Reusable mask and method for coating substrate

Details Reusable mask and method for coating substrate Reusable mask and method for coating substrate

1999-09-08

2001-08-28

Loney, Donald J. (Department: 1772)

Stock material or miscellaneous articles

Structurally defined web or sheet

Including variation in thickness

C428S172000, C428S192000, C428S195100, C427S259000, C427S282000, C118S504000, C118S505000

Reexamination Certificate

active

06280821

ABSTRACT:

The present invention relates to a reusable mask used to prevent selected portions of a substrate like a glass-containing transparency from being coated with a film or coating whereby the appearance of the coating is improved.
Recent advances in automotive technology have resulted in novel multifunctional uses for vehicle transparencies. More specifically, windshields have been designed to incorporate heating arrangements, as disclosed in U.S. Pat. No. 4,820,902 to Gillery, and antenna systems, as disclosed in U.S. Pat. No. 4,849,766 to Inaba et al. and U.S. Pat. No. 5,083,135 to Nagy et al. These developments use a transparent metallic coating applied to selected portions of a major surface of the windshield glass in specific patterns. The coating may be applied using techniques well known in the art, e.g. physical vapor deposition techniques which include magnetic sputtering vacuum deposition (MSVD) and chemical vapor deposition techniques. One method used to form these patterns is to use tape to outline the desired coating configuration and protect selected portions of the glass sheets from being coated by the film. However, this procedure is time-consuming and labor intensive in both applying the tape before coating and removing the tape after coating. In addition, the tape cannot be reused and must be discarded after each use.
In U.S. Pat. No. 5,492,750 for a mask for coated glass by Shumaker et. al. a reusable mask for coating glass transparencies is disclosed. This mask has two members, sections, or portions to provide an edge where the mask meets the deposited coating on the glass substrate to reduce the ghosting effect of the coated glass. This “ghosting” condition is a visually observable change in the coloration of the coating where the coating/mask interface was and where the mask may have shaded the glass during coating. This ghosting effect may be reduced by reducing the thickness of the mask but as thickness is reduced, the rigidity of the mask is also reduced, resulting in increased difficulty in handling the mask. In addition, if the mask becomes too thin, it may be too light in weight to lay flush against the surface of the substrate, resulting in a poor quality edge outlining the coating. Any such edge of the mask should be durable to be reusable without sustaining nicks and breaks along the edge that would affect the appearance and performance of the coating in regards to ghosting. Furthermore, the mask may be too flimsy to be cleaned and reused in subsequent masking operations. The durability and longevity of such masks could be improved so that the masks can experience more cycles through the cleaning process to remove the coating from the surface of the mask that is exposed to the coating process.
Additionally recent developments in the use of transparencies on motor vehicles include telepeage for the automatic identification of vehicles and the recording of highway tolls. Signals used in télépéage for automatic toll collection need to traverse the transparency to communicate with a device in the motor vehicle. Some coatings on the transparencies can interfere with these signals so the transparencies need to have selected voids or deletions in the coating to permit the passing of signals such as electromagnetic signals to appropriate communication devices within the vehicle. Generally such deletions of the coating are separate or isolated from border deletions of the coating around the periphery of the transparency although such selected deletions could be part of the border deletion as long as the void in the coating allows sufficient area for the passage of the signals.
Generally the masks for obtaining the border deletions are larger than masks for the deletions for signal passage. When these smaller masks are isolated from the border masks in placement on the transparency during coating, the independent mask or masks should not move or shift very much during the coating process. Also as with the border masks it is desirable that any independent masks are reusable and can withstand as many cleaning cycles as possible to remove coating from the masks. Also the masks should allow for the reduction in ghosting of the coating on substrates like transparencies from the areas of the deletions that are in view or sight of the user or observer of the coated transparency.
It would be advantageous to have a reusable mask to provide deletions in coatings on substrates like transparencies that minimize ghosting along the periphery of the coating around the deletions and that can withstand numerous cycles through the cleaning process to remove the coating from the mask and additionally that have a simple construction and have improved durability.
SUMMARY OF THE INVENTION
The foregoing objects of the invention and other objects gleaned from the following disclosure are accomplished by the mask article and method of coating the substrate like transparencies with the mask of the present invention. The mask is a semi-rigid device having two major generally opposing surfaces and one or more sides between such surfaces with at least one one-piece edge. One of these surfaces is of a larger area than the other surface to provide for at least one of the sides that is involved as an edge in the substrate-mask-coating interface to have an inward sloping outline having an angle from the horizontal of one of the surfaces from greater than 0° to less than 90° somewhere along the side between the larger surface and the smaller surface. This distance along the side could be at the beginning of the side from the larger surface area or in the middle of the side between the larger and smaller surface areas as long as the distance from the larger surface area to the start of the sloping outline of the side is 0.03 inch (0.076 cm.) or less. The contour of the side with the sloping outline can be straight or curved as in a concave contour or a combination of these without any convex extensions past the sloping outline. Also this angle is measured from an imaginary vertex on the larger or smaller surface to the outermost extension of the side with the sloping outline. The sloping outline of the side should extend a distance sufficient to provide an adequate edge at the larger surface to reduce the ghosting effect. The larger area surface has the configuration of the shape of a deletion for the coating. The generally opposing smaller area surface can have the similar configuration allowing for the sloping or inclined outline of the one or more sides or any other general configuration that would assist in its use or placement on the substrate or coating.
The mask is adapted for secure placement on the substrate during the coating process and removal therefrom after the coating process. With the one or more sloping sides for the substrate-mask-coating interface, the thickness of the coating is more uniform from any planned or selected deletion. The secure placement of the mask during coating can be accomplished by the weight of the mask itself during horizontal or near horizontal coating of the substrate or from the use of at least one friction enhancing member present on the larger surface area of the mask. In mass production of the coated substrate, it can be convenient to stack the masks after coating of the substrates. Such a stack or stacks can be conveyed to the beginning of the coating line for reuse of the masks or to a periodic cleaning operation at some point in the process to remove coating from the non-substrate contacting surface of the mask. With the friction enhancing members present on the mask, removal of individual masks from the stack can be complicated. Therefore, optionally, the mask has recesses on the surface generally opposing the surface immediately adjacent to the substrate. These recesses in this surface generally match the number, shape and configuration of the friction enhancing member.
The method of applying a coating to a substrate utilizing the mask described above involves covering the substrate with the semi-rigid mask. The coverage is such that the surfa

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