Ion exchangeable silicate glass

Abstract

the glass has high three-dimensional (3D) forming capabilities. The 3D forming capabilities of a cover glass can be enhanced by lower glass transition temperature and decreasing CTE. The glass composition is well suited for 3D forming and has high toughness, better service durability and high impact strength.

Description

[Technical Field]

[0001] This invention relates to a chemically strengthened silicate glass. More specifically, this invention relates to a protective glass composition with good 3D forming capability. Even more specifically, this invention relates to three-dimensional forming parameters (TDFP) for determining the 3D forming capability of glass. [Previous Technology]

[0002] In recent years, glass substrates have been widely used to protect the display screens of various electronic devices such as mobile phones, entertainment devices, tablets, laptops, digital cameras, and wearable devices. With the increase in display screen size and the decrease in the thickness of electronic devices, protective glass becomes more susceptible to scratches and breakage when subjected to impacts (e.g., contact with hard, angular objects). For this reason, the demand for chemically strengthened glass with high strength and durability has been generated. Furthermore, the use of curved or flexible displays is attracting increasing attention in the consumer electronics market. Therefore, protective glass used in electronic devices is now evolving from flat (2D) to curved (3D) forms or shapes. Since 3D protective glass helps to reinforce the corners / edges of curved or flexible displays, glass compositions with good 3D forming capabilities are required.

[0003] Furthermore, the properties of the protective glass are highly dependent on the reaction temperature and glass composition. Various compounds in different proportions have been used as raw materials for the production of protective glass. In addition, the protective glass is chemically strengthened through various processes such as ion exchange. This chemically strengthened glass exhibits excellent performance properties. A protective glass composition with appropriate 3D forming capability, thermal expansion properties, and annealing temperature is required. In view of the foregoing, a method for determining the 3D forming capability of the glass composition is needed.

[0004] Objects of the Invention Some objects of the present invention are described herein. One object of the present invention is to provide a protective glass composition. Another object is to provide a protective glass composition having high strengthening properties.

[0005] Another object of the present invention is to provide a protective glass composition having a high three-dimensional forming parameter (TDFP) describing high 3D forming capability. TDFP is defined as 1 / (glass transition temperature (Tg) × coefficient of thermal expansion (CTE)).

[0006] Another object of the present invention is to provide a protective glass composition with a TDFP value greater than 220. Protective glass with a TDFP value greater than 220 has good 3D molding capability.

[0007] Another object of the present invention is to provide a protective glass composition with higher toughness, lower density and longer service life.

[0008] Another object of the present invention is to subject the protective glass composition to multiple ion exchange processes.

[0009] Other objects and advantages of the present invention will become more apparent from the following description, which is not intended to limit the scope of the invention. [Summary of the Invention]

[0010] In one embodiment of the present invention, a protective glass composition has been disclosed. The present invention discloses a protective glass composition having high three-dimensional forming parameters (TDFP).

[0011] In one embodiment, TDFP is defined as 1 / (glass transition temperature (Tg) × coefficient of thermal expansion (CTE)).

[0012] In one embodiment, the TDFP of the glass should be greater than 220. When the TDFP is greater than 220, the glass has good 3D forming properties. When the TDFP is less than 220, the glass is not suitable for 3D forming. Glass with high strength and excellent 3D forming capability has better durability, high crack resistance, high strength retained after damage, and high sharp impact strength, and can withstand more device drops before failure.

[0013] In one embodiment, the protective glass composition has reduced non-crosslinked oxygen (NBO), which increases the toughness of the glass.

[0014] In one embodiment, the amount of SiO2 in the protective glass composition is reduced, which is compensated for by increasing the amount of B2O3 and Al2O3. The increase in the amount of Al2O3 keeps the basicity of the glass constant. The increase in the amount of Al2O3 results in a good ion exchange process during the preparation of the glass composition.

[0015] In one embodiment, the glass composition further comprises an alkali metal oxide. In one embodiment, the alkali metal oxide is selected from the group consisting of Li₂O, Na₂O, or K₂O. In one embodiment, the glass composition further comprises an alkaline earth metal oxide. In one embodiment, the alkaline earth metal oxide may be at least one of MgO, CaO, SrO, or BaO.

[0016] In one embodiment, the protective glass composition comprises about 40 mol% to about 70 mol% of SiO2, about 1 mol% to about 18 mol% of B2O3, and about 10 mol% to about 32 mol% of Al2O3. In one embodiment, the glass composition further comprises an alkali metal oxide, wherein the total sum of the alkali metal oxides present in the glass composition, R2O, is about 6 mol% to 38 mol%, and wherein R is at least one of Li, Na, or K. In one embodiment, the alkali metal oxide is selected from the group consisting of Li2O, Na2O, or K2O. In one embodiment, the glass composition further comprises an alkaline earth metal oxide, wherein MgO is about 0 mol% to about 5 mol%. In one embodiment, the glass composition further comprises about 0 mol% to about 7 mol% of P2O5 and about 0 mol% to about 5 mol% of ZnO. In one embodiment, the glass composition further comprises about 0 mol% to about 2.5 mol% of one or more refining agents, such as SnO2, Fe2O3, CeO2, chlorides, and sulfates. The glass composition further comprises about 0 mol% to about 5 mol% of TiO2.

[0017] In one embodiment, the shield glass can be provided with high strength via a chemical strengthening treatment involving multiple ion exchanges. In one embodiment, the glass composition is well-suited for a dual ion exchange process.

[0018] In one embodiment, the dual ion exchange process includes a first step of ion exchange followed by a second step of ion exchange on an outer surface region of the glass. In one embodiment, the ion exchange process is based on ion size. When larger ions from an external ion exchange bath exchange with smaller ions in the glass, the larger ions envelop the surface region previously occupied by the smaller ions, resulting in compressive stress on the glass surface and consequently increasing the strength of the glass material. It has been reported that the resulting compressive stress is proportional to the volume of glass in which the ion exchange occurs.

[0019] In one embodiment, the protective glass can be used as a substrate for a touch panel display and a back cover for such displays, such as liquid crystal displays (LCDs), field emission displays (FEDs), plasma displays (PDs), electroluminescent displays (ELDs), organic light-emitting diode displays (OLEDs), micro LEDs, or similar displays. The glass can also be used as a substrate for solar cell protective glass, a disk substrate, and a window glass panel. Furthermore, the glass is used as a protective window associated with various modes of transportation (such as air, sea, or land), and for wind protection in non-transportation applications. It is also used as fire-resistant glass. However, the protective glass is not limited to the above applications and can also be used as, for example, a coated substrate, a cooktop, a semiconductor interposer, a semiconductor carrier, a hard disk, an internal display, an automotive windshield, and many other applications.

[0020] These and other aspects, advantages and distinctive features of the present invention will become apparent from the following detailed description.

Implementation Method

[0022] In the following description, in the various views shown in the figures, the same reference numerals denote the same or corresponding parts. It should also be understood that, unless otherwise specified, terms such as "top," "bottom," "outward," "inward," and similar terms are convenient words and should not be construed as restrictive terms. Furthermore, whenever a group is described as comprising at least one of a set of elements or a combination thereof, it should be understood that the group may individually or in combination with each other comprise any number of those elements, substantially constitute or consist of them. Similarly, whenever a group is described as consisting of at least one of a set of elements or a combination thereof, it should be understood that the group may individually or in combination with each other consist of any number of those elements. Unless otherwise stated, when listing a range of values, it includes the upper and lower limits of the range and any range in between. As used herein, unless otherwise stated, the indefinite article "a / an" and the corresponding definite article "the" mean "at least one" or "one or more." It should also be understood that the various features disclosed in the specification and drawings can be used in any and all combinations.

[0023] As used herein, the term "glass article" is used in its broadest sense to include any object made wholly or partially of glass. Unless otherwise stated, all compositions are expressed as mole percentages (moles %). Unless otherwise stated, all temperatures are expressed in degrees Celsius (°C). Unless otherwise stated, the coefficient of thermal expansion (CTE) is expressed as 10⁻⁷ / °C and represents a value measured over a temperature range of about 50°C to about 300°C. As used herein, the term "annealing point" refers to the temperature at which the viscosity of the glass is approximately 1 × 10¹³.2 poise.

[0024] It should be noted that the terms “generally” and “about” may be used herein to indicate the degree of uncertainty inherent in any quantitative comparison, value, measurement or other representation. These terms are also used herein to indicate the extent to which a quantitative representation may differ from the stated reference without causing a change in the fundamental function of the subject matter.

[0025] Recently, with technological advancements, glass has been molded to form 3D curved protective glass. 3D curved protective glass offers advantages such as being lightweight, thin, transparent, clean, fingerprint-resistant, anti-glare, hard, scratch-resistant, and weather-resistant. Furthermore, the curved surface of 3D curved protective glass provides additional functionality for displays, enhancing their aesthetics or making them more appealing. As described below, protective glass is used to protect the display screens (e.g., touch-based displays) of electronic devices such as mobile phones, smartphones, tablets, wearable devices, and digital cameras. Protective glass used on the back of devices provides strength and also facilitates better electromagnetic transmission. However, protective glass is not limited to the above applications and can also be used in touch panel displays, solar cell glass, magnetic disks, automotive interior and exterior parts, signage, windows in transportation vehicles, and other applications.

[0026] This invention describes in detail various protective glass compositions. This invention primarily describes lithium aluminum borosilicate (LABS) glass and compositions thereof. The glass composition contains one or more chemical components, such as SiO2, B2O3, Al2O3, Li2O, and Na2O. It may also contain other chemical components, such as K2O, ZnO, MgO, SrO, BaO, CaO, P2O5, and TiO2 and their analogues. Furthermore, it may also contain refining agents, such as SnO2, Fe2O3, CeO2, chlorides, sulfates, and their analogues.

[0027] The manufacturing process of the protective glass is greatly affected by the molar percentage content of the glass composition components. The molar percentage content of the components and the reaction temperature are important factors affecting the properties of the protective glass.

[0028] 3D forming capability is an important aspect of LABS protective glass compositions, enabling their use in various applications. To ensure the protective glass composition possesses 3D forming capability, it is necessary to understand the molar range and properties of the components in the glass composition. The coefficient of thermal expansion (CTE) and glass transition temperature are key parameters characterizing glass materials.

[0029] Therefore, the present invention describes a model for calculating three-dimensional forming parameters (TDFP) to predict the 3D forming capability of a protective glass. Specifically, the present invention discloses a protective glass composition with a high TDFP. TDFP is defined as the inverse ratio of the product of the glass transition temperature (Tg) and the coefficient of thermal expansion (CTE). For example, TDFP can be expressed by the following equation (1): (1)

[0030] The calculated TDFP value may help understand the 3D forming capability of the glass composition. The above equation can be understood as follows: Tg represents the viscosity of the glass at a constant temperature (10¹³ poise or 10¹² Pa·s). Therefore, a lower Tg is expected to result in a lower viscosity at the same 3D forming temperature. Consequently, 3D forming will be easier. On the other hand, a lower CTE will result in lower residual stress in the glass article after 3D forming. Therefore, the reciprocal of the product of Tg and CTE, i.e., TDFP, represents the 3D formability of the glass, where a higher TDFP indicates better 3D formability.

[0031] In one embodiment, when TDFP is greater than 220, the glass has good 3D forming properties. When TDFP is less than 220, the glass is not suitable for 3D forming. Glass with high strength and excellent 3D forming capability has better durability, high crack resistance, high strength retained after damage and high sharp impact strength, and the glass can withstand more device drops before failure.

[0032] In one embodiment, the lower the Tg and CTE of the glass, the higher its 3D forming capability. Lower Tg and CTE values ​​can be obtained by increasing the content of B2O3 or by decreasing the content of at least one of Al2O3 or SiO2.

[0033] In one embodiment, the protective glass has reduced non-bridging oxygen (NBO), which increases the toughness of the glass.

[0034] In one embodiment, the glass composition for obtaining the protective glass includes various components such as SiO2, Al2O3, and B2O3. In one embodiment, the glass composition further includes at least one of other components such as R2O, RO, P2O5, ZnO, ZrO2, SnO2, TiO2, CeO2, or Fe2O3.

[0035] In one embodiment, SiO2 is a component forming the glass network. When the SiO2 content is too high, the glass is difficult to melt and form, or the coefficient of thermal expansion of the glass is too low, making it difficult to have the same coefficient of thermal expansion as the surrounding materials. On the other hand, when the SiO2 content is too low, vitrification is difficult. Furthermore, the coefficient of thermal expansion of such glass increases, and its thermal shock resistance tends to decrease. Therefore, the glass composition requires an optimal molar percentage of SiO2. In one embodiment, the amount of SiO2 in the protective glass composition is reduced, and this is compensated by increasing the amount of B2O3 and Al2O3. In one example, the glass composition may include about 40 molar percentage to about 70 molar percentage of SiO2. When the SiO2 content is low, the glass composition exhibits higher acid loss.

[0036] In one embodiment, B2O3 is a component that has the effect of reducing the liquidus temperature, high-temperature viscosity, and density of the glass, and further has the effect of improving the glass's adaptability to multiple ion exchange. B2O3 may help remove unbridged oxygen atoms (NBO). B2O3 converts NBO into bridged oxygen atoms by forming BO4 tetrahedra, thereby increasing the toughness of the glass by minimizing the amount of weak NBO. B2O3 reduces the hardness of the glass, and the increased toughness resulting from the removal of NBO reduces brittleness, thus producing a mechanically durable glass. The B2O3 content can be from about 1 mole% to about 18 moles%. When SiO2 is replaced by B2O3, the acid loss of the glass composition increases.

[0037] In one embodiment, increasing the amount of Al2O3 in the glass composition keeps the basicity of the glass constant. In one embodiment, Al2O3 is a component that enhances suitability for multiple ion exchange. In one example, the glass composition may include about 10 mol% to about 32 mol% of Al2O3. When SiO2 is replaced by Al2O3, the acid loss of the glass composition increases.

[0038] In one embodiment, the glass composition further comprises an alkali metal oxide, wherein the total amount of the alkali metal oxides, R2O, is in the range of about 6 mol% to about 38 mol%. In one embodiment, the alkali metal oxide is selected from the group consisting of Li2O, Na2O, or K2O.

[0039] A higher content of alkali metal oxides can promote melting, thereby softening the glass, enabling ion exchange, reducing melt resistivity, and disrupting the glass network, thereby increasing thermal expansion and reducing durability. The glass composition may include about 3 mol% to about 18 mol% of Na₂O, about 3 mol% to about 18 mol% of Li₂O, and about 0 mol% to about 2 mol% of K₂O. In one embodiment, the Al / R₂O ratio is about 0.5 to about 1.7 for the glass composition to be used as a protective glass.

[0040] In one embodiment, the glass composition further comprises an alkaline earth metal oxide, wherein MgO is in the range of about 0 mol% to about 5 mol%. In one embodiment, the alkaline earth metal oxide may be at least one of MgO, CaO, SrO, or BaO. Alkaline earth metal oxides may help to produce a steeper viscosity profile for the glass. Replacing alkali metal oxides with alkaline earth metal oxides results in an increase in the annealing point and strain point of the glass, while reducing the melting temperature required to produce high-quality glass.

[0041] In one embodiment, the glass composition further comprises about 0 mol% to about 7 mol% of P2O5. P2O5 is a component that improves the ion exchange adaptability of the glass, and is particularly effective in increasing the depth of the compressive stress layer. When SiO2 is replaced by P2O5, a higher P2O5 content may result in a higher devitrification temperature of the glass composition.

[0042] In one embodiment, the glass composition may or may not include ZnO. In one exemplary embodiment, the glass may be ZnO-free. In another exemplary embodiment, the glass may include about 0 mol% to about 5 mol% of ZnO. In one embodiment, the glass composition further includes about 0 mol% to about 2.5 mol% of one or more refining agents, such as SnO2, Fe2O3, CeO2, chlorides, and sulfates. In one embodiment, the glass composition further includes about 0 mol% to 5 mol% of TiO2, which facilitates the preparation of glass-based articles, such as glass ceramics.

[0043] This invention describes the optimal molar percentages of various components of the composition. The protective glass composition comprises about 40 molar percentages to about 70 molar percentages of SiO2, about 10 molar percentages to about 32 molar percentages of Al2O3, and about 1 molar percentages to about 18 molar percentages of B2O3. In one embodiment, the glass composition further comprises an alkali metal oxide, wherein the total sum of the alkali metal oxides present in the glass composition, R2O, is about 6 molar percentages to 38 molar percentages. In one embodiment, the alkali metal oxide is selected from the group consisting of Li2O, Na2O, or K2O. In one embodiment, the glass composition further comprises an alkaline earth metal oxide, wherein MgO is about 0 molar percentages to about 5 molar percentages. In one embodiment, the glass composition further comprises about 0 molar percentages to about 7 molar percentages of P2O5 and about 0 molar percentages to about 5 molar percentages of ZnO. In one embodiment, the glass composition further comprises about 0 mol% to about 2.5 mol% of one or more refining agents, such as SnO2, Fe2O3, CeO2, chlorides, and sulfates. The glass composition further comprises about 0 mol% to about 5 mol% of TiO2.

[0044] Table 1 illustrates non-limiting exemplary glass compositions and their corresponding physical properties, including glass transition temperature (Tg), density, Young's modulus (YM), coefficient of thermal expansion (CTE), annealing temperature, Poisson's ratio, shear modulus, acid test loss, and TDFP. Moer% 1 2 3 4 5 6 7 8 SiO2 45.54 49.61 54.02 41.35 50.20 48.01 54.20 55.21 B2O3 10.29 8.18 6.81 11.20 7.27 8.22 9.21 7.81 Al2O3 25.74 23.70 21.17 27.89 23.25 23.44 20.00 17.48 Na2O 10.71 9.75 8.68 10.89 8.70 9.81 10.00 9.00 Li2O 7.42 8.04 8.05 7.74 8.30 6.84 6.50 7.60 K2O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.33 ZnO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 MgO 0.00 0.00 0.00 0.00 0.03 0.17 0.00 0.00 P2O5 0.22 0.64 1.18 0.85 2.17 3.43 0.00 2.50 SnO2 0.080 0.080 0.080 0.080 0.080 0.080 0.080 0.080 TiO2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Al / R2O 1.42 1.33 1.27 1.50 1.37 1.41 1.21 1.03 nature Tg (°C) 552 554 560 550 558 556 588 554 CTE (×10 -7 ) / ℃(50-300℃) 73.0 75.0 77.0 72.0 76.0 74.0 72.0 76.0 Density (g / cc) 2.43 2.42 2.42 2.43 2.42 2.41 2.40 2.38 YM (GPa) 79.7 77.5 - - - - 75.9 73.0 Annealing temperature (°C) 562 564 570 560 568 566 598 564 Poisson's ratio 0.25 0.23 - - - - 0.24 - Shear modulus (GPa) 31.9 31.5 - - - - 30.6 - Acid test loss (5% HCl, 24 hours, 95℃) (mg / cm³) 2 ) - - - - - - - 53.6 TDFP 248.2 240.7 231.9 252.5 235.8 243.0 236.2 237.5 Table 1: Illustrative Composition and Physical Properties of Glass

[0045] Table 2 illustrates non-limiting exemplary glass compositions and their corresponding physical properties, including glass transition temperature (Tg), density, Young's modulus (YM), coefficient of thermal expansion (CTE), annealing temperature, Poisson's ratio, shear modulus, acid test loss, and TDFP. Moer% 9 10 11 12 13 14 15 16 SiO2 54.29 55.09 55.25 55.50 55.60 57.75 57.20 65.42 B2O3 7.81 7.10 6.17 8.00 7.20 6.17 7.00 1.78 Al2O3 18.00 18.20 18.20 18.10 18.50 17.40 17.40 12.00 Na2O 9.00 9.00 9.90 8.50 8.50 9.40 8.50 8.39 Li2O 8.00 8.00 7.30 7.42 7.42 7.30 7.42 6.82 K2O 0.33 0.33 0.90 0.40 0.40 0.90 0.45 0.00 ZnO 0.00 0.00 0.00 0.50 0.80 0.00 0.45 3.51 MgO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 P2O5 2.50 2.20 2.20 1.50 1.50 1.00 1.50 2.00 SnO2 0.080 0.080 0.082 0.082 0.082 0.082 0.082 0.073 Fe2O3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.009 TiO2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Al / R2O 1.04 1.05 1.01 1.11 1.13 0.99 1.06 0.79 Properties Tg (°C) 550 570 577 574 583 577 579 630 CTE (×10 -7 ) / ℃(50-300℃) 77.0 77.9 78.0 71.0 73.0 81.6 76.0 74.0 Density (g / cc) 2.38 2.38 2.40 2.40 2.40 2.39 2.39 2.44 YM (GPa) 74.0 - 74.4 74.0 75.0 75.0 75.0 76.0 Annealing temperature (°C) - - 587 584 593 587 589 637 Poisson's ratio - - 0.22 0.22 0.24 0.22 0.22 0.23 Shear modulus (GPa) - - 30.5 30.3 30.2 30.7 30.7 30.7 Acid test loss (5% HCl, 24 hours, 95℃) (mg / cm³) 2 ) - - 45.6 - - - - - TDFP 236.1 225.2 222.2 245.4 235.0 212.4 227.3 214.5 Table 2: Illustrative Composition and Physical Properties of Glass

[0046] Table 3 illustrates non-limiting exemplary glass compositions and their corresponding physical properties, including glass transition temperature (Tg), density, Young's modulus (YM), coefficient of thermal expansion (CTE), annealing temperature, Poisson's ratio, shear modulus, acid test loss, and TDFP. Moer% 17 18 19 20 twenty one twenty two twenty three twenty four SiO2 60.42 60.42 58.42 58.42 59.00 57.25 57.99 56.91 B2O3 3.20 3.20 5.20 5.20 4.50 5.41 6.44 7.10 Al2O3 19.11 19.11 18.11 17.11 18.00 17.45 17.68 18.10 Na2O 8.56 8.56 9.56 9.56 9.50 9.21 9.33 8.50 Li2O 6.35 5.35 6.35 7.35 6.50 8.35 6.20 7.10 K2O 0.14 0.14 0.14 0.14 0.22 0.13 0.14 0.14 ZnO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 MgO 0.82 1.32 0.82 0.82 0.60 0.79 0.80 0.76 P2O5 1.37 1.87 1.37 1.37 1.60 1.32 1.34 1.37 SnO2 0.020 0.020 0.020 0.023 0.080 0.084 0.0849 0.023 TiO2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Al / R2O 1.27 1.36 1.13 1.00 1.11 0.99 1.13 1.15 nature Tg (°C) 648 652 616 585 608 - - 589 CTE (×10 -7 ) / ℃(50-300℃) 73.0 74.1 71.6 76.3 76.0 - - 71.2 Density (g / cc) 2.41 2.40 2.40 2.40 2.40 - 2.39 2.39 YM (GPa) - - - 76.5 - - 75.0 72.5 Annealing temperature (°C) 658 662 626 595 618 - - 599 Poisson's ratio - - - 0.23 - - 0.23 0.26 Shear modulus (GPa) - - - 31.1 - - 30.5 28.9 Acid test loss (5% HCl, 24 hours, 95℃) (mg / cm³) 2 ) - - - - - - - TDFP 211.4 206.9 226.7 224.0 216.4 - - 238.5 Table 3: Illustrative Composition and Physical Properties of Glass

[0047] Table 4 illustrates non-limiting exemplary glass compositions and their corresponding physical properties, including glass transition temperature (Tg), density, Young's modulus (YM), coefficient of thermal expansion (CTE), annealing temperature, Poisson's ratio, shear modulus, acid test loss, and TDFP. Moer% 25 26 27 28 29 30 31 32 SiO2 57.63 57.00 57.85 57.43 57.43 58.70 55.16 59.42 B2O3 7.10 6.00 5.20 5.20 5.20 5.77 4.24 4.20 Al2O3 17.11 17.74 17.25 18.10 18.10 17.11 17.59 18.11 Na2O 8.90 9.50 9.70 9.56 9.56 9.00 9.10 9.56 Li2O 6.90 7.35 7.70 7.35 6.91 7.35 11.50 6.35 K2O 0.14 0.51 0.65 0.14 0.58 0.14 0.08 0.14 ZnO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 MgO 0.82 0.45 0.45 0.82 0.82 0.48 1.14 0.82 P2O5 1.37 1.37 1.37 1.37 1.37 1.37 1.07 1.37 SnO2 0.023 0.080 0.025 0.023 0.025 0.075 0.020 0.020 TiO2 0.00 0.00 0.00 0.00 0.00 0.0006 0.11 0.00 total 100.00 100.00 100.20 100.00 100.00 100.00 100.00 100.00 Al / R2O 1.07 1.02 0.96 1.06 1.06 1.04 0.85 1.13 nature Tg (°C) 575 - 585 600 601 585 566 618 CTE (×10 -7 ) / ℃(50-300℃) 70.0 - - 79.0 79.0 71.1 73.9 75.0 Density (g / cc) 2.38 2.40 2.40 2.40 2.40 2.39 2.42 2.40 YM (GPa) 71.3 73.5 73.5 75.0 75.6 75.0 76.9 73.3 Annealing temperature (°C) 585 - - 610 611 595 576 628 Poisson's ratio 0.25 0.25 0.24 0.25 0.23 0.22 0.22 0.24 Shear modulus (GPa) 28.5 29.5 29.5 30.0 30.8 30.7 31.5 29.5 Acid test loss (5% HCl, 24 hours, 95℃) (mg / cm³) 2 ) 37.4 49.9 - TDFP 248.4 - - 211.0 210.6 240.4 239.1 215.7 Table 4: Illustrative Composition and Physical Properties of Glass

[0048] In one exemplary embodiment, when the glass composition of the protective glass comprises about 58.70 mol% SiO2, about 5.77 mol% B2O3, about 17.11 mol% Al2O3, about 9.00 mol% Na2O, about 7.35 mol% Li2O, about 0.14 mol% K2O, about 0.48 mol% MgO, about 1.37 mol% P2O5, about 0.075 mol% SnO2, and about 0.0006 mol% TiO2, the properties of the glass include a glass transition temperature of 585°C, a CTE of 71.1 × 10⁻⁷ / °C, a density of 2.39 g·cm⁻³, a Young's modulus of 75 GPa, an annealing point of 595°C, a Poisson's ratio of 0.22, and a shear modulus of 30.7 GPa. Here, the TDFP of the glass composition is 240.4. Since the TDFP value is greater than 220, the glass composition has good 3D molding capability.

[0049] In another exemplary embodiment, when the glass composition of the protective glass comprises about 57.43 mol% SiO2, about 5.20 mol% B2O3, about 18.10 mol% Al2O3, about 9.56 mol% Na2O, about 7.35 mol% Li2O, about 0.14 mol% K2O, about 0.82 mol% MgO, about 1.37 mol% P2O5, and about 0.023 mol% SnO2, the properties of the glass include a glass transition temperature of 600°C, a CTE of 79 × 10⁻⁷ / °C, a density of 2.40 g·cm⁻³, a Young's modulus of 75 GPa, an annealing point of 610°C, a Poisson's ratio of 0.25, and a shear modulus of 30.0 GPa. Here, the TDFP of the glass composition is 211.0. Because the TDFP value is less than 220, the glass composition is not suitable for forming 3D curved shapes.

[0050] A 3D forming capability test was conducted on first and second glass covers formed from two different glass compositions to determine their 3D forming capability in a furnace.

[0051] The first protective glass 102 is formed of a glass composition 30, which includes about 58.70 mol% of SiO2, about 5.77 mol% of B2O3, about 17.11 mol% of Al2O3, about 9.00 mol% of Na2O, about 7.35 mol% of Li2O, about 0.14 mol% of K2O, about 0.48 mol% of MgO, about 1.37 mol% of P2O5, about 0.075 mol% of SnO2 and about 0.0006 mol% of TiO2.

[0052] The second protective glass 104 is formed of a glass composition 16, which includes about 65.42 mol% of SiO2, about 1.78 mol% of B2O3, about 12.00 mol% of Al2O3, about 8.39 mol% of Na2O, about 6.82 mol% of Li2O, about 3.51 mol% of ZnO, about 0.073 mol% of SnO2, about 0.009 mol% of Fe2O3 and about 2.00 mol% of P2O5.

[0053] Figures 1A-1C show images of the first and second protective glass under different furnace conditions according to an embodiment of the present invention. The first protective glass 102 and the second protective glass 104 were held in the furnace for a 3D forming capability test. As shown in Figure 1A, before the furnace was opened, the first protective glass 102 and the second protective glass 104 were planar at room temperature. Once the furnace was opened, the first protective glass 102 and the second protective glass 104 were held in the furnace at 650°C for 10 minutes. Referring to Figure 1B, the first protective glass 102 was bent to a certain extent compared to the second protective glass 104. The first protective glass 102 and the second protective glass 104 were further held in the furnace at 670°C for 10 minutes. Referring to Figure 1C, the first protective glass 102 was bent further compared to the second protective glass 104. The furnace was then turned off, and the first protective glass 102 and the second protective glass were gradually cooled to room temperature.

[0054] Figure 1D shows a perspective view of the first and second protective glass after a 3D forming capability test according to an embodiment of the present invention. Figure 1E shows a side view of the first and second protective glass after a 3D forming capability test according to an embodiment of the present invention. As shown in Figures 1D and 1E, the first protective glass 102 is curved, while the second protective glass 104 is planar. As mentioned in Tables 2 and 4, the TDFP value of the first protective glass 102 is greater than 220, while the TDFP value of the second protective glass 104 is less than 220. The test demonstrates that the glass with a TDFP value greater than 220 has a higher 3D forming capability compared to the glass with a TDFP value less than 220.

[0055] In one embodiment, for a two-step ion exchange process of alkali metal silicate glass, such as lithium aluminum silicate glass, the alkali metal ions to be replaced are lithium ions (Li+). Preferably, the salt bath used is a sodium ion (Na+) bath and a potassium ion (K+) bath. More preferably, the salt bath used contains salts of NaNO3 and KNO3. In the first step of the ion exchange, lithium ions are replaced by at least sodium ions within the surface of the glass material. Furthermore, in the second step of the ion exchange, lithium ions or sodium ions are replaced by at least potassium ions within the surface of the glass material.

[0056] In one embodiment, during a two-step ion exchange process, one ion pair is first exchanged, followed by another ion exchange, which introduces the initial ions or another ion into the outermost surface layer. In one embodiment, the ion exchange process is based on the principle that ions present in the glass are exchanged by ions of different sizes. When larger ions from an external ion exchange bath exchange smaller ions in the glass, the larger ions completely fill the surface, causing it to compress using internal equilibrium tensile stress. It has been reported that the resulting compressive stress is proportional to the volume of glass that has undergone ion exchange. Once ion exchanged, the glass exhibits high crack resistance.

[0057] In one exemplary embodiment, the glass sample composition undergoes a two-step ion exchange process, wherein the glass is first immersed in a molten salt bath containing more than 45 wt% KNO3 and less than 55 wt% NaNO3 (maintained at a temperature between 300°C and 500°C) for a fixed period of time, such as greater than 1.5 hours, followed by immersion in a molten salt bath containing more than 85 wt% KNO3 and less than 15 wt% NaNO3 (maintained at a temperature between 300°C and 500°C) for a fixed period of time, such as greater than 0.3 hours. This dual ion exchange process increases compressive stress (CS), wherein each compressive layer on the surface has a compressive stress of at least 150 MPa. Furthermore, in the dual ion exchange process, the first layer depth extends from the glass surface to a minimum depth of 130 μm and a maximum depth of 10 μm for the second layer depth.

[0058] Table 5 illustrates exemplary samples of the maximum layer depth (DOL) and compressive stress (CS) of each step of a dual ion exchange process under different reaction conditions for defining a specific glass composition, such as glass composition 30. Sample number Step 1 Step 2 Step 1 Step 2 Fitting data from step 1 and step 2 CT (MPa) KNO3 (wt%) Temperature (°C) Time (minutes) KNO3 (wt%) Temperature (°C) Time (minutes) CS (MPa) DOL (μm) CS (MPa) DOL (μm) CS (MPa) DOC (μm) CS k (MPa) DOL (μm) 1 60% 415 110 97% 380 40 179.728 154.271 1182.665 5.156 1182.853 153.252 166.386 6.750 85.977 2 60% 415 110 97% 380 40 195.937 151.785 1163.035 5.292 1163.779 150.669 180.689 6.950 86.769 3 60% 415 110 97% 380 60 192.822 154.568 1170.113 5.876 1170.236 154.897 179.005 7.547 87.197 4 60% 415 110 97% 380 60 188.093 147.879 1164.822 5.782 1164.825 146.279 176.147 7.750 86.079 5 60% 415 110 97% 390 60 235.679 130.667 1175.610 5.587 1176.488 130.848 219.605 7.150 89.072 6 60% 415 110 97% 390 60 186.628 148.281 1164.203 5.563 1165.695 146.102 171.411 7.500 85.079 7 60% 415 110 97% 380 90 169.358 161.101 1164.668 5.945 1165.029 154.322 159.426 6.100 80.020 8 60% 415 110 97% 380 90 176.456 143.478 1156.285 5.979 1156.306 140.211 182.356 6.500 89.442 9 60% 415 110 97% 380 90 191.756 140.102 1170.932 5.921 1171.023 137.757 184.914 6.950 89.168 10 60% 415 110 97% 390 90 186.463 146.722 1179.938 5.990 1179.980 145.862 176.524 5.900 82.996 11 60% 415 110 97% 390 90 180.436 152.597 1162.249 6.052 1163.474 149.316 161.079 6.275 84.091 12 60% 415 110 90% 390 60 202.292 149.740 965.955 4.901 966.225 150.494 192.793 3.875 89.672 13 60% 415 110 100% 390 20 191.958 138.020 1528.341 3.126 1528.365 136.837 191.144 4.425 81.755 14 60% 415 110 100% 390 40 185.925 145.557 1500.696 4.541 1528.737 145.698 183.104 3.425 83.132 15 60% 415 150 97% 380 60 167.823 158.851 1121.418 5.227 1121.842 152.590 153.097 7.875 83.050 16 60% 415 150 97% 380 60 186.958 156.959 1127.874 5.338 1128.273 154.243 166.458 7.250 87.400 17 60% 415 150 97% 380 60 194.227 148.199 1134.173 5.795 1135.226 146.337 180.430 5.200 91.386 18 60% 415 150 97% 380 60 171.324 163.485 1135.180 5.759 1136.856 158.881 165.333 5.325 82.221 19 60% 415 150 97% 380 60 217.056 139.274 1102.399 5.990 1103.405 138.878 199.769 5.275 87.457 20 60% 415 150 97% 380 60 175.242 162.763 1135.176 5.799 1144.815 156.950 160.583 5.275 83.165 21 50% 415 150 97% 380 60 187.144 149.175 1096.187 5.153 1097.519 148.069 175.771 7.375 89.176 22 50% 415 150 97% 380 60 178.084 155.878 1098.605 5.160 1100.845 153.821 168.646 7.250 91.213 23 55% 415 150 97% 380 60 183.496 148.025 1053.368 5.109 1053.386 146.585 172.590 7.925 88.763 24 55% 415 150 97% 380 60 176.726 155.367 1088.811 5.133 1091.140 154.234 166.570 7.200 90.100 25 65% 415 150 97% 380 60 244.113 132.252 1107.595 5.126 1108.068 133.247 231.458 7.750 94.203 26 65% 415 150 97% 380 60 208.194 142.937 1118.563 5.190 1118.565 143.187 194.397 7.500 91.554 27 70% 415 150 97% 380 60 170.377 149.838 1077.927 6.254 1078.299 147.425 159.172 7.600 92.460 28 70% 415 150 97% 380 60 166.458 149.984 1052.971 6.498 1053.761 148.586 160.679 7.900 92.102 29 70% 415 150 97% 380 60 230.975 132.835 1113.418 5.935 1113.428 132.869 215.512 5.575 87.561 30 70% 415 150 97% 380 60 218.530 135.843 1110.074 6.013 1110.882 136.321 204.205 5.325 86.712 31 75% 415 150 97% 380 60 224.002 130.396 1140.791 7.182 1140.842 131.276 206.163 8.325 86.232 32 75% 415 150 97% 380 60 186.301 146.308 1119.884 7.089 1121.143 146.815 168.578 8.950 86.500 33 80% 415 150 97% 380 60 161.257 155.608 1144.334 8.019 1150.638 153.901 156.257 6.075 86.699 34 60% 430 130 97% 380 60 173.766 157.539 639.414 4.761 641.577 156.412 172.394 4.550 90.716 35 75% 415 150 97% 380 60 176.693 147.860 1143.228 7.316 1143.350 148.459 163.865 9.300 90.312 36 75% 415 150 97% 380 60 169.434 148.493 1118.239 7.075 1119.504 148.070 157.182 8.930 87.892 37 75% 415 150 97% 380 60 169.771 139.629 1123.578 7.980 1123.652 139.819 153.230 9.080 84.374 38 75% 415 150 97% 380 60 154.663 146.360 1131.141 7.943 1131.683 143.664 150.948 8.980 89.309 39 75% 415 150 97% 380 60 200.652 139.662 1153.731 7.915 1154.606 140.394 184.862 8.350 89.284 40 75% 415 150 97% 380 60 159.448 146.718 1137.348 7.951 1124.025 144.096 154.053 8.780 89.890 41 75% 415 150 97% 380 60 188.845 141.773 1130.485 7.305 1130.488 142.603 170.681 8.850 86.245 42 75% 415 150 97% 380 60 236.213 131.103 1131.929 7.210 1132.422 132.579 209.946 8.230 88.576 43 75% 415 150 97% 380 20 202.955 128.832 1097.609 8.509 1097.609 130.109 189.811 10.050 89.444 44 75% 415 150 97% 380 20 183.800 135.493 1077.412 8.094 1078.135 140.144 182.902 8.725 81.878 Table 5: Illustrative samples and DOC and CS for each step of the double ion exchange process

[0059] In one exemplary embodiment, the glass composition of the protective glass comprises approximately 58.70 mol% SiO2, approximately 5.77 mol% B2O3, approximately 17.11 mol% Al2O3, approximately 9.00 mol% Na2O, approximately 7.35 mol% Li2O, approximately 0.14 mol% K2O, approximately 0.48 mol% MgO, approximately 1.37 mol% P2O5, approximately 0.075 mol% SnO2, and approximately 0.0006 mol% TiO2. The protective glass undergoes a dual ion exchange process. For the first ion exchange process, the alkali metal bath contains 25% NaNO3 and 75% KNO3 by weight. This glass substrate is immersed in the alkali metal bath at a temperature of 415°C for a period of 2.5 hours. The glass exhibits a compressive stress of 186.301 MPa, corresponding to a depth of 146.308 μm. After immersion in the first bath, the protective glass undergoes a second ion exchange treatment. The second ion exchange bath contains 3% NaNO3 and 97% KNO3 by weight. The glass substrate is immersed in the second ion exchange bath at 380°C for 1 hour. The material exhibits a compressive stress of 1119.884 MPa, corresponding to a depth of 7.089 μm. The fitted compressive stress and compression depth (DOC / DOL_zero) of the first ion exchange treatment are 1121.143 MPa and 146.815 μm, respectively. The fitted compressive stress (CSk) and compression depth (DOC) of the second ion exchange treatment are 168.578 MPa and 8.950 μm, respectively. Since the magnitude of the central tension determines the glass's breakage, the central tension of this double ion exchange glass is 86.500 MPa.

[0060] The protective glass composition is used as a back cover for touch panel displays and display screens, such as liquid crystal displays (LCDs), field emission displays (FEDs), plasma displays (PDs), electroluminescent displays (ELDs), organic light-emitting diode displays (OLEDs), micro LEDs, or the like. However, the protective glass is not limited to the aforementioned applications and can also be used as, for example, a substrate for touch panel displays, a protective glass for solar cells, a disk substrate, and window glass.

[0061] In one particular embodiment, the protective glass serves as a protective window associated with various modes of transportation (such as air, sea, or land), and as windproof in non-transportation applications. Furthermore, it is also used as fire-resistant glass. Additionally, the protective glass is used as a substrate for hard drives. Furthermore, it can also be used as a semiconductor interposer and semiconductor carrier. By adding a nucleating agent, it can also be used as a cooktop in a ceramicized form. Finally, the protective glass serves as a coating substrate in various applications.

[0062] In a particular embodiment, the present invention further focuses on a back cover glass for protecting the back of electronic devices such as mobile phones, smartphones, tablets, wearable devices, and digital cameras. The back cover glass used on the device provides strength and is also necessary for better electromagnetic transmission. For design reasons, a colored, opaque appearance is possible. One way to achieve this is by including one or more transition elements in the glass melt. The one or more transition elements may be at least one of Nb₂O₅, ZrO₂, Fe₂O₃, V₂O₅, Y₂O₃, MnO₂, NiO, CuO, Cr₂O₃, Co₃O₄, CoO, Co₂O₃, etc.

[0063] The present invention provides a composition of protective glass with excellent 3D forming capability. By determining the TDFP of the glass composition, the present invention helps to control the composition in a more efficient manner. Specifically, the present invention relates to a silicate glass composition that can have better durability, high crack resistance, high post-damage strength retention and high impact strength.

[0064] Although typical embodiments have been described for illustrative purposes, the foregoing description should not be construed as limiting the scope of the invention or the appended claims. Therefore, various modifications, adjustments and substitutions will be conceived by those skilled in the art without departing from the spirit and scope of the invention. [Simplified Explanation of the Diagram]

[0021] The novel features of this invention are specifically set forth in the appended claims. Embodiments of the invention will be described below in conjunction with the accompanying drawings, in order to illustrate but not limit the scope of the claims, wherein like reference numerals denote like elements, and in the drawings: Figures 1A-1C show images of a first protective glass and a second protective glass under different furnace conditions according to an embodiment of the invention; Figure 1D shows a perspective view of the first protective glass and the second protective glass after a 3D forming capability test according to an embodiment of the invention; and Figure 1E shows a side view of the first protective glass and the second protective glass after a 3D forming capability test according to an embodiment of the invention.

Claims

1. An ion-exchangeable silicate glass comprising: 40 mol% to 70 mol% SiO2, 1 mol% to 18 mol% B2O3, and 10 mol% to 32 mol% Al2O3, wherein the glass is advantageous to have a three-dimensional (3D) form when the three-dimensional forming parameter (TDFP) of the glass is greater than 220, and wherein the TDFP is defined by the following expression: TDFP = 1 / (glass transition temperature (Tg) × coefficient of thermal expansion (CTE)).

2. The glass of claim 1, further comprising: 3 mol% to 18 mol% Na2O, 3 mol% to 18 mol% Li2O, 0 mol% to 2 mol% K2O, 0 mol% to 5 mol% MgO, 0 mol% to 5 mol% ZnO, 0 mol% to 7 mol% P2O5, 0 mol% to 2.5 mol% SnO2, and 0 mol% to 5 mol% TiO2.

3. The glass of claim 2, wherein the glass composition comprises 6 mol% to 38 mol% R2O, wherein R2O represents the total amount of alkali metal oxides present in the glass composition.

4. The glass of claim 3, wherein the ratio of Al2O3 to R2O (Al2O3 (moles%) / R2O (moles%)) is in the range of 0.5 to 1.

7.

5. The glass of claim 1, wherein the glass transition temperature Tg is below 700°C.

6. The glass of claim 1, wherein the coefficient of thermal expansion (CTE) is less than 100 × 10⁻⁷ / ℃.

7. The glass of claim 1, wherein the glass undergoes a double ion exchange process.

8. The glass of claim 1, wherein the glass is a lithium aluminum borosilicate protective glass for a display.

Images