John D. Affinito

A new method for fabricating transparent barrier layers

The Polymer Multi-Layer (PML) process for the vacuum flash evaporation of acrylic monomers has been combined with conventional oxide sputtering and evaporation processes to produce multilayer barrier coatings in a vacuum web coating process. Polymer/oxide/polymer layers have been deposited on 2 mil polyester substrates. For a 1 μm polymer layer over the substrate, followed by a 255 A Al2O3 layer capped by a 0.24 μm polymer layer, O2 permeation rates were below 0.0155 cc m−2 (24 h)−1 and H2O permeation rates were less than 0.0155 g m−2 (24 h)−1. These exceptional permeation rates are believed to result from the substrate smoothing effect of the initial polymer layer. This layer eliminates substrate defects, prior to deposition of the oxide layer, and permits the oxide layer to grow with a minimum of pinholes. The capping polymer layer protects the oxide film during wind-up and subsequent handling.

PML/oxide/PML barrier layer performance differences arising from use of UV or electron beam polymerization of the PML layers

Abstract Polymer/oxide/polymer barrier coatings have been fabricated on 50 μm thick and 100 μm thick polyethylene terephthalate (PET) substrate in a roll-to-roll coating process. The oxide layer was either sputtered or e-beam evaporated Al2O3 and the polymer layers were deposited by the polymer multilayer (PML) method 1 , 2 . The monomer curing method employed to polymerize the PML layers was a parameter affected by varying the cross-linking irradiation between ultraviolet light (UV), electron beam irradiation (eb), and UV followed by eb. O2 and water vapor permeation rates for the three layer structures were up to four orders of magnitude lower than for the PET substrate alone and up to three orders of magnitude lower than for PET with a single oxide layer without PML layers. Significantly better performance was found for sputtered Al2O3 when compared with e-beam evaporated Al2O3, with or without the use of PML layers. Marginally better performance was obtained when PML layers were UV-cured, as compared with eb curing, with sputtered Al2O3, while the reverse was true when the Al2O3 was e-beam evaporated. Distinct differences in surface topography are observed between UV and e-beam-cured samples with UV-cured samples having significantly smoother surfaces and as low as 8.5 A RMS surface roughness. While both e-beam and UV curing appear to remove all traces of substrate surface roughness, the e-beam-cured surfaces appear to have a new, smoother, broader, and longer wavelength, surface roughness relative to the original substrate. We hypothesize that this new surface topography is due to electrostatic repulsion of the trapped electrons distorting the liquid monomer layer before the material is fully solidified.

Vacuum deposited polymer/metal multilayer films for optical application

Abstract Vacuum-deposited polymer/silver/polymer reflectors and tantalum/polymer/aluminum Fabry-Perot interference filters were fabricated in a vacuum web coating operation on polyester substrates with a new, high-speed deposition process. Reflectivities were measured in the wavelength range from 0.3 μm to 0.8 μm. This new vacuum processing technique has been shown to be capable of deposition line speeds in excess of 500 linear m min −1 (D.G. Shaw and M.G. Langlois, Proc. 7th Int. Conf. Vacuum Web Coating , November 1993, p. 268). Central to this technique is a new vacuum deposition process for the high-rate deposition of polymer films. This polymer process involves the flash evaporation of an acrylic monomer onto a moving substrate. The monomer is subsequently cured by an electron beam or ultraviolet light. This high-speed polymer film deposition process has been named the polymer multi-layer process. Also, vacuum-deposited, index-matched, polymer/CaF 2 composites were fabricated from monomer slurries that were subsequently cured with ultraviolet light. This second technique is called the liquid multi-layer process. Each of these polymer processes is compatible with each other and with conventional vacuum deposition processes such as sputtering or evaporation.

A new method for vacuum deposition of polymer films

In recent years a number of papers have been written concerning vacuum web coating of acrylate films onto a variety of substrates, for a variety of applications, utilizing the polymer multi-layer (PML) process for flash evaporation of monomer fluids. While of interest to many, widespread implementation of the PML process has not occurred, in part due to certain process limitations and stability issues. A new vacuum monomer technique (VMT), which utilizes a new low temperature source design to produce gaseous monomer, has been developed that allows vacuum deposition of acrylate films with the same properties (ultra smooth and pinhole-free) as PML deposited films. The new VMT process should permit sub-micron or multiple-micron thick films to be deposited at web speeds in excess of 100 m/min as in the PML process. There is a large overlap between the classes of starting monomers used in the PML and VMT processes so a great deal of insight into the VMT process can be gleaned from the PML literature. The VMT process will be described, a complete mathematical description and model for the process will be developed, and data relevant to barrier films and optical coatings will be presented.