最新刊期
期 10 ， 2020
- 摘要：Ni/Au coating films plated on traditional direct plated copper (DPC) ceramic substrates will strongly absorb ultraviolet (UV) light. To enhance light extraction efficiency (LEE) of deep ultraviolet light emitting diodes (DUV LEDs), a DPC ceramic substrate plated with two metal coating films was designed and prepared. A Ni/Au film covering the pad of the DPC ceramic substrate can provide electrical interconnection for LEDs, and a high-reflection Al film partly covering the Ni/Au film can provide superior reflection for UV light. Optical, electrical and thermal properties of the DUV LED packaged by the Al-plated DPC ceramic substrate and traditional DPC ceramic substrate with only one Ni/Au coating film were measured, and models of the packaged LED were established and analyzed. As a result, by using the Al-plated DPC ceramic substrate, the light output power (LOP) of the DUV LED is enhanced by 19.2%, while the wall plug efficiency (WPE) and the external quantum efficiency (EQE) are enhanced by 1.20 and 1.19 times, respectively. Furthermore, after aging tests for 160 h, LEDs packaged by Al-plated DPC ceramic substrates showed better reliability. This Al-plated DPC ceramic substrate provides a feasible way to improve the LEE of DUV LEDs by packaging.关键词：DUV LED packaging;DPC ceramic substrate;optical property;thermal resistance
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发布时间：2020-09-28 - 摘要：At present, liquid crystal with fused heterocyclic ring is an important direction of molecular structure design and development. In this paper, a new liquid crystal compound with 5, 6-difluorobenzofuran ring structure was synthesized via palladium catalyzed coupling reaction and ring closing reaction of cyclohexyl substituted acetylene ando-iodophenol derivative. The total yield was 54%. Its structure was characterized by 1H NMR and MS, and its phase transition temperatures were tested by DSC and POM. It is found that the melting point and the clear point of the compound is 118℃ and 202℃ respectively, and the nematic temperature range is 84℃. The physical properties test shows that the birefringence is about 0.13, the dielectric anisotropy is 12.6 and the rotational viscosity is 420 mPa·s. Compared with the similar 3, 4-difluorobenzene liquid crystal compound, the birefringence of the compound containing 5, 6-difluorobenzofuran ring increases by 65%, the dielectric constant increases by 97%, and the clear point increases by 66%. As a new kind of fluorine-containing building block, 5, 6-difluorobenzofuran has outstanding comprehensive performance and good application prospect in the field of liquid crystal display.关键词：fluorinated liquid crystal;benzofuran;synthesis;birefringence;dielectric anisotropy
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发布时间：2020-09-28 - 摘要：Al-doped ZnO (AZO) high-resistance films with the doping mole fraction between 5%~20% are prepared by Sol-Gel method. The sheet resistance of the films are characterized by the square resistance method. The morphology of the films are characterized by scanning electron microscopy (SEM). Nano Measurer 1.2 software is used to measure the mean particle radius of the film grains, and the spectral transmittance of the film was characterized by a spectrophotometer. When the doping mole fraction of Al is between 5%~20%, the sheet resistance gradually increases between 2~405 MΩ/□, the grain size gradually decreases between 24.35~17.53 nm, and the visible light transmittance can reach about 80%. The liquid crystal lenses with modal control of AZO high-resistance layers with different Al doping mole fraction are prepared and their optical interference characteristics are studied. AZO films with the doping mole fraction between 10% and 15% can meet the requirements of liquid crystal lenses for film transparency and square resistance.关键词：Sol-Gel;AZO film;sheet resistance;liquid crystal lens;modal control
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发布时间：2020-09-28
Material Physics
- 摘要：Volume grating waveguide as a solution to realize augmented reality display, its core is the fabrication of volume grating. This work proposes a simple, easy-to-build asymmetric exposure optical path with a diffraction efficiency of up to 80% for the fabricated slanted volume grating. A 632.8 nm He-Ne laser was used to monitor the evolution of the grating. The results showed that the grating reaction was completed within 25 s, forming the resulting grating. The SEM image proves the tilt characteristics of the grating and is consistent with the theoretical calculation results. The diffraction efficiency detuning curve of the fabricated slanted volume grating shows a good agreement with the coupled wave theory, and its FWHM is 3.22°. The slanted volume grating can be switched by an external electric field. The 90% and 10% switching field strengths are 5.1 V/μm and 11.25 V/μm, respectively. This work provides positive guidance and reference for the fabrication of slanted liquid crystal/polymer volume gratings.关键词：liquid crystal/polymer grating;slanted volume grating;diffraction efficiency mismatch;electrical switching
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发布时间：2020-09-28 - 摘要：The different specifications of LED smart glass display screens have different LED dot matrix connection sequences due to the manufacturing process and the actual requirements of the application site. Therefore, in actual applications, it is necessary to rewrite the hardware program to realize the lighting of the LED smart glass display screens. It brings a lot of inconvenience to the application of the product, so it is proposed to a PC software design for mapping video pixels to the LED smart glass dot matrix. The Piccolo frame is used to build the node and the "child" node to realize the mapping of the LED smart glass display. The Socket network programming is used to realize the remote transmission of the mapping data. In practical application, only the dot matrix drawing of LED intelligent glass on the upper computer interface can realize the display lighting of LED intelligent glass. The design of the mapping software makes the hardware system driving the LED smart glass display more adaptable, sensitive and versatile, and improve the efficiency of construction.关键词：LED smart glass display;lattice mapping;Piccolo framework;Socket network programming
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发布时间：2020-09-28 - 摘要：The gate electrode of thin film transistor(TFT) is a step in cross section, it is covered by gate insulator(GI), source and data electrode(SD electrode) in sequence, and the degree of coverage is measured by the step coverage, which is the ratio of the horizontal thickness to the vertical thickness of GI layer at the step. In this paper, combining the manufacturing process of HADS product in Chongqing BOE company, the influence of gate thickness and profile on the GI layer step coverage is studied. Then, the difference of SD etching degree between step and non-step is explored based on step coverage. After that, the relationship between gate profile, step coverage, Cu corrosion and other defects are analyzed based on defect information in mass production. At last, the corresponding yield up measures are proposed. The experimental results show that the tate profile is a key factor affecting step coverage, and gate profile has a negative linear relationship with GI coverage. When the gate thickness varies from 280 nm to 500 nm, the GI coverage decreases by 20% for every 10° increase in the gate profile. SD layer covers the step, and will be thinned at this place, which leads to an increase in the degree of SD etching. If the gate profile is large, the GI layer at the step will be thinned or generates micro-cracks, the corrosive medium in manufacturing process will pass through the thinned GI layer or crack to react with gate electrode to form corrosion. Whats more, a larger gate profile will cause SD line to be open at the step. A gentle gate profile can be obtained to avoid the above yield risk by changing etchant, adjusting etchant composition, optimizing etch process. In addition, it is a useful method to adjust GI deposition parameter to improve GI coverage to avoid gate corrosion; and the solution containing improving photo-resist adhesion, widening the SD line at the step can be tried to avoid SD line open.关键词：thin film transistor;gate profile;step coverage;data line open;gate corrosion
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发布时间：2020-09-28
Device Physics & Device Preparation
- 摘要：Contrapose data line and common line invisible short(DCS Invisible) in production of copper process array substrate, a new method based on cutting for locating the position of DCS Invisible is presented. Based on the result of data and failure analysis, an observation experiment of layer section with different ashing process time is designed to explore the mechanism. In ashing process, reaction gas SF6 below the photoresist which looks like the shape of roof will corrode copper metal of common line. Under the condition of high humidity, the corrosion will be aggravated. Corrosion products grow up and can't be covered by thin film of GI/Active. After thin film process of SD(Source & Drain), the data line will connect with corrosion products and finally cause DCS which is invisible on the front side of array substrate. Based on the research, the experiment of reaction gas consumption of SF 6 in ashing process, relative humidity, waiting time from Ashing to 2nd Gate Wet Etch and design improvement is proceeded. Finally, DCS Invisible is solved by reducing reaction gas consumption of SF6, decreasing relative humidity, controlling waiting time from Ashing to 2nd Gate Wet Etch and insuring space H of slotting design larger.关键词：copper process;invisible;data line;common line;short
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发布时间：2020-09-28 - 摘要：Negative liquid crystals is an effective way to increase the transmittance and contrast ratio for the high-resolution small size fringe field switching (FFS) mode display. Bright line comes up on dark state at the edge of display monitor by using negative liquid crystals, which is called line Mura. The line Mura is analyzed by electric and optical simulation and experiments. Dummy pixel around the display monitor is found to be the direct cause, which leads to anomalous electric field in crab region to switch liquid crystal on dark state. The influence factors of line Mura are analyzed, and improvement method is proposed, which provides good guidance for the design of negative LCD in FFS mode in the future.关键词：line Mura;negative liquid crystals;dummy pixel;crab;fringe field switching
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发布时间：2020-09-28
Driving & Controlling
- 摘要：In the liquid crystal display (LCD) system, the main reasons for the low quality of moving image are the characteristic of holding type display and the slow response. In order to study the influencing factors of moving image quality of LCD, a simulation model of moving image perception effect of LCD is established. The simulation model takes the different response speeds of the display, frame rates and backlight duty ratios as parameters, and simulates the moving image effect of the final perception of the human eye for different types of display images. Through the visual perception experiment, the simulation image is evaluated and the experimental results are statistically analyzed. The results show that the backlight duty ratio modulation can effectively improve the quality of moving image. The speed of response is positively related to the quality of moving image. The improvement of frame rate on the quality of moving image is limited by the response speed, that is, there is a cross influence between the two. The research results can provide theoretical reference for improving the moving image quality of LCD system.关键词：motion blur;liquid crystal response;visual perception;dynamic modulation transfer function
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发布时间：2020-09-28 - 摘要：In order to handle the image denoising problem, a non-local mean image denoising method based on Poisson distribution is proposed in this paper. Each pixel in image is modeled as a poisson distribution. The parameters of Poisson distribution are estimated according to the maximum likelihood of the pixels in a non-local region. The difference between two pixels is calculated by the L2 norm distance corresponding to the Poisson distribution. Moreover, the similarity weights are defined by the sum of L2 norms between two pixels in their neighborhood points. The image Poisson denoising is carried out by using the principle of non-local mean. The experimental results show that the proposed algorithm can preserve the image details well, and the denoised image has a high peak signal-to-noise rate over 22 dB. The proposed method can be effectively used for image denoising.关键词：Poisson denoising;L2 norm;Poisson distribution;nonlocal means
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发布时间：2020-09-28 - 摘要：Aiming at the common display methods such as image superimposition and cross-screen stitching in the current video display field, the two functions often cannot be implemented in the same system at the same time, resulting in limitation of application scenarios. A hardware structure design of a multifunctional video stitching system is proposed. The system is based on a bilinear interpolation image algorithm. The pipeline design ideas are used to optimize the algorithm. At the same time, a single-chip computer is used to complete the calculation of the zoom factor and the transmission of display parameters before and after video processing. The whole process reduces the consumption of hardware resources, and also improves the efficiency of the algorithm. The design is verified in Diamond that is the development environment of Lattice. The results show that the FPGA can simultaneously process four input video stream storage operations and output four video signals of any resolution. In a 2×2 stitching matrix, the image overlay and cross-screen stitching can be achieved simultaneously. The stitching system supports a maximum resolution of 1 920×1 080 and an output with a minimum resolution of 50×50, achieving the expected result.关键词：screen overlay;cross-screen stitching;bilinear interpolation;FPGA chip;arbitrary resolution
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发布时间：2020-09-28 - 摘要：A Finite Impulse Response(FIR) digital filter based on Field Programmable Gate Array(FPGA) is designed and implemented for signal processing in strain signal acquisition system. Firstly, based on MATLAB, Blackman window function is used to design a 15 order digital filter with 16 length, and the signal is composed of white Gaussian noise and sine wave with frequency of 2 kHz and 8 kHz. Then the 12 bit coefficients are quantized, and the coefficient file is imported into QuartusⅡ 13.1 software. Combining with the IP core of digital filter in FPGA, FIR digital filter is designed from top to bottom. Finally, it is simulated in Simulink environment. The results show that the mean square error of the synthesized signal decreases by 28.5% before and after filtering, which can improve the quality of low frequency signal and enhanced the function and integration of the strain signal acquisition system.关键词：signal acquisition;FIR digital filter;FPGA;IP core
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发布时间：2020-09-28 - 摘要：In order to improve the visibility of aerial image in the foggy weather, an image defogging algorithm based on dual-threshold position and transmittance constraint is proposed. Firstly, according to the features of non-sky and rich details from aerial images, both the gradient threshold and brightness threshold are used to keep positional limitation of the atmospheric light and therefore the accuracy has been improved effectively. Secondly, the transmittance is estimated by creating constraint, then the precise value is obtained by performing bi-exponential edge preserving filtering. Finally, a tone mapping method for restored image is proposed based on the perception law of human vision to the signal fluctuation. Simulation results show that the restored images not only remove fog effectively, but also keep color natural and real. The average entropy and gradient from test images are 7.659 and 16.631, which achieve a degree of improvement compared with other algorithms. The proposed algorithm gets satisfactory restoration for different landforms and detail features, thereby it can meet the application requirement of aerial image defogging.关键词：image defogging;aerial image;transmittance;atmospheric scattering Model;image restoration
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发布时间：2020-09-28
Display & Image Processing
- 摘要：In order to grasp and understand the Volatile Organic Compounds(VOCs)emission characteristics of various process links in the production process of the TFT-LCD industry, a domestic TFT-LCD manufacturing company was selected as an example to study the VOCs concentration distribution of each production workshop. The results showed that the average concentration of VOCs in the Array production workshop was 4.14~11.19×10-6 in a whole year. The photoresist composition in the CF production workshop was more complex, and the average VOCs concentration of green production line was the highest, which was 4.6~14.50×10-6 in a whole year. The highest VOCs concentration was found at VCD of Array and CF workshop.The key to reduce the concentration of VOCs in the TFT-LCD production workshop lies in source control. Adding zeolite rotor adsorption equipment had a significant effect on reducing the concentration of VOCs in the production workshop, and could remove about 60.71%~71.33% of organic waste gas.关键词：TFT-LCD production;VOCs;emission characteristics;photoresist
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发布时间：2020-09-28
Industrial Technology
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