Azimuthal Anchoring Energy Research Articles

40.3: Effect of Birefringent Alignment Layer on Azimuthal Anchoring Energy Measurement

Birefringent alignment layer contributes to the optics of the liquid crystal cell, which is significant for optical method of azimuthal anchoring energy measurement. We obtained analytical equation to compute the corrected value of liquid crystal twist angle subject to alignment layer retardation. The data on azimuthal anchoring energy measurements of AtA‐2 and AtA‐0042 azo‐dye photoalignment materials are obtained: above >10−4J/m2 within the wide range of exposure doses 0.04 – 5.12 J/cm2.

Electro-optic characteristics of fringe-field-switching mode with controllable anchoring strength of liquid crystal alignment

A photoalignment technique used in preparation of fringe-field-switching (FFS) mode cells is presented. The azimuthal anchoring energy (AAE) of photoalignment is controllable by tuning the UV exposure and if the value of AAE is as strong as that of the rubbing method. The electro-optical properties of FFS cells are optimized with different electrode configurations and high quality dark states of various types of cells are achieved to create the high contrast ratio. The great thermal stability shown after applying voltage and heat confirms that photoalignment is suitable for FFS mode applications.

P‐115: New Photoalignment Material: Azimuthal Anchoring Energy Decreases at Very High Photo‐Induced Order Parameters

We developed new azo‐dye photoalignment material with extremely high values of photoinduced anisotropy: order parameter S∼0.85, dichroic ratio DR∼17.5. Experiment reveals decrease of azimuthal anchoring energy for highly oriented azo‐dye layers, contradicting with regular expectations. High quality patterned λ/4 retarder based on RM mesogens with ∼3 µm pattern disclination width are obtained.

P‐114: The Application of Photoalignment on Fringe Field Switching Cells

A photoalignment technique used in preparation of fringe‐field‐switching (FFS) mode cells is presented. The azimuthal anchoring energy (AAE) of photoalignment is controllable by tuning the UV exposure condition and the value of AAE is as strong as that of the rubbing method. The electro‐optical properties of FFS cells are optimized with different electrode configurations and high quality dark states of various type of cells are achievedto provide the high contrast ratio. The great stability of voltage and thermal stress tests confirm that photoalignment is suitable for FFS/IPS applications.

28.4: Late‐News Paper: Effects of Azimuthal Anchoring Energy on In‐Plane Switching Mode LCD

AbstractThe azimuthal anchoring energies (A.A.E.) of rubbed and UV‐exposed polyimides (PIs) alignment layers were measured more precisely by using improved optical measurement systems and modified cell configurations, and their effects on the alignment stabilities and liquid crystal (LC) response properties in an IPS‐mode LCD were studied. It is proved that (1) the relatively high A.A.E. is necessary for the alignment stability under high temperature stresses, and (2) the falling time of LC becomes shorter by about 0.7 ms with one order increase of an A.A.E. value. So we propose that the A.A.E. level of 1 × 10−2 ∼ 5 × 10−2 J/m2 is required for an alignment layer in an IPS‐mode LCD in order to guarantee the alignment stability and LC response property.

Measurement of the Azimuthal Anchoring Energy of Liquid Crystals in Contact with Oligo(ethylene glycol)-Terminated Self-Assembled Monolayers Supported on Obliquely Deposited Gold Films

We report measurements of the orientations and azimuthal anchoring energies of the nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) on polycrystalline gold films that are deposited from a vapor at an oblique angle of incidence and subsequently decorated with organized monolayers of oligomers of ethylene glycol. Whereas the gold films covered with monolayers presenting tetra(ethylene glycol) (EG4) lead to orientations of 5CB that are perpendicular to the plane of incidence of the gold, monolayers presenting tri(ethylene glycol) (EG3) direct 5CB to orient parallel to the plane of incidence of the gold during deposition of the gold film. We also measure the azimuthal anchoring energy of the 5CB to be smaller on the surfaces presenting EG3 (3.2 +/- 0.8 microJ/m2) as compared to EG4 (5.5 +/- 0.9 microJ/m2). These measurements, when combined with other results presented in this paper, are consistent with a physical model in which the orientation and anchoring energies of LCs on these surfaces are influenced by both (i) short-range interactions of 5CB with organized oligomers of ethylene glycol at these surfaces and (ii) long-range interactions of 5CB with the nanometer-scale topography of the obliquely deposited films. For surfaces presenting EG3, these short- and long-range interactions oppose each other, leading to small net values of anchoring energies that we predict are dependent on the level of order in the EG3 SAM. These measurements provide insights into the balance of interactions that control the orientational response of LCs to biological species (proteins, viruses, cells) on these surfaces.

Measurement of Genuine Azimuthal Anchoring Energy in Consideration of Liquid Crystal Molecular Adsorption on Alignment Film

The photopolymer material of poly(vinyl cinnamate) (PVCi) is known as a liquid-crystal (LC) alignment film whose surface azimuthal anchoring energy is relatively small. However, the results of an experiment on LC reorientation under an electric field suggest that the genuine azimuthal anchoring energy is one order of magnitude higher than that measured by the conventional torque balance method and/or the Néel wall method. Here we clarified that this inconsistency is due to the LC molecular adsorption on the alignment film occurring during the isotropic-nematic phase transition process. In this paper, we propose an improved torque balance method by which the genuine azimuthal anchoring energy can be estimated.

2A03 光配向におけるアンカリングと照射エネルギーの関係(物理・物性)

2A03 光配向におけるアンカリングと照射エネルギーの関係(物理・物性)

P‐79: Influence of Multiple Beam Interference on Azimuthal Anchoring Energy Measurement Using Liquid Crystals with Different Chiralities

AbstractThe influence of multiple beam interference on azimuthal anchoring energy measurement using liquid crystals with different chiralities was investigated using 4 * 4 matrix method. It is shown that there are suitable measurement conditions to minimize the influence of multiple beam interference, improving the anchoring energy measurement. Calculation results and the measurement method are discussed.

An Improved Azimuthal Anchoring Energy Measurement Method Using Liquid Crystals with Different Chiralities

An improved method for measuring the azimuthal anchoring energy of liquid crystals has been developed. Without knowing the easy axes of the cells precisely, it is possible to measure their anchoring energy precisely, using the same liquid crystals but with different chiralities for the divided cells. The principles and measurements are discussed.

Materials and Rubbing Dependence on Azimuthal Anchoring Energy of Rubbed Polyimide Surfaces

To study the alignment of liquid crystal molecules, the relationship between the optical phase retardation of rubbed polyimide films and the azimuthal anchoring energy was reported. For this work, we investigated the effects of the side chain of polyimide and the rubbing parameter on optical phase retardation of the rubbed polyimide surfaces and azimuthal anchoring energy. One main chain type and two side chain type polyimide were used.

Influence of the Azimuthal Anchoring Energy on the Smectic Layer Formation in Ferroelectric Liquid Crystals

We have investigated the influence of surface treatment on the memory angle θm in chevron FLC-cells. Surface anisotropy with different azimuthal anchoring energies was produced either by illumination or by rubbing of a PVA layer containing an azo dye. Due to the low pretilt angle (θp <2°), we suppose that the measured value of θm is governed by the tilt angle δ of the smectic layers. A model is presented which relates the equilibrium value of δ to a balance between the azimuthal anchoring energy and the bend energy of the smectic layers in the chevron structure.

New Optical Method for the Measurement of the Azimuthal Anchoring Energy of Nematic Liquid Crystals

Abstract We propose a simple symmetry based optical technique for the measurement of the azimuthal anchoring energy of nematic liquid crystals on solid substrates. It can be applied even in the case of strong anchoring and for arbitrarily large surface director deviations. The proposed technique is applied to measure the azimuthal anchoring energy of the nematic 5CB on obliquely evaporated SiO layers.

Measurements of the Azimuthal Anchoring Energy of a Nematic Liquid Crystal (5CB) Aligned on As-Stacked Polyimide Langmuir-Blodgett Films

Abstract We have proposed a new optical method for measuring the twist angle of twisted nematic cells. The method is applied to estimate the azimuthal anchoring energy of a nematic liquid crystal 5CB aligned on the as-stacked polyimide Langmuir–Blodgett (PI-LB) films. The measured values of the anchoring energies are shown to range from 2 × 10−6 J/m2 to 1 × 10−5 J/m2, which depend on the LB deposition conditions and show the optimum condition for the deposition. The values of the azimuthal anchoring energy are known to be one or two orders of magnitude lower than the corresponding polar anchoring energy.