Sony Develops Low-reflection Conductive Film for Smartphones

Jun 20, 2012
Naoki Tanaka, Tech-On!
The exhibit on the low-reflection conductive film developed by the Sony Group
The exhibit on the low-reflection conductive film developed by the Sony Group
[ If it clicks, the expanded picture will open ]
The exhibit to show the effects of the new conductive film and the low-reflection film with a moth-eye structure. From the top, (1) a case where a traditional conductive film is used for the touch panel, (2) a case where the new conductive film is used for the touch panel and (3) a case where the new conductive film is used for the touch panel and the moth-eye low-reflection film is placed on the OLED panel.
The exhibit to show the effects of the new conductive film and the low-reflection film with a moth-eye structure. From the top, (1) a case where a traditional conductive film is used for the touch panel, (2) a case where the new conductive film is used for the touch panel and (3) a case where the new conductive film is used for the touch panel and the moth-eye low-reflection film is placed on the OLED panel.
[ If it clicks, the expanded picture will open ]
The exhibit to show that the new film can prevent the deterioration of image quality as much as the use of OCA (optical clear adhesive). From the top, (1) a case where the new conductive film is used for the touch panel and the moth-eye low-reflection film is placed on the OLED panel, (2) a case where a traditional conductive film is used for the touch panel and the gap is filled with OCA and (3) a case where the new conductive film is used for the touch panel and the gap is filled with OCA.
The exhibit to show that the new film can prevent the deterioration of image quality as much as the use of OCA (optical clear adhesive). From the top, (1) a case where the new conductive film is used for the touch panel and the moth-eye low-reflection film is placed on the OLED panel, (2) a case where a traditional conductive film is used for the touch panel and the gap is filled with OCA and (3) a case where the new conductive film is used for the touch panel and the gap is filled with OCA.
[ If it clicks, the expanded picture will open ]

The Sony Group developed a low-reflection conductive film that can improve the image quality of a display equipped with a touch panel such as a smartphone screen.

The film was announced by Sony Corp and Sony Chemical & Information Device Corp at SID 2012 (thesis number: 44.1) and exhibited at the booth of Sony Chemicals Corp of America.

Conductive films are used for the sensor electrodes of touch panels. Normally, low- and high-refractive materials are accumulated on a base film, and an ITO (indium tin oxide) conductive film is formed on top of it. By stacking materials with different refraction indexes, the reflection of external light, which deteriorates image quality, is reduced.

However, its effect is limited. For example, when sensor electrodes are formed by patterning ITO, the reflectance of external light is different between an area where there are ITO sensor electrodes and an area where there are no ITO sensor electrodes, generating a streaky surface. Also, because the reflectance for the low wavelength region of visible light is especially high, the screen becomes whitish.

To solve such a problem, the Sony Group developed the new conductive film by using a sputtering method to form an ITO conductive film on a low-reflection film with a moth-eye structure. The low-reflection film with a moth-eye structure has minute, regularly-arranged concave and convex structures on its surface.

The new film's reflectance of external light is almost uniform regardless of the existence of ITO sensor electrodes. In addition, the new film's reflectance of external light is less dependent on wavelength than the reflectances of existing conductive films, and the reflectance is equivalent to or less than those of existing conductive films.

At the booth of Sony Chemicals Corp of America, there were two exhibits to show the effect of the new film by comparison. Both of them used OLED panels attached with a touch panel.

First, three structures were exhibited to show the effects of the new conductive film and the moth-eye structure. All of them had a structure in which there was an air gap between the OLED panel and the tough panel. They were for comparison among the following three cases: (1) a case where a traditional conductive film is used for the touch panel, (2) a case where the new conductive film is used for the touch panel and (3) a case where the new conductive film is used for the touch panel and the moth-eye low-reflection film is placed on the OLED panel. The deterioration of image quality was smallest in the third case and largest in the first case.

The second exhibit was to show that the new film can prevent the deterioration of image quality as much as the use of OCA (optical clear adhesive) for filling the gap between the display panel and the touch panel. The exhibit was for comparison among the following three cases: (1) a case where the new conductive film is used for the touch panel and the moth-eye low-reflection film is placed on the OLED panel, (2) a case where a traditional conductive film is used for the touch panel and the gap is filled with OCA and (3) a case where the new conductive film is used for the touch panel and the gap is filled with OCA. The first and second cases showed almost the same image quality. And, in the third case, the deterioration of image quality was smallest. Sony plans to propose the third method for high-end smartphones.