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Samsung Display, shows advanced product such as stretchable display in SID 2017

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Samsung Display participates in ‘SID 2017’ exhibition hosted by the world-renowned Society for Display Experts ‘SID (The Society for Information Display)’ to show advanced future display products.

 
Samsung Display will exhibit advanced display products that have never been revealed before, such as a stretchable display and a non-eyewear 3D OLED at the LA Convention Center in Los Angeles on 23rd (local time).

 
Samsung Display participates in this SID 2017, and is showing the unrivaled display technology leadership and confidence by showing high-tech products and publishing outstanding papers.

 
Samsung Display unveiled a 9.1 inch stretchable OLED product with stretching screen.  The stretchable display is the next generation display technology that extends the screen flexibly, and it is considered to be the most suitable technology for wearable, Internet (IoT), AI (AI), and car display.

<source : Samsung Display>

 

Compared to the existing flexible OLEDs that can be deformed in only one direction, such as bending, folding, or rolling a screen, a stretchable OLED can be deformed in more than two directions.  This is a much higher level of implementation difficulty and is often referred to as the end point of flexible display technology in the industry.

 
The product displayed this time, when the screen is pressed from above, the screen is dented like a rubber balloon, and then returns to its original flat shape.  On the contrary, when pressed from below, the screen stretched up and had the elasticity to recover.  Samsung Display has developed a high level of stretchable technology that maintains the original picture quality while increasing the screen to a depth of up to 12mm when the display is pressed through steady research and development.

 
In addition, Samsung Display will exhibit ‘non-eyewear 3D OLED’ products. This 5.09-inch product realizes a real-life image that looks a bit different depending on the viewer’s position on the display, and expresses a more realistic 3-D image.

Especially, due to the contrast ratio close to infinity of OLED, it shows more natural stereoscopic image than LCD product. This technology is expected to be utilized in various fields requiring 3D image technology such as 3D pop-up book, 3D game, VR and etc.

 

On the other hand, this exhibition will have booths that enable users to experience the OLED technologies of Samsung Display. Including 3.5-inch size, 858ppi optimized for VR devices, 120Hz for wearable and tablet OLED products for smooth picture quality are exhibited.

In addition, much improved image quality of OLED, HDR (High Dynamic Range) and low power consumption technology can be confirmed.  Samsung Display also offers a ‘Design Innovation’ corner that introduces the development of smartphone display design, a unique flexible OLED technology.

From round OLEDs applied to mobile phones for the first time in the world after the successful production of flexible OLEDs in 2013, to recent full-screen OLEDs with the highest picture quality rating of ‘Excellent A +’ from DisplayMate, an image quality evaluation agency, it is able to show the flexible OLED technology accumulated by Samsung Display at a glance.

 
In addition, a high-resolution 65-type frameless LCD curved TV that minimizes screen reflections by applying ultra-low reflection POL (polarizer) and achieves 100% color expression power (DCI-P3 standard), 34-inch QHD + (3440X1440) LCD curved monitor with 21: 9 aspect ratio maximizes information transfer efficiency and 27-inch FHD (1920X1080) LCD curved monitor capable of 144 Hz high-speed screen operation are exhibited as a product that embodies innovative technology

Meanwhile, a paper entitled “Extendable Screen with Stretchable OLED Display” of Hong Jong-ho, researcher of Samsung Display Research Institute selected as SID 2017 Distinguished Paper.

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

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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.

UNIST 박장웅 교수, 투명전극의 현재와 미래에 대해 논하다.

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11월 26일 개최된 ‘2015 국제 신소재 및 응용기술전참관 및 그래핀 투명전극 소재 별 기술 개발 동향 및 발전방향 세미나’에서 울산과학기술대학교 박장웅 교수는 ‘그래핀과 Ag nano wire의 복합체를 이용한 고기능 유연투명전극 기술 개발동향 및 발전방향’이라는 주제로 투명전극에 대한 신기술과 개발 성과 등에 대한 심도 있는 강연을 했다.

투명전극은 통상 80% 이상의 고투명도와 면저항 500Ω/ㅁ 이하의 전도도를 가지는 전자 부품으로 LCD 전면 전극, OLED 전극 등 디스플레이, 터치스크린, 태양전지, 광전자 소자 등 전자분야에 광범위하게 사용되는 기술이다.

박교수는 투명전극의 주된 시장은 디스플레이와 터치스크린이라고 설명하며 2015년 US$3,400million 규모인 투명전극 시장이 2020년에는 US$4,800million까지 성장할 것으로 전망된다고 발표했다.

현재 주로 채용되고 있는 전극재료는 증착법이나 sputtering에 의해 제조되는 ITO(Indium Tin Oxide) 필름이다. ITO는 면저항이 낮아 전기전도성이 우수하고 대량생산에 적합하다는 장점이 있다. 하지만 주원료인 인듐이 중국에서 독점하고 있는 희소성이 있는 물질이며, 공정온도가 높다는 단점이 있어 대체물질을 찾기 위한 연구가 지속되고 있다.

이런 연구를 통해 그래핀과 CNT(Carbon Nano Tube), Ag nano wire, metal mesh 등이 ITO를 대체할 수 있는 물질로 각광받고 있다. 하지만 박교수는 현재 개발되고 있는 투명전극들은 전기적 광학적 특성 등에서 ITO를 넘어서기 힘들다고 강조했다. 대신 디스플레이의 형태가 변화됨에 따라 ITO가 사용될 수 없는 형태의 디스플레이에 대체 물질이 쓰일 수 있을 것이라고 설명했다.

현재 ITO는 평면 디스플레이의 주요 전극 재료로 쓰이고 있다. 하지만 mechanical stress에 취약하기 때문에 유연성에 한계가 있어 플렉서블 디스플레이에 적용되기 힘들 것이라는 시각이 있었다. 이와 관련해 박교수는 “디스플레이의 곡률반경에는 ITO의 특성보다 기판의 두께가 더 중요한 요소이기 때문에 기판의 두께가 얇아진다면 플렉서블 뿐만 아니라 폴더블 디스플레이에도 ITO가 충분히 적용될 수 있을 것이다.”라며 “구부려지는 것은 상관없지만 문제는 잡아당길 때 특성이 파괴되기 때문에 stretchable 디스플레이가 불가능하다.”고 밝혔다.

박교수는 smartwatch를 포함한 wearable 디스플레이 시장이 성장하기 위해서는 사용자가 느끼는 착용감이 중요하다고 강조하며 “사람의 인체는 곡률반경이 정해져 있지 않기 때문에 기존 wearable 디스플레이의 착용감을 높이기 위해 다양한 축의 구부림이 가능한 stretchable 패널 적용이 필수적이며 이를 위해서 ITO를 대체할 수 있는 투명전극이 필요하다.”고 발표했다.

예를 들어, 시계 형태의 애플리케이션은 손목을 감는 스트랩 부분까지 stretchable 디스플레이로 대체할 수 있으며, 안경 형태의 애플리케이션은 렌즈와 같은 곡면 부위에도 stretchable 디스플레이를 적용할 수 있다. 또한 섬유산업에서도 스마트 섬유라는 개념으로 전자회로화 할 수 있는 연구가 속속 선보이고 있다.

박교수는 ITO를 대체하는 투명전극에 대한 연구결과로 그래핀과 Ag nano wire의 복합 구조체를 제시하였다. Ag nano wire는 그래핀의 높은 면저항을 낮추어주는 역할을 하고 그래핀은 Ag nano wire의 산화를 막는 역할을 하기 때문에 서로 상호보완적인 관계가 될 수 있다고 설명했다. 또한 박교수는 연구를 통해 90%이상의 투과율과 30Ω/ㅁ이하의 면저항을 달성했다고 밝히면서 “특히 stretchability를 100%까지 높였기 때문에 stretchable 디스플레이에 적용하기 적절하다.”고 강조했다.

박교수는 해당 투명 전극은 디스플레이뿐만 아니라 투명 stretchable 센서와 투명 TFT 등에도 적용할 수 있다고 밝히며 이와 관련된 연구도 지속하고 있다고 하며 발표를 마쳤다.