英国爱丁堡大学 (The University of Edinburgh): 偶氮染料在VA-LCD中的应用

2.2 Applications 

应用

A remarkable property of azo-dye aligning layers gives a good chance to provide a high photoalignment quality of ferroelectric liquid crystal (FLC) using the azo-dye layer. 

偶氮染料对准层的一个显著特性提供了一个高光配铁电液晶（FLC）使用偶氮染料层质量的好机会。

The photo-aligned FLC cell appeared to be better than prepared by buffing, if the UV-irradiation time of the azo-dye layer is high enough [27]. The FLC row addressing response time ofτ≈ 100 μ s at the voltage pulse amplitude of U=  ±15V was demonstrated [27, 28]. Large FLC cell gaps of 5 μ m and 7 μ m were used, which is easy in manufacturing. Perfect electrooptical performance of the photo-aligned FLC display with a memorized gray scale was demonstrated. http://ukthesis.org/ygsslwdx/

使用5μm和7微米大的FLC细胞间隙，这是很容易制造的。有记忆的灰度照片对齐FLC显示完美的电光性能证明。

A prototype of passively addressed passive matrix FLC display based on the photo-alignment technique was developed [28]. Recently photoaligned bistable FLC with dichromatic (two color) [29] and almost achromatic (black/white) [30] switching were realized. 1 60×160 passive matrix addressed bistable 5um FLC display was demonstrated with the driving voltage of ±13V and 5um cell gap [31]. Images can be saved for very long time without any power supply.  VAN-LCD has become very popular for LCD TV applications because of the high contrast and wide viewing angle it affords. In experiment [32] the commercially available polyimide (PI) for homeotropic alignment was used in a combination with azo-dye for varying the pretilt angle fromthe homeotropic direction. The composition of 1% of azo-dye in solution with PI was prepared and the photo-aligning films were illuminated by a slantwise nonpolarized light. 

在实验 [32] 中，市场可买到的聚酰亚胺（PI）为垂直排列中，从各向同性方向使用偶氮染料的组合与不同的预倾斜角。制备1％的偶氮类染料组合物，在溶液中与PI的光取向膜，由一个倾斜的非偏振光照明。

For comparison the aligning film of a pure PI was prepared by rubbing technique to align the LC molecules in a homeotropic state with some pretilt angle. The measured value of the pretilt angle from the homeotropic alignment was about 1.4°, which is higher than in other photo-alignedVAN LC cell (0.53 ° ). Later the pretilt angles of 2-30 from the homeotropic LC orientation were obtained using the mixture of homeotropic PI and photopolymerized azo-dye SDA-2 [11].  The measured value of the contrast ratio between “off” and “on” states in all the cases exceeds 1000:1 in the monochromatic light. Thus it is concluded that azo-dyes are suitable for the alignment of VA-LCD. 

测量值之间“关”和“开”的状态在所有的情况下，对比度超过1000:1单色光。因此可以得出结论，偶氮染料适合VA-LCD的取向。#p#分页标题#e#

We fabricated truly bistable π-BTN display, based on photoaligning technology [33]. The strong anchoring surface was achieved by the usual rubbed polyimide (PI) layer. Such PI layer provides a strong polar anchoring energy of 1.5 x10-3 J/m2. We found that the polar anchoring energy of photo-polymerized azo-dye SDA-1 (SDA-2) can be adjusted to 1.5-2.8 ⋅ 10-4 J/m2, while azimuthal anchoring to 3.6-5.6⋅ 10-5 J/m2by changing the exposure time, which wa s suitable for obtaining  π-BTN bistability by surface anchoring breaking. The π-BTN LCD was switched between –22.50 and 157.50, exhibiting a high contrast ratio (CR>140) and wide viewing angles [33]. π -BTN was also successfully made on flexible plastic substrates using photo-alignment technology [34]. This facilitates the implementation of low-power consumption bistable liquid crystal display into smart cards [34].  

π-BTN液晶在-22.50和157.50之间切换，表现出高对比度（CR>140）和宽视角[33]。 π-BTN也成功用于柔性塑料基板上，使用光取向技术[34]。这有利于实现低功耗双稳态液晶显示器智能卡[34]。

We have also investigated the properties of azo-dye alignment on plastic substrates  [35]. Excellent alignment with a high anchoring energy was achieved with the exposure energy less than 1.0 J/cm2, which corresponds to the azimuthal anchoring energy > 10-4 J/m2. We used a mixture of azo-dye SD-1 with a mentioned above thermo-polymerized azo-dye SDA-2 for the display fabrication. The LC pretilt angle of about 50on the plastic substrate was made by a double exposure method. To demonstrate the alignment quality on plastic substr ates a 9-digit reflective passive matrix TN-LCD mounted in smart card was fabricated. To maintain a uniform cell gap of 8 μ m (second Mauguin minimum of MLC-6809-000 Merck LC mixture), semi-dry adhesive spacers were chosen. The electrooptical performance of the photo-aligned plastic display was very similar to common TN-LCD  http://ukthesis.org/ygsslwdx/  fabricated for comparison by usual rubbing method on glass substrate. 

保持均匀的单元间隙8μ米（第二Mauguin最小的MLC-6809-000默克LC混合物），选择半干燥粘合间隔物。照片对齐的塑料显示器的电光性能是非常相似，共同的TN-LCD制造，在玻璃基板上用于比较通常的摩擦方法。