Papers

ICMCTF1998 Session G6: Large-area Production Coatings for Webs/Plasma Cleaning and Pretreatment of Large Surfaces

Wednesday, April 29, 1998 1:30 PM in Room Town & Country

Wednesday Afternoon

Start	Invited?	Item
1:30 PM		G6-1 Progress in Pulsed Plasma Technologies S. Schiller (Fraunhofer Inst. F. Elektronenstrahl und. Plasmatechnik, Germany); V. Kirchhoff (Consultant); M. Schulze (Frauenhofer Institut Elektronenstrahl- und Plasmatechnik, FEP, Germany) In the last years the pulsed plasma technologies came in the limelight. The used pulse rates are in the range of 10 kHz - 100 kHz. Magnetron Sputtering in pulsed mode gives the possibilities to coat highly insulated layers with high rates under long-term stable conditions. Glass coaters are an outstanding application. The behavior in production lenses will be explained. Plasmaactivated evaporation in pulsed mode is a way to coat highly insulated layers like Al₂O₃ with extremely high rates in the range of 400 nm per second. High deposition rates require pretreatment technologies with high area throughput. In production lines the randomly grown impurities are of a disturbing factor. It will be shown that pulsed plasma pretreatment will solve this connected difficulties. The process and the main parameters will be explained.
1:50 PM		G6-2 Pulse Duration in Pulse-power Reactive Sputtering of Dielectrics A. Belkind (Abe Belkind and Associates); A. Freilich (Stevens Institute of Technology); R. Scholl (Advanced Energy Industries) Pulse-power reactive magnetron sputtering of dielectrics is a rece= ntly developed variation of DC sputtering. It avoids arcing that are caus= e by large electrical charges. These charges appear on surfaces of dielec= tric films that grow on the target, substrate and surrounding walls. In t= he pulsed-power, the negative voltage is applied to the target during ton= time. During ton the magnetron is on although its current reaches a stab= le level with a certain delay. The negative pulse is follows a pulse of s= mall positive voltage of duration toff. During this time the residual pla= sma charges discharge the surfaces. In this work, the effects of duration= s ton and toff and their frequency on reactive sputtering of aluminum oxi= de are investigated. Influence of gas pressure and discharge current on t= he pulse-power sputtering is also studied. Experiments are done using a p= lanar magnetron and metal target. Optimum conditions are determined and d= iscussed.
2:50 PM		G6-5 Deposition of Functional Layer Stacks on Web by Pulse Magnetron Sputtering M. Fahland (Frauenhofer Institut Elektronenstrahl- und Plasmatechnik, FEP, Germany); F. Milde, Ch. Charton (Consultant); N. Schiller (Frauenhofer Institut Elektronenstrahl- und Plasmatechnik, FEP, Germany) Plastic films coated with functional layer stacks show an increasing market potential. Examples are films coated with electrochromic, antireflective and antistatic layer systems as well as solar control and low-e films. For example, layer materials like SiO₂, TiO₂, and ITO are of very high importance in this field. In many cases, conventional dc magnetron sputtering leads to layer defects due to arcing and process instabilities due to electrode covering with insulation compounds. However, especially for web coating a very high process stability is needed. Here, the pulse magnetron sputtering (PMS) process is a solution which allows the stable deposition of a great variety of compounds at very high rates and excellent layer quality. At hand of different layer systems recent results obtained with pulse magnetron sputtering will be discussed with respect to web coating applications.
3:10 PM		G6-6 Reactive Sputtering of Oxides with Dual Magnetrons for Large Area Applications D. Schulze, J. Strumpfel, G. Beister, M. Dimer (Von Ardenne Anlagentechnik, GmbH, Germany) Optical coatings are used for heat reflection and sun protection on large area glass surfaces worldwide. Multilayers for antireflection coating may be applied to large areas by reactive magnetron sputtering, too. There is a growing interest for both applications to deposit such optical coatings not only on float glass, bu also for foils. Precondition for the generation of such oxide layer stacks in production lines is the availability of medium and large-sized double magnetron sputter sources for reactive sputtering in the AC mode. The key characteristics of this type of magnetrons disposing of well adjusted magnetic field configuration, an active target cooling and permitting an uncomplicated change of targets will be presented. The productivity of large coaters is directly influenced by largely uniformity both related to coating width and length of the substrate. Technological solutions are presented for process stabilization during reactive sputtering by means of the Plasma Emission Monitor (PEM) control loop for the dosed reactive gas inlet. Furthermore, selection criteria are raised for the positioning of the gas inlet at double magnetron sputter sources and effects therof on the coating rate to be achieved for TiO₂ layers. The uniformity of the coating thickness in production lines over the total substrate width up to 3.2 m is displayed. The depositon of low-index SiO₂ layers requires particular solutions for the stabilizing the operating point at the medium-frequency power supply, which may be combined with measures for balance regulation. A comparative view will be taken on the reactive coating process for metal or partially oxidized targets displaying the changes in properties of ITO SnO₂ and TiO₂ layers.
3:30 PM		G6-7 Comparison of SnO₂ Films Prepared by DC and MF Reactive Sputtering J. Szczyrbowski, J. Bartella (Leybold Systems GmbH, Germany); G. Bräuer, J. Pistner, M. Ruske, J. Schroeder (Leybold Systems, Germany) Thin films of SnO₂ were prepared by conventional DC and mid frequencey (40 kHz) TwinMag^r sputtering arrangement on glass substrates. The mid frequency technology possesses two special properties which may remarkably influence the thinf ilm growth. On one hand, the substrate is continuously bombarded by positiviely charged ions of high energy - the values measured here were up to 200eV while fro DC-sputtering the maximum energy was smaller than 20 eV. On the other hand, the TwinMag^r allows deposition of SnO₂ films in the metallic mode of the cathode characteristic, leading to a stable sputtering process and a very high deposition rate, which is of particular interest for large scale industrial applications. It was the aim of this work to compare the properties of SnO₂ films prepared by both methods. The structural properties were investigated by SEM. Optical constants are calculated from measured transmission and reflection spectra. Mass determination by use of a micro balance served as a basis for evaluation of the film density. The investigations include also the measurement of film stress and micro hardness.
3:50 PM		G6-8 Better Aluminum Mirrors by Integrating Plasma Pretreatment, Sputtering, and Plasma Polymerization for Large Scale Car Headlight Production H. Grünwald, W. Dicken, S. Kunkel, K. Nauenburg (Leybold Systems GmbH, Germany) The move to abandon lacquering in today's car lighting manufacture has revealed new challenges at the plastic interface, especially reduced adhesion of the coating and outgassing (mainly water) that can effect the aluminum quality. Under the increased temperatrues inside head and fog lights, further outgassing often leads to hazy appearance of the reflector or the front lens by droplet condensation. These problems can be solved by a process sequence that includes some oxidizing plasma pretreatment that ensures good bonding of the aluminum to the plastic and also enhances desorption of water. In addition, some plasma polymerized adhesion promoting base coat (if required, also desorption blocking) may be deposited. After aluminum deposition, first a corrosion protective layer and finally, a hydrophilic coating that suppresses hazing effects by spreading out any condensing vapours to some optically neutral layer are deposited. The plasma sources in the "DynaMet" are powerful enough to deposit the base coat and the anti haze top coat in addition to the other process within the usual cycle time of the machine.
4:30 PM		G6-10 Economic Aspects and Potential of Large-Area Sol-Gel Coatings H.K. Schmidt (Institut für Neue Materialien GmbH, Germany) The sol-gel process is a chemical route to inorganic and composite materials. It basically represents a precipitation process from solution to nanoparticulate suspensions which are kept stable by electric charges surrounding the individual particles. Due to the small diametres of the particles, which is, in general, far below the Rayleigh scattering limit, they can form transparent layers after depositing them on glass surfaces. Due to the variability of chemical synthesis principles, a large variety of compositions is accessable by this route, such as oxides including all kinds of glass compositions, chalcogenides, carbides but also metals in form of colloids and combinations. For coating techniques, almost any wet coating technique can be employed, but for obtaining high optical quality specific requirements have to be fulfilled. So far, a large potential exists from the material point of view. Drawbacks are the restricted availability of tailor-made materials, since the volumes needed, in most cases, are too small for conventional materials suppliers and for this reason a lack of subsequent coating technologies also exists. Strategies how to overcome these obstacles and to exploit this potential will be discussed in the paper. Through the development of new inorganic organic hybrid materials, another potential has been opened up, since these materials do not need high curing temperatures and can be employed in thick layers also. These coatings can be outfitted with interesting properties like ion-conductive, easy-to-clean or antifogging behaviour and architectural as well as automotive glazing may benefit from these developments. In the presentation, an overview will be given over the materials potential (AR or reflective coatings, coloured coatings, photochromic and electric coatings, easy-to-clean and hydrophilic coatings), and the required technology, the economic potential and the route how to exploit it will be discussed.
5:10 PM		G6-12 High Speed Pretreatment of Plastic Webs F. Milde, N. Schiller (FhG-FEP, Germany) Aluminum coated OPP films is widely being used as barrier film for packaging applications. To achieve superior barrier properties, the plastic web has to be pretreatet in-line prior to the coating process. The effects of a plasma or ion beam pretreatment on the adhesion strength of Aluminum will be discussed. The success of the pretreatment does not only depend on the specific polymer type, but also on the intensity and type of pretreatment. Since the layer adhesion often reaches a maximum at extremely low doses of pretreatment, the application of available plasma and ion sources allows to implement web speeds in a range of some meters per second. A system, which allows pretreatment of wide webs at high winding speeds, will be presented. Furthermore, the utilization of the novel Magnetron Activated Deposition (MAD) Process for "in-process treatment" will be discussed.
5:30 PM		G6-13 Pulse-power Hollow Cathode A. Belkind (Abe Belkind and Associates); A. Freilich (Stevens Institute of Technology); R. Scholl (Advanced Energy Industries) An oxygen plasma generated by a linear multiorifice hollow cathode= (LMHC) is used for oil removal from metal strips using. To operate the s= ource with a DC power the cathode is constructed from stainless steel. T= he source has a power limit that determined by cathode overheating and co= nsequential appearance of arcs that destroy the cathode. Stainless steel = replacement by aluminum would substantially improve cathode cooling and i= ncrease the power limit. Unfortunately DC discharge in oxygen with an alu= minum cathode is accompanied with arcing. One way to avoid arcing in to u= se pulse-power. In this work, pulse-power hollow cathode discharge is inv= estigated. Pulse durations and frequency influences on an oxygen plasma g= enerated in various hollow cathodes are studied. Implementation of pulse-= powered aluminum hollow cathode for oil removal is described.