WO2019070788A1

WO2019070788A1 - Glass laminate with low cs, high depth of layer, chemically strengthened inner glass layer and method

Info

Publication number: WO2019070788A1
Application number: PCT/US2018/054071
Authority: WO
Inventors: Peter Joseph Lezzi
Original assignee: Corning Incorporated
Priority date: 2017-10-06
Filing date: 2018-10-03
Publication date: 2019-04-11

Abstract

A glass laminate article and related method for providing a chemically strengthened glass sheet with a low surface compressive stress (CS) and deep, depth of layer (DOL) is provided. The method includes chemically strengthening a first glass sheet with a molten salt including alkali ions such that the alkali ions of the molten salt replace smaller alkali ions of the first glass sheet generating compressive surface stress (CS) along a first major surface of the first glass sheet. The temperature of the molten salt composition during treatment of the first glass layer is greater than the glass transition temperature of the glass material (Tg) minus 100 degrees C. This may form a glass sheet with a compressive surface stress (CS) of less than 250 MPa having a depth of layer (DOL) of 20-100 microns, and this glass sheet may form the inner layer of a glass laminate article.

Description

GLASS LAMINATE WITH LOW CS, HIGH DEPTH OF LAYER, CHEMICALLY STRENGTHENED INNER GLASS LAYER AND

METHOD

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S.

Provisional Application Serial No. 62/568,886 filed on October 6, 2017, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

[0002] The disclosure relates generally to a laminate comprising a strengthened glass layer, and specifically to a laminate article having an inner glass layer that is chemically strengthened to have a relatively low compressive surface stress (CS) with a relatively high depth of layer (DOL). Glass laminates may be used as windows and glazing in various applications including architectural and transportation applications (e.g., vehicles including automobiles and trucks, rolling stock, locomotive and airplanes). Inner and/or outer glass layers of the glass laminate may be strengthened, through chemical strengthening, thermal tempering or otherwise. However, in contrast to the present disclosure, the art recognizes a desirability to have an inner glass layer with a high strength resulting from a high CS level.

SUMMARY

[0003] One embodiment of the disclosure relates to a method for forming a glass laminate article. The method includes chemically strengthening a first glass sheet. The first glass sheet comprises a first glass composition by treatment with a molten salt including alkali ions such that the alkali ions of the molten salt replace smaller alkali ions of the first glass sheet generating compressive surface stress (CS) along a first major surface of the first glass sheet. The first glass composition includes a glass transition temperature (Tg), and a temperature of the molten salt composition during treatment of the first glass layer is greater than Tg minus 100 degrees C. The method includes bonding the first glass sheet to a second glass sheet with a polymer interlayer located between the first glass sheet and the second glass sheet, after the chemical strengthening step.

[0004] An additional embodiment of the disclosure relates to a method for chemically strengthening a glass sheet formed from a first glass composition. The method includes treating the glass sheet with a molten salt composition including alkali ions such that the alkali ions of the molten salt composition replace smaller alkali ions of the glass sheet generating compressive surface stress (CS) at a major surface of the glass sheet. The first glass composition includes a glass transition temperature (Tg), and a temperature of the molten salt composition during treatment of the glass sheet is greater than Tg minus 50 degrees C.

[0005] An additional embodiment of the disclosure relates to glass laminate article. The glass laminate article includes a strengthened inner glass layer. The inner glass layer includes an inner surface, an outer surface opposite the inner surface and an average thickness between the inner and outer surfaces in a range from 0.05 mm to 1.2 mm. The inner glass layer includes a compressive surface stress (CS) along the inner surface of less than 250 MPa having a depth of layer (DOL) in a range from about 20 to about 100 microns. The glass laminate article includes an external glass layer. The glass laminate article includes an inner surface and an outer surface. The glass laminate article includes an interlayer disposed between the inner glass layer and the external glass layer.

[0006] Additional features and advantages will be set forth in the detailed description that follows, and, in part, will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings.

[0007] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understand the nature and character of the claims.

[0008] The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain principles and the operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a cross-sectional view of a glass laminate article, according to an exemplary embodiment.

[0010] FIG. 2 is a flow diagram of a process for forming a glass laminate, according to an exemplary embodiment.

[0011] FIG. 3 is a perspective view of a vehicle utilizing the glass laminate article of FIG. 1 as a vehicle window, according to an exemplary embodiment

DETAILED DESCRIPTION

[0012] Referring generally to the figures, various embodiments of a glass laminate article having an inner glass layer with a relatively low level of CS with a relatively high DOL. In addition, Applicant has developed a process for forming glass layers with the relatively low level of CS with the relatively high DOL. It is Applicant's understanding that in typical glass laminate applications, particularly auto glass laminate applications, it is typically thought to be desirable for the inner glass layer to have a very high level of CS providing the high level of mechanical strength associated with the very high level of CS. However, in some instances, Applicant has determined that it may be desirable for most (if not essentially all) of the mechanical strength of at least some glass laminates to be provided by the external layer, and based on this understanding and contrary to conventional wisdom, Applicant has developed a glass laminate article and related chemical strengthening method that produces glass material for the inner layer of a glass laminate that has a relatively low level of CS.

[0013] However, while Applicant has determined that a low level of CS is satisfactory for the inner glass laminate layer, Applicant has also determined that the low CS should have a relatively deep DOL which allows the inner glass layer to maintain sufficient mechanical strength following abrasion (e.g., as determined by the Arizona grit test). Limiting the impact of abrasion that may occur on the inner glass layer ensures that abrasion does not unduly weaken the inner glass layer to the point where mechanical failure of the glass laminate is no longer dictated by the strength of the outer glass layer.

[0014] The process for chemically strengthening the inner glass layer discussed herein produces the low level of CS with the high DOL by ion exchanging the glass of the inner glass layer at relatively high temperatures for relatively short times in an ion exchange bath (e.g., a bath of molten salt including alkali ions). Utilizing high temperatures for the ion exchange bath (e.g., temperatures such as greater than Tg minus 100 degrees C or Tg minus 50 degrees C) is counterintuitive to those in the field of glass laminates because these high temperatures prevent high levels of CS from forming due to the relatively high rate of stress relaxation that occurs at these temperatures relative to the rate of ion exchange. It should be noted that the low level of CS with the high DOL may also be achieved through thermal strengthening processes or mechanical strengthening processes. In some embodiments, the low level of CS with the high DOL may be achieved using a combination of strengthening processes (e.g., chemically and mechanically strengthening, mechanically and thermally strengthening, or chemically and thermally strengthening). Mechanical strengthening utilizes a mismatch of the coefficient of thermal expansion between portions of the glass layer to create a compressive stress region and a central region exhibiting a tensile stress. Thermal strengthening heats the glass layer to a temperature below the glass transition point and then rapidly quenches the glass layer. [0015] However, Applicant has determined that, while resulting in low CS levels, these high temperatures do provide for high CS DOL, sufficient for abrasion resistance. In addition, Applicant has determined that these high ion exchange temperatures allow for formation of the low CS, high DOL, chemically strengthened layer while also allowing for substantial decreases in processing time exposure to the ion exchange bath. Reducing the time of the chemical strengthening procedure provides a much more efficient and lower cost process for forming glass laminate articles. Lastly, Applicant has determined that the chemical strengthening process discussed herein allows for the formation of an abrasion resistant CS layer even in soda lime glass (SLG) materials, which may allow for formation of glass laminates utilizing inner layers formed from thin SLG rather than more expensive specialty glasses typically understood to be more suitable for cost-effective chemical strengthening.

[0016] Applicant believes that the process discussed herein provides a glass material that is beneficial in a variety of ways. Providing an ion-exchanged inner glass layer with a deep DOL and low CS will allow for retained mechanical strength even after abrasion formation on the surface of the inner glass layer. In various embodiments, Applicant believes that a majority of the CS is annealed out due to the high temperature during the ion exchange, providing the low, but deep CS layer as described herein, and Applicant believes this results in a glass sheet that is not frangible. Ion exchange can be performed on glass of any thickness and on glass that is flat or curved which is useful for the various shapes employed in various applications such as in auto glazing. Cost savings may be provided by allowing for shorter ion-exchange times.

[0017] Referring to FIG. 1, a glass laminate article 10 is shown according to an exemplary embodiment. Glass laminate article 10 includes a first glass sheet, shown as inner glass layer 12, an interlayer 14, and a second glass sheet, shown as outer glass layer 18. As shown in FIG. 1, inner glass layer 12 includes an inner surface 20 and an outer surface 22. Interlayer 14 is located or disposed between outer surface 22 of inner glass layer 12 and inner surface 24 of outer glass layer 18. Interlayer 14 acts to bind inner glass layer 12 and outer glass layer 18 into glass laminate article 10.

[0018] In general, inner glass layer 12 is formed from a thin layer of glass. In one or more embodiment, the thin layer of glass may be unstrengthened. In one or more embodiments, the thin layer of glass may be strengthened (e.g., chemically strengthened). In one or more specific embodiments, the inner glass layer 12 has a relatively low level of CS, shown as CS layer 28, located along inner surface 20, that has a relatively deep DOL as shown in FIG. 1. In various embodiments, CS at inner surface 20 is less than 350 MPa, and specifically is less than 250 MPa. In various embodiments, CS at inner surface 20 is 25 MPa to 350 MPa, and specifically is 25 MPa to 250 MPa. In various embodiments, given any of these CS levels, DOL is 20-100 microns. In some embodiments, given any of these CS levels, DOL is greater than 40 microns, and more specifically is greater than 70 microns. As will be explained in more detail below, Applicant has developed a process for chemically strengthening inner glass layer 12 in a manner that results in these CS levels and DOL levels in a particularly efficient manner.

[0019] Interlayer 14 may be a wide variety of materials suitable for bonding together the various layers of glass laminate article 10. In general, interlayer 14 is a polymer binding layer. In specific embodiments, interlayer 14 is a polymer interlayer selected from the group consisting of polyvinyl butyral (PVB), ethylenevinylacetate (EVA), polyvinyl chloride (PVC), ionomers, and thermoplastic polyurethane (TPU). The interlayer may be applied as a preformed polymer interlayer. In some instances, the polymer interlayer can be, for example, a plasticized polyvinyl butyral (PVB) sheet. In various embodiments, the polymer interlayer can comprise a monolithic polymer sheet, a multilayer polymer sheet, or a composite polymer sheet.

[0020] Outer glass layer 18 includes an inner surface 24 and an outer surface 26. In general, interlayer 14 is located between inner surface 24 of outer glass layer 18 and outer surface 22 of inner glass layer 12. In this arrangement, outer surface 26 of outer glass layer 18 defines the exterior surface of glass laminate article 10, and inner surface 20 of inner layer 12 defines the interior surface of glass laminate article 10.

[0021] To provide a sufficiently strong but also light weight glass laminate article, in specific embodiments, outer layer 18 is thicker than inner layer 12. Thus, referring to FIG. 1, inner glass layer 12 has an average thickness, Tl, and outer glass layer 18 has an average thickness, T2. In specific embodiments, Tl is in a range from 0.05 mm to 1.5 mm, and more specifically from 0.05 mm to 1.2 mm. In some embodiments, inner layer 12 is formed from a soda lime silicate glass composition, an aluminosilicate glass composition, an alkali aluminosilicate glass composition, or an alkali aluminoborosilicate glass composition. In one or more embodiments, Tl may be 0.1 mm and 0.8 mm, specifically Tl is less than or equal to 0.7 mm, is about 0.5 mm (e.g., 0.5 mm plus or minus 10%) or is about 0.7 mm (e.g., 0.7 mm plus or minus 10%). In other specific embodiments, inner layer 12 is formed from an SLG material, and in such embodiments, Tl is 0.9 mm to 1.1 mm. In further embodiments, T2 is greater than Tl and in specific embodiments, T2 is in a range from 1 mm to 4 mm. [0022] In various embodiments, interlayer 14 includes an average thickness, T3, and in various embodiments, T3 is between 0.1 mm and 1 mm, and specifically is between 0.7 mm and 0.8 mm. In addition, by utilizing a thin, inner glass layer 12 combined with a thicker outer glass layer 18, glass laminate article 10 has a relatively low total average thickness, T4, and in specific embodiments, T4 is less than 4 mm.

[0023] In one or more embodiments, inner glass layer 12 is formed from a first glass composition having mobile cations suitable for ion-exchange-based strengthening as discussed below. In specific embodiments, outer glass layer 18 is formed from a second glass composition that is different from the first glass composition of inner glass layer 12. In some specific embodiments, inner glass layer 12 is formed from a chemically strengthened alkali alumino silicate glass composition or an alkali aluminoboro silicate glass composition, and the external glass layer is formed from a soda lime glass (SLG) composition. In other embodiments, both inner glass layer 12 and outer glass layer 18 are formed from the same glass composition, and in some such embodiments, both inner glass layer 12 and outer glass layer 18 are formed from a soda lime glass material.

[0024] In one or more embodiments, layers 12 and 18 of glass laminate article 10 may be formed from a glass article/sheet that is strengthened, as described herein. In one or more embodiments, inner glass layer 12 comprises a chemically strengthened glass, while outer glass layer 18 is not strengthened. In one or more embodiments, inner glass layer 12 comprises a chemically strengthened glass, while outer glass layer 18 is annealed. In one or more embodiments, inner glass layer 12 comprises a chemically strengthened glass, while outer glass layer 18 is strengthened in different manner than the first glass layer (e.g., outer layer 18 is mechanically and/or thermally strengthened). In one or more embodiments, inner glass layer 12 comprises a chemically strengthened glass, while outer glass layer 18 is also chemically strengthened.

[0025] Glass laminate article 10 can be used for a variety of different applications, devices, uses, etc. In various embodiments, glass laminate article 10 may form the sidelights, windshields, rear windows, windows, rearview mirrors, and sunroofs of a vehicle, such as car 30 shown in FIG. 3. As used herein, vehicle includes automobiles, rolling stock, locomotive, boats, ships, and airp lanes, helicopters, drones, space craft and the like.

[0026] Referring to FIG. 2, a process 50 for forming a glass laminate article, such as article 10, is shown according to an exemplary embodiment. At step 52, a first glass sheet that comprises a first glass composition is chemically strengthened, and then may be used to form inner layer 12 of glass laminate article 10 as discussed above. The chemical strengthening at step 52 is performed by treating the first glass sheet with a molten salt that includes alkali ions, and the alkali ions of the molten salt replace smaller alkali ions of the first glass sheet which generates compressive surface stress (CS) along a first major surface (e.g., surface 20 of inner layer 12) of the first glass sheet.

[0027] As will be generally understood, glass materials containing alkali ions, e.g. Na+, may be treated with a molten salt containing larger alkali ions, e.g. K+, at a temperature below the glass transition temperature (Tg) of the glass material. Although alkali ions rest in specific positions within the rigid glass network, they possess the ability to jump between sites. As a result, when an alkali-containing glass material is immersed in a molten salt containing another type of larger alkali ions, some larger alkali ions from the molten salt will exchange with the smaller alkali ions in the outer layers of the glass. If this process is performed at a temperature below the glass transition temperature of the glass material, the stress relaxation is sluggish compared to the rate of ion-exchange, the large alkali ions will find themselves stuffed into rigid sites that are too small. Since the glass structure cannot relax to accommodate the newly acquired larger ions, a hydrostatic compressive stress is formed. In conventional processes, this ion exchange process is carried out at relatively low temperatures relative to Tg (e.g., less than 450 degrees for some glass compositions) for relatively long times (e.g., 5.5 hours or more) in order to form very strong glass with very high levels of CS.

[0028] In various embodiments and in contrast to conventional ion exchange processes, Applicant has found the relatively low CS with deep DOL as discussed herein may be generated in the first glass sheet via an inventive chemical strengthening process in which the molten alkali salt is maintained at a high temperature and the first glass sheet is exposed to the molten alkali salt for a short amount of time. As will generally be understood, the first glass composition of the first glass sheet has a glass transition temperature (Tg). Applicant has found that in order to form the relatively low CS with deep DOL as discussed herein, the molten salt composition during step 52 is maintained at a relatively high temperature relative to Tg.

[0029] In one embodiment, the temperature of the molten salt is maintained at greater than Tg minus 100 degrees during step 52, and in a more specific embodiment, the molten salt composition during step 52 is maintained at a temperature greater than Tg minus 50 degrees. In specific embodiments, the temperature of the molten salt is maintained above either Tg minus 100 degrees or Tg minus 50 degrees, but is also maintained less than Tg. Applicant has found that these high temperatures (particularly when combined with the short exposure times discussed herein) produce the desired CS and DOL in the glass sheet. While temperature will depend on Tg of the glass materials being strengthened, the temperature during step 52 typically is greater than 450 degrees C, specifically greater than 500 degrees C, and more specifically greater than 550 degrees C.

[0030] In various embodiments, during step 52, the first glass sheet is exposed to the molten salt for less than 8 hours, specifically for less than 4 hours, and more specifically for less than 1 hour. In a specific embodiment, the first glass composition is an alkali aluminosilicate glass composition or an alkali aluminoborosilicate glass composition, and the first glass sheet is exposed to the molten salt during step 52 for less than 35 minutes. In one specific embodiment, the first glass composition is an alkali aluminosilicate glass

composition or an alkali aluminoborosilicate glass composition, and the first glass sheet is exposed to the molten salt during step 52 for 30 minutes or less, and a CS of 25 MPa to 350 MPa having a DOL of 30-60 microns is formed. In specific embodiments, while the temperature will depend on the specific glass Tg, for these types of glass materials, the ion exchange temperature during step 52 will be greater than 500 degrees C, specifically greater than 550 degrees C, and more specifically greater than 600 degrees C. In some such embodiments, the Tg of the glass materials strengthened at these temperatures is 580-640 degrees C, and specifically from 600-620 degrees C. As a comparison, ion exchange bath exposure times or 5.5 hours at a low temperature (e.g., less than 450 degrees C) is typical for conventional chemical strengthening of these types of glass compositions.

[0031] In another embodiment, the first glass composition is a soda lime glass composition, and the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 8 hours. In specific embodiments where the first glass composition is a soda lime glass composition, an ion-exchange of 4-6 hours may be utilized to achieve the DOL of 30-60 μιη.

[0032] Referring to FIG. 2, at step 54, the first glass sheet (e.g., inner layer 12) is bonded to a second glass sheet (e.g., outer layer 18) via a polymer interlayer (e.g., layer 14). As shown in FIG. 1, the polymer interlayer is located between inner layer 12 and outer layer 18, and specifically bonds the outer surface of inner layer 12 to the inner surface of outer layer 18 as discussed above.

[0033] Referring to FIG. 3, in specific embodiments, glass laminate article 10 may be used as a glass component (e.g., a glazing component) of a vehicle, such as car 30. As shown, a car 30 includes one or more window 32, and glass laminate article 10 forms all of or part of window 32. In general, window 32 is supported within an opening defined by vehicle frame or body 34 such that inner surface 20 of glass laminate article 10 faces the vehicle interior/passenger compartment. In this arrangement, outer surface 26 of glass laminate article 10 faces toward the exterior of car 30 and may define the outermost surface of window 32.

Test Examples

[0034] As one example, a sheet of Glaverbel SLG float glass having a thickness of 1.1 mm was ion-exchanged for various times at a temperature of 510°C (Tg-45°C) rather than the typical 420°C-5.5 hour treatment. At times greater than 2 hours the FSM was unable to measure CS, likely due to the formation of an irregular stress profile but it could be measured by RNF. As will generally be understood RNF is a well know technique for measuring stress by measuring the refractive index profile, details and explanation of which can be found in US Patent Application Publications US 2014/0118740, which is incorporated by reference in its entirety. This example demonstrates that one can achieve deep DOL if they are willing to sacrifice CS which may be suitable in many applications, such as the laminate applications discussed herein. CS, CT and DOL for various ion-exchange tests are shown in Table 1 below.

[0035] Table 1

[0036] For comparison, in typical process, SLG is ion exchanged at 420 degrees C for 5.5 hours which generates CS of 550 MPa, CT of 5.5 MPa and a DOL of 10.6. As another comparison, Gorilla Glass available from Corning Inc. is typically ion exchanged at 420 degrees C for 5.5 hours which generates CS of 750 MPa, CT of 31 MPa and a DOL of 44.

CS and DOL Measurement Techniques

[0037] CS is measured using those means known in the art, such as 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 by those methods that are known in the art, such as fiber and four point bend methods, both of which are described in ASTM standard C770-98 (2013), entitled "Standard Test Method for Measurement of Glass Stress-Optical Coefficient," the contents of which are incorporated herein by reference in their entirety, and a bulk cylinder method. As used herein CS may be the "maximum compressive stress" which is the highest compressive stress value measured within the compressive stress layer. In some

embodiments, the maximum compressive stress is located at the surface of the glass substrate. In other embodiments, the maximum compressive stress may occur at a depth below the surface, giving the compressive profile the appearance of a "buried peak."

[0038] DOL may be measured by FSM or by a scattered light polariscope (SCALP) (such as the SCALP-04 scattered light polariscope available from Glasstress Ltd., located in Tallinn Estonia), depending on the strengthening method and conditions. When the glass substrate is chemically strengthened by an ion exchange treatment, FSM or SCALP may be used depending on which ion is exchanged into the glass substrate. Where the stress in the glass substrate is generated by exchanging potassium ions into the glass substrate, FSM is used to measure DOC. Where the stress is generated by exchanging sodium ions into the glass substrate, SCALP is used to measure DOL. Where the stress in the glass substrate is generated by exchanging both potassium and sodium ions into the glass, the DOL is measured by SCALP, since it is believed the exchange depth of sodium indicates the DOL and the exchange depth of potassium ions indicates a change in the magnitude of the compressive stress (but not the change in stress from compressive to tensile); the exchange depth of potassium ions in such glass substrates is measured by FSM. Central tension or CT is the maximum tensile stress and is measured by SCALP.

Examples of Glass Materials, Chemical Strengthening and Related Properties

[0039] In various embodiments, inner glass layer 12 may be formed from any of a variety of strengthened glass compositions. Examples of glasses that may be used for inner glass layer 12 of glass laminate article 10 described herein may include alkali aluminosilicate glass compositions or alkali aluminoborosilicate glass compositions, though other glass

compositions are contemplated. Such glass compositions may be characterized as ion exchangeable. As used herein, "ion exchangeable" means that the layer comprising the composition is capable of exchanging cations located at or near the surface of the glass layer with cations of the same valence that are either larger or smaller in size. In one exemplary embodiment, the glass composition of inner glass layer 12 comprises S1O2, B2O3 and NaiO, where (Si(¾ + B2O3) > 66 mol. %, and Na20 > 9 mol. %. Suitable glass compositions for inner glass layer 12, in some embodiments, further comprise at least one of K2O, MgO, and CaO. In a particular embodiment, the glass compositions used in inner glass layer 12 can comprise 61-75 mol.% S1O2; 7-15 mol.% AI2O3; 0-12 mol.% B2O3; 9-21 mol.% Na₂0; 0-4 mol.% K₂0; 0-7 mol.% MgO; and 0-3 mol.% CaO.

[0040] A further example of glass composition suitable for inner glass layer 12 comprises: 60-70 mol.% Si0₂; 6-14 mol.% AI2O3; 0-15 mol.% B₂0₃; 0-15 mol.% Li₂0; 0-20 mol.% Na₂0; 0-10 mol.% K₂0; 0-8 mol.% MgO; 0-10 mol.% CaO; 0-5 mol.% Zr0₂; 0-1 mol.% Sn02; 0-1 mol.% Ce02; less than 50 ppm AS2O3; and less than 50 ppm Sb203; where 12 mol.%

< (Li₂0 + Na₂0 + K₂0) < 20 mol.% and 0 mol.% < (MgO + CaO) < 10 mol.%.

[0041] A still further example of glass composition suitable for inner glass layer 12 comprises: 63.5-66.5 mol.% Si0₂; 8-12 mol.% A1₂0₃; 0-3 mol.% B₂0₃; 0-5 mol.% Li₂0; 8- 18 mol.% Na₂0; 0-5 mol.% K₂0; 1-7 mol.% MgO; 0-2.5 mol.% CaO; 0-3 mol.% Zr0₂; 0.05- 0.25 mol.% Sn02; 0.05-0.5 mol.% Ce02; less than 50 ppm AS2O3; and less than 50 ppm Sb₂0₃; where 14 mol.% < (Li₂0 + Na₂0 + K₂0) < 18 mol.% and 2 mol.% < (MgO + CaO)

< 7 mol.%.

[0042] In a particular embodiment, an alkali aluminosilicate glass composition suitable for inner glass layer 12 comprises alumina, at least one alkali metal and, in some embodiments, greater than 50 mol.% S1O2, in other embodiments at least 58 mol.% S1O2, and in still other embodiments at least 60 mol.% S1O2, wherein the ratio ((AI2O3 + Β2θ3)/∑ modifiers)>l, where in the ratio the components are expressed in mol.% and the modifiers are alkali metal oxides. This glass composition, in particular embodiments, comprises: 58-72 mol.% S1O2; 9- 17 mol.% AI2O3; 2-12 mol.% B₂0₃; 8-16 mol.% Na₂0; and 0-4 mol.% K₂0, wherein the ratio((Al₂0₃ + B₂03)/∑modifiers)>l .

[0043] In still another embodiment, the inner glass layer 12 may include an alkali aluminosilicate glass composition comprising: 64-68 mol.% S1O2; 12-16 mol.% Na20; 8-12 mol.% AI2O3; 0-3 mol.% B2O3; 2-5 mol.% K₂0; 4-6 mol.% MgO; and 0-5 mol.% CaO, wherein: 66 mol.% < S1O2 + B₂0₃ + CaO < 69 mol.%; Na₂0 + K₂0 + B₂0₃ + MgO + CaO + SrO > 10 mol.%; 5 mol.% < MgO + CaO + SrO < 8 mol.%; (Na₂0 + B₂0₃) - A1₂0₃ < 2 mol.%; 2 mol.% < Na₂0 - AI2O3 < 6 mol.%; and 4 mol.% < (Na₂0 + K₂0) - AI2O3 < 10 mol.%.

[0044] In an alternative embodiment, inner glass layer 12 may comprise an alkali aluminosilicate glass composition comprising: 2 mol% or more of AI2O3 and/or Zr02, or 4 mol% or more of AI2O3 and/or Zr(¾. In one or more embodiments, inner glass layer 12 comprises a glass composition comprising S1O2 in an amount in the range from about 67 mol% to about 80 mol%, AI2O3 in an amount in a range from about 5 mol% to about 11 mol%, an amount of alkali metal oxides (R2O) in an amount greater than about 5 mol% (e.g., in a range from about 5 mol% to about 27 mol%). In one or more embodiments, the amount of R2O comprises L12O in an amount in a range from about 0.25 mol% to about 4 mol%, and K2O in an amount equal to or less than 3 mol%. In one or more embodiments, the glass composition includes a non-zero amount of MgO, and a non-zero amount of ZnO.

[0045] In other embodiments, inner glass layer 12 is formed from a composition that exhibits S1O2 in an amount in the range from about 67 mol% to about 80 mol%, AI2O3 in an amount in the range from about 5 mol% to about 11 mol%, an amount of alkali metal oxides (R2O) in an amount greater than about 5 mol% (e.g., in a range from about 5 mol% to about 27 mol%), wherein the glass composition is substantially free of L12O, and a non-zero amount of MgO; and a non-zero amount of ZnO.

[0046] In other embodiments, inner glass layer 12 is formed from an aluminosilicate glass article comprising: a glass composition comprising S1O2 in an amount of about 67 mol% or greater; and a sag temperature in a range from about 600 °C to about 710 °C. In other embodiments, inner glass layer 12 is formed from an aluminosilicate glass article comprising: a glass composition comprising S1O2 in an amount of about 68 mol% or greater; and a sag temperature in a range from about 600 °C to about 710 °C (as defined herein). In some embodiments, glass laminate article 10 and/or inner glass layer 12 is a glass article that can be pair sagged with another glass article that differs in any one or more of composition, thickness, strengthening level, and forming method (e.g., float formed as opposed to fusion formed). In one or more embodiments, the glass article described has a sag temperature of about 710 °C, or less or about 700 °C or less. In one or more embodiments, the glass article described herein may be pair sagged with a SLG article. In one or more embodiments, this glass article comprises a glass composition comprising S1O2 in an amount in the range from about 68 mol% to about 80 mol%, AI2O3 in an amount in a range from about 7 mol% to about 15 mol%, B2O3 in an amount in a range from about 0.9 mol% to about 15 mol%; a non-zero amount of P2O5 up to and including about 7.5 mol%, L12O in an amount in a range from about 0.5 mol% to about 12 mol%, and Na20 in an amount in a range from about 6 mol% to about 15 mol%.

[0047] In some embodiments, the glass composition of inner glass layer 12 may include an oxide that imparts a color or tint to the glass articles. In some embodiments, the glass composition of inner glass layer 12 includes an oxide that prevents discoloration of the glass article when the glass article is exposed to ultraviolet radiation. Examples of such oxides include, without limitation oxides of: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ce, W, and Mo.

[0048] As shown in FIG. 1, embodiments of glass laminate article 10 include a first major outer surface 26 which is the outer surface of outer glass layer 18, an opposing second major surface 20, which is the inner surface of inner glass layer 12. A thickness T4 is defined between the first major surface and the second major surface.

[0049] In one or more embodiments, T4 may be about 3 millimeters or less (e.g., in the range from about 0.01 millimeter to about 3 millimeters, from about 0.1 millimeter to about 3 millimeters, from about 0.2 millimeter to about 3 millimeters, from about 0.3 millimeter to about 3 millimeters, from about 0.4 millimeter to about 3 millimeters, from about 0.01 millimeter to about 2.5 millimeters, from about 0.01 millimeter to about 2 millimeters, from about 0.01 millimeter to about 1.5 millimeters, from about 0.01 millimeter to about 1 millimeter, from about 0.01 millimeter to about 0.9 millimeter, from about 0.01 millimeter to about 0.8 millimeter, from about 0.01 millimeter to about 0.7 millimeter, from about 0.01 millimeter to about 0.6 millimeter, from about 0.01 millimeter to about 0.5 millimeter, from about 0.1 millimeter to about 0.5 millimeter, or from about 0.3 millimeter to about 0.5 millimeter.)

[0050] Glass laminate article 10 and/or its glass layers 12 and 18 may be substantially planar sheets, although other embodiments may utilize a curved or otherwise shaped or sculpted article. In some instances, the surfaces of glass laminate article 10 may have a 3D or 2.5D shape. Additionally or alternatively, the thickness of the glass laminate article 10 may be constant along one or more dimension or may vary along one or more of its dimensions for aesthetic and/or functional reasons. For example, the edges of the glass article may be thicker as compared to more central regions of the glass article. The length, width and thickness dimensions of the glass article may also vary according to the article application or use. In some embodiments, glass laminate article 10 may have a wedged shape in which the thickness at one end is greater than the thickness at an opposing end. Where the thickness varies, the thickness ranges disclosed herein are the maximum thickness between the major surfaces.

[0051] Glass laminate article 10 and/or its glass layers may have a refractive index in the range from about 1.45 to about 1.55. As used herein, the refractive index values are with respect to a wavelength of 550 nm. [0052] Glass laminate article 10 and/or its glass layers may be characterized by the manner in which it is formed. For instance, the glass article may be characterized as float-formable (i.e., formed by a float process), down-drawable and, in particular, fusion-formable or slot- drawable (i.e., formed by a down draw process such as a fusion draw process or a slot draw process).

[0053] In one or more embodiments, glass laminate article 10 and/or its glass layers described herein may exhibit an amorphous micro structure and may be substantially free of crystals or crystallites. In other words, in such embodiments, the glass articles exclude glass- ceramic materials.

[0054] In one or more embodiments, inner glass layer 12 exhibits an average total solar transmittance of about 88% or less, over a wavelength range from about 300 nm to about 2500 nm, when inner glass layer 12 has a thickness of 0.7 mm. For example, inner glass layer 12 exhibits an average total solar transmittance in a range from about 60% to about 88%, from about 62% to about 88%, from about 64% to about 88%, from about 65% to about 88%, from about 66% to about 88%, from about 68% to about 88%, from about 70% to about 88%, from about 72% to about 88%, from about 60% to about 86%, from about 60% to about 85%, from about 60% to about 84%, from about 60% to about 82%, from about 60% to about 80%, from about 60% to about 78%, from about 60% to about 76%, from about 60% to about 75%, from about 60% to about 74%, or from about 60% to about 72%.

[0055] In one or embodiments, inner glass layer 12 exhibits an average transmittance in the range from about 75% to about 85%, at a thickness of 0.7 mm or 1 mm, over a wavelength range from about 380 nm to about 780 nm. In some embodiments, the average transmittance at this thickness and over this wavelength range may be in a range from about 75% to about 84%, from about 75% to about 83%, from about 75% to about 82%, from about 75% to about 81 %, from about 75% to about 80%, from about 76% to about 85%, from about 77% to about 85%, from about 78% to about 85%, from about 79% to about 85%, or from about 80% to about 85%. In one or more embodiments, inner glass layer 12 exhibits T_Uv-38o or T_Uv-4oo of 50% or less (e.g., 49% or less, 48% or less, 45% or less, 40% or less, 30% or less, 25% or less, 23% or less, 20% or less, or 15% or less), at a thickness of 0.7 mm or 1 mm, over a wavelength range from about 300 nm to about 400 nm.

[0056] In one or more embodiments, inner glass layer 12 may be strengthened to include compressive stress that extends from a surface to a depth of compression (DOC) or depth of layer (DOL). The compressive stress regions are balanced by a central portion exhibiting a tensile stress. At the DOL, the stress crosses from a positive (compressive) stress to a negative (tensile) stress.

[0057] As noted above, inner glass layer 12 may be chemically strengthening by ion exchange. In the ion exchange process, ions at or near the surface of inner glass layer 12 are replaced by - or exchanged with - larger ions having the same valence or oxidation state. In those embodiments in which inner glass layer 12 comprises an alkali aluminosilicate glass, ions in the surface layer of the article and the larger ions are monovalent alkali metal cations, such as Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺. Alternatively, monovalent cations in the surface layer may be replaced with monovalent cations other than alkali metal cations, such as Ag⁺ or the like. In such embodiments, the monovalent ions (or cations) exchanged into inner glass layer 12 generate a stress.

[0058] Aspect (1) of this disclosure pertains to a method for forming a glass laminate article, the method comprising: chemically strengthening a first glass sheet comprising a first glass composition by treatment with a molten salt including alkali ions such that the alkali ions of the molten salt replace smaller alkali ions of the first glass sheet generating compressive surface stress (CS) along a first major surface of the first glass sheet, wherein the first glass composition includes a glass transition temperature (Tg), wherein a temperature of the molten salt during treatment of the first glass layer is greater than Tg minus 100 degrees C; and after the chemical strengthening step, bonding the first glass sheet to a second glass sheet with a polymer interlayer located between the first glass sheet and the second glass sheet.

[0059] Aspect (2) of this disclosure pertains to the method of Aspect (1), wherein an average thickness between opposing major surfaces of the first glass sheet is in a range from 0.05 mm to 1.5 mm, and wherein the first major surface of the first glass sheet defines an interior surface of the glass laminate article and a surface of the second glass sheet defines an exterior surface of the glass laminate article.

[0060] Aspect (3) of this disclosure pertains to the method of Aspect (1) or Aspect (2), wherein CS along the first major surface of the first glass sheet is between 25 MPa and 350 MPa.

[0061] Aspect (4) of this disclosure pertains to the method of Aspect (1) or Aspect (2), wherein CS along the first major surface of the first glass sheet is less than 250 MPa.

[0062] Aspect (5) of this disclosure pertains to the method of any one of Aspects (1) through (4), wherein the CS along the first major surface of the first glass sheet has a depth of layer of 20-100 microns. [0063] Aspect (6) of this disclosure pertains to the method of any one of Aspects (1) through (4), wherein the CS along the first major surface of the first glass sheet has a depth of layer greater than 40 microns.

[0064] Aspect (7) of this disclosure pertains to the method of any one of Aspects (1) through (4), wherein the CS along the first major surface of the first glass sheet has a depth of layer greater than 70 microns.

[0065] Aspect (8) of this disclosure pertains to the method of any one of Aspects (1) through (7), wherein the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 8 hours.

[0066] Aspect (9) of this disclosure pertains to the method of any one of Aspects (1) through (7), wherein the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 4 hours.

[0067] Aspect (10) of this disclosure pertains to the method of any one of Aspects (1) through (7), wherein the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 1 hour.

[0068] Aspect (1 1) of this disclosure pertains to the method of any one of Aspects (1) through (7), wherein the first glass composition is an alkali aluminosilicate glass composition, or an alkali aluminoborosilicate glass composition, wherein the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 35 minutes.

[0069] Aspect (12) of this disclosure pertains to the method of any one of Aspects (1) through (7), wherein the first glass composition is a soda lime glass composition, wherein the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 8 hours.

[0070] Aspect (13) of this disclosure pertains to a method for chemically strengthening a glass sheet formed from a first glass composition, the method comprising: treating the glass sheet with a molten salt composition including alkali ions such that the alkali ions of the molten salt composition replace smaller alkali ions of the glass sheet generating compressive surface stress (CS) at a major surface of the glass sheet; wherein the first glass composition includes a glass transition temperature (Tg), wherein a temperature of the molten salt composition during treatment of the glass sheet is greater than Tg minus 50 degrees C.

[0071] Aspect (14) of this disclosure pertains to the method of Aspect (13), wherein the CS along the major surface of the glass sheet is less than 350 MPa.

[0072] Aspect (15) of this disclosure pertains to the method of Aspect (13), wherein the CS along the major surface of the glass sheet is less than 250 MPa. [0073] Aspect (16) of this disclosure pertains to the method of any of Aspects (13) through (15), wherein the CS has a depth of layer of 20-100 microns.

[0074] Aspect (17) of this disclosure pertains to the method of any of Aspects (13) through

(15), wherein the CS has a depth of layer (DOL) greater than 40 microns.

[0075] Aspect (18) of this disclosure pertains to the method of any of Aspects (13) through

(15), wherein the CS has a depth of layer (DOL) greater than 70 microns.

[0076] Aspect (19) of this disclosure pertains to the method of any of Aspects (13) through

(18), wherein a duration of the treating step is less than 8 hours.

[0077] Aspect (20) of this disclosure pertains to the method of any of Aspects (13) through (18), wherein a duration of the treating step is less than 4 hours.

[0078] The method of any one of claims 13-18, wherein a duration of the treating step is less than 1 hour.

[0079] The method of any one of claims 13-21, wherein the first glass composition is an alkali aluminosilicate glass composition, or an alkali aluminoboro silicate glass composition, wherein a duration of the treating step is 35 minutes or less.

[0080] The method of any one of claims 13-21, wherein the first glass composition is a soda lime glass composition, wherein a duration of the treating step is less than 8 hours.

[0081] The method of any one of claims 13-23, wherein a maximum thickness of the glass sheet measured between opposing major surfaces is in a range from 0.05 mm to 1.2 mm.

[0082] A glass laminate article comprising:

a strengthened inner glass layer comprising:

an inner surface;

an outer surface opposite the inner surface; and an average thickness between the inner and outer surfaces in a range from 0.05 mm to 1.2 mm; and

a compressive surface stress (CS) along the inner surface of less than 250 MPa having a depth of layer (DOL) of 20-100 microns;

an external glass layer comprising:

an inner surface; and

an outer surface; and

an interlayer disposed between the inner glass layer and the external glass layer.

[0083] The glass laminate article of claim 25, wherein an average thickness between the inner and outer surfaces of the external glass layer is in a range from 0.9 mm to 4 mm. [0084] The glass laminate article of claims 25 or 26, wherein the inner glass layer comprises an alkali aluminosilicate glass composition, or an alkali aluminoborosilicate glass composition, wherein the interlayer is a polymer selected from a group consisting of polyvinyl butyral, ethylenevinylacetate, polyvinyl chloride, ionomers, and thermoplastic polyurethane.

[0085] The glass laminate article of claims 25, 26 or 27, wherein the inner glass layer is formed from a first glass composition and the external glass layer is formed from a second glass composition different from the first glass composition.

[0086] A vehicle comprising:

a body comprising an interior;

an opening in the body in communication with interior; and

a window disposed in the opening, the window comprising the glass laminate article of any one of claims 25-28.

[0087] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that any particular order be inferred. In addition, as used herein, the article "a" is intended to include one or more than one component or element, and is not intended to be construed as meaning only one.

[0088] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the disclosed embodiments. Since modifications, combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the embodiments may occur to persons skilled in the art, the disclosed embodiments should be construed to include everything within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A method for forming a glass laminate article, the method comprising:

chemically strengthening a first glass sheet comprising a first glass composition by treatment with a molten salt including alkali ions such that the alkali ions of the molten salt replace smaller alkali ions of the first glass sheet generating compressive surface stress (CS) along a first major surface of the first glass sheet, wherein the first glass composition includes a glass transition temperature (Tg), wherein a temperature of the molten salt during treatment of the first glass layer is greater than Tg minus 100 degrees C; and after the chemical strengthening step, bonding the first glass sheet to a second glass sheet with a polymer interlayer located between the first glass sheet and the second glass sheet.

2. The method of claim 1, wherein an average thickness between opposing major surfaces of the first glass sheet is in a range from 0.05 mm to 1.5 mm, and wherein the first major surface of the first glass sheet defines an interior surface of the glass laminate article and a surface of the second glass sheet defines an exterior surface of the glass laminate article.

3. The method of claim 1 or 2, wherein CS along the first major surface of the first glass sheet is between 25 MPa and 350 MPa.

4. The method of claim 1 or 2, wherein CS along the first major surface of the first glass sheet is less than 250 MPa.

5. The method of any one of claims 1-4, wherein the CS along the first major surface of the first glass sheet has a depth of layer of 20-100 microns.

6. The method of any one of claims 1-4, wherein the CS along the first major surface of the first glass sheet has a depth of layer greater than 40 microns.

7. The method of any one of claims 1-4, wherein the CS along the first major surface of the first glass sheet has a depth of layer greater than 70 microns.

8. The method of any one of claims 1-7, wherein the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 8 hours.

9. The method of any one of claims 1-7, wherein the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 4 hours.

10. The method of any one of claims 1-7, wherein the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 1 hour.

11. The method of any one of claims 1-7, wherein the first glass composition is an alkali aluminosilicate glass composition, or an alkali aluminoboro silicate glass composition, wherein the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 35 minutes.

12. The method of any one of claims 1-7, wherein the first glass composition is a soda lime glass composition, wherein the first glass sheet is exposed to the molten salt during the chemical strengthening step for less than 8 hours.

13. A method for chemically strengthening a glass sheet formed from a first glass composition, the method comprising:

treating the glass sheet with a molten salt composition including alkali ions such that the alkali ions of the molten salt composition replace smaller alkali ions of the glass sheet generating compressive surface stress (CS) at a major surface of the glass sheet;

wherein the first glass composition includes a glass transition temperature (Tg), wherein a temperature of the molten salt composition during treatment of the glass sheet is greater than Tg minus 50 degrees C.

14. The method of claim 13, wherein the CS along the major surface of the glass sheet is less than 350 MPa.

15. The method of claim 13, wherein the CS along the major surface of the glass sheet is less than 250 MPa.

16. The method of any one of claims 13-15, wherein the CS has a depth of layer of 20-100 microns.

17. The method of any one of claims 13-15, wherein the CS has a depth of layer (DOL) greater than 40 microns.

18. The method of any one of claims 13- 15, wherein the CS has a depth of layer (DOL) greater than 70 microns.

19. The method of any one of claims 13-18, wherein a duration of the treating step is less than 8 hours.

20. The method of any one of claims 13-18, wherein a duration of the treating step is less than 4 hours.

21. The method of any one of claims 13-18, wherein a duration of the treating step is less than 1 hour.

22. The method of any one of claims 13-21, wherein the first glass composition is an alkali aluminosilicate glass composition, or an alkali aluminoborosilicate glass composition, wherein a duration of the treating step is 35 minutes or less.

23. The method of any one of claims 13-21, wherein the first glass composition is a soda lime glass composition, wherein a duration of the treating step is less than 8 hours.

24. The method of any one of claims 13-23, wherein a maximum thickness of the glass sheet measured between opposing major surfaces is in a range from 0.05 mm to 1.2 mm.

25. A glass laminate article comprising:

a strengthened inner glass layer comprising:

an inner surface;

an external glass layer comprising:

an inner surface; and

an outer surface; and

26. The glass laminate article of claim 25, wherein an average thickness between the inner and outer surfaces of the external glass layer is in a range from 0.9 mm to 4 mm.

27. The glass laminate article of claims 25 or 26, wherein the inner glass layer comprises an alkali aluminosilicate glass composition, or an alkali aluminoborosilicate glass composition, wherein the interlayer is a polymer selected from a group consisting of polyvinyl butyral, ethylenevinylacetate, polyvinyl chloride, ionomers, and thermoplastic polyurethane.

28. The glass laminate article of claims 25, 26 or 27, wherein the inner glass layer is formed from a first glass composition and the external glass layer is formed from a second glass composition different from the first glass composition.

29. A vehicle comprising:

a body comprising an interior;

an opening in the body in communication with interior; and