Cold-formed laminates
The principles and embodiments of the present disclosure relate generally to complexly curved laminates made from a complexly curved substrate and a flat substrate, such as automotive window glazings, and methods of cold forming complexly-curved glass products from a curved substrate and a flat substrate. In one or more embodiments, the laminate includes first complexly-curved glass substrate with a first surface and a second surface opposite the first surface, a second complexly-curved glass substrate with a third surface and a fourth surface opposite the third surface with a thickness therebetween; and a polymer interlayer affixed to the second convex surface and third surface, wherein the third surface and fourth surface have compressive stress values respectively that differ such that the fourth surface has as compressive stress value that is greater than the compressive stress value of the third surface.
1. A laminate comprising:
a first complexly-curved glass substrate comprising a first surface, a second surface opposite the first surface, and a first thickness therebetween;
a second complexly-curved glass substrate comprising a third surface, a fourth surface opposite the third surface, and a second thickness therebetween; and
a polymer interlayer affixed to the second surface and the third surface, wherein:
the first complexly-curved glass substrate is hot-formed and curved along at least a first axis and a second axis, and
the second complexly-curved glass substrate is cold-formed against the first complexly-curved glass substrate via the polymer interlayer at a temperature that is 200° or more below a softening point of the second complexly-curved glass substrate.
2. The laminate of claim 1 , wherein the first complexly-curved glass substrate comprises a soda lime glass or an alkali-containing borosilicate glass.
3. The laminate of claim 2 , wherein the second complexly-curved glass substrate comprises a soda lime glass or an alkali aluminosilicate glass.
4. The laminate of claim 1 , wherein the polymer interlayer comprises a thickness that is greater than or equal to 0.3 mm and less than or equal to 2.0 mm, wherein the polymer interlayer comprises polyvinyl butyral, ethylene-vinyl acetate, an ionomer, a polyvinyl chloride copolymer, or a thermoplastic polyurethane.
5. The laminate of claim 1 , wherein the laminate exhibits a radius of curvature of 5 m or less along at least one of the first axis and the second axis.
6. The laminate of claim 1 , wherein the first thickness is more than two times the second thickness.
7. The laminate of claim 1 , wherein:
the second complexly-curved glass substrate is chemically strengthened and comprises a surface compressive stress that is 300 MPa or greater,
the second complexly-curved glass substrate comprises a depth of layer that is 30 μm or greater, and
the second complexly-curved glass substrate exhibits a maximum central tension value that is greater than 20 MPa and less than 100 MPa.
8. The laminate of claim 1 , wherein the laminate comprises a windshield, a backlight, a sunroof, a roof panel, or a sidelight.
9. The laminate of claim 1 , wherein:
the second complexly-curved glass substrate is fusion-formed and comprises an as-formed Ra surface roughness that is less than 0.3 nm, and
the first complexly-curved glass substrate is float-formed and comprises an as-formed Ra surface roughness that is greater than or equal to 0.6 nm.
10. The laminate of claim 1 , wherein a central area of the laminate does not exhibit visible optical distortion in transmission, wherein optical distortion is evaluated according to ASTM Standard C1036-06.
11. The laminate of claim 10 , wherein the first thickness is greater than or equal to 1.6 mm and less than or equal to 3.85 mm.
12. The laminate of claim 11 , wherein the second thickness is greater than or equal to 0.5 mm and less than or equal to 1.4 mm.
13. The laminate of claim 1 , wherein the laminate exhibits a radius of curvature that is less than 750 mm.
14. The laminate of claim 1 , wherein at least one of the first complexly-curved glass substrate and the second complexly curved glass substrate comprises at least one surface that is flat such that a 1 cm lengthwise profile along that surface stays within 50 μm of a straight line.
15. The laminate of claim 1 , wherein the second complexly curved glass substrate is substantially free of wrinkles.
16. The laminate of claim 1 , wherein, from second complexly-curved glass substrate being cold-formed:
the third surface experiences tensile stresses, and
the fourth surface experiences compressive stresses.
17. A laminate comprising:
a first complexly-curved glass substrate comprising a first surface, a second surface opposite the first surface, and a first thickness therebetween;
a second complexly-curved glass substrate comprising a third surface, a fourth surface opposite the third surface, and a second thickness therebetween; and
a polymer interlayer affixed to the second surface and the third surface, wherein:
the first complexly-curved glass substrate is hot-formed and curved along at least a first axis and a second axis,
the second complexly-curved glass substrate is cold-formed against the first complexly-curved glass substrate via the polymer interlayer at a temperature that is 200° or more below a softening point of the second complexly-curved glass substrate,
from second complexly-curved glass substrate being cold-formed, the third surface experiences tensile stresses and the fourth surface experiences compressive stresses, and
prior to being cold-formed, the third surface and the fourth surface exhibit either: (a) no appreciable compressive stress; or (b) equal compressive stresses.
18. The laminate of claim 17 , wherein:
the first complexly-curved glass substrate comprises a soda lime glass or an alkali-containing borosilicate glass, and
the second complexly-curved glass substrate comprises a soda lime glass or an alkali aluminosilicate glass.
19. The laminate of claim 18 , further comprising a coating disposed on the fourth surface, wherein:
the laminate exhibits a radius of curvature of 5 m or less along at least one of the first axis and the second axis,
the first thickness is more than two times the second thickness,
the first thickness is greater than or equal to 1.6 mm and less than or equal to 3.85 mm, and
the second thickness is greater than or equal to 0.5 mm and less than or equal to 1.4 mm.
20. The laminate of claim 19 , wherein cold-forming of the second complexly-curved glass substrate does not result in visible degradation of the transmitted optical distortion of the second complexly-curved glass substrate, evaluated according to ASTM Standard C1036-06.