Optical bonding – what is important when choosing a contractor

Optical bonding – what is important when choosing a contractor

Optical bonding – what is important when choosing a contractor

Optical bonding is used to laminate touchscreens or cover glass to display. A special glue and a unique manufacturer’s technology are required for the entire operation. What do we get? High quality products that have better optical performance, durability, and other benefits, described later in the article.

Optical bonding technology also allows to connect a display with transparent layers of electromagnetic protection or with special coatings, e.g. AG (anti–glare), AR (anti–reflective), HC (hard coating) and polarizing filters.

The use of optical bonding in smartphones, in car cockpit displays (Tesla electric cars) had a huge impact on the development and popularity of this technology. Optical bonding is also often used in industrial solutions, e.g. in medical, military or industrial applications, where quality, durability and optical specification are critical.

The process of optical bonding can be divided into three main stages:

  • Preparation – comes down to display and touch screen surface decontamination, and selection of the right adhesive depending on various parameters (eg screen size, application environment, operating temperatures etc.)
  • Glue dispensing – the glue must be applied precisely on the entire surface of the display
  • Bonding and curing – the most important stage of the entire process, the touch panel is layered onto the LCD module so there are no gaps or bubbles. Then the adhesive is hardened with UV light ( no heat treatment reduces the risk of material contraction).

The advantages of optical bonding:

  • Reduction of light reflections and better image quality – in air bonding, light from an external source passes through the panel and air gap (between the display and the glass) ,causing its refraction. This phenomenon means that some of the light is reflected back, creating reflections on the screen.

The same effect goes the other way – light generated by the backlight of the LCD module, goes through the boundaries of materials with different refractive index, which causes partial deflection. The results are reduced contrast and legibility of the display. The adhesive used in optical bonding reduces the refraction effect, as the refractive index of the adhesive is similar to glass.

Moisture condensation prevention and dust protection – moisture and dirt can penetrate into the gap between the module layers, which has a negative impact on the readability of the display. The glue–filled space avoids this problem, the image is readable in any environment, e.g. outdoors, in production halls and warehouses, in hospitals.

Increased physical endurance – eliminating the gap with resin (glue) increases its physical strength, which allows the use of a ready module in public places, factories and military applications. Optical bonding allows to obtain the standard IK7 – protection against mechanical impacts of 2J.

optical bonding

The risk of cooperation with inexperienced partners

Depending on the final application and the operating environment , we will help you to choose the right type / mix of resin glue to counteract possible negative effects:

  • mura effect – tensioning of the glue, which can cause mechanical stress of the TFT LCD panel, especially visible when displaying dark content and in poor lightning. Carefully selected glue and staged curing process helps to minimize stress concentration and significantly reduces the chances of the mura effect.
  • shrinkage of the adhesive (delamination of the module) – shrinkage of the adhesive at high temperatures may cause delamination of the adhesive with the top material. Our technology allows to increase adhesion to materials that are combined throughout the process. The thermal test carried out showed that at 85 °C the effect does not occur.
  • yellowing – poorly matched mixture of resin glue may turn yellow under exposure to chemicals or UV radiation, which adversely affects the visual reception of the module. That is why we help you to choose the right mix depending on the application’s requirements.

The high quality of the service and the advantages described above allow the use of optical bonding in every application, especially when the operating environment is demanding, e.g. working in a wide temperature range, in direct sunlight. It is an excellent solution for use in a rigorous environment, especially in medical, military and factory automation projects.

To get additional data, please  contact us.

Monika Musielak

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