Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-11-07
1999-11-30
Krass, Frederick
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523200, 523205, 523208, 523210, 428413, 428415, 428416, 428417, 428418, 42840221, C08L 6302
Patent
active
059944293
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a halogen-free flame-retardant epoxy resin composition, a prepreg containing the epoxy resin composition, and a laminate, copper-clad laminate and printed wiring board which are formed by using the prepregs.
BACKGROUND OF ART
Recently, as world-wide environmental problems and safety to a human body arouse concern, it has been increasingly required that electric/electronic products be less harmful and more safe, in addition to flame retardancy requirement. More specifically, the electric/electronic products are needed hardly to burn and scarcely to generate a harmful gas and fume. Conventional printed wiring boards, on which electric/electronic products are to be mounted, usually have a substrate formed of glass-epoxy. Generally, a brominated epoxy resin, in particular, a tetrabromobisphenol A type epoxy resin, containing bromine which serves as a flame-retardant, is used as the epoxy resin in the substrate.
Such a brominated epoxy resin has good flame retardance. However, it generates a harmful hydrogen halide (hydrogen bromide) gas when burned. For this reason, the use of the brominated epoxy resin is being suppressed. In the circumstances, compositions have been developed, in which a non-halogen flame-retardant such as a nitrogen compound, phosphorus compound or an inorganic compound is added to the conventional epoxy resin (see, for example, British Patent No. 1,112,139 and Jpn. Pat. Appln. KOKAI Publication No. 2-269730). However, these additives imparting flame retardance have problems: they impose undesirable effects on curing of the epoxy resin, decrease the moisture vapor resistance of the cured composition, and impair impregnation of the composition into a glass cloth.
Another feature which is important equally to the flame retardance, and which the printed wiring board should have in view of safety improvement, is tracking resistance. The tracking resistance is particularly required for a substrate having a high voltage circuit, such as a printed wiring board for use in air conditioners and televisions.
To impart the tracking resistance, a chain hydrocarbon, a cyclic compound or an inorganic material has been added to a resin composition for use in the printed wiring board, as a substance which is hardly carbonized. However, these substances are disadvantageous in that the chain hydrocarbon and cyclic compound reduce heat resistance of the printed wiring board, and the inorganic material must be used in a large amount.
Accordingly, an object of the present invention is to provide an epoxy resin composition which exhibits good flame retardance, without containing and also good tracking resistance.
Another object of the present invention is to provide a prepreg impregnated with such an epoxy resin, as well as a laminate, copper-clad laminate and printed wiring board which are formed by using the prepregs.
DISCLOSURE OF THE INVENTION
To attain the aforementioned objects, the present invention provides a halogen-free flame-retardant epoxy resin composition comprising (A) a bisphenol A type epoxy resin, (B) a curing agent, (C) red phosphorus particles each of which is covered with a covering layer, with at least the outermost layer of the covering layer being formed of a resin, and (D) an inorganic filler.
The present invention further provides a prepreg impregnated with the halogen-free flame-retardant epoxy resin composition of the invention, and provides a laminate, copper-clad laminate and printed wiring board which are formed by using the prepregs. The prepreg of the present invention comprises a glass substrate impregnated with the epoxy resin composition of the present invention. The laminate of the present invention comprises a plurality of prepregs of the present invention laminated one over another, in which the epoxy resin composition is cured. The copper-clad laminate of the present invention comprises a laminate of the invention having a copper foil clad on at least one surface thereof. The printed wiring board of the present inventi
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Derwent Abstracts 91-157381, "Fire Retardant Aromatic Polyepoxide Composition", May 1991.
Derwent Abstracts 90-196912, "Flame Retardant Phenol Resin Prepreg ", May 1990.
Obera et al., Chemical Abstracts, vol. 111, No. 18, abstract No.155117, Oct. 30, 1989 (Exhibit 3) ; and.
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Honda Nobuyuki
Sugiyama Tsuyoshi
Krass Frederick
Toshiba Chemical Corporation
White John P.
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