Touch Solutions for OLED Displays. 2 Capacitive Touch Panel options: External type/ In-cell type...

Thursday, June 16, 2022

"Technology always comes from human nature", human nature is to control everything. As we know smartphones allow people to master, see-through information, and touch our thoughts, which completely changes people's habits and also people enjoy dominance and pleasure.

Buttons in the past, touch panels today; in the past CRT, and LCD today are bright and dazzling self-emitting OLED, no electronic radiation, no backlight; a green and environmentally friendly communication technology - TP OLED.

Touch panels (TP) can be divided into resistive touch panels (RTP) and capacitive touch panels (CTP) based on electrical characteristics. Winstar OLED touch solutions are mainly based on capacitive touch panels (CTP) as shown in Figure 1 below as reference.

[Figure 1: Capacitive Touch Solution]


TP-OLED modules are divided into two categories, one is external touch panel module, and the other is in-cell touch module (as shown in Figure 2). External touch panel solution refers to a touch panel module attached to the existing OLED panel. The advantages of those modules are that there is no need to change the OLED panel design, no need to change the manufacturing process, no need to make a fixture, save the change cost, and can widely apply to the existing various sizes, to fulfill customer's request for Touch OLED modules.

[Figure 2: Structure of OLED Touch Panel]


The bonding process of attaching an external touch panel to the OLED panel is divided into two types: Air-bonding and Direct / Optical-Bonding. The former one has a simpler bonding process, which can be easily attached to various types of OLED panels and has a lower price. The optical-bonding process is more rigorous, using OCA (Optical Clear Adhesive) to bond the touch panel with the OLED panel, the bonding strength is much increased, and the boundary between the display area and the non-display area is not obvious, and the panel's light transmittance and stereopsis can be enhanced. There are obvious visual differences between the two types of lamination modules. This is because there is an air layer in the air-bonding touch panel lens and the OLED panel (as shown in Figure 3).

[Figure 3: theory of Air-bonding (left) vs. Optical-Bonding (right)]


Taking Winstar 1.54" TP-OLED module (WEO012864AWPP3A00000) as an example, the visual effect of optical bonding is quite good as shown in Figure 4.

[Figure 4: visual effect the Optical-bonding (left) vs. Air-bonding (right)]


In-cell TP-OLED module design, the driver IC is built-in with a touch circuit design and a display circuit design, called TDDI (Touch with Display Driver IC). Compared with the external TP-OLED module, the in-cell TP-OLED module has the advantages of lightness and thinness, saving film and adhesive, and has advantages in cost. The simple design structure helps simplify the circuit design and shorten the development process. Take Winstar 0.91" in-cell TP-OLED module WEO012832MWAP3J00000 as an example (as shown in Figure 5), the visual effect of optical bonding is quite good on module.

[Figure 5: Winstar 0.91” in-cell touch panel module]


Winstar offers a wide range of TP-OLED touch solutions for different product applications to customers. These TP-OLED can be applied to markets such as wearable devices, smart home equipment, meters, and industrial control panels to meet customer needs. Please refer to the below table 1 of Winstar touch solution module list:

Model No.SizeResolutionModule StructureTP- Structure
WEO012832M-CTP 0.91” 128x32 COG In-cell
WEO128128D-CTP 1.18” 128x128 COG External
WEO012864A-CTP 1.54” 128x64 COG External
WEP012832A-CTP 2.23” 128x32 COG+PCB+FR External
WEO012864G-CTP 2.42” 128x64 COG External
WEO012864J-CTP 2.42” 128x64 COG+PCB+FR External
WEO012864Q-CTP 2.7” 128x64 COG External
WEP012864Q-CTP 2.7” 128x64 COG+PCB+FR External
WEP012864U-CTP 2.7” 128x64 COG+PCB+FR External
WEN025664A-CTP 2.8” 256x64 COF+PCB+FR External
WEX025664B-CTP 3.12” 256x64 COF External
WEN025664B-CTP 3.12” 256x64 COF+PCB+FR External
WEO025664D-CTP 3.55” 256x64 COG External
WEN025664D-CTP 5.5” 256x64 COF+PCB+FR External