High ortho-ortho bonded novolak binder resins and their use in radiation-sensitive compositions

A phenolic novolak composition having a weight average molecular weight from 3,000 to 40,000, having ortho--ortho bonding of between 55% and 70% of the methylene bonds between the phenolic moieties in the novolak, and a time to clear of at least 20 seconds per micron, and prepared by a process comprising the steps of:

• (1) reacting a first phenolic monomer comprising a major portion of at least one trifunctional phenolic monomer with a first aldehyde source in the absence of a catalyst at a reaction temperature from about 100.degree. C. to about 200.degree. C. and at a reaction pressure of about 2 to about 15 atmospheres to form a phenolic oligomer having a weight average molecular weight from about 500 to about 2,000, having ortho--ortho bonding of about 55% to about 75% of the methylene bonds between the phenolic moieties, and having a time to clear of less than 125 seconds per micron;
• wherein the mole ratio of said first aldehyde source to said first phenolic monomer is from about 0.3:1.0 to about 0.55:1.0;
• and
• (2) then reacting said oligomer with a second aldehyde source and an optional second phenolic monomer at a temperature from about 80.degree. C. to about 150.degree. C. to form a phenolic novolak having a weight average molecular weight of 3,000 to 40,000, having ortho--ortho bonding of between 55% and 70% of the methylene bonds between the phenolic moieties, and having a time to clear of at least 20 seconds per micron;
• wherein the mole ratio of said second aldehyde source to said phenolic moieties is less than about 0.8:1.0.