Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-09-22
2001-10-30
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06310119
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a film-shaped encapsulating agent for electronic parts, more particularly to a film-shaped encapsulating agent for electronic parts which enables the continuous encapsulation of electronic parts without requiring any expensive apparatus because of good processability (therefore, no cost increase is incurred) and is excellent in heat resistance and electrical insulation after the encapsulation.
(2) Description of the Prior Art
In general, various electronic parts are often encapsulated with various materials at the final production step in order to avoid the bad influence of moisture, dust and the like in air. Such encapsulation of electronic parts have heretofore been carried out, for example, by encapsulation with a thermosetting resin by transfer molding, or by placing an electronic part in a box-shaped pot, and then pouring a resin into the pot to encapsulate the part (potting method), or by using, as an encapsulating agent, a film obtained by coating a substrate such as cellulose or the like with a B-stage resin (for example, epoxy resin).
However, in the encapsulation with a thermosetting resin by transfer molding, a high cost is incurred because an expensive transfer-molding machine and an expensive mold must be used. In the potting method, continuous operation is difficult and hence the number of operational steps is large, the maintenance of quality is hence difficult and, in addition, the preparation of a pot is necessary; therefore, a high cost is incurred. In the method using a film obtained by coating the above-mentioned substrate with a B-stage resin, the film has a short life because the resin is in the B-stage and, moreover, the maintenance of quality is difficult.
SUMMARY OF THE INVENTION
The present invention aims at overcoming the above-mentioned problems of the prior art and providing a film-shaped encapsulating agent for electronic parts which enables the continuous encapsulation of electronic parts without requiring any expensive apparatus because of good processability (therefore, no cost increase is incurred) and is excellent in heat resistance and electrical insulation after the encapsulation.
According to the present invention, there is provided, a film-shaped encapsulating agent for electronic parts which is composed essentially of a polycarbodiimide resin and an epoxy resin, wherein the polycarbodiimide resin has a polystyrene-reduced number-average molecular weight of 3,000 to 50,000 as determined by gel permeation chromatography and the epoxy resin is contained in a proportion of 20 to 150 parts by weight per 100 parts by weight of the polycarbodiimide resin, or a film-shaped encapsulating agent which is composed essentially of a polycarbodiimide resin, an epoxy resin and a colorant, wherein the polycarbodiimide resin has a polystyrene-reduced number-average molecular weight of 3,000 to 50,000 as determined by gel permeation chromatography and the epoxy resin is contained in a proportion of 20 to 150 parts by weight per 100 parts by weight of the polycarbodiimide resin.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is explained in detail below.
In the first case, the film-shaped encapsulating agent for electronic parts of the present invention is composed essentially of a polycarbodiimide resin and an epoxy resin. As this polycarbodiimide resin, there can be used those produced by various methods. There can be used isocyanate-terminated polycarbodiimides produced fundamentally by the conventional method for producing a polycarbodiimide [U.S. Pat. No. 2,941,956; JP-B-47-33,279; J. Org. Chem., 28, 2069-2075 (1963); Chemical Review 1981, Vol. 81, No. 4, pages 619-621], specifically by the carbon dioxide removal and condensation reaction of an organic polyisocyanate.
In the above-mentioned method, as the organic polyisocyanate which is the starting material for synthesizing the polycarbodiimide compound, there can be used, for example, aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates and mixtures thereof, and specifically, there can be mentioned 1,5-naphthalene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, methylcyclohexane diisocyanate, tetramethylxylylene diisocyanate, 2,6-diisopropylp henyl diisocyanate, and 1,3,5-triisopropylbenzene-2,4-diisocyana te.
Among them, those obtained from at least one aromatic polyisocyanate are preferable as the polycarbodiimide resin to be used in the present invention. Incidentally, the aromatic polyisocyanate refers to an isocyanate having, in the, molecule, at least two isocyanate groups bonded directly to the aromatic ring.
As the above-mentioned polycarbodiimide, there can also be used those polycarbodiimides whose terminals are blocked with a compound (e.g. a monoisocyanate) reactive with the terminal isocyanates of polycarbodiimide and whose polymerization degrees are controlled at an appropriate level.
As the monoisocyanate for blocking the terminals of polycarbodiimide to control the polymerization degree thereof, there can be mentioned, for example, phenyl isocyanate, tolylene isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate, butyl isocyanate, and naphthyl isocyanate.
As the other compounds reactive with the terminal isocyanates of polycarbodiimide, there can be used, for example, aliphatic compounds, aromatic compounds or alicyclic compounds having —OH group (such as methanol, ethanol, phenol, cyclohexanol, N-methylethanolamine, polyethylene glycol monomethyl ether, polypropylene glycol monomethyl ether and the like), ═NH group (such ad diethylamine, dicyclohexylamine and the like), —NH
2
group (such as butylamine, cyclohexylamine and the like), —COOH group (such as propionic acid, benzoic acid, cyclohexanecarboxylic acid and the like), —SH group (such as ethylmercaptan, allylmercaptan, thiophenol and the like), epoxy group, or the like.
The carbon dioxide removal and condensation reaction of the above organic polyisocyanate proceeds in the presence of a carbodiimidation catalyst. As the carbodiimidation catalyst, there can be used, for example, phosphorene oxides such as 1-phenyl-2-phosphorene-1-oxide, 3-methyl-1-phenyl-2-phosphorene-1-oxide, 1-ethyl-2-phosphorene-1-oxide, 3-methyl-2-phosphorene-1-oxide, 3-phosphorene isomers thereof, and the like. Among them, 3-methyl-1-phenyl-2-phosphorene-1-oxide is suitable from the standpoint of reactivity.
The polycarbodiimide resin used in the present invention has a polystyrene-reduced number-average molecular weight of 3,000 to 50,000, preferably 10,000 to 30,000, and more preferably 15,000 to 25,000, as measured by gel permeation chromatography (GPC) regardless of whether or not the above-mentioned terminal-blocking agent is used. When the number-average molecular weight is smaller than 3,000, no sufficient film-formability or heat resistance can be obtained. When the number-average molecular weight exceeds 50,000, a long period of time is required for the synthesis of polycarbodiimide resin and, in addition, the polycarbodiimide resin varnish obtained has an extremely short pot life (service life). Therefore, such number-average molecular weights are not practical.
As the epoxy resin used in the present invention, there can be mentioned epoxy resins having at least two epoxy groups in the molecule, for example, glycidyl ether type epoxy resins, representatives of which are bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenolic novolac type epoxy resins and cresol novolac type epoxy resins; alicyclic epoxy resins; glycidyl ester type epoxy resins; heterocyclic epoxy resins; and liquid rubber-modified epoxy re
Imashiro Yasuo
Ito Takahiko
Nakamura Norimasa
Tomita Hideshi
Kubovcik & Kubovcik
Michl Paul R.
Nisshinbo Industries Inc.
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