Multilevel imaging of photopolymer relief layer for the preparation of casting molds

Claim 2

A process for photofabricating master relief patterns for the production of casting molds using a photo hardenable, solvent soluble layer having a front and a back surface and a thickness D in the range of 0.010 to 0.5 inch (0.25 to 12.7 mm), comprising the steps of: (1) exposing the layer through the back surface to a first imagewise modulated actinic radiation for a predetermined duration selected to penetrate the layer and render it imagewise insoluble to a first maximum preselected depth d 1 which measured from the back surface is less than the total thickness of the photohardenable layer, (2) exposing the layer a second time through the back surface to unmodulated actinic radiation for a time sufficient to render insoluble the photohardenable layer to a second preselected depth d 2 less than the first preselected depth by an amount equal to the desired maximum relief of a background pattern, (3) exposing the layer through the front surface to a second imagewise modulated actinic radiation, for a time sufficient to render insoluble the photohardenable layer to a depth at least as great ad D-d 2 as measured from the front surface, and (4) subjecting the layer to the action of a solvent to remove any rotions of the layer, not rendered solvent insoluble in steps (1) through (3).

Claim 3

A process according to claim 1 wherein exposure steps (1) and (2) are reversed.

Claim 4

A process according to claim 1 wherein the photohardenable layer is prepared from a composition comprising a polymer of a conjugated diolefin hydrocarbon, a nongaseous ethylenically unsaturated compound and an organic, radiation-sensitive, free radical generating photoinitiator or photoinitiator system.

Claim 5

A process according to claim 3 wherein the conjugated diolefin hydrocarbon polymer is a polymer selected from butadiene/acrylonitrile, butadiene/acrylonitrile/acrylic acid, butadiene/styrene, styrene-butadiene-styrene block copolymer and styrene-isoprene-styrene block copolymer.

Claim 6

A process according to claim 1 wherein the solvent used in step (4) is taken from the group consisting of organic solvent, aqueous solution and mixtures thereof.

Claim 7

A process according to claim 1 wherein the solvent used in step (4) is water.

Claim 8

A process for production of a casting mold using a master relief pattern photofabricated from a photohardenable, solvent soluble layer having a front and back surface and a thickness D in the range of 0.010 to 0.5 inch (0.25 to 12.7 mm), comprising the steps of: (1) exposing the layer through the back surface to a first imagewise modulated actinic radiation for a predetermined duration selected to penetrate the layer and render it imagewise insoluble to a first maximum preselected depth d 1 which measured from the back surface is less than the total thickness of the photohardenable layer, (2) exposing the layer a second time through the back surface to unmodulated actinic radiation for a time sufficient to render insoluble the photohardenable layer to a second preselected depth d 2 which measured from the back surface is less than the first preselected depth by an amount equal to the desired maximum relief of a background pattern, (3) exposing the layer through the front surface to a second imagewise modulated actinic radiation, for a time sufficient to render insoluble the photohardenable layer to a depth at least as great as D-d 2 as measured from the front surface, (4) subjecting the layer to the action of a solvent to remove any portions of the layer not rendered solvent insoluble in steps (1) through (3), and (5) applying a suitable mold-making composition over the master relief pattern produced as described in steps (1) through (4) to form a casting mold.

Claim 9

A process for production of a casting mold using a master relief pattern photofabricated from a photohardenable, solvent soluble layer having a front and back surface and a thickness D in the range of 0.010 to 0.5 inch (0.25 to 12.7 mm), comprising the steps of: (1) exposing the layer through the back surface to a first imagewise modulated actinic radiation for a predetermined duration selected to penetrate the layer and render it imagewise insoluble to a first maximum preselected depth d 1 which measured from the back surface is less than the total thickness of the photohardenable layer, (2) exposing the layer a second time through the back surface to unmodulated actinic radiation for a time sufficient to render insoluble the photohardenable layer to a second preselected depth d 2 which measured from the back surface is less than the first preselected depth by an amount equal to the desired maximum relief of a background pattern, (3) exposing the layer through the front surface to a second imagewise modulated actinic radiation, for a time sufficient to render insoluble the photohardenable layer to a depth at least as great as D-d 2 as measured from the front surface, (4) subjecting the layer to the action of a solvent to remove any portions of the layer not rendered solvent insoluble in steps (1) through (3), and (5) applying a suitable mold-making composition over the master relief pattern produced as described in steps (1) through (4) to form a casting mold.