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
2002-11-08
2004-05-18
Harlan, Robert D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S525000, C525S454000, C524S428000, C524S413000, C524S461000, C524S473000, C524S474000, C524S480000
Reexamination Certificate
active
06737474
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a modified polyvinyl acetal resin, a modifier for curable resins, a curable resin composition, and laminated products.
The modified polyvinyl acetal resin of the present invention is excellent not only in dielectric characteristics but in compatibility with various solvents and thermosetting resins and in adhesiveness. The resin is hence useful as an electrical insulating material.
The modifier for curable resins of the invention comprises the specific modified polyvinyl acetal resin. By adding this modifier to a curable resin, a curable resin composition can be provided which has excellent adhesiveness and is suitable for use as an electrical insulating material, etc.
The curable resin composition of the invention comprises a curable resin/curing agent combination compounded with a specific modified polyvinyl acetal resin. The composition has greatly improved film-forming properties and can hence be applied to various substrates to form a stable, homogeneous film. Since the film combines excellent adhesiveness to substrates and flexibility, the composition is especially suitable for use as an adhesive.
The laminated products of the invention comprise a substrate layer and a layer of a curable resin composition containing a specific modified polyvinyl acetal resin and/or of a cured composition obtained by curing the curable resin composition. Since the layer of the curable resin composition has greatly improved film-forming properties, it can be applied to various substrates to form a stable, homogeneous film, which combines excellent adhesiveness to the substrates and flexibility. The laminated products are hence used especially as adhesives having excellent flexibility and high adhesiveness.
BACKGROUND OF THE INVENTION
Curable resins, which mostly comprise low-molecular weight compounds, are applied in the form of a solution in a solvent or in a melt form to substrates and then cured under given conditions to thereby exhibit adhesiveness to the substrates. As a result, satisfactory laminated products can be obtained. Furthermore, by superposing an adherend on the surface of the thus-applied solution or melt of an uncured curable resin and then curing the resin, a three-layer laminated product composed of the substrate, an adhesive layer, and the adherend can be obtained in which the resin exhibits adhesiveness to the adherend and which also is satisfactory. Besides being used in such applications, curable resins are extensively used as matrix resins in an application in which fibers or an inorganic or organic filler is mixed with a solution or melt of the curable resin and the mixture is cured alone to obtain a satisfactory composite, or in an application in which the mixture is likewise applied to a substrate and united with an adherend.
In the case of using a solid curable resin, a solution prepared by dissolving the resin in a solvent is applied to a substrate and the solvent which has become unnecessary is removed thereafter to form an exceedingly hard film. However, because the resin has a low-molecular weight, the film is highly brittle and is apt to readily peel off the substrate or develop cracks. In the case of using a liquid curable resin, a solution thereof is prepared and applied in the same manner and the solvent is then removed. In this case, however, there are many problems, for example, that the resin, upon solvent removal, returns to the original liquid state and, as a result, it becomes difficult to maintain an even film thickness, making it difficult to exhibit even and stable adhesive strength, and that the resin surface has tackiness and this necessitates significantly complicated operations. Because of these drawbacks, a technique is used in which the curing reaction is caused to proceed to some degree to thereby increase the molecular weight of the resin, i.e., bring the resin into the so-called B-stage. Although this technique is effective in improving evenness of film thickness, it is difficult to control the B-stage and to stably maintain the B-stage over long. In addition, as the molecular weight increases, the ability to wet an adherend decreases, resulting in reduced adhesion strength. Consequently, this technique is not a satisfactory technique for improvements.
In contrast, an attempt has been made to maintain applicability and film properties without increasing the molecular weight of a curable resin as a whole, by adding thereto a rubber, thermoplastic resin, etc. However, curable resins do not always have satisfactory compatibility with rubbers or thermoplastic resins. There are cases where even though the composition has been homogenized with a solvent, it undergoes phase separation upon solvent volatilization, or undergoes phase separation upon curing reactions after solvent vaporization and coagulates at the composition/substrate interface or, conversely, at the composition/air interface, resulting in an insufficient effect of improvement.
One measure in overcoming the problem described above is proposed, e.g., in JP-A-5-186667 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), which is an epoxy resin composition comprising an epoxy compound, a curing agent, and a polyvinyl acetal resin having a peculiar structure highly compatible with the epoxy compound/curing agent combination.
However, this epoxy resin composition was found to have drawbacks that application of the composition to a substrate results in cissing on the substrate surface and that curing the applied composition significantly reduces the flexibility of the substrate.
On the other hand, various insulating materials are known for use in the field of electronics industry as overcoat materials, interlayer dielectric materials, or the like in semiconductors, ICs, hybrid ICs, wiring circuit boards, display devices, display parts, etc. Examples thereof include passivation films, soldering resists, plating resists, interlayer dielectric materials, and moisture-proof protective films. These insulating materials also have come to be desired to have higher performances and higher reliability with the recent trend in electronic parts toward miniaturization, weight reduction, density increase, and speed increase.
In order for an insulating material to have a smaller dielectric loss, even in a slight degree, it should have a lower dielectric constant and a smaller dielectric loss tangent.
As such materials are used thermosetting resins such as phenolic resins, epoxy resins, and polyimide resins and thermoplastic resins such as fluororesins and polyolefin resins.
However, these thermosetting resins have had difficulties in attaining higher speeds and higher reliability because they usually have a dielectric constant as high as 4.0 or higher and a dielectric loss tangent as large as 0.01 or above.
The thermoplastic resins, on the other hand, have had problems, for example, that they have poor workability, poor adhesiveness, and insufficient reliability.
SUMMARY OF THE INVENTION
Objects of the invention are (i) to provide a modified polyvinyl acetal resin excellent in dielectric characteristics and in compatibility with thermosetting resins and adhesiveness, (ii) to provide a modifier for curable resins which has excellent compatibility with curable resins and which, when added to a curable resin, improves the dielectric characteristics, film-forming properties, and flexibility of the resin, (iii) to provide a curable resin composition in which the modified polyvinyl acetal resin has excellent compatibility with the curable resin and which is excellent in film-forming properties and flexibility and adhesiveness, and (iv) to provide a laminated product in which a stable and even film having excellent adhesiveness to the substrate can be formed and which has flexibility.
The present inventors made intensive investigations in view of the circumstances described above. As a result, they have found that (i) a modified polyvinyl acetal resin having a specific structure is excellent not only in die
Enda Jun
Katayama Hiroo
Tanaka Toshiyuki
Harlan Robert D.
Mitsubishi Chemical Corporation
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