Single layer polymer films and electronic devices

1. A single layer polymer film comprising:

60 to 99 wt % of a crosslinked polyimide having a gel fraction in the range of from 20 to 100% and a refractive index of 1.74 or less; and

1 to 40 wt % of a colorant, wherein a surface of the single layer polymer film has been textured and has a maximum roughness (S pv ) of 6 μm or more, an L* color of 30 or less and a 60° gloss of 15 or less.

2. The single layer polymer film of claim 1 , further comprising a matting agent.

3. The single layer polymer film of claim 1 , wherein the crosslinked polyimide comprises a dianhydride selected from the group consisting of aromatic dianhydrides, aliphatic dianhydrides and mixtures thereof.

4. The single layer polymer film of claim 3 , wherein the dianhydride is selected from the group consisting of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), cyclobutane dianhydride (CBDA), 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), bisphenol A dianhydride (BPADA), 4,4′-oxydiphthalic anhydride (ODPA), bis (3,4-dicarboxyphenyl) sulfoxide dianhydride (DSDA) and hexahydro-4,8-ethano-1H,3H-benzo[1,2-c:4,5-c′]difuran-1,3,5,7-tetrone (BODA) and mixtures thereof.

5. The single layer polymer film of claim 1 , wherein the crosslinked polyimide comprises a diamine selected from the group consisting of aromatic diamines, aliphatic diamines and mixtures thereof.

6. The single layer polymer film of claim 5 , wherein the diamine is selected from the group consisting of 1,6-hexamethylenediamine (HMD), trans-1,4-diaminocyclohexane (CHDA), 3-(4-aminophenyl)-1,1,3-trimethyl-5-indanamine (PIDA), isophoronediamine (IPDA), m-tolidine (MTB), 2,2′-bis(trifluoromethyl) benzidine (TFMB), m-phenylenediamine (MPD), 1,3-bis-(4-aminophenoxy) benzene (RODA), 2,2-bis-(4-[4-aminophenoxy]phenyl) propane (BAPP), and 3,4′-diaminodiphenyl ether (3,4-ODA) and mixtures thereof.

7. The single layer polymer film of claim 1 , wherein the single layer polymer film has a thickness in the range of from 2 to 125 μm.

8. The single layer polymer film of claim 1 , wherein the crosslinked polyimide has a refractive index of 1.69 or less.

9. The single layer polymer film of claim 1 , wherein the colorant comprises a low conductivity carbon black.

10. A coverlay for a printed circuit board comprising the single layer polymer film of claim 1 .

11. A process for forming a single layer polymer film comprising a crosslinked 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;

the polymer film has an L* color of 30 or less and a 60° gloss of 15 or less; and

the crosslinked polyimide film is formed by:

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

(b) imidizing the polyamic acid solution to form a substantially imidized solution;

(c) adding a crosslinking agent and a colorant to the substantially imidized solution;

(d) casting the substantially imidized solution on a removeable substrate having a textured surface with a maximum roughness (S pv ) of 6 μm or more to form a film;

(e) crosslinking the polyimide while drying the film; and

(f) removing the single layer polymer film from the textured substrate.

12. A process for forming a single layer polymer film comprising a crosslinked 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;

the polymer film has an L* color of 30 or less and a 60° gloss of 15 or less; and

the crosslinked 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 first substantially imidized solution;

(c) precipitating the first substantially imidized solution with an antisolvent;

(d) filtering and drying the first substantially imidized solution to obtain a solid polyimide resin;

(e) dissolving the solid polyimide resin in a second solvent and adding a crosslinking agent and a low conductivity carbon black to form a second substantially imidized solution;

(f) casting the second substantially imidized solution on a removeable substrate having a textured surface with a maximum roughness (S pv ) of 6 μm or more to form a film;

(g) crosslinking the polyimide while drying the film; and

(h) removing the single layer polymer film from the textured substrate.

13. The process of claim 12 , wherein after (e) and before (f), the second substantially imidized solution is filtered to remove insoluble constituents of the solution.

14. The process of claim 12 , wherein the first and second solvents are the same or different.