TDK Corp. exhibited "a method to keep fingerprints at a constant quality" as a reference presentation at CEATEC Japan 2007.

This method is used to quantitatively evaluate the influence of fingerprints on touch panel displays, mobile phone handsets, optical media, etc.

In the course of the development of optical disc media, TDK reportedly had a trouble in properly evaluating the recording/playback quality that was influenced by fingerprints on discs. Specifically, the company had to quantitatively evaluate the influence of fingerprints when it decided to eliminate the cartridge initially provided to hold the Blu-ray Disc media.

"At that time, we transferred fingerprints manually by touching the discs each time we conducted the evaluation," said a demonstrator. "But the number of fingerprints left on the discs differed depending on the conditions of the day," he added. "It was far from a quantitative evaluation." So the company developed the method that was on display at the event.

According to the method, a cloudy solution called "artificial fingerprint reagent" consisting of an oil such as a higher fatty acid, dust, etc. is prepared first. The company reportedly holds a patent on the solution component (estimated to be Japanese Patent No. 3886519, etc.). Test powder obtained from the loamy layer of the Kanto region in Japan, which is specified by Japanese Industrial Standards (JIS) Z8901, was used for the dust.

Although the standard stipulates the component of artificial fingerprint reagent under the article "JIS K2246: Rust Preventive Oil," it was determined for use in the performance evaluation of rust preventive oils. Therefore, the reagent was hard to handle in the evaluation of optical discs and the like, said the company.

In the proposed method, the newly-developed reagent is dropped on a disc used as a stamp pad, and then the reagent is thinly spread by spin coating. Next, a stamp shaped like a rubber stopper is pressed against the stamp pad so that the reagent is adhered to the stamp. (The contact surface of the stamp is appropriately roughened.) Finally, a stamp is pressed against the test piece with a constant pressure to transfer the fingerprints.

Recently, mobile phones equipped with a touch panel display are becoming increasingly popular. In addition, anti-fingerprint property is an issue for antireflection coatings and functional films attached on flat-screen TVs. In view of such circumstances, TDK decided to see how visitors react to the company's proprietary quantitative evaluation method exhibited as a reference presentation.