Synthesis, Properties, and Photopolymerization of Liquid-Crystalline Oxetanes: Application in Transflective Liquid-Crystal Displays

Zande, B. M. I. van der; Roosendaal, S. J.; Doornkamp, C.; Steenbakkers, J.; Lub, Johan

doi:10.1002/adfm.200500359

Cited by 23 publications

(25 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[28][29][30] All polymers were copolymers, containing the monomer 2, to which the oxetane functionality is attached. For the green-and red-light-emitting polymers, chromophores emitting in the respective wavelength region were also copolymerized into the polymer chain.…”

Section: Full Papermentioning

confidence: 99%

Solution‐Processed Full‐Color Polymer Organic Light‐Emitting Diode Displays Fabricated by Direct Photolithography

Gather

Köhnen

Falcou

et al. 2007

Adv Funct Materials

280

203

View full text Add to dashboard Cite

The first full‐color polymer organic light‐emitting diode (OLED) display is reported, fabricated by a direct photolithography process, that is, a process that allows direct structuring of the electroluminescent layer of the OLED by exposure to UV light. The required photosensitivity is introduced by attaching oxetane side groups to the backbone of red‐, green‐, and blue‐light‐emitting polymers. This allows for the use of photolithography to selectively crosslink thin films of these polymers. Hence the solution‐based process requires neither an additional etching step, as is the case for conventional photoresist lithography, nor does it rely on the use of prestructured substrates, which are required if ink‐jet printing is used to pixilate the emissive layer. The process allows for low‐cost display fabrication without sacrificing resolution: Structures with features in the range of 2 μm are obtained by patterning the emitting polymers via UV illumination through an ultrafine shadow mask. Compared to state‐of‐the‐art fluorescent OLEDs, the display prototype (pixel size 200 μm × 600 μm) presented here shows very good efficiency as well as good color saturation for all three colors. The application in solid‐state lighting is also possible: Pure white light [Commision Internationale de l'Éclairage (CIE) values of 0.33, 0.33 and color rendering index (CRI) of 76] is obtained at an efficiency of 5 cd A–1 by mixing the three colors in the appropriate ratio. For further enhancement of the device efficiency, an additional hole‐transport layer (HTL), which is also photo‐crosslinkable and therefore suitable to fabricate multilayer devices from solution, is embedded between the anode and the electroluminescent layer.

show abstract

Section: Full Papermentioning

confidence: 99%

Solution‐Processed Full‐Color Polymer Organic Light‐Emitting Diode Displays Fabricated by Direct Photolithography

Gather

Köhnen

Falcou

et al. 2007

Adv Funct Materials

280

203

View full text Add to dashboard Cite

show abstract

“…After stirring for 16 h at room temperature, the mixture was filtered over 12 g of silica and the solvent allowed to evaporate; 9.6 g (83%) of the product was obtained as a white powder after recrystallization from ethanol at 5uC. 1 …”

Section: Synthesismentioning

confidence: 99%

“…96uC (lit 92uC [17]). 1 After evaporation of the ethanol, 50 ml of diethyl ether was added and the organic layer was extracted twice with 60 ml of 5% aqueous sodium hydroxide and then with 50 ml of saturated aqueous sodium chloride. After evaporation of the diethyl ether, intermediate 14 was obtained which was dissolved in 25 ml of ethanol that contained 0.5 ml concentrated HCL.…”

Section: Synthesismentioning

confidence: 99%

“…Current state-of-the-art retardation foils are formed by carefully stretching extruded plastic sheets to a fixed retardation value. As a result, the front-of-screen performance cannot be optimized for both the transmissive and reflective modes, forcing a compromise between contrast and viewing angle or contrast and brightness [1,2]. In order to improve on the front-of-screen performance, and simultaneously on the reduction of thickness, weight and costs, subpixelated micrometer-thin film retarder foils can be created.…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Patterned retarders prepared by photoisomerization and photopolymerization of liquid crystalline films

et al. 2006

Self Cite

View full text Add to dashboard Cite

Isomerizable diacrylates derived from cinnamic acid are designed, synthesized and mixed with liquid crystalline diacrylates with the aim of making films with alternating birefringent and isotropic domains by applying the E-Z isomerization process at room temperature. The effects of the structure of the isomerizable-mesogenic group on the isotropization efficacy, the efficiency of the E-Z isomerization reaction, and film formation are discussed. Compounds derived from cyclohexyl cinnamate are proved to be good candidates that meet a whole set of parameters related to processing and application. These compounds exhibit a low nematic-toisotropic transition temperature. In addition, they show no yellowing upon irradiation, unlike similar compounds derived from phenyl cinnamate. To elucidate the origin of isotropization of the film by irradiation, the pure Z-isomer is prepared by photolysis of the E-isomer and subsequent chromatographic separation of both isomers. Analysis of reference samples containing the pure isomers reveals that the decrease in transition temperature can be attributed exclusively to the E-Z photoisomerization process. Finally, thin films with alternating birefringent and isotropic parts of 1006100 mm 2 are obtained by using a combination of photoisomerization in air and photopolymerization in a nitrogen atmosphere, which is referred to as photo-patterning.

show abstract

“…The low viscosity of the reactive liquid crystals facilitates easy alignment, while the in situ photopolymerization provides freedom in choosing the polymerization temperature and conditions enabling the selection of the optimum phase and molecular order. [7] This technology has been applied in the preparation of numerous optical foils, for example, patterned retarders, [8,9] broadband circular polarizers, [10] wide viewing angle films, [11] and cholesteric color filters. [12] We utilize this technology for the preparation of guest-host polarizers.…”

mentioning

confidence: 99%

High‐Contrast Thin‐Film Polarizers by Photo‐Crosslinking of Smectic Guest–Host Systems

et al. 2006

Self Cite

View full text Add to dashboard Cite

The most essential passive optical element in liquid-crystal displays (LCDs) is the polarizer. Polarizers are indispensable for the displaying of the information content and important front-of-screen performance parameters, such as brightness and contrast, are strongly influenced by the performance of the polarizer. Currently, the most widely used polarizers for LCD applications are derivatives of the H-sheet polarizer as invented by E. H. Land in 1938.[1] These dichroic polarizers are based on uniaxially stretched poly(vinyl alcohol) that is impregnated with iodine or doped with dichroic dyes. These sheet polarizers show excellent optical performances that can be expressed by the polarization efficiency (PE) in combination with the single-piece transmittance (T sp ; transmission of unpolarized light through a single polarizer) aswhere T p and T c are defined as the transmission of unpolarized light through two polarizers with their transmission axis parallel and perpendicular, respectively, and where A ʈ and A ⊥ are defined as the absorbance parallel and perpendicular to the average orientation of the long axis of the chromophores, respectively. The polarizer performance can also be expressed by a single parameter; the dichroic ratio (N)For high-end sheet polarizers such as those applied in LCD monitors or flat-panel televisions, the performance exceeds a polarization efficiency (PE) of 99.9 % at a single-piece transmission of 43.5 %, corresponding to N exceeding 50. Unfortunately, two triacetylcellulose (TAC) layers are needed in conventional polarizers to protect the stretched poly(vinyl alcohol) film on both sides against moisture and to obstruct relaxation effects under influence of heat and/or humidity by which the PE value would deteriorate. Further, an adhesive layer is needed in order to laminate the polarizer to the display. The necessary use of protective and adhesive layers adds unnecessary thickness to H-sheet polarizers. Finally, these polarizers show limited thermal stability and low resistivity against solvents. Numerous advantages are foreseen when the traditional sheet polarizers are replaced by ultrathin coatable polarizers situated on the inside of the cell (in-cell). Apart from a significant reduction in display thickness and weight, the positioning of the polarizers inside the cell eliminates all parallax-related issues and is beneficial to the robustness of the display. Furthermore, substrates that otherwise would be rejected because of their birefringence, e.g., thin, low-weight, and strong plastic foils or cheap, low-quality glass substrates, can be used when the polarizers are situated inside the LCD cell. The optimal position of the coatable polarizers inside the LCD cells can vary between display designs, however, it is beneficial to place the polarizers beneath the electrodes in order to prevent the need for increased driving voltages of the LCD panels.One possible approach to obtaining thin, coatable polarizers is based on the use of lyotropic liquid-crystalline dyes that form a crys...

show abstract

Synthesis, Properties, and Photopolymerization of Liquid-Crystalline Oxetanes: Application in Transflective Liquid-Crystal Displays

Cited by 23 publications

References 21 publications

Solution‐Processed Full‐Color Polymer Organic Light‐Emitting Diode Displays Fabricated by Direct Photolithography

Solution‐Processed Full‐Color Polymer Organic Light‐Emitting Diode Displays Fabricated by Direct Photolithography

Patterned retarders prepared by photoisomerization and photopolymerization of liquid crystalline films

High‐Contrast Thin‐Film Polarizers by Photo‐Crosslinking of Smectic Guest–Host Systems

Contact Info

Product

Resources

About