| CPC C09J 7/385 (2018.01) [C09J 11/08 (2013.01); C09J 2203/318 (2013.01); C09J 2203/326 (2013.01); C09J 2301/412 (2020.08); C09J 2301/414 (2020.08); C09J 2433/00 (2013.01); G02B 1/08 (2013.01); H10K 59/00 (2023.02); Y10T 428/2891 (2015.01)] | 15 Claims |
|
1. An adhesive film formed of an adhesive composition comprising a (meth)acrylic copolymer comprising an alkylene glycol group and a cyclic functional group, the adhesive film satisfying the following Equations 3 and 4:
γ1 after 10 cycles of foldability testing=about 2.50% to about 5.00%, [Equation 3]
|γ2−γ1|[10]/|γ2−γ1|[1000]×100=about 80% to about 120%, [Equation 4]
where |γ2−γ1|[10] is an absolute value (unit: %) of a difference between γ2 and γ1 after 10 cycles of foldability testing, and |γ2−γ1|[1000] is an absolute value (unit: %) of a difference between γ2 and γ1 after 1,000 cycles of foldability testing, wherein each cycle of foldability testing refers to an operation of applying a force consisting of a shear stress of 2,000 Pa and a normal force of 1 N to a cylindrical specimen at −20° C. in a clockwise direction for 5 seconds and completely removing the force from the cylindrical specimen for 5 seconds using an upper jig of a dynamic viscoelasticity instrument, with upper and lower surfaces of the cylindrical specimen secured to the upper jig and a lower jig of the dynamic viscoelasticity instrument, respectively, in which the cylindrical specimen is prepared by stacking the adhesive film in plural layers and punching a stack of the adhesive films to have a circular cross-section having a diameter of 8 mm; γ1 (unit: %) refers to a value calculated by the following Equation 1 upon application of the force to the specimen for 5 seconds; and γ2 refers to a value (unit: %) calculated by the following Equation 2 after 1 cycle of foldability testing:
γ1=A/B×100, [Equation 1]
where A is a movement distance (unit: μm) of one point on the specimen upon application of the force to the specimen for 5 seconds and B is an initial thickness of the specimen (unit: μm),
γ2=C/B×100, [Equation 2]
where C is a movement distance (unit: μm) of one point on the specimen after 1 cycle of foldability testing, and B is the initial thickness of the specimen (unit: μm),
wherein the (meth)acrylic copolymer comprising the alkylene glycol group and the cyclic functional group comprises a copolymer of a monomer mixture comprising a hydroxyl group-containing (meth)acrylate, an alkyl group-containing (meth)acrylate, an alkylene glycol group-containing (meth)acrylate, and a cyclic (meth)acrylate having a glass transition temperature of about 80° C. or less in a homopolymer phase,
wherein the cyclic (meth)acrylate having a glass transition temperature of about 80° C. or less in a homopolymer phase is present in an amount of about 10 wt % to about 40 wt % in the monomer mixture, and the cyclic (meth)acrylate having a glass transition temperature of about 80° C. or less in a homopolymer phase comprises at least one of cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, or 3,3,5-trimethylcyclohexyl (meth)acrylate,
wherein the alkylene glycol group-containing (meth)acrylate is present in an amount of 30 wt % to about 60 wt % in the monomer mixture,
wherein the hydroxyl group-containing (meth)acrylate is present in an amount of about 10 wt % to about 40 wt % in the monomer mixture, and
wherein the alkylene glycol group-containing (meth)acrylate is greater in amount than the hydroxyl group-containing (meth)acrylate in the monomer mixture.
|