Glass panel with barrier coating and related methods

Details Glass panel with barrier coating and related methods Glass panel with barrier coating and related methods

2001-11-21

2004-05-04

Vincent, Sean (Department: 1731)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

With viewing layer of specified composition

C428S001320, C428S001500, C428S001620, C428S430000, C428S431000, C428S432000, C428S434000

Reexamination Certificate

active

06730373

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO MICROFICHE APPENDIX
Not applicable.
BACKGROUND OF THE INVENTION
The present invention relates generally to improving the environmental durability of coated glass panels that are used in displays and similar applications, and more particularly to a coated glass panel that has been treated to remove particles before backfilling the voids left by the particles with an overcoat material.
Glass panels are used in a wide variety of display technology. Displays that can use glass panels include television sets, computer screens, and instrument panels, to name a few. The glass panels are often coated or otherwise treated to improve the performance characteristics or meet a specified requirement of the display. For example, a panel might be slightly etched to reduce reflectivity, or an anti-reflective film or coating might be applied to the front and/or back surface of the glass panel.
Films or coatings might be applied in a variety of ways. One approach applies a self-adhesive sheet of polyethylene terephthalate (“PET”) to a glass panel. The PET sheet may be coated itself, such as with an anti-reflective (“AR”) coating. The AR coating is typically a layer or layers of materials that improve the optical match between the PET and the air. Other techniques deposit a layer or layers of material directly onto the surface of the glass panel.
Some display products generate electromagnetic interference (“EMI”), and glass panels used in such displays might be treated to reduce the EMI radiated from the panel into the environment, particularly toward a user. In some instances, a fine wire mesh is attached to or imbedded in a glass panel assembly to reduce emissions. The wire mesh is typically grounded through a wire. Such an assembly can be expensive and reduce the clarity or resolution of the display. Another approach has been to deposit a low-emissivity (“lowE”) coating onto the surface of the glass panel. LowE coatings have been developed by, and are available from, a number of suppliers and often contain silver, copper, or gold incorporated into a layer or layers of the coating. LowE coatings typically have better than 45% transmission in the visible spectrum and a sheet resistivity of less than 5 Ohms per square, and in some instances have a sheet resistivity of about 0.5 Ohms per square.
Unfortunately, lowE coatings are often moisture sensitive, and moisture intrusion can induce corrosion in the coating layers. In particular, humidity can infiltrate the low-E coating and cause “blooms” to appear, which degrade the appearance of the panel. Moisture typically infiltrates through a defect in the coated layers. Several techniques address reducing the formation of defects, and other techniques have been developed to seal the defects. One approach is to attach a sheet of PET to the lowE coating with pressure-sensitive adhesive to seal the defects. The relatively thick PET layer protects the lowE coating from environmental moisture. The front surface of the PET sheet is coated to reduce reflections in some instances, typically in a roll coater before the PET sheet is applied to the glass.
However, using such a polymer sheet increases the number of components and assembly steps required for the glass panels. This in turn increases costs and decreases product yield and mechanical durability
Therefore, a glass panel that can provide EMI shielding, high clarity, and that is resistant to moisture-induced corrosion is desirable.
BRIEF SUMMARY OF THE INVENTION
A thin-film barrier overcoat is deposited directly over a moisture-sensitive coating on a glass panel to provide environmental protection to the moisture-sensitive coating. In a particular embodiment, the moisture-sensitive coating contains a metallic layer, such as are common in lowE coatings. In a further embodiment, the barrier overcoat is an AR coating. Nodules, which otherwise might propagate defects through the thin-film barrier overcoat, have been removed from the lowE coating prior to the barrier overcoat deposition process. In one embodiment, the panel is tempered in an oxygen-containing atmosphere to facilitate the removal of nodules and to harden the lowE coating sufficiently for mechanical cleaning. Other coatings might not be tempered or need hardening to facilitate removal of the nodules. In a particular embodiment, the final thin-film layer of the barrier overcoat is a low-friction material, such as MgF
2
. A second AR coating can be applied to the other surface of the glass to enhance the transmission of light through the panel from a display such as a plasma display, or that surface of the glass might support a device such as an organic light-emitting diode.
In another embodiment, a polymer sheet is attached to the surface of the glass substrate, which can be tempered or untempered, on the side opposite the lowE and AR coatings. A second AR coating can be applied to the polymer sheet before it is attached to the glass.


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