Method of separating strengthened glass
A method of cutting a glass sheet that has been thermally or chemically strengthened along a predetermined line, axis, or direction with high speed and with minimum damage on the cut edges. The strengthened glass sheet may be an aluminoborosilicate glass material having at least one alkali metal oxide modifier, and the ratio Al 2 O 3 ( mol % ) + B 2 O 3 ( mol % ) ∑ modifiers ( mol % ) > 1. At least one damage line is formed within the strengthened glass sheet. The at least one damage line is formed outside the strengthened compressive stress surface layers and within the tensile stress layer of the strengthened glass sheet. The at least one damage line may be formed by laser treatment. A crack is initiated in the strengthened glass sheet and propagated along the at least one damage line to separate the strengthened glass sheet along the predetermined line, axis, or direction into at least two pieces.
1. A method of separating a strengthened glass sheet, the method comprising:
providing the strengthened glass sheet, the strengthened glass sheet having a first surface and a second surface, wherein:
each of the first surface and the second surface has a strengthened surface layer under a compressive stress and extending from the surface to a depth of layer, and wherein the strengthened glass sheet has a central region under tensile stress; and
the strengthened glass sheet comprises an aluminoborosilicate glass material having at least one alkali metal oxide modifier, and the ratio
Al
2
O
3
(
mol
%
)
+
B
2
O
3
(
mol
%
)
∑
modifiers
(
mol
%
)
>
1
;
forming at least one laser-induced damage line in the central region at a predetermined depth below the first surface by irradiating the strengthened glass sheet with a nanosecond pulsed laser, wherein the nanosecond pulsed laser is operated at a power of less than about 4W; and
initiating and propagating a crack to separate the strengthened glass sheet into at least two pieces along the at least one damage line.
2. The method of claim 1 , wherein forming the at least one damage line in the central region comprises forming a first damage line and a second damage line in the central region, the second damage line being located between the strengthened surface layer of the first surface and the first damage line, the first damage line and the second damage line defining a plane perpendicular to the first surface and the second surface.
3. The method of claim 1 , wherein the strengthened surface layers of the first surface and the second surfaces are chemically strengthened surfaces.
4. The method of claim 1 , wherein the strengthened surface layers are ion exchanged chemically strengthened surfaces.
5. The method of claim 4 , wherein the strengthened surface layers of the first surface and the second surfaces have a compressive stress of at least about 400 MPa, the depth of layer is at least about 15 μm, and the central region has a tensile stress greater than about 15 MPa.
6. The method of claim 4 , wherein the aluminoborosilicate glass material comprises:
60-72 mol % SiO 2 ; 9-16 mol % Al 2 O 3 ; 5-12 mol % B 2 O 3 ; 8-16 mol % Na 2 O; and 0-4 mol % K 2 O.
7. The method of claim 1 , wherein
Al
2
O
3
(
mol
%
)
+
B
2
O
3
(
mol
%
)
∑
modifiers
(
mol
%
)
>
1.45
.
8. The method of claim 1 , wherein the strengthened glass sheet has a Vickers median/radial crack initiation threshold of at least 10 kgf.
9. A method of separating a strengthened glass sheet, the method comprising:
providing the strengthened glass sheet, the strengthened glass sheet having a first surface and a second surface, wherein:
each of the first surface and the second surface have a strengthened surface layer under a compressive stress and extending from the surface to a depth of layer, and wherein the strengthened glass sheet has a central region under a tensile stress; and
the strengthened glass sheet comprises an aluminoborosilicate glass material having at least one alkali metal oxide modifier, and the ratio
Al
2
O
3
(
mol
%
)
+
B
2
O
3
(
mol
%
)
∑
modifiers
(
mol
%
)
>
1
;
forming a first laser-induced damage line in the central region at a predetermined depth below the first surface;
forming a second laser-induced damage line, wherein:
the second laser-induced damage line is located between the strengthened surface layer of the first surface and the first laser- induced damage line;
the second laser-induced damage line is parallel to the first laser-induced damage line; and
the first laser-induced damage line and the second laser-induced damage line define a plane being perpendicular to the first surface and the second surface; and
wherein the first and second laser-induced damage lines are formed by irradiating the strengthened glass sheet with a nanosecond pulsed laser, wherein the nanosecond pulsed laser is operated at a power of less than about 4W; and
initiating and propagating a crack to separate the strengthened glass sheet into at least two pieces, wherein at least one of the pieces has at least one of a predetermined shape and a predetermined dimension.
10. The method of claim 9 , wherein the strengthened surface layers are ion exchanged chemically strengthened surfaces.
11. The method of claim 10 , wherein the strengthened surface layers of the first surface and the second surfaces have a compressive stress of at least about 400 MPa, the depth of layer is at least about 15 μm, and the central region has a tensile stress greater than about 15 MPa.
12. The method of claim 11 , wherein the aluminoborosilicate glass material comprises: 60-72 mol % SiO 2 ; 9-16 mol % Al 2 O 3 ; 5-12 mol % B 2 O 3 ; 8-16 mol % Na 2 O; and 0-4 mol % K 2 O.
13. The method of claim 9 , wherein
Al
2
O
3
(
mol
%
)
+
B
2
O
3
(
mol
%
)
∑
modifiers
(
mol
%
)
>
1.45
.