This disclosure relates ion exchanged glass, more particularly to masking for ion exchange baths.
Ion exchanged glass typically involves immersing a piece of glass into an ion exchange bath. Typically, glass parts are immersed in a hot salt solution, and potassium ions in the solution migrate into the glass surface, replacing the smaller sodium ions originally in the glass. The glass part is then removed from the bath and cooled. As it cools, the larger potassium ions compress the glass and form a tough surface.
To control design complex, stress-varied ion exchanged glass undergoes masking prior to immersion. The masking blocks the ion exchange from a region or region of the glass so it does not become hardened or protected. The masked regions will break easier and allow control where the glass will break. Blocking the ion exchange may also alter the optical properties of the glass.
Currently, masking involves the use of thin films as masks, or complicated gasket systems. These methods may become cost-prohibitive. In addition, the use of gaskets limits the process by temperature and time because the gaskets melt. This limits the amount of time the glass can be immersed in the bath, reducing the effectiveness of the coating that forms in the non-masked regions.
One embodiment is a method of masking glass in an ion exchange bath that includes applying a dissolvable sealant to a cover material, adhering the cover material to a glass part to form a mask on the glass part, immersing the glass part into an ion exchange bath. removing the glass part from the ion exchange bath, and using a solvent to dissolve the sealant and the cover material from the glass part.
Another embodiment is a mask on glass having a piece of glass, and a dissolvable sealant on a cover material, the dissolvable sealant comprising an inorganic material and a silicate, the dissolvable sealant between the cover material and the piece of glass.
The portion 14 of the glass shows that the potassium ions have become resident in the glass 10. One should note that this is just for ease of discussion. The exchange between ions occurs across the unmasked portions of the glass part simultaneously. The masked portions such as that under the cover material piece 16 either do not undergo ion exchange or undergo it at rate slower than the rest of the part. This reduces the likelihood that the protective barrier mentioned above will form. The result is a glass part with a varied stress profile. Having a varied stress profile may have several advantages including the ability to control at what region the glass will break, can affect the optical properties to cause an optical gradient, and create shape distortions.
As shown in
The mask portion 14 may attach to the glass part with an adhesive or sealant. In the embodiments, here, the sealant is dissolvable. In one embodiment, the adhesive has a thickness sufficient to ensure that there is no contact between the glass part and the ion bath. Referring back to
The sealant then adheres the cover material to the glass at 32. Once the glass has the cover material attached, it is immersed in the ion bath. The ion bath may consist of sodium nitrate, or potassium nitrate, depending upon the sealant, the solvent used later to dissolve it, and the substrate. The combinations of the sealant, bath ingredients and the solvent are shown in the table below:
The sodium doped silicate glass using sodium silicate in the AgNO3/NaNO3 bath does not create any stress gradients in the bath. This creates a dopant gradient, such as Ag+ ions. This type of bath is shown in
Returning to
In this manner, one can provide a piece of glass having a varied stress profile. This allows control of different variables to achieve a desired profile. This may include controlling regions where breaks may occur.
It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
This invention was made with Government support under HR0011-16-C-0087 ONLY-DUST awarded by DARPA. The Government has certain rights in this invention.