Multi-layer laminated film

1. A multi-layer laminated film comprising layers composed of a crystalline thermoplastic resin A (A layers) and layers composed of a non-crystalline thermoplastic resin B as a major component (B layers), which A layers and B layers are alternately laminated in 51 or more layers, wherein the multi-layer laminated film is biaxially stretched in the longitudinal and transverse directions at a temperature from 80° C. to 120° C. with a draw ratio of 2 to 6 for each direction, heat-treating the film at a temperature from 160° C. to 220° C., and subjecting the heat-treated film to cooling at a temperature that is 80° C. of higher; and wherein said film has:

a heat shrinkage stress of not less than 0.5 MPa and not more than 5 MPa at 150° C. in longitudinal and width directions of said film; and

a heat shrinkage stress kick-off temperature of 110° C. or lower in both the longitudinal and width directions of said film, said heat shrinkage stress kick-off temperature being defined as, in a heat shrinkage stress curve determined under a condition where temperature is 25° C. to 200° C. and a heating rate is 5° C./min, the temperature at an intersection between a baseline preceding an initial rise of said heat shrinkage stress curve and a tangent line drawn at a point where said heat shrinkage stress curve has a maximum slope after said initial rise.

2. The multi-layer laminated film according to claim 1 , wherein said film has an average reflectance of 15% or less at a wavelength of 400 to 700 nm.

3. The multi-layer laminated film according to claim 1 , wherein said film has a heat shrinkage stress of not less than 0.5 MPa and not more than 5 MPa at 130° C. in both the longitudinal and width directions.

4. The multi-layer laminated film according to claim 1 , wherein said film has a heat shrinkage stress of not less than 0.5 MPa and not more than 5 MPa at 110° C. in at least one of the longitudinal and width directions.

5. The multi-layer laminated film according to claim 1 , wherein a difference in the heat shrinkage stress at 100° C. between the longitudinal and width directions is 0.05 N/mm 2 or less.

6. The multi-layer laminated film according to claim 1 , wherein a difference in a dimensional change rate at 100° C. between the longitudinal direction of said film and the direction perpendicular thereto is 0.5% or less.

7. The multi-layer laminated film according to claim 1 , wherein

said thermoplastic resin A is composed of a polyethylene terephthalate resin; and

said thermoplastic resin B is composed of a copolymerized polyethylene terephthalate resin in which a spiroglycol component(s) and a cyclohexane dicarboxylic acid component(s) are copolymerized.

8. The multi-layer laminated film according to claim 1 , wherein said film has an average reflectance of 15% or less in a wavelength range of 400 nm to 700 nm and 70% or higher in a wavelength range of 850 nm to 1,200 nm.

9. The multi-layer laminated film according to claim 1 , wherein said film has an average reflectance of 40% or higher in a wavelength range of 1,200 nm to 1,400 nm.

10. The multi-layer laminated film according to claim 1 , wherein said film has a heat shrinkage rate of 6% or less at 150° C. in the longitudinal and width directions.

11. A molded article comprising said multi-layer laminated film according to claim 1 and a support laminated via an interlayer on at least one side of said multi-layer laminated film.

12. A heat-shielding article comprising:

the multi-layer laminated film according to claim 1 ;

interlayers each of which is arranged on each side of said multi-layer laminated film; and

transparent substrates each of which is arranged on a surface opposite said multi-layer laminated film on each of said two interlayers.

13. A heat-shielding article comprising:

a multi-layer laminated film;

interlayers each of which is arranged on each side of said multi-layer laminated film; and

transparent substrates each of which is arranged on a surface opposite to said multi-layer laminated film on each of said two interlayers,

wherein said multi-layer laminated film comprises layers composed of a crystalline thermoplastic resin A (A layers) and layers composed of a non-crystalline thermoplastic resin B as a major component (B layers), which A layers and B layers are alternately laminated in 51 or more layers wherein the multi-layer laminated film is biaxially stretched in the longitudinal and transverse directions at a temperature from 80° C. to 120° C. with a draw ratio of 2 to 6 for each direction, heat-treating the film at a temperature from 160° C. to 220° C., and subjecting the heat-treated film to cooling at a temperature that is 80° C. of higher;

said laminated film has an average reflectance of 15% or less at a wavelength of 400 to 700 nm and 60% or higher at a wavelength of 900 to 1,200 nm; and

the difference in the heat shrinkage stress at 100° C. between the longitudinal direction of said film and the direction perpendicular thereto is 0.05 N/mm 2 or less.