Pressure-sensitive adhesive composition for foldable display
Provided is a pressure-sensitive adhesive composition for a foldable display, more particularly, a pressure-sensitive adhesive composition for a foldable display which, by satisfying a specific range of storage modulus at high temperature as well as at low temperature and room temperature, not only allows excellent folding properties to be realized but also satisfies excellent adhesion, excellent heat resistance, and excellent recovery rate requirements at the same time.
1. A pressure-sensitive adhesive composition for a foldable display, the pressure-sensitive adhesive composition comprising an acrylic polymer and a crosslinking agent and satisfying the following conditions (1) to (3):
60×10 4 Pa≤ A≤ 95×10 4 Pa (1)
8×10 4 Pa≤ B≤ 11×10 4 Pa (2)
2×10 4 Pa≤ C≤ 5×10 4 Pa (3)
wherein, in the condition (1), A is a storage modulus of the pressure-sensitive adhesive composition after curing as measured at a temperature of −20° C., an angular frequency of 6.28 rad/s, and a strain of 1%,
in the condition (2), B is a storage modulus of the pressure-sensitive adhesive composition after curing as measured at a temperature of 25° C., an angular frequency of 6.28 rad/s, and a strain of 1%, and
in the condition (3), C is a storage modulus of the pressure-sensitive adhesive composition after curing as measured at a temperature of 200° C., an angular frequency of 6.28 rad/s, and a strain of 1%.
2. The pressure-sensitive adhesive composition of claim 1 , wherein the acrylic polymer includes a compound represented by the following Chemical Formula 1:
wherein, in Chemical Formula 1, R 1 is a C1-C20 alkyl group, R 2 is a carboxyl group, a carboxymethyl ester group, a 2-carboxyethyl ester group, a 3-carboxypropyl ester group, a 4-carboxybutyl ester group, a 5-carboxypentyl ester group, or a 6-carboxyhexyl ester group, R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 are each independently —H or a C1-C10 alkyl group, m is a rational number satisfying a range of 87 to 95, and n is a rational number satisfying a range of 5 to 13.
3. The pressure-sensitive adhesive composition of claim 1 , wherein the crosslinking agent includes one or more selected from among ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N,N,N,N′-tetraglycidyl-m-xylenediamine, and glycerin diglycidyl ether.
4. The pressure-sensitive adhesive composition of claim 1 , wherein the crosslinking agent is included in an amount of 0.1 part by weight to 10 parts by weight relative to 100 parts by weight of the acrylic polymer.
5. The pressure-sensitive adhesive composition of claim 1 , further satisfying the following conditions (4) to (6):
4×10 4 Pa≤ D≤ 8×10 4 Pa (4)
3×10 4 Pa≤ E≤ 5.5×10 4 Pa (5)
2.5×10 4 Pa≤ F≤ 5×10 4 Pa (6)
wherein, in the condition (4), D is a storage modulus of the pressure-sensitive adhesive composition after curing as measured at a temperature of 60° C., an angular frequency of 6.28 rad/s, and a strain of 1%,
in the condition (5), E is a storage modulus of the pressure-sensitive adhesive composition after curing as measured at a temperature of 100° C., an angular frequency of 6.28 rad/s, and a strain of 1%, and
in the condition (6), F is a storage modulus of the pressure-sensitive adhesive composition after curing as measured at a temperature of 150° C., an angular frequency of 6.28 rad/s, and a strain of 1%.
6. The pressure-sensitive adhesive composition of claim 1 , further satisfying the following conditions (7) to (9):
75%≤ G (7)
85%≤ H (8)
90%≤ I (9)
wherein, in the condition (7), G is a recovery rate at 600 seconds after deformation of the cured pressure-sensitive adhesive composition as determined by Relational Formula 1 at a temperature of −20° C.,
in the condition (8), H is a recovery rate at 600 seconds after deformation of the cured pressure-sensitive adhesive composition as determined by Relational Formula 1 at a temperature of 25° C., and
in the condition (9), I is a recovery rate at 600 seconds after deformation of the cured pressure-sensitive adhesive composition as determined by Relational Formula 1 at a temperature of 60° C.,
Recovery rate at 600 seconds after deformation (%)=(Strain after 600 seconds of deformation−Residual strain at 600 seconds after deformation)/Strain after 600 seconds of deformation×100. [Relational Formula 1]
7. The pressure-sensitive adhesive composition of claim 1 , which has a glass transition temperature (Tg) of −32° C. to −27° C.
8. The pressure-sensitive adhesive composition of claim 1 , which has an acid value of 8 mgKOH/g to 19 mgKOH/g.
9. The pressure-sensitive adhesive composition of claim 1 , which has an adhesion of 700 gf/inch to 1200 gf/inch when peeled at a rate of 300 mm/minute and 180° after being attached to a non-alkali glass plate.
10. The pressure-sensitive adhesive composition of claim 1 , which satisfies the following Relational Formula 2:
4.5
≤
A
(
B
+
C
)
≤
7.5
[
Relation
Formula
2
]
wherein, in Relational Formula 2, A is a storage modulus of the pressure-sensitive adhesive composition after curing as measured at a temperature of −20° C., an angular frequency of 6.28 rad/s, and a strain of 1%, B is a storage modulus of the pressure-sensitive adhesive composition after curing as measured at a temperature of 25° C., an angular frequency of 6.28 rad/s, and a strain of 1%, and C is a storage modulus of the pressure-sensitive adhesive composition after curing as measured at a temperature of 200° C., an angular frequency of 6.28 rad/s, and a strain of 1%.