Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
1999-10-15
2002-08-13
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S060000, C528S065000, C528S075000, C528S085000, C525S124000, C427S385500, C428S423100
Reexamination Certificate
active
06433123
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to thermosetting resin compositions for overcoats of flexible circuits, which are excellent in low shrinkage during curing and flexibility, and particularly in that the resulting overcoats are difficult to deteriorate in qualities, e.g., to overharden, to increase in curling, and the like, even after being allowed to stand for a long time at elevated temperatures. It relates also to a film carrier coated with an overcoat agent comprising, as the main ingredient, such a resin composition for overcoat of flexible circuit, as well as to a film device where such film carrier is used.
2. Prior Art
The surface protective films of flexible wiring circuits have heretofore been formed, e.g., by cutting polyimide films, called as coverlay films, using a die made corresponding to the pattern, which are then adhered onto a substrate with an adhesive, or by applying a ultraviolet rays- curable or thermosetting overcoat composition the film from which is imparted with flexibility, according to the screen printing method, followed by curing. However, the coverlay film method is undesirable in workability, and the method where an overcoat agent is used is unsatisfying in curling upon curing and also in flexibility, and there have been known no methods of forming surface protective films for flexible wiring circuits which can meet the required performances.
On the other hand, recently, the so-called TAB method has got increasingly employed where film carriers which are, as an IC package for liquid-crystals driving, suitable for high-densifying or thinning. The basic structure of a film carrier is mainly composed of heat-resistant, insulating film base such as polyimide or the like, and an electrical conductor such as copper foil or the like, glued onto the film base through an adhesive layer composed mainly of an epoxy resin as the main ingredient, the wiring pattern having been formed on the copper foil by etching. And, a film carrier device is made by connecting an IC to such tape carrier followed by confining with the use of a confining resin. To prevent the reliability from being decreased due to pattern shortening, erosion, migration, whisker occurrence, or the like, a surface protective film is usually formed on such film carrier, using an overcoat agent. As such overcoat agent for film carriers, an epoxy-based one and a polyimide-based one are used. However, the former has not been satisfactory in curling during curing and flexibility of the coat film formed, and the latter has not been satisfactory in adhesiveness to the IC confining resin, workability or the like. For these reasons, at present, two or more different overcoat agents are concurrently used to compensate each other (See Japanese patent application laid-open (kokai) No. 283,575/'94) .
On the other hand, the present inventor had studied intensively to solve the above problems, and, as the results, found that curable resin compositions having properties required, e.g., of overcoats for flexible circuit, such as low shrinkage during curing, and whose cured products have satisfactory properties such as flexibility, adherence, electrical insulation, chemical resistance, heat resistance, etc., can be prepared by mixing a polyol with a number-average molecular weight of 1,000-8,000 and having 2-10 hydroxyl groups per molecule, or a polyol with a number-average molecular weight of 200-600 and having 2-10 hydroxyl groups per molecule, with a polyol with a number-average molecular weight of 13,000-30,000 and having 2-10 hydroxyl groups per molecule, and a polyblock isocyanate, and that, inter alia, a polyol or a polyblock isocyanate each having a polybutadiene skeleton is effective in providing flexibility and low shrinkage during curing. See Japanese patent applications Nos. 219,610/'97 and 219,611/'97.
An overcoat formed by using a resin composition comprising an ingredient with a polybutadiene skeleton is, however, apt to be oxidized, and therefore, undergo such changes that the coat film gets overhardened and the curling is increased, when it is left, e.g., in an elevated-temperature environment.
In particular, if such resin composition is used as an overcoating agent for printed circuit bases such as flexible circuit, there may be involved such trouble that the coat film gets overhardened and the curling is increased, because such printed circuit bases are made to pass, during their production process, through more than 150° C. environment, several times or for a long time.
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
It is an object of the present invention to provide an overcaoting agent which can give a coat film involving no such trouble that the coat film gets overhardened and the curling is increased. Other objects will be apparent from what will be described below.
Means for solving the problems
The present inventor has studied intensively to solve the above problems, and as the results, found that the use of a resin whose double bonds in the polybutadiene skeleton, have been added with hydrogen atoms, i.e., a resin which has a hydrogenated polybutadiene skeleton, can avoid the above-mentioned trouble. The present invention has been completed on the basis of these findings.
Accordingly, the present invention relates to:
1. A curable resin composition for overcoat of flexible circuit which comprises a hydrogenated polybutadiene polyol with a number-average molecular weight of 1,000-8,000 and having 2-10 hydroxyl groups per molecule (Polyol A), and a polybutadiene polyblock isocyanate (Isocyanate X);
2. A curable resin composition for overcoat of flexible circuit which comprises a hydrogenated polybutadiene polyol with a number-average molecular weight of 1,000-8,000 and having 2-10 hydroxyl groups per molecule (Polyol A), and a hydrogenated polybutadiene polyblock isocyanate with a number-average molecular weight of 1,000-8,000 and having 2-10 blockisocyanate groups per molecule (Isocyanate Xa), said hydrogenated polybutadiene polyblock isocyanate (Isocyanate Xa) being in an amount of 0.8-3.5 gram equivalents based on (i.e., per) one gram equivalent of the total hydroxyl groups of said Polyol A;
3. A curable resin composition for overcoat of flexible circuit which comprises a hydrogenated polybutadiene polyol with a number-average molecular weight of 1,000-8,000 and having 2-10 hydroxyl groups per molecule (Polyol A), a hydrogenated polybutadiene polyblock isocyanate with a number-average molecular weight of 1,000-8,000 and having 2-10 blockisocyanate groups per molecule (Isocyanate Xa), and a hydrogenated polybutadiene polyol with a number-average molecular weight of 13,000-30,000 and having 2-10 hydroxyl groups per molecule (Polyol B), wherein the weight ratio (as solid content) of said two polyols is (Polyol A):(Polyol B)=40:60-90:10, and said polyblock isocyanate (Isocyanate Xa) is in an amount of 0.8-3.5 gram equivalents based on, i.e., per one gram equivalent of, the total hydroxyl groups of the two polyols (Polyol A plus Polyol B);
4. A curable resin composition for overcoat of flexible circuit which comprises a polyol with a number-average molecular weight of 200-600 and having 2-10 hydroxyl groups per molecule (Polyol C), a hydrogenated polybutadiene polyblock isocyanate with a number-average molecular weight of 1,000-8,000 and having 2-10 blockisocyanate groups per molecule (Isocyanate Xa), and a hydrogenated polybutadiene polyol with a number-average molecular weight of 13,000-30,000 and having 2-10 hydroxyl groups per molecule (Polyol B), wherein the weight ratio (as solid content) of the two polyols is (Polyol C):(Polyol B)=20:80-50:50 and said polyblock isocyanate (Isocyanate Xa) is in an amount of 0.8-3.5 gram equivalents based on one gram equivalent of the total hydroxyl groups of the polyols;
5. The curable resin composition for overcoat of flexible circuit as set forth above which further comprises fine rubber particles and/or fine polyamide particles;
6. A film carrier coated on
Ajinomoto Co. Inc.
Gorr Rachel
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