IOP Groups
Large Area Coatings
22 February 2005
This one-day meeting was held on 22 Feb 2005 at the Institute of Physics, 76 Portland Place, London W1N 4AA
Organised by the Vacuum Group of the Institute of Physics
Co-sponsored by the Ion and Plasma Surface Interactions Group, the Thin Films and Surfaces Group and the Polymer Physics Group
Chairman's Summary
This meeting had 3 invited talks (the talk from Neil Morrison, CCR Technology, had to be cancelled), 2 contributed talks and several posters, with an attendance of 33. Bursaries were provided for 4 students.
The meeting opened with the first invited talk by Dr Hazel Assender, Oxford University, on "Vacuum Web Deposition of Acrylate and Inorganic Coatings on Polymers". She described their recently installed pilot-scale vacuum web coater for deposition of gas barrier layers, optical coatings, and electronically active layers, using a sequence of plasma pre-treatment (e.g. in nitrogen), flash evaporation (e.g. aluminium), and dual magnetron sputtering. A liquid precursor and atomiser spray are used with electron beam curing to deposit acrylate coatings of various thicknesses from nm to microns. She also described the tests that they were using to assess these coatings for pin-holes. Alternative coatings were deposited from HMDSO and oxygen to provide silicon oxide layers on PET or PEN, with lower compressive stress compared with similar PECVD oxide coatings.
The second invited talk by Dr. Alan Hynes, Dow Corning Plasma Solutions, on "Generation and Control of Wide Area, Homogenous Atmospheric Pressure Glow Discharges for Industrial Coating Applications" described the development of a pilot plant and a laboratory-scale plant for this novel process. He started with a concise introduction to plasma types and a description of the surface analytical facilities at Dow Corning in Cork. Atmospheric pressure plasmas are commonly of the corona discharge type (non-homogeneous and filamentary), but a more uniform plasma is generated by the dielectric barrier configuration. In the first equipment that they developed (using liquid precursors from Prof Badyal at Durham University, for hydrophobic coatings), the multi-kW, 10-70 kHz plasma was struck in helium, between multiple planar, glass-covered, metal electrodes. The precursor was injected through ultrasonic nebulisers, replaced by gas atomisers in later designs. In the later equipment the metal electrodes (which were cooled with a flowing sheet of water) were replaced with electrolyte solution behind machined plastic sheets (which could be air-cooled). It was noted that oxygen may not be added to this type of plasma without degrading its homogeneity. Various diagnostics were discussed, to provide process control for the treatment of ~2m wide web, fed at up to 30m/min. Applications include the provision of oleophobic coatings, hydrophilic coatings, functionalised surfaces. [Talk available on IoP webpage]
The third invited talk by Dr. Kevin D. Sanderson, Pilkington European Technical Centre was on "Coatings for Self Cleaning Applications". These are based on the hydrophilic and photocatalytic behaviour of TiO2 coatings on architectural glass. The float glass process runs at 10-15 m/min, producing 3.2m wide sheet: any coating technique should be compatible with this. We were given a description of the gas delivery system for the ~15nm thick TiO2 coating. The subsequent effect of UV is to induce surface wetting and to decompose any surface organic soiling (e.g. bacteria). Complete wetting occurs after only 45 minutes of exposure to bright sunlight. The testing procedure and the measurement of durability and transparency in various situations showed that the coating was able to provide a greatly enhanced performance over uncoated glass.
Two shorter, contributed presentations were on different coating techniques again. Dr Nick Bazin, AWE, spoke on sol-gel "Formation of Anti-reflective Coated Polymer Films to Act as a Debris Disposable Shield for Use on High Power Pulsed Laser Systems" and Dr. I M Dharmadasa, Sheffield University, spoke on "Large Area Semiconductor Layers by Electrodeposition for Photovoltaic Solar Cell Applications".
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