(19)
(11)EP 2 819 960 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
13.07.2022 Bulletin 2022/28

(21)Application number: 13709663.2

(22)Date of filing:  28.02.2013
(51)International Patent Classification (IPC): 
C03C 3/089(2006.01)
C03C 3/091(2006.01)
(52)Cooperative Patent Classification (CPC):
C03C 3/089; C03B 17/02; Y02P 40/57; Y10T 428/24942; B32B 17/00; C03C 3/091
(86)International application number:
PCT/US2013/028145
(87)International publication number:
WO 2013/130700 (06.09.2013 Gazette  2013/36)

(54)

HIGH CTE POTASSIUM BOROSILICATE CORE GLASSES AND GLASS ARTICLES COMPRISING THE SAME

KALIUMBOROSILIKAT KERNGLÄSER MIT HOHEM CTE UND GLASARTIKEL ENTHALTEND DIESE

VERRE DE COEUR DE POTASSIUM BOROSILICATE AYANT UN CTE ÉLEVÉ ET ARTICLES EN VERRE COMPRENANT CEUX-CI


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 29.02.2012 US 201261604869 P

(43)Date of publication of application:
07.01.2015 Bulletin 2015/02

(73)Proprietor: Corning Incorporated
Corning, New York 14831 (US)

(72)Inventor:
  • MAURO, John Christopher
    Corning, New York 14830 (US)

(74)Representative: Elkington and Fife LLP 
Prospect House 8 Pembroke Road
Sevenoaks, Kent TN13 1XR
Sevenoaks, Kent TN13 1XR (GB)


(56)References cited: : 
US-A- 3 597 305
US-A1- 2003 092 556
US-A1- 2010 300 536
US-A- 3 673 049
US-A1- 2007 037 686
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    BACKGROUND


    Field



    [0001] The present specification generally relates to glass compositions and, more specifically, to high CTE potassium borosilicate glass compositions and glass articles comprising the same.

    Technical Background



    [0002] Glass articles, such as cover glasses, glass backplanes and the like, are employed in both consumer and commercial electronic devices such as LCD and LED displays, computer monitors, automated teller machines (ATMs) and the like. Some of these glass articles may include "touch" functionality which necessitates that the glass article be contacted by various objects including a user's fingers and/or stylus devices and, as such, the glass must be sufficiently robust to endure regular contact without damage. Moreover, such glass articles may also be incorporated in portable electronic devices, such as mobile telephones, personal media players, and tablet computers. The glass articles incorporated in these devices may be susceptible to damage during transport and/or use of the associated device. Accordingly, glass articles used in electronic devices may require enhanced strength to be able to withstand not only routine "touch" contact from actual use, but also incidental contact and impacts which may occur when the device is being transported.

    [0003] Glass articles are commonly strengthened by thermal tempering and/or by ion exchange treatment. In either case, the glass article is subjected to additional processing steps after the glass article is formed. These additional processing steps may increase the overall cost of the glass article. Moreover, the additional handling required to carry out these processing steps increases the risk of damage to the glass article which decreases manufacturing yields and further increases production costs and the ultimate cost of the glass article.

    [0004] Accordingly, a need exists for alternative glass compositions which may be used to produce strengthened glass articles without the need for additional processing steps and glass articles manufactured from such compositions.

    [0005] US 2010/0300536 A1 relates to fusion-formable, high strain point sodium free, silicate, aluminosilicate and boroaluminosilicate glasses.

    SUMMARY



    [0006] According to one embodiment, a glass composition may include from about 70 mol.% to about 80 mol.% SiO2; from about 0 mol.% to about 8 mol.% Al2O3; and from about 3 mol.% to about 10 mol.% B2O3 as glass network formers. The glass composition further includes alkali oxides such as from about 0 mol.% to about 2 mol.% Na2O and from about 10 mol.% to about 15 mol.% K2O. In addition, the glass composition includes from about 5 mol.% to about 6 mol.% alkaline earth oxide. The alkaline earth oxide includes SrO, BaO or combinations thereof. However, the glass composition is substantially free from MgO and TiO2. The glass composition comprises a coefficient of thermal expansion which is greater than or equal to 75×10-7/°C averaged over a temperature range from 20°C to 300°C and a liquidus viscosity greater than or equal to 25 kPa•s (250 kPoise). The glass composition is particularly well suited for use as a core glass layer in a laminated glass article, such as a laminated glass article formed by a fusion laminate process.

    [0007] In one set of embodiments, a glass article includes a glass core layer disposed between a first glass cladding layer and a second glass cladding layer. In some of these embodiments, the core glass may have a first surface and a second surface opposite the first surface, where the first glass cladding layer may be fused to the first surface of the glass core layer and a second glass cladding layer may be fused to the second surface of the glass core layer. In other embodiments, a first diffusive glass layer may be disposed between the glass core layer and the first glass cladding layer; additionally a second diffusive glass layer may be disposed between the glass core layer and the second glass cladding layer; these diffusive layers may be formed during, for example, the fusion forming process. The glass core layer is formed from a glass composition which includes from about 70 mol.% to about 80 mol.% SiO2; from about 0 mol.% to about 8 mol.% Al2O3; and from about 3 mol.% to about 10 mol.% B2O3 as glass network formers. The glass composition further includes alkali oxides such as from about 0 mol.% to about 2 mol.% Na2O and from about 10 mol.% to about 15 mol.% K2O. In addition, the glass composition includes from about 5 mol.% to about 6 mol.% alkaline earth oxide. The alkaline earth oxide includes SrO, BaO or combinations thereof. However, the glass composition is substantially free from MgO and TiO2. The glass composition comprises a coefficient of thermal expansion which is greater than or equal to 75×10-7/°C averaged over a temperature range from 20°C to 300°C.

    [0008] Additional features and advantages of the glass compositions and glass articles formed from the glass compositions described herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

    [0009] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0010] 

    FIG. 1 schematically depicts a cross section of a laminated glass article according to one or more embodiments shown and described herein; and

    FIG. 2 schematically depicts a fusion draw process for making the glass article of FIG. 1.


    DETAILED DESCRIPTION



    [0011] Reference will now be made in detail to embodiment of glass compositions having high coefficients of thermal expansion and glass articles incorporating the same, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. The glass compositions described herein generally have relatively high coefficients of thermal expansion and, as such, may be utilized in conjunction with cladding glass compositions having relatively low coefficients of thermal expansion to produce laminated glass articles which are compressively stressed without being ion-exchanged or thermally tempered. In one embodiment, a glass composition may include from about 70 mol.% to about 80 mol.% SiO2; from about 0 mol.% to about 8 mol.% Al2O3; and from about 3 mol.% to about 10 mol.% B2O3 as glass network formers. The glass composition further includes alkali oxides such as from about 0 mol.% to about 2 mol.% Na2O and from about 10 mol.% to about 15 mol.% K2O. In addition, the glass composition includes from about 5 mol.% to about 6 mol.% of alkaline earth oxide. The alkaline earth oxide includes SrO, BaO or combinations thereof. However, the glass composition is substantially free from MgO and TiO2. The glass compositions and glass articles formed from the glass compositions will be described in more detail herein with specific reference to the appended drawings.

    [0012] The term "liquidus viscosity, as used herein, refers to the shear viscosity of the glass composition at its liquidus temperature.

    [0013] The term "liquidus temperature," as used herein, refers to the highest temperature at which devitrification occurs in the glass composition.

    [0014] The term "CTE," as used herein, refers to the coefficient of thermal expansion of the glass composition averaged over a temperature range from about 20°C to about 300°C.

    [0015] The term "substantially free," when used to describe the absence of a particular oxide constituent in a glass composition, means that the constituent is present in the glass composition as a contaminant in a trace amount of less than 1 mol.%.

    [0016] In the embodiments of the glass compositions described herein, the concentration of constituent components (e.g., SiO2, Al2O3, B2O3 and the like) are given in mole percent (mol.%) on an oxide basis, unless otherwise specified.

    [0017] The glass compositions described herein have properties, such as the liquidus viscosity and the liquidus temperature, which make the glass compositions particularly well suited to use with fusion forming processes, such as the fusion down draw process and/or the fusion lamination process. These properties are attributable to the specific compositions of the glasses, as will be described in more detail herein.

    [0018] In the embodiments of the glass compositions described herein SiO2 is the largest constituent of the composition and, as such, SiO2 is the primary constituent of the resulting glass network. SiO2 is utilized in the glass compositions described herein to obtain the desired liquidus viscosity while, at the same time, offsetting the amount of Al2O3 added to the composition, as will be described in further detail herein. Accordingly, a high SiO2 concentration is generally desired. However, if the content of SiO2 is too high, the formability of the glass may be diminished as higher concentrations of SiO2 increase the difficulty of melting the glass which, in turn, adversely impacts the formability of the glass. In the embodiments described herein, the glass composition generally comprises SiO2 in an amount greater than or equal to about 70 mol.%. For example, in some embodiments, the amount of SiO2 in the glass composition is greater than or equal to about 70 mol.% and less than or equal to about 80 mol.%. In some other embodiments SiO2 is present in the glass composition in an amount greater than or equal to about 73 mol.% and less than or equal to about 77 mol.%.

    [0019] In some embodiments, the glass compositions may further comprise Al2O3. Al2O3, when present, also serves as a glass network former, similar to SiO2. Like SiO2, Al2O3 increases the viscosity of the glass composition due to its tetrahedral coordination in a glass melt formed from the glass composition. However, when the concentration of Al2O3 is balanced against the concentration of SiO2 and the concentrations of alkali and/or alkaline earth oxides in the glass composition, the Al2O3 can reduce the liquidus temperature of the glass melt, thereby enhancing the liquidus viscosity and improving the compatibility of the glass composition with certain forming processes such as, for example, the fusion draw process. However, the presence of Al2O3 in the glass compositions also increases the mobility of alkali constituents in the glass components because the alkali constituents used by aluminum for charge compensation are more loosely bound to the glass network relative to alkali constituents used for charge compensating boron, or other alkali constituents, which contribute to the formation of non-bridging oxygen in the glass network. Accordingly, the amount of Al2O3 in the glass compositions should be minimized.

    [0020] In the embodiments of the glass compositions described herein, the concentration of Al2O3 in the glass compositions, when present, is generally less than or equal to about 10 mol.% in order to achieve a glass composition having the desired liquidus temperature. For example, in some embodiments, the concentration of Al2O3 in the glass compositions is greater than or equal to about 0 mol.% and less than or equal to about 8 mol.%. In some embodiments, the concentration of Al2O3 in the glass compositions is less than or equal to about 6 mol.%. For example, in some embodiments, the concentration of Al2O3 in the glass compositions is greater than or equal to about 0 mol.% and less than or equal to about 5 mol.% or even greater than or equal to about 0 mol.% and less than or equal to about 4 mol.%. In some other embodiments, the concentration of Al2O3 is the glass compositions is greater than or equal to about 0 mol.% and less than or equal to about 3 mol.%.

    [0021] The glass compositions in the embodiments described herein further comprise B2O3. Like SiO2 and Al2O3, B2O3 contributes to the formation of the glass network. Conventionally, B2O3 is added to a glass composition in order to decrease the viscosity of the glass composition. However, in the embodiments described herein, B2O3 works in conjunction with additions of K2O and Al2O3 (when present) to increase the annealing point of the glass composition, increase the liquidus viscosity, and inhibit alkali mobility. The interactions with K2O and, optionally, Al2O3, will be described in further detail herein.

    [0022] In the embodiments described herein, B2O3 is generally present in the glass compositions in an amount greater than or equal to about 3 mol.%. For example, in some embodiments, B2O3 is present in the glass compositions in a concentration greater than or equal to about 3 mol.% and less than or equal to about 10 mol.%. In other embodiments described herein, B2O3 is present in the glass compositions in a concentration of less than about 8 mol.%. For example, in some embodiments, the concentration of B2O3 in the glass composition is greater than or equal to about 3 mol.% and less than or equal to about 8 mol.%, or even less than or equal to about 7 mol.%. In some other embodiments, the concentration of B2O3 in the glass compositions is greater than or equal to about 4 mol.% and less than or equal to about 5 mol.%.

    [0023] The glass compositions in the embodiments described herein also include alkali oxides. Specifically, the glass compositions described herein include at least K2O. The addition of alkali oxides such as K2O to the glass compositions increases the average coefficient of thermal expansion of the resultant glass and also decreases the liquidus temperature of the glass. K2O is used as the primary alkali oxide constituent as the relatively large ionic radius of K2O (relative to other alkali oxides such as Na2O and Li2O) decreases the diffusivity of K2O in the glass. Low K2O diffusivity is particularly important when the glass composition is used to form backplanes for displays and the diffusion of K2O from the glass to thin film transistors deposited on the glass damages the transistors. In embodiments where the glass composition is utilized to form a glass core layer of a laminated glass article, the presence of K2O in the composition may facilitate ion-exchange strengthening of the cladding layers at the interface between the glass core layer and the glass cladding layers fused to the glass core layer.

    [0024] In the embodiments described herein, the concentration of K2O in the glass compositions is generally less than about 15 mol.%. For example, in some embodiments, the concentration of K2O in the glass compositions is greater than or equal to about 10 mol.% and less than or equal to about 15 mol.%. In some other embodiments, the concentration of K2O is greater than or equal to about 11.5 mol.% and less than or equal to about 12.5 mol.%.

    [0025] As noted hereinabove, K2O in the glass compositions works in conjunction with B2O3 to increase the viscosity of the glass and to inhibit alkali diffusivity. In particular, in the embodiments of the glass compositions described herein, the concentration of K2O is greater than the sum of the concentration of B2O3 and the concentration of Al2O3 (i.e., K2O (mol.%) > B2O3 (mol.%) + Al2O3 (mol.%)). This excess of alkali oxide alters several characteristics of the resulting glass. Specifically, Al2O3 utilizes alkali metals, such as the potassium from K2O, for charge stabilization. Once the aluminum is charge-stabilized, excess potassium in the glass composition interacts with boron in the glass composition and converts the boron from its standard trigonal (threefold-coordinated) configuration into a tetrahedral (fourfold-coordinated) configuration. The change in the coordination of the boron from trigonal to tetrahedral increases the annealing point and liquidus viscosity of the glass while inhibiting alkali diffusivity as the excess alkali (i.e., potassium) is bound to the boron.

    [0026] In some embodiments of the glass compositions described herein, the glass compositions may comprise an additional alkali oxide such as, for example Na2O. In embodiments where Na2O is present in the glass composition, the Na2O may be introduced in the composition when sodium-containing glass cullet, such as recycled glass cullet, is utilized to produce the glass composition. In the embodiments described herein, the concentration of Na2O may be greater than or equal to about 0 mol.% and less than or equal to about 2 mol.%. In some other embodiments, the concentration of Na2O in the glass composition may be greater than or equal to about 0 mol.% and less than or equal to about 1 mol.%. In some embodiments where Na2O is present in the glass compositions, the Na2O may be present in a concentration greater than or equal to about 0.1 mol.%. For example, in some embodiments the concentration of Na2O in the glass compositions may be greater than or equal to about 0.1 mol.% and less than or equal to about 2 mol.%. In some other embodiments, the concentration of Na2O in the glass compositions may be greater than or equal to about 0.1 mol.% and less than or equal to about 1 mol.%.

    [0027] The glass compositions described herein further comprises one or more alkaline earth oxide. The alkaline earth oxides improve the melting behavior of the glass composition, lower the melting temperature of the glass composition, and inhibit the diffusion of alkali constituents in the glass composition. In the embodiments of the glass compositions described herein the alkaline earth oxide includes aSrO, BaO or combinations thereof. In some embodiments, the primary alkaline earth oxide present in the glass composition is BaO which is utilized to minimize alkali diffusivity. However, in other embodiments, the alkaline earth oxide primarily comprises SrO to lower the density of the glass composition. In still other embodiments, the glass compositions are substantially free from BaO, such as when the glass composition is a "SuperGreen" or environmentally friendly glass composition.

    [0028] In the embodiments described herein, the glass compositions comprise greater than or equal to about 5 mol.% and less than or equal to about 6 mol.% alkaline earth oxide. In some particular embodiments, the alkaline earth oxide comprises SrO in a concentration greater than or equal to about 1.5 mol.% and BaO in a concentration greater than or equal to about 0 mol.% and less than or equal to about 2 mol.%. As noted hereinabove, in some embodiments, the glass compositions are substantially free from BaO.

    [0029] The embodiments of the glass compositions described herein include one or more alkaline earth oxides. However, in all embodiments described herein, the glass compositions are substantially free of MgO. Accordingly, in the embodiments of the glass compositions described herein, MgO is present in the glass compositions in a concentration of less than 1 mol.%. The MgO may be introduced in the composition when magnesium-containing glass cullet, such as recycled glass cullet, is utilized to produce the glass composition.

    [0030] The glass compositions described herein may optionally further comprise one or more fining agents. The fining agents may include, for example, SnO2, As2O3, Sb2O3 or combinations thereof. The fining agents may be present in the glass compositions in an amount greater than or equal to about 0 mol.% and less than or equal to about 0.5 mol.%. In exemplary embodiments, the fining agent is SnO2 which is present in the glass composition in an amount greater than about 0 mol.% and less than or equal to about 0.2 mol.%.

    [0031] In some embodiments described herein, the glass compositions may further comprise trace amounts of Fe2O3 and/or ZrO2. For example, in some embodiments, the glass compositions may comprise Fe2O3 in a concentration greater than or equal to 0 mol.% and less than or equal to 0.2 mol.%. Alternatively or additionally, the glass compositions may comprise ZrO2 in a concentration greater than or equal to 0 mol.% and less than or equal to about 0.08 mol.%. Further, the glass compositions may comprise TiO2 in a concentration which is greater than or equal to 0 mol.% and less than or equal to 2 mol.%.

    [0032] In some embodiments described herein, the glass compositions are substantially free of heavy metals and compounds containing heavy metals. Glass compositions which are substantially free from heavy metals and compounds containing heavy metals may also be referred to as "SuperGreen" glass compositions The term "heavy metals," as used herein, refers to Ba, As, Sb, Cd, and Pb.

    [0033] The glass compositions described herein generally have a coefficient of thermal expansion (CTE) which is greater than or equal to about 75×10-7/°C averaged over the range from 20°C to 300°C. In some embodiments, the CTE of the glass compositions may be greater than or equal to about 85×10-7/°C in a range from 20°C to 300°C. In yet other embodiments, the CTE of the glass compositions may be greater than or equal to about 95×10-7/°C in a range from 20°C to 300°C. The high CTE values of the composition are attributable to, at least in part, the relatively high alkali concentration (i.e., the concentration of K2O and Na2O, when present) in the glass compositions. Accordingly, in general, increasing the amount of alkali oxide in the glass composition also increases the CTE of the resultant glass. These relatively high CTEs make the glass compositions particularly well suited for use as a glass core layer in a fusion-formed laminated glass article. Specifically, when the high CTE of the glass core layer is paired with glass cladding layers having lower CTEs during the fusion lamination process, the difference in the CTEs of the glass core layer and the glass cladding layers results in the formation of a compressive stress in the glass cladding layers upon cooling. Accordingly, the glass compositions described herein may be utilized to form a strengthened laminated glass article without the need for an ion exchange treatment or thermal tempering.

    [0034] The glass compositions described herein have a liquidus viscosity which renders them suitable for use in a fusion draw process and, in particular, for use as a glass core composition in a fusion laminate process. In some embodiments, the liquidus viscosity is greater than or equal to about 25 kPa•s (250 kPoise). In some other embodiments, the liquidus viscosity may be greater than or equal to 35 kPa•s (350 kPoise) or even greater than or equal to 50 kPa•s (500 kPoise). The high liquidus viscosity values of the glass compositions described herein are attributable to the combination of high SiO2 content in conjunction with the high concentration of tetragonal boron due to excess alkali constituents (i.e., M2O-Al2O3) in the glass composition.

    [0035] The glass compositions described herein have a low liquidus temperature which, like the liquidus viscosity, renders the glass compositions suitable for use in a fusion draw process and, in particular, for use as a glass core layer in a fusion laminate process. A low liquidus temperature prevents devitrification of the glass during the fusion draw fusion. This ensures high-quality homogeneous glass and consistent flow behavior. In some embodiments, the glass compositions have a liquidus temperature less than or equal to about 1050°C. In some other embodiments, the liquidus temperature may be less than or equal to about 1000°C or even less than or equal to about 950°C. In some embodiments, the liquidus temperature of the glass compositions may be less than or equal to 900°C. The liquidus temperature of the glass composition generally decreases with increasing concentrations of B2O3, alkali oxides and/or alkaline earth oxides.

    [0036] Based on the foregoing, it should be understood that various embodiments of high CTE glasses are disclosed herein. In a first exemplary embodiment of a glass composition having a high CTE, the glass composition includes SiO2 in a concentration greater than or equal to about 70 mol.% and less than or equal to about 80 mol.%; Al2O3 in a concentration greater than or equal to about 0 mol.% and less than or equal to about 8 mol.%; and B2O3 in a concentration greater than or equal to about 3 mol.% and less than or equal to about 10 mol.% as glass network formers. The glass composition further includes alkali oxide. The alkali oxide includes Na2O in a concentration greater than or equal to about 0 mol.% and less than or equal to about 2 mol.% and K2O in a concentration greater than or equal to about 10 mol.% and less than or equal to about 15 mol.%. The glass composition further includes alkaline earth oxide in a concentration greater than or equal to about 5 mol.% and less than or equal to about 6 mol.%. The alkaline earth oxide comprises SrO, BaO or combinations thereof. Moreover, the glass composition is substantially free from MgO and TiO2. The glass composition comprises a coefficient of thermal expansion which is greater than or equal to 75×10-7/°C averaged over a temperature range from 20°C to 300°C and a liquidus viscosity greater than or equal to 25 kPa•s (250 kPoise).

    [0037] In a second exemplary embodiment, the glass composition includes SiO2 in a concentration greater than or equal to about 73 mol.% and less than or equal to about 77 mol.%; Al2O3 in a concentration greater than or equal to about 0 mol.% and less than or equal to about 3 mol.%; and B2O3 in a concentration greater than or equal to about 4 mol.% and less than or equal to about 5 mol.% as glass network formers. The glass composition further includes alkali oxide. The alkali oxide includes Na2O in a concentration greater than or equal to about 0 mol.% and less than or equal to about 2 mol.% and K2O in a concentration greater than or equal to about 11.5 mol.% and less than or equal to about 12.5 mol.%. The glass composition further includes alkaline earth oxide in a concentration greater than or equal to about 5 mol.% and less than or equal to about 6 mol.%. The alkaline earth oxide comprises SrO, BaO or combinations thereof. Moreover, the glass composition is substantially free from MgO and TiO2. The glass composition comprises a coefficient of thermal expansion which is greater than or equal to 75×10-7/°C averaged over a temperature range from 20°C to 300°C and a liquidus viscosity greater than or equal to 25 kPa•s (250 kPoise).

    [0038] In a third exemplary embodiment, the glass compositions includes SiO2 in a concentration greater than or equal to about 70 mol.% and less than or equal to about 80 mol.%; Al2O3 in a concentration greater than or equal to about 0 mol.% and less than or equal to about 8 mol.%; and B2O3 in a concentration greater than or equal to about 3 mol.% and less than or equal to about 10 mol.% as glass network formers. The glass composition further includes alkali oxide. The alkali oxide includes Na2O in a concentration greater than or equal to about 0 mol.% and less than or equal to about 2 mol.% and K2O in a concentration greater than or equal to about 10 mol.% and less than or equal to about 15 mol.%. The glass composition further includes alkaline earth oxide in a concentration greater than or equal to about 5 mol.% and less than or equal to about 6 mol.%. The alkaline earth oxide comprises SrO in a concentration greater than or equal to about 1.5 mol.% and BaO in a concentration from about 0 mol.% to about 2 mol.%. Moreover, the glass composition is substantially free from MgO may. The glass composition comprises a coefficient of thermal expansion which is greater than or equal to 75×10-7/°C averaged over a temperature range from 20°C to 300°C and a liquidus viscosity greater than or equal to 25 kPa•s (250 kPoise).

    [0039] In a fourth exemplary embodiment, the glass composition includes SiO2 in a concentration greater than or equal to about 70 mol.% and less than or equal to about 80 mol.%; Al2O3 in a concentration greater than or equal to about 0 mol.% and less than or equal to about 8 mol.%; and B2O3 in a concentration greater than or equal to about 3 mol.% and less than or equal to about 10 mol.% as glass network formers. The glass composition further includes alkali oxide. The alkali oxide includes Na2O in a concentration greater than or equal to about 0.1 mol.% and less than or equal to about 2 mol.% and K2O in a concentration greater than or equal to about 10 mol.% and less than or equal to about 15 mol.%. The glass composition further includes alkaline earth oxide in a concentration greater than or equal to about 5 mol.% and less than or equal to about 6 mol.%. The alkaline earth oxide comprises SrO, BaO or combinations thereof. Moreover, the glass composition is substantially free from MgO and TiO2. The glass composition comprises a coefficient of thermal expansion which is greater than or equal to 75×10-7/°C averaged over a temperature range from 20°C to 300°C and a liquidus viscosity greater than or equal to 25 kPa•s (250 kPoise).

    [0040] In a fifth exemplary embodiment, the glass composition includes SiO2 in a concentration greater than or equal to about 70 mol.% and less than or equal to about 80 mol.%; Al2O3 in a concentration greater than or equal to about 0 mol.% and less than or equal to about 8 mol.%; and B2O3 in a concentration greater than or equal to about 3 mol.% and less than or equal to about 10 mol.% as glass network formers. The glass composition further includes alkali oxide. The alkali oxide includes Na2O in a concentration greater than or equal to about 0 mol.% and less than or equal to about 2 mol.% and K2O in a concentration greater than or equal to about 10 mol.% and less than or equal to about 15 mol.%. In this embodiment, the concentration of K2O is greater than the sum of the concentration of B2O3 and the concentration of Al2O3. The glass composition further includes alkaline earth oxide in a concentration greater than or equal to about 5 mol.% and less than or equal to about 6 mol.%. The alkaline earth oxide comprises SrO, BaO or combinations thereof. Moreover, the glass composition is substantially free from MgO and TiO2. The glass composition comprises a coefficient of thermal expansion which is greater than or equal to 75×10-7/°C averaged over a temperature range from 20°C to 300°C and a liquidus viscosity greater than or equal to 25 kPa•s (250 kPoise).

    [0041] While exemplary glass compositions have been described hereinabove with reference to specific compositional ranges for various constituent components (such as SiO2, Al2O3, B2O3, and the like) of each glass composition, it should be understood that each compositional range of each constituent component may include one or more narrower compositional ranges for that constituent component, as described above. Further, it should also be understood that these narrower ranges of the constituent components and/or the relationships between various constituent components may be incorporated in any of the embodiments of the glass compositions described herein in order to produce a glass having the desired properties.

    [0042] Referring now to FIG. 1, the glass compositions described herein may be used to form a glass article, such as the laminated glass article 100 schematically depicted in cross section in FIG. 1. The laminated glass article 100 generally comprises a glass core layer 102 and a pair of glass cladding layers 104a, 104b. The glass compositions described herein are particularly well suited for use as the glass core layer due to their relatively high coefficients of thermal expansion, as will be discussed in more detail herein.

    [0043] FIG. 1 illustrates the glass core layer 102 shown comprising a first surface 103a and a second surface 103b which is opposed to the first surface 103a. A first glass cladding layer 104a is fused to the first surface 103a of the glass core layer 102 and a second glass cladding layer 104b is fused to the second surface 103b of the glass core layer 102. The glass cladding layers 104a, 104b are fused to the glass core layer 102 without any additional materials, such as adhesives, coating layers or the like, disposed between the glass core layer 102 and the glass cladding layers 104a, 104b. Thus, a first surface of the glass core layer is directly adjacent the first glass cladding layer, and a second surface of the glass core layer is directly adjacent the second glass cladding layer. In some embodiments, the glass core layer 102 and the glass cladding layers 104a, 104b are formed via a fusion lamination process. Diffusive layers (not shown) may form between the glass core layer 102 and the glass cladding layer 104a, or between the glass core layer 102 and the glass cladding layer 104b, or both. In such case, the average cladding coefficient of thermal expansion of the first diffusive layer has a value between that of an average cladding coefficient of thermal expansion of the core and an average cladding coefficient of thermal expansion of the first clad layer, or the average cladding coefficient of thermal expansion of the second diffusive layer has a value between that of an average cladding coefficient of thermal expansion of the core and an average cladding coefficient of thermal expansion of the second clad layer.

    [0044] In the embodiments of the laminated glass article 100 described herein, the glass core layer 102 is formed from a first glass composition having an average core coefficient of thermal expansion CTEcore and the glass cladding layers 104a, 104b are formed from a second, different glass composition which has an average cladding coefficient of thermal expansion CTEclad. The CTEcore is greater than CTEclad which results in the glass cladding layers 104a, 104b being compressively stressed without being ion exchanged or thermally tempered.

    [0045] Specifically, the glass articles 100 described herein may be formed by a fusion lamination process such as the process described in U.S. Patent No. 4,214,886. Referring to FIG. 2 by way of example, a laminate fusion draw apparatus 200 for forming a laminated glass article includes an upper isopipe 202 which is positioned over a lower isopipe 204. The upper isopipe 202 includes a trough 210 into which a molten glass cladding composition 206 is fed from a melter (not shown). Similarly, the lower isopipe 204 includes a trough 212 into which a molten glass core composition 208 is fed from a melter (not shown). In the embodiments, described herein, the molten glass core composition 208 has an average coefficient of thermal expansion CTEcore which is greater than the average coefficient of thermal expansion CTEclad of the molten glass cladding composition 206.

    [0046] As the molten glass core composition 208 fills the trough 212, it overflows the trough 212 and flows over the outer forming surfaces 216, 218 of the lower isopipe 204. The outer forming surfaces 216, 218 of the lower isopipe 204 converge at a root 220. Accordingly, the molten glass core composition 208 flowing over the outer forming surfaces 216, 218 rejoins at the root 220 of the lower isopipe 204 thereby forming a glass core layer 102 of a laminated glass article.

    [0047] Simultaneously, the molten glass cladding compositions 206 overflows the trough 210 formed in the upper isopipe 202 and flows over outer forming surfaces 222, 224 of the upper isopipe 202. The molten glass cladding composition 206 is outwardly deflected by the upper isopipe 202 such that the molten glass cladding composition 206 flows around the lower isopipe 204 and contacts the molten glass core composition 208 flowing over the outer forming surfaces 216, 218 of the lower isopipe, fusing to the molten glass core composition and forming glass cladding layers 104a, 104b around the glass core layer 102.

    [0048] As noted hereinabove, the molten glass core composition 208 generally has an average coefficient of thermal expansion CTEcore which is greater than the average cladding coefficient of thermal expansion CTEclad of the molten glass cladding composition 206. Accordingly, as the glass core layer 102 and the glass cladding layers 104a, 104b cool, the difference in the coefficients of thermal expansion of the glass core layer 102 and the glass cladding layers 104a, 104b cause a compressive stresses to develop in the glass cladding layers 104a, 104b. The compressive stress increases the strength of the resulting laminated glass article without an ion-exchange treatment or thermal tempering treatment.

    [0049] Referring again to the laminated glass article 100 depicted in FIG. 1, the glass core layer 102 of the laminated glass article is formed from a glass composition with a relatively high average coefficient of thermal expansion, such as the glass compositions described herein which have coefficients of thermal expansion greater than or equal to 75×10-7/°C.

    [0050] For example, in one embodiment, the glass core layer is formed from a glass composition having a high CTE, such as the glass compositions described hereinabove which comprise from about 70 mol.% to about 80 mol.% SiO2; from about 0 mol.% to about 8 mol.% Al2O3; and from about 3 mol.% to about 10 mol.% B2O3 as glass network formers. The glass composition may also comprise from about 0 mol.% to about 2 mol.% Na2O; and from about 10 mol.% to about 15 mol.% K2O. The glass composition further comprises from about 5 mol.% to about 6 mol.% of alkaline earth oxide. The alkaline earth oxide in the compositions comprises SrO, BaO or combinations thereof. However, the glass composition is substantially free from MgO and TiO2.

    [0051] In another embodiment, the glass core layer may be formed from a glass composition with a high CTE which includes from about 73 mol.% to about 77 mol.% SiO2; from about 0 mol.% to about 3 mol.% Al2O3; and from about 4 mol.% to about 5 mol.% B2O3 as glass network formers. The glass composition further includes from about 0 mol.% to about 2 mol.% Na2O and from about 11.5 mol.% to about 12.5 mol.% K2O. The glass composition further comprises from about 5 mol.% to about 6 mol.% of alkaline earth oxide. The alkaline earth oxide in the compositions comprises SrO, BaO or combinations thereof. However, the glass composition is substantially free from MgO and TiO2.

    [0052] While specific glass compositions for use as the glass core layer 102 have been described herein, it should be understood that any of the glass compositions described herein may be used to form the glass core layer 102 of the laminated glass article 100.

    [0053] While the glass core layer 102 of the glass laminate structure has been described hereinabove as being formed from a glass composition having a relatively high average coefficient of thermal expansion, the glass cladding layers 104a, 104b of the glass article 100 are formed from glass compositions which have a lower average coefficient of thermal expansion to facilitate the development of compressive stress in the cladding layers upon cooling of the laminated glass article following fusion formation. For example, the glass cladding layers may be formed from a glass composition such as a composition described in co-pending US 20157037553 A1 entitled "Low CTE Alkali-Free BoroAluminosilcate Glass Compositions and Glass Articles Comprising the Same" assigned to Corning Incorporated, which have coefficients of thermal expansion less than or equal to 40×10-7/°C in a temperature range from 20°C to 300°C. For example, the glass cladding layers may be formed from a glass composition which comprises: from about 60 mol.% to about 66 mol.% SiO2; from about 7 mol.% to about 10 mol.% Al2O3; from about 14 mol.% to about 18 mol.% B2O3; and from about 9 mol.% to about 16 mol.% alkaline earth oxide, wherein the alkaline earth oxide comprises at least CaO and the CaO is present in the glass composition in a concentration from about 3 mol.% to about 12 mol% and the glass composition is substantially free from alkali metals and compounds containing alkali metals. However, it should be understood that other glass compositions may also be used to form the glass cladding layers 104a, 104b of the laminated glass article 100, so long as the coefficients of thermal expansion of the glass cladding layers 104a, 104b are less than the average coefficient of thermal expansion of the glass core layer 102.

    Examples



    [0054] The embodiments of the glass compositions described herein will be further clarified by the following examples.

    [0055] A plurality of exemplary glass compositions were prepared according to the batch compositions listed in Tables 1-3 below. Batches of the oxide constituent components were mixed, melted and formed into glass plates. The properties of the glass melt (i.e., liquidus temperature, annealing point, etc.) and the resultant glass article were measured and the results are reported in Tables 1-3.

    [0056] Referring to Tables 1-3, the composition and properties of inventive glass compositions (i.e., Examples A1-A3, A5-A10 and A12) and comparative glass compositions (i.e., Examples A4, A11 and C1-C13) are provided. As indicated in the Tables, Examples A1-A3, A5-A10 and A12 each exhibited a relatively high liquidus viscosity (greater than about 25 kPa•s (250 kPoise)), and a relatively high coefficient of thermal expansion (greater than or equal to about 75×10-7/°C) which makes the glass compositions well suited for use with fusion forming processes and, in particular, for use as glass core layers in fusion-formed laminated glass articles.

    [0057] Comparative Examples A4, A11 and C1-C13 were formed from non-inventive compositions and are presented herein solely for purposes of comparison. Comparative Examples C1 and C2 were utilized to explore low liquidus regions in the potassium-barium-silicate ternary space. Comparative Examples C4-C6, C9, and C11 contained high concentrations of K2O which decreased the liquidus viscosity of the compositions to less than 25 kPa•s (250 kPoise). Comparative Examples C7 and C8 included high concentrations of B2O3 which also had the effect of decreasing the liquidus viscosity of the composition to less than 25 kPa•s (250 kPoise). Comparative Example C10 included high concentrations of Na2O which also had the effect of decreasing the liquidus viscosity of the composition. Comparative Examples 12 and 13 each had relatively low concentrations of SiO2 and high concentrations of K2O, which, in conjunction with one another, significantly depressed the liquidus viscosity of the glass composition.
    Table 1: Exemplary Glass Compositions
    Batched (mol %)C1C2A1A2A3C3C4C5C6A4
    SiO2 79.38 74.11 76.11 76.11 76.11 75.11 72.11 72.11 72.11 71.11
    TiO2 0 0 0 0 0 1 0 0 0 0
    Al2O3 0 0 0 0 0 0 0 0 0 0
    B2O3 0 5.27 5.27 5.27 5.27 5.27 7.27 7.27 7.27 9.27
    Na2O 0 0 0 0 1 0 0 0 0 0
    K2O 15.25 15.25 13.25 13.25 12.25 13.25 15.25 15.25 15.25 14.25
    CaO 0 0 0 0 0 0 0 0 0 0
    SrO 0 0 0 2.63 0 0 0 2.63 5.27 2.63
    BaO 5.27 5.27 5.27 2.64 5.27 5.27 5.27 2.64 0 2.64
    SnO2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
    Total 100 100 100 100 100 100 100 100 100 100
    Anneal Pt (C): 494 563 585 599 572 591 583 593 607 609
    Strain Pt (C): 449 515 536 551 522 542 538 548 563 566
    Soft Pt (C): 694.1 749.3 773.7 782.2 762.2 774 756.5 762.2 776 772.5
    Log[Eta_inf (Pa-s)]: -2.3 -1.8 -1.8 -1.8 -1.8 -1.8 -1.4 -1.5 -1.5 -1.4
    Tg (C): 487.7 575.1 593.1 599.7 581.1 600.4 604.8 608.2 620.0 628.1
    Fragility: 29.1 38.2 38.6 37.5 37.3 39.0 41.7 42.5 43.0 45.9
    Density (g/cm^3): 2.578 2.622 2.615 2.574 2.61 2.626 2.638 2.597 2.553 2.605
    CTE (x10^-7/C): 103 93.6 86.7 83.7 84.8 85.2 91.1 91.1 89.1 85.6
    Liquidus Temp (C): 835 895 885 890 880 1040 970 980 970 990
    Primary Devit Phase: Cristobalite Cristobalite Cristobalite Cristobalite Cristobalite Rutile Quartz Quartz Quartz Quartz
    Liquidus Visc (Pa•s) ((Poise)): 6.34E+04 (6.34E+0 5) 2.39E+04 (2.39E+0 5) 5.75E+04 (5.75E+0 5) 8.78E+04 (8.78E+0 5) 5.98E+04 (5.98E+0 5) 1.56E+03 (1.56E+0 41 4.91E+03 (4.91E+0 41 3.17E+03 (3.17E+0 41 5.47E+03 (5.47E+0 41 2.35E+03 (2.35E+0 41
    Poisson's Ratio: 0.224 0.223 0.221 0.223 0.222 0.212        
    Shear Modulus (GPa) (Mpsi): 22.787 (3.305) 25.331 (3.674) 26.448 (3.836) 27.172 (3.9411 27.221 (3.948) 27.495 (3.878)        
    Young's Modulus (GPa) (Mpsi): 55.806 (8.094) 61.956 (8.986) 64.597 (9.369) 66.452 (9.638) 66.528 (9.649) 64.8 (9.4)        
    Refractive Index 1.51006 1.518255 1.519175 1.514445 1.518175 1.52227        
    Table 2: Exemplary Glass Compositions
    Batched (mol %)C7C8A5A6A7A8C9A10
    SiO2 70.11 71.11 74.11 72.11 70.11 72.11 72.11 72.11
    TiO2 0 0 0 0 0 0 0 0
    Al2O3 0 0 2 4 6 2 2 4
    B2O3 11.27 11.27 5.27 5.27 5.27 7.27 5.27 5.27
    Na2O 0 0 0 0 0 0 0 0
    K2O 13.25 12.25 13.25 13.25 13.25 13.25 15.25 13.25
    CaO 0 0 0 0 0 0 0 1.75
    SrO 2.63 5.27 2.63 2.63 2.63 2.63 2.63 1.76
    BaO 2.64 0 2.64 2.64 2.64 2.64 2.64 1.76
    SnO2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
    Total 100 100 100 100 100 100 100 100
    Anneal Pt (C): 623 633 616 625 631 626 599 633
    Strain Pt (C): 582 592 569 579 586 581 554 587
    Soft Pt (C): 781.9 793.1 300 813 826 803 774 823
    Log[Eta_inf (Pa-s)]: -1.4 -1.4 -1.6 -1.6 -1.9 -1.2 -1.6 -1.6
    Tg(C): 638.8 644.7 616.0 608.0 601.0 635.3 594.3 624.0
    Fragility: 46.7 46.0 38.5 36.5 33.0 42.1 38.1 36.7
    Density (g/cm^3): 2.61 2.556 2.569 2.565 2.563 2.577 2.581 2.526
    CTE (x10^- 79.7 77.4 82.7 82.6 82.4 80.3 89.8 80.9
    7/C):                
    Liquidus Temp (C): 1000 1000 880 920 985 920 920 895
    Primary Devit Phase: Quartz Quartz Quartz Quartz Quartz Quartz Quartz Quartz
    Liquidus Visc (kPa•s) ((Poise)): 2.22E+03 (2.22E+0 4) 3.14E+03 (3.14E+0 4) 1.99E+05 (1.99E+0 6) 7.34E+04 (7.34E+0 5) 2.75E+04 (2.75E+0 5) 5.67E+04 (5.67E+0 5) 2.75E+04 (2.75E+0 5) 2.81E+05 (2.81E+0 6)
    Poisson's Ratio:                
    Shear Modulus (GPa) (Mpsi):                
    Young's Modulus (GPa) (Mpsi):                
    Refractive Index                
    Table 3: Exemplary Glass Compositions
    Batched (mol %)A11A12C10C11C12C13
    SiO2 74.11 74.11 74.11 70.11 66.11 62.11
    Al2O3 2 2 2 3 4 5
    B2O3 5.26 5.26 5.26 6.26 7.26 8.26
    Na2O 0 0 13.25 0 0 0
    K2O 13.25 13.25 0 15.25 17.25 19.25
    CaO 2.64 0 2.64 2.64 2.64 2.64
    SrO 2.64 5.28 2.64 2.64 2.64 2.64
    SnO2 0.1 0.1 0.1 0.1 0.1 0.1
    Total 100 100 100 100 100 100
    AMPL Anneal (C): 625 625 625 625 625 625
    Anneal Pt (C): 627 625 563 621 608 591
    Strain Pt (C): 583 580 524 580 567 552
    Soft Pt (C): 811.5 809.3 727.8 797.7 784 762.5
    Log[Eta_inf (Pa-s)]: -1.6 -1.6 -1.1 -1.1 -0.9 -1.2
    Tg (C): 621.0 617.0 569.5 625.1 620.0 597.1
    Fragility: 38.7 38.6 40.9 43.0 44.4 42.3
    Density (g/cm^3): 2.494 2.532 2.512 2.506 2.515 2.522
    CTE (x10^-7/C): 82.7 82.9 76.7 88.5 93.9 98
    Liquidus Temp (C): 930 900 990 955 970 1010
    Primary Devit Phase: Quartz Quartz Tridymite Quartz Quartz Quartz
    Liquidus Vise (kPa•s) (kPoise): 50.04 (500.42) 104.00 (1053.98) 1.56 (15.65) 11.98 (119.82) 5.61 (56.08) 1.60 (16.03)
    Poisson's Ratio: 0.21 0.215 0.214 0.224 0.223 0.234
    Shear Modulus (GPa) (Mpsi): 24.041 (4.067) 27.65 (4.01) 31.461 (4.563) 27.689 (4.016) 27.110 (3.932) 26.510 (3.845)
    Young's Modulus (GPa) (Mpsi): 67.879 (9.845) 67.196 (9.746) 76.048 (11.082) 67.810 (9.835) 66.314 (9.618) 65.424 (9.489)
    Refractive Index            


    [0058] It should now be understood that the glass compositions described herein have a relatively high average coefficient of thermal expansion. As such, the glass compositions described herein are particularly well suited for use in conjunction with glass compositions having relatively lower coefficients of thermal expansion to form compressively stressed laminated glass articles by the fusion laminate process. These glass articles may be employed in a variety of consumer electronic devices including, without limitation, mobile telephones, personal music players, tablet computers, LCD and LED displays, automated teller machines and the like.

    [0059] It should also be understood that the properties of the glass compositions described herein (e.g., the liquidus viscosity, the liquidus temperature, and the like) make the glass compositions well suited for use with fusion forming processes, such as the fusion down draw process or the fusion lamination process.

    [0060] Moreover, the mobility of alkali ions in the glass compositions is significantly reduced due to the low concentration of Al2O3 as well as the higher concentration of B2O3 in the glass compositions. Accordingly, the glass compositions described herein may be particularly well suited for use as backplane substrates of LCD, LED and OLED displays where the presence of highly mobile alkali ions in the backplane substrate may damage the thin film transistors on the substrate. The glass compositions described herein may be used to form the entire backplane substrate or, alternatively, may be used as a glass core layer enveloped by alkali-free glass cladding layers in a laminated glass substrate.

    [0061] Further, while specific reference has been made herein to the use of the glass compositions as glass core layers in a laminated glass article, it should be understood that the glass compositions may also be used independently (i.e., not as part of a laminated structure) to form glass articles such as cover glasses for electronic devices and other, similar glass articles.


    Claims

    1. A glass composition comprising:

    from 70 mol.% to 80 mol.% SiO2;

    from 0 mol.% to 8 mol.% Al2O3;

    from 3 mol.% to 10 mol.% B2O3;

    from 0 mol.% to 2 mol.% Na2O;

    from 10 mol.% to 15 mol.% K2O; and

    from 5 mol.% to 6 mol.% of alkaline earth oxide, wherein:

    the alkaline earth oxide is SrO, BaO or a combination thereof;

    the glass composition comprises a coefficient of thermal expansion which is greater than or equal to 75x10-7/°C averaged over a temperature range from 20°C to 300°C;

    the glass composition comprises a liquidus viscosity greater than or equal to 25 kPa•s (250 kPoise);

    the glass composition is substantially free from TiO2; and

    the glass composition is substantially free from MgO.


     
    2. A glass article comprising:
    a glass core layer disposed between a first glass cladding layer and a second glass cladding layer, wherein the glass core layer is formed from a glass composition comprising:

    from 70 mol.% to 80 mol.% SiO2;

    from 0 mol.% to 8 mol.% Al2O3;

    from 3 mol.% to 10 mol.% B2O3;

    from 0 mol.% to 2 mol.% Na2O;

    from 10 mol.% to 15 mol.% K2O; and

    from 5 mol.% to 6 mol.% of alkaline earth oxide, wherein:

    the alkaline earth oxide is SrO, BaO or a combination thereof;

    the glass composition comprises a coefficient of thermal expansionwhich is greater than or equal to 75×10-7/°C averaged over a temperature range from 20°C to 300°C:

    the glass composition is substantially free from TiO2; and

    the glass composition is substantially free from MgO.


     
    3. The glass composition of claim 1 or the glass article of claim 2, wherein the alkaline earth oxide comprises:

    greater than or equal to 1.5 mol.% SrO; and

    from 0 mol.% to 2 mol.% BaO.


     
    4. The glass composition of claim 1 or claim 3 or the glass article of claim 2 or 3, wherein the glass composition comprises:

    from 73 mol.% to 77 mol.% SiO2;

    from 0 mol.% to 3 mol.% Al2O3;

    from 4 mol.% to 5 mol.% B2O3;

    from 0 mol.% to 2 mol.% Na2O; and

    from 11.5 mol.% to 12.5 mol.% K2O.


     
    5. The glass composition of any of claims 1 and 3 to 4 or the glass article of any of claims 2 to 4, wherein a concentration of Na2O in the glass composition is greater than or equal to about 0.1 mol.%.
     
    6. The glass composition of any of claims 1 and 3 to 5 or the glass article of any of claims 2 to 5, wherein a concentration of K2O (mol.%) in the glass composition is greater than a sum of a concentration of B2O3 (mol.%) in the glass composition and a concentration of Al2O3 (mol.%) in the glass composition.
     
    7. The glass composition of any of claims 1 and 4 to 6 or the glass article of any of claims 2 to 6, wherein the glass composition is substantially free of BaO.
     
    8. The glass composition of any of claims 1 and 4 to 7 or the glass article of any of claims 2 to 7, wherein the glass composition further comprises at least one of SnO2, As2O3, and Sb2O3 as a fining agent.
     
    9. The glass composition of any of claims 1 and 4 to 8 or the glass article of any of claims 2 to 8, wherein the glass composition comprises a coefficient of thermal expansion which is greater than or equal to 85×10-7/°C averaged over a temperature range from 20°C to 300°C or greater than or equal to 95×10-7/°C averaged over a temperature range from 20°C to 300°C.
     
    10. The glass composition of any of claims 1 and 4 to 9 or the glass article of any of claims 2 to 9, wherein the glass composition comprises a liquidus viscosity greater than or equal to 35 kPa•s (350 kPoise).
     
    11. The glass composition of any of claims 1 and 4 to 10 or the glass article of any of claims 2 to 10, wherein the glass composition is substantially free from heavy metals.
     
    12. The glass article of any of claims 2 to 11, wherein:

    the glass core layer has an average core coefficient of thermal expansion CTEcore; and

    the first glass cladding layer and the second glass cladding layer have an average cladding coefficient of thermal expansion CTEclad which is less than the average core coefficient of thermal expansion CTEcore.


     
    13. The glass article of any one of any of claims 2 to 12, wherein a first surface of the glass core layer is directly adjacent the first glass cladding layer, and wherein a second surface of the glass core layer is directly adjacent the second glass cladding layer.
     
    14. The glass article of any one of claims 2 to 12, wherein a diffusive layer is disposed between at least one of the first glass cladding layer or the second glass cladding layer and the glass core layer, and the average coefficient of thermal expansion of the diffusive layer has a value between that of an average core coefficient of thermal expansion of the glass core layer and an average cladding coefficient of thermal expansion of the at least one of the first glass cladding layer or the second glass cladding layer.
     
    15. A use of the glass composition of any one of claims 1 and 4 to 11, or the glass article of any one of claims 2 to 14, for cover glass or glass backplane applications in consumer or commercial electronic devices including LCD and LED displays, computer monitors, automated teller machines (ATMs), for touch screen or touch sensor applications, for portable electronic devices including mobile telephones, personal media players, and tablet computers, for photovoltaic applications, for architectural glass applications, for automotive or vehicular glass applications, or for commercial or household appliance applications.
     


    Ansprüche

    1. Glaszusammensetzung, umfassend:

    70 Mol-% bis 80 Mol-% SiO2;

    0 Mol-% bis 8 Mol-% Al2O3;

    3 Mol-% bis 10 Mol-% B2O3;

    0 Mol-% bis 2 Mol-% Na2O;

    10 Mol-% bis 15 Mol-% K2O; und

    5 Mol-% bis 6 Mol-% Erdalkalioxid, wobei:

    das Erdalkalioxid SrO, BaO oder eine Kombination davon ist;

    die Glaszusammensetzung einen Wärmeausdehnungskoeffizienten umfasst, der größer als oder gleich 75×10-7/°C gemittelt über einen Temperaturbereich von 20 °C bis 300 °C ist;

    die Glaszusammensetzung eine Liquidusviskosität größer als oder gleich 25 kPa•s (250 kPoise) umfasst;

    die Glaszusammensetzung im Wesentlichen frei von TiO2 ist; und

    die Glaszusammensetzung im Wesentlichen frei von MgO ist.


     
    2. Glasartikel, umfassend:
    eine Glaskernschicht, die zwischen einer ersten Glasmantelschicht und einer zweiten Glasmantelschicht angeordnet ist, wobei die Glaskernschicht aus einer Glaszusammensetzung gebildet ist, umfassend:

    70 Mol-% bis 80 Mol-% SiO2;

    0 Mol-% bis 8 Mol-% Al2O3;

    3 Mol-% bis 10 Mol-% B2O3;

    0 Mol-% bis 2 Mol-% Na2O;

    10 Mol-% bis 15 Mol-% K2O; und

    5 Mol-% bis 6 Mol-% Erdalkalioxid, wobei:

    das Erdalkalioxid SrO, BaO oder eine Kombination davon ist;

    die Glaszusammensetzung einen Wärmeausdehnungskoeffizienten umfasst, der größer als oder gleich 75×10-7/°C gemittelt über einen Temperaturbereich von 20 °C bis 300 °C ist;

    die Glaszusammensetzung im Wesentlichen frei von TiO2 ist; und

    die Glaszusammensetzung im Wesentlichen frei von MgO ist.


     
    3. Glaszusammensetzung nach Anspruch 1 oder Glasartikel nach Anspruch 2, wobei das Erdalkalioxid Folgendes umfasst:

    größer als oder gleich 1,5 Mol-% SrO; und

    0 Mol-% bis 2 Mol-% BaO.


     
    4. Glaszusammensetzung nach Anspruch 1 oder Anspruch 3 oder Glasartikel nach Anspruch 2 oder 3,
    wobei die Glaszusammensetzung Folgendes umfasst:

    73 Mol-% bis 77 Mol-% SiO2;

    0 Mol-% bis 3 Mol-% Al2O3;

    4 Mol-% bis 5 Mol-% B2O3;

    0 Mol-% bis 2 Mol-% Na2O; und

    11,5 Mol-% bis 12,5 Mol-% K2O.


     
    5. Glaszusammensetzung nach einem der Ansprüche 1 und 3 bis 4 oder Glasartikel nach einem der Ansprüche 2 bis 4, wobei eine Konzentration von Na2O in der Glaszusammensetzung größer als oder gleich etwa 0,1 Mol-% ist.
     
    6. Glaszusammensetzung nach einem der Ansprüche 1 und 3 bis 5 oder Glasartikel nach einem der Ansprüche 2 bis 5, wobei eine Konzentration von K2O (Mol-%) in der Glaszusammensetzung größer als eine Summe einer Konzentration von B2O3 (Mol-%) in der Glaszusammensetzung und einer Konzentration von Al2O3 (Mol-%) in der Glaszusammensetzung ist.
     
    7. Glaszusammensetzung nach einem der Ansprüche 1 und 4 bis 6 oder Glasartikel nach einem der Ansprüche 2 bis 6, wobei die Glaszusammensetzung im Wesentlichen frei von BaO ist.
     
    8. Glaszusammensetzung nach einem der Ansprüche 1 und 4 bis 7 oder Glasartikel nach einem der Ansprüche 2 bis 7, wobei die Glaszusammensetzung ferner zumindest eines von SnO2, As2O3 und Sb2O3 als Läutermittel umfasst.
     
    9. Glaszusammensetzung nach einem der Ansprüche 1 und 4 bis 8 oder Glasartikel nach einem der Ansprüche 2 bis 8, wobei die Glaszusammensetzung einen Wärmeausdehnungskoeffizienten umfasst, der größer als oder gleich 85×10-7/°C gemittelt über einen Temperaturbereich von 20 °C bis 300 °C oder größer als oder gleich 95×10-7/°C gemittelt über einen Temperaturbereich von 20 °C bis 300 °C ist.
     
    10. Glaszusammensetzung nach einem der Ansprüche 1 und 4 bis 9 oder Glasartikel nach einem der Ansprüche 2 bis 9, wobei die Glaszusammensetzung eine Liquidusviskosität größer als oder gleich 35 kPa•s (350 kPoise) umfasst.
     
    11. Glaszusammensetzung nach einem der Ansprüche 1 und 4 bis 10 oder Glasartikel nach einem der Ansprüche 2 bis 10, wobei die Glaszusammensetzung im Wesentlichen frei von Schwermetallen ist.
     
    12. Glasartikel nach einem der Ansprüche 2 bis 11, wobei:

    die Glaskernschicht einen durchschnittlichen Kernwärmeausdehnungskoeffizienten CTEcore aufweist; und

    die erste Glasmantelschicht und die zweite Glasmantelschicht einen durchschnittlichen Mantelwärmeausdehnungskoeffizienten CTEclad aufweisen, der weniger als der durchschnittliche Kernwärmeausdehnungskoeffizient CTEcore ist.


     
    13. Glasartikel nach einem der Ansprüche 2 bis 12, wobei eine erste Oberfläche der Glaskernschicht direkt benachbart zu der ersten Glasmantelschicht ist und wobei eine zweite Oberfläche der Glaskernschicht direkt benachbart zu der zweiten Glasmantelschicht ist.
     
    14. Glasartikel nach einem der Ansprüche 2 bis 12, wobei eine Diffusionsschicht zwischen zumindest einer von der ersten Glasmantelschicht oder der zweiten Glasmantelschicht und der Glaskernschicht angeordnet ist und der durchschnittliche Wärmeausdehnungskoeffizient der Diffusionsschicht einen Wert zwischen demjenigen eines durchschnittlichen Kernwärmeausdehnungskoeffizienten der Glaskernschicht und eines durchschnittlichen Mantelwärmeausdehnungskoeffizienten von der zumindest einen von der ersten Glasmantelschicht oder der zweiten Glasmantelschicht aufweist.
     
    15. Verwendung der Glaszusammensetzung nach einem der Ansprüche 1 und 4 bis 11 oder des Glasartikels nach einem der Ansprüche 2 bis 14 für Deckglas- oder Glasrückwandanwendungen in Verbraucher- oder kommerziellen elektronischen Vorrichtungen, beinhaltend LCD- und LED-Anzeigen, Computermonitore, Geldausgabeautomaten (ATMs), für Berührungsbildschirm- oder Berührungssensoranwendungen, für tragbare elektronische Vorrichtungen, beinhaltend Mobiltelefone, persönliche Mediaplayer und Tablet-Computer, für Photovoltaikanwendungen, für Architekturglasanwendungen, für Automobil- oder Fahrzeugglasanwendungen oder für kommerzielle oder Haushaltsgeräteanwendungen.
     


    Revendications

    1. Composition de verre comprenant :

    de 70 mol.% à 80 mol.% SiO2;

    de 0 mol.% à 8 mol.% Al2O3 ;

    de 3 mol.% à 10 mol.% B2O3 ;

    de 0 mol.% à 2 mol.% Na2O ;

    de 10 mol.% à 15 mol.% K2O ; et

    de 5 mol.% à 6 mol.% d'oxyde alcalinoterreux, où :

    l'oxyde alcalinoterreux est SrO, BaO ou une combinaison de ceux-ci ;

    la composition de verre comprend un coefficient de dilatation thermique qui est supérieur ou égal à 75×10-7/°C, valeur moyenne obtenue dans une gamme de température de 20°C à 300°C ;

    la composition de verre a une viscosité en phase liquidus supérieure ou égale à 25 kPa•s (250 kPoise) ;

    la composition de verre est essentiellement exempte de TiO2; et

    la composition de verre est essentiellement exempte de MgO.


     
    2. Article de verre comprenant :
    une couche centrale de verre disposée entre une première couche de revêtement en verre et une deuxième couche de revêtement en verre, dans lequel la couche centrale de verre est formée d'une composition de verre comprenant :

    de 70 mol.% à 80 mol.% SiO2;

    de 0 mol.% à 8 mol.% Al2O3 ;

    de 3 mol.% à 10 mol.% B2O3 ;

    de 0 mol.% à 2 mol.% Na2O ;

    de 10 mol.% à 15 mol.% K2O ; et

    de 5 mol.% à 6 mol.% d'oxyde alcalinoterreux, où :

    l'oxyde alcalinoterreux est SrO, BaO ou une combinaison de ceux-ci ;

    la composition de verre a un coefficient de dilatation thermique qui est supérieur ou égal à 75×10-7/°C, valeur moyenne obtenue dans une gamme de température de 20°C à 300°C ;

    la composition de verre est essentiellement exempte de TiO2; et

    la composition de verre est essentiellement exempte de MgO.


     
    3. Composition de verre selon la revendication 1 ou article de verre selon la revendication 2, où l'oxyde alcalinoterreux comprend :

    au moins 1,5 mol.% SrO ; et

    de 0 mol.% à 2 mol.% BaO.


     
    4. Composition de verre selon la revendication 1 ou la revendication 3, ou article de verre selon la revendication 2 ou 3, où la composition de verre comprend :

    de 73 mol.% à 77 mol.% SiO2;

    de 0 mol.% à 3 mol.% Al2O3 ;

    de 4 mol.% à 5 mol.% B2O3 ;

    de 0 mol.% à 2 mol.% Na2O ; et

    de 11,5 mol.% à 12,5 mol.% K2O.


     
    5. Composition de verre selon l'une quelconque des revendications 1 et 3 à 4, ou article de verre selon l'une quelconque des revendications 2 à 4, où une concentration de Na2O dans la composition de verre est supérieure ou égale à environ 0,1 mol.%.
     
    6. Composition de verre selon l'une quelconque des revendications 1 et 3 à 5, ou article de verre selon l'une quelconque des revendications 2 à 5, où une concentration de K2O (mol.%) dans la composition de verre est supérieure à une somme d'une concentration de B2O3 (mol.%) dans la composition de verre et d'une concentration de Al2O3 (mol.%) dans la composition de verre.
     
    7. Composition de verre selon l'une quelconque des revendications 1 et 4 à 6, ou article de verre selon l'une quelconque des revendications 2 à 6, où la composition de verre est essentiellement exempte de BaO.
     
    8. Composition de verre selon l'une quelconque des revendications 1 et 4 à 7, ou article de verre selon l'une quelconque des revendications 2 à 7, où la composition de verre comprend en outre au moins l'un de SnO2, As2O3 et Sb2O3 comme agent d'affinage.
     
    9. Composition de verre selon l'une quelconque des revendications 1 et 4 à 8 ou article de verre selon l'une quelconque des revendications 2 à 8, où la composition de verre a un coefficient de dilatation thermique qui est supérieur ou égal à 85×10-7/°C, valeur moyenne obtenue dans une gamme de température de 20°C à 300°C, ou supérieur ou égal à 95×10-7/°C, valeur moyenne obtenue dans une gamme de température de 20°C à 300°C.
     
    10. Composition de verre selon l'une quelconque des revendications 1 et 4 à 9, ou article de verre selon l'une quelconque des revendications 2 à 9, où la composition de verre a une viscosité en phase liquidus supérieure ou égale à 35 kPa•s (350 kPoise).
     
    11. Composition de verre selon l'une quelconque des revendications 1 et 4 à 10, ou article de verre selon l'une quelconque des revendications 2 à 10, où la composition de verre est essentiellement exempte de métaux lourds.
     
    12. Article de verre selon l'une quelconque des revendications 2 à 11, dans lequel :

    la couche centrale de verre a un coefficient de dilatation thermique central moyen CTEcore; et

    la première couche de revêtement en verre et la deuxième couche de revêtement en verre ont un coefficient de dilatation thermique moyen de revêtement CTEclad qui est inférieur au coefficient de dilatation thermique central moyen CTEcore.


     
    13. Article de verre selon l'une quelconque des revendications 2 à 12, dans lequel une première surface de la couche centrale de verre est directement adjacente à la première couche de revêtement en verre, et dans lequel une deuxième surface de la couche centrale de verre est directement adjacente à la deuxième couche de revêtement en verre.
     
    14. Article de verre selon l'une quelconque des revendications 2 à 12, dans lequel une couche diffusive est disposée entre au moins l'une de la première couche de revêtement en verre ou de la deuxième couche de revêtement en verre et la couche centrale de verre, et le coefficient de dilatation thermique moyen de la couche diffusive a une valeur entre celle du coefficient de dilatation thermique central moyen de la couche centrale de verre et d'un coefficient de dilatation thermique moyen de revêtement de l'au moins une première couche de revêtement en verre ou deuxième couche de revêtement en verre.
     
    15. Utilisation de la composition de verre selon l'une quelconque des revendications 1 et 4 à 11, ou de l'article de verre selon l'une quelconque des revendications 2 à 14 pour applications comme cache de verre ou panneau arrière de verre dans des dispositifs électroniques de consommateurs ou industriels, tels que des affichages LCD et LED, écrans d'ordinateurs, guichets automatiques bancaires (ATM), pour écrans tactiles ou capteurs tactiles, pour appareils électroniques portables tels que : téléphones portables, lecteurs de média personnels et tablettes électroniques, pour applications photovoltaïques, pour verre architectural, pour verre d'automobiles ou de véhicules, ou pour appareils industriels ou domestiques.
     




    Drawing








    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description