Polyimide and polyimide film comprising the same
This invention relates to polyimide, which includes amorphous silica particles having OH groups thereon and is thus highly heat-resistant, colorless and transparent, and to a polyimide film manufactured using the polyimide.
1. A polyimide, comprising amorphous silica particles having OH groups thereon,
wherein an amount of the amorphous silica particles is 0.01-0.1 parts by weight based on 100 parts by weight of the polyimide; and
wherein the polyimide is obtained by (a) providing a partially imidized polyimide resin solid; (b) mixing a dispersion of the amorphous silica and the partially imidized polyimide resin solid; and (c) subjecting the resulting mixture obtained in (b) to imidization, wherein the dispersion of the amorphous silica contains the amorphous silica in a concentration of 0.01-1.0 wt % in a solvent.
2. The polyimide of claim 1 , wherein the partially imidized polyimide resin solid is prepared by copolymerizing a dianhydride, an aromatic dicarbonyl compound and a diamine.
3. A polyimide film, comprising the polyimide of claim 1 , wherein the polyimide film has on optical transmittance of 88% or more at a wavelength of 550 nm.
4. The polyimide film of claim 3 , which has a haze of 2.0 or less.
5. The polyimide film of claim 3 , which has a coefficient of thermal expansion of 15 ppm/° C. or less at 50-250° C., and a yellow index of 7 or less.
6. The polyimide film of claim 3 , wherein the polyimide film is obtained by polymerizing a dianhydride, an aromatic dicarbonyl compound and a diamine in a first solvent to prepare a polyamic acid solution, imidizing the polyamic acid solution to prepare an imidized solution, which is then added to a second solvent, filtered and dried to obtain a polyimide resin solid, mixing the polyimide resin solid with amorphous silica particles having OH groups thereon dispersed in the first solvent to prepare a mixture, and then subjecting the mixture to a film forming process.
7. The polyimide film of claim 6 , wherein the polyimide film is obtained by performing additional thermal treatment at 300-500° C. for 1 min-3 hr, after the film forming process.
8. The polyimide film of claim 6 , wherein the first solvent is at least one selected from the group consisting of m-cresol, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetone and diethylacetate, and the second solvent is at least one selected from among water, alcohols, ethers and ketones.
9. A substrate for a display, comprising the polyimide film of claim 3 .