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Latent Thermal Curing Agents for Cationic Photoimagable Epoxy Systems

IP.com Disclosure Number: IPCOM000102608D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 95K

Publishing Venue

IBM

Related People

Day, RA: AUTHOR [+3]

Abstract

Disclosed here is an example of an epoxy composition which contains a thermal curing agent that is compatible with cationic photoinitiators. The use of such curing agents enables photo-curable epoxy systems containing sulfonium type undergoing photoinitiated polymerization.

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Latent Thermal Curing Agents for Cationic Photoimagable Epoxy Systems

       Disclosed here is an example of an epoxy composition
which contains a thermal curing agent that is compatible with
cationic photoinitiators.  The use of such curing agents enables
photo-curable epoxy systems containing sulfonium type undergoing
photoinitiated polymerization.

      Typically, photoimagable epoxy resin systems containing
sulfonium salt photoinitiators are quite stable thermally. The epoxy
resins will autopolymerize at about 180oC, and the sulfonium
initiators are quite slow to react at those temperatures.  At room
temperatures, these systems are extremely stable and thus have long
shelf lives.  A typical process entails exposure to actinic radiation
to photolyze the initiator, followed by heating to advance the
polymerization.  While some polymerization will indeed occur at room
temperatures following the photolysis of the initiator, both steps
are necessary to achieve a high degree of cure.  In a photoimagable
epoxy system, a typical process flow would be a photoimage step
consisting of exposure to actinic radiation through a phototool
followed by a heat treatment to advance the image in the areas
exposed, developing the image in a suitable solvent, followed by a
second exposure to actinic radiation and a heat step to advance the
degree of polymerization to achieve the desired end properties.  In
such a scheme, both the expose and the heating steps are needed to
polymerize the epoxy resin system for both the image and final cure
process.

      In many applications, the advantages of a photoimage procedure
is necessary, but the second expose step is undesirable.  In these
applications, a combination of a photoinitiated system and a
thermally cured system is needed.  The properties of a suitable
thermal initiator for such a system would be a negligible effect on
the shelf life, no interference with the photoreaction, and not
initiating a reaction during the heat treatment step of the
photoimage procedure (120-130oC).

      Typical thermal initiators for epoxy systems are amine
compounds.  These are not suitable at all for the above application
because they act as a base (which reacts with the acid generated in
the photoiniti...