Written by Woo-keun Lee, senior researcher at LG Economic Research Institute
Popularity of smartphones and tablet gadgets enabled the arrival of the post PC era, where displays have surpassed its initial role to transfer image, but now with added computer function. The lines categorizing between TV, monitor, notebook and cell phones are now being blurred, and the arrival of new display apparatuses like Google glasses and smart watches is imminent. Not only are consumers becoming accustomed to the functions or technology of the display itself, but they are now also growing more accustomed to user-friendly interface. Having said this, one question remains: What is the next step in display that will truly meet the growing standards and demands of consumers of today? No matter how great the concept or idea may be, without the proper materials, realization into an actual product is an impossibility.
Innovative Materials for More Realistic Image
A realistic image of mesmerizing sunset cascading over an emerald lucent beach can make us feel like we are actually at the spot to experience this beauty of nature. Displays surpass the limitations of time and space to provide a vivid landscape of information. The most fundamental function for displays is to be able to pass on sharp and lifelike images. In order to convey the diverse representation of the world as is, display technology has been advancing accordingly as well. The key to this technology relies on the materials.
In order to deliver more realistic image, the most vigorous research is being done for the materials of OLED. OLED technology has already been popularized in mobile use, and recently LG and Samsung have begun mass production of OLED TV as they are in the process of expanding in the large display market. OLED technology can display excellent definition characteristics, in terms of color saturation, range image, viewing angle, and etc., compared to LCDs. While current LCDs use liquid crystal materials, various films, and backlighting, OLEDs produce their own light while also controlling the amount on its own. As a result, OLED materials have a large impact on the performance of display products. As the importance of materials grows, the level of difficulty to synthesize has also increased, along with the process of tasks. OLED material companies are also digging deep to discover new materials for enhancement in longevity, effectiveness and color saturation.
As OLEDs are gaining attention, QD (Quantum Dot)1 which can convey color vividness in the level of OLED when applied to LCDs, is also garnering interest. 3M and Nanosys' QDEF (Quantum Dot Enhancement Film) won a grand prize at the 'Society for Information Display' held in Canada last May. 3M plans to mass produce QDEF in beginning of the second quarter next year. This film consists of a blue LED light which changes between red and green depending on the particle size, and it can materialize the three primary colors of the RGB2 color scale including the original blue LED light. Like OLED, QD material can be utilized as spontaneous emission material and is also called QLED or QDLED. Organic matter needs to be changed if initial OLEDs need to change color – but QLEDs, which use QD, only require a change in the size of QD which is much simpler structure to make a luminous body. But since the size of the particle is in nanometer and color fluctuates according to the size, it requires that much more tedious work put in. In addition, most materials use metal cadmium as a base, so development of materials that do not use cadmium as a material is also in the works.
1 Quantum Dot: Fine semiconductor components, not seen in traditional physics, as quantum confinement effect is called Quantum Dot. Although quantum dot is made up of the same materials, depending on the size of the dot, the optical absorption wavelength changes like the colors of a rainbow. As the size of the particle decreases, the light emitted are from the short wave group blue waves, the size can be adjusted and can emit light from a wavelength of choice. Vigorous, non-stop research is being done and being applied in areas of optical devices, photoelectric transformation elements, bio-imaging, and other various fields. Nanosys, Nanoco, QD Vison are among few companies that are active in R&D.
2 RGB, also known as Red, green and blue are the light's 3 primary colors. Among these colors, blue is the most difficult to produce. Blue needs a lower wavelength and higher energy difference, and requires a much more complex research. For these reasons, a deeper color of blue, 'Deep Blue' is usually the main task for any material companies.
Fluorescent and Phosphorescent Materials
OLED, Organic Light Emitting Diode is also called Organic EL (Electroluminescence) in short. EL refers to the device that exhibits light using electric energy and falls into two methods: fluorescence and phosphorescence. While fluorescence method has 25% effect, phosphorescence can attain up to 100% making it more ideal in material development. However, partial phosphorescence methods have patent issues while also having a high level of difficulty in material synthesis, limiting its commercialization. Until recently, OLED materials mostly applied fluorescent methods and partial phosphorescent materials. UDC (Universal Display Corporation), is a representative company in the US researching phosphorescent material innovation.
Materials for Clearness and Flexibility
Clear and flexible displays have been introduced many times at home electronic exhibition shows recently. Existing LCDs have the ability to be used as clear displays. LCDs are nonluminous displays and require backlight, but in order to create a clear display, exterior lights must be used instead of a backlight. Surrounding exterior light's intensity is darker than the backlight being used, making the screen darker overall. It is not easy to produce a clear display from the existing LCDs, and making displays flexible from LCDs is even more difficult. The cell gap of LCDs needs to be fixed at certain measure to maintain panel movement characteristics or color.
But on the other hand, OLEDs do not have these restrictions making it more competitive than LCDs in this area. Recently, LG and Samsung respectively begun mass producing curve type OLED TVs, and plan to release mobile devices using plastic boards in the second half of the year.
In order for displays to be clear and flexible, not only do they need luminescent materials but also components making up the display need to be both clear and flexible.
Up until now, Indum Tin Oxide(ITO) has been on the center for transparent electrode materials. But ITO is not suitable for flexible display, thus requiring new innovation for transparent electrodes fast. Many companies are working hard for the commercialization of next-generation translucent electrodes such as carbon nano tubes, grapheme, silver nano wires, transparent conductive oxide materials, high molecular electronic conductors and hybrid transparent electrodes. Among these, grapheme and carbon nano tubes consist of a chemical structure with the carbon atom combined in the same plane in a honey comb shape, making it stronger than a diamond, not easily bendable, more transparent and as a better conductor of electricity, making it a better contender than other existing materials.
The quality of 'sponginess' needed for the future of displays is also another characteristic that cannot be done with hard silicone material. To achieve this, soft nano materials which combine the flexibility of organic materials and high ability of silicones are also being researched. This technology has the potential to be broadened to other human friendly electronic devices such as electric contact lenses, self-diagnostic biochips, freely changing mobiles, electronic skin, electronic paper, etc. Among these, molecular electronics, that uses the concept of self-assembly molecules which are the main elements of electronic devices, masses small particles in sizes much smaller than the typical nanometer by using a Bottom-up approach, making it possible to produce a highly integrated, but low cost electronic device. As a result, there is potential to replace and supplement current silicone semiconductor devices, so world renowned universities and research facilities are in the process of vigorous research. As material innovation is making the future of displays a reality, smart phones and tablets will be combined into one by folding 10 inch tablets horizontally and vertically once, making it 5 inches folded. This will be great news for consumers who carry around both their smart phones and tablets, or for those who choose to carry a tablet instead of both due to the inconvenience.
Environmentally Friendly and Cost Efficient Material for Display
While enriching our lives by surrounding ourselves with these great displays is our main goal, reducing the environmental footprint and the cost of displays must also be our absolute priority. This cost would not only pertain to the manufacturing process but also the maintenance of the display material.
Since vacuum and high temperature thermal processing has been used for the traditional LCDs, Printed Electronics technology was required in order to lower the cost. Printed Electronics refers to the process that uses either conductive or functional ink pressed on a circuit board to produce electronic displays, parts and/or modules. By simplifying the traditional multi-step manufacturing process, Printed Electronics technology not only reduces the risk of product defects, but also minimizes the production cost for the manufacturer as the need for high cost vacuum and high temperature equipment would be eliminated. These changes make lower cost options possible to replace expensive traditional materials needed for high temperature to inexpensive materials in manufacturing, reducing the retail price for consumers as well. The technology also serves to reduce the wastewater created as a byproduct from the manufacturing process, and this is possible with a large part of the previously mentioned materials used to add flexibility to the products. Also, there is soluble OLED material. Along with the application of real display technology or transparent flexible technology, OLED can be an inexpensive option for display if soluble material technology is applied to its making process. Many material manufacturers in pursuit of this vacuum disposition method are also currently dedicating their research on soluble OLED materials. After its acquisition of the CDT (Cambridge Display Technology), Sumitomo Chemical is currently working on developing high polymerized soluble OLED while Panasonic presented its 56" 4K OLED TV at the 2013 CES on the same technological basis. As the manufacturer of liquid crystal which is the primary material for LCD, Merck is working on developing a soluble OLED material based on the existing low polymerized material, in collaboration with Epson known for its inkjet printing technology. This may serve as a critical factor in competing with the relatively low cost LCD market for the OLED industry.
Another factor to consider is that although display is an electronic technology, suspending the existing electric energy would lower the cost for the consumers without the added electronic costs. Researches on piezoelectricity that converts external pressure and vibration to electric energy and on solar based electrochromic, are also currently in process. Even in the absence of a perfect supplier of electricity, a hybrid form of the supplier would still serve greatly to reduce electricity use.
Creating the "Wow Effect" through Material Innovation
As explored previously, vivid displays, transparent and flexible screens, cost and power efficient technology, and hologram technology all can only be realized with strong material technological basis. Perhaps consumers now expect future displays that surpass micro and nano materials to quantum material, requiring transformation of technology paradigm by switching from classical mechanics to quantum mechanics. And regardless of the innovativeness of new technology, cost-effectiveness will still remain as the selling factor for any new product. The Wow Effect can only be manifested through a groundbreaking change that meets all of the criteria.
While the types of display material have the potential to diversify in the future, the different materials that would go into one single display needs to be simplified and OLED is one such example. While LCD requires a screen, color filter and a backlight, OLED only requires the OLED emitting display board. For this reason, extensive OLED research is being carried out in not only display enterprises but also at major petrochemical companies such as BASF, Sumitomo Chemical and Idemitsu Kosan.
As discussed, innovation in display technology material will continue to further blur the lines between different markets in the future.
*Note: The contents of this report are solely the responsibility of the authors and do not necessarily represent the official views of LG Display.
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