Transparent button for capacitive touch screen

Abstract

The button allows a good detection quality, a good transparency level and a haptic and/or acoustic feedback.

1 . Button configured to be placed on a touch sensor surface of a capacitive touch sensor and configured to allow the touch sensor to detect a clicked state and an unclicked state,
 the button comprising:
 a support member comprising a support surface configured to face the touch sensor surface, wherein the support surface comprises a click detection portion allowing the detection of the clicked state of the button in the touch sensor, 
 an activation member which is movable by a user relative to the support member, 
   wherein the activation member in the clicked state is moved closer to the support member than in the unclicked state,   wherein the activation member comprises:
 a user contact surface which is configured to be touched by a user for moving the activation member, thereby actuating the button, the user contact surface being at least partially transparent so as to transfer information displayed on the touch sensor surface under the user contact surface to the user, and, 
   characterized in that it comprises:
 a transparent conductive layer capacitively connected to the user contact surface, 
 switch means configured to
 conductively connect the transparent conductive layer with the click detection portion, when the button is in the clicked state, 
 conductively separate the transparent conductive layer from the click detection portion, when the button is in the unclicked state, and 
 provide an haptic click feedback and/or an acoustic click feedback, when the button changes from the unclicked state to the clicked state and/or vice-versa, 
 
   wherein the switch means comprise a dome-shaped spring comprising a conductive portion,   and wherein the switch means comprise a conductive means between the conductive portion of the dome-shaped spring and the click detection portion, so that when the dome-shaped spring is in a collapsed state, said conductive portion contacts the click detection portion via the conductive means.   
     
     
         2 . The button of  claim 1 , wherein the activation member comprises a fixed conductive connection rod, the fixed conductive rod being conductively connected to the conductive portion of the dome-shaped spring. 
     
     
         3 . The button of  claim 1 , wherein the activation member comprises a movable conductive connection rod, the support member comprising a recess, so that when the activation member is activated, the movable conductive connection rod moves in the recess so as to contact in the clicked state the conductive portion of the dome-shaped spring. 
     
     
         4 . The button of  claim 3 , comprising spring means around the movable conductive connection rod for further improving the haptic click feedback. 
     
     
         5 . The button of  claim 1 , a material of the transparent conductive layer being encapsulated for not coming in contact with ambient air or with the user. 
     
     
         6 . The button of  claim 1 , wherein the material of the transparent conductive layer is a transparent conducting oxide, in particular of an indium tin oxide. 
     
     
         7 . The button of  claim 1 , wherein the user contact surface is insulated from the transparent conductive layer such that charges of a user contacting the user contact surface are not electrically conducted to the transparent conductive layer, and/or such that a capacitance is created between a user contacting the user contact surface and the transparent conductive layer. 
     
     
         8 . The button of  claim 1 , wherein the activation member comprises a bottom surface facing towards the touch sensor surface and a top surface being opposite to the bottom surface, wherein the transparent conductive layer is arranged on the bottom surface covered by a protective layer. 
     
     
         9 . The button of  claim 1 , wherein the button comprises a cavity under the user contact surface and/or under the transparent conductive layer. 
     
     
         10 . The button of  claim 1 , wherein the activation member is rigid and the button is configured to allow a translational movement of the activation member with regard to the support member towards the touch sensor surface. 
     
     
         11 . The button of  claim 1 , the support member comprising a PCB, the PCB comprising the click detection portion and the conductive means, the conductive means being preferably a via of the PCB. 
     
     
         12 . The button of  claim 1 , the activation member comprising a lens for magnifying the size of the information displayed on the touch sensor surface under the transparent user contact surface to the user, said lens being preferably a convex lens. 
     
     
         13 . System comprising a capacitive touch sensor and a button according  claim 1 ,
 wherein the capacitive touch sensor comprises a touch sensor surface, wherein the button is placed with the support surface of the support member on the touch sensor surface,   wherein the touch sensor surface comprises a plurality of touch pixels distributed over the touch sensor surface wherein each touch pixel accessible to a user is configured to capacitively detect a finger of the user in the vicinity of the touch pixel,   wherein at least one of the touch pixels which arranged under the click detection portion is configured to capacitively detect a touch of the finger of the user on the user contact surface, when the button is in the clicked state.