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- Osterman, Jesper, 1971-
(författare)
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Investigations of Optical Properties and Photo-Alignment in Bistable Nematic Liquid Crystal Displays
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years portable electronic devices, such as mobile phones and personal digital assistants, have increased the demand for high performance displays with low power consumption. An interesting candidate with the potential of fulfilling these demands is the reflective single-polarizer surface controlled bistable twisted nematic liquid crystal display. The main focus of this work involves the optical properties of displays based on these bistable structures. In the investigations, the display is considered as an integrated optical system, containing not only the liquid crystal cell, but also components such as polarizers and retardation films. The specific aim of the thesis was to derive new optical modes of the reflective single-polarizer bistable twisted nematic device using the Jones matrix method to study the interaction between the polarization of light and the optically anisotropic media. The electro-optical properties of the derived modes have been studied and evaluated both theoretically and experimentally. The modes possess excellent brightness and high contrast ratio. By introducing a quarter-wave retardation film into the optical configuration, the contrast ratio can be significantly increased by preventing spectral leakage of light in the dark state. To experimentally realize the derived optical modes, special layers for the alignment of the liquid crystal molecules on the cell substrate surface have been proved needed. Therefore, also the photo-alignment technology of nematic liquid crystals on novel alignment materials has been studied with the aim to control liquid crystal cell parameters such as pretilt angle and anchoring energy, both critical for the bistable switching. The results of this thesis will increase the understanding of the optical properties of the reflective single-polarizer bistable twisted nematic liquid crystal display and will be valuable when considering this type of device for practical applications.
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- Osterman, Jesper, et al.
(författare)
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Mechanically stabilized bistable FLC cells on plastic substrates
- 2005
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Ingår i: Proceedings of the twenty-fifth international display research conference, Eurodisplay 2005.
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Konferensbidrag (refereegranskat)abstract
- The electro-optical properties of a full v flexible photo-aligned FLC cell are investigated. Two different methods, sticky spacers together with a photo-sensitive monomer and polymer spacers in a regular pattern formed by photo-lithography, are proposed to stabilize the structure in order to increase the bending tolerance of the FLC material during deformation of the cell.
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- Osterman, Jesper, et al.
(författare)
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Optical Modes for Single Polarizer Reflective BTN
- 2002
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Ingår i: Proceedings of the 22nd International Display Research Conference, Eurodisplay, Nice, France. - Nice, France. ; , s. 479-
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Tidskriftsartikel (refereegranskat)
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- Osterman, Jesper, et al.
(författare)
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Properties of azo-dye alignment layer on plastic substrates
- 2005
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Ingår i: Journal of the Society for Information Display. - : Wiley. - 1071-0922 .- 1938-3657. ; 13:12, s. 1003-1009
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Tidskriftsartikel (refereegranskat)abstract
- The alignment properties of the azo dye photo-alignment material SD-1/SDA-2 on plastic substrates are investigated. Excellent alignment with high anchoring energy can be achieved with a polarized UV dose less than 1.0 J/cm2. A reflective 6-digit flexible passive matrix driven TN-LCD for smart card applications showing excellent electro-optical properties is demonstrated.
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- Selo Mustafa, Muhammed, et al.
(författare)
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Synthesis, spectroscopic characterisation and alignment of novel azobenzene containing monomers
- 2005
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Ingår i: Liquid crystals (Print). - : Informa UK Limited. - 0267-8292 .- 1366-5855. ; 32:7, s. 901-908
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Tidskriftsartikel (refereegranskat)abstract
- A series of novel bifunctionalized photochromic monomers were synthesized, focusing on those with polymerizable acrylic/methacrylic groups attached to both ends of an azobenzene core via flexible spacers. The phase behaviour of the monomers was investigated using DSC, polarizing optical microscopy and X‐ray diffraction. The change in UV‐vis absorbance of the monomers under illumination with non‐polarized/polarized UV light was studied for both solutions and thin films; also studied was its relaxation in the dark. On illumination with LPUV light, in‐plane reorientation of the molecules normal to the polarization of the exciting UV light, and aggregation of the molecules in the films, were found.
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- Skarp, Kent, et al.
(författare)
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Development of flexible LCDs
- 2002
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Ingår i: Asian symposium on information display.
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Konferensbidrag (refereegranskat)
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- Tunell, Helena, et al.
(författare)
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Synthesis and Characterization of Main Chain Polyimides Containing Chalcone Derivatives for LC Alignment
- 2006
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Ingår i: Polymer Journal. - 0032-3896 .- 1349-0540. ; 38:7, s. 716-723
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Tidskriftsartikel (refereegranskat)abstract
- Two soluble polyimides containing chalcone derivatives in the main chains were successfully prepared using the Mitsunobu reaction at room temperature, reacting diols with diimides. With this reaction procedure the high temperature imidization step normally needed for the synthesis of polyimides is avoided and the polymers can be used for temperature sensitive applications. The main chain polyimides were characterized with FT-IR, NMR and DSC and the extent of the photoreaction was measured with FT-IR and UV-vis spectroscopy. Isobestic points were observed in the absorption spectral changes at the early stage of UV irradiation as a result of a single photochemical process. Further photoirradiation is accompanied by deviation from the isobestic points, implying that another photochemical process has started. With FT-IR investigations it was concluded that photodimerization is the process occurring at low UV exposure doses and that trans-cis isomerization is starting simultaneously at higher doses. The optical anisotropic properties were investigated upon exposure of the polymers as thin films to linearly polarized UV (LPUV) light of different doses. Selected crosslinking in the parallel direction relative to the direction of the LPUV light and subsequent optical anisotropy in the film were achieved.
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- Valyukh, Iryna, et al.
(författare)
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Monochromatic bistable reflective and transfiective ferroelectric LCDs
- 2005
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Ingår i: Proceedings of the 25th International Display Research Conference, Eurodisplay 2005. ; , s. 305-308
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Konferensbidrag (refereegranskat)abstract
- We study single and double polarizer monochromatic bistable reflective and transfective direct view ferroelectric liquid crystal displays (FLCDs). Three types of monochromatic displays are considered Black & White, Black & Yellow, Black & Green. Theoretical approach for finding optimal parameters of an FLCD is presented.
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