US-12624260-B2 - Optically clear silicone acrylate adhesive composition

US12624260B2US 12624260 B2US12624260 B2US 12624260B2US-12624260-B2

Abstract

A composition includes: (a) 10-90 mass-percent of an organopolysiloxane resin; (b) 10-90 mass-percent of a (meth)acrylate component consisting of: (i) at least one monofunctional (meth)acrylate that contains an ether group and/or a hydroxyl group; and optionally (ii) at least one monofunctional (meth)acrylate containing alkyl groups and that is free of ether and hydroxyl groups; where the molar ratio of (ii) to (i) is in a range of 0:1 to 22:1 and wherein when the (meth)acrylate component comprises a monofunctional (meth)acrylate that contains a hydroxyl group then it also comprises as part of component (i) at least one of a monofunctional (meth)acrylate that contains an ether group and/or component (ii) a monofunctional (meth)acrylate containing alkyl groups and that is free of ether and hydroxyl groups; (c) 0.11-11 mass-percent of a crosslinker; and (d) 0.1-10 mass-percent of a photoradical initiator; where mass-percentages are relative to the combined mass of components (a)-(c).

Inventors

Juyoung YOOK
Minkyu KYEONG
Hyochul KIM

Assignees

DOW SILICONES CORPORATION

Dates

Publication Date: 20260512
Application Date: 20230808

Claims (10)

1 . A composition comprising the following components: (a) 10 to 90 mass-percent of an organopolysiloxane resin containing at least 60 mole-percent T siloxane units where the molar ratio alkyl groups to aryl groups in the organopolysiloxane resin is in a range of 0:1 to 4:1; (b) 10 to 90 mass-percent of a (meth) acrylate component consisting of: (i) at least one monofunctional (meth) acrylate that contains an ether group and/or a hydroxyl group; and optionally (ii) at least one monofunctional (meth) acrylate containing alkyl groups and that is free of ether and hydroxyl groups; where the molar ratio of (ii) to (i) is in a range of 0:1 to 22:1 and wherein when the (meth) acrylate component comprises a monofunctional (meth) acrylate that contains a hydroxyl group then it also comprises as part of component (i) at least one of a monofunctional (meth) acrylate that contains an ether group and/or component (ii) a monofunctional (meth) acrylate containing alkyl groups and that is free of ether and hydroxyl groups; (c) 0.1 to 11 mass-percent of a crosslinker having an average of at least two ethylenically unsaturated double bonds per molecule; and (d) 0.1 to 10 mass-percent of a photoradical initiator; where mass-percentages are relative to the combined mass of components (a)-(c) and wherein the mass percentage of components (a)-(c) add up to 100 mass-percent.
2 . The composition of claim 1 , wherein the concentration of the component (a) is 10 to 60 mass percent and the combined concentration of component (b) and component (c) is 40-90 mass-percent relative to the combine mass of components (a)-(c).
3 . The composition of claim 1 , wherein component (a) has an average chemical composition (I): M a D b T c Q d (I) where: subscript a is the molar ratio of M siloxane units relative to moles of all siloxane units and has an average value in a range of zero to 0.35; subscript b is the molar ratio of D siloxane units relative to moles of all siloxane units and has an average value in a range of zero to 0.35; subscript c is the molar ratio of T siloxane units relative to moles of all siloxane units and has an average value in a range of 0.50 to 1.00; subscript d is the molar ratio of Q siloxane units relative to moles of all siloxane units and has an average value in a range of zero to 0.50; the sum of subscripts a+b+c+d is equal to 1.00; the molar ratio of alkyl and aryl groups is in a range of 0:1 to 4:1; the concentration of OZ groups is in a range of zero to 100 mole-percent based on moles of organopolysiloxane resin; and the ratio of subscripts a/c is in a range of zero to 0.5, the ratio of subscripts b/c is in a range of zero to 0.5; the ratio of subscript d/c is in a range of zero to 0.8.
4 . The composition of claim 1 , wherein component (b) (i) is one or a combination of more than one compound selected from (meth) acrylate functional ethylene glycol, (meth) acrylate functional propylene glycol, (meth) acrylate functional polyethers comprising multiple ethylene oxide and/or a propylene oxide units, and hydroxyl functional (meth) acrylate functional compounds.
5 . The composition of claim 1 , wherein component (c) is a compound comprising on average at least two ethylenically unsaturated double bonds where at least one of the ethylenically unsaturated double bonds is part of a (meth) acryloyloxy group.
6 . The composition of claim 1 , wherein the composition is free of plasticizer.
7 . A process comprising using the composition of claim 1 as an adhesive, the process comprising the steps of applying the composition onto a first object and then applying a second object to the composition so as to sandwich the composition between and in contact with the first and second objects.
8 . The process of claim 7 , further comprising curing the composition while between and in contact with the first and second objects by exposing the composition to ultraviolet light.
9 . The process of claim 7 , further comprising pre-curing the composition by exposing the composition to ultraviolet light after applying the composition to the first object and before applying the second object to the composition.
10 . The process of claim 7 , wherein a concentration of the component (a) in the composition is 10 to 60 mass percent, a combined concentration of component (b) and component (c) is 40 to 90 mass-percent relative to the combined mass of components (a)-(c), and the composition is applied to the first object using an inkjet method.

Description

FIELD OF THE INVENTION The present invention relates to curable silicone-based compositions that cure under ultraviolet light exposure to optically clear adhesive materials. INTRODUCTION Photocurable optically clear adhesives, particularly photocurable liquid optically clear adhesives, have application in optical bonding for electronic devices such as optical displays. Photocurable optically clear adhesives optically couple elements in display applications where optically coupled elements can include display panels, glass plates, touch panels, diffuser, stiffness compensators, heaters and flexible films such as polarizers and retarders. (Meth)acrylate materials are common in photocurable adhesives. However, (meth)acrylate compositions tend to suffer from shrinkage when they cure, particularly when large amounts of acrylate monomer is present to keep the composition viscosity low enough to facilitate inkjet printing of the composition. Shrinkage corresponds to dimensional instability, which is undesirable in an adhesive because it can result in pulling away or delamination from the elements the adhesive is to be adhering together. It is known that adding plasticizer to a (meth)acrylate composition can reduce shrinkage of the composition during curing, but then the composition retains residual plasticizer and that is often undesirable. So it would be desirable to avoid use of plasticizers. It would advance the art of photocurable optically clear adhesives to identify a (meth)acrylate composition that serves as s photocurable adhesive that has a viscosity at 25 degrees Celsius (° C.) in a range of 10-100,000 millipascal*seconds (mPa*s), and preferably that has a viscosity of at least 10 mPa*s at 25° C. while at the same time having a viscosity of 50 mPa*s or lower at 60° C. so it is suitable for inkjet applications, and that after photocuring has a transparency of greater than 90% at 550 nanometers through a one millimeter thick film of cured composition, a shear storage modulus in a range of one to 5,000 kiloPascals (kPa) at one hertz and 1% shear rate over 25-80° C., peal adhesion to polyethylene terephthalate (PET) of greater than 38.6 Newtons per meter (greater than 100 gram force per inch) and that experiences less than 8% shrinkage upon curing as described herein below. It is particularly desirable to achieve those properties without use of a plasticizer. BRIEF SUMMARY OF THE INVENTION The present invention solves the problem of providing a photocurable optically clear adhesive in the form of a (meth)acrylate composition having a viscosity at 25 degrees Celsius (° C.) in a range of 10-100,000 millipascal*seconds (mPa*s), and even can have a viscosity of at least 10 mPa*s at 25° C. while at the same time having a viscosity of 50 mPa*s or lower at 60° C. so it is suitable for inkjet applications, and that after photocuring has a transparency of greater than 90% at 550 nanometers through a one millimeter thick film of cured composition, a storage modulus in a range of one to 5,000 kiloPascals (kPa) at one hertz and 1% shear rate over 25-80° C., peal adhesion to PET of greater than 38.6 Newtons per meter (greater than 100 gram force per inch) and that experiences less than 8% shrinkage upon curing as described herein below. It has been discovered that the composition of the present invention can achieve these properties without use of a plasticizer. It has also been discovered that the inventive composition can be inkjet dispensable. The present invention is a result of surprisingly and unexpectedly discovering that including in the (meth)acrylate photocurable composition of the present invention an organopolysiloxane resin containing at least 50 mol-percent (mol %) “T” siloxane units where the molar ratio of alkyl to aryl groups in the organopolysiloxane resin is in a range of 0:1 to 4:1 and the concentration of hydroxyl and alkoxyl groups (collectively “OZ” groups) bonded to silicon atoms in the organopolysiloxane is in a range of zero to 100 mole-percent based on moles of organopolysiloxane resin serves as an adhesion promoter and enables solving the aforementioned problems. Of particular surprise is the fact that the organopolysiloxane resin reduces shrinkage of the composition upon curing. In a first aspect, the present invention is a composition comprising the following components: (a) 10 to 90 mass-percent of an organopolysiloxane resin containing at least 50 mole-percent T siloxane units where the molar ratio alkyl groups to aryl groups in the organopolysiloxane resin is in a range of 0:1 to 4:1; (b) 10 to 90 mass-percent of a (meth)acrylate component consisting of: (i) at least one monofunctional (meth)acrylate that contains an ether group and/or a hydroxyl group; and optionally (ii) at least one monofunctional (meth)acrylate containing alkyl groups and that is free of ether and hydroxyl groups; where the molar ratio of (ii) to (i) is in a range of 0:1 to 22:1 and wherein when the (meth)acrylate com