Article with substrate and multilayer thin-film coating with improved resistance to intra-coating delamination

Abstract

An article including a substrate with a primary surface and a multilayer thin-film coating disposed over the primary surface. The multilayer thin-film coating includes at least one bilayer. Each bilayer includes a high-index layer of a high-index material and a low-index layer of a low-index material on the high-index layer. The low-index material exhibits an index of refraction that is lower than an index of refraction that the high-index material exhibits. The article exhibits no delamination within the multilayer thin-film coating extending from a damage track visibly observable under 50X magnification after contacting the damage track with petroleum jelly. A method of making the article including a low-index sputtering step that employes a gas pressure that is greater than or equal to 2.0 mTorr (~0.27 Pa).

Description

Attorney Docket: SP24-251ARTICLE WITH SUBSTRATE AND MULTILAYER THIN-FILM COATING WITH IMPROVED RESISTANCE TO INTRA-COATING DELAMINATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Application Serial No. 63 / 697,085, filed on September 20, 2024, the content of which is relied upon and incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to articles comprising substrates with multilayer thin-film coatings, particularly coatings with alternating high-index and low-index layers, and to methods for manufacturing such coated articles with improved mechanical durability and optical performance and resistance to chemical delamination.BACKGROUND

[0003] Sometimes a cover article separates an electronic display or other components from an external environment. For example, personal mobile devices (e.g., smart phones, smart watches, audio devices), vehicles, and appliances sometimes include a cover article separating an electronic display from the external environment. Sometimes the electronic display has touch screen capability. In such cases, the cover article encounters the touch from a finger of a person attempting to utilize the touch screen capability.

[0004] The cover article sometimes includes a substrate and one or more layers of thin film over the substrate. The one or more layers of thin film are included to impart the cover article with one or more improved properties, such as anti-reflectance, scratch resistance, or easy-to-clean characteristics. The composition, among other things, of the one or more layers of thin film may dictate the one or more improved properties.

[0005] However, there is a problem in that the one or more layers of thin film can delaminate from the substrate. For example, abrading the one or more layers of thin film can create a path of ingress for substances commonly found on the human finger, such as petroleum jelly, mineral oil, and water between the layers. The substances then facilitate delamination of the layers. Delamination of the one or more layers of thin film is problematic, among other reasons, because the one or more layers of thin film may no longer impart the cover article with the desired improved propertiesAttorney Docket: SP24-251 after delamination and because the delamination can be visible and make the aesthetics less than optimal.SUMMARY

[0006] The present disclosure addresses that problem with a multilayer thin-film coating where the low-index layers are formed via sputtering using a gas pressure that is greater than or equal to 2.0 mTorr. Such a gas pressure is higher than the industry accepted gas pressure of 1.0 mTorr or lower. It has been surprisingly discovered that forming the low-index layers (e.g., S1O2) with the higher-than-normal gas pressure produces a multilayer thin-film coating that is much more resistant to delamination after the coating is damaged and then contacted with such substances like petroleum jelly.

[0007] According to a first aspect of the present disclosure, an article comprises: (a) a substrate comprising a primary surface; and (b) a multilayer thin-film coating disposed over the primary surface, the multilayer thin-film coating comprising at least one bilayer, each of the at least one bilayer comprising a high-index layer of a high-index material and a low-index layer of a low- index material on the high-index layer, the low-index material exhibiting an index of refraction that is lower than an index of refraction that the high-index material exhibits, wherein, the article exhibits no delamination within the multilayer thin-film coating extending from a damage track visibly observable under 5 OX magnification with an optical microscope after (i) creation of the damage track in the multilayer thin-film via a single cycle of back-and-forth abrasion with a % inch diameter (6.25 mm) H-l 8 abraser under a load of 1 kg at a cycle speed of 20 cycles per minute and a stroke length of 50 mm, (ii) contacting the article at and around the damage track with petroleum jelly for 15 minutes at room temperature, and (iii) removing the petroleum jelly from the article with a polyester wipe followed by rinsing the multilayer thin-film with isopropyl alcohol.

[0008] According to a second aspect of the present disclosure, the article of the first aspect is presented, wherein the substrate comprises a glass composition, a glass-ceramic composition, or a ceramic composition.

[0009] According to a third aspect of the present disclosure, the article of any one of the first through second aspects is presented, wherein (i) the multilayer thin-film coating comprises N number of the bilayers of the high-index layer and the low-index layer, and (ii) N is an integer within a range of from 1 to 6.Attorney Docket: SP24-251

[0010] According to a fourth aspect of the present disclosure, the article of any one of the first through third aspects is presented, wherein the index of refraction of the low-index material is within a range of from 1.40 to 1.70.

[0011] According to a fifth aspect of the present disclosure, the article of any one of the first through fourth aspects is presented, wherein the index of refraction of the high-index material is within a range of from 1.71 to 2.60.

[0012] According to a sixth aspect of the present disclosure, the article of any one of the first through fifth aspects is presented, wherein the low-index material comprises one or more of SiO2, MgF2, YF3, and YbF3.

[0013] According to a seventh aspect of the present disclosure, the article of any one of the first through sixth aspects is presented, wherein the high-index material comprises one or more of ZrO2, HfO2, Ta2O5, Nb2O5, TIO2, Y2O3, S13N4, SrTiO3, WO3, SiuAlvOxNy, A1NX, S13N4, A10xNy, SiOxNy, SiNx, SiNx:Hy, A12O3, TiNbOx, and MoO3.

[0014] According to an eighth aspect of the present disclosure, the article of any one of the first through seventh aspects is presented, wherein (i) the low-index material comprises SiO2, and (ii) the high-index material comprises Nb2Os.

[0015] According to a ninth aspect of the present disclosure, the article of any one of the first through eighth aspects is presented, wherein (i) for each of the at least one bilayer, the low-index layer has a low-index thickness orthogonal to the primary surface of the substrate and the high- index layer has a high-index thickness orthogonal to the primary surface of the substrate, (ii) the low-index thickness is within a range of from 10.0 nm to 120 nm, and (iii) the high-index thickness is within a range of from 10.0 nm to 120 nm.

[0016] According to a tenth aspect of the present disclosure, the article of any one of the first through ninth aspects is presented, wherein the multilayer thin-film coating further comprises an initial low-index layer of a low-index material on the primary surface, the initial low-index layer sandwiched between the primary surface of the substrate and the at least one bilayer.

[0017] According to an eleventh aspect of the present disclosure, the article of any one of the first through tenth aspects is presented, wherein the multilayer thin-film coating has a total thickness measured orthogonal to the primary surface of the substrate that is less than 450 nm.

[0018] According to a twelfth aspect of the present disclosure, the article of any one of the first through eleventh aspects is presented, wherein the article exhibits, at the multilayer thin-filmAttorney Docket: SP24-251 coating, a first surface average reflectance of less than 0.50% throughout an entirety of a wavelength range of from 450 nm to 650 nm.

[0019] According to a thirteenth aspect of the present disclosure, the article of any one of the first through twelfth aspects is presented, wherein the article exhibits a reflected color at all viewing angles throughout a range of from 0 to 10 degrees characterized by the CIELAB color space with an a* value within a range of from -4.0 to 0.0 and a b* within a range of from -4.0 to 0.0.

[0020] According to a fourteenth aspect of the present disclosure, the article of any one of the first through thirteenth aspects is presented, wherein the article exhibits a transmittance of electromagnetic radiation having a wavelength of 940 nm that is greater than 85.0%.

[0021] According to a fifteenth aspect of the present disclosure, the article of any one of the first through fourteenth aspects is presented, wherein the article exhibits a hardness, measured via a Berkovich nanoindentation test at about 100 nm indentation depth into the multilayer thin-film coating, that is greater than or equal to 5.0 GPa.

[0022] According to a sixteenth aspect of the present disclosure, the article of the fifteenth aspect is presented, wherein the hardness that the article exhibits is within a range of from 5.0 GPa to 10.0 GPa.

[0023] According to a seventeenth aspect of the present disclosure, the article of the sixteenth aspect is presented, wherein the hardness that the article exhibits is within a range of from 5.0 GPa to 8.0 GPa.

[0024] According to an eighteenth aspect of the present disclosure, the article of any one of the first through seventeenth aspects is presented, wherein the article exhibits an elastic modulus, measured via a Berkovich nanoindentation test at about 100 nm indentation depth into the multilayer thin-film coating, that is greater than 50 GPa.

[0025] According to a nineteenth aspect of the present disclosure, the article of the eighteenth aspect is presented, wherein the elastic modulus that the article exhibits is within a range of from 50 GPa to 110 GPa.

[0026] According to a twentieth aspect of the present disclosure, the article of any one of the first through nineteenth aspects is presented, wherein the article exhibits a failure stress that is greater than 850 MPa.Attorney Docket: SP24-251

[0027] According to a twenty-first aspect of the present disclosure, the article of any one of the first through twentieth aspects is presented, wherein the article exhibits a strain-to-failure that is within a range of from 0.8% to 2.0%.

[0028] According to a twenty-second aspect of the present disclosure, a method of manufacturing a cover article, the method comprising: a bilayer formation sequence comprising: (a) a high-index sputtering step comprising sputtering a high-index layer of a high-index material over a primary surface of a substrate, the sputtering of the high-index sputtering step occurring within a chamber and in the presence of an inert gas having a gas pressure; and (b) a low-index sputtering step comprising sputtering a low-index layer of a low-index material over the high-index layer, the sputtering of the low-index sputtering step occurring within a chamber and in the presence of an inert gas having a gas pressure, and the low-index material exhibiting an index of refraction that is lower than an index of refraction that the high-index material exhibits, wherein, the gas pressure of the inert gas during the low-index sputtering step is greater than or equal to 2.0 mTorr (-0.27 Pa).

[0029] According to a twenty-third aspect of the present disclosure, the method of the twenty- second aspect is presented, wherein the substrate has one of a glass, a glass-ceramic, and a ceramic material.

[0030] According to a twenty-fourth aspect of the present disclosure, the method of any one of the twenty-second through twenty-third aspects is presented, wherein the low-index material comprises one or more of SiCh, MgF2, YF3, and YbFs.

[0031] According to a twenty-fifth aspect of the present disclosure, the method of any one of the twenty-second through twenty-fourth aspects is presented, wherein the high-index material comprises one or more of ZrCh, HfCh, Ta2Os, Nb2Os, TiCh, Y2O3, SislS , SrTiCh, WO3, SiuAlvOxNy, AM, S13N4, AlOxNy, SiOxNy, SiNx, SiNx:Hy, AI2O3, TiNbOx, and MoO3.

[0032] According to a twenty-sixth aspect of the present disclosure, the method of any one of the twenty-second through twenty-fifth aspects is presented, wherein (i) the low-index material comprises SiCh, and (ii) the high-index material comprises bfeOs.

[0033] According to a twenty-seventh aspect of the present disclosure, the method of any one of the twenty-second through twenty-sixth aspects is presented, wherein the inert gas is argon.

[0034] According to a twenty-eighth aspect of the present disclosure, the method of any one of the twenty-second through twenty- seventh aspects is presented, wherein the gas pressure of the inertAttorney Docket: SP24-251 gas during the low-index sputtering step is within a range of from 2.0 mTorr (-0.27 Pa) to 7.0 mTorr (-0.93 Pa).

[0035] According to a twenty-ninth aspect of the present disclosure, the method of the twentyeighth aspect is presented, wherein the gas pressure of the inert gas during the low-index sputtering step is within a range of from 4.5 mTorr (-0.60 Pa) to 5.5 mTorr (-0.73 Pa).

[0036] According to a thirtieth aspect of the present disclosure, the method of any one of the twenty-second through twenty-ninth aspects is presented, wherein the gas pressure of the inert gas during the high-index sputtering step is within a range of from 0.5 mTorr (-0.07 Pa) to 7.0 mTorr (-0.93 Pa).

[0037] According to a thirty-first aspect of the present disclosure, the method of the thirtieth aspect is presented, wherein the gas pressure of the inert gas during the high-index sputtering step is within a range of from 0.5 mTorr (-0.97 Pa) to 1.5 mTorr (-0.20 Pa).

[0038] According to a thirty-second aspect of the present disclosure, the method of the thirtieth aspect is presented, wherein the gas pressure of the inert gas during the high-index sputtering step is within a range of from 4.5 mTorr (-0.60 Pa) to 5.5 mTorr (-0.73 Pa).

[0039] According to a thirty-third aspect of the present disclosure, the method of any one of the twenty-second through thirty-second aspects is presented, wherein the gas pressure of the inert gas during the low-index sputtering step is greater than or equal to the gas pressure of the inert gas during the high-index sputtering step.

[0040] According to a thirty-fourth aspect of the present disclosure, the method of any one of the twenty-second through thirty-third aspects further comprises a performance of the low-index sputtering step occurring before the bilayer formation sequence.

[0041] According to a thirty-fifth aspect of the present disclosure, the method of any one of the twenty-second through thirty-fourth aspects further comprises performing the bilayer formation sequence N number of times in succession.

[0042] According to a thirty-sixth aspect of the present disclosure, the method of the thirty-fifth aspect is presented, wherein N is an integer within a range of from 1 to 6.

[0043] According to a thirty-seventh aspect of the present disclosure, the method of any one of the twenty-second through thirty-sixth aspects is presented, wherein after the bilayer formation sequence is performed 1 time, the low-index layer furthest away from the substrate exhibits a surface roughness (Ra) that is greater than 0.8 nm.Attorney Docket: SP24-251

[0044] According to a thirty-eighth aspect of the present disclosure, the method of the thirty-sixth aspect is presented, wherein after the bilayer formation sequence is performed 2 times, the low- index layer furthest away from the substrate exhibits a surface roughness (Ra) that is greater than 0.9 nm.

[0045] According to a thirty-ninth aspect of the present disclosure, the method of any one of the twenty-second through thirty-eighth aspects is presented, wherein after the bilayer formation sequence is performed 2 times, (i) the high-index layer furthest away from the substrate exhibits a compressive stress that is greater than 275 MPa and (ii) the low-index layer furthest away from the substrate exhibits a compressive stress that is greater than 275 MPa.

[0046] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0047] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the description serve to explain principles and operation of the various embodiments.BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In the Drawings:

[0049] FIG. 1 is a perspective view of an article of the present disclosure, illustrating a multilayer thin-film coating disposed on a first primary surface of a substrate;

[0050] FIG. 2 is a side view of the article;

[0051] FIG. 3 is a magnified elevation view of area III of FIG. 2, illustrating the multilayer thin- film coating including one or more bilayers of a high-index layer and a low-index layer upon the high-index layer and optionally an initial low-index layer between the one or more bilayers and the first primary surface of the substrate;

[0052] FIG. 4 is a schematic diagram of a method of the present disclosure, illustrating a high- index sputtering step and a low-index sputtering step to form the one or more bilayers;Attorney Docket: SP24-251

[0053] FIG. 5 is a photograph illustrating a substrate with a multilayer thin- film coating thereupon ready to be contacted with a Wearaser coupled to a Linear Abraser 5750 surface testing machine;

[0054] FIG. 6 is a photograph illustrating the Wearaser having made a single back and forth cycle contacting the multilayer thin-film coating and forming damage tracks therein;

[0055] FIG. 7 is a series of photographs illustrating the damage tracks at 5 OX and 200X magnification before being contacted with petroleum jelly (left two photographs) and after having been contacted with petroleum jelly (right two photographs), illustrating the multilayer thin-film coating having delaminated after being contacted with the petroleum jelly;

[0056] FIG. 8 is a series of photographs illustrating other damage tracks at 5 OX and 200X magnification before being contacted with water (left two photographs) and after having been contacted with water (right two photographs), illustrating the multilayer thin-film coating having delaminated after being contacted with water;

[0057] FIG. 9 is a series of scanning electron microscope (top three) and transmission electron microscope (bottom) images, collectively illustrating delamination, after contact with petroleum jelly, of the multilayer thin-film coating occurring between the layers of the multilayer thin-film coating and not between the primary surface of the underlying substrate and the multilayer thin- film coating as a whole;

[0058] FIG. 10 is an explanatory diagram transposed next to a section of the transmission electron microscope image from FIG. 9, illustrating the delamination having occurred between the low- index layer of SiCh and the high-index layer of bfeOs within the first bilayer of the multilayer thin-film coating (with the lighter shade layer of Nb2Os clearly visible still upon the substrate);

[0059] FIG. 11, pertaining to Comparative Examples 10-12, is a collection of photographs showing damage tracks before and after contact with petroleum jelly, illustrating delamination present in the after photographs;

[0060] FIG. 12, pertaining to Examples 8 and 9, is a collection of photographs showing damage tracks before and after contact with petroleum jelly, illustrating a lack of delamination present in the after photographs;

[0061] FIG. 13 is a pair of schematic diagrams of multilayer thin-film coatings with compressive stress values presented within each layer, one of the multilayer thin-film coatings having been produced via sputtering with a gas pressure of 1 mTorr and the other of the multilayer thin-filmAttorney Docket: SP24-251 coatings having been produced via sputtering with a gas pressure of 5 mTorr, illustrating that the higher gas pressure results in higher compressive stress values (more negative) for any given layer;

[0062] FIG. 14 reproduces a pair of graphs, one graph (left) plotting surface roughness (Ra) as a function of the layer of the multilayer thin- film coating and the gas pressure used to form the layer and the other graph (right) plotting compressive stress as a function of the layer of the multilayer thin-film coating and the gas pressure used to form the layer, showing that surface roughness and compressive stress both increase as a function of increasing gas pressure;

[0063] FIG. 15, pertaining to Comparative Example 18 and Example 14, is a pair of graphs generated after X-ray photoelectron spectrometry analysis, illustrating that the lower gas pressure used to form the top most layer of SiCh used more sputtering time than an equivalent layer formed with higher gas pressure, indicating that the lower pressure layer had a higher density than the higher pressure layer; and

[0064] FIG. 16, pertaining to Example 15 and Comparative Example 19, is a graph plotting failure probability during ring-on-ring load testing as a function of failure stress for samples of the article of the present disclosure where the low-index layers were formed using a gas pressure of 5.0 mTorr (Example 15) and samples where the low-index layers were formed using a gas pressure 1.0 mTorr (Comparative Example 19), illustrating that the higher gas pressure during sputtering resulted in higher failure stress values.DETAILED DESCRIPTION

[0065] Reference will now be made in detail to the present preferred embodiments, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

[0066] Referring to FIGS. 1 and 2, an article 10 of the present disclosure is herein described. The article 10 includes a substrate 12 and a multilayer thin-film coating 14 on the substrate 12. The substrate 12 includes a first primary surface 16 and a second primary surface 18. Each of the first primary surface 16 and the second primary surface 18 can be planar and parallel to each other. The first primary surface 16 and the second primary surface 18 can face in opposite directions. The substrate 12 can thus take the form of a sheet. The substrate 12 can have a substrate thickness 20, measured as the shortest straight-line distance between the first primary surface 16 and the second primary surface 18. The substrate thickness 20 can be within a range of from 50 pm to 5.0 mm. For example, the substrate thickness 20 can be 50 pm, 100 pm, 200 pm, 300 pm, 400 pm, 500Attorney Docket: SP24-251 pm, 600 pm, 700 pm, 800 pm, 900 pm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, 4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm, 5.0 mm, or within any range bound by any two of those values (e.g., from 500 gm to 3.1 mm, from 1.0 mm to 2.0 mm, and so on). However, the substrate thickness 20 can be less than 50 gm or greater than 5.0 mm. In embodiments, the substrate 12 has one or more of a glass composition, a glass-ceramic composition, and a ceramic composition. For example, the substrate 12 can have a glass composition, and the glass composition is an aluminoborosilicate composition. Other compositions for the substrate 12 (e.g., polymer) are envisioned.

[0067] As mentioned, the article 10 further includes the multilayer thin-film coating 14. The multilayer thin-film coating 14 is disposed on the first primary surface 16 of the substrate 12. In embodiments, the multilayer thin-film coating 14 directly contacts the first primary surface 16 of the substrate 12.

[0068] Referring to FIG. 3, the multilayer thin-film coating 14 includes at least one bilayer 22. Each bilayer 22 includes a high-index layer 24 of a high-index material and a low-index layer 26 of a low-index material. The low-index layer 26 is disposed over the high-index layer 24, with the high- index layer 24 disposed closer to the first primary surface 16 of the substrate 12 than the low- index layer 26. “Low-index” and “high-index” refer to the index of refraction of the material making up the layer relative to each other. For example, the low-index material exhibits an index of refraction that is lower than an index of refraction that the high-index material exhibits. Unless otherwise noted herein, the term “index of refraction” refers to the refractive index of the referenced material at 550 nm.

[0069] The multilayer thin-film coating 14 includes N number of the bilayers 22 of the high- index layer 24 and the low- index layer 26. N is an integer that is greater than or equal to 1. In embodiments, N is within a range of from 1 to 6. For example, N can be 1, 2, 3, 4, 5, 6, or within any range bound by any two of those values. N can be greater than 6 (e.g., 10, 15, 20, or more).

[0070] In embodiments, the index of refraction of the low-index material is within a range of from 1.40 to 1.70. For example, the index of refraction of the low-index material can be 1.40, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, 1.50, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, 1.60, 1.61, 1.62, 1.63, 1.64, 1.65, 1.66, 1.67, 1.68, 1.69, 1.70, or within any range bound byAttorney Docket: SP24-251 any two of those values (e.g., from 1.47 to 1.54, from 1.49 to 1.68, and so on). The index of refraction of the low-index material can be less than 1.40 or greater than 1.70 as long it is less than the index of refraction of the high-index material. Values for index of refraction provided here are as measured for a wavelength of 550 nm and at room temperature.

[0071] In embodiments, the index of refraction of the high-index material is within a range of from 1.71 to 2.60. For example, the index of refraction of the high-index material can be 1.71, 1.72, 1.73, 1.74, 1.75, 1.76, 1.77, 1.78, 1.79, 1.80, 1.81, 1.82, 1.83, 1.84, 1.85, 1.86, 1.87, 1.88, 1.89,1.90, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, 2.00, 2.01, 2.02, 2.03, 2.04, 2.05, 2.06,2.07, 2.08, 2.09, 2.10, 2.11, 2.12, 2.13, 2.14, 2.15, 2.16, 2.17, 2.18, 2.19, 2.20, 2.21, 2.22, 2.23,2.24, 2.25, 2.26, 2.27, 2.28, 2.29, 2.30, 2.31, 2.32, 2.33, 2.34, 2.35, 2.36, 2.37, 2.38, 2.39, 2.40,2.41, 2.42, 2.43, 2.44, 2.45, 2.46, 2.47, 2.48, 2.49, 2.50, 2.51, 2.52, 2.53, 2.54, 2.55, 2.56, 2.57,2.58, 2.59, 2.60, or within any range bound by any two of those values (e.g., from 2.00 to 2.25, from 1.78 to 2.31, and so on). The index of refraction of the high-index material can be less than 1.75 or greater than 2.60, as long as it is greater than the index of refraction of the low-index material.

[0072] The low-index material can be any composition that provides the desired index of refraction of the low-index layer 26. For example, the low-index material can be one or more of SiC>2, MgF2, YF3, and YbF3. The low-index material of one of the bilayers 22 need not be the same as the low-index material of another one of the bilayers 22.

[0073] The high-index material can be any composition that provides the desired index of refraction of the high-index layer 24. For example, the high-index material can be one or more of ZrO2, HfO2, Ta2O5, Nb2O5, TIO2, Y2O3, S13N4, SrTiO3, WO3, SiuAlvOxNy, A1NX, S13N4, A10xNy, SiOxNy, SiNx, SiNx:Hy, AI2O3, TiNbOx, and MoOs. The high-index material of one of the bilayers 22 need not be the same as the high-index material of another one of the bilayers 22. In embodiments, low-index material is or includes SiO2while the high-index material is or includes Nb2O5.

[0074] For each of the at least one bilayer 22, the low-index layer 26 has a low- index thickness 28 and the high-index layer 24 has a high-index thickness 30. In embodiments, the low- index thickness 28 is within a range of from 10.0 nm to 120 nm. For example, the low-index thickness 28 can be 10.0 nm, 15.0 nm, 20.0 nm, 25.0 nm, 30.0 nm, 35.0 nm, 40.0 nm, 45.0 nm, 50.0 nm, 55.0 nm, 60.0 nm, 65.0 nm, 70.0 nm, 75.0 nm, 80.0 nm, 85.0 nm, 90.0 nm, 95.0 nm, 100.0 nm,Attorney Docket: SP24-251105 nm, 110 nm, 115 nm, 120 nm, or within any range bound by any two of those values (e.g., from 40.0 nm to 65.0 nm, from 50.0 nm to 95.0 nm, and so on). In embodiments, the high-index thickness 30 can be within a range of from 10.0 nm to 120 nm. For example, the high-index thickness 30 can be 10.0 nm, 12.0 nm, 14.0 nm, 16.0 nm, 18.0 nm, 20.0 nm, 22.0 nm, 24.0 nm, 26.0 nm, 28.0 nm, 30.0 nm, 32.0 nm, 34.0 nm, 40.0 nm, 45.0 nm, 50.0 nm, 55.0 nm, 60.0 nm, 65.0 nm, 70.0 nm, 75.0 nm, 80.0 nm, 85.0 nm, 90.0 nm, 95.0 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm or within any range bound by any two of those values (e.g., from 12.0 nm to 30.0 nm, from 18.0 to 26.0 nm, from 40.0 nm to 115 nm, and so on). The low-index thicknesses 28 of each of the N bilayers 22 need not be the same. The high-index thicknesses 30 of each of the / V bilayers 22 need not be the same. In embodiments, the value for N, the index of refraction for each of the high-index layers 24, the index of refraction for each of the low-index layers 26, the high-index thicknesses 30, and the low-index thicknesses 28 are predetermined (e.g., engineered) so that the article 10 exhibits one or more desired optical properties, such as through operation of destructive interference of electromagnetic radiation transmitting through the article 10. In general, the greater the value of N, the more precise the anti-reflective property can be tailored to any particular wavelength or wavelength range of electromagnetic radiation. However, in general, the higher the value of N, the greater the cost and time to manufacture the multilayer thin-film coating 14. Thus, the value of N is often a balance between the cost and time to manufacture the multilayer thin-film coating 14 and the precision of the optical properties that the article 10 exhibits.

[0075] In embodiments, the multilayer thin-film coating 14 further includes an initial low- index layer 32 of a low-index material on the first primary surface 16 of the substrate 12. The initial low-index layer 32 is sandwiched between the first primary surface 16 of the substrate 12 and the at least one bilayer 22. When utilized, the initial low-index layer 32 is disposed directly upon (e.g., contacts) the first primary surface 16 of the substrate 12. The initial low-index layer 32 can include any of the low-index materials previously mentioned (e.g., SiCh). The initial low-index layer 32 is thought to generally improve adhesion of the at least one bilayer 22 to the substrate 12.

[0076] The multilayer thin-film coating 14 has a total thickness 34. The total thickness 34 is measured orthogonal to the first primary surface 16 of the substrate 12 as the shortest straight-line distance between the first primary surface 16 of the substrate 12 and an exterior facing surface 36 of the multilayer thin-film coating 14. The exterior facing surface 36 may be directly exposed to an external environment 38. However, in other instances, one or more further functional layers 40Attorney Docket: SP24-251(e.g., an easy-to-clean layer) are disposed over the exterior facing surface 36. The one or more further functional layers 40 are typically relatively thin (e.g., less than 5 nm) and only negligibly affect desired optical properties imparted by the multilayer thin- film coating 14. In embodiments, the total thickness 34 is less than 450 nm. The total thickness 34 can be less than 350 nm or even less than 300 nm. For example the total thickness 34 can be 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, 320 nm, 340 nm, 360 nm, 380 nm, 400 nm, 420 nm, 440 nm, 450 nm, or within any range bound by any two of those values (e.g., from 160 nm to 220 nm, from 200 nm to 400 nm, and so on).

[0077] As mentioned, the article 10 exhibits one or more properties. In particular, the article 10 exhibits greater resistance to delamination within the multilayer thin-film coating 14. The article 10 exhibits no delamination within the multilayer thin-film coating 14 extending from a damage track 42 (see, e.g., FIG. 7) visibly observable under 50X magnification with an optical microscope. The damage track 42 is created via a single cycle of back-and-forth abrasion with a % inch diameter (6.25 mm) H-18 abraser under a load of 1 kg at a cycle speed of 20 cycles per minute and a stroke length of 50 mm. The article 10 at and around the damage track 42 thus generated, before the observation under the optical microscope, is contacted with petroleum jelly (or some other lamination inducing substance such as sunscreen or water) and left to sit for a period of time (e.g., 15 minutes) at room temperature. The substance is then removed from the article 10 with a polyester wipe and then rinsed with isopropyl alcohol. Then the article 10 around the damage track 42 is observed with the optical microscope at 50X magnification. With the article 10 of the present disclosure, no delamination within the multilayer thin-film coating 14 is observed. For example, the high-index layer 24 of one bilayer 22 is not observed to have delaminated from the low-index layer 26 of another bilayer 22. Similarly, the low-index layer 26 of one bilayer 22 is not observed to have delaminated from the high-index layer 24 of the bilayer 22. The delamination testing protocol is further expounded upon below in the Examples.

[0078] In embodiments, the article 10 exhibits, at the multilayer thin-film coating 14, a first surface average reflectance of less than 0.50% throughout an entirety of a wavelength range of from 450 nm to 650 nm. The first surface average reflectance can be less than 0.40%, less than 0.35%, less than 0.30%, less than 0.25%, less than 0.20%, less than 0.15%, or even less than 0.10%. For example, the first surface average reflectance can be 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, or within any range bound by any two of those values (e.g., fromAttorney Docket: SP24-2510.15% to 0.50%, from 0.20% to 0.30%, and so on). The first surface average reflectance can be greater than 0.50%. The first surface average reflectance value is determined under D65 illumination at an incident illumination angle of 0 degrees. First surface average reflectance simulates the human eye response, weighting reflectance and wavelength spectrum according to human eye sensitivity. The first surface average reflectance (RP) is calculated pursuant to the following equation:650 nm{RP) = J 7?(A) x 7(A) x y(A)dA450 nm where 7? (A) is the spectral reflectance over the wavelength range, 7(A) is the illuminant spectrum, and y(A) is the luminosity function related to the eye's spectral response as established by the Commission Internationale de 1'Eclairage (CIE). The first surface average reflectance is a “singlesided” measurement where the reflectance from the second primary surface 18 of the substrate 12 is removed by coupling an index-matched absorber thereto.

[0079] In embodiments, the article 10 exhibits a reflected color space characterized by the CIELAB color space with an a* value within a range of from -4.0 to 0.0 and a b* within a range of from -4 to 0. The reflected color space described herein is at the multilayer thin-film coating 14 and with a D65 illuminant at all viewing angles throughout a range of from 0 to 10 degrees. For example, the a* value can be -4.0, -3.9, -3.8, -3.7, -3.6, -3.5, -3.4, -3.3, -3.2, -3.1, -3.0, -2.9, -2.8, -2.7, -2.6, -2.5, -2.4, -2.3, -2.2, -2.1, -2.0, -1.9, -1.8, -1.7, -1.6, -1.5, -1.4, -1.3, -1.2, -1.1, -1.0, -0.9, -0.8, -0.7, -0.6, -0.5, -0.4, -0.3, -0.2, -0.1, 0.0, or within any range bound by any two of those values (e.g., from -3.5 to -0.2, from -3.1 to -1.9, and so on). The a* value can be less than -4.0 or greater than 0.0. The b* value can be -4.0, -3.9, -3.8, -3.7, -3.6, -3.5, -3.4, -3.3, -3.2, -3.1, -3.0, -2.9, -2.8, -2.7, -2.6, -2.5, -2.4, -2.3, -2.2, -2.1, -2.0, -1.9, -1.8, -1.7, -1.6, -1.5, -1.4, -1.3, -1.2, -1.1, -1.0, -0.9, -0.8, -0.7, -0.6, -0.5, -0.4, -0.3, -0.2, -0.1, 0.0, or within any range bound by any two of those values (e.g., from -3.5 to -0.2, from -3.1 to -1.9, and so on). The b* value can be less than - 4.0 or greater than 0.0.

[0080] In embodiments, the article 10 exhibits a transmittance of electromagnetic radiation having a wavelength of 940 nm that is greater than 85.0%. The transmittance can be greater than 86.0%, 87.0%, 88.0%, or even higher than 89.0%. For example, the transmittance can be 85.0%, 85.5%, 86.0%, 86.5%, 87.0%, 87.5%, 88.0%, 88.5%, 89.0%, or within any range bound by any two of those values (e.g., from 86.0% to 88.5%, from 86.5% to 88.0%, and so on). The transmittance canAttorney Docket: SP24-251 be less than 85.0%. As used herein, the term “transmittance” is defined as the percentage of incident optical power within the specified wavelength transmitted through a material (e.g., the cover article 10, the substrate 12, the multilayer thin-film coating 14, or portions thereof). Transmittance is considered at an angle of incidence of 0 degrees.

[0081] In addition to optical properties, the article 10 exhibits physical properties. In embodiments, the article 10 exhibits a hardness that is greater than or equal to 5.0 GPa. The hardness that the article 10 exhibits can be greater than or equal to 6.0 GPa, or even greater than or equal to 7.0 GPa. For example, the hardness that the article 10 exhibits can be 5.0 GPa, 5.2 GPa, 5.4 GPa, 5.6 GPa, 5.8 GPa, 6.0 GPa, 6.2 GPa, 6.4 GPa, 6.6 GPa, 6.8 GPa, 7.0 GPa, 7.2 GPa, 7.4 GPa, 7.6 GPa, 7.8 GPa, 8.0 GPa, 8.2 GPa, 8.4 GPa, 8.6 GPa, 8.8 GPa, 9.0 GPa, 9.2 GPa, 9.4 GPa, 9.6 GPa, 9.8 GPa, 10.0 GPa, or within any range bound by any two of those values (e.g., from 5.0 GPa to 10.0 GPa, from 7.6 GPa to 8.6 GPa, from 5.0 GPa to 8.0 GPa, and so on).

[0082] The hardness is measured via a Berkovich nanoindentation test at about 100 nm indentation depth into the multilayer thin-film coating 14. The Berkovitch indenter test includes testing to measure the hardness by indenting the article 10 at the multilayer thin-film coating 14 with a diamond Berkovitch indenter to form an indentation having an indentation depth of about 100 nm from the surface and measuring the maximum hardness from this indentation along the entire indentation depth range or a segment of this indentation depth, generally using the methods set forth in Oliver, W. C.; Pharr, G. M. An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments, J. Mater. Res., Vol. 7, No. 6, 1992, 1564-1583; and Oliver, W. C.; Pharr, G. M. Measurement of Hardness and Elastic Modulus by Instrument Indentation: Advances in Understanding and Refinements to Method, J. Mater. Res., Vol. 19, No. 1, 2004, 3-20. As used herein, hardness refers to a maximum hardness, and not an average hardness.

[0083] Typically, in nanoindentation measurement methods (such as by using a Berkovich indenter) of a coating that is harder than the underlying substrate, the measured hardness may appear to increase initially due to development of the plastic zone at shallow indentation depths and then increases and reaches a maximum value or plateau at deeper indentation depths. Thereafter, hardness begins to decrease at even deeper indentation depths due to the effect of the underlying substrate. Where a substrate having an increased hardness compared to the coating isAttorney Docket: SP24-251 utilized, the same effect can be seen; however, the hardness increases at deeper indentation depths due to the effect of the underlying substrate.

[0084] The indentation depth range and the hardness values at certain indentation depth range(s) can be selected to identify a particular hardness response of the optical film structures and layers thereof, described herein, without the effect of the underlying substrate. When measuring hardness of the optical film structure (when disposed on a substrate) with a Berkovich indenter, the region of permanent deformation (plastic zone) of a material is associated with the hardness of the material. During indentation, an elastic stress field extends well beyond this region of permanent deformation. As indentation depth increases, the apparent hardness and modulus are influenced by stress field interactions with the underlying substrate. The substrate influence on hardness occurs at deeper indentation depths (i.e., typically at depths greater than about 10% of the optical film structure or layer thickness). Moreover, a further complication is that the hardness response requires a certain minimum load to develop full plasticity during the indentation process. Prior to that certain minimum load, the hardness shows a generally increasing trend.

[0085] At small indentation depths (which also may be characterized as small loads) (e.g., up to about 50 nm), the apparent hardness of a material appears to increase dramatically versus indentation depth. This small indentation depth regime does not represent a true metric of hardness but instead, reflects the development of the aforementioned plastic zone, which is related to the finite radius of curvature of the indenter. At intermediate indentation depths, the apparent hardness approaches maximum levels. At deeper indentation depths, the influence of the substrate becomes more pronounced as the indentation depths increase. Hardness may begin to drop dramatically once the indentation depth exceeds about 30% of the optical film structure thickness or the layer thickness.

[0086] In embodiments, the article 10 exhibits an elastic modulus that is greater than 50 GPa. The elastic modulus that the article 10 exhibits can be greater than 60 GPa, greater than 70 GPa, or even greater than 80 GPa. For example, the elastic modulus can be 50 GPa, 55 GPa, 60 GPa, 65 GPa, 70 GPa, 75 GPa, 80 GPa, 85 GPa, 90 GPa, 95 GPa, 100 GPa, 105 GPa, 110 GPa, or within any range bound by any two of those values (e.g., from 50 GPa to 110 GPa, from 60 GPa to 70 GPa, and so on). The elastic modulus is measured via a Berkovich nanoindentation test at about 100 nm indentation depth into the multilayer thin- film coating 14.Attorney Docket: SP24-251

[0087] In embodiments, the article exhibits a failure stress that is greater than 850 MPa. For example, the failure stress that the article exhibits can be greater than 950 MPa, greater than 1050 MPa, greater than 1150 MPa, or even greater than 1800 MPa. The failure stress that the article exhibits can be 850 MPa, 950 MPa, 1050 MPa, 1150 MPa, 1250 MPa, 1350 MPa, 1450 MPa, 1550 MPa, 1650 MPa, 1750 MPa, 1850 MPa, 1950 MPa, 2000 MPa, or within any range bound by any two of those values (e.g., from 850 MPa to 2000 MPa, from 1800 MPa to 2000 MPa, and so on). The failure stress that the article exhibits can be less than 850 MPa or greater than 2000 MPa. In embodiments, the article exhibits a strain- to-failure that is within a range of from 0.8% to 2.0%. For example, the strain-to-failure that the article exhibits can be 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or within any range bound by any two of those values (e.g., from 1.8% to 2.0%, from 1.1% to 1.6%, and so on). The strain-to-failure that the article exhibits can be less than 0.8% or greater than 2.0%. Both “failure stress” and “strain-to- failure” are determined in accordance with ASTM C1499-19, titled Standard Test Method for Monotonic Equibiaxial Flexural Strength of Advanced Ceramics at Ambient Temperature. A substrate thickness 20 of 0.8 mm is utilized. In general terms, testing in accordance with ASTM Cl 499- 19 places the cover article 10 between a load ring and a support ring. The diameter of the support ring is greater than the diameter of the load ring. A load is then applied to the load ring until a breaking load (the load that breaks the cover article 10) is determined. From the breaking load, the failure stress can be determined. After the test is preformed numerous times (each time with a different sample), the failure probability as a function of failure stress can be determined. This is sometimes referred to as a Weibull distribution from which the failure stress that would cause a 63.5% failure probability can be determined. The 63.5% failure probability is sometimes referred to as the characteristic strength. The “failure stress” values provided herein are that which provides the 63.5% failure probability. The “strain-to-failure” in turn is calculated as a function of elastic modulus and Poisson’s ratio.

[0088] Referring now to FIG. 4, a method 100 of manufacturing the cover article 10 is now described herein. The method 100 includes a bilayer 22 formation sequence that, in each instance thereof, includes a high-index sputtering step 102 and a low-index sputtering step 104. The high- index sputtering step 102 includes sputtering the high-index layer 24 of the high-index material over the first primary surface 16 of the substrate 12. The low-index sputtering step 104 includes sputtering the low-index layer 26 of the low-index material over the high-index layer 24.Atorney Docket: SP24-251

[0089] Sputering is a known term in the art that refers to a physical vapor deposition process where target material (e.g., the high-index material or the low- index material, as the case may be) is bombarded with energetic ions, such as from a plasma of an inert gas. The bombardment of the target material causes molecules thereof to transfer from the target material to the primary surface of the substrate 12. Sputering occurs within a chamber within which the air pressure can be lowered. The inert gas is introduced and has a gas pressure. The chamber utilized for the high- index sputering step 102 can be the same as the chamber used for the low-index sputering step 104 but need not be. The inert gas utilized for the high-index sputtering step 102 can be the same as the inert gas utilized for the low- index sputtering step 104 but need not be. The inert gas can be argon, although other gases are possible (e.g., other noble gases such as krypton).

[0090] The gas pressure of the inert gas during the low-index sputtering step 104 is greater than or equal to 2.0 mTorr (-0.27 Pa). For example, the gas pressure of the inert gas during the low- index sputering step 104 can be 2.0 mTorr, 2.5 mTorr, 3.0 mTorr, 3.5 mTorr, 4.0 mTorr, 4.5 mTorr, 5.0 mTorr, 5.5 mTorr, 6.0 mTorr, 6.5 mTorr, 7.0 mTorr, or within any range bound by any two of those values (e.g., from 2.0 mTorr (-0.27 Pa) to 7.0 mTorr (-0.93 Pa), from 4.5 mTorr (-0.60 Pa) to 5.5 mTorr (-0.73 Pa), and so on).

[0091] Such a gas pressure is contrary to industry practice and surprisingly leads to the resistance against delamination within the multilayer thin-film coating 14 that the article 10 exhibits. The industry practice is for the gas pressure to be lower, which indicates that the chamber has been evacuated fully (or as fully as possible). Further, it has been universally understood that the gas pressure being lower generates a denser and harder layer. However, in connection with this disclosure, it has been discovered that the gas pressure being higher than traditionally accepted (e.g., greater than or equal to 2.0 mTorr) leads to the multilayer thin-film coating 14 exhibiting dramatically better resistance to delamination without a significant decrease in hardness. Further, those skilled in the art would have thought that the gas pressure being so high (e.g., greater than or equal to 2.0 mTorr) would have altered the optics of the low-index layer 26 due to increased water absorption.

[0092] In embodiments, the gas pressure of the inert gas during the high-index sputtering step 102 is within a range of from 0.5 mTorr (-0.07 Pa) to 7.0 mTorr (-0.93 Pa). For example, the gas pressure of the inert gas during the high- index sputtering step 102 can be 0.5 mTorr, 1.0 mTorr, 1.5 mTorr, 2.0 mTorr, 2.5 mTorr, 3.0 mTorr, 3.5 mTorr, 4.0 mTorr, 4.5 mTorr, 5.0 mTorr, 5.5 mTorr,Attorney Docket: SP24-2516.0 mTorr, 6.5 mTorr, 7.0 mTorr, or within any range bound by any two of those values (e.g., from 0.5 mTorr (-0.97 Pa) to 1.5 mTorr (-0.20 Pa), from 4.5 mTorr (-0.60 Pa) to 5.5 mTorr (-0.73 Pa), and so on). The gas pressure of the inert gas during the low-index sputtering step 104 can be greater than or equal to the gas pressure of the inert gas during the high-index sputtering step 102. It was another surprising discovery that the gas pressure of the inert gas during the high-index sputtering step 102 can be a traditionally used value (e.g., 0.5 mTorr) and the resulting article 10 still exhibits resistance to delamination within the multilayer thin- film coating 14. Only the gas pressure of the inert gas during the low-index sputtering step 104 seems to make a difference in the resistance to delamination.

[0093] In embodiments, the method 100 further includes a performance of the low- index sputtering step 104 before the bilayer 22 formation sequence is performed. The performance of the low-index sputtering step 104 produces the initial low-index layer 32 of the low- index material on the first primary surface 16 of the substrate 12. The gas pressure for the performance of the low-index sputtering step 104 can likewise be greater than or equal to 2.0 mTorr (-0.27 Pa).

[0094] In embodiments, the method 100 further includes performing the bilayer 22 formation sequence N number of times in succession. That results in the multilayer thin- film coating 14 of the article 10 having N number of bilayers 22.

[0095] In embodiments, after the bilayer 22 formation sequence is performed 1 time, the low- index layer 26 furthest away from the substrate 12 exhibits a surface roughness (Ra) that is greater than 0.8 nm. Similarly, after the bilayer 22 formation sequence is performed 2 times, the low- index layer 26 furthest away from the substrate 12 exhibits a surface roughness (Ra) that is greater than 0.9 nm. These surface roughness values also are contrary to industry accepted values. Lower surface roughness values are generally desired in order to improve abrasion test results. The higher the surface roughness, the greater the height of the peaks from the valleys in the surface topography. The greater the height of the peaks, the more material is broken loose from the peaks to deposit in the valleys during the abrasion test. The greater the amount of material that is broken loose and deposited, the more visible the abrasion becomes. The increased visibility decreases not only aesthetics but can suboptimally alter other optical properties (e.g., haze). Without being bound by theory, it is thought that the higher surface roughness values that result from the method 100 of the present disclosure decrease lamination within the multilayer thin- film coating 14 by increasing mechanical interlocking of the high-index layer 24 to the low-index layer 26.Attorney Docket: SP24-251

[0096] In embodiments, after the bilayer 22 formation sequence is performed 2 times, both the high- index layer 24 and the low-index layer 26 furthest away from the substrate 12 exhibit a compressive stress that is greater than 275 MPa. In connection with this disclosure, it has been discovered that higher than normal gas pressure used during the low-index sputtering step 104 results in higher than normal compressive stress at both the low-index layer 26 and the high-index layer 24 of each bilayer 22 of the multilayer thin-film coating 14. The higher than normal compressive stress is thought to resist delamination within the multilayer thin-film coating 14.

[0097] The article 10 and the method 100 of the present disclosure address the problem described in the Background, among others, in a variety of ways. For example, the method 100 includes the low-index sputtering step 104 where the sputtering of the low-index material (e.g., S1O2) occurs while the gas pressure is greater than or equal to 2.0 mTorr. Such a gas pressure is much higher than the industry accepted gas pressure of about 1.0 mTorr or less. Without being bound by theory, the relatively high gas pressure utilized during the deposition of the low-index layer 26 of the at least one bilayer 22 increases the surface roughness of the low-index layer 26. The increased surface roughness increases the degree of mechanical interlocking between the one or more high- index layers 24 adjacent to the low-index layer 26. The increased mechanical interlocking increases resistance to delamination. Further, the relatively high gas pressure increases the compressive stress of the low-index layer 26. The increase in compressive stress appears to play a role in resisting delamination, possibly by resisting ingress of water, petroleum jelly, and other substances from the external environment 38 that would otherwise promote delamination between layers of the multilayer thin-film coating 14.

[0098] EXAMPLES

[0099] Comparative Example 1 - For Comparative Example 1, samples of an article that include a multilayer thin-film coating upon a substrate were obtained. The multilayer thin-film coating imparts an antireflective property to the article. The multilayer thin-film coating includes an initial low-index layer of SiCh (a low-index material) on the primary surface of the substrate and then three sequential bilayers of ISfeOs (a high- index material) and SiCh over the initial low-index layer. The initial low-index layer, and the low-index layer and the high-index layer of each of the bilayers, are known to have been deposited via sputtering at a gas pressure of about 1 mTorr.Attorney Docket: SP24-251

[0100] The samples were then subjected to delamination testing. First, damage tracks were introduced into the article at the multilayer thin- film coating. In particular, a H-18 Calibrade Wearaser from Taber Industries (North Tonawanda, New York, USA) was obtained. The Wearaser has a generally cylindrical shape with a diameter of % inch. The Wearaser was secured within a Wearaser collet of a Linear Abraser 5750 surface testing machine from Taber Industries. Weight discs collectively weighing 1 kg were disposed on the spline shaft above and in communication with the collet with the H-l 8 Wearaser. The stroke length was adjusted mechanically to be 1 inch (~25 mm) for each back-and-forth movement of a stroke cycle (e.g., in one direction 1 inch, then back in the opposite direction 1 inch). At the human-machine interface of the Linear Abraser 5750, the surface testing machine was commanded to move the Wearaser at a speed of 20 cycles per minute and perform one back-and-forth damage introducing cycle. The sample to be tested was then secured with clamps onto a horizontal platform below the Wearaser collet. See FIG. 5. The H-18 Wearaser was then rested upon the article contacting the multilayer thin-film coating. The Linear Abraser 5750 was then commanded to perform the back-and-forth damage introducing cycle. The cycle was performed and the cycle introduced damage tracks into the article at the multilayer thin-film coating. See FIG. 6. Debris was removed from the article with a soft camel brush and compressed air. The damage tracks mimic commonly occurring scratches that are introduced during normal use of such articles. The sample, with the damage tracks, was then removed from the horizontal platform.

[0101] The sample, at and near the damage tracks into the multilayer thin-film coating, was then viewed with an optical microscope at 50X (eyepiece 10X, objective 5X) and then 200X (eyepiece 10X, objective 20X) magnifications. Images were captured. The images are reproduced at the left column of FIG. 7.

[0102] Petroleum jelly (Vaseline® brand, Unilever United States) was then applied onto the article at, within, and around the damage tracks into the multilayer thin-film coating. In particular, while wearing a glove, a dab (e.g., approximately half a teaspoon) was withdrawn from the container of the petroleum jelly with a finger. The dab of petroleum jelly was then applied onto the article at, within, and around the damage tracks with the finger with about 25 to 30 circular motions. The article with the petroleum jelly thereupon was then left to sit at room temperature for about 15 minutes. A polyester wiper (AlphaWipe® TX1009 from Texwipe, Kernersville, North Carolina, USA) was then utilized to remove most of the petroleum jelly from the article, using circularAttorney Docket: SP24-251 motions on the article and applying finger pressure. A second polyester wiper was used to remove more of the petroleum jelly still remaining on the article. The article was then rinsed with isopropyl alcohol. Petroleum jelly was selected because users of the article commonly have petroleum jelly upon their finger. The petroleum jelly contacting the article reflects real- world use of the article.

[0103] The sample at and around the damage tracks was then viewed again with the optical microscope under 50X and 200X magnification. Images were again captured. The images are reproduced at the right column of FIG. 7. Review of the images reveals delamination of one or more layers of the multilayer thin-film coating extending from the damage tracks parallel to the primary surface of the substrate.

[0104] New samples of the article were obtained. Damage tracks were made in the same manner as described above. Instead of petroleum jelly, water was utilized to contact the article at, in, and around the damage tracks into the multilayer thin-film coating. The water was allowed to contact the article for 15 minutes. Thereafter, the water was removed. Images were captured of the article before and after contact with the water. The images are reproduced at FIG. 8. Review of the images reveals that the water contacting the damage tracks caused delamination of one or more layers of the multilayer thin-film coating.

[0105] A scanning electron microscope (SEM) and a transmission electron microscope (TEM) were utilized to capture images of the article around the damage tracks. The images are reproduced at FIG. 9. Analysis of the images shows that the delamination was occurring within the multilayer thin-film coating and not between the primary surface of the substrate and the multilayer thin-film coating. Closer examination of the TEM image reveals that the delamination occurred within the first bilayer (the bilayer closest to the primary surface of the substrate). The layer of high-index material (Nb20s) of the first bilayer remained upon the initial layer of low-index material (S 1O2) but the layer of low-index material (SiCh) of the first bilayer had separated from the layer of high- index material of the first bilayer. See FIG. 10.

[0106] Comparative Examples 2-15 - For each of Comparative Examples 2-15, a substrate was subj ected to a low-index sputtering step to generate an initial low- index layer of low- index material ( S i O2) on the first primary surface of the substrate. Then, one or more (as the case may be) bilayer formation sequences were performed to deposit, via a high-index sputtering step, a high-index layer of a high-index material (Nb20s) and, via a low-index sputtering step, a low-index layer of a low-index material (SiCh). The index of refraction and thickness of each of the layers for each ofAttorney Docket: SP24-251 the Comparative Examples 2-15 are as set forth in Table 1 below. As will become apparent, Comparative Examples 6-9 did not include each of the layers set forth below but otherwise were made according to the table.

[0107] In Table 1 above, “ILIL” means the initial low-index layer. “HI-1,” “HI-2,” and “HI-3” mean the high-index layer of the first bilayer, the high-index layer of the second bilayer, and the high-index layer of the third bilayer, respectively. Similarly, “LI-1,” “LI-2,” and “LI-3” mean the low-index layer of the first bilayer, the low-index layer of the second bilayer, and the low-index layer of the third bilayer, respectively.

[0108] The gas pressure utilized for each of the sputtering sessions is as indicated in Table 2 below.

[0109] Each of the resulting articles of Comparative Examples 2-15 was then subjected to the same damage track creation, contact with petroleum jelly, and delamination observation steps asAttorney Docket: SP24-251Comparative Example 1. Delamination was observed at all the articles of Comparative Examples 2-15. Hardness and modulus values were determined for each of the articles using a Berko vitch diamond indenter. Where 100 nm of multilayer thin- film coating was not available, the indenter was set to press 1 / 3 of the way into the thickness of the multilayer thin- film coating. Further, compressive stress (denoted as a negative value) under “Stress” and surface roughness (Ra) were determined. The values for each article are reproduced in Table 3 below.In Table 3 above, “Delam” means whether delamination within the multilayer thin-film coating was observed with “Y” meaning yes. Images of the damage tracks before and after being contacted with the petroleum jelly are reproduced at FIG. 11 for Comparative Examples 10-12.

[0110] Examples 1-10 - The articles of Examples 1 and 10 were prepared according to the present disclosure. The index of refraction and the thickness of the layers are as set forth in Table 1 above. The gas pressures utilized are set forth in Table 4 below.Attorney Docket: SP24-251

[0111] Each of the resulting articles of Examples 1-10 was then subjected to the same damage track creation, contact with petroleum jelly, and delamination observation steps as Comparative Example 1. Delamination was not observed for any of the articles of Examples 1-10, denoted by the “N” for “no” in Table 4 below. Hardness, modulus, compressive stress, and surface roughness values were determined for each of the articles. The values for each article are reproduced in Table 5 below. Images of the damage tracks before and after being contacted with the petroleum jelly are reproduced at FIG. 12 for Examples 8 and 9.

[0112] Comparing Comparative Examples 1-15 with Examples 1-10, it is clear that the gas pressure utilized during the low-index sputtering step of the bilayer formation sequence affects whether delamination occurs within the multilayer thin-film coating after being damaged and contacted with petroleum jelly. In particular, the while a gas pressure of 1.0 mTorr for any of the low-index sputtering steps (aside from the initial low-index layer) lead to eventual delamination within the multilayer thin-film coating (as seen in the Comparative Examples 1 -15), a gas pressure of 5.0 mTorr of the low-index sputtering steps (aside from the initial low-index layer) prevented delamination from occurring (as seen in Examples 1-10).Attorney Docket: SP24-251

[0113] With a series of related samples, the stress and surface roughness (Ra) were measured after each layer was deposited via sputtering, with one set using a gas pressure of 1 mTorr for each layer deposition and the other set using a gas pressure of 5 mTorr. The results are summarized in the diagram reproduced at FIGS. 13 and 14. The compressive stress and surface roughness are generally higher at each layer level when a higher gas pressure is used during sputtering. The lower compressive stress and surface roughness of the low-index layer of the first bilayer when a gas pressure of 1.0 mTorr is used appears to play a role in the delamination that occurs there.

[0114] Examples 11-13 and Comparative Examples 16 and 17 - For each of Examples 11-13 and Comparative Examples 16 and 17 an article with an initial low-index layer of SiCh and then three bilayers of a high-index layer of bfeOs and a low-index layer of SiCh were deposited via sputtering. The index of refraction and thickness of each of the layers is as set forth above in Table 1. The gas pressure utilized for each of the articles is denoted in Table 6 below. Various measurements of optical and physical properties were taken for each of the articles. Further, the delamination testing as described above was performed for each of the articles as well. The results are set forth in Tables 6-8 below.In Table 6 above, “Reflect” refers to first surface average reflectance throughout the wavelength range of from 450 nm to 650 nm. “Trans” refers to an average transmittance after measuring at nine locations on each article. Utilizing higher gas pressures than the normal 1.0 mTorr does not negatively affect reflectance or transmittance.Attorney Docket: SP24-251In Table 7 above, “Reflected Color” is the reflected color space characterized by the CIELAB color space at a viewing angle of 8 degrees. Hardness and Modulus are as described above. Utilizing higher gas pressures than the normal 1.0 mTorr does not negatively affect perceived reflected color, hardness, or modulus.In Table 8 above, “Stress” and “Ra” mean compressive stress (denoted by the negative number) and surface roughness (Ra). The higher gas pressure of Examples 11-13 lead to higher surface roughness.

[0115] Example 14 and Comparative Example 18 - For Example 14 and Comparative Example 18, identical articles were made with an initial low-index layer of SiCh, a single bilayer of a high- index layer of bfeOs and a low-index layer of SiCh. The thicknesses and indices of refraction for these layers are as set forth in Table 1 above. The sputtering used to form the layers for Example 14 used a gas pressure of 5.0 mTorr, while the sputtering used to form the layers for Comparative Example 18 used a gas pressure of 1.0 mTorr. After being subjected to the delamination testing described above, the article of Comparative Example 18 exhibited delamination within the multilayer thin-film coating while the article of Example 14 did not.

[0116] X-ray photoelectron spectrometry (XPS) was performed on both articles in order to correlate the thickness of the top most low-index layer of SiCh with the sputtering time required to form the layer. The results reveal that the use of lower gas pressure for Comparative Example 18 requires a longer sputtering time. The longer sputtering time to form the top most low-index layer of equal thickness to that of the article of Example 14 requiring a shorter sputtering time means that lower gas pressure results in a denser layer. In short, the top most low-index layer of SiC>2 for Comparative Example 18 was denser than the top most low-index layer of SiCh for Example 14. The lower density resulting from the use of higher than normal gas pressure for the sputtering might be a factor in the improved resistance to delamination after damage trackAttorney Docket: SP24-251 formation that the articles of the present disclosure exhibit. Graphs of the XPS results are reproduced at FIG. 15.

[0117] Example 15 and Comparative Example 19 - For Example 15, samples of the article of the present disclosure with the low- index layers having been formed via sputtering at 5.0 mTorr gas pressure. For Comparative Example 19, samples of otherwise identical articles were formed with the low-index layers having been formed via sputtering at 1.0 mTorr gas pressure. For the samples of both Example 15 and Comparative Example 19, the substrate thickness was 0.8 mm and the indicies of refraction and layer thicknesses were as set forth in Table 1 above.

[0118] The samples were then subjected to testing under ASTM Cl 499- 19 to determine the Weibull distribution of failure probability as a function of failure stress and the strain-to-failure. A graph showing the Weibull distribution is reproduced at FIG. 16. As the graph reveals, the samples of Example 15 exhibited failure stresses that were much higher than failure stresses that the samples of Comparative Example 19 exhibited. The utilization of the higher gas pressure during sputtering to form the low-index layers appears to increase the failure stress of the resulting articles. More particularly, the failure stress providing a 63.5% failure probability for Example 15 was about 1950 MPa, while the failure stress providing a 63.5% failure probability for Comparative Example 19 was about 1750 MPa. As for strain-to-failure, the samples of Example 15 exhibited a strain-to-failure within a range of from 1.8% to 2.0%. In contrast, the samples of Comparative Example 19 exhibited a strain-to-failure within a range of from 1.5 to 1.7%.

[0119] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claims.

Claims

1. Attorney Docket: SP24-251CLAIM(S)What is claimed is:

1. An article comprising: a substrate comprising a primary surface; and a multilayer thin-film coating disposed over the primary surface, the multilayer thin-film coating comprising at least one bilayer, each of the at least one bilayer comprising a high-index layer of a high-index material and a low-index layer of a low-index material on the high-index layer, the low-index material exhibiting an index of refraction that is lower than an index of refraction that the high-index material exhibits, wherein, the article exhibits no delamination within the multilayer thin-film coating extending from a damage track visibly observable under 5 OX magnification with an optical microscope after (i) creation of the damage track in the multi-layer thin-film via a single cycle of back-and-forth abrasion with a % inch diameter (6.25 mm) H-l 8 abraser under a load of 1 kg at a cycle speed of 20 cycles per minute and a stroke length of 50 mm, (ii) contacting the article at and around the damage track with petroleum jelly for 15 minutes at room temperature, and (iii) removing the petroleum jelly from the article with a polyester wipe followed by rinsing the multilayer thin film with isopropyl alcohol.

2. The article of claim 1 , wherein the substrate comprises a glass, a glass-ceramic, or a ceramic material.

3. The article of any one of claims 1-2, wherein the multilayer thin-film coating comprises N number of the bilayers of the high- index layer and the low-index layer, andN is an integer within a range of from 1 to 6.

4. The article of any one of claims 1-3, wherein the index of refraction of the low-index material is within a range of from 1.40 to 1.70, and the index of refraction of the high-index material is within a range of from 1.71 to 2.60.Attorney Docket: SP24-2515. The article of any one of claims 1-4, wherein the low-index material comprises one or more of SiCh, MgF2, YF3, and YbFs, and the high-index material comprises one or more of ZrCh, HfCh, Ta20s, bfeOs, TiCh, Y2O3, S13N4, SrTiO3, WO3, SiuAlvOxNy, A1NX, S13N4, A10xNy, SiOxNy, SiNx, SiNx:Hy, AI2O3, TiNbOx, and MoOs.

6. The article of any one of claims 1-5, wherein the low-index material comprises SiCh, and the high-index material comprises bfeOs.

7. The article of any one of claims 1-6, wherein for each of the at least one bilayer, the low-index layer has a low-index thickness orthogonal to the primary surface of the substrate and the high-index layer has a high-index thickness orthogonal to the primary surface of the substrate, the low- index thickness is within a range of from 10.0 nm to 120 nm, and the high-index thickness is within a range of from 10.0 nm to 120 nm.

8. The article of any one of claims 1-7, wherein the multilayer thin-film coating further comprises an initial low-index layer of a low-index material on the primary surface, the initial low-index layer sandwiched between the primary surface of the substrate and the at least one bilayer.

9. The article of any one of claims 1-8, wherein the multilayer thin-film coating has a total thickness measured orthogonal to the primary surface of the substrate that is less than 450 nm.

10. The article of any one of claims 1-9, wherein the article exhibits, at the multilayer thin-film coating, a first surface average reflectance of less than 0.50% throughout an entirety of a wavelength range of from 450 nm to 650 nm.Attomey Docket: SP24-25111. The article of any one of claims 1-10, wherein the article exhibits a reflected color at all viewing angles throughout a range of from 0 to 10 degrees characterized by the CIELAB color space with an a* value within a range of from -4.0 to 0.0 and a b* within a range of from -4.0 to 0.0.

12. The article of any one of claims 1-11, wherein the article exhibits a transmittance of electromagnetic radiation having a wavelength of 940 nm that is greater than 85.0%.

13. The article of any one of claims 1-12, wherein the article exhibits a hardness, measured via a Berkovich nanoindentation test at about 100 nm indentation depth into the multilayer thin-film coating, that is greater than or equal to 5.0 GPa.

14. The article of any one of claims 1-13, wherein the article exhibits an elastic modulus, measured via a Berkovich nanoindentation test at about 100 nm indentation depth into the multilayer thin-film coating, that is greater than 50 GPa.

15. The article of any one of claims 1-14, wherein the article exhibits a failure stress that is greater than 850 MPa, and the article exhibits a strain-to-failure that is within a range of from 0.8% to 2.0%.

16. A method of manufacturing a cover article, the method comprising: a bilayer formation sequence comprising: a high-index sputtering step comprising sputtering a high-index layer of a high- index material over a primary surface of a substrate, the sputtering of the high-index sputtering step occurring within a chamber and in the presence of an inert gas having a gas pressure; and a low-index sputtering step comprising sputtering a low-index layer of a low-index material over the high-index layer, the sputtering of the low-index sputtering step occurring within a chamber and in the presence of an inert gas having a gas pressure, and the low-Attorney Docket: SP24-251 index material exhibiting an index of refraction that is lower than an index of refraction that the high-index material exhibits, wherein, the gas pressure of the inert gas during the low-index sputtering step is greater than or equal to 2.0 mTorr (-0.27 Pa).

17. The method of claim 16, wherein the substrate comprises a glass, a glass-ceramic, or a ceramic material.

18. The method of any one of claims 16-17, wherein the low-index material comprises one or more of SiCh, MgF2, YF3, and YbFs, and the high-index material comprises one or more of ZrCh, HfCh, Ta20s, bfeOs, TiCh, Y2O3, S13N4, SrTiO3, WO3, SiuAlvOxNy, A1NX, S13N4, A10xNy, SiOxNy, SiNx, SiNx:Hy, AI2O3, TiNbOx, and MoOs.

19. The method of any one of claims 16-18, wherein the low-index material comprises SiCh, and the high-index material comprises bfeOs.

20. The method of any one of claims 16-19, wherein the inert gas is argon.

21. The method of any one of claims 16-20, wherein the gas pressure of the inert gas during the low-index sputtering step is within a range of from 2.0 mTorr (-0.27 Pa) to 7.0 mTorr (-0.93 Pa), and the gas pressure of the inert gas during the high-index sputtering step is within a range of from 0.5 mTorr (-0.07 Pa) to 7.0 mTorr (-0.93 Pa).

22. The method of claim 21, wherein the gas pressure of the inert gas during the high-index sputtering step is within a range of from 0.5 mTorr (-0.97 Pa) to 1.5 mTorr (-0.20 Pa) or within a range of from 4.5 mTorr (-0.60 Pa) to 5.5 mTorr (-0.73 Pa).Attorney Docket: SP24-25123. The method of any one of claims 16-22, wherein the gas pressure of the inert gas during the low-index sputtering step is greater than or equal to the gas pressure of the inert gas during the high-index sputtering step.

24. The method of any one of claims 16-23, further comprising: performing the low-index sputtering step before the bilayer formation sequence.

25. The method of any one of claims 16-24, further comprising: performing the bilayer formation sequence N number of times in succession, and N is an integer within a range of from 1 to 6.

26. The method of any one of claims 16-25, wherein after the bilayer formation sequence is performed 1 time, the low-index layer furthest away from the substrate exhibits a surface roughness (Ra) greater than 0.8 nm.

27. The method of claim 26, wherein after the bi-layer formation sequence is performed 2 times, the low-index layer furthest away from the substrate exhibits a surface roughness (Ra) greater than 0.9 nm.

28. The method of any one of claims 16-27, wherein after the bilayer formation sequence is performed 2 times, (i) the high-index layer furthest away from the substrate exhibits a compressive stress greater than 275 MPa and (ii) the low-index layer furthest away from the substrate exhibits a compressive stress greater than 275 MPa.

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