Stabilizers for use with photoacid precursor formulations
AssigneeE. I. Du Pont de Nemours and Company
InventorsJohn Alan Lawton, William John Nebe, Glen Anthony Thommes
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Abstract
The present invention discloses stabilizers for formulations containing photoacid precursors and cationically polymerizable materials. The stabilizers have a limited solubility in the formulations and are in solubility equilibrium in the formulation. The stabilizers being present as a solid phase in the formulation in excess of their solubility limit, the concentration of the stabilizers is continuously replenished as the stabilizer reacts with undesired free acid.
Claims11
A stabilized photohardenable epoxy composition comprising:
- a photohardenable epoxy, a photoacid precursor useful for initiation of cationic polymerizations and a stabilizer having a limited solubility in the composition and having a density which is different from that of the composition, wherein the stabilizer is a salt of a Group IA or a Group IIA metal ion and a weak acid having a solubility in the composition that is at least more than 1.times.10.sup.-4 g/l but less than 0.5 g/l and wherein the weak acid is an acid having a pKa in water that is greater than 3.0. and wherein the stabilizer is present in an amount that is in excess of its solubility.
A method of stabilizing a photoacid precursor formulation comprising a photohardenable epoxy and a photoacid precursor useful for initiation of cationic polymerization comprising the steps of
- a. contacting the formulation with a stabilizer having a limited solubility in the composition and having a density which is different from that of the composition wherein the stabilizer is a salt of a of Group IA or Group IIA metal ion and a weak acid having a solubility in the composition that is at least more than 1.times.10.sup.-4 g/l but less than 0.5 g/l and wherein the weak acid is an acid having a pKa in water that is greater than 3.0 and wherein the stabilizer is present in an amount that is in excess of its solubility.
- b. reacting the free acid present in the formulation with the stabilizer so as to neutralize or remove the acid;
- and
- c. maintaining the concentration of any dissolved stabilizer by having an excess of the amount of the stabilizer in contact with the formulation beyond that which is sufficient to saturate the formulation.
A method for reducing the entrapment of bubbles and improving the cleanability of objects formed in a layer by layer solid imaging process, the method comprising the steps of:
- using a stabilized photoacid precursor formulation comprising a photohardenable epoxy, a photoacid precursor useful for initiation of cationic polymerizations and a stabilizer having a limited solubility in the composition and having a density which is different from that of the composition wherein the stabilizer is a salt of a of Group IA or a of Group IIA metal ion and a weak acid having a solubility in the composition that is at least more than 1.times.10.sup.-4 g/l but less than 0.5 g/l and wherein the weak acid is an acid having a pKa in water that is greater than 3.0 and wherein the stabilizer is present in an amount that is in excess of its solubility;
- forming contiguous layers of the cured formulation by imagewise exposure of the formulation so as to form the object;
- and
- maintaining the dissolved concentration of stabilizer substantially near the stabilizer solubility limit.
A method for improving the image resolution of objects formed in a layer by layer solid imaging process, the method comprising the steps of:
- using a stabilized photoacid precursor formulation comprising a photohardenable epoxy, a photoacid precursor useful for initiation of cationic polymerizations and a stabilizer having a limited solubility in the composition and having a density which is different from that of the composition wherein the stabilizer is a salt of a of Group IA or a of Group IIA metal ion and a weak acid having a solubility in the composition that is at least more than 1.times.10.sup.-4 g/l but less than 0.5 g/l and wherein the weak acid is an acid having a pKa in water that is greater than 3.0 and wherein the stabilizer is present in an amount that is in excess of its solubility;
- forming contiguous layers of the cured formulation by imagewise exposure of the formulation so as to form the object;
- and
- maintaining the dissolved concentration of stabilizer substantially near the stabilizer solubility limit.
Dependencies are inferred from the claim text.