Adhesive composition, protective film for a polarizing plate, polarizing plate, and liquid crystal display

1. A polarizer comprising:

a polarizing film or polarizing element; and

a protective film attached to a side or both sides of the polarizing film or polarizing element,

wherein the protective film comprises:

a base film on the polarizing film or polarizing element, and

a pressure sensitive adhesive layer in direct contact with a side of the base film opposite to the polarizing film or polarizing element,

wherein the base film is a cycloolefine polymer film or an acrylic film,

wherein a stress optical coefficient of the base film is 6 brewster or less and wherein the pressure sensitive adhesive layer is a cured product of a pressure-sensitive adhesive composition satisfying a condition of General Formula 1 given below and wherein the pressure-sensitive adhesive composition comprises a base resin comprising an aromatic ring-containing monomer or the pressure-sensitive adhesive composition comprises a compound having a positive stress optical coefficient:

Δ X≤ 2 nm,  [General Formula 1]

wherein ΔX represents an absolute value of a phase retardation (R in ) in a surface-direction, the phase retardation being measured by an equation, R in ={(n x −n y )×d}, when a sheet-shaped pressure-sensitive adhesive that has a width of 10 mm and a length of 20 mm and that is prepared by using the pressure-sensitive adhesive composition is elongated by 500 μm in a longitudinal direction at 23° C., wherein n x represents a refractive index along a horizontal axis in a surface of the sheet-shaped pressure-sensitive adhesive, n y represents a refractive index along a vertical axis in the surface of the sheet-shaped pressure-sensitive adhesive, and d represents a thickness of the sheet-shaped pressure-sensitive adhesive.

2. The polarizer of claim 1 , wherein the protective film includes only one base film.

3. The polarizer of claim 1 , wherein the stress optical coefficient of the base film is 3 brewster or less.

4. The polarizer of claim 1 , wherein the ΔX of the General Formula 1 is 1.5 nm or less.

5. The polarizer of claim 1 , wherein the ΔX of the General Formula 1 is 1 nm or less.

6. The polarizer of claim 1 , wherein the compound having the positive stress optical coefficient is expressed by Formula 3 or Formula 4:

where B represents a single bond, —CH═N—, —N═N—, —N═N(O)—, —COO—, —CH 2 O—, —C(R 7 ) 2 —CO—, —COO—CH 2 —, —CH═CH—, —C≡C—, —S—, —SO 2 —, -φ(R 7 )—, —CH═N-φ(R 7 )—N═CH—, —CH═CH-φ(R 7 )—N═CH—, —CH═CH-φ(R 7 )—CH═CH—, —CH═CH-φ(R 7 )-φ(R 8 )—CH═CH—, —CH═N-φ(R 7 )(R 8 )—N═CH—, —CH═N-φ(R 7 )-φ(R 8 )—CH═CH—, —N═N-φ(R 7 )—N═CH—, —C(═O)—O-φ(R 7 )—C(CH 3 ) 2 —, a naphthalene core, or an anthracene core, X, Y, R 7 , and R 8 represent independently hydrogen, halogen, cyano, amino, hydroxy, alkyl, alkoxy, aryl, dialkylamine, and cumyl, a represents an integer of 0 to 3, and b represents an integer of 1 to 3 when a is 0, and an integer of 0 to 3 when a is an integer of 1 to 3:

wherein

is

is

is

is

Z is C—W or N;

Q 1 to Q 16 and W are independently hydrogen, halogen, cyano, perfluoroalkyl, perfluoroalkyloxy, —R 9 , —OR 9 , —NHR 9 , —N(R 9 ) 2 , —C(═O)R 9 , —SR 9 , —SO 2 R 9 , —C(═O)NR 9 , —NR 9 C(═O)R 9 , —C(═O)OR 9 , —OC(═O)R 9 , or —OC(═O)OR 9 ;

R 9 is hydrogen, alkyl, alkenyl, alkynyl, or —(R 10 O) q R 11 , R 10 is alkylene, R 11 is alkyl, and q is an integer of 1 to 5;

l, m, n, and o are independently an integer of 0 to 2, and l+m+n+o is an integer greater than 2;

E and F are independently hydrogen, halogen, cyano, —R 9 , —OR 9 , —NHR 9 , —N(R 9 ) 2 , —NCO, —NCS, —C(═O)R 9 , or Si(R 90 ) 3 ; and

G 1 , G 2 , and G 3 , are independently a single bond, —O—, —R 10 O—, —NR 10 —, —S—, —SO—, —SO 2 —, alkylene, alkenylene, alkynylene, or —U-T-V—, U and T are independently a single bond, —S—, —NR 10 —, —O(CH 2 ) p —, carbonyl or —O—, V is a single bond, —O—, carbonyl, —NR 10 —, —S—, —(CH 2 ) p —, —O(CH 2 ) p —, or —(CH 2 ) p O—, and p is an integer of 0 to 5.

7. The polarizer according to claim 1 , wherein the base resin has a weight average molecular weight of 500,000 or more.

8. The polarizer of claim 7 , wherein the base resin is a polymer of a monomer mixture comprising a (meth)acrylic acid ester monomer; and a crosslinking monomer.

9. The polarizer of claim 1 , wherein the base resin is a polymer of a monomer mixture and wherein the monomer mixture comprises a (meth)acrylic acid ester monomer; a crosslinking monomer and a compound expressed by Formula 2 given below:

where R 6 represents hydrogen or alkyl, A represents an alkylene, n represents an integer of 0 to 3, Q represents a single bond, —O—, —S—, or an alkylene, and P represents a substituted or unsubstituted aromatic group.

10. The polarizer of claim 9 , wherein the pressure-sensitive adhesive composition further comprises a crosslinking agent crosslinking the base resin and wherein the crosslinking agent consists of one or more selected from a group consisting of an isocyanate compound, an epoxy compound, an aziridine compound, and a metal chelate compound.

11. A liquid crystal display comprising a liquid crystal panel and the polarizer of claim 1 , wherein the pressure-sensitive adhesive layer is attached on the liquid crystal panel.