Photoimageable compositions

Claim 1

A photoimageable composition comprising a homogeneous solution of (a) between about 10 and about 40 wt. percent of a flowable, film-forming polymeric binder which has an acid number of about 100 or greater and is soluble in alkaline aqueous solution, said binder being selected from the group consisting of acrylic polymers and copolymers and saponified styrene-maleic anhydride copolymers, (b) between about 5 and about 25 wt. percent of a cross-linking agent for said polymeric binder selected from the group consisting of melamine-formaldehyde condensation products, and urea-formaldehyde resins, which cross-linking agent is reactive with complementary group of said polymeric binder, (c) between about 15 and about 35 wt. percent of a polymerizable acrylic substance, (d) between about 0.01 and about 15 wt. percent of a photosensitive, free radical-generating initiator chemical system which in the presence of actinic radiation initiates polymerization of said acrylic substance to form a three-dimensional chemical structure that renders actinic radiation-exposed portions of said photoimageable composition insoluble to alkaline aqueous solutions, (e) between about 20 and about 50 wt. percent of an epoxy resin composition which is curable with heat to harden said photoimageable composition subsequent to exposure to actinic radiation, and (f) between about 0.01 and about 5 wt. percent of a cure catalyst for said epoxy resin selected from the group consisting of polycarboxylic acid anhydrides, dicyandiamides, complexes of amines with boron trifluoride or boron trichloride, latent boron difluoride chelates, aromatic polyamines and imidazoles, said polymeric binder being sufficiently soluble in alkaline aqueous solution and used at a sufficient level that said photoimageable composition as a whole is developable in alkaline aqueous solution, said components (a)-(f) being selected to be mutually miscible and mixed together to form said homogeneous solution, said cross-linking agent reacting with said polymer binder in a controlled manner, whereby said photoimageable composition may be mildly heated to render said photoimageable composition non-tacky, yet developable in alkaline aqueous solution, said epoxy resin being selected so that any curing of said epoxy resin during said mild heating conditions leaves said photoimageable composition soluble in alkaline aqueous solution.

Claim 11

A method of preparing a dry film comprising: (1) providing a photoimageable composition comprising a homogeneous solution of (a) between about 10 and about 40 wt. percent of a flowable, film-forming polymeric binder which has an acid number of about 100 or greater and is soluble in alkaline aqueous solution, said binder being selected from the group consisting of acrylic polymers and copolymers and saponified styrene-maleic anhydride copolymers; (b) between about 5 and about 25 wt. percent of a cross-linking agent for said polymeric binder selected from the group consisting of melamine-formaldehyde condensation products, and urea-formaldehyde resins, which cross-linking agent under mild heating conditions cross-links said binder to render said photoimageable composition non-tacky, while leaving said photoimageable composition solution soluble in alkaline aqueous solution, which cross-linking agent is reactive with complementary groups of said polymeric binder; (c) between about 15 and about 35 wt. percent of a polymerizable acrylic substance; (d) between about 0.1 and about 15 wt. percent of a photosensitive, free radical-generating initiator chemical system which in the presence of actinic radiation initiates polymerization of said acrylic substance to form a three-dimensional chemical structure which renders actinic radiation-exposed portions of said photoimageable composition insoluble to alkaline aqueous solutions; (e) between about 20 and about 50 wt. percent of an epoxy resin composition which is curable for sufficient time and/or high temperature to harden said photoimageable composition subsequent to exposure to actinic radiation, said epoxy resin being selected to be insufficiently cured under said mild heating conditions to render said photoimageable composition insoluble in alkaline aqueous solution, and (f) between about 0.01 and about 5 wt. percent of a cure catalyst for said epoxy resin selected from the group consisting of polycarboxylic acid anhydrides, dicyandiamides, complexes of amines with boron trifluoride or boron trichloride, latent boron difluoride chelates, aromatic polyamines and imidazoles, said components (a)-(f) being selected to be mutually miscible and mixed together to form said homogeneous solutions, (2) applying said photoimageable composition as a film on a backing sheet, and (3) heating said film of photoimageable composition for such time and temperature as to sufficiently cross-link said binder to render said film non-tacky yet still soluble in alkaline aqueous solution.

Claim 12

A method of preparing a dry film comprising: (1) providing a photoimageable composition comprising a homogeneous solution of (a) between about 10 and about 40 wt. percent of a flowable, film-forming polymeric binder which has an acid number of about 100 or greater and is soluble in alkaline aqueous solution, said binder being selected from the group consisting of acrylic polymers and copolymers and saponified styrene-maleic anhydride copolymers; (b) between about 5 and about 25 wt. percent of a cross-linking agent for said polymeric binder selected from the group consisting of melamine-formaldehyde condensation products, and urea-formaldehyde resins, which cross-linking agent under mild heating conditions cross-links said binder to render said photoimageable composition non-tacky, while leaving said photoimageable composition solution soluble in alkaline aqueous solution, which cross-linking agent is reactive with complementary groups of said polymeric binder; (c) between about 15 and about 35 wt. percent of a polymerizable acrylic substance; (d) between about 0.1 and about 15 wt. percent of a photosensitive, free radical-generating initiator chemical system which in the presence of actinic radiation initiates polymerization of said acrylic substance to form a three-dimensional chemical structure which renders actinic radiation-exposed portions of said photoimageable composition insoluble to alkaline aqueous solutions; (e) between about 20 and about 50 wt. percent of an epoxy resin composition which is curable for sufficient time and/or high temperature to harden said photoimageable composition subsequent to exposure to actinic radiation, said epoxy resin being selected to be insufficiently cured under said mild heating conditions to render said photoimageable composition insoluble in alkaline aqueous solution, and (f) between about 0.01 and about 5 wt. percent of a cure catalyst for said epoxy resin selected from the group consisting of polycarboxylic acid anhydrides, dicyandiamides, complexes of amines with boron trifluoride or boron trichloride, latent boron difluoride chelates, aromatic polyamines and imidazoles, said components (a)-(f) being selected to be mutually miscible and mixed together to form said homogeneous solutions, (2) applying said photoimageable composition as a film on a backing sheet, and (3) heating said film of photoimageable composition for such time and temperature as to sufficiently cross-link said binder to render said film non-tacky yet still soluble in alkaline aqueous solution.