Abstract: A re-releasable adhesive agent comprises a radiation-reactive polymer and a radiation polymerization initiator, the radiation-reactive polymer has a side chain derived from at least one monomer expressed by the formula (1): CH2?CR1COOR2 (1), where R1 is a hydrogen atom or a methyl group, and R2 is a C6 or higher alkyl group, and a side chain having one carbon-carbon double bond, and the monomer of formula (1) is contained in a ratio of less than 50 mol % with respect to the total monomer constituting the main chain of the radiation-reactive polymer.

Abstract: The present invention aims to provide a patch and a patch preparation that do not require an acrylic polymer, and are capable of maintaining a large amount of an organic liquid component in an adhesive layer. The present invention provides a patch containing a support and an adhesive layer provided on at least one surface of the support, wherein the adhesive layer contains polyisobutylene, a liquid rubber component having a crosslinkable functional group in a molecule, and an organic liquid component, the adhesive layer is crosslinked.