JOURNALS

High-Current Operation of Vertical-type Organic Transistor with Preferentially Oriented Molecular Film

AIP Advances, Vol.6, No.4, 045010, pp. 045010.1-045010.6 (2016) (You will leave the NHK website)
Hirohiko FUKAGAWA, Yasuyuki WATANABE^*1, Kazuhiro KUDO^*2, Jun-ichi NISHIDA^*3, Yoshiro YAMASHITA^*3, Hideo FUJIKAKE^*4, Shizuo TOKITO^*5, Toshihiro YAMAMOTO
*1 Tokyo University of Science, *2 Chiba University, *3 Tokyo Institute of Technology, *4 Tohoku University, *5 Yamagata University

We have been researching organic transistors for use in flexible displays. Because it is easy for carriers to flow parallel to the substrate in materials for general organic transistors, “planar-type organic transistors,” in which current flows in this direction, have been widely studied. However, with horizontal-type transistors, sufficient electron mobility and current could not be achieved to apply them to matrix elements used in large displays. This is because parallel-to-the-substrate organic thin films have two crystal axes. Thus, it is difficult for the carrier flow direction in the organic film to be aligned with the carrier transport direction within the transistor. In contrast to horizontal-type transistors, we have developed a “vertical-type transistor.” We succeeded in forming an organic thin film that is a clear departure from the general materials used for organic transistors. This film enables current to flow easily in directions perpendicular to the substrate, and the transistor is capable of modulating a high current density at a low driving voltage. Although the development of vertical-type transistors has been reported in the past, an organic thin film suitable for vertical-type transistor was not found, and high performance was not possible. The organic thin film we have developed has one axis, so the carrier flow direction is easily aligned with the carrier transport direction within the transistor. By using this organic thin film, we succeeded in developing an organic transistor that achieves a current about 1,000 times greater than that of conventional organic transistors and a modulated drain current density exceeding 1 A/cm² at a low drive voltage of 5 V or less.

Extended Image Dynamic Range System for UHDTV Broadcasting

SMPTE Motion Imaging Journal, Vol.125, No.4, pp.1-8 (2016) (You will leave the NHK website)
Yuichi KUSAKABE, Yoshitaka IKEDA, Noriyuki SHIRAI, Kenichiro MASAOKA, Takayuki YAMASHITA, Yukihiro NISHIDA, Tetsuomi IKEDA, Masayuki SUGAWARA^*1
*1 NEC Corporation

Full-featured 8K Super Hi-Vision seeks to provide a greater sense of realism to viewers — the sense of being there and the sense of realness — by featuring 7,680 × 4,320 pixels, a 120-Hz frame rate, and a wide color gamut. In addition, it employs a high dynamic range (HDR), which is the ability to reproduce a wide range of luminance. In this paper, we present the requirements to adopt HDR in broadcasting (video signals representing relative luminance values, compatibility with current systems, adjustment methods under various ambient environments). As a method for fulfilling these conditions, we proposed Hybrid Log-Gamma (HLG) technology, which combines a power function and a logarithmic function. We also conducted three HDR-related experiments. The results revealed the following: when video production is carried out using a display with high peak luminance, the percentage of video signals assigned to highlights increased; the least perceptible luminance is influenced by the peak luminance of the display, the test signals, and the luminance of viewing environment and is about 0.1 cd/m² in a home viewing environment and 0.001-0.01 cd/m² in a production environment; and when displaying standard dynamic range (SDR) images, the preferred peak luminance of the display is influenced by the luminance of viewing environment and is roughly 500 cd/m² in a home viewing environment. These findings are expected to be useful for the test satellite broadcasting of Super Hi-Vision.

Required Bit Rates Analysis for a New Broadcasting Service Using HEVC/H.265

IEEE Transactions on Broadcasting, Vol.62, No.2, pp.417-425 (2016) (You will leave the NHK website)
Atsuro ICHIGAYA and Yukihiro NISHIDA

The required bit rates for providing high-quality ultrahigh-definition television (UHDTV) services in broadcasts using High Efficiency Video Coding (HEVC)/H.265, the latest video compression standard, were determined through subjective evaluation. A set of ten 8K (7680 × 4320/60/P) test images with a variety of coding criticality were selected, from which 4K (3840 × 2160/60/P), and 2K (1920 × 1080/60/P and 1920 × 1080/60/I) images were produced by down-conversion emulating actual cameras. The HEVC test model with the Main 10 profile for 10-bit depth video was used to encode the test images. Video experts participated in the subjective evaluation tests using the Double Stimulus Impairment Scale (DSIS) method with the five-grade impairment scale. The desired image quality was considered to satisfy the permissible limit (the mean opinion score of 3.5) for nine of the ten test images. The results showed that the required bit rates for 4320/60/P, 2160/60/P, 1080/60/P, and 1080/60/I formats were 80-100 Mbit/s, 30-40Mbit/s, 10-15Mbit/s, and 10-15Mbit/s, respectively.