| 摘要 |
PROBLEM TO BE SOLVED: To reduce an addition amount of a chemical foaming agent, reduce a chemical radical generation amount and suppress ultraviolet excessive radia tion, by forming an ultraviolet cross-linked foam insulation layer composed of ultraviolet cross-linkable foaming resin composition compounding a solid particle or fiber. SOLUTION: For instance, in an ultraviolet cross-linkable resin composittion adding 3 pts.wt. acetophenone photoinitiator to 80 pts.wt. urethane acrylate oligomer and 20 pts.wt. monomer having an acrylsoyl group, 3 pts.wt., silicon dioxide of 7/1000μm mean grain size and 2 pts.wt. heat decomposition foaming agent are added, thereby a foaming composition is obtained. This composition is applied onto a conductor 1 of 32AWG conductor size by 40μm thickness, is made to pass through in the electric furnace for 1.8sec, and a foamed insulation layer 2 of 75 to 80μm thickness is formed, then it is cross-linked and cured by performing ultraviolet irradiation. Here, a foaming degree of the layer 2 is 60%, the high foaming degree is obtained as compared with 40% in the case not containing silicon dioxide of solid particle.
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