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Development of Multilayer Metal/Dielectric Coatings for Solar Control Applications, 18-R9572

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Principal Investigator
Kent Coulter

Inclusive Dates:  08/08/05 – 10/26/05

Background - Solar control is a generic term used for a variety of different types of coatings used in architectural and automotive applications. A common design is an optimized multilayer coating that has a high infrared (IR) reflectance, which reduces the heat gain from the sun that in turn reduces the load on the air conditioning systems and also has high visible transmittance. While these coatings are well known for use in windows and windshields where visual transparency is important, application of these films where the solar rejection is required and the appearance of the underlying substrate is important is an area of development that is gaining interest. Conversion of the vacuum-deposited metal/dielectric solar control coatings into pigments that can be incorporated into paint is an undeveloped area.

Approach - The primary object of this project was to deliver a proof-of-principle film samples for a client-specific application that exhibited improved performance and lower cost compared to commercially available solar control films. To achieve this objective, a chamber upgrade and process calibration to establish a capability that could produce as many quality coated substrates in each batch was required. Optimization of the coatings and the individual layer characteristics on as large an area as possible utilizing relatively fast processes enables the deposition onto releasable substrates to comminute the films into pigments. The demonstrated capability to prototype sophisticated optical coatings that can be converted into pigments for improving the performance will uniquely position SwRI in the vacuum coating community.

Accomplishments - A transparent solar control thin film that can be comminuted into a pigment was developed for application in automotive clear coat paint. A silver, titanium dioxide, silica multilayer thin-film structure exhibited visually transparency and a near infrared reflectance. The first steps were to install some key ancillary components such as upgrading the planetary sample holder, reconfiguring the pumping geometry, plumbing in a nitrogen purge system, and installing deposition shielding in the optics chamber. Next, an MDC e-beam system was installed and test witnesses of aluminum, silver, silica, and titanium dioxide were coated to calibrate the crystal monitor and map the deposition zone in the chamber. Upon establishing the equipment and deposition baseline capabilities, multilayer films on polyester and glass slides were coated using theoretical designs modeled in TFCalc. The optics chamber is now capable of consistently producing multilayer metal dielectric films on areas approaching 8 inches in diameter at coating rates of 1.0 to 10Å/s. Films on the order of 1 to 2 micrometers thick have good substrate adhesion and no evidence of degradation caused by stress. Multiple coating runs (6) were completed with the release layer incorporated in the design, and all produced flakes with same optical design that was comminuted into pigment. Film samples and a small quantity of pigment for incorporation into a clear coat binder were provided to the client.

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