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. 2018 Nov 6;8(11):911.
doi: 10.3390/nano8110911.

Enhancement of Image Quality in LCD by Doping γ-Fe₂O₃ Nanoparticles and Reducing Friction Torque Difference

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Free PMC article

Enhancement of Image Quality in LCD by Doping γ-Fe₂O₃ Nanoparticles and Reducing Friction Torque Difference

Lin Gao et al. Nanomaterials (Basel). .
Free PMC article

Abstract

Improving image sticking in liquid crystal display (LCD) has attracted tremendous interest because of its potential to enhance the quality of the display image. Here, we proposed a method to evaluate the residual direct current (DC) voltage by varying liquid crystal (LC) cell capacitance under the combined action of alternating current (AC) and DC signals. This method was then used to study the improvement of image sticking by doping γ-Fe₂O₃ nanoparticles into LC materials and adjusting the friction torque difference of the upper and lower substrates. Detailed analysis and comparison of residual characteristics for LC materials with different doping concentrations revealed that the LC material, added with 0.02 wt% γ-Fe₂O₃ nanoparticles, can absorb the majority of free ions stably, thereby reducing the residual DC voltage and extending the time to reach the saturated state. The physical properties of the LC materials were enhanced by the addition of a small amount of nanoparticles and the response time of doping 0.02 wt% γ-Fe₂O₃ nanoparticles was about 10% faster than that of pure LC. Furthermore, the lower absolute value of the friction torque difference between the upper and lower substrates contributed to the reduction of the residual DC voltage induced by ion adsorption in the LC cell under the same conditions. To promote the image quality of different display frames in the switching process, we added small amounts of the nanoparticles to the LC materials and controlled friction technology accurately to ensure the same torque. Both approaches were proven to be highly feasible.

Keywords: friction torque; image sticking; liquid crystal; residual DC voltage; γ-Fe2O3 nanoparticles.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Optical path diagram of dynamic response.
Figure 2
Figure 2
The polarized optical microscope (POM) images of parallel-aligned nematic (PAN) cell with and without γ-Fe2O3 nanoparticles. (a) 0.00 wt%; (b) 0.02 wt%; (c) 0.05 wt%; (d) 0.08 wt%; and (e) 0.11 wt%.
Figure 3
Figure 3
(a) Natural state of liquid crystal (LC) molecules and ionic impurities in the PAN cell. (b) Distribution of LC molecules and ionic impurities under applied voltage in the PAN cell.
Figure 4
Figure 4
Capacitance of the LC cell varies with the voltage and the principle of evaluating residual direct current (DC) voltage.
Figure 5
Figure 5
Driving voltage applied to the LC cell.
Figure 6
Figure 6
Residual DC voltage with time under different bias voltages in pure LC materials.
Figure 7
Figure 7
(a) Saturated residual DC voltage of different concentrations at different DC bias voltages. (b) Saturated time of different concentrations at different DC bias voltages.
Figure 8
Figure 8
(a) γ-Fe2O3 nanoparticles doped at low concentrations and (b) γ-Fe2O3 nanoparticles doped at relatively high concentrations.
Figure 9
Figure 9
Response time of 0.00 wt% and 0.02 wt% γ-Fe2O3 nanoparticle-doped LC materials.
Figure 10
Figure 10
Wavelength-transmittance (λ-T) curves of four types of LC cells.
Figure 11
Figure 11
Three-dimensional topography of alignment layer of four LC cells (a) Cell 1; (b) Cell 2; (c) Cell 3; and (d) Cell 4.
Figure 12
Figure 12
The thickness of alignment layers of four LC cells.
Figure 13
Figure 13
Variation in residual DC voltage with time, in which the inserted graph shows the relation between saturated residual DC voltage and friction torque difference.

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