| abstract |
The purpose of the present invention is to provide a hydrogel which has excellent adhesiveness to an electrode element, shows little lowering in tackiness or adhesiveness to the electrode element or to a subject to which the hydrogel has been applied even after absorbing moisture such as sweat or humidity, yet has the optimum tack strength to the skin surface and hardly damages the skin upon peeling, etc. A hydrogel 1 having a layered structure consisting of layer A 10 and layer B 20 is characterized in that: layer A 10 contains a monomer-derived component, water, a humidifier, a water-insoluble polymer having tackiness and an amphipathic polymer; the water-insoluble polymer is contained in an amount of 3-20 wt% relative to the total amount of layer A; the amphipathic polymer is polyvinyl alcohol having a saponification degree of 50-75% and is contained in an amount of 0.05-5 wt% relative to the total amount of layer A; layer B 20 contains a monomer-derived component, water and a humidifier but is substantially free from a water-insoluble polymer having tackiness and polyvinyl alcohol; the content of water relative to the total amount of layer B corresponds to the content of water relative to the total amount of layer A with an amplitude of ±10wt%; and the content of the humidifier relative to the total amount of layer B corresponds to the content of the humidifier relative to the total amount of layer A with an amplitude of ±10wt%. |