Pressure sensitive adhesive composition
Provided are a pressure-sensitive adhesive composition, a pressure-sensitive adhesive optical laminate, a pressure-sensitive adhesive polarizing plate and a display device. The pressure-sensitive adhesive composition offers a pressure-sensitive adhesive that has excellent durability and processability in manufacturing due to increased hardness even when the pressure-sensitive adhesive layer is formed thinner than a typical adhesive composition, and that can prevent a pressure mark and leakage of the pressure-sensitive adhesive, as well as a bending problem generated when applied on an optical member such as a polarizing plate, etc.
1. A pressure-sensitive adhesive composition, consisting of:
a pressure-sensitive adhesive polymer including a polymerization unit of a first monomer which forms a homopolymer having a glass transition temperature of less than 0° C., a polymerization unit of a second monomer which forms a homopolymer having a glass transition temperature of 0° C. or more, and a polymerization unit of a cross-linking monomer, and having an acid value of 1 mgKOH/g or less;
a cross-linking agent at 0.01 to 10 parts by weight, relative to 100 parts by weight of the pressure-sensitive adhesive polymer;
a cross-linking catalyst in an amount of 1 to 40 ppm;
optionally at least one of other monomers for copolymerization;
optionally a silane coupling agent;
optionally a tackifier; and
optionally one or more additives selected from the group consisting of a curing agent, a UV light stabilizer, an antioxidant, a coloring agent, a reinforcing agent, a filler, an antifoaming agent, a surfactant and a plasticizer, wherein the pressure sensitive adhesive composition has a storage elastic modulus at 30° C. and 1 rad/sec ranging from 0.01 MPa to 0.5 MPa in a state in which a cross-linked structure is formed.
2. The pressure-sensitive adhesive composition of claim 1 , wherein the homopolymer formed of the first monomer has a glass transition temperature ranging from −100° C. to −20° C.
3. The pressure-sensitive adhesive composition of claim 1 , wherein the homopolymer formed of the second monomer has a glass transition temperature ranging from 5° C. to 200° C.
4. The pressure-sensitive adhesive composition of claim 1 , wherein the second monomer is an acyclic monomer.
5. The pressure-sensitive adhesive composition of claim 1 , wherein the pressure-sensitive adhesive composition has a glass transition temperature ranging from −50° C. to 50° C. in a state in which a cross-linked structure is formed.
6. The pressure-sensitive adhesive composition of claim 1 , wherein the cross-linking catalyst is at least one selected from the group consisting of trialkylaminoalkylethanol amine, N,N,N′,N′-tetraalkylhexanediamine, trialkylamine, imidazole, naphthenic acid cobalt, dialkyltin diacetate, dialkyltin diacetylacetonate, trialkyltin hydroxide, dialkyltin dilaurate, and a combination thereof.
7. A pressure-sensitive adhesive optical laminate comprising:
an optical film; and
a pressure-sensitive adhesive layer formed on either or both sides of the optical film, and containing the pressure-sensitive adhesive composition of claim 1 which is cross-linked.
8. A pressure-sensitive adhesive polarizing plate comprising:
a polarizer film; and
a pressure-sensitive adhesive layer formed on either or both sides of the polarizer film, and containing the pressure-sensitive adhesive composition of claim 1 which is cross-linked.
9. A display device comprising the optical laminate of claim 7 .
10. A display device comprising the polarizing plate of claim 8 .
11. The pressure-sensitive adhesive composition of claim 1 , wherein the silane coupling agent is a compound of Formula 1 or Formula 2:
(R 1 ) n Si(R 2 ) (4-n) [Formula 1]
(R 3 ) n Si(R 2 ) (4-n) [Formula 2]
wherein R 1 is a beta-cyanoacetyl group or a beta-cyanoacetylalkyl group, R 3 is an acetoacetyl group or an acetoacetylalkyl group, R 2 is an alkoxy group and n is an integer of 1 to 3.
12. The pressure-sensitive adhesive composition of claim 1 , wherein the silane coupling agent is acetoacetylpropyl trimethoxysilane, acetoacetylpropyl triethoxysilane, beta-cyanoacetylpropyl trimethoxysilane, or beta-cyanoacetylpropyl triethoxysilane.
13. The pressure-sensitive adhesive composition of claim 1 , wherein the tackifier is selected from the group consisting of hydrocarbon resins, hydrogenated hydrocarbon resins, rosin resins, hydrogenated rosin resins, rosin ester resins, hydrogenated rosin ester resins, terpene resins, hydrogenated terpene resins, terpene phenol resins, hydrogenated terpene phenol resins, polymerized rosin resins, polymerized rosin ester resins, and a combination thereof.
14. The pressure-sensitive adhesive composition of claim 1 , wherein the at least one of other monomers is selected from the group consisting of a styrene-based monomer and a monomer containing a glycidyl group.
15. The pressure-sensitive adhesive composition of claim 13 , wherein the styrene-based monomer is methyl styrene.
16. The pressure-sensitive adhesive composition of claim 14 , wherein the monomer containing a glycidyl group is glycidyl (meth)arylate.
17. The pressure-sensitive adhesive composition of claim 1 , wherein the pressure-sensitive adhesive composition has a gel fraction of 70 wt % to 80 wt % calculated using the following Equation 1 after forming a cross-linked structure:
Gel fraction (%)= B/A× 100 [Equation 1]
wherein in Equation 1, A is a mass of the pressure-sensitive adhesive composition forming a cross-linked structure, B is a dry mass of the insoluble fraction which is obtained by depositing the pressure-sensitive adhesive composition having a mass of A in ethyl acetate for 24 hours, in the state in which the pressure-sensitive adhesive composition is laid in the mesh having a size of 200 meshes at room temperature.