Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1996-05-23
2002-11-12
Gulakowski, Randy (Department: 1746)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S488000, C525S530000, C525S532000, C525S922000
Reexamination Certificate
active
06479596
ABSTRACT:
The present invention relates to novel epoxy acrylates of higher molecular weight and to novel polymolecular carboxyl group-containing epoxy acrylates, to the preparation thereof, to the use of said acrylates in photoresist formulations, and to the use of said formulations, in particular in the field of printed wiring boards and printing plates.
Epoxy acrylates are known in abundance and are also used, inter alia, in compositions used as photoresist formulations, for example in GB 2 175 908, in which resins derived from an unsaturated polybasic acid anhydride and a reaction product of an epoxy acrylate and an unsaturated monocarboxylic acid are used.
Formulations for solder resists that contain reaction products of epoxy novolak resins with acrylic acid and cyclic carboxylic anhydrides are disclosed, inter alia, in EP 0 273 729. They are developable in aqueous alkaline media and have good thermal resistance and photosensitivity. Their resistance to chemicals, however, is unsatisfactory.
EP 0 418 011 discloses compositions for solder masks that are likewise based on reaction products of epoxy cresol novolaks with acrylic acid and cyclic dicarboxylic anhydrides, using 0.4 to 0.9 equivalent of acrylic acid per equivalent of epoxy group, such that the final product simultaneously contains acid and epoxy groups in the same molecule. A second thermal crosslinking reaction between these two functionalities is thereby made possible in the application of these resist compositions. The problem here is, however, aside from the preparation of the products (danger of gelation in the reaction with the anhydride), the storage stability, as the formulation containing such reaction products has a certain reactivity even at room temperature.
All these cited epoxy acrylates are quite generally relatively low-molecular.
Photochemically or thermally cured epoxy acrylates that are derived from low molecular epoxy resins and epoxy novolaks are known for their good thermal and mechanical properties as well as for their good resistance to aggressive chemicals. However, the tackiness and edge coverage of the resist films obtained with these systems on conductors owing to the fairly low relative molar mass are unsatisfactory. In practical application it is therefore often necessary to avoid these shortcomings by adding highly polymerised polymer binders. Such binders normally contain no functional acrylate groups and do not react concurrently during the photochemical or thermal cure, i.e. they are not incorporated as “passive” components in the network and therefore result in a dilution of the network density, which, in turn, adversely affects in particular the resistance to chemicals and the electrical properties of processed resist layers. Furthermore, the photosensitivity decreases as a consequence of the “dilution” of the acrylate groups. The addition of highly polymerised polymer binders induces high viscosity of these formulations even if the solids content is relatively low and therefore often results in serious problems in coating.
Japanese patent Kokai Hei 04-294352 discloses the modification of epoxy-novolak resins by reaction with an unsaturated monocarboxylic acid and subsequently with an unsaturated anhydride of a polycarboxylic acid and the use thereof in photosensitive aqueous formulations.
It is therefore the object of this invention to provide acrylates that do not have the shortcomings referred to above.
This object is achieved in the practice of this invention by novel epoxy acrylates and novel carboxyl group-containing epoxy acrylates of higher molecular weight which, when used in resist formulations, are able to function without or with only minor amounts (<10% by weight) of additional polymer binders. They are obtained by reaction of so-called “advanced” epoxy resins with, typically, (meth)acrylic acid.
Specifically, the invention provides novel epoxy acrylates of formula II
wherein
M is the group of formula
R
1
is —H or —CH
3
, R
2
—H, —CH
3
or phenyl,
R is C
1
-C
4
alkyl or halogen, preferably CH
3
or Br,
x is an integer from 0 to 3, preferably 0 or 1, and
Y is a linking group of formula
wherein R
3
and R
4
are each independently of the other hydrogen or C
1
-C
4
alkyl, or R
3
and R
4
, together with the linking carbon atom, form a 5- or 6-membered hydrocarbon ring, and the aromatic radicals of the linking group Y are unsubstituted or substituted by halogen or C
1
-C
4
alkyl,
X is —S—, —O—, or —SO
2
—, and
n is an integer from 0 to 300, preferably from 0 to 30, with the proviso that at least 10 mol % of the radicals M have the structure of formula
in which R
1
and R
2
are as defined above.
If the aromatic radicals of the linking group Y are substituted, then suitable halogen substituents are fluoro, chloro and, preferably, bromo; and suitable C
1
-C
4
alkyl substituents are straight-chain or branched C
1
-C
4
alkyl groups such as methyl, ethyl, n- and isopropyl, n-, sec- and tert-butyl.
Particularly preferred linking groups Y have the formula
wherein R
3
and R
4
are as defined above and, in particular, have the formulae
Preferred epoxy acrylates have the formula II, wherein R is —H (for x═O) or —CH
3
, R
1
is —H or —CH
3
, R
2
is —H, x is 0 or 1, n is an integer from 0 to 30, and Y is a linking group of formula
wherein R3 and R4 are —H or C
1
-C
4
alkyl and the aromatic radicals of the linking group are unsubstituted or substituted by halogen or C
1
-C
4
alkyl.
The novel epoxy acrylates of formula II may be obtained by reacting an advanced epoxy novolak of formula I
wherein R, Y, n and x are as defined for formula II, with an ethylenically unsaturated monocarboxylic acid, if necessary in the presence of a catalyst and of a polymerisation inhibitor, at elevated temperature.
The advanced epoxy novolaks of formula I are known (q.v. inter alia JP patent Kokai Hei 1-195056) and are prepared from a bisphenol of formula HO—Y—OH, wherein Y is as defined above, and an epoxy novolak, in known manner, the molar amount of bisphenol being conveniently 0.01 to 0.1 mol per epoxy group in the epoxy novolak.
These advanced epoxy novolaks of formula I carry secondary aliphatic hydroxyl groups.
The reaction of the advanced epoxy novolaks of formula I to give the novel epoxy acrylates of formula II is carried out in known manner, conveniently by reaction with an ethylenically unsaturated monocarboxylic acid of formula
Suitable acids are crotonic acid, cinnamic acid and, preferably, acrylic acid or methacrylic acid or a mixture thereof. R
1
and R
2
have the meanings given above.
It is preferred to use a catalyst in this reaction. Particularly suitable catalysts are metal salts such as chromium compounds, amines such as triethylamine or benzyldimethyl-amine, also ammonium salts such as benzyltrimethylammonium chloride, or also triphenylphosphine and triphenylbismuth.
A solvent may be added to the reaction, as the advanced epoxy resins of formula I are in the form of solids. However, the solvent must be inert to the educt. Suitable solvents include: ketones such as acetone, methyl ethyl ketone, cyclohexanone; esters such as ethyl and butyl acetate, ethoxyethyl acetate or methoxypropyl acetate; ethers such as dimethoxyethane and dioxane; aromatic hydrocarbons such as toluene, benzene and xylenes, as well as mixtures of two or more of these solvents.
The temperature will conveniently be in the range from 80 to 140° C., the reaction with acrylic acid being preferably carried out in the range from 80 to 120° C. and that with methacrylic acid preferably in the range from 80 to 140° C.
A polymerisation inhibitor may also be added to the reaction medium, suitably hydroquinone, hydroquinone monomethyl ether and 2,6-di-tert-butyl-p-cresol.
It is desirable to introduce air or a mixture of nitrogen/oxygen into the reaction medium, as some of the aforementioned polymerisation inhibitors are effective only in the presence of oxygen. Depending on the amount of ethylenically unsaturated monocarboxylic acid used, epoxy acrylates of formula II that are completely or only partially acry
Meier Kurt
Roth Martin
Sailer Bernhard
Salvin Roger
Wiesendanger Rolf
Gulakowski Randy
Neuman, Esq. Kristin H.
Proskauer Rose LLP
Vantico Inc.
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