TRADIM Develops Flexible LCD Display by Using Roll-to-roll Method

Mar 29, 2012
Tetsuo Nozawa, Nikkei Electronics
The new panel bent in a convex direction (c) TRADIM
The new panel bent in a convex direction (c) TRADIM
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The panel bent in a concave direction
The panel bent in a concave direction
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The Technology Research Association for Advanced Display Materials (TRADIM) announced that it has developed the "Curved LCD Display," an LCD panel formed on a film substrate, by using a roll-to-roll (R2R) method.

It can be bent in both concave and convex directions with a curvature radius of up to 30cm without deteriorating its display performance. As a result of the development, it became possible to make "thin, light-weight and unbreakable" LCD panels, TRADIM said.

This time, TRADIM developed a 3.5-inch (diagonal line: about 8.9cm) LCD panel whose resolution, thickness (excluding its backlight unit) and weight are 114ppi, 0.49mm and 7g, respectively. It was realized by using a R2R method to combine (1) a film substrate that has a high thermal resistance and a low coefficient of thermal expansion, (2) polarizing and phase difference film components, (3) color filter component, (4) TFT component and (5) backlight component.

TRADIM is an industry group that was established in July 2002 for developing an LCD panel formed on a film substrate. Before 2009, the group used films as substrates but could not make a flexible LCD display.

"When a film substrate was used to make a panel, the entire panel was hard," the group said. "When we tried to bend it by sheer force, it broke."

This time, TRADIM succeeded in softening the entire panel by, for example, lowering the coefficients of elasticity of materials such as sealants and adhesive materials. As a result, it drastically improved flexibility. Though there is no in-depth data about the bending limit of the panel, no problem occurs to the image displayed on it until it is bent to a curvature radius of about 15cm, the group said.

In the case of the curvature radius of 30cm, a durability test for JIS (Japanese Industrial Standards) has already been conducted with the panel. Specifically, the panel passed two tests. One was conducted for 1,000 hours at a temperature of 80°C, and the other was conducted for 1,000 hours at a temperature of 35°C and with a relative humidity of 85%.

Currently, TRADIM consists of 13 companies including chemical makers (Kuraray Co Ltd, Sumitomo Chemical Co Ltd, Sumitomo Bakelite Co Ltd, etc), electronic manufactures (Sharp Corp, NEC Corp, Hitachi Displays Ltd, etc), Dai Nippon Printing Co Ltd and Toppan Printing Co Ltd. However, the group will be dissolved in March 2012 because it has already achieved its goal. And the commercialization of the new panel will be dependent on each of the member companies.