Application-specific displays
Non-standard solutions
If a standard display does not fit or additional functions need to be integrated, we can provide you with a solution.
The display is the heart of an HMI application. Unfortunately, a standard model does not always fit, or its parameters do not meet the requirements of the application. This includes, for example, the brightness or service life of a backlight, a built-in driver for this, or the integration of a touch sensor with the appropriate front glass.
This is where application-specific displays come into play. Sometimes a small modification such as changing a flex foil or a connector is sufficient, in other cases the module has to be completely rebuilt starting with the TFT mother glass. This allows for completely customized solutions that are worthwhile starting at 1,000 units.
Custom display adaptations
Even though major manufacturers guarantee a product life of between three and five years, application-specific solutions can offer a significantly longer service life. If, for example, the display glass is no longer manufactured, the manufacturer can fall back on a similar product, so that the customer receives a model that is compatible in terms of form, fit, and function, requiring no changes to the system hardware or software and thus significantly extending availability.
The high degree of integration allows all functions available on the display—touchscreen, backlight driver, brightness and presence sensor—to be connected to the host system via a single Flexfoil connector. This simplifies assembly and increases reliability.
Of course, the front glass does not have to be uniformly printed in black; the dimensions, contour, and printing (color, logo, recesses) are defined individually according to the requirements of the project. Reflections are minimized when the display is optically bonded to the front glass. This enhances the appearance of the device and increases readability.
Customization
For projects involving 1,000 units or more, adjustments can be made that are worth the additional cost in order to customize the TFT module (e.g., cover glass) or adapt it to the application (e.g., interface). The following section lists the available options.
Liquid crystal and polarizing filter
Since the TFT cell is supplied without a polarizing filter and liquid crystal, materials with specific properties can be selected according to your own specifications. Some projects require an extended temperature range, while others are more concerned with savings when using a normal polarizing filter.
Backlight
Once you have found the module that meets all the desired parameters, it may still lack the brightness required for outdoor use. By replacing the LED types or designing a backlight with more LEDs, the brightness can be increased or the service life (half-life) of the backlight can be extended.
System integration is easier if the converter for the LEDs is located directly on the module and the backlight can be operated at a fixed voltage and its brightness dimmed via a PWM signal.
Controller IC and interface
Even if the TFT glass is designed for a specific controller chip, there are some compatible types available. They may have an interface that fits better into the system or other features, such as a sleep mode with lower display refresh rates or an image memory that reduces the load on the CPU.
Flexible foil design
For mechanical integration, the flexible foil should be placed in the device as close as possible to the display connector. Under certain circumstances, the pin assignment may need to be adapted to the previous model in order to avoid hardware changes in the device.
The application is particularly easy when all components—display, touchscreen, and LED backlight—are connected to a single connector. This simplifies assembly and minimizes sources of error.
Cover glass design
In professional applications, the sensitive display is always protected by a cover glass – the front is formed by the polarizing filter, which is sensitive to scratches and moisture. It does not matter whether there is a touchscreen behind the cover glass. The cover glass can be printed; in the simplest case, this is a black mask that conceals the edge of the display. The printing is located behind the glass so that it is scratch-resistant and does not wear out during operation.
The color of the printing can be chosen as desired. It is baked on using ceramic inks and can withstand extreme temperatures as well as permanent UV radiation outdoors. The size and shape of the glass can also be customized – rounded corners and polished edges are part of the standard repertoire.
Optical bonding
To ensure maximum display quality even in difficult lighting conditions, such as in assembly halls with ceiling lighting or outdoors, the cover glass is bonded to the display over its entire surface rather than with adhesive tape around the edges. This significantly reduces reflections from incident light. A pleasant side effect is the sealing, so that neither dust nor moisture can penetrate the gap between the display and the cover glass.
Integration of a touchscreen
If the display is to be used interactively, a touch sensor is laminated behind the cover glass. In most cases, the touchscreen uses PCAP technology, in which the smallest changes in capacity are evaluated as touch events. Its function can be parameterized in a wide range of areas – from single-finger operation to gesture control, from operation with work gloves to wetting with water and other liquids.
For optimum optical performance and electrical function, the touch sensor is laminated to the front glass and this composite is bonded to the display module. Here, there is the freedom to bond the components using a circumferential adhesive tape or optical bonding. Current technologies such as OCA also enable repairs to be carried out in the factory after production without damaging or destroying the components involved.
Selecting the touch controller
The functions mentioned above are implemented by selecting a suitable touch controller. This is also integrated into the display's flexible film. A high-performance controller can cover all use cases. If the application is simple (only one finger, no environmental influences), a simple controller can keep costs low.
Additional sensors
Variable printing on the glass surface allows a viewing window to be kept free for a sensor that measures the ambient brightness and influences the display brightness. A photodiode for an infrared remote control can also be installed in the cover glass. A presence detector only switches the display on or to full brightness when an operator is in front of it.
Additional touch surfaces
If a graphical HMI is to be equipped with additional buttons, the evaluation electronics can be integrated on the flexible foil. A separate structure for volume, on/off, or cleaning mode is no longer necessary.
Indicator LEDs
Just like additional key surfaces, LEDs can be integrated behind the glass. They can be used both as ambient lighting around the entire display and individually to indicate operating states. Multicolor diodes are particularly suitable for this purpose, as they can indicate different machine states using specific colors.
Consulting and contact
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