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WO2017035291A1 - Composite présentant une phase bleue iii et une mémoire électro-optique d'un échafaudage - Google Patents

Composite présentant une phase bleue iii et une mémoire électro-optique d'un échafaudage Download PDF

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WO2017035291A1
WO2017035291A1 PCT/US2016/048525 US2016048525W WO2017035291A1 WO 2017035291 A1 WO2017035291 A1 WO 2017035291A1 US 2016048525 W US2016048525 W US 2016048525W WO 2017035291 A1 WO2017035291 A1 WO 2017035291A1
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blue phase
phase iii
polymer
composite
liquid crystal
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Liang-Chy Chien
Minsu Kim
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Kent State University
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Kent State University
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/02—Liquid crystal materials characterised by optical, electrical or physical properties of the components, in general
    • C09K19/0275—Blue phase
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/38—Polymers
    • C09K19/3833—Polymers with mesogenic groups in the side chain
    • C09K19/3842—Polyvinyl derivatives
    • C09K19/3852—Poly(meth)acrylate derivatives
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/52—Liquid crystal materials characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
    • C09K19/58—Dopants or charge transfer agents
    • C09K19/586—Optically active dopants; chiral dopants
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/13793—Blue phases

Definitions

  • the present disclosure relates to liquid crystal composites that exhibit blue phase III.
  • Liquid crystal displays have become increasingly popular due to high- end display performance, wide viewing angle, high resolution, and suitability for large devices (e.g., televisions). Faster switching in LCDs may be achieved by a polymer- stabilized blue phase LCD mode.
  • Liquid crystalline blue phases include blue phase I (or BP I), blue phase II (or BP II), and blue phase III (or BP III, also known as "blue fog” or "foggy phase”).
  • Blue phase I has a face-centered cubic structure.
  • Blue phase II has a body-centered cubic structure.
  • Blue phase III has an amorphous structure.
  • Blue phases are typically only stable in a very narrow temperature range in the vicinity of the phase transition from the cholesteric to the isotropic phase.
  • Polymer-stabilized blue phase compositions can exhibit sub-millisecond response times of Kerr switching and optically isotropic properties.
  • the fast switching times and alignment-free characteristics of polymer-stabilized blue phase materials makes them useful for the development of a field sequential color LCD.
  • the switching mechanism gives rise to intrinsic issues such as (1 ) an increased driving voltage due to strong anchoring of the blue phase liquid crystal at a polymer network; (2) inconsistent response under ascending and descending electric fields which causes hysteresis of transmittance with respect to an applied voltage for on-off or gray-to-gray switching; and (3) reflection of bluish light due to the Bragg reflection of the periodic cubic structure, so that the initial state is not sufficiently dark at a certain wavelength range.
  • Landau-de Gennes implicitly describes the local order of blue phases in thermodynamic equilibrium, so that the local order parameter near the disclination core is gradually reduced to zero.
  • defect theory has been used to calculate the free energy per unit length of a single disclination, which in turn the order parameter becomes zero.
  • the cubic lattices of blue phase I and blue phase II stand in different orientations with respect to the surface of a substrate and crystalline growth occurs simultaneously at multiple locations.
  • the crystalline structure of blue phase usually grows within multiple domains with different orientations and sizes.
  • a mono domain cubic blue phase has been proposed.
  • annealing requires an extensive time period and it is thermally challenging to grow a mono domain structure over a larger area.
  • the light leakage issue in the dark state of multi-domain polymer-stabilized blue phases is due to a color appearance at a certain range of wavelength, which inhibits the high contrast ratio of devices.
  • the present disclosure relates to liquid crystal composites that exhibit blue phase III.
  • Devices containing the composites and methods for making and using the composites and devices are also disclosed.
  • a composite including from about 10 wt% to about 40 wt% of a polymer; a chiral dopant having a helical twisting power of at least about 100 pm "1 ; and a liquid crystal compound having a dielectric anisotropy of at least about +40.
  • the composite exhibits a blue phase III.
  • the composite may contain from about 20 wt% to about 30 wt% of the polymer.
  • the chiral dopant has a helical twisting power of at least about 1 10 ⁇ 1 .
  • the liquid crystal compound may have a dielectric anisotropy of at least about +50.
  • the composite exhibits the blue phase III over a temperature range of at least about 80°C.
  • the composite may exhibit the blue phase III at room temperature.
  • the polymer is formed from a mixture comprising a reactive mesogen.
  • the reactive mesogen may be a mesogenic diacrylate monomer.
  • the mixture further includes a difunctional acrylate monomer.
  • a liquid crystal display including a first transparent substrate; a second transparent substrate; and a composite layer between the first transparent substrate and the second transparent substrate.
  • the composite layer includes from about 10 wt% to about 40 wt% of a polymer; a chiral dopant having a helical twisting power of at least about 100 pm "1 ; and a liquid crystal compound having a dielectric anisotropy of at least about +40.
  • the composite exhibits a blue phase III.
  • a method for producing a composite includes curing a mixture.
  • the mixture contains from about 10 wt% to about 40 wt% of monomer units that form a polymer network during the curing; a chiral dopant having a helical twisting power of at least about 100 pm "1 ; and a liquid crystal compound having a dielectric anisotropy of at least about +40.
  • the composite exhibits a blue phase III.
  • a method for forming a nanostructured scaffold includes forming a blue phase mixture in a desired phase (e.g., blue phase I, blue phase II, and blue phase III), stabilizing the desired phase by imprinting a polymer network, and removing the liquid crystal molecules.
  • a desired phase e.g., blue phase I, blue phase II, and blue phase III
  • FIG. 1a includes phase diagrams for some of the compositions of Example 4. From left to right, the reactive monomer concentrations are 30 wt%, 20 wt%, and 10 wt%. The lower temperature star and the higher temperature star indicate the temperatures at which the images were taken for blue phase III and isotropic phase in FIG. 1b, respectively.
  • FIG. 1 b includes transmission polarizing optical micrographs of blue phase III and isotropic phase (scale bar, 500 pm). The brightness of images increases by 80%.
  • FIG. 1c includes graphs illustrating the intensity of light leakage with respect to a comparing blue phase III to isotropic phase. The curves are fitted to discrete measurement points. Error bars were obtained from the experimental standard deviation of 10 repeated measurements.
  • FIG. 2b and c illustrate reflectance of before and after stabilization, respectively, of sample 2 with respect to temperature and wavelength. The inset in FIG. 2b shows the peak wavelength of reflectance in blue phase I with respect to temperature.
  • FIG. 2d and e illustrate optical rotatory power with respect to temperature for before and after stabilization, respectively. Error bars were obtained from the experimental standard deviation of repeated 10 measurements.
  • FIG. 2 f-h are confocal laser scanning micrographs of stabilized blue phase III: sample 2 (inset scale bar, 5 pm), stabilized isotropic phase: sample 5, and stabilized blue phase I: sample 6 (scale bar, 15 pm), respectively.
  • FIG. 3a-c are confocal laser scanning micrographs of polymer molds fabricated by blue phase III: sample 2, isotropic phase: sample 5 and blue phase I: sample 6, respectively (scale bars, 15 pm).
  • FIG. 3d includes scanning electron micrographs of polymer molds fabricated by blue phase III (scale bars, 500 nm).
  • FIG. 3f, h, and j are light scattering images (scale bars, 1 cm) of polymer molds fabricated by blue phase III (FIG. 3e and f), isotropic phase (FIG. 3g and h) and blue phase I (FIG. 3i and j).
  • the light scattering images were taken in a dark room with halogen light source, and polymer molds are sandwiched by glass substrates.
  • FIG. 4a and b are polarizing optical micrographs of blue phase III.
  • FIG. 4d and e are polarizing opitical micrographs of isotropic phase.
  • Micrographs of original stabilized phases (FIG. 4a and d) and achiral liquid crystals refilled phases (FIG. 4b and e) are included (scale bars, 500 pm)
  • FIG. 4c and f illustrate optical rotatory power with respect to temperature for refilled into the polymer molds of blue phase III (FIG. 4c) and isotropic phase (FIG. 4f).
  • FIG. 4g-i are confocal laser scanning micrographs of the refilled phases, which are fabricated by blue phase III (FIG. 4g): sample 2, isotropic phase (FIG. 4h): sample 5 and blue phase I (FIG. 4i): sample 6 (scale bars, 15 pm).
  • FIG. 5a-c are confocal laser scanning microscope images of scaffolds derived from blue phase III, the isotropic phase, and blue phase I. Scale bars are 15 pm for the complete images and 3 pm for the enlarged regions.
  • FIG. 5d and e are scanning electron microscope images of scaffolds derived from blue phase III and the isotropic phase.
  • the term “comprising” may include the embodiments “consisting of” and “consisting essentially of.”
  • the terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases that require the presence of the named ingredients/steps and permit the presence of other ingredients/steps.
  • compositions, mixtures, or processes as “consisting of” and “consisting essentially of” the enumerated ingredients/steps, which allows the presence of only the named ingredients/steps, along with any impurities that might result therefrom, and excludes other ingredients/steps.
  • approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially,” may not be limited to the precise value specified, in some cases.
  • the modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 2 to about 4" also discloses the range “from 2 to 4.”
  • the term “about” may refer to plus or minus 10% of the indicated number. For example, “about 10%” may indicate a range of 9% to 1 1 %, and “about 1 " may mean from 0.9-1.1.
  • each intervening number there between with the same degree of precision is explicitly contemplated.
  • the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the number 6.0, 6.1 , 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated.
  • the blue phase III of liquid crystals (e.g., cholesteric liquid crystals) is useful for a wide range of electro-optical applications due to its sub-millisecond switching time and no Bragg reflection in the visible spectrum.
  • the double-twisted cylinders formed by liquid crystal molecules in the blue phase I and blue phase II cannot continuously occupy three-dimensional space and, therefore, need to be stabilized by a lattice of topological defects, known as disclinations.
  • the polymer-stabilized blue phase III mode devices of the present disclosure may exhibit blue phase III over a wide temperature range (e.g., greater than 60 K or greater than 80 K), enhanced dark state level (e.g., by an order of magnitude), and less hysteresis than polymer-stabilized blue phase I devices.
  • the monomer and chiral dopant and their amounts are selected to have a chirality that approaches the length of a pitch (e.g., less than about 500 nm for cubic blue phases and less than about 200 nm for amorphous blue phase).
  • the polymer-stabilized blue phase III composites of the present disclosure can exhibit enhanced dark state and hysteresis-free performance relative to a polymer- stabilized blue phase I mode device. Without wishing to be bound by theory, it is believed that these benefits can be achieved due to the random structure of disclination line in blue phase III and no asymmetry in ascending and descending applied voltage when switching.
  • the lattice structure standing in different orientation of multiple domains causes inconsistency in its electro-optical response.
  • the periodicity of the structure in blue phase I implies selective Bragg diffraction, reflection, and/or scattering and the color appearance inhibits perfection of the dark state at a certain wavelength range when the electric field is free.
  • the enhanced dark state of polymer-stabilized blue phase III was quantified as -1 order of magnitude than polymer-stabilized blue phase I and the reflectance of polymer-stabilized blue phase III demonstrates almost flat wavelength dependence with low level reflectivity.
  • the polymer-stabilized blue phase III composites of the present disclosure show significantly enhanced stability, hysteresis, and dark states properties.
  • a cell fabricated in accordance with some embodiments of the present disclosure has been kept stable (for 2 months) and never went bad with -1 order of magnitude level of the dark state compared to polymer-stabilized blue phase I as well as almost no hysteresis. These features can be applied to fast-switching liquid crystal displays.
  • the temperature range of blue phases is only a few K between chiral nematic (N*) and isotropic (Iso) phases.
  • N* chiral nematic
  • Iso isotropic
  • texture generally cannot be observed due to the random structure that is optically isotropic.
  • Blue phases are optically isotropic states.
  • An applied electric field can induce birefringence whose optic axis will be along the direction of the applied electric field.
  • ⁇ is the angle between the optic axis of induced birefringence and one of the crossed polarizers.
  • the detected light intensity can be given as
  • Hysteresis may be defined by the following equation
  • E p denotes electric fields at peak intensity
  • E asc denotes half of the peak during ascending electric field
  • E de s denotes half of the peak during descending electric field.
  • the polymer molding in accordance with some embodiments of the present disclosure may position the location of disclinations in blue phase III, memorize the anchoring information at nano-scale, and reveal the difference in correlation length of different blue phases.
  • One of the most convenient ways to recognize liquid crystalline phases is texture identification using a polarizing optical microscopy.
  • the periodicity of cubic-type blue phases shows platelet or mosaic type textures from the Bragg scattering, and the appeared color is similar for a consistent chiral pitch.
  • a as a constant including Boltzmann constant, ⁇ ⁇ 50 as transition temperature between blue phase and isotropic phase, T as temperature near ⁇ ⁇ 50 , ⁇ as interfacial tension between isotropic core and elastic continuum, R max as the cut-off radius of elastic continuum that is co-axial to the disclination, K as the simplified Frank elastic constant considering the splay K-n , twist K22 and bend K 33 distortion of the director between R c and R max , and K 24 is the saddle-splay elastic constant.
  • the 1 st term describes the free energy cost maintaining the disclination core below ⁇ ⁇ 50 at T.
  • the 2nd term arises for an interfacial energy between the core and elastic continuum.
  • the 3rd term is the elastic free energy of elastic continuum that is specified by the radial distance from R c and R max .
  • the last term only with negative sign, describes the interfacial elastic free energy of elastic continuum at R c in face with disclination, which is against the other terms in F d i S c- Because blue phases include large interfacial area associated with disclination, so that the last term, sum of twist and saddle-splay elastic energy, cannot be neglected.
  • the non-mesogenic monomer rather exists in isotropic region due to the miscibility (entropy-driven phase separation).
  • the polymerization of the non-mesogenic monomer mainly occurs in disclinations and RM may be polymerized closer to liquid crystals up to a certain local order parameter that still does not interfere with the existence of blue phases as Landau-de Gennes theory describes the gradual change in the local order parameter in blue phases.
  • the free energy description of stabilized blue phases may need to be revised as: 1 ) the 1 st term is removed; 2) interfacial free energy in the 2nd term is replaced as between the elastic continuum and polymer mold; 3) the interfacial elastic free energy is maximized as the polymer is replaced at core so that R c becomes R p0 i y (R p0 i y » R c ); 4) and added to the description of an interaction energy between polymer and elastic continuum that demonstrates anchoring of 3D morphology.
  • the formula is simplified, but describes phenomenological polymer stabilization of the disclinations in blue phases.
  • the free energy after stabilization is reduced due to the absence of the 1 st term; the additional free energy cost is from the change in chiral pitch dependent upon temperature.
  • the phase-stability may undermine where free energy becomes positive by increase in the 2nd and 4th terms.
  • the polymer casting approach in accordance with some embodiments of the present disclosure enables wide exploration of frustrated phases [not limited to blue phases] to directly visualize the complexity of three-dimensional topology at nanoscale.
  • the achromatic dark state of stabilized blue phase III enables a high contrast ratio and symmetric optical property from all viewing angles in response to external electric fields, thereby permitting the development of advanced electro-optical devices that have not been possible.
  • a polymer scaffold that imitates the complex three- dimensional nanostructure of blue phase III by forming a reactive mesogen polymer network along topological defects in blue phase III.
  • the polymer replica of blue phase III enables the first direct and conclusive morphological observation of the amorphous structure of blue phase III.
  • the nanostructured scaffold of blue phase III may be used as a reusable electro-optical device that retains the blue phase III ordering, chirality, optical isotropy, and sub-millisecond electro-optical switching characteristics (i.e., EO-memory) of the blue phase III even after removal of the cholesteric blue phase liquid crystal and subsequent refilling with different liquid crystals (e.g., nematic liquid crystals).
  • the polymer scaffold induces three-dimensional blue phase III ordering into nematic liquid crystals that cannot display blue phase III by themselves.
  • the EO-memory scaffolds may be formed by a process that includes forming a blue phase mixture, selecting a desired phase (e.g., blue phase I, blue phase II, blue phase III, or isotropic phase), stabilizing the phase by imprinting a polymer network (e.g., via photopolymerization of reactive mesogen monomers), and removing the liquid crystal molecules (e.g., by solvent extraction).
  • a desired phase e.g., blue phase I, blue phase II, blue phase III, or isotropic phase
  • stabilizing the phase by imprinting a polymer network (e.g., via photopolymerization of reactive mesogen monomers), and removing the liquid crystal molecules (e.g., by solvent extraction).
  • blue phase III can be distinguished from the isotropic phase due to its optical activity which results in the observation of different colors (brownish and bluish-gray) when the analyzer is rotated slightly (e.g., 3-4°) to the left or right, that is, when the value of the deviation angle ⁇ is positive or negative.
  • This color difference and the bluish-gray color at negative values of ⁇ may become more prominent in the polymer stabilized blue phase III, more so when the temperature of polymer-stabilized blue phase III is lowered closer towards room temperature.
  • UV ultraviolet
  • the Bragg peak was clearly observed in a range between about 410 and about 440 nm for blue phase I.
  • the periodicity of the structure in blue phase I implied selective Bragg diffraction, reflection, or scattering, and the color appearance inhibited the perfection of the dark state at certain wavelength when the electric field was free. No such peak and a low level of reflectance over the entire visible wavelength range were observed for blue phase III. Because of the dark state whose level is less than that of polymer stabilized blue phase I (e.g., by -1 order of magnitude), polymer stabilized blue phase III can enhance electro-optic performance (e.g., contrast ratio, color generation, and viewing angle properties).
  • the response time of electro-optic performance of the polymer stabilized blue phase III device was also found to be less than one millisecond.
  • the measured response time is subject to switching between 10% and 90% of transmittance by applying 185 V, resulting in 0.04 ms for the rise and 0.27 ms for the decay.
  • a glass substrate was deposited by indium-tin-oxide and patterned to have interdigitated electrodes to apply an in-plane electric field, and then assembled to a plane glass substrate using ultraviolet curable adhesive (Noland, NOA65), which was mixed with 10 m spherical spacers for a uniform cell gap.
  • Noland, NOA65 ultraviolet curable adhesive
  • the reactive monomers in the composite were photopolymerized at designated temperatures using collimated ultraviolet light (Uvata, spot UV LED) with irradiance of 0.8 mW/cm 2 at 365 nm while the phases were monitored by a polarizing optical microscope (Nikon Corp.). Photographs of the cells were taken with a digital camera. [0065] Photomicrographs were automatically acquired while temperature was ramped up and down for verification of the phase sequence. Cubic blue phases were examined by textures. Blue phase III was distinguished from isotropic phase by observing optical activity in blue phase III. The optical activity in blue phase III was confirmed by photomicrographs taken at a few degrees of positive and negative deviation angles between an analyzer and a polarizer. The reflection spectra were measured by a spectrometer (Ocean Optics, USB2000+) from a collimated tungsten halogen light source (Ocean Optics, LS-1 ) after photopolymerization.
  • a spectrometer Ocean Optics, USB2000
  • a thin top glass substrates ( ⁇ 100 pm) was assembled onto the substrate with the interdigitated electrodes to satisfy the working distance of an objective lens with magnification.
  • the deviation at positive and negative angles contributes differently to corresponding wavelength ranges.
  • the stabilized phases were well maintained over 80 °C (the range of the stabilized blue phase III was from below 0 °C to 87 °C).
  • the photos of the cells and the micrographs showed similar dark states for blue phase III and the isotropic phase, whereas blue phase I exhibited light leakage corresponding to Bragg diffraction.
  • the reflection spectra of the stabilized blue phase III and isotropic phase revealed similar behaviors but slightly higher reflectance was observed for the stabilized blue phase III than that of the isotropic phase near short-wavelength range, whereas a peak or seemingly overlapped peaks were measured in the stabilized blue phase I.
  • the blue phase III cell was switched from the dark state to the bright state and back to the dark state.
  • the corresponding photomicrographs of the switching behavior showed excellent optical contrast between the field-off and field-on states.
  • the on-state photomicrograph showed a large field-induced birefringence in between the electrodes and the stripes indicating that no electric field contributed to the induced birefringence on the center of the electrodes.
  • the electro-optical behaviors of the stabilized cells were investigated with transmittance versus applied electric fields curves with red (e.g., 633 nm), green (e.g., 514 nm), and blue (e.g., 460 nm) light sources for blue phase III, isotropic phase, and blue phase I.
  • the measured hysteresis H with RGB light sources was minimum for the stabilized blue phase III (R: 0.5%, G: 0.5%, B: 2.2%) but significant for the stabilized isotropic phase (R: 6.0%, G: 8.8%, B: 1 1 .3%) and relatively less significant for the stabilized blue phase I (R: 5.9%, G: 3.7%, B: 4.2%).
  • the polymer network actually imitates the disclinations of blue phase III. Consequently, polymerization occurs around disclinations in blue phase III.
  • isotropic phase the short-range reflection is relatively uniform although the overall topology is similar to that of the stabilized blue phase III.
  • phase separation occurs in the isotropic phase.
  • the entropy-driven randomness guides the polymer network growing bulky, and liquid crystals are confined in a pore-type space such as the polymer-dispersed liquid crystal. In the center region of the pore, liquid crystal molecules are not anchored strongly enough to memorize their original orientations due to relatively low anchoring strength.
  • the analysis supports the idea that residual light leakage is generated in the isotropic phase.
  • the topology revealed grains with boundaries and each grain has a periodic lattice structure.
  • the periodic lattices were deformed under the applied electric field (i.e., electrostriction effect took place). After applying the electric field, the topological deformation in the periodic undulations remained.
  • the isotropic phase showed no color due to the symmetry.
  • Cubic blue phases also implied an optically isotropic state owing to the cubic symmetry, but colorful platelet and/or mosaic type textures were observed because of Bragg reflection.
  • the symmetry of blue phase III was similar to that of the isotropic phase and had neither long-range order nor structural periodicity.
  • the different localized reflection may result from surface roughness and may imply a structural and topological difference between the stabilized blue phase III and the isotropic phase.
  • the degree of hysteresis upon the applied electric fields in the stabilized blue phase III and isotropic phase tends to be higher at short wavelengths, which is consistent with the Kerr effect. However, the opposite tendency was found for the stabilized blue phase I. Without wishing to be bound by theory, it is believed that the electrostriction effect and/or complex topology contribute to the electric switching as well. As the lattice is elongated along the electric field, which is perpendicular to the direction of light traveling, the wavelength range corresponding to transmittance shifts to long wavelength range.
  • the saturation electric field of the stabilized blue phase III was approximately 1 .68 and 1 .09 times greater than that of the stabilized isotropic phase and blue phase I, respectively.
  • the stabilized blue phase III achieved excellent achromatic dark state, 17.9 and 7.6 times less hysteresis at a wavelength of 514 nm, and 81.4 and 8.7 times faster response time than that of the stabilized isotropic phase and blue phase I, respectively.
  • FIG. 1a shows the phase diagrams for variations of RM concentration with respect to the chiral dopant concentration. Because of mesogenic characteristics of RM, the similar chiral dopant concentration exhibited different chirality depending on the amount of RM, which makes the entire diagram shift along the axis of chiral fraction. For example, blue phase III appears at a relatively lower chiral fraction as well as at a smaller amount of RM in the composite as shown in FIG. 1a.
  • chirality is denoted by ⁇ and relative chirality is denoted by ⁇ ' without and with counting RM for mesogenic contribution, respectively.
  • blue phase III begins to appear at temperature ranges of 353.7 - 356.8 K, 348.9 - 352.5 K, and 343.2 - 348.8 K for the sample 2, 3 and 4, respectively.
  • those chiral dopant concentrations of three samples by counting the amount of RM as a mesogen can be transferred to reveal ⁇ 4.5 wt%, that gives rise to ⁇ ' approximately 5.1 pm ⁇ 1 .
  • the liquid crystal material (HTG 135200-100, HCCH) was mixed with a chiral dopant (R501 1 , HCCH), and reactive monomers mixture consisting of a mesogenic diacrylate monomer (RM257, Merck) and Bisphenol A dimethacylate (Aldrich) to verify the phase sequence for the phase diagram in various concentrations.
  • a small quantity of photo-initiator, 2,2-Dimethoxy-1 ,2- diphenylethan-1 -one (Irgacure 651 , Aldrich) was mixed in the reactive monomer and liquid crystal solution.
  • NOA65 ultraviolet curable adhesive
  • a polarizing optical microscope (Nikon) was used to acquire polarizing optical micrographs for observing textures of chiral nematic phase and blue phases with a hot stage and calibrated temperature controller (Instec) in an accuracy of ⁇ 0.1 K.
  • the optical rotatory power was measured by spatial mean brightness (gray-scale) of polarizing optical micrographs at various deviation angles of analyzer a with a halogen lamp as a light source.
  • the spatial mean brightness was batch-measured by open software (Image J).
  • the reflection spectrum was measured by a spectrometer (USB2000+, Ocean Optics) with a halogen lamp as the light source.
  • the spectrometer is calibrated with standard bright (mirror) and dark (velvet cloth) states.
  • the samples were exposed to ultraviolet light (spot UV LED, Uvata) with irradiance of 0.8 mW/cm 2 , 365 nm at designated phases.
  • the dosage of ultraviolet exposure was carefully retained at sufficiently low intensity as not to disturb or destroy the equilibrium state while observing the textures by a polarizing optical microscope in situ.
  • a thin top glass substrate ( ⁇ 100 pm) was assembled to refer to the distance between an objective lens to blue phase layer for the observation by a confocal laser scanning microscope (LEXT OLS3100, Olympus).
  • a summary table including information about the chemical compositions, photo- polymerization temperatures, and extended temperature ranges of the stabilized phases for 8 samples is provided below.
  • the weight percentages refer to the weight of each constituent to the weight of the liquid crystal.
  • T pho to and T ex t denote photo-polymerization temperature and extended temperature range of the stabilized phase, respectively.
  • chirality was estimated by assuming a helical twisting power of 1 15 pm "1 for R501 1 and 50 pm "1 for ISO- (60BA) 2 at fixed temperature without counting RM257 as a mesogen. Samples 1 and 8 were prepared using chiral dopant ISO-(60BA) 2 .
  • 1c shows the intensity variation as a function of a.
  • the sign of a at the minimum intensity, where the slope of curves is zero is positive for blue phase III in opposition to isotropic phase, which manifests the appearance of blue phase III below the isotropic phase.
  • reflectance of sample 2 demonstrated the difference in phase- behavior of before and after photo-polymerization.
  • the selective reflectance peak shows the temperature range of blue phase I, and the inset in FIG. 2b specifies the peak range approximately from 424 to 456 nm.
  • the reflectance of blue phase III demonstrates no verification even though the reflectance after photo-polymerization shows disappearance of selective peaks in the phase-behavior as shown in FIG. 2c.
  • FIG. 2d and 2e compare the optical rotary power before and after photo- polymerization, respectively.
  • the magnitude of optical rotatory power jumps at the transition from blue phase III to blue phase I due to the transition in the structure, but gradually changes between isotropic phase and blue phase III.
  • the transition is associated with the coexistence of isotropic phase and blue phase III.
  • this phenomenon is not observed for the stabilized blue phase III seemingly because of the interaction between the polymer mold and liquid crystal molecules (FIG. 2e).
  • the optical rotatory power of stabilized blue phase III shows almost linear dependence on temperature below the abrupt transition from isotropic phase.
  • the slopes of linear fit for both before and after stabilization are approximately -4.07 and - 2.13, respectively, which implies that the optical rotatory power after stabilization is in association of not only liquid crystals but also the coexistence of a polymer mold.
  • the behavior of optical rotation below the temperature range of blue phase III may be in different regimes with the polymer mold because of the interaction of liquid crystals and polymer, i.e., the dependence of chiral pitch with respect to temperature can be interfered by the interaction.
  • CLSM can provide topological surface information rather than polarizing optical information.
  • the CLSM observation gives direct imaging of the surface of stabilized sample 2, 5 and 6 for blue phase III, isotropic phase and blue phase I as shown in FIG. 2f, FIG. 2g, and FIG. 2h, respectively, blue phase I shows mosaic texture at room temperature.
  • the periodicity of blue phase I is clearly visualized at some domains in FIG. 2h.
  • the surface of blue phase III shows localized tendency of periodic undulations from chirality as shown in insets of FIG. 2f.
  • Further observations of CLSM images are shown in FIG. 3a-c for polymer mold after evacuating chiral liquid crystal mixture, and in FIG. 4g-i for the surface of stabilized phases after refilling achiral liquid crystals.
  • the shorter correlation length in blue phase III implies that the shorter pitch in blue phase III gives rise to the amorphous entanglement of disclinations, which ends up with melting into the isotropic phase.
  • the lattice in blue phase I seems to locally twist and squeeze so that the series of singularity, i.e., disclination line may be curved and entangled, as it is in a melted state.
  • the SEM images of the polymer molds successfully visualize the 3D entanglement of disclinations in blue phase III, and the visualized result of SEM images are in good agreement with the visualization of blue phase III by a theoretical model.
  • CLSM images after refilling achiral liquid crystals show the surface of rebuilt phases in FIG. 4g,h,i for blue phase III (sample 2), isotropic phase (sample 5) and blue phase I (sample 6), respectively.
  • FIG. 4g no local undulation is observed unlike in FIG. 4f due to achirality of host liquid crystals.
  • FIG. 4i shows the domain of blue phase I with the texture as well as in FIG. 2h.
  • a blue phase mixture was formed.
  • the mixture contained 4.41 wt% of a chiral additive (R501 1 , Merck), 19.88 wt% of a mesogenic diacrylate monomer (RM257, Merck), 2.09 wt% of a difunctional acrylate monomer (bisphenol A dimethacrylate, Sigma-Aldrich), 0.08 wt% of a photoinitiator (Irgacure 651 , Sigma-Aldrich), and 73.54 wt% of a nematic mixture (HTG135200-100, HCCH).
  • In-plane switching cells were made by depositing indium-tin-oxide on a glass substrate in an interdigitated electrode (indium tin oxide) pattern. The patterning was performed using photolithography in a cleanroom environment. The patterned substrate was assembled onto a plain glass substrate using UV-curable adhesive (NOA 68, Norland) mixed with 5 pm spherical spacers for a uniform cell gap.
  • UV-curable adhesive NOA 68, Norland
  • the cells were exposed to UV light from a collimated UV light emitting diode (Uvata Precision Optoelectronics) with an intensity of 1 .5 mW/cm 2 for 30 minutes at 80.4 °C for polymer-stabilized blue phase I, 82.6 °C for polymer-stabilized blue phase III, and 91 °C for polymer-stabilized isotropic phase in order to polymerize the reactive mesogens.
  • the cells were immersed in a 70:30 v/v solution of hexane and dichloromethane for 48 hours to remove the cholesteric liquid crystal. The solvent was refreshed after 24 hours.
  • the scaffolds were refilled by capillary injecting a nematic mixture (HTG135200-100, HCCH), which was washed out using the above procedure and later refilled with 4-cyano-4'-pentylbiphenyl (5CB, HCCH).
  • HTG135200-100 HCCH
  • HCCH 4-cyano-4'-pentylbiphenyl
  • the cells were kept at an elevated temperature (100 °C for refilling HTG and 50 °C for refilling 5CB) on a hot stage overnight. After refilling, the cells were kept at room temperature for at least 24 hours before characterization.
  • Cells were placed between crossed polarizers (a fixed polarizer and a freely rotating analyzer) such that the direction of the applied electric field was maintained at an angle of 45° to the optical axes of the polarizers.
  • the cells were driven by an AC electric field (rectangular pulses) with amplitude 40 V/pm and frequency 1 kHz.
  • the transmitted light intensity was recorded as a function of time during the switch-on and switch-off processes and the characteristic response time was defined as the time taken to switch between 10% and 90% of the maximum transmittance. All measurements were performed at 20 °C. Photographic images of cells in the field-off and field-on state were taken using the digital camera of a mobile phone, while the cells were placed between crossed polarizers against a white backlight. Photomicrographs of the cells in the field-off and field-on state were taken using a polarizing optical microscope (Nikon).
  • blue phase I was easy to identify due to its characteristic blue platelet texture and selective Bragg reflection.
  • the amorphous structure of blue phase III exhibited an optically isotropic symmetry with no Bragg reflection in the visible spectrum. This means that no birefringent textures can be observed in POM and it is difficult to distinguish blue phase III from the isotropic phase between crossed polarizers.
  • Blue phases are optically active and rotate the optic axis of linearly polarized light as it passes through them. This attribute of blue phases allows blue phase III to be distinguished from the isotropic phase.
  • polymer-stabilized blue phase III shows a perfect dark state with no birefringence and appears identical to the isotropic phase.
  • the deviation at positive and negative values of ⁇ contributes differently to corresponding wavelength ranges.
  • the polymer-stabilized isotropic phase however, lacks optical activity and hence, shows identically colored brownish textures at positive and negative values of ⁇ .
  • the optical rotary power was measured by the spatial mean brightness (a gray intensity in pixels) of POM images.
  • the spatial mean brightness was batch measured using the Jay-based image processing program ImageJ.
  • a blue phase liquid crystal film was prepared on a copper grid using a mixture containing 55 wt% of a nematic liquid crystal (LC BL 006, Merck) and 45 wt% of a chiral dopant (R81 1 , Merck).
  • LC BL 006, Merck nematic liquid crystal
  • R81 1 chiral dopant
  • FIG. 5a-c are confocal laser scanning microscope images of scaffolds derived from blue phase III, the isotropic phase, and blue phase I. Scale bars are 15 pm for the complete images and 3 pm for the enlarged regions.
  • FIG. 5d and e are scanning electron microscope images of scaffolds derived from blue phase III and the isotropic phase. Scale bars are 500 nm. Due to the brittle nature of the blue phase I scaffold, it is difficult to perform SEM imaging without damaging the sample. Thus, only CLSM was used.
  • the cholesteric liquid crystals were washed out to obtain the porous polymer scaffolds.
  • the scaffolds were refilled with HTG without chiral dopant.
  • the HTG nematic mixture had a clearing temperature of 97 °C, is achiral, and does not form blue phases by itself.
  • the HTG-refilled scaffolds were subjected to the same POM and EO characterization as the original stabilized phases.
  • 4-cyano-4'-pentylbuphenyl 5CB
  • polymer scaffolds nano-engineered from blue phase III may also be as chirality-induction agents.
  • the refilled blue phase Ill-mimicking scaffolds displayed a lack of Bragg reflection peaks in the visible spectrum and hence, an achromatic dark state similar to the original polymer- stabilized blue phase III. This characteristic is particularly useful in display applications, where the device should be clear in the visible spectral region.
  • nematic LCs were refilled in scaffolds derived from the isotropic phase, they also display textures similar to the original polymer-stabilized isotropic phase, that is, perfectly dark between crossed polarizers and brownish at both positive and negative deviation angles, with no indication of optical activity.
  • EO merit parameters such as the driving electric field and switch-on ( ⁇ ⁇ ) and switch-off (T 0 ff) response times of the original stabilized phases, were compared with those of the EO-memory scaffolds after refilling with HTG and 5CB.
  • the transmitted light intensity of cells was plotted as a function of the applied electric field to estimate the driving electric field of the original stabilized phases and refilled scaffolds.
  • the EO response times for the rise (switch-on) and decay (switch-off) processes were determined by using a photodiode detector to measure the electric field-induced change in transmitted light intensity through cells placed between crossed polarizers.
  • the response time is defined as the time taken by the cell to switch between 10% and 90 % of the maximum transmittance.
  • Photographic images and POM images of the cells were taken in the field-off and field-on states for visual observation of EO switching.
  • the EO behavior of the original stabilized phases and the refilled scaffolds follows the Kerr effect, which is a non-linear, second-order EO effect wherein, an applied electric field induces a birefringence in a medium that is optically isotropic in zero electric field.
  • the driving electric field was ⁇ 40 V/pm for all original phases and their respective refilled scaffolds.
  • the transmittance-electric field curves of the original polymer-stabilized blue phase III and its corresponding scaffold after refilling with HTG and 5CB are almost overlapping, underlining the EO-memory effect of the scaffolds.
  • Both switch-on and switch-off times of polymer-stabilized blue phase III, polymer-stabilized isotropic phase and polymer-stabilized blue phase I are shorter than 0.2 ms and remain in the sub- millisecond range ( ⁇ ⁇ ⁇ 0.1 ms, T 0 ff ⁇ 0.5 ms) after refilling the corresponding scaffolds with HTG and 5CB.
  • the comparable sub-millisecond switching times of the original stabilized phases and their respective refilled scaffolds successfully demonstrate the EO-memory effect of the scaffolds.
  • the switch-on times of the refilled scaffolds were much shorter than those of the original stabilized phases from which they are nano-engineered and follow the order: T on (5CB-refilled scaffold) ⁇ T on (HTG-refilled scaffold) ⁇ T on (original stabilized phase).
  • the 5CB-refilled scaffolds show switch-on times of only a few tens of microseconds, which is shorter than the response times of previously reported in- plane switching-driven polymer-stabilized blue phases ( ⁇ 0.5 ms) and blue phase- templated nematics ( ⁇ 0.1 ms).
  • the res onse time is given by
  • ⁇ is the rotational viscosity of the system
  • P is the pitch length of the cholesteric liquid crystal
  • k is the elastic constant.
  • the rotational viscosity is dependent upon the viscosity of the host LC, which in this case was HTG mixed with chiral dopant for the original stabilized phases and either HTG or 5CB without chiral dopant for the refilled scaffolds.
  • the viscosity of HTG in the original stabilized phases is even higher since it is mixed with a chiral dopant.
  • the viscosity of 5CB (0.082 Pa s) is an order of magnitude lower than that of HTG, since 5CB is a smaller molecule with no bulky, polar groups. While the balance of several properties is required for optimum EO performance, a low viscosity LC is usually favorable from the response time viewpoint. As a result, the shortest switch-on times are achieved in scaffolds containing the lowest viscosity LC.
  • the transition temperature is accurately determined, one can safely assume (for the blue phase mixture) that the system will be in the blue phase III phase for at least a 1 -1 .5 °C below the identified blue phase lll-isotropic transition temperature.
  • the mixture can then be photopolymerized at a temperature that is about 1 °C below the identified blue phase lll- isotropic transition temperature.
  • a disturbance appears in the texture at 83.6 °C. This disturbance can be described as whitish ripples or flashes (for lack of a better word) against the brownish-orange background.
  • These ripples/flashes indicate the blue phase III to isotropic transition. The ripples/flashes grow till 84.6 °C and then start receding.

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Abstract

L'invention concerne un composite qui comporte d'environ 10 % en poids à environ 40 % en poids d'un polymère; un dopant chiral ayant un pouvoir de torsion hélicoïdale d'au moins environ 100 µm-1; et un composé à cristaux liquides ayant une anisotropie diélectrique d'au moins environ +40. Le composite présente une phase bleue III.
PCT/US2016/048525 2015-08-25 2016-08-25 Composite présentant une phase bleue iii et une mémoire électro-optique d'un échafaudage Ceased WO2017035291A1 (fr)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018206524A1 (fr) * 2017-05-11 2018-11-15 Merck Patent Gmbh Procédé de fabrication d'un affichage à cristaux liquides stabilisé par polymère
WO2020180922A1 (fr) * 2019-03-04 2020-09-10 The Trustees Of The University Of Pennsylvania Programmation de symétries émergentes avec élasticité d'énergie libre de distorsion
WO2022164971A1 (fr) * 2021-01-29 2022-08-04 Ohio State Innovation Foundation Surfaces poreuses imprégnées de cristaux liquides et leurs procédés de fabrication et d'utilisation

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102443402A (zh) * 2011-10-27 2012-05-09 北京科技大学 一种宽温蓝相液晶复合材料的制备方法
WO2014053204A1 (fr) * 2012-10-02 2014-04-10 Merck Patent Gmbh Milieu à cristaux liquides et affichage à cristaux liquides
WO2014210165A2 (fr) * 2013-06-25 2014-12-31 Kent State University Film de cristaux liquides de phase bleue dispersés dans un polymère
CN103361080B (zh) * 2013-07-12 2015-07-01 石家庄诚志永华显示材料有限公司 一种蓝相液晶组合物

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102443402A (zh) * 2011-10-27 2012-05-09 北京科技大学 一种宽温蓝相液晶复合材料的制备方法
WO2014053204A1 (fr) * 2012-10-02 2014-04-10 Merck Patent Gmbh Milieu à cristaux liquides et affichage à cristaux liquides
WO2014210165A2 (fr) * 2013-06-25 2014-12-31 Kent State University Film de cristaux liquides de phase bleue dispersés dans un polymère
CN103361080B (zh) * 2013-07-12 2015-07-01 石家庄诚志永华显示材料有限公司 一种蓝相液晶组合物

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018206524A1 (fr) * 2017-05-11 2018-11-15 Merck Patent Gmbh Procédé de fabrication d'un affichage à cristaux liquides stabilisé par polymère
CN110612476A (zh) * 2017-05-11 2019-12-24 默克专利股份有限公司 经聚合物稳定的液晶显示器的制造方法
WO2020180922A1 (fr) * 2019-03-04 2020-09-10 The Trustees Of The University Of Pennsylvania Programmation de symétries émergentes avec élasticité d'énergie libre de distorsion
US12038667B2 (en) 2019-03-04 2024-07-16 The Trustees Of The University Of Pennsylvania Programming emergent symmetries with saddle-splay elasticity
WO2022164971A1 (fr) * 2021-01-29 2022-08-04 Ohio State Innovation Foundation Surfaces poreuses imprégnées de cristaux liquides et leurs procédés de fabrication et d'utilisation

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