Improvement of the diffraction properties in holographic polymer dispersed liquid crystal bragg gratings

Liu, Yanjun; Zhang, Bin; Yu, Jie-Ping; Xu, Kang

doi:10.1016/s0030-4018(03)01171-4

Cited by 70 publications

(38 citation statements)

References 8 publications

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“…[25][26][27][28] In case of TMPTA, considerably high concentration was used. Mono-functional NVP adjusts the initial polymerization rate and final conversion of acrylate functional groups by lowering the concentration of cross-linkable double bonds.…”

Section: -10mentioning

confidence: 99%

Formation of Stable Holographic Polymer Dispersed Liquid Crystal Grating with High Diffraction Efficiency Assisted by in situ Hydrolysis-Condensation of Trialkoxysilylalkyl Group of Methacrylate Component

Cho

Suzuki

Kawakami

2007

Polym J

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ABSTRACT:Stable transmission holographic polymer dispersed liquid crystal grating with reasonably high diffraction efficiency (72%, induction period 576 s) could be prepared via radical network formation of trimethylolpropane triacrylate (only 10 wt %, photo-cross-linkable, further diluted with 10 wt % 1-vinyl-2-pyrrolidone) and 3-methacryloxypropyltrimethoxysilane (80 wt %, non cross-linkable by radical polymerization, but cross-linkable by hydrolysiscondensation) in the presence of 35 wt % TL 203 as a liquid crystal, assisted by simultaneous hydrolysis-condensation of trimethoxysilyl group. The hydrolysis-condensation was induced by moisture in reagents and proton species produced from 3, 3 0 -carbonylbis[7 0 -diethylaminocoumarine] as a photo-sensitizer and diphenyliodonium hexafluorophosphate as a photo-initiator. Grating could not be formed for the same system with 3-methacryloxypropyltrimethylsilane (non hydrolyzable and not cross-linkable).Rather decreased efficiency of 3-methacryloxypropyltriethoxysilane system (13% efficiency, 693 s induction period) was remarkably improved to 75% (75 s induction period) by introducing hydrophilic urethane group into the spacer to facilitate easier hydrolysis. The long grating spacing of 0.9 mm indicates very small volume shrinkage. The maximum diffraction efficiency (85%) was observed at 60-70 wt % 3-N-(2-methacryloxyethoxycarbonyl)aminopropyltriethoxysilane, but with a little larger volume shrinkage.Introduction of aminoalcohol group in the spacer could further shorten the induction period to 18 s, but the diffraction efficiency was rather low (20% In recent years, holographic polymer dispersed liquid crystal (HPDLC) systems has attracted much interest due to their unique switching property by electric field to make them applicable to information displays, optical shutters, and information storage media. 1-10Photo-polymerizable materials, typically multi-functional acrylates, have been mostly studied as materials for HPDLC because of their advantages of large refractive index modulation, low cost, and easy fabrication and modification.11-17 However, these HPDLC materials still have significant drawbacks such as volume shrinkage, low reliability, and poor long term stability.Since the performance of HPDLC is governed by the stability of precisely formed periodic polymer rich layer and LC rich layer created by interference of two incident laser beams, control of the formation of polymer matrix and phase separation of LC are very important. [18][19][20][21][22][23][24] The principal role of multi-functional acrylate in grating formation is to make the LC phase-separate by the formation of cross-linked polymer matrix. Control of the rate and density of crosslinking in polymer matrix is one of the most important factors, which determines the size, distribution, and shape of phase-separated LC domains, accordingly the final morphology and performance. In order to obtain clear phase separation of LC from polymer matrix to homogeneous droplets, high cross linking density, but...

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Section: -10mentioning

confidence: 99%

Formation of Stable Holographic Polymer Dispersed Liquid Crystal Grating with High Diffraction Efficiency Assisted by in situ Hydrolysis-Condensation of Trialkoxysilylalkyl Group of Methacrylate Component

Cho

Suzuki

Kawakami

2007

Polym J

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“…Particularly, HPDLCs are expected to be the most promising materials in tunable holographic devices. HPDLC has unique properties due to the incorporation of liquid crystals as materials susceptible to change its refractive index by applying an external electric field [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

A dynamic beam splitter using polymer dispersed liquid crystal materials

et al. 2012

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We build a dynamic beam splitter with a holographic optical element (HOE). The laser light goes through the HOE and a fraction of intensity diffracted and transmitted could be tuned by an electric signal. We use holographic polymer dispersed liquid crystals materials. It is made by holographic recording in which the liquid crystal molecules diffuse to dark zones in the diffraction grating and they can be oriented by means of an electric field. The orientation of the liquid crystal produces a refraction index variation which changes the diffraction efficiency and therefore the grating has a dynamic behavior.

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“…They found that the grating is preceded in time by an isotropic concentration grating, and that the development of the anisotropic grating can be delayed until several seconds after laser exposure. Liu et al (12) investigated the dependence of the diffraction efficiency on different monomers, LC content, exposure energy, and exposure temperature. They optimised fabrication conditions and obtained a highest diffraction efficiency of over 80%.…”

Section: Introductionmentioning

confidence: 99%

Rotation of director during holographic recording in polymer‐dispersed liquid crystals

et al. 2008

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The formation of holographic polymer-dispersed liquid crystals was investigated in detail. The director was found to rotate during holographic recording owing to the change in morphology and migration of liquid crystals. A strongly anisotropic grating was constructed with variable diffraction efficiency that can be controlled by applying an analogue voltage to the nematic liquid crystal. Effects of post-curing on electro-optical properties were also investigated and the switching characteristics were strongly affected by the intermediate layer between the polymer and liquid crystal.

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Improvement of the diffraction properties in holographic polymer dispersed liquid crystal bragg gratings

Cited by 70 publications

References 8 publications

Formation of Stable Holographic Polymer Dispersed Liquid Crystal Grating with High Diffraction Efficiency Assisted by in situ Hydrolysis-Condensation of Trialkoxysilylalkyl Group of Methacrylate Component

Formation of Stable Holographic Polymer Dispersed Liquid Crystal Grating with High Diffraction Efficiency Assisted by in situ Hydrolysis-Condensation of Trialkoxysilylalkyl Group of Methacrylate Component

A dynamic beam splitter using polymer dispersed liquid crystal materials

Rotation of director during holographic recording in polymer‐dispersed liquid crystals

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