02 Mar 2004
One LCD can display images on both sides thanks to transparent backlights.
Japan’s Mitsubishi Electric has developed a “reversible” liquid crystal display (LCD) that can display images on both its front and rear surfaces. The firm says this could provide a lighter, thinner and cheaper alternative to the two separate displays that many folding cell phones use today.
The secret is that the reversible LCD makes use of two transparent backlights. This means that it contains only one liquid crystal glass panel, which is sandwiched between the backlights.
Many folding cell phones have two displays: a large, main display and a smaller sub-display, which is used when the handset is folded shut. As LCD backlights usually have non-transparent white diffusible light guide plates, conventional designs require two separate LCDs in order to display images on both surfaces.
In contrast, the light guide plates in Mitsubishi’s backlights are made up of invisible fine light reflecting prisms which appear transparent when switched off and bright when switched on. Switching the transparent backlights on or off enables the LCD to display images on its front side, rear side or on both at the same time.
The display is said to have a brightness of 150 cd/m2, which is equivalent to that of conventional LCD modules. Image quality is also said to rival that of conventional module designs.
The company has filed for four Japanese patents relating to this technology and one patent is currently pending outside Japan. The company is now looking for potential customers.
Siân Harris is features editor of Opto & Laser Europe magazine.