Application of Novel Base Amplifiers with 3-Nitropentan-2-yl Group to Photoreactive Materials

Abstract

In order to enhance the photosensitivity of photoreactive materials utilizing base-catalyzed reactions, we developed base amplifiers that decompose autocatalytically to generate newborn amine molecules. Actually, we reported that the addition of base amplifiers to the photoreactive materials such as photoresists and UV-curing materials resulted in the marked improvement photosensitivity. However, conventional base amplifiers have aromatic rings such as fluorenyl groups and phenyl groups. Consequently, these base amplifiers have strong absorption of UV light which is a trigger of photolysis of a photobase generator. This leads to the hindrance of the photolysis. We report here novel base amplifiers with 3-nitropentan-2-yl group which has no aromatic rings.

The base amplifiers decomposed autocatalytically to generate newborn amine molecules at an elevated temperature in solution and a polystyrene film in the presence of a catalytic amount of amines. Moreover, combining the base amplifiers with UV-curing materials consisting of a photobase generator and liquid epoxy resins resulted in the improvement of curing efficiency. To apply the base amplifier to photopatterning materials, we synthesized novel silicone resins with 3-nitropentan-2-yl groups as base-amplifying polymers. A film of the resin decomposed autocatalytically to generate amino groups in its side chains at an elevated temperature in the presence of a catalytic amount of amines. Furthermore, we demonstrated that the resins sensitized with a photobase generator provided negative- and positive-working photopolymers in the following ways. A thin film of the resin containing 10 wt% of a photobase generator became soluble in an acidic aqueous solution after 254 nm light irradiation of an exposure dose of 1 mJ/cm² and subsequent baking at 50 oC for 20 min. This is because of formation of amino groups in its side chains. On the other hand, the film became insoluble in organic solvents after 254 nm light irradiation of an exposure dose of 1 mJ/cm² and subsequent heat treatment at 50 oC for 40 min, this arises from that the photobase-catalyzed hydrolytic condensation of residual ethoxysilyl units of the resin proceeded to form crosslinked networks.