A one-layer and simpler polarizer replacement scheme has been developed as an alternative to COE in OLED

This year, Samsung Display and BOE introduced a new pol-less display technology to customers as a low-cost alternative to color filter on encapsulation (COE). 

Compared with the original COE structure, the low-cost pol-less technology removes the entire color filter (CF) and black matrix (BM) layer. Additionally, it replaces the initial over-coating layer with low transparency over-coating (OC) material (see Figure 1).

1. Figure 1: COE and low-cost pol-less structure comparison

Source: Omdia

Figure 1 shows one layer of BM and CF in the upper structure is removed, and another layer is replaced by low-transparency OC. Because the entire BM and CF layer has been removed, the relative photomasks are saved. Furthermore, the new OC layer may be merged with the on-cell touch display’s OC layer. 

Based on the improvement to the structure in Figure 1, the low-cost pol-less technology only requires one mask or does not require a photomask. Therefore, the new technology can greatly reduce the cost of pol-less displays because

• By requiring minimal or no additional exposure and development equipment, depreciation cost is saved
• By replacing the original five to six materials with one material, the bill of materials (BOM) cost is reduced
• By shortening the process, the yield rate is increased

   

In general, achieving cost savings requires sacrificing performance. For example, COE can save 25–30% of power compared with polarizers. Meanwhile, this low-cost pol-less technology can only save 15% of power and may result in a small increase in reflectivity. Although increasing the brightness of the light-emitting OLED can allow this polarizer replacement scheme to compensate for the loss of the display’s contrast ratio to a certain degree, the power saving of the design will be poorer compared with using polarizers. 

However, smartphone makers have limited choices of displays to stimulate the market. If foldable displays are widely used in the future, then the low-cost pol-less displays may be a cost-saving option for displays after COEs are widely used. Omdia opines that if smartphone makers are urged to improve their products, using tandem OLED material stacks may be better than COE in the smartphone market, though, they are all expensive.