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Realization of Multi-Stable Ground States in a Nematic Liquid Crystal by Surface and Electric Field Modification.

Gwag JS, Kim YK, Lee CH, Kim JH - Sci Rep (2015)

Bottom Line: Because of a growing market demand on such devices, the LCD that can be of numerous surface alignments of directors as its ground state, the so-called multi-stable LCD, comes into the limelight due to the great potential for low power consumption.We demonstrate experimentally and theoretically that a battery of stable surface alignments can be achieved by the field-induced surface dragging effect on an aligning layer with a weak surface anchoring.The simplicity and stability of the proposed system suggest that it is suitable for the multi-stable LCDs to display static images with low power consumption and thus opens applications in various fields.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Yeungnam University, Gyeongsan 712-749, Korea.

ABSTRACT
Owing to the significant price drop of liquid crystal displays (LCDs) and the efforts to save natural resources, LCDs are even replacing paper to display static images such as price tags and advertising boards. Because of a growing market demand on such devices, the LCD that can be of numerous surface alignments of directors as its ground state, the so-called multi-stable LCD, comes into the limelight due to the great potential for low power consumption. However, the multi-stable LCD with industrial feasibility has not yet been successfully performed. In this paper, we propose a simple and novel configuration for the multi-stable LCD. We demonstrate experimentally and theoretically that a battery of stable surface alignments can be achieved by the field-induced surface dragging effect on an aligning layer with a weak surface anchoring. The simplicity and stability of the proposed system suggest that it is suitable for the multi-stable LCDs to display static images with low power consumption and thus opens applications in various fields.

No MeSH data available.


Related in: MedlinePlus

Theoretical estimation of the rotation angle ϕ of the surface director  in the presence of an electric field.(a) Electric field E dependence of ϕ under the surface condition of PMMA layer at T = 45 °C; the surface viscosity γs of PMMA surface at T = 45 °C is γs = 3⋅10−4 N⋅s/m. (b) Surface viscosity dependence of ϕ in the presence of E = 10 V/μm under the surface conditions of PMMA layer at T ≤ 45 °C.
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f4: Theoretical estimation of the rotation angle ϕ of the surface director in the presence of an electric field.(a) Electric field E dependence of ϕ under the surface condition of PMMA layer at T = 45 °C; the surface viscosity γs of PMMA surface at T = 45 °C is γs = 3⋅10−4 N⋅s/m. (b) Surface viscosity dependence of ϕ in the presence of E = 10 V/μm under the surface conditions of PMMA layer at T ≤ 45 °C.

Mentions: In our system, ϕ(t → ∞) = ϕe and τ = γsξe/K2 because the surface anchoring W of PMMA layer (WPMMA ≈ 10−7−10−8 N/m) is much smaller than K2/ξe ≈ 2.5 × 10−5 N/m. Therefore, if a strong E (>E*) is applied for a sufficient time t (>t*), on the PMMA layer can be reoriented even at . With Eq. (3), the azimuthal rotating angle ϕ of with t is estimated as a function of E (Fig. 4a) and γs (Fig. 4b). Figure 4a shows that even under the surface condition of PMMA layer at T = 45 °C (γs = 3⋅10−4 N⋅s/m), can be reorientated. For instance, the theoretical plot indicates that can be fully realigned at T = 45 oC when E = 10 V/μm is applied for t > 15 s (red curve in Fig. 4a). Indeed, we could experimentally re-enact the alteration of ground states in Fig. 2 at T = 45 °C by applying E = 10 V/μm for t = 30 s. Figure 4b shows the γs dependence of the rotation of when E = 10 V/μm is introduced. The theoretical plot (blue and green curves in Fig. 4b) clearly indicates that can be modified even at T < 45 °C; γs = 1.3⋅10−3 N⋅s/m (blue curve) correspond to the surface viscosity of PMMA at T = 25 °C. The transformation of ground states at T = 25 °C was experimentally demonstrated as shown in Fig. 5.


Realization of Multi-Stable Ground States in a Nematic Liquid Crystal by Surface and Electric Field Modification.

Gwag JS, Kim YK, Lee CH, Kim JH - Sci Rep (2015)

Theoretical estimation of the rotation angle ϕ of the surface director  in the presence of an electric field.(a) Electric field E dependence of ϕ under the surface condition of PMMA layer at T = 45 °C; the surface viscosity γs of PMMA surface at T = 45 °C is γs = 3⋅10−4 N⋅s/m. (b) Surface viscosity dependence of ϕ in the presence of E = 10 V/μm under the surface conditions of PMMA layer at T ≤ 45 °C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4477365&req=5

f4: Theoretical estimation of the rotation angle ϕ of the surface director in the presence of an electric field.(a) Electric field E dependence of ϕ under the surface condition of PMMA layer at T = 45 °C; the surface viscosity γs of PMMA surface at T = 45 °C is γs = 3⋅10−4 N⋅s/m. (b) Surface viscosity dependence of ϕ in the presence of E = 10 V/μm under the surface conditions of PMMA layer at T ≤ 45 °C.
Mentions: In our system, ϕ(t → ∞) = ϕe and τ = γsξe/K2 because the surface anchoring W of PMMA layer (WPMMA ≈ 10−7−10−8 N/m) is much smaller than K2/ξe ≈ 2.5 × 10−5 N/m. Therefore, if a strong E (>E*) is applied for a sufficient time t (>t*), on the PMMA layer can be reoriented even at . With Eq. (3), the azimuthal rotating angle ϕ of with t is estimated as a function of E (Fig. 4a) and γs (Fig. 4b). Figure 4a shows that even under the surface condition of PMMA layer at T = 45 °C (γs = 3⋅10−4 N⋅s/m), can be reorientated. For instance, the theoretical plot indicates that can be fully realigned at T = 45 oC when E = 10 V/μm is applied for t > 15 s (red curve in Fig. 4a). Indeed, we could experimentally re-enact the alteration of ground states in Fig. 2 at T = 45 °C by applying E = 10 V/μm for t = 30 s. Figure 4b shows the γs dependence of the rotation of when E = 10 V/μm is introduced. The theoretical plot (blue and green curves in Fig. 4b) clearly indicates that can be modified even at T < 45 °C; γs = 1.3⋅10−3 N⋅s/m (blue curve) correspond to the surface viscosity of PMMA at T = 25 °C. The transformation of ground states at T = 25 °C was experimentally demonstrated as shown in Fig. 5.

Bottom Line: Because of a growing market demand on such devices, the LCD that can be of numerous surface alignments of directors as its ground state, the so-called multi-stable LCD, comes into the limelight due to the great potential for low power consumption.We demonstrate experimentally and theoretically that a battery of stable surface alignments can be achieved by the field-induced surface dragging effect on an aligning layer with a weak surface anchoring.The simplicity and stability of the proposed system suggest that it is suitable for the multi-stable LCDs to display static images with low power consumption and thus opens applications in various fields.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Yeungnam University, Gyeongsan 712-749, Korea.

ABSTRACT
Owing to the significant price drop of liquid crystal displays (LCDs) and the efforts to save natural resources, LCDs are even replacing paper to display static images such as price tags and advertising boards. Because of a growing market demand on such devices, the LCD that can be of numerous surface alignments of directors as its ground state, the so-called multi-stable LCD, comes into the limelight due to the great potential for low power consumption. However, the multi-stable LCD with industrial feasibility has not yet been successfully performed. In this paper, we propose a simple and novel configuration for the multi-stable LCD. We demonstrate experimentally and theoretically that a battery of stable surface alignments can be achieved by the field-induced surface dragging effect on an aligning layer with a weak surface anchoring. The simplicity and stability of the proposed system suggest that it is suitable for the multi-stable LCDs to display static images with low power consumption and thus opens applications in various fields.

No MeSH data available.


Related in: MedlinePlus