Abstract:
An OLED device comprised of: an OLED means, a capacitive proximity sensing means for sensing a change in a capacitance, a mechanical element, and a means to provide a signal, wherein the OLED means and the mechanical element are movable relative to each other upon operation by a user and can assume a first position or a second position, wherein the capacitance is adapted to change between a first capacitance and a second capacitance when the OLED means and mechanical element are moved between the first position and the second position by an operator, and wherein the signal depends upon the capacitance.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to organic light emitting diodes, and in particular to the integration of organic light emitting diodes and capacitive proximity sensors. 
       BACKGROUND OF THE INVENTION 
       [0002]    Organic Light Emitting diodes (OLED) devices are comprised of two electrodes and an organic light emitting layer. The organic layer is disposed between the two electrodes. One electrode is the anode and the other electrode is the cathode. The organic layer is structured such that when the anode has a voltage bias that is sufficiently positive relative to the cathode, holes are injected from the anode and electrons are injected from the cathode. The necessary voltage bias depends upon the materials used for the organic layers. The holes and electrons recombine within the organic layer to induce an exited state in a molecule comprising the organic layer. Light is emitted during the process of excited molecules relaxing to their ground state. The anode is typically manufactured from a high work function material such as a Transparent Conducting Oxide (TCO), and the cathode is typically manufactured from a highly reflecting material such as aluminum or silver. However, there exist many different electrode designs which allow light to exit the cathode, the anode, or through both the cathode and the anode. The organic layer can be comprised of a single organic film, or it can be comprised of a stack of multiple organic films. OLED devices are useful as indicators and displays can be constructed from patterned arrays of OLED devices. 
         [0003]    Capacitive switching devices operate by sensing a change in capacitance. Touch sensors are capacitive switching devices that operate by sensing the change in capacitance of an electrode with respect to ground. These types of sensors typically sense the change in capacitance caused by the proximity of an operator&#39;s finger. Capacitive switching devices can also function by sensing the capacitance or change in capacitance between two conductive objects. 
         [0004]    U.S. Pat. No. 7,242,393 B2 discloses a combined OLED capacitive touch sensor and separately discloses the use of configurations and structures that provide tactile feedback. U.S. Patent application publication US 2005/0088417 A1 discloses a tactile touch sensing system that uses a capacitive sensor. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention provides for an organic light emitting diode with capacitive proximity sensing means. Embodiments of the invention are given in the dependant claims. 
         [0006]    The proximity of two conductors relative to each other can be sensed by using a capacitive proximity sensor. The capacitance between two conductive objects increases as the objects are brought closer together. A capacitive proximity sensor as understood herein is a sensor that functions either by measuring or detecting a change in the capacitance between two conductors. 
         [0007]    Current OLED devices do not integrate tactile feedback. In many applications, both tactile feedback and the illumination of a control are desired. Embodiments of the invention provide for the use of the OLED device as a part of a capacitive switch in combination with a mechanical element to provide tactile feedback. For example, a flexible dome foil placed on top of OLED can be used. By pressing the dome foil it snaps back onto the OLED glass surface. This effect gives a tactile feedback to the user. At the same time the effective capacitance between the OLED surface and ground is changed. The capacitance change can be easily detected using a capacitance sensor. The sensor can have an output which produces a signal based on this capacitance. The signal can be integrated into other electronics or can be used as an input of a control system. This dome foil and OLED combination can be easily adapted to different application areas where differently patterned foils can be used to display different illuminated symbols. This arrangement can be inverted, i.e. the flexible and tactile giving mechanical support structure can be placed under the OLED. The OLED can be supported by an elastomer frame surrounding the OLED. It provides support and allows vertical movement. 
         [0008]    Embodiments of the invention provide for an OLED means, a capacitive proximity sensing means, a mechanical element, and a means for providing a signal. The OLED means provides a visual indicator for the operator. The capacitive proximity sensing means allows a means of detecting when the device is operated. The mechanical element is moveable relative to the OLED means. The combined OLED means and mechanical element can be moved relative to each other and can be operated by the user. The means to provide a signal provide embodiments of the invention the ability to be included in a control system or to be embedded within parts of an electronic circuit. The combination of the mechanical element with the OLED means is very advantageous, because it provides for that tactile feedback and it also provides for a variety of different types of switching mechanisms using the capacitive touch screen technology. Possible embodiments are: push button type switches, toggle switches, and sliders. 
         [0009]    In another embodiment, the OLED means is adapted to provide tactile feedback to the user. This has the advantage that the user has an indication when the switch has been activated. Adding tactile feedback also gives the possibility of having a control which senses how hard the user presses. 
         [0010]    In another embodiment the mechanical element is adapted to provide tactile feedback. Capacitively switched touch panels generally have no feedback for the user providing the mechanical element that provides feedback makes it easier for the user to determine when they press and how hard they are activating the switch. Incorporating a mechanical element also allows a variety of means of activating the switch, a push button, a switch, a slider are examples of how this could be implemented. 
         [0011]    In another embodiment, the signal is adapted in several different ways. The signal can indicate a transition between the first and the second position. This has the advantage that a switch can be used as a pushbutton to toggle between two different states. The OLED functionality could be toggled also. This signal can also be adapted to indicate if the mechanical element is in the first or the second position. This has the advantage that the switch can be used to control something which goes between two states. The signal can also be adapted to indicate whether the switch is in the first position, the second position or if it is in the intermediate position. This has the advantage that the switch can be used to control not only an on or off function or being in one of two specific positions but the switch can be variable. The switch can be used for example on a video gaming system where dependent upon how hard one presses the control varies or on an MP3 player. For example, an embodiment of the invention could be incorporated in an MP3 player where the speed of the fast forward function is controlled by how hard the person pushes on the button. 
         [0012]    In another embodiment a capacitance is formed between the OLED device and ground. This has the advantage that the mechanical element can provide feedback to the user. In a normal touch panel the user has no tactile feedback. The mechanical element controls or actually restricts the operation of the touch panel by pressing harder or pushing the mechanical element a certain distance the user becomes close enough and the capacitance changes and then the switch is activated. 
         [0013]    In another embodiment the OLED means is comprised of a first electrode layer or organic emitting layer and a second electrode layer. An organic light emitting layer is between the first electrode layer and the second electrode layer. Also in this embodiment the mechanical element is comprised of a conductive element. The conductive element is located adjacent to either the first or the second electrode layer. Then a capacitance is formed between the conductive element and the electrode layer which the conductive element is located next to. When the OLED means and the mechanical means are operated by a user the capacitance between the conductive element and the electrode changes, this is detected by a capacitance sensor and is used to control the switching function. This is an extremely advantageous arrangement, because the ground no longer forms part of the current path used for the touch panel. This also has advantages over normal switches, because most switches are mechanical and the capacitive element will not wear out. 
         [0014]    In another embodiment the OLED device is connected to the mechanical element by an elastic element. The elastic element enables the relative movement between the mechanical element and the OLED means. The function of the elastic element is to return the OLED device and the mechanical element to the original position before the OLED means was operated by the user. This has the advantage of allowing a construction of a push button type switch. The elastic element also enables the capacitance between the capacitance measurement to vary as a function of how much force is used to operate the OLED means and the mechanical element. 
         [0015]    In another embodiment the elastic element is comprised of a mechanical element. The elastic element can be the mechanical element or the elastic element can be partially comprised of the mechanical element. This has the advantage that a dome type switch can be used for implementing embodiments of the invention. A clicker switch can be constructed from an embodiment of the invention. A clicker switch is a switch that physically switches between two states. Clicker switches typically emit a clicking sound, and provide tactile feed back as the switch switches between its two states. 
         [0016]    In another embodiment the elastic element is located between the OLED device and the mechanical element. This has the advantage that a mechanical element can be designed which allows the user to feel when the switch has been activated or how much the switch has been activated in the case of a switching device which gives a variable signal depending upon how much it is pressed. 
         [0017]    Another embodiment of the invention is further comprised of a mounting structure and the OLED device. The mounting structure is comprised of a front surface and a mounting recess. The mechanical element is comprised of a conducting element which is mounted within the mounting recess. The OLED means are attached to the elastic element, and the elastic element is attached directly to the mounting structure. An electrode of the OLED means is adjacent to the conductive element. Essentially the OLED means are embedded in the elastic element. This has the advantage of providing a switch with a large dynamic range and motion. It also has the advantage that elastic elements which are adapted to transmit light can be used to take advantage of edge light from the OLED means. The OLEDs emit light from the edge this could be transmitted through the elastic element and then directed so that the user can see lights on the panel. 
         [0018]    In another embodiment, the elastic element is adapted to transmit light. This has the advantage that the elastic element particularly in the case where surrounding the OLED means or when the OLED means is embedded in the OLED device can be lit by the edge light from the OLED device. 
         [0019]    In another embodiment of the invention, the mechanical element is adapted to transmit light. This has the advantage that switches which are backlit can be constructed. The OLED would transmit light through the mechanical element which would be visible to a user. 
         [0020]    In another embodiment of the invention the OLED device can also be patterned. This has the advantage that decorative patterns can be applied and it also has the advantage that labeling can be applied to switches and buttons that are embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    In the following preferred embodiments of the invention will be described, by way of example only, and with reference to the drawings in which: 
           [0022]      FIG. 1  is a functional schematic showing an embodiment of the invention where the capacitive switch functions by measuring the capacitance between the OLED device and a conductive element, 
           [0023]      FIG. 2  is a functional schematic showing an embodiment of the invention where the capacitance between ground and the OLED means is sensed, 
           [0024]      FIG. 3  shows a diagram of an embodiment of the invention where the OLED means is supported by an elastic element, 
           [0025]      FIG. 4  shows a diagram of an embodiment of the invention where the OLED means is supported by a dome switch, 
           [0026]      FIG. 5  shows a diagram of an embodiment of the invention where the OLED means is imbedded in the elastic element, 
           [0027]      FIG. 6  shows a diagraph of an embodiment of the invention where a deformable dome foil provides tactile feedback. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0028]    Like numbered elements in these figures are either identical elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later figures if the function is identical. 
         [0029]      FIG. 1  is a functional schematic showing an embodiment of an OLED device  100  that functions by measuring the capacitance between the OLED means  102  and a conductive element  116 . The OLED means is comprised of an anode  104 , a cathode  106 , an organic emissive layer  108  and a substrate  114 . The OLED means is activated by providing a voltage source  110 . When it is activated, light  112  is emitted from the organic layer  108 . The cathode  106  is connected in this embodiment to the negative portion of a DC power supply  110  and the anode  104  is connected to the positive terminal on the ADC power supply  110 . A capacitive sensor  118  is connected to a conductive element  116  and in this embodiment to the cathode  106 . 
         [0030]    The finger of an operator  122  operates the OLED means  102 . As the operator&#39;s finger  122  presses on the OLED means  102 , the distance  164  between the conductive element  116  and the cathode  106  changes. The distance  164  changes and the capacitance formed between the conductive element  116  and the cathode  106  changes. This change in the capacitance is detected by the capacitive sensor  118 . The capacitive sensor is then integrated into a control system or into other electronics at the capacitive sensor output  120 . Depending upon the embodiment of the invention this could take a variety of forms, it could be a digital signal, it could be an analogue signal or it could be a simple output of an electronic circuit. 
         [0031]    In alternative embodiments the conductive element can be operated instead of the OLED means  102 . In another alternative embodiment, the capacitance could also be formed between the conductive element  116  and the anode  104 . Anodes are typically constructed from Indium Tin Oxide (ITO), which is an optically transparent oxide. This allows light, to exit through the anode layer. However, either or both electrodes can be optically transparent in OLED devices. The capacitance between either or both of the electrodes and the conductive element can be used. 
         [0032]      FIG. 2  shows a functional schematic showing an embodiment an OLED device  200  where the capacitance between the ground and the OLED means is sensed. In this figure, the OLED means  102  is again comprised of an anode  104 , a cathode  106  and an organic emissive layer  108 . Again the cathode  106  is connected to the negative input of a DC voltage  110  and the anode is connected to the positive input of a DC voltage  110 . In this embodiment a capacitance is formed between the finger  122  of a user  128  and the anode  104  of the OLED means  102 . As the distance  130  between the finger  122  and the anode  104  changes, the capacitance  134  between the anode  104  and the finger  122  changes. There is then a conducting path  136  through the body of the operator to the ground  140 . This capacitance is represented by capacitance  138 . This embodiment works by measuring the leakage current, the leakage current is represented as  132 . As the distance  130  between the finger  122  and the anode  104  changes this leakage current changes and is able to be detected by a capacitive sensor  118 . Typically an AC signal would be put on a surface with a sensor  118  and a leakage current  132  is measured. This capacitive sensor can either be directly connected to the ground  140  or in most cases the device is capacitively coupled to ground anyway. This is represented by capacitance  142 . As the capacitance changes this is indicated using the capacitive sensor output  120 . Again this can be a digital signal, an analogue signal or it can just be integrated into an electronic circuit directly. In this embodiment the mechanical element  126  restricts the motion of the operator&#39;s finger  122 . Tactile feedback is provided by the mechanical element  126 . This embodiment shows a surface which is deformed but the mechanical element could also be a slider or other element. The capacitive sensor  118  could also be implemented using other means too. 
         [0033]      FIG. 3  shows a diagram of an embodiment of an OLED device  300  where the OLED means  102  is supported by an elastic element. In this figure a substrate  114  is in contact with the anode  104 . On the other surface of the anode is an organic emissive layer  108  and on the other side of the organic emissive layer is the cathode  106 . The two electrodes are connected to the voltage supply system, the OLED power leads  146 . The OLED means  102  is encased within a seal. The OLED means is sensitive to moisture and the seal is there to seal it and prolong lifetime of the OLED means. On the sides of the substrate  114  is located the OLED frame  144 . The entire OLED means  102  is mounted onto an elastic element  150 . The elastic element is mounted between the OLED means and a conductive element  116 . A capacitance  124  is formed between the conductive element  116  and the cathode  106  of the OLED means. The elastic element provides a means of operating and changing the distance between the anode  104  and the conductive element  116 . The conductive element  116  is mounted on a printed circuit board  152  in this embodiment and then the printed circuit board  152  is mounted onto a mounting structure  154 . The mounting structure could either be a casing and the switch could be mounted in a case or the mounting structure could be part of a control panel and the switch could be integrated into the control panel. In this embodiment the switch is operated by a user pressing on the substrate  114 , as the substrate is depressed the distance between the cathode  106  and the conductive element  116  changes. This changes the capacitance  124 . These capacitances can then be used by a capacitance sensor to generate a capacitive sensor output for controlling the control system or for controlling an electronic circuit or providing an analogue signal. 
         [0034]    In  FIG. 3 , the OLED is placed on a deformable support, e.g. foam. The capacitance change between one OLED electrode to an electrode on the printed circuit board is detected. 
         [0035]      FIG. 4  shows a diagram of an embodiment of an OLED device  400  where the OLED means is supported on a dome switch. This is very similar to the embodiment shown in  FIG. 3 , except instead of an elastic element the elastic element is comprised of the conductive element  116 . As the dome switch is depressed the capacitance between the dome switch and the cathode  108  changes. This change in capacitance is then used by a capacitive sensor to generate a capacitive sensor output  120 . This is used in the same way as the embodiment shown in  FIG. 3 .  FIG. 4  same like  FIG. 3  except that foam has been replace by a dome foil which allows the construction of a clicker switch. 
         [0036]      FIG. 5  shows a diagram of an embodiment of an OLED device  500  where the OLED means is embedded in the elastic element. This embodiment is further comprised of a mounting structure  154  and a mounting recess  160 . The conductive element  116  is mounted on a printed circuit board  152  that is mounted in the mounting recess  160 . The OLED means  102  is then mounted directly to the mounting recess  160  by an elastic element  150 . In this embodiment the OLED means  102  is shown as being flush with a front surface  158  of the mounting structure  154 . In this embodiment the mounting structure could be a panel or it could be a housing for a switch. The elastic element could be made of a variety of materials. In this embodiment the elastic element is shown as being made of a material that is adapted for transmitting light. In this case the edge light of the OLED device travels through the OLED means and into the elastic element  150 . Then edge light  156  is transmitted through the elastic means  150  and directed away from the front surface  158 . This is an advantage because the edge light is not wasted and also depending upon the material used for the elastic element  150 , a variety of effects can be achieved such as using a translucent material which scatters light or even color. Materials could be used to obtain different color edge lighting effect around the OLED device. 
         [0037]    In the embodiment of the OLED device  500  shown in  FIG. 5 , silicone can be used as the elastic element. The OLED can be imbedded in silicone to fix the OLED in place and to enable vertical motion of the OLED means. The optical transparency of silicone allows it to transmit edge light of the OLED to the front surface of the OLED device. In addition, the elastic element can have its color changed by using colored silicone. 
         [0038]      FIG. 6  shows an embodiment of an OLED device  600  where a flexible dome foil provides tactile feedback. In this embodiment the OLED means  102  and the OLED frame  144  are mounted onto a printed circuit board  152 . The printed circuit board is mounted on the mounting structure  154 . A flexible dome foil  162  is then located in front of the substrate  114  of the OLED means  102 . The purpose of the dome foil is to provide tactile feedback to an operator. In this embodiment an operator depresses the flexible dome foil with a finger  122 . To provide a switching means the capacitance between the anode  104  and the operator&#39;s finger  122  is detected. This embodiment is identical with the embodiment presented in  FIG. 2 . This is a highly desirable switch configuration, because the OLED device itself is not moving. The flexible dome switch foil is placed on top of the OLED device. The dome switch foil acts a bi-stable mechanical device. Once a pre-described force is applied to the dome, the foil immediately flattens and gives the user a signal for a successful button press. This abrupt change in distance between a finger tip and one of the OLED electrodes can be detected electronically by capacitive measurements. The dome foil itself can be completely transparent or partially transparent with a symbol printed on. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
         
           
               100  OLED device that senses the capacitance between the OLED device and a conductive element 
               102  OLED means 
               104  Anode 
               106  Cathode 
               108  Organic emissive layer 
               110  Electrical power source 
               112  Emitted light 
               114  Substrate 
               116  Conductive element 
               118  Capacitive sensor 
               120  Capacitive sensor output 
               122  Finger 
               124  Capacitance between OLED electrode and conductive element 
               126  Mechanical element 
               128  Operator 
               130  Distance between anode and finger 
               132  Leakage current 
               134  Capacitance between anode and finger 
               136  Conduction through body of operator 
               138  Capacitance between operator and ground 
               140  ground 
               142  Capacitance between capacitive sensor and ground 
               144  OLED frame 
               146  OLED power lead 
               148  Seal 
               150  Elastic element 
               152  Printed Circuit Board 
               154  Mounting structure 
               156  Edge light 
               158  Front surface 
               160  Mounting recess 
               162  Dome foil 
               164  Distance between cathode and conductive element 
               200  OLED device that senses ground leakage current 
               300  OLED device supported by elastic element 
               400  OLED device supported by dome switch 
               500  OLED device imbedded in elastic element 
               600  OLED device with deformable dome foil