A key preloading structure including a base, a set of switches and a set of keys is provided. The set of switches is arranged on the base. The set of keys has a rotating shaft and two actuators. The rotating shaft is assembled on the base. One end of each actuator is fixedly connected to the rotating shaft, and another end is disposed on a switch of the set of switches. Each of the two actuators preloads the set of switches with a force less than a triggering force for starting the set of switches.

A key preloading structure including a base, a set of switches and a set of keys is provided. The set of switches is arranged on the base. The set of keys has a rotating shaft and two extended elastomers. The rotating shaft is assembled on the base. One end of each extended elastomer is fixedly connected to the rotating shaft, and another end is disposed on the set of switches. Each of the two extended elastomers preloads the set of switches with a gravity less than a triggering force for starting the set of switches.

An illuminated keyboard with an optical switch is provided. The illuminated keyboard includes a circuit board and plural keys. The circuit board includes plural light-emitting elements. Each light-emitting element is aligned with the corresponding key. The key includes a keycap, a housing, a triggering post, a light guide element and a light guide frame. The keycap is located over the housing. The triggering post, the light guide element and the light guide frame are disposed within the housing. Moreover, the light guide frame is arranged around the triggering post. After a light beam emitted by the light-emitting element is introduced into the housing, the light beam is guided to the light guide frame by the light guide element, and the light beam is scattered to a region around the triggering post and outputted from the keycap.

An illuminated keyboard with an optical switch is provided. The illuminated keyboard includes a circuit board and plural keys. The circuit board includes plural light-emitting elements. Each light-emitting element is aligned with the corresponding key. The key includes a keycap, a housing, a triggering post, a light guide element and a light guide frame. The keycap is located over the housing. The triggering post, the light guide element and the light guide frame are disposed within the housing. Moreover, the light guide frame is arranged around the triggering post. After a light beam emitted by the light-emitting element is introduced into the housing, the light beam is guided to the light guide frame by the light guide element, and the light beam is scattered to a region around the triggering post and outputted from the keycap.