Photo‐aligning by azo‐dyes: Physics and applications

Chigrinov, Vladimir G.; Kwok, Hoi Sing; Takada, Hirokazu; Takatsu, Haruyoshi

doi:10.1080/14645180600617908

Cited by 78 publications

(68 citation statements)

References 40 publications

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“…The micron-sized pattern of LC alignment is difficult to achieve by rubbing but easy to achieve by photoaligning. Surface-mediated photoalignment is also effective for the fabrication of flexible and rewritable displays [31], gradientindex lenses [32], and other devices [33].…”

Section: Photo-isomerization In Azo-compound-containing Polymer/dye Fmentioning

confidence: 99%

Photo-Alignment Technology

Lin

2014

Topics in Applied Physics

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LCDs are used in many everyday devices, including mobile phones, notebook computers and wide screen televisions. A typical LCD is composed of two glass substrates between which is a gap that is filled with LC. The arrangement of the LC is controlled by the boundary condition of an alignment film. A long-range orientational interaction causes the preferable alignment of a LC by the surface boundary to extend into the LC bulk. The alignment layer is typically rubbed with a special cloth to induce a unidirectional alignment of the LC. In the first devices based on twisted LCs, these LCs were aligned only by rubbing transparent electrodes. The rubbing technique became much more reliable when the glass substrate was covered with a rubbed polymer layer. The rubbing of polymers is a very simple technique and it is now extensively utilized in both small scientific laboratories and large LCD factories.Despite the extensive use of rubbing in LCD manufacturing, it has some serious shortcomings that arise from the contact involved in rubbing. These critically affect the production of the most recent generation of LCDs and miniature LC photonic devices. First, rotational rubbing for the polymer surface causes the accumulation of static charges and the formation of fine dust particles. The accumulation of static electricity may destroy the transistors or diodes in the LCD. The second shortcoming is the effect of decreasing in manufacturing yield. Rubbing for large and high-resolution active matrix LCDs (AMLCDs) involve additional difficulties that are associated with the precise control of the rubbing characteristics. Other problems are the difficulty of producing local structures with the required LC director alignment in the selected areas of the device. Finally, this method cannot be used to align LCs in closed volumes.For all of the above reasons, new alignment solutions and approaches are sought. There are some alternative methods of rubbing include laser writing, micro-rubbing, ion beam irradiation and photoalignment. Of these methods, the

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Section: Photo-isomerization In Azo-compound-containing Polymer/dye Fmentioning

confidence: 99%

Photo-Alignment Technology

Lin

2014

Topics in Applied Physics

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“…Several efforts have already been made to stabilize the azo dye photoalignment with LCP, including polymer azo dye composite [7], LCP layer on the top of the azo dye [8], and introduction of the polarizable moiety in the azo dye itself [4]. For the polymer composite azo dye alignment layer, it has been proposed to utilize azo dye and LCP mixture with a proper ratio to form a photo-stable photoalignment, but voltage holding ratio (VHR) and the residual DC (RDC) do not meet the industrial standards [9].…”

Section: Introductionmentioning

confidence: 99%

P-118: Azo Dye, Liquid Crystals Polymer Composite Photo-Alignment Layer for Modern Liquid Crystal Displays

Meng

Tseng

Lee

et al. 2016

SID Symposium Digest of Technical Papers

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In this article, a photoalignment layer, based on the azo dye and liquid crystal polymer (LCP) composite is proposed. The alignment layer offers easy processing and high photo and thermal stabilities. The high VHR (99.1%) and low RDC (30mV) have been achieved that is comparable with the conventional PI rubbing alignment layer. The proposed alignment layer shows low pre-tilt angle and small image sticking which is highly desirable for IPS display. Furthermore, the ability of multi-domain alignment has been demonstrated that shows a great potential to find applications in a range of electro-optical devices particularly those requiring in-plane LC director modulations.

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“…[19] Recently, these derivatives have also found numerous new applications ranging from optical waveguides [20] and data storage devices [21] to lightswitchable receptors [22] , and it is likely that new applications and discoveries will be made as the chemistries and structures are further refined. [23] In contrast, very few examples of the synthesis or utilization of (N-phenyl-N'- [1,3,5]triazinyl)diazenes [24,25] , and even less of bis- [1,3,5]triazinyl diazenes [26,27] , can be found in the literature.…”

Section: Introductionmentioning

confidence: 99%

Preparation and characterization of bis‐[1,3,5]triazinyl diazenes and their utilization as flame retardants in polypropylene films

Tirri

Aubert

Pawelec

et al. 2014

J of Applied Polymer Sci

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A series of bis- [1,3,5]triazinyl diazenes and two metal complexes thereof were synthesized and tested as new flame retardants in polypropylene films. It was observed that electron withdrawing triazinyl ring substituents (i.e. Cl and phenyl moieties) improved the thermal stability of diazene compounds, whereas electron donating groups (i.e. methoxy, dimethylamino and ethylthio moieties) had a destabilizing effect. TGA, DTA/DSC, NMR and ATR-FTIR were used for the characterization. Quantum mechanical modeling (Gaussian 09) was also utilized to facilitate the interpretation of the NMR data. Bis-(4,6-dichloro-[1,3,5]triazin-2-yl)-diazene 1 and bis-(4,6-dimethoxy-[1,3,5]triazin-2-yl)-diazene 2 were found to be effective flame retardants in polypropylene films and DIN4102-1 B2 classification was reached already at a loading of 0.5 wt%. Interestingly, the copper complex of 2 showed even higher fire retardant activity than its precursor 2, whereas the corresponding zinc complex exhibited lower flame retardant efficacy than its precursor.

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Photo‐aligning by azo‐dyes: Physics and applications

Cited by 78 publications

References 40 publications

Photo-Alignment Technology

Photo-Alignment Technology

P-118: Azo Dye, Liquid Crystals Polymer Composite Photo-Alignment Layer for Modern Liquid Crystal Displays

Preparation and characterization of bis‐[1,3,5]triazinyl diazenes and their utilization as flame retardants in polypropylene films

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