Transparent Electrode Needs Development for Next Generation Display to Surge

Recently, with various research results regarding transparent electrode, interest in next generation transparent electrode is increasing.

 

In early December, UNIST (Ulsan National Institute of Science and Technology) developed printing technology that can arrange the Ag nanowire in the direction chosen on top of substrate. Ag nanowire is transparent electrode that can be applied to large area flexible touch panel and display products. This technology allows the surface to be flat through the fusion of nanotechnology to the existing printing process and increases transmittance.

 

Around the same time, ETRI (Electronics and Telecommunications Research Institute) developed technology that replaces thin metal electrode on top of OLED substrate with graphene transparent electrode. The metal electrode that were being used in OLED was mostly silver (Ag) material, but due to the reflection of internal light, the viewing angle changed depending on the angle. The external light also affected picture quality due to reflection. The newly developed technology used graphene that mostly does not reflect internal/external light as transparent electrode and improved transmittance and picture quality.

 

At present, ITO (indium tin oxide) is most widely used as transparent electrode materials. However, the supply is limited and flexible electronic device application is narrow. As such, the demand for the development of new materials that can replace this is greatly increasing. Particularly, as ITO is not suitable for stretchable device, the next generation transparent electrode development is considered to be a key issue for future display.

 

At 2016 Production/Process Technology Development and Application Cases by Flexible Transparent Electrode and Film Materials Seminar (December 17) held in Seoul, South Korea, Dr. Won Mok Kim of KIST (Korea Institute of Science and Technology) discussed, of many flexible transparent electrodes, TCO (transparent conductive oxide) production and process technology through presentation titled ‘TCO based flexible transparent electrode production and process technology development trend and applications’.

 

Of the transparent conductive materials, oxides have been researched the longest, and they are most widely used transparent conductive materials. Oxide including conductive materials have optical band gap of ≥3.0 eV and therefore has high transmittance and can be flexible. Kim revealed that TCO needs further improvement in conductivity and transmittance for display application.

 

Regarding transparent body, when refractive indexes of components are different, the path of light through the transparent body is refracted. When this occurs, the object becomes hazy although transparent. Haze is quantified and used to assess the transparent body’s performance. Kim explained that for solar cell the haze is purposefully increased to transmit more light to the internal active materials. However, if the display is clouded the clarity of image is reduced and therefore haze has to be lowered. To achieve this, Kim reported that the TCO’s surface roughness has to be reduced.

 

Kim revealed that there are two issues, temperature and flexibility, when TCO is used as transparent electrode. ITO’s conductivity is highest at 300 ℃, and for ZnO it is around 200 ℃. Channel cracks could occur with TCO when higher than bending strain is applied, and the crack could snap when it is bent further, destroying the device performance. Kim explained that to increase the bending strain, the thickness has to be reduced. However, when doing so as the sheet tension increases, the process has to be designed carefully considering the tradeoff.

 

Transparent electrode could be applied to display, solar cell, touch panel, and lighting among others and therefore requires much development. Although oxides have been long researched as transparent electrode materials, Kim concluded that even more diverse value can be created through fusion with next generation materials.

 

그림1

OLED and Graphene Together Achieves Innovative Technology

By Choong Hoon Yi

 

Korean research team is expected to greatly improve display’s transmittance and picture quality through fusing graphene technology, focus of much attention as the new material to OLED technology.

 

On December 15, ETRI (Electronics and Telecommunications Research Institute) replaced the thin metal electrode that was used as transparent electrode on top of the OLED substrate with graphene transparent electrode, and succeeded in developing original technology that is conductive and transparent.

 

This research results were presented in Scientific Reports, a journal from the publishers of Nature on December 2.

 

The metal electrode used in OLED until now has been mostly silver material, but due to the reflection of internal light, the viewing angle changed depending on the angle. The external light also affected picture quality due to reflection.

 

In order to solve this problem, ETRI research team focused on graphene that mostly does not reflect internal/external light. By replacing the material, the team reported that the transmittance increased by approximately 40% and reflectance improved by approximately 60%.

 

OLED was successfully lighted by attaching graphene transparent electrode to the organic layer on top of the film form (23 x 23 mm, 30 ㎛ thickness) of substrate. The research team believes this will be able to contribute much when applied to transparent OLED display and white OLED-based large area OLED display in future.

 

Particularly, unlike the existing vacuum process OLED production method, this technology can be employed via lamination where film is attached to the organic layer and graphene. Therefore, OLED can be produced through simpler process. It is expected that this can be evolved into production technology using roll to roll process.

 

Additionally, ETRI, together with Hanwha Techwin, is working on applying graphene transparent electrode to OLED’s lower electrode through collaboration of high quality graphene thin film electrode materials. The related technology development results were published online by The IEEE (Institute of Electrical and Electronics Engineers) of Selected Topics in Quantum Electronics.

 

ETRI’s Dr. Jeong-Ik Lee (soft I/O interface research section) anticipated that “this technology will be able to play a role in widening the gap with latecomer countries in OLED industry where challenging latecomers are strong”.

 

This research was carried out through Korea’s Ministry of Science, ICT and Future Planning and Institute for Information & Communications Technology Promotion (IITP)’s “Energy reducing environment adapting I/O platform technology development for future advertisement service” project and Ministry of Trade, Industry and Energy and Korea Evaluation Institute of Industrial Technology’s “Substrate size 5.5 generation or larger graphene film and OLED device/panel foundation and application technology development for graphene materials OLED transparent electrode and thin film encapsulation application”.

 

ETRI is planning to additionally develop sheet tension reducing technology by manufacturing metal in thin, grid forms and enlargement technology to produce mobile display size within 2016.

 

Through this technology, the research team produced 6 international patent applications and 6 papers. ETRI is intending to transfer the technology to graphene film and display panel companies among others. Commercialization is estimated to begin after 3 years.

1.Graphene transparent electrode applied lit OLED

1. Graphene transparent electrode applied lit OLED

 

2. OLED with existing thin metal electrode and graphene electrode OLED comparison (Left: Graphene, Right: Thin Metal, Ag)

2. OLED with existing thin metal electrode and graphene electrode OLED comparison (Left: Graphene, Right: Thin Metal, Ag)

 

3.Film including graphene transparent electrode applied to lamination process using OLED production

3. Comparison graph of existing thin metal electrode OLED and graphene electrode OLED

 

4.Film including graphene transparent electrode applied to lamination process using OLED production

4. Film including graphene transparent electrode applied to lamination process using OLED production

 

5.Graphene transparent electrode OLED Production Process

5. Graphene transparent electrode OLED Production Process

 

[Process Explanation]

After manufacturing laminated film, formed with bonding layer (BL) and PET film, using surface treated substrate, graphene transparent electrode is transferred on to the bonding layer. By laminating the laminated film that includes graphene transparent electrode on the substrate (lower electrode and organic layer), OLED where graphene transparent electrode is used as upper electrode is complete.

 

6.Graphene OLED of diverse colors

6. Graphene OLED of diverse colors

Now is the Time to Invest for OLED to be the Next Generation Display

By Hyun Jun Jang

 

이창희

 

 

On December 10, a seminar specializing company bizocean held ‘2016 Next Generation Display’s Latest Trend and Cutting Edge Industry Application Issues and Business Creation Seminar’ in Korea Technology Center. Professor Changhee Lee of Seoul National University, the first speaker of the seminar, announced that as OLED will become the technology for future display, now is the time for investment by the companies.

 

Lee reported that the display follows camera’s resolution, and although resolution has been developed up to UHD, he forecast that it will advance further. He also added that higher the resolution, the display performance that consumers demand will increase.

 

Regarding the current display market status, Lee explained that as the LCD’s margin is falling the market has to turn to OLED, but it is still expensive and capacity is low. Additionally, from the way consumers are still using the term liquid crystal regarding Samsung’s AMOLED smartphone, Lee speculated that people have difficulty in distinguishing between LCD and OLED. He told the audience that the industry should inform the public of the OLED’s differences from LCD through transparent, flexible displays that show OLED’s superior traits, and open the market through product differentiation strategy.

 

For the future display, Lee pointed out printing OLED. He explained that although printing OLED’s lifetime, particularly blue’s, falls short compared to vacuum evaporation, it is estimated to reach commercialization stage after 2-3 years. Despite the flaws in terms of materials, Lee reported that the advantages such as reduced production cost, fast tact time, and material usage efficiency will lead to the opening of the market. For these reasons, Samsung and LG are carrying out development.

 

Lee forecast that LCD, in its maturity stage of the industry life cycle, will lead the market for a while, but OLED technology will rapidly evolve and become the focus of the next generation display market. Regarding OLED TV, Lee mentioned that large area OLED mass production through printing technology is urgent in order to achieve price competitiveness. At present, OLED’s capacity is less than 1/100 of LCD. As such, even if there is demand, supply may not be able to meet it and Lee suggested the need for investment to the companies. He added that if there is low supply when the number of customers is high, the opening of the market could be delayed.

 

이창희2

Display Market Forecast Source: Professor Changhee Lee Presentation Material

 

Lee mentioned QLED as another future display technology. QLED has the same structure as OLED but uses quantum dot as the emitting materials, changing colors through different sizes. Lee reported that the color gamut is high as the wavelengths are shorter than OLED emitting materials. Also as the same material is used, QLED has an advantage of reduced material production cost and development of micro display with 2,000 ppi is complete. However, Lee added that as the lifetime is nowhere near sufficient, commercialization stage is still far away.

[2015 OLED Evaluation Seminar] Oxide TFT Technology that 2015 should Spotlight

By Hyun Jun Jang

 

During the 2015 OLED Evaluation Seminar (December 4) hosted by UBI Research, Professor Jin-Seong Park of Hanyang University gave a presentation titled OLED Oxide TFT Technology Trend, discussing oxide TFT, related industry, and technological issues as well as TFT technology that should receive the spotlight in 2016.

 

Oxide TFT has an advantage of high mobility and large area uniformity compared to a-Si TFT. As such, it is being more applied to large area OLED panel and used in LG Display’s OLED TV.

 

Park revealed that there are mainly 4 issues regarding oxide TFT and led with the reliability issue. Oxide TFT is essentially in amorphous state but when crystalized, the density and crystallizability increase; as oxygen does not move away and stay in place, defects occur less and reliability is high. Japan’s SEL and Sharp published CAAC (C-Axis Aligned Crystal) structure related oxide TFT paper, and Cornell University produced CAAC oxide TFT by increasing the substrate temperature and adjusting oxygen’s partial pressure.

 

The second issue is composition ratio. Park reported that composition ratio is the most closely related characteristic to TFT’s mobility. He revealed that recently research is being carried out centering around IGZO (indium gallium zinc oxide), but also oxide TFT research with different composition ratio is continually published. For example, ITZO (indium tin zinc oxide)’s mobility has been reported to reach 30cm/Vsec, and BOE is working on the related research. Research results, which showed increased mobility and reliability for IGZTO, which is IZTO with G added, was published, as well as ZnON (zinc oxide nitride) TFT’s 100cm/Vsec mobility. BOE demonstrated ZnO TFT applied 14.1inch AMOLED.

 

The third issue is the device structure. Park explained that efficiency can increase when top gate structure is used to oxide TFT as parasitic capacitor is not needed, but that the process is difficult. However, Park reported that JOLED revealed when self-alignment is used the number of masks used can be reduced and increases performance. This structure is applied to OLED TV by LG Display.

 

Lastly, Park gave the safety of device as the last issue. Oxide TFT can exhibit degradation effects from light, oxygen, hydrogen, and moisture. Park reported that hydrogen particularly has great effect on the safety. He explained that although the current prevailing OLED TFT is LTPS, as the panel becomes larger there will be technological competition between oxide and LTPS. Reporting that TFT which is cost efficient and shows high performance in diverse factors such as resolution will dominate the market, Park concluded his presentation.

 

 

 

박진성교수

[2015 OLED Evaluation Seminar] Professor Hong Mun-Pyo of Korea University Retraces Flexible OLED’s Key Issues

By Hyun Jun Jang

 

During the 2015 OLED Evaluation Seminar (December 4) hosted by UBI Research, Professor Hong Mun-Pyo of Korea University gave a talk titled Flexible AMOLED Gas Barrier Technology Development Status. Through this presentation, he discussed in detail flexible OLED’s outline, technological issues, and encapsulation among other key issues.

 

Flexible display signifies a display that was produced on top of flexible substrate, and not an existing glass substrate, which can bend, fold, or roll without breaking. Hong emphasized flexible display is the next generation display that can simultaneously satisfy consumers and panel makers, and an area that OLED can be more valuable compared to LCD.

 

There are 3 essential issues in flexible display, substrate, TFT array, and display processes, as well as ancillary issues such as application and cost. Hong reported key issues regarding substrate and display process.

 

Flexible display uses plastic substrate, instead of glass, that is strong against shock and can bend. Therefore, handling technology that manages plastic substrate is considered a key technology in flexible display production. Hong revealed that for handling technology, a film lamination method and vanish coating method are mainly used. A film lamination method is where plastic substrate is attached to carrier glass using adhesive before being processed and a vanish coating method is where the PI substrate is coated to the carrier glass before processing. He emphasized that no matter which method is used, the debonding technology used to detach the plastic substrate from the glass plays a crucial role in deciding yield.

 

Hong followed the substrate discussion with encapsulation technology. Encapsulation technology prevents moisture and oxygen that affect OLED panel’s performance from infiltrating in order to increase the display’s lifetime. As it is a core process that decides OLED panel’s yield, OLED panel production companies are focusing on optimum encapsulation technology development.

 

Key issues of encapsulation technology that is currently being applied to flexible OLED, barrier coating related issues are considered the most important. Barrier coating is the coating applied to the plastic substrate to overcome the limitations that occur as existing glass substrate is replaced by plastic. For flexible encapsulation, as can type or frit seal technologies that were used for glass encapsulation cannot be used, face seal or TFE technologies that can be applied to flexible are used. Also, as the permeability of oxygen and moisture has to be 10-6g/m2day or less, high performing barrier coating technology is needed.

 

When barrier coating is used to flexible OLED, generally 3 problems occur. Firstly, physically cracks or particles can develop. Regarding this, Hong explained that this issue can be solved if process is properly maintained. The second problem is micro defects that can arise on the surface of plastic film, which can be solved through optimized process, according to Hong. Lastly, nano-sized pin holes can come up. Hong revealed that multi-layers of barrier coating can solve this problem.

 

Generally, when OLED panel is produced the thickness of encapsulation layer is not a big issue. However, Hong emphasized that the thickness becomes a core issue when producing flexible OLED panel. He reported that hybrid structure of encapsulation where gas barrier cover plate is attached to passivation layer placed via PECVD can be the solution.

 

Although the most suitable process technology for hybrid encapsulation production is R2R, as appropriate results are not obtained when CVD is applied to R2R, Hong reported that research is being carried out toward the sputtering using direction. He revealed that if reflection plate is added to the sputtering equipment and neutron beam release is induced, defects that occur during the sputtering process can be reduced as the target thin film stabilizes.

 

홍문표 교수2

[Expert Talk] Interview with SAES Group’s Dr. Mauro Riva

Dr. Mauro Riva, SAES Group’s OLED/OLET business developer, kindly answered a few questions regarding OLED for OLEDNET. He will be speaking at the 2nd OLED KOREA Conference (February 24-25, 2016) in Seoul, Korea.

 

With much thanks to Dr. Riva for taking the time to answer some questions, here is the full script of the interview.

 

  • What is your personal opinion on OLED’s marketability?

I believe that OLEDs have just to leverage on their unique, distinctive properties, in order to enable brand new market segments, rather than entering competition in already crowded and established markets. I mean that the specificities of organic materials make them the only candidates for creating an entire future portfolio of portable, flexible, feather-light and, possibly, low power high definition display devices.

Thus, the ability to generate really new, fancy, conformable and sustainable displays is, in my opinion, the first ingredient to boost OLED’s marketability. The second ingredient could be, in the long run, lower raw material and manufacturing costs, with respect to competing display technologies.

 

  • Is there a particular reason for your choice to speak at the OLED specific conference rather than a more general IT conference?

As an advanced materials Company, SAES Group have developed a comprehensive portfolio of functionalized polymer composites, to be integrated in a plurality of OLED device architectures. For this reason, an OLED specific conference is the perfect place to directly discuss the important theme of encapsulation, with the people working everyday on this peculiar technology. We wanted to have a direct and frank debate with scientists and technicians specifically involved in OLEDs, rather than in general IT themes, in order to be far more focused on the manifold organic diode encapsulation issues.

 

  • What are the latest issues on OLED encapsulation?

I think that OLEDs are nowadays facing the same issues they had since the beginning: basically, OLED materials are extremely sensitive to oxidizing agents and, especially, to moisture. This requires encapsulation materials with exceptionally high barrier properties, and active fillers or getters, capable of absorbing water on a single molecule basis. The optimization of many functional properties in single encapsulating materials is a very complex materials science problem. The fact that OLED materials can also be very sensitive to heat or radiations, generates many process constraints as well.

It turns out that encapsulation materials must be specifically engineered taking into account the OLED structure, the device architecture, the chemical and physical nature of the materials and, nevertheless, the specific processes to be applied. Perfecting OLED encapsulation is thus a very challenging task, which requires deep technical interaction between advanced encapsulation materials providers and OLED makers.

 

  • Could you tell me about development concept and characteristics? Also perhaps recent performances and outcome?

As far as the Organic Electronics Business Development Area is concerned, we provide a very large portfolio of active edge sealants, active transparent fillers, dispensable getters. These products come as the result of our deep know-how in functional polymer composites, and they are specially tailored to address customers’ specific OLED designs and processes. Leveraging on our functional polymer composite technology, we have been able to develop solventless formulations, with water sorption capacities exceeding 13 percent in weight and very high flexibility and adhesiveness for fully bendable devices. Our products can be applied via screen printing, blading, syringe, ink-jetting, ODF and even be employed in thin film encapsulation structures, to make them simpler and more reliable.

Together with the functional polymer composite based products, we also provide high performance tape dryers, as thin as 110 microns, for R&D and small scale bottom emission OLEDs. Another important class of products is related to AlkaMax: this technology offers an efficient and safe method of depositing ultrapure alkali metals. Our alkali metal dispensers and pills keep the alkali metal pure in the form of a stable salt, until it is thermally activated in the evaporation chamber.

 

  • What are OLED related main manufacturing equipment type and who are your main clients?

We see syringe dispensing as one of the main methods for dispensing our functional polymer composites. Ink-jetting is also becoming more and more widespread, together with ODF, especially for active fillers. As of today, we get the most revenues in this field from PMOLED makers. The AMOLED market is broadening, and we have some very good customers there as well, who are especially in need of effective solutions for smartphone and tablet size high definition displays. OLED lighting is still early stage, but we are already collaborating with the major players in that field, so far at R&D or pre-production stage. The main market for our products for the organic electronics market is indeed Asia.

 

  • Are there any areas where you are collaborating with material companies?

We have many collaborations worldwide, with other material companies as well. Regarding the functional polymer composite technology, we are collaborating in the areas of organic electronics, specialized food packaging and gas barrier films.

We are also engaged in very fruitful collaborations with specialized equipment makers.

 

  • Is there anything you would like to add?

I would just kindly invite everyone who is interested in OLED encapsulation to visit our website and to directly contact us, for deepening all the technical aspects about our product portfolio.

The proactive and collaborating approach with our customers and the Research and Innovation focus have always been the heart of our Company way of doing: the OLEDs world offers us a real exciting and challenging arena for making innovation happen, together with all the players involved in this fascinating emerging technology.

 

 

Professor Jang-Ung Park of UNIST Discusses Transparent Electrode’s Present and Future

During the International Advanced Materials & Application Technology Expo (November 25-27), Professor Jang-Ung Park of Ulsan National Institute of Science and Technology (UNIST) gave an in-depth lecture on transparent electrode’s new technology and research results under the presentation title of ‘Technology Trend and Development Direction of High Performance Transparent & Stretchable Electrodes Using Graphene and Ag Nanowire Complex’.

 

Transparent electrode is an electronic component with usually ≥80% transparency, and sheet tension of ≤500Ω/ㅁ of conductivity. This technology is widely used in electronics including LCD front electrode and OLED electrode in display, touchscreen, solar cell, and optoelectronic device.

 

Park explained that the main market for transparent electrode is display and touchscreen, and announced that the transparent electrode market is to grow into US$4,800 million in 2020 from 2015’s US$ 3,400 million.

 

The electrode materials that is mainly being used at present is ITO (indium tin oxide) film produced through evaporation or sputtering. ITO’s merits include good conductivity from the low sheet tension and suitable for mass production. However, China is the main producer of the rare main material, indium, and has a drawback of high processing temperature. As such, research for indium replacement is continuing.

 

Graphene, CNT (carbon nano tube), Ag nanowire, and metal mesh are some of the materials that are in the spotlight as ITO replacement. However, Park emphasized that transparent electrodes that are being developed at present have difficulty in surpassing ITO in terms of electronical and optical properties. Instead, he explained that as the display shape changes, the replacement material can be used for displays where ITO cannot be applied.

 

At present, ITO is being used as the main electrode material for flat display. However, its weakness against mechanical stress and limitation in flexibility led to some views that flexible display application will be difficult. Regarding this Park explained that thickness of substrate is more important than ITO’s traits for display’s curvature radius and therefore if substrate becomes thinner, ITO can be applied even to foldable display as well as flexible. He added that although folding the display is acceptable, stretchable display is impossible as the properties are destroyed when pulled.

 

Park emphasized that in order for the wearable display market, including the smartwatch market, to grow, the comfort of the user is important. He reported as a human body does not conform to a specific curvature radius, to improve the user comfort, stretchable panel that can bend in diverse directions is a necessity. For this to be possible, transparent electrode that can replace ITO is required.

 

For example, watch shaped application can be replaced with stretchable display up to the strap part that wraps around the wrist. Glasses shaped application can have stretchable display for curved areas such as lenses. Also, within textiles industry, research into smart textiles through electronic circuit application is continuing.

 

As the transparent electrode that can replace ITO, Park suggested graphene and Ag nanowire complex. Ag nanowire reduces high sheet tension of graphene, and graphene prevents Ag nanowire’s oxidization, complementing each other. Park revealed that ≥90% transmittance and ≤30Ω/ㅁ was achieved through research. He emphasized as stretchability increased to 100%, it is suitable for stretchable display.

 

According to Park, transparent electrode can be applied to transparent stretchable sensor and transparent TFT as well as display. With confirmation of continued research regarding this issue, Park concluded his presentation.

ETRI Reveals Graphene Applied OLED Lighting

At R&D Korea 2015 (November 19-21), ETRI (Electronics and Telecommunications Research Institute) revealed OLED lighting and graphene related research results.

 

Since 2013, ETRI has been participating in ‘Graphene Applied OLED Device/Panel Technology Development’ project as a supervising organization. This project is a part of ‘Graphene Device/Component Commercialization Technology Business’, which is a Korean national project. This project’s ultimate aims include development of graphene electrode material with ≥15Ω sheet resistance, ≥90% transmittance, 3nm thickness, ≤5% sheet resistance uniformity, ≤5nm surface profile, and ≥5.5 generation area, graphene based protection layer that can be used for 5.5 generation 55inch OLED panel with ≤10-6 g/m2 WVTR, graphene anode OLED with ≥90% external quantum efficiency compared to ITO anode OLED, and diagonally 1300mm OLED panel prototype.

 

ETR1

 

In this exhibition, ETRI presented OLED lighting that used graphene as the electrode. ETRI’s Dr. Jeong-Ik Lee explained that recently interest in graphene electrode is increasing to replace ITO electrode and to apply graphene electrode, optical, electrical, and process issues have to be considered. When graphene is used as OLED electrode instead of ITO, thickness and refractive index change optically and electrically energy levels change, and these have to be considered when designing. He also emphasized that in terms of process, it has to be designed keeping in mind of before and after process of electrode procedure. Dr. Lee revealed that at present optical and electrical issues are solved while the process issues are in research stage, and they are planning to present the results of this research within this year.

 

Graphene, with its high resistivity, is known as next generation electrode material favorable to flexible and foldable. Dr. Lee pointed out that graphene has wider viewing angle than ITO when used as transparent electrode is another important advantage, and particularly as white light source’s spectrum cannot change according to the viewing angle, graphene is suitable for application.

 

Graphene is a key material with a wide arrange of applications, it is being developed in diverse areas such as OLED encapsulation as well as in electrode sector. The Ministry of Science, ICT and Future Planning of Korea estimated that domestic graphene market will record 19 billion KRW until 2025. Korea Evaluation Institute of Industrial Technology, the organization in charge of this national project, gave their target as developing 9 top technology through graphene and achieve 17 billion KRW sales. Regarding this, Dr. Lee emphasized compared to other countries, Korean investment in graphene is relatively low and that now is the time for the Korean corporations and government agencies to pay more attention higher value-added businesses.

[Expert Talk] Dr. Mauro Riva, SAES Group’s OLED/OLET Business Developer, on Encapsulation

Dr. Mauro Riva, SAES Group’s OLED/OLET business developer, discussed his views on OLED in general as well as SAES Group’s technology through his interview with the OLEDNET and presentation at the OLEDs World Summit (October 27-29) titled ‘The Encapsulation Question’.

 

Encapsulation is required to prevent the oxidation of emitting and electrode materials by blocking moisture and oxygen. It also protects the device from mechanical and physical shocks. The basic configurations of encapsulation can be divided into 3: glass-to-glass, barrier film lamination, and thin film encapsulation methods. Glass-to-glass configuration is applied to rigid AMOLED for mass produced mobile, barrier film lamination and thin film encapsulation methods are used for flexible AMOLED, and barrier film lamination is used for large area AMOLED panel for TV.

 

Source: SAES Group, OLEDs World Summit 2015

Source: SAES Group, OLEDs World Summit 2015

 

According to Dr. Riva OLED encapsulation is still facing the same issues it had since the beginning: OLED materials’ extreme sensitivity to oxidizing agents and moisture in particular. He added that OLED materials can also be very sensitive to heat or radiations, generating many process constraints. Encapsulation technology is directly related to the lifetime of the OLED device and Dr. Riva raised several questions regarding the current issues surrounding the technology including the appropriate target lifetime, best definition of “lifetime”, and reliability of the “accelerated tests”. He emphasized that while much progress have been made, a “single optimal, universal solution” does not exist yet to meet various encapsulation requirements depending on OLED architecture, materials, environment, applications, etc. As such, encapsulation materials have to be specifically engineered to meet different types of OLED devices while having “exceptionally high barrier properties, and active fillers or getters, capable of absorbing water on a single molecule basis”. Thus, perfecting this technology is a very challenging task, and, according to Dr. Riva, something that requires in depth collaboration between advance encapsulation materials providers and OLED makers.

 

For their part in this technology progression, Dr. Riva reported that SAES Group provides a very large portfolio of active edge sealants, active transparent fillers, and dispensable getters. He explained that the portfolio is the results of deep know-how in functional polymer composites (FPC), “specially tailored to address customers’ specific OLED designs and processes”. Discussing the FPC during his talk in OLEDs World Summit, Dr. Riva emphasized the versatility of this approach.

 

Source: SAES Group, OLEDs World Summit 2015

Source: SAES Group, OLEDs World Summit 2015

 

Regarding application methods for SAES Group’s FPC products, Dr. Riva explained that they can be dispensed via screen printing, blading, syringe, ink-jetting, ODF (one drop filling), and even be employed in thin film encapsulation structures, to make them simpler and more reliable. Furthermore, Dr. Riva reported that while SAES Group considers syringe dispensing as one of the main methods for applying their FPC, “ink-jetting is also becoming more and more widespread, together with ODF, especially for active fillers”.

 

Dr. Riva believes the FPC could play an important role in making the encapsulation more effective, and that SAES Group can “leverage on its advanced materials expertise” and in-depth getter/purification knowledge, to “perfect FPC based encapsulation solutions for OLEDs”. 11% of SAES Group’s net sales is allocated to Research and Innovation every year with strong cooperation with universities and R&D centers. The company is collaborating with many companies in diverse areas of interest such as OLED lighting, manufacturing equipment, specialized food packaging, and gas barrier films. This proactive and collaborating approach will enable the SAES Group to play a key role in developing more marketable OLED devices.

 

Visionox Reveals 604PPI High Resolution AMOLED

On November 12, Visionox announced that they recently developed 604ppi (approximately 4.85inch) high resolution full color OLED panel through FMM (fine metal mask) using evaporation technology.

 

Visionox Z-Type(Source : OLED-info)

Visionox Z-Type(Source : OLED-info)

 

In 2014, Visionox developed 570ppi RGB AMOLED panel with newly developed pixel structure, Z-Type. This Z-Type arrangement had larger blue sub-pixel with green and red sub-pixels beside it. The new panel has resolution of 604ppi which is a 35ppi increase from the 2014 panel. With this new reveal, Visionox displayed their high resolution OLED technology improvement.

 

The 604ppi panel combined the self-developed pixel layout under proprietary intellectual property rights and co-developed Chinese FMM. The resolution is 2,560 × 1,440, manufactured using real RGB method and not pentile.

 

Chinese companies are developing their high resolution AMOLED panel technology at a fast pace. In August, EverDisplay presented 734ppi 6inch panel, and the technology difference with Korean panel companies is rapidly decreasing.

 

Visionox revealed that this OLED panel shows Visionox’s research development for high resolution OLED is continuing and aptly demonstrated the current results.

 

604 PPI High Resolution Display Panel (real RGB) (Source: Visionox)

604 PPI High Resolution Display Panel (real RGB) (Source: Visionox)