High-color and high-hardness optical film structure and cover plate product with constant color tone

Abstract

A cover panel article is described, the cover panel article comprising: a substrate comprising an outer major surface and an inner major surface, the outer major surface and the inner major surface opposite each other; and an optical film structure including an outermost layer surface disposed on the outer main surface or the inner main surface of the substrate. The optical film structure includes a plurality of alternating high refractive index layers and low refractive index layers. The refractive index of each high refractive index layer is greater than the refractive index of each low refractive index layer. In addition, the cover panel article exhibits a substantially constant reflective hue under a D65 illuminant, as follows: (a) the hue angle (h *) of the color exhibited varies by less than 60 degrees over the viewing angle range of 0 to 60 degrees; or (b) exhibiting a gray hue or a silver hue, each having a chroma (c *) of less than 10.

Description

[0001] CLAIM OF PRIORITY

[0002] This application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Application No. 63 / 455,670, filed March 30, 2023. The entire contents of this application are hereby incorporated by reference herein for all purposes. TECHNICAL FIELD

[0003] The present disclosure relates to durable and scratch-resistant optical film structures and cover sheet articles, and more specifically, to optical film structures and cover sheet articles that exhibit high hardness, a particular color or hue, high color saturation, and little color or hue variation at various viewing angles. BACKGROUND

[0004] Cover sheet articles are commonly used to protect critical devices within electronic products, to provide a user interface for input and / or display, and / or for many other functions. Such products include mobile devices such as smartphones, mp3 players, smartwatches, and tablets. Cover sheet articles also include architectural articles, transportation articles (e.g., articles for automotive applications, trains, airplanes, sea vessels, etc.), appliance articles, or any article that requires some degree of transparency, scratch resistance, abrasion resistance, or a combination thereof. These applications often require both scratch resistance (e.g., embodied by high hardness) and excellent optical performance characteristics such as maximum light transmission and minimum reflectance.

[0005] For example, these cover sheet articles can be used as a cover sheet substrate for protective covers and / or housings for display devices (e.g., a back cover for a smartphone screen). Additionally, some applications of these cover sheet articles also benefit from or otherwise require the presentation of a reflective color and / or a limited transmission color (e.g., a smartphone screen that presents a red reflective hue). The need for these cover sheet articles to exhibit certain colors or hues can be for functional (e.g., to enhance digital display characters) and / or customer-desired aesthetic (e.g., a smartphone with a blue color as a fashion accent) considerations. There is also a need for such cover sheet articles to exhibit the desired color or hue with high saturation and limited color variation at various viewing angles. SUMMARY

[0006] In general, the present disclosure relates to optical film structures and cover sheet articles that address the aforementioned needs and other needs in the art. The disclosed cover sheet articles employ an optical film structure disposed on a substrate (e.g., a glass substrate, a plastic substrate, etc.) that exhibits a particular color or hue, high color saturation, and little color or hue variation at various viewing angles.

[0007] Gorilla Optical film structures for use in electronic devices, such as cover plate articles, product, glass-ceramic substrates, and the like. These optical film structures and cover plate articles have high hardness and advantageous optical properties suitable for a variety of applications including smart phone and mobile phone displays and covers. The optical film structures of the cover plate articles are a designed multilayer film structure and the cover plate articles of the present disclosure reflect a new system level design configured to exhibit a particular color or hue with high saturation and limited color variation over a wide range of viewing angles.

[0008] According to one aspect of the present disclosure, a cover plate article is provided that includes a substrate including an outer major surface and an inner major surface, the outer major surface and the inner major surface being opposite each other, and an optical film structure including an outermost surface disposed on the outer major surface or the inner major surface of the substrate. The optical film structure includes a plurality of alternating high refractive index layers and low refractive index layers. The refractive index of each high refractive index layer is greater than the refractive index of each low refractive index layer. In addition, the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as a change in hue angle (h*) of the exhibited color over a viewing angle range of 0 to 60 degrees of less than 50 degrees. This aspect can serve as a durable and / or scratch resistant cover plate article for electronic devices, and more specifically, a cover plate article that exhibits hardness, a particular color or hue, high color saturation, and less variation in color or hue at various viewing angles.

[0009] According to one aspect of the present disclosure, a cover plate article is provided that includes a substrate including an outer major surface and an inner major surface, the outer major surface and the inner major surface being opposite each other, and an optical film structure including an outermost surface disposed on the outer major surface or the inner major surface of the substrate. The optical film structure includes a plurality of alternating high refractive index layers and low refractive index layers. The refractive index of each high refractive index layer is greater than the refractive index of each low refractive index layer. In addition, the cover plate article exhibits a substantially neutral reflected color under a D65 illuminant, manifested as exhibiting a gray or silver hue each having a chroma (c*) of less than 10. This aspect can serve as a durable and / or scratch resistant cover plate article for electronic devices, and more specifically, a cover plate article that exhibits hardness, a neutral color, high neutral color saturation, and less variation in neutral color at various viewing angles.

[0010] According to another aspect of the disclosure, there is provided a cover plate article comprising: a substrate comprising an outer major surface and an inner major surface, the outer major surface and the inner major surface opposing each other; and an optical film structure comprising an outermost surface disposed on the outer major surface or the inner major surface of the substrate. The optical film structure comprises a plurality of alternating high refractive index layers and low refractive index layers. Each high refractive index layer has a refractive index greater than each low refractive index layer. Further, the optical film structure also has a physical thickness in the range of 1000 nm to 4000 nm. One high refractive index layer is a scratch resistant layer having a physical thickness of 500 nm to 3000 nm. One low refractive index layer is a capping layer disposed above the scratch resistant layer. A portion of the plurality of alternating high refractive index layers and low refractive index layers are between the scratch resistant layer and the substrate. Further, the optical film structure exhibits a hardness of at least 12 GPa when measured from the outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm using a Berkovich Indenter Hardness Test. Moreover, the cover plate article exhibits a substantially constant reflective hue under a D65 illuminant, manifested as a change in hue angle (h*) of the exhibited color over a viewing angle range of 0 to 60 degrees of less than 50 degrees. This aspect can serve as a durable and / or scratch resistant cover plate article for electronic devices, and more specifically, a cover plate article that exhibits high hardness, a particular color or hue, high color saturation, and less change in color or hue at various viewing angles.

[0011] According to another aspect of the disclosure, a cover plate article is provided that includes a substrate including an outer major surface and an inner major surface that are opposite each other, and an optical film structure including an outermost surface disposed on the outer major surface or the inner major surface of the substrate. The optical film structure includes a plurality of alternating high refractive index layers and low refractive index layers. Each high refractive index layer has a refractive index that is greater than a refractive index of each low refractive index layer. Additionally, the optical film structure further has a physical thickness in a range from 1000 nm to 4000 nm. One high refractive index layer is a scratch resistant layer having a physical thickness of 500 nm to 3000 nm. One low refractive index layer is a cover layer disposed over the scratch resistant layer. A portion of the plurality of alternating high refractive index layers and low refractive index layers are between the scratch resistant layer and the substrate. Additionally, the optical film structure exhibits a hardness of at least 12 GPa when measured from the outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm using a Vickers hardness test. Further, the cover plate article exhibits a substantially neutral reflected color under a D65 illuminant, manifested as exhibiting a gray or silver color hue each having a chroma (c*) of less than 10. This aspect can serve as a durable and / or scratch resistant cover plate article for electronic devices, and more specifically, a cover plate article that exhibits high hardness, neutral color, high neutral color saturation, and less variation in neutral color at various viewing angles.

[0012] According to another aspect of the disclosure, a cover plate article is provided that includes a substrate including an outer major surface and an inner major surface that are opposite each other, and an optical film structure including an outermost surface disposed on the outer major surface or the inner major surface of the substrate. The optical film structure includes a plurality of alternating high refractive index layers and low refractive index layers. Each high refractive index layer has a refractive index that is greater than a refractive index of each low refractive index layer. Additionally, the optical film structure further has a physical thickness in a range from 250 nm to 1000 nm. Additionally, the optical film structure exhibits a hardness of at least 8 GPa when measured from the outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm using a Vickers hardness test. Further, the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as a color exhibited having a hue angle (h*) that varies by less than 50 degrees over a range of viewing angles from 0 to 60 degrees. This aspect can serve as a durable and / or scratch resistant cover plate article for electronic devices, and more specifically, a cover plate article that exhibits hardness, a particular color or hue, high color saturation, and less variation in color or hue at various viewing angles.

[0013] According to another aspect of the disclosure, a cover plate article is provided that includes a substrate including an outer major surface and an inner major surface, the outer major surface and the inner major surface being opposite each other, and an optical film structure including an outermost surface disposed on the outer major surface or the inner major surface of the substrate. The optical film structure includes a plurality of alternating high refractive index layers and low refractive index layers. Each high refractive index layer has a refractive index that is greater than a refractive index of each low refractive index layer. Additionally, the optical film structure also has a physical thickness in a range from 250 nm to 1000 nm. Additionally, the optical film structure exhibits a hardness of at least 8 GPa when measured from the outermost surface of the optical film structure to a depth of from about 100 nm to about 300 nm using a Pencil Hardness Test. Furthermore, the cover plate article exhibits a substantially neutral reflected color under a D65 illuminant, manifested as exhibiting a gray or silver color hue, each having a chroma (c*) of less than 10. This aspect can serve as a durable and / or scratch resistant cover plate article for electronic devices, and more specifically, a cover plate article that exhibits hardness, neutral color, high neutral color saturation, and less variation in neutral color at various viewing angles.

[0014] Additional features and advantages will be set forth in the detailed description that follows, and in part will be apparent to those skilled in the art from the description, or can be learned by practice of the embodiments described herein, including the detailed description that follows, the claims, and the appended drawings.

[0015] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are intended to provide a further explanation of the nature and features of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification, illustrate one or more embodiments, and together with the description serve to explain principles and operation of the various embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 、 1A FIGS. 1A and IB are cross-sectional side views of cover plate articles according to one or more embodiments of the present disclosure;

[0017] Figure 2 FIG. 1C is a schematic diagram illustrating expressing a color by a hue angle (h*) and a chroma (c*) in a 1964 CIE (L*, c* and h*) color space;

[0018] Figure 2A and 2B are front and back schematic views, respectively, of an exemplary article in an “OFF” state that can be incorporated into any of the cover plate articles of the present disclosure; FIG. 1C is a schematic diagram illustrating expressing a color by a hue angle (h*) and a chroma (c*) in a 1964 CIE (L*, c* and h*) color space;

[0019] Figure 2C is an exemplary article according to one or more embodiments of the present disclosure in an "ON" state Figure 2A and 2B is a front view schematic of an exemplary article of

[0020] Figure 3A is a plot of first surface reflectance color (a* and b*) exhibited by comparative cover plate article examples at viewing angles from 0° to 90°;

[0021] Figure 3B is a plot of hue angle (h*) and chroma (c*) exhibited by comparative cover plate article examples at viewing angles from 0° to 90°;

[0022] Figure 4A is a plot of first surface reflectance of cover plate articles of the present disclosure at near normal incidence (about 6°) across the visible and near infrared spectrum;

[0023] Figure 4B is a plot of hue angle (h*) and chroma (c*) exhibited by cover plate articles of Figure 4A at viewing angles from 0° to 90°;

[0024] Figure 4C is a plot of first surface reflectance color (a* and b*) from a D65 illumination source exhibited by cover plate articles of Figure 4A at viewing angles from 0° to 90°;

[0025] Figure 5A is a plot of first surface reflectance of cover plate articles of the present disclosure at near normal incidence (about 6°) across the visible and near infrared spectrum;

[0026] Figure 5B is a plot of hue angle (h*) and chroma (c*) exhibited by cover plate articles of Figure 5A at viewing angles from 0° to 90°;

[0027] Figure 5C is a plot of first surface reflectance color (a* and b*) from a D65 illumination source exhibited by cover plate articles of Figure 5A at viewing angles from 0° to 90°;

[0028] Figure 6A is a plot of first surface reflectance of cover plate articles of the present disclosure at near normal incidence (about 6°) across the visible and near infrared spectrum;

[0029] Figure 6B is a plot of hue angle (h*) and chroma (c*) exhibited by cover plate articles of Figure 6A at viewing angles from 0° to 90°;

[0030] Figure 6C is a plot of first surface reflectance of the cover plate article of the present disclosure in the visible and near infrared spectrum at near normal incidence angles (about 6°); Figure 6A

[0031] Figure 7A is a plot of first surface reflectance of the cover plate article of the present disclosure in the visible and near infrared spectrum at near normal incidence angles (about 6°);

[0032] Figure 7B is a plot of hue angle (h*) and chroma (c*) exhibited by the cover plate article of the present disclosure at viewing angles from 0° to 90°; Figure 7A

[0033] Figure 7C is a plot of first surface reflectance of the cover plate article of the present disclosure in the visible and near infrared spectrum at near normal incidence angles (about 6°); Figure 7A

[0034] Figure 8A is a plot of first surface reflectance of the cover plate article of the present disclosure in the visible and near infrared spectrum at near normal incidence angles (about 6°);

[0035] Figure 8B is a plot of hue angle (h*) and chroma (c*) exhibited by the cover plate article of the present disclosure at viewing angles from 0° to 90°; Figure 8A

[0036] Figure 8C is a plot of first surface reflectance of the cover plate article of the present disclosure in the visible and near infrared spectrum at near normal incidence angles (about 6°); Figure 8A

[0037] Figure 9A is a plot of first surface reflectance of the cover plate article of the present disclosure in the visible and near infrared spectrum at near normal incidence angles (about 6°);

[0038] Figure 9B is a plot of hue angle (h*) and chroma (c*) exhibited by the cover plate article of the present disclosure at viewing angles from 0° to 90°; Figure 9A

[0039] is a plot of first surface reflectance of the cover plate article of the present disclosure in the visible and near infrared spectrum at near normal incidence angles (about 6°); Figure 9C Figure 9A is a plot of first surface reflectance of the cover plate article of the present disclosure in the visible and near infrared spectrum at near normal incidence angles (about 6°);

[0040] Figure 10A is a plot of first surface reflectance of the cover plate article of the present disclosure in the visible and near infrared spectrum at near normal incidence angles (about 6°);​​​​​​

[0041] Figure 10B yes Figure 10A A graph of the first surface reflected color (a* and b*) of the cover sheet product from D65 illumination at viewing angles of 0° to 90°;

[0042] Figure 11A is a graph of first surface reflectance of a cover sheet article of the present disclosure at near normal incidence (about 6°) across the visible and near infrared spectrum;

[0043] Figure 11B yes Figure 11A A diagram showing hue angle (h*) and chromaticity (c*) of a cover sheet product at a viewing angle of 0° to 90°;

[0044] Figure 11C yes Figure 11A A graph of the first surface reflected color (a* and b*) of the cover sheet product from D65 illumination at viewing angles of 0° to 90°;

[0045] Figure 12A is a graph of first surface reflectance of a cover sheet article of the present disclosure at near normal incidence (about 6°) across the visible and near infrared spectrum;

[0046] Figure 12B yes Figure 12A A diagram showing hue angle (h*) and chromaticity (c*) of a cover sheet product at a viewing angle of 0° to 90°;

[0047] Figure 12C yes Figure 12A A graph of the first surface reflected color (a* and b*) of the cover sheet product from D65 illumination at viewing angles of 0° to 90°;

[0048] Figure 13A is a graph of first surface reflectance of a cover sheet article of the present disclosure at near normal incidence (about 6°) across the visible and near infrared spectrum;

[0049] Figure 13B yes Figure 13A A diagram showing hue angle (h*) and chromaticity (c*) of a cover sheet product at a viewing angle of 0° to 90°;

[0050] Figure 13C yes Figure 13A A graph of the first surface reflected color (a* and b*) of the cover sheet product from D65 illumination at viewing angles of 0° to 90°;

[0051] Figure 14A is a graph of first surface reflectance of a cover sheet article of the present disclosure at near normal incidence (about 6°) across the visible and near infrared spectrum;

[0052] Figure 14B yes Figure 14A A diagram showing hue angle (h*) and chromaticity (c*) of a cover sheet product at a viewing angle of 0° to 90°;

[0053] Figure 14C yes Figure 14A A graph of the first surface reflected color (a* and b*) of the cover sheet product from D65 illumination at viewing angles of 0° to 90°;

[0054] Figure 15A is a graph of first surface reflectance of a cover sheet article of the present disclosure at near normal incidence (about 6°) across the visible and near infrared spectrum;

[0055] Figure 15B yes Figure 15A A diagram showing hue angle (h*) and chromaticity (c*) of a cover sheet product at a viewing angle of 0° to 90°;

[0056] Figure 15C yes Figure 15A A graph of the first surface reflected color (a* and b*) of the cover sheet product from D65 illumination at viewing angles of 0° to 90°;

[0057] Figure 16A is a graph of first surface reflectance of two cover sheet articles of the present disclosure at near normal incidence (about 6°) across the visible and near infrared spectra;

[0058] Figure 16B yes Figure 16A A graph of the first surface reflected color (a* and b*) of the cover sheet product from D65 illumination at viewing angles of 0° to 90°. DETAILED DESCRIPTION

[0059] In the following detailed description, for the purpose of explanation rather than limitation, exemplary embodiments of the disclosure are set forth to provide a thorough understanding of the various principles of the present disclosure. However, it will be apparent to those skilled in the art who benefit from this disclosure that the disclosure may be practiced in other embodiments that depart from the specific details disclosed herein. In addition, descriptions of well-known devices, methods, and materials may be omitted to avoid obscuring the description of the various principles of the present disclosure. Finally, wherever applicable, like reference numerals refer to like elements.

[0060] In this document, ranges can be presented as from "about" one particular value and / or to "about" another particular value. When such ranges are expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that each end point is important and that the endpoints are independent of one another.

[0061] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0062] Unless specifically stated otherwise, no method steps described herein are intended to be performed in any particular order, and nothing herein is intended to require a particular order of performing the steps of any method. Thus, in an embodiment, the order of steps in any method is not limited to the order presented unless explicitly stated otherwise. This is not intended to mean that the present disclosure is limited to any particular order of steps, unless explicitly stated otherwise. This is also not intended to mean that any particular order of steps is required, unless explicitly stated otherwise. Any process descriptions or representations of processes in this document are non-limiting and are provided for illustrative purposes only.

[0063] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component" includes aspects with two or more such components unless the context clearly indicates otherwise.

[0064] As used herein, the term "disposed" includes the application of materials to a surface using any known or to be developed method in the art. The disposed material can constitute a layer as defined herein. As used herein, the phrase "disposed on" includes embodiments where a material is formed on a surface such that the material is in direct contact with the surface, as well as embodiments where a material is formed on a surface with one or more spacer materials disposed between the material and the surface. The one or more spacer materials can constitute a layer as defined herein.

[0065] As used herein, the terms "low-RI layer" and "high-RI layer" refer to the relative values of the refractive index ("RI") of the layers of the optical film structure of the cover sheet article according to the present disclosure (i.e., low-RI layer < high-RI layer). Thus, the refractive index value of a low-RI layer is less than the refractive index value of a high-RI layer. Further, as used herein, "low-RI layer" and "low refractive index layer" are interchangeable and have the same meaning. Likewise, "high-RI layer" and "high refractive index layer" are interchangeable and have the same meaning.

[0066] As used herein, the term "strengthened substrate" refers to a substrate that has been strengthened, e.g., by ion exchange of larger ions for smaller ions in the surface of the substrate, employed in the cover sheet articles of the present disclosure. However, other strengthening methods known in the art, such as thermal tempering, or the use of a mismatch in the coefficient of thermal expansion between portions of the substrate to create a compressive stress and central tension zone, can also be utilized to form a strengthened substrate.

[0067] As used herein, "Vickers Indentation Hardness Test" and "Vickers Hardness Test" are used interchangeably to mean a test that measures the hardness on a surface of a material by pressing a concave surface with a diamond Vickers indenter. The Vickers Indentation Hardness Test includes pressing the outermost surface (e.g., the exposed surface) of the outer ply of the cover sheet articles of the present disclosure (e.g., the outermost surface of the optical film structure 120 shown in FIG. 1 and discussed in detail below) with a diamond Vickers indenter to form an indentation having an indentation depth in the range of about 50 nm to about 1000 nm (or the entire thickness of the optical film structure, whichever is less), and measuring the maximum hardness of the indentation along the entire indentation depth range or a segment of this indentation depth range (e.g., in the range of about 100 nm to about 600 nm, about 100 nm to about 500 nm, to 200 nm depth, etc.). The Vickers Indentation Hardness Test is generally measured using the methods shown 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. 7, 6, 1564-1583 (1992); and Oliver, W. C.; Pharr, G. M., Measurement of Hardness and Elastic Modulus by Instrument Indentation: Advances in Understanding and Refinements to Methodology. J. Mater. Res. 19, 1, 3-20 (2004). As used herein, "hardness" and "maximum hardness" each interchangeably refer to the maximum hardness measured along the indentation depth range, rather than the average hardness. Figure 1-1B

[0068] ​Generally, in nanoindentation measurement methods (e.g., Berkovich indenter hardness testing) of coatings or films having a greater hardness than the underlying substrate, the measured hardness can appear to initially increase due to the development of a plastic zone at shallow indentation depths, then increase and reach a maximum or plateau level at deeper indentation depths. Thereafter, the hardness begins to decrease at even deeper indentation depths due to the influence of the underlying substrate. The same effect can be seen when utilizing a substrate having a higher hardness than the coating; however, the hardness increases at deeper indentation depths due to the influence of the underlying substrate. The indentation depth range and hardness values at certain indentation depth ranges can be selected to identify the particular hardness response of the optical film structures described herein and their individual layers, without the influence of the underlying substrate.

[0069] When measuring the hardness of the outer film of the cover sheet article of the present disclosure according to the Berkovich indenter hardness test, a permanently deformed zone of the material (the plastic zone) is associated with the hardness of the material. During indentation formation, the elastic stress field extends well beyond this permanently deformed zone. As the indentation depth increases, the apparent hardness and modulus can be influenced by the stress field interaction with the underlying substrate. The influence of the substrate on the hardness occurs at deeper indentation depths (i.e., generally at depths greater than about 10% of the optical film structure or layer thickness). Furthermore, another complication is that the hardness response requires some minimum load to produce full plasticity during indentation formation. Prior to reaching this some minimum load, the hardness generally shows an increasing trend.

[0070] At shallow indentation depths (which can also be characterized by small loads) (e.g., up to about 50 nm), the apparent hardness of the material appears to increase sharply with respect to indentation depth. This shallow indentation depth range does not represent a true hardness indicator, but rather 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 a maximum level. At deeper indentation depths, the influence of the substrate becomes more apparent as the indentation depth increases. Once the indentation depth exceeds about 30% of the outer film of the cover sheet article of the present disclosure (e.g., the optical film structure 120 shown in FIG. 1C and discussed in detail below), the hardness begins to decrease sharply. Figure 1-1B

[0071] As used herein, the term "transmittance" is defined as the percentage of incident light power that is transmitted through a material (e.g., a cover sheet article, a substrate, an outer film, or a portion thereof) within a given wavelength range. Similarly, the term "reflectance" is defined as the percentage of incident light power that is reflected from a material (e.g., a cover sheet article, a substrate, or an outer film, or a portion thereof) within a given wavelength range. Transmittance and reflectance are measured using a particular line width. As used herein, "average transmittance" refers to the average amount of incident light power that is transmitted through a material within a defined wavelength range. As used herein, "average reflectance" refers to the average amount of incident light power that is reflected by a material.​

[0072] Further, "average reflectance" can be determined over the visible spectrum, the infrared spectrum, or other wavelength ranges, according to measurement principles understood by one of skill in the art of the present disclosure. Unless otherwise indicated, all reflectance values reported or otherwise mentioned in the present disclosure are associated with testing through the outer film of the cover article and over the major surface of the substrate on which the outer film is disposed, e.g., "first surface" average reflectance over a specified wavelength range, "first surface" reflectance at a particular wavelength, etc.

[0073] Further, "average transmittance" can be determined over the visible spectrum, the infrared spectrum, or other wavelength ranges, according to measurement principles understood by one of skill in the art of the present disclosure. Unless otherwise indicated, all transmittance values reported or otherwise mentioned in the present disclosure are associated with testing through the major surface of the substrate and the outer film of the cover article, e.g., "double surface" average transmittance over a specified wavelength range, "double surface" transmittance at a particular wavelength, etc.

[0074] As used herein, "reflective color" and "transmissive color" refer to the color, i.e., the color in the CIE L*, a*, b* color system, of a color reflected or transmitted through a cover article of the present disclosure under a D65 illuminant. More specifically, the "reflective color" or "transmissive color" can be given by 2 +b* 2 ) or in a*, b* coordinates, as these color coordinates are measured by reflectance or transmittance through the major surface of the substrate of the cover article under a D65 illuminant over a range of incident angles, e.g., 0 degrees to 10 degrees, 0 degrees to 45 degrees, 0 degrees to 90 degrees, etc.

[0075] As used herein, in the cylindrical 1964 CIE (L*, C*, h*) color space, "chroma (c*)" is the magnitude of the distance from the origin (c* (ab) ); "hue angle (h*)" is the angle from 0° to 360° (h (ab) ); and color saturation is defined as s*(L (ab) ) = (c*(L (ab) ) / L* (see Figure 2 ). It should be understood that the hue angle (h*) shown in Figure 2 should not be confused with the viewing angle (e.g., 0° to 90°), which indicates the angle between the viewer and a particular cover article (or product of such cover articles). Further, from Figure 2It can also be readily apparent, and as used herein, that a "hue angle (h*) change" over a given viewing angle range (e.g., 0° to 90°) is used to quantify the constancy of color exhibited by the cover plate articles of the present disclosure. Thus, a smaller change in hue angle over a given viewing angle range (e.g., 0° to 30°, 0° to 60°, 0° to 90°, etc.) indicates a cover plate article with high color constancy. Additionally, a high chroma (c*) value indicates a high color saturation for the cover plate articles of the present disclosure. From Figure 2 It can also be readily apparent, and as used herein, that for the cover plate articles of the present disclosure with a chroma (c*) value > 10, a hue angle (h*) of about 90° corresponds to yellow, a hue angle (h*) of about 0° corresponds to red, a hue angle (h*) of about 270° corresponds to blue, and a hue angle (h*) of about 180° corresponds to green. Cover plate articles with hue angles between the foregoing values can exhibit other colors, for example, cover plate articles with a hue angle (h*) > 270° and < 360° can exhibit purple (see Figure 2 ). Additionally, cover plate articles with a low chroma (c*) value < 10 exhibit a gray or silver hue, independent of the hue angle (h*).

[0076] Aspects of the present disclosure are directed to cover plate articles that employ optical film structures disposed on a substrate (e.g., a glass substrate, Gorilla products, glass-ceramic substrates, etc.). These cover plate articles and their optical film structures have high hardness and favorable optical properties suitable for a variety of applications including smart phone and mobile phone displays and covers. The optical film structures of the cover plate articles indicate a designed multilayer film structure, and the cover plate articles of the present disclosure reflect a new system-level design that is configured to exhibit a specific color or hue with high saturation and low color change over a wide viewing angle range.

[0077] The cover sheet articles and optical film structures of the present disclosure can be used in a variety of applications, including as a protective cover sheet for display devices (e.g., a smartphone faceplate) and / or a cover sheet substrate for a housing (e.g., a back cover sheet for a smartphone faceplate). In addition, some applications of these cover sheet articles also benefit from or otherwise require the presentation of a reflective color and / or the absence of a transmitted color to the presentation of a limited transmitted color (e.g., a smartphone screen presenting a red reflective hue). The need for these cover sheet articles to exhibit certain colors or hues can be due to functional (e.g., enhancing digital display characters) and / or customer-desired aesthetic (e.g., a smartphone with a blue color as a fashion accent) considerations. It can also be desirable for such cover sheet articles to exhibit the desired color or hue with high saturation and limited color variation at various viewing angles. In some configurations, ink can be applied to the back surface of these cover sheet articles to provide enhanced color reflectivity or even an ink color gradient to achieve different decorative color reflection effects. Conversely, for certain applications without ink and requiring transmission, the cover sheet articles of the present disclosure can exhibit little or no color, which can be attractive for dead front applications (e.g., as a cover sheet article for a smartphone display; see also Figure 2C Exemplary electronic devices and corresponding descriptions below). In contrast, conventional cover sheet articles in the field of the present disclosure have exhibited beneficial levels of hardness and required optical properties, but they have exhibited colors and / or hues that vary greatly with viewing angle, low color saturation, and / or limited flexibility in exhibiting the desired color or hue over a range of viewing angles.

[0078] In some embodiments, the cover sheet articles of the present disclosure employ optical film structures having a physical thickness of 1000 to 4000 nm (or 2500 to 4000 nm) and can be classified according to five categories in the 1964 CIE (L*, c*, and h*) color space: A) pink or red, hue angle (h*) of 320° to 40°; B) yellow, hue angle (h*) of 40° to 135°; C) green, hue angle (h*) of 135° to 200°; D) blue or purple, hue angle (h*) of 200° to 320°; and E) silver or gray, hue angle (h*) of any angle and chroma (c*) < 10. According to other embodiments, the cover sheet articles of the present disclosure employ optical film structures having a physical thickness of 250 to 1000 nm (or 400 to 700 nm) and exhibit colors and hues according to the foregoing categories A) - E).

[0079] Reference will now be made in detail to various embodiments of cover sheet articles, examples of which are illustrated in the accompanying drawings. Reference is made to Figure 1-1BAccording to one or more embodiments disclosed herein, a cover product 100 may include a substrate 110 and an optical film structure 120 disposed on the substrate 110. The substrate 110 may include opposite major surfaces 112 and 114. The optical film structure 120 may be disposed on the substrate 110. Figure 1-1B 112; however, the optical film structure 120 may be disposed on the inner major surface 114 of the substrate 110 in addition to or in lieu of being disposed on the outer major surface 112. The optical film structure 120 forms the outermost surface 122. Additionally, the optical film structure 120 may include a scratch resistant layer 150 (e.g., Figure 1A In some embodiments, the outermost surface 122 of the optical film structure 120 forms an air interface and generally defines the edge of the optical film structure 120 and the edge of the entire cover article 100 (e.g., as shown in FIG. Figure 1 In other embodiments, an additional coating 140 is provided on the outermost surface 122 of the optical film structure 120 (e.g., as shown in FIG. Figure 1A and Figure 1B ). According to some embodiments, substrate 110 may be substantially transparent, as described herein.

[0080] The optical film structure 120 includes at least one layer of at least one material. The term "layer" may include a single layer, or may include one or more sub-layers. These sub-layers may be in direct contact with each other. The sub-layers may be formed of the same material or two or more different materials. In one or more alternative embodiments, the sub-layers may be provided with spacer layers of different materials therebetween. In one or more embodiments, the layer may include one or more continuous and uninterrupted layers and / or one or more discontinuous and discontinuous layers (i.e., layers of different materials formed adjacent to each other). The layer or sub-layer may be formed by any known method in the art, including discrete deposition methods or continuous deposition methods. In one or more embodiments, the layer may be formed using only continuous deposition methods, or alternatively, using only discrete deposition methods.

[0081] Figure 1-1BThe physical thickness of the optical film structure 120 depicted in FIG can be about 0.25 μm (250 nm) or greater. In some examples, the physical thickness of the optical film structure 120 can be in the following ranges: about 0.25 μm to about 10 μm, about 0.25 μm to about 7.5 μm, about 0.25 μm to about 5 μm, about 0.5 μm to about 5 μm, about 0.5 μm to about 4 μm, and all thickness values ​​of the optical film structure 120 between these thickness values. In some embodiments, the physical thickness of the optical film structure 120 can be 250 nm to 1000 nm, 300 nm to 900 nm, 400 nm to 700 nm, and all thickness values ​​and thickness value ranges therebetween. In other embodiments, the physical thickness of the optical film structure 120 can be 1000 nm to 5000 nm, 1000 nm to 4000 nm, 1500 nm to 3500 nm, 2000 nm to 4000 nm, 2500 nm to 4000 nm, and all thickness values ​​and thickness value ranges therebetween. For example, the physical thickness of the optical film structure 120 can be approximately 0.25 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.25 μm, 1.5 μm, 1.75 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, and all thickness values ​​therebetween.

[0082] In addition, if Figure 1-1B As shown in FIG, the optical film structure 120 includes a plurality of alternating layers (130A, 130B). In one or more embodiments, the optical film structure 120 may include a periodic structure comprising two or more layers. In one or more embodiments, the two or more layers may be characterized as having different refractive indices from one another. In one embodiment, the period includes a first low RI layer 130A and a second high RI layer 130B. The difference in refractive index between the first low RI layer 130A and the second high RI layer 130B may be about 0.01 or greater, about 0.05 or greater, about 0.1 or greater, or even about 0.2 or greater.

[0083] like Figure 1 and 1AAs shown in , the optical film structure 120 may include alternating low refractive index layers 130A and high refractive index layers 130B to form a plurality of periodic structures. A single periodic structure may include low RI layers 130A and high RI layers 130B, such that when multiple periodic structures are provided, the first low RI layers 130A (designated "L" for ease of illustration) and the second high RI layers 130B (designated "H" for ease of illustration) alternate in the following layer sequence: L / H / L / H or H / L / H / L, thereby causing the low RI layers 130A and the high RI layers 130B to appear to alternate along the physical thickness of the optical film structure 120. Figure 1 In the example depicted in , the optical film structure 120 includes three (3) periodic structures, each periodic structure including a low RI layer 130A and a high RI layer 130B, as well as an additional low RI layer 130A (i.e., an outermost low RI layer 130A). Figure 1A In the example depicted in , the optical film structure 120 includes four (4) periodic structures, each periodic structure including a low RI layer 130A and a high RI layer 130B, as well as an additional low RI layer 130A, a scratch resistant layer 150, and a cover layer 131. Figure 1B In the example depicted in , the optical film structure 120 includes two (2) periodic structures, each periodic structure including a low RI layer 130A and a high RI layer 130B, as well as an additional low RI layer 130A (ie, an outermost low RI layer 130A).

[0084] In some embodiments, the optical film structure 120 may include up to twenty-five (25) periodic structures. For example, Figure 1-1B , the optical film structure 120 may include from about 2 to about 25 periodic structures, from about 2 to about 20 periodic structures, from about 2 to about 15 periodic structures, from about 2 to about 10 periodic structures, or any other number of periodic structures within these ranges. For example, the optical film structure 120 may include 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 periodic structures formed by alternating low RI layers 130A and high RI layers 130B.

[0085] exist Figure 1A In the embodiment shown in , the optical film structure 120 may include an additional cover layer 131, which may include a material with a lower refractive index than the high RI layer 130B. In some embodiments, one of the low refractive index layers 130A in the optical film structure 120 is designated as a cover layer (e.g., as shown in FIG. Figure 1 and 1B ).

[0086] As used herein, the terms "low RI" and "high RI" refer to the relative values of the refractive indices of the layers 130A and 130B with respect to each other (e.g., low RI < high RI). In one or more embodiments, the term "low RI" when used in reference to the low RI layer 130A includes a range of about 1.3 to about 1.7 or 1.75. In one or more embodiments, the term "high RI" when used in reference to the high RI layer 130B includes a range of about 1.7 to about 2.6 (e.g., about 1.85 or greater).

[0087] Suitable materials for the optical film structure 120 include: SiO2, Al2O3, GeO2, SiO, AlO x N y , AlN, SiN x , SiO x N y , Si u Al v O x N y , Ta2O5, Nb2O5, TiO2, ZrO2, TiN, MgO, MgF2, BaF2, CaF2, SnO2, HfO2, Y2O3, MoO3, DyF3, YbF3, YF3, CeF3, polymers, fluorine-containing polymers, plasma-polymerized polymers, siloxane polymers, silsesquioxane, polyimide, fluorinated polyimide, polyetherimide, polyethersulfone, polyphenylsulfone, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, acrylic polymers, urethane polymers, polymethyl methacrylate, the following listed as other materials suitable for scratch-resistant layers, and other materials known in the art. Some examples of suitable materials for the low RI layer 130A include SiO2, Al2O3, GeO2, SiO, AlO x N y , SiO x N y , Si u Al v O x N y , MgO, MgAl2O4, MgF2, BaF2, CaF2, DyF3, YbF3, YF3, and CeF3. The nitrogen content of the material for the first low RI layer can be minimized (e.g., in materials such as Al2O3 and MgAl2O4). Some examples of suitable materials for the high RI layer 130B include Si u Al v O x N y , Ta2O5, Nb2O5, AlN, Si3N4, AlO x N y , SiO x Ny 、SiN x 、SiN x :H y , HfO2, TiO2, ZrO2, Y2O3, Al2O3, MoO3 and diamond-like carbon.

[0088] In an example, the high RI layer 130B may also be a high hardness layer or a scratch resistant layer (e.g. Figure 1A In some embodiments, the oxygen content of the materials of the high RI layer 130B and / or the scratch resistant layer 150 can be minimized, especially SiN x or AlN x In other embodiments, the high RI layer 130B and / or the scratch resistant layer 150 each comprise SiN x or SiO x N y In some embodiments, AlO x N y The material can be considered as oxygen-doped AlN x That is, these oxygen-doped AlN x The material may have AlN x crystal structure (eg, wurtzite), but not necessarily the AlON crystal structure.

[0089] The hardness of the high RI layer 130B and / or the scratch-resistant layer 150 can be specifically characterized. In some embodiments, the maximum hardness of the high RI layer 130B and / or the scratch-resistant layer 150 can be about 8 GPa or greater, about 10 GPa or greater, about 12 GPa or greater, about 15 GPa or greater, about 18 GPa or greater, or about 20 GPa or greater when measured by a Bosch indenter hardness test at an indentation depth of about 100 nm or greater. In some cases, the high RI layer 130B material can be deposited as a single layer and can be characterized as a scratch-resistant layer (e.g., scratch-resistant layer 150), and the thickness of this single layer can be between about 200 nm and 10,000 nm for repeatable hardness measurements. When the high RI layer 130B is deposited as a single layer (e.g., as the scratch-resistant layer 150, e.g., Figure 1A In other embodiments (depicted in ), the physical thickness of this layer can be about 200 nm to about 10,000 nm, about 200 nm to about 5,000 nm, about 500 nm to about 5,000 nm, about 1,000 nm to about 4,000 nm, about 1,500 nm to about 4,000 nm, about 1,500 nm to about 3,000 nm, and all thickness values ​​therebetween.

[0090] In one or more embodiments, one or more of the low-RI layers 130A and high-RI layers 130B of the optical film structure 120 can include a particular physical thickness range. These layers 130A and / or 130B of the optical film structure 120 can include a physical thickness in a range from about 1 nm to about 400 nm, from about 5 nm to about 300 nm, from about 5 nm to about 200 nm, from about 10 nm to about 200 nm, or from about 10 nm to about 250 nm. In some embodiments, all or a majority of the layers in the optical film structure 120 can each have a physical thickness in a range from about 1 nm to about 400 nm, from about 5 nm to about 300 nm, from about 5 nm to about 200 nm, from about 10 nm to about 200 nm, or from about 10 nm to about 250 nm. In some embodiments, the physical thickness of the outermost high-RI layer 130B of the cover article 100 is greater than 150 nm, greater than 200 nm, or even greater than 225 nm. In other embodiments of the cover article 100, greater than 50%, greater than 55%, or even greater than 60% of the outermost physical thickness of the optical film structure 120 comprises a high-RI material, i.e., the material of the high-RI layers 130B. In other embodiments, the physical thickness of the outermost high-RI layer 130B exceeds the physical thickness of the outermost low-RI layer 130A or the cover layer 131, which can enhance the hardness value of the optical film structure 120 and its cover article 100.

[0091] In some embodiments, as Figure 1A and 1B exemplarily shown in FIGS. 1-3, an additional coating 140 can be disposed on top of the outermost low-RI layer 130A or the cover layer 131. This additional coating 140 can comprise a low-friction coating, an oleophobic coating, or an easy-to-clean (ETC) coating. In some embodiments, the outermost low-RI layer 130A and / or the cover layer 131 exhibit an extremely low thickness (e.g., about 10 nm or less, about 5 nm or less, or about 2 nm or less) that has minimal impact on optical performance when added to the substantially thicker outermost high-RI layer 130B or scratch-resistant layer 150 (e.g., as exemplarily shown in FIGS. 4-6). Figure 1A and 1B The low-RI layer 130A with an extremely low thickness can comprise Si02, an oleophobic or low-friction layer, or a combination of Si02and an oleophobic material. Exemplary low-friction layers can comprise diamond-like carbon. These materials (or one or more layers of the optical film structure 120) can exhibit a coefficient of friction less than 0.4, less than 0.3, less than 0.2, or even less than 0.1.

[0092] In one or more embodiments, the combined physical thickness of the one or more high-RI layers 130B can be characterized. The combined thickness is the calculated combination of the individual high-RI layers 130B in the optical film structure 120, even when there are one or more spacer low-RI layers 130A or one or more other layers. In some embodiments, the combined physical thickness of the one or more high-RI layers 130B can be greater than 30% of the total physical thickness of the optical film structure 120, which can also include a high-hardness material (e.g., a nitride or oxynitride material). For example, the combined physical thickness of the one or more high-RI layers 130B can be about 25% or greater, 30% or greater, 35% or greater, 40% or greater, about 50% or greater, or even about 60% or greater of the total physical thickness of the optical film structure 120.

[0093] As previously mentioned, the cover sheet article 100 can include one or more additional coatings 140 disposed on the optical film structure 120, as shown in illustrative form in Figure 1A and 1B In one or more embodiments, the additional coating 140 can include an easy-to-clean (ETC) coating. Examples of suitable ETC coatings are described in U.S. Patent Application No. 13 / 690,904, entitled "Process for Making of Glass Articles with Optical and Easy-to-Clean Coatings," filed November 30, 2012, published as U.S. Patent Application Publication No. 2014 / 0113083 on April 24, 2014, and important portions of which are incorporated herein by reference in their entirety. The easy-to-clean coating can have a thickness in a range from about 5 nm to about 50 nm and can include known materials, such as fluorinated silanes. The easy-to-clean coating can alternatively or additionally comprise a low-friction coating or surface treatment. Exemplary low-friction coating materials can include diamond-like carbon, silanes (e.g., fluorosilanes), phosphonates, olefins, and alkynes. In some embodiments, the easy-to-clean coating can have a thickness in a range from about 1 nm to about 40 nm, about 1 nm to about 30 nm, about 1 nm to about 25 nm, about 1 nm to about 20 nm, about 1 nm to about 15 nm, about 1 nm to about 10 nm, about 5 nm to about 50 nm, about 10 nm to about 50 nm, about 15 nm to about 50 nm, about 7 nm to about 20 nm, about 7 nm to about 15 nm, about 7 nm to about 12 nm, or about 7 nm to about 10 nm, as well as all ranges and sub-ranges therebetween.

[0094] In other embodiments, the additional coating 140 may include one or more scratch-resistant layers (e.g., having a composition similar to that of the scratch-resistant layer 150). In some embodiments, the additional coating includes a combination of an easy-to-clean material and a scratch-resistant material. In one example, the combination includes an easy-to-clean material and diamond-like carbon. The thickness of these additional coatings may range from about 5 nm to about 20 nm. The components of the additional coatings may be provided in separate layers. For example, the diamond-like carbon may be provided as a first layer, and the easy-to-clean material may be provided as a second layer on the first layer of diamond-like carbon. The thicknesses of the first and second layers may be within the ranges provided above for the additional coatings. For example, the thickness of the first layer of diamond-like carbon may be from about 1 nm to about 20 nm or from about 4 nm to about 15 nm (or, more specifically, about 10 nm), and the thickness of the second layer of easy-to-clean material may be from about 1 nm to about 10 nm (or, more specifically, about 6 nm). The diamond-like coating may include tetrahedral amorphous carbon (Ta-C), Ta-C:H, and / or aCH.

[0095] As mentioned in this article, Figure 1A The optical film structure 120 of the cover article 100 depicted in FIG. 1 includes a scratch-resistant layer 150, which may be disposed on the optical film structure 120 (eg, Figure 1A ), disposed directly on the substrate 110 (not shown) or at the outermost surface 122 of the optical film structure 120 (not shown). In some embodiments, the scratch-resistant layer 150 can be disposed between the layers of the optical film structure 120 such that a portion of the optical film structure 120 is above the scratch-resistant layer 150 (e.g., the anti-reflective region) and another portion of the optical film structure 120 is below the layer 150 and above the substrate 110. In other embodiments (e.g., Figure 1A ), a portion of the plurality of low RI layers 130A and high RI layers 130B of the optical film structure 120 is located between the scratch-resistant layer 150 and the substrate 110, and the remaining portion of the optical film structure 120 (the cover layer 131) is disposed above the scratch-resistant layer 150. In some embodiments, the portion of the optical film structure 120 below the layer 150 acts as an optical interference layer or region, which can function to bridge the refractive index difference between the substrate 110 and the scratch-resistant layer 150, and comprises alternating high refractive index layers 130B and low refractive index layers 130A. The two sections of the optical film structure 120 (i.e., the optical interference region disposed between the scratch-resistant layer 150 and the substrate 110 and the anti-reflection region disposed on the scratch-resistant layer 150) may have different thicknesses from each other or may have substantially the same thickness as each other. The layers of the two sections of the optical film structure 120 may be the same as each other or may be different from each other in composition, order, thickness, and / or configuration. Additionally, the layers of the two sections of the optical film structure 120 may include the same number of periodic structures, or the sections may each have a different number of periodic structures from one another.

[0096] Exemplary materials used in the scratch resistant layer 150 (or a scratch resistant layer used as an additional coating, as previously mentioned) may include inorganic carbides, nitrides, oxides, diamond-like materials, or combinations thereof. Examples of materials suitable for the scratch resistant layer 150 include metal oxides, metal nitrides, metal oxynitrides, metal carbides, metal oxycarbides, and / or combinations thereof. Exemplary metals include B, Al, Si, Ti, V, Cr, Y, Zr, Nb, Mo, Sn, Hf, Ta, and W. Specific examples of materials that can be used for the scratch resistant layer 150 or coating may include Al2O3, AlN, AlO x N y 、Si3N4、SiN x 、SiO x N y 、Si u Al v O x N y , diamond, diamond-like carbon, Si x C y 、Si x O y C z 、ZrO2、TiO x N y and combinations thereof. The scratch-resistant layer 150 may also include a nanocomposite material, or a material with a controlled microstructure, to improve hardness, toughness, or abrasion / wear resistance. For example, the scratch-resistant layer 150 may include nanocrystallites having a size ranging from about 5 nm to about 30 nm. In embodiments, the scratch-resistant layer 150 may comprise transformation-toughened zirconia, partially stabilized zirconia, or zirconia-toughened alumina. In embodiments, the scratch-resistant layer 150 exhibits a fracture toughness value greater than about 1 MPa√m and simultaneously exhibits a hardness value greater than about 8 GPa.

[0097] The scratch resistant layer 150 may include a single layer (e.g. Figure 1A ), or multiple sub-layers or a single layer exhibiting a refractive index gradient. When multiple layers are used, these layers form a scratch-resistant coating. For example, the scratch-resistant layer 150 may include Si u Al v O x N ycompositions gradients in which the concentration of any one or more of Si, Al, O, and N is varied to increase or decrease the refractive index. Refractive index gradients can also be formed using porosity. Such gradients are more fully described in U.S. Patent Application No. 14 / 262,224, filed April 25, 2014, entitled "Scratch-Resistant Articles with a Gradient Layer," now issued as U.S. Patent No. 9,703,011 on July 11, 2017, the important portions of which are hereby incorporated by reference in their entirety.

[0098] According to some embodiments, the scratch-resistant layer 150 (e.g., as shown in Figure 1A may have a physical thickness of about 200 nm to about 5000 nm. In some embodiments, the physical thickness of the scratch-resistant layer 150 is about 100 nm to about 10,000 nm, about 200 nm to about 7500 nm, about 200 nm to about 5000 nm, about 200 nm to about 3000 nm, about 500 nm to about 5000 nm, about 500 nm to about 3000 nm, about 500 nm to about 2500 nm, about 1000 nm to about 4000 nm, about 1500 nm to about 4000 nm, about 1500 nm to about 3000 nm, about 1750 nm to about 2250 nm, and all thickness values between these thicknesses. For example, the physical thickness of the scratch-resistant layer 150 can be 100 nm, 150 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, 2000 nm, 2100 nm, 2200 nm, 2300 nm, 2400 nm, 2500 nm, 2600 nm, 2700 nm, 2800 nm, 2900 nm, 3000 nm, 3500 nm, 4000 nm, 4500 nm, 5000 nm, 7500 nm, 10,000 nm, and all thickness sub-ranges and thickness values between the foregoing thicknesses.

[0099] In one illustrative embodiment of the cover sheet article 100 of the present disclosure, as depicted in illustrative form in Figure 1 The optical film structure 120 includes a plurality of alternating low RI layers 130A and high RI layers 130B, e.g., 2 to 15 periodic structures. The optical film structure 120 can also include an outermost low RI layer 130A (e.g., as shown in Figure 1Additionally, the refractive index of each high-RI layer 130B is greater than the refractive index of each low-RI layer 130A. Such a cover plate article 100 of the present disclosure can exhibit a substantially constant reflective hue under a D65 illuminant, as evidenced by: (a) a change in hue angle (h*) of the exhibited color over a range of viewing angles from 0° to 60° of less than 60°; or (b) an exhibited gray color hue or silver color hue, each having a chroma (c*) of less than 10.

[0100] In another illustrative embodiment of a cover plate article 100 of the present disclosure, as depicted in Figure 1A Additionally, the refractive index of each high-RI layer 130B is greater than the refractive index of each low-RI layer 130A. Additionally, the physical thickness of the optical film structure 120 can be in a range from 1000 nm to 4000 nm or 2500 nm to 4000 nm. Additionally, one of the high-RI layers in the optical film structure 120 is a scratch resistant layer 150 having a physical thickness of 500 nm to 3000 nm. The optical film structure 120 can also include an outermost low-RI layer 130A or cap layer 131 disposed on the scratch resistant layer 150 (as depicted in Figure 1A Additionally, in such a configuration, a portion of the plurality of low-RI layers 130A and high-RI layers 130B in the optical film structure 120 are disposed between the scratch resistant layer 150 and the substrate 110. Such a cover plate article 100 of the present disclosure can exhibit a substantially constant reflective hue under a D65 illuminant, as evidenced by: (a) a change in hue angle (h*) of the exhibited color over a range of viewing angles from 0° to 60° of less than 60°; or (b) an exhibited gray color hue or silver color hue, each having a chroma (c*) of less than 10. Additionally, such a cover plate article 100 can exhibit a hardness of at least 12 GPa when measured from the outermost surface 122 of the optical film structure 120 to a depth of about 100 nm to about 300 nm using a Berkovich Indenter Hardness Test.

[0101] In Figure 1AIn certain embodiments of the cover plate article 100 depicted in

[0102] In another illustrative embodiment of the cover plate article 100 of the present disclosure, as Figure 1B In the illustrative form depicted in Figure 1 In the illustrative form depicted in

[0103] In certain embodiments of the cover plate article 100 depicted in Figure 1B In certain embodiments of the cover plate article 100 depicted in

[0104] The optical film structure 120 and / or cover article 100 can be described in terms of hardness as measured by a Bosch Indenter Hardness Test. As previously mentioned, the Bosch Indenter Hardness Test involves indenting the outermost surface 122 of the cover article 100 of the present disclosure with a diamond Bosch Indenter (see Figure 1-1B ) or the surface of any layer or layers in the optical film structure 120 to form an indentation with a depth in the range of about 50 nm to about 1000 nm (or the entire thickness of the optical film structure 120 or its layers, whichever is smaller) or about 100 nm to about 500 nm, and measuring the maximum hardness of this indentation along the entire indentation depth range or a section of this indentation depth (for example, at an indentation depth of 100 nm or greater, in the range of about 100 nm to about 250 nm, etc.).

[0105] In some embodiments, the cover sheet article 100 (e.g., as measured at the outermost surface 122) is Figure 1-1B ) can exhibit a hardness of about 8 GPa or greater, about 10 GPa or greater, or about 12 GPa or greater (e.g., about 14 GPa or greater, about 16 GPa or greater, about 18 GPa or greater, or about 20 GPa or greater). These measured hardness values ​​can be exhibited by the optical film structure 120 and / or cover article 100 along an indentation depth of about 50 nm or greater or about 100 nm or greater (e.g., about 50 nm to about 300 nm, about 50 nm to about 400 nm, about 50 nm to about 500 nm, about 50 nm to about 600 nm, about 100 nm to about 300 nm, about 100 nm to about 400 nm, about 100 nm to about 500 nm, or about 100 nm to about 600 nm, about 200 nm to about 300 nm, about 200 nm to about 400 nm, about 200 nm to about 500 nm, or about 200 nm to about 600 nm). These hardness values ​​can also be measured from the outermost surface 122 of the optical film structure 120 to a depth of 200 nm. In one or more embodiments, the cover article 100 exhibits a hardness greater than the hardness of the substrate 110 (which can be measured on a surface opposite the outermost surface 122, such as the inner major surface 114).

[0106] According to some embodiments of the cover plate product 100 of the present disclosure, Figure 1-1BAs depicted in exemplary form in FIG, the cover sheet article further exhibits a dual-surface average photopic transmittance of greater than about 60%, 70%, 80%, or even 85% at normal or near-normal viewing angles (0° to 6°). For example, the cover sheet article 100 may exhibit a dual-surface average photopic transmittance of 60%, 65%, 70%, 75%, 80%, 85%, 90%, and all transmittance values ​​therebetween at normal or near-normal viewing angles. Additionally, in some embodiments, the cover sheet article 100 may exhibit a transmittance color having a chromaticity (c*) of less than 20, less than 15, less than 10, less than 8, or even less than 5.

[0107] The cover plate product 100 of the present disclosure (such as Figure 1-1B ) exhibits a substantially constant reflective hue under D65 illuminant, as indicated by: (a) exhibiting a color with a hue angle (h*) that varies by less than 60° over a viewing angle range of 0° to 60°; or (b) exhibiting a gray or silver hue, each having a chroma (c*) of less than 10. For embodiments of the cover sheet article 100 that exhibit color, the variation in hue angle (h*) may be less than 225 degrees, 200 degrees, 175 degrees, 150 degrees, 125 degrees, 100 degrees, less than 80 degrees, less than 60 degrees, less than 40 degrees, less than 20 degrees, less than 10 degrees, or even less than 5 degrees over a viewing angle range of 0-30°, 0-60°, or even 0-90°. For these embodiments that exhibit color, the near-normal incidence angle or maximum chroma (c*) value may be higher, for example, greater than 15, greater than 30, greater than 40, greater than 50, or even greater than 60. For embodiments of the cover article 100 exhibiting a gray or silver hue, the hue angle (h*) can vary without limitation, while these articles exhibit a chroma (c*) of less than 10, less than 7.5, less than 5, or even less than 2.5 over a viewing angle range of 0-30°, 0-60°, or even 0-90°.

[0108] In some embodiments of the disclosed cover sheet product 100, as Figure 1-1B As depicted in exemplary form in FIG, the cover sheet article can exhibit a substantially constant reflective hue under D65 illuminant, appearing to be pink or red, with a hue angle (h*) of 320 to 40 degrees and a chroma (c*) greater than 15.

[0109] In some embodiments of the disclosed cover sheet product 100, as Figure 1-1B As depicted in exemplary form in FIG, the cover sheet article can exhibit a substantially constant reflective hue under D65 illuminant, appearing to exhibit a yellow color with a hue angle (h*) of 40 to 135 degrees and a chroma (c*) greater than 15.

[0110] In some embodiments of the cover sheet product 100 of the present disclosure, as Figure 1-1BAs depicted in illustrative form, the cover sheet article can exhibit a substantially constant reflected color hue under D65 illuminant, appearing to exhibit a green color having a hue angle (h*) of 135 degrees to 200 degrees and a chroma (c*) greater than 15.

[0111] In some embodiments of the cover sheet article 100 of the present disclosure, as Figure 1-1B As depicted in illustrative form, the cover sheet article can exhibit a substantially constant reflected color hue under D65 illuminant, appearing to exhibit a blue or violet color having a hue angle (h*) of 200 degrees to 320 degrees and a chroma (c*) greater than 15.

[0112] In some embodiments of the cover sheet article 100 of the present disclosure, as Figure 1-1B As depicted in illustrative form, the cover sheet article can exhibit a substantially constant reflected color hue under D65 illuminant, appearing to exhibit a gray or silver color hue having any hue angle (h*) (e.g., 0 to 320 degrees) and a chroma (c*) less than 5 or even less than 2.5.

[0113] The substrate 110 can comprise an inorganic material, and can comprise an amorphous substrate, a crystalline substrate, or a combination thereof. The substrate 110 can be formed from man-made materials and / or naturally occurring materials, such as quartz and polymers. For example, in some cases, the substrate 110 can be characterized as organic, and in particular, can be a polymer. Examples of suitable polymers include, but are not limited to, thermoplastics, including polystyrene (PS) (including styrene copolymers and blends); polycarbonate (PC) (including copolymers and blends); polyesters (including copolymers and blends, including polyethylene terephthalate and polyethylene terephthalate copolymers); polyolefins (PO) and cyclic polyolefins (cyclic PO); polyvinyl chloride (PVC); acrylic polymers, including polymethyl methacrylate (PMMA) (including copolymers and blends); thermoplastic urethane (TPU); polyetherimide (PEI); and blends of these polymers with one another. Other exemplary polymers include epoxy resins, styrene resins, phenolic resins, melamine resins, and silicone resins.

[0114] In some embodiments, the substrate 110 can specifically exclude polymeric materials, plastics, and / or metallic materials. The substrate 110 can be characterized as an alkali- containing substrate (i.e., the substrate 110 includes one or more alkali metals). In one or more embodiments, the substrate 110 exhibits a refractive index in a range from about 1.45 to about 1.55. In particular embodiments, the skilled artisan in the field of the present disclosure will appreciate that the substrate 110 can exhibit an average strain-to-failure of 0.5% or greater, 0.6% or greater, 0.7% or greater, 0.8% or greater, 0.9% or greater, 1% or greater, 1.1% or greater, 1.2% or greater, 1.3% or greater, 1.4% or greater, 1.5% or greater, or even 2% or greater at a surface on one or more opposing major surfaces when measured using ball-on-ring testing using at least 5, at least 10, at least 15, or at least 20 samples. In particular embodiments, the substrate 110 can exhibit an average strain-to-failure of about 1.2%, about 1.4%, about 1.6%, about 1.8%, about 2.2%, about 2.4%, about 2.6%, about 2.8%, or about 3% or greater at a surface on one or more opposing major surfaces.

[0115] Suitable substrates 110 can exhibit an elastic modulus (or Young's modulus) in a range from about 30 GPa to about 120 GPa. In some cases, the elastic modulus of the substrate can be in a range from about 30 GPa to about 110 GPa, from about 30 GPa to about 100 GPa, from about 30 GPa to about 90 GPa, from about 30 GPa to about 80 GPa, from about 30 GPa to about 70 GPa, from about 40 GPa to about 120 GPa, from about 50 GPa to about 120 GPa, from about 60 GPa to about 120 GPa, from about 70 GPa to about 120 GPa, and all ranges and sub-ranges therebetween.

[0116] In one or more embodiments, the amorphous substrate can include a glass, which can be strengthened or unstrengthened. Examples of suitable glasses include soda-lime glass, alkali-aluminosilicate glass, alkali-containing borosilicate glass, and alkali-aluminoborosilicate glass. In some variations, the glass can be free of lithium oxide. In one or more alternative embodiments, the substrate 110 can include a crystalline substrate, such as a glass-ceramic substrate (which can be strengthened or unstrengthened) or can include a single crystal structure, such as sapphire. In one or more particular embodiments, the substrate 110 includes an amorphous base (e.g., a glass) and a crystalline cladding layer (e.g., a sapphire layer, a polycrystalline alumina layer, and / or a spinel (MgAl2O4) layer).

[0117] The hardness of the substrate 110 of one or more embodiments can be less than the hardness (as measured by the Berkovich Indenter Hardness Test described herein) of the overall cover article 100. Unless otherwise indicated, the hardness of the substrate 110 is measured using the Berkovich Indenter Hardness Test.

[0118] The substrate 110 can be substantially optically clear, transparent, and free of light- scattering elements. In these embodiments, the substrate 110 can exhibit an average light transmission in the optical wavelength range of about 85% or greater, about 86% or greater, about 87% or greater, about 88% or greater, about 89% or greater, about 90% or greater, about 91% or greater, or about 92% or greater. In some embodiments, these light reflectance and transmission values can be total reflectance or total transmission (accounting for reflectance or transmission on both major surfaces 112, 114 of the substrate 110), or can be observed on a single side of the substrate 110 (i.e., only on the outermost surface 122 of the optical film structure 120, without accounting for the opposing surface). Unless otherwise indicated, the average reflectance or transmission of the substrate 110 alone is measured at an incident illumination angle of 0 degrees relative to the substrate major surface 112 (however, these measurements can also be provided at an incident illumination angle of 45 degrees or 60 degrees). The substrate 110 can optionally exhibit a color, such as white, black, red, blue, green, yellow, orange, etc.

[0119] Additionally or alternatively, the physical thickness of the substrate 110 can vary along one or more dimensions thereof for aesthetic and / or functional reasons. For example, the edges of the substrate 110 can be thicker compared to more central regions of the substrate 110. The length, width, and physical thickness dimensions of the substrate 110 can also vary depending on the application or use of the cover article 100.

[0120] The substrate 110 can be provided using a variety of different processes. For example, where the substrate 110 comprises an amorphous substrate, such as glass, various formation methods can include float glass processes and down-draw processes, such as fusion down-draw and slot down-draw.

[0121] Upon formation, the substrate 110 can be strengthened to form a strengthened substrate. As used herein, the term “strengthened substrate” can refer to a substrate that has been strengthened through chemical strengthening, for example, by ion exchange of larger ions for smaller ions in the surface of the substrate. However, other strengthening methods known in the art, such as thermal tempering, or the use of a mismatch in the coefficient of thermal expansion between portions of the substrate to create a compressive stress and central tension zone, can also be utilized to form a strengthened substrate.

[0122] When the substrate 110 is chemically strengthened by ion exchange, ions in the surface layer of the substrate are replaced or exchanged with larger ions of the same valence or oxidation state. The ion exchange method is typically performed by immersing the substrate in a molten salt bath containing larger ions to be exchanged with smaller ions in the substrate. Those skilled in the art will appreciate that the parameters of the ion exchange method are typically determined by the composition of the substrate and the desired compressive stress (CS) and depth of compressive stress layer (or depth of layer DOL or depth of compression DOC) of the substrate caused by the strengthening operation, including but not limited to bath composition and temperature; immersion time; number of immersions of the substrate in one or more salt baths; use of multiple salt baths; and additional steps such as annealing and washing. For example, ion exchange of an alkali-containing glass substrate can be achieved by immersing the substrate in a molten bath of at least one salt containing larger alkali metal ions, such as, but not limited to, nitrates, sulfates, and chlorides. The temperature of the molten salt bath is typically in the range of about 380°C to about 450°C, and the immersion time is in the range of about 15 minutes to about 40 hours. However, temperatures and immersion times different from those described above may also be used.

[0123] Additionally, non-limiting examples of ion exchange processes in which a glass substrate is immersed in multiple ion exchange baths with washing and / or annealing steps between each immersion are described in U.S. Patent Application No. 12 / 500,650, filed July 10, 2009, by Douglas C. Allan et al., entitled “Glass with Compressive Surface for Consumer Applications,” which claims priority to U.S. Provisional Patent Application No. 61 / 079,995, filed July 11, 2008, in which a glass substrate is strengthened by multiple, sequential ion exchange treatments in salt baths of varying concentrations; and in U.S. Patent Application No. 12 / 500,650, filed July 10, 2009, by Christopher M. Lee et al., entitled “Dual Stage Ion Exchange for Chemical Strengthening of No. 8,312,739, filed on July 29, 2008, which claims priority to U.S. Provisional Patent Application No. 61 / 084,398, filed on July 29, 2008, in which a glass substrate is strengthened by ion exchange in a first bath diluted with effluent ions followed by immersion in a second bath having a lower concentration of effluent ions than the first bath. The contents of U.S. Patent Application No. 12 / 500,650 and U.S. Patent No. 8,312,739 are incorporated herein by reference in their entirety.

[0124] The degree of chemical strengthening achieved by ion exchange can be quantified in terms of central tension (CT), surface CS, and depth of compression (DOC) parameters. Compressive stress, including surface CS, can be measured by surface stress meter (FSM), using a commercially available instrument, such as the FSM-6000 manufactured by Orihara Industrial Co., Ltd. Surface stress measurements rely on accurate measurement of the stress-optical coefficient (SOC) associated with the birefringence of the glass. SOC, in turn, is measured according to Procedure C (glass disk method) described in ASTM Standard C770-16 entitled "Standard Test Method for Measurement of Glass Stress-Optical Coefficient," the contents of which are incorporated herein by reference in their entirety. The maximum CT value is measured using scattered light polariscope (SCALP) techniques known in the art. As used herein, DOC means the depth at which the stress in a chemically strengthened alkali-aluminosilicate glass article described herein changes from being self-compressive to tensile. DOC can be measured by FSM or SCALP, depending on the ion exchange treatment. When the stress in the glass article is created by exchanging potassium ions into the glass article, DOC is measured using FSM. When the stress is created by exchanging sodium ions into the glass article, DOC is measured using SCALP. When the stress in the glass article is created by exchanging both potassium and sodium ions into the glass, DOC is measured by SCALP because the exchange depth of sodium is believed to be indicative of DOC, and the exchange depth of potassium is believed to be indicative of a change in the magnitude of the compressive stress (but not the change in stress from compressive to tensile); the exchange depth of potassium in such glass articles is measured by FSM.

[0125] In one embodiment, the surface CS of the substrate 110 can be 200 MPa or more, 250 MPa or more, 300 MPa or more, such as 400 MPa or more, 450 MPa or more, 500 MPa or more, 550 MPa or more, 600 MPa or more, 650 MPa or more, 700 MPa or more, 750 MPa or more, or 800 MPa or more. The strengthened substrate can have a DOC (previously referred to as DOL) of 10 pm or more, 15 pm or more, 20 pm or more (such as 25 pm, 30 pm, 35 pm, 40 pm, 45 pm, 50 pm or more), and / or a CT of 10 MPa or more, 20 MPa or more, 30 MPa or more, 40 MPa or more (such as 42 MPa, 45 MPa, or 50 MPa or more), but less than 100 MPa (such as 95, 90, 85, 80, 75, 70, 65, 60, 55 MPa or less). In one or more particular embodiments, the strengthened substrate has one or more of a surface CS greater than 500 MPa, a DOC (previously referred to as DOL) greater than 15 pm, and a CT greater than 18 MPa.

[0126] Example glasses that can be used in the substrate 110 can include alkali- alumino-silicate glass compositions or alkali-alumino-boro-silicate glass compositions, although other glass compositions are contemplated. These glass compositions are capable of being chemically strengthened by an ion exchange process. One example glass composition includes Si02, B203, and Na20, where (Si02+ B203) > 66 mol% and Na20 > 9 mol%. In one embodiment, the glass composition includes at least 6 wt% alumina. In another embodiment, the substrate includes a glass composition that includes one or more alkaline earth metal oxides such that the content of alkaline earth metal oxides is at least 5 wt%. In some embodiments, suitable glass compositions also include at least one of K20, MgO, and CaO. In one particular embodiment, the glass composition used in the substrate can include 61-75 mol% Si02; 7-15 mol% Al203; 0-12 mol% B203; 9-21 mol% Na20; 0-4 mol% K20; 0-7 mol% MgO; and 0-3 mol% CaO.

[0127] Another example glass composition suitable for the substrate 110 comprises: 60-70 mol% Si02; 6-14 mol% AI2O3; 0-15 mol% B203; 0-15 mol% Li20; 0-20 mol% Na20; 0-10 mol% K20; 0-8 mol% MgO; 0-10 mol% CaO; 0-5 mol% Zr02; 0-1 mol% Sn02; 0-1 mol% Ce02; less than 50 ppm As203; and less than 50 ppm Sb203; wherein 12 mol% < (Li20 + Na20 + K20) < 20 mol% and 0 mol% < (MgO + CaO) < 10 mol%.

[0128] Another example glass composition suitable for the substrate 110 comprises: 63.5-66.5 mol% Si02; 8-12 mol% AI2O3; 0-3 mol% B203; 0-5 mol% Li20; 8-18 mol% Na20; 0-5 mol% K20; 1-7 mol% MgO; 0-2.5 mol% CaO; 0-3 mol% Zr02; 0.05-0.25 mol% Sn02; 0.05-0.5 mol% Ce02; less than 50 ppm As203; and less than 50 ppm Sb203; wherein 14 mol% < (Li20 + Na20 + K20) < 18 mol% and 2 mol% < (MgO + CaO) < 7 mol%.

[0129] In one particular embodiment, an alkali-aluminosilicate glass composition suitable for the substrate 110 comprises alumina, at least one alkali metal, and in some embodiments greater than 50 mol% Si02, in other embodiments at least 58 mol% Si02, and in yet other embodiments at least 60 mol% Si02, wherein the ratio (AI2O3 + B2O3) / Σ modifiers (i.e., the sum of the modifiers) is greater than 1, wherein in the ratio the components are expressed in mol% and the modifiers are alkali oxides. In a particular embodiment, this glass composition comprises: 58-72 mol% Si02; 9-17 mol% AI2O3; 2-12 mol% B2O3; 8-16 mol% Na20; and 0-4 mol% K20, wherein the ratio (AI2O3 + B2O3) / Σ modifiers (i.e., the sum of the modifiers) is greater than 1.

[0130] In yet another embodiment, the substrate 110 can comprise an alkali aluminosilicate glass composition comprising: 64-68 mol% Si02; 12-16 mol% Na20; 8-12 mol% AI2O3; 0-3 mol% B203; 2-5 mol% K20; 4-6 mol% MgO; and 0-5 mol% CaO, wherein: 66 mol% < Si02+ B203+ CaO < 69 mol%; Na20 + K20 + B203+ MgO + CaO + SrO > 10 mol%; 5 mol% < MgO + CaO + SrO < 8 mol%; (Na20 + B203) - AI2O3 < 2 mol%; 2 mol% < Na20 - AI2O3 < 6 mol%; and 4 mol% < (Na20 + K20) - AI2O3 < 10 mol%.

[0131] In an alternative embodiment, the substrate 110 can comprise an alkali aluminosilicate glass composition comprising: 2 mol% or more of AI2O3 and / or Zr02, or 4 mol% or more of AI2O3 and / or Zr02.

[0132] When the substrate 110 comprises a crystalline substrate, the substrate can comprise a single crystal, which can comprise AI2O3. Such single crystal substrates are referred to as sapphire. Other suitable materials for crystalline substrates include polycrystalline alumina layers and / or spinel (MgAI2O4).

[0133] Optionally, the substrate 110 can be crystalline, and comprise a glass-ceramic substrate, which can or can not be strengthened. Examples of suitable glass-ceramics can include Li20-Al203-Si02system (i.e., LAS system) glass-ceramics, MgO-Al203-Si02system (i.e., MAS system) glass-ceramics, and / or glass-ceramics comprising a primary crystalline phase comprising β-quartz solid solution, β-spodumene ss, cordierite, and lithium disilicate. The glass-ceramic substrates can be strengthened using the chemical strengthening methods disclosed herein. In one or more embodiments, the MAS system glass-ceramic substrates can be strengthened in a Li2SO4molten salt, whereby the 2Li + and Mg 2+ are exchanged.

[0134] Substrates 110 according to one or more embodiments can have a physical thickness in various portions of the substrate 110 in a range from about 50 pm to about 5 mm. Example substrates 110 have a physical thickness in a range from about 50 pm to about 500 pm (e.g., 50, 75, 100, 200, 300, 400, or 500 pm). Other example substrates 110 can have a physical thickness in a range from about 50 pm to about 5000 pm (e.g., 50, 75, 100, 250, 500, 600, 700, 800, 900, 1000, 1250, 1500, 1750, 2000, 2500, 3000, 3500, 4000, 4500, or 5000 pm). The physical thickness of the substrate 110 can be greater than about 1 mm (e.g., about 2, 3, 4, or 5 mm). In one or more particular embodiments, the physical thickness of the substrate 110 can be 2 mm or less, or less than 1 mm. The substrate 110 can be subjected to acid polishing or other means to remove or reduce the effects of surface defects.

[0135] Referring again to the cover plate article 100 of the present disclosure, as Figure 1-1B The optical film structure 120, as depicted in illustrative form in Without being bound by theory, such a method adjustment can be used to preserve a maximum level of induced compressive stress of the chemical strengthening in the strengthened glass or transparent glass-ceramic substrate 110.

[0136] Figure 2A The cover plate article 100, as depicted in illustrative form in

[0137] Exemplary articles in which any of the cover plate articles disclosed herein can be incorporated are Figure 2A and 2B, such as a smartwatch, smart ring, or smart glasses. In this configuration, wearable electronic device 300 includes a strap 330; a housing 302 having a front surface 304 and a rear surface 306; electronic components (not shown) at least partially or completely within housing 302; and a display 310. Display 310 is located at or near front surface 304 of housing 302. A cover 313 is disposed above or coincident with rear surface 306. At least one of cover 313 or a portion of housing 302 can include any of the cover articles 100 disclosed herein. Thus, wearable electronic device 300, particularly cover 313 and / or housing 302 at front surface 304 and / or rear surface 306, can advantageously exhibit a desired color (e.g., blue, red, etc.) or a desired neutral color (e.g., neutral gray or silver) with minimal color or hue variation over a wide viewing angle.

[0138] In addition, if Figure 2C As shown in FIG, the wearable electronic device 300, in particular the cover 313 and / or the housing 302 at the front surface 304 and / or the rear surface 306 thereof, when in the “closed” state, can advantageously display a desired color (e.g., blue, red, etc.) or a desired neutral color (e.g., neutral gray or silver) with minimal color or hue variation over a wide viewing angle range. Figure 2A As shown in FIG, the wearable electronic device 300 can be operated as a hidden display in the “on” state, wherein the wearable electronic device 300 is displayed as a hidden display in the “off” state (e.g., Figure 1A ), there is very little (if any) transmissive color in the "on" state, for example to allow readability of the display indication 310a.

[0139] Examples

[0140] Various embodiments will be further illustrated by the following examples, which are Figure 1B The cover articles described in (Examples 1-4, 4A, 4B and 5) and Comparative Example 1 The cover plate products (Examples 6-9, 9A and 10) and two comparative examples (Comparative Example 1 and Comparative Example 2) described in the present disclosure are consistent. It will be understood by those skilled in the art of the present disclosure that the optical properties of these examples (such as first surface reflectance, first surface reflected color in CIE L*, a* and b* coordinate system, and first surface reflected color in CIE L, c* and h* cylindrical coordinate system) are modeled using computational techniques, particularly transfer matrix modeling techniques, to simulate film performance. x N y and SiN xprevious thin film reactive sputtering, laboratory experiments, and thin film properties (e.g., refractive index values) obtained from higher volume sputter machines.

[0141] In previous experiments, the refractive index (as a function of wavelength) of each of the layers formed and the glass substrate were measured using a spectroscopic ellipsometer. Then, the reflectance spectra of the examples were calculated using the refractive indices thus measured. For convenience, these examples use a single refractive index value in their descriptive tables, which corresponds to the point selected from the dispersion curve at a wavelength of about 550 nm.

[0142] In the following examples, the articles exhibit a combination of optimized selected color or hue attributes (e.g., reflected color of red, etc.) with minimal color change (e.g., small change in hue angle (h*) or optimized hue (e.g., a neutral reflected gray color) and minimal change in hue (e.g., exhibited as low chroma (c*) < 10) over a large range of viewing angles, and desirable mechanical properties (e.g., high hardness). In contrast, comparative articles can exhibit good mechanical properties, but their color changes significantly with viewing angle.

[0143] Figure 3A

[0144] A strengthened glass substrate was coated with the optical film structure of Table 1 below, designated as Comparative Example 1. Specifically, the optical film structure of Comparative Example 1 had a total of 13 layers with a total thickness of 2513.8 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 13th layer with a thickness of 25.0 nm), and an oxide-containing cap layer (i.e., the 1st layer with a thickness of 88.5 nm) at the outermost position of the stack.

[0145] Referring to Figure 3A A plot of the first surface reflected color (a* and b*) of Comparative Example 1 over a viewing angle of 0° to 90° is provided in FIG. 1. From Comparative Example 2 It is apparent that this cover article exhibits a sharp change in color with viewing angle. Specifically, this comparative example exhibits a change in hue angle (h*) of > 225° over a viewing angle range of 0° to 90°, and the perceived color is not particularly vibrant, with a maximum chroma (c*) of about 2.9.

[0146] Table 1 - Comparative Example 1, Cover Article

[0147]

[0148] Figure 3B

[0149] A strengthened glass substrate was coated with the optical film structure of Table 1A below, designated as Comparative Example 2. Specifically, the optical film structure of Comparative Example 2 had a total of 11 layers with a total thickness of 2598.2 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 11th layer having a thickness of 25.0 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., the 1st layer having a thickness of 78.2 nm).

[0150] Referring to Example 1 A plot of the hue angle (h*) and chroma (c*) of Comparative Example 2 at viewing angles from 0° to 90° is provided in FIG. 1. As is evident from the plot, this example exhibits a blue color with a high color change over the viewing angle range from 0° to 90°. In addition, the chroma (c*) of this comparative example is low at near-normal viewing angles. Specifically, the change in hue angle (h*) is greater than 20° over the viewing angle (AOI) range from 0-30°, and greater than 60° over the viewing angle (AOI) range from 0-60°. More specifically, this comparative example exhibits a maximum chroma (c*) of 51.41; a maximum saturation (s*) of 1.07; a change in hue angle (h*) over the viewing angle range from 0-10° of 2.60°; a change in hue angle (h*) over the viewing angle range from 0-30° of 21.40°; a change in hue angle (h*) over the viewing angle range from 0-60° of 60.65°; and a change in hue angle (h*) over the viewing angle range from 0-90° of 102.83°.

[0151] Table 1A - Comparative Example 2, Cover Sheet Article

[0152]

[0153] Figure 4A

[0154] A strengthened glass substrate was coated with the optical film structure of Table 2 below, designated as Example 1. Specifically, the optical film structure of Example 1 had a total of 13 layers with a total thickness of 3583.57 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 13th layer having a thickness of 25.0 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., the 1st layer having a thickness of 223.50 nm).

[0155] Referring to Figure 4B A plot of the first surface reflectance of the cover sheet article of this example in the visible and near infrared spectra at near-normal incidence (about 6°) is provided in FIG. 2. As is evident from the plot, Example 1 exhibits a peak reflectance wavelength of 683 nm, and the reflectance at the peak reflectance wavelength is 57.3%.

[0156] Referring to Figure 4CFIG. 2 provides a plot of the hue angle (h*) and chroma (c*) of the first surface of the cover plate article of Example 1 at viewing angles from 0° to 90°. From the plot, it is evident that Example 1 exhibits a pink color having a hue angle (h*) of 320-40°, a small change in hue angle (h*) over the 0-90° viewing angle range, and a high chroma (c*) value, resulting in a high saturation. More specifically, Example 1 exhibits a maximum chroma (c*) of 17.29; a maximum saturation (s*) of 0.35; a change in hue angle (h*) over the 0-10° viewing angle range of 0.51°; a change in hue angle (h*) over the 0-30° viewing angle range of 5.15°; a change in hue angle (h*) over the 0-60° viewing angle range of 16.57°; and a change in hue angle (h*) over the 0-90° viewing angle range of 38.04°. Figure 4B FIG. 3 provides a plot of the first surface reflectance color (a* and b*) of the first surface of the cover plate article of Example 1 at viewing angles from 0° to 90° from a D65 illumination source. From the plot, it is evident that Example 1 exhibits a pink color having a hue angle (h*) of 320-40°, a small change in hue angle (h*) over the 0-90° viewing angle range, and a high chroma (c*) value, resulting in a high saturation. More specifically, Example 1 exhibits a maximum chroma (c*) of 17.29; a maximum saturation (s*) of 0.35; a change in hue angle (h*) over the 0-10° viewing angle range of 0.51°; a change in hue angle (h*) over the 0-30° viewing angle range of 5.15°; a change in hue angle (h*) over the 0-60° viewing angle range of 16.57°; and a change in hue angle (h*) over the 0-90° viewing angle range of 38.04°. Example 2 and 4C It is evident from the plots that Example 2 exhibits a pink color having a hue angle (h*) of 320-40°, a small change in hue angle (h*) over the 0-90° viewing angle range, and a high chroma (c*) value, resulting in a high saturation. More specifically, Example 2 exhibits a maximum chroma (c*) of 17.29; a maximum saturation (s*) of 0.35; a change in hue angle (h*) over the 0-10° viewing angle range of 0.51°; a change in hue angle (h*) over the 0-30° viewing angle range of 5.15°; a change in hue angle (h*) over the 0-60° viewing angle range of 16.57°; and a change in hue angle (h*) over the 0-90° viewing angle range of 38.04°.

[0157] Table 2 - Example 1, Cover Plate Article

[0158]

[0159] Figure 5A

[0160] A strengthened glass substrate was coated with the optical film structure of Table 3 below, designated as Example 2. Specifically, the optical film structure of Example 2 had a total of 9 layers with a total thickness of 2684.76 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 9th layer having a thickness of 25.0 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., the 1st layer having a thickness of 82.87 nm).

[0161] FIG. 4 provides a plot of the first surface reflectance of the first surface of the cover plate article of Example 2 at near-normal incidence (about 6°) in the visible and near-infrared spectra. From the plot, it is evident that Example 2 exhibits a peak reflectance wavelength of 690 nm, and the reflectance at the peak reflectance wavelength is 29.1%. Figure 5B FIG. 5 provides a plot of the hue angle (h*) and chroma (c*) of the first surface of the cover plate article of Example 2 at viewing angles from 0° to 90°. From the plot, it is evident that Example 2 exhibits a pink color having a hue angle (h*) of 320-40°, a small change in hue angle (h*) over the 0-90° viewing angle range, and a high chroma (c*) value, resulting in a high saturation. More specifically, Example 2 exhibits a maximum chroma (c*) of 17.29; a maximum saturation (s*) of 0.35; a change in hue angle (h*) over the 0-10° viewing angle range of 0.51°; a change in hue angle (h*) over the 0-30° viewing angle range of 5.15°; a change in hue angle (h*) over the 0-60° viewing angle range of 16.57°; and a change in hue angle (h*) over the 0-90° viewing angle range of 38.04°.

[0162] Figure 5C FIG. 6 provides a plot of the first surface reflectance color (a* and b*) of the first surface of the cover plate article of Example 2 at viewing angles from 0° to 90° from a D65 illumination source. From the plot, it is evident that Example 2 exhibits a pink color having a hue angle (h*) of 320-40°, a small change in hue angle (h*) over the 0-90° viewing angle range, and a high chroma (c*) value, resulting in a high saturation. More specifically, Example 2 exhibits a maximum chroma (c*) of 17.29; a maximum saturation (s*) of 0.35; a change in hue angle (h*) over the 0-10° viewing angle range of 0.51°; a change in hue angle (h*) over the 0-30° viewing angle range of 5.15°; a change in hue angle (h*) over the 0-60° viewing angle range of 16.57°; and a change in hue angle (h*) over the 0-90° viewing angle range of 38.04°. Figure 5B and Example 3 5C ​​It is evident that this example exhibits a yellow color with a hue angle (h*) of 40-125°, with little to no change in the hue angle (h*) over a 0-90° viewing angle range, and with a high chroma (c*) value, resulting in a high saturation. More specifically, this example exhibits a maximum chroma (c*) of 43.07; a maximum saturation (s*) of 1.08; a change in the hue angle (h*) over a 0-10° viewing angle range of 0.67°; a change in the hue angle (h*) over a 0-30° viewing angle range of 3.18°; a change in the hue angle (h*) over a 0-60° viewing angle range of 3.43°; and a change in the hue angle (h*) over a 0-90° viewing angle range of 5.08°.

[0163] Table 3 - Example 2, Cover Plate Article

[0164]

[0165] Figure 6A

[0166] A strengthened glass substrate was coated with the optical film structure of Table 4 below, designated as Example 3. Specifically, the optical film structure of Example 3 had a total of 17 layers with a total thickness of 3212.53 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 17th layer with a thickness of 25.0 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., the 1st layer with a thickness of 85.47 nm).

[0167] Referring to Figure 6B , a plot of the first surface reflectance of the example cover plate article in the visible and near infrared spectrum at near normal incidence (about 6°) is provided. It is evident from the plot that Example 3 exhibits a peak reflectance wavelength of 532 nm, and the reflectance at the peak reflectance wavelength is 35.4%.

[0168] Referring to Figure 6C , a plot of the hue angle (h*) and chroma (c*) of the example cover plate article at viewing angles from 0° to 90° is provided. Additionally, referring to Figure 6B , a plot of the first surface reflected color (a* and b*) of the example cover plate article at viewing angles from 0° to 90° from a D65 illuminant is provided. From Example 4 and 6CIt is evident that this example exhibits green color with a hue angle (h*) of 135-200°, little to no change in hue angle (h*) over a 0-90° viewing angle range, and a high chroma (c*) value resulting in a high saturation. More specifically, this example exhibits a maximum chroma (c*) of 62.72; a maximum saturation (s*) of 1.36; a change in hue angle (h*) over a 0-10° viewing angle range of 1.67°; a change in hue angle (h*) over a 0-30° viewing angle range of 11.41°; a change in hue angle (h*) over a 0-60° viewing angle range of 39.13°; and a change in hue angle (h*) over a 0-90° viewing angle range of 304.15°.

[0169] Table 4 - Example 3, Cover Plate Article

[0170]

[0171] Figure 7A

[0172] A strengthened glass substrate was coated with the optical film structure of Table 5 below, designated as Example 4. Specifically, the optical film structure of Example 4 had a total of 17 layers with a total thickness of 2884.04 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., layer 17 with a thickness of 25.0 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., layer 1 with a thickness of 124.93 nm).

[0173] Referring to Figure 7B , a plot of the first surface reflectance of the cover plate article of this example in the visible and near infrared spectrum at near normal incidence (about 6°) is provided. It is evident from the plot that Example 4 exhibits a peak reflectance wavelength of 435 nm, and the reflectance at the peak reflectance wavelength is 90.2%.

[0174] Referring to Figure 7C , a plot of the hue angle (h*) and chroma (c*) of the cover plate article of this example at viewing angles from 0° to 90° is provided. In addition, referring to Figure 7B , a plot of the first surface reflected color (a* and b*) of the cover plate article of this example at viewing angles from 0° to 90° from a D65 illuminant is provided. From Example 4A and 7CIt is evident that this example exhibits a blue or violet color with a hue angle (h*) of 200-325°, little to no change in hue angle (h*) over a 0-90° viewing angle range, and a high chroma (c*) value resulting in a high saturation. More specifically, this example exhibits a maximum chroma (c*) of 51.13; a maximum saturation (s*) of 0.93; a change in hue angle (h*) over a 0-10° viewing angle range of 0.86°; a change in hue angle (h*) over a 0-30° viewing angle range of 3.24°; a change in hue angle (h*) over a 0-60° viewing angle range of 4.33°; and a change in hue angle (h*) over a 0-90° viewing angle range of 26.82°.

[0175] Table 5 - Example 4, Cover Sheet Article

[0176]

[0177] Figure 8A

[0178] A strengthened glass substrate was coated with the optical film structure of Table 6 below, designated as Example 4A. Specifically, the optical film structure of Example 4A had a total of 17 layers with a total thickness of 2784.11 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 17th layer with a thickness of 25.0 nm), and an oxide-containing cap layer (i.e., the 1st layer with a thickness of 25.0 nm) at the outermost position of the stack. Compared to the cover sheet article of Example 4, the cover sheet article in this example (Example 4A) has a thinner cap layer (25 nm vs. 125 nm), which tends to improve hardness while maintaining strong color performance (e.g., color constancy).

[0179] Referring to Figure 8B , a plot of the first surface reflectance of the example cover sheet article in the visible and near infrared spectrum at near normal incidence (about 6°) is provided. It is evident from the plot that Example 4A exhibits a peak reflectance wavelength of 439 nm, and the reflectance at the peak reflectance wavelength is 90.3%.

[0180] Referring to Figure 8C , a plot of the hue angle (h*) and chroma (c*) of the example cover sheet article at viewing angles from 0° to 90° is provided. Additionally, referring to Figure 8B , a plot of the first surface reflected color (a* and b*) of the example cover sheet article at viewing angles from 0° to 90° from a D65 illuminant is provided. From Example 4B and 8CIt is evident that this example exhibits blue or violet color with a hue angle (h*) of 200-325°, with little to no change in the hue angle (h*) over a 0-90° viewing angle range, and with a high chroma (c*) value, resulting in high saturation. More specifically, this example exhibits: a maximum chroma (c*) of 43.64; a maximum saturation (s*) of 0.70; a change in the hue angle (h*) over a 0-10° viewing angle range of 0.95°; a change in the hue angle (h*) over a 0-30° viewing angle range of 3.82°; a change in the hue angle (h*) over a 0-60° viewing angle range of 3.82°; and a change in the hue angle (h*) over a 0-90° viewing angle range of 12.45°.

[0181] Table 6 - Example 4A, Cover Sheet Article

[0182]

[0183] Figure 10A

[0184] A strengthened glass substrate was coated with the optical film structure of Table 7 below, designated as Example 4B. Specifically, the optical film structure of Example 4B had a total of 17 layers with a total thickness of 2884.04 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 17th layer with a thickness of 25.0 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., the 1st layer with a thickness of 124.93 nm). The cover sheet article of this example (Example 4B) had a strengthened glass ceramic substrate compared to the cover sheet article of Example 4, while the optical film structures of these examples remained the same.

[0185] Referring to Figure 10B , a plot of the first surface reflectance of the cover sheet articles of this example and Example 4 (having a glass ceramic substrate and a strengthened glass substrate, respectively) is provided in the visible and near infrared spectrum at near normal incidence (about 6°). Referring to Figure 10A , a plot of the first surface reflected color (a* and b*) from a D65 illuminant exhibited by the two cover sheet articles of this example (i.e., Examples 4 and 4B) is provided over a 0° to 90° viewing angle. From Example 5 and 10B It is evident that it can be seen that the design performance of this optical film structure design is approximately fully matched and can be readily applied to a glass ceramic substrate even with the same optical film structure layer thicknesses and without further optical tuning.

[0186] Table 7 - Example 4B, Cover Sheet Article

[0187]

[0188] Figure 9A

[0189] A strengthened glass substrate was coated with the optical film structure of Table 8 below, designated as Example 5. Specifically, the optical film structure of Example 5 had a total of 13 layers with a total thickness of 2685.75 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 13th layer with a thickness of 25.0 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., the 1st layer with a thickness of 25.0 nm).

[0190] Referring to Figure 9B , a plot of the first surface reflectance of the present example cover plate article in the visible and near infrared spectrum at near normal incidence (about 6°) is provided. As is evident from the plot, Example 5 exhibits an average reflectance of 36.05% in the visible spectrum (400 nm to 700 nm).

[0191] Referring to Figure 9B , a plot of the hue angle (h*) and chroma (c*) of the present example cover plate article at viewing angles from 0° to 90° is provided. As is evident from Figure 9C , the present example exhibits a gray or silver hue with any hue angle (h*) and maximum chroma (c*) less than 2 over the range of viewing angles from 0-90°, resulting in low saturation. Notably, the reflected color is almost entirely on the L* axis, which represents a black (0) to white (100) scale. L* values in the middle of this axis result in a visually perceptible silver color. Additionally, the present example exhibits a maximum chroma (c*) of 1.84, a maximum saturation (s*) of 0.03, and an L* at normal incidence of 66.82.

[0192] Additionally, referring to Figure 9C , a plot of the first surface reflected color (a* and b*) of the present example cover plate article at viewing angles from 0° to 90° from the D65 illumination source is provided. As is evident from the plot, this design (Example 5) shows a* and b* values near the origin at all viewing angles, and thus shows such low chroma (c*) (resulting in low saturation) that the reflected color is almost entirely on the L* axis, which represents a black (0) to white (100) scale. L* values in the middle of this axis result in a visually perceptible silver color. Additionally, as is evident from Example 6 , the present example exhibits a maximum a* value of 0.01, a maximum b* value of 0.01, a maximum chroma (c*) of 0.02, a maximum saturation (s*) of 0.01, and an L* at normal incidence of 66.82.

[0193] Table 8 - Example 5, Cover Plate Article

[0194]

[0195] Figure 11A

[0196] A strengthened glass substrate was coated with the optical film structure of Table 9 below, designated as Example 6. Specifically, the optical film structure of Example 6 had a total of 7 layers with a total thickness of 624.29 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., layer 7 having a thickness of 25.0 nm), and an oxide-containing capping layer at the outermost position of the stack (i.e., layer 1 having a thickness of 81.52 nm). In addition, the optical film structure in Example 6 had a total of 56.21% high refractive index material.

[0197] See Figure 11B , provides a graph of the first surface reflectance of the cover sheet product of this example at a near normal incidence angle (about 6°) across the visible and near infrared spectra. As is apparent from the graph, Example 6 exhibits a peak reflection wavelength of 700 nm and a reflectance of 56.21% at the peak reflection wavelength.

[0198] See Figure 11C , provides a graph of the hue angle (h*) and chroma (c*) of the cover sheet product of this example at viewing angles of 0° to 90°. Figure 11B , provides a graph of the first surface reflected color (a* and b*) of the cover sheet product of this example from a D65 illuminant at viewing angles of 0° to 90°. Example 7 and 11C It is clear that this example exhibits a pink color with a hue angle (h*) of 320-40°, minimal to no change in the hue angle (h*) within the viewing angle range of 0-90°, and a high chroma (c*) value, resulting in high saturation. More specifically, this example exhibits: a maximum chroma (c*) of 21.27; a maximum saturation (s*) of 1.07; a hue angle (h*) change of 2.02° within the viewing angle range of 0-10°; a hue angle (h*) change of 6.16° within the viewing angle range of 0-30°; a hue angle (h*) change of 6.82° within the viewing angle range of 0-60°; and a hue angle (h*) change of 16.44° within the viewing angle range of 0-90°.

[0199] Table 9 - Example 6, Cover Plate Article

[0200]

[0201] Figure 12A

[0202] A strengthened glass substrate was coated with the optical film structure of Table 10 below, designated as Example 7. Specifically, the optical film structure of Example 7 had a total of 5 layers with a total thickness of 636.94 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 5th layer with a thickness of 25.0 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., the 1st layer with a thickness of 92.27 nm). In addition, the optical film structure in Example 7 had a total of 76.23% high refractive index material.

[0203] Referring to Figure 12B , a plot of the first surface reflectance of the example cover plate article in the visible and near infrared spectrum at near normal incidence (about 6°) is provided. As is evident from the plot, Example 7 exhibits a peak reflectance wavelength of 632 nm, and the reflectance at the peak reflectance wavelength is 11.4%.

[0204] Referring to Figure 12C , a plot of the hue angle (h*) and chroma (c*) of the example cover plate article at viewing angles from 0° to 90° is provided. In addition, referring to Figure 12B , a plot of the first surface reflected color (a* and b*) of the example cover plate article at viewing angles from 0° to 90° from a D65 illuminant is provided. As is evident from Example 8 and 12C , the present example exhibits a yellow color with a hue angle (h*) from 40-125°, little to no change in the hue angle (h*) over the range of viewing angles from 0-90°, and a high chroma (c*) value resulting in a high saturation. More specifically, the present example exhibits a maximum chroma (c*) of 39.49; a maximum saturation (s*) of 1.15; a change in the hue angle (h*) over the range of viewing angles from 0-10° of 0.12°; a change in the hue angle (h*) over the range of viewing angles from 0-30° of 2.84°; a change in the hue angle (h*) over the range of viewing angles from 0-60° of 8.21°; and a change in the hue angle (h*) over the range of viewing angles from 0-90° of 9.30°.

[0205] Table 10 - Example 7, Cover Plate Article

[0206]

[0207] Figure 13A

[0208] A strengthened glass substrate was coated with the optical film structure of Table 11 below, designated as Example 8. Specifically, the optical film structure of Example 8 had a total of 7 layers with a total thickness of 686.55 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 7th layer with a thickness of 25.0 nm) and an oxide-containing overcoat layer at the outermost position of the stack (i.e., the 1st layer with a thickness of 12.62 nm). In addition, the optical film structure in Example 8 had a total of 64.51% high refractive index material.

[0209] Referring to Figure 13B , a plot of the first surface reflectance of the example cover plate article in the visible and near infrared spectrum at near normal incidence (about 6°) is provided. As is evident from the plot, Example 8 exhibits a peak reflectance wavelength of 529 nm, and the reflectance at the peak reflectance wavelength is 30.5%.

[0210] Referring to Figure 13C , a plot of the hue angle (h*) and chroma (c*) of the example cover plate article at viewing angles from 0° to 90° is provided. In addition, referring to Figure 13B , a plot of the first surface reflected color (a* and b*) of the example cover plate article at viewing angles from 0° to 90° from a D65 illuminant is provided. As is evident from Example 9 and 13C , the present example exhibits a green color with a hue angle (h*) of 135-200°, little to no change in the hue angle (h*) over the viewing angle range of 0-90°, and a high chroma (c*) value resulting in a high saturation. More specifically, the present example exhibits a maximum chroma (c*) of 48.59; a maximum saturation (s*) of 0.95; a change in the hue angle (h*) over the viewing angle range of 0-10° of 0.91°; a change in the hue angle (h*) over the viewing angle range of 0-30° of 4.83°; a change in the hue angle (h*) over the viewing angle range of 0-60° of 26.42°; and a change in the hue angle (h*) over the viewing angle range of 0-90° of 105.27°.

[0211] Example 11 - Example 8, Cover Plate Article

[0212]

[0213] Figure 14A

[0214] A strengthened glass substrate was coated with the optical film structure of Table 12 below, designated as Example 9. Specifically, the optical film structure of Example 9 had a total of 7 layers with a total thickness of 458.83 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., layer 7 with a thickness of 25.25 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., layer 1 with a thickness of 8.00 nm). In addition, the optical film structure in Example 9 had a total of 71.13% high refractive index material.

[0215] Referring to Figure 14B , a plot of the first surface reflectance of the example cover plate article in the visible and near infrared spectrum at near normal incidence (about 6°) is provided. As is evident from the plot, Example 9 exhibits a peak reflectance wavelength of 418 nm, and the reflectance at the peak reflectance wavelength is 43.9%.

[0216] Referring to Figure 14C , a plot of the hue angle (h*) and chroma (c*) of the example cover plate article at viewing angles from 0° to 90° is provided. In addition, referring to Figure 14B , a plot of the first surface reflected color (a* and b*) of the example cover plate article at viewing angles from 0° to 90° from a D65 illuminant is provided. As is evident from Example 9A and 14C , the present example exhibits a blue or violet color with a hue angle (h*) of 200-325°, little to no change in the hue angle (h*) over the viewing angle range of 0-90°, and a high chroma (c*) value resulting in a high saturation. More specifically, the present example exhibits a maximum chroma (c*) of 53.76; a maximum saturation (s*) of 1.53; a change in the hue angle (h*) over the viewing angle range of 0-10° of 0.34°; a change in the hue angle (h*) over the viewing angle range of 0-30° of 1.06°; a change in the hue angle (h*) over the viewing angle range of 0-60° of 10.19°; and a change in the hue angle (h*) over the viewing angle range of 0-90° of 30.81°.

[0217] Table 12 - Example 9, Cover Plate Article

[0218]

[0219] Figure 16A

[0220] A strengthened glass substrate was coated with the optical film structure of Table 13 below, designated as Example 9A. Specifically, the optical film structure of Example 9A had a total of 7 layers with a total thickness of 458.83 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 7th layer with a thickness of 25.25 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., the 1st layer with a thickness of 8.0 nm). In comparison to the cover sheet article of Example 9, the cover sheet article in this example (Example 9A) had a strengthened glass ceramic substrate, while the optical film structures of these examples remained the same.

[0221] Referring to Figure 16B , a plot of the first surface reflectance of the cover sheet article of this example and Example 9 (having a glass ceramic substrate) is provided at near normal incidence (about 6°) in the visible and near infrared spectrum. Referring to Figure 16A , a plot of the first surface reflected color (a* and b*) from a D65 illumination source exhibited by both cover sheet articles of this example (i.e., Examples 9 and 9A) is provided over a viewing angle of 0° to 90°. From Example 10 and 16B It is evident that the design performance of this optical film structure design can be seen to match approximately perfectly even with the same optical film structure layer thicknesses and without further optical tuning, and can be readily applied to a glass ceramic substrate.

[0222] Example 13 - Cover Sheet Article of Example 9A

[0223]

[0224] Figure 15A

[0225] A strengthened glass substrate was coated with the optical film structure of Table 14 below, designated as Example 10. Specifically, the optical film structure of Example 10 had a total of 7 layers with a total thickness of 679.7 nm, including alternating high and low refractive index layers, a low RI layer in contact with the substrate (i.e., the 7th layer with a thickness of 25.0 nm), and an oxide-containing cap layer at the outermost position of the stack (i.e., the 1st layer with a thickness of 65.18 nm).

[0226] Referring to Figure 15B , a plot of the first surface reflectance of the cover sheet article of this example is provided at near normal incidence (about 6°) in the visible and near infrared spectrum. It is evident from the plot that Example 10 exhibited an average reflectance of 29.28% in the visible spectrum (400 nm to 700 nm).

[0227] Referring to Figure 15BFIG. 2 provides a plot of the hue angle (h*) and chroma (c*) of the first surface reflected color (a* and b*) of the cover plate article of Example 1 at viewing angles from 0° to 90°. From the plot it is evident that this design (Example 1) shows a* and b* values near the origin at all viewing angles, and thus shows such low chroma (c*) (resulting in low saturation) that the reflected color is almost entirely on the L* axis, which represents a black (0) to white (100) scale. L* values in the middle of this axis result in a visually perceptible silver color. Additionally, from Figure 15C It is evident that this example exhibits a gray or silver hue with any hue angle (h*) and maximum chroma (c*) less than 4 over a viewing angle range of 0-90°, resulting in low saturation. Notably, the reflected color is almost entirely on the L* axis, which represents a black (0) to white (100) scale. L* values in the middle of this axis result in a visually perceptible silver color. Additionally, this example exhibits: a maximum chroma (c*) of 3.89; a maximum saturation (s*) of 0.05; and an L* at normal incidence of 61.61.

[0228] Additionally, referring to Figure 15C FIG. 2 provides a plot of the hue angle (h*) and chroma (c*) of the first surface reflected color (a* and b*) of the cover plate article of Example 1 at viewing angles from 0° to 90°. From the plot it is evident that this design (Example 1) shows a* and b* values near the origin at all viewing angles, and thus shows such low chroma (c*) (resulting in low saturation) that the reflected color is almost entirely on the L* axis, which represents a black (0) to white (100) scale. L* values in the middle of this axis result in a visually perceptible silver color. Additionally, from Summary of Optical and Mechanical Properties for Examples 1-10 It is evident that in this example

[0229] Table 14 - Example 10, Cover Plate Article

[0230]

[0231] Figure 1A

[0232] The optical and mechanical properties of Examples 1-10 are summarized in Tables 15A-15E below. Tables 15A-C below show the reflectivity properties of the cover plate articles and optical film structures of the foregoing examples. Among these metrics, some of the most important properties to note are the normal incidence angle (0 degrees) chroma (c*) value, the normal incidence hue angle (h*) value, and the change in hue angle (h*) over a viewing angle range of 0-30, 0-60, and 0-90 degrees (“Ah*”). Unless otherwise noted, the color metrics listed in Tables 15A-C are for the first surface (the surface of the substrate with the optical film structure) reflectivity. Additionally, unless otherwise noted, all color values are reported using the CIE D65 illuminant.

[0233] Referring again to Tables 15A-C below, normal incidence color coordinates are provided with maximum chromaticity (c*), hue angle (h*), and calculated saturation (s*). Also provided are particularly attractive performance parameters for these designs, showing minimal variation in hue angle across a range of incident viewing angles. Additionally, the silver and gray designs (Examples 5 and 10) have very low maximum chromaticity (c*) values. Compared to the other color designs (Examples 1-4 and 6-9), low maximum chromaticity (c*) is more important than hue angle (h*) for designs targeting silver or gray hues.

[0234] The first six examples in these tables are described in detail above and Figure 1B The bottom five examples in these tables are the same as those described in detail above and Figure 1A . Furthermore, for viewing angles of 0-30 degrees, the change in hue angle (h*) (also referred to in these tables as "reflectance hue (h*) delta") can be less than 15 degrees, less than 10 degrees, less than 8 degrees, less than 6 degrees, or even less than 5 degrees. The reflectance hue (h*) delta at viewing angles of 0-60 degrees can be less than 50 degrees, less than 40 degrees, less than 30 degrees, less than 20 degrees, less than 10 degrees, or even less than 5 degrees. The calculated reflectance values ​​for Examples 1-10 are listed in Tables 15A-C; however, examples where cells are denoted with (**) indicate a specific parameter not relevant to the specific example (e.g., hue angle change / delta for neutral gray or silver examples).

[0235] Table 15A - Reflectivity Properties of Cover Sheet Articles (Examples 1-10)

[0236]

[0237] Table 15B - Reflectivity Properties of Cover Sheet Articles (Examples 1-10)

[0238]

[0239] Table 15C - Reflectivity Properties of Cover Sheet Articles (Examples 1-10)

[0240]

[0241] The transmittance properties of the cover sheet article examples (Examples 1-10) are provided in Table 15D below. The normal incidence color coordinates with maximum chromaticity (c*), hue angle (h*), and calculated saturation (s*) are provided. The first six examples in these tables are similar to those described in detail above and Figure 1B The bottom five examples in these tables are the same as those described in detail above and Figure 1AThe cover plate articles depicted in FIGS. 15A-15D are consistent with the designs described in the specification. In some applications, such as direct view display applications, the photopic average transmittance (Y) can be greater than 60%, 70%, 80%, or 85%. In some cases, the transmitted color can have a chroma (c*) value of less than 20, less than 15, less than 10, less than 8, or even less than 5. The calculated transmittance measurements for Examples 1-10 are listed in Table 15D.

[0242] Table 15D - Transmittance Properties of Cover Plate Articles (Examples 1-10)

[0243]

[0244] The mechanical properties of the cover plate article examples (Examples 1-10) are provided in the following Table 15E. As with the transmittance properties, the mechanical properties of the cover plate articles depicted in FIGS. 15A-15D are consistent with the designs described in the specification. Figure 1B The cover plate article designs consistent with the cover plate articles (Examples 1-5) depicted in FIGS. 15A-15D use a layer configuration that includes a 2000 nm scratch resistant layer on top of the optical film structure, which helps these articles exhibit their overall high hardness values. As with the transmittance properties, the mechanical properties of the cover plate articles depicted in FIGS. 15A-15D are consistent with the designs described in the specification. ​ The cover plate article designs consistent with the cover plate articles (Examples 6-10) depicted in FIGS. 15A-15D use a layer configuration that uses a high refractive index layer collectively as a scratch resistant layer and constitutes >50% of the overall volume or thickness of the optical film structure stack. Additionally, the optical film structures of these designs have an outermost high refractive index hard layer that maintains a greater thickness than the outermost low refractive index layer, which also helps these articles exhibit their overall high hardness values. The complete hardness measurements are listed in Table 15E (far right column), and the examples for which the cell is denoted as (**) do not have complete hardness measurements. The other columns in Table 15E represent the modeled structural parameters for the particular example (e.g., total thickness of the optical film structure, nm; % high RI material, etc.).

[0245] Table 15E - Mechanical Properties of Cover Plate Articles (Examples 1-10)

[0246]

[0247] The various features described in the specification can be combined in any and all combinations, for example, the following examples. It should also be understood that, where necessary, the B- side (i.e., the interior major surface 114) of the substrate 110 can include surface treatments to provide additional desired appearances, as necessary. For example, these surface treatments can include engineered levels of surface roughness, one or more additional dielectric layers, and / or one or more ink layers.

[0248] Example 1. A cover plate article is provided, the cover plate article comprising: a substrate comprising an exterior major surface and an interior major surface, the exterior major surface and the interior major surface opposing one another; and an optical film structure comprising an outermost surface disposed on the exterior major surface or the interior major surface of the substrate. The optical film structure comprises a plurality of alternating high refractive index layers and low refractive index layers. Each of the high refractive index layers has a refractive index greater than a refractive index of each of the low refractive index layers. Additionally, the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as a change in hue angle (h*) of the exhibited color over a range of viewing angles from 0 to 60 degrees of less than 50 degrees.

[0249] Example 2. The cover plate article of Example 1 is provided, wherein the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as a change in hue angle (h*) of the exhibited color over a range of viewing angles from 0 to 90 degrees of less than 225 degrees.

[0250] Example 3. The cover plate article of Example 1 or Example 2 is provided, wherein the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as a change in hue angle (h*) of the exhibited color over a range of viewing angles from 0 to 30 degrees of less than 15.

[0251] Example 4. The cover plate article of any of Examples 1 to 3 is provided, wherein the cover plate article exhibits an average photopic transmittance of greater than 60% at a normal viewing angle of about 0 degrees.

[0252] Example 5. The cover plate article of any of Examples 1 to 4 is provided, wherein the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as exhibiting a pink or red color having a hue angle (h*) of 320 degrees to 40 degrees and a chroma (c*) of greater than 15.

[0253] Example 6. The cover plate article of any of Examples 1 to 4 is provided, wherein the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as exhibiting a yellow color having a hue angle (h*) of 40 degrees to 135 degrees and a chroma (c*) of greater than 15.

[0254] Example 7. The cover plate article of any of Examples 1 to 4 is provided, wherein the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as exhibiting a green color having a hue angle (h*) of 135 degrees to 200 degrees and a chroma (c*) of greater than 15.

[0255] Example 8. There is provided the cover sheet article of any of Examples 1-4, wherein the cover sheet article exhibits a substantially constant reflected color hue under D65 illuminant, manifested as exhibiting a blue or purple color having a hue angle (h*) of 200 to 320 degrees and a chroma (c*) greater than 15.

[0256] Example 9. There is provided a cover sheet article comprising: a substrate comprising an exterior major surface and an interior major surface, wherein the exterior major surface and the interior major surface are opposite each other; and an optical film structure comprising an outermost surface disposed on the exterior major surface or the interior major surface of the substrate. The optical film structure comprises a plurality of alternating high refractive index layers and low refractive index layers. Each of the high refractive index layers has a refractive index greater than each of the low refractive index layers. The optical film structure has a physical thickness in the range of 1000 nm to 4000 nm. One of the high refractive index layers is a scratch resistant layer having a physical thickness of 500 nm to 3000 nm. One of the low refractive index layers is a cover layer disposed over the scratch resistant layer. A portion of the plurality of alternating high refractive index layers and low refractive index layers are between the scratch resistant layer and the substrate. The optical film structure exhibits a hardness of at least 12 GPa when measured from the outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm using the Knoop hardness test. Additionally, the cover sheet article exhibits a substantially constant reflected color hue under D65 illuminant, manifested as the exhibited color having a change in hue angle (h*) of less than 50 degrees over a viewing angle range of 0 to 60 degrees.

[0257] Example 10. There is provided the cover sheet article of Example 9, wherein the cover sheet article exhibits a substantially constant reflected color hue under D65 illuminant, manifested as the exhibited color having a change in hue angle (h*) of less than 20 degrees over a viewing angle range of 0 to 60 degrees.

[0258] Example 11. There is provided the cover sheet article of Example 10, wherein the scratch resistant layer is a nitride or oxynitride and has a physical thickness of 800 nm to 2500 nm, and wherein the cover layer is an oxide.

[0259] Example 12. There is provided the cover sheet article of any of Examples 9-11, wherein the cover layer is in contact with the scratch resistant layer, is the outermost layer of the optical film structure, and has a physical thickness of 20 nm to 250 nm.

[0260] Example 13. There is provided the cover sheet article of any of Examples 9-11, wherein the cover layer is the only layer over the scratch resistant layer, having a physical thickness greater than 20 nm.

[0261] Example 14. There is provided a cover sheet article according to any of Examples 9-13, wherein one of the low refractive index layers is in contact with an exterior major surface or an interior major surface of the substrate, and the optical film structure comprises 5 to 19 layers.

[0262] Example 15. There is provided a cover sheet article according to any of Examples 9-14, wherein the cover sheet article exhibits a substantially constant reflected color hue under a D65 illuminant, manifested as exhibiting a pink or red color having a hue angle (h*) of 320 degrees to 40 degrees and a chroma (c*) greater than 15.

[0263] Example 16. There is provided a cover sheet article according to any of Examples 9-14, wherein the cover sheet article exhibits a substantially constant reflected color hue under a D65 illuminant, manifested as exhibiting a yellow color having a hue angle (h*) of 40 degrees to 135 degrees and a chroma (c*) greater than 15.

[0264] Example 17. There is provided a cover sheet article according to any of Examples 9-14, wherein the cover sheet article exhibits a substantially constant reflected color hue under a D65 illuminant, manifested as exhibiting a green color having a hue angle (h*) of 135 degrees to 200 degrees and a chroma (c*) greater than 15.

[0265] Example 18. There is provided a cover sheet article according to any of Examples 9-14, wherein the cover sheet article exhibits a substantially constant reflected color hue under a D65 illuminant, manifested as exhibiting a blue or violet color having a hue angle (h*) of 200 degrees to 320 degrees and a chroma (c*) greater than 15.

[0266] Example 19. There is provided a cover sheet article comprising: a substrate comprising an exterior major surface and an interior major surface, wherein the exterior major surface and the interior major surface are opposite each other; and an optical film structure comprising an outermost surface disposed on the exterior major surface or the interior major surface of the substrate. The optical film structure comprises a plurality of alternating high refractive index layers and low refractive index layers. Each of the high refractive index layers has a refractive index greater than that of each of the low refractive index layers. The optical film structure has a physical thickness in the range of 250 nm to 1000 nm. The optical film structure exhibits a hardness of at least 8 GPa when measured from the outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm using a Berkovich Indenter Hardness Test. Additionally, the cover sheet article exhibits a substantially constant reflected color hue under a D65 illuminant, manifested as exhibiting a color having a change in hue angle (h*) of less than 50 degrees over a viewing angle range of 0 to 60 degrees.

[0267] Example 20. There is provided the cover plate article of Example 19, wherein each of the high refractive index layers is a nitride or oxynitride, and the low refractive index layers are oxides.

[0268] Example 21. There is provided the cover plate article of Example 19 or Example 20, wherein one of the low refractive index layers is in contact with the outer major surface or the inner major surface of the substrate, and the optical film structure comprises 5 to 12 layers.

[0269] Example 22. There is provided the cover plate article of any of Examples 19-21, wherein the high refractive index layers collectively comprise more than 50% of the volume or physical thickness of the optical film structure.

[0270] Example 23. There is provided the cover plate article of any of Examples 19-22, wherein the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as exhibiting a pink or red color having a hue angle (h*) of 320 degrees to 40 degrees and a chroma (c*) greater than 15.

[0271] Example 24. There is provided the cover plate article of any of Examples 19-22, wherein the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as exhibiting a yellow color having a hue angle (h*) of 40 degrees to 135 degrees and a chroma (c*) greater than 15.

[0272] Example 25. There is provided the cover plate article of any of Examples 19-22, wherein the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as exhibiting a green color having a hue angle (h*) of 135 degrees to 200 degrees and a chroma (c*) greater than 15.

[0273] Example 26. There is provided the cover plate article of any of Examples 19-22, wherein the cover plate article exhibits a substantially constant reflected hue under a D65 illuminant, manifested as exhibiting a blue or violet color having a hue angle (h*) of 200 degrees to 320 degrees and a chroma (c*) greater than 15.

[0274] Example 27. A cover plate article is provided, the cover plate article comprising: a substrate comprising an exterior major surface and an interior major surface, wherein the exterior major surface and the interior major surface are opposite one another; and an optical film structure comprising an outermost surface disposed on the exterior major surface or the interior major surface of the substrate. The optical film structure comprises a plurality of alternating high refractive index layers and low refractive index layers. Each of the high refractive index layers has a refractive index that is greater than a refractive index of each of the low refractive index layers. Additionally, the cover plate article exhibits a substantially neutral reflected color under D65 illumination, manifested as exhibiting a gray or silver color tone, each having a chroma (c*) of less than 10.

[0275] Example 28. The cover plate article of Example 27 is provided, the cover plate article exhibits a substantially neutral reflected color under D65 illumination, manifested as exhibiting a gray or silver color tone, each having a chroma (c*) of less than 5.

[0276] Example 29. The cover plate article of any of Examples 26-27 is provided, wherein the optical film structure has a physical thickness in a range from 1000 nm to 4000 nm, one of the high refractive index layers is a scratch resistant layer having a physical thickness of 500 nm to 3000 nm, one of the low refractive index layers is a cover layer disposed over the scratch resistant layer, a portion of the plurality of alternating high refractive index layers and low refractive index layers are between the scratch resistant layer and the substrate, and the optical film structure exhibits a hardness of at least 12 GPa when measured from the outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm using a Berkovich Indenter Hardness Test.

[0277] Example 30. The cover plate article of any of Examples 26-27 is provided, wherein the optical film structure has a physical thickness in a range from 250 nm to 1000 nm, and the optical film structure exhibits a hardness of at least 8 GPa when measured from the outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm using a Berkovich Indenter Hardness Test.

Claims

1. A cover plate product, comprising: a substrate comprising an outer major surface and an inner major surface, wherein the outer major surface and the inner major surface are opposite to each other; and an optical film structure comprising an outermost surface disposed on the outer major surface or the inner major surface of the substrate, The optical film structure comprises a plurality of alternating high refractive index layers and low refractive index layers. wherein the refractive index of each of the high refractive index layers is greater than the refractive index of each of the low refractive index layers, and The cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, as indicated by a hue angle (h*) variation of less than 50 degrees within a viewing angle range of 0 to 60 degrees.

2. The cover sheet product of claim 1 , wherein the cover sheet product exhibits a substantially constant reflected hue under D65 illuminant, as indicated by a hue angle (h*) variation of less than 225 degrees over a viewing angle range of 0 to 90 degrees.

3. The cover sheet product of claim 1 or claim 2, wherein the cover sheet product exhibits a substantially constant reflected hue under D65 illuminant, as indicated by a hue angle (h*) variation of less than 15 degrees over a viewing angle range of 0 to 30 degrees.

4. The cover sheet article of any one of claims 1 to 3, wherein the cover sheet article exhibits an average photopic transmittance greater than 60% at a normal viewing angle of about 0 degrees.

5. The cover sheet product according to any one of claims 1 to 4, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to be pink or red, with a hue angle (h*) of 320 degrees to 40 degrees and a chroma (c*) greater than 15.

6. The cover sheet product according to any one of claims 1 to 4, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to be yellow, with a hue angle (h*) of 40 degrees to 135 degrees and a chroma (c*) greater than 15.

7. The cover sheet product of any one of claims 1 to 4, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to exhibit a green color with a hue angle (h*) of 135 to 200 degrees and a chroma (c*) greater than 15.

8. The cover sheet product according to any one of claims 1 to 4, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to be blue or purple, with a hue angle (h*) of 200 to 320 degrees and a chroma (c*) greater than 15.

9. A cover product, comprising: a substrate comprising an outer major surface and an inner major surface, wherein the outer major surface and the inner major surface are opposite to each other; and an optical film structure comprising an outermost surface disposed on the outer major surface or the inner major surface of the substrate, The optical film structure comprises a plurality of alternating high refractive index layers and low refractive index layers. wherein the refractive index of each of the high refractive index layers is greater than the refractive index of each of the low refractive index layers, wherein the optical film structure has a physical thickness in the range of 1000 nm to 4000 nm, One of the high refractive index layers is a scratch resistant layer having a physical thickness of 500 nm to 3000 nm, One of the low refractive index layers is a cover layer disposed above the scratch resistant layer, wherein a portion of the plurality of alternating high refractive index layers and low refractive index layers is located between the scratch-resistant layer and the substrate, wherein the optical film structure exhibits a hardness of at least 12 GPa when measured using a Berkovich Indenter Hardness Test from the outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm, and The cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, as indicated by a hue angle (h*) variation of less than 50 degrees within a viewing angle range of 0 to 60 degrees.

10. The cover sheet product of claim 9, wherein the cover sheet product exhibits a substantially constant reflected hue under D65 illuminant, as indicated by a hue angle (h*) variation of less than 20 degrees over a viewing angle range of 0 to 60 degrees.

11. The cover sheet article of any one of claims 9 to 10, wherein the scratch-resistant layer is a nitride or an oxynitride and has a physical thickness of 800 nm to 2500 nm, and wherein the capping layer is an oxide.

12. The cover article according to any one of claims 9 to 11, wherein the cover layer is in contact with the scratch-resistant layer, is the outermost layer of the optical film structure and has a physical thickness of 20 nm to 250 nm.

13. The cover sheet article according to any one of claims 9 to 11, wherein the cover layer is the only layer located above the scratch-resistant layer and has a physical thickness greater than 20 nm.

14. The cover article of any one of claims 9 to 13, wherein one of the low refractive index layers is in contact with an exterior major surface or an interior major surface of the substrate, and the optical film structure comprises 5 to 19 layers.

15. The cover sheet product according to any one of claims 9 to 14, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to be pink or red, with a hue angle (h*) of 320 degrees to 40 degrees and a chroma (c*) greater than 15.

16. The cover sheet product of any one of claims 9 to 14, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to be yellow, with a hue angle (h*) of 40 to 135 degrees and a chroma (c*) greater than 15.

17. The cover sheet product of any one of claims 9 to 14, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to exhibit a green color with a hue angle (h*) of 135 to 200 degrees and a chroma (c*) greater than 15.

18. The cover sheet product of any one of claims 9 to 14, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to be blue or purple, with a hue angle (h*) of 200 to 320 degrees and a chroma (c*) greater than 15.

19. A cover product, comprising: a substrate comprising an outer major surface and an inner major surface, wherein the outer major surface and the inner major surface are opposite to each other; and an optical film structure comprising an outermost surface disposed on the outer major surface or the inner major surface of the substrate, The optical film structure comprises a plurality of alternating high refractive index layers and low refractive index layers. wherein the refractive index of each of the high refractive index layers is greater than the refractive index of each of the low refractive index layers, wherein the optical film structure has a physical thickness in the range of 250 nm to 1000 nm, wherein the optical film structure exhibits a hardness of at least 8 GPa when measured from the outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm using a Bosch indenter hardness test, and The cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, as indicated by a hue angle (h*) variation of less than 50 degrees within a viewing angle range of 0 to 60 degrees.

20. The cover sheet product of claim 19, wherein each of the high refractive index layers is a nitride or an oxynitride, and the low refractive index layer is an oxide.

21. The cover article of claim 19 or claim 20, wherein one of the low refractive index layers is in contact with an exterior major surface or an interior major surface of the substrate, and the optical film structure comprises 5 to 12 layers.

22. The cover article of any one of claims 19 to 21, wherein the high refractive index layers collectively comprise greater than 50% of the volume or physical thickness of the optical film structure.

23. The cover sheet product of any one of claims 19 to 22, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to be pink or red, with a hue angle (h*) of 320 to 40 degrees and a chroma (c*) greater than 15.

24. The cover sheet product of any one of claims 19 to 22, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to be yellow, with a hue angle (h*) of 40 to 135 degrees and a chroma (c*) greater than 15.

25. The cover sheet product of any one of claims 19 to 22, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to exhibit a green color with a hue angle (h*) of 135 to 200 degrees and a chroma (c*) greater than 15.

26. The cover sheet product of any one of claims 19 to 22, wherein the cover sheet product exhibits a substantially constant reflective hue under D65 illuminant, appearing to be blue or purple, with a hue angle (h*) of 200 to 320 degrees and a chroma (c*) greater than 15.

27. A cover board product, comprising: a substrate comprising an outer major surface and an inner major surface, wherein the outer major surface and the inner major surface are opposite to each other; and an optical film structure comprising an outermost surface disposed on the outer major surface or the inner major surface of the substrate, The optical film structure comprises a plurality of alternating high refractive index layers and low refractive index layers. wherein the refractive index of each of the high refractive index layers is greater than the refractive index of each of the low refractive index layers, and The cover sheet article exhibits a substantially neutral reflected color under D65 illuminant, manifested as exhibiting a gray hue or a silver hue, each having a chroma (c*) of less than 10.

28. The cover sheet article of claim 27, wherein the cover sheet article exhibits a substantially neutral reflected color under D65 illuminant, manifested as exhibiting a gray hue or a silver hue, each having a chroma (c*) of less than 5.

29. The cover sheet product according to any one of claims 27 to 28, wherein: The optical film structure has a physical thickness in the range of 1000 nm to 4000 nm, One of the high refractive index layers is a scratch resistant layer having a physical thickness of 500 nm to 3000 nm, One of the low refractive index layers is a cover layer disposed above the scratch resistant layer, A portion of the plurality of alternating high and low refractive index layers is located between the scratch resistant layer and the substrate, and The optical film structure exhibits a hardness of at least 12 GPa when measured using a Bosch Indenter Hardness Test from an outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm.

30. The cover sheet product according to any one of claims 27 to 28, wherein: The optical film structure has a physical thickness in the range of 250 nm to 1000 nm, and The optical film structure exhibits a hardness of at least 8 GPa when measured using a Bosch Indenter Hardness Test from an outermost surface of the optical film structure to a depth of about 100 nm to about 300 nm.

Images