Epoxy acrylates

Details Epoxy acrylates Epoxy acrylates

1994-06-28

2004-06-08

Sellers, Robert (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C522S014000, C522S100000

Reexamination Certificate

active

06747101

ABSTRACT:

The present invention relates to epoxy acrylates of higher molecular weight and to carboxyl group-containing epoxy acrylates of higher molecular weight, to the preparation thereof, to the use of said epoxy acrylates in photoresist formulations, and to the use of said formulations, in particular in the field of printed wiring boards, typically as solder resists or as primary resists (etch resists or galvanoresists), and of printing plates.
Epoxy acrylates are known in abundance and are also used, inter alia, in compositions used as photoresist formulations.
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 mask 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.
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 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 of additional polymer binders. They are obtained by reaction of so-called “postglycidylated” epoxy resins (PGER) with, typically, (meth)acrylic acid.
Batzer and Zahir (J. Appl. Polym. Sci., 19, 609 (1975)) describe the postglycidylation of a low molecular liquid diglycidyl ether of bisphenol A. U.S. Pat. No. 4,623,701 discloses postglycidylated epoxy resins and the cure thereof with various epoxy hardeners; and U.S. Pat. No. 4,074,008 discloses photocrosslinked epoxy resins containing more than 2 epoxy groups in the molecule, at least 2 of which originate from a postglycidylation reaction. The photo-crosslinkable groups in the molecular chain constitute &agr;,&bgr;unsaturated carbonyl systems (chalcone groups). Derivatives containing (meth)acrylyl groups are not described therein.
It is also known that the photosensitivity of an &agr;,&bgr;unsaturated carbonyl system that is photocrosslinkable by a 2+2-cycloaddition mechanism is substantially lower compared with the photopolymerisation of acrylates.
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. Furthermore, European patent application 0 292 219 discloses photosensitive systems that contain epoxy compounds of bisphenol A that are modified with acrylic acid.
Specifically, the invention provides epoxy acrylates of formula III
wherein
Q is hydrogen or a group of formula
R
1
is —H or —CH
3
, R
2
is —H, —CH
3
or phenyl
T is the radical of an aromatic bifunctional compound, and
M is each independently hydrogen or a group of formula
R
1
and R
2
are as defined above,
A is the radical of an aromatic bifunctional compound,
n is an integer from 0 to 300, and
L is a group of formula
 with the proviso that in formula III not all radicals M may simultaneously be hydrogen or a group of formula
 but at least 10 mol %, preferably 20-100 mol %, of the radicals M that are not present in the end groups Q and L denote a group of the formula
The epoxy acrylates of formula III are obtained by reacting a postglycidylated epoxy resin of formula II
wherein
E is hydrogen or a group of formula
F represents the groups of formula —O—A—OG or
G is —H or the radical
 as in formula III, at least 10 mol % of the radicals G in formula II that are not present in the end groups E and F, represent the group of formula
A, T, and n have the given meanings,
with an ethylenically unsaturated monocarboxylic acid in the presence of a catalyst and a polymerisation inhibitor, at elevated temperature.
If n in formula III is 0, then Q is —H and L is the group of formula
In preferred epoxy acrylates of formula III, n is an integer from 0 to 50, preferably from 0 to 30, and the symbols A and T have the preferred meanings of A and B given in Japanese patent Kokai Hei 1-195056.
Preferred bifunctional aromatic compounds A and T are linking groups of formulae
in which R
4
and R
5
are each independently of the other —H or C
1
-C
4
alkyl, Z is —S—, —O— or —SO
2
, and the aromatic radicals of the linking group A or T are unsubstituted or substituted by halogen or C
1
-C
4
alkyl. C
1
-C
4
Alkyl is preferably —CH
3
and halogen is preferably bromo.
Particularly preferred linking groups A and T each independently of the other have the formula
wherein R
4
and R
5
are as defined above and the phenyl radicals of the linking group are unsubstituted or substituted by bromo, and, preferably have the formulae
Throughout this specification, epoxy acrylates are taken to mean reaction products of epoxy compounds with (meth)acrylic acid.
Some of the postglycidylated epoxy resins of formula II are known and are prepared from the corresponding known advanced epoxy resins of formula I
by a glycidylation reaction, wherein in formula I
U is hydrogen or the group of formula
 and
D is the group of formula
 or the radical —O—A—OH, and the symbols A, T and n are as defined in connection with formula III.
The advanced epoxy resins of formula I on the other hand are obtained by known polyaddition of a bisphenol of formula
HO—A—OH
to a diepoxy of formula
wherein A and T are the radical of a bifunctional aromatic compound.
The bisphenols HO—A—OH or HO—T—OH are preferably known bisphenols, more particularly bisphenol A and tetrabromobisphenol A, as well as those that are described in Japanese patent Kokai Hei 1-195056, preferably bisphenol A, bisphenol F, tetrabromobisphenol A and tetrabromobisphenol F.
To prepare the advanced epoxy resins, an excess of the above diepoxy is used, so that the advanced epoxy resins of formula I carry epoxy end groups. It i

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