Multilayer laminate film
The invention provides a multilayer laminated film with alternately laminated birefringent and isotropic layers. The birefringent layers have a first monotonically increasing region of optical thickness and contain monotonically increasing region 1 A of maximum optical thickness of 100 nm or less, and monotonically increasing region 1 B of minimum optical thickness of more than 100 nm, and ratio 1 B/ 1 A of slope 1 B of monotonically increasing region 1 B to slope 1 A of monotonically increasing region 1 A is more than 0 and less than 0.8. The isotropic layers have a second monotonically increasing region of optical thickness and contain monotonically increasing region 2 A of maximum optical thickness of 200 nm or less and monotonically increasing region 2 B of minimum optical thickness of more than 200 nm, and ratio 2 B/ 2 A of slope 2 B of monotonically increasing region 2 B to slope 2 A of monotonically increasing region 2 A is more than 1.5 and 10 or less.
1. A multilayer laminated film comprising a multilayer laminate in which a birefringent layer comprising a first resin and an isotropic layer comprising a second resin are alternately laminated,
the multilayer laminated film being capable of reflecting light with a wavelength of 380 to 780 nm due to optical interference caused from the lamination structure of the birefringent layer and the isotropic layer,
a series of the birefringent layers having a first monotonically increasing region of optical thickness, wherein the first monotonically increasing region comprises a monotonically increasing region 1 A in which the maximum optical thickness is 100 nm or less, and a monotonically increasing region 1 B in which the minimum optical thickness is more than 100 nm, and a ratio 1 B/ 1 A of a slope 1 B of the monotonically increasing region 1 B to a slope 1 A of the monotonically increasing region 1 A is more than 0 and less than 0.8,
a series of the isotropic layers having a second monotonically increasing region of optical thickness, wherein the second monotonically increasing region comprises a monotonically increasing region 2 A in which the maximum optical thickness is 200 nm or less and a monotonically increasing region 2 B in which the minimum optical thickness is more than 200 nm, and a ratio 2 B/ 2 A of a slope 2 B of the monotonically increasing region 2 B to a slope 2 A of the monotonically increasing region 2 A is more than 1.5 and 10 or less.
2. The multilayer laminated film according to claim 1 , wherein the monotonically increasing region 1 A has an average optical thickness of 65 nm or more and 85 nm or less, and the monotonically increasing region 1 B has an average optical thickness of 140 nm or more and 160 nm or less.
3. The multilayer laminated film according to claim 2 , wherein the monotonically increasing region 2 A has an average optical thickness of 130 nm or more and 155 nm or less, and the monotonically increasing region 2 B has an average optical thickness of 250 nm or more and 290 nm or less.
4. The multilayer laminated film according to claim 3 , wherein the ratio 2 B/ 2 A is more than 1.5 and less than 5.
5. The multilayer laminated film according to claim 4 , wherein the multilayer laminated film has an average reflectance of light polarized parallel to a reflection axis at normal incidence of 85% or more in a wavelength range of 380 nm to 780 nm.
6. The multilayer laminated film according to claim 3 , wherein the ratio 2 B/ 2 A is 5 or more and 10 or less.
7. The multilayer laminated film according to claim 6 , wherein the multilayer laminated film has an average reflectance of light polarized parallel to a reflection axis at normal incidence of 85% or more in a wavelength range of 380 nm to 780 nm.
8. The multilayer laminated film according to claim 1 , wherein the monotonically increasing region 2 A has an average optical thickness of 130 nm or more and 155 nm or less, and the monotonically increasing region 2 B has an average optical thickness of 250 nm or more and 290 nm or less.
9. The multilayer laminated film according to claim 1 , wherein the ratio 2 B/ 2 A is more than 1.5 and less than 5.
10. The multilayer laminated film according to claim 1 , wherein the ratio 2 B/ 2 A is 5 or more and 10 or less.
11. The multilayer laminated film according to claim 1 , wherein the multilayer laminated film has an average reflectance of light polarized parallel to a reflection axis at normal incidence of 85% or more in a wavelength range of 380 nm to 780 nm.