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We made improvements on the previously reported hard-coat for cartridge-free Blu-ray disc from a viewpoint of an antifingerprint property. As a result of this study, two types of the hard-coat have been obtained. One is for Blu-ray discs of ROM and write-once types, and the other is for that of rewritable type. The former well inhibited a deterioration of bit error rate (bER) of the signal written prior to the fingerprint adhesion. The later exhibited low bER for the data signals written both before and after the fingerprint adhesion. These results are attributable to the area ratio of drops of fingerprint-ingredient on the disc surface, and the low area ratio resulted in a low bER. Moreover, it was confirmed that the disc with higher contact angle of oily compound exhibited the lower area ratio ofthe fingerprint.

This paper reports the result of experiments made of the effect of grinding, lapping and barrelfinishing operations on the fatigue strength of quenched and tempered 13 Cr stainless steel used for compressor valve.The reversed plane-bending fatigue tests were carried out by means of Schenk-type fatigue testing machine of 10kgm at about 1500rpm.The results obtained can be summarized as follows (1) In longitudinal grinding the fatigue limit of roughly ground specimens was almost the same as finely ground ones, but in transverse grinding the latter was about 10% higher than the former.(2) In rough grinding the fatigue limit of transversely ground specimens was contrary to general expectations, nearly equal to that of longitudinally ground ones, but in fine grinding the former was about 20% higher than the latter.(3) The lapped specimens, when barrel-finished, get their surface roughness reduced by half, with but little increase in fatigue limit.(4) In the surface finishing operations under the conditions used in this experiment it was necessary that the residual stress both in the surface layer and the surface roughness should be taken into consideration as having influence on the fatigue strength.

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