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The characteristics of ion beam (IB) irradiated polyethylene glycol (PEG) films were analyzed to determine their potential use as a liquid crystal (LC) alignment layer. The transmittance of the PEG films at various IB intensities was measured to verify the possibility of using it as an alignment layer. Anti-parallel cells with the PEG film were fabricated to examine the LC alignment characteristics. Perfectly dark cross-polarized microscopy images were obtained at an intensity of 700 eV, which indicates uniform LC alignment, and pre-tilt angle measurements supported this finding. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyses were conducted to determine the effect of the IB irradiation on the PEG film on the surface modification. After exposure at an IB intensity of 700 eV where uniform LC alignment was achieved, remarkable chemical composition modification of the PEG film, including the reduction of C-O bonds that affected the uniform LC alignment, was observed via the XPS analysis. Furthermore, the AFM analysis revealed that low kurtosis value was obtained at this IB intensity. Therefore, we are convinced that the PEG films irradiated at this low IB intensity show potential as alternative alignment layer in LC applications. [ABSTRACT FROM AUTHOR]

We investigated the surface modification induced by the ion-beam (IB) irradiation of a polyethylene glycol (PEG) film and its liquid crystal (LC) alignment characteristics. The X-ray photoelectron spectroscopy analysis revealed the chemical modification; as the IB incidence angle increased, the number of surface C–O bonds decreased, inducing an anisotropic dipole moment on the PEG film surface. In addition, the physical modification was demonstrated via atomic force microscopy analysis using three-dimensional images as a function of the IB incidence angle. The surface roughness was analyzed; the modification with the smoothest surface was observed for an IB incidence angle of 45°. This modification affected the LC alignment state of the PEG film, as demonstrated by the polarized optical microscopy analysis with pre-tilt angle measurements. Furthermore, for the same IB incidence angle, the residual DC measured using the capacitance–voltage curves was extremely low. Hence, a PEG film irradiated with an IB incidence angle of 45° could be a suitable LC alignment layer. [ABSTRACT FROM AUTHOR]

Abstract Ultra-violet nanoimprint lithography was utilized to transfer a one-dimensional nano pattern onto a hydrophilic ultra-violet cured polymer surface for use in liquid crystal displays. A master mold with the one-dimensional nano pattern was initially constructed using laser interference lithography, which is a fast and maskless process that can be employed over a large area. The UV cured polymer showed a hydrophilic characteristic, and was used as a homogeneous alignment layer. The nano-patterned ultra-violet polymer successfully aligned the liquid crystal molecules without defects. Additionally, the liquid crystal cell was characterized by high thermal stability due to the high thermal endurance of UV cured polymer. Therefore, the proposed ultra-violet nanoimprint lithography technique is beneficial for advanced liquid crystal devices with high brightness and resolution with numerous switching components that require a high thermal cost. Graphical abstract Image 1 Highlights • UV imprinting lithography has the advantages of a large processing capacity, cost-effectiveness, and high thermal endurance. • The master mold created using laser interference lithography has the advantage of maskless and fast patterned processing. • Hydrophilic UV-cured polymer surface allowed the homogeneous alignment of LCs. • The topographic grating of a one-dimensional nanopattern to act as a director for unidirectionally aligning the LCs. • The high thermal endurance of the LC cell based on the UV-cured polymer the nanopattern was achieved up to 180 °C. [ABSTRACT FROM AUTHOR]

Uniform and defect-free homogeneous alignment of liquid crystal (LC) molecules on solution-derived bismuth-doped tin oxide (TBO) films has been achieved using ion-beam (IB) irradiation. We performed measurements and physicochemical analysis to verify and establish the cause of the successful LC alignment. In addition, we measured the electro-optical characteristics of twisted-nematic cells with IB-irradiated TBO films to explore the suitability of this material for liquid crystal displays (LCDs). The results indicate that this approach will allow the fabrication of high-performance enhanced LCD devices. [ABSTRACT FROM AUTHOR]

Liquid crystal (LC) alignment characteristics were investigated using a solution-derived lanthanum-doped zinc oxide (La:ZnO) film that was exposed to various intensities of ion-beam (IB) irradiation. At an IB intensity of 1700 eV, uniform and homogeneous LC alignment was achieved, as revealed by cross-polarized optical microscopy and pre-tilt angle measurement. Field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were used to verify that the IB irradiation induced physical and chemical surface reformation of the La:ZnO film that relate to LC alignment. FE-SEM and AFM revealed that the IB irradiation reformed the existing surface structure into a new structure with an altered surface roughness. The XPS results showed that the van der Waals force with anchoring energy increased as the IB intensity increased, and this profoundly affected the state of LC alignment. The capacitance-voltage (C-V) hysteresis curve was measured as a function of IB intensity to characterize the accumulated charge as a residual DC. Nearly zero C-V hysteresis was achieved at an IB intensity of 1700 eV. Therefore, a solution-derived La:ZnO film with an IB intensity of 1700 eV has great potential for high-quality LC applications. [ABSTRACT FROM AUTHOR]

Abstract The characteristics of a solution-derived indium-doped zinc oxide (In:ZnO) film exposed to ion-beam (IB) irradiation as a liquid crystal (LC) alignment layer were investigated. Solution processing was conducted to deposit a thin layer on a substrate and irradiation at various IB irradiation energies was used as an LC alignment method, all of which achieved uniform and homogeneous LC alignment. Atomic force microscopy using three-dimensional imaging and numerical analyses showed that the IB irradiation reduced the surface roughness. Through the X-ray photoelectron spectroscopy, it was revealed that the modification of the chemical composition due to the IB irradiation affected the state of the LC alignment. Increased polarizability of the surface and oxygen vacancies induced strong van der Waals forces between the In:ZnO film surface and the LC molecules, thereby subsequently achieving uniform and homogeneous LC alignment. The electro-optical (EO) characteristics of a twisted-nematic cell made with IB-irradiated In:ZnO film at an IB irradiation energy of 2200 eV, with which outstanding EO performance was observed. Therefore, using the solution-derived In:ZnO film with the IB irradiation as an alignment shows remarkable potential for use in LC device. Highlights • In:ZnO film layer was deposited by using solution-process. • IB irradiation was conducted as an LC alignment method. • Physical and chemical surface modification due to the IB irradiation. • Enhanced electro-optical characteristics using the In:ZnO film with the IB irradiation. [ABSTRACT FROM AUTHOR]

We investigated the induced uniform alignment of liquid crystals (LCs) on a polyurethane (PU) ion-beam (IB) irradiated at a certain incidence angle. Polarized optical microscopy (POM) and the crystal rotation method were used to evaluate the LC alignment state. On PU films IB-irradiated with incidence angles of 60° or less, the LC cells exhibit a clear and uniform alignment. At an incidence angle of 75°, light scattering was observed via POM, indicating the randomly aligned state of the LC cells. Moreover, the calculated pretilt angles for LC cells on IB-irradiated PU at incidence angles of 15°, 30°, 45°, and 60° were 0.05°, 0.05°, 0.20°, and 0.18°, respectively. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to confirm the effect of varying the IB irradiation incidence angle. The PU surface irradiated by IB was modified differently as the incidence angle changed. IB irradiation at low incidence angles broke C–C, C–O/C–N, and N–C(O)–O bonds and caused C=O bond formation by the dissociation of the N–C(O)–O bonds. The van der Waals interactions between the PU and LC matched the LC molecular interactions and the anisotropic characteristics could be maintained, thereby achieving a stable homogeneous LC alignment. [ABSTRACT FROM PUBLISHER]

This letter demonstrates liquid crystal (LC) alignment on solution-derived Zn-doped GaO (ZnGaO) films using an ion beam (IB) method. Homogeneous and uniform LC alignment was achieved on IB-irradiated ZnGaO films. X-ray photoelectron spectroscopy was used to analyze the chemical bonding states of the IB-irradiated ZnGaO surfaces to verify the compositional behavior for LC alignment. In addition, ZnGaO films with twisted nematic cells exhibited electro-optical characteristics comparable with those of a conventional polyimide layer for potential LC display applications. [ABSTRACT FROM AUTHOR]

We demonstrated uniform LC alignment using IB-irradiated poly(methyl methacrylate) (PMMA) as an alignment layer. We confirmed the topographical changes on PMMA caused by IB irradiation. Moreover, the wettability and chemical modification of the PMMA surface were investigated as functions of incidence angle. The results show that PMMA irradiated with IB at an incidence angle of 30° had a higher molecular polarity than PMMA irradiated with IB at other incidence angles, resulting in strong van der Waals interactions between the surface and LC molecules. The LC cells containing PMMA irradiated with IB at an incidence angle of 30° exhibited good thermal stability (180°) compared with LC cells containing conventional rubbing PI (150°). In addition, LC molecules on PMMA irradiated with IB at an incidence angle of 30° were observed to switch faster than those on conventional rubbing PI. Therefore, PMMA irradiated with IB under the optimal conditions may allow for PMMA to be applied in advanced LC devices as an alternative alignment layer. [ABSTRACT FROM AUTHOR]

We demonstrated a homogeneous liquid-crystal (LC) alignment state on yttrium aluminum oxide (YAlO) films, where the alignment was induced by ion-beam (IB) irradiation. Topographical analysis was performed by atomic force microscopy as a function of annealing temperature. Higher annealing temperatures yielded a smoother surface, accompanied by reduced light scattering. Transparency in the visible region increased on the surface fabricated at higher annealing temperatures. LC alignment mechanism was determined by X-ray diffraction (XRD) analysis. Moreover, IB-irradiated YAlO films annealed at temperatures greater than 200 °C exhibited good thermal stability and low capacitance–voltage hysteresis. The IB-irradiated YAlO films are suitable as alternative alignment layers in advanced LC display applications. [ABSTRACT FROM AUTHOR]