Stabilisation of reverse twisted nematic structure by forming polymer matrix in the vicinity of the alignment layer

Takatoh, Kohki; Watanabe, I.; Goda, Kazuya

doi:10.1080/02678292.2020.1733682

Cited by 3 publications

(4 citation statements)

References 4 publications

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“…The chiral pitch is known to cause length increase, and the decrease in physical properties (e.g., the dielectric constant anisotropy, and the elastic constant) under heating. The chiral pitch was elongated to 16.8 µm (Figure 3) and the physical properties changed (Table 1) at 353 K. The physical properties at 353 K were estimated from multiplying nominal values at room temperature (298 K) by the ratio of measured values at 298 K to measured values at 353 K. The tilt angle in the vicinity of the alignment layer may be lower than that in the previous study [14], because the sustain voltage is low. The pretilt angle for LCDs has been reported to be controllable by polymer matrix formation in the vicinity of the alignment layers by application of an electric voltage [14,21,22].…”

Section: Resultsmentioning

confidence: 91%

“…The chiral pitch was elongated to 16.8 µm (Figure 3) and the physical properties changed (Table 1) at 353 K. The physical properties at 353 K were estimated from multiplying nominal values at room temperature (298 K) by the ratio of measured values at 298 K to measured values at 353 K. The tilt angle in the vicinity of the alignment layer may be lower than that in the previous study [14], because the sustain voltage is low. The pretilt angle for LCDs has been reported to be controllable by polymer matrix formation in the vicinity of the alignment layers by application of an electric voltage [14,21,22]. The pretilt angle was assumed 15 • because the RTN structure was maintained by UV irradiation with application of 1 V, while the pretilt angle is 6.0 • for MLC-2173 without chiral dopant and RM at room temperature.…”

Section: Resultsmentioning

confidence: 91%

“…The RTN structure appears when the p/d ratio is more than three. Moreover, our group has developed a stabilization method for the RTN structure by UV irradiation using reactive mesogens (RMs) with application from 1.25 to 1.5 V [14]. The driving voltage for the RTN-LCD is reduced compared with the TN-LCD (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Stabilization of Long-Pitch Supertwisted Nematic Structures

2021

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Stabilized reverse twisted nematic liquid crystal devices (RTN-LCDs) were fabricated using formation of a polymer matrix under UV irradiation with an applied voltage (sustain voltage) in the vicinity of the alignment layers. In the absence of an applied voltage, the non-stabilized RTN structure gradually returns to a splay twist structure. The sustain voltage was decreased with an increase in temperature. A stabilized long-pitch supertwisted nematic (LPSTN) structure could also be formed during the RTN structure stabilization process with a much lower sustain voltage at a temperature near the clearing point. The chiral pitch for the LPSTN structure is longer than that for a typical STN structure. LPSTN-LCDs similar to RTN-LCDs show a large reduction in both the threshold and saturation voltage compared with those for TN-LCDs consisted of the same LC materials. Furthermore, a notable feature of LPSTN-LCDs is a change to a TN structure when a high voltage is applied. A black state can be realized due to the change from the LPSTN structure to the RTN structure unlike the typical STN mode under the crossed nicols condition. In contrast STN-LCDs retain their color due to the retardation because the RTN and LPSTN states are considered topologically equivalent.

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 91%

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Stabilization of Long-Pitch Supertwisted Nematic Structures

2021

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“…The usage of UV-curable RMs and nonpolarized UV light irradiation with/without a voltage for stabilizing the LC molecular arrangement has been explored. A polymer matrix is formed in the vicinity of the PI alignment layer or inside the LC layer to stabilize the LC structure [7][8][9][10] or decrease the response time (as in polymer sustained alignment LCs 11) and nano-phase separated LCs 12,13) ). For example, a PI alignment layer mixed with UV-curable RMs yielded a surfacecontrolled vertical alignment mode with the first response time.…”

Section: Introductionmentioning

confidence: 99%

Electro-optical property of polymerized liquid crystal devices using linearly polarized UV irradiation

Ito¹,

Kajiwara²,

Takatoh³

2022

Jpn. J. Appl. Phys.

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Display characteristics have a fairly strong dependence on the configuration of the liquid crystal (LC) molecules and interactions between the LC molecules and the alignment layer surface. To obtain LC devices with a fast response, the usage of reactive mesogens (RMs) have been studied. RMs polymerize in the vicinity of the alignment layer. We assessed the effectiveness of linearly polarized UV light for polymer formation. Three kinds of UV light, namely (i)non-polarized (ii)parallel to, and (iii)perpendicular to the rubbing direction, were used to irradiate LC cells with RM concentrations of 5wt% and 10wt%. For both RM concentrations, LC devices using LPUV parallel to the rubbing direction yielded the shortest decay times. SEM observation revealed that the fibrils polymerized linearly in the same direction on using LPUV parallel to the rubbing direction. The decay time was presumably shortened by the strong anchoring force and high alignment ability of the linear fibrils.

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