Os dispositivos emissores de luz orgânicos OLEDs têm despertado um enorme interesse tanto da comunidade científica quanto das empresas presentes no mercado mundial de displays. As características de elevado ângulo de visão, alta eficiência energética, possibilidade de confecção de displays flexíveis que não necessitam retroiluminação, baixo peso, fácil processabilidade, dentre outras, fazem com que os displays fabricados com materiais orgânicos apresentem um enorme potencial para as mais diversas aplicações. O presente trabalho teve como objetivo contribuir para a construção e caracterização de displays monocromáticos à base de polímeros luminescentes depositados pela técnica Ink Jet. Para tanto foram preparados os padrões de linhas x colunas, formadores dos pontos luminosos (pixels) de matrizes passivas e desenvolvidos processos para deposição dos filmes finos de polímeros semicondutores. A utilização da deposição por Ink Jet aparece como uma técnica chave para a produção de dispositivos poliméricos. Nesta pesquisa, como material luminescente foi utilizado um polímero da família do polifluoreno, de fácil processamento e elevada eficiência luminosa, enquanto que como eletrodos foram utilizados o óxido de estanho e índio (ITO) e Alumínio. O ITO foi utilizado por possuir baixa resistividade elétrica, elevada função de trabalho e elevada transmitância na região do visível. O processo de encapsulamento do display se deu por meio do acondicionamento destes dispositivos em ambiente isento de oxigênio e umidade, evitando-se os efeitos já conhecidos da foto-oxidação das camadas poliméricas. Os dispositivos, uma vez preparados, foram caracterizados por meio de medidas ópticas (fotoluminescência), elétricas (eletroluminescência, condutividade) e de desempenho (eficiência luminosa e luminância). / Organic Light Emitters Diodes OLEDs is a promising field of study and a huge market opportunity to semiconductor players. Thanks to its potential characteristics to replace the main todays display technologies like lightweight, low voltage, wide viewing angle, high resolution, fast switching, broad color range and the possibility to fabricate flexible devices, makes the organic semiconductors a potential candidate to develop, in a near future, devices and systems that even could not be imagined before. This work aims to contribute to the manufacturing process field and to the characterization of displays made by ink jet deposition technique. To achieve this objective, line x column patterns were produced, in which the pixels are generated at the crossing of lines and columns. The ink jet printing of materials is playing an important role in industry because it provides a low-cost manufacture environment potential. In this work, we studied the morphology of the ink jet deposition of polyfluorene over Indium Tin Oxide (ITO) substrates treated by different procedures. Those materials where used because the polyfluorene polymer presents high light emission efficiency and easiness of processing. The electrodes were prepared with ITO (due its low resistivity, high work function and high transmittance in the visible spectrum) and aluminum. The processed displays were sealed inside an inert ambient with positive pressure to avoid the photo-oxidation of the semiconductor luminescent polymer layers. The devices were characterized by optical (photoluminescence), electrical (electroluminescence) and performance (brightness, luminous efficiency) measurements.

Os dispositivos emissores de luz orgânicos OLEDs têm despertado um enorme interesse tanto da comunidade científica quanto das empresas presentes no mercado mundial de displays. As características de elevado ângulo de visão, alta eficiência energética, possibilidade de confecção de displays flexíveis que não necessitam retroiluminação, baixo peso, fácil processabilidade, dentre outras, fazem com que os displays fabricados com materiais orgânicos apresentem um enorme potencial para as mais diversas aplicações. O presente trabalho teve como objetivo contribuir para a construção e caracterização de displays monocromáticos à base de polímeros luminescentes depositados pela técnica Ink Jet. Para tanto foram preparados os padrões de linhas x colunas, formadores dos pontos luminosos (pixels) de matrizes passivas e desenvolvidos processos para deposição dos filmes finos de polímeros semicondutores. A utilização da deposição por Ink Jet aparece como uma técnica chave para a produção de dispositivos poliméricos. Nesta pesquisa, como material luminescente foi utilizado um polímero da família do polifluoreno, de fácil processamento e elevada eficiência luminosa, enquanto que como eletrodos foram utilizados o óxido de estanho e índio (ITO) e Alumínio. O ITO foi utilizado por possuir baixa resistividade elétrica, elevada função de trabalho e elevada transmitância na região do visível. O processo de encapsulamento do display se deu por meio do acondicionamento destes dispositivos em ambiente isento de oxigênio e umidade, evitando-se os efeitos já conhecidos da foto-oxidação das camadas poliméricas. Os dispositivos, uma vez preparados, foram caracterizados por meio de medidas ópticas (fotoluminescência), elétricas (eletroluminescência, condutividade) e de desempenho (eficiência luminosa e luminância). / Organic Light Emitters Diodes OLEDs is a promising field of study and a huge market opportunity to semiconductor players. Thanks to its potential characteristics to replace the main todays display technologies like lightweight, low voltage, wide viewing angle, high resolution, fast switching, broad color range and the possibility to fabricate flexible devices, makes the organic semiconductors a potential candidate to develop, in a near future, devices and systems that even could not be imagined before. This work aims to contribute to the manufacturing process field and to the characterization of displays made by ink jet deposition technique. To achieve this objective, line x column patterns were produced, in which the pixels are generated at the crossing of lines and columns. The ink jet printing of materials is playing an important role in industry because it provides a low-cost manufacture environment potential. In this work, we studied the morphology of the ink jet deposition of polyfluorene over Indium Tin Oxide (ITO) substrates treated by different procedures. Those materials where used because the polyfluorene polymer presents high light emission efficiency and easiness of processing. The electrodes were prepared with ITO (due its low resistivity, high work function and high transmittance in the visible spectrum) and aluminum. The processed displays were sealed inside an inert ambient with positive pressure to avoid the photo-oxidation of the semiconductor luminescent polymer layers. The devices were characterized by optical (photoluminescence), electrical (electroluminescence) and performance (brightness, luminous efficiency) measurements.

No description available.

This research project has investigated the light fastness of ink jet and electrophotographic printed materials by the means of an extensive accelerated and natural ageing test programme. The effect of visible radiation of different wavebands on the deterioration of a selection of ink jet printed materials has also been assessed. The findings of the research indicate that all of the ink jet printed materials tested are sensitive to light and should not therefore, be put on permanent display. Most of the ink jet printed samples exhibited greater light sensitivity to the shorter wavelengths of the visible spectrum, than the longer wavelengths, with damage decreasing as wavelength increases. This relationship was not evident with the cyan and blue printed samples, which showed that their light sensitivity was determined by the spectral absorption characteristics of the printed patch. Some of the ink jet printed materials produced erratic fading rates on exposure to light. This phenomenon was attributed to either the occurrence of photochromism or the disintegration of the dye particles in the ink, but further testing needs to be conducted to gain a better understanding of this reaction. Other factors also influenced the light fastness of the ink jet materials, such as the type of paper employed for printing, ink concentration and ink combination. The electrophotographic printed materials were found to be more stable to light, although the yellow toner from some of the systems would show noticeable fading after approximately 65 to 325 years on permanent display (at 50 lux for eight hours per day). A range of basic conservation treatments was also been investigated and the results indicated that ink jet print materials are very sensitive to all forms of aqueous treatments. Finally, thermal/dark ageing has been performed on the digital printed papers employed in this investigation. The conclusion is that all of the papers are prone to yellowing in storage.

The purpose of this research was to explore two ways of the application of chitosan, a biopolymer, for ink jet printing of textiles. 1) To apply chitosan as a post-treatment on the fabric ink jet printed with pigment based inks for the fixation of pigments on the fabric. 2) To incorporate chitosan as a binder in pigment based ink jet ink formulations. The incorporation of chitosan was carried out in two ways. 1) Direct addition of chitosan into the ink formulations containing surface modified pigments. 2) Preparation of chitosan encapsulated pigment nanoparticles using complex coacervation technique and using these nanoparticles for the formulation of ink jet ink. The degree of deacetylation (DD) was determined using FTIR spectroscopy. Various protocols proposed by researchers were used to determine the DD of chitosan samples used in the present study. The protocol proposed by Raut was found to be fairly accurate in determining the DD of chitosan samples. The molecular weight of chitosan was estimated using dilute solution viscometry method. The characterisation of the film forming ability of chitosan was evaluated using scanning electron microscopy (SEM). The colour strength (K/S), colour difference, colour characteristics and colour fastness to laundering and rubbing of ink jet printed fabrics post treated with chitosan were evaluated using standard methods. Post-treatment (pad-dry-cure method) of cotton fabric ink jet printed with pigment based inks revealed that chitosan could effectively fix the pigments on cotton compared to the commercial textile binders and the water-soluble derivative of chitosan. The chemical interaction between chitosan and cotton fabric was illustrated by FTIR-ATR analysis and through determination of carboxyl group content. The ink jet printed cotton fabric post treated with 3gpl chitosan (MW 156,156) maintained almost 86% of bacterial reduction against Klebsiella Pneumoniae even after 50 launderings. Inks containing chitosan were formulated and were found to be stable in terms of mean particle size and viscosity over a period of one month and for 4 freeze/thaw cycles. A magenta ink containing chitosan was selected for ink jet printing of cotton fabric. It was found that the DF was around 97% for magenta ink containing chitosan compared to around 53% fixation for magenta ink without chitosan on cotton fabric. Surface modified carbon black pigment with carboxylated (COO-) surface functionality was selected to prepare chitosan encapsulated pigment nanoparticles by complex coacervation technique. Chitosan encapsulated pigment nanoparticles with mean particle size diameter of 876 nm and 742 nm were formed when 5 ml of 0.1% w/v pigment was mixed with 2ml and 3ml of 0.1% w/v chitosan, respectively. However, no correlation was found between the particle size of the nanoparticles formed and the concentration of chitosan. The DF with ink containing chitosan encapsulated pigment nanoparticles was found to be around 98% while the blank ink with only surface modified carbon black pigment showed 44% fixation.

A numerical model has been developed to simulate the firing of an inkjet printhead. The model evaluates the heat generation and diffusion within the thin film structure, the phase change and vapor bubble growth in the ink, and the subsequent flow of ink from the orifice. The heat transfer is modeled numerically throughout the printhead's thin film structure and ink through an asymptotic integration algorithm. The bubble growth and fluid flow are coupled and modeled through conservation of momentum, conservation of energy, and state equations. The heat transfer model has been validated with simple theoretical solutions and ink drop weight and velocity have been compared to empirical data. To test the usefulness of the model as a design tool, parametric studies have been made which characterize pen performance as a function of several system parameters. The results show that although the model does not reflect every detail in the firing process, it is useful for predicting trends and investigating new design concepts. / Graduation date: 1997

Additive manufacturing processes, which utilize selective deposition of material rather than traditional subtractive methods, are very promising due to their ability to build complex, highly specific geometries in short periods of time. Three-dimensional direct inkjet printing is a relatively new additive process that promises to be more efficient, scalable, and financially feasible than others. Due to its novelty, however, numerous technical challenges remain to be overcome before it can attain widespread use. This thesis identifies those challenges and finds that material limitations are the most critical at this point. In the case of deposition of high viscosity polymers, for example, it is found that droplet formation is a limiting factor. Acoustic resonance jetting, a technology recently developed at Georgia Institute of Technology, may have the potential to address this limitation because it generates droplets using a physical mechanism different from those currently in use. This process focuses ultrasonic waves using cavity resonances to form a standing wave with high pressure gradients near the orifice of the nozzle, thereby ejecting droplets periodically. This thesis reports initial exploratory testing of this technologys performance with various material and process parameters. In addition, analytical and numerical analyses of the physical phenomena are presented. Results show that, while the pressures generated by the system are significant, energy losses due to viscous friction within the nozzle may prove to be prohibitive. This thesis identifies and begins evaluation of many of the process variables, providing a strong basis for continued investigation of this technology.

No description available.

No description available.

Thesis (M.S. in mechanical engineering)--Washington State University, May 2008. / Includes bibliographical references (p. 54-55).