LOW STORED TENSILE ENERGY DICING GLASS AND PREFERENTIAL CRACK FRAGMENTATION

Abstract

A glass substrate comprises: a first position, wherein a tensile stress of the glass substrate is insufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate; and a second position, wherein the glass substrate is bent relative to the first position, and wherein the tensile stress of the glass substrate is sufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate. The glass substrate can include a first surface and a second surface. In the first position, the first surface and the second surface of the glass substrate can be planar. In the second position, the first surface and the second surface of the glass substrate can be planar. The small pieces can be generally cubic. In the second position, the glass substrate can be bent uniaxially along a bend axis of the glass substrate.

Claims

1. A glass substrate comprising: a first position, wherein a tensile stress of the glass substrate is insufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate; and a second position, wherein the glass substrate is bent relative to the first position, and wherein the tensile stress of the glass substrate is sufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate.

2. The glass substrate of claim 1, a first surface and a second surface; wherein, in the first position, the first surface and the second surface of the glass substrate are planar.

3. The glass substrate of claim 1, a first surface and a second surface; wherein, in the second position, the first surface and the second surface of the glass substrate are planar.

4. The glass substrate of claim 1, wherein, the small pieces are generally cubic shaped.

5. The glass substrate of claim 1, in the second position, the glass substrate is bent uniaxially along a bend axis of the glass substrate.

6. The glass substrate of claim 1, in the second position, the glass substrate is bent biaxially along two bend axes of the glass substrate.

7. The glass substrate of claim 1, wherein, in the first position, the glass substrate is flatter than the glass substrate is in the second position.

8. The glass substrate of claim 1, wherein, in the second position, the glass substrate is flatter than the glass substrate is in the first position.

9. The glass substrate of claim 1, further comprising: a thickness of 2 mm or less.

10. (canceled)

11. (canceled)

12. (canceled)

13. (canceled)

14. A method of reducing the size of the pieces that a glass substrate fragments into upon fracture of the glass substrate comprising: providing a glass substrate that fragments into pieces having a first size upon fracture of the glass substrate; and bending the glass substrate to a second position and maintaining the glass substrate in the second position, such that when the glass substrate fragments into pieces having a second size upon fracture of the glass substrate; wherein, the pieces having the second size are smaller than the pieces having the first size.

15. The method of claim 14, wherein, the glass substrate comprises a thickness of 2 mm or less.

16. The method of claim 14, wherein, bending the glass substrate includes biaxial bending of the glass substrate.

17. The method of claim 16, wherein, when the glass substrate fragments, in the second position, upon fracture of the glass substrate, the pieces form an in-plane isotropic fracture pattern.

18. The method of claim 14, wherein, bending the glass substrate includes uniaxial bending of the glass substrate along a bend axis of the glass substrate.

19. (canceled)

20. (canceled)

21. The method of claim 14, wherein, bending and maintaining the glass substrate in the second position is achieved at ambient temperature by a structural component of a product that utilizes the glass substrate.

22.-31. (canceled)

32. A product comprising: a glass substrate having a first position, wherein a tensile energy of the glass substrate is insufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate; and a component that bends and maintains the glass substrate in a second position, wherein the tensile energy of the glass substrate is sufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate.

33. The product of claim 32, wherein, the product is a consumer electronic device that is configured to be worn on a wrist of a person.

34. The product of claim 32, wherein, the product is safety glass.

35. The product of claim 32, wherein, the product is an automotive interior cover glass system.

36. The product of claim 32: wherein, the glass substrate has a first surface and a second surface; and wherein, in the second position, the first surface has a higher compressive stress than the second surface.

37. (canceled)

38. (canceled)

39. (canceled)

40. (canceled)

41. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a perspective view of a glass substrate in a first position, the glass substrate having a thickness defined by the distance between a first surface and a second surface, a width extending from a first side to a second side, and a width;

[0029] FIG. 2 is an elevational view of the glass substrate of FIG. 1;

[0030] FIG. 3 is a close up schematic view of the glass substrate of FIG. 1, illustrating a central region of tensile stress between a first layer and a second layer of compressive stress, the tensile stress and compressive stress imparted via tempering;

[0031] FIG. 4 is a perspective view of the glass substrate of FIG. 1, illustrating a fracture in the glass substrate extending the length of the glass substrate, and illustrating the glass substrate not fragmenting into small pieces as a result of the fracture;

[0032] FIG. 5 is a perspective view of the glass substrate of FIG. 1 having been bent from the first position of FIG. 1 to a second position along a bend axis;

[0033] FIG. 6 is a graph illustrating a stress profile of the glass substrate of FIG. 1, imparted via tempering, while in the first, unbent position;

[0034] FIG. 7 is a graph illustrating a profile of the stress imparted via bending upon the glass substrate of FIG. 1 after bending the glass substrate to and maintaining the glass substrate in the second position illustrated in FIG. 5;

[0035] FIG. 8 is a graph illustrating that the degree of fragmentation of the glass substrate of FIG. 1 upon fracture while in the second (bent) position (represented by the squared stress integral K.sub.f.sup.2) is dependent upon both the tensile stress (central tension) imparted via tempering and the tensile stress imparted via bending (bending stress);

[0036] FIG. 9 is a picture of a tempered glass substrate after fracture while in the second position (bent) illustrating that the tensile stress added via bending to the tensile stress imparted via tempering (left part of picture) results in a higher degree of fragmentation upon fracture (smaller pieces, more pieces) than the tensile stress imparted via tempering alone (right part of picture—larger pieces, less pieces);

[0037] FIG. 10 is a magnified view of an area of the picture of FIG. 9;

[0038] FIG. 11 is a series of pictures of tempered glass substrates after fracture while in the second position (bent) illustrating that the degree of fragmentation is a function of the radius of the bend (smaller bend radius imparts more tensile stress resulting in higher degree of fragmentation) and a function of the thickness of the glass substrate (larger thickness results in a higher degree of fragmentation);

[0039] FIG. 12A is a perspective view of a glass substrate (tempered) like the glass substrate of FIG. 1 but having a first surface and a second surface that is curved in a first position (no applied bending);

[0040] FIG. 12B is a perspective view of the glass substrate of FIG. 12A, illustrating fragmentation of the glass substrate into pieces of a first size (large) upon fracture;

[0041] FIG. 13A is a perspective view of a product (safety glass) incorporating the glass substrate of FIG. 12A, illustrating the glass substrate having been bent to a second position along a bend axis such that the first surface and the second surface are flat, and a component of the product maintaining the glass substrate in the second position;

[0042] FIG. 13B is a perspective view of the product of FIG. 13A incorporating the glass substrate of FIG. 12A, illustrating the glass substrate fragmenting into pieces of a second size (small pieces) due to the additional tensile stress imparted to regions of the glass substrate via bending the glass substrate to the second position;

[0043] FIG. 14A is a perspective view of a glass substrate (tempered) like the glass substrate of FIG. 1, having a first surface and a second surface that is flat in a first position (no applied bending);

[0044] FIG. 14B is a perspective view of the glass substrate of FIG. 14A, illustrating fragmentation of the glass substrate into pieces of a first size (large) upon fracture;

[0045] FIG. 15A a perspective view of a product (a watch) incorporating the glass substrate of FIG. 14A, illustrating the glass substrate having been biaxially bent to a second position along a first bend axis and a second bend axis such that the first surface and the second surface are curved, and a component of the product maintaining the glass substrate in the second position;

[0046] FIG. 15B is a perspective view of the product of FIG. 15A incorporating the glass substrate of FIG. 14A, illustrating the glass substrate fragmenting into pieces of a second size (small pieces) due to the additional tensile stress imparted to regions of the glass substrate via bending the glass substrate to the second position;

[0047] FIG. 16 is a graph illustrating that the orientation bias OB of fractures (i.e., which direction the fractures are biased to propagate) within the glass substrate of FIG. 1 while in the second (bent) position of FIG. 5 is dependent upon both the tensile stress (central tension) imparted via tempering and the tensile stress imparted via bending (bending stress);

[0048] FIG. 17 is a graphical representation of a dynamic fracture simulation performed on a computer to produce a visualization of fragmentation of the glass substrate of FIG. 1 in the second position of FIG. 5 upon fracture, and the graphical representation illustrates propagation of the fracture generally parallel to the bend axis (the y-axis);

[0049] FIG. 18 is a blown-up perspective view of a consumer electronic device incorporating a glass substrate like the glass substrate of FIG. 1 but having a first surface and a second surface that are curved in a first position (not yet bent), and the glass substrate is disposed above a display screen;

[0050] FIG. 19 is a perspective view of the consumer electronic device of FIG. 18, illustrating a component of the consumer electronic device bending the glass substrate along a bend axis into a second position and maintaining the glass substrate in the second position where the first surface and the second surface are flat;

[0051] FIG. 20 is an elevational view of a cross section of the consumer electronic device of FIG. 18 while the glass substrate is in the second position (bent) in FIG. 19, taken along line XX-XX of FIG. 19;

[0052] FIG. 21 is an overhead view of the consumer electronic device of FIG. 19 illustrating a fracture in the glass substrate propagating toward a second side of the glass substrate in a direction generally parallel to the bend axis;

[0053] FIG. 22 is a blown-up perspective view of a consumer electronic device incorporating a glass substrate like the glass substrate of FIG. 1 but having a first surface and a second surface that are curved in a first position (not yet bent), and the glass substrate is disposed above a display screen with an adhesive layer between the glass substrate and the display screen;

[0054] FIG. 23 is a perspective view of the consumer electronic device of FIG. 22, with a portion of a backing plate cut away to show the adhesive layer maintaining the glass substrate in a second position (bent);

[0055] FIG. 24 illustrates a person holding a variety of consumer electronic devices that incorporate the glass substrate of FIG. 1 in the second position (bent) of FIG. 5, such as the watch of FIG. 15A, a tablet, and a smart phone; and

[0056] FIG. 25 is a perspective view of an automotive interior system including the glass substrate in a second position (bent).

DETAILED DESCRIPTION

[0057] Referring now to FIGS. 1 and 2, a glass substrate 10 includes a first surface 12 and a second surface 14. The first surface 12 and the second surface 14 are the major surfaces of the glass substrate 10—that is, surfaces of the glass substrate 10 having the greatest surface area. A side surface 16 connects the first surface 12 and the second surface 14. The glass substrate 10 has a thickness 18 and is defined as the maximum distance between the first surface 12 and the second surface 14. In the illustrated embodiment, the glass substrate 10 has a thickness 18 that is substantially constant. The glass substrate 10 has a width 20 defined as a first maximum dimension of one of the first surface 12 or the second surface 14 orthogonal to the thickness 18. In the illustrated embodiment, the width 20 is thus the distance between a first side 22 of the glass substrate 10 and a second side 24 along the first surface 12. The glass substrate 10 has a length 26 defined as a second maximum dimension of one of the first surface 12 or the second surface 14 orthogonal to both the thickness 18 and the width 20.

[0058] As used herein, the term “glass substrate” 10 is used in its broadest sense to include any object made wholly or partly of glass. Glass substrates 10 include laminates of glass and non-glass materials, laminates of glass and crystalline materials, and glass-ceramics (including an amorphous phase and a crystalline phase). The glass substrate 10 may be transparent or opaque. In one or more embodiments, the glass substrate 10 may include a colorant that provides a specific color. Suitable glass compositions to form the glass substrate 10 include soda lime glass compositions, aluminosilicate glass compositions, borosilicate glass compositions, boroaluminosilicate glass compositions, alkali-containing aluminosilicate glass compositions, alkali-containing borcleosilicate glass compositions, and alkali-containing boroaluminosilicate glass compositions.

[0059] Unless otherwise specified, the compositions of the glass substrates 10 disclosed herein are described in mole percent (mol %) as analyzed on an oxide basis.

[0060] In one or more embodiments, the glass composition may include SiO.sub.2 in an amount in a range from about 66 mol % to about 80 mol %, from about 67 mol % to about 80 mol %, from about 68 mol % to about 80 mol %, from about 69 mol % to about 80 mol %, from about 70 mol % to about 80 mol %, from about 72 mol % to about 80 mol %, from about 65 mol % to about 78 mol %, from about 65 mol % to about 76 mol %, from about 65 mol % to about 75 mol %, from about 65 mol % to about 74 mol %, from about 65 mol % to about 72 mol %, or from about 65 mol % to about 70 mol %, and all ranges and sub-ranges therebetween.

[0061] In one or more embodiments, the glass composition includes Al.sub.2O.sub.3 in an amount greater than about 4 mol %, or greater than about 5 mol %. In one or more embodiments, the glass composition includes Al.sub.2O.sub.3 in a range from greater than about 7 mol % to about 15 mol %, from greater than about 7 mol % to about 14 mol %, from about 7 mol % to about 13 mol %, from about 4 mol % to about 12 mol %, from about 7 mol % to about 11 mol %, from about 8 mol % to about 15 mol %, from 9 mol % to about 15 mol %, from about 10 mol % to about 15 mol %, from about 11 mol % to about 15 mol %, or from about 12 mol % to about 15 mol %, and all ranges and sub-ranges therebetween. In one or more embodiments, the upper limit of Al.sub.2O.sub.3 may be about 14 mol %, 14.2 mol %, 14.4 mol %, 14.6 mol %, or 14.8 mol %.

[0062] In one or more embodiments, the glass substrate 10 is described as an aluminosilicate glass substrate or including an aluminosilicate glass composition. In such embodiments, the glass composition or substrate formed therefrom includes SiO.sub.2 and Al.sub.2O.sub.3 and is not a soda lime silicate glass. In this regard, the glass composition or substrate formed therefrom includes Al.sub.2O.sub.3 in an amount of about 2 mol % or greater, about 2.25 mol % or greater, about 2.5 mol % or greater, about 2.75 mol % or greater, or about 3 mol % or greater.

[0063] In one or more embodiments, the glass composition comprises B.sub.2O.sub.3 (e.g., about 0.01 mol % or greater). In one or more embodiments, the glass composition comprises B.sub.2O.sub.3 in an amount in a range from about 0 mol % to about 5 mol %, from about 0 mol % to about 4 mol %, from about 0 mol % to about 3 mol %, from about 0 mol % to about 2 mol %, from about 0 mol % to about 1 mol %, from about 0 mol % to about 0.5 mol %, from about 0.1 mol % to about 5 mol %, from about 0.1 mol % to about 4 mol %, from about 0.1 mol % to about 3 mol %, from about 0.1 mol % to about 2 mol %, from about 0.1 mol % to about 1 mol %, from about 0.1 mol % to about 0.5 mol %, and all ranges and sub-ranges therebetween. In one or more embodiments, the glass composition is substantially free of B.sub.2O.sub.3.

[0064] As used herein, the phrase “substantially free” with respect to the components of the composition means that the component is not actively or intentionally added to the composition during initial batching, but may be present as an impurity in an amount less than about 0.001 mol %.

[0065] In one or more embodiments, the glass composition optionally comprises P.sub.2O.sub.5 (e.g., about 0.01 mol % or greater). In one or more embodiments, the glass composition comprises a non-zero amount of P.sub.2O.sub.5 up to and including 2 mol %, 1.5 mol %, 1 mol %, or 0.5 mol %. In one or more embodiments, the glass composition is substantially free of P.sub.2O.sub.5.

[0066] In one or more embodiments, the glass composition may include a total amount of R.sub.2O (which is the total amount of alkali metal oxide such as Li.sub.2O, Na.sub.2O, K.sub.2O, Rb.sub.2O, and Cs.sub.2O) that is greater than or equal to about 8 mol %, greater than or equal to about 10 mol %, or greater than or equal to about 12 mol %. In some embodiments, the glass composition includes a total amount of R.sub.2O in a range from about 8 mol % to about 20 mol %, from about 8 mol % to about 18 mol %, from about 8 mol % to about 16 mol %, from about 8 mol % to about 14 mol %, from about 8 mol % to about 12 mol %, from about 9 mol % to about 20 mol %, from about 10 mol % to about 20 mol %, from about 11 mol % to about 20 mol %, from about 12 mol % to about 20 mol %, from about 13 mol % to about 20 mol %, from about 10 mol % to about 14 mol %, or from 11 mol % to about 13 mol %, and all ranges and sub-ranges therebetween. In one or more embodiments, the glass composition may be substantially free of Rb.sub.2O, Cs.sub.2O or both Rb.sub.2O and Cs.sub.2O. In one or more embodiments, the R.sub.2O may include the total amount of Li.sub.2O, Na.sub.2O, and K.sub.2O only. In one or more embodiments, the glass composition may comprise at least one alkali metal oxide selected from Li.sub.2O, Na.sub.2O, and K.sub.2O, wherein the alkali metal oxide is present in an amount greater than about 8 mol %.

[0067] In one or more embodiments, the glass composition comprises Na.sub.2O in an amount greater than or equal to about 8 mol %, greater than or equal to about 10 mol %, or greater than or equal to about 12 mol %. In one or more embodiments, the composition includes Na.sub.2O in a range from about 8 mol % to about 20 mol %, from about 8 mol % to about 18 mol %, from about 8 mol % to about 16 mol %, from about 8 mol % to about 14 mol %, from about 8 mol % to about 12 mol %, from about 9 mol % to about 20 mol %, from about 10 mol % to about 20 mol %, from about 11 mol % to about 20 mol %, from about 12 mol % to about 20 mol %, from about 13 mol % to about 20 mol %, from about 10 mol % to about 14 mol %, or from 11 mol % to about 16 mol %, and all ranges and sub-ranges therebetween.

[0068] In one or more embodiments, the glass composition includes less than about 4 mol % K.sub.2O, less than about 3 mol % K.sub.2O, or less than about 1 mol % K.sub.2O. In some instances, the glass composition may include K.sub.2O in an amount in a range from about 0 mol % to about 4 mol %, from about 0 mol % to about 3.5 mol %, from about 0 mol % to about 3 mol %, from about 0 mol % to about 2.5 mol %, from about 0 mol % to about 2 mol %, from about 0 mol % to about 1.5 mol %, from about 0 mol % to about 1 mol %, from about 0 mol % to about 0.5 mol %, from about 0 mol % to about 0.2 mol %, from about 0 mol % to about 0.1 mol %, from about 0.5 mol % to about 4 mol %, from about 0.5 mol % to about 3.5 mol %, from about 0.5 mol % to about 3 mol %, from about 0.5 mol % to about 2.5 mol %, from about 0.5 mol % to about 2 mol %, from about 0.5 mol % to about 1.5 mol %, or from about 0.5 mol % to about 1 mol %, and all ranges and sub-ranges therebetween. In one or more embodiments, the glass composition may be substantially free of K.sub.2O.

[0069] In one or more embodiments, the glass composition is substantially free of Li.sub.2O.

[0070] In one or more embodiments, the amount of Na.sub.2O in the composition may be greater than the amount of Li.sub.2O. In some instances, the amount of Na.sub.2O may be greater than the combined amount of Li.sub.2O and K.sub.2O. In one or more alternative embodiments, the amount of Li.sub.2O in the composition may be greater than the amount of Na.sub.2O or the combined amount of Na.sub.2O and K.sub.2O.

[0071] In one or more embodiments, the glass composition may include a total amount of RO (which is the total amount of alkaline earth metal oxide such as CaO, MgO, BaO, ZnO, and SrO) in a range from about 0 mol % to about 2 mol %. In some embodiments, the glass composition includes a non-zero amount of RO up to about 2 mol %. In one or more embodiments, the glass composition comprises RO in an amount from about 0 mol % to about 1.8 mol %, from about 0 mol % to about 1.6 mol %, from about 0 mol % to about 1.5 mol %, from about 0 mol % to about 1.4 mol %, from about 0 mol % to about 1.2 mol %, from about 0 mol % to about 1 mol %, from about 0 mol % to about 0.8 mol %, from about 0 mol % to about 0.5 mol %, and all ranges and sub-ranges therebetween.

[0072] In one or more embodiments, the glass composition includes CaO in an amount less than about 1 mol %, less than about 0.8 mol %, or less than about 0.5 mol %. In one or more embodiments, the glass composition is substantially free of CaO.

[0073] In some embodiments, the glass composition comprises MgO in an amount from about 0 mol % to about 7 mol %, from about 0 mol % to about 6 mol %, from about 0 mol % to about 5 mol %, from about 0 mol % to about 4 mol %, from about 0.1 mol % to about 7 mol %, from about 0.1 mol % to about 6 mol %, from about 0.1 mol % to about 5 mol %, from about 0.1 mol % to about 4 mol %, from about 1 mol % to about 7 mol %, from about 2 mol % to about 6 mol %, or from about 3 mol % to about 6 mol %, and all ranges and sub-ranges therebetween.

[0074] In one or more embodiments, the glass composition comprises ZrO.sub.2 in an amount equal to or less than about 0.2 mol %, less than about 0.18 mol %, less than about 0.16 mol %, less than about 0.15 mol %, less than about 0.14 mol %, less than about 0.12 mol %. In one or more embodiments, the glass composition comprises ZrO.sub.2 in a range from about 0.01 mol % to about 0.2 mol %, from about 0.01 mol % to about 0.18 mol %, from about 0.01 mol % to about 0.16 mol %, from about 0.01 mol % to about 0.15 mol %, from about 0.01 mol % to about 0.14 mol %, from about 0.01 mol % to about 0.12 mol %, or from about 0.01 mol % to about 0.10 mol %, and all ranges and sub-ranges therebetween.

[0075] In one or more embodiments, the glass composition comprises SnO.sub.2 in an amount equal to or less than about 0.2 mol %, less than about 0.18 mol %, less than about 0.16 mol %, less than about 0.15 mol %, less than about 0.14 mol %, or less than about 0.12 mol %. In one or more embodiments, the glass composition comprises SnO.sub.2 in a range from about 0.01 mol % to about 0.2 mol %, from about 0.01 mol % to about 0.18 mol %, from about 0.01 mol % to about 0.16 mol %, from about 0.01 mol % to about 0.15 mol %, from about 0.01 mol % to about 0.14 mol %, from about 0.01 mol % to about 0.12 mol %, or from about 0.01 mol % to about 0.10 mol %, and all ranges and sub-ranges therebetween.

[0076] In one or more embodiments, the glass composition may include an oxide that imparts a color or tint to the glass substrate 10. In some embodiments, the glass composition includes an oxide that prevents discoloration of the glass substrate 10 when the glass substrate 10 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.

[0077] In one or more embodiments, the glass composition includes Fe expressed as Fe.sub.2O.sub.3, wherein Fe is present in an amount up to (and including) about 1 mol %. In some embodiments, the glass composition is substantially free of Fe. In one or more embodiments, the glass composition comprises Fe.sub.2O.sub.3 in an amount equal to or less than about 0.2 mol %, less than about 0.18 mol %, less than about 0.16 mol %, less than about 0.15 mol %, less than about 0.14 mol %, or less than about 0.12 mol %. In one or more embodiments, the glass composition comprises Fe.sub.2O.sub.3 in a range from about 0.01 mol % to about 0.2 mol %, from about 0.01 mol % to about 0.18 mol %, from about 0.01 mol % to about 0.16 mol %, from about 0.01 mol % to about 0.15 mol %, from about 0.01 mol % to about 0.14 mol %, from about 0.01 mol % to about 0.12 mol %, or from about 0.01 mol % to about 0.10 mol %, and all ranges and sub-ranges therebetween.

[0078] Where the glass composition includes TiO.sub.2, TiO.sub.2 may be present in an amount of about 5 mol % or less, about 2.5 mol % or less, about 2 mol % or less, or about 1 mol % or less. In one or more embodiments, the glass composition may be substantially free of TiO.sub.2.

[0079] An exemplary glass composition includes SiO.sub.2 in an amount in a range from about 65 mol % to about 75 mol %, Al.sub.2O.sub.3 in an amount in a range from about 8 mol % to about 14 mol %, Na.sub.2O in an amount in a range from about 12 mol % to about 17 mol %, K.sub.2O in an amount in a range of about 0 mol % to about 0.2 mol %, and MgO in an amount in a range from about 1.5 mol % to about 6 mol %. Optionally, SnO.sub.2 may be included in the amounts otherwise disclosed herein.

[0080] The glass composition chosen can be formed into the glass substrate 10 using any method capable of producing the glass substrate 10 that can be tempered. Example methods capable of producing the glass substrate 10 include down-draw methods that form sheets of the glass substrate 10. Down-draw methods include, but are not limited to, fusion draw and slot draw methods. Down-draw methods are used in the large-scale manufacture of flat glass substrates 10, such as display glass and ion-exchangeable glass (capable of being chemical tempered). The fusion draw method uses a forming body that has a channel for accepting molten glass raw material. The channel has weirs that are open at the top along the length of the channel on both sides of the channel. When the channel fills with molten material, the molten glass overflows the weirs. Due to gravity, the molten glass flows down the outside surfaces of the isopipe. These outside surfaces extend down and inwardly so that they join at an edge below the drawing tank. The two flowing glass surfaces join at this edge to fuse and form a single flowing sheet. The fusion draw method offers the advantage that, since the two glass films flowing over the channel fuse together, neither outside surface of the resulting glass sheet comes in contact with any part of the apparatus. Thus, the surface properties are not affected by such contact. The glass substrate 10 is formed initially without a layer of compressive stress at the first surface 12 and the second surface 14.

[0081] Referring now to FIG. 3, the glass substrate 10 is then tempered, either chemically tempered, thermally tempered, or both, or otherwise tempered. After such tempering, the glass substrate 10 has compressive stress imparted to the first surface 12 and extending through a first layer 28 of the thickness 18 referred to as a depth of compression (DOC) 30. The tempering additionally imparts compressive stress to the second surface 14 and extending through a second layer 32 of the thickness 18 referred to as a depth of compression (DOC) 34. The tempering further imparts tensile stress within a central region 36 between the first layer 28 and the second layer 32. This tensile stress is sometimes referred to as “central tension.” The tensile stress within the central region 36 balances the compressive stress within the first layer 28 and the second layer 32.

[0082] In FIGS. 1-3, the glass substrate 10 is illustrated in an embodiment of a first position 38. In this embodiment of the first position 38, the first surface 12 and the second surface 14 of the glass substrate 10 are planar. In other words, the first surface 12 and the second surface 14 are flat. However, as discussed further below, the first surface 12 and the second surface 14 need not be flat in the first position 38.

[0083] Referring now to FIG. 4, this disclosure assumes that the tempering of the glass substrate 10 results in tensile energy at the central region 36 of the glass substrate 10 that is insufficient, when the glass substrate 10 is in the first position 38, to cause fragmentation of the glass substrate 10 into pieces 40 having a sufficiently small size upon fracture 42 of the glass substrate 10 for the desired application of the glass substrate 10. In other words, when the glass substrate 10 fractures 42, the glass substrate 10 fragments into pieces 40 that are large (having a large surface area) upon fracture 42, compared to the surface area (length 26×width 20) of the glass substrate 10 before fracture 42. The tensile stress was too small.

[0084] Referring now to FIG. 5, the glass substrate 10 is in a second position 44. In the second position 44, the glass substrate 10 is bent relative to the first position 38. Because the first surface 12 and the second surface 14 of the glass substrate 10 in the first position 38 (FIG. 1) were planar (that is, flat), the first surface 12 and the second surface 14 of the glass substrate 10 in the second position 44 are not planar (that is, not flat—the first surface 12 and the second surface 14 now being curved). In the illustrated embodiment, the glass substrate 10 is flatter in the first position 38 than in the second position 44. In the illustrated embodiment, the glass substrate 10 is bent uniaxially along a bend axis 46 of the glass substrate 10.

[0085] In one or more embodiments, the glass substrate 10 is bent uniaxially along the bend axis 46 by cold-bending. As used herein, the terms “cold-bent,” or “cold-bending” refers to curving the glass substrate at a cold-bend temperature which is less than the softening point of the glass. Often, the cold-bend temperature is room temperature. The term “cold-bendable” refers to the capability of a glass substrate to be cold-bent. A feature of a cold-bent glass substrate is asymmetric surface compressive stress between the first surface 12 and the second surface 14 (as shown in FIG. 5). In one or more embodiments, prior to the cold-bending process or being cold-bent, the respective compressive stresses in the first surface 12 and the second surface 14 of the glass substrate are substantially equal. In one or more embodiments in which the glass substrate is unstrengthened, the first surface 12 and the second surface 14 exhibit no appreciable compressive stress, prior to cold-bending. In one or more embodiments in which the glass substrate is strengthened (as described herein), the first surface 12 and the second surface 14 exhibit substantially equal compressive stress with respect to one another, prior to cold-bending. In one or more embodiments, after cold-bending, the CS on the surface having a concave shape after cold-bending (e.g., second surface 14) increases, while the CS on the surface having a convex shape after cold-bending (e.g., the first surface 12) decreases. In other words, the compressive stress on the concave surface (e.g., second surface 14) is greater after cold-bending than before cold-bending.

[0086] The bending of the glass substrate 10 affects the stress profile of the glass substrate 10 (the distribution of compressive stress and tensile stress throughout the glass substrate 10) that the glass substrate 10 has after tempering, as will be discussed. In particular, because the bending forms a uniaxial bend in the direction towards the second surface 14, the bending adds to the compressive stress at the second layer 32 and subtracts from the compressive stress at the first layer 28. In addition, by affecting the stress profile of the tempered glass substrate 10, the bending affects the degree of fragmentation (more pieces 40 of smaller size) that the tempered glass substrate 10 experiences upon fracture 42 by increasing the degree of fragmentation to cause more pieces 40 having a smaller size.

[0087] An analytical model illustrates these points. For the analytic model, it can be assumed that the glass substrate 10, after tempering, has a stress profile as illustrated in FIG. 6, based on an underlying assumption of a thickness 18 of 0.55 mm. The stress profile profiles the stress of the glass substrate 10 as a function of position through the thickness 18 of the glass substrate 10 after tempering. A negative stress value is compressive stress, while a positive stress value is tensile stress. The compressive stress, as mentioned, extends from the first surface 12 through the DOC 30 of the first layer 28, and extends from the second surface 14 through the DOC 34 of the second layer 32. The tensile stress, as mentioned, extends within the central region 36 between the first layer 28 and the second layer 32 of compressive stress.

[0088] Next, the analytical model can account for the stress that uniaxial bending of the glass substrate 10 induces along the bend axis 46 of the bend as a function of a z-axis position through the thickness 18 of the glass substrate 10 via a linear equation. The linear equation is:

[00001]${\sigma }_{\mathrm{bending}}\left(z\right)=-\frac{2\left({\sigma }_{\mathrm{bendingmax}}\right)\left(z\right)}{t}$

The variable z is the value of the z-axis position through the thickness t 18 of the glass substrate 10. The variable σ.sub.bendmax is an assigned value and is the maximum bending stress at the first surface 12. If we assume again that the thickness t 18 of the glass substrate 10 is 0.55 mm and the maximum bending stress σ.sub.bendmax applied to the glass substrate 10 is 137 MPa, then the results of the linear equation above can be plotted. Such plotting is illustrated in FIG. 7. In this analytical model, the bending of the glass substrate 10 occurs along the bend axis 46, which is the y-axis in this model. Therefore, the largest bending stresses are experienced along the y-axis. However, bending the glass substrate 10 along the y-axis will also induce stress along the x-axis, albeit a lesser stress than along the y-axis, because of the Poisson ratio effect. Note that the bending stress from the first surface 12 to the middle of the thickness 18 of the glass substrate 10 is a tensile stress, which counters the compressive stress generated via tempering within the first layer 28 and adds to the tensile stress generated via tempering in the central region 36 from the middle of the thickness 18 toward the first layer 28. In addition, note that the bending stress from the middle of the thickness 18 to the second surface 14 is a compressive stress, which counters the tensile stress generated via tempering from the middle of the thickness 18 toward the second layer 32 and adds to the compressive stress generated via tempering within the second layer 32.

[0089] Therefore, the analytical model proves a novel method of increasing compressive stress within a layer of the glass substrate 10 (either the first layer 28 or the second layer 32, depending on the direction of the bend). That method includes forming the glass substrate 10, as described above. The method further includes imparting, via tempering the glass substrate 10, the first compressive stress within the first layer 28 from the first surface 12, and within the second layer 32 from the second surface 14. The method then includes bending the tempered glass substrate 10 along the bend axis 46 of the glass substrate 10 in the direction of the second surface 14 to add compressive stress to the first compressive stress within the second layer 32. Contrarily, if the desire were to add compressive stress to the first compressive stress within the first layer 28, then the method would include bending the tempered glass substrate 10 along the bend axis 46 in the direction of the first surface 12. Imparting the first compressive stress within the first layer 28 and the second layer 32 of the glass substrate 10, in an embodiment of the method, includes thermal tempering of the glass substrate 10. Imparting the first compressive stress within the first layer 28 and the second layer 32 of the glass substrate 10, in an embodiment of the method, includes chemical tempering of the glass substrate 10. In an embodiment of the method, the second surface 14 of the glass substrate 10 is a top surface of the glass substrate 10. This method of increasing the compressive stress at either the first layer 28 or the second layer 32 of the glass substrate 10, is especially beneficial when the glass substrate 10 has a relatively thin thickness 18 (2 mm or less, 1.8 mm or less, 1.6 mm or less, 1.5 mm or less, 1.4 mm or less, 1.2 mm or less, 1 mm or less, or 0.75 mm or less, or 0.55 mm or less, for examples), because chemical tempering such a thin glass substrate 10 might not be able to impart a requisite compressive stress at the second layer 32.

[0090] Continuing the analytical model, a one-dimensional stress profile of the glass substrate 10 after tempering and after bending can be calculated as a function of the z-axis position along the thickness t 18 of the glass substrate 10, according to the following equation:

[00002]$\sigma \left(z\right)=-\frac{12{\sigma }_{\mathrm{CT}}{z}^2}{t^2}+{\sigma }_{\mathrm{CT}}+\frac{2{\sigma }_{\mathrm{bendmax}}z}{t}$

The variable σ(z) is the total stress as a function of the position z along the z-axis thickness t 18 of the glass substrate 10. The variable σ.sub.CT is the maximum tensile stress within the central region 36 of the glass substrate 10 as a result of tempering alone. As explained above, the variable σ.sub.bendmax is the maximum bending stress at the first surface 12.

[0091] Squaring and integrating the above equation provides a squared stress integral, which provides a relative degree of fragmentation of the glass substrate 10 upon fracture 42. This equation is as follows:

[00003]$K_f^2={\int }_{z^1}^{z^2}{\sigma }^2\left(z\right)\mathrm{dz}=\frac{\sqrt{12{\sigma }_{\mathrm{dt}}^2+{\sigma }_{\mathrm{bendmax}}^2}\left(144{\sigma }_{\mathrm{CT}}^4+24{\sigma }_{\mathrm{bendmax}}^2{\sigma }_{\mathrm{CT}}^2+{\sigma }_{\mathrm{bendmax}}^4\right)t}{1620{\sigma }_{\mathrm{CT}}^3}$

The symbol K.sub.f.sup.2 denotes the squared stress integral. The variables z.sup.1 and z.sup.2 are the roots of the squared stress integral function corresponding to the z-axis positions through the central region 36 of thickness t 18 from one depth of layer DOC (z.sup.1) to the other depth of layer DOC (z.sup.2). As FIG. 8 illustrates, the squared stress integral K.sub.f.sup.2 increases as the maximum bending stress increases σ.sub.bendmax, which corresponds to a high degree of fragmentation (i.e., more pieces 40 and smaller size of pieces 40) upon fracture 42. In other words, even if tempering imparts a relatively low amount of tensile stress (central tension) into the central region 36 (i.e., too low to cause fragmentation into pieces 40 having a small size upon fracture 42), bending adds tensile stress to the tensile stress already imparted via tempering at a portion of the central region 36 away from the direction of the bend. The increased tensile stress increases the squared stress integral K.sub.f.sup.2 and, thus, the degree of fragmentation upon fracture. Accordingly, even if the tensile stress imparted to the central region 36 of the glass substrate 10 via tempering was insufficient to cause fragmentation of the glass substrate 10 into pieces 40 having a small size upon fracture 42, the added tensile stress imparted via bending the glass substrate 10 may be sufficient to cause such a high degree of fragmentation.

[0092] Applicant has confirmed the analytical model through physical experimentation. Applicant formed a glass substrate 10 having a thickness t 18 of 0.7 mm. Applicant imparted the glass substrate 10 with tensile stress via chemical tempering. Specifically, Applicant submitted the glass substrate 10 to ion exchange at 420° C. for 5.5 hours. As a result, the glass substrate 10 had a maximum tensile stress (central tension) σ.sub.CT at the central region 36 of 70 MPa.

[0093] Applicant then applied a bending stress to the glass substrate 10 using a 4-point bend apparatus. The middle two points of the bending apparatus were placed 9 mm from center of the glass substrate 10. The outer two points of the bending apparatus were placed 18 mm from center of the glass substrate 10. The apparatus applied bending stress until the glass substrate 10 fractured 42. The bending stress that caused the glass substrate 10 to fracture 42 was approximately 480 MPa. At FIG. 9, a picture of the glass substrate 10 after fracture 42 is depicted below a graph illustrating the bending stress applied to the glass substrate 10 as a function of position along the width 20 of the glass substrate 10. FIG. 10 shows the same thing but magnified to show a region where bending stress was applied and a region where bending stress was not applied. The drop in bending stress from approximately 480 MPa to zero coincides with the picture of FIG. 10 and represents where one of the middle 2 points of the 4-point bend apparatus was applied to the glass substrate 10. The glass substrate 10 experienced the bending stress of approximately 480 MPa between the two middle points of the bending apparatus. The glass substrate 10 exhibits a high degree of fragmentation (small pieces 40) where the bending stress of approximately 480 MPa was applied to the glass substrate 10. In contrast, the glass substrate 10 exhibits a low degree of fragmentation (large pieces 40) where no bending stress was applied (approximately between the inner point and the outer point on each side of the apparatus), which demonstrates that the tensile stress in the central region 36 from tempering alone was insufficient to cause a high degree of fragmentation (small pieces 40) upon fracture 42. The contrast demonstrates that bending stress can add the tensile stress required for the glass substrate 10 to exhibit a high degree of fragmentation upon fracture 42, when tempering the glass substrate 10 did not add sufficient tensile stress to achieve a high degree of fragmentation.

[0094] Referring now to FIG. 11, in another physical experiment, Applicant chemically tempered nine samples of the glass substrate 10. The nine samples were grouped into three thicknesses 18, three samples each of 0.4 mm, 0.55 mm, and 0.7 mm thickness. The chemical tempering via ion-exchange imparted compressive stress of 825 MPa at the first layer 28 and the second layer 32 of each sample glass substrate 10. The compressive stress depth of layer (DOC) was 42.5 μm. The resulting tensile stress was insufficient to cause fragmentation of the glass substrate 10 into small pieces 40 upon fracture 42. One glass substrate 10 of each thickness 18 was cylindrically (uniaxially) bent at constant radii of 250 mm, 500 mm, and 1000 mm from the first position 38 to the second position 44, maintained in the second position 44 (bent), and then indented in the center until the glass substrate 10 fractured 42.

[0095] As the pictures reproduced at FIG. 11 demonstrate, the more aggressive the bend (that is, the smaller the bend radius), the smaller the pieces 40 of fragmentation upon fracture 42 of the glass substrate 10. For example, for the three samples having the thickness 18 of 0.4 mm, the glass substrate 10 subjected to the bending radius of 500 mm produced smaller pieces 40 of fragmentation upon fracture 42 than the glass substrate 10 subjected to the bending radius of 1000 mm. The glass substrate 10 subjected to the bending radius of 250 mm produced still smaller pieces 40 of fragmentation upon fracture 42 than the glass substrate 10 subjected to the bending radius of 500 mm. Therefore, the more aggressive the bend imposed on the glass substrate 10 to change the glass substrate 10 from the first position 38 to the second position 44, the more likely the glass substrate 10 fragments into small pieces 40 upon fracture 42.

[0096] In addition, the pictures reproduced at FIG. 11 demonstrate the thicker the thickness 18 of the glass substrate 10, the smaller the pieces 40 of fragmentation upon fracture 42 of the glass substrate 10. For example, for the three samples bent at a constant radius of 500 mm, the glass substrate 10 having a thickness 18 of 0.55 mm produced smaller pieces 40 of fragmentation upon fracture 42 than the glass substrate 10 having a thickness 18 of 0.4 mm. The glass substrate 10 having a thickness 18 of 0.7 mm produced still smaller pieces 40 of fragmentation upon fracture 42 than the glass substrate 10 having the thickness 18 of 0.55 mm. Therefore, the thicker the thickness 18 of the glass substrate 10, the more likely the glass substrate 10 fragments into small pieces 40 upon fracture 42 for any given bend radius imposed on the glass substrate 10.

[0097] Referring now to FIGS. 12A-15B, Applicant has, therefore, discovered a novel method of reducing the size of the pieces 40 that the glass substrate 10 fragments into upon fracture 42 of the glass substrate 10. The method includes forming the glass substrate 10 that fragments into pieces 40 having a first size 48 upon fracture 42 of the glass substrate 10 (see FIGS. 12A and 12B). As discussed, the glass substrate 10 as formed is in the first position 38 and is tempered. However, the resulting tensile stress of the glass substrate 10 is insufficient to cause the glass substrate 10 to fragment into small pieces 40 upon fracture 42. The method further includes bending the glass substrate 10 to the second position 44 and maintaining the glass substrate 10 in the second position 44. A component 50, such as a structural component like a windowpane frame or a material such as an adhesive, can maintain the glass substrate 10 in the second position 44. In other words, in an embodiment, bending and maintaining the glass substrate 10 in the second position 44 is achieved at an ambient temperature by a structural component of a product 52 that utilizes the glass substrate 10. In one or more embodiment, an adhesive may be used to permanently hold the glass substrate 10 in the second position 44 by bonding the glass substrate to a curved underlying surface (not shown).

[0098] Maintained in the second position 44, the glass substrate 10 fragments into pieces 40 having a second size 54 upon fracture 42 of the glass substrate 10. The pieces 40 having the second size 54 are smaller than the pieces 40 having the first size 48. In some embodiments, the pieces 40 having the second size 54 have a length 56 and a width 58 that are approximately equal to each other, and, in some embodiments, approximately equal to the thickness 18 (i.e., dicing fragmentation behavior). In an embodiment, forming the glass substrate 10 includes forming the glass substrate 10 with the thickness 18 of 2 mm or less. In an embodiment, bending the glass substrate 10 includes uniaxial bending of the glass substrate 10 along the bend axis 46 of the glass substrate 10, as in the embodiment illustrated in FIGS. 12A-13B. In an embodiment, forming the glass substrate 10 includes forming the glass substrate 10 with a first surface 12 that is curved, as in the embodiment illustrated in FIGS. 12A and 12B. Annealing the glass substrate 10 can form the glass substrate 10 with the first surface 12 that is curved while in the first position 38. In an embodiment, bending the glass substrate 10 to the second position 44 includes bending the glass substrate 10 so that the first surface 12 is less curved in the second position 44 than in the first position 38, or not curved, as is in the embodiment illustrated in FIG. 13A.

[0099] In an embodiment, as in the embodiment illustrated in FIGS. 14A-15B, bending the glass substrate 10 includes biaxial bending. Biaxial bending of the glass substrate 10 is bending of the glass substrate 10 at a first bend axis 46a and a second bend axis 46b. Note that in the embodiment illustrated at FIGS. 14A-B, forming the glass substrate 10 includes forming the glass substrate 10 with the first surface 12 that is flat (that is, not curved). The component 50 of the product 52 bends the glass substrate 10 to the second position 44 or hold the glass substrate 10 in the second position 44. Fragmentation of the glass substrate 10 upon fracture 42 in the second position 44 generates pieces 40 of the second size 54 that are smaller than the pieces 40 of the first size 48 generated when the glass substrate 10 fractures 42 in the first position 38. Because the glass substrate 10 is biaxially bent in the second position 44, when the glass substrate 10 fragments upon fracture 42 of the glass substrate 10, the pieces 40 form an in-plane isotropic fracture pattern 60.

[0100] In any event, the glass substrate 10 is formed and tempered in the first position 38 but can be forced into the second position 44. In the first position 38, the tensile energy of the glass substrate 10 (imparted via tempering) is insufficient to cause fragmentation of the glass substrate 10 into pieces 40 having the small second size 54 upon fracture 42. Instead, the tensile energy causes fragmentation of the glass substrate 10 into the pieces 40 having the first size 48 (the larger size). However, upon bending the glass substrate 10 to the second position 44, the stress profile of the glass substrate 10 is altered relative to the first position 38, increasing the tensile stress at a certain portion of the central region 36. Thus, in the second position 44, the tensile energy of the glass substrate 10 is sufficient to cause fragmentation of the glass substrate 10 into pieces 40 having the second size 54 (i.e., small pieces 40) upon fracture 42 of the glass substrate 10. In some embodiments, such as that illustrated in FIG. 14A, the glass substrate 10 is formed and tempered flat. In other words, in the first position 38, the first surface 12 and the second surface 14 of the glass substrate 10 are planar. Therefore, in the first position 38, the glass substrate 10 is flatter than the glass substrate 10 is in the second position 44. In some embodiments, such as that illustrated at FIG. 13B, the pieces 40 of the second size 54 (the small pieces) are generally cubic, having the length 56, the width 58, and the thickness 18 that are all generally of equal value. In some embodiments, such as that illustrated in FIGS. 13A and 13B, the glass substrate 10 is bent uniaxially along the bend axis 46 in the second position 44. In some embodiments, such as that illustrated in FIGS. 15A and 15B, the glass substrate 10 is bent biaxially along two bend axes 46a, 46b (the first bend axis 46a and the second bend axis 46b) in the second position 44. In some embodiments, the thickness 18 of the glass substrate 10 is 2 mm or less.

[0101] However, in other embodiments, such as that illustrated in FIGS. 12A-13B, the glass substrate 10 is formed and tempered curved. In other words, in the first position 38, the first surface 12 and the second surface 14 of the glass substrate 10 are curved (not flat). The glass substrate 10 is then bent to the second position 44. In the second position 44, the glass substrate 10 is flatter than the glass substrate 10 is in the first position 38. For example, in the second position 44, the first surface 12 and the second surface 14 can be planar (not curved).

[0102] In some embodiments, the glass substrate 10 is incorporated into the product 52. The product 52 comprises the glass substrate 10 and the component 50 that bends the glass substrate 10 away from the first position 38, in which the glass substrate 10 is formed and tempered, and to the second position 44. In one or more embodiments, product 52 comprises the glass substrate 10 and the component 50 that maintains or secures the glass substrate 10 in the second position 44. In the first position 38, the tensile energy of the glass substrate 10 is insufficient to cause fragmentation of the glass substrate 10 into pieces of the second size 54 (that is, small pieces) upon fracture 42 of the glass substrate 10. In the second position 44, which the component 50 forces the glass substrate 10 to take or in which the component 50 secures the glass substrate 10, the tensile energy of the glass substrate 10 is sufficient to cause fragmentation of the glass substrate 10 into pieces 40 of the second size 54 (that is, small pieces) upon fracture 42 of the glass substrate 10. In an embodiment, such as that illustrated at FIGS. 13A-13B, the product 52 is a safety glass 62, where the glass substrate 10 must fragment into small pieces 40 and eject outwards upon fracture 42. Note that in this embodiment, the glass substrate 10 has the first surface 12 and the second surface 14 facing in opposite directions. Because the component 50 is bending the glass substrate 10 along the bend axis 46 in a direction that compresses the first surface 12 (or the component 50 is securing the glass substrate in the second position along bend axis 46 in a direction that compresses the first surface 12), the first surface 12 has a higher compressive stress than the second surface 14. That may be especially beneficial for the safety glass 62. In the embodiment of FIGS. 15A and 15B, the product 52 is a consumer electronic device 64, such as a watch 66, that is configured to be worn on a wrist of a person 68 (see also FIG. 19). In one or embodiments, the product 52 is an automotive interior cover glass used in an automotive interior system.

[0103] To continue the analytical model, the squared stress integral K.sub.f.sup.2 can be determined for each stress component in the x-y plane (σ.sub.x and σ.sub.y) and then compared to determine the orientation bias of the fragmentation (i.e., which direction over the x-y plane the fragmentation will generally be directed) upon uniaxial bending. If the glass substrate 10 is bent along the y-axis (the bend axis 46 in the running example), the bending stress is experienced along the x direction and the y direction experiences no bending stress. Therefore, the squared stress integral along the x direction, K.sub.fx.sup.2, will be different than the squared stress integral along the y direction, K.sub.fy.sup.2. The equations for K.sub.fx.sup.2 and K.sub.fy.sup.2 will be equal except for the bending stress σ.sub.bendmax experienced only along the x direction. Therefore, assuming σ.sub.y is along the bend axis 46 and therefore has a σ.sub.bendmax value of zero, and σ.sub.x has all the bending stress and therefore a value for σ.sub.bendmax, the orientation bias OB of the fragmentation can be quantified as follows:

[00004]$\mathrm{OB}=\frac{K_{\mathrm{fx}}^2}{K_{\mathrm{fy}}^2}=\frac{\sqrt{12{\sigma }_{\mathrm{CT}}^2+{\sigma }_{\mathrm{bendmax}}^2}(144{\sigma }_{\mathrm{CT}}^4+24{\sigma }_{\mathrm{bendmax}}^2{\sigma }_{\mathrm{CT}}^2+{\sigma }_{\mathrm{bendmax})}^4}{\sqrt{12{\sigma }_{\mathrm{CT}}^2}\left(144{\sigma }_{\mathrm{CT}}^4\right)}$

[0104] Referring now to FIG. 16, the orientation bias OB of the fragmentation is graphed as a function of the tensile stress already existing from tempering (central tension, σ.sub.CT) and the tensile stress added to the glass substrate 10 from bending (bending stress, σ.sub.bendmax). The graph illustrates that the more bending stress that is added, the more the orientation bias of fragmentation. In this instance, because the bend is along the y-axis and therefore adds stress along the x direction, the orientation of the fragmentation is biased along the bend axis 46 (here, the y-axis). In other words, the fracture 42 between two pieces 40 is biased to be parallel the bend axis 46.

[0105] Referring now to FIG. 17, a dynamic fracture simulation, which utilized Peridynamic theory, was performed on a computer to produce a visualization of fragmentation of a glass substrate 10 upon fracture 42. The simulation assumed that the glass substrate 10 was tempered but not fragmenting into small pieces 40 upon fracture 42, with a central tension (tensile stress) of 105.27 MPa. The simulation assumed that the glass substrate 10 had dimensions of 5 mm of width 20, 5 mm of length 26, and 0.55 mm of thickness 18. The residual stress profile of the glass substrate 10 after tempering is that illustrated as FIG. 6. The simulation assumed that the bend axis 46 was vertical and an applied bending surface stress of 137 MPa. The bending stress profile applied to the glass substrate 10 is that illustrated as FIG. 7. The calculated orientation bias OB of the fragmentation was 1.39. The right positioned bar (0 to 0.5) represents material volume damage, where values greater than 0.34 represent the fracture 42 breaking through to the first surface 12. As the visualization of FIG. 17 illustrates, the fragmentation upon fracture 42 results in the fracture 42 extending generally parallel to the bend axis 46 (y-axis, up-down), with the fracture bifurcating 70 after a relatively short distance (relatively short vertical fracture 42 segments). The bending increases stress in the horizontal, x, direction and causes the relatively short vertical fracture 42 segments.

[0106] The above analytical model demonstrates that applying a uniaxial bend to the glass substrate 10 can generally direct the fracture 42 of the glass substrate 10 in a particular direction. In this regard, referring now to FIGS. 18-23, the consumer electronic device 64 includes a glass substrate 10. The glass substrate 10 is disposed over a display screen 72. The glass substrate 10 need not be abutting the display screen 72 to be disposed over the display screen 72 but can be. As discussed above, the glass substrate 10 has the length 26 and the width 20. The width 20 extends from the first side 22 to the second side 24 of the glass substrate 10. The consumer electronic device 64 further includes the component 50 that bends the glass substrate 10 along the bend axis 46 from the first position 38 (FIG. 18) to the second position 44 (FIGS. 19 and 20). The component 50 can be a structural component, such as a cover or frame. Note that in this embodiment of the glass substrate 10, the glass substrate 10 is bent in the first position 38, and bent to become flat in the second position 44. Further note that in this embodiment of the glass substrate 10, the bend axis 46 of the glass substrate 10 is generally parallel to the width 20 of the glass substrate 10. As explained above with the analytical model, upon formation of the fracture 42 of the glass substrate 10 in the second position 44 (FIG. 21), the fracture 42 propagates generally toward either the first side 22 or the second side 24 of the glass substrate 10, which is generally parallel to the bend axis 46. Note that the fracture 42 can bifurcate 70 while still generally propagating toward either the first side 22 or the second side 24 of the glass substrate 10. It is advantageous with consumer electronic devices 52 for the fracture 42 to propagate to either the first side 22 or the second side 24 of the glass substrate 10, so that the fracture 42 terminates as quickly as possible. In addition, forcing (via bending of the glass substrate 10) the fracture 42 to propagate to the first side 22 or the second side 24 of the glass substrate 10 prevents the fracture 42 from propagating along the entire length 26 of the glass substrate 10. A user often reads text that the display screen 72 displays from left-to-right (or from right-to-left, depending on language). A fracture 42 propagating along the length 26 of the glass substrate 10 would decrease the user's ability to read such text.

[0107] As discussed above, the glass substrate 10 can be (and in this embodiment is) tempered while in the first position 38 so that the first layer 28 of compressive stress extends from the first surface 12 of the glass substrate 10 to the depth of layer (DOC) within the thickness 18 of the glass substrate 10. Further as discussed above, by bending the glass substrate 10 in this manner from the first position 38 to the second position 44, the component 50 increases the compressive stress within the first layer 28. Bending of the glass substrate 10 within the consumer electronic device 64 thus provides two benefits—forced biasing of the fracture 42 to along the bend axis 46 (and therefore to the first side 22 or the second side 24) and an increased compressive stress at the first layer 28, which can help lower the risk of the glass substrate 10 of fracturing in the first instance.

[0108] In the illustrated embodiment, as mentioned above, the component 50 that bends the glass substrate 10 from the first position 38 to the second position 44 can be a structural component like the frame that compresses the glass substrate 10 from the first position 38 to the second position 44. Alternatively, the component 50 that causes the glass substrate 10 to bend from the first position 38 to the second position 44 can pull the glass substrate 10 to the second position 44. For example, as in the embodiment illustrated in FIGS. 22 and 23, the consumer electronic device 64 or automotive interior system (as shown in FIG. 25) can include an adhesive layer 74 that secures the glass substrate 10 in the second position 44. In other words, the component 50 that bends the glass substrate 10 from the first position 38 to the second position 44 is the adhesive layer 74. In the embodiment, the adhesive layer 74 is disposed between the glass substrate 10 and the display screen 72, with a backing plate 76 supporting the glass substrate 10 and the display screen 72. The consumer electronic device 64 can be any electronic device that the person 68 (see FIG. 24) utilizes, such as a phone 78, the watch 66, or a tablet 80. Note that in the embodiment of the watch 66, the glass substrate 10 can be non-planar (curved) in the second position 44, while in the embodiments of the phone 78 and the tablet 80, the glass substrate 10 can be planar (flat). In any event, the glass substrate 10 is bent from the first position 38 to the second position 44 during assembly of the consumer electronic device 64, to achieve the benefits described above.

[0109] Referring now to FIG. 25, the automotive interior system 100 can include a single or plurality of glass substrates 10 that are in a second position, which is curved at least uniaxially. In FIG. 24, the automotive interior system includes a center console 111 that includes two glass substrates 10 that are maintained, secured or held in a second position by a component 110. In one or more embodiments, the automotive interior system 10 includes a dashboard 200 with a curved component 220 that maintains, secures or holds the glass substrate 10 in a second position. Optionally, the instrument panel 250 also includes a component 240 that maintains, secures or holds glass substrate 10 in a second position. Steering wheel 300 of the automotive interior system 10 may include a component 320 that maintains, secures or holds glass substrate 10 in a second position. In each of these examples shown in FIG. 24, the glass substrate 10 is disposed over a display screen and/or a touch pane or touch enabled surface. As discussed above, the glass substrate 10 has the length 26 and the width 20. The width 20 extends from the first side 22 to the second side 24 of the glass substrate 10. The component in each of these embodiments can be a structural component, such as a cover or frame. The component may include an adhesive or plurality of adhesives that maintain, secure or hold the glass substrate in a second position. The automotive interior system may include an instrument panel, display, touch screen or touch-enabled surface that is disposed on a dashboard, a center console, an arm rest, a seat back, a headrest or other surface inside an automobile, seacraft, aircraft, drone or the like.

[0110] As discussed above, the glass substrate 10 can be (and in this embodiment is) tempered while in the first position 38 so that the first layer 28 of compressive stress extends from the first surface 12 of the glass substrate 10 to the depth of layer (DOC) within the thickness 18 of the glass substrate 10. Further as discussed above, by bending the glass substrate 10 in this manner from the first position 38 to the second position 44, the component 50 increases the compressive stress within the first layer 28. Bending of the glass substrate 10 within the automotive interior system 64 thus provides two benefits—forced biasing of the fracture 42 to along the bend axis 46 (and therefore to the first side 22 or the second side 24) and an increased compressive stress at the first layer 28, which can help lower the risk of the glass substrate 10 of fracturing in the first instance.

[0111] In the illustrated embodiment, as mentioned above, the component 50 that bends the glass substrate 10 from the first position 38 to the second position 44 (and maintains, secures or holds the glass substrate in the second position 44) can be a structural component like the frame and/or adhesive that compresses the glass substrate 10 from the first position 38 to the second position 44 and maintains, secures or holds the glass substrate in the second position.

[0112] Aspect (1) pertains to a glass substrate comprising: a first position, wherein a tensile stress of the glass substrate is insufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate; and a second position, wherein the glass substrate is bent relative to the first position, and wherein the tensile stress of the glass substrate is sufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate.

[0113] Aspect (2) pertains to the glass substrate of Aspect (1) further comprising: a first surface and a second surface; wherein, in the first position, the first surface and the second surface of the glass substrate are planar.

[0114] Aspect (3) pertains to the glass substrate of Aspect (1) or Aspect (2) further comprising: a first surface and a second surface; wherein, in the second position, the first surface and the second surface of the glass substrate are planar.

[0115] Aspect (4) pertains to the glass substrate of any one of Aspects (1) through (3), wherein, the small pieces are generally cubic shaped.

[0116] Aspect (5) pertains to the glass substrate of any one of Aspects (1) through (4), in the second position, the glass substrate is bent uniaxially along a bend axis of the glass substrate.

[0117] Aspect (6) pertains to the glass substrate of any one of Aspects (1) through (5), in the second position, the glass substrate is bent biaxially along two bend axes of the glass substrate.

[0118] Aspect (7) pertains to the glass substrate of any one of Aspects (1) through (6), wherein, in the first position, the glass substrate is flatter than the glass substrate is in the second position.

[0119] Aspect (8) pertains to the glass substrate of any one of Aspects (1) through (7), wherein, in the second position, the glass substrate is flatter than the glass substrate is in the first position.

[0120] Aspect (9) pertains to the glass substrate of any one of Aspects (1) through (8) further comprising: a thickness of 2 mm or less.

[0121] Aspect (10) pertains to a method of increasing compressive stress at a layer of a glass substrate comprising: providing a glass substrate; imparting a first compressive stress within a first layer from a first surface, and within a second layer from a second surface of the glass substrate; and bending the glass substrate along an axis of the glass substrate to add compressive stress to the first compressive stress within the second layer.

[0122] Aspect (11) pertains to the method of Aspect (10), wherein, imparting the first compressive stress within the first layer and the second layer of the glass substrate includes thermal tempering, mechanical tempering or chemical tempering of the glass substrate.

[0123] Aspect (12) pertains to the method of Aspect (10) or Aspect (11), wherein, imparting the first compressive stress within the first layer and within the second layer of the glass substrate includes chemical tempering of the glass substrate.

[0124] Aspect (13) pertains to the glass substrate of any one of Aspects (10) through (12), wherein, the second surface of the glass substrate is a top surface of the glass substrate.

[0125] Aspect (14) pertains to a method of reducing the size of the pieces that a glass substrate fragments into upon fracture of the glass substrate comprising: providing a glass substrate that fragments into pieces having a first size upon fracture of the glass substrate; and bending the glass substrate to a second position and maintaining the glass substrate in the second position, such that when the glass substrate fragments into pieces having a second size upon fracture of the glass substrate; wherein, the pieces having the second size are smaller than the pieces having the first size.

[0126] Aspect (15) pertains to the method of Aspect (14), wherein, forming the glass substrate includes forming the glass substrate with a thickness of 2 mm or less.

[0127] Aspect (16) pertains to the method of Aspect (14) or Aspect (15), wherein, bending the glass substrate includes biaxial bending of the glass substrate.

[0128] Aspect (17) pertains to the method of Aspect (16), wherein, when the glass substrate fragments, in the second position, upon fracture of the glass substrate, the pieces form an in-plane isotropic fracture pattern.

[0129] Aspect (18) pertains to the method of any one of Aspects (14) through (17), wherein, bending the glass substrate includes uniaxial bending of the glass substrate along a bend axis of the glass substrate.

[0130] Aspect (19) pertains to the method of any one of Aspects (14) through (18), wherein, forming the glass substrate includes forming the glass substrate with a first surface that is flat.

[0131] Aspect (20) pertains to the method of any one of Aspects (14) through (19), wherein, forming the glass substrate includes forming the glass substrate with a first surface that is curved; and wherein, bending the glass substrate to the second position includes bending the glass substrate so that the first surface is less curved in the second position than in the first position.

[0132] Aspect (21) pertains to the method of any one of Aspects (14) through (20), wherein, bending and maintaining the glass substrate in the second position is achieved at ambient temperature by a structural component of a product that utilizes the glass substrate.

[0133] Aspect (22) pertains to a product comprising: a glass substrate having a first position, wherein a tensile energy of the glass substrate is insufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate; and a component that bends the glass substrate away from its first position to a second position, wherein the tensile energy of the glass substrate is sufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate.

[0134] Aspect (23) pertains to the product of Aspect (22), wherein, the product is a consumer electronic device that is configured to be worn on a wrist of a person.

[0135] Aspect (24) pertains to the product of Aspect (22), wherein, the product is safety glass.

[0136] Aspect (25) pertains to the product of Aspect (22), wherein, the product is an automotive interior cover glass system.

[0137] Aspect (26) pertains to the product of any one of Aspects (22) through (24), wherein, the glass substrate has a first surface and a second surface; and wherein, in the second position, the first surface has a higher compressive stress than the second surface.

[0138] Aspect (27) pertains to a consumer or automotive interior electronic device comprising: a glass substrate disposed over a display screen, the glass substrate having a length, and a width extending from a first side to a second side; and a component that bends the glass substrate along a bend axis from a first position to a second position bent relative to the first position, such that upon fracture of the glass substrate in the second position, the fracture propagates generally toward the first side or the second side of the glass substrate; wherein, the bend axis is generally parallel to the width of the glass substrate.

[0139] Aspect (28) pertains to the product of Aspect (27), wherein, in the first position, the glass substrate has a first layer of compressive stress extending from a first surface; and

[0140] wherein, the component that bends the glass substrate to the second position increases the compressive stress within the first layer.

[0141] Aspect (29) pertains to the consumer or automotive interior electronic device of Aspect (27) or Aspect (28), wherein, the component that bends the glass substrate compresses the glass substrate from the first position to the second position.

[0142] Aspect (30) pertains to the consumer or automotive interior electronic device of any one of Aspects (27) through (29), wherein, the component that bends the glass substrate is an adhesive layer.

[0143] Aspect (31) pertains to the consumer or automotive interior electronic device of any one of Aspects (27) through (30), wherein the consumer electronic device is a smart phone, tablet, a watch or automotive display.

[0144] Aspect (32) pertains to a product comprising: a glass substrate having a first position, wherein a tensile energy of the glass substrate is insufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate; and a component that bends and maintains the glass substrate in a second position, wherein the tensile energy of the glass substrate is sufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate.

[0145] Aspect (33) pertains to the product of Aspect (32), wherein, the product is a consumer electronic device that is configured to be worn on a wrist of a person.

[0146] Aspect (34) pertains to the product of Aspect (32), wherein, the product is safety glass.

[0147] Aspect (35) pertains to the product of Aspect (32), wherein, the product is an automotive interior cover glass system.

[0148] Aspect (36) pertains to the product of any one of Aspects (32) through (35), wherein, the glass substrate has a first surface and a second surface; and wherein, in the second position, the first surface has a higher compressive stress than the second surface.

[0149] Aspect (37) pertains to a consumer or automotive interior electronic device comprising: a glass substrate disposed over a display screen, the glass substrate having a length, and a width extending from a first side to a second side; and a component that bends and maintains the glass substrate along a bend axis from a first position in a second position bent relative to the first position, such that upon fracture of the glass substrate in the second position, the fracture propagates generally toward the first side or the second side of the glass substrate; wherein, the bend axis is generally parallel to the width of the glass substrate.

[0150] Aspect (38) pertains to the consumer or automotive interior electronic device of Aspect (37) wherein, in the first position, the glass substrate has a first layer of compressive stress extending from a first surface; and wherein, the component that bends the glass substrate to the second position increases the compressive stress within the first layer.

[0151] Aspect (39) pertains to the consumer or automotive interior electronic device of Aspect (37) or Aspect (38) wherein, the component that bends the glass substrate compresses the glass substrate from the first position to the second position.

[0152] Aspect (40) pertains to the consumer or automotive interior electronic device of any one of Aspects (37) through (39), wherein, the component that bends the glass substrate is an adhesive layer.

[0153] Aspect (40) pertains to the consumer or automotive interior electronic device of any one of Aspects (37) through (40), wherein the consumer electronic device is a smart phone, tablet, a watch or an automotive display.

[0154] 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 claims.