In-plane Switching Liquid Crystal Display Research Articles

P‐13: Picture Quality of In‐Plane Switching Liquid Crystal Displays with Deep Black

In‐Plane Switching (IPS) liquid crystal display (LCD) is one of leading technologies in display industrials because of its superior picture quality. This paper provides picture quality of high contrast IPS LCD in terms of color contrast, dynamic range, color expression and PQ‐EOTF accuracy in HDR compared to conventional IPS LCD. Furthermore, to evaluate its performance as a gaming display, reaction time between two IPS LCDs have different contrast ratio was tested. Experimental results indicate that observer's reaction time for high contrast IPS LCD was faster than conventional IPS LCD because of superior color contrast and color gamut at low luminance level.

Optical compensation methods for eliminating the off-axis light leakage in in-plane switching liquid crystal display

Optical compensation methods for eliminating the off-axis light leakage in in-plane switching liquid crystal display

Optimization of the display viewing angle for automotive application

We studied the optimization of viewing angle properties of the in-plane switching (IPS) liquid crystal display (LCD) for automotive applications. We studied the optical properties inside the automotive viewing zone (AVZ) with narrow vertical and wide horizontal viewing angle range defined in German OEM specifications. The average dark state transmittance (TRd) and contrast ratio (CR) of the IPS-LCD compensated with a + A and a + C plate could be enhanced by 2.5% and 0.8%, respectively, in the AVZ by inserting an additional -C plate. The uniformity of TRd and CR in the AVZ zone also improved by 39.3% and 24.9%, respectively. Enhancement of optical properties by the additional -C plate was also observed in the IPS-LCD compensated with a Z plate. On the other hand, the optical properties of the IPS-LCD compensated with a -B and a + C plate were optimal when R th of the existing + C plate is optimized for automotive displays.

Enhanced thin-film transistor driven high-aperture in-plane switching liquid crystal displays without common line and black matrix

We developed active-matrix in-plane switching liquid crystal displays (IPS-LCDs) with a new vertical structure composed of thin-film transistors (TFTs) that have an aperture ratio of 60% to reduce energy consumption. The novel TFT has a channel and a back channel made of a hydrogenated amorphous-silicon semiconductor layer sandwiched by thin silicon oxide insulating layers. The transfer characteristics are enhanced by uniformly shifting the threshold voltage to be higher than the maximum LC driving voltage (typically > 5 V). The enhanced TFT characteristics provided with a new driving scheme and shielding electrodes enables both the common line and black matrix to be eliminated. We fabricated an IPS TFT-LCD panel with aperture and contrast ratios that are 160% those of the conventional pixel structure.

3‐2: Invited Paper: A Wide Color Gamut LCD with a Polarized Laser Backlight

We have developed a 17.3‐inch 8K wide color gamut in‐plane switching LCD (IPS‐LCD) with a polarized laser backlight. By applying a zero—zero‐birefringence polymer, the polarized laser backlight emits polarized light with 88% polarization. The IPS‐LCD with the developed polarized laser backlight achieves a wide color gamut with high efficiency.

Preparation of polyimide alignment films with high photosensitivity and low solid content

ABSTRACT In order to reduce the cost, a polyimide (BF-CA) with high photosensitivity and low solid content was prepared by one-step method using 2,2-bis (3-amino-4-hydroxyphenyl) propane (BAP), 4,4ʹ- (hexafluoroisopropyl) phthalic anhydride (6FDA) as monomer and cinnamoyl chloride as photosensitive group. The BF-CA films exhibit good alignment performance after non-polarised ultraviolet light (NPUVL) irradiation for 20 minutes. Meanwhile, the effect of solid content on the alignment performance is mainly discussed, because reducing solid content helps to reduce costs. In addition, the BF-CA shows good thermal stability. The pretilt angle of the liquid crystal cells is 0.5°, which meet the requirements of practical application in In-Plane Switching liquid crystal display.

Evaluation and improvement of image sticking in in-plane switching liquid crystal display

Image sticking in liquid crystal display (LCD) can affect the display quality. The saturated residual direct current voltage (SRDCV) can be obtained by analyzing the change in the capacitance of LC cell under the direct current bias, through which image sticking can be evaluated. On this basis, the image sticking was evaluated in the in-plane switching (IPS) cell filled in the LC with negative dielectric anisotropy for different electrode structures, cell gaps (i.e. 3.8, 5.8, and 7.5 µm), and doping concentrations of γ-Fe2O3 nanoparticles (i.e. 0.068, 0.136, 0.204, and 0.272 wt%). The SRDCV decreases under the same conditions by adjusting the ratio of electrode width and electrode gap and it decreases with the cell gap increases. For the thickness of 3.8 µm, the SRDCV initially decreases and then increases as the doping concentration of γ-Fe2O3 nanoparticles increases; while for the thicknesses of 5.8 µm and 7.5 µm, the SRDCV decreases as the doping concentration of γ-Fe2O3 nanoparticles increases. The results show that the structure design of the IPS-LCD and the doping of nanoparticles can effectively improve image sticking and provide useful guidance for enhancing the display quality of LCD.

A high transmittance and fast response in-plane switching liquid crystal display with the zero-azimuth anchoring layers on the electrodes

An in-plane switching (IPS) liquid crystal display (LCD) containing the zero-azimuth anchoring layers formed only on the electrodes and rubbed polyimide (PI) covered on the other areas was successfully developed. This configuration was realized using photoreactive PI with photo-radical generation units and the mask exposure technique. The maximum transmittance (Tmax) of this LCD was 1.12 times higher than that of a conventional IPS LCD. This was attributed to a large aperture in the voltage-on state because the nematic liquid crystals (NLCs) on the electrodes were barely anchored to the surface, such that the NLCs could be rotated by applying a small in-plane electric field above the electrodes, and by an elastic torque caused by the twisted NLCs between the electrodes. Furthermore, the response times of this LCD were equivalent to those of a conventional IPS LCD because the NLCs between the electrodes quickly recovered to their initial orientation after removing the electric field, and the NLCs on the electrodes followed this movement. This novel LCD is termed a ‘partially zero-azimuth anchoring IPS (PZ-IPS) LCD’, which is the first practical LCD utilizing these weak anchoring characteristics in the history of LCDs.

Dynamics control of an in-plane-switching liquid crystal cell using heterogeneous substrates.

The control of surface anchoring strength can be achieved by using heterogeneous substrates. In contrast to conventional substrates that control the anchoring strength by using temperature or chemical processes, heterogeneous substrates provide surface anchoring to liquid crystal molecules by using a mixed composition of (1) a zero anchoring surface and (2) planar-anchoring patches. To study the dynamics of in-plane-switching liquid crystal displays (IPS-LCDs) under external fields, a new particle-based numerical algorithm is developed to simulate both nematic liquid crystals and heterogeneous surfaces. This new method allows us to create different heterogeneous surfaces easily by adopting predefined distributions of numerical particles. The generated effective anchoring strength from the heterogeneous surface is thus calculated, and the dynamical response is found to be similar to that of conventional homogeneously processed substrates. The results suggest that the use of a heterogeneous LCD cell is a suitable alternative for creating desirable LCD substrates, for which chemical/temperature dependence can be transferred to a more controllable configurational dependence. Interestingly, we found master curves in the peak transmittance/recovery time phase space, and they appeared to be dependent solely on the cell thickness. This discovery clarifies the fundamental optical dynamics of IPS-LCD cells.

TFT-LCD Contrast Ratio Improvement by Using Design for Six Sigma Disciplines

The current market demands for thin-film transistor (TFT) liquid crystal display (LCD) is high; however, the LCD televisions still have contrast ratio-related issues. To resolve this, researchers conventionally use trial and error methods for parameter optimization and adjustment. However, this method is slow and can delay the development of new products. Therefore, this study focused on the high contrast ratio of the in-plane switching (IPS) panel. The Define–Measure–Analyze–Design–Verify procedure, comprising the methodology of the Design for Six Sigma, was used to help the researchers enhance the ultra-high contrast ratio of LCD panels. In this study, customer requirements were confirmed, after which the quality function deployment method was used to establish the technical requirements of the enhanced high contrast ratio of LCD. The contradiction matrix of TRIZ was then used to find the corresponding principles and thus propose the design scheme for the LCD contrast ratio. Methodologies, such as design failure modes and effect analysis, Taguchi’s parameter design, and reliability tests were used to enhance the ultra-high LCD contrast ratio. After the implementation of an actual case, the ultra-high contrast ratio of LCD panel was enhanced to 1000000:1; the benefits of such an improvement exceeded U.S. \\(9.5 million. This has also driven market orders for TFT IPS LCD. This study can serve as a reference for product design, product performance enhancement, pilot run yield improvement, and patent applications of LCD panel plants.

66‐1: Invited Paper: Fast‐response IPS‐LCDs used in VR applications

We discuss the moving picture characteristics of display devices required for virtual reality head‐mounted displays (VR‐HMDs). We propose a fast response in‐plane switching (IPS) liquid crystal display (LCD) mode, called the short‐range lurch control IPS (SLC‐IPS) LCD mode, for VR‐HMDs based on experimental results of its response properties.

Novel in-plane switching liquid crystal display with an extremely high transmittance using a well-designed bottlebrush as a zero-azimuth anchoring material

In this study, a one-side zero-azimuth anchoring in-plane switching (OZ-IPS) liquid crystal display (LCD) employing poly(n-hexyl methacrylate) (PHMA) bottlebrush polymers as an application-type zero-azimuth anchoring material was successfully developed. The twist anchoring coefficient A2 measured for the nematic liquid crystal (NLC) on the PHMA bottlebrush at 25 °C was comparable to that of the same NLC on high-density PHMA brushes. Optimizing the optical design increased the transmission efficiency (TE) of the OZ-IPS cell with the negative NLC to 95%, which was significantly higher than that of conventional IPS cells. Using optical simulation, the OZ-IPS LCDs with a negative NLC clearly exhibited the highest TE (≃107% of TN LCDs) for LCDs developed thus far. Moreover, the higher transmittance of the OZ-IPS LCDs was also confirmed for the practical TFT LCD, which exhibited a maximum luminance that was 30% higher than conventional IPS TFT LCDs.

Papers] Transfer Fabrication of Liquid Crystal Devices with Microgroove and Wall Structure on Plastic Substrate for Flexible In-plane Switching Liquid Crystal Displays

In this paper, we propose the in-plane switching liquid crystal device with a microgroove and wall structure, fabricated by a transfer method for printable manufacturing of large-area flexible liquid crystal displays. We confirmed that the liquid crystal devices have a higher transmittance than conventional devices, and that a reduction of the thickness of the residual polymer film is necessary to decrease the driving voltage. Similar to the technique used on glass substrates, fabrication of flexible liquid crystal devices using a plastic substrate is possible using silicone elastomer.

Suppressing pretilt angle for enhancing black quality in diagonal viewing angle of homogenously aligned liquid crystal display

ABSTRACTThe diagonal viewing angle light leakage in a black state of in-plane switching (IPS) liquid crystal display (LCD) associated with pretilt angle has been investigated. The mechanical rubbing process with a cloth causes relatively high pretilt angle in the homogenously aligned liquid crystals (LCs) so that the tilted LC director results in increase of a light leakage in a black state at diagonal viewing angles. In this study, we theoretically estimated using classical optic theory how the light leakage in a black state at diagonal viewing angle is associated with the pretilt angle and also proposed an effective method to reduce the pretilt angle from 1.5° to 0° in rubbed IPS LCD by utilising polymer stabilisation. With this approach, we could successfully acquire a better black quality in all viewing angles as compared with normal IPS LCD.

Investigation on newly designed low resistivity polyimide-type alignment layer for reducing DC image sticking of in-plane switching liquid crystal display

ABSTRACTSoluble polyimide-type alignment layer is widely used in in-plane switching (IPS) liquid crystal display (LCD) because of its excellent reliability owing to high imidisation ratio during long-term driving, high voltage-holding ratio and low ion density. Nevertheless, it exhibits slow direct current (DC) discharging property due to its high resistivity, causing significant DC image-sticking problem. In this study, we doped inorganic salt to control the resistivity of soluble polyimide-type alignment layer and found that this approach reduced DC image sticking greatly without any loss of reliability property in IPS-LCD.

Optimisation of alignment materials for minimising residual retardation in in-plane switching liquid crystal display

ABSTRACTThe light leakage in a black state of in-plane switching (IPS) liquid crystal display (LCD) associated with rubbing process has been investigated. The mechanical rubbing process with a cloth caused orientation disorders in the liquid crystal directors and these partial orientation disorders result in residual retardations of the IPS LCD, causing the light leakages at the black state. In this study, we theoretically estimated how the light leakage is associated with the rubbing uniformity using 2 × 2 Jones matrix equation and also experimentally confirmed how it is associated with structural properties of the alignment layer. The light leakage was clearly reduced in the alignment layer with reduced crystallinity and flexibility.

P-117: The Investigation of Photo Alignment Polyimide Material for Large Size IPS Display

A new photo alignment (PA) polyimide for in-plane switching (IPS) liquid crystal display has been presented and it has good alignment performance. It realizes alignment by irradiating linearly polarized light with wavelength of 313nm. In this paper, we have study a novel 313nm PA polyimide with only one UV step. And we also have investigated the relationship between the image sticking performance and PA polyimide structure. The optical and image sticking performance of different PA polyimide are discussed in IPS mode, respectively.

측면시야각에서의 대칭적 명암대비비 향상을 위한 IPS-LCD 광학보상

In this study, we proposed an optical compensation method to improve the symmetricity of contrast ratio for wide viewing angle IPS (in-plane switching) LCD. First, the phase retardation depending on the thickness of compensation film is calculated, and then the phase change is presented at the sphere. The phase retardation and the polarization state of the light passing through the optical elements are caculated by using the EJMM (extended Jones matrix method). In addition, the transmittance and the contrast countour are also calculated by using the Berremann`s matrix method. The simulation is carried out for a IPS LC cell with positive A/C/A compensation film. From the standard deviation of the contrast ratio, we confirmed the symmetricity at each viewing angle is inversely proportional to the standard deviation and calculated the optimum design condition of the uniaxial compensation film for the IPS LCD.

低驱动电压和快速响应的共面转换液晶显示器

低驱动电压和快速响应的共面转换液晶显示器

A semi-empirical equation for the response time of in-plane switching liquid crystal display and measurement of twist elastic constant

A semi-empirical equation is developed to characterize the optical decay time of in-plane switching (IPS) and fringe field switching (FFS) liquid crystal displays. This equation takes the effects of elastic constants, cell gap, liquid crystal material, rubbing angle, and anchoring strength into account simultaneously. Good agreement between simulation and experiment is obtained. Moreover, this equation can be used to measure the twist elastic constant K22 of liquid crystals. The measured temperature-dependent K22 values of 5CB agree well with previously published results. Hence, our equation not only describes the response time of IPS and FFS cells but also provides a simple yet accurate method to determine the twist elastic constant of liquid crystal materials.