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Touch Panel Technology

Air Gap Bonding

Air Gap Bonding is the most common method for touch panel attachment. An adhesive is applied between the display and touch panel using the inactive area around the perimeter of the module. This bonding method results in some inactive space 'air gap' between the touch panel substrate and the display. Manufacturing yield for this processing is very high 98% (or higher), so this is the most cost-effective and common solution.

Optical Bonding

Optical Bonding has become quite popular in some applications due to the improved viewing performance that is achieved. For optical bonding specific optically clear adhesive is applied over the entire surface between the display assembly and touch panel. This bonding method removes all air and air bubbles from the viewing area providing a more rugged and optically attractive solution. Removal of 'air gap' between the module and touch panel eliminates surface-to-surface reflections which degrade contrast and ultimately viewing angles, especially significant in sunlight conditions. 

FOG - RTP

Film-On-Glass (FOG) is the most common technology of touch panel in products currently. It offers a cost-effective and proven solution of user interface. Most offerings from OSD Displays can find an FOG-RTP technology touch solution from the open market that is compatible for most customer applications. This technology works by two thin electrically conductive layers are placed on a substrate. When an activation force (detailed in the specification) is applied to the top surface, the top and bottom layers pass electrical current from layer to layer. With known resistive properties, an X- and Y- coordinate can be obtained from the output to determine the location. Since force activates the touch instance, gloves can be worn while using RTP technology. FOG-RTP technology has a film on glass, so the top surface is a thin film. This material is suitable for normal office and consumer environments, but would be worn heavily by solvents or chemicals or other environmental factors like heat and humidity that will degrade such films. FOG-RTP is durable for 2M to 3M touches within a panel's life cycle.

GOG - RIP

Glass-On-Glass (GOG) is an industrial type of touch panel. It offers a solution with function quite similar to the FOG-RTP such that it uses an activation force to initiate two conductive layers to pass current. Due to the linear resistance of the panel, both X- and Y- Coordinates can be extrapolated into a position. GOG technology will vary from FOG such that the top surface exposed is more rugged than a film The device structure is typically structured such that a top 'cover' of glass compresses to another layer of glass with a conductive film layered between them. The conductive film compresses to a lower conductive glass layer. GOG-RTP is a resistive solution, so environments with gloved operators is acceptable and with a rugged glass top cover solvents and other chemicals can be maintained without damage to the function. GOG-RTP is an industrial solution and typically offers a high reliability of 30M+ touches of life-cycle. 

ST - CTP

Single-Touch Capacitive Touch Panels (ST-CTP) are increasing in popularity in consumer and industrial applications. Capacitive touch panels operate by application of a small voltage generates and expected electrostatic field. Conductive human fingers when touching the top surface essentially create a capacitor, and the embedded controller on the touch panel can estimate position through changes in capacitance. Advantages of capacitive touch panels include calibrated and provided controllers. Most controllers operate with serial interface such as I2C to system controllers. Calibrated solutions can often provide more accurate location detection than mechanically extrapolated solutions. Capacitive technologies are also more rugged since there is no movement or gap within the touch panels. Single-Touch solutions limitations are to only detect a single point or touch on the screen at any instance since the entire touch panel area is treated as a single sensor. Activities such as sliding a finger can be tracked by this technology, but using the movement and detection of only a single point. 

MT - CTP

Multi-Touch Capacitive Touch Panels (MT-CTP) solutions go one step further than ST-CTP by detecting rows and columns on the touch panel sensor individually. This enhanced sensing allows for detection most accurately of 2 points simultaneously and tracking of gestures such as pinch zoom and rotational movements. OSD Displays most common technology for gestures is a 2-point tracking solution since it can give the most accurate positions for 2 points and detect and track these positions accurately. MT-CTP solutions are compatible with many of the most modern operating systems for mobile and desktop device design. 

 
Technology FOG-RTP GOG-RTP ST-CTP MT-CTP
Gestures No No No Yes
Solvents No Yes Yes Yes
Gloves Yes Yes No No
Costs $$$ $$  $$$
Optical Bonding  Optional Optional Optional Optional
On-Flex Controller No No Yes Yes
Opt. Gorilla Glass  No No Yes Yes