Electrically debondable UV activated adhesives
Curable and cured compositions as well as articles containing the curable or cured compositions are provided. The cured compositions are typically a semi-structural or structural adhesive. Advantageously, the cured compositions can be removed (e.g., de-bonded) from the various surfaces of the articles after the useful lifetime of the articles, to correct misplacement of a part during manufacturing, or to repair the electronic device. The separation step occurs using a direct current electric potential across the cured composition.
1 . A curable composition comprising:
a film forming polymeric material;
an epoxy resin;
a photoacid generator; and
an ionic liquid that has a melting point less than 100 degrees Celsius and that has an anion selected from SbF 6 − , PF 6 − , or a mixture thereof.
2 . The curable composition of claim 1 wherein the film forming polymeric material comprises a (meth)acrylic-based block copolymer, a statistical (meth)acrylic-based copolymer, or a combination thereof.
3 . The curable composition of claim 1 wherein the curable composition comprises (meth)acrylic-based block copolymer, wherein the (meth)acrylic-based block copolymer is a triblock copolymer of formula A-B-A with the A blocks microphase separating from the B block, wherein the A block has a glass transition temperature equal to at least 50 degrees Celsius and the B block has a glass transition temperature equal to no greater than 20 degrees Celsius as measured using Dynamic Mechanical Analysis.
4 . The curable composition of claim 2 wherein the curable composition comprises 10 to 40 weight percent of the (meth)acrylic-based block copolymer based on a total weight of resin components in the curable composition.
5 . The curable composition of claim 2 wherein the curable composition comprises greater than 40 wt. % of the (meth)acrylic-based block copolymer based on a total weight of resin components in the curable composition.
6 . The curable composition of claim 2 wherein the curable composition comprises statistical (meth)acrylic-based copolymer having a glass transition temperature no greater than 20 degrees Celsius when measured using Dynamic Mechanical Analysis.
7 . The curable composition of claim 2 wherein the statistical (meth)acylate-based copolymer is crosslinked.
8 . The curable composition of claim 2 wherein the curable composition contains 20 to 60 weight percent of the statistical (meth)acrylic-based copolymer based on a total weight of resin components in the curable composition.
9 . The curable composition of claim 2 wherein the curable composition comprises greater than 60 weight percent up to 90% of the statistical (meth)acrylic-based copolymer based on a total weight of resin components in the curable composition.
10 . The curable composition of claim 2 wherein the statistical (meth)acrylic-based copolymer comprises monomeric units derived from a (meth)acrylate macromer having a number average molecular weight of at least 300 Daltons, a polyol, or a combination thereof.
11 . The curable composition of claim 1 wherein the statistical (meth)acrylic-based comprises at least 10 wt. % of polymerized units of a (meth)acrylate monomer having a Tg of at least 30° C.
12 . The curable composition of claim 1 wherein the film forming polymeric material comprises polyurethane, polyester, polyvinyl acetal, a block copolymer of styrene and isoprene or butadiene, or a combination thereof.
13 . The curable composition of claim 1 wherein the film forming polymeric material has a molecular weight greater than 50,000 Daltons.
14 . The curable composition of claim 1 wherein the photoacid generator is an aryl-containing iodonium salt or a triaryl sulfonium salt.
15 . The curable composition of claim 1 wherein the ionic liquid is an ammonium salt of Formula (VI), a sulfonium salt of Formula (VII), an imidazolium salt of Formula (VIII), a pyridinium salt of Formula (IX), or a pyrrolidinium salt of Formula (X)
wherein
each R 20 , R 21 , R 22 , R 23 , and R 24 is independently an alkyl, a hydroxy-substituted alkyl, or an ether-containing group of formula —(R 30 —O) y —R 31 wherein R 30 is an alkylene, R 31 is an alkyl, and y is an integer in a range of 1 to 10; and
X − is SbF 6 − or PF 6 − .
16 . A first article comprising:
a layer of a curable composition according to claim 1 wherein the curable composition has a first surface and a second surface opposite the first surface; and
a first substrate or a first release liner positioned adjacent to a first surface of the first curable composition.
17 . The first article of claim 16 wherein the layer of curable composition comprises an electrically conductive layer.
18 . A second article comprising:
a first substrate;
a second substrate; and
a layer of cured composition of claim 1 positioned between the first substrate and the second substrate, wherein the first substate is bonded to the second substrate with the first cured composition.
19 . The second article of claim 18 wherein the first substrate, the second substrate, or both are electrically conductive or the layer of cured composition comprises an electrically conductive layer.
20 . A method for separating the second article of claim 18 the comprising applying a direct current electric potential across the cured composition to separate the first substrate from the second substrate.