The advantages of printing and display technology

The starting gun of printing and display industrialization is officially fired. Recently, reporters from the "printing display industrialization and industry chain technology seminar" to understand, printing display technology, materials, equipment and other key elements have gradually mature, our country printing display industrialization order

The starting gun of printing and display industrialization is officially fired. Recently, reporters understood from the "printing display industrialization and industry chain technology seminar", printing display technology, materials, equipment and other key elements have gradually mature, our country printing display industrialization prologue is about to open. TCL Huaxing displayed new printed OLED technologies ranging from 17 inches to 65 inches at the conference site, with various performance advantages over the current mainstream OLED technology. TCL has developed a 274PPI printing display technology that can be used in IT products such as notebooks and tablets. In the future, printed OLED technology has the opportunity to be applied to TV, Monitor, Notebook, Tablet and other products, flexibly realizing production capacity turnover.

So what is the advantage and charm of print display, so that many of the world's leading display panel companies set up their trial and research production lines to study it? Today we will take a closer look at its characteristics.

The printing display has a simple preparation process and can be applied to various sizes of products

At present, the mainstream technology of small and medium-sized OLED is FMM-OLED technology, which is adopted by Chinese OLED panel enterprises. For domestic companies, there are mainly problems such as foreign patent monopoly, high cost and difficult to break through large size. From a technical point of view, FMM-OLED adopts vacuum evaporation method, which is mainly to heat and sublimate organic materials, and form organic film layers of red, green and blue OLED devices by using high-precision metal mask plates. High precision metal mask plates need to use materials with very low thermal deformation coefficient to make, the size of the holes in the micron level, the positioning accuracy requirements are very high, so the cost is high. At the same time, the effect of gravity will also lead to the deformation of high-precision metal mask plate. Any small deformation will have a significant impact on the alignment and evaporation area, and the larger the size, the more serious the deformation problem, so the application of large generation line is extremely difficult.

In contrast to the vacuum evaporation of HFM-OLED, JPP-OLED uses inkjet printing technology to configure organic materials into a solution, and then prints them in a pixel pit on a pre-prepared substrate through a high-precision nozzle that precisely controls the volume of the droplet (skin level, 10-12L) and the location of the inkjet. After vacuum drying, the organic film layer formed by OLED device eventually forms red, green and blue luminous units. OLED technology, printing process is very simple, can be like a "print" to print the screen, don't require expensive vacuum evaporation process at the same time, also need not be expensive and high precision metal mask board, can be applied to all kinds of size range of products (TV/Monitor/Notebook/Tablet).

picture

Printing display product structure is simple, cost competitive advantage is obvious

In terms of large-size products, the world's mainstream OLED technologies are mainly WOLED and QD-OLED. Both WOLED and QD-OLED have very complex device structure and luminous structure. WOLED and QD-OLED also adopt vacuum evaporation method, and use metal mask plate patterning. WOLED is an organic film layer formed on the glass substrate of the whole white OLED device, and then through the patterned anode and color filter to form white, red, green and blue luminous units, in which the white OLED device requires about 18-20 layers of evaporation. The difference between QD-OLED and WOLED is that the organic film layer formed on the lower glass as a whole multilayer OLED device emits blue light, and then on the upper glass substrate, patterned quantum dot light-color conversion layer and whole-surface packaging layer are printed. Finally, patterned color filters are combined to form red, green and blue luminous units. The stacked devices require about 22-24 layers of evaporation.

picture

In contrast, printed OLED only needs to form 5-6 layers of organic film through inkjet printing to form red, green and blue luminous units. The device structure and luminous structure are very simple, and the material utilization rate is as high as 90%, and there is no need for complex technological process and vacuum evaporation equipment. As a result, printed OLED production is expected to be cheaper than both WOLED and QD-OLED in large and medium-size display applications. For example, when producing 65-inch TVS on 10 generation lines, printed OLeds are estimated to reduce BOM costs by 10-20% compared to WOLED and QD-OLED. Meanwhile, the competitiveness of printed OLED extends to the small and medium size display market, where it can reduce BOM costs by about 10 percent compared to the FMM OLED process used in the production of 13.3-inch panels on the 6gen line. In addition, compared with WOLED, QD-OLED, and FMM-OLED, IJP also has lower initial investment costs in equipment and plant construction, and lower operating costs during production.

Printed display opening rate is higher, the product is expected to achieve longer life

The opening rate is the ratio of the effective luminous area of a pixel to the overall area of the pixel. For OLED display, the higher the opening rate, the smaller the current density corresponding to the luminous work of pixel OLED device under the condition of the same brightness display, the slower the device attenuation, and the longer the product life. Therefore, OLED display needs to maximize the luminous area and improve the pixel opening rate.

FMM-OLED requires the use of a high-precision metal mask plate to define the luminous region of the pixel. The high-precision metal mask plate is perforated in the position corresponding to the pixel luminous area on the whole metal plate. When the EL material is steamed, the EL material can be steamed in the OLED luminous area through the perforated area. Instead of the metal in the perforated area, it acts as a support. As mentioned above, high-precision metal mask plate has a very high requirement on shape variables, and the metal in the non-perforated area has a certain width requirement. If the width of the non-perforated area is too small, the strength will be affected, and the deformation will be caused, thus affecting the pattern process. Therefore, with the continuous increase of product pixel density, the total pixel size is gradually reduced, while the area of non-open hole area cannot be reduced, only the area of open hole area can be reduced. Therefore, the smaller the opening proportion of high-precision metal mask plate, the lower the opening rate of pixel.

picture

Printed OLED has no mask plate restriction and can achieve higher opening rate. Therefore, for OLED products with higher pixel density, printed OLED technology can achieve a higher pixel opening rate, and the higher the pixel density, the more obvious the advantage of pixel opening rate. As mentioned above, the higher the opening rate, the smaller the current density corresponding to the luminous work of pixel OLED devices under the condition of the same brightness display, the slower the device attenuation, and the products produced are expected to achieve a longer life.

picture

Printing shows obvious advantages of PPI, and the terminal products show clear visual effect

With TVS, computers, laptops and tablets all striving for higher resolution, we've gone from HD to 4K and even 8K ultra HD in a flash. According to the survey, the screen performance and performance of the monitor are closely related to the productivity and user experience. As a result, display technologies have been upgrading their specifications over the past few years to increase screen size and improve resolution, and high resolution has become a mainstream trend for larger and larger products.

picture

It is understood that both WOLED technology and QD-OLED technology are currently being studied in terms of improving resolution. However, it is difficult to achieve high PPI because WOLED needs white, red, green and blue child pixels. However, QD-OLED has the problem of "color crosstalk". Taking the display of pure blue screen as an example, when PPI is too high, the blue OLED at the bottom will glow around, which results in the red and green pixels that should not be displayed will glow due to the excitation of the blue light at the bottom. Therefore, it is difficult to improve PPI.

picture

In contrast, printed OLED has the most advantages in achieving high PPI among the three technologies due to its simple structure. According to the latest research and development achievements of TCL Huaxing and JOLED on printing display technology, the PPI of 21.6 inch printed OLED products on sale has reached 204, and has completed the successful verification of 274PPI printing without color mixing and visual mura, and the printing technology of more than 300PPI is also under development and verification. After all, the mainstream 65-inch 8K TV has a PPI of only 136, so the resolution of 274PPI is already higher than 8K, and the high resolution of 274PPI also makes it possible for printed displays to cope with small and medium-sized products.

Compared with the traditional vacuum evaporation process, the printing display process is simple, does not require expensive vacuum evaporation machine and high precision metal mask plate, and the material utilization rate can reach more than 90%. It not only has obvious cost advantages, but also can achieve high PPI and longer life. Therefore, printed OLED technology is considered as an important technical way to break through the evaporation route in the field of full-size products.