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Philips 'paints' a thin display

Posted: 16 May 2002 ?? ?Print Version ?Bookmark and Share

Keywords:Philips? flat panel display? LCD? display?

Scientists from Philips have fabricated flat-panel displays using a coating technique similar to painting. It could mean the production of cheaper and thinner displays.

Using the technique, displays can be built on a variety of substrates, including plastic. This means they can be made very thin and more cheaply than current methods.

LCDs are usually constructed between two evenly spaced glass plates, containing electrodes, switches and colour filters. In the Philips technique, the complete displays are built from the bottom up on a single substrate by coating all functional layers one by one, in processes similar to painting.

According to Philips, the crucial step is the fabrication of liquid-crystal cells without the vacuum suction process. This is achieved by a process called photo-enforced stratification (PES).

First, a material containing liquid crystal and a polymer-forming material is applied to the substrate. Specific parts of the layer are exposed to UV light. The light reacts with the material and causes the blend to split up into a liquid crystal part and a polymer part.

The parts that are exposed form rigid walls of polymer material, making up the sides of the individual cells. In the second step, the complete layer is exposed, causing the formation of a liquid crystal layer on the bottom and a polymer cover layer on top of the cells.

Professor Dirk Broer, from Philips Research Laboratories said: "The main advantages are cost freedom in display design. The cost is reduced by the fact that the manufacturing becomes much simpler and the upper glass plate can be omitted.

"The freedom in design is largely enhanced due to the fact the substrate material can be freeley chosen, as long as the electrode structure can be incorporated."

The thickness of the active layer with its polymer cover and additional optical films is in the order of 30 to 405m and substrate thickness can be made as thin as 0.4mm in the case of glass and 0.1mm in the case of plastic.

"We believe the display thickness is important, especially for portable applications such as phones and PDAs," said Prof Broer.

The next steps are to produce active matrix-driven LCDs: "The project is in the research stage and we still need to do a lot of work to make larger sizes, full color and improve further on the reliability."

? Sara Sowah

EE Times

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