Various skin surface adhesion type external agents have been heretofore developed, inclusive of one for covering the surfaces of healthy skin and wounded skin for protection and one for percutaneous administration of a drug into a body through the skin. Since these external agents are adhered to the skin surface, they are required to have superior handling property in application, skin surface movement-following capability, and low irritation to the skin to suppress damages to keratin.
Of these, handling property in application and low irritation to the skin can be dealt with by altering the composition of the adhesive itself to appropriately decrease the adhesive power to the skin or by adding a liquid component (e.g., water and oily component) to the adhesive layer to make a water-containing gel or oily gel, thereby imparting softness to the adhesive layer. In the latter method, a crosslinking agent may be also used to impart a cohesive power to the adhesive to retain the liquid component in the adhesive layer. This crosslinking agent reacts, at plural sites, with the functional group that the adhesive possesses, such as carboxyl group, hydroxyl group and amino group. As a result, the adhesive layer has a net structure that enables retention of the liquid component. In this reaction, when the liquid component, additive, drug and the like have a functional group capable of reacting with the crosslinking agent, the crosslinking agent first reacts with them rather than with the adhesive, because they have low molecular weights and superior dispersibility, and this tends to occur actually. Consequently, due to the absence of crosslinking of the adhesive by the action of a crosslinking agent, the liquid component cannot be retained in the adhesive layer and the inherent effects of the liquid component, additive, drug and the like cannot be exerted.
The present invention aims at solving the above-mentioned problems, and achieves low irritation property by retaining a liquid component in an adhesive layer, and provides a production method thereof.