Polyimide laminated film and method of preparing polyimide laminated film

1. A polyimide laminated film comprising:

a porous polyimide layer that has a porosity of from 30% to 90% and pores having a spherical shape, the porous polyimide layer comprising an organic compound and a resin other than a polyimide resin; and

a non-porous polyimide layer that has a porosity of 5% or less,

wherein a content of the resin other than the polyimide resin is from 0.29% by weight to 0.45% by weight with respect to the porous polyimide layer, and

wherein the organic compound is at least one selected from the group consisting of 2-dimethyl aminoethanol, 2-diethyl aminoethanol, 2-dimethyl aminopropanol, N-methyl morpholine, N-ethyl morpholine, 1,2-dimethyl imidazole, N-methyl piperidine, and N-ethyl piperidine.

2. The polyimide laminated film according to claim 1 , wherein the polyimide laminated film satisfies the following Expressions (1) and (2):

Tp>Tn   (1)

10μm≤ Tp+Tn≤ 100μm  (2)

wherein Tp represents an average film thickness of the porous polyimide layer (in a case of including a plurality of the porous polyimide layers, a sum of respective average film thicknesses of the porous polyimide layers), and Tn represents an average film thickness of the non-porous polyimide layer (in a case of including a plurality of the non-porous polyimide layers, a sum of respective average film thicknesses of the non-porous polyimide layers).

3. The polyimide laminated film according to claim 1 ,

wherein the porous polyimide layer contacts the non-porous polyimide layer.

4. The polyimide laminated film according to claim 3 ,

wherein in a cross-section in a direction orthogonal to an interface between the non-porous polyimide layer and the porous polyimide layer, a maximum cross-section height Zt obtained from a sum of a maximum value of a mountain height Zp of a contour curve of the interface and a maximum value of a valley depth Zv is 0.5 μm or less.

5. The polyimide laminated film according to claim 1 ,

wherein the porosity of the porous polyimide layer is 50% to 90%.

6. The polyimide laminated film according to claim 1 ,

wherein Tp is from 5 μm to 100 μm.

7. The polyimide laminated film according to claim 1 ,

wherein Tp is from 5 μm to 70 μm.

8. The polyimide laminated film according to claim 1 ,

wherein Tn is from 1 μm to 100 μm.

9. The polyimide laminated film according to claim 1 ,

wherein Tn is from 1 μm to 50 μm.

10. The polyimide laminated film according to claim 1 ,

wherein a ratio of Tp to Tn (Tp/Tn) is more than 1/1 and is 100/1 or less.

11. A method of preparing the polyimide laminated film according to claim 1 , the method comprising:

preparing a first polyimide precursor solution containing a solvent and a first polyimide precursor, and not containing first resin particles which are not dissolved in the first polyimide precursor solution or containing the first resin particles such that a volume ratio of the first resin particles is 5% or less after film formation;

preparing a second polyimide precursor solution containing an aqueous solvent, a second polyimide precursor, and an organic amine compound, and further containing second resin particles which are not dissolved in the second polyimide precursor solution such that a volume ratio of the second resin particles is 30% or more after film formation;

forming a first film on a substrate with the first polyimide precursor solution;

forming a second film on the first film with the second polyimide precursor solution;

heating the first film and the second film concurrently or separately to imidize the first film and the second film; and

removing first and second resin particles from the first and second films.

12. The method of preparing a polyimide laminated film according to claim 11 ,

wherein the forming of the first film includes drying the first film such that a content of a solvent remaining in the first film is from 5% by weight to 100% by weight with respect to a weight of the first polyimide precursor.

13. The method of preparing a polyimide laminated film according to claim 11 ,

wherein the second resin particles have an acidic group on a surface thereof.

14. The method of preparing a polyimide laminated film according to claim 13 ,

wherein the acidic group is at least one selected from the group consisting of a carboxy group, a sulfonyl group, and a phenolic hydroxyl group.

15. The method of preparing a polyimide laminated film according to claim 11 ,

wherein the removing of the first and second resin particles is performed using an organic solvent that dissolves the first resin particles and the second resin particles.

16. The method of preparing a polyimide laminated film according to claim 11 ,

wherein the removing of the first and second resin particles is performed by heating the first resin particles and the second resin particles.