Liquid Crystal Display Televisions Research Articles

Liquid crystal research at Tsinghua University in the 1970s and 1980s

Liquid crystal (LC) research in China started during the Cultural Revolution years in the late 1960s. It was motivated partly by the potential application in liquid-crystal display (LCD) digital television (TV) and movies, deemed good for the government’s political propaganda agenda. The large-screen LCD TV/ movie project was initiated and done at the Tsinghua University, Beijing, which became successful in 1976 with prototypes built. Although it never reached the commercial stage, the research achievement was world-leading then. Here, the history of this project and other LC research at the Tsinghua University in the 1970s and 1980s are described for the first time, with appropriate historical backgrounds provided. Tsinghua’s significant contributions in basic LC research and a description of the founding and workings of the Chinese Liquid Crystal Society are also included. Finally, lessons drawn from this piece of science history are presented.

Blue Light Intensity in Organic Light-Emitting Diode and Liquid-Crystal Display Televisions

Exposure to artificial blue light from screens, especially at evening or nighttime hours, can suppress melatonin production, throw the circadian rhythm off balance, and lead to general difficulty falling asleep. This study sought to investigate the difference in blue light intensity in organic light-emitting diode (OLED) and liquid-crystal display (LCD) screens, specifically in the form of televisions. An observational and quasi-experimental method was used, using a photometer to measure light intensity and a longpass optical filter to block out light ranging from 415 to 515 nanometers, serving as the wavelength of blue light for this study. Two televisions—one OLED and one LCD—were used, with five colors being displayed on each one, one at a time. The LCD television contained more relative blue light than the OLED television for four out of the five colors displayed. On average for all colors, the LCD television emitted 24.92% more blue light than the OLED television, relative to their overall brightnesses. Limitations in scope and the potential of confounding variables interfering with data prevent any definitive conclusions from being drawn, however this study still contributes to the current body of knowledge with evidence towards a trend of lessened blue light intensity in OLED screens compared to LCD screens, which correlates with speculation by other researchers. This study sets the ground for future research investigating the potential of OLED technology in lowering exposure to blue light, thus lessening the negative impacts it can have on individuals.

The use of relative potential risk as a prioritization tool for household WEEE management in Thailand

Waste electrical and electronic equipment (WEEE) has become one of the major global concerns in solid waste management due to its continuously increasing volume and adverse effects on the environment and human health. This study aims to use the relative potential risk as a specific device to prioritize 8 WEEE types in Thailand based on contents and toxicity of toxic metals in printed circuit boards (PCBs), including arsenic, cadmium, chromium, copper, and lead, in terms of potential harm indicator (PHI) and quantity of PCBs. The results indicated that the most significant type of WEEE based on relative potential risk is liquid crystal display television, while the least significant types of WEEE are refrigerator and washing machine. However, PCBs also contain precious metals (gold, silver, and palladium) which are crucial for WEEE recycling economy. Thus, the ratio between precious metals and toxic heavy metal was determined as a simple tool to assess the cost and benefit. According to the results, mobile phone has been the highest economic wealthiest while refrigerator has been the lowest. The findings in this study will be useful as a tool for policy makers to decide the sustainable WEEE management.

Birth of the Innovative Overdrive Technology for Liquid Crystal: Paving the Way for Practical Use of LCD Televisions

This article describes our experience developing innovative display technologies with the aim of providing hints for researchers to break away from conventional wisdom. In the 1990s, we focused mainly on liquid crystal display (LCD) technologies for creating and developing the new flat-panel TV market, despite claims that the motion blur problem for LCD TVs could not be solved without materials featuring ultrafast response times. We then discovered that motion blur is not due to a binary response, as was commonly believed at the time, but rather a drastically degraded gray-level response and decreased driving voltage due to electrostatic capacity change according to dynamic rotation of liquid crystal molecules. On the basis of a novel image-lag mechanism, we invented the overdrive method to emphasize the voltage applied to the liquid crystal for only a certain period according to change in picture brightness for high-speed response LCD TVs. This overdrive technology is now a de facto standard technology for LCD TVs, though the time-to-market exceeded 13 years. This article describes why so much time was required and how many issues were resolved to realize this revolutionary innovation.

The TVs of Tomorrow: How RCA's Flat-screen Dreams Led to the First LCDs by Benjamin Gross

Reviewed by: The TVs of Tomorrow: How RCA's Flat-screen Dreams Led to the First LCDs by Benjamin Gross Michael Aaron Dennis (bio) The TVs of Tomorrow: How RCA's Flat-screen Dreams Led to the First LCDs By Benjamin Gross. Chicago: University of Chicago Press, 2019. Pp. 288. We live surrounded by LCD (liquid crystal display) screens; Ben Gross's volume explains the origins of this technology at RCA and how the iconic American firm failed to deliver it to the world. This fascinating story of industrial research, corporate politics, and technological change blends science, technology, and business histories. Gross locates the emergence, efflorescence, and decline of LCD screens at the intersection of three distinct axes—the material logic of LCDs, that is their physical chemistry and often recalcitrant behavior plus the infrastructure for their creation and use; RCA's strategic goals as well as the Sarnoff Laboratory's role in fulfilling them; and the interactions among researchers, their managers, and other RCA divisions. One of the many interesting things readers learn is that the technology dominating our lives received so little support from RCA management. Indeed, they ultimately seemed to value LCD patents more than developing televisions based on this novel display technology. Noteworthy are Gross's discussions about the problem of finding the sources needed to write the history of late twentieth-century corporate R&D. RCA's quest for a follow-up to its color television came in 1951, with legendary founder David Sarnoff's challenge to develop a light amplifier. Efforts ensued to find alternatives to the standard display technology, the CRT (cathode ray tube). RCA pioneered the mass production of these glass bubbles, and it proved hard to break from this anchoring technology. Only after it became clear that CRTs could not be flattened in order to hang from walls and display a quality picture did researchers and management explore and develop alternatives. By 1964, the company's research included liquid crystals and their chemistry; however, as Gross points out, it was never really a large research group. Compared to the well-studied RCA video disc, called a "Manhattan Project," RCA's work on LCDs was a modest effort. Although [End Page 1240] public relations people hyped the research and its potential, this was never a corporate moon shot. Gross rightly highlights the problems in manufacturing the new technology once researchers overcame problems at the bench. Using laboratory notebooks, he delineates how researchers solved the issue of LCDs working at room temperature. Building bridges with RCA's manufacturing divisions became as vital as laboratory research to keep LCD work alive, while management paid more attention to a struggling computer effort and the firm's traditional color television business. Even once the multiple manufacturing problems were solved, the LCDs produced by RCA were for watch displays, not the wall-hanging televisions of the future. The initial secrecy surrounding LCD research demonstrated how highly it was valued, yet RCA soon viewed patents as the real source of value compared to physical products, given the costs and difficulties of profitably manufacturing LCDs in America. Gross's interviews and archival work display the full range of skills required to move lab products to the factory, including individuals with the requisite social skills to borrow resources from other groups. This social aspect of intra-laboratory relations is especially well portrayed. Gross plays with Clayton Christensen's ideas of disruptive innovation in explaining why RCA failed to capitalize on its role as a pioneer in LCD research. He follows LCD researchers at RCA to a new start-up, Optel that fails to take advantage of new LCD chemistry, instead sticking to RCA-based technologies. Small size did not prevent an aversion to change. In his final eloquent chapter, Gross explains that it was only once LCD technology had left RCA that it really grew and developed—as multiple firms, first on the West Coast and then in Japan, invested in significant R&D with specific products in mind. Seiko developed a watch-sized LCD television more advanced than Dick Tracy's, while Sharp demonstrated a fourteen-inch color display in 1988. Ironically, Sharp had approached RCA in 1970 about...

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.

Stocks and environmental release of mercury in backlight cold cathode fluorescence lamps.

Cold cathode fluorescent lamps (CCFLs), with mercury as their essential component, were widely used as backlight in liquid crystal display (LCD) appliances before 2008. Since 2008, the mercury-free light emitting diode started to be used as a substitute for CCFLs and the replacement finished in about 2014. Nowadays, CCFLs are obsolete products from the viewpoint of manufacture but they are important as waste. In recent years, large amounts of CCFLs are flowing to waste phase for treatment and this has become a major issue in most countries. To better understand and control the risk of CCFLs, the stock of mercury in CCFLs, its flow to waste phase and mercury emission with the life cycle of CCFLs in mainland China were estimated in this study. Results showed that there was 15.2 tons of mercury stocked in CCFLs in main LCD appliances (i.e., LCD televisions, LCD monitors, and laptop monitors) from 2003-2015. CCFLs and mercury started to flow to waste phase around the year 2007 and will likely peak in 2018 with an annual flow of 324.8 million units and 1.5 tons respectively, then will likely decline dramatically till 2030. Dismantling and production were the two main life stages of CCFLs with mercury vapor release, during which approximately 2.1 tons and 1.2 tons of mercury were released to the atmosphere respectively. The research also indicates that mercury recycling in specialized facilities was another life stage with high mercury emission risk in which the processes of shredding, separation, and residue disposal are inevitably accompanied by mercury release.

Integrated a-Si:H Gate Driver With Low-Level Holding TFTs Biased Under Bipolar Pulses

A hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) gate driver on array with low-level holding TFTs (LLH TFTs) biased under bipolar pulse is investigated. It is shown that the bipolar bias at low frequency significantly alleviates the threshold voltage shift of the LLH TFTs. As a result, the lifetime of the proposed gate driver is demonstrated to be several times of that under the conventional unipolar pulse bias. In addition, the improvement in the lifetime becomes more significant at the higher work temperature. The liquid crystal display television panels (32-in, $1366\times \textrm {RGB}\times 768$ ) with the proposed a-Si:H gate drivers integrated on array are manufactured, and the feasibility of the proposed driving scheme is well verified.

폐 LCD (Liquid Crystal Display) 해체 후 분리된 CCFL (Cold Cathode Fluorescence Light) 내 수은의 건식 제거 공정

LCD TV와 컴퓨터 모니터에는 스크린을 밝게 할 목적으로 냉음극관이 장치되어 있는데 이러한 냉음극관 대부분에는 수은이 봉입되어 있으므로 폐 LCD의 재활용 시 적절히 취급되어야 한다. 아울러 이러한 폐 LCD내의 냉음극관의 처리는 2002년에 채택된 EU의 WEEE 와 RoHS 지침에 따라 취급되고 제거되어야만 한다. 본 연구에서는 폐 LCD의 몰드 프레임에 장착된 CCFL을 안전하고 효율적으로 제거한 다음 여기 함유된 수은과 형광체 화합물을 환경친화적으로 분리하여 무해화 처리할 수 있는 건식 공정을 개발하였다. 이를 통해서 실용적이고 경제성 있는 폐디스플레이 자원 재활용 통합공정 개발에 기여할 목적으로 CCFL 무해화 시스템의 설계 및 제작, 이를 운용한 수은/형광체 화합물의 환경친화적 무해화 처리 효율을 평가해 보았다. CCFL 무해화 시스템을 이용하여 처리된 CCFL내 잔류 수은의 양을 정량적으로 평가해 본 결과 무해화율 99% 이상을 달성하였다. LCD televisions and monitors use cold cathode fluorescence lamps (CCFLs) to illuminate the screen. Most CCFLs contain mercury and they have to be carefully handled at the end of their lives as per minimum treatment standards under the Waste Electrical and Electronic Equipment (WEEE) and Restriction of Hazardous Substances (RoHS) directives. CCFLs were carefully separated from mold frames of waste LCD units for primary decontamination of mercury/fluorescent compound mixture using CCFL decontamination system designed and fabricated in the present research. Residual mercury was further removed by employing a pyro-process, where crushed CCFL tubes transferred from primary decontamination process were subject to heat treatment at <TEX>$550^{\circ}C$</TEX> in a box furnace: more than 99% of mercury was removable from waste CCFLs.

The dynamics of incremental costs of efficient television display technologies

We study the evolution of the incremental cost and price of efficiency for televisions in the U.S. market. We focus on televisions due to their rapid technological evolution and large number of annual shipments, such that costs and prices evolve on short timescales as compared to other consumer durable goods. Using the experience curve approach, we compare manufacturing costs and selling prices of two liquid crystal display (LCD) technologies. We find a mean experience rate of 27% for less efficient cold cathode fluorescent lamp LCD televisions and 14% for more efficient light emitting diode LCD televisions, using price data. This corresponds to an annual decline of approximately 17% per year in price for both television types. Our results also suggest that the incremental cost or price of efficiency, holding other major features constant, declines much more rapidly than the baseline cost or price. We find that the incremental cost or price declines at roughly 50% per year. The fitted parameters do depend on the specific technology modeled, as well as on whether cost or price data are used. Our results for LCD televisions are qualitatively similar to other display technologies, even very mature ones, suggesting that the cost and price decline extends many years after a technology is considered mature. We also analyze the selling prices of ENERGY STAR® and non-ENERGY STAR televisions, which support our main findings. These results highlight the consumer benefits of efficient display technologies, and how the dynamics of incremental costs differ from baseline costs.

Decontamination of Mercury contained in CCFLs (Cold Cathode Fluorescence Light) disassembled from Waste LCDs (Liquid Crystal Display)

LCD televisions and monitors use cold cathode fluorescence lamps (CCFLs) to illuminate the screen. Most CCFLs contain mercury and they have to be carefully handled at the end of their lives as per minimum treatment standards under the Waste Electrical and Electronic Equipment (WEEE) and Restriction of Hazardous Substances (RoHS) directives. CCFLs were carefully separated from mold frames of waste LCD units for primary decontamination of mercury/fluorescent compound mixture using CCFL decontamination system designed and fabricated in the present research. Residual mercury was further removed by employing a pyro-process, where crushed CCFL tubes transferred from primary decontamination process were subject to heat treatment at 550 o C in a box furnace: more than 99% of mercury was removable from waste CCFLs.

Precautionary Measures Necessary in Liquid Crystal Display (LCD) Television Maintenance by Electronic Technicians

The study was carried out to determine precautionary measures necessary in liquid crystal display (LCD) television maintenance by electronic technician. The population for the study was 3209 consisting of 11 electronic teachers and 3198 electronic technicians. 11 electronic teachers and 155 electronic technicians selected by simple random sampling were used for the study. Questionnaire consisting of 57 items was used to elicit responses from electronic teachers and electronic technicians regarding the two research questions. Data collected were analyzed using mean while t-test for independent sample was used to test the two null hypotheses at 0.05 level of significance. Analysis revealed the important components of LCD television that may occasionally developed faults and important precautionary measures that should be taken in LCD television maintenance. It was concluded that electronic technicians should carry out maintenance of LCD televisions by observing the precautionary measures to be taken in maintenance of LCD televisions.

A thermal simulation of the DDI development of a multi-channel package for high-definition LCD panels

A multi-channel display driver integrated circuit (DDI), which is the core part of a liquid crystal display (LCD) television (TV), was proposed. The introduction of multi-channel DDIs in LCD TVs results in thermal problems because of increased power in LCD TVs. DDIs are investigated at package and module levels to solve this thermal problem, and extracting the junction temperature (Tj) of DDI at a system level is also necessary. The objectives of this research are as follows. First, a standard temperature-measurement environment that is centered on consumers should be defined. Second, the defined measurement method needs to generalize analysis models (Ushaped compact model) based on the size in inches of LCD modules. Third, a cooling method based on multi-channel DDI needs to be proposed. Afterward, the effect of the proposal needs to be verified. The contributions of this study to the development of DDI products are as follows: first, this study performs heat dissipation parameters in multi-channel DDIs by using a generalized compact model. When the compact model is used, it can easily handle boundary conditions and accurately predict the temperature. Consequently, the temperature in the DDI can be calculated easily at a system level. We also propose a cooling plan to protect DDIs from overheating. This cooling plan can be utilized in the DDI design. Second, the thermal problem in conventional chip on films (CoF), which is caused by increased power, is solved by proposing a thermally enhanced CoF (TECoF), thereby reducing costs because of the reduced number of DDIs. For reference, an international patent is applied for the TECoF. Third, an estimated equation of Y (DDI temperature) for X’s is used in a package development system to predict the temperature in the early stage of the development and to prepare various countermeasures.

Development of Novel Polyimide Alignment Films for Liquid Crystal Display Televisions

We developed novel organic-solvent-soluble polyimide (PI) alignment films with a steroidal structure for liquid crystal display (LCD) televisions (TVs). The PIs can generate any desired pretilt angles between 3 - 90 °, which are needed to realize LCD-TVs such as twisted nematic, optically compensated bend, and vertical alignment LCD modes. The PIs also showed very stable pretilt angles, together with good electrical properties. The developed PI alignment films have been widely used for large screen size LCD-TVs with the display performance such as high contrast, fast response time, and wide viewing angle.

可搬型蛍光Ｘ線分析計による各種製品部材中ＲｏＨＳ指令対象物質のスクリーニング調査

The content of hazardous substances restricted by the European Union directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment 2002/95/EC (RoHS directive) in various consumer products including electrical and electronic equipments (EEE), household products, recycled products etc. were analyzed by using a handheld X-ray fluorescence (XRF) analyzer. Among 358 products investigated, one third failed RoHS compliance for Br when assuming all Br derived from polybrominated biphenyls and/or polybrominated diphenyl ethers (PBDEs), and all passed the RoHS threshold for Hg levels. About half of EEE examined contained more than 0.1 wt% of Br with the maximum concentration of approximately 20 wt% in rear casing of a computer monitor, indicating some sort of brominated flame retardants (BFRs) were intentionally added. From the XRF analysis of chassis of televisions (TV) and personal computer (PC) monitors, it was revealed that the percentage of products which exceeded Br thresholds in liquid crystal display TVs and PC monitors were less than those in cathode-ray tube TVs and PC monitors, suggesting the shift of type of flame retardants used over time. As use of PBDEs was restricted by RoHS directive in 2006, the consumer-electronics makers started using alternative flame retardants including novel non-PBDE BFRs and phosphorus flame retardants as well.

Modelling competition in global LCD TV industry

This work analyses global shipments of Liquid Crystal Display Televisions (LCD TVs) by considering mutualism among multiple generations of LCD TVs. In applying the revised Lotka–Volterra equations, this study analyses the dynamic competitive relationship among producers of 26-, 32- and 37-inch LCD TVs. Equilibrium analysis is used to evaluate whether future shipment orbit could converge to equilibrium status. The prediction abilities of Bass growth model and Lotka–Volterra model are further compared to examine whether the Lotka–Volterra model, which incorporates the mutualism among multi-generation LCD TVs, performs better. The result shows that the relationships between 26- and 32-inch LCD TVs, and 37- and 32-inch LCD TVs are commensal. Sales of 32-inch LCD TVs are promoted by increased sales of 26- or 37-inch LCD TVs. Results of the equilibrium analysis indicate that competition among various sizes of LCD TVs will not be stable. The interactions among multiple generations of LCD TVs will influence each other, leading to great fluctuations in sales. Since this study incorporates the interactive relationships among various sizes of LCD TVs in the proposed Lotka–Volterra equations, the ability of the Lotka–Volterra model to predict the market evolution of LCD TVs is superior to that of the Bass model.

Energy-Recycling (ER) Technique for a Direct-Lit Intelligent Power Management Backlight Unit (BLU)

A field-sequential-color (FSC) liquid crystal display (LCD) technique with a direct-lit red, green, and blue LED backlight driver is proposed to achieve low weight, thin, perfect image quality, and low-power consumption of LCD television. The FSC technique performs a pseudorandom color sequence in the spatial and temporal domains to reduce color-breakup and motion-blur effects. The direct-lit RGB-LED backlight driver increases brightness, contrast, and uniformity due to the removal of a color filter. In this paper, the proposed FCS-LCD controller uses a single LED driver to switch the driving voltage alternatively between 36 V for driving 12-series G- or B-LEDs and 24 V for 12-series R-LEDs. The proposed energy-recycling technique can harvest the extra energy when the driving voltage switches from 36 to 24 V. Experimental results show that energy saving is higher than 17% of the conventional driving method.

Propagation of a Light-Emitting Wave-Front in a Fine Tube Positive Column Discharge

The propagation velocity of a light-emitting wave-front is observed to be up∼2×10+5 m/s before Townsend breakdown and up∼5×10+6 m/s after Townsend breakdown along a discharge tube of inner diameter ro∼1.2 mm and length of 900 mm relevant to liquid crystal display television backlighting. Before Townsend breakdown, the origin of this wave is the ambipolar diffusion of plasma flux with the propagation speed up∝Da/ro for the plasma bounded by the radius ro with the diffusion coefficient Da along the positive column. After Townsend breakdown, the light-emitting wave-front propagates with the electron plasma wave generated by the pulses of driving voltage. The electron plasma wave propagates such a long distance along the tube without damping due to the effect of localized plasma generation by electron impact ionization collisions. The propagation velocity is described by up∼2ue2/ud, which is larger than the electron thermal velocity ue as well as the electron drift velocity ud.

Forecasting global adoption of crystal display televisions with modified product diffusion model

Liquid crystal display televisions (LCD TVs) embody properties of durable and high-technological products. In this work, we relax the restrictive assumptions of constant internal influence in the conventional growth model for worldwide diffusion of LCD TV innovation. Based upon the price impact on the imitating behaviors, we incorporate price factor into the Bass model to study evolutions of LCD TV market. Effects of innovation, imitation, price elasticity and potential market factors are systematically considered. Two different models, the conventional Bass model and the modified one are thus numerically solved and optimized to estimate the market dynamics of LCD TVs, where the results among the models as well as the collected data in the past decade are compared and validated for the best accuracy. The results of this study exhibit that LCD TV diffusion is mainly driven by consumers’ word of mouth and 32-inch LCD TV remains to occupy the largest potential market among various size levels of LCD TVs. Previous LCD TV adopters persuade the potential ones to imitate the former in the TV transaction decisions. In particular, this model illustrates that LCD TV price reduction stimulates such imitating behaviors of successive LCD TV consumers. Due to the significance of the modeled price effect in LCD TV adoptions, the model with considering the effect of price performs better in fitness, prediction capability and parameter stability than the conventional one.

Thin cell fringe-field-switching liquid crystal display with a chiral dopant

A fringe-field-switching (FFS) liquid crystal display (LCD) using a thin cell doped with a reverse-handed chiral compound is proposed. Such a FFS LCD exhibits a fast response time (∼8ms), high transmittance (&amp;gt;90%), low operating voltage (5Vrms), and intrinsically wide viewing angle. Its application for LCD televisions in order to reduce image blurring is emphasized.