Stretched laminate, method of manufacturing thin polarizer, thin polarizer manufactured by the method, and polarizing plate including the thin polarizer
Provided is a stretched laminate for manufacturing a thin polarizer while increasing the degree of orientation of a polyvinyl alcohol-iodine complex without problems such as breakage. In addition, there are provided a method of manufacturing a thin polarizer having superior optical characteristics by using the stretched laminate, a thin polarizer manufactured by the method, and a polarizing plate including the thin polarizer.
1. A stretched laminate formed by stretching a laminate comprising: a non-stretched polymer film; and a non-stretched polyvinyl alcohol-based film attached to at least one surface of the non-stretched polymer film, wherein L, expressed by Formula 1 below, satisfies 0<L ≦0.125,
L
=
[
{
(
d
sub
′
d
o
,
sub
′
)
-
(
d
PVA
d
o
,
PVA
)
}
2
+
{
(
W
sub
′
W
o
,
sub
′
)
-
(
W
PVA
W
o
,
PVA
)
}
2
]
0.5
[
Formula
1
]
where d o,sub′ refers to a thickness of the polymer film before stretching, d sub′ refers to a thickness of the polymer film after stretching, d o,PVA refers to a thickness of the polyvinyl alcohol-based film before stretching, d PVA refers to a thickness of the polyvinyl alcohol-based film after stretching, W o,sub′ refers to a width of the polymer film before stretching, W sub′ refers to a width of the polymer film after stretching, W o,PVA refers to a width of the polyvinyl alcohol-based film before stretching, and W PVA refers to a width of the polyvinyl alcohol-based film after stretching,
wherein the polymer film and the polyvinyl alcohol-based film are attached to each other by using an attractive force therebetween or an adhesive,
wherein, in the stretched laminate, an adhesive force between the polyvinyl alcohol-based film and the polymer film is 2 N/2 cm or less, and
wherein the polymer film is a thermoplastic polyurethane film.
2. A method of manufacturing a thin polarizer, the method comprising:
forming a laminate by attaching a non-stretched polyvinyl alcohol-based film to at least one surface of a non-stretched polymer film; and
stretching the laminate such that L, expressed by Formula 1 below, satisfies 0<L ≦0.125,
L
=
[
{
(
d
sub
′
d
o
,
sub
′
)
-
(
d
PVA
d
o
,
PVA
)
}
2
+
{
(
W
sub
′
W
o
,
sub
′
)
-
(
W
PVA
W
o
,
PVA
)
}
2
]
0.5
[
Formula
1
]
where d o,sub′ refers to a thickness of the polymer film before stretching, d sub′ refers to a thickness of the polymer film after stretching, d o,PVA refers to a thickness of the polyvinyl alcohol-based film before stretching, d PVA refers to a thickness of the polyvinyl alcohol-based film after stretching, W o,sub′ refers to a width of the polymer film before stretching, W sub′ refers to a width of the polymer film after stretching, W o,PVA refers to a width of the polyvinyl alcohol-based film before stretching, and W PVA refers to a width of the polyvinyl alcohol-based film after stretching,
wherein the polymer film and the polyvinyl alcohol-based film are attached to each other by using an attractive force therebetween or an adhesive,
wherein, in the stretched laminate, an adhesive force between the polyvinyl alcohol-based film and the polymer film is 2 N/2 cm or less, and
wherein the polymer film is a thermoplastic polyurethane film.
3. The method of claim 2 , wherein the stretching of the laminate is performed in such a manner that the polyvinyl alcohol-based film has a thickness of 60 μm or less before the stretching and a thickness of 10 μm or less after the stretching.
4. The method of claim 2 , wherein the stretching of the laminate is performed within a temperature range of 20° C. to 80° C. at a stretching ratio of 5 times to 15 times.
5. The method of claim 2 , wherein the stretching of the laminate is performed in an aqueous boric acid solution having a boric acid content of 1 wt % to 5 wt %.
6. The method of claim 2 , wherein after the stretching of the laminate, a width of the polymer film measured in a direction perpendicular to a stretching direction is reduced by 30% to 80% as compared to that of the polymer film measured before the stretching, and a thickness of the polymer film is reduced by 30% to 80% as compared to that of the polymer film measured before the stretching.
7. The method of claim 2 , wherein before the stretching of the laminate, the method further comprises dyeing the non-stretched polyvinyl alcohol-based film with one or more of iodine and a dichroic dye.
8. The method of claim 2 , wherein after the stretching of the laminate, the method further comprises separating the stretched polyvinyl alcohol-based film from the stretched polymer film.
9. The method of claim 8 , wherein the separating of the stretched polyvinyl alcohol-based film from the stretched polymer film is performed by applying a peel force of 2 N/2 cm or less.