Shuichi Uchikoga

LED packaging by ink-jet microdeposition of high-viscosity resin and phosphor dispersion

— An ink-jet-printing method applied to the microdeposition of high-viscosity resin, including optimization of phosphor dispersion for light-emitting-diode (LED) packaging was examined for the first time. An ultrasonic ink-jet-printing method was used, in which ink droplets are ejected by a focused ultrasonic beam from a nozzle-less printhead. To fabricate white LEDs, high-viscosity phosphor-dispersed resin was deposited to form an encapsulant dome. Two types of methods to control phosphor sedimentation for color uniformity were examined; one is heating the lead frame during the resin deposition, and the other is hydrophobic surface treatment of the lead frame base enabling the fabrication of a small encapsulant dome. For light direction control, a silicone micro lens was deposited on an encapsulant dome using the ink-jet method. The results show that ultrasonic ink-jet printing is an applicable technique to optimize and modify on-demand optical characteristics of LED devices.

A back‐side passivation film on a‐Si:H thin film transistor

Silicon nitride (SiNx) films of various quality were deposited on the back‐side of a‐Si:H thin film transistors (TFTs) as a passivation layer. Although the films were not deposited directly on the channel region, the N/Si ratio of the film affected the TFT performance. It changed the threshold voltage and the subthreshold slope. In the linear region, the effect of the passivation layer was explained by assuming fixed charges in the nitride layer. Furthermore, the current‐voltage characteristics in the saturation region were explained by a parasitic TFT model. It was determined that a nitrogen rich passivation film is preferrable for liquid crystal displays.

Analysis of electro-optical properties of polymer-stabilized OCB and the application to TFT-LCDs

— A 9-in. full-color polymer-stabilized OCB TFT-LCD with stable bend alignment in the absence of an electric field was developed. The condition of the polymer stabilization, the characteristics of UV-curable monomers, and their influence on the configurations of the polymer network in the cell were studied. Possible models of the configuration were proposed and their relationship to the electro-optical properties was analyzed using a novel simulation method considering the distribution of anchoring effects from both alignment surfaces and the polymer network. It was suggested that a good performance such as high contrast ratio and fast response could be expected in the polymer network originating from newly developed monomers composed of multifunctional LC acrylates due to a relatively weak-anchoring effect and presumably its localization near the alignment surfaces. By using the newly developed monomers under the optimized polymer-stabilizing process, a high contrast ratio of 250:1 and fast response nearly equal to that of a conventional OCB cell were achieved.

17.3: Electro‐Optical Properties of Polymer‐Stabilized OCB and Its Application to TFT‐LCD

To eliminate an initial transition from splay to bend alignment, polymer-stabilized OCB was developed. The influences of the monomer concentration and the applied voltage during UV irradiation were studied, and stable bend alignment in the absence of electric field was obtained. The large retardation change and the fast response were achieved by using a mixture of multifunctional LC acrylate monomers, and a 9-inch full-color polymer-stabilized OCB TFT-LCD with initial bend alignment and the contrast ratio of 250:1 was successfully developed.

54.4L: Late‐News Paper: Input‐Output Integrated Flexible Display System

We have made a prototype of flexible display system integrated with bend-input function. It consists of flexible display, flexible backlight unit with bending sensor, and MPU connected to PC. Zooming in/out in Google Earth and paging up/down in PDF files have been successfully done by bending the flexible display.

54.1: LED Packaging by Ink‐jet Microdeposition of High‐Viscosity Resin and Phosphor Dispersion

The applicability of an ink-jet printing method to microdeposition of high-viscosity resin and phosphor dispersion for light-emitting-diode (LED) packaging was examined for the first time. An ultrasonic ink-jet printing method was used, in which ink droplets are ejected by focused ultrasonic beam from nozzle-less printhead. for fabricating white LEDs, high-viscosity phosphor-dispersed resin was deposited to form an encapsulant dome, and hydrophobic surface treatment of the lead frame substrate enabled fabrication of a small encapsulant dome to improve color uniformity. A silicone microlens was deposited on an encapsulant dome using the ink-jet method for light directivity control. The results show the ultrasonic ink-jet printing is an applicable technique to optimize and modify on demand optical characteristics of the LED devices.

Micromachined Thermal Effect Array by Joule Heating for Bio Applications

We have developed a micro local heating device for bio applications using micro-electro-mechanical systems (MEMS) technology. The device has a two-dimensional microdish array, which contains a series of diodes. The microdish array is fabricated by means of a combination of complementary metal–oxide–semiconductor (CMOS) technology and MEMS post-processing. The microdish array has a miniature cavity for thermal separation from substrate. These microdish arrays can be generated by a large forward current based on Joule heating. In this paper, we describe the direct heating of the whole microdish array and just an arbitrary portion of the microdish consisting of the device by Joule heating. In the localized selective heating, the highest temperature, 62.6 °C, from all the dishes was confirmed. More than twice the heat effect was achieved in heating an arbitrary portion compared with heating the whole microdish.

67.3: Electrochemical Reaction Display with Dual Reflective and Emissive Modes

We have developed an electrochemical reaction display (ECRD) that can be operated in dual reflective and emissive modes in an entire pixel area of a single device. The ECRD utilizes electrochromic (EC) and electrogenerated chemiluminescence (ECL) reactions. These two electrochemical reactions can be controlled independently by adding a luminescent molecule to a liquid electrolyte of an EC cell with three electrodes. In the reflective mode, the ECRD cell exhibits high reflectance (47%) and high contrast ratio (6:1). In the emissive mode, the cell can show luminescent moving images because of the fast response time (10 ms).

31.2: Invited Paper: Various Inkjet Methods for Thin Film Transistor Array Fabrication

Fabrication of electronic devices by printing technique is attracting interest in the expectation of lowering production cost. There is an ongoing work using various printing methods. This paper outlines some of the important aspect of printing in terms of fabricating thin film transistor (TFT) arrays. Appropriate combination of inkjet head and the ink material must be considered. Non-piezoelectric inkjet printing methods, such as ultrasonic inkjet printing and electrostatic inkjet printing are also introduced for fabricating all-solution-processed organic thin-film transistor.

33.1: A 3.2‐in. LCD Panel using Amorphous Silicon TFT Formed with Novel Selective and Dispersive Transfer Technique

A novel formation process for TFT using our proposed novel selective transfer technique, which enables low cost TFT fabrication on a large and flexible substrate, is proposed. This technique is used to fabricate a 3.2-inch LCD Panel using amorphous silicon TFT transferred on glass substrate for the first time.