Localization of the core materials of foldable phones that Japan blocked exports

New materials have been localized to solve the wrinkles of foldable displays. In 2019, it is a fluorine-based polyimide film, one of the three semiconductor and display materials that Japan regulated exports to Korea.

The Korea Institute of Industrial Technology (Director Lee Nak-kyu) announced on the 10th that Dr. Sung-Woo Hong, a research team at the research section of eco-friendly convergence materials, has developed a high-intensity transparent flexible optical film with reliability of flexion while maintaining the light characteristics of existing glass-based materials.

When the display is folded, the compression force inside the inside and the tensile force on the outside can result in repeatedly folding the display, and the surface can be broken or cracked, and the wrinkles can occur.

The polyimide optical film used for foldable displays form a unique structure called a charge-dong-dong complex (CTC), and has good mechanical properties. The resilience is good, shocked, and can be made in a thin film through the continuous unveiling process. That’s why you can create a light and flexible display.

On the other hand, due to the structural characteristics of the CTC that easily absorbs the light of the lower wavelength, there is a disadvantage of the film yellow. The optical characteristics and mechanical properties of the polyimide film show the ‘trade-off’ phenomenon that is inversely proportional to each other.

Dr. Sung-Woo Hong succeeded in developing fluorine-based polyimide films that use both optical and mechanical characteristics. Introducing a bulky fluoride with a bulky carbonization in the polyimide, the CTC has reduced the distance between the polyimide chains, which is strongly combined, to ensure the light characteristics.

In addition, in order to solve the problem of decreasing mechanical physical properties in proportion to controlling physical distances, the polyimide chain between hydrogen binding and metal ion binding is increased. This amplified the interaction of the CTC to overcome the trade-off phenomenon.

The polyimide film developed by the researchers showed more than 8 ㎬ of elasticity, 90%of the total transmittance, and less than 3 yellow index. Even if you folded more than 200,000 times, there was no break, cracking, and wrinkles.

Dr. Hong Sung-woo said, We have noticed the fluorine polyimide in that it is a key material for the development of next-generation displays and urgent materials for localization. I will focus on the development of materials.

This study was published in the International Materials, an international journal of materials.


An analysis asking “Is it meaningful for 8K resolution?” The best thing for human eye specifications is

The resolution when video games are drawn on the screen has continued to improve as hardware advances. High-definition images have been demanded, and in recent years, 4K-compatible equipment has also become widespread, and equipment that steps into 8K areas with high resolution has appeared. Overseas media Ars Technica has composed analysis that responds to the question, “How much benefits are high resolution?”

What is resolution

The resolution shows the fineness of the screen display. For example, monitors with a resolution of 1920 x 1080 are generally popular for PCs. This figure indicates how much pixels (pixels) the screen are composed. In other words, the monitor with a resolution of 1920 × 1080 represents the screen with 1920 pieces side by side and 1080 vertically. The higher the resolution and density, the higher the screen looks. On the other hand, if you approach low resolution or large displays, you will see pixels independently. This is because each pixel is larger depending on the display area, and the gap between pixels becomes wider. When this independence is recognized, humans feel that the displayed video is rough. The roughness that you feel when you play low-resolution videos is also due to the enlarged and displayed pixels.

In recent years, resolution has been improved. The number of monitors and TVs that support resolutions 4K (3840 x 2160) are also popular, and the number of equipment that can output 4K resolution on home game consoles and PC side is increasing. In addition, 8K (7680 x 4320, etc.) compatible displays that enable high-resolution drawing are also available, and high-definition images are pursued. PlayStation 5 plans to support 8K resolution in the future, and NVIDIA, which is familiar with gamers GPUs, has also appealed to 8K HDR resolution. However, what is worrisome here is, “How much high resolution is needed for human eyes?”

Is 8k necessary

In conclusion, “8K is basically not necessary.” According to the analysis of, an overseas home appliance review site, it seems that 8K resolution contributes to “good image quality”. As an example, when viewing a 35V TV at a distance of 0.6 meters, there is a benefit of 4K or more. In other words, if there is a 4K and 8K display in a 35V size, comparing it from the distance of 0.6 meters, it can be understood for some people.

However, the 35V type is about 77cm in width and 43cm in height. It is no longer the dimension of the top plate of a small desk. When I thought a paper bag of the size that was close to the actual size as a display, I simulated a 0.6-meter view distance, and it was likely that I had to swing my head quite a bit. If you work or games in this environment, you will surely break your neck or eyes. On the other hand, when viewing a little away from a distance of 1.2 meters, a 65V or higher display is required to recognize the difference between 4K and 8K. In the 65V type, the width of the display portion is 143 cm and the height is 80cm. In apartments and apartment housing, it is a size that seems to be too much.

It is important to note that depending on the size of the display, the appropriate viewing distance changes. Watching a large screen at a short distance is not a comfortable environment for humans. The American Movie Television Engineers Association states that the appropriate viewing distance is that the display accounts for at least 30 degrees in the horizontal viewing angle. Also, when seeking an experience like a movie theater, it seems that about 40 degrees is a guide. According to this standard, the appropriate viewing distance of the 65V display is 1.8 meters to 2.4 meters. The layout that can be relaxed by keeping this viewing distance will be limited to the living room. As an example, when measured in my own room environment, the distance of 1.8 meters from the monitor was in a closet. In any case, there is a great deal of concern that the 8K display will be over-spec in a general living environment in Japan.

In addition, when viewing a 65V display at a viewing distance of 1.8 meters to 2.4 meters, 8K resolution is not usually required. In the case of a person with a visual acuity of 1.0, the difference of less than one-minute (1 minute) at a viewing angle cannot be determined. In other words, if you calculate roughly, a display that fills 30 degrees in the horizontal view angle will not be able to determine more details in the first place if the horizontal resolution is 1800. Therefore, the display is 4K (3840 x 2160) resolution, and it is more than enough for many people. If you have more than 1.0 eyesight or want to approach the monitor and watch it, the situation will change, but they are rare cases.

4K benefits are susceptible

On the other hand, if you switch from a monitor with 1080p (1920 x 1080) to 4K, you can feel the difference. For example, in a general 24V monitor, it seems that 4K resolution can benefit from around 0.9 meters of viewing distance with a visual acuity of 1.0. Isn’t this viewing environment applied to many people? To summarize a series of analysis, the 4K is enough resolution that matches the “spec” of the human eye. The benefits of 8K will be demonstrated in limited cases, such as those who have good visual acuity with large monitoring.

Nevertheless, there are fields that benefit from 8K and even higher resolution. VR device. In VR, there is a display at a close range of the eyes, so that the human vision is widened. Unlike the normal display you see away, you need high resolution and pixel density. High resolution technology will be more and more expensive in such areas. After that, I would like to hope that 4K gaming monitors will be a little easier to seek.