51.3: Cholesteric Color Filters: optical Characteristics, Light Recycling, and Brightness Enhancement

Hochbaum, A.; Jiang, Yingqiu; Li, L.; Vartak, S.; Faris, S. M.

doi:10.1889/1.1833950

“…Several methods have been explored for making cholesteric color filters. [3,4] The reflection wavelength can, for instance, be adjusted by changing the amount or composition of chiral components (x i ) [4] or the polymerization temperature. [3] However, with these methods a number of processing steps are needed in order to obtain the required array of red, green, and blue pixels.…”

Section: Introductionmentioning

confidence: 99%

“…[3,4] The reflection wavelength can, for instance, be adjusted by changing the amount or composition of chiral components (x i ) [4] or the polymerization temperature. [3] However, with these methods a number of processing steps are needed in order to obtain the required array of red, green, and blue pixels. A simpler method for making cholesteric materials that reflect different colors in different areas is based on a UV-lightinduced change of the pitch of cholesteric copolymers.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Properties of Photoisomerizable Derivatives of Isosorbide and Their Use in Cholesteric Filters

Lub

¹

,

Nijssen

²

,

Wegh

³

et al. 2005

Adv Funct Materials

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This paper describes the synthesis of photoisomerizable derivatives of isosorbide. These derivatives contain a stilbene or cinnamate moiety and can therefore be used as photoisomerizable chiral compounds in cholesteric liquid‐crystalline mixtures. The reflection wavelength of cholesteric layers made from these mixtures is increased by UV irradiation due to the fact that the Z‐isomers of these derivatives exhibit a lower helical twisting power than the corresponding E‐isomers. The cinnamate derivatives are very suitable for use in cholesteric color filters that find application in liquid‐crystal displays.

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“…For this reason, several methods to make cholesteric color filters have been explored. [8,9] However, to obtain the array of red, green, and blue pixels with these methods a number of processing steps are needed. The light-induced color change with the materials described above provides a very simple way to produce the color filter array: a polymer is prepared with a composition chosen so that it forms a blue reflecting film after coating.…”

Section: Methodsmentioning

confidence: 99%

“…In this paper we demonstrate a fluorescence-based, homogenous RNA detection method that couples the specificity of these RNA±peptide binding events with the optical amplification of conjugated polymers and oligomers. [8] The concept is illustrated using the binding of the transactivator (Tat) peptide to the transactivation responsive element RNA sequence (TAR RNA) of HIV-1. [9,10] The assay contains three elements: a cationic conjugated polymer (CP + ), a protein probe (protein-C*, where C* is a reporter fluorophore), and the negatively charged target RNA.…”

Section: ±2mentioning

confidence: 99%

Stable Photopatterned Cholesteric Layers Made by Photoisomerization and Subsequent Photopolymerization for Use as Color Filters in Liquid‐Crystal Displays

Lub

¹

,

Witte

²

,

Doornkamp

³

et al. 2003

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Hollow spheres represent a special class of materials that can find application in the fields of medicine, pharmaceutics, the paint industry, and other materials sciences.[13] Their applications include product-encapsulation, protection of light-sensitive components, and catalysis, and as coatings, composites, and fillers. Hence, we have applied this methodology to the encapsulation of guest molecules. A fluorescent dye (pyranine: 3-hydroxy-1,3,6-pyrenetrisulfonic acid, trisodium salt) was dissolved in aqueous solution before the preparation of the spherical particles. The particles that adsorbed on the substrate were removed from the solution and microscopic observations were carried out. It is evident that the dye molecules are incorporated in the particles because the particles emit green fluorescence (Fig. 3b). Since the fluorescent microparticles maintain spherical shape with high symmetry, it is strongly suggested that the dye molecules are included in the cavity of the particles. These results clearly demonstrate the applicability of the present hollow particles to the encapsulation of various materials. In summary, we incorporated the use of hydrophilic interfaces into a solution-based self-assembly technique. This methodology produces hollow spheres of bola-form amide, whereas the usual self-assembly method leads only to the formation of fibers. The use of hydrophilic surfaces also provides a means of squeezing-out intermediate phases during the selfassembly processes, taking advantage of the different chemical properties of the phases, and thereby making self-assembly processes applicable to the generation of materials that are completely different from those produced via conventional self-assembly techniques. ExperimentalThe synthesis of Val 2 C 10 has been published before [6]. FTIR measurements were carried out using a Perkin±Elmer System 2000 apparatus. Optical microscopic images and fluorescence micrographs were obtained using an Olympus IMT-2 microscope. SEM measurements were carried out with a JEOL JSM-5600 instrument operating at 20 kV and a TOPCON DS-720 (FE-SEM) operating at 5 kV. Samples for SEM analysis were sputter-coated with~3 nm thick Pt. SLS experiments were performed on a DLS-7000 instrument (Otsuka Electronics) using a He±Ne laser (633 nm). The refractive index increment (dn/dc) of the sample solution was measured using a DRM-1030 (Otsuka Electronics) apparatus. As the concentration of Val 2 C 10 in water was~10 4 g cm ±3, the difference in the Rayleigh ratio DR(q) is given by DR(q) = K´c´M w´P (q), where c is the concentration of the solute, M w is the weight-average molecular mass of the aggregates, P(q) is the particle-form factor, and K is an optical constant given by K = 4´p 2´n 0 2´( dn/dc) 2 / N A´k 4 (N A is Avagadro's number). The scattering vector q is defined by q = (4´p´n 0 / k)´sin (h / 2) with n 0 and k being the refractive index of the solvent (1.34 for water at 25 C) and the wavelength of incident light, respectively. The scattering angle was varied from 30 to 130 in 5...

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“…Clearly, it is possible to design elements to selectively reflect or transmit particular handedness by careful selection of components and dopants; stable filters are made by crosslinking polymerization of the films by use of reactive mesogen molecules [45] or by vitrifying the helical phase structure into stable glassy structure (with high T g ) [46][47][48]. These elements are of huge interest for patterned reflector surfaces to replace expensive pigmented color filter layers [49][50][51][52]. • Lasers -this application takes advantage of the chiral nematic phase's periodic helical structure, which is effectively a 1D photonic crystal (or photonic band gap), and may offer certain advantages over solid state semiconductor technology [53][54][55].…”

Section: Applications Of Chiral Nematic Phasesmentioning

confidence: 99%

Design and Synthesis of Chiral Nematic Liquid Crystals

Taugerbeck

¹

,

Booth

²

2014

Handbook of Liquid Crystals

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The article contains sections titled: Introduction to the Chiral Nematic Phase and Its Properties Formulation and Application of Chiral Nematic Liquid Crystal Mixtures Applications of Chiral Nematic Phases Classification of Chiral Nematic Liquid‐Crystalline Compounds Aspects of Molecular Symmetry for Chiral Nematic Phases Type I Chiral Nematic Liquid Crystals Azobenzenes and Related Mesogens Azomethine ( S chiff's Base) Mesogens Stable Phenyl, Biphenyl, Terphenyl, and Phenylethylbiphenyl Mesogens Ester Mesogens Derivatives of Chiral Alcohols Type II Chiral Nematic Liquid Crystals Type IIa Twin Systems Using Chiral Flexible Spacers Type IIb Materials Using Achiral Flexible Spacers and Chiral Terminal Groups Type IIc and d Materials Using One or Two Chiral Cores Type III Chiral Nematic Liquid Crystals Cholesteryl Esters Chiral Mesogens Derived from Cyclohexane Chiral Heterocyclic Mesogens Axially Chiral Liquid Crystals Axially Chiral Alkenes and Overcrowded Alkenes Allenes Tricyclo[4.4.0.0 3,8 ]decane or Twistane Derived Mesogens Sterically Hindered Biphenyl Derivatives Spirobiindane Derivatives Concluding Remarks

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51.3: Cholesteric Color Filters: optical Characteristics, Light Recycling, and Brightness Enhancement

Cited by 25 publications

References 0 publications

Synthesis and Properties of Photoisomerizable Derivatives of Isosorbide and Their Use in Cholesteric Filters

Synthesis and Properties of Photoisomerizable Derivatives of Isosorbide and Their Use in Cholesteric Filters

Stable Photopatterned Cholesteric Layers Made by Photoisomerization and Subsequent Photopolymerization for Use as Color Filters in Liquid‐Crystal Displays

Design and Synthesis of Chiral Nematic Liquid Crystals

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