Antimicrobial articles with copper nanoparticles and methods of making and using same

ANTIMICROBIAL ARTICLES WITH COPPER NANOPARTICLES AND METHODS OF MAKING AND USING SAME

[0001] This application claims the benefit of priority under 35 U.S.C. § 1 19 of U.S.

Provisional Application Serial No. 62/038993 filed on August 19, 2014 the content of which is relied upon and incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates generally to antimicrobial articles. Embodiments described herein relate to glass and glass-ceramic articles having improved antimicrobial behavior, as well as to methods of making and using the articles. The embodiments include surfaces of such articles that contain copper and/or copper oxide particles.

BACKGROUND

[0003] Touch-activated or -interactive devices, such as screen surfaces (e.g., surfaces of electronic devices having user- interactive capabilities that are activated by touching specific portions of the surfaces), have become increasingly more prevalent. In general, these surfaces should exhibit high optical transmission, low haze, and high durability, among other features. As the extent to which the touch screen-based interactions between a user and a device increases, so too does the likelihood of the surface harboring microorganisms (e.g., bacteria, fungi and viruses) that can be transferred from user to user.

[0004] To minimize the presence of microbes on these surfaces, so-called "antimicrobial" properties have been imparted to a variety of glass and glass-ceramic articles. Such articles, regardless of whether they are used as screen surfaces of touch-activated devices or in other applications, can exhibit poor antimicrobial efficacy under ordinary use conditions despite performing adequately under generally-accepted or standardized testing conditions; can exhibit poor optical or aesthetic properties when exposed to certain conditions during fabrication and/or ordinary use; and/or can be costly to manufacture (e.g., when expensive metals or alloys are used as the antimicrobial agent or when additional steps are required to introduce the antimicrobial agent into or onto the surface). These deficiencies ultimately can make it impractical to implement the antimicrobial articles.

[0005] The biological activity of copper is due in a large part to its ability to exist in what is termed the "free" state as metallic copper or "ionic" state as a copper salt or oxide. While copper is almost always combined with other elements or minerals, under certain conditions copper can exist in the ionic or free copper state, both of which are biologically active and thus give copper the ability to kill bacteria, viruses and fungi.

[0006] Copper and its salts and oxides, have been used since antiquity to treat a wide variety of ailments and injuries. Medical uses of copper date back to Egyptian medical texts written between 2600 and 2200 B.C., some of which describe using copper to sterilize chest wounds and drinking water. Other ancient Greek texts (written around 1500 B.C.) describe medicinal uses of copper, in metallic, salt and oxide forms. In addition, for many centuries it was known that water could be transported in copper containers with little or no slime formation. Copper coins or bars were placed in wooden or clay water vessels for the same purpose.

[0007] With the discovery of the existence of microbes in the 1800s, the antimicrobial properties of copper and its compounds became more widely investigated, and these investigations have continued to the present day. While there has been some discussion in the literature of using elemental copper and copper ions as antimicrobial agents, most of it has been generalized. There has not been a description of the specific nature of how particular copper species and forms (e.g., copper nanoparticles) can be employed to obtain and optimize antimicrobial efficacy without detriment to other properties and capabilities of the product.

[0008] There accordingly remains a need for technologies that provide glass, glass- ceramics or other types of articles with improved antimicrobial efficacy under both ordinary use and generally-accepted testing conditions. It would be particularly advantageous if such technologies did not adversely affect other desirable properties of the articles, such as optical or aesthetic properties. It would also be advantageous if such technologies could be produced in a relatively low-cost manner. It is to the provision of such technologies that the present disclosure is directed.

BRIEF SUMMARY

[0009] Described herein are various antimicrobial glass and glass-ceramic articles that have improved antimicrobial efficacy, along with methods for their manufacture and use.

[0010] Embodiments are directed to providing the antimicrobial property of Cu to a glass or glass-ceramic article through the deposition of Cu-containing nanoparticles to one or more surfaces of the article. Processes by which this can be accomplished include but are not limited to dip-coating, spin coating, slot coating, curtain coating or spray coating onto the surface of the glass or glass-ceramic from a suspension of Cu, Ο¾0 or CuO nanoparticles in water or a solvent. The glass or glass-ceramic is then heated in air or an inert atmosphere (e.g., nitrogen or helium) to a temperature sufficient to seal, embed, infuse or otherwise adhere the particles to the glass or glass-ceramic. In one aspect, the process can employ CuO as the base composition for the initial nanoparticles, and a subsequent step can be conducted to reduce the initial CuO nanoparticles to nanoparticles that include primarily Cu or a Cu shell and CuO core. The nanoparticle composition and concentration of the nanoparticles on the surface of a transparent substrate that comprises glass or a glass-ceramic determine the ultimate optical transmission. Further, the extent of the reduction of the CuO particles to pure or virtually pure Cu nanoparticles or nanoparticles having a CuO core and Cu shell is dependent on the reduction process parameters employed, including the reducing atmosphere, temperature and exposure time. Consequently, it is possible to provide antimicrobial action to an otherwise transparent glass or glass-ceramic, including a glass or glass-ceramic that has been thermally or chemically strengthened, for example, chemically strengthened by ion- exchanges of larger cations from an ion-exchange bath for smaller cations present in the glass or glass-ceramic.

[0011] The antimicrobial action from the Cu-containing nanoparticles on the surface of a glass or glass-ceramic can also be in addition to antimicrobial properties afforded from other antimicrobial agents, such as Ag⁺ ions, incorporated into the surface and depth of the article through ion exchange processes. In addition, a coating of a material that facilitates easy cleaning of the surface of the glass or glass-ceramic, for example a fluorosilane compound, or other coating that resists or minimizes the effects of fingerprint transfer or smudging, can be applied to the Cu-containing nanoparticle- lad en surface of the glass or glass-ceramic without affecting the antimicrobial function.

[0012] With regard to Cu, CuO, and Ο¾0, all have shown antibacterial behavior at different surface concentrations, but only Cu has shown antiviral behavior. CuO is not an antiviral material; therefore, in order to have an antimicrobial effect, in the case of using CuO as the initial nanoparticle, it is necessary to have a reduction step. In some aspects, after sintering and/or ion-exchange, the Cu-containing nanoparticles on the glass or glass-ceramic are reduced to Cu-containing or Cu and CuO -containing nanoparticles. The Cu-containing nanoparticle composition and concentration placed on the glass, glass-ceramic or other substrate can be tuned to an optimized optical transmission so it is possible to provide antimicrobial action to an otherwise transparent glass or glass-ceramic, or chemically- strengthened and/or antimicrobial agent-enhanced glass or glass-ceramic. Further, the Cu- containing nanoparticle composition and concentration can be tuned to provide self- passivation of the particles upon exposure to oxidizing conditions associated with the application environment of the antimicrobial article employing the nanoparticles, thus enhancing the antimicrobial efficacy of these articles over the complete life of the article. In some implementations, self-passivation capability is obtained by reducing CuO nanoparticles such that that the average radius of the remaining CuO core relative to the average total radius of the nanoparticles (i.e., the reduced nanoparticles now include a Cu° shell) is 35% or less.

[0013] One type of an improved antimicrobial article includes an article having a glass or glass-ceramic composition and a plurality of primary surfaces; and an antimicrobial structure disposed on at least one of the primary surfaces. The antimicrobial structure comprises a plurality of copper nanoparticles configured to self-passivate under lifetime conditions of the article.

[0014] Another type of an improved antimicrobial article includes an article having a glass or glass-ceramic composition and a plurality of primary surfaces; a compressive stress region in the article extending from at least one of the primary surfaces to a first selected depth in the article; and an antimicrobial structure disposed on at least one of the primary surfaces. The antimicrobial structure comprises a plurality of copper nanoparticles configured to self-passivate under lifetime conditions of the article.

[0015] A further type of an improved antimicrobial article includes an article having a glass or glass-ceramic composition and a plurality of primary surfaces; a compressive stress region in the article extending from at least one of the primary surfaces to a first selected depth in the article; an antimicrobial region containing a plurality of silver ions extending from at least one of the primary surfaces to a second selected depth in the article; and an antimicrobial structure disposed on at least one of the primary surfaces. The antimicrobial structure comprises a plurality of copper nanoparticles configured to self-passivate under lifetime conditions of the article.

[0016] These types of antimicrobial articles can further include an additional layer disposed on the surface of the article. The additional layer can include a reflection-resistant coating, a glare-resistant coating, fingerprint-resistant coating, smudge-resistant coating, a color-providing composition, an environmental barrier coating, or an electrically conductive coating.

[0017] In certain implementations of these antimicrobial articles, the copper nanoparticles comprise nanoparticles having a copper metal shell and a copper oxide core. In some aspects, the average core radius of these nanoparticles is less than or equal to 35%, 25% or 20% of an average radius of the core and the shell.

[0018] In certain implementations of these improved antimicrobial articles, a compressive stress of the compressive stress layer can be about 200 megapascals to about 1.2 gigapascals, and/or the depth of the compressive stress layer can be greater than or equal to about 25 micrometers and less than or equal to about 100 micrometers.

[0019] In some implementations of these types of improved antimicrobial articles, the antimicrobial region can include a cationic monovalent silver species, cationic monovalent copper species, cationic divalent zinc species, and/or a quaternary ammonium species.

[0020] In certain situations, an antimicrobial agent concentration of an outermost 3 nanometers of the antimicrobial region is up to about 10 atomic percent, based on a total number of atoms of the outermost 3 nanometers of the antimicrobial region.

[0021] These types of antimicrobial articles can exhibit at least a 1 log reduction in a concentration of at least Staphylococcus aureus, Enterobacter aerogenes, and Pseudomonas aeruginosa bacteria under testing conditions consistent with the Test Method for Efficacy of Copper Alloy Surfaces as a Sanitizer, approved by the U.S. Environmental Protection Agency ("EPA-approved Dry Test"). The EPA-approved Dry Test is conducted under ambient conditions (i.e., at < 42% RH, ~23°C). Certain aspects of these antimicrobial articles can also exhibit at least a 3 log reduction in a concentration of at least Staphylococcus aureus, Enterobacter aerogenes, and Pseudomonas aeruginosa bacteria under the EPA-approved Dry Test.

[0022] These types of improved antimicrobial glass articles can serve as a portion of a touch-sensitive display screen or cover plate for an electronic device, a non-touch-sensitive component of an electronic device, a surface of a household appliance, a surface of medical equipment, a surface of an architectural component, a biological or medical packaging vessel, or a surface of a vehicle component.

[0023] In one embodiment, a method of making an antimicrobial article having a glass or glass-ceramic composition comprises the deposition of a copper oxide nanoparticle coating onto the surface of the article by dip-coating, spin coating, spraying or other coating method(s) that are capable of depositing a suspension of CuO or CU2O nanoparticles at about 5 to 10 wt% in water, or other suitable fluid, onto a surface of the glass or glass-ceramic and drying the suspension on the surface. Drying can be carried out at a temperature in the range of 100°C to 130°C. The drying time can range from 1 hour to 4 hours, for example. In a subsequent step, the copper-containing nanoparticles can be embedded into a surface of the glass or glass-ceramic article by a thermal treatment in air, typically at 650°C to 700°C. Next, the copper-containing nanoparticles are subjected to a reduction process at 450°C to 700°C for about 1 hour to 5 hours in a reducing atmosphere, such as 100% H₂ gas, at a time and temperature sufficient to reduce the nanoparticles such that the average radius of the copper oxide core relative to the average total radius of the nanoparticles (i.e., the reduced nanoparticles now include a Cu° shell) is 35% or less. As applicable, further ion exchange processes can be conducted to chemically strengthen the glass or glass-ceramic article and/or impart additional antimicrobial agents (e.g., Ag⁺ ions) into the surface and depth of the article.

[0024] In one aspect, the method of making an antimicrobial article includes providing a glass or glass-ceramic substrate having a compressive stress layer that extends inward from a surface of the substrate to a first depth, and forming an antimicrobial agent-containing region that extends inward from the surface of the substrate to a second depth, such that the second depth is less than or equal to about 200 nanometers.

[0025] In some cases, the method can also include forming an additional functional layer on at least a portion of the surface of the substrate, wherein the additional functional layer comprises a reflection-resistant coating, a glare-resistant coating, fingerprint-resistant coating, smudge-resistant coating, a color-providing composition, an environmental barrier coating, or an electrically conductive coating.

[0026] In some cases, the step of forming the additional functional layer can occur before the step of forming the antimicrobial agent-containing region.

[0027] In some cases, providing the glass or glass-ceramic substrate having the compressive stress layer can involve providing the substrate; and forming the compressive stress layer in the substrate by thermal tempering or chemical ion exchanging.

[0028] In some cases, forming the antimicrobial agent-containing region can involve contacting at least a portion of the surface of the glass or glass-ceramic substrate with an antimicrobial agent-containing solution effective to introduce antimicrobial agents on and into the substrate to the second depth. It is possible for the contacting step to occur for less than or equal to about 24 hours at a temperature of less than or equal to about 120 degrees

Celsius.

[0029] It is to be understood that both the foregoing brief summary and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a schematic an antimicrobial article with an antimicrobial structure disposed on a primary surface according to an aspect of the disclosure.

[0031] FIG. 2 is a schematic of a method of reducing copper-containing nanoparticles employed in an antimicrobial structure according to an aspect of the disclosure.

[0032] FIG. 3 is a schematic that depicts passivation of copper nanoparticles in an antimicrobial structure according to a further aspect of the disclosure.

[0033] FIG. 4 is a graph of absorption spectra for an antimicrobial structure comprising copper nanoparticles before and after exposure to 85°C and 85% RH environmental conditions for 1 and 7 days according to an aspect of the disclosure. The copper nanoparticles were initially deposited with an aqueous solution containing 5% CuO nanoparticles and then reduced at 600°C for 1 hour.

[0034] FIG. 5 is a graph of absorption spectra for an antimicrobial structure comprising copper nanoparticles before and after exposure to 85°C and 85% RH conditions for 1 , 3, 7 and 14 days according to a further aspect of the disclosure. The copper nanoparticles were initially deposited with a water solution of 10% CuO and reduced at 600°C for 5 hours.

[0035] FIG. 6 is a bar chart depicting antimicrobial efficacy of the antimicrobial structures depicted in FIG. 5 under the EPA-approved Dry Test according to an aspect of the disclosure.

DETAILED DESCRIPTION

[0036] Referring now to the figures, wherein like reference numerals represent like parts throughout the several views, exemplary embodiments will be described in detail.

Throughout this description, various components may be identified having specific values or parameters. These items, however, are provided as being exemplary of the present disclosure. Indeed, the exemplary embodiments do not limit the various aspects and concepts, as many comparable parameters, sizes, ranges, and/or values may be implemented. Similarly, the terms "first," "second," "primary," "secondary," "top," "bottom," "distal," "proximal," and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Further, the terms "a," "an," and "the" do not denote a limitation of quantity, but rather denote the presence of "at least one" of the referenced item. [0037] As used herein, the term "antimicrobial," means an agent or material, or a surface containing the agent or material that will kill or inhibit the growth of microbes from at least two families consisting of bacteria, viruses and fungi. The term as used herein does not mean it will kill or inhibit the growth of all species of microbes within such families, but that it will kill or inhibit the growth of one or more species of microbes from such families. When an agent is described as "antibacterial," "antiviral" or "antifungal," it means that the agent will kill or inhibit the growth of only bacteria, viruses or fungi, respectively. All the samples identified in this disclosure were prepared using commercially available Corning® 2318 aluminosilicate glass (Corning Incorporated).

[0038] As used herein, the term "Log Reduction," "log kill" or "LR" means -log(C_a/C₀), where C_a = the colony form unit (CFU) number of the antimicrobial surface containing Cu nanoparticles and Co = the colony form unit (CFU) or the control glass surface that does not contain Cu nanoparticles. That is, LR = -log(C_a/Co). As an example, a log kill of 3 = 99.9% of bacteria or virus killed and a log kill of 5 = 99.999% of bacteria or virus killed

[0039] Throughout this specification, the term "compressive stress layer" shall be used to refer to the layer or region of compressive stress, and the term "antimicrobial agent- containing region" shall be used to refer to the layer or region containing the antimicrobial agent. This usage is for convenience only, and is not intended to provide a distinction between the terms "region" or "layer" in any way.

[0040] Described herein are various antimicrobial articles that have improved antimicrobial efficacy both under ordinary use conditions and under generally-accepted testing conditions, along with methods for their manufacture and use. In general, the improved articles and methods described herein involve the use of an antimicrobial structure disposed on at least one surface of the glass, or glass-ceramic substrate. The antimicrobial structure beneficially provides the article with improved antimicrobial efficacy both under ordinary use conditions and under generally-accepted testing conditions relative to similar or identical articles that lack an antimicrobial structure. In addition, and as will be described in more detail below, the articles can exhibit appropriate transmission, haze, and/or durability, among other features that may be desired for a particular application.

[0041] The improved antimicrobial articles described herein generally include a glass or glass-ceramic article having a plurality of primary surfaces and an antimicrobial structure disposed on at least one of the primary surfaces. The antimicrobial structure comprises a plurality of copper nanoparticles configured to self-passivate under lifetime conditions of the article. In some implementation, the articles include a compressive stress layer or region that extends inward from a surface of the substrate to a first depth, and/or an antimicrobial region comprising an antimicrobial agent (e.g., silver ions) that extends inward from a surface of the substrate to a second depth therein. Further, the second depth can be shallower than the first depth in certain aspects.

[0042] Utilizing the present disclosure it is possible to make a transparent cover glass or glass-ceramic for applications such as, but not limited to, touch screen devices that embody antimicrobial properties. Moreover, for such antimicrobial applications, additional requirements are necessary, among which are a way to keep the surface clean (handling can seriously limit the antimicrobial activity). Other requirements can include: enhanced mechanical strength that can be afforded by chemical means such as ion-exchange ("IOX"), the durability of any coating place on the antimicrobial article, and the non-interference or minimal interference of any coating with antimicrobial activity. Although it is known that Ag and Cu can provide antimicrobial behavior to some extent, it is not at all obvious how to incorporate this antimicrobial behavior in combination with some or all of the above requirements and properties. It is also not obvious how to accomplish this so as to have the antimicrobial activity at a log kill of > 3 (99.9%).

[0043] In this disclosure, we describe methods by which nanoparticles of (¾0, CuO or Cu can be deposited onto a glass or glass-ceramic that can be IOX-strengthened, and additionally coated with a fluorosilane layer to keep it clean while maintaining the high level of antimicrobial behavior. Direct deposition of (¾0- or CuO-containing nanoparticles onto the glass or glass-ceramic article, although producing the desired antimicrobial behavior immediately after deposition, will not typically suffice for a final antimicrobial article since the subsequent IOX treatment is highly oxidizing and will oxidize the nanoparticles back to primarily CuO. CuO nanoparticles can demonstrate antibacterial properties, but are only weakly antiviral.

[0044] In the present disclosure, one embodiment is directed developing the

antimicrobial properties of Cu present on a glass or glass-ceramic surface through the deposition of CuO-containing (or Cu₂0-containing) nanoparticles to the surface and their reduction to Cu-containing nanoparticles. The processes for depositing 0_¾0 or CuO nanoparticles can include dip-coating, spin-coating, spray coating or the like onto the surface of the glass or glass-ceramic article or substrate from a suspension of Q1₂O or CuO nanoparticles in water. After deposition of the C¾0 or CuO nanoparticles, the glass or glass- ceramic is then heated (in air, 2 or another inert gas) to a temperature sufficient to seal or bond the nanoparticles to the glass or glass-ceramic. In general, a subsequent processing step includes a reduction step to reduce the (¾0 or CuO nanoparticles to Cu-containing nanop articles. In the examples herein, the reduction is carried out in a hydrogen atmosphere, but other reducing atmospheres could be employed as understood by those with ordinary skill in the field. Further, the nanoparticle composition and concentration can determine the ultimate optical transmission of the glass or glass-ceramic article.

[0045] It should be understood that such particles may be reduced to create pure or virtually pure Cu nanoparticles or nanoparticles having a Cu shell and a (¾0 or CuO core. In either case, the reduction is conducted for a time and temperature sufficient to develop a copper-containing nanoparticle that can self-passivate under subsequent manufacturing conditions, such as IOX processing, and environmental conditions of the final antimicrobial article. As such, the subsequent processing and environmental conditions do not lead to a complete oxidization of the copper-containing nanoparticles on the glass or glass-ceramic article, ensuring that the antimicrobial properties obtained from Cu are present over the lifetime of the article.

[0046] Using the teachings presented herein it is possible to provide antimicrobial action to an otherwise transparent and/or chemically strengthened glass or glass-ceramic. In one embodiment, the glass compositions are selected from the group consisting of soda lime glass, alkali alumino silicate glasses and alkali aluminoborosilicate glasses. In a further

embodiment, after the nanoparticles are in the form of Cu-containing nanoparticles that are present on the surface of the glass or glass-ceramic article (or substrate), the article can be treated with a fluorosilane material to give it an easy-to-clean surface enabling the removal of smudges or other matter from the surface without detriment to the antimicrobial properties of the surface of the glass or glass-ceramic. It should be understood that the antimicrobial properties described herein can be imparted to alkali aluminosilicate, alkali

aluminoborosilicate and soda lime glasses whether they are chemically strengthened or non- chemically strengthened. Further, by using the methods described herein, it is preferred in some implementations to start with a non-chemically strengthened glass or glass-ceramic, impart the antimicrobial properties by virtue of the antimicrobial structure having copper- containing nanoparticles, and then chemically strengthen the glass or glass-ceramic by an ion-exchange process. Given the relatively high reduction temperatures (> 450°C) employed in aspects of this disclosure to reduce CuO or Cu₂0-containing nanoparticles to Cu- containing particles, it may not be feasible to perform the reduction step after subjecting the glass or glass-ceramic to an ion exchange process. The high temperatures of the reduction step, sufficient to provide self-passivation capability, would likely lead to significant diffusion of the ion-exchanged layer, thus undermining the compressive stress levels generated at the surface of the article.

[0047] The choice of glass or glass-ceramic material is not limited to a particular composition, as improved antimicrobial efficacy can be obtained using a variety of glass or glass-ceramic compositions according to this disclosure. For example, with respect to glasses, the material chosen can be any of a wide range of silicate, borosilicate, alumino silicate, or boroaluminosilicate glass compositions, which optionally can comprise one or more alkali and/or alkaline earth modifiers.

[0048] By way of illustration, one family of compositions includes those having at least one of aluminum oxide or boron oxide and at least one of an alkali metal oxide or an alkali earth metal oxide, wherein -15 mol%≤ (R₂0 + R'O - A1₂0₃ - Zr0₂) - B₂0₃≤ 4 mol%, where R can be Li, Na, K, Rb, and/or Cs, and R' can be Mg, Ca, Sr, and/or Ba. One subset of this family of compositions includes from about 62 mol% to about 70 mol% Si0₂; from 0 mol% to about 18 mol% A1₂0₃; from 0 mol% to about 10 mol% B₂0₃; from 0 mol% to about 15 mol% Li₂0; from 0 mol% to about 20 mol% Na₂0; from 0 mol% to about 18 mol% K₂0; from 0 mol% to about 17 mol% MgO; from 0 mol% to about 18 mol% CaO; and from 0 mol% to about 5 mol% Zr0₂. Such glasses are described more fully in U.S. Patent

Application No. 12/277,573 by Matthew J. Dejneka et al, entitled "Glasses Having Improved Toughness And Scratch Resistance," filed November 25, 2008, and claiming priority to U.S. Provisional Patent Application No. 61/004,677, filed on November 29, 2008, the contents of which are incorporated herein by reference in their entireties as if fully set forth below.

[0049] Another illustrative family of compositions includes those having at least 50 mol% Si0₂ and at least one modifier selected from the group consisting of alkali metal oxides and alkaline earth metal oxides, wherein [(A1₂0₃ (mol%) + B₂0₃(mol%))/(∑ alkali metal modifiers (mol%))] > 1. One subset of this family includes from 50 mol% to about 72 mol% Si0₂; from about 9 mol% to about 17 mol% A1₂0₃; from about 2 mol% to about 12 mol% B₂0₃; from about 8 mol% to about 16 mol% Na₂0; and from 0 mol% to about 4 mol% K₂0. Such glasses are described in more fully in U.S. Patent Application No. 12/858,490 by Kristen L. Barefoot et al., entitled "Crack And Scratch Resistant Glass and Enclosures Made Therefrom," filed August 18, 2010, and claiming priority to U.S. Provisional Patent

Application No. 61/235,767, filed on August 21, 2009, the contents of which are incorporated herein by reference in their entireties as if fully set forth below. [0050] Yet another illustrative family of compositions includes those having S1O2, AI2O₃, P2O5, and at least one alkali metal oxide (R₂0), wherein 0.75 < [(P₂0₅(mol%) + R₂0(mol%))/ M₂0₃ (mol%)] < 1.2, where M₂0₃ = A1₂0₃ + B₂0₃. One subset of this family of

compositions includes from about 40 mol% to about 70 mol% S1O2; from 0 mol% to about 28 mol% B2O3; from 0 mol% to about 28 mol% AI2O3; from about 1 mol% to about 14 mol% P2O5; and from about 12 mol% to about 16 mol% R2O. Another subset of this family of compositions includes from about 40 to about 64 mol% S1O2; from 0 mol% to about 8 mol% B2O₃; from about 16 mol% to about 28 mol% AI2O₃; from about 2 mol% to about 12 mol% P2O5; and from about 12 mol% to about 16 mol% R2O. Such glasses are described more fully in U.S. Patent Application No. 13/305,271 by Dana C. Bookbinder et al., entitled "Ion Exchangeable Glass with Deep Compressive Layer and High Damage Threshold," filed November 28, 201 1, and claiming priority to U.S. Provisional Patent Application No.

61/417,941, filed November 30, 2010, the contents of which are incorporated herein by reference in their entireties as if fully set forth below.

[0051] Yet another illustrative family of compositions includes those having at least about 4 mol% P₂0₅, wherein (M₂03(mol%)/R_xO(mol%)) < 1, wherein M₂0₃ = A1₂0₃ + B₂0₃, and wherein R_xO is the sum of monovalent and divalent cation oxides present in the glass. The monovalent and divalent cation oxides can be selected from the group consisting of L12O, Na₂0, K₂0, Rb₂0, Cs₂0, MgO, CaO, SrO, BaO, and ZnO. One subset of this family of compositions includes glasses having 0 mol% B2O₃. Such glasses are more fully described in U.S. Provisional Patent Application No. 61/560,434 by Timothy M. Gross, entitled "Ion Exchangeable Glass with High Crack Initiation Threshold," filed November 16, 201 1, the contents of which are incorporated herein by reference in their entirety as if fully set forth below.

[0052] Still another illustrative family of compositions includes those having AI2O₃, B2O₃, alkali metal oxides, and contains boron cations having three-fold coordination. When ion exchanged, these glasses can have a Vickers crack initiation threshold of at least about 30 kilograms force (kgf). One subset of this family of compositions includes at least about 50 mol% S1O2; at least about 10 mol% R2O, wherein R₂0 comprises Na₂0; AI2O₃, wherein -0.5 mol%≤ Al₂0₃(mol%) - R₂0(mol%)≤ 2 mol%; and B₂0₃, and wherein B₂0₃(mol%) - (R20(mol%) - Ai203(mol%)) > 4.5 mol%. Another subset of this family of compositions includes at least about 50 mol% S1O2, from about 9 mol% to about 22 mol% AI2O₃; from about 4.5 mol% to about 10 mol% B2O₃; from about 10 mol% to about 20 mol% Na₂0; from 0 mol% to about 5 mol% K₂0; at least about 0.1 mol% MgO and/or ZnO, wherein 0 < MgO + ZnO < 6 mol%; and, optionally, at least one of CaO, BaO, and SrO, wherein 0 mol% < CaO + SrO + BaO < 2 mol%. Such glasses are more fully described in U.S. Provisional Patent Application No. 61/653,485 by Matthew J. Dejneka et al, entitled "Ion Exchangeable Glass with High Damage Resistance," filed May 31, 2012, the contents of which are incorporated herein by reference in their entirety as if fully set forth below.

[0053] Similarly, with respect to glass-ceramics, the material chosen can be any of a wide range of materials having both a glassy phase and a ceramic phase. Illustrative glass- ceramics include those materials where the glass phase is formed from a silicate, borosilicate, aluminosilicate, or boroaluminosilicate, and the ceramic phase is formed from β-spodumene, β -quartz, nepheline, kalsilite, or carnegieite. In some implementations, it is preferable to select a glass-ceramic composition having a relatively high percentage of a glassy phase. It is believed that the glassy phase of the glass-ceramic retains or otherwise facilitates the embedding of the Cu-containing nanoparticles in one or more primary surfaces of the antimicrobial article. Consequently, some aspects of the disclosure are optimized with regard to the percentage of glassy phase in the glass-ceramic and the relative loading of the copper- containing suspensions used to deploy the CuO or Cu₂0-containing nanoparticles onto one or more primary surfaces of the antimicrobial article.

[0054] In one aspect of the disclosure, an antimicrobial article 100 is depicted in FIG. 1. The antimicrobial article has a substrate 10 with a glass or glass-ceramic composition and a plurality of primary surfaces 12. In certain implementations, the substrate 10 of the article 100 can include a compressive stress region 24 that extends from at least one of the primary surfaces 12 to a first selected depth 22. In some implementations, the substrate 10 of the antimicrobial article 100 may include an antimicrobial region 28 containing a plurality of silver ions extending from at least one of the primary surfaces 12 to a second selected depth 26 within the substrate. It should be understood that antimicrobial region 28 and the compressive stress region 24 are optional. Furthermore, regions 24 and 28 may be simultaneously present in the antimicrobial article 100.

[0055] The antimicrobial article 100 depicted in FIG. 1 further contains an antimicrobial structure 50 disposed on at least one of the primary surfaces 12. The antimicrobial structure 50 comprises a plurality of copper nanoparticles 40 configured to self-passivate under lifetime conditions of the article. In some implementations, the copper nanoparticles 40 have a copper metal shell and a copper oxide core. Preferably, the average core radius of such copper nanoparticles 40 is less than or equal to 35% of an average radius of the shell and core, less than or equal to 30% of an average radius of the shell and core or less than or equal to 25% of an average radius of the shell and core.

[0056] These types of antimicrobial articles 100 can exhibit at least a 1 log reduction in a concentration of at least Staphylococcus aureus, Enterobacter aerogenes, and Pseudomonas aeruginosa bacteria under testing conditions consistent with the Test Method for Efficacy of Copper Alloy Surfaces as a Sanitizer, approved by the U.S. Environmental Protection Agency ("EPA-approved Dry Test"). The EPA-approved Dry Test is conducted under ambient conditions (i.e., at < 42% RH, ~23°C). Certain aspects of these antimicrobial articles 100 can also exhibit at least a 3 log reduction in a concentration of at least Staphylococcus aureus, Enterobacter aerogenes, and Pseudomonas aeruginosa bacteria under the EPA- approved Dry Test.

[0057] According to another aspect of the disclosure, a method 200 is depicted in FIG. 2 for developing the antimicrobial properties of Cu present on a glass or glass-ceramic surface through the deposition of CuO -containing (or Cu₂0-containing) nanoparticles to the surface and their reduction to Cu-containing nanoparticles. In particular, method 200 is a reduction process for developing Cu-containing nanoparticles with a self-passivation capability. The prior processes for depositing Ο¾0 or CuO nanoparticles (i.e., process steps employed before the method 200 for reducing the nanoparticles) can include dip-coating, spin-coating, spray coating or the like onto the surface of the glass or glass-ceramic article or substrate from a suspension of Ο¾0 or CuO nanoparticles in water. After deposition of the Ο½0 or CuO nanoparticles, the glass or glass-ceramic is then heated (in air, 2 or another inert gas) to a temperature sufficient to seal or bond the nanoparticles to the glass or glass-ceramic.

[0058] In general, the method 200 show in FIG. 2 involves a process to reduce the Q1₂O or CuO-containing nanoparticles to Cu-containing nanoparticles. Initially, Q1₂O or CuO- containing nanoparticles 32 are provided having a radius, ro. The reduction according to the method 200 is then carried out in step 120, typically in a hydrogen atmosphere, but other reducing atmospheres could be employed as understood by those with ordinary skill in the field. In step 120, a Q12O or CuO-containing core 36 having a core radius and a copper- containing shell 38 having a shell radius, r₂, are developed. The reduction process is then continued for a sufficient time and temperature to develop a self-passivation capability in the nanoparticles 40. As depicted in FIG. 2, the core 36 of the nanoparticles gradually shrinks at steps 140 and 160 during the reduction as the size of the shell 38 increases. This evolution is by virtue of the reduction process that changes the initial CU₂O or CuO-containing nanoparticles 32 into primarily copper-containing nanoparticles 40. Preferably, the average core radius rj of such copper nanoparticles 40 is less than or equal to 35% of an average radius of the shell 38 and the core 36 (i.e., r_} + r₂), less than or equal to 30% of an average radius of the shell and core or less than or equal to 25% of an average radius of the shell and core.

[0059] It should be understood that such nanoparticles 32 depicted in FIG. 2 may be reduced to create pure or virtually pure Cu nanoparticles 40 or nanoparticles 40 having a Cu shell and a Ο¾0 or CuO core according to the method 200. In either case, the reduction according to the method 200 is conducted for a time and temperature through steps 120, 140 and 160 sufficient to develop a copper-containing nanoparticle 40 that can self-passivate under subsequent manufacturing conditions, such as IOX processing, and environmental conditions of the final antimicrobial article (e.g., an antimicrobial article 100). As such, the subsequent processing and environmental conditions do not lead to a complete oxidization of the copper-containing nanoparticles 40 on the glass or glass-ceramic article, ensuring that the antimicrobial properties obtained from Cu are present over the lifetime of the article.

[0060] According to aspects of the disclosure, chemically strengthening a glass or glass- ceramic with a primary surface having Cu-containing nanoparticles 40 is not a

straightforward process. When the article (e.g., antimicrobial article 100) with the reduced Cu-containing nanoparticles 40 (e.g., by virtue of method 200) is placed in a K O₃ bath for chemical strengthening by IOX, the result is that the Cu-containing nanoparticles 40, while in the bath, can be re-oxidized to a CuO state. This phenomenon is depicted schematically in FIG. 3.

[0061] More specifically, FIG. 3 depicts passivation method 300, a method for passivating or otherwise oxidizing the copper-containing nanoparticles 40, typically embedded with an antimicrobial structure 50 of an antimicrobial article 100. It should be understood that passivation method 300 can also depict other oxidative environments (e.g., ambient humidity and moisture associated with the life conditions of the final antimicrobial article 100), besides IOX processes, applied to the antimicrobial article containing the copper-containing nanoparticles 40 that were developed according to the reduction method 200. As shown, steps 220, 240 and 260 depict the progression of a copper oxide outer shell 42 having a radius, r^, within the initial copper-containing nanoparticles 40 to passivated copper-containing nanoparticles 44. At the end of the oxidative exposure in step 260, the passivated copper-containing nanoparticles 44 generally possess a shell 42 consisting essentially of a copper oxide shell having a relatively fixed radius, r^. That is, the radius rs is not expected to appreciably increase in size upon the exposure of the passivated copper- containing nanoparticles 44 to additional oxidative environments. As such, copper shell 38 can continue to provide antimicrobial property benefits over the lifetime of the final antimicrobial article 100.

[0062] FIG. 4 is a graph of absorption spectra for an antimicrobial structure (e.g., an antimicrobial structure 50) comprising copper nanoparticles 40 before and after exposure to 85°C and 85% RH environmental conditions for 1 and 7 days according to an aspect of the disclosure. The copper nanoparticles 40 were initially deposited on a glass substrate with an aqueous solution containing 5% CuO nanoparticles (e.g., a colloidal copper (Π) oxide dispersion employing Nano Arc® 23-27 nm average particle size powder in water) and then reduced at 600°C for 1 hour (e.g., according to a method 200). Absorbance measurements were made using a Perkin Elmer, Inc. spectrophotometer in the wavelength range of 350-900 nm. As depicted in FIG. 4, the as-prepared sample with no exposure to the 85°C and 85% RH environmental condition has a plasmon resonance peak at about 584 nm, suggesting an average core radius of copper oxide that is 25% of the total radius of the nanoparticles having a copper shell (developed by virtue of the reduction at 600°C for 1 hour). Upon 1 day of exposure to the 85°C and 85% RH environmental condition (e.g., one example of the passivation method 300), the plasmon peak has broadened suggesting some development of an oxide shell (e.g., the oxide shell 42 shown in FIG. 3) within the nanoparticles. Yet, at 7 days of exposure to the 85°C and 85% RH environmental conditions, the plasmon peak has not significantly broadened further, evidencing the development of a self-passivation capability.

[0063] Referring to FIG. 5, a graph of absorption spectra is provided for an antimicrobial structure (e.g., an antimicrobial structure 50) comprising copper nanoparticles 40 before and after exposure to 85°C and 85% RH conditions for 1, 3, 7 and 14 days according to a further aspect of the disclosure. The copper nanoparticles were initially deposited on a glass substrate with a water solution of 10% CuO and reduced at 600°C for 5 hours. Here, the as- prepared sample with no exposure to the 85°C and 85% RH environmental condition also has a plasmon peak of about 584 nm, again suggesting an average core radius of copper oxide that is 25% of the total radius of the nanoparticles having a copper shell. Upon 1 day of exposure to the 85°C and 85% RH environmental condition, the plasmon peak has broadened suggesting some development of an oxide shell (e.g., as in passivation method 300) within the nanoparticles. However, at 3, 7 and 14 days of exposure to the 85°C and 85% RH environmental conditions, the plasmon peak has not significantly broadened further, evidencing the development of a self-passivation capability. [0064] In one aspect of the disclosure, a method of making an antimicrobial article 100 having a glass or glass-ceramic composition comprises the deposition of a copper oxide nanoparticle coating onto the surface 12 of the article 100 by dip-coating, spin coating, spraying or other coating method(s) that are capable of depositing a suspension of CuO or CU2O nanoparticles at about 5 to 10 wt% in water, or other suitable fluid, onto a surface 12 of the glass or glass-ceramic and drying the suspension on the surface. Drying can be carried out at a temperature in the range of 100°C to 130°C. The drying time can range from 1 hour to 4 hours, for example. In a subsequent step, the copper-containing nanoparticles (e.g., nanoparticles 32) can be embedded into a surface 12 of the glass or glass-ceramic article by a thermal treatment in air, typically at 650°C to 700°C. Next, the copper-containing

nanoparticles are subjected to a reduction process at 450°C to 700°C for about 1 hour to 5 hours in a reducing atmosphere (e.g., by method 200), such as 100% H₂ gas, at a time and temperature sufficient to reduce the nanoparticles (e.g., to copper-containing nanoparticles 40) such that the average radius of the copper oxide core relative to the average total radius of the nanoparticles (i.e., the reduced nanoparticles now include a Cu° shell) is 35% or less. As applicable, further ion exchange processes can be conducted to chemically strengthen the glass or glass-ceramic article and/or impart additional antimicrobial agents (e.g., Ag⁺ ions) into the surface and depth of the article.

[0065] A substrate (e.g., substrate 10) employed in the antimicrobial articles (e.g., antimicrobial articles 100) of this disclosure can adopt a variety of physical forms. That is, from a cross-sectional perspective, the substrate can be flat or planar, or it can be curved and/or sharply-bent. Similarly, it can be a single unitary object, a multi-layered structure, or a laminate.

[0066] Regardless of its composition or physical form, the substrate 10 of the

antimicrobial article 100 may, as detailed earlier, include a layer or region 24 under compressive stress that extends inward from a surface of the substrate to a first selected depth 22 therein. This compressive stress layer 24 can be formed from a strengthening process (e.g., by thermal tempering, chemical ion-exchange, or like processes). The amount of

compressive stress (CS) and the depth 22 of the compressive stress layer (DOL) can be varied based on the particular use for the article, with the proviso that the CS and DOL should be limited such that a tensile stress created within the substrate as a result of the compressive stress layer does not become so excessive as to render the article frangible.

[0067] As also detailed earlier, the substrate 10 may include, in some implementations, an antimicrobial agent-containing layer or region 28 that extends inward from a surface of the substrate to a second selected depth 26 therein. The antimicrobial agent can be chosen from any of a variety of species that provide antimicrobial behavior, examples of which include cationic monovalent silver (Ag⁺), cationic monovalent copper (Cu^, cationic divalent zinc (Zn²⁺), a quaternary ammonium species ( H₄⁺), and the like. In general, the average depth 26 of the antimicrobial agent-containing region (DOR) will generally be limited to less than or equal to about 200 nanometers (nm).

[0068] In certain implementations, the antimicrobial articles 100 can include an additional functional layer disposed on the surface of the substrate. The optional additional layer(s) can be used to provide additional features to the antimicrobial article 100 (e.g., reflection resistance or anti-reflection properties, glare resistance or anti-glare properties, fingerprint resistance or anti-fingerprint properties, smudge resistance or anti-smudge properties, color, opacity, environmental barrier protection, electronic functionality, and/or the like). Materials that can be used to form the optional additional layer(s) generally are known to those skilled in the art to which this disclosure pertains. By way of example, in one implementation, the optional additional layer might include a coating of S1O2 nanoparticles bound to at least a portion of the substrate to provide reflection resistance to the final article. In another implementation, optional additional layer might comprise a multi-layered reflection-resistant coating formed from alternating layers of polycrystalline T1O2 and S1O2. In another implementation, the optional additional layer might comprise a color-providing composition that comprises a dye or pigment material. In another implementation, the optional additional layer might comprise a fingerprint-resistant coating formed from a hydrophobic and oleophobic material, such as a fluorinated polymer or fluorinated silane. In yet another implementation, the optional additional layer might comprise a smudge-resistant coating formed from an oleophilic material.

[0069] Methods of making the above-described antimicrobial articles 100 generally include the steps of providing a substrate 10, developing an antimicrobial structure 50 on a primary surface 12 of the substrate with copper-containing nanoparticles 40 such that the nanoparticles are configured to self-passivate under lifetime conditions of the article. In some aspects, the method also includes forming a compressive stress layer 24 that extends inward from a surface of the substrate 10 to a first depth 22, and forming an antimicrobial agent-containing region 28 that extends inward from the surface 12 of the substrate 10 to a second depth 22. In those embodiments where the optional additional layer is implemented, the methods generally involve an additional step of forming the additional layer on at least a portion of the surface of the substrate. [0070] The selection of materials used in the glass or glass-ceramic substrates 10, antimicrobial agent, and optional additional layers can be made based on the particular application desired for the final article. In general, however, the specific materials will be chosen from those described above.

[0071] Provision of the substrate 10 can involve selection of a glass or glass-ceramic object as-manufactured, or it can entail subjecting the as-manufactured glass or glass-ceramic object to a treatment in preparation for forming the optional functional layer or the antimicrobial coating. Examples of such pre-coating treatments include physical or chemical cleaning, physical or chemical etching, physical or chemical polishing, annealing, shaping, and/or the like. Such processes are known to those skilled in the art to which this disclosure pertains.

[0072] Once the substrate 10 has been selected and/or prepared, including the development of the antimicrobial structure 50 containing a plurality of copper-containing nanoparticles 40 configured to self-passivate under lifetime conditions of the antimicrobial article, the compressive stress layer 24 can be formed therein. Formation of the compressive stress layer 24 can be accomplished in a variety of ways, of which thermal tempering and chemical ion exchange are the most common. Such techniques are known to those skilled in the art to which this disclosure pertains.

[0073] Once the substrate 10 with the compressive stress layer 24 has been formed, the antimicrobial agent-containing region 28 can be formed or, if desired, the optional additional functional layer can be disposed on the surface of the substrate 10. That is, in situations where the antimicrobial article 100 includes the optional additional functional layer(s), the optional additional functional layer(s) can be formed before or after the antimicrobial agent- containing region 28.

[0074] The antimicrobial agent-containing region 28 can be formed via chemical diffusion (which optionally can be accompanied by the exchange of a cation out from the substrate) of the antimicrobial agent from an antimicrobial agent-containing solution that is contacted with at least a portion of the surface of the substrate.

[0075] The antimicrobial agent-containing solution generally includes the antimicrobial agent, or a precursor to the antimicrobial agent, at least partially dissolved in a solvent. In most implementations, the antimicrobial agent can be at least partially dissolved in the solvent in the form of a salt of the antimicrobial agent. By way of example, when the antimicrobial agent is Ag⁺, it can be dissolved in the solvent as silver nitrate, silver chloride, silver acetate, silver cyanide, silver lactate, silver methanesulfonate, silver triflate, silver fluoride, silver permanganate, silver sulfate, silver nitrite, silver bromate, silver salicylate, and silver iodate, to name a few. Similar such salts can be made for other antimicrobial agents, including Cu⁺, Zn²⁺, ΝΙ¾⁺, and the like.

[0076] The solvent used in the antimicrobial agent-containing solution can be chosen from any of a variety of solvents, with the proviso that the solvent does not adversely affect (e.g., react with, decompose, volatilize, or the like) the substrate, the compressive stress layer, or the optional additional functional layer(s). Examples of such solvents include water, alcohols (e.g., methanol, ethanol, propanol, butanol, and the like), polar aprotic solvents (e.g., tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide, methylpyrrolidone, and the like), and the like.

[0077] In certain cases, it may be desirable to include additional components in the antimicrobial agent-containing solution. For example, the antimicrobial agent-containing solution can further include an alkali metal cation dissolved therein for the purpose of altering the stress profile of the compressive stress layer. Such cations can also synergistically enhance the antimicrobial efficacy of the final article. In certain examples, the antimicrobial agent-containing solution can include a stabilizer, surfactant, wetting agent, pH modifiers, or the like for enhancing the shelf life of the antimicrobial agent-containing solution.

[0078] Once the antimicrobial agent-containing solution is formed or selected, it can be contacted with the substrate 10 to form the antimicrobial agent-containing region 28. Such contacting can take the form of partial or complete immersion of the substrate in the antimicrobial agent-containing solution, spraying the antimicrobial agent-containing solution on the surface of the substrate, and/or the like. The contacting step optionally can be performed at an elevated temperature, with the proviso that the temperature should not 1) exceed a temperature at which the CS in the compressive stress layer is substantially affected (i.e., by greater than about 2 percent) during the contacting or 2) a boiling temperature of the antimicrobial agent-containing solution. In many implementations, the temperature of the contacting step generally will be less than or equal to about 120 degrees Celsius (°C). The duration of the contacting step will be less than or equal to about 100 hours, but in most implementations will be less than or equal to about 24 hours.

[0079] Depending on the materials chosen, the optional additional layer(s) can be disposed or formed on the surface of the substrate 10 using a variety of techniques. For example, the optional additional layer(s) can be fabricated independently using any of the variants of chemical vapor deposition (CVD) (e.g., plasma-enhanced CVD, aerosol-assisted CVD, metal organic CVD, and the like), any of the variants of physical vapor deposition (PVD) (e.g., ion-assisted PVD, pulsed laser deposition, cathodic arc deposition, sputtering, and the like), spray coating, spin-coating, dip-coating, inkjetting, sol-gel processing, or the like. Such processes are known to those skilled in the art to which this disclosure pertains.

[0080] By way of example, one implementation of a method where optional additional functional layers are formed before the antimicrobial agent-containing region 28 entails spin- coating a fluorinated silane material on the surface of the substrate to form a fingerprint- resistant coating, spin-coating a color-providing composition on the surface of the substrate, and immersing the substrate into an aqueous AgN03 solution to ion exchange Ag⁺ therein.

[0081] By way of another example, one implementation of a method where the antimicrobial agent-containing region 28 is formed before an optional additional functional layer entails immersing the substrate into an aqueous CuCl solution to ion exchange Cu⁺ therein, followed by coating the substrate with a multi-layered reflection-resistant coating.

[0082] It should be noted that between any of the above-described steps, the substrate 10 can undergo a treatment in preparation for any of the subsequent steps. As described above, examples of such treatments include physical or chemical cleaning, physical or chemical etching, physical or chemical polishing, annealing, shaping, and/or the like.

[0083] Once the antimicrobial article 100 is formed, it can be used in a variety of applications where the article will come into contact with undesirable microbes. These applications encompass touch-sensitive display screens or cover plates for various electronic devices (e.g., cellular phones, personal data assistants, computers, tablets, global positioning system navigation devices, and the like), non-touch-sensitive components of electronic devices, surfaces of household appliances (e.g., refrigerators, microwave ovens, stovetops, oven, dishwashers, washers, dryers, and the like), medical equipment, architectural applications, biological or medical packaging vessels, and vehicle components, just to name a few devices.

[0084] Given the breadth of potential uses for the improved antimicrobial articles, e.g., antimicrobial articles 100, described herein, it should be understood that the specific features or properties of a particular article will depend on the ultimate application therefor or use thereof. The following description, however, will provide some general considerations.

[0085] There is no particular limitation on the average thickness of the substrate 10 of the antimicrobial articles 100 contemplated herein. In many exemplary applications, however the average thickness will be less than or equal to about 25 millimeters (mm). If the antimicrobial article 100 is to be used in applications where it may be desirable to optimize thickness for weight, cost, and strength characteristics (e.g., in electronic devices, or the like), then even thinner substrates (e.g., less than or equal to about 5 mm) can be used. By way of example, if the antimicrobial article 100 is intended to function as a cover glass for a touch screen display, then the glass substrate can exhibit an average thickness of about 0.02 mm to about 2.0 mm.

[0086] While the ultimate limit on the CS and DOL is the avoidance of rendering the substrate frangible, the average DOL of the compressive stress layer 24 generally will be less than about one-third of the thickness of the substrate 10. The CS and DOL can be measured using a surface stress meter, which is an optical tool that generally uses the photoelastic constant and index of refraction of the substrate material itself, and converts the measured optical interference fringe patterns to specific CS and DOL values. In most applications, the average DOL will be greater than or equal to about 25 μιη and less than or equal to about 100 μιη. Similarly, the average CS across the depth of the compressive stress layer generally will be between about 200 megapascals (MPa) and about 1.2 gigapascals (GPa). In most applications, the average CS will be greater than 400 MPa.

[0087] As stated above, the average thickness of the antimicrobial agent-containing region 28 should be less than or equal to about 200 nm. In most applications, the average DOR will be greater than or equal to about 2 nm and less than or equal to about 100 nm. In embodiments where the substrate 10 is susceptible to visible coloration from the

antimicrobial agent, the average DOR should be less than or equal to about 50 nm.

[0088] Within this region, antimicrobial agent concentrations at the outermost portion of this region 28 (which includes about the outermost 3 nm) of up to about 10 atomic percent, based on the total number of atoms of this portion of the antimicrobial agent-containing region, can be attained, as measured using, for example, X-ray photoelectron spectroscopy (XPS). In most implementations, the antimicrobial agent concentration in the outermost portion of this region will be about 1 atomic percent to about 6 atomic percent.

[0089] When an optional additional layer is used, the average thickness of such a layer will depend on the function it serves. For example if a glare- and/or reflection-resistant layer is implemented, the average thickness of such a layer should be less than or equal to about 200 nm. Coatings that have an average thickness greater than this could scatter light in such a manner that defeats the glare and/or reflection resistance properties. Similarly, if a fingerprint- and/or smudge-resistant layer is implemented, the average thickness of such a layer should be less than or equal to about 100 nm.

[0090] In general, the optical transmittance of the antimicrobial article 100 will depend on the type of materials chosen. For example, if a glass or glass-ceramic substrate 10 is used without any pigments added thereto and/or any optional additional layers are sufficiently thin, the article can have a transparency over the entire visible spectrum of at least about 85%. In certain cases where the antimicrobial article 100 is used in the construction of a glass or glass-ceramic touch screen for an electronic device, for example, the transparency of the antimicrobial article can be at least about 90% over the visible spectrum. In situations where the substrate 10 comprises a pigment (or is not colorless by virtue of its material constituents) and/or any optional additional layers are sufficiently thick, the transparency can diminish, even to the point of being opaque across the visible spectrum. Thus, there is no particular limitation on the optical transmittance of the antimicrobial article itself.

[0091] Like transmittance, the haze of the antimicrobial article 100 can be tailored to the particular application. As used herein, the terms "haze" and "transmission haze" refer to the percentage of transmitted light scattered outside an angular cone of ± 4.0° in accordance with ASTM procedure D1003, the contents of which are incorporated herein by reference in their entirety as if fully set forth below. For an optically smooth surface, transmission haze is generally close to zero. In those situations when the antimicrobial article 100 is used in the construction of a glass or glass-ceramic touch screen for an electronic device, the haze of the article can be less than or equal to about 5%.

[0092] Regardless of the application or use, the antimicrobial articles 100 described herein offer improved antimicrobial efficacy relative to identical articles that lack an antimicrobial structure 50 containing copper nanoparticles configured to self-passivate, an antimicrobial-agent containing region 28, and/or have deeper antimicrobial-agent containing regions 28 using the same overall amount of antimicrobial agent.

[0093] The antimicrobial activity and efficacy of the antimicrobial articles, such as antimicrobial articles 100, described herein can be quite high. In FIG. 6, a bar chart depicts antimicrobial efficacy of the antimicrobial structures on glass substrates as described in connection with FIG. 5 under the EPA-approved Dry Test according to an aspect of the disclosure. In particular, the EPA antimicrobial efficacy testing was conducted at 23 °C and 40% RH. Notably, each of these antimicrobial articles demonstrates a log kill value of at least 4 (e.g., a 99.99% kill rate) in the as-prepared state and after 1, 7 and 14 days of exposure to an 85°C and 85% RH environmental condition. As controls, two sets of log kill data are provided for pure Cu metal samples before and after 14 days of exposure to the 85°C and 85% RH environmental condition. Consequently, it is evident that antimicrobial articles having antimicrobial structures with copper-containing nanoparticles can be prepared according to the disclosure having antimicrobial efficacy after significant environmental exposure - i.e., 14 days at 85°C and 85% RH.

[0094] While the embodiments disclosed herein have been set forth for the purpose of illustration, the foregoing description should not be deemed to be a limitation on the scope of the disclosure or the appended claims. Accordingly, various modifications, adaptations, and alternatives may occur to one skilled in the art without departing from the spirit and scope of the present disclosure or the appended claims.