Colored polyimide films and methods relating thereto

1. A method of increasing optical density comprising: incorporating carbon black in to a colored polyimide composition to obtain a colored polyimide film comprising:

i) 48 to 94 weight percent of a polyimide, the polyimide is derived from at least one aromatic diamine and at least one aromatic dianhydride;

ii) 5 to 25 weight percent pigment;

iii) 0.05 to 1 weight percent carbon black; and

wherein the colored polyimide film has an optical density of at least 1.4 as measured with a Macbeth TD904 optical densitometer.

2. The method of claim 1 , wherein the carbon black incorporated is from 0.1 to 1 weight percent and the colored polyimide film comprises from 0.1 to 1 weight percent carbon black.

3. The method of claim 1 , wherein the carbon black incorporated is from 0.5 to 1 weight percent and the colored polyimide film comprises from 0.5 to 1 weight percent carbon black.

4. The method of claim 1 , wherein the colored polyimide film additionally comprises 10 to 25 weight percent of a filler selected from the group consisting of: thermally conductive fillers, dielectric fillers, electrically conductive fillers and mixtures thereof.

5. The method of claim 1 , wherein the colored polyimide film additionally comprises from 10 to 25 weight percent of a filler selected from the group consisting of: talc, mica, silica, kaolin, titanium dioxide, boron nitride, barium titanate, sepiolite, aluminum nitride or mixtures thereof.

6. The method of claim 1 , wherein the pigment is selected from, diketopyrrolopyrrole pigment, Perylene Red or Ultramarine Blue.

7. The method of claim 1 , wherein the carbon black is selected from the group consisting of: a carbon black having a volatile content greater than or equal to 13%, a furnace black, a channel black and mixtures thereof.

8. The method of claim 1 , wherein the polyimide is derived from pyromellitic dianhydride and 4,4′-oxydianiline.

9. The method of claim 1 , wherein the polyimide is derived from pyromellitic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydianiline and paraphenylene diamine.

10. The method of claim 1 , wherein the polyimide is derived from at least 45 mole percent of 3,3′,4,4′-biphenyltetracarboxylic dianhydride, based on a total dianhydride content of the polyimide, and at least 50 mole percent of 2,2′-bis(trifluoromethyl) benzidine based on a total diamine content of the polyimide.

11. The method of claim 1 , wherein the polyimide is derived from pyromellitic dianhydride, 4,4′-oxydianiline and paraphenylene diamine.