NTT DoCoMo Inc. exhibited a mobile phone that uses electronic paper to display its keys at CEATEC Japan 2007 in a reference presentation.
The e-paper was manufactured by SiPix Imaging Inc. It has a structure in which small chambers called Microcups filled with white particles and a colored liquid are formed on a plastic substrate. The e-paper thus allows the presentation of two colors, i.e., white using the white particles and another color using the dyed liquid.
At present, SiPix Imaging is reportedly able to provide five types of two-color e-paper using blue, red, green, yellow and black liquids. NTT DoCoMo prototyped five models in colors that correspond to the five colors displayed on the e-paper.
"We tried to achieve the effect of highlighting the display of the keys by matching the handset color with the color on the e-paper," said NTT DoCoMo.
According to NTT DoCoMo, two years have passed since the company started working on a mobile phone that uses e-paper to display its keys. The company initially considered using e-paper available from E Ink Corp., Fujitsu Ltd. and Bridgestone Corp. in addition to SiPix Imaging.
"The resistance to pressure when pressed with a finger is higher and the company has experience with volume production," NTT DoCoMo said when asked why it chose the SiPix Imaging product.
NTT DoCoMo came to the conclusion that E Ink's e-paper has a lower resistance to pressure because it uses microcapsules and that Fujitsu's product doesn't fit NTT DoCoMo's concept because Fujitsu is focused on the development of color e-paper. Regarding Bridgestone's product, NTT DoCoMo said that the company "did not have enough experience in volume production at that time." However, the company said it will reconsider which e-paper to use in commercial products.
There are two major reasons why it took NTT DoCoMo two years to exhibit the prototype. First, the company tried to display different kinds of letters and characters in one button area. Initially, one area could only show one kind of letter or character, but now it is capable of displaying three kinds.
The second reason is that the company had to enhance the speed required for switching (redrawing) the display. Now, the display can be switched in roughly one second.
NTT DoCoMo intends to make further improvements to these two issues. More specifically, the company aims to increase the types of letters and characters that can be displayed to more than three and reduce the time required to redraw the display to about half a second.
Correction Notice: We added the sentence, "However, the company said it will reconsider which e-paper to use in commercial products," at the end of the seventh paragraph after NTT DoCoMo suggested this change.