage

This study demonstrated the use of a thermally crosslinked polyimide (PI) for the liquid crystal (LC) alignment layer of an LC display (LCD) cell. Polyamic acid was prepared using 4,4′-oxydianiline (ODA) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA). The 6FDA−ODA-based polyimide (PI) prepared by the thermal cyclic dehydration of the polyamic acid (PAA) was soluble in various polar solvents. After forming a thin film by mixing trifunctional epoxide [4-(oxiran-2-ylmethoxy)-N,N-bis(oxiran-2-ylmethyl)aniline] with the 6FDA−ODA-based PAA, it was confirmed that thermal curing at −110 °C caused an epoxy ring opening reaction, which could result in the formation of a networked polyimide not soluble in tetrahydrofuran. The crosslinked PI film showed a higher rigidity than the neat PI films, as measured by the elastic modulus. Furthermore, based on a dynamic mechanical analysis of the neat PI and crosslinked PI films, the glass transition temperatures (Tgs) were 217 and 339 °C, respectively, which provided further evidence of the formation of crosslinking by the addition of the epoxy reagent. After mechanical rubbing using these two PI films, an LC cell was fabricated using an anisotropic PI film as an LC alignment film. LC cells with crosslinked PI layers showed a high voltage holding ratio and low residual direct current voltage. This suggests that the crosslinked PI has good potential for use as an LC alignment layer material in advanced LCD technologies that require high performance and reliability.

Improving Color Tracking in In-Plane Switching Mode Liquid-Crystal Displays

MRS Bulletin ◽  
2002 ◽  
Vol 27 (11) ◽  
pp. 870-873
Author(s):  
Yuka Utsumi ◽  
Shinichi Komura ◽  
Ikuo Hiyama ◽  
Makoto Tsumura ◽  
Katsumi Kondo
Keyword(s):  
Liquid Crystal ◽  
High Performance ◽  
Liquid Crystal Displays ◽  
Source Image ◽  
Alignment Layer ◽  
Actual Use ◽  
Directional Alignment ◽  
Switching Mode ◽  
Color Tracking

AbstractColor tracking describes the ability of a display to faithfully reproduce the color quality of the source image. In liquid-crystal displays (LCDs), color tracking is dependent on brightness. In order to achieve high-performance color reproduction in LCDs, the accuracy of color tracking needs to be improved. By analyzing the characteristics of twisted-nematic (TN) and in-plane switching (IPS) modes of display, the cause of poor color tracking in each mode and the differences in their causes can be clarified. In TN mode displays, both chromaticity and brightness relate to the director configuration, that is, the directional alignment of the rod-like molecules of the liquid crystals, which varies with applied voltage. The ideal IPS LCD, by virtue of its operating principle, theoretically achieves perfect color tracking; however, in actual use, the color tracking is less than optimal due to twist deformation caused by the fixed directors on the alignment layer. Based on our analysis of these phenomena, we propose strategies for improving color tracking in IPS LCDs.

Enhancement of Contrast Ratio by Using Ferroelectric Nanoparticles in the Alignment Layer of Liquid Crystal Display

2008 ◽  
Vol 47 (6) ◽  
pp. 4751-4754 ◽  
Author(s):  
Sudarshan Kundu ◽  
Mitsuhiro Akimoto ◽  
Itaru Hirayama ◽  
Masaru Inoue ◽  
Shunsuke Kobayashi ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystal Display ◽  
Contrast Ratio ◽  
Alignment Layer

Star-shaped arylacetylene resins derived from silicon

2020 ◽  
Vol 40 (8) ◽  
pp. 676-684
Author(s):  
Niping Dai ◽  
Junkun Tang ◽  
Manping Ma ◽  
Xiaotian Liu ◽  
Chuan Li ◽  
...  
Keyword(s):  
High Performance ◽  
Room Temperature ◽  
Mechanical Test ◽  
Flexural Modulus ◽  
Mechanical Analysis ◽  
Reinforced Composites ◽  
Scanning Calorimetry ◽  
Chemical Structures ◽  
Structures And Properties ◽  
High Performance Resin

AbstractStar-shaped arylacetylene resins, tris(3-ethynyl-phenylethynyl)methylsilane, tris(3-ethynyl-phenylethynyl) phenylsilane, and tris (3-ethynyl-phenylethynyl) silane (TEPHS), were synthesized through Grignard reaction between 1,3-diethynylbenzene and three types of trichlorinated silanes. The chemical structures and properties of the resins were characterized by means of nuclear magnetic resonance, fourier-transform infrared spectroscopy, Haake torque rheomoter, differential scanning calorimetry, dynamic mechanical analysis, mechanical test, and thermogravimetric analysis. The results show that the melt viscosity at 120 °C is lower than 150 mPa⋅s, and the processing windows are as wide as 60 °C for the resins. The resins cure at the temperature as low as 150 °C. The good processabilities make the resins to be suitable for resin transfer molding. The cured resins exhibit high flexural modulus and excellent heat-resistance. The flexural modulus of the cured TEPHS at room temperature arrives at as high as 10.9 GPa. Its temperature of 5% weight loss (Td5) is up to 697 °C in nitrogen. The resins show the potential for application in fiber-reinforced composites as high-performance resin in the field of aviation and aerospace.

scholarly journals Photocontrollable Resistivity Change in Nanoparticle-Doped Liquid Crystal Alignment Layer: Voltage Holding and Discharging Properties of Fringe-Field Switching Liquid Crystal Modes

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 268
Author(s):  
Jeong-Hoon Ko ◽  
Jun-Chan Choi ◽  
Dong-Jin Lee ◽  
Jae-Won Lee ◽  
Hak-Rin Kim
Keyword(s):  
Liquid Crystal ◽  
Power Saving ◽  
Low Frequency ◽  
Fringe Field ◽  
Resistance Level ◽  
Alignment Layer ◽  
Experimental Scheme ◽  
Tunable Range ◽  
Crystal Alignment ◽  
Operation Frequency

In liquid crystal (LC) displays, deriving an optimum resistance level of an LC alignment polyimide (PI) layer is important because of the trade-off between the voltage holding and surface-discharging properties. In particular, to apply a power-saving low-frequency operation scheme to fringe-field switching (FFS) LC modes with negative dielectric LC (n-LC), delicate material engineering is required to avoid surface-charge-dependent image flickering and sticking problems, which severely degrade with lowering operation frequency. Therefore, this paper proposes a photocontrolled variable-resistivity PI layer in order to systematically investigate the voltage holding and discharging properties of the FFS n-LC modes, according to the PI resistivity (ρ) levels. By doping fullerene into the high-ρ PI as the photoexcited charge-generating nanoparticles, the ρ levels of the PI were continuously controllable with a wide tunable range (0.95 × 1015 Ω∙cm to 5.36 × 1013 Ω∙cm) through Ar laser irradiation under the same LC and LC alignment conditions. The frequency-dependent voltage holding and discharge behaviors were analyzed with photocontrolled ρ variation. Thus, the proposed experimental scheme is a feasible approach in PI engineering for a power-saving low-frequency FFS n-LC mode without the image flickering and image sticking issues.

scholarly journals Alignment Layer of Liquid Crystal Using Plant-Based Isoeugenol-Substituted Polystyrene

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 547
Author(s):  
DaEun Yang ◽  
Kyutae Seo ◽  
Hyo Kang
Keyword(s):  
Liquid Crystal ◽  
Surface Energy ◽  
Polymer Film ◽  
Uv Irradiation ◽  
Molar Content ◽  
Polymer Modification ◽  
Alignment Layer ◽  
Energy Value ◽  
Alignment System ◽  
Molar Percent

We synthesized a series of renewable and plant-based isoeugenol-substituted polystyrenes (PIEU#, # = 100, 80, 60, 40, and 20, where # is the molar percent content of isoeugenol moiety), using polymer modification reactions to study their liquid crystal (LC) alignment behavior. In general, the LC cells fabricated using polymer film with a higher molar content of isoeugenol side groups showed vertical LC alignment behavior. This alignment behavior was well related to the surface energy value of the polymer layer. For example, vertical alignments were observed when the polar surface energy value of the polymer was smaller than approximately 3.59 mJ/m2, generated by the nonpolar isoeugenol moiety with long and bulky carbon groups. Good alignment stability at 100 °C and under ultraviolet (UV) irradiation of 15 J/cm2 was observed for the LC cells fabricated using PIEU100 as a LC alignment layer. Therefore, renewable isoeugenol-based materials can be used to produce an eco-friendly vertical LC alignment system.

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