Laminated glass article with ceramic phase and method of making the article

Abstract

A method for forming a laminated glass article with a ceramic phase, such as a beta-spodumene phase, located at least at the junctures between a glass core and directly adjacent glass clad layers, and in some embodiments located throughout the laminated glass article. In some embodiments, a method is disclosed herein for forming a beta-spodumene glass-ceramic sheet, or a laminated glass article having a ceramic phase, or a laminated glass article having a beta-spodumene glass-ceramic, is disclosed.

Claims

1. A method for forming a laminated glass article having a ceramic phase, the method comprising: forming, via fusion draw, a laminate glass sheet having cladding layers formed from a first glass composition rich in a first alkali and a core layer formed from a second glass composition rich in a second alkali, wherein the first alkali is lithium and the second alkali is sodium and the laminate glass sheet comprises diffusive glass layers disposed between the cladding layers and the core layer; heat treating the laminate glass sheet to exchange ions of the first and second alkalis between the core and cladding layers; and heat treating the laminate glass sheet a second time to nucleate and grow a ceramic phase in the laminate glass sheet after the heat treating the laminate glass sheet to exchange ions, wherein the ceramic phase is located only in the diffusive glass layers at junctures between the cladding layers and the core layer.

2. The method of claim 1 wherein the laminate glass sheet is heated sufficient to compressively stress at least one of the cladding layers.

3. The method of claim 1 wherein the ceramic phase is a beta-spodumene phase.

4. The method of claim 1 further comprising cutting the laminate glass sheet subsequent to the forming step and prior to the heat treating the laminate glass sheet to nucleate and grow a ceramic phase step.

5. A method for forming a laminated glass article having a ceramic phase, the method comprising: forming, via fusion draw, a laminate glass sheet having cladding layers formed from a first glass composition rich in a first alkali and a core layer formed from a second glass composition rich in a second alkali, wherein the first alkali is lithium and the second alkali is sodium, the cladding layers have an average cladding coefficient of thermal expansion CTE.sub.clad, the core layer has an average core coefficient of thermal expansion CTE.sub.core, CTE.sub.clad is less than CTE.sub.core, and a differential between CTE.sub.clad and CTE.sub.core is less than 510.sup.7/ C.; heat treating the laminate glass sheet to exchange ions of the first and second alkalis between the core and cladding layers; and heat treating the laminate glass sheet a second time to nucleate and grow a ceramic phase in the laminate glass sheet after the heat treating the laminate glass sheet to exchange ions.

6. The method of claim 5 wherein the laminate glass sheet is heated sufficient to compressively stress at least one of the cladding layers.

7. The method of claim 5 wherein the ceramic phase is a beta-spodumene phase.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

DETAILED DESCRIPTION

(3) Reference will now be made in detail to embodiments of glass-ceramic compositions disclosed herein and 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.

(4) The term liquidus viscosity, as used herein, refers to the shear viscosity of the glass composition at its liquidus temperature.

(5) The term liquidus temperatures, as used herein, refers to the highest temperature at which devitrification occurs in the glass composition

(6) 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.

(7) The term substantially free, when used to described the absence of a particular oxide component in a glass composition, means that the component is present in the glass composition as a contaminant in a trace amount of less than 1 mol. %.

(8) In the embodiments of the glass compositions described herein, the concentration of constituent components (e.g., SiO.sub.2, Al.sub.2O.sub.3, Na.sub.2O and the like) are given in mole percent (mol. %) on an oxide basis, unless otherwise specified.

(9) The glass compositions described herein may optionally include one or more fining agents. The fining agents may include, for example, SnO.sub.2, As.sub.2O.sub.3, Sb.sub.2O.sub.3 and 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 SnO.sub.2. In these embodiments, SnO.sub.2 may be present in the glass composition in a concentration which is greater than about 0 mol. % and less than or equal to about 0.2 mol. % or even less than or equal to about 0.15 mol. %.

(10) In some embodiments described herein, the glass compositions may further comprise trace amounts of other oxides.

(11) 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.

(12) The glass compositions disclosed herein have a liquidus viscosity which renders them suitable for use in a fusion draw process and, in particular, for use as a glass cladding composition or a glass core composition in a fusion laminate process.

(13) Referring now to FIG. 1, the glass compositions described herein may be used to form an 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 claddings layers, as will be discussed in more detail herein.

(14) 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 directly to the first surface 103a of the glass core layer 102 and a second glass cladding layer 104b is fused directly to the second surface 103b of the glass core layer 102. Post-ceramming, the glass cladding layers 104a, 104b are fused to the glass core layer 102 without any additional materials, such as adhesives, polymer layers, coating layers or the like, being 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.

(15) In at least some embodiments of the laminated glass article 100 described herein, the glass cladding layers 104a, 104b are formed from a first glass-ceramic composition having an average cladding coefficient of thermal expansion CTE.sub.clad and the glass core layer 102 is formed from a second, different glass composition which has an average coefficient of thermal expansion CTE.sub.core.

(16) Specifically, the glass articles 100 described herein may be formed by a fusion lamination process such as the process described in U.S. Pat. No. 4,214,886, which is incorporated herein by reference. 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 appropriately high liquidus viscosity to be run over the lower isopipe 204.

(17) 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 structure.

(18) Simultaneously, the molten glass-ceramic 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-ceramic cladding composition 206 has a lower liquidus viscosity requirement to be run on the upper isopipe 202, and will have a CTE either equal to or less than the glass core composition 208 (for example, within about 510.sup.7/ C.) when present as a glass. The molten glass-ceramic 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 pre-cerammed glass cladding layers 104a, 104b around the glass core layer 102.

(19) In some embodiments, in the laminated sheet so formed, the clad thickness will also be significantly thinner than the core glass thickness so that the clad goes into compression and the core into tension. But as the CTE difference is low, the magnitude of the tensile stress in the core will be very low (e.g on the order of 10 MPa or lower) which will allow for the production of a laminated sheet that will be relatively easy to cut off the draw due to its low levels of core tension. Sheets can thus be cut from the laminate structure that is drawn from the fusion draw apparatus, and after the sheets are cut, the cut product can then be subjected to a suitable heat treatment(s).

(20) The laminated glass articles disclosed herein 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.

(21) In some embodiments, the laminated glass article may comprises one or more layers which are opaque, transparent or translucent, such as a clad derived from a glass composition wherein the clad layer is opaque, transparent or translucent after heat treatment(s). Furthermore, the use of glass in sheet form can be utilized.

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