Polyimide films and electronic devices

1. A polyimide film comprising:

a dianhydride and a diamine, wherein:

the dianhydride, the diamine or both the dianhydride and the diamine comprise an alicyclic monomer, an aliphatic monomer or both an alicyclic monomer and an aliphatic monomer; and

the polyimide film has an L* of at least 90, a b* of 1.25 or less, a yellowness index of 2.25 or less and a haze of less than 1% for a film thickness of 50 μm; and the polyimide film is formed by:

(a) polymerizing the dianhydride and the diamine in the presence of a first solvent to obtain a polyamic acid solution;

(b) imidizing the polyamic acid solution to form a substantially imidized solution, wherein greater than 85% of the amic acid groups are converted to polyimide, as determined by infrared spectroscopy;

(c) casting the substantially imidized solution to form a film; and

(d) drying the film.

2. The polyimide film of claim 1 , wherein after (b) and before (c), the substantially imidized solution is filtered to remove insoluble constituents of the solution.

3. The polyimide film of claim 1 , wherein the dianhydride is selected form the group consisting of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride and mixtures thereof.

4. The polyimide film of claim 3 , wherein the dianhydride further comprises an alicyclic dianhydride selected from the group consisting of cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, hexahydro-4,8-ethano-1H,3H-benzo[1,2-c:4,5-c′]difuran-1,3,5,7-tetrone, 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic 1,4:2,3-dianhydride and meso-butane-1,2,3,4-tetracarboxylic dianhydride.

5. The polyimide film of claim 1 , wherein the diamine comprises a fluorinated aromatic diamine.

6. The polyimide film of claim 5 , wherein the fluorinated aromatic diamine comprises 2,2′-bis(trifluoromethyl) benzidine.

7. The polyimide film of claim 1 , wherein the diamine comprises an aliphatic diamine selected from the group consisting of 1,2-diaminoethane, 1,6-diaminohexane, 1,4-diaminobutane, 1,5 diaminopentane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,16-hexadecamethylenediamine, 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, isophoronediamine, bicyclo[2.2.2]octane-1,4-diamine and mixtures thereof.

8. The polyimide film of claim 1 , wherein the diamine comprises an alicyclic diamine selected from the group consisting of cis-1,3-diaminocyclobutane trans-1,3-diaminocyclobutane, 6-amino-3-azaspiro[3.3]heptane, and 3,6-diaminospiro[3.3]heptane, bicyclo[2.2.1]heptane-1,4-diamine, isophoronediamine, bicyclo[2.2.2]octane-1,4 diamine, cis-1,4 cyclohexane diamine, trans-1,4 cyclohexane diamine, 1,4-bis(aminomethyl)cyclohexane, 4,4′-methylenebis(cyclohexylamine), 4,4′-methylenebis(2-methyl-cyclohexylamine), bis(aminomethyl)norbornane and mixtures thereof.

9. The polyimide film of claim 1 , wherein the polyimide film has a thickness in the range of from 10 to 150 μm.

10. An electronic device comprising the polyimide film of claim 1 .

11. The polyimide film of claim 1 , wherein the polyimide film has a b* of 1.0 or less for a film thickness of 50 μm.

12. The polyimide film of claim 1 , wherein the polyimide film has a yellowness index of 2.0 or less for a film thickness of 50 μm.