AU Optronics touch display technology: from Air Bond to Direct Bond
Date:2026-06-09
Comprehensive analysis of AU Optronics touch display technology: from Air Bond to Direct Bond
In the fields of industrial displays, self-service terminals, medical equipment, in car entertainment systems, and intelligent retail, touch display has become the core way of human-computer interaction. However, the same projected capacitive (P-Cap) or resistive (R-TP) touch screen may have significant differences in optical performance, durability, cost, and user experience due to different bonding processes with LCD modules. In its Q2 2026 product roadmap, AUO Display Plus clearly distinguishes between Air Bond (air bonding) and Direct Bond (direct bonding, also known as optical bonding) processes and provides a wide range of Total Solution modules. This article will focus on these two bonding techniques, combined with the principles of resistive and capacitive touch, to conduct a comprehensive comparative analysis, and cite specific models in the roadmap for explanation.
I. Fundamentals of Touch Technology: Resistive and Capacitive
Before discussing the bonding method, it is necessary to first understand the two basic touch sensing technologies in the AU product line:
1. Resistive Touch Panel (R-TP)
Working principle: By pressing, the upper and lower conductive layers come into contact, generating a voltage change to locate the touch position.
Advantages: Supports operation with any object (gloves, pens, nails); Low cost; Strong anti-interference ability.
Disadvantages: Low light transmittance (usually around 80%); Surface easily scratched; Does not support multi touch (or only supports two-point); It requires a certain degree of pressure.
Representative models: G043FTT01.0 (4.3-inch WQVGA, air bonded, EOL), G043FAT02.0 (4.3-inch, mass-produced in Q2 2026, RS technology, air bonded), G070VTT01.0 (7-inch WVGA, air bonded) in the document.
2. Projected Capacitive Touch (P-Cap)
Working principle: Use the capacitance change between the human electric field and the touch screen electrode to detect the touch position.
Advantages: High transmittance (>87%); Support multi touch (10 points or even more); Sensitive response; Durable surface (can be covered with glass).
Disadvantage: Requires conductor (finger or specialized capacitive pen) operation; High cost; The design of anti electromagnetic interference is complex.
Representative models: A large number of total solution modules in the roadmap, such as G070VAT01.0 (7-inch WVGA, AHVA, air bonding), G101EAT02.6 (10.1-inch WXGA, AHVA, air bonding), G238HAT01. x (23.8-inch FHD, AHVA, direct bonding), etc.
AU provides "Total Solution Models", which integrate LCD panels and touch screens for shipment, reducing the need for customers to assemble them themselves. The bonding methods are mainly divided into Air Bond and Direct Bond.
II. Air Bond: A Cost Choice for Traditional Craftsmanship
2.1 Process Definition
Air Bond refers to the use of double-sided tape (usually foam tape) to bond the edges of a touch screen (Touch Panel) to the frame of an LCD module, leaving a layer of air gap (approximately 0.1-0.5mm) between the touch screen and LCD. This process is also commonly referred to as "frame pasting".
2.2 Performance Characteristics
Optical influence: Due to the presence of an air layer, light will undergo two refractions and reflections when passing through the touch screen glass, air layer, and LCD surface, resulting in:
The transmittance decreases (usually by 5% to 10%).
In strong light environments, the internal reflection caused by air gaps is significantly enhanced, reducing readability.
Thickness: The overall module is thicker because the air gap occupies a certain amount of space.
Impact resistance: The air layer can provide a certain buffering effect, and in extreme cases, touch screen breakage may not directly damage the LCD panel.
Maintainability: If the touch screen is damaged, it can be relatively easy to separate and replace because only the edges are bonded.
Cost: Simple process, low material cost, no need for expensive fully bonded optical adhesives or equipment.
2.3 Air Bond Examples in AU Products
According to the 2026 Q2 roadmap, the vast majority of total solution modules (especially resistive and early capacitive) use Air Bond:
G043FAT02.0 (4.3 inches, RS resistive, air bonded, mass-produced in Q2 2026)
G070VAT01.0 (7-inch WVGA, AHVA P-Cap, air bonding, mass production in Q4 2023)
G101EAT02.6 (10.1-inch WXGA, AHVA P-Cap, air bonding, in mass production)
G170ETT01.0 (17 inch SXGA, P-Cap, air fit, planned 2026 Q3 EOL)
G190ETT01.1 (19 inch SXGA, P-Cap, air fit, 2026 Q4 EOL)
G240HVT01.0 (24 inch FHD, AMVA P-Cap, air fit)
These products are widely used in cost sensitive and optical demanding scenarios such as industrial control panels, self-service ordering machines, and public information kiosks.
III. Direct Bond: The Performance Choice for High End Applications
3.1 Process Definition
Direct Bond (also known as optical bonding or full bonding) uses transparent optical adhesive (OCR, Optical Clear Resin or OCA, Optical Clear Adhesive) to completely bond the entire back of the touch screen to the entire display area of the LCD module, leaving no air layer in between. The refractive index of optical adhesive is usually close to that of glass (about 1.5), greatly reducing interface reflection.
3.2 Performance Characteristics
Optical Enhancement:
The transmittance can be increased to over 90%.
Eliminating air gaps reduces internal reflectivity by about 80% to 90%, significantly improving contrast under strong light.
The display appears to be "floating" on the surface, creating a more transparent visual effect.
Thickness reduction: The overall module is thinner, which is conducive to lightweight design of the equipment.
Impact resistance and durability: Full lamination enhances the structural strength of the touch screen and LCD, reducing the probability of delamination or damage when subjected to impact; At the same time, it effectively prevents dust and water vapor from entering the gap and causing pollution.
Reliability: In harsh environments such as high temperature, high humidity, and vibration, Direct Bond has better stability than Air Bond.
Maintainability: Once the touch screen or LCD is damaged, the repair cost is extremely high because it is difficult to separate them without damage; Usually, the entire assembly needs to be replaced.
Cost: Precision dispensing or bonding equipment is required, optical adhesive materials are expensive, the process time is long, and the overall cost is significantly higher than Air Bond.
3.3 Direct Bond Examples in AU Products
There are relatively few models clearly labeled as "Direct Bond" in the roadmap, mainly aimed at high-end industrial or professional display applications:
G238HAT01. x (23.8-inch FHD, AHVA, P-Cap, direct bonding): Brightness of 300 nits, working temperature of 0-50 ° C, suitable for high-end interactive terminals in medical or retail applications.
G270HAN01.3 (27 inch FHD, AHVA, direct bonding): 1000 nits high brightness, 10 bit LVDS interface, can be used for outdoor self-service terminals.
In addition, although not individually labeled in the document, some 27 inch UHD models (such as G270ZAN02.1) mention "Direct Bond" as an optional configuration in the description.
It is worth noting that in AU's 2026 plan, an increasing number of newly launched P-Cap total solutions tend to adopt Direct Bond, such as the 23.8-inch G238HAT02. y (planned), which may also continue the direct fit route.
IV. Air Bond vs Direct Bond: Comprehensive Comparison Table
Comparative dimension | Air Bond | Direct Bond |
Adhesive medium | Surrounding foam adhesive | Full area optical adhesive（OCR/OCA） |
Air gap | Existence | Nothing |
Transmittance | 85%~88% | 90%~93% |
Readability under strong light | Poor (obvious internal reflection) | Excellent (extremely low reflectivity) |
Module thickness | Thicker | Thin (reduced by 0.5~1mm) |
Impact resistance | General | Good (structurally enhanced) |
Dustproof and Moistureproof | Poor (prone to dust) | Excellent (fully sealed) |
Convenience of maintenance | Can replace touch screen separately | The entire assembly needs to be replaced |
Cost | Low | High (usually+30%~50%) |
Typical Applications | Indoor industrial control, POS machine, household appliances | Medical imaging, outdoor Kiosk, aviation and navigation |
Representative model of AU | G070VAT01.0, G101EAT02.6, G190ETT01.1 | G238HAT01.x, G270HAN01.3 |
V Selection guide: When to choose Air Bond and when to choose Direct Bond?
5.1 Priority selection of Air Bond scenarios
The equipment is mainly used indoors in environments with controllable lighting, such as factory control rooms and cash registers.
The project budget is limited and there is a need to reduce costs in touch functionality.
The device may face frequent touch screen replacement needs (such as vulnerable parts of public facilities).
Not sensitive to the thickness of the entire machine, or there is already a standard structural design that adapts to the frame pasting module.
The working environment is clean and not prone to dust or condensation.
5.2 Priority selection of Direct Bond scenarios
The device needs to be clearly readable in strong light (including outdoor sunlight), such as outdoor self-service gas stations and electric vehicle charging stations.
High color accuracy and contrast are required, such as medical diagnostic displays and professional image editors.
The product requires narrow borders and a lightweight design to enhance its overall quality.
The equipment operates in harsh environments (high temperature, high humidity, vibration, salt spray) and requires high reliability.
Supporting waterproof and dustproof (meeting IP level requirements), direct bonding helps with sealing.
VI Additional advantages of AU's overall solution
In addition to the bonding method itself, AU's Total Solution Models also provide the following additional value:
Unified signal interface: integrated touch controller, output USB/I ² C interface, simplifying customer motherboard design.
Environmental adaptability optimization: Some models support wide temperature range (-20~70 ℃) and long-lasting backlight (50K hours).
Anti electromagnetic interference: Optimize touch sensitivity for industrial strong interference scenarios.
Customized cover plate: can add anti glare (AG), anti fingerprint (AF), and anti reflection (AR) coatings.
For example, although G101EAT02.6 uses Air Bond, its brightness reaches 400 nits, operating temperature is -20~70 ℃, and backlight life is 50K hours, which is sufficient to cope with most indoor industrial environments. The future G238HAT02. y planned model is likely to use Direct Bond for medical or high-end retail purposes.
VII Future trend: Full lamination sinking and integration of new technologies
With the gradual reduction of optical adhesive costs and the improvement of automated bonding yield, Direct Bond is penetrating mainstream industrial displays from ultra high end fields such as medical and military industries. In AU's 2026 roadmap, most of the newly launched 10.1-inch and above total solutions plan for the Direct Bond option. At the same time, AU is also developing borderless touch fit technology, combined with ultra narrow bezel (SNB) LCD, to achieve a true edge to edge touch experience.
In addition, the curved surface bonding technology of flexible OLEDs may also be introduced into the industrial LCD field in the future, but currently, AU still focuses on rigid LCDs, and the bonding methods are still divided between Air Bond and Direct Bond.
Conclusion
Air Bond and Direct Bond are not simply a matter of superiority or inferiority, but rather a trade-off between cost and performance for different application scenarios. The AU Display Plus clearly offers two bonding options in its product roadmap, covering multiple total solution modules ranging from 4.3 inches to 27 inches. Understanding the differences between these two technologies can help system integrators and product managers make the right design decisions in the early stages of a project: Air Bond is capable of handling budget sensitive and environmentally controllable scenarios; When pursuing optical performance, reliability, and high-end brand image, Direct Bond is a long-term investment worthy choice. With the development of industrial Internet of Things and smart cities, the application proportion of Direct Bond is expected to continue to rise, while Air Bond will still maintain its vitality in entry-level and maintenance friendly devices.
