First surface mirror with chromium nitride layer

Abstract

A mirror (e.g., first surface mirror) is provided with a layer of or including chromium nitride (CrNx). In certain example embodiments, the CrNx layer may be the primary reflective layer of the mirror. Surprisingly and unexpectedly, it has been found the addition of nitrogen to the chromium to form CrNx reduces pinhole formations in the resulting layer. In certain example embodiments, the more nitrogen which is introduced into the layer, the smaller the number and / or size of pinholes in the Cr inclusive layer. In certain example embodiments, it has also been found that the addition of nitrogen to Cr may improve durability.

Description

[0001] This application is related to a first-surface mirror including a layer of or including chromium nitride (CrNx). In certain example embodiments, a reflective layer of the mirror comprises chromium nitride, and is nitrided to an extent so as to reduce undesirable pinhole formation and / or improve adhesion. In certain example non-limiting instances, such first surface mirrors may be used in the context of a projection television (PTV) apparatus, automotive mirrors, or in any other suitable application. BACKGROUND OF THE INVENTION [0002] Mirrors for various uses are known in the art. For example, see U.S. Pat. Nos. 5,923,464 and 4,309,075 (all hereby incorporated herein by reference). Mirrors are also known for use in projection televisions and other suitable applications. In the projection television context, see for example U.S. Pat. Nos. 6,275,272, 5,669,681 and 5,896,236 (all hereby incorporated herein by reference). [0003] One type of mirror is a second or back surface mirro...

AI Technical Summary

Benefits of technology

This patent describes a new mirror design that includes a layer of chromium nitride (CrNx) which has improved durability and reduced pinhole formation. The addition of nitrogen to chromium can also enhance the mirror's reflective properties. The resulting mirror can be used in various applications such as projection televisions, copiers, scanners, bar code readers, and automotive mirrors. The method of making the mirror involves sputtering a target with chromium in an atmosphere containing nitrogen gas. The nitrogen gas flow during sputtering can range from 1% to 21% of the total gas flow.

Problems solved by technology

In certain instances, passing through the glass substrate twice can create ambiguity in directional reflection and imperfect reflections may sometimes result.

Unfortunately, such first surface mirrors with a structure of glass / Cr suffer from pinhole related problems.

In particular, such a mirror structure is susceptible to pinhole formation in the metallic Cr layer, especially as the Cr layer thickness increases in applications where lower transmission (e.g., 0.5% visible transmission) are desired.

Light tends to leak through such pinholes making large numbers of them especially undesirable in mirror applications where reflectance (not transmission) of light is desired.

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