Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Noninterengaged fiber-containing paper-free web or sheet...
Reexamination Certificate
1999-04-29
2001-04-10
Sellers, Robert E. L. (Department: 1712)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Noninterengaged fiber-containing paper-free web or sheet...
C428S297400, C428S415000, C428S416000, C428S901000, C428S921000, C525S485000, C525S486000, C525S490000, C525S524000
Reexamination Certificate
active
06214455
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an epoxy resin composition as well as a prepreg and a laminate containing the composition, and more particularly to a halogen-free flame-retardant epoxy resin composition, a prepreg impregnated with such composition, as well as to a laminate, copper-clad laminate and printed wiring board manufactured by using such prepreg.
BACKGROUND ART
In recent years, safety to humans including, for example, the air pollution problem attracts world-wide attentions. In this connection, electric and electronic appliances are required to be more harmless and more safe in addition to the requirement of a high flame retardancy. To be more specific, the electric and electronic appliances are required to be resistant to flame and, at the same time, not to generate noxious gases. It has been customary in the past to use a glass/epoxy as a substrate of a printed wiring board on which electric and electronic appliances are to be mounted. In general, a brominated epoxy resin containing bromine as a flame-retardant, particularly, tetrabromobisphenol-A type epoxy resin, is used for forming the substrate of the printed wiring board.
The brominated epoxy resin certainly exhibits a high flame retardancy, but generates a noxious hydrogen halide (hydrogen bromide) gas when burned. To overcome the difficulty, epoxy resin compositions containing non-halogen flame-retardants such as nitrogen compounds, phosphorus compounds, inorganic compounds, etc., have been developed, as reported in, for example, British Patent No. 1,112,139 and Japanese Patent Disclosure (Kokai) No. 2-269730, However, these flame-retardants give rise to a detrimental effect to the curing of the epoxy resin and impairs the humidity resistance of the cured composition. In addition, a glass cloth is less likely to be impregnated with the epoxy resin composition if the composition contains the non-halogen flame-retardants mentioned.
The present invention is intended to provide an epoxy resin composition which does not contain a halogen element but exhibits a good flame retardancy and which permits overcoming the above-noted problems inherent in the prior art.
The present invention is also intended to provide a prepreg impregnated with such an epoxy resin composition as well as a laminate, copper-clad laminate and printed wiring board using such a prepreg sheet.
DISCLOSURE OF INVENTION
According to a first embodiment of the present invention, there is provided a halogen-free flame-retardant epoxy resin composition, comprising (A) a bisphenol A type epoxy resin, (B) a novolak type epoxy resin, (C) a nitrogen-containing phenolic resin acting as a curing agent, (D) a curing accelerator, and (E) an inorganic filler, wherein the nitrogen-containing henolic resin serves to impart a flame retardancy to the composition.
The nitrogen-containing phenolic resin may be an aminophenolic resin. However, it is preferable to use a co-condensation resin formed by the reaction among a phenolic compound, a guanamine compound and an aldehyde compound.
According to a second embodiment of the present invention, there is provided a halogen-free flame-retardant epoxy resin composition, comprising (A) a bisphenol A type epoxy resin, (B) a novolak type epoxy resin, (C) a phosphorus- and nitrogen-containing phenolic resin acting as a curing agent, (D) a curing accelerator, and (E) an inorganic filler, wherein the phosphorus- and nitrogen-containing phenolic resin serves to impart a flame retardancy to the composition.
The phenolic resin containing both phosphorus and nitrogen atoms should desirably be a reaction product among a phenolic compound, a guanamine compound, an aldehyde compound and a reactive phosphoric acid ester.
According to a third embodiment of the present invention, there is provided a halogen-free flame-retardant epoxy resin composition, comprising (A) a bisphenol A type epoxy resin, (B) a novolak type epoxy resin, (C-1) a reactive phosphoric acid ester, (C-2) a co-condensation resin of a phenolic compound, a guanamine compound, and an aldehyde compound, (D) a curing accelerator, and (E) an inorganic filler.
The present invention also provides a prepreg impregnated with the halogen-free flame-retardant epoxy resin composition according to the present invention as well as a laminate, copper-clad laminate and printed wiring board prepared by using the prepreg.
BEST MODE OF CARRYING OUT THE INVENTION
The present invention will be described in detail below.
The epoxy resin composition of the present invention contains a bisphenol A type epoxy resin as component (A). As widely known to the art, the bisphenol A type epoxy resin is a reaction product between bisphenol A and, for example, epichlorohydrin. The bisphenol A type epoxy resin used in the present invention generally has an epoxy equivalent of at least 170, However, it is undesirable for the epoxy equivalent to exceed 1,000 because the resultant composition is less likely to be impregnated into a glass cloth. The bisphenol A type epoxy resin used in the present invention is commercially available including, for example, EPIKOTE series manufactured by Yuka Shell Inc., Japan and ARALDITE series manufactured by Ciba Geigy Inc. It is possible to use a single kind or a plurality of different kinds of the bisphenol A type epoxy resin in the resin composition of the present invention.
A novolak type epoxy resin is used as component (B) in the epoxy resin composition of the present invention. As widely known to the art, the novolak type epoxy resin is a resin obtained by a reaction between a novolak resin and epichlorohydrin. The novolak resin is a resin obtained by a condensation reaction between a phenolic compound and formaldehyde, which is carried out in the presence of an acidic catalyst. The phenolic compounds used for producing the novolak resin by the reaction with formaldehyde include, for example, phenol, cresol, and bisphenol A. The novolak type epoxy resin used in the present invention should desirably have a softening point of 70 to 130° C., more preferably, 80 to 100° C. Such a novolak resin is commercially available from, for example, Toto Kasei K.K., Japan and Dai-Nippon Ink and Chemicals, Inc. It is possible to use a single kind or a plurality of different kinds of novolak type epoxy resins in preparing the resin composition of the present invention.
The epoxy resin composition of the present invention also comprises as a curing agent (C) a phenolic resin containing nitrogen in the resin molecule. The nitrogen-containing phenolic compound serves to impart a flame retardancy to the epoxy resin composition. Needless to say, the phenolic resin is a reaction product between a phenolic compound and an aldehyde compound such as formaldehyde. The nitrogen atom contained in the nitrogen-containing phenolic resin may be present in any of the phenolic resin. For example, the nitrogen atom may be provided by an amino group substituted on the phenolic ring. In other words, an aminophenolic resin is an example of the nitrogen-containing phenolic resin used in the present invention.
However, in a preferred embodiment of the present invention, the nitrogen-containing phenolic resin is provided by a co-condensation resin among a phenolic compound, a guanamine compound and an aldehyde compound.
The co-condensation resin can be prepared by reacting a phenolic compound, an aldehyde compound and a guanamine compound, in the presence of an acid catalyst such as oxalic acid or p-toluene sulfonic acid. In carrying out the reaction, it is preferred that the molar ratio of the aldehyde compound to the phenolic compound should be less than 1.0, preferably 0.5 to less than 1.0, and one mole of aldehyde compound should be used for one primary amino group (—NH
2
) contained in the guanamine compound (for example, in the case of using melamine as the guanamine compound, it is desirable to use 3 moles of formaldehyde relative to one mol of melamine. Likewise, in the case of using benzoguanamine, it is desirable to use 2 moles of formaldehyde relative to one mol of benzoguana
Honda Nobuyuki
Sugiyama Tsuyoshi
Suzuki Tetsuaki
Cooper & Dunham LLP
Sellers Robert E. L.
Toshiba Chemical Corporation
White John P.
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