About Y-OCTA knowledge introduction
For manufacturers of smart phone organic light-emitting diode (OLED) panels (especially Samsung Display), continuous progress is being made to integrate touch panel structures into displays in order to achieve thin film integration and reduce panel thickness. This development is particularly prominent when comparing rigid OLED panels with flexible OLED panels-this integration can produce very thin panels that can be folded or even rolled.
The unit touch solution enables the display market to move closer to flexible products, which is the basic technology of the Y-OCTA mechanism. In essence, Y-OCTA eliminates a separate touch screen layer on the display by integrating the touch-sensitive part of the screen into the unit.
On-cell TSP for rigid OLED
The picture above shows the traditional structure of a rigid OLED display, where an on-cell with a touch sensor panel (TSP) can be found on the surface of the encapsulation glass. The rigid OLED panel itself has two glass substrates-encapsulation glass and substrate glass on the backplane.
is sealed (made of glass frit or resin) between the package and the back glass; the TSP sensor is located on the surface of the package glass. On the cover window side, the OLED polarizer and the cover window are laminated by optically transparent adhesive (OCA) or optically transparent resin (OCR). In this case, the TSP is located on top of the encapsulation glass.
The entire OLED module has eight layers, including touch and cover windows. From top to bottom are cover window, decorative film, OCA/OCR, polarizer, TSP sensor, packaging glass, OLED light-emitting layer and backplane substrate.
In-cell TSP of rigid OLED
In this structure, the TSP moves from on-cell to in-cell, so that the TSP sensor is under the encapsulation glass. Except for the location of the TSP, the embedded structure is basically the same as the on-cell TSP structure of a rigid OLED.
The eighth floor remains the same, but the order is now slightly different. From top to bottom, including cover window, decorative film, OCA/OCR, polarizer, encapsulation glass, TSP sensor, OLED light-emitting layer and backplane substrate. With this structure, the in-cell touch shows better sensitivity and response.
TSP sensor on plastic film
For flexible OLED displays, plastic substrates are used instead of glass substrates. In theory, it is impossible to fabricate a TSP sensor layer on a plastic substrate. Therefore, flexible OLED panel manufacturers, especially Samsung Display and LG Display, have developed a special plastic layer called TSP base film. Only the TSP base film for the touch TSP sensor is laminated with the OLED panel using OCA/OCR.
Due to the addition of TSP base film, the entire structure has 10 layers. From top to bottom, the 10 layers include: cover window, decorative film, OCA/OCR, TSP sensor, TSP base film, OCA/OCR, OLED polarizer, encapsulation layer, OLED light-emitting layer and backplane plastic substrate. Because the more layers, the more complex the structure, panel manufacturers are also beginning to seek better solutions.
TSP sensor on the polarizer
The use of TSP on plastic films is complicated by the addition of a TSP base film, so the new idea is to combine the TSP base film with an OLED polarizer. Through the development and improvement of thin film encapsulation (TFE), combined with the polarizer and TSP base film, the OCA/OCR layer is no longer needed for lamination. This successfully reduced the number of layers from 10 to 8.
The eight layers from top to bottom are: cover window, decorative film, OCA/OCR, TSP sensor, OLED polarizer, thin film packaging, OLED light-emitting layer and backplane plastic substrate.
Y-OCTA: Thin-film packaged TSP sensor
As the most advanced structure at present, Y-OCTA is a term developed by Samsung Display to describe the special structure of flexible displays. As described in the On-cell touch solution, this is a major improvement of flexible AMOLED. The most important feature is to put the TSP sensor directly on the TFE to obtain a solution on the battery. Compared with additional contacts, On-cell has the following advantages:
· Using on-cell technology, the optical properties of the touch layer and the bending area have been improved, because the touch layer is located under the polarizer, allowing manufacturers to use ITO materials to make transparent conductive films.
The polarizer is placed closer to the protective lens, which solves some of the visibility problems on the curved edge.
On-Cell type does not require a support film, and has the undesirable effect of preventing the touch layer from being flat on the curved area when it is transferred to the module manufacturer. Eliminating the support film reduces the total panel thickness, production cost and lamination process.
The on-chip structure is more suitable for flexible products because the structure has fewer layers compared to the add-on type.
In this case, the eight layers from top to bottom are: cover window, decorative film, OCA/OCR, polarizer, TSP thin film packaging, thin film packaging, OLED light emitting layer and plastic substrate backplane.
Y-OCTA structure is applied to the latest flexible OLED panel used in Samsung Galaxy Note 7 Edge. "Y" stands for "Youm", which is what Samsung calls flexible AMOLED technology. Samsung Display has a firm foothold in the smartphone market through its OCTA technology and hopes to maintain a leading position in the flexible OLED market, which is why it uses the flexible touch solution of the Galaxy S6 and its successor models.
Samsung Display may have chosen on-cell touch as the transition technology to Y-OCTA. However, the company seems to have considered the development trend of component suppliers and new panel manufacturers, which is more likely to become the decisive reason for selection. In addition, the on-cell structure can be as innovative as Y-OCTA, especially if the manufacturer can reduce the number of polarizers and touch layers.
