Adhesive film, optical member including the same, and optical display including the same
An adhesive film, an optical member including the same, and an optical display including the same are disclosed. The adhesive film has a folding evaluation parameter 1 of about 900% to about 1,300% at 25° C., as calculated by Equation 1 and a folding evaluation parameter 2 of about 40% to about 95% at 60° C., as calculated by Equation 2, and includes a hydroxyl group-containing (meth)acrylic copolymer.
1. An adhesive film comprising:
an adhesive composition comprising a hydroxyl group-containing (meth)acrylic copolymer, organic nanoparticles, and an initiator, the adhesive film having a folding evaluation parameter 1 of about 900% to about 1,300% at 25° C., as calculated by Equation 1 and a folding evaluation parameter 2 of about 40% to about 95% at 60° C., as calculated by Equation 2,
Folding evaluation parameter 1=( X 1 )/( X 0 )×100 Equation 1
Folding evaluation parameter 2=(1−( X 2 )/( X 3 ))×100 Equation 2
wherein, in Equation 1, X 1 is a stretched length in μm of the adhesive film upon application of 90 kPa to the adhesive film during pulling the adhesive film at a speed of 300 mm/min to a length X 3 in of 1,000% of X 0 , an initial thickness thereof in μm,
wherein, in Equation 2, X 2 is a stretched length in μm of the adhesive film after stretching the adhesive film to the length X 3 in μm of 1,000% of the initial thickness X 0 thereof, maintaining the adhesive film at the length X 3 for 10 seconds, and restoring the adhesive film to the unloaded state at the speed of 300 mm/min, and
wherein X 1 , X 2 , and X 3 are obtained using a specimen prepared by attaching two polyethylene terephthalate (PET) films to each other via the adhesive film such that two respective ends of the PET films are attached to each other by the adhesive film in the order of a first end of one PET film/the adhesive film/a second end of the other PET film such that the specimen has a contact area of 20 mm×20 mm between the adhesive film and each of the PET films, two jigs are fastened to the respective ends of the PET films, and, with one of the jigs secured, the other jig is pulled at the speed of 300 mm/min until the adhesive film has the length X 3 of 1,000% of the initial thickness X 0 , and the length X 3 is maintained for 10 seconds.
2. The adhesive film according to claim 1 , wherein the adhesive film also has a haze of about 1% or less at a wavelength of about 380 nm to about 780 nm.
3. The adhesive film according to claim 1 , wherein the hydroxyl group-containing (meth)acrylic copolymer is a copolymer of a hydroxyl group-containing (meth)acrylate, a reactive or non-reactive (meth)acrylate, and a macromonomer.
4. The adhesive film according to claim 1 , wherein the organic nanoparticles have an average particle diameter of about 10 nm to about 400 nm.
5. The adhesive film according to claim 1 , wherein the organic nanoparticles are core-shell particles.
6. The adhesive film according to claim 5 , wherein the core and the shell satisfy Equation 3:
Tg ( c )< Tg ( s ), Equation 3
wherein Tg(c) is a glass transition temperature of the core and Tg(s) is a glass transition temperature of the shell.
7. The adhesive film according to claim 1 , wherein the organic nanoparticles are present in an amount of 0.1 wt % to 20 wt % in the adhesive film, based on the total weight of the adhesive film.
8. The adhesive film according to claim 5 , wherein the core is formed of at least one selected from poly(butyl acrylate) and a polysiloxane, and the shell is formed of poly(methyl methacrylate).
9. The adhesive film according to claim 3 , wherein the hydroxyl group-containing (meth)acrylic copolymer is a copolymer of a monomer mixture comprising about 4 wt % to about 40 wt % of the hydroxyl group-containing (meth)acrylate, about 55 wt % to about 95 wt % of the reactive or non-reactive (meth)acrylate, and about 0.1 wt % to about 20 wt % of the macromonomer, based on the total weight of the monomer mixture.
10. The adhesive film according to claim 3 , wherein the hydroxyl group-containing (meth)acrylic copolymer is a copolymer of a monomer mixture comprising about 5 wt % to about 45 wt % of the hydroxyl group-containing (meth)acrylate and about 55 wt % to about 95 wt % of the reactive or non-reactive (meth)acrylate, based on the total weight of the monomer mixture.
11. The adhesive film according to claim 3 , wherein the reactive or non-reactive (meth)acrylate is a (meth)acrylic monomer.
12. The adhesive film according to claim 11 , wherein the (meth)acrylic monomer is an alkyl (meth)acrylate.
13. The adhesive film according to claim 1 , wherein the adhesive composition further comprises at least one selected from a silane coupling agent and a crosslinking agent.
14. An optical member comprising an optical film and the adhesive film according to claim 1 on at least one surface of the optical film.
15. An optical display comprising the adhesive film according to claim 1 .