Process for producing polyimide optical waveguide

A process for producing a polyimide optical waveguide, which comprises the steps of:

• (a) forming an undercladding layer on a substrate,
• (b) forming a photosensitive polyimide resin precursor composition layer on the undercladding layer,
• (c) irradiating the photosensitive polyimide resin precursor composition layer, excepting a region corresponding to a core pattern, with a UV light through a mask, followed by heating after exposure,
• (d) removing a UV-unexposed area of the photosensitive polyimide resin precursor composition layer by development,
• (e) heating a UV-exposed area of the photosensitive polyimide resin precursor composition layer to imidize the UV-exposed area, thereby forming a cladding layer having a desired pattern,
• (f) coating the region corresponding to the core pattern and a surface of the cladding layer with a polyamic acid that forms a polyimide resin having a higher refraction index than the polyimide resin of the cladding layer, and imidizing the polyamic acid by heating to form a core layer, and
• (g) forming an overcladding layer on the core layer,
• wherein the photosensitive polyimide resin precursor composition comprises:
• (i) a polyamic acid obtained from a tetracarboxylic dianhydride and a diamine;
• and
• (ii) a photosensitive agent comprising a 1,4-dihydropyridine derivative represented by formula (I):
• wherein Ar represents an aromatic group having a nitro group at an ortho-position with respect to the bonding position to the 1,4-dihydropyridine ring;
• R1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms;
• and R2, R3, R4 and R5 each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms.