Effects of Ultraviolet-Light on Polyimide Films for Liquid Crystal Alignment

1998 ◽  
Vol 508 ◽  
Author(s):  
Shaoqin Gong ◽  
Jerzy Kanicki ◽  
Lan Ma ◽  
John Z. Z. Zhong
Keyword(s):  
Liquid Crystal ◽  
Photoelectron Spectroscopy ◽  
Uv Light ◽  
Polyimide Film ◽  
Polyimide Films ◽  
Film Property ◽  
Uv Illumination ◽  
Angle Measurements ◽  
Property Changes ◽  
Pretilt Angle

AbstractUV-light effects on the polyimide films have been studied by characterizing the film property changes and by measuring the liquid crystal pretilt angle. Infrared, UV-visible and X-ray photoelectron spectroscopy measurements indicate that bond-breaking and oxidation occur during broadband UV-illumination of the film in the air. Free radicals are formed during UV-illumination as evidenced by the analysis of electron spin resonance spectra. Surface tension and polarity are increased after UV-illumination based on the contact angle measurements. While the pretilt angle on the rubbed polyimide film is decreased after nonpolarized UV-illumination, polarized UV-light generates a relatively small pretilt angle on a nonrubbed surface.

Effect of 172-nm UV irradiation on polyimide and its application in surface modification by grafting

2020 ◽  
Vol 32 (7) ◽  
pp. 761-774
Author(s):  
Lopamudra Das ◽  
John C Poutsma ◽  
Michael J Kelley
Keyword(s):  
Uv Irradiation ◽  
Photoelectron Spectroscopy ◽  
Secondary Ion Mass Spectrometry ◽  
Mechanical Stability ◽  
Uv Light ◽  
Force Microscopy ◽  
Angle Measurements ◽  
Wide Range ◽  
Grafting Reactions ◽  
Sample Position

Polyimides (PIs) have a wide range of industrial and scientific applications due to their excellent thermal and mechanical stability and chemical resistance. Their response to ultraviolet (UV) irradiation is of further interest in high-value applications such as spacecraft technology and electronics packaging. In this work, we investigated the effect of 172-nm UV xenon excimer lamp irradiation on samples of pyromellitimido-oxydianiline (PMDA-ODA) commercial films in the absence of oxygen. The average irradiance received at the sample position was 90 mW/cm2, and the total radiation dosage varied from 0 to 64 J/cm2. X-Ray photoelectron spectroscopy, time-of-flight-secondary ion mass spectrometry, atomic force microscopy, and contact angle measurements were used to characterize the effect. Calculated UV-visible spectroscopy absorption spectra were obtained using the ZINDO//B3LYP/3-21G method to give an indication of which orbitals are involved in the transitions near 172 nm. The reactivity of the different UV-treated PI samples toward nitrogen-borne heptafluorodecene vapor was then investigated using the above techniques. Grafting reactions occurred on the surface of the photochemically activated polymer. This study explored the potential for modification of PI surfaces using UV-light-assisted grafting to impart valuable functionalities.

Orientation of Ferroelectric Liquid Crystals by Self-Assembled Bilayer Molecular Assembly

2001 ◽  
Vol 709 ◽  
Author(s):  
Sukhmal C. Jain ◽  
Vivechana Dixit ◽  
Vinod K. Tanwar ◽  
S. M. Shivaprasad
Keyword(s):  
Liquid Crystal ◽  
Indium Tin Oxide ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Uv Light ◽  
Uv Spectroscopy ◽  
Large Change ◽  
Molecular Assembly ◽  
Ferroelectric Liquid Crystal ◽  
Assembly Technique

ABSTRACTMolecular films of amino propyl triethoxy silane (APTES) attached with cinnamoyl moieties were deposited on indium tin oxide (ITO) coated glass and quartz substrates by self-assembly technique. The deposition of the monolayer films resulted in a large change in the wettability of the substrates. X-ray photoelectron spectroscopy (XPS) and UV-spectroscopy were used to study the structure and properties of the grown films. The molecular assembly was photodimerized by irradiating it with a linearly polarized UV-light. Thus created polymer-solid interface has been shown to produce good, stable planar orientation of ferroelectric liquid crystal mixtures. The electro-optical and switching properties of the ferroelectric liquid crystal cells have been investigated and found to be quite similar to those prepared in conventional manner.

scholarly journals P-64: UV-Light-Modified Polyimide Films for Liquid-Crystal Alignment

1998 ◽  
Vol 29 (1) ◽  
pp. 722 ◽  
Author(s):  
S. Gong ◽  
J. Kanicki ◽  
L. Ma ◽  
J. Z. Z. Zhong
Keyword(s):  
Liquid Crystal ◽  
Uv Light ◽  
Polyimide Films ◽  
Liquid Crystal Alignment ◽  
Crystal Alignment

Characterization of Fluorinated Polyimide Films

1992 ◽  
Vol 264 ◽  
Author(s):  
Pradnya V. Nagarkar ◽  
Jiong Ping Lu ◽  
David Volfson ◽  
Klavs F. Jensen ◽  
Stephen D. Senturia
Keyword(s):  
Photoelectron Spectroscopy ◽  
Polyimide Film ◽  
Binding Energies ◽  
Polyimide Films ◽  
Chemical Modifications ◽  
X Ray ◽  
Fluorinated Polyimide ◽  
Peak Assignment ◽  
Good Agreement

Abstract:X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) have been used to characterize the polyimide film based on 4,4′ hexafluoro-isopropylidene -bis pthalic anhydride (HFDA) and 4,4′ -bis (4-aminophenoxy) biphenyl (APBP). Films of varying thicknesses made from diluted precursors were studied by IR and XPS. An elemental analysis and a tentative peak assignment for C 1s in XPS is presented. The HFDA-APBP thick films are stoichiometric in composition and binding energies are in good agreement with data on hexafluorodianhydride-oxydianiline (HFDA-ODA). For thinner films, certain chemical modifications were observed at high cure temperatures.

Anisotropic Reflectivity of Rubbed Polyimide Liquid Crystal Alignment Layer

2010 ◽  
Vol 428-429 ◽  
pp. 309-316
Author(s):  
Wen Jun Zheng
Keyword(s):  
Liquid Crystal ◽  
Optical Anisotropy ◽  
Polyimide Films ◽  
Alignment Layer ◽  
Liquid Crystal Alignment ◽  
Surface Optical ◽  
Crystal Alignment ◽  
Pretilt Angle

The surface optical anisotropy of rubbed polyimide films has been detected using reflection anisotropy spectroscopy. The amplitude of the reflection anisotropy signals increases with the rubbing strength. Rubbing also causes changes in pretilt angle of liquid crystal molecules which are in contact with the rubbed polyimide. An increase in rubbing strength results in an increase in the pretilt angel. The pretilt of the liquid crystal molecules was found to linearly correlate with the amplitude of the RA signals.

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