ICMDT2009, Jeju Island, Korea, June 25-26, 2009

ELDisplay Printed on Curved Surface

Taik-Min Lee*, Jae-Ho Noh**, Jeongdai Jo*, and Dong-Soo Kim*

*Nano Convergence Machinery Research Division, KIMM, Daejeon, KOREA

**Dept. of Mechanical Engineering, Hanbat National Univ., Daejeon, KOREA

This paper presents the electro-luminescence (EL) display lamp which is patterned on a curved surface by the pad printing method. Due to the superior price competitiveness to the existent semi-conductor, the printing technology has begun to get into the spotlight as a micro fabrication technology. The printing methods, including the gravure, screen, flexo, inkjet, and pad printing, have an advantage of one-step direct patterning. However, in general, the printing and semi-conductor process, except pad printing method, cannot be applied for patterning on a curved surface. Thus, in this paper, we used pad printing method for patterning an EL display lamp on a curved surface.

The EL display lamp consists of 5 layers as shown in Fig.1: Bottom electrode; Dielectric layer; Phosphor; Transparent electrode; Bus electrode. For proper pad printing, the ink of each layer should be formulated and the pad printing condition should be well controlled. As the bottom electrode, silver ink and carbon ink were used. Since the resistance of silver is low enough for electrodes, 1 time printing results in the sufficient conductivity, even though the printed thickness is as thin as 1.4m. However, in case of carbon, we printed 5 times for the sufficient conductivity. The pattern height of carbon was 5.77m. Since the dielectric layer should be thick in order to prevent a short circuit at a high voltage, we printed this layer 5 times. The phosphor and transparent layer was also printed 5 times for sufficient layer thickness. The bus electrode is same as the bottom electrode. However, since the bus electrode is printed on the transparent electrode, the adherence between the layers is critical. The adherence of the carbon ink is almost 5 times better than the adherence of the silver ink. We used the carbon ink for the bus electrode.

Fig.2 shows the fabrication results of the pad printed EL display lamp. The PEN film was used first in order to realize the pad printing process condition of each layer. The pad printed EL display lamp on PEN film is flexible as much as a radius of curvature 5 mm.Finally, we printed EL display lamp on a dish as shown in Fig.2. The dish has a radius of curvature 80mm. The EL display lamp was driven at AC 200V of 1kHz. The difference between the PEN film and the dish is surface adherence. The adherence of dish is so bad that the carbon ink was used for the bottom electrode. Consequently, we can conclude that EL display lamp was fabricated on a curved surface by using pad printing method, which has a great potential as the micro fabrication technique onto various shapes.

Keywords:EL, Printed EL, Pad Printing, Printed Electronics.

Fig.1 Design and fabrication process of the EL display lamp printed on a curved surface. / Fig.2 EL display lamp pad-printed on a dish having radius of curvature 80mm.

 Corresponding Author: Taik-Min Lee

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