Foldable cover article with reduced hazardous projections
A foldable cover article has a total thickness t≤300 μm, which is bendable to a minimum bending radius r≤20 mm without breakage and a pencil hardness HR≥HB. The foldable cover article includes a glass or glass-ceramic substrate with a thickness 5 μm≤t 1 ≤150 μm and a polymer layer and/or a hard material coating with a total thickness 5 μm≤t 2 ≤150 μm. For each 20 mm width of the foldable cover article, when the foldable cover article is broken upon bending along the direction perpendicular to the width, a number of projections with a longest linear extension L≥5 mm is less than 10 and/or a number of projections with a longest linear extension L<5 mm is less than 50.
1 . A foldable cover article having a total thickness t≤300 μm, which is bendable to a minimum bending radius r≤20 mm without breakage and a pencil hardness HR≥HB, and comprises:
a glass or glass-ceramic substrate with a thickness 5 μm≤t 1 ≤150 μm; and
a polymer layer and a hard material coating with a total thickness t 2 of the polymer layer and the hard material coating being 5 μm≤t 2 ≤150 μm; wherein for each 20 mm width of the foldable cover article, when the foldable cover article is broken upon bending along the direction perpendicular to the width, a number of projections with a longest linear extension L≥5 mm is less than 10 and/or a number of projections with a longest linear extension L<5 mm is less than 50, wherein at least one surface of the glass or glass ceramic substrate is coated with the hard material coating or a multi-layer coating of the hard material coating having a total thickness t 3 c≥ 1 μm, and each layer of the hard material coating or the multi-layer coating of the hard material coating is made of poly(methyl methacrylate) (PMMA) with inorganic nanoparticles, wherein the polymer layer is disposed on a first side of the glass or glass-ceramic substrate and the hard material coating is exposed and disposed on a second side of the glass or glass-ceramic substrate that is opposite the first side.
2 . The foldable cover article of claim 1 , wherein the glass or glass-ceramic substrate is toughened and has a minimum bending radius r 1 in millimeter r 1 ≤100000*t 1 /CS, wherein CS is a compressive stress in MPa measured on both surfaces of the glass or glass-ceramic substrate.
3 . The foldable cover article of claim 2 , wherein CT≤700 MPa, wherein CT is a center tension in MPa in a middle plane of the glass or glass-ceramic substrate.
4 . The foldable cover article of claim 2 , wherein the glass or glass-ceramic substrate has a depth of ion-exchange layer DoL≥1 μm and/or DoL≤t 1 /2.
5 . The foldable cover article of claim 2 , wherein the glass or glass-ceramic substrate has a two point bending strength BS≥700 MPa.
6 . The foldable cover article of claim 1 , wherein the polymer layer comprises a single polymer layer or multiple polymer layers with a total thickness t 3 p≥ 1 μm and/or of t 3 p< 150 μm.
7 . The foldable cover article of claim 6 , wherein the polymer layer or multiple polymer layers have a Young's modulus Ep≤10 GPa and/or Ep≥0.1 GPa.
8 . The foldable cover article of claim 6 , wherein the polymer layer or multiple polymer layers are made of a polymer selected from the group consisting of Parylene, thermoplastic polyurethane (TPU), polycarbonate (PC), polysulfone (PS), polyethersulfone (PES), polyetheretherketone (PEEK), polyamide (PA), polyamideimide (PAI), polyimide (PI), poly(methyl methacrylate) (PMMA), polyimethylsiloxane (PDMS), and combinations thereof.
9 . The foldable cover article of claim 1 , wherein t 3 c< 150 μm.
10 . The foldable cover article of claim 9 , wherein the hard material coating or multiple hard material coatings have a Young's modulus Eh≥1 GPa and/or Eh≤15 GPa.
11 . The foldable cover article of claim 9 , wherein the hard material coating or multiple hard material coatings are further made of at least one of an organic polymer material, an acrylate, a modified form of acrylate, an inorganic-organic hybrid polymer material, a polysiloxane, a modified form of polysiloxane, or an epoxy-siloxane hybrid.
12 . The foldable cover article of claim 1 , wherein the foldable cover article has a pencil hardness less than 8H on a side laminated with the polymer layer and the hard material coating.
13 . The foldable cover article of claim 1 , wherein the polymer layer comprises a layer of polyethylene terephthalate (PET).
14 . The foldable cover article of claim 13 , wherein the polymer layer comprises multiple polymer layers, wherein one of the multiple polymer layers comprises PET and one of the multiple polymer layers comprises an acrylate.
15 . A foldable cover article having a total thickness t≤300 μm, which is bendable to a minimum bending radius r≤20 mm without breakage and a pencil hardness HR≥HB, and comprises:
a glass or glass-ceramic substrate with a thickness 5 μm≤t 1 ≤150 μm; and
a hard material coating applied to a first surface of the glass or glass-ceramic substrate, the hard material coating or a multi-layer coating of the hard material coating having a total thickness t 3 c≥ 1 μm; wherein for each 20 mm width of the foldable cover article, when the foldable cover article is broken upon bending along the direction perpendicular to the width, a number of projections with a longest linear extension L≥5 mm is less than 10 and/or a number of projections with a longest linear extension L<5 mm is less than 50, each layer of the hard material coating or the multi-layer coating of the hard material coating comprising poly(methyl methacrylate) (PMMA), wherein the hard material coating is an exposed material layer; and
an adhesive layer applied to a second surface of the glass or glass-ceramic substrate that is opposite the first surface.
16 . The foldable cover article of claim 15 , wherein each layer of the hard material coating or the multi-layer coating of the hard material coating comprises PMMA with inorganic nanoparticles.
17 . The foldable cover article of claim 15 , wherein the adhesive layer comprises an optical clear adhesive.
18 . The foldable cover article of claim 15 , further comprising a polymer layer, the adhesive layer being sandwiched between the polymer layer and the glass or glass-ceramic substrate.
19 . The foldable cover article of claim 15 , wherein the total thickness t 3 c is no more than 150 μm.