I recently had the chance to interview Mr. Corey Hewitt and Dr. James Buntaine from Kodak OLED Systems. Kodak is where OLEDs were first discovered, and they are still in the fore-front of the technology. This is going to be a long article - these guys have given me a lot of background info, even before answering my questions. But first let's introduce Corey and James:
Mr. Corey Hewitt, Operations Manager & Vice President, Kodak OLED Systems
Mr. Hewitt's responsibilities include worldwide operations, finance, marketing and business development. Corey has traveled and worked closely on a worldwide basis with Dr. Buntaine in determining the future strategy for OLED technology and how it relates to Eastman Kodak Company. Corey received his Business Administration/Finance degree from the University at Buffalo and subsequently completed his Masters of Business Administration from the Rochester Institute of Technology. Corey has joined Kodak in 1999, and held several positions before becoming the Operations Manager and VP of Kodak OLED Systems.
Dr. James Buntaine, Chief Technical Officer & Vice President, Kodak OLED Systems
Dr. James R. Buntaine's responsibilities include business and technology development, product delivery, and intellectual property creation. James earned his Ph.D. at Cornell University in Solid State Chemistry (1980), investigating the metal-non-metal transition in a lithium-base system. He joined Eastman Kodak in January, 1980, in the Solid State Chemistry laboratory where he studied the paramagnetic resonance properties of transition metal dopants in silver halide materials. The technologies and product commercialization under his direction included silver halide materials, photographic products, MicroEncapsulation printing system, thermal printing system, laser printing system, pilot and scale-up media operations, and flexible electronic displays. In 2004 he moved to the Display and Components Business Unit as Technology Director.
Overview of Kodak and OLED Technology
Here's what Kodak has to say about their OLED business:
Kodak discovered organic light emitting diode technology in the late 1970s and has since played a leadership role in commercialization of OLED technology. Our expertise and experience in material discovery, development, and manufacturing, as well as color science and device research have factored into our ability to help manufacturers quickly take advantage of OLED technology.
Kodak is enabling the industry
- Pioneer in OLED technology with 25 years of experience
- Deep understanding of device physics and chemistry
- First AMOLED commercialized product in the world
- More than 1,900 worldwide OLED patents; More than 15 OLED licensees
- One of the world’s most recognized and respected brands
- Global OLED R&D enterprise
Kodak’s OLED Display Technology Covers a Wide Spectrum
- OLED material science and architecture
- Low cost manufacturing solutions
- Industry collaborations
Kodak is Making Better OLEDs for the Industry via:
- Device Design Expertise
- World leading OLED Architecture
- Advanced Materials
- Mechanistic Understanding
- Analytical Capability
Kodak is working with a number of companies to extend its leadership position in areas such as know-how, White OLED, materials, and low-cost manufacturing solutions, providing optimal value for Kodak and it’s future partner.
Kodak is the leader in OLED technology including material deposition (>90% yield). Kodak's concern is ensuring the backplane is ready for commercialization. This is a critical factor in choosing a partner. The industry offers various types of backplane. Kodak is studying the risks and progress of each type to confirm suitability for future Kodak OLED products. Kodak is taking a very hard look at every potential partner’s backplane technology to ensure OLED is successful.
Kodak's White Active Matrix OLED architecture
Based on years of experience, Kodak is convinced the path to a low cost, high performing AMOLED display is through the use of WOLED (white-emitting OLED). The benefits include scalability, no need for shadow mask (faster TACT time), and overall better production yield. For OLED to compete successfully in the large-size TV market, the manufacturing approach chosen must be low cost and high yield. Part of "low-cost" means that OLED deposition process must be practiced on the same large glass sizes that are used for LCD TV's (e.g. Gen 8 2160X2400mm, – glass the size of a queen sized bed) in machines with very high throughput.
Kodak has focused its development (OLED materials, white formulations, Tandem Architecture, deposition sources, sub-pixel layouts, display designs, and color filter materials) to enable scale-up to these large sizes with high throughput. The key difference between the Kodak approach and the approach pursued by others is that the Kodak approach is based upon uniform deposition of white-emitting OLED materials (WOLED), whereas others are pursuing the precision patterned deposition of red, green, and blue emitting materials according to the sub-pixel pattern inside the display area (the so-called RGB approach).
Precision patterned deposition involves depositing millions of separate sub-millimeter sized spots with-in tolerances of a few microns, which by nature is a slow operation. The two primary approaches to precision patterned deposition are: 1) evaporation through fine metal masks – which are commonly believed to be limited to small glass sizes only up to up to Gen 4 (730x950mm); and 2) laser transfer of the material spot-by-spot. Laser transfer has only been demonstrated on very small glass sizes.
The White approach and some of the RGB approaches (i.e. Sony’s current 11" TV) to OLED TV manufacturing require color filters patterned according to the sub-pixel pattern. These color filters are typically fabricated using photolithographic methods, which are already scaled to the large glass sizes as they are used for LCD TV's. Kodak's white-emitting OLED approach, therefore, is fully scalable to Gen 8 glass sizes since the only precision patterning required is the same patterning currently used for LCD TV's.
To give a specific comparison, consider the RGB approach used by Sony, presently the only manufacturer of OLED TV's greater than 10 inches diagonal. Sony uses a top-emitter display design, which requires precision deposition of every organic layer to produce the R, G, and B sub-pixels and to keep the cathode contact-vias open. In an OLED stack, there are commonly about 4 layers (often more) – hole injection, hole transport, emission, and electron transport. Thus in the Sony approach there are approximately 12 layers that must be precision deposited.
For the Kodak White OLED approach, there are no operations that require precision-shadow-mask patterning materials for the individual sub-pixels – the same materials are used everywhere. This facilitates high-speed processing by eliminating slow alignment operations or slow laser-transfer operations, enables scale-up to large displays and large-size sheets of mother-glass, and permits the concept of a machine with a continuous flow-through deposition operation.
At this years Society for Information Display (SID) 2008 Trade Show, Kodak demonstrated the world’s first, public 8", White AMOLED, 100% NTSC panel. Kodak's technology allows for fully scalable large TV size panels for the future. Frost & Sullivan also recognized Kodak for excellence and innovation in OLED Display Technology Leadership. Kodak was recognized as a company that is predicted to encourage significant growth in the OLED industry, has identified emerging trends before they become a standard in the marketplace, and have created advanced technologies that will catalyze their industries in the near future.
Kodak's work on this technology in terms of deposition techniques and manufacturing
OLED production techniques continue to evolve to minimize facilities requirements and take advantage of conventional technology and processes. Kodak provides technology expertise; services and materials to help licensing partners begin manufacturing operations. Precision material deposition is crucial to superior displays. Kodak’s advances in deposition techniques and equipment continue to bring more control and efficiency to manufacturing – including the number of substrates that can be processed. OLED screens are easy to integrate into a wide range of devices. Today, active OLED displays are manufactured using the same TFT process used to build circuitry on the glass substrate.
Kodak's Vapor Injection Source (VIS) Technology
Kodak's Vapor Injection Source technology enables low cost OLED manufacturing by increasing OLED materials utilization (to 50-90%), increasing organic deposition rates (2 min or less TACT times), and increasing equipment up time (95% or more). In addition this technology has been demonstrated at Gen 5 scale (see picture below) and is easily scalable to Gen 7 and larger substrates. The technology also enables high yield and easier manufacturing control due to low degradation multi-component deposition from a single source, eliminating out of spec depositions due to incorrect layer compositions or thermal degradation of organic materials (such as some blue singlet dopants and most triplet dopants).
Global Mura Compensation (GMC) Technology
OLED is current driven, unlike LCD which is voltage driven. This makes OLED susceptible to current variations. Because a Thin Film Transistor (TFT) is supplying the current, the display's luminance uniformity is affected by variations in TFT performance. Many pixel-driving technologies, such as current programming and voltage programming, have been developed in the past to get rid of this phenomenon. However, none were completely satisfactory.
Kodak’s method, Global Mura Compensation (GMC) detects and compensates for these variations by using an external driver IC. This is far more flexible than previous compensation techniques. This allows Global Mura Compensation to compensate for the variation almost perfectly. Many report that they cannot see any difference between the mura (Japanese word meaning "error") in OLEDs and the mura in LCDs.