Laminated porous film, separator for lithium cell, and cell
View Patent ↗Provided is a laminated porous film having excellent shutdown characteristics and breakdown characteristics, good tearing strength and dimensional stability, and B activity. The laminated porous film comprises layer A, the main component of which is a polypropylene resin, and layer B which contains a polyethylene resin, and the ratio of the rearing strength (H MD ) in the machine direction (MD) of the laminated porous film and the tearing strength (H TD ) in the transverse direction (TD) of the laminated porous film with respect to the machine direction (H MD ) (H TD ) is 0.08 to 2.0.
1. A laminated porous film, comprising:
a layer A comprising a polypropylene resin as a main component thereof; and
a layer B comprising a polyethylene resin,
wherein the laminated porous film has a β activity, and
wherein a ratio (H MD /H TD ) of a tear strength (H MD ) in a flow direction (MD) of the laminated porous film to a tear strength (H TD ) in a direction (TD) perpendicular to the flow direction (MD) is 0.08 to 2.0.
2. The film of claim 1 , wherein the tear strength H MD is not less than 4.5 N/cm.
3. The film of claim 1 , wherein a ratio (T MD /T TD ) of a tensile strength (T MD ) in a flow direction (MD) of the laminated porous film to a tensile strength (T TD ) in a direction (TD) perpendicular to the flow direction (MD) is 0.5 to 10.
4. The film of claim 3 , wherein the tensile strength T TD is not less than 30 MPa.
5. The film of claim 1 , wherein, when the film is stretched by 3% in a flow direction (MD) thereof, a tensile modulus of elasticity is not less than 500 MPa.
6. A laminated porous film, comprising:
a layer A comprising a polypropylene resin as a main component thereof; and
a layer B comprising a polyethylene resin,
wherein the laminated porous film has a β activity,
wherein when the laminated porous film is heated at 105° C. for one hour in a direction (TD) perpendicular to a flow direction (MD) of the laminated porous film, a shrinkage factor S TD2 is not more than 10%; and
when the laminated porous film is heated at 105° C. for one hour in the flow direction (MD) and in the direction (TD) perpendicular to the flow direction, a ratio of a shrinkage factor S MD2 in the flow direction (MD) to a shrinkage factor S TD2 in the direction (TD) perpendicular to the flow direction (MD) is 0.1 to 3.0.
7. The film of claim 6 , wherein, when the film is heated at 40° C. for one hour in the direction (TD) perpendicular to the flow direction (MD), a shrinkage factor S TD1 is less than 1%.
8. The film of claim 6 , wherein, when the film is heated at 150° C. for one hour in the direction (TD) perpendicular to the flow direction (MD), a shrinkage factor S TD3 is not more than 25%.
9. The film of claim 6 , wherein, when the film is heated at 40° C. for one hour in the flow direction (MD), a shrinkage factor S MD1 is less than 1%, and
wherein, when the film is heated at 105° C. for one hour in the flow direction (MD), a shrinkage factor S MD2 is not more than 10%.
10. The film of claim 6 , wherein, when the film is heated at 105° C. for one hour in the flow direction (MD), a shrinkage factor S MD3 is not more than 18%.
11. The film of claim 6 , wherein a ratio of a molecular orientation O MD found from a wide-angle X-ray diffraction measurement in the flow direction (MD) to a molecular orientation O TD found from the wide-angle X-ray diffraction measurement in the direction (TD) perpendicular to the flow direction (MD) is not less than five.
12. The film of claim 1 , wherein, the layer B further comprises at least one member selected from the group consisting of a modified polyolefin resin, an alicyclic saturated hydrocarbon resin, a modified alicyclic saturated hydrocarbon substance, an ethylene copolymer, and a wax.
13. The film of claim 1 , having a porosity of 15 to 80%.
14. The film of claim 1 , having an air permeability at 25° C. of 10 to 1000 seconds/100 ml,
wherein the air permeability is not less than 10000 seconds/100 ml when the laminated porous film is heated at 135° C. for five seconds.
15. A separator for a lithium-ion battery, comprising the laminated porous film of claim 1 .
16. A battery, comprising the separator for a lithium-ion battery of claim 15 , incorporated therein.
17. The film of claim 6 , wherein, the layer B further comprises at least one member selected from the group consisting of modified polyolefin resin, alicyclic saturated hydrocarbon resin, a modified alicyclic saturated hydrocarbon substance, an ethylene copolymer, and wax.
18. The film of claim 6 , having an air permeability at 25° C. of 10 to 1000 seconds/100 ml,
wherein the air permeability is not less than 10000 seconds/100 ml when the laminated porous film is heated at 135° C. for five seconds.
19. A separator for a lithium-ion battery, comprising the laminated porous film of claim 6 .
20. A battery, comprising the separator for a lithium-ion battery of claim 19 , incorporated therein.