In the field of mobile devices such as smartphones and tablet PCs, the market is starting to see products with a haptic function to create tactile sensations that can be felt by the fingertips. Many of these products comprise a piezoelectric element attached to glass or other material, and are at the current moment still unable to produce enough vibratory displacement with hard glass, etc. In addition, there is a problem that having to attach an element to the back of cover glass limits the installability of the element in the thickness direction.
For example, Patent Literature 1 below describes a structure comprising piezoelectric elements attached to glass. Patent Literature 1 discloses a touch panel device having a touch panel, a display part provided on the back side of the touch panel, a transparent protective plate formed on the front side of the touch panel, and a piezoelectric vibrating element. It is characterized in that the protective plate is constituted by joining a first glass plate on the front side and a second glass plate on the touch panel side, a step part thicker than the thickness of the piezoelectric vibrating element is provided in the thickness direction on either the first or second glass plate on the joined side, the piezoelectric vibrating element is placed in the step part, and the piezoelectric vibrating element is joined to the first glass plate.