Multilayer film and biaxially oriented polyester film
An objective of the present invention is to provide a film that has a high rigidity and is superior in dimension stability under high temperatures and transparency after heating processes, as well as in moldability within a wide temperature range, which has not been achieved by conventional techniques, and this objective has been achieved by a laminated film that includes 50 or more layers each of which is made of a thermoplastic resin and has a thickness of less than 30 nm or a biaxial oriented polyester film that has a density in a range from 1 to 1.4 g/cm 3 , a heat shrinkage of −2 to 2% in the longitudinal direction at 180° C. and a breaking elongation in a range of 100 to 1000% in at least one direction.
1. A laminated film comprising: 50 or more layers, the layers being adjacent to each other with each layer being made of a thermoplastic resin and each layer having a thickness of less than 15 nm.
2. The laminated film according to claim 1 , which is made from at least two kinds of thermoplastic resins.
3. The laminated film according to claim 1 , which is a biaxially extended film.
4. A laminated film according to claim 1 , which is biaxially oriented and has a density in a range from 1 to 1.4 g/cm 3 , a heat shrinkage of −2 to 2% in the longitudinal direction at 180° C. and a breaking elongation in a range of 100 to 1000% in at least one direction.
5. The laminated film according to claim 1 , which is made from at least two kinds of crystalline resins having different crystal structures.
6. The laminated film according to claim 1 , wherein a periodic structure is contained in the layers.
7. The laminated film according to claim 1 , wherein the thickness of each layer is set to 0.1 to 8 times the crystal size of the resin forming the layer.
8. The laminated film according to claim 1 , characterized in that two or more endothermic peaks of crystal fusion, which are measured as 8 J/g or more, are observed by differential scanning calorimetry measurements carried out on the film.
9. The laminated film according to claim 1 , wherein the number of laminated layers is 1000 or more and the precision of lamination is 50% or less.
10. The laminated film according to claim 1 , wherein the elongation percentage to stress characteristic at room temperature at least in one direction satisfies the following expression (1):
0.9≦σ2/σ1≦1.2 expression (1)
σ1: stress at 50% in elongation percentage (MPa)
σ2: stress at 100% in elongation percentage (MPa)
11. The laminated film according to claim 1 , wherein the elongation percentage to stress characteristic at room temperature at least in one direction satisfies the following expressions (2) to (4):
σ1≦120 expression (2)
σ2≦140 expression (3)
σ3≦110 expression (4)
σ1: stress at 50% in elongation percentage (MPa)
σ2: stress at 100% in elongation percentage (MPa)
σ3: yield point stress (MPa)
12. The laminated film according to claim 1 , wherein the average Young's modulus in the film longitudinal direction as well as in the film width direction is set in a range from 3 to 5 GPa.
13. The laminated film according to claim 1 , further comprising:
50 or more layers formed by layers made from a thermoplastic resin A and layers made from a thermoplastic resin B,
wherein an α relaxation temperature, obtained in dynamic viscoelasticity measurements, is observed between (α relaxation temperature of thermoplastic resin B+10)° C. and (α relaxation temperature of thermoplastic resin A−10)° C., with two or more melting points.
14. The laminated film according to claim 1 , wherein the thermal expansion coefficient is set to 110 ppm or less.
15. The laminated film according to claim 1 , wherein a raised haze value after a heating test is set to 15% or less.
16. The laminated film according to claim 1 , wherein, upon measurements on X-ray small angle scattering, spot-shaped scattering is observed in the end direction and/or the edge direction.
17. The laminated film according to claim 1 , wherein a difference (ΔTm) between the melting point and the cooling crystallization temperature of thermoplastic resin A and/or thermoplastic resin B is set to 60° C. or less.
18. The laminated film according to claim 1 , wherein: a raised haze value after a heating test is set to 5% or less; the laminated film includes 500 or more layers formed by layers made from thermoplastic resin A and layers made from thermoplastic resin B; an α relaxation temperature, obtained in dynamic viscoelasticity measurements, is observed between (α relaxation temperature of thermoplastic resin B+10)° C. and (α relaxation temperature of thermoplastic resin A−10)° C.; and the elongation percentage to stress characteristic at room temperature at least in one direction satisfies the following expression (1):
0.9≦σ2/σ1≦1.2 expression (1)
σ1: stress at 50% in elongation percentage (MPa)
σ2: stress at 100% in elongation percentage (MPa)
19. The laminated film according to claim 1 , wherein the film thickness is set to 1 μm or more to 600 μm or less.
20. A molded body which is formed by using the laminated film according to claim 1 .
21. A transferring foil which is formed by using the laminated film according to claim 1 .
22. A lithium ion battery outer jacketing member which is formed by using the laminated film according to claim 1 .