superC Touch -- [ 2023.09.20] Micro-compartment: SuperC-Touch new structure patented full-color electronic paper innovative technology
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[ 2023.09.20] Micro-compartment: SuperC-Touch new structure patented full-color electronic paper innovative technology

Micro-compartment: SuperC-Touch new structure patented full-color electronic paper innovative technology
2023/09/20 09:07:01
Economic Daily Weng Yongquan
Microcapsules and microcups are the main technologies for producing electronic ink films, which require a high degree of craftsmanship. The weak structure of the film is a major factor in production difficulties and low yield. Just imagine, removing 70% of the volume of a thin plastic film that is only half the diameter of a human hair and filling it with liquid electronic ink is more fragile and fragile than household cling film. Production and processing require technological capabilities.

SuperC-Touch recommends that the microcup structure be made directly on the Array substrate or color filter substrate using the mature process of the panel. The hardness of the material used is higher than 3H and is very strong, which can omit the most difficult electronic ink film production process. Samsung proposed this concept as early as 2006 and applied for a patent (US7,715,089), and EINK also applied for a related patent (TW I774223) in 2021. SuperC-Touch is further enhanced and the patent is named "Micro Partition", which is like making a tiny partition wall on a glass substrate.
The biggest advantages of making micro-partitions on glass substrates are easy production, high yield, strong structure and hardness greater than 3H, low cost, and can be perfectly aligned with pixel electrodes. Micro-walls as compartments can be designed between pixels to block the movement of electronic ink in the compartment across pixels.
Traditional microcapsules and microcups cannot be aligned with pixels. As shown in the picture above, the left side is the shape of the microcup, the middle is the size of the pixel electrode and the shape of the microcup taken at the same microscopic magnification, and the right side is the merged image. It is convenient to see the relative position of the two. There will be some microcups that span two pixels. When the voltage polarity of the two pixels is opposite, the movement direction of the charged color particles inside will cross the pixels, causing color distortion.

This problem is especially serious in color display. In the area circled in red in the picture below, the microcup wall in the picture falls within the pixel area, which is a dead zone where the image cannot be displayed, and will further cause color distortion and reduced reflectivity.


In the color electronic paper using the color filter solution (as shown in the picture above), the filter and the electronic ink are separated by a layer of protective film (transparent plastic substrate in the picture) and optical glue (the total thickness is H). This thickness will cause some When light is reflected, it is absorbed across different colors, reducing reflectivity. You can imagine it like this: the light reflected by the filter color blocks in some areas is absorbed by other filter color blocks and becomes ineffective. The thicker the thickness H, the larger the ineffective area of ​​the filter color block, and the smaller the area that can reflect light, so the reflectivity becomes worse.

In addition, the thickness of the electronic ink film is difficult to make very thin due to limitations of the manufacturing process. The thicker the electronic ink film, the farther the color particles in the ink need to move. The farther the distance, the smaller the charge thrust from the control electrode below, and the slower the movement speed. Therefore, the screen refresh rate will naturally deteriorate. . The color particle distribution near the upper common electrode surface will also be relatively dispersed, reducing the light reflectivity (the blue circled part in the above picture).
The picture above illustrates an example of a solution using the panel manufacturing process. The microcup can be made on Color filter glass, sprayed with electronic ink, and then attached to Array glass. The key factor is the height of the microcup wall. The higher the height. The more difficult it is to implement, conversely, the lower the height, the easier it is to implement. SuperC-Touch recommends that the wall height be set to 10um.
[Production method] After the color filter glass has completed the gap layer process after 3 layers of filter color blocks (please refer to the illustration below), do three consecutive photoresist coating and exposures (repeat the procedures 4&5 3 times). The thickness of each photoresist coating is 3.5um. Finally, the middle groove is developed and washed out to complete the microcup groove with a depth of 10.5um. Two new photoresist coating and exposure steps are added. It is estimated that the production cost of the color filter glass will not increase by more than 25%.


[Supporting Measures] When the volume containing the electronic ink is reduced, without affecting the reflectivity, double the concentration of the electronic ink to maintain a constant number of reflective particles in the volume.
It is estimated that the cost of electronic paper using this panel process solution will be much lower than the process of laminating the electronic ink film to the control substrate. By then, panel manufacturers will have the opportunity to fully penetrate the color e-paper market and be quite competitive (home field advantage). This panel factory can also activate and decommission old equipment (such as a-Si 5th generation line). As long as the device that sprays liquid crystal is adjusted to be able to spray electronic ink, mass production preparations can be completed. It not only revitalizes old equipment, but also allows mass production of high-margin color electronic paper without investing too much capital, which is a huge benefit for panel manufacturers.
After all, the cost of buying electronic ink is very different from buying electronic ink film, not to mention that the patents for black and white ink will expire or have expired (EINK US7002728 2004/2/9 application), or there may be New participants join. For example, BOE applied for a patent for producing new electronic ink in 2015 (WO2015/090025) and Guangzhou OEDI tech. The rapid growth of the color electronic paper market will attract more manufacturers to invest in the production of black and white electronic ink.
Let’s further discuss the difference in display quality between these two solutions. First of all, the panel factory can make a new solution. The microcup walls can be designed in alignment so that they will not cross the pixel electrodes, and the charged color particles will not move and diffuse across different pixels. This greatly helps with color accuracy and contrast. Secondly, a shorter microcup wall (for example, 10um) can shorten the moving distance of color particles, speed up the picture update, increase the stacking density of reflective particles, and increase the light reflectivity; furthermore, the color filter layer can be tightly Attaching reflective particles (equivalent to a thickness H close to 0, and the effective reflective area of ​​the filter color block is 100) further improves the light reflection efficiency and greatly helps increase color saturation and brightness. Offers many advantages over existing solutions.
The above solution is just a further evolution of the microcup structure. The higher concentration of electronic ink is clustered together due to the mutual attraction of charged particles. The driving principle is still limited by the EINK patent. The next article will introduce how to break through the patent limitations of EINK in the driving method and solve the problem of particle agglomeration.