Abstract: A key switch structure includes a key top, a membrane sheet, a plate member, and a light source. The key top on which an unpainted character portion that is permeable to light is formed. The membrane sheet comprises a contact portion and is permeable to light. The plate member is disposed below the membrane sheet and is permeable to light. The light source is disposed below the plate member. The unpainted character portion of the key top is lighted via the plate member and the membrane sheet by causing the light source to emit light.

Abstract: A key switch structure includes a key top, a membrane sheet, a plate member, and a light source. The key top on which an unpainted character portion that is permeable to light is formed. The membrane sheet comprises a contact portion and is permeable to light. The plate member is disposed below the membrane sheet and is permeable to light. The light source is disposed below the plate member. The unpainted character portion of the key top is lighted via the plate member and the membrane sheet by causing the light source to emit light.

Abstract: A key switch includes an elastic member having a circular open end and a membrane sheet on which the elastic member is disposed. The membrane sheet includes two flexible sheets and an insulating resin sheet sandwiched between them. The insulating sheet includes an opening, which has a shape different from that of the open end.

Abstract: A key switch includes an elastic member having a circular open end and a membrane sheet on which the elastic member is disposed. The membrane sheet includes two flexible sheets and an insulating resin sheet sandwiched between them. The insulating sheet includes an opening, which has a shape different from that of the open end.

Abstract: A keyboard unit having a base plate, and a plurality of key switches provided on the base plate. Each of the key switches has an electric contact provided within a membrane sheet on the base plate, an elastic dome portion formed on the base plate so as to cover the electric contact, a bearing portion provided on base plate, and a key cap having a support shaft which engages the bearing portion, and an engaging portion which engages the dome portion. When the key cap is depressed, the dome portion is elastically deformed so that an inner surface of the dome portion presses against the electric contact, and when the key cap is not depressed, deformation of the dome portion is removed so that the inner surface of the dome portion is separated from the electric contact and the key cap is pushed up by the dome portion.