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
2001-12-28
2004-11-16
Buttner, David J. (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...
C525S111000, C525S113000, C525S114000, C525S119000, C525S120000, C525S122000, C525S130000, C525S236000, C525S523000, C525S524000, C525S525000, C525S528000, C525S529000, C525S530000, C525S531000, C525S532000, C525S533000, C528S392000
Reexamination Certificate
active
06818702
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an epoxy resin-based thermosetting composition affording a cured coated film which is reduced in warp caused by cure shrinkage and is excellent in flexibility, and also to an overcoating material for a flexible circuit board using the same. Further, it relates to a film carrier coated with the overcoating material and to a film device wherein the film carrier is used.
BACKGROUND ART
Upon the adhesion between flexible substrates such as packaging materials, films or the like, or upon the coating of these surfaces, it is necessary to reduce as far as possible the influences of cure shrinkage of adhesives or coating materials (i.e., coating agents) to be used therefor or the influences of hardness of the cured products. Therefore, the adhesive or coating agent to be used for such fields of application should necessarily be those which exhibit a small cure shrinkage as far as possible and at the same time, afford cured products having a sufficient flexibility. As thermosetting resin compositions affording flexible cured products, there have hitherto been known compositions comprising, as the main component, a natural or synthetic rubber, urethane-based resin, silicon-based resin, or modified epoxy resin having the skeleton of such rubber or resin. However, such rubber-based resin compositions can be indeed produced relatively at a low cost and the cured products thereof are excellent in flexibility, but they are inferior in weather resistance, heat resistance and chemical resistance. Although it has been attempted to solve these defects, the effects have not been satisfactory. On the contrary, there have been pointed out problems that it is withheld to use chlorinated resins from the viewpoint of the increased understanding of environmental problems, and the like, because such resins sometimes suffer dechlorination upon their use in elevated humidity and temperature environment. Moreover, urethane-based resins also afford cured products excellent in flexibility, but they cannot be said to be satisfactory in weather resistance, chemical resistance, heat resistance, and the like. Furthermore, silicone-based resins whose cured products exhibit both of flexibility and the performances such as weather resistance, chemical resistance, thermal resistance and the like, similarly have defects that the cost of law materials thereof is high and undercoating treatment with a primer is necessary because of their poor adhesiveness to other substrates, and the like. On the other hand, resin compositions comprising, as the main component, an epoxy resin modified with rubber, urethane, or silicon have widely been used because their cured products have an appropriate flexibility and at the same time, performances such as weather resistance, chemical resistance, thermal resistance, and the like. However, any modified epoxy resisin composition has not been yet obtained, whose cured product is sufficiently statisfactory in flexibility and cure shrinkage.
Moreover, with regard to thermosetting resin compositions, as the fields of application thereof which requires electric insulation property, plating resistance and the like, in addition to the above various properties, there may be mentioned surface protecting films for flexible circuit boards whose needs have rapidly increased in recent years. It has been the mainstream to use polyimide films called coverlay films, as the surface protecting films for flexible wiring circuits. The formation of the protecting film using such coverlay film comprises steps of making a die corresponding to the circuit pattern, punching a film for forming the protecting film with the use of the die, and further adhering the punched film onto a substrate with an adhesive. Thus, it is not so preferable in view of the workability because of the complicated steps. On the other hand, a method has been also known, wherein a thermosetting-type overcoating agent as mentioned above, comprising, as the main component, a modified epoxy resin having flexibility or the like, is applied by a screen printing method and then cured. This method is preferable in view of the workability owing to the simple steps, but is still unsatisfactory from the viewpoints of the properties of the cured products such as warp caused by cure shrinkage, flexibility, and the like, so that the method is mainly applied to only the substrates of low added value.
Furthermore, recently, the so-called TAB method using film carriers has been increasingly employed for the purpose of imparting a higher density and a less thickness to an IC package, making use of the technology for forming flexible circuit boards. This method is mainly employed for forming an IC package for driving liquid-crystals. The basic structure of such 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 containing an epoxy resin as the main component, 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 sealing with the use of a scaling resin. To prevent the decrease of reliability owing to pattern short, erosion, migration, whisker occurrence, or the like, during the steps before the IC connection, a surface protecting film is usually formed also on such film carrier, using an overcoating agent. As such overcoating agent for film carriers, there have been used an epoxy-based one and a polyimide-based one. However, the former is not satisfactory in warp during curing and flexibility of the coated film, and the latter is not satisfactory in adhesiveness to the IC sealing resin, workability or the like. For these reasons, at present, two or more different overcoating agents are concurrently used to compensate each other (Japanese Patent Application Laid-Open No. 283575/1994).
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a thermosetting resin composition which is improved in the occurrence of warp caused by cure shrinkage and the insufficiency in flexibility of the cured products thereof, which are the problems of conventional thermosetting resin compositions. It is another object thereof to provide an epoxy resin-based overcoating agent or material for flexible circuit boards, which has basic properties required of general insulation protective films such as tight adhesiveness, electric insulation property, chemical resistance, thermal resistance, and Sn-plating resistance, and the like. It is still another object of the present invention to provide an overcoating agent which can be used for film carriers for the TAB method. And, it is a further object thereof to provide a film carrier formed by applying the overcoating agent thereonto and a film carrier device using the film carrier.
The present inventors have studied intensively to achieve the above objects, and as the results, found that the concurrent use of not only a single resin having a flexible skeleton as in the prior art, but also a resin whose molecular weight and functional group number per one molecule are restricted to a certain range, as the components of a thermosetting resin composition, results in that the crosslinking density of the cured product thereof can be appropriately regulated, whereby a cured coated film remarkably reduced in warp caused by cure shrinkage and also more excellent in flexibility can be afforded, with the basic properties given by common thermosetting compositions such as tight adhesiveness, electric insulation property, chemical resistance, thermal resistance, and the like being maintained. The present invention has been accomplished on the basis of these findings.
Accordingly, a first thermosetting resin composition of the present invention comprises an epoxy-group(-containing) resin (Component (A)), and a resin (Component (B)) containing a functional group capable of reacting with the epoxy group, such as carbo
Orikabe Hiroshi
Sakamoto Hiroshi
Yokota Tadahiko
Ajinomoto Co. Inc.
Buttner David J.
Keehan Christopher
LandOfFree
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