Abstract: A spark plug including a center electrode that has a large-diameter portion having an outside diameter that is largest in the center electrode. The large-diameter portion is retained at a rear facing surface in an axial hole of an insulator. A metal shell has a diameter increased portion on a rear end side with respect to the center electrode, the diameter increased portion having an inside diameter that is increased toward the rear end side. The insulator has a first portion which is a portion of the insulator in a region from a rear end of the rear facing surface to a front end of the diameter increased portion. The first portion has a thickness that is the largest in the region, and is disposed at least on an outer periphery of the large-diameter portion.

Abstract: A spark plug including a center electrode that has a large-diameter portion having an outside diameter that is largest in the center electrode. The large-diameter portion is retained at a rear facing surface in an axial hole of an insulator. A metal shell has a diameter increased portion on a rear end side with respect to the center electrode, the diameter increased portion having an inside diameter that is increased toward the rear end side. The insulator has a first portion which is a portion of the insulator in a region from a rear end of the rear facing surface to a front end of the diameter increased portion. The first portion has a thickness that is the largest in the region, and is disposed at least on an outer periphery of the large-diameter portion.

Abstract: A spark plug including a cylindrical insulator having a step portion; a center electrode provided in an axial hole of the insulator; and a cylindrical metal shell having a ledge portion, the metal shell holding the insulator from an outer circumferential side in a state in which the step portion is engaged with the ledge portion via a packing, wherein a recess is formed on a part contacting with the packing, of one of the step portion and the ledge portion, and a projection which at least partially overlaps the recess in the axial-line direction is formed on a part contacting with the packing, of the other of the step portion and the ledge portion.

Abstract: In the spark plug, an insulator is held by a metal shell via a packing. The packing includes a base material and a metal layer formed on a surface of the base material. In a cross section including the axial line, of distances between end points of the metal layer on a first contact surface of the insulator that contacts with the metal layer and first points which are intersections of the first contact surface and first perpendiculars extending to the first contact surface from first corners at which a first surface and third surfaces of the base material intersect each other is longer than a thickness of the metal layer at a middle position on the third surface that corresponds to half a length measured along the third surface.

Abstract: A thermosetting resin composition contains a liquid epoxy resin, a solid epoxy resin having a softening point of 125° C. or lower, an aromatic diamine compound including benzoate group and a main chain including polymethylene group, a solvent soluble polyimide resin having Tg of 200° C. or higher and a weight average molecular weight Mw of 50000 or smaller, and a phenoxy resin having Tg of 130° C. or higher. A total of amounts of the solvent soluble polyamide resin and the phenoxy resin is 15 weight parts or more and 150 weight parts or less, provided that 100 weight parts are assigned to a total of amounts of the liquid epoxy resin, the solid epoxy resin and the aromatic diamine compound.

Abstract: An object of the present invention is to provide a thermosetting resin composition having a low dielectric constant, a low dielectric loss tangent, a low thermal expansion coefficient and an excellent peel strength at a low surface roughness after roughening adapted to additive process. The present invention provides a thermosetting resin composition comprising (a) 100 weight parts of polyfunctional vinyl benzyl ether compound, (b) 1 to 100 weight parts of solvent soluble polyimide resin, and (c) 0.01 to 10 weight parts of a catalyst for thermosetting reaction.

Abstract: A thermosetting resin composition comprises (a) epoxy resin, (b) setting agents comprising a novolak-type phenol resin and a benzooxazine compound and (c) a siloxane-modified polyamide-imide resin satisfying the following relationship. 0.6?m+n?2, 0.5?m?1.2, and 0.1?n?1.0 (“m” represents the hydroxyl group equivalent of (b) said novolak-type phenol resin with respect to the epoxy equivalent of (a) said epoxy resin of 1, and “n” represents the hydroxyl group equivalent of (b) the benzooxazine compound after thermal decomposition with respect to the epoxy equivalent of (a) the epoxy resin of 1. The thermosetting resin composition comprises (c) the siloxane-modified polyamide-imide resin in a content of 2 to 50 weight parts with respect to the total content of (a) the epoxy resin and (b) the setting agents of 100 weight parts.