Printed electronics requires a variety of new materials in the form of printable inks for forming devices, wiring circuits, sealing, bonding, and even film substrates. Metallic nanomaterials are promising candidates for wiring materials, competing with other candidates such as organic materials (PEDOT⁄PSS), carbon materials (nanotubes), and ceramic nanomaterials (typically ITO). The main advantage of metallic inks is their low electrical resistivity, reaching up to the order of 10^-5 to 10^-6 Ω ·cm, whereas those of the other candidates are higher by one or two orders. In this study, we reviewed a large number of advanced technologies in printed electronics, such as printing technologies, metallic nanoparticle inks, metallo-organic decomposition inks, and fabrication methods for metallic wirings, using an ink-jet printer.

View full abstract

We succeeded in forming a minute circuit with a maximum line spacing of 20 μm by a printing method for the inner coating of a ceramic substrate having a small size and low density and an internal wiring circuit comprising ceramic package parts. The filling process involves enclosed-type pressure printing achieved by the contact print method. A steady print can be obtained using the newly developed snap-off mechanism.

View full abstract

Our company entered the market of printable electronics in 2000 and started off with the manufacture of coating equipment for liquid crystal display (LCD) alignment films. We then started conducting research and development (R&D), on request, to determine whether a 100-μm fine line can be printed. We discovered that it is important to collaborate amongst different fields to improve our technical expertise level of printable electronics by means of gravure and letterpress. Since much small-sized R&D equipment has already been installed by users, we hope that many of them will upgrade to the next stage of production equipment. Such upgraded production equipment will be necessary to achieve targets of large size and super-fine resolution.

View full abstract

Organic electron devices are now being widely studied for their merits of being ultrathin and ultra-lightweight and offering the possibilities of wide area and flexible applications. In this review, we present ink-jet printing (IJP) technologies for organic electron devices. First, we show a self-alignment (SA) IJP technology for organic light-emitting devices (OLEDs). Using this technology, a flexible multicolor SA IJP panel with a size of 100 mm², 150 ppi, and 6.3-V operation is demonstrated. Second, an IJP pattern-laminated OLED, named light-emitting seal, is presented. We also demonstrate printed-coil-driven OLEDs for a noncontact-type electromagnetic power supply. These technologies are promising for recently developed light-emitting components such as light-emitting seals, light-emitting graphics, light-emitting tags, and light-emitting RFID cards.

View full abstract

The use and size of liquid crystal displays (LCDs), the most successful type of flat panel displays (FPDs), in a wide range of applications is continuously increasing. In LCD production, the two main structures (substrates), thin-film-transistor arrays (TFT) and color filters, are manufactured by photolithography using large-size photomasks (LSPMs) as the master form for transferring fine patterns. Here, we first describe the fundamental structure of an LCD and a typical manufacturing flow using the LSPM. Next, we describe three technical trends of LSPMs: 1) their upsizing, 2) half-tone exposure technology with multitone masks (MTMs), and 3) precision pattern enhancement techniques. These trends have a close relationship with LCD development. Upsizing of LSPMs is driven by upsizing of LCDs, especially for TV applications. LSPMs for generation-eight LCD technology are larger by 1 m on each side and weigh over 50 kg. MTMs reduce the number of steps required in the lithography process and are therefore "indispensible" for cost reduction. A key success factor in the half-tone exposure process is "actual transmittance (T_A), " a unique concept for MTM. Precision pattern enhancement of an LSPM is necessary for achieving both high total panel quality and production yield control. We are certain that further development of LSPMs in each phase is beneficial for advancements in LCD technology.

View full abstract

Since the advent of the iPhone and the iPad, the projective-type capacitive touch screen is rapidly developing in the input device industry. The main feature of this type of touch screen is the multi-touch technology, which is the driving force of rapid market expansion. The results achieved by this new touch screen technology cannot be achieved by conventional resistive touch screen technology. This new technology is realized by integrating technologies of controllers, censors, and line circuits. This technology is different from printable electronics. In this book, recent trends in the technology of a projective-type touch screen and its materials are described.

View full abstract

On the possibility of obtaining spectral data multispectral imaging provides a feasible method to estimate the spectral reflectance of the images. This technique utilizes more than three-channel imaging, for instance, by applying several color filters in front of a CCD or digital camera. The aim of this study is to estimate the spectral information of printed samples from camera response data under two illuminants. For this purpose, a 2250 chart was generated and printed; the images of the printed charts were captured under two different light sources. A feed-forward Back-Propagation neural network with 6 input neurons of camera responses, one hidden layer containing 20 neurons, and an output layer of 31 neurons of spectral reflectance values were applied. It was shown that the proposed method was capable of accurately reconstructing the spectral reflectance of the printed samples with an average GFC value of 0.999. The mean of color difference was about 1.5 CIEDE2000 (1:1:1) unit. Moreover, the neural network was applied to investigate the colorimetric characterization of the camera under two illuminations. It was shown that the CIEL*a*b* values of the samples under two light sources can be estimated using the proposed neural network with a single hidden layer of 11 neurons. Consequently, by applying suitable illuminating and capturing condition, it is possible to estimate the spectral data of the printed samples from the camera responses under two illuminations. Back-Propagation neural network can be feasibly applied for modeling the relation between camera responses and spectral data.

View full abstract