The display market is undergoing significant change. With growing demand for consumer products such as smartphones, tablets, and wearables, leading display manufacturers are increasingly focusing on this high-growth sector while withdrawing from the industrial segment. This development has direct consequences: a reduced selection of industrial displays, longer lead times, and more challenging long-term availability.
Despite these shifts, high-quality displays remain indispensable in demanding HMI applications. Brilliant image quality, robustness, precision, and reliable long-term use are essential. New technologies such as MicroLED and optical bonding offer additional opportunities to make human–machine interactions safer and more efficient. Early integration into the application’s development process and careful display selection are more important today than ever.
Cleanroom Assembly and Display Quality
Displays are the central interface in industrial and medical applications—whether in machine control, process visualization, diagnostic monitoring, or surgical assistance systems. Their quality directly determines usability, safety, and efficiency.
Compared to standard consumer devices, displays in industrial and medical technology must meet significantly higher requirements. Optical performance, robustness, long-term availability, and compliance with standards are essential. Advances in display technologies—from MicroLED to optical bonding—are opening up new opportunities for safer and more efficient human–machine interaction. This requires early and targeted integration of display selection into the design-in process.
Procurement Channels and Long-Term Availability
To ensure reliable supply in the long term, a broad procurement network is essential. Depending on project volume, budget, customization needs, and product lifecycle, sourcing can be carried out either directly from manufacturers or through distributors and partners.
In highly demanding industries such as medical technology, a minimum availability of 5–10 years is often required. This can only be achieved by working with experienced, well-established suppliers who can guarantee supply security even under changing market conditions.
Design-In: The Basis for a Future-Proof Solution
A successful design-in requires selecting a display that is optimally suited to the specific application—including the appropriate driving electronics. A wide range of diagonals, formats, and technologies is available, from TFT color LCDs and OLEDs to e-paper displays and modules, all qualified for both industrial and medical use. Targeted, application-oriented display selection, combined with early integration into the design-in process, are key success factors for developing a future-proof solution.
Displays with Cover Glass: Optimizing Optics and Material Combination
In high-resolution displays with high pixel density, the use of cover glass with an anti-glare surface can lead to a sparkling effect. Special surface treatments prevent this. The suitability of cover glass can be precisely evaluated using an optical sparkling measurement system—ensuring the optimal combination of display and cover glass.
The choice of suitable adhesives is equally critical, with the refractive index requiring exact alignment. Only the interaction of micro-etched cover glass and optical adhesives (e.g., OCA) in the bonding process guarantees a high-quality visual result.
Bonding Methods: Integration of Display Units
For the mechanical integration of displays into applications, either air gap or optical bonding methods are used, depending on the requirements. In these processes, cover glass, touch sensors, and displays are combined into a functional unit using different bonding technologies.
- Air Gap Bonding In air gap bonding, the display is mounted in a cleanroom directly behind the touch sensor or onto the printed backside of the cover glass using a peripheral adhesive frame. A small air gap remains between the display and the glass. This method is simple, cost-efficient, and suitable for applications with lower optical requirements.
- Optical Bonding For applications with higher optical demands, two qualified optical bonding methods are available:
- Liquid Optical Bonding (LOCA) A UV-curing liquid adhesive (silicone-free, aging-resistant, UV-stable) is applied bubble-free into the air gap between display and touch sensor and then cured. The result is a bond with high optical clarity and enhanced robustness.
- Dry Optical Bonding (OCA / OCF) A precisely cut, optically transparent adhesive film is laminated in a vacuum process between the display and the touch-laminated cover glass. This method requires high precision and is not compatible with all display types.
Regardless of the method, the components undergo plasma pretreatment. This increases the surface tension of the bonding partners and optimizes adhesion, ensuring a stable and durable connection.
Optimisation Through Optical Bonding
Optical bonding significantly enhances the performance of modern touch displays. The advantages are manifold: by fully bonding the display, touch sensor, and cover glass, reflections are eliminated, light refraction is minimized, and both contrast and image sharpness are greatly improved. This results in optimised readability—even under challenging lighting conditions.
The stable, homogeneous connection also increases mechanical robustness against pressure, shock, and vibration. At the same time, the closed structure prevents condensation as well as the ingress of moisture, dust, or dirt. Heat dissipation is also improved by filling the air gap. In addition, optical bonding has a positive impact on the functionality of PCAP touch systems: the consistent material structure supports precise and long-term stable controller calibration.
In both industrial and medical technology, optical bonding has established itself as the standard and is now the leading method for optimising HMI displays.
Viewing Angle
For a reliable user experience, the display must provide consistently high readability and color accuracy even when viewed from the side—regardless of the user’s viewing angle. The viewing angle is therefore a decisive selection criterion.
Display Technologies in the Industrial Sector
- LCD (TFT-LCD) TFT displays with industrial-grade specifications are the current standard in many applications. They are considered a robust, proven, and widely available solution, offering a broad range of formats, brightness levels, and interfaces.
- OLED OLED displays (Organic Light Emitting Diodes) consist of self-emitting pixels that are printed directly onto the substrate. They stand out with brilliant color reproduction and high contrast.
- E-Paper (E-Ink) E-paper displays are an energy-efficient alternative, particularly for applications with static content. They consume power only when the image changes and, thanks to their reflective display technology, provide excellent readability even in direct sunlight. For use in dark environments, e-paper displays are equipped with integrated light guides, as they do not emit their own light source.
