Emerging firms in an emerging field: an analysis of patent citations in electronic-paper display technology

USPTO patent data covering the years 1994–2008 is used in this study to examine the citation networks of electronic-paper display technology. Our primary aim is to provide a better understanding of the ways in which emerging firms interact with, and learn from, technology diffusers. Two implications can be drawn from our analysis. Firstly, emerging firms within an emerging industry can enhance their technological capabilities through positive external learning activity. Secondly, despite the fact that technology diffusers have clear technological advantages, with the emergence of a new field, their influence within the network could potentially be decayed if they fail to remain proactive in terms of the absorption of available external knowledge.     

二极管型碳基膜场发射显示器的制作(英文)

介绍了一套简单、低成本的制作二极管型碳基膜场发射显示器模块的制作方法.该显示单元模块为16 * 16矩阵型点阵,可根据实际需要拼接成各种尺寸.器件的阴极和阳极均采用丝网印刷技术,包括:阴极导电图形、CNT图形、阳极荧光图形的印刷.各膜层图形经过精心设计以实现矩阵选址.使用低玻粉将阴极和阳极烧结之后,采用超高真空排气台进行排气,然后装配上驱动电路,即实现了单元碳基膜场发射显示器模块的制作.另外,为了改善CRT荧光粉的黏附性差和电阻率低的问题,我们往CRT荧光粉浆料中分别加入了碳纳米管和硝酸镁,得到了更好的发光性能.     

Field emission characteristics of an individual carbon nanotube inside a field emission-scanning electron microscope

Field emission (FE) properties of individual single-walled carbon nanotubes (SWCNT) were investigated inside a field emission-scanning electron microscopy. The individual SWCNT turned on a voltage of 23 V defined to produce a current of 10 pA, and was saturated at around 43 V and 880 nA. The FE characteristic of individual SWCNT also followed a conventional Fowler-Nordheim (F-N) theory in which a single linear slope in the F-N plots is measured below their limit of current level corresponding to the saturation regime of emission current. Energy-dispersive X-ray spectroscopy analysis showed that carbon atoms were deposited on the anode surface by the local heating of SWCNT tip during the FE processes and indicated about atomic 83% of carbon atoms. The carbon atoms were newly found to be evaporated and deposited on the anode surface during the FE process such that it was assumed that the degradation of FE was caused by evaporation and deposition of carbon atoms during the FE process.     

The patterned electron field emission of printed carbon nanotube films by image transfer technology

The patterned electron field emission of printed carbon nanotube (PCNT) films using image transfer technology is reported. If we transfer an image to the surface of PCNT films, such as using a stamp, the emission image of PCNT films will be the transferred pattern. Based on many experiments, we are convinced that the essential feature of pattern emission from PCNT films by image transfer technology is the great emission enhancement of the image transferred area and the reduced emission from the raw area. According to the results from field emission scanning electron microcopy (FESEM), we suggest that the connecting CNT bundles protruding from the substrate result in the emission enhancement of the image transferred area. At the same time, the emission current increase causes the external and internal voltage drop to increase which results in a decrease in the emission from the untreated area. Using image transfer technology, a well-resolved emission image of PCNT films could easily be obtained without any post-treatment.     

一种提高大面积碳纳米管场发射能力方法

碳纳米管(CNT)具有良好的场发射特性,研究表明,垂直于基板的碳纳米管具有较其他取向更大的场发射能力,本文介绍一种在大面积基板上使碳纳米管取向垂直的方法,通过有关参数的实验测试,研究了解场发射能力提高程度,并估算场增强因子。本方法对制备大屏幕场发射显示器(FED)具有积极意义。     

The high contrast ratio and fast response time of a liquid crystal display lit by a carbon nanotube field emission backlight unit

We report on the fabrication of a carbon nanotube field emission backlight unit (CNT-BLU) and its application for liquid crystal displays (LCD). The CNT-BLU was operated with locally controllable luminance and impulse-type scanning. The local luminance control, which is based on a very small block size of 1?cm(2), consisted of local dimming and local brightening. This resulted in the contrast ratio of the LCD-TV to be as high as 300?000:1. A fast response time of ～5.7?ms was also achieved from the LCD-TV lit by CNT-BLU, originating from the impulse-type scanning. In addition, the CNT-BLU showed long-term emission stability and high luminance uniformity.     

Application of carbon nanotube in wireless sensor network to monitor carbon dioxide

Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Over the years, new discoveries have led to new applications, often taking advantage of their unique electrical properties, extraordinary strength and efficiency in heat conduction. Since industrialisation, human activities have resulted in steadily increasing concentrations of the greenhouse gases. Excess amount of carbon dioxide (CO₂) in living environment is toxic and unsuitable for human consumption. Thus, a need exists for accurate, inexpensive, long-term monitoring of environmental contaminants using sensors that can be operated on site. Over the past decade, many wireless sensor network (WSN)-based monitoring applications have been proposed. This article reviews the developments of sensing elements to monitor CO₂ in the environment. The cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science, as well as potential sensing element in wireless sensor technology. They exhibit extraordinary strength and unique electrical properties, and are efficient thermal conductors. The unique properties of CNT makes it a potential sensing element in the WSN technology.     

Periodic deviations of the field emission current of a carbon nanotube from the Fowler-Nordheim law

Carbon nanotubes (CNTs) have been studied using a field electron microscope (electron projector) and a dispersive electron energy analyzer. In the range of emission voltages studied, the field-emitted electron energy distributions showed periodic transformations. The corresponding probe current-voltage characteristics exhibited periodic deviations (reaching 20 and 50% for the two CNT samples studied) from the Fowler-Nordheim law toward lower values of the current. The observed phenomenon is explained in terms of the interference model of thermoelectron emission at high voltages.     

Effects of welding head on the carbon nanotube field emission in ultrasonic nanowelding

Ultrasonic nanowelding technique was used to improve the field emission properties of carbon nanotube (CNT) cathodes. Two kinds of welding heads were used and the effects of the head on the emission properties were studied. The results show that cathodes welded by Al₂O₃ flat head demonstrate excellent field emission properties with high emission current density and good current stability. The improved field emission performance is attributed to the reliable and low resistance contact between CNTs and metal substrates. Cathodes welded by steel matrix head show a lower turn-on electric field due to the protruding CNTs at the edge of the welded pits.     

Geometry dependence of the electrostatic and thermal response of a carbon nanotube during field emission

In this paper we present an analysis to simulate heating within an isolated carbon nanotube (CNT) attached to an etched tungsten tip during field emission of an electron beam. The length, radius, wall thickness and shape of the tip (closed with a hemispherical shape or open and flat) of the CNT and its separation distance from the flat surface are considered as variables. Using a finite element method, we predict the field enhancement, emission current and temperature of the CNT as a function of these parameters. The electrostatic and transient thermal analyses are integrated with the field-emission models based on the Fowler-Nordheim approximation and heating/cooling due to emitting energetic electrons (the Nottingham effect). These simulations suggest that the main mechanism responsible for heating of the CNT is Joule heating, which is significantly larger than the Nottingham effect. Results also indicate that the electrostatic characteristics of CNTs are very sensitive to the considered parameters whereas the transient thermal response is only a function of the CNT radius and wall thickness. Further, the thermal response of the CNT is independent of its geometry, meaning that, as long as a given set of geometrical conditions are present that result in a given emission current, the maximum temperature a CNT attains will be the same.     

基于专利分析的碳纤维汽车技术创新趋势研究

对Innography专利数据库1973~2015年全球应用于汽车领域的碳纤维技术专利文献进行了统计分析,以了解目前汽车用碳纤维技术的创新研发态势、技术热点和竞争格局。分析表明:随着对汽车轻量化研究的逐渐深入,碳纤维材料的应用研究早已成为热门领域,2010年后,应用于汽车领域的碳纤维技术研究进入了快速发展阶段,研究较多的国家是中国、日本、德国、美国和韩国;中国的专利较多,但偏重于国内专利申请,具有雄厚研发实力的企业少,而德国、法国、日本、美国则更注重知识产权在全球的保护,形成自己的专利布局;核心专利数量不多,仅45件,其中大部分来自美国,美国掌握着大部分关键技术;目前碳纤维技术主要应用于汽车轮胎、摩擦材料、增强材料、成型制品、饰品和加热零部件等。     

Identifying technological topics and institution-topic distribution probability for patent competitive intelligence analysis: a case study in LTE technology

An extended latent Dirichlet allocation (LDA) model is presented in this paper for patent competitive intelligence analysis. After part-of-speech tagging and defining the noun phrase extraction rules, technological words have been extracted from patent titles and abstracts. This allows us to go one step further and perform patent analysis at content level. Then LDA model is used for identifying underlying topic structures based on latent relationships of technological words extracted. This helped us to review research hot spots and directions in subclasses of patented technology in a certain field. For the extension of the traditional LDA model, another institution-topic probability level is added to the original LDA model. Direct competing enterprises’ distribution probability and their technological positions are identified in each topic. Then a case study is carried on within one of the core patented technology in next generation telecommunication technology-LTE. This empirical study reveals emerging hot spots of LTE technology, and finds that major companies in this field have been focused on different technological fields with different competitive positions.     

A study on the mechanical and electrical reliability of individual carbon nanotube field emission cathodes

Individual carbon nanotube (CNT) field emission characteristics present a number of advantages for potential applications in electron microscopy and electron beam lithography. Mechanical and electrical reliability of individual CNT cathodes, however, remains a challenge and thus device integration of these cathodes has been limited. In this work, we present an investigation into the reliability issues concerning individual CNT field emission cathodes. We also introduce and analyze the reliability of a novel individual CNT cathode. The cathode structure is composed of a multi-walled carbon nanotube (MWNT) attached by Joule heating to a nickel-coated Si microstructure. The junction of the CNT and the Si microstructure is mechanically and electrically robust to withstand the strong electric field conditions that are typical for field emission devices. An optimal Ni film coating of 25?nm on the Si microstructure is required for mechanical and electrical stability. Experimental current-voltage data for the new cathode structure definitively demonstrates carbon nanotube field emission. Additionally, we demonstrate that our new nanofabrication method is capable of producing sophisticated cathode structures that were previously not realizable, such as one consisting of two parallel MWNTs, with highly controlled CNT lengths with 40?nm accuracy and nanotube-to-nanotube separations of less than 10?μm.     

Effect of nano-silver particles in bonding material on field emission properties for carbon nanotube cathodes

Effects of bonding materials in a screen-printing paste on field emission properties were investigated for carbon nanotube (CNT) cathodes. The CNT cathodes were characterized for their dependence on current density in terms of the sintering behavior of the bonding material. As the diameter of the Ag particles in the bonding material decreased from 1000 nm to 10 nm, the current density of the CNT cathode increased. The sintering temperature of bonding materials was decreased for small silver (Ag) particles in bonding material. The higher current density for a CNT cathode fabricated with smaller Ag particles was primarily due to the lower sheet resistance of the bonding material after heat treatment.     

Patenting trends in biometric technology of the Big Five patent offices

We examined the overall trends in biometric technology based on patent documents. Using PATSTAT database, we extracted 37,462 patent documents applied at the Big Five patent offices between 1990 and 2016. Latent Dirichlet allocation was applied to their abstracts to observe annual trends by topic. Our results are as follows: Fingerprint-enabled car anti-theft systems have been undergoing rapid technological development since 2014. In response, biometric signal transmitting models are becoming popular owing to concerns about theft of biometric templates. While fingerprint, face, and iris authentication technologies continue to advance, finger vein, voice, and signature authentication technologies are lagging. Use of biometric technologies in financial transactions, server networks, and digital media content security are decreasing as well. A citation analysis discovered key topics and patent applicants: Surprisingly, the quantitative growth rate of topics and the effect on the knowledge network showed an inverse relationship. US firms had the most citations, but fewer backward citations of own work, unlike Japanese companies. We provide practical insights to stakeholders of biometric technology.     

Analysis of developing a specific technological field using the theme code of Japanese patent information

The paper was to establish an easy and effective method to investigate and develop a specific technological field from Japanese patent information. The walking technique of the biped humanoid robot was used as an example to study the relative research capabilities and patent citation conditions for patent owners and patent map by the searching method of the theme code for FI (File Index) and F-term classification system of the Japanese Patent Office (JPO). A formulated technical matrix of patent map was established to indicate that the ZMP (Zero Moment Point) control means was the main technology to achieve stabilized walking control of the humanoid biped robot. This method can aid to establish a specific technological matrix from the specific selected term codes (single viewpoint or multiple viewpoints) of the F-term list in the theme code of the JPO system through Boolean logical operations. The resulting particular technical fields were developed to improve the technological capability or seek the merging technology opportunities.     

An integrated approach for detecting and quantifying the topic evolutions of patent technology: a case study on graphene field

Scientometrics - Comprehensive, in-depth and accurate analyses of patent technology topic evolutions become increasingly significant since the analytical results can offer related personnel the...     

Growth of carbon nanotube field emitters on single strand carbon fiber: a linear electron source

The multi-stage effect has been revisited through growing carbon nanotube field emitters on single strand carbon fiber with a thickness of 11 μm. A prepared linear electron source exhibits a turn-on field as low as 0.4 V μm(-1) and an extremely high field enhancement factor of 19,300, when compared with those results from reference nanotube emitters grown on flat silicone wafer; 3.0 V μm(-1) and 2500, respectively. In addition, we introduce a novel method to grow nanotubes uniformly around the circumference of carbon fibers by using direct resistive heating on the continuously feeding carbon threads. These results open up not only a new path for synthesizing nanocomposites, but also offer an excellent linear electron source for special applications such as backlight units for liquid crystal displays and multi-array x-ray sources.     

Nanocrystalline silicon as the light emitting material of a field emission display device

A nanocrystalline Si-based paste was successfully tested as the light emitting material in a field emission display test device that employed a film of carbon nanofibers as the electron source. Stable emission in the 550-850?nm range was obtained at 16?V?μm(-1). This relatively low field required for intense cathodoluminescence (CL) from the PSi paste may lead to longer term reliability of both the electron emitting and the light emitting materials, and to lower power consumption. Here we describe the synthesis, characterization, and analyses of the light emitting nanostructured Si paste and the electron emitting C nanofibers used for building the device, including x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The corresponding spectra and field emission curves are also shown and discussed.