Curable silicone optically clear adhesives and uses thereof
Silicone optically clear adhesives compositions and films with pressure sensitive properties are described. The silicone optically clear adhesives compositions are thermal, UV curable, or UV-moisture dual curable. The silicone optically clear adhesives are suitable for sealing and bonding cover glasses, touch panels, diffusers, rigid compensators, heaters, and flexible films, polarizers and retarders in the optical display devices, and are particularly suitable in flexible and foldable displays.
1. A thermally curable silicone optically clear adhesive comprising:
(a) about 95 to about 99.999% of a reaction product of:
(i) about 1 to about 30% of a hydroxy terminated siloxane polymer having a number average molecular weight greater than about 50,000 g/mol;
(ii) about 10 to about 50% of a hydroxy terminated siloxane polymer having a number average molecular weight less than about 30,000 g/mol;
(iii) about 10 to about 50% of a reactive silicone resin;
(iv) about 0.1 to about 10% of a vinylalkoxy functional silane; and
(v) about 0.001 to about 1% of (v1) an acid having a pKa value equal to or less than −6 or (v2) a base catalyst having a pKa value equal to or greater than 15;
(b) about 0.1 to about 10% of a hydride functional siloxane polymer; and;
(c) about 0.001 to about 5% of a thermally curing catalyst.
2. The thermally curable silicone optically clear adhesive of claim 1 , wherein the hydroxy terminated siloxane polymer is polydimethylsiloxane polymers with α,ω-endcapped hydroxy.
3. The thermally curable silicone optically clear adhesive of claim 1 , wherein the (iii) reactive silicone resin is tetrafunctional siloxy units (SiO4/2) and triorganosiloxy units (R3Si01/2),
wherein the R is hydroxy group and methyl group,
wherein the mole ratio of the units of the SiO4/2 to the R3SiO1/2 is from 1:2 to 2:1, and
wherein the number average molecular weight of the reactive silicon resin is from about 500 to 200,000 g/mol.
4. The thermally curable silicone optically clear adhesive of claim 1 , wherein the (iv) vinylalkoxy functional silane is selected from the group consisting of vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane and mixtures thereof.
5. The thermally curable silicone optically clear adhesive of claim 1 , wherein the (v) catalyst is selected from the group consisting KOH, NaOH, LiOH, organolithium reagents, Grignard reagents, methanesulfonic acid, sulfuric acid, and mixtures thereof.
6. The thermally curable silicone optically clear adhesive of claim 1 , wherein the (b) hydride functional siloxane polymer is polydimethylsiloxane polymer or oligomer with (1) terminal functional groups of SiMe2H, (2) pedant functional groups of SiMeH, or (3) mixtures thereof;
wherein the number average molecular weight (Mn) of the reactive silicon resin is from about 200 to 50,000 g/mol.
7. The thermally curable silicone optically clear adhesive of claim 1 , wherein the (c) thermally curing catalyst is Speier's catalyst H2PtCl6, Karstedt's catalyst or mixtures thereof.
8. A cured composition of the thermally curable silicone optically clear adhesive of claim 1 , wherein the cured composition has
an elastic shear modulus (G′) at 25° C., less than about 1.5×106 dyn/cm, and
T-peel adhesion, greater than about 1 oz/in between two PET films according to ASTM D1876.
9. An article comprising the cured composition of the thermally curable silicone optically clear adhesive of claim 8 .
10. A method of forming a thermally curable silicone optically clear adhesive comprising the steps of:
(1) preparing a reaction product by mixing in an organic solvent at about 60 to about 150° C. of:
(i) about 1 to about 30% of a hydroxy terminated siloxane polymer having a number average molecular weight greater than about 50,000 g/mol;
(ii) about 10 to about 50% of a hydroxy terminated siloxane polymer having a number average molecular weight less than about 30,000 g/mol;
(iii) about 10 to about 50% of a reactive silicone resin;
(iv) about 0.1 to about 10% of a vinylalkoxy functional silane; and
(v) about 0.001 to about 1% of (v1) an acid having a pKa value equal to or less than −6 or (v2) a base catalyst having a pKa value equal to or greater than 15; and
(2) adding about 0.1 to about 5% of a (b) hydride functional siloxane polymer and (c) about 0.001 to about 5% of a thermally curing catalyst at room temperature.