Debondable compositions
Dual-cure compositions for use in high temperature adhesive applications, and particularly for temporarily adhesively attaching one substrate to another substrate, are provided. These dual-cure adhesives are silicone-based compositions that can be B-staged by exposure UV radiation to provide initial green strength, followed by a C-stage cure to give adhesives that can survive high temperature processes above 200° C., especially above 300° C., yet easy to debond afterwards to allow separation of the top and bottom substrates.
1. A composition radiation curable to form a pressure sensitive adhesive, comprising:
at least one photoinitiator selected from an acyl phosphine oxide photoinitiator, an alpha-hydroxyl ketone photoinitiator and a phenylglyoxalate photoinitiator; and
a mixture of polysiloxane resins including:
a polysiloxane resin (a) having a vinylsiloxane unit, a molecular weight (Mw) of 2323 to 242352 and a structure represented by:
a polysiloxane resin (b) having at least two (meth)acrylate groups and a structure selected from at least one of:
wherein the composition is free of hydridosilane and hydridopolysiloxane; and the weight ratio of polysiloxane resin (a) to polysiloxane resin (b) in the composition is within the range of 97:3 to 40:60 and the vinyl functionality to acrylate functionality in the composition is within the range of 21:1 to 0.29:1; or the weight ratio of polysiloxane resin (a) to polysiloxane resin (b) in the composition is within the range of 99:1 to 90:10 and the vinyl functionality to acrylate functionality in the composition is within the range of 19:1 to 1.4:1.
2. The composition of claim 1 ; wherein the composition further comprises a thermal initiator.
3. The composition of claim 1 ; wherein the polysiloxane resins therein consist of polysiloxane resin (a) and polysiloxane resin (b).
4. The composition of claim 1 ; wherein:
1) the composition further comprises a thermal initiator; and
2) the polysiloxane resins therein consist of polysiloxane resin (a) and polysiloxane resin (b).
5. The composition of claim 1 wherein exposure in a photorheometer to UVA radiation at 230 mW/cm 2 for 5 minutes forms a pressure sensitive adhesive having a storage modulus (G′) of less than or equal to 3.0×10 5 Pa, at 25° C. and 1 Hz.
6. The composition of claim 1 , wherein the polysiloxane resin (a) has a mole % of vinylmethylsiloxane units in the range of 4.0-13.0%.
7. The composition of claim 1 , wherein
(i) the photoinitiator is a combination of
and further comprising 1,1-di-(t-amylperoxy)-cyclohexane as a thermal initiator, or
(ii) the photoinitiator is
and the composition further comprises 3,5-dimethyl-hexyn-3-ol.
8. The composition of claim 1 , wherein the polysiloxane resin (a) has
a mole % of vinylmethylsiloxane units in the range of 1-99%.
9. Cured reaction products of the composition of claim 1 .
10. An assembly comprising: a substrate,
a carrier, and the composition of claim 1 disposed between the carrier and the substrate.
11. A method for bonding a substrate to a carrier comprising:
(a) providing a substrate;
(b) providing a carrier;
(c) disposing the composition of claim 1 onto at least one of the substrate or the carrier;
(d) contacting the substrate and carrier so that the composition is disposed between the carrier and the substrate, forming an assembly; and
(e) radically curing the composition by
(i) exposing the assembly to radiation in the electromagnetic spectrum;
(ii) exposing the assembly to elevated temperature conditions, or
(iii) (i) followed by (ii).
12. A method for debonding a substrate from a carrier to which the substrate is adhesively bonded, comprising:
(a) providing an assembly comprising the substrate and the carrier with the composition of claim 1 therebetween; and
(b) separating the substrate from the carrier.