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Multicolor Patterning Via Adjusting The States Of A Single Dye Species

Posted on:2010-02-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:W HuFull Text:PDF
GTID:1101360272496140Subject:Polymer Chemistry and Physics
Abstract/Summary:PDF Full Text Request
Multicolor patterning with organic dyes is of technological importance for a wide range of applications, e.g. full color displays, information storage, sensor arrays, distributed feedback lasers and organic optoelectronic devices. Normally, multicolor patterns are composed of multiple materials, integrated either in a fashion of side-by-side deposition, or in a multilayer structure on spatial defined positions through selective adsorption, shadow mask evaporation or ink jet etc. A multi-step process for the fabrication is thus unavoidable, which limits the spatial resolution and increases the fabrication cost. Therefore, alternative methods for fast, easy, inexpensive multicolor patterning of dye molecules with high resolution are highly demanded.The property of a dye species is determined by both its molecular structure and aggregation state. The property of dye monomer is usually quite different from their aggregates, which results from the non-covalent interactions among neighbour dye molecules in aggregates. Dyes will assemble into aggregate when deposited onto compact solid substrates for the strong intermolecular interactions, while the same dye will molecularly disperse into polymer bulks by immersing them into dilute dye solution, or mixing polymers and dyes in the melting phase. During vacuum thermal evaporation (VTE), dyes are deposited onto polymer substrates gaseously. Just like the above two cases, dye molecules will stay in monomer state because they are able to diffuse into polymer bulks. Therefore, if we integrate two or more different materials onto a same surface, we can control the states and corresponding optical properties of a given dye. That suggests us a new strategy for multicolour patterning.In this thesis, following work have been carried out:1. We respectively deposited four kinds of dyes, including quinacridone (DBQA), 3-(9-anthrye) pyrazole (ANP) rhodamine 6G (Rh-6G) and DCM1, onto different substrates through VTE and studied their morphology, crystallization, UV absorption and photo luminescence properties. We found dyes would condense on compact inorganic substrates such as quartz and show different optical properties comparing with diluted solutions, such as absorption spectra red shift, photo luminescence spectra red shift and the emergence of a new unstructured broad excimer spectrum peak. The same dyes would diffuse into the bulk of polymer substrates such as PDMS and PU, and display similar optical properties to diluted solution of the same dye. The diffusion process, influencing factors and solubility of two deposited dyes (DBQA and ANP) have been investigated. We used free volume theory and positron annihilation lifetime spectroscopy (PALS) measurements studying the diffusibility and solubility of dye molecules in polymers. There are two phases in the diffusion process: first is the transference of dye molecules from gas to polymer surface layer, this phase is determined by evaporating rate and maximum diffusion rate. Second is the diffusion in polymer bulk and dye transference from aggregates on surface to polymer bulk. The endpoint of diffusion is the thermodynamic equilibrium state at given conditions. The diffusion coefficient (D) of dye molecules in polymers could be calculated by free volume theory. The influencing factors of D include temperature, the size and shape of a single dye molecule, structure and mobility of polymer chains, and intermolecular interactions. Solubility of a dye species in a polymer is the maximum dye loading capacity of the polymer at thermodynamic equilibrium and its influencing factors are similar to D. Based on the variation of diffusibility and solubility of a given dye among different polymers and different cured same polymer, we accomplished thermodynamically unstable and stable PL color-tuning of a same dye species separately. (Color ranges from monomer emission to eximer emission)2. Based on the investigation on relationship between dye states and substrate materials, we fabricated 2D & 3D PDMS/quartz heterogeneous micro structures by combining photo lithography with nanoimprint lithography; fabricated PMMA/quartz heterogeneous micro/nano structures through nanoimprint lithography; fabricated different cured NOA-63 patterns through photo lithography; fabricated (PVP/PAA) and (PAH/PAA) multilayer patterns by room temperature nanoimprint; and then deposited one dye species onto them through VTE, finally we accomplished dualcolor patterning in a single process. The shape and size of dualcolor patterns is only determined by pre-patterned substrates. Dualcolor patterns with feature size down to 200 nm have been achieved; however, further increase resolution is possible if stamp with smaller structures is used. Besides that, multicolor patterning have also been demonstrated based on the dye loading capability tuning of different regions on an NOA-63 substrate, which are differently crosslinked after exposing through a gray scale photo mask or by twice UV photolithography with a same binary photo mask respectively.Herein we originally demonstrated a concept for constructing patterned surfaces with different colors by using a single step vacuum thermal evaporation of one dye species on pre-patterned solid substrates. This may allow a new and simple route to designing multicolor patterns with very high spatial resolution. The novel technique has broadly potential applications and is worthy of further investigations.
Keywords/Search Tags:Dye, Photoluminescence patterning, Nanoimprint lighography, Quinacridone, Rhodamine 6G, Vacuum thermal evaporation, Spectra shift
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