Curable Epoxy Resin Composition, Cured Body Thereof, and Use Thereof

A curable epoxy resin composition comprising at least the following components:

• (I) an epoxy resin;
• (II) a curing agent for an epoxy resin;
• (III) a diorganosiloxane that is used in an amount of 0.1 to 100 parts by weight per 100 parts by weight of the sum of components (I) and (II) and is represented by the following general formula:
• A-R2—(R12SiO)nR12Si—R2-A
• where R1 designates the same or different unsubstituted or substituted monovalent hydrocarbon groups which are free of unsaturated aliphatic bonds;
• R2 designates a bivalent organic group;
• “A” designates a siloxane residual radical represented by the following average unit formula:
• (XR12SiO1/2)a(SiO4/2)b
• where R1 is the same as defined above, and “X” is a single bond, a hydrogen atom, a group designated by R1, an epoxy-containing monovalent organic group, or an alkoxysilylalkyl group;
• however, in one molecule at least one group designated by “X” is a single bond, at least two groups designated by “X” are epoxy-containing alkyl groups;
• “a” is a positive number;
• “b” is a positive number;
• and “a/b” is a number ranging from 0.2 to 4, and where “n” is an integer equal to or greater than 1, and
• (IV) an inorganic filler.