US20240043315A1

Movatterモバイル変換

Info

Publication number: US20240043315A1
Application number: US18/380,764
Authority: US
Inventors: Xiaoju Guo; Peter Joseph Lezzi; Jian Luo
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2019-11-26
Filing date: 2023-10-17
Publication date: 2024-02-08
Also published as: KR20220108079A; US20210155527A1; JP2023503879A; EP4065527A2; WO2021137950A2; WO2021137950A3; US11827556B2; TW202120448A; CN114728836A

Abstract

A glass composition includes: Si2O, greater than 0 mol % to less than or equal to 24 mol % Al2O3, B2O3, K2O, greater than or equal to 10 mol % to less than or equal to 38 mol % MgO, Na2O, and Li2O. The glass composition may have a fracture toughness of greater than or equal 0.80 MPa√m and a Young's modulus of greater than or equal to 80 GPa to less than or equal to 120 GPa. The glass composition is chemically strengthenable. The glass composition may be used in a glass article or a consumer electronic product.

Description

This application is a continuation of U.S. patent application Ser. No. 17/095,814 filed on Nov. 12, 2020, which claims the benefit of priority of U.S. Provisional Application Ser. No. 62/940,301 filed on Nov. 26, 2019, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUNDField

The present specification generally relates to glass compositions suitable for use as cover glass for electronic devices. More specifically, the present specification is directed to magnesium containing aluminosilicate glasses that may be formed into cover glass for electronic devices.

Technical Background

The mobile nature of portable devices, such as smart phones, tablets, portable media players, personal computers, and cameras, makes these devices particularly vulnerable to accidental dropping on hard surfaces, such as the ground. These devices typically incorporate cover glasses, which may become damaged upon impact with hard surfaces. In many of these devices, the cover glasses function as display covers, and may incorporate touch functionality, such that use of the devices is negatively impacted when the cover glasses are damaged.

There are two major failure modes of cover glass when the associated portable device is dropped on a hard surface. One of the modes is flexure failure, which is caused by bending of the glass when the device is subjected to dynamic load from impact with the hard surface. The other mode is sharp contact failure, which is caused by introduction of damage to the glass surface. Impact of the glass with rough hard surfaces, such as asphalt, granite, etc., can result in sharp indentations in the glass surface. These indentations become failure sites in the glass surface from which cracks may develop and propagate.

Glass can be made more resistant to flexure failure by the ion-exchange technique, which involves inducing compressive stress in the glass surface. However, the ion-exchanged glass will still be vulnerable to dynamic sharp contact, owing to the high stress concentration caused by local indentations in the glass from the sharp contact.

It has been a continuous effort for glass makers and handheld device manufacturers to improve the resistance of handheld devices to sharp contact failure. Solutions range from coatings on the cover glass to bezels that prevent the cover glass from impacting the hard surface directly when the device drops on the hard surface. However, due to the constraints of aesthetic and functional requirements, it is very difficult to completely prevent the cover glass from impacting the hard surface.

It is also desirable that portable devices be as thin as possible. Accordingly, in addition to strength, it is also desired that glasses to be used as cover glass in portable devices be made as thin as possible. Thus, in addition to increasing the strength of the cover glass, it is also desirable for the glass to have mechanical characteristics that allow it to be formed by processes that are capable of making thin glass articles, such as thin glass sheets.

Accordingly, a need exists for glasses that can be strengthened, such as by ion exchange, and that have the mechanical properties that allow them to be formed as thin glass articles.

SUMMARY

According to aspect (2), the glass of aspect (1) is provided, wherein the composition has a liquidus viscosity of less than 100 Poise.

According to aspect (3), the glass of any of aspects (1) to the preceding aspect is provided, wherein the composition has a fracture toughness of greater than or equal 0.80 MPa√m.

According to aspect (4), the glass of any of aspects (1) to the preceding aspect is provided, wherein the composition has a fracture toughness of greater than or equal 0.90 MPa√m.

According to aspect (5), the glass of any of aspects (1) to the preceding aspect is provided, wherein the composition has a Young's modulus of greater than or equal to 80 GPa to less than or equal to 120 GPa.

According to aspect (6), the glass of any of aspects (1) to the preceding aspect is provided, wherein the composition has a hardness of greater than or equal to 6.5 GPa to less than or equal to 9.2 GPa.

According to aspect (7), a glass is provided. The glass has a composition including: Si₂O; greater than 0 mol % to less than or equal to 24 mol % Al₂O₃; B₂O₃; K₂O; greater than or equal to 10 mol % to less than or equal to 38 mol % MgO; Na₂O; and Li₂O. The glass has a fracture toughness of greater than or equal 0.80 MPa√m, and a Young's modulus of greater than or equal to 80 GPa to less than or equal to 120 GPa.

According to aspect (8), the glass of aspect (7) is provided, further comprising CaO.

According to aspect (9), the glass of any of aspects (7) to the preceding aspect is provided, comprising greater than or equal to 34 mol % to less than or equal to 59 mol % SiO₂.

According to aspect (10), the glass of any of aspects (7) to the preceding aspect is provided, comprising greater than or equal to 0.80 mol % to less than or equal to 23.60 mol % Al₂O₃.

According to aspect (11), the glass of any of aspects (7) to the preceding aspect is provided, comprising greater than or equal to 1.35 mol % to less than or equal to 13.50 mol % B₂O₃.

According to aspect (12), the glass of any of aspects (7) to the preceding aspect is provided, comprising greater than or equal to 0 mol % to less than or equal to 15.80 mol % CaO.

According to aspect (13), the glass of any of aspects (7) to the preceding aspect is provided, comprising greater than or equal to 0.20 mol % to less than or equal to 0.50 mol % K₂O.

According to aspect (14), the glass of any of aspects (7) to the preceding aspect is provided, comprising greater than or equal to 9.80 mol % to less than or equal to 37.40 mol % MgO.

According to aspect (15), the glass of any of aspects (7) to the preceding aspect is provided, comprising greater than or equal to 3.00 mol % to less than or equal to 9.00 mol % Na₂O.

According to aspect (16), the glass of any of aspects (7) to the preceding aspect is provided, comprising greater than or equal to 4.00 mol % to less than or equal to 9.00 mol % Li₂O.

According to aspect (17), the glass of any of aspects (7) to the preceding aspect is provided, wherein the composition has a fracture toughness of greater than or equal 0.90 MPa√m.

According to aspect (18), the glass of any of aspects (7) to the preceding aspect is provided, wherein the composition has a liquidus viscosity of less than 100 Poise.

According to an aspect (19), a glass-based article is provided. The glass-based article is formed by ion exchanging a glass-based substrate. The glass-based article includes a compressive stress region extending from a surface of the glass-based article to a depth of compression. The glass-based substrate may have any of the compositions according to the preceding aspects.

According to aspect (20), a consumer electronic product is provided. The consumer electronic product includes: a housing comprising a front surface, a back surface and side surfaces; electrical components at least partially within the housing, the electrical components comprising a controller, a memory, and a display, the display at or adjacent the front surface of the housing; and a cover disposed over the display. At least a portion of at least one of the housing or the cover includes the glass-based article according to aspect (19).

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

It is to be understood that both the foregoing general description 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

FIG.1 schematically depicts a cross section of a glass having compressive stress layers on surfaces thereof according to embodiments disclosed and described herein;

FIG.2A is a plan view of an exemplary electronic device incorporating any of the glass articles disclosed herein; and

FIG.2B is a perspective view of the exemplary electronic device ofFIG.2A.

DETAILED DESCRIPTION

Reference will now be made in detail to magnesium containing alkali aluminosilicate glasses according to various embodiments. Alkali aluminosilicate glasses have good ion exchangeability, and chemical strengthening processes have been used to achieve high strength and high toughness properties in alkali aluminosilicate glasses. Sodium aluminosilicate glasses are highly ion exchangeable glasses with high glass formability and quality. Lithium aluminosilicate glasses are highly ion exchangeable glasses with high glass quality. The substitution of Al₂O₃into the silicate glass network increases the interdiffusivity of monovalent cations during ion exchange. By chemical strengthening in a molten salt bath (e.g., KNO₃or NaNO₃), glasses with high strength, high toughness, and high indentation cracking resistance can be achieved. The stress profiles achieved through chemical strengthening may have a variety of shapes that increase the drop performance, strength, toughness, and other attributes of the glass articles.

Therefore, alkali aluminosilicate glasses with good physical properties, chemical durability, and ion exchangeability have drawn attention for use as cover glass. In particular, lithium containing aluminosilicate glasses, which have higher fracture toughness and fast ion exchangeability, are provided herein. Through different ion exchange processes, greater central tension (CT), depth of compression (DOC), and high compressive stress (CS) can be achieved. However, the addition of lithium in the alkali aluminosilicate glass may reduce the melting point, softening point, or liquidus viscosity of the glass.

In embodiments of glass compositions described herein, the concentration of constituent components (e.g., SiO₂, Al₂O₃, Li₂O, and the like) are given in mole percent (mol %) on an oxide basis, unless otherwise specified. Components of the alkali aluminosilicate glass composition according to embodiments are discussed individually below. It should be understood that any of the variously recited ranges of one component may be individually combined with any of the variously recited ranges for any other component. As used herein, a trailing 0 in a number is intended to represent a significant digit for that number. For example, the number “1.0” includes two significant digits, and the number “1.00” includes three significant digits.

Disclosed herein are magnesium containing lithium aluminosilicate glass compositions that exhibit a high fracture toughness (K_IC). In some embodiments, the glass compositions are characterized by at least one of a K_ICfracture toughness value of at least 0.80 MPa√m. Without wishing to be bound by any particular theory, it is believed that the high fracture toughness of the glasses described herein is due at least in part to the concentration of the high field strength components contained in the glass composition.

In embodiments, the glass composition may be substantially free or free of TiO₂. As used herein, the term “substantially free” means that the component is not added as a component of the batch material even though the component may be present in the final glass in very small amounts as a contaminant, such as less than 0.01 mol %. The inclusion of TiO₂in the glass composition, the glass may become susceptible to devitrification and/or exhibit an undesirable coloration.

In embodiments, the glass composition may be substantially free or free of ZrO₂. The inclusion of ZrO₂in the glass composition may result in the formation of undesirable zirconia in the glass, due at least in part to the low solubility of ZrO₂in the glass.

In embodiments, the glass composition may be substantially free or free of P₂O₅. The inclusion of P₂O₅in the glass composition may undesirably reduce the meltability and formability of the glass composition, thereby impairing the manufacturability of the glass composition. It is not necessary to include P₂O₅in the glass compositions described herein to achieve the desired ion exchange performance. For this reason, P₂O₅may be excluded from the glass composition to avoid negatively impacting the manufacturability of the glass composition while maintaining the desired ion exchange performance.

In embodiments, the glass composition may optionally include one or more fining agents. In some embodiments, the fining agents may include, for example, SnO₂. In such embodiments, SnO₂may be present in the glass composition in an amount less than or equal to 0.2 mol %, such as from greater than or equal to 0 mol % to less than or equal to 0.1 mol %, and all ranges and sub-ranges between the foregoing values. In other embodiments, SnO₂may be present in the glass composition in an amount from greater than or equal to 0 mol % to less than or equal to 0.2 mol %, or greater than or equal to 0.1 mol % to less than or equal to 0.2 mol %, and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may be substantially free or free of SnO₂.

In embodiments, the glass composition may be substantially free of one or both of arsenic and antimony. In other embodiments, the glass composition may be free of one or both of arsenic and antimony.

In embodiments, the glass composition may be substantially free of Fe₂O₃. Iron is often present in raw materials utilized to form glass compositions, and as a result may be detectable in the glass compositions described herein even when not actively added to the glass batch.

Physical properties of the alkali aluminosilicate glass compositions as disclosed above will now be discussed. These physical properties can be achieved by modifying the component amounts of the alkali aluminosilicate glass composition, as will be discussed in more detail with reference to the examples.

Glass compositions according to embodiments have a high fracture toughness. Without wishing to be bound by any particular theory, the high fracture toughness may impart improved drop performance to the glass compositions. As utilized herein, the fracture toughness refers to the K_ICvalue, and is measured by the chevron notched short bar method. The chevron notched short bar (CNSB) method utilized to measure the K_ICvalue is disclosed in Reddy, K. P. R. et al, “Fracture Toughness Measurement of Glass and Ceramic Materials Using Chevron-Notched Specimens,” J. Am. Ceram. Soc., 71 [6], C-310-C-313 (1988) except that Y*_mis calculated using equation 5 of Bubsey, R. T. et al., “Closed-Form Expressions for Crack-Mouth Displacement and Stress Intensity Factors for Chevron-Notched Short Bar and Short Rod Specimens Based on Experimental Compliance Measurements,” NASA Technical Memorandum 83796, pp. 1-30 (October 1992). Additionally, the K_ICvalues are measured on non-strengthened glass samples, such as measuring the K_ICvalue prior to ion exchanging a glass article.

In embodiments, the glass composition may have a shear modulus (G) of from greater than or equal to 35 GPa to less than or equal to 41 GPa, such as from greater than or equal to 36 GPa to less than or equal to 40 GPa, from greater than or equal to 37 GPa to less than or equal to 39 GPa, greater than or equal to 38 GPa, and all ranges and sub-ranges between the foregoing values. The shear modulus values recited in this disclosure refer to a value as measured by a resonant ultrasonic spectroscopy technique of the general type set forth in ASTM E2001-13, titled “Standard Guide for Resonant Ultrasound Spectroscopy for Defect Detection in Both Metallic and Non-metallic Parts.”

In embodiments, the glass compositions may have a Poisson's ratio (ν) of from greater than or equal to 0.2 to less than or equal to 0.27, such as 0.26, and all ranges and sub-ranges between the foregoing values. The Poisson's ratio value recited in this disclosure refers to a value as measured by a resonant ultrasonic spectroscopy technique of the general type set forth in ASTM E2001-13, titled “Standard Guide for Resonant Ultrasound Spectroscopy for Defect Detection in Both Metallic and Non-metallic Parts.”

From the above compositions, glass articles according to embodiments may be formed by any suitable method. In embodiments, the glass compositions may be formed by rolling processes.

The glass composition and the articles produced therefrom may be characterized by the manner in which it may be formed. For instance, the glass composition may be characterized as float-formable (i.e., formed by a float process) or roll-formable (i.e., formed by a rolling process).

In one or more embodiments, the glass compositions described herein may form glass articles that exhibit an amorphous microstructure and may be substantially free of crystals or crystallites. In other words, the glass articles formed from the glass compositions described herein may exclude glass-ceramic materials.

As mentioned above, in embodiments, the glass compositions described herein can be strengthened, such as by ion exchange, making a glass article that is damage resistant for applications such as, but not limited to, display covers. With reference toFIG.1, a glass article is depicted that has a first region under compressive stress (e.g., first and second

compressive layers

120,122 inFIG.1) extending from the surface to a depth of compression (DOC) of the glass article and a second region (e.g., central region130 inFIG.1) under a tensile stress or central tension (CT) extending from the DOC into the central or interior region of the glass article. As used herein, DOC refers to the depth at which the stress within the glass article changes from compressive to tensile. At the DOC, the stress crosses from a positive (compressive) stress to a negative (tensile) stress and thus exhibits a stress value of zero.

According to the convention normally used in the art, compression or compressive stress is expressed as a negative (<0) stress and tension or tensile stress is expressed as a positive (>0) stress. Throughout this description, however, CS is expressed as a positive or absolute value—i.e., as recited herein, CS=|CS|. The compressive stress (CS) has a maximum at or near the surface of the glass article, and the CS varies with distance d from the surface according to a function. Referring again toFIG.1, afirst segment120 extends from first surface110 to a depth d₁and asecond segment122 extends from second surface112 to a depth dz. Together, these segments define a compression or CS of glass article100. Compressive stress (including surface CS) may be measured by surface stress meter (FSM) using commercially available instruments such as the FSM-6000, manufactured by Orihara Industrial Co., Ltd. (Japan). 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 C770-16, entitled “Standard Test Method for Measurement of Glass Stress-Optical Coefficient,” the contents of which are incorporated herein by reference in their entirety.

In one or more embodiments, Na⁺ and K⁺ ions are exchanged into the glass article and the Na⁺ ions diffuse to a deeper depth into the glass article than the K⁺ ions. The depth of penetration of K⁺ ions (“Potassium DOL”) is distinguished from DOC because it represents the depth of potassium penetration as a result of an ion exchange process. The Potassium DOL is typically less than the DOC for the articles described herein. Potassium DOL is measured using a surface stress meter such as the commercially available FSM-6000 surface stress meter, manufactured by Orihara Industrial Co., Ltd. (Japan), which relies on accurate measurement of the stress optical coefficient (SOC), as described above with reference to the CS measurement. The Potassium DOL of the glass articles may be from greater than or equal to 5 μm to less than or equal to 30 μm, such as from greater than or equal to 6 μm to less than or equal to 25 μm, from greater than or equal to 7 μm to less than or equal to 20 μm, from greater than or equal to 8 μm to less than or equal to 15 μm, or from greater than or equal to 9 μm to less than or equal to 10 μm, and all ranges and sub-ranges between the foregoing values.

The compressive stress of both major surfaces (110,112 inFIG.1) is balanced by stored tension in the central region (130) of the glass article. The maximum central tension (CT) and DOC values may be measured using a scattered light polariscope (SCALP) technique known in the art. The refracted near-field (RNF) method or SCALP may be used to determine the stress profile of the glass articles. When the RNF method is utilized to measure the stress profile, the maximum CT value provided by SCALP is utilized in the RNF method. In particular, the stress profile determined by RNF is force balanced and calibrated to the maximum CT value provided by a SCALP measurement. The RNF method is described in U.S. Pat. No. 8,854,623, entitled “Systems and methods for measuring a profile characteristic of a glass sample”, which is incorporated herein by reference in its entirety. In particular, the RNF method includes placing the glass article adjacent to a reference block, generating a polarization-switched light beam that is switched between orthogonal polarizations at a rate of between 1 Hz and 50 Hz, measuring an amount of power in the polarization-switched light beam and generating a polarization-switched reference signal, wherein the measured amounts of power in each of the orthogonal polarizations are within 50% of each other. The method further includes transmitting the polarization-switched light beam through the glass sample and reference block for different depths into the glass sample, then relaying the transmitted polarization-switched light beam to a signal photodetector using a relay optical system, with the signal photodetector generating a polarization-switched detector signal. The method also includes dividing the detector signal by the reference signal to form a normalized detector signal and determining the profile characteristic of the glass sample from the normalized detector signal.

The high fracture toughness values of the glass compositions described herein also may enable improved performance. The frangibility limit of the glass articles produced utilizing the glass compositions described herein is dependent at least in part on the fracture toughness. For this reason, the high fracture toughness of the glass compositions described herein allows for a large amount of stored strain energy to be imparted to the glass articles formed therefrom without becoming frangible. The increased amount of stored strain energy that may then be included in the glass articles allows the glass articles to exhibit increased fracture resistance, which may be observed through the drop performance of the glass articles. The relationship between the frangibility limit and the fracture toughness is described in U.S. patent application Ser. No. 16/565,899, titled “Glass-based Articles with Improved Fracture Resistance,” filed Sep. 10, 2019, the entirety of which is incorporated herein by reference. The relationship between the fracture toughness and drop performance is described in U.S. patent application Ser. No. 16/425,217, titled “Glass with Improved Drop Performance,” filed May 29, 2019, the entirety of which is incorporated herein by reference.

As noted above, DOC is measured using a scattered light polariscope (SCALP) technique known in the art. The DOC is provided in some embodiments herein as a portion of the thickness (t) of the glass article. In embodiments, the glass articles may have a depth of compression (DOC) from greater than or equal to 0.15 t to less than or equal to 0.25 t, such as from greater than or equal to 0.18 t to less than or equal to 0.22 t, or from greater than or equal to 0.19 t to less than or equal to 0.21 t, and all ranges and sub-ranges between the foregoing values.

The ion exchange process may be performed in an ion exchange solution under processing conditions that provide an improved compressive stress profile as disclosed, for example, in U.S. Patent Application Publication No. 2016/0102011, which is incorporated herein by reference in its entirety. In some embodiments, the ion exchange process may be selected to form a parabolic stress profile in the glass articles, such as those stress profiles described in U.S. Patent Application Publication No. 2016/0102014, which is incorporated herein by reference in its entirety.

After an ion exchange process is performed, it should be understood that a composition at the surface of an ion exchanged glass article is be different than the composition of the as-formed glass substrate (i.e., the glass substrate before it undergoes an ion exchange process). This results from one type of alkali metal ion in the as-formed glass substrate, such as, for example Li⁺ or Na⁺, being replaced with larger alkali metal ions, such as, for example Na⁺ or K⁺, respectively. However, the glass composition at or near the center of the depth of the glass article will, in embodiments, still have the composition of the as-formed non-ion exchanged glass substrate utilized to form the glass article.

The glass 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, and the like), architectural articles, transportation articles (e.g., automobiles, 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 articles disclosed herein is shown inFIGS.2A and2B. Specifically,FIGS.2A and2B show a consumer electronic device200 including ahousing202 havingfront204, back206, and side surfaces208; 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 display210 at or adjacent to the front surface of the housing; and acover212 at or over the front surface of the housing such that it is over the display. In embodiments, at least a portion of at least one of thecover212 and thehousing202 may include any of the glass articles described herein.

Examples

Embodiments will be further clarified by the following examples. It should be understood that these examples are not limiting to the embodiments described above.

Glass compositions were prepared and analyzed. The analyzed glass compositions had the components listed in Table I below, and were prepared by conventional glass forming methods. In Table I, all components are in mol %, and the K_ICfracture toughness, the Poisson's Ratio (ν), the Young's modulus (E), the shear modulus (G), and the liquidus viscosity of the glass compositions were measured according to the methods disclosed in this specification.

TABLE I

Composition	1	2	3	4	5	6

SiO₂	45.45	43.21	38.78	41.59	39.64	36.76
Al₂O₃	2.06	4.17	8.34	2.04	4.25	4.27
B₂O₃	12.21	12.15	12.29	12.19	11.58	11.40
MgO	27.92	28.15	28.31	31.98	32.66	36.03
CaO	0.08	0.09	0.09	0.09	0.10	0.11
Li₂O	3.99	3.98	3.95	3.91	3.94	3.93
Na₂O	8.04	8.02	8.02	7.97	7.67	7.38
K₂O	0.24	0.23	0.22	0.22	0.16	0.11
Fe₂O₃	0.01	0.01	0.01	0.01	0.01	0.01
K_IC	—	0.818	0.818	0.821	0.802	—
(MPa√m)
Young's	89.6	89.4	88.5	92.3	92.4	94.9
modulus
(GPa)
Shear	35.9	35.6	35.4	36.7	36.8	37.8
modulus
(GPa)
Poisson's	0.247	0.254	0.247	0.256	0.254	0.255
ratio
Liquidus	26	—	—	—	—	—
viscosity
(Poise)

Composition	7	8	9	10	11	12

SiO₂	44.44	43.47	37.99	40.21	37.08	34.96
Al₂O₃	2.00	4.30	8.15	2.01	3.99	3.91
B₂O₃	13.55	12.09	13.27	12.94	13.02	13.32
MgO	26.44	27.63	27.18	32.00	32.75	34.45
CaO	0.18	0.19	0.19	0.21	0.21	0.22
Li₂O	9.02	8.67	8.99	8.88	8.87	8.79
Na₂O	3.97	3.42	3.88	3.70	3.72	3.90
K₂O	0.40	0.20	0.34	0.03	0.35	0.42
Fe₂O3	0.01	0.01	0.01	0.02	0.02	0.01
K_IC	—	—	—	—	—	—
(MPa√m)
Young's	96.7	—	97.8	101.1	99.6	99.8
modulus
(GPa)
Shear	38.7	—	39.0	40.1	39.4	39.4
modulus
(GPa)
Poisson's	0.249	—	0.253	0.26	0.264	0.265
ratio
Liquidus	26	33	23	17	19	18
viscosity
(Poise)

Additional glass compositions were prepared having the components listed in Table II below. The additional glass compositions were prepared by conventional glass forming methods. In Table II, all components are in mol %, and the Young's modulus (E) and the hardness of the glass compositions were measured according to the methods disclosed in this specification.

TABLE II

Composition	13	14	15	16	17	18	19	20

SiO₂	45.95	46.93	53.36	47.69	53.83	47.47	49.12	48.22
Al₂O₃	23.61	19.40	9.67	17.88	9.01	20.52	13.65	19.00
B₂O₃	7.18	10.41	13.50	10.95	13.50	8.31	13.50	8.86
MgO	9.76	9.76	9.97	9.99	10.16	10.21	10.23	10.43
CaO	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
Li₂O	9.00	9.00	9.00	9.00	4.00	9.00	9.00	9.00
Na₂O	4.00	4.00	4.00	4.00	9.00	4.00	4.00	4.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	96.81	93.05	83.06	92.47	79.71	95.12	84.82	94.65
Modulus
(GPa)
Hardness	7.29	7.17	6.8	7.19	6.64	7.26	6.73	7.27
(GPa)

Composition	21	22	23	24	25	26	27	28

SiO₂	47.63	49.60	54.00	54.00	48.01	54.00	54.00	48.75
Al₂O₃	22.39	12.85	15.96	13.00	21.62	4.04	1.01	20.11
B₂O₃	5.94	13.50	6.00	6.00	6.23	6.00	6.00	6.79
MgO	10.54	10.55	10.57	10.61	10.65	10.70	10.73	10.86
CaO	0.00	0.00	0.97	3.89	0.00	12.76	15.76	0.00
Li₂O	9.00	4.00	9.00	9.00	9.00	9.00	9.00	9.00
Na₂O	4.00	9.00	3.00	3.00	4.00	3.00	3.00	4.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	97.41	82.58	94.77	93.21	95.78	101	103.78	96.5
Modulus
(GPa)
Hardness	7.34	6.66	7.55	7.62	7.39	8.1	8.37	7.41
(GPa)

Composition	29	30	31	32	33	34	35	36

SiO₂	49.84	49.27	50.35	54.00	54.00	54.00	50.85	51.90
Al₂O₃	17.87	21.20	18.97	10.81	7.89	4.94	20.05	17.86
B₂O₃	7.61	4.74	5.58	6.00	6.00	6.00	3.58	4.42
MgO	11.18	11.29	11.60	11.91	11.94	11.98	12.02	12.32
CaO	0.00	0.00	0.00	4.78	7.67	10.58	0.00	0.00
Li₂O	9.00	9.00	9.00	9.00	9.00	9.00	9.00	9.00
Na₂O	4.00	4.00	4.00	3.00	3.00	3.00	4.00	4.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	94.83	97	95.15	96.83	96.23	98.65	96.32	95.19
Modulus
(GPa)
Hardness	7.28	7.42	7.33	7.83	7.76	7.94	7.37	7.41
(GPa)

Composition	37	38	39	40	41	42	43	44

SiO₂	52.39	59.03	58.88	55.07	55.36	53.88	54.00	42.43
Al₂O₃	18.94	1.03	1.13	4.62	4.24	17.85	12.28	16.20
B₂O₃	2.45	13.50	13.50	13.50	13.50	1.35	6.00	13.50
MgO	12.73	12.95	13.00	13.32	13.40	13.42	14.31	14.38
CaO	0.00	0.00	0.00	0.00	0.00	0.00	0.92	0.00
Li₂O	9.00	4.00	9.00	9.00	4.00	9.00	9.00	9.00
Na₂O	4.00	9.00	4.00	4.00	9.00	4.00	3.00	4.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	94.97	—	82.1	82.17	78.67	95.06	94.69	95.58
Modulus
(GPa)
Hardness	7.38	—	7.36	7.18	6.89	7.47	7.56	7.34
(GPa)

Composition	45	46	47	48	49	50	51	52

SiO₂	54.00	37.75	42.67	51.97	52.27	54.00	54.00	37.76
Al₂O₃	0.96	20.48	15.38	5.78	5.33	10.22	7.45	19.69
B₂O₃	6.00	13.50	13.50	13.50	13.50	6.00	6.00	13.50
MgO	14.47	14.77	14.95	15.25	15.40	15.48	15.52	15.56
CaO	12.08	0.00	0.00	0.00	0.00	1.81	4.53	0.00
Li₂O	9.00	9.00	4.00	9.00	4.00	9.00	9.00	4.00
Na₂O	3.00	4.00	9.00	4.00	9.00	3.00	3.00	9.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	102.69	98.78	89.86	87.64	82.22	96.42	95.79	96.14
Modulus
(GPa)
Hardness	8.38	7.36	7.02	7.1	6.85	7.77	7.68	7.29
(GPa)

Composition	53	54	55	56	57	58	59	60

SiO₂	54.00	54.00	47.89	48.21	43.59	43.85	54.00	54.00
Al₂O₃	4.67	1.87	9.48	8.84	13.38	12.60	8.97	6.29
B₂O₃	6.00	6.00	13.50	13.50	13.50	13.50	6.00	6.00
MgO	15.56	15.61	15.63	15.95	16.04	16.55	17.66	17.71
CaO	7.27	10.02	0.00	0.00	0.00	0.00	0.87	3.50
Li₂O	9.00	9.00	9.00	4.00	9.00	4.00	9.00	9.00
Na₂O	3.00	3.00	4.00	9.00	4.00	9.00	3.00	3.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	100.96	101.21	88.97	86.23	89.06	89.19	97.02	96.54
Modulus
(GPa)
Hardness	8.09	8.14	6.94	6.93	7.01	7	7.81	7.8
(GPa)

Composition	61	62	63	64	65	66	67	68

SiO₂	54.00	54.00	53.81	53.67	50.70	50.87	37.01	46.76
Al₂O₃	3.61	0.90	1.01	1.11	2.22	2.03	15.87	5.67
B₂O₃	6.00	6.00	13.50	13.50	13.50	13.50	13.50	13.50
MgO	17.75	17.80	18.18	18.23	20.08	20.11	20.12	20.57
CaO	6.14	8.79	0.00	0.00	0.00	0.00	0.00	0.00
Li₂O	9.00	9.00	4.00	9.00	9.00	4.00	9.00	9.00
Na₂O	3.00	3.00	9.00	4.00	4.00	9.00	4.00	4.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	99.72	102.27	—	87.37	91.26	86.85	103.82	90.88
Modulus
(GPa)
Hardness	8.11	8.28	—	7.55	7.45	7.27	7.68	7.18
(GPa)

Composition	69	70	71	72	73	74	75	76

SiO₂	54.00	54.00	46.97	54.00	36.98	42.62	42.80	38.28
Al₂O₃	5.98	3.42	5.24	0.86	15.08	9.30	8.67	13.11
B₂O₃	6.00	6.00	13.50	6.00	13.50	13.50	13.50	13.50
MgO	20.69	20.75	20.80	20.80	20.94	21.08	21.53	21.62
CaO	0.83	3.33	0.00	5.84	0.00	0.00	0.00	0.00
Li2O	9.00	9.00	4.00	9.00	4.00	9.00	4.00	9.00
Na₂O	3.00	3.00	9.00	3.00	9.00	4.00	9.00	4.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	99.56	99.68	88.74	102.67	99.18	95.73	92.12	100.3
Modulus
(GPa)
Hardness	7.95	8.06	7.16	8.34	7.53	7.41	7.21	7.63
(GPa)

Composition	77	78	79	80	81	82	83	84

SiO₂	38.32	48.77	48.65	54.00	54.00	44.74	44.89	40.64
Al₂O₃	12.36	0.99	1.09	3.26	0.82	4.45	4.09	7.97
B₂O₃	13.50	13.50	13.50	6.00	6.00	13.50	13.50	13.50
MgO	22.32	23.24	23.27	23.45	23.51	23.82	24.02	24.40
CaO	0.00	0.00	0.00	0.79	3.18	0.00	0.00	0.00
Li₂O	4.00	4.00	9.00	9.00	9.00	9.00	4.00	9.00
Na₂O	9.00	9.00	4.00	3.00	3.00	4.00	9.00	4.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	94.26	—	93.25	101.21	101.88	97.61	94.13	104.89
Modulus
(GPa)
Hardness	7.35	—	7.69	8.09	8.28	7.73	7.55	8.07
(GPa)

Composition	85	86	87	88	89	90	91	92

SiO₂	40.74	36.33	36.30	54.00	43.81	43.90	39.85	39.93
Al₂O₃	7.41	11.67	10.96	0.78	1.07	0.97	4.36	4.02
B₂O₃	13.50	13.50	13.50	6.00	13.50	13.50	13.50	13.50
MgO	24.85	25.00	25.74	25.96	28.13	28.13	28.78	29.05
CaO	0.00	0.00	0.00	0.76	0.00	0.00	0.00	0.00
Li₂O	4.00	9.00	4.00	9.00	9.00	4.00	9.00	4.00
Na₂O	9.00	4.00	9.00	3.00	4.00	9.00	4.00	9.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	100.69	107.84	103.04	105.9	101.68	—	107.73	101.2
Modulus
(GPa)
Hardness	7.8	8.04	7.77	8.48	8.08	—	8.21	7.84
(GPa)

Composition	93	94	95	96	97	98	99	100

SiO₂	35.71	35.68	39.13	39.19	35.14	35.13	34.62	34.62
Al₂O₃	7.82	7.28	1.05	0.96	4.29	3.96	1.03	0.94
B₂O₃	13.50	13.50	13.50	13.50	13.50	13.50	13.50	13.50
MgO	29.47	30.04	32.82	32.86	33.57	33.92	37.35	37.44
CaO	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
Li₂O	9.00	4.00	9.00	4.00	9.00	4.00	9.00	4.00
Na₂O	4.00	9.00	4.00	9.00	4.00	9.00	4.00	9.00
K₂O	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
Young's	109.54	104.95	112.15	105.82	116.32	110.29	123.3	117.66
Modulus
(GPa)
Hardness	8.25	7.95	8.57	8.2	8.65	8.42	9.12	8.67
(GPa)

All compositional components, relationships, and ratios described in this specification are provided in mol % unless otherwise stated. All ranges disclosed in this specification include any and all ranges and subranges encompassed by the broadly disclosed ranges whether or not explicitly stated before or after a range is disclosed.

It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.