CA1114986A

CA1114986A - Curable compositions containing epoxy resins, polyvinyl acetal and an aromatic onium salt

Info

Publication number: CA1114986A
Application number: CA287,740A
Authority: CA
Inventors: James V. Crivello
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1976-10-14
Filing date: 1977-09-29
Publication date: 1981-12-22

Abstract

Curable compositions are provided based on the use of an aromatic onium salt with a blend of epoxy resin and polyvinyl acetal resin. The curable compositions in the form of a cast film can be used directly as a dry film photoresist by being applied to a substrate, such as a copper clad laminate, and cured with ultraviolet light.

Description

1~14~ RD-9473 The present invention relates to curable compositions useful as or for making dry film photoresist and insulating coating on various substrates in the cured state.
The curable compositions of the present invention comprise by weight (A) 0.5% to 98~ of epoxy resin, and (B) 0.5% to 98% of polyvinyl acetal, and (C) 0.1% to 10% of aromatic onium salt, where the sum of (A) and (B) and (C) is 100%, and (C) is selected from an aromatic iodonium salt of the formula ~- (1) [ (R)a (R )b I]c [MQd]

or an aromatic onium salt of a Group Va element of the formula ( )f (R )g (R )h E] [MQ ]-(d-e) or an aromatic onium salt of a Group VIa element of the formula i )k (R )m G]c [MQ ]~(d-e) where R is a monovalent aromatic organic radical, R is a divalent aromatic organic radical, R2 and R4 are monovalent - 20 organic aliphatic radicals selected from alkyl, cyclo alkyl and substituted alkyl, R3 and R5 are polyvalent organic radicals forming a heterocyclic ring structure or a fused ring structure with E or G, E is a Group Va element selected from N, P, As, Sb and Bi, G is a Group VIa element selected from S, Se and Te, M is a metal or a metalloid, Q is a halogen selected from F and Cl, ,,` - 1 - ~

~L4~

a is a whole number equal to 0 or 2, b is a whole number equal to 0 or 1 and the sum of a + 2b is equal to 2, f is a whole number equal to 0 to 4 inclusive, g is a whole number equal to 0 to 2 inclusive, h is a whole number equal to 0 to 2 inclusive and the sum of (f + g) + h times the valence of R3 is equal to 4, j is a whole number equal to 0 to 3 inclusive, k is a whole number equal to 0 to 2 inclusive, m is a whole number equal to 0 or 1 and the sum of (j+k)+m times the valence of R is equal to 3, e is equal to the valence of M and is an integer equal to 2 to 6 inclusive, d is greater than e and is an integer having a value up to 7, and c = d - e.
Radicals included by R can be the same or different aromatic carbocyclic or heterocyclic radicals having from 6 to 20 carbon atoms, which can be substituted with from 1 to 4 mono-valent radicals selected from C(l 8) alkoxy, C(l 8) alkyl, nitro, chloro, etc., R is more particularly phenyl, chlorophenyl, nitrophenyl, methoxyphenyl, pyridyl, etc. Radicals included by Rl are divalent radicals, such as ~CH2) R2 and R4 radicals include C(l 8) alkyl, such as methyl, ethyl, etc., substituted alkyl, such a~ -C2H40CH3, -CH2COOC2H5, -CH2COCH3, etc. R3 and R5 radicals include such structures as ~/

- where Q' is selected from 0, CH2, N R and S; Z is selected from ~ R' -~ -0~ -S- and -N-, and R' is a monovalent radical selected from hydrogen and hydrocarbon.
Metal or metalloids included by M of formula l are transition metals such as Sb, Fe, Sn, Bi, Al, Ga, In, Ti, Zr, Sc, V, Cr, Mn, Cs, rare earth elements such as the lanthanides, for example, Cd, Pr, Nd, etc., actinides, such as Th, Ta, U, Np, etc., and metalloids such as B, P, As, etc. Complex anions -(d-e) included by MQd are, for example, BF4 , PF6 , AsF6 , SbF6 , FeC14 , SnC16 , SbC16 , BiC15 , etc.

~ `'~ RD-9473 /0d'~ r ~ u~
hYt4~ salts ~r~kon~rd by formuls 1 are, for ex~mple, : I+BF4 I+PF6 I+BF4 I+SbF6 I+BF4 Group Va onium salts included by formula 2 are, for example, +N-CH2-C ~ BF4 , .

<~ N+CH2-C--@\ SbF6-, .

~ ,r.

CH2 C ~ BF4- ~ r (~

- CH2 C ~> BF4, 4P+ B~4, (~3P+-CH2-C~ A F ~
. .

(~3P CH2COOC2H5 ~6 ~
` , -' ' ' ~ ' :' ~ ~ ~4~ RD-9473 ( ~ 3~r ~ 3F

0 3 BF4 , H

( ~ BF4 , '`' - ~ As+-CH2-C ~ BF ~

( ~ 3Bi-CH2-C ~ F4 ~

Group VIa onium salts included by formula ~ are, for example, C-CH2-5 \ 3F4-, : CH3 ~ C-CH2-5 02N ~ C-CH2-5 Br~C-CH2-S ~ SbF -C-CH2-5 ~ ~ FeC14 , C-CH2-5~ SnC16 , ,.

~ S+ SbC16-,, .. , . ... , .. ., ... ... . . ~ . .. .. . . . . . . ..

] ~lC15-, ' ~ . J
S BF4 , .

~ C-CH2Se ~ PF6 , etc.

The onium salts of formulas 1-3 can be made by different method~. In formula 1, the photoinitiator can be made by effect-ing contact under aqueous conditions between an arylhalonium bisulfate and the corresponding hexafluoro acid or salt, such as YlMF6, where yl can be hydrogen, an alkali metal ion, alka-line earth metal ion or transition metal ion.
In addition to the above-described metathesis for making the corresponding halonium salts, the halonium salts of the present invention, also can be prepared by using silver compounds, such as silver oxide, or silver tetrafluoroborate, which were reacted with ~he appropriate diarylhalonium salt, as shown by M. C. Cas~rio et al., J. Am. Chem. So~. 81, 336 (1959) or M. C. Beringer et al., J. Am. CHem. Soc. 81, 342 (1959). Methods for making Group VIa compounds, such as sul-fonium, selenium ~nd tellurium compounds can be made by pro-cedures shown in J. W. Knapczyk and W. E. McEwen, J. Am. Chem.

-B-, . ... . , . ~ .. . . . . . . . . . . . .

?

Soc., 91 145, (1969); A. L. M~ycock and G. A. Berchtold, J.
Org. Chem., 35 No. 8,2532 (1970); H.M. Pitt, U. S. Patent

2,807,648, E. Goethals and P. De Radzetzky, Bul. Soc. Chlm.
Belg., 73 546 (1964); H. M. Leichester and F. W. Bergstrom, J. Am. Chem. Soc., 51 3587 (1929), etc. - A
Among the procedures which can be used to make Group Va onium salts, arsonium, antimonium and bismuthonium salt can be found in Goerdeler, Methoden der Organishen Chimie llJ2, 591-640 (1958) and K. Sasse, idid, 12/1 79-112 (1963).
The term "epoxy resin" as utilized in the description of the curable compositions of the present invention, includes any monomeric, dimeric or oligomeric or polymeric epoxy material containing one or a plurality of epoxy functional groups. For example, those resins which result from the reaction of bis-phenol-A (4,4'-isopropylidenediphenol) and Qpichlorohydrin, or by the reaction of low molecular weight phenol-formaldeh,yde resins (Novolak resins) with epichlorohydrin, can be used alone or in combinatnion with an epoxy containing compound as a reactive diluent. Such diluents as phenyl glycidyl ether, 4-vinylcyclohexene dioxide, limonene dioxide, 1,2-cyclohexene -oxide, glycidyl acrylate, glycidyl methacrylate, styrene oxide, allyl glycidyl ether, etc., may be added as viscosity modify-ing agents.
In addition, the range of these compounds can be extended to include polymeric materials containing terminal or pendant epoxy groups. Examples of these compounds are vinyl copolymers containing glycidyl acrylate or methacrylate as one of the comonomers. Other classes of epoxy containing polymers amenable to cure using the above catalysts are epoxy-siloxane resins, epoxy-polyurethanes and epoxy-polyesters. Such polymers ,. . . . ..... ..... . .... . . .

4 ~

usually have epoxy functional groups at the end~ of their chalns. t Epoxy-siloxane resins and method for making are more particularly ¦-shown by E. P. Plueddemann and G. Fanger, J. Am. CHem. Soc. 80 ' ~i 632-5 (1959). As described in the literature, epoxy resins can also be modified in a number of standard ways such as reactions with amines, carboxylic acids, thiols, phenols, alcohols, etc., as shown in patents 2,935,488; 3,235,620; 3,369,055; 3,379,653;

3,398,211; 3,403,199; 3,563,850; 3,567,797; 3,677,995; etc.
Further examples of epoxy resin~ which can be used are shown ln the Encyclopedia of polymer science and technology, Vol. 6, 1967, Interscience Publishers, New York, pp 209,271.
The polyvinyl acetals which can be used in the curable compositions of the present invention can be mixtures of units, e.g., --FCH-CH2-CH-CH2 ~_ LOH OH J , and CH

chemically combined with - CH2-CH-cH-cH2_ -\cl ~ -where the polymers can have an average of from about 5 to 5000 units and R6 is selected from hydrogen~ C(l 8) alkyl, such as methyl, ethyl, butyl and mixtures thereof. Additional polyvinyl .. . ..

1~L14~

acetals which can be used in the practice of the invention are shown in the Encyclopedia of Polymer Science and Technology, H. F. Mark and N. G. Gaylord, Vol. 14, 149 (1971).
The curable compositions of the present invent~on can be cast from organic solvent solutions to produce dry film photoresists. Suitable organic solvents which can be employed include, for example, methylene chloride, chloroform, methyl ethyl ketone, cellosolve acetate, tetrahydrofuran, acetonitrile, etc., at from 0 to 80% by weight of the curable composition. The curable compositions can be heat cured at temperatures of from 100C to 200C. If desired, as shown in my Canadian applica-tion Serial Number 277,774, filed May 5, 1977 and assigned to - the same assignee as the present invention, 0.5% to 10% by weight of a reducing agent can be added to the curable compositions in order to facilitate the heat cure of the curable composition .
particularly when employed to make insulating coating on aluminum and copper conductors. --Preferably, the curable compositions of the present ~ invention can be converted to the solvent resistant state when 20 exposed to ultraviolet light as cast films. When used as dry film photor~sist, the film can be patterned with,a mask using W irradiation having a wavelength of from 1849 A to 4000 A
and an intensity of at least 5,000-80,000 microwatts per cm2.
- The lamp systems used to generate such radiation can consist of ultraviolet lamps such as from 1 to 50 discharge lamps, for exa~ple, xenon, metallic halide, metallic arc, such as a low, medium or high pressure mercury vapor discharge lamp, etc., ~- having an operating pressure of from a few millimeters to about 10 atmospheres, etc., can be employed. The lamps can include envelopes capable of transmitting light of a wavelength of from RD-9473 ~.

o o o O
about 1849 A to 4000 A, and preferably 2400 A to 4000 A. The ~' ~3 lamp envelope can consist of quartz, such as Spectrocii, or of ~ 1' Pyrex, etc. Typical lamps which can be employed for providing , ultraviolet radiation are, for example, medium pressure mercury arcs, such as the GE HT37 arc and the Hanovia 450 W arc lamp. i;
The cures may be carried out with a combination of various lamps, some or all of which can operate in an inert atmosphere. When using W lamps, the irradiation flux on the substrate can be at least 0.01 watts per square inch to effect cure of the dry film photoresist.
The curable compoæitions may contain inactive ingre-dientq, such as inorganic fillers, dyes, pigments, extenders, viscosity control agents, process aids, UV-screens, etc., in amounts of up to 100 parts filler per 100 of ~epoxy resin. The curable compositions can be applied to such substrates as metal, rubber, plastic, molded parts of films, paper, wood, glass, ~, cloth, con~rete, ceramic, etc. -In order that those skilled in the art will be better able to practice the invention, the following examples are given by way of illustration and not by way of limitation. All parts -~
are by weight. -Example 1.
A solution of 10 parts of polyvinylformal ~Monsanto Formvar 12/85), 2.5 parts of Ciba-Geigy Araldite ECNl299 cresol-novolac epoxy resin, 0.3 part of triphenylsulfonium hexafluoroantimonate, and about B0 parts ~f chloroform was cast - as a 5 mil film onto a glass plate. The film was removed and exposed through a glass contact mask to ultraviolet light from - a GE HT37 medium pressure mercury arc lamp for 3 minutes at a distance of 6 inches. After irradiation, a visible image was .

~ ~ ; RD-9473 observed in the film. The latent image was developed by immers-ing the film in chloroform. A clear upraised negative image of the mask in the film resulted.
Example 2.
A solution was prepared cons~sting of 10 parts of Formvar 15/95E polyvinylformal, S parts of the epoxy resin of Example 1 (ECN 1299), 0.3 part of triphenyl sulfonium hexafluoro-antimonate, 80 parts of methylene chloride was cast as a 5 mil film onto a polyethylene terephthalate substrate. A contact mask was then placed on top of the resulting composite, which was then exposed for 3 minutes under ultraviolet light as described in Example 1. The resulting composite was then dev-eloped by immersing it in 2-ethoxyethylacetate. There was obtained a polyethylene terephthalate substrate having a negative image of the mask on its surface, which was useful as a printing `- plate.
Example 3.
A curable composition was prepared by dissolving 10 parts of Formvar 15/95E, 0.3 part of triphenylsulfonium hexa-fluoroarsenate and 5 parts of Araldite ECN 1299 and about 80 parts of methylene chloride. The resulting solution was then cast onto a glass plate. A translucent film was obtained from the resulting solution upon evaporation of the solvent. The film was then removed from the glass substrate and placed in contact with a mask. The film was then irradiated as described in Example 1, for a period of about 1.5 minutes. The film was then heated in an oven at 100C for 5 minutes. There was obtained a clear negative reproduction of the mask when the film was developed using chloroform.

~ RD-9473 Example 4.
A film was cast onto a glass plate of A curable composition consisting of 10 parts of the reaction product of s polyvinyl alcohol and butyraldehyde (Butvar B-74), 2.5 parts of Araldite ECN 1299, 0.3 part of triphenylsulfonium hexafluoro arsenate and about 90 parts of methylene chloride. The film was removed from the glass plate and then laminated onto a cop-per-clad epoxy-glass circuit board at 130C under pressure.
The laminated board was then exposed to ultraviolet light as 10in Example 1, using a contact mask. The laminate was then developed using chloroform to produce a negative image of the curable resin on copper. The copper laminate was then etched using ferric chloride. There was obtained a copper-clad lamin-ate having a positive image of the mask in copper on the sur-face of the epoxy glass substrate.
Example 5.
A curable compo~ition was prepared as described in `Example 4, except there was employed triphenyl sulfonium hexa-fluoroantimonate as the photoinitiator and there was utilized 20in the composition 0.1 part of Dayglo T-13 pigment. A film was cast onto a sheet of polyethyleneterephthalate. After the film dried, it was covered with a contact mask and exposed to ultraviolet light as described in Example 1. The irradiated photosensitive film-polyethyleneterephthalate composite was then contacted to plain white paper and heated to 130C under pressure. There was obtained a clear negative image of the mask on the white paper. It was found that the composite could be used to transfer sharp negative images of the mask to several additional pieces of paper following the same procedure.
Based on the above results, the curable compositions ' 1 ~ 14~ RD 9473 of the present invention csn be employed as dry film photo-resist to produce printing plates, copper-clad laminates, etc.
As shown in United States Patent Number 4,026,705 issued Mby 31, 1977. and assigned to the same assignee as the present invention, visible light curable compositions are described, based on the use of diarylhalonium salts in com-bination with certain organic dyes as a photoinitiator for epoxy resins. Such visible light photoinitiators also can be used in the practice of the present invention as shown by the following example.-ExamPle 6.
A methylene chloride solution was cast onto a Mylar film, consisting of 10 parts of Formvar 15/95E, 2.5 parts of Araldite ECN 1299, 0.3 part of diphenyliodonium hexafluoro-arsenate, 0.1 part of benzoflavin and about 80 parts of methyl-ene chloride. When the film was dry it was subjected to image-wise exposure using a GE 375W photoflood lamp, which is a visible light source. Irradiation for 5 minutes produced a clear image in the film. The latent image was developed using .

~ 20 chloroform, 2-ethoxyethyleacetate or methylene chloride, .
;~ - resulting in a clear upraised reproduction of the mask.
The above procedure was repeated except that in place of benzoflavin, there was used acridine orange. In addition, a third film was cast using phosphene-R dye in place of the benzoflavin. It was found that substantially equivalent results -' were obtained with each of the aforementioned dyes, which were substituted for benzoflavin.
A curable composition was prepared as described above in which Formvar 15/95E was substituted with an equivalent weight -- 30 of ethylcellulose. A film was cast from this mixture and sub-~ ~ected to image-wise exposure using a contact mask. It was ~ - .

.. ,.. ,.. " . . j,, .. ;.. ,. .... ~ .. ~.. ,." .1~,...... . ... .

found that the resulting exposed film dissolved completely ~n chloroform when development of the film was attempted. Thl~ ?
indicated that no cross-linking had occurred in the absence of the polyvinylacetal which was required to make a dry film photoresist.
In addition to the above shown dyes employed in the visible light curable compositions of the present invention, other dyes which can be used in combinatnion with the diphenyl-iodonium salts, used in the practice of the invention, are cat-ionic dyes, such as shown in volume 20, page 194-7 of the Kirk-Othmer Encyclopedia, second edition 1965, John Wiley Sons, New York. In addition to the aforementioned cationic : dyes, basic dyes also can be used which are shown in volume 7, .; pages 532-4 of the Kirk-Othmer Encyclopedia as cited above.
Some of the cationic dyes which can be used are, for example, Acridine orange C.I. 46005 Acridine yellow C.I. 46025 Setoflavin T C.I. 49005.
In addition, some of the basic dyes which can be used are, for example, Haematoporphyrin

4,4'-bisdimethylaminobenzophenone 4,4'-bisdiethylaminobenzophenone, etc.
Although the above examples are limited to only a - few of the very many variables out of which the compositions of the present invention can be made,'it should be understood that the compositions of the present invention are broadly directed to the use of epoxy resin, polyvinylacetals and onium salt which are more particularly defined in the description preceding these examples.

Claims

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A curable composition which comprises by weight:
(A) 0.5% to 98% of epoxy resin, and (B) 0.5% to 98% of polyvinyl acetal, and (C) 0.1% to 10% of aromatic onium salt, where the sum of (A) and (B) and (C) is 100%, and (C) is selected from an aromatic iodonium salt of the formula [(R)a (R1)b I]? [MQd]-(d-e) or an aromatic onium salt of a Group Va element of the formula [(R)f (R2)g (R3)h E]? [MQd]-(d-e) or an aromatic onium salt of a Group VIa element of the formula [(R)j (R4)k (R5)m G]? [MQd]-(d-e) where R is a monovalent aromatic organic radical, R1 is a divalent aromatic organic radical, R2 and R4 are monovalent organic aliphatic radicals selected from alkyl, cyclo alkyl and substituted alkyl, R3 and R5 are polyvalent organic radicals selected from aliphatic radicals and aromatic radicals and forming a heterocyclic ring structure or a fused ring structure with E or G, E is a Group Va element selected from N, P, As, Sb and Bi, G is a Group VIa element selected from S, Se and Te, M is a metal or a metalloid, Q is a halogen selected from F and Cl, a is a whole number equal to 0 or 2, b is a whole number equal to 0 or 1 and the sum of a + 2b is equal to 2, f is a whole number equal to 0 to 4 inclusive, g is a whole number equal to 0 to 2 inclusive, h is a whole number equal to 0 to 2 inclusive and the sum of (f+g)+h times the valence of R3 is equal to 4, j is a whole number equal to 0 to 3 inclusive, k is a whole number equal to 0 to 2 inclusive, m is a whole number equal to 0 or 1 and the sum of (j+k)+m times the valence of R5 is equal to 3, e is equal to the valence of M and is an integer equal to 2 to 6 inclusive, d is greater than e and is an integer having a value up to 7, and c = d - e.

2. An organic solvent solution of a curable composition in accordance with claim 1.

3. A curable composition in accordance with claim 1, in the form of a film on a substrate.

4. A curable composition in accordance with claim 1, where the polyvinyl acetal consists essentially of a mixture of from about 5 to about 5000 units selected from and and chemically combined with where R6 is selected from hydrogen and C(1-8) alkyl.

5. A curable composition in accordance with claim 4, where R6 is methyl.

6. A curable composition in accordance with claim 4, where R6 is butyl.

7. A curable composition in accordance with claim 1, where the aromatic onium salt is an aromatic iodonium salt.

8. A curable composition in accordance with claim 1, where the aromatic onium salt is a salt of a Group Va element.

9. A curable composition in accordance with claim 1, where the aromatic onium salt is a salt of a Group VIa element.

10. A curable composition in accordance with claim 1, where the aromatic onium salt is a triphenylsulfonium hexa-fluoroantimonate.

11. A curable composition in accordance with claim 1, where the aromatic onium salt is diphenyliodonium hexafluoro-arsenate.

12. A curable composition in accordance with claim 1, where the aromatic onium salt is triphenylsulfonium hexafluoro-arsenate.

13. A curable composition in accordance with claim 1, where the vinylacetal is polyvinylformal.

14. A curable composition in accordance with claim 1, where the vinylacetal is a reaction product of polyvinyl alcohol and butyraldehyde.

15. A curable composition in accordance with claim 2, comprising a chloroform solution of polyvinylformal, a cresol-novolak epoxy resin and triphenylsulfonium hexafluoroantimonate.

16. A methylene chloride solution of a composition in accordance with claim 2, comprising a reaction product of poly-vinyl alcohol and butyraldehyde, a cresol-novolak epoxy resin and triphenylsulfonium hexafluoroarsenate.

17. A curable composition in accordance with claim 4, where R6 is hydrogen.