Invented by JEON; Seo Jeong, LEE; Changmin, LEE; Yeon Soo, BAE; Jun, KIM; Jun Ki, SEO; Hanwook, MUN; Soung Yun, KIM; Kyung Soo, DUK SAN NEOLUX CO., LTD.

Pixel defining layers are a key part of display screens like OLED TVs, smartphones, and tablets. They help make pictures clear, sharp, and colorful. A new patent application is offering a fresh way to make these layers, helping displays last longer and look better. In this article, we’ll explain why this technology matters, the science behind it, and exactly what’s new about this invention.

Background and Market Context

Displays are everywhere. You see them on your phones, TVs, watches, and even in your cars. People want screens that are brighter, last longer, and use less power. Companies making screens are always looking for new ways to improve their products and stand out from the crowd.

One of the most important parts of a display is the pixel defining layer. This layer helps control which parts of the screen light up and what colors you see. In OLED displays, each pixel makes its own light. The pixel defining layer stops colors from mixing and keeps the picture sharp. If this layer doesn’t work well, you might see blurry images, faded colors, or even black spots where pixels have died.

But making good pixel layers is hard. The process needs to be fast, cheap, and safe for the delicate materials inside the screen. The layer also needs to be strong, stick well to other parts, and not let out any nasty chemicals that could damage the screen or hurt the people making them. A big problem in older methods is something called “outgas.” These are tiny bits of chemicals that escape from the layer after it’s made. Too much outgas can cause pixels to shrink, make the screen less bright, or even cause the display to stop working.

Most companies use several steps to make these layers, including adding colors, baking, shining light on the layer, and heating. Each step can make the process longer and more expensive. More steps also mean more chances for something to go wrong. A method that can make the layer in fewer steps, with less outgas, and with bright, clear colors would be a big win for the industry. That’s where this new patent comes in.

With the rise of flexible screens, such as those that bend or fold, the need for better pixel layers has grown. Old ways of blocking light and keeping colors clean, such as using polarizing films, don’t work well on screens that bend. The new method can help make flexible screens more reliable and colorful, opening the door for more exciting gadgets in the future.

Scientific Rationale and Prior Art

To understand the new invention, let’s look at how pixel defining layers are made now and why there are problems. In current displays, the pixel layer is made using a process called photolithography. This means putting a thin film on the screen, shining light through a pattern (called a mask), and then washing away parts not needed. This creates lines and shapes that keep pixels apart.

To make the colors, companies mix in special dyes or pigments. These can be red, green, blue, or black. The colors need to be bright and pure, but they also need to stick well to the screen and not bleed into each other. In older methods, the colored layer can sometimes release outgas — small molecules that escape and cause trouble. Too much outgas can cause “dark spots,” where a pixel dies, or make the screen fade over time. Outgas can also make the screen less reliable and shorten its life.

Other ways to block stray light — such as using an extra layer called a polarizer — can help. But polarizers don’t bend well, so they aren’t good for flexible screens. Some companies have tried using an inorganic film or a color filter instead, but these don’t always give the sharpness or bright colors people want. They also can’t replace the polarizer entirely.

Another problem is that older methods use many steps, and sometimes the layer needs to be heated several times. Each time you heat the screen, you risk damaging delicate parts or causing the colors to fade. More steps also mean more cost and more chances for things to go wrong, like the layer peeling off or getting bubbles.

Past inventions have tried to solve these problems by changing the way the layer is made, or by using different chemicals. Some added special resins to make the layer tougher. Others played with the way the light is shined on the layer, using different kinds of masks to get sharper lines. But so far, no one has found a way to make a pixel defining layer that is easy to make, gives bright colors, produces very low outgas, and works well even on flexible screens.

The big challenge is finding a process that removes as much outgas as possible before the screen is finished, but does not damage the screen. If you heat the layer too much, you might burn it or cause it to peel off. If you don’t heat it enough, you leave behind chemicals that will leak out later. Getting just the right amount of heat, at the right time, is a very tricky job.

Another issue is making the colored pattern in just one go, rather than building it up in several layers. If you can do it all at once, the process gets faster and cheaper, and there’s less risk of something going wrong. But making different thicknesses in one exposure is hard, because the light must be very carefully controlled.

This is where the new invention makes a difference. The inventors have found a way to use a special mask that lets through three levels of light (none, some, and full), so you can make different thicknesses in the layer in just one go. They also found the best heat and timing steps to get rid of outgas without damaging the layer. This is a big step up from what has been done before, and it can help make displays that are brighter, last longer, and work better, especially for flexible screens.

Invention Description and Key Innovations

The heart of this new patent is a smart way to build the pixel defining layer using fewer steps, better materials, and clever control over the heating and light exposure. Let’s break it down in simple words.

First, the layer is made by coating a liquid photosensitive mix onto the display surface. This mix contains colorants — the stuff that gives you red, green, blue, or black — and special resins that help the layer stick and stay strong. The mix is spread out smoothly using a machine called a spin coater (for small screens) or a slit coater (for large ones).

Next, the coated layer is gently heated (pre-baked) to remove some of the solvent and make sure it’s not too runny. This happens at around 80 to 150 degrees Celsius for about 1 to 3 minutes. If you skip this, the layer might not harden properly in the next step, or it might stick to the mask and ruin the pattern.

After the pre-bake, the layer is exposed to light through a mask. This mask is special: it has three levels of see-through-ness — totally dark (0%), half see-through (20% to 50%), and fully clear (100%). This lets you make different thicknesses in the layer in one go, which is great for making sharp, colorful patterns. The light used is strong but not too strong — between 20 and 350 units (mJ/cm²) — just enough to start the hardening process.

Then comes the development step. The layer is washed with a special liquid that removes the parts that weren’t exposed to light. In this invention, the parts exposed to the most light become the thickest (about 3.2 to 3.4 micrometers), and the parts exposed to half the light are thinner (about 1.3 to 1.95 micrometers). This “one process, multi-layer” trick saves time and makes sharper patterns.

After that, the layer is hit with more light (post-exposure) to make it even harder and tougher. This light is stronger — between 50 and 1000 units (mJ/cm²) — and makes sure the layer won’t fall apart during the next heating step.

The final big step is post-heat treatment. Here’s where the outgas problem is solved. The layer is heated in an oven at a temperature between 210 and 300 degrees Celsius, usually for 30 to 120 minutes. This high heat makes any leftover chemicals (fume) escape, so they won’t leak out later and damage the display. The inventors found that if you make at least 98 ppm of fume during this step, then after the heat treat, the layer will only release less than 40 ppm of outgas. This is low enough to stop pixel shrinkage or dark spots, making the screen last much longer.

The photosensitive mix is also special. It contains colorants in the right amount (1% to 40% by weight), along with resins that help the layer form a strong, flexible film. The resins can be acrylic types, cardo-based types, or a mix of both. The cardo-based resins are especially good at keeping the layer tough and sticking to the display, even at high heat. The mix also has a reactive compound to help the layer set quickly when hit by light, and a photoinitiator to start the reaction.

The patent also describes how the pigments are treated before use. They are mixed with dispersants and sometimes water-soluble salts, making them break up into tiny pieces (20 to 110 nanometers) so the color is bright and even.

All these steps and materials work together to make a pixel defining layer that is vivid, doesn’t shrink, and doesn’t leak chemicals after it’s made. The process is faster, cheaper, and safer, and it can be used on flexible displays as well as regular ones.

The inventors tested different heating times and temperatures to find the best results. If you don’t heat enough, outgas is too high and the screen might fail. If you heat too much, the layer can shrink or peel off. The sweet spot is between 210 and 300 degrees, for about 30 to 120 minutes. At these settings, almost all the bad stuff is burned off, and the layer stays strong.

Another key insight is the use of a single exposure step with a mask that gives three levels of light. This is much more efficient than older methods, where you had to do one layer at a time. Doing it all at once means fewer chances for mistakes, and the display can be made more quickly.

This method can be used to make any kind of coloring pattern — red, green, blue, or black — and can be used for OLED displays, LCDs, and other types. The final display is brighter, lasts longer, and doesn’t suffer from dark spots or fading.

Because the layer is so stable and clean, it’s also easier to make displays that bend or fold, since the layer won’t crack or peel when the screen is flexed.

In short, this invention combines:
– A smart mask for single-step, multi-thickness patterning,
– Careful control of heat to remove almost all outgas,
– Specially treated pigments and resins to keep colors bright and layers tough,
– And a process that works for both flat and flexible screens.

Conclusion

The new method for making pixel defining layers is a big step forward for the display industry. It solves old problems of outgas, slow production, and weak layers, while making screens brighter and longer lasting. The process is simple, safe, and easy to use for both regular and flexible displays. As more companies look to make better and more creative screens, this invention will likely become a key part of the next wave of display technology. If you care about having sharper, more colorful, and longer-lasting screens, keep an eye on this new way of building pixel defining layers.

Click here https://ppubs.uspto.gov/pubwebapp/ and search 20250221288.