Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Patent
1998-01-14
1999-11-23
Berman, Susan W.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
522 80, 522 83, 522 84, 522 85, 522100, 522103, 4302811, 4302861, 528365, 528406, 428209, G03C 1725, G03C 173, C08G 5917, C08K 320
Patent
active
059901896
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with improvements in and relating to coating compositions and more particularly is concerned with coating compositions for the production of photopolymerizable coatings upon substrates.
In order to provide for the attachment of electrical components to a printed circuit board of the type comprising a patterned layer of an electroconductive metal (generally copper) on an electrically non-conductive substrate (generally a plastics impregnated substrate) a patterned layer of a solder resist is applied to the board so as to expose parts of the patterned metal layer and the so-coated board is contacted with molten solder so that the solder adheres to the patterned metal layer at the exposed portions thereof. Generally, before the board is contacted with the solder, the electrical components are placed on the other side of the board (although, of course, not in the case of surface-mounted boards) with conducting elements extending therefrom passing through holes in the board into the exposed portions of the patterned metal layer.
U.S. Pat. No. 4,100,045 discloses a radiation-curable vehicle for coating and printing ink composition obtainable as the reaction product of a polyepoxide, a saturated dicarboxylic acid, an ethylenically unsaturated monocarboxylic acid, and optionally, a saturated monocarboxylic acid. These materials have low acid values and set-hard upon UV curing.
It has now been found that a patterned solder resist may be formed from a photopolymerizable composition comprising a modified epoxy resin, as hereinafter defined, by exposing a layer of such a composition to actinic radiation through a suitable transparent substrate bearing an opaque image, and subsequently, in a "development" step, removing unexposed composition with a solvent therefor, namely an aqueous alkaline solution, due to the high acid value of the material.
According to one embodiment of the invention, therefore, there is provided an ethylenically unsaturated polymerizable reaction product of a polyepoxide and a mixture of (i) a major proportion of an ethylenically unsaturated carboxylic acid and (ii) a minor proportion of a saturated aliphatic or aromatic carboxylic acid, further modified by a reaction with an anhydride of a dicarboxylic acid.
The invention also provides a coating composition, for the production of a photopolymerizable coating, comprising a modified reaction product as described above together with a photopolymerization initiator for the said polymerizable reaction product and a liquid carrier.
Preferably, the composition also contains an inert organic filler, the said filler and the said reaction product suitably being present in a ratio of from 5 to 25 parts by weight of filler to from 95 to 75 parts by weight of the modified reaction product.
The invention also provides a method of forming a photopolymerizable coating upon a substrate which comprises applying a coating of a coating composition as defined above to the substrate and allowing it to dry by evaporation of the liquid carrier.
The modified reaction product of polyepoxide and ethylenically unsaturated carboxylic acid, generally acrylic acid or methacrylic acid, is hereinafter simply referred to as the "modified epoxy acrylate". The modified epoxy acrylate should preferably be solid or semi-solid at ambient temperature, e.g. should preferably have a ring and ball softening point (determined according to British Standard Specification No. 4692 of 1971) of at least 30.degree. C. preferably at least 60.degree. C. The unmodified epoxy acrylate is one derived from. the reaction of a polyepoxide and a mixture of an ethylenically unsaturated carboxylic acid or reactive derivative thereof and a saturated aliphatic or aromatic carboxylic acid or reactive derivative thereof. The polyepoxide is preferably an aromatic polyepoxide. Aromatic polyepoxides are polyepoxides containing phenyl groups (polyphenyl polyepoxides) such as polyepoxides derived from the reaction of bisphenols, especially polynuclear bisphenols such as bisphenol-A, wi
REFERENCES:
patent: 4100045 (1978-07-01), Bogan et al.
patent: 4714751 (1987-12-01), Schornick et al.
patent: 4935330 (1990-06-01), Hofmann et al.
Hall Stephen Anthony
Ivory Nicholas Eric
Berman Susan W.
Coates Brothers PLC
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