Large‐screen displays using metal—insulator—metal cathode arrays

Abstract— Large‐screen (32‐in. WXGA and 17‐in. VGA) displays using metal—insulator—metal (MIM) cathode arrays have been developed. A cathode structure with low‐resistance electrodes and low‐capacitance emitters shortens signal delay and decreases the voltage drop in large MIM‐cathode arrays. By using a dual‐scan method, the signal delay was suppressed to less than 30% of the horizontal scan time in the 32‐in. WXGA panel. Emission efficiency of the cathode array was improved to 3% by reducing the surface work function of the top electrode from 4.7 to 3.9 eV. The cathode life was also improved to more than 10,000 hours. The display panel incorporating the cathode arrays and high‐efficiency P22‐phosphor screens with 3‐mm spacers showed high screen brightness (average brightness, 378 cd/m²; peak brightness, 832 cd/m²) at an anode voltage of 10 kV.     

Inorganic EL devices with high‐performance blue phosphor and application to 34‐in. flat‐panel televisions

Abstract— A high‐performance inorganic electroluminescence (EL) device has been successfully developed by using an EL structure with a thick dielectric layer (TDEL) and sputtered BaAl₂S₄:Eu blue phosphor. The luminance and efficacy were higher than 2300 cd/m² and 2.5 lm/W at L⁶⁰, 120 Hz, respectively. Furthermore, the luminance at L⁶⁰, 1.2 kHz was more than 23,000 cd/m². The phosphor layer has a single‐phase and a highly oriented crystalline structure. The phosphor also shows high stability in air. A 34‐in. high‐definition television (HDTV) has been developed by combining a TDEL structure and color‐conversion materials. The panels with an optimized color filter demonstrated a peak luminance of 350 cd/m², a color gamut of more than 100% NTSC, and a wide viewing angle similar to that of plasma‐display panels. The high reproducibility of the 34‐in. panels using our pilot line has been confirmed.     

High‐luminance and highly luminous‐efficient AC‐PDP with DelTA cell structure

To improve PDP performance, we developed an AC‐PDP with the Delta Tri‐Color Arrangement (DelTA) cell structure and arc‐shaped electrodes. The experimental panel has a pixel pitch of 1.08 mm and luminous efficacy of 3 lm/W at a luminance of 200 cd/m² despite its conventional gas mixture of Ne and Xe (4%) and conventional phosphor set. Moreover, its peak luminance can be greater than 1000 cd/m². The strong dependence of luminous efficacy on the sustain voltage is also discussed in this paper.     

Printable phosphorescent organic light‐emitting devices

Abstract— A new approach to full‐color printable phosphorescent organic light‐emitting devices (P²OLEDs) is reported. Unlike conventional solution‐processed OLEDs that contain conjugated polymers in the emissive layer, the P²OLED's emissive layer consists of small‐molecule materials. A red P²OLED that exhibits a luminous efficiency of 11.6 cd/A and a projected lifetime of 100,000 hours from an initial luminance of 500 cd/m², a green P²OLED with a luminous efficiency of 34 cd/A and a projected lifetime of 63,000 hours from an initial luminance of 1000 cd/m², a light‐blue P²OLED with a luminous efficiency of 19 cd/A and a projected lifetime 6000 hours from an initial luminance of 500 cd/m², and a blue P²OLED with a luminous efficiency of 6.2 cd/A and a projected lifetime of 1000 hours from an initial luminance of 500 cd/m² is presented.     

Mercury‐free 18‐in. flat fluorescent lamp with good uniformity

We have developed an 18‐in. 287 × 359‐mm flat fluorescent lamp (FFL) that uses a xenon dielectric barrier discharge and analyzed its electro‐optical characteristics. The surface luminance of the lamp having a diffuser sheet thickness of 3 mm was 5600 cd/m² and the luminance uniformity was 92% at an applied voltage of 950 Vrms. The luminous efficacy of the FFL was 24.5 lm/W for a luminance of 4200 cd/m² when driven by a sine‐wave voltage.     

Mercury‐free 18‐in. flat fluorescent lamp with good uniformity

Abstract— We have developed an 18‐in. 287 × 359‐mm mercury‐free flat fluorescent lamp (FFL) having a new structure that utilizes dielectric barrier discharge and contains pure xenon gas. The electro‐optical characteristics have been analyzed. The surface luminance of the lamp having a diffuser sheet is 5600 cd/m² and the luminance uniformity is 92% at an applied voltage of 1050 Vrms and an applied frequency of 20 kHz in the form of a sine wave.     

A low‐cost low‐temperature thin‐film‐transistor backplane based on oxide semiconductor

Abstract— An indium‐gallium‐zinc‐oxide (IGZO) thin‐film transistor (TFT) based on an anodized aluminum‐oxide gate dielectric and photoresist passivation has been fabricated. The TFT showed a field‐effect mobility of as high as 18 cm²/V‐sec and a threshold voltage of only 0.5 V. A 50 × 50 AMOLED display based on this type of TFT was designed and fabricated. The average luminance of the panel was 150 cd/m², and the maximum pixel luminance was 900 cd/m².     

High‐performance white OLEDs with high color‐rendering index for next‐generation solid‐state lighting

Abstract— Several white‐OLED structures with a high color‐rendering index (CRI) were investigated for lighting applications. A two‐unit fluorescent/phosphorescent hybrid white OLED achieved an excellent CRI of 95, high luminous efficacy of 37 lm/W, and long lifetime of over 40,000 hours at 1000 cd/m². White‐OLED lighting panels of 8 × 8 cm for high‐luminance operation were fabricated, and a stable emission at 3000 cd/m² was confirmed. Quite a small variation in chromaticity in a different directions was achieved by using an optimized optical device structure. With a light‐outcoupling substrate, a higher efficacy of 56 lm/W, high CRI of 91, and longer half‐decay lifetime of over 150,000 hours at 1000 cd/m² was achieved. All‐phosphorescent white OLEDs placed on the light‐outcoupling substrate show a high CRI of 85 and higher efficacy of 65 lm/W with a fairly good half‐decay lifetime of over 30,000 hours. With a further voltage reduction and a high‐index spherical extractor, 128 lm/W at 1000 cd/m² has been achieved.     

Fabrication and cathodoluminescent properties of the ZnO‐Cu,Ga and ZnS‐Cu,Ga film phosphors

Abstract— A novel technique for cathodoluminescent screen fabrication using a new method of film phosphor doping has been developed. The crystalline structure and morphology of the films were investigated. Cathodoluminescence spectra were measured at different excitation levels and temperatures (300 and 77 K). The luminance is 200 cd/m² for ZnS:Cu, Ga and 1100 cd/m² for ZnO:Cu, Ga films at a temperature of 300 K and 3700 cd/m² for ZnO:Cu, Ga film at a temperature of 77 K. The films show more saturated green color than commercial phosphors.     

High‐efficiency red‐phosphorescent organic light‐emitting diode with the organic structure of 2‐TNATA/Bebq2:SFC‐411/SFC‐137

Abstract— High‐efficiency and simple‐structured red‐emitting phosphorescent devices based on the hole‐injection layer of 4,4′,4″‐tris(2‐naphthylphenyl‐phenylamino)‐triphenylamine [2‐TNATA] and the emissive layer of bis(10‐hydroxybenzo[h] quinolinato)beryllium complex [Bebq²] doped with SFC‐411 (proprietary red phosphorescent dye) have been researched. The fabricated devices are divided into three types depending on whether or not the hole‐transport layer of N,N′‐bis(1 ‐naphthyl)‐N, N'‐diphenyl‐1,1′‐biphenyl‐4,4′‐diamine [NPB] or the electron‐transport layer of SFC‐137 (proprietary electron transporting material) is included. Among the experimental devices, the best electroluminescent characteristics were obtained for the device with an emission structure of 2‐TNATA/Bebq²:SFC‐411/SFC‐137. In this device, current density and luminance were found to be 200 mA/cm² and 15,000 cd/m² at an applied voltage of 7 V, respectively. Current efficiencies were 15 and 11.6 cd/A under a luminance of 500 and 5000 cd/m². The peak wavelength in the electroluminescent spectral distribution and color coordinates on the Commission Internationale de I'Eclairage (CIE) chart were 628 nm and (0.67, 0.33), respectively.     

Very‐high‐brightness diodes for passive‐matrix display applications

Abstract— The development of a high‐brightness low‐voltage yellow‐light‐emitting polymer system suitable for use in low‐cost passive‐matrix displays will be reported. Average device efficiencies of 16 lm/W at 100 and 1000 cd/m² are achieved at 2.1 and 2.4 V, respectively. A luminance level of 100,000 cd/m² is achieved at 5.5 V.     

Reduction of defects and improvement in the performance of blue phosphor for thick‐dielectric electroluminescent displays using Color‐by‐Blue

Abstract— Defect‐free large‐area inorganic thick‐dielectric EL (TDEL) displays using Color by Blue (CBB) technology have been successfully developed. We have achieved the world's highest blue‐phosphor luminance of 900 cd/m² for a single‐pixel device by using CBB and by optimizing the e‐beam gun configuration and the flow rate of H₂S in the vacuum chamber. By analyzing the defects on panels with triple‐pattern phosphors and CBB panels, we also found that the number of defects on CBB panels can be drastically reduced compared with those on triple‐pattern panels. The defect‐free 17‐in. VGA CBB panels show better characteristics, a high peak luminance of 600 cd/m² and a high contrast ratio of 1000:1, compared with those of triple‐pattern panels.     

Recent research and development on 71‐in.‐diagonal color PDPs

Abstract— The World's first 71‐ and 76‐in.‐diagonal ACPDPs with full high‐definition resolution (1920 × 1080), a high luminance of 800 cd/m², and a dark‐room contrast ratio of 1200:1 have been developed using a highly efficient barrier‐rib structure. Also a new MgO protective layer and a film‐type optical filter were developed to improve picture quality. To fabricate large‐sized panels over 70 in. on the diagonal, an improved uniform exposing technology for the patterning of electrodes, a green sheet method for the transparent dielectric layer, and a co‐processed bus and black‐matrix (CPBB) method were used.     

Characteristics of a high‐Xe‐concentration 4‐in. PDP

The performance of two 4‐in. color PDP test panels with a default and a high‐Xe‐concentration gas mixture will be discussed. The default panel with a gas mixture of 3.5% Xe in Ne and a filling pressure of 665 hPa was compared with a panel containing a gas mixture of 13.5% Xe in Ne and a filling pressure of 800 hPa. The panels contain a green phosphor, YBO₃:Tb, which showed less saturation at high UV load compared with a Willemite phosphor. The panel performance was compared in addressed conditions. For the default panel, a white luminance of 710 cd/m² and an efficacy of 1.6 lm/W was found, while for the high‐Xe‐partial‐pressure panel, a white luminance of 2010 cd/m² and an efficacy of 3.8 lm/W was realized. The increase of the driving voltages, about 20–30 V, is moderate. Finally, color saturation is improved at high Xe partial pressure.     

Practical CNT‐FED structure for high‐luminance character displays

Abstract— A high‐luminance CNT‐FED character display using a simple line rib structure was constructed. The display panel had 48 × 480 dots and the subpixel pitch was 1 mm. The greatest benefit of a display using CNT technology is high luminance performance with low‐power consumption. The luminance of the green‐color dot wasca. 10,000 cd/m² under 1/1 6 duty‐cycle driving at a 6‐kV anode voltage. The high luminance of the display panel can provide good visibility when installed even in outdoor locations, and the power consumption was ca. 4 W at the character displaying module. This, a CNT‐FED for character displays also has potential multifunctionality, which could be battery driven. It should be useful for public displays even under emergency no‐power conditions. In this work, a practical structure and process technologies for making ribs with reasonable cost were developed. The newly introduced 2‐mm‐tall line ribs as spacers were formed by using innovative production processes; i.e., the rib paste was pushed out of a multi‐slit nozzle, and the rib shape was formed by UV‐light irradiation. The developed panel structure and manufacturing processes also had the advantages of size flexibility and high production yield.     

Development of new high‐luminance green EL devices based on Eu‐doped calcium thioaluminate materials system

Abstract— A new green EL phosphor with excellent brightness, efficiency, and color saturation was developed. This phosphor is based on the europium‐activated calcium thioaluminate materials system. The performance of this phosphor is greatly enhanced by the addition of Gd as a co‐dopant. Similarly, the addition of ZnS layers on the top and bottom of the phosphor film improved the device luminance considerably. The luminance of the EL devices can be as high as 1700 cd/m² with CIE color coordinates (0.190, 0.645) which were tested by using 32‐μsec‐wide square pulses with a frequency of 120 Hz. The device efficiency was over 2 lm/W.     

A large high‐resolution electroluminescent display

A new high‐resolution electroluminescent display with a luminance of 100 cd/m² (30 fL) and 6‐bit gray scale to support real‐time video up to a bandwidth of 45 MHz has been developed under the Defense Advanced Research Projects Agency's Technology Reinvestment Project. Production units are now installed in the M1A2 Abrams Main Battle Tank upgrade program and are used to display the tank commander's new infrared “second‐generation FLIR” imagery.     

Fluorescent‐based tandem white OLEDs designed for display and solid‐state‐lighting applications

Abstract— Highly efficient tandem white OLEDs based on fluorescent materials were developed for display and solid‐state‐lighting (SSL) applications. In both cases, the white OLED must have high power efficiency and long lifetime, but there are a number of attributes unique to each application that also must be considered. Tandem OLED technology has been demonstrated as an effective approach to increase luminance, extend OLED lifetime, and allow for use of different emitters in the individual stacks for tuning the emission spectrum to achieve desired performance. Here, examples of bottom‐emission tandem white OLEDs based on small‐molecule fluorescent emitters designed for displays and for SSL applications are reported. A two‐stack tandem white OLED designed for display applications achieved 36.5‐cd/A luminance efficiency, 8500K color temperature, and lifetime estimated to exceed 50,000 hours at 1000 cd/m². This performance is expected to meet the specifications for large AMOLED displays. A two‐stack tandem white OLED designed for SSL applications achieved 20‐lm/W power efficiency, 38‐cd/A luminance efficiency, 3500K color temperature, and lifetime estimated to exceed 140,000 hours at 1000 cd/m². With the use of proven light‐extraction techniques, it is estimated that this tandem device will exceed 40 lm/W with more than 500,000‐hour lifetime, performance that should be sufficient for first‐generation lighting products.     

High‐efficiency OLED microdisplay with microlens array

A high‐efficiency organic light‐emitting diode (OLED) microdisplay has been developed with some new technologies including microlens array. We focused on the improvement of the out‐coupling efficiency and achieved three times higher efficiency as compared with conventional OLED. By using our developed technologies, it is possible to improve the maximum luminance from 1600 to 5000 cd/m² while maintaining same lifetime.     

Ink‐jet‐printable phosphorescent organic light‐emitting‐diode devices

Abstract— A novel method for the fabrication of ink‐jet‐printed organic light‐emitting‐diode devices is discussed. Unlike previously reported solution‐processed OLED devices, the emissive layer of OLED devices reported here does not contain polymeric materials. The emission of the ink‐jet‐printed P²OLED (IJ‐P²OLED) device is demonstrated for the first time. It shows good color and uniform emission although it uses small‐molecule solution. Ink‐jet‐printed green P²OLED devices possess a high luminous efficiency of 22 cd/A at 2000 cd/m² and is based on phosphorescent emission. The latest solution‐processed phosphorescent OLED performance by spin‐coating is disclosed. The red P²OLED exhibits a projected LT50 of >53,000 hours with a luminous efficiency of 9 cd/A at 500 cd/m². The green P²OLED shows a projected LT50 of >52,000 hours with a luminous efficiency of 35 cd/A at 1000 cd/m². Also discussed is a newly developed sky‐blue P²OLED with a projected LT50 of >3000 hour and a luminous efficiency of 18 cd/A at 500 cd/m².