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我们研究了可用于光致取向液晶(LCs)偶氮染料的合成和性质,提出了偶氮染料的结构与合成过程。偶氮染料光致取向完全是因为分子吸收振子垂直于UV光偏振方向的再取向。讨论了在偏振光场中,偶氮染料分子旋转扩散现象的定性模型。测量了波长为372nm时,偏振吸收光谱的有序参数S=-0.4(80%的最大绝对值Sm=-0.5)。对一个偶氮染料膜,利用在正常的正入射偏振光之后,紧跟一个斜入射的非偏振光两步曝光,可以获得温度稳定的5.3°预倾角。光致取向基片的方位角锚定能为Aφ≈10-4Jm-2,这与摩擦聚酰亚胺(PI)层的锚定能相同。我们发现,光致取向液晶盒的电压保持率甚至比摩擦PI层取向的还高,因此,偶氮染料完全可以用作有源矩阵液晶显示器的取向层。光致取向偶氮染料层的热稳定性很高,但UV稳定性需通过诸如聚合等来改良。于是,我们设想了一种新的基于聚合偶氮染料层的LCD取向技术。
We have studied the synthesis and properties of azo dyes that can be used in photo-aligned liquid crystals (LCs) and proposed the structure and synthesis of azo dyes. The photoinduced orientation of azo dyes is entirely due to the molecular orientation of the molecules that absorb the vibrator perpendicular to the polarization of UV light. The qualitative model of the phenomenon of azo dye molecules’ spin diffusion in the polarized light field is discussed. The order parameter S = -0.4 (maximum absolute value Sm = -0.5 at 80%) of the polarization absorption spectrum was measured at a wavelength of 372 nm. For an azo dye film, a temperature stable 5.3 ° pretilt can be achieved with a normal normal incident polarized light, followed by an obliquely incident, unpolarized two-step exposure. The azimuthal anchoring energy of the photo-oriented substrate is Aφ ≈10-4 Jm-2, which is the same as the anchoring energy of the rubbed polyimide (PI) layer. We found that the photo-alignment cell voltage retention even higher than the friction PI layer orientation, therefore, azo dyes can be fully used as the active matrix liquid crystal display alignment layer. The thermal stability of the photo-oriented azo dye layer is high, but the UV stability needs to be improved by such as polymerization. Thus, we envision a new LCD orientation technology based on polymeric azo dye layers.