UV-curable polymers

Uv-curable polymers Uv devices Uvilon Uvithane 893 Uv light stabilizers... 

Traditionally, UV curable polymers have been utilized as coatings for wood and vinyl floors, but their applications have increased dramatically over the last twenty years to encompass many diverse areas, including optical fiber coatings (7), adhesives (2), disc replications (3-5), and microelectronics (6). This widespread use of UV cross-linked systems is attributed to their rapid, energy efficient curing and their solvent free, one piece formulations. Typically, UV curable systems require only a small fraction of the power normally utilized in thermally cured systems and their solvent free nature offers an environmentally safer alternative. 

Commonly used monomers for UV curing include acrylates (7), styrene/unsaturated polyesters (8,9), and thiol-ene compositions (10-12). Currently, acrylate-functional systems constitute a major share of the UV curable polymers market, mainly due to their rapid curing via free radical chain polymerization. 

Laser patterning is another writing technique whereby a laser is used to directly expose or polymerize a material. A common application is stereolithography where a reservoir of UV-curable polymer is selectively exposed to a UV laser to fabricate complex three-dimensional (3D) structures in a layer-by-layer fashion. For each layer, the laser beam traces a cross section of the part on the surface of the UV-curable polymer. Exposure to UV laser solidifies the pattern traced on the resin and adheres it to the layer below. 

UV-curable polymers HjO vapor (exponential decrease of R with relative humidity) Cho et at. (2008)... 

UV-curable polymer systems typically contain monomer or oligomer (unreacted polymer), a light-sensitive photoinitiator, and other additives for colour and mechanical properties. 

Several ETFE soft stamps are then transferred on to a tensioned belt, which loops continuously over two rollers. The soft stamp imprints the nanoscale pattern onto the conveying coated substrate (Fig. 13.9). Continuous roU-to-roU imprinting has been demonstrated using a 10 cm wide pattern. The polymer-coated substrate is imprinted and simultaneously UV cured, before the rolling stamp detaches from the imprinted polymer. The UV-curable polymer resist used is low viscosity liquid epoxysilicone [62]. 

Based on the molecular orientational tilting of LCs, various structures have been suggested to vary voltages onto LCs and thus change optical properties [5,6]. Choi et al. fabricated a two-dimensional LC microlens array using a surface relief structure of ultraviolet (UV)-curable polymer [5]. The microlens array cell was made with indium tin oxide (TTO) glass substrates. One substrate had a specific surface relief structure of the photopolymer used and the other had only the ITO layer. 

To develop a surface relief structure, the UV-curable polymer was spin coated on the substrates at a rate of 4000 rpm for 30 sec. The resultant thickness of the spin coated polymer film was about 3 pm. After a polymer film formed on the glass substrate, spatially modulated UV light was irradiated onto the film through a photomask. The photomask was designed to generate the intensity modulation of the UV light to form a pattern of microlens arrays. The irradiation led to the diffusion of monomers in the polymer composites from the unexposed to exposed regions. The result was the formation of a lens-shaped surface relief structure. 

Figure 6.11. Illustration of assembly of high-surface-tension fluids on a carboxylic-acid-terminated SAM. The stamp shown in Figure 6.10 was used to produce 10 pm diameter circles of a hydrophilic SAM on to which a UV-curable polymer was assembled...

Master Bond Inc. Master Bond Inc, Hackensack, NJ, has developed a new single-component, flexible, UV-curable polymer system called UVi4 3 that is readily removable using most conventional solvents. It is a ioo% reactive, moderate viscosity liquid at ambient temperatures and does not contain any solvents or other volatiles. 

N.A. Vaz, G.W. Smith, G.P. Montgomery Jr., A light control film composed of liquid crystal droplets dispersed In a UV-curable polymer. Mol. Cryst. Liq. Cryst. 146, 1-15 (1987)... 

Lovinger AJ, Amundson KR, Davis DD (1994) Mtnphological investigation of UV curable polymer dispersed liquid crystal (PDLQ materials. Chtan Mater 6 1726-1736 Lu Y, Wei J, Shi Y, Jin O, Guo J (2013) Effects of fabrication condition on the network morphology and electro-optical characteistics of polymCT-dispersed bistable smectic A liquid crystal device. Liq Cryst 40 581-588... 

UV-curable (polymer) A polymer basecoat material that can be cured by exposure to ultraviolet radiation, thus avoiding the pollution problems associated with heat-curable polymers. 

To make a the photo-tailorable SMP (PT-SMP), a commercially available UV curable polymer (Norland Optical Adhesive (NOA) 63, Norland Products, Inc.) was cured using a high intensity ultraviolet lamp (365 nm, Spectronics Corporation, Model SB-1 OOP) isolated with a box for safety. To prepare smooth PT-SMP films, two quartz plates (2 cm x 3 cm) were employed to form the top and bottom mold surfaces with a spacer (1.5 mm thickness) being placed between the plates. A distance separating the UV lamp and the mold was set at 5 cm. After curing for prescribed periods of time, crosslinked PT-SMP samples were removed from the quartz substrate by placement on a hot plate heated to 70 °C, a temperature allowing convenient pealing away of the film from the mold. 

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