An ink composition includes a polymerization initiator; an ester or amide of a mono-functional acrylic acid having an alkylene oxide repeating unit in a molecule; and a colorant, and preferably further includes a sensitizing dye. The amount of the polar or ionic or aromatic or linearly conjugated compound included in the composition is about 0. The Path Switch Request message includes an eNB UE S1AP ID, a Tracking Area Identifier, and cell Identifier. A part can be cleaned by, for example, inserting hydrogen into the plasma and exposing the part to the hydrogen-enriched plasma.