Patent Description:
Portable electronic devices, such as, smartphones, tablets, and wearable devices (such as, for example, watches and fitness trackers) continue to get smaller and more complex. As such, materials that are conventionally used on at least one external surface of such portable electronic devices also continue to get more complex. For instance, as portable electronic devices get smaller and thinner to meet consumer demand, the display covers and housings used in these portable electronic devices also get smaller and thinner, resulting in higher performance requirements for the materials used to form these components. <CIT> relates to methods for strengthening glass articles using a steam treatment.

Accordingly, a need exists for materials that exhibit higher performance, such as resistance to damage, along with lower cost and ease of manufacture for use in portable electronic devices.

The invention relates to a glass-based article. The glass-based article comprises: a hydrogen-containing layer extending from the surface of the glass-based article to a depth of layer, wherein a hydrogen concentration of the hydrogen-containing layer decreases from a maximum hydrogen concentration to the depth of layer; a compressive stress layer extending from the surface of the glass-based article to a depth of compression, wherein the compressive stress layer comprises a compressive stress of greater than or equal to <NUM> MPa; and a composition at the center of the glass-based article comprising:.

The invention further relates to a method comprising: exposing a glass-based substrate to a saturated water vapor environment with a temperature of greater than or equal to <NUM> to form a glass-based article with compressive stress layer extending from the surface of the glass-based article to a depth of compression and a hydrogen-containing layer extending from the surface of the glass-based article to a depth of layer. The compressive stress layer comprises a compressive stress of greater than or equal to <NUM> MPa, a hydrogen concentration of the hydrogen-containing layer decreases from a maximum hydrogen concentration to the depth of layer, and the glass-based substrate comprises:.

These and other aspects, advantages, and salient features will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

In the following description, like reference characters designate like or corresponding parts throughout the several views shown in the figures. It is also understood that, unless otherwise specified, terms such as "top," "bottom," "outward," "inward," and the like are words of convenience and are not to be construed as limiting terms. Unless otherwise specified, a range of values, when recited, includes both the upper and lower limits of the range as well as any sub-ranges therebetween. As used herein, the indefinite articles "a," "an," and the corresponding definite article "the" mean "at least one" or "one or more," unless otherwise specified. It also is understood that the various features disclosed in the specification and the drawings can be used in any and all combinations.

As used herein, the term "glass-based" is used in its broadest sense to include any objects made wholly or partly of glass, including glass ceramics (which include a crystalline phase and a residual amorphous glass phase). Unless otherwise specified, all compositions of the glasses described herein are expressed in terms of mole percent (mol%), and the constituents are provided on an oxide basis. Unless otherwise specified, all temperatures are expressed in terms of degrees Celsius (°C).

It is noted that the terms "substantially" and "about" may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. For example, a glass that is "substantially free of K<NUM>O" is one in which K<NUM>O is not actively added or batched into the glass but may be present in very small amounts as a contaminant, such as in amounts of less than about <NUM> mol%. As utilized herein, when the term "about" is used to modify a value, the exact value is also disclosed. For example, the term "greater than about <NUM> mol%" also discloses "greater than or equal to <NUM> mol%.

Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying examples and drawings.

The glass-based articles disclosed herein are formed by steam treating a glass-based substrate to produce a compressive stress layer extending from surface of the article to a depth of compression (DOC). The glass-based substrate compositions and the treatment methods are selected to avoid the formation of haze on the surface of the glass-based articles. The compressive stress layer includes a stress that decreases from a maximum stress to the depth of compression. In some embodiments, the maximum compressive stress may be located at the surface of the glass-based article. As used herein, depth of compression (DOC) means the depth at which the stress in the glass-based article changes from compressive to tensile. Thus, the glass-based article also contains a tensile stress region having a maximum central tension (CT), such that the forces within the glass-based article are balanced.

The glass-based articles further include a hydrogen-containing layer extending from a surface of the article to a depth of layer. The hydrogen-containing layer includes a hydrogen concentration that decreases from a maximum hydrogen concentration of the glass-based article to the depth of layer. In some embodiments, the maximum hydrogen concentration may be located at the surface of the glass-based article.

The glass-based articles may be formed by exposing glass-based substrates to environments containing water vapor, thereby allowing hydrogen species to penetrate the glass-based substrates and form the glass-based articles having a hydrogen-containing layer and/or a compressive stress layer. As utilized herein, hydrogen species includes molecular water, hydroxyl, hydrogen ions, and hydronium. The composition of the glass-based substrates may be selected to promote the interdiffusion of hydrogen species into the glass. As utilized herein, the term "glass-based substrate" refers to the precursor prior to exposure to a water vapor containing environment for the formation of a glass-based article that includes hydrogen-containing layers and/or compressive stress layers. Similarly, the term "glass-based article" refers to the post exposure article that includes a hydrogen-containing layer and/or a compressive stress layer.

The glass-based articles disclosed herein may exhibit a compressive stress layer without undergoing conventional ion exchange, thermal tempering, or lamination treatments. Ion exchange processes produces significant waste in the form of expended molten salt baths that require costly disposal, and also are applicable to only some glass compositions. Thermal tempering requires thick glass specimens as a practical matter, as thermal tempering of thin sheets utilizes small air gap quenching processes which results in sheet scratching damage that reduces performance and yield. Additionally, it is difficult to achieve uniform compressive stress across surface and edge regions when thermal tempering thin glass sheets. Laminate processes result in exposed tensile stress regions when large sheets are cut to usable sizes, which is undesirable.

The water vapor treatment utilized to form the glass-based articles allows for reduced waste and lower cost when compared to ion exchange treatments as molten salts are not utilized, and alkali-free glass-based substrates may be employed. The water vapor treatment is also capable of strengthening thin (<<NUM>) low-cost glass that would not be suitable for thermal tempering at such thicknesses. Additionally, the water vapor treatment may be performed at the part level, avoiding the undesirable exposed tensile stress regions associated with laminate processes. In sum, the glass-based articles disclosed herein may be produced with a low thickness and at a low cost while exhibiting a high compressive stress and deep depth of compression.

A representative cross-section of a glass-based article <NUM> according to some embodiments is depicted in <FIG>. The glass-based article <NUM> has a thickness t that extends between a first surface <NUM> and a second surface <NUM>. A first compressive stress layer <NUM> extends from the first surface <NUM> to a first depth of compression, where the first depth of compression has a depth d<NUM> measured from the first surface <NUM> into the glass-based article <NUM>. A second compressive stress layer <NUM> extends from the second surface <NUM> to a second depth of compression, where the second depth of compression has a depth d<NUM> measured from the second surface <NUM> into the glass-based article <NUM>. A tensile stress region <NUM> is present between the first depth of compression and the second depth of compression. In embodiments, the first depth of compression d<NUM> may be substantially equivalent or equivalent to the second depth of compression d<NUM>.

The compressive stress layer of the glass-based article includes a compressive stress of at greater than or equal to <NUM> MPa, such as greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, or more. In some embodiments, the compressive stress layer may include a compressive stress of from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, such as from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, or any sub-ranges formed from any of these endpoints.

In some embodiments, the DOC of the compressive stress layer may be greater than or equal to <NUM>, such as greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, or more. In some embodiments, the DOC of the compressive stress layer may be from greater than or equal to <NUM> to less than or equal to <NUM>, such as from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, or any sub-ranges that may be formed from any of these endpoints.

In some embodiments, the glass-based articles may exhibit a deep depth of compression and a high compressive stress. For example, the glass-based articles may have a depth of compression greater than or equal to <NUM> and a compressive stress of greater than or equal to <NUM> MPa.

In some embodiments, the glass-based articles may have a DOC greater than or equal to <NUM>. 05t, wherein t is the thickness of the glass-based article, such as greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, or more. In some embodiments, the glass-based articles may have a DOC from greater than or equal to <NUM>t to less than or equal to <NUM>t, such as from greater than or equal to <NUM>t to less than or equal to <NUM>. <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, or any sub-ranges formed from any of these endpoints.

Compressive stress (including surface CS) is measured by surface stress meter using commercially available instruments such as the FSM-<NUM> (FSM), manufactured by Orihara Industrial Co. Surface stress measurements rely upon the accurate measurement of the stress optical coefficient (SOC), which is related to the birefringence of the glass. SOC in turn is measured according to Procedure C (Glass Disc Method) described in ASTM standard C770-<NUM>, entitled "Standard Test Method for Measurement of Glass Stress-Optical Coefficient". DOC is measured by FSM. The maximum central tension (CT) values are measured using a scattered light polariscope (SCALP) technique known in the art.

The hydrogen-containing layer of the glass-based articles may have a depth of layer (DOL) greater than <NUM>. In some embodiments, the depth of layer may be greater than or equal to <NUM>, such as greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, or more. In some embodiments, the depth of layer may be from greater than <NUM> to less than or equal to <NUM>, such as from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, or any sub-ranges formed by any of these endpoints. In general, the depth of layer exhibited by the glass-based articles is greater than the depth of layer that may be produced by exposure to the ambient environment.

The hydrogen-containing layer of the glass-based articles may have a depth of layer (DOL) greater than <NUM>t, wherein t is the thickness of the glass-based article. In some embodiments, the depth of layer may be greater than or equal to <NUM>. 010t, such as greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, greater than or equal to <NUM>t, or more. In some embodiments, the DOL may be from greater than <NUM>t to less than or equal to <NUM>t, such as from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>. 090t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, from greater than or equal to <NUM>t to less than or equal to <NUM>t, or any sub-ranges formed by any of these endpoints.

The depth of layer and hydrogen concentration are measured by a secondary ion mass spectrometry (SIMS) technique that is known in the art. The SIMS technique is capable of measuring the hydrogen concentration at a given depth but is not capable of distinguishing the hydrogen species present in the glass-based article. For this reason, all hydrogen species contribute to the SIMS measured hydrogen concentration. As utilized herein, the depth of layer (DOL) refers to the first depth below the surface of the glass-based article where the hydrogen concentration is equal to the hydrogen concentration at the center of the glass-based article. This definition accounts for the hydrogen concentration of the glass-based substrate prior to treatment, such that the depth of layer refers to the depth of the hydrogen added by the treatment process. As a practical matter, the hydrogen concentration at the center of the glass-based article may be approximated by the hydrogen concentration at the depth from the surface of the glass-based article where the hydrogen concentration becomes substantially constant, as the hydrogen concentration is not expected to change between such a depth and the center of the glass-based article. This approximation allows for the determination of the DOL without measuring the hydrogen concentration throughout the entire depth of the glass-based article. The presence of the hydrogen-containing layer may be indicated by the formation of a compressive stress layer in the glass-based article as a result of the water vapor treatment.

Without wishing to be bound by any particular theory, the hydrogen-containing layer of the glass-based articles may be the result of an interdiffusion of hydrogen species for ions contained in the compositions of the glass-based substrate. Hydrogen-containing species, such as H<NUM>O+, H<NUM>O, and/or H+, may diffuse into the glass-based substrate to form the glass-based article. Water could penetrate the glass-based substrates by forming silanol groups, breaking the network structure and causing a volume expansion of the glass. Such a volume expansion may generate a compressive stress layer in the glass-based articles. The compressive stress and depth of compression of the compressive stress layer may depend on the composition of the glass-based substrate utilized to form the glass-based article, and the water vapor treatment conditions, such as temperature, pressure, water content, and duration. The stress profile of the glass-based articles produced by the water vapor treatment may be similar to stress profiles produced by potassium for sodium ion exchange strengthening processes.

The glass-based articles that have compressive stress layers also exhibit weight gain when compared to the glass-based substrates prior to the water vapor treatment process. The weight gain of the glass-based articles indicates the formation of a hydrogen-containing layer as a result of the water vapor treatment. The amount of weight gain is directly related to the amount of hydrogen species that enter the glass-based article as a result of the water vapor treatment process.

The glass-based articles disclosed herein may be incorporated into another article such as an article with a display (or display articles) (e.g., consumer electronics, including mobile phones, tablets, computers, navigation systems, wearable devices (e.g., watches) and the like), architectural articles, transportation articles (e.g., automotive, trains, aircraft, sea craft, etc.), appliance articles, or any article that requires some transparency, scratch-resistance, abrasion resistance or a combination thereof. An exemplary article incorporating any of the glass-based articles disclosed herein is shown in <FIG>. Specifically, <FIG> show a consumer electronic device <NUM> including a housing <NUM> having front <NUM>, back <NUM>, and side surfaces <NUM>; electrical components (not shown) that are at least partially inside or entirely within the housing and including at least a controller, a memory, and a display <NUM> at or adjacent to the front surface of the housing; and a cover substrate <NUM> at or over the front surface of the housing such that it is over the display. In some embodiments, at least a portion of at least one of the cover substrate <NUM> and the housing <NUM> may include any of the glass-based articles disclosed herein.

The glass-based articles may be formed from glass-based substrates having any appropriate composition. The composition of the glass-based substrate may be specifically selected to promote the diffusion of hydrogen-containing species, such that a glass-based article including a hydrogen-containing layer and a compressive stress layer may be formed efficiently, and to avoid the formation of haze as a result of the water vapor treatment process. The glass-based substrates have a composition that includes SiO<NUM>, Al<NUM>O<NUM>, P<NUM>O<NUM>, and Li<NUM>O, and K<NUM>O. In some embodiments, the hydrogen species does not diffuse to the center of the glass-based article. Stated differently, the center of the glass-based article is the area least affected by the water vapor treatment. For this reason, the center of the glass-based article has a composition that is substantially the same, or the same, as the composition of the glass-based substrate prior to treatment in the water containing environment.

The glass-based substrate includes an appropriate amount of SiO<NUM>. SiO<NUM> is the largest constituent and, as such, SiO<NUM> is the primary constituent of the glass network formed from the glass composition. If the concentration of SiO<NUM> in the glass composition is too high, the formability of the glass composition may be diminished as higher concentrations of SiO<NUM> increase the difficulty of melting the glass, which, in turn, adversely impacts the formability of the glass. The glass-based substrate includes SiO<NUM> in an amount from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, such as from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, <NUM> mol%, or any sub-ranges formed by any of these endpoints.

The glass-based substrate includes an appropriate amount of Al<NUM>O<NUM>. Al<NUM>O<NUM> may serve as a glass network former, similar to SiO<NUM>. Al<NUM>O<NUM> may increase the viscosity of the glass composition due to its tetrahedral coordination in a glass melt formed from a glass composition, decreasing the formability of the glass composition when the amount of Al<NUM>O<NUM> is too high. However, when the concentration of Al<NUM>O<NUM> is balanced against the concentration of SiO<NUM> and the concentration of alkali oxides in the glass composition, Al<NUM>O<NUM> can reduce the liquidus temperature of the glass melt, thereby enhancing the liquidus viscosity and improving the compatibility of the glass composition with certain forming processes, such as the fusion forming process. The inclusion of Al<NUM>O<NUM> in the glass-based substrate prevents phase separation and reduces the number of non-bridging oxygens (NBOs) in the glass. Additionally, Al<NUM>O<NUM> can improve the effectiveness of ion exchange. The glass-based substrate includes Al<NUM>O<NUM> in an amount of from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, such as from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, <NUM> mol%, or any sub-ranges formed by any of these endpoints.

The glass-based substrate includes an amount of P<NUM>O<NUM> sufficient to produce the desired hydrogen diffusivity. The inclusion of phosphorous in the glass-based substrate promotes faster interdiffusion. Thus, the phosphorous containing glass-based substrates allow the efficient formation of glass-based articles including a hydrogen-containing layer. The inclusion of P<NUM>O<NUM> also allows for the production of a glass-based article with a deep depth of layer (e.g., greater than about <NUM>) in a relatively short treatment time. The glass-based substrate includes P<NUM>O<NUM> in an amount of from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, such as from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, <NUM> mol%, or any sub-ranges formed by any of these endpoints.

The glass-based substrate includes Li<NUM>O in an appropriate amount. The inclusion of Li<NUM>O in the glass-based substrate increases the resistance of the glass-based article to haze formation as a result of steam strengthening. The content of Li<NUM>O in the glass-based substrate is directly correlated with reduction in the <NUM> P temperature of the glass-based substrate and the coefficient of thermal expansion of the glass-based substrate. The glass-based substrate includes Li<NUM>O in an amount of from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, such as from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, <NUM> mol%, or any and all sub-ranges formed from these endpoints.

The glass-based substrate includes K<NUM>O in an appropriate amount. The inclusion of K<NUM>O in the glass-based substrate increases the steam strengthening susceptibility of the glass-based article to a greater degree than other alkali metal oxides. The glass-based substrate includes K<NUM>O in an amount of from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, such as from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, or any and all sub-ranges formed from these endpoints.

The glass-based substrate may include Na<NUM>O in any appropriate amount. In some embodiments, the glass-based substrate may include Na<NUM>O in an amount of from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%. In embodiments, the glass-based substrate may be substantially free or free of Na<NUM>O.

The glass-based substrates may additionally include a fining agent. In some embodiments, the fining agent may include tin. In embodiments, the glass-based substrate may include SnO<NUM> in an amount from greater than or equal to <NUM> mol% to less than or equal to <NUM> mol%, such as from greater than <NUM> mol% to less than or equal to <NUM> mol%. In embodiments, the glass-based substrate may be substantially free or free of SnO<NUM>.

In some embodiments, the glass-based substrates may have a Young's modulus that is greater than or equal to <NUM> GPa. In embodiments, the glass-based substrates have a Young's modulus that is greater than or equal to <NUM> GPa, such as greater than or equal to <NUM> GPa, greater than or equal to <NUM> GPa, greater than or equal to <NUM> GPa, greater than or equal to <NUM> GPa, greater than or equal to <NUM> GPa, greater than or equal to <NUM> GPa, greater than or equal to <NUM> GPa, greater than or equal to <NUM> GPa, or more. In some embodiments, the glass-based substrates may have a Young's modulus in the range from greater than or equal to <NUM> GPa to less than or equal to <NUM> GPa, such as from greater than or equal to <NUM> GPa to less than or equal to <NUM> GPa, from greater than or equal to <NUM> GPa to less than or equal to <NUM> GPa, from greater than or equal to <NUM> GPa to less than or equal to <NUM> GPa, from greater than or equal to <NUM> GPa to less than or equal to <NUM> GPa, <NUM> GPa, or any and all sub-ranges formed from these endpoints.

In some embodiments, the glass-based substrates may have a <NUM> Pa•s (<NUM> P) temperature of less than or equal to <NUM>, such as less than or equal to less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, or less. The low <NUM> Pa•s (<NUM> P) temperature improves the meltability and thereby manufacturability of the glass-based substrate compositions.

In some embodiments, the glass-based substrates may have a liquidus viscosity of greater than or equal to <NUM> kPa•s (<NUM> kP), such as greater than or equal to <NUM> kPa•s (<NUM> kP), greater than or equal to <NUM> kPa•s (<NUM> kP), or more. Increases in the Li<NUM>O content of the glass-based substrate decrease the liquidus viscosity of the glass-based substrate composition. Maintaining the liquidus viscosity of the glass-based substrate at greater than about <NUM> kPa•s (<NUM> kP) allows the glass-based substrates to be produced on a variety of manufacturing platforms. If the liquidus viscosity decreases too much, the manufacturability of the glass-based substrates is decreased.

The glass-based substrate may have any appropriate geometry. In some embodiments, the glass-based substrate may have a thickness of less than or equal to <NUM>, such as less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, or less. In embodiments, the glass-based substrate may have a thickness from greater than or equal to <NUM> to less than or equal to <NUM>, such as from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, or any and all sub-ranges formed from these endpoints. In some embodiments, the glass-based substrate may have a plate or sheet shape. In some other embodiments, the glass-based substrates may have a <NUM>. 5D or 3D shape. As utilized herein, a "<NUM>. 5D shape" refers to a sheet shaped article with at least one major surface being at least partially nonplanar, and a second major surface being substantially planar. As utilized herein, a "3D shape" refers to an article with first and second opposing major surfaces that are at least partially nonplanar. The glass-based articles may have dimensions and shapes substantially similar or the same as the glass-based substrates from which they are formed.

The glass-based articles may be produced from the glass-based substrate by exposure to water vapor under any appropriate conditions. The exposure may be carried out in any appropriate device, such as a furnace with relative humidity control. The exposure may also be carried out at an elevated pressure, such as a furnace or autoclave with relative humidity and pressure control.

In some embodiments, the glass-based articles may be produced by exposing a glass-based substrate to an environment with a pressure greater than ambient pressure and containing water vapor. The environment may have a pressure greater than <NUM> MPa and a water partial pressure of greater than or equal to <NUM> MPa, such as greater than or equal to <NUM> MPa. The elevated pressure allows in the exposure environment allows for a higher concentration of water vapor in the environment, especially as temperatures are increased. As the temperature increases the amount of water available for diffusion into the glass-based substrates to form glass-based articles decreases for a fixed volume, such as the interior of a furnace or autoclave. Thus, while increasing the temperature of the water vapor treatment environment may increase the rate of diffusion of hydrogen species into the glass-based substrate, reduced total water vapor concentration and stress relaxation at higher temperatures produce decreased compressive stress when pressure is constant. As temperatures increase, such as those above the atmospheric pressure saturation condition, applying increased pressure to reach the saturation condition increases the concentration of water vapor in the environment significantly.

At atmospheric pressure (<NUM> MPa), the water vapor saturation condition is <NUM>. As the temperature increases the amount of water available for diffusion into the glass-based substrates to form glass-based articles decreases for a fixed volume, such as the interior of a furnace or autoclave. Thus, while increasing the temperature of the water vapor treatment environment may increase the rate of diffusion of hydrogen species into the glass-based substrate, reduced total water vapor concentration may reduce the effectiveness of the treatment.

As temperatures increase, such as those above the atmospheric pressure saturation condition, applying increased pressure to reach the saturation condition increases the concentration of water vapor in the environment significantly. The saturation condition for water vapor as a function of pressure and temperature is shown in <FIG>. As shown in <FIG>, the regions above the curve will result in condensation of water vapor into liquid which is undesirable. Thus, the water vapor treatment conditions utilized herein may preferably fall on or under the curve in <FIG>, with further preferred conditions being on or just under the curve to maximize water vapor content. For these reasons, the water vapor treatment of the glass-based substrates may be carried out at elevated pressure.

High temperature and pressure conditions have been shown to produce glass-based articles with a hazy appearance. The hazy appearance is correlated to the concentration of added hydrogen species in the glass-based article, with higher temperature and pressure conditions producing higher concentrations of hydrogen species in the glass-based article. The formation of haze during the water treatment process may be addressed by utilizing the lithium containing compositions described herein or by selecting the treatment conditions to manage the amount of hydrogen species added to the glass-based article. For example, at high temperatures treatment pressures below the saturation pressure may be utilized to reduce the concentration of hydrogen species in the glass-based article. The concentration of the hydrogen species may be reduced by decreasing the total amount of hydrogen species diffused into the glass-based article, as evidenced by reduced weight gain during water vapor treatment, or by increasing the depth of layer for the same amount of weight gain. The approaches for mitigating haze, composition and treatment conditions, may be utilized in conjunction.

The lithium containing glass-based substrates described herein are exposed to a water vapor treatment in a saturated steam environment at a temperature of greater than or equal to <NUM>. The glass-based substrates containing lithium allow the use of a wider process window with higher temperatures and pressures while avoiding haze, thereby decreasing treatment times and increasing the efficiency of the strengthening process. The glass-based articles produced utilizing these haze mitigation strategies are substantially haze-free or haze-free in appearance.

In some embodiments, the glass-based substrates may be exposed to an environment at a pressure greater than or equal to <NUM> MPa, such as greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, greater than or equal to <NUM> MPa, or more. In embodiments, the glass-based substrates may be exposed to an environment at a pressure of from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, such as from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, from greater than or equal to <NUM> MPa to less than or equal to <NUM> MPa, <NUM> MPa, or any and all sub-ranges formed from any of these endpoints.

In some embodiments, the glass-based substrates are exposed to an environment at with a temperature of greater than or equal to <NUM>, such as greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, or more. In some embodiments, the glass-based substrates may be exposed to an environment with a temperature from greater than or equal to <NUM> to less than or equal to <NUM>, such as from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, from greater than or equal to <NUM> to less than or equal to <NUM>, <NUM>, or any and all sub-ranges formed from any of these endpoints.

In some embodiments, the glass-based substrate may be exposed to the water vapor containing environment for a time period sufficient to produce the desired degree of hydrogen-containing species diffusion and the desired compressive stress layer. In some embodiments, the glass-based substrate may be exposed to the water vapor containing environment for greater than or equal to <NUM> hours, such as greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, greater than or equal to <NUM> hours, or more. In some embodiments, the glass-based substrate may be exposed to the water vapor containing environment for a time period from greater than or equal to <NUM> hours to less than or equal to <NUM> days, such as from greater than or equal to <NUM> hours to less than or equal to <NUM> days, from greater than or equal to <NUM> hours to less than or equal to <NUM> days, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, from greater than or equal to <NUM> hours to less than or equal to <NUM> hours, <NUM> hours, or any and all sub-ranges formed from any of these endpoints.

In some embodiments, the glass-based substrates may be exposed to multiple water vapor containing environments. In embodiments, the glass-based substrate may be exposed to a first environment to form a first glass-based article with a first compressive stress layer extending from a surface of the first glass-based article to a first depth of compression, and the first glass-based article may then be exposed to a second environment to form a second glass-based article with a second compressive stress layer extending from a surface of the second glass-based article to a second depth of compression. The first environment has a first water partial pressure and a first temperature, and the glass-based substrate is exposed to the first environment for a first time period. The second environment has a second water partial pressure and a second temperature, and the first glass-based article is exposed to the second environment for a second time period.

At least one of the first environment and the second environment has a relative humidity of <NUM>%. In embodiments, the first and second environments may be, independently, a saturated steam environment.

The first compressive stress layer includes a first maximum compressive stress, and the second compressive stress layer includes a second maximum compressive stress. In embodiments, the first maximum compressive stress is less than the second maximum compressive stress. The second maximum compressive stress may be compared to a compressive stress "spike" of the type formed through multi-step or mixed bath ion exchange techniques. The first and second maximum compressive stress may have any of the values disclosed herein with respect to the compressive stress of the glass-based article. In embodiments, the second maximum compressive stress may be greater than or equal to <NUM> MPa.

The first depth of compression may be less than or equal to the second depth of compression. In some embodiments, the first depth of compression is less than the second depth of compression. The first depth of compression and the second depth of compression may have any of the values disclosed herein with respect to the depth of compression. In embodiments, the second depth of compression is greater than <NUM>.

The first temperature may be greater than or equal to the second temperature. In embodiments, the first temperature is greater than the second temperature. The first and second temperatures may be any of the temperatures disclosed in connection with the elevated pressure method.

The first time period may be less than or equal to the second time period. In embodiments, the first time period is less than the second time period. The first and second time periods may be any of the time periods disclosed in connection with the elevated pressure method.

In embodiments, any or all of the multiple exposures to a water vapor containing environment may be performed at an elevated pressure. For example, at least one of the first environment and the second environment may have a pressure greater than <NUM> MPa. The first and second environments may have any pressure disclose in connection with the elevated pressure method.

In some embodiments, the multiple water vapor environment exposure technique may include more than two exposure environments. In embodiments, the second glass-based article may be exposed to a third environment to form a third glass-based article. The third environment has a third water partial pressure and a third temperature, and the second glass-based article is exposed to the third environment for a third time period. The third glass-based article includes a third compressive stress layer extending from a surface of the article to a third depth of compression and having a third maximum compressive stress. The third water partial pressure may be greater than or equal to <NUM> MPa or greater than or equal to <NUM> MPa. The values of any of the properties of the third environment and third glass-based article may be selected from those disclosed for the corresponding properties in connection with the elevated pressure method.

In some embodiments, the first glass-based article may be cooled to ambient temperature or otherwise removed from the first environment after the conclusion of the first time period and prior to being exposed to the second environment. In some embodiments, the first glass-based article may remain in the first environment after the conclusion of the first time period, and the first environment conditions may be changed to the second environment conditions without cooling to ambient temperature or removing the first glass-based article from the water vapor containing environment.

The methods of producing the glass-based articles disclosed herein may be free of an ion exchange treatment with an alkali ion source. In embodiments, the glass-based articles are produced by methods that do not include an ion exchange with an alkali ion source. Stated differently, in some embodiments the glass-based substrates and glass-based articles are not subjected to an ion exchange treatment with an alkali ion source.

The exposure conditions may be modified to reduce the time necessary to produce the desired amount of hydrogen-containing species diffusion into the glass-based substrate. For example, the temperature may be increased to reduce the time required to achieve the desired degree of hydrogen-containing species diffusion and depth of layer into the glass-based substrate.

The methods and glass-based substrate compositions disclosed herein may produce glass-based articles that have a substantially haze-free or haze-free appearance.

Glass compositions that are particularly suited for formation of the glass-based articles described herein were formed into glass-based substrates, and the glass compositions are provided in Table I below. The density of the glass compositions was determined using the buoyancy method of ASTM C693-<NUM>(<NUM>). The strain point and anneal point were determined using the beam bending viscosity method of ASTM C598-<NUM>(<NUM>). The softening point was determined using the parallel plate viscosity method of ASTM C1351M-<NUM>(<NUM>). The Young's modulus and Poisson's ratio values refer to values as measured by a resonant ultrasonic spectroscopy technique of the general type set forth in ASTM E2001-<NUM>, titled "Standard Guide for Resonant Ultrasound Spectroscopy for Defect Detection in Both Metallic and Non-metallic Parts. " The stress optical coefficient (SOC) was measured according to Procedure C (Glass Disc Method) described in ASTM standard C770-<NUM>, entitled "Standard Test Method for Measurement of Glass Stress-Optical Coefficient. " The refractive index was measured at a wavelength of <NUM>. The liquidus temperature was measured in accordance with ASTM C829-<NUM> (<NUM>), titled "Standard Practice for Measurement of Liquidus Temperature of Glass by the Gradient Furnace Method. " The liquidus viscosity was determined by measuring the viscosity of the glass at the liquidus temperature in accordance with ASTM C965-<NUM>(<NUM>), titled "Standard Practice for Measuring Viscosity of Glass Above the Softening Point.

Samples having the compositions shown in Table I were exposed to water vapor containing environments to form glass articles having compressive stress layers. The sample composition and the environment the samples were exposed to, including the temperature, pressure, and exposure time, are shown in Table II below. The exposure environments were saturated where possible based on the temperature and pressure conditions. The resulting maximum compressive stress and depth of compression as measured by surface stress meter (FSM) is also reported in Table II.

Claim 1:
A glass-based article, comprising:
a hydrogen-containing layer extending from the surface of the glass-based article to a depth of layer, wherein a hydrogen concentration of the hydrogen-containing layer decreases from a maximum hydrogen concentration to the depth of layer;
a compressive stress layer extending from the surface of the glass-based article to a depth of compression, wherein the compressive stress layer comprises a compressive stress of greater than or equal to <NUM> MPa; and
a composition at the center of the glass-based article comprising:
greater than or equal to <NUM> mol% to less than or equal to <NUM> mol% SiO<NUM>,
greater than or equal to <NUM> mol% to less than or equal to <NUM> mol% Al<NUM>O<NUM>,
greater than or equal to <NUM> mol% to less than or equal to <NUM> mol% P<NUM>O<NUM>,
greater than or equal to <NUM> mol% to less than or equal to <NUM> mol% Li<NUM>O, and
greater than or equal to <NUM> mol% to less than or equal to <NUM> mol% K<NUM>O.