Appeal No. 94-1549
Application 07/945,540
comprising” about 5-40% water. The remaining claims on appeal all depend directly or
indirectly from claim 2.
Durham is directed to positive working photosensitive elements which are coated
with a formulation containing a novolak or polyvinyl phenol resin, a diazide sensitizer,
and a solvent mixture comprising propylene glycol alkyl ether and propylene glycol
alkyl ether acetate. At column 1, lines 19-26, Durham indicates that prior art positive
photoresist formulations were formed by dissolving the resin and diazide sensitizer in
an organic solvent or mixture of solvents. This latter disclosure forms a reasonable
basis to conclude that in this art, the final positive photoresist composition is formed
using a separate source of the solvent mixture as a starting material. The examples of
Durham set forth in column 7 form resist formulations from a novolak resin, a sensitizer,
and a solvent mixture of propylene glycol alkyl ether and propylene glycol alkyl ether
acetate in weight proportions encompassed by claim 1 on appeal.
Reading the exemplified formulations at column 7 of Durham in light of the prior
art teaching referenced at column 1 of the reference that such formulations are
conventionally formed by dissolving the resin and sensitizer in a preformed mixture of
solvents, we hold that one of ordinary skill in the art would have found it prima facie
obvious to form a mixture of propylene glycol alkyl ether and propylene glycol alkyl
ether acetate having the weight ratios disclosed in the examples of Durham which will
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