有机发光二极管显示屏的喷墨打印研究与展望

近年来,有机发光二极管(OLED)被广泛应用于智能手机等中小尺寸显示屏,并逐步进入电视等大尺寸显示领域和照明市场。随着OLED平板显示新时代的到来,对显示屏的彩色化与图案化研究提出了更高要求。与传统真空蒸镀技术相比,喷墨打印技术更容易实现大面积器件的彩色化和复合功能材料的图案化,且工艺简单,成本低廉,并可进行柔性器件加工。本文综述了采用喷墨打印技术制备OLED显示屏的研究现状,并系统介绍了喷墨打印设备的发展历程,通过优化bank结构提高显示屏的分辨率,优化墨水配方及组成配比抑制喷墨液滴的“咖啡环”效应,从而提高显示器发光均匀性,最后对国内外该技术产业进行了概述与展望。     

Investigation of a pulsed waveguide piezoelectric pressure sensor

The problem of pulsed mechanical action on a stepped acoustic waveguide with a sensitive piezoceramic element in the presence of a perfectly rigid boundary is considered. The dependence of the stress generated by the piezoelectric element on time, measuring circuit parameters, and external perturbing action is obtained analytically. A calibration of the waveguide piezoceramic sensor of the proposed design, which is intended for measuring the pressure of shock waves incident on a solid obstacle, is performed by the thumper method.     

Direct fabrication of copper patterns by reactive inkjet printing

Reactive inkjet printing (RIP) was applied to fabricate arbitrary copper (Cu) patterns. RIP prints reactive inks which can provide desired materials after the reaction on a substrate. Here, Cu precursors and reducing agents were dissolved together in one solution as a printable ink instead of conventional Cu nanoparticle inks. The prepared reactive ink was applied to the RIP method to provide dot arrays, lines, and films of Cu. The synthesis of Cu was confirmed to occur successfully by thorough analysis. The RIP method can reduce the process cost and resolve critical drawbacks of the conventional inkjet printing such as a nozzle clogging problem. Furthermore, utilizing reactive precursor inks broadens the choice of materials that can be processed by inkjet printing.     

Surface physical-morphological and chemical changes leading to performance enhancement of atmospheric pressure plasma treated polyester fabrics for inkjet printing

Without any preprocessing, polyester fabric has lower ability to hold on water due to the smooth morphology and chemistry property of polyester fibers. Therefore, patterns directly printed with pigment inks have poor color yields and easily bleed. In this paper, atmospheric pressure plasma was used to pretreat polyester fabric in order to provide an active surface for the inkjet printing. The results showed that surface-modified polyester fabrics could obtain the effects of features with enhanced color yields and excellent pattern sharpness. SEM images indicated that the rough surface of plasma treated fibers could provide more capacities for the fabric to capture inks and also facilitate the penetration of colorant particles into the polyester fabric. XPS analysis revealed that air + 50%Ar plasma introduced more oxygen-containing groups onto the fabric surface than air plasma. Although AFM images indicated that etching effects generated by air plasma treatments were more evident, the air/Ar plasma treated sample has higher K/S value and better color performance. These studies have also shown that the chemical modification of plasma appears to be relatively more significant for improving the effect of inkjet printing.     

Synthesis and characterization of copper ink and direct printing of copper patterns by inkjet printing for electronic devices

Among the conventional metallic inks used in the printing process, silver exhibits high conductivity and thermal stability. Nevertheless, due to the high cost of silver, it cannot be extensively used for the fabrication of inks. As a competitive alternative, copper can be considered as a substitute for silver; however, copper ink oxidizes under certain atmospheric conditions. To meet these shortcomings, a cost effective, highly conductive, and oxidation-free copper-based ink has been synthesized in this study, wherein, oxidation of the copper particles in the copper-based ink was prevented by using copper complexes. The copper ink thus fabricated was printed on chemically treated Si/SiO₂ substrates followed by the characterization of the printed copper films. The results of this study confirmed that the synthesized copper ink exhibited properties suitable for its use in the inkjet printing process for fabrication of various electronic devices.     

Improvements in carbon fibre reinforced composites by inkjet printing of thermoplastic polymer patterns

A thermoplastic polymer solution was inkjet printed in a pre‐defined hexagonal pattern onto carbon fibre reinforced epoxy resin (CFRP), leading to a significant increase in strength, stiffness and toughness of the final aerospace grade compo‐site system. The approach consisted of depositing low‐viscosity polymer microdroplets having chemically and me‐chanically comparable properties to epoxy polymer, onto CFRP before curing and solidification. The microdroplets remained arrested between composite plies without direct contact with the neighbouring microdroplets ensuring preservation of the structural integrity of the new composite system after curing. The key to achieving this synergistic effect was in appropriately selected additive materials; however, the novel aspects also included the method itself, which enabled an accurate crack arrest mechanism.

     

Effects of nozzles array configuration on cross-talk in multi-nozzle electrohydrodynamic inkjet printing head

This paper presents the analysis of a triangular array of nozzles in a multi-nozzle electrohydrodynamic (EHD) inkjet printing head. A methodology has been proposed to minimize the “end effect” by changing the traditional linear array of nozzles to triangular array of nozzles in multi-nozzle EHD printing head. Interaction (cross-talk) between the electrically charged neighboring jets is investigated and analyzed both numerically and experimentally using three glass nozzles with independent voltage connections and independent ink supply to each nozzle. In order to scrutinize the performance of triangular array multi-nozzle EHD inkjet printing head, comparative study of triangular array multi-nozzle EHD inkjet printing head to the linear array multi-nozzle EHD inkjet printing head has been made on the basis of electric field simulations and experiments. Experimental results illustrate that in triangular array multi-nozzle EHD inkjet printing head, the over potential requirement is low and individual capillaries are operating with more independence as compared to linear array multi-nozzle EHD inkjet printing head.     

Selective growth of ZnO nanowires on substrates patterned by photolithography and inkjet printing

Zinc oxide nanowires (ZnO NWs) were grown by a two-step growth method, involving the deposition of a patterned ZnO thin seeding layer and the chemical vapor deposition (CVD) of ZnO NWs. Two ways of patterning the seed layer were performed. The seeding solution containing ZnO precursors was deposited by sol–gel/spin-coating technique and patterned by photolithography. In the other case, the seeding solution was directly printed by inkjet printing only on selected portion of the substrate areas. In both cases, crystallization of the seed layer was achieved by thermal annealing in ambient air. Vertically aligned ZnO NWs were then grown by CVD on patterned, seeded substrates. The structure and morphology of ZnO NWs was analyzed by means of X-ray diffraction and field emission scanning electron microscopy measurements, respectively, while the vibrational properties were evaluated through Raman spectroscopy. Results showed that less-defective, vertically aligned, c-axis oriented ZnO NWs were grown on substrates patterned by photolithography while more defective nanostructures were grown on printed seed layer. A feature size of 30 µm was transferred into the patterned seed layer, and a good selectivity in growing ZnO NWs was obtained.     

压电驱动金刚石对顶砧加压装置的研制和应用

金刚石对顶砧加压装置广泛用于物理、化学、材料等许多科学领域。自Bridgman发明金属对顶砧及随后发展金刚石对顶砧以来,对顶砧装置设计和加压技术得到不断发展。文章介绍采用压电驱动金刚石对顶砧来产生高压,实现低温20 K下原位连续加压,连续加压范围约2—4 GPa。该加压装置具有体积小、操作方便,可装在小型低温恒温器中使用等优点。     

Multi-nozzle electrohydrodynamic inkjet printing of silver colloidal solution for the fabrication of electrically functional microstructures

In this paper, multi-nozzle electrohydrodynamic (EHD) inkjet printing of a colloidal solution containing silver nanoparticles in a fully controlled fashion is reported. For minimizing interaction, i.e. cross-talk, between neighboring jets, the distance between the nozzles was optimized numerically by investigating the magnitude of the electric field strength around the tip of each nozzle. A multi-nozzle EHD inkjet printing head consisting of three nozzles was fabricated and successfully tested by simultaneously printing electrically conductive lines of a colloidal solution containing silver nanoparticles onto a glass substrate. The printed results show electrical resistivity of 5.05×10⁻⁸ Ω m, which is almost three times larger than that of bulk silver. These conductive microtracks demonstrate the feasibility of the multi-nozzle EHD inkjet printing process for industrial fabrication of microelectronic devices.     

Flexural resonance vibrations of piezoelectric ceramic tubes in Besocke-style scanners

Flexural resonance vibrations of piezoelectric ceramic tubes in Besocke-style scanners with nanometer resolution are studied by using an electro-mechanical coupling Timoshenko beam model.Meanwhile,the effects of friction,the first moment,and moment of inertia induced by mass loads are considered.The predicted resonance frequencies of the ceramic tubes are sensitive to not only the mechanical parameters of the scanners,but also the friction acting on the attached shaking ball and corresponding bending moment on the tubes.The theoretical results are in excellent agreement with the related experimental measurements.This model and corresponding results are applicable for optimizing the structures and performances of the scanners.     

Investigation of the effect of uniaxial pressure on antiferromagnetic resonance in KFe11O17 Crystals

The deformation dependence of the resonance field in KFe₁₁O₁₇ single crystals was investigated by the AFMR method. The measurements were performed at T=77 K and ν=47.52 GHz for two orientations of the external pressure. The experimental data are discussed in terms of a model of a very simple easy-plane antiferromagnet taking account of the elastic and magnetoelastic contributions to the thermodynamic potential. The magnetostriction, magnetoelastic, and elastic contants are calculated and the results are λ=1.94×10⁻⁵, B ₁=2.75×10⁸ erg/cm³, and C ₁₁−C ₁₂=1.42×10¹³ erg/cm³, respectively. The alues of these constants imply that the origin of the initial gap in the AFMR spectrum is not of magnetoelastic origin. Fiz. Tverd. Tela (St. Petersburg) 40, 513–515 (March 1998)     

基于虚拟仪器的压电陶瓷驱动技术研究

针对压电陶瓷驱动器的非线性应变,以压电陶瓷微位移驱动原理为基础,分析了扫频激光器腔长控制原理;在硬件时钟的定时下,分析了压电陶瓷的驱动特性,并通过调整驱动信号的步长电压来调节压电陶瓷的非线性。设计了基于虚拟仪器的控制系统,并对线性化方法进行了原理分析和实验。实验结果表明,该测量系统可以使压电陶瓷在其伸长范围内线性地伸长。     

A new open-loop driving method of piezoelectric actuator for periodic reference inputs

The hysteresis characteristic of piezoelectric actuators is one of the major deficiencies in a wide variety of precise tracking positioning controls. In this paper, a novel mathematical model is proposed to describe hysteresis precisely and an open-loop tracking controller is implemented with the proposed model to compensate the hysteresis for tracking periodic sinusoidal inputs. Finally, some tracking control experiments based on a micro-positioning stage for the desired sinusoidal trajectory are performed according to the proposed method and the experimental results demonstrate that the positioning precision is noticeably improved in the open-loop operation compared to the conventional open-loop control without any compensation. In comparison to the regular PID closed-loop controller, the proposed feedforward control method has better tracking performance.     

The influence of pressure on recombination centres in piezoelectric luminophores

The present paper shows that a recombination centre of the Cu⁺-[S^–] type in the ZnS lattice has local piezoelectric properties. On the basis of this fact some phenomena of triboluminescence are explained and a periodic generator of light is proposed.     

Research on coupling between thermoacoustic resonance pipe and piezoelectric acoustic source

Piezoelectric loudspeakers have been used in thermoacoustic refrigerators for operating at the high frequency to miniaturize the system. Then the coupling between the piezoelectric loudspeaker and resonance pipe becomes an important factor for improving the performances of the system. By the equivalent circuit model, the expressions of the acoustic output power and electroacoustic transfer efficiency at a low operating frequency are obtained, and then the structures of the piezoelectric loudspeaker and resonance pipe, as well as the operating frequency, are optimized to achieve a high electroacoustic transfer efficiency and a large acoustic output power. It is also shown that when the total reactance of the system equals zero, the resonance frequency of the resonance pipe is the optimized operating frequency and a high acoustic output power can be achieved. However, the highest transfer efficiency and largest acoustic power cannot be obtained simultaneously, therefore a trade-off condition must be adopted.     

Determination of elastic, anelastic, and piezoelectric coefficients of piezoelectric materials from a single specimen by acoustic resonance spectroscopy

We describe an advanced methodology to determine all the independent elastic-stiffness coefficients Cijkl, the associated internal frictions Qijkl(-1), and piezoelectric coefficients eijk of piezoelectric materials from a single monocrystal specimen using resonant-ultrasound spectroscopy with laser-Doppler interferometry. The mechanical-resonance frequencies of a piezoelectric solid depend on all of the elastic and piezoelectric coefficients, and their accurate measurement allows one to determine the elastic and piezoelectric coefficients simultaneously. Resonance-peak-width measurements yield the internal-friction tensor. Successful determination requires correct vibration-mode identification for the observed resonance frequencies. This is achieved unambiguously by measuring deformation distributions on the vibrating-specimen surface with laser-Doppler interferometry and comparing them with calculated displacement distributions. The methodology is applied to lithium niobate (LiNbO3) and langasite (La3Ga5SiO14) crystals.     

Identification of the piezoelectric material coefficients using the finite element method with an asymptotic waveform evaluation

A rapid identification of the piezoelectric material constants for a piezoelectric transducer is proposed. The validity of a three-dimensional finite element routine was confirmed experimentally. The asymptotic waveform evaluation (AWE) was adopted for a fast frequency sweep of the finite element analysis. The three-dimensional finite element method with an AWE and a design sensitivity method was used for a material inversion scheme of piezoelectric transducers. In order to confirm the inversion routine of the material constants, the mechanical displacements, which mean the mode shape, were calculated along the vertical and lateral position of the sample transducer.     

Identification of the piezoelectric material coefficients using the finite element method with an asymptotic waveform evaluation

A rapid identification of the piezoelectric material constants for a piezoelectric transducer is proposed. The validity of a three-dimensional finite element routine was confirmed experimentally. The asymptotic waveform evaluation (AWE) was adopted for a fast frequency sweep of the finite element analysis. The three-dimensional finite element method with an AWE and a design sensitivity method was used for a material inversion scheme of piezoelectric transducers. In order to confirm the inversion routine of the material constants, the mechanical displacements, which mean the mode shape, were calculated along the vertical and lateral position of the sample transducer.