Multi-layer layered film
A multi-layer, layered film includes a multi-layer, alternately layered body containing birefringent first layers including a first resin and isotropic second layers including a second resin, in which the multi-layer, layered film has a layer thickness profile with which light at a wavelength of from 380 to 780 nm can be reflected due to optical interference between each of the first layers and each of the second layers, in which a layer thickness profile for an optical thickness of the first layers has a first monotonically increasing region which meets specific requirements, and in which a layer thickness profile for an optical thickness of the second layers has a second monotonically increasing region which meets specific requirements.
1. A multi-layer, layered film comprising:
a multi-layer, alternately layered body containing birefringent first layers including a first resin and isotropic second layers including a second resin,
wherein the multi-layer, layered film has a layer thickness profile with which light at a wavelength of from 380 to 780 nm can be reflected due to optical interference between each of the first layers and each of the second layers,
wherein a layer thickness profile for an optical thickness of the first layers has a first monotonically increasing region, the first monotonically increasing region including a 1A monotonically increasing region with a maximum optical thickness of up to 100 nm and a 1B monotonically increasing region with a minimum optical thickness of over 100 nm,
wherein a ratio 1B/1A of a slope 1B in the 1B monotonically increasing region to a slope 1A in the 1A monotonically increasing region is from 0.8 to 1.5,
wherein a layer thickness profile for an optical thickness of the second layers has a second monotonically increasing region, the second monotonically increasing region including a 2A monotonically increasing region with a maximum optical thickness of up to 200 nm and a 2B monotonically increasing region with a minimum optical thickness of over 200 nm, and
wherein a ratio 2B/2A of a slope 2B in the 2B monotonically increasing region to a slope 2A in the 2A monotonically increasing region is from 5 to 10.
2. The multi-layer, layered film according to claim 1 , wherein an average optical thickness in the 1A monotonically increasing region is from 75 to 95 nm, and an average optical thickness in the 1B monotonically increasing region is from 120 to 140 nm.
3. The multi-layer, layered film according to claim 2 , wherein an average optical thickness in the 2A monotonically increasing region is from 140 to 165 nm, and an average optical thickness in the 2B monotonically increasing region is from 250 to 290 nm.
4. The multi-layer, layered film according to claim 2 , wherein the ratio 1B/1A is from 1.0 to 1.5.
5. The multi-layer, layered film according to claim 1 , wherein an average optical thickness in the 2A monotonically increasing region is from 140 to 165 nm, and an average optical thickness in the 2B monotonically increasing region is from 250 to 290 nm.
6. The multi-layer, layered film according to claim 5 , wherein the ratio 1B/1A is from 1.0 to 1.5.
7. The multi-layer, layered film according to claim 1 , wherein the ratio 1B/1A is from 1.0 to 1.5.
8. The multi-layer, layered film according to claim 1 , wherein an average reflectance in a wavelength range of from 380 nm to 780 nm of light polarized parallel to a reflection axis at normal incidence is 85% or more.