In order to preserve the foldability of foldable display module (FDM) under a various folding environment such as temperature or folding radius, it needs an accurate architecture technique of FDM. Especially, the define of Optical Clear Adhesive(OCA) properties is very serious issue on FDM and it might be impossible to correctly simulate the OCA behaviors with various folding environment. Furthermore, the OCA properties are main key factor to architect the stable FDM because OCA is more sensitively reacted with changing of folding environment than the other film material. In this work, we first analyze the strain‐stress distribution of FDM and then we investigate the proper OCA properties based on the simulation results. As a result, we suggest a foldable display architecture technique depending on various folding environment.

Colorless polyimide (CPI) film is one of promising candidates for a foldable display because of its excellent mechanical and optical properties. To achieve a good and high reliable foldability, engineers must take into account thickness for foldability and mechanical hardness for pen touch function. To compromise this trade‐off relationship, LG Display chose CPI as a base film of the cover window and double‐sided thin hard coating for a pen touch solution. This paper shows why LG Display choose the proposed configuration with detail data.

Russian Foundation of Basic Research;Russian Academy of Sciences;Eur. Off. Aerospace R and D of the US AirForce;Society for Information Display;Russian JSC ChipExpo

Various dichroic dyes were synthesized and applied to two different host materials for the study of optimized molecular structures of guest–host system for the coatable polarizer using liquid crystalline polymers. The host material containing planar and linear mesogens had an advantage in exhibiting high orientation orders, but easily formed disclinations due to causing the strong intermolecular attraction between the guest and host molecules. The balance of intermolecular attraction and repulsion between the guest and host molecules is important to simultaneously achieve high orientations and uniform alignments without disclinations. The highest dichroic ratio of coatable polarizers was obtained when the π-conjugation lengths of guest and host molecules have an appropriate ratio. Also, the guest molecules with a long π-conjugation length improved the orientation of host molecules.

Guest–host coatable polarizers were manufactured by liquid crystalline polymers and dichroic azo dyes. The highest dichroic ratio of the polarizers was observed within the permissible limit of guest concentration, because any increase in the guest concentrations beyond the permissible limit decreased the alignment ability of the host. The orientational behavior of dye molecules in guest–host systems tend to be more sensitive to intermolecular steric hindrance as compared to that in PVA-based polarizing films. Also, the polarity difference between guest and host molecules had a great effect on the alignment of the guest–host system. Long conjugation, abundant π-electrons for transfer and the charge distribution without deviation from the long axis are required for a highly anisotropic transition dipole moment.

A compartmentalized multidomain alignment state of a layer of liquid crystal display is achieved using an ultrathin, highly transparent, and ultrafast-responsive alignment layer fabricated by a simple method. The ultrathin alignment layer consists of a self-assembled oligomer layer of poly(dimethylsiloxane) (PDMS) formed by utilizing the oligomers that diffuse out from a PDMS elastomer stamp during a contact printing process.

We have demonstrated the feasibility of thin‐film coatable type polarizer for high contrast. New liquid crystalline materials were developed and the manufacturing process was optimized to achieve high performance polarization characteristics. We made a 9.7 inch XGA prototype with our newly developed polarizer, and obtained good image quality and high electro‐optical performance. More approaches to get higher polarization performance in terms of materials and manufacturing process were discussed.

We developed an inorganic-organic hybrid thin film via the sol-gel method for a new liquid crystal alignment layer and investigated the influence of an organic species on the alignment characteristics of the liquid crystals (LCs). A thin film of methyl-doped amorphous silicon oxide (a-SiOx:CH3) was fabricated from the hydrolysis and condensation reaction of the initial precursors of methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) at a proper ratio. A low-energy ion beam (IB) treatment gives rise to the homogeneous alignment of LC in an IB condition on a-SiOx:CH3 thin film; however, it is difficult to control the LC alignment on a-SiOx thin film derived only from TEOS as a precursor. The LC alignment depending on the chemical structure of the silica thin film was investigated and analyzed in terms of the sensitivity of the axis-selective destruction of the chemical bonding on the surface of the thin silica film.

Highly transparent and efficient red phosphorescent inverted top-emitting organic light emitting diodes were investigated by using a surface-modified tungsten oxide (WO(3))/silver/WO(3) (WAW) anode. A thin buckminsterfullerene (C60) dipole layer was introduced for the surface treatment of the WAW anode, and the thickness of the surface-modified WO(3) was controlled to optimize the WAW anode for hole injection. The optimum thickness of the surface-modified WO(3) was 5 nm, and the C60 dipole layer further improved the hole injection from the WAW anode to the hole transport layer.

The pretilt angles of liquid crystals (LCs) can be controlled over the range 0 degrees to 90 degrees using ion beam treated 4-alkylphenoxymethyl-substituted polystyrene films as alignment layers, where the alkyl group is -(CH2)(n)H (n = 1, 2 or 4), by changing the ion beam irradiation time, incidence angle and energy. In general, LC cells made using a polymer film with a longer irradiation time, higher irradiation incidence angle with respect to the planar direction and higher irradiation energy exhibited lower pretilt angles relative to the planar direction. Furthermore, the LC cells produced using polymer films containing longer alkyl groups and a higher molar content of 4-alkylphenoxymethyl side groups exhibited greater pretilt angles under similar irradiation conditions. The LC alignment behaviour demonstrated good correlation with the wettability of the polymer films, due to fragmentation of the side groups on the polymer surfaces during ion beam irradiation. The electro-optical characteristics of the LC cells formed using these polymer films were similar to those produced using rubbed polyimide films, which are the LC alignment layers most commonly encountered.

Advanced organic light-emitting diodes (OLEDs), based on a multiple structure, were achieved in combination with a quantum dot (QD) interfacial layer. The authors used core/shell CdSe/ZnS QDs passivated with trioctylphosphine oxide (TOPO) and TOPO-free QDs as interlayers. Multiple-structure OLEDs (MOLEDs) with TOPO-free QDs showed higher device efficiency because of a well-defined interfacial monolayer formation. Additionally, the three-unit MOLED showed high performance for device efficiency with double-structured QD interfacial layers due to the enhanced charge balance and recombination probability.

Long-term stability of intermediate liquid crystal pretilt angles on a poly(dimethylsiloxane) (PDMS) ultrathin film grafted onto a surface was realized simply and easily via low-energy ion beam (IB) treatment. The composition and surface energy of the thin film could be controlled by varying the low-energy IB treatment. This treatment results in the permanent chemical modification of the film surface, converting it from organic PDMS to a mixed layer of organic PDMS and inorganic silica. The partial transformation of a PDMS surface gives rise to the control of the pretilt angle via the formation of the inhomogeneous surface and the stabilization of the pretilt angle via the cross-linking reaction of broken chemical bonds through IB irradiation. As a result, a continuous variation of pretilt angles that maintained their initial value with long-term stability was obtained. Thus, the unique chemical transformation of the PDMS surface using IB treatment may allow for the production of durable intermediate liquid crystal pretilt angles.

The vertical alignment of liquid crystals having negative dielectric anisotropy on an amorphous silicon oxide (a-SiO(x)) thin film is the consequence of the anisotropic interaction between liquid crystals and a-SiO(x) thin films. To investigate the mechanism of the vertical alignment, we changed the physicochemical characteristics of alignment layers by controlling the composition, since the anisotropic interaction depends on the nature of both liquid crystals and an alignment layer. The variation of composition gives rise to a change in the polarizability, which is a simple measure of induced-dipole strength at the surface of the alignment layer. There is a critical transition point from planar to vertical alignment of liquid crystals, and it is the long-range van der Waals interaction that is responsible for the vertical alignment. The competition between long-range van der Waals interaction and short-range dipolar interaction were investigated and analyzed in terms of the interfacial energy between liquid crystals and an alignment layer.

The relationship between the liquid crystal (LC) alignment and the density of the silicon oxide alignment layer was studied by theoretical and experimental approaches. The thin films were deposited by various methods and conditions, and then their densities were analyzed by x-ray reflectivity measurement. The alignment of LC was highly dependent on their densities, which we found to be closely related to the number of interacting dipoles. Ultimately, a-SiOx thin film with lower density gives rise to the uniform vertical alignment of liquid crystal.

The authors have developed a semitransparent, multilayered cathode of indium tin oxide (ITO)/Ag/tungsten oxide (WO3) for transparent organic light-emitting diodes. The device showed a weak negative differential resistance (NDR), until the operating voltage of 8V was reached. NDR was due to the resonant tunneling by both the quantum barrier and quantum well. The silver oxide (Ag2O) on the Ag metal was confirmed by x-ray photoelectron spectroscopy, and the energy levels of Ag2O were quantized due to the quantum size effect and this produced the resonant tunneling channels. The device using ITO∕Ag∕WO3 with a LiF∕Al bilayer was superior to those devices which only used ITO or WO3, mainly because the out coupling was enhanced by employing a WO3 material, which is much more transparent than ITO.

The vertical alignment of liquid crystal (LC) on an inorganic silicon oxide layer, which is fabricated by a simple photoinduced transformation process of an ultrathin poly(dimethylsiloxane) (PDMS) layer is reported. While the PDMS layer shows a random orientation of LC, the silicon oxide layer, fabricated by UVO treatment, vertically aligns the LC. In addition, the silicon oxide layer shows a stable alignment of LC in harsh conditions.

The authors have demonstrated efficient polymeric tandem organic light-emitting diodes (OLEDs) with a self-organized interfacial layer, which was formed by differences in chemical surface energy. Hydrophilic poly(styrene sulfonate)-doped poly(3,4-ethylene dioxythiophene) (PEDOT:PSS) was spin coated onto the hydrophobic poly(9,9-dyoctilfluorene) (PFO) surface and a PEDOT:PSS bubble or dome was built as an interfacial layer. The barrier heights of PEDOT:PSS and PFO in the two-unit tandem OLED induced a charge accumulation at the interface in the heterojunction and thereby created exciton recombination at a much higher level than in the one-unit reference. This effect was confirmed in both the hole only and the electron only devices.

We study the alignment properties of liquid crystals (LCs) with a negative dielectric anisotropy on a hydrogenated silicon carbide (SiC:H) film, which is an alternative alignment material. SiC:H layers align LC molecules with a negative dielectric anisotropy via ion beam (IB) irradiation and control the pretilt angle in a range from 90 to 75° depending on the change of IB irradiation angle. Also, when they are exposed to high temperatures for a long time, they show robust properties without degradation. We conclude that although the SiC:H alignment layers are not sensitive to IB irradiation compared with the SiC layers, they show a potential as alternative LC alignment layers for IB irradiation method.