Planar and tilted uniform alignment of liquid crystals by plasma-treated substrates
Planar and tilted uniform alignment of liquid crystals by plasma-treated substrates
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通过等离子体处理的基板实现液晶的平面和倾斜均匀排列
DOI：
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发表时间：
2004
期刊：
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通讯作者：
O. Lavrentovich
中科院分区：
文献类型：
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作者：
O. Yaroshchuk;R. Kravchuk;A. Dobrovolskyy;L. Qiu;O. Lavrentovich
我们描述了一种新的取向技术，产生均匀的平面或倾斜取向的液晶在不同的有机和无机基板。该方法是基于倾斜照射的对准基板与部分准直通量的加速等离子体。片状等离子体通量是由阳极层推力器与赛道几何形状的放电通道。对于具有正介电各向异性的液晶，该技术产生两种均匀排列模式：（1）易轴在等离子体束的入射平面中;（2）易轴垂直于入射平面。随着辐照剂量的增加，模式1转变为模式2。在模式1中，预倾角可以通过改变照射参数如入射角、电流密度和粒子能量来控制。在模式2中，预倾角为零（平面对准）。对于第一种排列，方位角锚定系数相对较弱（W a ≥ 10−6 J m−2），而对于第二种排列，方位角锚定系数相对较强（W a≥10−4 J m−2，与摩擦的聚合物基底相当）。双模式对准特征可用于控制对准特性并创建对准图案。该方法摆脱了传统拓片技术的常见缺点。我们讨论了可能的机制的两种模式的排列，并表明，等离子体引起的修改的基板形貌可能是一个重要的因素，在液晶取向。
We describe a new aligning technique that yields uniform planar or tilted orientation of a nematic liquid crystal at different organic and inorganic substrates. The method is based on the oblique irradiation of an aligning substrate with a partially collimated flux of accelerated plasma. The sheet-like plasma flux is produced by an anode layer thruster with a race track geometry of the discharge channel. For liquid crystals with a positive dielectric anisotropy the technique produces two modes of uniform alignment: (1) with the easy axis in the incident plane of the plasma beam; (2) with the easy axis perpendicular to the plane of incidence. Mode 1 transforms into mode 2 as the irradiation dose increases. In mode 1, the pretilt angle can be controlled by changing the parameters of irradiation such as incidence angle, current density and particle energy. In mode 2, the pretilt angle is zero (planar alignment). The azimuthal anchoring coefficient is relatively weak (W a∼10−6 J m−2) for the first type of alignment and strong (W a≥10−4 J m−2, comparable to rubbed polymer substrates) for the second type. The two-mode alignment feature can be used to control alignment properties and to create alignment patterns. The method is free from the usual shortcomings of the traditional rubbing technique. We discuss possible mechanisms of the two-mode alignment and show that plasma-induced modifications of the substrate topography might be an important factor in liquid crystal alignment.