Specializing in TFT LCD and Capacitive Touch Screens.

The solution of Sunlight readable--3.Optical Bonding

Technology News


When you check your display under the sunlight, many people have experiences that they can not see the display clearly under sunlight, at this time, you would need sunlight readable display, in this article, we would introduce these solution about sunlight readable tft.
1>Provide high Luminance backlight source,used to resist strong light.
2>Transflective solution.
3>If with Touch panel,optical bonding is a better solution.
This article describes the third solution:
3>optical bonding
With touch panel attached to LCM, the display suffers not only brightness going down but also the deteriorating in display quality. Especially the reflection of ambient light causes the dark image being not as dark as it supposed to be.


By adding the process of Optical Bonding, we can reduce the brightness loss and avoid the influence of ambient light.


Optical bonding is the process of laminating cover glass or touchscreens to the LCD cell. It is a process that applies a layer of transparent material such as OCA (Optically Clear Adhesive) or OCR (Optically Clear Resin) between the layers to completely fill the air gap. The adhesive  is  completely transparent, the structure and color of the adhesive will not transform through the use of time.

The solution of Sunlight readable--3.Optical Bonding

Reflection appears when light propagates through media with different optical indices. The reflection energy is around 4% of incident light at each air-glass interface. As touch panel attached to LCM with air gap, two additional air-dielectric interfaces contribute to light reflection.


Optical bonding technique fills the air gap with Optical Clear Adhesive or OCA. While the optical index of OCA is designed to be very close to that of glass, light reflection at those two interfaces is minimized. Since less ambient light is bounced off the interfaces with optical bonding, the dark image remains as dark as it should be and the contrast ratio as well as the color saturation are restored back to the level when touch panel was not there. Likewise, back light of LCM experiences less reflection loss when it propagates through the interfaces with OCA, and the brightness off the touch panel is up as if the TP was not there.


Optical bonding is implemented by either liquid or sheet form OCA. Attachment process is performed in the air with liquid OCA and either UV or thermal curing process is needed after attachment. On the other hand, vacuum condition is necessary when sheet form OCA is applied. The high cost of both processes is mainly due to un-recoverable yield loss issue. The countermeasure regarding re-work process is already developed in Disea Electronics Co., LTD.