3rd generation optical coatings for large area architectural glazing (3RD GENLAC)

Heuristic model of reactive sputtering

This result is related to the mounting of ceramic rotatable targets on the cylindrical backing tube. Due to the strong difference in themal expansion coefficients of metal and the ceramic target material, a bonding process by metallic soldering - unless performed as in result No. X - is often problematic. To circumvent the problems related to thermal expansion stress, bonding using an adhesive material is an alternative. Since most adhesives are not applicable to vacuum processes due to strong outgassing and neither thermally stable, the development of an improved and thermally stable adhesive material suited for vacuum processes is the issue solved within this result. The new adhesive material is described within the European patent application, which is cited within this result.

This result is especially related to the development of long rotatable ceramic zinc aluminom oxide (ZAO) targets, however it can be applied for the bonding of alternative ceramic target materials as well. Ceramic ZAO target material is fabriated as zylindrical segments which are bonded onto a cylindrical backing tube by metallic soldering. The main problem of this method is that cracks and delamination occurs due to non-matching thermal expansion coefficients. Thus a refined method of solidering ceramic ZAO target segments onto a cylindrical backing tubes has been developed and protected by a European patent application.

This result is related to large-area magnetron sputtering technology using cylindrical, rotatable targets. One of the major issues in large area coating technology is the deposition of thin films at a very high homogeneity, e. g. for certain multiple-Ag based solar control coatings for architectural glazing, film thickness deviations of less than 1% are demanded. It is furthermore known, that - due to target erosion - the process characteristics of a magnetron sputtering source are gradually changing throughout its lifetime. Thus, regular calibration is required to maintain stable process conditions within a production campaign. To overcome these problems we present a new coating technology concept for a cylindrical rotatable sputtering source with a build-in measurement equipment for the target erosion rate. This measurement equipment is realized as a secondary, planar D.C. sputtering cathode operating under pure Argon at a defined sputtering rate. The material of the secondary cathode is partially removed by the sputtering process of the primary cathode and afterwards the remaining fraction of the secondary material is measured by X-ray fluorescence. By maintaining a constant X-ray fluorescence signal the erosion rate of the magnetron can be kept on a constant level.

A double-Ag sun control coating has been developed using a jumbo-sized in-line sputter coater comprising only 27 compartments in total. This development benefits from the use of ceramic targets for the zinc-aluminium-oxide (ZAO) dielectric layers close to the silver films. Due to the small reactive gas consumption of the ceramic ZAO target sputter process, a significant number of pumping compartments, which are usually required for gas separation, could be omitted. Furthermore, the use of ceramic ZAO targets seems to be advantageous in terms of the resulting specific silver conductivity. The resulting layer stack has a visible transmittance of 53% (EN410), an energy transmittance of 27% and a selectivity of 2.0. A normal emissivity of 2% of the layer stack was measured by a Lambda-900 spectrometer from Perkin Elmer. The resulting k-Value within a double-glazing unit is 1.0 W/m²K.

Software for an online patentdatabase based on PostGreSQL has been developed which can be accessed by web browsers. The patents in the database are collected in patent families referred to as "inventions". A data structure comprising key features, specific characteristics and invention-related materials helps to obtain an immediate overview of the main ideas of an invention. The legal state of an invention can be followed by the patent family, where all patent documents i.e. applications, research reports etc. are stored together with publication codes, application and publication dates. A table of inventors and applicants is contained which are assigned to the inventions. Invention reports for each applicant and person can be generated. This database is suited for multi-user access. With a history function, each data changes are documented. By identifying the search-method for each invention, the development in technical areas can be monitored e. g. by applying the same search methods after a certain period of time.

As shown by the figures below, Semco Glastechnik GmbH and Scheuten Glasgroep BV succeeded in developing a new layer stack, which properties are almost unchanged by heat treatment at temperatures above 600°C. The colour shift induced by the high temperature process is quite low and can be tuned such, that tempered and untempered coatings may be mounted into a fassade adjacent to each other without a visible colour difference. Furthermore the reduction of the film emissivity by more than 30% means a strong improvement of films properties by the high temperature process. The coating emissivity drops from 4 % to 3 %after tempering. This fact allows using this coating together with untempered 3% emissivity coatings, which is the new generation of low-e coatings. For these reasons, the developed coating provides high potentials on the market, to be used as a 4 %-emissivity coating without heat treatment or as a 3 % - coating after heat treatment in one fassade. In the following, the data for a double-glazing with this coating before and after heat treatment are summarized. Before After high temperature process Light transmission(D 65) %: 80,2 81,6 Energy transmission EN 410: 66 64,5 b-value (transmission): 2,07 2,4 a-value (transmission): -1,4 -1,1 b-value(reflection glass): -6,7 -11,1 a-value(reflection glass): -1,9 -0,4 b-value(reflection film): -9,1 -12,1 a-value(reflection film): -1,0 0,1 Emissivity: 4,5% 3% Haze: 0 0,06 Leaving away a certain layer within the stack we could reduce the colour shift, especially the b-shift strongly from about 4 to 2,5 only. With these results it should be even possible to place the untempered und tempered product adjacent to each other in one facade without a visible colour shift.

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