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
2002-04-26
2004-07-20
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...
C525S525000
Reexamination Certificate
active
06765071
ABSTRACT:
FIELD OF TECHNOLOGY
This invention relates to a resin composition containing an aromatic episulfide. The resin composition is used as a liquid resin molding material which exhibits excellent moldability required for sealing electrical parts, electronic parts and semiconductor chips by potting or casting and excellent moisture resistance after curing. Furthermore, the resin composition is used as optical materials such as plastic lenses, prisms, optical fibers, optical films and filters, adhesives for the aforementioned optical materials and coatings and also used in sealing light-emitting devices and light sensors.
BACKGROUND TECHNOLOGY
With a rapid growth of electronics in recent years, semiconductor devices such as IC and LSI are used in various fields and a trend to lower cost and higher integration has brought forth a variety of new packaging schemes; dual in-line package by transfer molding with the use of a conventional mold is being replaced by moldless spot sealing of bare chips such as hybrid IC, chip on board, tape carrier package and plastic pin grid array. Curing agents for these liquid epoxy resin molding materials include amines such as dicyandiamide and dihydrazideaminimide compounds and liquid acid anhydrides such as hexahydrophthalic acid anhydride, tetrahydrophthalic acid anhydride and methylhimic anhydride. They were defective, however, as the former were strongly polar to lower the bias properties while hydrolyzed extensively in the pressure cooker test (PCT) and suffered from deterioration of adhesiveness after absorption of moisture. For this reason, an attempt was made to use solid novolac type phenolic resin as a curing agent, but the molding material became highly viscous with some loss in moldability and, to its disadvantage, required the simultaneous use of an organic solvent.
In the cases where liquid epoxy resin such as bisphenol A type epoxy resin and alicyclic epoxy resin is cured by an acid anhydride curing agent for ease of molding a composition, the optimal epoxy resin to acid anhydride ratio which gives the highest glass transition temperature and the lowest water absorption is decided (for example, epoxy group/acid anhydride group=1.0/0.75-1.0/0.9 on a mole basis in case a tertiary amine catalyst is used); still the water absorption is high in excess of 2% and the refractive index is unsatisfactorily 1.55 or less.
Novel alkylsulfide type episulfides, their compositions and cured products are proposed in JP9-71580 A(1997) and JP9-110979 A(1997). An alkylsulfide type episulfide cures by the use of an amine catalyst into a good optical material with a softening point of 100° C. or more, a refractive index of 1.69 or more and an Abbe number of 35 or more. In the patents, an explanation is found of a composition which uses a primary amine or an acid anhydride as a curing agent; however, an example in which a primary amine is used gives a cured product with a low softening point of 100° C. or less and records no concrete data such as refractive index and water absorption regarding the cured product by the use of an acid anhydride and the effect of the curing agent used is not clear. Moreover, a compound containing a mixture of epoxy and episulfide groups presents a problem of curing with low heat resistance and/or low strength and no concrete description is found of a composition containing this kind of compounds and an acid anhydride as a curing agent and of the properties of cured product.
Nishikubo et al. have reported that a combination of a thioester initiator and a quaternary ammonium salt catalyst is the most active in the polymerization of episulfide compounds; refer, for example, to Polymer Journal, 28(1), pp 68-75, 1996 or Prpg. Polymn. Sci, Vol. 18, pp 963-995, 1993. J. P. Bell et al. are conducting research on the curing reaction involving an episulfide compound and a primary amine. No literature in public knowledge refers to the curing reaction involving an episulfide compound and an acid anhydride curing agent.
Transparent resins are attracting attention as optical materials and they are used in optical lenses, films, prisms and base materials for optical disks because of their lightweight, impact resistance and ease of molding. Moreover, they are used extensively in optical fibers for utilization of their optical properties and also used as manufacturing aids such as sealing materials for optical disks, light-emitting devices and light sensors, coatings, and adhesives.
Resins which are practically used in optical applications at the present time include poly(methyl methacrylate), poly[diethylene glycol bis(aryl carbonate)], polystyrene and polycarbonate as optical lenses and poly(methyl methacrylate) and poly[diethylene glycol bis(aryl carbonate)] as lenses for correction of faulty vision.
However, both poly(methyl methacrylate) and poly[diethylene glycol bis(aryl carbonate)] show a low refractive index on the order of 1.50. When the methacrylic resin is used as a lens for correction of faulty vision, it suffers from the defect of the thickness of lens at the edge becoming greater compared with a lens of inorganic glass and it has additional weakness as it is apt to absorb moisture, deform and change in refractive index and shows a heat resistance of 100° C. or less. On the other hand, the polycarbonate is high in both refractive index and heat resistance, but it shows a defective tendency to absorb moisture and deform.
In those devices which utilize light such as optical disks, optical fibers, optical films for use in liquid crystal displays and light-emitting devices, operations such as pasting, joining and sealing are performed by the use of transparent resins as adhesives, coatings and sealing materials. The properties required for these optical materials include not only transparency but also low birefringence, low moisture absorption, high heat resistance, good quality for precision molding and matching in refractive index to components to be joined (refer, for example, to JP10-67977 A(1998) and Polyfile, July issue, p. 28, 1999).
Transparent resins of thermal crosslinking type are proposed in consideration of the aforementioned points and heat-curable optical materials possessing a thiourethane structure obtainable from the reaction of a polythiol and a polyisocyanate are proposed in JP4-58489 B(1992), JP5-148340 A(1993) and JP10-120676 A(1998). However, the materials in question are defective in that the pot life from mixing of the resin components to molding is short and no reference is found in these patents to lowering of water absorption.
An object of this invention is to provide a liquid resin molding material suitable for sealing semiconductors which is liquid before curing, cures with a high rate with good productivity, possesses after curing a glass transition temperature higher than the pressure cooker test (PCT) temperature of 121° C., and is characterized by high heat resistance, low moisture absorption, good workability and excellent moisture resistance reliability after packaging.
Another object of this invention is to provide a curable resin composition which is characterized not only by transparency but also by low moisture absorption, high heat resistance, quality for precision molding and matching in refractive index to components to be joined and to provide the cured composition as an optical material.
DISCLOSURE OF THE INVENTION
This invention relates to a resin composition which comprises an aromatic episulfide compound (component A) having two or more reactive groups represented by the following formula (1)
(wherein X is O or S with S accounting for 50 mol % or more of X on the average and R
1
-R
4
are independently a hydrogen atom, a halogen atom or an alkyl group with 1-4 carbon atoms) in its molecule, at least one kind of glycidyl compound (component B) selected from an aromatic glycidyl ether compound (B1) having two or more glycidyl groups in its molecule and a glycidyl ester compound (B2) having two or more glycidyl groups in its molecule, an acid anhydride (
Fujishiro Koichi
Ogata Hiroshi
Ohmori Fumihiro
Nippon Steel Chemical Co. Ltd.
Rader & Fishman & Grauer, PLLC
Sellers Robert
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